JPH02158349A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain a thermal head superior in printing image quality, durability, and high speed properties with low cost by providing the following films on a substrate : a resistor film formed by applying and baking a coating liquid containing an organic acid salt of ruthenium and an organic substance having titanium in its structure ; a wiring conductive film for passing an electric current to the resistor film ; and a wear-resistant protective film covering the resistor film and the wiring conductive film. CONSTITUTION:In a construction in the vicinity of heating elements of a thermal head, a numeral 1 is an alumina substrate, 2 is glaze layer, 3a, 3b represent wiring conductive films, the 3a is a common electrode commonly connecting to respective ends of the heating elements, the 3b is a discrete electrode connecting to a semiconductor element 4, is a resistor film obtained by printing and calcining a coating liquid, and 5 is a wear-resistant protective film. The resistor film 4 is formed in the following method : 2-ethylhexanoic ruthenium and titanic tetra(n-butyl) are dissolved in a ketone solvent with a nitrocellulose in a 2:3 titanium/ ruthenium ratio to form the resistant coating liquid; this resistant coating liquid is printed all over the alumina substrate 1 provided with the glaze layer 2 thereon and calcined at 750 deg.C in atmosphere, this is exposed to light with a predetermined mask, and an unnecessary part is removed by etching to form a pattern. Then, this film becomes a resistor film having a superior adhesion, a small resistance temperature coefficient, and an appropriate value of resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a thermal head used in thermal recording terminals, facsimile machines, and the like.

Conventional thermal recording methods are used in various terminal recording devices, facsimile machines, etc. as a method for obtaining easy-to-maintain note copies, and thermal heads are used as the central device in these devices.

2ノ＼-/ In general, thermal heads are divided into thin film types and thick film types depending on the film forming process. The thin-film type is produced using a method similar to a semiconductor process, and has excellent image quality, power consumption, and high speed, but costs are high because vacuum equipment is required for manufacturing.

On the other hand, the thick film type can be manufactured at low cost by printing and baking, but is inferior in performance because the resistor film is a thick film made of a mixture of RuO2 powder and glass frit. In order to solve the above problems, the present inventors have developed a thermal head using a thin film resistor formed by coating and baking a coating liquid containing an organic metal. The above-mentioned thermal head can create a thin film type thermal head without using a vacuum device, achieving both cost and performance.

Problems to be Solved by the Invention In order to speed up thermal recording using a thermal head, recording must be performed using short pulses of several m5ec. To do this, a large amount of power is applied to the resistor to generate heat of about 400°C. In this case, if the resistance value of the resistor film is small, the current value required for printing becomes large, causing the following two problems. One is that the resistance value of the electrode can no longer be ignored, and the difference in the length of the electrode causes a difference in the amount of heat generated by the resistor film, resulting in uneven printing.

The second problem is that the current capacity of the drive circuit must be increased. From the above points, thin film resistors for thermal heads need to have stability at high temperatures and high resistance values.

The ruthenium oxide thread thin film resistor used in the present invention has a resistivity of only about 500 μΩ・m when ruthenium oxide is used alone, and achieves a sheet resistance value of 1 to 3 Ω/mm, which is necessary for high-speed recording. In order to achieve this, the film thickness must be 50.8 or less, which makes control during manufacturing difficult and the film quality unstable. The present inventors have discovered that the resistivity can be increased by adding an organic material having an alkaline earth metal in its structure to a coating solution using an organic material having ruthenium in its structure and firing the coating solution.

However, there are three problems in this case. The first problem is that unlike sputter deposition, the film is not formed using activated high-energy particles, so interdiffusion and the formation of intermediate compounds, which are factors that increase adhesion, are less likely to occur, resulting in poor adhesion. That's true.

The second problem is that the temperature coefficient of resistance is too large, and when alkaline earth metals are used as additives, Ω2/[]
The temperature coefficient of resistance of the resistive film, which shows the sheet resistance value of Ω/hole in ~3, is ±300 to 11000I)I)/'C. If the temperature coefficient of resistance is too negative, the resistor is driven with a constant voltage, so the power increases, the drive circuit becomes overloaded, the amount of heat generated increases too much, and the resistor film is likely to break.

However, if it is too large, the amount of heat generated will be insufficient.

For high-speed thermal heads, the temperature coefficient of resistance is -500 to +
It must be within the range of 11,000 pI)/°C, and the closer it is to 0, the more accurate printing will be.

The third problem occurs in the baking process after applying the coating liquid. Generally, the thermal decomposition of organic metals ends at around 400°C.
The formed film has a sintered body structure made up of fine particles having a particle size of about 1,008. If the firing temperature is further increased, in the case of ruthenium oxide alone, fine particles will grow to 400 to 800 particles, and at a firing temperature of π°C 5 h/°C or higher, ruthenium oxide will also vaporize, so there will be many voids. The homogeneity of the film is impaired.

This becomes even more pronounced when alkaline earth metals are added, and when multi-element oxides are formed at 400-600'C,
Extreme grain growth occurs at a certain temperature, resulting in a grain size of about 1,000 particles, and since there is little contact between grains, the resistance value becomes too high and the resistance value varies widely.

Therefore, an object of the present invention is to provide a high-performance, inexpensive thermal head that solves the problems of the ruthenium oxide thin film resistor described above.

Means for Solving the Problems In order to solve the above problems, the present invention uses a method such as spin coating, dipping, printing, etc. to apply a coating solution containing an organic salt of ruthenium and an organic substance having titanium in its structure. The structure is such that a resistor film is formed by coating and baking the resistor film.

Effect: By having the above structure, the temperature coefficient of resistance is small, the structure is dense and uniform, so printing performance is excellent, and the durability is 6 to 10000. be able to.

Example Examples of the present invention will be described below.

That is, the present invention involves forming a resistor film by applying and baking a coating liquid containing an organic salt of ruthenium and an organic substance having titanium in its structure using a method such as spin coating, dipping, or printing. Features.

A coating solution prepared by dissolving ruthenium 2-ethylhexanoate and tetra-n-butyl titanate in a ketone solvent is applied onto a so-called glazed alumina substrate, which is a glass glaze with a softening point of γ30°C or higher formed on alumina. When the thin film produced by firing at 40° C. was observed with a scanning electron microscope, it was found to have a dense sintered structure and the particle size of the fine particles was about 100. Firing temperature is 500℃
Even when the temperature was ~1000'C, the grain size increased to 20~400°C, but the dense sintered structure remained close to that level. When the X-ray diffraction pattern was measured, it was found that the material was a solid solution with a rutile crystal structure. Ru
Since both O2 and TiO2 have a rutinoto-type crystal structure and the ionic radius is about the same, it is thought that they are likely to form a solid solution in this way, and this allows the film to maintain a dense structure without vaporization or abnormal grain growth. This is thought to be the cause.

In addition, the adhesion of the resistive film is determined by the firing temperature (4O0~1000'
It is good regardless of C), and when compared with L and RuO2 film made using only ruthenium 2-ethyl-xanoate, Ru
The O2 film can be easily removed by scrubbing with a scraper or a brass needle, but the Ru-T1-0 film of the present invention cannot be removed even if rubbed with these tools.

When the composition in the depth direction of the films fired at 50°C was investigated by Auger electron spectroscopy, the diffusion of the glass component of the substrate was found to be the same in both films.

Therefore, it is thought that the reason why the Ru-Ti-Q film has better adhesion is that Ti forms an intermediate compound with the substrate component at the interface.

Regarding the temperature coefficient of resistance, the sheet resistance value is 1 Ω/mouth ~
±2 for membranes that are 6Ω/mouth (film thickness 1000 people)
001) I) m/°C or less.

In the above examples, ruthenium 2-ethylhexanoate and tetra-n-butyl titanate are used, but as an organic substance having titanium in its structure, titanium (IV) oxyoctylate or titanium NV) oxyacetylacetonate, ruthenium Similar effects and numerical values were obtained using ruthenium naphthenate as the organic acid salt.

For these reasons, when the coating liquid according to the present invention is fired, it is possible to create a resistor film with excellent film quality and adhesion, a small resistance temperature coefficient, and an appropriate resistance value. By using this, it is possible to create an inexpensive, high-performance thin-film thermal head.

An example of creating a thermal head will be specifically described below.

FIG. 1 shows a perspective view of the vicinity of the heating element of the thermal head produced according to this example. In Figure 1, 1 is an alumina substrate, 2 is a glaze layer, 3a and sb9 are conductor films for wiring, 32L is a common electrode that commonly connects one end of the heating element, and 3b is connected to a semiconductor element. Individual electrodes. 4 is a resistor film obtained by printing and baking a coating solution according to the present invention, and 5 is an abrasion-resistant protective film. Next, the resistor film 4 will be explained in detail.

Ruthenium di-ethylhexanoate and tetra-n-butyl titanate were dissolved in a ketone solvent together with nitrocellulose so that the ratio of titanium to ruthenium was 2:3, and this was used as a resistance coating liquid. This resistive coating liquid was printed on the entire surface of the alumina substrate 1 on which the glaze layer 2 having a softening point of 730'C or higher was formed, and baked at 750°C in the atmosphere. The resistor film 4 is fired at 70% in order to obtain thermal stability as a resistor and adhesion with the gold electrode formed using gold resinate.
It is necessary to carry out at 0-800°C. Baked resistor film 4
The sheet resistance value was 1.5 Ω/hole, and the film thickness was 1Q○08. The sheet resistance value required for the thin film resistor of a thin film type thermal head varies depending on the specifications, but is 100 to 3
niΩ/mouth. Resistor film 4 according to the present invention (Ftuj
OO, TixOy) can obtain a resistance value within the above range by setting the composition to X=2010Heno~60at%. Next, gold resinate (manufactured by Engelhard) was similarly printed on the entire surface and baked at 750°C. After that, a photoresist was applied and exposed using a predetermined mask to remove unnecessary parts by etching to form the pattern shown in the drawing (the part without the wear-resistant protective film 5 in the drawing).
. Furthermore, a printing paste containing hard glass as a main component was printed on the portion that would come into contact with the paper, and baked at 750°C to form an abrasion-resistant protective film 5, thereby producing the thermal head shown in the drawings. Note that in the drawings, the wear-resistant protective film 5 is partially omitted for convenience of explanation.

The temperature coefficient of resistance of the thermal head of this example prepared in this manner was -130 ppm/°C.

When a thermal head having a similar resistance value is prepared by adding barium di-ethylhexanoate instead of tetra-n-butyl titanate, the temperature coefficient of resistance is -360 ppm/°C. Pulse width 1m5ec, pulse period 10m for both
Continuous pulse application was performed at 5 ec to compare durability.

Comparing the power per unit area (rupture power, unit W/my2) of the resistor film that gives a resistance value variation of 10% with 11△ pulses applied 6X10' times, R
The u-Ba -0 series was 40 W/my2, and the Ru-Ti-0 series was 63 W/my2, greatly improving durability1.Also, when comparing the resistance value variation in B4 size and 8 pieces/familiar, Ru- Ba-0 system within ±10 coefficient, Ru-Ti
-0 series was within ±3 inches, and the thermal head according to the present invention was superior. This is thought to be due to the fact that the Ru-Ti-0 resistor film has a small temperature coefficient of resistance and a dense and uniform structure. From the above, the Ru-Ti-0 system was also superior in print image quality.

As described above, the thermal head according to the present invention has improved print image quality,
It has excellent durability, high speed, and low cost compared to other thin film thermal heads made using vacuum equipment, making it extremely valuable for industrial use.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of a thermal head according to the present invention. 1... Alumina substrate, 2... Craze layer, 31
L. 3b... Conductor film for wiring, 4... Resistor film, 5.
・Abrasion-resistant protective film.

Claims (1)

[Claims] A resistor formed by applying and baking a coating liquid containing an organic salt of ruthenium and an organic substance having titanium in its structure on a substrate whose surface has at least an insulating property, using a method such as spin coating, dipping, or printing. A thermal head comprising a body film, a wiring conductor film for supplying current to the resistor film, and an abrasion-resistant protective film covering the resistor film and the wiring conductor film.