JPH04299175A - Imaging method and photographic printing paper therefor - Google Patents

Abstract

PURPOSE:To achieve excellent thermal transfer sensitivity and fixing properties by bringing an ink ribbon containing leuco pigment precursor into contact with a photographic printing paper containing an interlayer compound imparted with ion exchange capacity with leuco pigment and having developing function. CONSTITUTION:When an interlayer compound, i.e., non-treated montomorillonite 1, to be employed in the image receiving layer of photographic printing paper is swollen with water and added with organic cations, e.g. quaternary ammonium ions 3, ion exchange takes place and the organic cations 3 are taken in between layers in place of sodium ions 2 being held therein. When an ink ribbon containing leuco pigment precursors is pushed against such photographic printing paper and thermal stimulus is imparted through a thermal head or the like, the leuco pigment precursors move quickly to the image receiving layer of the photographic printing paper and transferred thereto. Thus transferred leuco pigment precursors develop a color through developing function of the image receiving layer while at the same time they are taken in between layers of montomorillonite 1 where they are fixed firmly through ion bond.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method for forming a dye image on photographic paper by a thermal transfer method, and more particularly to photographic paper used in this image forming method.

0002

2. Description of the Related Art For example, attempts have been made to form images using a thermal transfer method in order to print out images taken with an electronic still camera or the like onto photographic paper in the same way as silver halide photographs. This thermal transfer method involves bringing an ink ribbon containing dye into contact with photographic paper on which an image-receiving layer has been formed.
The ink ribbon is heated by a thermal head or the like, and the dye in the ink ribbon is transferred to the image-receiving layer of the photographic paper. The image-receiving layer of photographic paper is made of polyester, etc.
Furthermore, disperse dyes and the like are used as dyes for ink ribbons.

By the way, it is not known that the disperse dyes normally used in this type of system have been devised in various ways as disclosed in JP-A-1-259989, JP-A-1-275096, etc. In other words, after transferring to the image-receiving layer, it is merely retained in the image-receiving layer by interactions with the image-receiving layer polymer such as van der Waals force, dipole force, and hydrogen bonding. Therefore, if the dye comes into contact with a resin or solvent that has a higher affinity for the dye after image formation, or if enough thermal energy is supplied to cancel out these interactions, the dye may migrate or elute, or the image may become damaged. Inconveniences such as blurring occur.

[0004] Under such circumstances, for example, Japanese Patent Application Laid-open No. 1983-
78893, JP 60-2398, JP 60-110494, JP 60-22078
5, JP-A-60-260381, JP-A-6
As seen in Japanese Patent No. 0-260391, etc., means based on the formation of chemical bonds have also been proposed.

The method disclosed in these documents uses a dye having a group capable of reacting with an epoxy group or an isocyanate group, and contains a compound having the corresponding group in the image-receiving layer.
There is also a method of containing a compound having active hydrogen in the image-receiving layer using a dye having an acryloyl group or a methacryloyl group, and a method of containing a metal compound in the image-receiving layer using a dye capable of forming a metal complex, and a method of containing a metal compound in the image-receiving layer using a dye that can form a metal complex. (or a methylene group) is sublimated and transferred to react with an aldehyde (nitroso) compound in the image-receiving layer to form a dye.

However, with the method based on the formation of chemical bonds, the reactivity of the dye and the image-receiving layer is high and the storage stability is poor, the reaction does not complete in a short time and it takes a long time to form a stable image, and the dye There are drawbacks such as difficulty in preparation and limited types of dyes that can be used, and even with these methods, it cannot be said that the fixing properties are sufficient.

On the other hand, the coloring materials used in the thermal transfer method include
For example, attempts have been made to use leuco dyes, as described in JP-A-59-16780. However, when using the leuco dye disclosed in these,
Since the coloring material has a relatively strong sublimation property, the thermal stability of the image is poor, and there is a problem that the color is easily erased due to the presence of moisture or plasticizer.

[0008]

As described above, in the conventional thermal transfer system, dye transfer due to lack of fixing performance is a major obstacle to practical application, and improvement of this problem is desired. The present invention was proposed in view of the above-mentioned conventional circumstances, and it is possible to obtain images that have excellent thermal transfer sensitivity and have fixing properties comparable to silver salt photographic images. The object of the present invention is to provide an image forming method and furthermore, a photographic paper.

[0009]

[Means for Solving the Problems] As a result of intensive research to achieve the above object, the present inventors have developed an intercalation compound ( We have discovered that when a leuco dye is imagewise transferred to a clay mineral (clay mineral), this dye image is converted into an insoluble and infusible pigment image and is firmly fixed. The present invention was completed based on this knowledge.

That is, the image forming method according to the first invention of the present application involves applying a leuco dye precursor to a photographic paper that contains an intercalation compound that has an ion exchange ability with a leuco dye and also has a color developing function. The leuco dye precursor is transferred from the ink ribbon to the photographic paper by thermal stimulation, and the leuco dye developed by the color developing function is fixed.

Further, the photographic paper according to the second invention of the present application contains a leuco dye, an intercalation compound substituted with ion-exchangeable ions, and a binder polymer, and the image-receiving layer having a color developing function is attached to the support. It is characterized by being formed on the top.

The present invention is directed to the formation of an ionic bond between the cation moiety of a leuco dye and the anion moiety on the surface of an intercalation compound (organic-clay composite) that is swollen in a non-aqueous medium and included in the image-receiving layer of photographic paper. Image fixation is performed based on this basic principle. Therefore, an ink ribbon containing a leuco dye,
An image is formed using photographic paper containing the intercalation compound. However, when a leuco dye that is colored by an oxidation reaction is used in the ink ribbon, it exhibits hydrophilicity due to the presence of a cationic moiety, which prevents the dye from transferring to the image-receiving layer, which is swollen by the binder polymer and made hydrophobic. Therefore, in the present invention, an unionized leuco dye precursor (herein, a reduced leuco dye in a decolorized state is referred to as a leuco dye precursor for convenience) is used in the ink ribbon, and after transfer to the image-receiving layer, it is developed. It will be converted into a color-forming leuco dye using a coloring agent.

[0013] Leuco dyes used as coloring materials develop or change color through redox reactions, and include triphenylmethane phthalides, fluorans, thiofluorans, indolylphthalides, rhodamine lactams, and azaphthalides. Typical examples include leuco dyes having a lactone ring.

Specifically, examples of triphenylmethane phthalides include crystal violet lactone and malachite green lactone, and examples of fluorans include 3-diethylamino-6-methyl-7-chlorofluorane and 3-diethylamino-6-methyl-7-chlorofluoran. -7-methoxyfluorane, 3-diethylamino-6-benzyloxyfluorane, 1,2-benz-6-diethylaminofluorane, 3
, 6-di-p-toluidino-4,5-dimethylfluorane-phenylhydrazide-γ-lactam, 3-amino-
5-methylfluorane, 2-methyl-3-amino-6-
Methyl-7-methylfluorane, 2,3-butylene-6
-di-n-butylaminofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7
-para-toluidinofluorane, 7-acetamino-3-
Examples include diethylaminofluoran, 2-bromo-6-cyclohexylaminofluoran, 2,7-dichloro-3-methyl-6-n-butylaminofluoran, and the like.

[0015] Examples of thiofluoranes include 3-diethylamino-6-methyl-7-dimethylaminothiofluoran and 3-diethylamino-7-dibenzylaminothiofluorane, and examples of indolyl phthalides include 8-(4-diethylaminophenyl)-8-(1
-ethyl-2-methylindol-8-yl)phthalide, 3,3-bis(1-ethyl-2-methyl-8-yl)
Phthalide, 3,3-bis(2-phenylindole-3
-yl)phthalide, 3-(4-di-n-butylaminophenyl)-3-(2-phenylindol-3-yl)
Phthalide, 8-[4-(dimethylamino)phenyl]-
Examples include 3-[N,N-bis-(4-octylphenyl)amino]phthalide. Furthermore, examples of rhodamine lactams include rhodamine lactone, and examples of azaphthalides include 3,3-bis(1-ethyl-2-methylindol-3-yl)-7-azaphthalide.

In addition, leucobasic cyanine, leucomalachite green, leuco crystal violet, p,p'-tetradimethyldiaminobenzophenone (
Michler's ketone), oxazine-based leuco thermosensitive dyes (manufactured by Hodogaya Chemical Co., Ltd., trade name: CSB-12, etc.), spiropyran-based leuco thermosensitive dyes (manufactured by Hodogaya Chemical Co., Ltd., trade name: C)
SR-13, etc.), quinoline-based leuco thermosensitive dyes (manufactured by Hodogaya Chemical Co., Ltd., trade name CSY-13, etc.), redox indicators, pH indicators, viologen, etc. can also be used. The above-mentioned leuco dyes may be used alone or in combination of two or more to control color tone and the like. Further, the amount added may be appropriately set depending on the type of leuco dye, etc.

[0017] The above-mentioned leuco dye is dissolved or dispersed in a binder polymer in the state of a non-ionized precursor, and a film is formed on a film support to form an ink layer, thereby producing an ink ribbon for thermal transfer. Of course, depending on the type of dye, it is also possible to form an ink layer using only the leuco dye precursor. At this time, if the amount of leuco dye precursor is too small, the color density will be insufficient, so leuco dye precursor
It is preferably contained in a proportion of 100% by weight.

On the other hand, intercalation compounds used in photographic paper include clay minerals having a layered structure and having exchangeable cations between the layers. Typically, it is a montmorillonite group mineral. Montmorillonite group minerals have the following general formula (X, Y)2~3Z4 O10(OH)2 mH2
O・(W1/3) [However, X=Al, Fe(III)
, Mn(III), Cr(III), Y=Mg
, Fe(II), Mn(II), Ni, Zn, Li,
Z=Si, Al, W=K, Na, Ca, H2O
represents interlayer water, and m represents an integer. ] It is a clay mineral represented by

Here, depending on the combination of X and Y and the difference in the number of substitutions, montmorillonite, magnesian montmorillonite, iron montmorillonite, iron magnesian montmorillonite, beidellite, aluminum ambeidellite, nontronite, aluminum annontronite, saponite, aluminum Many types of natural products exist, such as nian saponite, hectorite, and sauconite, but in addition to these natural products, synthetic products in which the OH group in the above formula is substituted with fluorine are also commercially available.

In addition to the above-mentioned montmorillonite group minerals, sodium silicic mica, sodium taeniolite,
Mica group minerals such as lithium taeniolite can be used. Kaolinite, talc, pyrophyllite, etc., which have a layered structure but do not have exchangeable cations between the layers, are unsuitable. Furthermore, although zeolite has alkali metal ions or alkaline earth metal ions as exchangeable cations, its structure is network-like and the pore size is small, so its performance is somewhat inferior.

These intercalation compounds are used with organic cations bonded by ion exchange between the layers. Suitable organic cations include quaternary ammonium ions and substituted phosphonium ions, such as alkylphosphonium ions and arylphosphonium ions. However, for example, in the case of a quaternary ammonium ion, the four alkyl groups have 4 or more carbon atoms, preferably 8 or more carbon atoms, and these 4
Preferably, the two alkyl groups are the same. If the number of long-chain alkyls is small, a sufficient interlayer distance cannot be ensured, and there is a possibility that the exchange ability for leuco dyes will be insufficient.

[0022] The above-mentioned organic cation expands the interlayer distance of the intercalation compound, and also changes the interlayer of the intercalation compound, which is originally hydrophilic, to be hydrophobic due to its hydrophobic chain. It plays the role of facilitating compatibility with. Therefore, by ion-exchange bonding an organic cation such as a quaternary ammonium ion or a substituted phosphonium ion to an intercalation compound, it is imparted with ion-exchange ability with a leuco dye, and at the same time is made non-aqueous solvent swellable.

[0023] The intercalation compound, which is endowed with ion exchange ability with the leuco dye and is swellable in a non-aqueous solvent, is mixed and dispersed with a binder polymer, and applied to a film-like support in a state in which the binder polymer is swollen. By forming a film, an image-receiving layer is formed and used as photographic paper. The film-like support includes paper, synthetic paper, plastic film, metal plate, metal foil, aluminum-deposited plastic film, etc.
Optional.

Furthermore, as the binder polymer, a wide range of general thermoplastic resins can be used, but substituents that inhibit the fixing action, such as those that are more likely to undergo ion exchange between clay layers than cationic dyes, can be used as the binder polymer. Those containing ammonium groups etc. are not preferred. Further, the glass transition Tg of the binder polymer may be, for example, at room temperature or below, as long as it does not cause any practical problems (as long as blocking due to viscosity or the like is not a problem). The amount of the intercalation compound imparted with ion exchange ability is preferably 5 to 90% by weight based on the solid content of the image-receiving layer. The lower limit of the amount added is determined by the fixing ability, and if it is less than 5% by weight, the fixing effect may be insufficient. The upper limit is determined by the practical property of film formation, and is 90% by weight.
If it exceeds this value, a soft and good film cannot be formed.

In some cases, it is preferable for photographic paper to have a high degree of whiteness, and one method is to add a fluorescent brightener to the image-receiving layer. Compounds may also be used. Further, a plasticizer may be added to the image-receiving layer in order to control the glass transition point Tg of the binder polymer, and auxiliary additives for other purposes may be added, as long as they do not impede the fixing properties.

The image-receiving layer needs to have a color developing function for the leuco dye precursor, and usually a color developer is dispersed and mixed in the image-receiving layer. As the color developer, various electron-accepting compounds having a phenolic hydroxyl group can be used. For example, tert-butylphenol, nonylphenol, dodecylphenol, styrenated phenols, 2,2-methylenebis-(4-methyl-6-t
ert-butylphenol), α-naphthol, β-naphthol, hydroquinone monomethyl ether, guaiacol, eugenol, p-chlorophenol, p-bromophenol, o-chlorophenol, o-bromophenol, p-phenylphenol, o-phenylphenol , p-(p-chlorophenyl)phenol, o-(
o-chlorophenyl)phenol, methyl p-oxybenzoate, ethyl p-oxybenzoate, propyl p-oxybenzoate, butyl p-oxybenzoate, octyl p-oxybenzoate, dodecyl p-oxybenzoate, 3- Isopropylcatechol, p-tert-butylcatechol, 4,4-methylenediphenol, 4,4-thio-bis-(6-tert-butyl-3-methylphenol)
, 1,1-bis-(4-hydroxyphenyl)cyclohexane, 4,4-butylidene-bis-(6-tert-
butyl-3-methylphenol), bisphenol A,
Bisphenol S, 1,2-dioxynaphthalene, 2,
3-Dioxynaphthalene, chlorocatechol, bromocatechol, 2,4-dihydroxybenzophenone, phenolphthalein, o-cresolphthalein, methyl protocatechuate, ethyl protocatechuate, propyl protocatechuate, protocatechuate Octyl acid, dodecyl protocatechuate, 2,4,6-trioxymethylbenzene, 2,3,4-trioxyethylbenzene, methyl gallate, ethyl gallate, propyl gallate, butyl gallate, hexyl gallate, Dodecyl gallate, cetyl gallate, stearyl gallate, 2,3
, 5-trioxynaphthalene, tannic acid, etc.

Alternatively, an acidic resin having a function as a color developer may be used as the binder polymer. Acidic resin is a general term for resins that have the possibility of strongly ionic interaction with the above-mentioned leuco dye (basic dye), that is, polymers that have active anions in their molecules. Therefore, inferred from the molecular structure, resins etc. in which acidic groups such as sulfone groups and carboxyl groups are incorporated into the main chain or side chain of the polymer are considered. Furthermore, as seen in acrylic fibers, fibers containing acid residues such as potassium persulfate, which is a polymerization catalyst, at the molecular terminals are also considered to correspond to this category.

Specifically, a color former (leuco dye precursor) is added to a non-aqueous solution of the target resin, and the resultant film is cast to determine whether the dried film is colored or not. As a result of such preliminary tests, vinylidene chloride-acrylonitrile copolymer (manufactured by Aldrich), carboxylated vinyl chloride polymer (manufactured by Aldrich), etc. were found to be resins exhibiting significant acidity.

In forming an image, an ink ribbon may be brought into contact with the photographic paper, and thermal stimulation may be selectively applied to the ink ribbon using a thermal head or the like in accordance with an image signal. Note that the means for applying the thermal stimulation is not limited to the thermal head, and any means proposed so far in the thermal transfer method can be employed.

[0030]

[Function] Montmorillonite, which is a typical example of the intercalation compound used in the image-receiving layer of photographic paper in the present invention, has a layered structure consisting of a repeating three-layer structure with a regular octahedron as its basic skeleton. holds interlayer water and alkali metal ions, which are exchangeable cations. This state is shown in FIG. That is, untreated montmorillonite 1 retains sodium ions 2 as exchangeable cations between its layers. Let the interlayer distance at this time be d1.

When the montmorillonite 1 is swollen with water and an organic cation, for example, quaternary ammonium ion 3 is added, ion exchange occurs as shown in FIG. 2, and the quaternary ammonium ion 3 replaces the sodium ion 2.
is incorporated between the layers. The interlayer distance d2 at this time is
It is larger than the interlayer distance d1 of untreated montmorillonite, and is provided with ion exchange ability with the leuco dye.

The montmorillonite imparted with ion exchange ability retains quaternary ammonium ions 3 having a hydrophobic chain between its layers, so it is dispersed and swollen in a non-aqueous binder polymer, and is used as an image-receiving layer of photographic paper. be done. Then, when an ink ribbon containing a leuco dye precursor is pressed against the photographic paper on which such an image-receiving layer is formed and thermal stimulation is applied using a thermal head or the like, the leuco dye precursor ( (It is hydrophobic because it is not ionized.) is quickly transferred to the image-receiving layer of photographic paper and transferred.

The transferred leuco dye precursor is compatible with the non-aqueous image-receiving layer, is oxidized and colored by the color developing function of the image-receiving layer, and at the same time enters between the layers of montmorillonite. Then, ion exchange occurs between the quaternary ammonium ions 3 and the ionized leuco dye 4, and the leuco dye 4 is incorporated between the layers of the montmorillonite 1, as shown in FIG. The leuco dye 4 incorporated between the layers of montmorillonite 1 forms an ionic bond with montmorillonite 1 and is firmly fixed to the image receiving layer.

[0034]

EXAMPLES The present invention will be explained below based on specific experimental results.

A. Simulation of fixing operation A-1
Preparation of organic-clay composite: Disperse 20 g of montmorinite in 1 liter of water to swell it, add an equal amount of ethanol to this dispersion, and add various quaternary ammonium salts dissolved in 200 cc of ethanol while stirring. (20 mg equivalent) was added dropwise. As a result, granular aggregation and sedimentation occurred. After this dispersion was allowed to stand for one week, the precipitate was filtered off and washed with a large amount of ethanol to remove unreacted quaternary ammonium salt.

Subsequently, the washed precipitate was dried under reduced pressure at room temperature to obtain an off-white powder. The interplanar spacing d001 of the (001) plane of this powder, that is, the interlayer distance, was measured by powder X-ray diffraction analysis. The results are shown in Table 1.

[Table 1]

A-2 Fixing operation of leuco dye The quaternary ammonium-substituted montmorillonite obtained by the above treatment procedure was added to an acetone solution containing the leuco dye shown in the following chemical formula 1 (manufactured by Hodogaya Chemical Co., Ltd., trade name CF51). , an almost colorless dispersion was obtained by ultrasonic irradiation.

[Chemical formula 1]

When hydrochloric acid was added to this dispersion to develop a leuco dye and the mixture was allowed to stand, only the montmorillonite substituted with a tetraalkyl type quaternary ammonium ion having 8 or more carbon atoms in Table 1 produced a black precipitate. The supernatant liquid became colorless and transparent. Note that the concentration conditions are as follows. Concentration condition 1 Quaternary ammonium-substituted montmorillonite
2.0 parts by weight Leuco dye

0.03 parts by weight acetone

200 parts by weight hydrochloric acid
0.01 part by weight

The precipitate was collected and washed with water, ethanol, acetone, and toluene in that order, but no elution of the dye was observed. The elution of the dye was examined by adding an acetone solution of perchloric acid to the washing solution and checking for color development. On the other hand, for quaternary ammonium substituted products other than tetraalkyl type quaternary ammonium having 8 or more carbon atoms, the supernatant liquid remained colored, and the recovered substituted product (less colored) was easily decolored by washing with acetone.

Next, similar operations were carried out using the substituted product that showed fixing behavior and changing the concentration conditions. Concentration condition 2 Tetra-n-decylammonium-substituted montmorillonite 2.5 parts by weight Leuco dye

0.1 part by weight
acetone

50 parts by weight hydrochloric acid

0.01-0.1 part by weight

The interlayer distance of the recovered colored composite was measured and plotted as a function of the amount of hydrochloric acid added, and is shown in FIG. As a result, although the interlayer distance decreased slightly when the amount of hydrochloric acid added was within the range of 2 milliequivalents/g (expressed as milliequivalents per gram of substituted powder),
The value became constant at about 22.6 Å.

The above phenomenon is thought to be due to a unique reaction between a clay-based intercalation compound having an exchangeable cation and a hydrophobized organic cation; A similar fixing effect cannot be expected with clays, alumina, silica gel, and other silicates.

B. Example 1 B-1 Preparation of ink ribbon Precursor of leuco dye (trade name CF51) (reduction color erasing type)
, polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., trade name PV)
Methyl ethyl ketone (MEK) that dissolves B3000K)
) to prepare a coating solution with the following composition. Composition polyvinyl butyral
1 part by weight leuco dye precursor
1 part by weight MEK
50 parts by weight

0
[044] Using a wire bar, apply this solution to a polyethylene terephthalate film (P) having a heat-resistant slipping layer on the back side.
ET film) and dried with hot air at 120° C. for 2 minutes to obtain an ink ribbon having a colorless transparent layer with a dry thickness of about 1 μm.

B-2 Preparation of photographic paper A solution containing vinylidene chloride-acrylonitrile copolymer (hereinafter referred to as PVCL-AN, manufactured by Aldrich) in the following weight ratio was prepared and used as coating stock solution 1. Composition of coating stock solution 1 Octyl gallate 3 parts by weight PVC
L-AN 2 parts by weight Silicone oil 0.3 parts by weight MEK
20 parts by weight also tetra-n
- Decylammonium-substituted montmorillonite was ultrasonically dispersed and swollen in MEK with the following weight composition to prepare coating stock solution 2. Composition of coating stock solution 2 Tetra-n-decylammonium-substituted montmorillonite 2 parts by weight MEK

30 parts by weight

0046
] These coating stock solutions 1 and 2 were mixed in an equal weight ratio and further dispersed by ultrasonic irradiation to obtain a coating solution. Apply this coating liquid to a thickness of 180 mm using a doctor blade.
It was coated on a μm synthetic paper and dried under reduced pressure at 60° C. for 30 minutes. By this operation, a photographic paper having a film having a dry thickness of about 5 μm as an image-receiving layer was produced. Next, in order to improve the surface properties, heat and pressure treatment was applied to form a glossy pale yellow image receiving layer.

B-3 Printing Experiments Images were formed in a practical form using the ink ribbon and photographic paper prepared in B-1 and B-2. Specifically, we attached the ink ribbon we made to the ribbon cassette of a Sony color video printer and the photographic paper to the photographic paper cassette, and printed a solid (full color) print in a single color.
A green-black glossy image was obtained. After output, 100℃
When heated for about 20 seconds, the image density further increased.

A part of this image was placed in hot water at 80° C., but no fading occurred even after 2 hours. Therefore, when we measured the reflection density of the image before and after immersion in hot water, we found that
O. Although the D value decreased slightly from 2.1 to 1.9, no blurring of the image was observed, including the areas that had been in contact with water vapor.

C. Example 2 C-1 Production of photographic paper Synthetic mica (manufactured by Topy Industries, trade name DMA-350,
The dry powder of the raw material with an interlayer distance of 12.40 Å) was sieved to collect components with a particle size of several μm or less, and 20 g of it was
Disperse and swell in 1 liter of water, add an equal amount of ethanol to this dispersion, and stir for 20 minutes.
13.2 g (20 mg equivalent) of tetra-n-decylammonium bromide dissolved in 0 cc of ethanol was added dropwise. As a result, granular aggregation and sedimentation occurred. After this dispersion was allowed to stand for one week, the precipitate was filtered off, washed with a large amount of ethanol to remove unreacted quaternary ammonium salt, and then dried under reduced pressure at room temperature. The synthetic mica subjected to the ammonium ion substitution treatment exhibits a white color, and the interlayer distance is 29.14.
It was Å.

Using this synthetic mica, a coating solution having the following composition was prepared according to the recipe B-2, and an image-receiving layer was prepared. Composition of coating stock solution 1 Carboxylated vinyl chloride polymer
0.5 parts by weight Bisphenol A

0.5 parts by weight silicone oil

0.5 parts by weight Fluorescent brightener

0.01 part by weight (manufactured by Ciba Geigy, trade name UVITEXOB) MEK

20 parts by weight Composition of coating stock solution 2 Tetra-n-decylammonium substituted synthetic mica
1.5 parts by weight MEK

30 parts by weight

These coating stock solutions 1 and 2 were mixed in an equal weight ratio and further dispersed by ultrasonic irradiation to obtain a coating solution. It was applied to synthetic paper with a thickness of 180 μm using a doctor blade, and was applied under reduced pressure for 6 days.
It was dried at 0°C for 30 minutes. Through this operation, a photographic paper having a film with a dry thickness of about 5 μm as an image-receiving layer was produced.
Furthermore, in order to improve the surface properties, heat and pressure treatment was added to obtain glossy pure white photographic paper.

C-2 Printing Experiment and Evaluation of Migration Using the ink ribbon prepared in B-1, an image was formed in a practical form on the photographic paper prepared in C-1. Specifically, when we attached an ink ribbon to the ribbon cassette of a Sony color video printer and photographic paper to the photographic paper cassette, we performed single-color step printing (gradation printing). An image was obtained.

[0053] In addition, in order to evaluate the transferability, ordinary copy paper was used as the material to be transferred, and the photographic paper on which the image was formed and the copy paper were stacked and placed in an environment of 60°C and 80% relative humidity. Although it was left for one week, almost no image migration was observed. On the other hand, images produced in a similar manner using photographic paper prepared by adding acidic alumina particles instead of quaternary ammonium-substituted synthetic mica in the coating solution for forming the image-receiving layer, show that the concentration of 80 of
More than % has shifted to copy paper. From the above evaluation results, it is clear that the present invention provides a thermal transfer image forming method with extremely excellent fixing properties.

[0054]

Effects of the Invention As is clear from the above explanation, according to the present invention, the fixing properties of thermally transferred leuco dyes can be dramatically improved, and the fixing properties are comparable to those of silver salt-based photographic images. It is possible to obtain an image with . In addition, since a hydrophobic leuco dye precursor is used as the coloring material and ionic bonding is used to bond the leuco dye to the image-receiving layer, transfer and fixation are instantaneous, achieving excellent thermal transfer sensitivity. It is possible to do so.

Furthermore, the photographic paper used in the present invention is
Since it uses general-purpose pigments, clay minerals, etc., and is manufactured in accordance with conventional photographic paper manufacturing methods, it is easy to manufacture and can be provided at low cost. Furthermore, since the image-receiving layer of the photographic paper contains clay minerals, a suitable surface hardness is imparted to the paper, making it possible to write on it with, for example, a pencil.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the structure of montmorillonite.

FIG. 2 is a schematic diagram of montmorillonite substituted with quaternary ammonium ions.

FIG. 3 is a schematic diagram of montmorillonite ion-exchanged with a leuco dye.

FIG. 4 is a characteristic diagram showing the relationship between the amount of hydrochloric acid added and the interlayer spacing of montmorillonite.

Claims (2)

[Claims] Claim 1: An ink ribbon containing a leuco dye precursor is brought into contact with a photographic paper containing an intercalation compound imparted with ion exchange ability with a leuco dye and also has a color developing function, and the ink is thermally stimulated. An image forming method characterized by transferring a leuco dye precursor from a ribbon to the photographic paper and fixing the leuco dye developed by the color developing function. 2. A print characterized in that an image-receiving layer containing a leuco dye, an interlayer compound substituted with ion-exchangeable ions, and a binder polymer and having a color developing function is formed on a support. paper.