JPH06305263A - Thermal recording - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a thermal recording material having good ink receptivity of UV ink. [Structure] In a thermosensitive recording medium having a thermosensitive coloring layer and an overcoat layer containing a water-soluble resin on the surface of a support, the surface of the support has an HLB value of 1.0 or more and 3.9 or less. A back coat layer containing an agent is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having excellent ink receptivity for UV ink used in heat-sensitive labels for POS.

[0002]

2. Description of the Related Art A thermosensitive recording medium is generally provided on one side of a support made of paper, synthetic paper, plastic film, or the like.
A thermosensitive color-forming layer containing a colorless or light-colored color-forming substance such as an electron-donating color-forming dye and a color-developing compound such as an electron-accepting phenolic compound. When the dye and the electron-accepting color-developing compound are melted by heat energy, a reaction occurs and a color-recorded image can be obtained.

Such a thermal recording system has the advantages that the recording apparatus is compact and inexpensive, and that it is easy to maintain, and is used only as a recording medium for facsimiles, automatic ticket vending machines, and scientific measuring machines. Not a POS label,
Widely used in various printers and plotters for medical images such as CAD and CRT. As a drawback of the thermal recording material,
When various chemicals or oils adhere, the recorded image may be discolored or fog may occur. These drawbacks are serious problems in practical use, and an overcoat layer containing a water-soluble resin is provided on the thermosensitive color-developing layer to improve the preservation of the thermosensitive recording medium. For example, JP-A-48-3195.
No. 8, JP-A-53-61346, JP-A-56.
No. 146794 is disclosed.

A thermosensitive recording medium having a multi-layer coating on one side of such a support is apt to curl and tends to cause a problem in running property of the thermal recording medium in a printer or the like. It has been proposed to provide a back coat layer on the back surface of the support. Such examples are disclosed in JP-A-53-61346 and JP-A-58-58.
23994, JP-A-58-23995, JP-A-58-203092, and JP-A-59-9091.
JP-A-61-57386, JP-A-61-57386
It is disclosed in Japanese Patent Laid-Open No. 139482, Japanese Patent Laid-Open No. 62-32081 and the like.

However, the heat-sensitive recording material containing a water-soluble resin in the overcoat layer has a problem that oily UV ink does not uniformly transfer in a printing machine, resulting in defective inking.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the receptivity of UV ink to a thermal recording material containing a water-soluble resin in the overcoat layer.

[0007]

Means for Solving the Problems The present inventors have completed the present invention as a result of studying the improvement of the ink receptivity of a UV-sensitive recording material containing a water-soluble resin in the overcoat layer. . That is, the present invention provides a thermosensitive coloring layer containing, on the surface of a support, a colorless or light-colored electron-donating coloring dye and an electron-accepting color-developing compound for coloring the coloring dye by heating. A heat-sensitive recording material having an overcoat layer containing a water-soluble resin on the back and a backcoat layer on the back surface of the support, wherein the backcoat layer has an HLB value of 1.0 or more and 3.9 or less. The thermosensitive recording medium is characterized by containing 0.1 to 5.0 parts by weight of the surface active agent in 100 parts by weight of the total solid content of the backcoat layer.

The mechanism for improving the ink receptivity of the UV ink in the overcoat layer by adding a surfactant having an HLB value of 1.0 or more and 3.9 or less to the backcoat layer is not always clear, but in the manufacturing process. Since the thermal recording medium is placed in a rolled-up form, the overcoat layer and the backcoat layer of the thermal recording medium adhere to each other, and the HLB of the backcoat layer
It is considered that the surfactant having a value of 1.0 or more and 3.9 or less is transferred to the surface of the overcoat layer and the lipophilicity of the surface of the overcoat layer is increased, so that the ink receptivity of the oily UV ink is improved. .

The HLB value is WDGriffin (J.Soc.Cosm) as an index showing the degree of hydrophilicity and lipophilicity of a surfactant.
etic Chem., 5,294 (1954)), and is widely used as a measure of hydrophilicity and lipophilicity of surfactants. The surfactant having an HLB value of 1.0 or more and 3.9 or less used in the present invention has a small HLB value and thus has strong lipophilicity.

As a surfactant having an HLB value of 1.0 or more and 3.9 or less, ethylene glycol distearate (HL
B value = 1.3), ethylene glycol monostearate (HLB
Value = 2.9), propylene glycol monostearate (HL
Alkylene glycol ester type such as B value = 3.4), sorbitan monooleate (HLB value = 1.8), sorbitan tristearate (HLB value = 2.1), sorbitan sesquioleate (HLB value = 3.7), sorbitan trioleate ( HLB
Value = 1.8), sorbitan ester type, glyceryl dioleate (HLB value = 1.8), glyceryl monooleate (H
LB value = 3.4), glyceryl monostearate (HLB value = 3.
8), glyceryl ester type such as diglyceryl sesquioleate (HLB value = 3.5), decaglyceryl dekaoleate (HLB value = 3.0), others, lanolin alcohol (HLB
Value = 1.0), oleic acid (HLB value = 1.0), sucrose distearate (HLB value = 3.0) and the like.

Such a surfactant can be used in a proportion of 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the total solid content of the backcoat layer coating composition. further,
It is preferably used in a proportion of 0.5 to 3.0 parts by weight. If the amount of the surfactant is less than 0.1 parts by weight, the effect of improving the ink receptivity of the UV ink is not recognized, and if it is more than 5.0 parts by weight, coating defects such as pinholes occur when the paint is applied. It will be easier. When the HLB value is less than 1.0, the lipophilicity is too strong to dissolve in the paint and to separate easily.
When the HLB value is larger than 3.9, the effect of improving the ink receptivity of the UV ink is poor, and the object of the present invention is not always met.

Examples of the adhesive used for the back coat layer of the present invention include polyvinyl alcohol, oxidized starch,
Modified starch, gum arabic, gelatin, casein, chitosan, methyl cellulose, hydroxyethyl cellulose,
Hydroxymethyl cellulose, polyvinylpyrrolidone,
Polyacrylic acid salt, polyacrylic amide, styrene-
Maleic anhydride copolymer salt, methyl vinyl ether-maleic anhydride copolymer salt, water-soluble resin such as isopropylene-maleic anhydride copolymer salt, and, for example, styrene-
Butadiene latex, acrylic emulsion, vinyl acetate-acrylic acid ester copolymer emulsion, polyurethane emulsion, polyvinyl chloride emulsion, polyvinylidene chloride emulsion, methacrylic acid ester copolymer emulsion, acrylic acid ester copolymer emulsion, etc. Hydrophobic resins can be used.

If desired, auxiliary additive components such as a dispersant and a crosslinking agent may be added to the back coat layer. Examples of the cross-linking agent include formalin, acetaldehyde, glyoxal, aldehyde compounds such as dialdehyde starch, polyamine compounds such as polyethyleneimine, epoxy compounds, polyamide resins, dimethylol urea, and ammonium persulfate and ferric chloride, and Inorganic compounds such as magnesium chloride can be used. The coating method is Mayer bar method, air knife method, blade method, reverse roll method,
A method such as a slit die method can be used.

The backcoat layer in the present invention has a coating amount after drying of 0.01 to 10.0 g / m ² , preferably 0.05 to 10.0 g / m ² .
It is recommended to coat it to 7.0 g / m ² . The amount of coating is 0.
01G / m ² less than or 10.0 g / m large, the curling aptitude than ² has the disadvantage that deteriorates. Further, the surface of the back coat layer can be smoothed by using a super calendar, a gloss calendar, a machine calendar, or the like.

The support material used in the present invention is not particularly limited and includes, for example, high quality paper, glossy paper, medium quality paper, coated paper, art paper, cast coated paper, synthetic fiber paper, synthetic paper, laminated paper. , A synthetic resin film or the like, or a laminated body of these materials can be appropriately used. The coating amount of the thermosensitive coloring layer provided on the support is generally 3 to 10 g / m ²
Is preferred. As the coating method of the thermosensitive coloring layer, the same method as that of the back coat layer can be used. As the color-forming dye, a colorless or light-colored electron-donating dye capable of reacting with an electron-accepting color-developing compound under heating to form a color is used.

Examples of the color-forming dye include 3,3-bis (P-dimethylaminophenyl) -6-dimethylaminophthalide as a triarylmethane compound and 4,4'-bis- as a diphenylmethane compound. Dimethylaminobenzhydrin benzyl ether, N-2,
4,5-Trichlorophenyl leuco auramine, N-
2,4,5-Trichlorophenyl leuco auramine, as a xanthene compound, rhodamine B-anilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-butylaminofluorane, 3- ( N-isoamyl-N-ethyl) amino-6
-Methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3
-Piperidino-6-methyl-7-anilinofluorane,
3-Ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-cyclohexyl-methylamino-6-
Methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7- (β-ethoxyethyl) aminofluorane, 3-diethylamino-6-chloro-7- (γ-
Chloropropyl) aminofluorane and the like.

Examples of the electron-accepting color developing compound that can be used in the present invention include phenol derivatives and aromatic carboxylic acid derivatives. Specific examples thereof include p-octylphenol and p-tert as phenols.
-Butylphenol, p-phenylphenol, 2,
2'-bis (p-hydroxyphenyl) propane, 2,
2'-bis (p-hydroxyphenyl) pentane, 1,
1'-bis (p-hydroxyphenyl) hexane, 2,
2'-bis (p-hydroxyphenyl) hexane, 1,
1'-bis (p-hydroxyphenyl) -2-ethylhexane, 2,2'-bis (4-hydroxy-3,5-dichlorophenyl) propane, dihydroxydiphenyl ether, 4,4'-dihydroxydiphenylsulfone,
4-hydroxy-4'-isopropyloxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone and the like can be mentioned. Examples of the aromatic carboxylic acid derivative include p-hydroxybenzoic acid, butyl p-hydroxybenzoate, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and the above carboxylic acids. And polyvalent metal salts thereof.

Among these electron-accepting color-developing compounds,
Sulfone-containing phenolic substances, especially 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, and bis- (3-allyl-4-hydroxyphenyl) sulfone are good in storage stability. Gives more favorable results. These electron-accepting color-developing compounds are used in a proportion of 1 to 5 parts by weight, preferably 1.5 to 3 parts by weight, based on 1 part by weight of the entire electron-donating color-forming dye.

Further, a sensitizer may be used to improve the sensitivity of the thermosensitive recording medium. For example, dibenzyl terephthalate, di-o-chlorobenzyl adipate, dibenzyl oxalate, di-p-chlorobenzyl oxalate,
Di-p-methylbenzyl oxalate, 1-hydroxy-2
-Phenyl naphthoate, 1,2-bis (3,4-dimethylphenyl) ethane, parabenzyl biphenyl, 1,2
-Di (3-methylphenoxy) ethane or the like can be used. These sensitizers are used in an amount of 0.5 to 4 parts by weight, more preferably 1 to 4 parts by weight, based on 1 part by weight of the entire electron-donating color forming dye.
Use 2 parts by weight.

As the adhesive used in the thermosensitive color developing layer of the present invention, a water-soluble resin and / or a hydrophobic resin can be used, and examples thereof include those similar to the case of the back coat layer. If necessary, a pigment, a dispersant, a storability improver and the like may be added to the heat-sensitive color forming layer.

As the pigment, for example, calcium carbonate,
Magnesium carbonate, kaolin, clay, talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate,
Inorganic pigments such as zinc oxide, titanium oxide, aluminum hydroxide and barium sulfate, and urea-formalin resin,
Examples thereof include styrene-methacrylic acid copolymer and organic resin fine powder such as polystyrene resin.

Phenolic compounds are effective as the storability improver, for example, 1,3,5-tris (4-t).
-Butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane,
1,1,3-tris (2-methyl-4-hydroxy-5)
-Cyclohexylphenyl) butane, 1,1-bis (2
-Methyl-4-hydroxy-5-t-butylphenyl)
Butane, 4,4 '-(1-phenylethylidene) bisphenol, 4,4'-[1,4-phenylenebis (1-
Methyl ethylidene)] bisphenol, 4,4'-
[1,3-Phenylenebis (1-methylethylidene)]
Examples thereof include bisphenol.

The overcoat layer in the present invention has a coating amount after drying of 0.5 to 10.0 g / m ² , preferably 2.0 to
It is recommended to coat it to 8.0 g / m ² . The amount of coating is 0.
If it is less than 5 g / m ² , the coating film will not be formed uniformly,
Since coating defects such as pinholes are likely to exist, the coating amount is 1
If it is more than 0.0 g / m ² , the recording sensitivity may be lowered and the printed matter may become unreadable. As the coating method for the overcoat layer, the same method as for the backcoat layer can be used.

Examples of the water-soluble resin usable in the overcoat layer of the present invention include polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, oxidized starch, modified starch, gum arabic, gelatin, casein, chitosan, methyl cellulose. , Hydroxyethyl cellulose, hydroxymethyl cellulose, polyvinylpyrrolidone, polyacrylic acid salt, polyacrylic amide, styrene-maleic anhydride copolymer salt, methyl vinyl ether-maleic anhydride copolymer salt, isopropylene-maleic anhydride copolymer salt Etc. can be used. In order to strengthen the water resistance of the coating film, a resin containing a reactive group such as an acetoacetyl group, a carboxyl group, or an amide may be used in combination with a crosslinking agent.

As the cross-linking agent, for example, the same one as in the case of the back coat layer can be mentioned. A pigment, a dispersant, and a lubricant may be added to the overcoat layer as needed. As the pigment, for example, the same pigments as in the case of the thermosensitive coloring layer can be mentioned.

Examples of the lubricant include fatty acid amides such as stearic acid amide, ethylenebisstearic acid amide, oleic acid amide, palmitic acid amide, coconut fatty acid amide, behenic acid amide, and methylol stearic acid amide, and stearic acid. Zinc, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax and the like can be used. Recording sensitivity can be improved by smoothing the surface of the overcoat layer using a super calendar, a gloss calendar, a machine calendar or the like. Various kinds of modifications such as providing an undercoat layer under the heat-sensitive recording layer can be carried out if necessary.

[0027]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples. In each example, “part” means “part by weight”. Formation of thermosensitive coloring layer Coloring dye dispersion liquid A 3- (N-isoamyl-N-ethyl) amino-6-methyl-7-anilinofluorane 50 parts Polyvinyl alcohol 10% aqueous solution 50 parts water 10 parts

Electron-accepting color developing compound dispersion liquid B 4-hydroxy-4'-isopropoxydiphenyl sulfone 50 parts Polyvinyl alcohol 10% aqueous solution 50 parts water 10 parts

Sensitizer dispersion C solution Di-p-methylbenzyl oxalate 50 parts Polyvinyl alcohol 10% aqueous solution 50 parts Water 10 parts The preparation compositions of solutions A, B and C are averaged with a sand grinder. Separately pulverized to a particle size of 1.5 μm.

Liquid A, liquid B, liquid C, calcium carbonate 60%
Slurry (liquid D), zinc stearate 30% dispersion liquid (E
Liquid), polyvinyl alcohol 10% aqueous solution (F liquid), S
The weight ratio of BR latex [L-1537, solid content 50% made by Asahi Kasei] (G liquid) after drying was A: B: C: D :.
E: F: G = 10: 20: 20: 25: 5: 5: 15 were mixed to obtain a thermosensitive coloring layer coating material. Basis weight 50g
/ M ² of high-quality paper coated on one side after drying is 7.0g / m ²
The above thermosensitive color developing layer coating material was applied so as to obtain a thermosensitive color developing layer.

Formation of overcoat layer As an adhesive, a polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry, Gohsenol NH-17Q (polymerization degree 1700, completely saponified type)) aqueous solution (H solution) was used, and kaolinite clay was used as a pigment. 60% dispersion (Liquid I), glyoxal 40% aqueous solution (Liquid J) as cross-linking agent, and zinc stearate
The weight ratio after drying the 30% dispersion liquid (K liquid) was H: I:
J: K = 70: 20: 6: 4 were mixed to obtain an overcoat layer coating material. The coating liquid for overcoat layer was applied on the thermosensitive coloring layer so that the coating amount after drying was 2.0 g / m ^2, and the coating liquid was dried.

Formation of Backcoat Layer As the water-soluble resin, modified starch (Petrocoat C8: manufactured by Nitto Kagaku) was used, and as shown in Table 1, surfactants having different HLB values were added to prepare each component. The mixture ratios after drying were mixed to obtain a back coat layer paint. After coating the overcoat layer, the coating amount after drying on the back surface of the support is 2.0 g.
Each back coat layer coating liquid was applied so as to be / m ² and dried to form a roll-shaped roll. Then, super calendering was performed so that the overcoat layer had a Beck smoothness of 1100 seconds.

Test Method Table 1 shows the results. The separation state of the back coat layer paint in the table was visually determined. The heat-sensitive recording material obtained as described above was allowed to stand for 1 day at room temperature as it was wound, and then U-shaped using a printing tester RI-II type manufactured by Akira Seisakusho.
After printing with V-curable ink (manufactured by Dainippon Ink and Chemicals, Inc., 59 indigo Z for MV seal), it was irradiated with UV (ultraviolet light) and visually inspected to see if the ink was uniformly inked (ink inking property) . For comparison, after coating the back coat layer, a thermal recording medium not in the form of winding was also subjected to the same super calendering as above and then subjected to a printing test.

[0034]

[Table 1]

[0035]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain a heat-sensitive recording material having a UV ink inking property in the heat-sensitive recording material provided with an overcoat layer containing a water-soluble resin.

Claims (1)

[Claims] 1. A thermosensitive color-forming layer containing a colorless or light-colored electron-donating color-forming dye and an electron-accepting color-developing compound for coloring the color-forming dye by heating is provided on the surface of a support.
A heat-sensitive recording material comprising an overcoat layer containing a water-soluble resin on the thermosensitive color-developing layer and a backcoat layer on the back surface of the support, wherein H is contained in the backcoat layer.
A thermosensitive recording medium containing 0.1 to 5.0 parts by weight of a surfactant having an LB value of 1.0 or more and 3.9 or less based on 100 parts by weight of the total solid content of the backcoat layer. .