JPH07101058A - Inkjet head - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain an inkjet head having high density, high responsiveness, and stable printing. [Structure] (110) Multiple pressure chambers 1 in a silicon substrate
01 and a nozzle communication path 121 that is narrower in width than the pressure chamber 101 and connected to the pressure chamber 101, improves the dischargeability of bubbles accumulated in the pressure chamber 101.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a nozzle for ejecting ink, a pressure chamber communicating with the nozzle for applying a pressure to the ink, and a pressure generating means, and the nozzle is controlled by a driving voltage applied to the pressure generating means. The present invention relates to an on-demand type inkjet head that ejects more ink.

[0002]

2. Description of the Related Art In recent years, as demands for high-speed, high-density, low-cost inkjet printers have increased, various methods have been considered to realize them.
A method using a photosensitive resin, a method using anisotropic etching of a silicon substrate, and the like, which are found in Japanese Patent Publications and the like, are known.

An ink jet head having a flow path formed of a silicon substrate is shown in FIG.
No. 09 publication is known, and a (100) silicon substrate is used in this example.

As an example of an ink jet head using a (110) silicon substrate, "KEP" shown in FIG.
etersen, `Fabrication of anIntegrated, PlanarSilicon
Ink-Jet Structure, 'IEEE transactions onelectronde
vices, vol.ED-26, No.12, December 1979 "are known.

[0005]

However, the above-mentioned prior art has the following problems.

First of all, in the method using resin injection molding and the method using a photosensitive resin described in Japanese Patent Publication No. 4-15095, the releasability in injection molding and the shape accuracy in photosensitive resin are improved. In order to secure the pattern, the pattern cannot be made too deep and the flow path resistance increases, which deteriorates the responsiveness.In addition, the denser the flow path becomes, the more rigid the side wall between the pressure chambers becomes due to the pressure of the adjacent pressure chambers. Deformation occurs due to insufficient pressure, and the member that seals the pressure chamber also bends, causing crosstalk. Furthermore, since the side wall of the pressure chamber formed of the photosensitive resin has poor wettability, the ability to discharge bubbles in the flow path is impaired, resulting in ejection failure.

Further, in the case of using the (100) silicon substrate 61 described in Japanese Patent Publication No. 58-40509, the (111) plane appearing as a result of etching is (100).
Since it has an inclination with respect to the surface, the depth cannot be more than a certain ratio with respect to the pattern width, so that it has a trapezoidal or triangular cross-sectional shape as shown in FIG. Therefore, by arranging multiple channels in high density, the depth becomes shallow,
Similar to the above, high responsiveness cannot be obtained.

Further, in the case of a so-called face eject type head having a flat plate having nozzles arranged on one surface of the substrate and ejecting ink by changing the volume of the pressure chamber by the electromechanical converting means from the back surface of the substrate, FIG. It is difficult to arrange the electromechanical conversion means in the pressure chamber 62 having a trapezoidal or triangular cross section as shown in FIG.

On the other hand, as shown in the example of FIG. 12, (110)
Anisotropic etching with the silicon substrate 71 can produce a deep pattern, so that the flow path resistance can be reduced even if the width is narrow.
Even if a plurality of pressure chambers are arranged at a high density, a high response is easily obtained. However, in this example, the ink supply passage 72 is formed by a separate member, and the cross-sectional area and the length of the supply passage 72 depend on the positional accuracy of bonding. However, in order to stabilize the ejection characteristics by accurately narrowing the supply path, which is generally performed, a high-level assembly technique is required. In addition, a step is formed at the connecting portion between the pressure chamber 73 and the supply passage 72, which impairs the ability to discharge bubbles in the passage, which causes defective ejection.

Further, in the example of FIG. 12, a bimorph using a piezoelectric element 74 is used as the pressure generating means, but when the width of the pressure chamber 73 becomes smaller, sufficient displacement cannot be obtained, so the pressure chambers are arranged at a high density. I can't.

The present invention solves the above problems in view of such a situation, and an object of the present invention is to enable stable printing without causing defective printing due to bubble entrainment and crosstalk. It is an object to provide an ink jet head that is easy to use, has high density, and has high responsiveness at low cost.

[0012]

The ink jet head of the present invention is an ink jet head having a plurality of pressure chambers, one end of which communicates with an ink reservoir through an ink supply passage and the other end of which communicates with an ink droplet discharge nozzle. (11
0) In the silicon substrate, the plurality of pressure chambers, which are partitioned by side walls having (111) planes perpendicular to the surface of the (110) silicon substrate as wall surfaces, are connected to one end portion of the pressure chambers. A nozzle communication passage having a width narrower than the pressure chamber, the nozzle communication passage and the pressure chamber being sealed, and the ink droplet ejection nozzle formed on a nozzle forming substrate that is bonded to the silicon substrate, The pressure chamber and one of the side walls of the nozzle communication passage are opened in the communication passage, and a common (111) formed in the silicon substrate.
The surface is a wall surface, and one of the side walls of the ink supply passage formed in the silicon substrate has a (111) surface that is not common to the nozzle communication passage of the pressure chamber as a common wall surface. .

Alternatively, in an ink jet head having a plurality of pressure chambers, one end of which communicates with an ink reservoir through an ink supply path and the other end of which communicates with an ink droplet discharge nozzle, the pressure chambers are formed in a (110) silicon substrate. Is formed on a (111) plane perpendicular to the surface of the (110) silicon substrate as a wall surface, and the ink droplet ejection nozzle is formed on a nozzle forming substrate that seals the pressure chamber and joins the silicon substrate. The ink droplet ejection nozzle is opened at the acute angle side formed by the two wall surfaces at one end of the pressure chamber with respect to the central axis of the pressure chamber, and the acute angle is formed at one end of the pressure chamber. It is characterized in that the two side walls that form the (1) face have a (111) plane that is not common to the ink supply passage.

[0014]

EXAMPLES The structure of the ink jet head of the present invention will be described in detail below with reference to examples.

FIG. 1 shows an ink jet head of one embodiment of the present invention, FIG. 2 is a sectional view of FIG. 1, and FIG. 1 is a (110) silicon substrate,
The side walls of the pressure chamber 101, the supply path 102, and the ink reservoir 103 are formed by anisotropic etching from both sides. The formation shape of the pressure chamber is substantially a parallelogram when viewed from the (110) plane. In order to improve the wettability, improve the bubble discharging property, and improve the ink resistance, after the pattern formation, thermal oxidation treatment is performed.

Pressure chambers 101 are provided on both sides of the silicon substrate 1.
Nozzle plate 2 having a nozzle 201 corresponding to
Are bonded, and the piezoelectric element 4 is attached to the back surface of the vibration plate 3 at the position of each pressure chamber 101. The nozzle plate 2 is a metal plate having a thickness of 0.1 mm and a nozzle 201 having a diameter of 40 μm.
Is provided. The opposite side of the piezoelectric element 4 from the vibration plate 3 is bonded to the block 5 at a portion shown by a wavy line A, while the block 5 is shown near the supply path 102 which is a free end of the cantilever structure shown by a wavy line D in the vicinity of the vibration plate. It is glued to 3. The vibrating plate 3 is extremely thin from the supply path 102 to the pressure chamber 101 as shown in FIG. 2, and since the silicon substrate 1 also has a cantilever structure at this portion, it is damaged by the force of the piezoelectric element 4. It is possible to effectively reinforce the vibrating plate 3, the silicon substrate 1 and the nozzle plate 2 by bending the block 5 at this portion. It is more preferable to fix the block 5 and the diaphragm 3 near the nozzle 201. The vibrating plate 3 is provided with a protrusion 301 for each pressure chamber 101, so that the displacement of the piezoelectric element 4 is effective.
A volume change within 01 is generated.

FIG. 3 shows a nozzle 201 in the pressure chamber 101.
It is a perspective view which showed the position of with the dotted line. In this embodiment, the nozzle is provided in the vicinity of a tangent line E where two side walls of the pressure chamber 101 are in contact with each other, which are indicated by surfaces F and G. Since the surface F and the surface G are in contact with each other at an acute angle, bubbles near the tangent line E are caught on both side walls of the surface F and the surface G and are very difficult to escape. Therefore, in this embodiment, as shown in FIG. 3, the nozzle 121 is arranged at a position where the outer edge of the nozzle is substantially in contact with the surfaces F and G,
The distance between the tangent line E and the nozzle is shortened, and the bubbles are easily discharged from the nozzle by smoothly flowing the ink along the tangent line E by the pressure at the time of suction or ejection from the nozzle 121. The bubbles were effectively discharged when the shortest distance between the surfaces F and G and the outer edge of the nozzle was within 50 μm.

On the contrary, the nozzle 121 is placed at the position shown in FIG.
When the bubble is provided, the bubble in the portion E has a long distance from the nozzle and the ink flow vortex is swirled in the portion H in the figure, so that the bubble is easily drawn from the nozzle 121 and is difficult to be discharged. Since bubbles existing in the pressure chamber 101 cause ejection failure, it is necessary to increase the number of cleaning operations (bubble discharging operation by suction from the nozzle direction) per print amount, which also affects the printing speed. Further, when the pressure is applied, the ink that bounces off on the side wall near E causes turbulence in the ink flow in the pressure chamber, making the ink meniscus in the nozzle unstable, making it difficult to improve responsiveness. In the present embodiment, by disposing the nozzle in the vicinity of the side wall where air bubbles are likely to accumulate, the above-mentioned adverse effect could be eliminated.

A supply path 102 is formed at one end facing the nozzle. The supply passage 102 has a width smaller than that of the pressure chamber 103 to increase the flow passage resistance, and sends the ink to the nozzle 201 side communicating with the diagonal of the parallelogram-like pressure chamber. At the same time, the outflow to the ink reservoir 103 is also reduced to prevent the influence (crosstalk) on other nozzles through the ink reservoir. As shown in FIG. 3, the supply path 102 is arranged at a position where the surface I and the surface J of the pressure chamber 101 are originally in contact with each other at an acute angle so as to improve the bubble discharging property, and shares one continuous (111) surface I. Was set up. If it is not provided at the above-mentioned position, an acute angle portion formed by the surfaces I and J of the two side walls will form a portion where bubbles are easily caught. Further, the supply passage 102 and the nozzle 201 are connected to the pressure chamber 1.
Since the ink droplet ejection pressure due to the volume change of the pressure chamber is propagated to the nozzle along the side wall by arranging them in the positions separated from each other in 01, the ink flow in the pressure chamber becomes smooth and stable to the nozzle. Ink supply is possible.

In the present embodiment, the nozzle plate 2 is formed by pressing a nozzle 201 on a metal plate and the nozzle plate 2 and the silicon substrate 1 are adhered to each other. However, the nozzle plate 2 may be formed of glass and joined by anodic bonding. Alternatively, the nozzle plate 2 may be formed of a (100) silicon substrate and diffusion bonded. Since the rigidity of the nozzle plate is improved, it is also effective in suppressing crosstalk. It is also possible to widen the nozzle entrance shape in accordance with the shape of the pressure chamber to further obtain bubble discharging property and discharge stability.

The diaphragm 3 is made by electroforming nickel,
The thickness of the pressure chamber 101 portion around the protrusion 301 of the diaphragm 3 is 2
The thickness of the other portions and the protrusions 301 was 20 μm. The diaphragm may be formed by etching metal foil on a resin foil such as polyimide to form protrusions.

The ink is supplied from the pipe 6 to the block 5 through the through hole 7, the supply port 8, the ink reservoir 103, and the supply path 1.
02, is supplied to the pressure chamber 101.

Next, the ink droplet ejection operation will be briefly described with reference to FIG. When a voltage is applied to the piezoelectric element 4 whose one end is fixed to the block 5 in a state where the pressure chamber 101 is filled with ink, the piezoelectric element 4 contracts in the direction of arrow B, and the other end of the piezoelectric element 4 is bonded to the vibrating plate 3. The part corresponding to the pressure chamber 101 is pulled to increase the volume of the pressure chamber 101. Although the piezoelectric element 4 is directly fixed to the block 5 in this embodiment, it may be fixed via another member therebetween. At this time, the ink forms a meniscus at the nozzle 201, and the ink is supplied from the ink reservoir 103 in order to counter the force drawn by the increase in the volume of the pressure chamber 101 due to the surface tension. Then, by rapidly discharging the charged electric charge of the piezoelectric element 4, the volume of the pressure chamber 101 is decreased, and ink is ejected from the nozzle 201. At this time, the pressure inside the pressure chamber 101 is said to be about 1 to 3 atm depending on the conditions. In the head having such a structure, when the flow path and the support portion of the nozzle plate are formed of resin or the like. Since the rigidity is low, the partition wall with the adjacent pressure chamber 101 is bent by this pressure, the entire flow path is deformed in the thickness direction, the amount of ejected ink is reduced, and the nozzle 201 not performing another ejecting operation So-called crosstalk may occur in which ejection occurs. However, in the present invention, since the rigidity of silicon is much higher than that of resin or the like, such a situation is unlikely to occur, and the thickness of the silicon substrate is 5
The range of 0 μm or more and 0.5 mm or less is particularly effective.

Further, since the partition wall between the adjacent pressure chambers 101 has a cantilever structure, both surfaces of the partition wall having low rigidity are fixed by the nozzle plate 2 and the vibration plate 3, and further reinforced by the block 5 as described above. Therefore, it has sufficient strength. Moreover, since the material itself is fragile silicon and has elasticity in a cantilever structure, there is an effect of mitigating thermal stress due to a difference in thermal expansion coefficient between the nozzle plate 2, the diaphragm 3 and the block 5 and cracking due to impact.

In the present embodiment, a silicon substrate 1 having a thickness of 0.2 mm is used, and a pressure chamber 101 having a width of 0.1 mm is set to 0.1 mm.
Arranged at a pitch of 141 mm, a response frequency of 7 kHz was achieved. Since the supply passage 102 and the pressure chamber 101 are formed at the same time in one component, the shape accuracy, which is an advantage of silicon etching, can be utilized, and the variation in characteristics between the flow paths and the variation between lots can be reduced. did it. Furthermore, since the pattern penetrates all the layers and the etching rate is slow, the permissible range of condition variation in the etching process is wide, and a very stable quality can be secured. Further, the depth of the flow path from the ink reservoir 103 to the pressure chamber 101 is the same, there is no step, and since the nozzle position is taken into consideration, the bubble discharging property is particularly excellent.

In this embodiment, the direction in which the piezoelectric element 4 expands and contracts when an electric field is applied is set to be substantially perpendicular to the wafer surface.
For example, when using a bimorph as shown in FIG.
When the pressure chambers 101 are arranged at a density higher than about 1 mm pitch, ink cannot be discharged because the volume of the pressure chambers 101 changes little. The arrangement of the piezoelectric elements performed in this embodiment can generate a large displacement even if the pressure chamber 101 has a small area due to a high density, so that the advantages of high precision and high density in the silicon substrate can be fully utilized. .

FIG. 5 shows an example of an ink jet head capable of printing with a higher density with a larger number of nozzles than the embodiment shown in FIG. Since the basic structure is similar to that of FIG. 1, only the pattern of the silicon substrate is shown here. All of these patterns are penetrating patterns surrounded by the (111) plane. In this embodiment, the supply path 102, the pressure chamber 101, and the nozzle (not shown) are set to 26 sets at a pitch of 0.141 mm and 0.0
Two rows were arranged with a shift of 7 mm.

The supply port 8 in the figure is a pattern of the silicon substrate 1.
It is not included in the list but is included for explanation. In both rows, a total of four groups, that is, the uppermost and lowermost groups in the figure, do not actually eject ink, and the partition wall between the pressure chamber 101 and the adjacent pressure chamber is in the same state so that the ejection characteristics are aligned. The group is installed for the purpose of positively allowing air bubbles mixed in the ink reservoir 103 to flow into other pressure chambers. With this configuration, an inkjet head having 360 dots per inch and 48 nozzles can be obtained. 3 inches (1
10) Since 30 main patterns can be taken at the same time from a silicon wafer, the etching time per piece and the material cost are very small, and it can be manufactured at low cost. Ink is supplied from the supply passage 8 to the ink reservoir 103 and each supply passage 1 as in the embodiment of FIG.
It is supplied to the pressure chamber 101 via 02.

In the figure, 9 and 10 are nozzle plates as shown in FIG.
This is a hole for inserting a positioning pin when assembling the diaphragm, block, etc. The portion of the wavy line C that is serrated is such that the pattern can be formed entirely on the (111) plane only, but in order to prevent air bubbles from being caught in this portion, it is serrated. The depth of the valley is 50
It is made to be less than μm.

By combining with the following embodiments, it is possible to further obtain the effect on the bubble discharging property. Another embodiment will be described below with reference to FIG.

FIG. 6 is a perspective view showing the main part of the ink jet head of this embodiment. The other basic structure is shown in FIG.
Since it is the same as, it is omitted here. In this embodiment, the width of the pressure chamber 101 is narrowed toward the nozzle to reduce the volume, and the nozzle communication path 121 is communicated with the nozzle 201 via the nozzle 201. Nozzle communication path 1
Since 21 is narrower than the pressure chambers in the pressure chamber arrangement direction, it is possible to guide the ink to the nozzle portion while increasing the ink flow velocity and pressure, and the ink flow velocity can be increased in the vicinity of the nozzle 201. The discharge efficiency has improved. At the same time, the ink stably flows in one direction along the side wall, so that the turbulence of the ink flow is reduced and the ejection can be stabilized. Furthermore, since the distance between the nozzle 201 and the tangent line between the surfaces where the bubbles are likely to accumulate is shortened, the bubble discharging property is improved. Furthermore, since the partition wall between the adjacent pressure chambers, which is the support portion around the nozzle, is made thicker and the rigidity of the support portion of the nozzle plate is increased, a greater effect is also obtained against crosstalk due to vibration of the partition wall and the nozzle plate. Has been obtained. In this structure, bubbles are likely to accumulate due to the protrusions shown in the L portion, and the accumulated bubbles are difficult to escape. Therefore, it is desirable to provide the step difference of 50 μm or less, ideally to eliminate the protrusion as shown in FIG. 7 and to provide the side wall of the nozzle communication passage 121 so as to share the (111) plane M plane of the side wall of the pressure chamber.

Similar effects can be obtained with the structure shown in FIG. In FIG. 8, the pressure around the supply passage 102 is dispersed by increasing the volume around the supply passage 102,
Ink can be prevented from flowing out to an ink reservoir (not shown) through the supply path 102. Therefore, the ink can be efficiently sent to the nozzle 201, the ejection efficiency can be improved, and the amount of the ink sent from the supply path 102 is reduced, which is also effective in suppressing crosstalk.

Further, in the structure shown in FIG. 9, the ink communication passage 121 is displaced from the center line in the longitudinal direction of the pressure chamber, and the area of the silicon surrounding the nozzle communication portion 121 and supporting the nozzle is increased, so that the adjacent nozzles are connected to each other. It is possible to reduce the influence and obtain a further effect on crosstalk.

As yet another embodiment, an embodiment of a so-called edge eject type ink jet head for horizontally ejecting ink from the silicon substrate surface will be described with reference to FIG. The shapes of the pressure chamber 101, the ink supply port 102, and the nozzle communication passage 121 are almost the same as those in the first embodiment, but the arrangement is changed so that the ink ejection surface is continuous (111).
The nozzle 201 is formed on the surface. The silicon substrate 1 is sandwiched between the diaphragm 3 and the canopy plate 12. In this structure, the bubbles remaining in the acute angle portion are easily removed like the above-described embodiment, and since the piezoelectric element is parallel to the printing surface, it is possible to obtain a head outer shape that is thinner in the ejection direction than before. it can. The nozzle can also be formed by etching a silicon substrate as described above.

Here, an example in which printing of 180 dots per inch is possible is shown, but two double-patterned silicon substrates are bonded to each other by shifting them by 70 μm in the nozzle array direction through a canopy plate, and thereby double density is achieved. An inkjet head capable of printing can be obtained, and high-speed printing of an image of 360 dots per inch is possible.

According to the present invention, the same effect can be obtained by a so-called thermal ink jet system in which the ink is instantaneously film-boiling by energizing the heating element and the ink is ejected by the pressure of the bubbles.

[0037]

EFFECT OF THE INVENTION Since the flow of ink from the supply passage to the pressure chamber is smooth, bubbles are less likely to collect, and bubbles are easily removed, the bubble discharge property is improved, and stable printing characteristics can be secured. Further, by increasing the rigidity around the nozzle, there is an effect that crosstalk caused by vibration of the side wall and the nozzle plate can be suppressed.

[Brief description of drawings]

FIG. 1 is a perspective view of an inkjet head according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the inkjet head according to the first embodiment of the present invention.

FIG. 3 is a perspective view showing a main part of the inkjet head according to the first embodiment of the present invention.

FIG. 4 is a perspective view showing a comparative example of the ink jet head of the first embodiment of the invention.

FIG. 5 is a plan view of an inkjet head according to a second embodiment of the present invention.

FIG. 6 is a perspective view showing a main part of an inkjet head according to a third embodiment of the present invention.

FIG. 7 is a perspective view showing a main part of an inkjet head according to a fourth embodiment of the present invention.

FIG. 8 is a perspective view showing a main part of an inkjet head according to a fifth embodiment of the present invention.

FIG. 9 is a perspective view showing a main part of an inkjet head according to a sixth embodiment of the present invention.

FIG. 10 is a perspective view of an inkjet head according to a sixth embodiment of the present invention.

FIG. 11 is a perspective view showing a configuration example of a flow path of a conventional inkjet head using a (100) silicon substrate.

FIG. 12 is a sectional view of a conventional inkjet head using a (110) silicon substrate.

[Explanation of symbols]

 1 (110) Silicon substrate 2 Nozzle plate 3 Vibration plate 101 Pressure chamber 121 Nozzle communication passage 201 Nozzle

Claims (5)

[Claims] 1. An ink jet head having a plurality of pressure chambers, one end of which communicates with an ink reservoir through an ink supply passage and the other end of which communicates with an ink droplet discharge nozzle.
10) A plurality of pressure chambers, which are partitioned by a side wall having a (111) plane perpendicular to the surface of the (110) silicon substrate as a wall surface, are connected to one end of the pressure chamber. A nozzle communication passage having a width narrower than the pressure chamber, the nozzle communication passage and the pressure chamber being sealed, and the ink droplet ejection nozzle formed on a nozzle forming substrate that is bonded to the silicon substrate, An inkjet head characterized by being opened in a communication path. 2. The ink jet head according to claim 1, wherein one of the side walls of the pressure chamber and the nozzle communication passage has a common (111) surface formed in the silicon substrate as a wall surface. . 3. The (111) plane that is not common to the nozzle communication passage of the pressure chamber has a common wall surface on one side wall of the ink supply path formed in the silicon substrate. 2. The inkjet head according to 2. 4. In an ink jet head having a plurality of pressure chambers, one end of which communicates with an ink reservoir through an ink supply path and the other end of which communicates with an ink droplet discharge nozzle, the pressure chambers being within a (110) silicon substrate. In this (11
0) The (111) plane perpendicular to the surface of the silicon substrate is formed as a wall surface, and the ink droplet ejection nozzle is formed on a nozzle forming substrate that seals the pressure chamber and is joined to the silicon substrate. An inkjet head characterized in that the discharge nozzle is opened on the acute angle side formed by the two wall surfaces at one end of the pressure chamber with respect to the central axis of the pressure chamber. 5. The two side walls forming an acute angle at one end of the pressure chamber are not common to the ink supply passage (11).
The ink jet head according to claim 4, wherein the surface 1) is a wall surface.