JP2001113696A - Ink-jet head and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ease a positioning accuracy between a piezoelectric element and an adhesive layer on the piezoelectric element and eliminate problems in relation to a liquid adhesive in the prior art, etc., in an on-demand type ink-jet head with the piezoelectric element. SOLUTION: A plurality of piezoelectric elements 2 are arranged in parallel and a diaphragm part 3 of a diaphragm is joined between the piezoelectric elements in the ink-jet head. The diaphragm part is joined to the piezoelectric elements by a film-like adhesive having two slits 5b and 5b formed opposite to each other (more correctly, an adhesive 5a which is a body of the film-like adhesive). The slits 5b and 5b are formed in parallel to an arrangement direction of the piezoelectric elements while spaced by a larger distance D than a breadth W of the diaphragm part. According to the head, high-quality images can be stably formed even when nozzles are set with a high density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drop-on-demand type ink-jet head which forms and discharges ink droplets only when recording is required and performs ink recording on a desired recording medium. The present invention relates to a structure of a multi-nozzle head having the above-described ink droplet discharge nozzle and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, continuous jet type, intermittent jet type, ink mist type, on-demand type and the like are known as ink jet recording heads. Further, an on-demand type ink jet head uses a piezoelectric element as a driving means (Japanese Patent Publication No. 2-51734), or a type which heats ink to generate bubbles and discharges ink by the pressure (special purpose). Japanese Patent Publication No. 61-59911).

An ink jet head using a piezoelectric element generates a pressure wave by applying an electric signal to the piezoelectric element.
Since the ink droplet is ejected by the pressure wave, there is an advantage that the ink droplet can be ejected only when necessary. Further, in this ink jet head, since a pressure pulse corresponding to an electric signal can be generated, there is an advantage that a driving circuit and an entire structure are simple.

FIG. 7 is a schematic sectional view showing a typical conventional example of such an ink jet head. In this head, a piezoelectric element 42, a frame 50, an electrode (not shown), and the like
And a diaphragm portion 43, which is a main part of a vibration plate 44, is bonded on the actuator portion 40 with an adhesive 45. Further, on the vibration plate 44, a liquid chamber 47, a common liquid chamber 49, and a nozzle plate 46 are provided. Reference numeral 48 denotes a fluid resistance, and reference numeral 46a denotes a nozzle.
In the actuator section 40, the frame 50 surrounds the periphery of the piezoelectric element 42, and the frame 50 further includes a liquid chamber 47.
It is joined with and supports this.

In the above-mentioned head, a pressure is applied to a liquid chamber 47 joined on the diaphragm 44 (more precisely, on the diaphragm 43) due to a volume change of the piezoelectric element 42 due to voltage application, and a common liquid chamber 49 is formed. The ink in the liquid chamber 47 filled with the ink flowing from the nozzle 46a is ejected from the nozzle 46a as ink droplets.

In manufacturing an ink jet head as shown in FIG. 7, when the piezoelectric element 42 is joined to the diaphragm 44 (diaphragm 43), the positioning between the piezoelectric element 42 and the diaphragm 43 is performed accurately. It is important to ensure that these bonds are made evenly. Further, when the nozzles are provided at a high density, it is necessary to particularly increase the accuracy of the alignment. Otherwise, since the vibration of the piezoelectric element 42 is not accurately transmitted to the diaphragm 43, stable ejection of ink droplets cannot be obtained.

In the prior art, a liquid adhesive has been used for joining the piezoelectric element and the diaphragm. However, with this liquid adhesive, (1) the cured component protrudes at the time of curing and contaminates the piezoelectric element.
(2) In order to cure, it is usually necessary to heat at a high temperature for a long time. (3) Before the actual bonding, a bonding step for maintaining the alignment state between the piezoelectric element and the diaphragm is required. (4) Therefore, there is a problem that it is difficult to mass-produce a high-quality head with good yield.

As a means for solving this problem, it has been proposed to use a so-called film adhesive. As an example of the film-like adhesive, a heat-reactive (thermosetting) adhesive is coated on one side of a release paper in a film (thin film) form instead of a liquid state. The agent is the body of the film adhesive.

In order to use the film adhesive, the surface of the main body is adhered to the surface to be joined of one member A, and the release paper is removed. After the film is transferred and applied, the other member B is overlaid on the adhesive body on the member A, and then the members A and B are joined by thermocompression bonding.

However, when a film-like adhesive is used, the film (the main body of the film-like adhesive, that is, the adhesive) is deformed by the load of the thermocompression bonding, so that the adhesive is protruded or uniformly bonded. A new problem has arisen, such as the inability to do so.

In the head disclosed in Japanese Patent Application Laid-Open No. 9-39243 (Title of Invention: Laminated ink jet recording head, its manufacturing method, and recording apparatus), a film-like adhesive provided with through holes is used. This solves the problem of the adhesive protruding as described above. However, in this head, it is necessary to align the member to be bonded and the through hole, and when the nozzles have a high density, high-precision alignment is required, and the alignment state is determined by thermocompression bonding. There was a risk that the data could easily become out of order (prone to misalignment).

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide an on-demand type ink jet head having a piezoelectric element as a driving member for ink ejection. By joining the piezoelectric element and the diaphragm of the diaphragm using a predetermined film adhesive, the alignment accuracy between the piezoelectric element and the adhesive layer on the piezoelectric element can be reduced, and the liquid bonding in the conventional technology can be reduced. To provide an inexpensive inkjet head that is highly reliable, mass-producible, and can prevent problems associated with the adhesive and troubles such as sticking out of the adhesive when using a conventional film adhesive. is there.

[0013]

According to the first aspect of the present invention, there is provided an ink jet head (see FIGS. 1 to 3) in which a plurality of piezoelectric elements 2 are arranged in parallel, and a diaphragm 4 is provided at a position corresponding to the piezoelectric elements 2. In the ink jet head in which the diaphragm portions 3 are joined and the ink droplets are ejected from the nozzles 6a using the volume change of the piezoelectric element 2, the diaphragm portion 3 has two slits 5b, 5b facing each other. The piezoelectric element 2 is bonded to the piezoelectric element 2 by a film-like adhesive 5 formed more precisely (more precisely, the main body of the film-like adhesive 5, that is, the adhesive 5a), and the slits 5b, 5b are arranged in the direction in which the piezoelectric element 2 is arranged. It is characterized by being parallel.

According to the first aspect of the present invention, the positional accuracy of the adhesive layer formed on the piezoelectric element is reduced, and a head having high-density nozzles and excellent in image quality can be manufactured with high productivity. it can.

According to a second aspect of the present invention, in the inkjet head according to the first aspect, the adhesive body constituting the film adhesive is a heat-reactive adhesive.
According to the present invention, the piezoelectric element and the diaphragm of the diaphragm can be firmly joined in a short time, and a head having excellent image quality can be manufactured with high productivity.

According to a third aspect of the present invention, in the ink jet head according to the first aspect, the adhesive body constituting the film adhesive is an epoxy-based adhesive. According to the present invention, the piezoelectric element and the diaphragm of the diaphragm can be particularly firmly joined, and a head having excellent image quality can be manufactured with high productivity.

According to a fourth aspect of the present invention, in the ink jet head according to the second aspect, the epoxy adhesive is a heat-reactive adhesive. According to the present invention, the piezoelectric element and the diaphragm of the diaphragm can be particularly firmly joined in a short time, and a head having excellent image quality can be manufactured with higher productivity.

According to a fifth aspect of the present invention, in the ink jet head according to any one of the first to fourth aspects, a groove is formed in a portion corresponding to a space between the piezoelectric elements adjacent to each other on a surface of the vibration plate facing the piezoelectric element. It is characterized by being formed. According to the present invention, since the adjacent diaphragm portions are separated from each other, even when a large number of diaphragm portions are arranged at a small pitch in increasing the density of the nozzles, interference between the diaphragm portions is reduced, so that image quality is reduced. A head excellent in quality can be manufactured with good yield. Further, since the excess adhesive escapes into the groove, the adhesive is prevented from protruding, and the gap (interval) between the vibration plate and the piezoelectric element becomes uniform, which also contributes to the improvement of image quality.

According to a sixth aspect of the present invention, in the ink jet head according to any one of the first to fifth aspects, the surface roughness of the bonding surface of the piezoelectric element surface with the film adhesive is such that the adhesive constitutes the film adhesive. It is characterized by being smaller than the thickness of the main body. According to the present invention, the amount of adhesive flowing into the uneven portion on the surface of the piezoelectric element is reduced, so that the diaphragm portion can be joined to the piezoelectric element without unevenness, and the gap between the diaphragm and the piezoelectric element becomes uniform. Thus, a head having excellent image quality can be manufactured.

According to a seventh aspect of the present invention, in the ink jet head according to any one of the first to sixth aspects, a groove is formed on a surface of the diaphragm portion on a side facing the piezoelectric element. According to this invention, the same operation and effect as those of the ink jet head according to claim 5 can be obtained.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the thickness of the adhesive body of the film adhesive is smaller than the thickness of the diaphragm. According to the present invention, the amount of excess adhesive is reduced, so that contamination of the piezoelectric element and the like due to the protrusion of the adhesive is prevented, and the uniformity of the gap between the diaphragm and the piezoelectric element is facilitated. A head with excellent quality can be obtained.

According to a ninth aspect of the present invention, there is provided a method for manufacturing an ink jet head according to the second aspect, wherein a heat-reactive adhesive is applied on release paper, and two slits face each other. Prepare the formed film adhesive, bond the film adhesive to the piezoelectric element by heating, remove the release paper, remove the release paper, and transfer the vibration-sensitive adhesive to the remaining heat-reactive adhesive transferred to the piezoelectric element. And the piezoelectric elements are joined by thermocompression bonding (heating under pressure) via the heat-reactive adhesive. According to the present invention, the inkjet head according to the second aspect can be manufactured with a high yield by a simple process.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 1 is a schematic cross-sectional view showing a main structure of an ink jet head, and FIG. 2 is a plan view of FIG. FIG. 3 is a plan view showing a film adhesive used for manufacturing the above-described inkjet head. FIG. 4 is an explanatory diagram of a diaphragm portion of a diaphragm constituting the inkjet head.

As shown in FIGS. 1 and 2, in this ink jet head, an actuator section composed of a piezoelectric element 2, a frame, electrodes (not shown) and the like is joined on a substrate 1. A large number of piezoelectric elements 2 are arranged on the substrate 1 in a line at equal intervals.
Are joined together by an adhesive layer 5a formed by the film adhesive 5 shown in FIG. The diaphragm 4 has the diaphragm portion 3 on the lower surface side, and the upper surface forms the bottom surface of the liquid chamber 7a. Each of the diaphragm portions 3 is an elliptical shape that is substantially congruent with each other (FIGS. 2 and 4).

The piezoelectric element 2 and the diaphragm 3 correspond one to one. Further, the liquid chambers 7 a are arranged on the diaphragm 4 directly above the diaphragm 3 so as to correspond to the diaphragm 3 on a one-to-one basis. Therefore,
The liquid chamber 7a is located immediately above the piezoelectric element 2. As described above, the diaphragm 3 is a part of the vibration plate 4 and serves as a joint with the piezoelectric element 2. In FIG. 1, reference numeral 6 denotes a nozzle plate, reference numeral 6a denotes a nozzle, reference numeral 8 denotes a common flow path,
Reference numeral 9 denotes an ink supply path.
a is an annular groove surrounding the diaphragm portion 3.

As shown in FIG. 3, the film adhesive 5 is coated on one side of a release paper with, for example, a heat-reactive (thermosetting) adhesive to form a film-like adhesive layer 5a. The two slits 5b, 5b are formed so as to face each other in a parallel state. Therefore, the adhesive layer 5a is the main body of the film adhesive 5. In FIG. 3, reference numeral 5c denotes a belt-like portion.

In manufacturing the ink jet head shown in FIG. 1, an ink jet head having a form in which a number of piezoelectric elements 2 are arranged in a line on a substrate 1 is prepared. Then, the film adhesive 5
Are placed on the upper surfaces of the piezoelectric elements 2, 2,..., And heated and pressed by a hot roll to adhere the film-like adhesive 5 to the upper surface of the piezoelectric elements 2. In this case, the band-shaped portion 5c between the slits 5b, 5b is aligned with the upper surface of the piezoelectric element 2. Then, by peeling the release paper, the other surface of the adhesive layer 5a is exposed, and the diaphragm portion 3 of the diaphragm 4 is overlapped with the exposed adhesive layer 5a in a state where the diaphragm portion 3 is aligned with the band portion 5c. The piezoelectric element 2 and the diaphragm unit 3 are pressed and heated by the heat roll,
Temporary bonding is performed via the adhesive layer 5a. Thereby, the liquid chamber 7
a is disposed directly above the piezoelectric element 2. Thereafter, the piezoelectric element 2 and the diaphragm portion 3 are thermocompression-bonded to each other via an adhesive layer 5a by a press equipped with a pulse heater to perform the actual bonding. According to the pulse heater, the adhesive layer 5a can be heated to a predetermined temperature in a short time.

When a heat-reactive epoxy adhesive is used as the adhesive layer 5a and is heated to 150 ° C., the curing is completed within a few minutes, and a sufficient adhesive hardness can be obtained. Further, even if no pressure is applied to cure the adhesive layer 5a, for example, the diaphragm portion 3 and the piezoelectric element 2 are temporarily bonded at 150 ° C. × 2 minutes, and then the head cover is bonded at 120 ° C. × 1 hour. Under the conditions described above, the curing of the adhesive layer 5a progresses, and good adhesive strength with vibration resistance can be obtained.

The film-like adhesive 5 is one in which an adhesive layer is formed on one surface of one piece of release paper, and the above-mentioned joining operation is performed on the vibration plate 4 having the diaphragm 3 on the piezoelectric element 2. Is bonded by the adhesive layer 5a, so that a film adhesive having a three-layer structure of release paper / adhesive layer / release paper can be used instead of the film adhesive 5.

The operation of the head is the same as that of the head shown in FIG. 7. In FIG. 1, ink is supplied from an ink supply port 9 to each liquid chamber 7a through a common flow path 8. Then, due to a change in volume of the piezoelectric element 2 due to the application of a voltage, a pressure is applied to the liquid chamber 7 a on the diaphragm portion 3, and the ink in the liquid chamber 7 a is ejected from the nozzle 6 a of the nozzle plate 6 as an ink droplet. You.

As shown in FIG. 2, the slits 5b,
The band-like portion 5c between 5b covers the entire diaphragm portion 3 (slits 5b are arranged outside both ends in the width direction of the diaphragm portion 3). In the slit 5b, the annular groove 3a surrounding the diaphragm portion 3 is formed. A part and both ends in the width direction of the piezoelectric element 2 are exposed. By using the film adhesive 5 and by setting the positional relationship between the adhesive 5 and the piezoelectric element 2 and the diaphragm portion 3 as described above, intrusion of the adhesive and contact with the adhesive are avoided. Extrusion of the adhesive to a desired portion is suppressed, and the bonding area by the adhesive is reduced, so that the protruding amount is also reduced. Further, there is an advantage that the positional accuracy of the adhesive layer 5a does not depend on the nozzle density of the head.

In FIG. 2, the interval D between the slits 5b is preferably larger than the width W of the diaphragm. In this case, the positional accuracy of the adhesive layer 5a is required only in the longitudinal direction of the piezoelectric element 2, and the positional accuracy in the lateral direction is not required.

In the ink jet head of the present invention, it is important that the piezoelectric element 2 and the diaphragm portion 3 are firmly joined to each other. For this purpose, the adhesive, which is the main body of the film adhesive, is an epoxy adhesive. Is preferable, and a heat reaction type epoxy adhesive is particularly preferable. With this heat-reactive epoxy-based adhesive, the curing of the adhesive proceeds only by heating, so that a bond having high adhesive strength can be obtained without applying pressure and applying a load.
Commercially available film adhesives include, for example,
"Heat-reactive film adhesive for flexible printed circuit boards: ThreeBond 1650" manufactured by ThreeBond Co., Ltd.
(Product name). In this method, a heat-reactive epoxy-based adhesive is applied to one side of a 30 μm-thick release paper with a thickness of 5 μm.
m.

As the material of the piezoelectric element 2, a laminate of PZT, that is, Pb (Zr, Ti) O ₃ ceramics can be used. The material and thickness of the substrate 1 are not particularly limited, but the material is similar to the piezoelectric element 2 and can be cut at the same time as the piezoelectric element. For example, ceramics such as alumina, zirconia, and barium titanate are preferable. Is mentioned. Note that the substrate thickness is preferably about 0.5 to 2 mm.

Second Embodiment FIG. 5 is a schematic plan view showing a main structure of an ink jet head, and FIG. 6 is a sectional view taken along line AA of FIG. As shown in FIG. 6, by forming a groove 5d between the adjacent diaphragm portions 3, 3, the diaphragms 4, 4 are separated from each other, so that vibration is not transmitted between the channels. Also, when the nozzles are increased in density, the bonding strength between the diaphragm 4 and the liquid chamber wall 7b may be reduced. In this case, the separated diaphragms are shown in FIGS. Thus, by adhering via the film-like adhesive (the adhesive layer 5a thereof), stable ink ejection can be obtained even when the diaphragm is separated. Also,
Since the protrusion of the adhesive is prevented by the groove 5d,
A good bonding state can be obtained. That is, by forming the grooves 5d between the diaphragms and laminating the adhesive layer 5a across these diaphragms, the excess adhesive when performing the actual bonding by heating under pressure is formed. Since it escapes into 5d, the joint strength between diaphragm 4 (diaphragm section 3) and liquid chamber wall section 7b can be made sufficient without contaminating the surroundings.

[0036]

Embodiments of the present invention will be described below. Example 1 An ink jet head shown in FIG. 1 was produced. Piezoelectric elements made of PZT and having a width of 96 μm and a length of 2.5 mm were arranged on the substrate at a pitch of 165 μm. An elliptical diaphragm portion (FIG. 4) is formed by etching a predetermined portion of a stainless steel diaphragm having a thickness of 5 μm, and its dimension is set to width 2
mm × length 45 μm × thickness 35 μm. A liquid chamber made of stainless steel was joined on the diaphragm (at a position directly above the diaphragm portion 3) using a film-like adhesive made of a heat-reactive epoxy adhesive. The film adhesive was also used for joining the piezoelectric element to the diaphragm and joining the head cover.

That is, after the liquid chamber was formed, the liquid chamber was temporarily bonded on the vibration plate using the film adhesive. This temporary bonding was performed at 110 ° C. using a heat roller. The displacement of the adhesive at this time was 20 μm in the longitudinal direction of the piezoelectric element.
Had occurred. Thereafter, the liquid chamber and the piezoelectric element were aligned, and then the actual bonding was performed. The heating condition for this permanent bonding is 160
C. × 2 minutes. Then, the head cover was joined to 160
C. for 2 hours. When the ink was ejected with the head manufactured in this manner, good printing was obtained. At this time, the variation in the ink ejection speed between bits was 11%, and when the channels on both sides were driven, the ejection speed increased by 6%.

Example 2 A head was manufactured in the same manner as in Example 1 except that a groove having a width of 30 μm was formed between the diaphragm portions. The rate of increase in the ejection speed when the channels on both sides were driven was 1% or less.

Example 3 A head was manufactured in the same manner as in Example 1 except that a groove having a width of 5 μm and a depth of 8 μm was formed in the diaphragm portion (self). In this case, the variation of the ink ejection speed between bits is 3
% Or less.

[0040]

As is clear from the above description, the following effects can be obtained according to the present invention. (1) Effect of the invention of claim 1 Positional accuracy of an adhesive layer formed on a piezoelectric element is relaxed,
A head having high density nozzles and excellent image quality can be manufactured with high productivity. (2) Effect of the Second Invention The piezoelectric element and the diaphragm of the diaphragm can be firmly joined in a short time, and a head having excellent image quality can be manufactured with high productivity.

(3) Advantageous Effects of the Third Embodiment The piezoelectric element and the diaphragm of the diaphragm can be particularly firmly joined to each other, and a head having excellent image quality can be manufactured with high productivity. . (4) Advantageous Effect of the Invention According to Claim 4 A head excellent in image quality, in which a piezoelectric element and a diaphragm portion of a diaphragm can be particularly firmly joined in a short time,
It becomes possible to manufacture with higher productivity. (5) Advantageous Effects of the Invention Since the adjacent diaphragm portions are separated from each other, even when a large number of diaphragm portions are arranged at a small pitch in increasing the density of the nozzle, interference between the diaphragm portions is reduced. Therefore, a head having excellent image quality can be manufactured with good yield. Further, since the excess adhesive escapes into the groove, the adhesive is prevented from protruding, and the gap (interval) between the vibration plate and the piezoelectric element becomes uniform, which also contributes to the improvement of image quality.

(6) Effect of the invention of claim 6 Since the amount of adhesive flowing into the uneven portion on the surface of the piezoelectric element is reduced, the diaphragm portion can be joined to the piezoelectric element without unevenness, and the gap between the diaphragm and the piezoelectric element can be improved. Is uniform, so that a head having excellent image quality can be manufactured. (7) Effects of the Invention of Claim 7 The same effects as those of the ink jet head of claim 5 can be obtained. (8) Effect of the invention of claim 8 Since the amount of excess adhesive is reduced, contamination of the piezoelectric element and the like due to the protrusion of the adhesive is prevented, and the uniformity of the gap between the diaphragm and the piezoelectric element is easily achieved. Therefore, a head having excellent image quality can be obtained.

(9) Effect of the invention of claim 9 The inkjet head according to claim 2 can be manufactured with a high yield by simple steps.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a main part structure of an inkjet head according to a first embodiment.

FIG. 2 is a plan view of FIG.

FIG. 3 is a plan view showing a film adhesive used for manufacturing the ink jet head of FIG.

FIG. 4 is an explanatory diagram of a diaphragm portion of a diaphragm constituting the ink jet head of FIG. 1;

FIG. 5 is a schematic plan view illustrating a main structure of an inkjet head according to a second embodiment.

FIG. 6 is a sectional view taken along line AA of FIG. 5;

FIG. 7 is a schematic cross-sectional view illustrating a main part structure of a conventional ink jet head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Piezoelectric element 3 Diaphragm part 3a Annular groove 4 Vibration plate 5 Film adhesive 5a Adhesive layer (film adhesive main body) 5b Slit 5c Band 5d Groove 6 Nozzle plate 6a Nozzle 7a Liquid chamber 7b Liquid chamber wall Reference Signs List 8 common flow path 9 ink supply port 40 actuator section 41 substrate 42 piezoelectric element 43 diaphragm section 44 vibrating plate 45 adhesive 46 nozzle plate 46a nozzle 47 liquid chamber 48 fluid resistance 49 common liquid chamber 50 frame

Claims (9)

[Claims] 1. A plurality of piezoelectric elements are arranged in parallel, and a diaphragm portion of a diaphragm is joined to a position corresponding to the piezoelectric elements.
In the ink jet head configured to eject ink droplets from a nozzle using a change in volume of the piezoelectric element, the diaphragm portion is formed by a film-like adhesive in which two slits are formed facing each other. Wherein the two slits are parallel to an arrangement direction of the plurality of piezoelectric elements. 2. The ink jet head according to claim 1, wherein the adhesive body constituting the film adhesive is a heat-reactive adhesive. 3. The ink jet head according to claim 1, wherein the adhesive body constituting the film adhesive is an epoxy adhesive. 4. The ink jet head according to claim 3, wherein the epoxy adhesive is a heat-reactive adhesive. 5. The groove according to claim 1, wherein a groove is formed in a portion of the surface of the vibrating plate facing the piezoelectric element, the groove corresponding to a portion between the piezoelectric elements adjacent to each other. An inkjet head according to any one of the above. 6. The method according to claim 1, wherein the surface roughness of the surface of the piezoelectric element joined to the film adhesive is smaller than the thickness of an adhesive body constituting the film adhesive. 5. The inkjet head according to any one of 5. 7. The ink jet head according to claim 1, wherein a groove is formed on a surface of the diaphragm portion facing the piezoelectric element. 8. The ink jet head according to claim 1, wherein the thickness of the adhesive body of the film adhesive is smaller than the thickness of the diaphragm. 9. When manufacturing the ink jet head according to claim 2, a heat-sensitive adhesive is applied on a release paper, and a film-like adhesive having two slits formed opposite to each other is used as the piezoelectric element. Then, the release paper is removed by heating and laminating to remove the release paper, and the diaphragm portion of the vibration plate is aligned with the heat-reactive adhesive remaining on the piezoelectric element. A method for manufacturing an ink jet head, wherein the bonding is performed by thermocompression bonding via an adhesive.