JPH08258263A - Ink jet recording head - Google Patents

Abstract

PURPOSE: To control an abnormal temp. rise by providing a heating control layer composed of a substance positive in resistance temp. coefficient in contact with a heating resistor layer generating heat. CONSTITUTION: A heating control layer 5 is formed on a substrate 6 and the heating part thereof is removed by photo-etching to form a heating resistor layer 4 on the etched part and the part other than the heating part is removed by photo-etching. Membrane metal 3 of an intermediate layer is formed thereon and a membrane electric conductor 2 is further formed thereon. The heating part and the conductor 2 therearound are removed by photo-etching and, next, a protective film 1 is formed. By forming the conductor part where a current flows from the conductor 2 to the heating resistor layer 4 as an extremely thin film, heating control action is imparted to this part. When the heating resistor layer 4 rises in temp. abnormally, the electric resistance of the control layer 5 close to the heating resistor layer 4 becomes large to lower the current to the heating resistor layer 4 to stop abnormal temp. rise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides an electrothermal converter having an ink flow path for ejecting ink and a heating resistor for applying thermal energy to the ink on the heat acting surface to eject the ink. The present invention relates to an inkjet recording head provided on a supporting substrate.

[0002]

2. Description of the Related Art A method for recording by heating and foaming ink with a heating resistor and ejecting liquid droplets from a nozzle, that is, an ink jet method is capable of high-speed, high-density, high-definition and high-quality recording. It is also suitable for colorization and compactness, not only for printers but also for copying machines, facsimiles,
It has been applied to calculators, etc., and has been attracting attention in recent years.

In this type of ink jet system,
Since the recording liquid such as ink is ejected by utilizing the thermal energy, there is a heat acting portion that applies heat to the liquid. This heat acting part is similar to the structure of the conventional so-called thermal head, but it is in direct contact with the liquid, and is exposed to mechanical shock (cavitation erosion) due to repeated bubbling and defoaming of ink. 1000 ° C for an extremely short time of the order of 10 ^-1 to 10 microseconds
In terms of being exposed to near temperature rises and falls,
The fundamental technology is greatly different from that of a thermal head.

Therefore, in the conventional ink jet recording head, SiO ₂ , SiC, S is formed on the heating resistor.
Oxidation prevention and electrical insulation layer by i ₃ N ₄ etc. and Ta on it
It is common to have a structure in which a cavitation / erosion layer such as the above is provided to protect the heat acting part from the environment of use.

The protective layer as described above is formed by a sputtering method, a CV method.
The thickness is set to 0.5 μm to 2 μm in consideration of the life of the inkjet recording head by the D method or the like.

Further, as the heating resistor, tantalum nitride, titanium nitride, hafnium boride, etc. are relatively excellent in heat resistance and have high reliability, and the specific resistance value is 100 to 100 by controlling the composition of the thin film. It has been put to practical use because it is easy to obtain one having 300 μΩ · cm.

Such a heating resistor layer has a thickness of 0.05 μm on a substrate such as silicon or glass whose surface is oxidized.
Generally, it is formed in the range of 0.2 μm to 0.2 μm.

[0008]

Since the protective layer needs to be formed thicker than the heating resistor layer, the heating resistor layer acts while receiving a large film stress of the protective layer. In general, when the protective layer is formed by a sputtering method, a CVD method, or the like, the stress of the protective layer is negative, that is, it tends to be a compressive stress. This means that the protective layer essentially has the property of being easily separated from the heating resistor layer. If the protective layer is peeled off from the heating resistor even a little, the heat dissipation generated by the heating resistor layer will be extremely reduced, causing an abnormal temperature rise and accelerating melting of the heating resistor or swelling of the film. And can cause chain reaction.

In order to avoid the above problems, the protective layer is positive,
That is, when the protective layer is formed so as to have a tensile stress, a force that tears the film is generated with the cross section having the protective layer itself as a boundary. This shortens the life of the ink jet recording head that is exposed to cavitation erosion, leading to a decrease in reliability.

[0010]

Means for Solving the Problems The present invention can be solved by providing a new layer in contact with the heat generating resistor layer as a result of extensive studies aimed at solving the problems in the prior art of the ink jet recording head described above. The inventors have found that and reached the present invention.

That is, according to the present invention, in an ink jet recording head for foaming and ejecting ink by thermal energy generated by energization, heat generation control is made of a substance having a positive resistance temperature coefficient in contact with a heat generating resistor layer which generates heat. An inkjet recording head having a layer.

In the present invention described above, the layer made of a substance having a positive temperature coefficient of resistance means that a heat generation control layer is formed as its function and effect.

In the manufacture of the ink jet recording head of the present invention, the general procedure for forming the heat generation control layer will be briefly described with reference to FIG.
The heat generation control layer 5 is formed thereon. The heat generating portion is removed by photoetching. However, if the heat generation control layer has high temperature durability, this removing step can be omitted. A heating resistor layer 4 is formed on this, and the portions other than the heating portion are removed by photoetching. An intermediate thin-film metal 3 is formed on this, and a thin-film electrical conductor 2 is further formed thereon. The heat generating portion and the thin film electric conductor 2 around it are removed by photoetching. Next, the protective layer 1 is formed.

In the above-mentioned ink jet recording head of the present invention, the width of the abnormal rise of the heat generation temperature of the heat generating resistor is reduced, and the defective rate and life are remarkably improved as compared with the conventional example.
That is, by forming a conductor portion in which a current flows from the thin film electric conductor 2 to the heating resistor layer 4 into an extremely thin film,
The feature is that this part has a heat generation control action. When the temperature of the heating resistor layer 4 rises abnormally, the temperature of the adjacent heating control layer 5 also rises significantly.
Has an effect of reducing the current to the heating resistor layer 4 and stopping an abnormal temperature rise.

In the present invention, as the material for forming the heat generation control layer 5, a substance having a positive temperature coefficient of resistance, that is, many metals, barium titanate oxide, and silicon semiconductor can be used. . To exemplify the temperature coefficient of resistance, titanium is 5.5 × 10 ⁻³ / κ and silicon semiconductor is
1.3 × 10 ^-2 / κ, barium titanate-based oxide,
1.4 to 1.9 × 10 ⁻¹ / κ, and the like. The thickness of the heat generation control layer is preferably in the range of 100 Å to 20 μm and is suitable for the material. When it is less than 100 Å, the temperature coefficient of resistance is less likely to be positive, and when it is 20 μm or more, the effect of lowering the current is small.

The thin film metal intermediate layer 3 and the heat generation control layer 5 are
It is better to use the same substance, and if different substances,
The alloy formation lowers the temperature coefficient of resistance and weakens the effect of lowering the current. When the intermediate layer and the heat generation control layer are made of the same material, the heat generation control layer can be formed simultaneously with the formation of the intermediate layer. However, the temperature coefficient of resistance of the intermediate layer and the heat generation control layer in this case must be positive.

Suitable materials for forming the heat generation control layer include titanium, aluminum, platinum, nickel, cobalt, silver, gold, tungsten, tantalum, iron, palladium, rhodium, iridium, chromium, molybdenum, osmium, and Copper etc. can be mentioned.

Suitable materials for forming the intermediate layer of the thin film metal include titanium, platinum, nickel, cobalt, silver, gold, tungsten, tantalum, chromium, molybdenum and the like. In this case, the commonly used thickness is in the range of 20 to 200Å.

The method of forming the heat generation control layer employed when manufacturing the ink jet recording head of the present invention is usually performed by the sputtering method or the vacuum evaporation method as in the case of forming a general thin film. Further, the method of forming the heating resistor layer, the intermediate thin film metal layer, and the thin film electric conductor is also the same as the technique in the manufacture of a general inkjet recording head. Further, the technique of removing the heat-generating portion from the heat-generation control layer by photoetching or removing the portion other than the heat-generating portion from the heat-generating resistor layer by photoetching is the same as the technique in the manufacture of a general inkjet recording head.

[0020]

The present invention will be further described with reference to examples.

Example 1 A layer made of a material having a positive temperature coefficient of resistance, that is, a layer made of titanium having a thickness of 100 to 200Å is formed as a heat generation control layer on a substrate. Then, the heat generating portion is removed by photoetching. A hafnium boride layer is formed thereon as a heating resistor layer, and a portion other than the heating portion is removed by photoetching. A 20 to 200 Å layer of titanium is formed as an intermediate layer of the thin film metal, and a thin film electric conductor is further formed thereon. Next, the heat generating portion and the thin film electric conductors around it are removed by photoetching. Next, a protective layer was formed.

When a practical test was carried out using the ink jet recording head manufactured by the above method, the width of the abnormal rise in the heat generation temperature of the heat generating resistor layer was reduced, and the life of the ink jet recording head was longer than that of the conventional example. It turned out to be improved in width.

In the present invention, since the heat generation control layer is provided around the heat generation resistor layer, heat generated when the heat generation resistor layer is slightly peeled off from the substrate or the protective layer should be released to other portions. It is possible to increase the temperature,
It is possible to alleviate, and it is possible to suppress an abnormal rise in heat generation that occurs in a chain.

Examples 2 and 3 In place of titanium used in Example 1, tungsten and nickel were used as the materials for forming the heat generation control layer, respectively, and an ink jet recording head manufactured in the same manner as in Example 1 was used. When the test was conducted, almost the same experimental results as when the titanium layer was formed were obtained.

[0025]

EFFECT OF THE INVENTION By providing a heat generation control layer made of an extremely thin film in a conductor portion where a current flows from a thin film electric conductor to a heat generation resistor layer, a heat generation control action can be obtained, and an abnormal temperature rise in this portion can be controlled. You can

[Brief description of drawings]

FIG. 1 shows an example of a basic structure of a main part of an inkjet recording head according to the present invention.

[Explanation of symbols]

 1 Protective Layer 2 Thin Film Electrical Conductor 3 Intermediate Layer of Thin Film Metal 4 Heating Resistor Layer 5 Heating Control Layer 6 Substrate

Claims (9)

[Claims] 1. In an ink jet recording head for foaming and ejecting ink by thermal energy generated by energization, a heat generation control layer made of a substance having a positive resistance temperature coefficient is provided in contact with a heat generation resistor layer which generates heat. An inkjet recording head characterized by the above. 2. The ink jet recording head according to claim 1, wherein the heat generation control layer is selected from the group consisting of metals, barium titanate-based oxides and silicon-based semiconductors. 3. The ink jet recording head according to claim 1, wherein the heat generation control layer has a thickness in the range of 10Å to 20 μm. 4. The ink jet recording head according to claim 1, wherein an intermediate layer of thin film metal is provided between the heat generation control layer and the heat generation resistor layer and the thin film electric conductor. 5. The ink jet recording head according to claim 4, wherein the materials for forming the intermediate layer of the thin film metal and the heat generation control layer are the same substance. 6. The material forming the heat generation control device is titanium,
6. The method according to claim 1, which is selected from the group consisting of aluminum, platinum, nickel, cobalt, silver, gold, tungsten, tantalum, iron, palladium, rhodium, iridium, chromium, molybdenum, osmium, and copper. The inkjet recording head according to 1. 7. The material forming the intermediate layer of the thin film metal is selected from the group consisting of titanium, platinum, nickel, cobalt, silver, gold, tungsten, tantalum, chromium and molybdenum. The inkjet recording head according to any one of 1. 8. The thickness of the intermediate layer of thin film metal is 20 to 200.
The ink jet recording head according to claim 7, which has a range of Å. 9. An ink jet recording apparatus incorporating the ink jet recording head according to any one of claims 1 to 8.