JP2000177157A - Color thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a print speed by shortening a light fixation time. SOLUTION: During a primary fixation by an ultraviolet lamp 32 for magenta, a lowest illuminance-detecting circuit 56 detects a lowest illuminance value of ultraviolet rays emitted from the ultraviolet lamp 32. A refixation necessity- judging circuit 57 determines based on the lowest illuminance value whether or not refixation is necessary. In starting the refixation, a speed-setting circuit 52 sets a transfer speed for a color thermal recording paper 10 in an opposite direction in accordance with an initial illuminance value of the ultraviolet lamp 32 being turned on and the lowest illuminance value at the primary fixation. During the refixation, a correction speed-setting circuit 58 sets a correction value of the transfer speed according to the illuminance of the ultraviolet lamp 32, and a transfer motor-controlling circuit 59 adjusts a voltage or current of a transfer motor 19 thereby adjusting the transfer speed. At this time, the transfer speed is increased when the illuminance of the ultraviolet lamp 32 rises, while the transfer speed is decreased when the illuminance descends.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color thermal printer which irradiates ultraviolet light to a color thermal recording paper immediately after thermal recording to perform optical fixing. More specifically, the color thermal recording paper is relatively moved twice. The present invention relates to a color thermal printer in which main fixing is performed by irradiating ultraviolet rays at a first time, and re-fixing is performed by irradiating ultraviolet rays at a second time.

[0002]

2. Description of the Related Art In a color thermal printer, a color thermal recording paper is used in which a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, and a yellow thermosensitive coloring layer are sequentially formed on a support.
In this color thermosensitive recording paper, the yellow thermosensitive coloring layer as the uppermost layer has the highest thermal sensitivity, and the cyan thermosensitive coloring layer as the lowermost layer has the lowest thermal sensitivity. Printing on color thermosensitive recording paper is performed by utilizing the difference in thermal sensitivity between each thermosensitive coloring layer.While moving the color thermosensitive recording paper and the thermal head relatively, each thermosensitive coloring layer is pressed by the thermal head.・ Color by heating. As is well known, a thermal head has a large number of heating elements arranged in a line, and generates thermal energy according to a color to be thermally recorded and a color density.

Thermal recording on a color thermosensitive recording paper is performed in order from the thermosensitive coloring layer on the front side. Immediately after the heat recording, the thermosensitive coloring layer is irradiated with ultraviolet rays in a wavelength range specific to the thermosensitive coloring layer so that the thermosensitive coloring layer is not heat-recorded again. Has lost.
Generally, an ultraviolet lamp is used to generate the ultraviolet light for light fixing.

At the time of light fixing of the yellow thermosensitive coloring layer, if the amount of irradiation of ultraviolet rays is too large, the magenta thermosensitive coloring layer is also partially fixed and its coloring characteristics are changed, so that the emission intensity of the ultraviolet lamp is controlled. Is adjusted so that the amount of irradiation of ultraviolet rays is constant. Further, in the light fixing of the magenta thermosensitive coloring layer, only insufficient fixing becomes a problem. Therefore, the ultraviolet lamp emits full light with a drive pulse having a duty ratio of 100% without controlling the light emission intensity.

[0005] In the ultraviolet lamp, the luminous intensity changes depending on the tube wall temperature. As shown in FIG. 8, the luminous intensity is low when the tube wall temperature is low, and the luminous intensity increases as the tube wall temperature increases. At higher temperatures, the emission intensity decreases. FIG. 8 shows emission characteristics when the ultraviolet lamp is driven by a drive pulse having a duty ratio of 100%.

When a normal ultraviolet lamp emits full light, as shown by a dashed line in FIG. 9, the light emission intensity becomes substantially constant after a predetermined time has elapsed after lighting. However, as the number of uses of the ultraviolet lamp increases, the deposited mercury adheres to the inside of the tube wall. As shown by the solid line in the figure, the ultraviolet lamp with mercury adhered to the inside of the tube has almost the same luminous intensity as the normal ultraviolet lamp at the time of lighting, but the luminous intensity gradually decreases thereafter, and the mercury adheres to the state. It has the characteristic that it decreases to the lowest value determined accordingly and then increases gradually again.

In order to prevent insufficient fixing due to a change in light emission intensity, thermal recording and main fixing are simultaneously performed while the color thermal recording paper and the thermal head move relative to each other. It is known that the second relative movement is performed while the light is turned on to supplementarily perform re-fixing (Japanese Patent Laid-Open No. 7-32625). Further, in the color thermal printer described in Japanese Patent Application Laid-Open No. 9-174891, a minimum illuminance value of ultraviolet rays emitted from a magenta ultraviolet lamp is detected during the light fixing of the magenta thermosensitive coloring layer, and based on the minimum illuminance value. In addition to determining whether or not re-fixing is necessary, when performing re-fixing, the second relative movement is performed at a speed corresponding to the minimum illuminance value.

[0008]

However, in all of the conventional color thermal printers, the relative speed at the time of re-fixing is low so that an appropriate exposure can be obtained even when the ultraviolet lamp maintains the minimum illuminance value. Because it is decided, it takes a long time to print.

The present invention has been made in consideration of the above circumstances, and has as its object to provide a color thermal printer capable of shortening the light fixing time and increasing the printing speed.

[0010]

In order to achieve the above object, a color thermal printer according to the present invention is provided which includes a main fixing and re-fixing step for irradiating ultraviolet light emitted from a second ultraviolet lamp during main fixing and re-fixing of the second thermosensitive coloring layer. An illuminance sensor for measuring a value, a minimum illuminance value detecting means for detecting a minimum illuminance value of ultraviolet light emitted from the second ultraviolet lamp during the main fixing, and a means for determining whether re-fixing is necessary based on the minimum illuminance value Speed setting means for measuring an initial illuminance value of the second ultraviolet lamp being turned on at the start of the second relative movement, and determining a relative speed according to the initial illuminance value and the minimum illuminance value; During the second relative movement, based on the initial illuminance value, the speed adjustment is performed to increase the relative speed when the illuminance of the second ultraviolet lamp increases and to decrease the relative speed when the illuminance of the second ultraviolet lamp decreases. Means and It is intended.

[0011]

FIG. 2 shows the structure of a color thermal printer according to the present invention. The sheet-like color thermal recording paper 10 is stacked in a paper feed tray 11.
A paper feed roller 12 is provided above the paper feed tray 11, rotates at the start of printing, and sends out the color thermal recording paper 10 at the top from the paper feed path 13. The color thermosensitive recording paper 10 sent out from the paper feed path 13 is nipped by a pair of transport rollers 15 including a nip roller 15a and a drive roller 15b, and is forwardly moved from the paper feed tray 11 side to the paper discharge path 16 side. The paper is alternately conveyed in the opposite direction from the paper path 16 toward the paper feed tray 11.

FIG. 3 shows an example of the layer structure of the color thermosensitive recording paper 10. The color thermosensitive recording paper 10 is formed by layering a cyan thermosensitive coloring layer 21, a magenta thermosensitive coloring layer 22, a yellow thermosensitive coloring layer 23, and a protective layer 24 in this order on a support 20. Each of the thermosensitive coloring layers 21 to 23 is provided from the surface 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 23 and the magenta thermosensitive coloring are used. Layer 22
And the positions are swapped. An intermediate layer (not shown) is provided between the layers.

The yellow thermosensitive coloring layer 23 loses its coloring ability when irradiated with near ultraviolet rays near 420 nm.
Further, the magenta thermosensitive coloring layer 22 loses its coloring ability when irradiated with 365 nm ultraviolet rays.

In FIG. 2, a small-diameter platen roller 17 and a color thermosensitive recording paper 10 supported thereon are pressed and heated between a paper feed tray 11 and a conveying roller pair 15 to record an image. A thermal head 18 is provided. As is well known, the thermal head 18 has a large number of heating elements arranged in a line, and generates thermal energy according to a color to be thermally recorded and its color density. The driving roller 15b is rotated by the transport motor 19.

Two ultraviolet lamps 31 and 32 for light fixing are arranged between the pair of conveying rollers 15 and the paper discharge path 16. UV lamp 31 for yellow is almost 420n
m, the magenta ultraviolet lamp 32 emits ultraviolet light having an emission peak at about 365 nm, and the color thermosensitive recording paper 1
Irradiate on zero.

Behind the ultraviolet lamps 31, 32, a reflector 33 is arranged. The inner wall of the reflector 33 is a reflection surface, and reflects the light emitted to the back side of the ultraviolet lamps 31, 32 toward the color thermosensitive recording paper 10 side. Illuminance sensors 34 and 35 are provided near the ultraviolet lamps 31 and 32. Illuminance sensors 34, 3
5 measures the illuminance of the ultraviolet rays radiated from the ultraviolet lamps 31 and 32 and outputs a measured illuminance signal. Reference numeral 38 in the figure is a temperature sensor for measuring the environmental temperature, and is provided at an appropriate position in the printer.

In this color thermal printer, when printing a yellow image and a magenta image, thermal recording and main fixing are simultaneously performed while the color thermal recording paper 10 is conveyed in the forward direction, respectively. While the paper 10 is transported in the reverse direction, re-fixing is performed supplementarily. Also,
When printing a cyan image, thermal recording is performed while the color thermosensitive recording paper 10 is transported in the forward direction, and is not transported in the reverse direction. The yellow ultraviolet lamp 31 is turned on during printing of the yellow image, and the magenta ultraviolet lamp 3 is turned on.
2 lights up during printing of the magenta image.

As shown in FIG. 1, two illuminance sensors 3
The measured illuminance signals of the A / D converter 4
The digital data is converted into illuminance data at 1 and 42 and then sent to the microcomputer 50. The temperature signal measured by the temperature sensor 38 is digitally converted by the A / D converter 43 and converted into temperature data, which is then sent to the microcomputer 50.

The microcomputer 50 includes a tube wall temperature determining circuit 51, a speed setting circuit 52, and a target illuminance setting circuit 5.
3, a differential amplifier 54, a duty ratio adjustment circuit 55, a minimum illuminance value detection circuit 56, a re-fixing necessity determination circuit 57, a correction speed setting circuit 58, and a transport motor control circuit 59. The tube wall temperature discrimination circuit 51 includes a temperature sensor 38.
UV lamps 31, 32 based on the temperature data from
It is determined whether or not the tube wall temperature is a temperature at which a sufficient amount of ultraviolet rays necessary for light fixing can be emitted.

The speed setting circuit 52 carries the transport speeds VY1, VM1, and VC1 of the color thermosensitive recording paper 10 in the forward direction at the time of printing each of a yellow image, a magenta image, and a cyan image.
And transport speeds VY2 and VM2 in the opposite directions, and output respective speed signals. Transport speed VY in forward direction
1, VM1 and VC1 are predetermined in accordance with the thermal sensitivities of the thermosensitive coloring layers 21 to 23 to be thermally recorded. The transport speeds VY2 and VM2 in the opposite directions are set based on the illuminance of the ultraviolet lamps 31 and 32, respectively.

The ROM 45 stores predetermined values of the transport speeds VY1, VM1, and VC1 in the forward direction and the arithmetic expressions for setting the transport speeds VY2 and VM2 in the reverse direction. .

The target illuminance setting circuit 53 sets a target illuminance value of ultraviolet rays emitted from the yellow ultraviolet lamp 31 based on the illuminance data from the yellow illuminance sensor 34. In the present embodiment, a value obtained by multiplying the measured illuminance value by a constant K is set as the target illuminance value. Note that the constant K specifies the illuminance level of the target illuminance value with respect to the light emitting ability of the ultraviolet lamp 31, and may be set to, for example, about 0.9.

The differential amplifier 54 includes a target illuminance setting circuit 53
And the measured illuminance value obtained by the illuminance sensor 34 is calculated, and this difference signal is output. The duty ratio adjustment circuit 55 adjusts the duty ratio of the drive pulse supplied to the yellow ultraviolet lamp 31 based on the difference signal of the differential amplifier 54. The magenta ultraviolet lamp 32 is driven by a lamp driver 46 with a drive pulse having a duty ratio of 100%.

The minimum illuminance value detection circuit 56 monitors the illuminance change of the ultraviolet lamp 32 based on the illuminance data from the magenta illuminance sensor 35, and detects the minimum illuminance value of the emitted ultraviolet light. The re-fixing necessity determination circuit 57 is based on the minimum illuminance value detected by the minimum illuminance value detection circuit 56,
It is determined whether re-fixing is necessary for the magenta image.

The correction speed setting circuit 58 obtains the correction speed of the transport speed VM2 according to the illuminance value of the ultraviolet lamp 32 during the re-fixing of the magenta image, and outputs a correction speed signal.

The transport motor control circuit 59 adjusts the voltage or current of the transport motor 19 according to the speed determined by the speed setting circuit 52 or the correction speed setting circuit 58, and adjusts the rotation direction and rotation speed of the drive roller 15b. I do.

The above series of functions are processed by software inside the microcomputer 50.

Next, the operation of the present embodiment will be described.
When print start is instructed, a print preparation operation is performed according to the flow shown in FIG. First, the temperature sensor 3
8 measures the environmental temperature in the printer. Temperature sensor 38
The measured temperature signal is converted into temperature data by the A / D converter 43, and then sent to the tube wall temperature discriminating circuit 51 via the microcomputer 50. In the tube wall temperature determination circuit 51,
Based on the temperature data from the temperature sensor 38, a comparison is made between the measured environmental temperature T and the reference environmental temperature T _S. The reference environmental temperature T _S is for estimating the state of the tube wall temperature of the ultraviolet lamps 31 and 32. In this embodiment, the ambient temperature "12 when the wall temperature is the lowest temperature T _L that can emit ultraviolet light of intensity I _S required optical fixation (see FIG. 8)
° C ”was defined as the reference environmental temperature T _S.

When the measurement environment temperature T is equal to or higher than the reference environment temperature T _S , since the tube wall temperature of the ultraviolet lamps 31 and 32 is a temperature sufficient to radiate the required amount of ultraviolet light for light fixing, printing is performed as it is. Move to operation.

When the measurement environment temperature T is lower than the reference environment temperature T _S , the tube wall temperature is lower than the minimum temperature T _L , so that the ultraviolet lamps 31 and 32 are turned on to heat the respective tube walls. Can be During the pre-lighting of the ultraviolet lamps 31, 32, the illuminance L of the ultraviolet lamps 31, 32 is monitored based on the illuminance data from the illuminance sensors 34, 35, respectively. The ultraviolet lamp 31 is turned off when the illuminance L is equal to or greater than prescribed illuminance L _S.

By the above-described print preparation operation, the tube wall temperatures of the ultraviolet lamps 31 and 32 are adjusted, and the ultraviolet lamps 31 and 32 are always ready to emit the necessary amount of ultraviolet light for light fixing.

When the print preparation operation is completed, the print operation is started. First, the color thermosensitive recording paper 10 is fed. When the paper feed roller 12 rotates, the paper feed tray 1
The color thermosensitive recording paper 10 stacked on the uppermost portion of the recording paper 1 is sent out from the paper feed passage 13. While the color thermal recording paper 10 is being fed, the thermal head 18 is set at a position away from the platen roller 17. When the color thermosensitive recording paper 10 passes between the thermal head 18 and the platen roller 17 and the leading end thereof is nipped by the conveying roller pair 15,
The rotation of the paper feed roller 12 stops.

Simultaneously with the start of sheet feeding, printing of a yellow image is started according to the flow of FIG. The microcomputer 50 controls the duty ratio adjustment circuit 55 so that the yellow ultraviolet lamp 31 has a duty ratio of 10
Full lighting with 0% drive pulse. The yellow illuminance sensor 34 measures the illuminance of the ultraviolet light emitted from the ultraviolet lamp 31 and sends the illuminance data to the microcomputer 50.

The microcomputer 50 takes in the measured illuminance value L ₀ measured by the illuminance sensor 34, for example, 0.5 seconds after the ultraviolet lamp 31 starts lighting, and sends it to the target illuminance setting circuit 53. The target luminance setting circuit 53, the constant K is multiplied to the measured illuminance value L ₀ is the target luminance value L _Y is set.

After the target illuminance value L _Y is set, the illuminance data from the illuminance sensor 34 is sent to the differential amplifier 54. In the differential amplifier 54, based on the illuminance data, calculates the difference between the measured illuminance value L and the target illuminance value L _Y, and sends the difference signal to the duty ratio adjusting circuit 55. The duty ratio adjustment circuit 55 is released from the control of the microcomputer 50, and instead adjusts the duty ratio of the drive pulse of the ultraviolet lamp 31 according to the difference signal. In this case, measured illuminance value L when less than the target luminance value L _Y is adjusted duty ratio is larger emission intensity of the ultraviolet lamp 31 is increased. On the other hand, when the measured illuminance value L is the target illuminance value L _Y or more, the emission intensity of the ultraviolet lamps 31 are adjusted duty ratio is small is suppressed. Thus, the illuminance of ultraviolet rays emitted from the ultraviolet lamp 31 is adjusted to the target illuminance value L _Y.

On the other hand, in the speed setting circuit 52, the ROM 45
, The transport speed VY1 according to the thermal sensitivity of the yellow thermosensitive coloring layer 23 is set. When the transport speed VY1 is set, the thermal head 18 is moved to a position where the thermal head 18 presses the color thermal paper 10. Then, the transport motor control circuit 5
9 rotates the drive roller 15b by the transport motor 19, transports the color thermosensitive recording paper 10 in the forward direction at the speed VY1, and performs the first relative movement.

During the first relative movement of the color thermosensitive recording paper 10, a yellow image is recorded line by line while passing through the front surface of the thermal head 18. In the thermal recording of this yellow image, each heating element of the thermal head 18
The yellow heat-sensitive coloring layer 23 generates heat energy according to the coloring characteristics and coloring density.

The color thermosensitive recording paper 10 on which the yellow image is recorded is subjected to main fixing while passing through the front surface of the ultraviolet lamp 31 for yellow. UV lamp 31 is approximately 42
It emits ultraviolet light of 0 nm and has a yellow thermosensitive coloring layer 2
3 loses its coloring ability. At this time, the ultraviolet lamp 31
Is adjusted to the target illuminance value L _Y , so that the irradiation amount of ultraviolet light becomes uniform over the entire surface of the color thermosensitive recording paper 10.

When the rear end of the color thermosensitive recording paper 10 passes through the thermal head 18, the recording of the yellow image is completed.
The thermal head 18 moves to a position away from the color thermosensitive recording paper 10. When the rear end of the color thermal recording paper 10 reaches the position of the pair of transport rollers 15, the color thermal recording paper 10
Is stopped.

Next, the speed setting circuit 52 sets the transport speed VY2 of the color thermosensitive recording paper 10 in the reverse direction.

The conveying speed VY1 target illuminance value L _Y and the recording paper 10 in yellow fixing lamp 31, VY2
And has a total light amount S _T of ultraviolet rays irradiated during the main fixing and during re-fixing is defined such that the predetermined amount. Irradiation light amount of the ultraviolet rays, since it is defined by the multiplication value between the irradiation time and intensity values of the ultraviolet ray, the total amount S _T of ultraviolet rays irradiated during printing of the yellow image, the formula _{S T = L Y × (T} Y1 + T _Y2 ). Note that T _Y1 and T _Y2 in the equations are irradiation times of the ultraviolet rays at the time of main fixing and at the time of re-fixing.
1, VY2. Accordingly, the conveying speed VY2 in the reverse direction is determined on the basis of the conveying speed VY1 in the forward direction and the target irradiance value L _Y.

[0042] At this time, high target irradiance value L _Y is, when the light quantity of ultraviolet light emitted during a main fixing is large, the conveying speed VY2 in the opposite direction is set to a high speed, the irradiation time of ultraviolet rays during recolonization T _Y2 is shortened. The target illuminance value L _Y is low, when the small amount of light irradiated ultraviolet during the main fixing the conveying speed VY2 is set to low speed, irradiation time T _Y2 UV at the time of re-fixing is long.

When the transport speed VY2 is set, the drive roller 15b is rotated by the transport motor 19, the color thermosensitive recording paper 10 is transported in the reverse direction at the speed VY2, and the second relative movement is started. Then, the color thermosensitive recording paper 10 passes through the front surface of the ultraviolet lamp 31 again and
Irradiation with UV light of 20 nm is performed. Even during the conveyance in the reverse direction, the ultraviolet lamp 31 is adjusted to the target illuminance value L _Y , so that the color thermosensitive recording paper 10 is uniformly and appropriately irradiated with an appropriate amount of ultraviolet light, and a yellow image is formed. It is firmly established.

When the leading end of the color thermosensitive recording paper 10 passes through the ultraviolet lamp 31, the ultraviolet lamp 31 is turned off. Then, the leading end of the color thermosensitive recording paper 10 is set to the conveying roller pair 1.
When the sheet reaches the position 5, the conveyance of the color thermosensitive recording paper 10 is stopped, and the printing of the yellow image is completed.

Next, a magenta image is printed in accordance with the flow of FIG. FIG. 7 is a graph showing a change in the illuminance of the magenta ultraviolet lamp 32 during magenta image printing. The microcomputer 50 drives the lamp driver 46 to turn on the magenta ultraviolet lamp 32 with a drive pulse having a duty ratio of 100%. The magenta illuminance sensor 35 measures the illuminance of the ultraviolet lamp 32 and sends the illuminance data to the microcomputer 50.

The microcomputer 50 reads the measured illuminance value L measured by the illuminance sensor 35 at t ₁ seconds, for example, 0.5 seconds after the ultraviolet lamp 32 starts lighting.
₁ is taken and sent to the minimum illuminance value detection circuit 56. In minimum illuminance value detecting circuit 56, a minimum illuminance value measured illuminance value L ₁ L
Set as the initial value of _min .

On the other hand, in the speed setting circuit 52, the ROM 45
, The transport speed VM1 according to the thermal sensitivity of the magenta thermosensitive coloring layer 22 is set. When the transport speed VM1 is set, the thermal head 18 is moved to a position where the thermal head 18 presses on the color thermal paper 10. Then, the transport motor control circuit 5
9 rotates the drive roller 15b by the transport motor 19, transports the color thermosensitive recording paper 10 in the forward direction at the speed VM1, and performs the first relative movement.

During the first relative movement, the magenta image is recorded line by line while the color thermosensitive recording paper 10 passes through the thermal head 18. In the thermal recording of the magenta image, each heating element of the thermal head 18 generates thermal energy according to the coloring characteristics and coloring density of the magenta thermosensitive coloring layer 22.

The color thermosensitive recording paper 10 on which the magenta image is recorded is subjected to main fixing while passing through the front surface of the ultraviolet lamp 32 for magenta. The ultraviolet lamp 32 is almost 3
The magenta thermosensitive coloring layer 22 emits 65 nm ultraviolet rays.
Loses its coloring ability.

During the main fixing of the magenta image, the illuminance data from the illuminance sensor 35 is sent to the minimum illuminance value detection circuit 56. Minimum illumination value detection circuit 56 monitors the illumination changes of the ultraviolet lamp 32 based on the illuminance data, detects a minimum luminance value L _min of the emitted ultraviolet light in the main fixing.

When the rear end of the color thermosensitive recording paper 10 passes through the thermal head 18, the recording of the magenta image is completed.
The thermal head 18 moves to a position away from the color thermosensitive recording paper 10. When the rear end of the color thermosensitive recording paper 10 reaches the position of the pair of conveying rollers 15, the conveyance is stopped.

When the conveyance of the color thermosensitive recording paper 10 is stopped, the re-fixing necessity judging circuit 57 judges whether re-fixing of the magenta image is necessary. First, the minimum illuminance value detection circuit 5
6 on the basis of the minimum illuminance value L _min detected in, it calculates the minimum light amount S _min of UV that is at least irradiated during the main fixing. Since the irradiation light amount of the ultraviolet light is defined by a multiplication value of the illuminance value and the irradiation time, the minimum light amount S _min is obtained by the formula S _min = L _min × T _M1 . T _M1 in the equation is the irradiation time of the ultraviolet ray at the time of main fixing (see FIG. 7), and the transport speed VM in the forward direction is
Determined by 1.

[0053] When the minimum light amount S _min is calculated, and the minimum light amount S _min, is compared with the minimum required specific light amount S _M to the optical fixing of the magenta image is carried out.

[0054] As shown in FIG. 7, the total light quantity of ultraviolet light is actually irradiated at the main fixing is a quantity obtained by adding the minimum amount S _min and quantity S _0. Therefore, when the minimum light amount S _min is equal to or _larger than the specified light amount SM, the specified light amount S
_Since ultraviolet rays of _M or more have been irradiated, there is no need to perform re-fixing. In this case, the microcomputer 50
There controls the conveyance motor control circuit 59, the recording paper 10, is conveyed in the reverse direction at the highest conveying speed V _max of the color thermal printer. When the leading end of the color thermosensitive recording paper 10 reaches the position of the pair of conveying rollers 15, the conveyance is stopped. The ultraviolet lamp 32 is turned off when the leading end of the color thermosensitive recording paper 10 passes through the front surface.

On the other hand, when the minimum light amount S _min is less than the prescribed amount S _M, there is a possibility that the irradiation light quantity of ultraviolet light is insufficient, re-fixing is performed. First, the initial illuminance value L ₂ of the ultraviolet lamp 32 during lighting is measured. The speed setting circuit 52 sets the conveying speed VM2 in the opposite direction on the basis of the initial illuminance value L ₂ and the minimum light amount S _min.

[0056] conveying speed VM2, when performing the re-fixing while maintaining the ultraviolet lamp 32 to the initial illuminance value L _2,
The sum of the amount of ultraviolet light irradiated during re-fixing and the minimum light amount S _min irradiated during main fixing is determined to be a specified light amount S _M, and the equation VM2 = (L ₂ × x) / (S _M −S _min ). Note that the constant x in the equation is the transport distance, and is the length of the color thermosensitive recording paper 10 in the transport direction.

After the transport speed VM2 is set, the illuminance data from the illuminance sensor 35 is sent to the correction speed setting circuit 58. The correction speed setting circuit 58 sets the correction speed V of the transport speed VM2 according to the measured illuminance value L of the ultraviolet lamp 32, and sends the speed signal to the transport motor control circuit 59.
The correction speed V is obtained by the equation V = VM2 × (L / L ₂ ). Correcting speed V, the conveying speed V when the illuminance of the ultraviolet lamp 32 is higher than the initial illuminance value L ₂
M2 fast set than the illuminance is set slower becomes lower than the initial intensity value L _2.

The transport motor control circuit 59 transports the color thermosensitive recording paper 10 in the reverse direction while adjusting the rotation speed of the drive roller 15b in accordance with the speed signal from the correction speed setting circuit 58, and performs the second relative Make the move. The color thermosensitive recording paper 10 is re-fixed while passing through the ultraviolet lamp 32.

During the re-fixing of the magenta image, when the illuminance of the ultraviolet lamp 32 is increased, the transport speed is increased to shorten the ultraviolet irradiation time, and when the illuminance is reduced, the transport speed is decreased and the ultraviolet irradiation time is reduced. Becomes longer, so that the amount of ultraviolet irradiation becomes uniform over the entire surface of the color thermosensitive recording paper 10. In addition, the light emitting ability of the ultraviolet lamp 32 is effectively utilized, and it is possible to irradiate the insufficient amount of ultraviolet light onto the color thermosensitive recording paper 10 in a shortest time without any excess or shortage. Therefore, the re-fixing time is shorter and the printing speed is faster than in a color thermal printer that conveys color thermal recording paper at a constant speed determined according to the minimum illuminance value at the time of main fixing.

When the leading end of the color thermosensitive recording paper 10 passes through the ultraviolet lamp 32, the ultraviolet lamp 32 is turned off. Then, the leading end of the color thermosensitive recording paper 10 is set to the conveying roller pair 1.
When the position reaches 5, the conveyance of the color thermosensitive recording paper 10 is stopped, and the printing of the magenta image is completed.

Next, printing of a cyan image is started. First, the thermal head 18 moves to a position where it presses on the color thermal paper 10. The color thermosensitive recording paper 10 has a transport speed VC determined according to the thermal sensitivity of the cyan thermosensitive coloring layer 21.
At 1, the cyan image is conveyed in the forward direction, and the cyan image is recorded line by line by the thermal head 18.

When the recording of the cyan image is completed, the thermal recording paper 10 on which the thermal recording has been performed is conveyed to the paper discharge path 16 side and discharged to a paper discharge tray (not shown).

In the case of continuous printing, the emission intensity is high because the ultraviolet lamp is warm. In such a case, the amount of ultraviolet light irradiated during the main fixing is
If the amount of light required for light fixing has been reached, re-fixing is not performed even when printing a yellow image.

In the above-described embodiment, the magenta ultraviolet lamp always emits full light.
After adjusting the light emission intensity so that the illuminance value of the ultraviolet lamp is constant and determining whether re-fixing is necessary based on the minimum illuminance value during main fixing, when re-fixing, the ultraviolet lamp is fully illuminated and full color is emitted. The transport speed of the thermal recording paper may be adjusted.

In the above-described embodiment, the magenta ultraviolet lamp is turned on only when printing a magenta image. However, in order to eliminate the yellow color of the color thermosensitive recording paper, it is turned on during printing a cyan image. Is good.

Further, although the color thermosensitive recording paper is reciprocated, the color thermosensitive recording paper may be wound around a platen drum and rotated in the same direction. In addition, since the emission intensity of the ultraviolet lamp is reduced when the tube wall temperature is too high, for a magenta ultraviolet lamp that emits full light, the fan is cooled when the tube wall temperature reaches a certain temperature or higher. Is good.

[0067]

As described above, according to the color thermal printer of the present invention, at the time of re-fixing, the relative speed is adjusted according to the change in the illuminance of the ultraviolet lamp, so that the light emitting ability of the ultraviolet lamp is effectively utilized. In addition, it is possible to irradiate the insufficient amount of ultraviolet light in the shortest time without excess or deficiency. Therefore,
The light fixing time is shorter and the printing speed is higher than in a conventional color thermal printer in which the relative speed at the time of re-fixing is determined to be constant.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an electrical configuration of a color thermal printer embodying the present invention.

FIG. 2 is a schematic view of a color thermal printer embodying the present invention.

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

FIG. 4 is a flowchart of a print preparation operation.

FIG. 5 is a flowchart illustrating a printing sequence of a yellow image.

FIG. 6 is a flowchart illustrating a printing sequence of a magenta image.

FIG. 7 is a graph showing a change in illuminance of a magenta ultraviolet lamp during printing of a magenta image.

FIG. 8 is a graph showing a relationship between a tube wall temperature and a light emission amount of an ultraviolet lamp.

FIG. 9 is a graph showing light emission characteristics of an ultraviolet lamp having mercury adhered in a tube wall.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 color thermosensitive recording paper 18 thermal head 21 cyan thermosensitive coloring layer 22 magenta thermosensitive coloring layer 23 yellow thermosensitive coloring layer 31 yellow ultraviolet lamp 32 magenta ultraviolet lamp 34,35 illuminance sensor 52 speed setting circuit 56 minimum illuminance value detection circuit 57 re Fixing necessity determination circuit 58 Correction speed setting circuit 59 Transport motor control circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shigeru Tagaya 3-13-45 Izumi, Asaka-shi, Saitama F-Term in Fuji Photo Film Co., Ltd. (reference) 2C058 AB08 AC06 AC15 AF04 AF23 GA07 GA09 GB03 GB11 GB29 GB49 2C065 AA01 AB01 CJ02 CJ05 DC21 DC24 DC25 DC26 2H026 AA07 AA14 AA32

Claims (1)

[Claims] 1. A thermal head and a color thermosensitive recording paper are moved relative to each other by using a color thermosensitive recording paper in which at least first to third thermosensitive coloring layers having different colors and different thermal sensitivities are sequentially formed. During the movement, the color thermosensitive recording paper is heated by the thermal head to record the first thermosensitive coloring layer, and then is irradiated with ultraviolet light of the first wavelength range emitted from the first ultraviolet lamp to fix the light, and then the light is fixed. After recording the second thermosensitive coloring layer with a thermal head, irradiating ultraviolet rays in the second wavelength range emitted from the second ultraviolet lamp to fix the light, and then recording the third thermosensitive coloring layer with the thermal head, At least the second thermosensitive coloring layer is subjected to main fixing by the second ultraviolet lamp during the first relative movement, and
A color thermal printer that performs replenishment re-fixing during the second relative movement; an illuminance sensor for measuring an illuminance value of ultraviolet light emitted from the second ultraviolet lamp during main fixing and re-fixing of the second thermosensitive coloring layer; A minimum illuminance value detecting unit for detecting a minimum illuminance value of the ultraviolet light emitted from the second ultraviolet lamp during the main fixing, a unit for determining whether re-fixing is necessary or not based on the minimum illuminance value;
At the start of the second relative movement, a speed setting means for measuring an initial illuminance value of the second ultraviolet lamp being turned on and determining a relative speed according to the initial illuminance value and the minimum illuminance value; Speed adjusting means for increasing the relative speed when the illuminance of the second ultraviolet lamp increases, and decreasing the relative speed when the illuminance of the second ultraviolet lamp decreases, based on the initial illuminance value during the relative movement. Color thermal printer.