JPH0441079B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a multicolor thermal transfer medium comprising a transfer sheet and a receiving sheet and which provides transferred images of different colors at different transfer temperatures.

[Prior art]

Conventionally, various proposals have been made for multicolor thermal transfer media that provide transferred images of different tones at different transfer temperatures, but these generally transfer multiple thermal inks with different melting temperatures. The ink is contained in the layer, and during transfer, only the ink showing the desired coloring is selectively heated and melted, and the molten colored material is transferred to a receiving sheet such as paper. For example, according to Japanese Patent Application Laid-open No. 57-150600,
A multicolor recording medium for thermal transfer has been proposed in which a transfer ink layer formed by incorporating a heat-sensitive coloring ink that melts or sublimates at a relatively high temperature into a solid heat-sensitive ink that melts or sublimates at a relatively low temperature is provided on a support. ing.

However, with all of these conventional multicolor thermal transfer media, although the color tone of the transferred image obtained when heated at a low temperature is good, the color tone of the transferred image obtained when heated at a high temperature is different from that produced at a low temperature. It has the disadvantage that the color tone when heated becomes a mixture of colors.

〔the purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to provide a multicolor thermal transfer medium that provides a transferred image that is free from the color mixing that occurs when heated at a high temperature and at a low temperature, that is, has excellent color separation between high and low temperature transfers. shall be.

〔composition〕

According to the present invention, a high-temperature transfer layer containing a hot-melt ink composition forms a lower layer, a low-temperature transfer layer contains a leuco dye and develops a color different from the ink composition and forms an upper layer. A multicolor heat-sensitive transfer medium comprising a transfer sheet having a leuco dye, a receiving sheet having a decolorizing agent layer for the leuco dye forming a lower layer, and a receiving layer containing a color developer for the leuco dye forming an upper layer. provided.

The multicolor thermal transfer medium of the present invention consists of a transfer sheet and a receiving sheet having the above-described structure. By performing thermal printing at a predetermined temperature from the back side of the sheet or the back side of the receiving sheet, a desired transfer image can be formed on the receiving sheet. In this case, when low-temperature heating is applied, the leuco dye in the low-temperature transfer layer transfers to the receiving layer of the receiving sheet and a colored image is formed on the receiving sheet due to the reaction between the leuco dye and the color developer. According to the paper, the color-forming reaction between the leuco dye and the color developer is suppressed by the action of the decolorizing agent on the receiving sheet, so that the melt of the heat-melting ink composition that forms the high-temperature transfer layer is transferred onto the receiving sheet. The molten ink composition forms a colored image on the receiving sheet. According to the present invention, the transferred image formed on the receiving sheet by high-temperature heating is accompanied by color mixing due to the low-temperature coloring image, because coloring by the low-temperature transfer layer is suppressed by the action of the decoloring agent, as described above. Therefore, it is possible to obtain a high-quality two-color transfer image in which both the thick and thin lines forming the image are very clear.

As the heat-melting ink composition used for forming the high-temperature transfer layer in the present invention, conventionally known ones can be used, and usually those in which pigments are dispersed in a heat-melting substance are used. In this case, the heat-melting substances include carnauba wax, montan wax, paraffin wax, microcrystalline wax, various waxes such as beeswax, or mixtures thereof, polyvinyl chloride, polyvinyl acetate, and vinyl chloride. / Vinyl acetate copolymer, polyethylene, polypropylene, polyacetal, ethylene/vinyl acetate copolymer, polystyrene, low molecular weight polystyrene, polyacrylic ester, polyamide, ethyl cellulose, as well as epoxy resin,
Xylene resin, ketone resin, petroleum resin, rosin or its derivatives, coumaron indene resin, terpene resin, polyurethane resin, or thermofusible materials such as styrene/butadiene rubber, polyvinyl butyral, nitrile rubber, acrylic rubber, ethylene/propylene rubber, etc. Examples include polymeric substances.
As the pigment (or coloring agent), heat-fusible or heat-infusible pigments are used, such as black pigments such as carbon black, triiron tetroxide, and nigrosine base, cyanine blue, oil blue, and alkaline blue. In addition to blue pigments, Iozole Red, Rose Bengal, Crisil Violet Lactone,
Examples include brilliant green. When a heat-melting pigment is used, its melting point is set higher than the melting reaction temperature of the low-temperature transfer layer.

The ink composition used in the present invention can contain various commonly used auxiliary ingredients, such as animal and vegetable oils, mineral oils, dioctyl phthalate, tricresyl phosphate, dibutyl phthalate,
Oils and fats such as lanolin, calcium carbonate, magnesium carbonate, diatomaceous earth, kaolin, white carbon,
Extender pigments such as silicic acid fine powder, as well as dipolyoxyethylene alkyl ether phosphoric acid, tripolyoxyethylene alkyl ether phosphoric acid, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether ,
A nonionic surfactant such as polyoxyethylene stearyl ether can be added to the pigment as a dispersant. Examples of the formulation of the ink composition used in the present invention are as follows.

Pigment 10-20 parts by weight Waxes 0-50 parts by weight Thermofusible polymer 10-30 parts by weight Oils and fats 0-25 parts by weight Extender 0-25 parts by weight Dispersant 0-2 parts by weight Ink composition If necessary, an organic solvent such as toluene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, butyl butyrate, dioxane, or ethylbenzene can be used for dispersion. This ink composition is applied onto a support by a hot melt method or a solvent coating method to form a high temperature transfer layer. The melting temperature of this high-temperature transfer layer is appropriately selected in relation to the melting reaction temperature of the low-temperature transfer layer, but is usually 85 to 150°C, preferably
It is preferable to use an ink composition that melts as sharply as possible at 90 to 120°C. The amount of the ink composition applied onto the support is 1 to 10 g, preferably 2 to 4 g per m ² of the support.

As the leuco dye used as a component of the low-temperature transfer layer in the present invention, any of those conventionally used for pressure-sensitive paper and thermal paper can be used, including triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran. Applicable to the system. Main specific examples 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-diethylamino- 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 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, beyzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrylospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrylospirane, 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.

As the decolorizing agent for the leuco dye, any known decolorizing agent that acts on the coloring system of the leuco dye and the color developer can be used. A specific example is as follows.

(1) Specific alcohols (Japanese Patent Publication No. 50-17865) stearyl alcohol, polypropylene glycol, pentamethylglycerin, dimethylpentaglycerin.

(2) Polyether or polyethylene glycol derivatives (Japanese Patent Publication No. 50-17866) Polyethylene oxide, polyoxydecamethylene, trimethylene oxide, polyoxyethylene oleyl ether, polyoxyethylene cetyl ether, polyethylene glycol monostearate.

(3) Alkylene oxide adduct of bisphenols (JP-A-54-139741) Ethylene oxide (2.6 mol) to bisphenol A
Bisphenol A is an addition reaction of ethylene oxide (6.0 mol) and propylene oxide (4.5 mol).
A compound that undergoes an addition reaction with (mol).

(4) Ethylene oxide adduct of terephthalic acid (JP-A-Sho
55-2306) A compound obtained by adding ethylene oxide (2 moles) to terephthalic acid (1 mole).

In the present invention, the decoloring agent is provided in the lower layer on the receiving sheet, and the amount used is preferably 0.5 to 5.0 parts by weight, preferably 1 to 3 parts by weight, per 1 part by weight of the leuco dye.
Parts by weight.

In the present invention, an electron-accepting substance, such as a phenolic substance, an organic acid, or a salt or ester thereof, is used as the color developer used to form the receptor layer of the receptor sheet, and from the viewpoint of practicality, preferably Those with a melting point of 200℃ or less are applicable. Specific examples of color developers 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), 4tert-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'-isopropylidenediphenol (156), 4,4'-isopropylidenebis(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) (168), 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-hydroxysalicylic 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), para-toluic acid (181), orthochlorobenzoic acid (142), metaoxybenzoic acid (200), 2,4-dihydroxyacetophenone (97), resorcinol monobenzoate (135), 4-hydroxybenzophenone ( 133),
2,4-dihydroxybenzophenone (144), 2
- Naftytsk Ash (184), 1-Hydroxy-2-Naftytsk Ash (195), 3,4
-dihydroxybenzoic acid ethyl ester (128),
3,4-dihydroxybenzoic acid phenyl ester (189), 4-hydroxypropiophenone (150),
salicyl salicylate (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 monothiohydroxynone with the corresponding dihalogen alkyl 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; in this case, the ether group may be present in the main chain of the alkylene group, or may be present 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.

To create the transfer sheet of the present invention, a high temperature transfer layer made of the above-mentioned meltable ink composition is provided on a support, and then a low temperature transfer layer containing a leuco dye is provided thereon. In this case, the support may be paper,
Synthetic paper, plastic film, etc. are used, and the amount of adhesion of the high temperature transfer layer formed on the support is 1
~10g/ ^m2 , preferably about 2-4g/ ^m2 ,
The adhesion amount of the low temperature transfer layer is about 0.5 to 5 g/m ² , preferably about 1 to 3 g/m ² . In the present invention, the melting reaction temperature of the low-temperature transfer layer that occurs between the receiving layer and the receiving layer is as follows:
The melting temperature of the high temperature transfer layer is typically at least 20
℃, preferably 20 to 50℃, but generally the melting reaction temperature is 60 to 100℃,
Preferably, the temperature is set at 65 to 80°C. Also,
The melting temperature of the high temperature transfer layer is preferably set at 85 to 105°C, preferably 90 to 120°C, in relation to the melting reaction temperature of the low temperature transfer layer. The melting point range of the color erasing agent used in combination with the leuco dye is such that it does not substantially melt during low temperature transfer and does not exhibit its color erasing effect, but it melts and exhibits its color erasing effect during high temperature transfer. This is a range.

In the present invention, the oil absorption amount for the receptor layer and/or low temperature transfer layer is 50ml/100g.
(according to JISK5101 method) or more, preferably 150ml/
It is preferable to contain 100 g or more of porous filler. When contained in the receptor layer, the porous filler is 0.01 part by weight or more per 1 part by weight of the color developer,
It is usually in the range of 0.05 to 10 parts by weight, preferably 0.1 to 3 parts by weight. The proportion of the porous filler contained in the low-temperature transfer layer is 0.01 to 1 part by weight, preferably 0.03 to 0.5 part by weight, per 1 part by weight of the leuco dye. Specific examples of porous fillers include:
Examples include inorganic and organic fine powders such as silica, aluminum silicate, alumina, aluminum hydroxide, magnesium hydroxide, urea-formalin resin, and styrene resin.

In the present invention, the receptor layer and/or
Alternatively, the low-temperature transfer layer may contain an appropriate amount of a thermofusible substance having a melting point of 200°C or lower, preferably 150°C or lower. Preferred specific examples of the thermofusible substance in this case include lauric acid amide, caproic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, N-methylstearic acid amide, N-cyclohexyl stearic acid amide, etc. , N-stearylbenzamide, N
-Amides such as stearyl acetamide, 4-hydroxybenzoic acid phenyl ester, 4-hydroxybenzoic acid-2-methoxyphenyl ester,
Salicylic acid-2-methoxyphenyl ester, benzoic acid-4-benzyl phenyl ester, benzoic acid-4-methoxyphenyl ester, 4-benzoyloxybenzoic acid methyl ester, 4-benzoyloxybenzoic acid phenyl ester, etc. However, it is of course not limited to these.

When a low-temperature transfer layer or receiving layer is provided on each support, conventional binders are used, such as polyvinyl alcohol, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone,
Water-soluble, organic solvent-soluble or aqueous emulsion-forming materials such as polyacrylamide, polyacrylic acid, starch, gelatin, polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, etc. can be used.

In the present invention, when forming a low temperature transfer layer,
As a binder, especially one having a melting point or softening point of 50 to
Resins having a temperature of 130°C, such as polyethylene, polypropylene, polystyrene, petroleum resins, acrylic resins, vinyl chloride resins, vinyl acetate resins, vinylidene chloride resins, polyvinyl alcohol, cellulose resins, polyamides, polyacetals, polycarbonates, polyesters, fluororesins, Examples include silicone resin, natural rubber, chlorinated rubber, butadiene rubber, olefin rubber, phenol resin, urea resin, melamine resin, epoxy resin, and polyimide. These resins are homopolymers, copolymers,
Alternatively, it may be used appropriately in the form of a mixture of a plurality of resins. In the present invention, it is preferable to use a material having an SP value (meltability parameter) of 8 or more, preferably 9 or more. When forming a low-temperature transfer layer using these resins as a binder, the low-temperature transfer layer 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... Cohesive energy density of resin (cal/mole) V... Molar volume of resin (cc/mole) [Effect] The present invention As mentioned above, multicolor thermal transfer media use a color reaction between a leuco dye and a color developer to form a transferred image on a receiving sheet in low-temperature transfer, and a heat-melt ink composition in high-temperature transfer. A transferred image is formed on the receiving sheet by adhering a melted material of As a result, the resulting transferred image does not exhibit color mixing that occurs during low-temperature transfer, and provides a clear multicolor image with excellent color separation.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Note that all parts and percentages shown below are based on weighted standards.

Example 1 (High temperature transfer layer forming composition) Rose Bengal 18 parts Carnauba wax 10 parts Parafine wax (MP97°C) 23 parts Ethylene/vinyl acetate copolymer 3 parts Kaolin 7 parts The above ink composition was heated at a temperature of 100°C. A heat-melt ink composition was prepared by uniformly kneading the ink composition for 2 hours using a three-roll mill, and this ink composition was coated onto condenser paper (15 g/m ² ) by hot melt coating to a coating weight of 2.7 g/m 2 . A high temperature transfer layer of ² was formed.

(Low temperature transfer layer forming composition) 3-N-methyl-N-cyclohexyl 12 parts Amido-6-methyl-7-anilino fluoran Silica fine particles (oil absorption 145ml/100g) 1 part Vinyl chloride/vinyl acetate copolymer 2 parts 100 parts of methyl ethyl ketone After mixing and dispersing the leuco dye composition in a ball mill for 24 hours, apply a coating amount on the high temperature transfer layer.
A low-temperature transfer layer was formed by coating and drying at 2.0 g/m ² to prepare a transfer sheet in the present invention.

(Decoloring agent layer forming composition) Ethylene oxide adduct of bisphenol A (average number of added moles of ethylene oxide = 2.6) 15 parts Stearamide 5 parts Polyvinyl alcohol (15% aqueous solution) 30 parts Water 48 parts Above decoloring The agent composition was applied to the surface of high-quality paper (35 g/m ² ) using a wire bar, dried, and the adhesion amount was determined.
A decolorizing agent layer of 3.2 g/m ² was formed.

(Receptive layer forming composition) n-octyl 4-hydroxybenzoate 10 parts Ester 1,1-bis(4'-hydroxyphenyl) 20 parts Octane Silica fine particles (oil absorption 200ml/100g) 7 parts Polyvinyl alcohol 4 parts Water 100 parts The above composition was mixed and dispersed for 24 hours using a ball mill, and then applied and dried on the decolorizing agent layer to form a receiving layer with a coating weight of 4.5 g/m ² to form a receiving sheet in the present invention. It was created.

Next, the transfer sheet was stacked on the receiving sheet obtained as described above so that the transfer layer was in contact with the receiving layer of the receiving sheet, and printing was performed from the back side of the transfer sheet using a thermal head at a temperature of 70°C. A clear black image was formed on the receiving sheet, and then when printed at a temperature of 100°C, a clear red image was obtained. In this case, the color separation of the image was good, and both the thin and thick lines forming the image showed clear black and red, respectively.

Comparative Example 1 A comparative receiving sheet was prepared in the same manner as in Example 1 except that the decoloring layer was not provided.

When thermal transfer was performed using this receptor sheet in the same manner as in Example 1, a clear black image was formed in the low-temperature transfer at 70°C, but fine lines were black in the image obtained in the high-temperature transfer at 100°C. The color of the bold line was red, and the central part of the thick line was black-red, and the peripheral part was black, indicating poor color separation.

Examples 2 to 4 In Example 1, instead of the ethylene oxide adduct of bisphenol A in the decolorizer composition, () polyethylene glycol (Example 2) () polyethylene glycol monostearate Example 3 () A receiving sheet was prepared in the same manner except that terephthalic acid (1 mol) to which ethylene oxide (2 mol) was added (Example 4) was used. When thermal transfer was carried out in the same manner as in Example 1 using each of the receiving sheets obtained in this way, the resulting images all had excellent color separation and showed clear black and red colors for both thick and thin lines. Ta.

Claims (1)

[Claims] 1. A transfer sheet having a high-temperature transfer layer containing a hot-melt ink composition forming a lower layer, and a low-temperature transfer layer containing a leuco dye forming an upper layer and developing a color different from that of the ink composition. A multicolor thermal transfer medium comprising: a receiving sheet having a decolorizing agent layer for the leuco dye forming a lower layer, and a receiving layer containing a color developer for the leuco dye forming an upper layer.