JP2001080070A - Piezoelectric type driving body and ink-jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric type driving body and an ink jet recording head superior in displacement efficiency. SOLUTION: In the piezoelectric type driving body having a piezoelectric element fixed to a substrate via an adhesive layer, when a film thickness of the adhesive layer is (a) (μm) and a Young's modulus of the adhesive layer is b (N/m2), the film thickness and a material of the adhesive layer are selected to hold a relationship between the film thickness and Young's modulus of the adhesive layer of 2.0×10-8<=a/b<=2.6×108. The Young's modulus of the adhesive layer is preferably in a range of 1×108 to 1×109 (Nxm2). Moreover, the film thickness of the adhesive layer is preferably 12 (μm) or smaller. Preferably, a Young's modulus of the substrate is 1×1011 (N×102) or larger.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric driver and an ink jet recording head, and more particularly to an adhesive layer for fixing a piezoelectric displacement element used in a recording head of an ink jet recording apparatus to a base.

[0002]

2. Description of the Related Art Hitherto, when a piezoelectric driver is fixed to a fixed substrate via an adhesive layer in a piezoelectric element, the adhesive layer has been studied mainly from the viewpoint of improvement in the construction method and stress relaxation. For example, Japanese Patent Application Laid-Open No. 10-100421 (hereinafter referred to as Conventional Example 1) provides a structure for relaxing the stress of the adhesive layer. Specifically, in the case of an ink jet head, stress is reduced by making cuts in the adhesive layer and the substrate member thereunder. In Japanese Unexamined Patent Publication No. Hei 5-77431 (hereinafter referred to as Conventional Example 2), in a laminated piezoelectric motor including an active region / an inactive region, adhesion to a substrate is performed only by an inactive portion, so that stress relaxation and The displacement characteristics are improved.

An example of handling the physical properties of the adhesive layer is disclosed in JP-A-6-305155 (hereinafter referred to as Conventional Example 3). This shows the relationship between the thickness of the adhesive layer and the Young's modulus,
The characteristics are stabilized. However, in this case, the droplet ejection apparatus having a limited structure is targeted, and the adhesive layer at the interface with the fixed substrate is not targeted.

[0004] The basic operation of a piezoelectric driving body is that the piezoelectric element is polarized by an electric field, thereby causing expansion and contraction to generate displacement chromaticity. The expansion and contraction moves the entire driving body. Stress acts on the adhesive layer that fixes the body to the substrate surface or the like. In order to release this stress and facilitate the driving of the driving body, it is preferable that the rigidity of the adhesive layer be low. However, if the rigidity is excessively reduced, the driving body is also absorbed by the adhesive layer, and the effective displacement is reduced. Therefore, it is desirable to optimize this, but usually this point is not considered,
The displacement is increased by other means.

[0005]

In order to increase the displacement, the simplest method is to increase the electric field, that is, increase the applied voltage. However, in this case, there is a disadvantage that power consumption increases. To prevent this, there is a method of increasing the effective electric field by applying a voltage to each layer as a laminated structure and increasing the number of layers, but increasing the number of layers increases the manufacturing cost and the element size. There is a problem of being connected. From these points, it is most desirable to optimize the displacement efficiency without changing the basic configuration.

The present invention has been made to solve these problems. To improve the driving efficiency of the piezoelectric driving body, more specifically, to optimize the amount of displacement, the piezoelectric driving body is fixed to a fixed substrate. It is an object of the present invention to provide a piezoelectric driving body and an ink jet recording head which have excellent displacement efficiency by using an adhesive layer.

[0007]

In order to solve the above-mentioned problems, according to the present invention, in a piezoelectric driver in which a piezoelectric element is fixed to a substrate via an adhesive layer, the thickness of the adhesive layer is set to a.
(Μm), and when the Young's modulus of the adhesive layer is b (N / m ² ), the relationship between the film thickness of the adhesive layer and the Young's modulus is 2.0 × 10 ^−8.
The thickness and material of the adhesive layer are selected so that ≦ a / b ≦ 2.6 × 10 ⁻⁸ . Therefore, it is possible to provide a piezoelectric driver having excellent displacement characteristics.

The Young's modulus of the adhesive layer is 1 × 10 ⁸ (N
/ M ² ) to 1 × 10 ⁹ (N / m ² ). Further, the thickness of the adhesive layer is desirably 12 (μm) or less. The Young's modulus of the substrate is 1 × 10 ¹¹ (N /
m ² ) or more.

According to another aspect of the present invention, there is provided an ink pressurizing chamber which communicates with an ink nozzle for ejecting ink and pressurizes filled ink, and is disposed in a part of the ink pressurizing chamber.
According to the ink jet recording head having a piezoelectric element that expands and contracts by applying a voltage pulse to increase or decrease the volume of the ink pressurizing chamber, the thickness and material of the adhesive layer that fixes the piezoelectric element to the base are determined by the thickness of the adhesive layer. When the thickness is a (μm) and the Young's modulus of the adhesive layer is b (N / m ² ), the relationship between the thickness of the adhesive layer and the Young's modulus is 2.0 × 10 ⁻⁸ ≦ a / b ≦
It is selected so as to be 2.6 × 10 ⁻⁸ . Therefore,
A fine ink jet recording head with low power consumption can be obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS When the thickness of the adhesive layer is a (μm) and the Young's modulus is b (N / m ² ), the relationship between the thickness of the adhesive layer and the Young's modulus is 2.0 × 10 ^{−. 8} ≦ a / b ≦ 2.6 × 10
^The thickness and material of the adhesive layer are selected so as to be ^-8 .

[0011]

FIG. 1 is a characteristic diagram showing the relationship between the Young's modulus of an adhesive layer and the amount of displacement of a piezoelectric drive according to one embodiment of the present invention.
As can be seen from the figure, when the displacement amount is measured while changing the Young's modulus of the adhesive layer, the thicknesses of 4 (μm) and 8 (μm) having different film thicknesses are different.
Experiments have revealed that the displacement amount takes a maximum value at a certain Young's modulus for each of the three types of adhesive layers m) and 12 (μm).

FIG. 2 is a characteristic diagram showing the relationship between the thickness of the adhesive layer and the Young's modulus of the adhesive layer at which the amount of displacement is maximum in this embodiment. As can be seen from the figure, the value changes almost linearly up to a certain film thickness, and beyond that, the value of the Young's modulus, which has a maximum value, does not change even if the film thickness is increased. When the relationship between the linear regions is examined in more detail, the thickness of the adhesive layer for fixing the piezoelectric driving body to the fixed substrate is represented by a (μ).
m) and when the Young's modulus is b (N / m ² ), the value of a / b is 2.0 × 10 ⁻⁸ or more and 2.6 × 10 ⁻⁸ or less.

FIG. 1 shows that the value of the Young's modulus which takes the maximum value is within the range of 1 × 10 ⁸ to 1 × 10 ⁹ (N / m ² ). From FIG. 2, even if the film thickness is further increased, it does not deviate from this range. Conversely, if the film thickness is reduced, there is a possibility that the thickness will be out of this range, but a thinner adhesive layer is not practical in terms of the construction method and characteristics.

From FIG. 2, the above relational expression of a / b holds when the thickness of the adhesive layer is about 12 μm or less. Exceeding this range deviates from the relational expression, but if the film thickness is further increased, the maximum displacement itself decreases and there is a problem of fixing strength, which is not appropriate.

The above properties of the adhesive layer may be related to the properties of the substrate to be fixed, and were examined by experiments. FIG. 3 shows the result. The figure shows the result of measuring the maximum displacement when the thickness of the adhesive layer was fixed at 8 (μm) and the Young's modulus of the adhesive layer and the Young's modulus of the substrate were changed. From this, the Young's modulus of the substrate was 1.7.
At 7 × 10 ¹¹ (N / m ² ) or more, there is not much difference in characteristics, but when it is lower than 7 × 10 ¹¹ (N / m ² ), the characteristics are extremely deteriorated. Therefore, the Young's modulus of the substrate will be approximately 1 × 10
^{If it is 11} (N / m ² ) or more, there is no large difference in the characteristics, but if it is lower than this, the maximum displacement decreases extremely. From the above points, the Young's modulus of the substrate is 1
It is desirable to be × 10 ¹¹ (N / m ² ).

Next, the present invention makes it possible to provide a piezoelectric driver with low power consumption and high integration, so that it is suitable for application to an ink jet recording head. less than,
An example in which the present invention is applied to an ink jet recording head having a structure as shown in FIG. 4 will be described. Here, the thickness of each of the 14 piezoelectric elements 13 in the active region laminated on the fixed substrate 11 with the adhesive layer 12 therebetween is 35 (μm). Inactive portions are formed above and below the active portion including the 14 piezoelectric elements, and the total thickness is 675 (μ).
m). The length of the active part is 2000 (μm),
The width is 100 (μm). Inactive part length is 3
00 (μm). The internal electrode 14 has a thickness of 5 (μm). The piezoelectric element 13 has a displacement of d33 and a piezoelectric constant of 6.0.
3 × 10 ¹⁰ (m / V), density 8000 (kg /
m ³ ) and the Poisson's ratio is 0.36. The fixed substrate 11 for fixing this has a Young's modulus of 1.77 × 1.
0 ¹¹ (N / m ² ), density 5700 (kg / m ³ ) and Poisson's ratio 0.3. The following table summarizes the results of examining the amount of displacement of the surface of the piezoelectric element by changing the film thickness a and the Young's modulus b of the adhesive layer in such a configuration, and obtaining the above-described relational expression (a / b). Was. As can be seen from the table, when the film thickness is in the range of 12 (μm) or less, the value of a / b is 2.0.
It can be seen that it is within the range of not less than × 10 ^{−8 and not} more than 2.6 × 10 ⁻⁸ . Further, the thickness of the adhesive layer is set to 8 (μ
m) and the maximum displacement when the Young's modulus of the adhesive layer and the Young's modulus of the substrate were changed, as can be seen from FIG. 3, the Young's modulus of the substrate was 1.77 × 10 ¹¹ (N / m). ² )
Although there is no difference in the characteristics as described above, it can be seen that the characteristics are extremely deteriorated when the value is lower than this.

[0017]

[Table 1]

The present invention is not limited to the above embodiment, and needless to say, various modifications and substitutions can be made within the scope of the claims.

[0019]

As described above, according to the present invention in the piezoelectric driving body in which the piezoelectric element is fixed to the substrate via the adhesive layer, the thickness of the adhesive layer is a (μm), and the Young of the adhesive layer is When the modulus is b (N / m ² ), the relationship between the thickness of the adhesive layer and the Young's modulus is 2.0 × 10 ⁻⁸ ≦ a / b ≦ 2.6 × 10 ⁻⁸
The thickness and material of the adhesive layer are selected so that
Therefore, it is possible to provide a piezoelectric driver having excellent displacement characteristics.

The Young's modulus of the adhesive layer is 1 × 10 ⁸ (N
/ M ² ) to 1 × 10 ⁹ (N / m ² ). Further, the thickness of the adhesive layer is desirably 12 (μm) or less. The Young's modulus of the substrate is 1 × 10 ¹¹ (N /
m ² ) or more.

According to another aspect of the present invention, there is provided an ink pressurizing chamber which communicates with an ink nozzle for ejecting ink and pressurizes the filled ink, and is disposed in a part of the ink pressurizing chamber.
According to the ink jet recording head having a piezoelectric element that expands and contracts by applying a voltage pulse to increase or decrease the volume of the ink pressurizing chamber, the thickness and material of the adhesive layer that fixes the piezoelectric element to the base are determined by the thickness of the adhesive layer. When the thickness is a (μm) and the Young's modulus of the adhesive layer is b (N / m ² ), the relationship between the thickness of the adhesive layer and the Young's modulus is 2.0 × 10 ⁻⁸ ≦ a / b ≦
It is selected so as to be 2.6 × 10 ⁻⁸ . Therefore,
A fine ink jet recording head with low power consumption can be obtained.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a relationship between an adhesive layer Young's modulus and a displacement amount of a piezoelectric driving body according to one embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between an adhesive layer film thickness and an adhesive layer Young's modulus at which the amount of displacement is maximum in the present embodiment.

FIG. 3 is a characteristic diagram showing the relationship between the Young's modulus of the adhesive layer and the amount of displacement for each Young's modulus of the substrate in this example.

FIG. 4 is a cross-sectional view illustrating a structure of an ink jet recording head to which the present invention is applied.

[Explanation of symbols]

11: fixed substrate, 12: adhesive layer, 13: piezoelectric element, 1
4: Internal electrode.

Claims (5)

[Claims] 1. A piezoelectric driver in which a piezoelectric element is fixed to a substrate via an adhesive layer, wherein the thickness of the adhesive layer is a (μm), and the Young's modulus of the adhesive layer is b (N / m ² ). In this case, the thickness and the material of the adhesive layer are set such that the relationship between the thickness of the adhesive layer and the Young's modulus is 2.0 × 10 ⁻⁸ ≦ a / b ≦ 2.6 × 10 ^−8. A piezoelectric driver, which is selected. 2. The adhesive layer has a Young's modulus of 1 × 10 ⁸ (N
^{/ M 2) ~1 × 10 9} (N / m 2) Piezoelectric drive of claim 1, wherein in the range of. 3. The piezoelectric driver according to claim 1, wherein the thickness of the adhesive layer is 12 (μm) or less. 4. The substrate has a Young's modulus of 1 × 10 ¹¹ (N /
m ² ) or more. 5. An ink pressurizing chamber that communicates with an ink nozzle that ejects ink and pressurizes the filled ink.
A piezoelectric element disposed in a part of the ink pressurizing chamber, the piezoelectric element expanding and contracting by application of a voltage pulse to increase or decrease the volume of the ink pressurizing chamber, wherein the piezoelectric element is fixed to a base. Assuming that the thickness of the adhesive layer is a (μm) and the Young's modulus of the adhesive layer is b (N / m ² ), the thickness and the material of the adhesive layer are the same as those of the adhesive layer. The relationship is 2.0 × 10 ⁻⁸ ≦ a / b ≦ 2.6 ×
An ink jet recording head, which is selected so as to satisfy 10 ^-8 .