JP3359978B2 - Color adjustment method for color printer and color thermal printer - Google Patents

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 .

[0002]

2. Description of the Related Art In a video printer that records a full-color image based on a color image signal, color adjustment is performed by performing color matching while observing a print result.

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 thermally record each color for each rotation. At the same time, the images are fixed by light and the three color surfaces are sequentially recorded, and a full-color image is recorded on a color thermosensitive recording sheet. Examples of the color thermosensitive recording sheet include, for example, JP-A-61-2131.
No. 69, a magenta thermosensitive coloring layer,
A layer in which a cyan thermosensitive coloring layer and a yellow thermosensitive coloring layer are sequentially formed on a support is used.

[0004] However, there is a problem that the color adjustment in the video printer does not have the reference color information and is performed while looking at the print result, which is very troublesome.
Further, the recording sheet in a color thermal printer has a property that when the moisture content of each thermosensitive coloring layer changes due to environmental humidity, the sensitivity changes and the color density changes. For this reason, a so-called humidity-dependent density correction is performed in which the density correction is performed in accordance with the sensitivity change. In this density correction, since a number of test prints are performed to adjust the density, a large amount of test prints must be performed before the density correction value is determined, and there is a problem that recording sheets are wasted. Further, it is not easy to determine how much the density correction value is to be narrowed down, and there is a problem that the humidity-dependent density correction cannot be easily performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is a color thermal printer capable of easily performing color adjustment and humidity-dependent density correction without wasting recording sheets. The purpose is to provide.

[0006]

In order to achieve the above object, a color thermal printer according to claim 1 is provided by a yellow thermal printer.
-, Magenta and cyan thermosensitive coloring layers with high coloring sensitivity
Color thermal recording sheet provided sequentially from the upper layer,
Press the thermal head and press each heating element of the thermal head.
Color heat energy corresponding to the image data
After recording, the recorded thermosensitive coloring layer is optically fixed.
Color thermal printer that records full-color images
A density correction value according to a change in sensitivity of the recording sheet.
Density correction value input means for inputting the
The value is stored, and the thermal
Density correction means for correcting the density by controlling the heating value of the head
Means for storing pattern data for density adjustment;
A print mode for printing based on data,
Trial printing based on density adjustment pattern data
Mode switching means for switching to the printing mode.
The density adjustment pattern data is input with a density correction value.
Density area corresponding to each density correction value input by
Have

According to a second aspect of the present invention, there is provided a color thermal printer in which each of the yellow, magenta and cyan thermosensitive coloring layers is colored.
Color thermal recording provided from upper layer in order of sensitivity
Using a sheet, many heating elements are arranged in a line in the main scanning direction
The recording head and the thermal head
While moving the head relatively in the sub-scanning direction,
The thermal head against the recording sheet and
Giving the heating element color heat energy corresponding to the image data
After recording each color, the recorded thermosensitive coloring layer is
A color that fixes light and records a full-color image
A density correction value input means for inputting a density correction value according to a change in sensitivity of a recording sheet in a thermal printer ;
A density correction unit that stores the density correction value and controls the heat generation amount of the thermal head based on the density correction value to correct the density, a unit that stores density adjustment pattern data, and performs printing based on the image data. A print mode, and mode switching means for switching to a test printing mode for performing test printing based on the density adjustment pattern data, wherein the density adjustment pattern data includes density correction values input by density correction value input means. Has a density area corresponding to.

According to a third aspect of the present invention, there is provided the color thermal printer according to the second aspect, wherein a test printing recording sheet is used in the test printing mode, and the recording sheet is used in advance.
The density adjustment pattern is formed by optically fixing the other color development heat-sensitive layers except for the heat-sensitive layer having the lowest color development sensitivity, and the density adjustment pattern is configured by arranging density areas in the order of density change. One or both of the lengths in each direction are shortened so that a plurality of prints can be arranged side by side in the main scanning direction or the sub-scanning direction, and the recording position of the density adjustment pattern is sequentially determined according to the number of test prints. It is staggered.

[0009]

When performing color adjustment, the mode is switched to the test printing mode. In the test printing mode, the color sample preparation data is read from the storage unit, and the test printing is performed based on the data. The color sample is composed of, for example, a pattern in which four colors of yellow, magenta, cyan, and gray are separately applied, and is prepared in advance by a printer in a reference state using each set value as a reference value. Then, by comparing and observing the test print and the color sample obtained by the trial printing,
A density correction value for each color is determined. The density adjustment of each color is performed based on this density correction value.

In the color thermal printer, the mode is switched to the test printing mode, and the humidity-dependent density correction is performed. In the test printing mode, a density pattern corresponding to each density correction value input by the density correction value input means is provided, and a test pattern in which these density areas are arranged in, for example, a density change order is recorded. The density of each density area of the test pattern is compared, and the number of the density area serving as the reference density is input. Based on this density area number, the printer shifts the density correction value by the step value of the input density area number. Therefore, the reference density can be easily set.

In the test printing mode, a test printing recording sheet is used. This recording sheet is prepared in advance by exposing other color forming layers except for the color forming layer having the lowest color developing sensitivity to light, so that only the color forming layer having the lowest color developing sensitivity, for example, only the cyan thermosensitive coloring layer is colored. . In addition, the length in each direction, for example, the length in the sub-scanning direction is shortened so that a plurality of density adjustment patterns can be printed side by side in the main scanning direction or the sub-scanning direction of the print area. The recording position of the density adjustment pattern is sequentially shifted according to the number of times of printing. Therefore, the recording sheet for test printing can be used many times within the range of the print area, and the recording sheet is not wasted.

[0012]

EXAMPLE In this example, a color thermosensitive recording sheet 4 having a layer structure as shown in FIG. 2 is used. The recording sheet 4 is constituted by sequentially providing a cyan thermosensitive coloring layer 6, a magenta thermosensitive coloring layer 7, a yellow thermosensitive coloring layer 8, and a protective layer 9 on a support 5 in layers. Each of these thermosensitive coloring layers 6 to 8 is provided from the surface in the order of thermal recording. For example, when thermal recording is performed in the order of magenta, yellow, and cyan, a yellow thermosensitive coloring layer and a magenta thermosensitive coloring layer are provided. Is replaced.

FIG. 3 shows the coloring characteristics of the thermosensitive coloring layers 6-8. Color thermal recording sheet 4 of this embodiment
The yellow heat-sensitive coloring layer 8 has the lowest coloring heat energy, and the cyan heat-sensitive coloring layer 6 has the highest coloring heat energy.
In the case of thermal recording of the yellow Y pixel, the color thermal recording sheet 4 adds a constant bias thermal energy BY to a thermal expression recording energy GY _J determined by adding a gradation expression thermal energy GY _J determined in accordance with the gradation level J of the pixel. Given. This bias thermal energy BY is thermal energy immediately before the yellow thermosensitive recording layer 8 develops a color. Since the same applies to magenta M and cyan C, only symbols are given.

Referring to FIG. 4 schematically showing a color thermal printer embodying the present invention, a platen drum 10 holds a color thermal recording sheet 4 on its outer periphery, and uses a pulse motor 12 through a belt 13 by a pulse motor 12 during thermal recording. Rotated in the direction. The platen drum 10 includes a clamp member 14.
Is attached, and fixes the leading end 4 a of the color thermal recording sheet 4 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 by one line with the four motor drive pulses. The platen drum 10, the pulse motor 1
A recording sheet transport system 17 is constituted by the belt 2, the belt 13, and the clamp member 14.

On the outer periphery of the platen drum 10, a thermal head 20 and first and second optical fixing units 21 and 22 are provided in the normal rotation direction of the platen drum 10 as indicated by arrows. The thermal head 20 has a large number of heating elements 20.
are arranged in a line, and are pressed against the platen drum 10 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 has approximately 420 n
A rod-shaped ultraviolet lamp 21a having an emission peak at m is provided, and the yellow thermosensitive coloring layer is optically fixed. The second optical fixing device 22 includes a rod-shaped ultraviolet lamp 22a having an emission peak at approximately 365 nm, and optically fixes the magenta thermosensitive coloring layer.

A transport roller pair 26 is disposed in the paper supply / discharge passage 25, and 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 supply / discharge passage 25. A separation claw 27 is formed on the platen drum 10 side of the paper supply / discharge passage 25 to guide the rear end of the color thermosensitive recording sheet 4 to the paper supply / discharge passage 25 during paper discharge. In this embodiment, one passage is used for both the paper supply passage and the paper discharge passage, but these may be provided separately. Further, in this embodiment, a reverse rotation paper discharging method in which the platen drum 10 is rotated in a direction opposite to the printing direction to discharge the paper is adopted. However, this method releases the clamp member 14 to rotate the platen drum 10 forward. The paper may be discharged in the forward rotation discharge mode.

A home position sensor 29 is provided on the outer periphery of the platen drum 10. Home position sensor 29 detects the position of clamp member 14 to detect the home position of platen drum 10. This home position detection signal is transmitted to the system controller 16.
Sent to During 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 and the leading end of the recording sheet 4 is placed on the platen drum. Fix to 10.

The system controller 16 is composed of a well-known microcomputer. The system controller 16 performs sequence control of each unit to perform color thermal recording in the order of three color planes, and also performs density correction according to a change in sensitivity. For this purpose, an operation unit 30, a power switch 31, a tray sensor 32, and a display 33 are connected to the system controller 16. As described above, the change in sensitivity occurs due to a change in water content due to a change in environmental humidity, deterioration with time, exposure to light, and the like.

The operation unit 30 has a freeze key 30a, a print key 30b, a menu key 30c, left and right cursor keys 30d and 30e, and an execution key 30f. The freeze key 30a is, as shown in FIG.
This is for taking the video signal of the gradation image input from the camera into the three-color frame memories 51R, 51G, and 51B.
Is pressed, the video signal of the gradation image on the monitor screen is written to each of the frame memories 51R, 51G, and 51B. The print key 30b is pressed when printing the captured image data, and by operating the key, the thermal head is driven based on the video signal 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 on the display 33, the left and right cursor keys 30f.
After selecting a command or data with d and 30e,
By operating f, the selected command or data is taken into the system controller 16. Menu key 3
The menu selected by Oc includes a humidity-dependent density correction mode described above, a field switching mode for selecting “odd field” and “even field”,
There are a switching mode for switching between "frame mode" and "field mode", and a test print mode.

As shown in FIG. 5, the system controller 16 controls the memory controller 50 when writing image data to the frame memories 51R, 51G, and 51B and reading image data. Also, the system controller 1
6 controls the recording sheet transport system 17 and controls the recording sheet 4;
Is transported. In addition, when various modes are selected, commands and data in these modes are input.

By pressing the menu key 30c once, each mode is sequentially set, and this mode is 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, the user operates the cursor keys 30d and 30e and the execution key 30f while looking at the display 33 to input a density correction value.

FIG. 6 shows an example of the display screen 35 in the humidity-dependent density correction mode, which includes a title image 35a indicating the humidity-dependent density correction, a density correction value image 35b indicating the density correction value, and And a cursor 35c for selecting one of the displayed density correction value images 35b. In this embodiment, “−2” to “+”
It is possible to input five levels of density correction values up to "2". Then, when it is desired to set the density correction value to “+1”,
By operating the right cursor key 30e shown in FIG. 4, the cursor 35c is shifted rightward on the monitor screen 35, and the cursor 35c is positioned at the corresponding density correction value "+1".
After this, by pressing the execution key 30f, the cursor 3
The density correction value “+1” indicated by 5c is selected and stored in the memory 16a in the system controller 16. Note that, in this embodiment, in order to make the display of the selected density correction value easier to understand, it is displayed as a small circular dot 36a before selection, and when selected, this is replaced with a rectangular dot 36b larger than the circular dot 36a. It has been changed.

As shown in FIG. 4, in the memory 16a,
A voltage correction value for correcting the drive voltage of the thermal head 20 in accordance with 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 is obtained in advance through experiments or the like, and as the density correction value increases, the voltage correction value also increases.

FIG. 7 shows an example of the relationship between the density correction value DC and the voltage correction value VC.
Is determined as a correction value for the reference voltage Vb.
According to the experimental results, in the case of the color thermosensitive recording sheet having the layer structure shown in FIG. 2, the fluctuation of the coloring sensitivity due to the change of the water content is different in each thermosensitive coloring layer, and increases in the order of cyan, yellow and magenta. With respect to such a variation in the color sensitivity, a voltage correction value (VCc <VCy <
VCm). FIG. 7 is an example, and when a color thermosensitive recording sheet having different humidity-dependent characteristics is used, the voltage correction value is newly determined by an experiment or the like.

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

As shown in FIG. 4, a power-off signal from the power switch 31 is input to the system controller 16, whereby the system controller 16 controls to turn off the power. The tray sensor 32 detects that the tray 23 has been pulled out. This tray pull-out signal is input to the system controller 16. The system controller 16 inputs this signal to the tray 2
3 is detected as being pulled out, thereby detecting that a new recording sheet 4 is set on the tray 23.

When a power-off signal or a tray pull-out signal is input, the system controller 16 resets the density correction value and the voltage correction value stored in the memory 16a to the initial setting values. In the case of the tray pull-out signal, the buzzer 38 is sounded thereafter to notify the operator that the density correction value has been reset to the initial set value. Further, the system controller 16 automatically switches to the humidity-dependent density correction setting mode, and displays a 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 mode automatically changes to the density correction value reset input mode. 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 a power-off signal, the system controller 16 resets the density correction value and the voltage correction value stored in the memory 16a and returns them to the initial set values, and then performs power-off processing. . In the power off process,
When data such as video adjustment values must not be erased, the power is turned off after storing these adjustment values in a memory having a backup function.

In the test print mode, the memory 1
Based on the density adjustment pattern data stored in 6a, a density adjustment test pattern 70 as shown in FIG. 8 is thermally recorded on the test printing recording sheet 4a. The test print recording sheet 4a is created in advance in the test print recording sheet creation mode. In this preparation mode, the thermal recording sheet 4 is set on the platen drum 10, and the yellow and magenta light fixing units 21 and 22 emit light and rotate once without performing thermal recording, thereby producing the test printing recording sheet 4a. Is done. Therefore, since the yellow and magenta heat-sensitive coloring layers are optically fixed, even if coloring heat energy is applied during cyan recording thereafter, these coloring layers do not develop color, and only cyan is recorded.

The test pattern 70 is obtained by arranging density areas 70a to 70e in which the density is changed in five steps from "-2" to "+2" in accordance with the density correction value in the density correction mode, in order of density. The gradation data for recording this test pattern and the pulse number data of the bias pulse are recorded in the memory 16a for each type of sheet. In the present embodiment, the reference voltage applied to each heating element of the thermal head is set so that coloring is started at the position of “0”. Thermal energy is applied. In the present embodiment, the correction thermal energy is generated by changing the number of gradation pulses or bias pulses. However, this may be performed by changing the duty ratio of each pulse. Therefore, when the test print is performed in the adjusted state, the density area corresponding to “0” is colored as in the test pattern of the third test print in FIG.
As “1” and “2” are set, the density of each density area increases by the density correction value. "-2", "-1"
Does not develop in the density area corresponding to.

The length of the test pattern 70 in the sub-scanning direction is shortened, so that ten times of the test pattern 70 can be recorded in the print area PA. In this case, the same test print recording sheet 4a is used to shift the position of the test pattern 70 so as to shift the feed pitch L1 to about 1/10 of the total feed length L of the print area PA, and to record. The recording position can be determined by inputting the number of test prints by the operator in the test print mode and multiplying the number of test prints by the feed pitch amount L1 to determine the test pattern recording start position.

By observing each density area of the test pattern 70 of the obtained test print, the density correction value can be easily determined. That is, since the density area of the test pattern is set such that the density areas 70c, 70d, and 70e of "0" or more are colored based on "0", the correction value of the colored area is directly used as the density correction value. Become. For example, when the lowest density area is 70d in the first test print shown in FIG. 8 and this correction value is “+1”, by inputting this +1, the voltage correction value is raised by one step. Is sent to the voltage control circuit 37. Also, in the second test print shown in FIG. 8, the minimum density area is 70b, and the correction value in this case is "-1". Voltage control circuit 37
Sent to The magenta and yellow density correction values that are not test printed can be obtained from the relationship in FIG. 7 based on the cyan density correction values.

FIG. 5 is a block diagram showing an electric circuit of the color thermal printer. A video camera, a VTR, a still video player, a video game machine, and the like are connected to the input terminal 41, and a video signal of a gradation image is input to the input terminal 41.
Is input to the synchronization separation circuit 42 and the analog signal processing circuit 43 via the The sync separation circuit 42 separates a composite sync signal (C. SYNC) from the input video signal, and further separates a vertical sync signal (V. SYNC) from the composite sync signal.
C) and the horizontal synchronization signal (H.SYNC).
The sync separation circuit 42 has an internal horizontal sync signal oscillator, and outputs a 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 synchronization separation circuit 42 sends the H-level or L-level composite synchronization signal, the vertical synchronization signal, and the horizontal synchronization signal to the synchronization determination circuit 44, and sends the composite synchronization signal to an SSG (synchronization signal generator) 45.

Further, the sync separation circuit 42 generates a field determination 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 synchronization signal and the horizontal synchronization signal is different. Therefore, this phase relationship is detected, and a field discrimination signal whose signal level is inverted for each field is generated. When a video signal of only one field is input to the input terminal 41, the phase relationship between the vertical synchronizing signal and the horizontal synchronizing signal does not change, so that the field determination 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 synchronization signal input from the synchronization separation circuit 42.
And 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 the adjusted signals. Each of the color signals is sampled for each pixel by the A / D converter 47 and then converted into a digital signal.
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 as to be alternately arranged for each scanning line. Writing and reading of image data of each color are performed by the memory controller 50.

When the freeze key 30a and print key 30b of the operation unit 30 are pressed, "freeze"
One of the operations of “print” is instructed. When the menu key 30c is pressed, the mode is set to the field switching mode. In this field switching mode, "odd field" and "even field" are selected. Further, the system controller 16 writes the image data into the frame memories 51R, 51G, and 51B and reads the image data.
Control 0. Further, the system controller 16 controls the recording sheet transport system 17 to transport the recording sheet 4.

When the frame mode is designated at the time of writing the image data, the memory controller 50 writes the image data of the even and odd fields into the frame memories 51R, 51G and 51B. When the field mode is instructed, the memory controller 50 stores the data in the frame memories 51R, 51G, and 51B.
Image data of one field is written, and after this writing, a complementing process is performed, and the image data converted into a frame image is written to the frame memories 51R, 51G, and 51B.

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

The monitor system comprises a D / A converter 48 and an analog signal processing circuit 49. D / A converter 4
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 the input RGB signal into an NTSC format video signal,
A frame image is displayed on a monitor (for example, a home TV).

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

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

Next, the operation of the color thermal printer of this embodiment will be described with reference to FIG. Before printing, press the menu key 30
Press c (see FIG. 4) to select the test print mode. In this mode, input of the number of test prints is first instructed. Then, a numerical value is displayed on the display 33 in order to input the number of times of test printing performed on the test printing recording sheet 4a. This numerical value can be changed by pressing the cursor keys 30d and 30e of the operation unit 30. For example, the right cursor key 30e is set to 1
When pressed once, "1" is added to the displayed numerical value and displayed. When the left cursor key 30d is pressed once, "1" is subtracted from the displayed numerical value and displayed. In this way, by pressing the corresponding cursor keys 30d and 30e a predetermined number of times, the number of the number of times of steep printing can be displayed. Thereafter, by pressing the execution key 30f, the selected numeral is taken into the system controller 16. The system controller 16 determines the print start position of the test pattern by multiplying the number of test prints by the feed pitch amount L1.

Then, the test pattern is recorded from the print start position based on the test pattern creation data.
In the test pattern data, the heating element for recording the density area 70c located at the density correction value "0" is thermally recorded as gradation data "1" at the reference applied voltage. Also, for the heating element that records the density area 70d located at the density correction value “1”, gradation data which becomes the density recorded by the applied voltage when the correction voltage value for one step is added to the reference applied voltage, for example, It is assumed that the heating element for recording the density area 70e which is recorded with the number of gradation pulses "10" and similarly located at the density correction value "2" is obtained by adding the correction voltage value for two steps to the reference applied voltage. The gradation data is recorded with the density recorded by the applied voltage, for example, the gradation pulse number “20”. Similarly, the density area 7 located at the density correction value “−1”
The heating element for recording 0b is recorded with gradation data of the density recorded by the applied voltage when the correction voltage value for one step is subtracted from the reference applied voltage. In this case, since the gradation data is negative, it is impossible to perform the correction by reducing the number of gradation pulses. Therefore, by reducing the number of bias pulses, the correction voltage for one step is added to the reference applied voltage. It is recorded with bias data that becomes the density recorded by the applied voltage when the value is subtracted. Similarly, the density area 70a located at the density correction value "-2" is recorded.

Therefore, in the case of a heat-sensitive recording sheet whose sensitivity has changed due to a change in water content or deterioration over time, even if a test pattern is recorded based on the test pattern data,
Since the sensitivity has changed, the density area where color development starts will be shifted. Therefore, the density correction value can be easily determined by reading the density correction value of the density area where the color development has started. For example, in the first test pattern shown in FIG. 8, since the density area where color development is started is at the density correction value “1”, it can be easily known that the density correction value is “1”. Similarly, in the second test pattern, the density correction value is “−1” because the density area where the color development is started is at the density correction value “−1”.

Next, the menu key 30c is pressed to select the humidity-dependent density correction mode. In the density correction mode, the display screen 35 as shown in FIG. 6 is displayed. By operating the cursor key 30d or 30e, the density correction value obtained in the test print mode, for example, "1" in the case of the first test pattern 70 Enter "1". This density correction value is input by moving the cursor 3 to the density correction value of “1”.
After moving 5c, this is performed by pressing the execution key 30f, and the system controller 16 takes in the density correction value “1” selected by the cursor 35c.

The system controller 16 calculates the correction value VC (V) of the driving voltage of the heating element corresponding to the density correction value “1” by using the LUT obtained by using the graph shown in FIG.
Cy, VCm, VCc). This voltage correction value VC
Is sent to the voltage control circuit 37. The voltage control circuit 37
The drive voltage of the thermal head 20 is corrected based on the voltage correction value VC.

In the print mode, as shown in FIG.
At the time of sheet feeding, the platen drum 10 is
Is stopped at the home position where it is almost vertical. The transport roller pair 26 nips the color thermal recording sheet 4 supplied from the tray 23 and
It is transported toward zero. The transport roller pair 26 stops once when the leading end of the color thermal recording sheet 4 enters between the platen drum 10 and the clamp member 14. After the clamp member 14 clamps the leading end of the color thermal recording sheet 4, the platen drum 10 and the conveying roller pair 26 rotate, so that the color thermal recording sheet 4 is wound around the outer periphery of the platen drum 10.

The pulse motor 12 steps the rotation of the platen drum 10 for one line in four pulses.
Since the step is slightly fed, 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 sends a predetermined number of bias pulses BP to each heating element 20a of the thermal head 20 as shown in FIG. A gradation pulse PG corresponding to the pixel density is applied to heat. As a result, the first line yellow image is recorded at the recording start position of the print area PA. Similarly, a yellow image of each line is recorded one after another.

At the time of this recording, the voltage control circuit 3 based on the voltage correction value VCy for correcting the sensitivity change due to humidity dependency.
At 7, the driving voltage of the thermal head 20 is controlled. Therefore, even if the color sensitivity changes due to aging or exposure of the recording sheet, the voltage can be changed in response to the change, 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 light fixing device 21. As a result, the diazonium salt compound remaining in the yellow thermosensitive coloring layer 8 undergoes photolysis to lose its coloring ability.

When the recording start position of the print area is positioned at the heating element of the thermal head after the platen drum 10 has rotated substantially once, a magenta image of the first line is recorded. Similarly, magenta images of each line are recorded one after another.

At the time of this printing, the voltage correction value V for correcting the sensitivity change due to the humidity dependency is the same as at the time of yellow printing.
The drive voltage of the thermal head 20 is controlled by the voltage control circuit 37 based on Cm. Therefore, even when the coloring sensitivity of the recording sheet changes due to deterioration over time or the like, the voltage can be changed correspondingly, so that a magenta image can be thermally recorded at an appropriate density. When the portion where the magenta image is thermally recorded reaches the optical fixing device 22, the magenta thermosensitive coloring layer 7 is optically fixed by the magenta light fixing device 22 here.
As a result, the diazonium salt compound remaining in the magenta thermosensitive coloring layer 7 undergoes photolysis to lose its coloring ability.

Hereinafter, in the same manner, the cyan thermosensitive coloring layer 6
The thermal image of the cyan image is recorded. Also in this case, since the correction of the humidity dependency due to the deterioration with time or the like is performed by the voltage correction value VCc, the cyan image is thermally 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 supply / discharge path 25 by the separation claw 27, and is nipped by the transport roller pair 26. Thereafter, the clamp member 14 is opened, and the thermally-recorded color thermosensitive recording sheet 4 is discharged to a discharge tray (not shown) via a supply / discharge passage 25.

When the power is turned off, or when the sheet feeding tray 23 is opened without turning off the power, the system controller 16 resets the density correction value to the initial set value and sets the voltage correction value. Is also reset to the default value. Therefore, at the time of the next printing, the previously set density correction value is not used, so that the 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. Therefore, it is possible to suppress the occurrence of printing failure due to this. Note that the configuration for resetting the density correction value and the voltage correction value to the initial setting values as described above may be omitted.

In the above embodiment, the display 33
The menu, commands and various data of various modes are displayed on the screen, and after selecting them with the cursor keys 30d and 30e, the execution key 30f is pressed to input the commands and various data. As shown in (1), the input of the density correction value may be performed using a density adjustment dial 81 attached to the variable resistor 80 and an A / D converter 82. The same components as those in the above embodiment are denoted by the same reference numerals. Also in this case, a humidity-dependent density correction mode is selected by the menu key 30c of the operation unit 30, and after setting the system controller 16 to this mode, the density adjustment dial 81 is turned to set a predetermined value. . In this case, the density correction value can be set finely. Note that a slider may be used instead of the dial 81. Also, in the case of inputting the density correction value from the display screen 35 as shown in FIG. 6, the density correction value can be 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.

In the above embodiment, the operation unit 30 is operated by the freeze key 30a, the print key 30b, and the menu key 3.
0c, left and right cursor keys 30d, 30e, execution key 3
Although the operation unit 30 is simplified by constructing from 0f, numerical data may be directly input by using a numeric keypad or the like.

FIG. 11 shows a test pattern 90 for color adjustment according to another embodiment. This test pattern 90
It is composed of areas 90a, 90b, 90c, and 90d that are separately painted in four colors of yellow, magenta, cyan, and gray. Then, a density correction value is determined for each color by comparing and observing the obtained test pattern 90 and a sample having the same pattern prepared in advance. This test pattern data is written in the memory 16a in the system controller 16 in advance as in the above embodiment. The input of the determined density correction value may be performed by adjusting a variable resistor for density adjustment for each color in addition to selecting the density correction mode as in the above-described embodiment. . In this case, the color adjustment is performed according to the flowchart shown in FIG.

The color correction performed using the test patterns of the four colors is not limited to a full-color thermal printer, and ink is applied to a recording sheet using another full-color printer, for example, an ink ribbon. The present invention can also be applied to a thermal melting type or sublimation type thermal printer that performs transfer when performing the above-described color correction.

In the above embodiment, the voltage applied to each heating element of the thermal head is controlled based on the density correction value. In addition, the density correction is performed by increasing or decreasing the number of bias pulses and gradation pulses. You may. Further, the density may be corrected by changing the duty ratio of each pulse. Furthermore, density correction may be performed by using these density correction methods together.

Further, in the above embodiment, as shown in FIG. 8, the test patterns 70 of each time are recorded so as to be arranged in the sub-scanning direction. May be recorded so as to be shifted. In this case, only the heating element at the position corresponding to the number of times of test printing is drive-controlled, and a pattern similar to the test pattern 70 is printed long in the sub-scanning direction. Hereinafter, only the corresponding heating element is driven and controlled in accordance with the number of test prints, and the test patterns are recorded so as to be arranged in the main scanning direction.

[0064]

As described above, according to the present invention,
Since the density adjustment pattern is composed of density areas corresponding to each density correction value input by the density correction value input means, the density correction value can be easily known from the density pattern obtained by the test print.

A recording sheet for trial printing is used. The recording sheet is prepared by previously optically fixing other thermosensitive coloring layers except for the thermosensitive coloring layer having the lowest color developing sensitivity. One or both of the lengths in each direction are shortened so that a plurality of areas can be printed side by side in the main scanning direction or the sub-scanning direction, and the recording position of the density adjustment pattern according to the number of test prints. Are shifted in order, the recording sheet for test printing can be used until the print area is filled with the density adjustment pattern, and waste of the recording sheet can be eliminated.

Further, by storing the color sample preparation data, a test print is performed based on the color sample preparation data, and the test print based on the test print is compared with the sample prepared in advance, thereby making it easy. The color correction value can be determined quickly and quickly, and color adjustment can be easily performed.

[Brief description of the 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 the coloring characteristics of a color thermosensitive recording sheet.

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

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

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

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

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

FIG. 9 is an explanatory diagram showing a bias pulse and a gradation pulse 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.

FIG. 11 is an explanatory diagram showing an example of a color adjustment test pattern in another embodiment.

FIG. 12 is a flowchart illustrating a procedure of a color adjustment process in the embodiment.

[Explanation of symbols]

 Reference Signs List 4 color thermal recording sheet 4a test printing 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 unit 31 power switch 32 tray sensor 33 display 37 voltage control circuit 54 Thermal head driver 70 Test pattern for humidity-dependent density correction 70a to 70d Density area 80 Density adjustment dial 90 Color adjustment test pattern

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification symbol FI H04N 9/79 H04N 9/79 H (58) Field surveyed (Int.Cl. ⁷ , DB name) H41J 2/325 H41J 2 / 36 H04N 1/23 102 H04N 1/46 H04N 1/60 H04N 9/79

Claims (3)

(57) [Claims] 1. A thermosensitive light source for each of yellow, magenta, and cyan
Color layers with color layers with higher color sensitivity
ー Press the thermal head against the thermal recording sheet to
Coloring heat corresponding to image data for each heating element of the multi-head
After recording each color by applying energy, this recorded
Fix the thermosensitive coloring layer by light to record a full-color image
In a color thermal printer, a density correction value is input according to a change in sensitivity of the recording sheet.
Density correction value input means for storing the density correction value, and
Correct the density by controlling the amount of heat generated by the thermal head
Density correction means, means for storing density adjustment pattern data , a print mode for printing based on image data,
Perform test printing based on the density adjustment pattern data
Mode switching means for switching to the test printing mode.
Wherein the density adjustment pattern data, the density correction value input means
Has a density area corresponding to each density correction value input in
Color thermal printer. 2. A thermal head in which a large number of heating elements are arranged in a line in the main scanning direction using a color thermosensitive recording sheet having yellow, magenta, and cyan thermosensitive coloring layers in order from the one having the highest coloring sensitivity in an upper layer. While moving the recording sheet and the thermal head relatively in the sub-scanning direction, the thermal head is pressed against the recording sheet to give each color heating energy corresponding to the image data to each heating element of the thermal head, thereby recording each color. After that, the recorded thermosensitive coloring layer is optically fixed, and a color correction printer for recording a full-color image in a frame-sequential manner is a density correction value input for inputting a density correction value according to a change in sensitivity of a recording sheet. Means for storing the density correction value, and controlling the heat generation amount of the thermal head based on the density correction value to correct the density. Means, and means for storing the density adjustment pattern data, and a print mode for printing based on image data,
A mode switching unit for switching to a test printing mode for performing test printing based on the density adjustment pattern data, wherein the density adjustment pattern data is a density corresponding to each density correction value input by a density correction value input unit. A color thermal printer having an area. 3. The color thermal printer according to claim 1 , wherein a recording sheet for trial printing is used in the trial printing mode.
This recording sheet is prepared in advance by optically fixing the other color-forming heat-sensitive layers except for the heat-sensitive layer having the lowest color-forming sensitivity, and the density adjustment pattern is formed by arranging density areas in the order of density change. One or both of the lengths in each direction are shortened so that a plurality of patterns can be printed side by side in the main scanning direction or the sub-scanning direction of the print area, and are used for density adjustment according to the number of test prints. A color thermal printer characterized by sequentially shifting recording positions of patterns.