JPH08169119A - Head for ink jet printer and production thereof - Google Patents

Abstract

PURPOSE: To perform stable printing generating no impedance change without requiring an ageing process by forming an oxide film at least on the surface of the exposed part of an electrode. CONSTITUTION: Predetermined DC voltage is applied to the respective electrodes 3a, 3b exposed to the interior of an ink chamber 6 to form oxide films 17a, 17b at least on the surfaces of the exposed parts of the electrodes 3a, 3b. In this case, since an ageing process is not required, the thickness of the oxide films can be arbitrarily controlled according to the level of DC voltage without being accompanied by the emission of ink and the oxide films having uniform thickness can be formed. As a result, since the change due to the emission of ink such as oxidation reaction or melting reaction due to the electrochemical reaction of the electrodes and conductive ink can be suppressed, stable printing generating no impedance change can be performed and a head of high image quality for an ink jet printer can be produced in low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a head for an ink jet type printer and an ink jet type printer for ejecting ink droplets used in the ink jet type printer manufactured by the method to record it on printer paper. It is about the head.

[0002]

2. Description of the Related Art In recent years, with the increase in performance, size and cost of computers, it has become one of the output devices for computers.
As for the printer, which is one of them, high performance, miniaturization, and cost reduction are required, and the dot printer is switched to the laser printer and the ink jet printer. The printing method of this ink jet printer includes a method of pushing out the ink by deformation of the piezoelectric element, a method of heating and boiling the ink with a heater to eject the ink, and an ink having conductivity (hereinafter referred to as conductive ink). It is known that the conductive ink is boiled by self-heating and the conductive ink is discharged (hereinafter referred to as a conductive heating method), and the like. It has a simpler configuration than other methods and is widely used.

A conventional ink jet printer head using an electric heating method will be described below with reference to the drawings. FIG. 9 is a schematic cross-sectional view of an essential part showing an ink jet printer using a conventional head for an ink jet printer by an electric heating method, and FIG.
It is a C-C line sectional view. 1 "is a head for an ink jet printer using a conventional electric heating method, 2 is a substrate made of a non-conductive material such as glass or ceramics such as alumina, and 3a and 3b are titanium (Ti), gold (Au), platinum ( A pair of electrodes 4 made of Pt), nickel (Ni) or the like and formed on the upper surface of the substrate 2 at a predetermined interval and laminated on the upper surface of the substrate 2 and each of the electrodes 3a and 3b. An insulating film 5 is formed by exposing a predetermined portion of each of the electrodes 3a and 3b in contact with a conductive ink 9 described later (hereinafter referred to as an electrode exposed portion) and forming an ink supply path 5 described later to form a laminated layer. Etc. in FIG. 9 DD '
The center lines of the ink chamber 6 and the nozzle hole 7 described later, which are indicated by the lines, and the center normals between the electrode facing portions of the electrodes 3a and 3b indicated by the points E in FIG. The resin sheet 6 is formed by the substrate 2, the electrodes 3a, 3b, and the insulating film 4, and the groove portion having a substantially inverted convex cross-section and the opening formed in the lower surface of the resin sheet 5 in a substantially trapezoidal shape. The ink chamber 7 communicates with the ink chamber 6 and the resin sheet 5
Nozzle holes formed in the ink chamber, 8 is an ink supply passage communicating with the ink chamber 6, 9 is conductive ink filled from the ink supply passage 8 into the ink chamber 6 and the nozzle hole 7, 10 is an electrode 3a, Bubbles generated between 3b, 11 ink drops ejected from the nozzle holes 7, 12 printer paper arranged above the nozzle holes 7, 13 printing attached to the printer paper 12, and 14 will be described later. A control unit that is electrically connected to each of the electrodes 3a and 3b via a wiring 16 and applies a predetermined alternating energization voltage described below to each of the electrodes 3a and 3b, and 15 is electrically connected to the control unit 14 through the wiring 16. A power supply unit for supplying a current / voltage, and 16 for the electrodes 3a and 3b and the control unit 1
4, and wiring for electrically connecting the control unit 14 and the power supply unit 15.

A method of manufacturing the ink jet printer head according to the conventional electric heating method having the above-described structure will be described below. First, Ti, A is formed on the upper surface of the substrate 2 made of glass or ceramics such as alumina.
Conductive materials such as u, Pt, and Ni are laminated with a predetermined thickness by a physical film forming method such as a vapor deposition method, a sputtering method, or a plating method to form a metal film (not shown). Next, a pattern of the electrodes 3a and 3b is formed by a photolithography method or the like, and a portion other than the electrodes 3a and 3b is removed by an ion milling method or a chemical etching method or the like, and a predetermined lateral width, a space between the electrode facing portions, or the like is set. Then, the electrodes 3a and 3b are formed. Next, an insulating material (not shown) is formed on the upper surfaces of the electrodes 3a, 3b and the substrate 2 by laminating an insulating material such as an organic polymer or ceramics with a predetermined thickness by coating or sputtering. . Next, a pattern of the insulating film 4 for forming the electrode exposed portions of the electrodes 3a and 3b is formed by a photolithography method or the like, and the insulating layer corresponding to the electrode exposed portions of the electrodes 3a and 3b is ion milled or chemically etched. Then, the insulating film 4 is formed by removing the insulating film 4. On the other hand, the opening of the ink chamber 6 and the nozzle hole 7 are formed in a predetermined portion of a resin sheet (not shown) made of an insulating material such as an organic polymer by an excimer laser processing method or the like to form the resin sheet 5. Finally, the resin sheet 5 is formed on the upper surface of the substrate 2 on which the electrodes 3a and 3b and the insulating film 4 are laminated, as shown by D in FIG.
The center line of the opening of the ink chamber 6 and the nozzle hole 7 indicated by the line -D 'and the center perpendicular between the electrode facing portions of the pair of electrodes 3a and 3b indicated by the point E in FIG. . In this way, the ink jet printer head 1 ″ according to the conventional electric heating method is completed.

The operation of the ink jet printer using the ink jet printer head according to the conventional electric heating system manufactured as described above will be described below with reference to the drawings. FIG. 11 is a timing chart showing the waveform of the alternating energizing voltage applied to the conductive ink. Here, the alternating energization voltage is an information signal applied with a predetermined voltage level and a pulse cycle during a predetermined printing cycle. First, the pair of electrodes 3a, 3 from the control unit 14
print cycle for discharging one dot between b, 5 kHz,
An alternating energizing voltage having a pulse period of 3 MHz and a voltage level (hereinafter referred to as an alternating energizing voltage level) of 25 V is applied. Next, when an alternating energizing voltage is applied to the conductive ink 9 through the electrodes 3a and 3b, the electric field in the conductive ink 9 vibrates and Joule heat is generated to heat the conductive ink 9. To do. Next, when the conductive ink 9 is heated, the conductive ink 9 boils and bubbles 1 are generated between the electrodes 3a and 3b.
0 is formed. Next, as the bubble 10 expands, the conductive ink 9 filled in the ink chamber 6 is pushed upward from the ink chamber 6 to the nozzle hole 7 and ejected as an ink droplet 11 from the nozzle hole 7. It Next, the ink droplets 11 ejected from the nozzle holes 7 are
By flying and adhering onto the surface 2, the print 13 is recorded. By repeating the above operation,
Recording information is printed on the printer paper 12. here,
The printing cycle of the alternating energizing voltage is set longer than the time required for the conductive ink 9 to boil, and the pulse cycle is set to match the ink dot flying frequency according to the resolution which is the printing quality. In addition, as the repeated life of ink boiling and ink ejection, the cartridge type in which the ink jet printer head and the ink container (not shown) are integrated is generally tens of millions of times, and the ink jet printer head is The permanent type with the printer installed in the printer body guarantees several hundred million times.

[0006]

However, in the above-mentioned conventional structure, when an alternating energizing voltage is applied between the electrodes in order to eject the conductive ink from the nozzle holes, an electrochemical reaction occurs between the electrodes and the conductive ink. As a result, there is a problem that chemical changes such as oxidation reaction and dissolution reaction occur on the surface of the electrode. For this reason, in the ink jet printer head, in particular, in order to avoid a change in the shape of the electrode due to dissolution, the electrode material and the components of the conductive ink are usually selected so that a slight oxidation reaction is dominant. There is. However, there has been a problem that when the oxidation reaction progresses on the electrode surface due to energization, the impedance change on the electrode surface is caused. In particular, since the oxide film is unstable until the electrode surface is covered with an oxide film having a certain thickness or more, there is a problem that the alternating energization voltage applied to the conductive ink is changed. Was there. When the impedance of the electrode surface changes, in the ink jet printer head driven at a constant voltage, the time required from the start of applying the voltage to the electrode until the conductive ink is ejected from the nozzle hole (hereinafter referred to as ink ejection ( However, there is a problem in that the print quality is affected and the print quality is deteriorated. Therefore, in the manufactured ink jet printer head, since the electrode material and the conductive ink are optimized so that the oxidation reaction does not occur on the electrode surface as described above, the impedance of the electrode surface becomes constant. Up to a certain number of times, an aging process of ejecting the ink a certain number of times is required in advance, the number of times of ink ejection in the aging process is required to be about 5 million times, an aging time of about 15 minutes is required, and workability is lacking. Was.

The present invention solves the above-mentioned conventional problems, and provides a highly reliable ink jet printer head capable of performing stable printing without impedance change without requiring an aging process with a high yield. To provide a method for manufacturing a head for an ink jet printer, which has stable workability, productivity, and mass productivity, and to oxidize or dissolve an electrode and a conductive ink by an electrochemical reaction during ink ejection. It is an object of the present invention to provide a head for an ink jet printer which can suppress reactions and the like, can suppress impedance change, can always perform stable printing, and is excellent in reliability.

[0008]

In order to achieve this object, the present invention has the following arrangement. That is, the method for manufacturing an ink jet printer head according to claim 1 is a method for manufacturing an ink jet printer head including at least a pair of electrodes and a conductive ink filled between the electrodes. And a predetermined DC voltage is applied to each electrode to form an oxide film on at least the surface of the electrode exposed portion of the electrode.

An ink jet printer head according to a second aspect of the present invention is the ink jet printer head manufactured by the method for manufacturing an ink jet printer head according to the first aspect, wherein at least each electrode is provided. It has a structure provided with an oxide film formed on the surface of the electrode exposed portion.

Here, as the material of the electrode, Ti, A
A metal such as u, Pt, or Ni or an alloy composed of two or more kinds of these metals is preferably used. The thickness of the electrodes and the distance between the electrodes facing each other are not particularly limited, but the level and application time of the DC voltage applied to each electrode in the oxide film forming step depend on the oxidation formed on the surface of the electrode. It is preferably selected as appropriate according to the thickness of the film. The thickness of the oxide film is appropriately determined according to the electric resistance and electrostatic capacity of the electrode surface determined by the entire circuit of the ink jet printer. Further, the oxide film may be formed at least on the surface of the electrode exposed portion exposed in the ink chamber. A high-frequency square wave voltage is preferably used as the alternating energizing voltage in an ink jet printer head that employs an energizing heating method in which an alternating energizing voltage is applied to each electrode as print information. Since the driver that controls the ink jet printer is driven by a DC voltage, a square wave voltage is used instead of a sine wave alternating energization voltage, so that the DC voltage is a relay circuit composed of transistors, ICs, etc. It can be turned on / off with and frequency control can be easily performed. Further, since each pulse of the square wave voltage is a DC voltage, it is formed on the surface of the electrode or the electric double layer formed at the interface (or surface) between the electrolyte contained in the conductive ink and each electrode. The current flowing in the electric circuit in which the electrostatic capacitance component such as the oxide film is connected in series is an exponential current based on the time constant of the circuit determined by the electrostatic capacitance component and the electric resistance of the electric circuit. Does not flow, and current cannot flow unless the voltage applied between the electrode facing parts of the pair of electrodes is always reversed, but the use of high frequency makes it easy to flow current between the electrode facing parts of the pair of electrodes. You can

[0011]

With this structure, the oxide film forming step of applying a predetermined DC voltage to each electrode to form an oxide film on the surface of the electrode is provided, so that at least the surface of the electrode exposed portion of the electrode has a uniform film thickness. It is possible to form an oxide film having As a result, the aging process is not required, ink is not discharged, the thickness of the oxide film can be arbitrarily controlled by the level of the DC voltage, and the oxide film can be formed to have a uniform thickness. . Therefore, by providing an oxide film formed on the surface of the electrode exposed portion that is in contact with the conductive ink of at least each electrode, changes due to ink discharge such as oxidation reaction or dissolution reaction due to electrochemical reaction of the electrode and conductive ink Can be suppressed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ink jet printer head according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of an essential part showing an ink jet printer head according to an embodiment of the present invention. 2 is a substrate, 3a and 3b are electrodes, 4 is an insulating film, 5 is a resin sheet,
Reference numeral 6 is an ink chamber, 7 is a nozzle hole, and 9 is a conductive ink. Since these are the same as in the conventional example, the same reference numerals are given and description thereof is omitted. The difference from the conventional example is an ink jet printer head 1 according to an embodiment of the present invention.
Is an oxide film 1 formed with a thickness of about 0.1 μm on the electrode exposed portions of the electrodes 3a and 3b exposed in the ink chamber 6.
7a and 17b are provided.

The manufacturing method of the ink jet printer head in the embodiment of the present invention constructed as above will be described below with reference to the drawings. Figure 2
FIG. 2A is a schematic cross-sectional view of an essential part showing an oxide film forming step on one electrode, and FIG.
3A is a schematic cross-sectional view taken along the line AA, FIG. 3A is a schematic cross-sectional view of an essential part showing an oxide film forming step in the other electrode, and FIG. 3B is BB ′ in FIG. 3A. It is a line cross-section schematic diagram. 2 and 3, reference numeral 1'denotes an ink jet type printer head in which an oxide film 17a is formed on the surface of an electrode exposed portion of one electrode 3a, and 18a and 18b denote a DC power source described later through a wiring 20 described later. Switch parts electrically connected in series with the parts 19a and 19b, 19a and 19b DC power supply parts, 20 electrodes 3a and 3b, switch parts 18
a, 18b and DC power supply units 19a, 19b are electrically connected in series. The electrodes 3a and 3b, the switch parts 18a and 18b, and the DC power supply parts 19a and 19b.
Are connected so that one of the electrodes 3a, 3b is on the anode side when one of the switch portions 18a, 18b is turned "on". First, the thickness of 2 μm is formed on the upper surface of the substrate 2 made of glass or ceramics such as alumina by a sputtering method or the like.
A metal thin film (hereinafter referred to as a Ti film; not shown) made of Ti is formed. Next, a pattern of the electrodes 3a, 3b is formed by a photolithography method or the like, and the electrodes 3a, 3b are formed.
Parts other than the above are removed by wet etching or the like to form electrodes 3a and 3b with a lateral width of 20 μm and a distance between the electrode facing parts of 10 μm. Thereafter, the ink jet printer head 1 ″ is formed in the same manner as the conventional manufacturing method.
Next, from the ink supply passage 8 of the ink jet printer head 1 ″ to the ink chamber 6 and the nozzle hole 7, a specific resistance of 20 Ωc
A conductive ink 9 having a conductivity of m is supplied. next,
As shown in FIGS. 2 and 3, a circuit for the oxide film forming step is configured. Next, as shown in FIG. 2A, the switch portion 18a is turned on, and a DC voltage of 15V is applied to the electrodes 3a,
Apply to 3b. As a result, an oxide film 17a is formed on the surface of the electrode exposed portion of the electrode 3a exposed in the ink chamber 6, as shown in FIGS. Next, the electrode 3a
An oxide film 17a having a uniform film thickness of about 0.1 μm is formed on the entire surface of the exposed electrode part of No. 3, and when the DC voltage of 15 V stops flowing to the electrodes 3a, 3b, the switch part 18a is turned off. " Next, as shown in FIG. 3A, the switch section 18b is turned on and a DC voltage of 15V is applied to the electrodes 3a and 3b. As a result, FIG.
As shown in (a) and (b), an oxide film 17b is formed on the surface of the electrode exposed portion of the electrode 3b exposed in the ink chamber 6. Next, an oxide film 17b having a uniform film thickness of about 0.1 μm is formed on the entire surface of the electrode exposed portion of the electrode 3b, and the switch is activated when the DC voltage of 15V stops flowing to the electrodes 3a, 3b. The part 18b is turned off. As a result, the ink jet printer head according to the embodiment of the present invention is completed. Here, when the oxide films 17a and 17b are grown, the metal ions that form the electrodes 3a and 3b are deposited on the electrodes 3a and 3b.
The electrode 3 receives the acting force due to the electric field generated between a and 3b.
This is performed by causing an oxidation reaction by coming into contact with the conductive ink 9 through the oxide films 17a and 17b formed on the surfaces of a and 3b. In addition, the oxide film 17a and 17b formed on the surfaces of the electrodes 3a and 3b is grown to grow the oxide film 17a.
The electric field gradient in a and 17b is reduced, the acting force from the electric field on the metal ions is weakened, and the metal ions are transferred to the electrodes 3a and 3b.
When it becomes impossible to pass through the oxide films 17a and 17b formed on the surface of b, the current stops flowing in the circuit for the oxide film forming step, and the growth of the oxide films 17a and 17b stops. The time required during this period is about several minutes, which is shorter than the time required for the conventional aging process.

The operation of the ink jet printer using the head for the ink jet printer according to the embodiment of the present invention manufactured as described above will be described below. An ink jet printer using the ink jet printer head in one embodiment of the present invention operates in the same manner as the conventional example, and a description thereof will be omitted.

An ink jet printer head in one embodiment of the present invention which operates as described above, an ink jet printer head which is not aged,
A performance comparison test was performed using a conventional ink jet printer head that had been aged. The results will be described below.

(Experimental example 1) First, an electrode was formed on the above-mentioned substrate using Ti with a thickness of 2 μm, a width of 20 μm, and a distance between electrode facing portions of 10 μm, and aging was performed by filling a conductive ink having a specific resistance of 20 Ωcm. A head for an ink jet printer that has not been prepared was prepared. Next, the voltage level of 25 V, the printing cycle of 5 kHz, and the pulse cycle of 3 shown in FIG.
While the alternating energization voltage of MHz is applied to the electrodes to perform 100 million times of ink ejection, the ink ejection (start) time is measured at any number of ink ejections, and the change of the ink ejection (start) time with respect to the number of ink ejections I checked. The result is shown in FIG. FIG. 4 is a characteristic diagram showing the dependency of ink ejection (start) time on the number of ink ejections. Next, using the ink jet printer head that has not been subjected to the aging described above, a sine wave voltage having a voltage level of 1 V and a pulse period of 3 MHz is applied to the electrodes, and ink ejection is repeated 100 million times. Ink frequency is 1V, frequency is 3MH
A sine wave voltage of z was applied to the electrodes, the electric resistance and the electrostatic capacitance (hereinafter collectively referred to as circuit impedance) were measured, and changes in the circuit impedance with respect to the number of ink ejections were examined. The result is shown in FIG. FIG. 5 is a characteristic diagram showing the dependency of circuit impedance on the number of ink ejections.

As is clear from FIG. 4, aging
Power to the ink jet printer head that is not performing
Then, the ink is ejected until it reaches about 4 million times.
Ejection (start) time increases, and the number of ink ejections after that
Ink ejection (start) time is approximately constant up to 100 million times
I understood. In addition, as is clear from FIG.
The change in pedance is the same as the change in ink ejection (start) time.
The same tendency is shown, and the number of ink ejections reaches about 4 million times.
Until then, both electrical resistance and capacitance increase
After that, electrical resistance and
It was found that all of the electrostatic capacitances showed almost constant values.
Was. As a result, the change in ink ejection (start) time is
Due to the change in impedance on the pole surface,
The resistance and time constant of the entire linter circuit change,
As a result, the current flowing through the circuit changes and the circuit impedance
It was confirmed that this was due to changes in Also, the electrode table
The change in the impedance of the surface is caused by the difference between the electrodes and the conductive ink.
Oxidation progresses on the electrode surface due to the gas chemical reaction, and the oxide film
It is thought that it is because he grew up. That is, the electrodes and
Electrode material on the electrode surface due to the electrochemical reaction of the conductive ink
Oxide of (Ti) (TiO ₂ Etc.) are formed. Soshi
At the start of energization, the oxide film formed on the electrode surface
Because the thickness is thin, the withstand voltage of the capacitor may not be sufficient.
Shows low electrical resistance and low electrical resistance,
The oxide film becomes thicker as the number of times
Qi resistance increases. And the number of ink ejections is about 400
When the number of cycles reaches 10,000 times, the thickness of the oxide film increases
The electric field gradient in the film is reduced and the metal ions at the electrode
The acting force from the
The growth of the film stops, and the electric resistance and capacitance become approximately constant values.
It shows that you are calm. Therefore, conventionally, ink ejection is performed.
Approximately 4 million times or more, usually about 500 times of ink ejection
It requires an aging process that requires 10,000 ink ejections.
It was confirmed that In addition, in FIG. 4 and FIG. 5, ink ejection is performed.
Ink discharge (start) time and
The region where the circuit impedance is stable is called the saturation region.
I shall.

(Experimental Example 2) First, an ink jet printer head according to an embodiment of the present invention was prepared, and as shown in FIG.
Ink was ejected by changing the voltage level with the alternating energizing voltage of the printing cycle of 5 kHz and the pulse cycle of 3 MHz shown in (4), and the change of the circuit impedance with respect to the voltage level was measured. The result is shown in FIG. FIG. 6 is a characteristic diagram showing the dependency of the circuit impedance on the voltage level.

As is apparent from FIG. 6, when the ink jet printer head in one embodiment of the present invention is energized while changing the voltage level, both the electric resistance and the electrostatic capacitance change as the voltage level increases. I found out that Further, it was found that the voltage level at which the electric resistance becomes approximately the same as the electric resistance in the saturation region shown in FIG. 5 is about 15V. However, it was found that the capacitance at that time showed a value of about 1.5 times. This is because of the film quality of the oxide film formed on the electrode of the ink jet printer head that has not been subjected to aging and the oxide film formed on the electrode of the ink jet printer head in one embodiment of the present invention. It shows that the film quality is different. That is, when the ink jet printer head that has not been aged is energized, the conductive ink is ejected and the maximum temperature of the conductive ink is about 300 ° C.
Since the electrode surface is heated to a high temperature, the electrode surface is oxidized at a high temperature, and as a result, the oxide film formed on the electrode surface is accompanied by defects such as impurities such as Ti hydroxide. . For this reason, since complete TiO ₂ is a dielectric substance, an electrostatic capacitance is formed on the electrode surface and the electrostatic capacitance becomes large, but in the ink jet printer head, it shows a considerable electric conductivity and the electrostatic capacitance is large. It is getting smaller. This is also the case with a conventional ink jet printer head that has been aged. On the other hand, since the oxide film formed on the electrode of the ink jet printer head in one embodiment of the present invention has a composition closer to TiO ₂ , it is considered that the capacitance is large. . Further, the capacitance increases as the thickness of the oxide film decreases, and therefore, the oxide film formed on the electrode of the ink jet printer head in one embodiment of the present invention is an ink jet that is not aged. It is considered that the film thickness is smaller than the film thickness of the oxide film formed on the electrodes by energizing the head for the mold printer. Here, when the oxide film forming the capacitor has few defects and the withstand voltage is sufficient, the larger the capacitance of the capacitor, the larger the time constant of the circuit of the ink jet printer, and as a result, as shown in FIG. In the case of the ink jet printer head of the energization heating type which is driven by using the alternate energizing voltage, the attenuation of the current is small and the efficiency is good. Therefore, the ink jet printer head in one embodiment of the present invention can be expected to have higher efficiency in the operation of the ink jet printer and the like, as compared with the ink jet printer head that has been aged or not. It was also found that this highly efficient ink jet printer head can be manufactured with high efficiency.

(Experimental Example 3) First, an ink jet type printer head in one example of the present invention and a conventional ink jet type printer head aged were prepared. Here, a conventional ink jet printer head that has been aged has a thickness of 2 μm and a width of 20 μm on the substrate.
μm, an electrode is formed using Ti with a distance between the electrode facing portions of 10 μm, and a conductive ink having a specific resistance of 20 Ωcm is used.
With the alternating energization voltage shown in FIG.
It was used after aging 10,000 times. Next, the film thickness of the oxide film formed on each electrode surface was measured. Here, the film thickness of the oxide film was measured using an Auger spectroscope (manufactured by Perkin Elmer Co .; trade name PH1650 scanning Auger electron spectroscope). The result is shown in FIG. 7. Figure 7
FIG. 4 is a characteristic diagram showing the relationship between the distance from the electrode facing portion and the film thickness of the oxide film.

As is clear from FIG. 7, in the conventional ink jet printer head that has been aged,
The film thickness of the oxide film formed on the electrode becomes thicker as it approaches the electrode facing portion, but in the ink jet printer head in one embodiment of the present invention, the film thickness of the oxide film formed on the electrode is It was found that the electrodes were formed almost uniformly regardless of the location of the electrodes. This is because in the conventional ink jet printer head that has been aged, when aging,
The oxide film formed on the electrode acts as a capacitor due to the electrostatic capacitance component, and a transient current flows.Therefore, the current flowing through the electrode facing portion increases due to the shape of the electrode, and as a result, the oxide film near the electrode facing portion is increased. Is thick.
However, in the ink jet printer head in one embodiment of the present invention, although the oxide film formed on the electrode facing portion becomes thick at the very early stage of the oxide film forming step, as described above, Due to the action of the electric field gradient in the inside, the electric current is concentrated in a place where the oxide film is thin, an oxide film is formed on the entire electrode, and the oxidation ends when the thickness of the oxide film reaches a constant film thickness. It was found that the oxide film was formed with a uniform film thickness because no current flows through the oxide film.

(Experimental Example 4) First, an ink jet type printer head according to an embodiment of the present invention and a conventional ink jet type printer head aged as described above were prepared. Next, the ink was discharged 100 times with the alternating energization voltage shown in FIG. 11, and the change in the ink discharge (start) time with respect to the number of ink discharges was measured. The result is shown in FIG. FIG. 8 is a characteristic diagram showing the dependency of the ink ejection (start) time on the number of ink ejections.

As is clear from FIG. 8, in the ink jet printer head according to the embodiment of the present invention,
It was found that the ink ejection (start) time was substantially constant and the stability of the ink ejection (start) time was superior to that of the conventional aged ink jet printer head. It is considered that this is because the thermal change of the circuit impedance is small. That is, when the conductive ink is heated by energization to eject the conductive ink, the maximum temperature of the conductive ink rises to about 300 ° C., and
The maximum temperature of the conductive ink is the central position between the electrodes where the current density is maximum in the conductive ink. For this reason, the temperature rise of the electrode is large near the electrode facing portion. The temperature rise near the electrode facing portion causes an increase in the electrical resistance of the oxide film, and in the conventional aged ink jet printer head, the oxide film at the electrode facing portion is thick. Therefore, the increase in the electric resistance of the electrode facing portion was large, and as a result, the impedance due to heat was large. Therefore, when the conductive ink is ejected, the heat accumulation of the electrodes is different between the first ejection and the hundreds of consecutive ejection, and when the impedance change due to the heat is large, the ink ejection frequency is increased. As a result, the impedance change becomes large, and the change in the ink ejection (start) time becomes large.
However, in the ink jet printer head in one embodiment of the present invention, since a substantially uniform oxide film is formed over the entire surface of the electrode exposed portion, there is no impedance change due to heat, and ink ejection (start I found that there was no change in time.

[0024]

As described above, the present invention has the following excellent effects. That is, 1) The method for producing an ink jet printer head of the present invention is a method for producing an ink jet printer head including at least a pair of electrodes and a conductive ink filled between the electrodes. Since a predetermined oxide film is applied to each electrode by applying a predetermined DC voltage to form an oxide film on the surface of the electrode exposed portion of the electrode, at least the surface of the electrode exposed portion of the electrode is not required An oxide film having a uniform film thickness can be formed. Further, the thickness of the oxide film formed on the surface of the electrode can be arbitrarily controlled according to the level of the DC voltage, and the oxide film having a uniform thickness can be formed. As a result, low cost, high image quality and high reliability ink jet printer heads that can perform stable printing without impedance change can be manufactured stably with high yield. It is possible to realize an excellent method for manufacturing a head for an ink jet printer.

2) The ink jet printer head of the present invention is the ink jet printer head manufactured by the above-described method for manufacturing an ink jet printer head, wherein at least conductive ink for each electrode is used. Since it has an oxide film formed on the surface of the exposed electrode contact,
Ink jet type with excellent reliability, which can suppress oxidation reaction and dissolution reaction due to electrochemical reaction between electrodes and conductive ink, which can suppress impedance change and always perform stable printing from the beginning of use. It is possible to realize a printer head.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of essential parts showing a head for an ink jet printer according to an embodiment of the present invention.

2A is a schematic cross-sectional view of an essential part showing an oxide film forming step on one electrode, and FIG. 2B is a schematic cross-sectional view taken along the line AA ′ in FIG.

3A is a schematic cross-sectional view of an essential part showing an oxide film forming step on the other electrode, and FIG. 3B is a schematic cross-sectional view taken along line BB ′ of FIG. 3A.

FIG. 4 is a characteristic diagram showing the dependency of ink ejection (start) time on the number of ink ejections.

FIG. 5 is a characteristic diagram showing the dependency of circuit impedance on the number of ink ejections.

FIG. 6 is a characteristic diagram showing dependence of circuit impedance on voltage level.

FIG. 7 is a characteristic diagram showing the relationship between the distance from the electrode facing portion and the film thickness of the oxide film.

FIG. 8 is a characteristic diagram showing the dependency of ink ejection (start) time on the number of ink ejections.

FIG. 9 is a schematic cross-sectional view of a main part showing an ink jet printer using a conventional head for ink jet printer by an electric heating method.

10 is a sectional view taken along line CC ′ in FIG. 9.

FIG. 11 is a timing chart showing a waveform of an alternating energizing voltage applied to the conductive ink.

[Explanation of symbols]

 1, 1 ′, 1 ″ head for ink jet printer 2 substrate 3a, 3b electrode 4 insulating film 5 resin sheet 6 ink chamber 7 nozzle hole 8 ink supply path 9 conductive ink 10 air bubble 11 ink drop 12 printer paper 13 printing 14 Control unit 15 Power supply unit 16 Wiring 17a, 17b Oxide film 18a, 18b Switch unit 19a, 19b DC power supply unit 20 Wiring

Claims (2)

[Claims] 1. A method for manufacturing an ink jet type printer head comprising at least a pair of electrodes and a conductive ink filled between the electrodes, wherein at least the surface of an electrode exposed portion of the electrode is oxidized. A method for manufacturing an ink jet printer head, comprising an oxide film forming step of forming a film. 2. An ink jet printer head manufactured by the method for manufacturing an ink jet printer head according to claim 1, wherein an oxide film is formed on at least a surface of an electrode exposed portion of each electrode. A head for an ink jet printer, which is characterized by including.