JP2533791B2 - Image forming method for heat developable copying material - Google Patents

Description

The present invention relates to an image forming method for a copying material in which a diazo compound (diazonium salt) is encapsulated in microcapsules.
The present invention relates to an image forming method for a copying material which has a particularly good shelf life and can obtain a high color density even by low temperature thermal development.

<Prior Art> As a copying material utilizing the photosensitivity of a diazo compound, roughly three types are known. One is a type known as wet development type, in which a photosensitive layer containing a diazo compound and a coupling component as a main component is provided on a support, and this material is superposed on an original document and exposed to an alkaline solution. It is to develop. The second is a type known as a dry development type, which is different from the wet type in that development is performed with ammonia gas. The third type is known as a heat development type, which contains a type of ammonia gas generating agent such as urea that can generate ammonia gas by heating in the photosensitive layer and trichloroacetic acid in the photosensitive layer. There are a type containing an alkali salt of an acid which loses its properties as an acid by various heating, a type utilizing activation of a diazo compound and a coupling component by heating and melting using a higher fatty acid amide as a color forming aid.

In the wet type, it takes time to replenish and dispose of the liquid because it uses a developer, and in addition to maintenance problems such as a large device, it is not possible to add it immediately because it is wet immediately after copying, It has some problems such as the copied images cannot be stored for a long time. In addition, the cyclic type requires replenishment of the developing solution as well as the wet type, and also needs gas absorption equipment to prevent the generated ammonia gas from leaking to the outside. , I have problems such as smell of ammonia immediately after copying. On the other hand, unlike the wet type and dry type, the heat development type has an advantage in maintenance because it does not require a developing solution, but all the conventionally known types require a high development temperature of 150 ° C to 200 ° C. Moreover, unless the temperature is controlled to about ± 10 ° C., there is a problem that the development cost becomes insufficient and the color tone changes, resulting in a high apparatus cost. Further, the diazo compound used for such high temperature development also needs to have high heat resistance, but such a compound is often disadvantageous for forming a high concentration. Attempts at low temperature development (90 ° C to 130 ° C) have been made frequently, but there was a drawback that the shelf life of the material itself was shortened.

As described above, the heat-development type is expected to have a merit in maintenance as compared with the wet type and the dry type, but is not yet the mainstream of the diazo copying system.

Now, in order to obtain a desired color density by heating a material provided with a layer containing a diazo compound, a coupling component and a color-forming aid on a support, each component is instantly melted, diffused and reacted by heating. Therefore, it is necessary to generate a coloring dye.
Designing a material that can sufficiently develop color and obtain a high concentration even if the heating temperature is low, as a matter of course, there is a possibility that this reaction will occur even during storage at room temperature before copying, and it will always turn white. It appears as a phenomenon in which the background area that must be colored becomes colored.

In order to solve this seemingly incompatible problem, the inventors of the present invention have made extensive studies, and as a result, in a copying material provided with a heat-developable photosensitive layer containing a diazo compound, a coupling component and a color-forming auxiliary on a support. Have found that the inclusion of the diazo compound in a microcapsule is one of the basic solutions. However, sufficient effect was not obtained by that alone, and further study was conducted to arrive at the present invention.

Therefore, a first object of the present invention is to provide an image forming method of a copying material which can obtain a high color density even by low temperature development.

A second object of the present invention is to provide a simple and easy-to-maintain image forming method in which a latent image forming process by exposure and a developing process by heating are combined using the above copying material.

<Means for Solving Problems> The above-mentioned objects of the present invention are to provide a support on which a heat-developable photosensitive layer containing a microcapsule containing a diazo compound, a coupling component and a color-forming aid is provided. An image forming method for a heat-development type copying material for forming an image on a copying material, wherein a latent image is formed on the photosensitive layer by performing exposure corresponding to an image of an original, and a portion other than the image forming portion is fixed by light irradiation. A first step, and a second step of uniformly wetting the entire photosensitive layer of the copying material with water after the first step,
This is accomplished by an image forming method for a heat-developable copying material, which is characterized by comprising a third step of developing by heating with a heating means. At this time, the wall of the microcapsule is preferably made of a polymer substance formed by polymerizing around the core substance after emulsifying the core substance of the microcapsule, and the polymer substance is selected from polyurethane and polyurea. It is preferably formed of at least one kind.

<Function> As a result of investigation aimed at lowering the heat development temperature, the present inventors provided water so that the entire photosensitive layer was uniformly wetted before the heat development, so that the development was performed as compared with the case where it was not. We have made a surprising discovery that a sufficiently high color density can be obtained even if the temperature is lowered by 30 ° C or more.

However, it is in accordance with the object of the present invention that this moisture is provided before the heat development, and the presence of the same amount of moisture in the photosensitive layer during storage before copying causes a marked increase in background density. . Further, even if this water content was provided to the photosensitive layer after thermal development, no further increase in color density was observed.

Moisture (fountain solution) provided before heat development in the present invention can be conveniently provided by any method as long as it can uniformly wet the photosensitive layer. the amount is preferably adjusted so as to be ^{0.1g / m 2 ~20g / m 2} .

The fountain solution used in the present invention can be used as an aqueous solution of a known anionic or nonionic surfactant for uniformly wetting the photosensitive layer. Preferred surfactants include sodium alkylbenzenesulfonate, sodium alkylsulfate, dioctyl sodium sulfosuccinate, polyalkylene glycol (eg, polyoxyethylene nonyl phenyl ether), and the like.

The fountain solution in the present invention can be provided to the photosensitive layer from the support side or the opposite side. The method can be selected from ordinary spray coating, dip coating, coating bar coating, and the like, for example, the method described in Yuji Harazaki, “Coating Engineering,” page 253 (published by Asakura Shoten in 1973). it can.

The fountain solution used in the present invention is a pigment dispersant, a thickener,
A flow modifier, an antifoaming agent, a foam suppressor, a release agent, a coloring agent and the like can be appropriately blended and used as necessary.

The diazo compound and the coupling component contained in the photosensitive layer of the present invention are those which come into contact with each other by heating to develop a color, and the diazo compound decomposes when receiving a light of a specific wavelength before the coloring reaction. A photodegradable compound is used.

The photodecomposable diazo compound as used in the present invention mainly refers to an aromatic diazo compound, and more specifically, refers to an aromatic diazonium salt, a diazosulfonate compound, or a diazoamino compound. It is generally said that the photodecomposition wavelength of a diazo compound is its absorption maximum wavelength. It is known that the maximum absorption wavelength of the diazo compound changes from about 200 nm to about 700 nm depending on its chemical structure. ("Photolysis and Chemical Structure of Photosensitive Diazonium Salts" Takahiro Tsunoda, Nobuo Yamaoka Journal of the Photographic Society of Japan 29 (4) 197-205 (1965))
When a diazo compound is used as a photodegradable compound, it decomposes with light having a specific wavelength according to its chemical structure. Further, by changing the chemical structure of the diazo compound, the hue of the dye after the reaction can be changed even when the coupling reaction with the same coupling component is carried out.

The diazo compound is a compound represented by the general formula ArN ₂ ⁺ X ⁻ . (In the formula, Ar represents a substituted or unsubstituted aromatic ring, N ₂ ⁺
Represents a diazonium group, and X ⁻ represents an acid anion. In the present invention, it is also possible to obtain a multicolor heat development type copying amount by using diazo compounds having different photolytic wavelengths or different photolytic rates.

Specific examples of the cation moiety of the diazo compound used in the present invention include the followings.

Specific examples of the acid that forms the diazonium salt with the cation portion of the diazo compound include the following examples.

C _n F _{2n + 1} COOH (n is an integer of 1 to 9), C _m F _{2m + 1} SO ₃ H (m is an integer of 1 to 9), boron tetrafluoride, tetraphenyl boron, hexafluorophosphoric acid, Aromatic carboxylic acid, aromatic sulfonic acid, metal halide (zinc chloride, cadmium chloride, tin chloride, etc.) The coupling component used in the present invention forms a dye by coupling with a diazo compound in a basic atmosphere. There are so-called active methylene compounds having a methylene group next to a carbonyl group, phenol derivatives, naphthol derivatives and the like, and specific examples include the following.

These coupling components can be used alone or in combination of two or more, and any hue can be obtained if necessary.

These diazo compounds and coupling components can be synthesized by a conventionally known synthesis method, for example, The Aromat
ic Diazo Compounnds and Their Technical Applicatio
ns (published by MABSo, published in London 1949) and the like can be synthesized.

As one of the color-developing aids of the present invention, it is preferable to add a basic substance, if necessary, for the purpose of making the system basic during heat development to promote the coupling reaction.

As the basic substance, a hardly water-soluble or water-insoluble basic substance or a substance which generates an alkali by heating is used.

As the basic substance, inorganic and organic ammonium salts, organic amines, amides, urea and thiourea and derivatives thereof, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines, Triazoles, morpholines,
Examples thereof include nitrogen-containing compounds such as piperidines, amidines, formamidines and pyridines. Two or more of these basic substances can be used in combination.

In addition to the compounds contained in the color forming aid of the present invention, a phenol derivative, a naphthol derivative, an alkoxy-substituted benzene, an alkoxy-substituted naphthalene, and a hydroxy group are contained in the photosensitive layer so that thermal development can be rapidly and completely performed with low energy. Compounds, amide compounds, sulfonamide compounds can be added. It is considered that these compounds lower the melting point of the coupling component or the basic substance or improve the heat permeability of the microcapsule wall, and as a result, high color density can be obtained.

The coloring aid of the present invention also includes a heat-soluble substance. The heat-fusible substance is a substance that is solid at room temperature and melts by heating and has a melting point of 50 ° C. to 150 ° C., and is a substance that dissolves a diazo compound, a coupling component, or a basic substance. Specific examples of these compounds include fatty acid amides, N-substituted fatty acid amides, ketone compounds, urea compounds,
Esters and the like can be mentioned.

The microcapsules containing the diazo compound of the present invention can be prepared, for example, by the method described in JP-A-59-190886. Polyurea and polyurethane forming the walls of the microcapsules can be obtained by polymerizing the corresponding monomers by the method described above, but the amount of the monomers used is such that the average particle size of the microcapsules is 0.3 μ to 12 μ, and the wall thickness is 0.01.
It is decided to be ~ 0.3. The diazo compound is preferably applied in an amount of 0.05 to 5.0 g / m ² .

The microcapsules containing the diazo compound of the present invention dissolve the diazonium salt and the same or different compounds that react with each other to form a polymeric substance in a non-aqueous solvent having a boiling point of 40 ° C. or higher and 95 ° C. or lower at normal pressure. The resulting solution was dispersed and emulsified in a hydrophilic protective colloid solution, and the system was heated while reducing the pressure in the reaction vessel to distill off the non-aqueous solvent to move the wall forming substance to the oil droplet surface, and at the oil droplet surface. The substantially solvent-free microcapsules produced by advancing a polymer formation reaction by polyaddition and polycondensation to form a wall film are particularly preferable for achieving a good shelf life.

In the present invention, the coupling component is 0.1 to 30 parts by weight, and the basic substance is 0.1 to 30 parts by weight with respect to 1 part by weight of the diazo compound.
It is preferable to use 30 parts by weight.

A coupling component used in the present invention, a basic substance,
Other color forming aids are preferably used by solid dispersion with a water-soluble polymer by a sand mill or the like. Preferred water-soluble polymers include water-soluble polymers used when preparing microcapsules (see, for example, JP-A-59-59).
No. 190886). In this case, the diazo compound, the coupling component, and the color-developing aid are added so as to be 5 to 40% by weight with respect to the water-soluble polymer solution. The dispersed particle size is preferably 10 μm or less.

To the copying material of the present invention, a free radical generator (a compound that generates a free radical upon irradiation with light) used in a photopolymerizable composition or the like for the purpose of reducing yellowing of the background after copying can be added. . Examples of the free radical generator include aromatic ketones, quinones, benzoin, benzoin ethers, azo compounds, organic disulfides, acyloxime esters and the like. The amount to be added is the diazo compound 1
0.01 to 5 parts by weight of the free radical generator is preferable with respect to parts by weight.

Similarly, a polymerizable compound having an ethylenically unsaturated bond (hereinafter referred to as a vinyl monomer) can be used for the purpose of reducing yellow coloring. The vinyl monomer is a compound having at least one ethylenically unsaturated bond (vinyl group, vinylidene group, etc.) in its chemical structure and has a chemical form of monomer or prepolymer. Examples thereof include unsaturated carboxylic acids and salts thereof, esters of unsaturated carboxylic acids with aliphatic polyhydric alcohols, amides of unsaturated carboxylic acids with aliphatic polyhydric amine compounds, and the like. The vinyl monomer is used in a proportion of 0.2 to 20 parts by weight with respect to 1 part by weight of the diazo compound.

The free radical generator and the vinyl monomer are preferably used by being contained in a microcapsule together with the diazo compound.

In the present invention, in addition to the above materials, citric acid, tartaric acid, oxalic acid, boric acid, phosphoric acid, pyrophosphoric acid and the like can be added as an acid stabilizer.

For the copying material of the present invention, a coating solution containing a microcapsule containing a diazo compound or the like, a coupling component, a basic substance and other additives is prepared, and the coating solution is applied onto a support such as paper or a synthetic resin film. Bar coating, blade coating,
A photosensitive layer having a solid content of 2.5 to 30 g / m ² is provided by coating and drying by a coating method such as air knife coating, gravure coating, roll coating, spray coating, and dip coating. In the copying material of the present invention, the microcapsules, the coupling component, the base and the like may be contained in the same layer as described in the above method, or may have a laminated structure in which they are contained in different layers. You can also

It is also possible to apply a photosensitive layer after providing an intermediate layer described in Japanese Patent Application No. 59-177669 or the like on a support.

As the support of the present invention, any of pressure sensitive papers, thermal papers, and paper supports used for dry or wet diazo copying papers can be used, and a neutral sizing agent such as alkyl ketene dimer can be used. Neutral paper of sized pH 6 to 9 (described in Japanese Patent Application No. 55-14281), JP-A-57-1
Paper satisfying the relationship between Steckigt sizing degree and metric weight described in 16687 and having a Beck smoothness of 90 seconds or more.
Paper having an optical surface roughness of 8 μm or less and a thickness of 30 to 150 μm described in 58-136492, and a density described in JP-A-58-69091.
Paper having an optical contact rate of 15% or more and 0.9 g / cm ³ or less, Canadian standard freeness described in JP-A-58-69097 (JIS P812
Paper that is made from pulp that has been beaten to 400 cc or more in 1) to prevent the coating liquid from seeping in, and the glossy surface of the base paper made by the Yankee machine described in JP-A-58-65695 is used as the coating surface for color density and resolution. For improving
It is also possible to use a paper or the like having the coating suitability improved by subjecting the base paper described in 35985 to corona discharge treatment.

Further, the synthetic resin film used as the support in the present invention does not deform even by heating during the development process and can be arbitrarily selected from known materials having dimensional stability. Examples of such a film include polyester films such as polyethylene terephthalate and polybutylene terephthalate, cellulose derivative films such as cellulose triacetate film, polystyrene films, polypropylene films, polyolefin films such as polyethylene, and the like. Can be used. As the thickness of the support, 20 to 200μ
What is used.

The following method is preferable for forming an image on the copying material of the present invention. In the first step of performing exposure corresponding to the image of the original to form a latent image on the photosensitive layer and fixing the portions other than the image forming portion by light irradiation, the exposure light source is
Various fluorescent lamps, xenon lamps, mercury lamps, etc. are used, and the fact that the emission spectrum is almost the same as the absorption spectrum of the diazo compound used in the copying material enables efficient optical fixing of the parts other than the image forming part. Is preferable. Further, in the third step of heating and developing the entire surface of the photosensitive layer of the material by a heating means, a heating pen, a thermal head, an infrared ray, a high frequency wave, a heat block, a heat roller or the like can be used as the heating means.

<Effects of the Invention> Microcapsules containing a diazo compound on a support,
In a method for forming an image on a heat-developable copying material in which an image is formed on a copying material provided with a photosensitive layer containing a coupling component and a color-forming auxiliary, a latent image is formed on the photosensitive layer by performing exposure corresponding to the image of the original. In addition, the entire photosensitive layer of the copying material is uniformly wetted with water between the first step of fixing the portion other than the image forming portion by light irradiation and the third step of heating and developing by the heating means. By providing the second step, low temperature development is possible. The development temperature can be arbitrarily set depending on the characteristics of the material such as the diazo compound to be used and the development conditions, but according to the present invention, the development temperature of 150 ° C. or lower, which has hitherto been impossible, can be freely selected.

The heat development temperature of the present invention is determined by several factors such as that the copy after development is completely dry, curling is not large, and copying speed is fast, but it is in the range of 60 ° C to 140 ° C. Can be set to.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Examples> 1-morpholino-2,5-dibutoxybenzene-4-diazonium hexafluorophosphate (3.45 parts), xylylene diisocyanate and trimethylolpropane (3: 1)
18 parts of the adduct was added to a mixed solvent of 6 parts of tricresyl phosphate and 5 parts of ethyl acetate, and dissolved by heating. This solution of the diazo compound was mixed with an aqueous solution in which 5.2 parts of polyvinyl alcohol was dissolved in 58 parts of water, and emulsified and dispersed at 20 ° C. to obtain an emulsion having an average particle size of 2.5 μm. 100 parts of water was added to the obtained emulsion, and the mixture was heated to 60 ° C. with stirring, and after 2 hours, a capsule solution containing a diazo compound in the core substance was obtained.

Next, 10 parts of 2-hydroxy-3-naphthoic acid anilide and 10 parts of triphenylguanidine were added to 200 parts of a 5% polyvinyl alcohol aqueous solution and dispersed by a sand mill for about 24 hours,
A dispersion having an average particle size of 3 μ was obtained.

To 50 parts of the diazo compound capsule solution obtained as described above, 50 parts of a dispersion of the coupling component and triphenylguanidine and 10 parts of a 40% calcium carbonate dispersion were added to prepare a coating solution. This coating liquid is a smooth high-quality paper (75g / m ² )
The coating material was applied to a dry weight of 10 g / m ² using a coating bar and dried at 50 ° C. for 1 minute to prepare Copy Material A.

A test manuscript (tracing paper having a circle having a diameter of 3 cm uniformly painted black with a 2B pencil) was overlaid on the copy material A and exposed with a fluorescent lamp. At this time, a lamp having an emission spectrum of a fluorescent lamp having a maximum value at 420 nm was used.
Then, the image was heated by a heat block heated to 120 ° C. for 3 seconds to form an image. Similarly, the heat block temperature was tested at 80 ° C and 100 ° C. On the other hand, 2 g / m ² of water was applied to the copying material A with a coating bar before heating after exposure and then heated with a heat block in the same manner. Also, at 40 ° C and 90% RH to test the shelf life
After storage for 24 hours, exposure was performed in the same manner and development was performed at each temperature. A 24-hour storage test at 60 ° C. and 30% RH was also performed. The densities of the colored portion and the background portion of the sample obtained by each test were measured with a Macbeth densitometer. Firstly, the result of the test in which the heating temperature was changed and secondly, the result of the pre-copy storage test were shown.

As shown in Table 1, it can be seen that when development is performed in the presence of dampening water, a sufficient color density can be obtained even at a low temperature. When combined with the results shown in Table 2, the effect of the present invention becomes clear.

Claims (1)

(57) [Claims] 1. An image of a heat-developable copying material for forming an image on a copying material, which comprises a support and a heat-developable photosensitive layer containing a microcapsule containing a diazo compound, a coupling component and a color-forming aid. In the forming method, a first step of performing exposure corresponding to an image of a document to form a latent image on the photosensitive layer and fixing other than the image forming portion by light irradiation, and a step of copying the copy material after the first step An image forming method for a heat-developable copying material, comprising a second step of uniformly moistening the entire photosensitive layer with water, and a third step of subsequently developing by heating with a heating means.