JP3310789B2 - Color thermal printing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-head one-pass color thermal printing method using color thermal recording paper.

[0002]

2. Description of the Related Art As a color thermosensitive recording paper, there is known a color thermosensitive recording paper in which a magenta thermosensitive coloring layer, a cyan thermosensitive coloring layer and a yellow thermosensitive coloring layer are sequentially formed on a support. In this color thermosensitive recording paper, the lower the thermosensitive coloring layer, the lower the thermal recording sensitivity, and the yellow and magenta thermosensitive coloring layers have the property of being light-fixed by ultraviolet rays in different wavelength ranges.

When a full-color image is thermally recorded on a color thermosensitive recording paper, a thermal head in which a plurality of heating elements are arranged in a line is used. The yellow thermosensitive coloring layer on the uppermost layer is thermally recorded by a thermal head. After the thermal recording of the yellow thermosensitive coloring layer, the yellow thermosensitive coloring layer is light-fixed by irradiating ultraviolet rays in a wavelength range that photodecomposes only the uncolored diazonium salt compound of the yellow thermosensitive coloring layer.
Next, using a higher thermal energy than the thermal recording of the yellow thermosensitive coloring layer, thermal recording of the magenta thermosensitive coloring layer,
The magenta thermosensitive coloring layer is light-fixed by irradiating ultraviolet rays in a wavelength range that photodecomposes only the uncolored diazonium salt compound of the magenta thermosensitive coloring layer. Finally, the cyan thermosensitive coloring layer is thermally recorded using large thermal energy.

As a color thermal recording method, one head 3
There are a pass method and a three-head one-pass method. The one-head three-pass system uses one thermal head, and heat-records the color thermosensitive recording paper three times through the thermal head. The three-head one-pass method uses three thermal heads and feeds a color thermosensitive recording paper in one direction to thermally record a full-color image at one time. The three-head one-pass method requires three thermal heads, but has the advantage that printing can be performed at high speed.

[0005]

In the three-head, one-pass system, all three thermal heads are energized. However, when energization is started at the same timing, a large current transiently flows, causing a head voltage drop. . Since the thermal energy becomes smaller than a predetermined value due to the voltage drop, the color density decreases, and density unevenness occurs only in that portion. To prevent a large voltage drop of the head voltage, it is sufficient to increase the power supply capacity. However, this will increase the cost and increase the size of the device.

[0006] The present invention is intended to solve the above problems, without increasing the size of the apparatus, a color thermal printing method of the voltage drop of the energization start time of the head voltage of the head can be minimized The purpose is to provide.

[0007]

In order to achieve the above object, a color thermal printing method according to the present invention provides a color thermal printing method in which
Color impression provided with different first to third thermosensitive coloring layers
First to the first to heat recording of each thermosensitive coloring layer using thermal recording paper
Between the third thermal head and these thermal heads
A first and a second ultraviolet lamp provided,
While moving the thermal recording paper in a certain direction, the first layer
The thermosensitive coloring layer was thermally recorded by a first thermal head,
After the recording, the ultraviolet light unique to the first thermosensitive coloring layer is applied to the first thermosensitive coloring layer.
The light is fixed by irradiating it with an ultraviolet lamp.
After thermally recording the thermochromic layer with the second thermal head, the second
UV light peculiar to the heat-sensitive coloring layer is irradiated with a second UV lamp.
And fix it with light, and finally the third layer in the bottom layer
Three heads 1 for thermally recording a coloring layer with a third thermal head
In the pass-type color thermal printing method,
During the bias heating period of the thermal head that
The timing for starting the energization of the first to third thermal heads is shifted so that the energization of the thermal head is started. As a result, a large voltage drop of the head voltage is prevented, so that predetermined heat energy can be generated, and a decrease in color density can be suppressed.

[0008]

FIG. 2 shows a color thermal printer. Three platen rollers 10,
The platen rollers 10 and 12 are rotated by pulse motors 13, 14 and 15, respectively. Also, each of the platen rollers 10 to 12
On both sides thereof, pairs of transport rollers 16, 17, 18 are arranged. The two transport roller pairs 16 are the platen rollers 10
, And the two transport roller pairs 17 rotate in conjunction with the platen drum 11. Further, the two transport roller pairs 18 rotate in conjunction with the platen drum 12. The color thermosensitive recording paper 19 is transported in the direction of the arrow by these transport roller pairs 16 to 18.

On the upper part of each platen roller 10-12,
A thermal head 20 for yellow, a thermal head 21 for magenta, and a thermal head 22 for cyan are provided. At the lower end of each of the thermal heads 20 to 22, a heating element array in which a plurality of heating elements are arranged in a line is provided.

A yellow fixing lamp 25 is disposed between the yellow thermal head 20 and the magenta thermal head 21. A magenta fixing lamp is disposed between the magenta thermal head 21 and the cyan thermal head 22. 26 are provided. Yellow fixing lamp 2
Reference numeral 5 includes a rod-shaped ultraviolet lamp 25a having a light emission peak of approximately 420 nm and a reflector 25b. The magenta fixing lamp 26 includes an ultraviolet lamp 26a having an emission peak of approximately 365 nm and a reflector 26b.

Photosensors 30, 31, and 32 are provided in front of the platen rollers 10 to 12, respectively, and send a leading edge detection signal to the system controller 33 when the leading edge of the color thermosensitive recording paper 19 is detected. The system controller 33 counts the number of drive pulses of the pulse motor from the time when the tip detection signal is received. From this count value, it is determined whether or not the leading end of the recording area of the color thermal recording paper 19 has reached the thermal head. Based on this determination, the corresponding thermal head is driven, and the three-color image is thermally recorded correctly in the recording area without causing color misregistration. A black bar may be provided on the back of the color thermosensitive recording paper 19, and when the photo sensor detects the black bar, the leading end of the recording area may face the thermal head.

An electronic still camera or a color scanner is connected to the color thermal printer. An input video signal is digitally converted and color-converted by an image processing unit (not shown), and then the frame memories 35, 36, 37. The frame memory 35 stores yellow image data, the frame memory 36 stores magenta image data, and the frame memory 37 stores cyan image data.

The memory controller 38 controls writing and reading of three-color image data to and from the frame memories 35 to 37. The three-color image data for one line read from the frame memories 35 to 37 is stored in a line memory 39.
~ 41. Actually, a plurality of line memories are provided for each color so that reading from the line memories is not interrupted.

One line of image data read from each of the line memories 39 to 41 is stored in the head drivers 42 and 4.
3, and are converted into drive pulses for each color.
This drive pulse, as shown in FIG. 1, includes a drive pulse for bias heating and a drive pulse for gradation heating, and is sent to the corresponding thermal heads 20 to 22. These head drivers 42 to 44 are connected to the respective thermal heads 20 to
22 is driven by the head voltage of the voltage Vc.

One pixel recording cycle includes a bias heating period, a gradation heating period, and a cooling period, and all three colors have the same period. During the bias heating period, each heating element is driven by a bias drive pulse and provides bias thermal energy just before the color to be printed develops. In this embodiment, one bias heating drive pulse having a long pulse width is used, but a fixed number of bias heating drive pulses may be used instead. The number of drive pulses for gradation heating corresponding to the image data representing the gradation level is used, and the color to be printed is colored to a predetermined density.
During the cooling period, each heating element is not energized, and natural cooling or forced cooling by air is performed.

For example, when one pixel of a yellow image is recorded, as shown in FIG. 1, one bias heating drive pulse Pby and a plurality of gradation heating drive pulses Pby
gy is given. The gradation heating period changes depending on the gradation level. For example, the gradation period becomes shorter as the gradation level becomes lower and the number of gradation heating drive pulses Pgy becomes smaller.
cy becomes longer. However, the sum of the gradation heating period and the cooling period is constant. The same applies to the pixels of magenta and cyan, so only the reference numerals are given and the description is omitted. Here, since the head voltage is applied to the thermal heads 20 to 22, the voltage of the drive pulse has the same voltage value Vc as the head voltage.

As shown in FIG. 1, the system controller 33 outputs the motor driving pulses (A), (B) and (C) whose phases have been shifted by an appropriate time T via motor drivers 48, 49 and 50. Send to pulse motors 13-15. Thus, the rotation of the pulse motor 14 is started with a delay of the time T after the rotation of the pulse motor 15 is started. Further, the pulse motor 13 starts rotating after a time T from the start of the rotation of the pass motor 14. At the time of printing, printing for one line is performed in synchronization with the driving pulses (A), (B), and (C). Further, the system controller 33 performs sequence control of each unit.

FIG. 3 shows an example of the color thermosensitive recording paper 19. On the support 52, a cyan thermosensitive coloring layer 5
3, magenta thermosensitive coloring layer 54, yellow thermosensitive coloring layer 55
Are sequentially provided. The cyan thermosensitive coloring layer 53 has the lowest thermal sensitivity, and develops cyan when high thermal energy is applied. The magenta thermosensitive coloring layer 54 has a medium heat sensitivity, and develops magenta color by heating. When the magenta heat-sensitive coloring layer 54 is irradiated with ultraviolet light having a wavelength of about 365 nm, the coloring ability is lost and the recorded magenta image is fixed. The yellow thermosensitive coloring layer 55 has the highest thermal sensitivity and develops yellow with the smallest thermal energy. This yellow thermosensitive coloring layer 55 has 420
When irradiated with ultraviolet light having a wavelength of about nm, the coloring ability is lost and the recorded yellow image is fixed.

Since the yellow heat-sensitive coloring layer 55 has a small coloring heat energy, a driving pulse Pby for bias heating and a driving pulse Pby for gradation heating having a narrow pulse width are used. Since the cyan heat-sensitive coloring layer 53 has a large coloring heat energy, a bias heating drive pulse Pbc and a gradation heating drive pulse Pgc having a wide pulse width are used.
Here, the start of energization of each of the thermal heads 20 to 21 is shifted by a time T in order to prevent a significant decrease in head voltage.

Next, the operation of the above embodiment will be described. First, the yellow image data of the image to be printed,
The magenta image data and the cyan image data are written in the frame memories 35 to 37, respectively. When a print key (not shown) is operated after the writing, the memory controller 38 reads one line of yellow image data, magenta image data, and cyan image data from the frame memories 35 to 37 and reads them from the line memories 42 to 37. Write to the respective 44.

Further, the color thermosensitive recording paper 19 is pulled out from a cassette (not shown) and conveyed to the yellow thermal head 20. During this conveyance, the color thermal recording paper 19 is moved by the photo sensor 30 and the conveyance roller pair 1.
6 and reaches the platen roller 20. After the end of the color thermal recording paper 30 is detected by the photo sensor 30,
The rotation amount of the platen roller 10 is measured. The distance between the photo sensor 30 and the thermal head 20 for yellow,
Since the length from the leading end of the color thermal recording paper 19 to the recording area is known, it can be determined from the rotation amount of the platen roller 10 whether the recording area has reached the thermal head 20 for yellow.

The recording area is a thermal head 2 for yellow.
When it has reached 0, the system controller 33
Starts the thermal recording of the yellow image in synchronization with the motor drive pulse (A). When printing this yellow image, one line of yellow image data is read from the line memory 39 and sent to the head driver 42. As shown in FIG. 1, the head driver 42 supplies a driving pulse Pby for bias heating to each heating element of the thermal head 20 for yellow to generate bias thermal energy immediately before the yellow thermosensitive coloring layer 55 develops a color. Next, the head driver 42 applies the number of gradation heating drive pulses Pgy corresponding to the image data of each pixel to each heating element to generate gradation heat energy. In this way, each heating element gives the bias heat energy and the gradation heat energy to cause the yellow thermosensitive coloring layer 55 to develop yellow dots according to the image data.

Simultaneously with the start of the recording of one line of the yellow image, the motor driver 48 sends a motor drive pulse (A) to the pulse motor 13 and
Rotate 3 One motor drive pulse (A) is generated during one pixel recording cycle to intermittently rotate the pulse motor 13, but since the pulse motor 13 and the platen drum 10 are connected by a belt or the like, the platen roller 10 rotates almost continuously. Also, together with the platen roller 10, the two pairs of transport rollers 16 on both sides rotate by the same amount.

During the recording of the first line of the yellow image, the second line of yellow image data is read from the frame memory 35 and sent to the head driver 42 via the line memory 42. As described above, the head driver 4
2 drives the yellow thermal head 20 to thermally record the second line of the yellow image on the color thermosensitive recording paper 19. Hereinafter, similarly, while the platen roller 10 is being rotated, the yellow image is thermally recorded line by line.

When the color thermosensitive recording paper 19 on which the yellow image is thermally recorded reaches the yellow fixing lamp 25, 420 nm ultraviolet light emitted from the lamp is irradiated. The diazonium salt remaining in the yellow thermosensitive coloring layer 55 is decomposed by the ultraviolet rays, and the coloring ability of the yellow thermosensitive coloring layer 55 is lost.

The leading end of the color thermosensitive recording paper 19 that has passed through the yellow fixing lamp 25 is detected by the photo sensor 31. When a predetermined time has elapsed from the detection point, the system controller 33 determines that the recording area has reached the magenta thermal head 21 and performs thermal recording of the magenta image in synchronization with the motor drive pulse (B). Let it start. In the thermal recording of the magenta image, one line of magenta image data is read from the line memory 40 and sent to the head driver 43.

The head driver 43 supplies a drive pulse Pbm for bias heating to each heating element of the magenta thermal head 21 as shown in FIG. Each heating element generates bias heat energy immediately before the magenta thermosensitive coloring layer 54 develops a color. Next, the head driver 42
Applies a number of drive pulses Pbm for gradation heating corresponding to the image data of each pixel to each heating element to generate gradation heat energy. Thus, each heating element gives the bias heat energy and the gradation heat energy to cause the magenta thermosensitive coloring layer 54 to develop magenta dots according to the image data.

At the same time that the recording of one line of the magenta image is started, the motor driver 49 sets the motor driving pulse (B)
Is sent to the pulse motor 14, and the pulse motor 14 is rotated. One motor drive pulse (B) is generated during one pixel recording cycle, and the pulse motor 14 is rotated. Thus, the magenta image is thermally recorded on the color thermal recording paper 19 line by line.

The color thermosensitive recording paper 19 that has passed through the magenta thermal head 21 is irradiated with ultraviolet rays of 365 nm by a magenta fixing lamp 26. The diazonium salt remaining in the magenta thermosensitive coloring layer 54 is decomposed by the ultraviolet rays, and the coloring ability of the magenta thermosensitive coloring tank is lost.

After the thermal recording and light fixing of the magenta image, the leading end of the color thermal recording paper 19 is detected by the photo sensor 32. When a predetermined time has elapsed from the detection point, the system controller 33 determines that the recording area has reached the thermal head 22 for cyan, and starts thermal recording of the cyan image. In recording the cyan image, one line of cyan image data is read from the line memory 41 and sent to the head driver 44.

The head driver 44 applies a bias heating drive pulse P to each heating element of the cyan thermal head 22.
bc. Each heating element is provided with a cyan thermosensitive coloring layer 53.
Generates bias thermal energy just before the color develops. Next, the head driver 42 applies gradation heating drive pulses Pgc corresponding to the image data of each pixel to each heating element to generate gradation heat energy. Thus, each heating element gives the bias heat energy and the gradation heat energy to cause the cyan thermosensitive coloring layer 53 to develop a cyan dot having a wavelength corresponding to the image data. Even when this cyan image is recorded line by line, the motor driver 50 rotates the pulse motor 15 with the motor drive pulse (C).

By the thermal recording of the yellow, magenta and cyan images, a full-color image is recorded on the color thermosensitive recording paper 19. This recorded color thermal recording paper 1
9 is discharged to a tray (not shown).

When a yellow image, a magenta image, and a cyan image are thermally recorded by the thermal heads 20 to 22, as shown in FIG.
The start of the bias heating for the three colors is shifted so that they do not coincide. In this embodiment, the cyan bias heating drive pulse Pbc is generated by the time T earlier than the magenta bias heating drive pulse Pbm. The bias heating drive pulse Pbm for magenta is generated earlier by the time T than the bias heating drive pulse Pby for yellow. Note that these time differences are not the same time T but may be different.

Although the motor drive pulses (A) to (C) are out of phase by the time T, the transport rollers 16 to 18 and the platen rollers 10 to 12 can rotate substantially continuously. There is no pulling between the pairs of transport rollers. Of course, even if the color thermal recording paper 19 is intermittently transported, the width of one line in the paper feed time is about 12
The length is about 0 to 150 microns, and such a length is not formed between the two pairs of conveying rollers.

Each of the thermal heads 20 to 22 has a voltage value V
The head is driven by a head voltage of c.
A voltage drop occurs at the start of a pixel recording cycle. if,
When the three thermal heads 20 to 22 simultaneously start one pixel recording cycle, a large voltage drop occurs. When the head voltage drops significantly, even if the same drive pulse is given,
The generated heat energy becomes small, and as a result, a predetermined color density cannot be obtained. However, as shown in FIG. 1, in the present invention, the system controller 33 shifts the start time of one pixel recording cycle of each of the thermal heads 20 to 22, so that the voltage drop of the head voltage is one of the thermal heads. Minutes, and a large voltage drop can be prevented.

Also, in order to prevent a voltage drop from occurring during the gradation heating, in this embodiment, the one-pixel recording cycle for cyan is made the fastest and the one-pixel recording cycle for yellow is made the last. That is, when the one-pixel recording cycle of yellow is started first, the driving pulse for bias heating of yellow has a narrow pulse width. Therefore, depending on the head voltage and coloring characteristics, one pixel of cyan is driven after the start of gradation heating of yellow. A recording cycle may be started. In this case, it is impossible to appropriately perform yellow gradation heating that requires fine thermal energy control.

In the above embodiment, the writing to the line memory is changed for each color in accordance with the shift of one pixel recording cycle. However, the image data may be delayed. As shown in FIG. 4, a delay circuit 55 is provided between the line memory 39 and the head driver 42. Similarly, a delay circuit 5 is provided between the line memory 40 and the head driver 43.
6 are provided. In this embodiment, image data of three colors is simultaneously read out from the frame memory and written into each of the line memories 39 to 41.
1 are simultaneously read. Since the delay circuits 58 and 59 are provided, one pixel recording cycle can be shifted by the time T. Of course, since the positions of the thermal heads 20 to 22 are shifted, the position of the line read from each frame memory differs depending on the color.

In the above embodiment, the color thermosensitive recording paper is conveyed in a straight line. However, a platen drum having a large diameter is used, and three thermal heads are provided on the outer periphery thereof. The present invention can also be used for recording images. Further, the platen roller and the two pairs of transport rollers on both sides of the platen roller are driven by using three pulse motors. However, even if three platen rollers are driven by one pulse motor. Good.

[0039]

As described above, according to the color thermal printer of the three-head one-pass system of the present invention , the communication
During the bias heating period of the thermal head that
So that the energization of the thermal head is started.
Since the start timing of energization to the third thermal head is shifted , a voltage drop occurring at the start of energization can be minimized . Therefore, without providing a large-capacity power supply, the reduction in color density is suppressed, and the occurrence of density unevenness is reduced.
It can be.

[Brief description of the drawings]

FIG. 1 is a waveform diagram showing a driving state of a thermal head.

FIG. 2 is a schematic view showing a color thermal printer.

FIG. 3 is an explanatory diagram showing a layer structure of a color thermosensitive recording paper.

FIG. 4 is a block diagram showing another embodiment.

[Explanation of symbols]

 19 color thermal recording paper 20 thermal head for yellow 21 thermal head for magenta 22 thermal head for cyan

Claims (1)

(57) [Claims] 1. A first to third thermal head for thermally recording each thermosensitive coloring layer using color thermosensitive recording paper provided with first to third thermosensitive coloring layers having different colors to be developed,
First and second ultraviolet lamps provided between these thermal heads are provided. The first thermal coloring layer on the uppermost layer is thermally recorded by the first thermal head while moving the color thermal recording paper in a certain direction. Then, after this thermal recording, ultraviolet rays specific to the first thermosensitive coloring layer are irradiated with the first ultraviolet lamp to fix the photothermographic layer, and then the second thermosensitive coloring layer is thermally recorded with a second thermal head. After that, ultraviolet rays peculiar to the second heat-sensitive coloring layer are irradiated with a second ultraviolet lamp to fix the light, and finally the lowermost third heat-sensitive coloring layer is thermally recorded by a third thermal head. In the three-head, one-pass color thermal printing method, the bias heating period of the thermal head that has just started energization immediately before
A color thermal printing method, characterized in that the timing of starting energization of the first to third thermal heads is shifted so that energization of another thermal head is started within the interval .