JPH1134509A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a sufficient coloring sensitivity by an arrangement wherein a thermal recording layer contains a homopolymer or copolymer of a specified hydroxystyrene derivative and a sensitizer, i.e., at least one kind of specified acylacetate anilide derivative or diphenylsulfone derivative. SOLUTION: A thermal recording layer contains a homopolymer or copolymer of a hydroxystyrene derivative shown by formula I (where, R1 represents a hydrogen atom or an alkyl group of 1-8C) and a sensitizer, i.e., at least one kind of acylacetate anilide derivative shown by formula II (where, R<2> represents an alkyl group of 1-8C, an aryl group of 6-18C or an alkyl aryl group, R3 , R4 , R5 represents a hydrogen atom, a halogen atom or an alkyl or alkoxy group of 1-8C, independently) or diphenylsulfone derivative shown by formula III (where, R5 , R7 R8 , R9 , R10 , R11 represents a hydrogen atom, a halogen atom or an alkyl or alkoxy group of 1-8CR2 , independently).

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 having improved storage stability, and more particularly to a heat-sensitive recording material containing a polymer or copolymer of a hydroxystyrene derivative, and as a sensitizer, an acylacetic acid anilide derivative or diphenyl sulfone. The present invention relates to a heat-sensitive recording material having not only excellent coloring sensitivity but also improved storage stability such as heat resistance, light resistance and oil resistance by containing at least one derivative.

[0002]

2. Description of the Related Art A heat-sensitive recording material is usually composed of a colorless or pale-colored color-forming substance and a color developer which forms a color-forming substance under the action of heat. And other additives together with a support such as paper, synthetic paper, plastic film or sheet. And
In a recording apparatus, when a heating element such as a thermal head or a hot pen comes into contact, a color-forming substance reacts with a developer to produce a color such as black, and is recorded. Such a recording medium does not require complicated processing such as development and fixing as compared with other recording mediums, recording can be performed with a relatively simple apparatus and in a short time, noise generation is small, and Due to the advantages of low environmental pollution and low cost, not only copying of books and documents, but also various recording papers for measurement,
It is widely used as a recording material for vending machines such as computers, facsimile machines, telex and ticket, prepaid cards, labels and the like.

[0003] In a conventional heat-sensitive recording material, an initial combination of a color-forming substance (leuco dye), a developer for thermally developing the color-forming substance and a sensitizer to be used as necessary is used. From the viewpoints of color development sensitivity and background soiling (background fogging), practically satisfactory ones have been obtained.

However, when these heat-sensitive recording materials are exposed to sunlight, lighting, or the like for a long period of time, not only the printed portion becomes faint or disappears, but also the background portion turns yellow, and the facsimile is disadvantageous. If a printout such as a receiving paper, a word processor, or a personal computer is left on a desk, the recorded image becomes unclear and there is a problem in document storage.

Further, conventional heat-sensitive recording materials are not only inferior in light resistance, but also when stored under high-temperature and / or high-humidity conditions. There is a drawback, and there has been a strong demand for improving the storage stability of the heat-sensitive recording material.

[0006] Among the developers, it is known that a polymer of a hydroxystyrene derivative is relatively excellent in preservability. For example, JP-A-56-72991 and JP-A-5-52991.
JP-A-286254, JP-A-6-320872, and the like propose that the use of a polymer of a hydroxystyrene derivative improves the stability of a color image to a plasticizer or the stability of a background portion. . However, the color sensitivity was still insufficient, and was not practically satisfactory.

[0007]

In view of the above situation, the present inventors have remarkably improved the color-forming sensitivity and storage stability when a homopolymer or copolymer of a hydroxystyrene derivative is used as a developer. As a result of intensive studies to achieve this objective, this object was achieved by including a specific acylacetic acid anilide derivative or diphenylsulfone derivative as a sensitizer in addition to a homopolymer or copolymer of a hydroxystyrene derivative in a thermal recording material. And reached the present invention.

That is, the present invention relates to a thermosensitive recording layer containing a homopolymer or a copolymer of a hydroxystyrene derivative represented by the following general formula (I) and a sensitizer represented by the general formula (II): And at least one of a diphenylsulfone derivative represented by the general formula (III) and an acylacetic acid anilide derivative represented by the general formula (III).

[0009]

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[0010]

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[0011]

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Hereinafter, the heat-sensitive recording material of the present invention having the above gist will be described in more detail.

In the compounds of the general formulas (I), (II) and (III) used in the present invention, the alkyl group having 1 to 8 carbon atoms represented by R _{1 to} R ₁₁ is methyl, ethyl,
Propyl, isopropyl, butyl, sec-butyl, tert-butyl, isobutyl, amyl, tert-amyl, hexyl, heptyl, octyl, isooctyl, tert-octyl, 2-
Ethylhexyl and the like, and examples of the alkoxy group represented by R _{3 to} R ₁₁ include an alkoxy group derived from the above alkyl group, and examples of the halogen atom include chlorine, bromine, and fluorine, and are represented by R ₂ Aryl or alkylaryl groups include phenyl, naphthyl, 3-
Methylphenyl, 4-methylphenyl, 4-tert-butylphenyl, 2,4-dimethylphenyl and the like can be mentioned.

In the present invention, a copolymer of a hydroxystyrene derivative represented by the general formula (I) can be used. Other monomers to be combined as the copolymer include styrene, methylstyrene, and 4-styrene. Styrene derivatives such as methoxystyrene, methyl acrylate,
Ethyl acrylate, butyl acrylate, t-acrylate
Acrylates such as butyl; methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and t-butyl methacrylate;

As specific representative examples of the homopolymer or copolymer of the hydroxystyrene derivative represented by the above general formula (I) to be added to the heat-sensitive recording material of the present invention, the following compounds can be mentioned. .

[0016]

[Table 1]

The polymer or copolymer of the hydroxystyrene derivative represented by the above general formula (I) used in the present invention can be easily produced by carrying out a polymerization reaction by a conventionally known method. Especially when the weight average molecular weight is 3
Those in the range of 00 to 150,000 are preferred in terms of color sensitivity, and those in the range of 500 to 100,000 are more preferred.

Specific representative examples of the acylacetic acid anilide derivative represented by the general formula (II) include the following compounds.

[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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[0025]

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[0026]

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Further, specific representative examples of the diphenylsulfone derivative represented by the general formula (III) include the following compounds.

[0028]

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[0029]

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[0030]

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[0031]

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The amount of the homopolymer or copolymer of the hydroxystyrene derivative used in the present invention depends on the required performance and recording suitability, the type and use of the color-forming substance (dye) or other additives used in combination. Although it varies depending on the amount, it is not particularly limited, but is usually 0.01 to 10 parts by weight relative to 1 part by weight of the chromogenic substance (dye).
Preferably, 0.1 to 5 parts by weight is used. When the amount of the homopolymer or copolymer of the hydroxystyrene derivative is less than 0.01 part by weight based on 1 part by weight of the chromogenic substance (dye), The effect of improving the preservability is poor, and even if it is used in an amount exceeding 10 parts by weight, the effect is not further increased and it is uneconomical.

The amount of the acylacetic acid anilide derivative or diphenylsulfone derivative used in the present invention depends on the type, required performance and recording suitability, the type of the color-forming substance (dye) or the type of other additive used in combination. Although it is not particularly limited, it varies depending on the amount used and is usually 0.1 to 5 parts by weight, preferably 0.2 to 3 parts by weight, per 1 part by weight of the hydroxystyrene derivative polymer.
Parts by weight are used. When the amount of the acylacetic acid anilide derivative or the diphenylsulfone derivative is less than 0.1 part by weight per 1 part by weight of the homopolymer or copolymer of the hydroxystyrene derivative, the coloring sensitivity becomes insufficient,
Further, if the amount exceeds 5 parts by weight, the effect is not increased any more and it is uneconomical.

Various dyes are generally known as colorless or pale-colored coloring substances used in the present invention, and are not particularly limited as long as they are used in general thermosensitive recording paper.

Specific examples of these coloring substances (dyes) include, for example, (1) 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide,
(P-dimethylaminophenyl) -3- (2-phenyl-3-indolyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethyl-3-indolyl) phthalide, 3,3- Bis (9-ethyl-3-carbazolyl) -5-dimethylaminophthalide, 3,3-bis (2-phenyl-3-indolyl) -5-dimethylaminophthalide, 3- (4-diethylaminophenyl) -3
-(1-ethyl-2-methylindol-3-yl) phthalide, 3,3-bis [2- (4-dimethylaminophenyl) -2- (4-methoxyphenyl) vinyl] -4,
Triarylmethane compounds such as 5,6,7-tetrachlorophthalide; (2) 4,4-bis (dimethylamino) benzhydrin benzyl ether, N-2,4,5
Diphenylmethane compounds such as trichlorophenylleuco auramine; (3) rhodamine-β-anilinolactam, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluoran, 3-diethylamino -7-octylaminofluoran, 3-diethylamino-7- (2-chloroanilino) fluoran,
3-diethylamino-7- (2-fluoroanilino) fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7
-(2,4-dimethylanilino) fluoran, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-6-chloro-7- (β-ethoxyethylamino) fluoran, 3-diethylamino-6-chloro -7- (γ-chloropropylamino) fluoran, 3-
(N-ethyl-N-isoamylamino) -6-methyl-
7-anilinofluoran, 3- (N-ethyl-N-ethoxyethylamino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl -7-anilinofluoran, 3-
(N-ethyl-N-tolylamino) -6-methyl-7-
Anilinofluoran, 3- (N, N-dibutylamino)
-6-methyl-7-anilinofluoran, 3-dibutylamino-7- (2-chloroanilino) fluoran, 3-
Dipentylamino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3- (4-anilino) anilino-6-methyl-7
-Xanthene compounds such as chlorofluorane; (4)
Thiazine compounds such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue;
(5) Spiro compounds such as 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho- (3-methoxybenzo) spiropyran; (6) Other 3, 5 ',
6-tris (dimethylamino) -spiro [9H-fluorene-9,1 '(3'H) -isobenzofuran] -3'
-One, 1,1-bis [2- (4-dimethylaminophenyl) -2- (4-methoxyphenyl) ethenyl]-
4,5,6,7-tetrachloro (3H) isobenzofuran-3-one, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl)- 4-azaphthalide, 3- (4-diethylamino-2-methylphenyl) -3- (1-ethyl-
2-methylindol-3-yl) -4-azaphthalide and the like, and these dyes can be used as a mixture of several kinds.

Further, as described above, the homopolymer or copolymer of the hydroxystyrene derivative used in the present invention itself has an effect as a color developer, so that it is not necessary to use another color developer. However, when it is necessary to increase the color sensitivity, a known developer such as a phenol type, a carboxylic acid type or a metal salt type can be used in combination.
In addition, by using these other developers in combination, the amount of the homopolymer or copolymer of the hydroxystyrene derivative of the present invention can be reduced.

As these color developers, for example, p-
Octylphenol, p-tert-butylphenol, p-
Phenylphenol, p-hydroxyacetophenone,
α-naphthol, β-naphthol, p-tert-octylcatechol, 2,2′-dihydroxybiphenyl, bisphenol-A, 1,1-bis (p-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl )
Heptane, 2,2-bis- (3-methyl-4-hydroxyphenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, 2,2-bis (3,5-dichloro -4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, bis (3,4-dihydroxyphenyl) sulfone, 2,
4'-dihydroxydiphenyl sulfone, 1,1-bis (4-hydroxyphenyl) cyclohexane, bis (4
-Hydroxyphenyl) ether, bis [2- (4-hydroxyphenylthio) ethoxy] methane, 4- (4-
Isopropoxybenzenesulfonyl) phenol, 4-
Dimethyl hydroxyphthalate, butyl bis (4-hydroxyphenyl) acetate, benzyl p-hydroxybenzoate, 3,5-ditert-butylsalicylic acid, 2,4-dihydroxybenzanilide, 2,4-dihydroxy-2′-
Methoxybenzanilide, 2,4-dihydroxy-
2 ', 4'-dimethylbenzanilide, 2,4, -dihydroxy-2'-methoxy-5'-methylbenzanilide, bis (4- (2,4-dihydroxyphenylcarbonylamino) -3-methoxyphenyl) methane And phenols such as 4-methylbenzenesulfonic acid-2-hydroxyanilide, resorcinols, organic carboxylic acids such as benzoic acid, and metal salts such as zinc salicylate. Particularly, it is preferable to use a phenol-based developer. .

Other sensitizers can be used in combination to increase the color sensitivity of the heat-sensitive recording material of the present invention. Examples thereof include zinc acetate, zinc octylate, zinc laurate, zinc stearate, and zinc oleate. Metal salts of organic acids such as zinc behenate, zinc benzoate, zinc salt of salicylic acid dodecyl ester, calcium stearate, magnesium stearate, aluminum stearate; stearic acid amide, methylolamide stearate, stearoyl urea, acetanilide, acetotoluide, benzoic acid Acid stearylamide, ethylenebisstearic acid amide,
Amide compounds such as hexamethylenebisoctylamide; 1,2-bis (3,4-dimethylphenyl) ethane, m-terphenyl, 1,2-diphenoxyethane,
1,2-bis (3-methylphenoxy) ethane, p-benzylbiphenyl, p-benzyloxybiphenyl, diphenyl carbonate, bis (4-methylphenyl) carbonate, dibenzyl oxalate, bis (4-methylbenzyl) oxalate Phenyl 1-hydroxy-2-naphthalenecarboxylate, benzyl 1-hydroxy-2-naphthalenecarboxylate, phenyl 3-hydroxy-2-naphthalenecarboxylate, methylenedibenzoate,
1,4-bis (2-vinyloxyethoxy) benzene, 2
-Benzyloxynaphthalene, benzyl 4-benzyloxybenzoate, dimethylphthalate, dibenzyl terephthalate, dibenzoylmethane, p-toluenesulfonic acid anilide, 4-methylphenoxy-p-biphenyl and the like can be used.

When a particularly high storage stability is required, a known storage stabilizer can be used in combination, if necessary.

As storage stabilizers which can be used in the heat-sensitive recording material of the present invention, for example, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1 , 3-Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,
4'-butylidenebis (2-tert-butyl-5-methylphenol), 4,4'-thiobis (2-tert-butyl-5
-Methylphenol), hindered phenol compounds such as 2,2′-thiobis (6-tert-butyl-4-methylphenol), 2,2′-methylenebis (6-tert-butyl-4-methylphenol), -Benzyloxy-
4 '-(2-methylglycidyloxy) diphenyl sulfone, sodium-2,2'-methylenebis (4,6-
Di-tert-butylphenyl) phosphate, etc.
These storage stabilizers are usually used in an amount of 0.1 to 10 parts by weight based on 1 part by weight of the chromogenic substance (dye).

The polymer or copolymer of the hydroxystyrene derivative represented by the general formula (I) used in the present invention, the acylacetic acid anilide derivative represented by the general formula (II), and the above-mentioned general formula (III) The diphenylsulfone derivative represented by, a color-forming substance (dye), other developers and other sensitizers used as necessary, storage stabilizers, and the like are usually used for polishing such as a ball mill, an attriser, and a sand grinder. Pulverized by a crusher or a suitable emulsifying device,
Depending on the purpose, various additional materials are further added to form a coating liquid.

The coating liquid usually contains polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose,
Binders such as polyvinylpyrrolidone, polyacrylamide polymers, starches, styrene-maleic anhydride copolymers, vinyl acetate-maleic anhydride copolymers, styrene-butadiene copolymers or modified products thereof, kaolin,
Fillers such as silica, diatomaceous earth, talc, titanium dioxide, calcium carbonate, magnesium carbonate, aluminum hydroxide, and melamine are compounded. In addition, metal soaps,
Amides, waxes, light stabilizers, water resistance agents, dispersants, defoamers and the like can be used as needed.

By applying this coating solution to paper or various films, a desired heat-sensitive recording material can be obtained.
The obtained heat-sensitive recording material can be used for various applications to which the heat-sensitive recording material is applied, such as facsimile paper, printer paper, labels, price tags, and tickets.

[0044]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by the following examples.

Example 1 20 g of 3- (N, N-dibutylamino) -6-methyl-7-anilinofluoran and 100 g of a 10% aqueous solution of polyvinyl alcohol were sufficiently ground with a ball mill to obtain a dispersion A. did.

20 g of a 4-hydroxystyrene homopolymer (compound No. I-1) having a weight average molecular weight of 2,000 was added to 10
The mixture was sufficiently ground in a ball mill together with 100 g of a 100% aqueous solution of polyvinyl alcohol to obtain a dispersion B.

20 g of the sample compound (Table 2) was sufficiently ground with a ball mill together with 100 g of a 10% aqueous solution of polyvinyl alcohol to obtain a dispersion C.

The dispersions A, B and C were mixed in a weight ratio of 1: 2: 2, and 50 g of calcium carbonate was added to 200 g of the mixture, and the mixture was sufficiently dispersed to form a coating liquid. / m was applied in a thickness of 32μm to ² of base paper to obtain a heat-sensitive recording material was dried.

Using the obtained heat-sensitive recording material, the color density and background density (initial density) of a recorded image printed with a pulse width of 0.8 msec using a thermal printing apparatus (TH-PMD: manufactured by Okura Electric Co., Ltd.) ) Was measured using a Macbeth densitometer (model RD-933, manufactured by Macbeth).

The color-developed heat-sensitive recording material was stored at 60 ° C. for 24 hours under a dry condition, and the density change of the background and the color-developed portion was measured to evaluate the heat-resistant storage stability.

The color-developed heat-sensitive recording material was placed in a carbon arc fade meter, and after irradiating for 6 hours, the density of the printed portion was measured to evaluate the light-resistant storage stability. The density of the background was measured using a yellow filter.

Further, after dioctyl phthalate was stamped on the printed portion and the background portion of the color-developed thermosensitive recording material, the density was measured after storing under dry conditions at 40 ° C. for 24 hours, and the oil resistance was evaluated. .

The results are shown in Table 2 below.

[0054]

[Table 2]

[0055]

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[0056]

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[0057]

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Example 2 20 g of 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluoran and 100% aqueous solution of polyvinyl alcohol 100
g was sufficiently ground with a ball mill to obtain Dispersion A.

Acetoacetic acid-2-methylanilide (compound
No. II-2) Dispersion B was prepared by sufficiently grinding 20 g and 100 g of a 10% aqueous solution of polyvinyl alcohol with a ball mill.
I got

20 g of the sample compound (Table-3, Table-1)
This was thoroughly ground in a ball mill together with 100 g of a 0% polyvinyl alcohol aqueous solution to obtain a dispersion C.

The above dispersions A, B and C were mixed at a weight ratio of 1:
Mix at a ratio of 2: 2: and fully disperse to form a coating solution.
This coating solution was applied on a 50 g / m ² base paper at a thickness of 32 μm and dried to obtain a thermosensitive recording material.

Using the obtained heat-sensitive recording material, the same test as in Example 1 was performed. The results are shown in Table 3 below.

[0063]

[Table 3]

[0064]

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[0065]

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As is clear from the examples, when a sensitizer other than the acylacetic acid anilide derivative or the diphenylsulfone derivative was used, the density of the printed portion was significantly reduced. In addition, even when a sensitizer of an acylacetic acid anilide derivative or a diphenylsulfone derivative is used, when a conventional low-molecular phenol is used as a developer, there is no problem with initial color development sensitivity and background fog, Preservability is not satisfactory.

On the other hand, when the polymer or copolymer of the hydroxystyrene derivative of the present invention is used in combination with the acylacetic acid anilide derivative or diphenylsulfone derivative, the initial color density is good and the storage is excellent. It is excellent in stability, and it is clear that even after the storage test, decoloration of the color-developed portion and fog of the background are extremely small.

[0068]

EFFECTS OF THE INVENTION By containing a polymer or copolymer of a hydroxystyrene derivative and an acylacetic acid anilide derivative or a diphenylsulfone derivative, even after storage under severe conditions, discoloration of the color-developed portion and discoloration of the background portion are achieved. And a heat-sensitive recording material excellent in storage stability.

Claims (2)

[Claims] 1. A heat-sensitive recording layer containing a homopolymer or copolymer of a hydroxystyrene derivative represented by the following general formula (I), and represented by the following general formula (II) as a sensitizer: A heat-sensitive recording material characterized by containing at least one of an acylacetic acid anilide derivative or a diphenylsulfone derivative represented by the following general formula (III). Embedded image Embedded image Embedded image 2. The heat-sensitive recording material according to claim 1, wherein the weight average molecular weight of the homopolymer or copolymer of the hydroxystyrene derivative represented by the general formula (I) is from 500 to 100,000.