JPH0662004B2 - Thermal recording paper - Google Patents

Description

The present invention relates to a heat-sensitive recording paper, and more specifically, it is usually a colorless or light-colored electron-donating dye and an electron-accepting property which develops a color by reacting with the electron-donating dye. It relates to a thermosensitive recording paper containing a substance.

(Prior Art) A heat-sensitive recording paper for obtaining a recorded image by reacting an electron-donating colorless dye precursor (hereinafter referred to as a color former) and an electron-accepting compound (hereinafter referred to as a developer) by heating is disclosed in JP-B-45. -140
No. 39, Japanese Examined Patent Publication No. 43-4160 and the like.
In recent years, these thermal recording papers have been used for electronic computers, terminal printers of various measuring devices, facsimile recording devices, and the like.

On the other hand, a drawback of the heat-sensitive recording paper is that when various chemicals or oil adheres, the recorded image is discolored or fog occurs. These drawbacks are serious problems in practical use, and improvement is desired.

For the purpose of improving these, a protective layer is provided on the heat-sensitive layer. The heat-sensitive recording paper provided with a protective layer is described in, for example, JP-A-48-30347 and JP-A-48-3195.
No. 8, JP-A-53-19840, JP-A-54-147.
51, JP-A-54-53545, JP-A-54-11
1837, JP-A-54-128349, JP-A-56.
-126193, JP-A-56-139993, JP-A-57-10530, JP-A-57-29491, JP-A-57-105392, and JP-A-57-107884.
JP-A-58-53484, JP-A-58-1931
No. 89 and the like. Further, by providing a back coat layer composed of a water-soluble polymer binder and an inorganic organic pigment on the back surface of the support, the running property of the actual machine is improved and further,
The sheet curl can be straightened and chemical resistance from the back side can be imparted, and the commercial value of the thermal paper provided with the 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 swelling of the back coat layer under high humidity causes adhesion between the front surface and the back surface (hereinafter referred to as blocking). ) Occurred, and the commercial value was impaired. The use of an alkali salt of an isobutylene-maleic anhydride copolymer has been disclosed as a countermeasure (Japanese Patent Laid-Open No. 59-9091), but it is insufficient in water resistance.

(Object of the Invention) An object of the present invention is to provide a thermal recording paper which improves the above-mentioned drawbacks of the conventional backing layer, is excellent in water resistance, and has improved sheet curl and running property with less blocking. Is.

(Structure of the Invention) The heat-sensitive recording paper according to the present invention comprises a heat-sensitive recording layer containing a color-forming agent and a color-developed image that reacts with the color-forming agent to form a color image, and a water-soluble polymer binder on the recording layer. A heat-sensitive recording paper having a protective layer containing a pigment on a support, and a back coat layer containing colloidal silica on the back surface of the support.

To form the back coat layer of the present invention, a coating layer containing colloidal silica is applied to the back surface of the support.

The back coat layer of the thermal paper according to the present invention preferably contains a binder. As the binder, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, starches, gelatin, gum arabic,
Casein, styrene-maleic anhydride copolymer hydrolyzate, ethylene-maleic anhydride copolymer hydrolyzate, isobutylene-maleic anhydride copolymer hydrolyzate, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, etc. Dispersions of molecules and hydrophobic polymers such as styrene-butadiene rubber latex, acrylic resin emulsion and vinyl acetate emulsion can be used. A water-soluble polymer is particularly preferable. The amount of binder used is preferably not more than twice the weight of colloidal silica.

Further, the back coat layer of the thermal recording paper according to the present invention preferably contains a pigment. The pigment is preferably an inorganic pigment such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, wax, kaolin, calcined kaolin or aluminum hydroxide, or an organic pigment such as urea formalin resin or polyethylene.

The coating amount (dry weight) of the back coat layer is 0.2 to 5.
0 g / ^{m 2,} preferably from 0.2 to 3.0 g / ^{m 2.}

Further, in order to satisfy the running property of an actual machine, the smoothness of the back coat layer is preferably 30 to 500 seconds (JIS P8119), and particularly preferably 80 to 150 seconds (JISP8119).

A surfactant may be added to the coating liquid for stability and defoaming of the coating liquid after dispersion.

In order to form the thermosensitive color developing layer of the present invention, in addition to the color former and the color developer that are usually used in this field, if necessary, a coating containing a thermoplastic material organic or inorganic pigment, a binder, etc. is applied to a paper or synthetic paper. Apply to resin film base.

The color former and the developer are separately dispersed in the water-soluble polymer (binder) using a means such as a ball mill. The ether compound of the present invention is similarly dispersed, or pre-mixed with a color former or a developer and simultaneously dispersed. The dispersion is performed until the volume average particle diameter becomes 5 μm or less, and more preferably 2 μm or less. After the dispersion is completed, the three are mixed to form a heat-sensitive coating liquid.

Examples of the color former used in the present invention include triarylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds, spiropyran compounds, and the like. Examples of some of these include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (ie, crystal violet letolactone),
3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,
3-dimethylindol-3-yl) phthalide, 3-
(P-Dimethylaminophenal) -3- (2-methylindol-3-yl) phthalide and the like, and diphenylmethane compounds include 4,4'-bis-dimethylaminobenzhydrin benzyl ether and N-halophenyl. -Leuco auramine, N-2,4,5-trichlorophenyl leuco auramine and the like, and the xanthene compound rhodamine (p-nitroanilino) lactam, rhodamine B (p-chloroloanilino) 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-inilino-3-methyl-6-N-
Ethyl-N-isoamylaminofluorane, 2-o-chloroanilino-6-diethylaminofluorane, 2-m
-Chloroalinino-6-diethylaminofluorane, 2
-(3,4-Dichloroanilino) -6-diethylaminofluorane, 2-octylamino-6-diethylamanofluorane, 2-dihexylamino-6-diethylaminofluorane, 2-m-trichloromethylanilino-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-dibutyl Aminofluorane, 2-p-chloroanilino-3-ethoxy-6-diethylaminofluorane, 2-phenyl-
6-diethylaminofluorane, 2-o-chloroanilino-6-p-butylanilinofluorane, 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-Diethylaminofluorane, 2-anilino-3
-Methyl-6-N-isoamyl-N-ethylaminofluorane and the like, thiazine-based compounds include benzoylleuco methylene blue, p-nitrobenzyl leuco methylene blue and the like, 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, 3-propyl-spiro-dibenzopyran and the like. These may be used alone or as a mixture.

The color developer used in the present invention includes 2,2-bis (4 '
-Hydroxyphenyl) propane (bisphenol A), 2,2-bis (4-hydroxyphenyl) pentane, 2,2-bis (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-pentane, 1,1
-Bis (4'-hydroxyphenyl) -2-ethyl-hexane, bisphenols of 1,1-bis (4'-hydroxyphenyl) dodecane, 3,5-di-α-methylbenzylsalicylic acid, 3, 5-
Salicylic acids such as di-tert-butyl salicylic acid, 3-α, α-dimethylbenzyl salicylic acid or polyvalent metal salts thereof (particularly zinc and aluminum are preferable), p-hydroxybenzoic acid benzyl ester, p-hydroxybenzoic acid Examples thereof include oxybenzoic acid esters such as 2-ethylhexyl ester and phenols such as p-phenylphenol, 3,5-diphenylphenol, cumylphenol, and bisphenols are particularly preferable.

As the binder, a compound that is soluble in 5% or more in water at 25 ° C. is desirable, and specifically, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, starches, gelatin, gum arabic, casein, styrene-maleic anhydride copolymer Combined hydrolyzate,
Examples thereof include ethylene-maleic anhydride copolymer hydrolyzate, isobutylene-maleic anhydride copolymer hydrolyzate, polyvinyl alcohol, and carboxyl-modified polyvinyl alcohol.

As the oil-absorbing pigment, inorganic pigments such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, wax stone, kaolin, aluminum hydroxide, calcined kaolin, urea formalin resin, organic pigments such as polyethylon powder Is used.

As the metal soap, higher fatty acid metal salts are used, such as zinc stearate, calcium stearate, and aluminum stearate.

As the waxes, polyethylene wax, carnauba wax, paraffin wax, microcrystalline wax, fatty acid amide and the like are used.

If necessary, an antioxidant, a UV absorber, an image storability improver, etc. may be added thereto.

Examples of the image storability improver include phenols or derivatives thereof in which at least one of 2- or 6-positions is substituted with an alkyl group, and among them, at least one of 2- or 6-positions is substituted with a branched alkyl group. Preferred are phenols and their derivatives. Further, 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 liquid is applied and dried on a support such as neutral paper, high-quality paper, and plastic film. When preparing the coating liquid, all the components may be mixed and pulverized at the same time from the beginning, or may be pulverized and dispersed separately in an appropriate combination and then mixed.

To form the protective layer according to the present invention, a coating layer comprising a water-soluble polymer binder and an inorganic or organic pigment is coated on the thermosensitive coloring layer.

As the water-soluble polymer binder, polyvinyl alcohol,
Methyl cellulose, starch, carboxymethyl-cellulose, styrene-maleic acid copolymer, diisobutylene-
Examples thereof include maleic acid copolymers, polyamide resins, polyacrylamide resins and the like, and derivatives thereof.

As the pigment, inorganic pigments such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, lithopone, talc, wax, kaolin, calcined kaolin and aluminum hydroxide, and organic pigments such as urea formalin resin and polyethylene powder are used.

The coating amount (dry weight) of the protective layer is 0.2 to 5.0 g / m
² , preferably 0.5 to 3 g / m ² .

The lower the coating amount, the lower the resistance to various chemicals, which is the object of the present invention, and the higher the coating amount, the worse the thermal response of the thermosensitive color developing layer. Therefore, the coating amount is determined according to the requirements of both properties.

(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 thermosensitive recording layer 2-anilino-3-methyl-6-N-cyclohexyl-N-methylaminofluorane 10 g, which is a color former
0% polyvinyl alcohol (saponification degree 98%, polymerization degree 1
000) Dispersion liquid A was obtained by dispersing it together with an aqueous solution (25 g) and water (25 g) in a ball mill overnight. Similarly, 10 g of benzyl p-oxybenzoate, 2,2'-methylene-bis- (4
-Methyl-6-Tert-butylphenol) 5 g, calcium carbonate (manufactured by Shiraishi Kogyo, Brilliant 15) 15
25 g of an aqueous solution of 10% polyvinyl alcohol (saponification degree: 98%, polymerization degree: 1000) together with 50 g of water was dispersed in a ball mill for one day to obtain a dispersion liquid (B).

The dispersion liquid (A) and the dispersion liquid (B) were mixed at a weight ratio of 1: 3, and 15 g of a 21% zinc stearate dispersion liquid was added to 200 g of the mixed liquid and sufficiently dispersed to obtain a heat-sensitive coating liquid. It was adjusted.

The adjusted coating liquid was applied onto a base paper having a basis weight of 478 / m ² so that the solid content was 5 g / m ² and dried at 60 ° C. for 1 minute to prepare a base thermosensitive recording paper.

On the thermosensitive color-developing layer, a protective layer coating solution having the following composition was applied so as to obtain a coating amount of 2.5 g / m ² in solid form, and dried at 50 ° C. for 2 minutes to form a protective layer, Calendar processing was performed to obtain a heat-sensitive recording paper having a smoothness of 850 seconds (JIS P8119).

Protective Layer Coating Liquid 10% polyvinyl alcohol 100 g, 40% kaolin (caobrite) 25 g, and water 40 g were mixed and dispersed to obtain a protective layer coating liquid.

On the back surface of the thermal recording paper obtained as described above, a coating solution for the back coat layer having the following composition was added in a solid content of 2.5 g / m ^2.
Was applied to obtain a coating amount, and dried at 50 ° C. for 2 minutes to form a back coat layer to obtain a heat-sensitive recording paper of the present invention.

Back coat layer coating liquid 20% colloidal silica (manufactured by Nissan Kagaku Co., Ltd., Snowtex 20 particle size 10-20 mμ, pH 9.5-10) Example 2 In Example 1, the back layer was changed to the following to obtain a thermal recording paper.

20% colloidal silica (Snowtex C particle size 10-20 mμ, pH 8.5-9.0, manufactured by Nissan Kagaku) Example 3 In Example 1, the thermal recording paper was obtained by changing the back layer to the following.

25% styrene-maleic acid copolymer ammonium salt (manufactured by Arakawa Chemical Co., Polymalon 385, polymerization degree 2000)
1.5 g and 25 g of 20% colloidal silica (Snowtex C manufactured by Nissan Kagaku Co., Ltd.) were used as a mixed dispersion liquid.

Comparative Example 1 A thermal recording paper was obtained in the same manner as in Example 1, except that the back coat layer was changed to the following.

10% polyvinyl alcohol (Kuraray, saponification degree 98
%, Polymerization degree 1000) 30 g, 40% kaolin dispersion liquid (Caobrite, manufactured by Shiraishi Industry Co., Ltd.) 10 g, and water 32.5 g or more were mixed to prepare a dispersion liquid.

Comparative Example 2 In Example 1, the back coat layer was changed to the following to obtain a thermal recording paper.

15 g of 25% diisobutylene-maleic acid copolymer ammonium salt (Isoban 04, manufactured by Kuraray), 12.5 g of 50% calcium carbonate, and 12.5 g or more of water were mixed and dispersed.

Comparative Example 3 In Example 1, the back coat layer was changed to the following to obtain a thermal recording paper.

20% starch (manufactured by Solar Eclipse, MS-4600) 10 g, 5
6 g of 0% calcium carbonate and 17 g of water were mixed and dispersed.

Comparative Example 4 In Example 1, the back coat layer was changed to the following to obtain a thermal recording paper.

20% silica gel (trade name "Mizukasil P527, manufactured by Mizusawa Chemical Co., Ltd., particle size 1.7 μm) Comparative test Comparative experiments of the thermal recording papers obtained in Examples and Comparative Examples were carried out as follows.

(1) Blotting 0.5 μm of water was dropped on the surface of the recording paper, and the base paper was placed on top of it and air-dried for 1 hour, and the strength of adhesion between the peeled recording paper and the base paper was observed. Better not to glue.

The evaluation is expressed as good, good or bad.

(2) Sheet curl A4 size recording paper is 1 at 30 ° C and 90% in a constant temperature and humidity chamber.
After conditioning the humidity for 2 hours (at 25 ° C., 65% for 1 hour, further) at 20 ° C., 35% for 1 hour, the heights of the four corners of the recording paper were measured and averaged. The evaluation is represented by the following symbols.

(3) Runnability The thermal recording paper obtained as described above was printed with a thermal sensitive facsimile (Matsushita Electric Co., Ltd., UF-920) and tested for sticking and adhesion to a 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 sticking, blocking and sheet curl points.

Claims (1)

[Claims] 1. A heat-sensitive recording layer containing a colorless or light-colored electron-donating dye precursor and an electron-accepting substance that develops a color by reacting with the electron-donating dye precursor, and a water-soluble layer on the recording layer. A thermosensitive recording paper having a protective layer containing a polymer binder and a pigment on a support, wherein the backside of the support has a back coat layer containing colloidal silica.