JPH047718B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to thermal recording paper, and more particularly, it relates to a thermosensitive recording paper, and more specifically, to a thermosensitive recording paper, and more particularly to a heat-sensitive recording paper, it relates to a normally colorless or light-colored electron-donating dye and an electron-accepting dye that develops color by reacting with the electron-donating dye. Related to thermal recording paper containing substances (prior art) Electron-donating colorless dye precursor (hereinafter referred to as color former) and electron-accepting compound (hereinafter referred to as color developer)
Heat-sensitive recording paper for producing a recorded image by reacting with heat is disclosed in Japanese Patent Publication No. 45-14039, Japanese Patent Publication No. 43-4160, etc. In recent years, these thermal recording papers are
It has been used in electronic computers, terminal printers for various measuring devices, facsimile recording devices, etc. On the other hand, a drawback of thermal recording paper is that when various chemicals, oils, etc. adhere to it, the recorded image may become discolored or fog may occur. These drawbacks are a serious problem in practice, and improvements are desired. For the purpose of these improvements, a protective layer is provided on the heat-sensitive layer. Thermal recording paper provided with a protective layer is disclosed in, for example, JP-A-48-30347 and JP-A-Sho.
No. 48-31958, Japanese Patent Publication No. 1984-1984, Japanese Patent Publication No. 1984-
No. 14751, JP-A-54-53545, JP-A-54-111837
No., JP-A-54-128349, JP-A-56-126193,
JP-A-56-139993, JP-A-57-10530, JP-A-57-29491, JP-A-57-105392, JP-A-57
−107884, JP-A-58-53484, JP-A-58-
It is disclosed in No. 193189, etc. In addition, by providing a back coat layer consisting of a water-soluble polymer binder and an inorganic organic pigment on the back surface of the support, running properties on actual machines can be improved, sheet curl can be corrected, and chemical resistance can be imparted from the back surface. The commercial value of the thermal paper provided with the above-mentioned protective layer can be improved. However, the conventional back coat layer has poor water resistance due to the water-soluble polymer binder contained therein, and the back coat layer swells under high humidity, resulting in poor adhesion between the front and back surfaces (hereinafter referred to as blocking). ), which has the disadvantage of damaging the product value. As a countermeasure to this problem, the use of an alkali salt of isobutylene-maleic anhydride copolymer has been disclosed (Japanese Patent Laid-Open No. 59-9091), but this is insufficient in terms of water resistance. (Object of the Invention) An object of the present invention is to provide a heat-sensitive recording paper that improves the above-mentioned drawbacks of the conventional back layer and has excellent water resistance, less occurrence of blocking, and improved sheet curling and running properties. be. (Structure of the Invention) The heat-sensitive recording paper according to the present invention comprises a heat-sensitive recording layer containing an electron-donating dye precursor, which is usually colorless or light-colored, and an electron-accepting substance that develops color by reacting with the electron-donating dye precursor. , is a heat-sensitive recording paper having a protective layer on a support that contains a water-soluble polymeric binder and a pigment on the recording layer, and contains an alkali salt of a styrene-maleic acid copolymer on the back side of the support. This is a heat-sensitive recording paper characterized by having a back coat layer. To form the back coat layer of the present invention, a coating layer containing a styrene-maleic acid copolymer alkali salt is applied to the back surface of the support. Examples of the styrene-maleic acid copolymer alkali salt used in the back coat layer of the present invention include styrene-maleic acid copolymer sodium salt and styrene-maleic acid copolymer ammonium salt. It is a polymeric ammonium salt. The degree of polymerization of the styrene-maleic acid copolymer alkali salt is preferably 500 to 5000, particularly 1500 to 2500.
Preferably, the range is . Further, a part of the ammonium salt may be esterified, and the degree of esterification is preferably 35% to 50%. The back coat layer of the thermal recording paper according to the present invention preferably contains a pigment. Preferred pigments include inorganic pigments such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, waxite, kaolin, calcined kaolin, and aluminum hydroxide, and organic pigments such as urea-formalin resin and polyethylene. The coating amount (dry weight) of the back coat layer is 0.2
~5.0 g/ ^m2 , preferably 0.2-3.0 g/ ^m2 .
Further, the amount of the styrene-maleic acid copolymer alkali salt in the back coat layer is 10 to 200% by weight, more preferably 25 to 75% by weight of the pigment. In addition, in order to satisfy running properties on actual machines, the smoothness of the back coat layer is preferably 30 to 500 seconds (JIS P8119), most preferably 80 to 150 seconds (JIS P8119). A surfactant may be added to the coating liquid for stability and defoaming of the coating liquid after dispersion. In order to form the heat-sensitive coloring layer of the present invention, in addition to the coloring agent (leuco dye) and color developer that are usually used in this field, thermofusible substances, organic or inorganic pigments, binders, etc. are added as necessary. A coating layer containing the material is applied to a paper or synthetic resin film base. The color former and the color developer are each separately dispersed in a water-soluble polymer (binder) using a means such as a ball mill. The ether compound of the present invention can be similarly dispersed, or it can be mixed with a color forming agent or developer in advance and then dispersed at the same time. Dispersion is determined by the volume average particle size.
Continue until the thickness is 5 μm or less, more preferably 2 μm.
Continue until it becomes less than m. After dispersion, the three components are mixed to form a heat-sensitive coating liquid. Color formers used in the present invention include triarylmethane compounds, diphenylmethane compounds,
Examples include xanthene compounds, thiazine compounds, and spiropyran compounds. Some examples of these include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (i.e. crystal violet lactone), 3,3-
bis(p-dimethylaminophenyl) phthalide,
3-(p-dimethylaminophenyl)-3-(1,
3-dimethylindol-3-yl)phthalide,
3-(p-dimethylaminophenyl)-3-(2-
methylindol-3-yl) phthalide, etc. Diphenylmethane compounds include 4,
4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl leuco auramine, N-2,4,5-trichlorofer leuco auramine, etc., xanthene compounds rhodamine (p-nitroanilino) lactam, rhodamine B(p-chloroanilino)lactam, 2-dibenzylamino-6-diethylaminofluorane, 2
-anilino-6-diethylaminofluorane, 2
-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-N-
cyclohexyl-N-methylaminofluorane,
2-anilino-3-methyl-6-N-ethyl-N
-isoamylaminofluorane, 2-o-chloroanilino-6-diethylaminofluorane, 2-
m-chloroanilino-6-diethylaminofluorane, 2-(3,4-dichloroanilino)-6-diethylaminofluorane, 2-octylamino-
6-diethylaminofluorane, 2-dihexylamino-6-diethylaminofluorane, 2-m
-Trichloromethylnilino-6-diethylaminofluorane, 2-butylamino-3-chloro-6
-diethylaminofluorane, 2-ethoxyethylamino-β-chloro-6-diethylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-diphenylamino-6
-diethylaminofluorane, 2-anilino-3
-Methyl-6-diphenylaminofluorane, 2
-anilino-3-methyl-5-chloro-6-diethylaminofluorane, 2-anilino-3-methyl-6-diethylamino-7-methylfluorane, 2-aniline-3-methoxy6-dibutylaminofluorane, 2 -o-chloroanilino-6-
Dibutylaminofluoran, 2-p-chloroanilino-3-ethoxy-6-diethylaminofluoran, 2-phenyl-6-diethylaminofluoran, 2-o-chloroanilino-6-p-butylanilinofluoran, 2-anilino -3-pentadecyl-6-diethylaminofluorane, 2-anilino-3-ethyl 6-dibutylaminofluorane, 2-anilino-3-ethyl-6-N-ethyl-N-isoamylaminofluorane, 2-anilino- 3-Methyl-6-N-ethyl-N-γ-methoxypropylaminofluorane, 2-anilino-
3-phenyl-6-diethylaminofluorane,
2-diethylamino-3-phenyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-N-isoamyl-N-ethylaminofluoran, etc. Thiazine compounds include benzoylleucomethylene blue, p-nitro There are benzylleucomethylene blue, etc., and spiro-based compounds include 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,
3'-dichloro-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methyl-naphtho-(3-methoxy-benzo)-spiropyran,
Examples include 3-propyl-spiro-dibenzopyran. These may be used alone or in combination. The color developer used in the present invention includes 2,2-bis(4'-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxyphenyl)pentane, and 2,2-bis(4'-hydroxyphenyl)pentane. (4'-hydroxy-3',5'-dichlorophenyl)propane, 1,
1-bis(4'-hydroxyphenyl)cyclohexane, 2,2-bis(4'-hydroxyphenyl)
Hexane, 1,1-bis(4'-hydroxyphenyl)propane, 1,1-bis(4'-hydroxyphenyl)butane, 1,1-bis(4'-hydroxyphenyl)pentane, 1,1 -bis(4'-hydroxyphenyl)hexane, 1,1-bis(4'-hydroxyphenyl)heptane, 1,1-bis(4'-hydroxyphenyl)octane, 1,1-
Bis(4'-hydroxyphenyl)-2-methyl-
Bisphenols of pentane, 1,1-bis(4-hydroxyphenyl)-2-ethyl-hexane, 1,1-bis(4'-hydroxyphenyl)dodecane, 3,5-di-α-methylbenzyl salicylic acid,
3,5-Di-tert-siabutylsalicylic acid, 3-
Salicylic acids such as α,α-dimethylbenzylsalicylic acid or polyvalent metal salts thereof (particularly preferred are zinc and aluminum), p-hydroxybenzoic acid benzyl ester, p-hydroxybenzoic acid benzyl ester, p-hydroxybenzoic acid benzyl ester,
Examples include oxybenzoic acid esters such as -hydroxybenzoic acid-2-ethylexyl ester, and phenols such as p-phenylphenol, 3,5-diphenylphenol, and cumylphenol, with bisphenols being particularly preferred. . The binder is preferably a compound that dissolves 5% or more in water at 25°C, specifically methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, starches, gelatin, gum arabic, casein, styrene-maleic anhydride copolymer. Examples include a combined hydrolyzate, an ethylene-maleic anhydride copolymer hydrolyzate, an isobutylene-maleic anhydride copolymer hydrolyzate, polyvinyl alcohol, and carboxy-modified polyvinyl alcohol. Oil-absorbing pigments include inorganic pigments such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, waxite, kaolin, aluminum hydroxide, calcined kaolin, urea-formalin resin, polyethylene powder, and organic pigments. is used. As the metal soap, higher fatty acid metal salts are used, such as zinc stearate, calcium stearate, aluminum stearate, and the like. Waxes include polyethylene wax,
Carnauba wax, paraffin wax, microcrystalline wax, fatty acid admixture, etc. are used. Antioxidants, ultraviolet absorbers, image storage improvers, etc. can be added to this as necessary. Examples of image storage improvers include phenols or derivatives thereof in which at least one of the 2nd or 6th positions is substituted with an alkyl group, and among these, one or more of the 2nd or 6th positions is substituted with a branched alkyl group. phenols or derivatives thereof are preferred. Moreover, those having a plurality of phenol groups in the molecule are preferable, and those having 2 to 3 phenol groups are particularly preferable. The coating solution is applied to a support such as neutral paper, high-quality paper, or plastic film and dried. When preparing a coating liquid, all the components may be mixed and pulverized at the same time from the beginning, or they may be combined in appropriate combinations, pulverized and dispersed separately, and then mixed. To form the protective layer according to the present invention, a coating layer consisting of a water-soluble polymeric binder and an inorganic or organic pigment is applied onto the thermochromic layer. Examples of the water-soluble polymer binder include polyvinyl alcohol, methyl cellulose, starch, carboxymethyl cellulose, styrene-maleic acid copolymer, diisobutylene-maleic acid copolymer, polyamide resin, polyacrylamide resin, and the like. As the pigment, inorganic pigments such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, waxite, kaolin, calcined kaolin, and aluminum hydroxide, and organic pigments such as urea-formalin resin and polyethylene powder are used. The amount of protective layer applied (dry weight) is 0.2 to 5.0 g/
^m2 is preferably 0.5 to 3 g/ ^m2 . If the coating amount is too low, the resistance to various chemicals, which is the object of the present invention, will be lowered, and if the coating amount is too large, the thermal responsiveness of the heat-sensitive coloring layer will be poor, so the coating amount is determined depending on the requirements for both performances. (Examples of the Invention) Examples will be shown below, but the present invention is not limited to these examples. Example 1 Preparation of coating liquid for heat-sensitive recording layer Color former, 2-anilino-3methyl-6-
10g of N-cyclohexyl-N-methylaminofluorane, 10% polyvinyl alcohol (saponification degree 98
%, degree of polymerization 1000) and 25 g of water in a ball mill overnight to obtain dispersion A. Similarly, 10 g of benzyl p-oxybenzoate, 5 g of 2,2'-methylene-bis-(4-methyl-6-Tert-butylphenol), 15 g of calcium carbonate (Brilliant 15, manufactured by Shiraishi Kogyo), 10% polyvinyl alcohol ( Saponification degree 98%, polymerization degree 1000) 25g of aqueous solution
The mixture was dispersed with 50 g of water in a ball mill for one day to obtain a dispersion (B). Mix dispersion liquid (A) and dispersion liquid (B) at a weight ratio of 1:3, and then add 15 g of 21% zinc stearate dispersion to 200 g of the mixed liquid and sufficiently disperse to prepare a heat-sensitive coating liquid. did. The prepared coating liquid was applied onto a base paper having a basis weight of 47 g/m ² so that the solid content was 5 g/m ² and then heated at 60°C for 1 hour.
This was dried for a minute to prepare a base thermosensitive recording paper. On this heat-sensitive color forming layer, a coating layer coating liquid consisting of the following formulation was applied to obtain a coating amount of 2.5 g/m ² in terms of solid content, dried at 50°C for 2 minutes to form a coating layer, and then calendered. Processed to achieve smoothness of 850 seconds (JIS
P8119) was obtained. Coating layer coating liquid 100 g of 10% polyvinyl alcohol, 25 g of 40% kaolin (kaobrite), and 40 g of water were mixed and dispersed to obtain a coating liquid. On the back side of the thermal recording paper obtained as described above, a back coat layer coating liquid consisting of the following composition is applied in solid form.
Apply to obtain a coating amount of 2.5g/ ^m2 ,
℃ for 2 minutes to form a back coat layer to obtain the thermal recording paper of the present invention. Back coat layer coating liquid 25% styrene maleic anhydride copolymer ammonium salt (manufactured by Arakawa Chemical, Polymalon 385, polymerization degree
2000) 15g, 50% calcium carbonate (Shiraishi Kogyo,
12.5 g of Brilliant 15) dispersion and 12.5 g of water were mixed to prepare a dispersion. Example 2 A thermosensitive recording paper was obtained in Example 1 except that the back coat layer was changed as follows. 25% styrene-maleic acid copolymer sodium salt (Screepset, manufactured by Monsanto) 15g, 50
% calcium carbonate and 12.5 g of water were mixed to prepare a dispersion. Example 3 A thermosensitive recording paper was obtained in Example 1 except that the back coat layer was changed as follows. 25% styrene-maleic acid copolymer ammonium salt partial esterified product (SMA1440, manufactured by ARCO Chemical) 15g, 50% calcium carbonate 12.5g, water
12.5g of the above were mixed to form a dispersion. Comparative Example 1 A thermosensitive recording paper was obtained in Example 1 except that the back coat layer was changed to the following. A dispersion was prepared by mixing 30 g of 10% polyvinyl alcohol (manufactured by Kuraray, saponification degree 98%, polymerization degree 1000), 10 g of a 40% kaolin dispersion (Kaobrite, manufactured by Shiraishi Industries), and 32.5 g or more of water. Comparative Example 2 A thermosensitive recording paper was obtained in Example 1 except that the back coat layer was changed to the following. 25% diisobutylene-maleic acid copolymer ammonium salt (isoban 04, manufactured by Kuraray) 15g, 50%
12.5 g of calcium carbonate and 12.5 g or more of water were mixed and dispersed. Comparative Example 3 A thermosensitive recording paper was obtained in Example 1 except that the back coat layer was changed to the following. 20% starch (MS-4600 manufactured by Solar Eclipse) 10g, 50
% calcium carbonate and 17 g of water were mixed and dispersed. Comparative Test A comparative test of the heat-sensitive recording papers obtained in Examples and Comparative Examples was conducted as follows. (1) Blocking 0.5 μm of water was dropped on the surface of the recording paper, the base paper was placed on top of it, and after being air-dried for 1 hour, it was peeled off and the strength of the adhesion between the recording paper and the base paper was examined. It is better not to glue. The evaluation is expressed as good, fair, or poor. (2) Sheet curl A4 size recording paper at 30℃ and 90℃ in a constant temperature and humidity room.
% for 1 hour, then 25°C and 65% for 1 hour, and then 20°C and 35% for 1 hour, then the heights of the four corners of the recording paper were measured and evaluated as an average. The evaluation was expressed using the numbers below. −←±→＋ Curling on the back coated surface Almost no curling Curling on the thermosensitive coloring layer (3) Runnability The thermal recording paper obtained as above was printed using a thermal facsimile machine (Matsushita Densen, UF-920). We printed, stamped, and tested adhesion to the platen roll. The results are shown in Table 1, and it can be seen that the thermal recording paper according to the present invention is excellent in terms of sticking, blocking, and sheet curl. 【table】

Claims (1)

[Claims] 1. A heat-sensitive recording layer containing a normally colorless or light-colored electron-donating dye precursor and an electron-accepting substance that develops color by reacting with the electron-donating dye precursor, and a water-soluble polymer binder on the recording layer. 1. A heat-sensitive recording paper having a protective layer on a support containing a pigment and a back coat layer containing an alkali salt of a styrene-maleic acid copolymer on the back surface of the support.