JPS6410358B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material that has improved the disadvantage that a colored image fades when it comes into contact with a synthetic resin film. Conventionally, heat-sensitive recording materials utilize a coloring reaction between a basic colorless dye and a coloring agent that develops color when it comes into contact with the colorless dye, and bring both coloring substances into contact with each other using heat to obtain a colored image. is well known. Such heat-sensitive recording media are relatively inexpensive, and the recording equipment is compact and relatively easy to maintain.
It is used not only as a recording medium for facsimile machines and various computers, but also in a wide range of fields. For example, its use is expanding into fields such as product price display labels and commuter passes for automatic ticket gates. Price display labels are generally used by attaching them directly to the product using an adhesive treated on the back of the label, but in the case of perishable foods or products containing moisture, various synthetic resin films such as wraps for product packaging are used. Since it is packaged with a film, it is used by pasting it on top of the film. Furthermore, in the case of commuter passes, the surface is covered with a synthetic resin film to prevent counterfeiting of written information. However, if the heat-sensitive recording medium is used in contact with a synthetic resin film, especially a soft film, the colored image on the recording medium will fade over time, and in extreme cases, it will fade within a few days. The problem is that it disappears completely. The reason why colored images fade or disappear when they come into contact with synthetic resin films is not necessarily clear, but plasticizers such as dibutyl phthalate contained in such synthetic resin films may be involved in some way. I think that the. In view of the current situation, the present inventors have developed a heat-sensitive recording material that exhibits less fading of the colored image even when placed in contact with any kind of synthetic resin film, and of course does not completely eliminate the colored image. As a result of intensive research, we have completed the present invention. The present invention provides a thermosensitive recording material provided with a coloring layer containing a basic colorless dye and a coloring agent that develops a color when it comes into contact with the colorless dye, in which a fatty acid metal salt and a carbon number of gallic acid are contained in the coloring layer. This heat-sensitive recording material is characterized in that it contains both a water-insoluble gallic acid derivative consisting of 12 to 24 alkyl esters. In the present invention, the basic colorless dye contained in the coloring layer is not particularly limited, but examples include the following. 3.3-bis(p-dimethylaminophenyl)-
6-dimethylaminophthalide, 3.3-bis(p-
dimethylaminophenyl) phthalide, 3-(p-
triallylmethane dyes such as dimethylaminophenyl)-3-(1.2-dimethylindol-3-yl)phthalide, 4.4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halofenyl-leucoauramine, N- 2.4.5-Diphenylmethane dyes such as trichlorophenyl leuco auramine, benzoyl leucomethylene blue, p-
Thiazine dyes such as nitrobenzylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-
Spiro dyes such as propyl-spiro-dibenzopyran, 2-anilino-3-methyl-6-(N-ethyl-p-toluidino)fluoran, 2-p-toluidino-3-methyl-6-(N-ethyl- p-
toluidino) fluorane, 3-diethylamino-
6-Methyl-7-anilinofluorane, 3-diethylamino-7-(2-carbomethoxyanilino)fluorane, 3-(N-cyclohexyl-N
-Methylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-arylinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-diethylamino- 6-Methyl-7-chlorofluorane, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-diethylamino-6-
Methyl-7-xylidinofluorane, 3-diethylamino-7-chloroanilinofluorane, 7-
Diethylamino-3-chlorofluorane, 7-dimethylamino-3-chloro-2-methylfluorane, 3-methyl-6-(N-p-tolyl-N-ethylamino)fluorane, 3-pyrrolidino-6-
Methyl-7-p-butylanilinofluorane, 2
-Fluoran dyes such as phenylamino-3-methyl-6-(N-ethyl-Np-tolyl)aminofluorane, etc. Further, the coloring agent used in the present invention includes inorganic and organic acidic substances as exemplified below, but is not limited thereto. Inorganic acidic substances such as activated clay, acid clay, attapulgite, bentonite, colloidal silica, aluminum silicate, 4-tert-butylphenol, 4-hydroxyphenol, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4 -tert-octylcatechol, 2.2'-
Dihydroxyphenol, 2.2′-methylenebis(4-methyl-6-tert-isobutylphenol), 4.4′-isopropylidenebis(2-tert-butylphenol), 4.4′-sec-butylidenephenol, 4-phenylphenol, 4.4′-isopropylidene diphenol, 2.2′-methylenebis(4
―Chlorphenol), Hydroquinone, 4.4′―
Phenolic compounds such as cyclohexylidene diphenol, novolak type phenolic resin, phenolic polymer, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid. Terephthalic acid, 3-
sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3.5-
Dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3-
(α-methylbenzyl) salicylic acid, 3-chloro-5-(α-methylbenzyl) salicylic acid, 3.5
-Di-tert-butylsalicylic acid, 3-phenyl-
5-(α,α-dimethylbenzyl)salicylic acid,
Aromatic carboxylic acids such as 3.5-di-α-methylbenzylsalicylic acid, and their phenolic compounds, combinations of aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel. Organic acidic substances such as salts, etc. In the heat-sensitive recording material of the present invention, the ratio of the basic colorless dye and coloring agent in the coloring layer is appropriately selected depending on the type of colorless dye and coloring agent used, and is not particularly limited. Generally, 1 to 50 parts by weight, preferably 4 to 10 parts by weight of coloring agent are used per part by weight of colorless dye. The present invention has an important feature in that the coloring layer consisting of the above-mentioned basic colorless dye and coloring agent further contains both a fatty acid metal salt and a specific water-insoluble gallic acid derivative. . Heat-sensitive recording materials made of a combination of fatty acid metal salts and phenols such as gallic acid have been known for some time.
It is rarely used because its coloring density is extremely low and it also has the drawback of causing unnecessary coloring called paint fog and moisture fog. However, when both a fatty acid metal salt and a water-insoluble gallic acid derivative are included in the coloring layer made of a basic colorless dye and an acidic substance as in the present invention, the recording material after recording comes into contact with the synthetic resin film. This greatly improves the serious defect of the prior art, which is the resulting decrease in the density of the colored image. The fatty acids of the fatty acid metal salt used in the present invention include lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, and isomyristic acid. Straight chain or branched saturated fatty acids having 12 to 24 carbon atoms such as , isopalmitic acid and isostearic acid are preferably used, and among these, myristic acid, palmitic acid and stearic acid are particularly preferably used. Examples of the metal of the metal salt include iron, nickel, cobalt, chromium, lead, zinc, mercury, cadmium, copper, vanadium, etc. Among these, iron, nickel, etc. are preferably used. In the present invention, an alkyl ester of gallic acid having 12 to 24 carbon atoms is used as the water-insoluble gallic acid derivative. In such alkyl gallates, alcohols constituting gallic acid and esters include lauryl alcohol, tridecyl alcohol, myristyl alcohol, bentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, nonadecyl alcohol, eicosyl alcohol, doco Syl alcohol, 1-tetracosanol, 12-methyltridecanol, 14-methylpentadecanol, 16-methylheptadecanol, etc. where the alkyl group has 12 carbon atoms
Preference is given to linear or branched aliphatic saturated alcohols of 2 to 24. Of course, secondary or tertiary alcohols may be used, but primary alcohols as described above are most preferably used. The number of carbon atoms in the alkyl group of alkyl gallate is important, for example, if the number of carbon atoms is
If it is less than 11, the solubility of alkyl gallate in water increases rapidly, resulting in paint fogging. However, since these higher alcohols are generally extracted and manufactured from natural products, those with carbon numbers of 25 or more have low industrial utility value. Therefore, the alkyl group preferably has 12 to 24 carbon atoms, most preferably 14 to 22 carbon atoms. In the present invention, the ratio of fatty acid metal salt and water-insoluble gallic acid derivative to be used is appropriately selected depending on the type of fatty acid metal salt and gallic acid derivative used, and is not particularly limited. From 0.1 to 10 parts by weight, preferably from 0.3 to 5 parts by weight, of gallic acid derivatives are used per part by weight of salt. In addition, the ratio of the basic colorless dye and acidic coloring agent to the fatty acid metal salt and gallic acid derivative may be selected as appropriate, but the ratios may vary depending on color development sensitivity, moisture fog resistance, paint fog, and the desired effects of the present invention. It is desirable to use 5 to 100 parts by weight, preferably 10 to 50 parts by weight, of fatty acid metal salts and gallic acid derivatives based on 100 parts by weight of basic dye and coloring agent because of their excellent balance. To prepare a coating solution containing these substances, generally water is used as a dispersion medium, and dyes,
It is prepared as a coating liquid by dispersing a coloring agent, fatty acid metal salt, and gallic acid derivative. In addition, the coating liquid usually contains starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene/maleic anhydride copolymer salt, styrene/acrylic acid copolymer salt as binders. , styrene-butadiene copolymer emulsion, etc. are used in an amount of 10 to 40% by weight, preferably 15 to 30% by weight of the total solid content. Furthermore, various auxiliary agents can be added to the coating liquid. For example, sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate,
Examples include dispersants such as lauryl alcohol sulfate/sodium salt and fatty acid metal salts, ultraviolet absorbers such as benzophenone and triazole, antifoaming agents, fluorescent dyes, and coloring dyes.
In order to prevent sticking when the heat-sensitive recording material comes into contact with a recording device or a recording head, a dispersion or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, calcium stearate, ester wax, etc. may be added to the paint. It can also be added. Inorganic materials such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, and activated clay may be added to improve the adhesion of residue to the recording head. In addition, stearic acid amide, stearic acid methylene bisamide, oleic acid amide,
Palmitic acid amide, matcha oleic acid amide, coconut fatty acid amide, etc. can also be added as a sensitizer. Supports include paper, plastic film,
Synthetic paper and the like can be used, but paper is most preferably used in terms of cost, applicability, etc. Note that the method of forming the coloring layer is not particularly limited, and can be formed according to conventionally well-known and commonly used techniques, such as a method of applying and drying a coating liquid by air knife coating, blade coating, etc. It is formed by etc. Further, the amount of the coating liquid applied to the support is not particularly limited, but is usually in the range of 2 to 12 g/m ² , preferably 3 to 10 g/m ² in terms of dry weight. EXAMPLES Hereinafter, in order to make the effects of the present invention even clearer, Examples and Comparative Examples are listed, but the present invention is not limited to these. Furthermore, % and parts in the examples represent weight % and parts by weight unless otherwise specified. Example 1 Preparation of liquid A 2-phenylamino-3-methyl-6-(N-
Ethyl-N-p-tolyl) aminofluorane 25 parts Stearamide 10 parts Methyl cellulose 5% aqueous solution 35 parts Water 105 parts This composition was ground to an average particle size of 3 microns using a sand grinder. Preparation of Solution B 4.4'-isocyclohexylidene diphenol 100 parts Stearic acid amide 40 parts Methyl cellulose 5% aqueous solution 140 parts Water 420 parts This composition was ground with a sand grinder to an average particle size of 3 microns. Preparation of Solution C Ferric stearate 25 parts 10% polyvinyl alcohol aqueous solution 15 parts Water 85 parts This composition was ground in a ball mill for 48 hours. Solution D Preparation Lauryl gallate 25 parts Polyvinyl alcohol 10% aqueous solution 15 parts Water 85 parts This composition was ground in a ball mill for 48 hours. Formation of coloring layer After adding and dispersing 500 parts of a 20% aqueous dispersion of calcium carbonate (manufactured by Bihoku Funka Co., Ltd., Softon 1800) to 700 parts of B liquid prepared above, 125 parts of C liquid and D liquid were added.
125 parts, 50% styrene-butadiene copolymer emulsion (manufactured by Dow Chemical Company, Dow-1571)
100 parts of the liquid was added thereto, and 175 parts of liquid A was further mixed and dispersed to obtain a coating liquid with a solid content concentration of 22.4%. 50% of this coating liquid
After coating and drying on a base paper of g/m ² so that the coated amount after drying was 8 g/m ² , a heat-sensitive recording paper was obtained by applying a light supercalender. Comparative Examples 1 to 4 In Example 1, liquids C and D (comparative example 1), liquid C (comparative example 2), liquid D (comparative example 3), and liquids A and B (comparative example 4) were used, respectively. The coating liquids were prepared in the same manner as in Example 1 except that the coating liquids were prepared in the same manner as in Example 1 to obtain four types of coating liquids having solid content concentrations of 22.6%, 22.5%, 22.5%, and 23.9%. Each of the obtained coating liquids was applied and dried in the same manner as in Example 1, and then subjected to supercalender treatment to obtain four types of heat-sensitive recording paper. Example 2 The procedure was carried out in the same manner as in Example 1, except that nickel palmitate was used in place of ferric stearate in liquid C, and dodecyl gallate was used in place of lauryl gallate in liquid D. A thermosensitive recording paper was obtained. Example 3 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that ferric myristate was used instead of ferric stearate in liquid C. Comparative Example 5 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that decyl gallate was used instead of lauryl gallate in Solution D. A quality comparison test was conducted on the eight types of thermal recording paper thus obtained. That is, after color printing was performed on eight types of thermal recording paper using a thermal printer (PC-100A, manufactured by Texas Instruments) at room temperature, the reflection density of the printed and non-printed areas was measured. Color development sensitivity and paint fog were evaluated. In addition, record paper with the above eight types of printed colors was placed in an atmosphere of 30℃ and 90%RH for 24 hours.
After being exposed for a period of time, the reflection density of the non-printed area was measured to evaluate moisture fog resistance. On the other hand, a soft vinyl chloride film for food packaging (Hyrap, manufactured by Mitsui Toatsu Co., Ltd.)
After applying it closely and leaving it at room temperature and humidity for 7 days,
The fading resistance of the printed portion was visually evaluated. The results of the above quality comparison test are shown in Table 1.

[Table] As is clear from the results in Table 1, the thermal recording paper obtained in each example of the present invention had a well-balanced quality in terms of color development sensitivity, paint fog, moisture fog resistance, and fading resistance. It was an excellent thermal recording paper.

Claims (1)

[Claims] 1. A thermosensitive recording material provided with a coloring layer containing a basic colorless dye and a coloring agent that develops color when in contact with the colorless dye, in which a fatty acid metal salt and gallic acid having 12 to 24 carbon atoms are included in the coloring layer. 1. A heat-sensitive recording material comprising a water-insoluble gallic acid derivative consisting of an alkyl ester of.