JP2000103060A - Ink jet head and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head capable of increasing the density of nozzles while suppressing a shortening of life and a decrease in piezoelectric constant, and a method of manufacturing the same. is there. SOLUTION: On one surface of a substrate provided with a pressure chamber, a piezoelectric element having a vibration plate 3 for discharging ink and a piezoelectric body 7 having a perovskite crystal structure is formed.
In the ink jet head provided with an ink flow path 10 on the other surface of the substrate, the substrate is made of a photosensitive glass substrate 1 capable of anisotropic etching, and the diaphragm 3 and the piezoelectric Are both formed of a thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a substrate provided with a pressure chamber, wherein one surface of the substrate is provided with an ink flow path, and the other surface of the substrate is provided with a vibrating plate for discharging ink and a perovskite crystal. The present invention relates to an ink jet head having a piezoelectric element formed of a piezoelectric material having a structure and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, printers using ink jet recording apparatuses as printing apparatuses for personal computers and the like have been widely used because of their good printing performance, easy handling, and low cost. This ink jet recording apparatus includes a device that generates bubbles in ink by thermal energy and discharges ink droplets by pressure waves generated by the bubbles, a device that suctions and discharges ink droplets by electrostatic force, and a vibrator such as a piezoelectric element. There are various systems such as those using pressure waves.

Among the above-mentioned ink jet recording apparatuses, those using a piezoelectric element include, for example, an ink flow path communicating with an ink discharge port, a pressure chamber communicating with the ink flow path, and a piezoelectric chamber provided in the pressure chamber. It is composed of a diaphragm or the like to which the body is joined. When a predetermined voltage is applied to the piezoelectric body, the piezoelectric body expands and contracts, causing the piezoelectric body and the vibration plate to vibrate in a drum-like shape, thereby compressing the ink in the pressure chamber. The configuration is such that droplets are ejected.

In recent years, color ink jet recording apparatuses have become widespread instead of black and white. However, in such ink jet recording apparatuses, improvement in printing performance, particularly, high resolution and high speed printing are required. Therefore, it has been attempted to realize high resolution and high-speed printing using a multi-nozzle head structure by miniaturizing the ink jet head, and in order to achieve the miniaturization of the ink jet head, a piezoelectric element for supplying ink is required. There is a strong demand for miniaturization. In order to reduce the size of the piezoelectric element, a method is possible in which the thickness of the piezoelectric body is reduced, a flexural vibration is generated using a diaphragm, and ink is ejected. However, the displacement of the piezoelectric body itself with respect to the voltage is very small,
Therefore, when the piezoelectric element is miniaturized, the ink cannot be ejected without generating sufficient stress or vibration due to a decrease in piezoelectricity. Therefore, in order to realize a high-resolution, high-speed printer having a small, multi-nozzle head, it is necessary to develop a piezoelectric thin film material having sufficient piezoelectricity even at a small film thickness and to establish a manufacturing method thereof. .

However, a small-sized piezoelectric element and an ink head having characteristics necessary for sufficient ink ejection cannot be realized by using a thin piezoelectric material as described above. In particular, in the case of a piezoelectric material of a sintered body that has been conventionally used, the element has been reduced in size by mechanical processing such as cutting. However, mechanical processing has a limitation in downsizing and causes deterioration of piezoelectric characteristics, It was difficult to achieve both miniaturization and high resolution.

Therefore, as shown below, a piezoelectric element or a diaphragm constituting a piezoelectric element has been proposed to be thinned to obtain a shape which can be finely processed, which is generally used in a semiconductor process. ing. Specifically, (11
Using a silicon substrate having a crystal orientation of 0), pressure chambers are formed by anisotropic etching utilizing a difference in etching rate between the (110) plane and the (111) plane of silicon, and sputtering is performed on the silicon substrate. P by evaporation method
ZT [Pb (Ti _1-x Zr _x ) O ₃ : x = 0.53] This is a method of forming a piezoelectric body such as a thin film.

However, simply forming a piezoelectric body using a sputter deposition method has a problem that a piezoelectric body having a perovskite crystal structure does not have a (001) plane as a main component, so that a high piezoelectric constant cannot be obtained. is there. Further, when the pressure chamber is formed by anisotropic etching utilizing the difference in etching rate between the (110) plane and the (111) plane of silicon, the cross-sectional shape of the pressure chamber becomes a parallelogram. Sometimes, the diaphragm is not uniformly pressed, and the life of the diaphragm is shortened.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to increase the density of nozzles while suppressing a shortened life and a decrease in piezoelectric constant. An object of the present invention is to provide an inkjet head and a method for manufacturing the same.

[0009]

According to a first aspect of the present invention, there is provided a pressure-chamber having a vibration chamber for discharging ink on one surface of a substrate having a pressure chamber. A piezoelectric element having a plate and a piezoelectric body having a perovskite crystal structure is formed, and the other surface of the substrate is provided with an ink flow path. The vibration plate and the piezoelectric body are both formed of a thin film.

As described above, when a photosensitive glass substrate is used as the substrate, the cross-sectional shape of the pressure chamber does not become a parallelogram as when a silicon substrate is used as the substrate. Therefore, since the diaphragm is uniformly pressed, the life of the diaphragm is extended and the life of the ink jet head is also extended. In addition, since both the diaphragm and the piezoelectric body are formed of thin films, fine processing becomes possible, and the density of the nozzle can be increased.

As disclosed in Japanese Patent Application Laid-Open No. Hei 5-177831, it has been conventionally proposed to use a photosensitive glass substrate as a substrate capable of performing anisotropic etching. However, since the ink jet head disclosed in the above publication is considered to be not a thin film but a bulk laminated structure, the piezoelectric body and the diaphragm are formed by bonding,
Alternatively, it is necessary to use a glass vibrating plate as the vibrating plate and fuse the glass vibrating plate and the piezoelectric body. However, in the former case, it is difficult to increase the density because the adhesive may protrude, and in the latter case, the Young's modulus of the glass diaphragm is small, and the ink ejection power is reduced. This causes a problem that the discharge speed of the liquid crystal becomes slow.
Therefore, the effect as in the present invention cannot be obtained.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, the piezoelectric body is made of a PZT thin film. If the piezoelectric body is composed of a PZT thin film, the ink jet head function is further improved.

According to a third aspect of the present invention, in the first or second aspect, the crystal orientation of the piezoelectric body is (0).
01) The surface is a main component. As for the crystal orientation of the piezoelectric body, if the (001) plane is the main component, a high piezoelectric constant can be obtained (the piezoelectricity is improved), so that sufficient flexural vibration can be generated in the diaphragm.

According to a fourth aspect of the present invention, in the third aspect of the invention, between the vibration plate and the piezoelectric body, the crystal orientation of the piezoelectric body is likely to have a (001) plane as a main component. Characterized in that an auxiliary film is formed. When such an auxiliary film is formed, the effect described in claim 3 is further exhibited.

According to a fifth aspect of the present invention, in the fourth aspect, platinum is used as the auxiliary film. When platinum is used as the auxiliary film,
It has been confirmed by experiments that the crystal orientation of the piezoelectric body is likely to have the (001) plane as a main component.

According to a sixth aspect of the present invention, in the fourth or fifth aspect, a PLT film is provided between the piezoelectric body and the auxiliary film.
When a PLT film is provided between the piezoelectric body and the auxiliary film, the crystal orientation of the piezoelectric body is more likely to have the (001) plane as a main component. This is because the piezoelectric (PZ) is directly on the auxiliary film.
When the (T film) is formed, Zr is likely to adhere in the initial stage, so that the (111) component is slightly increased in the crystal orientation of the piezoelectric body. Therefore, the crystal orientation is (001)
By forming a PLT film containing no Zr between the piezoelectric body and the auxiliary film, the inconvenience is eliminated.

In order to achieve the above object, according to a seventh aspect of the present invention, a thin-film ink is ejected onto one surface of a photosensitive glass substrate capable of anisotropic etching. A diaphragm forming step of forming a diaphragm for forming a thin film having a perovskite crystal structure on the diaphragm, and forming a pressure chamber by etching from the other surface of the photosensitive glass substrate And a piezoelectric body forming step of forming a piezoelectric body by etching the thin film having the perovskite crystal structure.

According to the above manufacturing method, the ink jet head according to the first aspect can be easily manufactured.
Further, since there is no need to bond or weld the piezoelectric body and the diaphragm as in the ink jet head disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-177831, it is possible to easily achieve a high-density nozzle. In addition, since the thickness of the photosensitive glass substrate may be equal to the height of the pressure chamber, the thickness of the photosensitive glass substrate can be reduced. Therefore,
The material cost of the inkjet head can be reduced, and the size of the inkjet head can be reduced.

The invention according to claim 8 is the invention according to claim 7, further comprising an exposure step of exposing a portion corresponding to the pressure chamber before the thin film forming step.
As the thin film forming step, a high-frequency sputter deposition method performed in a temperature range of 450 ° C. to 550 ° C., particularly preferably 510 ° C. to 540 ° C. is used. According to such a method, in the exposure step, only the exposed portion has a large crystal nucleus, and further, in the thin film forming step, the exposed portion becomes crystallized glass (other than the exposed portion is amorphous glass). Therefore, at the time of etching in the pressure chamber forming step, only the crystallized glass is etched, and the amorphous glass part is hardly etched, so that the pressure chamber can be formed smoothly without over-etching.

It should be noted that the temperature in the high frequency sputter deposition method is restricted to a range of 450 ° C. to 550 ° C. When the temperature is lower than 450 ° C., the piezoelectric constant of the piezoelectric element is deteriorated. This is because there is a disadvantage of becoming crystallized glass.

The invention according to claim 9 is the same as that in claim 8.
In the above invention, the energy density in the exposure step is
1.5 to 2.0 J / cm^Two Characterized by the range of
And Regulating energy density in this way is
Energy density is 1.5J / cm ^Two If the value is less than
And the crystallization of the exposed area becomes insufficient.
Lugie density is 2.0 J / cm^Two Over exposure
During etching in the pressure chamber formation process.
This is due to the possibility of causing switching.

According to a tenth aspect of the present invention, in the seventh, eighth or ninth aspect, the piezoelectric body is a PZT.
It is characterized by comprising a thin film. According to an eleventh aspect of the present invention, in the seventh, eighth, ninth, or tenth aspect, the crystal orientation of the piezoelectric body has a (001) plane as a main component. The invention according to claim 12 is:
12. The auxiliary film forming step of forming an auxiliary film in which the crystal orientation of the piezoelectric body is likely to have a (001) plane as a main component between the vibration plate forming step and the thin film forming step. Is included.

The invention according to claim 13 is the first invention.
3. The invention according to item 2, wherein platinum is used as the auxiliary film. According to a fourteenth aspect of the present invention, in the twelfth or thirteenth aspect, a PLT film forming step of forming a PLT film is included between the auxiliary film forming step and the thin film forming step. Features.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a plan view of an inkjet head according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the inkjet head of FIG.
(A)-(h) is sectional drawing which shows the manufacturing process of the inkjet head of FIG.

As shown in FIGS. 1 and 2, the ink jet head of the present invention has a photosensitive glass substrate 1 having a thickness of 0.2 mm. (Not shown), and a pressure chamber 2 for storing ink is formed. A vibrating plate 3 (thickness: 2.0 μm) made of Cr and also serving as a common electrode is formed on one surface of the photosensitive glass substrate 1, and the vibrating plate 3 is vibrated by a piezoelectric body 7 described later. Ink droplets are ejected from the ink ejection ports. Further, C constituting the diaphragm 3
While the Young's modulus of the r film is 12 × 10 ¹⁰ N / m ² , the Young's modulus of the PZT film constituting the piezoelectric body 7 described below is 6
× 10 N / m ² , and the Young's modulus of the Cr film is PZT
It is about twice as large as the Young's modulus of the film. Thereby, the piezoelectric element operates smoothly.

A Ti film 4 (thickness:
0.1 μm) and the Pt film 5 (thickness: 0.3
μm) and a PLT film 6 (thickness: 0.1 μm) are sequentially formed. The Ti film 4 serves as a barrier layer that improves the adhesion between the diaphragm 3 and the Pt film 5 and that prevents the diffusion of Cr and Pt. The Pt film 5 and the PLT film 6 are composed of PZT
The crystal orientation of the film acts so that the (001) plane is the main component. On the PLT film 6, a piezoelectric body made of PZT having a perovskite crystal structure and having a crystal orientation of (001) plane as a main component by the action of the Pt film 5 and the PLT film 6 described above. 7 are formed,
An individual electrode (upper electrode) 8 made of Pt is formed on the piezoelectric body 7. On the other hand, a flat plate 10 in which an ink flow path 9 communicating with the pressure chamber 2 is formed is adhered to the other surface of the photosensitive glass substrate 1.

Here, the ink jet head having the above structure was manufactured as follows. First, a photosensitive glass having a predetermined thickness is polished to a thickness of 0.2 mm to form a photosensitive glass substrate 1 having the same thickness as the depth of the pressure chamber.
Then, as shown in FIG. 3 (a), Cr was applied to one surface of the photosensitive glass substrate 1 by high-frequency sputter deposition (sputtering conditions: normal temperature, time: 1 hour).
The diaphragm 3 was formed by depositing 0 μm. Next, FIG.
As shown in (b), only the part constituting the pressure chamber 2 in the subsequent step on the other surface of the photosensitive glass substrate 1 (that is, the part which penetrates the photosensitive glass substrate in the subsequent step) is made of Cr. A Cr mask 11 that is not covered (that is, only the part constituting the pressure chamber 2 is transparent) is arranged and exposed. At this time, only the exposed portion 12 has a large crystal nucleus, and becomes a crystallized glass due to heat at the time of performing a high-frequency sputtering deposition method or the like as a subsequent process. The exposure condition at this time is a condition that exposure is performed with light having a wavelength of 365 nm and energy of 1.8 J / cm ² .

Next, as shown in FIG. 3C, 0.1 μm of Ti is deposited on the vibrating plate 3 by a high-frequency sputter deposition method (sputtering condition: normal temperature, time: 10 minutes). After the film 4 is formed, Pt is deposited to 0.3 μm by high frequency sputter deposition (sputtering conditions: temperature: 530 ° C., time: 10 minutes) to form a Pt film 5, and PLT
To a high frequency sputter deposition method (sputter condition: temperature is 530)
(For 10 minutes) to form a PLT film 6. Thereafter, as shown in FIG. 3D, PZT is deposited on the PLT film 6 by high-frequency sputter deposition (sputtering conditions: temperature: 530 ° C., time: 2 hours) to 4.0.
The PZT film 13 was formed by depositing a thickness of μm. In the step of forming the Pt film 5 and the PLT film 6, since the sputtering temperature is as high as 530 ° C., the exposed portion 12 in the exposure step is crystallized.
It cannot be sufficiently crystallized. However, the PZT film 1
In the forming step 3, since the sputtering temperature is as high as 530 ° C. and the sputtering time is long, the exposed portion 12 can be surely crystallized.

Thereafter, as shown in FIG. 3E, the substrate temperature is lowered to room temperature, and the PZT film 13 is formed.
Pt is deposited 1.0 μm on the top by sputter deposition to form Pt.
The t film 14 was formed. Next, as shown in FIG.
From the lower surface side (A direction in the figure) of the photosensitive glass substrate 1, 30
% Hydrofluoric acid solution was sprayed to etch the crystallized exposed portion 12 to form a pressure chamber 2. Next, as shown in FIG. 3 (g), after a resist pattern is formed on the Pt film 14, RIE (reactive ion.
Etching was performed by the (etching) method to form individual electrodes (upper electrodes) 8. Thereafter, a resist pattern for individualizing the PZT film 13 is formed, and HF and HNO _{3 are} further formed.
The piezoelectric body 7 is etched by an aqueous solution mixed with
Was formed. Thereby, an actuator of the inkjet head can be obtained. Lastly, an ink jet head was manufactured by etching or pressing a SUS thin plate and bonding the flat plate 10 on which the ink flow path 9 was formed to the lower surface of the photosensitive glass substrate 1.

Here, the diaphragm 3 is not limited to the Cr film, but may be SUS, Ti, W, Mo, polysilicon or the like. Further, a-Si ₃ N
_It can be manufactured by forming a film of _{4-xO x} (0.02>X> 3.5) by a plasma CVD method. The thickness of the diaphragm 3 is not limited to 2.0 μm as described above, but is preferably in the range of 1.0 to 5.0 μm. If the thickness of the vibration plate 3 is less than 1.0 μm, sufficient stress and vibration will not be generated, while if the thickness of the vibration plate 3 exceeds 5.0 μm, the thickness of the piezoelectric body 7 will increase accordingly. This is because there is a problem that the necessity arises and the size of the inkjet head is increased.

Further, a Ti film 4, a Pt film 5, and a PLT film 6
The thickness of is not limited to the values shown above,
The Ti film 4 has a range of 0.05 to 0.1 μm, the Pt film 5 has a range of 0.1 to 0.5 μm, and the PLT film 6 has a thickness of 0.05 to 0.1 μm.
Within the range of 0.1 μm, the same effect as above can be obtained.
The reason why such a range is preferable is that each of the films 4, 5, 6
If the value is less than the minimum value, the functions of the films 4, 5, and 6 cannot be sufficiently exhibited. On the other hand, if the values of the films 4, 5, 6 exceed the maximum value, the size of the ink jet head is increased. Because it has. In addition, the upper electrode 8 is not limited to Pt but may be Au.
Further, as a method of forming the upper electrode 8, a vacuum evaporation method can be used.

The etching of the photosensitive glass substrate 1 is not limited to the spray method, but may be performed by a dipping method. However, when the dip method is used, the working time is long and the possibility of over-etching is high, so that the spray method is preferable. Further, when the photosensitive glass substrate 1 is etched, it is desirable that the deposition surface (side surface) of the PZT film 13 and the like be covered with a resist or the like to protect it from the HF solution. In addition, the time for forming the PZT film 13 is not limited to 2 hours, and the same effect as described above can be obtained if it is in the range of 1.5 to 3 hours.

[0033]

EXAMPLES Example 1 In Example 1, an ink jet head manufactured by the method described in the above embodiment of the present invention was used. The ink jet head manufactured in this manner is hereinafter referred to as head A of the invention.

COMPARATIVE EXAMPLE A piezoelectric material (Pt film and PLT film) made of PZT was formed on a silicon substrate by high-frequency sputtering deposition.
An ink-jet head was manufactured by forming a piezoelectric body having no film. The ink jet head thus manufactured is hereinafter referred to as a comparative head X.

[Experiment] The piezoelectric constant (d ₃₁ ) of the head A of the present invention and the comparative head X was examined. In the head A of the present invention, d ₃₁ = 100 pC / N, which is a very high value. Therefore, in the comparative head X, d ₃₁ = 45 pC /
N was found to be a very low value.

[0036]

As described above, according to the present invention,
It is possible to increase the density of the nozzles while suppressing the shortening of the life of the inkjet head and the reduction of the piezoelectric constant, and it is possible to easily produce such an excellent inkjet head.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of the inkjet head of FIG.

3 (a) to 3 (h) are cross-sectional views showing the steps of manufacturing the ink jet head of FIG.

[Explanation of symbols]

 1: photosensitive glass substrate 2: pressure chamber 3: diaphragm 4: Ti film 5: Pt film 6: PLT film 7: piezoelectric body 8: individual electrode 9: ink flow path 10: flat plate 11: Cr mask 12: exposure part 13: PZT film 14: Pt film

Claims (14)

[Claims] A piezoelectric element having a vibrating plate for ejecting ink and a piezoelectric body having a perovskite crystal structure is formed on one surface of a substrate having a pressure chamber, and is provided on the other surface of the substrate. Is an ink jet head provided with an ink flow path, wherein the substrate is made of a photosensitive glass substrate capable of anisotropic etching, and both the vibration plate and the piezoelectric body are made of a thin film. Ink jet head. 2. The ink jet head according to claim 1, wherein said piezoelectric body is made of a PZT thin film. 3. The ink jet head according to claim 1, wherein the crystal orientation of the piezoelectric body has a (001) plane as a main component. 4. The ink jet head according to claim 3, wherein an auxiliary film is formed between the vibration plate and the piezoelectric body so that the crystal orientation of the piezoelectric body tends to have a (001) plane as a main component. . 5. The ink jet head according to claim 4, wherein platinum is used as said auxiliary film. 6. A piezoelectric element between the piezoelectric body and the auxiliary film.
The inkjet head according to claim 4, further comprising an LT film. 7. A vibrating plate forming step of forming a vibrating plate made of a thin film for ejecting ink on one surface of a photosensitive glass substrate capable of anisotropic etching, and forming a perovskite crystal on the vibrating plate. A thin film forming step of forming a thin film having a structure; a pressure chamber forming step of etching a photosensitive glass substrate from the other surface of the photosensitive glass substrate to form a pressure chamber; and etching the thin film having a perovskite crystal structure. And a piezoelectric body forming step of forming a piezoelectric body. 8. An exposing step of exposing a portion corresponding to the pressure chamber to light before the thin film forming step, wherein the thin film forming step is performed at 450 ° C. to 550 ° C., particularly preferably 510 ° C. to 540 ° C. The method for manufacturing an inkjet head according to claim 7, wherein a high-frequency sputter deposition method performed in a temperature range is used. 9. The method according to claim 8, wherein the energy density in the exposure step is in a range of 1.5 to 2.0 J / cm ² . 10. The method for manufacturing an ink jet head according to claim 7, wherein the piezoelectric body is made of a PZT thin film. 11. The method for manufacturing an ink jet head according to claim 7, wherein the crystal orientation of the piezoelectric body has a (001) plane as a main component. 12. An auxiliary film forming step of forming an auxiliary film in which the crystal orientation of the piezoelectric body has a (001) plane as a main component is included between the vibration plate forming step and the thin film forming step. The method for manufacturing an ink jet head according to claim 11, wherein: 13. The method according to claim 13, wherein platinum is used as the auxiliary film.
A method for manufacturing an ink jet head according to claim 12. 14. The method according to claim 12, wherein a PLT film forming step of forming a PLT film is included between the auxiliary film forming step and the thin film forming step.