JPH08149253A - Ink jet recording device - Google Patents

Abstract

PURPOSE: To attain stable recording by forming an electrode array on the surface of a head base and supplying ink formed by dispersing a color agent into a solvent to the electrode array on the surface of the base so as to exert an electrostatic force to the color agent component thereby preventing the discharge on the electrode. CONSTITUTION: An electrode array 13 is provided to the surface of a base 12 and ink 11 formed by dispersing a color agent in a solvent in an ink circulation mechanism 18 is circulated to the mechanism 18 via an ink supply path 15 and an ink recovery flow path 17. Through the constitution above, the ink 11 is supplied to the array 13 on the base 12 to prevent the exposure of the array 13 and while preventing discharge by the electrode 13, the color agent in the ink 11 is jetted by an electrostatic force action via the electrode 13 to apply ink jet recording to a recording medium 21. Thus, it is not required to form a tip of the electrode array to be a sharp edge and a damage due to discharge of the electrode array is not caused and stable recording is made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and in particular, a liquid ink in which a colorant is dispersed in a solvent is used, and the colorant component in this ink is aggregated and ejected onto a recording medium for recording. The present invention relates to an inkjet recording device.

[0002]

2. Description of the Related Art An apparatus for ejecting liquid ink as small droplets called ink particles on a recording medium to form recording dots and recording an image has been put into practical use as an inkjet printer. This ink jet printer has the advantages that it is less noisy than other recording methods and does not require processing such as development and fixing, and is attracting attention as a plain paper recording technology. Many methods of inkjet printers have been devised up to now, but in particular, (a) a method of ejecting ink droplets by the pressure of steam generated by the heat of a heating element (for example, Japanese Patent Publication Nos. 56-9429 and 61-59).
911) or (b) a method in which ink droplets are ejected by a mechanical pressure pulse generated by a piezoelectric element (for example, Japanese Patent Publication No. 53-12138), and a multi-nozzle that records a plurality of dots in parallel. The type is typical.

A recording head used in an ink jet printer is mounted on a carriage and is in a direction (main scanning direction) orthogonal to a recording paper conveyance direction (sub scanning direction).
A serial scanning type head is used in which recording is performed while moving to. With this serial scanning type head, it is difficult to increase the recording speed because recording is performed while moving mechanically. Therefore, the recording head is made a long head of the same size as the width of the recording paper to reduce the mechanical moving parts,
A so-called line scanning head capable of increasing the recording speed is also considered, but it is not easy to realize such a line scanning head for the following reason.

In the ink jet recording system, the concentration and concentration of the ink are likely to occur locally due to the evaporation and volatilization of the solvent, which causes the clogging of individual thin nozzles corresponding to the resolution. Therefore, in the method of using the pressure of vapor for forming the inkjet, insoluble matter is attached by thermal or chemical reaction with the ink, and in the method of using the pressure of the piezoelectric element, the ink flow path is complicated. The different structure makes it easier to induce clogging. Serial scanning heads that use several tens to hundreds of nozzles can reduce the frequency of clogging, but line scanning heads that require thousands of nozzles. The probability of clogging occurs at a fairly high frequency, which is a major problem in terms of reliability.

Further, there is a problem that the conventional ink jet recording apparatus is not suitable for improving the resolution. That is, it is difficult to generate ink particles having a diameter of 20 μm or less (which corresponds to a recording dot having a diameter of about 50 and several μm on the recording paper) by the method using the pressure of vapor, and the pressure generated by the piezoelectric element is used. This is because in the method of using, the recording head has a complicated structure, and it is difficult to form a head with high resolution due to processing technology problems.

In order to overcome these drawbacks, an ink jet recording system has been devised in which a voltage is applied to a thin film electrode array and the electrostatic force is used to fly the ink or the colorant component therein from the liquid surface of the ink. Specifically, a method of ejecting ink by using electrostatic attraction (Japanese Patent Laid-Open No. 49-62).
No. 024, JP-A-56-4467, etc.) or a method in which ink containing a charged coloring material component is used to increase the density of the coloring material and fly (WO93 / 11866: PCT / AU92 / 00).
665) and the like have been proposed. In these methods, the recording head configuration is a slit-shaped nozzle configuration that does not require a nozzle for each individual dot (FIG. 35), or a nozzleless configuration that does not require a partition of an ink flow path for each individual dot (FIG. 36). Therefore, it is effective in preventing and recovering from clogging, which was a major obstacle in realizing a line scanning type recording head. The latter is particularly suitable for high resolution because it can stably generate and fly ink particles having a very small diameter.

In the ink jet recording system in which the coloring agent is ejected by such electrostatic force, the structure of the recording head is as shown in FIG.
5 and FIG. 36, a so-called edge shooter type head in which the tip of the electrode array 13 is arranged at the edge portion of the head substrate 12 has been conventionally used. However, since the electrodes are exposed in the recording head having such a configuration, the electrode array is likely to be damaged by the discharge generated by the strong electric field, and the flow of the ink becomes unstable, resulting in a large variation in the operating characteristics. There is a problem. A method of depositing an insulating film on the surface of the electrode is also conceivable, but since the insulating film needs to be extremely thin, there is a high possibility of damage or dielectric breakdown due to contact, and there is a problem in terms of reliability.

Further, in the recording head using the edge portion of the electrode as described above, it is difficult to process the edge with high precision, so that the yield is poor, and there are major problems in terms of ease of manufacturing, uniformity of characteristics, and recording quality. There is. In particular, in the case of a line scanning printhead that needs to print several thousands of dots in parallel, the overall good product rate can be obtained by multiplying the good product rate of individual dots by the number of dots several times, so it is extremely reliable. Otherwise, the production yield and recording quality will be seriously affected.

Further, in the above-mentioned conventional recording head, since the electrode for generating the electric field for aggregating the colorant in the ink and the electrode for flying the ink aggregating the colorant are the same, the colorant Since it is impossible to separately control the agglomeration of the ink and the flight of the ink, it is necessary to finely adjust the ink flow velocity and the applied voltage in order to agglomerate the colorant at a high concentration and fly the agglomerated ink.

Furthermore, when a multi-head like a line scanning type recording head is constructed, it is necessary to lower the voltage applied to the electrodes to prevent electric field interference between adjacent electrodes. If the voltage for flying the color material is reduced by reducing the distance between them, the electric field for aggregating the color material inside the nozzle cross section also decreases.
As a result, the voltage required for agglomeration of the colorant and the voltage for flying the ink must be higher in the latter than in the former, but by lowering the voltage for flying the ink, the high-low relationship between the two is increased. There is a problem that it is reversed and it becomes impossible to fly the ink in which the coloring material is aggregated. Further, when the recording head and the recording medium are brought close to each other, fogging is likely to occur, and stable image formation becomes difficult.

[0011]

As described above, in the recording head used in the ink jet recording system in which the coloring material component in the liquid ink is ejected by the conventional electrostatic force, the electrode for applying the electrostatic force is exposed. Therefore, stable recording cannot be performed due to electrode damage due to discharge generated by a strong electric field.Moreover, since it is an edge shooter type in which the tip of the electrode is placed at the edge portion of the head substrate, it is easy to manufacture and the characteristics are uniform. There was a problem in terms of recording quality.

Further, since the conventional recording head of this type cannot separately control the aggregation and the flight of the coloring material component in the ink, it is necessary to agglomerate the coloring material component at a high concentration and to fly the aggregated ink. Requires delicate adjustment of ink flow velocity and applied voltage.
When the distance between the recording head and the recording medium is reduced in order to prevent the electric field interference between the adjacent electrodes to reduce the voltage for flying the colorant component, the voltage required for the aggregation of the colorant component is The voltage is higher than the voltage for flying, it becomes impossible to fly the ink in which the colorant components have aggregated, and fogging easily occurs when the print head and print medium are brought close to each other, and stable image formation is achieved. There was a problem that it would be difficult.

An object of the present invention is to discharge ink at an electrode for acting an electrostatic force on a colorant component in a system in which the colorant component in ink is aggregated by using electrostatic force to fly to a recording medium for recording. It is an object of the present invention to provide an ink jet recording apparatus that can effectively prevent the above and perform stable recording.

Another object of the present invention is to prevent discharge at an electrode for acting an electrostatic force on a colorant component and to cause the colorant in the ink to flow from the plane portion of the head substrate in a direction perpendicular to the plane of the head substrate. It is an object of the present invention to provide an ink jet recording apparatus which can be made to fly to a recording medium with the initial velocity component, and which is easy to manufacture and has excellent property uniformity and recording quality.

Another object of the present invention is to provide an ink jet recording apparatus capable of separately controlling aggregation and flying of a coloring material in ink.

[0016]

SUMMARY OF THE INVENTION The present invention uses an ink jet recording apparatus which uses a liquid ink in which a colorant is dispersed in a solvent and causes the colorant components in the ink to aggregate and fly onto a recording medium for recording. In, the electrode array is formed on the surface of the head substrate, and the ink in which the colorant is dispersed in the solvent is supplied onto at least the electrode array on the surface of the head substrate, and the ink in the ink supplied onto the electrode array is The basic feature is that at least a voltage for causing the colorant component to fly toward the recording medium is applied to the electrode array.

Here, the head substrate gives an initial velocity component in the direction perpendicular to the surface of the head substrate to the colorant component flying toward the recording medium by the electrode array, and the receiving point of the colorant component of the recording medium is further provided. It is located above a plane extending from the surface of the head substrate and has an angle of 90 degrees with the plane at the receiving point.
It is preferably arranged with respect to the recording medium so as to be less than or equal to °.

More specifically, the electrode array is composed of a plurality of individual electrodes, and a voltage according to an image signal is applied to these individual electrodes.

According to one embodiment, the individual electrode is preferably formed on the surface of the head substrate at a position retracted from the end surface on the recording medium side, and the common electrode is formed on the back surface of the head substrate. Then, a predetermined bias voltage is applied to this common electrode.

According to another aspect, the individual electrode is preferably formed on the surface of the head substrate at a position receding from the end surface on the recording medium side, and the auxiliary electrode is provided on the surface of the head substrate at a position close to the individual electrode. It is formed. The auxiliary electrode may be an electrode divided corresponding to the individual electrode, or may be an electrode commonly provided for each individual electrode. Then, a predetermined bias voltage is applied to this auxiliary electrode.

According to still another aspect, the individual electrodes are formed such that their respective tips project on the surface of the head substrate, and the thin layer of ink is formed on at least the projecting portions of the individual electrodes. It is preferable that the protrusion has a shape in which the bottom on the surface of the head substrate is wide and the width is narrower toward the top. A plurality of individual electrodes and protrusions of the individual electrodes are arranged in the main scanning direction, and a plurality of columns are provided in the sub-scanning direction, and the protrusions on different columns are arranged at different positions in the main scanning direction. Is desirable.

Another ink jet device according to the present invention is
In an ink jet recording apparatus that performs recording by aggregating a colorant in an ink in which a colorant is dispersed in a solvent in accordance with an image signal and flying the aggregated colorant toward a recording medium, It is characterized by separately providing an aggregating means for aggregating the above in a solvent and a flying means for flying the agglomerated colorant toward a recording medium.

Here, when the ink is composed of an insulating solvent and a colorant having an electric charge, an electric field generating means is used as the aggregating means, and an electric field generating means of the aggregating means is used as the pressure generating means which is a flying means. Different electric field generating means are used.

More specifically, the electric field generating means as the aggregating means includes a pair of adjacent electrodes provided in the ink transport direction,
It is constituted by a voltage applying means for applying different voltages to both electrodes. The electric field generating means as the flying means is composed of an electrode pair provided on an insulating substrate via an insulating layer, and a voltage means for applying different voltages to the electrode pair.

Further, in order to facilitate the flight, it is desirable that the charge injection from the electrode is carried out by bringing the ink in contact with the electrode generating the flight electric field.

Further, it is desirable to have a means for removing the remaining aggregated ink after the coloring agent in the ink aggregated by the aggregating means is ejected.

On the other hand, when the ink is composed of an insulating solvent and a magnetic coloring agent, a magnetic field generating means is used as the aggregating means, and as a flying means, electric charges are injected into the agglomerated coloring material and caused to fly by using an electric field. Means are used.

[0028]

In the present invention, ink is supplied onto at least the electrode array, that is, the individual electrodes on the head substrate. That is, the ink is supplied onto the head substrate so that the electrodes are covered with the ink during recording to which a high electric field is applied so that the electrode array is not exposed to the atmosphere, which is likely to occur in the conventional inkjet recording apparatus. Damage to the tip of the electrode due to a severe discharge phenomenon in the air can be prevented by using a material that blocks discharge as a solvent for the ink, and stable recording is possible.

Only a recording apparatus using an edge shooter type recording head has been proposed in the case of making a multi-head by a conventional ink jet recording method in which a coloring material in a liquid ink is aggregated and jetted by electrostatic force for recording. The main reasons are: (1) Even if an electrode with a sharp tip is formed in the substrate plane by the printed wiring technology, the direction of the strongest electric field strength generated is still the same as the pattern plane or it is extended. Therefore, the strong electric field appears only at the edge part where the substrate is cut, and (2) the substrate on which the electrode array is formed and another substrate paired with it are parallel to each other via the spacer. If overlapped, an ink flow path with a slit-shaped opening can be easily formed at the edge of the substrate, and the point at which the strongest electric field is generated coincides with the colorant flying start point. It is to be formed UNA edge portion.

However, if an electric field as strong as the electric field at the tip of the electrode used in the edge shooter can be generated in the direction perpendicular to the head substrate surface, the edge of the head substrate is directed inward toward the substrate surface. Since it is possible to fly the colorant from the receding plane part and patterning to the edge part is not required, it is possible to use a normal in-plane manufacturing process such as the photolithography technology used in the manufacture of ICs to achieve reliability. It is possible to manufacture an ink jet recording head that uses electrostatic force with high property and high accuracy. Therefore, a side shooter type ink jet recording apparatus can be realized by a method utilizing electrostatic force.

In the present invention, the initial velocity component in the direction perpendicular to the surface of the head substrate is given to the coloring agent flying toward the recording medium, and the receiving point of the coloring agent in the recording medium extends the surface of the head substrate. The head substrate is positioned relative to the recording medium so that the head substrate is positioned above the above plane and the angle formed with the plane at the receiving point is 90 ° or less. That is, a side shooter type ink jet recording apparatus using an electrostatic force is realized by retracting the colorant flying start point within the head substrate plane and directing the colorant flying direction above the head substrate surface. It is possible to achieve ease of manufacture, uniformity and stability of characteristics, and improvement of recording quality.

In this case, in the present invention, the shape of the electrode tip located at the colorant flying start point and the surrounding electrodes surrounding it are used to generate a strong electric field component in the direction perpendicular to the plane of the substrate surface. It is possible to realize the flight in which the initial velocity component in the vertical direction is given to the coloring material in the ink. Specifically, as a first means therefor, the common electrode is arranged on the entire back surface of the head substrate on which the electrode array of the individual electrodes is formed. By applying a voltage to this common electrode, it is possible to generate an electric field oriented in the vertical direction from the substrate surface. The direction of the strongest electric field generated at the tip of the individual electrodes on the substrate surface is the horizontal direction, but when the electric fields in the vertical direction from the common electrode on the back surface of the substrate are added together, they are bent outward from the substrate and the vertical component is removed. The strongest electric field vector possessed can be generated.

As a second means for generating a strong electric field component in the direction perpendicular to the plane of the substrate surface, the auxiliary electrode (common electrode or individual electrode) may be provided close to the tip of the individual electrode on the head substrate surface. However, it may be arranged). When a voltage having the same polarity as the voltage applied to the individual electrodes is applied to the auxiliary electrode, the lines of electric force are bent in a repulsive manner so that an electric field having a vertical component is formed. Also with this method, the strongest electric field vector generated at the tip of the individual electrode can be generated in the direction outward from the substrate.

Further, the position of the colorant receiving point for receiving the colorant flying the recording medium such as the recording paper is above the plane extending the surface of the recording head substrate and at the head at the colorant receiving point of the recording medium. The angle formed with the plane that extends the substrate surface is 9
By adopting the structure of 0 ° or less, it is possible to stably receive the flying colorant with the velocity component in the vertical direction.

The phenomenon in which the coloring agent dispersed and suspended in the liquid in a colloidal state is concentrated and the solvent is left behind and jumps out into the air, which is used in this technique, has been industrially used in the past or research presentations. Although there are very few cases where it is done, there are points that the interpretation is still insufficient in terms of theory,
The present inventors have confirmed the facts and phenomena with repeated observations and experiments. According to these experimental facts,
Two things can be achieved:

One is related to the range of the voltage applied to the common electrode installed on the same head substrate surface as the individual electrode array or the auxiliary electrode installed on the back surface in order to give a velocity vector component in the vertical direction to the flying colorant. is there. In the experiments by the inventors, normally, a bias of 1 kV to 2 kV and a pulse voltage in the range of 100 V to 700 V are superimposed and applied to individual electrodes, but these common electrodes and auxiliary electrodes are bias voltage of the individual electrodes. It is known that stable operation is possible in the range from to the voltage on which the signal voltage is superimposed. That is, a voltage in the range of 1.0 kV to 2.7 kV can be applied to these common electrodes or auxiliary electrodes.

The other relates to the shape of the tips of the electrodes of the electrode array. According to the experiments by the inventors, it is confirmed that the flying of the coloring material becomes unstable when the tip of the electrode is too sharp, but it becomes stable when the radius of curvature of the tip is in the range of R = 15 μm to 100 μm. That is, the tip shape of the individual electrode to which a voltage corresponding to the image signal forming the array electrode formed on the surface of the substrate is applied is R = 15 μm to 1
The arc shape in the range of 00 μm can further stabilize the flight of the coloring material.

When the protrusion is formed at the tip of the individual electrode, the ink is supplied at least on the protrusion of the individual electrode, so that the surface of the protrusion is always covered with a thin layer of ink, and the protrusion is formed. The discharge problem is solved by ejecting ink droplets from the part. That is, by forming such a protrusion, even if the tip of the protrusion is exposed from the ink surface, the liquid is generated when the voltage is applied to the electric field generated by capillary action or voltage application, or the needle-shaped electrode. A thin ink layer is stably formed at the tip portion of the protrusion due to the effect of flowing toward the head. Therefore, it is possible to prevent the protruding portions of the individual electrodes from being destroyed by electric discharge, and in addition, it is possible to realize stable image recording.
In addition, since the ink is ejected from the tip of the protruding portion, basically no nozzle is required, and a slit or a hole for allowing the ink to pass is sufficient. Therefore, the problem of nozzle clogging can be solved as described above. It is the same.

Further, in this case, a plurality of individual electrodes and their protrusions are arranged in the main scanning direction and a plurality of columns are provided in the sub-scanning direction, and then the protrusions on different columns are mainly arranged in the main scanning direction. 1 / k of array pitch in scanning direction
By arranging them at different positions shifted by (k: an integer), it is possible to perform recording with a resolution equivalent to 1 / k of the arrangement pitch in the main scanning direction.

Further, by using an ink in which a charged coloring agent exists in the solvent as the ink, it becomes possible to concentrate the coloring agent only by aggregating the coloring agent by applying a voltage to the individual electrodes. It is also possible to record an image having a high density by concentrating and ejecting only the ink in the portion to be ejected by using the ink having a low density that is easy to convey. Further, by forming the protrusions on the individual electrodes, it is possible to concentrate the ink at the portion where the ink is ejected. Further, by using a charged colorant, the repulsive force between the drive electrode and the colorant works, so that the drive voltage can be lowered and the IC can also drive the electrostatic force, which has been difficult in the past. Also, it becomes easy to realize a line scanning type head by a method of ejecting ink.

Further, in the conventional method of aggregating and flying the colorant in the ink, the same nozzle is provided for the electrode for generating the electric field for aggregating the colorant in the ink and the electrode for generating the electric field for flying the agglomerated ink. I used to adjust the bias voltage and the flight voltage with a delicate balance, whereas
In the present invention, the aggregation of the coloring agent in the ink solvent and the flight of the aggregated ink are performed by independent electrodes, and the ink aggregated to an arbitrary concentration is separated by the flight electrode. For aggregation of the coloring material, a different voltage is applied to adjacent electrodes to provide a strong electric field for aggregation against the flow of ink, and the aggregation is efficiently performed at a low voltage.

As described above, in the present invention, the aggregating electrode for actively controlling the agglomeration of the colorant is provided separately from the electrode for the ink flying electric field, and the voltage is independent of the flying voltage. Since the colorant can be aggregated, the colorant can be sufficiently aggregated even with a low flight voltage that prevents interference between the adjacent nozzles. As a result, multi-heading without mutual interference is possible.

The aggregating electrode is composed of, for example, adjacent electrodes provided on the substrate, different voltages are applied to both electrodes, and an electric field force in the direction opposite to the ink transport direction on the substrate plane is applied to the colorant to cause coloration. Prevents agent migration and causes aggregation. The agglomeration of the colorant arranges the electrodes on the thin insulating layer in two rows and applies a voltage that creates an electric field against the ink flow that prevents the migration of the colorant.
In this way, the flying electric field and the cohesive electric field are formed by the electrodes corresponding to the individual dots, and the applied voltage is further reduced to form the necessary electric field, so that the interference with the adjacent electrodes can be removed and a multi-nozzle can be realized. I have to. In this case, if an electrode that forms a high electric field is formed in the flat portion that recedes from the end face of the substrate,
It becomes possible to realize a highly reliable and accurate inkjet recording device using electrostatic force in a planar process by photolithography technology of IC manufacturing technology.

Further, in the present invention, the charge is injected into the solvent in the aggregating ink before the ink is jetted, so that the ink can be jetted with a low electric field. In addition, the aggregating colorant remaining after the ink has been ejected generates a reverse electric field at the aggregating electrode and is conveyed along with the ink flow to be removed, so that a new ink layer is always conveyed and image deterioration such as blurring is prevented. . A voltage whose voltage value and pulse width are controlled is applied to these electrodes,
Fog is removed at the same time by controlling the image density and image size. The ink used here is not limited to an ink having a charged colorant, and a magnetic ink may be used to aggregate the colorant in the ink with a magnetic field.

[0045]

EXAMPLES Examples of the present invention will be described in detail below.

(First Embodiment) FIG. 1 is a schematic configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. In the figure, the ink 11 is made by suspending a positively chargeable colorant together with a charge control agent, a binder, etc. in a colloidal state in an insulating solvent of 10 ⁻⁸ Ωcm or more. The ink 11 is an ink supply channel 15 formed between a head substrate 12 and an upper cover 14 arranged on the surface of the head substrate 12 with a spacer having a thickness of about 300 μm.
Is supplied by the positive pressure applied by the ink recirculation mechanism 18. On the head substrate 12, individual electrodes 13 corresponding to recording dots, which are stripe array electrodes extending in the left-right direction in the drawing, are adhered and formed, and the ink 11 is supplied along the ink supply flow path 15 with the individual electrodes 13. Flow over the electrode 1
Head to the colorant flying point 13a at the tip of 3.

The ink 11 that has reached the colorant flying point 13a passes through the portion where the individual electrode 13 and the upper cover 14 are discontinued, and then passes around the front edge of the head substrate 12 and wraps around to the back surface side of the head substrate 12. The ink 11 that has flown around to the back surface side of the head substrate 12 is an ink recovery flow formed between the head substrate 12 and the lower cover 16 that is arranged on the back surface through the spacers, similar to the ink supply channel 15. The ink is returned to the ink recirculation mechanism 18 through the path 17 by the negative pressure, that is, the suction force given by the ink recirculation mechanism 18. The ink recirculation mechanism 18 is composed of a pump and a pipe connected to the ink supply flow path 15 and the ink recovery flow path 17, and the action of the pump causes the ink 11 to pass through the ink supply flow path 15 and the ink recovery flow path 17. To circulate.

Here, at the time of recording, the individual electrode 13 is constantly biased from the bias voltage source 20 such as DC1.5.
A voltage of kV is applied, and a pulse voltage of 500 V, for example, is superposed on the signal voltage according to the image signal from the drive circuit 19 when the voltage is ON. On the other hand, the counter electrode 22 is set to the ground potential (0V) as shown. Now, when the individual electrode 13 is turned on (the state where 500 V is applied) and a voltage of 2 kV in which a pulse voltage of 500 V is superimposed on the bias DC of 1.5 kV is applied, a coloring agent flying point 13a at the tip of the electrode 13 is applied. The aggregated colorant in the ink 11 is ejected and pulled by the counter electrode 22 provided on the back surface of the recording medium 21 which also serves as a platen, and is ejected and landed on the recording medium (for example, recording paper) 21. .

The characteristic point of this embodiment is that the individual electrode 13 is not exposed to the atmosphere at all. When a similar voltage is applied to the electrode exposed to the atmosphere as in the conventional example shown in FIGS. 35 and 36, the tip of the electrode is damaged by a spark discharge into the atmosphere, but according to the present embodiment, such discharge occurs. Can be prevented.

The colorant may be negatively charged. In that case, it suffices to consider the voltages applied to the electrodes described below as all having opposite polarities.

(Second Embodiment) FIG. 2 is a schematic configuration diagram of an ink jet recording apparatus according to another embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals, and the difference from the first embodiment will be mainly described. In this embodiment, the top cover 14 is removed at a position where the tip of the upper cover 14 is retracted from the tip of the head substrate 12. An open region without the upper cover 14 is formed on the individual electrode 13. Then, the ink 11 flows as a layer having a thickness of about 50 μm on the individual electrode 13 in this open region, and goes to the colorant flying point at the tip of the electrode 13. The flow of the ink 11 thereafter is similar to that of the first embodiment. After the ink 11 passes through the portion where the electrode 13 is interrupted, the ink 11 wraps around to the back surface side of the head substrate 12 through the leading edge portion of the head substrate 12. Further, the ink is returned to the ink recirculation mechanism 18 through the ink recovery flow path 17 formed between the head substrate 12 and the lower cover 16 arranged on the back surface thereof.

As described above, in this embodiment, the upper cover 14
Since a free area is formed on the tip side of the recording head portion, the concentrated color in the ink 11 flying from the coloring material flying point of the individual electrode 13 by applying the bias voltage and the signal voltage to the individual electrode 13. The agent flies with an initial velocity component in the direction perpendicular to the surface of the head substrate 12. Therefore, the recording medium 21 and the counter electrode 22 are arranged above the head at an angle such that the oblique information of the recording head portion leans toward the recording head portion.

In this embodiment, not only the individual electrodes 13 are formed on the front surface of the head substrate 12, but the common electrode 23 is formed on the back surface of the head substrate 12. The common electrode 23 is for generating an electrostatic repulsive force against the colorant from the back surface side of the head substrate 12, and the common electrode 23 has, for example, a bias voltage and a signal applied to the individual electrode 13. DC2.0 corresponding to the total voltage of the voltage
A voltage of kV is applied by the bias voltage source 24.

With such a structure, the above-mentioned side shooter type ink jet recording apparatus is realized.

FIG. 3 is a perspective view showing the structure of the recording head portion in the second embodiment. As a material for the head substrate 12, glass is used because a smooth and flat surface can be easily obtained and it is a low dielectric constant material, and its thickness is 0.5 m.
It is about m to 1.0 mm. On the front surface of the head substrate 12, an array of individual electrodes 13 respectively corresponding to individual recording dot positions is formed, and on the back surface of the head substrate 12, a common electrode 23 is formed over the entire surface. Although only three individual electrodes 13 are shown in FIG.
In the case of an actual recording head, for example, a line scanning head having a resolution of 400 dpi and a size of A4 in the longitudinal direction, about 4
Individual electrodes for 800 elements are arranged in a line.

What is important in the operation of this head is the coloring agent flying start point 13a in which a small radius R is attached to the tip of the individual electrode 13 so as to generate a strong electric field as shown in FIG.
Is the direction of the electric field at. This colorant flying start point 13
The common electrode 2 on the back surface side of the head substrate 12 so that the direction of the maximum electric field vector at a is directed outward from the front surface.
An appropriate bias voltage, for example, 2 kV, is applied to 3. However, as described above, this voltage is not limited to 2 kV and may be in the range of 1.0 kV to 2.7 kV. Further, as shown in FIG. 4, R of the tip portion of the individual electrode 13 may be within the range of an arc having a radius of 15 μm to 100 μm, and is not particularly limited.

FIG. 5A is a diagram for explaining the strength of the electric field in the recording head portion by the density of the lines of electric force, which is indicated by A- in FIG.
The cross section along the line A'is shown. When no signal voltage is applied, DC 1.5 kV is applied as a bias to the individual electrode 13,
Since DC 2.0 kV is applied to the common electrode 23, the electric field from the common electrode 23 leaks from between the arrays of the individual electrodes 13. This leakage electric field exerts a force to push the positively charged colorant in the ink 11 toward the inside of the surface of the individual electrode 13. In the method of using a common flow channel without dividing each dot, various combinations of electric fields may be formed in the electrode array, and in some cases, the electric field may cause the coloring material to escape to a distant portion. However, such escape of the colorant can be prevented by utilizing the leakage electric field from between the arrays of the individual electrodes 13 having a stripe shape as in the present embodiment. That is, this leakage electric field acts as if it were a partition of the ink flow path of the individual nozzle.

FIG. 5B also shows a vertical section taken along the line BB ′ of FIG. 3 when no signal voltage is applied. When the flow of the ink 11 passes the flying point of the coloring material, the electric field from the back surface of the head substrate 12 also receives a force for stopping only the coloring material, and the ink 11 having a high density to some extent is obtained.
It is believed that b is retained in this part. When the stopping power is set to be fairly strong, there is an adverse effect such that only the coloring material is deposited and dried, and the flow is clogged. Therefore, the voltage applied to the common electrode 23 is lowered at each recording cycle to cause leakage. It is desirable to release the electric field.

FIG. 5C is a diagram for explaining the applied state of the signal voltage. When a pulse voltage of 500 V is applied as the signal voltage, a very strong electric field is generated at the coloring material flying start point 13a at the tip of the individual electrode 13. When no signal voltage is applied, the coloring agent 11b, which has been held back by the potential wall at a point slightly ahead of this, receives the repulsive force from this strong electric field, and thus the direction of the maximum electric field vector, that is, from the tip of the electrode 13 to the head substrate 12. Jump forward diagonally to the surface of.

FIG. 6 starts from two points, that is, a color material flying start point 13a on the head substrate 12 of FIG. 3 and an intermediate point 13b between the color material flying points adjacent to each other, and the counter electrode 2 of FIG.
The electric potential along the line of electric force until reaching 2 is shown as a relation to the distance normalized by each total path length. As can be seen from this figure, the electric field strength, which is the gradient of the electric potential, spreads three-dimensionally from the colorant flying start point, and therefore sharply decreases in inverse proportion to the square of the distance.

On the other hand, since there is no sharp electrode end portion at a place deviating from the colorant flying start point, the electric field strength is not so strong, the electric field strength decreases gently toward the counter electrode 22, and the electric field from other points gradually. It has almost the same strength as. Therefore, after passing through the strong electric field region, the potential (=
The coloring material flies in the gutter-shaped potential distribution in which the minimum points of the electric field potential) are continuous, and the flying direction can be stabilized.

As described above, when the tip of the individual electrode 13 on the front surface of the head substrate 12 has a sharp shape like the colorant flying start point 13a, the common electrode 23 on the rear surface side of the head substrate 12 is Not only when a voltage higher than the voltage applied to the individual electrode 13 is applied, but also a somewhat low voltage can form the gutter-shaped electric field shape as described above.

As described above, by giving the initial velocity of the flying coloring material in the direction away from the surface of the head substrate,
It is possible to set the flight start point within the surface that is recessed inward from the edge of the head substrate 12. As a result, it is possible to avoid the conventional problem that the manufacturing process is difficult and the characteristics are not uniform. In other words, the patterning of the substrate edge portion, which was necessary when flying the substrate surface from the edge portion of the head substrate 12 in the direction in which the substrate surface is extended, is not performed, but the recording head portion is formed only by patterning in the substrate plane with high accuracy and reliability. You will be able to make it.

(Third Embodiment) FIG. 7 is a perspective view showing the structure of a recording head portion according to this embodiment. In this embodiment, the arrangement and shape of the electrodes on the head substrate 12 are different from those of the recording head portion of FIG. That is, in the recording head portion of FIG. 3, the individual electrode 13 is provided on the front surface side of the head substrate 12 and the common electrode 23 is provided on the back surface side thereof, but in the present embodiment, the first electrode (on the front surface side of the head substrate 13 ( An individual electrode) 31 and a second electrode (auxiliary electrode) 32 are formed. Both the first electrode 31 and the second electrode 32 have a sawtooth shape,
They are combined so as to mesh with each other in contact with each other. Further, the shape of the tip portion of the second electrode 32 is such that the coloring agent flying start point 31a, which is the tip portion of the first electrode 31 where the strongest electric field is generated so that the coloring agent does not fly from here.
It has a semi-arcuate shape with a larger radius than.

Also in the operation of the recording head portion of this embodiment, what is important is the direction of the electric field at the colorant flying start point 31a. A voltage is applied to the second electrode 32 so that the direction of the maximum electric field vector at the colorant flying start point 31a is directed outward from the surface. First electrode 3
Similar to the individual electrode 13 in the previous embodiment, 1 is an individual electrode corresponding to a recording dot, for example, a voltage of DC 1.5 kV is always applied as a bias, and a signal voltage corresponding to an image signal is, for example, 500 V when ON. Pulse voltage is superimposed. The second electrode 32 is, for example, a common electrode connected in common to all dots, and for example, the individual electrode 31.
2.0 kV, which is the total voltage of the signal voltage and bias voltage applied to, is applied.

Next, the operation of this embodiment will be described.

FIG. 8 (a) is a diagram for explaining the strength of the electric field by the density of the lines of electric force, and shows a vertical cross section taken along the line CC 'of FIG. The flow of ink 11 is the flight point 31a
When it reaches the vicinity, the electric field from the second electrode 32 receives a force for stopping only the coloring material, and the ink 11b having a high density to some extent is held in this portion. When the stopping power is set to be fairly strong, there is an adverse effect such that only the coloring material is deposited and dried, and the flow is clogged. Therefore, the voltage applied to the common electrode 23 is lowered at each recording cycle to cause leakage. The need to release the electric field is the same as in the previous embodiment.

FIG. 8B is a diagram for explaining a signal voltage application state. As the signal voltage, 500 V is the first electrode 31.
, A very strong electric field is generated at the colorant flying start point 31a. Second electrode 3 when no signal voltage is applied
Colorant 31b that was blocked by the potential wall from 2
Receives a repulsive force from this strong electric field, and pops out in the direction of the maximum electric field vector, that is, from the tip of the electrode in a diagonally forward direction with respect to the surface of the head substrate 12.

The electric field formed by the second electrode 32 having a concave tip shape with respect to the color material after flight is the local minimum point of the electric field along the color material flight path, as in the embodiment of FIG. Since a gutter-shaped electric field distribution is formed, the flying direction can be stabilized.

As described above, also in the present embodiment, the initial velocity of the flying coloring material is given in the direction away from the surface of the head substrate, so that the flying starts inside the surface of the head substrate 12 receded inward from the edge. It is now possible to set points. As a result, it is possible to avoid the conventional problem that the manufacturing process is difficult and the characteristics are not uniform. That is, the recording head can be made only by patterning in the plane of the substrate, which is highly accurate and reliable, without performing the patterning of the substrate edge portion, which was necessary when flying in the direction in which the substrate surface is extended from the edge portion of the head substrate. Like

(Fourth Embodiment) FIG. 9 is a perspective view showing the structure of a recording head section according to the fourth embodiment. In this embodiment, the common electrode 23 on the back surface side of the head substrate 12, which is the characteristic of the second embodiment, and the first electrode 31 and the second electrode 31 on the front surface side of the head substrate 12, which is the characteristic of the third embodiment. It also has an electrode 32. With such a configuration, it is possible to avoid the inconvenience that the head substrate 12 has a dielectric constant slightly higher than that of air, and thus there are many lines of electric force flowing to the back surface side. That is, by increasing the potential on the back surface side of the head substrate 12, the lines of electric force can be pushed out to the front surface side, and the operating voltage can be lowered and the efficiency can be improved.

Further, the second electrode 3 in the third embodiment
Although 2 is an individual electrode having a shape that meshes with the first electrode 31, the second electrode 31 may have a simple linear pattern extending in the main scanning direction as in the present embodiment. Since this is simpler, reliability in the manufacturing process increases.

(Fifth Embodiment) In the first and second embodiments, the ink supply flow path 15 and the ink recovery flow path 17 are formed on the front surface side and the back surface side of the head substrate 12, respectively. As shown in FIG. 10, there may be a system in which ink does not wrap around at the edge of the head substrate 12 and ink is allowed to flow in only one direction on the surface of the head substrate 12.

(Sixth Embodiment) In the third embodiment, the first
Electrode 31 has a triangular tip shape, and the second electrode 3
Although 2 has a rounded tip shape, it is not limited to such a shape. For example, as shown in FIG. 11, each may have a rectangular tip shape and may be engaged with each other.

In addition, the present invention can be carried out in various modified forms. For example, the common electrode 23 in the third embodiment is
Although the entire back surface of the substrate 12 is covered, only the back surface of the flying point may be provided, or the electrodes may be separated into comb shapes corresponding to the individual electrodes on the front surface of the head substrate 12.

Further, in the third embodiment, the first electrode 31 is the individual electrode and the second electrode 32 is the common electrode, but the opposite relationship, that is, the first electrode is the common electrode, The two electrodes may be individual electrodes.

Further, as a method of flowing the ink on the surface of the head substrate 12, a method without a cover that directly contacts the air may be used, or only a circumference of the colorant flying point may be slit-shaped in the array direction. The sink may be closed with a board that opens. In the latter case, the ink channel can be used as it is as a wide and thin ink channel. In that case, a positive pressure can be applied before slitting and a negative pressure can be applied after slitting.

(Seventh Embodiment) FIG. 12 is an enlarged perspective view showing a part of a recording head portion of an ink jet recording apparatus according to a seventh embodiment, and FIGS. FIG. 13 is a cross-sectional view taken along lines AA ′ and BB ′ of FIG. 12, respectively. 12 and 13, the head substrate 12
A so-called cone-shaped projection 12c having a thick base and a thinner shape toward the tip is formed on the top of the. The individual electrode 13 is connected to the cone-shaped projection 12c, and the surface of the projection 12c is covered with a conductive substance continuous with the individual electrode 13. The conductive material that covers the protrusion 12c is referred to as a protruding electrode 13c. That is, at the tip of the individual electrode 13, a protrusion formed to protrude on the surface of the head substrate 12 is formed as the protruding electrode 13c. The individual electrodes 13 are connected to drive ICs (not shown),
A voltage can be applied to the protruding electrode 13c.

On the head substrate 12, an upper cover 14 having slits 14a is attached in parallel with the head substrate 12 via a spacer (not shown). The cone-shaped projection 12c is located inside the slit 14a and is exposed from the upper cover 14. Head substrate 12 and upper cover 14
An ink flow path is formed between them, and the ink 11 is supplied thereto. The tip of the cone-shaped protrusion 12c, that is, the protrusion-shaped electrode 13c is slightly exposed from the liquid surface of the ink 11.

With such a configuration, when a signal voltage is applied to the individual electrode 13 according to an image, an ink droplet 11e is ejected from the tip of the cone-shaped projection 12c in a direction perpendicular to the surface of the head substrate 12, and is not shown. An image is recorded on the recording medium by flying toward the recording medium. The ink 11 flows, for example, in a direction indicated by an arrow in FIG. 13A by a water pressure difference, a pump, or an electrostatic force,
New ink 11 is supplied one after another.

As described above, the feature of this embodiment is that the protrusion 12c having a three-dimensional structure is formed on the head substrate 12 and the ink droplet 11e is ejected from the tip of the protrusion 12c.

Next, the recording operation of this embodiment will be described in more detail with reference to FIG. FIG. 14 shows a cone-shaped protrusion 12c.
It is a figure which expands and shows the front-end | tip vicinity. Cone-shaped projection 12
c has a height of several μm to 100 μm, and the ink 11
From the liquid surface of several μm to several tens of μm. However, at the tip of the cone-shaped protrusion 12c, the ink 11 forms a thin layer on the protrusion-shaped electrode 13c formed on the protrusion 12c by a capillary phenomenon, and always wets the surface of the protrusion-shaped electrode 13c. That is, the ink 11 is supplied so as to cover the protruding electrodes 13c of the individual electrodes 13.

The ink 11 is composed mainly of an insulating solvent 11c in which a colorant 11d composed of a pigment or the like is dispersed, as in the previous embodiment. Further, it is desirable that the coloring agent 11d be charged with, for example, a positive charge as illustrated. As such ink 11, a normal liquid developing toner used in an electrostatic recording system or an electrophotographic recording system can be used. In the ink jet recording apparatus of this embodiment, as the coloring agent 11d, those having various sizes from submicron to several μm can be used.

From the bias voltage source 20 to the individual electrode 13, the counter electrode 2 also serving as a platen (recording drum) is provided.
For example, a positive DC bias voltage is applied to No. 2 as shown. This DC bias voltage also has the effect of pushing up the ink on the projection-shaped electrode 13c toward the tip of the cone-shaped projection 12c. Further, by applying the DC bias voltage, an electric field is formed between the counter electrode 22 and the protruding electrode 13c with the recording medium 21 sandwiched therebetween. This electric field also exerts a force to attract the ink 11 toward the surface of the protruding electrode 13c. By these actions, the protruding electrode 1
The surface of 3c is always wet with the ink 11.
Since the surface of the protruding electrode 13c is wet with the ink 11 as described above, the ink 11 is smoothly supplied, and ink droplets are stably ejected and ejected, and at the same time, between the individual electrode 13 and the counter electrode 22. It is possible to prevent discharge when a large electric field is applied.

Further, in this embodiment, since the coloring agent 11d that charges the ink 11 is used and the positive DC bias voltage is applied to the protruding electrode 13c, the coloring agent 11d is concentrated on the surface of the ink 11. It will be in a state of gathering. When the liquid developing toner is used as the ink 11 in the present embodiment, the concentration of the coloring agent is usually several%, so that it is generally too thin to be used as an ink for inkjet recording.
However, due to the effect of gathering only the colorant 11d near the surface as described above, the concentration of the colorant 11d is 10% to several 10%.
Since it can be concentrated up to, it is possible to use a normal liquid developing toner in the ink jet recording apparatus of this embodiment.

As described above, the DC bias voltage is always applied to the individual electrode 13 from the bias voltage source 20, but the pulse voltage is superposed on the DC bias voltage as the signal voltage corresponding to the image signal from the drive circuit 19. And then applied. The colorant 11d aggregated as a thin ink layer near the tip of the protruding electrode 13c repels the signal voltage applied to the individual electrode 13 and is attracted to the opposite electrode 22 side in the opposite manner. The ejection is performed according to the signal voltage.

Here, the DC bias voltage is about 1 kV, and the signal voltage is about several 100V. These voltages are much lower than those of a conventional inkjet system that ejects ink by electrostatic force. The reason why the recording operation can be realized with such a low driving voltage is that the ink in which the color material 11d is charged is used as described above.
That is, the repulsive force is generated between the protruding electrode 13c and the color material 11d, and the ink droplet 11e is easily ejected even at a low voltage.

Further, in the present embodiment, since the ink droplet 11e is ejected from the tip of the protruding electrode 13c, it is also a great feature that basically no nozzle is required as in the previous embodiment.
Therefore, the problem of clogging caused by the drying of the ink is considerably improved, and the line scanning recording head as shown in FIG. 12 can be easily realized.

(Eighth Embodiment) FIG. 15 shows an eighth embodiment of the present invention. In the seventh embodiment, ink droplets are ejected in a direction perpendicular to the bed substrate 12 from the protruding electrodes 13c formed on the cone-shaped protrusions 12c formed on the plane. That is, it is possible to form the ink ejection mechanism at the tip of the head entirely on a plane. Due to such characteristics, there is an advantage that the production of the recording head becomes easier as compared with the conventional method of forming the ink ejection mechanism on the end surface of the head substrate. Further, by forming the ink ejection mechanism on the flat surface of the head substrate 12, there is an advantage that high resolution can be realized by the head configuration as shown in FIG.

FIG. 15 is a plan view of the cone-shaped projection 12c seen from a direction perpendicular to the surface of the head substrate 12. As shown in the figure, the individual electrodes 13 cannot be brought closer than the distance indicated by the pitch P. Cone-shaped projection 12c
The bottom surface of the upper protruding electrode 13c has a certain radius,
This is because it is necessary to separate the adjacent protruding electrodes so as not to contact them. Furthermore, if the protruding electrode 13c comes too close to the adjacent electrode, a signal voltage is applied to one electrode and a discharge is generated between the two electrodes when the signal voltage is not applied to the other electrode. For these reasons, the cone-shaped protrusion, that is, the protrusion-shaped electrode 13c
When the size of the pitch P is determined, the pitch P is limited, and recording with a resolution higher than the pitch P cannot be performed.

However, when the ink ejection mechanism can be formed on a plane, the individual electrodes 13 and the protruding electrodes 13c are staggered, that is, they are alternately arranged in two rows as shown in FIG. Is possible. Protruding electrode 1
When 3c are arranged in a line, it is impossible to record at a resolution equal to or lower than the arrangement pitch P. On the other hand, if the protruding electrodes 13c are displaced in the main scanning direction (arrangement direction) by ½ pitch (P / 2) and arranged in two rows as in the present embodiment, recording with double the resolution is possible. Become. In this case, with respect to the distance L between the two rows of the protruding electrodes 13c, by setting the relationship of L = P * (2 * n + 1) * (1/2) (n is an integer), the sub-scanning direction can also be obtained. The resolution can be doubled. However, in the case where the protruding electrodes 13c are arranged in two rows in this way, the timing of applying the voltage to each electrode row is delayed by (n + 1) main scanning lines, and therefore the operation of delaying the signal voltage is performed. Will be required.

As described above, according to this embodiment, even when the protruding electrodes 13c can be arranged only at the pitch corresponding to the resolution of 400 dpi, high-resolution recording of 800 dpi is performed in both the main scanning direction and the sub-scanning direction. It will be possible. Although the drawing shows an example in which two rows of the slits 14a are formed, the slits 14a may be one row when the two rows of the individual electrodes 13 are close to each other.

In this embodiment, L = P * m (m is an integer), and in that case, the resolution in the sub-scanning direction is the same as in the case where the individual electrodes 13 are in one line. Further, if L = P * m * (1 / k) (m and k are integers), the resolution in the main scanning direction can be doubled and the resolution in the sub scanning direction can be doubled.

FIG. 16 shows an example in which recording is performed at a resolution four times the arrangement pitch P of the protruding electrodes 13c. In this case, the relationship of L = P * m * (1 / k) (m and k are integers) needs to be satisfied. Here, when m is an odd number and k = 4, the resolution in the sub-scanning direction can be quadrupled.

(Ninth Embodiment) FIG. 17 shows a ninth embodiment. In the seventh embodiment, the slit 14a is formed in the upper cover 14 at the position where the cone-shaped projections 12c are arranged in a line. On the other hand, in this embodiment, the cone-shaped projection 1
The seventh point is that a hole (this is called an ink passage hole) 14b is formed in the upper cover 14 at a position where 2c are arranged in a line.
Is different from the embodiment described above. FIG. 18A shows a cone-shaped protrusion 12c.
2B is a cross-sectional view taken along a plane parallel to the row of protrusions passing through the apex of FIG. 2B, and FIG. 7B is a cross-sectional view taken along a plane perpendicular to the row of protrusions passing through the apex of the cone-shaped projection 12c.

According to the present embodiment, the upper cover 14 can suppress the vibration of the ink liquid surface which occurs when the adjacent image points are recorded. When the diameter of the ink passage hole 14b is reduced, it also functions as a nozzle like an ordinary ink jet. However, in the ink jet recording apparatus of the present invention, since the ink is ejected from the tip of the cone-shaped projection 12c, the ink passage hole 14b does not regulate the size of the ink droplet like the nozzle, and therefore can withstand a large pressure. Instead, it only has to function to suppress the vibration of the adjacent ink liquid surface. Therefore, this ink passage hole 14b is different from the conventional ordinary inkjet nozzle in that the diameter may be larger than the resolution.

(Tenth Embodiment) Next, various examples of the cone-shaped projection 12c will be described with reference to FIGS. In the seventh to ninth embodiments, an example in which the conical cone-shaped projection as shown in FIG. 19A is used has been shown, but the cone-shaped projection has a thick root and a thin tip. Any shape can be used as long as it has a different shape.

For example, projections for ejecting ink droplets are formed in a polygonal pyramid shape as shown in FIGS. 19B, 19C and 19D, or as a bump-like shape as shown in FIG. 19E. Can be used as. In any case, the same effect can be obtained as long as it is a cone-shaped projection having a shape in which the root is thick and becomes thinner toward the tip. With such a shape, capillarity or the individual electrode 13
Since the tip of the protrusion can be constantly wetted with the ink by applying a voltage to the ink, the ink can be smoothly supplied, the ink can be stably ejected and ejected from the tip of the protrusion, and the individual electrode 13 and Discharge due to an electric field applied between the counter electrodes 22 can be prevented.

Further, the cone-shaped projection does not necessarily have to be thinned to the tip, and may have a shape as shown in FIG. 20 (a) is a truncated cone, (b) (c)
(D) has a polygonal truncated pyramid, and (e) has a shape in which the tip end of a bump-shaped protrusion is cut off. When the tip is sharply pointed, the direction and size of the ejected ink may be different due to a slight difference in the way the tip is formed, or it may fluctuate over time, but as shown in FIG. Such a phenomenon does not occur if the shape does not exist. Furthermore, even if a protrusion as shown in FIG. 20 is actually formed, the tip portion may not always be flat and has a rounded shape having a certain radius of curvature depending on the forming method. Even in such a case, it can be used as a projection for ejecting ink droplets.

(Eleventh Embodiment) FIG. 21 shows still another embodiment of the ink ejection projection. In the examples so far,
Although an example in which one cone-shaped protrusion and protrusion-shaped electrode are used for one image point has been shown, FIG. 21 shows an example in which a plurality of protrusion-shaped electrodes are associated with one image point. In this embodiment, a type in which the ink passage hole 14b is formed in the upper cover 14 as shown in FIG. 17 will be described. Figure 21
In this embodiment, as shown in FIG.
On the other hand, a cone-shaped projection group 12d in which a large number of fine cone-shaped projections are gathered is made to correspond.

When producing cone-shaped projections, it is difficult to obtain projections having exactly the same characteristics unless the manufacturing process is stable. Further, in the present invention, as described above, basically no discharge occurs, but when discharge occurs, the characteristics may change during use due to the influence. As a result, stable image points cannot be formed, the density and formation position of the image points become unstable, and in some cases no image points are formed. On the other hand, when a projection group 12d composed of a plurality of cone-shaped projections is made to correspond to one image point as in this embodiment, a large number of projections are present even if there are some projections whose characteristics are not uniform. Since one image point is formed by, the characteristic of the image point can be stabilized. That is, even if there are some protrusions from which ink droplets are not ejected, ink can be ejected from the other protrusions to compensate.

(Twelfth Embodiment) FIG. 22 is a perspective view showing the structure of the main part of the recording head portion in this embodiment.
In the seventh to eleventh embodiments, each cone-shaped protrusion is formed independently, but in this embodiment, a continuous protrusion 12e having a triangular prismatic cross section is provided continuously in the main scanning direction.
The individual electrodes 13 formed with the pitch P on e are extended to form protruding electrodes 13c. Also in such a continuous protrusion 12e, when the cross section from the sub-scanning direction is seen,
Since the root has a shape that is thick and becomes thinner toward the front,
The same effect as when using the cone-shaped projection is obtained.
Also, since it is not necessary to make each cone independent,
It has the advantage of being easy to manufacture.

FIG. 23 is a diagram showing an example in which the configuration of this embodiment is expanded to achieve higher resolution. That is, the continuous protrusions 12e having a triangular cross section are formed in two rows in the sub-scanning direction by being separated by L = P * (1/2) * (2 * n + 1) (n is an integer), and pitches are formed on the respective continuous protrusions 12e. By extending the individual electrode 13 formed of P to form the protruding electrode 13c and shifting the individual electrode 13 by 1/2 of the pitch P in the main scanning direction, the main scanning / sub scanning is performed as compared with FIG. The resolution is doubled for both scanning.

Although the triangular shape is shown as the sectional shape of the continuous protrusion 12e in this embodiment, the sectional shape is not limited to this, and the sectional shape may be a part of a circle or an ellipse, or as shown in FIG. It is also possible to use a frustum shape having a flat upper part as described above, or a shape in which the tip portion is naturally rounded when producing protrusions of these shapes. That is, even in the case of the continuous protrusion, the same effect can be obtained as in the case of the cone-shaped protrusion as long as the bottom has a wide width and the upper portion has a narrower width.

(Thirteenth Embodiment) In this embodiment, some specific examples of the structures and manufacturing methods of the cone-shaped protrusion 12c and the protrusion-shaped electrode 13c will be described. FIG. 24 is a cross-sectional view showing various examples of the cone-shaped protrusion 12c and the protrusion-shaped electrode 13. In the seventh to twelfth examples, as shown in FIG. 24A, after the cone-shaped protrusion 12c is formed on the head substrate 12, the protrusion-shaped electrode 1 of the individual electrode 13 is further formed thereon.
The method of forming 3c has been described. In this case, the cone-shaped protrusion 12c may be an insulating material or a conductive material.
The method of processing Si or conductive Si in the semiconductor manufacturing process is the simplest method because it is necessary to accurately make fine things.

On the other hand, in the example shown in FIG. 24 (b), the cone-shaped individual electrode 13c is formed on the head substrate 12 and attached. That is, the inside of the cone-shaped electrode 13c is the cavity 41. In the example of FIG. 24C, the entire cone-shaped projection is integrally made of the same conductive material as the individual electrode 13 (projection-shaped electrode 13c), and the projection-shaped electrode 13c also serves as the cone-shaped projection. Here is an example.

24 (d) (e) (f), the insulating layer 42 including the protruding electrodes 13c is formed on the surface of the individual electrode 13 shown in FIGS. 24 (a) (b) (c). Here is an example. When the individual electrode 13 and the protruding electrode 13c made of a metal or a conductive substance are exposed, when the charging colorant in the ink touches the individual electrode 13 and the protruding electrode 13c, the individual electrode 13 and the protruding electrode 13c are formed. Charge injection from the electrode 13c to the coloring material may occur, and the coloring material may be charged more than necessary. Furthermore, the individual electrode 13 and the protruding electrode 13
Variations in characteristics between the colorant directly injected with electric charge from c and another colorant also occur. In such a state, the ink ejection characteristic becomes unstable, and it becomes impossible to continue recording an image with a constant density. Although such a problem can be addressed by configuring the ink so as to control the charge amount of the coloring material, the method of forming the insulating layer 42 on the surfaces of the individual electrodes 13 and the projecting electrodes 13c also has the same effect. It is possible to solve such a problem.

As a method of forming the insulating layer 42, there is a method of applying a resin on the surface of the individual electrode 13 and the protruding electrode 13c to a thickness of submicron to several tens of microns. There is also a method of applying an insulating film such as SiO ₂ . Further, when the individual electrode 13 is formed of conductive Si or the like, it can be realized by a method of forming an insulating film by oxidizing the electrode surface.

(Fourteenth Embodiment) FIG. 25 is a diagram showing the structure of the recording head portion according to the present embodiment. In this embodiment, another example of a method of applying a voltage to the electrodes will be described. In this embodiment, first, the colorant concentration electrode 51 is uniformly formed on the head substrate 12. The insulating layer 52 is formed on the colorant concentration electrode 51, and the cone-shaped protrusion 12c, the individual electrode 13 and the protruding electrode 13c are formed on the insulating layer 52. Then, an ink flow path is formed by covering the upper cover 14 in which the slits 14a are formed via a spacer (not shown), and the ink 11 is supplied thereto. Top cover 14
Are formed of a conductive material in this example.

Counter electrode 22 in contact with recording medium 21
A positive bias voltage is applied from the acceleration bias voltage source 53 between the upper cover 14 and the upper cover 14, and a positive bias voltage is applied from the colorant aggregation bias voltage source 54 between the upper cover 14 and the colorant concentration electrode 51. Bias voltage is applied. When this bias voltage for colorant concentration is applied, an electric field is formed between the upper cover 14 and the colorant concentration electrode 51. Since the colorant is designed to be positively charged, it is affected by this electric field and gathers around the upper cover 14. That is, the colorant is concentrated in the upper layer portion of the ink 11. In this manner, the portion where the colorant density is high rides on the flow of the ink 11 as shown by the arrow in the figure, and flows from upstream to downstream one after another, and the concentrated ink also near the apex of the cone-shaped projection 12c. Will be supplied. Here, when a pulse voltage is applied to the individual electrode 13 from the drive circuit 55 as a signal voltage corresponding to an image signal, an ink droplet is ejected from the upper portion of the protruding electrode 13c. The ejected ink droplets are accelerated by the electric field formed by the acceleration bias voltage and fly toward the recording medium 21.

According to the present embodiment, it is possible to concentrate and eject the ink by using different power supplies, that is, the bias voltage source 54 for concentrating the colorant and the drive circuit 55. In the method of simultaneously concentrating and ejecting ink as shown in FIG. 14, as described above, a bias voltage for concentration of about 1 kV is applied to several hundreds of volts.
It is necessary to superimpose the ejection pulse voltages of, and it is necessary to use an IC having a withstand voltage equal to or higher than the superposed voltage.
On the other hand, when the ink concentration and the ejection are separated as shown in FIG. 25, the respective bias voltages need to be applied in common and only the ejection pulse voltage of several hundreds of volts is controlled. It becomes possible to use an IC having a low breakdown voltage, which greatly contributes to miniaturization and stabilization of the inkjet recording apparatus.

Although the bias voltage from the acceleration bias voltage source 53 is a DC voltage in this embodiment, it may be a pulse voltage synchronized with the recording signal. However, in that case, an electrode (corresponding to the upper cover 14) for applying an acceleration bias voltage is provided as an individual electrode so that a pulsed acceleration voltage can be applied to each protrusion. 1
It is necessary to separately provide the three items.

(Fifteenth Embodiment) In the seventh to fourteenth embodiments, as shown in FIG. 13, the cone-shaped projection 12c and the projection-shaped electrode 13c are slightly exposed from the liquid surface of the ink. As described above, the ink droplets can be ejected even with the configuration shown in FIG.

FIG. 26A shows an example in which the apex of the protruding electrode 13c exists below the liquid surface of the ink 111. Even when the projecting electrodes 13c are buried in the ink in this way, the coloring agent is agglomerated in the upper portion of the ink 11 due to the bias voltage, and the density is high. Here, the signal voltage is applied to the individual electrodes 13. When applied, the ink that has aggregated near the apex of the protruding electrode 13c is ejected and flies. Therefore,
Since the apex of the protruding electrode 13c is always in the liquid of the ink 11 and the apex is always wet, there is an advantage that the discharge problem can be solved more reliably.

Further, as shown in FIG. 26 (b), even when the cone-shaped protrusion 12c and the protrusion-shaped electrode 13c almost come out of the ink liquid 11, when the protrusion 12c is small, it is a capillary phenomenon and the protrusion When 12c is large, a thin ink layer can be formed at the apex of the protruding electrode 13c by further applying a voltage, so that it is possible to eject ink. Since such a thin layer of ink on the surface of the protruding electrode 13c is formed more stably as it is farther from the liquid surface of the ink 11, stable ink ejection is possible and an image can be recorded more stably.

However, when the projecting electrodes 13c are separated from the liquid surface of the ink 11 in this way, they tend to dry. Therefore, when the electrodes are not used for a while, the ink in the vicinity of the projections 12c is drained, and when the ink is used, the ink is re-used. It is good to inject. At the time of injecting the ink, the ink is once infused with a slightly higher pressure to wet the apex of the projecting electrode 13c, and then a negative pressure is applied to bring the ink state as shown in the figure. By doing so, the apex of the protruding electrode 13c gets wet with the ink, so that the ink can be smoothly supplied by applying a voltage.

(Sixteenth Embodiment) FIG. 27 is a conceptual diagram of a recording head portion of an ink jet recording apparatus according to a sixteenth embodiment, in which charged colorants in ink are aggregated by an electric field between separated electrodes. Then, the agglomerated colorant is caused to fly in the vertical direction by the electric field in the vertical direction generated by the electrodes intersecting with each other with the insulating layer sandwiched therebetween.

FIG. 28 is a schematic sectional view of a single nozzle of the recording head portion in this embodiment. In this recording head portion, flying electrodes 102 having a width of about 100 μm corresponding to recording dots are formed at regular intervals on a head substrate 101 made of glass or a ceramic substrate having a thickness of about 1 mm or made of glass. Many are formed along the longitudinal direction. An insulating layer 104 such as a glass layer is applied on the flying electrode 102 to a thickness of several μm to several tens of μm except for the recording image area 103 having a size of about 50 μm. An electric charge is directly injected into the ink from the flying electrode 102 in the recording image area to facilitate the flight of the coloring material in the ink. Insulating layer 1 in the direction orthogonal to the flying electrode 102
04, 100 μm to agglomerate the charged colorant in the ink
By providing a pair of aggregating electrodes 105 and 106 having a certain interval, and by coating the aggregating electrodes 105 and 106 with a SiO ₂ film of several μm or less,
The charge injection from the aggregating electrodes 105 and 106 into the ink solvent is prevented, and at the same time, the discharge with the flying electrode is prevented. The thickness of the flying electrode 102 and the aggregating electrodes 105 and 106 is about several thousand angstroms.

Next, the operation of aggregating and flying the coloring material in the conveyed ink will be described with reference to FIG. Figure 2
8 (a) shows a step of aggregating the coloring material in the ink. The ink 107 used here is 10 ⁻⁸ which is a kind of petroleum.
It is a colloidal dispersion of a coloring agent in which a pigment and a control agent for positive charging are mixed together with a binder in an ink solvent composed of an insulating kerosene of Ωcm or more. Further, the coloring agent may have a negative polarity, and in that case, all the applied voltages to the electrodes have opposite polarities. The ink 107 having the positively charged coloring material in the ink solvent is conveyed in a direction parallel to the head substrate 101 in the direction of arrow 108. In order to aggregate the charged coloring agent in the ink 107,
The aggregating electrodes 105 and 106 are set to a ground potential and a voltage of +50 V, respectively, and a force in the direction opposite to the flow of the ink 107 acts on the coloring material (~ 2 × 10 ⁴ V / c).
m). Due to this high electric field, the charged colorant in the ink 107 is obstructed against the flow of the ink 107, and the charged colorant is recorded image area 103 between the aggregating electrodes 105 and 106.
To agglomerate. This aggregated colorant is shown at 110. The ink solvent 111 in which the colorant has aggregated and the colorant concentration has decreased flows in the direction of arrow 112 without being obstructed by the electric field.

FIG. 28B shows a step of ejecting the ink 107, in which the coloring agent is aggregated, by electrostatic force. In order to form a strong vertical electric field for flight, the aggregation electrode 10
5 and 106 are grounded together, and the aggregating electrodes 105 and 1
06 and the flying electrode 10 sandwiching the insulating layer 104.
2 is set to a high voltage 113 of plus 200V. By doing so, a high electric field (-10 ⁵ V / cm) is formed in the recording image area 103 of 100 μm between the aggregating electrodes 105 and 106 in the direction toward the recording medium 116, and the positively charged and agglomerated colorant is formed. 110 becomes flying particles 114 and arrow 11
It flies in the direction of the recording medium 116 as indicated by 5. The recording medium 116 such as plain paper is arranged at a distance of several hundred μm above the electrodes, and the counter electrode 117 which also functions as a platen is arranged on the back surface thereof. At the time of flying the color material, a positive charge is injected into the ink in the recording image area of the flying electrode 102, and the aggregated color material is efficiently flying.

(Seventeenth Embodiment) Next, an embodiment applied to a multi-head having an ink transport path provided with a large number of ink jetting electrodes will be described in detail with reference to FIGS. FIG. 29 is a schematic sectional view of a multi-head according to the present invention. Similar to the sixteenth embodiment, the head substrate 1
01, a large number of flight electrodes 102 having a width of 100 μm corresponding to the recording dots are provided at regular intervals along the longitudinal direction of the head substrate 101. An insulating layer 104 such as a glass layer is coated on the flying electrode 102 except for a recording image area of about 50 μm, and a pair of common aggregating electrodes orthogonal to the flying electrode 102 are present at 100 μm intervals on the insulating layer. To do. A SiO ₂ film of several μm or less is coated on the aggregating electrode to prevent charge injection from the aggregating electrode into the ink solvent. At the same time, it also has a function of preventing discharge from the flight electrode 102.

The recording head portion is provided with the ink supply flow path 20.
1 and an ink recovery system cover 202 having an ink recovery channel 202. Head substrate 101 and cover 2
03 are arranged at a constant distance via a spacer of about 50 μm. The cover 203 is provided with ink ejection holes 204 corresponding to the respective flight electrodes 102. In addition, the flying electrode 102 is drawn out of the cover 203,
A signal voltage source 205 of 200 V is individually connected from the outside. A pair of aggregating electrodes (not shown in FIG. 29) provided in common on the flying electrode 102 are drawn out from the side (not shown) of the head substrate 101 and used for aggregating the coloring agent in the ink from the outside. Voltage is applied.

The cover 203 is made of a resin having a dielectric constant similar to that of the ink solvent so as not to disturb the electric field formed by the electrodes. Static pressure is applied to the ink supply channel 201 formed by the spacer at a constant distance by a reflux mechanism configured by a pump (not shown), and the ink supplied from the ink supply channel 201 is transferred to the head substrate 101. It flows out to the ink recovery channel 202, which is an open area on the side surface.
A recirculation mechanism (not shown) including a pump that applies a suction force due to a negative pressure is added to the ink recovery flow path 202 to control the flow of ink. The ink thus transported is uniformly transported along the head substrate 101 in the direction indicated by the dotted arrow 206 to the image point forming region on each flight electrode 102. The ink layer flows with a constant thickness of 50 μm on the aggregating electrode by the cover 203. A recording medium such as plain paper is arranged on the cover 203 at a distance of about several hundred microns, and a counter electrode (not shown) serving as a platen is provided on the back surface of the recording medium.

FIG. 30 shows the electrode 1 for aggregating the coloring agent in the ink.
05 and 106 are agglomerated by the electric field, and the agglomerated colorant is caused to fly by the signal voltage applied to the flight electrode 102, and the residual colorant after the flight is peeled off by the opposite polarity electric field applied to the agglomeration electric field,
It shows the movement of the ink until it is conveyed and removed together with the ink.

FIG. 30A shows the aggregating electrodes 105 and 10.
The step of applying a voltage to 6 causes the coloring agent in the ink to aggregate. The positively charged coloring material in the ink solvent is parallel to the head substrate 101 and the ink 107 along with the arrow 10
A fixed amount is conveyed in the direction of 8. Common aggregating electrode 105
Is set to the ground potential, a voltage 109 of plus 50 V is applied to the other aggregating electrode 106, and an electric field (up to 2 × 10 ⁴⁾ between the aggregating electrodes 105 and 106 formed by this voltage is applied.
V / cm) causes a force opposite to the ink flow to act on the charged coloring material. In this way, the coloring agent in the ink is aggregated in the area 103 between the aggregation electrodes 105 and 106 against the ink flow, as indicated by reference numeral 110. FIG. 30 (b) shows the flight of the ink composed of the aggregated coloring material. Both the aggregating electrodes 105 and 106 are set to the ground potential, and the signal voltage 20 of plus 200 V is applied to the flying electrode 102 provided below the aggregating electrodes 105 and 106 with the insulating layer interposed therebetween.
5 is applied. By doing so, a high vertical electric field (-10 ⁵ V / cm) independent for each recording dot is formed in the gap of 100 μm between the aggregating electrodes 105 and 106, and the positively charged aggregating colorant is generated in the recording medium. The ink particles 114 repel in the direction 115 and become the recording medium direction 11
Fly to 5. At this time, a positive charge is directly injected into the ink solvent containing the aggregated colorant from the flying electrode 102, so that the ink particles can fly efficiently. The voltage or pulse width of the signal voltage that determines the amount of injected charges is changed for each recording dot, and the amount of injected charges of ink is changed to modulate the dot size, enabling gradation recording.

Next, a process of removing the coloring material remaining on the common aggregating electrodes 105 and 106 together with the ink flow is shown in FIG.
This will be described using 0 (c). The aggregating electrode 106 is set to the ground potential, and a voltage of plus 50 V is applied to the aggregating electrode 105.
6 is applied to form an electric field having a polarity opposite to that of the electric field for aggregation.
The residual color material 207 that has not been jetted is pushed out together with the ink flow in response to the force in the direction of the arrow 208, is cleaned after each flight, and a new ink layer is always conveyed to the flight area. In this way, the colorant is stably ejected by always making the initial state.

FIG. 31 is a diagram showing the timing of the aggregating voltage and the ink flying signal voltage. (A) is the signal voltage applied to the aggregating electrode 105, and (b) is the aggregating electrode 10.
6 shows the signal voltage added to 6, and (c) shows the signal voltage applied to the flying electrode 102. At timing t1, a voltage of 50 V is applied to the aggregating electrode 106 to bring the aggregating electrode 105 to the ground potential. As a result, an electric field in which the positively charged coloring material opposes the ink flow 110 in FIG. 30 acts between the flight electrodes 105 and 106, and the coloring material in the ink aggregates. Only the ink solvent after the colorants of the ink have aggregated flows by the ink recirculation mechanism. At timing t2, both aggregating electrodes 105 and 106 are set to the ground potential,
A signal voltage of 200 V is applied to the flying electrode 102. By doing so, a high electric field in the vertical direction acts on the agglomerated colorant in the ink between the aggregating electrodes 105 and 106 intersecting with the flying electrode 102, and the ink with the agglomerated colorant passes through the ink opened in the cover. It flies vertically through the holes. At this time, electric charges are directly injected from the flying electrode 102 into the aggregated ink to facilitate the flight. A thin SiO ₂ film is coated on the aggregating electrode 102 to prevent injection of charges of opposite polarity from the flying electrode 102. At timing t3, a voltage of 50 V is applied to the aggregating electrode 105 to bring the aggregating electrode 106 to the ground potential, and an electric field force in the same direction as the ink flow is applied to the positively charged aggregating colorant remaining between the flying electrodes 102. , And is removed together with the ink flow, and is initialized at the timing of t4. In this manner, stable flying of the ink in which the colorants have been agglomerated is always performed.

(Eighteenth Embodiment) Next, an embodiment using magnetic ink will be described with reference to FIGS. 32 and 33. FIG. 32 is a diagram showing the structure of the recording head portion of this embodiment. In this embodiment, instead of the aggregating electrode for aggregating the colorant in the ink shown in the sixteenth embodiment, a magnetic field generating electromagnet 301 for aggregating the magnetic colorant in the ink is used.
Are arranged on the back surface of the head substrate 101. Further, a flying electrode 302 that forms an ink flying electric field in the vertical direction is provided on the surface of the head substrate 101 so as to correspond to each recording dot, and a common induction electrode 303 that intersects each flying electrode 302 is made of glass or the like. It is provided via an insulating layer 304 with a coating of several μm. The insulating layer is removed from the area 305 corresponding to the recording image point on the flying electrode 302 in order to inject charges into the ink.

FIG. 33 is a diagram showing a process of causing a magnetic colorant to aggregate and fly, and FIG. 33A shows a step of aggregating the magnetic colorant in the ink. In the magnetic ink 307 conveyed on the surface of the head substrate 101 in the direction of arrow 306, the magnetic coloring agent dispersed in the ink solvent by the voltage applied to the electromagnet 301 aggregates on the head substrate 101 as indicated by reference numeral 308. FIG. 33B shows a configuration in which aggregated magnetic ink is ejected. A signal voltage of 200 V is applied to the flying electrode 302, an electric charge is injected into the ink 308 in which the magnetic coloring agent has aggregated, and a strong vertical electric field is formed between the flying electrode 302 and the induction electrode 303 at the ground potential. The ink containing the particles is repelled and flies as particles 310 toward the recording medium 309. After the ink has flown, the remaining agglomerated ink is carried and removed together with the carried ink by turning off the magnetic field of the electromagnet.

In addition, the present invention can be implemented with various modifications. For example, in the sixteenth embodiment, the flying electrode and the aggregating electrode have a three-dimensional structure in which a thin insulating layer is sandwiched. However, the flying electrode and the aggregating electrode have a structure in which both sides of the flying electrode are sandwiched. The electrodes may be provided on the same head substrate.
Alternatively, the flying electrode may be a common electrode and the aggregating electrode may be an individual electrode. Furthermore, the ink discharge holes of the cover may not be provided individually, but may be slit-shaped.

Finally, a concrete example of the construction of the entire ink jet printer to which the ink jet recording apparatus of the present invention is applied will be described with reference to FIG.

In FIG. 34, the recording paper 1 supplied from a paper cassette (not shown) is supplied to the periphery of the recording drum 3 by the paper feed roller 2 and further pressed against the recording drum 3 by the paper guide 4 and the paper pressing roller 5. It is configured to be. While the recording paper 1 is pressed against the recording drum 3, the ink jet recording head 10 ejects an ink droplet 11 containing at least a colorant component according to an image signal, and a character 7 is formed on the recording paper 1 and recording is performed. Done. When the recording is completed, the recording paper 1 is ejected to the paper ejection tray 6. The ink jet recording head 10 used here is a line scanning type head capable of recording the length of the recording paper 1 in the width direction as shown in the figure, and the head according to the present invention described in the above embodiments is used. To be

[0133]

As described above, according to the present invention, the surface of the electrode is covered with the ink during recording, so that the stable coloring required for the flight of the coloring material component in the ink can be achieved without causing damage due to discharge. Since a strong electric field can be obtained, it is possible to realize an inkjet recording apparatus in which the flying colorant particles are small and the electrostatic force of a slit nozzle suitable for line scanning recording is used.

Further, according to the present invention, since a strong electric field vector is formed by adding a vertical direction component different from the plane direction component formed by the head substrate surface, the flying colorant has an angle with the substrate plane. The initial speed can be given. Therefore, not only is it possible to fly the color material from a position retracted from the edge of the substrate, but it is also possible to fly the color material from any internal position within the plane of the substrate. The inkjet recording head can be realized. That is, it is possible to realize a practical line scanning type ink jet recording head by using only the in-plane patterning process, which has good reliability in the manufacturing process and uniform characteristics in operation.

Furthermore, it is also possible to adopt a structure in which an electric field that repels the coloring material is generated in the gap between the wiring patterns of the individual electrodes. In that case, the effect that the coloring agent can be efficiently collected while the ink flows, or can be stored at the flight start point,
It is also possible to have an effect of stabilizing the flight direction by forming a gutter-shaped potential in which the minimum points of the electric field are continuous along the spatial path along which the colorant flies.

Further, in the present invention, by forming a protruding portion at the tip of the individual electrode and supplying ink onto the protruding portion, it is possible to prevent the individual electrode from being destroyed by electric discharge, and more stable image recording is possible. In addition, since the ink is ejected from the tip of the protruding portion, basically no nozzle is required, and a slit or hole for allowing the ink to pass is sufficient, so the problem of nozzle clogging is solved. It Further, a plurality of individual electrodes and their protrusions are arranged in the main scanning direction, and a plurality of columns are provided in the sub-scanning direction, and then the protrusions on different columns are arranged at different positions in the main scanning direction in the main scanning direction. By arranging them respectively, it becomes possible to form image points at intervals smaller than the arrangement pitch in the main scanning direction and perform high resolution recording.

Further, in the conventional ink jet recording head, the electrode for ink aggregation and the electrode for flying ink are not separated from each other. Therefore, if the distance between the head and the recording medium is reduced to prevent the interference with the electric field due to the adjacent image point, The voltage required for agent aggregation is higher than the flying voltage, and it was impossible to fly the aggregated coloring agent. However, according to the present invention, the coloring agent aggregation in the ink and the flying electric field are performed by separate electrodes. Therefore, it is possible to realize a head which is capable of aggregating colorants and which does not cause interference.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an inkjet recording apparatus according to a first embodiment.

FIG. 2 is a schematic configuration diagram of an inkjet recording apparatus according to a second embodiment.

FIG. 3 is a schematic configuration diagram of a recording head unit according to a second embodiment.

FIG. 4 is an explanatory view of a shape of a tip portion of an individual electrode and a stable operation range in the embodiment.

FIG. 5 is a conceptual diagram of an electric field distribution around a head substrate showing the principle of the same embodiment.

FIG. 6 is a diagram showing a graph of distance vs. potential and electric field strength showing generation of a gutter-shaped potential in the same Example.

FIG. 7 is a schematic configuration diagram of a recording head unit according to a third embodiment.

FIG. 8 is a conceptual diagram of an electric field distribution around a head substrate showing the principle of the embodiment.

FIG. 9 is a schematic configuration diagram of a recording head unit according to a fourth embodiment.

FIG. 10 is a schematic configuration diagram according to a fifth embodiment.

FIG. 11 is a schematic configuration diagram of a recording head unit according to a sixth embodiment.

FIG. 12 is a schematic configuration diagram of a recording head unit according to a seventh embodiment.

13 is a sectional view taken along the line AA ′ and the line BB ′ of FIG.

FIG. 14 is a diagram for explaining the operation of the embodiment.

FIG. 15 is a plan view of an essential part of a recording head unit according to an eighth embodiment.

FIG. 16 is a plan view of a main portion of another recording head portion according to the eighth embodiment.

FIG. 17 is a perspective view of a main part of a recording head unit according to a ninth embodiment.

FIG. 18 is a cross-sectional view taken along a plane parallel to and perpendicular to the row of protrusions that pass through the apex of the cone-shaped protrusions in the example.

FIG. 19 is a view showing various examples of cone-shaped projections according to the tenth embodiment.

FIG. 20 is a view showing various examples of cone-shaped projections according to the tenth embodiment.

FIG. 21 is a view showing various examples of ink ejection projections according to the eleventh embodiment.

FIG. 22 is a perspective view of the essential parts showing the basic structure of the recording head section according to the twelfth embodiment.

FIG. 23 is a perspective view of a main part of a high-resolution recording head unit according to a twelfth embodiment.

FIG. 24 is a cross-sectional view showing various configurations of a cone-shaped protrusion and a protrusion-shaped electrode in a recording head section according to a thirteenth embodiment.

FIG. 25 is a diagram for explaining the configuration and operation of the recording head unit according to the fourteenth embodiment.

FIG. 26 is a cross-sectional view of the main parts of the recording head section according to the fifteenth embodiment.

FIG. 27 is a schematic configuration diagram of a recording head unit according to a sixteenth embodiment.

FIG. 28 is a diagram showing a step of aggregating the charged colorant in the ink and a step of flying the ink having the aggregative colorant in the example.

FIG. 29 is a schematic configuration diagram of a recording head unit according to a seventeenth embodiment.

FIG. 30 is a process diagram showing ink ejection from the recording head unit in the example.

FIG. 31 is a timing chart of the signal voltage of each part from the aggregation of the coloring material in the ink to the end of ink flight in the example.

FIG. 32 is a schematic configuration diagram of a recording head according to an eighteenth embodiment.

FIG. 33 is a process diagram showing agglomeration and flight of coloring material in the magnetic ink in the example.

FIG. 34 is an overall configuration diagram of an inkjet recording apparatus according to the present invention.

FIG. 35 is a configuration diagram of a head tip portion of an edge shooter type inkjet recording head which is a first conventional example.

FIG. 36 is a configuration diagram of a head tip portion of an ink jet recording head of a second conventional example in which electrodes are exposed.

[Explanation of symbols]

 11 ... Ink 11a ... Ink in concentrated colorant 11b ... Ink in concentrated colorant 11c ... Solvent 11d ... Colorant 11e ... Ink drop 12 ... Head substrate 12a ... Edge part of head substrate 12b ... Intermediate point 12c of flying point of colorant ... Cone-shaped projection 12d ... Cone-shaped projection group 12e ... Continuous projection having a triangular prism shape in section 13 ... Individual electrode (electrode array) 13a ... Colorant flying point 13c ... Projection-shaped electrode 14 ... Top cover 14a ... Slit 14b ... Ink droplet passage hole 15 ... Ink supply channel 16 ... Lower cover 17 ... Ink recovery channel 18 ... Ink recirculation mechanism 19 ... Drive circuit 20 ... Bias voltage source 21 ... Recording medium 22 ... Counter electrode 23 ... Common electrode 31 ... First electrode 31a ... Colorant flying point 32 ... Second electrode 41 ... Cavity 42 ... Conductive layer 51 ... Colorant concentration electrode 52 ... Insulating layer 5 3 ... Acceleration bias voltage source 54 ... Colorant aggregation bias voltage source 55 ... Driving circuit 101 ... Head substrate 102 ... Individual flight electrodes 105, 106 ... Common aggregation electrode 113 ... Colorant aggregate ink 114 ... Flying ink Particles 116 Recording medium 117 Counter electrode 201 Ink supply channel 202 Ink recovery channel 203 Cover 205 Signal voltage 301 Electromagnet 307 Magnetic ink

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[Procedure amendment]

[Submission date] October 24, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Inkjet recording apparatus

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and in particular, a liquid ink in which a colorant is dispersed in a solvent is used, and the colorant component in this ink is aggregated and ejected onto a recording medium for recording. The present invention relates to an inkjet recording device.

[0002]

2. Description of the Related Art An apparatus for ejecting liquid ink as small droplets called ink particles on a recording medium to form recording dots and recording an image has been put into practical use as an inkjet printer. This ink jet printer has the advantages that it is less noisy than other recording methods and does not require processing such as development and fixing, and is attracting attention as a plain paper recording technology. Many methods of inkjet printers have been devised up to now, but in particular, (a) a method of ejecting ink droplets by the pressure of steam generated by the heat of a heating element (for example, Japanese Patent Publication Nos. 56-9429 and 61-59).
911) or (b) a method in which ink droplets are ejected by a mechanical pressure pulse generated by a piezoelectric element (for example, Japanese Patent Publication No. 53-12138), and a multi-nozzle that records a plurality of dots in parallel. The type is typical.

A recording head used in an ink jet printer is mounted on a carriage and is in a direction (main scanning direction) orthogonal to a recording paper conveyance direction (sub scanning direction).
A serial scanning type head is used in which recording is performed while moving to. With this serial scanning type head, it is difficult to increase the recording speed because recording is performed while moving mechanically. Therefore, the recording head is made a long head of the same size as the width of the recording paper to reduce the mechanical moving parts,
A so-called line scanning head capable of increasing the recording speed is also considered, but it is not easy to realize such a line scanning head for the following reason.

In the ink jet recording system, the concentration and concentration of the ink are likely to occur locally due to the evaporation and volatilization of the solvent, which causes the clogging of individual thin nozzles corresponding to the resolution. Therefore, in the method of using the pressure of vapor for forming the inkjet, insoluble matter is attached by thermal or chemical reaction with the ink, and in the method of using the pressure of the piezoelectric element, the ink flow path is complicated. The different structure makes it easier to induce clogging. Serial scanning heads that use several tens to hundreds of nozzles can reduce the frequency of clogging, but line scanning heads that require thousands of nozzles. The probability of clogging occurs at a fairly high frequency, which is a major problem in terms of reliability.

Further, there is a problem that the conventional ink jet recording apparatus is not suitable for improving the resolution. That is, it is difficult to generate ink particles having a diameter of 20 μm or less (which corresponds to a recording dot having a diameter of about 50 and several μm on the recording paper) by the method using the pressure of vapor, and the pressure generated by the piezoelectric element is used. This is because in the method of using, the recording head has a complicated structure, and it is difficult to form a head with high resolution due to processing technology problems.

In order to overcome these drawbacks, an ink jet recording system has been devised in which a voltage is applied to a thin film electrode array and the electrostatic force is used to fly the ink or the colorant component therein from the liquid surface of the ink. Specifically, a method of ejecting ink by using electrostatic attraction (Japanese Patent Laid-Open No. 49-62).
No. 024, JP-A-56-4467, etc.) or a method in which ink containing a charged coloring material component is used to increase the density of the coloring material and fly (WO93 / 11866: PCT / AU92 / 00).
665) and the like have been proposed. In these methods, the recording head has a slit-shaped nozzle configuration that does not require a nozzle for each individual dot (FIG. 35 ), or a nozzleless configuration that does not require an ink flow path partition for each individual dot (FIG. 36 ). Therefore, it is effective in preventing and recovering from clogging, which was a major obstacle in realizing a line scanning type recording head. The latter is particularly suitable for high resolution because it can stably generate and fly ink particles having a very small diameter.

[0007] In the ink jet recording method of flying coloring material in such electrostatic force, FIG. 2 as a structure of the recording head
8 and 29 , a so-called edge shooter type head in which the tip of the electrode array 13 is arranged at the edge portion of the head substrate 12 has been conventionally used. However, since the electrodes are exposed in the recording head having such a configuration, the electrode array is likely to be damaged by the discharge generated by the strong electric field, and the flow of the ink becomes unstable, resulting in a large variation in the operating characteristics. There is a problem. A method of depositing an insulating film on the surface of the electrode is also conceivable, but since the insulating film needs to be extremely thin, there is a high possibility of damage or dielectric breakdown due to contact, and there is a problem in terms of reliability.

Further, in the recording head using the edge portion of the electrode as described above, it is difficult to process the edge with high precision, so that the yield is poor, and there are major problems in terms of ease of manufacturing, uniformity of characteristics, and recording quality. There is. In particular, in the case of a line scanning printhead that needs to print several thousands of dots in parallel, the overall good product rate can be obtained by multiplying the good product rate of individual dots by the number of dots several times, so it is extremely reliable. Otherwise, the production yield and recording quality will be seriously affected.

[0009]

As described above, in the recording head used in the ink jet recording system in which the coloring material component in the liquid ink is ejected by the conventional electrostatic force, the electrode for applying the electrostatic force is exposed. Therefore, stable recording cannot be performed due to electrode damage due to discharge generated by a strong electric field.Moreover, since it is an edge shooter type in which the tip of the electrode is placed at the edge portion of the head substrate, it is easy to manufacture and the characteristics are uniform. There was a problem in terms of recording quality.

An object of the present invention is to discharge ink at an electrode for acting an electrostatic force on a colorant component in a system in which the colorant component in ink is aggregated by using electrostatic force and is made to fly to a recording medium for recording. It is an object of the present invention to provide an ink jet recording apparatus that can effectively prevent the above and perform stable recording.

Another object of the present invention is to prevent discharge at an electrode for acting an electrostatic force on a colorant component, and to cause the colorant in the ink to flow from the plane portion of the head substrate in a direction perpendicular to the plane of the head substrate. It is an object of the present invention to provide an ink jet recording apparatus which can be made to fly to a recording medium with the initial velocity component, and which is easy to manufacture and has excellent property uniformity and recording quality.

[0012]

SUMMARY OF THE INVENTION The present invention uses an ink jet recording apparatus which uses a liquid ink in which a colorant is dispersed in a solvent and causes the colorant components in the ink to aggregate and fly onto a recording medium for recording. In, the electrode array is formed on the surface of the head substrate, and the ink in which the colorant is dispersed in the solvent is supplied onto at least the electrode array on the surface of the head substrate, and the ink in the ink supplied onto the electrode array is The basic feature is that at least a voltage for causing the colorant component to fly toward the recording medium is applied to the electrode array.

Here, the head substrate gives an initial velocity component in the direction perpendicular to the surface of the head substrate to the colorant component flying toward the recording medium by the electrode array, and the receiving point of the colorant component of the recording medium is It is located above a plane extending from the surface of the head substrate and has an angle of 90 degrees with the plane at the receiving point.
It is preferably arranged with respect to the recording medium so as to be less than or equal to °.

More specifically, the electrode array is composed of a plurality of individual electrodes, and a voltage according to an image signal is applied to these individual electrodes. According to one embodiment, the individual electrode is preferably formed on the surface of the head substrate at a position retracted from the end surface on the recording medium side, and the common electrode is formed on the back surface of the head substrate. Then, a predetermined bias voltage is applied to this common electrode.

According to another aspect, the individual electrode is preferably formed on the surface of the head substrate at a position retracted from the end surface on the recording medium side, and the auxiliary electrode is provided on the surface of the head substrate at a position close to the individual electrode. It is formed. The auxiliary electrode may be an electrode divided corresponding to the individual electrode, or may be an electrode commonly provided for each individual electrode. Then, a predetermined bias voltage is applied to this auxiliary electrode.

According to still another aspect, the individual electrodes are formed so that their respective tips project above the surface of the head substrate, and the thin layer of ink is formed at least on the projections of the individual electrodes. It is preferable that the protrusion has a shape in which the bottom on the surface of the head substrate is wide and the width is narrower toward the top. A plurality of individual electrodes and protrusions of the individual electrodes are arranged in the main scanning direction, and a plurality of columns are provided in the sub-scanning direction, and the protrusions on different columns are arranged at different positions in the main scanning direction. Is desirable.

[0017]

In the present invention, ink is supplied onto at least the electrode array, that is, the individual electrodes on the head substrate. That is, the ink is supplied onto the head substrate so that the electrodes are covered with the ink during recording to which a high electric field is applied so that the electrode array is not exposed to the atmosphere, which is likely to occur in the conventional inkjet recording apparatus. Damage to the tip of the electrode due to a severe discharge phenomenon in the air can be prevented by using a material that blocks discharge as a solvent for the ink, and stable recording is possible.

Only a recording apparatus using an edge shooter type recording head has been proposed in the case where a conventional ink jet recording system for recording is performed by aggregating and flying the coloring agent in the liquid ink by electrostatic force for recording. The main reasons are: (1) Even if an electrode with a sharp tip is formed in the substrate plane by the printed wiring technology, the direction of the strongest electric field strength generated is still the same as the pattern plane or it is extended. Therefore, the strong electric field appears only at the edge part where the substrate is cut, and (2) the substrate on which the electrode array is formed and another substrate paired with it are parallel to each other via the spacer. If overlapped, an ink flow path with a slit-shaped opening can be easily formed at the edge of the substrate, and the point at which the strongest electric field is generated coincides with the colorant flying start point. It is to be formed UNA edge portion.

However, if an electric field as strong as the electric field at the tip of the electrode used in the edge shooter can be generated in the direction perpendicular to the head substrate surface, the edge of the head substrate is directed inward toward the substrate surface. Since it is possible to fly the colorant from the receding plane part and patterning to the edge part is not required, it is possible to use a normal in-plane manufacturing process such as the photolithography technology used in the manufacture of ICs to achieve reliability. It is possible to manufacture an ink jet recording head that uses electrostatic force with high property and high accuracy. Therefore, a side shooter type ink jet recording apparatus can be realized by a method utilizing electrostatic force.

In the present invention, the initial velocity component in the direction perpendicular to the surface of the head substrate is applied to the coloring agent flying toward the recording medium, and the receiving point of the coloring agent in the recording medium extends the surface of the head substrate. The head substrate is positioned relative to the recording medium so that the head substrate is positioned above the above plane and the angle formed with the plane at the receiving point is 90 ° or less. That is, a side shooter type ink jet recording apparatus using an electrostatic force is realized by retracting the colorant flying start point within the head substrate plane and directing the colorant flying direction above the head substrate surface. It is possible to achieve ease of manufacture, uniformity and stability of characteristics, and improvement of recording quality.

In this case, according to the present invention, the shape of the electrode tip located at the colorant flying start point and the surrounding electrodes surrounding it are used to generate a strong electric field component in the direction perpendicular to the plane of the substrate surface. It is possible to realize the flight in which the initial velocity component in the vertical direction is given to the coloring material in the ink. Specifically, as a first means therefor, the common electrode is arranged on the entire back surface of the head substrate on which the electrode array of the individual electrodes is formed. By applying a voltage to this common electrode, it is possible to generate an electric field oriented in the vertical direction from the substrate surface. The direction of the strongest electric field generated at the tip of the individual electrodes on the substrate surface is the horizontal direction, but when the electric fields in the vertical direction from the common electrode on the back surface of the substrate are added together, they are bent outward from the substrate and the vertical component is removed. The strongest electric field vector possessed can be generated.

As a second means for generating a strong electric field component in the direction perpendicular to the plane of the substrate surface, an auxiliary electrode (common electrode or individual electrode) is provided close to the tip of the individual electrode on the head substrate surface. However, it may be arranged). When a voltage having the same polarity as the voltage applied to the individual electrodes is applied to the auxiliary electrode, the lines of electric force are bent in a repulsive manner so that an electric field having a vertical component is formed. Also with this method, the strongest electric field vector generated at the tip of the individual electrode can be generated in the direction outward from the substrate.

Further, the position of the coloring agent receiving point for receiving the flying coloring agent of the recording medium such as the recording paper is above the plane extending the surface of the recording head substrate and at the coloring agent receiving point of the recording medium. The angle formed with the plane that extends the substrate surface is 9
By adopting the structure of 0 ° or less, it is possible to stably receive the flying colorant with the velocity component in the vertical direction.

The phenomenon of colloidal dispersion / floating in the liquid, which is used in this technology, is concentrated and the solvent is left behind and jumps out into the air. Although there are very few cases where it is done, there are points that the interpretation is still insufficient in terms of theory,
The present inventors have confirmed the facts and phenomena with repeated observations and experiments. According to these experimental facts,
Two things can be achieved:

One is related to the range of voltage applied to the common electrode installed on the same head substrate surface as the individual electrode array or the auxiliary electrode installed on the back surface in order to give a velocity vector component in the vertical direction to the flying color material. is there. In the experiments by the inventors, normally, a bias of 1 kV to 2 kV and a pulse voltage in the range of 100 V to 700 V are superimposed and applied to individual electrodes, but these common electrodes and auxiliary electrodes are bias voltage of the individual electrodes. It is known that stable operation is possible in the range from to the voltage on which the signal voltage is superimposed. That is, a voltage in the range of 1.0 kV to 2.7 kV can be applied to these common electrodes or auxiliary electrodes.

The other relates to the shape of the tips of the electrodes of the electrode array. According to the experiments by the inventors, it is confirmed that the flying of the coloring material becomes unstable when the tip of the electrode is too sharp, but it becomes stable when the radius of curvature of the tip is in the range of R = 15 μm to 100 μm. That is, the tip shape of the individual electrode to which a voltage corresponding to the image signal forming the array electrode formed on the surface of the substrate is applied is R = 15 μm to 1
The arc shape in the range of 00 μm can further stabilize the flight of the coloring material.

When the protrusion is formed at the tip of the individual electrode, the ink is formed at least on the protrusion of the individual electrode, so that the surface of the protrusion is always covered with a thin layer of ink, and the protrusion is formed. The discharge problem is solved by ejecting ink droplets from the part. That is, by forming such a protrusion, even if the tip of the protrusion is exposed from the ink surface, the liquid is generated when the voltage is applied to the electric field generated by capillary action or voltage application, or the needle-shaped electrode. A thin ink layer is stably formed at the tip portion of the protrusion due to the effect of flowing toward the head. Therefore, it is possible to prevent the protruding portions of the individual electrodes from being destroyed by the electric discharge, and in addition, it is possible to realize stable image recording. Also, since the ink is ejected from the tip of the protrusion,
Basically, nozzles are not required, and slits or holes for allowing ink to pass therethrough are sufficient, so that the problem of nozzle clogging can be solved as described above.

Further, in this case, a plurality of individual electrodes and their protrusions are arranged in the main scanning direction and a plurality of columns are provided in the sub-scanning direction, and then the protrusions on different columns are mainly arranged in the main scanning direction. 1 / k of array pitch in scanning direction
By arranging them at different positions shifted by (k: an integer), it is possible to record at a resolution equivalent to 1 / k of the arrangement pitch in the main scanning direction.

Further, by using an ink in which a charged coloring agent is present in the solvent as the ink, it becomes possible to concentrate the coloring agent only by aggregating the coloring agent by applying a voltage to the individual electrodes. It is also possible to record an image having a high density by concentrating and ejecting only the ink in the portion to be ejected by using the ink having a low density that is easy to convey. Further, by forming the protrusions on the individual electrodes, it is possible to concentrate the ink at the portion where the ink is ejected. Furthermore, since the repulsive force between the driving electrode and the coloring material works by using the charged coloring material, the driving voltage can be lowered, and the driving by the IC becomes possible. It is also easy to realize a line scanning head in which ink is ejected with electric power.

[0030]

EXAMPLES Examples of the present invention will be described in detail below. (First Embodiment) FIG. 1 is a schematic diagram of an ink jet recording apparatus according to an embodiment of the present invention. In the figure,
The ink 11 is obtained by suspending a positively chargeable colorant together with a charge control agent, a binder, etc. in a colloidal state in an insulating solvent of 10 ⁸ Ωcm or more. The ink 11 is applied to the head substrate 12 and an upper cover 14 disposed on the surface of the head substrate 12 via a spacer having a thickness of about 300 μm.
The ink is supplied to the ink supply flow path 15 formed between and by the positive pressure applied by the ink recirculation mechanism 18. On the head substrate 12, individual electrodes 13 corresponding to recording dots, which are stripe array electrodes extending in the left-right direction in the drawing, are adhered and formed, and the ink 11 is supplied along the ink supply flow path 15 with the individual electrodes 13. Flow toward the colorant flying point 13a at the tip of the electrode 13.

The ink 11 that has reached the colorant flying point 13a passes through the portion where the individual electrode 13 and the upper cover 14 are discontinued, and then passes around the front edge of the head substrate 12 and wraps around to the back surface side of the head substrate 12. The ink 11 that has flown around to the back surface side of the head substrate 12 is an ink recovery flow formed between the head substrate 12 and the lower cover 16 that is arranged on the back surface through the spacers, similar to the ink supply channel 15. The ink is returned to the ink recirculation mechanism 18 through the path 17 by the negative pressure, that is, the suction force given by the ink recirculation mechanism 18. The ink recirculation mechanism 18 is composed of a pump and a pipe connected to the ink supply flow path 15 and the ink recovery flow path 17, and the action of the pump causes the ink 11 to pass through the ink supply flow path 15 and the ink recovery flow path 17. To circulate.

Here, at the time of recording, the individual electrode 13 is constantly biased from the bias voltage source 20 such as DC1.5.
A voltage of kV is applied, and a pulse voltage of 500 V, for example, is superposed on the signal voltage according to the image signal from the drive circuit 19 when the voltage is ON. On the other hand, the counter electrode 22 is set to the ground potential (0V) as shown. Now, when the individual electrode 13 is turned on (the state where 500 V is applied) and a voltage of 2 kV in which a pulse voltage of 500 V is superimposed on the bias DC of 1.5 kV is applied, a coloring agent flying point 13a at the tip of the electrode 13 is applied. The aggregated colorant in the ink 11 is ejected and pulled by the counter electrode 22 provided on the back surface of the recording medium 21 which also serves as a platen, and is ejected and landed on the recording medium (for example, recording paper) 21. .

A characteristic point of this embodiment is that the individual electrode 13 is not exposed to the atmosphere at all. When a similar voltage is applied to the electrode exposed to the atmosphere as shown in FIGS. 28 and 29, which is a conventional example, the electrode tip is damaged by spark discharge into the atmosphere, but according to the present embodiment, such discharge occurs. Can be prevented.

The colorant may be negatively charged. In that case, it suffices to consider the voltages applied to the electrodes described below as all having opposite polarities. (Second Embodiment) FIG. 2 is a schematic configuration diagram of an ink jet recording apparatus according to another embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals, and different points from the first embodiment will be mainly described. Is
An open area without the upper cover 14 is formed on the individual electrode 13. Then, the ink 11 flows as a layer having a thickness of about 50 μm on the individual electrode 13 in this open region, and goes to the colorant flying point at the tip of the electrode 13. The flow of the ink 11 thereafter is similar to that of the first embodiment. After the ink 11 passes through the portion where the electrode 13 is interrupted, the ink 11 wraps around to the back surface side of the head substrate 12 through the leading edge portion of the head substrate 12. Further, the ink is returned to the ink recirculation mechanism 18 through the ink recovery flow path 17 formed between the head substrate 12 and the lower cover 16 arranged on the back surface thereof.

As described above, in this embodiment, the upper cover 14
Since a free area is formed on the tip side of the recording head portion, the concentrated color in the ink 11 flying from the coloring material flying point of the individual electrode 13 by applying the bias voltage and the signal voltage to the individual electrode 13. The agent flies with an initial velocity component in the direction perpendicular to the surface of the head substrate 12. Therefore, the recording medium 21 and the counter electrode 22 are arranged above the head at an angle such that the oblique information of the recording head portion leans toward the recording head portion.

In this embodiment, not only the individual electrodes 13 are formed on the front surface of the head substrate 12, but the common electrode 23 is formed on the back surface of the head substrate 12. The common electrode 23 is for generating an electrostatic repulsive force against the colorant from the back surface side of the head substrate 12, and the common electrode 23 has, for example, a bias voltage and a signal applied to the individual electrode 13. DC2.0 corresponding to the total voltage of the voltage
A voltage of kV is applied by the bias voltage source 24.

With such a structure, the above-described side shooter type ink jet recording apparatus is realized. FIG. 3 is a perspective view showing the configuration of the recording head unit in the second embodiment. As the material of the head substrate 12, glass is used because a smooth and flat surface can be easily obtained and it is a low dielectric constant material, and its thickness is 0.5 mm to
It is about 1.0 mm. On the surface of the head substrate 12,
Individual electrode 1 for each recording dot position
3 arrays are formed, and the common electrode 23 is formed on the entire back surface of the head substrate 12. Although only three elements of the individual electrode 13 are shown in the figure, in the case of an actual recording head, for example, a line scanning type head having a resolution of 400 dpi and a size of A4 longitudinal direction, it is about 480.
Individual electrodes for 0 elements are arranged in a line.

What is important in the operation of this head is a coloring agent flying start point 13a in which a small radius R is attached to the tip of the individual electrode 13 so as to generate a strong electric field as shown in FIG.
Is the direction of the electric field at. This colorant flying start point 13
The common electrode 2 on the back surface side of the head substrate 12 so that the direction of the maximum electric field vector at a is directed outward from the front surface.
An appropriate bias voltage, for example, 2 kV, is applied to 3. However, as described above, this voltage is not limited to 2 kV and may be in the range of 1.0 kV to 2.7 kV. Further, as shown in FIG. 4, R of the tip portion of the individual electrode 13 may be within the range of an arc having a radius of 15 μm to 100 μm, and is not particularly limited.

FIG. 5A is a diagram for explaining the strength of the electric field in the recording head portion by the density of the lines of electric force, which is indicated by A- in FIG.
The cross section along the line A'is shown. When no signal voltage is applied, DC 1.5 kV is applied as a bias to the individual electrode 13,
Since DC 2.0 kV is applied to the common electrode 23, the electric field from the common electrode 23 leaks from between the arrays of the individual electrodes 13. This leakage electric field exerts a force to push the positively charged colorant in the ink 11 toward the inside of the surface of the individual electrode 13. In the method of using a common flow channel without dividing each dot, various combinations of electric fields may be formed in the electrode array, and in some cases, the electric field may cause the coloring material to escape to a distant portion. However, such escape of the colorant can be prevented by utilizing the leakage electric field from between the arrays of the individual electrodes 13 having a stripe shape as in the present embodiment. That is, this leakage electric field acts as if it were a partition of the ink flow path of the individual nozzle.

FIG. 5B also shows a vertical section taken along the line BB ′ of FIG. 3 when no signal voltage is applied. When the flow of the ink 11 passes the flying point of the coloring material, the electric field from the back surface of the head substrate 12 also receives a force for stopping only the coloring material, and the ink 11 having a high density to some extent is obtained.
It is believed that b is retained in this part. When the stopping power is set to be fairly strong, there is an adverse effect such that only the coloring material is deposited and dried, and the flow is clogged. Therefore, the voltage applied to the common electrode 23 is lowered at each recording cycle to cause leakage. It is desirable to release the electric field.

FIG. 5C is a diagram for explaining the applied state of the signal voltage. When a pulse voltage of 500 V is applied as the signal voltage, a very strong electric field is generated at the coloring material flying start point 13a at the tip of the individual electrode 13. When no signal voltage is applied, the coloring agent 11b, which has been held back by the potential wall at a point slightly ahead of this, receives the repulsive force from this strong electric field, and thus the direction of the maximum electric field vector, that is, from the tip of the electrode 13 to the head substrate 12. Jump forward diagonally to the surface of.

FIG. 6 starts from two points, that is, a color material flying start point 13a on the head substrate 12 of FIG. 3 and an intermediate point 13b between the color material flying points adjacent to each other, and the counter electrode 2 of FIG.
The electric potential along the line of electric force until reaching 2 is shown as a relation to the distance normalized by each total path length. As can be seen from this figure, the electric field strength, which is the gradient of the electric potential, spreads three-dimensionally from the colorant flying start point, and therefore sharply decreases in inverse proportion to the square of the distance.

On the other hand, since there is no sharp electrode end portion at a place deviating from the colorant flying start point, the electric field strength is not so strong, the electric field strength decreases gently toward the counter electrode 22, and the electric field from other points gradually. It has almost the same strength as. Therefore, after passing through the strong electric field region, the potential (=
The coloring material flies in the gutter-shaped potential distribution in which the minimum points of the electric field potential) are continuous, and the flying direction can be stabilized.

As described above, when the tip of the individual electrode 13 on the surface of the head substrate 12 has a pointed shape like the colorant flying start point 13a, the common electrode 23 on the back side of the head substrate 12 is Not only when a voltage higher than the voltage applied to the individual electrode 13 is applied, but also a somewhat low voltage can form the gutter-shaped electric field shape as described above.

As described above, by giving the initial velocity of the flying coloring material in the direction away from the surface of the head substrate,
It is possible to set the flight start point within the surface that is recessed inward from the edge of the head substrate 12. As a result, it is possible to avoid the conventional problem that the manufacturing process is difficult and the characteristics are not uniform. In other words, the patterning of the substrate edge portion, which was necessary when flying the substrate surface from the edge portion of the head substrate 12 in the direction in which the substrate surface is extended, is not performed, but the recording head portion is formed only by patterning in the substrate plane with high accuracy and reliability. You will be able to make it.

(Third Embodiment) FIG. 7 is a perspective view showing the structure of a recording head portion according to this embodiment. In this embodiment, the arrangement and shape of the electrodes on the head substrate 12 are different from those of the recording head portion of FIG. That is, in the recording head portion of FIG. 3, the individual electrode 13 is provided on the front surface side of the head substrate 12 and the common electrode 23 is provided on the back surface side thereof, but in the present embodiment, the first electrode (on the front surface side of the head substrate 13 ( An individual electrode) 31 and a second electrode (auxiliary electrode) 32 are formed. Both the first electrode 31 and the second electrode 32 have a sawtooth shape,
They are combined so as to mesh with each other in contact with each other. Further, the shape of the tip portion of the second electrode 32 is such that the coloring agent flying start point 31a, which is the tip portion of the first electrode 31 where the strongest electric field is generated so that the coloring agent does not fly from here.
It has a semi-arcuate shape with a larger radius than.

Also in the operation of the recording head portion of this embodiment, what is important is the direction of the electric field at the colorant flying start point 31a. A voltage is applied to the second electrode 32 so that the direction of the maximum electric field vector at the colorant flying start point 31a is directed outward from the surface. First electrode 3
Similar to the individual electrode 13 in the previous embodiment, 1 is an individual electrode corresponding to a recording dot, for example, a voltage of DC 1.5 kV is always applied as a bias, and a signal voltage corresponding to an image signal is, for example, 500 V when ON. Pulse voltage is superimposed. The second electrode 32 is, for example, a common electrode connected in common to all dots, and for example, the individual electrode 31.
2.0 kV, which is the total voltage of the signal voltage and bias voltage applied to, is applied.

Next, the operation of this embodiment will be described. FIG.
(A) is a figure explaining the strength of an electric field by the density of the lines of electric force, and shows a vertical cross section taken along the line CC 'of FIG. When the flow of the ink 11 reaches the vicinity of the flying point 31a, the electric field from the second electrode 32 receives a force for stopping only the coloring material, and the ink 11b having a high density to some extent is obtained.
Is held in this part. When the stopping power is set to be fairly strong, there is an adverse effect such that only the coloring material is deposited and dried, and the flow is clogged. Therefore, the voltage applied to the common electrode 23 is lowered at each recording cycle to cause leakage. The need to release the electric field is the same as in the previous embodiment.

FIG. 8B is a diagram for explaining a signal voltage application state. As the signal voltage, 500 V is the first electrode 31.
, A very strong electric field is generated at the colorant flying start point 31a. Second electrode 3 when no signal voltage is applied
Colorant 31b that was blocked by the potential wall from 2
Receives a repulsive force from this strong electric field, and pops out in the direction of the maximum electric field vector, that is, from the tip of the electrode in a diagonally forward direction with respect to the surface of the head substrate 12.

The electric field formed by the second electrode 32 having a concave tip shape with respect to the color material after the flight is similar to the embodiment of FIG. 3, and the local minimum point of the electric field is along the flight path of the color material. Since a gutter-shaped electric field distribution is formed, the flying direction can be stabilized.

As described above, also in this embodiment, by giving the initial velocity of the flying coloring material in the direction away from the surface of the head substrate, the flying starts in the surface retreated inward from the edge of the head substrate 12. It is now possible to set points. As a result, it is possible to avoid the conventional problem that the manufacturing process is difficult and the characteristics are not uniform. That is, the recording head can be made only by patterning in the plane of the substrate, which is highly accurate and reliable, without performing the patterning of the substrate edge portion, which was necessary when flying in the direction in which the substrate surface is extended from the edge portion of the head substrate. Like

(Fourth Embodiment) FIG. 9 is a perspective view showing the structure of a recording head section according to the fourth embodiment. In this embodiment, the common electrode 23 on the back surface side of the head substrate 12, which is the characteristic of the second embodiment, and the first electrode 31 and the second electrode 31 on the front surface side of the head substrate 12, which is the characteristic of the third embodiment. It also has an electrode 32. With such a configuration, it is possible to avoid the inconvenience that the head substrate 12 has a dielectric constant slightly higher than that of air, and thus there are many lines of electric force flowing to the back surface side. That is, by increasing the potential on the back surface side of the head substrate 12, the lines of electric force can be pushed out to the front surface side, and the operating voltage can be lowered and the efficiency can be improved.

Further, the second electrode 3 in the third embodiment
Although 2 is an individual electrode having a shape that meshes with the first electrode 31, the second electrode 31 may have a simple linear pattern extending in the main scanning direction as in the present embodiment. Since this is simpler, reliability in the manufacturing process increases.

(Fifth Embodiment) In the first and second embodiments, the ink supply flow path 15 and the ink recovery flow path 17 are formed on the front surface side and the back surface side of the head substrate 12, respectively. As shown in FIG. 10, there may be a system in which ink does not wrap around at the edge of the head substrate 12 and ink is allowed to flow in only one direction on the surface of the head substrate 12.

(Sixth Embodiment) In the third embodiment, the first
Electrode 31 has a triangular tip shape, and the second electrode 3
Although 2 has a rounded tip shape, it is not limited to such a shape. For example, as shown in FIG. 11, each may have a rectangular tip shape and may be engaged with each other.

In addition, the present invention can be implemented by being modified in various ways. For example, the common electrode 23 in the third embodiment is
Although the entire back surface of the substrate 12 is covered, only the back surface of the flying point may be provided, or the electrodes may be separated into comb shapes corresponding to the individual electrodes on the front surface of the head substrate 12.

In the third embodiment, the first electrode 31 is the individual electrode and the second electrode 32 is the common electrode. However, the opposite relationship is true, that is, the first electrode is the common electrode. The two electrodes may be individual electrodes.

Furthermore, as a method of flowing the ink on the surface of the head substrate 12, a method without a cover that directly contacts the air may be used, or only a circumference of the colorant flying point may be slit-shaped in the array direction. The sink may be closed with a board that opens. In the latter case, the ink channel can be used as it is as a wide and thin ink channel. In that case, a positive pressure can be applied before slitting and a negative pressure can be applied after slitting.

(Seventh Embodiment) FIG. 12 is an enlarged perspective view showing a part of a recording head portion of an ink jet recording apparatus according to a seventh embodiment, and FIGS. FIG. 13 is a cross-sectional view taken along lines AA ′ and BB ′ of FIG. 12, respectively. 12 and 13, the head substrate 12
A so-called cone-shaped projection 12c having a thick base and a thinner shape toward the tip is formed on the top of the. The individual electrode 13 is connected to the cone-shaped projection 12c, and the surface of the projection 12c is covered with a conductive substance continuous with the individual electrode 13. The conductive material that covers the protrusion 12c is referred to as a protruding electrode 13c. That is, at the tip of the individual electrode 13, a protrusion formed to protrude on the surface of the head substrate 12 is formed as the protruding electrode 13c. The individual electrodes 13 are connected to drive ICs (not shown),
A voltage can be applied to the protruding electrode 13c.

On the head substrate 12, an upper cover 14 having slits 14a is attached in parallel with the head substrate 12 via a spacer (not shown). The cone-shaped projection 12c is located inside the slit 14a and is exposed from the upper cover 14. Head substrate 12 and upper cover 14
An ink flow path is formed between them, and the ink 11 is supplied thereto. The tip of the cone-shaped protrusion 12c, that is, the protrusion-shaped electrode 13c is slightly exposed from the liquid surface of the ink 11.

With such a structure, when a signal voltage is applied to the individual electrode 13 according to an image, an ink droplet 11e is ejected from the tip of the cone-shaped projection 12c in a direction perpendicular to the surface of the head substrate 12, and is not shown. An image is recorded on the recording medium by flying toward the recording medium. The ink 11 flows, for example, in a direction indicated by an arrow in FIG. 13A by a water pressure difference, a pump, or an electrostatic force,
New ink 11 is supplied one after another.

As described above, the feature of this embodiment is that the protrusion 12c having a three-dimensional structure is formed on the head substrate 12 and the ink droplet 11e is ejected from the tip of the protrusion 12c. Next, the recording operation of this embodiment will be described in more detail with reference to FIG. FIG. 14 is an enlarged view showing the vicinity of the tip of the cone-shaped projection 12c. The cone-shaped protrusion 12c is several μ
It has a height of about m to 100 μm and protrudes from the liquid surface of the ink 11 by several μm to several tens of μm. However, at the tip of the cone-shaped protrusion 12c, the ink 11 forms a thin layer on the protrusion-shaped electrode 13c formed on the protrusion 12c by a capillary phenomenon, and always wets the surface of the protrusion-shaped electrode 13c.
That is, the ink 11 is the protruding electrode 13 of the individual electrode 13.
It is supplied so as to cover c.

The ink 11 is composed mainly of an insulating solvent 11c in which a colorant 11d composed of a pigment or the like is dispersed, as in the previous embodiment. Further, it is desirable that the coloring agent 11d be charged with, for example, a positive charge as illustrated. As such ink 11, a normal liquid developing toner used in an electrostatic recording system or an electrophotographic recording system can be used. In the ink jet recording apparatus of this embodiment, as the coloring agent 11d, those having various sizes from submicron to several μm can be used.

From the bias voltage source 20 to the individual electrode 13, the counter electrode 2 also serving as a platen (recording drum) is provided.
For example, a positive DC bias voltage is applied to No. 2 as shown. This DC bias voltage also has the effect of pushing up the ink on the projection-shaped electrode 13c toward the tip of the cone-shaped projection 12c. Further, by applying the DC bias voltage, an electric field is formed between the counter electrode 22 and the protruding electrode 13c with the recording medium 21 sandwiched therebetween. This electric field also exerts a force to attract the ink 11 toward the surface of the protruding electrode 13c. By these actions, the protruding electrode 1
The surface of 3c is always wet with the ink 11.
Since the surface of the protruding electrode 13c is wet with the ink 11 as described above, the ink 11 is smoothly supplied, and ink droplets are stably ejected and ejected, and at the same time, between the individual electrode 13 and the counter electrode 22. It is possible to prevent discharge when a large electric field is applied.

Further, in the present embodiment, since the coloring agent 11d that charges the ink 11 is used and the positive DC bias voltage is applied to the protruding electrode 13c, the coloring agent 11d is concentrated on the surface of the ink 11. It will be in a state of gathering. When the liquid developing toner is used as the ink 11 in the present embodiment, the concentration of the coloring agent is usually several%, so that it is generally too thin to be used as an ink for inkjet recording.
However, due to the effect of gathering only the colorant 11d near the surface as described above, the concentration of the colorant 11d is 10% to several 10%.
Since it can be concentrated up to, it is possible to use a normal liquid developing toner in the ink jet recording apparatus of this embodiment.

As described above, the DC bias voltage is constantly applied to the individual electrode 13 from the bias voltage source 20, and, for example, a pulse voltage is superimposed on the DC bias voltage as a signal voltage corresponding to the image signal from the drive circuit 19. And then applied. The colorant 11d aggregated as a thin ink layer near the tip of the protruding electrode 13c repels the signal voltage applied to the individual electrode 13 and is attracted to the opposite electrode 22 side in the opposite manner. The ejection is performed according to the signal voltage.

Here, the DC bias voltage is about 1 kV, and the signal voltage is about several 100V. These voltages are much lower than those of a conventional inkjet system that ejects ink by electrostatic force. The reason why the recording operation can be realized with such a low driving voltage is that the ink in which the color material 11d is charged is used as described above.
That is, the repulsive force is generated between the protruding electrode 13c and the color material 11d, and the ink droplet 11e is easily ejected even at a low voltage.

Further, in this embodiment, since the ink droplet 11e is ejected from the tip of the projecting electrode 13c, it is also a great feature that basically no nozzle is required as in the previous embodiment.
Therefore, the problem of clogging caused by the drying of the ink is considerably improved, and the line scanning recording head as shown in FIG. 12 can be easily realized.

(Eighth Embodiment) FIG. 15 shows an eighth embodiment of the present invention. In the seventh embodiment, ink droplets are ejected in a direction perpendicular to the bed substrate 12 from the protruding electrodes 13c formed on the cone-shaped protrusions 12c formed on the plane. That is, it is possible to form the ink ejection mechanism at the tip of the head entirely on a plane. Due to such characteristics, there is an advantage that the production of the recording head becomes easier as compared with the conventional method of forming the ink ejection mechanism on the end surface of the head substrate. Further, by forming the ink ejection mechanism on the flat surface of the head substrate 12, there is an advantage that high resolution can be realized by the head configuration as shown in FIG.

FIG. 15 is a plan view of the cone-shaped projection 12c viewed from a direction perpendicular to the surface of the head substrate 12. As shown in the figure, the individual electrodes 13 cannot be brought closer than the distance indicated by the pitch P. Cone-shaped projection 12c
The bottom surface of the upper protruding electrode 13c has a certain radius,
This is because it is necessary to separate the adjacent protruding electrodes so as not to contact them. Furthermore, if the protruding electrode 13c comes too close to the adjacent electrode, a signal voltage is applied to one electrode and a discharge is generated between the two electrodes when the signal voltage is not applied to the other electrode. For these reasons, the cone-shaped protrusion, that is, the protrusion-shaped electrode 13c
When the size of the pitch P is determined, the pitch P is limited, and recording with a resolution higher than the pitch P cannot be performed.

However, when the ink ejection mechanism can be formed on a plane, as shown in FIG. 15, the individual electrodes 13 and the projecting electrodes 13c are arranged in a zigzag pattern, that is, in a staggered manner in two rows to achieve high resolution. Is possible. Protruding electrode 1
When 3c are arranged in a line, it is impossible to record at a resolution equal to or lower than the arrangement pitch P. On the other hand, if the protruding electrodes 13c are displaced in the main scanning direction (arrangement direction) by ½ pitch (P / 2) and arranged in two rows as in the present embodiment, recording with double the resolution is possible. Become. In this case, with respect to the distance L between the two rows of the protruding electrodes 13c, by setting the relationship of L = P * (2 * n + 1) * (1/2) (n is an integer), the sub-scanning direction can also be obtained. The resolution can be doubled. However, in the case where the protruding electrodes 13c are arranged in two rows in this way, the timing of applying the voltage to each electrode row is delayed by (n + 1) main scanning lines, and therefore the operation of delaying the signal voltage is performed. Will be required.

As described above, according to this embodiment, even when the protruding electrodes 13c can be arranged only at the pitch corresponding to the resolution of 400 dpi, high-resolution recording of 800 dpi is performed in both the main scanning direction and the sub-scanning direction. It will be possible. Although the drawing shows an example in which two rows of the slits 14a are formed, the slits 14a may be one row when the two rows of the individual electrodes 13 are close to each other.

In the present embodiment, L = P * m (m is an integer), and in that case, the resolution in the sub-scanning direction is the same as in the case where the individual electrodes 13 are in one line. Further, if L = P * m * (1 / k) (m and k are integers), the resolution in the main scanning direction can be doubled and the resolution in the sub scanning direction can be doubled.

FIG. 16 shows an example in which recording is performed at a resolution four times the arrangement pitch P of the protruding electrodes 13c. In this case, the relationship of L = P * m * (1 / k) (m and k are integers) needs to be satisfied. Here, when m is an odd number and k = 4, the resolution in the sub-scanning direction can be quadrupled.

(Ninth Embodiment) FIG. 17 shows a ninth embodiment. In the seventh embodiment, the slit 14a is formed in the upper cover 14 at the position where the cone-shaped projections 12c are arranged in a line. On the other hand, in this embodiment, the cone-shaped projection 1
The seventh point is that a hole (this is called an ink passage hole) 14b is formed in the upper cover 14 at a position where 2c are arranged in a line.
Is different from the embodiment described above. FIG. 18A shows a cone-shaped protrusion 12c.
2B is a cross-sectional view taken along a plane parallel to the row of protrusions passing through the apex of FIG. 2B, and FIG. 7B is a cross-sectional view taken along a plane perpendicular to the row of protrusions passing through the apex of the cone-shaped projection 12c.

According to this embodiment, the upper cover 14 can suppress the vibration of the ink surface which occurs when the adjacent image points are recorded. When the diameter of the ink passage hole 14b is reduced, it also functions as a nozzle like an ordinary ink jet. However, in the ink jet recording apparatus of the present invention, since the ink is ejected from the tip of the cone-shaped projection 12c, the ink passage hole 14b does not regulate the size of the ink droplet like the nozzle, and therefore can withstand a large pressure. Instead, it only has to function to suppress the vibration of the adjacent ink liquid surface. Therefore, this ink passage hole 14b is different from the conventional ordinary inkjet nozzle in that the diameter may be larger than the resolution.

(Tenth Embodiment) Next, various examples of the cone-shaped projection 12c will be described with reference to FIGS. In the seventh to ninth embodiments, an example in which the conical cone-shaped projection as shown in FIG. 19A is used has been shown, but the cone-shaped projection has a thick root and a thin tip. Any shape can be used as long as it has a different shape.

For example, projections for ejecting ink droplets have a polygonal pyramid shape as shown in FIGS. 19B, 19C and 19D or a bump-like shape as shown in FIG. 19E. Can be used as. In any case, the same effect can be obtained as long as it is a cone-shaped projection having a shape in which the root is thick and becomes thinner toward the tip. With such a shape, capillarity or the individual electrode 13
Since the tip of the protrusion can be constantly wetted with the ink by applying a voltage to the ink, the ink can be smoothly supplied, the ink can be stably ejected and ejected from the tip of the protrusion, and the individual electrode 13 and Discharge due to an electric field applied between the counter electrodes 22 can be prevented.

Further, the cone-shaped projection does not necessarily have to be thinned to the tip, and may have a shape as shown in FIG. 20 (a) is a truncated cone, (b) (c)
(D) has a polygonal truncated pyramid, and (e) has a shape in which the tip end of a bump-shaped protrusion is cut off. When the tip is sharply pointed, the direction and size of the ejected ink may be different due to a slight difference in the way the tip is formed, or it may fluctuate over time, but as shown in FIG. Such a phenomenon does not occur if the shape does not exist. Furthermore, even if a protrusion as shown in FIG. 20 is actually formed, the tip portion may not always be flat and has a rounded shape having a certain radius of curvature depending on the forming method. Even in such a case, it can be used as a projection for ejecting ink droplets.

(Eleventh Embodiment) FIG. 21 shows still another embodiment of the ink ejection projection. In the examples so far,
Although an example in which one cone-shaped protrusion and protrusion-shaped electrode are used for one image point has been shown, FIG. 21 shows an example in which a plurality of protrusion-shaped electrodes are associated with one image point. In this embodiment, a type in which the ink passage hole 14b is formed in the upper cover 14 as shown in FIG. 17 will be described. Figure 21
In this embodiment, as shown in FIG.
On the other hand, a cone-shaped projection group 12d in which a large number of fine cone-shaped projections are gathered is made to correspond.

When producing cone-shaped projections, it is difficult to obtain projections having exactly the same characteristics unless the manufacturing process is stable. Further, in the present invention, as described above, basically no discharge occurs, but when discharge occurs, the characteristics may change during use due to the influence. As a result, stable image points cannot be formed, the density and formation position of the image points become unstable, and in some cases no image points are formed. On the other hand, when a projection group 12d composed of a plurality of cone-shaped projections is made to correspond to one image point as in this embodiment, a large number of projections are present even if there are some projections whose characteristics are not uniform. Since one image point is formed by, the characteristic of the image point can be stabilized. That is, even if there are some protrusions from which ink droplets are not ejected, ink can be ejected from the other protrusions to compensate.

(Twelfth Embodiment) FIG. 22 is a perspective view showing a structure of a main part of a recording head portion in this embodiment.
In the seventh to eleventh embodiments, each cone-shaped protrusion is formed independently, but in this embodiment, a continuous protrusion 12e having a triangular prismatic cross section is provided continuously in the main scanning direction.
The individual electrodes 13 formed with the pitch P on e are extended to form protruding electrodes 13c. Also in such a continuous protrusion 12e, when the cross section from the sub-scanning direction is seen,
Since the root has a shape that is thick and becomes thinner toward the front,
The same effect as when using the cone-shaped projection is obtained.
Also, since it is not necessary to make each cone independent,
It has the advantage of being easy to manufacture.

FIG. 23 is a diagram showing an example in which the structure of this embodiment is expanded to achieve higher resolution. That is, the continuous protrusions 12e having a triangular cross section are formed in two rows in the sub-scanning direction by being separated by L = P * (1/2) * (2 * n + 1) (n is an integer), and pitches are formed on the respective continuous protrusions 12e. By extending the individual electrode 13 formed of P to form the protruding electrode 13c and shifting the individual electrode 13 by 1/2 of the pitch P in the main scanning direction, the main scanning / sub scanning is performed as compared with FIG. The resolution is doubled for both scanning.

In the present embodiment, the triangular shape is shown as the sectional shape of the continuous protrusion 12e, but the sectional shape is not limited to this, and the sectional shape may be a part of a circle or an ellipse, or as shown in FIG. It is also possible to use a frustum shape having a flat upper part as described above, or a shape in which the tip portion is naturally rounded when producing protrusions of these shapes. That is, even in the case of the continuous protrusion, the same effect can be obtained as in the case of the cone-shaped protrusion as long as the bottom has a wide width and the upper portion has a narrower width.

(Thirteenth Embodiment) In this embodiment, some specific examples of the structures and manufacturing methods of the cone-shaped protrusion 12c and the protrusion-shaped electrode 13c will be described. FIG. 24 is a cross-sectional view showing various examples of the cone-shaped protrusion 12c and the protrusion-shaped electrode 13. In the seventh to twelfth examples, as shown in FIG. 24A, after the cone-shaped protrusion 12c is formed on the head substrate 12, the protrusion-shaped electrode 1 of the individual electrode 13 is further formed thereon.
The method of forming 3c has been described. In this case, the cone-shaped protrusion 12c may be an insulating material or a conductive material.
The method of processing Si or conductive Si in the semiconductor manufacturing process is the simplest method because it is necessary to accurately make fine things.

On the other hand, in the example shown in FIG. 24 (b), the cone-shaped individual electrode 13c is formed on the head substrate 12 and attached thereto. That is, the inside of the cone-shaped electrode 13c is the cavity 41. In the example of FIG. 24C, the entire cone-shaped projection is integrally made of the same conductive material as the individual electrode 13 (projection-shaped electrode 13c), and the projection-shaped electrode 13c also serves as the cone-shaped projection. Here is an example.

24 (d) (e) (f), the insulating layer 42 including the protruding electrodes 13c is formed on the surface of the individual electrode 13 shown in FIGS. 24 (a) (b) (c). Here is an example. When the individual electrode 13 and the protruding electrode 13c made of a metal or a conductive substance are exposed, when the charging colorant in the ink touches the individual electrode 13 and the protruding electrode 13c, the individual electrode 13 and the protruding electrode 13c are formed. Charge injection from the electrode 13c to the coloring material may occur, and the coloring material may be charged more than necessary. Furthermore, the individual electrode 13 and the protruding electrode 13
Variations in characteristics between the colorant directly injected with electric charge from c and another colorant also occur. In such a state, the ink ejection characteristic becomes unstable, and it becomes impossible to continue recording an image with a constant density. Although such a problem can be addressed by configuring the ink so as to control the charge amount of the coloring material, the method of forming the insulating layer 42 on the surfaces of the individual electrodes 13 and the projecting electrodes 13c also has the same effect. It is possible to solve such a problem.

As a method of forming the insulating layer 42, there is a method of applying a resin to the surface of the individual electrode 13 and the protruding electrode 13c to a thickness of submicron to several tens of microns. There is also a method of applying an insulating film such as SiO ₂ . Further, when the individual electrode 13 is formed of conductive Si or the like, it can be realized by a method of forming an insulating film by oxidizing the electrode surface.

(Fourteenth Embodiment) FIG. 25 is a diagram showing the structure of a recording head portion according to this embodiment. In this embodiment, another example of a method of applying a voltage to the electrodes will be described. In this embodiment, first, the colorant concentration electrode 51 is uniformly formed on the head substrate 12. The insulating layer 52 is formed on the colorant concentration electrode 51, and the cone-shaped protrusion 12c, the individual electrode 13 and the protruding electrode 13c are formed on the insulating layer 52. Then, an ink flow path is formed by covering the upper cover 14 in which the slits 14a are formed via a spacer (not shown), and the ink 11 is supplied thereto. Top cover 14
Are formed of a conductive material in this example.

Counter electrode 22 in contact with recording medium 21
A positive bias voltage is applied from the acceleration bias voltage source 53 between the upper cover 14 and the upper cover 14, and a positive bias voltage is applied from the colorant aggregation bias voltage source 54 between the upper cover 14 and the colorant concentration electrode 51. Bias voltage is applied. When this bias voltage for colorant concentration is applied, an electric field is formed between the upper cover 14 and the colorant concentration electrode 51. Since the colorant is designed to be positively charged, it is affected by this electric field and gathers around the upper cover 14. That is, the colorant is concentrated in the upper layer portion of the ink 11. In this manner, the portion where the colorant density is high rides on the flow of the ink 11 as shown by the arrow in the figure, and flows from upstream to downstream one after another, and the concentrated ink also near the apex of the cone-shaped projection 12c. Will be supplied. Here, when a pulse voltage is applied to the individual electrode 13 from the drive circuit 55 as a signal voltage corresponding to an image signal, an ink droplet is ejected from the upper portion of the protruding electrode 13c. The ejected ink droplets are accelerated by the electric field formed by the acceleration bias voltage and fly toward the recording medium 21.

According to the present embodiment, it is possible to concentrate and discharge the ink by using different power supplies, that is, the bias voltage source 54 for concentrating the colorant and the drive circuit 55. In the method of simultaneously concentrating and ejecting ink as shown in FIG. 14, as described above, a bias voltage for concentration of about 1 kV is applied to several hundreds of volts.
It is necessary to superimpose the ejection pulse voltages of, and it is necessary to use an IC having a withstand voltage equal to or higher than the superposed voltage.
On the other hand, when the ink concentration and the ejection are separated as shown in FIG. 25, the respective bias voltages need to be applied in common and only the ejection pulse voltage of several hundreds of volts is controlled. It becomes possible to use an IC having a low breakdown voltage, which greatly contributes to miniaturization and stabilization of the inkjet recording apparatus.

Although the bias voltage from the acceleration bias voltage source 53 is a DC voltage in this embodiment, it may be a pulse voltage synchronized with the recording signal. However, in that case, an electrode (corresponding to the upper cover 14) for applying an acceleration bias voltage is provided as an individual electrode so that a pulsed acceleration voltage can be applied to each protrusion. 1
It is necessary to separately provide the three items.

(Fifteenth Embodiment) In the seventh to fourteenth embodiments, as shown in FIG. 13, the cone-shaped projection 12c and the projection-shaped electrode 13c are slightly exposed from the liquid surface of the ink. As described above, the ink droplets can be ejected even with the configuration shown in FIG.

FIG. 26A shows an example in which the apex of the protruding electrode 13c exists below the liquid surface of the ink 111. Even when the projecting electrodes 13c are buried in the ink in this way, the coloring agent is agglomerated in the upper portion of the ink 11 due to the bias voltage, and the density is high. Here, the signal voltage is applied to the individual electrodes 13. When applied, the ink that has aggregated near the apex of the protruding electrode 13c is ejected and flies. Therefore,
Since the apex of the protruding electrode 13c is always in the liquid of the ink 11 and the apex is always wet, there is an advantage that the discharge problem can be solved more reliably.

Further, as shown in FIG. 26B, even when the cone-shaped protrusion 12c and the protrusion-shaped electrode 13c are almost out of the ink liquid 11, when the protrusion 12c is small, it is a capillary phenomenon, and the protrusions are small. When 12c is large, a thin ink layer can be formed at the apex of the protruding electrode 13c by further applying a voltage, so that it is possible to eject ink. Since such a thin layer of ink on the surface of the protruding electrode 13c is formed more stably as it is farther from the liquid surface of the ink 11, stable ink ejection is possible and an image can be recorded more stably.

However, when the projecting electrodes 13c are separated from the liquid surface of the ink 11 in this way, they easily dry. Therefore, when the projecting electrodes 13c are not used for a while, the ink near the projections 12c is drained and the ink is re-used when used. It is good to inject. At the time of injecting the ink, the ink is once infused with a slightly higher pressure to wet the apex of the projecting electrode 13c, and then a negative pressure is applied to bring the ink state as shown in the figure. By doing so, the apex of the protruding electrode 13c gets wet with the ink, so that the ink can be smoothly supplied by applying a voltage.

Finally, a concrete example of the construction of the entire ink jet printer to which the ink jet recording apparatus of the present invention is applied will be described with reference to FIG. In FIG. 27, the recording paper 1 supplied from a paper cassette (not shown) is fed by the paper feed roller 2
Is supplied to the periphery of the recording drum 3 and is further pressed against the recording drum 3 by the paper guide 4 and the paper pressing roller 5. While the recording paper 1 is pressed against the recording drum 3, the ink jet recording head 10 ejects an ink droplet 11 containing at least a colorant component according to an image signal, and a character 7 is formed on the recording paper 1 and recording is performed. Done. When the recording is completed, the recording paper 1 is ejected to the paper ejection tray 6. The ink jet recording head 10 used here is a line scanning type head capable of recording the length of the recording paper 1 in the width direction as shown in the figure, and the head according to the present invention described in the above embodiments is used. To be

[0098]

As described above, according to the present invention, the surface of the electrode is covered with the ink during recording, so that the stable coloring required for the flight of the coloring material component in the ink can be achieved without causing damage due to discharge. Since a strong electric field can be obtained, it is possible to realize an inkjet recording apparatus in which the flying colorant particles are small and the electrostatic force of a slit nozzle suitable for line scanning recording is used.

Further, according to the present invention, since a strong electric field vector is formed by adding a vertical direction component different from the plane direction component formed by the head substrate surface, the flying colorant has an angle with the substrate plane. The initial speed can be given. Therefore, not only is it possible to fly the color material from a position retracted from the edge of the substrate, but it is also possible to fly the color material from any internal position within the plane of the substrate. The inkjet recording head can be realized. That is, it is possible to realize a practical line scanning type ink jet recording head by using only the in-plane patterning process, which has good reliability in the manufacturing process and uniform characteristics in operation.

Furthermore, it is possible to adopt a structure in which an electric field that repels the coloring material is generated in the gap between the wiring patterns of the individual electrodes. In that case, the effect that the coloring agent can be efficiently collected while the ink flows, or can be stored at the flight start point,
It is also possible to have an effect of stabilizing the flight direction by forming a gutter-shaped potential in which the minimum points of the electric field are continuous along the spatial path along which the colorant flies.

Further, in the present invention, by forming a protruding portion at the tip of the individual electrode and supplying ink onto the protruding portion, it is possible to prevent the individual electrode from being destroyed by electric discharge, and to provide more stable image recording. In addition, since the ink is ejected from the tip of the protruding portion, basically no nozzle is required, and a slit or hole for allowing the ink to pass is sufficient, so the problem of nozzle clogging is solved. It Further, a plurality of individual electrodes and their protrusions are arranged in the main scanning direction, and a plurality of columns are provided in the sub-scanning direction, and then the protrusions on different columns are arranged at different positions in the main scanning direction in the main scanning direction. By arranging them respectively, it becomes possible to form image points at intervals smaller than the arrangement pitch in the main scanning direction and perform high resolution recording.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an inkjet recording apparatus according to a first embodiment.

FIG. 2 is a schematic configuration diagram of an inkjet recording apparatus according to a second embodiment.

FIG. 3 is a schematic configuration diagram of a recording head unit according to a second embodiment.

FIG. 4 is an explanatory view of a shape of a tip portion of an individual electrode and a stable operation range in the embodiment.

FIG. 5 is a conceptual diagram of an electric field distribution around a head substrate showing the principle of the same embodiment.

FIG. 6 is a diagram showing a graph of distance vs. potential and electric field strength showing generation of a gutter-shaped potential in the same Example.

FIG. 7 is a schematic configuration diagram of a recording head unit according to a third embodiment.

FIG. 8 is a conceptual diagram of an electric field distribution around a head substrate showing the principle of the embodiment.

FIG. 9 is a schematic configuration diagram of a recording head unit according to a fourth embodiment.

FIG. 10 is a schematic configuration diagram according to a fifth embodiment.

FIG. 11 is a schematic configuration diagram of a recording head unit according to a sixth embodiment.

FIG. 12 is a schematic configuration diagram of a recording head unit according to a seventh embodiment.

13 is a sectional view taken along the line AA ′ and the line BB ′ of FIG.

FIG. 14 is a diagram for explaining the operation of the embodiment.

FIG. 15 is a plan view of an essential part of a recording head unit according to an eighth embodiment.

FIG. 16 is a plan view of a main portion of another recording head portion according to the eighth embodiment.

FIG. 17 is a perspective view of a main part of a recording head unit according to a ninth embodiment.

FIG. 18 is a cross-sectional view taken along a plane parallel to and perpendicular to the row of protrusions that pass through the apex of the cone-shaped protrusions in the example.

FIG. 19 is a view showing various examples of cone-shaped projections according to the tenth embodiment.

FIG. 20 is a view showing various examples of cone-shaped projections according to the tenth embodiment.

FIG. 21 is a view showing various examples of ink ejection projections according to the eleventh embodiment.

FIG. 22 is a perspective view of the essential parts showing the basic structure of the recording head section according to the twelfth embodiment.

FIG. 23 is a perspective view of a main part of a high-resolution recording head unit according to a twelfth embodiment.

FIG. 24 is a cross-sectional view showing various configurations of a cone-shaped protrusion and a protrusion-shaped electrode in a recording head section according to a thirteenth embodiment.

FIG. 25 is a diagram for explaining the configuration and operation of the recording head unit according to the fourteenth embodiment.

FIG. 26 is a cross-sectional view of the main parts of the recording head section according to the fifteenth embodiment.

FIG. 27 is an overall configuration diagram of an inkjet recording apparatus according to the present invention.

FIG. 28 is a configuration diagram of a head tip portion of an edge shooter type inkjet recording head which is a first conventional example.

FIG. 29 is a configuration diagram of a head tip portion of an ink jet recording head of a second conventional example in which electrodes are exposed.

[Explanation of Codes] 11 ... Ink 11a ... Ink in concentrated colorant 11b ... Ink in concentrated colorant 11c ... Solvent 11d ... Colorant 11e ... Ink drop 12 ... Head substrate 12a ... Head substrate edge portion 12b ... Flying colorant Midpoint of points 12c ... Cone-shaped projection 12d ... Cone-shaped projection group 12e ... Continuous projection having a triangular prism shape in section 13 ... Individual electrode (electrode array) 13a ... Colorant flying point 13c ... Projection-shaped electrode 14 ... Top cover 14a ... Slit 14b Ink drop passage hole 15 Ink supply flow path 16 Lower cover 17 Ink recovery flow path 18 Ink recirculation mechanism 19 Drive circuit 20 Bias voltage source 21 Recording medium 22 Counter electrode 23 Common electrode 31 Electrode 1a 31a ... Colorant flying point 32 ... Second electrode 41 ... Cavity 42 ... Conductive layer 51 ... Colorant concentration electrode 52 ... Insulating layer 53 ... Bias voltage source for acceleration 54 ... Bias voltage source for aggregation of colorant 55 ... Driving circuit

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

FIG.

[Fig. 2]

[Figure 4]

[Figure 5]

[Figure 7]

[Figure 8]

[Figure 3]

[Figure 9]

[Figure 10]

[Fig. 12]

[Fig. 13]

[Figure 6]

FIG. 26

FIG. 11

FIG. 14

FIG. 15

FIG. 16

FIG. 17

FIG. 18

FIG. 19

FIG. 20

FIG. 28

FIG. 21

FIG. 22

FIG. 23

FIG. 24

FIG. 25

FIG. 27

FIG. 29

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yuko Nomura Yuko Nomura, Komukai-shi, Kawasaki-shi, Kanagawa No. 1, Toshiba Research and Development Center (72) Inventor Koichi Ishii Komukai-Toshiba, Kawasaki-shi, Kanagawa Town No. 1 In stock company Toshiba Research & Development Center (72) Inventor Teruo Murakami No. 1 Komukai Toshiba Town, Kouki-ku, Kawasaki City, Kanagawa Prefecture No. 72 Company Incorporated Toshiba Research & Development Center (72) Inventor Hideyuki Nakao Kawasaki City, Kanagawa Prefecture Komukai-Toshiba-cho 1-ku, Toshiba Research & Development Center

Claims (10)

[Claims] 1. A head substrate, an electrode array formed on the surface of the head substrate, and ink for supplying an ink in which a colorant is dispersed in a solvent onto at least the electrode array on the surface of the head substrate. And a voltage applying means for applying a voltage to the electrode array to cause at least a coloring material component in the ink supplied onto the electrode array by the ink supplying means to fly toward the recording medium. An inkjet recording device characterized by the above. Cudget recording device. 2. The head substrate imparts an initial velocity component in a direction perpendicular to the surface of the head substrate to a colorant component flying toward the recording medium by the electrode array, and further, the color of the recording medium. The receiving point of the agent component is located above a plane extending from the surface of the head substrate, and is arranged so that an angle formed with the plane at the receiving point is 90 ° or less. Item 2. The inkjet recording device according to item 1. 3. A head substrate provided facing a recording medium, a plurality of individual electrodes formed on the surface of the head substrate at a position receding from the end face on the recording medium side, and a coloring agent in a solvent. Ink supplying means for supplying the dispersed ink to at least the individual electrodes on the surface of the head substrate, and recording at least the colorant component in the ink supplied on the surface of the head substrate by the ink supplying means. A voltage applying unit that applies a voltage according to an image signal for flying toward the medium to the individual electrode, wherein the head substrate is configured to apply a colorant component flying toward the recording medium from the individual electrode. An initial velocity component in the direction perpendicular to the surface of the head substrate is given, and the receiving point of the colorant component of the recording medium is located above a plane extending the surface of the head substrate, and the receiving point is Angle with the plane at 9
An inkjet recording apparatus, wherein the inkjet recording apparatus is arranged so as to be 0 ° or less. 4. A head substrate, a plurality of individual electrodes formed on the surface of the head substrate, and an ink in which a coloring agent is dispersed in a solvent is supplied to at least the individual electrodes on the surface of the head substrate. And a voltage according to an image signal for causing at least the coloring material component in the ink supplied on the surface of the head substrate by the ink supply means to fly toward the recording medium. An ink jet recording apparatus, comprising: 5. A head substrate provided so as to face a recording medium, a plurality of individual electrodes formed on a surface of the head substrate at a position receding from the end face on the recording medium side, and a back surface of the head substrate. A common electrode formed on the upper surface of the head substrate; an ink supply unit that supplies ink in which a colorant is dispersed in a solvent to at least the individual electrodes on the surface of the head substrate; and the surface of the head substrate by the ink supply unit. A voltage is applied to the individual electrodes while applying a voltage corresponding to an image signal for causing at least a coloring material component in the ink supplied above to fly toward a recording medium, and a predetermined bias voltage is applied to the common electrode. An inkjet recording apparatus comprising: 6. A head substrate provided to face a recording medium, a plurality of individual electrodes formed on a surface of the head substrate at a position receding from an end face on the recording medium side, the head substrate having a plurality of individual electrodes. An auxiliary electrode formed on the surface in the vicinity of the individual electrode, an ink supply means for supplying an ink in which a colorant is dispersed in a solvent to at least the individual electrode on the surface of the head substrate, and the ink A voltage according to an image signal for causing at least the colorant component in the ink supplied onto the surface of the head substrate by the supply means to fly toward the recording medium is applied to the individual electrode, and a predetermined voltage is applied to the auxiliary electrode. And a voltage applying means for applying the bias voltage of 1. 7. The ink jet recording apparatus according to claim 3, wherein each of the individual electrodes is formed so that its tip portion projects above the surface of the head substrate. 8. A head substrate, a plurality of individual electrodes formed on the surface of the head substrate, each tip of which protrudes on the surface of the head substrate, and a colorant dispersed in a solvent. Ink supplying means for supplying different inks to at least the protrusions of the individual electrodes on the surface of the head substrate, and recording at least the colorant component in the ink supplied on the surface of the head substrate by the ink supplying means. An ink jet recording apparatus comprising: a voltage applying unit that applies a voltage corresponding to an image signal for flying toward a medium to the individual electrode. 9. The individual electrodes and the plurality of protrusions of the individual electrodes are arranged in the main scanning direction and are provided in a plurality of columns in the sub-scanning direction, and the protrusions on different columns are located at different positions in the main scanning direction. The ink jet recording apparatus according to claim 8, wherein the ink jet recording apparatus is arranged in each. 10. A colorant component in an ink in which a colorant is dispersed in a solvent is aggregated in the solvent according to an image signal, and at least the aggregated colorant component in the ink is ejected toward a recording medium. In an ink jet recording apparatus for performing recording by performing the recording, an aggregating unit that aggregates the colorant component in a solvent and a flying unit that fly the colorant component aggregated by this unit toward a recording medium are separately provided. Characteristic inkjet device.