JPH08201960A - Image forming material and image forming method - Google Patents

Abstract

PURPOSE: To obtain an image forming material capable of forming an image with satisfactory resolution and sensitivity by safe and simple dry processing by disposing a photosensitive layer contg. a specified onium salt, a leuco dye developing a color by oxidation and a radical generating agent on a substrate. CONSTITUTION: An image forming material with a photosensitive layer contg. at least one of onium salts represented by formulae I-III, a leuco dye developing a color by oxidation and a radical generating agent on the substrate is imagewise exposed and heated to form a positive image. In the formulae I-III, each of R1 -R4 is alkyl, aryl or aralkyl, each of R5 -R7 is alkyl or aryl, R5 -R7 may bond to one another to form a ring, each of R8 and R9 is aryl and X<-> is a counter anion, preferably a halogen ion, especially preferably a Cl or Br ion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel image forming material and an image forming method, and more specifically, it uses an onium salt (phosphonium salt, sulfonium salt, iodonium salt), an oxidative coloring leuco dye and a radical generator. The present invention relates to an image forming material and an image forming method.

[0002]

2. Description of the Related Art As an image forming method using a leuco dye, a thermosensitive coloring method and a pressure-sensitive coloring method have been widely put into practical use. In these methods, an image is recorded by heat applied from the thermal head or external pressure from a pencil, so that the resolution depends on the thermal head or a writing device such as a pencil.

In order to obtain a higher resolution image by using a leuco dye that develops color by oxidation (oxidation coloring leuco dye), a polyhalide is mixed with an aromatic amine and imagewise exposed to form an image. After that, a method is known in which the polyhalide in the non-exposed area is sublimated and removed by heating and fixing is performed. However, the fixing method of sublimating the polyhalide is not preferable because the halide volatilizes in the air and is harmful to the human body.

Japanese Patent Publication No. 43-19161 discloses a method in which bisimidazole is irradiated with ultraviolet rays in a form not using halogen to generate radicals to develop a leuco dye, and then an image is fixed by visible light. ing. This method is safe because it does not generate halogen, but has the drawback that sufficient image density cannot be obtained. Furthermore,
In this method, an image is formed by light, which is different from the present invention in which a latent image is formed by light and a color image is formed by heat.

As another form, there has been reported a method of obtaining an image by using radicals produced by photolysis or thermal decomposition of an onium salt. For example, Bull. Although a method for obtaining the same has been disclosed, it has been found that a combination of a leuco dye and an onium salt, or a combination of a leuco dye and a radical generator does not develop color even when heat is applied.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art. That is, a first object of the present invention is to provide an image forming material capable of forming an image having a good resolution and sensitivity by a safe and simple dry process, and a second object thereof is the image forming material. An object of the present invention is to provide an image forming method for forming a stable image by using the. A third object is to provide an image forming material which can be easily fixed and gives a light stable image.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found an unexpected result that color development is possible only by a combination of an oxidative coloring leuco dye, an onium salt and a radical generator, and It came to completion.

That is, the above object of the present invention is to provide at least one onium salt represented by the following general formula (I), (II) or (III), an oxidative coloring leuco dye and a radical generator on a support. And an image-forming method having an image-wise exposure of the image-forming material and then heating to form a positive image.

[0009]

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In the formula, R ₁ , R ₂ , R ₃ and R ₄ each represent an alkyl group, an aryl group or an aralkyl group, and R ₅ , R ₆
And R ₇ each represent an alkyl group or an aryl group.

R ₅ , R ₆ and R ₇ may combine with each other to form a ring. R ₈ and R ₉ each represent an aryl group, and X ⁻ represents a counter anion.

The counter anion of the onium salt is preferably a halogen ion, and particularly preferably a chlorine ion or a bromine ion.

First, the phosphonium salt compound represented by the general formula (I) (hereinafter referred to as the phosphonium salt of the present invention) will be described in detail.

Specific examples of the substituents represented by R _{1 to} R ₄ are as follows.

The alkyl group includes straight chain and branched alkyl, and examples thereof include methyl, ethyl, butyl, i-butyl, hexyl, octyl, stearyl and the like. From the viewpoint of color density, an alkyl group having 1 to 10 carbon atoms is preferable, and a butyl group is particularly preferable. These alkyl groups may combine with each other to form a ring, and as a cycloalkyl group, 5
Those having 7 to 7 membered rings (eg, cyclopentyl, cyclohexyl, etc.) are preferable.

Examples of the aryl group include phenyl and naphthyl, and examples of the aralkyl group include benzyl and phenethyl.

These groups may be further substituted,
As a substituent, a halogen atom, a cyano group, a nitro group, an alkyl group, an aryl group, a hydroxyl group, an amino group (including an alkyl-substituted amino group), an alkoxy group, a carbamoyl group, -COOR, -OCOR (R is an alkyl group, Organic groups such as aryl groups).

The counter anion represented by X ⁻ is not particularly limited as long as it is a monovalent anion, but is preferably a halogen ion, and chlorine and bromine anions are more desirable in terms of color density. Specific examples of the counter anion include bromide, chloride, iodide, fluoride,
Examples thereof include perchlorate, benzoate, thiocyanate, acetate, trifluoroacetate, hexafluorophosphate, nitrate and salicinate.

Next, the sulfonium salt compound represented by the general formula (II) (hereinafter referred to as the sulfonium salt of the present invention) will be described in detail.

Specific examples of the substituents represented by R _{5 to} R ₇ are as follows.

The alkyl group includes straight chain and branched alkyl, and examples thereof include methyl, ethyl, butyl, i-butyl, hexyl, octyl, stearyl and the like. From the viewpoint of color density, an alkyl group having 1 to 10 carbon atoms is preferable, and a butyl group is particularly preferable. These alkyl groups may combine with each other to form a ring, and as a cycloalkyl group, 5-7
Those having a member ring (eg, cyclopentyl, cyclohexyl, etc.) are preferable.

Examples of the aryl group include phenyl and naphthyl.

Examples of the ring formed by R ₅ , R ₆ and R ₇ together with S ⁺ include a benzothiathiopyrylium ring.

These groups may be further substituted,
Examples of the substituent include the same groups as those described in the general formula (I).

The counter anion represented by X ^- is represented by the general formula (I)
Of X ^- as synonymous.

Further, an iodonium salt compound represented by the general formula (III) (hereinafter referred to as an iodonium salt of the present invention)
Will be described in detail.

Examples of the aryl group represented by R ₈ and R ₉ include phenyl, naphthyl and the like. These groups may be further substituted, and the substituents are the same as those described in the above general formula (I). The same groups as those mentioned above can be mentioned.

The counter anion represented by X ^- is represented by the general formula (I)
Of X ^- as synonymous.

The addition amount of the onium salt of the present invention varies depending on the type and usage of the onium salt.
0.2-5 g per m ² is preferred.

Typical examples of the onium salt of the present invention will be given below.

[0031]

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[0032]

[Chemical 4]

[0033]

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Next, the oxidative coloring leuco dye (hereinafter referred to as the leuco dye of the present invention) will be described in detail.

The oxidative coloring leuco dye of the present invention includes
It is a substantially colorless compound that develops a color upon reaction with an onium salt, and is stable in a light-sensitive material under ordinary storage conditions.

The leuco dye preferably used is
Triarylmethane leuco dyes typified by crystal violet lactone, phenothiazine leuco dyes typified by benzoyl leuco methylene blue, xanthene, thioxanthene, acridine, phenoxazine, phenazine, diphenylmethane, India Any of amine-based, fluoran-based, rhodamine-lactam-based, spiropyran-based leuco dyes and the like may be used as long as they are colored in the manner of the present invention. Among these, triphenylmethane-based and phenothiazine-based leuco dyes represented by the following general formula (IV) or (V) are preferable in terms of good color developability.

[0037]

[Chemical 6]

In the formula, X ₁ , X ₂ and X ₃ each represent a group capable of substituting on the benzene ring, and m ₁ , n and p ₁ are each 0 to 5
Of the above, m ₂ and p ₂ each represent an integer of 0 to 3.
When m ₁ , m ₂ , n, p ₁ or p ₂ is an integer of 2 or more, a plurality of X ₁ , X ₂ and X ₃ may be the same or different. R ₁₁ and R ₁₂ each represent an alkyl group, and two R ₁₁ and R ₁₂ may be the same or different.

The group capable of substituting on the benzene ring represented by X ₁ , X ₂ and X ₃ is preferably an alkyl group, an alkoxy group, an amino group, an alkoxycarbonyl group, an aryl group or a halogen atom.

Specific examples of the oxidative coloring leuco dye of the present invention include, for example, JP-A-56-126831, page 9, line 4 to page 39, 1
The dyes described in the second line, the dyes described in JP-A-62-94841, page 5 and the like can be mentioned. The addition amount of the leuco dye varies depending on the type and usage of the leuco dye, but image-forming material 1 m ²
It is preferably 0.5 to 20 g.

Next, the radical generator will be described.

According to the mode of the present invention, any radical generator may be used as long as it generates a radical by light and interacts with the onium salt of the present invention by heat to form a leuco dye. Halides (α-haloacetophenones, trichloromethyltriazines, etc.), azo compounds, aromatic carbonyl compounds (benzoin esters, ketals, acetophenones,
Examples thereof include o-acyloxyiminoketones, acylphosphine oxides), hexaarylbisimidazole compounds, peroxides, and the like, with preference given to bisimidazole derivatives. Specific examples are shown below, but the present invention is not limited to these.

[0043]

[Chemical 7]

The amount of the radical generator of the present invention to be added varies depending on the type of radical generator and the form of use, but is preferably 0.1 to 10 g per 1 m ^{2 of} the image forming material.

For the photosensitive layer, an onium salt, a radical generator and a leuco dye are dissolved in a solvent together with a binder, or dispersed in the solvent in the form of fine particles to prepare a photosensitive layer coating solution, which is prepared on a support. It can be formed by coating and appropriately drying.

The dry thickness of the photosensitive layer is preferably 5 to 100 μm.

Any support can be used as long as it has good dimensional stability and can withstand heating during development, and a transparent plastic film support having excellent heat resistance can be used. Specific examples include polymers such as polyethylene terephthalate, polysulfone, polycarbonate, and polyimide.

The thickness of the support is usually preferably 10 to 200 μm.

As the binder used in the photosensitive layer,
Solvent-soluble polymers such as vinyl chloride, vinyl chloride-vinyl acetate copolymer resin, acrylic resin, methacrylic resin, polystyrene, polycarbonate, polysulfone, polyether sulfone, polyvinyl butyral, styrene-acrylonitrile, polyvinyl acetal, nitrocellulose, ethyl cellulose are preferable. .

These binders may be used by dissolving one or more kinds in an organic solvent and using them in the form of latex dispersion. The amount of the binder used varies depending on the purpose of the image-forming material of the present invention and whether it has a single-layer structure or a multi-layer structure.
It is preferably 1.0 to ²⁰ g per m ² .

The photosensitive layer may contain a sensitizer as a photosensitive substance in order to extend the photosensitive region of the radical initiator of the present invention, and a carbocyanine dye or an acridine dye is preferably used.

The image forming material may have auxiliary layers such as an intermediate layer, a protective layer and an undercoat layer in addition to the photosensitive layer containing an onium salt.

Next, an image forming method using the image forming material of the present invention will be described.

When the image forming material is imagewise exposed, a latent image is formed according to the exposure amount. Continue heating (preferably
80 to 180 ° C), the leuco dye develops color in inverse proportion to the exposure amount, and a positive image is obtained. Since color formation can be suppressed by exposure, fixing of an image is easier than other methods.

The image forming material of the present invention can be used as a material for recording a monochrome image by selecting a leuco dye to be used.

The exposure of the image forming material is performed by sunlight,
A tungsten light, a mercury lamp, a halogen lamp, a xenon lamp, a laser light, a light emitting diode, a CRT or the like can be used.

[0057]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 (Preparation of Image-Forming Material) The following raw materials were mixed to prepare a photosensitive layer coating liquid according to the present invention, and a wire bar was used on a polyethylene terephthalate (PET) base having a thickness of 100 μm. Image forming material 1 was prepared by applying and drying so that the applied amount after drying was 7.0 g / m ² .

Onium salt (QS-1) 4g Leuco dye (L-1) 8g Radical generator (A-1) 4g Vinyl chloride-vinyl acetate copolymer resin 20g (VYHH: Union Carbide Co.) cyclohexanone 2.5cc acetone 180cc The image forming materials 2 to 19 of the present invention having the same constitution as the image forming material 1 were prepared except that the combination of the onium salt, the leuco dye and the radical generator was changed as shown in Table 1. Furthermore,
For comparison, the image-forming materials 20, 21 and 22 obtained by removing the radical initiator from the image-forming materials 1, 18 and 13 and the image-forming materials 23 and 24 in which only a leuco dye and a radical generator are combined without using an onium salt. And 25, and an image forming material 26 in which the onium salt was replaced with dodecylbenzenesulfonic acid was prepared.

[0060]

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(Formation of Image) An image wedge was superposed on each of the above-mentioned image-forming materials 1 to 26, and the image-forming material was exposed to ultraviolet light for image formation. After exposure, each material was heated at 150 ° C for 5 seconds,
Materials 1 to 4, 6 to 10 and 17 to 19 were able to form a gradation image of blue, 5 and 11 to 13 were magenta, and 14 to 16 were yellow in inverse proportion to the exposure dose.

On the other hand, in Comparative Materials 20 to 25, no image formation was observed, and in Comparative Material 26, a negative gradation image corresponding to the exposure amount was obtained.

Materials 1-4, 6-10 and 17-19 are red light,
5 and 11 to 13 are green light, and 14 to 16 are the transmission densities (Dmax of unexposed areas) of the images measured with blue light.

[0064]

[Table 1]

Next, each image-forming material was stored at room temperature under a fluorescent lamp for 3 days, and then the density was measured to determine the difference (ΔD) from the initial density. ~ 19
In Comparative Material 26, printout due to color development of the leuco dye was observed, although there was almost no change in density.

Example 2 Image-forming materials 1, 4 and 9 of the present invention prepared in Example 1
Was further exposed to ultraviolet light and then heat-developed, but Dmax and ΔD did not change, and it was found that the image was completely fixed.

Example 3 Image-forming materials 1, 4 and 9 of the present invention prepared in Example 1
UGRA Plate Control Wedge (PCW 82)
It was exposed to UV light using a 1982 and heated at 130 ° C for 10 seconds. The obtained image reproduced a line width of 4 μm and was found to have high resolution.

Example 4 Image-forming materials 1, 4 and 9 of the present invention prepared in Example 1
The image forming materials 27 to 29 were prepared in the same manner as described above except that the leuco dye of No. 1 was replaced with an equimolar mixture of L-1, L-2 and L-3.
It was created. When an image wedge was superimposed on this material and exposed to ultraviolet light and heated at 130 ° C. for 10 seconds, a gradation image of substantially neutral gray was obtained in inverse proportion to the exposure amount.

[0069]

As shown in the examples, according to the present invention,
An image can be formed with high resolution and high sensitivity by a simple dry development process, and a stable image with higher density and no background contamination can be obtained by heat treatment or acid treatment. By selecting an appropriate leuco dye, yellow, magenta, and cyan color images can be formed.
It is also possible to form a black image by using one kind or a mixture of three kinds.

Claims (4)

[Claims] 1. A support represented by the following general formulas (I) and (II):
Or at least one of the onium salts represented by (III),
An image-forming material having a photosensitive layer containing an oxidative coloring leuco dye and a radical generator. Embedded image [In the formula, R ₁ , R ₂ , R ₃ and R ₄ each represent an alkyl group, an aryl group or an aralkyl group, and R ₅ , R ₆ and R ₇ each represent an alkyl group or an aryl group. In addition, R ₅ ,
R ₆ and R ₇ may combine with each other to form a ring. R ₈
And R ₉ each represent an aryl group, and X ⁻ represents a counter anion. ] 2. The image-forming material according to claim 1, wherein the counter anion represented by X ⁻ is a halogen ion. 3. The image forming material according to claim 2, wherein the halogen ion is chlorine ion or bromine ion. 4. An image forming method, which comprises exposing the image forming material of claim 1 imagewise and then heating to form a positive image.