JPH0584907A - Ink jet type printing head - Google Patents

Abstract

PURPOSE:To realize a miniaturized head which is difficult to generate migration, high in reliability and excellent in driving stability at a high temperature by a method wherein for a piezoelectric element to be mounted on an ink jet head, a plate formed piezoelectric element to which a required conductive layer is formed, is adhered to each other in layers with a polyimide adhesive to be formed into a laminated type PZT of which a bond layer thickness (t) is controlled to 2mum or under. CONSTITUTION:An electrically conductive layer 13 is formed in a required form to a preliminarily sintered piezoelectric element plate 14. A laminated type PZT wherein respective plates 14 are adhered to each other in layers with a polyimide adhesive 16 to 2mum or under in thickness, is fixed to a base stand 11. Thereafter, the laminated type PZT is worked by cutting so as to correspond to an ink discharge opening formed to a nozzle plate 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head used in an ink jet printer.

[0002]

2. Description of the Related Art A conventional ink jet print head is
As shown in Japanese Patent Publication No. 60-8953, a plurality of nozzle openings are formed on the wall surface of a container constituting an ink tank, and the expansion and contraction directions are aligned so as to face each nozzle opening. A piezoelectric element is arranged and configured. In this print head, a drive signal is applied to a piezoelectric element to expand and contract the piezoelectric element, and the dynamic pressure of ink generated at this time causes ink droplets to be ejected from nozzle openings to form dots on printing paper.

In a print head of this type,
It is desirable that droplet formation efficiency and flight force are large. However, since the unit length of the piezoelectric element and the expansion / contraction rate per unit voltage are extremely small, it is necessary to apply a high voltage in order to obtain the flying force required for printing, which complicates the drive circuit and electrical insulation measures. There is a problem of turning into.

In order to solve such a problem, as disclosed in Japanese Patent Laid-Open No. 63-295269, ink jet printing in which electrodes and piezoelectric materials are alternately laminated in a sandwich form and simultaneously sintered. Piezoelectric elements for heads have been proposed. According to this piezoelectric element, the distance between the electrodes can be made as small as possible, so that the voltage of the drive signal can be lowered.

[0005]

However, since most of the conductive materials inside such a piezoelectric element use Ag / Pd, if the conductive material is exposed, Ag migration will occur in the creeping portion and reliability will be improved. It was a factor that caused the decrease. In order to avoid this problem, the most effective means is not to use Ag as the conductive material, but conventionally, the type of conductive material that can be selected is limited to Ag / Pd for the following reasons.

1. In the thick film simultaneous sintering method in which the piezoelectric material and the conductive material are simultaneously fired, the piezoelectric material is sintered in an oxidation furnace,
The conductive material is also oxidized.

2. When the sintering temperature of the piezoelectric material is higher than the melting point of the conductive material, the conductive material diffuses in the piezoelectric material, which leads to deterioration of insulation resistance and deformation of the piezoelectric element.

As described above, the conductive material is hard to oxidize and is limited to Ag / Pd having a high melting point.

Further, it has been difficult to miniaturize the stack type actuator which has been conventionally used.

The object of the present invention is to provide a low price, high reliability,
An object of the present invention is to provide an inkjet print head using a piezoelectric element that can be easily miniaturized.

[0011]

In order to solve the above-mentioned problems, in the present invention, a conductive layer is formed in a desired shape on a single plate of a piezoelectric element which is pre-sintered, and each layer is formed by a polyimide adhesive. It has a laminated structure. Further, the thickness t of one layer of the polyimide adhesive is set to t ≦ 2 μm.

[0012]

1 shows an example of an ink jet type print head according to the present invention. In FIG. 1, 11 is a base, 12 is an adhesive, 13 is a conductive layer, 14 is a piezoelectric element plate, 15 is a laminated piezoelectric element, 16 is a polyimide adhesive layer, and 17 is a plate material (hereinafter, It is called a nozzle plate.), 18
Is an ink flow path.

This head is manufactured by the following steps.

First, a piezoelectric element plate 14 is formed by sintering a green sheet of lead zirconate titanate-based composite perovskite ceramic or the like manufactured by a doctor blade method, an extrusion method or the like. Next, as shown in FIG. 2, the piezoelectric element plate 1
Conductive layers 13 made of Cr, Ni, Al, Au or the like are formed on both surfaces of No. 4 in a desired shape. The conductive layer 13 may be formed by a thin film method such as sputtering or vapor deposition, or a thick film method such as printing. However, since the piezoelectric material is fragile and easily broken, it is formed by a thin film method that is relatively easy to handle. It is desirable to do. Next, as shown in FIG. 3, an adhesive 31 is applied to the piezoelectric element plate 14 on which the conductive layer 13 is formed by a transfer method, a printing method, or the like. After that, in order to prevent an electric field from being applied through the adhesive 31, the piezoelectric element plates 14 are attached so that the surfaces of the conductive layer 13 having the same polarity face each other, and the piezoelectric element plate 14 is pressed into a high temperature atmosphere, or if necessary. Then, it is left in a reduced pressure environment and the adhesive is cured to obtain the laminated shape shown in FIG. The adhesive used here preferably has the following properties.

1. High Young's modulus after curing.

In the case of the laminated type PZT of the pasting type, it is preferable that the adhesive has a small Young's modulus and does not suppress the movement of the PZT in order to effectively obtain the displacement amount. However, since the adhesive layer of PZT laminated with such an adhesive is soft, it causes chipping of PZT and generation of microcracks during machining in a later step.

2. Low viscosity In order to effectively obtain the displacement amount with an adhesive having a large Young's modulus as described above, it is preferable to apply the adhesive as thinly as possible. For that purpose, the adhesive must have a low viscosity.

3. Being a solvent-free type Since an adhesive containing a solvent generates bubbles during curing and forms a porous layer inside the adhesive layer, chipping will occur if the portion is machined during subsequent machining.

4. High heat resistance The heat resistance of the adhesive is required to be about 200 ° C. when heat is generated by driving the laminated PZT at high speed, or assuming an ink jet print head using hot melt ink.

After the above-mentioned steps, a desired shape and size are cut by a cutting method using a fixed abrasive grain outer peripheral blade or a cutting method using free abrasive grains such as a wire saw and a band saw, as shown in FIG. In this manner, the conductive layers 13 are alternately exposed at the end portion 51 every other layer. Then, in order to pull out the conductive layer 13 to the outside, the conductive film 52 is formed on both ends 51 by the thin film method,
The piezoelectric element 15 is obtained by forming using a thick film method. As shown in FIG. 6, the piezoelectric element 15 manufactured as described above is fixed on the base 11 on which the individual electrodes 61 are formed by using an adhesive 71 as shown in FIG. The thus-fixed piezoelectric element 15 is finely cut at the same pitch as the individual electrode pitch, as shown in FIG. After that, the individual electrode 61 and the piezoelectric element array 81 with the cut are connected.
Since the adhesive here needs to electrically connect the conductive film 52 and the individual electrode 61 formed on the base 11,
It is optimal to use a conductive paste 82 such as solder or a conductive adhesive.

Next, as shown in FIG. 9, the common electrode 19 is connected, and the periphery of the piezoelectric element is protected by a moisture resistant material or the like so as to prevent the ink from flowing in for improving the reliability.
Here, it is desirable to perform processing such as vacuum degassing in order to remove air bubbles from entering the moisture resistant material. Next, the ink flow path and the nozzle plate are formed, and as a result, the head structure shown in FIG. 1 is obtained.

Next, a laminated PZT using a polyimide adhesive as an adhesive satisfying the above conditions and a laminated PZT using a silicone adhesive were manufactured as prototypes for comparison. The results are shown below. ..

FIG. 10 shows the shape of this prototype PZT 101.

Trial evaluation results Trial specifications Thick electric element plate 102 specifications Thickness t = 30 (μm) Piezoelectric constant d31 = 300 × 10 ⁻¹² (m / V) Drive unit length 103 la = 3.7 (mm) Adhesive specifications Table 1 shows the specifications of the two types of adhesive used.

[0025]

[Table 1]

Conductive layer specifications First conductive layer 104 material Cr sputter thickness t = 1
00 (Å) Second conductive layer 105 material Ni sputter thickness t = 20
00 (Å) ・ Evaluation results Table 2 shows the evaluation results.

[0027]

[Table 2]

The displacement amount δ of the PZT is proportional to the voltage V, the drive portion length la, and the piezoelectric constant d31 as shown in the following equation, and the thickness t
Inversely proportional to.

Δ = d31laV / t Here, the specifications of the prototype PZT are substituted into the above equation, and the voltage 3
Calculating the displacement amount when 0 V is applied, δ = 300 × 10
^-12 · 3.7 × 10 ⁻³ · 30 / (30 × 10 ⁻⁶ ) = 1.11 × 10 ⁻⁶ (m)

According to the evaluation results shown in Table 2, the displacement amount of the sample coated with the polyimide adhesive having a thickness of 3 to 6 μm was 0.8 μm, which was smaller than the calculated value. This is because displacement was suppressed because a polyimide adhesive having a large Young's modulus was applied thickly. With a silicone-based adhesive having a small Young's modulus, it was possible to obtain a displacement amount almost as calculated even if the adhesive layer was thickened to 3 to 8 μm. Here, the influences of the Young's modulus of the adhesive and the adhesive thickness on the displacement are illustrated in FIGS. 11A and 11B, respectively. In FIG. 11, the vertical axis represents the displacement ratio when the adhesive layer thickness was varied and the horizontal axis represents 1 when the adhesive was not applied. For example, when an adhesive having a Young's modulus of 1 × 10 ¹¹ is applied to a thickness of about 4 μm, it is about 80% when the adhesive is not applied.
It shows that it is suppressed to the displacement of%.

From the above results, the heat-resistant temperature is high, chipping and microcracks are less likely to occur during manufacturing, and
In order to obtain a displacement efficiently (90% or more with respect to the displacement without the adhesive layer), the adhesive is a polyimide adhesive having a large Young's modulus, and the adhesive layer thickness is preferably 2 μm or less. I understand.

In addition, since the crystal grain size of a sintered body such as PZT is as large as 2 to 3 μm, these crystal grains serve as a gap agent, and it is difficult to control the thickness of the adhesive layer to 2 μm or less. There are cases. In such a case, it is effective to lap both surfaces of the PZT plate before forming the conductive layer to smooth the unevenness.

Epoxy adhesives are excluded from this evaluation because they have a low heat resistance temperature.

[0034]

According to the present invention, a laminated piezoelectric element in which plate-shaped piezoelectric elements are laminated in a layered manner with a polyimide adhesive is mounted on an ink jet head, so that migration is unlikely to occur and high reliability is achieved. It is possible to realize an inkjet print head with excellent high temperature driving stability. In addition, by setting the thickness of the adhesive layer to 2 μm or less, a piezoelectric element with good displacement efficiency can be obtained, and the head can be miniaturized.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of an ink jet print head of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the inkjet print head of the present invention.

FIG. 3 is a cross-sectional view showing the manufacturing process of the inkjet print head of the present invention.

FIG. 4 is a cross-sectional view showing a manufacturing process of the inkjet print head of the present invention.

FIG. 5 is a cross-sectional view showing a manufacturing process of the inkjet print head of the present invention.

FIG. 6 is a diagram showing a manufacturing process of the inkjet print head of the present invention.

FIG. 7 is a diagram showing a manufacturing process of the inkjet print head of the present invention.

FIG. 8 is a diagram showing a manufacturing process of the inkjet print head of the present invention.

FIG. 9 is a diagram showing a manufacturing process of the inkjet print head of the present invention.

FIG. 10 is a cross-sectional view showing a prototype of a laminated piezoelectric element of the present invention.

FIG. 11 is a graph showing the influence of Young's modulus and thickness of the adhesive on the displacement of the laminated PZT.

[Explanation of symbols]

 11 Base 12 Adhesive 13 Conductive Layer 14 Piezoelectric Element Plate 15 Multilayer Piezoelectric Element 16 Polyimide Adhesive 17 Nozzle Plate 18 Ink Channel

Claims (2)

[Claims] 1. In an ink jet print head, wherein a piezoelectric element is arranged corresponding to a nozzle opening, and ink is discharged to the outside from the nozzle opening by a drive signal to the piezoelectric element. An ink jet print head, which is a laminated piezoelectric element in which a plurality of formed piezoelectric materials are adhered in layers by an insulating material, and the insulating material is a polyimide resin. 2. The ink jet print head according to claim 1, wherein the thickness t of the polyimide resin is t ≦ 2 μm.