JPH08297364A - Image forming sheet, image forming method and simple proof - Google Patents

Abstract

PURPOSE: To obtain an image forming sheet producing difference in heat adhesive strength between exposed and unexposed parts of the photosensitive layer by exposure with semiconductor laser light, capable of forming an image on an image receiving body by hot press transfer and having satisfactory shelf stability even in an environment at high temp. and humidity and to produce a simple proof using the image forming sheet. CONSTITUTION: A photosensitive layer 2 contg. a coloring material, a photopolymerizable compd. having an ethylenically unsatd. group, a heat adhesive binder made of an org. polymer having no photopoly-merizability, a photopolymn. initiator made of a complex of a near IR absorbing cationic dye with a borate anion and a shelf stabilizer consisting of a bisimidazole compd. and a hindered phenol compd. or a hindered amine compd. is formed on a substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to form a monochromatic image or a multicolor superposed color image that can be used as a simple proof print (hereinafter referred to as "simple proof") in a printing process or a hard copy of a computer image. Image forming sheet, an image forming method using the same, and a simple proof formed by the image forming sheet, in particular, a difference in thermal adhesiveness between the exposed portion and the unexposed portion of the photosensitive layer due to semiconductor laser exposure, The present invention relates to an image forming sheet capable of forming an image on an image receptor by thermal pressure transfer and having good storage stability even in a high temperature and high humidity environment, and a simple proof produced using the image forming sheet.

[0002]

2. Description of the Related Art In the printing process, a proof print is generally produced and used to confirm the intention of the orderer, but in addition to this, a temporary printed matter called a simple proof is often produced. This simple proof is, for example, the finish of a color separation film obtained by performing color separation with a color scanner from an original such as a color film on which a subject is photographed, or the state of a color separation film obtained by directly exposing an image produced by a computer. It is used in the printing process for the purpose of confirming, etc., but recently it has begun to be partially applied to proof printing for external printing made by a pressure type flatbed proofing machine.

As a method for obtaining a simple proof by superposing multiple colors, there are an overlay method and a surprint method. The overlay method is a method in which simple proof films of a single color produced by color separation are superposed according to the number of separated colors and observed by transmitted light, and there is an advantage that multicolor printed matter can be easily inspected. However, there are drawbacks such as interference of reflected light due to the presence of the support, reproduction of halftone dots and the like on the finished printed matter, and texture of the image on the printed image.

On the other hand, in the surprint method, a monochromatic image layer formed of a photographic photosensitive material, toner or the like is sequentially laminated on a transparent or opaque image receptor to form a color image. The method is advantageous in that reproducibility such as halftone dot shape is good, and an image similar to a finished printed matter can be obtained by selecting an image receptor. However, image formation by this surprint method requires liquid development after exposure of the photographic photosensitive layer, or electrostatic development of colored toner, so that the process is complicated and much time is required for the production of a simple proof. It takes labor.

A method for producing a simple proof which has improved the problems in the surprint method is disclosed in, for example, JP-A-63-14.
7154 and the like. This method uses a photosensitive sheet in which a colored photosensitive layer is provided between a support and a cover sheet, and the photosensitive layer is formed by a radical polymerization initiator sensitive to ultraviolet rays and generated. Including a photopolymerizable compound that is cured by radicals,
When ultraviolet rays are radiated from a mercury lamp light source or the like through the color separation film, a difference in adhesive force with respect to the image receptor is generated between the exposed portion and the unexposed portion when heat is applied.

Therefore, when the color-separated image is exposed on this photosensitive sheet, the cover sheet is peeled off, and the support is peeled off while thermocompression-bonding the photosensitive layer and the image-receiving paper. The part of the large photosensitive layer is transferred and an image of that color is formed. A simple color proof can be obtained by aligning this operation on the same image receiving paper and repeating the number of separated colors.

In this method, an image is transferred by utilizing the difference in the adhesive force to the image receptor when the exposed portion and the unexposed portion of the photosensitive layer are heated. Therefore, the adhesive force to the image receptor and the photosensitive layer itself are transferred. A fine image can be reproduced by appropriately balancing the cohesive force, and a simple proof can be easily produced on printing paper by thermocompression bonding without the need for complicated development processing, and by selecting the coloring material in the photosensitive layer. It has many advantages such that it can reproduce a color tone similar to that of proof printing ink, and the thickness of the photosensitive layer is close to the thickness of the printing ink, so that the texture can be made similar to the finished printed matter.

However, it has been difficult to apply this photosensitive sheet to the output of a layout scanner or a character image integrating system which has been used in the printing industry in recent years. The layout scanner captures a large number of image originals as digital image data into a computer,
It is a system that allows you to freely edit the layout and layout within a computer.The character image integration system adds character information to this and also performs design and editing comprehensively. The decomposed image data is output as a digital signal.

If an attempt is made to produce a simple proof from these digital signals by using the above-mentioned UV-sensitive sheet, as a suggestion, the laser light is modulated using this signal,
A method is conceivable in which this is used as a light source and the ultraviolet-sensitive sheet is planarly scanned. However, since this photosensitive sheet is sensitive to ultraviolet rays, a laser device capable of continuously oscillating high-power ultraviolet rays necessary for exposure is required. As such a laser device, a He—Cd laser, an Ar laser, and the like are known, but all of them are large in size and expensive, and have many problems in running cost, handleability, stability, etc. and are not practical.

Therefore, in practice, a digital signal of image data is once subjected to scanning exposure on a positive or negative film, liquid development is carried out to produce a color-separated image film, and this image film is superposed on the above-mentioned photosensitive sheet to form a mercury lamp. It was necessary to perform a complicated operation of performing ultraviolet light exposure such as. Therefore, the advantage of the layout scanner and the character image integration system that digitally collectively processes image data and character data cannot be fully utilized.

Recently, in order to solve this problem, development of an image forming method using a small and relatively inexpensive semiconductor laser capable of direct light intensity modulation by a driving current as a light source has been advanced. Since a semiconductor laser generally oscillates near infrared rays, an image forming sheet having sensitivity to near infrared rays is required for this purpose. Regarding these image-forming sheets, including proposals for near-infrared sensitive polymerization initiators, for example, JP-A-64-13142, JP-A-64-13140, JP-A-64-13141, JP-A-64-13144, JP-A-64-1
7048, JP-A-64-72150, JP-A-1-2290053, and JP-A-1-298348.
Japanese Patent Laid-Open No. 2-292560, Japanese Patent Laid-Open No. 2-2
It is described in Japanese Patent Application Laid-Open No. 91561 and Japanese Patent Application Laid-Open No. 3-221506. Further, JP-A-5-265204, JP-A-5-197139, and JP-A-6-594.
No. 50 discloses an image forming method in which near-infrared exposure is performed by a semiconductor laser and a peeling phenomenon described in Japanese Patent Publication No. 43-22901 is used.

Further, the inventors of the present invention previously invented a peeling type photoreceptor having sensitivity to near infrared rays and a photoreceptor having a constitution in which oxygen inhibition during exposure is prevented (Japanese Patent Application No. 5-258730).
No. 5-352239, Japanese Patent Application No. 5-352239), an image forming sheet for simple proof having good near infrared sensitivity and good handleability is obtained. However, in any of the above techniques, an image forming sheet which maintains sufficient sensitivity to a semiconductor laser beam when stored in a hot and humid atmosphere such as a printing work site has not been obtained. This problem of storage stability under high temperature and high humidity has hindered the use of these image forming sheets as a simple proof.

In addition to the above, as a method for producing a simple proof, an electrophotographic method, a sublimation transfer method, an ink jet method and the like are known. For example, "Digital Proof System (DDCP)" was developed as a system for directly producing a simple proof from digital data of images and characters, and its outline is "Printing Magazine Vol. 73.8, 9".
No. ”,“ Journal of the Printing Society of Japan, Vol. 27, No. 4, ”and the like.

The simple electrophotographic proof has good color reproducibility because it is easy to match the color tone of the toner pigment to that of the proof printing ink, but the device configuration is complicated and the device becomes large and expensive. There are drawbacks.

The sublimation transfer method is a method in which a simple proof is obtained by transferring a color image from a donor film containing a dye which is sublimated by heat of a thermal head or semiconductor laser light to an image receiving paper to obtain a simple proof. Is advantageous in that it is small and inexpensive, but there is a problem in the color reproducibility of sublimation dyes and the reproducibility of gradation expression due to the amount of dye sublimation, and the color tone of a simple finished proof is difficult to match with proof prints. Halftone dot reproduction is also unsatisfactory. In addition, since a dedicated image-receiving paper and a sublimable ink sheet are required, running costs increase.

The multi-color ink jet system, the multi-color thermal transfer ink ribbon system, the multi-color dot impact ink ribbon system, etc. may be used as a proof for printed matter, as long as the resolution is about the color output of a personal computer. At present, it is difficult to obtain as high a resolution as possible.

[0017]

[Problems to be Solved by the Invention] As described above,
With current DDCPs and color printers, it is difficult to inexpensively and stably produce high-quality color images that are similar to printed matter, and the current simple proof photosensitive sheet materials can be exposed to DDCP. However, there is a problem that devices such as a laser and a modulation / scanning optical system are expensive and large. In addition, it is difficult to put a photosensitive material whose composition such as a spectral sensitizer and a polymerization initiator is adjusted to have sufficient sensitivity to semiconductor laser light into practical use due to the problem of storage stability under high temperature and high humidity environment. Met.

The present invention has been made to solve the above problems, and therefore an object thereof is to provide a simple proof or a color image having a texture close to that of a proof and an image quality level from a digital signal such as image data. The present invention provides an image forming sheet which can be produced at a relatively low cost and is easy, and has excellent storage stability under a high temperature and high humidity environment, an image forming method, and a simple proof using the same.

[0019]

Means for Solving the Problems The above-mentioned problems are caused by the heat-adhesiveness of a color material on a support, a photopolymerizable compound having an ethylenically unsaturated group, and an organic polymer having no photopolymerizability. A photosensitive layer containing a binder, a photopolymerization initiator composed of a complex of a near infrared absorbing cationic dye and a borate anion, and a storage stabilizer composed of a bisimidazole compound and a hindered phenol compound or a hindered amine compound. The problem can be solved by providing the provided image forming sheet. Here, the photopolymerization initiator is a compound having the following general formula (1).

[0020]

Embedded image

In the formula (1), D ⁺ is a cationic dye having light absorption in the near infrared region, and R ₁ , R ₂ , R ₃ and R ₄
Are each independently alkyl, aryl, alkaryl,
From the group consisting of allyl, aralkyl, alkenyl, alkynyl, silyl, alicyclic, saturated or unsaturated heterocyclic, substituted alkyl, substituted aryl, substituted alkaryl, substituted allyl, substituted aralkyl, substituted alkenyl, substituted alkynyl and substituted silyl. Selected residues, provided that at least one residue of R ₁ , R ₂ , R ₃ or R ₄ has 1 carbon atom
~ 8 alkyl groups.

The above bisimidazole compound has the following general formula (2).

[0023]

[Chemical 4]

In the formula (2), L ₁ , L ₂ and L ₃ are each independently an aryl group such as a phenyl group or a substituted aryl group.

In the above-mentioned image-forming sheet, both the above-mentioned bisimidazole compound and the hindered phenol compound or the hindered amine compound are within the range of 0.1 to 5 parts by weight per 1 part by weight of the photopolymerization initiator. And the hindered phenol compound or hindered amine compound is contained in the bisimidazole compound 1
It is preferably contained in the range of 1 to 5 parts by weight per part by weight.

When forming an image using the above-mentioned image-forming sheet, the image-forming sheet is irradiated with a semiconductor laser beam corresponding to the original image so that the exposed portion and the unexposed portion of the photosensitive layer are thermally tacky. It is preferable that the photosensitive layer is superposed on the image receptor and transferred by heat and pressure to form an image on the image receptor. The present invention also provides a simple proof formed by the above image forming method.

[0027]

Since the photosensitive layer contains the near-infrared absorbing photopolymerization initiator, when the near-infrared ray such as a semiconductor laser beam is irradiated to the original image, the photopolymerizable compound is polymerized to expose the exposed portion. And the unexposed area changes the adhesiveness during heating. That is, a latent image of an image with changed thermal adhesiveness is formed. When this photosensitive layer is superposed on the image receptor and subjected to heat and pressure, the portion having increased thermal adhesiveness is transferred as an image from the support to the image receptor by pressure bonding. A storage stabilizer composed of a bisimidazole compound and a hindered phenol compound or a hindered amine compound has an action of increasing the storage stability of this system against high temperature and high humidity.

Hereinafter, the present invention will be described in more detail with reference to examples. FIG. 1 shows a preferred embodiment of the image forming sheet of the present invention. Image forming sheet 10 of this embodiment
The photosensitive layer 2 is provided on the transparent support 1, and the transparent protective film 3 is further laminated thereon. The support 1 is made of a biaxially stretched polyethylene terephthalate film, and the photosensitive layer 2 is composed of a coloring material, a photopolymerizable compound, a heat-adhesive binder having no photopolymerization property, and a near-infrared absorbing cationic dye. And a borate anion complex, and a storage stabilizer containing a bisimidazole compound and a hindered phenol compound or a hindered amine compound. The protective layer 3 is made of a release-treated transparent polyethylene terephthalate film.

To produce, for example, a simple proof using this image forming sheet, first, color separated image data produced on a computer or the like is converted into a digital signal, and a semiconductor laser scanner is driven to drive the image forming sheet 10. A near-infrared beam based on the above digital signal is emitted from the support 1 side or the protective layer 3 side. By this image exposure, a polymerization latent image of a photopolymerizable compound corresponding to an image is formed on the photosensitive layer 2. Next, the protective film 3 is peeled off from the image forming sheet 10, and the photosensitive layer 2 and the image receiving paper are superposed and sandwiched between hot pressing rolls or the like to apply uniform heat and pressure. As a result, the portion of the photosensitive layer 2 having the increased thermal adhesiveness is transferred to the image receiving paper side, and a monochromatic image is formed on the image receiving paper. By simply aligning and heat-transferring image forming sheets containing color materials that have been similarly imagewise exposed according to the number of color separations on the same image receiving paper, a color image is formed on the image receiving paper and a simple proof is obtained. To be

The image exposure by the semiconductor laser light may be performed from the protective film 3 side or the support 1 side.
Irradiation may be performed from the one that absorbs the laser light used less. The latent images formed on the photosensitive layer 2 are mirror images of each other from the protective film 3 side and the support 1 side, but the output from the semiconductor laser can be easily inverted on the computer. This selection may be made depending on whether irradiation is from the side.

As a support used for forming the image forming sheet 10, it is preferable that the support has suitable rigidity and can support the photosensitive layer stably with flatness and dimensions even when a heat and pressure load is applied. Any sheet may be used as long as it is an infrared ray transmissive sheet. Examples thereof include acetate film, polyvinyl chloride film, polyethylene film, polypropylene film, polycarbonate film, polyethylene terephthalate film and the like. In particular, a biaxially stretched polyethylene terephthalate film, which has high dimensional stability against heat and water and is excellent in workability during coating of the photosensitive layer and operability during exposure and transfer, is suitable.

These supports may be used as they are, but in order to control the adhesion with the photosensitive layer and form a good transferred image, a release treatment with an appropriate oil-repellent substance such as silicone resin or fluororesin is carried out. Alternatively, surface treatment such as easy adhesion treatment by corona discharge or plasma treatment can be applied.

In the image-forming sheet of the present invention, the coloring material used in the photosensitive layer may be any conventionally used dye or pigment, or may be a mixture thereof. Generally, when making a color simple proof,
A set of four image forming sheets containing yellow, magenta, cyan, and black coloring materials respectively is required.
In addition to the above dyes, for example, metal powder, white pigment, fluorescent pigment, extender pigment, etc. may be used supplementarily. Therefore, these are also included in the "coloring material" in this specification.

As the coloring material that can be used in the image-forming sheet of the present invention, in addition to commercially available coloring materials, for example, "Dye Handbook" (edited by the Society of Synthetic Organic Chemistry, published in 1945), "Latest Pigment Handbook" (Japan Those described in, for example, Pigment Technology Association, published in 1976) can be used. Some of these wide range of colorants are azo, phthalocyanine,
Examples thereof include various quinacridone-based, anthraquinone-based, indigo-based, methine-based organic pigments and dyes, and various inorganic pigments.

For these dyes and pigments, a known suitable dispersant may be used if necessary, the surface of the particles may be modified, and a known disperser may be used to add or not add a solvent. Mix uniformly with the other components that make up the photosensitive layer. If necessary for adjusting the texture of the image, powder or liquid matting agent may be added together with these coloring materials.

The photopolymerizable compound used in the image-forming sheet of the present invention is a compound having a free radical addition-polymerizable or crosslinkable ethylenically unsaturated group, which is one or more ethylenically unsaturated groups. , A monomer or oligomer having a vinyl group or an allyl group, or a polymer having an ethylenically unsaturated group at the terminal or side chain. Examples thereof include acrylic acid and its salts,
Acrylic acid esters, acrylamides, methacrylic acid and its salts, methacrylic acid esters, methacrylamides, maleic anhydride, maleic acid esters, itaconic acid esters, styrenes, vinyl ethers,
Examples thereof include vinyl esters, N-vinyl heterocycles, allyl ethers, allyl esters and derivatives thereof.

More specific examples of the photopolymerizable compound include (meth) acrylic acid, methyl (meth) acrylate, butyl (meth) acrylate, cyclohexane (meth) acrylate and dimethylaminoethyl (meth).
Acrylate, benzyl (meth) acrylate, carbitol (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, 2
-Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylamide, N-methylol (meth) acrylamide, styrene, acrylonitrile, N-vinylpyrrolidone, ethylene glycol diacrylate, Diethylene glycol diacrylate,
Triethylene glycol diacrylate, polyethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,4-butanediol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, Low molecular weight compounds such as trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, (meth) acrylate of alkylene oxide adduct of phenol, polymers in which (meth) acrylate is bonded to the end of epoxy resin or polyester resin, acrylate of petroleum resin Examples include modified compounds and high molecular weight compounds such as unsaturated polyester resins. These may be used alone or in combination of two or more.

The binder used in the photosensitive layer of the image-forming sheet is made of an organic polymer having no photopolymerization property, which is blended in the photosensitive layer to serve as a dispersion medium for the coloring material and also as an adhesive adjusting agent. Is also used. It is desirable that the binder be compatible with the photopolymerizable compound described above.
Examples of common binders include polyvinyl chloride, poly (meth) acrylic acid, poly (meth) acrylic acid ester, polyvinyl ether, polyvinyl acetal, polyurethane resin, epoxy resin, polyamide, polyester, vinylidene chloride-acrylonitrile copolymer. Examples thereof include polymers, vinylidene chloride-methacrylate copolymers, vinylidene chloride-vinyl acetate copolymers, cellulose derivatives, polyolefins, diallyl phthalate resins and various synthetic rubbers such as butadiene-acrylonitrile copolymers.

As this binder, a composition known as a heat-sensitive adhesive can be used alone or in a mixture with the above-mentioned binder. This heat-sensitive adhesive is, for example,
It is a composition composed of an elastic body, a heat-adhesiveness imparting agent, a plasticizer, a filler, an antiaging agent and the like, and is classified into a rubber type, an acrylic type, a silicone type and the like depending on the elastic body used. The elastic body is, for example, natural rubber, recycled rubber, synthetic rubber such as styrene-butadiene rubber, butadiene rubber,
Chloroprene, butadiene-acrylonitrile rubber, isobutylene-isoprene rubber, ethylene-propylene rubber, silicone rubber, polyacrylic acid ester or a derivative thereof, a silicone resin, etc., the thermal adhesion imparting agent is, for example, rosin and its derivatives, polyterpene resin, It is coumarone-indene resin, petroleum resin, terpene phenol resin and the like, and the plasticizer is, for example, liquid polybutene, mineral oil, lanolin, liquid polyisoprene, liquid polyacrylate and the like. In addition, additives such as antioxidants, antioxidants, and inorganic pigments may be included if necessary.

The photopolymerization initiator used in the photosensitive layer of the image forming sheet of the present invention comprises a complex of a near infrared absorbing cationic dye and a borate anion. Examples of suitable photopolymerization initiators are shown in Tables 1 to 4 together with their absorption wavelengths (λ, peak values).

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

This photopolymerization initiator has a function of inducing photopolymerization of the above-mentioned photopolymerizable compound by infrared rays, and is 0.01% by weight based on the weight of the photopolymerizable compound used in the photosensitive layer. It is preferable to blend in the range of 10 to 10% by weight, more preferably 0.1 to 5% by weight.

Along with this photopolymerization initiator, an autoxidizer capable of absorbing oxygen which is a factor inhibiting the free radical chain reaction may be used. An example of this autoxidizer is N, N-dialkylaniline, and its o-, m
Examples thereof include those in which one or more of the-or p-position is substituted with an alkyl group, a phenyl group, an acetyl group, an ethoxycarbonyl group, a carbonyl group, a carboxylate group, a silyl group, or an alkoxy group. In particular, 2,6-diisopropyl-N, N- substituted at the o-position with an alkyl group
Dimethylaniline, 2,6-diethyl-N, N-dimethylaniline, N, N, 2,4,6-pentamethylaniline, pt-butyl-N, N-dimethylaniline and the like are preferable. The addition amount thereof is preferably 0.01% by weight to 10% by weight, more preferably 0.1% by weight to 5% by weight, based on the weight of the photopolymerizable compound used in the photosensitive layer.

Further, a sensitizer may be used in combination with the above photopolymerization initiator. Examples of this sensitizer include a quaternary ammonium boron salt represented by the following general formula (3), a quaternary phosphine boron salt, N-phenylglycine, and an organic peroxide.

[0048]

Embedded image

In the formula (3), R ₁ , R ₂ , R ₃ and R ₄ are each independently alkyl, aryl, alkaryl, allyl, aralkyl, alkenyl, alkynyl,
Silyl, alicyclic, saturated or unsaturated heterocyclic, substituted alkyl, substituted aryl, substituted alkaryl, substituted allyl,
A residue selected from the group consisting of a substituted aralkyl, a substituted alkenyl, a substituted alkynyl and a substituted silyl, provided that at least one residue of R ₁ , R ₂ , R ₃ or R ₄ is an alkyl group having 1 to 8 carbon atoms. is there. R ₅ , R ₆ , R ₇ and R ₈ are each independently hydrogen, alkyl, aryl,
Alkaryl, allyl, aralkyl, alkenyl, alkynyl, silyl, alicyclic, saturated or unsaturated heterocyclic,
It is a residue selected from the group consisting of substituted alkyl, substituted aryl, substituted alkaryl, substituted allyl, substituted aralkyl, substituted alkenyl, substituted alkynyl and substituted silyl.

Preferred examples of the quaternary ammonium-boron salt include tetramethylammonium n-butyltriphenylboron, tetramethylammonium n-butyltrianisylboron, tetramethylammoniumn-
Octyl triphenyl boron, tetramethyl ammonium n-octyl trianisyl boron, tetraethyl ammonium n-butyl triphenyl boron, tetraethyl ammonium n-butyl trianisyl boron, trimethyl hydrogen ammonium n-butyl triphenyl boron, triethyl hydrogen ammonium n-butyl tri Examples thereof include phenyl boron, ammonium tetrahydrogen n-butyl triphenyl boron, tetramethyl ammonium tetrabutyl boron, tetraethyl ammonium tetrabutyl boron and the like.

Fourth suitable as sensitizer for photopolymerization initiator
Examples of the secondary phosphine boron salt include triphenylmethylphosphine n-butyltriphenylboron, triphenylethylphosphine n-butyltriphenylboron,
Examples thereof include triphenylmethylphosphine n-butyltrianisylboron, triphenylethylphosphine n-butyltrianisylboron, tetraphenylphosphine n-butyltriphenylboron and tetraphenylphosphine n-butyltrianisylboron.

Examples of organic peroxides suitable as sensitizers for photopolymerization initiators include diacetyl peroxide, dilauroyl peroxide, dibenzoyl peroxide,
p, p'-dichlorodibenzoyl peroxide, p,
Diacyl peroxides such as p'-dimethoxydibenzoyl peroxide and p, p'-dinitrosodibenzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, and 2,5-dimethylhexane-2,5-dihydroperoxide And the like, ketone peroxides such as methyl ethyl ketone peroxide, t-butyl peroxide benzoate and peroxy carbonates such as 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone. . In particular, dibenzoyl peroxide, 3,3 ′, 4,
4'-Tetra (t-butylperoxycarbonyl) benzophenone and the like are suitable sensitizers.

These sensitizers are used in an amount of 0.1 to 10 parts by weight, preferably 0.1% by weight, based on 1 part by weight of the photopolymerization initiator.
Within the range of 1 part by weight to 5 parts by weight, they can be added alone or as a mixture.

Table 5 shows suitable examples of the bisimidazole compound used as a storage stabilizer in the photosensitive layer of the image forming sheet of the present invention.

[0055]

[Table 5]

The bisimidazole compound is used alone or in a mixture within the range of 0.1 to 10 parts by weight, preferably 0.1 to 5 parts by weight, relative to 1 part by weight of the photopolymerization initiator. Can be used. If it is less than 0.1 part by weight, the effect as a storage stabilizer is not sufficiently exhibited, and if it exceeds 10 parts by weight, it is inconvenient in terms of solubility.

It has been reported that the bisimidazole compound of the formula (2) can be combined with a photopolymerization initiator composed of a complex of a cationic dye and a borate anion to achieve high sensitivity (JP-A-4-272904). Japanese Patent Laid-Open No. 6-59450). However, according to the tests conducted by the present inventors, the sensitizing effect of the combination of these bisimidazole compounds and a cationic dye as a photopolymerization initiator-borate anion complex shows that a peroxide is added under near infrared rays, for example. It was found to be lower than when On the other hand, surprisingly, when these compounds were combined with a hindered phenol compound or a hindered amine compound, it was found that the storage stability of the cationic dye-borate anion complex under high temperature and high humidity environment was significantly increased, and the present invention was reached. .

Examples of suitable hindered phenol compounds and hindered amine compounds which can be used in combination with the above-mentioned bisimidazole compounds are shown in Tables 6 to 9.
Shown in These may be used alone or in combination of two or more.

[0059]

[Table 6]

[0060]

[Table 7]

[0061]

[Table 8]

[0062]

[Table 9]

These hindered phenol compounds or hindered amine compounds are used in an amount of 0.1 part by weight to 10 parts by weight, preferably 0.1 part by weight, relative to 1 part by weight of the photopolymerization initiator.
It can be used within the range of 5 to 5 parts by weight. 0.
When it is less than 1 part by weight, the effect as a storage stabilizer is not sufficiently exhibited, and when it exceeds 10 parts by weight, compatibility is inconvenient. It is preferable to use the bisimidazole compound in an amount within the range of 1 to 5 parts by weight per 1 part by weight.

In addition to the above-mentioned storage stabilizer, the photosensitive layer may be blended with other storage stabilizers, thermal polymerization inhibitors, etc. within the range of types and amounts that do not inhibit the action as the stabilizer. . Examples of these additives include, for example, p-methoxyphenol, benzoquinone, hydroquinone, pyrogallol, pyridine, aryl phosphate, 2,6-
Examples thereof include di-t-butyl-p-cresol. These may be used alone or in combination of two or more. The addition amount of these is 10 parts by weight or less, preferably 0.0 part by weight, relative to 1 part by weight of the photopolymerization initiator.
It is in the range of 1 to 2 parts by weight.

The photosensitive layer of the image-forming sheet of the present invention may contain an appropriate amount of wax in addition to the above-mentioned various components. This wax adjusts the thermal fluidity and cohesive force of the photosensitive layer during the thermal transfer of the exposed image forming sheet to enable smooth transfer, and also adjusts the gloss of the image such as a simple proof obtained by the transfer. You can also Examples of waxes that can be used include various natural waxes such as animal-based, plant-based, mineral-based and petroleum-based waxes, synthetic hydrocarbon-based waxes, modified wax-based waxes, aliphatic alcohol-based waxes,
Various synthetic or semi-synthetic waxes such as fatty acid type, fatty acid ester type, glyceride type, hydrogenated wax type, synthetic ketone type, synthetic amine type, amide type, chlorinated hydrocarbon type, synthetic animal wax type, α-olefin wax type Can be mentioned.

Further, the photosensitive layer of the image forming sheet of the present invention may contain a known polymerization initiator having sensitivity to ultraviolet rays, if necessary. Examples include benzophenone,
4,4-bis (diethylamino) benzophenone, 4-
Methoxy-4-dimethylaminobenzophenone, 2-ethylanthraquinone, phenanthraquinone, benzoin, benzoin methyl ether, benzoin phenyl ether, isobutyl benzoin ether, isopropyl benzoin ether, benzoin ethyl ether, 2,
2-diethoxyacetophenone, 2-hydroxy-2-
Methylpropiophenone, 4'-isopropyl-2-hydroxy-2-methylpropiophenone, pt-butyltrichloroacetophenone, Michler's ketone, benzyl dimethyl ketal, 2,2-dimethoxy-2-phenylacetophenone, hydroxycyclohexylphenyl ketone , Azobisisobutyronitrile, 2-chlorothioxanthone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone and the like. These can be used alone or as a mixture. These known polymerization initiators having sensitivity to ultraviolet rays are effective for fixing the image after transferred to the image receptor by ultraviolet irradiation.

The photosensitive layer of the image-forming sheet of the present invention is prepared by mixing and dispersing each of the above components in the presence or absence of a suitable solvent, and using a bar coater, a spin coater, or other various mass-produced coaters. It can be formed by coating on a support using the above. The solvent used at this time is preferably an aromatic hydrocarbon-based solvent such as toluene, xylene or isopropylbenzene, a ketone-based solvent such as methyl ethyl ketone or methyl isobutyl ketone, or a mixture thereof, which dissolves the binder used. Select and use.

The thickness of the photosensitive layer depends on the concentration of the coloring material, the adhesiveness and cohesive force of the composition to the support, the thermal adhesiveness to the image receptor and the breaking force, and the optical property of the image required on the image receptor. Although it varies depending on the density and the like, it is usually preferable to set it in the range of 0.5 μm to 5 μm. If the thickness is less than 0.5 μm, the image transferred onto the image receptor will not have sufficient optical density, and
If it exceeds μm, the resolution of the image is lowered or blurring occurs.

In the image forming sheet of the present invention, the surface of the photosensitive layer formed on the support is preferably covered with a peelable protective film. This protective film is preferably transparent to near infrared rays so that the photosensitive layer can be exposed from the protective film side. As the material, any of the same materials as those used for the support can be used, but since oxygen becomes an inhibiting factor during photopolymerization, the adhesiveness so that an oxygen layer is not formed between the material and the photosensitive layer. It is preferable that it has a good releasability and an appropriate peeling property. Examples thereof include a polyethylene film, a polypropylene film, or a polyethylene terephthalate film that has been appropriately released.

Next, a method of forming an image on an image receptor using the image forming sheet of the present invention will be described by taking a case of a simple color proof as an example. First, prepare an image forming sheet with color tone and number of colors such as yellow, magenta, cyan, and black that have been separated, and make holes for register pins in each image forming sheet to prevent misalignment during image exposure of each color. And other positioning means. The photosensitive layer of each image forming sheet is image-exposed with a semiconductor laser beam modulated by color separation image data and the exposed portion is cured to form a latent image corresponding to each color image on the photosensitive layer. The protective film is peeled off, the photosensitive layer and the image receptor such as paper are superposed on each other, and heat pressure is applied to transfer the heat-adhesive portion of the photosensitive layer to the image receptor. Immediately after transfer, the support is peeled off from one end thereof to form a monochrome transfer image on the image receiver. The desired color simple proof can be obtained by repeating the above procedure for each color after aligning on the same image receptor.

Needless to say, if a simple proof of a single color is produced, the above-mentioned transfer operation may be performed only once. In addition, a transfer image can also be obtained by basically the same operation on an image receptor other than the simple proof. The heat-sensitive layer is easy to design so that the unexposed portion is transferred under heat and pressure, and although it is generally preferable, it is also possible to design so that the exposed portion is transferred as necessary. In the transfer process, you can control the image quality and image by stacking matting sheets that partially remove the photosensitive layer during the transfer process and then applying heat and pressure to peel it off. In the case where sticking or color misregistration occurs due to the presence of the light, the image can be fixed by post-curing with light and / or heat.

The image-forming sheet of the present invention can be advantageously used for producing a simple proof, but other non-mass-produced printed matter,
For example, it can be easily applied to signboards, posters, ornaments, name plates, and the like. In this case, the image receiver is not limited to paper, and may be another face material such as a plastic plate, a metal plate, or a glass plate.

[0073]

EXAMPLES The present invention will be described in more detail by way of examples. In the following examples, parts represent parts by weight, and% represents% by weight.

Example 1 A photosensitive layer composition comprising the following components was prepared. Polyester (Byron 300, manufactured by Toyobo Co., Ltd.) 15.0 parts Tetraethylene glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) 1.0 part Trimethylolpropane triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) 9.0 parts Near infrared polymerization start Agent (Complex 6-A in Table 2) 0.3 part Tetramethylammonium n-butyltriphenylboron 0.3 part Bisimidazole compound (A-2 in Table 5) 0.3 part 2,4-bis (n -Octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine (Irganox 565, manufactured by Nippon Ciba-Geigy) 0.15 parts Carbon black (MA-7) , Mitsubishi Kasei) 4.4 parts Methyl ethyl ketone 40 parts Toluene 28 parts

This photosensitive layer composition was vibrated with 2 mmφ glass beads in a vibrating mill (5400N2 type, manufactured by Red Devil Co., Ltd.) for 10 minutes or more to disperse, to prepare a colored photosensitive solution.

The surface of 25 μm-thick polyethylene terephthalate serving as a support was subjected to corona treatment, and
It was applied by a wire bar coater so that the film thickness after drying would be 1 μm, and dried by a warm air dryer at 100 ° C. for 2 minutes. Next, an 80 μm-thick polyethylene film serving as a protective film was adhered to this surface while laminating at 70 ° C. at a speed of 1 m / min to prepare an image forming sheet for a semiconductor laser of Example 1.

Example 2 A photosensitive layer composition consisting of the following components was prepared. Diallyl orthophthalate prepolymer (Daiso Dap K, manufactured by Daiso) 15.0 parts Dipentaerythritol hexaacrylate (KAYARAD / DPHA, manufactured by Nippon Kayaku Co., Ltd.) 10.2 parts Near-infrared polymerization initiator (Complex 1 in Table 1) ) 0.3 part Tetramethylammonium n-butyltriphenylboron 0.3 part Bisimidazole compound (A-1 in Table 5) 0.3 part Dimethyl succinate / 1- (2-hydroxyethyl) -4-hydroxy -2,2,6,6-Tetramethylpiperidine polycondensate (Tinuvin 622LD, manufactured by Ciba-Geigy) 0.15 parts Carbon black (MA-7, manufactured by Mitsubishi Kasei Co.) 4.4 parts Methyl ethyl ketone 40 parts Toluene 28 Department

Using this photosensitive layer composition, dispersion, coating and lamination were carried out in the same manner as in Example 1 to prepare an image forming sheet for a semiconductor laser of Example 2.

Examples 3 to 5 Instead of 4.4 parts of carbon black in the photosensitive layer composition used in Example 2, yellow, magenta and cyan color pigments were used, respectively. In Example 3, lionol yellow FG1310 (manufactured by Toyo Ink Co., Ltd.) for yellow is used.
Is a carmine 7BFG4412 for magenta (manufactured by Toyo Ink Co., Ltd.), and Example 5 includes lionol blue FG7330 (manufactured by Toyo Ink Co., Ltd.) for cyan, each containing carbon black so that the solid content is 18%. In the same manner as in Example 1, dispersion, coating and lamination were carried out in the same manner as in Example 1, and Example 3 was used for yellow images, Example 4 was used for magenta images, and Example 5 was used for cyan images. A sheet was prepared.

Comparative Example 1-1 For comparison with Example 1, the photosensitive layer composition of Example 1 was used to prepare the bisimidazole compound (A-2 in Table 5) and 2,4-bis (n-octylthio). ) -6- (4-Hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine (Irganox 565) was used, except that the same composition as in Example 1 was used. An image forming sheet of Comparative Example 1-1 was produced in the same manner as in 1.

Comparative Example 1-2 In order to compare with Example 1, the photosensitive layer composition of Example 1 was used to prepare 2,4-bis (n-octylthio) -6- (4-hydroxy-3,5-). J-t
-Butylanilino) -1,3,5-triazine (Irganox 565) was omitted, and the same composition as in Example 1 was used to prepare an image forming sheet of Comparative Example 1-2 in the same manner as in Example 1. did.

(Comparative Example 1-3) For comparison with Example 1, the same as Example 1 except that the bisimidazole compound (A-2 in Table 5) was excluded from the photosensitive layer composition of Example 1. Using the above composition, an image forming sheet of Comparative Example 1-3 was prepared in the same manner as in Example 1.

Comparative Example 2-1 For comparison with Example 2, the photosensitive layer composition of Example 2 was used to prepare the bisimidazole compound (A-1 in Table 5) and dimethyl succinate / 1-.
(2-hydroxyethyl) -4-hydroxy-2,2
6,6-Tetramethylpiperidine polycondensate (Tinuvin 6
22LD) was excluded, and the same composition as in Example 2 was used to prepare an image forming sheet of Comparative example 2-1 in the same manner as in Example 2.

Comparative Example 2-2 In order to compare with Example 2, the photosensitive layer composition of Example 2 was used to prepare dimethyl succinate / 1.
-(2-hydroxyethyl) -4-hydroxy-2,
An image forming sheet of Comparative Example 2-2 was prepared in the same manner as in Example 2 except that the 2,6,6-tetramethylpiperidine polycondensate (Tinuvin 622LD) was excluded. did.

(Comparative Example 2-3) In order to compare with Example 2, the same as Example 2 except that the bisimidazole compound (A-1 in Table 5) was excluded from the photosensitive layer composition of Example 2. An image forming sheet of Comparative Example 2-3 was prepared in the same manner as in Example 2 using the above composition.

(Test Example 1) The image forming sheet samples of Examples 1 to 5 and Comparative Examples 1-1 to 1-3 and Comparative Examples 2-1 to 2-3 are described below. The laser light sensitivity after fabrication and the laser light sensitivity after storage under high temperature and high humidity conditions were measured and compared. The laser recording apparatus used was a semiconductor laser (SLU304 manufactured by Sony Corporation) as a laser light irradiation system.
XR) and laser driver (made by Global Electronics Co., Ltd.,
GSB3530) and an XY stage (PS120EX • Y, manufactured by Chuo Seiki Co., Ltd., controller CAT-II, driver pack SD-P set) as a measurement medium moving system.

The movement of the XY stage is controlled by a program written in the controller, and the raster scanning exposure on the image forming sheet is sequentially accelerated from the stopped state of the main scanning,
This is performed by repeating a series of movements including constant speed movement, stopping from the constant speed movement state, movement of a sub-scan for a certain distance, and return in the main scanning reverse direction. At this time, the light output of the semiconductor laser is gradually increased for each sub-scan, the exposure light amount is changed within the scanning range, and the laser light sensitivity of the image forming sheet is measured.

The laser recording device was set up as follows. Beam diameter: 100 μmφ (50%) Main scanning speed: 40 mm / sec, Sub-scanning pitch: 100 μm Scanning range: 15 × 10 mm Laser light irradiation intensity (change width during one test exposure): 0.
6-60mW (equivalent to 10-1000mJ / cm ² )

Each of the image-forming sheets test-exposed for sensitivity measurement was brought into close contact with a printing paper (Kanzaki Paper Co., Ltd., Super Art Paper), and heat pressure was applied through a laminator set at 100 ° C., 2 m / sec and 2 kg pressure. Immediately, the both were peeled off, and the scanned image was transferred to the printing paper side. This image was examined carefully, and the output of the semiconductor laser beam corresponding to the part where the transfer of the image was not recognized was taken as the sensitivity of this image forming sheet. next,
Each unexposed image forming sheet sample is heated at a temperature of 40 ° C. and a humidity of 75.
The image-forming sheet was stored in a thermo-hygrostat set to% RH for 30 days, and stored in a high-temperature and high-humidity environment in the same manner as above, and the sensitivity of the image-forming sheet was measured. The results are shown in Table 10.

[0090]

[Table 10]

From the results shown in Table 10, the samples of the comparative examples containing neither the bisimidazole compound nor the hindered phenol compound or the hindered amine compound were inactivated under the set storage conditions. It can be seen that the sensitivity of the samples of each of the examples including the storage stabilizer was not substantially decreased even after storage under the above-mentioned high temperature and high humidity conditions. This indicates that the storage life at normal room temperature is several times longer.

(Test Example 2) Each positive film obtained by color-separating a 175-line test color original into four colors of black, yellow, magenta, and cyan, and Examples 1 and 2 corresponding to each color. Example 3 to Example 5
The four color image forming sheets of 4 are aligned by register pins and overlapped with each other, then wound around and fixed on a drum rotating at 1.5 m / sec, and driven by the same laser driver as used in Test Example 1 above. The produced semiconductor laser beam was irradiated with the beam diameter adjusted to 40 × 20 μm by an optical lens system, exposed with an optical output of 80 mW, and baked.

Each of the exposed image forming sheets was precisely aligned with one sheet of the printing paper and overlapped,
Similar to Test Example 1, the operation of hot-press transfer with a laminator was repeated to obtain a simple color proof of a test color original.
The obtained color simple proof had a sufficiently satisfactory resolution, and the test original was reproduced well from the highlight portion to the shadow portion. The simple color proof obtained here was equivalent to the ultraviolet light type simple color proof in terms of both texture and resolution. This test was repeated on a sample of the image forming sheet stored under the same high temperature and high humidity atmosphere as in Example 1, but substantially the same color simple proof was obtained. This result shows that the image forming sheets of the respective examples have high storage stability against high temperature and high humidity.

[0094]

EFFECT OF THE INVENTION Since the photosensitive layer of the image-forming sheet of the present invention contains a photopolymerizable compound and a photopolymerization initiator sensitive to near infrared rays, a latent image whose thermal adhesiveness is changed by exposure to near infrared rays is formed. The obtained image is directly transferred to the image receptor without the need for an intermediate image receptor or a specially treated image receiving paper by heat-pressure transfer to the image receptor by utilizing the difference in thermal adhesiveness between the exposed portion and the unexposed portion. In addition to being able to form an image, the photosensitive layer contains a storage stabilizer composed of a bisimidazole compound and a hindered phenol compound or a hindered amine compound, so that it can be stored in a hot and humid environment such as a work site. The resulting image-forming sheet has high storage stability and high practical value.

Further, since the image forming sheet of the present invention has the above-mentioned characteristics, it is exposed to a semiconductor laser beam corresponding to the original image for image exposure to expose the exposed portion of the photosensitive layer and the unexposed portion. If a photosensitive layer is made to have a difference in thermal adhesiveness and then the photosensitive layer is transferred to an image receiving paper by heat and pressure, a simple proof having a high resolution and a good texture can be easily obtained. Therefore, when the image forming sheet of the present invention is used, DD
It becomes possible to easily and quickly produce a simple proof or a color image that is extremely close to the texture and resolution of a printed matter directly from digital image data output from a CP or a high quality color printer.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an image forming sheet of the present invention.

[Explanation of symbols]

 1 ... Support 2 ... Photosensitive layer 3 ... Protective layer 10 ... Image forming sheet

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03F 7/029 G03F 7/029 7/20 505 7/20 505 7/34 7/34 (72) Inventor Shuichi Sugita 1-1-1 Onodai, Midori-ku, Chiba-shi, Chiba Prefecture Showa Denko K.K. (72) Inventor Hirotoshi Kamada 1-1-1 Onodai, Midori-ku, Chiba-shi Chiba Denko K.K.

Claims (4)

[Claims] 1. A color material on a support, a photopolymerizable compound having an ethylenically unsaturated group, a heat-adhesive binder made of an organic polymer having no photopolymerizability, and a general formula (1) ) [Chemical 1] (In the formula, D ⁺ is a cationic dye having light absorption in the near infrared region, and R ₁ , R ₂ , R ₃ and R ₄ are each independently alkyl, aryl, alkaryl, allyl, aralkyl, alkenyl, alkynyl. A residue selected from the group consisting of: silyl, alicyclic, saturated or unsaturated heterocyclic, substituted alkyl, substituted aryl, substituted alkaryl, substituted allyl, substituted aralkyl, substituted alkenyl, substituted alkynyl and substituted silyl. Where at least one residue of R ₁ , R ₂ , R ₃ or R ₄ is an alkyl group having 1 to 8 carbon atoms) and a light comprising a complex of a near infrared absorbing cationic dye and a borate anion. A polymerization initiator and the following general formula (2): A photosensitive material containing a bisimidazole compound represented by the formula (wherein L ₁ , L ₂ and L ₃ are each independently an aryl group or a substituted aryl group) and a storage stabilizer comprising a hindered phenol compound or a hindered amine compound. An image forming sheet provided with a layer. 2. The bisimidazole compound and the hindered phenol compound or hindered amine compound are contained in an amount of 0.1 to 5 parts by weight per 1 part by weight of the photopolymerization initiator, and the hinder is used. The image forming sheet according to claim 1, wherein the dephenol compound or the hindered amine compound is contained in the range of 1 to 5 parts by weight per 1 part by weight of the bisimidazole compound. 3. The image forming sheet according to claim 1 or 2 is irradiated with a semiconductor laser beam corresponding to an original image to generate a difference in thermal adhesive force between an exposed portion and an unexposed portion of the photosensitive layer. And an image forming method of forming an image on the image receiving body by superimposing this photosensitive layer on the image receiving body and transferring it under heat and pressure. 4. A simple proof print formed by the image forming method according to claim 3.