JPS6168269A - Thermal printer with preheating means - Google Patents

Abstract

PURPOSE:To save independent heat sources for preheating and accelerate radiation of heat from a driving circuit, by preheating a thermal recording paper through utilizing waste heat from the driving circuit. CONSTITUTION:Air heated by heat generated by the driving circuit 2 is directed as close as possible to the direct upstream of a thermal head by an airflow guide 7 and a fan 6, and hot air is blown to either one or both of an image- receiving sheet 9 and an ink sheet 4 through a blow-off port 7a to preheat the one or both of the sheets 9, 4. In the figure, the guide 7 has a part thereof broken off so that the fan 6 and the driving circuit 2 enclosed therein can be seen. Thus, the fan 6 and the guide 7 constitute the preheating means. Accordingly, it is unnecessary to provide independent heat sources for preheating, and radiation of heat from the driving circuit is accelerated. In addition, since the recording paper is preheated, the current-passing time for each printing dot can be shortened, so that printing speed is enhanced, and printing can be conducted by consuming a smaller amount of electric power.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a thermal printer used for thermal image recording, and particularly to a thermal printer provided with preheating means.

(Background of the Invention) A method of reproducing an image in the form of a photocopy, such as a photograph, from an electrical image signal obtained from a television, video camera, video disc, electronic camera, etc. has been actively researched. The most effective method among these is the thermal image recording method that uses a thermal printer.Basically, this thermal printer uses a large number of resistor dots arranged in a line in the main scanning direction and energizes each dot. A thermal head (1) consisting of a pair of electrode groups for the dots, and a drive circuit (1) for selectively energizing and generating heat in the dot groups based on image signals.
2) It is made up of. Then, heat-sensitive recording paper (this includes not only heat-sensitive color-forming types but also those in which an image-receiving sheet and a heat-transferable ink sheet are layered) is placed in the thermal head.
The dots are selectively energized and heated based on the input image signal, one line of pixels is printed on the recording paper by this heat, and the recording paper is then moved one line.
Printing and movement are repeated in the same way based on the image signal of the next row, thereby completing one two-dimensional image.

By the way, in order to obtain the desired density on the recording paper by energizing the dots, the ink layer and the recording paper must reach a recordable temperature, but the presence of the ink support between the dots and the recording paper reduces the heat conduction efficiency. This makes high-speed printing difficult.

Therefore, it has been proposed that a preheating means be installed in front of the head to heat the recording paper in advance to near the recordable temperature.
(For example, JP 58-98275, JP 58-9827
6, No. 58-128878).

However, all of the proposed preheating means are new heating elements such as radiant phasors, and therefore have the disadvantage that power consumption is correspondingly high for thermal printers.

(Object of the Invention) An object of the present invention is to provide a thermal printer that preheats without providing such a new heating element.

(Summary of the invention) The thermal printer has a drive circuit as described above, which takes in a 100 port AC IF source and rectifies it.
In addition, there is a constant voltage circuit that steps down the voltage to about 10 ports and stabilizes it, and the constant voltage circuit generates a relatively high amount of heat.
Since the circuit itself is damaged due to the heat generated, it is necessary to actively dissipate (cool) the heat using a heat sink or other means.

The present inventors have discovered that by using the high heat generated by this drive circuit as a heat source for preheating, heat dissipation and preheating can be performed at the same time.
As a result, they came up with the idea of reducing power consumption, and came up with the present invention.

Therefore, the present invention provides a thermal printer including a thermal head (1) and a drive circuit (2) for selectively energizing and generating heat in the resistor dots of the thermal head based on an image signal. To provide a thermal printer characterized in that it is provided with a preheating means for preheating a thermosensitive recording paper by guiding the heat generated in the circuit (2).

Examples of preheating means used in the present invention include (1
(2) A method uses air as a heat medium and preheats the thermal recording paper by guiding the heated air in front of the head using a fan and a blower guide, and (2) A method uses a heat pipe as a heat medium. Hereinafter, the present invention will be explained in more detail with reference to Examples.

(Example 1) Fig. 1 is a perspective conceptual diagram showing the main parts of the thermal printer of this example, with a part of the ventilation guide (7) H partially cut out, and the inside fan (4) and drive circuit ( 2) should be visible. In Figure 1, (1) is a thermal head,
(2) is a drive circuit, (3) is an ink sheet supply roller,
(4) is an ink sheet, (5) is an ink sheet take-up roller, (6) is a fan, (7) is an air blowing guide, (8) is a platen, and (9) is an LD image receiving sheet.

The drive circuit (2), especially the constant voltage circuit, may be placed in the position shown in the figure, but the air heated by the heat generated here is transferred to the thermal head using the blower guide (7) and the blower fan (4). the air outlet (7a).
Hot air is blown toward either or both of the image receiving sheet (9) and the ink sheet (4) to preheat them.

Therefore, here we introduce the fan (4) and the ventilation guide" (7).
) constitutes the preheating means of the present invention.

(Example 2) FIG. 2 is a perspective conceptual diagram showing the main parts of the thermal printer of this example. In the figure, (1) is the thermal head, (
25 is a box containing the drive circuit (2), (3) is an ink sheet supply roller, (4) is an ink sheet, (5) is an ink sheet take-up roller, (8) is a platen, (9)
is an image receiving sheet, (10) is a heat pipe, and (11) is a preheating rod.

The heat generated in the drive circuit (2) is absorbed by the heat absorption part of the heat pipe (10) through the air in the box (η), and is radiated by the heat radiation part of the heat pipe to heat the preheating rod (11). Then, the heated preheating rod (11) comes into contact with either or both of the image receiving sheet (9) and the ink sheet (4) to preheat them.

Therefore, here, the beat pipe (1 piece) and the preheating rod (1 piece) constitute the preheating means of the present invention.

A temperature sensor is provided just before the thermal head (1) to detect the degree of preheating of the image receiving sheet (9) or ink sheet (4), and feeds back this detection signal to the drive circuit (2) to control the thermal head. The optimum printing temperature may be maintained by controlling the voltage value or applied pulse width applied to the resistor dots of the head.

(Effects of the Invention) As described above, in the present invention, waste heat from the drive circuit is used to preheat the thermal recording paper, so an independent preheating source can be saved.
Therefore, power consumption is reduced and heat dissipation from the drive circuit is also promoted. Note that by preheating the recording paper, the printing speed becomes faster (because the time when electricity is applied to the dots can be shortened), and less power is required.On the other hand, by preheating the ink sheet, Wrinkling can also be prevented when condenser paper is used as the ink sheet paste.

[Brief explanation of drawings]

FIG. 1 is a conceptual perspective view of the main parts of a thermal printer shown in Embodiment 1 of the present invention. FIG. 2 is a conceptual perspective view of the main parts of a thermal printer according to a second embodiment of the present invention. [Explanation of symbols of main parts] 1... Thermal head 2... Drive circuit 3... Ink sheet supply roller 4...
Ink sheet 5... Ink sheet take-up roller 8...
・Platen 9...Image receiving sheet

Claims (1)

[Scope of Claims] A thermal printer comprising a thermal head (1) and a drive circuit (2) for selectively energizing and generating heat in resistor dots of the thermal head based on an image signal, comprising: A thermal printer characterized by being provided with a preheating means for preheating thermal recording paper by guiding the heat generated in the circuit (2).