JPH11286104A - Ink recorder and method for ink recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nozzleless type ink recorder capable of eliminating problems due to mutual interference of waves propagating on a surface of ink and residual vibration remaining on a printed section after the printing is performed. SOLUTION: Ink 1 is supplied on a substrate 2 by having a free surface 1a. When a high frequency voltage (B) is continuously applied to a sound transducer 3, a stable liquid column 1b is formed by an ultrasonic wave emitted into the liquid. When an external force for printing is applied to the liquid column in this condition, a constriction is formed at a top of the liquid column (C), a liquid drop (D) is ejected to be moved on an image recording medium. After the liquid drop 1c is ejected (E), the liquid column maintains its state by the high frequency voltage continuously applied to the sound transducer 3 even when the external force for the printing is not applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink recording apparatus for forming an image by forming a liquid column having a predetermined height on an ink free surface and moving the ink at the tip of the liquid column onto an image recording medium. And an ink recording method.

[0002]

2. Description of the Related Art Conventionally, an apparatus for recording an image by forming dots by making liquid ink into liquid droplets and flying and moving the liquid ink on an image recording medium has been put into practical use as an ink jet printer. A general ink jet recording apparatus has a problem that clogging occurs because ink droplets are ejected from fine nozzles corresponding to the resolution. For example, in the case where a pressure generated by a bubble using a heating element is used, clogging occurs due to the insoluble matter due to a thermal or chemical reaction with ink adhering to the inner wall of the nozzle. When the pressure by the piezoelectric element is used, there is a problem that clogging occurs due to a complicated structure such as an ink flow path. Usually, various measures are taken to prevent clogging. However, in a line scanning type head in which nozzles are arranged in the main scanning direction, the frequency of clogging becomes extremely high, and the reliability of the ink jet apparatus is significantly reduced. . Further, when high resolution is required to record a high-definition image, it is necessary to process the nozzle to a minute diameter of about several tens of μm. When thousands of nozzles are required as in the case of a line type head, a technique for processing this recording head is required, and it is extremely difficult in manufacturing to increase the resolution with the line type head.

In order to overcome these problems, an apparatus for moving ink droplets from an ink surface by using an ultrasonic beam has been proposed as a system which does not require a nozzle.
No. 943, JP-A-63-162253, JP-A-63-166545, and JP-A-8-238764.
JP, JP-A-8-290587, JP-A-9-3
No. 9224, JP-A-9-94957, JP-A-2-175157, JP-A-2-55139, JP-A-2-103152, JP-A-2-164
546 and JP-A-7-276622. These methods are nozzle-less configurations, so that the above-described problems such as clogging hardly occur.

[0004] Such a nozzleless type ink jet printer can easily arrange the printing sections in the main scanning direction as compared with a nozzle type ink jet printer, and is effective for high speed printing. However, since the nozzles are nozzleless, there is a new problem that mutual interference between adjacent printing units occurs largely. For example,
The vibration of the ink liquid surface that occurs after printing propagates to other printing sections, hinders the flight of ink droplets, destabilizes the protruding direction, and causes blank shots where ink droplets do not move. Obstacles come out.

As a configuration for preventing these obstacles, there is JP-A-6-238884. In the printing method described in this publication, a large-diameter porous cover is attached to the free surface of each ink on the free surface of the ink, and the free surface area is partitioned by the large-diameter portion of the printing portion to prevent waves propagating to other printing portions. it can. However, the ink wave blocked by the cover is reflected by the cover, and the reflected wave returns to the original printing section. Therefore, even if it is possible to prevent the propagation to other printing sections, the wave returns to the printing section where printing has been performed, thereby causing the same adverse effect as mutual interference. Normally, printing is performed after the influence of the above-described obstacle is eliminated or reduced. Therefore, it is disadvantageous for high-speed printing, and deteriorates the performance as an ink recording apparatus. In addition, partitioning with a cover or the like has a disadvantage in supplying ink to the printing unit because the contact resistance between the ink and the supply path is increased, so that ink is supplied at high speed.

In the method in which ink droplets are moved from the free surface of the ink, there are residual vibrations remaining in the printing section after printing, in addition to the above-described propagated waves, with respect to the waves on the ink surface. If you try to print again while the residual vibration is occurring, the movement of the ink droplets will be hindered, as in the case of mutual interference, and the protruding direction will become unstable. Would. As a method of reducing the influence of residual vibration, pressure control such as disclosed in JP-A-2-175157, JP-A-5-338150, and JP-A-5-278218, which reduces residual vibration, can be used. There is a control method for performing printing in synchronization with residual vibration. Since these control methods are generally controlled in an open loop, it is difficult to accurately suppress and synchronize vibration. In addition, when a method of detecting and feeding back a vibration is adopted, a technology for sensing a minute liquid level and a highly accurate timing control technology are required, and are difficult with the current technology. In addition, this leads to an increase in the size and cost of the apparatus, which makes it impossible to use a low-cost, small-sized apparatus which is an advantage of a desktop type ink jet printer.

[0007] As a conventional technique for reducing the energy for moving, there are Japanese Patent Application Laid-Open Nos. 62-251153 and 7-276622. JP-A-7-2766
Japanese Patent Application Publication No. 22-214400 makes a solitary wave scan in the main scanning direction, and performs printing when the solitary wave reaches a printing unit.
As a result, the energy for moving the ink droplets may be small, but the effect of the wave propagating to other printing units cannot be removed. JP-A-62-25115
Japanese Patent Application Laid-Open No. 3 (1999) -2003 discloses a method in which a standing surface wave is entirely formed on a free surface in the main scanning direction. Thereby, Japanese Patent Application Laid-Open No. 7-276
As in Japanese Patent No. 622, the energy for moving the ink droplets may be small. However, it is a configuration in which a standing surface wave cannot be formed independently for each printing unit, and by utilizing the peaks and valleys formed to maintain the balance of the surface by vibrating the entire ink free surface. Is what it is. For this reason, the locally generated vibration may cause the balance of the entire ink free surface to be lost, and may cause the entire liquid surface to be unstable. Further, even though standing surface waves can be formed in one line in the main scanning direction of the free surface of the ink, a configuration in which a two-dimensional printing arrangement is not possible is impossible.

The nozzleless ink jet recording apparatus capable of high-speed printing has the above-mentioned major problems. These are summarized in the following two points. Fluctuations in the direction of ink droplet movement due to the effect of waves propagating on the ink surface after printing, and blank shots. Fluctuations in the direction of movement of the ink droplets due to the effects of residual vibrations remaining in the printing area after printing, and blank shots. The problem described above is a problem that is not present in the nozzle type ink jet recording apparatus and is a problem peculiar to the nozzleless system. The problem (1) also exists in a nozzle type ink jet recording apparatus, and attempts are being made to solve the problem by the control technique described in Japanese Patent Application Laid-Open No. 5-338150 or the like.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in a nozzleless ink recording system, mutual interference due to the waves propagating on the ink surface described above remains in a printing portion after printing. It is an issue to solve two points of residual vibration. By solving these problems, an ink recording apparatus and an ink recording method that employ a nozzleless method that is advantageous for high-speed printing and that can perform high-speed printing that could not be performed by the conventional nozzleless method due to vibration of the ink liquid level are provided. It is intended for.

[0010]

According to the present invention, there is provided an ink recording apparatus for moving ink from an ink free surface and performing printing on an image recording medium located at a position facing the ink free surface. A liquid column forming means for forming a liquid column maintaining a constant height in the portion; and a moving means for forming ink droplets from the liquid column and moving the ink to the image recording medium.

The present invention also relates to an ink recording method for moving ink from an ink free surface and performing printing on an image recording medium located at a position facing the ink free surface. A liquid column maintaining the height is formed, and the ink is formed into droplets from the liquid column and moved to the image recording medium.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of the principle configuration of the present invention. In the figure, 1 is an ink, 1a is an ink free surface, 1b is a liquid column, 2 is a substrate, 3 is an acoustic transducer, 4 is a high frequency power supply, and 5 is an acoustic wave. FIG. 1A shows a state in which the high-frequency power supply 4 is off. Substrate 2
Is supported with a free surface 1a thereon. Acoustic transducer 3 for generating ultrasonic waves on substrate 2
So that the ultrasonic vibration can be irradiated toward the ink free surface 1a. In this figure, the substrate 2 is
A conductor or a material having conductivity by providing a conductive layer on the surface on the side of the acoustic transducer 3 was connected to the ground potential, and was connected to one electrode of the plurality of acoustic transducers 3 in common. However, it is not always necessary that the substrate 2 has conductivity, and leads may be drawn from each acoustic transducer 3. In FIG. 1A, as described above, the high-frequency power supply 4 is
FF, and therefore, the voltage applied to the acoustic transducer 3 is 0 V as shown in FIG.

FIG. 1B is a diagram in which the high-frequency power supply 4 is turned on. As shown in FIG. 1D, the high-frequency power supply 4 is constantly applied to the acoustic transducer 3 to generate an acoustic wave 5 in the ON state. By acoustic waves,
The liquid column 1b is formed. Printing is performed by moving ink from the liquid column to an image recording medium (not shown). The movement of the ink is performed by applying energy to the formed liquid column 1b so that the liquid droplet can be separated.

As the acoustic transducer 3, an appropriate element such as a piezoelectric element or a magnetostrictive element that can emit an acoustic wave into the ink by an applied voltage can be used.

FIG. 2 is an explanatory view of the formation of the liquid column. In the figure, the same parts as those in FIG. The illustration of the high-frequency power supply is omitted.

FIG. 2A shows a state in which the voltage of the high frequency power supply is not applied to the acoustic transducer 3. In the description of FIG. 2, a piezoelectric element is used as the acoustic transducer 3.

FIG. 2B shows a state in which a high-frequency voltage has been applied to the acoustic transducer 3. The high frequency voltage is
A pulse voltage having a constant period was used. Acoustic waves 5 are radiated from the acoustic transducer 3 into the ink 1, and the radiation pressure causes a bulge of the ink on the ink free surface 1 a at the center of the acoustic transducer 3. However, when the voltage is low, the raised surface of the ink is somewhat unstable.

FIG. 2C shows a state where the voltage is increased. The bulge of the ink caused by the radiation pressure of the acoustic wave 5 becomes high, and the liquid column 1b starts to stabilize.

FIG. 2D shows that when the voltage applied to the acoustic transducer 3 is further increased, the liquid column 1b is completely stabilized.

FIG. 2E shows a state in which the voltage applied to the acoustic transducer 3 is further increased. The liquid column 1b is higher and stable. There is a voltage region in which a stable liquid column 1b can be formed at a voltage-dependent height.

FIG. 2F shows a state in which the voltage applied to the acoustic transducer 3 is increased beyond the stable region. The liquid column 1b starts to oscillate and becomes unstable.

FIG. 2G shows a state in which the voltage applied to the acoustic transducer 3 is further increased. Liquid column 1b
Begins to deform and the shape becomes increasingly unstable.

FIG. 2H shows a state where the voltage applied to the acoustic transducer 3 is further increased. In the figure, atomized ink comes out from the unstable liquid column 1b.

As described above, when the ultrasonic energy radiated into the liquid is gradually increased from zero, a liquid column is gradually formed on the free surface of the ink. When the energy is very small, the liquid column is slightly unstable, but is stabilized when the energy exceeds a certain value. When the energy is applied beyond this stable range, the liquid column becomes unstable again. When a certain energy or more is applied, fine droplets are scattered in all directions from each part of the liquid column.

Considering the state in which fine droplets atomized in the unstable region come out, the driving frequency of the ultrasonic wave generating means is about 5
It was found that atomized ink was produced when the frequency was lower than MHz. If the driving frequency exceeds 5 MHz, such fine droplets do not scatter.

FIG. 3 is a schematic explanatory view of a conventional nozzleless type ink jet recording apparatus using an ultrasonic beam. In the figure, the same parts as those in FIG. 1c is a droplet. FIG. 3A shows a state where no voltage is applied to the acoustic transducer 3. As shown in FIG. 3B, a high-frequency voltage for a predetermined period for printing is applied. Ultrasonic waves are radiated into the liquid by the high frequency voltage, and a liquid column 1b is instantaneously formed as shown in FIG. Next, as shown in FIG. 3D, the constriction at the top of the liquid column 1b is cut, so that the droplet 1c flies and moves to an image recording medium (not shown). FIG. 3E shows a state after the droplet 1c flies. When the application of voltage is stopped and the formed liquid column collapses and falls, the ink free surface 1
a, an instantaneous concave surface is formed, the liquid level in the concave portion rises, and a vibration wave is generated on the ink free surface 1a.

The formation of the droplet of the present invention will be described with reference to FIG. 4 in comparison with FIG. In the figure, the same parts as those in FIGS. 2 and 3 are denoted by the same reference numerals, and description thereof will be omitted. FIG. 4A shows a state where a high-frequency voltage is constantly applied to the acoustic transducer 3 continuously. FIG. 4B shows a high-frequency voltage for forming a liquid column. Ultrasonic waves are radiated into the liquid by the high-frequency voltage, and the stable liquid column 1b is formed as described with reference to FIGS. In a state where the liquid column 1b is formed in a stable state, when an external force for printing is applied to the liquid column 1b, a constriction occurs at the top of the liquid column 1b as shown in FIG. Next, as shown in FIG. 3 (D), the droplet 1c flies by cutting the constricted portion and moves to an image recording medium (not shown).

FIG. 4E shows a state after the droplet 1c flies. Even when the external force for printing disappears, the liquid column continues to be formed since the high frequency voltage is continuously applied to the acoustic transducer 3. Due to the separation of the droplet 1c, the height of the liquid column 1b is instantaneously reduced,
The liquid column 1b is caused by the continuously applied high frequency voltage.
Recovers to a stable state.

The external force applied to the formed liquid column 1b for printing may be a pressure by a bubble or a pressure by another ultrasonic wave generating means. The external force to be applied in the present invention may be smaller than that for cutting the constriction of the liquid column described with reference to FIG. That is, in the present invention, since the liquid column is formed in advance, the external force for forming the liquid droplet may be smaller than the external force for flying the ink droplet from the state where the liquid column is not formed. If the liquid column is formed in advance, for example, about one-third of the energy (force) required to fly an ink droplet from a flat liquid surface
Can cause ink droplets to fly.

FIG. 5 is a graph showing an example of the relationship between the energy of the external force and the vibration amplitude and vibration time of the liquid surface. FIG.
As shown in (A), the larger the energy of the external force applied when the ink droplet flies, the larger the vibration amplitude of the liquid surface after the ink droplet flies. Similarly, FIG.
As shown in (B), the greater the energy of the external force applied when the ink droplet flies, the longer the time required for the vibration of the liquid surface to converge after the ink droplet flies. As described above, by forming the liquid column in advance, the energy of the external force required to cause the ink droplet to fly can be reduced to about の of the energy required to cause the ink droplet to fly from a flat liquid surface. Degree is fine. As shown in FIG. 5 (A),
As shown in (B), the vibration amplitude and the vibration time after the ink droplet is caused to fly are also reduced to about 1/2 to 1/3. Therefore, the waiting time from the time when the ink droplet flies to the time when the next ink droplet flies can be significantly reduced. For this reason, it is possible to perform printing at a higher speed than in the conventional nozzleless method, without having to worry about ejection instability due to residual vibration or mutual interference after printing.

Further, in the conventional nozzleless method described with reference to FIG. 3, the vibration generated on the free ink surface after the disappearance of the print signal is large, and this vibration greatly affects the next printing and the adjacent printing section. On the other hand, in the present invention, the vibration generated on the free surface of the ink after the constriction is cut is small, and the vibration wave propagating from the other printing section is lower than the liquid column which is always formed. The waves of the
Although the propagating wave may slightly shake the liquid column, the top of the liquid column remains fairly stable and the effect is small. Therefore, in the present invention, the influence of the vibration wave is sufficiently small as compared with the influence of the vibration wave propagating in the print portion to the ink free surface without the liquid column. Therefore, the present invention can provide a significant improvement effect on the above two problems.

FIG. 6 is a schematic configuration diagram of an example of an embodiment of the ink recording apparatus of the present invention. In the figure, 10, 11, 1
2, 13, 14 are recording heads, 10a is a liquid column forming means,
Reference numeral 15 denotes an image recording medium. 1b is the liquid column described with reference to FIGS. 1 and 2, and is formed by the liquid column forming means 10a. As the liquid column forming means 10a, it is needless to say that the above-described acoustic transducer can be used, and in addition, a means that can apply a local force to the liquid surface may be used. Is also good. In the following description, an acoustic transducer will be used as the liquid column forming means.

FIG. 6A shows a liquid column forming means 10a inside.
FIG. 4 is an explanatory diagram of a recording head provided with. Liquid column forming means 10
By applying the high-frequency voltage to the acoustic transducer a, the liquid columns 1b corresponding to the pixels of the print are formed in a line. FIG. 6B is a schematic configuration diagram for performing full-color printing. 11 is Y (yellow), 12 is M (magenta), 13 is C (cyan), 1
Reference numeral 4 denotes K (black) heads. Print head 1
1, 12, 13, and 14 are arranged in tandem for four colors. However, the present invention is not limited to the arrangement of the recording heads in FIG. 6, but is applicable to various device layouts. The image recording medium 15 is transported to a recording head unit by a transport unit (not shown). Before the image recording medium 15 reaches the recording head section, a liquid column 1b having a predetermined height is formed for each pixel in the recording head of each ink color. As shown in FIG. 6C, the operation of printing each pixel in order to move the ink to the image recording medium 15 and form a desired image on the image recording medium 15 is performed by using the ink droplets described with reference to FIG. Performed by flight. When the image recording is completed, as shown in FIG. 6D, it is preferable to stop the formation of the liquid column 1b and make the original flat ink free surface from the viewpoint of energy loss. When an image is formed on an incoming image recording medium, the image may be recorded on the next image recording medium while the liquid column is formed. If the image recording medium is always conveyed to the recording head section, such as continuous paper, the recording heads of the respective colors are supplied to the recording heads of the required colors only when the required image recording area passes. Columns may be formed. When the image recording area is intermittent, the liquid column may be continuously formed.

FIG. 7 is an explanatory view of another method of forming a liquid column in the recording head described with reference to FIG. FIG. 6 has described the method of forming the liquid columns on all the print heads for each print head and the method of forming the liquid columns only on the print heads of the required colors. Therefore, the method of forming all the liquid columns in the recording head in which the liquid columns are formed has been described.

However, depending on the print image, it is not necessary to form all the liquid columns for a print head of one color. In FIG. 7, liquid columns corresponding to all pixels are not always formed during image recording, but only liquid columns corresponding to necessary pixels are selectively formed. Explaining with reference to FIGS. 6B and 6C, for example, in the case where the recording in the transport direction (sub-scanning direction) of the image recording medium 15 is set as a column, the recorded image data is read in advance and is in a certain column. If the color record is not longer than a predetermined length, the liquid column in the row is prevented from being formed therebetween. This method can reduce the energy as compared with FIG. 6 and can freely control the wave on the entire free surface of the ink. Therefore, it is also possible to control the generated vibration wave to cancel by forming a liquid column. It becomes possible. Therefore, by selectively forming the liquid column, there is an advantage that it is possible to efficiently suppress mutual interference between the printing units corresponding to adjacent pixels.

FIGS. 6 and 7 show a configuration in which the printing sections of each recording head are arranged in a line in the main scanning direction.
A configuration of a dimensional printing unit may be adopted. FIG. 8 is an example of a two-dimensional array. The formation of the liquid column is indicated by a circle. FIG. 8A is a perspective view, and shows a state where a plurality of rows are arranged in the sub-scanning direction in the liquid column forming portions arranged in the main scanning direction. FIG. 8B illustrates the positional relationship in a plan view.
In contrast to the first column, the second to fourth columns have a pitch P of 1 between pixels.
They are arranged so that the phase is shifted by / 4. The pitch in the sub-scanning direction was also set to P. By moving the image recording medium by 1 / 4P, it is possible to record an image at a pixel density four times as large as P. In FIG. 8, the arrangement of four columns is illustrated, but the arrangement is not limited to four columns, and a two-dimensional arrangement can be performed in an arrangement of two or more columns.

FIG. 9 is an explanatory view of a first embodiment of an external force applying means for applying an external force to the formed liquid column. In the figure, the same parts as those in FIGS. 1 and 4 are denoted by the same reference numerals, and description thereof is omitted. 21 is an ink support, 22 is a top plate, 23 is an opening, and 24 is a piezoelectric element. In this embodiment, a pressure change caused by driving the piezoelectric element is used as the external force applying means. As shown in FIG. 9A, the ink 1 is supplied to a substantially conical space formed in the ink support 21. A cylindrical space is formed below the conical space, and a piezoelectric element 24 is provided around the cylindrical space so as to surround the cylindrical space. An ink tube is formed by the conical space and the cylindrical space, and ink is supplied from an ink supply tube (not shown). The acoustic transducer 3 is provided at a position corresponding to the bottom of the cylindrical space. On the upper surface of the ink support 21, a top plate 22 having a highly accurate opening 23 is attached. When an appropriate high-frequency voltage is applied to the acoustic transducer 3, the liquid column 1 b is formed through the opening 23, and the surface of the top plate 22 is also overflowed with ink to form an ink free surface. . The ink may be supplied to the free ink surface.

As shown in FIG. 9B, the piezoelectric element 24
Vibrates in the radial direction in the cylindrical tube according to the print signal. Accordingly, the ink 1 filled in the ink tube is compressed in the radial direction of the cylinder due to the reduced volume in the tube, and expands in the release direction in the ink tube. The ink in the expanded ink tube rises in the conical space, is amplified as the cross-sectional area decreases, and further lifts the liquid column 1b to attempt to expand through the opening 23 toward the ink free surface. Therefore, the top of the liquid column 1b is
Since the droplets are formed and fly by a small external force, only a small force is required as compared with a case where a normal piezoelectric element is driven. The flying droplet 1c adheres to an image recording medium (not shown) and recording is performed.

FIG. 9C shows an example in which the printing portions for one dot shown in FIG. 9A are arranged in one line in the main scanning direction. Basically, it is necessary to determine the interval between the cylindrical ink tubes according to the resolution required for performing image recording. However, as described with reference to FIG. By arranging them in a row, each row may be arranged in one row at a pitch wider than the resolution required for image recording.

FIG. 10 is a modification of the first embodiment described with reference to FIG. In the figure, the same parts as those in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted. In the first embodiment, the piezoelectric element is wound in a cylindrical shape. In this modified example, the piezoelectric element is mounted in a beam shape on a part of the wall surface in the tube. That is, as shown in FIG. 10A, an ink tube having a rectangular cross section was formed on the ink support 21, the acoustic transducer 3 was provided at the bottom thereof, and the piezoelectric element 24 was provided on the side wall. The piezoelectric elements 24 may be provided on four side walls, or may be provided partially, for example, on one side wall. In FIG. 10, the piezoelectric element 24 is provided only on one surface. Also in this case, by supplying a print signal to the piezoelectric element 24 in a state where the liquid column 1b is formed by driving the acoustic transducer 3, the volume in the ink tube is reduced as shown in FIG. The ink in the ink tube expands toward the free surface of the ink. As a result, the liquid column top can be made into a droplet, and the droplet 1c can be made to fly to an image recording medium (not shown).

FIG. 11 is an explanatory view of a second embodiment of the external force applying means for applying an external force to the formed liquid column. In the figure,
Parts similar to those in FIG. 9 are denoted by the same reference numerals, and description thereof is omitted. 25 is a heating element, 26 is a direction regulating member, 27 is a bubble, and 28 is an ink tube. In this embodiment, a bubble generated by driving the heating element 25 as an external force means is used, and a pressure change due to bubble growth is used. The heating element 25 generates heat by receiving an electric signal, and is based on the same principle as a bubble jet type ink jet recording head.

As shown in FIG. 11A, an ink tube 28 is formed in a space provided in the ink support 21, and an acoustic transducer 3 is provided at the bottom thereof. A ring-shaped heating element 25 is provided on the side of the upper part of the ink tube 28 so as to surround the ink tube 28, and a direction regulating member 26 for regulating the growth direction of bubbles generated above the ring-shaped heating element 25 is provided. Column 1 by pressure change due to
An external force is applied to b.

As shown in FIG. 11B, the heating element 25
Is supplied with a print signal, the ink in contact with the surface of the heating element 25 is vaporized, and a bubble (bubble) 27 is generated. This phenomenon is the same as the phenomenon applied to a general bubble jet type ink jet recording head. In this embodiment, the cylindrical ink tube 28 is provided, and the acoustic transducer 3 is provided at the bottom. However, the ink tube 28 is provided only for irradiating the ultrasonic wave to the ink free surface. Yes, not a particularly required configuration. A print signal is given to the heating element 25, and the growth direction of the generated bubble 27 is directed to the top of the liquid column 1b by the direction regulating member 26, so that the droplet is efficiently formed from the top of the liquid column 1b. The droplet 1c can be made to fly toward an image recording medium (not shown) to form an image. The heating element 25 is not limited to a structure attached to the upper part of the ink tube 28 in a ring shape as shown in FIG. 11, but may be attached to a part of the upper surface of the ink tube 28.

FIG. 12 is an explanatory view of a third embodiment of the external force applying means for applying an external force to the formed liquid column. In the figure,
9 and 11 are denoted by the same reference numerals and description thereof is omitted. 29 is a photothermal conversion layer. In this example,
An external force is applied using bubbles generated by heat. As shown in FIG. 12A, a light-to-heat conversion layer 29 is provided so as to be in contact with the side wall of the rectangular tubular ink tube 28. In addition, the ink support 2 on the photoelectric conversion layer 28 side
1 is formed of a transparent material so as to transmit light. The light-to-heat conversion layer 29 used in this embodiment is, for example, several μm.
Although it is formed of a thin aluminum layer having a thickness of m to several tens of μm, any material may be used as long as the light receiving portion absorbs light and generates heat.

As shown in FIG. 12B, the point of the photothermal conversion layer 29 irradiated with light from the outside absorbs light and rapidly generates heat. Due to the heat generation, bubbles 27 are generated at the interface between the light-to-heat conversion layer 29 and the ink as shown in FIG. This causes the ink in the ink tube to move toward the free ink surface. As a result, the top of the liquid column 1b is turned into droplets,
The droplet 1c can be caused to fly onto an image recording medium (not shown).

FIG. 13 is an explanatory view of a fourth embodiment of the external force applying means for applying an external force to the formed liquid column. In the figure,
The same parts as those in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted. 30 is an acoustic transducer. In this example, as shown in FIG. 13A, two types of acoustic transducers were used. Among the two types of acoustic transducers, the acoustic transducer 3 is for forming a liquid column, and the acoustic transducer 30 is used as an external force applying means. In the illustrated configuration, the upper side is an external force applying unit, and the lower side is for forming a liquid column. However, the configuration may be upside down. The frequency at which the acoustic transducer 3 for forming the liquid column is driven does not need to match the frequency of the acoustic transducer 30 used as external force applying means.
Usually, the frequency is lower than the frequency of the acoustic transducer used as the external force applying means. Since the acoustic transducer 30 used for the external force applying means performs printing once using several high frequency pulses, the frequency at which the acoustic transducer 30 of the external force applying means is driven with respect to the application time of the print signal It is necessary to set the period to be sufficiently short, and several MH
Used at high frequencies from z to several tens of MHz. If the frequency of the high-frequency power source that drives the acoustic transducer 3 that always forms a liquid column and the frequency of the print signal that drives the acoustic transducer 30 that is driven to apply an external force are set to be the same frequency, the sound for forming the liquid column The frequency of the high frequency power supply for driving the transducer 3 is also high.
Of course, such driving may be performed, but power consumption is increased. Therefore, from the viewpoint of energy efficiency, the acoustic transducer 3 as the external force applying means
It is desirable to drive at a high frequency and set the acoustic transducer for forming the liquid column to the low frequency side.

As shown in FIG. 13B, by giving a print signal to the acoustic transducer 30, the acoustic wave radiated by the acoustic transducer 30 is different from the acoustic wave radiated into the ink tube by the acoustic transducer 3. In addition, the liquid drop 1c extends from the tip of the liquid column 1b.
Can be caused to fly to an image recording medium (not shown).

FIG. 14 is an explanatory view of a fifth embodiment of the external force applying means for applying an external force to the formed liquid column. In the figure,
The same parts as those in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted. In this example, as shown in FIG. 14A, one type of acoustic transducer was used. This corresponds to a case where the two types of acoustic transducers described in FIG. 13 are combined into one acoustic transducer. A drive signal for forming a liquid column and a drive signal based on a print signal are superimposed and given to one acoustic transducer 3, but the two drive signals have different frequencies. That is, one acoustic transducer 3 is driven at two different frequencies. As shown in FIG. 14C, the acoustic transducer 3 is constantly driven by a driving signal for forming a liquid column. The print signal is superimposed on the driving signal for forming the liquid column as shown in FIG. 14D, and causes the droplet 1c to fly onto an image recording medium (not shown) as shown in FIG.

As described above, in order to use two frequencies, it is preferable to use the acoustic transducer 3 having two resonance peak frequencies in impedance characteristics. By using a drive signal having a frequency that matches the resonance frequency, the acoustic transducer 3 can efficiently generate ultrasonic waves. Of the two resonance peak frequencies, the lower frequency side is used for forming a liquid column, and the higher frequency side is used for external force applying means. Thereby, it is possible to obtain substantially the same result as that of the fourth embodiment described with reference to FIG.

FIG. 15 is an explanatory view of a sixth embodiment of the external force applying means for applying an external force to the formed liquid column. In the figure,
The same parts as those in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted. 15 is an image recording medium, 31 and 32 are electrodes, and 33 is a print signal. In this embodiment, an electrostatic attraction force is used as the external force applying means. As shown in FIG. 15A, the surface of the top plate 22 supporting the ink is flush with the surface of the top plate 22.
One electrode 31 is arranged on the ink support 21 and the recording medium 1 conveyed to a position facing the free ink surface 1a.
5, the other electrode 32 is arranged on the back surface side, and a print signal 33 is applied between the two electrodes to form an electric field, thereby giving an electric charge to the liquid column 1b formed on the free ink surface. I have. The electrode 31 on the ink support 21 side used here may be ring-shaped or may be separated symmetrically. The electrodes 32 arranged on the back side of the image recording medium 15 are arranged independently for each printing section, and are arranged so as to be paired with the electrodes 31 on the ink support 21 side. One electrode may be provided commonly to a plurality of printing units.

As shown in FIG. 15B, the print signal 33
Is applied between the electrodes 31, 32, the ink support 21
If the electrode 31 on the side is a negative electrode, a positive charge accumulates below the ink in contact with the negative electrode. Conversely,-charges accumulate on the ink free surface side, and-charges on the top of the liquid column 1b are sucked toward the + electrode disposed on the back side of the image recording medium 15, and the ink on the top of the liquid column 1b is Fly over the image forming medium 15. The print signal disappears, the electric field between the two electrodes is eliminated, and the liquid column 1b extended by the external force toward the image recording medium becomes a liquid column of the original height formed by the acoustic transducer 3 due to the ink surface tension. Return.

FIG. 16 is an explanatory view of a seventh embodiment of the external force applying means for applying an external force to the formed liquid column. In the figure,
Parts similar to those in FIG. 15 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the basic configuration shown in FIG. 16A is the same as that of the sixth embodiment described with reference to FIG.

When the print signal shown in FIG. 16B is applied, the top of the liquid column 1b is extended by the electrostatic attraction force, but is adhered to the image recording medium 15 as a liquid column without forming a liquid droplet. . This can be realized by adjusting the height of the liquid column 1b constantly formed by the acoustic transducer 3, the height of the image recording medium 15, and the like.

When the print signal is extinguished and the electric field between both electrodes is eliminated, as shown in FIG.
The liquid column 1b extended by the external force in the direction of 5 returns due to the surface tension of the ink.
5 and the liquid column 1b is cut off. The cut liquid column 1b returns to the original liquid column 1b formed by the acoustic transducer 3.

The method of adding the leading end of the liquid column to the image recording medium without forming droplets as in this embodiment is not limited to the seventh embodiment, but can be applied to the above-described embodiments. Therefore, "moving" in the claims means that the tip of the liquid column is formed into droplets and attached to the image recording medium, or that the tip of the liquid column is attached to the image recording medium and then cut. Is included.

In a general nozzleless ink jet recording apparatus using an ultrasonic beam, as shown in FIG. 3, an ultrasonic transducer irradiates a free liquid surface with a short duration by an acoustic transducer in one ink ejection, as shown in FIG. The droplet is caused to fly by cutting off a constricted portion at the top of the liquid column when the liquid column is instantaneously formed. In this case, in order to make the droplet fly, it is necessary to give a certain or more ultrasonic power. Otherwise, a liquid column is formed, but the droplet does not fly.

FIG. 17 shows a periodic view for forming a liquid column.
Of Acoustic Transducer when Ultrasonic Wave Is Irradiated
It is a conceptual diagram of a method. Fig. 17 shows an acoustic transducer
(A) As intermittently driven as shown in FIG.
Periodically irradiates the printed portion on the free surface of the ink
You. That is, the period T as shown in FIG._ABecome
As shown in FIG. 17A, the pulse voltage is applied for a period T._on
Only for the period T_offIndicates pulse-like voltage
Do not add. Such a period T_onAcoustic transformer
Drive and period T_offDrive stop repeatedly in
As a result, ultrasonic waves are periodically generated. Then, FIG.
As shown in (C), the radiation pressure is equal to the period T._on, T _offAccording to
To the printing portion of the ink free surface periodically. here
If the frequency at which ultrasonic waves are periodically generated is f, the frequency
The wave number f is f = 1 / (T_on+ T_off). Ma
Further, the drive voltage frequency for generating ultrasonic waves is f_AToss
Then, the driving voltage frequency f_AIs f_A= 1 / T_AWith
available.

FIGS. 18 to 20 are explanatory views schematically showing the relationship between the frequency f and the state of the liquid surface when irradiating ultrasonic waves periodically. FIGS. 18 to 20 show the behavior of the liquid level in the printing unit when the frequency f at which the above-described ultrasonic waves are periodically generated is set to different values. First, the behavior of the liquid surface when the frequency f is small is considered in FIG. The voltage waveform applied to the acoustic transducer at this time is shown in FIG. When the frequency f is small, when the ultrasonic wave is turned on, the liquid column is once formed at a stable height as shown in FIG. However, when the ultrasonic wave is turned off in this state, the liquid surface tries to return to the height of the stationary state by the action of surface tension and gravity. Further, due to the inertial force, a depression is once formed on the liquid surface as shown in FIG. Ultrasonic on / off
When f is repeated, the liquid column shown in FIG.
The depression shown in FIG. 3C is formed repeatedly. for that reason,
As shown by a solid line and a broken line in FIG. 18D, the liquid level of the printing portion vibrates between two heights.

As shown in FIG. 19A, when the frequency f is increased to some extent, when the ultrasonic wave is turned on, the liquid column starts to form, but before the ultrasonic wave is formed to a sufficient height, the ultrasonic wave is turned off. State, and the liquid column starts to fall. Therefore, FIG.
As shown in (B), the height of the liquid column when the ultrasonic wave is on is slightly lower than in the case of FIG. 18 (B). Further, although the liquid column is lowered by the ultrasonic wave being turned off, the liquid column is turned on again before the height of the liquid column is sufficiently lowered, and the height of the liquid column starts to increase. As a result, as shown in FIG. 19C, even when the ultrasonic waves are off, some liquid columns are formed. Therefore, the liquid column is always formed, but is not stable, and vibrates at a constant amplitude as shown by a solid line and a broken line in FIG.

As shown in FIG. 20A, the frequency f
Is gradually increased, the amplitude of the vibration of the liquid column gradually decreases, and when the frequency f exceeds a certain level (about 1000 Hz), the ultrasonic wave is turned on as shown in FIGS. A liquid column whose height does not change between the time of the off and the time of the off is formed. Therefore, the liquid column is stabilized at a constant height as shown in FIG. In this manner, the liquid column having a constant height can be formed by irradiating the printing portion on the free surface of the ink periodically with the ultrasonic wave from the acoustic transducer.

As a method of driving an acoustic transducer for forming a liquid column by the method of periodically irradiating ultrasonic waves shown in FIG. 17A, a driving voltage frequency for generating ultrasonic waves is used. f _A and
The drive voltage amplitude may be set to such a value that a liquid column can be formed and droplets are not formed. In addition, the frequency f at which ultrasonic waves are periodically generated is set to a value at which a stable liquid column can be formed. Usually, the frequency f and the drive voltage frequency f _A are f << f _A
Have a relationship. Time T _off of the ultrasonic wave in one period of time T _on and off to on may be the same length, but may be in a different length. Further, time T
By adjusting the ratio of _on and _Toff , the height of the stable liquid column can be changed.

FIG. 21 is a diagram showing the relationship between the influence of the wave propagating on the free surface of the ink and the height of the liquid column. This indicates how much the propagating wave oscillates the liquid column. The vertical axis indicates the fluctuation amount of the liquid surface of the printing unit, and the horizontal axis indicates the height of the liquid column that is always formed. The case where the liquid column height is 0 is a conventional one in which the liquid column is not always formed. The fluctuation amount becomes smaller as the liquid column becomes higher. However, when the height exceeds a certain height, the fluctuation amount becomes large, which indicates that when the liquid column is made too high and high energy is applied, the fluctuation becomes unstable as described with reference to FIG. .

As described above, in the present invention, the liquid column forming means for constantly forming the liquid column is used. In an example of the liquid column forming means, a bulge as a liquid column is provided on the free ink surface by applying an ultrasonic radiation pressure to the free ink surface from within the liquid, and the ink is moved from the liquid column to the image recording medium according to a print signal. The configuration is such that The ultrasonic radiation pressure is applied independently to each printing unit. Therefore, the liquid column formed on the free surface of the ink is formed by the radiation pressure given from one ultrasonic generation source, and the influence of the wave rushing from the other printing part is affected by the radiation pressure from the liquid and the liquid surface. Reduced by swelling. Also, the force (energy) required to move the ink from the liquid column to the image recording medium
May be smaller than before because it is given in advance by radiation pressure. Therefore, the force of the waves coming from the other printing units is weaker than before, and the mutual interference of the printing units is further reduced. The fact that the force for moving the ink in accordance with the print data may be smaller than in the prior art means that the residual vibration remaining in the printing unit after printing is also weakened, so that the above two problems can be solved at once. It is also possible to produce higher effects by combining the present invention with a conventional residual vibration control method.

[0064]

As is apparent from the above description, according to the present invention, when printing is performed by an ink jet printer or the like having a nozzleless configuration, the problem of mutual interference occurring between adjacent printing units and the residual vibration after printing are reduced. It is possible to provide a high-speed ink recording apparatus that has the effect of suppressing the printing, does not provide a time delay for each printing, and can perform stable printing.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is an explanatory view of formation of a liquid column.

FIG. 3 is a schematic explanatory view of a conventional nozzleless type ink jet recording apparatus using an ultrasonic beam.

FIG. 4 is a schematic explanatory view of a nozzleless ink recording apparatus of the present invention using an ultrasonic beam.

FIG. 5 is a graph showing an example of the relationship between the energy of external force and the vibration amplitude and vibration time of the liquid surface.

FIG. 6 is a schematic configuration diagram illustrating an example of an embodiment of an ink recording apparatus according to the invention.

FIG. 7 is an explanatory diagram of another method of forming a liquid column in the recording head described in FIG.

FIG. 8 is a diagram illustrating an example of the configuration of a printing unit according to the present invention.

FIG. 9 is an explanatory view of a first embodiment of an external force applying means for applying an external force to the formed liquid column.

FIG. 10 is a modification of the first embodiment described with reference to FIG.

FIG. 11 is an explanatory view of a second embodiment of the external force applying means for applying an external force to the formed liquid column.

FIG. 12 is an explanatory view of a third embodiment of an external force applying means for applying an external force to the formed liquid column.

FIG. 13 is an explanatory view of a fourth embodiment of an external force applying means for applying an external force to the formed liquid column.

FIG. 14 is an explanatory view of a fifth embodiment of the external force applying means for applying an external force to the formed liquid column.

FIG. 15 is an explanatory view of a sixth embodiment of the external force applying means for applying an external force to the formed liquid column.

FIG. 16 is an explanatory view of a seventh embodiment of the external force applying means for applying an external force to the formed liquid column.

FIG. 17 is a conceptual diagram of a method of driving an acoustic transducer when periodically irradiating ultrasonic waves to form a liquid column.

FIG. 18 is an explanatory view schematically showing a voltage waveform and a state of a liquid level when a frequency f when periodically irradiating an ultrasonic wave is small.

FIG. 19 is an explanatory view schematically showing a voltage waveform and a state of a liquid level when a frequency f when periodically irradiating an ultrasonic wave is higher than that in FIG. 18;

FIG. 20 is an explanatory diagram schematically showing a voltage waveform and a state of a liquid level when a frequency f when periodically irradiating an ultrasonic wave is higher than that in FIG. 19;

FIG. 21 is a diagram showing the relationship between the effect of waves propagating on the free surface of the ink and the height of the liquid column.

[Explanation of symbols]

1 ... ink, 1a ... ink free surface, 1b ... liquid column, 1c
... droplets, 2 ... substrates, 3 ... acoustic transducers, 4 ... high-frequency power supplies, 5 ... acoustic waves, 10, 11, 12, 13, 14
... recording head, 10a ... liquid column forming means, 15 ... image recording medium, 21 ... ink support, 22 ... top plate, 23 ... opening, 24 ... piezoelectric element, 25 ... heating element, 26 ... direction regulating member, 27 ... bubbles, 28 ... ink tubes, 29 ... photothermal conversion layers, 30 ... acoustic transducers, 31, 32 ... electrodes,
33 ... Print signal.

Claims (14)

[Claims] (1) moving ink from an ink free surface;
In an ink recording apparatus for performing printing on an image recording medium located at a position opposed to an ink free surface, a liquid column forming means for forming a liquid column maintaining a constant height in a printing portion of the ink free surface, and the liquid column An ink recording apparatus, further comprising a moving unit for moving ink to the image recording medium. 2. The ink recording apparatus according to claim 1, wherein an acoustic transducer provided independently for each printing unit is used as the liquid column forming unit. 3. The ink recording apparatus according to claim 1, wherein a piezoelectric element provided separately from the liquid column forming means and a driving means for driving the piezoelectric element are used as the moving means. 4. The ink recording apparatus according to claim 1, wherein a heating element provided separately from the liquid column forming means and a driving means for driving the heating element are used as the moving means. 5. The ink recording apparatus according to claim 1, wherein an acoustic transducer provided separately from the liquid column forming means and a driving means for the acoustic transducer are used as the moving means. 6. An acoustic transducer in which an image recording signal is superimposed on a drive signal for forming a liquid column, using the same acoustic transducer as the liquid column forming means as the moving unit. 3. The ink recording apparatus according to claim 2, wherein the ink recording apparatus drives the image recording apparatus. 7. The method according to claim 1, wherein the moving means includes an electrostatic force generating means for applying an electrostatic attraction force to the image recording medium, and a driving means for driving the electrostatic force generating means. The ink recording device according to claim 1. 8. Moving ink from the free ink surface,
In an ink recording method for performing printing on an image recording medium located at a position opposed to an ink free surface, a liquid column that maintains a constant height is formed in a printing portion of the ink free surface, and ink is applied to the image from the liquid column. An ink recording method characterized by moving the recording medium to a recording medium. 9. The ink recording method according to claim 8, wherein an acoustic transducer for forming the liquid column is provided independently for each printing unit. 10. The ink recording method according to claim 8, wherein the ink is moved from the liquid column to the image recording medium by utilizing a pressure change generated by driving a piezoelectric element. . 11. The image forming apparatus according to claim 8, wherein a heat generating mechanism is disposed, and the ink is moved from the liquid column to the image recording medium by using a pressure received from a bubble generated in the ink liquid. The ink recording method described in the above. 12. The ink recording method according to claim 9, wherein the ink is moved from the liquid column to the image recording medium by driving an acoustic transducer different from the acoustic transducer. 13. The method according to claim 13, wherein another image recording signal is superimposed on a driving signal for forming a liquid column applied to the acoustic transducer, thereby moving ink from the liquid column to the image recording medium. Claim 9
3. The ink recording method according to item 1. 14. The ink recording method according to claim 8, wherein an electrostatic attraction force is generated to move the ink from the liquid column to the image recording medium.