JPH058415A - Image recording method and apparatus - Google Patents

Abstract

PURPOSE:To obtain a color printing method which can record so as to present modulation in black color or a character when an image is recorded. CONSTITUTION:An image is recorded on a thermal recording material 12 by three colors of Y, M, C colors based on an image data of four colors of Y, M, C, K colors. The four colors image data of Y, M, C, K colors is converted to a three colors data of Y, M, C colors with a conversion circuit 32 to be stored in each frame memory 34. A thermal head 46 is heated based on this stored data, and an image of a color corresponding to this heating is formed on a thermal recording material 12. At that time, when black color or a character is colored, recording is performed so that a colored density of each coloring layer corresponding to the black color or the character becomes higher than the maximum value of each coloring density of the image other than black. Therefore, the black color or the character which was recorded on the thermal recording material 12 becomes higher than the density of each color of the image. Therefore, the black color or the character can be recorded in the density easy to be discriminated.

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 apparatus, and more particularly to an image recording method and apparatus for recording an image 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 of 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. Therefore, 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 separated into Y (yellow), M (magenta), C (cyan), and K (black) color image data for each color component, and the color image is processed based on the image data of each color. An image is recorded on each heat sensitive layer.

In addition, when a character is recorded on an image, character data may be separately input so that the image and the character can be easily distinguished.

By the way, it is complicated to manufacture a heat-sensitive material having a heat-sensitive layer corresponding to each color as described above, and the cost is high. Therefore, three colors of Y, M and C are used. There is a demand for a method of recording an image on the heat-sensitive material.

However, when a black image and characters are recorded on the multicolor thermosensitive recording material by the combination of three colors of Y, M and C as described above, each black color component is close to the density of the color image. There was no sharpness. Therefore, if a character and a color image are recorded on the same screen, there is a problem that the character and the image are not well separated and it is difficult to distinguish the character.

There is also a heat-sensitive recording material for recording an image by irradiating light beams of different wavelength ranges. Such a heat-sensitive recording material as a light-sensitive material is one in which two components of a two-component type heat-sensitive color developing medium are separated and arranged with a microcapsule containing a photocurable composition separated (Japanese Patent Laid-Open No. 52-
No. 89915), a layer containing a vinyl monomer having an acidic group and a photopolymerizable composition, an isolation layer, and a layer composed of an electron-donating colorless dye (JP-A-61-1238).
No. 38), a plurality of photosensitive layers that emit different colors are provided, and each photosensitive layer has a central wavelength (JP-A 1-2).
No. 24930, Japanese Patent Laid-Open No. 2-19710) and the like have been proposed. According to this, for example, by irradiating the heat-sensitive recording material with a light beam having a different ultraviolet wavelength range depending on the recorded image, the coloring of the hue corresponding to the irradiated light beam area and the light beam wavelength range is suppressed. To be done. Then, by heating the heat-sensitive recording material, the heat-sensitive recording material in the region not irradiated with the light beam is colored to form an image.

Even if this light-sensitive type heat-sensitive recording material is used, there are the same problems as described above.

[0010]

SUMMARY OF THE INVENTION In consideration of the above facts, it is an object of the present invention to provide an image recording method capable of recording an image in a black color so that the image has a sharp contrast.

In addition to the above object, it is another object of the image recording apparatus to provide an image recording apparatus capable of recording in black and characters so that the characters are sharp.

[0012]

In order to achieve the above object, the invention according to claim 1 develops different colors by being supplied with heat energy, and when they all have the same density, they are black. When recording an image on a thermosensitive recording material in which a plurality of color forming layers are laminated, recording is performed so that the color forming density of each color forming layer is lower than the maximum color forming density of each color forming layer when a color other than black is formed. In addition, when the black color is developed, the color density of each color forming layer in the area corresponding to the black color is recorded so as to be higher than the maximum value of the color density of the area surrounding the area corresponding to the black color. .

According to a second aspect of the present invention, a heat-sensitive recording material is formed by laminating a plurality of color-developing layers that develop different colors by being supplied with heat energy and that turn black when they all have the same density. When recording an image other than characters, the image is recorded so that the color density of each color forming layer is lower than the maximum color density of each color forming layer, and at least one of the color forming layers is recorded. When a character image is recorded by coloring, the color density of each color forming layer in the part corresponding to the character image should be higher than the maximum value of the color density of the part around the part corresponding to the character image. Is characterized by.

According to a third aspect of the present invention, there is provided a heat source for supplying heat energy to a heat-sensitive recording material in which a plurality of color-developing layers that develop different colors according to the amount of heat energy supplied are laminated.
Irradiation means for irradiating each color-developing layer with light of a wavelength corresponding to each color-developing layer so that each color-developing layer in a region not recorded by the heat source does not develop color, and when recording an image other than black, each color-developing according to the image. A portion corresponding to black when recording black by controlling the heat source so that heat energy is supplied so that the color density of the layer becomes lower than the maximum color density of each color layer and by causing all of the color layers to color. In the above, by controlling the heat source so that the color density of each color layer is higher than the maximum value of the color density of the area around the area corresponding to the black color, the high heat energy from the color layer that develops with a small amount of heat energy After controlling the heat source so as to supply different heat energy to each color forming layer in the order of the color forming layers to be colored, and after the heat energy is supplied to each color forming layer. Is characterized in that a control means for controlling said irradiating means to irradiate light of a wavelength region that is not recorded in the color developing layer corresponds to the respective color developing layer so as not to color.

According to a fourth aspect of the invention, there is provided a heat source for supplying heat energy to the heat-sensitive recording material in which a plurality of color-developing layers which develop different colors according to the amount of heat energy supplied are laminated.
Irradiation means for irradiating each color-developing layer with light having a wavelength corresponding to each color-developing layer so that each color-developing layer at a portion not recorded by the heat source does not develop color, and when recording an image other than a character, each color-developing according to the image. When the character image is recorded by recording the character image by controlling the heat source so that the heat energy is supplied so that the color density of the layer is lower than the maximum color density of each color layer, and by causing the at least one color layer to color. From the coloring layer that controls the heat source so that the coloring density of each coloring layer in the portion corresponding to is higher than the maximum value of the coloring density of the surrounding portion of the portion corresponding to the character The heat source is controlled so as to supply different heat energy to each color forming layer in the order of the color forming layers that are colored by high heat energy, and the heat is applied to each color forming layer. A control means for controlling the irradiation means so as to irradiate light of a wavelength corresponding to each of the color-developing layers so that the unrecorded portion of the color-developing layer does not develop color after the energy is supplied. It has a feature.

[0016]

According to the invention described in claim 1, the heat-sensitive recording material has a plurality of color-developing layers which are colored in different colors when heat is supplied. Further, when all of the color forming layers develop the same density, the color becomes black. For example, as a heat-sensitive recording material on which an image is formed according to the amount of heat supplied, there are materials that develop different colors depending on the amount of heat supplied. Further, as a heat-sensitive recording material on which an image is formed according to the wavelength of the irradiated light beam, there is a heat-sensitive recording material provided with a medium that develops different colors by a light beam of a different wavelength or a medium that suppresses color development. . When a color other than black is to be developed on these thermosensitive recording materials, recording is performed so that the color density of each color-forming layer is lower than the maximum color density of each color-forming layer. Also, when coloring black,
It is recorded so that the color density of each color-developing layer in the area corresponding to black is higher than the maximum value of the color density in the area surrounding the area corresponding to black. Therefore, the black portion recorded on the heat-sensitive recording material has a higher density than each color of the image. Therefore, black is recorded with a good density that is easy to identify.

The image recording method of the invention described in claim 2 records a character image on the heat-sensitive recording material. When a character image is recorded by coloring at least one of the plurality of coloring layers, the coloring density of each coloring layer in the portion corresponding to the character image is the maximum of the coloring density of the portion surrounding the portion corresponding to the character image. It should be higher than the value. Therefore, the density of the character image in the image is higher than the density of the surroundings. Therefore, a character image having a good density that is not buried in the image is recorded.

Further, the image recording apparatus of the present invention records an image on the heat-sensitive recording material by the heat source. This heat-sensitive recording material is provided with a plurality of heat-sensitive coloring layers that develop different colors. Further, this heat source supplies the heat-sensitive recording material with a heat quantity corresponding to the image data inputted from the control means. The control means controls the heat source so that the maximum density of each color of the image is lower than the maximum color density of each color forming layer. Here, in the image recording apparatus according to claim 3, when the control means records an image so that all the color-forming layers are colored to make it black, each color-forming layer has a higher density than the maximum density of each color of the image. Control the heat source. Further, in the image recording apparatus according to the fourth aspect, when the character image is recorded by coloring at least one coloring layer, the heat source is controlled so that each coloring layer becomes higher than the maximum density of each color of the image. Therefore, when black is recorded, the black portion recorded on the heat-sensitive recording material becomes higher than the density of each color of the image. Therefore, black is recorded with a good density that is easy to identify. Further, when a character image is recorded, the density of the character image in the image recorded on the thermosensitive recording material becomes higher than the density around it.
Therefore, the black and characters in the image are sharp.
Therefore, the image recording method can be easily realized by using this image recording apparatus. In addition, since black is recorded with the three colors of YMC, the black color development process can be omitted and the apparatus can be simplified.

[0019]

Embodiments of the present invention will now be described in detail with reference to the drawings.

In this embodiment, the present invention is applied to a digital color printer 10. [First Embodiment] First, the heat-sensitive recording material 12 used in the first 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 recording materials on a support 22.
The thermosensitive coloring layers comprising the thermosensitive recording layers 20, 18 and 16 are sequentially laminated. A protective layer 14 is coated on the surface of the third thermosensitive recording layer 16 in order to protect the color developing 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 00 ± 20 nm and a coupler that reacts with the diazonium salt compound under heat to develop a color.

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 a diazonium salt contained in the third heat-sensitive recording layer 16 is added. Color the coupler. Then 400 ± 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 been 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 generate sufficient heat 3 for recording the first heat-sensitive recording layer 20. 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 is already decomposed and the color forming ability is lost.

Here, in the present embodiment, the first, second and third
The coloring hues of the respective heat-sensitive recording layers are selected so as to be the three primary colors in the subtractive color mixture, 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 heat-sensitive 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 heat energy. That is, the Y layer 16 is colored according to the thermal energy in the thermal energy region Py, and the thermal energy region Pm is generated.
The M layer 18 is colored in accordance with the heat energy in the inside, and the C layer 20 is colored in accordance with the heat energy in the heat energy region Pc.

Next, a digital color printer 10 applicable to the first 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 on the downstream side of the transport roller 54 so that the heat-sensitive recording material 12 is guided. Therefore, the thermal recording material 12 is conveyed in a substantially C shape by the plurality of guide plates 56.

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 according to the insertion or unloading of the thermosensitive 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 heat-sensitive recording material 12, corresponding to the side of the heat-sensitive recording material 12 on which the coloring layer 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 as a recording head is arranged on the other side of the conveying path of the thermal recording material 12. A heating element 62 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 in accordance with the image signal to heat the thermal recording material 12. . The amount of heat generated by the heating element 62 can be changed depending on the heating time.

A positioning signal is also output from the controller 26 to the thermal head 46.
A positioning signal is output at the time of heat recording of the first dye layer (Y dye layer in this embodiment), and bar-shaped positioning marks are recorded. It should be noted that this positioning mark is recorded after a lapse of a predetermined time from the time when the tip portion of the thermosensitive recording material 12 is detected by the first photoelectric sensor 70. Based on this positioning mark, the recording time for recording the other dye 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 transport roller 64. This second photoelectric sensor 72
Is connected to the control device 26 so as to detect the positioning mark 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 rotary 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 according to a signal from the control device 26.

The wavelength of the light emitted from the light source 78 is
It can be switched between about 365 nm and 420 nm, and is used for fixing the Y dye layer and the M dye layer of the thermal recording material 12.

A transport path switching means 74 having a cam 76 is provided on the downstream side of the transport roller 64 and the thermal recording material 12 is transported by rotating the cam 76 in response to a signal from the control device 26. The discharge direction is the route (right side in Fig. 2)
Alternatively, the loop direction (upper side in FIG. 2) is switched.

Thermal recording material 12 guided in the discharge direction
Are transported to the vicinity of the transport roller 54. Here, by rotating the conveyance roller 54 in the reverse direction, the heat-sensitive recording material 12 guided and conveyed 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 the present embodiment, since the same surface is scanned (heated) three times, the table 52
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,
The thermosensitive recording material 12 is taken out to the table 52 with the cam 76 in the ejecting direction.

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. The conversion circuit 32 converts the input digital image signal into a signal for each color of Y, M and C and outputs it to the corresponding frame memory 34. An image signal for one image of a color corresponding to each frame memory 34 is stored. In addition, the host computer 30
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 transferred to the conversion circuit 32 and the frame memory 3.
4 and is synchronized.

YMC output from the frame memory 34
The signal, that is, the image density data is converted into a YMC color drive value according to the color density by a look-up table (hereinafter referred to as LUT) 36, and is then output to the line buffer 42 for each line via the switch 38. Has been done. Here, the switch 38 is connected to the controller 40, and a signal corresponding to the color at the time of recording is supplied to the line buffer 42.

The line buffer 42 includes a controller 4
A vertical sync signal is input from 0, and a signal is output to the thermal head 46 via the driver 44 based on the vertical sync 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 the 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 hue recorded on the thermosensitive recording material 12. As a result, the light source 78 is set to 365 nm and 420 nm.
thermal recording material 12 by switching to a light beam having a wavelength of nm
It is designed to irradiate.

By doing so, recording of Y in the first scanning, recording of M in the second scanning,
In the third scanning, C is recorded.

Next, the look-up table (LUT) will be described with reference to FIGS. 6 and 7. In the thermal recording material 12, for example, the characteristic of the color density D with respect to the printing energy E according to the image density data is not optimum as shown in FIG. As a result, even if recording is performed in order to obtain a desired color density, the color density of the thermosensitive 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 printing energy E is optimized. For example, with the printing energy Ea, the thermosensitive recording material 12 has the color density Da. Desired color density D at this printing energy Ea
Has a density Da ', the printing energy Ea' is required. Therefore, a table is prepared in which the printing energy Ea 'corresponds to the density Da' of the coloring density D. That is, as shown in FIG. 7, a characteristic of the driving value (heat quantity) of the thermal head that can obtain the optimum color density according to the image density data is prepared, and this characteristic is used as the LUT.

Here, the handling of the image density data in this embodiment will be described. First, in the case of subtractive color mixing, it is known that Y, M, and C colors are mixed at a predetermined mixing ratio to produce black. If this is shown by the formula,
The following expression (1) is obtained.

Dm (K, i) = Dm (Y, i) + Dm (M, i) + Dm (C, i) (1) where i = 1, 2, 3 (corresponding to Y, M, C) Dm (K, i): Maximum density of black (density of color i) Dm (Y, i): Maximum density of yellow (〃) Dm (M, i): Maximum density of magenta (〃) Dm (C, i) : Maximum density of cyan (〃) Further, the density of black is expressed by the following equation (2), D (K, i) = Dk (Y, i) + Dk (M, i) + Dk (C, i) (2) , I = 1, 2, 3 (corresponding to Y, M, C) D (K, i): Black density (density of color i) Dk (Y, i): Yellow density when black is color-separated (〃) Dk (M, i): Density of magenta when color-separating black (〃) Dk (C, i): Density of cyan when color-separating black (〃)

Further, in this embodiment, when an image is recorded on the heat-sensitive recording material, the maximum density of each color of the image is lower than the maximum color density of each color forming layer. At this time,
When an image is recorded so as to become black by coloring a plurality of coloring layers, each coloring layer is recorded so as to have a higher density than the maximum density of each color of the image. Therefore, the relationship between the image densities can be expressed by the relationship shown in the following expression (3).

Dmr (i) <Dmk (i) ≦ Dm (i) ----- (3) However, i = 1, 2, 3 (corresponding to Y, M, C) Dmr (i): in each color Maximum density of image Dmk (i): Maximum density of each color after black color separation Dm (i): Maximum density at which the material of each color can develop Note that when additional character data is input, Dmr (i) <Dmc (i) ≦ Dm (i) where i = 1, 2, 3 (corresponding to Y, M, C) Dmc (i): It can be replaced with the maximum density of each color after color separation of the character color. At this time, for example, when the change area of the image density is the linear area, the relationship shown in the following expression (4) is established.

1 / αi · Dmr (i) = 1 / βi · Dmk (i) = Dm (i) (4) where i = 1, 2, 3 (corresponding to Y, M, C) αi <βi, βi ≦ 1 As a result, the density Dp (i) at the time of recording is represented by the following equation (5): Dp (i) = αi · D (i) + βi · Dk (i) ----- (5 ) However, i = 1, 2, 3 (corresponding to Y, M, and C) D (i): Density of each color of image data of Y, M, and C to be input Dk (i): Black color to be input It can be expressed as the density of each color after decomposition.

Therefore, by obtaining these coefficients αi and βi, black can be easily converted into three colors of Y, M and C.

The inventor performed a recording experiment by performing conversion based on the data shown in Table 1 below, and it was shown by the experiment that a good result that an image having a sharp contrast in black was recorded was obtained. I'm confirming.

[0054]

[Table 1]

The operation of this embodiment will be described below with reference to FIGS. 8 and 9 according to the flow chart of the control circuit.

First, when the main routine shown in FIG. 8 is executed, an image data conversion subroutine described later is executed in step 102. In this subroutine, the coefficient for converting the input image data (Y, M, C, K, characters) into the data (Y, M, C) corresponding to the color at the time of recording is calculated. Since the character data is the same as the black data, it will be described below with reference to the black data.

When the subroutine ends, step 10
4, the pixel data D (i) is fetched, and step 1
Proceed to 06. In step 106, Y at the time of recording,
The densities of the three colors M and C are calculated and stored in the frame memory 34 in step 108. In step 110, it is judged whether or not the reading of all the pixel data is completed, and if it is not completed, the process returns to step 104,
The conversion of pixel data for one screen is repeatedly executed. When the conversion of the pixel data is completed, the process proceeds to step 112, the image data for one line is read, and the operation value of the thermal head 46 is determined by referring to the LUT 36.
Is output to. In step 114, image recording for one line is performed for each color in accordance with this operation value.
When the image recording for one line is completed, the process proceeds to step 116, it is judged whether or not the recording of one screen for one color is completed, and if it is not completed, the process returns to step 112 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 hue at the time of recording and the line buffer 42 are electrically connected.

When the recording of one screen for one color is completed, the process proceeds to step 118 and all colors (Y, M,
It is determined whether or not the recording of the image data for C) is completed. If not completed, ultraviolet light corresponding to the color for which one screen has been recorded in step 120 is radiated for a predetermined time and the process returns to step 112, and all colors (Y, M,
The image is repeatedly recorded until the recording of the image data for C) is completed.

Next, a subroutine for converting image data (Y, M, C, K, characters) into data (Y, M, C) corresponding to the color at the time of recording will be described with reference to FIG. In this subroutine, black, Y, M, and C described above are used.
The coefficient when converting to the three colors is calculated.

When this subroutine is executed, the routine proceeds to step 150, where the counter value i is set to 1. In addition,
As the counter value i, 1 corresponds to Y color, 2 corresponds to M color, and 3 corresponds to C color. In step 152, the maximum density value Dm (i) for each color forming layer of the thermosensitive recording material 12 is fetched, and the process proceeds to step 154. In step 154, the density setting value, that is, the maximum value Dmk of the black density for each color forming layer of the thermal recording material 12 is set.
(I) and the maximum image density value Dmr (i) are captured.

When the reading of the respective values is completed in step 152 and step 154, step 156
To the coefficient αi and β including the coefficient for converting the black data into the three colors from the captured maximum density value and density setting value.
i is calculated and stored in a memory (not shown) of the control device 26. The coefficients αi and βi are obtained for each of the three colors Y, M, and C (steps 158 and 16).
0). When all the coefficients have been calculated, this subroutine ends.

As described above, in this embodiment, Y, M and C3 are not provided in the heat-sensitive recording material without newly providing a black heat-sensitive layer.
Using a heat-sensitive material with two heat-sensitive recording layers, Y, M, C
Since black recording can be performed by scanning once, the black recording step can be omitted. Therefore, the process can be simplified and the device can be made simple without providing a black recording step. Further, when recording an image so that it becomes black by coloring a plurality of coloring layers, each recording layer is recorded so as to have a density higher than the maximum density of each color of the image. It has the unique effect of Further, since the image recording is not performed at the maximum density of the thermosensitive recording material, the color mixture of the color image is reduced, and the recording energy (heat amount) at the time of image recording can be reduced.
The thermal head has a unique effect that the life of the thermal head is extended because the frequency of continuous recording in the high temperature state is reduced.

[Second Embodiment] In the first embodiment, an example in which different colors are formed by applying different thermal energy to the thermal recording material 12 using the thermal head 46 has been described. As a second embodiment, an example in which different colors are produced by irradiating light beams having different wavelengths will be described.

First, the thermosensitive recording material 1 used in the second embodiment.
2 will be described. When the heat-sensitive recording material 12 is irradiated with light beams in different ultraviolet wavelength ranges, color development of a hue corresponding to the range of the irradiated light beam and the wavelength range of the light beam is suppressed. Then, by heating the heat-sensitive recording material 12, the heat-sensitive recording material 12 in the area not irradiated with the light beam is colored to form an image. The heat-sensitive recording material 12 as such a light-sensitive material is
A two-component thermosensitive coloring medium in which two components are separated and arranged with a microcapsule containing a photocurable composition (JP-A-52-89915), a vinyl monomer having an acidic group and a photopolymerizable composition. Which contains a layer containing a compound, an isolation layer, and a layer composed of an electron-donating colorless dye (Japanese Patent Laid-Open No. 61-123838), and is provided with a plurality of photosensitive layers that emit different colors, each photosensitive layer having a central wavelength. Those which have (Japanese Patent Laid-Open Nos. 1-224930 and 2-19710) have been proposed.

For example, when a latent image is formed on the photocurable composition by exposure to ultraviolet light and then a visible image is formed by heating, the exposure amount E increases as shown in FIG. The color density D decreases as the temperature increases.

Next, the digital color printer 10 used in the second embodiment will be described. Since this digital color printer 10 is substantially the same as that of the first embodiment, the same parts are designated by the reference numerals and detailed description thereof will be omitted. In the second embodiment, since the latent image corresponding to each color is formed by one exposure, the conveyance path is set in the discharge direction (see FIG. 2) as in the first embodiment.
It is not necessary to switch to the right) or the loop direction (upper in FIG. 2). Further, instead of the thermal head 46 as a recording head, a semiconductor laser that develops each color on a thermosensitive recording material is used as an exposure section.

As shown in FIG. 10, the exposure section includes semiconductor lasers 80a, 80b and 80c. The semiconductor lasers 80a, 80b, 80c are
a semiconductor laser 80 driven by a, 81b, and 81c.
a outputs an ultraviolet laser beam L1 having a wavelength of 355 nm, for example, and semiconductor lasers 80b and 80c emit laser beams L2 having wavelengths of 390 nm and 410 nm, respectively.
Output L3. Further, the laser beams L1, L2, L3
The wavelength of corresponds to each color of Y, M, and C that is colored by exposing the heat-sensitive recording material 12 to heat development.

On the laser beam emitting side of the semiconductor laser 80a, a collimator lens 82a for converting the laser beam L1 into a parallel light beam, a cylindrical lens 84a and a reflecting mirror 86 are arranged in order, and the laser beam emitted from the semiconductor laser 80a is arranged. L1 is configured to reach the optical path 88. A collimator lens 82b, a cylindrical lens 84b, and a dichroic mirror 90a are sequentially arranged on the laser beam emission side of the semiconductor laser 80b, and the laser beam L2 emitted from the semiconductor laser 80b reaches the same optical path 88 as described above. Is configured. Similarly, a collimator lens 82c, a cylindrical lens 84c, and a dichroic mirror 90b are sequentially arranged on the laser beam emitting side of the semiconductor laser 80c, and the laser beam L2 emitted from the semiconductor laser 80c is directed to the same optical path 88 as described above. It is configured to reach.

Laser beam L reaching the same optical path 88
1, L2 and L3 are reflected by the two reflecting mirrors 92 and then incident on the polygon mirror 94. The polygon mirror 94 rotates in the direction of the arrow, and the laser beams L1, L2, and L3 reflected by the polygon mirror 94 pass through the fθ lens 96 and are reflected by the cylindrical mirror 98 for correcting the surface tilt, and the thermosensitive recording material 12 The main scanning is performed in the direction of arrow A above. The thermosensitive recording material 12 is transported by a transport roller or the like in a sub-scanning direction (arrow B direction) substantially orthogonal to the main scanning direction. Therefore, the thermal recording material 12 is irradiated with the light beam corresponding to the image for one line by the main scanning. Then, the heat-sensitive recording material 12 is sequentially sub-scanned for one image, so that a light beam corresponding to the image is emitted.

Further, the control device 26 includes a driver 81a,
81b and 81c, and each driver is connected to the semiconductor laser. The digital color printer 10 also includes a heater 48 (FIG. 11), and an image is formed on the thermal recording material 12 by the heat of the heater 48. At this time, in the thermosensitive recording material 12, the color development of the portion irradiated with the light beam by the semiconductor laser is suppressed.

Next, the control device 26 of the second embodiment will be described with reference to FIG. Control device 26 of the second embodiment
Since LUTs 36a, 36b, and 36c are the same as those of the control device 26 of the first embodiment, reference numerals are given and detailed description thereof will be omitted and transition to LUT 36 will be described.

YMC output from the frame memory 34
The signal, that is, the image density data, is converted into a YMC color drive value corresponding to the color density by a look-up table (hereinafter referred to as LUT) 36, and then the buffer 4 corresponding to the YMC color is used.
It is output to 3a, 43b, 43c. Here, each of the buffers 43a, 43b, 43c is connected to the controller 40, and the values stored in each buffer according to the signal from the controller 40 are the respective drivers 81a, 81b,
81c.

The drivers 81a, 81b, and 81c have respective semiconductor lasers 80a, 80b, and 80 according to the input value.
drive c. As a result, the thermal recording material 12 is irradiated with the light beam to record an image.

The controller 40 is connected to the motor 68 via the driver 69 and sends a signal to rotate the platen roller 60. Also, the controller 4
0 is connected to the heater 48 via the heater driver 49, and controls the heater 48 to reach a predetermined temperature. When the thermal recording material 12 passes through the heater 48, the image on the thermal recording material 12 recorded by the semiconductor laser is developed.

Although the driver is used to drive the semiconductor laser in the second embodiment, a modulation element (such as an acousto-optic element) for directly modulating the intensity of light and a modulation circuit may be used.

Next, the LUT will be described. In the thermosensitive recording material 12 used in the second embodiment, the characteristics of the image density data and the color density D are not optimum, as in the first embodiment. As a result, even if exposure is performed 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, as in the first embodiment, a table is created so that the characteristics of the color density D are optimized according to the exposure amount E. That is, a characteristic of the driving value (driving current or the like) of the laser beam that provides the optimum color density according to the image density data is prepared, and this characteristic is used as the LUT.

The operation of the second embodiment will be described below with reference to FIG. 12 according to the flow chart stored in the control device.

First, when the main routine shown in FIG. 12 is executed, the above-mentioned image data conversion subroutine is executed in step 202. In this subroutine, as described in the first embodiment, when the input image data (Y, M, C, K, characters) is converted into the data (Y, M, C) corresponding to the color at the time of recording. The coefficient is calculated. Since the character data is the same as the black data, it will be described below with reference to the black data.

When the subroutine ends, step 20
4, the pixel data D (i) is fetched, and step 2
Proceed to 06. In step 206, Y at the time of recording,
The densities of the three colors M and C are calculated and stored in the frame memory 34 in step 208. In step 210, it is determined whether or not reading of all pixel data is completed. If not completed, the process returns to step 204,
The conversion of pixel data for one screen is repeatedly executed.

When the pixel data conversion is completed, step 2
Go to 12 and read the image data of 1 pixel and LU
The operating value of each semiconductor laser 80 is stored in the buffer 43 with reference to T36. In step 214, one pixel of image recording is performed by simultaneously driving each of the semiconductor lasers 80a, 80b, 80c corresponding to each color to be emitted in accordance with the operation value. When the image recording of one pixel is completed, the process proceeds to step 216, it is determined whether the irradiation of the light beam for one line (main scanning) is completed,
If it has not been completed, the process returns to step 212 and recording is repeated until the recording for one line is completed.
When the recording for one line is completed, the process proceeds to step 218, and it is determined whether or not the irradiation of the light beam for the sub-scan is completed. If not completed, the process returns to step 212 to return to 1
Recording is repeated until the screen irradiation is completed.
When the irradiation of one screen is completed, the process proceeds to step 220, the thermal recording material 12 is thermally developed, and an image is formed on the thermal recording material 12.

As described above, in the second embodiment, the thermosensitive recording material 12 is simultaneously turned on by scanning three semiconductor lasers corresponding to the color to be colored on the thermosensitive recording material 12.
Since the recording of each hue that develops is simultaneously performed, the step for black recording can be omitted, and an image can be recorded by one screen scan without recording according to the color to be developed. Therefore, the processing steps can be simplified.

Further, since the exposure amount is determined so that the density of each color forming layer with respect to the density of black becomes higher than the maximum density of each color of the image, there is a peculiar effect that the recorded image becomes sharp in black. Furthermore, since the color density of the thermosensitive recording material is controlled by controlling the exposure amount of the laser beam, it is possible to control the exposure amount delicately. As a result, an image can be expressed in a subtle gradation that cannot be obtained by thermal recording using a recording head such as a thermal head. Further, by irradiating a light beam having a wavelength corresponding to the coloring layer of the thermosensitive recording material, the thermosensitive recording material 1
2 develops a color corresponding to the wavelength of the light beam. Since the wavelength of this light beam can be easily selected, there is a peculiar effect that the color of the color image formed on the thermosensitive recording material 12 is reduced by developing a color corresponding to the wavelength of the light beam.

In the above embodiment, the case where the character color is black has been described, but the present invention is not limited to this, and can be easily applied to the case where the character color is other than black. That is, when the character color is other than black, the data after conversion of the three colors of Y, M, and C becomes data according to the character color. Furthermore, since the density of each color of Y, M, and C is set to be higher than the maximum density of each color of the image, the color of the characters in the recorded image becomes sharp.

Further, in the above embodiment, Y, M and C are based on five types of data (Y, M, C, K colors and characters).
The example of the case where the conversion and the conversion coefficient when converting into the data of three colors are obtained by calculation has been described.
It may be configured by an electric circuit in which a digital-analog conversion circuit, an amplifier circuit, and the like are combined.

The inventor conducted an experiment by carrying out a conversion based on the data shown in Table 2 below, and conducted an experiment to confirm that a good result that an image with sharpness in black and characters was recorded was obtained. Have confirmed by.

[0086]

[Table 2]

Further, in the above embodiment, an example in which a color image is recorded on the thermosensitive recording material by subtractive color mixing is described, but the present invention is not limited to this, and a color image is formed by additive color mixing. The case of recording can be easily adapted. For example, it can be used for a color display that emits RGB colors. This color display turns black when it is off, so by determining the light emission so that the brightness for black characters and images is lower than the brightness of each color of the image, the displayed image becomes sharp in black. Has the effect. Further, in this color display, since white is formed by mixing RGB colors, it can be realized by replacing the black density used in the above-mentioned embodiment with white. Therefore, by determining the light emission so that each color emission luminance of a white image or character is higher than the maximum luminance of each color of the image, there is an effect that the display image has a sharp white color.

[0088]

As described above, according to the invention described in claim 1, since the density of black is higher than the density of each color of the image, the black formed on the heat-sensitive recording material is sharp. There is an effect.

According to the invention described in claim 2, since the density of characters recorded is higher than the density of each color of the image,
There is an effect that the characters in the recorded image are not discriminated and the characters formed on the thermosensitive recording material are sharp.

Further, by using the image recording apparatus described in the present invention, it is possible to use the heat-sensitive materials of the three heat-sensitive recording layers without newly providing the black heat-sensitive layers, and without providing the black recording step. The processing can be simplified and the device can have a simple structure. Further, the number of cases where the recording head is heated to a high temperature so as to obtain the maximum concentration of the heat-sensitive material is reduced, so that the life of the heat-sensitive recording head can be extended.
There is an effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a control device according to a first embodiment.

FIG. 2 is a cross-sectional view showing a schematic configuration of a digital color printer 10.

FIG. 3 is a cross-sectional view showing the structure of a heat-sensitive recording material used in this example.

FIG. 4 is a diagram showing a relationship between printing energy and color density according to the first embodiment.

FIG. 5 is a diagram showing a relationship between an exposure amount and a color density according to the second embodiment.

FIG. 6 is a diagram showing the relationship between printing energy (image density data) and color density.

FIG. 7 is a diagram showing a relationship between printing energy (image density data) and a drive value.

FIG. 8 is a flowchart showing a control main routine of the first embodiment.

FIG. 9 is a flowchart showing a subroutine for converting image data of four colors into data of hues of three colors.

FIG. 10 is a perspective view showing a configuration of an exposure unit in the second embodiment.

FIG. 11 is a block diagram showing a configuration of a control device of a second embodiment.

FIG. 12 is a flowchart showing a control main routine of the second embodiment.

[Explanation of symbols] 10 Digital color printer 12 Thermal recording material 26 Control device 32 conversion circuit 46 thermal head 80 Semiconductor laser

Claims (4)

[Claims] 1. An image is formed on a heat-sensitive recording material in which a plurality of color-developing layers each of which develops a different color by being supplied with heat energy and which becomes substantially black when they all develop to substantially the same density are formed. When recording, when recording a color other than black, recording is performed so that the color density of each color forming layer becomes lower than the maximum color density of each color forming layer, and when black color is generated, the above-mentioned portion in the portion corresponding to the black color is recorded. An image recording method, wherein recording is performed such that the color density of each color layer is higher than the maximum value of the color density of a portion around the portion corresponding to the black color. 2. An image is formed on a heat-sensitive recording material in which a plurality of color-developing layers each of which develops a different color by being supplied with heat energy and which becomes substantially black when all develop to substantially the same density are laminated. When recording an image other than characters, the image is recorded so that the color density of each color forming layer is lower than the maximum color density of each color forming layer, and at least one of the color forming layers is recorded.
When a character image is recorded by coloring two colors, the color density of each color forming layer in the area corresponding to the character image is set to be higher than the maximum value of the color density of the area surrounding the area corresponding to the character image. An image recording method characterized by the above. 3. A heat source for supplying heat energy to a heat-sensitive recording material, in which a plurality of color-forming layers that develop different colors according to the amount of heat energy supplied, are laminated, and each color-forming layer at a portion not recorded by the heat source. Irradiation means for irradiating each color-forming layer with light having a wavelength corresponding to each color-forming layer so as not to develop color, and when recording an image other than black, the color-forming density of each color-forming layer is the maximum depending on the image. When the black color is recorded by controlling the heat source so as to supply the heat energy that is lower than the color density and by recording all the color layers, the color density of each color layer in the portion corresponding to black is the black color. The heat source is controlled so as to be higher than the maximum value of the coloring density of the portion around the portion corresponding to The heat source is controlled so as to supply different heat energy to each color forming layer in the order of the color forming layers to be colored, and after the heat energy is supplied to each color forming layer, the unrecorded portion of the color forming layer is An image recording apparatus comprising: a control unit that controls the irradiation unit so as to irradiate light having a wavelength corresponding to each of the color-developing layers so as not to develop color. 4. A heat source for supplying heat energy to a heat-sensitive recording material, in which a plurality of color-forming layers that develop different colors according to the amount of heat energy supplied, are laminated, and each color-forming layer at a portion not recorded by the heat source. Irradiation means for irradiating each color-forming layer with light having a wavelength corresponding to each color-forming layer so as not to develop color, and when recording an image other than characters, the color-forming density of each color-forming layer is the maximum depending on the image. When the character image is recorded by controlling the heat source so as to supply the heat energy that is lower than the color density and coloring the at least one color-developing layer, the coloring of each of the color-developing layers in the portion corresponding to the character image. The coloring layer that controls the heat source so that the density is higher than the maximum value of the coloring density of the area around the area corresponding to the character and that develops with a small amount of heat energy. The heat source is controlled to supply different heat energies to the respective color forming layers in order of the color forming layers that are colored by high heat energy, and the recording of the color forming layers is performed after the heat energy is supplied to the respective color forming layers. An image recording apparatus, comprising: a control unit that controls the irradiation unit so as to irradiate light having a wavelength corresponding to each of the color-developing layers so that an unexposed portion does not develop color.