JPH0890921A - Reversible thermosensitive recording paper - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the printing surface quality of reversible thermosensitive recording paper. [Structure] The surface of the reversible heat-sensitive layer coated on a support such as paper has an air leak type paper smoothness meter (Parker Print Surf) measured value of 3.8 μm or less under a pressure condition of 20 kg / cm ² , and The value measured by the paper smoothness meter on the surface of the protective layer provided on the heat-sensitive layer is 4 μm or less under a pressure condition of 20 kg / cm ² . [Effect] Excellent in print quality and color development and decolorization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording paper which can be colored and decolored by heating, and more specifically, it is excellent in surface quality and prevents coloring of printed characters and is excellent in coloring and decoloring. Reversible thermosensitive recording paper.

[0002]

2. Description of the Related Art Conventionally, an electron-donating dye, which is usually colorless or light-colored (hereinafter, referred to as a color former), and an electron-accepting acidic substance (hereinafter, referred to as a developer) which develops color by heating with the color former are mainly used. The heat-sensitive recording material as a component is widely known and is widely used in the output of electronic computers, facsimiles, vending machines, printers of scientific measuring machines, printers for CRT medical measurement, and the like. However, conventional heat-sensitive recording materials are irreversible and it is not possible to alternately repeat coloring and erasing by heating.

By the way, according to the patent publication, a number of reversible thermosensitive recording materials have been proposed, which are capable of alternately repeating coloring and decoloring by heating. For example, JP-A-52-1
In 40483, a color former and an oxybenzoic acid ester are mixed and applied on a support, color is developed by heating, and the color is erased by removing the temperature. No. 53-102922, a color former, a compound having a phenolic hydroxyl group or a carboxyl group such as 4-tert-butylphenol and methyl p-oxybenzoate, and a nonionic surfactant are blended, and a paraffin wax-like substance is further added. Added. Same as 55-6329
No. 3, No. 55-157677, No. 57-90085.
No. 57-123283, No. 57-167380.
No. 59-120492 and No. 59-156790, compounds having a color former and a phenolic hydroxyl group and their metal salts or carboxylic acid metal salt compounds, and compounds selected from alcohols, ketones, esters and the like. Microencapsulate the three components of. Same as 56-166093
Japanese Patent Laid-Open Publication No. 1989-331, in which 1-phenyl ether alcohol and 1,1 dimethyl- are added to a coating solution containing a color former and a phenol compound.
A water-insoluble alcohol having no aromatic ring such as 2-phenylethanol is added.

JP-A-57-76072 discloses a color former, a 1,2,3 triazole compound, and a boiling point of 150 ° C. at room temperature.
One of the above alcohols or amides is allowed to coexist. JP-A-58-191190 discloses a coloring agent and phloroglycinol, a developing agent selected from gallic acid and 2,4,6-trihydroxyacetophenone, and cellulose acetate,
A transparent film is coated with a binder selected from ethyl cellulose and the like. In JP-A-59-100175, a phosphite triester is added to an ink containing a color former and a novolac type phenol resin as an aromatic alcohol or ethylene glycol monophenyl ether. Same as 60-58
No. 481 discloses a color-developing agent, a color-developing agent, and an atomic group represented by -CH = N-, which has an aliphatic residue, a substituted aliphatic residue, an aromatic residue, a substituted aromatic residue, and a hetero group at both ends. A ring residue or a group selected from the atomic groups of substituted amino groups is bonded to one or two of the atomic groups bonded to at least one of the aromatic residue or the substituted aromatic residue. Azomethines having the same molecule are mixed. Ibid 60-152586
In the publication, a color developing agent and a color developing agent selected from guanidine derivatives are mixed with a desensitizing agent selected from alcohols, esters, ketones, ethers, acid amides, carboxylic acids and hydrocarbons.

In JP-A-60-173028, a color former, a color developer and a mixed acid polyhydric alcohol ester compound are blended with a polyolefin resin. Same 60-184586
In the publication, a benzothiazole derivative and a benzothiazolyl derivative are used as color developers, and a color former and a desensitizer are mixed. Same 6
A composition in which a compound selected from a ferrocene (derivative) is further contained in a compound selected from a color former, a developer, alcohols, ethers and the like in JP-A 0-219289. No. 60-228589, No. 60-229981
No. 60-264285, No. 61-2786, No. 61-9488, color formers and C _{2 to} C ₅ aliphatic carboxylic acids, acidic phosphoric acid esters and metal salts thereof,
A nitro compound, an ester, which determines the color change temperature of a developer selected from a 1,2,3-triazole derivative and a C _{2 to} C ₅ halohydrin derivative and controls its sensitivity,
Microcapsules mixed with ketones, acid amides, and (di) sulfides. JP 63-15877 A discloses color formers and developers and alcohols, esters, ketones, ethers, thiols, (di) sulfides, sulfoxides, sulfones, aliphatic carboxylic acids, acid amides. ,
It contains a desensitizing component selected from hydrocarbons and the like.

Japanese Patent Laid-Open No. 63-27587 discloses a film formation of a mixture of a color former, a developer and a crystalline polymer such as polyethylene, poly (meth) acrylate and polyacrylamide having a melting point and a freezing point lower than that. A reversible thermochromic material. 63-173684, JP-A-1-
No. 121394 discloses a color former and ascorbic acid-6-
A recording layer containing an o-amyl derivative. JP-A-63-251
No. 487, aliphatic higher alcohols, aliphatics,
Melting substances such as acid amides, esters and ethers, color formers and compounds such as 4-hydroxycoumarin, and α-
A title warming agent having a wide discoloration temperature range, which exhibits a sharp discoloration and has a furyldioxime. No. 63-315287 and No. 63-315288, a moving image display using a color-forming agent and an alkylphenol that is liquid at room temperature and utilizing changes between states different from solid-liquid. JP-A-1-253
In JP-A-480, a thermoreversible color-changing granular material capable of completely erasing a high-concentration image by containing a color former, a color developer and a specific alcohol / acrylonitrile adduct. Same as 1-3
No. 01770 discloses a thermosensitive color-forming ink dispersed in a vehicle composed of a specific color-developing agent, a color-developing agent, and a specific acrylic copolymer. No. 2-188293, No. 2-188294
Japanese Patent Laid-Open Publication No. 2003-242242 discloses a reversible thermosensitive recording medium comprising a color former and bis (hydroxyphenyl) acetic acid or bis (hydroxyphenyl) butyric acid or gallic acid and higher aliphatic amine.

JP-A-3-17181 discloses a reversible thermochromic material containing a color former, a salicylic acid co-condensation resin and a non-volatile hydrophobic compound. JP-A-3-213389 discloses a thermoreversible discoloring material which is excellent in thermal responsiveness and is composed of a color developing agent, a color developing agent and a non-polar organic solvent which is liquid at room temperature.
No. 4-46986, No. 4-502289, No. 4-50
Nos. 290 and 5-177931 disclose an amphoteric compound having a color former and at least one of a phenolic hydroxyl group and a carboxyl group and containing an amino group as a functional group or as a part of a salt compound and a heat-fusible compound. A reversible heat extinguishing composition containing a sex sensitizer. In JP-A 4-198282, a color-forming agent, a color-developing agent, and a discoloration temperature controlling agent such as n-cetyl alcohol are blended to form a microcapsule. Ibid 4-247984
In the publication, a reversible thermochromic composition comprising a color former, a 6-o-acyl derivative of ascorbic acid or arabo ascorbic acid, and a higher fatty acid. No. 4-247985, No. 4-3
No. 08790 discloses a color former and an organic phosphate compound or α
A reversible thermosensitive recording material comprising an aqueous emulsion having a pH of 6 to 9 as a polymer binder, using an organic acid having a hydroxyl group at the -position carbon. JP-A-5-32045 discloses that a thermoreversible recording sheet mainly composed of a microcapsule containing a color-developing agent, a color-developing agent, a color-changing temperature controlling compound and a low-volatile solvent and a binder is an ultraviolet absorber. Contains.

JP-A-5-177934 contains a specific azaphthalide compound, a color developer and a desensitizer. JP-A-5-221130 discloses a reversible thermosensitive recording layer comprising a color former and a developer on a support through a vinyl chloride, a vinyl group-containing phosphate ester and a copolymer adhesive layer mainly composed of a vinyl monomer. To be installed. In JP-A-5-221152, a reversible thermosensitive recording sheet coated with a color former and a developer having a long-chain aliphatic group is provided with one or more elastic layers containing a polymer having rubber elasticity as a main component. . Same as 5-221128
Japanese Patent Laid-Open Publication No. 2004-242242 discloses that a protective layer made of a heat resistant film having a melting point of 180 ° C. or higher is provided on a reversible thermosensitive recording medium. The examples described in these are characterized by the composition of the intermediate layer, the reversible heat-sensitive layer, the protective layer, etc., and most of the supports have a high print density, and synthetic papers and films having excellent repeatability are used. ing. However, synthetic papers and films are expensive due to the complexity of raw materials and manufacturing processes, and are not suitable for general purposes. In that respect, the paper is suitable for inexpensive and general-purpose OA word processor printer paper. However, since the printing surface quality is poor, the printing density is low, and since the decoloring property is also poor, the sharpness of the printed image at the time of repetition is lacking, which is not practically sufficient.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above problems found in the prior art when paper is used as a base paper, improves the printing surface quality, and is excellent in coloring and decoloring property by heating. It is to provide a reversible thermosensitive recording paper.

[0010]

As a result of extensive research and experimentation, the present inventor has found that a reversible heat-sensitive layer containing a color former and a reversible developer as main components and a protective layer above the base paper. In the reversible thermosensitive recording paper provided, the surface of the thermosensitive layer has a measured value of 3.8 μ under an air leak type paper smoothness meter (parker print surf, called PPS) under a pressure condition of 20 Kg / cm ^2.
m or less, and the surface of the protective layer is under the pressing condition of 20 Kg / c
The present invention has been accomplished with the knowledge that the object can be achieved by setting the thickness to 4 μm or less under m ² . The base paper used in the present invention is produced by a paper machine using pulp fibers and chemicals for internal addition as appropriate, but the pulp fibers are not particularly limited with respect to their type, production, etc., for example, softwood pulp ( N material), hardwood pulp (L material), hemp pulp, synthetic pulp, waste paper pulp and the like. The filler used in the present invention is, for example, clay, talc, kaolin, calcined kaolin,
White inorganic fillers such as light calcium carbonate, heavy calcium carbonate, magnesium carbonate, aluminum hydroxide, calcium hydroxide, silicon dioxide, titanium dioxide; white organic synthetic fillers such as polystyrene resin, polyethylene resin, acrylic resin, urea-formaldehyde resin And one kind or a mixture of two or more kinds is used. The filler used in the present invention is 3 parts by weight with respect to 100 parts by weight of pulp fiber in the base paper.

The chemicals for internal addition include known water-soluble polyvalent metal compounds, sizing agents, retention aids, and paper strength enhancers,
For example, sulfuric acid band, polyaluminum hydroxide, alkyl ketene dimer size, alkenyl succinic anhydride size, cationic synthetic size, stearic anhydride size, petroleum resin size, rosin size, wax size, higher fatty acid size , Various starch, polyacrylamide, polyethyleneimine, polyamine, polyamide,
Urea-formaldehyde resin, epichlorohydrin resin and the like can be mentioned, and one kind or a mixture of two or more kinds is used.
Further, in the present invention, a Fourdrinier paper machine, a cylinder paper machine, a twin wire paper machine, a combination paper machine, a Yankee paper machine is added by adding a fluorescent dye, a pH adjusting agent, a defoaming agent, a pitch control agent, and a slime control agent, if desired. And so on. Further, in order to improve the surface strength of the paper or the coating suitability of the reversible heat-sensitive layer provided on the base paper, a water soluble polymer such as starch or polyvinyl alcohol is used in a conventional size press, a gate roll size press or a metaling blade system. 1 to 3 g / m ² (dry weight solid content) is applied by a method such as a size press, bill blade, and short dull coater. Further, the surface is smoothed by a smoothing device such as a super calender and a soft calender.

The reversible developer which is the main component of the reversible thermosensitive layer used in the present invention is disclosed in JP-A-6-171225 and 6-2.
No. 10954, No. 6-210955, No. 6-2271
No. 25, the particularly preferable reversible developer is an N- (4-hydroxyphenyl) -N′-alkylurea having an alkyl group having 8 to 21 carbon atoms, specifically N- (4-hydroxyphenyl) -N'-octylurea, N- (4-hydroxyphenyl) -N'-nonylurea, N- (4-hydroxyphenyl) -N'-decylurea, N- (4-hydroxyphenyl) ) -N'-undecyl urea, N- (4-hydroxyphenyl) -N'-dodecyl urea, N- (4-hydroxyphenyl) -N'-tridecyl urea, N- (4-hydroxyphenyl) -N '.
-Tetradecyl urea, N- (4-hydroxyphenyl)
-N'-pentadecyl urea, N- (4-hydroxyphenyl) -N'-hexadecyl urea, N- (4-hydroxyphenyl) -N'-heptadecyl urea, N- (4-hydroxyphenyl) -N'-octadecyl Urea, N-
(4-hydroxyphenyl) -N'-nonadecyl urea,
Examples thereof include N- (4-hydroxyphenyl) -N'-icosylurea and N- (4-hydroxyphenyl) -N'-henicosylurea.

Examples of the reversible color developer and the color former which develops color upon heating used in the present invention include phthalide compounds, fluorane compounds, spiropyran compounds, diphenylmethane compounds and thiazine compounds. Examples of the phthalide compound include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide and 3-
(P-Dibenzylaminophenyl) -3- (1 ', 2'
-Dimethyl-3'-indolyl) -7-azaphthalide,
3,3-bis (4'-dimethylaminophenyl) -phthalide, 3- (4-dimethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindole-3-
Yl) -4-azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -7-azaphthalide, 3,
3-bis [2- (p-dimethylaminophenyl) -2-
Phenylethenyl] phthalide, 3,3-bis [2- (p
-Pyrrolidiphenyl) -2- (p-methylphenyl) ethenyl] phthalide, 3- (p-methoxyphenyl) -3
-[1,1-bis (p-dimethylaminophenyl) ethylene-2-yl] -6-dimethylaminophthalide and the like can be mentioned.

Examples of fluoran compounds include 3,
6-dimethoxyfluorane, 4-amino-8-diethylamino-benzo [a] fluorane, 2-amino-8-diethylamino-benzo [a] fluorane, 4-benzylamino-8-diethylamino-benzo [a] fluorane, 3 -Diethylamino-6-methylfluorane, 3-
Diethylamino-7-aminofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-
6-methyl-7-chlorofluorane, 2-methyl-6-
(Np-tolyl-N-ethylamino) fluorane, 1
0-diethylaminobenzo [c] fluorane, spiro (xanthene-9-1'-phthalane) -6-diethylamino-2-phenyl-3'-one, spiro (xanthene-9,1'-phthalane) -3-diethylamino- 2-methoxy-3′-one, spiro (xanthene-9,1′-
Phthalane) -3-diethylamino-6-methoxy-3 '
-One, spiro (xanthene-9,1'-phthalane)-
6-diethylamino-2- (N-methyl-N-acetamino) -3'-one, 3-cyclohexylamino-6-
Chlorofluorane, 3-diethylaminobenzo [a] fluorane, 3-diethylamino-6,8-dimethylfluorane, 3-benzylamino-6-chlorofluorane,
3-cyclohexylamino-7-methylfluorane, 2
-Methoxy-8-diethylamino-benzo [c] fluorane, 2-anilino-3-methyl-6-N-cyclohexyl-N-methylaminofluorane, 3- (N, N-diethylamino) -7-bis (dimethylbenzyl) ) Aminofluorane, 3-diethylamino-7-N-cyclohexyl-N-benzylaminofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-diethylamino-6-methyl-7-p-butylanilinofluorane , 3-diethylamino-6-methyl-7-p-phenetidinofluorane, 3-diethylamino-6-methyl-
7-anilinofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-chloroanilinofluorane, 3-diethylamino-7- (2-carbomethoxyanilino) fluorane, Two
-Anilino-3-methyl-6- (N-ethyl-p-toluidino) fluorane, 2-p-toluidino-3-methyl-6- (N-ethyl-p-toluidino) fluorane, 3
-(N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-
Methyl-7-anilinofluorane, 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- N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-
Diethylamino-7- (m-trifluoromethylanilino) fluorane, 3-Nn-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-
Chlor-7-anilinofluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane and the like can be mentioned.

As the spiropyran compound, for example, 2,
2'-spiro (benzo [f] chromene), spiro (3-
Methylchromene-2,2'-7'-diethylaminochromene), spiro (3-methyl-benzo [5,6-a] chromene-2,2'-7'-diethylaminochromene),
Examples include spiro (3-methylchromene-2,2'-7'-dibenzylaminochromene) and 3-methyl-di-β-naphthospiropyran. Examples of the diphenylmethane compound include 4,4′-bis (4,4′-tetramethyldiaminodiphenylmethylamino) diphenylmethane, bis [4,4′-bis (dimethylamino-benzhydryl)] ether, N, N′- Screw [bis (4'-
Dimethylaminophenyl) methyl] 1,6-hexamethylenediamine, N-bis (4-dimethylaminophenyl) methyl-glycine ethyl ether, 4,4′-bis-dimethylaminobenzhydrylbenzyl ether and the like can be mentioned.

Examples of thiazine compounds include 3,7
-Bis (dimethylamino) -10-benzoylphenothiazine, 10- (3 ', 4', 5'-trimethoxy-benzoyl) -3,7-bis (dimethylamino) phenothiazine, 3-diethylamino-7- (N-methylanilino) ) -10-Benzoylphenothiazine, 4H-7-diethylamino-4,4′-bis- (9′-ethyl-3 ′)
-6'-carbazolyl) -2-t-butyroylamino-
3,1-benzothiazine, 4H-7-diethylamino-
4- (p-diethylaminophenyl) -4- (9'-ethyl-3'-methyl-6'-carbazolyl) -2-bivaloylamino-3,1-benzothiazine, 4H-6-methyl-4,4- Bis (p-dimethylaminophenyl)-
2-bivaloylamino-3,1-benzothiazine, 4H
-7-Dibenzylamino-4,4-bis (p-dimethylaminophenyl) -2-phenyl-3,1-benzothiazine, 4H-7-dibenzylamino-4,4-bis (p
-Dimethylaminophenyl) -2-bivaloylamino-
3,1-benzothiazine, 4H-7-dibenzylamino-2-isoptoxycarbonylamino-4,4-bis (p-dimethylaminophenyl) -3,1-benzothiazine, 4H-7-diethylamino-4,4- Screw [p-
[N-ethyl-N- (p-tolyl)] aminophenyl]
-2-Bivaloylamino-3,1-benzothiazine and the like can be mentioned, and among these, one kind or two or more kinds are mixed.

The use ratio of the color former and the reversible developer used in the present invention varies depending on the kinds of the color former and the reversible developer and is not particularly limited, but generally 100 parts by weight of the color former is used. The reversible color developer is 100 to 1000 parts by weight, preferably 200 to 500 parts by weight. The reversible thermosensitive layer of the present invention is formed by mixing a binder and a white pigment, and examples of the binder include water-soluble polymers such as starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein and polyvinyl alcohol. And latexes such as polyvinyl acetate, polyurethane, polyacrylic acid ester, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, ethylene / vinyl acetate copolymer. Examples of white pigments include clay, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium dioxide, zinc oxide,
Examples thereof include silicon dioxide, aluminum hydroxide, magnesium hydroxide, barium sulfate, aluminum oxide, zinc stearate, calcium stearate, urea-formaldehyde resin, polystyrene and the like, and they are used alone or in combination of two or more.

Further, in the present invention, if desired, waxes such as carnauba wax and paraffin wax; water-proofing agents such as formaldehyde, glyoxal, epoxy resin, melamine, melamine-folimaldehyde resin; UV absorbers typified by benzophenone A wetting agent such as sodium dialkyl sulfosuccinate; a dispersant such as sodium polyacrylate, styrene maleic anhydride copolymer ammonium and an alkylene glycol mixture; a defoaming agent or the like is appropriately added as an auxiliary agent for the reversible thermosensitive layer The coating liquid is 1 to 10g on the surface of the base paper by the coating method of air knife, curtain, bar, gravure, roll coater, etc.
/ M ² (dry weight solid content), particularly preferably 2 to 5 g /
A reversible heat-sensitive layer is provided by coating and drying so that the thickness becomes m ² .

The protective layer provided on the reversible heat-sensitive layer of the present invention is a water-soluble polymer such as polyvinyl alcohol or modified polyvinyl alcohol used in the reversible heat-sensitive layer, or a two-layer structure acrylate-based copolymer having a core and an outer layer. Latex and their crosslinkers. Further, white pigments such as aluminum hydroxide and magnesium carbonate are contained. Examples of the crosslinking agent used in the present invention include glyoxal, formalin, borax, dialdehyde starch, melamine resin, polyamide resin, polyethyleneimine resin, polyamide-
Epichlorohydrin resin, ketone-aldehyde resin, glycine, glycidyl ester, glycidyl ether, ketene dimer, dimethylol urea, ammonium chloride,
Examples thereof include magnesium chloride, calcium chloride, aluminum sulfate, magnesium sulfate, calcium hydroxide, and zirconium carbonate-ammonium carbonate, with polyamide-epichlorohydrin resin being particularly preferred. Further, in the present invention, if desired, a heat-fusible substance such as zinc stearate, calcium stearate, aluminum stearate, carnauba wax, paraffin wax, polyethylene wax, etc .; a dispersant; And a coating amount of 0.3 to 5 g / m ² (dry weight solid content) on the reversible thermosensitive layer formed on the surface of the base paper by a coating method such as an air knife, a bar, a curtain, a gravure, and a roll coater. Preferably, a protective layer is provided by coating and drying so that the coating amount is 0.5 to ² g / m ² .

The reversible heat-sensitive layer used in the present invention is an air leak type paper smoothness meter, and the value of PPS is 20 kg / c under pressure conditions.
m ² under 3.8 μm, the protective layer is under the pressure condition 20
It is 4 μm or less under Kg / cm ² . If the reversible heat-sensitive layer exceeds 3.8 μm or the protective layer exceeds 4 μm, the printing surface quality deteriorates and the decoloring property deteriorates, which is not practical. That is, since the thermal head prints on a reversible thermosensitive recording paper by contacting with pressure, the surface roughness-smoothness of the paper and the compressibility have an important relationship. Even if the surface roughness is rough, it is excellent if the compressibility is high. Print quality can be obtained. Factors that affect the smoothness during compression include, in the base paper, pulp blending and fiber length, Canadian Standard Freeness (hereinafter referred to as “freeness”), freeness, additives such as softeners, and size press liquid. , Density, thickness, calender pressure, smoothness, and the like, and examples of the reversible thermosensitive layer and protective layer include compounding material and particle size, coating amount, water content, calender pressure, smoothness, and the like.

Since the reversible thermosensitive recording paper of the present invention is repeatedly colored and decolored by heating, a water-soluble polymer, latex, white pigment, etc. are added to the base paper to prevent stickiness and wrinkles of the base paper. Apply on the back side. Further, in order to further improve the printing density, it is preferable to apply a porous white pigment or an organic polymer between the base paper and the reversible thermosensitive layer to provide an intermediate layer.

[0022]

The preferred embodiments of the present invention and excellent effects will be specifically described below with reference to the most typical examples. The following parts are all parts by weight, and% means% by weight.

Example 1 LBKP (freeness: 200 ml) 800 parts NBKP (freeness: 200 ml) 200 parts Rosin size 30 parts Sulfuric acid band 60 parts Talc 50 parts Kaolin 80 parts Retention aid (polyacrylamide) 0.4 parts The above composition 4% of the 1.2% slurry of
% Oxidized starch (trade name; solar eclipse MS-3800, manufactured by Nippon Shokubai Co., Ltd.) aqueous solution was size-pressed to a coating amount of 1.5 g / m ² (dry weight solid content), and then 100 K
Super calendering was performed under a pressure of g / cm ² to obtain a reversible thermosensitive recording paper base paper having a basis weight of 60 g / m ² .

2-anilino-3-methyl-6-N-cyclohexyl-N-methylfluorane 80 parts N- (4-hydroxyphenyl) -N′-octadecylurea 200 parts 10% aqueous polyvinyl alcohol solution 224 parts (trade name) Gocelan L-3266, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) Water 896 parts The above mixed dispersion liquid was ball-milled to have an average particle diameter of 1 μm.
The resulting mixture was pulverized to obtain a 20% color developer / reversible color developer mixed pulverized liquid (A). After mixing 1.5 parts of 40% sodium polyacrylate aqueous solution (trade name; Aron T-40, manufactured by Toagosei Kagaku Co., Ltd.) with 100 parts of water, magnesium carbonate (trade name: Venus, Kajima Kagaku Co., Ltd.) 100 parts) was gradually added and dispersed, and 20% color developer / reversible color developer mixed pulverized liquid (A) 1400 parts, 10% polyvinyl alcohol (trade name; Gohsenol NM-11, Nippon Synthetic Chemical Industry Co., Ltd.)
1000 parts of aqueous solution and 1240 parts of diluting water were sequentially mixed to obtain a 12.5% reversible reversible thermosensitive coating solution. A coating amount of 4 g / m ^{2 of} this coating solution was applied onto the base paper obtained above.
After coating and drying with an air knife coater so as to have a (dry weight solid content), soft calendering was performed under a pressure condition of 40 kg / cm ² to provide a reversible thermosensitive layer.

40 parts of 50% magnesium carbonate (Venus) dispersion in 1525 parts of water, 1000 parts of 10% polyvinyl alcohol (Gothenol NM-11) aqueous solution, 30%
35 parts of a polyamide-epichlorohydrin resin aqueous solution were sequentially mixed to obtain a 5% coating solution for protective layer. This coating solution was coated on the heat-sensitive layer obtained above by an air knife coater so that the coating amount was 1.2 g / m ² (dry weight solid content), and then under a pressure of 40 Kg / cm ^2. A soft reversible thermosensitive recording paper was prepared by soft-calendering.

Example 2 2-anilino-3-methyl-6-N-cyclohexyl-N-methylfluorane 80 parts N- (4-fodoxyphenyl) -N'-octylurea 150 parts 10% polyvinyl alcohol (goselan L-3266) Aqueous solution 184 parts Water 736 parts The above mixed solution was pulverized by a ball mill until the average particle diameter became 1 μm, to obtain a 20% color developer / reversible developer mixed pulverized solution (B). To 730 parts of water, 40 parts of 50% magnesium carbonate (Venus) dispersion, 20% of 20% color developer / reversible developer dispersion (B), and 400 parts of 10% aqueous solution of polyvinyl alcohol (Gothenol NM-11) are sequentially mixed. Thus, a 12.5% reversible heat-sensitive layer coating solution was obtained. This coating solution was coated on the base paper of Example 1 with an air knife coater so that the coating amount was 2 g / m ² (dry weight solid content), dried, and then soft calendered under a pressure condition of 30 kg / cm ^2. Then, a reversible thermosensitive layer was provided. 20 parts of 50% magnesium carbonate (Venus) dispersion in 1346 parts of water, 10%
A polyvinyl alcohol (Gosenol NM-11) aqueous solution (1000 parts) and a 30% polyamide-epichlorohydrin resin aqueous solution (35 parts) were sequentially mixed to obtain a 5% protective layer coating solution. This coating solution was coated on the heat-sensitive layer obtained above with an air knife coater so that the coating amount was 1 g / m ² (dry weight solid content), and then soft under a pressure condition of 30 Kg / cm ^2. A reversible thermosensitive recording paper was prepared by calendering.

Example 3 2-anilino-3-methyl-6-N-cyclohexyl-N-methylfluorane 150 parts N- (4-hydroxyphenyl) -N'-henicosylurea 250 parts 10% polyvinyl alcohol (Goselan L -3266) Aqueous solution 320 parts Water 1280 parts The above mixed solution was pulverized by a ball mill until the average particle size became 1 μm, to obtain a 20% color developer / reversible developer mixed pulverized solution (C). To 1260 parts of water, 100 parts of 50% magnesium carbonate (Venus) dispersion, 2000 parts of 20% color developer / reversible color developer mixed pulverized liquid (C), 1200 parts of 10% aqueous solution of polyvinyl alcohol (Gothenol NM-11) are sequentially added. A 12.5% reversible heat-sensitive layer coating liquid was obtained by mixing.
This coating solution was applied onto the base paper of Example 1 in an amount of 6 g / m ^2.
60K after coating and drying to achieve (dry weight solid content)
Soft calendering was performed under a pressure of g / cm ² to provide a reversible thermosensitive layer. 80 parts of 50% magnesium carbonate (Venus) dispersion in 1885 parts of water, 1000 parts of 10% polyvinyl alcohol (Gohsenol NM-11) aqueous solution
Parts, and 35 parts of a 30% polyamide-epichlorohydrin resin aqueous solution were sequentially mixed to obtain a 5% protective layer coating solution. The coating amount of this coating liquid on the heat-sensitive layer obtained above was 1.5 g /
A reversible thermosensitive recording paper was prepared by applying and drying with an air knife coater so as to have a m ² (solid content by dry weight), and then performing soft calendar finishing under a pressure condition of 60 Kg / cm ² .

Example 4 LBKP (freeness: 250 ml) 900 parts NBKP (freeness: 250 ml) 100 parts Heavy calcium carbonate 250 parts Alkyl ketene dimer 2 parts Cationic starch 2 parts Yield improver (polyacrylamide) 0.6 parts 4.5% of the compounded 1% slurry was made on a Fourdrinier paper machine.
% Oxide starch (Nissan MS-3800) aqueous solution was size pressed to a coating amount of 1.5 g / m ² (dry weight solid content), and then supercalendered under a pressure of 50 Kg / cm ^2. This was performed to obtain a reversible thermosensitive recording paper base paper having a basis weight of 60 g / m ² . The 12.5% reversible heat-sensitive layer coating solution of Example 1 was applied onto the base paper obtained above at a coating amount of 3 g /
After coating and drying with an air knife coater so as to have a m ² (solid content by dry weight), soft calendering was performed under a pressure condition of 25 Kg / cm ² to provide a reversible thermosensitive layer. On the heat-sensitive layer, the 5% protective layer coating solution of Example 1 was applied and dried with an air knife coater so that the coating amount was 1 g / m ² (dry weight solid content), and then 30 Kg / cm ²
A reversible thermosensitive recording paper was prepared by soft calendering under the pressure condition of.

Example 5 On the base paper of Example 4, the 12.5% reversible heat-sensitive layer coating solution of Example 3 was aired to a coating amount of 4.5 g / m ² (dry weight solid content). After coating and drying with a knife coater, soft calendering was performed under a pressure of 40 Kg / cm ² to provide a reversible heat-sensitive layer. On the heat-sensitive layer, the coating liquid for the 5% protective layer of Example 3 was applied in an amount of 1.2 g /
A reversible thermosensitive recording paper was prepared by applying and drying with an air knife coater so as to have a m ² (dry weight solid content), and then performing soft calendar finishing under a pressure condition of 40 Kg / cm ² .

Example 6 LBKP (freeness; 300 ml) 900 parts NBKP (freeness; 300 ml) 100 parts Rosin size 5 parts Sulfuric acid band 18 parts Talc 50 parts Polyacrylamide 4.5 parts 1.2% slurry of the above composition is long-meshed. Papermaking with a paper machine,
A 3.5% aqueous solution of oxidized starch (eclipse MS-3800) was added to 1.
It was size-pressed to 5 g / m ² (dry weight solid content) and subjected to supercalendering under a pressure of 110 Kg / cm ² to obtain a reversible thermosensitive recording paper base paper having a basis weight of 60 g / m ^2. A reversible thermosensitive recording paper was prepared by providing a reversible thermosensitive layer and a protective layer in the same manner as in Example 1 except for the above.

Example 7 A reversible thermosensitive recording sheet having a reversible thermosensitive layer and a protective layer formed by the same method except that the base paper for reversible thermosensitive recording paper of Example 2 was replaced with the base paper of Example 6. It was created.

Example 8 A reversible thermosensitive recording paper was prepared by providing a reversible thermosensitive layer and a protective layer in the same manner except that the base paper for reversible thermosensitive recording paper of Example 3 was replaced with the base paper of Example 6. It was created.

Example 9 After mixing 1.5 parts of a 40% sodium polyacrylate (Aron T-40) aqueous solution with 100 parts of water, 100 parts of magnesium carbonate (Venus) was added and dispersed, and then 10% polyvinyl alcohol (goshenol) was added. NM-11) 200 parts aqueous solution,
180 parts of diluting water was sequentially mixed to obtain a 25% intermediate layer coating solution. This coating solution was applied between the base paper of Example 1 and the reversible heat-sensitive layer with an air knife coater so that the applied amount was 4 g / m ² (dry weight solid content), and then dried at 50 kg / c.
A reversible thermosensitive recording paper was prepared by providing a reversible thermosensitive layer and a protective layer in the same manner as in Example 1 except that soft calendering was performed under a pressure of m ² .

Example 10 A reversible thermosensitive layer and a protective layer were provided by the same method except that the coating solution for the intermediate layer of Example 9 was provided as an intermediate layer between the base paper of Example 2 and the reversible thermosensitive layer. A reversible thermosensitive recording paper was prepared.

Example 11 A reversible heat-sensitive layer and a protective layer were provided by the same method except that the coating solution for the intermediate layer of Example 9 was provided as an intermediate layer between the base paper of Example 3 and the reversible heat-sensitive layer. A reversible thermosensitive recording paper was prepared.

Comparative Example 1 A reversible thermosensitive layer and a protective layer were provided in the same manner as in Example 1 except that the super calendering after size pressing in the base paper making process for reversible thermosensitive recording paper was not carried out. A thermosensitive recording paper was prepared.

Comparative Example 2 A reversible thermosensitive recording paper was prepared in the same manner as in Example 1 except that soft calendering was not performed in the step of providing the protective layer on the reversible thermosensitive layer.

Comparative Example 3 LBKP (freeness; 350 ml) 950 parts NBKP (freeness; 350 ml) 50 parts Rosin size 7 parts Sulfuric acid band 21 parts Talc 90 parts Polyacrylamide 3 parts A 1.2% slurry of the above composition is fourdrinier paper machine. Papermaking with 6
% Oxide starch (Nissan MS-3800) aqueous solution was size pressed to a coating amount of 1.5 g / m ² (dry weight solid content), and then supercalendered under a pressure of 50 Kg / cm ^2. This was carried out to obtain a reversible thermosensitive recording layer base paper having a basis weight of 60 g / m ² . The reversible heat-sensitive layer coating solution of Example 1 was applied to the base paper obtained above using an air knife coater so that the coating amount was 4.5 g / m ² (dry weight solid content), and then 20 kg / m ² Soft calendering was performed under a pressure of cm ² to provide a reversible thermosensitive layer. On the heat-sensitive layer obtained above, the coating solution for protective layer of Example 1 was applied and dried by an air knife coater so that the coating amount was 1 g / m ² (dry weight solid content), and then 50 kg / cm ²
A reversible thermosensitive recording paper was prepared by soft calendering under the pressure condition of.

Comparative Example 4 LBKP (freeness; 100 ml) 300 parts NBKP (freeness; 100 ml) 700 parts Polyacrylamide 2 parts Talc 20 parts 1.2% slurry of the above composition was made into paper by a Fourdrinier paper machine,
A 3.8% aqueous solution of oxidized starch (eclipse MS-3800) was size-pressed to a coating amount of 1.5 g / m ² (dry weight solid content), and then super pressed under a pressure of 150 Kg / cm ^2. Calendering was performed to obtain a reversible thermosensitive recording paper base paper having a basis weight of 60 g / m ² . The reversible heat-sensitive layer coating solution of Example 1 was applied onto the base paper obtained above at a coating amount of 3 g / m ^2.
After coating and drying with an air knife coater so as to have (dry weight solid content), soft calendering was performed under a pressure condition of 30 kg / cm ² to provide a reversible thermosensitive layer. On the heat-sensitive layer obtained above, the coating amount of the coating solution for protective layer of Example 1 was 1. 30K after coating and drying with an air knife coater to ² g / m ² (dry weight solid content)
A reversible thermosensitive recording paper was prepared by soft calendering under a pressure of g / cm ² .

Comparative Example 5 Reversible thermosensitive recording was carried out by providing a reversible thermosensitive layer and a protective layer in the same manner except that the intermediate layer of Example 9 was provided between the base paper of Comparative Example 4 and the reversible thermosensitive layer. I made paper.

Comparative Example 6 100 parts of magnesium carbonate (Venus) of the coating solution for the reversible thermosensitive layer of Example 1 was replaced with heavy calcium carbonate (trade name; Softon # 2200, manufactured by Shiraishi Industry Co., Ltd.) in the same amount. A reversible thermosensitive recording paper was prepared by providing a reversible thermosensitive layer and a protective layer in the same manner except for the above.

Comparative Example 7 40 parts of a 50% magnesium carbonate (Venus) dispersion of the reversible heat-sensitive layer coating solution of Example 2 was mixed with 50% light calcium carbonate (trade name: Tamapearl TP222H; Okutama Industry Co., Ltd.).
A reversible thermosensitive recording paper was prepared by providing a reversible thermosensitive layer and a protective layer in the same manner except that the same amount of the dispersion liquid was replaced.

Comparative Example 8 100 parts of a 50% magnesium carbonate (Venus) dispersion of the coating solution for the reversible heat-sensitive layer of Example 3 was mixed with 50% titanium dioxide (trade name: Typake A-220; manufactured by Ishihara Industry Co., Ltd.). A reversible thermosensitive layer was prepared in the same manner except that the same amount of the dispersion was replaced.
A reversible thermosensitive recording paper was prepared by providing a protective layer.

Comparative Example 9 The same as in Example 1 except that 40 parts of the 50% magnesium carbonate (Venus) dispersion of the protective layer coating solution was replaced with the same amount of 50% heavy calcium carbonate (Softon # 2200) dispersion. A reversible thermosensitive recording paper was prepared by providing a reversible thermosensitive layer and a protective layer by the method.

Comparative Example 10 The same method was used except that 20 parts of 50% magnesium carbonate (Venus) dispersion in the protective layer coating solution of Example 2 was replaced with 50% light calcium carbonate (Tamapearl TP222H) dispersion. A reversible thermosensitive recording paper was prepared by providing a reversible thermosensitive layer and a protective layer.

Comparative Example 11 The same method was used except that 80 parts of 50% magnesium carbonate (Venus) dispersion of the coating solution for protective layer of Example 3 was replaced with 50% titanium dioxide (Taipaque A-220) dispersion. A reversible thermosensitive recording paper was prepared with.

[Test Method] Examples 1 to 11 and Comparative Examples 1 to 1
The reversible thermosensitive recording paper obtained in No. 11 was measured by the following test method, and the results are shown in Tables 1 and 2 and Tables 3 and 4. * Measured pressure conditions 20 Kg / cm ² under the smoothness of a pressurized condition 20 Kg / cm ² under the smoothness of the air leakage type paper smoothness tester Parker purine de Surf (PPS), the fine irregularities It is shown in μm value. The smaller the μm value is, the better the smoothness is. * Printed color density The color density printed by the high speed mode (density dial; max) of the word processor WD-A560 manufactured by Sharp Corp. is a densitometer (using the Ambe filter manufactured by Macbeth Corp.).
It was measured at. The higher the value, the higher the print density. * Printed surface quality The printed surface quality when printed with the above word processor was visually inspected, and the evaluation results are shown by ○ and × marks. ○: No character breaks and excellent surface quality. X mark: The characters are cut off, misread and inferior. * Whiteness Measured with a densitometer (same as above). The smaller the value, the higher the whiteness. * Decoloring property The sheet colored with the above word processor was passed through a 110 ° C hot roll to decolor the colored part, and the density of the decolorized part was measured with a densitometer (the same as above). The smaller the value, the better the erasability.

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[Table 1]

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[Table 2]

[0050]

[Table 3]

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[Table 4]

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INDUSTRIAL APPLICABILITY In a reversible thermosensitive recording paper having a reversible thermosensitive layer and a protective layer provided on a base paper, as is apparent from the present invention, the surface of the thermosensitive layer is an air leak type paper smoothness meter (PPS). When the measured value is 3.8 μm or less under a pressure condition of 20 Kg / cm ² , and the surface of the protective layer is 4 μm or less under a pressure condition of 20 Kg / cm ² , the printing surface quality is improved, and accordingly the printing is performed. The density was excellent, and a reversible thermosensitive recording paper suitable as a word processor / printer paper for OA could be provided.

Claims (1)

[Claims] 1. A reversible thermosensitive layer comprising an electron-donating dye, which is usually colorless or light-colored, and an electron-accepting acidic substance having a reversibility that develops and decolors by heating the dye on a base paper, and an upper layer thereof. In the reversible thermosensitive recording paper provided with a protective layer, the surface of the thermosensitive layer has an air leak type paper smoothness meter (Parker Print Surf) measurement value of 3.8 μm or less under a pressure condition of 20 kg / cm ² . The surface of the protective layer is under the pressing condition 2
A reversible thermosensitive recording paper characterized by having a thickness of 4 μm or less under 0 kg / cm ² .