JPH11165424A - Method and apparatus for controlling thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for controlling a line thermal head for two-color thermal paper capable of preventing color mixture of a low temp. coloring part adjacent to a high temp. coloring forming part. SOLUTION: Two kinds of correcting applying pulses for performing correction on the basis of the presence of the high temp. coloring dot adjacent to a low temp. coloring dot are added to conventional low and high temp. coloring applying pulses, and a low temp. coloring dot correcting data is formed by right or left shift circuits 4, 5, an exclusive OR circuit 8, and an AND circuit 9, and printing operation is performed four times to make the developed color densities of all of low temp. coloring parts the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method and an apparatus for controlling a thermal head of a printer, an electronic blackboard, a facsimile, etc., for printing using two-colored thermal paper.

[0002]

2. Description of the Related Art As already known, a thermal recording paper capable of two-color development is constituted by sequentially applying a high-temperature coloring layer and a low-temperature coloring layer on a base paper. The high-temperature coloring layer develops a certain color (for example, red) by applying a predetermined heat,
The low-temperature coloring layer develops another color (for example, black) by applying less heat than the high-temperature coloring layer. Hereinafter, as an example, a description will be given assuming that the color of high-temperature coloring is red and the color of low-temperature coloring is black. FIG. 4 is a timing chart of a line thermal head thermal printer when printing is performed by heating using two colored thermal papers. When printing on such thermal paper, first, the logical OR data of the red print data and the black print data is transferred to the thermal head, and the low-temperature coloring (black) is performed.
Is given to the dots based on the print data to print black print data. Next, only the red print data is transferred to the thermal head again and high-temperature coloring (red)
The red print data is printed by applying a predetermined heat necessary for the printing. At this time, the high-temperature coloring is performed by applying necessary predetermined heat in two separate steps. The energy ratio of heat required for high-temperature coloring and low-temperature coloring depends on the type of heat-sensitive recording paper to be used.
On the other hand, low-temperature coloring is about 6. The amount of heat applied is adjusted by the length of the pulse width applied to the line thermal head when printing. When the applied pulse width is long, the amount of heat is large, and when it is short, the amount of heat is small. As an example of a thermal head control method, see Japanese Patent Application Laid-Open No. 6-6 / 1994.
The technique described in Japanese Patent No. 4211 is known.

[0003]

In the method for controlling a line thermal head for two-color thermal paper shown in FIG. 4, the two-color thermal paper has a structure in which a high-temperature coloring layer and a low-temperature coloring layer are sequentially applied. The color to be developed is selected according to the amount of heat to be heated. For this reason, in a portion where two colors are printed adjacent to each other, the heat of high-temperature coloring (red) affects the portion of low-temperature coloring, and the portion of low-temperature coloring (black) develops brown, resulting in poor print quality. There is. The present invention has been made in view of such circumstances, and has as its object to provide a thermal head control method and apparatus capable of preventing color mixing of a low-temperature coloring portion adjacent to a high-temperature coloring portion.

[0004]

According to a first aspect of the present invention, there is provided an image buffer for storing high-temperature coloring data and low-temperature coloring data, and shifting the high-temperature coloring data by one bit to the right or left. Shift means for outputting data; logical sum means for outputting a logical sum of the high-temperature coloring data and the low-temperature coloring data; and outputting an exclusive logical sum of the shift data and the output data of the logical sum means. Exclusive OR means for performing the operation, AND means for outputting a logical product of the output data of the exclusive OR means and the output data of the logical OR means, output data of the OR means, Input selection means for sequentially selecting output data and the high-temperature coloring data and outputting the data to the thermal head; and applying the data to the thermal head in synchronization with the data output by the input selection means. Varying the that pulse width, characterized in that a applying pulse generating circuit which outputs a pulse.

According to a second aspect of the present invention, the high-temperature coloring dots and the low-temperature coloring dots have a pulse width shorter than the pulse width required for low-temperature coloring by the sum of the pulse widths applied in the second and third steps. A first process of printing by heating with an applied pulse, the low-temperature coloring dot having a high-temperature coloring dot on the left side, the low-temperature coloring dot having no high-temperature coloring dot on both sides,
A second step of heating and printing the high-temperature coloring dots with an application pulse having a shorter pulse width than the pulse applied in the first step, and the low-temperature coloring dots having a high-temperature coloring dot on the right side, The third step of heating and printing the low-temperature coloring dots and the high-temperature coloring dots having no high-temperature coloring dots with an applied pulse having the same width as the pulse applied in the second step.
And heating the high-temperature coloring dots with an applied pulse having a pulse width shorter than the pulse width required in the first, second, and third steps by the sum of the pulse widths required for the high-temperature coloring. And a fourth step.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a thermal head control device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of the embodiment. In FIG. 1, reference numeral 1 denotes an image buffer for storing print image data divided into high-temperature coloring data 2 and low-temperature coloring data 3. Reference numeral 4 denotes a right shift circuit that shifts the high-temperature coloring data 2 by one bit to the right and outputs it. Reference numeral 5 denotes a left shift circuit that shifts the high-temperature coloring data 2 by one bit to the left and outputs it. Reference numeral 6 denotes a switching circuit for switching and outputting two systems of output data from the right shift circuit 4 and the left shift circuit 5. Reference numeral 7 denotes a logical sum circuit that outputs a logical sum of the high-temperature coloring data 2 and the low-temperature coloring data 3. Reference numeral 8 denotes an exclusive OR circuit that outputs an exclusive OR of the output data of the OR circuit 7 and the output data of the switching circuit 6. Reference numeral 9 denotes an AND circuit that outputs a logical product of the output data of the exclusive OR circuit 8 and the output data of the OR circuit 7. Reference numeral 10 denotes an input selection circuit that selects one of three systems of the high-temperature coloring data 2, the output data of the AND circuit 9, and the output data of the OR circuit 7, and outputs the selected system to the thermal head. Reference numeral 11 denotes an applied pulse generating circuit capable of outputting an applied pulse of an arbitrary width for the thermal head to perform printing. Reference numeral 4a denotes shift data obtained by shifting the high-temperature coloring data 2 by the right shift circuit 4, and 5a denotes shift data obtained by shifting the high-temperature coloring data 2 by the left shift circuit 5. Reference numeral 7a is the logical sum data output by the logical sum circuit 7. Reference numeral 8a denotes output data of the switching circuit 6 (shift data 4a or shift data 5a).
And exclusive OR data of OR data 7a. Reference numeral 9a is logical product data of the exclusive logical sum data 8a and the logical sum data 7a. Reference numeral 11a denotes an applied pulse generation circuit 1.
This is the applied pulse output from 1.

FIG. 2 is a timing chart showing the printing timing of the embodiment. FIG. 3 is an explanatory diagram showing a data string output from each circuit of the embodiment and an applied pulse width. In FIG. 3, symbols (A) to (G) indicate data, and (1) to (18) indicate dot positions of each data. The symbol (A) is a print image for one line shown as an example, and one line is printed at 18 dots. The symbol (e) is the pulse width of each dot of the applied pulse 11a used for low-temperature coloring, (q) is the pulse width of each dot of the applied pulse 11a used for right shift correction, and (s) is the pulse width of the applied pulse used for left shift correction. Pulse width of each dot,
(Se) is the pulse width of each dot of the applied pulse used for high-temperature coloring. The symbol (S) is the total of the pulse widths applied to each dot, and represents the total of the pulse widths applied by the symbols (E), (K), (S), and (C).

Next, the operation will be described with reference to FIGS. 1, 2 and 3. The explanation of the operation is as follows. The minimum unit of the pulse width is 1
Assuming that the sum of the applied pulse widths required for high-temperature coloring is 10,
The description will be made on the assumption that the total of the applied pulse widths necessary for low-temperature coloring is 6. Print data input from a personal computer or the like is separately stored in the image buffer 1 as high-temperature coloring data 2 and low-temperature coloring data 3. Printing is performed four times for one line as shown in FIG. First, the first print is
The input of the input selection circuit 10 is switched to the output from the OR circuit 7, and the OR data 7a (see FIG. 3D) of the high-temperature coloring data 2 and the low-temperature coloring data 3 is output to the thermal head. At the same time, the application pulse generation circuit 11 generates an application pulse 11a for low-temperature coloring (see FIG. 3E) and performs printing. In the second printing, the input of the switching circuit 6 is switched to the output from the right shift circuit 4, and the shift data 4a (see FIG. 3 (f)) output by the right shift circuit and the logical sum output by the logical sum circuit 7 are output. The data 7a and the exclusive OR circuit 8 are input. Next, the exclusive OR data 8a (see FIG. 3 (g)) output from the exclusive OR circuit 8 and the OR data 7a are input to the AND circuit 9. Further, the input selection circuit 10 is switched to the output of the AND circuit 9, and the AND data 9a (see FIG. 3C) is output to the thermal head. At the same time, the application pulse generation circuit 11 generates a right shift correction application pulse 11a (see FIG. 3G) and performs printing.

In the third printing, the input of the switching circuit 6 is switched to the output from the left shift circuit 5, and the shift data 5a (see FIG. 3C) output from the left shift circuit and the OR data 7a are output. Input to exclusive OR circuit 8. Next, the exclusive OR data 8a output by the exclusive OR circuit 8
(See FIG. 3 (c)) and the logical sum data 7a are logically ANDed by the logical product circuit 9
Enter Further, the input selection circuit 10 is switched to the output of the logical product circuit 9 to generate logical product data 9a (see FIG. 3C).
Is output to the thermal head. At the same time, the application pulse generating circuit 11 generates a left shift correction application pulse 11a (see FIG. 3 (S)) and performs printing. At this time, the low-temperature coloring dots having no high-temperature coloring dots on both sides (FIG. 3 (16)
(See FIG. 3 (S) and (16)), the color becomes low-temperature coloring (black). Also,
In the case of a low-temperature coloring dot having a high-temperature coloring dot only on the right or left side (see FIGS. 3 (7) and (12)), the total of applied pulses is 5 (FIG. 3 (S), (7) and (S) ( 12)), and in the case of a low-temperature coloring dot having a high-temperature coloring dot on both sides (see FIG. 3 (3)), the total of applied pulses is 4
(See (3) and (3) in FIG. 3), and the color does not reach the predetermined energy for low-temperature color development, so that the color density is low.

In the fourth printing, the input switching circuit 10
Is switched to high-temperature coloring data 2 and high-temperature coloring data 2 (see FIG. 3A) is output to the thermal head. At the same time, the application pulse generation circuit 11 generates an application pulse 11a for high-temperature coloring (see FIG. 3C) and performs printing. At this time, the high-temperature colored dots have a total pulse width of 10 ((2), (4), (8), (1) in FIG.
1), (14) and (18)), so that the color develops as a high-temperature color (red). When there is a high-temperature coloring dot only on the right or left side, the total of applied pulses is 5 (FIG. 3).
(See (7) and (12) in (G)), but because of the influence of the heat of the adjacent high-temperature coloring dots, the heat is added to be equivalent to one of the applied pulse width, and thus the color of low-temperature coloring (black) Color develops. When there are high-temperature coloring dots on both sides, the total of applied pulses is 4 (see FIG. 3 (S) and (3)). However, since the left and right high-temperature coloring dots are affected by heat, respectively. Since the heat is applied in an amount equivalent to 2 of the applied pulse width, the color is developed into a low-temperature color (black).

By performing printing four times in this way, the color density of all low-temperature color dots can be made the same. In addition, when the energy ratio of heat required for coloring changes due to the difference of the thermal paper, the application pulse for low-temperature coloring applied to the thermal head, the application pulse for left shift correction,
The same printing can be performed by changing the pulse width of the right shift correction application pulse and the high-temperature coloring application pulse in accordance with the energy ratio. Although FIG. 1 illustrates the embodiment by implementing the circuit, the same processing can be implemented by software, so that the present invention may be implemented by a computer program.

[0012]

As described above, according to the present invention,
Conventional high-temperature coloring application pulse and low-temperature coloring application pulse
Heating and printing are performed by applying four types of application pulses including a right shift correction application pulse and a left shift correction application pulse, so that a high temperature color and a low temperature color are formed in a low temperature color portion adjacent to a high temperature color portion. The effect of preventing color mixture can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a timing chart showing printing timing of the embodiment shown in FIG.

FIG. 3 is an explanatory diagram showing a data string output from each circuit of the embodiment shown in FIG. 1 and an applied pulse width.

FIG. 4 is a timing chart showing the printing timing of a conventional two-color thermal paper line thermal head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image buffer 2 ... High-temperature coloring data 3 ... Low-temperature coloring data 4 ... Right shift circuit 5 ... Left shift circuit 6 ... Switching circuit 7 ... OR circuit 8 ... Exclusive OR circuit 9 ... AND circuit 10 ... Input selection circuit 11 ... Applied pulse generation circuit

Claims (2)

[Claims] 1. An image buffer for storing high-temperature coloring data and low-temperature coloring data; shift means for shifting the high-temperature coloring data by one bit to the right or left to output shift data; and the high-temperature coloring data. AND means for outputting a logical sum of the shift data and the low-temperature coloring data; exclusive OR means for outputting an exclusive OR of the shift data and output data of the logical OR means; and the exclusive OR AND means for outputting a logical product of the output data of the means and the output data of the OR means; and sequentially selecting the output data of the OR means, the output data of the AND means, and the high-temperature coloring data. Selecting means for outputting a pulse to the thermal head in response to the selection of the input selecting means, and changing the pulse width applied to the thermal head to output a pulse. A thermal head control device comprising: 2. A high-temperature coloring dot and a low-temperature coloring dot,
A first process of heating and printing with an applied pulse having a pulse width shorter by the sum of the pulse widths applied in the second and third processes than the pulse width required for low-temperature coloring, and a high-temperature coloring dot on the left side. Heating the low-temperature coloring dots, the low-temperature coloring dots having no high-temperature coloring dots on both sides thereof, and the high-temperature coloring dots with an applied pulse having a shorter pulse width than the pulse applied in the first step, and printing the second dot. Process, the low-temperature coloring dot having a high-temperature coloring dot on the right side, the low-temperature coloring dot without a high-temperature coloring dot on both sides, and the high-temperature coloring dot, with an applied pulse having the same width as the pulse applied in the second process. A third step of printing by heating, wherein the high-temperature coloring dots have a pulse width shorter than the pulse width required for high-temperature coloring by the sum of the pulse widths applied in the first, second, and third steps. Application Thermal head control method characterized by comprising a fourth step of printing by heating at scan, the.