JPH0516409A - Image recording method - Google Patents

Abstract

PURPOSE:To provide an image recording method whereby the density irregularity between the elements caused when an image is recorded with the use of a plurality of the elements can be reduced. CONSTITUTION:The image density data of a Y (yellow) color stored in a frame memory 34a is converted to an ideal recording energy value in a lookup table 36a and input to a resistance value correcting table 37a. The resistance value correcting table 37a corrects the input data so as to make the characteristics of a plurality of heat generating elements of a thermal head 46 agree with each other, and outputs the corrected data. The output data of one line is stored in a line buffer 42. As a driver 44 is driven on the basis of the data stored in the line buffer 42, an image is recorded to a heat sensitive recording material 12 by the thermal head 46. This recording process is carried out for an M (magenta) and a C (cyan) colors. Accordingly, the irregularity of each heat generating element is corrected and the color image can be recorded without the density irregularity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording method, and more particularly, it relates to an image recording method for successively recording images on a multicolor thermosensitive recording material.

[0002]

2. Description of the Related Art At present, there is a heat-sensitive recording method as a method for recording an image on a recording sheet using a heating element. In this heat-sensitive recording method, a heat-sensitive recording material in which a color former and a developer are applied to a support such as paper or synthetic paper is used, and the heat-sensitive recording material is heat-treated by a thermal head for recording. For example, a thermosensitive recording material in which a plurality of electron-donating dye precursors and an electron-accepting compound coexist is prepared, and different temperatures are applied by utilizing the fact that each electron-donating dye precursor has a different color initiation temperature. It has been proposed to obtain images of different hues (Japanese Patent Publication No. 49-69).

In such a recording field, along with the rapid development of the information industry, there is a demand for easily obtaining a color hard copy from a terminal of an information device such as a computer or facsimile. There is a digital color printer as a printer that meets this demand. In this digital color printer, a color image is Y (yellow) for each color component,
An image is recorded on each corresponding heat-sensitive layer based on image data of M (magenta), C (cyan), or the like. However, in order to make the thermosensitive recording material multi-colored, it is necessary to incorporate a coloring mechanism corresponding to the number of coloring colors on the same support and to control and act each coloring mechanism. Although it has been done, there was not enough in terms of hue of color development and color separation.

Here, the present applicant provides a substantially thermosensitive color-developing image, which is unprecedented, by providing a coloring layer which is substantially transparent and develops different hues on one surface of the support. A thermal recording material was proposed (Japanese Patent Application No. 63-29).
3714). According to this, it is possible to obtain a multicolor image having excellent hue, excellent color separation property, and good image storability which have heretofore not been obtained depending on the thermal recording method. The image obtained by selecting the support can be a transmission image or a reflection image.

Since such a thermosensitive recording material is provided with multiple coloring layers, it is the uppermost layer (the layer closest to the surface).
Is heated and colored with heat energy to such an extent that the other layers are not heated, the color-developing layer is fixed, and the heat treatment of the other color-developing layers is sequentially performed.

However, the characteristics of the heat-sensitive recording material, that is, the relationship between heat energy and color density is often not a linear relationship. Therefore, the color density corresponding to the image data may not be obtained, and the image may not be properly recorded. In order to solve this, a lookup table (LUT) representing the relationship between image data and color density
A method is generally used to correct the relationship between image data and color density so as to approximate a straight line.

Further, there is a recording head such as a line head in which a plurality of heating elements are arranged in order to record one line at the same time. The heating element of the line head has a predetermined resistance value and generates heat by the input power. However, it is difficult to manufacture each element in this line head so as to show the same characteristic, and as a result, a plurality of heating elements show different characteristics. That is, the resistance value varies from heating element to heating element. Therefore, when the line head is driven by using one LUT, the thermal energy supplied changes due to the variation in the resistance value due to the element, and the color is not developed at an appropriate density. Therefore, a correction table is provided to correct the variations among the plurality of elements.

[0008]

However, in the heat-sensitive recording material which develops a plurality of colors like the above-mentioned heat-sensitive recording material, the range of heat energy used for recording an image is wide, so that each color-forming layer is formed. The resistance value changes in each thermal energy range for color development, and the correction shifts. Therefore, there is a problem that an appropriate image cannot be recorded.

The present invention has been made to solve the above-mentioned problems, and minimizes the variation between the respective elements that occurs when an image is recorded by using a plurality of elements, and sufficiently corrects the density of each color. An object is to provide an image recording method that can be performed.

[0010]

In order to achieve the above object, the present invention provides a thermosensitive recording material in which a plurality of color-developing layers that develop different colors when heat energy is supplied are laminated, according to an input signal. In recording a color image by simultaneously supplying heat energy based on image data by a heat source equipped with a plurality of heating elements that generate heat energy,
A correction value for correcting the relationship between the input signal and the heat energy generated from each heating element based on the input signal so as to be substantially the same for each heating element is stored and recorded in association with each heating element. It is characterized in that a color image is recorded by correcting the image data to be stored based on the stored correction value, and developing each color in accordance with the corrected image data.

[0011]

According to the present invention, the heat-sensitive recording material has a plurality of color-developing layers which are colored in different colors when heat energy is supplied. To this heat-sensitive recording material, heat energy based on image data is simultaneously supplied by a heat source having a plurality of heating elements to record a color image. Each heating element has a relationship between an input signal and heat energy generated from each heating element based on the input signal.
A correction value for correcting this heating element so as to be substantially the same is stored in association with each heating element. Then, the image data to be recorded is corrected based on the stored correction value. As a result, the respective heating elements are brought into a relationship in which the input signal, that is, the signal corresponding to the image data, and the thermal energy generated from the respective heating elements match. A color image is recorded by developing each color in accordance with the corrected image data. Therefore, the thermal energy generated from each of the plurality of heating elements is the same due to the same image data. For this reason, the variation for each heating element is corrected, and even if the image is recorded by the heat source having a plurality of heating elements, the image can be recorded without density unevenness.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. In this embodiment, the digital color printer 10 is used.
The present invention is applied to.

First, the thermal recording material 12 as a recording material used in the embodiment of the present invention will be described.

As shown in FIG. 3, the heat-sensitive recording material 12 used in this embodiment has first, second and third heat-sensitive recording materials on a support 22.
The thermosensitive color forming layers comprising the thermosensitive recording layers 20, 18 and 16 are sequentially laminated. A protective layer 14 is applied to the surface of the third thermosensitive recording layer 16 in order to protect the color forming layer from scratches and the like. Similarly, a back coat layer 24 is applied to the surface of the support 22. The first thermosensitive coloring layer 20 contains an electron-donating dye precursor and an electron-accepting compound as main components. The second heat-sensitive layer 18 contains a diazonium salt compound having a maximum absorption wavelength of 360 ± 20 nm, and a coupler that reacts with the diazonium salt compound to produce a color when heated. The third heat-sensitive layer 16 has a maximum absorption wavelength of 4
It contains a diazonium salt compound having a wavelength of 20 ± 20 nm and a coupler that reacts with the diazonium salt compound to produce a color when heated.

The procedure for recording an image on the heat-sensitive recording material 12 is as follows. First, heat 1 sufficient for recording on the third heat-sensitive recording layer 16 is applied, and the diazonium salt contained in the third heat-sensitive recording layer 16 is added. Color the coupler. Then 420 ± 20 nm
Of light UV1 to irradiate the heat-sensitive recording material 12 to decompose the diazonium salt contained in the third heat-sensitive recording layer 16 and give heat 2 sufficient for the second heat-sensitive recording layer 18 to record,
The coupler and the diazonium salt contained in the heat-sensitive recording layer 18 are developed. At this time, strong thermal energy is applied to the third heat-sensitive recording layer 16, but no color is developed because the diazonium salt has already decomposed and the color-forming ability has been lost. Then, the heat-sensitive recording material 12 is irradiated with light UV2 of 360 ± 20 nm to decompose the diazonium salt contained in the second heat-sensitive recording layer 18, and the heat 3 sufficient for recording the first heat-sensitive recording layer 20 is generated. Then, the coupler and the diazonium salt contained in the first thermosensitive recording layer 20 are colored. At this time, strong thermal energy is applied to the third thermosensitive recording layer 16 and the second thermosensitive recording layer 18, but no color is developed because the diazonium salt has already been decomposed and the color forming ability is lost.

Here, in this embodiment, the first, second and third
The coloring hue of each heat-sensitive recording layer is selected so as to be the three primary colors in subtractive color mixing, cyan, magenta, and yellow. That is, each of the first thermosensitive recording layers has a cyan coloring hue of the C layer 20, the second thermosensitive recording layers have a magenta coloring hue of the M layer 18, and the third thermosensitive recording layers have a yellow coloring hue. Which is the Y layer 16. Therefore, full-color image recording can be performed on the heat-sensitive recording material 12 by recording according to the above procedure.

Further, the thermal recording material 12 used in this embodiment.
Is a Y layer 16, an M layer 18 and a C layer 2 as shown in FIG.
0 develops a color with a color density corresponding to different recording energy (heat energy). That is, the Y layer 16 is colored in accordance with the heat energy in the heat energy region Py, the M layer 18 is colored in accordance with the heat energy in the heat energy region Pm, and C is determined in accordance with the heat energy in the heat energy region Pc.
Layer 20 develops color.

Next, a digital color printer 10 applicable to the embodiment of the present invention will be described with reference to the schematic structure shown in FIG.

A table 52 of the heat-sensitive recording material 12 is projected from the right side surface of the casing 50 in FIG. The thermosensitive recording material 12 is conveyed to the table 52 in the direction of arrow A in FIG. 2 by inserting the thermosensitive recording material 12 with the recording layer facing upward and inserting the tip of the thermosensitive recording material 12 into the casing 50.

A pair of conveying rollers 54 are arranged on the downstream side of the table 52 so as to sandwich and convey the thermosensitive recording material 12. A plurality of guide plates 56 are sequentially arranged in a substantially C shape on the downstream side of the transport roller 54 so that the thermal recording material 12 can be guided.
Therefore, the heat-sensitive recording material 1 is formed by the plurality of guide plates 56.
2 is conveyed in a substantially C shape.

The carrying roller 54 is connected to a rotating shaft of a motor (not shown). The motor is connected to the control device 26, and the rotation of the motor in the forward and reverse directions is controlled by the control device 26 in response to insertion or unloading of the thermal recording material 12.

A pair of conveying rollers 58 is arranged between each of the plurality of guide plates 56. These transport rollers 58 are connected by a belt, and this belt is connected to the rotating shaft of a motor 66. The motor 66 is connected to the control device 26, and a signal from the control device 26 causes 1
It is designed to be rotated in the direction (counterclockwise in FIG. 2).

On one side of the conveying path of the thermal recording material 12, one corresponding to the side where the color forming layer of the thermal recording material 12 is not formed,
A platen roller 60 is arranged. The platen roller 60 is connected to the rotating shaft of the motor 68 via a drive belt. The motor 68 is rotated in one direction by a signal from the control device 26.

A line type thermal head 46 is disposed on the other side of the transport path for the thermal recording material 12. A heating element 62 composed of a set of a plurality of heating elements is attached to one end of the thermal head 46, and when an image signal is supplied from the control device 26, heat is generated according to the image signal and the thermal recording material 12 is obtained. Is designed to be heated. The amount of heat generated by the heating element 62 can be changed depending on the heating time.

The heating of the heating element 62 is performed by energization. That is, as shown in FIG. 9, the plus side power supply line 4 for heating the heating element 62.
A resistor 61 and a resistor 63 forming a heating element 62 are connected in series between the No. 5 and the minus power supply line 47. These are arranged in parallel by the same number or more as the number of pixels for one row. A pulse width for energizing the resistor 61 is set in the register 63. Therefore, the pulse width of the register 63 is set according to the output signal output from the line buffer 42, and the thermal head 4
The heat treatment time of the heating element 62 for each pixel of 6 is set. Therefore, when the energization is started from the plus side power supply line 45, a current flows through the resistor 61 for a time corresponding to the pulse width set in the register 63, the heating element 62 generates heat and the heat-sensitive recording material 12 is heated. Become. Here, since the thermal recording material 12 of this embodiment has three layers, scanning (heating treatment) with the pulse width set as described above is performed three times.

A positioning signal is also output from the control device 26 to the thermal head 46, and a positioning signal is output during the heating recording of the first color layer (Y color layer 16 in this embodiment). A bar-shaped positioning mark 71 as shown by 10 is recorded. In addition,
The positioning mark 71 is recorded after a predetermined time from the time when the front end of the thermosensitive recording material 12 is detected by the first photoelectric sensor 70. Based on the positioning mark 71, the recording time for recording the other color layers (M layer, C layer) is determined.

A pair of conveying rollers 64 are arranged on the downstream side of the platen roller 60 so that the thermal recording material 12 is nipped by the conveying rollers 64. A second photoelectric sensor 72 is attached between the platen roller 60 and the conveyance roller 64. This second photoelectric sensor 72
Is connected to the control device 26 so as to detect the positioning mark 71 and output the detected signal.

The two sets of conveying rollers 64 are connected via a drive belt. The transport roller 64 is connected to a rotating shaft of a motor (not shown), and rotates in one direction in response to a signal from the control device 26.

Two light sources 78 for irradiating the surface (coloring layer side) of the thermosensitive recording material 12 with a light beam are provided between the two sets of conveying rollers 64. The light source 78 is turned on and off in response to a signal from the control device 26. The wavelength of the light emitted from the light source 78 is
It can be switched to about 365 nm and 420 nm, and is used for fixing the Y color layer and the M color layer of the thermal recording material 12, respectively.

On the downstream side of the conveying roller 64, a conveying path switching means 74 having a cam 76 is provided, and the cam 76 rotates in response to a signal from the control device 26 to convey the thermosensitive recording material 12. The discharge direction (right side in Figure 2)
Alternatively, the loop direction is switched (upward in FIG. 2).

Thermal recording material 12 guided in the discharge direction
Are transported to the vicinity of the transport roller 54. Here, by rotating the conveying roller 54 in the reverse direction, the thermosensitive recording material 12 guided and guided by the guide plate is nipped and conveyed onto the table 52.

On the other hand, the heat-sensitive recording material 12 guided in the loop direction passes through the hole provided in the guide plate 56, is pinched again by the transport roller 58, and reaches the loop-shaped transport path. That is, in this embodiment, since the same surface is scanned (heated) three times, the table 52 is used.
The thermosensitive recording material 12 inserted from above is guided to the loop-shaped conveyance path by the cam 76, and after the third scanning,
With the cam 76 in the discharging direction, the thermosensitive recording material 12 is taken out to the table 52.

Next, the control device 26 will be described with reference to FIG. The control device 26 includes a host computer 30.
Are connected.

Image data is stored in the host computer 30 as a digital image signal, and the digital image signal supplied from the host computer 30 is input to the conversion circuit 32.

Here, in the case of subtractive color mixing, Y, M, C
It is known that black is obtained by mixing the respective colors at a predetermined mixing ratio. For example, black (character) data can be converted and output by outputting black (character) data as the same density for each of Y, M, and C colors. Therefore, the conversion circuit 32 converts the input digital image signal into Y, M
And C signals are converted into signals for respective colors, and the converted Y, M, and C signals are then converted into corresponding frame memories 3.
4a, 34b, 34c.

Each frame memory 34a, 34b, 34c
An image signal for one image of a color corresponding to each frame memory 34 is stored in the memory. Also, the host computer 3
0 is connected to the controller 40, and the horizontal sync signal and the vertical sync signal from the host computer 30 are input to the controller 40. The horizontal synchronizing signal and the vertical synchronizing signal are output to the conversion circuit 32 and the frame memory 34 for synchronization.

Each frame memory 34a, 34b, 34c
Is a lookup table (hereinafter, LUT) 36a, 3
6b and 36c, each frame memory 34
The YMC signals output from a, 34b, and 34c, that is, the image density data are LUTs 36a, 36b, and 36c.
Entered in. Each of the LUTs 36a, 36b, 36c has a resistance value correction table (hereinafter, RT) 37a, 37.
b, 37c, and converted into YMC color drive values (recording data) according to the color density in each LUT, and the recording data are converted into RT37a, 37b, 37c.
Entered in. RTs 37a, 37b, 37c are connected to a line buffer 42 via a switch 38, and R
The recording data output from each of T37a, 37b, and 37c is output to the line buffer 42 for each row via the switch 38. Here, RT37a, 37b, 3
Each of 7c is connected to the controller 40, and outputs a value corresponding to each heating element of the heating element 64, which will be described in detail later. Further, the switch 38 is connected to the controller 40, and the RTs 37a, 3c are provided so that the image density data corresponding to the color at the time of recording is supplied to the line buffer 42 according to the signal from the controller 40.
Any one of 7b and 37c and the line buffer 42 are connected.

The look-up table is different depending on the characteristics of the thermal recording material 12. That is, in the thermal recording material 12 used in this example, for example,
As shown in FIG. 5, the characteristic of the color density D with respect to the recording energy E corresponding to the image density data is not appropriate.
As a result, even if recording is performed in order to obtain a desired color density, the color density of the thermal recording material 12 is different, and an image having the desired density cannot be obtained. Therefore, the table is created so that the characteristic of the color density D with respect to the recording energy (heat energy) E becomes appropriate. For example, the recording energy E
In a, the thermosensitive recording material 12 has a coloring density Da. At this recording energy Ea, the desired color density D is the density D
Since it is a ', the recording energy Ea' is required. Therefore, a table is prepared in which the recording energy Ea 'corresponds to the density Da' of the coloring density D. That is, as shown in FIG. 6, a characteristic of the drive value (thermal energy) of the thermal head that provides an appropriate color density according to the image density data is prepared, and this characteristic is used as the LUT. Further, in this embodiment, in order to develop different colors, different thermal energies are supplied to the thermosensitive recording material after being shifted by a predetermined thermal energy for each color. Therefore, this shifting thermal energy is also taken into account. A separate circuit may be added for this shift of heat energy.

The line buffer 42 includes the controller 4
A vertical synchronizing signal is input from 0, and a signal is output to the thermal head 46 via the driver 44 based on the vertical synchronizing signal, and the thermal head 46 is heated. An image is recorded on the heat-sensitive recording material 12 by this heat.

The controller 40 is connected to the motor 68 via a driver 69 and sends a signal to rotate the platen roller 60. Also, the controller 4
0 is connected to the light source 78 via the driver 79,
A control signal is sent according to the color image recorded on the thermosensitive recording material 12. As a result, the light source 78 emits light of 365 nm and 4
The thermal recording material 12 is irradiated by switching to a light beam having a wavelength of 20 nm.

The resistance value correction table for correcting the relationship between the image data and the thermal energy of each of the heating elements in this embodiment will be described in detail.

First, when recording each color of Y, M and C by the conventional recording method, the LUT of each color is referred to and the following equation (1), D (i) = LUT _i (C (i))- -(1) where i = 1, 2, 3 (corresponding to Y, M, C) D (i): recording energy LUT _i (X) for obtaining color density when image data of i color is recorded : Function for calculating recording energy corresponding to input image data based on i-color LUT C (i): Input image data (tone) can be expressed. According to this equation (1), for example,
When the image data of each color is input in 256 gradations,
Print data (recording energy) corresponding to the input image data is calculated.

However, since the characteristics of the heating elements of the plurality of thermal heads are different, the characteristics of generating the recording energy change for each heating element. That is, as shown in FIG. 11, even if the same image density data is used, the heat energy generated from each heating element of the heating element 62 is different. As a result, the color density of the portion recorded by each heating element is different. For example, when recording is performed by the heating element 1 having a resistance value smaller than that of the heating element having an ideal resistance value, in order to obtain the color density of the heating element having the ideal resistance value with the same image density data, it is ideal. It requires more heat energy than a resistance heating element.
On the other hand, in the case of the heating element 2 having a larger resistance value than the heating element having an ideal resistance value, the same density as the color density produced by the heating element having an ideal resistance value is obtained with less heat energy than the heating element having an ideal resistance value. Can be obtained.

Therefore, as shown in FIG. 12, by correcting the image density data so that the resistance value of each heating element becomes an ideal resistance value, the ideal resistance value of each heating element is It is possible to generate heat energy having characteristics matching the heating elements. It should be noted that this correction may be performed on the image density data, or may be performed after the image density data is converted into recording energy (heat energy).

In this embodiment, for each heating element,
Correct so that the characteristics match. For example, an example of the case where the heat energy generated according to the amount of change in the resistance value of each heating element changes is shown by the following formula (2), P (i) = (Q _i / α _ij ) · D (i) --- (2) where i = 1, 2, 3 (corresponding to Y, M, C) j = 1, 2, ... (corresponding to the number of heating elements) P ( i): recording energy for obtaining an appropriate color density when recorded with image data C (i) α _ij : correction value when recording i color with the j-th heating element (measurement of resistance of each heating element) Value or expected resistance value)) Q _i : It can be expressed as an ideal resistance value when recording i color. In this way, the energy supplied to each heating element is corrected so that an appropriate density is obtained. Therefore, the recording energies of the heating elements when recording with the same image data are the same.

The operation of this embodiment will be described below with reference to FIGS. 7 and 8 in accordance with the flow chart of the control circuit.

First, when the main routine shown in FIG. 7 is executed, the device is initialized in step 102. When the initialization is completed, the process proceeds to step 104. In step 104, image data of one pixel (pixel data) is fetched, and the process proceeds to step 106. In step 106, Y, M, C at the time of recording the input image data
Data of each of the three colors are stored in the frame memory 34 corresponding to each of the three colors, and the process proceeds to step 110. In step 110, it is determined whether or not reading of all pixel data has been completed. If not completed, the process returns to step 104, and pixel data for one screen is repeatedly converted. Therefore, each frame memory 34 stores pixel data for one screen of each of Y, M, and C colors. When the pixel data conversion for one screen is completed, the process proceeds to step 112, and an image recording subroutine described later is executed. In this subroutine, images are sequentially recorded on the thermosensitive recording material 12. When the recording of the image ends, this main routine ends.

Next, the image recording subroutine will be described with reference to FIG. In this subroutine, when the image data in the frame memory 34 described above is recorded in an overlapping manner, the image data to be recorded is corrected for each heating element, and the thermosensitive recording material 12 is corrected based on the corrected data. The control for recording the image of each color is performed.

When this subroutine is executed, the routine proceeds to step 150, where the counter value i is set to 1. Also,
The measured value α _ij (i = 1, 2 _,, i) of the resistance value of the heating element with the thermal energy for each color used when correcting the image data
3. j = 1, 2, ...) Is taken in. In addition, the ideal resistance value Q _i (i
= 1, 2, 3) is taken in. As the counter value i, 1 corresponds to Y color, 2 corresponds to M color, and 3 corresponds to C color at the time of recording. Further, the counter value j corresponds to the number of heating elements. In step 152, the counter value j corresponding to the order of the heating elements of the thermal head 46 is set to 1, and the process proceeds to step 154. In step 154, the image data C (i) for one color of one pixel is read from the frame memory of the corresponding color, and step 156
Go to. In step 156, L of the color corresponding to the value of i
The ideal operating value D of the thermal head 46 is output by referring to the UT, and the routine proceeds to step 158. In step 158, the correction data Q _i and α _ij of the position of the thermal head corresponding to the RT (resistance value correction table) of the color to be recorded are read. The correction data Q _i and α _ij are the ideal resistance value and the actual resistance measurement value of each heating element, as described above. When the reading of the correction data is completed, the process proceeds to step 160,
The corrected operation value P is calculated based on the read correction data based on the above equation (2). The operating value corresponds to the heat energy, that is, the energizing pulse time (heating time).

When the calculation of the operating value P is completed, step 16
2, the operation value of the thermal head 46 in which the image data is corrected for each heating element is stored in the line buffer 42. In step 164, it is determined whether or not the image recording for one line is completed. If not completed, the counter value j is incremented by 1 in step 166, and then the process returns to step 154 to display the image for one line. This is repeated until the storage of data is completed. Therefore, the line buffer 42 stores the operation value of the thermal head 46 corrected for each heating element according to the image data for one line.

When the storage of the operating value for one line is completed, in step 168, the image recording for one line is performed according to the operating value stored in the line buffer 42.
At the time of this recording, the operation value is corrected according to the characteristics of each heating element of the thermal head 46. When the image recording for one line is completed, the process proceeds to step 170, and it is determined whether or not the recording of one screen for one color is completed. If not completed, the process returns to step 152 and the recording of one screen is completed. The recording is repeated until it is done. When recording with the thermal head 46, the controller 40 outputs a control signal to the switch 38 so that the LUT 36 for the color used during recording and the line buffer 42 are electrically connected.

If it is determined in step 170 that one screen has been recorded for one color,
Proceeding to step 172, it is determined whether or not the recording of the image data for all the colors (Y, M, C) is completed by determining whether i = 3. If recording of all colors has not been completed, the process proceeds to step 174, and it is determined whether or not the color for which recording is completed is the Y color by determining whether i = 1. After the Y-color recording is completed, ultraviolet light UV1 having a wavelength of 420 nm is irradiated for a predetermined time in step 176, and the process proceeds to step 180. This wavelength 420nm
The irradiation of the ultraviolet light UV1 suppresses the area where the Y color image is not recorded from being colored by the thermal energy at the time of recording after the next time, that is, the thermal energy at the time of recording of the M and C colors. After M color recording is completed, ultraviolet light UV2 having a wavelength of 365 nm is irradiated for a predetermined time in step 178, and the process proceeds to step 180. This wavelength 365
By irradiating the ultraviolet light UV2 having a wavelength of nm, it is possible to prevent the portion where the M color image is not recorded from being colored by the thermal energy at the time of the next C color recording. In step 180, the counter value i is incremented by 1, and the process returns to step 152. On the other hand, if i = 3 in step 172, it is determined that the recording of images for all colors (Y, M, C) is completed, and this subroutine is completed.

Therefore, a Y-color image is recorded,
When the recording of the Y-color image is completed, UV light UV1 having a wavelength of 420 nm is irradiated for a predetermined time so that the unrecorded portion of the Y-color does not develop color, and after fixing, the density of the image is measured.
A color image is recorded, and when the recording of the M color image is completed, UV2 with a wavelength of 365 nm is irradiated for a predetermined time so that the unrecorded part of the M color does not develop color, and after fixing, the image density is measured. Finally, the C color image is recorded. Further, at the time of recording of each color, the image data at the time of recording is changed for each heating element of the thermal head so that the thermal energy at the time of recording has the same characteristic for each heating element.

As described above, in this embodiment, when recording images of Y, M, and C colors on the thermal recording material,
Since the image data is changed so that the characteristics of the color density of each image are the same for each color, it is possible to reduce the density unevenness even if images of one line are simultaneously printed by using a plurality of heating elements. Further, even when a plurality of colors are mixed to express a specific color, the above correction is performed for each color, so that the image of each color has an appropriate density, and it is possible to record an image without color unevenness. Become.

The present inventor actually measured the resistance value of each heating element of the thermal head, created a resistance value correction table, and recorded an image of constant density for each color using this resistance value correction table. Sometimes, it was confirmed by experiments that the image was recorded uniformly and the reduction of density unevenness in the image for each color could be visually confirmed. is doing.

In the above embodiment, an example in which different colors are formed by applying different heat energy to the thermal recording material 12 using the thermal head 46 has been described, but the present invention is not limited to this. Instead, for example, it can be used when recording is performed so that heat energy due to irradiation of a light beam is supplied to the heat-sensitive recording material to develop different colors. In this case, the same effect as that of the above embodiment can be obtained by replacing the thermal head 46 of the above embodiment with an optical head that emits a light beam and controlling the irradiation energy of the light beam, that is, the heat energy. A recording material that emits different colors by irradiating light beams having different wavelengths in the order of image recording, for example, a recording material that emits each color of YMC by irradiating light beams having different wavelengths λ1, λ2, and λ3. It can be easily adapted even when using.

In the above examples, the heat-sensitive recording material provided with a plurality of color-developing layers for coloring different colors has been described, but the present invention is not limited to this, and a single-color color-developing layer is provided. It is also applicable to a recording material and a recording material in which a plurality of color forming layers that emit the same color are laminated. For example, when the present invention is applied to a line drawing device such as a plotter as an apparatus, an image, that is, recording without density unevenness and color unevenness in an overlapping portion of line images is possible.
You can prevent thick lines from overlapping at the thin lines. This enables precise drawing.

In the above embodiment, in order to correct the resistance value of each heating element, the resistance value was measured in advance and the image data was corrected based on the measured value. However, a densitometer is provided. It is also possible to measure the concentration by using the measured concentration, calculate the resistance value of the heating element based on the measured concentration, and correct the resistance value based on the calculated resistance value.

In the above embodiment, the case where the heat energy generated changes according to the amount of change in the resistance value of each heating element has been described, but the relationship between the image density data and the color density is predetermined. It can also be used when it is a function.

In the above embodiment, the case where the resistance value correction table is provided to correct the resistance value of each heating element has been described. However, the LUT is directly corrected without providing the resistance value correction table. You can Furthermore, the resistance value correction table can be configured by an electric circuit such as an amplifier circuit.

In the above embodiment, an example in which digital data is input for each pixel as image data has been described, but the present invention is not limited to the type of data, and the density of an image is directly read. Use a scanner,
The present invention can be applied to analog data output from a scanner or the like.

[0062]

As described above, according to the present invention, since a plurality of heating elements are corrected so that the heat energies generated when the same image data is the same, a plurality of heating elements are used. The image density can be evenly recorded even when the image is recorded by using a plurality of heating elements, and even when the color image is recorded using a plurality of heating elements, the image density of each color is the optimum density. Since the image is recorded evenly, there is an effect that an image can be recorded without unevenness in density depending on the color to be recorded.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a control device for a digital color printer according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a schematic configuration of a digital color printer.

FIG. 3 is a cross-sectional view showing a thermal recording material used in an example of the present invention.

FIG. 4 is a diagram showing the relationship between recording energy (image data) and color density for developing three colors of YMC in a thermal recording material.

FIG. 5 is a diagram showing the relationship between recording energy (image data) and color density for a specific color of the thermosensitive recording material.

FIG. 6 is a diagram showing a relationship between recording energy (image data) and a driving value in a specific color of the thermosensitive recording material.

FIG. 7 is a flowchart showing a control main routine according to the embodiment of the present invention.

FIG. 8 is a flowchart showing a subroutine for controlling image recording.

FIG. 9 is a schematic diagram showing an internal configuration of a thermal head.

FIG. 10 is a front view showing a thermosensitive recording material used in this example.

FIG. 11 is a line showing the relationship between recording energy (image density data) and color density when recording is performed with a heating element having an ideal resistance value in a specific color of a thermal recording material and a heating element of a specific thermal head. It is a figure.

FIG. 12 is a diagram showing respective correction characteristics for matching the heating element of the thermal head with the heating element having an ideal resistance value.

[Explanation of symbols]

 10 Digital Color Printer 12 Thermosensitive Recording Material 26 Control Device 37 Resistance Value Correction Table 46 Thermal Head 61 Resistance 62 Heating Element

Claims (1)

Claim: What is claimed is: 1. A heat-sensitive recording material comprising a plurality of color-developing layers which are colored in different colors when heat energy is supplied to the heat-sensitive recording material. When a heat source having an element is used to simultaneously supply heat energy based on image data to record a color image, the relationship between the input signal and the heat energy generated from each of the heating elements based on the input signal has the relationship A correction value for correcting the heating elements so as to be substantially the same is stored in association with each of the heating elements, the image data to be recorded is corrected based on the stored correction values, and each color is corrected in accordance with the corrected image data. An image recording method, wherein a color image is recorded by developing a color.