JPH04371890A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material not lowered in whiteness or recording density even under a high temp. condition by adding a colorless or light-colored basic dye and a specific developer to the thermal recording layer formed on a support. CONSTITUTION:As a colorless or light-colored basic dye, a known one can be used. As a developer, a compound represented by formula 1 is used and a compound represented by formula 2 is especially pref. This developer may be used together with other developer. The coating solution applied to a support is prepared by generally using water as a dispersing medium and dispersing the basic dye and the developer in said medium. A binder is usually compounded with the coating solution and can be used together with other auxiliary agents, pigment, an ultraviolet absorber or a sensitizer.

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 highly sensitive heat-sensitive recording material that exhibits extremely little reduction in whiteness even when placed in a high-temperature environment.

0002

[Prior Art] Conventionally, heat-sensitive recording materials have been well known, which utilize the reaction between a colorless or light-colored basic dye and a coloring agent to bring both coloring substances into contact with each other using heat to obtain a recorded image. . Such heat-sensitive recording media are used in a wide range of fields because they are relatively inexpensive, and the recording equipment is compact and maintenance-free.

[0003] However, heat-sensitive recording materials are sometimes left at temperatures of about 40° C. for long periods of time during transportation or storage in warehouses, and the coloring reaction progresses, resulting in color fogging. Particularly in the case of high-sensitivity thermosensitive recording materials, there is a problem in that the whiteness is significantly reduced. Therefore, there is a strong demand for a heat-sensitive recording material that does not lose its whiteness even when exposed to such high-temperature conditions for a long period of time.

[0004] Furthermore, heat-sensitive recording materials generally have a problem in the storage stability of recorded images, and particularly under high temperature conditions, the recorded images have the disadvantage of fading in a relatively short period of time. In order to improve the storage stability of such recorded images, methods using various storage improvers have been proposed; Even those that are effective in improving the storage stability of recorded images under high-temperature conditions are accompanied by new drawbacks such as a decrease in whiteness, and no satisfactory results have been obtained.

[0005] Therefore, there is a strong demand for a heat-sensitive recording material that does not reduce the whiteness of the recording layer even when stored under high-temperature conditions and that can stably maintain a recorded image.

[0006]

[Problems to be Solved by the Invention] In view of the current situation, the inventors of the present invention have carried out extensive studies in order to obtain a heat-sensitive recording material that does not cause a decrease in whiteness or recording density even when exposed to high temperature conditions. As a result, the inventors discovered that the above-mentioned problems could be solved by using a specific compound as a coloring agent, leading to the completion of the present invention.

[0007]

[Means for Solving the Problems] The present invention provides a heat-sensitive recording material in which a support is provided with a heat-sensitive recording layer containing a colorless or light-colored basic dye and a coloring agent capable of forming a color upon contact with the dye. This is a heat-sensitive recording material characterized by containing a compound represented by [Chemical formula 1] as a coloring agent.

[0008]

[Chemical formula 1]

[0009]

[Function] In the present invention, the amount of the compound [Formula 1] to be used is not particularly limited, but it is generally 1 to 1000 parts by weight, preferably 10 to 700 parts by weight, per 100 parts by weight of the basic dye. It is desirable to adjust the amount within a range of about parts by weight. Moreover, the compound represented by [Chemical formula 2] is preferable because it is excellent in the effects of the present invention.

0010

[Case 2]

[0011] In the present invention, various known dyes can be used as the colorless or light-colored basic dye constituting the heat-sensitive recording layer, and specific examples include the following. 3,3-bis(p-dimethylaminophenyl)-6
-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindole-3
-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3,3-bis(1,2-dimethylindol-3-yl)-5-dimethyl Aminophthalide, 3,3-bis(1
,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazol-3-yl)-6-dimethylaminophthalide, 3,3
-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylpyrrol-3-yl)-6-dimethylaminophthalide, etc. Allylmethane dye, 4,
4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoolamine, N-2
, diphenylmethane dyes such as 4,5-trichlorophenylleucoolamine, thiazine dyes such as benzoylleucomethylene blue and p-nitrobenzoylleucomethylene blue, 3-methyl-spiro-dinaphthopyran,
3-ethyl-spiro-dinaphthopyran, 3-phenyl-
Spiro dyes such as spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine ( Lactam dyes such as 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-cyclohexylamino-6-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-7-N-diethylaminofluorane,
3-(N-ethyl-p-toluidino)-6-methyl-7
-phenylaminofluorane, 3-(N-ethyl-p-
toluidino)-6-methyl-7-(p-toluidino)fluorane, 3-dimethylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-dimethylamino-6-methyl-7-phenylaminofluorane, -n-butylamino-6-methyl-7-phenylaminofluorane, 3-di-n-pentylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7-(2
-carbomethoxy-phenylamino)fluorane, 3-
(N-cyclohexyl-N-methylamino)-6-methyl-7-phenylaminofluorane, 3-pyrrolidino-
6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane,
3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluorane, 3-di-n-butylamino-7
-(o-chlorophenylamino)fluorane, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3-(N-methyl-Nn-amyl)amino-6-methyl-7-phenylamino Fluorane, 3-(
N-ethyl-Nn-amyl)amino-6-methyl-7
-phenylaminofluorane, 3-(N-ethyl-N-
isoamyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-methyl-Nn-hexyl)amino-6-methyl-7-phenylaminofluorane, 3
-(N-ethyl-N-n-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-β-ethylhexyl)amino-6-methyl-7-
Phenylaminofluorane, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-cyclopentyl)amino-6-methyl-7- Phenylaminofluorane, 2,2-bis{4-[6'-(N-cyclohexyl-N-methylamino)-3'-methylspiro(phthalido-3,9'-xanthene)-2'-ylamino]
Fluoran dyes such as phenyl}propane, etc. Of course, the dyes are not limited to these dyes, and two or more types of dyes can be used in combination.

Furthermore, among these dyes, 3-(N
-ethyl-N-iso-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-
N-tetrahydrofurfuryl)amino-6-methyl-7
- If a dye with a melting point of 180°C or less, such as anilinofluorane or 3-(N-ethyl-N-cyclopentyl)amino-6-methyl-7-anilinofluorane, is used, the desired effect will be fully exhibited. This method is more preferable because it not only provides a heat-sensitive recording material with high whiteness in the white paper portion.

[0013] In the present invention, the compound [Formula 1] is used as a coloring agent, but other coloring agents may be used in combination as long as the object of the present invention is not impaired. For example, the following are exemplified. Ru. 4-tert-butylphenol, α-naphthol, β-naphthol, 4-acetylphenol, 4
-tert-octylphenol, 4,4'-sec
-butylidene diphenol, 4-phenylphenol,
4,4'-dihydroxy-diphenylmethane, 4,4'
-isopropylidene diphenol, hydroquinone, 4
, 4'-cyclohexylidene diphenol, 4,4'-
(1,3-dimethylbutylidene)bisphenol, 2,
2-bis(4-hydroxyphenyl)-4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis(6-tert-butyl-3-methylphenol), 4,4'-dihydroxydiphenyl Sulfone, 2,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone,
4-hydroxy-4'-methoxydiphenyl sulfone,
4-Hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-3',4'-trimethylenediphenylsulfone, 4-hydroxy-3',4'-tetramethylenediphenylsulfone, 3,4-dihydroxy-
4'-methyldiphenylsulfone, bis(3-allyl-
4-hydroxyphenyl)sulfone, 1,3-di[2-
(4-hydroxyphenyl)-2-propyl]benzene, hydroquinone monobenzyl ether, bis(4-hydroxyphenyl)acetic acid butyl ester, 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,4,4'-trihydroxy Benzophenone, 2,
2',4,4'-tetrahydroxybenzophenone, 4
-Dimethyl hydroxyphthalate, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoate-se
c-butyl, pentyl 4-hydroxybenzoate, 4-
Phenyl hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, p-chloro 4-hydroxybenzoate benzyl, 4-
Phenolic compounds such as p-methoxybenzyl hydroxybenzoate, novolac type phenolic resin, phenol polymer, benzoic acid, p-tert-butylbenzoic acid,
Trichlorobenzoic 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, 3,5-di-
tert-butylsalicylic acid, 3-benzylsalicylic acid, 3-(α-methylbenzyl)salicylic acid, 3-chloro-5-(α-methylbenzyl)salicylic acid, 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid, 3
, 5-di-α-methylbenzyl salicylic acid, and these phenolic compounds, aromatic carboxylic acids such as zinc, magnesium, aluminum, etc.
Organic acidic substances such as salts with polyvalent metals such as calcium, titanium, manganese, tin, and nickel.

[0014] Preparation of a coating liquid containing these is generally carried out by using water as a dispersion medium and dispersing the dye, the above-mentioned specific compounds, etc. together or separately using a stirring/pulverizing machine such as a ball mill, attritor, or sand mill. It is prepared by Such coating liquids usually contain starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic,
Polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, sulfone group-modified polyvinyl alcohol, silicon-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, graft copolymer of vinyl alcohol/vinyl acetate copolymer and acrylamide/acrylic acid allyl acetoacetate, Styrene/maleic anhydride copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion, etc. are blended in an amount of about 2 to 40% by weight, preferably about 5 to 25% by weight of the total solid content.

Various auxiliary agents can be further added to the coating solution, such as dioctylsulfosuccinic acid sodium salt, dodecylbenzenesulfonic acid sodium salt,
Examples include dispersants such as sodium lauryl alcohol sulfate ester and fatty acid metal salts, antifoaming agents, fluorescent dyes, and coloring dyes. In addition, it is also possible to use the said compound illustrated as a binder as a dispersion aid.

In order to improve the adhesion of residue to the recording head, kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine particulate anhydrous silica,
Inorganic pigments such as activated clay, organic pigments such as styrene microspheres, nylon powder, polyethylene powder, urea/formalin resin fillers, and starch particles can also be added. Furthermore, a dispersion or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax, or the like may be added to prevent sticking from contact with a recording device or a recording head.

Furthermore, in the heat-sensitive recording material of the present invention, for example, stearic acid amide, stearic acid methylene bisamide, stearic acid ethylene bisamide, oleic acid amide, palmitic acid amide, coconut fatty acid may be added to the extent that the desired effects of the present invention are not inhibited. Fatty acid amide such as amide, 2
, 2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(6-t
ert-butyl-3-methylphenol), 1,1,3
-tris(2-methyl-4-hydroxy-5-tert
-butylphenyl)butane, 1,1,3-tris(2-
Hindered phenols such as methyl-4-hydroxy-5-cyclohexylphenyl)butane, biphenyls such as p-benzylbiphenyl and p-(4-tolyloxy)biphenyl, 1,5-bis(4-methoxyphenoxy)
-3-oxapentane, 1,2-bis(phenoxy)
Ethane, 1,2-bis(4-methylphenoxy)ethane, 1,2-bis(3-methylphenoxy)ethane, 1-
Ethers such as (2-methylphenoxy)-2-(4-methoxyphenoxy)ethane, 2-naphtholbenzyl ether, dibenzyl terephthalate, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester, oxalic acid Esters such as di(4-methylbenzyl) ester, oxalic acid di(4-chlorobenzyl) ester, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-hydroxy-4-benzyloxybenzophenone It is also possible to use ultraviolet absorbers such as, and various known thermofusible substances as sensitizers. The amount of the thermofusible substance to be used is not particularly limited, but is generally 50 to 1000 parts by weight, preferably 100 to 500 parts by weight, per 100 parts by weight of the basic dye.
It is desirable to use within the range of parts by weight.

Paper, plastic film, synthetic paper, etc. can be used as the support, and paper is preferably used in terms of cost and coatability. In the present invention, the method of forming the recording layer is not particularly limited, and can be formed according to conventionally well-known and commonly used techniques. For example, a coating liquid for a heat-sensitive recording layer is applied onto a support using an air knife coater,
Blade coater, bar coater, gravure coater,
Examples of methods include coating and drying using a suitable coating device such as a curtain coater or a short dwell coater. Further, the amount of the coating liquid to be applied is not particularly limited, and is generally adjusted within the range of 2 to 12 g/m<2>, preferably 2 to 8 g/m<2> in terms of dry weight. Note that it is also possible to provide an overcoat layer on the recording layer for the purpose of protecting the recording layer, etc. A protective layer may be provided on the back side of the support, or an undercoat layer may be provided between the support and the heat-sensitive recording layer. Of course, it is also possible to provide a heat-sensitive recording material, and furthermore, various known techniques in the field of manufacturing heat-sensitive recording materials, such as applying adhesive processing, can be added.

[0019]

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present 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 ■ Preparation of liquid A 3-(N-ethyl-N-iso-amyl)amino-6-methyl-7-phenylaminofluorane

10 copies
Stearic acid ethylene bisamide
25
Part Methylcellulose 5% aqueous solution

Part 5 Water

50 parts of this composition was ground in a sand mill until the average particle size was 0.8 μm. ■ Preparation of B solution Dihydroxy para-quarter phenyl (above [
Compound 2) 20 parts Methyl cellulose 5%
aqueous solution
Part 5 Water


55 parts of this composition was ground in a sand mill until the average particle size was 1.0 μm. ■ Formation of recording layer 90 parts of liquid A, 80 parts of liquid B, silicon oxide pigment (oil absorption 180 parts)
ml/100g) 7 parts, light calcium carbonate (oil absorption 9
0ml/100g), 50 parts of a 20% polyvinyl alcohol aqueous solution, 15 parts of a 30% zinc stearate aqueous dispersion, and 10 parts of water were mixed and stirred to obtain a coating liquid. The obtained coating liquid was applied to a base paper with a basis weight of 50 g/m2 so that the coating amount after drying was 6 g.
/m2 and dried to obtain heat-sensitive recording paper.

Example 2 In preparing solution A, 3-(N-ethyl-N-iso-
Example except that 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-anilinofluorane was used instead of amyl)amino-6-methyl-7-phenylaminofluorane. A thermosensitive recording paper was obtained in the same manner as in 1.

Example 3 In preparing solution A, 3-(N-ethyl-N-iso-
Example 1 except that 3-(N-methyl-N-cyclohexyl)amino-6-methyl-7-phenylaminofluorane was used instead of amyl)amino-6-methyl-7-phenylaminofluorane. A thermosensitive recording paper was obtained in the same manner.

Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1, except that 4,4'-isopropylidene diphenol was used instead of dihydroxy para-quaterphenyl in the preparation of liquid B. Each thermal recording paper obtained as described above was heated using a Matsushita simulator MF-1 (applied voltage 16 V, pulse width 5 m).
s). The density of the obtained recording layer was measured using a Macbeth densitometer (model RD-914, manufactured by Macbeth), and the results are shown in Table 1.

After recording, the thermal recording paper was kept in a hot air dryer at 80° C. for 5 hours, and then the density of the recorded image was measured again using a Macbeth reflection densitometer to evaluate the storage stability under high temperature conditions. At the same time, the whiteness of the white paper area after the same treatment was also measured to evaluate the background fog, and the results are also listed in Table 1.

[0025]

[Table 1]

[0026]

EFFECTS OF THE INVENTION As is clear from the results in Table 1, all of the heat-sensitive recording materials of the present invention were highly sensitive heat-sensitive recording materials that showed extremely little decrease in whiteness even when placed in a high-temperature environment.

Claims (1)

[Claims] [Claim 1] In a heat-sensitive recording material in which a heat-sensitive recording layer containing a colorless or light-colored basic dye and a coloring agent capable of forming a color upon contact with the dye is provided on a support, [ A heat-sensitive recording material characterized by containing a compound represented by the following formula: [Chemical formula 1]