JP3066197B2 - Sublimation type thermal printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head in which a plurality of heating resistors are arranged in a line to control the amount of current supplied to each heating resistor, thereby changing the sublimation amount of a sublimation dye to obtain gradation characteristics. The present invention relates to a sublimation type thermal printer that reproduces an image having the following.

[0002]

2. Description of the Related Art Conventionally, in this type of sublimation type thermal printer, the quality of a reproduced image fluctuates due to the influence of the surrounding thermal environment. In particular, the head temperature of a thermal head greatly affects the reproduced image quality. Had been given.

Further, in a sublimation type thermal printer, an image is printed by controlling the amount of current applied to each heating resistor of a thermal head, but all heat energy generated at the time of this current application is transmitted to an ink sheet and sublimated. Instead of causing a reaction, a part of the heat energy is also transmitted to the head main body, causing an increase in the head temperature, that is, the heat storage of the head. Then, the recording density increases due to the heat storage of the head, and a difference occurs in the recorded image between the start and end of the recording.

For this reason, recently, a method has been proposed in which a temperature sensor such as a thermistor is embedded in a thermal head, and the amount of current supplied to each heating resistor of the thermal head is controlled based on the head temperature detected by the temperature sensor. Proposed.

[0005] With this energization control method, even if the temperature of the thermal head changes due to the thermal storage of the thermal head or the cooling of the thermal head due to the influence of the outside air, etc.
There is no large difference between the printed images at the start of printing and at the end of printing, and the reproduced image can always be printed without being affected by the surrounding thermal environment.

[0006]

However, since it is difficult to directly measure the temperature of the heating resistor of the thermal head in the above-described power supply control method, the temperature of the thermal head on the base side is detected. For this reason, there is a time lag required for the temperature change of the heating resistor of the thermal head which directly affects the reproduced image quality to transfer heat to the substrate side. In particular, the heat storage state of the heating resistor during image printing is accurately grasped. That was impossible.

Further, when a different amount of current is applied to each heating resistor according to gradation data as in a sublimation type thermal printer, the heat storage state of each heating resistor is different. In this case, uneven printing density occurred, and a high-quality image could not be reproduced.

[0008] The present invention has been made in view of such a point, and not only the head temperature during image printing, but also
An object of the present invention is to provide a sublimation-type thermal printer in which printing density unevenness does not occur by performing energization control in consideration of the heat storage state of each heating resistor.

According to the present invention, an image having gradation can be obtained by changing the amount of sublimation of a sublimation dye by controlling the amount of current supplied to each heating resistor of a thermal head having a plurality of heating resistors arranged in a line. In a sublimation type thermal printer for reproducing, a temperature detecting means for detecting a temperature of the thermal head, and a main pulse signal having an energizing power corresponding to gradation data is supplied to each of the heating resistors at a constant cycle to record on a recording medium. A printing unit for printing an image on a line, and a distributed type defined between the printing of the image of each line by the printing unit and based on the temperature detected by the temperature detecting unit and the gradation data. A preheating means for supplying a preliminary pulse signal to each of the heating resistors to preheat the heating resistors, wherein the preliminary pulse signal is a temperature of each of the heating resistors once increased by applying the main pulse signal. There after reaching the predetermined temperature that does not lead to marked copy, until the next line printing is started, the sublimation-type thermal printer is to maintain the temperature of the heating resistors substantially constant.

[0010]

According to the present invention, as a means for preheating between image printing of each line, energization control is performed in consideration of not only the head temperature but also the input gradation data of each heating resistor. At the start of printing, each heating resistor is maintained at a predetermined temperature.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A sublimation type thermal printer according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a schematic configuration of a printing section of a sublimation type thermal printer according to the present invention.

In FIG. 1, reference numeral 1 denotes an image memory for storing gradation data of an input image, and reference numeral 2 denotes a line memory for storing and holding gradation data input from the image memory 1 line by line. Reference numeral 3 denotes a printing control unit for controlling the entire printer, and outputs various control signals such as a printing instruction or a preheating instruction in accordance with a control program stored in the ROM 4 to execute overall control. Reference numeral 5 denotes a thermistor as temperature detecting means for detecting the temperature of a thermal head 6 in which a plurality of heating resistors are arranged in a line. Reference numeral 7 denotes a head drive circuit, which drives the thermal head 6 to a platen roller 8
An ON / OFF signal is generated for a head drive motor (not shown) for pressing and separating the head. Reference numeral 9 denotes a head driver control circuit, which converts one line of gradation data from the line memory 2 according to a control signal from the printing control unit 3
An energizing pulse signal is output to each heating resistor of the thermal head 6 at a printing cycle of 0 msec / line.

More specifically, a main pulse signal having an energizing power corresponding to each gradation data of one line from the line memory 2 is supplied to each heating resistor to respond to the input gradation data on the recording medium. After printing the image of one line, and after outputting the main pulse signal, the head temperature detected by the thermistor 5 and a preliminary pulse signal having a power supply corresponding to the input gradation data are supplied to each heating resistor. Each heating resistor is preheated to a predetermined temperature (about 50 ° C. in this embodiment) at which the sublimation dye does not develop color or transfer on the recording medium.

Reference numeral 10 denotes an ink sheet, on the surface of which three colorants of yellow, magenta, and cyan are applied by a sublimation dye in a face-to-face manner, and stretched by a supply roll 11 and a sheet winding roll 12. Has been established. Reference numeral 13 denotes a recording paper as a recording medium, which is coated with an image receiving agent for fixing a sublimation dye to reproduce an image,
After being conveyed by the thermal head 4 and passing between the thermal head 6 and the platen roller 8, the paper is discharged to the outside of the sublimation type thermal printer by the paper discharge roller 15.

In this embodiment, the energizing power of the main pulse signal and the spare pulse signal is variably controlled according to the energizing width.
A dispersion pulse of sec is used.

The ROM 4 stores a table of the width of the main pulse signal with respect to the input gradation data, a table of the input gradation data, and a table of the number of dispersed pulses of the preliminary pulse signal with respect to the head temperature.

FIG. 2 is a diagram showing the relationship between the conduction width of the main pulse signal stored in the ROM 4 and the input gradation data in the table.
3 shows a relationship between the input gradation data of the table of the number of dispersed pulses of the preliminary pulse signal stored in the ROM 4 and the head temperature. Here, FIG. 3 shows that the head temperature is 30 ° C., 40 ° C.,
Although only the case of 50 ° C. is shown, the ROM 4 has a temperature of 30 ° C. to maintain each heating resistor at about 50 ° C.
A table of the number of dispersed pulses for input gradation data for each head temperature of 1 ° C. at 50 ° C. is stored.

Next, the printing operation of the sublimation type thermal printer of the present invention will be described with reference to the flowchart of FIG.

First, prior to the start of printing, the head temperature T of the thermal head 6 is detected by the thermistor 5 (S
1) It is determined whether the head temperature T has reached 50 ° C. (S3).

In step S3, the head temperature T
If the temperature does not reach 50 ° C., the main pulse width of 7.9 msec for the input gradation data of 127 gradations is read from the ROM 4, and the main pulse signal of the conduction width is applied to all the heating resistors of the thermal head 6. (S5), returning to step S1. Thereby, the temperature of the thermal head is increased until the head temperature T reaches 50 ° C. Note that the thermal head 6 is separated from the platen roller 8 at the same time when printing is completed.

If it is determined in step S3 that the head temperature T has reached 50.degree. C., the process proceeds to step S7, where the heads of the ink sheet 10 and the recording paper 13 are located and positioned, and the thermal printing is performed. The head 6 is pressed against the platen roller 8.

Then, the process proceeds to a step S9, wherein the line memory 2
To output a printing start signal. Thereby, the image memory 1
, And reads out the gradation data for one line, and inputs the gradation data to the printing control unit 3.

In step S11, a main pulse signal having a current width corresponding to the input gradation data is supplied to each heating resistor to print an image on the recording paper 13. Specifically, the main pulse width corresponding to the input gradation data of each heating resistor for one line is read out from the ROM 4 and the main pulse signal of each energization width is transferred to the head driver control circuit 7 to generate each heating pulse. Energize the resistor. The energization of the main pulse signal causes each of the heating resistors to generate heat, thereby printing one line on the recording paper 13 in accordance with the input gradation data.

Next, the head temperature T of the thermal head 6 is detected by the thermistor 5 (S13), and the next step S
Go to 15.

In step S15, a preliminary pulse signal corresponding to the head temperature detected by the thermistor 5 and the input gradation data is supplied to each heating resistor to maintain each heating resistor at about 50.degree. More specifically, the head temperature and the number of dispersed pulses corresponding to the input gradation data for each heating resistor are read from the ROM 4, respectively, and prior to printing the next line, a preliminary pulse signal of the number of dispersed pulses for each heating resistor is read. Is transferred to the head driver control circuit 7 to energize each heating resistor. By the supply of the preliminary pulse signal, the supply start temperature of the main pulse signal of each line, that is, the printing start temperature of each line is maintained at about 50 ° C.

Then, the process proceeds to the next step S17, where it is determined whether or not the printing has been completed in accordance with the gradation data of the input image stored in the image memory 1. And the printing operation is completed with the completion of printing of all lines.

FIG. 5 shows a temperature change diagram of the heating resistor of the thermal head 6 by the printing operation. FIG. 5 shows a case where the detected head temperature is 50 ° C.

As shown in FIG. 5, when the first line is a high-density printing, for example, 127-tone printing, the main pulse width for 127 tones is 7.9 msec as shown in FIG. First, a main pulse signal having a conduction width of 7.9 msec is applied to the heating resistor. In this case, the maximum temperature of the heating resistor T _1T
Is that the sublimation dye is sufficiently higher than the threshold temperature T _{TH at} which diffusion transfer starts on the recording paper 13, and the heating resistor temperature is maintained at T _TH or higher for a long period of time. It is diffusion-transferred on.

Then, as shown in FIG.
Since the number of dispersion pulses for 0 ° C. and 127 gradations of gradation data is 0, the preliminary pulse signal is not applied to the heating resistor, and the operation shifts to the printing operation of the second line.

When no printing is performed on the second line, that is, in the case of 0 gradation printing, the main pulse width for 0 gradation is 1.8 msec as shown in FIG. .
A main pulse signal of 8 msec is applied to the heating resistor. In this case, since the maximum temperature T _2T of the heating resistor is always lower than the threshold temperature T _TH , the sublimation dye is not transferred onto the recording paper 13 by diffusion.

Then, as shown in FIG.
The number of dispersion pulses for 0 ° C. and 0 gradation data is 18
As a result, the dispersion pulse having a duty ratio of 50% and a period of 100 μsec as the preliminary pulse signal during the 18.1 msec.
It is applied to the heating resistor prior to printing the line. As a result, the temperature of the heating resistor is maintained at about 50 ° C. without lowering to 50 ° C. or less at the start of printing of the third line.

The third line is a medium density printing, for example, the 60th floor
In the case of signature printing, as shown in FIG.
The main pulse width is 5.1 msec.
A main pulse signal of msec is applied to the heating resistor. This place
The maximum temperature T of the heating resistor _3TMeans that the sublimation dye is recording paper 1
3 is a threshold temperature T at which diffusion transfer is started._THHigher than
Temperature T for high density printing_1TLower than. Further
In addition, the temperature of the heating resistor is equal to the threshold temperature T._THEnergization time exceeding
Sublimation dye is recorded because it is less than in high density printing
The amount of diffusion-transfer onto paper 13 is also higher than in high-density printing.
Less.

Then, as shown in FIG.
The number of dispersed pulses for 60 ° C. and 60 gradations is 8
Therefore, a dispersion pulse having a duty ratio of 50% and a period of 100 μsec is applied to the heating resistor as a preliminary pulse signal for a period of 8.4 msec before printing the fourth line. As a result, the heating resistor temperature becomes 5 at the start of the printing of the fourth line.
It is maintained at about 50 ° C. without dropping below 0 ° C.

As described above, the temperature of each heating resistor at the start of printing of each line is determined by the head temperature of the thermal head 6 and the preliminary pulse signal determined based on the input gradation data of each heating resistor. It is always maintained at about 50 ° C. by energization. Further, since the dispersion type pulse is used as the preliminary pulse signal, fine adjustment of each heating resistor temperature is facilitated, and highly accurate temperature control becomes possible.

[0036]

[0037]

As described above, according to the present invention, as a preheating means between image printing of each line, energization control is performed in consideration of not only the head temperature but also the input gradation data of each heating resistor. At the same time, the temperature of the heating resistor, which has risen once by applying the main pulse signal as a preliminary pulse signal, is substantially constant from when the temperature reaches a predetermined temperature at which no printing is performed until the next line printing is started. Is used, each heating resistor is maintained at a predetermined temperature before the start of image printing of each line.

Therefore, the heat storage state of each heating resistor during image printing can be accurately grasped, and the heat storage state can be surely reflected in the temperature control of the heating resistor before the start of printing. It is possible to stably reproduce a high-quality image without density unevenness.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a printing unit of a sublimation type thermal printer of the present invention.

FIG. 2 is a diagram showing a relationship between a conduction width of a main pulse signal stored in a ROM 4 and input gradation data of a table.

FIG. 3 is a diagram showing a relationship between input grayscale data of a table of a dispersion pulse number of a preliminary pulse signal stored in a ROM 4 and a head temperature.

FIG. 4 is a flowchart showing a printing operation of the sublimation type thermal printer of the present invention.

FIG. 5 is a temperature change diagram of a heating resistor of a thermal head by a printing operation of the sublimation type thermal printer of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image memory 2 Line memory 3 Printing control part 4 ROM 5 Thermistor (temperature detecting means) 7 Head driver control circuit

Claims (1)

(57) [Claims] An image having a gradation is reproduced by changing the amount of sublimation of a sublimation dye by controlling the amount of current supplied to each heating resistor of a thermal head in which a plurality of heating resistors are arranged in a line. In a sublimation type thermal printer, a temperature detection unit for detecting a temperature of the thermal head,
A printing means for printing an image on a recording medium by supplying a main pulse signal having a power supplied according to the gradation data to each of the heating resistors at a constant period, and an image of each line by the printing means; And a pre-heating means for pre-heating the heating resistors by supplying a distributed preliminary pulse signal defined based on the temperature detected by the temperature detecting means and the gradation data to each of the heating resistors. The preliminary pulse signal, after the temperature of each heating resistor once increased by applying the main pulse signal reaches a predetermined temperature at which printing does not reach, until the printing of the next line is started, A sublimation type thermal printer that maintains the temperature of each heating resistor substantially constant.