JPH02147253A - Thermal head - Google Patents

Abstract

PURPOSE:To improve a printing time constant, heat efficiency and printing quality by forming a heating resistor layer from a decomposition reaction product of a org. compound containing a metal or metalloid while forming an abrasion-resistant layer from a baked film of glass having a low softening point. CONSTITUTION:For example, an electrode layer 2 is formed on a glazed alumina substrate 11 by the printing and baking or photolithographic etching of the paste of an org. compound containing gold and a line-shaped heating resistor layer 13 is formed thereon by a printing and baking method. Next, an abrasion-resistant layer 14 is formed by the printing and baking of the paste of glass having a softening point of 550 deg.C, for example, the paste of PbO-B2O3 type low softening point glass (softening point; 450 deg.C or lower) to prepare a thermal head. By this constitution, the thickness of the heating resistor layer 13 can be made thin and heat capacity can be reduced and the uniform dispersion of respective components becomes easy to obtain and, therefore, a time constant of heating printing, printing heat efficiency and printing quality can be improved. Since the mutual diffusion of the components of the heating resistor layer and those of the abrasion-resistant layer at the time of the formation of the abrasion-resistant layer 14 can be suppressed, the irregularity of the resistance value of the heating resistor layer 13 and that of printing density can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a thermal head used in printing devices such as facsimiles, full-color printers, and word processors, and particularly relates to a thermal head with excellent print quality.

BACKGROUND OF THE INVENTION There are two conventional types of thermal heads used in printing devices such as thermal transfer and thermal printing printers. The first one is as shown in Figures 3(a) and (b).
Ta- obtained by a vacuum thin film forming process such as vapor deposition or sputtering on the glazed alumina substrate 31
A heating resistor layer 33 made of 51 or the like, electrode layers 32a and 32b made of Cr or the like, and a wear-resistant layer 34 made of SIC or the like are patterned using photolithography, and is a so-called thin-film thermal head. It is called. The second one is shown in Figure 4(a), (
As shown in b), on the glazed alumina substrate 41,
The electrode layers 42a, 42b1, the heating resistor layer 43, and the wear-resistant layer 44 are formed by printing and firing pastes, respectively, and are called a so-called original model thermal head.

Problems to be Solved by the Invention The two types of thermal heads mentioned above each have advantages and disadvantages. In other words, in a thin-film thermal head, the shape (area, thickness, etc.) of the heating resistor layer is uniform between each dot, and the heat capacity is uniform, so heat is transferred uniformly to the paper during printing. It will be done. Furthermore, the resistance value between each dot is uniform up to a certain level, and overall the thermal head has excellent printing quality. In addition, since the thickness of the heating resistor layer is thin < 1000 to 5000.4, the heat capacity is small, and the rise and fall time constants of the heating resistor layer temperature when pulse application is ON and OFF are excellent, resulting in excellent printing. It also has high heat generation efficiency. However, with conventional thin-film thermal heads, it is difficult to reduce the variation in resistance value between dots to less than ±5%, and it is difficult to expect even better printing quality.

Furthermore, since it is a thin film process, there are many problems that need to be solved in terms of productivity and cost reduction, such as equipment costs and batch production.

On the other hand, thick film thermal heads have many advantages such as low equipment costs and easy continuous production because they use a printing and firing method, but the heating resistor layer is made of metal oxide powder such as ruthenium oxide powder and glass frit. Since it is formed by printing and firing a paste consisting of a mixture of . In a thick-film thermal head, it is possible to reduce this variation in resistance value to ±1% or less by using an overload trimming method. However, when focusing on the microscopic current path within a single dot, non-uniformity of trimming remains as an issue that needs improvement. These disadvantages are largely due to the large heat capacity of the heating resistor layer of the thick-film thermal head, resulting in a large time constant during heating printing, poor printing thermal efficiency, and poor printing quality. There is.

In order to overcome the above problems, the inventors have previously provided a thermal head using a heating resistor layer with a thickness of 1.0 μm or less made of a decomposition reaction product of an organic compound containing a metal or metal-like metal. (Patent application 1843511i, 1986)
issue). Although the thermal head was greatly improved in printing thermal efficiency, the printing quality was slightly inferior to that of the thin film type thermal head.

The present invention aims to improve the printing time constant, thermal efficiency, and printing quality, and relates to the improvement of a thermal head using a print-baking method.

Means for Solving the Problems In order to solve the above problems, the thermal system of the present invention includes a heating resistor layer on a substrate that covers a specific area of the substrate;
An electrode layer for supplying current to the heating resistor layer and a wear-resistant layer covering all of the heating resistor layer and a part of the electrode layer are provided, and the heating resistor layer is made of an organic compound containing a metal or a similar metal. The wear-resistant layer is a fired film of low softening point glass having a softening point of 550° C. or less.

Function: In the thermal head of the present invention, the heating resistor layer is made of a decomposition reaction product of an organic compound containing a metal or a metal-like metal, so that the thickness of the heating resistor layer is reduced, and the heat capacity of the heating resistor layer is reduced. This makes it possible to reduce the size of the heating resistor layer, and also makes it easier to obtain uniform dispersion of each component of the heating resistor layer.
It is possible to improve the time constant of heat-generating printing, printing thermal efficiency, printing quality, etc. Furthermore, by forming the wear-resistant layer with a fired film of low-softening glass having a softening point of 550°C or less, mutual diffusion between the heating resistor layer components and the wear-resistant layer components can be suppressed during the formation of the wear-resistant layer. Therefore, variations in the resistance value of the heating resistor layer and variations in print density can be reduced.

Example Examples of the present invention will be shown below according to the drawings.

Example 1 As shown in FIG. 1, an electrode layer 12 is formed on a glazed alumina substrate II having a thickness of 0.8+UE by printing and firing a paste of an organic compound containing gold and photolithography. On top of this, a line-shaped heating resistor layer (thickness of several thousand amps) 13 was formed by a printing and baking method. The heating resistor paste used for printing was Ruthenium.

It is a mixed composition paste consisting of lamb fatty acid ester (7 carbon atoms, liquid), lead fatty acid ester, boron fatty acid ester, silicon fatty acid ester, ethyl cellulose, and terpineol. Next, a wear-resistant layer (M thickness: approximately 5 μm) 14 was formed by printing and baking a paste of PbO-B2O3-based low softening point glass (softening point: 450 DEG C. or less) to create a thermal head.

Example 2 In Example 1, after forming the heat generating resistor layer, alumina and zirconium oxide powder (average particle size of each is 0.5
A wear-resistant layer (film thickness of about 4 μm) was formed by printing and firing a PbO-B2Os-based low softening point glass paste in which um) was dispersed, and a thermal head was fabricated in the same manner as above.

Example 3 A thermal head was produced in the same manner as in Example 1, except that a heating resistor paste using a ruthenium polycyclic organic compound instead of the ruthenium fatty acid ester was printed and fired.

Example 4 In Example 1, a heating resistor paste in which half of the ruthenium fatty acid ester was replaced with the ruthenium polycyclic organic compound used in Example 3 was printed and fired, and a thermal head was created in the same manner as in Example 3. Example 5 Printing a heating resistor paste consisting of liquid fatty acid ester of ruthenium (7 carbon atoms), solid fatty acid ester of ruthenium (20 carbon atoms), Alcolade of lead, Alcolade of silicon, Alcolade of boron, ethyl cellulose, and terpineol. A thermal head was produced in the same manner as in Example 1 except that it was fired to form a heating resistor layer.

Comparative Example 1 A thermal head was prepared in the same manner as in Example 1, except that a paste with a mixed composition of ruthenium oxide powder, borosilicate glass frit, ethyl cellulose, and terpineol was used as the heating resistor paste, and other configurations and materials were the same.

Comparative Example 2 A thermal head was produced in the same manner as in Example 1 except that a printed and fired borosilicate lead glass paste was used as the wear-resistant layer.

Comparative Example 3 On the same glazed alumina substrate used in Example 1,
A thermal head is fabricated by forming an electrode layer made of a conventional electrode layer, a heating resistor layer made of a Ta-51 alloy, and a wear-resistant layer made of SIC by a vapor deposition method.

Table 1 shows the characteristics of the thermal heads of Examples of the present invention and Comparative Examples. The resistance value variation in the table shows the value obtained by dividing the standard deviation of each dot resistance value by the average resistance value. Variations in printing density can be determined by the current overload trimming method (method of adjusting the resistance value using self-generated Joule heat of the heating resistor layer), which is the resistance value of each heating part of each dot after the thermal head is formed.
After adjusting the resistance value of the heat generating part within ± 0% by trimming using
The results of printing on thermal paper under the driving conditions of 4 duty and IG+as/cycle and measuring the density of the coloring point of each dot with a micro densitometer are shown. Further, the time constant was calculated from the temperature profile of the heat generating part determined using an infrared microscope.

(Margin below) Table 1 As shown in Table 1, the thermal heads shown in Examples 1 to 5 have a much thinner heating resistor than the conventional thermal head (Comparative Example 1) that uses glass frit as a binder. Because it is possible to obtain a heat-generating resistor layer (with a thickness of 1 μm or less), the heat capacity of the heat-generating resistor layer can be reduced, and uniform dispersion of the decomposition reaction products of the heat-generating resistor layer can be easily obtained, which reduces resistance value variations. , the print density variation is small, and the time constant is also fast.

In addition, the fatty acid ester of lead, the fatty acid ester of boron, and the fatty acid ester of silicon used in the heating resistor paste in Examples 1 to 4 were one or two of these.
Similar results were obtained using only species. Furthermore, similar results were obtained with Alcolade of lead, Alcolade of boron, and Alcolade of silicon used in the heating resistor paste in Example 5, even if only one or two of these were used. .

FIG. 2 shows the relationship between the firing temperature of the wear-resistant layer of the thermal head and the variation in print density in Example 1. From this figure, it can be seen that by using a fired film of low softening point glass with a firing temperature of 550°C or less as the wear-resistant layer, the conventional fired film of lead borosilicate glass shown in Comparative Example 2 (with a firing temperature of 600°C or less) can be used as the wear-resistant layer.
It has become clear that variations in print density can be made smaller than with a thermal head using a thermal head (800°C).

This is because the firing temperature of the wear-resistant layer can be lowered by using a fired film of low-softening glass with a firing temperature of 550''C or less as the wear-resistant layer. This seems to be due to the suppression of mutual diffusion of the components.In particular, PbO-B2Os-based low softening point glass has a particularly low softening point, so it gives good results.

Furthermore, a thermal head (Example 2) using a fired film of low softening point glass made by dispersing ceramic powders of alumina and zirconium oxide as an abrasion-resistant layer has durability without impairing the characteristics of the thermal head of Example 1. We were able to improve the abrasion resistance. As the ceramic powder,
Those with excellent wear resistance are preferred, and it was particularly effective to use alumina, zirconium oxide, silicon carbide, silicon nitride, and titanium carbide alone or in a mixture of 2M or more.

In addition, organic compounds containing metals or similar metals are selected from the group consisting of platinum group metals, gold, silver, nickel, chromium, silicon, germanium, tantalum, aluminum, zirconium, titanium, boron, bismuth, vanadium, and lead. Effects similar to those of the above-mentioned examples could be obtained if a small amount of the compound (including one or more metals or similar metals) was used.

In addition, organic compounds containing the above metals or similar metals are
They can be used alone or in a mixture of two or more.

Furthermore, examples of compounds containing metals or similar metals include fatty acid salts with up to 20 carbon atoms, fatty acid esters, polycyclic organometallic compounds such as alcoholades, mercaptides, and cyclic carboxylates, and other resinates and rhosinates ( It was found that 11 types or a mixture of two or more types is sufficient.

Effects of the Invention As described above, according to the present invention, since glass frit is not used as a binder, a heating resistor layer having a very thin thickness can be obtained. As a result, the heat capacity of the heating resistor layer becomes smaller, making it equivalent to that produced by a thin film process, so a thermal head with excellent characteristics in terms of ON/OFF time constants and printing quality can be used continuously at low cost. can be produced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a typical configuration of a thermal head according to an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the firing temperature of the wear-resistant layer and print density variation in the thermal head according to an embodiment of the present invention. Characteristic curve diagram, Figure 3 (a), (b)
4(a) and 4(b) are a plan view and a sectional view showing a typical configuration of a conventional thermal head. 11.31.41... Brace alumina substrate, 12.
32a, 32b, 42a, 42b* e e electrode)! !
, 13,33,43...Fist heating resistor layer, 14,3
4,44... wear-resistant layer. Name of agent: Patent attorney Shigetaka Kurino

Claims (5)

[Claims] (1) A heating resistor layer on a substrate that covers a specific area of the substrate, an electrode layer for supplying electricity to the heating resistor layer, and a wear-resistant layer that covers all of the heating resistor layer and a part of the electrode layer. wherein the heating resistor layer is made of a decomposition reaction product of an organic compound containing a metal or similar metal, and the wear-resistant layer is made of a fired film of low softening point glass having a softening point of 550°C or less. thermal head. (2) The thermal head according to claim 1, wherein the wear-resistant layer is made of a fired film of PbO-B_2O_3-based low softening point glass. (3) The wear-resistant layer is made of a fired film of low softening point glass in which at least one ceramic powder selected from the group consisting of alumina, zirconium oxide, silicon carbide, silicon nitride, and titanium carbide is dispersed. 2. The thermal head described in 2. (4) Organic compounds containing metals or similar metals include platinum group metals, gold, silver, nickel, chromium, silicon, germanium, tantalum, aluminum, zirconium, titanium,
The thermal head according to any one of claims 1 to 3, which is an organic compound containing at least one metal or similar metal selected from the group consisting of boron, bismuth, vanadium, and lead. (5) The organic compound containing a metal or similar metal is a single substance or a mixture of fatty acid salts, fatty acid esters, alcoholades, mercaptides, polycyclic organometallic compounds, other resinates, and rhosinates having up to 20 carbon atoms. The thermal head according to any one of claims 1 to 4.