JPH0958031A - Fixing device of thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust promptly an ultraviolet ray lamp to a predetermined intensity of luminescence, and control it stably. SOLUTION: A gain decision mode is carried out at the time of performing assembly adjustment and lamp replacement or every time of printing a predetermined number of sheets. In this gain decision mode, a switch 32 changes to a contact (a). The controller permits ultraviolet ray lamp 18 for yellow to be in a full-luminescence. In the full-luminescence, an intensity of illumination is measured by an illumination sensor 21. A gain value K is read out according to the measured illumination value from the table data of LUT 33 and then stored in ROM 34. In a print mode, a gain value K is read out from ROM 34 and then set in a multlplicator 37. During the fixing period, the gain value K is multiplied to the difference between the aimed illumination value and the measured illumination value. The correction value obtained is integrated by an integrator 38, the integrated results are sent to an inverter as a lump control value. The inverter controls a duty ratio of driving pulses for driving the ultraviolet ray lamp 18 for yellow according to the control value of the lamp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for a thermal printer, and more particularly to a fixing device for irradiating ultraviolet rays to fix an image after recording an image on the thermosensitive coloring layer.

[0002]

2. Description of the Related Art In a thermal printer, a thermosensitive recording paper having a thermosensitive coloring layer formed on a support is used. An image is recorded on the thermosensitive coloring layer by pressing and heating the thermosensitive recording paper with a thermal head, and then ultraviolet rays are applied. Irradiate to fix the image. Further, 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 on a support is also known.

In color thermosensitive recording paper, 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, when the 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.
The magenta ultraviolet lamp may be adjusted so that the irradiation amount is constant, but since it does not cause the problem of over-fixing, it is normally fully illuminated.

For example, in a yellow ultraviolet lamp, a feedback control system including an illuminance sensor is used to control the emission intensity of the yellow ultraviolet lamp so that the measured illuminance value becomes the target illuminance value. In this feedback control system, the difference between the measured illuminance value from the illuminance sensor and the target illuminance value for obtaining an appropriate irradiation amount is calculated in consideration of the transport speed of the color thermosensitive recording paper. This illuminance value difference is multiplied by a constant gain value to obtain a correction value, the lamp control value is corrected with this correction value, and feedback control is performed so that the measured illuminance value converges to the target illuminance value.

[0007]

The ultraviolet lamp has a large difference in emission intensity between different production lots, and the emission intensity varies even within the same production lot. In the conventional fixing device, since the gain of the feedback control system is constant, it takes a long time to converge to the target illuminance with an ultraviolet lamp having a small emission intensity, and the control is unstable with a large emission intensity. . For these reasons, it is difficult to perform uniform fixing on the entire surface of the thermal recording paper.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device for a thermal printer which can perform quick and stable dimming even if the emission intensity of an ultraviolet lamp varies.

[0009]

In order to achieve the above object, in a thermal printer of the present invention, an illuminance sensor for detecting the illuminance of an ultraviolet lamp and a difference between a measured illuminance value from the illuminance sensor and a target illuminance value. A first calculation means for obtaining
Secondly, the correction value is obtained by multiplying the difference in illuminance value by the gain value.
And a third calculating means for correcting the lamp control value by adding the correction value to the original lamp control value, and a lamp for controlling the emission intensity of the ultraviolet lamp according to the corrected lamp control value. Control means, a memory that stores the relationship between the measured illuminance value of the ultraviolet lamp and the gain value, and when the gain is set, the ultraviolet lamp emits light with a predetermined intensity, and the illuminance sensor measures the illuminance at that time. The control means for determining the gain value with reference to the memory is provided.

An inverter is used for light control of the ultraviolet lamp, and a drive pulse having a duty ratio according to the lamp control value is generated, and the ultraviolet lamp is turned on by this drive pulse.

The gain is determined not only at the time of shipment adjustment at the factory or when the lamp is replaced, but also every time the specified number of prints is reached in consideration of the deterioration with time of the ultraviolet lamp.
The ultraviolet lamp at the time of determining the gain is driven with a constant lamp control value. For convenience, a lamp control value for full emission is used.

[0012]

When the gain is determined, the ultraviolet lamp emits light with a constant lamp control value. When the ultraviolet lamp emits light with a predetermined intensity, the illuminance from the ultraviolet lamp is measured by an illuminance sensor. The gain value corresponding to the obtained measured illuminance value is read from the memory. Using the determined gain value, feedback control of the ultraviolet lamp is performed during fixing, and the emission intensity of the ultraviolet lamp is adjusted so that the target illuminance value is obtained.

[0013]

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. Further, the yellow thermosensitive coloring layer is 420
When it is irradiated with nm near-ultraviolet rays, the coloring ability disappears. The magenta thermosensitive coloring layer loses its coloring ability when irradiated with ultraviolet rays of 365 nm.

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

The fixing device 17 has an emission peak of 420 nm.
An ultraviolet lamp 18 for yellow which generates near ultraviolet light,
A magenta ultraviolet lamp 19 that emits ultraviolet light having an emission peak of 365 nm. A reflector 20 is arranged behind these ultraviolet lamps 18 and 19.

The illuminance sensor 21 receives the ultraviolet rays emitted from the yellow ultraviolet lamp 18 and indirectly measures the illuminance on the color thermosensitive recording paper 12. Note that reference numeral 2
Reference numeral 2 is a position sensor that detects the front end of the color thermosensitive recording paper 12.

In FIG. 2, the measurement signal of the illuminance sensor 21 is digitally converted by the A / D converter 25 and sent to the controller 26 as a measurement illuminance value. The controller 26 determines the optimum gain value according to the magnitude of the measured illuminance value when determining the gain. At the time of fixing, this gain value is used to perform feedback control of the ultraviolet lamp.
In this embodiment, the dimming of the yellow ultraviolet lamp 18 is performed by feedback control, but the magenta ultraviolet lamp 19 is fully illuminated. Of course, the magenta ultraviolet lamp 19 may also be dimmed.

When the dimming of the ultraviolet lamp is 256 steps, the controller 26 sets the lamp control value to "0".
A numerical value within the range of "255" is sent to the inverters 27 and 28. For example, when the lamp control value is "155", the duty ratio of the drive pulse for driving the ultraviolet lamp is 50%. When the lamp control value is "255", the duty ratio is 100%. A / D converter 25
The measured illuminance value output from is also converted into a numerical value within the range of "0" to "255" according to the magnitude of the measurement signal.

The controller 26 detects the position of the color thermosensitive recording paper 12 based on the signal from the position sensor 22, and controls the rotation speed and the rotation direction of the pulse motor 16 via the driver 29.

FIG. 3 is a functional block of the controller showing the feedback control system of the yellow ultraviolet lamp. The switch 32 contacts the contact a in the gain determination mode, and contacts the contact b in the print mode. In this gain determination mode, the measured illuminance value output from the A / D converter 25 is sent to the LUT (lookup table) 33. As shown in FIG. 4, table data representing the relationship between the measured illuminance value and the gain value is written in the LUT 33, and the gain value K is obtained by using the measured illuminance value as an address.
Can be read as data. This read data is stored in a writable ROM (EEPROM) 34
Is written to.

In the print mode, the measured illuminance value is added to the addition point 36 via the switch 32. This addition point 36 calculates the difference (illuminance value difference) between the predetermined target illuminance value and the measured illuminance value. The multiplier 37 includes a ROM 34
The gain value K read from is set. The gain value K is multiplied by the illuminance value difference to obtain a correction value. Integrator 38
Integrates the correction value, that is, adds the correction value to the original lamp control value, and sends the addition result to the inverter 27 as the lamp control value. Note that the magenta UV lamp 19
Emits full light without dimming, so the lamp control value of "255" is directly sent to the inverter 28 as the target illuminance value.

Next, the operation of the above embodiment will be described. When assembling and adjusting in the factory or when the ultraviolet lamp is replaced, operate the switch inside the device to
As shown in, the gain determination mode is set. In this gain determination mode, the controller 26 switches the switch 3
2 is switched to the contact a, and the lamp control value is set to "25.
The value “5” is directly output to the inverter 27.

When the lamp control value of "255" is input, the inverter 27 generates a drive pulse having a duty ratio of 100%, and the yellow UV lamp 18 is turned on by this drive pulse. As a result, the yellow ultraviolet lamp 18 emits full light.

When the yellow UV lamp 18 is fully emitting light, the illuminance sensor 21 measures the illuminance of the yellow UV. This measurement signal is digitally converted by the A / D converter 25. The gain value K is read from the LUT 33 and stored in the memory 34 using the obtained measured illuminance value as an address signal. This gain determination mode determines the optimum gain value K according to the emission characteristics of each yellow UV lamp.

Further, the ultraviolet lamp deteriorates with time as it is used, and the emission intensity decreases. Therefore, FIG. 5 (B)
As shown in, the gain determination mode is executed every time the number of prints reaches the specified number of prints, for example, 1000 prints. This is to count the number of prints with a counter,
The gain setting mode may be executed when the count value reaches the maximum value “1000”.

When printing an image with a color thermal printer, a print key (not shown) is operated after the image data is captured. When this print key is operated, the controller 26 executes the print mode.
In this print mode, the gain value K stored in the ROM 34 is read out and set in the multiplier 37, and the switch 32 switches to the contact b.

Next, 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
Is set to a retracted position away from the platen roller 13. The color thermal recording paper 12 is the thermal head 10.
And the platen roller 13 and the conveying roller pair 1
Nip to 5.

After the nip of the conveying roller pair 15, the pulse motor 16 rotates to convey the color thermosensitive recording paper 12.
During this conveyance, when the front end of the color thermosensitive recording paper 12 is detected by the position sensor 22, the yellow printing process is started. First, the thermal head 10 swings clockwise to move to the printing position where the color thermosensitive recording paper 12 is pressed. Heating element array 10a of thermal head 10
Is driven by the heat data for yellow and records a yellow image line by line in the recording area of the color thermosensitive recording paper 12.

Further, at the time of recording a yellow image, the controller 26 adds a predetermined target illuminance value and sends it to the combining point 36. At the start of lighting, this target illuminance value is sent to the multiplier 37 as it is and multiplied by the gain value K. The obtained correction value is sent to the inverter 27 as a lamp control value.
The inverter 27 sets the duty ratio of the drive pulse according to the lamp control value. This drive pulse turns on the yellow ultraviolet lamp 18.

While the yellow UV lamp 18 is lit,
The illuminance sensor 21 measures the illuminance of ultraviolet rays for yellow. This measurement signal is digitally converted by the A / D converter 25, and the obtained measured illuminance value is added to the addition point 36 via the switch 32. At this addition point 36, the difference between the target illuminance value and the measured illuminance value is calculated, and this illuminance value difference is sent to the multiplier 37.

The multiplier 37 multiplies the difference in illuminance value by the gain value K to obtain a correction value. This correction value is added to the original lamp control value in the integrator 38. Therefore, the integrator 38
Calculates the lamp control value by eventually integrating the correction value. The inverter 27 sets the duty ratio of the drive pulse according to the lamp control value.

By performing the feedback control in this way, the yellow ultraviolet lamp 18 is attenuated toward a predetermined light emission intensity at which the target illuminance value is obtained. At this time, since the optimum gain value K is set according to the emission characteristics of each yellow UV lamp, stable attenuation control with a small amplitude is performed, and the predetermined emission intensity is achieved in a short time. You can UV lamp 18 for yellow
Since the feedback control is performed even after the emission intensity of is in the steady state, the emission intensity is maintained at the predetermined value.

When a portion on which a yellow image is recorded comes under the yellow ultraviolet lamp 18 under the feedback control, the near ultraviolet rays emitted from the yellow ultraviolet lamp 18 are irradiated and fixed.

The carry amount of the color thermosensitive recording paper 12 is measured by counting the drive pulses of the pulse motor 16. When it is detected from this count value that the rear end of the color thermosensitive recording paper 12 has reached the return start position near the conveying roller pair 15, the printing process of the yellow image ends.

Next, the controller 26 turns off the yellow ultraviolet lamp 18, and at the same time, the thermal head 1
Swing 0 counterclockwise to move to the retracted position. At the same time, the reverse rotation of the pulse motor 16 is started, and the color thermosensitive recording paper 12 is returned to the print start position shown in FIG.

When the color thermosensitive recording paper 12 is returned to the print start position, the pulse motor 16 starts normal rotation, and the thermal head 10 moves to the print position to start recording a magenta image. During the recording of the magenta image, the controller 26 sends the lamp control value of "255" to the inverter 28, and the magenta ultraviolet lamp 1
9 is fully illuminated.

In the magenta printing process, a magenta image is recorded line by line in the recording area. The portion on which this magenta image is recorded is the magenta ultraviolet lamp 19
While passing through, the magenta image is fixed by the ultraviolet rays emitted from the magenta ultraviolet lamp 19 which emits full light. The magenta ultraviolet lamp 19 is lit until the paper discharge is completed.

When the process of printing the magenta image is completed, the pulse motor 16 is rotated in the reverse direction to return the color thermosensitive recording paper 12 to the print start position. Next, when the cyan printing process is started, the pulse motor 16 again rotates in the forward direction to convey the color thermosensitive recording paper 12 at a constant speed. During this conveyance, the thermal head 10 records a cyan image line by line in the recording area.

The color thermosensitive recording paper 12 on which a full-color image is recorded in the three-color frame sequence is discharged to a paper discharge tray (not shown) while being irradiated with magenta ultraviolet rays.

In the above embodiment, the ultraviolet lamp is made to emit full light when the gain value is determined, but it is not limited to full light emission and may be made to emit light at a predetermined emission intensity. Further, the fixing of the yellow image and the magenta image may be performed not only by feeding the color thermosensitive recording paper 12 but also by returning it.
This makes it possible to use a small-sized and inexpensive ultraviolet lamp having a small emission intensity. Further, the yellow UV lamp and the magenta UV lamp may be attached to a rotatable holder while keeping an appropriate angle, and this holder may be rotated so that one UV lamp faces the color thermosensitive recording paper. In this case, the ultraviolet irradiation positions are the same for both yellow and magenta, and the transport distance of the color thermosensitive recording paper during printing is small, so the width of the thermosensitive printer can be reduced.

Alternatively, a platen drum having a large size may be used, and a color thermosensitive recording paper may be wound around the platen drum to record one color for each rotation. Further, the color thermosensitive recording paper may have a four-layer structure in which a black thermosensitive coloring layer is provided in addition to the yellow thermosensitive coloring layer, the magenta thermosensitive coloring layer and the cyan thermosensitive coloring layer. Of course, a thermosensitive recording paper on which a thermosensitive coloring layer of one color is recorded can be used. In this case, only one type of ultraviolet lamp is required.

[0043]

According to the present invention having the above-described structure, the gain value of the feedback control system is determined to be an optimum value according to the emission characteristics of each ultraviolet lamp, so that the ultraviolet lamp can be adjusted to a predetermined emission intensity in a short time. In addition, stable control with a small amplitude can be performed.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a color thermal printer of the present invention.

FIG. 2 is a block diagram showing an electrical configuration.

FIG. 3 is a functional block diagram of a feedback control system.

FIG. 4 is a graph showing an LUT table.

FIG. 5 is a flowchart of gain determination.

[Explanation of symbols]

 10 Thermal Head 12 Color Thermal Recording Paper 15 Conveyor Roller Pair 17 Fixing Device 18 Yellow UV Lamp 19 Magenta UV Lamp 21 Illuminance Sensor

Claims (3)

[Claims] 1. A thermal printer in which an image is recorded on a thermal recording paper by a thermal head and then fixed by irradiating ultraviolet rays from an ultraviolet lamp to fix the illuminance sensor for detecting the illuminance of the ultraviolet lamp and the illuminance sensor. First calculating means for obtaining the difference between the measured illuminance value and the target illuminance value, second calculating means for obtaining the correction value by multiplying this illuminance value difference by the gain value, and this correction value as the original lamp control Third calculation means for correcting the lamp control value by adding it to the value, lamp control means for controlling the emission intensity of the ultraviolet lamp according to the corrected lamp control value, measured illuminance value and gain value of the ultraviolet lamp And the memory that stores the relationship between the UV lamp and the UV lamp that emits light with a predetermined lamp control value when the gain is set, and the illuminance sensor measures the illuminance of the UV lamp. Fixing apparatus characterized in that a control means for determining a gain value with reference to Li. 2. The fixing device according to claim 1, wherein the control unit determines the gain value each time the specified number of prints is reached. 3. The fixing device according to claim 1, wherein the lamp control means is an inverter, and adjusts the duty ratio of the lamp drive pulse supplied to the ultraviolet lamp based on the lamp control value. .