JPS6063194A - Thermal transfer printing medium - Google Patents

Abstract

PURPOSE:To provide a thermal transfer printing medium capable of producing a stable transferred image with high density while consuming a minute amount of energy, wherein a fine powder of a metal having a low melting point is incorporated in a transfer layer comprising a leuco dye, in a recording medium utilizing a color forming reaction between a leuco dye and a color developer. CONSTITUTION:In a thermal recording medium constituted of a transfer sheet provided with a transfer layer comprising a leuco dye as a main constituent and a receiving sheet provided with a receiving layer comprising a color developer for the dye as a main constituent, a powder of a metal (e.g., Bi, Pb or Sn) having a melting point of 30-100 deg.C and a particle diameter of not larger than 10mum is incorporated into the transfer layer, preferably, in an amount of 0.05-0.5pts. wt. per 1pt.wt. of the leuco dye, to obtain the objective thermal transfer medium.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a thermal transfer medium that utilizes a color 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 include those consisting 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, or a heat-fusible material. A combination of a transfer sheet with a pigment or dye transfer layer on a support and a receiving sheet is known.The former uses a heat sublimable dye, so the dye image on the receiving sheet has a long shelf life. The transfer layer is inferior in quality and requires an overcoat to be applied on the transferred image, and since the latter is a transfer layer with pigment or dye dispersed in a thermofusible material, a large amount of pigment is required to obtain a high-density image. If a large amount of thermofusible material is used, the transfer efficiency will be lowered, making it difficult to obtain a high-density image. When separating the transfer sheet and the receiving sheet, the transfer sheet moves to the receiving sheet side.
There were drawbacks such as not peeling off smoothly and image areas of fine lines becoming unclear.

On the other hand, there is also known a thermal transfer medium in which substances that react with each other and discolor due to heat are supported on separate supports, and these support layers are brought into mutually facing contact to perform thermal printing.
This kind of thing is reactive, so when you come into contact with it face-to-face,
If the transfer layer simply transfers to the receiving layer, a sufficient coloring reaction will not occur, resulting in a low-density image.If the heating conditions are set to higher temperature and longer thermal printing to promote sufficient reaction, Although the image on the receiving sheet becomes a higher-density image, there is a drawback in that the coloring reaction progresses even on transfer sheets 1 to 1, and image formation occurs.

〔the purpose〕

The present invention provides a stable transfer image with high density by using a small amount of thermal energy, and also provides a uniform image density even after multiple transfers by transferring a small amount of leuco dye component from the transfer layer to the receiving layer. The purpose is to provide a thermal transfer medium.

〔composition〕

According to the present invention, the transfer sheet includes a transfer sheet having a transfer layer containing a leuco dye as a main component, and a receiving sheet having a receiving layer containing a color developer for the leuco dye as a main component, and the transfer layer has a melting point of 30 to 30. Provided is a thermal transfer medium characterized by containing metal powder having a temperature of 100° C. and a particle size of 10 μrn or less.

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 a desired color is usually developed on the surface of the receiving sheet by thermal printing from the back side of the transfer sheet. An image is formed, and in the present invention, as described above, the transfer layer of the transfer sheet contains fine metal powder with a low melting point, thereby forming a colored image on the receiving sheet with high thermal sensitivity. I can do it.

In order to improve thermal sensitivity, it has generally been attempted to incorporate a thermofusible organic substance into the transfer layer, but this method is still unsatisfactory due to the poor thermal conductivity of the thermofusible organic substance. It wasn't something that should have been done. Further, even if fine metal powder with a high melting point is added, it does not give satisfactory results because it does not have thermal melting properties. The use of the low melting point metal fine powder used in the present invention provides a thermal transfer medium with increased thermal sensitivity.

Conventionally known low melting point metals (including alloys) are used in the present invention, and there are many types, such as alloys of bismuth, lead, tin, cadmium, indium, mercury, etc. . Typical examples of alloy compositions are shown below.

Table 1 The low-temperature melting metal powder used in the present invention has a melting point of 30 to 1
It is advantageous to use particles having a temperature of 00° C., and the particle size (particle diameter) is preferably defined to be 10 μm or less, preferably 5 μm or less. If the particle size of the metal powder exceeds 10 μm, it is not preferable because the resulting image will lack clarity.

The amount of the low melting point metal powder used is 0.01 to 1 part by weight, preferably 0.05 to 0.5 part by weight, per 1 part by weight of the leuco dye.

The transfer sheet used in the present invention is one in which a transfer layer containing a leuco dye and a low-melting metal powder is provided on a support such as paper, synthetic paper, or plastic film. In this case, any leuco dye that has been conventionally used for pressure-sensitive paper or thermal paper can be used, including 1-rephenylmethane, fluoran, phenothiazine, auramine, and spiropyran. Preferably applied. 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-dibutylaminophenyl, 3,3-bis(p-dimethylaminophenylchlorphthalide, 3,3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorfur) orane, 3-dimethylamino-5,7-dimethylfluorane, 3
-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane 53-diethylamino-6
-Methyl-7-chlorofluorane.

3-(N-p-1-crew N-dithylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-(N-(3' -1~lifluoromethylphenyl)amino)-6-dinithylaminofluorane, 2-(3
, 6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran, 3-diethylamino-7-(0- 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-benzoindolino-pyrylospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrylospirane, 3-(2'- 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 applied to the support.
Usually 0.3~30g/m'', preferably 0.5~20
garn”.

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, an electron-accepting substance such as a phenolic substance, an organic acid or a salt or ester thereof is used as the color developer, 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 parentheses indicate the melting point.

4-tert-butylphenol (98), 4-hydroxydiphenyl ether (84), 1-naphthol (
98), 2-naphthol (121), methyl-4-hydroxybenzoate (1,31), 4-hydroxyacetophenone (109), 2,2'-dihydroxydiphenyl ether (79), 4-phenylphenol (1
66), 4-tert-octylcatechol (1'
09), 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'-isopropylidene bis(2-chlorophenol) (90), 4,4'-isopropylidene bis(2,6
-dibromophenol) (172), 4,4'-inpropylidene bis(2-terL-butylphenol)
(110), 4,4'-isopropylidene bis(2-
Methylphenol) (136), 4,4'-isopropylidene bis(2,6-dimethylphenol) (16g
), 4.4'-5ec-butylidene diphenol (1
19), 4.4'-'5ee-butylidene bis(2-
methylphenol) (142), 4,4'-cyclohexylidene diphenol (180), 4,4'-cyclohexylidene bis(2-methylphenol) (18
4), salicylic acid (163), salicylic acid methalyl ester (74), salicylic acid phenacyl ester (11)
θ), 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 (11
9), 5-hydroxysalicylic acid (200), 5-chlorsalicylic acid (172), 3-chlorsalicylic acid (17)
8), thiosalicylic acid (164), 2-chloro-5-nitrobenzoic acid (165), 4-methoxyphenol (5
3), 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-hydroxybenzophenone (133), 2,4-
Dihydroxybenzophenone (144), 2-naphthoic acid (184), 1-hydroxy-2-naphthoic acid (195), 3,4-dihydroxybenzoic acid ethyl ester (128), 3,4-dihydroxybenzoic acid phenyl ester (189), 4-hydroxypropiophenone (150), salicyl salicyle-1-(148), phthalic acid monobenzyl ester (
107).

Further, in the present invention, a phenolic compound represented by the general formula (wherein R is an alkylene group containing 1 to 5 ether bonds) can be used as a color developer. This phenolic substance can be easily produced in high yield and purity by reacting monothiohydroquinone with the corresponding dihalogenoalkyl ether under alkaline conditions.
Moreover, it can be synthesized relatively inexpensively.

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. 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 are:
It contains 1 to 3 ether bonds and has 2 to 7 carbon atoms.

In the present invention, an oil absorbing layer of 50 m Q / 100 g (JIS K
5101 method) or more preferably 150 m Q /
Preferably, it contains 100 g or more of porous filler. The porous filler contained in the receptor layer is 0.01 part by weight or more, usually 0.0 part by weight, per 1 part by weight of the color developer.
The amount ranges from 5 to 10 parts by weight, preferably from 0.1 to 3 parts by weight. The proportion of the porous filler contained in the 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 inorganic and organic fine powders such as silica, aluminum silicate, alumina, aluminum hydroxide, magnesium hydroxide, urea-formalin resin, and styrene resin.

In addition, in the present invention, if necessary, the transfer layer and/or the receiving layer may have a melting point of 200
Thermofusible substances having a melting point below 0°C, preferably below 150°C can be added. These include fatty acid amides, aromatic carboxylic acid amides, amides having a cyclohexyl ring, phenyl esters of hydroxybenzoic acid, phenyl benzoic acid esters,
Includes benzoyloxybenzoic acid esters, etc.
It is possible to use what has been commonly applied in the past.

When providing a transfer layer and a receiving layer on each support, conventional binders are used, such as polyvinyl alcohol, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylamide, and polyacrylic acid. ,
Water-soluble, organic solvent-soluble or aqueous emulsion-forming materials such as starch, gelatin, polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, etc. can be used, but especially in the case of the transfer layer,
Resins having a melting point or softening point of 50 to 130°C, such as polyethylene, polypropylene, polystyrene, petroleum resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, vinylidene chloride resin, polyvinyl alcohol, cellulose resin, polyamide, polyacetal, polycarbonate , polyester, fluororesin, silicone resin, natural rubber, chlorinated rubber, butadiene rubber, olefin rubber, phenol resin, urea resin, melamine resin, epoxy resin, polyimide, etc. are preferably used 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 creating a transfer sheet 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 C (Cal/cc)”) = (E/V)
"E...Cohesive energy density of resin (Cal/mol
e) 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 receptor layer containing the thermofusible substance should be During or after layer formation, it is advantageous to perform heat treatment to a temperature higher than the melting point of the thermofusible substance to heat-melt the thermofusible substance once, and furthermore, to apply a transfer layer containing a leuco dye. When forming, it is also a preferable means to use a coating liquid containing a leuco dye in a dissolved state.

Furthermore, the surface smoothness (Beckman smoothness, JIS-P8119) of the transfer layer and/or the receiving layer is 200-1.
It is also effective to adjust the time to 000 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 attritor, 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/rl.

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 provided uniformly over the entire surface of the support. It may be provided in a shape.

A transfer sheet with a non-image transfer layer has a layer on the surface of the support.
It can be obtained by simply applying a transfer layer forming liquid. On the other hand, those having an image-like transfer layer can be obtained by applying a transfer layer forming liquid onto the surface of a support in the form of a desired image (including letters) by letterpress printing or gravure printing. Alternatively, paper, synthetic paper,
Appropriate supports such as plastic films are stacked one on top of the other, and the image is pressed from the support side or the transfer sheet side using a suppressing means such as a typewriter or iron pen, or a heating suppressing means such as a thermal head or a thermal pen to transfer the image. An imageless transfer layer of the sheet can be obtained by imagewise application to the surface of another suitable support.

To carry out the thermal transfer of the present invention, for example, when using a transfer sheet having a transfer layer in the form of a single image, a receiving sheet is placed on the surface of this transfer layer so that the receiving layer is in contact with the surface, 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 transfer sheets 1 to 1, and , can be done by direct heating printing using a thermal printer,
Alternatively, the receiving layer of the receiving sheet is placed on the transfer layer surface of the transfer sheet, and an original drawing written in black ink is placed on the back side of the transfer sheet, and infrared rays are irradiated from the side of the receiving sheet surface. This can be done by selectively heating only the black image area in (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 repeatedly performing the above operations using the same transfer sheets 1 to 1. In addition, when obtaining multicolor copies, create transfer sheets using leuco dyes of different tones as main coloring components, for example, create a transfer sheet 1- with blue leuco dye and a transfer sheet with red leuco dye, By forming a transfer image on the same receiving sheet by transfer, blue and red colored images can be formed on the same sheet.

〔effect〕

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 was seen 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., it is completely fixed). (It is a sexual thing). Furthermore, since it is highly thermally sensitive, high density images can be obtained with a small amount of heating energy, and it is also economical because 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.

Example 1 3-N-methyl-N-cyclohexyl 10g amino-
Composition consisting of 1 g of 6-methyl-7-anilinofluoran bismuth, lead, tin, and cadmium alloy (M-5 in Table 1, mp 70°C, particle size 5 μm), 2 g of vinyl chloride-vinyl acetate copolymer, and 100 g of methyl ethyl ketone. After dispersing the material for 24 hours using a ball mill, it was applied onto the surface of a 6 μm thick polyester film using a wire bar and dried to prepare a transfer sheet with a coating weight of 3 g/nf.

On the other hand, n-butyl 4-hydroxybenzoate 20g ester silica fine particles (oil absorption 200m Q /100g) 1
A composition consisting of 0 g polyvinyl alcohol 3 g water 100 g was dispersed for 24 hours using a ball mill, and then dispersed using a wire bar on high-quality paper (3'5 g/day).
A receiving sheet with an adhesion amount of 5 g/rrf was prepared by coating and drying on the surface of.

Next, this transfer sheet and the receiving sheet were superimposed and heating energy of 1 mJ was applied using a thermal head, and a clear black image with an image density of 1 and 25 was obtained.

Next, for comparison, a transfer sheet similar to that of the example except that it did not contain hot-melting metal powder was prepared, and when it was superimposed on the above-mentioned receiving sheet and heated with 11 WJ of heating energy by a thermal head, the image density was It was 1.07. As is clear from the above results, the present invention is a thermal transfer medium with excellent thermal sensitivity.

Example 2 715 g of 3-diethylamino-6-methyl-anilinofluoran bismuth, lead, silk, and indium alloy 2 g (M-6 in Table 1, +np58°C, particle size 3 μm) Urea-formalin resin fine particles 2 g ( Oil absorption D 300 m 12 / 1-00 g) After dispersing a composition consisting of 2 g of acrylic sesame oil and 100 g of tetrahydrofuran in a ball mill for 24 hours, it was coated on the surface of a 6 μm thick polyester film using a wire bar and dried to adhere. Amount 5g/rr? A transfer sheet was created. When these transfer sheets 1 to 1 were stacked with the receiving sheet of Example 1 and heating energy of ImJ was applied using a thermal head, a black image with an image density of 1.16 was obtained. The image density after repeating the above operation five times was 1.09. As described above, the present invention provides a thermal transfer medium with high thermal sensitivity and excellent multi-printing performance.

Example 3 A transfer sheet was created in the same manner as in Example 1, except that the heat-fusible metal was replaced with an alloy of bismuth, tin, and indium (M-4 in Table 1, mp 78.8°C, particle size 5 μm). did. Layer this transfer sheet and the receiving sheet of Example 1,
．． When 2n+J heating energy was applied, the image density was 1.
．． 22 black images were obtained.

Patent applicant Rico Co., Ltd. Representative Patent Attorney Toshiaki Ikeura

Claims (1)

[Claims] (1) Consisting of a transfer sheet having a transfer layer containing a leuco dye as a main component, and a receiving sheet having a receiving layer containing a color developer as a main component for the leuco dye, the transfer layer has a melting point of 3
A thermal transfer medium characterized by containing metal powder having a temperature of 0 to 100°C and a particle size of 10 μm or less.