JP2002036720A - Heat sensitive recording paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording paper excellent in tear strength, and also excellent in recording sensitivity and recording image quality. SOLUTION: The heat sensitive recording paper has, on at least one face of a paper supporting body, a heat sensitive coloring layer which contains leuco dye and developer. As a means to solve the above assignment, the recording paper is made to contain some non-woody pulp whose Runkel ratio (a value obtained by dividing two times of a pulp wall thickness by a lumen's width) is 3 to 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium utilizing a color development reaction between a leuco dye and a color developer.

[0002]

2. Description of the Related Art Thermal recording media utilizing a color development reaction between a leuco dye and a developer by heat are well known. Such a thermosensitive recording medium is relatively inexpensive, and is widely used as a recording medium of a facsimile, a printer, and the like because the recording device for the thermosensitive recording is compact, the maintenance is easy, and there is no odor or noise during recording. ing.

In recent years, the use of heat-sensitive recording paper has been remarkable as an outdoor meter reading paper especially for electricity, gas, water and the like. However, conventional thermosensitive recording paper is easily torn and has a problem in paper strength. Further, the meter reading for such use is highly public, and the use of recycled paper is obligated by the so-called Green Purchasing Law.

Japanese Patent Application Laid-Open No. 2-88286 discloses a thermosensitive recording medium in which a paper containing kenaf pulp having a Runkel ratio of about 2 as a non-wood pulp is used as a support for the thermosensitive recording medium. There is a demand for improved recording image quality and recording sensitivity.

[0005] Further, a heat-sensitive recording medium using paper containing deinked recycled pulp as a support for the heat-sensitive recording medium is disclosed in Patent 27
JP-A-85057, JP-A-3-140287, JP-A-4-65288, and the like, the recycled pulp has a more rigid fiber (Referred to the Textile Society of Japan; 1999, G-8.
Partially described in “Pulp Quality Changes Due to Recycling”),
The paper strength such as tensile strength and tear strength is reduced, and the recycled pulp contains more keratinized fibers, which deteriorates the contact with the thermal head and lowers the dot reproducibility. As a result, the heat from the thermal head is dissipated and the recording sensitivity is reduced.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording paper which is excellent in tear strength, recording sensitivity and recording quality.

[0007]

Means for Solving the Problems In a heat-sensitive recording paper having a heat-sensitive coloring layer containing a leuco dye and a color developer on at least one surface of a paper support, as one means for solving the above-mentioned problems, Non-wood pulp having a Runkel ratio (a value obtained by dividing twice the wall thickness of the pulp by a lumen width) of 3 to 5 is contained in the paper support.

As another means, the non-wood pulp is used in an amount of 5 to 50% by weight based on the total solid content of the paper support, and the non-wood pulp uses a chemical pulp obtained from bamboo as a raw material. It is. Further, the recycled pulp is contained in the paper support in an amount of 30 to 90% by weight based on the total solid content of the paper support, and such means can provide an excellent environmental effect.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a specific non-wood pulp having a Runkel ratio (a value obtained by dividing twice the wall thickness of pulp by a lumen width) of 3 to 5 as a support for thermosensitive recording paper. When the Runkel ratio of a specific non-wood pulp is less than 3, the effect of increasing the recording sensitivity is reduced, and when the Runkel ratio exceeds 5, the recorded image quality may be deteriorated. .

[0010] The specific non-wood pulp is obtained, for example, by exposing a chemical pulp produced by a kraft method using bamboo as a raw material or a sulfite method. The average fiber length of bamboo pulp is about 1.5 to 4.4 mm, the average fiber width is about 7 to 27 μm, and the Runkel ratio is about 4. In addition, bamboo is inexpensive and has attracted attention because it is a non-timber plant that is effective in protecting the environment, such as its growth rate and photosynthetic ability.

Although the content of the specific non-wood pulp is not particularly limited, it is 5 to 50% based on the total solid content of the paper support.
% By weight. Particularly, even in a paper support containing about 30 to 90% by weight of a recycled pulp subjected to deinking treatment or the like, the recording sensitivity is high if a specific non-wood pulp is contained in the paper support. The recording image quality and the tear strength are improved.

The recycled pulp (DIP) used for producing the base paper of the present invention is obtained by deinking the ink of printed matter such as newspapers, magazines, etc., or re-disintegrating unprinted paper. .

The paper support may contain, if necessary, general-purpose fillers such as clay, talc, calcium carbonate, various paper-strengthening agents, sizing agents, bands, coloring dyes, fluorescent dyes and other various chemicals used in general paper production. Kinds can be used. Further, the paper support is obtained by acidic papermaking or neutral papermaking, and surface processing such as size press and spraying is also possible depending on the application.

The leuco dye and the developer contained in the thermosensitive coloring layer are not particularly limited, but for example, various known dyes can be used. Specific examples of such leuco dyes include the following. (1) Triarylmethane compound 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3- (p-dimethylaminophenyl) -3-
(1,2-dimethylindol-3-yl) phthalide,
3- (p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis (p-ethylcarbazol-3-yl) -3-dimethylaminophthalide, 3,3 -Bis (2-phenylindol-3-yl) -5-dimethylaminophthalide and the like;

(2) Diphenylmethane compounds 4,4-bis-dimethylaminobenzhydrin benzyl ether, N-halophenylleuco auramine, N-
2,4,5-trichlorophenylleuco auramine and the like;

(3) Xanthene compounds rhodamine B-anilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-butylaminofluoran, 3-diethylamino-7- (2-chloroanilino) Fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-
Piperidino-6-methyl-7-anilinofluoran, 3
-Ethyl-tolylamino-6-methyl-7-anilinofluoran, 3-cyclohexyl-methylamino-6-methyl-7-anilinofluoran, 3-diethylamino-
6-chloro-7- (β-ethoxyethyl) aminofluoran, 3-diethylamino-6-chloro-7- (γ-chloropropyl) aminofluoran, 3-diethylamino-6-chloro-7-anilinofluoran , 3-N-cyclohexyl-N-methylamino-6-methyl-7-anilinofluoran, 3-diethylamino-7-phenylfluoran, 3- (N-isoamyl-N-ethylamino)
-6-methyl-7-anilinofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran and the like;

(4) Thiazine compounds benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue and the like;

(5) Spiro compounds 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methylnaphtho- (3-methoxy-benzo) -spiropyran and the like.

Specific examples of the color developing agent include, for example, color developing agents combined with the leuco compound in the thermosensitive coloring layer, for example, 4,4'-isopropylidene diphenol, 1,1-bis (4-hydroxyphenyl) ) Cyclohexane, benzyl 4-hydroxybenzoate, 4,4 ′
-Dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis (3-allyl-
4-hydroxyphenyl) sulfone, 4-hydroxyphenyl-4′-benzyloxydiphenyl sulfone,
1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 2,2′-thiobis (3-
phenolic compounds such as tert-octylphenol),
Thiourea compounds such as N, N'-di-m-chlorophenylthiourea, N- (p-tolylsulfonyl) carbamoyl acid-p-cumylphenyl ester, N- (p-tolylsulfonyl) carbamoyl acid-p-benzyloxy Phenyl ester, N- (p-tolylsulfonyl) -N'-
(P- tolyl) having a -SO ₂ NH- bond in the molecule, such as urea, - [2-(p- methoxyphenoxy) ethyloxy] zinc salicylate, 4- [3- (p- tolylsulfonyl) propyloxy] Zinc salicylate, 5- [p
-(2-p-methoxyphenoxyethoxy) cumyl] and zinc salts of aromatic carboxylic acids such as zinc salicylate.

The ratio of the leuco dye to the colorant is appropriately selected according to the type of the leuco dye or the colorant used, and is not particularly limited. 1 to 10 parts by weight, preferably 2 to
About 6 parts by weight of a color former is used. Further, two or more leuco dyes and developers may be used in combination.

Among them, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, -Hydroxyphenyl-4'-benzyloxydiphenylsulfone and benzyl p-hydroxybenzoate are preferred because they have little effect on the paper support containing the recycled pulp, that is, decrease in background fog resistance and storage resistance of the recording portion.

The thermosensitive coloring layer may contain a storability improver for improving the storage stability of the recording portion, and a sensitizer for improving the recording sensitivity. Specific examples of such a preservability improver include, for example, 2,2′-ethylidenebis (4,6-di-tert-butylphenol), 4,4′-
Thiobis (2-methyl-6-tert-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-
Hindered phenol compounds such as tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 4-benzyloxy-4′- (2-
Examples include epoxy compounds such as methyl glycidyloxy) diphenyl sulfone, diglycidyl terephthalate, phenol novolak type epoxy resin, and bisphenol A type epoxy resin.

Specific examples of the sensitizer include, for example, stearic acid amide, methylenebisstearic acid amide, 2-naphthylbenzyl ether, m-terphenyl, p-benzylbiphenyl, di (p-methoxyphenoxyethyl)
Ether, 1,2-di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,
2-di (4-methoxyphenoxy) ethane, 1,2-diphenoxyethane, 1,4-di (phenylthio) butane, p-acetotoluizide, p-acetophenethidide,
Examples include N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, di-p-chlorobenzyl oxalate, di-p-methylbenzyl oxalate, dibenzyl oxalate, and the like.

The amounts of these preservability improvers and sensitizers are not particularly limited, but are generally desirably about 1 to 4 parts by weight with respect to 1 part by weight of the color former.

The heat-sensitive color-forming layer is formed by using water as a dispersion medium, a ball mill, an attritor, a leuco dye, a color former, and if necessary, a sensitizer and a storage stability improver together or separately.
Average particle size of 3μ by agitator / pulverizer such as sand mill
m, preferably 2 μm or less, and then formed by applying and drying a coating solution for a thermosensitive coloring layer prepared by adding at least an aqueous adhesive onto a paper support.

Specific examples of the aqueous adhesive added to the coating solution for the thermosensitive coloring layer include starches, methylcellulose, carboxymethylcellulose, casein, gum arabic, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol. , Silicon polyvinyl alcohol, diisobutylene
Water-soluble adhesives such as maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, and urethane resin latex and acrylic resin Latex,
Water-dispersible adhesives such as acrylonitrile / butadiene resin latex and styrene / butadiene resin latex are exemplified. The amount of the adhesive used is about 5 to 40% by weight based on the total solid content of the thermosensitive coloring layer.

Further, various auxiliaries can be added to the heat-sensitive coloring layer coating solution as required. For example, kaolin, calcium carbonate, calcined kaolin, amorphous silica, aluminum hydroxide, urea-formalin resin filler Pigments, etc.
Dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, etc .; waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax; defoaming agents , A crosslinking agent, a coloring dye, and the like.

A protective layer containing an adhesive having a film-forming property can be provided on the thermosensitive coloring layer. The protective layer is a protective layer prepared by mixing and stirring, for example, an adhesive which can be contained in the heat-sensitive coloring layer coating solution and, if necessary, an auxiliary agent which can be added to the heat-sensitive coloring layer coating solution, using water as a medium. It is formed by applying and drying the layer coating solution on the thermosensitive coloring layer.

Between the paper support and the thermosensitive coloring layer, calcium carbonate, kaolin,
Inorganic pigments such as talc, calcined kaolin, amorphous silica, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, or urea formalin resin filler having an average particle size of about 0.5 to 30 μm, hollow acrylic resin An undercoat layer mainly composed of a filler, a hollow styrene resin filler, a hollow vinylidene chloride resin filler, and other pigments and an adhesive may be provided in an amount of 5 to 15 g / m ² .

The adhesive used for the undercoat layer includes those which can be used in the above-mentioned thermosensitive coloring layer. The amount of the adhesive used is 5 to 3 with respect to the undercoat layer.
About 0% by weight is preferable.

Examples of the coating method for the thermosensitive coloring layer, the undercoat layer, and the protective layer coating solution include an air knife method, a Meyer bar method, a pure blade, a method rod blade method, a reverse roll method, a gravure method, a slit die method, and the like. Curtain type and the like are mentioned.

The thermosensitive recording paper of the present invention may further comprise a magnetic coloring layer provided on the other side of the paper support or between the paper support and the thermosensitive coloring layer, a glossy layer provided on the protective layer, a paper support. Various known paper processing techniques such as providing an adhesive layer on the other surface of the body can be added.

[0033]

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

Example 1 (1) Preparation of Paper Support 500 parts of a 2% slurry (250 ml according to Canadian standard freeness) of deinked newspaper recycled paper pulp, bleached kraft made from bamboo and having a Runkel ratio of 4 A pulp slurry consisting of 100 parts of a 2% slurry of pulp (250 ml of Canadian standard freeness) and 400 parts of a 2% slurry of bleached kraft pulp (LBKP) (250 ml of Canadian standard freeness) has an average particle size of 1 μm. 15% light calcium carbonate based on total solids of paper support
And an alkyl ketene dimer sizing agent (trade name: SPK287, manufactured by Arakawa Chemical Industry Co., Ltd.) was added so as to be 1% based on the total solid content of the paper support.
50 g / m ^{2 of} rice tsubo and a tension of 0.
8. A paper support having an air permeability of 150 seconds was obtained.

(2) Preparation of coating liquid for undercoat layer Calcined kaolin (trade name: Ansilex, oil absorption 80 m)
1/100 g, manufactured by Engelhard Co., Ltd.) 70 parts, light calcium carbonate 10 parts, hollow styrene resin filler (average particle diameter 1 μm, film thickness 0.3 μm) 40% dispersion 50
Parts, 5 parts of a 20% aqueous solution of sodium polyacrylate (dispersant), 15 parts of a styrene-butadiene resin-based latex (solid content concentration: 50%), 60 parts of polyvinyl alcohol (trade name: Poval 105, manufactured by Kuraray Co., Ltd.) and water 150
Was mixed and stirred to obtain a coating liquid for an undercoat layer.

Preparation of Solution A 10 parts of 3-di-butylamino-6-methyl-7-anilinofluoran, 10% of sulfone-modified polyvinyl alcohol (trade name: Goselan L-3360, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) A composition comprising 10 parts of an aqueous solution and 20 parts of water was pulverized by a sand mill until the average particle diameter became 0.8 μm to obtain a liquid A.

Preparation of Solution B 10 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone, sulfone-modified polyvinyl alcohol (trade name: Goselan L-3360, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
A composition comprising 10 parts of a 10% aqueous solution of water and 20 parts of water was pulverized with a sand mill until the average particle diameter became 1.5 μm to obtain a liquid B.

Preparation of Solution C A composition comprising 10 parts of m-terphenyl, 10 parts of a 10% aqueous solution of sulfone-modified polyvinyl alcohol (trade name: Goceran L-3360, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 20 parts of water was sand-milled. Was pulverized until the average particle diameter became 1.0 μm to obtain a liquid C.

(3) Preparation of Coating Solution for Thermosensitive Coloring Layer Forty parts of solution A, 80 parts of solution B, 40 parts of solution C, 60 parts of polyvinyl alcohol (trade name: Poval 205, manufactured by Kuraray Co., Ltd.) and 50 parts of water The mixture was stirred to obtain a coating solution for a thermosensitive coloring layer.

(4) Preparation of Coating Solution for Protective Layer Silicon-modified polyvinyl alcohol (trade name: Poval®)
800 parts of a 10% aqueous solution of -1130, manufactured by Kuraray Co., Ltd., 20 parts of amorphous silica (trade name: Mizukasil P-527, manufactured by Mizusawa Chemical Industry Co., Ltd.) and 200 parts of water are mixed and stirred to obtain a coating liquid for a protective layer. Was.

(5) Preparation of heat-sensitive recording paper On one surface of the above-mentioned paper support, the coating amount of the undercoat layer coating liquid, the heat-sensitive recording layer coating liquid and the protective layer coating liquid after drying was 8 g / m 2.
^{2, 4g / m 2, 3g} / m 2 and so as to sequentially applied and dried to undercoat layer was provided with a thermal color-forming layer and the protective layer, UV-curable resin ink (trade name: Light Set APOKO-
02 varnish, manufactured by Osaka Printing Ink Mfg. Co., Ltd.) using an offset printing machine to apply (print) 1 g / m ² on the above protective layer, and apply a UV-cured thermosensitive recording paper having a glossy layer cured. Obtained. After the undercoat layer, the thermosensitive coloring layer and the protective layer were provided, each was subjected to a super calender treatment.

Example 2 In preparing the paper support of Example 1, 500 parts of a 2% slurry of deinked recycled newspaper pulp and a 2% slurry of bleached kraft pulp with a Runkel ratio of 4 using bamboo as a raw material 100 parts and hardwood bleached kraft pulp 2% slurry 4
Instead of 00 parts 400 parts, 500 parts and 1 part respectively
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 00 parts were used.

Example 3 In the same manner as in Example 1 except that the paper support obtained in the preparation of the following paper support was used in place of the paper support used in the preparation of the thermosensitive recording paper in Example 1. Thus, a thermosensitive recording paper was obtained.

(1) Preparation of Paper Support 850 parts of a 2% slurry of deinked recycled newspaper pulp (250 ml in Canadian standard freeness) and 2 of bleached kraft pulp with a Runkel ratio of 4 from bamboo Light calcium carbonate having an average particle size of 1 μm is supported on a paper in a pulp slurry comprising 75 parts of a 75% slurry (250 ml according to Canadian standard freeness) and 75 parts of a 2% slurry of bleached hardwood kraft pulp (250 ml according to Canadian standard freeness). 5% based on the total solid content of the body, and then an alkyl ketene dimer sizing agent (trade name:
SPK287, manufactured by Arakawa Chemical Industry Co., Ltd.) so as to be 1% with respect to the total solid content of the paper support, and 50 g / m ^{2 of} rice tsubo, tension of 0.8, air permeability using a twin-wire paper machine. 150
A second paper support was obtained.

Comparative Example 1 In preparing the paper support of Comparative Example 1, a 2% slurry of bleached kraft pulp having a Runkel ratio of 4 using bamboo as a raw material was used.
In place of the section, 2 of deinked recycled newspaper pulp
% Slurry (250 ml with Canadian standard freeness) 1
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 00 parts were used.

Comparative Example 2 In preparing the paper support of Comparative Example 1, a 2% slurry of bleached kraft pulp having a Runkel ratio of 4 using bamboo as a raw material was used.
The heat-sensitive recording paper was obtained in the same manner as in Example 1 except that 100 parts of a 2% slurry of bleached kraft pulp having a Runkel ratio of 2 using kenaf as a raw material was used instead of parts.

The following evaluation test was performed on the thus obtained heat-sensitive recording paper, and the obtained results are shown in Table 1.

Recording image quality and recording sensitivity Thermal recording paper was recorded with a Canon Handy Terminal Printer HT9000, and the recording density of the recorded image was measured with a Macbeth densitometer (RD-914, Macbeth).
Further, the reproducibility (recording quality) of one dot was visually evaluated as follows. ：: Dots (circles) are reproduced uniformly. Δ: Dots (circles) are reproduced almost uniformly. ×: Reproducibility of dots (circles) is slightly inferior.

Tear Strength The tear strength of the thermosensitive recording paper was measured based on JIS P 8116-1994.

[0050]

[Table 1]

[0051]

The thermal recording paper of the present invention has excellent recording sensitivity and recording image quality (dot reproducibility) even when a large amount of recycled pulp is used, and has the effect of increasing tear strength.

Claims (4)

[Claims] 1. A thermosensitive recording paper having a thermosensitive coloring layer containing a leuco dye and a color developing agent on at least one surface of a paper support, wherein the runner ratio (2% of the pulp wall thickness) is contained in the paper support. A heat-sensitive recording paper comprising a non-wood pulp having a value obtained by dividing a fold by a lumen width) of 3 to 5. 2. The heat-sensitive recording paper according to claim 1, wherein the non-wood pulp is 5 to 50% by weight based on the total solid content of the paper support. 3. The heat-sensitive recording paper according to claim 1, wherein the non-wood pulp is a chemical pulp using bamboo as a raw material. 4. The paper support according to claim 1, wherein the recycled pulp is contained in an amount of 30 to 90% by weight based on the total solid content of the paper support.
4. The heat-sensitive recording paper according to any one of 3.