JPH02286288A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance the storage stability of recording and to prevent fogging by using at least 3-dibutylamino-6-methyl-7-phenylaminofluorane as a basic dye and containing a color former capable of forming a color upon the contact with the basic dye and 1,3,5-tris(4-hydroxycumyl)benzene. CONSTITUTION:3-dibutylamino-6-methyl-7-phenylaminofluorane is used as a basic dye and 1,3,5-tris(4-hydroxycumyl)benzene is together used as a preservability improving agent along with a color former. The use amount of 1,3,5-tris(4-hydroxycumyl)benzene is regulated to 2 - 50pts.wt., pref., 5 - 30pts. wt. per 100pts.wt. of the color former but desirably set to about 20pts.wt. or less per 100pts.wt. of 3-butylamino-6-methyl-7-phenylaminofluorane when various colorless - light-colored basic dyes are together used. The use ratio of the color former is 100 - 700pts.wt. per 100pts.wt. of the basic dye.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a heat-sensitive recording medium, and particularly to a heat-sensitive recording medium that has excellent whiteness of the recording medium and storage stability of recorded images.

(Prior art) Conventionally, heat-sensitive recording materials 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 a recoloring substance into contact with heat. well known.

However, such a heat-sensitive recording medium has a problem in that -i does not have sufficient storage stability of the recorded image, and the color fades over time. In particular, as a basic dye, 3-dibutylamino-6-
Thermal recording materials using methyl-7-phenylaminofluorane have the advantage of being highly white, but on the other hand, the recorded image disappears in a relatively short period of time when stored at high temperatures or high humidity. There are drawbacks.

In order to improve the storage stability of such recorded images, heat-sensitive recording materials to which various storage improvers are added have been proposed, but the improvements come with new drawbacks such as a decrease in whiteness. Satisfactory results have not always been obtained.

(Problems to be Solved by the Invention) In view of the current situation, the present inventors have developed 3-dibutylamino-
1, 3. as a preservability improver for a thermosensitive recording medium containing 6-methyl-7-phenylaminofluorane and a coloring agent.
The present inventors have discovered that containing 5-tris(4-hydroxycumyl)benzene provides an excellent effect of improving the storage stability of recorded images without reducing whiteness, leading to the completion of the present invention. .

(Means for Solving the Problems) The present invention uses at least 3-dibutylamino-6-methyl-7-phenylaminofluoran as a colorless or light-colored basic dye, and develops color upon contact with the basic dye. This is a heat-sensitive recording medium characterized in that it contains a coloring agent that can be used as a coloring agent, and 1°3.5-tris(4-hydroxycumyl)benzene.

(Function) The present invention uses 3-dibutylamino-6-
In a thermosensitive recording medium using methyl-7-phenylaminofluorane, 1°3.5-)lith(4
-Hydroxycumyl)benzene is used in combination as a storage improver.

1.3.5-Tris(4-hydroxycumyl)benzene is known as a coloring agent, but it can be used alone as a coloring agent for 3-dibutylamino-6-methyl-7-phenylaminofluorane. When used, it is not always possible to obtain a heat-sensitive recording material that is satisfactory in terms of the storage stability of recorded images.

Furthermore, in general, when two or more color formers are used in combination, although recording sensitivity is improved, there is a drawback that background fog is likely to occur. However, 1,3,5-tris(4-hydroxycumyl)benzene does not cause any risk of background fogging even when used in combination with other coloring agents, and it is also used as a basic dye in 3-dibutylamino. -6-Methyl-7-phenylaminofluorane, when used as a storage improver for heat-sensitive recording materials, provides a high whiteness of the recording layer, and also maintains the storage stability of recorded images even when exposed to high temperatures or under high-temperature conditions. It has been discovered that a heat-sensitive recording material having extremely excellent properties can be obtained.

In the heat-sensitive recording material of the present invention, 1,3.5-tris(4
-Hydroxycumyl)benzene is generally used in an amount of 2 to 50 parts by weight, preferably 5 parts by weight, per 100 parts by weight of the coloring agent.
It is desirable to adjust the box size to 30 parts by weight.

In the present invention, 3-dibutylamino-6 is used as a basic dye.
-Methyl-7-phenylaminofluorane is used, but various colorless or light-colored basic dyes can also be used in combination as long as the effects of the present invention are not impaired. In that case, the combined ratio is preferably about 20 parts by weight or less per 100 parts by weight of 3-dibutylamino-6-methyl-7-phenylaminofluoran, although it is not necessarily limited.

Examples of such basic dyes include the following.

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(1,2-dimethylindol-3-yl)-
5-dimethylaminophthalide, 3,3-bis(12-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-
Triallylmethane dyes such as (1-methylpyrrol-3-yl)-6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether,
N-herophenyl leukoolamine N-2,4,5-
) Diphenylmethane dyes such as dichlorophenyl leuco auramine, thiazine dyes such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue, 3-me, thyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl- Spiro
Spiro dyes such as dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine (P- Lactam dyes such as nitroanilino)lactam and rhodamine (0-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-1
-luidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluoran Orane, 3-diethylamino-7-(N-methyl-N-benzylamino)fluorane, 3-diethylamino-7-
(N-chloroethyl-N-methylamino)fluorane,
3-diethylamino-7-N-diethylaminofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-
p-Toluidino)-6-methyl-7-(p-1-luidino)fluoran, 3-diethylamino-6-methyl-7
-phenylaminofluorane, 3-diethylamino-7
-(2-Carbomethoxy-phenylamino)fluorane, 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-phenylaminofluorane, 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)
Fluoran, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-phenylaminofluoran, 3-(N-methyl- N-n-propyl)amino-6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-p-butylph, -nylaminofluorane, 3-(N-ethyl-N-
n-propyl)amino-6-methyl-7-phenylaminofluorane, 3-(N~ethyl-N-isobutyl)amino-6-methyl-7-phenylaminofluorane, 3
~(N-methyl-N-n-hexylamino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-
Fluoran dyes such as Nn-hexyl)amino-6-methyl-7-phenylaminofluorane and 3-(N-ethyl-N-cyclopentyl)amino-6-methyl-7-phenylaminofluorane. Of course, the dyes are not limited to these dyes.

Moreover, various compounds can be used as a coloring agent, for example, the following are exemplified.

Inorganic acidic substances such as activated clay, acid clay, attapulgite, bentonite, colloidal silica, aluminum silicate, 2.2-bis(4-hydroxyphenyl)-4-
Methylpentane, 4-tert-butylphenol, 4
-Hydroxyphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-ter
t-octylcatechol, 2.2''-dihydroxydiphenol, 2゜2'-methylenebis(4-methyl-6-
tert-isobutylphenol), 4,4'-isopropylidene bis(2-tert-butylphenol)
, 4゜4''-5ec-butylidenediphenol, 4-phenylphenol, 4.4'-isopropylidenediphenol, 2,2°-methylenebis(4-chlorophenol), hydroquinone, 4.4'-cyclohexyl Dendiphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroxymonobenzyl ether, 4-hydroxy-4°-isoprobyloxydiphenyl sulfo 7.3',4'-tetramethylene-4-hydroxydiphenyl Sulfone, 4,4
″-(1,3-dimethylbutylidene)bisphenol,
4.4”-(1-phenylethylidene) bisphene/-)
Li, phenolic compounds such as 4,4"-(p~phenylene diisopropylidene) diphenol, 4,4'-(m-) nylene diisopropylidene) diphenol, novolak 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-benzylsalicylic acid, 3-(α-methylbenzyl)salicylic acid, 3-chloro-5-(α-methylbenzylsalicylic acid, 3,5-tertiarybutylsalicylic acid, Aromatic carboxylic acids such as 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid, 3,5-di-α-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids and, for example, zinc, magnesium , salts with polyvalent metals such as aluminum, calcium, titanium, manganese, tin, nickel, etc., and salts of polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, etc. with antipyrine, pyridine. , organic acidic substances such as complex compounds with organic compounds such as dimethylaminoantipyrine, and the like.

The proportion of the basic dye and coloring agent used is not necessarily limited, but is preferably 100 to 700 parts by weight, more preferably 150 to 400 parts by weight per 100 parts by weight of the basic dye. agent is added.

Preparation of coating liquids containing these generally uses water as a dispersion medium,
Prepared by dispersing basic dye, coloring agent, 1,3.5-tris(4-hydroxycumyl)benzene, etc. together or separately using a stirring/pulverizing machine such as a ball mill, attritor, or sand mill. be done.

Such coating liquids usually contain starches and binders as binders.
Hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene/maleic anhydride copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion, etc. have a total solid content. It is blended in an amount of about 10 to 40% by weight, preferably about 15 to 30% by weight.

Furthermore, various auxiliary agents can be added to the coating liquid.
For example, dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, ultraviolet absorbers such as triazoles, and other antifoaming agents,
Examples include fluorescent dyes and colored dyes. In addition, to prevent sticking of the heat-sensitive recording material due to contact with a recording device or recording head, a dispersion or emulsion of stearic acid, polyethylene carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax, etc. should be added. You can also do it.

Further, fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, valmitic acid amide, coconut fatty acid amide, 2,2'-methylene bis(4
-methyl-5-tert-butylphenol), i, 1
．． 3-tris(2-methyl-4-hydroxy-5-te
Hindered phenols such as rt-butylphenyl)butane, 1゜2-bis(phenoxy)ethane, 1.2-bis(4-methylphenoxy)ethane, 1.2-bis(3
-Ethers such as methylphenoxy)ethane, 2-naphthol benzyl ether, benzyl-4-methylthiophenyl ether, 1-hydroxy-2-naphthoic acid phenyl ester, dibenzyl terephthalate, benzyl-
Even better recording sensitivity can be obtained by using various known thermofusible substances such as esters such as 4-methylthiophenyl ether.

In addition, inorganic pigments such as kaolin, clay, talc, calcined calcium carbonate, titanium oxide, diatomaceous earth, particulate anhydride, silicic acid, and activated clay can be added to improve the adhesion of residue to the recording head. .

In the heat-sensitive recording material of the present invention, the method for forming the recording layer is not particularly limited (it can be formed according to conventionally well-known and commonly used techniques, such as air knife coater, blade coater, bar coater, gravure coater, gravure coater, etc.). It is formed by a method of coating and drying with a suitable coating device such as a coater or curtain coater.The amount of the coating liquid that forms the heat-sensitive recording layer to be applied to the support is not particularly limited, and is usually 2 to 2 to 10% by dry weight. 12g/bo, preferably 3-10g/
It is adjusted within a range of about rrl.

As the support, paper, plastic film, synthetic paper, etc. can be used, but paper is most preferably used in terms of cost, coatability, etc. Note that it is also possible to provide an overcoat layer on the heat-sensitive recording layer for the purpose of protecting the heat-sensitive recording layer, and of course it is also possible to provide a protective layer on the back side of the support or provide an undercoat layer on the support. This is possible, and various known techniques in the field of heat-sensitive recording material production, such as applying an adhesive to the back surface of the support, can be added.

"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 percentages in the examples indicate parts by weight and percentages by weight, respectively.

Example 1 ■ Formation of undercoat layer Ultrafine particle anhydrous silica (product name: Mizuka Seal P-527
．． Manufactured by Mizusawa Chemical Co., oil absorption 190mf/100g) 100
Part, hydroxyethylated starch (product name: Abelex 2
530, Abebe Co., Ltd. 1) (7) 250 parts of 12% aqueous solution, styrene-butadiene copolymer emulsion (trade name, D
A coating liquid was obtained by mixing 20 parts of OW-1571 (manufactured by Asahi Dow Co., Ltd., 48% solids content). This coating liquid was applied to a base paper of 4 s g/rrr using an air knife coater, and the coating amount after drying was Lo.
g/nf, dried, and supercalendered to obtain a base paper provided with an undercoat layer.

■ AWL preparation 3-dibutylamino-6-methyl-7-phenylaminofluorane 10 parts 132-di(3
-Methylphenoxy)-ethane 30 parts Methylcellulose 5% aqueous solution 20 parts Water
80 parts of this composition was ground to a particle size of 1 μm using a sand grinder.

■ Bee preparation 4.4° -isopropylidene diphenol 20 parts Methyl cellulose 5% aqueous solution 20 parts water
30 parts of this composition was ground to a particle size of 2 μm using a sand grinder.

■ Preparation of Solution C 1.3.5-tris(4-hydroxycumyl)benzene) 7 parts methylcellulose 5% aqueous solution 3 parts water
15 parts of this composition was ground to a particle size of 2 μm using a sand grinder.

■ Formation of heat-sensitive recording layer 140 parts of liquid A, 70 parts of liquid B, 25 parts of liquid C, 15 parts of silicon oxide pigment, modified polyvinyl alcohol (solid content concentration 15 parts)
%), 5 parts of calcium carbonate, 27 parts of zinc stearate emulsion (solid content concentration 30%), and 60 parts of water were mixed and stirred to obtain a coating liquid for a heat-sensitive recording layer. This coating liquid was applied onto the undercoat layer so that the coating amount after drying was 6 g/rrf, dried to form a heat-sensitive recording layer, and then supercalendered to obtain a heat-sensitive recording material.

Example 2 In the preparation of Solution B of Example 1, 4=hydroxy-4 was used instead of 20 parts of 4,4°-isopropylidene diphenol.
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 20 parts of ``-isopropoxydiphenyl sulfone was used.

Example 3 In preparing Solution A of Example 1, everything was the same as Example 1 except that benzyl-4-methylthiophenyl ether was used instead of 1,2-di(3-methylphenoxy)-ethane.
A thermosensitive recording material was obtained in the same manner as above.

Comparative Example 1 A thermosensitive recording material was obtained in the same manner as in Example 1 except that Liquid C was not used.

Comparative Example 2 A thermosensitive recording material was obtained in the same manner as in Example 2 except that Liquid C was not used.

Comparative Example 3 A thermosensitive recording material was obtained in the same manner as in Example 3 except that Liquid C was not used.

Comparative Example 4 In the preparation of Solution A of Example 1, 3-dibutylamino-6-
3- instead of methyl-7-phenylaminofluorane
(N-ethyl-N-isoamyl)amino-6-methyl-
A thermosensitive recording material was obtained in the same manner as in Example 1 except that phenylaminofluorane was used.

Comparative Example 5 In the preparation of Solution A of Example 1, 3-dibutylamino-6-
3- instead of methyl-7-phenylaminofluorane
A thermosensitive recording material was obtained in the same manner as in Example 1 except that (N-methyl-N-cyclohexyl)amino-6-methyl-7-phenylaminofluorane was used.

Comparative Example 6 In the preparation of Solution B in Example 1, 1,3°5-tris(4-
A thermosensitive recording material was obtained in the same manner as in Example 1 except that hydroxycumyl)benzene was used.

The following evaluation tests were conducted on the nine types of heat-sensitive recording paper thus obtained.

L iron density thermosensitive recording paper (Hitachi, HIFAX-400) was used to record the recorded density (D,), and the Macbeth densitometer (RD-1) was used to record the recorded density (D,).
00 type, amber filter), and the results are shown in Table 1.

The whiteness of the n-100 degree thermal recording paper was measured using a Hunter whiteness meter, and the results are shown in Table 2.

The thermal recording paper after printing was left for 24 hours in an atmosphere of 40° C. and 90% RH, and then the recording density (D2) was measured again using a Macbeth densitometer. Table 1 also shows the recording density residual rate (%) according to the following formula.

Recording density residual rate (%) = D! /D, X100 After the printed thermal recording paper was left in an atmosphere of 60° C. and 10% RH for 24 hours, the recording density (D,) was measured again using a Macbeth densitometer.

Table 1 also shows the recording density residual rate (%) according to the following formula.

Recording density residual rate (%) = D3 /D,
After being left in an atmosphere at 10% RH for 24 hours, the fog color density of the white paper portion was measured using a Macbeth densitometer. The results are also shown in Table 2.

Table 1 Table 2 (Effects) As is clear from the results in Tables 1 and 2, the heat-sensitive recording materials of the present invention are all characterized by poor storage stability.
In addition, the heat-sensitive recording material exhibited almost no fogging or coloring due to improved storage stability.

Claims (1)

[Claims] (1) At least 3-dibutylamino-6-methyl-7-phenylaminofluoran is used as a colorless or light-colored basic dye, and a coloring agent capable of forming a color when it comes into contact with the basic dye; A heat-sensitive recording material containing 3,5-tris(4-hydroxycumyl)benzene.