JP3681508B2 - Color thermal color recording method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color thermosensitive color recording method and apparatus.
[0002]
[Prior art]
In color thermosensitive color recording, a color thermosensitive recording paper is heated by a thermal head and a color image is recorded directly on the color thermosensitive recording paper, which is also called direct thermosensitive 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 formed on a support. The yellow thermosensitive coloring layer on the most surface side has high thermal sensitivity and develops yellow with a small amount of heat energy. The cyan thermosensitive coloring layer, which is the lowermost layer, has low thermal sensitivity and develops cyan when large heat energy is applied. In addition, the yellow and magenta thermosensitive coloring layers have fixing properties, and when they are exposed to electromagnetic radiation in the wavelength range unique to each thermosensitive coloring layer, for example, ultraviolet rays, the uncolored coloring components decompose and develop coloring ability. Is lost.
[0003]
Each thermosensitive coloring layer develops a color corresponding to the thermal energy, so that when high thermal energy is applied, a high density dot is recorded. In conventional color thermosensitive color recording, when one dot is recorded on one thermochromic layer, a voltage corresponding to the thermochromic 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 this OFF state, and this period is called a cooling period.
[0004]
When energized continuously, the heating element becomes very hot, and the heating element and the color thermal recording paper may be thermally destroyed. Therefore, a driving device is known in which each heating element is driven by a plurality of drive pulses when each dot is recorded so that the heating element does not reach a high temperature (Japanese Patent Publication No. 8-15791). In this drive device, the number of drive pulses is proportional to the value of the image data. For example, when the value of the image data is N (the gradation level is N), the heating element is driven with N drive pulses.
[0005]
FIG. 6 shows the recording state of the thermosensitive coloring layer that develops color at the coloring temperature CH. The color thermal recording paper is continuously conveyed in the sub-scanning direction. When the heating element records one dot, it is driven by the number of drive pulses corresponding to the image data to generate heat. The period from the end of heat generation to the start of driving by the driving pulse based on the next image data is the cooling period. The sum of the heat generation period and the cooling period is constant, and those having a small image data value have a small heat generation period and a long cooling period.
[0006]
[Problems to be solved by the invention]
A transparent resin protective layer is formed on the surface of the color thermal recording paper. This protective layer is softened at the glass transition point GT in order to improve the thermal contact with the thermal head. The protective layer softens during time T1 to T2, but the protective layer remains solidified without being softened during time T2 to T3. When the ratio of the cooling period to the line cycle is large as in the case of low-density printing, the surface of the color thermal recording paper has irregularities corresponding to the ratio of the heat generation period to the cooling period, and the surface gloss deteriorates. . In addition, since the softening and solidification are repeated, the dynamic friction coefficient increases, the stability of recording paper conveyance deteriorates, and density unevenness tends to occur.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a color thermal recording method and apparatus that improve glossiness at the time of low density printing and suppress the occurrence of density unevenness.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, a color thermosensitive recording paper in which a plurality of thermosensitive coloring layers and protective layers having different thermal sensitivities and colors to be developed and a protective layer are sequentially formed on a support, and a plurality of heating elements are arranged in a line. Using the formed thermal head and repeating the heating with the thermal head and the fixing with electromagnetic radiation, when color recording is performed sequentially from the thermosensitive coloring layer on the surface side, it occurs at a fixed cycle regardless of the value of the image data The heating elements are driven using the first to Nth N driving pulses, the voltage of each driving pulse is set according to the thermosensitive coloring layer to be recorded, and each according to the value of the image data The width of the drive pulse is set.
[0009]
According to the second aspect of the invention, the width of each drive pulse is set according to the generation number of the drive pulse in addition to the value of the image data.
[0010]
According to a third aspect of the present invention, a color thermosensitive recording paper in which a plurality of thermosensitive color-developing layers and protective layers having different thermal sensitivities and colors to be developed and a protective layer are sequentially provided on a support, and a plurality of heating elements are arranged in a line. Color thermal color recording that records color images on color thermal recording paper by using the thermal head that is formed and repeating color heating and heating with an electromagnetic radiation, and then recording color from the uppermost thermal color development layer. In the apparatus, the energization time ROM for generating energization time data according to the value of the image data, the clock counter for counting the clock, and the count value of the clock counter and the energization time data are compared to correspond to the energization time data. And a comparator for generating a drive pulse of width, reading of the energization time ROM, count operation of the clock counter, and comparator The comparison operation is repeated to generate N drive pulses, and the voltage of each drive pulse is set according to the thermosensitive coloring layer to be recorded, and N drive pulses having a width corresponding to the value of the image data are 1 This is to record dots.
[0011]
In the invention of claim 4, a drive pulse counter that counts the number of generated drive pulses is provided, and the energization time ROM stores energization time data determined by the value of image data and the generation number of the drive pulse, The energization time data is read based on the image data and the drive pulse generation number.
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIG. 2, the color thermosensitive recording paper 2 has a cyan thermosensitive color developing layer 4, a magenta thermosensitive color developing layer 5, a yellow thermosensitive color developing layer 6, and a protective layer 7 sequentially arranged on a support 3. Each of these thermosensitive coloring layers 4 to 6 is 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 yellow thermosensitive coloring layer 6 and the magenta thermosensitive coloring layer. The position with 5 can be swapped. Further, a black thermosensitive coloring layer that develops black or a skin thermosensitive coloring layer that develops skin color may be added to form a four-layer or five-layer structure. The protective layer 7 is formed by applying a transparent resin.
[0013]
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. When the magenta thermosensitive coloring layer 5 is irradiated with electromagnetic rays, for example, ultraviolet rays of 365 nm after color recording, the uncolored components are decomposed and the coloring ability is lost, so that the magenta image is fixed. Similarly, when the yellow thermosensitive coloring layer 6 is irradiated with electromagnetic rays, for example, ultraviolet rays of 420 nm, the uncolored components are decomposed and the coloring ability is lost. Since the cyan thermosensitive coloring layer 4 is in the lowermost layer and there is no thermosensitive coloring layer to be recorded next, fixing property by electromagnetic radiation is not given.
[0014]
FIG. 3 shows a characteristic curve of each thermosensitive coloring layer when the thermal head is pressed against the color thermosensitive recording paper with a predetermined pressing force and heated. The horizontal axis represents the heat energy generated by the heating element. The yellow thermosensitive coloring layer 6 has the highest thermal sensitivity and develops color with small heat energy. Since the cyan thermosensitive coloring layer 4 is the lowermost layer, the heat energy generated by the heating element is difficult to be 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.
[0015]
In FIG. 1, yellow, magenta, and cyan image data captured from a scanner or a TV camera is written in the frame memory 10. The frame memory 10 reads the image data of the color to be printed line by line by the writing controller 11 and sends it to the line memory 12. The write controller 11 is controlled by the print controller 13 and performs reading of the frame memory 10 and writing to the line memory 12. Note that image data of three colors of red, green, and blue is written in the frame memory 10, and a color correction circuit arranged between the frame memory 10 and the line memory 12 is used to calculate yellow, magenta by a matrix arithmetic expression. , May be converted into cyan image data.
[0016]
The print controller 13 divides the recording period of 1 dot into N cycles and controls each unit so that one drive pulse is generated in each cycle. At the start of each cycle, the print controller 13 sends one signal to the drive pulse counter 14. This drive pulse counter 14 counts the signal to check the number of drive pulses, and sends this count value to the energization time ROM 15. The drive pulse counter 14 is set to “1” when one more signal is received after the count value reaches N. Therefore, the drive pulse counter 14 cyclically counts “1” to “N”.
[0017]
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 energization time ROM 15 in response to a read start signal from the print controller 13. In this energization time ROM 15, a plurality of pages corresponding to the total number of drive pulses are prepared, and energization time data corresponding to each image data is written in each page. Therefore, desired energization time data can be read from the energization time ROM 15 based on the number of generated drive pulses and the image data.
[0018]
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 in the latch array 17, each energization time data is sent to the comparator array 18.
[0019]
The comparator array 18 includes 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. Thus, a control pulse having a width corresponding to the energization time data is output from each comparator.
[0020]
The clock generator 20 generates a clock having a constant period. Each clock is counted by the clock counter 19. For example, when the image data is “1”, when 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 performs a cyclic operation between “1” and “M”. The clock counter 19 sends a signal to the print controller 13 when the count value becomes “M”.
[0021]
The control pulse for one line output from the comparator array 18 is sent to the head driver 21. The head driver 21 includes a switching element array for one line, and a voltage from the 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.
[0022]
The thermal head 22 is provided with one line of heating elements 23 on the lower surface thereof. Each heating element 23 is connected in series to the corresponding switching element, and is turned on while a control pulse is input. Thus, each heating element 23 has a voltage value from the voltage regulator 28 and is energized with a drive pulse having the same width as the control pulse to generate heat.
[0023]
The color thermal recording paper 2 is conveyed at a constant speed in the sub-scanning direction by a conveyance roller pair 26 connected to a motor 25. The color thermal recording paper 2 is pressed and heated between the platen roller 27 that rotates freely and the thermal head 22 while being conveyed in the direction of the arrow. 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.
[0024]
A fixing device 29 is disposed in the vicinity of the conveyance roller pair 25. The fixing device 29 includes a yellow ultraviolet lamp 30 that emits ultraviolet light having an emission peak of 420 nm, and a magenta ultraviolet lamp 31 that emits ultraviolet light having an emission peak of 365 nm.
[0025]
Next, the operation of the above apparatus will be described with reference to FIG. Three-color image data of a color image to be printed is taken into the frame memory 10. When the printing is instructed after the image data of the three colors of yellow, magenta, and cyan are taken in, the yellow image recording is started first. In this yellow image recording, the voltage regulator 28 sends a voltage corresponding to the thermal sensitivity of the yellow thermosensitive coloring layer 6 to the head driver 21 in response to a signal from the print controller 13. Further, the print controller 13 turns on the yellow ultraviolet lamp 30 of the fixing device 29.
[0026]
Next, the controller 13 rotates the conveyance roller pair 26 via the motor 25. The transport roller pair 26 transports the color thermal recording paper 2 fed from a paper feed mechanism (not shown) at a constant speed in the direction of the arrow. Further, the controller 13 rotates the thermal head 22 via a motor (not shown) to press the heating element array against the color thermal recording paper 2.
[0027]
Further, the print controller 13 sends a write start signal to the write controller 11. The write controller 11 reads yellow image data for one line from the frame memory 10 and writes it to the line memory 12.
[0028]
Next, the print controller 13 sends a signal to the drive pulse counter 14. The drive pulse counter 14 has a count value “1” and sends this to the energization time ROM 15. Thereafter, the print controller 13 sends a read start signal to the read controller 16.
[0029]
The read controller 16 reads yellow image data one by one from the line memory 12 and sends it to the energization 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 image data and energization time data is tabulated on the first page, desired energization time data is read using the image data as an address. The energization time data is determined by the drive pulse number and the image data value.
[0030]
Each yellow image data for one line is converted into energization time data by the energization time ROM 15 and then sent to the latch array 17. When the energization time data for one line is latched in the latch array 17, the print controller 13 starts the count operation of the clock counter 19.
[0031]
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 is inverted to “L” when the count value becomes larger than the energization time data. Accordingly, the comparator array 18 outputs a control pulse having a width corresponding to the energization time data for one line, and sends this to the head driver 21.
[0032]
The head driver 21 includes one line of switching elements connected to each heat generating element 23, and the corresponding switching element is turned ON by a control pulse of one line. In recording a yellow image, since a voltage corresponding to the yellow image is applied to the head driver 21, 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 to generate heat by the driving pulse for one line.
[0033]
The count value of the clock counter 19 counts up sequentially from “1”, and when the maximum value “M” is reached, the first cycle ends. The clock counter 19 sends a signal indicating that the first cycle has ended to the print controller 13.
[0034]
When the print controller 13 receives the cycle end signal, it sends the signal to the drive pulse counter 14. Further, the print controller 13 sends a read start signal to the read controller 16, and again reads yellow image data for one line and converts energization time data. 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 into 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 the second drive pulse generated from the head driver 21 to generate heat.
[0035]
As described above, the first cycle to the Nth cycle are executed, and N driving pulses having a constant cycle are generated. Each heating element 23 is driven in accordance with these drive pulses, and one yellow dot is recorded in color 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.
[0036]
Similarly, a yellow image is color-coded and recorded line by line in the recording area of the color thermal recording paper 2 being continuously conveyed. When the recording area passes through the thermal head 22 and the recording of the yellow image is completed, the print controller 13 rotates the thermal head 22 and retracts it from the color thermal recording paper 2.
[0037]
The energization time of the first cycle is T1on, and the OFF time is T1off. Similarly, the energization time of the Nth cycle is TNon, and the OFF time is TNoff. In each cycle, the ratio of the energization time to the cycle is the duty ratio. The larger the duty ratio, the wider the pulse width and the greater the heat generation energy per drive pulse.
[0038]
The total energization time for recording one yellow dot is T1on + T2on +... TNon. Since thermal energy corresponding to the total energization time is given to the color thermal recording paper 2, T1on to TNon are continuously applied. As a result, almost the same concentration is obtained as when the current is applied. After the protective layer 7 is softened in the first line, the protective layer 7 remains soft until the final line. Therefore, the surface unevenness does not occur, and the density unevenness is reduced with stable recording paper conveyance.
[0039]
When the portion that has passed through the thermal head 22 reaches the fixing device 29 during the recording of the yellow image, the 420 nm ultraviolet light emitted from the yellow ultraviolet lamp 30 is irradiated onto the color thermal 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 in the recording area of the color thermal recording paper 2 is fixed.
[0040]
When the recording area of the color thermal recording paper 2 passes through the fixing device 29, the print controller 13 turns off the yellow ultraviolet lamp 30 and then reverses the pulse motor 25. As a result, the color thermal recording paper 2 on which the yellow image is recorded is returned. When the leading edge of the color thermal recording paper 2 reaches the conveying roller pair 26, the reverse rotation of the pulse motor 25 is stopped.
[0041]
Next, recording of a magenta image is started. As described above, the thermal head 22 is pressed against the color thermal recording paper 2, and the magenta ultraviolet lamp 31 is turned on. 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 thermosensitive coloring layer 5 is lower than that of the yellow thermosensitive coloring layer 6, the voltage for magenta is higher than the voltage for yellow described above.
[0042]
One line of magenta image data is read from the frame memory 10 and executed from the first cycle to the Nth cycle according to the above-described procedure, and N driving pulses having a constant cycle are generated. Each heat generating element 23 is driven in accordance with the N drive pulses, and one magenta dot is recorded on the magenta thermosensitive coloring layer 5 by color development.
[0043]
In this way, a magenta image is color-coded and recorded line by line in the recording area of the color thermal recording paper 2. When the recording of the magenta image is completed, the thermal head 22 is retracted from the color thermal recording paper 2. The portion on which the magenta image is recorded is fixed by being irradiated with 365 nm ultraviolet rays emitted from the magenta ultraviolet lamp 31.
[0044]
After the color recording / fixing of the magenta image, the thermal head 22 is retracted and then the color thermal recording paper 2 is returned again. Next, the thermal head 22 is pressed against the color thermal recording paper 2 to start recording a cyan image. Even in the cyan image recording, the magenta ultraviolet lamp 31 is kept lit, and the high-heated and pale yellow color portion generated during the cyan image recording is bleached. The voltage regulator 28 supplies a voltage corresponding to the thermal sensitivity of the cyan thermosensitive coloring layer 4 to the head driver 21.
[0045]
Each of the heat generating elements 23 is driven by N drive pulses based on each cyan image data read from the frame memory 10 and records one cyan dot on the cyan thermosensitive coloring layer 4 in color. The color thermal recording paper 2 is bleached by irradiating 365 nm ultraviolet rays emitted from a magenta ultraviolet lamp 31 after a cyan image is developed and recorded line by line by the thermal head 22. After this bleaching, the paper is discharged to a paper discharge tray (not shown). After the paper discharge, the magenta ultraviolet lamp 31 is turned off.
[0046]
FIG. 3 shows the width of the drive 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 thermal recording paper does not color. When the image data is “127”, the pulse width is slightly increased, and a medium density dot is recorded. When the image data is “255”, the pulse width is the largest and the highest density dot is recorded. In this example, when the values of the image data are the same, drive pulses having the same width are used for all three colors.
[0047]
In the apparatus, the width of the drive pulse is changed depending on the cycle number, but the same energization time data may be used in all cycles by omitting the drive pulse counter 14. In this way, the energization time ROM 15 only needs to store data for one page, so a ROM with a small storage capacity can be used.
[0048]
Further, since commercially available color thermosensitive recording paper has a slight difference in γ in each thermosensitive coloring layer, it is preferable to change the width of N drive pulses depending on the color to be recorded. In this case, energization time data is prepared for each color in the energization time ROM 15 and is selected according to the color to be pre-inscribed.
[0049]
【The invention's effect】
In the present invention, when one dot is recorded, N drive pulses are generated for all image data at a constant period, and the pulse width is changed according to the value of the image data. The heating element is driven according to the driving pulse. Therefore, since no cooling period is provided as in the prior art, even when the value of the image data is small, unevenness does not occur on the surface, and a color print having a good glossiness can be obtained. Further, since the recording paper conveyance is stabilized, 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 showing a layer structure of color thermal recording paper.
FIG. 3 is a graph showing color development characteristics of each heat-sensitive color development layer.
FIG. 4 is an explanatory diagram showing a relationship between a drive 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 Conveying roller pair 29 Fixing device

Claims (3)

Using a color thermosensitive recording paper in which a plurality of thermosensitive coloring layers and protective layers having different thermal sensitivities and colors to be developed are sequentially layered on a support, and a thermal head in which a plurality of heating elements are formed in a line, In a color thermosensitive color recording method of recording a color image on a color thermosensitive recording paper by recording colors in order from the thermosensitive color developing layer on the surface side while repeating heating with a thermal head and fixing with electromagnetic radiation,
Regardless of the value of the image data, the heating element is driven using the first to Nth N driving pulses generated one by one in each cycle in which the recording period of 1 dot is divided into N, Color thermosensitive coloring recording, wherein the voltage of each driving pulse is set according to the thermosensitive coloring layer to be recorded, and the width of each driving pulse is set according to the value of the image data and the generation number of the driving pulse Method. Using a color thermosensitive recording paper in which a plurality of thermosensitive coloring layers and protective layers having different thermal sensitivities and colors to be developed are sequentially layered on a support, and a thermal head in which a plurality of heating elements are formed in a line, In a color thermosensitive color recording device for recording color images on a color thermosensitive recording paper by recording colors in order from the thermosensitive color developing layer on the surface side while repeating heating with a thermal head and fixing with electromagnetic radiation,
The energization time ROM that generates energization time data according to the value of the image data, the clock counter that counts the clock, and the count value of this clock counter and the energization time data are compared to drive the width according to the energization time data And a comparator that generates pulses, and repeats the reading of the energization time ROM, the count operation of the clock counter, and the comparison operation of the comparator, and the 1st to Nth N driving pulses are set to the recording period of 1 dot. One is generated in each of the N divided cycles, and the voltage of each driving pulse is set according to the thermosensitive coloring layer to be recorded, and one by N driving pulses having a width corresponding to the image data. A color thermosensitive color recording apparatus characterized by recording dots. A drive pulse counter that counts the number of generated drive pulses is provided, and the energization time ROM stores energization time data determined by the value of the image data and the generation number of the drive pulse, thereby generating image data and drive pulses. 3. The color thermosensitive color recording apparatus according to claim 2, wherein the energization time data is read by the number.

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