JPH02310085A - Thermal recording paper - Google Patents

Abstract

PURPOSE:To reduce the adhesion and sticking of refuse to a thermal head due to a thermal layer by forming an under coat layer containing a metal salt of higher fatty acid having an m.p. of 90 deg.C or higher between a support and a thermal color forming layer. CONSTITUTION:An under coat layer containing metal salt of higher fatty acid having an m.p. of 90 deg.C or higher is provided between a support and a thermal color forming layer. When the m.p. of a metal salt of higher fatty acid is lower than 90 deg.C, effect is confirmed in the reduction of the adhesion amount of refuse but sensitivity is lowered markedly and there is no much effect in the improvement of sticking. As a metal salt of higher fatty acid, a metal salt, for example, lithium, zinc, barium or manganese salt of stearic acid, palmitic acid, myristic acid, undecylic acid or lauric acid is pref. The amount of a metal salt of higher fatty acid in the under coat layer is usually set to a range of 0.1-10 pts., especially pref., 0.5-2 pts. on the basis of the total solid in the under coat layer. A filler, a binder or the like can be contained in the under coat layer other than a metal salt of higher fatty acid.

Description

[Detailed Description of the Invention] [Prior Art] Thermal recording paper is preferred because it allows color images to be obtained by simply heating it, and the recording device can be made relatively simple and compact. It is widely used as a variety of information recording paper.

Particularly in recent years, thermal facsimiles and thermal printers using such thermal recording paper have been improved in terms of equipment, and high-speed recording, which was previously difficult, has become possible.

As the speed of such equipment and hardware increases, the thermal recording paper used is required to have improved recording sensitivity, and many proposals have been made in this regard. This thermosensitive recording paper generally comprises a support such as paper, plastic film, synthetic paper, etc., and a single or multilayer thermosensitive coloring layer containing a binder or a thermochromic substance as a main component.

It is known that there are several problems when such a system is put into practical use. One is that coloring substances that are in a molten state when heated (consisting of coloring agents such as leuco dyes and phenols, and thermofusible organic compounds called sensitizers) transfer and adhere to the thermal head. .

This phenomenon is called "scum adhesion," and it gradually accumulates during continuous recording.As a result, it impairs the adhesion between the thermal head and the thermosensitive coloring layer, reduces heat conduction, and reduces recorded image quality and recording density. It will bring about.

Another problem is that when heat is applied, the surfaces of the thermal head and the thermosensitive coloring layer become sticky or sticky. This phenomenon is called "sticking," and when it occurs, it prevents the smooth feeding of the heat-sensitive recording material, resulting in skipped recordings and image disturbances, and in extreme cases, the heat-sensitive coloring layer or the thermal head. Continuous recording may become impossible due to sticking. In order for recording to be carried out smoothly and continuously, one of the conditions that the heat-sensitive recording material must satisfy is the absence of the above-mentioned scum and sticks.

In order to suppress this scum and stick, it is possible to reduce the amount of molten components that cause scum and stick in the heat-sensitive coloring layer and increase the pigment blending ratio, but this is due to the demand for higher sensitivity accompanying high-speed printing. Although it is possible to suppress the occurrence of backward printing, scum, and stickiness, there is a problem in that sufficient color density cannot be obtained with low energy during high-speed printing. In addition, proposals to incorporate highly oil-absorbing pigments were made, for example, in 1986-56
Although this method was disclosed in Japanese Patent No. 118, it was still insufficient to meet the demands for higher sensitivity accompanying higher speeds, as the print density decreased.

In order to improve the adhesion of residue and sticking, for example, Japanese Patent Application Laid-Open No. 19231/1983 describes a method of incorporating waxes with a melting point of 40 to 100° C. into the heat-sensitive coloring layer to improve thermal responsiveness. , also special public official show 51. -2
7599 Bow Publication describes a method of using fatty acid amide and petroleum wax D1 in the heat-sensitive coloring layer to improve thermal response and dust adhesion, but none of these methods is a sufficient improvement method, especially for high-speed recording. Further improvements are desired in terms of thermal responsiveness, non-printing color development, and head masochability such as dregs (=1 wear).

[Problems to be Solved by the Invention] An object of the present invention is to solve the drawbacks of the conventional thermal recording paper, and specifically to provide a thermal recording paper with good thermal response and high recording density. More specifically, it is an object of the present invention to provide a heat-sensitive recording paper capable of forming clear records with less adhesion of residue and excellent high-speed printing suitability without causing printing problems due to sticking.

A further object of the present invention is to provide such an excellent thermal recording paper that does not have any protective layer.

[Means for Solving Problem f1] As a result of repeated research to achieve this objective, the present inventors found that in thermosensitive recording paper, the melting point between the support and the thermosensitive coloring layer is 90°C or higher. It has been discovered that by forming an undercoat layer containing a higher fatty acid metal salt, it is possible to obtain a thermal recording paper free from adhesion of residue and sticking to the thermal head due to the thermal layer without deteriorating various quantities and qualities related to recording, and the present invention has been made based on the present invention. I was able to complete it.

The present inventors have carried out research into such a material in order to realize a heat-sensitive recording paper that does not require any protective layer and exhibits performance without the phenomenon of residue adhesion or sticking.

As a result, it was found that among various substances, higher fatty acid metal salts having a melting point of 90° C. or higher are effective.

That is, the problems of the present invention are solved by providing an undercoat layer containing such a higher fatty acid metal salt between the support and the heat-sensitive coloring layer.

The metal salt of higher fatty acid must have a melting point of 90°C or higher. When the melting point is lower than 90°C, = 5 - = 4 - Although an effect is recognized in reducing the amount of deposited residue, the sensitivity is significantly lowered because thermal energy during color development of the heat-sensitive layer is taken away.

It was also found that it was not very effective in improving sticking.

Examples of such higher fatty acid metal salts include stearic acid, palmitic acid, myristic acid, undecylenic acid,
Metal salts such as lauric acid, eg lithium, zinc, barium, manganese and the like are preferred. The higher fatty acid metal salt is included in the undercoat layer. The amount thereof is usually in the range of 0.1 to 10 parts, preferably 0.5 to 2 parts, based on the total solid content in the undercoat layer.

The undercoat layer may contain fillers, binders, etc. in addition to the higher fatty acid metal salt.

As fillers in this case, inorganic, advantageous pigments used for membrane papermaking and coating may be optionally used, and specific examples include the following.

Calcium carbonate, kaolin, talc, zinc oxide, aluminum hydroxide, silica, magnesilla silicate, polystyrene resin, urea-formaldehyde resin, etc.

As the binder, generally known water-soluble polymer substances and aqueous emulsions are used, and specific examples include those shown below.

Polyvinyl alcohol, methylcellulose, hydroxyethylcellulose, starch, starch derivatives, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, inbutylene-maleic anhydride copolymer, polyamide, SBR latex, polystyrene-acrylic acid Ester emulsion, polyvinyl acetate emulsion, etc.

The weight ratio of filler to binder in this undercoat layer is arbitrarily determined depending on the selected components, and is generally between 20: and 1:
It is between Ko.

When forming this undercoat layer, the coating thickness is 1 to 1.
5g/rrf' (dry weight) is common, and the coating T
This is readily accomplished by coating a suitable conventional support such as paper, plastic film, synthetic paper, metal foil, etc. using conventional coating equipment.

The heat-sensitive coloring layer formed on the undercoat layer is formed by a conventional method. For example, the following can be used as colorless or pale color-forming lactone compounds.

Crystal violet)・Rough)・N3-(N-ethyl-N-isopentylamino)-6-methyl=7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3 -diethylamino-6-methyl-7-(o,p-dimethylanilino)fluoran 3- (N-ethyl-p-1-luidino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6- Methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-(N-cyclohexine-N-methylamino)-6
-Methyl-7-anilinofluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-diethylamino-7-(m-)□lifluoromethylanilino)fluoran, 3-diethylamino-6-methyl- Chlorofluorane, 3-diethylamino-6-methylfluorane, 3-cyclohexylamino-6-chlorofluorane.

Color developers made of phenols or organic acids are the same (for example, the following are representative examples):

Bisphenol A1 Benzyl p-hydroxybenzoate, n-butyl di(4-hydroxyphenyl)acetate, Bisphenol 51 4-hydroxy, 4'-isopropyloxydiphenyl sulfone, 1.1-di(4-hydroxyphenyl)cyclohexine, - -1,7-di(hydroxyphenylthio)-3,5-dioxahebutane.

As the so-called sensitizer, a known thermofusible organic compound having a melting point of 50 to 150°C is generally used, and the following representative examples can be listed.

p-hydroxynaphthoic acid phenyl ester, p-benzylbiphenyl, benzylnaphthyl ether penzyl terephthalate, benzyl p-benzyloxybenzoate, diphenyl carbonate, ditolyl carbonate.

The organic or inorganic pigments used in the heat-sensitive coloring layer are not limited by oil absorption or the like, and include, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay,
In addition to inorganic fine powders such as talc, surface-treated calcium carbonate and silica, organic fine powders such as urea-formalin resin, styrene/methacrylate oxidation polymer, and polystyrene resin meet the requirements of the present invention. Used within a range.

Furthermore, the heat-sensitive coloring layer of the present invention can contain various waxes as required. Known waxes such as paraffin, amide wax, bisimide wax, and metal salts of higher fatty acids may be used.

In addition, as adhesives, polyvinyl alcohol of various molecular weights, starch and its derivatives, Metkin cellulose,
Cellulose derivatives such as carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic amide/acrylic ester copolymer, acryl amide/acrylic ester/methacrylic acid ternary copolymer, styrene/maleic anhydride In addition to water-soluble polymers such as acid copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, and styrene/
Use latex such as butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/butadiene/acrylic copolymer, etc. I can do it.

[Example] Next, the present invention will be explained using specific examples. Unless otherwise specified, parts and % in the examples indicate parts by weight and % by weight, respectively.

Example ] Water 1.00
100 parts 100 parts 10% polyvinyl alcohol (Nippon Gosei GL-05) 10 parts Manganese stearate (melting point 105°C) 1. ．． 5 parts 5
After dispersing with a homogenizer for a minute, the mixture was mixed with 50 parts of 10% polyvinyl alcohol (GHL7 manufactured by Nihon Kosei Co., Ltd.) to prepare an undercoat layer coating solution.

This undercoat layer coating solution was applied to a -1-quality paper of 5 (hr/rd) at a coating amount of 7 g/rd and dried.

= 12- On the other hand, coating liquids A and B were prepared after dispersion as coating liquids for heat-sensitive layers.

■ Preparation of dispersion A 3-(N-ethyl-N-iso-amyl)-6-methyl-7-phenylaminofluorane 20 parts by weight 10% polyvinyl alcohol 10 parts by weight water
70 parts by weight of this composition was ground to an average particle size of 2 μm using a sand grinder.

■ Preparation of dispersion B 4. 10 parts by weight of 4'-isopropylidene diphenol 10 parts by weight p-benzylbiphenyl 10% polyvinyl alcohol 10 parts by weight Water
70 parts by weight ■ Preparation of coloring layer 40 parts of the above liquid A, 160 parts of liquid B, 4 parts of calcium carbonate pigment
0 parts, 20 parts of a 30% paraffin dispersion, and 180 parts of a 10% polyvinyl alcohol aqueous solution were mixed and stirred to prepare a coating liquid.

The obtained coating liquid was applied to Andaco-1 paper so that the coating amount after drying was 4.5 g1rd, and dried to obtain a heat-sensitive recording paper.

Example 2 A thermosensitive recording paper was produced by repeating Example 1 except that the same amount of magnesium myristate (melting point 132° C.) was used in place of the manganese stearate used in Example 1.

Comparative Example 1 A thermosensitive recording paper was produced in the same manner as in Example 1, except that manganese stearate was omitted in preparing the undercoat layer coating solution.

Comparative Example 2 A thermosensitive recording paper was obtained in the same manner as in Example 1, except that calcium oleate (melting point: 84° C.) was used instead of manganese stearate in preparing the undercoating liquid.

The recording sensitivity of the thermosensitive recording paper was measured and the −14= evaluation was performed on dregs and stain ink for three types of examples and comparative examples. The results are shown in Table 1.

Recording sensitivity was measured using a commercially available heat-sensitive facsimile modified for testing purposes. 1 line recording time 10m5ec
, the scanning line density was 8 x 8 dots)-/mm, the pulse width was changed to 0.2 mm, and the applied energy per dot was 0.2 mm.
The printing speed was changed to 4 mj and 0.39 mj, and 64 lines were printed. Macbeth Densitometer RD-
914, and the value was taken as a representative value of the recording sensitivity of thermal paper.

The residue adhesion test on the thermal head was conducted using the above testing machine.
The applied energy per dot is 0.45 mj, and 1
00m was printed.

In the table, the mark ○ indicates that the amount of residue adhering to the head is very small and does not affect the image at all, the mark Δ indicates that the adhesion of residue is clearly observed, and the mark x indicates that the amount of adhesion of residue is extremely large. Furthermore, in order to investigate the occurrence of sticking, 80
The lines were printed.

The O mark in the table indicates that no sticking occurred.
The mark indicates that a sticking sound was detected, and the cross mark indicates that a large sticking sound occurred, causing disturbances in both the image and the line spacing.

117- [Effects of the Invention] The present invention has made it possible to provide a heat-sensitive recording material that does not have a decrease in recording sensitivity, has little residue adhesion, and does not cause sticking.

Claims (1)

[Claims] (1) In a thermosensitive recording material having a thermosensitive coloring layer containing a colorless or light-colored leuco dye and an electron acceptor that causes the dye to develop color when heated, an undercoat layer containing a higher fatty acid metal salt having a melting point of 90° C. or higher is provided. A thermal recording paper featuring