JPH09314999A - Thermal recording paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain thermal recording paper which is little in curling in an environmental change of surroundings and after recording, and excellent in accomodating properties and travelling properties by a method wherein the thermal recording paper is divided into two layers to make a difference in extensibility in water-exposure between a front and a rear of the thermal recording paper measured by a J.TAPPI No.27-78 specifying method A a specific value or under. SOLUTION: Thermal recording paper of at most a 0.5% of difference in extensibility in water-exposure between a front and a rear is used. For a method for measuring extensibility in water on the front and the rear of the thermal recording paper, the thermal recording paper is divide into front and rear two layers by a dry method, and respective front an rear divided materials are evaluated for extensibility in water by a method A specified in J.TAPPI No.27-78. Though there is also a method of dividing manually the paper layers as the dividing layer method, it is preferably carried out that an inner strength tester JTC-9000 is used, a rotary speed of a roll is set up at 50rpm, and the sample is separated in layers. Though a thermally coloring layer side is separated generally by about 10wt.% more than a base paper layer side, it is a weight of the thermally coloring layer, and the base paper is divided almost by a ratio of 50:50.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thermal recording paper. In particular, the present invention relates to a heat-sensitive recording paper which has a small curl even when the humidity of the environment changes or is heated during printing, and which is excellent in running property and storage property on hardware.

[0002]

2. Description of the Related Art Conventionally, a leuco dye which is an electron donor and an organic developer such as a phenolic acidic substance which is an electron acceptor have been used to generate a color from a thermosensitive head, thereby applying heat to both of them. A heat-sensitive recording material for obtaining a color image by dissolution, contact and color reaction is well known. Since such a thermal recording paper is relatively inexpensive and the recording device is compact and its maintenance is relatively easy, it is used not only as a recording medium for a facsimile or a printer but also in a wide range of fields. In recent years, the diversification of applications and the higher performance of devices have advanced, and along with this, the quality requirements for heat-sensitive recording paper have become more sophisticated. In particular, due to the high performance of facsimiles and printers, it is desired that the thermal recording roll paper has good running property on hardware and good storage after recording, but the thermal recording paper is used as a thermosensitive coloring layer and a base paper. Since the size of the dimensional change when the humidity of the paper used changes with the temperature of the paper used for printing, a large curl occurs, which deteriorates the running property and the storage property.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermosensitive recording paper which has a small change in the surrounding environment and a small curl after recording and is excellent in storability and running property.

[0004]

DISCLOSURE OF THE INVENTION As a result of intensive studies to improve the above-mentioned drawbacks, the inventors of the present invention have found that the difference in the water-immersion elongation of a heat-sensitive recording paper between front and back sides (the sensitive recording paper is divided into two layers. J. TAP
PI No. 27-78 measurement method A) is 0.
It has been found that the problem caused by the environmental change and curl after recording can be solved by using the one having the content of 5% or less. Further, as a means for realizing the difference between the front and back sides, a base paper mainly composed of pulp having a water immersion elongation value of 4.5% or less is used, and a water immersion elongation value of the thermal recording paper is 5% or less. In addition, it was found that a back coat layer containing a water-soluble binder or a water-proofing agent that improves the dimensional stability of the base paper is provided on the opposite side of the thermosensitive coloring layer of the base paper, and the present invention is completed. Came to.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The thermal recording paper according to the present invention has a difference in front and back of the water immersion elongation (the thermal recording paper is divided into two layers, J.TA.
PPI No. By using a resin having a value of 0.5% or less (measured by the A method described in 27-78), no running failure or poor accommodation due to curling after environmental changes or after recording occurred. Further, as means for realizing the difference between the front and back sides, the water immersion elongation value of the base paper mainly composed of pulp is set to 4.5% or less, and the water immersion elongation value of the thermal recording paper is set to 5%.
% Or less, and it was found that a back coat layer containing a water-soluble binder or a water-proofing agent that improves the dimensional stability of the base paper is provided on the opposite side of the thermosensitive coloring layer of the base paper, and the present invention It came to completion.

The method for measuring the water immersion elongation of the front and back sides of a thermosensitive recording paper is as follows. TAPPI No. 27-7
8. The water immersion elongation was evaluated by the method A described in 8. As a division method, for example, MD (Machine directi)
After making a cut with a cutter in the middle of the paper layer in the (on) direction, the CD (cross machine) starts from the cut.
There is also a method of manually separating the paper layers in the direction (direction), but it is desirable to use the internal strength tester JTC-900.
0 (manufactured by SMT Corp.) and the rotation speed of the roll was 50 rpm. And the sample is delaminated. Usually, the ripening color forming layer side is peeled off by about 10% in weight percentage from the base paper (base paper) layer side. This is the weight of the heat sensitive color forming layer, and the division ratio of the base paper is about 50:50. Become. The water immersion elongation of each of the divided samples was measured according to J. TAPPI
No. It is measured by the method A described in 27-78, but it is desirable that the sample is left in water for 1 hour or more. It is well known that the water immersion elongation evaluation value has a correspondence relationship with the size change of paper due to humidity change and the like. The present inventors have found that the curl in the thermal recording paper is caused by a difference in dimensional change between the thermal recording layer side and the base paper layer side at the time of environmental change or recording, and the larger the difference, the larger the curl. It has been found that curl is improved by reducing the difference in dimensional stability of the layers.

Further, it has been found from various studies that the difference in dimensional stability between the front and back sides of this thermal recording paper occurs because the coating layer such as the color-developing layer suppresses the dimensional change of the base paper. As long as the dimensional stability of the base paper used is 4.5% or less as the water immersion elongation value, it is possible to achieve the difference between the front and back sides, so that it is possible to avoid any running failure or accommodation failure due to environmental changes or curling after recording. It started. As the pulp composition of this base paper, it is desirable to use a pulp slurry having a beating degree of 450 ml or less, which is composed mainly of LBKP having relatively short fibers. Papermaking conditions include J / W
It is desirable to set the ratio within 100% (conditions where the stock jet speed and the wire speed are the same) to within ± 1%, and the shrinkage ratio in the CD direction in the entire drying process (predyer and after dryer) on the paper machine is 5.5. % Or less is desirable.

The thermal recording paper has a coating method as follows.
After coating the color-developing layer on one surface of the base paper, water is applied to the non-coated surface of the base paper with a coating device such as a roll coater to correct curl after coating. By using a water-soluble binder or a water-proofing agent that improves the dimensional stability of the base paper in this back coat liquid, the difference between the front and back can be achieved, and running defects and poor storage properties due to environmental changes and curling after recording can be achieved. Was found to occur at all. As the water-soluble binder, PVA is most preferable, and if the degree of polymerization of PVA to be used is too high, the coating suitability is lowered due to an increase in solution viscosity, so that it is preferably in the range of 300 to 2000,
The degree of saponification is not problematic as long as it is in the water-soluble range, but preferably 85 mol% to 100 mol%. The concentration of the back coat solution of PVA is preferably 1.5 to 2.5% in weight percent from the viewpoint of coating suitability, and the amount of adhesion to the thermal recording paper is preferably about 0.5 g / m ² .

Further, as the water-proofing agent, a melamine resin,
Polyamide polyurea resin is preferable, but any water-proofing agent may be used even with special SBR (styrene-butadiene latex) as long as it improves the dimensional stability of the base paper. The concentration of the water-proofing agent in the backcoat solution is preferably 2 to 3% by weight from the viewpoint of coating suitability, and the amount attached to the thermal recording paper is 0.5 g / m ^2.
A degree is desirable.

In making the base paper of the present invention, internal sizes such as rosin, alkyl ketene dimer and alkenyl succinic acid, and fillers such as clay, calcium carbonate and talc can be used if necessary. Further, a paper strength enhancer such as polyacrylamide and starch, a moisture resistant resin and the like may be added. Further, a starch, SBR, styrene-maleic anhydride, etc. are surface-sized or coated, and a calendar,
The treatment may be performed with a smoothing device such as a soft calendar.

A recording layer is formed on the base paper thus produced by a conventional method, and various leuco dyes used in the recording layer of the present invention are known. The leuco dye used in the present invention is not particularly limited, but triphenylmethane type, fluorane type, fluorene type, divinyl type and the like are preferable, and specific examples thereof are shown below.

<Triphenylmethane type leuco dye> 3,
3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide [also known as crystal violet lactone]

<Fluoran Leuco Dye (I)> 3-Diethylamino-6-methyl-7-anilinofluorane,
3- (N-ethyl-p-toluidino) -6-methyl-
7-anilinofluorane, 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (o, p-
Dimethylanilino) fluorane, 3-pyrrolidino-6-
Methyl-7-anilinofluorane, 3-piveridino-6
-Methyl-7-anilinofluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-7- (m-trifluoromethylanilino) fluorane , 3-N-n-dibutylamino-6-methyl-7-anilinofluorane,
3-N-n-dibutylamino-7- (o-chloroanilino) fluorane, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-methyl-7-anilinofluorane, 3-dibutylamino-6 -Methyl-7- (o, p-
Dimethylanilino) fluorane, 3- (N-methyl-N)
-Propylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-dieteramino-7 -(O-
Chloranilino) fluorane, 3-diethylamino-6
-Methyl-chlorofluorane, 3-diethylamino-6
-Methyl-fluorane, 3-cyclohexylamino-6
-Chlorfluorane, 3-diethylamino-benzo [a] -fluorane, 3-n-dibentylamino-6-
Methyl-7-anilinofluorane, 2- (4-oxo-
Hexyl) -3-dimethylamino-6-methyl-7-anilinofluorane, 2- (4-oxo-hexyl) -3
-Diethylamino-6-methyl-7-anilinofluorane and 2- (4-oxo-hexyl) -3-dipropylamino-6-methyl-7-anilinofluorane

<Fluorene-based leuco dye>3,6,6'-
Tris (dimethylamino) spiro [fluorene-9,3 '
-Phthalide] and 3,6,6'-tris (diethylamino) spiro [fluorene-9,3'-phthalide]

<Fluoran Leuco Dye (II)> 2-
Methyl-6-p- (p-dimethylaminophenyl) aminoanilinofluorane, 2-methoxy-6-p- (p-
Dimeter aminophenyl) aminoanilinofluorane,
2-chloro-3-methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane, 2-chloro-
6-p- (p-dimethylaminophenyl) aminoanilinofluorane, 2-nitro-6-p- (p-diethylaminophenyl) aminoanilinofluorane, 2-amino-6-p- (p-diether Aminophenyl) aminoanilinofluorane, 2-diethylamino-6-p- (p-
Diethylaminophenyl) aminoanilinofluorane,
2-Phenyl-6-methyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane, 2-benzyl-6-p- (p-phenylaminophenyl) aminoanilinofluorane, 2-hydroxy- 6-p- (p-phenylaminophenyl) aminoanilinofluorane, 3
-Methyl-6-p- (p-dimethylaminophenyl) aminoanilinofluorane, 3-diethylamino-6-p
-(P-Diethylaminophenyl) aminoanilinofluorane and 3-diethylamino-6-p- (p-dibutylaminophenyl) aminoanilinofluorane

<Divinyl-based leuco dye> 3,3-bis-
[2- (p-Dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4,5,6,7-tetrabromophthalide 3,3-bis- [2- (p-dimethylaminophenyl) ) -2- (p-Methoxyphenyl) ethenyl] -4,5,6,7-tetrachlorophthalide, 3,3-bis- [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl ] -4,5,6,7-Tetrabromophthalide and 3,3-bis- [1- (4-methoxyphenyl)-
1- (4-pyrrolidinophenyl) ethylene-2-yl]
-4,5,6,7-tetrachlorophthalide

<Others> 1,1-bis- [2 ', 2', 2 ",
2 "-tetrakis- (p-dimethylaminophenyl)-
Ethenyl] -2,2-dinitrileethane, 1,1-bis-
[2 ', 2', 2 ", 2" -tetrakis- (p-dimethylaminophenyl) -ethenyl] -2-=-naphthoylethane, 1,1-bis- [2 ', 2', 2 ", 2" -Tetrakis-
(P-Dimethylaminophenyl) -ethenyl] -2,2
-Diacetylethane and bis- [2,2,2 ', 2'-tetrakis- (p-dimethylaminophenyl) -ethenyl]
Methylmalonic acid dimethyl ester These dyes can be used alone or in admixture of two or more.

Various kinds of organic color developing agents are known which are colored by contact with a leuco dye. In the present invention, as the organic developer, bisphenol A, 4-hydroxybenzoic acid ester, 4-hydroxyphthalic acid diester,
Phthalic acid monoesters, bis- (hydroxyphenyl) sulfides, 4-hydroxyphenyl aryl sulfones, 4-hydroxyphenyl aryl sulfonates, 1,3- [2- (hydroxyphenyl) -2-propyl] -benzene Examples thereof include 4-hydroxybenzoyloxybenzoic acid esters and bisphenol sulfones. Specific examples of these are shown below.

<Bisphenol A> 4,4′-isopropylidenediphenol (alias: bisphenol A),
4,4'-cyclohexylidene diphenol, p, p '
-(1-methyl-normalhexylidene) diphenol and 1,7-di (4-hydroxyphenylthio) -3,
5-dioxaheptane

<4-hydroxybenzoic acid esters> 4
-Benzyl hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, isopropyl 4-hydroxybenzoate, butyl 4-hydroxybenzoate and isobutyl 4-hydroxybenzoate and 4-
Methylbenzyl hydroxybenzoate

<4-Hydroxyphthalic acid diesters>
Dimethyl 4-hydroxyphthalate and diisopropyl 4-hydroxyphthalate, dibenzyl 4-hydroxyphthalate and dihexyl 4-hydroxyphthalate

<Phthalic acid monoesters> Phthalic acid monobenzyl ester, phthalic acid monocyclohexyl ester, phthalic acid monophenyl ester, phthalic acid monomethylphenyl ester, phthalic acid monoethylphenyl ester, phthalic acid monopropylbenzyl ester, phthalic acid Monohalogen benzyl ester and phthalic acid monoethoxybenzyl ester,

<Bis- (hydroxyphenyl) sulfides> bis- (4-hydroxy-3-tert-butyl-6-methylphenyl) sulfide, bis- (4-hydroxy-2,5-dimethylphenyl) sulfide, bis -(4-hydroxy-2-methyl-5-ethylphenyl) sulfide, bis- (4-hydroxy-2-methyl-5-isopropylphenyl) sulfide, bis- (4
-Hydroxy-2,3-dimethylphenyl) sulfide, bis- (4-hydroxy-2,5-dimethylphenyl) sulfide, bis- (4-hydroxy-2,5-diisopropylphenyl) sulfide, bis- (4-hydroxy -2,3,6-trimethylphenyl) sulfide,
Bis- (2,4,5-trihydroxyphenyl) sulfide, bis- (4-hydroxy-2-cyclohexyl-5)
-Methylphenyl) sulfide, bis- (2,3,4-trihydroxyphenyl) sulfide, bis- (4,5-
Dihydroxy-2-tert-butylphenyl) sulfide, bis- (4-hydroxy-2,5-diphenylphenyl) sulfide and bis- (4-hydroxy-2-)
tert-octyl-5-methylphenyl) sulfide

<4-Hydroxyphenylarylsulfones>4-hydroxy-4'-isopropoxydiphenylsulfone,4-hydroxy-4'-propoxydiphenylsulfone,4-hydroxy-4'-n-butyloxydiphenylsulfone, 4 -Hydroxy-4'-n-propoxydiphenyl sulfone

<4-Hydroxyphenylarylsulfonates> 4-hydroxyphenylbenzenesulfonate, 4-hydroxyphenyl-p-tolylsulfonate, 4-hydroxyphenylmethylenesulfonate, 4
-Hydroxyphenyl-p-chlorobenzenesulfonate, 4-hydroxyphenyl-p-tert-butylbenzenesulfonate, 4-hydroxyphenyl-p-isopropoxybenzenesulfonate, 4-hydroxyphenyl-1'-naphthalenesulfonate and 4-hydroxyphenyl-2'-naphthalene sulfonate

<1,3-di [2- (hydroxyphenyl) -2-propyl] benzenes> 1,3-di [2-]
(4-Hydroxyphenyl) -2-propyl] benzene, 1,3-di [2- (4-hydroxy-3-alkylphenyl) -2-propyl] benzene, 1,3-di [2
(2,4-Dihydroxyphenyl) -2-propyl] benzene and 1,3-di [2- (2-hydroxy-5-methylphenyl) -2-propyl] benzene

<Resorcinols> 1,3-dihydroxy-6 (α, α-dimethylbenzyl) -benzene <4-hydroxybenzoyloxybenzoic acid ester>
Benzyl 4-hydroxybenzoyloxybenzoate, 4
-Methyl hydroxybenzoyloxybenzoate, ether 4-hydroxybenzoyloxybenzoate, propyl 4-hydroxybenzoyloxybenzoate, butyl 4-hydroxybenzoyloxybenzoate, isopropyl 4-hydroxybenzoyloxybenzoate, 4-hydroxybenzoyloxybenzoic acid Tert-Butyl acid, hexyl 4-hydroxybenzoyloxybenzoate, octyl 4-hydroxybenzoyloxybenzoate, nonyl 4-hydroxybenzoyloxybenzoate, cyclohexyl 4-hydroxybenzoyloxybenzoate, 4-hydroxybenzoyloxybenzoic acid =- Phenethyl, phenyl 4-hydroxybenzoyloxybenzoate, 4-hydroxybenzoyloxybenzoic acid = -naphthyl and 4-hydroxybenzoi Oxybenzoate sec- butyl

<Bisphenol sulfones (l)> Bis- (3-1-butyl-4-hydroxy-6-methylphenyl) sulfone, bis- (3-ethyl-4-hydroxyphenyl) sulfone, bis- (3- Propyl-4-hydroxyphenyl) sulfone, bis- (3-methyl-4-)
Hydroxyphenyl) sulfone, bis- (2-isopropyl-4-hydroxyphenyl) sulfone, bis- (2
-Ethyl-4-hydroxyphenyl) sulfone, bis-
(3-chloro-4-hydroxyphenyl) sulfone, bis (2,3-dimethyl-4-hydroxyphenyl) sulfone, bis (2,5-dimethyl-4-hydroxyphenyl) sulfone, bis- (3-methoxy-4) -Hydroxyphenyl) sulfone, 4-hydroxyphenyl-2'-
Ethyl-4'-hydroxyphenyl sulfone, 4-hydroxyphenyl-2'-isopropyl-4'-hydroxyphenyl sulfone, 4-hydroxyphenyl-3'-isopropyl-4'-hydroxyphenyl sulfone, 4-
Hydroxyphenyl-3'-sec butyl-4'-hydroxyphenyl sulfone, 3-chloro-4-hydroxyphenyl-3'-isopropyl-4'-hydroxyphenyl sulfone, 2-hydroxy-5-t-butylphenyl-
4'-hydroxyphenyl sulfone, 2-hydroxy-
5-t-aminophenyl-4'-hydroxyphenyl sulfone, 2-hydroxy-5-t-isopropylphenyl-4'-hydroxyphenyl sulfone, 2-hydroxy-5-t-octylphenyl-4'-hydroxyphenyl sulfone, 2-hydroxy-5-t-butylphenyl-3′-chloro-4′-hydroxyphenyl sulfone,
2-hydroxy-5-t-butylphenyl-3'-methyl-4'-hydroxyphenyl sulfone, 2-hydroxy-5-t-butylphenyl-3'-isopropyl-4 '
-Hydroxyphenyl sulfone, 2-hydroxy-5-
t-Butylphenyl-3'-chloro-4'-hydroxyphenyl sulfone, 2-hydroxy-5-t-butylphenyl-3'-methyl-4'-hydroxyphenyl sulfone, 2-hydroxy-5-t-butylphenyl -3'-
Isopropyl-4'-hydroxyphenyl sulfone and 2-hydroxy-5-t-butylphenyl-2'-methyl-4'-hydroxyphenyl sulfone

<Bisphenolsulfonic acid (II)> 4,
4'-sulfonyldiphenol, 2,4'-sulfonyldiphenol, 3,3'-dichloro-4,4'-sulfonyldiphenol, 3,3'-dibromo-4,4'-sulfonyldiphenol, 3, 3 ', 5,5'-tetrabromo-4,4'-
Sulfonyldiphenol and 3,3'-diamino-4,4 '
-Sulfonyldiphenol

<Others> p-tert-butylphenol, 2,4-dihydroxybenzophenone, novolac type phenol resin, 4-hydroxyacetophenone, p
-Phenylphenol, benzyl-4-hydroxyphenylacetate and p-benzylphenol

In the present invention, the use ratio of the leuco dye and the color developer is appropriately selected according to the types of the leuco dye and the color developer used. To prepare a coating liquid containing these substances, water is generally used as a dispersion medium, and a leuco dye and a color developer are dispersed together and separately by a stirrer such as a ball mill, attritor, or sand mill, and a pulverizer. , Prepared as a coating liquid.

In this coating solution, as a binder,
Various binders are added. As the binder used in the present invention, completely saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxy modified polyvinyl alcohol, amide modified polyvinyl alcohol, sulfonic acid modified polyvinyl alcohol, butyral modified polyvinyl alcohol, other modified polyvinyl alcohol,
Hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer and ethyl cellulose, cellulose derivatives such as acetyl cellulose, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic ester, Examples thereof include polyvinyl butyral polystyrol and copolymers thereof, polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, and coumarone resin. These polymeric substances are used by dissolving them in solvents such as water, alcohols, ketones, esters, hydrocarbons, etc., and are also used in a state of being emulsified or pasty dispersed in water or other medium, and used in combination depending on the required quality. You can also do it.

Further, in the present invention, a known stabilizer p-nitrobenzoic acid metal salt (Ca, Zn) or phthalic acid monobenzyl ester metal salt (Ca, Zn) is used within a range that does not impair the effects of the present invention. It is also possible to add.

As a sensitizer, if necessary, fatty acid amides such as stearic acid amide and palmitic acid amide, ethylene bisamide, montan wax, polyethylene wax, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, diester. -P-tolyl carbonate, p-benzyl biphenyl, phenyl = -naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, 1,2-
Di- (3-methylphenoxy) ethane, di (p-oxalate)
-Methylbenzyl), = -benzyloxynaphthalene,
4-biphenyl p-tolyl ether, o-xylelin-
Bis- (phenyl ether), 4- (m-methylphenoxymethyl) biphenyl and the like can also be added.

The filler used in the present invention is silica,
Inorganic or organic fillers such as calcium carbonate, kaolin, calcined kaolin, diatomaceous, tank, titanium oxide, aluminum hydroxide and the like can be mentioned.

In addition to these, a release agent such as a fatty acid metal salt, a lubricant such as waxes, a benzophenone-based or triazole-based UV absorber, a water-proofing agent such as glyoxal, a dispersant, an antifoaming agent, etc. should be used. You can

The amount of the stabilizer and leuco dye used in the present invention and the types and amounts of various other components are determined according to the required performance and recording suitability, and are not particularly limited, but usually 1 part of the leuco dye. Against organic developer 1
.About.8 parts, 0.25 to 2.5 parts of stabilizer, and 1 to 20 parts of filler are used, and 10 to 25% of the total solid content of the binder is suitable.

The above-mentioned organic developer, leuco dye and materials to be added as required are atomized by a crusher such as a ball mill, an attritor, a sand grinder or an appropriate emulsifying device until the particle diameter becomes several microns or less,
A binder and various additive materials are added depending on the purpose to prepare a coating liquid.

In the present invention, the method for forming the recording layer is not particularly limited, and for example, a method of coating and drying the coating liquid on the base paper with a coating device equipped with an appropriate coater head such as an air knife coater or a blade coater. Is formed by. The coating amount of the coating liquid is usually 2 to 12
g, preferably in the range of about 3 to 10 g.

An undercoat layer may be provided between the base paper and the recording layer, or an overcoat layer may be provided on the recording layer for the purpose of protecting the recording layer. It is also possible to carry out a back coat for straightening the curl and, if necessary, provide a smoothing treatment such as soft calendering. Further, various publicly known techniques in the field of thermal recording paper, such as adhesive processing on the back surface, can be added.

[0041]

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. The parts and% in the examples are parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 (Production of base paper) As a raw material pulp for papermaking, the freeness was 28.
For 90 parts of hardwood kraft pulp beaten to 0 ml (Canadian standard freeness) and 10 parts of softwood kraft pulp beaten to 300 ml freeness, a pulp suspension consisting of 0 parts of alkenyl succinic anhydride was used. 0.2%, calcium carbonate 20%, cationized starch 0.
The pulp slurry was adjusted by adding 5%.
This pulp slurry was used with a Fourdrinier paper machine to obtain a J / W ratio of 10
Paper was made at 1%, styrene acrylic resin as a surface sizing agent was applied to the recording layer coated surface at 0.5 g / m ² by a 2-roll size press, dried and then calendered,
At a machine speed of 700 m / min, the amount of filler is 17% and the basis weight is 47 g / m.
^2. A heat-sensitive recording base paper having a water immersion elongation of 3.5% at the edge of the paper machine was manufactured.

(Preparation of underlayer) After that, an underlayer coating liquid containing the following components was dried on the above base paper at a dry weight of 6 g / m 2.
^An under layer was obtained by applying a coating amount of 300 m / min with a blade coater so as to obtain ² and drying.

Calcined kaolin (XCI3OOFECC oil absorption 70 ml / 100 g) 100 parts Dispersant 0.2 part 10% PVA solution 5 parts 48% styrene-butadiene copolymer latex 11 parts Water 50 parts

(Preparation of coating liquid for recording layer) As liquid A (developer dispersion liquid), 10% PVA aqueous solution 18.8 parts 4-hydroxy-4'-isopropoxydiphenyl sulfone 6.0 parts water 11.2 Part and dispersed using a sand grinder to obtain an average particle size of 1 μm.
crushed to m.

To prepare the liquid B (dye dispersion), 3-N-n-dibutylamino-6-methyl-7-anilinopulolane 2.0 parts 10% PVA aqueous solution 4.6 parts water 2.6 parts Disperse and use a sand grinder to obtain an average particle size of 1 μm.
crushed to m.

To prepare the liquid C (sensitizer dispersion liquid), 4-biphenyl p-tolyl ether 4.0 parts 10% PVA aqueous solution 5.0 parts water 3.0 parts are dispersed and an average particle diameter is obtained using a sand grinder. lμ
crushed to m.

Next, adjusted (solution A), (solution B), (C)
Liquid) to prepare a ripening layer coating liquid consisting of the following components,
The above under layer was coated with an air knife coater at 300 m / min so that the dry weight was 5 g / m ² , and dried.

Liquid A 36.0 parts Liquid B 9.2 parts Liquid C 12.0 parts Calcium carbonate (Brilliant-15 Shiraishi Kogyo's average particle size 0.20 = 50% dispersion liquid) 12.0 parts

(Backcoat) Next, the uncoated surface of the base paper was coated with water at a rate of 300 m / min by a roll coater, dried, and the curl was adjusted after coating, and then the recording layer surface was coated with a soft calender. The heat-sensitive recording paper of the present invention was obtained by finishing so as to have a smoothness of 600 to 800 seconds.

Comparative Example 1 (Production of base paper) As a raw material pulp for papermaking, the freeness was 23
To 90 parts of hardwood kraft pulp beaten to 0 ml (Canadian standard freeness) and 10 parts of softwood kraft pulp beaten to 300 ml freeness, a alkenylsuccinic anhydride was added to a pulp suspension. 0.2%, calcium carbonate 20%, cationized starch 0.
The pulp slurry was adjusted by adding 5%.
This pulp slurry was made to have a J / W ratio of 98 with a Fourdrinier paper machine.
%, And a styrene acrylic resin, which is a surface sizing agent, is applied to the recording layer coated surface by a 2-roll size press.
After applying 5 g / m ² and drying, calendering was performed, and at a speed of 700 m / min, the amount of filler was 17%, the basis weight was 47 g / m ² ,
A heat-sensitive recording base paper having a water immersion elongation of 5.3% at the end position of the paper machine was manufactured. A thermal recording paper was obtained on the above base paper in the same manner as in Example 1.

Example 2 An underlayer and a recording layer were provided on the base paper prepared in Comparative Example 1 in the same manner as in Example 1, and a back coating liquid was applied to the non-coated surface of the base paper at 300 m / min by a roll coater. 2% P
VA (Kuraray Poval PVA-117, Kuraray Co., Ltd.)
After coating an aqueous solution at 0.5 g / m ² and drying, adjusting the curl after coating, finishing with a soft calender so that the Beck smoothness of the recording layer surface is 600 to 800 seconds, to obtain a thermosensitive recording paper. It was

Example 3 The base paper prepared in Comparative Example 1 was provided with an under layer and a recording layer in the same manner as in Example 1, and a melamine-based resin Sumireze manufactured by Sumitomo Chemical Co., Ltd. was used as a back coating liquid. Resin 61
3 to 100 parts of ammonium chloride 20 as a catalyst
Part, 5 parts of a 3% aqueous solution of DL-malic acid, which is a reaction accelerator, by a roll coater at 300 m / min, 0.5 g
/ M ² coating, drying, coating, and after adjusting the curl, the soft calender has a Beck smoothness of 600 on the recording layer surface.
The heat-sensitive recording paper was obtained by finishing so as to be about 800 seconds.

Example 4 An underlayer and a recording layer were provided on the base paper prepared in Comparative Example 1 in the same manner as in Example 1, and a back coating liquid was applied to the non-coated surface of the base paper at 300 m / min by a roll coater. 3% polyamide polyurea resin (Sumiraz resin 500
1. 0.5 g / m ^{2 of} an aqueous solution of Sumitomo Chemical Co., Ltd. was applied and dried, and the curl was adjusted after coating, and then the Beck smoothness of the recording layer surface was 600 to 800 with a soft calender.
The heat-sensitive recording paper was obtained by finishing so as to reach the second.

The five types of thermal recording papers thus obtained were evaluated as follows, and the evaluations obtained are shown in Table 1.

(Measurement of elongation on both sides in water and evaluation of difference between sides)
The thermosensitive recording paper was used with an internal strength tester JTC-9000 (manufactured by SMT Co., Ltd.) and the roll speed was 50 rp.
m. , And after separating the layers into two layers,
The water immersion elongation in the CD direction on each of the recording layer side and the back coating side was measured according to J. TAPPI No. It was measured by the method A described in 27-78. The difference between the front and back of the water immersion elongation was determined by subtracting the water immersion elongation value on the recording layer side from the water immersion elongation value on the back coat side.

(Small Roll Processing of Sensitive Recording Paper) The heat-sensitive recording paper was wound around a 1-inch paper tube with the recording layer as the upper roll for 100 m to form a small roll. This is wrapped in vinyl and sealed to prevent dimensional changes, and usually stored for about three months, which is about the same as the period until the product is put on the market.

(Pre-printing, post-printing curl and runnability / accommodation test) The small roll taken out from the package was set on each of two types of facsimiles, UF-1000 and UF-B55 manufactured by Matsushita Electric Transport Co., Ltd. , And printing and running tests were carried out. The size of the paper to be ejected was B4 size, and the upper winding of the small winding roll was subjected to a continuous printing test of 50 sheets, and then the lower winding of the small winding roll was subjected to a continuous printing test of 50 sheets. The thermal recording paper between the upper roll and the lower roll was discarded as peeled paper with a cutter or the like. For the curl evaluation before printing, both upper and lower curls of the printing grain were cut into B4 size cutters, and the average curl heights at the four corners were evaluated on a flat plate. For the curl evaluation after printing, an average value of curl heights at four corners was evaluated on a flat plate of a B4 size thermal recording paper punched out by a facsimile. The environmental conditions for performing each of these evaluations are 10 ° C and 30 ° C.
% R. H. low temperature and low humidity condition, 20 ° C. 60% R. Humidity conditioning condition, 30 ° C. 80% R.H. It was carried out under the three conditions of high temperature and high humidity of H.

The curl was evaluated as follows based on the curl height before and after printing. Curl height evaluation rank ◎ Excellent (for example, curl or curl change is small) ○ Slightly curl but good △ Slightly inferior (for example, curl is slightly large or curl change is relatively large) × Inferior (for example, curl is (Large changes in curl)

Next, the runnability evaluation was ranked as follows according to the number of jams in the evaluation hardware. Runnability evaluation rank ○ 50 sheets, no jamming △ △ Jam count 1-2 times (or a slight jam occurs) × Inferior 2 times or more (or jam frequency is high)

Next, the accommodability evaluation was ranked as follows according to the number of stacking defects in the accommodating section attached to the evaluation hardware. Runnability evaluation rank ○ 50 sheets No jam All △ Jam count 1-2 times (or some jam occurs) × Inferior 2 times or more (or jam frequency is high) The results are shown in Tables 1 and 2.

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[Table 1]

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[Table 2]

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As is clear from the results shown in Table 1, the thermal recording paper of the present invention has little curl even when the humidity of the environment changes and is heated for printing, and has excellent running and storage characteristics during use. I have.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroki Midorikawa 1 Kubota Tokojo, Nakoso-cho, Iwaki City, Fukushima Prefecture Nakoso Mill, Nippon Paper Industries Co., Ltd. (72) Nobuo Takeuchi 5-21-1 Oji, Kita-ku, Tokyo Japan Central Research Institute of Paper Manufacturing Co., Ltd.

Claims (7)

[Claims] 1. A heat-sensitive recording paper comprising a base paper and a thermosensitive coloring layer containing a color former and a color developer as main components.
The heat-sensitive recording paper is divided into two layers, and J. TAPPI No.
27-78, The heat-sensitive recording paper is characterized in that the difference in the water immersion elongation of the heat-sensitive recording paper measured by the method A is 0.5% or less. 2. A thermosensitive recording paper comprising a thermosensitive coloring layer containing a color former and a color developer as main components on a base paper.
The heat-sensitive recording paper, characterized in that the base paper mainly composed of pulp has a water immersion elongation value of 4.5% or less. 3. A thermosensitive recording paper comprising a base paper and a thermosensitive coloring layer containing a color former and a color developer as main components, the thermosensitive recording paper comprising:
The heat-sensitive recording paper, wherein the water-immersion elongation value of the heat-sensitive recording paper is 5% or less. 4. A thermosensitive recording paper comprising a base paper and a thermosensitive coloring layer containing a color former and a color developer as main components.
A sensitized recording paper having a back coat layer containing a water-soluble binder or a water-proofing agent for improving the dimensional stability of the base paper on the opposite side of the thermosensitive color developing layer of the base paper. 5. The polymerization degree of the water-soluble binder is 300 to 2
000 range, saponification degree 85 mol% to 100 m
The sensitized recording paper according to claim 4, which is ol% PVA. 6. The heat-sensitive recording paper according to claim 4, wherein the waterproofing agent is a melamine resin. 7. The heat-sensitive recording paper according to claim 4, wherein the waterproofing agent is a polyamide polyurea resin.