JPS6315783A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance stability to water of recorded images and moisture resis tance, by incorporating a specified heat-fusible substance into a recording layer of a thermal recording material whose layer comprises a basic dye and a color reaction agent for developing the color of the dye when being heated. CONSTITUTION:A heat-fusible substance of the formula, wherein each of R1-R6 is H, a halogen, 1-8C alkyl or 1-8C alkoxyl, is incorporated in a recording layer of a thermal recording material which layer comprises a colorless or light-colored basic dye and a color reaction agent for developing the color of the dye when being heated. The heat-fusible substance of the formula may be 2-[2-hydroxy-3,5-bis(alpha,alpha-dimethylbenzyl)phenyl]-2H-benzotriazole, 2-[2- hydroxy-3,5-bis(alpha,alpha-dimethylbenzyl)phenyl]-5-chloro--2H-benzot riazole or the like, and is preferably used in an amount of about 0.05-5pts.wt. per 1pt.wt. of the dye.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-sensitive recording medium, and more particularly to a heat-sensitive recording medium with excellent storage stability of recorded images.

``Prior art'' Heat-sensitive recording materials that utilize a color reaction between a colorless or light-colored basic dye and an organic or inorganic coloring agent to obtain a recorded image by bringing both coloring substances into contact with heat are well known. Are known.

Such heat-sensitive recording media are relatively inexpensive, and the recording devices are compact and relatively easy to maintain, so they are used not only as recording media for facsimiles and various computers, but also in a wide range of fields.

For example, one of the fields of use is POS at retail stores, etc.
(Point of 5ales) With the expansion of systemization, the number of cases in which they are used as labels is increasing.2 However, when POS systems are introduced in supermarkets, etc., labels often come into contact with water, plastic wrap, and oil. As a result, a defect in which the recorded image (print) on the heat-sensitive label fades due to its influence is observed.

Therefore, thermal recording materials are required to have qualities such as water resistance, plasticizer resistance, and oil resistance.

``Problems to be Solved by the Invention'' In order to improve the storage stability of recorded images, methods of adding various storage improvers have been proposed, but with the improvement, the whiteness of the recording layer decreases. However, new drawbacks such as the occurrence of fogging at high temperatures have not necessarily been achieved, and therefore satisfactory results have not always been obtained.

When a hensitriazole compound as described in JP-A-58-87093 is contained in the recording layer, excellent effects can be obtained in terms of plasticizer resistance and color fog suppression effect, but water resistance is The improvement effect is not necessarily sufficient.

In view of the current situation, the inventors of the present invention have conducted extensive research on storage improvers to be included in the recording layer, and have found that the following general formula (
When the thermofusible substance represented by r) is used, the water stability and moisture resistance of the recorded image are significantly improved, and color fogging does not occur, and the material is also excellent in plasticizer resistance, oil resistance, etc. The present inventors have discovered that the present invention can achieve the following effects, and have completed the present invention.

[Means for Solving the Problems] The present invention provides a heat-sensitive recording material provided with a recording layer containing a colorless or light-colored basic dye and a coloring agent that causes the basic dye to develop color when heated. This is a heat-sensitive recording material characterized by containing a thermofusible substance represented by the following general formula (1).

[In the formula, R3 to R6 each represent a hydrogen atom, a halogen atom, a C1 to C8 arunal group, or a C1 to B alkoxyl group. [1 action] Specific examples of the thermofusible substance represented by the above general formula (1) used in the present invention include 2-[2-hydroxy-3,5-bis(α,α-dimethylpencil), ) phenyl)-28-hensitriazole, 2-[2-hydroxy-3,5-bis(α.

α-dimethylhensyl)phenyl]-5-chloro-2
IT-Hensetriazole, 2-[2-hydroxy-3
,5-bis(α,α-dimethylbenzyl)phenyl]=
4.5.7-) dichloro-2H-benzotriazole,
Examples include 2-[2-hydroxy-3°5-bis(α,α-dimethylbenzyl)phenyl]-5-methyl-2H-benzotriazole.

Among these, 2-[2-hydroxy-3゜5-bis(α,α-dimethylbenzyl)phenyl]-2H-hensitriazole is particularly preferably used because the desired effects of the present invention can be significantly obtained. .

The amount of these thermofusible substances to be used is adjusted as appropriate depending on the type of thermofusible substance, basic dye, and coloring agent used, but generally 0 to 1 part by weight of dye. .05
It is desirable to use about 5 parts by weight.

Although it is not clear why the water resistance and humidity resistance of the heat-sensitive recording material are significantly improved by adding the substance represented by the general formula (1), the benzotriazole derivative described in JP-A-58-87093 mentioned above It is presumed that since the α,α-dimethylhensyl group is introduced, the hydrophobicity becomes stronger compared to the above, and as a result, the effect of improving water resistance and moisture resistance is promoted.

In the present invention, the basic dye contained in the recording layer includes various known colorless or light-colored basic dyes. For example, 3,3-bis(p-dimethylaminophenyl)
-6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl)phthalide, 3- (p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3,3-bis(l,2-dimethylindole-3)
-yl)-5-dimethylaminophthalide, 3.3-bis(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3゜3-bis(9-ethylcarbazol-3-yl) ) = 6-dimethylaminophthalide, 3
．． 3-bis(6-2-phenylindol-3-yl)-6-dimethylaminophthari, 3-p-dimethylaminophenyl-3-
Triallylmethane dyes such as (1-methylpyrrol-3-yl)-6-dimethylaminophthari F, 4,4'-bis-dimethylaminohenzhydrylhenzyl ether,
N-halophenyl-leukoolamine, N-2,4,5
-Diphenylmethane dyes such as 1-lichlorophenylleucoauramine, hendiylleucomethylene blue, p
- Thiazine dyes such as nitrohendiylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-hensyl-spiro-dinaphthopyran, 3-methyl-naphtho- (6'-methoxyhenzo)
spiro dyes such as spiropyran, 3-propyl-spiro-dihenzopyran, rhodamine-B anilinolactam,
Lactam dyes such as rhodamine (p-nitroanilino)lactam and rhodamine (O-chloroanilino)lactam, 3-dimethylamino-7-methoxyfluorane, 3-
Diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-
Methyl-7-chlorofluorane, 3-diethylamino-6゜7-dimethylfluorane, 3-(N-ethyl-
p-Toluidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylamino Fluoran, 3-diethylamino-7-N-methyl-N-
Benzylaminofluorane, 3-diethylamino-7-
N-chloroethyl-N-methylaminofluorane, 3-
Diethylamino-'1-N-diethylaminofluorane, 3-(N-ethyl-1)-)luidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-
p-Toluidino)-6-methyl-7-(p-toluidino)fluoran, 3-diethylamino-6-methyl-7-
Phenylaminofluorane, -'l-3-diethylamino-7-(2-carbomethoxy-phenylamino)fluorane, 3-(N-cyclohexyl-
N-methylamino)-6-methyl=7-phenylaminofluorane, 3-pyrrolidino-6-methyl-phenylaminofluorane, 3-piperidino-6-methyl-7
-phenylaminofluorane, 3-diethylamino-6
-methyl-7-xylidinofluorane, 3-diethylamino-7-(0-chlorophenylamino)fluoran,
3-dibutylamino-7-(0-chlorophenylamino)fluoran, 3-pyrrolidino-6-methyl-7-p-
Butylphenylaminofluorane, 3-diethylamino-7-(0-fluorophenylamino)fluorane, 3
-dibutylamino-7-(0-fluorophenylamino)fluorane, 3-(N-methyl-N-n-amyl)amino-6-methyl-7-phenylaminofluorane, 3
-(N-ethyl-N7n-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-
N-iso-amyl)amino-6-1〇-methyl-7-phenylaminofluorane, 3-(N-methyl-Nn-hexyl)amino-6-methyl-7-phenylaminofluorane, 3- (N-ethyl-N-n-
Examples include fluoran dyes such as (hexyl)amino-6-methyl-7-phenylaminofluoran and 37(N=ethyl-N-β-ethylhexyl)amino-6-methyl-7-phenylaminofluoran. In addition, two or more types of these basic dyes can be used in combination as necessary.

In addition, examples of the coloring agent include inorganic or organic acidic substances that develop color when in contact with the basic dye, and in particular, 4-hydroxydiphenylsulfone coloring agents represented by the following general formula CI+) and general Formula [111) or general formula (rV)
The 4-hydroxyhenzenesulfonylnaphthalene coloring agent represented by the formula (1) can be used in combination with the specific hensitriazole derivative represented by the general formula (1) to produce a heat-sensitive recording material with more excellent fastness of recorded images. It is preferably used because it can be obtained.

110- [In the formula, R7 to R8 each represent a hydrogen atom, a halogen atom, a C9 to Io alkyl group, a C1 to Io alkoxyl group, a hensyloxy group, an aryloxy group, or a hydroxyl group. Note that R1 and R8 or R6 and R1 may be bonded to each other to form a ring. [In the formula, RI2 to R21 are a hydrogen atom, a halogen atom, a C3-10 alkyl group, a CI to IG alkoxyl group, a hensyloxy group,
Indicates an aryloxy group or a hydroxyl group. ] Specific examples of the coloring agent represented by the -e formula (IT) include 4,4'-dihydroxydiphenylsulfone, 4-
4-hydroxydiphenylsulfones such as hydroxy-4'-chlorodiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-isopropyloxydiphenylsulfone, and 4-hydroxy-4'-butoxydiphenylsulfone derivatives and 3'
.

4'-trimethylene-4-hydroxydiphenylsulfone, 3',4'-trimethylene-2,6-cymethyl-4
-Hydroxydiphenylsulfone, 3',4'-tetramethylene-4-hydroxydiphenylsulfone, 3',
Examples include 4-hydroxydiphenylsulfone derivatives having rings at the 3' and 4' positions, such as 4'-tetramethylene-2-methyl-4-hydroxydiphenylsulfone.

Specific examples of the coloring agent represented by general formula (I[I) or (IV) include 1-(4-hydroxybenzenesulfonyl)naphthalene, 1-(4-hydroxybenzenesulfonyl)-4-methylnaphthalene, etc. , 1-(4-hydroxybenzenesulfonyl)-4-methoxybenzyl, 1
Examples include -(4-hydroxybenzenesulfonyl)-4-chloronaphthalene, 1-(4-hydroxy-2-methylhenzenesulfonyl)naphthalene, and 2-(4-hydroxybenzenesulfonyl)naphthalene.

Coloring agents other than those mentioned above that can be used in the present invention include, for example, activated clay, acid clay, acpulgite, bentonite, colloidal silica, inorganic acidic substances such as aluminum silicate, 4-tert-butylphenol, 4-hydroxydiphenoxide, etc. , α-naphthol, β-naphthol,
4-Hydroxyacetophenol, 4-tert-octylcatechol, 2゜2'-dihydroxydiphenol, 4,4'-isopropylidene bis(2''tert-butylphenol), 4.4'-5ec-butylidene diphenol, 4 -Phenylphenol, 4.4'-isopropyritine diphenol (bisphenol A), 2゜2'-methylenebis (4-chlorophenol), hydroquinone, 4.4'-cyclohexylidene diphenol, 4.4'-dihydroxy diphenyl sulfide, hydroquinone monobenzyl ether, 4-hydroxybenzophenone, 2.4-=12-dihydroxybenzophenone, 2,4.4'-)dihydroxybenzophenone, 2.2',4.4'-tetrahydroxybenzophenone, Dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4
-5ec-butyl hydroxybenzoate, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate phenethyl 4-hydroxybenzoate, 4-hydroxybenzoic acid
Phenolic compounds such as p-chlorobenzyl, p-methoxybenzyl 4-hydroxybenzoate, novolac type phenolic resin, phenol polymer, benzoic acid, p-
tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-3ec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3
゜5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3-(α-methylhensyl)salicylic acid, 3-chloro-5-(α-methylhensyl) ) salicylic acid, 3゜5-di-tert-butylsalicylic acid, 3-phenyl-5-(α,α-dimethylhensyl)salicylic acid, 3,5-di-α-methylhensylsalicylic acid, and other aromatic carboxylic acids; These phenolic compounds, organic acidic substances such as salts of aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel are exemplified.

Incidentally, it is of course possible to use two or more of these coloring agents in combination as necessary.

In the present invention, the usage ratio of the basic dye and coloring agent is appropriately selected depending on the type of basic dye and coloring agent used, and is not particularly limited, but in general, 1 weight of the basic dye 1 to 50 parts by weight, preferably 2 to 50 parts by weight
About 10 parts by weight of coloring agent is used.

Coating liquids containing these substances are generally prepared using water as a dispersion medium. The thermofusible substance represented by the general formula (1) may be added to the coating liquid as an aqueous dispersion, or may be added and dispersed in the process of dispersing the dye or coloring agent.

The coating liquid usually contains starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, diisobutylene/maleic anhydride copolymer salt, styrene, etc. Maleic anhydride copolymer salt, ethylene/acrylic acid copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion,
Urea resin, melamine resin, amide resin, etc. account for 1% of the total solid content.
It is used in an amount of 0 to 70%, preferably 15 to 50%.

Furthermore, various auxiliary agents can be added to the coating liquid as necessary, such as sodium dioctyl sulfosuccinate, sodium dodecylhenzenesulfonate, sodium lauryl alcohol sulfonate, fatty acid metal salts, etc. dispersants, ultraviolet absorbers such as benzophenone,
Other antifoaming agents, fluorescent dyes, coloring dyes, etc. may be added as appropriate.

In addition, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and varnish wax, kaolin, clay, talc, calcium carbonate, fired clay, titanium oxide, algae, Inorganic pigments such as fine particulate anhydrous silica and activated clay may also be added.

The thermofusible substance represented by the general formula (1) also exhibits a sensitizing effect, but other sensitizers may be used in combination depending on the purpose. Specific examples of other sensitizers include stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, fatty acid amide such as coconut fatty acid amide, 2,2'-methylene bis(4 −
methyl-6-tert-butylphenol), 4.4'
-Butylidenebis(6-tert-butyl-3-methylphenol) 1.1,1. ．． 3-) Lis(2-methyl-
4-Hydroxy-5-tert-butylphenyl)butane, 2,21-methylenebis(4-ethyl76,-te
rt-butylphenol), 2,4-di-tert-butyl-3-methylphenol, 4,4'-thiobis(3
Hindered phenols such as -methyl-6, -Le, r t-butylphenol), 2-(2'-hydroxy-
UV absorbers such as 5'-methylphenyl)hensitriazole and 2-hydroxy-4-hensyloxyhensiphenone, 1,2-di(3-methylphenoxy)ethane,
1.2-diphenoxyethane, 1-hue, tsukishi 2-
Examples include (4-methylphenoxy)ethane, dimethyl terephthalate, dimethyl terephthalate, dibutyl terephthalate, dihenzyl terephthalate, dibutyl isophthalate, phenyl 1-hydroxynaphthoate, and various known thermofusible substances. It will be done.

The amount of the sensitizer used is not particularly limited, but is generally within the range of 4 parts by weight or less per 1 part by weight of the coloring agent.
- In the heat-sensitive recording material of the present invention, the method of forming the recording layer is not particularly limited, and may be formed, for example, by a method of applying and drying a coating liquid by air knife coating, blade coating, or the like. Further, the amount of the coating liquid to be applied is not particularly limited, and is usually prepared in a dry weight range of 2 to 12 g/=, preferably 3 to 10 g/%.

Since the heat-sensitive recording material of the present invention contains the specific thermofusible substance in the recording layer, it exhibits excellent recorded image storage properties such as water resistance and moisture resistance. In order to further improve machinability, oil resistance, etc., an overcoat layer containing a water-soluble polymer compound as a main component may be provided on the recording layer.

Examples of water-soluble polymer compounds used in the overcoat layer include 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, Examples thereof include polyvinylpyrrolidone, polyacrylamide, styrene-maleic acid copolymer salt, polyurethane resin, urea resin, melamine resin, polyamide resin, and polyamide resin. These polymer compounds are of course 2
You may use a mixture of two types.

Among these water-soluble polymer compounds, acetoacetyl group-modified polyvinyl alcohol is particularly preferably used because it exhibits excellent effects when combined with the specific thermofusible substance of the present invention.

Pigments can be added to the overcoat layer, if necessary, in order to improve printability and sticking. Specific examples of pigments include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc,
Examples include inorganic pigments such as kaolin, clay, calcined clay, and colloidal silica, and organic pigments such as styrene micropol, nylon powder, polyethylene powder, urea/formalin resin filler, and raw starch granules.

The amount of rod used is generally 5 to 100 parts by weight of the resin component.
It is preferable to adjust the amount between about 500 parts by weight.

Furthermore, if necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, and surfactants such as sodium dioctyl sulfosuccinate may be added to coating liquids containing water-soluble polymer compounds as the main component. Various auxiliary agents such as agents (dispersants, lubricants) and antifoaming agents can also be added as appropriate.

In addition, to further improve water resistance, glyoxal,
Hardening agents such as boric acid, dialdehyde starch, and epoxy compounds can also be added.

In the present invention, the coating liquid forming the overcoat layer is
Generally, it is prepared as an aqueous coating solution, and after being thoroughly mixed and dispersed using a mixing/stirring machine such as a mixer, attritor, ball mill, or roll mill, if necessary, it is coated onto the heat-sensitive recording layer using a suitable coating device. The coating amount is not particularly limited, but if the dry weight exceeds 20 g/rrr, the recording sensitivity of the heat-sensitive recording medium may decrease significantly, so it is generally 0.1 to 20 g/m, preferably 0.5 to 10 g.
It is desirable that the adjustment be made within a range of approximately /rrr.

- Thus, the heat-sensitive recording material of the present invention in which the overcoat layer is provided on the recording layer does not cause color fog and exhibits extremely excellent recorded image retention even under severe conditions.

Note that it is also possible to further improve the storage stability by providing a protective layer on the back side of the heat-sensitive recording material, if necessary. Furthermore, various known techniques in the field of heat-sensitive recording material production may be added as necessary, such as providing an undercoat layer on the support, applying an adhesive treatment to the back surface of the recording material, and processing it into an adhesive label.

As the support, paper, plastic film, synthetic paper, etc. can be used, but paper is most preferably used in terms of cost, coatability, etc.

"Example" I The present invention will be described in more detail with reference to Examples below, but the invention is of course not limited to these.

Note that "parts" and "%" in the examples indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 ■ Lacquer preparation A 3-(N-cyclohexyl-N-methylamino) = 6-
Methyl-7-phenylaminofluorane 10 parts Methyl cellulose 5% aqueous solution 5 parts water
40 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ r3N/& Preparation Hensyl 4-hydroxybenzoate 20 parts Methyl cellulose 5% aqueous solution 5 parts water
55 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ Lacquer preparation 2-[2-hydroxy-3,5-bis(α,α-dimethylhensyl)phenyl)-2H-benzotriazole (
Product name: Tinuvin 2341 (manufactured by Ciba Geigy Japan)
5 parts methylcellulose 5% aqueous solution 2 parts water
20 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

(2) Formation of Recording Layer 55 parts of liquid A, 80 parts of liquid B, 27 parts of liquid C, 50 parts of a 15% polyvinyl alcohol aqueous solution, and 10 parts of calcium carbonate were mixed and stirred to prepare a coating liquid. The obtained coating liquid was coated and dried on a 50 g/r/base paper so that the coated amount after drying was 6 g/g to obtain a heat-sensitive recording material.

Example 2 A thermosensitive recording material was obtained in the same manner as in Example 1 except that 4-hydroxy-4'-methyldiphenylsulfone was used in place of benzyl 4-hydroxybenzoate in the preparation of lacquer B.

23-Example 3 A thermosensitive recording material was obtained in the same manner as in Example 1 except that in the preparation of B lacquer, zinc salt of monobenzyl phthalate was used instead of benzyl 4-hydroxybenzoate.
・Example 4 ■ Lacquer preparation D 4.4'-isopropylidene diphenol 20 parts Methyl cellulose 5% aqueous solution 5 parts water
, 55 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ Formation of recording layer 55 parts of liquid A, 80 parts of liquid D, 27 parts of liquid C, 20% stearamide dispersion (trade name: Hydrin B-'934.
A one-heat recording medium was obtained in the same manner as in Example 1, except that 100 parts of a 15% polyvinyl alcohol aqueous solution, and 10 parts of calcium carbonate were used in a mixing stirrer. .

Comparative Examples 1 to 4 Sensitive and thermal recording materials were obtained in the same manner as Examples 1 to 4, except that liquid C was not used in forming the recording layer.

Comparative Example 5 In the preparation of C lacquer, 2-(5-methyl-2-hydroxyphenyl ) A thermosensitive recording material was obtained in the same manner as in Example 1 except that hensitriazole was used.

The following evaluation tests were conducted on the nine types of heat-sensitive recording bodies thus obtained, and the results are listed in Table 1.
.

[Whiteness]

After evaluating the degree of color fog, the whiteness of the recording layer was measured using a Hunter whiteness meter. 1 [Color density] Thermal printer (manufactured by Texas Instruments, PC
The color density of the recorded image obtained by printing with a Machhes densitometer (manufactured by Machhes Co., Ltd.).

RD-100R model).

〔water resistance〕

After printing, the heat-sensitive recording material was immersed in water and left at room temperature for 48 hours, after which the water resistance was evaluated from the print density.

◎: No decrease in print density is observed.

○: Print density slightly decreases.

Δ: A decrease in print density is clearly observed.

×: Print density decreases significantly.

[Polluting agent resistance]

Wrap vinyl chloride wrap film (manufactured by Mitsui Toatsu Co., Ltd.) three times around a polypropylene vibe (40++ mφ tube).
A heat-sensitive recording material with printed colors is sandwiched on top of it so that the colored side of the print is facing outward, and then a vinyl chloride lamp film is wrapped three times over it, and after being left at room temperature for 12 hours, the print density is determined by the plasticizer. The gender was evaluated.

○: There is almost no decrease in print density.

Δ: There is clearly a decrease in print density.

×: Print density decreases significantly.

[Temperature resistance]

Color fog was evaluated after the unprinted thermal recording material was left in an atmosphere of 60° C., 150% RI for 24 hours.

○: Almost no color fogging is observed.

Δ: Color fogging is clearly observed.

×: Significant color fogging.

Table 1 −27= Example 5 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Example 2.

■ Formation of overcoat layer Polyvinyl alcohol (Product name: PVA-11
0, manufactured by Kuraray Co., Ltd.), 20 parts of calcium carbonate, and 50 parts of water were mixed and stirred, and a coating solution obtained was applied onto the recording layer of the heat-sensitive recording material, so that the coating amount after drying was 6 g/rd. The mixture was coated and dried to obtain a heat-sensitive recording material having an overcoat layer.

Comparative examples 6-7 ■ Formation of recording layer A thermosensitive recording material was obtained in the same manner as in Comparative Examples 1 and 2.

(2) Formation of overcoat layer A thermosensitive recording material having an overcoat layer was obtained in the same manner as in Example 5 except that the above thermosensitive recording material was used.

The three types of heat-sensitive recording materials thus obtained were subjected to the same evaluation test as described above, except that the plasticizer resistance was evaluated by the following method, and the results are listed in Table 2.

[Plasticizer resistance]

A vinyl chloride lamp film (manufactured by Mitsui Toatsu Co., Ltd.) was wrapped three times around a polypropylene pipe (401 diameter pipe), and a heat-sensitive recording material with colored print was placed on top of it, with the colored side of the print facing outward. A vinyl chloride lamp film was wrapped three times over it, and the film was left at 40° C. for 24 hours, after which the print density was evaluated to evaluate the desiccant resistance.

◎: There is no decrease in print density at all.

0: There is almost no decrease in print density.

Δ: There is a clear decrease in print density.

×: Print density decreases significantly.

Table 2-130 - "Effects" As is clear from the results in Tables 1 and 2, the heat-sensitive recording materials of the present invention are all excellent in the storage stability of recorded images, and are particularly effective in improving water resistance. Moreover, it was an excellent recording medium with no noticeable color fogging and no staining.

Claims (1)

[Claims] (1) In a heat-sensitive recording material provided with a recording layer containing a colorless or light-colored basic dye and a coloring agent that causes the basic dye to develop color when heated, the recording layer contains a compound represented by the following general formula [I]. A heat-sensitive recording material characterized by containing a thermofusible substance. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [I] [In the formula, R_1 to R_6 are hydrogen atoms, halogen atoms, alkyl groups of C_1_ to _8, or C_1_ to _8, respectively.
represents an alkoxyl group. ]