JPS623565A - Driving system for thermal head - Google Patents

Abstract

PURPOSE:To prevent uneven contrast of recording by using plural heaters not adjacent to each other in heaters on a line thermal head as one block, dividing all the heaters into plural blocks and driving sequentially each block to reduce the effect from the adjacent heaters. CONSTITUTION:Plural heaters not adjacent to each other in heaters on the line thermal head are used as one block, all the heaters on the line thermal head are divided into plural blocks and each block is driven sequentially. For example, 64 heaters each selected out of 512 heaters at an interval of 7 heaters in a line thermal head are used as one block and the total heaters are into 8 blocks. Then one block is driven at first as the order of application of voltage and the voltage is applied sequentially to the left side block at an interval of two heaters afterward. Then the heaters are always heated from the heaters heated just before at an interval of at least two heaters, then the effect of residual heat of other heaters is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for driving a line thermal head used in a thermal printer that records information entirely by heat sensitivity or thermal transfer.

<Summary of the Invention> The present invention is a method for driving a line thermal head used in a thermal printer that thermally performs two recordings. By dividing the entire heating element into a plurality of blocks and sequentially driving each block, it is possible to prevent unevenness in recording density.

<Prior art> In a thermal printer using a general line thermal printer, recording is performed by applying electric power to each heating element on the line thermal head, but when trying to record one entire line at a time, For example, 5 on the line thermal head.
Assuming that there are 12 heating elements and the maximum power required for one heating element is O, SW, a power supply that can supply instantaneous power of 512 x 0.5 = 256 W to record one entire line in black. The problem has been that the power supply device becomes larger and the cost becomes higher.

In order to solve this problem, conventionally, as shown in FIG. 3, a fixed number of mutually adjacent heating elements on the line thermal head are grouped together and divided into a plurality of blocks.
A method is used to reduce the instantaneous power by applying one-time power to each block for recording.

For example, if 512 heating elements are divided into 8 blocks of 64 heating elements, the maximum power required for one heating element is 0.
Assuming that it is 5W, even when recording one entire line in black, it can be driven with a power supply device that can supply instantaneous power of 512×0.5÷8=32W.

<Problem to be solved by the invention> However, in the conventional method described above, the heating element that generates heat only on one side of the adjacent heating element is the same as the heating element that generates heat on both sides of the adjacent heating element temperature becomes lower. (Figure 4 shows the temperature distribution when the line thermal head is activated. In this figure, the solid line is the temperature distribution of each block, and the broken line is the temperature distribution of the entire line thermal head.) For this reason, as shown in Figure 4, the temperature is high at the center of each block, and the temperature decreases toward both ends.When looking at the entire line thermal head, this occurs at the boundaries of each block, as shown by the broken lines. There will be areas where the temperature is low.

Therefore, when printing with such a line thermal head, density differences occur at the same position for each line, and when viewed from the printed paper itself, many white lines appear in the vertical direction, which impairs the recording quality. was occurring.

<Means for Solving the Problems> In the present invention, a plurality of heating elements that are not adjacent to each other among the heating elements on the line thermal head are made into one block,
All of the heating elements on the line thermal head are divided into blocks γ, and each processor is sequentially driven.

<Function> Therefore, it is possible to reduce the influence from adjacent heating elements and prevent unevenness in recording density.

<Embodiments> (a) First Embodiment Table 1 shows the block division state of the heating element on the line thermal head driven by this drive method.

First, in this embodiment, one line is divided into four blocks and all recording is performed. As shown in Table 1, one pronk is divided into 128 heating elements selected from every third heating element out of the 512 heating elements that make up the line thermal head.

Table 1 Next, a circuit for performing the above operation will be explained using FIG. 1.

First, one line of gradation data to be recorded is sequentially input to the address bus of the RAM 2 by software according to the calculation time of cpMx.

RAM 2 stores data calculated in advance by performing processing such as color correction and gradation correction from the gradation data of one pixel.
Written from CPUI.

Therefore, correction data corresponding to the gradation data is converted and output from the RAM 2 in real time, and the data is written into the line memory (RAM 3). The output of the counter 6 and the output of the counter 7 are inputted to the RAM 3 via the multiplexer 9, and the output of the counter 6 is inputted to the address when writing, and the output of the carantuff is inputted to the address when reading.

When 1 line of 512 bytes of data is written to RAM3, RAM3 goes into read mode.Reference clock 4
The count 7 is sequentially counted up at MHz, and the output thereof is inputted to the address of RAM "3" via the multiplexer 9.

On the other hand, 2 bits of preset data corresponding to bronc 5 is input from the CPU 1 to the flip-flop 10 and latched. Every time the counter counts 512, the counter increases by 8 or 1.

The output of the counter 8 and the data in the RAM 3 are passed through the comparator 4 and converted into head data of serial data.

Head data is 1" when RAM3≧count 8
Outputs “O” when RAM3 < count 8.

XNOR11 is the preset data (2 bits) output from the CPU via the flip-flop 110 and the
The input signal to the comparator 4 is controlled so that the conversion operation is executed when the address output (lower two bits) of M3 match.

CP tJ I The recording time data for one gradation is input to the latch circuit 12, and its output and oscillator 13 (100KHz
) is used as an input clock and the comparator 15 compares the outputs of the recording time counter 2. If they match, a one-shot signal is generated, and i'L is used as a head latch signal. Once the first hendranch signal of each block is counted by counter 7, it is 512.
When counted, a one-shot signal is generated.

A reference clock 4λ...2 is input as a head clock signal.

When the counter 8 matches the number of gradations, the head strobe signal is turned off, and recording of one block is completed. It is managed by ``Pro7ri End 1d'cPU''.

In order to record the next block, preset data is input to the flip-flop 10 from the CPUI, and the following operations are the same as above, and the shell line recording is completed by returning the 4 lines (b) Second embodiment FIG. 2 shows the voltage waveform applied to the heating element on the cylindrical thermal head by this driving method.

In this embodiment, the line thermal head has 512 heating elements, each of which is divided into eight blocks, with 64 heating elements selected from every seventh heating element as one block. As for the order of voltage application, one block is first driven, and then the voltage is sequentially applied to the blocks on the left, which are opened by two heating elements each. Therefore, the heating element that generates heat immediately before it always generates heat with an interval of at least two heating elements, so that it is not affected by the residual heat of other heating elements.

<Effects of the Invention> As described above, in this invention, a plurality of closely adjacent heating elements among the heating elements on the line thermal head are divided into a plurality of blocks, and each heating element is divided into a plurality of blocks. By sequentially driving the blocks, it is possible to reduce the influence from adjacent heating elements and prevent uneven shading in the recording, and there are no vertical white lines on the recorded paper, which improves the recording quality. can be improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a control circuit used in a first embodiment of the present invention. FIG. 2 is a voltage waveform diagram applied to a heating element on a line thermal head according to a second embodiment of the present invention. Figure 3 is a diagram of the voltage waveform applied to the heating element above the line thermal generator driven by the conventional method, and Figure 4 is the voltage waveform diagram applied to the line thermal generator driven by the conventional method.
FIG. Agent Ben Sokushi Fukushi Aihiko (and 2 others) Sunamoto 54
15/f:xD

Claims (1)

[Claims] 1. In a thermal printer that performs thermal recording using a line thermal head in which a plurality of heating elements are arranged in series, a plurality of heating elements that are not adjacent to each other among the heating elements on the line thermal head are connected to one another. The thermal head driving method comprises dividing all the heating elements on the line thermal head into a plurality of blocks and sequentially driving each of the blocks.