JPH0572275B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to improvements in heat-sensitive recording materials containing leuco dyes as color formers. [Prior Art] Thermosensitive recording materials generally have a thermosensitive coloring layer containing a thermochromic composition as a main component on a support such as paper, synthetic paper, or plastic film.
Colored images can be obtained by heating with a thermal pen, laser light, strobe lamp, etc. Compared to other recording materials, this type of recording material does not require complicated processing such as development and fixing, can produce records in a short time using relatively simple equipment, and generates less noise and pollutes the environment. Due to its advantages such as low cost, it is used not only for copying books and documents, but also as a recording material in a wide range of applications such as electronic computers, facsimile machines, ticket vending machines, labels, and recorders. Thermochromic compositions used in such heat-sensitive recording materials generally consist of a color former and a color developer that causes the color former to develop color when heated. Examples of the color former include lactone, lactam, or colorless or spiropyran ring-containing compositions. Light-colored leuco dyes and organic acids and phenolic substances have conventionally been used as color developers. Recording materials containing a combination of a color forming agent and a color developing agent are widely used because they have the advantage that the resulting image has a clear color tone, a high degree of background whiteness, and a high image density. However, in recent years, heat-sensitive recording methods have replaced other conventional recording methods, and as demand has increased, demands for improving the quality of heat-sensitive recording materials have also increased, with particular emphasis placed on the reliability of recorded images. In this field, one of the essential conditions for heat-sensitive recording materials is to provide colored images that are highly stable against oils and fats such as fingerprints, plasticizers contained in plastic erasers and commuter pass cases, and against aging and light. It's summery. In the past, several methods have been proposed to improve the plasticizer resistance, oil resistance, alcohol resistance, etc. of images. -215393) and a method using zinc salicylate as a color developer are known. However, although these methods improve image stability, in the former case, background fogging (background coloration, background discoloration) is significant, and in the latter case, the background part is exposed to plasticizers or solvents. etc., and this poses a major problem in practical use. [Purpose] The present invention overcomes the problems of the prior art as described above, and provides excellent stability of colored images (plasticizer resistance, oil resistance, solvent resistance, etc.) as well as excellent background stability. The purpose of the present invention is to provide a heat-sensitive recording material. [Structure] According to the present invention, a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and a color developer is characterized in that a tribromomethyl phenyl sulfone compound is used as the color developer. A heat-sensitive recording material is provided. The tribromomethyl phenyl sulfone compound used as a color developer in the present invention includes not only tribromomethyl phenyl sulfone itself but also derivatives of tribromomethyl phenyl sulfone, particularly those in which the phenyl group has a substituent. Specific examples of such derivatives include tribromomethyl-p-methylphenyl sulfone, tribromomethyl-p-
Chlorophenyl sulfone, tribromomethyl-p
-Nitrophenyl sulfone, tribromomethyl-
Examples include o-methylphenyl sulfone and tribromomethyl-p-isopropylphenyl sulfone, but the present invention is not limited thereto. The color developer is usually used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, per 1 part by weight of the leuco dye. The leuco dye used in the present invention may be used alone or in combination.
These leuco dyes can be applied in a mixture of more than one species, and any of the leuco dyes that have been applied to this type of heat-sensitive material can be used, such as triphenylmethane, fluoran, phenothiazine, auramine, etc. , leuco compounds of spiropyran dyes and the like are preferably used. Specific examples of such leuco dyes include those shown below. Di-(p-dimethylaminophenyl)-phenylmethane, Di-(p-diethylaminophenyl)-phenylmethane, Tris-(p-dimethylaminophenyl)methane, Tris-(p-diethylaminophenyl)methane, Tris- (o-chloro-p-dimethylaminophenyl)methane, tris(p-dimethylaminophenyl)-cyanomethane, 3,3-bis(p-dimethylaminophenyl)
-phthalide, 3,3-bis(p-dimethylaminophenyl-
6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis(p-dimethylphenyl)-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-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, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N-
benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-
phenylethylamino)fluoran, 3-(N-ethyl-p-toluidino)-7-(α
-phenylethylamino)fluoran, 3-diethylamino-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-
phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3-(N-methyltoluidino)-7
-(p-n-butylanilino)fluorane, 3-(N-benzyl-N-cyclohexylamino)-5,6-benzo-7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-methyl -7-mesitidino-4',5'-benzofluorane, etc. In the present invention, conventionally used phenolic substances, organic or inorganic acidic substances, etc. can be used in combination as color developers, if necessary. Examples of such color developers include the following. Gallic acid, salicylic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5
-di-tert-butylsalicylic acid, 3,5-di-α
-Methylbenzylsalicylic acid, 4,4'-isopropylidene diphenol, 4,4'-isopropylidene bis(2-chlorophenol), 4,4'-isopropylidene bis(2,6-dipromophenol), 4, 4'-isopropylidene bis(2,6-
dichlorophenol), 4,4'-isopropylidene bis(2-methylphenol), 4,4'-isopropylidene bis(2,6-dimethylphenol), 4,4'-isopropylidene bis(2-tert-
butylphenol), 4,4'-sec-butylidenephenol, 4,4'-cyclohexylidenebisphenol, 4,4'-cyclohexylidenebis(2-
methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 3,5-xylenol, thymol, methyl-
4-hydroxybenzoate, 4-hydroxyacetophenone, novolak type phenolic resin,
2,2'-thiobis(4,6-dichlorophenol), catechol, resorcinol, hydroquinone,
Pyrogallol, phloroglycin, phloroglycin carboxylic acid, 4-tert-octylcatechol,
2,2'-methylenebis(4-chlorophenol),
2,2'-methylenebis(4-methyl-tert-butylphenol), 2,2'-dihydroxydiphenyl, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, p-hydroxy Benzyl benzoate, p-
p-chlorobenzyl hydroxybenzoate, p-
Hydroxybenzoic acid-o-chlorobenzyl, p-
p-methylbenzyl hydroxybenzoate, p-
n-octyl hydroxybenzoate, benzoic acid,
Zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, zinc 2-hydroxy-6-naphthoic acid, 4-hydroxydiphenylsulfone, 4-hydroxy-4'-chlorodiphenylsulfone, Bis(4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, zinc 3,5-di-tert-butylsalicylate, tin 3,5-di-tert-butylsalicylate, tartaric acid, oxalic acid, maleic acid , citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, etc. In the present invention, in order to bind and support the leuco dye and color developer on the support, various commonly used binders can be used as appropriate, such as polyvinyl alcohol, starch and its derivatives, methoxycellulose, hydroxyl, etc. Cellulose derivatives such as ethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose,
Sodium polyacrylate, polyvinylpyrrolidone,
Acrylic amide/acrylic ester copolymer, acrylic amide/acrylic ester/methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt, poly In addition to water-soluble polymers such as acrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, and butyl methacrylate,
Latexes such as ethylene/vinyl acetate copolymers and styrene/butadiene/acrylic copolymers can be used. In addition, in the present invention, in addition to the leuco dye and color developer, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, surfactants, heat-melting substances ( or lubricant), etc. can be used in combination. In this case, fillers include, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium and silica. ,
Organic fine powders such as urea-formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin can be mentioned, and examples of the thermofusible substance include higher fatty acids or their esters, amides, or metal salts. , various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, 3,4-epoxy-
Dialkyl hexahydrophthalate, higher ketone,
Examples include other thermofusible organic compounds having a melting point of about 50 to 200°C. The heat-sensitive recording material of the present invention can be produced, for example, by applying a heat-sensitive layer-forming coating solution containing each of the above-mentioned components onto a suitable support such as paper, synthetic paper, or plastic film, and drying it. It is used in various recording fields, especially as a heat-sensitive recording material that requires high image stability. The heat-sensitive recording material of the present invention can be used in various fields, but in particular, it can be advantageously used as a heat-sensitive recording label sheet or a heat-sensitive recording magnetic ticket paper by taking advantage of the above-mentioned excellent color image stability. be able to. In the case of a heat-sensitive recording type label sheet, a heat-sensitive coloring layer containing the above-mentioned fluoran compound and phenolic compound is provided on one side of the support, and a release mount is provided on the other side of the support via an adhesive layer. In the case of magnetic ticket paper, a magnetic recording layer containing a ferromagnetic material and a binder as main components may be provided in place of the release mount. [Effect] By using a tribromomethyl phenyl sulfone compound as a color developer, a heat-sensitive recording material with extremely high image and background stability can be obtained. [Example] Next, the present invention will be explained in more detail with reference to Examples. Note that parts and percentages below are based on weight. Example 1 Solutions A to D were prepared by dispersing or dissolving each mixture having the following composition in a ball mill. [Liquid A] Tris-p-dimethylaminophenylmethane
10 parts Hydroxyethyl cellulose 10% aqueous solution 10 parts Water 30〃 [Liquid B] Tribromomethylphenylsulfone 30 parts Polyvinyl alcohol 10% aqueous solution 30〃 Water 90〃 [Liquid C] Calcium carbonate 30 parts Methylcellulose 5% aqueous solution 30〃 Water 60 [Liquid D] Isobutylene maleic anhydride ammonium salt 20% aqueous solution 5 parts A, B, C, and D solutions obtained as above were mixed in a ratio of 1:1:1:1 to prepare a coating liquid. death,
This coating solution was coated and dried on a high-quality paper having a basis weight of 50 g/m ² so that the dry adhesion amount of the dye was 0.5 g/m ² to form a heat-sensitive coloring layer, thereby obtaining a heat-sensitive recording material. Example 2 In Example 1 above, Tris-(p-
A heat-sensitive recording material of the present invention was obtained in the same manner except that tris-(4-diethylamino-o-tolyl)methane was used instead of dimethylaminophenyl)methane. Example 3 In Example 1 above, Tris-(p-
Tris-(p-diethylamino-o-chlorophenyl) instead of dimethylaminophenyl)methane
A heat-sensitive recording material of the present invention was obtained in the same manner except that methane was used. Comparative Example 1 A comparative heat-sensitive recording material was obtained in the same manner as in Example 1, except that bisphenol A was used instead of tribromomethylphenyl sulfone in liquid B. Comparative Example 2 A comparative heat-sensitive recording material was obtained in the same manner as in Comparative Example 1 except that crystal violet lactone was used instead of tris-(p-dimethylaminophenyl)methane. The heat-sensitive recording materials of the present invention and comparative heat-sensitive recording materials obtained as described above were tested using a commercially available thermal gradient tester.
After printing at 140° C. and leaving it at room temperature, the image density and background density were measured using a Macbeth RD-514 type densitometer. The results are shown in Table-1. Furthermore, the printed samples were tested for plasticizer resistance, oil resistance, and alcohol resistance. These tests were conducted by applying a plasticizer (DOP), cottonseed oil, and ethyl alcohol to a sample, and measuring the concentrations in the image area and the background area one day later. The results are shown in Table-1.

[Table] As is clear from the above results, it can be seen that the heat-sensitive recording material of the present invention is significantly superior in oil resistance, plasticizer resistance, and alcohol resistance compared to the comparative examples.

Claims (1)

[Claims] 1. A heat-sensitive recording material that utilizes a color reaction between a leuco dye and a color developer, characterized in that a tribromomethyl phenyl sulfone compound is used as the color developer.