JPH07227989A - Thermal printer - Google Patents

Abstract

PURPOSE:To perform proper printing even when a recording material is replaced or a thermal printer is made to stand for a long period of time by providing a correction quantity resetting means returning the density correction quantity of a density correction means to an initial set value when the opening of a housing part is detected by an opening detection means. CONSTITUTION:The voltage correction value correcting the drive voltage of a thermal head 20 corresponding to a density correction value is preliminarily stored in the memory 16a of a system controller 16 in the form of a lookup table memory and, at the time of recording, the drive voltage of the thermal head 20 is controlled on the basis of the correction value correcting a sensitivity change due to humidity dependence by a voltage control circuit 37. When a power supply is turned OFF or a paper supply tray 23 is opened without turning the power supply OFF, the system controller 16 resets the density correction value to an initial set value and also resets a correction voltage value to the initial set value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer.

[0002]

2. Description of the Related Art Thermal printers include thermal transfer printers and thermal printers. In the former thermal transfer printer,
There are a melt type and a sublimation type. These are a type in which an ink film is superposed on a recording paper, a thermal head is pressed against the back of the ink film to heat it, and the ink of the ink film is transferred to the recording paper. In the latter thermal printer, the thermal recording paper is heated by a thermal head so that the thermal recording paper is colored to thermally record ink dots.

For example, in a color thermal printer, a color thermal recording sheet is wound around a platen drum, a thermal head is brought into contact with the color thermal recording sheet, and the platen drum is rotated three times to record each color every one rotation. By doing so, three-color sequential recording is performed, and a full-color image is recorded on the color thermosensitive recording sheet. As the color thermosensitive recording sheet, for example, a magenta thermosensitive coloring layer, a cyan thermosensitive coloring layer, and a yellow thermosensitive coloring layer as described in JP-A-61-213169 are sequentially formed on a support.

[0004]

By the way, the above-mentioned color thermosensitive recording sheet has a property that the color forming sensitivity is changed due to changes in water content, deterioration with time, exposure to light and the like. When the color development sensitivity changes, not only the density cannot be finished properly, but also the color thermosensitive recording sheet loses the gray balance, which makes it impossible to finish the color properly. Therefore, perform a test print, observe the obtained test print, enter the density correction amount,
The density is being corrected.

After performing the density correction in this way,
If the recording sheet is left unused for a long time after use, the sensitivity of the recording sheet may change due to deterioration over time or changes in environmental humidity during the next use. In this case, if the previous correction amount is stored, the density correction is performed based on this, and it becomes impossible to obtain an appropriate print. Further, for the same reason, if the color thermosensitive recording sheet is replaced with a new one or is replenished during use, there is a problem that proper printing cannot be performed with the correction amount used until then.

The present invention has been made to solve the above problems, and is a thermal printer capable of performing proper printing even when a recording material is replaced or left unused for a long period of time. It is intended to provide.

[0007]

In order to achieve the above object, a thermal printer according to a first aspect of the present invention comprises a density correction amount input means for inputting a density correction amount according to a sensitivity change of a recording material, and the density. A density correction unit that stores the correction amount and controls the heat generation amount of the thermal head based on the density correction amount to correct the density, an opening detection unit that detects the opening of the storage unit that stores the recording material, and the opening unit. And a correction amount resetting unit for returning the density correction amount of the density correcting unit to the initial setting value when the detection unit detects the opening of the storage section. The opening of the storage unit is detected by pulling out the tray, opening the tray lid, or the like.

A thermal printer according to a second aspect is the thermal printer according to the first aspect, wherein the correction amount resetting means resets the density correction amount to the initial setting value when the power is turned off. .

A thermal printer according to a third aspect of the present invention is the thermal printer according to the second aspect, wherein the correction amount resetting means resets the correction amount to the initial setting value and stores that the resetting is performed, and a means after the resetting. It is provided with reset instruction means for instructing to reset the density correction amount when the power is turned on or after the storage section is closed. The instruction for resetting is given by displaying a density correction instruction on the display and also by sounding a buzzer. Further, the display on the display and the generation of the alarm sound by the buzzer are used together.

[0010]

The density correction amount is reset after being left for a long period of time or after exchanging the recording material. In the resetting of the density correction amount, for example, the density correction amount is input by selecting the density correction amount displayed on the display in the density correction amount setting mode, and the density correction amount is turned by turning the density adjustment dial. It is entered directly and is stored. The thermal printer controls the driving voltage of the thermal head, for example, based on the input density correction amount to adjust the coloring heat energy. As a result, appropriate density correction is performed on the recording material whose sensitivity has changed due to deterioration over time, changes in water content, exposure to light, and the like.

After the density correction, when the recording material container is opened, the density correction amount is reset to the initial value. Therefore, the recording material newly set based on the previously recorded density correction amount is not thermally recorded,
Printing with poor density will not occur. Similarly, after the power is turned off, the previously recorded density correction amount is reset, so the previously used density correction amount should be used for recording materials that have been left for a long period of time and have changed color development sensitivity. Therefore, it is possible to prevent defective printing from being performed.

[0012]

EXAMPLE In this example, the color thermosensitive recording sheet 4 has a layer structure as shown in FIG. The recording sheet 4 includes a support 5, a cyan thermosensitive coloring layer 6, a magenta thermosensitive coloring layer 7, a yellow thermosensitive coloring layer 8 and a protective layer 9 which are sequentially layered. These thermosensitive coloring layers 6 to 8 are layered from the surface in the order of thermal recording. For example, in the case of thermal recording in the order of magenta, yellow, and cyan, the yellow thermosensitive coloring layer and the magenta thermosensitive coloring layer. And are interchanged.

FIG. 3 shows the coloring characteristics of the thermosensitive coloring layers 6-8. Color thermosensitive recording sheet 4 of this embodiment
Has the lowest coloring heat energy of the yellow thermosensitive coloring layer 8 and the highest coloring heat energy of the cyan thermosensitive coloring layer 6.
When thermal recording is performed on the yellow Y pixel, the coloring thermal energy obtained by adding the gradation expression thermal energy GY _J determined according to the gradation level J of the pixel to the constant bias thermal energy BY is applied to the color thermal recording sheet 4. Given. The bias heat energy BY is heat energy immediately before the yellow heat-sensitive recording layer 8 develops color. The same applies to magenta M and cyan C, so only the reference numerals are attached.

In FIG. 4, which schematically shows a color thermal printer embodying the present invention, a platen drum 10 holds a color thermal recording sheet 4 on the outer periphery thereof, and a pulse motor 12 is used by a pulse motor 12 via a belt 13 at the time of thermal recording. Is rotated in the direction. A clamp member 14 is attached to the platen drum 10.
Is attached, and the front end portion 4a of the color thermosensitive recording sheet 4 is fixed to the platen drum 10. The rotation of the pulse motor 12 is controlled by a system controller 16 described later via a motor driver 15. The system controller 16 generates a motor drive pulse and rotates the platen drum 10 for one line by four pulses of this motor drive pulse. Platen drum 10 and pulse motor 1
2, the belt 13 and the clamp member 14 constitute a recording sheet conveying system 17.

A thermal head 20 and first and second optical fixing devices 21 and 22 are provided on the outer periphery of the platen drum 10 in the normal direction of rotation of the platen drum 10 as indicated by the arrow. The thermal head 20 has a large number of heating elements 20.
a is arranged in a line shape, and is pressed against the platen drum 10 side during thermal recording. The thermal head 20 is driven by a strobe signal generated by the print controller 24 in response to a command signal from the system controller 16.

The first optical fixing device 21 is approximately 420n.
A rod-shaped ultraviolet lamp 21a having a light emission peak at m is provided to optically fix the yellow thermosensitive coloring layer. The second optical fixing device 22 is equipped with a rod-shaped ultraviolet lamp 22a having an emission peak at about 365 nm, and optically fixes the magenta thermosensitive coloring layer.

A pair of conveying rollers 26 is arranged in the paper feeding / discharging path 25, whereby the color thermosensitive recording sheet 4 is sent to the platen drum 10 side. The recording sheets 4 are pulled out one by one from the paper feed tray 23 and sent to the paper feed / discharge path 25. Further, on the platen drum 10 side of the paper feeding / discharging passage 25, a separation claw 27 for guiding the rear end of the color thermosensitive recording sheet 4 to the paper feeding / discharging passage 25 at the time of paper discharging is formed. In this embodiment, one passage is used as both the paper feed passage and the paper discharge passage, but they may be provided separately. Further, in the present embodiment, a reverse paper discharge method is adopted in which the platen drum 10 is rotated in the opposite direction to that during printing and discharged, but this involves releasing the clamp member 14 and rotating the platen drum 10 in the normal direction. It is also possible to adopt a forward paper ejection method in which the paper is ejected after that.

A home position sensor 29 is provided on the outer periphery of the platen drum 10. The home position sensor 29 detects the position of the clamp member 14 to detect the home position of the platen drum 10. This home position detection signal is sent to the system controller 16
Sent to. At the time of thermal recording, the clamp member 14 is open at this home position, and when the leading end of the recording sheet 4 is inserted into the clamp member 14, the clamp member 14 is closed to fix the leading end of the recording sheet 4 to the platen drum. Fix at 10.

The system controller 16 is composed of a well-known microcomputer, and controls each part in sequence to perform color thermosensitive recording in three-color plane sequence, and also performs density correction according to sensitivity change. Therefore, the system controller 16 is connected to the operation unit 30, the power switch 31, the tray sensor 32, and the display 33. The change in sensitivity is caused by a change in water content due to a change in environmental humidity, deterioration over time, exposure to light, etc. as described above.Hereinafter, the concentration correction due to such a change in sensitivity is referred to as humidity-dependent concentration correction. .

The operation unit 30 includes a freeze key 30a, a print key 30b, a menu key 30c, left and right cursor keys 30d and 30e, and an execute key 30f. The freeze key 30a, as shown in FIG.
This is for taking in the video signal of the gradation image input from the three-color frame memories 51R, 51G, and 51B, and the freeze key 30a while watching the monitor screen.
By pressing, the video signal of the gradation image on the monitor screen is written in each frame memory 51R, 51G, 51B. The print key 30b is pressed when printing the captured image data, and by operating this key, the thermal head is driven based on the video signals written in the frame memories 51R, 51G, and 51B, and thermal recording is performed.

The menu key 30c is for selecting various modes. Left and right cursor keys 30d, 3
0e and the execution key 30f are for inputting commands and data in the various modes, and while looking at the display of the display 33, the left and right cursor keys 30f
After selecting commands and data with d and 30e, execute key 30
By operating f, the selected command and data are taken into the system controller 16. Menu key 3
The menus selected by 0c include the humidity-dependent concentration correction mode described above, a field switching mode for selecting “odd field” and “even field”,
There is a switching mode for switching between the “frame mode” and the “field mode”, and a test print mode.

As shown in FIG. 5, the system controller 16 controls the memory controller 50 at the time of writing image data to and reading image data from the frame memories 51R, 51G and 51B. Also, the system controller 1
6 controls the recording sheet conveying system 17 to control the recording sheet 4
To transport. In addition, when selecting various modes, commands and data in these modes are input.

By pressing the menu key 30c once, the modes are sequentially set, and the modes are displayed on the display 33. The desired mode can be set by pressing the menu key 30c until the corresponding mode is displayed. Then, in the density correction mode, by operating the cursor keys 30d and 30e and the execution key 30f while observing the display 33, the density correction value is input.

FIG. 6 shows an example of the display screen 35 in the humidity-dependent density correction mode state. A title image 35a showing the humidity-dependent density correction and a density correction value image 35b showing the density correction value are shown. , And a cursor 35c for selecting any one of the displayed density correction value images 35b is displayed. In this embodiment, "-2" to "+"
It is possible to input 5 levels of density correction values up to 2 ”. Then, when the density correction value of “+1” is desired,
The right cursor key 30e shown in FIG. 4 is operated to shift the cursor 35c to the right on the monitor screen 35 to position the cursor 35c at the corresponding density correction value "+1".
After this, by pressing the execution key 30f, the cursor 3
The density correction value "+1" designated by 5c is selected and stored in the memory 16a in the system controller 16. In the present embodiment, in order to make the display of the selected density correction value easy to understand, it is displayed as a small circular dot 36a before selection, and when selected, this becomes a rectangular dot 36b larger than the circular dot 36a. It is supposed to change.

As shown in FIG. 4, in the memory 16a,
A voltage correction value for correcting the drive voltage of the thermal head 20 corresponding to the density correction value is stored in advance in the form of a look-up table memory (LUT). The relationship between the density correction value and the voltage correction value has been previously obtained by experiments or the like, and the voltage correction value increases as the density correction value increases.

FIG. 7 shows an example of the relationship between the density correction value DC and the voltage correction value VC. The voltage correction value VC is shown in FIG.
Is calculated as a correction value for the reference voltage Vb.
Generally, the voltage correction value VC tends to increase as the color recording sensitivity decreases (VCy <VCm <V).
Cc). Further, the larger the density correction value DC, the larger the voltage correction value VC.

When any one of the density correction values "-2" to "+2" is selected, the system controller 16 sends a voltage correction value VC corresponding to this to the voltage control circuit 37. The voltage control circuit 37 corrects the drive voltage to the thermal head 20 based on this voltage correction value VC. As a result, each heating element 20a of the thermal head 20 is driven by the drive voltage after density correction.
Is driven, the humidity-dependent concentration correction is performed.
Instead of storing the relationship between the density correction value and the voltage correction value, the LUT may store the density correction value and the driving voltage value corrected by the voltage correction value in association with each other.

As shown in FIG. 4, the power-off signal from the power switch 31 is input to the system controller 16, which causes the system controller 16 to turn off the power. Further, the tray sensor 32 detects that the tray 23 is pulled out. This tray pull-out signal is input to the system controller 16. The system controller 16 receives the signal to input the tray 2
It is detected that 3 has been pulled out, and thereby, it is detected that a new recording sheet 4 is set on the tray 23.

The system controller 16 resets the density correction value and the voltage correction value stored in the memory 16a when the power off signal or the tray pull-out signal is input, and returns them to the initial setting values. In the case of the tray pull-out signal, after this, the buzzer 38 is sounded to inform the operator that the density correction value has been reset to the initial setting value. Further, the system controller 16 automatically switches to the humidity-dependent density correction setting mode and displays the display screen 35 of the density correction value input mode on the display 33 as shown in FIG. Therefore, tray 2
When 3 is pulled out, the density correction value resetting input mode is automatically entered. Therefore, the newly set recording sheet is not thermally recorded based on the previously set density correction value, and the recording sheet is not wasted.

In the case of the power-off signal, the system controller 16 resets the density correction value and the voltage correction value stored in the memory 16a to restore the initial setting value, and then performs the power-off processing. . In the process of power off,
For data such as video adjustment values that should not be erased, the power is turned off after the adjustment values are stored in the memory having the backup function.

In the test print mode, the memory 1
A test pattern 70 as shown in FIG. 8 is thermally recorded on the recording sheet 4 by the test pattern data stored in 6a. The test pattern 70 has the density changed in five steps from "-2" to "+2" corresponding to the density correction value in the density correction mode. The test pattern data is stored in the memory 16a for each type of recording sheet. It is recorded in.
In the present embodiment, the test pattern 70 is a test pattern in which only cyan is printed after performing yellow light fixing and magenta light fixing, and the position of the test pattern 70 is shifted using the same recording sheet 4. By going
The test print can be performed many times within the range of the print area PA. In this embodiment, the feed pitch amount L1 of the cyan test pattern 70 in the sub-scanning direction (feeding direction of the recording sheet) is set to about 1/10 of the total feed length L of the print area PA, and each test is performed. By controlling the pattern so that it is recorded below the previous test pattern, it is possible to perform 10 test prints with one recording sheet.

The density correction amount is determined by observing the density of the obtained test pattern 70 of the test print. In addition to such a cyan-only test pattern, a test pattern in which four colors of yellow, magenta, cyan, and gray are separately applied may be used to determine the density correction value for each color. Further, the density correction value may be determined by comparing and observing a sample provided in advance and a test print.

FIG. 5 shows a block diagram of an electric circuit of the color thermal printer. A video camera, a VTR, a still video player, a video game machine, etc. are connected to the input terminal 41, and a video signal of a gradation image is input terminal 41.
It is input to the sync separation circuit 42 and the analog signal processing circuit 43 via. The sync separation circuit 42 separates the composite sync signal (C.SYNC) from the input video signal, and further separates the composite sync signal from the vertical sync signal (V.SYNC).
C) and the horizontal synchronizing signal (H.SYNC) are separated.
Further, the sync separation circuit 42 includes an internal horizontal sync signal oscillator, and outputs the horizontal sync signal from the internal horizontal sync signal oscillator when the horizontal sync signal cannot be separated from the composite sync signal. Then, the sync separation circuit 42 sends the composite sync signal of H level or L level, the vertical sync signal and the horizontal sync signal to the sync determination circuit 44, and also sends the composite sync signal to the SSG (sync signal generator) 45.

Further, the sync separation circuit 42 generates a field discrimination signal (FIELD INDEX) from the phase relationship between the vertical sync signal and the horizontal sync signal. Normally, when an NTSC standard signal is input to the input terminal 41, between the odd field and the even field,
The phase relationship between the vertical sync signal and the horizontal sync signal is different. Therefore, this phase relationship is detected and a field discrimination signal whose signal level is inverted is generated for each field. Further, when the video signal of only one field is input to the input terminal 41, since the phase relationship between the vertical synchronizing signal and the horizontal synchronizing signal does not change, the field discrimination signal remains at the same signal level. This field determination signal is sent to the synchronization determination circuit 44.

The SSG 45 has an analog signal processing circuit 43, an A / D converter 47, and a D / A converter 48 at a timing based on the composite sync signal input from the sync separation circuit 42.
It also controls the analog signal processing circuit 49. The analog signal processing circuit 43 separates the input video signal into a red signal, a green signal, and a blue signal, adjusts the levels of these color signals, and outputs them. Each color signal is sampled by the A / D converter 47 for each pixel and then digitally converted.
The obtained red image data, green image data, and blue image data of each pixel are sent to the memory controller 50, respectively.

The red frame memory 51R, the green frame memory 51G, and the blue frame memory 51B are memories for storing image data of two fields of an odd field and an even field so that they are alternately arranged for each scanning line. The memory controller 50 writes and reads image data of each color.

By pressing the freeze key 30a or the print key 30b of the operation unit 30, "freeze",
One of the "print" operations is instructed. Further, when the menu key 30c is pressed, the field switching mode is set. In this field switching mode, "odd field" and "even field" are selected. Further, the system controller 16 causes the memory controller 5 to write the image data to the frame memories 51R, 51G, and 51B and read the image data.
Control 0. Further, the system controller 16 controls the recording sheet conveying system 17 to convey the recording sheet 4.

The memory controller 50 writes the image data of the even field and the odd field in the frame memories 51R, 51G and 51B when the frame mode is designated at the time of writing the image data. When the field mode is instructed, the memory controller 50 causes the frame memories 51R, 51G, 51B to
Image data of one field is written, and after this writing, complementary processing is performed to write image data frame-framed into the frame memories 51R, 51G, and 51B.

During monitoring, the memory controller 50 reads out image data from the frame memories 51R, 51G and 51B and sends it to the D / A converter 48 of the monitor system.
Further, the memory controller 50 reads the image data line by line from the frame memories 51R, 51G, and 51B and sends the image data to the print controller 24 of the print system during printing.

The monitor system comprises a D / A converter 48 and an analog signal processing circuit 49. D / A converter 4
Reference numeral 8 converts the image data of three colors into RGB signals of analog signals and sends them to the analog signal processing circuit 49. The analog signal processing circuit 49 converts an input RGB signal into an NTSC format video signal and connects the output terminal 53 to a TV.
A frame image is displayed on a monitor (for example, home TV).

The print system is the print controller 2
4, the thermal head drive unit 54, the voltage control circuit 37, and the thermal head 20. The print controller 24 performs masking processing using the image data of three colors, or converts the image data into yellow, cyan, and magenta image data. Of the image data of these three colors, only the color to be printed, for example, yellow image data is taken out line by line and sent to the thermal head drive unit 54. As shown in FIG. 9, the thermal head drive unit 54 generates a bias pulse PB for driving each heating element 20a from each pixel data and a number of grayscale pulses PG according to the grayscale level. Based on this, each heating element 20a is driven. The voltage control circuit 37 controls the drive voltage of the thermal head 20 by the voltage correction value based on the density correction value input in advance, and thereby the density change due to humidity dependency is corrected.

Therefore, each heating element 20a is driven so as to have a density corresponding to the image data, and one line is thermally recorded and each pixel is recorded at the density corresponding to each image data. After that, the platen drum 10 is intermittently rotated by a predetermined amount to feed the color thermosensitive recording sheet 4 by one line, and thereafter, each line is thermally recorded in the same manner. The bias pulse PB and the gradation pulse PG shown in FIG. 9 have different pulse widths, but they may have the same pulse width. Further, each of the pulses PB and PG may be composed of a pulse train composed of many sub-pulses.

Next, the operation of the color thermal printer of the present embodiment will be described based on FIG. 1 with reference to the drawings. Before printing, the menu key 30 of the operation unit 30
c (see FIG. 4) is pressed to select the test print mode. In this mode, first, the optical fixing devices 21, 22 perform the optical fixing of yellow and magenta on the recording sheet 4, and then the test pattern data stored in the memory 16a causes the cyan test as shown in FIG. The pattern 70 is thermally recorded. As described above, first, the yellow and magenta thermosensitive coloring layers are optically fixed, and then the cyan thermosensitive coloring layer is subjected to thermosensitive recording. Therefore, test printing can be repeatedly performed within the print area, and the recording sheet 4 is wasted. Disappears.

The density correction value is determined by observing the obtained test print. Next, the menu key 30c is pressed to select the humidity-dependent density correction mode. In this density correction mode, the display screen 3 as shown in FIG.
5, the cursor key 30d or 30e is operated,
The cursor 35c is moved to a predetermined density correction value. After that, the execute key 30f is pressed and the density correction value selected by the cursor 35c is fetched by the system controller 16.

The system controller 16 uses the LUT obtained using the graph shown in FIG. 7 to obtain the density correction value D.
Based on C, the correction value VC of the driving voltage of the heating element is obtained.
This voltage correction value VC is sent to the voltage control circuit 37. The voltage control circuit 37 corrects the drive voltage of the thermal head 20 based on the voltage correction value VC. After that, test printing is performed again with the voltage corrected. Observe the retest print, and if this is good, you can switch to the print mode. If the retest print is defective, the test print is performed again.

In the print mode, as shown in FIG.
At the time of paper feeding, the platen drum 10 holds the clamp member 14
Is stopped at the home position when it is almost vertical. The pair of transport rollers 26 nips the color thermosensitive recording sheet 4 supplied from the tray 23 and nips the platen drum 1
Transport toward 0. The conveying roller pair 26 is temporarily stopped when the front end of the color thermosensitive recording sheet 4 enters between the platen drum 10 and the clamp member 14. Then, after the clamp member 14 clamps the front end of the color thermosensitive recording sheet 4, the platen drum 10 and the conveying roller pair 26 rotate, so that the color thermosensitive recording sheet 4 is wound around the platen drum 10.

The pulse motor 12 feeds the rotation of the platen drum 10 for one line in steps of 4 pulses.
Since the number of step feeds is small, the platen drum 10 rotates at a substantially constant speed. When each heating element 20a of the thermal head 20 is located at the recording start position of the print area of the recording sheet, the system controller 16 causes each heating element 20a of the thermal head 20 to have a predetermined number of bias pulses BP as shown in FIG. A gradation pulse PG corresponding to the pixel density is applied to heat the pixel. As a result, the yellow image of the first line is recorded at the recording start position in the print area PA. Similarly, yellow images of each line are recorded one after another.

At the time of this recording, the drive voltage of the thermal head 20 is controlled by the voltage control circuit 37 based on the correction amount for correcting the sensitivity change due to the humidity dependence. Therefore, even if the color development sensitivity of the recording sheet changes due to deterioration with time or exposure to light, the voltage can be changed correspondingly, so that thermal recording can be performed at an appropriate density.

When the portion on which the yellow image is thermally recorded reaches the optical fixing device 21, the yellow thermosensitive coloring layer 8 is optically fixed by the yellow optical fixing device 21. As a result, the diazonium salt compound remaining in the yellow thermosensitive coloring layer 8 is photodecomposed and the coloring ability disappears.

When the platen drum 10 rotates almost once and the recording start position of the print area is located at the heating element of the thermal head, the magenta image of the first line is recorded. Similarly, magenta images of each line are recorded one after another.

In this recording, as in the case of yellow recording, the drive voltage of the thermal head 20 is controlled by the voltage control circuit 37 based on the correction amount for correcting the sensitivity change due to the humidity dependence. Therefore, even if the color-developing sensitivity of the recording sheet changes due to deterioration with time or the like, the voltage can be changed correspondingly, so that a magenta image can be heat-sensitively recorded at an appropriate density. When the portion on which the magenta image is thermally recorded reaches the optical fixing device 22, the magenta thermosensitive coloring layer 7 is optically fixed by the magenta optical fixing device 22. As a result, the diazonium salt compound remaining in the magenta thermosensitive coloring layer 7 is photodecomposed and the coloring ability disappears.

Thereafter, the cyan thermosensitive coloring layer 6 is similarly processed.
The cyan image is heat-sensitively recorded. Also in this case, since the humidity dependence is corrected due to deterioration over time, the cyan image is heat-sensitively recorded at an appropriate density. When the thermal recording of each layer is completed, the platen drum 10 and the conveying roller pair 26 are reversed. By the reverse rotation of the platen drum 10, the rear end of the color thermosensitive recording sheet 4 is guided to the paper feeding / discharging path 25 by the separating claw 27, and is nipped by the conveying roller pair 26. After that, the clamp member 14 is opened, and the thermally recorded color thermosensitive recording sheet 4 is discharged to the discharge tray (not shown) through the paper supply / discharge path 25.

Further, when the power is turned off or when the paper feed tray 23 is opened without turning off the power, the system controller 16 resets the density correction value to the initial setting value and the voltage correction value. Is also reset to the default value. Therefore, at the time of the next print, the previously set density correction value is not used.Therefore, thermal recording is performed on a newly set recording sheet or a recording sheet that has deteriorated with time based on the previously set density correction value. Since it does not exist, it is possible to suppress the occurrence of print defects.

The density correction value may be cleared instead of being reset to the initial setting value. In this case, when the paper feed tray is returned to its original state, or when the power is turned off and then turned on again, the density correction value reset mode is automatically set.

Further, in the above embodiment, the display 33
Although various mode menus, commands, and various data are displayed on the screen, and the cursor keys 30d and 30e are used to select them, the execute key 30f is pressed to input commands and various data. As shown in, the density correction value may be input using the density adjusting dial 81 attached to the variable resistor 80 and the A / D converter 82. The same components as those in the above embodiment are designated by the same reference numerals. Also in this case, the humidity-dependent density correction mode is selected by the menu key 30c of the operation unit 30, the system controller 16 is set to this mode, and then the density adjustment dial 81 is turned to set a predetermined value. . In this case, the density correction value can be set finely. A slider may be used instead of the dial 81. In the case of inputting the density correction value from the display screen 35 as shown in FIG. 6, the density correction value is increased by decreasing the step value of the density correction value and increasing the number of selectable density correction values. The value can be set finely.

Further, in the above embodiment, the case where the heat-sensitive recording is performed by using the color heat-sensitive recording sheet 4 has been described as an example, but a thermal melting type or sublimation type thermal printer for transferring the ink to the recording sheet using the ink ribbon. Also in this case, the present invention can be applied when the density correction as described above is performed.

Further, in the above embodiment, the voltage applied to each heating element of the thermal head is controlled based on the density correction value, but in addition to this, density correction is performed by increasing or decreasing the number of bias pulses and gradation pulses. Well. Further, the density may be corrected by changing the duty ratio of each pulse.

[0058]

As described above, according to the present invention,
A unit for inputting a density correction amount according to a change in sensitivity of the recording material, a unit for storing the density correction amount and controlling the heat generation amount of the thermal head according to the density correction amount to correct the density, and a recording material Since the means for detecting the opening of the storing section for storing and the means for returning the density correction amount to the initial setting value when the opening of the storing section is detected, the density correction amount is automatically set when the paper feed tray is opened. The recording material newly set based on the previously set density correction amount is not thermally recorded. Therefore, since thermal recording is not performed in a state where the density correction amount is different, wasteful printing is not performed and waste of recording material can be eliminated.

Further, since the density correction amount is returned to the initial setting value when the power is turned off, even when the built-in recording material deteriorates with time and the color development sensitivity is changed, the same is done in the same manner. Since the previously set density correction amount is reset, the recording material deteriorated with time based on the previously set density correction amount is not thermally recorded. Therefore, useless printing is not performed.

Further, a means for storing the fact that the correction amount has been returned to the initial setting value and having been reset, and a resetting instruction for resetting the density correction value when the power is turned on after the resetting or after the storage section is closed. By providing the setting instruction means, it is possible to surely perform the humidity-dependent density correction when the power is turned off or when the paper feed tray is opened. Therefore, it is possible to prevent wasteful printing without forgetting the density correction.

[Brief description of drawings]

FIG. 1 is a flowchart showing a main part of a processing procedure of a color thermal printer embodying the present invention.

FIG. 2 is an explanatory diagram showing an example of a layer structure of a color thermosensitive recording sheet used in the present invention.

FIG. 3 is a graph showing an example of color development characteristics of a color thermosensitive recording sheet.

FIG. 4 is a schematic view of a main part of a color thermal printer.

FIG. 5 is a block diagram showing an electrical configuration of a color thermal printer.

FIG. 6 is an explanatory diagram showing an example of a display screen for humidity-dependent density correction.

FIG. 7 is a graph showing an example of the relationship between the density correction value DC and the voltage correction value VC.

FIG. 8 is an explanatory diagram showing an example of a recording sheet on which a test pattern is recorded.

FIG. 9 is an explanatory diagram showing bias pulses and gradation pulses applied to each heating element of the thermal head.

FIG. 10 is a block diagram showing a main part of another embodiment for inputting a density correction value with a density adjustment dial.

[Explanation of symbols]

 4 Color thermal recording sheet 10 Platen drum 12 Pulse motor 16 System controller 16a Memory 20 Thermal head 20a Heating element 23 Tray 24 Print controller 30 Operation part 31 Power switch 32 Tray sensor 33 Display 37 Voltage control circuit 54 Thermal head drive part 80 Density adjustment Dial

Claims (3)

[Claims] 1. A thermal printer for thermal recording using a recording material whose sensitivity changes due to changes in water content, deterioration over time, and the like, and density correction amount input means for inputting a density correction amount according to the sensitivity change of the recording material; A density correction unit that stores the density correction amount and controls the heat generation amount of the thermal head based on the density correction amount to correct the density, and an opening detection unit that detects the opening of the storage unit that stores the recording material. A thermal printer, comprising: a correction amount resetting unit for returning the density correction amount of the density correcting unit to an initial setting value when the opening detecting unit detects the opening of the storage unit. 2. The thermal printer according to claim 1, wherein the correction amount resetting means resets the density correction amount to an initial setting value when the power is turned off. 3. The thermal printer according to claim 2, wherein the correction amount resetting means resets the correction amount to the initial setting value and stores that the resetting amount is stored, and the power supply is turned on after the resetting and the storage portion is provided. A thermal printer, comprising: resetting instruction means for instructing to reset the density correction amount after being closed.