JPH0595740U - Thermal head - Google Patents

Abstract

(57) [Summary] [Purpose] Performs thermal transfer printing on paper with a rough surface. [Structure] On the surface of the protective layer, a high thermal conductivity thin film having a thermal conductivity of 40 times or more of that of the protective layer was formed in a comb shape in the direction in which the ink moves from the position corresponding to the upper portion of the heating dot. [Effect] Even after pulse printing, heat is conducted to the ink by conducting through the high thermal conductivity layer, so that the solidification of the ink is delayed, and cohesive failure occurs when the ink sheet is peeled off so that the printing ink does not peel off from the paper.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a thermal head used for a video image or an output terminal of a computer device.

[0002]

[Prior Art]

 Conventionally, a thin film thermal head has a glaze layer 2 formed on the surface of an insulating substrate 1, a heating resistor is sputtered on the glaze layer 2 as shown in FIG. Is formed by forming a conductive layer as the electrode 4, and the surface thereof is covered with a protective layer 5. Then, when a voltage is applied to the electrode 4, a current flows through the portion of the heating element 3 existing between them and the resistor heats up. The heat is transferred to the thermal transfer ink 6 held between it and the platen via the protective layer 5, and the thermal transfer ink 6 melts and adheres to the recording paper 7. After the heat pulse is applied, the thermal transfer ink 6 and the recording paper 7 are moved from the position of the heating element 3 and the ink sheet portion 8 is peeled off by a separating mechanism for the recording paper 7 and the thermal transfer ink 6 not shown, and only the portion to which the thermal pulse is applied. Is transferred to the recording paper 7. Therefore, the mechanism is such that drawing is performed on paper by continuously repeating such operations.

[0003]

[Problems to be solved by the device]

 However, when thermal transfer printing is performed using a conventional thermal head and printing is performed on recording paper with a rough surface such as rough paper, when the thermal transfer ink is peeled from the ink sheet part, It remained on the sheet, and phenomena such as faint transfer characters and insufficient density occurred. Comparing rough paper and general thermal transfer paper using Beck's smoothness, the rough paper showed a value of 80 sec, which is less than one fifth of that of 450 sec of thermal transfer paper. Therefore, the ink transferred to the surface of the rough paper has a shape that forms a bridge on the rough surface as shown in FIG. 4, and the adhesiveness of the ink is very poor as compared with the thermal transfer paper shown in FIG. Recognize. When the solid ink peels off in such a low contact state, the ink is not transferred to the paper and most remains on the ink sheet. Therefore, in order to perform good printing in a poorly adhered state, it is necessary to improve the adhesiveness between the ink and the paper and further reduce the influence of the suction force from the base surface.

[0004]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, in this invention, the heat generated from the heat generating dots flows along the ink and the recording paper and flows on the surface of the thermal head, so that the heat transfer from the heat generating dots to the surface of the protective film is high in the moving direction of the ink sheet. The membrane was applied. Then, in order to prevent thermal interference due to the high thermal conductive film between adjacent dots, a high thermal conductive film patterned in a comb shape with a dot width size was formed.

[0005]

[Action]

 When the thermal head of the present invention is used, the heat generated from the heating dots is transmitted through the protective film and reaches the high thermal conductivity material layer. Further, it is transmitted to the ink sheet portion in contact therewith, and as a result, the ink is melted and the ink in the form of heating dots adheres to the paper. After that, the ink and the recording paper move on the high thermal conductivity material coated on the upper surface of the protective film, but since the high thermal conductivity material layer is laminated on the heating dot, the recording paper and the ink are not printed. While the sheet is moving, the heat generated from the heating dots is always transferred to the thermal transfer ink through the high thermal conductivity material layer, preventing the ink from cooling and solidifying. Further, since the high thermal conductivity layer is formed by patterning the heating dot width, heat flow flowing to other adjacent dots through the high thermal conductivity layer is prevented.

Even when printing is performed on a paper having a very rough surface, which is called rough paper, the moving ink after the application of the pulse and the recording paper maintain sufficient adhesion. If the ink base is peeled off in this state, since the ink is a low-viscosity fluid, the suction force on the base surface is relieved inside the ink and cohesive failure occurs. Moreover, since the adhesion between the paper and the ink is greater than when the ink is solid, the ink base peeling is completed without the ink peeling from the surface of the rough paper. As a result, good printing can be obtained without generating voids in rough paper printing.

[0007]

【Example】

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 and 2, glass paste is printed on an insulating substrate 1 made of aluminum and baked to form a glaze layer 2 for heat storage, and a Ta-SiO ₂ heating resistor is sputtered on the glaze layer 2. Biofilm was formed by ringing. Next, the resistor film was patterned by a photoetching process so that the heating elements 3 were arranged in a line. Al was sputtered thereon as an electrode layer 4, and the electrode was patterned by the same photoetching process. Further, sialon was sputtered thereon to form a protective layer 5 for abrasion resistance and electrical insulation of the heating head portion. Although the film deposition process of the conventional thermal head has been described above, in the present invention, the thermal head or ion beam evaporation in which the SiC film is further formed on the upper surface of the protective layer 5 as the high thermal conductivity layer 9 by sputtering. A thermal head is formed by vapor deposition of an AlN film by using the method, and the film formed on each of these thermal heads is patterned into a comb shape using an etching process to produce two types of thermal heads with high thermal conductivity layers. did.

In order to compare the printing performance of the above two types of thermal heads and the thermal head manufactured in the conventional process (FIG. 2), the pulse width / pulse period is 0.8 msec under the condition of applied power of 0.25 W / dot. The pattern ratio was changed by changing the print ratio at /5.5 msec and the void ratio of the printed image was measured. The print ratio indicates the ratio of heat generated by the heat-generating dots of the thermal head, and the void ratio indicates the ratio of white areas in the printed image. The black and white threshold value of the printed image was set to 0.8. The printed paper is generally called rough paper, and the paper with Beck's smoothness test value of 80 sec or less was used. Figure 6 shows the measurement results of the void ratio. The print rate should be inversely proportional to the void rate when normal printing is performed. In the conventional printing with a thermal head, the void rate does not decrease even if the printing rate is increased, because the ink is not transferred to the rough paper.

Next, two types of thermal heads with a high thermal conductivity layer were compared. The thermal head with a SiC film does not reduce the void ratio, so it is considered unsuitable for thermal transfer printing on rough paper. However, it can be confirmed that the thermal head with the AlN film is effective in thermal transfer printing on rough paper because the void rate is reduced in a manner that almost completely matches the printing rate. The thermal conductivity of SiC and AlN is 100 W / mK and 200 W / mK, respectively. In order to prevent the heat from diffusing to the surface of the protective film, a material of about 1 to 5 W / mK is generally used as the protective film material. The thermal conductivity of sialon used as the protective film is 5 W / mK. mK. From these results, it was confirmed that normal printing cannot be performed on rough paper unless printing is performed using a material such as AlN having a thermal conductivity of at least 40 times that of Sialon for the high thermal conductivity layer. ..

[0010]

[Effect of the device]

 As described above, according to the present invention, a thin film having a high thermal conductivity which is 40 times or more the thermal conductivity of the protective layer is formed on the surface of the protective layer of the thermal head in the direction in which the ink moves from the position corresponding to the upper portion of the heating dot. By forming the sheet-like shape, it is possible to obtain clean printing with few voids on rough paper such as rough paper.

[Brief description of drawings]

FIG. 1 is a sectional view of a thermal head of the present invention.

FIG. 2 is a top view of the thermal head of the present invention.

FIG. 3 is a cross-sectional view of a conventional thermal head.

FIG. 4 is a sectional view of a contact portion between rough paper and ink.

FIG. 5 is a sectional view of a contact portion of smooth paper and ink.

FIG. 6 is a relationship between a print rate and a void rate.

[Explanation of symbols]

 1 Insulating Substrate 2 Glaze Layer 3 Heating Resistor 4 Electrode 5 Protective Layer 6 Thermal Transfer Ink 7 Paper 8 Ink Sheet Base 9 High Thermal Conductivity Layer

Claims (3)

[Scope of utility model registration request] 1. A glaze layer formed on an insulating substrate, a heating resistor formed on the glaze layer, electrode wiring for supplying electric power to the heating resistor, and a surface of the heating resistor. What is claimed is: 1. A thermal head comprising a protective layer sequentially laminated for wear resistance and insulation, wherein a high thermal conductivity thin film is formed on the surface of the protective layer. 2. The thermal head according to claim 1, wherein the high thermal conductivity thin film is formed in a comb shape in the moving direction of the recording paper from the surface facing the heating dots. 3. The thermal head according to claim 1, wherein the thermal conductivity of the high thermal conductivity thin film is much higher than that of the protective layer.