JPH0452148A - Thermal head - Google Patents

Abstract

PURPOSE:To realize a required heating pattern by controlling current density with a resistance value of a heating element part by a method wherein a heating element part having, at least, two kinds of different specific resistance value is formed parallelly along a current direction flowing between conductor electrodes to form a heating element layer. CONSTITUTION:A heating element R of a thermal head is of a rectangular form. A central part of dividing this rectangle into three parts is made to be a small specific resistance part 1, and both side parts are made to be high specific resistance parts 2, 3. Further, conductor electrodes 4, 5 are formed on both sides of the heating element R. When voltage is impressed to the thermal head, a current passes the heating element R from the conductor electrode 4 to flow to the conductor electrode 5 as given by the arrow. Since the current converges to the small specific resistance part 1 of small resistance at that time, temperature distribution of the heating element R forms that from high temperature to low temperature centering the small specific resistance part 1. Therefore, the small specific resistance part 1 becomes capable of being heated by converging heating thereon, and the thermal head suitable for half tone thermal transfer can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Industrial Application Field) The present invention relates to a thermal head, and particularly to a thermal head with an improved heating resistor portion.

(Prior Art) A thermal transfer recording method using a thermal head is becoming widely used in various recording devices.

Generally, the heating resistor of a thermal head consists of a rectangular heating resistor part 71 as shown in FIG. 7, and conductor electrodes 72 and 73 sandwiching it.
1, and the temperature distribution becomes as shown in FIG. 8, where the temperature gradually decreases concentrically from the central high temperature area 81.

Printing is performed using thermal paper or thermal transfer film using the heat generated during this generation.

By the way, in order to perform halftone recording in melt-type thermal transfer, it is necessary to control the temperature distribution of the head.
A thermal head as shown in FIGS. 9 and 10 has been proposed in order to provide one or more portions on a heating resistor with a large amount of heat per unit area.

The thermal head shown in FIG. 9 consists of a diagonal heating resistor part 91 and conductor electrodes 92 and 93 sandwiching it.
The thermal head shown in Figure 0 has a heating resistor section 101 with a circular pattern and a conductor electrode 102.1 sandwiching it.
03, and the heat generating location is controlled by patterning.

However, in such a thermal head, it is necessary to change the shape of the resistor, and the shape also needs to be changed depending on the desired degree of heat concentration.

This causes difficulty in resistor patterning and an increase in the number of manufacturing steps for each batoninck.

(Problem to be solved by the invention) In a thermal head that concentrates heat locally by changing the shape of the resistor, when trying to make the pattern of heat concentration thinner, it becomes difficult to perform etching that follows the shape of the resistor. .

Further, even when using a diagonal resistor, the shape of the resistor must be changed depending on the desired heat distribution, and a different manufacturing process must be performed for each application.

For these reasons, there is a need for a thermal head that can realize a desired heat concentration pattern in a simpler manner.

The present invention has been made in response to such conventional circumstances, and an object of the present invention is to provide a thermal head that can freely control a heat concentration pattern without changing the shape of the resistor.

[Structure of the Invention] (Means for Solving the Problems) The thermal head of the present invention includes a base body, a heat generating resistor layer formed on the base body, and a heat generating resistor layer formed on opposite sides of the base body. In a thermal head that has a conductor electrode and performs thermal transfer recording by causing the heat-generating resistor layer to generate heat by supplying electricity to the heat-generating resistor layer, the heat-generating resistor layer has a conductor electrode that is arranged along the direction of current flowing between the conductor electrodes. The heating resistor portions having at least two different specific resistance values are formed in parallel.

In the present invention, the specific resistance value of the heating resistor layer can be locally changed by locally changing the metal content of the heating resistor using cermet, for example.

In the present invention, cermet is used as the heating resistor.

Then, a metal film of chromium, tungsten, molybdenum, tantalum, etc. is formed on the heating resistor layer,
The metal content of the heat generating resistor layer can be locally changed by partially diffusing the metal film into the heat generating resistor layer by laser irradiation or the like.

(Function) In the thermal head of the present invention, heating resistor portions having at least two different resistivity values are formed in parallel along the direction of a current flowing between conductor electrodes to form a heating resistor layer. ing.

Therefore, the current density is controlled by the resistance value of the heating resistor portion, and a desired heating pattern can be realized.

In other words, if the conductive electrode and the heat generating resistor are in direct contact with one side adjacent to each other, or if they are in direct contact with multiple heat generating resistor parts having different resistivity values that constitute the heat generating resistor, the small resistivity part with the small resistance value is The current density becomes higher and the temperature becomes higher than other parts.

In addition, when a high resistivity part with a high resistance value is interposed between the low resistivity part and the conductor electrode, the current density in the high resistivity part area near the low resistivity part becomes high. The temperature distribution is formed by the pattern of the heating resistor section.

In this way, it is possible to control the pattern of heat concentration, and it is possible to set a temperature distribution suitable for thermal transfer.

(Example) Next, an example of the thermal head of the present invention will be described using the drawings.

Embodiment 1 FIG. 1 is a plan view showing the main parts of a thermal head according to an embodiment of the present invention.

In the figure, the heat generating resistor R of the thermal head has a rectangular shape and is composed of a plurality of heat generating resistor parts having different resistivity values. That is, the central part of this rectangle divided into three parts becomes the low resistivity part 1, and the parts on both sides of the small resistivity part 1 are the high resistivity parts 2 and 3.

Furthermore, conductive electrodes 4.5 are formed on both sides of the heating resistor R.

These heating resistor R and conductor electrode 4.5 are formed as follows. First, a Ta-8in2 film is formed on an alumina substrate by sputtering.

Next, a Cr film is formed and patterned by etching.

The high resistivity parts 2 and 3 are etched with Cr before etching.
The film is heated by laser irradiation, and only a portion of the film is heated with C.
It is formed by diffusing r into the underlying Ta-3i02 film.

FIG. 2 is a diagram showing the current distribution when voltage is applied to this thermal head.

The current flows from the conductor electrode 4 through the heating resistor R and to the conductor electrode 5 as shown by the arrow. At this time, since the current is concentrated in the small resistivity section 1 having a low resistance, the temperature distribution of the heating resistor R becomes as shown in FIG. 3.

That is, a temperature distribution is formed from a high temperature to a low temperature centering on the low resistivity portion 1. Therefore, it becomes possible to generate heat concentrated in the small resistivity portion 1, and a thermal head suitable for halftone thermal transfer can be obtained.

In addition, in this thermal head, the shape of the resistor itself is not changed, and the Cr diffusion region can be controlled into the desired shape by controlling the heated part by laser irradiation, making it possible to change the degree of heat concentration depending on the application. is also possible.

Embodiment 2 Next, a thermal head according to another embodiment of the present invention will be described with reference to FIGS. 4 to 6.

FIG. 4 is a plan view showing the main parts of a thermal head according to another embodiment of the present invention.

In the figure, the heating resistor R of the thermal head has a rectangular shape, and two small rectangular low resistivity parts 41a, 41b are formed side by side in this rectangle. The other parts excluding the high resistivity part 42
It becomes.

Furthermore, conductive electrodes 43 and 44 are formed on both sides of the heating resistor R.

FIG. 5 is a diagram showing the current distribution when voltage is applied to this thermal head.

The current flows from the conductive electrode 43 to the heating resistor R as shown by the arrow.
and flows to the conductive electrode 44. At this time, the current is concentrated in the small resistivity portions 41g and 41b having low resistance, so that the temperature distribution of the heat generating resistor R becomes as shown in FIG.

That is, the maximum heat generating portion is the conductor electrode 43 in the heat generating resistor R.
44 and the small resistivity parts 41a and 41b (corresponding to the region of the high resistivity part 42).

This is because when the current concentrated in the low resistivity parts 41a and 41b passes through the high resistivity part 42, the maximum heat is generated there.

Therefore, as shown in FIG. 6, the temperature distribution of the heating resistor R is such that high-temperature regions are formed at the four corners, and the temperature gradually decreases from each high-temperature region, making it possible to obtain a thermal head suitable for block-shaped thermal transfer. Ta.

[Effects of the Invention] As described above, the thermal head of the present invention enables control of temperature distribution, that is, concentrated heat generation, without changing the shape of the resistor, and high-quality printing can be obtained in thermal transfer and the like.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the main part of the thermal head in an embodiment of the present invention, Fig. 2 is a diagram showing the current density distribution of the thermal head of Fig. 1, and Fig. 3 is a diagram showing the current density distribution of the thermal head of Fig. 1. FIG. 4 is a diagram showing the main parts of a thermal head according to another embodiment of the present invention. FIG. 5 is a diagram showing the current density distribution of the thermal head in FIG. 4. The figure shows the temperature distribution when current is applied to the thermal head in Figure 4, and Figure 7 shows the temperature distribution when current is applied to the thermal head in Figure 4.
The figure shows the main parts of a conventional thermal head. Figure 8 shows the temperature distribution of the thermal head in Fig. 7 when current is applied. Figures 9 and 10 show the main parts of a conventional thermal head. It is a diagram. 1.41a, 41b...Low resistivity section 2.3.42
...High specific resistance part 4.5.43.44 ...Conductor electrode R...
・Heating resistor applicant: Toshiba Corporation

Claims (2)

[Claims] (1) It has a base body, a heat generating resistor layer formed on the base body, and conductor electrodes formed facing each other with the heat generating resistor layer sandwiched therebetween, and the heat generating resistor layer is energized to generate electricity. In a thermal head that performs thermal transfer recording by causing a heating resistor layer to generate heat, the heating resistor layer has heating resistor portions having at least two different specific resistance values arranged in parallel along the direction of a current flowing between the conductor electrodes. A thermal head characterized by being formed. (2) By using a cermet as the heat generating resistor and locally changing its metal content or, if it contains multiple metals, the content of at least one metal, the heat generating resistor can be heated at different ratios. 2. The thermal head according to claim 1, comprising a heating resistor portion having a resistance value.