JPH10315516A - Color thermal recorder and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a color print in which gloss is enhanced while suppressing fluctuation of density. SOLUTION: A conduction time data being selected by the number of driving pulses and the value of an image data is stored in a conduction time ROM. A conduction time data for one line read out from the ROM is delivered through a latch array to a comparator array. The comparator array compares each conduction time data with the count of a clock counter and converts each conduction time data into a control pulse. The control pulse is converted through a head driver into a drive pulse having a voltage value corresponding to a color to be recorded and a width corresponding to an image data. Since each heating element is driven based on N drive pulses generated during a constant period within the recording interval of 1 dot, temperature fluctuation of a protective layer is suppressed within the recording interval of 1 dot. Consequently, the viscosity of the protective layer 7 is kept at a constant level resulting in a color print in which gloss is enhanced while suppressing fluctuation of density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color thermosensitive color recording method and apparatus.

[0002]

2. Description of the Related Art In color thermosensitive color recording, a color thermosensitive recording paper is heated by a thermal head to directly record a color image on the color thermosensitive recording paper. This is also called direct thermal recording. In this color thermosensitive recording paper, a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, a yellow thermosensitive coloring layer, and a transparent protective layer are sequentially provided on a support. The yellow thermosensitive coloring layer on the outermost side has high thermal sensitivity and develops yellow with small thermal energy. The cyan thermosensitive coloring layer, which is the lowermost layer, has low thermal sensitivity, and develops cyan when a large amount of thermal energy is applied. In addition, the yellow thermosensitive coloring layer and the magenta thermosensitive coloring layer have a fixing property, and when irradiated with electromagnetic radiation in a wavelength range peculiar to each thermosensitive coloring layer, for example, ultraviolet rays, uncolored coloring components are decomposed and the coloring ability is improved. Is lost.

Since each thermosensitive coloring layer develops a color at a density corresponding to the thermal energy, when a large thermal energy is applied, dots having a high density are recorded. In the conventional color thermosensitive color recording, when one dot is recorded on one thermosensitive coloring layer, a voltage corresponding to the thermosensitive coloring layer is applied to the thermal head, and heat is generated for a time corresponding to the value of the image data. The element is continuously energized to generate desired thermal energy. After this energization, each heating element is turned off. The heating element is cooled in the OFF state, and this period is called a cooling period.

[0004] When the power is supplied continuously, the temperature of the heating element becomes considerably high, so that the heating element and the color thermosensitive recording paper may be thermally damaged. Therefore, there is known a driving device in which each heating element is driven by a plurality of driving pulses when recording each dot so that the heating element does not become hot (Japanese Patent Publication No. 8-1).
No. 5791). In this driving device, the number of driving pulses is proportional to the value of the image data. For example, when the value of the image data is N (N in the gradation level), the heating element is driven by N driving pulses.

FIG. 6 shows a recording state of a thermosensitive coloring layer which develops a color at a coloring temperature CH. The color thermosensitive recording paper is continuously conveyed in the sub-scanning direction. When the heating element records one dot, the heating element is driven by the number of driving pulses corresponding to the image data to generate heat. After the heat generation is completed, a period until the driving is started by the driving pulse based on the next image data is a cooling period. The sum of the heat generation period and the cooling period is constant. When the value of the image data is small, the heat generation period is short and the cooling period is long.

[0006]

A protective layer made of a transparent resin is formed on the surface of the color thermosensitive recording paper. This protective layer is used for improving the thermal contact with the thermal head. Softens at point GT. The protection layer softens during the time T1 to T2, but remains solid without softening during the time T2 to T3. If the ratio of the cooling period to the line cycle is large, as in low-density printing, the surface of the color thermosensitive recording paper will have irregularities corresponding to the ratio of the heating period to the cooling period, and the surface gloss will deteriorate. . In addition, since softening and solidification are repeated, the coefficient of kinetic friction increases, the stability of recording paper conveyance deteriorates, and density unevenness tends to occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a color thermosensitive recording method and apparatus for improving the gloss at the time of low density printing and suppressing the occurrence of density unevenness.

[0008]

According to the first aspect of the present invention, there is provided a color thermosensitive recording paper in which a plurality of thermosensitive coloring layers and protective layers having different thermal sensitivities and colors to be formed are sequentially formed on a support. When using a thermal head in which a plurality of heating elements are formed in a line shape and repeating the heating by the thermal head and the fixing by the electromagnetic radiation, color recording is performed sequentially from the thermosensitive coloring layer on the front side, and the value of the image data is regardless of,
The heating elements are driven using the first to Nth N drive pulses generated in a fixed cycle, the voltage of each drive pulse is set according to the thermosensitive coloring layer to be recorded, and the image data is The width of each drive pulse is set according to the value.

According to the second aspect of the present invention, the width of each drive pulse is set according to the number of generation of the drive pulse in addition to the value of the image data.

According to the third aspect of the present invention, there is provided a color thermosensitive recording paper in which a plurality of thermosensitive coloring layers and protective layers having different thermal sensitivities and colors to be formed are successively formed on a support, and a plurality of heating elements. Using a thermal head formed in a line shape, while repeating heating by the thermal head and fixing by electromagnetic radiation, color recording is performed in order from the uppermost thermosensitive coloring layer,
In a color thermosensitive color recording apparatus for recording a color image on a color thermosensitive recording paper, an energizing time ROM for generating energizing time data corresponding to the value of image data, a clock counter for counting clocks, and a count value of the clock counter. A comparator for comparing the current with the energization time data and generating a drive pulse having a width corresponding to the energization time data, and reading out the energization time ROM, counting the clock counter, and comparing the comparator, N driving operations are repeated. A pulse is generated, and the voltage of each drive pulse is set according to the thermosensitive coloring layer to be recorded, so that one dot is recorded by N drive pulses having a width corresponding to the value of image data. Things.

According to a fourth aspect of the present invention, a drive pulse counter for counting the number of generated drive pulses is provided, and the energized time ROM stores energized time data determined by the value of image data and the number of generated drive pulses. The energization time data is read out based on the image data and the drive pulse generation number.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 2, a color thermosensitive recording paper 2 comprises a support 3 on which a cyan thermosensitive coloring layer 4, a magenta thermosensitive coloring layer 5, a yellow thermosensitive coloring layer 6, and a protective layer 7 are provided. They are layered sequentially. Each of these thermosensitive coloring layers is 4-6
Are arranged from the front side in the order of thermal recording. For example, when thermal recording is performed in the order of magenta, yellow, and cyan, the positions of the yellow thermosensitive coloring layer 6 and the magenta thermosensitive coloring layer 5 are switched. In addition, a black thermosensitive coloring layer that develops black and a skin color thermosensitive coloring layer that develops skin color are added.
It may have a four-layer or five-layer structure. The protective layer 7 is formed by applying a transparent resin.

The cyan thermosensitive coloring layer 4 develops cyan when heated. The magenta thermosensitive coloring layer 5 develops magenta, and the yellow thermosensitive coloring layer 6 develops yellow. The magenta thermosensitive coloring layer 5 is provided with an electromagnetic ray, for example, 36 mm after coloring recording.
Irradiation with ultraviolet light of 5 nm decomposes the uncolored components and loses the coloring ability, so that the magenta image is fixed. Similarly, the yellow thermosensitive coloring layer 6 is made of an electromagnetic ray, for example, 420 n.
When m ultraviolet rays are irradiated, the uncolored components are decomposed and the color forming ability is lost. The cyan thermosensitive coloring layer 4 is not provided with the fixing property by electromagnetic radiation because there is no thermosensitive coloring layer to be recorded next in the lowermost layer.

FIG. 3 shows a characteristic curve of each thermosensitive coloring layer when the thermal head is pressed against a color thermosensitive recording paper with a predetermined pressing force and heated. The horizontal axis is the heat energy generated by the heating element. The yellow thermosensitive coloring layer 6
It has the highest thermal sensitivity and develops color with small heat energy. Since the cyan thermosensitive coloring layer 4 is the lowermost layer, heat energy generated in the heating element is not easily transmitted. For this reason, in order to record the cyan thermosensitive coloring layer 4, it is necessary for the heating element to generate large thermal energy.

In FIG. 1, a frame memory 10 includes:
Yellow, magenta, and cyan image data captured from a scanner or a TV camera is written. This frame memory 10 is written by the write controller 11
The image data of the color to be printed is read out one line at a time and sent to the line memory 12. The write controller 11 is controlled by the print controller 13,
Reading from the frame memory 10 and writing to the line memory 12 are performed. Note that image data of three colors of red, green, and blue are written in the frame memory 10, and the color correction circuit arranged between the frame memory 10 and the line memory 12 is used to calculate yellow, magenta, and magenta in a matrix operation formula. , Cyan image data.

The print controller 13 divides the recording period of one dot into N cycles, and
Each part is controlled so that a number of drive pulses are generated. At the start of each cycle, the print controller 13
These signals are sent to the drive pulse counter 14. The drive pulse counter 14 counts the number of signals to check the number of drive pulses, and counts the count value as the energizing time ROM
Send to 15. When the drive pulse counter 14 receives one more signal after the count value reaches N,
Set to "1". Therefore, the drive pulse counter 14 cyclically counts “1” to “N”.

The read controller 16 reads the image data of the color to be recorded one by one from the line memory 12 and sends it to the power-on time ROM 15 in response to a read start signal from the print controller 13. A plurality of pages corresponding to the total number of drive pulses are prepared in the power-on time ROM 15, and power-on time data corresponding to each image data is written on each page. Therefore, desired energization time data can be read from the energization time ROM 15 based on the number of drive pulse generations and image data.

Each energization time data read from the energization time ROM 15 is sent to the latch array 17 and latched. When the energization time data for one line is latched by the latch array 17, each energization time data is sent to the comparator array 18.

The comparator array 18 comprises a number of comparators corresponding to the number of pixels in one line, and compares each energization time data with the count value of the clock counter 19. Each comparator becomes “H” when the energization time data is larger than the count value of the clock counter 19. As a result, each comparator outputs a control pulse having a width corresponding to the energization time data.

The clock generator 20 generates a clock having a constant cycle. Each clock is a clock counter 19
Is counted. For example, when the image data is “1” and the clock counter 19 becomes “2”, the output of the comparator is inverted to “0”. When the clock counter 19 counts up to the maximum value M of the energization time data, it is set to "1" at the next clock. Therefore, the clock counter 19 cyclically counts between "1" and "M". The clock counter 19 sends a signal to the print controller 13 when the count value becomes “M”.

1 output from the comparator array 18
The control pulse for the line is sent to the head driver 21. The head driver 21 includes a switching element array for one line, and a voltage from a voltage regulator 28 is applied to each switching element. The voltage regulator 28 is controlled by the controller 13 and outputs a voltage corresponding to the thermosensitive coloring layer to be recorded.

The thermal head 22 is provided with a heating element 23 for one line on the lower surface thereof. Each heating element 23
Are connected in series to the corresponding switching elements and are turned on while the control pulse is being input. As a result, each heating element 23 has a voltage value from the voltage regulator 28 and is energized by a drive pulse having the same width as the control pulse to generate heat.

The color thermosensitive recording paper 2 is conveyed at a constant speed in the sub-scanning direction by a pair of conveying rollers 26 connected to a motor 25. While the color thermosensitive recording paper 2 is conveyed in the direction of the arrow, the platen roller 2 that rotates freely
7 and the thermal head 22 are pressurized and heated. As is well known, the thermal head 22 has a large number of heating elements 23 formed in a line in the main scanning direction.

A fixing device 29 is arranged near the transport roller pair 25. The fixing device 29 has an emission peak of 42
UV lamp 30 for yellow that emits 0 nm UV light
And a magenta ultraviolet lamp 31 that emits ultraviolet light having an emission peak of 365 nm.

Next, the operation of the above device will be described with reference to FIG. The three-color image data of the color image to be printed is taken into the frame memory 10. This yellow,
When printing is instructed after image data of three colors, magenta and cyan, is taken, first, recording of a yellow image is started. In recording the yellow image, the voltage controller 28 sends a voltage corresponding to the thermal sensitivity of the yellow thermosensitive coloring layer 6 to the head driver 21 according to a signal from the print controller 13. Further, the print controller 13
The yellow ultraviolet lamp 30 of the fixing device 29 is turned on.

Next, the controller 13 rotates the transport roller pair 26 via the motor 25. The transport roller pair 26 transports the color thermosensitive recording paper 2 fed from a paper feed mechanism (not shown) at a constant speed in the direction of the arrow. Furthermore,
The controller 13 rotates the thermal head 22 via a motor (not shown) to press the heating element array against the color thermosensitive recording paper 2.

The print controller 13 sends a write start signal to the write controller 11. The writing controller 11 reads one line of yellow image data from the frame memory 10 and writes the yellow image data to the line memory 12.

Next, the print controller 13 sends a signal to the drive pulse counter 14. The count value of the drive pulse counter 14 becomes “1”, and sends the count value to the power-on time ROM 15. Thereafter, the print controller 1
3 sends a read start signal to the read controller 16.

The read controller 16 reads yellow image data one by one from the line memory 12 and sends it to the power-on time ROM 15. The energization time ROM 15 selects the first page based on the count value “1” from the drive pulse counter 14. Since the relationship between the image data and the energization time data is tabulated in the first page, desired energization time data is read using the image data as an address. These energization time data are determined by the number of the drive pulse and the value of the image data.

Each line of yellow image data is converted into energization time data by the energization time ROM 15 and sent to the latch array 17. This latch array 1
When the energization time data for one line is latched in 7, the print controller 13 starts the count operation of the clock counter 19.

The comparator array 18 compares each energization time data with the count value of the clock counter 19. Each comparator becomes “H” when the energization time data is larger than the count value, and inverts to “L” when the count value becomes larger than the energization time data.
As a result, the comparator array 18 outputs a control pulse having a width corresponding to the energization time data for one line, and sends it to the head driver 21.

The head driver 21 has one line of switching elements connected to each heating element 23, and the corresponding switching element is turned on by a one line control pulse. In the recording of a yellow image, a voltage corresponding to the yellow image is applied to the head driver 21, so that a driving pulse having this voltage value and the same width as the control pulse is generated from each switching element. Each heating element 23 is driven by the drive pulse for one line to generate heat.

The count value of the clock counter 19 is counted up sequentially from "1", and the first cycle ends when the count value reaches the maximum value "M". Clock counter 19
Sends a signal to the print controller 13 indicating that the first cycle has ended.

Upon receiving the cycle end signal, the print controller 13 sends a signal to the drive pulse counter 14. Further, the print controller 13 sends a read start signal to the read controller 16 to read out one line of yellow image data and convert the energization time data again. In this case, since the count value of the drive pulse counter 14 is “2”, the second page of the energization time data is selected, and each yellow image data is converted to the energization time data with reference to this second page. . Each energization time data is converted into a second control pulse by the comparator array 18. Based on this control pulse, each heating element 23 is driven by a second drive pulse generated from the head driver 21 to generate heat.

The first cycle to the Nth cycle are executed as described above, and N drive pulses having a constant cycle are generated. Each heating element 23 according to these drive pulses
Is driven to color-record one yellow dot on the yellow thermosensitive coloring layer 6. Since each heating element is arranged in a line in the main scanning direction, one line of yellow dots is recorded on the thermal recording paper 24 by N cycles.

Similarly, a yellow image is color-recorded line by line in the recording area of the color thermosensitive recording paper 2 which is continuously conveyed. When the recording area has passed the thermal head 22 and the recording of the yellow image has been completed, the print controller 13 rotates the thermal head 22 and retracts it from the color thermosensitive recording paper 2.

The energizing time of the first cycle is T1on,
The OFF time is set to T1off. Similarly, the energizing time of the Nth cycle is TNon, and the OFF time is TNoff. In each cycle, the ratio of the energizing time to the cycle is a duty ratio. The greater the duty ratio, the wider the pulse width and the larger the heat generation energy per drive pulse.

The total energizing time for recording one yellow dot is T1on + T2on +... TNon
Since the thermal energy according to the total of the energizing times is given to the color thermosensitive recording paper 2, T1on to TNo
Almost the same concentration can be obtained as when n is continuously energized.
After the protection layer 7 is softened in the first line, the protection layer 7 remains soft until the last line, so that no irregularities on the surface occur, the recording paper is conveyed stably, and the density unevenness is reduced.

During recording of the yellow image, when the portion that has passed through the thermal head 22 reaches the fixing device 29, the 420 nm ultraviolet light emitted from the yellow ultraviolet lamp 30 is irradiated on the color thermosensitive recording paper 2. The uncolored components in the yellow thermosensitive coloring layer 6 are decomposed by the ultraviolet light of 420 nm, and the coloring ability is lost. As a result, the yellow image recorded on the recording area of the color thermosensitive recording paper 2 is fixed.

When the recording area of the color thermosensitive recording paper 2 has passed the fixing unit 29, the print controller 13
The yellow ultraviolet lamp 30 is turned off, and then the pulse motor 25 is reversed. Thus, the color thermosensitive recording paper 2 on which the yellow image is recorded is returned. When the leading end of the color thermosensitive recording paper 2 reaches the transport roller pair 26, the reverse rotation of the pulse motor 25 stops.

Next, recording of a magenta image is started.
As described above, the thermal head 22 is pressed against the color thermosensitive recording paper 2, and the magenta ultraviolet lamp 31 is turned on. Further, the voltage regulator 28 outputs a voltage corresponding to the thermal sensitivity of the magenta thermosensitive coloring layer 5. Since the thermal sensitivity of the magenta coloring layer 5 is lower than the thermal sensitivity of the yellow coloring layer 6, the magenta voltage is higher than the above-mentioned yellow voltage.

The magenta image data for one line is read from the frame memory 10 and, according to the above-described procedure,
The first cycle to the Nth cycle are executed, and N drive pulses having a constant cycle are generated. Each of the heating elements 23 is driven in accordance with the N drive pulses, and one magenta dot is color-recorded on the magenta thermosensitive coloring layer 5.

In this way, the magenta image is color-recorded line by line in the recording area of the color thermosensitive recording paper 2.
When the recording of the magenta image is completed, the thermal head 22
Retreats from the color thermosensitive recording paper 2. The portion on which the magenta image is recorded is fixed by irradiating 365 nm ultraviolet rays emitted from the magenta ultraviolet lamp 31.

After the color recording and fixing of the magenta image, the thermal head 22 is retracted, and the color thermosensitive recording paper 2 is returned again. Next, the thermal head 22 is pressed against the color thermosensitive recording paper 2 to start recording a cyan image. Also in the recording of the cyan image, the magenta ultraviolet lamp 31 is kept turned on, and the high heat generated during the recording of the cyan image, which is discolored to pale yellow, is bleached. The voltage controller 28 supplies a voltage according to the thermal sensitivity of the cyan thermosensitive coloring layer 4 to the head driver 21.

Based on the cyan image data read from the frame memory 10, each heating element 23 is driven by N drive pulses to color-record one cyan dot on the cyan thermosensitive coloring layer 4. The color thermosensitive recording paper 2 is subjected to bleaching by irradiating 365 nm ultraviolet rays emitted from the magenta ultraviolet lamp 31 after the cyan image is color-recorded by the thermal head 22 line by line. After the bleaching, the paper is discharged to a paper discharge tray (not shown). After this discharge, the magenta ultraviolet lamp 31
Turns off.

FIG. 3 shows the width of the driving pulse when a 256-gradation yellow image is recorded. When the yellow image data is "0", the pulse width is the smallest and the color thermosensitive recording paper does not develop color. If the image data is "1
In the case of "27", the pulse width becomes slightly large, and a medium density dot is recorded. When the image data is "255", the pulse width is the largest and the dot with the highest density is recorded. In this example, when the values of the image data are the same, drive pulses having the same width for all three colors are used.

In the above apparatus, the cycle number
Although the width of the drive pulse is changed, the drive pulse counter 1
By omitting step 4, the same energization time data may be used in all cycles. In this case, the energization time RO
Since M15 only needs to store one page of data, a ROM having a small storage capacity can be used.

In a commercially available color thermosensitive recording paper, γ of each thermosensitive coloring layer is slightly different, but
Preferably, the width of the N drive pulses is changed according to the color to be recorded. In this case, the energization time data is prepared for each color in the energization time ROM 15 and is selected according to the color to be printed.

[0049]

According to the present invention, when one dot is recorded, N drive pulses are generated at a fixed period for all image data, and the pulse width is changed according to the value of the image data. The heating elements are driven according to the N drive pulses. Therefore, since a cooling period is not provided as in the related art, even when the value of the image data is small, unevenness does not occur on the surface, and a color print with good gloss can be obtained. Further, since the recording paper conveyance is stabilized, the density unevenness is reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a color thermosensitive color recording apparatus of the present invention.

FIG. 2 is an explanatory diagram illustrating a layer configuration of a color thermosensitive recording paper.

FIG. 3 is a graph showing the coloring characteristics of each thermosensitive coloring layer.

FIG. 4 is an explanatory diagram showing a relationship between a driving pulse and a temperature of a heating element.

FIG. 5 is a waveform diagram showing drive pulses having different pulse widths.

FIG. 6 is an explanatory diagram showing a conventional driving method.

[Explanation of symbols]

 2 Color Thermal Recording Paper 7 Protective Layer 22 Thermal Head 23 Heating Element 26 Transport Roller Pair 29 Fixer

Claims (4)

[Claims] 1. A color thermosensitive recording paper in which a plurality of thermosensitive coloring layers and protective layers having different thermal sensitivities and colors to be formed are sequentially formed on a support, and a thermal printing paper in which a plurality of heating elements are formed in a line. Using a head, while repeating the heating by the thermal head and the fixing by the electromagnetic radiation, color-recording in order from the heat-sensitive coloring layer on the front side, in a color thermosensitive color recording method of recording a color image on a color thermosensitive recording paper, Regardless of the value of the image data, the heating elements are driven by using the first to Nth N drive pulses generated in a fixed cycle, and the voltage of each drive pulse is determined according to the thermosensitive coloring layer to be recorded. And setting the width of each drive pulse in accordance with the value of the image data. 2. The color thermosensitive color recording method according to claim 1, wherein the width of each drive pulse is set according to the number of generation of the drive pulse in addition to the value of the image data. 3. A color thermosensitive recording paper in which a plurality of thermosensitive coloring layers and protective layers having different thermal sensitivities and colors to be formed are sequentially provided on a support, and a thermal printing paper in which a plurality of heating elements are formed in a line. A color thermosensitive color recording apparatus that uses a head and repeats heating by a thermal head and fixing by electromagnetic radiation, sequentially records and records color from the thermosensitive coloring layer on the front side, and records a color image on a color thermosensitive recording paper. A power-on time ROM for generating power-on time data corresponding to the value of image data, a clock counter for counting clocks, and comparing the count value of the clock counter with the power-on time data to drive a width corresponding to the power-on time data A pulse generating comparator is provided to read the energization time ROM, count the clock counter, and compare the comparator. Together to generate a N drive pulse repeatedly, and in accordance with the heat-sensitive coloring layer to be recorded and set the voltage of each driving pulse, of width corresponding to the image data N
A color thermosensitive color recording apparatus, wherein one dot is recorded by one driving pulse. 4. A driving pulse counter for counting the number of generations of the driving pulses is provided, and energizing time ROM is stored with energizing time data determined by a value of image data and a driving pulse generation number. 4. The color thermosensitive color recording apparatus according to claim 3, wherein the energization time data is read out based on the driving pulse generation number.