JP2001277510A - Ink jet recording head and ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance durability furthermore by preventing oxidation on the surface of a protective film layer thereby suppressing corrosion and elution of metal into ink. SOLUTION: The ink jet recording head comprises a protective film layer 11, an insulation layer 12, an aluminum electrode 13 for applying a voltage to a heater, a heater 14, an insulation layer 15, and a substrate 16 wherein the surface potential of the protective film layer is controlled by a potential control means 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head and an ink jet recording apparatus for discharging a desired ink by foaming bubbles by applying thermal energy to the ink, and more particularly to a layer for protecting a heating resistor. The present invention relates to an inkjet recording head and an inkjet recording device.

[0002]

2. Description of the Related Art Conventionally, an ink jet recording system has been known in which thermal energy is applied to ink to foam the ink, discharge the ink from nozzles, and deposit the ink on a recording medium to form an image. I have. This ink jet recording method can record high-definition, high-quality images at high speed and with low noise, and the head that performs this recording method requires a high density of ejection ports for ejecting ink. Therefore, there is an advantage that compactness and colorization are easy. For this reason, the ink jet recording system has recently been applied to printers, copiers, facsimile machines, calculators, and the like, and is rapidly developing.

As described above, since the ink jet recording method includes a step of discharging ink using thermal energy, the head is provided with a thermal action section for applying thermal energy to the ink. Since the heat acting portion is in direct contact with the ink and generates bubbles in the ink, it is susceptible to mechanical shock (cavitation erosion) due to repetition of foaming and defoaming of the ink, and has an extremely short time of several μsec. In addition, there is a problem that wear and deterioration are particularly severe because the temperature change of several hundred degrees easily affects the heat stress.

For this reason, in a conventional ink jet recording head, an insulating layer for preventing oxidation and electrically insulating a heater (heating resistor), and a protective film functioning as anti-cavitation erosion on the insulating layer. A configuration in which a layer is provided to protect the heat acting portion is generally known.

FIG. 4 is a view showing a configuration of a substrate portion in a liquid flow path in a conventional ink jet recording head.

As shown in FIG. 4, a substrate portion in a liquid flow path in a conventional ink jet recording head includes a substrate 46 made of silicon or the like and an insulating layer 45 provided on the substrate 46 made of SiO ₂ or the like. And an insulating layer 45 made of TaN or the like.
A heater 44 provided on the heater 44; an aluminum electrode 43 provided on the heater 44 for applying a voltage to the heater 44; and SiO, SiC, Si ₃ N _4, etc., covering the heater 44 and the aluminum electrode 43. And a protection film layer 41 made of Ta or the like and provided on the insulation layer 42, and only the protection film layer 41 is in direct contact with the ink.

FIG. 5 is a diagram for explaining the potential of the protective film layer 41 shown in FIG. As shown in FIG. 5, the protective film layer 41 shown in FIG. 5 is completely open or connected to the ground potential of the circuit via the impedance of the ink solution.

[0008]

In the conventional ink jet recording head as described above, since the heater is not in direct contact with the ink, it is not affected by mechanical shock due to repeated foaming and defoaming of the ink. Can protect the heater, but due to heat stress due to temperature fluctuations of several hundred degrees, various compositions in the ink solution, and differences in the pH of the ink solution, electrochemical protection between the protective film layer and the ink may occur. There is a problem that a reaction occurs, and the surface of the protective film layer is corroded, and the metal forming the protective film layer is eluted into the ink solution. For such a problem, effective means has not yet been obtained, and a new technique is desired.

Hereinafter, a description will be given of a reaction mode when the metal M shows a tendency to be oxidized to the ink solution when the metal M is used for the protective film layer 41.

The reaction equation when the metal M of the protective film layer 41 has a tendency to oxidize with respect to the ink solution is expressed by the following equation.

[0011] M → M ⁿ + + ne ^- this time, the electrode potential E _0, the Faraday constant F, absolute temperature T, the gas constant R, n the valency of the electron, [M ⁿ reaction energy of the metal M ⁺ ], The oxidation-reduction potential of the metal M is expressed by the following equation with reference to the Nernst equation.

E = E ₀ − (RT / nF) × ln [M ^{n +} ] Therefore, the potential on the surface of the protective film layer 41 becomes the oxidation-reduction potential E
In the case where the value exceeds the above, it is considered that the metal M forming the protective film layer 41 is easily oxidized, and the protective film layer 41 is corroded or the metal M is eluted into the ink solution.

FIG. 6 shows a heater current waveform and a potential on the surface of the protective film layer when a general ink solution is dripped with the protective film layer opened and the heater is driven in the ink jet recording head shown in FIG. It is the figure which monitored the waveform with the oscilloscope.

As shown in FIG. 6, the heater current waveform 61 when the heater is driven is compared with the insulating layer 42 shown in FIG.
Acts as a thin film capacitor, and a differential potential waveform 61 accompanied by the response of the ions of the dropped ink solution appears on the surface of the protective film layer. Here, in the example shown in FIG. 6, since the potential on the surface of the protective film layer 41 is repeated and overwritten, it was confirmed that the potential on the surface of the protective film layer 41 constantly fluctuated at a positive potential. it can.

The present invention has been made in view of the above-mentioned problems of the prior art, and prevents oxidation of the surface of a protective film layer and suppresses corrosion and elution of metal into ink. Accordingly, an object of the present invention is to provide an ink jet recording head and an ink jet recording apparatus which can further improve durability performance.

[0016]

In order to achieve the above object, the present invention provides a heating resistor for generating heat energy used for discharging ink, and an insulating layer provided on the heating resistor. And a protective layer provided on the insulating layer so as to be in contact with the ink, wherein the thermal potential generates bubbles in the ink to discharge the ink, and the surface potential of the protective layer is reduced. And a potential lower than a potential at which an oxidation reaction occurs in the protective layer by ink.

Further, the semiconductor device is characterized by having a potential control means for controlling a surface potential of the protective layer. Further, the surface potential of the protective layer is a ground potential.

Further, the protective layer is formed of tantalum. Further, in the inkjet recording apparatus, the inkjet recording head,
A potential control means for controlling a surface potential of the protective layer. (Function) In the present invention configured as described above, an insulating layer and a protective layer are sequentially laminated on the heating resistor in order to protect the heating resistor against the ink solution. The surface potential of the layer is adjusted to be equal to or lower than the potential at which an oxidation reaction occurs in the protective layer by the ink, or to the ground potential.

As described above, the surface potential of the protective layer is lower than the potential at which an oxidation reaction occurs in the protective layer by the ink, or
By being set to the ground potential, oxidation of the surface of the protective layer is prevented, and phenomena such as corrosion and elution of metal into the ink are suppressed.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing one embodiment of an ink jet recording head according to the present embodiment, and shows a configuration of a substrate portion in a liquid flow path.

In this embodiment, as shown in FIG. 1, a substrate 16 made of silicon, an insulating layer 15 made of SiO ₂ and provided on the substrate 16, and a insulating layer 15 made of TaN are provided on the insulating layer 15. A heater 14 and an aluminum electrode 1 provided on the heater 14 for applying a voltage to the heater 14
3 and SiN, heater 14 and aluminum electrode 1
3 and a protective film layer 1 made of Ta and serving as a protective layer provided on the insulating layer 12.
1 and a potential control means 17 connected to the protective film layer 11 and controlling the surface potential of the protective film layer 11.

Hereinafter, control of the potential of the protective film layer 11 in the ink jet recording head configured as described above will be described.

FIG. 2 shows that the protective film layer 11 shown in FIG. 1 is subjected to voltammetry via a general ink.
FIG. 9 is a diagram showing a result of performing the measurement. Here, voltammetry refers to a method of measuring a current change accompanying elution (oxidation or reduction) of a substance in an electrochemical system by using an appropriate electrolytic cell and an electrode, changing the potential of the electrode, Widely used for analysis of redox systems.

As shown in FIG. 2, the protective film layer 11 is
The current starts to flow at a potential of about 0.4 V with respect to the silver chloride electrode, and it can be confirmed that the protective film layer shows an oxidizing tendency at this voltage.

Therefore, if the potential on the surface of the protective film layer 11 is controlled by the potential control means 17 to a potential lower than the potential showing the tendency to oxidize, the surface of the protective film layer 11 is prevented from being oxidized, thereby causing corrosion. In addition, elution of metal into the ink solution can be suppressed, and the durability of the inkjet recording head can be further improved.

For example, the method of connecting the protective film layer 11 to the ground potential can be cited as an example of a practically simple countermeasure.

An embodiment of the present invention will be described below.

[0029]

First Embodiment First, wire bonding is performed on the end of the surface of the protective film layer 11 of the heater chip for an ink jet recording head, and the surface of the protective film layer 11 is pulled out as a pin. Is sealed so as not to come into contact with the ink liquid.

Subsequently, a ground potential was applied to the portion drawn as a pin to repeatedly drive the heater, and the current flowing through the heater was measured to confirm the durability of the head.

The heater is driven with a pulse width of 2.5 μs
c, The threshold voltage at which foaming starts was set to 7.6 V by observation using an acoustic sensor (NF Corporation). The ink solution used was an aqueous solution adjusted to pH = 10.0 with 15% diethylene glycol, 0.2% citric acid, and potassium hydroxide.

FIG. 3 is a diagram showing experimental results in the first embodiment of the ink jet recording head of the present invention, and shows the heater current value with respect to the number of times of driving of the heater. In FIG. 3, a heater current value with respect to the number of times of driving of the heater of this embodiment is a waveform 31, and as a comparison, a heater current value with respect to the number of times of driving of the heater according to the conventional example in which the protective film layer 11 is opened is a waveform 32.

As a result, in the conventional example, the number of driving times is 10 ⁸
It was confirmed that the heater started to deteriorate around the time,
In the present embodiment, the case where the protective film layer surface to ground potential, the deterioration in the vicinity is not confirmed 10 ⁹ times.

(Second Embodiment) The same experiment as in the first embodiment was performed with a pulse width of 2.5 μsec and a threshold voltage of 9.0 V at the time of heat driving. Also in this case, when the surface of the protective film layer is connected to the ground potential, the number of driving times is one.
No deterioration was observed even around ⁰⁹ times.

(Third Embodiment) An experiment similar to that of the first embodiment was carried out by controlling the potential on the surface of the protective film layer by a potential control means.
The test was performed by setting the voltage to -0.4V. Also in this case, 1
No deterioration was observed even around ⁰⁹ times.

In the above-described three embodiments, by controlling the potential of the protective film layer of the ink jet recording head to be equal to or lower than the ground potential, the durability is reduced by one digit or more in terms of the number of times of driving as compared with the conventional example. Can be improved.

The potential of the surface of the protective film layer of the ink jet recording head can be set to any potential other than the above as long as the surface of the protective film layer shows a tendency to reduce.

Further, even when the metal is eluted from the surface of the protective film layer into the ink solution due to excessive stress due to heating of the heater or mechanical shock, the potential of the protective film layer is reduced. What is necessary is just to control to the electric potential which shows a reduction tendency.

[0039]

As described above, the present invention relates to a heating resistor for generating thermal energy used for discharging ink, an insulating layer provided on the heating resistor, and an insulating layer provided on the heating resistor. An ink jet recording head having a protective layer provided so as to be in contact with the ink on the upper side and generating ink bubbles by thermal energy to discharge the ink.
Since the surface potential of the protective layer is configured to be equal to or lower than the potential at which an oxidation reaction occurs in the protective layer by the ink, or the ground potential, oxidation of the surface of the protective layer is prevented,
A phenomenon such as elution of metal into the ink can be suppressed, and the durability performance of the inkjet recording head can be further improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method for controlling a potential of a protective film layer of an inkjet recording head according to an embodiment.

FIG. 2 is a diagram illustrating a result of performing voltammetry on a protective film layer via an ink solution in an inkjet recording head.

FIG. 3 is a diagram illustrating durability of the inkjet recording head according to the present embodiment with respect to the number of times the heater is driven.

FIG. 4 is a diagram showing a configuration of a substrate portion in a liquid flow path in a conventional inkjet recording head.

FIG. 5 is a diagram for explaining a state of a potential of a protective film layer of a conventional inkjet recording head.

FIG. 6 is a diagram showing a potential waveform on the surface of a protective film layer when a heater is driven in a conventional inkjet recording head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Protective film layer 12 Insulating layer 13 Aluminum electrode 14 Heater (heating resistor) 15 Insulating layer 16 Substrate 17 Potential control means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akemi Ishizaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Tatsuo Furukawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Non-corporation F term (reference) 2C057 AF66 AG41 AG42 AG46 AG99 AQ02 BA03 BA13

Claims (5)

[Claims] 1. A heating resistor for generating thermal energy used for discharging ink, an insulating layer provided on the heating resistor, and provided on the insulating layer so as to be in contact with the ink. An ink jet recording head that generates bubbles in the ink by the thermal energy and discharges the ink, wherein a surface potential of the protective layer is equal to or lower than a potential at which an oxidation reaction occurs in the protective layer by the ink. An ink jet recording head, characterized in that: 2. The ink jet recording head according to claim 1, further comprising a potential control means for controlling a surface potential of said protective layer. 3. A heating resistor for generating thermal energy used for discharging ink, an insulating layer provided on the heating resistor, and provided on the insulating layer so as to be in contact with the ink. An ink jet recording head that has a protective layer and discharges ink by generating bubbles in the ink by the thermal energy, wherein a surface potential of the protective layer is a ground potential. 4. An ink jet recording head according to claim 1, wherein said protective layer is formed of tantalum. 5. An ink jet recording apparatus comprising: the ink jet recording head according to claim 1; and a potential control means for controlling a surface potential of the protective layer.