JPH07299905A - Ink jet head and production thereof - Google Patents

Abstract

PURPOSE:To obtain an ink jet head equipped with piezoelectric elements different in the quantity of electric strain from the comb-tooth tip parts to root parts thereof and achieved in the extension of life by preventing the crack and damage of the piezoelectric elements. CONSTITUTION:An ink jet head is equipped with a large number of pressure chambers 11 having nozzles 9 and receiving the supply of ink and a large number of piezoelectric elements 80 integrally formed thereto in a comb-tooth shape corresponding to the number of the pressure chambers 11 so that the tip parts thereof are in contact with the walls of the pressure chambers 11 and different in the quantity of electric strain from the tip parts to root parts thereof. Voltage is applied to the piezoelectric elements 80 to vibrate the walls of the pressure chambers 11 by the electric strain of the piezoelectric elements 80 to eject the ink 6 in the pressure chambers 11 from the nozzles 9.

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 for an ink jet printer and a method of manufacturing the same, and more particularly, to an ink jet head provided with a piezoelectric element having a different amount of electric strain from the tip to the root of a comb tooth shape. The present invention relates to a manufacturing method thereof.

Recently, an ink jet printer for directly recording fine particles of ink onto a print medium for recording has no limitation on the print medium, high-speed printing is possible, low noise, and easy colorization. It is spreading rapidly.

In the ink jet head of this ink jet printer, pressure is applied to a pressure chamber filled with ink through a vibrating plate by displacement due to electric strain of a piezoelectric element to eject ink from a nozzle to form dot printing. .

This piezoelectric element is formed in a strip shape corresponding to the number of nozzles, but since it is high in cost and easily damaged, it must be handled with care. A method of integrally forming has been proposed. But,
Although the cost can be improved, stress concentration at the comb-tooth-shaped root portion due to driving and cracks and breakage due to material fatigue are likely to occur, so a method that does not cause breakage is desired.

[0005]

2. Description of the Related Art FIG. 11 shows an outline of an ink jet printer. As shown in the figure, a guide shaft 3 is fitted to a carrier 2 having an inkjet head (hereinafter referred to as a print head) 1, and a feed screw 4 is screwed to the carrier 2.
The feed screw 4 is connected to a motor (not shown). The carrier 2 is arranged on the front surface of the platen 5, and is moved in parallel with the platen 5 in the directions of arrows A and B by the feed screw 4 by the forward and reverse rotations of the motor.

The print head 1 is opposed to the platen 5 with a predetermined gap and has a plurality of nozzles 9 _{1 to} 9n, which will be described later, at its tip.
(For example, 4 columns x 12 rows, 48 pieces). Therefore, while the carrier 2 moves, the print head 1 moves the nozzles 9 _{1 to} 9n.
Ink 6a is ejected from the ink to form a print on the printing paper 7 by matrix dots. The print sheet 7 is driven by a moving mechanism (not shown) and the platen 5 rotates to move the arrow C.
It is sent to the direction.

Next, the print head 1 will be described with reference to the side view of FIG. As shown in FIG. 12, the print head 1 includes a piezoelectric element.
80 _{1 to} 80n, a nozzle plate 10a provided with nozzles 9 _{1 to} 9n,
Pressure chambers corresponding to the nozzles 9 ₁ to 9 n together with the nozzle plate 10 a
It is composed of diaphragms 12 _{1 to} 12 n forming 11 ₁ to 11 n.

[0008] in a position where the nozzle plate 10a and the vibration plate 12 ₁ ～12N are opposed with respect to the pressure chamber 11 ₁ ～11N, the pressure chamber 11 ₁
The vibrating plates 12 _{1 to} 12 n and the corresponding vibrating plates 12 _{1 to} 12 n are bonded with an adhesive to support the piezoelectric element 80 supported by the substrates 13 ₁ to 13 n.
₁ ～80N is arranged so as to expand and contract in the vibration direction of the diaphragm 12 ₁ ~12n.

The diaphragms 12 _{1 to} 12 n are made of nickel (N
i) Piezoelectric element 80 _{1 to} 80 n made of a thin film formed by electroforming
Contact the tip of the pressure element to displace the piezoelectric elements 80 _{1 to} 80 n.
11 _{1 to} 11n are transmitted.

The piezoelectric elements 80 _{1 to} 80 n are formed of a ceramic plate, and have a common electrode (plus) 14 and a single electrode (minus) 15 that are drawn out to be polarized. When a voltage is applied to the piezoelectric element 80 ₁ ~80n, tip each is displaced by an electrical strain.

Accordingly, selectively applying a voltage to the piezoelectric element 80 ₁ ~80n (in fact, all of the piezoelectric elements 80 ₁ ~80n advance by applying a voltage, releases the selective voltage is applied) to , By vibrating the vibrating plates 12 ₁ to 12 n according to the displacement amount of the tip thereof, the pressure chambers 11 ₁ to
By applying pressure to 11n, the particles of the ink 6a are ejected from the nozzles 9 _{1 to} 9n as described above.

The above-mentioned piezoelectric elements 80 _{1 to} 80 n are individually formed in a strip shape and attached to the substrates 13 ₁ to 13 n, but since the cost is high, in order to reduce the cost, FIG.
As shown in FIG. 1, a method of integrally forming a comb-teeth shape (for a comb-teeth-shaped piezoelectric element, see, for example, Japanese Patent Laid-Open No. 63-218
No. 363, “Inkjet recording apparatus”) is proposed. That is, putting a plurality of slits 16 in a block-shaped piezoelectric material made of ceramic is processed into a comb-like piezoelectric 8a is formed by the base portion 17a and a single piezoelectric element 80a ₁ ~80an.

[0013]

According to the above conventional method, there has been proposed a method of integrally forming a plurality of piezoelectric elements in a comb-teeth shape in order to improve the cost of the piezoelectric element.
The comb-shaped piezoelectric element causes a slight bending motion in the longitudinal direction due to displacement due to electric strain, and bending stress concentrates at the root part, which easily causes cracks and damages due to material fatigue and causes failure. However, there is a problem in that the reliability of the print head deteriorates.

It is an object of the present invention to provide an ink jet head which can prevent the piezoelectric element from cracking and breaking and can have a long life, and a method of manufacturing the same.

[0015]

1 and 2 are principle diagrams of the present invention, FIG. 1 is a principle diagram corresponding to claim 1, and FIG. 2 is a principle diagram corresponding to claim 7, (a) FIG. 3A is a configuration diagram of an inkjet head, and FIG. 4B is a manufacturing process diagram of a piezoelectric body.

1) Means corresponding to claim 1 In FIG. 1, 6 is ink, 9 is a nozzle, 18 is a root,
Reference numeral 80 denotes a piezoelectric element, 11 a plurality of pressure chambers, each of which has a nozzle 9 and is supplied with ink 6, and 8 a plurality of pressure chambers 11.
Corresponding to, a plurality of piezoelectric elements 80 are integrally formed in the shape of a comb, the tip of each piezoelectric element 80 contacts the wall of each pressure chamber 11,
It is a piezoelectric body in which the amount of electric strain is different from each tip portion toward the root portion 18.

Therefore, a voltage is applied to the piezoelectric element 80 so that the electric strain of the piezoelectric element 80 causes the wall of the pressure chamber 11 to vibrate and the ink 6 in the pressure chamber 11 is ejected from the nozzle 9.

The piezoelectric element 80 of the piezoelectric body 8 reduces the amount of electric strain of the root portion 18 as compared with other portions (claim 2).
As the method, a method of forming the root portion 18 thick to have strength (claim 3 or claim 4), a method of reinforcing the root portion 18 with an elastic member (claim 5), or a root portion 18 of the piezoelectric element 80 is used. There is a method (claim 6) of applying a characteristic addition process to the.

2) Means corresponding to claim 7 In FIG. 2, 6 is ink, 9 is nozzle, 18 is root part,
19 is a characteristic addition processing, 80 is a piezoelectric element, 11 is provided with a plurality,
A pressure chamber having a nozzle 9 and to which ink 6 is supplied, a plurality of piezoelectric elements 80 are integrally formed in a comb shape corresponding to a plurality of pressure chambers 11, and a tip portion of each piezoelectric element 80 is The piezoelectric body is in contact with the wall of the pressure chamber 11 and has different amounts of electric strain from the respective tip portions toward the root portion 18.

Therefore, in the ink jet head which applies the voltage to the piezoelectric element 80 and vibrates the wall of the pressure chamber 11 by the electric strain of the piezoelectric element 80 to eject the ink 6 in the pressure chamber 11 from the nozzles 9, The element 80 is formed into a comb shape and then subjected to a characteristic addition process 19 to be processed from the tip to the root 18 of each element.
Towards different amounts of electrical strain.

As the characteristic addition processing 19, there is a method of heating the root portion 18 to a predetermined temperature (claim 8) or a method of applying an electric field of a predetermined strength to the root portion 18 (claim 9).

[0022]

[Action]

1) Action corresponding to claim 1 The amount of electric strain is different from the tip end portion of each piezoelectric element 80 of the piezoelectric body 8 toward the root portion 18, for example, by reducing the electric strain amount of the root portion 18. When a voltage is applied to the piezoelectric element 80 and the wall of the pressure chamber 11 is vibrated by the electric strain of the piezoelectric element 80, even if the longitudinal bending motion of the piezoelectric element 80 occurs, the stress is concentrated on the root portion 18. Can be mitigated, and the occurrence of cracks and damages due to material fatigue can be prevented.

2) Action corresponding to claim 7 The characteristic addition is performed by forming the plurality of piezoelectric elements 80 of the piezoelectric body 8 in a comb-tooth shape and then performing the characteristic addition process 19 for each piezoelectric element.
80 can be performed uniformly and the performance of the inkjet head can be improved. Further, the amount of electric strain is different from the tip of the piezoelectric element 80 toward the root portion 18, for example, by reducing the amount of electric strain of the root portion 18,
When a voltage is applied to the piezoelectric element 80 and the wall of the pressure chamber 11 is vibrated by the electric strain of the piezoelectric element 80, even if a bending motion in the longitudinal direction of the piezoelectric element 80 occurs, stress is concentrated on the root portion 18. It can be relaxed, and the occurrence of cracks and damages due to material fatigue can be prevented.

[0024]

EXAMPLES Examples 1 to 5 of the present invention will be described below with reference to FIGS.
This will be described with reference to FIG. The same reference numerals denote the same objects throughout the drawings.

1) Description of Embodiment 1 Embodiment 1 of the present invention (corresponding to claim 1, claim 2, claim 6, claim 7 and claim 8) will be described with reference to FIGS.
Will be explained. FIG. 3 is a side sectional view showing the first embodiment of the present invention,
FIG. 4 is a manufacturing process diagram of the piezoelectric body of Example 1, FIG. 5 is a diagram showing a relationship between a heating temperature and a displacement amount of the piezoelectric element, and FIG. 6 is a diagram showing displacement characteristics.

The heat treatment 19a in FIG. 4 corresponds to the characteristic addition treatment 19 in FIG. As shown in FIG. 3, the print head 1a
The piezoelectric elements 80a _{1 to} 80an are formed integrally with the pedestal portion 17a as the piezoelectric body 8a in a comb-tooth shape, and the displacement amount of the electrostriction differs in the direction from the tip to the root portion 18a. It is processed (heating process 19a described later) so that the amount becomes smaller than the other parts.

The piezoelectric element 80a ₁ ~80an electrode 14a for applying a voltage to, 15a are formed by electroless plating on both sides of the slit 16. One end of the electrode 14a has a common electrode 14A
, And one end of the electrode 15a is connected to an individual electrode 15A printed on the back substrate 13a. Electrodes 14A, 15A
Is connected to the drive circuit by a flexible printed circuit (FPC) not shown.

The tips of the piezoelectric elements 80a _{1 to} 80an are connected to the vibration plate 12 ₁
It is glued to ~ 12n. The ink 6a supplied to the portion surrounded by the vibrating plates 12 _{1 to} 12n, the pressure chambers 11 _{1 to} 11n formed of acrylic resin, and the nozzle plate 10a is ejected by driving the piezoelectric elements 80a _{1 to} 80an.

Next, the manufacturing process of the piezoelectric body 8a will be described with reference to FIG. As shown in Fig. 4 (a), each surface of the block B of the piezoelectric material made of ceramic is processed to a predetermined surface accuracy, and then as shown in (b), slitted by dicing processing.
16 to form a comb-tooth shape, the pedestal portion 17a and the piezoelectric element 80a ₁
Set to ~ 80an. In this case, sufficient accuracy is obtained with respect to the width, spacing, and tip position of each comb.

Next, as shown in (c), heat treatment 19a is performed. That is, the rear surface of the pedestal portion 17a is fixed on the hot plate 20 having a uniform surface temperature so that the rear end surface of the pedestal portion 17a contacts, and the piezoelectric body 8a is heated. The relationship between the temperature and the change in displacement in this case is
As shown in FIG. 5, when the temperature exceeds 170 ° C., the amount of displacement sharply decreases, so the temperature and time (for example, 200 ° C. for 5 seconds on the hot plate 20 surface) to set the desired amount of displacement are set. After the heat treatment 19a, as shown in (d), it is cooled to room temperature in a cooling liquid (for example, trade name: Fluorinert: manufactured by 3M). After cooling, the electrodes 14a, 15a are formed.

In this way, the piezoelectric element 80a _{1 of the} piezoelectric body 8a
By performing heating treatment 19a after processing ~ 80an into a comb-teeth shape, the comb-teeth portion comes into contact with air and acts as a heat dissipation plate, so that a temperature distribution occurs between the pedestal portion 17a and the tip,
As shown in FIG. 6, the heat treatment 19a reduces the piezoelectric constants (d constant and k constant) of the pedestal portion 17a and the root portion 18a, and the distribution of the displacement amount of the electric strain according to the temperature distribution is obtained. the displacement of the electrostrictive of the root portion 18a of the element 80a ₁ ~80an can be less than other portions of distal direction.

Therefore, when a voltage is applied to the piezoelectric elements 80a _{1 to} 80an to drive the piezoelectric elements 80a _{1 to} 80an, the displacement of the electrostriction of the root portion 18a is small. Therefore, even if a bending motion in the longitudinal direction occurs due to the driving, the root portion 18a. The bending stress concentration and material fatigue are reduced. Therefore, it is possible to prevent the occurrence of failure due to cracks or damage,
The reliability of the print head 1a can be improved.

2) Description of Embodiment 2 Referring to FIG. 7, Embodiment 2 (claim 1, claim 2, claim 6,
(Corresponding to claim 7 and claim 9) will be described. 7 is different from the first embodiment described with reference to FIGS. 3 to 6 in that the characteristic adding process of the piezoelectric body 8a is replaced with the heating process 19a and the electric field process is performed.

[0034] That is, as shown in FIG. 7, the field processing 19b paste the electrodes 24 and 25 on both sides of the root portion 18a of the piezoelectric elements 80a ₁ ~80an formed in a tooth shape of the piezoelectric element 8a. That is,
By applying a negative voltage between the electrodes 24 and 25 and applying a reverse electric field that is almost equivalent to the coercive electric field of the piezoelectric body, the piezoelectric characteristics of that part are weakened and a distribution in which the amount of displacement of electric strain is changed is obtained. it can be less than other portions of distal direction displacement amount of the electrical strain of the root portion 18a of the piezoelectric elements 80a ₁ ~80an. Therefore, the same effect as that of the first embodiment can be obtained.

3) Description of Example 3 Example 3 (claims 1, 2 and 3) will be described with reference to FIG.
Corresponding to)). 8 is different from the first and second embodiments described above in that instead of the heat treatment and the electric field treatment, the root portion of the piezoelectric element is formed into a tapered shape and is formed thicker than the tip.

[0036] That is, as shown in FIG. 8, the shape of the root portion 18b of the piezoelectric elements 80b ₁ ~80bn piezoelectric 8b, when the dicing in a tooth shape, a dicing blade tip is in tapered shape Due to the slit 16a processed and used, the tapered portion 21 is formed and becomes thick.

After dicing, the electrodes 14b and 15b are formed. That is, the electrode 14b, 15b from the distal end of the side surfaces of the piezoelectric elements 80b ₁ ~80bn to the middle of the tapered portion 21, for example, has been electrolessly plated.

With this structure, the electrodes 14b, 15
When a voltage is applied to b and the piezoelectric elements 80b _{1 to} 80bn are driven, the electric field strength of the root portion 18b becomes weak and the amount of displacement of electric strain is reduced, so that concentration of stress on the root portion 18b can be avoided. Since the base portion 18b is thickened by the taper portion 21, durability is improved and breakage and breakage can be prevented.

4) Description of Fourth Embodiment A fourth embodiment (corresponding to claim 1, claim 2 and claim 4) will be described with reference to FIG. 9 is different from that of Example 3 in that instead of the tapered shape of the base portion of the piezoelectric element, a step is formed to be thicker.

That is, as shown in FIG. 9, the piezoelectric elements 80c _{1 to} 80cn of the piezoelectric body 8c are formed in a comb-tooth shape by dicing, and a step 21a is provided at the bottom of the slit 16b to form a root portion. 18c is thickly formed by the step 21a. Electrodes 14c, 15c are formed from the tip of the side surfaces of the piezoelectric elements 80c ₁ ~80cn to the position of the step 21a.

The method for forming the electrodes 14c and 15c is to form the comb teeth by dicing, then perform electroless plating between the comb teeth, and then perform dicing to form the step 21a. Excessive plating at the bottom between the comb teeth is stripped in order to provide the step 21a and to make each electrode independent.

Therefore, by providing a step structure, the root portion is
18c is reinforced, and the durability against stress during driving can be improved. Further, since the step 21a can be formed and the excess plating can be removed at the same time, the cost can be reduced.

5) Description of Example 5 Example 5 (corresponding to claim 1, claim 2 and claim 5) will be described with reference to FIG. FIG. 10 shows Example 3 and Example 4.
What is different from is that instead of the taper shape and the step of the base portion of the piezoelectric element, a member having elasticity is attached to the base portion.

That is, as shown in FIG. 10, an elastic adhesive 21b having elasticity and moisture resistance after curing is attached to the bottom portion between the root portions 18a of the piezoelectric elements 80a _{1 to} 80an of the piezoelectric body 8d. As the elastic adhesive 21b, for example, a paste-like silicone adhesive that has fluidity when heated is used,
Penetrates to the bottom between 18a and extends to both sides and the bottom of the root 18a.

Therefore, when the elastic adhesive 21b is hardened, a roundness is formed at the bottom corners of the root portions 18a of the piezoelectric elements 80a _{1 to} 80an as shown in the figure, and the effect of suppressing the occurrence of strain when a voltage is applied is exerted. In addition, since stress concentration is avoided and the elastic adhesive 21b reinforces, cracks and damage can be prevented. Further, there is an effect that the insulation resistance is prevented from lowering due to the dew condensation caused by the temperature change at the root portion 18a, and the peeling of the wiring is prevented.

[0046]

As described above, according to the present invention, in claims 1 and 2, the amount of electric strain is different from the tip portion to the root portion of each piezoelectric element of the piezoelectric body, and the root portion is different. By reducing the amount of electrostriction, stress concentration and material fatigue on the root can be mitigated even if a longitudinal bending motion occurs when the piezoelectric element is driven, and cracks and damage are prevented. Therefore, the reliability of the inkjet head can be improved.

In the third aspect, the piezoelectric element is formed thicker in a taper shape from the predetermined position toward the root portion.
The electric field strength at the root is weakened, the amount of displacement of electric strain is reduced, it is possible to avoid concentration of stress on the root, and the root is thickened in a taper shape to improve durability and material fatigue. It is possible to prevent the occurrence of cracks and damages due to.

According to the present invention, since the base portion of the piezoelectric element is provided with a step and formed thick, the base portion is reinforced, the durability against the stress during driving is improved, and cracks or breakage due to material fatigue occur. Can be prevented. Further, since it is possible to simultaneously form the step and remove the extra plating, it is possible to reduce the cost.

According to the fifth aspect of the present invention, the elastic member is attached to the root of the piezoelectric element, so that the root is reinforced, stress concentration during driving is avoided, durability is improved, and cracks and damages due to material fatigue occur. Occurrence can be prevented. Further, it is possible to prevent the insulation resistance from being lowered and the wiring from being peeled off due to the dew condensation caused by the temperature change at the root portion.

In the sixth, seventh, eighth, and ninth aspects, a characteristic adding process is performed on a plurality of piezoelectric elements of the piezoelectric body, that is, the root portion is heated to a predetermined temperature, or an electric field is processed to a predetermined strength. By applying the property, it is possible to uniformly add the characteristics to each piezoelectric element and improve the performance of the inkjet head. In addition, the amount of electric strain is different from the tip of the piezoelectric element toward the root, and for example, by reducing the amount of electric strain at the root, even if a longitudinal bending motion occurs when the piezoelectric element is driven, It is possible to reduce stress concentration on the portion and material fatigue, prevent occurrence of cracks and damages, and improve the reliability of the inkjet head. There is an effect.

[Brief description of drawings]

FIG. 1 is a principle diagram corresponding to claim 1 of the present invention.

FIG. 2 is a principle diagram corresponding to claim 7 of the present invention.

FIG. 3 is a configuration diagram showing a first embodiment of the present invention.

FIG. 4 is a manufacturing process diagram of the piezoelectric body according to the first embodiment.

FIG. 5 is a diagram showing a relationship between a displacement amount of electric strain of a piezoelectric element and a heating temperature.

FIG. 6 is a diagram showing a piezoelectric constant between the tip of the piezoelectric element of Example 1 and the pedestal.

FIG. 7 is an explanatory diagram showing a characteristic adding process according to the second embodiment.

FIG. 8 is a configuration diagram of a piezoelectric body showing a third embodiment.

FIG. 9 is a configuration diagram of a piezoelectric body showing a fourth embodiment.

FIG. 10 is a configuration diagram of a piezoelectric body showing a fifth embodiment.

FIG. 11 is a perspective view showing an outline of an inkjet printer.

FIG. 12 is a side sectional view showing a print head.

FIG. 13 is a perspective view showing a comb-shaped piezoelectric body.

[Explanation of symbols]

1 is the print head, 6 and 6a are ink,
8,8a to 8d are piezoelectric bodies, 9,9 _{1 to} 9n are nozzles, 11,11 ₁
~ 11n are pressure chambers, 16, 16a are slits, 18, 18a ~ 18c
Is a root portion, 19 is a characteristic addition treatment, 19a is a heat treatment, 19b is an electric field treatment, 21 is a taper portion,
21a is a step, 21b is an elastic adhesive, 80 _{1 to} 80n, 80a ₁ to 8
0an, 80b _{1 to} 80bn, 80c _{1 to} 80cn are piezoelectric elements

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yuko Miyake 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Kazuo Tamamushi 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (9)

[Claims] 1. A plurality of pressure chambers (11) having nozzles (9) to which ink (6) is supplied, and a plurality of piezoelectric elements (80) corresponding to the plurality of pressure chambers (11). The piezoelectric element (80) is integrally formed in a comb shape, and the tip of each piezoelectric element (80) contacts the wall of each pressure chamber (11), and the amount of electric strain varies from each tip toward the root (18). A piezoelectric body (8), and a voltage is applied to the piezoelectric element (80) to vibrate the wall of the pressure chamber (11) by the electric strain of the piezoelectric element (80) to cause the pressure chamber (11)
An ink-jet head characterized in that the ink (6) therein is ejected from the nozzle (9). 2. The ink jet head according to claim 1, wherein the piezoelectric element (80) has a smaller amount of electric strain in the root portion (18) than in other portions. 3. The ink jet head according to claim 1 or 2, wherein the piezoelectric element (80) is formed thicker in a taper shape from a predetermined position toward the root portion (18). 4. The piezoelectric element (80) is formed thicker by providing a step at the root portion (18).
Alternatively, the inkjet head according to claim 2. 5. The ink jet head according to claim 1, wherein the piezoelectric element (80) has an elastic member attached to the root portion (18). 6. The ink jet head according to claim 1, wherein the piezoelectric element (80) has a characteristic adding process applied to the root portion (18). 7. A plurality of pressure chambers (11) having nozzles (9) to which ink (6) is supplied, and a plurality of piezoelectric elements (80) corresponding to the plurality of pressure chambers (11). The piezoelectric element (80) is integrally formed in a comb shape, and the tip of each piezoelectric element (80) contacts the wall of each pressure chamber (11), and the amount of electric strain varies from each tip toward the root (18). A piezoelectric body (8), and a voltage is applied to the piezoelectric element (80) to vibrate the wall of the pressure chamber (11) by electrostriction of the piezoelectric element (80) to
In an ink jet head characterized in that the ink (6) in 1) is ejected from the nozzle (9), the plurality of piezoelectric elements (80) are formed into the comb teeth shape, and then the roots are formed from the respective tips. A method for manufacturing an ink jet head, characterized by performing a characteristic adding process (19) so that the amount of electrostriction is different toward the portion (18). 8. The ink jet head according to claim 6 or 7, wherein the characteristic adding process (19) heats the root portions (18) of the plurality of piezoelectric elements (80) to a predetermined temperature. And its manufacturing method. 9. The characteristic adding process (19) according to claim 6 or 7, wherein an electric field of a predetermined strength is applied to the root portions (18) of the plurality of piezoelectric elements (80). Inkjet head and manufacturing method thereof.