JPH08324123A - Thermal recording - Google Patents

Abstract

(57) An object of the present invention is to provide a thermosensitive recording medium having excellent recording runnability and preservability against chemicals such as a plasticizer of a recorded image. A thermosensitive recording medium in which a recording layer containing a colorless or light-colored basic dye and a coloring agent, and a protective layer containing an aqueous polymer compound are sequentially provided on a support, and an average of the protective layers is A polypropylene wax having a particle diameter of 0.5 to 5 μm is used in an amount of 0.3 to 10 relative to the total solid amount of the protective layer.
A heat-sensitive recording material containing wt%.

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 utilizing a color-forming reaction between a leuco dye and a color-developing agent, and particularly to a heat-sensitive recording material excellent in recording running property and storage stability against chemicals such as a plasticizer of a recorded image. It is about.

[0002]

2. Description of the Related Art A heat-sensitive recording material is known in which a colored or light-colored leuco dye and an organic or inorganic coloring agent are used to obtain a recorded image by contacting both coloring substances with heat. Has been. Since such a thermal recording medium is relatively inexpensive, the recording device is compact, and its maintenance is easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

In particular, in recent years, the printing speed of a printer apparatus using such a heat-sensitive recording system has been increased, and along with that, the apparatus has been energetically promoted to be smaller and to save energy, and its applications have been expanded more and more.

From the above-mentioned current situation, the demands on the thermal recording medium have been diversified, and in recent years, especially in the field of small fax machines in parallel with the energy saving tendency of recording equipment,
High sensitivity and good slidability (low friction and easy slipping)
A thermal recording material is required. Further, a general heat-sensitive recording material has a drawback that a recorded image is easily faded or discolored due to an influence of oils and fats or a plasticizer contained in a plastic film. For this reason, there is an increasing demand for a thermal recording material having a high recording density, good slidability, and a recorded image which is not discolored due to the influence of oils and fats and plasticizers and which is excellent in storage stability of the recorded image.

Waxes are added to the outermost surface layer of the thermosensitive recording medium to improve the slidability, thereby reducing minute frictional heat generated by scratching, rubbing, etc., and unnecessary coloring of the recording layer, so-called " There is also a proposal to prevent "scratch coloring". However, when a lubricant such as a metal soap or wax is used by a conventional method in order to greatly improve the slidability of the heat-sensitive recording material, it is necessary to remarkably increase the addition amount. In such a case, a drastic decrease in recording density and adhesion of scum to the thermal head cannot be avoided. Further, depending on the type of lubricant used, a problem such as sticking at the time of recording may be accompanied.

On the other hand, there has been proposed a method of forming a protective layer containing a water-soluble polymer compound on the recording layer in order to improve the storability of the recorded image, but there is a problem in recording runnability.
However, in order to improve recording runnability, it is preferable to incorporate polyethylene wax as a lubricant in the protective layer.
As described in Japanese Patent No. 135684 and Japanese Unexamined Patent Publication No. 1-209177, there is a demand for a thermal recording material having more excellent recording runnability.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording medium which is excellent in recording runnability and storage stability against chemicals such as a plasticizer of a recorded image.

[0008]

DISCLOSURE OF THE INVENTION The present invention relates to a heat-sensitive recording material in which a recording layer containing a colorless or light-colored leuco dye and a coloring agent and a protective layer containing an aqueous polymer compound are sequentially provided on a support. Alternatively, a recording layer containing a leuco dye and a colorant, or a protective layer containing an aqueous polymer compound is sequentially provided on one surface of the support, and an aqueous polymer compound is contained on the other surface of the support. In the thermal recording medium provided with the back surface layer, the average particle size is 0.5 in the protective layer or the back surface layer.
By containing 0.3 to 10% by weight of polypropylene wax having a particle size of 5 μm with respect to the total solid amount of the protective layer, the above problems have been solved and completed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the heat-sensitive recording material of the present invention has an average particle size of 0.5 to 5 μm, more preferably 0.
A polypropylene wax having a thickness of 8 to 3 μm is contained in an amount of 0.3 to 10% by weight based on the total solid content of the protective layer. The polypropylene wax is particularly suitable for recording runnability and storability for chemicals such as a plasticizer of a recorded image. It is not always clear why the excellent effect is obtained. But,
According to the results of studies by the present inventors, heat resistance and slippability are improved by using a polypropylene wax having a higher softening point (or melting point) than conventional lubricants such as polyethylene wax, paraffin wax, and zinc stearate. As a result, it is presumed that the preferable effects as described above are exhibited. Furthermore, by including polypropylene wax having an average particle size of 0.5 to 5 μm in the protective layer or the back surface layer, for example, even if the back surface layer is formed of the rewetting adhesive paste, the protection layer surface and the back surface layer are attached. Do not block. If the average particle diameter of the polypropylene wax is less than 0.5 μm, the effect of improving slippage is not exhibited unless the addition amount is increased, and as a result, problems such as sticking and sticking of dust are accompanied. On the other hand, when the average particle diameter exceeds 5 μm, the sliding effect is exhibited, but the recording image quality deteriorates.

The amount of polypropylene wax added is 0.3 to 10% by weight based on the total solid amount of the protective layer or the back surface layer,
More preferably, it is desirable to adjust in the range of 0.6 to 6% by weight. If it is less than 0.1% by weight, the desired effect of the present invention cannot be obtained, and if it exceeds 10% by weight, not only the storability of a recorded image is significantly deteriorated, but also the suitability for equipment such as sticking and dust adhesion is reduced. Problems also arise.

In the present invention, specific examples of the aqueous polymer compound which constitutes the protective layer or the back surface layer together with the polypropylene wax having the above-mentioned average particle diameter of 0.5 to 5 μm include the following. Polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, starch and its derivatives, casein, sodium alginate, polyvinylpyrrolidone, polyacrylamide, styrene-maleic acid copolymer salt, polyurethane Resins, urea resins, melamine resins, polyamide resins, epichlorohydrinized polyamide resins, etc., of course, these aqueous polymer compounds may be used in a mixture of two or more kinds, if necessary, or further a styrene / butadiene copolymer emulsion. It is also possible to use synthetic polymer emulsions such as styrene-acrylic acid ester copolymer emulsion and polyacrylic ester copolymer emulsion. Kill. Among these water-based polymer compounds, acetoacetyl group-modified polyvinyl alcohol is particularly preferably used because it exhibits excellent action and effect in the preservation of recorded images.

If necessary, a pigment may be added to the protective layer or the back surface layer in order to improve printability and running properties. Specific examples of such pigments include:
Inorganic pigments such as calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, talc, kaolin, clay, calcined clay, colloidal silica, styrene microballs, nylon powder, urea filler, formalin resin Examples thereof include fillers and organic pigments such as raw starch granules. The amount used is not particularly limited, but it is desirable to adjust it in the range of 5 to 80% by weight, preferably 20 to 50% by weight, based on the total solid amount of the protective layer or the back surface layer.
In particular, aluminum hydroxide having an average particle diameter of 0.5 to 3.0 μm, preferably 0.8 to 2.5 μm, has less residue (head residue) attached to the thermal head during continuous recording and causes sticking. In addition, it is preferably used because it exerts excellent effects.

The method for preparing the coating liquid for the protective layer and the back surface layer is not particularly limited, and is generally prepared by mixing water with a dispersion medium and the specific polypropylene wax, the aqueous polymer compound and the pigment. Further, a lubricant such as zinc stearate, calcium stearate, carnauba wax, paraffin wax, or ester wax may be added to the coating liquid for the protective layer and the back surface layer, if necessary, within a range that does not impair the desired effects of the present invention. You can also Also,
Surfactants such as sodium dioctyl sulfosuccinate (as dispersants and wetting agents), glyoxal, boric acid,
Hardeners such as dialdehyde starch and epoxy compounds,
It is also possible to appropriately add various auxiliaries such as antifoaming agents, colored dyes and fluorescent dyes.

The leuco dye used in the recording layer is
Various known colorless or pale leuco dyes can be used,
Specifically, for example, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-
Diethylamino-2-methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (N-ethyl-Np-tolyl) amino-7-
N-methylanilinofluorane, 3-diethylamino-
7-anilinofluorane, 3-cyclohexylamino-
6-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-
Chlorofluorane, 3-diethylamino-7,8-benzofluorane, 3- (N-ethyl-p-toluidino)-
7-methylfluorane, 3-diethylamino-6,8-
Dimethylfluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluorane, 3
-(N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-
6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane,
3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-7-
(O-Chlorophenylamino) fluorane, 3-diethylamino-7- (o-fluorophenylamino) fluorane, 3-di (n-butyl) amino-7- (o-fluorophenylamino) fluorane, 3- (N-ethyl) -P
-Toluidino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3- (N-methyl-Nn-propylamino) -6-methyl-7. -Anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3
-Dibutylamino-6-methyl-7-m-toluidinofluorane, 3- (Nn-hexyl-N-ethyl) amino-6-methyl-7-anilinofluorane, 3- (N-
Ethyl-N-isobutyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-
7-p-ethoxyanilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 2,2-bis {4- [6 '-(N-cyclohexyl-N-methylamino) -3'-methylspiro [phthalide-3,9'-xanthen-2'-ylamino] phenyl} propane, 3
-Diethylamino-7- (3'-trifluoromethylphenyl) aminofluorane, 3,3-bis [1- (4-
Methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1,1-bis (4-pyrrolidinophenyl) ) Ethylene-2-yl] -4,5,6
7-Tetrabromophthalide, 3-p- (p-dimethylaminoanilino) anilino-6-methyl-7-chlorofluorane, 3-p- (p-chloroanilino) anilino-6
-Methyl-7-chlorofluorane, 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-
Dimethylamino) phthalide and the like can be mentioned. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Various kinds of colorants are known as the colorants used in combination with the above leuco dyes, for example, 4,4'-isopropylidenediphenol, 1,1.
-Bis (4-hydroxyphenyl) cyclohexane,
2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4'-dihydroxydiphenyl sulfone, 4-hydroxy -4'-isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxyphenyl-4'-benzyloxyphenyl sulfone, 3,4- Dihydroxyphenyl-4'-methylphenyl sulfone, bis (4-
Hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, butyl bis (p-hydroxyphenyl) acetate, methyl bis (p-hydroxyphenyl) acetate, 1,1-bis (4-hydroxyphenyl) -1-phenylethane,
1,4-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di (4- Phenolic compounds such as hydroxy-3-methylphenyl) sulfide, 2,2′-thiobis (3-tert-octylphenol) and 2,2′-thiobis (4-tert-octylphenol), N, N′-di-m −
Thiourea compounds such as chlorophenylthiourea, N-
(P-Toluenesulfonyl) carbamoyl acid p-cumylphenyl ester, N- (p-toluenesulfonyl) carbamoyl acid p-benzyloxyphenyl ester, N
-(O-toluoyl) -p-toluenesulfoamide, N
-(P-toluenesulfonyl) -N '-(p-tolyl)
Urea or the like having a —SO ₂ NH— bond in the molecule, 4
Zinc- [2- (p-methoxyphenoxy) ethyloxy] salicylate, Zinc 4- [3- (p-tolylsulfonyl) propyloxy] salicylate, 5- [p- (2-p-
Methoxyphenoxyethoxy) cumyl] zinc salicylate and the like can be mentioned. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

The use ratio of the leuco dye and the color-developing agent is appropriately selected depending on the types of the leuco dye and the color-developing agent used and is not particularly limited, but generally 1 part by weight of the leuco dye is used. 1-5 parts by weight, preferably 2-3
About a part by weight of the coloring agent is used.

Further, a sensitizer may be used in combination for increasing the recording sensitivity. Specific examples of such sensitizers include:
For example, stearic acid amide, methoxycarbonyl-N-
Stearic acid benzamylde, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebisstearic acid amide, behenic acid amide, methylenebisstearic acid amide, N-methylolstearic acid amide,
Dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-
Naphthylbenzyl ether, m-terphenyl, oxalic acid dibenzyl, oxalic acid di-p-chlorobenzyl ester, oxalic acid di-p-methylbenzyl ester, p-benzylbiphenyl, p-tolylbiphenyl ether, di (p-methoxyphenoxy) Ethyl) ether, 1,2-
Di (3-methylphenoxy) ethane, 1,2-di (4-
Methylphenoxy) ethane, 1,2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-
Methoxyphenoxy) -2- (3-methylphenoxy)
Ethane, p-methylthiophenylbenzyl ether,
1,4-di (phenylthio) butane, p-acetotoluidide, p-acetophenetide, N-acetoacetyl-
Examples thereof include p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like.

In the present invention, a storage stability improver may be added to the recording layer in order to enhance the storage stability of a recorded image.
Examples of such storability improvers include the following. 2,2'-methylenebis (4-methyl-6-tert-
Butylphenol), 2,2'-ethylidene bis (4,
6-di-tert-butylphenol), 4,4′-butylidenebis (6-tert-butyl-m-cresol), 1-
[Α-Methyl-α- (4′-hydroxyphenyl) ethyl] -4- [α ′, α′-bis (4 ″ -hydroxyphenyl) ethyl] benzene, 1,1,3-tris (2-methyl-) 4-hydroxy-5-cyclohexylphenyl)
Butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4′-
Dihydroxy-3,3 ', 5,5'-tetrabromodiphenyl sulfone, 2,2-bis (4-hydroxy-3,
5-dibromophenyl) propane, 2,2-bis (4-
Hydroxy-3,5-dichlorophenyl) propane,
Hindered phenol compounds such as 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,
4-diglycidyloxybenzene, 4,4'-diglycidyloxydiphenyl sulfone, 4-benzyloxy-
Epoxy compounds such as 4 '-(2-methylglycidyloxy) diphenyl sulfone, diglycidyl terephthalate, cresol novolac type epoxy resin, phenol novolac type epoxy resin, bisphenol A type epoxy resin, N, N'-di-2-naphthyl- Examples thereof include p-phenylenediamine, sodium or polyvalent metal salt of 2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate, and bis (4-ethyleneiminocarbonylaminophenyl) methane. Of these, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane is preferably used because it has an excellent effect on the water resistance of a recorded image and does not easily cause background fog.

The recording layer coating liquid containing these substances generally uses water as a dispersion medium and is mixed with a dyeing agent, a coloring agent, a sensitizer, a storability improving agent, etc. by a stirring and crushing machine such as a ball mill, an attritor or a sand mill. Are dispersed together or separately.

In the coating liquid, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, silicon modified polyvinyl alcohol are usually used as binders in the coating liquid. Diisobutylene / maleic anhydride copolymer salt, styrene /
Maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene /
At least one kind of butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane resin and the like is blended in the range of about 5 to 30% by weight based on the total solid content of the recording layer.

If desired, various auxiliary agents can be added to the coating solution. For example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts. , Zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and other waxes,
An antifoaming agent, a coloring dye, a pigment, etc. are added as appropriate.

Examples of the pigment include kaolin, clay,
Inorganic pigments such as calcium carbonate, aluminum hydroxide, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth, fine anhydrous silica, activated clay and styrene microballs,
Examples thereof include nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles.

The method of forming the recording layer, the protective layer and the back surface layer is not particularly limited, and examples thereof include air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating and die coating. The coating liquid for recording layer is applied and dried on the support by a suitable coating method, and then the coating liquid for protective layer is applied and dried on the recording layer. The support may be appropriately selected from paper, plastic film, synthetic paper, non-woven fabric, metal deposit, etc., and used. Further, the coating amount of the coating liquid for the recording layer is 2 to 12 in dry weight.
g / m ^2, 0.5 to 10 g preferably 3 to 10 g / m ² approximately, the coating amount of the protective layer or the back layer coating solution on a dry weight
/ M ² , preferably in the range of about ² to 6 g / m ² .

If necessary, an undercoat layer may be provided on the support, smoothing treatment such as super calendering may be applied after coating each layer, or an adhesive label may be applied to the back surface of the thermosensitive recording medium to prepare an adhesive label. If necessary, various known techniques in the field of producing a thermosensitive recording medium can be added such as providing a magnetic recording layer, a coating layer for printing, and a thermal transfer recording layer.

[0025]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, unless otherwise indicated, the part and% in an example show a weight part and weight%, respectively.

Example 1 Preparation of solution A 3-di (n-butyl) amino-6-methyl-7-anilinofluorane 10 parts, 1,2-di (3-methylphenoxy) ethane 20 parts, 5 parts of methylcellulose % Aqueous solution 5 parts and water 40 parts were pulverized with a sand mill until the average particle size became 2 μm.

Preparation of Solution B A composition consisting of 30 parts of 4-hydroxy-4′-isopropoxydiphenyl sulfone, 5 parts of a 5% aqueous solution of methylcellulose and 80 parts of water was used in a sand mill to give an average particle diameter of 2
It was pulverized to a size of μm.

Solution C Preparation 1,1,3-Tris (2-methyl-4-hydroxy-5)
A composition consisting of 30 parts of -cyclohexylphenyl) butane, 5 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water was pulverized with a sand mill until the average particle size became 1 µm.

Formation of Recording Layer 75 parts of solution A, 115 parts of solution B, 20 parts of solution C, 100 parts of 10% aqueous solution of polyvinyl alcohol, 4 parts of glyoxal
0% aqueous solution of 3 parts of aluminum hydroxide and 4 parts The mixture stirred to obtained coating liquid, as the coating amount after drying of 5 g / m ² on one surface of woodfree paper of 44 g / m ² coating It was dried to obtain a thermosensitive recording medium.

Formation of Protective Layer 210 parts of 10% aqueous solution of polyvinyl alcohol modified with acetoacetyl group, 40 parts of aluminum hydroxide having an average particle size of 1.0 μm, kaolin [trade name: UW-90, manufactured by EMC] 20 parts, average 40% dispersion of polypropylene wax with a particle size of 1 μm [Product name: Chemipearl WP-10
0, manufactured by Mitsui Petrochemical Co., Ltd.] 12 parts, 0.7 parts of an epoxy curing agent having a solid concentration of 30% [trade name: PA-800, manufactured by Nippon PMC], and 100 parts of water are mixed and stirred. The coating solution for protective layer thus obtained was applied and dried on the recording layer so that the coating amount after drying was 4 g / m ^2, and then supercalendering was performed to obtain a thermosensitive recording medium.

Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 40 parts of kaolin was used instead of 40 parts of aluminum hydroxide in forming the protective layer of Example 1.

Example 3 In the formation of the protective layer of Example 1, the average particle size was 1 μm.
4 parts of polypropylene wax having an average particle size of 1 μm instead of 12 parts of 40% dispersion of polypropylene wax
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 1 part of the 0% dispersion liquid was used.

Example 4 In the formation of the protective layer of Example 1, the average particle size was 1 μm.
4 parts of polypropylene wax having an average particle size of 3 μm instead of 12 parts of 40% dispersion of polypropylene wax
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 12 parts of 0% dispersion liquid was used.

Example 5 In the formation of the protective layer of Example 1, the average particle size was 1 μm.
4 parts of polypropylene wax having an average particle size of 1 μm instead of 12 parts of 40% dispersion of polypropylene wax
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 20 parts of 0% dispersion liquid was used.

Example 6 On the other side of the thermosensitive recording medium obtained in Example 1, 210 parts of a 10% aqueous solution of silicon-modified polyvinyl alcohol, 60 parts of kaolin, and a 40% dispersion of polypropylene wax having an average particle diameter of 1 μm were prepared. [Product name: Chemipearl WP-10
0, Mitsui Petrochemical Co., Ltd.] 12 parts, and a composition comprising 100 parts of water were mixed and stirred to obtain a back layer coating solution, which was coated and dried so that the coating amount after drying was 2 g / m ^2. Then, a super calender treatment was performed to obtain a heat sensitive recording material.

Example 7 In the formation of the protective layer of Example 6, the average particle size was 1 μm.
A thermosensitive recording medium was obtained in the same manner as in Example 6 except that 6 parts of a 30% dispersion of zinc stearate having an average particle diameter of 1 μm was used instead of 12 parts of the 40% dispersion of polypropylene wax.

Comparative Example 1 In forming the protective layer of Example 1, the average particle size was 1 μm.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 14 parts of a 36% dispersion of zinc stearate having an average particle diameter of 3 μm was used in place of 12 parts of the 40% dispersion of polypropylene wax.

Comparative Examples 2 to 6 In forming the protective layer of Example 1, the average particle size was 1 μm.
Instead of 12 parts of 40% dispersion of polypropylene wax, 40 parts of stearamide having an average particle size of 1 μm are used.
% Dispersion 12 parts (Comparative Example 2), 40% dispersion of ethylenebisstearoamide having an average particle size of 4 μm (Comparative Example 3), 40% dispersion of paraffin wax having an average particle size of 1.7 μm 12 parts (Comparative Example 4), average particle size 3μ
m of 30% dispersion of polyethylene wax (Comparative Example 5) and 12 parts of 40% dispersion of carnauba wax having an average particle size of 0.5 μm (Comparative Example 6) were used, respectively. Similarly, a thermal recording paper having 5 types of protective layers was obtained.

Comparative Example 7 In forming the protective layer of Example 1, the average particle size was 1 μm.
Polypropylene wax 4 having an average particle size of 0.4 μm instead of 12 parts of 40% polypropylene wax dispersion
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 12 parts of 0% dispersion liquid was used.

Comparative Example 8 In forming the protective layer of Example 1, the average particle size was 1 μm.
40% polypropylene wax 40% Polypropylene wax 40% with an average particle size of 6 μm instead of 12 parts
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 12 parts of the dispersion liquid was used.

Comparative Example 9 In the formation of the protective layer of Example 1, the average particle size was 1 μm.
40% polypropylene wax 40% Polypropylene wax 40% with an average particle size of 1 μm instead of 12 parts
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 0.5 part of the dispersion liquid was used.

Comparative Example 10 In the formation of the protective layer of Example 1, the average particle size was 1 μm.
40% polypropylene wax 40% Polypropylene wax 40% with an average particle size of 1 μm instead of 12 parts
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 30 parts of the dispersion liquid was used.

The thermal recording material thus obtained was subjected to the following evaluation tests, and the results are shown in Table 1. [Coloring property] Using a heat-sensitive evaluation machine [trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.], each heat-sensitive recording material is caused to develop color with an applied energy of 0.50 mJ / dot, and the color density of the obtained recorded image is determined by the Macbeth density. Measurement was carried out in visual mode with a total meter [RD-914 type, manufactured by Macbeth Co.], and the results are shown in the table.

[Recording Image Quality] The image quality of the recorded image obtained in the above [Coloring property] was visually evaluated as follows. ◯: The recorded image is uniform with no white spots (the areas that should have been colored are not spot-colored). X: The recorded image has white spots.

[High Temperature Resistance] The thermosensitive recording medium after recording in the above [color development] was left at 80 ° C. for 24 hours, and the color density and background density were measured with a Macbeth densitometer (visual mode). The high temperature resistance was evaluated.

[Slipping Suitability Test] According to JIS-P8147, a surface property measuring device (HEIDON-14D) was used to measure static on the protective layer surface and the back surface of the support in the longitudinal direction of the thermosensitive recording material (thermosensitive recording paper). The dynamic coefficient of friction was measured.

[Sticking] An image was recorded by an aviation tag auto-labeler (trade name: 201 type, manufactured by UBI), and the occurrence of sticking was observed. A: No sticking occurred. ◯: Sticking is slightly generated, but there is no problem in recording image quality. Δ: A little sticking occurred and the recorded image quality was a little poor. Poor: Sticking occurred remarkably, and recording failure occurred.

[Plasticizer resistance] polypropylene pipe (4
A vinyl chloride wrap film (made by Mitsui Toatsu Co., Ltd.) is wound three times on a 0 mm Φ tube, and each heat-sensitive recording material with print coloring is sandwiched so that the print coloring surface is on the outside. Wrap the vinyl chloride wrap film in five layers,
The print density after standing for 24 hours at 40 ° C. at a point of 0.45 mj / dot was measured by a Macbeth densitometer (visual mode), and the density maintenance rate was calculated. (The higher the number,
Good plasticizer resistance. )

[0049]

[Table 1]

[0050]

As is clear from the results shown in Table 1, the present invention is particularly excellent in preservability and is excellent in slidability, plasticizer resistance and preservability without causing a decrease in recording density or sticking. It was a thermosensitive recording medium.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masatoshi Okuda 4-3-1, Jokoji, Amakosaki City, Hyogo Prefecture Shin-Oji Paper Co., Ltd. Kanzaki Mill

Claims (3)

[Claims] 1. A thermosensitive recording medium comprising a support, on which a recording layer containing a leuco dye and a coloring agent, and a protective layer containing an aqueous polymer compound are sequentially provided, and the average particle size of the protective layer is 0. A heat-sensitive recording material, characterized in that a polypropylene wax of 0.5 to 5 μm is contained in an amount of 0.3 to 10% by weight based on the total solid amount of the protective layer. 2. A recording layer containing a leuco dye and a colorant, and a protective layer containing an aqueous polymer compound are sequentially provided on one surface of a support, and the aqueous polymer is provided on the other surface of the support. In a thermal recording material provided with a backside layer containing a compound, the average particle size is 0.5 to 5 μm in the protective layer or the backside layer.
A heat-sensitive recording material, characterized in that the polypropylene wax is contained in an amount of 0.3 to 10% by weight based on the total solid amount of the protective layer or the back surface layer. 3. The heat-sensitive recording material according to claim 1 or 2, wherein the protective layer further contains aluminum hydroxide in an amount of 5 to 50% by weight based on the total solid content of the protective layer.