JPH09141863A - Ink jet printing head and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the irregularity of applied voltage between the nozzles of an assembled printing head by forming the wall member between an ink chamber and a plezoelectric element from silicone rubber having specific thickness. SOLUTION: When an ink jet printing head 1 is constituted of orifices 2 injecting ink liquid droplets, an ink chamber 4 and the piezoelectric elements 6 bonded to a part of the wall of the ink chamber 4, the wall member between the ink chamber 4 and the piezoelectric elements 6 is formed from silicone rubber 7. The thickness of the wall member is set to 0.05-0.3mm. When the thickness of the silicone rubber 7 exceeds 0.3mm, the discharge of air bubbles floating in the silicone rubber 7 becomes difficult and, therefore, percent defective at a time of the production of a printing head becomes high. Further, it is difficult to reduce the thickness of the silicone rubber 7 to 0.05mm or less from an aspect of the attaching accuracy of the piezoelectric elements 6 and a housing 8. By this constitution, it becomes possible to restrict a setting range of applied voltage and the irregularity of applied voltage between nozzles can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet print head of a type that uses a piezoelectric element as a driving element for ejecting ink and a method for manufacturing the ink jet print head.

[0002]

2. Description of the Related Art The structure of a conventional ink jet print head is disclosed in USP 4,439,780 or Japanese Patent Publication No. 02-45985. Further, as a structure that does not use a diaphragm, USP 4,779,09
9 is disclosed.

[0003]

[Problems to be Solved by the Invention] Japanese Patent Publication No. 02-4598
In the structure disclosed in Japanese Patent Laid-Open No. 5-5, that is, the structure of an inkjet printhead with a diaphragm, the piezoelectric element repeatedly expands and contracts during printing, and the adhesive strength between the diaphragm and the silicone rubber is significantly reduced. Therefore, initially, there was a problem that a good print head also peeled off between the diaphragm and the silicone rubber due to aging and good ink droplets did not occur.

Further, in the structure disclosed in USP 4,779,099, that is, in the structure using no diaphragm, there is a problem that the ink leaks from the inside of the head because the silicone rubber is attacked by the ink.

Further, since the thickness of the silicone rubber cannot be controlled, there is a problem that the voltages for obtaining the predetermined ink droplet speeds of the respective nozzles are not uniform.

It is an object of the present invention to suppress variations in applied voltage between nozzles of an assembled printhead, and to reduce printhead assembly failure.

Another object of the present invention is to easily assemble the print head.

[0008]

In order to achieve this object of the present invention, an orifice for ejecting ink droplets, an ink chamber, and a piezoelectric element attached to a part of the wall of the ink chamber are used. In the ink jet print head, the wall member between the ink chamber and the piezoelectric element is made of silicone rubber. At this time, the wall member may have a thickness of 0.05 mm to 0.3 mm.
This makes it possible to limit the setting range of the applied voltage.

The above object can be achieved by forming an ink resistant protective film on the wall surface of the silicone rubber on the ink chamber side. With the above configuration, it is possible to prevent swelling and corrosion of the silicone rubber due to the ink.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a print head 1 according to the present invention.

The print head 1 has an orifice plate 10 having an orifice hole 2 which serves as an ejection port for ink droplets.
A base plate 3 forming an ink chamber 4, a housing 8, a piezoelectric element 6 having one end fixed to the housing 8, a foot 5 attached to the other end of the piezoelectric element 6, and the ink chamber. Silicone rubber 7 filled in the housing 8 so as to form the wall of 4 and cover the foot 5.
And an ink protection film 9 formed on the wall of the silicone rubber 7. In this embodiment, the silicone rubber 7 is Q3-6611 manufactured by Dow Corning.

An actual print head has a plurality of the constitutions shown in FIG. 1 in the direction perpendicular to the paper surface and has a multi-nozzle structure. (This print head has 48 ink chambers.) Next, the operation of the print head will be described.

In FIG. 1, when the ink chamber 4 is filled with ink and a pulsed voltage is applied to the piezoelectric element 6, the piezoelectric element 6 contracts and then returns to its original length, and the silicone rubber 7
The volume of the ink chamber 4 can be drastically changed via the, and ink droplets can be ejected from the orifice hole 2.

It is considered that the thinner the thickness δ of the silicone rubber 7 from the wall of the ink chamber 4 to the tip of the foot 5, the better the displacement transmission efficiency of the piezoelectric element 6.

Therefore, FIG. 3 shows the relationship between the applied voltage for ejecting ink droplets at a predetermined initial velocity and the thickness of the silicone rubber 7.

As shown in the drawing, the thinner the thickness δ of the silicone rubber 7 is, the lower the applied voltage is. Rather, it is understood that the thicker the silicone rubber 7, the better.

However, if the thickness of the silicone rubber 7 is increased, it becomes difficult to discharge the air bubbles floating in the silicone rubber 7. Therefore, the defective rate at the time of manufacturing the print head is (1
It becomes higher when 48 ink chambers are installed in the print head.
The change sharply increases when the thickness of the silicone rubber exceeds 0.3 mm.

The thickness of the silicone rubber 7 is 50 μm.
It is difficult to reduce the thickness to the following because of the mounting accuracy of the piezoelectric element 6 and the housing 8.

Therefore, the thickness δ of the silicone rubber 7 is 0.0
Controlling to 5 mm to 0.3 mm is effective in assembling.

FIG. 2 is a sectional view showing a method of manufacturing the print head 1.

FIG. 3A is a view in which the piezoelectric element 6 having the foot 5 is attached to the housing 8. FIG. 7B is a diagram in which the dummy plate 11 is attached to the bottom of the housing 8.
(C) is a diagram in which silicone 7 is filled. (D) is a view in which the print head is turned over and the dummy plate is peeled off. (E) is a diagram in which the ink protection film 9 is formed. (F) is a cover plate 3 and an orifice plate 1
It is a figure in which 0 is attached and wiring is further applied to the piezoelectric element 6.

Next, FIG. 2 shows a method of manufacturing the print head. 2A to 2F show steps of the head.

In (a), the foot 5 is attached to the housing 8.
The piezoelectric element 6 marked with is attached. If a conductive adhesive is used when the piezoelectric element 6 is attached to the housing 8, the common electrode of the piezoelectric element 6 can be easily formed.

In (b), the dummy plate 11 is attached to the bottom of the housing 8. As the dummy plate 11, a stainless plate may be attached with an adhesive, but a heat resistant tape (polyimide film tape)
Is easier to handle.

In (c), the silicone rubber 7 is filled in the housing 8. Here, it is necessary to fill the silicone rubber 7 in a vacuum state, or to leave the silicone rubber 7 in a vacuum state in advance to remove air bubbles in the silicone rubber 7. Then, the silicone rubber 7 is heated according to the curing conditions.

In (d), the print head is turned over and the dummy plate 11 is peeled off. Here, since the surface of the silicone rubber 7 from which the dummy plate 11 has been peeled has bubbles or irregularities, the surface of the silicone rubber 7 may be wrapped. Silicone rubber by wrapping 7
It is also possible to control the thickness .delta.

In (e), the ink protection film 9 is formed on the surface of the silicone rubber. As a method of forming the ink protective film 9, there is a method of sputtering or vapor depositing metal or nonmetal. For example, gold and titanium metal sputtering and silicon vapor deposition have been put to practical use. However, here, as a method for easily controlling the thickness of the protective film 9 and requiring less equipment, a method in which an epoxy adhesive having ink resistance is dissolved in a solvent (methyl ethyl ketone) and applied is adopted.

When the ink used is a heat-meltable ink, the print head is subjected to a thermal cycle, which causes distortion in the silicone rubber 7 and the ink protective film 9. In that case, the ink protective film 9 having a thermal expansion coefficient equal to that of the silicone rubber 7 is preferably used, but an adhesive (epoxy adhesive) may be used in this case as well.

In (f), the cover plate 3 and the orifice plate 10 are attached to the housing 8, and the piezoelectric element 6 is finally wired to complete the assembly of the print head.

[0031]

According to the present invention, the wall member between the ink chamber 4 and the piezoelectric element 6 is made of silicone rubber 7, and the wall member 7 is formed.
By defining the thickness of the print head from 0.05 mm to 0.3 mm, it is possible to suppress variations in the applied voltage between the nozzles of the assembled print head, and consequently to reduce print head assembly defects.

Further, by forming an ink resistant protective film on the wall surface of the silicone rubber 7 on the ink chamber 4 side, it is possible to prevent the silicone rubber 7 from swelling or corroding due to ink.

Further, the print head can be easily assembled.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a printhead according to the present invention.

FIG. 2 is a cross-sectional view showing an assembling process of FIG.

FIG. 3 is a graph showing the relationship between voltage and thickness of silicone rubber.

[Explanation of symbols]

1 is a print head, 2 is an orifice hole, 3 is a cover plate, 4 is an ink chamber, 5 is a foot, 6 is a piezoelectric element, 7
Is a silicone rubber, 8 is a body, 9 is an ink protective film, 1
0 is an orifice plate.

Front page continuation (72) Kenichi Kukai, 1060 Takeda, Hitachinaka City, Hitachinaka City, Ibaraki Prefecture, Hitachi Koki Co., Ltd. (72) Nobuhiro Kurosawa, 1060, Takeda, Hitachinaka City, Ibaraki Prefecture, Hitachi Machinery Co., Ltd. Kunihiro Hashi, 1060 Takeda, Hitachinaka, Ibaraki, Hitachi Koki Co., Ltd. (72) Keiji Watanabe, 1060, Takeda, Hitachinaka, Ibaraki, Hitachi Koki, Ltd.

Claims (3)

[Claims] 1. An orifice serving as an ink droplet ejection port,
In an ink jet print head having an ink chamber communicating with the orifice for accumulating ink and a piezoelectric element provided adjacently via a wall member of the ink chamber to provide energy for ejecting ink, The wall member between the piezoelectric element is made of silicone rubber having a thickness of 0.05 mm to 0.3 mm, and an ink-resistant protective film is formed between the ink chamber and the wall member. Inkjet print head. 2. The ink jet print head according to claim 1, wherein the ink resistant protective film is formed by applying an adhesive having high ink resistance. 3. An orifice which serves as an ejection port for ink droplets,
In an ink jet print head having an ink chamber communicating with the orifice for accumulating ink and a piezoelectric element provided adjacently via a wall member of the ink chamber to provide energy for ejecting ink, the piezoelectric element is A method for manufacturing an ink jet print head, comprising: forming a protective film having ink resistance after bonding silicone rubber, and finally laminating a plate that forms an ink chamber and an orifice.