JPH05238035A - Thermal head - Google Patents

Abstract

PURPOSE:To provide a thermal head in which a heating element is cooled based on the Peltier effect during the stop of a printer and a printing time is reduced. CONSTITUTION:A first Peltier element 8 is disposed between a heating element 2 and a head power source 3 and a second Peltier element 9 is disposed between the heating element 2 and a driver circuit 6. When a current is supplied from the first Peltier element 8 to the second Peltier element 9, the heating element 2 is heated. When a current is supplied in a reverse direction, the heating element 2 generates an endothermic reaction, so that it is cooled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head in a thermal transfer printer.

[0002]

2. Description of the Related Art A conventional thermal head 101 in a thermal transfer printer is shown in a circuit diagram of FIG. 6 and a sectional view of FIG. In both figures, the thermal head 101 is a line-type thermal head having a large number of heating elements 102 arranged in a line, and a shift register 104,
A driving I including a latch 105 and a driver circuit 106
It is equipped with C107. The driving IC 107 is provided for each of the plurality of heating elements 102, and a plurality of driving ICs 107 are present on the head substrate 103 in the line direction.

FIG. 8 shows the relationship between the temperature and current of the heating element 102 and time. In the thermal transfer printer, the recording period, that is, the printing time is determined by the energization time and the cooling time as shown in FIG. 8, and the cooling time is the heat conduction amount to the head substrate 103 and the heat conduction amount to the air by the forced cooling fan. Almost decided.

[0004]

In the above-mentioned conventional thermal head, it is necessary to increase the size of the head substrate 103 and the cooling fan in order to shorten the printing time.
There is a limit due to problems such as large size and high price of the device.

[0005]

In order to solve the above-mentioned problems, a thermal head according to the present invention includes a heating element, a drive circuit for driving the heating element, and a head for supplying driving power for the heating element. An electrode, a first Peltier element connected between the head electrode and one end of the heating element, a second Peltier element connected between the drive circuit and the other end of the heating element, and a first Peltier element during the printing period. The heating element is heated by energizing the Peltier element in the direction of the first Peltier element, and the heating element is cooled by energizing the second Peltier element from the second Peltier element during the stop period. And a control means.

Further, the thermal head of the present invention is characterized by comprising the above-mentioned control means, which is provided with a coil connected between the drive circuit and the second Peltier element.

Further, the thermal head of the present invention is characterized in that a bypass means for short-circuiting the coil is provided.

[0008]

In the above structure, when a current is passed from the first Peltier element to the second Peltier element, the metal piece that is in common contact with the two semiconductors generates heat, and conversely, from the second Peltier element. When a current is applied to the first Peltier element, the metal piece absorbs heat. (This phenomenon is called the Peltier effect.) During this heat absorption, the heating element itself is forcibly cooled, so that the temperature of the heating element drops sharply, the recording cycle becomes short, and the printing time can be shortened.

[0009]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing an outline of a circuit configuration of a thermal head of an embodiment of the present invention in a thermal transfer printer, FIG.
FIG. 3 is a schematic sectional view of the thermal head. The thermal head 1 is a line type thermal head having a large number of heating elements 2 arranged in a line, and a driving IC 7 including a shift register 4, a latch 5, a driver circuit 6 and the like on a head substrate 3.
It is equipped with. The driving IC 7 is provided for each of the plurality of heating elements 2, and a plurality of driving ICs 7 are present on the head substrate 3 in the line direction.

A first Peltier element 8 is provided at both ends of the heating element 2.
And a second Peltier element 9 are connected in a π-shape, and metal pieces 10 and 11 are joined to the respective Peltier elements on opposite sides of the heating element 2, and one is connected to the driving IC 7 and the other is connected to the control means. Is connected to the head electrode 13 via the coil 12.

The coil 12 is a means for generating a counter electromotive force, and when the direction from the head electrode 13 to the driving IC 7 is +, when an energizing pulse is flown as shown in FIG. Current flows in the opposite direction. That is, heat is generated when ON and heat is absorbed when OFF, and heating and cooling of the heating element 2 are alternately performed. The temperature change of the heating element 2 at that time is shown in FIG.

In this embodiment, in addition to the above structure, a bypass circuit is provided in the coil 12, and the switch 14 prevents the counter electromotive force generated in the coil 12 from occurring when the head temperature is low and rapid heating is required. And the ground can be shorted. Figure 5 shows the relationship between temperature and time at that time.
Shown in.

Further, in the embodiment, the characteristic of the coil 12 is used to reverse the current, but a method of reversing the direction of the current by a reverse switch may be used.

Next, the conventional thermal head 101 is shown in FIG.
The circuit configuration diagram and the cross-sectional view of FIG. 7 are shown. In both figures,
The thermal head 101 includes a large number of heating elements 102 arranged in a line.
Is a line-type thermal head including a drive IC 107 including a shift register 104, a latch 105, a driver circuit 106, and the like on a head substrate 103. The driving IC 107 is provided for each of the plurality of heating elements 102, and a plurality of driving ICs 107 are present on the head substrate 103 in the line direction.

FIG. 8 shows the relationship between the temperature and current of the heating element 102 and time. In the thermal transfer printer, the recording period, that is, the printing time is determined by the energization time and the cooling time as shown in FIG. 8, and the cooling time is the heat conduction amount to the head substrate 103 and the heat conduction amount to the air by the forced cooling fan. Almost decided.

[0016]

According to the thermal head of the present invention, the first and second Peltier elements are connected to both ends of the heating element, and current is supplied from the first Peltier element to the second Peltier element during the printing period. The heating element is heated by performing the above, and during the stop period, the heating element can be cooled by energizing the first Peltier element from the second Peltier element direction, and the heating element can be self-cooled. Moreover, there is an effect of reducing the printing time.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a circuit configuration of a thermal head according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a thermal head according to an embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between current and time of the thermal head according to the embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between temperature and time of a thermal head according to an embodiment of the present invention.

5 is a diagram showing a relationship between temperature and time when the switch is changed over in FIG.

FIG. 6 is a diagram showing a schematic circuit configuration of a conventional thermal head.

FIG. 7 is a schematic sectional view of a conventional thermal head.

FIG. 8 is a diagram showing changes in current and temperature of a conventional thermal head.

[Explanation of symbols]

 1 Thermal Head 2 Heating Element 3 Thermal Head (Head Substrate) 4 Drive Circuit (Shift Register) 5 Drive Circuit (Latch Circuit) 6 Drive Circuit (Driver Circuit) 7 Drive Circuit (Drive IC) 8 First Peltier Element 9th 2 Peltier element 10, 11 Thermal head (metal piece) 12 Control means (coil) 13 Head electrode 14 Switch

Claims (3)

[Claims] 1. A heating element, a drive circuit for driving the heating element, a head electrode for supplying driving power for the heating element, and a first electrode connected between the head electrode and one end of the heating element.
Of the Peltier element, the second Peltier element connected between the drive circuit and the other end of the heating element, and the heat is generated by energizing the first Peltier element in the direction of the second Peltier element during the printing period. A thermal head comprising: a heating means; and a control means for cooling the heating element by energizing the first Peltier element from the direction of the second Peltier element during a stop period. 2. The thermal head according to claim 1, further comprising a coil connected between the drive circuit and the second Peltier element, the control means including the coil. 3. The thermal head according to claim 2, further comprising bypass means for short-circuiting the coil.