JPS6387262A - Thermal printer - Google Patents

Abstract

PURPOSE:To prevent heat generating elements from being overheated and enhance printing quality in multicolor printing, by controlling the energy supplied to the heat generating elements based on past printing data. CONSTITUTION:Where the m-th bit in a line to be just printed is to be developed into red, when the m-th bits in the three lines preceding the current line are respectively black, black and red in that order, it is supposed that heat accumulation has occurred to a certain degree in the vicinity of a heat generating element for the m-th bit due to the printing in the preceding three lines, and accordingly, the number of times of printing for the m-th bit is set to be smaller. Also where a given bit is to be developed into black, the number of times of printing is determined on the basis of a reference table set in a ROM 20. The data set in a ROM 19 comprises not only frequency history of black and red printing data but also the past data weighted as mentioned above, so that optimum applied energy for each bit is set. Consequently, it is possible to control heat accumulation for each heat generating element and to appropriately effect development of colors on a multicolor thermal recording paper having different color developing temperatures.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thermal printer, and particularly to a thermal printer using heat-sensitive recording paper.

(Prior Art) Recently, thermal recording paper capable of producing a plurality of colors has been developed as thermal recording paper for thermal printers.

This thermosensitive recording paper has a plurality of color-forming layers laminated and applied, and each color is selectively developed in a predetermined temperature range.

In order to obtain the desired color development, thermal printers that use heat-sensitive recording paper like this use a cycle so that the color development energy (applied energy) in the past printed line does not affect the energy required for the current color development. Printing is slow.

(Problems to be Solved by the Invention) However, in such conventional thermal printers, when the printing speed is increased, the coloring energy of the past line affects the coloring of the current line to be printed.

In other words, for example, in thermal recording paper that produces two colors, red and black, if the coloring temperature of red is higher than the coloring temperature of black, 9 printed areas (unprinted areas) will become blackish due to heat accumulation after the red line continues. There have been problems in that the print quality is deteriorated because the black printed area becomes reddish.

(Purpose of the Invention) Therefore, the present invention prevents overheating of the heating element by controlling the energy supplied to the heating element based on past printing data of multiple times corresponding to multiple colors. The purpose is to maintain an appropriate element temperature and improve print quality in multicolor printing.

(Structure of the Invention) In order to achieve the above object, the present invention utilizes thermal recording paper capable of developing multiple colors, a thermal head having multiple heating elements in the main scanning direction, and print data corresponding to each color. In the thermal printer, the print control means outputs the control signals necessary for driving the heat generating elements, and the print control means outputs the control signals necessary for color development based on the past print data of a plurality of times corresponding to each color. The feature is that the applied energy is set and outputted for each heating element.

Hereinafter, the present invention will be specifically explained based on examples.

1 to 9 are diagrams showing one embodiment of the present invention.

FIG. 1 is a schematic diagram of a thermal printer.

In FIG. 1, 1 is a thermal printer, and the thermal printer 1 is provided with a thermal head 2 and a platen roller 3 in its recording section.

The thermal head 2 is urged with a predetermined pressure in the axial direction of the platen roller 3 by a pressure device (not shown), and a heating element formed on the thermal head 2 comes into contact with the platen roller 3.

A plurality of heating elements are arranged in parallel in the axial direction (main scanning direction) of the platen roller 3, and the heating elements are divided into four blocks due to the circuit configuration.

Here, for example, when the number of heating elements is 2048, the number of heating elements per block is 512.

A roll of thermal recording paper 4 is supplied between the thermal head 2 and the platen roller 3.
is conveyed in the F direction (sub-scanning direction) in the figure according to the rotation of the platen roller 3. As shown in FIG. 2, the thermosensitive recording paper 4 has a structure in which a high-temperature coloring layer 6 and a low-temperature coloring layer 7 are sequentially laminated and coated on a base paper 5.

In this embodiment, the high-temperature coloring layer 6 develops red at a predetermined temperature,
The low-temperature coloring layer 7 develops black at a predetermined temperature. Further, the coloring temperature ratio of red and black is 3:1.

Next, referring again to FIG. 1, the controller 8 controls each part of the thermal printer 1, outputs print data input from the outside to the print control circuit (print control means) 9, and also outputs the print data input from the outside to the print control circuit (print control means) 9. Outputs strobe signals and latch signals. The print control circuit 9 controls the applied energy necessary for printing based on the input red and black print data and outputs the print data to the thermal head driver IO, and the thermal head driver 10 controls the thermal head 20 based on this print data. Energy is selectively applied to the heating element. The print control circuit 9, as shown in FIG.
), RAM 3 (13), RAM 4 (14)
, IC1 (15), IC2 (16), IC3 (17
), IC4 (18), IC5 (19), ROM 2
0, a counter 21 and a data selector 22.

The RAMI (11) stores one line of newly input red print data, and the RAM 2 (12) stores the previous history of red print data (for example, the past three lines of print data). RAM3 (13) stores the newly input black print data for one line.
(14) stores the previous history of black print data (for example, the past three lines). I C1 (15) to IC4 (18) are master-srap type flip-flops, and I C1
(Is) and IC2 (16) read the new red print data stored in RAMI (11) based on the PRE-LINE DATA WR signal from controller 8, and read out the previous red print data stored in RAM2 (12). The print data of

On the other hand, I C3 (17) and I C4 (18) are RA
The new black print data stored in M3 (13) is read out, and the previous black print data stored in RAM 4 (14) is renewed based on the PRE-LINE DATA WR signal. IC5 (19) is a flip-flop, and the red print data of IC2 (16) and I
The black print data of C4 (18) is read bit by bit in synchronization with the timing of the master clock, and the data is stored in ROM2.
Output to address bus 0. The ROM 20 stores the input print data from the IC5 (19) at the counter 21.
Reference is made bit by bit sequentially from the second time onwards. The ROM 20 refers to the previous history of red and black print data bit by bit as address data, and reads out setting values corresponding to the address data from the reference table and outputs them. The reference table stores setting values corresponding to address data for each bit, and the setting values are made up of 31 pieces of print data.

This setting value controls the applied energy for each bit. The data selector 22 matches the 8-bit print data input from the ROM 20 with the count timing of the counter 21 and outputs it to the thermal head driver 10 as serial data. That is, the print control circuit 9 outputs print data to the thermal head driver 10, and the thermal head driver 10 selectively outputs the print data and strobe data based on the strobe signal from the controller 8 to the heating elements of the thermal head 2. and drives the heating element. Here, the relationship between the black print data and the red print data is as shown in Table 1.
A dot is composed of 2-bit data.

Table 1 Also, in this embodiment, due to the structure of the thermal recording paper mentioned above, the printing energy for the longevity printing and the black printing is set at 3:1, and the current red line data is (n>, , if the black line data is (n)8, the history weighting is, for example, (n-
1) * > (n-2) x > (n 1) m...
・It is set as

Next, the effect will be explained.

In the thermal printer 1, printing is performed in the following procedure.

First, print data input via the controller 8 is processed by the print control circuit 9, and the thermal head driver 1
It is input to 0. Based on this print data and the strobe signal from the controller 8, the thermal head driver 10 uses a shift register to apply energy to the heating elements of the thermal head 2 for each block, thereby selectively causing the heating elements to generate heat. This heat causes the heat-sensitive recording paper 4 supplied between the platen roller 3 and the heating element to generate any color of red or black to perform printing. The thermal recording paper 4 is fed by a predetermined amount each time one line is printed by the platen roller 3 to form an image. Here, this print data is first stored in RAM 1 (11
) and RAM 3 (13), and at the time of the θ-th readout by the counter 21, RAM 2 (12
) and the oldest data in RAM 4.14. That is, the red print data input to RAM 1 (11) is transferred to RAM 2 (
12), and as shown in FIG. 4, when the counter 21 reads the Oth time, the PRE-
When the LINE DATA WR signal is input, the oldest previous line data and the latest data are updated (see FIGS. 5(a) and 5(b)).

Also, RAM 3 (13) and RAM 4 (14)
The black print data stored in is also updated in the same way. R.A.
When the line data stored in M 2 (12) and RAM 4 (14) is updated, 1 of the counter 21
~ Every 31 counts, 1 block (512 bits) of red and black history data is read out, and IC3 (
17) to the address bus of the ROM 20.

The red and black print data input to the ROM 20 are referred to as address data, and print data with set values corresponding to this address data is input to the data selector 22. The print data input to the data selector 22 is 1
Each block is output to the thermal head driver 10 as serial print data.

When print data is input to the thermal head driver 10, conventionally, a launch signal and a strobe signal (apply pulse) are given to each block of print data to print one line (see Fig. 6(a). )reference).

However, in this embodiment, one line is read out 31 times within a predetermined time by the counter 21 for each block, and the RO
A latch signal and a strobe signal are provided every count based on the set value referenced by M20 (6th
(See figure (b)).

That is, each time the counter 21 counts from 1 to 31, print data corresponding to a data address that changes each time is read out from the ROM 20 and outputted block by block via the data selector 22. When printing of one block is completed, print data is sequentially read out block by block and printing is performed.

To explain this operation in detail, as shown in FIG. 7, line data (a) is read out from the counter (b) a predetermined number of times (31 times in this embodiment) for each block (512 bits). At this time, a strobe signal (d) is applied together with a head launch pulse (C) from the controller 8, and R
Energy is selectively applied to the heating elements of the thermal head 2 based on the print data referenced and set by the OM 20 . When printing for 1 block is completed, 2~
Four blocks are sequentially read out, processed in the same manner as described above, and output.

For example, when trying to color the m-th bit of the line to be printed red as shown in FIG. 8,
When all the m-th bits are white in the 3 lines of the previous history, it is expected that the heating element near the m-th bit is cold, so the number of times of printing of the m-th bit is set to be large, and the voltage required for red coloring is set. The amount of energy increases. At this time, if the first application time is 100 μs, 31
Since the pulse is applied twice, the printing pulse is applied to the m-th bit of this line for a total of 3.1 ms.

Similarly, when the m-th bit of the line to be printed is colored red, as shown in Figure 9, the first line before the m-th bit of the three previous lines is red, the second line before, and the third line before. When is black, 3 lines of the previous history are being printed, so it is expected that some heat is accumulated near the m-th bit heating element, and the number of times the m-th bit is printed is small (
Set. At this time, the application time per time is 100μ
Assuming that the voltage is applied 15 times in FIG. 9, the m-th bit of this line is applied for a total of 1.5 ms. Incidentally, in the case of producing black, the number of times of printing is determined based on the reference table set in the ROM 20, as in the case of producing red.

In this way, the applied energy for the current printing can be appropriately applied depending on the frequency of black and red print data in the previous history. In setting the printing energy, R
Since the data set in the OM 19 includes not only the frequency history of black and red print data but also previous history data and is weighted as described above, the optimum applied energy is set for each bit. As a result, even in high-speed printing or continuous printing, it is possible to control the amount of heat storage for each heating element and appropriately control the coloring temperature of multicolor thermosensitive recording paper having different coloring temperatures.

Therefore, even when printing in multiple colors, heat accumulation after consecutive red lines will prevent white from becoming blackish or black from becoming reddish (and the reproducibility of each color can be improved. Print quality can be further improved.

In this embodiment, the thermal recording paper 4 that develops black and red colors is used, but the present invention is not limited to this embodiment.
Even when a thermosensitive recording paper having color-forming layers or more color-forming layers is used, it is possible to appropriately give a color-forming temperature to each color-forming layer.

(Effects) According to the present invention, overheating of the heating element can be prevented and the element temperature can be set to an appropriate temperature for each color, and the reproducibility of each color in multicolor printing can be improved to further improve printing quality. can.

[Brief explanation of the drawing]

1 to 9 are diagrams showing one embodiment of the thermal printer of the present invention, and FIG. 1 is a schematic diagram of the thermal printer,
Figure 2 is a configuration diagram of the thermal recording paper of the thermal printer.
Figure 3 is a circuit diagram of the print control section of the thermal printer.
Figure 4 is a timing chart showing the relationship between the current print data of the thermal printer and the previous print data, and Figure 5 is the current print data input to the RAMI of the thermal printer and the previous history stored in RAM2. Fig. 6 shows the conventional printing method (a) of the thermal printer and the printing method according to this embodiment (b). ), FIG. 7 is a timing chart showing one line of printing by the thermal printer, FIG. 8 is a diagram showing the relationship between history print data and print data of the thermal printer, and FIG. 9 is a timing chart showing the printing of one line of the thermal printer. FIG. 3 is a diagram showing the relationship between history print data and print data of the thermal printer. 1... Thermal printer, 2... Thermal head, 4... Thermal recording paper, 9... Print control means. Figure 2 Figure S TV Rumors - Koru Address Worri No. 9
(Fig. m bi capture) Mo" 3 Rigo Wrestler Raptor 1;

Claims (1)

[Claims] A thermal recording paper capable of producing multiple colors, a thermal head with multiple heating elements in the main scanning direction, and a print control that outputs the control signals necessary to drive the heating elements based on print data corresponding to each color. In the thermal printer, the printing control means sets and outputs applied energy necessary for color development for each heating element based on past printing data corresponding to each color. A thermal printer with special features.