JPH06106766A - Sublimation type thermal printer - Google Patents

Abstract

PURPOSE:To provide a sublimation type thermal printer which causes no irregularity in printing density by controlling power supply under the condition that not only a temperature of a head detected during the printing of an image but also a heat accumulation state of each heating resistor is taken into consideration. CONSTITUTION:The printer has a temperature detecting means 5 for detecting a temperature of a thermal head 6 and printing means 3, 7 for sending a main pulse signal having electric power to be fed according to gradation data to each heating resistor and for printing an image on a recording medium 13. This sublimation type thermal printer has preheating means 3, 7 for sending a preliminary pulse signal having electric power to be fed according to the temperature detected by the temperature detecting means 5 and the gradation data to each heating resistor during the printing of the image on each line by the printing means 3, 7 and for preheating each heating resistor up to a predetermined temperature at which level printing is not carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention changes the sublimation amount of a sublimation dye by controlling the amount of electricity supplied to each heating resistor of a thermal head in which a plurality of heating resistors are arranged in a line, thereby producing gradation. Sublimation type thermal printer for reproducing an image having

[0002]

2. Description of the Related Art Conventionally, in a sublimation type thermal printer of this type, the quality of a reproduced image fluctuates under the influence of the surrounding thermal environment, and particularly the head temperature of a thermal head has a great influence on the reproduced image quality. Was being given.

Further, in the sublimation type thermal printer, the amount of electricity supplied to each heating resistor of the thermal head is controlled to perform image printing, but all the thermal energy generated at the time of electricity application is transferred to the ink sheet and sublimated. Rather than causing a reaction, a part of the thermal energy is transferred to the head body, leading to an increase in head temperature, that is, heat storage in the head. Then, the recording density increases due to the heat storage of the head, and a difference occurs in the recorded image at the start and the end of recording.

For this reason, recently, there has been a method of embedding a temperature sensor such as a thermistor in a thermal head and controlling the amount of electricity to each heating resistor of the thermal head based on the head temperature detected by the temperature sensor. Proposed.

With this energization control method, even if the temperature of the thermal head changes due to heat accumulation in the thermal head or cooling of the thermal head due to the influence of outside air,
It is possible to print the reproduced image without being affected by the surrounding thermal environment without causing a large difference between the printed images at the start of printing and at the end of printing.

[0006]

However, since it is difficult to directly measure the temperature of the heating resistor of the thermal head in the above energization control method, the temperature of the substrate side of the thermal head 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, and particularly the heat storage state of the heating resistor during image printing can be accurately grasped. It was impossible.

Further, when a different amount of electricity 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, so that only energization control by head temperature is required. However, the printing density unevenness occurred, and it was not possible to reproduce a high quality image.

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

[0009]

According to the present invention, there is provided a temperature detecting means for detecting the temperature of a thermal head, and a main pulse signal having an energizing power corresponding to gradation data is energized to each heating resistor to form a recording medium. Printing means for printing an image on the image forming device, and a spare having a temperature detected by the temperature detecting means and an energization power corresponding to the gradation data between the printing of the image of each line by the printing means. A sublimation type thermal printer comprising: a preheating unit that applies a pulse signal to each heating resistor to preheat each heating resistor to a predetermined temperature at which printing is not performed.

[0010]

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

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A sublimation type thermal printer of the present invention will be described below with reference to the drawings showing its embodiments.

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

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

Specifically, a main pulse signal having an energization power corresponding to each gradation data for one line from the line memory 2 is energized to each heating resistor to correspond to the input gradation data on the recording medium. An image for one line is printed, and after the main pulse signal is output, a head pulse detected by the thermistor 5 and a preliminary pulse signal having energization power corresponding to the input gradation data are energized to each heating resistor. The heating resistors are 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 a colorant of three colors of yellow, magenta, and cyan is applied in a face-sequential manner by a sublimation dye, which is stretched by a supply roll 11 and a sheet winding roll 12. It is set up. Reference numeral 13 is 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 sheet 4, the sheet passes between the thermal head 6 and the platen roller 8, and is then ejected by the sheet ejection roller 15 to the outside of the sublimation type thermal printer.

In the present embodiment, the energizing power of the main pulse signal and the auxiliary pulse signal is variably controlled by the energizing width, and the energizing rate is 50% and the cycle is 100 μm as the auxiliary pulse signal.
A dispersed pulse of sec is used.

Further, the ROM 4 stores a table of the energization width of the main pulse signal for the input gradation data, and a table of the dispersed pulse number of the preliminary pulse signal for the input gradation data and the head temperature.

FIG. 2 is a relational diagram with the input gradation data in the table of the energization width of the main pulse signal stored in the ROM 4, FIG.
FIG. 9 shows a relationship diagram between the input gradation data of the table of the dispersed pulse number of the preliminary pulse signal stored in the ROM 4 and the head temperature. Here, in FIG. 3, the head temperature is 30 ° C., 40 ° C.,
Although shown only for the case of 50 ° C., the ROM 4 stores a table of the number of dispersed pulses for input gradation data for each 1 ° C. of head temperature at 30 ° C. to 50 ° C.

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

First, before starting 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 127 gray levels is read from the ROM 4 as the input gray level data, and the main pulse signal of the energization width is applied to all the heating resistors of the thermal head 6. (S5), and returns to step S1. As a result, the temperature of the thermal head rises until the head temperature T reaches 50 ° C. The thermal head 6 is brought into contact with and separated from the platen roller 8 at the same time when printing is completed.

When it is determined in step S3 that the head temperature T has reached 50 ° C., the process proceeds to step S7, the ink sheet 10 and the recording paper 13 are indexed and positioned, and the thermal The head 6 is brought into pressure contact with the platen roller 8.

Next, in step S9, the line memory 2
The print start signal is output to. As a result, the image memory 1
The gradation data for one line is read out and the gradation data is input to the printing control unit 3.

In step S11, a main pulse signal having an energization width corresponding to the input gradation data is energized 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 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 heat. Energize the resistor. By energizing the main pulse signal, each heating resistor is caused to generate heat, and one line is printed on the recording paper 13 according to 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
Proceed to 15.

In step S15, a preliminary pulse signal having an energization width corresponding to the head temperature detected by the thermistor 5 and the input gradation data is energized to each heating resistor, and each heating resistor is printed. Preheat to 50 ° C. Specifically, the dispersed pulse numbers corresponding to the head temperature and the input gradation data for each heating resistor are read from the ROM 4, respectively, and the preliminary pulse signal of the dispersed pulse number for each heating resistor is read before printing the next line. To the head driver control circuit 7 to energize each heating resistor. By energizing the preliminary pulse signal, the temperature at the start of energization of the main pulse signal of each line, that is, the temperature at the start of printing of each line is about 5
Keep at 0 ° C.

Then, the process proceeds to the next step S17, and it is determined whether or not the printing is completed according to the gradation data of the input image stored in the image memory 1. If the printing is in process, the step S11 is performed. Then, when the printing of all lines is completed, the printing operation is completed.

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

As shown in FIG. 5, when the first line is high density printing, for example, 127 gradation printing, the main pulse width for 127 gradations 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 sufficiently higher than the threshold temperature T _{TH at} which the sublimation dye starts diffusion transfer onto the recording paper 13, and the temperature of the heating resistor is maintained at T _TH or higher for a long time. Diffused and transferred onto.

Then, as shown in FIG. 3, the head temperature is 5
Since the number of dispersed pulses for 0 ° C. and the gradation data for 127 gradations is 0, the preliminary pulse signal is not applied to the heating resistor and the printing operation of the second line is started.

When the second line is not printed, 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 to the recording paper 13 by diffusion.

Then, as shown in FIG. 3, the head temperature is 50
The number of dispersed pulses for ℃ and gradation data 0 gradation is 18
Therefore, the dispersed pulse having a duty ratio of 50% and a cycle of 100 μsec is 18.1 msec as the preliminary pulse signal, and the third pulse
It is applied to the heating resistor prior to printing the line. As a result, the temperature of the heating resistor does not drop below 50 ° C. and is maintained at about 50 ° C. at the start of printing the third line.

The third line is a medium density print, for example, the 60th floor.
In the case of signature printing, as shown in FIG.
Since the main pulse width is 5.1 msec, first the energization width 5.1
A main pulse signal of msec is applied to the heating resistor. This place
Temperature T of the heating resistor _3TSublimation dye is recording paper 1
Threshold temperature T at which diffusion transfer is started on_THHigher than
Temperature T for high density printing_1TLower than. Furthermore
And the temperature of the heating resistor is the threshold temperature T_THEnergization time exceeding
Compared with the case of high density printing, sublimation dye is recorded
Compared to the case of high density printing, the amount of diffused transfer on paper 13 is also
Less.

Then, as shown in FIG. 3, the head temperature is 50
The number of dispersed pulses for 8 degrees Celsius and 60 gradation data is 8
Therefore, a dispersed pulse having a duty factor of 50% and a period of 100 μsec is applied as a preliminary pulse signal to the heat generating resistor for the duration of 8.4 msec before printing the fourth line. As a result, the temperature of the heating resistor becomes 5 at the start of printing the fourth line.
It is maintained at about 50 ° C without lowering 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. By energizing, it is always maintained at about 50 ° C. Further, since the dispersed pulse is used as the preliminary pulse signal, it becomes easy to finely adjust the temperature of each heating resistor, and it becomes possible to perform temperature control with high accuracy.

In the above embodiment, the case where the energization power of the main pulse signal and the auxiliary pulse signal is variably controlled by the energization width has been described, but it may be variably controlled by the energization voltage.

[0037]

As described above, according to the present invention, energization control is performed in consideration of not only the head temperature but also the input gradation data of each heating resistor as a preheating means between image printing of each line. Therefore, each heating resistor is maintained at a predetermined temperature when the image printing of each line is started.

Therefore, it is possible to accurately grasp the heat storage state of each heating resistor during image printing, and it is possible to reproduce a high-quality image in which printing density unevenness does not occur.

[Brief description of 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 input gradation data of a table of energization width of a main pulse signal stored in a ROM 4.

FIG. 3 is a diagram showing a relationship between input gradation data of a table of dispersed pulse numbers of preliminary pulse signals stored in a ROM 4 and 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 due to a printing operation of a sublimation type thermal printer of the present invention.

[Explanation of symbols]

 1 image memory 2 line memory 3 printing control unit 4 ROM 5 thermistor (temperature detecting means) 7 head driver control circuit

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B41J 3/20 115 A

Claims (2)

[Claims] 1. A gradation head image is reproduced by changing the sublimation amount of a sublimation dye by controlling the amount of electricity 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, temperature detecting means for detecting the temperature of the thermal head, and a main pulse signal having energizing power corresponding to gradation data are energized to each heating resistor to print an image on a recording medium. Between the printing means for performing the printing and the printing of the image of each line by the printing means, a preliminary pulse signal having a temperature detected by the temperature detecting means and an energizing power according to the gradation data is generated for each heat generation. A sublimation type thermal printer, comprising: a preheating unit that energizes the resistors to preheat each of the heating resistors to a predetermined temperature at which printing is not performed. 2. The sublimation type thermal printer according to claim 1, wherein the preliminary pulse signal is a dispersion type pulse.