JPS5934518B2 - Improved thermal recording paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal recording paper, and more particularly to a thermal recording paper with improved gas adhesion to a thermal recording head.

Thermal recording paper used in the present invention consists of electron acceptors such as leuco dyes, organic acids, and phenolic compounds, which are usually almost colorless, and which have the property of developing a deep color when they come into contact with electron acceptors, and furthermore, adjusting the color development sensitivity. A composition consisting of a sensitizer, a binder, and other auxiliary materials added for the purpose of preventing contamination, improving storage stability, improving coatability, etc. is coated on a base paper.

Thermal recording paper has become widely used in facsimile machines, computer terminals, calculator printers, thermal pen recorders for medical measurement equipment, and other applications.
It has high whiteness like plain paper.2 It has excellent paper quality such as stiffness, tear strength, and dimensional stability.3 It has a color development sensitivity that is compatible with the machine.4 It has little gas adhesion to the heat source.5 Thermal head 6. It is required to have low wear and good shelf life.

′ Conventionally, for thermal recording heads used in facsimiles, printers, etc., an electrode pattern is formed on a ceramic substrate, a resistive paste such as ruthenium oxide is applied and baked on top of this to form a resistive heating element, and a protective layer is further applied. A so-called thick film structure was mainly used.

However, in heads with this structure, most of the heat generated by the resistive heating element is dissipated through the substrate, resulting in poor thermal efficiency.
It also had the disadvantage of low resolution. Therefore, in recent years, so-called thin-film heads have attracted attention, in which a glass film for heat insulation is formed on a ceramic substrate, tantalum or the like is sputtered and photo-etched in a nitrogen atmosphere, electrodes are further deposited, and a protective layer is formed. There is.

By using a thin film head, thermal efficiency is improved, resolution is improved, and the recording speed is also increased because the current application time is less than 10 minutes. By the way, switching from a thick film head to a thin film head shortens the energization time, but the head surface temperature becomes very high, which causes the problem that gas adhesion to the head becomes more likely. As a result of intensive studies to improve gas adhesion, which has recently become a major problem, the present inventors have developed a heat-sensitive layer composition including a colorless leuco dye, an electron acceptor that causes the dye to develop color when heated, and a fusible sensitizer. A composition in which 3 to 0.01% (by weight) of an alkyl fluoride activator was further added to these together with an aqueous binder was used, and this was applied to the base paper, dried, and surface treated. It has been found that thermal recording paper has very little gas adhesion.

Moreover, by using a fluorinated alkyl activator, a uniform coating film with no uneven coating can be obtained, and even when a solid black image is produced, the image has no unevenness in shading and has excellent resolution. Image quality is obtained.

More surprisingly, this recording paper had excellent image storage stability under high humidity conditions, and had the characteristic that image density hardly decreased even under high temperature and high humidity conditions. Note that if the amount of the alkyl fluoride activator added is less than 0.01%, the above excellent effects will not be exhibited, while if it is added more than 3%, the effect will be saturated and there will be a cost inconvenience. Only profits will increase. Conventionally, silicone resin has been known as a mold release material, but when it was used as a paper processing agent for information recording paper, etc., there were many difficulties in its use due to repellency on the coated surface, dispersion stability, etc. . In fact, when silicone resin is added to the heat-sensitive layer composition, repellency can be seen on the painted surface,
Although the repelling phenomenon did not occur, unevenness occurred on the painted surface and the solid black image usually deteriorated.

Furthermore, there was little effect on improving head gas adhesion. The inventors of the present invention have conducted studies to improve the above points, and have found that at least one of each of a colorless dye, an electron acceptor that causes the dye to develop color when heated, a fusible sensitizer, and a water-soluble binder has been developed. Furthermore, 5% to 0.1% (by weight) of a dimethylpolysiloxane aqueous dispersion and 3% to 0.001% of the heat-sensitive composition containing the dimethylpolysiloxane aqueous dispersion.
(by weight) of a composition containing an alkyl fluoride activator, which is coated on a base paper, dried, and surface-treated. It has been found that the image quality is low, the density is high, and the image storage stability under high temperature and high humidity conditions is excellent.

The fluorinated alkyl activator used in the present invention is an activator in which all or a part of the hydrogen atoms of an alkyl group having 5 to 30 carbon atoms are substituted with fluorine, such as perfluoroalkyl carboxylic acid salts, etc. Perfluorooctanoic acid ammonium salts, perfluoroalkyl phosphates or their phosphates, such as monoperfluoroalkyl ethyl phosphates, 3-perfluoroalkyl-1,2-propanediol phosphates, 2-perfluoroalkyl-1-methyl phosphates, ruethyl fluorophosphate ammonium salt, α・α・ω-disodium trihydroperfluoroalkyl phosphate, etc., perfluorosulfonate, perfluoroalkyltrimethylammonium salt, for example, N-[3
-(perfluorooctanoylamide)propyl]N-
N-N-trimethylammonium chloride, perchlorosulfonamide derivatives such as N-propyl-N-(2
-Hydroxyethyl) perfluorooctane sulfonamide, perfluorooctane sulfonic acid diethanolamide, perfluoroalkyl sulfonamidopropyl trimethylammonium iodide, and further N-[3-(perfluorooctane sulfonamide) propyl]-N.
N-dimethyl-N-carboxymethylammonium betaine, N-alkyl-N-[(perfluorooctane)
sulfonyl]glycine potassium salt, and its alkyl esters, disodium N-perfluorooctanesulfonylglutamate, sodium 3(N-perfluorooctanesulfonyl-N-ethylamino)-1-propanesulfonate, N-propylperfluoroalkylsulfonate Amidopropylsulfonyl-N-N-dimethyl-N-hydroxyethylammonium salt, others, N-fluoroalkanoyl-N-alkylglycine sodium, N-
(3-fluoroalkanoylamidopropyl)N-N-
Betaine dimethyl alpha monocarboxylate, disodium N-fluoroalkanoylglutamate, sodium p-(fluoroalkanoylamino)benzenecarboxylate, sodium perfluoroalkyloxybenzenesulfonate, sodium 4-perfluorosulfamide benzylsulfonate, 4-( α, α, ω-trihydroperfluoroalkyl) sodium benzenesulfonate, perfluoroalkyl ethylene oxide adducts, etc.

Leuco dyes that are usually almost colorless in themselves and used in the present invention include, for example, triphenylmethane-based 3,3-bis-(p-dimethylaminophenyl)phthalide, 3,3-bis-(p-dimethylaminophenyl) phthalide,
-bis-(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone)
, 3,3bis-(p-dimethylaminophenyl)-6-
Diethylaminophthalide, 4-hydroxy-4'-dimethylaminotriphenylmethane lactone, 4,4'-bisdihydroxy-3,3-bisdiaminotriphenylmethanelactone, etc., and fluoran-based 3-cyclohexylamino-6-chloro Fluoran, 3-dimethylamino-6methoxyfluorane, 3,6-bis-β-methoxyethoxyfluorane, 3-diethylamino-J■■mino-6-methyl-J[chlorofluoran, 3-diethylamino-6 -Methyl-J Me[anilinofluorane, 3.7
-bisdiethylaminofluorane, 3-diethylamino-Jmethoxyfluorane, etc., and spiropyran series such as 3-methyl-di-β-naphthospiropyran, 1, 3, 3
-trimethyl-6/-chloro-81-methoxyindolinobenzospiropyran, and leuco dyes such as auramine, rhodamine lactam, and phenothiazine are also used, but the present invention is not limited to these representative examples. do not have.

As the electron acceptor used in the present invention, inorganic compounds such as acid clay, kaolin, zeolite, and silicon oxide, organic acids such as oxalic acid, maleic acid, gallic acid, and benzoic acid, and metal salts thereof are also used. Phenol compounds that have low water solubility, a sharp melting point of 70° C. or higher, and excellent miscibility with dyes are preferred.

For example, 4-Tert-butylphenol, 4-phenylphenol, 2●2-bis(4-hydroxyphenyl)
Propane, 2,2-bis(4-hydroxyphenyl)-n-heptane, 4,41-cyclohexylidenephenol, 2,2'-methylenepis(4-chlorophenol)
, 4,4'-isopropylidene bis (2-chlorophenol), 4,4'-isopropylidene bis (2-methylphenol), and 4,4'-one ethylenebis (2-methylphenol). It is also possible to use a mixture of two or more of these phenolic compounds. Furthermore, in order to increase the coloring sensitivity of the recording paper, thermofusible sensitizers such as higher fatty acid amides such as stearamide, oleic acid amide, palmitic acid amide, methylolated stearic acid amide, or waxes such as montan acid wax are used. Use one agent or a mixture of two or more agents.

A binder is also used to bind these composition dispersions together and onto the base paper.

As the binder, water-soluble polymers are suitable since they are usually applied in the form of water-based paints, such as cellulose derivatives such as methyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose, starch, hydroxyethyl starch, carboxymethyl starch, oxidized starch, Starch compounds such as cationic starch and dialdehyde starch, polyvinyl alcohol, polyvinylpyrrolidone, casein, gelatin, gum arabic, polyacrylamide, alkali salts of styrene-maleic anhydride copolymers,
An alkali salt of methyl vinyl ether maleic anhydride copolymer is used. Furthermore, styrene-butadiene copolymer latex, acrylate emulsion, etc. can also be used. In this case, emulsions in which no or only a very small amount of activator is used are preferred in order to avoid adverse effects on the heat-sensitive layer. In addition, emulsions having crosslinking properties are also used to further improve water resistance. In addition, pigments such as clay, kaolin, talc, charcoal, titanium oxide, etc. are used as supplementary materials for various purposes such as improving the whiteness of thermal recording paper, improving writing properties, preventing adhesion to thermal heads, and preventing pressure fog. Waxes such as paraffin wax, microcrystalline wax, carnauba wax, polyethylene wax, and polypropylene wax, sensitivity and preservability modifiers such as diphenylamine derivatives, etc. can also be added.

To prepare a heat-sensitive recording composition from these components, usually an almost colorless leuco dye, an electron acceptor, a fusible sensitizer, and other additives as necessary are separately dispersed and Grind to a particle size of

A dispersion machine such as a ball mill, attritor, or sand mill is used for dispersion. During dispersion, 0.5 to 10% of polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, sodium alginate, etc. can be added as a protective colloid, if necessary. Next, a binder solution, pigments and other additives are added to the above dispersion to form a homogeneous composition. This composition is applied to the surface of high-quality paper using a coating method such as air knife coating, wire barcode coating, or blade coating, so that the coating amount is 3 to 77/M2, and after drying, a surface treatment device such as a calendar is used to check the base smoothness. Adjust to 100 seconds to 300 seconds.

Examples will be described below to further specifically explain the present invention.

Example 1 2-(N-31-trifluoromethylphenyl)amino-6-diethylaminofluorane 20% aqueous dispersion 10
parts, 20 parts of a 20% aqueous dispersion of 2,2-bis(4-hydroxyphenyl)propane, 20 parts of a 20% aqueous dispersion of a 1:1 mixture of stearamide and methylolated atearic acid amide, 10% aqueous cationic starch solution 40 copies,
2 parts of calcium carbonate and 3 parts of polyethylene oxide wax emulsion (20% solids) were mixed, and then 2-perfluoroalkyl-1-methyl-ethylphosphate ammonium salt, which is an alkyl fluoride activator, was mixed. 50%
A heat-sensitive coating liquid was prepared by blending 0.3 part of an aqueous solution.

Apply this to 547/wl high-quality paper (dry weight): 4.
Apply with an air knife coater so that it becomes 57/d, and
After drying at 0° C., a calender treatment was performed to obtain a heat-sensitive recording paper with a base smoothness of 200 seconds.

For comparison, heat-sensitive recording paper without a fluorinated alkyl activator was prepared. Table 1 shows the evaluation results of these samples.
It is shown in Figure 1.

Figure 1 uses a Toshiba KB-4800 receiver.
A solid black image obtained under the conditions shown in Note 2) at 45°C and 85%
It shows the degree of deterioration of image density when left in an RH atmosphere for 48 hours, where curve 1 is for the present example and curve 2 is for the comparative example.

It is clear that the image according to this example has greatly improved storage stability under high temperature and high humidity conditions. Example
2 10 parts of 20% aqueous dispersion of 2-(N-3'-trifluoromethylphenyl)amino-4-methyl-6-diethylaminofluorane, 20% aqueous dispersion of 2,2-bis(4hydroxyphenyl)propane 26 parts of liquid, 25 parts of a 2.0% aqueous dispersion of a 7:3 mixture of stearamide methylolate and palmitate amide methylolate, 40 parts of a 10% cationic starch aqueous solution, 2 parts of calcium carbonate, and a 40% aqueous dispersion of dimethylpolysiloxane. 1.5 parts of liquid, 2 parts of polyethylene wax emulsion (40% solids), and a fluorinated alkyl activator, N-alkyl-N-[
A heat-sensitive coating liquid was prepared by uniformly mixing 0.2 part of a 10% aqueous solution of potassium (perfluorooctane)sulfonylglycine salt.

Apply this on 507/M゜ high-quality paper in an amount (dry weight) of 40
Apply with an air knife coater so that the temperature is t/a at 70°C.
After drying, a calendering process was performed to obtain a heat-sensitive recording paper with a base smoothness of 260 seconds.

For comparison, a heat-sensitive recording paper containing no fluorinated alkyl activator was prepared. Table 2 shows the evaluation results of these samples.
It is shown in Figure 2.

Figure 2 shows a solid black image at 45°C and 85% R as in Figure 1.
This shows the change in image density when left in an H atmosphere, and the image of this example (curve 3) has significantly improved image storage stability compared to the comparative example (curve 4). The uniformity of the solid black portion of the image was very good, and the image quality was good.

Example 3 10 parts of a 20% aqueous dispersion of crystal violet lactone, 25 parts of a 20% aqueous dispersion of 2,2-pis(4-hydroxyphenyl)propane, 35 parts of a 20% aqueous dispersion of ethylene bisstearamide, 40 parts of a 10% cationic starch aqueous solution, 3 parts of clay, 0.5 part of a 40% dimethylpolysiloxane aqueous dispersion, 5 parts of polyethylene wax emulsion (20% solids), and the fluorinated alkyl activator N- 0.02 part of a 10% aqueous solution of (3-fluoroalkanoylamidopropyl)N-N-dimethyl-α-monocarboxylic acid betaine was uniformly mixed;
A heat-sensitive coating liquid was prepared.

This was coated on 457/I high-quality paper using an air knife coater to give a dry weight of 5.07/I, dried at 80°C, and then surface-treated using a calender to give a thermal recording paper with a smoothness of 180 seconds. I got it.

This recording paper is used in the thermal printer EN- manufactured by Oki Electric Industry Co., Ltd.
As a result of a printing test performed using a 1000 model machine, the image density was 1.02 and the image quality was good. There was no unevenness even in solid black areas. Further, no head stains were observed even after 2000 lines were printed. Examples 4, 5 and Comparative Examples 1 to 4 10 parts of 20% aqueous dispersion of 2-(3'-trifluoromethyl)anilino-6-diethylaminofluorane, 2.2
- 30 parts of a 20% aqueous dispersion of bis(4-hydroxyphenyl)propane, 20% aqueous dispersion of a 1:1 mixture of stearamide/stearamide methylolate 2
0 parts, 50 parts of a 10% cationic starch aqueous solution, and 5 parts of calcium carbonate, and further 40% of the active agent shown in Table 3.
0.3 parts of an aqueous solution (Examples 4 and 5 are fluorinated alkyl active agents, Comparative Examples 1 to 3 are ordinary surfactants),
A heat-sensitive coating liquid was prepared by uniformly stirring.

After drying, coat this on 52y/M゜ high-quality paper with a coating amount of 4.67/
Apply with an air knife coater to make it M2, 70
After drying at .degree. C., a calendering treatment was performed to obtain a heat-sensitive recording paper having a Beck smoothness of 200 to 300 seconds. The evaluation results of these samples are shown in Table 3, and the effects of the fluorinated alkyl activator of the present invention are clear.

[Brief explanation of the drawing]

FIG. 1 shows the image density maintenance rate of Example 1, and FIG. 2 shows the image density maintenance rate of Example 2. 1 and 3 are curves showing changes in values for the examples of the present application, and 2 and 4 are curves showing changes in values for comparative examples.

Claims (1)

[Claims] 1. A colorless dye and an electron acceptor that causes the dye to develop color when heated;
A composition obtained by adding 3% to 0.01% (by weight) of an alkyl fluoride activator to a heat-sensitive composition containing at least one kind of a fusible sensitizer and an aqueous binder is applied onto a base paper. Coated onto dry thermal recording paper. 2. A colorless dye and an electron acceptor that causes the dye to develop color when heated;
For the thermal composition containing at least one each of a fusible sensitizer and a water-soluble binder, 5% to 0.1% (by weight) of an aqueous dimethylpolysiloxane dispersion and 3% to 0.1% (by weight) of an aqueous dimethylpolysiloxane dispersion are added.
0.001% (by weight) of a composition containing a fluorinated alkyl activator is coated on a base paper and dried.