JPH04323082A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve a writability with pencil, a stamp ink bleeding, and a fogging, caused by a felt pen writing in a thermal recording material provided with a protective layer on a thermal color-forming layer made of an electron donative colorless dye and an electron accepting compound. CONSTITUTION:In a thermal recording material provided with a protective layer mainly composed of a pigment and a binder on a thermal color-forming layer, a rosin compound is incorporated in said protective layer.

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 a heat-sensitive coloring layer and a protective layer.

0002

2. Description of the Related Art Regarding thermal recording, many methods have been known for a long time. For example, heat-sensitive recording materials using electron-donating dye precursors and electron-accepting compounds are
14039, Japanese Patent Publication No. 43-4160, etc. A heat-sensitive recording material using a diazo compound is disclosed in Japanese Patent Application Laid-Open No. 190886/1986. In recent years, these thermal recording systems have been widely used in fax machines, printers,
It is used in many fields such as labels, medical image output, and prepaid cards, and needs are expanding.

[0003] Along with this, the number of cases in which various types of stationery are being used for heat-sensitive recording paper has also increased, and there is a strong demand for heat-sensitive recording materials that are easy to use for stationery.

Conventionally, heat-sensitive recording materials have been proposed in which a protective layer is provided on a heat-sensitive coloring layer from the viewpoint of chemical resistance.

However, although these methods impart chemical resistance, they do not provide sufficient suitability for stationery, as writing implements such as pencils cannot be used on the surface, or stamp ink smudges and cannot be used.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material suitable for stationery, specifically, suitable for writing with a pencil and stamping.

[0007]

[Means for Solving the Problems] An object of the present invention is to provide a heat-sensitive recording material in which a protective layer containing a pigment and a binder as main components is provided on a heat-sensitive coloring layer, in which a rosin compound is contained in the protective layer. This was achieved using a characteristic heat-sensitive recording material.

[0008] As pigments that can be used in the protective layer of the present invention, all general organic or inorganic pigments can be used.
In particular, the oil absorption specified by JIS-K5101 is 40cc/
It is preferable that the amount is 100 g or more, and specific examples include calcium carbonate, barium sulfate, titanium oxide, talc, rosite, kaolin, calcined kaolin, aluminum hydroxide, amorphous silica, urea-formalin resin powder, polyethylene resin powder, etc. Aluminum hydroxide is particularly preferred. These may be used alone or in combination.

[0009] Binders used in the protective layer include water-soluble polymers and water-insoluble binders, which may be used alone or in combination of two or more.

Examples of water-soluble polymers include methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, starches, gelatin, gum arabic, casein, styrene-maleic anhydride copolymer hydrolyzate, and ethylene-maleic anhydride copolymer hydrolyzate. Among them, polyvinyl alcohol and various modified polyvinyl alcohols are particularly preferred.

As the water-insoluble binder, synthetic rubber latex or synthetic resin emulsion is generally used, such as styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-
Examples include butadiene rubber latex and vinyl acetate emulsion. The amount of binder used is 10 to 500% by weight, preferably 50 to 500% by weight, based on the pigment contained in the protective layer.
It is 400% by weight.

[0012] The rosin compound that can be used in the present invention is generally used as a paper sizing agent and a paper strength enhancer, and is added to a rosin represented by abietic acid having a conjugated double bond, if necessary. After some formalin modification, maleic anhydride or fumaric acid is added to obtain a partially maleated (or fumarized) rosin, and an alkali is added to this to completely saponify the strengthened rosin compound, and the partially maleated ( A representative example is an emulsion-type rosin compound prepared by using rosin with various surfactants such as rosin soap as an emulsifier and dispersing it in water by an appropriate means. The amount of the rosin compound used is 1 to 40% by weight, preferably 5 to 20% by weight, based on the binder contained in the protective layer.

The protective layer coating liquid of the present invention is obtained by mixing a binder and a rosin compound with the pigment dispersion. Furthermore, a mold release agent, a waterproofing agent, a surfactant, aluminum sulfate, etc. may be added as necessary. The obtained protective layer coating solution is coated on the heat-sensitive coloring layer with a bar coater, an air knife coater,
The protective layer of the present invention is obtained by coating and drying using a device such as a blade coater. However, the protective layer may be coated at the same time as the heat-sensitive layer, or after coating the heat-sensitive layer, the heat-sensitive layer may be dried once and then coated thereon. The dry coating amount of the protective layer is preferably 0.5 to 5 g/m2, more preferably 1 to 3 g/m2. After applying the protective layer, calendering may be performed if necessary.

Next, a typical thermosensitive color forming layer of the present invention will be described. As an example, a heat-sensitive color forming layer using an electron-donating dye precursor (hereinafter referred to as a color former) and an electron-accepting compound (hereinafter referred to as a color developer) will be described. coloring agent,
The color developer is dispersed separately, generally together with an aqueous solution of a water-soluble polymer such as polyvinyl alcohol, to a size of several microns or less using a ball mill, sand mill, or the like. These dispersions are mixed after dispersion, and oil-absorbing pigments, binders, waxes, metal soaps, antioxidants, ultraviolet absorbers, surfactants, antistatic agents, etc. are added as necessary to form a heat-sensitive coloring layer coating solution. shall be.

Examples of color formers used in the present invention include triphenylmethane phthalide compounds, fluoran compounds, phenothiazine compounds, indolyl phthalide compounds, leucoauramine compounds, rhodamine lactam compounds, and triphenylmethane phthalide compounds. There are various compounds such as phenylmethane compounds, triazene compounds, spiropyran compounds, and fluorene compounds. Specific examples of phthalides are U.S. Reissue Patent Specification No. 23,024, U.S. Patent Specification No. 3,
No. 491,111, No. 3,491,112, No. 3
, No. 491,116 and No. 3,509,174,
Specific examples of fluorans are given in U.S. Patent No. 3,624,
No. 107, No. 3,627,787, No. 3,641
, No. 011, No. 3,462,828, No. 3,68
No. 1,390, No. 3,920,510, No. 3,9
No. 59,571, specific examples of spirodipyrans are given in U.S. Patent No. 3,971,808, and pyridine and pyrazine compounds are given in U.S. Patent No. 3,775,424.
No. 3,853,869, No. 4,246,31
No. 8, specific examples of fluorene compounds are given in Japanese Patent Application No. 61-24.
It is described in No. 0989, etc. Among these, 2-arylamino-3-H, halogen-, alkyl-, or alkoxy-6-substituted aminofluorane which produces black color is particularly effective. Specific examples include 2-anilino-3-methyl-6-
Diethylaminofluorane, 2-anilino-3-methyl-6-N-cyclohexyl-N-methylaminofluorane, 2-p-chloroanilino-3-methyl-6-dibutylaminofluorane, 2-anilino-3-methyl- 6-
Dioctylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-anilino-3
-Methyl-6-N-ethyl-N-isoamylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-
N-dodecylaminofluorane, 2-anilino-3-methoxy-6-dibutylaminofluorane, 2-o-chloroanilino-6-dibutylaminofluorane, 2-p-
Chloroanilino-3-ethyl-6-N-ethyl-N-isoamylaminofluorane, 2-o-chloroanilino-
6-p-butylanilinofluorane, 2-anilino-3
-pentadecyl-6-diethylaminofluorane, 2-
Anilino-3-ethyl-6-dibutylaminofluorane, 2-o-toluidino-3-methyl-6-diisopropylaminofluorane, 2-anilino-3-methyl-6-
N-isobutyl-N-ethylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-tetrahydrofurfurylaminofluorane, 2-anilino-3-chloro-6-N-ethyl-N- Isoamylaminofluorane, 2-anilino-3-methyl-6-N-methyl-N-
γ-Ethoxypropylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-γ-ethoxypropylaminofluorane, 2-anilino-3-methyl-6
-N-ethyl-N-γ-propoxypropylaminofluorane and the like.

Examples of the color developer used in the present invention include 2
, 2-bis(4'-hydroxyphenyl)propane (common name 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'-hydroxy) phenyl)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, 1,1-bis(4'-hydroxyphenyl) Dodecane, 1,4-bis(p-hydroxyphenylcumyl)benzene, 1,3-bis(p-
hydroxyphenylcumyl)benzene, bis(p-hydroxyphenyl)sulfone, bis(3-allyl-4-
Bisphenols such as hydroxyphenyl) sulfone, bis(p-hydroxyphenyl)acetic acid benzyl ester, 3,5-di-α-methylbenzyl salicylic acid, 3,
5-di-tert-butylsalicylic acid, 3-α-α-
Salicylic acid derivatives such as dimethylbenzyl salicylic acid and 4-(β-p-methoxyphenoxyethoxy) salicylic acid, or polyvalent metal salts thereof (particularly preferred are zinc and aluminum), benzyl erther p-hydroxybenzoate,
Oxybenzoic acid esters such as p-hydroxybenzoic acid-2-ethylhexyl ester and β-resorcinic acid-(2-phenoxyethyl) ester, p-phenylphenol, 3,5-diphenylphenol, cumylphenol, 4-hydroxy Examples include phenols such as -4'-isopropoxy-diphenylsulfone and 4-hydroxy-4'-phenoxy-diphenylsulfone. Among these, bisphenols are particularly preferred for the purpose of improving dot reproducibility. The color developer is preferably used in an amount of 50 to 800% by weight, more preferably 100% by weight of the color former.
~500% by weight. Further, two or more of the above electron-accepting compounds may be used in combination.

Further, the heat-sensitive recording material of the present invention contains a thermofusible substance (hereinafter referred to as a sensitizer) in any layer constituting the heat-sensitive recording material in order to improve thermal responsiveness. Good too. Examples of sensitizers include benzyl p-benzyloxybenzoate, β-naphthyl-benzyl ether, stearamide, stearyl urea, p-benzylbiphenyl, di(2-methylphenoxy)ethane, di(2-methoxy) phenoxy)ethane, β-naphthol-(p-methylbenzyl) ether, α-naphthyl-benzyl ether, 1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-isopropylphenyl ether, 1 , 4-butanediol-p-tertiary octylphenyl ether, 1-phenoxy-2-
(4-ethylphenoxy)ethane, 1-phenoxy-2
-(4-Chlorphenoxy)ethane, 1,4-butanediol phenyl ether, diethylene glycol-bis-(4-methoxyphenyl) ether, 4-ethoxyphenyl-p-chlorobenzyl ether, 1(4-methoxy-phenoxy)- 2-phenoxy-propane, 1,3
-bis-(4-methoxyphenoxy)propane, 3-methyl-4-chlorophenyl-p-methoxybenzyl ether, 3,5-dimethyl-4-chlorophenyl-p-methoxybenzyl ether, 4-chlorophenyl-p- Examples include methoxybenzyl ether, 1-phenoxy-2(4-methoxy-phenoxy)-propane, oxalic acid dibenzyl ester, oxalic acid di(p-methylbenzyl) ester, and the like. These sensitizers may be used alone or in combination. In order to obtain sufficient thermal responsiveness, it is preferably used in an amount of 10 to 200% by weight, more preferably 20 to 150% by weight, based on the color developer. The sensitizer can be added to either the color former, the color developer, or both and dispersed at the same time, or a thermal eutectic with the color former or color developer can be prepared in advance, cooled, and then dispersed. good.

The binder is preferably a compound that dissolves at least 5% by weight in water at 25°C, specifically,
Polyvinyl alcohol (including modified polyvinyl alcohols such as carboxy-modified, itaconic acid-modified, maleic acid-modified, silica-modified, etc.), methylcellulose, carboxymethylcellulose, starches (including modified starch), gelatin, gum arabic, casein, styrene-maleic anhydride Examples include acid copolymer hydrolysates, polyacrylamide, and saponified vinyl acetate-polyacrylic acid copolymers. These binders are used not only for dispersion but also for the purpose of improving coating film strength. For this purpose, styrene-butadiene copolymers, vinyl acetate copolymers,
Synthetic polymer latex binders such as acrylonitrile/butadiene copolymer, methyl acrylate/butadiene copolymer, and polyvinylidene chloride can also be used together. Further, a crosslinking agent suitable for the binder may be added depending on the type of the binder, if necessary.

Examples of pigments include calcium carbonate, aluminum hydroxide, barium sulfate, lithopone, rosite, kaolin, silica, and amorphous silica. Higher fatty acid metal salts are used as metal soaps, including zinc stearate,
Zinc myristate, calcium stearate, aluminum stearate are used.

Examples of wax include montan wax, paraffin wax, carnauba wax, microcrystalline wax, polyethylene wax, and the like.

Furthermore, if necessary, a back coat layer may be provided on the opposite side of the support of the heat-sensitive recording material from the heat-sensitive coloring layer. As the back coat layer, any material known as a back coat layer for heat-sensitive recording materials can be used. EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited only to the Examples below.

[0022] The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to the following Examples. All concentrations used herein are in weight percent.

[0023]

【Example】

(Preparation of heat-sensitive coating liquid) As a coloring agent, 2-anilino-3-
Methyl-6-N-dibutyl-aminofluorane, bisphenol A as a color developer, β-naphthyl- as a sensitizer
20 g of each benzyl ether was dispersed with 100 g of a 5% polyvinyl alcohol (Kuraray PVA-105) aqueous solution in a ball mill overnight to obtain an average particle size of 1.5 μm or less to obtain each dispersion. In addition, calcium carbonate 80
g was dispersed in a homogenizer together with 160 g of a 0.5% sodium hexametaphosphate solution to obtain a pigment dispersion. Each dispersion prepared as above was mixed with 5 g of color former dispersion, 10 g of color developer dispersion, 10 g of sensitizer dispersion, and 5 g of calcium carbonate dispersion, and then a 21% zinc stearate emulsion was added. 3 g was added to obtain a heat-sensitive coating liquid. The obtained heat-sensitive coating liquid was applied onto high-quality paper with a basis weight of 50 g/m2 using a wire bar so that the dry coating amount was 6 g/m2,
It was dried in an oven at 50°C to obtain thermal recording paper. On the heat-sensitive coloring layer of the obtained heat-sensitive recording paper, the protective layer coating solution of the following example was applied with a wire bar at a concentration of 2.5 g/m2, and dried in an oven at 50°C to form the heat-sensitive recording paper of the present invention. I got the material.

(Example-1) 80 g of aluminum hydroxide (manufactured by Showa Denko K.K., Hygilite H42) was dispersed with 160 g of a 0.5% aqueous solution of sodium hexametaphosphate using a homogenizer. To 60 g of this dispersion, 400 g of 15% polyvinyl alcohol (manufactured by Kuraray Co., Ltd., PVA-205), 3
0% reinforced rosin sizing agent (Arakawa Chemical Co., Ltd. Size Pine E)
) and 7.5 g of 30% zinc stearate (Hydrin Z-7-30, manufactured by Chukyo Yushi Co., Ltd.) were added to obtain a protective layer coating solution.

(Example 2) Instead of using the reinforced rosin sizing agent (Size Pine E manufactured by Arakawa Chemical Co., Ltd.) in Example-1, 20 g of a strengthened rosin sizing agent (Size Pine G manufactured by Arakawa Chemical Co., Ltd.) was used. A protective layer coating liquid was obtained in the same manner except that the protective layer coating liquid was prepared using

(Example-3) Instead of using the reinforced rosin sizing agent (Sizepine E manufactured by Arakawa Chemical Co., Ltd.) in Example-1, 20 g of an emulsion type sizing agent (Sizepine N-700 manufactured by Arakawa Chemical Co., Ltd.) was used. A protective layer coating liquid was obtained in the same manner except that the protective layer coating liquid was prepared by using the following method.

(Comparative Example-1) A protective layer coating liquid was obtained in the same manner as in Example-1 except that the protective coating liquid was prepared without using the reinforced rosin sizing agent (Size Pine E manufactured by Arakawa Chemical Co., Ltd.). .

(Comparative Example-2) Instead of using the reinforced rosin sizing agent of Example-1 (Sizepine E manufactured by Arakawa Chemical Co., Ltd.), a 30% paraffin wax dispersion (H manufactured by Chukyo Yushi Co., Ltd.) was used.
A heat-sensitive recording material was obtained in the same manner except that 20 g of idrin P-7) was used to prepare a protective layer coating solution.

(Comparative Example-3) Instead of using the reinforced rosin sizing agent (Sizepine E manufactured by Arakawa Chemical Co., Ltd.) of Example-1, 20 g of β-naphthylbenzyl ether dispersion was used in the coating liquid for the heat-sensitive coloring layer. A protective layer coating liquid was obtained in the same manner except that the protective layer coating liquid was prepared using

(Comparative Example 4) A heat-sensitive recording material without a protective layer was obtained.

The heat-sensitive recording material obtained as described above was surface-treated with a calender and the smoothness was adjusted to Bekk smoothness of 400±50 seconds to obtain a heat-sensitive recording material.

Pencil writing properties were measured using a mechanical pencil loaded with a lead of hardness B and 0.5 mm under a load of 500 g, and the density of the written portion was measured using Macbeth RD-918 (Visual). Regarding the stamp ink, I used Shachihatazol stamp pad red stamp ink to stamp.
The degree of bleeding is (A) barely noticeable.
Judgment was made into three levels: (B) the stamped characters were blurred but the stamped characters were readable, and (C) the stamped characters were blurred to the extent that they were unreadable. Also, regarding fog when using magic ink red, (A) there is almost no fog, (B) there is some discoloration but you can tell that it is red, (C) the discoloration is so large that you can't even tell that it is red. It was judged in three stages.

[0033] The color density was determined using a Kyocera printing tester with a printing energy of 20 mJ while using a pressure roll.
/mm2, and the color density was measured using a Macbeth reflection densitometer.

[0034]

【Effect of the invention】

[0035]

[Table 1]

From the results in Table 1, it can be seen that the recording material of the present invention is a heat-sensitive recording material with good pencil writing properties and stamp imprintability.

Claims (1)

[Claims] 1. A heat-sensitive recording material comprising a protective layer containing a pigment and a binder as main components on a heat-sensitive color forming layer, wherein the protective layer contains a rosin compound.