JPH07276642A - Printing head for ink jet and its manufacture - Google Patents

Abstract

PURPOSE:To provide a printing head for ink jet consisting of an ink heating electrode which is protected against its peeling-off and separation from a substrate and thereby free from its wear, and is long-lived, responsive at high speed and is driven at a low voltage. CONSTITUTION:A pair of low resistance areas of titanium silicide are formed on a part which comes into contact with the electroconductive ink 18 of a silicon substrate 11 by a solid-state reaction between titanium and silicon, and are used as electrodes 12a, 12b. In addition, an ink chamber 15 is provided by junctioning a structure 14 for the formation of an ink chamber tightly on the silicon substrate 11. Thus it is possible to obtain a printing head for ink jet with high functional stability which is free from the peeling-off of a heating electrode due to a corrosion reaction by the electroconductive ink and bubble pressure.

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 used in a printer and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, a print head based on a direct heating method of a conductive ink has been proposed for a print head for an ink jet type printer that locally ejects ink to eject the ink. As a method of locally heating the ink and causing it to fly to eject the ink, there is a method of directly energizing the conductive ink to generate Joule heat of the ink itself.

A conventional ink jet print head will be described below with reference to the drawings. FIG. 6A is a sectional view of a conventional inkjet printhead. Figure 6
FIG. 6B is a plan view of the conventional inkjet print head as viewed from above. That is, FIG. 6A is a sectional view taken along the line AA ′ of FIG.

In FIGS. 6A and 6B, an electrode 2 made of platinum or the like is formed on the surface of a substrate 1 made of glass or the like.
Is formed by, for example, a sputtering method, and the ink chamber 3 is provided on the substrate 1 by closely bonding the ink chamber forming structure 4 having a nozzle 5 for ejecting ink on a part thereof. The ink chamber 3 is filled with the conductive ink 6. In the actual printing operation, a voltage is applied from the electric wiring 10 connected to the electrode 2, and a current flows from the electrode 2 to the conductive ink 6, so that the conductive ink 6 locally heated by Joule heat of the ink itself is discharged. Bubble 7 is generated inside and ink chamber 3
The internal pressure of the ink becomes high, and the ink droplet 8 flies from the nozzle 5 in the direction of the arrow 9 to print on the recording paper.

[0005]

As described above, in the ink jet print head based on the above-described conductive ink direct heating system, the electrode 2 is in direct contact with the conductive ink 6, so that the electrode 2 is chemically and thermally treated. The conductive ink 6 is exposed to a harsh environment, and the conductive ink 6 penetrates to reach the interface between the platinum electrode 2 and the glass substrate 1 due to the capillary wave of the conductive ink 6 or the pressure wave caused by bumping, and the electrode corrosion and corrosion due to the formation of a local battery. The reaction causes the electrode to peel and drop due to bubble pressure, resulting in significant wear of the heating electrode.

[0006] As a countermeasure against this, the conventional method is to form the electrode with titanium instead of platinum, and to improve the adhesion between the electrode and the glass substrate by protecting the end portion of the electrode with a durable film. By using titanium silicide instead of the electrode to improve the adhesion between the electrode and the glass substrate, the consumption of the heating electrode is reduced and the life of the print head is extended. However, also in this case, there is a problem that the electrode is peeled off due to a large difference in thermal expansion coefficient between the titanium silicide and the glass substrate.

The present invention solves the above-mentioned conventional problems, and provides a low-voltage driven inkjet printhead having a long life and high-speed responsiveness that does not cause peeling of an electrode and a substrate, and a method of manufacturing the same. With the goal.

[0008]

In order to achieve this object, an ink jet print head according to the present invention comprises a titanium silicide or at least a part of an electrode formed by a solid phase reaction on a surface of a silicon substrate which is in contact with ink. An electrode substrate having a structure in which a pair of low resistance regions made of titanium were formed and an insulating film was formed on the silicon substrate excluding the low resistance regions was used.

[0009]

With this structure, the low resistance layer inside the silicon substrate, which serves as the heating electrode, is formed of titanium silicide, which is an intermetallic compound formed by the solid-phase reaction of silicon and titanium, so that the silicon substrate and the electrode are integrated. It has a different structure. For this reason, the conductive ink does not penetrate into the interface between the silicon substrate and the electrode composed of the low resistance layer, and therefore, the corrosion reaction and the peeling of the electrode due to bubble pressure are eliminated.
Further, since the silicon serving as the substrate is a good heat conductor and the thermal expansion coefficients of silicon and titanium silicide are almost the same, peeling of the heating electrode due to thermal expansion can also be prevented.

[0010]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. 1A and 2 are cross-sectional views showing the structure of an inkjet print head according to the first embodiment of the present invention, and FIG. 1B is a top view of the inkjet print head according to the first embodiment of the present invention. A plan view
1A and 2 are cross-sectional views taken along the line -A '. Figure 1
FIG. 3C is a perspective view of the ink chamber forming structure of the ink jet print head according to the first embodiment of the present invention.

In FIG. 1, 11 is a resistivity of 1 × 10 ⁶ Ω.
The silicon substrates 12a and 12b having cm have low resistance regions made of titanium silicide formed by solid-phase reaction with titanium on a part of the silicon substrate 11, and constitute ink heating electrodes. 13 is a low resistance region 12 of the silicon substrate
An insulating film made of SiO ₂ obtained by thermally oxidizing the surface of the silicon substrate 11 except the portions where a and 12b are formed, 14
In the ink chamber forming structure, as shown in FIG. 1C, a space for forming an ink chamber is provided inside by a heat-resistant resin, a nozzle 16 is provided at an upper portion, and a silicon substrate is provided at a lower portion. An opening 17 is provided, which is a surface that is in close contact with 11 and is provided.

Reference numeral 15 is an ink chamber formed by closely bonding the ink chamber forming structure 14 to the silicon substrate 11. The operation of the inkjet print head configured as described above will be described with reference to FIG.

First, the electrode 1 is fed from a voltage supply device (not shown).
When a voltage is applied to 2a and 12b, a current flows in the conductive ink 18 from the electrode 12a to the electrode 12b in the direction of arrow 19. At this time, the voltage is also applied to the inside of the silicon substrate 11, but since the resistivity of the silicon substrate 11 is sufficiently higher than the resistivity of the conductive ink 18, a current flows only in the conductive ink 18. Therefore, the conductive ink 18 self-heats due to the Joule loss of the current represented by I ² R (I: current, R: resistance of conductive ink), and bumping starts with the passage of time and bubbles (not shown) Occurs and expands.

With the expansion of the bubble, the current in the conductive ink 18 is bent to both sides of the bubble because the bubble is an insulator and the current cannot pass therethrough, and the current density becomes the highest on the bubble surface. Therefore, the bubble surface is heated most and the expansion of the bubble is further accelerated, and the expansion of the bubble causes the pressure of the conductive ink 18 in the ink chamber 15 to rapidly increase. This high-pressure conductive ink 18 is used for the nozzle 1
The ink droplets 20 are ejected from 6 in the direction of the arrow 21 to form the ink droplets 20 which are ejected and adhered to the recording paper 22 to form dots.

When the expansion of the bubble reaches the maximum level, the bubble occupies a considerable part of the current passage, so that the current flowing through the conductive ink 18 is reduced and the generation of Joule heat is suppressed. On the other hand, the heat of the bubble is taken to the conductive ink 18, the silicon substrate 11, and the ink chamber forming structure 14, so that the bubble rapidly contracts and disappears. That is, the heat of the bubble itself is removed in all directions, and the conductive ink 18 is cooled to almost the temperature in the initial state.

Since the silicon substrate 11 is a good heat conductor, the conductive ink 18 after the bubble disappears is cooled much faster than the print head using the conventional glass substrate. This makes it possible to realize high-speed response as an inkjet print head. The insulating film 13 prevents current from flowing on the surface of the silicon substrate 11, and heats the silicon substrate 1 to generate heat necessary for expanding bubbles.
It also has the effect of preventing excessive heat dissipation to the No. 1 device.

By repeating the above operation, a drive voltage is applied to the electrodes 12a and 12b according to a print signal sent from a computer or the like, and printing on the recording paper 22 becomes possible.

In the above embodiments, the silicon substrate 11 having only the low resistance regions 12a and 12b formed of titanium silicide as electrodes is used. However, titanium silicide and titanium film remaining without forming titanium silicide are used. FIG. 2 shows an example in which an electrode is composed of the parts. In the figure, reference numeral 25 denotes a part of the titanium film remaining without forming titanium silicide, and the low resistance regions 12a, 1 made of titanium silicide.
It is joined to 2b by a solid phase reaction. Also in this example, the operation of the inkjet print head is the same as described above.

Next, the substrate forming process, which is the first step of the method for manufacturing the ink jet print head of this embodiment, will be described with reference to FIG.
Will be explained. First, as shown in FIG. 3A, a silicon substrate 11 having a resistivity of 1 × 10 ⁶ Ω · cm is prepared as a base. Next, as shown in FIG. 3B, the silicon substrate 11
After removing the natural oxide film on the surface of, the titanium film 25 is grown to 0.5 μm by the vacuum evaporation method. The back pressure at this time was 1 × 10 ⁻⁶ Pa and the growth rate was 50 nm / sec.

Next, as shown in FIG. 3C, the electrode dimension is 50 μm except for unnecessary portions by photolithography technique.
A pair of titanium films 25 having a corner and a distance between electrodes of 30 μm are left.
Next, as shown in FIG. 3 (d), in a vacuum of 100 mPa, 55
Titanium in the titanium film 25 is diffused into the silicon substrate 11 by heat treatment at 0 ° C. for 30 minutes. As shown in the figure, the titanium in the titanium film 25 was diffused into the silicon substrate 11 by the diffusion process to form titanium silicide 26. After further heat treatment for 5 hours, as shown in FIG.
Almost all of the titanium in the titanium film 25 is the silicon substrate 11.
The low resistance regions 12a and 12b were diffused in and formed.

According to the cross-sectional analysis, the titanium silicon substrate 1
1 has a diffusion depth of about 1.5 μm, and has a low resistance region 12
The resistance values of a and 12b were 0.01 Ω · cm or less. Next, as shown in FIG. 3F, the low resistance regions 12a and 12b are
A nitride film 27 is formed on the silicon substrate 11 containing plasma by plasma CV.
After the film is formed by D, as shown in FIG. 3G, the film other than immediately above the low resistance regions 12a and 12b is removed by the photolithography method to leave the pair of nitride films 27.

Next, as shown in FIG. 3 (h), the nitride film 2 is heat-treated in steam at 850 ° C. for 30 minutes.
7 is not present, the exposed surface of the silicon substrate 11 is thermally oxidized to form the SiO ₂ insulating film 13. After that, FIG. 3 (i)
As shown in FIG. 5, the nitride film 27 is removed to obtain the silicon substrate 11 having the low resistance regions, that is, the electrodes 12a and 12b and the SiO ₂ insulating film 13.

Next, as shown in FIG. 1C, the ink chamber forming structure 14 is adhered and bonded onto the silicon substrate 11 obtained in the above substrate forming step, The inkjet print head as shown in FIG. 1A is formed. In the formation of the low resistance regions 12a and 12b by the diffusion process of titanium in the titanium film 25 into the silicon substrate 11, the diffusion temperature of the titanium film 25 into the silicon substrate 11 and the formation temperature of the titanium silicide 26 depend on the presence of impurities, especially oxygen. The diffusion treatment must be carried out in vacuum or in an inert gas since the temperature rises significantly. The formation of titanium silicide 26 occurs at 450 ° C. or higher, and the reaction rate increases as the temperature rises.

However, if the temperature becomes too high, the crystallinity of the titanium silicide 26 is disturbed and the number of defects such as amorphous grain boundaries and vacancies in the low resistance regions 12a and 12b increases remarkably, and the precipitation of silicon becomes remarkable. The ink heating electrode having a long life and high-speed response, which is the object of the present invention, cannot be realized. Therefore, the diffusion temperature needs to be 850 ° C. or lower.

On the other hand, a method of manufacturing an ink jet print head which can be driven at a low voltage in addition to the above-mentioned long life and high speed response will be described in a second embodiment.

(Embodiment 2) A second embodiment of the method for manufacturing an ink jet print head of the present invention will be described below with reference to the drawings. FIG. 4 is a first stage substrate forming process diagram illustrating a method of forming an ink jet print head according to a second embodiment of the present invention. A silicon substrate 28 having an oxide film 28a formed on its surface as shown in FIG.
To use. Next, as shown in FIG. 4B, a silicon film 29 is formed on the oxide film 28a of the silicon substrate 28, for example, C
It is formed by the VD method or the like. In this case, the thickness of the silicon film 29 is appropriately in the range of 1 to 3 μm. When the thickness is 1 μm or less, the thickness as an electrode is insufficient, and when the thickness is 3 μm or more, the film is easily peeled off.

Further, the adhesion between the silicon film 29 used here and the oxide film 28a of the silicon substrate 28 is excellent,
It has been established as a product technology for thin film transistors.
Next, as shown in FIG. 4C, a titanium film 25 is grown to 0.5 μm on the silicon film 29 by a vacuum evaporation method. This state corresponds to the state shown in FIG. 3B described in the first embodiment.
Next, as shown in FIG. 4D, a pair of titanium films 25 having an electrode dimension of 50 μm square and an interelectrode distance of 30 μm are left by removing unnecessary portions by photolithography.

Next, as shown in FIG. 4 (e), the titanium in the pair of titanium films 25 is diffused into the silicon film 29 by heat treatment at 550 ° C. for 30 minutes in a vacuum of 100 mPa, thereby forming a pair of titanium silicide. 26 was formed. Further, as shown in FIG. 4F, the titanium in the pair of titanium films 25 was diffused into the silicon film 29 by the heat treatment for further 5 hours to form the low resistance regions 12a and 12b. According to the cross-sectional analysis, the diffusion depth of titanium into the silicon film 29 was about 1.5 μm, and the resistance values of the low resistance regions 12a and 12b were 0.01 Ω · cm or less.

Next, as shown in FIG. 4G, after a nitride film 27 is formed by plasma CVD on the silicon film 29 including the low resistance regions 12a and 12b, as shown in FIG. The low resistance region 12 is formed by photolithography.
A film other than immediately above a and 12b is removed, and a pair of nitride films 27
Leave. Next, as shown in FIG.
By heat treatment at 0 ° C. for 30 minutes, a pair of nitride films 27
The surface of the exposed silicon film 29 is thermally oxidized without S.
The iO ₂ insulating film 13 is formed. After that, as shown in FIG. 4J, the pair of nitride films 27 is removed, and the low resistance region 12 is removed.
A silicon substrate 28 having a, 12b and the SiO ₂ insulating film 13 is obtained.

Next, using the silicon substrate 28 obtained in the above-described substrate forming step, as described in Example 1, the ink chamber forming chamber is formed on the silicon substrate 28 as shown in FIG. 1 (c). The ink jet print head is formed as shown in FIG. 1A through the ink chamber forming step of closely bonding the structures 14.

In the above, an example is shown in which the silicon substrate 28 having the oxide film 28a formed on the surface is used as an electrode substrate. However, when a glass substrate is used instead of the surface silicon oxide substrate, the first embodiment or An inkjet printhead having the same functions as obtained by the method of Example 2 is obtained. The thermal insulation of the material used here as the electrode substrate becomes higher in the order of the silicon substrate, the surface-oxidized silicon substrate, and the glass substrate, and the driving voltage required for bubble expansion of the conductive ink inside the print head composed of these electrode substrates is It becomes lower in order.

On the other hand, the magnitude of thermal stress due to thermal expansion shows the opposite tendency as described above, and if a substrate with a large thermal expansion is used, it affects the life of the print head due to peeling of electrodes and so on. desirable.

(Embodiment 3) Next, a third embodiment of the method for manufacturing an ink jet print head of the present invention will be described with reference to the drawings. FIG. 5 is a process drawing of a first stage substrate for explaining a method for producing an ink jet print head in a third embodiment of the present invention. As shown in FIG. 5A, a silicon substrate 11 is used, and as shown in FIG. 5B, a titanium film 25 is formed on the silicon substrate 11 by a vacuum deposition method.
Are grown to 0.5 μm.

Next, as shown in FIG. 5C, the electrode dimension is 50 μm except for unnecessary portions by photolithography technique.
A pair of titanium films 25 having a corner and a distance between electrodes of 30 μm are left.
Next, as shown in FIG. 5 (d), in a vacuum of 100 mPa, 55
A part of titanium in the pair of titanium films 25 is diffused into the silicon substrate 11 by heat treatment at 0 ° C. for 30 minutes, so that the titanium film 25 remaining without diffusion and the low resistance regions 12a and 12b made of titanium silicide. To form.

Next, as shown in FIG. 5E, the titanium film 2
A nitride film 27 is formed on the silicon film 11 containing 5 by plasma CV.
After the film is formed by D, as shown in FIG. 5F, the film other than immediately above the titanium film 25 is removed by the photolithography method to leave the pair of nitride films 27. Next, as shown in FIG. 5G, the exposed surface of the silicon substrate 11 is thermally oxidized by heat-treating it in water vapor at 850 ° C. for 30 minutes to remove the pair of nitride films 27, and the SiO ₂ insulating film 13 is formed. To form. After that, as shown in FIG. 5H, the pair of nitride films 2
7 is removed and a low resistance region 12 made of titanium silicide is formed.
The silicon substrate 11 provided with a, 12b, the titanium film 25, and the SiO ₂ insulating film 13 is obtained.

Next, the ink chamber forming structure shown in FIG. 1 (c) is formed on the silicon substrate 11 in the same manner as described in Example 1 using the silicon substrate 11 obtained in the above substrate forming process. An ink jet print head is formed as shown in FIG. 1A through an ink chamber forming step of closely bonding 14 together.

Ink jet print heads were manufactured by the methods of the first, second and third embodiments described above, and the life test of the low resistance regions 12a and 12b was conducted.
After applying a voltage of 10 V at a frequency of 5 MHz and repeatedly printing 20 million times, the low resistance regions 12a, 12
The consumption state of b was investigated. In the ink jet print head of the present invention, peeling due to the permeation of the conductive ink 18 between the silicon substrate 11 and the low resistance regions 12a and 12b does not occur,
It was about 0.1 μm in the thickness direction of the electrode and was in a concave shape that was consumed.

On the other hand, in the conventional heating electrode in which the titanium film is formed on the glass substrate by the sputtering method or the like, the film thickness of the titanium film is reduced, and the peeling and dropping are severe, and only about 40% of the area remains. It was In the first and second embodiments, the one in which titanium is completely diffused in the silicon substrate is used, but also in the heating electrode having the shape of the third embodiment in which titanium is partially left, the adhesion between the substrate and titanium is large. Was strong due to the formation of titanium silicide, and the peeling and separation of the heating electrode was suppressed, resulting in a longer life than the conventional heating electrode.

[0039]

As described above, according to the present invention, a low resistance region due to a solid-phase reaction of titanium and silicon is formed in a portion of a silicon substrate that comes into contact with conductive ink to form a heating electrode, and the ink chamber is provided on the substrate. An ink jet print head is formed by closely bonding the forming structure.
INDUSTRIAL APPLICABILITY The inkjet print head of the present invention can provide an inkjet print head having a long service life in which the heating electrode and the substrate are not separated.

Further, titanium silicide forming the low resistance region is a material which is electrochemically stable and has a characteristic of being less consumed by the electrode reaction.

Furthermore, since a silicon substrate is used as the substrate, heat is quickly dissipated and excellent in high-speed responsiveness, and since silicon and titanium silicide have substantially the same thermal expansion coefficient, there is an advantage that thermal stress is small. Further, as a method of suppressing the driving voltage in the printing operation, instead of the silicon substrate, a silicon substrate having an oxide film formed on the surface or a heat insulating substrate such as a glass substrate is used to form a heating electrode, thereby forming an inkjet print head. Drive voltage can be reduced.

In the solid-phase reaction method by diffusion as a method of forming the low resistance region according to the present invention, unlike the conventional electrode formed by the sputtering method or the like, the crystal structure with the silicon of the substrate continuously changes. By providing a heating electrode with very few defects and no deterioration, it is possible to realize an ink jet print head having high reliability, long life, and low voltage drive.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of an inkjet print head according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the structure of an inkjet print head in the first embodiment of the present invention.

FIG. 3 is a substrate making process diagram illustrating a method of making a heating electrode in the first embodiment of the present invention.

FIG. 4 is a first stage substrate production process diagram illustrating a method for producing an inkjet printing head in a second embodiment of the present invention.

FIG. 5 is a first stage substrate forming process diagram illustrating a method of forming an ink jet print head according to a third embodiment of the present invention.

FIG. 6A is a cross-sectional view of a conventional inkjet printhead. FIG. 6B is a plan view of the conventional inkjet printhead as viewed from above.

[Explanation of symbols]

 11, 28 Silicon substrate 12a, 12b Low resistance region (electrode) 13 Insulating film 14 Ink chamber forming structure 15 Ink chamber 16 Nozzle 25 Titanium film 26 Titanium silicide 27 Nitride film 28a Oxide film 29 Silicon film

Claims (6)

[Claims] 1. A silicon substrate, a pair of electrodes provided with an intermetallic compound region provided on a surface of the silicon substrate in contact with ink, an insulating film on the silicon substrate excluding the electrodes, and a part thereof. An ink jet print head comprising: an ink chamber forming structure having nozzles for ejecting ink. 2. The ink jet print head according to claim 1, wherein the intermetallic compound region is titanium silicide. 3. The ink jet print head according to claim 1, wherein the electrode is composed of the titanium silicide and a titanium excess region on the titanium silicide. 4. The ink jet print head according to claim 1, wherein the silicon substrate is composed of silicon coated with an oxide film and a silicon film formed on the surface thereof. 5. The ink jet print head according to claim 1, wherein the silicon substrate comprises a silicon film formed on the surface of glass. 6. A pair of titanium layers are formed on a silicon substrate by a photolithography method, and then 450 in a vacuum or an inert gas atmosphere of nitrogen, argon or helium.
By performing a heat treatment at a temperature of ℃ or more and 850 ° C or less to diffuse all or part of titanium into silicon,
A substrate forming step of forming a low resistance region for forming at least a part of a pair of electrodes made of titanium or titanium silicide in a plane of silicon, and forming an insulating film on the silicon substrate excluding the low resistance region; A method of manufacturing an ink jet print head, comprising a step of forming an ink chamber on a substrate by closely bonding a structure forming the ink chamber.