JP3314777B2 - Method of manufacturing inkjet head - Google Patents

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 which is a main part of a small and high-density ink-jet recording apparatus manufactured by applying a micro-machining technique, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Ink jet recording apparatuses have many advantages such as extremely low noise during recording, high-speed printing, and printing on inexpensive plain paper. The so-called ink-on-demand method, in which ink droplets are ejected only when necessary for recording, has become mainstream at present because collection of unnecessary ink droplets for recording is not required. As described in Japanese Patent Publication No. 2-51734, this ink-on-demand type ink jet head employs a piezoelectric element as a driving means, and an ink jet head as disclosed in Japanese Patent Publication No. 61-59911. There is a method in which ink is ejected with a pressure generated by heating air bubbles to generate air bubbles.

[0003]

However, the above-mentioned conventional ink jet head has the following problems. In the former method using a piezoelectric element,
The process of attaching the chip of the piezoelectric element to each vibration plate for generating pressure in the pressure chamber is complicated, and high-speed and high-quality printing is required especially for printing by a recent inkjet recording apparatus. In achieving multi-nozzles and increasing the density of nozzles to achieve this, it is extremely complicated to finely process the piezoelectric element and adhere it to each diaphragm. In order to increase the density, a piezoelectric element having a width of 1
Although it has become necessary to process with a size of 0 to 100 and several tens of microns, there has been a problem that the dimensional and shape accuracy in the conventional machining has a large variation in printing quality. In the latter method of heating the ink, since the driving means is formed by a thin-film resistance heating element, the above-mentioned problem did not exist, but rapid heating and cooling of the driving means were repeated, There is a problem that the life of the ink jet head is short because the resistance heating element is damaged by the impact when the bubbles disappear. In order to solve these problems, the present applicant has filed a patent application for an ink jet head of a system in which a vibration plate that generates pressure in a pressure chamber as a driving means is deformed by electrostatic force (Japanese Patent Application No. Hei.
This method has the advantages of small size, high density, high printing quality and long life. The configuration of the ink jet head of the present method, which has been proposed by the present applicant, has a configuration in which the concave portion (hereinafter, referred to as a cavity) and the vibrating plate, which are to be pressure chambers for pressurizing ink, are provided in the same Si substrate. It was formed by anisotropic etching. This configuration has the advantage that the above-described structure (concave portion and diaphragm) can be formed on one substrate, so that the manufacturing process is simple and the manufacturing cost is low. However, as shown in FIG. When the diaphragm and the diaphragm are formed on the same substrate, the diaphragm 7
Dimensions such as width W ₄ and thickness t are determined by the thickness T of the Si substrate 44.
And is uniquely determined by the dimensions of the width W ₅ of the cavity 5, there is no degree of freedom in design. In particular, high density of the cavities, i.e., when considering the high density of the nozzle, when narrowing the spacing between the cavities, the dimensions of the width W ₄ of the diaphragm 7 is extremely small, the ink-jet head is established in this configuration Did not. SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet head that uses an electrostatic force as a driving source and has a high density of nozzles. or,
An object of the present invention is to provide an ink jet head having high printing quality by improving the thickness accuracy of the diaphragm.

[0004]

A method of manufacturing an ink jet head according to the present invention comprises a nozzle for discharging an ink liquid, a pressure chamber communicating with each of the nozzles, and at least one wall of the pressure chamber. A first vibrating plate, a driving means for causing deformation of the vibrating plate, and a common ink chamber for supplying ink to the pressure chamber, wherein the nozzle and a concave portion to be the pressure chamber are formed. In a method for manufacturing an ink jet head having a step of bonding a Si substrate and a second Si substrate of the vibration plate, the second Si substrate bonded to the first Si substrate is thinned by etching or polishing. And a step of performing Further, the high-concentration p-type Si layer formed on one surface of the second Si substrate is opposed to the surface of the first Si substrate on which the opening is formed. The method further includes a step of joining the first Si substrate and the second Si substrate, and a step of thinning the second Si substrate by etching. Further, the second Si substrate includes an n-type Si layer. The n-type Si layer formed on one surface of the second Si substrate is opposed to the surface of the first Si substrate on which the opening is formed. The method further includes a step of bonding the first Si substrate and the second Si substrate, and a step of thinning the second Si substrate by etching.

The principle of operation of an ink jet head using electrostatic force as a driving source in the present invention is as follows. A pulse voltage is applied to the electrode or the diaphragm and a positive or negative charge is applied to the electrode or the diaphragm. The diaphragm is deformed by electrostatic attraction or repulsion, and ink in the pressure chamber is ejected from a nozzle.

[0005]

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described in detail. FIG. 1 is an exploded perspective view showing a structure of an ink jet head according to a first embodiment of the present invention, and shows a partial cross section. As shown in FIG. 1, the ink jet head of this embodiment has a diaphragm in which a nozzle 4, a cavity 5, an ink supply path 9, and the like are formed from a Si substrate 1 and a Si substrate 6 formed by alkali anisotropic etching. 7 and a glass substrate 2 on which an electrode 11, a groove 12 for forming a gap portion, and the like are formed and joined. The Si substrate 1 is a single-crystal Si substrate having a crystal plane orientation of (100). A plurality of nozzles 4 and a plurality of nozzles 4 are provided on the front surface (the upper surface in FIG. 1) of the Si substrate 1. 4, an ink supply path 9 formed at an end of each cavity 5 opposite to the nozzle 4, and a common ink chamber 8 for supplying ink to each ink supply path 9. Are formed. The vibration plate 7 is formed by reducing the thickness of the Si substrate 6 by etching and polishing the Si substrate 6. Further, the glass substrate 2 has an electrode 11 disposed in each of the cavities 5 formed on the Si substrate 1 with the vibration plate 7 interposed therebetween, and an opposition between the vibration plate 7 and the electrode 11. A groove 12 for maintaining a gap (gap) is formed. FIG. 2 shows a manufacturing process of the Si substrate 1 shown in FIG.
Shown in First, the front side of the wafer having the (100) plane orientation (FIG. 2)
The upper side is mirror-polished, and the 280 micron thick S
An i substrate 1 is formed, and the Si substrate 1 is subjected to a heat treatment at 1100 ° C. for 4 hours in an atmosphere of O ₂ and water vapor,
Forming a SiO ₂ film 15a and 15b having a thickness of 1 micron on both sides of the substrate 1 (FIG. 2 (a)). Then, the SiO
_{On the second} film 15a, a photoresist pattern 16 (not shown) corresponding to the shape of the nozzle 4, the cavity 5, etc. is formed, and the SiO ₂ film 15 is etched with a hydrofluoric acid-based etchant.
Then, the exposed portion a is removed by etching, and the photoresist pattern 16 is removed (FIG. 2B).

The design dimensions of each part of the photomask pattern 17 (not shown), which is the basis of the photoresist pattern 16, were determined as follows. The design dimension value of each component is determined from the ink ejection characteristics required for the ink jet head having this configuration. In this embodiment, the width W ₁ 100 micron diaphragm 7, the thickness t and 3.5 microns, also the spacing between the cavities and 41 microns, 141 microns as a nozzle pitch, i.e. 180dp
i (dot per inch). In the ink jet head having this configuration, the width of the cavity 5 is the same as the width W _{1 of the} diaphragm 7. Photomask pattern 17
The width value of the pattern corresponding to the cavity was adjusted to 98 microns by correcting the undercut in the etching. Next, etching with an alkaline solution is performed. Using a potassium hydroxide aqueous solution containing isopropyl alcohol as an etchant, a predetermined amount of 100 μm was etched (FIG. 2C). As is well known, when etching with an alkaline liquid, anisotropic etching can be performed on a Si single crystal because the difference in etching rate between crystal planes is large. Specifically, (111)
Since the etching rate of the crystal plane is the lowest, a structure is obtained in which the (111) plane remains as a smooth plane as the etching proceeds. As shown in FIG. 3, since the (111) plane 18 intersects the (100) plane 19 at an angle of about 55 degrees, the (111) plane 1
8 appears, and at the point 21 where the width W of the etching mask pattern 20 is small, all (111) planes on both sides finally appear, and further etching hardly proceeds. In addition, at a portion 22 where the width W of the etching mask pattern 20 is large, a structure is obtained in which a (111) plane is developed on both sides and a (100) plane remains at the bottom. In FIG. 2, the width W ₁ of the etching mask pattern corresponding to the cavity 5 is 98 μm, the width W ₂ of the etching mask pattern corresponding to the nozzle 4 is 40 μm, and the width W _{3 of} the etching mask pattern corresponding to the ink chamber 8.
Is 3 mm, so that the cross-sectional shape of the cavity 5 and the nozzle 4 is triangular, and further etching hardly proceeds. On the other hand, in the ink chamber 8, the bottom is from the (100) plane. It becomes the shape which becomes. In the structure of the ink jet head of the present invention, since the cavities and nozzles are required to have an accuracy in the volume and shape in terms of ink ejection characteristics, the shapes of the cavities and nozzles in the above structure are uniquely determined by the etching mask pattern. It is highly desirable. Further, since some errors are allowed in the volume and shape of the ink chamber 8, there is an advantage that the management of the etching amount does not need to be very strict. Finally, the SiO ₂ films 15a and 15b serving as an etching mask are removed with a hydrofluoric acid-based etchant to complete the Si substrate 1 shown in FIG. 1 (FIG. 2D). FIG. 4 shows a manufacturing process of the diaphragm 7 shown in FIG. First, a surface 23 on one side of a Si substrate 6 having a thickness of about 280 microns is mirror-polished, and the Si substrate 1 formed by the process shown in FIG. Joining was performed as follows by Si-Si direct joining. The Si substrates 1 and 6 are washed with a mixed solution of sulfuric acid and hydrogen peroxide solution (100 degrees Celsius), dried, and the Si substrates 1 and 6 are superposed and joined at room temperature. In a N ₂ atmosphere at 1100 ° C.
A joined body 25 which is firmly joined by heat treatment for one hour is obtained (FIG. 4A). Next, the other surface 24 of the Si substrate 6
On the other hand, by performing etching and polishing together, the thickness of the Si substrate 6 was reduced to 3.5 μm to form the vibration plate 7 (FIG. 4B). Finally, a hole for ink supply was provided at a predetermined position. 13a (not shown) is formed by electric discharge machining or the like.

Next, a manufacturing process of the glass substrate 2 shown in FIG. 1 is shown in FIG. One surface 2 of borosilicate glass substrate 2
A thin film of Cr (chromium) 28 and Au (gold) 27 is sequentially formed on the substrate 6 to form an etching mask 29 composed of a two-layer thin film (FIG. 5A), and then the groove shown in FIG. A photoresist pattern 30 corresponding to No. 12 was formed on Au27, and the exposed portions of Au27 and Cr28 were removed by etching (FIG. 5B). For etching Au, an iodine-potassium iodide solution was used, and for etching Cr, a ceric ammonium nitrate-nitric acid solution was used. Next, the glass substrate 2 was treated with a hydrofluoric acid-based etchant.
Etch the exposed part of. The amount of etching is determined by the dimension value of the facing distance between the diaphragm 7 and the electrode 11. From the ink ejection characteristics, the above dimension value is determined to be 0.5 μm, and the thickness of the Au / Cr two-layer film serving as the electrode 11 is 0.2 μm (Au is 0.15 μm, Cr is 0.05 μm). Micron), the amount of etching was adjusted to 0.7 microns (FIG. 5C). Next, the photoresist pattern 30, Au27, Cr28
Is completely removed, and an Au / Cr 2 layer film (Au 31 is 0.15 μm, Cr 32 is 0.05
Microns), a photoresist pattern 33 (not shown) corresponding to the electrode 11 is formed on the Au / Cr2 layer film, and unnecessary portions of Au31 and Cr32 are similarly etched away to remove the photoresist pattern 33. Then, a hole 13 (not shown) for supplying ink is formed, and the glass substrate 2 shown in FIG. 1 is obtained (FIG. 5D). The bonding between the Si substrate 1 on which the vibration plate 7 is formed and the glass substrate 2 is performed as follows.
This was performed by the anodic bonding method. Positioning is performed such that each cavity 5 formed on the Si substrate 1 and each electrode 11 formed on the glass substrate 2 are opposed to each other, and the diaphragm 7 and the glass substrate 2 are abutted to each other. While maintaining the temperature at 300 degrees Celsius above, with the diaphragm 7 on the positive side and the glass substrate 2 on the negative side, a DC voltage of 500 V was applied for 10 minutes to perform anodic bonding. Finally, a predetermined portion of the obtained joined body is cut and separated by dicing, and an ink supply pipe is attached to the hole 13 to complete an ink jet head.
As described above, according to this embodiment, the nozzle pitch is 1
A high-density inkjet head of 41 microns, that is, 180 dpi was obtained. Further, as described above, since the cavity 5 and the nozzle 4 can be formed with a desired shape with high precision, a high-quality ink jet head having little variation in ink ejection characteristics from each nozzle 4 was obtained.
In actual printing, the portion of the vibration plate 7 facing each cavity 5 is vibrated by an oscillation circuit 14 connected to the electrode 11 corresponding to each cavity 5 to pressurize the ink in each cavity 5. Then, an ink droplet is ejected from each nozzle 4.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described in detail. FIG. 6 is a cross-sectional view of the ink jet head according to the present embodiment. The structure of the Si substrate 1a on which the nozzles 4a and the cavities 5a are formed and the glass substrate 2a on which the electrodes 11a are formed are the same as those of the ink jet head according to the first embodiment of the present invention, so that the description is omitted. The diaphragm 7a in this embodiment is formed of a high-concentration p-type Si layer whose dopant is B (boron). It is known that the etching rate in the Si etching with alkali has a dopant concentration dependency, but when the dopant is B, the etching rate becomes extremely small in a high concentration (about 5 × 10 ¹⁹ cm ⁻³ or more) region. I have. In the present embodiment, utilizing this fact, a high-concentration p-type Si layer 36 having the same thickness as the desired diaphragm thickness is formed on one surface of the Si substrate 34 serving as the diaphragm, and is subjected to alkali anisotropic etching. The Si portion other than the high-concentration p-type Si layer is removed by etching to form a diaphragm having high thickness accuracy.

Manufacturing of the ink jet head shown in FIG.
The steps are shown in FIG. 280 micron thick Si substrate 34
1 μm thick SiO 2 by thermal oxidation_Two
The films 35a and 35b are formed (FIG. 7A). next,
The SiO_TwoProtect the film 35b with a photoresist film and
Notation SiO_TwoOnly the film 35a is removed with a hydrofluoric acid-based etchant
(FIG. 7B). Next, the Si on the Si substrate 34 is exposed.
The exposed surface 37 is B-doped. The processing method is as follows
It is on the street. Place the Si substrate 34 in a quartz tube with a quartz holder
And fix with N_Two BBr as a carrier_ThreeThe Baburi
Steamed steam_TwoTogether with the quartz tube. Celsius
After processing at 1100 degrees for a predetermined time, the Si substrate
34 is lightly etched with a hydrofluoric acid-based etching solution,
Then O_TwoDrive-in in the exposed S
A p-type Si layer 36 was formed on the i-plane 37 (FIG. 7C).
The design value of the thickness of the diaphragm 7a is the same as that of the first embodiment of the present invention.
3.5 microns as in the case, but the B doping treatment
At 3.5 microns from the surface of the Si surface 37
In the depth, the concentration of B is 5 × 10¹⁹cm^-3So that
The step of FIG. 7C was performed. That is, high concentration B-doped
The (p-type Si) layer 36 has a B concentration of 5 ×
10¹⁹cm^-3That's all. Next, the Si substrate 3
4 and the Si substrate 1a shown in FIG.
Already formed by the same method as the first embodiment.
You. However, the back surface of the Si substrate 1a (the nozzle 4a and the like are formed)
On the side opposite to the side that is
In alkaline etching, the Si substrate is etched.
SiO2 _TwoThe film 15c is left. )
And bonding. The bonding is performed by a Si-Si direct bonding method.
The procedure was as follows. First, the Si substrates 1a and 34 were
Washed with a mixture of acid and hydrogen peroxide (100 degrees Celsius)
After drying, the nozzle 4a and the cavity 5 of the Si substrate 1a are
a and the surface 37 of the Si substrate 34
Then, the Si substrates 1a and 34 are integrated
The formed joined body 38 is_Two1100 degrees Celsius in the atmosphere
Heat treatment for 1 hour to obtain a strong bonding state (Fig.
7 (d)). Next, the SiO on the Si substrate 34_Two Film 35b
Is removed with a hydrofluoric acid-based etchant.
Is subjected to alkali etching to obtain a high concentration
Only the B-doped (p-type Si) layer 36 is selectively left.
This is referred to as a diaphragm 7a,_Two Hydrofluoric acid for film 15c
It was removed with a system etchant (FIG. 7E). Then figure
6. The same method as in the first embodiment of the present invention shown in FIG.
The glass substrate 2a and the joint body 38 formed by the method
After the alignment between the bitty 5a and the electrode 11a,
Bonding was performed by the pole bonding method (FIG. 7F). After this,
As in the first embodiment, a predetermined position is cut by dicing.
Then, an inkjet head was obtained. In this embodiment
Forms a high-concentration B-doped layer, and
By allowing this to remain selectively, the diaphragm 7
The thickness of a is ± 3.5 μm with respect to the target thickness of 3.5 μm.
It could be formed with an accuracy of 0.2 microns. Follow
High quality ink with small variations in ink ejection characteristics
An ink jet head was formed.

Embodiment 3 Hereinafter, a third embodiment of the present invention will be described in detail. FIG. 8 is a cross-sectional view of the inkjet head according to the present embodiment. The Si substrate 1b on which the nozzles 4b and the cavities 5b are formed, and the glass substrate 2b on which the electrodes 11b and the like are formed are structurally the same as those of the ink jet head according to the first embodiment of the present invention. I do. Diaphragm 7 in this embodiment
b is an n-type Si layer. The n-type layer formed on the p-type Si substrate can be selectively left when etching is performed in an alkaline solution while applying a positive voltage to the n-type Si layer. By utilizing this, a diaphragm having high thickness accuracy is formed. FIG. 9 shows a manufacturing process of the ink jet head shown in FIG. (100)
Both surfaces of a p-type Si wafer having a plane orientation are mirror-polished to a thickness of 28.
A 0-micron Si substrate 39 is formed, and an n-type Si layer 41 is formed on one surface 40 of the Si substrate 39 by epitaxial growth with a thickness of 3.5 microns (FIG. 9).
(A)). Next, through the same steps as in the case of the second embodiment of the present invention, the Si substrate 1b (as described above, has already been formed by the same method as in the first embodiment of the present invention. On the back surface of the Si substrate 1b (the surface opposite to the surface on which the nozzles 4b and the like are formed), the SiO ₂ film 15d is left so that the Si substrate 1b is not etched in alkali etching performed later. ) And the n-type Si layer 41 are joined to form a joined body 42 (FIG. 9).
(B)). Next, the joined body 42 is subjected to electrochemical etching by the method shown in FIG. Referring to FIG.
The junction 42 is immersed in a KOH aqueous solution (70 degrees Celsius) containing isopropyl alcohol with the mold Si layer 41 being positive and the platinum plate 43 being negative and a DC voltage of 0.6 V being applied, and is etched. Was. When the p-type Si substrate 39 has been completely removed by etching, the n-type Si layer 41 is inactivated by a positive DC voltage, so that the etching does not proceed. The SiO ₂ film 15d as shown in FIG.
The joined body 42 in the state (c) is obtained. Next, the second embodiment of the present invention
In the same manner as in Example 1, the glass substrate 2b on which the electrodes 11b and the like were formed was joined to the joined body 42 (FIG. 9D), and a predetermined position was cut by dicing to obtain an ink jet head.

[0011]

As described above, the present invention has the following effects. The first S in which the nozzle cavity and the like are formed
By forming the diaphragm by thinning the second Si substrate adhered to the i-substrate by polishing or etching or the like, an ink jet head having a high-density nozzle can be obtained. Concentration p-type Si layer or n
By using the type Si layer, the thickness accuracy of the diaphragm is improved, and an ink jet head with high print quality can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a manufacturing process diagram of the ink jet head according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a cross-sectional shape of each part of the inkjet head according to the first embodiment of the present invention.

FIG. 4 is a manufacturing process diagram of the inkjet head according to the first embodiment of the present invention.

FIG. 5 is a manufacturing process diagram of the inkjet head according to the first embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a structure of an inkjet head according to a second embodiment of the present invention.

FIG. 7 is a manufacturing process diagram of an inkjet head according to a second embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a structure of an inkjet head according to a third embodiment of the present invention.

FIG. 9 is a manufacturing process diagram of the inkjet head according to the third embodiment of the present invention.

FIG. 10 is a diagram showing a method of electrochemical etching according to a third embodiment of the present invention.

FIG. 11 is a cross-sectional view illustrating a structure of an ink jet head according to the first, second, and third embodiments of the present invention.

FIG. 12 is a cross-sectional view illustrating a structure of a conventional inkjet head.

[Explanation of symbols]

1,6 Si substrate 2 Glass substrate 3 Pressure chamber 4 Nozzle 5 Cavity 7 Vibration plate 8 Ink chamber 9 Ink supply path 11 Electrode 12 Groove 13,13a Ink supply hole 14 Oscillation circuit 15a, 15b SiO ₂ film 16 Photoresist pattern 17 Photomask pattern 18 (111) plane 19 (100) plane

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Yotsuya 3-5-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation (58) Field surveyed (Int. Cl. ⁷ , DB name) B41J 2 / 045 B41J 2/055 B41J 2/16

Claims (4)

(57) [Claims] 1. A nozzle for discharging an ink liquid, a pressure chamber communicating with each of the nozzles, a diaphragm constituting at least one wall of the pressure chamber, and a drive for causing the diaphragm to deform. Means, a first Si substrate provided with a common ink chamber for supplying ink to the pressure chamber, the first Si substrate having a recess formed therein to serve as the nozzle and the pressure chamber, and a second Si substrate of the vibration plate. A method of manufacturing an ink jet head, comprising: bonding the first Si substrate to the second Si substrate by etching or polishing to reduce the thickness of the second Si substrate. Production method. 2. The method for manufacturing an ink jet head according to claim 1, wherein the high-concentration p-type Si layer formed on one surface side of the second Si substrate is the same as that of the first Si substrate. The first side is opposed to the surface on which the opening is formed.
Bonding the Si substrate to the second Si substrate, and thinning the second Si substrate by etching, the method further comprising: 3. The method for manufacturing an ink jet head according to claim 1, wherein the second Si substrate includes an n-type Si layer. 4. The method for manufacturing an ink jet head according to claim 3, wherein the n-type Si layer formed on one surface side of the second Si substrate is the opening in the first Si substrate. The first Si is opposed to the surface on which the
A method of manufacturing an ink-jet, further comprising: a step of bonding a substrate and the second Si substrate; and a step of thinning the second Si substrate by etching.