JP2001010050A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a thin film diaphragm having no pinhole defect by thinning the diaphragm by etching in an ink jet head having the diaphragm for forming a wall surface of a liquid chamber communicating with a nozzle for discharging an ink droplet. SOLUTION: In the ink jet head comprising a driving unit obtained by disposing a plurality of laminated piezoelectric elements in two rows in a row state, and a liquid chamber unit or the like, the liquid chamber unit is formed by sequentially laminating a diaphragm 31 thinned by etching, a liquid chamber partition wall member 32 of a two-layer structure formed of a photosensitive resin layer made of a dry film resist, and a nozzle plate 33 made of a metal plate and heat fusion bonding them. The diaphragm 31 has a thin-film diaphragm area 41, an island-like protrusion 42 formed at a center of the area 41 and connected to a piezoelectric element 12, a base connected to a frame member or the like. The portion 42 is connected to the element 12 by a photosensitive material 45.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head, and more particularly to an ink jet head using a diaphragm.

[0002]

2. Description of the Related Art An ink jet head in an ink jet recording apparatus used as an image forming apparatus (image recording apparatus) such as a printer, a facsimile, a copying machine, a plotter, etc. has a nozzle for discharging ink droplets and a discharge chamber ( A pressure chamber, a pressurized liquid chamber, a liquid chamber, an ink chamber, an ink flow path, etc.) and actuator means (energy generating means) for generating energy for pressurizing the ink in the discharge chamber. Driving the actuator means pressurizes the ink in the discharge chamber to discharge ink droplets from the nozzles. An ink-on-demand type that discharges ink droplets only when recording is necessary is the mainstream.

[0003] There are several types of actuators depending on the type of actuator means for ejecting ink droplets (recording liquid). For example, as described in Japanese Patent Application Laid-Open No. 10-100401, a part of the wall of the liquid chamber is formed as a thin diaphragm, and a piezoelectric element as an electromechanical conversion element is disposed corresponding to the thin diaphragm to apply voltage. A piezo system that discharges ink droplets by changing the pressure in the liquid chamber by deforming the diaphragm by deformation of the piezoelectric element that accompanies it. A heating element is arranged inside the liquid chamber, and a heating element is energized. In general, a bubble jet type in which bubbles are generated by heating the ink and ink droplets are ejected by the pressure of the bubbles is well known.

Further, as described in, for example, Japanese Patent Application Laid-Open No. 2-289351, a vibration plate forming a wall surface of a liquid chamber, and individual electrodes outside the liquid chamber disposed opposite to the vibration plate are provided. An electrostatic type in which the diaphragm is deformed by an electrostatic force generated by applying an electric field between the diaphragm and the electrode, and ink droplets are ejected from nozzles by changing the pressure / volume in the liquid chamber. Has also been proposed.

Here, as a diaphragm in an ink jet head, particularly a diaphragm in an ink jet head using an electromechanical transducer, as described in JP-A-8-187868, one surface of a thin metal film is used. A polymer material layer is formed by dipping, roll coating, spraying, etc., a thin metal film is etched to form an island, and the polymer material layer exposed by etching is used as a diaphragm, or metal An island portion formed by etching a thin plate is bonded to a stretched polymer film with an adhesive to form a diaphragm, and a laminate of a metal plate and a photosensitive resin as described in JP-A-9-76491 Japanese Patent Laid-Open No. 8-1
As described in Japanese Unexamined Patent Publication No. 950, there is known a diaphragm formed by forming a metal thin film by the electric method, or a Ni layer formed by sputtering an Au layer.

[0006]

In the ink jet head, the nozzle pitch tends to be small for high-speed, high-resolution recording, and as a result, the pitch between liquid chambers is also small. As the pitch of the nozzles and the liquid chambers becomes narrower, mutual interference between adjacent bits increases, which may cause unstable ejection or defective ejection.

In order to suppress the interference between adjacent bits and obtain an efficient diaphragm displacement, it is necessary to reduce the thickness of the diaphragm. For this reason, various types of diaphragms as described above have been proposed, but there is a problem that a pinhole is easily generated in the diaphragm portion (thin film portion).

The present invention has been made in view of the above problems, and has as its object to form a thin film diaphragm having no pinhole defects.

[0009]

In order to solve the above-mentioned problems, an ink jet head according to the present invention has a structure in which a diaphragm is thinned by etching.

Here, it is possible to adopt a configuration in which the diaphragm is joined to the electromechanical transducer via a photosensitive material. Further, the diaphragm can be a laminate of different metals, in which case the thickness of one of the different metals preferably does not exceed 10 μm, the different metals preferably have different etching rates, and the different metals have different etching rates. A structure in which only one metal is selectively etched can be employed.

The diaphragm may be a laminate of a metal and a material other than a metal. In this case, the thickness of the material other than the metal preferably does not exceed 10 μm, and the material other than the metal is thinned. be able to.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an exploded perspective view showing an example of an inkjet head to which the present invention is applied, and FIG.
FIG. 3 is an enlarged cross-sectional view of a main part of the head in the inter-row direction, and FIG. 3 is an enlarged cross-sectional view of a main part of the head in the inter-channel direction.

This ink jet head includes a drive unit 1, a liquid chamber unit 2, a head cover 3, and a spacer member 4. The drive unit 1 includes a plurality of stacked piezoelectric elements 12 arranged in two rows on a substrate 11 made of a barium titanate-based ceramic and joined thereto, and a resin surrounding the periphery of each of the two rows of piezoelectric elements 12. The frame member 13 made of ceramic or the like is joined by an adhesive. The plurality of piezoelectric elements 12 include piezoelectric elements (hereinafter referred to as “driving units”) 17 to which driving pulses for applying ink to droplets and flying are provided, and driving units 17, 17.
The piezoelectric elements (referred to as “non-driving parts”) 18, which are positioned between the piezoelectric elements 17 and serve as liquid chamber support members for simply fixing the liquid chamber unit 2 to the substrate 11 without applying a driving pulse, are alternately provided. To be configured.

As shown in FIG. 2, the piezoelectric element 12 has a thickness of 10 to 50 μm / layer of lead zirconate titanate (PZT) 20 and a thickness of several μm / layer of silver / paradium. A laminated piezoelectric element in which internal electrodes 21 made of (AgPd) are alternately laminated is used.

The internal electrodes 21 of each piezoelectric element 12 are left and right end face electrodes 22 and 23 made of AgPd every other layer (the opposing face sides of the two piezoelectric element rows are end face electrodes 22, and the non-opposing face sides are end face electrodes). 23). On the other hand, as shown in FIG.
Each pattern of the common electrode 24 and the individual electrode 25 is provided by Au plating, AgPt paste printing, AgPd paste printing, or the like.

The opposite end face electrodes 22 of each row of the piezoelectric elements 12 are connected to the common electrode 24 via a conductive adhesive 26.
On the other hand, the non-opposing end surface electrodes 23 of the piezoelectric elements 12 in each row are connected to the individual electrodes 25 via the conductive adhesive 26 in the same manner. Thereby, the driving unit 17
When a drive voltage is applied to the drive unit 17, an electric field is generated in the stacking direction, and the driving unit 17 is displaced in the stacking direction (d 33).
Direction displacement) occurs. As shown in FIG. 2, the common electrode 24 has a hole 13a formed in the frame member 13.
By filling the inside with the conductive adhesive 26, the pattern connected to each piezoelectric element is conducted.

On the other hand, the liquid chamber unit 2 is a liquid chamber partition member having a two-layer structure formed of a diaphragm 31 thinned by etching according to the present invention and a photosensitive resin layer made of a dry film resist (DFR). 32 and a nozzle plate 33 made of a metal material are sequentially laminated and formed by heat fusion. With these members, a pressurized liquid chamber 35 that is pressurized via the diaphragm 31 by the displacement of the piezoelectric element 12 (drive unit 17) in the laminating direction, and a pressurized liquid chamber positioned on both sides of the pressurized liquid chamber 35 is added. Common liquid chamber 3 for introducing ink to be supplied to pressure liquid chamber 35
6, 36, an ink supply path 37 that communicates the pressurized liquid chamber 35 with the common liquid chambers 36 and 36, and a nozzle 38 that communicates with the pressurized liquid chamber 35 to form one channel.
A plurality of these channels are provided in two rows.

The diaphragm 31 has a diaphragm region 4 of a thin film.
1, an island-shaped convex portion (island portion) 42 which is formed at the center of the diaphragm region 41 and which is to be connected to the piezoelectric element 2 which is to be the driving portion 17; And a base 44 to be formed. The island-shaped convex portion 42 of the vibration plate 31 and the piezoelectric element 12 are joined by a photosensitive material 45 used as a mask when the vibration plate 31 is thinned by etching.

The liquid chamber partition member 32 is formed by laminating a dry film resist on the diaphragm 31 side in advance, exposing it with a required mask, and developing it to form a first photosensitive resin layer 46 having a predetermined liquid chamber pattern. And a second photosensitive resin layer 47 having a predetermined liquid chamber pattern formed by laminating a dry film resist in advance on the nozzle plate 33 side, exposing with a required mask, and developing and forming a predetermined liquid chamber pattern. Become.

The nozzle plate 33 is formed of a metal material, for example, a Ni plating film by an electroforming method, and has a large number of nozzles 38 which are fine discharge ports for flying ink droplets. The inner shape (inner shape) of the nozzle 38 is formed in a horn shape (may be a substantially columnar shape or a substantially truncated cone shape). The diameter of the nozzle 38 is about 20 to 35 μm in diameter on the ink droplet outlet side.

The ink discharge surface (nozzle surface side) of the nozzle plate 33 is a water-repellent layer 48 which has been subjected to a water-repellent surface treatment as shown in FIG. For example, PTF
Ink physical properties such as E-Ni eutectoid plating, electrodeposition coating of fluororesin, vapor-deposited evaporative fluororesin (for example, pitch fluoride), baking after solvent application of silicon resin or fluorine resin The water-repellent treatment film selected according to the above is provided to stabilize the ink droplet shape and the flying characteristics so that high-quality image quality can be obtained.

The substrate 11 of the drive unit 1 and the piezoelectric element 12 and the frame member 13 are assembled by bonding with an adhesive 49, and the liquid chamber unit 2 is processed and assembled separately from the drive unit 1. After that, the vibration plate 31 of the liquid chamber unit 2 and the piezoelectric element 12 and the frame member 13 of the drive unit 1 are joined with a photosensitive material 45 to form an ink jet head.

Then, the substrate 11 is supported and held on a spacer member (head holder) 4 as a head support member,
A PCB substrate 52 on which a head driving IC (drive circuit) provided in the spacer member 4 is mounted, and each electrode 24 connected to each piezoelectric element 12 (drive unit 17) of the drive unit 1;
25 are connected via FPC cables 53, 53.

The nozzle cover 3 is made of a box-shaped metal material that covers the periphery of the nozzle plate 33 and the side surface of the head, and is joined to the periphery of the nozzle plate 33 with an adhesive. Further, in order to supply ink from an ink cartridge (not shown) to the liquid chamber, the ink supply holes 54 are provided in the spacer member 51, the substrate 11, the frame member 13, and the vibration plate 31, respectively.
To 57 are provided.

In the ink jet head configured as described above, by applying a drive waveform (pulse voltage of 10 to 50 V) to the drive unit 17 in accordance with the recording signal, a displacement in the stacking direction occurs in the drive unit 17, Diaphragm 31
The pressurized liquid chamber 35 is pressurized via the, and the pressure increases, and ink droplets are ejected from the nozzle 38. At this time, the ink supply paths 37, 37 communicating from the pressurized liquid chamber 35 to the common liquid chamber 36
The ink flow also occurs in the direction, but the ink supply path 3
By reducing the cross-sectional area of the nozzles 7 and 37, they function as a fluid resistance part to reduce the flow of ink to the common liquid chambers 36 and 36, thereby preventing a drop in ink ejection efficiency.

Thereafter, with the end of the ink droplet ejection, the ink pressure in the pressurized liquid chamber 35 decreases, and a negative pressure is generated in the pressurized liquid chamber 34 due to the inertia of the ink flow and the discharge process of the drive pulse. To the ink filling process. At this time, the ink supplied from the ink tank flows into the common liquid chambers 36, 36, and from the common liquid chambers 36, 36 to the ink supply paths 37, 3.
After that, it is filled into the pressurized liquid chamber 35. Then, the vibration of the ink meniscus surface near the outlet of the nozzle 38 is attenuated,
When the ink is returned to the vicinity of the outlet of the nozzle 38 due to surface tension (refill) and reaches a stable state, the operation shifts to the next ink droplet ejection operation.

Therefore, a first embodiment in which the present invention is applied to this ink jet head will be described with reference to FIG. In the following description, the diaphragm shows only the diaphragm region and the island-shaped convex portions for simplifying the description. First,
As shown in FIG. 1A, for example, a SUS having a thickness of 40 μm is used.
A substrate 61 is prepared, and as shown in FIG.
On one surface of the S substrate 61, a photosensitive material, for example, DFR (dry film resist), photosensitive polyimide or the like is laminated or applied. Here, a 25 μm thick DF
R62 was laminated.

Thereafter, as shown in FIG. 2C, the DFR 62 is patterned into the shape of the island-shaped projections 42 by lithography to form a mask pattern 63, and as shown in FIG. Using the pattern 63 as a mask, the SUS substrate 61 is etched (dry-etched or wet-etched) to make it thinner to form the diaphragm region 41, and to form the island-shaped protrusions 42 corresponding to the shape of the mask pattern 63, and D on the convex part 42
The diaphragm 31 having the photosensitive material 45 as the FR mask pattern 63 is obtained. At this time, the etching time was controlled so that the film thickness of the diaphragm region 41 as the thin film portion was 5 μm.

Then, as shown in FIG. 2E, the liquid chamber partition member 31 and the nozzle plate 33 are joined to the vibration plate 31 to form the liquid chamber unit 2 as described above. The piezoelectric element 12 and the island-shaped convex portion 42 of the vibration plate 31 are pressure-bonded using the photosensitive material (DFR) 45 used at the time of forming the vibration plate 31 as a bonding layer.

By forming the diaphragm 31 into a thin film by etching as described above, it is possible to obtain a diaphragm having an arbitrary thickness and no pinhole defect, and it is possible to obtain an ink jet head with less mutual interference. Here, diaphragm 3
By bonding the photosensitive material used as a mask when forming 1 by etching as a bonding layer with an electromechanical transducer (here, a piezoelectric element), the number of steps can be reduced and cost can be reduced.

Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. First, as shown in FIG.
A laminate 70 having a 10 μm-thick polyimide film 72 formed on a 20 μm-thick SUS substrate 71 is prepared, and as shown in FIG.
On one side, a photosensitive material, for example, DFR (dry film resist), photosensitive polyimide or the like is laminated or applied. Here, DFR73 having a thickness of 25 μm was laminated.

Thereafter, as shown in FIG. 3C, the DFR 73 is patterned into the shape of the island-shaped projections 42 by lithography to form a mask pattern 74, and as shown in FIG. The SUS substrate 71 is etched (dry-etched or wet-etched) using the pattern 74 as a mask. Further, the polyimide film 72 is etched to a desired film thickness (5 μm in this case) so as to be thinned by controlling the time, thereby forming the diaphragm region 41 made of the polyimide film 72 and corresponding to the shape of the mask pattern 74. Convex portion 4 made of SUS substrate 71 and polyimide film 72
2 is formed to obtain the diaphragm 31 in which the photosensitive material 45 which is the DFR mask pattern 74 is attached to the island-shaped convex portions 42.

Then, as shown in FIG. 5D, the liquid chamber partition member 31 and the nozzle plate 33 are joined to the vibration plate 31 as described above to form the liquid chamber unit 2, and then the drive unit 1 The piezoelectric element 12 and the island-shaped convex portion 42 of the vibration plate 31 are pressure-bonded using the photosensitive material (DFR) 45 used at the time of forming the vibration plate 31 as a bonding layer.

As described above, by forming a diaphragm by thinning by etching using a laminate of a metal and a material other than a metal, a diaphragm having an arbitrary thickness and having no pinhole defect can be obtained. An ink jet head with less interference can be obtained.

In the case where the laminate 70 in which the thickness of the polyimide film 72 is set to the thickness of the diaphragm region 41 is formed, only the SUS substrate 71 is etched without etching the polyimide film 72. In particular, when a laminate of a metal and a material other than the metal is used, the thickness of the layer of the material other than the metal is set to not exceed 10 μm, so that the material other than the metal is selectively etched to be thinned. can do.

Next, a third embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. First, as shown in FIG.
A SUS substrate 81 having a thickness of 20 μm is prepared, and a Ni plating having a thickness of 5 μm is formed on the SUS substrate 81 as shown in FIG.
An O film 82 is deposited by a CVD method to form a laminate 80 of a dissimilar metal.

Then, as shown in FIG. 3C, a photosensitive material, for example, DF
R (dry film resist), photosensitive polyimide, or the like is laminated or coated. Here, thickness 25μ
m of DFR83 were laminated.

Thereafter, as shown in FIG. 3D, the DFR 83 is patterned into the shape of the island-shaped protrusions 42 by lithography to form a mask pattern 84, and as shown in FIG. The SUS substrate 81 is etched (dry etching or wet etching) using the pattern 84 as a mask to form the diaphragm region 41 composed of the NiO film 82, and the SUS substrate 81 and the NiO film 8 corresponding to the shape of the mask pattern 74.
2 is formed, and the island-shaped protrusion 42 is
The diaphragm 31 with the photosensitive material 45 as the FR mask pattern 84 is obtained.

Then, as shown in FIG. 3 (f), the liquid chamber partition member 31 and the nozzle plate 33 are joined to the vibration plate 31 as described above to form the liquid chamber unit 2, and then the driving unit 1 The piezoelectric element 12 and the island-shaped convex portion 42 of the vibration plate 31 are pressure-bonded using the photosensitive material (DFR) 45 used at the time of forming the vibration plate 31 as a bonding layer.

As described above, by forming a diaphragm by thinning by etching using a laminate of dissimilar metals, a diaphragm having an arbitrary thickness and having no pinhole defect can be obtained, and an ink jet having little mutual interference can be obtained. You can get a head.

In this case, by selectively etching only one of the dissimilar metals, it is possible to obtain a diaphragm made of a metal material with high film thickness uniformity. In addition, by forming a laminate of different metals having different etching rates, only one metal can be selectively etched and the other metal can be left. In this case, by setting the thickness of one metal not to exceed 10 μm, it is possible to form a thin film region while leaving the metal whose thickness does not exceed 10 μm.

In the above embodiment, the present invention has been described as an example in which the present invention is applied to a piezo type ink jet head using an electromechanical transducer as an actuator. However, the present invention is also applied to an electrostatic type ink jet head using a diaphragm and a counter electrode. The same can be applied.

[0043]

As described above, according to the ink jet head according to the present invention, since the diaphragm is made thin by etching, it is possible to obtain a diaphragm having an arbitrary thickness and having no pinhole defect. As a result, an ink jet head with less mutual interference can be obtained.

Here, since the diaphragm is joined to the electromechanical transducer via the photosensitive material, the number of manufacturing steps can be reduced and the cost can be reduced.

Further, by forming a laminated body of different metals as the diaphragm, it is possible to reduce the thickness while leaving one metal. In this case, when the thickness of one of the dissimilar metals does not exceed 10 μm, only the other metal can be selectively etched to form a thin diaphragm. Further, by using different kinds of metals having different etching rates, it is possible to easily selectively etch only one of the metals. Then, by adopting a configuration in which only one of the dissimilar metals is selectively etched, a diaphragm having high film thickness uniformity can be obtained.

Further, by forming the diaphragm as a laminate of a metal and a material other than the metal, only the metal can be etched to make it thinner. In this case, the thickness of the material other than metal is 1
When the thickness does not exceed 0 μm, the thin film diaphragm can be easily formed by etching while leaving materials other than metal. Then, by thinning the material other than the metal, the material other than the metal can be thinned using the metal as a mask.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an example of an inkjet head to which the present invention is applied.

FIG. 2 is an enlarged sectional view of a main part of the head in a direction between rows.

FIG. 3 is an enlarged sectional view of a main part of the head in a direction between channels.

FIG. 4 is a process explanatory view illustrating a first embodiment in which the present invention is applied to the inkjet head.

FIG. 5 is a process explanatory view illustrating the second embodiment.

FIG. 6 is a process explanatory view illustrating a third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Drive unit, 2 ... Liquid chamber unit, 3 ... Nozzle cover, 4 ... Spacer member, 11 ... Substrate, 12 ... Piezoelectric element,
DESCRIPTION OF SYMBOLS 13 ... Frame member, 13b ... Through-hole, 24 ... Common electrode, 31 ... Vibration plate, 32 ... Liquid chamber partition member, 33 ... Nozzle plate, 41 ... Diaphragm area, 42 ... Island-shaped convex part,
45: photosensitive material, 61, 71, 81: SUS substrate, 6
2, 73, 83: DFR, 63, 74, 84: mask pattern, 70, 80: laminate, 72: polyimide film, 82: NiO film.

Claims (9)

[Claims] 1. An ink jet head comprising a diaphragm forming a wall surface of a liquid chamber to which a nozzle for discharging ink droplets communicates, wherein the diaphragm is thinned by etching. 2. The ink-jet head according to claim 1, wherein said diaphragm is joined to an electromechanical transducer via a photosensitive material. 3. The ink-jet head according to claim 1, wherein said diaphragm is a laminate of dissimilar metals. 4. The ink-jet head according to claim 3, wherein the thickness of one of the dissimilar metals does not exceed 10 μm. 5. The ink jet head according to claim 3, wherein the different metals have different etching rates. 6. The ink jet head according to claim 3, wherein only one of the dissimilar metals is selectively etched. 7. The ink jet head according to claim 1, wherein the diaphragm is a laminate of a metal and a material other than the metal. 8. The ink jet head according to claim 7, wherein the thickness of the material other than the metal does not exceed 10 μm. 9. The ink jet head according to claim 7, wherein the material other than the metal is thinned.