JPS59133079A - Heat-sensitive head - Google Patents

Abstract

PURPOSE:To provide an optimum temperature distribution on the surface of a head, enable to print at high speed and obtain a heat-sensitive head consuming less electric power, by a method wherein a printing head part of a protective layer is constituted of thermally conductive members independently provided for each head. CONSTITUTION:The distance over which heat is transmitted in the same period of time in the thermally conductive member 7 is 3-30 times larger than that in the protective layer 5. Therefore, the heat fed from a heating part 3a of a heating element 3 is rapidly transmitted to a printing dot part 6a of the surface 6 of the head, so that high-speed printing can be performed. In addition, since the temperature difference between the heating part 3a and the dot part 6a is small and the quantity of heat escaping to the surroundings is reduced, it is possible to markedly reduce an electrical input to the heating part 3. Further, since the dot part 6a is formed of a thermally conductive member 7, it is prossible to make uniform the temperature distribution at the dot part 6a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a thermal head, and particularly to a thermal head that provides an optimal temperature distribution on the head surface and enables high-speed printing.

[Prior art]

FIG. 1 shows the general configuration of a conventional thermal head. 1st
In the figure, 1 is a substrate made of ceramic or the like, 2 is a heat storage layer, 5 is a heating resistor, 4 is an electrode for supplying power to the heating element 5, and 5 is a protective layer. In the printing mechanism of a thermal printer equipped with this thermal head, when power is supplied to the heating element 6 through the electrode 4, the heat generated from the heating element 50 and the heating part z)a passes through the protective layer 5 and prints on the head surface B. The dot portion 6a is also transmitted to an ink film and an ink layer body (not shown), and the ink in the ink layer body is dissolved and attached to printing paper (not shown) to perform printing, or thermal paper (not shown) is used for printing.
The color is transmitted to a coloring layer (not shown), develops color, and prints.

Generally, in this type of thermal head, the protective layer 5 is made of a material with a poor thermal diffusivity K of about 10"10"ctl/s (for example, Si02.Ta2O, etc.), and has a high resistance to wear. , and a heating element 4. Since the electrode 4 plays a role of preventing oxidation, its thickness is also uniform and is approximately 5 to 10 μm.

Therefore, the thermal resistance between the heating part 5a of the heating element 50 and the printing dot part 6a becomes very large, and a large temperature difference occurs between the heating part 5a of the heating element 5 and the printing dot part 6a on the head surface A. Therefore, in order to raise the temperature of the printing dot part 6a on the head surface to the temperature required for printing,
In order to print at high speed with such a thermal head, which requires the temperature of the heat generating part 6a to be extremely high, it is necessary to raise the temperature of the single surface printing dot part 6a to a predetermined temperature in a short period of time. , the electrical input to the heating element 6 becomes large, and the temperature of the heating element 6 becomes higher than that in the case of low-speed printing, which may damage the head. Since the thermal resistance to the printing dot portion 6a is large, there is a large amount of heat escaping to the surroundings, and there is a drawback that most of the electrical input to the heating element 6 is not used for printing. [Object of the Invention] The purpose of the present invention is to provide an optimal temperature distribution on the head surface,
The purpose of the present invention is to provide a thermal head that enables high-speed printing and uses low power.

[Summary of the invention]

In the thermal head of the present invention, a heat conductive material is provided in a portion of the protective layer corresponding to the heat generating part, thereby reducing the thermal resistance between the heat generating part of the heat generating element and the printed dot part on the surface of the head. It is characterized in that the heat from the head quickly reaches the print portion on the head surface, and the temperature difference between the heat generating portion of the heating element and the print dot portion on the head surface is reduced.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. 1st
The same reference numerals as in the figure indicate the same parts. Reference numeral 7 denotes an electrically insulating heat conductive member, which is provided only in a portion of the protective layer 2 corresponding to the heat generating portion a of the heat generating element filter. This thermally conductive member 7 has a - side in thermal contact with the heat generating part 5a, and the other side is exposed to the head surface 6 and forms a printing dot part 6a.
For example, 8i0. Thermal diffusivity K such as Al2O3 is 0.1~
It is made of a material having a value of approximately I Cn1A. Therefore, compared to the surrounding protective layer 5, 10~
The thermal diffusivity K is 1000 times larger. Now, the rate of heat diffusion during time t is proportional to 7T in y', so the distance that heat reaches within the same time is 5 to 50 times wider in the heat conductive member 7 than in the protective layer 5. .

Therefore, the heat from the heat generating part 5a of the heat generating element 50 is quickly transferred to the printing dot part 6a on the head surface B, so high-speed printing is possible.
Since the temperature difference between the print dot portion 6a on the head surface and the print dot portion 6a on the head surface is small, and the escape of heat to the surroundings is also reduced, the electrical input to the heating element 6 can be significantly reduced. Since the portion 6a is formed of the heat conductive member 7, the temperature distribution of the printing dot portion 6a can be made uniform, and therefore high printing quality can be obtained.
The figure is a sectional view showing another embodiment of the thermal head of the present invention, and the same reference numerals as in FIG. 2 indicate the same parts. The cross-sectional width of the side 7a that contacts 5a is the printed dot part 6a.
It is thicker than the cross-sectional width of the side 7b (Fig. 5 shows the shape of the heat conducting member 7 in stages, and Fig.
This is an example in which the shape of is continuously changed. With this configuration, the heat passes through the inside of the heat conductive member 7 and reaches the printing part 6a, so the shape and size of the printing dont part 6a can be determined without being concerned with the shape and size of the heat generating part 5a. Therefore, by reducing the size of the printing dot portion 6a, high-definition printing becomes possible. Moreover, since the shape and dimensions of the heat generating part 5a can be determined independently of the shape and dimensions of the printing dot part 6a, there is also the advantage that there is a margin for setting the resistance value of the heat generating part 5a or the applied power. There is.

In the embodiments shown in FIGS. 2 to 4 described above, the heat conductive member 7 is placed directly on the upper surface of the heat generating portion 5a and is thermally connected to the heat generating portion 5a. Therefore, the heat conductive member 7 must be made of an electrically insulating material.

In the embodiment shown in FIG. 5, a heat conductive member 7 is provided on the upper surface of the heat generating portion 5a via an electrically insulating member 8 formed thinner than the protective layer 5. In this way, the heat conductive member 7 may be a conductive member such as metal, and the heat generating portion 5a
Even if the electrically insulating member 8 is interposed between the protective layer 5 and the thermally conductive member 7, the electrically insulating member 8 is formed thinner than the protective layer 5, so there is no large thermal resistance. By changing the cross-sectional shape of the heat conducting member 7 stepwise or continuously as shown in FIG. 5 and FIG. The shape and dimensions of the printed dot portion 6a can also be arbitrarily selected.

〔Effect of the invention〕

According to the present invention, the thermal resistance from the heating element to the printing dots on the head surface is reduced, and the heat from the heating element can be quickly transferred to the printing dots on the head surface, making high-speed printing possible. , it is possible to further reduce the electrical input to the heating element.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the main parts of an example of a conventional thermal head.
FIG. 2 is a sectional view showing a main part of one embodiment of the thermal head of the present invention, and FIGS. 5A and 5B are sectional views showing main parts of another embodiment of the thermal head of the invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Heat storage layer, 6... Heat generating resistor,
5a... Heat generating part of heating resistor, 4... Electrode, 5...
- Protective layer, 6... Head surface, 6a... Printed dot portion on head surface, 7... Heat conducting member, 8... Electrical insulating member. Representative Patent Attorney Akira Takahashi (1) Figure 1 Figure Z [2] Figure 3 Figure 4

Claims (1)

[Claims] 1. In a thermal head in which an electrode for supplying power to the heat storage layer 9, a heating resistor 1, and a protective layer are provided on a substrate, the printed dot portions of the protective layer are printed on a dot-by-dot basis. A thermal head characterized in that it is composed of independently formed thermally conductive members. 2. The heat-sensitive head according to claim 1, wherein the heat-conducting member has one surface directly in contact with the heat-generating resistor and is thermally bonded to the heat-generating resistor. The heat-sensitive head 4 according to claim 1, characterized in that an electrically insulating member is interposed between the heating element and the heating element, the heat-conducting member having a cross-sectional shape on the printing dont side that corresponds to the heating resistor. The thermal head according to any one of claims 1 to 6, characterized in that the cross-sectional shape of the thermal head is smaller than that of the body side. 5. The heat-sensitive head according to claim 4, wherein the heat-conducting member is formed so that its cross-sectional shape gradually decreases from the heating resistor side to the printed dot side. 6. The thermal head according to claim 4, wherein the heat conductive member is formed so that its cross-sectional shape becomes smaller continuously from the heating resistor side to the printed dot side.