JPH0958029A - Method of fixing in color thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with supplemental decoloring operation, and prevent printing speed from becoming high and mechanical components from wearing. SOLUTION: In the first forwarding operation, an yellow image is recorded by a thermal head and the fixation therefor is executed by a ultraviolet ray lamp for yellow. In the second forwarding operation, a magenta image is recorded and fixation therefor is conducted by a ultraviolet ray lamp for magenta. At the time of fixation of the magenta image, an intensity of illumination of ultraviolet ray for magenta in its full-luminescence is measured. An intensity of irradiation of ultraviolet ray for magenta in decoloring operation made in the third forwarding operation Is predicted from a measured illumination value LM obtained. With a prediction that a shortage of decoloring takes place, a reversing speed SM2 of color thermosensible recording paper is determined by taking a degree of the lack into consideration. By allowing the ultraviolet ray lamp for magenta to be In full-luminescence, a pre-decoloring operation is carried out while the color thermosensible recording paper is reversed at the reversing speed SM2 . In the third forwarding operation, a cyane image is recorded and decoloring by the ultraviolet ray for magenta is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing method used in a color thermal printer.

[0002]

2. Description of the Related Art In a color thermal printer, on a support,
A color thermosensitive recording paper in which a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer and a yellow thermosensitive coloring layer are sequentially formed is used. The uppermost yellow thermosensitive coloring layer has the highest thermal sensitivity, and the lowermost cyan thermosensitive coloring layer has the lowest thermal sensitivity. Utilizing this difference in thermal sensitivity, the thermal recording paper is pressed and heated by a thermal head while moving, and the respective thermal coloring layers are recorded in order from the uppermost layer. Immediately after recording, the yellow thermosensitive coloring layer and the magenta thermosensitive coloring layer are fixed by irradiating ultraviolet rays in a wavelength range specific to each thermosensitive coloring layer. By this fixation, the uncolored coloring components are photolyzed, and the coloring ability is lost.

An ultraviolet lamp for yellow is turned on to irradiate the yellow thermosensitive coloring layer with near-ultraviolet rays having an emission peak of 420 nm. However, if this irradiation amount is small, a part of the yellow coloring component is photodecomposed. It remains without being. The remaining yellow color-forming component develops color during recording on the magenta thermosensitive color-forming layer. Further, when the irradiation amount of the ultraviolet ray for yellow is too large, the coloring component of the magenta thermosensitive coloring layer is photodecomposed although it is slight. For this reason, it is necessary to keep the irradiation amount of the ultraviolet ray for yellow proper.

The magenta thermosensitive coloring layer is irradiated with ultraviolet rays having an emission peak of 365 nm. When the irradiation amount of the magenta ultraviolet ray is small, a part of the magenta coloring component remains without being photodecomposed. However, since no fixing property is given to the cyan thermosensitive coloring layer, there is no problem even if the irradiation amount of the magenta ultraviolet ray is larger than the appropriate value.

Further, each heating element supplies bias heat energy for heating the heat-sensitive coloring layer to be recorded to such an extent that coloring does not occur, and gradation heat energy corresponding to image data to form a dot having a desired density. Coloring is recorded. This bias heat energy is also applied to the heating element that does not record dots. Since the magenta thermosensitive coloring layer and the cyan thermosensitive coloring layer have low thermal sensitivity, a large amount of bias thermal energy is applied. Due to this bias heat energy, the white background portion changes to light yellow. This discoloration is called yellow stin and can be bleached by irradiating a proper amount of magenta ultraviolet rays.

Japanese Laid-Open Patent Publication No. 7-32625 discloses that the illuminance is measured immediately after the ultraviolet lamp is turned on and the fixing condition is set.
A method for determining the presence / absence of supplementary fixing and the rotation speed of the platen drum at the time of supplementary fixing is described. When replenishment fixing is required, the light emitting condition of the ultraviolet lamp is made the same as that at the time of fixing, and the platen drum is made to rotate once again at the rotation speed corresponding to the rank of the measured illuminance value. Also in the recording of a cyan image, the magenta ultraviolet lamp is turned on in a full light emission state, and the illuminance is measured immediately after this turning on to determine whether replenishment bleaching is necessary and the rotation speed at that time. If you need additional bleaching,
After recording the cyan image, the platen drum is rotated once again.

[0007]

In the above-described conventional fixing method, when the bleaching is insufficient, replenishment bleaching is performed after the cyan image is recorded. Therefore, it takes a long time to print and the mechanical parts such as the platen drum are worn. Cause of.

It is an object of the present invention to provide a fixing method for a color thermal printer which enables proper bleaching without replenishing bleaching.

[0009]

In order to achieve the above object, in the fixing method according to claim 1, a color in which at least first to third thermosensitive coloring layers having different colors and different thermal sensitivities are sequentially provided. Using the thermosensitive recording paper, the color thermosensitive recording paper being conveyed is heated by the thermal head to record the first thermosensitive coloring layer, and then irradiated with the ultraviolet rays of the first wavelength range emitted from the first ultraviolet lamp to be fixed. Then, after recording the second thermosensitive coloring layer with the thermal head, the second thermosensitive layer is irradiated with the ultraviolet rays of the second wavelength range emitted from the second ultraviolet lamp to fix it, and finally the third thermosensitive coloring layer is applied with the thermal head. Second after recording
In a color thermal printer that bleaches by irradiating ultraviolet rays in the wavelength range, the illuminance of ultraviolet rays in the second wavelength range is measured when fixing the second thermosensitive coloring layer, and from this measured illuminance value, When the irradiation amount is predicted and bleaching shortage occurs, pre-bleaching is performed with ultraviolet rays in the second wavelength region in consideration of the bleaching shortage before recording in the third thermosensitive coloring layer.

In the fixing method according to the second aspect of the invention, the color thermosensitive recording paper is nipped by the pair of conveying rollers and is movable in the first direction and the second direction opposite thereto, and in the first direction, it is downstream of the thermal head. First and second UV lamps are placed in
When the pair of conveying rollers conveys the color thermosensitive recording paper in the first direction at a constant first speed, the first thermosensitive coloring layer is recorded and the first thermosensitive coloring layer is recorded.
When fixing the color thermosensitive recording paper in the second direction at the second speed determined by the ultraviolet illuminance at the time of fixing by fixing with the ultraviolet in the wavelength range, supplementary fixing with the ultraviolet in the first wavelength is performed and the fixing is performed at a constant level. When the second speed at the third speed to convey in the first direction
Recording on the thermosensitive coloring layer and fixing with ultraviolet rays in the second wavelength region, and then returning to the second direction at the fourth speed according to the ultraviolet illuminance at the time of fixing, replenishment fixing with pre-bleaching with ultraviolet rays in the second wavelength region Then, the recording and bleaching of the third thermosensitive coloring layer is performed when the recording medium is conveyed again in the first direction at the constant fifth speed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG.
0, a heating element array 10a in which a large number of heating elements are arranged in a line is formed. This thermal head 1
0 is swingable about a shaft 11 as a fulcrum, and swings between a print position for pressing the color thermosensitive recording paper 12 on the platen roller 13 and a retracted position separated from the platen roller 13.

The color thermosensitive recording paper 12 is, as is well known,
On the support, a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer,
Yellow thermosensitive coloring layers are sequentially layered. The yellow thermosensitive coloring layer, which is the uppermost layer, has the highest heat sensitivity and develops yellow with a small amount of heat energy. The cyan thermosensitive coloring layer, which is the lowermost layer, has the lowest thermal sensitivity and develops cyan with a large amount of heat energy.

The yellow thermosensitive coloring layer loses its coloring ability when irradiated with near ultraviolet rays of 420 nm. The magenta thermosensitive coloring layer loses its coloring ability when irradiated with ultraviolet rays of 365 nm. The color thermosensitive recording paper 12 may be provided with a black thermosensitive coloring layer to have a four-layer structure.
In this case, it is necessary to provide the cyan thermosensitive coloring layer with a fixing property.

A transport roller pair 15 is disposed downstream of the thermal head 10 and is rotated in both forward and reverse directions by a pulse motor 16. The transport roller pair 15 reciprocates by nipping the color thermosensitive recording paper 12.

A fixing device 17 is arranged in the conveying path of the color thermosensitive recording paper 12. The fixing device 17 is composed of a yellow ultraviolet lamp 18 that emits near-ultraviolet light having an emission peak of 420 nm, a magenta ultraviolet lamp 19 that emits ultraviolet light having an emission peak of 365 nm, and a reflector 20 that covers the back of these lamps. ing.

When the ultraviolet lamps 18 and 19 selectively emit light, a part of the ultraviolet rays emitted from the ultraviolet lamps 18 and 19 enter the illuminance sensor 21. The illuminance sensor 21 indirectly moves the illuminance on the color thermosensitive recording paper 12 just before the front end of the recording area reaches the fixing device 17 by moving the color thermosensitive recording paper 12 by a predetermined distance L from the start of recording. taking measurement. Reference numeral 22 is a position sensor for detecting the front end of the color thermosensitive recording paper 12.

In FIG. 2, the controller 25 includes an illuminance sensor 21, a position sensor 22, and a speed control circuit 2.
6, a lamp illuminance adjusting circuit 27, a driver 28, a counter 29, and a ROM 33 are connected. Speed control circuit 26
Determines the rotation speed and direction of the pulse motor 16 when the color thermosensitive recording paper 12 is fed and returned, and controls the rotation of the pulse motor 16 via the driver 30.

The feeding speed of the pulse motor 16 when the color thermosensitive recording paper 12 is conveyed in the paper discharge direction is a constant value determined by the thermal sensitivity of the thermosensitive coloring layer. The returning speed of the pulse motor 16 when returning the color thermosensitive recording paper 12 is determined according to the measured illuminance value measured by the illuminance sensor 21.

The magenta thermosensitive coloring layer is photo-decomposed by ultraviolet rays having a wavelength of 420 nm, although the amount is small. Therefore, a lamp illuminance adjustment circuit 27 is provided for the yellow ultraviolet lamp 18 in order to accurately control the irradiation amount. The lamp illuminance adjustment circuit 27 includes a target illuminance setting circuit 32, a differential amplifier 33, a duty ratio adjustment circuit 34, and a ROM 35. This ROM
35, as shown in FIG. 4, the measured illuminance value L _Y of yellow ultraviolet light measured by the illuminance sensor 21 and the target illuminance value L
A table indicating the relationship with _S is stored. The unit of numerical values in FIG. 4 is mW.

The target illuminance setting circuit 32 reads the target illuminance value L _S stored in the ROM 35, using the measured illuminance value L _Y of yellow ultraviolet light as an address. Differential amplifier 33
Is the target illuminance value L _S set by the target illuminance setting circuit 32.
And the illuminance value during fixing are calculated, and this difference signal is sent to the duty ratio adjusting circuit 34. Duty ratio adjustment circuit 34
Adjusts the duty ratio of the drive pulse output from the driver 36.

As shown in FIG. 3, table data representing the relationship between the measured illuminance value of ultraviolet rays and the motor rotation speed is written in the ROM 33. In FIG.
(A) is a table for yellow, (b) is a table for magenta. In recording a yellow image and a magenta image, the corresponding ultraviolet lamp is turned on at the same time as or immediately before the start of printing. Then, from the start of printing, when the color thermosensitive recording paper 12 moves to the right by a distance L in FIG. 1, that is, immediately before reaching the fixing device 17,
The illuminance sensor 21 measures the illuminance of ultraviolet rays. From the measured illuminance value, the fixing conditions, the necessity of supplementary fixing, and the returning speed are determined.

In recording a yellow image, the pulse motor 1 is used.
6 rotates in the forward direction at the feed speed SY ₁ , and the color thermal recording paper 12
Is conveyed to the right in FIG. The feed speed SY ₁ is a constant value determined according to the thermal sensitivity of the yellow thermosensitive coloring layer. The target illuminance value L _S shown in FIG. 4 is set according to the rank of the measured illuminance value L _Y at the time when the color thermosensitive recording paper 12 moves by the fixed distance L. The yellow ultraviolet lamp 18 is dimmed so that the target illuminance value L _S is maintained.

After recording the yellow image, the pulse motor 1
6 in reverse at the returning speed SY ₂ to print color thermosensitive recording paper 1
The tip of 2 is returned to the position detected by the position sensor 22. This return speed SY ₂ is determined by the rank of the measured illuminance value L _Y. When the measured illuminance value L _Y has the highest rank, replenishment and fixing is not required, and therefore the yellow ultraviolet lamp 18 is turned off, and then the pulse motor 16 is reversely rotated at a constant yellow return speed SY ₂ . The yellow return speed SY ₂ is the yellow print speed SY ₁
Faster than.

When the measured illuminance value L _Y is low, insufficient fixing of the yellow image occurs, so the color thermosensitive recording paper 12
1 is replenished and fixed when returning to the left in FIG. In this supplemental fixing, the yellow ultraviolet lamp 18 is kept at the target illuminance value L _S at the time of recording, and the pulse motor 16 is rotated in reverse at the returning speed SY ₂ determined according to the measured illuminance value L _Y.
The rotation speed of the pulse motor 16 is slowed down so that the ultraviolet irradiation amount increases as the measured illuminance value L _Y decreases.

Since the illuminance of the yellow ultraviolet lamp 18 is measured not when it is turned on but when the tube wall is warmed and the emission intensity is increased, the measured illuminance value becomes higher than the conventional value.
In this case, since the target illuminance value becomes high, the number of cases where replenishment and fixing is not necessary increases. Even if replenishment and fixing are required, the color thermal recording paper 12 can be returned quickly,
The overall print time is reduced.

In recording a magenta image, the pulse motor 1 is used.
6 rotates at a constant feed speed SM ₁ , and the magenta ultraviolet lamp 19 emits full light without dimming. And
The measured illuminance value L _M is measured when moving by the distance L. From the magnitude of the measured illuminance value L _M , it can be known whether the fixing is insufficient. Further, since the bleaching after recording the cyan image is performed by irradiating the ultraviolet ray from the magenta ultraviolet lamp 19, it is possible to know whether or not the bleaching shortage occurs.
Therefore, both the fixing state and the bleaching state are determined from the measured illuminance value L _M.

Generally, when fixing is insufficient, bleaching is insufficient. To compensate for these shortfalls, FIG.
As shown in, the return speed SM ₂ of the pulse motor 16 is determined according to the rank of the measured illuminance value L _M. The lower the rank of the measured illuminance value L _M, the slower the returning speed SM ₂ and the larger the ultraviolet irradiation amount. When the pulse motor 16 reversely rotates at the returning speed SM ₂ and the color thermosensitive recording paper 12 is returned, the color thermosensitive recording paper 12 is irradiated with the ultraviolet rays from the magenta ultraviolet lamp 19 which is in a full light emission state. Pre-bleaching is done.

When the fixing and bleaching are proper, the replenishing fixing and the pre-bleaching are unnecessary.
At the fastest magenta return speed. At this time, the magenta ultraviolet lamp 19 may be turned off, but in cyan printing, the magenta ultraviolet lamp 19 is turned on for bleaching, the magenta ultraviolet lamp may be overfixed, and the number of times of ON / OFF is Considering that the life of the lamp is shortened if the number is large, the magenta ultraviolet lamp 19 is kept lit. Since the coloring heat energy of the magenta thermosensitive coloring layer is larger than that of the yellow thermosensitive coloring layer, the magenta feeding speed SM ₁ is slower than the yellow feeding speed SY ₁ . The feed speed SM ₁ is the return speed S
Slower than M ₂ .

Next, the operation of the above embodiment will be described with reference to FIG.
This will be described with reference to FIG. When a print start key (not shown) is operated, the paper feeding process is started first. The color thermosensitive recording paper 12 is sent out from a paper feed cassette (not shown) and conveyed toward the thermal head 10. During this paper feeding, the thermal head 10 moves the platen roller 1
It is set to the retracted position away from 3. The color thermal recording paper 12 includes a thermal head 10 and a platen roller 1.
When the leading edge of the sheet 3 is detected by the position sensor 22, the sheet feeding process ends.

When the paper feeding process is completed, the pair of conveying rollers 15
Moves to nip the color thermosensitive recording paper 12, and the thermal head 10 swings clockwise to move to the print position where the color thermosensitive recording paper 12 is pressed.

Since the yellow image is initially recorded, the controller 25 sets the duty ratio adjusting circuit 34 to the maximum value. As a result, the driver 36 turns on the yellow ultraviolet lamp 18 and fully emits it with the drive pulse having the maximum duty ratio.

At the same time that the yellow UV lamp 18 is turned on, the controller 25 causes the ROM 33 to send the feed speed SY.
₁ is read and sent to the speed control circuit 26. The speed control circuit 26 sends a motor drive pulse to the pulse motor 16 via the driver 30 to rotate it at a constant feed speed SY ₁ .

When the pulse motor 16 rotates at the feed speed SY ₁ , the color thermosensitive recording paper 12 nipped by the pair of carrying rollers 15 is carried toward the fixing device 17 at a constant speed.
During this conveyance, each heating element of the thermal head 16 generates heat energy according to the yellow image data, and one yellow image is formed in the recording area on the color thermosensitive recording paper 12.
Record each line.

The counter 29 is reset immediately before recording a yellow image, and counts the motor drive pulses from the driver 30. From the count value of the counter 29, the conveyance distance of the color thermosensitive recording paper 12 from the start of printing is measured. Then, when the color thermosensitive recording paper 12 has moved by a predetermined distance L and is in a state immediately before the leading end of the recording area reaches the fixing device 17, the illuminance sensor 21
Measures the illuminance of the yellow ultraviolet lamp 18 in the full light emission state and sends the obtained measured illuminance value L _Y to the controller 25.

The controller 25 refers to the yellow image table written in the ROM 33 and determines the returning speed SY ₂ and the necessity of replenishment fixing based on the measured illuminance value L _Y. Further, the controller 25 sends the measured illuminance value L _Y to the target illuminance setting circuit 32. This target illuminance setting circuit 32
Determines the target illuminance value L _S according to the measured illuminance value L _Y based on the table of the ROM 35 shown in FIG. And
The yellow ultraviolet lamp 18 is driven by the drive pulse whose duty ratio is adjusted according to the target illuminance value L _S.

While the portion recorded by the thermal head 10 passes through the fixing unit 17, the yellow ultraviolet lamp 18
Is irradiated with the near-ultraviolet rays from and fixed. Even during this fixing, the illuminance sensor 21 measures the illuminance, and the obtained illuminance value is sent to the differential amplifier 33. The differential amplifier 33 calculates the difference between the illuminance value and the target illuminance value L _S, and sends the difference signal to the duty ratio adjusting circuit 36.

The duty ratio adjusting circuit 36 responds to the difference signal.
Drive pallet that is also supplied to the yellow UV lamp 18.
Adjust the duty ratio of the switch. If the illuminance value is the target illuminance
Value L _SIs smaller than the duty ratio, the duty ratio adjusting circuit 34
Adjust the duty ratio greatly to increase the yellow UV
A large electric power is applied to the pump 18 to increase the light emission intensity.
On the contrary, when the illuminance value is large, the duty ratio is reduced.
To reduce the emission intensity. This makes the UV light for yellow
The illuminance value of the ultraviolet light emitted from the lamp 18 is always the target
Illuminance value L_SSince it is held in the
And uniform fixing is performed.

The counter 29 measures the transport distance of the color thermosensitive recording paper 12. From the count value of the counter 29, when the controller 25 determines that all recording in the recording area is completed, the controller 25 shifts the thermal head 10 to the retracted position. When the controller 25 determines from the count value that the trailing edge of the recording area has passed the fixing device 17, the controller 25 instructs the speed control circuit 26 to perform reverse rotation of the pulse motor 16 and return speed SY ₂ . The speed control circuit 26 temporarily stops the pulse motor 16 and then returns the return speed SY according to the rank of the measured illuminance value L _{Y.
At 2} , the pulse motor 16 is rotated in the reverse direction to return the color thermosensitive recording paper 12 to the position shown in FIG. This return speed SY ₂ is
The higher the rank, the faster the speed is set to shorten the irradiation time of ultraviolet rays.

When it is not necessary to replenish and fix the color thermosensitive recording paper 12 when returning it, the yellow ultraviolet lamp 18 is turned off. In this case, the pulse motor 16 rotates at a high yellow return speed to quickly return the color thermosensitive recording paper 12.

When supplementary fixing is required, the ultraviolet ray lamp 18 for yellow is controlled to emit light so that the target illuminance value L _S becomes the same as that at the time of fixing. This yellow UV lamp 1
The near-ultraviolet ray of 420 nm emitted from No. 8 is applied to the color thermosensitive recording paper 12 to replenish and fix the yellow image. When the position sensor 21 detects the leading edge of the color thermosensitive recording paper 12, the pulse motor 16 stops, and at the same time, the yellow ultraviolet lamp 17 stops emitting light. Since the shortage is compensated by the irradiation of ultraviolet rays at the time of this returning, the irradiation amount of ultraviolet rays for yellow becomes constant.

Next, recording of the magenta image is started.
The controller 25 moves the thermal head 10 to the recording position and turns on the magenta ultraviolet lamp 19 in a full light emission state via the driver 28. In addition, the controller 25 resets the counter 29 and then
The feed speed SM ₁ is read from the ROM 33 and sent to the speed control circuit 26. The speed control circuit 26 includes a driver 30.
Sends a motor drive pulse to the pulse motor 16 via
Rotate at constant feed speed SY ₁ .

When the color thermosensitive recording paper 12 is conveyed at a constant speed, the thermal head 10 records a magenta image line by line. When it is detected from the count value of the counter 29 that the color thermosensitive recording paper 12 has been conveyed by the distance L, the controller 25 causes the illuminance sensor 22 to operate.
The measured illuminance value L _M is acquired from. Using the measured illuminance value L _M as an address, the magenta image table of the ROM 33 is accessed to read the return speed SM ₂ and the necessity of replenishment fixing and pre-fixing.

The portion on which the magenta image is recorded is the fixing device 1.
When the number reaches 7, the ultraviolet rays of 365 nm emitted from the magenta ultraviolet lamp 19 which emits full light are irradiated and fixed. When the recording area passes the thermal head 10, the recording of the magenta image ends, and the thermal head 10
Moves to the retracted position.

When the recording area moves to the position where it passes the fixing device 17, the controller 25 causes the speed control circuit 26 to move.
Instructing the reverse rotation of the pulse motor 16 and the return speed SM ₂ . The speed control circuit 26 temporarily stops the pulse motor 16 and then reverses it at the returning speed SM ₂ . When the color thermosensitive recording paper 12 is returned, the magenta ultraviolet lamp 19 is kept on.

When replenishment fixing and pre-bleaching are unnecessary,
The color thermal recording paper 12 is returned at the fastest speed. When replenishment fixing and pre-bleaching are required, the color thermosensitive recording paper 12 is slowly returned in consideration of the shortage. When the front end of the color thermosensitive recording paper 12 is detected by the position sensor 21, the pulse motor 16 stops.

Next, the recording of the cyan image is started. The controller 25 rotates the pulse motor 16 at a constant rotation speed SC via the speed control circuit 26. While the color thermosensitive recording paper 12 is being conveyed at a constant speed, the thermal head 10 records a cyan image line by line. At the same time, the magenta ultraviolet lamp 19 fully emits light to bleach the color thermosensitive recording paper 12.

The color thermosensitive recording paper 12 is discharged onto a paper discharge tray (not shown) after recording and bleaching a cyan image. When the discharge of the color thermosensitive recording paper 12 is completed, the pulse motor 16 is stopped and the magenta ultraviolet lamp 19 is turned off. A full-color image is recorded on the color thermosensitive recording paper 12 in a three-color frame sequence.

In the above embodiment, the color thermosensitive recording paper 12 is used.
Although it is reciprocating, it is also possible to use a platen drum having a large diameter and wrap the color thermosensitive recording paper around the platen drum, and continuously rotate the platen drum in the same direction. If replenishment fixing or pre-bleaching is required, the platen drum makes one extra revolution before recording the next thermosensitive color developing layer. Also,
The UV lamp has a low emission intensity when the tube wall temperature is too high, so for magenta UV lamps that emit full light, cool the fan by rotating the fan according to the tube wall temperature.
It is good to keep the tube wall temperature constant.

Further, the illuminance may be measured during the whole period of magenta fixing, and the minimum illuminance value may be obtained to determine the necessity of replenishment fixing and pre-bleaching, and the transport speed of the color thermosensitive recording paper.
Also, when the change of the UV lamp with time is small, the illuminance of UV light depends on the temperature of the lamp tube wall.Therefore, instead of measuring the illuminance of UV light, the temperature of the UV lamp is measured, and the fixing conditions are based on this. The replenishment fixing conditions may be determined.

[0050]

As described in detail above, according to the present invention, the illuminance of ultraviolet rays in the second wavelength region is measured at the time of fixing the second thermosensitive coloring layer, and the second wavelength at the time of bleaching is measured from the measured illuminance value. When the bleaching shortage occurs by predicting the irradiation amount of ultraviolet rays in the region, pre-bleaching with ultraviolet rays in the second wavelength region, which takes into account the bleaching shortage, is performed before recording in the third thermosensitive coloring layer. Even if bleaching shortage occurs, replenishment bleaching is unnecessary. Therefore, the step of replenishing bleaching is unnecessary, the printing speed is increased, and the wear of mechanical parts is reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a color thermal printer embodying the present invention.

FIG. 2 is a block diagram showing a control device for an ultraviolet lamp and a pulse motor.

FIG. 3 is a table showing a relationship between a measured illuminance value and a rotation speed of a pulse motor, where (a) is yellow recording and (b) is a table.
Is used for magenta recording.

FIG. 4 is a table showing a relationship between a measured illuminance value of a yellow ultraviolet lamp and a target illuminance value.

FIG. 5 is a flowchart showing a printing procedure.

[Explanation of symbols]

 10 Thermal Head 12 Color Thermal Recording Paper 15 Conveyor Roller Pair 16 Pulse Motor 17 Fixer 18 UV Lamp for Yellow 19 UV Lamp for Magenta 21 Illuminance Sensor

Claims (2)

[Claims] 1. A color thermosensitive recording paper in which at least first to third thermosensitive coloring layers having different colors to be developed and different thermal sensitivities are sequentially formed, and the color thermosensitive recording paper being conveyed is heated by a thermal head. 1 After recording the thermosensitive coloring layer,
Irradiate and fix the first wavelength range ultraviolet rays emitted from the ultraviolet lamp, and then record the second thermosensitive coloring layer with the thermal head, and then record the second wavelength ultraviolet rays emitted from the second ultraviolet lamp. A color thermal printer which irradiates and fixes, and finally records a third thermosensitive coloring layer with a thermal head, and then bleaches by irradiating ultraviolet rays of a second wavelength range, wherein a second wavelength is applied when the second thermosensitive coloring layer is fixed. UV illuminance of the region is measured, and the irradiation amount of UV in the second wavelength region during bleaching is predicted from this measured illuminance value. If bleaching is insufficient, bleaching is insufficient before recording in the third thermosensitive coloring layer. Second considering the minutes
A fixing method characterized by performing pre-bleaching with ultraviolet rays in the wavelength range. 2. A color thermosensitive recording paper is nipped by a pair of conveying rollers and is movable in a first direction and a second direction opposite thereto, and first and second ultraviolet rays are provided downstream of the thermal head in the first direction. Fixing is performed by recording the first thermosensitive coloring layer and fixing with ultraviolet rays in the first wavelength region when a lamp is arranged and the pair of conveying rollers conveys the color thermosensitive recording paper in the first direction at a constant first speed. When the color thermosensitive recording paper is returned in the second direction at the second speed determined by the ultraviolet illuminance at that time, replenishment and fixing by the ultraviolet light in the first wavelength range is performed, and the first speed is maintained at the third speed.
When recording in the second direction, recording on the second thermosensitive coloring layer and fixing with ultraviolet rays in the second wavelength range are performed, and then when returning in the second direction at the fourth speed according to the ultraviolet illuminance at the time of fixing, the second wavelength range 2. The fixing according to claim 1, wherein replenishment fixing by ultraviolet rays and pre-bleaching are performed, and recording and bleaching of the third thermosensitive coloring layer are performed when the recording medium is conveyed again in the first direction at a constant fifth speed. Method.