JPH0758642B2 - Thermal head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used in a recording device such as a facsimile or a printer, and more specifically, to a resistor layer which is one of the main components of the thermal head. Regarding improvement.

2. Description of the Related Art A thermal head includes at least a pair of electrodes, a resistor layer in contact with the electrodes, a substrate having at least an insulating surface and supporting an insulating electrode and a resistor layer on the surface, and a resistor. It is basically composed of an abrasion resistant layer formed on the layer. There are a thin film type and a thick film type depending on how to make. The thin film type is one in which an electrode, a resistor layer, and a wear resistant layer are formed by sputtering in vacuum or vapor deposition. In the thick film type, for example, a gold electrode, RuO ₂ is dispersed by printing and firing a paste of a thermally decomposable organic compound of gold, a paste containing RuO ₂ and glass frit, and a paste of borosilicate glass frit, respectively. Since a glass layer is obtained, a high performance thermal head can be obtained at a lower cost than a thin film type.

The thermal head heats a specific area of the resistor layer that is in contact with both electrodes by passing an electric current between the pair of electrodes, thereby heating a specific area of a recording member, for example, a thermal recording paper, for one dot. To give a record of. Therefore, the important characteristics required for the thermal head are that the heat generated in the resistor layer is efficiently transmitted to the recording paper side and that the heat generated in the resistor layer between the individual electrode pairs, which are normally arranged in a line, is generated. It is uniform. If the resistances of these resistor layers are not uniform, the amount of heat generated is not uniform, so that the density of individual recording dots recorded on the recording paper becomes uneven, causing streaky streaks in the recording and resulting in poor recording quality. become worse. This characteristic is particularly important for a thermal head for a full-color printer that requires gradation recording.

As a cause of such recording density unevenness, there is a variation in resistance value of each resistor dot. In order to reduce such a variation in resistance values of individual resistor dots, the thick film type uses a trimming process. In this step, an overload pulse is applied to each dot of the resistor layer, which makes it possible to bring the resistance value to within ± 0.5% of the target. On the other hand, in the thin film type, by controlling the conditions of vapor deposition and sputtering for obtaining the resistor, the resistance value of the dot of each resistor can be controlled within ± 2.5%. However, it is difficult for the thin-film type head to further improve the current variation in resistance value, and for the thick-film type head, there are problems with the current method as described below.

The resistor layer of the current thick film type thermal head is formed by screen-printing a paste composed of RuO _2, which is a resistor component, glass frit, and an organic binder, and firing the paste. However, since the starting paste is a mixture of RuO ₂ powder and glass powder, the resulting resistor layer is also a mixture of both. Even if a RuO ₂ powder having a small particle size is used, the particle size is considerably large in the resulting resistor layer due to aggregation and poor dispersion in the glass matrix. As a result, current will flow through the RuO ₂ powders that are in contact with each other. Therefore, a considerable amount of RuO ₂ powder is required to obtain a resistor having a uniform resistance value. On the other hand, even if the dot resistance value is made constant by trimming, the resistance value changes preferentially in the part of one resistor dot that is particularly easily trimmed, so even if the dot resistance value reaches the target value, In the case of recording, heat is concentrated on a part of one dot, and a normal dot shape cannot be obtained. The bias of the current path in one resistor dot is caused by the non-uniform distribution of the resistance value, that is, the non-uniform distribution of the conductive element such as RuO ₂ in the resistor layer.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, it was difficult to obtain a resistor layer having a uniform resistance value with the conventional resistor layer made of a mixture of RuO ₂ and glass powder.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional inconveniences and to provide a thermal head having a resistor layer having a uniform resistance value and providing recording of excellent quality.

Means for Solving the Problems The thermal head of the present invention has at least a pair of electrodes, a resistor layer in contact with the quantity electrode, at least the surface of which is insulative, and the electrode and the resistor layer are provided on the surface thereof. In a thermal head having a supporting substrate, the resistor layer has a glass matrix and a metal of a resistor component element and /
Alternatively, the resistor element element is ruthenium or ruthenium and rhodium, and the ruthenium content of the resistor layer is 1 to 10% by weight.

The preferred method for obtaining the resistor layer of the thermal head of the present invention is to print and spin a coating of a paste containing a thermally decomposable organic compound of the resistor component element and a thermally decomposable organic compound of the element forming the glass matrix. A step of forming by a coating method, a drawing method, or the like, and a resistance consisting of a glass matrix obtained by thermally decomposing the organic compound in the paste by heat treatment and a metal and / or oxide of a resistor component element dispersed in the matrix. And forming a body layer.

The paste is preferably composed of the organic compounds, a solvent that dissolves these organic compounds, and an organic binder that is soluble in the solvent. In this paste, the organic compound of the resistor component element and the organic compound of the element forming the matrix of glass are mixed at the molecular level, and the thermal decomposition of these elements causes the oxidation of the element forming the glass matrix. And a metal and / or oxide of a resistor element element are formed, and the latter metal and / or oxide is incorporated into a glass matrix formed by fusion of the oxides to form a resistor layer. It In the resistor layer thus formed, the metal and / or oxide of the resistor component element is in a state of entering the atomic bond gaps of the glass matrix at the atomic or molecular level. Therefore, the resistor layer has a very uniform composition, and the amount of the resistor component element may be smaller than before.

FIG. 1 shows the relationship between the ruthenium element content of a resistor layer composed of a glass matrix and a ruthenium oxide dispersed in the glass matrix, and the variation in the resistance value of the resistor layer. . The vertical axis relating to the resistance value represents a value of 100 × σ /. Is the average resistance value, and σ is the standard deviation value.

In FIG. 1, A represents the characteristics of the resistor layer of the present invention, and B represents the characteristics of the conventional resistor layer. In the case of A, ruthenium or its oxide is dispersed in the glass matrix as a phase of several atoms or molecules, while in the case of B, it is dispersed as particles having a diameter of 5 μm or more. Therefore, in the case of B, when the Ru element content is less than 10% by weight, the resistance value suddenly increases. On the other hand, in the case of A, the variation in the resistance value of the Ru element content is at least very low.

The temperature dependency of the resistance value of the resistor layer using ruthenium is very large as shown in a of FIG. To improve this, it is preferable to use rhodium together. With the combined use of rhodium,
The temperature dependence of the resistance value is improved as shown by b in FIG. Further, the addition of rhodium also improves the film forming property of the resistor layer. When ruthenium and rhodium are used in combination, a weight ratio of 0 <Rh / Ru <5 is suitable.

Next, as the elements forming the glass matrix, there are boron, which constitutes the borosilicate glass, silicon, lead which constitutes the other lead borosilicate glass, lanthanum which constitutes the lanthanum glass, and other bismuth. .

In addition to the above, other platinum group elements, gold,
It is also possible to add silver, nickel, chromium, zirconium, titanium, vanadium, aluminum, tantalum, etc. as a variable resistance component or an additive element for improving the pulse resistance reliability of the resistor.

Examples of the thermally decomposable organic compounds of the above elements include alcoholates such as ethyl alkoxide and isopropoxide, fatty acid esters represented by hexanoic acid esters, polycyclic organic compounds such as menthol alcoholates and esters, and rosin compounds such as abietic acid salts. , Siloxanes, organic compounds of boric acid, etc.

The temperature at which a paste containing these organic compounds is heated to generate a desired metal or oxide varies depending on the compound used, but is usually 500 to 800 ° C., and an atmosphere containing oxygen is preferable.

The resistor layer according to the present invention can be practically obtained with a uniform film thickness of about 0.3 to 1 μm. In this way, since the thickness is thin and there are almost no defects such as bubbles,
The thermal efficiency during recording is also good.

Regarding the resistor layer according to the present invention, when the relationship between the dot resistance value and the ruthenium content is examined with a resolution of 6 lines / mm, when the film thickness is 0.3 μm, the ruthenium content is 1 to 10% by weight.
When the ruthenium content is out of this range, the resistance value becomes very high or low, which is not practical.

Third Embodiment FIG. 3 is a vertical cross-sectional view of an essential part showing a structural example of a thermal head according to the present invention.

Reference numeral 1 is a substrate having at least an insulating surface. A steel plate having a holo coating on the surface, an alumina substrate having a glaze layer on the surface, and the like are used. Reference numeral 2 is a resistor layer formed on the surface thereof. Reference numerals 3 and 4 are electrodes formed on the resistor layer 2. Usually, one electrode is a common electrode and the other is an individual electrode, and a large number of such electrode pairs are arranged in a line. Reference numeral 5 is a wear-resistant layer that covers the surfaces of the electrodes 3 and 4 and the resistor layer 2, and prevents the heat generated in the resistor layer from coming into contact with the recording paper and the electrodes and resistor layer from being worn away. To do.

FIG. 4 shows another configuration example of the thermal head. 11 is a substrate on which electrodes 13 and 14 are formed, and then the resistor layer 1
2 and the abrasion resistant layer 15 are formed.

Hereinafter, specific examples of the present invention will be described.

Example 1 A pair of electrode layers made of gold is formed on an alumina substrate having a glaze layer on its surface. A resistor layer with a width of 350 μm is printed between the electrode layers by contacting both electrodes with a resistor paste,
It is formed by firing. As resistor paste, Ru, Rh, Si,
A mixture of ethyl hexanoate of B and Bi and ethyl cellulose and terpineol (viscosity 50000 cp) was used. After drying, it was baked at 800 ° C. to form a resistor layer. An abrasion resistant layer is formed on the resistor layer by printing and baking a paste of borosilicate glass frit.

Example 2 On a holo substrate having a holo layer having a thickness of 100 μm, a paste film having a viscosity of 1000 cp was formed by further adding terpineol to the resistance paste of Example 1 using a spinner. The spinner rotation speed was 2000 rpm. After firing at 800 ° C., a resistor is formed in a predetermined pattern by the photolithographic etching method. However, a mixed solution of sulfuric acid and ammonium borate was used as the etching solution. Next, a gold layer is formed on the resistor layer by printing and firing a gold organometallic compound paste, and subsequently an electrode layer is formed in a predetermined pattern by a photolithographic etching method. An abrasion-resistant layer is formed on this by printing and firing a paste composed of ethyl alkoxides of Si, B, and Pb and ethyl cellulose and terpineol.

Example 3 A pair of electrode layers is formed on an alumina substrate having a glaze layer on its surface. A resistor layer having a width of 350 μm is formed between the electrode layers by printing and firing a resistor paste. As the resistor paste, a mixture of ethyl hexanoate of Ru, Si, B and Bi and a mixture of ethyl cellulose and terpineol (viscosity 50000 cp) was used. After drying, it was baked at 800 ° C. to form a resistor layer. A wear resistant layer is formed on the resistor layer by printing and firing a paste of borosilicate glass frit.

The characteristics of the thermal heads obtained in the above examples are shown in the table. For comparison, the characteristics of the conventional thermal head are also shown. Comparative Example 1 is a thick film type head, and Comparative Example 2 is a thin film type head.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to obtain a thermal head which gives excellent recording quality.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the Ru content in the resistor layer and the dispersion of the resistance value, FIG. 2 is a diagram showing the temperature dependence of the resistance value of the resistor layer, and FIGS. 3 and 4 are It is a principal part longitudinal cross-sectional view which shows the structural example of the thermal head of this invention. 1,11 ...... Substrate, 2,12 ...... Resistor layer, 3,4,13,14 ...... Electrode, 5,15 ...... Abrasion resistant layer.

Front page continued (72) Inventor Yoshihiro Watanabe 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yasuhiro Takeuchi 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) Reference Reference JP-A-50-30094 (JP, A) JP-A-62-46501 (JP, A)

Claims (2)

[Claims] 1. A substrate comprising at least a pair of electrodes, a resistor layer in contact with the electrodes, and a substrate having at least an insulating surface and supporting the electrode and the resistor layer on the surface. In a thermal head in which the resistor layer is composed of a glass matrix and a metal and / or an oxide of a resistor component element that has entered the atomic bond gaps of the matrix, the resistor component element is ruthenium. And the ruthenium content of the resistor layer is 1 to 10 by weight.
%, The thermal head. 2. At least a pair of electrodes, a resistor layer in contact with both electrodes, and a substrate having at least a surface having an insulating property and supporting the electrode and the resistor layer on the surface, In a thermal head in which the resistor layer is composed of a glass matrix and a metal and / or an oxide of a resistor component element that has entered the atomic bond gaps of the matrix, the resistor component element is ruthenium. A thermal head which is rhodium and has a ruthenium content of the resistor layer of 1 to 10% by weight.