JPH0461785B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a heat-sensitive transfer medium that utilizes a color-forming reaction between a leuco dye and a color developer. Furthermore, the present invention relates to a thermal transfer medium that provides a transferred image with uniform density even after multiple transfers. [Prior Art] Conventionally, thermal transfer media have been composed of a transfer sheet in which a heat-sublimable dye is provided on a support and a receiving sheet that receives a heat-sublimable dye image by thermal printing from the back side of the sheet. , a combination of a transfer sheet and a receiving sheet is known, in which a transfer layer of a heat-fusible material and a pigment or dye is provided on a support. The latter type of dye image has poor storage stability and requires an overcoat to be applied on the transferred image, and the latter type is a transfer layer with pigments or dyes dispersed in a thermofusible material, so it is difficult to maintain high-density images. If a large amount of pigment is included for the purpose of obtaining a Since the thermofusible substance migrates to the receiving sheet side, when the transfer sheet and the receiving sheet are peeled off, the transfer sheet and the receiving sheet cannot be peeled off smoothly, resulting in disadvantages such as the thin line image area becoming unclear. On the other hand, there is also known a thermal transfer medium in which substances that react with each other to form color due to heat are supported on separate supports, and the support layers are brought into mutually facing contact to perform thermal printing. Because it is a reactive type, when the transfer layer simply transfers to the receiving layer during face-to-face contact, a sufficient coloring reaction does not occur.
If the heating conditions are set to higher temperature and thermal printing for a longer time in order to promote sufficient reaction, the image on the receiving sheet will be a higher density image, but the image on the transfer sheet will also be lower. The drawback is that the coloring reaction progresses and image formation occurs. [Objective] The present invention provides a stable transferred image with high density by using minute thermal energy, and also provides a uniform transfer image even during multiple transfers by transferring a small amount of leuco dye component from the transfer layer to the receiving layer. The object is to provide a thermal transfer medium that provides image density. [Structure] According to the present invention, a transfer sheet is provided with a transfer layer containing a leuco dye as a main component on a support, and a receiving layer containing a color developer as a main component with respect to the leuco dye is provided on a support. The transfer layer consists of a receiving sheet, and the transfer layer has an oil absorption of 50 to
A thermal transfer medium is provided, characterized in that it is provided through a porous filler-containing layer of 300 ml/100 g. In the thermal transfer medium of the present invention, a receiving sheet is stacked on a transfer sheet so that its receiving layer is in contact with the transfer layer of the transfer sheet, and the surface of the receiving sheet is printed by thermal printing from the back side of the transfer sheet or the back side of the receiving sheet. In the present invention, a plastic film is used as a support for the transfer sheet, and the surface of the plastic has an oil absorption of 50 to 300 ml/100 g (JIS
K5101 method) is provided with a porous filler-containing layer,
At the same time as giving the uneven shape, the ability to retain the leuco dye component has been improved, so that the leuco dye component can be transferred smoothly and uniformly from the transfer layer to the receiving layer, especially during multiple transfers. Transfer images with image density can be easily obtained. In the present invention, as described above, a plastic film having a porous filler-containing layer on the surface is used as a support for the transfer layer. In this case, the porous filler has an oil absorption of 50 to 300 ml/100 g. use something If an oil absorption amount of less than 50 ml/100 g is used, it is not preferable because the density of the obtained image will decrease significantly after multiple transfers.
On the other hand, if an oil absorption amount of more than 300 ml/100 g is used, the transfer efficiency will deteriorate and it will be difficult to obtain a high-density image, which is not preferable. Specific examples of the porous filler used in the present invention include inorganic and organic fine powders such as silica, aluminum silicate, alumina, aluminum hydroxide, magnesium hydroxide, urea-formalin resin, and styrene resin. It will be done. Further, in the porous filler-containing layer provided on the support, the proportion of the porous filler used is preferably 0.5 to 2 g per 1 m ² of the support. There are various known plastic films used as the support, such as polyester films, polyamide films, polyvinyl chloride films, polyethylene films, and polypropylene films. The formation of the porous filler-containing layer on the support can be performed using various binders as described below, and the proportion of the binder used is 1 to 1 part by weight of the porous filler in solid terms. The proportion is 10 parts by weight. The transfer sheet used in the present invention is one in which a transfer layer containing a leuco dye as a main component is provided on the surface of a plastic film having a porous filler-containing layer on the surface as described above. As the leuco dye in this case, any of those conventionally used for pressure-sensitive paper and thermal paper can be used, and triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based ones are preferably used. be done. Specific examples of these leuco dyes are shown below. 3,3-bis(p-dimethylaminophenyl)
-phthalide, 3,3-bis(p-dimethylaminophenyl)
-6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis(p-dimethylaminophenyl)
-6-diethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)
-6-chlorphthalide, 3,3-bis(p-dibutylaminophenyl)
Phthalide, 3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-5,7-dimethylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran, 3-dimethylamino -7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-(N-p-tolyl-N-ethylamino)-6
-Methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-{N-(3'-trifluoromethylphenyl)
amino}-6-diethylaminofluorane, 2-{3,6-bis(diethylamino)-9-
(o-chloroanilino)xantylbenzoic acid lactam}, 3-diethylamino-6-methyl-7-(m-
trichloromethylanilino)fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3-N-methyl-N-amylamino-6-methyl-7- Anilinofluorane, 3-N-methyl-N-cyclohexylamino-
6-Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N,N-diethylamino)-5-methyl-
7-(N,N-dibenzylamino)fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolinopyrillospiran, 6'-bromo-3'-methoxy-benzoindolinopyrillospiran , 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide, 3-(2'-hydroxy-4'-dimethylaminophenyl)- 3-(2'-Methoxy-5'-nitrophenyl)phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide, 3-(2 '-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'-
methylphenyl) phthalide, In the present invention, the leuco dye is usually 0.3 to 30 g/m 2 , preferably 0.5 to 20 g/m ² , preferably 0.5 to 20 g/m 2
It is used at a rate of about g/ ^m2 . The receptor sheet used in the present invention is one in which a receptor layer containing a color developer for the leuco dye as a main component is provided on a support such as paper, synthetic paper, or plastic film. In this case, as the color developer, an electron-accepting substance such as a phenolic substance, an organic acid or its salt or ester is used, and from the viewpoint of practicality, one with a melting point of 200°C or less is preferably used. . Specific examples of the color developer preferably applied in the present invention are shown below. Note that the numbers in brackets indicate the melting point. 4-tert-butylphenol (98), 4-hydroxydiphenyl ether (84), 1-naphthol (98), 2-naphthol (121), methyl-4-
Hydroxybenzoate (131), 4-hydroxyacetophenone (109), 2,2'-dihydroxydiphenyl ether (79), 4-phenylphenol (166), 4-tert-octylcatechol (109), 2, 2′-dihydroxydiphenyl (103),
4,4'-methylenebisphenol (160), 2,
2'-methylenebis(4-chlorophenol)
(164), 2,2'-methylenebis(4-methyl-6
-tert-butylphenol) (125), 4,4'-isopropylidene diphenol (156), 4,4'-isopropylidene bis(2-chlorophenol)
(90), 4,4′-isopropylidene bis(2,6-
dibromophenol) (172), 4,4'-isopropylidene bis(2-tert-butylphenol)
(110), 4,4'-isopropylidene bis(2-methylphenol) (136), 4,4'-isopropylidene bis(2,6-dimethylphenol) (68),
4,4′-sec-butylidene diphenol (119),
4,4'-sec-butylidene bis(2-methylphenol) (142), 4,4'-cyclohexylidene diphenol (180), 4,4'-cyclohexylidene bis(2-methylphenol) (184), salicylic acid (163), salicylic acid methalyl ester (74),
Salicylic acid phenacyl ester (110), 4-hydroxybenzoic acid methyl ester (131), 4-hydroxybenzoic acid ethyl ester (116), 4-hydroxybenzoic acid propyl ester (98), 4-hydroxybenzoic acid isopropyl ester (86) ),
4-hydroxybenzoic acid butyl ester (71),
4-Hydroxybenzoic acid isoamyl ester (50), 4-hydroxybenzoic acid phenyl ester (178), 4-hydroxybenzoic acid benzyl ester (111), 4-hydroxybenzoic acid cyclohexyl ester (119), 5-hydroxybenzoic acid ( 200), 5-chlorsalicylic acid (172), 3-chlorsalicylic acid (178), thiosalicylic acid (164), 2
-Chloro-5-nitrobenzoic acid (165), 4-methoxyphenol (53), 2-hydroxybenzyl alcohol (87), 2,5-dimethylphenol (75), benzoic acid (122), orthotoluic acid (107) , metatoluic acid (111), paratoluic acid (181), orthochlorobenzoic acid (142), metaoxybenzoic acid (200), 2,4-dihydroxyacetophenone (97), resorcinol monobenzoate (135), 4-hydroxy Benzophenone (133), 2,4-dihydroxybenzophenone (144), 2-naftyk acid (184), 1
-Hydroxy-2-naftyk acid (195), 3,4-dihydroxybenzoic acid ethyl ester (128), 3,4-dihydroxybenzoic acid phenyl ester (189), 4-hydroxypropiophenone (150), salic Silsalicylate (148),
Phthalic acid monobenzyl ester (107). In addition, in the present invention, as a color developer, the general formula (In the formula, R is an alkylene group containing 1 to 5 ether bonds.) A phenolic compound represented by the following can be used. This phenolic substance is produced by reacting monothiohydroquinone with the corresponding dihalogenoalkyl ether under alkaline conditions.
It can be easily synthesized in high yield, with high purity, and at relatively low cost. In the phenolic substance represented by the above general formula, R is an alkylene group containing 1 to 5 ether groups, but in this case, the ether group may be in the main chain of the alkylene group, or in the side chain. It may be hot. The number of carbon atoms contained in this ether group-containing alkylene group is usually in the range of 2 to 15. Preferred ether group-containing alkylene groups contain 1 to 3 ether bonds and have 2 to 7 carbon atoms. In the present invention, the oil absorption amount for the receptor layer is
It is preferable to contain the porous filler in an amount of 50 ml/100 g (according to JIS K5101 method) or more preferably 150 ml/100 g or more. The porous filler contained in the receptor layer is 0.01 part by weight or more, usually 0.05 to 10 parts by weight, preferably 0.1 part by weight, per 1 part by weight of the color developer.
-3 parts by weight. Specific examples of porous fillers include silica, aluminum silicate,
Examples include inorganic and organic fine powders such as alumina, aluminum hydroxide, magnesium hydroxide, urea-formalin resin, and styrene resin. Further, in the present invention, a thermofusible substance having a melting point of 200° C. or less, preferably 150° C. or less can be added to the transfer layer and, if necessary, the receiving layer. The amount used is 0.1 to 50 parts by weight per 1 part by weight of the leuco dye. The thermofusible substances preferably used in the present invention are as follows. (1) Fatty acid amides represented by the following general formula () or () R ¹ NHCOR ² (In the formula, R ² is an alkyl group having 1 to 30 carbon atoms, R ¹ ,
(R ³ is an alkyl group having 10 to 30 carbon atoms, and R ⁴ and R ⁵ are hydrogen or a lower alkyl group.) Specific examples of such aliphatic amides include the following. decyl acetamide, decyl propionamide, undecyl acetamide, undecyl propionamide, lauryl acetamide, lauryl propionamide, tridecyl acetamide, tridecyl propionamide, myristyl acetamide, myristyl propionamide, pentadecyl acetamide, pentadecyl propionamide,
Palmitylacetamide, palmitylpropionamide, palmitylbutyramide, heptylacetamide, heptylpropionamide, stearylacetamide, stearylpropionamide, stearylbutyramide, stearylvaleramide,
Stearyl capronamide, stearyl laurinamide, stearyl palmitinamide, stearyl stearinamide, nonadecylacetamide,
Nonadecylpropionamide, behenylacetamide, behenylpropionamide, behenylstearamide, undecanoic acid methylamide, undecanoic acid ethylamide, lauric acid methylamide,
Lauric acid ethylamide, tridecanoic acid methylamide, tridecanoic acid ethylamide, myristic acid methylamide, myristic acid ethylamide, pentadecanoic acid methylamide, pentadecanoic acid ethylamide, palmitic acid methylamide, palmitic acid dimethylamide, palmitic acid butyramide,
Stearic acid methylamide, stearic acid ethylamide, stearic acid propylamide, stearic acid butylamide, stearic acid dimethylamide, stearic acid diethylamide, stearic acid dibutylamide, nonadecanoic acid methylamide, nonadecanic acid ethylamide, behenic acid methylamide, oleic acid methylamide, oleic acid ethylamide . (2) Aromatic carboxylic acid amides represented by the following general formula () (In the formula, R ⁶ is an alkyl group having 1 to 30 carbon atoms, R ⁷ ,
(R ⁸ is hydrogen, halogen, lower alkyl group or lower alkoxy group, and n is 0 or 1) Specific examples of such compounds include those shown below. N-stearylbenzamide, N-palmityl-2-chlorobenzamide, N-stearyl-2
-methoxybenzamide, N-stearyl-4-
Methylbenzamide, N-palmityl-2,4-
Dimethylbenzamide, N-behenylbenzamide, N-behenyl-2-methylbenzamide, N
-stearylphenylacetylamide, N-behenylphenylacetylamide. (3) Amides having a cyclohexyl ring represented by the following general formulas () and () (In the formula, R ⁹ is an alkyl group having 1 to 30 carbon atoms or a substituted or unsubstituted aryl group, R ¹⁰ is hydrogen,
halogen or lower alkyl group) (In the formula, R ¹¹ is an alkyl group having 1 to 30 carbon atoms,
(R ¹² is hydrogen, halogen or lower alkyl group) Specific examples of such compounds include, for example:
Examples include those shown below. N-cyclohexyl acetamide, N-cyclohexylpropionamide, N-cyclohexyl stearamide, N-cyclohexylbenzamide, N-cyclohexyl-2-methylbenzamide, N-cyclohexyl-2-chlorobenzamide, N-cyclohexyl-2, 4-dimethylbenzamide, N-cyclohexylpalmitic acid amide, N-(chlorohexyl) palmitic acid amide, N-(2-methylcyclohexyl) stearic acid amide, N-stearylhexahydrobenzamide. (4) Phenyl esters of hydroxybenzoic acid represented by the following general formula () (wherein, hydroxyl group, n is 0, 1, 2 or 3, and m is 1, 2 or 3) Specific examples of such compounds include, for example:
Examples include those shown below. 4-hydroxybenzoic acid phenyl ester, 4
-Hydroxybenzoic acid (2-methoxyphenyl)
ester, 4-hydroxybenzoic acid (2-methoxy-4-methylphenyl) ester, 4-hydroxybenzoic acid (3,5-dioxyphenyl) ester, 3-hydroxybenzoic acid (4-carboxyphenyl) ester, 4-hydroxybenzoic acid acid (-butoxyphenyl) ester, 4-hydroxybenzoic acid (4-chlorophenyl) ester, salicylic acid (2-chlorophenyl) ester, salicylic acid (4-chlorophenyl) ester, salicylic acid (2,3-dichlorophenyl) ester, salicylic acid (2-chlorophenyl) ester , 6-dichlorophenyl) ester, salicylic acid (2,4,6-trichlorophenyl) ester, salicylic acid (2-bromophenyl) ester, salicylic acid (4-bromophenyl) ester, salicylic acid (2,4-dibromophenyl) ester , salicylic acid (2,6-dibromophenyl) ester, salicylic acid (2,4,6
-tribromophenyl) ester, salicylic acid (3-methylphenyl) ester, salicylic acid (2,4-dimethylphenyl) ester, salicylic acid (4-tertiarybutylphenyl) ester, salicylic acid (4-tertiarybutylphenyl) ester, milphenyl) ester, salicylic acid (2-methoxyphenyl) ester, salicylic acid (2-ethoxyphenyl) ester, salicylic acid (3-methoxyphenyl) ester, salicylic acid (4-hydroxyphenyl) ester, salicylic acid (4-benzyl) ester phenyl) ester, salicylic acid (4-benzoylphenyl) ester, salicylic acid (2-methoxy-
4-allylphenyl) ester, salicylic acid (alphanaphthyl) ester, salicylic acid (beta-naphthyl) ester, salicylic acid (4-chloro-
3-methylphenyl) ester, salicylic acid (3
-hydroxyphenyl) ester, salicylic acid (4-propenylphenyl) ester, 5-chlorosalicylic acid (3-methylphenyl) ester,
3,5-dichlorosalicylic acid (2-methoxyphenyl) ester. (5) Benzoic acid phenyl esters represented by the following general formula () (In the formula, R ¹³ is an alkyl group or alkoxy group having 1 to 30 carbon atoms, halogen, nitro group, nitrile group, acyloxy group, substituted or unsubstituted aryl or aralkyl group, substituted or unsubstituted aryloxy or aralkyloxy group,
^R14 is hydrogen, an alkyl group or alkoxy group having 1 to 30 carbon atoms, a halogen, a nitro group, a nitrile group, an acyloxy group, a substituted or unsubstituted aryl or aralkyl group, a substituted or unsubstituted aryloxy or aralkyloxy or acyl group) as specific examples of such compounds, for example,
Examples include those shown below. Benzoic acid phenyl ester, benzoic acid-4-methylphenyl ester, benzoic acid-2,4-dichlorophenyl ester, benzoic acid-2,4,6-
Trichlorphenyl ester, benzoic acid-2-methyl-4-chlorophenyl ester, benzoic acid-
3-bromphenyl ester, benzoic acid-4-nitrile phenyl ester, benzoic acid-2,4-dibromphenyl ester, benzoic acid-3-iodophenyl ester, benzoic acid-3-nitrophenyl ester, 4-methyl-2,6-dichlorophenyl benzoate, 4-isopropylphenyl benzoate, 4-t-butylphenyl benzoate, 4-benzyl phenyl benzoate, benzoic acid -4-(1-naphthyl)phenyl ester, benzoic acid-2-benzoyloxyphenyl ester, benzoic acid-4-(2
-methyl)diphenyl ester, benzoic acid-2-
Phenylethyloxyphenyl ester, benzoic acid-2-acetoxyphenyl ester, benzoic acid-4-methoxyphenyl ester, benzoic acid-4
-(4-methyl)phenoxyphenyl ester,
4-Methylbenzoic acid phenyl ester, 4-methoxybenzoic acid phenyl ester, 4-phenoxybenzoic acid phenyl ester, 4-acetoxybenzoic acid phenyl ester, 4-methoxybenzoic acid-
4-methoxyphenyl ester, 2-acetoxybenzoic acid phenyl ester, 2-benzoyloxybenzoic acid phenyl ester, 2-nitrobenzoic acid-4-methylphenyl ester, 4-nitrobenzoic acid-4-methylphenyl ester ester, 4-benzoyloxybenzophenone, 2-benzoyloxy-4-methylbenzophenone. (6) Benzoyloxybenzoic acid esters represented by the following general formula () (In the formula, R ¹⁵ is hydrogen, an alkyl group or alkoxy group having 1 to 30 carbon atoms, or a halogen, and R ¹⁶ is an alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted aryl or aralkyl group) Specific examples of such compounds include, for example,
Examples include those shown below. 4-benzoyloxybenzoic acid methyl ester 4-benzoyloxybenzoic acid ethyl ester,
4-benzoyloxybenzoic acid-n-propyl ester, 4-benzoyloxybenzoic acid benzyl ester, 4-benzoyloxybenzoic acid phenyl ester, 2-benzoyloxybenzoic acid aenyl ester, 4-(4'-methylbenzoyloxy) ) Benzoic acid ethyl ester, 4-(4'-methoxybenzoyloxy)benzoic acid ethyl ester,
4-(4'-chlorobenzoyloxy)benzoic acid ethyl ester. When providing a transfer layer and a receiving layer on each support, a conventional binder is used,
For example, water-soluble, organic Solvent-soluble or aqueous emulsion-forming materials can be used, but in particular, in the case of the transfer layer, resins with a melting point or softening point of 50 to 130° C., such as polyethylene, polypropylene, polystyrene, petroleum resins, acrylic resins. , vinyl chloride resin, vinyl acetate resin, vinylidene chloride resin, polyvinyl alcohol, cellulose resin,
It is preferable to use polyamide, polyacetal, polycarbonate, polyester, fluororesin, silicone resin, natural rubber, chlorinated rubber, butadiene rubber, olefin rubber, phenolic resin, urea resin, melamine resin, epoxy resin, polyimide, etc. as the binder. . These resins are appropriately used in the form of homopolymers, copolymers, or mixtures of a plurality of resins, and it is particularly preferable to use those having an SP value (solubility parameter) of 8 or more, preferably 9 or more. When a transfer sheet is prepared using these resins as a binder, the transfer forming liquid can be applied by any of a solvent coating method, a hot melt coating method, or an aqueous emulsion coating method. Note that the SP value indicates the solubility parameter of the resin, and is expressed by the following formula. SP value [(Cal/cc) ^1/2 ] = (E/V) ^1/2 E...Resin cohesive energy density (Cal/cc)
mole) V... molar volume of resin (cc/mole) Furthermore, in the present invention, in order to obtain a transfer medium with higher heat sensitivity, the transfer layer and/or receiving layer containing the thermofusible substance should be During layer formation or after layer formation, it is advantageous to perform heat treatment to a temperature higher than the melting point of the thermofusible substance to once heat melt the thermofusible substance, and further to form a transfer layer containing a leuco dye. In this case, it is preferable to use a coating liquid containing a dissolved leuco dye. Furthermore, the surface smoothness (Beckman smoothness, JIS-P8119) of the transfer layer and/or receiving layer is 200.
It is also effective to adjust to ~1000 seconds. In the thermal transfer medium of the present invention, each layer-forming liquid is prepared by dispersing and dissolving the above-mentioned layer-forming components together with a solvent such as water using a pulverizing and mixing means such as a ball mill or an attriter, and this is applied onto each support. It can be obtained by coating and drying to a dry adhesion amount of 0.3 to 30 g/m ² . In the transfer sheet used in the present invention, the transfer layer provided on the surface thereof may be a so-called plain (no image) layer provided uniformly over the entire surface of the support, or may be coated with a desired image in advance. It may be provided in a shape. A transfer sheet having an image-free transfer layer can be obtained by simply applying a transfer layer forming liquid to the surface of a support.
On the other hand, those with an image-like transfer layer are produced by applying a transfer layer forming liquid onto the surface of the support in the form of a desired image (including letters) by letterpress printing or gravure printing. Alternatively, a suitable support surface such as paper, synthetic paper, plastic film, etc. can be placed on the surface of the non-image transfer layer of the above-mentioned transfer sheet, and a typewriter or iron pen can be used from the support side or the transfer sheet side. The image-free transfer layer of the transfer sheet can be applied to the surface of another suitable support by pressing it in an image-like manner using a pressing means such as a thermal head or a hot-pressing means such as a thermal pen. can. To carry out the thermal transfer of the present invention, for example, when using a transfer sheet having an image-shaped transfer layer, a receiving sheet is placed on the surface of the transfer layer so that the receiving layer is in contact with the surface of the transfer layer, and then this is rolled with a heating roll. On the other hand, when using a transfer sheet with a transfer layer without an image, the receiving layer of the receiving sheet is placed on the surface of the transfer layer of the transfer sheet, and the This can be done by direct heating printing using a thermal printer, or by overlaying the receiving layer of a receiving sheet on the transfer layer of the transfer sheet and then applying black ink to the back of the transfer sheet. This can be done by placing the written original drawing in close contact with each other, irradiating infrared rays from the side of the receiving sheet, and selectively heating only the black image area on the original drawing to a high temperature (note:
In this case, both the transfer sheet and the receiving sheet must be transparent to infrared rays). In thermal transfer as in the present invention, a large number of copies can be easily obtained by repeating the above operations using the same transfer sheet. Also, if you want to get a multicolored copy,
If you create transfer sheets using leuco dyes of different tones as main coloring components, for example, create a transfer sheet with blue leuco dye and a transfer sheet with red leuco dye, and form a transferred image on the same receiving sheet by transfer. , blue and red colored images can be formed on the same sheet. [Effects] In the present invention, since the leuco dye and its color developer are contained on separate supports, there is no problem of color fogging during production or storage, which occurs with conventional thermal paper. Furthermore, since the resulting copy contains only a color developer and no leuco dye in the non-image area, no color development occurs even if it is heated (i.e., completely fixed). Furthermore, it is economical because a high density image can be obtained with a small amount of heating energy and a large number of copies can be obtained using the same transfer sheet. Moreover, in the copies obtained in this case, the transfer of the leuco dye from the transfer layer of the transfer sheet to the receiving layer of the receiving sheet is uniform, and the dye transfer occurs little by little during transfer, so the image density of the obtained copies is low. It is homogenized. [Example] Next, the present invention will be explained in more detail with reference to Examples. Note that all percentages and parts shown in the following examples are based on weight. Preparation of Example Support (1): Acrylic polyol 15 parts Polyisocyanate 5 Silica fine particles (oil absorption 160 ml/100 g) 5 Methyl ethyl ketone 75 After dispersing the above composition in a ball mill for 24 hours, use a wire bar to disperse the composition to 12 μm. The support was coated on the surface of a polyester film with a coating weight of 1 g/m ² after drying.
I got (1). Preparation of Support (2): Support (2) was obtained in the same manner except that the oil absorption amount of the silica fine particles was changed to 200 ml/100 g. Preparation of Support (3): Support (3) was obtained in the same manner except that the silica fine particles were made of urea-formalin resin (oil absorption: 200 ml/100 g). Next, in order to create a heat-sensitive transfer sheet, a ball mill was used to disperse solution A consisting of 10 parts of crystal violet lactone, 10 parts of carnauba wax, 5 parts of ethyl cellulose, and 75 parts of water for 24 hours. Coat each on the surface of supports (1), (2) and (3) and dry to obtain a coating weight of 10g/
Transfer sheets (A), (B) and (C) of m ² were prepared. Next, in order to create a receptor sheet, a composition consisting of 20 parts of 4-hydroxybenzoic acid n-butyl ester, 10 parts of silica fine particles (oil absorption: 200 ml/100 g), 10 parts of polyvinyl alcohol, 3 parts of water, and 100 parts of water was prepared using a ball mill. After time dispersion, the mixture was coated on the surface of high-quality paper (35 g/m ² ) using a wire bar and dried to prepare a receiving sheet with a coating weight of 5 g/m ² . Comparative Example 1 The above liquid A was applied to the surface of the 12 μm thick unroughened polyester film of Example 1 in the same manner as in Example to prepare a comparative transfer sheet (D). Comparative Example 2 Silica fine particles of Example 1 (oil absorption 200ml/100
A comparative transfer sheet (E) was prepared in the same manner except that the oil absorption amount was changed to 10 ml/100 g. The transfer sheets (A), (B), (C), (D), and (E) obtained as described above were brought into contact with the receiving sheet, respectively, and heating energy of 1 mj was applied to the back side of the transfer sheet using a thermal head. Thermal transfer was performed. Table 1 shows the density (measured using a Macbeth densitometer) of the obtained transferred colored image. Next, the same transfer sheet (A) (B)
Transfer was performed repeatedly using (C), (D), and (E), and the color image density of the copies obtained at that time is shown in Table 1. From the results shown in Table 1, it can be seen that the transfer sheet of the present invention provides a higher and more uniform image density than that of the comparative example. 【table】

Claims (1)

[Claims] 1 Consisting of a transfer sheet on which a transfer layer containing a leuco dye as a main component is provided on a support, and a receiving sheet on a support with a receiving layer containing a color developer as a main component for the leuco dye, A heat-sensitive transfer medium characterized in that the layer is provided on the surface of a plastic film via a porous filler-containing layer having an oil absorption of 50 to 300 ml/100 g.