JPH08118650A - Heating element substrate of ink jet recording head - Google Patents

Abstract

PURPOSE: To obtain a heating element substrate excellent in durability by setting the concn. of Ar in a cavitation protective film to a predetermined concn. range. CONSTITUTION: An electrothermal conversion element 2 constituting a pair of electrodes 3a, 3b and a heating element 8 is provided on a substrate 1 and the protective film thereof is constituted of the protective layer 4-1 on the surface of the heating element, the cavitation protective layer 4-2 formed thereon and a separate protective layer 4-3 other than those protective layers 4-1, 4-2. By constituting the protective film on the surface of the heating element so as to set the concn. of Ar in the protective film to predetermined concn., the heating element substrate of an ink jet recording head excellent in durability can be obtained. Especially, by setting the concn. of Ar in the protective film to 2800-6000ppm in the cavitation protective film 4-2 formed of Ta, the cavitation resistance thereof is enhanced and the heating element substrate of the ink jet recording head excellent in durability can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element substrate of a recording head in an ink jet recording apparatus for ejecting ink to form ink droplets and adhering them to a recording material such as paper for recording.

[0002]

2. Description of the Related Art Ink jet recording means uses ink (recording liquid) from an orifice provided in an ink jet recording head.
It is a recording method that discharges and deposits it on a recording material such as paper to perform recording. It produces very little noise and enables high-speed recording, and does not use special recording paper such as plain paper. However, various types of recording heads have been developed, which have many advantages that recording can be performed. Among them, a recording head of a type in which thermal energy is applied to ink to be ejected from an orifice as described in JP-A-54-51837 and German publication (DOLS) 2843064, is used for recording signals. It has advantages such as good responsiveness and easy multi-orifice.

An example of a recording head of the type that uses thermal energy as such ink ejection energy is shown in FIG.
Shown in (A) and (B). The recording head is composed of a heating element substrate, a top plate 5 in which a flow path 6 and a liquid chamber 10 are formed. The heating element substrate of this recording head has an electrothermal converter 2 arranged on the surface of an insulating substrate 1 for converting electrical energy into thermal energy for ejecting ink. The protective layer 4 is formed on the pair of electrodes 3 and the heat generating resistance portion 8 sandwiched between the electrodes. The ink ejection energy in the recording head is applied by the pair of electrodes 3 and the heat generating resistor portion 8 located between these electrodes. That is, when an electric current is passed through the electrode 3 to heat the heat generating resistance portion 8, the ink in the flow path 6 near the heat generating resistance portion 8 is instantaneously heated, and bubbles are generated there, and the bubbles are generated. Ink droplets are ejected from the orifice due to the instantaneous volume expansion and contraction caused by the change in volume.

[0004]

In the recording head as described above, the protective layer (upper layer) on the heat-generating resistor portion of the substrate is generally an electrothermal converter by contact with ink and permeation of ink. In addition, a SiO ₂ film is formed to prevent electrolytic corrosion and electric breakdown in the electrodes. And
Further, a tantalum (Ta) film, for example, is used as a cavitation protection film in order to protect the upper layer from cavitation destruction at the time of defoaming air bubbles. This caused variation in head life.

Therefore, it is an object of the present invention to provide a heating element substrate for an ink jet recording head having improved cavitation resistance and excellent durability.

[0006]

In order to achieve the above object, the present invention provides a heating element substrate of an ink jet recording head, wherein a protective film formed on the surface of the heating element on the substrate is formed in the protective film. It is characterized in that it has a predetermined concentration of Ar. And, in the present invention, in particular, in the cavitation protective film formed of tantalum (Ta), the argon (Ar) concentration in the protective film is set to 2800 to 6000 ppm.

[0007]

When the protective film is formed as the protective layer (upper layer) on the heating resistor of the substrate, the film forming method includes a vapor deposition method, a sputtering method, and the like. Also varies in durability. The present invention has undergone many researches, and particularly in a film forming method using Ar gas, particularly when forming a cavitation protective film, if the Ar concentration mixed in the cavitation protective film is the same, the film forming method or Since the durability is almost the same even if the film forming conditions are different, it was found that the Ar concentration in the cavitation protection film is greatly related to the durability, and by setting it to a predetermined concentration range, durability can be improved. The heating element substrate having excellent properties is formed.

[0008]

EXAMPLES Next, the present invention will be specifically described based on Examples. [Embodiment 1] FIG. 3 is a constitutional view of a substrate for an ink jet recording head of the present invention. FIG. 3 (A) is a plan view of a main portion thereof, and FIG. 3 (B) is an X- line of FIG. 3 (A). It is a Y line sectional partial view. This substrate is provided with a pair of electrodes 3a and 3b and an electrothermal converter 2 constituting a heating resistor portion 8 on a base body 1, and a protective layer thereof is formed on a protective layer 4-1 on the surface of the heating element and on the protective layer 4-1. And a cavitation protective layer 4-2 and a protective layer 4-3 other than these.

Examples of the constituent material of the protective layer 4-1 include SiO ₂ , WO ₃ , Ta ₂ O _{3 and} other metal oxides, Si ₃ N ₄ , and A.
Mention may be made of materials such as high resistance oxides such as 1N or high resistance nitrides. Further, as the protective layer 4-2, T
Organic materials such as polyimide are preferable for the a and the protective layer 4-3.

To form the heating element substrate, first, HfB ₂ having a thickness of 1000 Å and a thickness of 6 are formed on the Si substrate 1.
After sputtering 000 Å of Al, the HfB ₂ heating resistor 8 and the Al electrodes 3a, 3
b is formed. After this, the protective layer 4-1 has a thickness of 1.9 μm.
m of SiO ₂ is sputtered. Three substrates prepared in the same process up to here are prepared.

FIG. 4 is a diagram showing the relationship between the sputtering gas pressure by Ar gas and the Ar concentration mixed in the Ta film in the sputtering process. In the figure, 101 is an MRC 603 type sputtering device (non-bias), and 102 is a Nichiden Anelva 1015 type sputtering device. Sputtering gas pressure and Ar mixed in the Ta film in the sputtering process
The concentration varies depending on the structure of the film forming apparatus, the cathode current, the presence / absence of bias, and the like. The pressure was set to 3 points in FIGS. 4A to 4C by an MRC 603 type sputtering apparatus, and the Ta film was sputtered under the conditions shown in Table 1. As a result, the Ar concentration in the Ta film was 2 in the case of A.
000 ppm, B 3000 ppm, C 3400
An Ar concentration of ppm was obtained.

[0012]

[Table 1] After that, Ta and SiO ₂ are patterned in a photolithography process and a durability test is performed. The durability test method is shown in FIG. The heater board 11 is a patterned substrate and has hundreds of elements. Every other bit of this element, 90 bits are connected to the power supply 12 in parallel. Heater board 11 in container 14 containing ink 13
Immerse only the heater part of and apply a pulse. The driving voltage was 1.25 times the foaming voltage, the pulse width was 7 μsec, the driving frequency was 4.5 kHz, application was performed up to 1 × 10 ⁸ pulses, and the residual ratios in the durability test results were compared. The results are shown in Fig. 1. 280 compared to A with an Ar concentration of 2000 ppm
It can be seen that the residual rate of B and C above 0 ppm is high.

[0013] [Example 2] forming a Ta under the conditions of Table 2 in NICHIDEN manufactured by ANELVA 1015 type sputtering apparatus that the SiO ₂ was prepared by the same process as in Example 1 was conducted a durability test.

[0014]

[Table 2] The results are also shown in FIG. 1. Even if the sputtering type, the pressure, the apparatus, and the like are different, the same Ar concentration shows the same durability. Further, it can be seen that the durability is high when the Ar concentration is 2800 ppm or more. Ar concentration is 7000p
Samples with a G point of pm and an H point of 9000 ppm had large internal stress and film peeling occurred immediately after film formation.

[0015]

As described above, according to the present invention, the protective film on the surface of the heating element is constituted so that the argon (Ar) concentration in the protective film becomes a predetermined concentration, whereby the durability is excellent. It is possible to obtain a heating element substrate for an inkjet recording head. In the invention, in particular, in a cavitation protective film formed of Ta, by forming a protective film having an Ar concentration of 2800 to 6000 ppm in the protective film, the cavitation resistance is improved and the durability is excellent. It is possible to obtain the heating element substrate of the inkjet recording head.

[Brief description of drawings]

FIG. 1 is a diagram showing a difference in Ar concentration and durability in a Ta film.

2 is a structural diagram showing an example of a recording head, and FIG.
FIG. 2B is an overall view thereof, and FIG. 2A is a partially enlarged sectional view of the heating element substrate.

FIG. 3 is a configuration diagram of an ink jet recording head substrate of the present invention, FIG. 3 (A) is a plan view of a main portion thereof, and FIG.
3B is a partial sectional view taken along line XY of FIG.

FIG. 4 is a diagram showing a gas pressure and an Ar concentration in a Ta film.

FIG. 5 is a configuration diagram of a durability test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2 Electrothermal converter 3 Electrode 4 Upper layer 5 Top plate 6 Flow path 7 Nozzle 8 Heat generation resistance part 9 Ink inlet 10 Liquid chamber 11 Heater board 12 Power supply 13 Ink 14 Container

Claims (4)

[Claims] 1. A heating element substrate of an ink jet recording head, wherein a protective film formed on the surface of the heating element on the substrate has a predetermined concentration of argon (Ar) in the protective film. A heating element substrate of an ink jet recording head characterized by the above. 2. The Ar concentration in the protective film is 2800-6.
The heating element substrate of the ink jet recording head according to claim 1, wherein the heating element substrate is 000 ppm. 3. The heating element substrate for an ink jet recording head according to claim 1, wherein the protective film is a cavitation protective film. 4. The heating element substrate for an ink jet recording head according to claim 3, wherein the protective film is made of tantalum (Ta).