JPH07214912A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material reduced in the lowering of whiteness with the elapse of time and having high sensitivity and preservability. CONSTITUTION:In a thermal recording material obtained by providing a thermal recording layer containing a colorless or light-colored electron donating color forming dye, 4,4'-bis(p-toluensullfonylaminocarbonylamino) diphenylmethane being an electron acceptive acidic substance reacting with the dye under heating to develop a color, petroleum wax and methylolated fatty acid amide on at least the single surface of a sheet like support, aluminum hydroxide is further added to the thermal recording layer as pigment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more specifically to a heat-sensitive recording material having a small decrease in whiteness with time, high sensitivity and storability.

[0002]

2. Description of the Related Art Conventionally, by utilizing a coloring reaction between an electron-donating color-forming dye and an electron-accepting acidic substance which is colored by contacting the color-forming dye, heat is applied to bring both color-forming substances into contact with each other to develop a color. Heat-sensitive recording materials for obtaining images are well known.
Such a thermal recording medium has advantages such as a compact recording apparatus, low cost, and easy maintenance, and is not only used as a recording medium for a facsimile, an automatic ticket vending machine, or a scientific measuring machine, POS label, CAD, CRT
It is widely used as an output medium for various printers and plotters for medical images.

However, the conventional thermal recording material has a problem that when it comes into contact with a chemical such as oil or a plasticizer, the recording density is lowered, and in the worst case, the recording is completely lost. In order to improve such storage stability, it has been proposed to provide an overcoat layer on the thermosensitive coloring layer. For example, JP-A-56-146794 discloses that an overcoat layer is formed using a hydrophobic polymer emulsion, and JP-A-58-199189 discloses that an overcoat layer is formed on a thermosensitive coloring layer. It is disclosed that a water-soluble polymer compound or a hydrophobic polymer emulsion is provided as an intermediate layer, and an overcoat layer is provided thereon by using an oil-based paint containing a hydrophobic polymer compound as a resin component. Although the effect of improvement was recognized by these means, it was not yet sufficient for long-term storage stability.

This is because the storability of the thermosensitive color developing layer itself is insufficient, and in order to improve this, one using an aromatic isocyanate compound and an imino compound as the color forming components (JP-A-58).
-38733, JP 58-149388, JP 59-11
5888, JP-A-4-164686, JP-A-4-284288, JP-A-4-305489) or those using a salicylic acid derivative or a metal salt thereof having high storage stability as an acidic developer (special Kaihei 4-65292, JP 4-119880 A, JP 4-211989 A) and the like are proposed.
However, none of the materials that can enhance the storage stability of the thermosensitive coloring layer have sufficient sensitivity. Further, there is also a problem that the whiteness is lowered when the thermal recording material is stored for a long time.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art, and to provide a thermosensitive recording medium having a small decrease in whiteness over time, high sensitivity and storability.

[0006]

Means for Solving the Problems The present invention for solving the above-mentioned problems includes an electron-donating color forming dye which is colorless or light-colored on at least one surface of a sheet-like support and which reacts under heating to develop an electron. A thermosensitive recording medium comprising a thermosensitive recording layer containing 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane as a receptive acidic substance, a petroleum wax and a methylolated fatty acid amide. It has aluminum hydroxide as a pigment.

4,4'-bis (P-toluenesulfonylaminocarbonylamino) is used as a developer for the thermosensitive coloring layer.
It has been known that a thermosensitive recording medium having high storage stability can be obtained by using diphenylmethane, but there is a problem in that sufficient sensitivity can be obtained. Therefore, we conducted intensive research into improving sensitivity. Conventionally, melting point 40
It has been proposed to increase the sensitivity by using waxes at -100 ° C as a carrier (JP-A-48-19231) or a combination of fatty acid amide and petroleum wax (JP-B-51-27599). ing. But,
These methods have some problems in improving the sensitivity, but have a problem in the storage stability of the background.

It has also been proposed to use benzyl P-oxybenzoate as a developer and use it in combination with a methylolated fatty acid amide (JP-A-57-1883).
94 publication). Then, the developer used in the present invention, 4,4′-bis (P-toluenesulfonylaminocarbonylamino) diphenylmethane, was used in combination with the methylolated fatty acid amide, but the effect of improving the sensitivity was not recognized. It was

Further, the developer used in the present invention was used in combination with a conventionally known petroleum wax, but the effect of improving the sensitivity was not obtained. Next, it was found that a significant sensitivity improving effect was obtained by using this petroleum wax in combination with the methylolated fatty acid amide with the color developer used in the present invention. I was not satisfied.

The present inventors have added to 4,4'-bis (P-toluenesulfonylaminocarbonylamino) benzene,
As a result of conducting a study to improve the preservability of the background of a system excellent in sensitivity improving effect using a combination of a methylolated fatty acid amide and a petroleum wax, it is possible to add aluminum hydroxide to the system. The present invention has been found to be effective and has led to the present invention.

As a result of investigating a pigment in order to solve this problem, it was found that the inclusion of aluminum hydroxide improves the preservability of the background and suppresses the decrease in whiteness with time. Although the reason is not clear, since aluminum hydroxide has a strong tendency to arrange plate-like surfaces in parallel with the surface to be coated, it is unlikely to be affected by the environment, and it seems that the reduction in whiteness is suppressed.

The blending ratio of aluminum hydroxide is 20 to 60% by weight, preferably 25 to 5% by weight based on the total solids of the thermosensitive coloring layer.
It is used by mixing at a ratio of 0% by weight. If it is less than 20% by weight, it is likely to be affected by the environment and the object of the present invention will not be met. If it is more than 60% by weight, aluminum hydroxide masks the color-developed portion, resulting in a decrease in sensitivity. The pigment can be used in combination with conventionally known organic or inorganic pigments as long as the desired effect is not impaired. Examples of such organic or inorganic pigments include clay, calcined clay, calcium carbonate, magnesium carbonate, talc, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, barium sulfate, and surface-treated calcium carbonate. Examples thereof include inorganic fine powder such as silica, and organic resin fine powder such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin.

Methylolated fatty acid amide is a high melting point wax-like substance in which formaldehyde is added to fatty acid amide.
It is represented by the general formula RCONHCH ₂ OH (R means a straight-chain aliphatic hydrocarbon, and preferably has 12 or more carbon atoms).
Methylol stearamide, which is commonly used as a methylolated fatty acid amide, usually has 18 and 16 carbon atoms.
The ratio of the saturated hydrocarbon mixture is about 7: 3. In the present invention, it does not matter particularly if the carbon number is within the above-mentioned numerical value.

Petroleum waxes are paraffin waxes,
There are polyolefin wax and microcrystalline wax, and examples thereof include paraffin wax having various melting points of 42 to 73 ° C, microcrystalline wax having various melting points of 50 to 120 ° C, and polyolefin wax such as polyethylene wax and polypropylene wax. This polyolefin wax usually has a molecular weight of 1,
Those of the order of 000 to 10,000, commonly known as polyolefin waxes, are usually obtained by high pressure and low pressure polymerization processes or by the thermal decomposition of high molecular weight polyolefins. In order to facilitate emulsification, it is also possible to oxidize these petroleum waxes and introduce polar groups such as hydroxyl groups, ester groups, carboxyl groups, aldehyde groups and peroxide groups into the waxes. Further, in order to lower the softening point of waxes and improve workability, these waxes may be used in combination. Further, these petroleum waxes preferably have a melting point of room temperature or higher, preferably 40 ° C. or higher.

The blending ratio is in the range of 1 to 2 parts by weight of petroleum wax relative to 1 part by weight of methylolated fatty acid amide. The total blending amount of methylolated fatty acid amide and petroleum wax is based on the total solid content of the thermosensitive coloring layer. Good results were obtained when 5 to 15 wt% was compounded. At higher compounding amounts,
Greater adherence of lees to the thermal head during printing. or,
If the amount is less than this, the sensitizing effect is poor.

The petroleum wax is blended in the thermosensitive coloring layer as dispersed particles. The petroleum wax is dispersed into particles as small as possible by a pulverizer such as a ball mill, specifically, a particle diameter of several μm or less. It is desirable to grind until it becomes. The petroleum wax may be dispersed and used as described above, or may be added in the form of emulsion using an emulsifier. Further, a surfactant such as a dispersant or an antifoaming agent can be used as a grinding aid, if necessary, a filler such as talc or clay as a whitening agent, a powdery starch as an anti-adhesive agent, and an improvement in coating property. If necessary, a surfactant or the like can also be used.

As the electron-donating color-forming dye contained in the heat-sensitive color-forming layer of the present invention, known colorless and light-colored electron-donating color-forming dyes can be used. Specifically, for example, 2,2 bis {4 -[6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthene] -2'-ylamido] phenyl} propane,
3-Diethylamino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-ani Rinofluorane, 3-diethylamino-7-chloroanilinofluorane, 3- [N
-Ethyl-N- (p-methylphenyl) amino] -6-
Methyl-7-anilinofluorane, 3-diethylamino-7- (metatrifluoromethyl) anilinofluorane, 3- (N-ethyl-N-tetrahydrofurfuryl)
Amino-6-methyl-7-anilinofluorane, 3-
(N-Ethyl-N-isopentyl) amino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-
It is composed of at least one member of a fluoran dye such as methyl-7-anilinofluorane.

The color developer used in the present invention is 4,
4′-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane is used. However, it can be used in combination with a conventionally known color developer composed of an electron-accepting acidic substance within a range that does not impair the desired effect. Such an electron-accepting acidic substance is a substance that liquefies or vaporizes at room temperature or higher, preferably at 70 ° C. or higher, and reacts with the color forming dye to develop a color. Examples of the electron-accepting acidic substance include 4,4′-isopropylidenediphenol, 4,
4'-isopropylidene bis (2-chlorophenol), 4,4'-isopropylidene bis (2-methylphenol), 4,4'-isopropylidene bis (2,6)
-Tert-butylphenol), 4,4'-sec-
Butylidene diphenol, 4,4'-cyclohexylidene diphenol, 4-tert-butylphenol, 4
-Phenylphenol, 4-hydroxydiphenoxide, naphthol, β-naphthol, methyl-4-hydroxybenzoate, 4-hydroxy-acetophenone,
Salicylic acid anilide, novolac type phenol, halogenated novolac type phenol resin, 4,4′-thiobis (3-methyl-6-tert-butylphenol), P
-Propyl hydroxybenzoate, isopropyl P-hydroxybenzoate, butyl P-hydroxybenzoate, P-
Aliphatic carboxylic acids such as benzyl hydroxybenzoate, methylbenzyl P-hydroxybenzoate, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid, stearic acid, benzoic acid, p-tert-butylbenzoic acid, phthalic acid, Gallic acid, salicylic acid, 3-isopropylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, bis (4-hydroxyphenyl) sulfide, 1,7-di (4-hydroxyphenylthio) -3,5-dioxa Heptane, p-nitrobenzoic acid, salts of these organic developers with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel,

4,4'-dihydroxydiphenyl sulfone, 2,4-dihydroxydiphenyl sulfone, 3,
3'-dihydroxydiphenyl sulfone, 3,3'-diamino-4,4'-dihydroxydiphenyl sulfone,
3,3'-diallyl-4,4'-dihydroxy-diphenyl sulfone, 3,3'-dichloro-4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-diphenyl sulfone, 4-hydroxy-4'-isopropyldiphenyl sulfone , 4-hydroxy-4'isopropyloxydiphenyl sulfone, 4-hydroxy-4'-benzyloxydiphenyl sulfone, 2,4-dihydroxydiphenyl sulfone, 2,4'-dihydroxy-4'-
Methyldiphenyl sulfone, 3,4-dihydroxyphenyl-p-trisulfone, N- (o-toluoyl) -p
-Toluenesulfoamide, N- (p-toluenesulfonyl) -N'-phenylurea, and the like.

The electron-accepting acidic substance is usually a color forming dye 1.
The mixture is used in a proportion of 1 to 5 parts by weight, preferably 1.5 to 3 parts by weight, based on parts by weight.

In the present invention, other materials constituting the thermosensitive coloring layer include adhesive resins, waxes, metal soaps, and auxiliary additives conventionally used in thermosensitive recording materials, such as, for example,
Examples thereof include dispersants, surfactants, antioxidants, UV inhibitors, colored dyes, and colored pigments.

The adhesive resin can be combined with a generally known adhesive resin. Examples thereof include polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, cationic group-modified polyvinyl alcohol, sulfone group-modified polyvinyl alcohol, silica-modified polyvinyl alcohol, starch and its derivatives, gum arabic,
Gelatin, casein, methyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, polyvinylpyrrolidone, polyacrylic acid salt, polyacrylic amide, styrene-maleic anhydride copolymer, methyl vinyl ether-maleic anhydride copolymer, isopropylene-maleic anhydride copolymer Water-soluble resin such as polymer, styrene-
Water-dispersible resins such as butadiene latex, vinyl acetate-acrylic acid ester copolymer emulsion, polyurethane emulsion, polyvinyl chloride emulsion, polyvinylidene chloride emulsion, methacrylic acid ester copolymer emulsion and acrylic acid ester copolymer emulsion can be used. .

In order to strengthen the water resistance of the coating film, a water-soluble and / or water-dispersible resin adhesive containing a reactive group such as an acetoacetyl group, a carboxyl group or an amide group is used. It is preferable to use it in combination with a crosslinking agent. As the cross-linking agent, glyoxal, glutaraldehyde, polyvalent aldehyde compounds such as dialdehyde starch, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, diglycidyl compounds such as glycerin diglycidyl ether, dimethylol urea. Compounds, and inorganic compounds such as ammonium persulfate, ferric chloride, and magnesium chloride, boric acid, or borax can be used.

Examples of auxiliary additives conventionally used in thermal recording materials include p- (4-methylphenoxy) diphenyl, 1,2-diphenoxyethane, 1,2-di (3-methylphenoxy) ethane, and the like. Oxalic acid di-p-methylbenzyl, oxalic acid di-p-chlorobenzyl, terephthalic acid dimethyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, isophthalic acid dibutyl ester, 1-hydroxynaphthoic acid phenyl ester, 1,2 -Di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 1-phenoxy-2
-(4-methylphenoxy) ethane, diphenyl carbonate,
Diphenyl sulfone, p-benzyl biphenyl, 2,
2'-methylenebis (4-methyl-6-t-butylphenol), 4,4'-butylidenebis (6-t-butyl-3-methylphenol), 1,1,3-tris (2-
Methyl-4-hydroxy-5-t-butylphenyl) butane, 2,2'-methylenebis (4-ethyl-6-t-)
Butylphenol), 2,4-di-t-butyl-3-methylphenol, 4,4'-thiobis (3-methyl-6)
-T-butylphenol) and other hindered phenols, 2-2'-hydroxy-5'-methylphenyl)-
Examples thereof include benzotriazole and 2-hydroxy-4-benzyloxybenzophenone.

Examples of the metal soap include higher fatty acid polyvalent metal salts, that is, zinc stearate, aluminum stearate, calcium stearate, zinc oleate and the like. The thermosensitive coloring layer paint is applied to one surface of the sheet-like support 3
It is applied so as to be ˜8 g / m ² (dry weight), thereby forming a thermosensitive coloring layer.

The sheet-shaped support material used in the present invention is not particularly limited. For example, high-quality paper, medium-quality paper, coated paper,
Art paper, cast coated paper, slightly coated paper, resin, laminated paper, polyolefin-based synthetic paper, synthetic fiber paper, synthetic resin film and the like can be appropriately used.

When the heat-sensitive recording material of the present invention requires quality such as printability or imprintability, one or more overcoat layers can be provided on the heat-sensitive color developing layer. The overcoat layer has a coating amount after drying a coating material containing an ultraviolet curable resin, an electron beam curable resin or a solvent-soluble, water-soluble or water-dispersible adhesive resin, a crosslinking agent, a pigment and, if necessary, a lubricant. ~ 7.0 g / m ² , preferably 1.0 ~ 4.0 g /
It can be obtained by applying m ² coating.

The resin / pigment ratio of the overcoat layer is 80/2
The range of 0 to 20/80 is good and the compounding ratio of resin is 80
If it exceeds%, there is a problem that sticking occurs during printing and the adhesiveness of printing ink decreases during label processing. The adhesive resin, cross-linking agent, and pigment used in the overcoat layer may be the same as those used in the thermosensitive coloring layer, and the coating method may be the same as that used for coating the thermosensitive layer. In the heat-sensitive recording material of the present invention, a back layer may be provided on the surface opposite to the heat-sensitive color forming layer to correct the curl. The same paint and coating method as the overcoat layer can be used for the back surface layer, and the coating amount, resin /
It does not matter even if you change the pigment ratio. Further, various kinds of modifications such as providing an undercoat layer under the thermosensitive coloring layer may be carried out as needed.

[0029]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples. In each example, “part” means “part by weight”.

Examples 1 to 3 Formation of thermosensitive coloring layer Liquid A (coloring dye dispersion liquid) 3-dibutylamino-6-methyl-7-anilinofluorane 40 parts Polyvinyl alcohol 10% aqueous solution 40 parts (trade name: L3266 Nippon Synthetic Chemical Co., Ltd.) Water 20 parts Liquid B (developer developer dispersion) 4,4′-bis (p-toluenesulfonylamino carbonylamino) diphenylmethane 40 parts Polyvinyl alcohol 10% aqueous solution 40 parts (trade name: L3266 Nippon Synthetic Chemical Industry) Made) 20 parts of water

Liquid C (heat fusible substance dispersion liquid) 40 parts of diphenyl sulfone 40% aqueous solution of polyvinyl alcohol 40 parts (Product name: L3266 manufactured by Nippon Synthetic Chemical Industry) Water 20 parts D liquid (pigment dispersion liquid) Aluminum hydroxide 60 parts (Product name: Heidilite H-42 Showa Denko) Dispersant 0.1 part (Product name: Poise 520 Kao) Water 40 parts

Liquids A, B, C and D are separately separated from each other by Ultra Viscomill (sand grinder manufactured by IMEX Co., Ltd.).
Were dispersed and pulverized, and the average particle diameters of the liquids A, B and C were adjusted to 1 μm or less, and the liquid D was adjusted to 2.5 μm. Liquid A 25
Parts, B liquid 50 parts, C liquid 25 parts, D liquid 67 parts, zinc stearate 30% dispersion liquid 7 parts, and 25% vinyl acetate grafted starch (Petrocoat C8 Nitto Kagaku) 30 parts as an adhesive, Each of the methylolated fatty acid amides shown in Table 1 and petroleum wax was mixed in an amount of 5 parts by dry weight to prepare a thermosensitive coloring layer coating material. This coating solution was applied on one side of a 50 g / m ² high-quality paper so that the coating amount after drying would be 6.0 g / m ^2, and after forming a thermosensitive coloring layer, it was applied with a super calender to obtain the Oken smoothness (J .TAPPI No. 5) was smoothed for 2000 seconds to obtain a thermosensitive recording medium, and the recording sensitivity and whiteness were measured.

The recording sensitivity is a high-speed facsimile manufactured by NEC Corporation: Nefax 23, standard chart N of the Institute of Image Electronics Engineers of Japan.
Printing was performed using 0.2, and the color density at that time was measured with a Macbeth densitometer RD-914, and set to a value representative of the recording sensitivity of the thermosensitive recording medium. The degree of coloring (whiteness) of the background was measured using a Hunter whiteness meter (blue filter). The results are shown in Table 1. As for storage stability, a vinyl chloride film (Mitsui Toatsu Co., Ltd. Hilap K
(MA) was brought into close contact, and the image after storage at 25 ° C. for 1 week was visually evaluated. In addition, the whiteness after standing for 1 week at 40 ° C 90% RH and 20 ° C 65% RH is shown in Table 1.

[0033]

[Comparative example]

Comparative Example 1 A thermosensitive recording medium was prepared by the same method except that the pigment and aluminum hydroxide in Example 2 were changed to clay (trade name: HG Clay Huber).

Comparative Example 2 Pigment in Example 3 Aluminum hydroxide baked clay (trade name: Ansilex 93ENGELHARD)
A thermosensitive recording medium was prepared using the same method except that the above was changed.

[0035]

[Table 1]

[0036]

According to the present invention, it is possible to provide a heat-sensitive recording material having a small decrease in whiteness with time and having high sensitivity and storage stability.

Claims (1)

[Claims] 1. A 4,4′-bis (p-toluene) as an electron-accepting acidic substance that reacts with a colorless or light-colored electron-donating color-forming dye on at least one surface of a sheet-like support to produce a color by reacting under heating. A heat-sensitive recording material provided with a heat-sensitive recording layer containing sulfonylaminocarbonylamino) diphenylmethane, petroleum wax and methylolated fatty acid amide, wherein the heat-sensitive recording layer further contains aluminum hydroxide as a pigment. Record body.