JPS6210136Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a thermal recording device such as a thermal printer or a thermal transfer printer. More specifically, the present invention can be used for example in 24×24 or 1
This invention relates to a heat-sensitive recording device that records characters, figures, etc. on a sheet of paper in a dot matrix by moving a heating head having 24 x 24 dot heating elements in a predetermined direction on the sheet of paper.

The recording density in such a thermal recording device is
Generally, it is determined by the thermal energy applied from the heating element to the color forming agent or transfer agent, and when thermally driven with high thermal energy, a dark recording is produced, and when thermally driven with low thermal energy, This is a poor record. On the other hand, the heat generating head is composed of a substrate with a certain area and a plurality of heat generating elements, and has a certain heat storage effect. For this reason, when recording is performed while moving the thermal head in one direction at high speed, the temperature of the thermal head itself gradually rises due to the heat storage effect. The disadvantage is that the recording becomes darker as it moves.

In order to eliminate these drawbacks, the heat storage effect of the thermal head can be eliminated, or the next thermal drive can be performed after waiting for the temperature of the thermal head to drop to a predetermined temperature. However, the former method is difficult in practice, and the latter method has the problem of not being able to perform high-speed recording.

It is an object of the present invention to provide a heat-sensitive recording device that can perform high-speed recording with uniform density with a simple configuration.

The device according to the present invention stores paper to be recorded.
The special feature is that the preheating plate is used to preheat the heat head so that there is a temperature gradient in the direction of movement of the heat head.

FIG. 1 is a perspective view showing an example of a device according to the present invention. Here, a case of a thermal transfer recording device will be exemplified. In the figure, 1 is a thermal head, 2 is a transfer ribbon in contact with the thermal head 1, 3 is a sheet of paper on which the ink layer of the transfer ribbon 2 is melted by the thermal energy of the thermal head 1, and recording is performed, and 4 is a sheet of paper on which recording is performed. It is a platen. Thermal head 1 and transfer ribbon 2
is mounted on a movable plate 10 that moves along a guide shaft 11, and is moved in the direction of arrow a via a thread 12 by a step motor 13 to perform recording. Further, the paper 3 is fed out by a certain amount in the direction of arrow b every time the thermal head 1 scans.

Reference numeral 5 denotes a preheating plate, which is a feature of the present invention, and is installed below the platen 4 (on the side from which the paper is fed out) so that the paper 3 is preheated before recording. As shown in FIG. 2, the preheating plate 5 has a triangular shape such that the width c in the conveying direction of the paper 3 (direction of arrow b) becomes narrower in the direction of movement of the thermal head 1 (direction of arrow a). It is configured. Although not shown, an electric heater is coupled to the preheating plate 5 to heat the preheating plate 5.

FIG. 4 is a connection diagram showing an example of a temperature control circuit for the electric heater 50 coupled to the preheating plate 5. FIG.
This circuit includes a bridge circuit B having a temperature detection element (for example, a thermistor) Rt for detecting room temperature, and controls the heating temperature of the preheating plate 5 according to the room temperature.

According to the device configured in this way, the paper 3 fed out in the direction of the arrow b is preheated at the preheating plate 5, and the temperature of the paper gradually rises, so that the paper temperature at each position in the moving direction of the thermal head 1 is adjusted. corresponds to the time during which the paper 3 is in contact with the preheating plate 5. Therefore, if the paper 3 is sequentially fed out in the direction of arrow b at a predetermined pitch at regular intervals, the preheating time will be longer for the left side portion of the paper 3 that has passed through the wide part of the preheating plate 5. Therefore, the right side of the paper, which has a high temperature and has passed through a narrow part, has a lower temperature because the preheating time is shorter, creating a temperature gradient as shown in Figure 3 in the direction of movement of the thermal head 1. The paper 3 is preheated so that it lasts. In addition,
In FIG. 3, the x-axis indicates the position of the paper in the direction of arrow a.

Note that the temperature gradient shown in FIG. 3 varies depending on the shape of the preheating plate 5, the temperature of the preheating plate 5 itself, the quality and thickness of the paper 3, the feeding speed of the paper 3, etc. Considering these conditions, the preheating plate 5
The shape of the preheating plate 5 and the temperature of the preheating plate 5 itself are determined.

In this way, when the paper 3 is preheated so that its temperature gradually decreases in the direction of movement of the thermal head 1, the paper temperature compensates for the increase in temperature of the thermal head itself due to the heat storage effect of the thermal head 1. Therefore, regardless of the moving position of the thermal head 1, uniform density recording can be performed at high speed.

In the above embodiment, a temperature gradient is created in the width direction of the paper by changing the shape of the preheating plate 5, but the preheating plate 5 is made into a flat plate and a plurality of electric heaters are used. The temperature of the preheating plate 5 itself may be made to have a gradient in the direction of the arrow a by providing two or more.

Further, although the case where thermal transfer recording is performed is illustrated here, the present invention can be similarly applied to a thermal printer or the like in which the paper is thermal paper.

As described above, according to the present invention, it is possible to realize a thermal recording device that can perform high-speed recording with uniform density.

[Brief explanation of the drawing]

Figure 1 is a perspective view of the main parts of an example of the device according to the present invention, Figure 2 is a diagram of the configuration of a preheating plate used in the device shown in Figure 1, and Figure 3 shows the preheating temperature distribution of paper. FIG. 4 is a temperature control circuit diagram of an electric heater connected to a preheating plate. 1... Heat head, 2... Transfer ribbon, 3... Paper, 4... Platen, 5... Preheating plate.

Claims (1)

[Scope of claims for utility model registration] (1) In a thermal recording device having a heat generating head,
A thermal recording device is provided with a preheating plate for preheating paper to be recorded, and the preheating plate preheats the paper so that the temperature of the paper gradually decreases in the direction of movement of the thermal head. (2) The thermal recording device according to claim 1, which uses a substantially triangular preheating plate whose width in the paper conveyance direction gradually narrows in the direction of movement of the thermal head.