JPH05169829A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance developed color density and the stability of a recording image by using a compound represented by a specific chemical formula as a basic dye in a thermal recording layer and using 2,4'-dihydroxydiphenylsulfone as a developer. CONSTITUTION:In a thermal recording material utilizing the color forming reaction of the colorless or light-colored basic dye and org. or inorg. developer contained in the thermal recording layer provided on a support and bringing both color forming substances into contact with each other under heating to obtain a recording image, at least one kind of a compound represented by the chemical formula (wherein R1 and R2 are a 1-4C alkyl group) such as 3,6- dimethoxyfluorane or 3,6-dibutoxyfluorene and 2,4'-dihydroxydiphenylsulfone is used as the developer. The use ratio of the developer is set to about 50-2000 pts.wt., pref., about 150-1500 pts.wt. per 100 pts.wt. of the basic dye.

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 particularly to a heat-sensitive recording material having high color density and excellent stability of recorded images.

[0002]

2. Description of the Related Art A heat-sensitive recording material which utilizes a color reaction between a colorless or light-colored basic dye and an organic or inorganic color-forming agent to bring a recording image by contacting both color-forming substances with heat is often used. Are known. Such a thermal recording material is relatively inexpensive,
Since the recording device is compact and easy to maintain, it is used not only as a recording medium for facsimiles and various computers, but also in a wide range of fields. In recent years, a thermal recording material is often used also as an output for a word processor, and a thermal recording paper which develops various colors such as red and blue has been demanded.

[0003]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted various studies to provide a thermosensitive recording material that develops yellow. However, a basic dye that develops yellow generally has a low coloring density and is fading after printing. Turned out to be remarkable.

[0004]

Means for Solving the Problems As a result of intensive studies by the inventors of the present invention to provide a heat-sensitive recording material which has a high color density and which is excellent in the stability of a recorded image and which develops yellow, a specific dye was identified. It has been found that the problem can be solved by combining the above compounds.

That is, the present invention provides a heat-sensitive recording material comprising a support and a heat-sensitive recording layer containing a colorless or light-colored basic dye and a color-developing agent capable of forming a color when contacted with the dye. At least one of the compounds represented by the following general formula [Chemical formula 1] is used as the basic dye, and 2,4 'is used as the color developing agent.
A heat-sensitive recording material characterized by using dihydroxydiphenyl sulfone.

[0006]

[Chemical 1]

(In the formula, R ₁ and R ₂ represent a C _{1 to} C ₄ alkyl group.)

[0008]

Specific examples of the basic dye represented by the general formula [Chemical Formula 1] used in the present invention include compounds such as 3,6-dimethoxyfluorane and 3,6-dibutoxyfluorane. Of course, the present invention is not limited to these, and two or more compounds represented by the general formula [Formula 1] may be used in combination.

The present invention is characterized in that the basic dye represented by the general formula [Chemical Formula 1] and the coloring agent 2,4'-dihydroxydiphenyl sulfone are used in combination. The use ratio of the basic dye and the coloring agent is not particularly limited, but about 50 to 2000 parts by weight, preferably 150 to 1500 parts by weight of the coloring agent is used with respect to 100 parts by weight of the basic dye. ..

The present invention is characterized in that 2,4'-dihydroxydiphenyl sulfone is used as a color-developing agent, but in order to make the effects of the present invention more effective, other known basic dyes and color-developing agents are used. It is also possible to use agents together. For example, the following is exemplified. 4-tert-butylphenol,
α-naphthol, β-naphthol, 4-acetylphenol, 4-tert-octylphenol, 4,4′-sec
-Butylidene diphenol, 4-phenylphenol,
4,4'-dihydroxydiphenylmethane, 4,4'-
Isopropylidene diphenol, hydroquinone, 4,
4'-cyclohexylidene diphenol, 4,4'-
(1,3-dimethylbutylidene) bisphenol, 2,
2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis (6-tert-butyl-3-methylphenol), 4,4'-dihydroxydiphenyl Sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxy-4'-methoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-3 ', 4'-trimethylene diphenyl sulfone. , 4-hydroxy-3 ', 4'-
Tetramethylene diphenyl sulfone, 3,4-dihydroxy-4'-methyldiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 1,3-di [2- (4-hydroxyphenyl) -2-propyl] Benzene, hydroquinone monobenzyl ether, bis (4
-Hydroxyphenyl) acetic acid butyl ester, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 4-hydroxyphthalic acid Dimethyl, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, 4
-Propyl hydroxybenzoate, -sec-butyl 4-hydroxybenzoate, pentyl 4-hydroxybenzoate,
Phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-p. -Chlorobenzyl,
4-hydroxybenzoic acid-p-methoxybenzyl, novolac type phenolic resin, phenolic compound such as 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, 3,5-di-tert-
Butyl salicylic acid, 3-benzyl salicylic acid, 3- (α
-Methylbenzyl) salicylic acid, 3-chloro-5- (α
-Methylbenzyl) salicylic acid, 3-phenyl-5-
(Α, α-Dimethylbenzyl) salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4- (2-p-methoxyphenoxyethoxy) salicylic acid, 4- (3-p-
Tolylsulfonylpropyloxy) salicylic acid, 5-
Aromatic carboxylic acids such as [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, and these phenolic compounds, aromatic carboxylic acids and, for example, zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, etc. Organic acid substances such as salts with polyvalent metals. As a matter of course, two or more kinds of the above-mentioned color developing agents can be used in combination. In particular, the use of 4,4'-isopropylidenediphenol, 4,4'-cyclohexylidenediphenol, bis (3-allyl-4-hydroxyphenyl) sulfone and 4-hydroxy-4'-isopropylpropenediphenol is essential. It is preferable because the object of the invention can be efficiently realized.

The coating liquid containing these is generally prepared by using water as a dispersion medium and a dye, the above-mentioned specific polyvalent metal salt, by a stirrer / pulverizer such as a ball mill, attritor or sand mill.
It is prepared, for example, by dispersing the color former together or separately.

In such a coating liquid, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, sulfo group-modified polyvinyl alcohol, silicon modified polyvinyl alcohol are usually used as binders. ,
Acetoacetyl group-modified polyvinyl alcohol, graft copolymer of vinyl alcohol / vinyl acetate copolymer and acrylamide / acrylic acid / allyl acetoacetate copolymer, diisobutylene / maleic anhydride copolymer salt,
Styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt,
Styrene / butadiene copolymer emulsion, colloidal silica particle composite styrene / acrylic acid ester copolymer emulsion, urea resin, melamine resin, amide resin, etc. are 1 to 40% by weight, preferably about 5 to 25% by weight of the total solid content. Be compounded. Of course, it is also possible to use two or more kinds of these binders.

Further, various auxiliaries can be added to the coating solution, for example, 2,2'-methylenebis (4,6-
Mixture of sodium salt of di-tert-butylphenyl) phosphate and magnesium silicate, dioctylsulphosuccinic acid sodium salt, sodium dodecylbenzenesulfonic acid salt, lauryl alcohol sulfate / sodium salt, dispersant such as fatty acid metal salt, benzophenone system,
Examples include cyanoacrylate-based and hydroxybenzoate-based ultraviolet absorbers, other defoaming agents, fluorescent dyes, coloring dyes, and the like.

Further, stearic acid ester wax, polyethylene wax, carnauba wax, microcrystalline wax, so as to prevent the thermal recording material from sticking due to contact with a recording device or recording head.
It is also possible to add a dispersion or emulsion of carboxy-modified paraffin wax, zinc stearate, calcium stearate or the like.

In addition, kaolin, clay, talc, calcium carbonate,
Magnesium carbonate, calcined clay, titanium oxide, diatomaceous earth,
Inorganic pigments such as particulate anhydrous silica and activated clay, organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch granules can also be added.

Further, in the heat-sensitive recording material of the present invention, fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, and coconut fatty acid amide are used as long as the desired effects of the present invention are not impaired. , 4,4'-butylidene bis (6-tert
-Butyl-3-methylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4)
Hindered phenols such as -hydroxy-5-cyclohexylphenyl) butane, m-terphenyl, p-benzylbiphenyl, p- (4-tolyloxy) biphenyl, 1,5-bis (4-methoxyphenoxy) -3-oxa -Pentane, 1,2-bis (phenoxy) ethane,
1,2-bis (4-methylphenoxy) ethane, 1,2
-Bis (3-methylphenoxy) ethane, 1- (2-methylphenoxy) -2- (4-methoxyphenoxy) ethane, ethers such as 2-naphtholbenzyl ether, dibenzyl terephthalate, 1-hydroxy-2-
Naphthoic acid phenyl ester, oxalic acid dibenzyl ester, oxalic acid di (4-methylbenzyl) ester, oxalic acid di (4-chlorobenzyl) ester, etc., 2- (2'-hydroxy-5'-methylphenyl) )
An ultraviolet absorber such as benzotriazole and 2-hydroxy-4-benzyloxybenzophenone and various known heat-fusible substances can be used together as a sensitizer.

The amount of the heat-fusible substance contained in the recording layer is not necessarily limited, but is preferably 50 to 100 parts by weight of the basic dye.
The amount is 500 parts by weight, more preferably 100 to 300 parts by weight.

In the heat-sensitive recording material of the present invention, the method of forming the recording layer is not particularly limited, and the recording layer can be formed according to a conventionally known and commonly used technique. For example, the coating liquid for the heat-sensitive recording layer is coated on a support with an appropriate coating device such as an air knife coater, a blade coater, a bar coater, a die coater, a gravure coater, and a curtain coater, and dried to form a recording layer.

The coating amount of the coating liquid is not particularly limited, and generally 1.0 to 12 g / m 2 in dry weight.
It is adjusted in the range of about ² , preferably 1.5 to 10 g / m ² .

As the support, paper, plastic film, synthetic paper and the like are used, but paper is most preferably used in terms of cost and coating suitability. When synthetic paper is used, it is more preferable that the color density is high and the image quality is high, but there is also a drawback that the cost becomes high.

In the present invention, a protective layer may be formed on the heat-sensitive recording layer to improve the storage stability. Examples of the water-soluble or water-dispersible polymer used for forming the protective layer include various binders as described above.
Among them, acetoacetyl group-modified polyvinyl alcohol and carboxyl group-modified porvinyl alcohol are particularly preferably used because they form a strong film.

A pigment may be added to the protective layer, if necessary, in order to further improve printability and sticking. Specific examples thereof include calcium carbonate,
Inorganic pigments such as zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, kaolin, clay, calcined kaolin, and colloidal silica, styrene microballs, nylon powder, polyethylene powder, ureapolmarin. Examples include resin fillers and organic pigments such as raw starch particles. The amount used is generally 5 to 5 with respect to 100 parts by weight of the resin component.
It is desirable to adjust within the range of about 00 parts by weight.

Furthermore, in the coating liquid for forming the protective layer, zinc stearate, calcium stearate,
Lubricants such as polyethylene wax, carnauba wax, paraffin wax and ester wax; surfactants (dispersants, lubricants) such as sodium dioctylsulfosuccinate; antifoaming agents; water-soluble polyvalent salts such as potassium alum and calcium acetate. Various auxiliaries can also be added as appropriate.
Further, a curing agent such as glyoxal, boric acid, dialdehyde starch, or an epoxy compound may be added to further improve water resistance. The coating liquid for forming the protective layer is generally prepared using water as a dispersion medium.

The coating solution for protective layer thus prepared is coated on the thermosensitive recording layer by an appropriate coating layer. When the coating amount exceeds 20 g / m ² on a dry weight basis, the recording sensitivity of the thermosensitive recording medium is remarkably reduced. Generally, 0.1-20
g / m ^2, preferably it is desired to be adjusted in the range of about 0.5 to 10 g / m ^2.

The heat-sensitive recording material of the present invention may be a multi-color heat-sensitive recording material by combining heat-sensitive recording layers that develop different color tones. Further, if necessary, a protective layer may be provided on the back side of the thermosensitive recording medium to further improve the storability. Furthermore, it is also possible to provide an undercoat layer between the support and the heat-sensitive recording layer, or to perform super calendering after coating each layer, and also to give a pressure-sensitive adhesive treatment on the back surface of the recording medium to process it into a pressure-sensitive adhesive label, etc. Various known techniques in the field of manufacturing thermal recording media can be added as necessary.

[0026]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, "part" and "%" in an example show "weight part" and "weight%", respectively, unless there is particular notice.

Example 1 Formation of Intermediate Layer Calcined clay (trade name: Ansilex, manufactured by EMC) 1
A composition comprising 00 parts, 15 parts of a styrene-butadiene copolymer latex (solid content: 50%), 30 parts of a 10% polyvinyl alcohol aqueous solution, and 200 parts of water is mixed,
A coating liquid for the intermediate layer was prepared. 50 g / m ^{2 of the} obtained coating liquid
Was coated and dried to give a dry weight of 7 g / m ² to form an intermediate layer.

Liquid A Preparation A composition comprising 10 parts of 3,6-dimethoxyfluorane, 25 parts of 1,2-bis (3-methylphenoxy) ethane, 15 parts of a 5% aqueous solution of methylcellulose, and 35 parts of water was averaged by a sand mill. It was pulverized until the particle diameter became 0.8 μm.

Preparation of Solution B 2,4′-dihydroxydiphenyl sulfone 30 parts, 5
% 15% aqueous solution of methyl cellulose and 45 parts of water were pulverized with a sand mill until the average particle size became 1.1 μm.

Formation of Recording Layer 85 parts of solution A, 90 parts of solution B, 35 parts of light calcium carbonate,
80% 10% aqueous polyvinyl alcohol solution, 100 parts 20% aqueous oxidized starch solution, 30% zinc stearate dispersion 4
0 part and 170 parts of water were mixed and stirred to obtain a coating liquid. The resulting coating liquid was applied onto the above intermediate layer so that the dry weight was 5 g / m ^2, and dried to obtain a thermosensitive recording medium.

Example 2 In the preparation of solution B, 15 parts of 2,4'-dihydroxydiphenyl sulfone and 15 parts of 4,4'-isopropylidenediphenol were used instead of 30 parts of 2,4'-dihydroxydiphenyl sulfone. A thermosensitive recording medium was obtained in the same manner as in Example 1 except for the above.

Example 3 In the preparation of solution B, 15 parts of 2,4'-dihydroxydiphenyl sulfone and 15 parts of 4,4'-cyclohexylidene diphenol were used in place of 30 parts of 2,4'-dihydroxydiphenyl sulfone. A thermosensitive recording medium was obtained in the same manner as in Example 1 except for the above.

Example 4 In the preparation of solution B, 15 parts of 2,4'-dihydroxydiphenyl sulfone and 15 parts of 4-hydroxy-4'-isopropoxydiphenyl sulfone were used instead of 30 parts of 2,4'-dihydroxydiphenyl sulfone. A thermal recording material was obtained in the same manner as in Example 1 except that it was used.

Example 5 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 3,6-dibutoxyfluorane was used in place of 3,6-dimethoxyfluorane in the preparation of solution A.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 4,4'-isopropylidenediphenol was used in place of 2,4'-dihydroxydiphenylsulfone in the preparation of solution B. ..

Comparative Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 4,4'-cyclohexylidenediphenol was used in place of 2,4'-dihydroxydiphenylsulfone in the preparation of solution B. ..

Comparative Example 3 A thermosensitive recording medium was prepared in the same manner as in Example 1 except that 4-hydroxy-4'-isopropoxydiphenylsulfone was used in place of 2,4'-dihydroxydiphenylsulfone in the preparation of solution B. Obtained.

Comparative Example 4 In the preparation of solution A, 3,6-dibutoxyfluorane was used in place of 3,6-dimethoxyfluorane, and in preparation of solution B, 2,4'-dihydroxydiphenyl sulfone was used instead of A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 4,4'-isopropylidenediphenol was used.

The nine types of thermal recording materials obtained as described above were recorded by a thermal transfer printing evaluation tester (resistance value 557Ω, applied voltage 12V, pulse width 4 ms). The obtained recorded image density was measured by a Macbeth reflection densitometer (RD-914 type, manufactured by Macbeth, yellow filter), and the results are shown in [Table 1]. Further, the density of the recorded image kept at 50 ° C. for 24 hours was measured again with a Macbeth reflection densitometer, and the results are also shown in [Table 1].

[0040]

[Table 1]

[0041]

As is clear from the results of [Table 1], each of the thermosensitive recording materials obtained in the respective examples of the present invention has high color density and is excellent in stability of recorded image. It was a body.

Claims (1)

[Claims] 1. A thermosensitive recording medium comprising a support and a thermosensitive recording layer containing a colorless or light-colored basic dye and a coloring agent capable of coloring when contacted with the dye. A heat-sensitive recording material comprising at least one compound represented by the following general formula [Chemical formula 1] and further using 2,4'-dihydroxydiphenyl sulfone as a color developing agent. [Chemical 1] (In the formula, R ₁ and R ₂ represent a C _{1 to} C ₄ alkyl group.)