JPH04364986A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve preserving stability of un-colored part and colored image by combining specific electron donative coloring compound to electron acceptive compound. CONSTITUTION:A thermal recording material is used by combining electron donative coloring compound to be expressed by a formula I to electron acceptive compound to be expressed by a formula II and/or a formula III, where R1, R2 represent halogen atom, alkyl group, cycloalkyl group or aryl group. As for the rate to be used, the total quantity of the compound expressed by the formula II and/or III is made to be about 100-500 pts.wt. to the compound of 100 pts.wt. expressed by the formula I. Fluoran compound expressed by the formula I, for example, is obtained by making 3-(N-isobutyl-N-2'- methoxyethylamino) phenol react on phthalic anhydride, thereafter, further making 4-methoxy-2-methyl diphenylamine react. Thus, deterioration of whiteness of un-colored part is prevented and preserving stability of colored image will be improved.

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 in which the storage stability of uncolored areas and colored images is significantly improved.

0002

BACKGROUND ART Heat-sensitive recording materials that utilize a color reaction between an electron-donating color-forming compound and an electron-accepting compound have been well known (for example, Japanese Patent Publication No. 43-4160, Japanese Patent Publication No. 45 -14039). Thermosensitive recording materials are relatively inexpensive, and recording devices are compact and maintenance-free, so they are widely used in the fields of facsimiles, recorders, and printers. However, these heat-sensitive recording materials, especially high-sensitivity heat-sensitive recording materials, have poor storage stability in the uncolored areas, and some color develops due to moisture or oil during storage, resulting in a significant decrease in the whiteness of the uncolored areas. However, it has the disadvantage that it cannot withstand use, the storage stability of the colored image is not sufficient, and there is also a disadvantage that the density of the colored image decreases or the colored image disappears due to moisture or oil. For this reason, there has been a strong demand for a heat-sensitive recording material that does not reduce the whiteness of uncolored areas even when stored under harsh conditions and can maintain stable colored images.

0003

[Problems to be Solved by the Invention] In order to meet the above-mentioned needs, it is an object of the present invention to provide a system in which the whiteness of uncolored areas does not decrease even when stored under harsh conditions, and furthermore, colored images are maintained stably. The objective is to obtain a durable heat-sensitive recording material.

0004

[Means for Solving the Problems] The present inventors have conducted intensive studies on combinations of electron-donating color-forming compounds and electron-accepting compounds. As a result, the inventors discovered that the above object can be achieved by combining a specific electron-donating color-forming compound and an electron-accepting compound, thereby completing the present invention. That is, the present invention provides a thermosensitive recording material containing an electron-donating color-forming compound and an electron-accepting compound, in which a compound represented by formula [I] (Chemical formula 4) is used as the electron-donating color-forming compound; The present invention relates to a heat-sensitive recording material characterized by using a compound represented by the general formula [II] (Chemical formula 5) and/or the general formula [III] (Chemical formula 6) as a chemical compound.

[0005]

[C4]

[0006]

[C5]

[0007]

embedded image The fluoran compound represented by formula [I] used in the present invention can be prepared, for example, by reacting 3-(N-isobutyl-N-2'-methoxyethylamino)phenol with phthalic anhydride. Furthermore, it can be obtained by a method such as reacting with 4-methoxy-2-methyldiphenylamine. The compound represented by the general formula [II] or [III] used in the present invention can be obtained, for example, by reacting an o-substituted or m-substituted phenol with sulfur chloride in the presence of a catalyst. . In the general formula [II], R1 represents a halogen atom, an alkyl group, a cycloalkyl group, or an aryl group, and as preferred specific examples, the halogen atom is a fluorine or chlorine atom, and the alkyl group is a methyl group, an ethyl group, an n A chain lower alkyl group such as -propyl group, isopropyl group or n-butyl group, a cyclohexyl group as the cycloalkyl group, and a phenyl group as the aryl group. Particularly preferred examples include bis-(3-methyl-4-hydroxyphenyl) sulfide, bis-(3-isopropyl-4-hydroxyphenyl) sulfide, bis-(3-cyclohexyl-4-hydroxyphenyl) sulfide, bis- (
3-phenyl-4-hydroxyphenyl) sulfide.

[0008] In the general formula [III], R2 represents a halogen atom, an alkyl group, a cycloalkyl group, or an aryl group, and as preferred specific examples, the halogen atom is a fluorine or chlorine atom, and the alkyl group is a methyl group, an ethyl group. Examples of the cycloalkyl group include a cyclohexyl group, and examples of the aryl group include a phenyl group. Particularly preferred examples include bis-(2-chloro-4-hydroxyphenyl) sulfide, bis-(2-methyl-4-hydroxyphenyl) sulfide, and bis-(2-ethyl-4-hydroxyphenyl) sulfide.
-hydroxyphenyl) sulfide, bis-(2-cyclohexyl-4-hydroxyphenyl) sulfide, and bis-(2-phenyl-4-hydroxyphenyl) sulfide.

The heat-sensitive recording material of the present invention has the general formula [II]
and/or a compound represented by the general formula [III] is used as an electron-accepting compound, but these compounds may be used alone or in combination of two or more;
When using a combination of two or more types, one or more compounds represented by the general formula [II] or the general formula [III] may be used in combination. The heat-sensitive recording material of the present invention comprises an electron-donating color-forming compound represented by the formula [I] and a general formula [I].
I] and/or the electron-accepting compound represented by the general formula [III] are used in combination, and the proportion of both is 100% by weight of the compound represented by the formula [I]. The total amount of the compound represented by the general formula [II] and/or the general formula [III] is 1
It is desirable to use 00 to 500 parts by weight, preferably 150 to 300 parts by weight.

Since the heat-sensitive recording material of the present invention uses a specific electron-donating color-forming compound and an electron-accepting compound, a thermofusible compound (with a melting point of about 80 to 130
Even when used in combination with a compound at a temperature of 0.3 °C, it has excellent characteristics in that there is very little staining of uncolored areas due to moisture or oil, and there is very little reduction in whiteness. Therefore, when the present invention is applied to a highly sensitive heat-sensitive recording material using a thermofusible compound, its effects are fully exhibited. Various known compounds can be used as the thermofusible compound. For example, amides such as stearic acid amide and palmitic acid amide, 1,2-bis(phenoxy)ethane, 1,2-bis(3-methylphenoxy)ethane, 2-benzyloxynaphthalene, 4-(4-methylphenoxy) ) ethers such as biphenyl, dibenzyl terephthalate, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid di(4-chlorobenzyl) ester, oxalic acid di(4-
Examples include esters such as methylbenzyl) ester, 4-benzylbiphenyl, and the like. In particular, 1,2-bis(3
-Methylphenoxy)ethane, 2-benzyloxynaphthalene, and oxalic acid di(4-methylbenzyl) ester are particularly preferably used because they yield high-quality, highly sensitive heat-sensitive recording materials. The amount of the thermofusible compound to be used is not necessarily limited, but is in the range of 50 to 500 parts by weight, preferably 100 to 300 parts by weight, based on 100 parts by weight of the compound represented by formula [I]. It is desirable to use it in

Although the present invention uses a specific electron-donating color-forming compound and an electron-accepting compound, electron-donating color-forming compounds other than the compounds of the present invention may be used as long as the desired effects of the present invention are not inhibited. It is also possible to use a chemical compound or an electron-accepting compound in combination. Examples of electron-donating color-forming compounds that can be used in combination include 3-diethylamino-6-methyl-7-anilinofluorane, 3-di(n-butyl)
Amino-6-methyl-7-anilinofluorane, 3-(
N-n-propyl-N-methyl)amino-6-methyl-
7-anilinofluorane, 3-(N-isobutyl-N-
methyl)amino-6-methyl-7-anilinofluorane, 3-(N-isoamyl-N-ethyl)amino-6-methyl-7-anilinofluorane, 3-(N-n-hexyl-N- Fluoran compounds such as ethyl)amino-6-methyl-7-anilinofluorane can be mentioned as preferred compounds, and as electron-accepting compounds,
For example, 2,2-bis(4-hydroxyphenyl)propane, 4-hydroxybenzoic acid benzyl ester, 4-
Preferred compounds include p-methoxyphenoxyethoxysalicylic acid and the like. When using electron-donating color-forming compounds and electron-accepting compounds other than those of the present invention, the proportion of these electron-donating color-forming compounds or electron-accepting compounds in the total electron-donating color-forming compounds and total electron-accepting compounds It is desirable that the proportion of the compound be 30% by weight or less.

In the heat-sensitive recording material of the present invention, the method for forming the recording layer is not particularly limited, and any known method can be used. For example, a coating liquid for a heat-sensitive recording layer is coated on a support using an air knife coater, a blade coater, a bar coater, a gravure coater, or the like.
After coating with a suitable coating device such as a curtain coater or a wire bar, the recording layer is formed by drying. Paper, plastic sheets, synthetic paper, etc. are used as supports.
Paper is particularly preferably used.

The coating solution for the heat-sensitive recording layer of the present invention is generally prepared by using water as a dispersion medium and using a stirring/pulverizing machine such as a ball mill, an attritor, or a sand mill to prepare an electron-donating color-forming compound, an electron-accepting compound, Furthermore, it is prepared by dispersing a thermofusible compound, which is added as necessary, together or separately. Coating liquids usually contain polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, epichlorohydrin-modified polyamide, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer as binders. , polyacrylic acid, polyacrylamide, methylol-modified polyacrylamide, starch derivatives, casein, gelatin, methylcellulose, carboxymethylcellulose, gum arabic, modified polyvinyl alcohol (for example, carboxy-modified polyvinyl alcohol), and the like.

Furthermore, pigments, water-insoluble binders, metal soaps, waxes, surfactants, ultraviolet absorbers, antifoaming agents, and the like may be added to the coating solution for the heat-sensitive recording layer of the present invention, if necessary. Pigments include zinc oxide, calcium carbonate,
Magnesium carbonate, barium carbonate, barium sulfate, titanium oxide, talc, waxite, kaolin, diatomaceous earth, magnesium hydroxide, alumina, silica, amorphous silica, urea-formalin filler, polyethylene particles, cellulose filler, etc. are used. It will be done. As water-insoluble binders, synthetic rubber latex or synthetic resin emulsion is generally used, such as styrene-butadiene rubber latex,
Acrylonitrile-butadiene rubber latex, methyl acrylate-butadiene rubber latex, vinyl acetate emulsion, etc. are used. As the metal soap, higher fatty acid metal salts are used, such as zinc stearate, calcium stearate, aluminum stearate, and the like. Waxes include paraffin wax, microcrystalline wax, carboxy-modified paraffin wax, carnauba wax, polyethylene wax,
Examples include polystyrene wax and higher fatty acid esters. Examples of the surfactant include alkali metal salts of sulfosuccinic acids, fluorine-containing surfactants, and the like.

[0015] The amount of coating liquid to be applied is not particularly limited, and is generally 1.5 to 12 g/m in terms of dry weight.
2, preferably in the range of 2.5 to 10 g/m2. Note that it is of course possible to provide a protective layer on the surface and/or back of the heat-sensitive recording layer, or to provide an undercoat layer between the support and the heat-sensitive recording layer, as required. Various known techniques for producing recording materials can be applied.

[0016]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples. In the examples, % represents weight %. Examples 1 to 9 20g each of the electron-donating color-forming compound, electron-accepting compound, and thermofusible compound (2-benzyloxynaphthalene) shown in Table 1 were added to 100g of 5% polyester. Dispersed with vinyl alcohol (Kuraray PVA105) aqueous solution in a ball mill for 24 hours to obtain particles with an average particle size of 3 μm.
Then, each dispersion was prepared. Further, the pigment used was prepared by dispersing 80 g of calcium carbonate with 160 g of a 0.5% aqueous solution of sodium hexametaphosphate using a homogenizer to prepare a dispersion. Each of the dispersions obtained as described above was mixed into an electron-donating color-forming compound dispersion liquid (hereinafter referred to as liquid A) 5.
g, electron-accepting compound dispersion (hereinafter referred to as liquid B) 1
0g, thermofusible compound dispersion 10g, pigment dispersion 22g
4 g of a water emulsion of zinc stearate and 5 g of a 2% aqueous solution of (2-ethylhexyl)-sodium sulfosuccinate were added to obtain a coating liquid. This coating liquid was applied with a wire bar to a dry coating amount of 6 g/m2 on high-quality paper with a basis weight of 50 g/m2.
After drying at °C, calendering was performed to obtain a heat-sensitive recording material.

[0017]

[Table 1]

Comparative Examples 1 to 5 In the above examples, heat-sensitive samples were prepared by the method described in the examples, except that the compounds in liquid A and/or liquid B were changed to the compounds shown in Table 2 (Table 2). Obtained recording materials. In addition, in Table 2, formula [IV] (Chemical formula 7) or formula [
V] (Chemical formula 8) is a fluoran compound represented by the following structural formula.

[0019]

[Table 2]

[0020]

[C7]

[0021]

embedded image The 14 heat-sensitive recording materials obtained as described above were recorded using a high-speed heat-sensitive facsimile (manufactured by Ricoh Co., Ltd., V-600S). The density of the resulting colored image and the density of the uncolored area were measured using a Macbeth reflection densitometer (model TR-524). The results are shown in Table 3 (Table 3). In addition, after the heat-sensitive recording material was subjected to a humidity resistance test and an oil-resistance test, the density of the colored image and the density of the uncolored area were measured again to evaluate the storage stability of each heat-sensitive recording material, and the results are shown in Table 3. Indicated. The moisture resistance test was conducted by storing the heat-sensitive recording material in an environment of 90% relative humidity and 60° C. for 24 hours. Further, the oil resistance test was conducted by applying dioctyl phthalate to the heat-sensitive recording material and then storing it at 25° C. for one week.

[0022]

[Table 3] As is clear from Table 3, the heat-sensitive recording materials of the present invention obtained in Examples 1 to 9 have better moisture resistance and It can be seen that the oil resistance is excellent, and there is very little decrease in the density of the colored image and decrease in the whiteness of the uncolored area.

[0023]

Effects of the Invention The present invention provides a heat-sensitive recording material with excellent moisture resistance and oil resistance, and the whiteness of uncolored areas does not decrease even when stored under harsh conditions, and the colored images are stable during storage. It is possible to provide a heat-sensitive recording material with extremely excellent properties.

Claims (1)

[Claims] Claim 1: In a thermosensitive recording material containing an electron-donating color-forming compound and an electron-accepting compound, a compound represented by formula [I] (Chemical formula 1) is used as the electron-donating color-forming compound, and the electron-accepting compound is A heat-sensitive recording material characterized in that a compound represented by general formula [II] (chemical formula 2) and/or general formula [III] (chemical formula 3) is used as a compound. [Chemical formula 1] [Chemical formula 2] [Chemical formula 3]