JPS6372560A - Thermal printer - Google Patents

Abstract

PURPOSE:To remove density irregularity as the white longitudinal line in a sub-scanning direction, by dividing a heat generating resistor row into a plurality of blocks and selecting the blocks Spaced apart from each other in a predetermined order. CONSTITUTION:At the start time of recording, at first, common gates 4-1, 4-3 are turned ON in order to drive three sets of heat generating resistor rows and the driver circuits 2 connected to said gates are turned ON to drive heat generating resistor rows 1-1-1-3. Next, common gates 4-10-4-12 are turned ON to drive heat generating resistor rows 1-10-1-12 in the same way. Hereinafter, common gates 4-4-4-6 are turned ON and, subsequently, common gates 4-7-4-9 are turned ON to drive N(=3) sets of the heat generating resistor rows M times in a divided state to record the second line. The third line is recorded by turning the common gates 4-3-4-5 ON and, at the time of the recording of the fourth line, the block dividing positions of the heat generating resistor rows become the same to those of the first line. Further, paper feed is performed between respective lines and the driving of the block continuously adjacent to the same block is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thermal printer, and more particularly to a thermal printer that performs recording using a heating resistor as a printing element.

(Prior Art) Conventionally, a line thermal printer that performs printing by adding a heat amount according to an input signal to a heat generating resistor array formed by arranging a plurality of heat generating resistors in the main scanning direction performs simultaneous driving of one line. The current consumption of the entire device is large, and as a result, the power supply capacity and the device itself become large-scale and expensive. Therefore, a divisional driving method is currently used in which the heating resistor array is time-divided into a plurality of blocks.

In this method, the recording density due to the block-length heating resistor array is low because when the amount of heat generation factor applied to each heating resistor is the same, both ends of the block length have a higher heat dissipation effect than the center. Become.

Particularly when gradation recording is performed, the difference in density becomes noticeable because the recording is performed in an unsaturated region of color density.

Therefore, the printing result is that the printing density is low at the block dividing point between each block in the paper conveyance direction (sub-scanning direction).
The color is K so that uneven density becomes noticeable as a white vertical line. In order to prevent this, recording at a uniform density can be achieved by varying the amount of heat generation factor applied to each heat generating resistor in the block-length heat generating resistor array according to the difference in heat dissipation efficiency.

However, in the conventional method as described above, the amount of heat generation factor - color density characteristic is set to different values at both ends and the center of the block length, and the amount of heat generation factor is also affected by the ambient temperature and the temperature of the thermal head itself. Therefore, a very complicated control method is required in terms of circuitry, and the device is expensive.

In order to solve this problem, for example, JP-A-61-12
There is a thermal printer disclosed in Japanese Patent No. 6867.

A configuration diagram of this thermal printer is shown in FIG. In the figure, 1 is a thermal recording head, and MX'N-groups of heating resistor arrays (1-1 to 1-12) each consisting of n heating resistors 1 are shown.
, provided that MXN=12) are arranged in a straight line.

Reference numeral 2 denotes a driver circuit, which includes a switching element (for example, a transistor, etc.) corresponding to each heat generating resistor, and driver means (one piece may be enough) for turning on the switching element, and a driver selection circuit 5 to be described later. When the common gate signal from the printer and the recording data both become printing instructions, the switching element becomes active by the driver means,
The heating factor amount is printed on the heating resistor array from a common power source (not shown). 3 is 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 recording data from the outside. A common gate 4 passes a common gate signal from a driver selection circuit 5 to be described later based on a gate control signal (not shown), and uses, for example, an AND gate element. 5 is a driver selection circuit, which connects each heating resistor row (1-1 to
1-12) Common gate signal 4-1 that instructs driving for each
~4-12 are 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 connected to each of the n switching elements in the driver circuit 2. connected to one end. Further, each other end of the n switching elements is connected to the other end of the power supply.

The other ends of each of the n switching circuits in the driver circuit 2 are connected to the shift register 3.

Therefore, the switching element is activated via the driver means in the driver circuit 2 by the AND of the common gate signal from the driver selection circuit 5 and the recording data via the shift register 3, and the thermal recording head 1 is driven. . M sets of heat generating resistor arrays each consisting of NXn heat generating resistors are sequentially switched M times to complete scanning of one row.

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

First, after inputting one line of recording data to the shift register 3,
Common gate signal 4-1 to drive the first block
By turning on ~4-3, the heating resistor array 1-1~
Drives 1-3. Next, the adjacent block similarly turns on the common gate signals 4-4 to 4-6 to turn on the heating resistor row 1.
-4 to 1-6 are driven. Below is the third. Similarly, the fourth block also receives common gate signals 4-7 to 4-9, heat generating resistor rows 1-7 to 1-9, and common gate signals 4-10 to 4.
-12, the heating resistor rows 1-10 to 1-12 are sequentially driven. In this way, the first row is recorded by driving the three sets of heating resistor columns for four blocks.

In the second line, after inputting data, the common gate signal is shifted to turn on the common gate signals 4-2 to 4-4, and the following steps are performed.
Turn on 4-5 to 4-7 as in the row, 4-8 to 4-10
is turned on, and 4-11 to 4-1 are sequentially divided and driven to record.

Next, the third line sets the common gate signal to 4-3 to 4-5.4.
-6 to 4-8. 4-9 to 4-11. 4-12 to 4-2 are turned on in the order of division driving and recording.

In the fourth line, the common gate signal is 4-4 to 4-6.4-
7 to 4-9. 4-10 to 4-12. 4-1 to 4-3 are turned on in the order of division driving and recording.

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

However, the selection of the block to be driven is done by reading data stored in a ROM (not shown), and since this data differs from line to line, it is necessary to move the block dividing point sequentially to continue printing. There was a problem that a large capacity ROM was required.

Therefore, as shown by the broken line, the common gate signals 4-1, 4-2.
Turn on 4-3 first, and finally turn on 4-10.4-11.
Even if 4-12 is turned on and the drive is the same as in the first row of tb, no problem will occur in block division, right?
Since the driving sequence of the common gate signal can be controlled in many ways from the 1st to 3rd lines, the ROM that controls this
It has the advantage of requiring less capacity. Therefore, conventionally, as shown by this broken line, the block division points from the first row to the third row are sequentially moved so that the fourth row becomes the same as the first row.

In this way, the 5th line is the 2nd line, and the 6th line is the 3rd line.
All lines were recorded by repeating the same control every third line.

(Problems to be Solved by the Invention) However, the thermal printer having the above configuration has the following problems.

Since the block dividing point is sequentially moved from one end of all the heat generating resistor rows to the other end, it corresponds to common gate signals 4-3 and 4-6, 4-6 and 4-7, etc. in the first row, for example. As adjacent blocks are driven one after the other, like a row of heating resistors, heat is transferred from the previously driven block to the next driven block, causing the dots at the joint to become preheated. The disadvantage is that the print density becomes darker if the temperature is high. In addition, because the off time interval of the common gate signal 4-1. There is a drawback that the dots in the heating resistor row 1-1, 1-2 become darker. Furthermore, for example, the common gate signal 4-
The dots in the heating resistor array corresponding to 3.4-6.4-9 have a low temperature because of the heat absorbed, and there is a drawback that density unevenness as a white vertical line in the sub-scanning direction becomes noticeable. In order to prevent these drawbacks, it is expected that good results can be obtained by randomly moving the block division points.
Since the control required to realize a circuit that moves randomly is complicated, it has not been possible to obtain stable printing quality at low cost.

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

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention uses a heating resistor array consisting of a plurality of heating resistors arranged in the main scanning direction, and each heating resistor has a heating factor. In a thermal printer that prints by applying a quantity, the heating resistor array is divided into a plurality of blocks and driven in a time division manner based on selection information, and the dividing position of the blocks is moved row by row. selecting means for selecting a block to be driven and providing selection information indicating the block to the driving means; The blocks are selected in a repeating order such that the rows return to the same position every predetermined number of rows.

(Operation) According to the present invention, since the thermal printer is configured as described above, the technical means operates as follows. The selection means is operative to select spaced apart blocks in a predetermined order and to provide selection information (corresponding to the aforementioned common gate signal) indicative of the selected blocks to the drive means. The driving means drives the blocks in a predetermined order based on the selection information without driving spaced apart blocks, ie, consecutively adjacent blocks. In this way, one line is printed by driving the heating resistor array in a time division manner. Next, the selection means provides the driving means with selection information of the block in which the dividing position of the block selected in the first line has been moved (shifted), and the driving means shifts the dividing position of the block according to the selection information and moves the dividing position of the block selected in the first line to the driving means. Drive columns in time division.

In this way, the selecting means selects the blocks and controls the driving means so that each block position returns to the block position selected in the first row several rows in advance. Therefore, the problems of the prior art described above can be solved.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention. In this figure, the same reference numerals as in FIG. 3 indicate the same components. Reference numeral 6 denotes a driver selection circuit corresponding to the driver selection circuit 5 in FIG. 3, which is different from the conventional one in the control of the driver circuit 2, that is, the timing of sending out the common gate signals 4-1 to 4-12. 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 explained with reference to FIGS. 1 and 2. However, M=4 and N=3.

First, after one row of recording data is input to the shift register, to start recording, common gate signals 4-1 to 4-3 are turned on in order to drive N (=3) sets of heating resistor arrays. The respective driver circuits 2 connected to are turned on and drive the heating resistor arrays 1-1 to 1-3. Next, the common gate signals 4-10 to 4-12 are turned on, and the heating resistor arrays 1-10 to 1-12 are similarly driven. Thereafter, sequentially turn on the common gate signals 4-4 to 4-6, then turn on the common gate signals 4-7 to 4-9.
is turned on, N (=3) sets of heating resistor arrays are turned on, and M (=4
) times and one line is recorded.

In the second row of the next row, the common gate signals 4-2 to 4-4 are turned on by starting recording after inputting data. After turning on the common gate signals 4-1.4-11.4-12 as in the first line, turning on the common gate signals 4-5 to 4-7, and finally turning on the common gate signals 4-8 to 4-7. 4-10 on and second
The line is recorded.

Next, in the third row, the common gate signals 4-3 to 4-5 are turned on, and the following 4-1.4-2.4-12 are turned on.
4-6 to 4-8 are turned on and finally 4-9 to 4-11 are turned on to record the third line.

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

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

(Effects of the Invention) As explained above, according to the present invention, the block division position of the block division recording method that divides a heating resistor array consisting of a large number of heating resistors into a plurality of blocks can be varied, and It is possible to make the interval between the recording timings of the blocks of a line and the next line approximately uniform, and it is less likely that adjacent blocks will be driven successively, and there will be less downtime between the same dots in the previous line and the next line. Also, there is no need for continuous driving.

This control can be achieved by repeating the control loop as short as possible, so the capacity of the ROM to control it is also small.
It is possible to provide a thermal printer that eliminates density unevenness and improves recording quality using a simple and inexpensive circuit system.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
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 resistor 1
-1 to 1-12... Heat generating resistor array 2... Driver circuit 3... Shift register 4... Common gate 6... Driver selection circuit

Claims (1)

[Scope of Claim] A thermal printer that uses a heating resistor array consisting of a plurality of heating resistors arranged in the main scanning direction and performs printing by applying a heating factor amount to each heating resistor, based on selection information. a driving means for dividing the heating resistor array into a plurality of blocks and driving them in a time-division manner; and a driving means for moving the dividing position of the blocks row by row to select a block to be driven and a selection indicating the block. selection means for supplying information to the driving means, the selection means selecting the separated blocks in a predetermined order, and selecting a repeating order such that the division positions of the blocks return to the same position every predetermined number of rows. A thermal printer characterized by selecting blocks with.