JPH068071B2 - Thermal recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Use) The present invention is a color developer which is usually composed of a colorless or slightly pale color-forming dye and an organic acid or a phenolic substance capable of coloring the color-forming dye by heating. And a thermosensitive recording material having a thermosensitive coloring layer containing a binder.

More specifically, this heat-sensitive recording material has storage properties, particularly water resistance of the coating film, water resistance of the color-developed portion, fading resistance (hereinafter referred to as plasticizer resistance) and meat that occur when adhered to a plastic film containing a large amount of plasticizer. The present invention relates to a heat-sensitive recording material having improved discoloration property (hereinafter referred to as oil resistance) generated when oil such as edible oil or edible oil is attached.

(Prior Art) Conventionally, various known heat-sensitive recording sheets are prepared by coating a support with a coating obtained by dispersing a lactone compound such as crystal violet lactone and a phenol compound such as bisphenol A in a binder such as a polyvinyl alcohol solution. JP-B-45-14039).

When this type of heat-sensitive recording sheet receives heat, a color-forming lactone compound chemically reacts with an organic acid or a phenol compound to develop a color. In this case, the basic properties required for the heat-sensitive recording sheet are that the color development is good, the appearance is as white as possible, there is a natural paper appearance, and it has a long-term storability.
(A) High sensitivity, (b) No staking (sticking), and (c) No thermal deposit on the residue are required, and compatibility with the thermal head is required. ing.

As described above, it is desired that the heat-sensitive recording material has the above-mentioned properties depending on its application. However, a dye-type coloring system of this kind is unstable to light, water, temperature, plasticizer, oil and the like. Therefore, the change with time during storage is always a problem. Therefore, when a desired printing is performed on such a recording sheet, the recording color develops extremely clearly, but a plastic film (for example, a vinyl chloride soft film) containing a large amount of a plasticizer in the color forming portion. However, there is a drawback in that the adhered part is discolored if it is adhered or stored with oil or fat attached. Further, it is always the case that marked discoloration occurs even when the colored portion is in contact with water for a long time.

These discolorations are particularly noticeable in a color-forming system, that is, a dye-coloring type heat-sensitive recording material using a dye mainly composed of a colorless or light-colored lactone compound, which occurs when the heat-sensitive recording material comes into contact with oil or a plasticizer. As a common problem, there has been a strong demand for its elimination.

It has been proposed to provide a water-soluble polymer compound overcoat layer on the heat-sensitive color-developing layer as an improvement of such storability in a conventional heat-sensitive recording material. Since this hinders the heat sensitivity, the heat sensitivity is deteriorated, and a coating process for the overcoat layer is required, resulting in a high cost. Further, in a heat-sensitive label or a heat-sensitive ticket produced by subjecting a heat-sensitive recording material coated with such an overcoat layer to a cutting process, an adhesive process, etc., oil or the like permeates from the cut surface to erase the decolored portion of the printed part. Such overcoat layer coating is not an essential solution, as it causes.

(Problems to be Solved by the Invention) The present invention intends to solve these problems and to provide a heat-sensitive recording material having long-term storage stability, which has water resistance, plasticizer resistance and oil resistance. For example, when used as a thermal recording type ticket for automatic ticket vending machines, of course, it is used for multiple tickets and commuter tickets that require preservation, and there are many fresh foods and oils due to the POS bar code planting system. Not only is it suitable for use as label paper that is attached to the packaging surface when it is wrapped in vinyl chloride film such as meat, but it also provides a thermal recording material that can be used as facsimile paper or printer paper for long-term storage. is there.

(Means for Solving the Problems) The inventors of the present invention have conducted diligent research to solve the above problems and found that a colorless or light-colored coloring material is usually used.
In a heat-sensitive recording material having a color-forming layer containing a color-developing agent that develops color by contacting with this color-developing agent, a fluoran-based lactone compound that is usually used as a color-developing material, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthene] -2'-ylamino] phenyl}
When propane is used together with a normally colorless or light-colored colorless fluoran dye having an anilino group at the 7-position of the fluoran skeleton, the heat-sensitivity is remarkably improved in storage stability such as water resistance, plasticizer resistance and oil resistance as described above. It has been found that a recording material can be obtained.

However, the compound of formula (I) is effective in improving the storage stability, but is not practical in terms of color development. Therefore, the mixing ratio of the above two kinds of color forming dyes is important. In order to fully exhibit the storage properties such as water resistance, plasticizer resistance, and oil resistance, the dye of formula I is added in an amount of 10% by weight based on the total amount of the color forming dye.
It must be above. On the other hand, the dye of the formula I must be 50% by weight or less in order to ensure sufficient color development.

By adopting the above-mentioned special compound as a color forming dye, it is not necessary to provide an overcoat layer containing a water-soluble polymer compound as a main component on the thermosensitive coloring layer, and when it is adhered to a soft film of polyvinyl chloride. It also enables proper prevention of discoloration caused by the adhesion of oils and fats, and exhibits excellent stability and storage stability.

The materials used for the heat-sensitive recording material of the present invention will be described in detail below.

As the color forming dye, 2,2-bis {4 having the formula (I) is used.
-[6 '-(N-cyclohexyl-N-methylamino)
-3'-methyl spiro [phthalide-3,9'-xanthene]
2'-ylamino] phenyl} propane and a normally colorless to light-colored fluorane-based colorless dye having an anilino group at the 7-position of the fluorane skeleton are optionally used as mixed dyes. As the latter, 3-diethylamino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-
Methyl-7-anilinofluorane, 3- (N-methyl-
N-cyclohexylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-7-chloroanilinofluorane, 3- [N-ethyl-N- (p-methylphenyl) amino] -6-methyl- 7-anilinofluorane, 3-diethylamino-7- (tatrifluoromethyl) anilinofluorane, 3- [N-ethyl-N-tetrahydrofurfuryl] amino-6-methyl-7-anilinofluorane, 3 -[N-ethyl-N-isopentyl]
Amino-6-methyl-7-anilinofluorane, 3-
Typical examples are fluorane dyes such as [N, N-dibutyl] amino-6-methyl-7-anilinofluorane. be able to. However, it is not limited to these representative examples.

In the present invention, the color developer is preferably at room temperature or higher, preferably 7
It is liquefied or vaporized at 0 ° C. or higher and reacts with the color forming dye to develop a color. For example, 4,4′-isopropylidene diphenol [bisphenol A], 4,4′-isopropylidene bis (2 -Chlorophenol), 4,4'-
Isopropylidene bis (2-methylphenol), 4,
4'-isopropylidene bis (2-chlorophenol), 4,4'-isopropylidene bis (2-methylphenol), 4,4'-isopropylidene bis (2,1-ter)
t-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 phenolic resin, halogenated novolac type phenolic resin, 4,4'-thio-bis (3-methyl-6)
-Tert-butylphenol), propyl p-hydroxybenzoate, isopropyl p-hydroxybenzoate,
Fatty acid carboxylic acids such as butyl p-hydroxybenzoate, isobutyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, methylbenzyl p-hydroxybenzoate, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid, stearic acid 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-dioxaheptane, 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'-dihydroxy-diphenyl sulfone, 3,
3'-diamino-4,4'-dihydroxy-diphenyl sulfone, 3,3'-diamino-4,4'-dihydroxydiphenyl 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- Examples thereof include dihydroxy-diphenyl sulfone, 2,4-dihydroxy-4'-methyldiphenyl sulfone and 3,4-dihydroxyphenyl-p-trisulfone. However, a developer that is apt to cause background fog is not preferable, and therefore bis- (3-allyl-4-hydroxyphenyl) -sulfone is excluded.

The color developer is 1 to 5 parts by weight per 1 part by weight of the color forming dye,
Preferably 1.5 to 3 parts by weight are used.

As the binder for the thermosensitive coloring layer, all known binders can be used. However, when mixed with each dispersion liquid of the color-forming dye and the color-developing substance, it is preferable that the liquid is not colored, aggregated, or has a high viscosity. Strong film formation,
It is required that there is no desensitizing effect and that the above-mentioned stacking is suitable.

Usual aqueous binders include polyvinyl alcohol, modified starch, arabic gum, gelatin, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl pyrrolidone, polyacrylic acid salt, polyacrylic amide, styrene-maleic anhydride copolymer,
Styrene-butadiene latex, an emulsion of acrylic acid ester copolymer and the like can be used.

In order to impart water resistance to the coating film, a combination of a water-soluble polymer substance containing a reactive group such as an acetoacetyl group, a carboxyl group, an amide group and a curing agent is desirable. As the curing agent, glyoxal, dialdehydes such as polyaldehyde, polyamines such as polyethyleneimine, epoxy polyamide resin, diglycidyl such as glycerin diglycidyl ether, ammonium persulfate and ferric chloride other than dimethylol urea, A known compound such as a metal salt such as magnesium chloride or ammonium chloride is used.

In addition, if necessary, the thermosensitive coloring layer may further contain auxiliary additives commonly used in thermosensitive recording materials of this type, such as fillers, surfactants, thermoplastic substances (or lubricants) and the like. It doesn't matter. In this case, as the filler, for example, calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, synthetic magnesium silicate, zinc oxide, titanium oxide, aluminum hydroxide, sulfuric acid. barium,
Inorganic fine powders such as surface-treated calcium carbonate and silica, as well as organic fine powders such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin can be mentioned. As, for example, stearic acid amide, stearic acid ethylenebisamide, oleic acid amide, palmitic acid amide, fatty acid amides such as palm fatty acid amide, behenic acid amide, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax. Waxes such as wax, ester wax, 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, p-benzylbiphenyl, 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-butyl) Hindered phenols such as phenol), 2- (2 '
Examples thereof include sensitizers such as -hydroxy-5'-methylphenyl) benzotriazole and 2-hydroxy-4-benzyloxybenzophenone, and various heat-fusible substances such as lubricants, antioxidants, and UV inhibitors. The amount of the heat-fusible substance added is not particularly limited, and is generally preferably in the range of about 4 parts by weight or less relative to 1 part by weight of the color developer.

The support used in the heat-sensitive recording material of the present invention includes high-quality paper, medium-quality paper, art paper, coated paper, cast coated paper,
Papers such as paperboard and thin paper are generally used, but plastic film, synthetic paper, laminated paper, aluminum foil and the like can also be used.

(Example) Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Parts in each example indicate parts by weight.

Example 1 (1) Preparation of solution A 2,2-bis {4- [6- (N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthene] -2'- Ilamino] phenyl} propane 6 parts 10% aqueous polyvinyl alcohol solution 6 parts water 10 parts (2) Preparation of solution B 3- (N-ethyl-N-isopentyl) amino-6-methyl-7-anilinofluorane 6 parts 10 % Polyvinyl alcohol aqueous solution 6 parts water 10 parts (3) C solution preparation 4,4'-dihydroxydiphenyl sulfone 25 parts 10% polyvinyl alcohol aqueous solution 25 parts water 40 parts The above-mentioned solutions A, B and C are separately separated. It was dispersed and pulverized with a sand grinder until the average particle size became 1 μm or less.

(3) Formation of thermosensitive coloring layer Liquid A 10 parts Liquid B 15 parts Liquid C 75 parts Calcium carbonate 60% water dispersion 25 parts Firing clay 60% water dispersion 25 parts 10% Polyvinyl alcohol 100 parts 10% Acetoacetylated PVA 100 parts 30% 1,13-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane dispersion 10
Parts 30% diphenyl carbonate dispersion 75 parts 30% polyaldehyde solution 3 parts 30% paraffin wax 10 parts 30% zinc stearate dispersion 17 parts Mix in the above proportions to form a coating solution. After coating this coating solution on a base paper of 50 g / m ^{2 so} that the dry weight becomes 6 g / m ² , super calendering treatment is applied to obtain a smoothness of 300 to 35.
A 0 second thermosensitive coloring layer was provided.

Comparative Examples 1 and 2 In the formation of the thermosensitive color developing layer of Example 1, 10 parts of solution A and B
Instead of 15 parts of liquid, 25 parts of liquid B (Comparative Example 1), 2 parts of liquid A,
A heat-sensitive recording material was obtained by operating under the same conditions as in Example 1 except that 23 parts of Solution B (Comparative Example 2) was used.

Each of the thermal recording materials of the above Examples and Comparative Examples was stored at room temperature for 3 hours.
After standing for a day, solid color black recording was performed with Copix 7100 (trade name, manufactured by Toshiba Electric Co., Ltd.), and a clear black color image was obtained at a high density of 1.2 or more with a Macbeth reflection densitometer (RD-514). Then, a predetermined supply piece was prepared from this by a conventional method, and the water resistance, the polyvinyl chloride film resistance and the oil resistance of the colored portion were measured by the following tests. The results are shown in Table 1. As is clear from this table, satisfactory results were obtained in each of the examples, but in each comparative example, an appropriate result was not obtained in some properties.

(1) Water resistance test: Specimens in water for 24 hours (at room temperature)
Evaluation is performed by taking out after immersion, elution state of the heat-sensitive layer, and residual concentration after drying.

(2) PVC film resistance test: Soft polyvinyl chloride film was overlaid on the test piece and left at each temperature of 20 ° C and 40 ° C for 24 hours under the load of 300 g / m ² Evaluate from the concentration.

(3) Oil resistance test: A cottonseed oil is applied to a supply piece by an ordinary method, and evaluated by the residual concentration after standing for 24 hours at each temperature of 20 ° C and 40 ° C.

Examples 2 to 12 (1) Preparation of liquid D 6 parts of fluorane color-forming dye shown in Table 6 10% polyvinyl alcohol aqueous solution 6 parts water 10 parts (2) Preparation of solution E 4,4'-dihydroxydiphenyl sulfone 15 parts 4,4'-cyclohexylidene diphenol 10 parts 10% aqueous solution of polyvinyl alcohol 25 parts The above solution D and solution E are separately averaged with a sand grinder. The particles were dispersed and pulverized until the particle size became 1 μm or less.

(3) Formation of thermosensitive coloring layer A solution 10 parts D solution 15 parts E solution 75 parts A thermosensitive recording material was obtained by the same operation as in Example 1 except that the above proportions were mixed, and a quality test was conducted. Is also shown in Table 2.

Comparative Example 3 In the formation of the thermosensitive coloring layer of Example 2, 10 parts of A liquid, D
A thermosensitive recording material was obtained by the same procedure as in Example 2 except that 25 parts of the liquid D of Example 2 (3-diethylamino-6-methyl-7-anilinofluorane) was used instead of 15 parts of the liquid. A quality test was conducted, and the results are also shown in Table 2.

As is clear from Table 1 and Table 2, Examples 1-1
In No. 2, it was possible to obtain excellent results in oil resistance and polyvinyl chloride film resistance as compared with Comparative Examples 1 to 3.

(Effect of the Invention) The heat-sensitive recording material of the present invention is capable of exhibiting excellent water resistance, plasticizer resistance, and oil resistance without providing any overcoat layer of a water-soluble polymer compound or the like. At the same time, the preservability of the heat-sensitive recording material is remarkably improved. As a result, there is an effect of expanding the applicability in a wider range of applications such as a commuter pass, a coupon ticket, a label paper, or a printer paper, which requires particularly long-term storability.

Claims (1)

[Claims] 1. A color-forming dye and a color-developing agent (however, bis- (3-
In a thermosensitive recording material having a thermosensitive color forming layer containing allyl-4-hydroxyphenyl) -sulfone), the coloring dye has a formula of 10% by weight or more and 50% by weight or less based on the total amount of the coloring dye. 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthene] -2'-ylamino] phenyl} propane represented by A heat-sensitive recording material comprising a normally colorless or pale-colored colorless dye having an anilino group at position 7 of the fluoran skeleton.