JPH06328757A - Thermal printer - Google Patents

Abstract

PURPOSE:To shorten the printing time by restraining welding of ink and roughening of a surface from occurring by a method wherein by varying printing time per one line of a color according to a coloring material to be used, coloring thermal energy optimum for the color is developed. CONSTITUTION:An image signal fetched from an image input part 11 such as a TV camera or the like is converted from an analog signal to a digital signal with an A/D converter 12, and written in frame memories 14y, 14m, 14c provided to each color. A pixel signal of each pixel read out from those frame memories is sent to an image signal processing part 15, tone corrected therein, and sent to table memories 16y, 16m, 16c per each color. Those table memories preliminarily store gradation control data, convert the image signal of each pixel to a driving time data which drives each heating element of a thermal head, and store that in a line buffer memory 17. A driving time data of one line content read out therefrom, is sent out to a gate 20 per each one line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer.

[0002]

2. Description of the Related Art Thermal printers include a thermal transfer printer that uses an ink sheet and a thermal printer that directly heats a thermal recording material to record an image. In these thermal printers, a thermal head in which a large number of heating elements (resistive elements) are arranged in a line is used. Thermal transfer printers include a melting type that transfers melted ink to recording paper and a sublimation type that changes the amount of ink transferred to the recording paper according to thermal energy.

[0003]

For example, in a sublimation type thermal printer, the print time per line for each color of yellow, magenta and cyan is set to be the same. Therefore, on the development side of the printing material, it is necessary to match the color forming sensitivities of the dyes of the respective colors to the printer, and there is a problem that the type of material used is limited.

For example, when the coloring sensitivity of the dye is lowered, it is necessary to increase the printing energy in order to secure a sufficient print density. Normally, the printing energy per unit time is increased or the energization time is lengthened. However, when the printing energy per unit time is increased, the temperature of the thermal head rises and sticking (sticking) between the recording paper and the ink sheet, ink welding,
Roughness is likely to occur. In addition, when the coloring sensitivity of each dye varies, it may not be possible to correct. Further, when the color development sensitivity is lowered, a sufficient density may not be obtained, which causes a problem that the image quality is deteriorated. Further, when the energization time of the thermal head is simply lengthened, there is a problem that the printing time as a whole becomes long.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a thermal printer capable of suppressing the occurrence of ink welding and surface roughening and shortening the printing time as a whole. And

[0006]

In order to achieve the above object, the invention described in claim 1 changes the printing time per line of the color according to the coloring material to be used,
This is to generate the coloring heat energy most suitable for the color.

According to a second aspect of the present invention, the printing time per line for each color is a driving pulse time by a plurality of driving pulses for performing bias heating and heating according to gradation, and The number of drive pulses per line is increased when printing a color with low sensitivity, and the rest time is lengthened so as not to exceed the upper limit heat generation amount.

[0008]

The printing time per line for each color can be changed so that the optimum color density is obtained according to the color developing sensitivity of each color. For example, in the case of a printing material in which the sensitivity of the color of yellow is halved corresponding to the colors of cyan and magenta, the printing time per line is longer than that of the other colors at the time of yellow recording, and the coloring So that the necessary and sufficient heat energy can be obtained. This printing time is composed of the sum of the driving pulse time by a plurality of driving pulses for performing bias heating and gradation heating according to gradation and the rest time between these driving pulses. While increasing the number of gradation pulses per line,
The dwell time is set long so as not to exceed the upper limit calorific value. Therefore, the head temperature is kept low, and sufficient thermal energy necessary for color development is applied to the thermal head, so that ink welding, surface roughening, and the like due to too high head temperature are suppressed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 2 showing the configuration of a sublimation type thermal printer, an image signal taken in from an image input section 11 such as a TV camera or a scanner is converted from an analog signal to a digital signal by an A / D converter 12. It is once written in the frame memories 14y, 14m and 14c provided for each color. This frame memory 14y, 14m, 14
The image signal of each pixel read from c is sent to the image signal processing unit 15, where the gradation is corrected and sent to the table memories 16y, 16m, 16c provided for each color.
The table memories 16y, 16m, and 16c store gradation control data in advance, convert the image signal of each pixel into drive time data for driving each heating element of the thermal head, and store it in the line buffer memory 17. To do. The drive time data for one line read from the line buffer memory 17 is sent to the gate 20 for each line.

The table memories 16y, 16m, 16
The memory writing unit 21 is connected to c. The drive time changing unit 22 is connected to the memory writing unit 21. The drive time changing unit 22 outputs the drive time data selected or input by the keyboard 23 to the memory writing unit 21. The memory writing unit 21 rewrites the drive time data of the table memories 16y, 16m, 16c based on this drive time data. As a result, the driving time data can be arbitrarily changed according to the coloring sensitivity of each dye of the ink sheet.

The gate 20 is connected to a pulse generator 25 which outputs a stationary pulse P _O having a waveform as shown in FIG. 3 (B). The steady pulse P _O is one bias pulse P 0 with a long cycle for raising the heating element to the ink sublimation temperature.
₁ and a gradation pulse train P ₂ that raises the temperature of the heating element according to the number of gradations of the pixel. Between the pulse train P ₂ and the next bias pulse P ₁ , the heating element of the thermal head 26 in order to prevent excessive temperature rise, rest period T _O to stop the driving one o'clock is provided. In addition,
Instead of the bias pulse having a long cycle, the gradation pulse train P ₂
You may use the bias pulse train which consists of a pulse train similar to.

The gate 20 is driven as shown in FIG.
Steady pulse P according to motion time data _OTo pass
To drive the drive pulse as shown in FIG.
To 27. The driver 27 changes the driving pulse to
Accordingly, the thermal head 26 is driven and each heating element 30
To generate heat according to the pixel data. Also the controller
28 is the frame memories 14y, 14m, 14c,
Image signal processing unit 15, table memories 16y, 16m,
16c, line buffer memory 17, connected to gate 20
Therefore, the entire device is controlled while synchronizing these.
Do your best.

The thermal head 26 has a width of, for example, 16
The heating element 30 having a length of 0 μ and a length of 120 μ is a recording paper 31.
Are arranged in a line at right angles to the conveyance direction of.
A platen drum 32 is provided below the thermal head 26, and an ink sheet 33 and a recording paper 34 are superposed between them and conveyed by a resin roller 35 and a rubber roller 36. The resin roller 35 and the rubber roller 36 are driven by motors 37 and 38, respectively. The controller 28 drives the motors 29 and 30 in synchronization with the drive pulse to intermittently convey the ink sheet 33 and the recording paper 34 for each recording pixel.

As shown in FIG. 4, the ink sheet 33 is
A heat resistant slipping layer 41 is provided on one side of the base film 40, and a dye layer (sublimation dye ink layer) 42 is provided on the other side.
Each of the yellow, magenta, and cyan ink areas is formed in order with a predetermined length according to the length of the recording size.
The recording paper 34 is an image receiving layer 44 provided on a base sheet 43. The ink sheet 33 may be an ink sheet of four colors having a black ink area in addition to the three colors.

Next, the operation of the above embodiment will be described.
A halftone image such as a photograph or a painting is converted into an image signal by the image input unit 11, and the obtained image signal is converted into an A / D converter 1.
Frame memory 14y, 14m, 1 for each color via 2
4c. At the time of three-color frame sequential printing, the image signal read from the yellow frame memory 14y is first subjected to gradation correction and color correction by the image signal processing unit 15, and then sent to the yellow table memory 16y. By the table memory 16y, the yellow image signal is converted into drive time data according to the recording density of one recording pixel and written in the line buffer memory 17.
Then, the controller 28 sequentially reads the drive time data for one line from the line buffer memory 17 and sends it to the gate 20.

The drive time data of the table memories 16y, 16m and 16c are individually set by the change data from the drive time changing section 22 according to the color developing sensitivity of each dye of the ink sheet 33 to be used. For example, as shown in FIG. 5, when the color density is set to 2.0 by using an ink sheet whose color developing sensitivity decreases in the order of cyan, magenta, and yellow, the number of gradation pulses is 3n during yellow thermal recording. , The number of gradation pulses is 2n during magenta thermal recording,
The number of gradation pulses becomes n during cyan thermal recording.

FIG. 6 is a diagram showing the relationship between the gradation data of yellow and the number of gradation pulses. For example, when the maximum density of yellow is 2.0 and 64 gradations are expressed, the number of gradation pulses is 3n when the maximum density is 2.0. Further, when the density is set to 1.0, the number of gradation pulses is 3n / 2.

From the pulse generator 25 to the gate 20 of FIG.
A steady pulse P _O as shown in (B) is input,
Driving time data T ₁ , T ₂ , T as shown in FIG.
_The stationary pulse P _O is made to pass based on ₃ and T _4, and drive pulses G ₁ , G ₂ , G ₃ and G ₄ as shown in FIG.
Is output to the driver 27. The driver 27 drives the thermal head 26 according to the driving pulses G ₁ , G ₂ , G ₃ , and G ₄ . The thermal head 26 is the ink sheet 3
The yellow ink area 3 is heated from the back surface. As a result, as shown in FIG. 4, the yellow sublimation dye of the ink sheet 33 is sublimated or melted and transferred to the image receiving layer 44 to be absorbed and fixed.

After thermal recording of the yellow image, the motor 38 is rotated in the reverse direction so that the front end of the magenta image recording area is set on the thermal head 26. Further, the motor 37 rotates in the normal direction, the recording start position of the next magenta ink area is set on the thermal head 26, and the cueing is completed. The image signal read from the magenta frame memory 14m is gradation-corrected and color-corrected by the image signal processing unit 15, and then sent to the magenta table memory 16m. With this table memory 16m, the magenta image signal is 1
It is converted into driving time data according to the recording density of the recording pixel and written in the line buffer memory 17. Then, the controller 28 sequentially reads the drive time data for one line from the line buffer memory 17 and sends it to the gate 20. Then, the thermal head 26 is driven via the gate 20 and the driver 27, and the magenta image is thermally recorded line by line.

After thermal recording of the magenta image, cueing is performed in the same manner as after thermal recording of the yellow image. After that, the image signal read from the cyan frame memory 14c is subjected to gradation correction and color correction by the image signal processing unit 15, and then sent to the cyan table memory 16c. With this table memory 16c, the cyan image signal is converted into drive time data according to the recording density of one recording pixel,
It is written in the line buffer memory 17. Then, the controller 28 sequentially reads the drive time data for one line from the line buffer memory 17, and the gate 2
Sent to 0. Then, the gate 20 and the driver 27
The thermal head 26 is driven via the, and a cyan image is thermally recorded line by line.

FIG. 7B is an explanatory diagram showing the drive pulse according to the present embodiment in comparison with the conventional drive pulse (FIG. 7A). Conventionally, when each color is thermally recorded, the printing time for one line is set to the same T ₁ even when the coloring sensitivities of the dyes are different, so that the printing time as a whole cannot be shortened. On the other hand, in the present embodiment, as shown in FIG. 7B, the print time Ty per line during thermal recording of each color of yellow, magenta, and cyan,
Tm and Tc are changed to Ty>Tm> Tc in the case of Sy <Sm <Sc according to the color development sensitivities Sy, Sm and Sc of the dyes.

Therefore, as shown in FIG. 1, the printing time Ty, Tm, Tc is optimally set in accordance with the coloring sensitivities Sy, Sm, Sc of the dyes during the three-color surface sequential thermal recording. As described above, unlike the case where the printing time for each color is made uniform, the printing time can be shortened in the case of highly sensitive dyeing.

In the case of a dye having a particularly low sensitivity, as shown in FIG. 8, the driving pulse number 3n is increased by α ((3
(n + α), and the pause period T _o between the grayscale pulses is set long so that the upper limit temperature of the thermal head 26 is not reached. As a result, as shown by the solid line E in FIG. 9, the temperature of the thermal head 26 does not exceed the upper limit temperature Tmax, and the occurrence of troubles due to heat can be suppressed. Moreover, the thermal energy to the thermal head 26 becomes the area A1, and the heating necessary and sufficient for color development is performed. On the other hand, if the number of gradation pulses is simply increased, the temperature of the thermal head 26 will exceed the upper limit temperature Tmax as shown by the dashed line F in FIG. 9, and various troubles due to heating will occur. That is, when the temperature of the thermal head 26 exceeds the upper limit temperature Tmax and enters the area A2, the ink sheet shrinks due to overheating, ink wrinkles and ink sheet breakage occur, and the image receiving layer side is thermally damaged and surface roughened. A decrease in gloss and a decrease in color density occur. Furthermore, sticking between the recording paper and the ink sheet and peeling of the dye occur. In the present embodiment, the number of gradation pulses and the rest period T _o are controlled so that the temperature of the thermal head 26 does not enter the area A2 that causes heat damage, so that various troubles due to overheating as described above occur. Can be suppressed. The double-dashed line H in the figure shows the time of yellow thermal recording in the above-mentioned embodiment.

Further, in the above embodiment, the sublimation type thermal printer has been described as an example, but the present invention is not limited to this, and the present invention can be applied to a thermal fusion type thermal printer or a thermal printer. Further, in addition to a color printer, when printing recording materials having different color development sensitivities in the same printer in a monochrome thermal printer, by slowing the printing speed while keeping the peak of printing energy the same, It is possible to reduce heat damage caused by the thermal head.

[0025]

As described above, according to the present invention,
Since the printing time can be optimally set according to the coloring sensitivity of the dye, the printing time as a whole can be shortened. Moreover, since the printing time is optimally set according to the coloring sensitivity of each dye, it is possible to suppress the occurrence of troubles such as sticking and ink welding due to the temperature rise of the thermal head.

Furthermore, since the printing time can be optimally set according to the coloring sensitivity of the dye, the coloring sensitivity of the dye of the recording material to be used can be widened. Therefore, the range of selection of recording materials is widened, and it becomes possible to use recording materials suitable for various applications.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a print time for each color in a thermal printer of the present invention in comparison with a conventional one.

FIG. 2 is a block diagram showing an electric circuit of the color thermal printer.

FIG. 3 is a timing chart showing drive time data, steady pulses, and drive pulses in the same color thermal printer.

FIG. 4 is an explanatory diagram showing a layer structure of an ink sheet and a recording sheet.

FIG. 5 is a diagram showing color development sensitivity of each color.

FIG. 6 is a diagram showing the relationship between the color density, the number of gradations, and the number of gradation pulses.

FIG. 7 is a diagram showing drive pulses of respective colors in comparison with a conventional one.

FIG. 8 is a diagram showing drive pulses in another example.

FIG. 9 is a diagram showing a temperature rise of the thermal head due to the drive pulse in comparison with other cases.

[Explanation of symbols]

 26 thermal head 30 heating element 33 ink sheet 34 recording paper

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B41J 3/20 117 C

Claims (2)

[Claims] 1. In a thermal printer having a thermal head in which a plurality of heating elements are arranged in a line, the printing time per line of the color is changed according to the coloring material to be used, and the optimum color is obtained. A thermal printer, which is characterized by generating colored heat energy. 2. The thermal printer according to claim 1, wherein a printing time per line for each color is a driving pulse time by a plurality of driving pulses for performing bias heating and heating according to gradation, and The number of drive pulses per line is increased when printing a color with low sensitivity, and the rest time is lengthened so as not to exceed the upper limit heat generation amount. Thermal printer.