JPH01215585A - Thermal transfer medium - Google Patents

Abstract

PURPOSE:To enhance rub resistance and heat resistance, by a method wherein a thermal recording medium is made of a transfer sheet having a leuco dye- containing transfer layer on a substrate and an accepting sheet having an accepting layer containing an ultrafine particle-form silica on a substrate. CONSTITUTION:A transfer sheet is formed by laminating a transfer layer containing a leuco dye on a substrate. On the other hand, an accepting sheet is formed by providing an accepting layer mainly composed of a color developer catalytically reacting with the leuco dye to produce a color on a substrate and incorporating a ultrafine particle-form silica with an average particle diameter of 5-50mum and a surface area of 150-400 m<2>/g by a BET method in the accepting layer. By using these transfer sheet and accepting sheet in combination, a thermal recording medium is composed. The color developer and the ultrafine particle-form silica are preferably used in the ratio of 0.005-0.5 pts.wt. to 1 pts.wt. of the color developer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a thermal transfer medium that has excellent abrasion resistance and provides a transferred image of uniform density.

[Prior Art] Conventionally, heat-sensitive 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, and paraffin-based transfer media. A combination of a transfer sheet and a receiving sheet is known, in which a transfer layer of a heat-fusible substance such as wax and a pigment or dye is provided on a support. The dye image on the sheet has poor storage stability, requiring an overcoat to be applied on the transferred image, and in the case of the latter, the transferred image may rub off because the paraffin used as a thermofusible material has low mechanical strength. There was a drawback that the image deteriorated due to friction such as. In addition, a method has been proposed to improve the printing quality by coating the receiving sheet with a thermofusible substance or filler (Japanese Patent Publication No. 16950/1982, Japanese Patent Application Laid-open No. 49997/1983), but this method Although the print quality is improved, the abrasion resistance of the transferred image is poor, and methods of coating with filler alone or a mixture of filler and a thermofusible substance have the disadvantage that the uniformity of the transferred image is poor.

[Objective] An object of the present invention is to provide a thermal transfer medium that provides a stable transfer image with high density and has excellent abrasion resistance and heat resistance.

[Structure] According to the present invention, a transfer sheet includes a transfer layer containing a leuco dye provided on a support, and a receiving layer containing a color developer that develops color by contact reaction with the leuco dye is provided on a support. In a thermal transfer medium consisting of a receptor sheet, the receptor layer has an average particle size of 5 to 50 mμ and a surface area of 150 to 40 mμ in the BET method.
A heat-sensitive transfer medium characterized by containing ultrafine particulate silica of 0 m/CJ is provided.

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 image is printed on the surface of the receiving sheet by thermal printing from the back side of the transfer sheet or the back side of the receiving sheet. A colored image is formed. In this case, in the present invention, the leuco dye contained in the transfer layer efficiently enters the receptor layer, which mainly consists of a color developer and ultrafine silica particles, so that a stable transferred image with high density can be obtained, and it can also be resistant to Transfer images with excellent friction properties and heat resistance can be obtained.

The fine particulate silica used in the present invention has an average particle size of 5 to 5
A value of 0 mμ is appropriate; silica with a thickness of less than 5 mμ currently does not exist, and a value exceeding 50 mμ deteriorates the uniformity of the image. In addition, the surface area in the BET method is 150 to 400-rrt/
If it is less than 150 m/C, the transferred image density will be low, and if it exceeds 400 Trt/CI, the image will bleed.

The appropriate proportion of the color developer and ultrafine particulate silica is 0.005 to 0.5 parts by weight per 1 part by weight of the color developer;
．． If it is less than 0.005 parts by weight, the abrasion resistance will be poor and the image density will be low. If it exceeds 1 part by weight, the thermal sensitivity will be poor and the image density will be low.

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 a support such as paper, synthetic paper, or plastic film. As the leuco dye in this case, any dye conventionally used for pressure-sensitive paper or thermal paper can be used, such as triphenylmethane-based,
Fluorane-based, phenothiazine-based, auramine-based, and spiropyran-based materials are preferably used. Specific examples of these leuco dyes are shown below. 3,3-bis(dimethylaminophenyl)-phthalide, 3,3-bis(dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis(p-dimethylamino phenyl)-6-dibutylaminophenyl, 3.3-bis(p-dimethylaminophenyl)-6-chlorphthalide, 3.3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorfur Oran, 3
-(N,N-diethylamino)-5-methyl-7-(N
, N-dibenzylamino)fluorane, 3-dimethylamino-5,7-dimethylfluorane, 3
-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 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)amine)-6-dinithylaminofluorane, 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)fluorane, benzoylleucomethylene 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. In the present invention, the leuco dye is applied to the support.
Usually o, i~30 (]/end, preferably 0.2~5c
It is used at a ratio of approximately +/m.

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.

As the color developer used in the present invention, an electron-accepting substance such as a phenolic substance, an organic acid or a salt or ester thereof, etc. is used, and from the viewpoint of practicality, preferably a melting point of 20
0'C or less applies.

Specific examples of color developers preferably applied in the present invention are shown below.

4-tert-butylphenol, 4-hydroxydiphenyl ether, 1-naphthol, 2-naphthol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, 2,2°-dihydroxydiphenyl ether, 4-phenylphenol, 4-tel”t- Octylcatechol, 2,2°-dihydroxydiphenyl,
4,4-methylenebisphenol, 2,2°-methylenebis(4-chlorophenol), 2,2°-methylenebis(4-methyl-6-tert-butylphenol,
4゜4-isopropylidene diphenol, 4,4-isopropylidene bis(2-chlorophenol), 4,4
゜-isopropylidene bis(2,6-dibromophenol), 4,4°-isopropylidene bis(2-methylphenol), 4,4°-isopropylidene bis(2-
.

tert-butylphenol), 4,4'-isopropylidene bis(2,6-dimethylphenol), 4.
4'-5eC-butylidene diphenol, 4.4'-5
eC-butylidene bis(2-methylphenol), 4
．． 4'-cyclohexylidene diphenol, 4,4°-
Cyclohexylidene bis(2-methylphenol), salicylic acid, salicylic acid methalyl ester, salicylic acid phenacyl ester, 4-hydroxybenzoic acid methyl ester, 4-hydroxybenzoic acid ethyl ester, 4-
Hydroxybenzoic acid isopropyl ester, 4-hydroxybenzoic acid butyl ester, 4-hydroxybenzoic acid isoamyl ester, 4-hydroxybenzoic acid phenyl ester, 4-hydroxybenzoic acid benzyl ester,
4-hydroxybenzoic acid cyclohexyl ester, 5-
Hydroxysalicylic acid, 5-chlorsalicylic acid, 3-chlorsalicylic acid, thiosalicylic acid, 2-chloro-5-nitrobenzoic acid, 4-methoxyphenol, 2-hydroxybenzyl alcohol, 2,5-dimethylphenol,
Benzoic acid, orthotoluic acid, metatoluic acid, paratoluic acid, orthochlorobenzoic acid, metaoxybenzoic acid, 2゜4-dihydroxyacetophenone, resorcinol monobenzoate, 4-hydroxybenzophenone,
2.4-dihydroxybenzophenone, 2-naphthoic acid, 1-hydroxy-2-naphthoic acid, 3,4-dihydroxybenzoic acid ethyl ester, 3,4-dihydroxybenzoic acid phenyl ester, 4
-Hydroxypropiophenone, salicyl salicylate, phthalic acid monobenzyl ester, zinc thiocyanate complex.

In the present invention, the color developer is usually applied to the support at 0.
．． It is used at a rate of about 1 to 60q/TIt, preferably about 0.6 to 15g/TIt.

Further, in the present invention, a heat-fusible substance having a melting point of 200'C or less, preferably 150'C or less can be added to the transfer layer or the receiving layer. The amount of the heat-melting substance used is 0.1 to 50 parts by weight of the color developer.
Parts by weight.

In addition, in the present invention, an undercoat layer made of an inorganic or organic filler and a resin may be provided on the receptor sheet, and the amount of the resin and filler used in the undercoat layer is based on 1 part by weight of the filler. A suitable amount is 0.05 to 5 parts by weight.

When a transfer layer and a receiving layer are provided on each support, the binder used is one such as polyvinyl alcohol, methoxycellulose, hydroxyethylcellulose methylcellulose, polyvinylpyrrolidone, polyacrylamide, Water-soluble, organic solvent-soluble or aqueous emulsion-forming materials can be used, such as polyacrylic acid, starch, gelatin, polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, styrene-butadiene rubber, etc. In particular, in the case of the transfer layer, resins having a melting point or softening point of 50 to 130°C, e.g.
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, chloride rubber, butadiene rubber, olefin rubber, phenolic resin, urea resin, melamine resin, epoxy resin,
It is preferable to use polyimide or the like as a binder.

[Effect] In the present invention, in the receiving layer of the receiving sheet, an average particle size of 5
~50mμ, surface area 150~400T in BET method
Because it contains ultrafine particulate silica of It/CI, the dye on the transfer sheet is efficiently transferred, a high-density transferred image is obtained, and an image with excellent abrasion resistance can be obtained. Since the sheet and the receiving sheet are separated and the leuco dye and its color developer are contained on separate supports, there is no problem of color fogging during manufacturing or storage that occurs with conventional thermal paper. The resulting copy contains only a color developer and no leuco dye in the non-image area, so no color develops even if it is heated (i.e., it does not completely develop). Furthermore, high density surroundings can be obtained with a small amount of heating energy, and the transferred image obtained in this case has excellent heat resistance.

[Example] Next, the present invention will be explained in more detail with reference to Examples. Note that both "parts" and "%" shown below are based on weight.

Examples 1 to 3 (1) Preparation of transfer sheet (A) 3-(N-methyl-N-cyclohexylamino)-6-
After dissolving a composition consisting of 10 parts of methyl-7-anirite fluorane, 1 part of ethyl cellulose, and 89 parts of methyl ethyl ketone, it was coated using a wire bar on the surface of a 6 μm thick polyester film with a heat-resistant polyester film on the back side and dried. A transfer sheet (A) with an adhesion amount of 0.5 (1/TIt) was prepared.

(2) Preparation of receptor sheet (B) 4-hydroxybenzoic acid benzyl ester 20 parts Ultrafine particulate silica (average particle size 12 mμ, surface area 2007 Ff
/g 1 part polyvinyl alcohol 10% aqueous solution 20 parts water
59
After dispersing the composition for 24 hours using a ball mill, it was dispersed using a wire bar on high-quality paper (52 g/TIt).
) and dried to form a receptor layer having an adhesion amount of 59 parts m to prepare a receptor sheet (B).

(3) Creation of receptor sheet (C) Ultrafine particle silica (average particle size 12 m) for receptor sheet (B)
μ, surface area 200Trt/Cl) and ultrafine particulate silica (
Except for the average particle size of 7 mμ and surface area of 380/q),
A receptor sheet (C) was prepared in the same manner as the receptor sheet (8).

(4) Preparation of receptor sheet (D) 4-hydroxybenzoic acid benzyl ester 8 parts 4-benzylbiphenyl (melting point 85°C) 12 parts Ultrafine particulate silica (average particle size 40 mμ, surface area 180 butts/g
2 parts 5% aqueous methyl cellulose solution 40 parts water
38
A receiving sheet (D) was prepared in the same manner except that the composition of the receiving sheet (8) was changed.

Comparative Examples 1-2 Preparation of Receiving Sheet (E) A receiving sheet ([) was prepared in the same manner as in the receiving sheet (B) of Example except that the ultrafine particulate silica was replaced with water.

Preparation of Receptive Sheet (F) A receptive sheet ([) was prepared in the same manner as in the receptive sheet (D) of Example except that the ultrafine particulate silica was replaced with water.

Combine the transfer sheet and receiving sheet created as above as shown in Table 1, overlap the transfer sheet and receiving sheet, and use a thermal head to print 1 mj from the back side of the transfer sheet.
When heating energy of 200 ml was applied, a clear black image was obtained. The image density was measured and the abrasion resistance was tested by rubbing the image 100 times with a cardboard under a load of 20 g/cri. The results are shown in Table 1.

Claims (1)

[Claims] In a heat-sensitive transfer medium comprising a transfer sheet having a transfer layer containing a leuco dye provided on a support, and a receiving sheet having a support layer provided with a receiving layer containing a color developer that develops color by contacting the leuco dye. , an average particle size of 5 to 50 mμ in the receptor layer,
A thermal transfer medium characterized by containing ultrafine particulate silica having a surface area of 150 to 400 m^2/g according to the BET method.