JP3348525B2 - Thermal recording medium - Google Patents

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 utilizing a color-forming reaction between a colorless or light-colored basic dye and a coloring agent, and relates to a heat-sensitive recording material having a high recording density and excellent head matching during printing. It relates to a recording medium.

[0002]

2. Description of the Related Art A thermosensitive recording medium which uses a color reaction between a colorless or light-colored basic dye and an organic or inorganic colorant to contact both coloring materials by heat to obtain a recorded image is often used. Are known. Such a thermosensitive recording medium is relatively inexpensive, and its recording equipment is compact and easy to maintain, so that it is used not only as a recording medium for facsimile machines and various computers but also in a wide range of fields.

As one of the fields of use, there is a recording medium for a handy terminal machine used for meter reading of meters and the like, and with the expansion of the system, miniaturization and high-speed of the device have been promoted. . Along with that, higher sensitivity has been required for thermal recording media,
On the other hand, problems such as poor matching with the recording head, that is, adhesion of head residues and sticking (printing noise) during recording have also occurred. Conventionally, there is a method of adding an oil-absorbing pigment to the recording layer to improve head residue adhesion and the like,
As the printing speed becomes higher and higher, a sufficient effect is not obtained.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording medium having high sensitivity, no sticking during printing, and little adhesion of head residue.

[0005]

Means for Solving the Problems The present inventors have developed a thermosensitive recording medium having a recording layer containing a colorless or pale-colored basic dye , a coloring agent and an adhesive on a support. The recording layer contains 0.01 to 2 parts by weight of aluminum hydroxide having an average particle size of 3 to 20 μm based on 1 part by weight of the basic dye.
Diisobutylene-maleic anhydride copolymer
Coal, ethylene-acrylic acid copolymer, styrene-
Lylic acid copolymer and styrene-maleic anhydride copolymer
Use at least one selected from ammonium salts of the body
-SO ₂ NHC (= X)-[wherein X
Represents an oxygen atom or a sulfur atom. ] Represented by
The inventors have found that the above-mentioned problems can be solved by using an aromatic compound having a group, and have completed the present invention.

[0006]

According to the present invention, aluminum hydroxide having an average particle diameter of 3 to 20 .mu.m is contained in a recording layer containing a colorless or pale-colored basic dye and a coloring agent in an amount of 0.01 to 2 parts by weight based on 1 part by weight of the basic dye.
It is characterized by containing by weight, and with such a configuration, a recording medium having extremely improved printing sound and excellent image quality can be obtained.
In particular, the average particle size of aluminum hydroxide is 5 to
A range of 15 μm is preferred. The average particle size of aluminum hydroxide was determined by an electron micrograph. Also,
The content of aluminum hydroxide is preferably adjusted to 0.01 to 2 parts by weight, more preferably 0.1 to 1 part by weight, based on the basic dye. The desired effect cannot be exhibited, and if the amount exceeds 2 parts by weight, the printing pixels are missing and the recording density is lowered.

In the present invention, it is not clear why aluminum hydroxide having a specific average particle diameter has a specific effect on improving the head matching property at the time of printing. When organic pigments such as starch and polystyrene are used, sticking noise tends to increase because of the heat from the thermal head, even if it is slightly melted. It is considered that the recording head is not only excellent in shape, but also does not cause contamination or damage of the recording head and plays a role of a good spacer.

As the adhesive in the recording layer, generally known adhesives are used, for example, polyvinyl alcohol, carboxy group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, cationic group-modified polyvinyl alcohol, sulfone group-modified polyvinyl alcohol, silica Various modified polyvinyl alcohols such as modified polyvinyl alcohol, starch and derivatives thereof, gum arabic, gelatin, casein, methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, polyacrylate, polyacrylamide, diisobutylene-anhydrous Maleic acid copolymer salt, ethylene-acrylic acid copolymer salt, styrene-acrylic acid copolymer salt, styrene-maleic anhydride copolymer Water-soluble resins such as methyl vinyl ether-maleic anhydride copolymer salt, isopropylene-maleic anhydride copolymer salt, styrene-butadiene latex, vinyl acetate-acrylate copolymer emulsion, polyurethane emulsion, polyvinyl chloride Water-dispersible resins such as emulsions, polyvinylidene chloride emulsions, methacrylate copolymer emulsions, and acrylate copolymer emulsions can be used. Among these, diisobutylene-maleic anhydride copolymer, ethylene-acrylic acid copolymer, styrene-acrylic acid copolymer, alkali salts of styrene-maleic anhydride copolymer, particularly ammonium salts are preferably used. . Alkali salts of these copolymers can be effectively submerged by the heat during recording, so that the role of the specific aluminum hydroxide as a spacer acts more effectively, and the head matching property is synergistically improved. .
The amount of the adhesive used was 10% of the total solids in the recording layer.
To 40% by weight, preferably 15 to 30% by weight.

In order to enhance the water resistance of the coating film, a reactive group such as a hydroxyl group, an acetoacetyl group,
It is preferable to use a water-soluble and / or water-dispersible resin adhesive containing a carboxyl group or an amide group in combination with a crosslinking agent. Examples of the crosslinking agent include glyoxal, glutaraldehyde, polyaldehyde 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 and ferric chloride, and magnesium chloride, zirconium ammonium carbonate, and the like, or boric acid and borax can be used.

In the present invention, the colorless or light-colored basic dye contained in the recording layer includes various known dyes, and specifically, for example, 3,3-bis (p-dimethylaminophenyl)- 6-dimethylaminophthalide, 3
-(4-diethylamino-2-methylphenyl) -3-
(4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-diethylamino-7-dibenzylamino-benzo [a] fluoran, 3- (N-ethyl-Np
-Tolyl) amino-7-N-methylanilinofluoran, 3-diethylamino-7-anilinofluoran, 3
-Diethylamino-7-dibenzylaminofluoran,
3,6-bis (diethylamino) fluoran-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluoran , 3- (N-ethyl-N-isoamyl) amino-
6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-
7-anilinofluoran, 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 3-di (n-
Pentyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-7- (o-chlorophenylamino) fluoran, 3-di (n-butyl) amino-7-
(O-fluorophenylamino) fluoran, 3- (N
-Ethyl-N-isobutyl) amino-7- (p-trifluoromethylanilino) fluoran, 3-diethylamino-7- (m-trifluoromethylanilino) fluoran, 3- (N-ethyl-N-isobutyl) Amino-7-
(O-trifluoromethylanilino) fluoran, 3-
(N-methyl-N-cyclohexyl) amino-7- (o
-Trifluoromethylanilino) fluoran, 3- (N
-Ethyl-p-toluidino) -6-methyl-7-anilinofluoran, 3- (N-ethyl-N-furfurylamino) -6-methyl-7-anilinofluoran, 3-diethylamino-6- Chloro-7-anilinofluoran, 3
-(N-methyl-NN-propylamino) -6-methyl-7-anilinofluoran, 3,3-bis [1- (4
-Methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3-p- (p-anilinoanilino) anilino-6-methyl-7 -Chlorofluoran, 2,2-
Bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro (phthalide-3,9'-
Xanthene) -2'-ylamino] phenyl} propane, 3,6, -bis (dimethylamino) fluorene-9
-Spiro-3 '-(6'-dimethylamino) phthalide,
3- (N-ethyl-N-isobutyl) amino-7- (p
-Trifluoromethylanilino) fluoran, 3- (N
-Ethyl-N-isobutyl) amino-7- (o-trifluoromethylanilino) fluoran, 3- (N-ethyl-N-isoamyl) amino-7- (p-trifluoromethylanilino) fluoran, 3- Di (n-butyl) amino-7- (m-trifluoromethylanilino) fluoran; These dyes may be used in combination of two or more. Generally, the content of the basic dye in the recording layer is preferably about 5 to 20% by weight of the dry weight of the recording layer.

Examples of the color former used in combination with the basic dye include the following known ones. 4-te
rt-butylphenol, α-naphthol, β-naphthol, 4-acetylphenol, 4-tert-octylphenol, 4,4′-sec-butylidenediphenol, 4
-Phenylphenol, 4,4'-dihydroxydiphenylmethane, 4,4'-isopropylidenediphenol (bisphenol A), hydroquinone, 4,4'-cyclohexylidenebisphenol, 4,4 '-(1,3
-Dimethylbutylidene) bisphenol, 2,2-bis (4-hydroxyphenyl) -4-methyl-pentane,
4,4'-dihydroxydiphenyl sulfide, 4,
4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4 '
-Methyldiphenylsulfone, 4-hydroxy-4'-
Methoxydiphenyl sulfone, 4-hydroxy-4'-
Isopropoxydiphenyl sulfone, 4-hydroxy-
3 ', 4'-trimethylenediphenylsulfone, 4-hydroxy-3', 4'-tetramethylenediphenylsulfone, 3,4-dihydroxy-4'-methyldiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) Sulfone, 1,3-di [2- (4-hydroxyphenyl) -2-propyl] benzene, hydroquinone monobenzyl ether, phenyl 4-hydroxybenzoate,
Benzyl-hydroxybenzoate, tolyl 4-hydroxybenzoate, p-hydroxy-N- (2-phenoxyethyl) benzenesulfonamide, 1,8-bis (4-hydroxyphenylthio) -3,6-dioxa-octane,
(4-hydroxyphenylthio) acetic acid-2- (4-hydroxyphenylthio) ethyl ester, a phenolic compound such as a novolak-type phenol resin, a phenol polymer, and -SO ₂ NHC (= X)- , An oxygen atom or a sulfur atom. And the like.

Among these, -SO ₂ NHC (= X)-
[In the formula, X represents an oxygen atom or a sulfur atom. An aromatic compound having a group represented by the following is preferably used, and the effect of the specific aluminum hydroxide of the present invention is remarkable,
The adhesion of head meal is significantly improved. More preferably,
-SO ₂ NHC (= X) NH- [wherein X represents an oxygen atom or a sulfur atom. Aromatic compounds having a group represented by the following are used, for example, JP-A-5-32061,
Japanese Unexamined Patent Application Publication No. 5-147357 is an example. Particularly preferably, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane and N- (p-toluenesulfonyl) -N'-phenylurea are used. A recording medium having excellent properties can be obtained. The amount of the color former to be used is preferably 50 to 500% by weight based on the colorless or light-colored basic dye.

In the heat-sensitive recording material of the present invention, a sensitizer can be added to the recording layer according to the purpose. Specific examples of the sensitizer include, for example, stearamide, methoxycarbonyl-N-stearic acid. Benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylene bistearic acid amide, behenic acid amide, methylene bisstearic acid amide, N-methylol stearic acid amide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, di-p-methylbenzyl oxalate, di-p-chlorobenzyl oxalate, 2-naphthylbenzyl ether, m- Terphenyl, p-benzylbiphenyl, tri Biphenyl ether, di (p- methoxyphenoxy) ether, 1,2-di (3-
Methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxy Ethane, 1- (4-methoxyphenoxy) -2- (2-methylphenoxy) ethane,
p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetotoluidide, p-
Examples include acetophenethidide, N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane, and the like. The use amount of these sensitizers is not particularly limited, but it is generally desirable to adjust the sensitizers within a range of about 400% by weight or less based on the color former.

Further, as long as the effects of the present invention are not impaired, a storability improving agent can be used in combination in order to further enhance the storability of the recorded image according to the purpose. Specific examples of such a preservability improver include, for example, 2,2'-methylenebis (4-
Ethyl-6-tert-butylphenol), 2,2'-methylenebis (4,6-di-tert-butylphenol),
2,2'-ethylidenebis (4,6-di-tert-butylphenol), 2,2'-methylenebis (4-methoxy-6-tert-butylphenol), 2,2'-methylenebis (6-tert-butylphenol) 4,4'-thiobis (2-methyl-6-tert-butylphenol),
4,4'-thiobis (5-methyl-6-tert-butylphenol), 4,4'-thiobis (2-ethyl-6-te
rt-butylphenol), 4,4'-butylidenebis (6-tert-butyl-m-cresol), 1,1,3-
Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4'-thiobis (3 -Methylphenol),
2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,
5-dichlorophenyl) propane, 2,2-bis (4-
Hindered phenol compounds such as hydroxy-3,5-dimethylphenyl) propane, epoxy compounds such as 1,4-diglycidyloxybenzene, 4,4'-diglycidyloxydiphenylsulfone, diglucidyl terephthalate, and bisphenol A type epoxy resin , 1- [α-methyl-α- (4′-hydroxyphenyl) ethyl] -4
-[Α ', α'-bis (4 "-hydroxyphenyl) ethyl] benzene, N, N'-di-2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-
Sodium di-tert-butylphenyl) phosphate and the like.

In preparing a coating solution for a recording layer containing these compounds, water is used as a dispersion medium, and a basic dye and a colorant, and a basic dye and a colorant are further mixed with a stirring / pulverizing machine such as a ball mill, an attritor, and a sand mill. A sensitizer or the like added as necessary is dispersed together or separately to prepare a coating solution.

Various auxiliaries can be added to the coating solution, for example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, alginates, fatty acid metal salts, and the like. Examples include benzophenone-based and triazole-based ultraviolet absorbers, other antifoaming agents, fluorescent dyes, coloring dyes, and the like. Further, if necessary, a lubricant such as zinc stearate and calcium stearate, kaolin, clay, talc, and the like within a range that does not impair the effects of the present invention.
It is also possible to add inorganic pigments such as calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica and activated clay.

In the present invention, the method for forming the recording layer is not particularly limited, and it can be formed according to a conventionally known and commonly used technique. For example, air knife coating, variver blade coating, pure blade coating, rod blade coating, It is formed by a method of applying and drying a coating liquid for a recording layer on a support by an appropriate coating method such as short dwell coating, curtain coating, and die coating. The support is appropriately selected from paper, plastic film, synthetic paper, nonwoven fabric, metal deposit, and the like. The coating amount of the recording layer coating liquid is adjusted in a range of ² to 12 g / m ² , preferably about 3 to 10 g / m ² by dry weight.

If necessary, a protective layer may be provided on the recording layer of the heat-sensitive recording medium and on the back side thereof to further enhance the storability. Further, in the heat-sensitive recording material manufacturing field, such as providing an undercoat layer on the support, applying a smoothing treatment such as super calendaring after coating each layer, or applying an adhesive treatment to the back surface of the recording material to process it into an adhesive label. Various known techniques can be added as needed.

[0019]

The present invention will be described in more detail with reference to the following Examples, but it should be understood that the present invention is by no means restricted thereto. Unless otherwise specified, “parts” and “%” in the examples indicate “parts by weight” and “% by weight”, respectively.

Reference Example 1 Preparation of Solution A 10 parts of 3-di (n-butyl) amino-6-methyl-7-anilinofluoran, 5% aqueous solution of methylcellulose 5
Parts and 40 parts of water were pulverized with a sand mill until the average particle size became 1.5 μm or less.

Solution B Preparation A composition comprising 20 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water is pulverized by a sand mill until the average particle diameter becomes 2 μm or less. did.

Preparation of Solution C A composition composed of 15 parts of 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane, 5 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water was sand-milled to have an average particle diameter of 2 μm. Crushed until below.

Formation of Recording Layer 55 parts of liquid A, 80 parts of liquid B, 230 parts of liquid C, 80 parts of a 10% aqueous solution of polyvinyl alcohol, 5 parts of aluminum hydroxide (average particle diameter 5 μ), 1 part of calcium carbonate, 15 parts of fixed silica, zinc stearate emulsion (30%
The solid concentration) 5 parts of mixture stirred to a coating solution is prepared, the resulting coating amount after drying on one surface of woodfree paper having a coating liquid 60 g / m ² is applied and dried such that the 6 g / m ² To form a recording layer, and subjected to a super calender treatment to obtain a thermosensitive recording medium.

[0024]

[0025]

[0026]

[0027] In forming the recording layer of Example 1 Reference Example 1, diisobutylene instead of 10% aqueous solution 80 parts polyvinyl alcohol - except for using a 15% aqueous solution of 53 parts of ammonium salt of maleic anhydride copolymer In the same manner as in Reference Example 1 , a thermosensitive recording medium was obtained.

[0028] In the formation of the recording layer of Comparative Example 1 Reference Example 1, except for using the starch granules (average particle size 5 [mu]) instead of aluminum hydroxide, ginseng
A thermosensitive recording medium was obtained in the same manner as in Example 1 .

[0029] In the formation of the recording layer of Comparative Example 2 Reference Example 1, except for using aluminum hydroxide (average particle size 5 [mu]) instead of aluminum hydroxide (average particle size 1 [mu]), in the same manner as in Reference Example 1 Thermal A recording was obtained.

[0030] In the formation of the recording layer of Comparative Example 3 Reference Example 1, except that aluminum hydroxide (average particle size 5 [mu]) 5 parts instead of aluminum hydroxide was used (average particle size 32μ) 25 parts Reference Example 1 In the same manner as in the above, a thermosensitive recording medium was obtained.

The following quality evaluation tests were performed on the thus-obtained thermosensitive recording media, and the results are shown in Table 1. Coloring Density Using a thermal recording evaluation device (TH-PMD type, manufactured by Okura Electric Co., Ltd.), the coloring density of a recorded image obtained by printing at an applied energy of 0.4 mJ / dot was measured using a Macbeth densitometer (RD-914R).
(Manufactured by Macbeth Corporation) in visual mode.

Adhesion of head residue Using a thermal recording evaluation device (TH-PMD type, manufactured by Okura Electric Co., Ltd.), printing was performed for 30 m at an applied energy of 0.4 mJ / dot, and the degree of head residue generated on the thermal head was visually observed. Judged. <Evaluation criteria> ：: There is almost no head residue, and there is no problem in practical use. ：: Slight adhesion of head residue, but no problem in practical use. Δ: Head residue adheres and there is a problem in long-term recording. X: Head residue is large and has a practical problem.

Sticking Using a heat-sensitive recording evaluation machine (TH-PMD type, manufactured by Okura Electric Co., Ltd.), applied energy 0.3 mJ / dot, pulse width 3 m
Printing was performed at s / L, and the printing sound was determined. <Evaluation Criteria> A: There is no printing noise at all, and there is no problem in practical use. ：: Printing noise is slightly generated, but there is no problem in practical use. X: The printing sound is loud and there is a problem in practical use.

[0034]

[Table 1]

[0035]

As is clear from the results shown in Table 1, all of the heat-sensitive recording materials of the present invention were excellent in heat sensitivity, had no sticking during printing, and had little head residue adhesion. .

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-64325 (JP, A) JP-A-5-301461 (JP, A) JP-A-5-330239 (JP, A) JP-A-6-64239 155909 (JP, A) JP-A-6-166269 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/28-5/34

Claims (1)

(57) [Claims] 1. A thermosensitive recording medium having a recording layer containing a colorless or light-colored basic dye , a coloring agent and an adhesive on a support, wherein the recording layer has an average particle size of 3 to 20 μm.
Of aluminum hydroxide in an amount of 0.01 to 2 parts by weight based on 1 part by weight of the basic dye , and the adhesive is diisobutylene-
Maleic anhydride copolymer, ethylene-acrylic acid copolymer
Body, styrene-acrylic acid copolymer and styrene-free
Water maleic acid copolymer, selected from ammonium salts
Is at least one, color acceptor is -SO ₂ NHC (=
X)-[wherein, X represents an oxygen atom or a sulfur atom. ]
A thermosensitive recording medium , which is an aromatic compound having a functional group represented by the formula: