JPH09118029A - Gradation image-recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming high definition gradation images without making a diameter of a beam light very small. SOLUTION: This is a method for forming gradation images with the use of a recording material that can form dot images with high-density energy light. A diameter of the high-density energy light is made equal at least to a maximum diameter (c) of a dot and, an intensity of energy of the high-density energy light is made low, so that dots (b), (a) of smaller diameters than the maximum diameter of the dot are formed in the recording material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation image forming method for forming gradation images by changing the area of halftone dots.

[0002]

2. Description of the Related Art In recent years, due to an increasing demand for more faithful reproduction of original images, gradation recording by area gradation or density gradation has been put to practical use by using a high-definition plate-making printing machine. As a gradation image by area gradation, halftone dot gradation is known in which the area of a pixel is varied to obtain gradation.

In order to express multiple gradations with halftone dots, it is generally necessary to form halftone dots with an accuracy of 1/200 or less of the unit size of halftone dots. Furthermore, in order to form a multicolor gradation image, the dot arrangement is made different for each color in order to prevent so-called color moire that occurs when the primary colors are superimposed. Particularly, in the case of halftone dot gradation, the halftone dot angle is changed, but in order to accurately express the halftone dot angle, generally, the halftone dot is formed with 1/10 or less of the unit size of the halftone dot. Precision is required.

[0004]

In order to satisfy the above-mentioned accuracy, a device capable of forming a scanning image having a vertical resolution of about 175 lpi and a horizontal resolution of 2000 dpi or more is usually used.
A recording head capable of irradiating a laser beam having a beam diameter of 25 μm or less is provided. However, in order to make the diameter of the laser light small, the beam light is narrowed down through a lens or the like, but as the beam diameter becomes smaller, higher optical accuracy is required, and the recording head becomes complicated and the manufacturing cost is reduced. There is a problem that is high.

Therefore, the present invention has been made in view of the above circumstances, and provides a gradation image forming method capable of obtaining a high-definition gradation image without reducing the diameter of the beam light. To aim.

[0006]

A gradation image forming method according to the present invention is a gradation image forming method using a recording material capable of forming a halftone image by irradiating high density energy light. The diameter of the high-density energy light is at least equal to the maximum diameter of the halftone dots, and the energy intensity of the high-density energy light is reduced to form halftone dots having a diameter smaller than the maximum diameter of the halftone dots on the recording material. It is a thing.

Further, a recording head in which a plurality of light sources for generating high-density energy light are arranged in the sub-scanning direction is moved in the main scanning direction orthogonal to the sub-scanning direction to form a multicolor halftone image on the recording material. A gradation image recording method for scanning recording, comprising:
The energy intensity of the high-density energy light is lowered to form halftone dots having a diameter smaller than the maximum diameter of the halftone dots on the recording material, and the installation angle of the recording head is set to a different angle for each color. The recording head is moved in a direction orthogonal to the longitudinal direction of the recording head.

According to the gradation image forming method of the present invention, when the diameter of the high density laser beam irradiated to the recording material is set to be equal to or larger than the maximum diameter of the halftone dot and fixed, and the diameter of the halftone dot is changed, , By changing the energy intensity of the high-density energy light. This invention focuses on the fact that the energy distribution of high-density energy light is a Gaussian distribution, and by changing the intensity of high-density energy light,
It utilizes the fact that the region exceeding the energy intensity threshold peculiar to the recording material changes.

Therefore, even when the recording material is irradiated with the high-density energy light having a large beam diameter, the energy density of the high-density energy light is changed so that the beam diameter of the high-density energy light actually irradiated is larger than that of the actual irradiation. It is possible to reproduce halftone dots of small diameter.

Further, a recording head in which a plurality of light sources for generating high-density energy light are arranged in the sub-scanning direction is moved in the main scanning direction orthogonal to the sub-scanning direction to form a multicolor halftone image on the recording material. In the gradation image recording method of scanning recording, the installation angle of the recording head is changed every time a halftone image of each color is recorded, and in this state, the recording head is moved in a direction orthogonal to the longitudinal direction of the recording head.

As a result, the array angle of the light source changes and the scanning direction changes every time each color is recorded. When changing the diameter of the halftone dot, the energy intensity of the high-density energy light is changed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the recording sensitivity of the laser light recording material applicable to the present invention. As shown in FIG. 1, the recording material has a unique threshold value for energy intensity, and the recording material is divided into a recording area and a recording area on the basis of this threshold value.

Since the energy distribution of the laser beam is a Gaussian distribution, a halftone dot image is formed on the recording material in the region where the energy level exceeds the specific threshold value of the recording material. When the energy intensity of laser light is increased,
Since the area exceeding the threshold value is enlarged, the diameter of the halftone dot formed on the recording material is increased.

FIG. 2 shows the relationship between the energy intensity of the laser beam and the diameter of the halftone dots formed on the recording material. As shown in FIG. 2, as the energy intensity of the laser light is increased, the area exceeding the threshold value is expanded in proportion to this and the diameter of the halftone dot is increased. Therefore, as shown in (c) in the figure, when the energy intensity of the laser light applied to the recording material is maximum, the predetermined energy region is set to exceed the threshold value, and the unit size of the halftone dot (maximum halftone dot diameter). And below,
As shown in (a) and (b) in the figure, the diameter of the halftone dot can be reduced by lowering the energy intensity of the laser light and reducing the energy region exceeding the threshold value.

In the above gradation image forming method, the case where a halftone image is formed using one beam has been described.
The case of forming a halftone image using a plurality of beams will be described.

FIG. 3 shows a case where a halftone image is formed by using two beams which are adjacent to each other in the sub-scanning direction. In the figure, a dark dot is the first scan and a light dot is the second scan. Is shown. In the figure, (a) shows a state in which the outlines of the unit size of the halftone dot overlap each other, the two beams 301 and 303 are adjacent to each other, and the halftone dot image is 50% at a halftone dot angle of 45 degrees with the scanning direction. It shows the case of forming.

Further, FIG. 3B shows a state in which approximately half of the unit size of the halftone dot overlap each other, and the two beams 305 and 307.
Are adjacent to each other, and a halftone dot image of 50% is formed at a halftone dot angle with the scanning direction. Since the halftone image shown in FIG. 3B has no interval between the halftone dots in the sub-scanning direction, a high-definition halftone image can be formed.

In the embodiments described above, the case where the light source is a laser beam has been described, but a light emitting diode may be used.

A case will be described below in which a gradation image is formed by changing the halftone dot angle for each primary color in order to prevent color moire when recording multiple colors in the above-mentioned area gradation. FIG. 4 shows a device for changing the dot angle. As shown in FIG. 4, the recording material 403 placed on the table 401 is optically recorded by an array head 405 that irradiates a plurality of laser beams in an array. The array head 405 is a ball screw 4 for moving the array head 405 in the main scanning direction by driving the motor 407.
It is supported by an arm 411 containing 09.

As shown in FIG. 5, the array head 405 has a light source section 503 in which a plurality of laser light sources 501 are arranged in the sub-scanning direction, and the light source section 503 rotates according to the halftone dot angle. The pitch of each laser light source is preferably set to be larger than 1/2 of the unit size of a halftone dot. Arm 4
11 is supported by ball screws 415 and guide rails 417 arranged on both sides of the table 401 in order to move the arm 411 in the sub scanning direction by driving the motor 413.

In this example, a heat roller 419 for laminating is provided as the recording material in order to correspond to the recording material (see the embodiment) in which the transfer sheet is laminated on the image receiving sheet. The heat roller 419 is the motor 4
The heat roller 419 is supported by ball screws 423 and guide rails 425 arranged on both sides of the table 401 in order to move the heat roller 419 in the sub-scanning direction by driving 21.

To change the angle of the halftone dots, the array head 4
05 is rotated by a required angle to set the position of the array head 405, and scanning is started with the upper left corner as the scanning start point. The scanning direction is a direction orthogonal to the installation angle of the array head.

FIG. 5 shows that when the halftone dot angles are 0 ° and 45 °,
The scanning direction of the array head 405 is shown. That is, as shown in FIG. 5A, when the halftone dot angle is 0 °, the array head 405 is set parallel to the sub-scanning direction,
The array head 405 moves in a direction orthogonal to the installation angle. When the halftone dot angle is 45 °, the array head 40
5 is rotated by 45 ° with respect to the sub-scanning direction and moved in a direction orthogonal to the angle of the array head 405.

There are various combinations of halftone dot angles for each primary color that can prevent color moire, for example, K (black) =
0 °, C (cyan) = 45 °, M (magenta) = 30
And Y (yellow) = 15 °. In this example, a case is shown in which a plurality of light sources moves the array head arranged in the sub-scanning direction in the main scanning direction, but an array head in which a plurality of light sources are arranged in the main scanning direction is set in the sub-scanning direction. You may move to.

[0025]

EXAMPLES The gradation image forming method of the present invention was carried out with a recording material having the following constitution. (1) Preparation of thermal transfer sheet (a) Preparation of light-heat conversion layer (i) Preparation of mother liquor for coating liquid 20 parts by weight of carbon black (Mitsubishi Chemical Co., Ltd., Mitsubishi carbon black, MA-100, CIPigment Black 7) Dispersion aid Agent 6 parts by weight (Johnson Polymer Co., Ltd., 30% aqueous solution of John Cryl J-62) Ion-exchanged water 80 parts by weight Isopropyl alcohol 20 parts by weight Glass beads 100 parts by weight Paint shaker (manufactured by Toyo Seiki Co., Ltd.) A mother liquor was prepared by using the dispersion treatment for 2 hours. (Ii) Preparation of coating liquid Mother liquor 100 parts by weight Polyvinyl alcohol 3 parts by weight (Kuraray Co., Ltd., Poval Type 205) Isopropyl alcohol 100 parts by weight Ion-exchanged water 450 parts by weight The above components are mixed with a stirrer with stirring. A coating solution for the photothermal conversion layer was prepared. (Iii) Preparation of support On the polyethylene terephthalate having a coating thickness of 7.5 μm for the photothermal conversion layer, a styrene-butadiene copolymer (thickness 0.5 μm) and gelatin (thickness 0.1 μm) were used as an undercoat layer.
A film provided with m) in this order was prepared as a support for a thermal transfer sheet. The coating solution for the photothermal conversion layer was applied onto this support for 1 minute by using a spin coater (foamer), and the coated product was dried for 2 minutes in an oven at 100 ° C. to obtain the light conversion layer. (Thick film by stylus thick film meter: 0.3 μm,
A light absorption rate of 90% at a wavelength of 488 nm was prepared. (B) Lamination of thermal release layer (i) Preparation of coating liquid 1 part by weight of nitrocellulose (Type RS1 / 2 manufactured by Daicel Corp.) 100 parts by weight of methyl ethyl ketone 20 parts by weight of propylene glycol monomethyl ether acetate While stirring the above components with a stirrer To prepare a heat release layer coating solution. (Ii) Application of thermal release layer On the surface of the photothermal conversion layer provided on the transfer sheet support,
The coating solution for the heat release layer was applied for 1 minute using a spin coater (Wola), and the coated product was dried in an oven at 100 ° C for 2 minutes. Further, the above-mentioned coating solution for thermal release layer was used to dry coat under the same conditions on a polyester film having a smooth surface. (C) Lamination of image forming layer (magenta) (i) Preparation of mother liquor for coating liquid Polyvinyl butyral 63 parts by weight (Denka Butyral # 2000-L manufactured by Denki Kagaku Kogyo Co., Ltd.) 20 wt% solution (solvent: n -Propyl alcohol) Color material 12 parts by weight (magenta pigment, manufactured by Toyo Ink Co., Ltd., Lionol Red 6B4290G, CI Pigment Red 57: 1) Dispersion aid 0.8 parts by weight (IC Corporation, Solspers S-20,000) ) N-Propyl alcohol 60 parts by weight Glass beads 100 parts by weight The above components were dispersed for 2 hours using a paint shaker (manufactured by Toyo Seiki Co., Ltd.) to prepare a mother liquor. (Ii) Preparation of coating liquid Mother liquor 10 parts by weight n-Propyl alcohol 60 parts by weight Surfactant 0.05 parts by weight (MegaFac F-176PF, manufactured by Dainippon Ink and Chemicals, Inc.) The above components are mixed with stirring with a stirrer. Then, a magenta image forming layer coating solution was prepared. (Iii) Application of Magenta Image Forming Layer Coating Liquid The above image forming layer coating liquid was dried on the surface of the heat release layer provided on the above-mentioned thermal transfer sheet support for 1 minute using a spin coater (fola). The coated product was dried in an oven at 100 ° C for 2 minutes, and the optical density with a Macbeth densitometer was 0.7.
The image forming layers of were laminated to prepare a thermal transfer sheet.

(2) Preparation of image-receiving element (a) Preparation of coating solution for image-receiving layer (i) Coating solution for image-receiving first layer Polyvinyl chloride 9 parts by weight (Zeon 25 manufactured by Nippon Zeon Co., Ltd.) Surfactant Agent 0.1 part by weight (manufactured by Dainippon Ink and Chemicals, Megafac F-177P) Methyl ethyl ketone 130 parts by weight Toluene 35 parts by weight Cyclohexanone 20 parts by weight Dimethylformamide 20 parts by weight (ii) Image receiving second layer coating liquid methyl methacrylate / Ethyl acrylate / methacrylic acid copolymer (Mitsubishi Rayon Co., Ltd., trade name Dianal BR-77) 17 parts by weight Alkyl acrylate / alkyl methacrylate copolymer (Mitsubishi Rayon Co., Ltd., trade name Dianal BR-) 64) 17 parts by weight Pentaerythritol tetraacrylate 22 parts by weight (Shin Nakamura Chemical ( ), Trade name A-TMMT) Surfactant 0.4 parts by weight (Dainippon Ink and Co., trade name Megafac F-177P) Methyl ethyl ketone 100 parts by weight Hydroquinone monomethyl ether 0.05 parts by weight 2,2- Dimethoxy-2-phenylacetophenone 1.5 parts by weight (photopolymerization initiator) (b) Coating of image receiving layer Polyethylene terephthalate (PET) having a thickness of 75 μm
Using the film as a support, the above-mentioned coating solution for the first layer was applied using a spin coater (Wola) and dried in an oven at 100 ° C for 2 minutes. The thick film of the obtained first layer was 1 μm. On the first layer, a coating was applied in the same manner using a coating liquid for a second layer, and an image receiving second layer having a dry film thickness of 26 μm was laminated to obtain an image receiving element.

An example of the process for producing a color proof by the surprint method by laser recording will be described below. 1) The image receiving layer and the thermal transfer sheet are laminated while the image forming layer of the thermal transfer sheet is in contact with the image receiving layer of the image receiving element. 2) High-density energy light (laser light) is focused on the photothermal conversion layer from the thermal transfer sheet support side with an appropriate beam diameter. A laser beam modulated with the color-separated image signal is scanned and recorded.

3) The laser-recorded thermal transfer sheet is separated from the image receiving element and peeled off and developed. 4) The thermal transfer sheet of the second hue is laminated on the image receiving element on which the image of the first hue is formed. 5) The position of the laser beam is aligned with the position of the first image, and the above steps 2) and 3) are repeated to form an image of the second hue on the first image.

6) Sequentially, a third and optionally a fourth hue resolution image is laser recorded on the same image receiving element. 7) Release the image receiving element to which the four-color separated image has been transferred. Then, the image-receiving layer on which the image is transferred is overlaid on the white paper, passed through a thermal laminator under heat and pressure, and adhered to the white paper.

8) When the image-receiving layer is photopolymerizable, the entire surface is exposed to ultraviolet light through the transparent support of the image-receiving element to photo-cur the image-receiving layer. 9) By peeling off the image receiving support, the transferred four-color image is obtained together with the photocurable image receiving layer on the white paper.

[0031]

According to the above-described invention, there is provided a gradation image forming method using a recording material capable of forming a halftone dot image by irradiating high density energy light, wherein the diameter of the high density energy light is changed. The diameter of the beam is at least equal to the maximum diameter of the halftone dots, and the energy intensity of the high-density energy light is lowered to form halftone dots having a diameter smaller than the maximum diameter of the halftone dots on the recording material. Without reducing
By reducing the high-density energy intensity, halftone dots having a diameter smaller than the beam diameter can be formed.

Further, a recording head in which a plurality of light sources for generating high-density energy light are arranged in the sub-scanning direction is moved in the main scanning direction orthogonal to the sub-scanning direction to form a multicolor halftone image on the recording material. A gradation image recording method for scanning recording, comprising:
The energy intensity of the high-density energy light is lowered to form halftone dots having a diameter smaller than the maximum diameter of the halftone dots on the recording material, and the installation angle of the recording head is set to a different angle for each color. Since the recording head is moved in the direction orthogonal to the longitudinal direction of the recording head, it is possible to accurately reproduce the halftone dot angle and avoid color moire without making the diameter of the high density energy light minute. You can

[Brief description of the drawings]

FIG. 1 is a diagram showing the recording sensitivity of a laser light recording material applicable to the present invention.

FIG. 2 is a diagram showing the relationship between the energy intensity of laser light and the diameter of halftone dots formed on a recording material.

FIG. 3 is a diagram showing a case where a halftone image is formed using two beams which are adjacent to each other in the sub-scanning direction.

FIG. 4 is a view showing an apparatus for changing a halftone dot angle.

FIG. 5 is a diagram showing the scanning direction of the array head when the halftone dot angles are 0 ° and 45 °.

[Explanation of symbols]

 301, 303, 305, 307 Laser beam 401 Table 403 Recording material 405 Array head 407, 413, 421 Motor 409, 415, 423 Ball screw 411 Arm 417, 425 Guide rail 419 Heat roller 501 Light source 503 Light source part

Claims (2)

[Claims] 1. A gradation image forming method using a recording material capable of irradiating a high density energy light to form a halftone dot image, wherein the diameter of the high density energy light is at least equal to the maximum diameter of the halftone dot. The gradation image forming method is characterized in that a halftone dot having a diameter smaller than the maximum diameter of the halftone dots is formed on the recording material by reducing the energy intensity of the high density energy light. 2. A recording head, in which a plurality of light sources for generating high-density energy light are arranged in the sub-scanning direction, is moved in the main scanning direction orthogonal to the sub-scanning direction to form a multicolor halftone image on the recording material. A gradation image recording method of scanning recording, wherein the energy intensity of the high-density energy light is reduced to form halftone dots having a diameter smaller than the maximum diameter of the halftone dots on the recording material, and A gradation image forming method characterized in that the installation angle is set to be different for each color and the recording head is moved in a direction orthogonal to the longitudinal direction of the recording head.