JPH0232871A - Thermal printer - Google Patents

Abstract

PURPOSE:To contrive a uniform printed density without need for assembly of a heater for a substrate or the like by causing a thermal head-driving circuit to perform preliminary energization of heat generating elements for a predetermined time before the start of a printing operation. CONSTITUTION:A known line-type thermal head 1 comprising a multiplicity of heat generating elements arranged in rows on a substrate and a thermal head-driving circuit 2 for controlling a printing operation by supplying printing pulses selectively to the elements, are provided. A preliminary energization controlling circuit 5 is provided between a data storage device 3 and the driving circuit 2. Energization at a predetermined level is applied to all of the heat generating elements arranged on the substrate of the thermal head 1, whereby the substrate is heated to a predetermined temperature. The driving circuit 2 drives the thermal head 1, and controls the printing operation for corresponding image data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] The present invention relates to a thermal printing apparatus using a line-type thermal head having a large number of heating elements arranged in rows on a substrate.

[Conventional technology]

Thermal printing devices using thermal heads, which are relatively easy to control and generate little noise, are now used in an extremely wide range of fields. Their functions have also become more sophisticated, and devices have been developed that can record and reproduce images with shading, that is, images with multiple gradations, with extreme fidelity.

As printing capacity improves, the requirements for image quality also become stricter. For example, when printing the background of an image at a constant density, a certain level of quality or higher is required for density unevenness in the main scanning direction or the sub-scanning direction.

Normally, when an image of a constant density is printed by a line-type thermal head without special control, and the printing density is measured in the sub-scanning direction, the result is as shown in FIG. 6.

FIG. 6 is a graph in which the vertical direction represents the print density and the horizontal direction represents the sub-scanning direction.

As you can see from this figure, even though a predetermined print pulse is supplied to the thermal head to print at the same density, the print density remains at the predetermined level for a certain period of time immediately after printing starts. The phenomenon of not reaching . This is based on the fact that at the start of printing, a part of the thermal energy generated by the heating element escapes to the substrate of the thermal head, and the energy for printing decreases accordingly.

Therefore, after printing several tens of lines, a predetermined stable printing density can be obtained.

If such density fluctuations occur, the quality of the printed image will be significantly degraded, so in the past, for example, a heater was built into the thermal head substrate, and after the printing device was turned on, the temperature of the thermal head substrate was kept at a predetermined temperature. Heat until
The method used was to control the temperature of the substrate at a constant level.

[Problems to be Solved by the Invention] However, in order to manage the temperature of the substrate of the thermal head, a control circuit or the like is required to appropriately turn on/off the heater incorporated in the substrate of the thermal head.

Additionally, devices incorporating such a mechanism need to wait several minutes after turning on the power until they are ready to print.
There was a problem that it could not be used immediately.

The present invention has been made with attention to the above points, and an object of the present invention is to provide a thermal printing device that does not require the incorporation of a heater into the substrate and achieves uniform printing density in the sub-scanning direction in a line-type thermal head. The purpose is to

[Means for Solving the Problems] A thermal printing apparatus of the present invention includes a line-type thermal head formed by arranging a large number of heat-generating elements in a row on a substrate, and selectively applying printing pulses to the heat-generating elements. a thermal head drive circuit that supplies electricity and controls the printing operation; and a preliminary energization control circuit that instructs the thermal head drive circuit to pre-energize the heating element for a predetermined period of time before starting the printing operation. It is characterized by having the following.

[Effect]

The above-described apparatus performs preliminary energization of the heating element before starting the printing operation, and raises the substrate temperature around the heating element to a predetermined temperature.

In addition, in this preliminary energization, in the normal case, for example,
A heating element is made to generate heat within a temperature range at which thermal paper does not develop color or ink from thermal transfer paper is not transferred.

On the other hand, if the thermal transfer paper has a non-ink-coated area, that is, a non-ink-coated area, if preliminary energization is performed on this non-ink-coated area, the heating element will generate heat at a high temperature, and the substrate will be quickly heated. It can be raised to a predetermined temperature.

〔Example〕

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of a thermal printing apparatus of the present invention.

This device includes a known line-type thermal head 1 in which a large number of heating elements (not shown) are arranged in a row on a substrate;
It has a thermal head drive circuit 2 that selectively supplies printing pulses to the heating elements to control printing operations. In addition, a data storage device 3 that stores image data for printing, and an address counter 4 that controls reading of image data from the data storage device 3 are provided.

The thermal printing apparatus of the present invention further includes a preliminary energization control circuit 5 inserted between the data storage device 5 and the thermal head drive circuit 2, as shown. The preliminary energization control circuit 5 includes a data selector 51 and a timing control circuit 52.

The data selector 51 receives the image data read from the data storage device 3 and the fixed data D output from the timing control circuit 52, selects one of them, and sends the image data to the thermal head drive circuit 2. This is a selection circuit for output. Further, the timing control circuit 52 is a circuit composed of a gate circuit and the like that outputs predetermined fixed data D and two types of control signals P+ and P2.

FIG. 2 shows a timing chart illustrating the contents of data output from the timing control circuit 52 and the operation of the apparatus of the present invention.

The timing control circuit 52 in the preliminary energization control circuit 5 shown in FIG. 1 outputs two types of control signals P1 and P2 as shown in FIGS. 2(a) and (b).

First, the control signal P1 falls at time t1, and at time t3
This is the signal that rises again. Further, the control signal P2 is a signal that falls at time t2 and rises at time t3. The thermal head 1 operates while the control signal P+ is at low level, and the address counter 4 operates while the control signal P2 is at low level.
is assumed to output an address signal for controlling readout of the data storage device 3.

Note that this device, as shown in FIG.
Until time t2, preliminary energization is performed to heat the substrate of the thermal head 1 to a predetermined temperature, and between time t2 and time t3, according to the image data read out from the data storage device 3 shown in FIG. , execute a predetermined printing operation.

In addition, fixed data D is output from the timing control circuit 52 during the preliminary energization time, that is, from time t1 to time t2 [FIG. 2(C)]. This fixed data D
is a level-adjusted signal so that when supplied to the thermal head drive circuit 2, the thermal head 1 generates heat to a level immediately before it colors the thermal paper or transfers ink to the thermal transfer paper.

Furthermore, when the control signal P2 is at a high level, the data selector 51 selects the fixed data D and outputs it to the thermal head drive circuit 2, and when the control signal P2 falls, it selects the fixed data D and outputs it to the data storage device 3. The circuit operates to select the image data M output from the thermal head drive circuit 2 and output it to the thermal head drive circuit 2.

When starting a printing operation using the circuit configured as described above, first, before starting the printing operation, the timing control circuit 52 of the preliminary energization circuit 5 lowers the control signal P1 at time t1. At the same time, the timing control circuit 52 outputs the fixed data D to the data selector 51. At this time, the control signal P2 is still at a high level, the address counter 4 does not start counting, the data selector 51 selectively outputs the company's data D to the thermal head drive circuit 5, and the thermal head 1 accordingly Power supply starts. That is, a predetermined level of current is applied to all of the heating elements arranged on the substrate of the thermal head 1, and the temperature of the substrate is raised to a predetermined temperature.

Next, when the control signal P2 falls at time t2, the address counter 4 starts supplying addresses to the data storage device 3 at a predetermined timing. The image data M read from the data storage device 3 by this address signal is input to the data selector 51. At this time, since the control signal P2 is falling, the data selector 51 selects the image data M and sends it to the thermal head drive circuit 2.
[Fig. 2(d)]. As a result, the thermal head drive circuit 2 drives the thermal head 1 and controls the printing operation for the corresponding image data. That is, as shown in FIG. 2 (8), fixed data for preliminary energization is first input to the thermal head drive circuit 2, and then image data for printing is input.

If the above control is performed, the heating element is pre-energized for a predetermined period of time before printing starts, and printing is started after the substrate has risen to a predetermined temperature. can be executed.

Incidentally, in the above embodiment, the fixed data D output from the timing control circuit 52 is such that the heating element conducts electricity at a relatively low level so as not to color the thermal paper. However, if the pre-energization energy is large, the pre-energization time can be made shorter. This can be accomplished by using thermal transfer paper as shown in FIG.

FIG. 3 is a plan view showing an embodiment of a thermal transfer paper suitable for carrying out preliminary energization as described above.

This thermal transfer paper 6 has ink coating areas 7 of several colors arranged on a base film. The ink application areas 7 adjacent to each other are, for example, yellow (Y),
Magenta (M) and cyan (C) color ink is applied. Here, on this thermal transfer paper 6, an ink non-applied area 8 is provided with a predetermined width between each ink applied area 7.

When printing using such thermal transfer paper 6, the third
As shown by the broken line in the figure, first, the thermal head 1 is made to face the non-ink applied area 8 and preliminary energization is performed. Then, when the preliminary energization is completed, the thermal head 1 during sub-scanning is set so as to just reach the ink application area 7. Thereafter, a printing operation is performed, and the thermal head is sub-scanned during the width of the figure, and the printing operation is completed.

If such a thermal transfer paper 6 is used, the thermal head 1 does not face the ink application area 7 during preliminary energization, so printing will not be performed even if the heating element is made to generate heat at a high temperature.

Therefore, it is possible to raise the substrate to a predetermined temperature in a shorter time, and it is possible to cope with the case where high-density printing is performed at the same time as printing starts.

The present invention is not limited to the above embodiments.

The configuration of the preliminary energization control circuit described above only needs to have a function of instructing the thermal head drive circuit 2 to execute preliminary energization, and can be freely replaced with a known circuit having an equivalent function. Further, the output of the control signals Pz, P2 and the fixed data D may be performed in a control circuit other than the preliminary energization control circuit.

〔Effect of the invention〕

According to the thermal recording device of the present invention described above, the thermal head substrate is preliminarily heated using the heating element provided in the thermal head. There is no need to provide a circuit for controlling the heater. Furthermore, since the drive circuit itself directly controls the thermal head drive circuit that prints image data, it is possible to equalize printing density and improve image quality with a relatively simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the thermal printing apparatus of the present invention, and FIG. 2 is a timing chart explaining its operation.
FIG. 3 is a front view of thermal paper used in another embodiment of the present invention, and FIG. 4 is a graph illustrating changes in print density of a conventional thermal printing apparatus. DESCRIPTION OF SYMBOLS 1... Thermal head, 2... Thermal head drive circuit, 3... Data storage device, 4... Address counter, 5... Preliminary energization control circuit, 6... Thermal paper, 7
...Ink application area, 8...Ink non-application area, 5
1-...Data selector, 52...Timing control circuit. Patent applicant Kunio Kakiki, representative of Victor Japan Co., Ltd. Figure 1

Claims (1)

[Claims] 1. A line-type thermal head consisting of a large number of heating elements arranged in rows on a substrate, and printing pulses being selectively supplied to the heating elements to control printing operations. A heat sensitive device characterized by comprising: a thermal head drive circuit; and a preliminary energization control circuit that instructs the thermal head drive circuit to carry out preliminary energization of the heating element for a predetermined period of time before the start of the printing operation. Printing device. 2. When printing using thermal transfer paper, the thermal transfer paper is provided with an ink-free area, and the preliminary energization control circuit turns on the preliminary energization when the thermal head faces the ink-free area. 2. The thermal printing apparatus according to claim 1, wherein the thermal printing apparatus performs the following steps.