JPH0632940B2 - Thermal printer - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer, and more particularly to a thermal printer that records using a heating resistor as a printing element.

(Prior Art) Conventionally, a line thermal printer that performs heating by adding heat generation amount according to an input signal to a heating resistor array formed by arranging a plurality of heating resistors in the main scanning direction performs simultaneous driving for one line. As a result, the current consumption of the entire device becomes large, and accordingly, the power supply capacity is extended and the device becomes large-scale and expensive. Therefore, at present, a decomposition drive method in which the heating resistor array is time-divided into a plurality of blocks is used.

In this method, the recording density by the heat-generating low-antibody column having the block length L is low because both ends of the block length L have a higher heat-radiating effect than the central portion when the same heat-generating factor amount is applied to each heat-generating low-antibody. Become. Particularly when gradation recording is performed, since the recording is performed in the unsaturated region of the color density, the density difference is remarkable. Therefore, in the print result, the print density becomes low at the block dividing points between the blocks in the paper transport direction (sub-scanning direction), and the density unevenness becomes conspicuous as a white vertical line. In order to prevent this, if the amount of heat generating member applied to each heat generating resistor of the heat generating resistor array having the block length L is varied according to the difference in heat radiation effect, it is possible to record at a uniform density.

However, in the conventional method as described above, the heat generation factor amount / coloring density characteristic is set to different values at both ends and the central portion of the block length L, and the heat generation factor amount is influenced by the ambient temperature and the temperature of the thermal head itself. However, it requires a very complicated control method in terms of a circuit, and has a drawback that the device becomes expensive.

In order to solve this problem, for example, JP-A-61-126867
There is a thermal printer disclosed in the publication. A configuration diagram of this thermal printer is shown in FIG. In the figure,
Reference numeral 1 is a thermal recording head, which is composed of n heating resistors 1a.
× N sets of heating resistor rows (1-1 to 1-12, where M × N =
12 cases) are arranged in a straight line.

Reference numeral 2 denotes a driver circuit, which includes a switching element (for example, a transistor or the like) corresponding to each of the heating resistors and driver means (may be one) for turning on the switching element. When both the common gate signal and the record data are print instructions, the switching element is activated by the driver means, and the heat generation factor amount is printed on the heat generating resistor 1a from the common power source (not shown). Reference numeral 3 denotes a shift register, which outputs a drive signal to a switching element in the driver circuit 2 corresponding to each heating resistor 1a based on externally recorded data. A common gate 4 is a driver selection circuit 5 described later.
The common gate signal from the device is passed based on a gate control signal (not shown), and an AND gate element or the like is used. Reference numeral 5 is a driver selection circuit, and each heating resistor row (1-1
~ 1-12) Common gate signal 4-to 4-1 for driving each
2 is supplied to the driver circuit 2.

One end of the n heating resistors 1a in the thermal recording head 1 is connected to one end of a power source (not shown) as a common electrode, and the other end is one end of each of the n switching elements in the driver circuit 2. It is connected to the. The other ends of the n switching elements are connected to the other end of the power source.
The other ends of the n switching circuits in the driver circuit 2 are connected to the shift register 3.

Therefore, the thermal recording head 1 is driven by the switching element being activated by the logical product of the common gate signal from the driver selection circuit 5 and the recording data via the shift register 3 via the driver means in the driver circuit 2. . The M sets of heating resistor rows each consisting of N × n heating resistors are sequentially switched M times to complete scanning of one row.

Next, the operation of the driver selection circuit 5 in FIG. 3 will be described based on FIG. 4 showing a time chart of the common gate signal. However, M = 4 and N = 3.

First, after the record data is input to the shift register 3 for one row,
Common gate signal 4-1 to drive the first block
~ 4-3 is turned on, heating resistor array 1-1 to 1
Drive -3. Similarly, in the next adjacent block, the common gate signals 4-4 to 4-6 are turned on to turn on the heating resistor string 1-4.
Drive ~ 1-6. Similarly, in the third and fourth blocks, the heating resistor string 1 is also generated by the common gate signals 4-7 to 4-9.
-7 to 1-9 and the common gate signals 4-10 to 4-12 sequentially drive the heating resistor rows 1-10 to 1-12. In this way 3
The first row is recorded by driving four sets of heating resistor rows.

In the second line, after the data is input, the common gate signal is shifted to turn on the common gate signals 4-2 to 4-4, and then 4-5 to 4-7 are turned on in the same manner as in the first line. Turn on 8 to 4-10,
4-11 to 4-1 are sequentially divided and driven for recording.

Then, in the third line, common gate signals 4-3 to 4-5, 4-
6 to 4-8, 4-9 to 4-11, and 4-12 to 4-2 are turned on in this order to perform divided driving for recording.

In line 4 of FIG. 4, common gate signals 4-4 to 4-6, 4-
7 to 4-9, 4-10 to 4-12, and 4-1 to 4-3 are turned on in this order and divided driving is performed for recording.

While sequentially moving the block dividing points in this manner, the fifth line and the sixth line are recorded.

However, the thermal printer having such a configuration has the following problems.

The block to be driven is selected by reading the data stored in the ROM (not shown). According to the conventional technique as described above, however, since this data is different for every row, a large capacity ROM is required. Furthermore, since the block dividing points are sequentially moved from one end to the other end of the entire heating resistor array, for example, common gate signals 4-3 and 4-6 or 4-6 and 4-7 in the first row are added. Like the corresponding heating resistor row, adjacent blocks are driven continuously and continuously, so heat is transferred from the previously driven block to the next driven block, and the dots at the joints are It is preheated to a high temperature, resulting in a dark print density.
Further, for example, the common gate signals 4-3 and 4- of the first row
The dots of the heating resistor arrays corresponding to Nos. 6, 4 and 9 are low in temperature because they are exposed to heat, and there is a drawback that density unevenness is conspicuous as a white vertical line in the sub-scanning direction. In order to prevent these drawbacks, it is expected that good results will be obtained if the block division points are moved randomly, but control is complicated to realize a circuit that moves randomly, so stable printing is possible. Quality could not be obtained at low cost.

The present invention eliminates the above-described density unevenness as white vertical lines in the sub-scanning direction and eliminates the problem that the dots at the joints of blocks become dark, and provides an inexpensive thermal printer with excellent recording quality. The purpose is to

(Means for Solving the Problem) According to the present invention, a plurality of heating resistor arrays each formed of a plurality of heating resistors arranged in the main scanning direction are provided.
In a thermal printer that performs printing by applying a heat generation factor amount to each heating resistor by driving each block that is composed of a predetermined number of heating resistor rows as a unit, based on selection information, the heating resistor Drive means for dividing the body row into a predetermined number of blocks and driving them in a time division manner, and moving the division position of the block for each row to be printed by one heating resistor row to sequentially select the blocks to be driven, And a selection unit for giving selection information indicating the selected block to the driving unit. In the selection line, the blocks at both ends are sequentially driven first as the reference division position in the print start line, and then the inner block is selected. Select the blocks to be driven so that they are driven sequentially, and if the division position of each block matches the reference division position, drive in the same order as in the case of this reference division position. Thermal printer that is configured to select to drive block is provided as.

(Operation) Each block is divided into a predetermined number of heating resistor rows. The selecting means moves the block division position for each row to be printed by one heating resistor row, and in the print start row, blocks at both ends are sequentially driven first as reference division positions, and then inner blocks are sequentially driven. The blocks to be driven are selected as described above, and when the division position of each block matches the reference division position, the blocks to be driven are selected in the same order as in the case of the reference division position. Selection information indicating the selected block (corresponding to the above-mentioned common gate signal) is given to the driving means. The driving means sequentially drives each block based on the selection information.
In this way, the rows of heating resistors are driven in a time division manner to print each row.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 3 denote the same components. Reference numeral 6 denotes a driver selection circuit corresponding to the driver selection circuit 5 shown in FIG. 3. The control of the driver circuit 2, that is, the timing of sending the common gate signals 4-1 to 4-12 is different from the conventional one. FIG. 2 shows a time chart of the common gate signal of the driver selection circuit 6 of this embodiment.

Next, the operation of this embodiment will be described with reference to FIGS. However, M = 4 and N = 3.

First, after the record data is input to the shift register for one row, the common gate signals 4-1 to 4-3 are turned on in order to drive the N (= 3) sets of heating resistor rows at the start of recording.
Each driver circuit 2 connected to this is turned on to drive the heating resistor rows 1-1 to 1-3. Next, common gate signal 4
-10 to 4-12 are turned on, and heating resistors 1-10 to 1-12 are also turned on.
To drive. Hereinafter, the common gate signals 4-4 to 4-6 will be sequentially described.
Is turned on, then 4-7 to 4-9 are turned on and N (= 3)
The set of heating resistor rows is dividedly driven M (= 4) times to record one row.

In the second line of the next line, the common gate signals 4-2 to 4-4 are turned on by recording start after data input. After turning on the common gate signals 4-1, 4-11, 4-12 as in the first row,
The common gate signals 4-5 to 4-7 are turned on, and finally the common gate signals 4-8 to 4-10 are turned on and the second row is recorded.

Then, in the third line, common gate signals 4-3 to 4-5 are turned on, and 4-1, 4-2 and 4-12 are turned on, and 4-6 to
Turning on 4-8 Finally, turning on 4-9 to 4-11, the third line is recorded.

In the fourth line, the common gate signals 4-1 to 4-3 are turned on, 4-10 to 4-12 are turned on, 4-4 to 4-6 are turned on, and 4-9 to 4-11. Is turned on and the fourth line is recorded.

When division driving is performed in this manner, the block division positions from the first row to the third row are moved row by row and become the same as the block division positions on the first row on the fourth row. Further, since the paper is fed between each row, the same block is not continuously driven, and the adjacent blocks are less likely to be driven.

(Effect of the Invention) As described above, according to the present invention, in the print start line, the blocks to be driven are set such that the blocks at both ends are sequentially driven first and the inner blocks are then sequentially driven as the reference division position. When the divided position of each block coincides with the reference divided position when selected, each block to be driven is selected in the same order as in the case of the reference divided position, so that the adjacent blocks are continuously driven. The block consisting of the same combination of heating resistor rows is driven at a very short cycle and at the same print timing of the row while reducing the number of lines. As described above, since it is possible to realize the selection of the block to be driven while reducing the number of times of driving the adjacent block successively, it is possible to store the drive block selection data R
The capacity of the storage means such as the OM can be greatly reduced, and the recording quality can be improved with a simple and inexpensive structure.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
3 is a block diagram of a conventional thermal printer, and FIG. 4 is a time chart of a conventional common gate signal. 1 ... Thermal recording head, 1a ... Heating resistors 1-1 to 1-12 ... Heating resistor string, 2 ... Driver circuit 3 ... Shift register, 4 ... Common gate 6 ... Driver selection circuit

Claims (1)

[Claims] 1. A plurality of heating resistor arrays each of which is composed of a plurality of heating resistors arranged in the main scanning direction, with each block consisting of a predetermined number of the heating resistor arrays as a unit. In a thermal printer that performs printing by applying a heat generation factor amount to each heating resistor by driving, a driving unit that divides the heating resistor row into blocks of a predetermined number based on selection information and drives in time division And a selecting means for sequentially selecting blocks to be driven by moving the division position of the blocks by one heating resistor column for each line to be printed and giving selection information indicating the selected blocks to the driving means. The selection means selects a block to be driven so that blocks at both ends are sequentially driven first and then inner blocks are sequentially driven as reference division positions in the print start line. In addition, when the division position of each block matches the reference division position, it is configured to select a block to be driven so as to be driven in the same order as in the case of the reference division position. Thermal printer.