JPH05229117A - Ink jet print head and production thereof - Google Patents

Abstract

PURPOSE:To enhance printing quality and ensure a high response to a printing signal by a method wherein a nozzle gap between a nozzle plate and a planar member is managed with high accuracy and, simultaneously, a dynamic ink pressure from a piezoelectric transducer is transmitted to the planar member without a loss. CONSTITUTION:A plurality of planar members 4 are respectively securely fixed to piezoelectric transducers 12a in the following processes: a process for positioning and temporarily fixing the planar members 4 through an easy- releasable adhesive 22, a process for securely fixing these members to the piezoelectric transducers 12a; and a process for removing the temporary fixing of the planar members. The planar members 4 are securely fixed to the piezoelectric transducers 12a using an adhesive B meeting such characteristics as a thermal expansion coefficient of 7X10<-5> [1/ deg.C] or less, a cure shrinkage of 1 [%] or less, and a rigidity (viscoelasticity coefficient) of 1X10<8>[N/m] [N/m] or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ink jet print recording, in which a piezoelectric transducer facing a nozzle opening is expanded and contracted by an electric signal to apply pressure to ink to eject an ink droplet from the nozzle opening. The present invention relates to an inkjet printhead that forms an ink image on a medium such as recording paper.

[0002]

2. Description of the Related Art There are three main types of ink jet type print heads. The first is a so-called bubble jet type in which a heater for instantaneously vaporizing ink is provided in the extension of the nozzle opening, and ink droplets are generated and flown by the expansion pressure during vaporization. In the second type, a piezoelectric element that is deformed by an electric signal is provided in a container that forms an ink tank portion, and ink is ejected as droplets by the pressure generated during the deformation. In the third type, a piezoelectric element is arranged in the ink tank portion so as to face the nozzle opening,
Due to the expansion and contraction of the piezoelectric element, a dynamic pressure is generated in the nozzle area to cause ink droplets to fly.

In the ink jet type print head of the third type, 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 portion, and each nozzle is formed. Piezoelectric elements are arranged so that the directions of expansion and contraction are aligned so as to face the openings.

In this print head, a print signal is applied as an electric signal to a piezoelectric element to expand and contract the piezoelectric element, and the dynamic pressure of the ink generated at this time causes ink droplets to eject from the nozzle openings to form dots on the printing paper. It is what makes them.

In a print head of this type,
It is desirable that droplet formation efficiency and flight force are large. Therefore, as disclosed in Japanese Patent Laid-Open No. 63-295269, a piezoelectric element for an ink jet print head has been proposed in which electrodes and piezoelectric materials are alternately laminated in a sandwich shape. 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.

[0006]

The dynamic pressure of the ink obtained by the piezoelectric transducer of the ink jet type print head is transmitted to the ink through the plate member on the wall surface of the ink tank portion. In order to stabilize the ink ejection characteristics, the gap formed by the plate member and the nozzle plate (hereinafter referred to as the nozzle gap) is managed with high accuracy, and in order to support high frequency driving, the movement of the piezoelectric transducer is changed. It must be transmitted to the ink with little loss and must be attenuated.

Therefore, the present invention solves such a problem. An object of the present invention is to stabilize the nozzle gap, to eject a reliable and stable ink droplet, and to have a high response to an input signal. To obtain an inkjet print head having properties.

[0008]

In order to achieve the above object, an ink jet type print head of the present invention is arranged in a plurality of nozzle openings of a nozzle plate in a one-to-one manner with a gap filled with ink. The plate member is fixed in position by being fixed to the piezoelectric transducer. The plate member and the piezoelectric converter have a coefficient of thermal expansion: 7 × 10 ⁻⁵ [1 / ° C. or less] Curing shrinkage ratio: 1 [%] or less Stiffness (viscoelastic coefficient): 1 × 10 ⁸ [N / m] It is characterized by being fixed by an adhesive satisfying the above characteristics.

Further, the manufacturing method of the present invention comprises a step of temporarily fixing the nozzle opening facing surfaces of a plurality of plate members with a simple peeling adhesive to fix the nozzle facing surfaces in place, and the plate members to a piezoelectric transducer. It is characterized by including a step of fixing and a step of removing the temporary fixing of the plate member.

[0010]

1 is a sectional view showing an embodiment of an ink jet type print head of the present invention, FIG. 2 is a partially enlarged view thereof, and FIG. 3 is an end view of III-III in FIG. Reference numeral 2 in the drawing is a support plate, which forms the ink flow path 1 and the cylindrical continuous body 3. The support plate 2 is made of highly rigid ceramic, metal or the like. The tubular continuum 3 of the support plate 2 has openings 3a and 3b at both ends, and the plate member 4 is provided in one opening 3a.
Is fixed, and the projection 15 of the nozzle plate 8 having the nozzle opening 6 is fixed to the plate member 4. Further, piezoelectric transducer rows 12, 12, 12, ... Fixed to the substrates 10, 10, 10, ... Are provided in the other opening 3b. Each piezoelectric transducer 12a of the piezoelectric transducer array 12
Is arranged such that its expansion and contraction direction faces the nozzle opening 6, and electric signals from the cables 16 and 18 are applied.

As shown in FIG. 2, the nozzle gap 14
Is determined by the positions of the nozzle plate 8 and the plate member 4.
Nozzle plate 8 forming one end of the nozzle gap 14.
Is positioned at the height h of the projection 15 of the nozzle plate 8, and the height h is determined by the height h of the projection 15, 15,
Since 15 ... Can be processed with high precision, it is extremely stable. The nozzle plate 8 can be accurately manufactured by, for example, electroforming or etching of a metal foil. However, since the plate member 4 forming the other end of the nozzle cap 14 is a portion that transmits the vibration of the piezoelectric transducer 12a to the ink, it must be configured to be displaceable in the nozzle opening 6 direction. Therefore, the nozzle gap 14 may fluctuate depending on how the plate member 4 is fixed to the piezoelectric converter 12a.

Further, since the plate member 4 must efficiently transmit the movement of the piezoelectric converter 12a to the ink, it is necessary to fix the plate member 4 to the piezoelectric converter 12a with high rigidity. Therefore, the position of the plate member 4 is determined by the fixing to the piezoelectric converter 12a, and the accuracy of the nozzle gap 14 is influenced thereby. In order to manage the plurality of nozzle gaps 14 with high accuracy, the position of the plate member 4 must be managed from the fixed portion 4a of the plate member 4, which is the reference surface. However, the position of the fixing portion 4a is set to the support plate 2 and the substrate 10.
And the piezoelectric transducer 12a are determined by the three members, and are greatly affected by the combination of the characteristics of the respective materials and the processing accuracy. The influence of the material characteristics can be most easily prevented by making the thermal expansion coefficients of the three members uniform. However, the piezoelectric converter 12a is made of a ceramic material such as PZT (lead zirconate titanate) and has a very small coefficient of thermal expansion, so that the support plate 2 and the substrate 10 are approximated to this. For example, a ceramic material having rigidity such as alumina, silicon nitride or zirconia, or a metal material such as SUS309, 42 alloy or Invar may be used. However, since the support plate 2 and the substrate 10 are microfabricated components, it is difficult or expensive to process them with the above-exemplified materials.

Therefore, in this embodiment, in consideration of the fine processing of the three members of the support plate 2, the substrate 10 and the piezoelectric transducer 12a and the material cost, the nozzle gap 14 is increased as follows in a wide range of materials. Made it possible to manage with precision.

As a precondition, there is an absolute condition that the plate member 4 and the three members must be fixed to each other with high rigidity in order to form a mechanism for generating an ink discharge dynamic pressure. The fixing portion 4a of the plate member 4 and the supporting plate 2, the supporting plate 2 and the substrate 10, and the fixing of the substrate 10 and the piezoelectric transducer 12a are fixed in a wide area having rigidity. Rigidity between members can be secured by fixing by pressure contact. However, the fixation between the plate member 4 and the piezoelectric converter 12a cannot be fixed by pressure contact because the piezoelectric converter 12a has a very fragile structure.

Therefore, in this embodiment, the adhesive B having a low coefficient of thermal expansion, a low curing shrinkage, and a high rigidity is used between the plate member 4 and the piezoelectric converter 12a. Properties of the adhesive B, for example a nozzle gap 14 30 [mu] m or less, within the tip processing accuracy 10μm plurality of piezoelectric transducers 12a, when the structure of the adhesive layer thickness 30 .mu.m, coefficient of thermal expansion: 7 × 10 ^- 5 [1 / ° C] or less Curing shrinkage ratio: 1 [%] or less Stiffness (viscoelastic coefficient): 1 × 10 ⁸ [N / m] By satisfying the above condition, the nozzle gap 14 is ± 1 of the design value.
High precision control within μm is possible. The rigidity between the plate member 4 and the piezoelectric transducer 12a was sufficiently ensured by the adhesive satisfying the above conditions even when the pressure contact was not performed. Further, variations in the tips of the piezoelectric transducers 12a due to the accuracy of the fixing process of the support plate 2, the substrate 10 and the piezoelectric transducers 12a and the processing precision of the plurality of piezoelectric transducers 12a are caused by the difference between the plate member 4 and the piezoelectric transducers 12a. Nozzle gap 14 became highly accurate by being absorbed by Adhesive B. As an adhesive satisfying these characteristics, a maleimide-based addition polymerization resin such as H
T-10 (Konishi Co., Ltd.), or a polyimide-based addition polymerization resin, for example, a prepolymer step in which a mixture of 4,4'-bismaleimidophenyl methane and 0.0,0'-diallyl bisphenol developed in-house was heated and reacted, An adhesive consisting of a step of applying a heat treatment to a material to be bonded and then heating and curing it.
Alternatively, there is a special modified epoxy resin, for example, Structobond EH-455NF (Mitsui Toatsu Chemical).

The curing shrinkage ratio can be made sufficiently small by the presence of the filler in the adhesive. However, in this structure, there is a concern that the load on the piezoelectric transducer 12a due to the filler at the time of bonding, the resin of the adhesive is It is marked as a characteristic that it should have. However, by using a filler with a limited particle size, a further effect on low curing shrinkage is obtained, and the accuracy of the nozzle gap 14 is improved.

FIG. 4 is a diagram for explaining a manufacturing method for making the nozzle gap 14 highly accurate, and is shown in a state where the top and bottom of FIG. 1 are reversed.

The plate member 4 and the support plate 2 are fixed to each other by pressure contact because the member thickness of the fixing portion is constant. At this time, the positions of the plurality of plate members 4 are not fixed in a floating state because the inside of the cylindrical continuous body 3 of the support plate 2 is hollow. Therefore, a plurality of plate members 4 are fixed as shown in FIG. At this time, since the position of the plate member 4 forming one end of the nozzle gap 14 is determined, the flat plate jig 20 having flatness, for example, silicon nitride or a zirconia plate is pressed and fixed. Adhesive 2 that can be easily fixed in later steps
2 (this is called a simple release adhesive), for example, a hot melt adhesive or lost wax that is softened at a high temperature is used for fixing. Since this fixing is temporary fixing, it is necessary to use an adhesive that can be easily peeled off and completely washed off. For example, hot melt adhesives can be easily washed with thinner and lost wax with trichlorethylene.
There are many target materials for the simple peeling adhesive 22, but since all of them have viscosity, a plurality of pressures A are applied to the flat plate jig 20 as shown in FIG. The plate member 4 is positioned and temporarily fixed. Figure 4 (b)
[Fig. 3] is a cross-sectional view and a top view showing a step of adhering the plate member 4 and the piezoelectric transducer array 12 to each other. The piezoelectric transducers 12a and the substrate 10 are manufactured in advance as a unit of the piezoelectric transducer array 12 forming a plurality of piezoelectric transducers 12a that are fixed and divided as shown in FIG. At this time, since the division processing is finished with a dicing saw and a wire saw, the tip position accuracy of the plurality of piezoelectric transducers 12a in the piezoelectric transducer array 12 varies, but this variation depends on the adhesive B as described above. Be absorbed. The piezoelectric transducer array 12 is a unit guide 2 having a plurality of guide portions 26a.
6 is inserted in the supporting plate 2 provided, and the substrate 10 is fixed to the supporting plate 2 by press contact. In this step, the substrate 10 and the supporting plate 2 are closely fixed to each other, and the piezoelectric converter 12a and the plate member 4 are fixed to each other at the same time. After the plate member 4 and the piezoelectric transducer 12a are fixed to each other, the temporary fixing of the plate member 4 is peeled off, the simple peeling adhesive 22 is washed, and the nozzle plate 8 is attached to the fixing portion 4 of the plate member 4.
The ink jet head is finished by being fixed on the surface a.

The relationship between the simple peeling adhesive 22 and the adhesive B between the plate member 4 and the piezoelectric transducer 12a is as follows.
It is a necessary condition that does not peel off when the adhesive B between the plate member 4 and the piezoelectric transducer 12a is cured. For example, the heat-softening type simple peeling adhesive requires a softening temperature higher than the curing temperature of the adhesive B between the plate member 4 and the piezoelectric transducer 12a. The position management of the plurality of plate members 4 can be performed by the above manufacturing process. Even when the adhesive B has a large curing shrinkage or thermal expansion coefficient, the height of the protrusion 15 of the nozzle plate 8 is corrected in consideration of the bonding condition or the operating temperature of the head to control the nozzle gap 14 with high accuracy. However, by using the adhesive B having the above-mentioned characteristics, complicated correction of the protrusion 15 of the nozzle plate 8 is not required, and the nozzle gap 14 can be managed with high accuracy in a wide temperature range.

The operating principle of the print head manufactured by the above manufacturing method will be briefly described with reference to FIG. When an electric signal is applied between the independent lead member 18 and the common lead member 16 in FIG. 1, the piezoelectric transducer 12a to which the signal is selectively applied by the independent lead member 16 expands and contracts, and the free end side is the axis. The piezoelectric transducer 12a pushes the ink on the front surface toward the nozzle opening 6 by displacing in the direction.
As a result, the ink receives the dynamic pressure and rushes into the nozzle opening 6, becomes an ink droplet, and flies in the external space to form a dot on the printing paper. When the application of the electric signal is stopped, the piezoelectric transducer 12a returns to the original state, and the ink flows into the gap between the nozzle plate 8 and the piezoelectric transducer 12a to prepare for the next ink drop generation.

[0021]

According to the present invention, the nozzle gap between the nozzle plate and the plate member can be controlled in a wide temperature range,
Since the dynamic pressure from the piezoelectric transducer is transmitted to the ink without loss, it is possible to obtain an inkjet head with stable print quality and capable of high frequency driving.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of an inkjet unit that ejects ink of an inkjet head that is an embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG.

3 is an end view of III-III in FIG.

4A and 4B are views for explaining an embodiment of an inkjet head manufacturing method for highly accurately controlling a nozzle gap of a head according to the present invention, in which FIG. 4A is a sectional view and FIG. 4B is a side view and a plan view at the same time. The figure.

FIG. 5 is a top view for explaining the structure of an example of the piezoelectric transducer array.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink flow path 2 Support plate 4 Plate member 6 Nozzle opening 8 Nozzle plate 10 Substrate 12 Piezoelectric converter row 12a Piezoelectric converter 14 Nozzle gap 15 Nozzle plate protrusion 16 Common electrode side lead wire 18 Independent electrode side lead wire 20 Flat plate jig 22 Simple Release Adhesive 24 Pressure Rubber 26 Unit Guide

Claims (2)

[Claims] 1. A plate member and a piezoelectric transducer are arranged in a one-to-one correspondence with the nozzle openings with respect to a nozzle plate having a plurality of nozzle openings with an interval filled with ink.
In an ink jet print head in which the piezoelectric transducer expands and contracts in response to an electric signal and ejects ink in the vicinity of the nozzle opening from the nozzle opening, the plate member and the piezoelectric converter have a coefficient of thermal expansion: 7 × 10 ^{− 5} [1 / ° C] or less Curing shrinkage ratio: 1 [%] or less Rigidity (viscoelastic coefficient): 1 × 10 ⁸ [N / m] Inkjet type characterized by being fixed by an adhesive satisfying the above characteristics Print head. 2. A plate member and a piezoelectric transducer are arranged in a one-to-one correspondence with the nozzle openings with respect to a nozzle plate having a plurality of nozzle openings with an interval filled with ink.
In a method for manufacturing an inkjet printhead in which the piezoelectric transducer expands and contracts in response to an electric signal to eject ink near the nozzle opening from the nozzle opening, a surface of the plate member facing the nozzle opening is temporarily fixed with a simple peeling adhesive. And the step of positioning and fixing the nozzle facing surface, the step of fixing the plate member to the piezoelectric converter, and the step of removing the temporary fixing of the plate member. Method.