JPS61130086A - Thermal recording body - Google Patents

Abstract

PURPOSE:To obtain a thermal recording body imparting a stable recording image excellent in fingerprint fading resistance, by containing a specific basic dye in a thermal recording layer. CONSTITUTION:One or more of basic dyes represented by formulae I, II are contained but the combined use ratio thereof is desirably regulated within a range of 10:90-90:10 on a wt. basis. In said formulae, R1 is a 1-4C alkyl group, R2 is a 1-2C alkyl group and R3 is a 1-2C alkyl group or a 5-6C cycloalkyl group. The tetrahydrofuryl group of the basic dye represented by the formula I acts on the basic dye represented by the formula II to obtain excellent acting effect based on special reciprocal action of both of them.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a heat-sensitive recording medium, and more particularly, to a heat-sensitive recording medium that is excellent in the stability of recorded images, particularly in fingerprint fading resistance.

``Prior Art'' Conventionally, heat-sensitive recording materials that utilize a color reaction between a colorless or light-colored basic dye and a coloring agent to bring both colored substances into contact with each other using heat to obtain a colored image are well known. It is being

Such heat-sensitive recording materials do not have sufficient stability of the recorded image in -rG, and the recorded image tends to fade over time. In particular, if a fingerprint is attached to the recorded image, the recorded image disappears in a relatively short period of time. Sometimes I end up doing it. Therefore, there is a strong demand for the development of a heat-sensitive recording material that has excellent stability of recorded images, especially fingerprint fading resistance.

[Problems to be Solved by the Invention] In view of the current situation, the present inventor has conducted extensive research on basic dyes in order to eliminate the above-mentioned defects of thermosensitive recording materials, and has developed the following general formula [■] and When one or more of the specific basic dyes represented by [II] are used in combination,
The inventors have discovered that it is possible to obtain a heat-sensitive recording material with excellent stability of recorded images, particularly in fingerprint fading resistance, and have completed the present invention.

"Means for Solving the Problem" The present invention provides a thermosensitive recording medium that utilizes a coloring reaction between a colorless or light-colored basic dye and a coloring agent that can develop a color when it comes into contact with the dye. This is a heat-sensitive recording material characterized by containing one or more types of basic dyes represented by the following general formulas [1) and (II) in the layer.

[In the formula, R8 is a C8-C4 alkyl group, R2 is 01-
The C2 alkyl group and R1 represent a C1-C2 alkyl group or a 05-C6 cycloalkyl group. 〕 ``Function'' It is not clear why the combination of the above-mentioned specific basic dyes exhibits an excellent improvement effect on the stability of recorded images, especially on fingerprint fading resistance, but it is expressed by the general formula [■]. The tetrahydrofurfuryl group of the basic dye has the general formula (
It is presumed that it has some effect on the basic dye represented by II), and that excellent effects are obtained through a special interaction between the two.

Specific examples of basic dyes represented by the general formula CI) that exhibit such properties include 1-N-methyl-N-tetrahydrofurfurylamino-
6-Methyl-7-anilinofluorane 3-N-ethyl-
N-tetrahydrofurfurylamino-6-methyl-7-
Examples include anilinofluorane.

Further, as a specific example of the basic dye represented by the general formula (II), for example, 3-(N-cyclohexyl-N-methylamino)-6-
Examples include methyl-7-anilinofluoran 3-(N-cyclopentyl-N-methylamino)-6-methyl-7-anilinofluoran 3-diethylamino-6-methyl-7-anilinofluoran.

As mentioned above, in the present invention, in the heat-sensitive recording layer, the above general formula CI)
and (II), but in order to obtain the desired effect of the present invention, the dye represented by the general formula [■], The weight ratio of the dye represented by the general formula C11) is 10:90 to 90 = 4-:10, more preferably 25:75 to 75:2.
It is desirable to adjust within the range of 5.

Note that, if necessary, it is also possible to use one or more of other various basic dyes in combination, but the proportion in which they are used in combination must be kept within a range that does not inhibit the desired effects of the present invention.

In the present invention, the coloring agent used in combination with the above-mentioned basic dye is not particularly limited; Various substances are used that have the property of coloring the material.

Typical specific examples include activated clay, acid clay, acpulgite, bentonite, colloidal silica, inorganic acidic substances such as aluminum silicate, 4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β- Naphthol, 4-human oxyacetophenol, 4-tert-octylcatechol, 2,2'
-dihydroxydiphenol, 2,2'-methylenebis(4-methyl-6-tert-isobutylphenol)
, 4.4'-isopropylidene bis(2-tert-butylphenol), 4. 4'-5ec-butylidene diphenol, 4-phenylphenol, 4,4'-
Isopropylidene diphenol (bisphenol A),
2.2'-methylenebis(4-chlorophenol), hydroquinone, 4.4'-cyclohexylidene diphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolac type phenolic resin, phenol Phenolic compounds such as polymers, benzoic acid, p-tert-butylbenzoic acid, 1-helichlorobenzoic acid, terephthalic acid,
3-sec-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-hensylsalicylic acid, 3-(α-methylhensyl)salicylic acid, 3-chloro-5-(α-methylbenzyl)salicylic acid, 3,5-di-tert-butylsalicylic acid, 3-phenyl-5-(α.

α-dimethylbenzyl) salicylic acid, 3. 5-C α
- aromatic carboxylic acids such as methylbenzylsalicylic acid,
Examples include organic acidic substances such as these phenolic compounds, salts of aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel.

Among these coloring agents, 4,4'-cyclohexylidene diphenol, Hensyl 4-hydroxybenzoate, and dimethyl 4-hydroxyphthalate have particularly excellent effects when combined with the above-mentioned specific basic dye. It is a coloring agent most preferably used in the present invention because it exhibits its effects.

The ratio of the basic dye to the coloring agent is generally 100 to 700 parts by weight, preferably 150 to 400 parts by weight, per 100 parts by weight of the dye. It should be noted that these coloring agents can of course be used in combination with two types of plates, if necessary.

Furthermore, fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, valmitic acid amide, coconut fatty acid amide, terephthalic acid dibenzyl ester, 1.2 -di(3-methylphenoxy)ethane, 1,2-diphenoxyethane, 2.2" -methylenebis(4-methyl-6L-t-butylphenol), 4
．． 4'-Butylidenebis(6-t-butyl-3-methylphenol), 1,1,3-tris(2-methyl-4-
Hindered phenols such as hydroxy-5-t-butylphenol)butane, 2-(2'-hydroxy-5°
Ultraviolet absorbers such as -methylphenyl)-benzotriazole and 2-hydroxy-4-benzyloxyhensiphenone, and various known thermofusible substances can be used in combination.

Among these thermofusible substances, terephthalic acid dibenzyl ester and 1,2-di(3-methylphenoxy)ethane are particularly useful in combination with the specific basic dyes of the present invention and the preferred color formers mentioned above. It is a substance that is preferably used in combination because it exhibits extremely excellent characteristics not only in the stability of recorded images but also in various properties such as high-speed recording characteristics.

Although the amount of the thermofusible substance used is not necessarily limited, it is generally 0 to 1 part by weight of the coloring agent.
．． It is desirable that it be blended in an amount of about 1 to 10 parts by weight, preferably about 0.5 to 5 parts by weight.

Coating solutions containing these substances are generally prepared by using water as a dispersion medium and dispersing the dye and coloring agent together or separately using a stirring/pulverizing machine such as a ball mill, attritor, or sand grinder. .

The coating solution usually contains binders such as starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene/maleic anhydride copolymer salt, styrene/butadiene copolymer emulsion, etc. 2-40% by weight of solids, preferably 5-25%
Weight % Weight % - given.

Furthermore, various auxiliary agents can be added to the coating liquid as necessary, such as dioctyl sulfosuccinate, sodium dodecyl sulfosuccinate, lauryl alcohol sulfate sodium salt, fat 11
A dispersant such as a metal salt of an acid, an antifoaming agent, a fluorescent dye, a coloring dye, etc. are added.

In addition, in order to improve the adhesion of residue to the recording head and further whiten the heat-sensitive recording layer, kaolin, clay, talc, etc.
Inorganic pigments such as calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, and activated clay can also be added. Furthermore, waxes such as stearic acid, polyethylene, carnano wax, nografine wax, calcium stearate, zinc stearate, and ester wax such as dispersion or emulsion can be used for recording.The recording layer will stay in place when it comes into contact with the gutter.・Can also be added to prevent knocking.

In the heat-sensitive recording material of the present invention, the method for forming the recording layer is not particularly limited, and can be formed according to conventionally well-known and commonly used techniques. For example, in a method of applying a heat-sensitive coating liquid to a support, an appropriate coating device such as an air knife coater or a blade coater is used.

Further, the coating amount of the coating liquid is not particularly limited, and is generally prepared in a dry weight range of 2 to 12 g/n (and preferably 3 to IO g/m).The support is also not particularly limited. First, paper, synthetic fibers, synthetic resin fills, etc. are used as appropriate, but paper is generally preferably used.

In general, it is also possible to provide an overcoat layer on the recording layer for the purpose of protecting the recording layer, and various known techniques in the field of heat-sensitive recording materials can be added, such as providing an undercoat layer on the support. It is.

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

Further, unless otherwise specified, parts and % in the examples do not indicate parts by weight and % by weight, respectively.

Example 1 ■ Preparation of liquid A 1l- 3-N-ethyl-N-tetrahydrofurfurylamino-
6-Methyl-7-anilinofluorane 5 parts 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-Ayu Riffle 15 parts 5 parts methylcellulose 5% aqueous solution 5 parts water
40 parts of this composition was ground with a sand grinder until the average particle size was 3 μm.

■ Preparation of B solution Benzyl 4-hydroxybenzoate 20 parts Methylcellulose 5% aqueous solution 5 parts Water
55 parts of this composition was ground with a sand grinder until the average particle size was 3 μm.

■ Formation of recording layer 55 parts of liquid A, 80 parts of liquid B, silicon oxide pigment (oil absorption 180 parts)
m1/100g), 50 parts of a 20% oxidized starch aqueous solution, and 13 parts of water were mixed and stirred to prepare a coating liquid. The obtained coating liquid was applied to a base paper of 50 g/m with a coating weight of 6 g/r after drying.
The coating was coated and dried to obtain heat-sensitive paper 81.

Examples 2-4 In the preparation of Part A, 5 parts of 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane and 3-(N-cyclohexyl-N-methylamino) Instead of 5 parts of -6-methyl-7-anilinofluorane, 5 parts of 3-N-methyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane and 3-
(N-cyclohexyl-N-methylamino)-6-medyru-7-ayurinofluorane 5 parts (Example 2), 3-N
7 parts of -ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane and 3 parts of 3-(N-cyclopentyl-N-methylamino)-6-methyl-7-anilinofluorane (working Example 3) and 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7
-5 parts of anilinofluorane and 3-diethylamino-6
Three types of thermal recording paper were obtained in the same manner as in Example 1, except that 5 parts of -methyl-7-anilinofluorane (Example 4) was used in each case.

Example 5 ■ Preparation of liquid A 3-N-ethyl-N-tetrahydrofurfurylamino-
6-methyl-7-anilinofluorane
3 parts 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluorane 7 parts methylcellulose 40 parts water This composition was ground to an average particle diameter of 3 μm using a sand grinder.
It was crushed until it was.

■ Bn Yagom Benzyl 4-hydroxybenzoate 20 parts Methyl cellulose 5% aqueous solution 5 parts water
55 parts of this composition was ground with a sand grinder until the average particle size was 3 μm.

■ 8 cycles of carbon terephthalic acid dibenzyl ester 20 parts methylcellulose 5% aqueous solution 5 parts water
55 parts of this composition was ground with a sand grinder until the average particle size was 3 μm.

■ Formation of recording layer 55 parts of liquid A, 80 parts of liquid B, 80 parts of liquid C, silicon oxide pigment (
A coating liquid was prepared by mixing and stirring 15 parts of oil absorption (180 ml/]OOg), 50 parts of a 20% oxidized starch aqueous solution, and 10 parts of water. The resulting coating solution was applied to a 50 g/m base paper so that the coated amount after drying was 6 g/m, and dried to obtain a heat-sensitive recording paper.

Example 6 3-N-edyl-N-teI-dihydrofurfurylamino-6-methyl-7-anilinofluorane 3 parts and 3-(N-cyclohexyl-N-methyl 5 parts of 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane and 3-(N- cyclohexyl-N-methylamino)-6
- using 5 parts of methyl-7-anilinofluorane, and B
A thermosensitive recording paper was obtained in the same manner as in Example 5, except that dimethyl 4-hydroxyphthalate was used instead of benzyl 4-hydroxybenzoate in the liquid preparation.

Example 7 B? 4,4'-cyclohexylidene diphenol was used instead of dimethyl 4-hydroxyphthalate in the & preparation, and 1,2-di(3- A thermosensitive recording paper was obtained in the same manner as in Example 6 except that methylphenoxy)ethane was used.

Comparative Examples 1 to 6 In preparing liquid A, 5 parts of 3-N-ethyl-N-tetrahydrofurfurylamine 7-6-methyl-7-anilinofluorane and 3-(N-cyclobexyl-N-methylamino)-6- Instead of 5 parts of methyl-7-anilinofluorane, 10 parts of 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane (Comparative Example 1), 3-N-methyl -N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane 10 parts (Comparative Example 2), 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinoflurane 10 parts of orane (Comparative Example 3), 10 parts of 3-(N-cyclopentyl-N-methylnamino)-6-methyl-7-anilinofluorane (Comparative Example 4), 3-diethylamino-6-methyl-7-
10 parts of anilinofluorane (Comparative Example 5), 3 parts of 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane and 3=(N~ethyl-
Six types of thermal recording paper were obtained in the same manner as in Example 1, except that 7 parts of N-iso-amyl)amino-6-methyl-7-anilinofluorane (Comparative Example 6) were used.

Regarding the 13 types of thermal recording paper thus obtained, G■
Type of practical high-speed thermal facsimile (HTF manufactured by Hitachi)
AX-700 model), and the color density of the recorded image (
Dl) using a Machhes densitometer (RD-100R manufactured by Machhes).
(type).

In addition, after recording, the thermal recording paper was left in an atmosphere of 40°C and 190% RH for 24 hours, and the color density (D2) was measured again using a Maches densitometer, and the residual rate of color density (%) was measured.
−(D2 /D,)XI 00 and the first
It is listed in the table.

Furthermore, after attaching a fingerprint to the recorded image, it was left to stand for one week and the state of disappearance of the recorded image was evaluated, and the results are listed in Table 1 as fingerprint resistance.

[Fingerprint resistance evaluation criteria]

◎: Extremely good (hardly disappeared) ○: Excellent (slightly disappeared) ×: Extremely poor (
"Effect" (almost disappeared) As is clear from the results in Table 1, the thermal recording papers obtained in each example of the present invention all had excellent high-speed recording suitability;
Furthermore, the thermal recording paper was excellent in the stability of recorded images, especially in fingerprint fading resistance and i) humidity, and had extremely well-balanced high quality.

Table 1

Claims (1)

[Claims] In a heat-sensitive recording material that utilizes a color reaction between a colorless or light-colored basic dye and a coloring agent that can develop a color when it comes into contact with the dye, the following general formula [ 1. A heat-sensitive recording material containing one or more of the basic dyes represented by [I] and [II]. ▲There are mathematical formulas, chemical formulas, tables, etc.▼[I] ▲There are mathematical formulas, chemical formulas, tables, etc.▼[II] [In the formula, R_1 is an alkyl group of C_1 to C_4, R_2
is an alkyl group of C_1 to C_2, R_3 is an alkyl group of C_1 to C_2
2 alkyl group or C_5 to C_6 cycloalkyl group. ]