JPH0281669A - Thermal recording element - Google Patents

Abstract

PURPOSE:To ensure high sensitivity and degree of whiteness and also that the degree of whiteness does not decrease, if it is exposed to high temperature by adding a specific coloring agent and a thermally fusible material of specific type. CONSTITUTION:A recording layer containing colorless or light-colored basic dye and a coloring agent which forms a color is provided on a support. At least, one kind of chemical is selected from among 4-hydroxy-4'- isopropyloxydiphenylsulfon, 4,4'-(1-3-dimethylbutylidene)bisphenol, 4,4'-(1- phenylethylidene)bisphenol, 4,4'-(p-phenylenediisopropylidene)bisphenol and 4,4'-(m- phenylenediisopropylidene)bisphenol as a coloring agent. In addition, a fusible substance expressed by a formula is added to the coloring agent. If this kind of compound is jointly used, a thermal recording element is obtained which not only has excellent high-speed recording properties but also shows no deterioration of the degree of whiteness in the recording layer, if the element is stored at high temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a heat-sensitive recording medium, which is particularly suitable for high-speed recording,
Moreover, the present invention relates to a heat-sensitive recording material that can stably maintain a recorded image without causing a decrease in whiteness in the blank paper portion.

``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.

Recently, with remarkable progress in thermal recording methods, thermal faxes and the like have become capable of high-speed printing, and it has become possible to record a standard A4 size original in 10 seconds or less. With the speed increase in the hardware field, there is a demand for heat-sensitive recording bodies that are excellent in suitability for high-speed recording.

Conventionally, as a means of improving the color development sensitivity of thermal recording materials, a thermofusible substance with a lower melting point than a basic dye or coloring agent is added to the recording layer, and the dye is first absorbed by the melted thermofusible substance. A widely known method is to lower the temperature at which color development starts by dissolving a coloring agent (JP-A-49-34842, JP-A-53-39139, etc.).

However, it is generally difficult to make one type of heat-fusible substance have the property of dissolving both a basic dye and a coloring agent, and it is difficult to make a heat-fusible substance with this property. However, the disadvantage is that the temperature at which color development starts falls excessively due to the melting point drop due to the eutectic phenomenon of the dye/coloring agent/thermofusible substance, resulting in a significant decrease in the whiteness of the recording layer.

Therefore, the present inventors previously proposed a phenyl-benzyl ether derivative as a thermofusible material that does not have the above-mentioned drawbacks (Japanese Patent Application Laid-Open No. 31287/1987). However, even in heat-sensitive recording materials using such phenyl-benzyl ether derivatives, the whiteness significantly decreases when stored under high-temperature conditions, and further improvements are required.

``Problems to be Solved by the Invention'' In view of the current situation, the present inventors have developed a thermal recording material that has high color development sensitivity and does not lose whiteness even when exposed to high temperature conditions, in addition to thermofusible materials. A wide range of coloring agents used in combination were also investigated. As a result, by using a phenyl-benzyl ether derivative represented by -J[(1) below as a thermofusible substance and selectively using a specific compound as shown below as a coloring agent, this objective can be achieved. The present invention was completed based on this discovery.

``Means for Solving the Problems'' The present invention provides a heat-sensitive recording material in which a recording layer containing a colorless or light-colored basic dye and a coloring agent that develops a color upon contact with the dye is provided on a support. , as a coloring agent, 4-hydroxy-4'-isopropyloxydiphenylsulfone, 4.4'-(1°3-dimethylbutylidene)bisphenol, 4°4'-(1-phenylethylidene)
At least one selected from bisphenol, 4.4'-(p-phenylene diisopropylidene) bisphenol, and 4.4'-(m-phenylene diisopropylidene) bisphenol, and represented by the following general formula (1). This is a heat-sensitive recording material characterized by containing a thermofusible substance.

(In the formula, X represents a hydrogen atom, a halogen atom, an alkyl group of 01 to 4, or an alkoxyl group of CI to 4.) "Function" In the present invention, a specific compound as described above is used as a coloring agent, In addition, when a compound represented by the above general formula (1) is used in combination as a thermofusible substance, it not only has excellent high-speed recording properties, but also provides a thermosensitive material that does not cause a decrease in the whiteness of the recording layer even when stored under high-temperature conditions. The reason why such a recording material is obtained is not necessarily clear, but it is presumed that this is because the coloring agent and the thermofusible substance exhibit high compatibility, and despite this, the drop in melting point due to the eutectic phenomenon is small. Ru.

Specific examples of the compound represented by general formula (1) include benzyl-4-methylthiophenyl ether, 4-chlorobenzyl-41-methylthiophenyl ether, 4-chlorobenzyl-41-methylthiophenyl ether,
-bromobenzyl-4'methylthiophenyl ether,
Examples include 4-methylbenzyl-4'-methylthiophenyl ether, 2-methylbenzyl-4'-methylthiophenyl ether, 4-butylbenzyl-4'-methylthiophenyl ether, 4-methoxybenzyl-4'-methylthiophenyl ether, etc. It will be done. Of course, the present invention is not limited to these compounds, and two or more kinds of compounds can also be used in combination.

In the present invention, 4-hydroxy-4'-isopropyloxydiphenylsulfone, 4°4'-(1
,3-dimethylbutylidene)bisphenol, 4.4'
-(1-phenylethylidene)bisphenol, 4.4
'-(p-phenylene diisopropylidene)bisphenol, 4.4'(m-phenylene diisopropylidene)
At least one kind selected from bisphenols is selectively used.

The ratio of the coloring agent and the thermofusible substance represented by the above general formula (1) is not particularly limited, but usually the thermofusible substance is used per 100 parts by weight of the coloring agent. 1
It is desirable to adjust the amount within a range of about 1000 parts by weight, preferably about 10 to 300 parts by weight.

In the heat-sensitive recording material of the present invention, various colorless or light-colored basic dyes are known as the colorless or light-colored basic dyes that constitute the recording layer together with a specific coloring agent and a thermofusible substance. Ru.

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-dimethylaminophthalide, 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-(l-methylpyrrol-3-yl)-6-dimethylaminophthalide, etc. Allylmethane dye, 4.
4'-bis-dimethylaminobenzhydrylbenzyl ether, N-herophenyl leukoolamine, N-2
, 4,5-t-lichlorophenylleucoolamine and other diphenylmethane dyes, benzoylleucomethylene blue, p-nitrobenzoylleucomethylene blue and other thiazine dyes, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, Spiro dyes such as 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilino lactam, rhodamine (p-nitroanilino)lactam,
Lactam dyes such as rhodamine (0-chloroanilino)lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxyfluoran, 3
-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-(N -ethyl-p-)luidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7 -dibenzylaminofluorane, 3-diethylamino-7-(N-methyl-N-benzylamino)fluoran, 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-
Toluidino) fluoran, 3-diethylamino-6-methyl-7-phenylaminofluoran, 3-dibutylamino-6-methyl-7-phenylaminofluoran, 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-(0-chlorophenylamino)fluoran, 3-
(N-ethyl-N-tetrahydrofurfuryl)amino-
6-Methyl-7-phenylaminofluorane, 3-(N
-Methyl-N-n-propyl)amino-6-methyl-7
-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluorane, 3-
(N-ethyl-N-n-propyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-
N-isobutyl)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-cyclopentyl)amino-6-methyl-
Fluoran dyes such as phenylaminofluorane. Of course, the dyes are not limited to these dyes, and two or more types of dyes can be used in combination.

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

Preparation of coating liquids containing these generally uses water as a dispersion medium,
It is prepared by dispersing a dye, a coloring agent, and a thermofusible substance represented by the general formula (N) together or separately using a stirring/pulverizing machine such as a ball mill, attritor, or sand mill.

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, lauryl alcohol sulfate sulfuric ester/storium salt, fatty acid metal salts, ultraviolet absorbers such as triazole type, oil cleaning agents thereof,
Examples include fluorescent dyes and colored dyes. In addition, dispersions or emulsions of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax, etc. are added to prevent sticking of the heat-sensitive recording material due to contact with recording equipment or recording heads. You can also do that.

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-6-tert-butylphenol), 1,1
．． 3-) Lis(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
-methylphenoxy)ethane, ethers such as 2-naphthol benzyl ether, dibenzyl terephthalate,
It is also possible to use various known thermofusible substances such as esters such as 1-hydroxy-2-naphthoic acid phenyl ester.

In addition, kaolin, clay, kurji, calcium carbonate, calcined clay,
Inorganic pigments such as titanium oxide, diatomaceous earth, particulate anhydrous silica, and activated clay may also be added.

The thermosensitive recording material of the present invention has an important feature in that it uses the above-mentioned specific compound as a coloring agent, but bisphenol A, 4.4' -cyclohexylidene diphenol,
Various known coloring agents such as p-hydroxybenzoic acid benzyl ester, 4-hydroxyphthalic acid dimethyl ester 1, and antipyrine complex of zinc thiocyanate can also be used in combination.

As the support, paper, plastic film, synthetic paper, etc. can be used, but paper is most preferably used in terms of cost, coatability, etc. Further, the amount of coating liquid forming the recording layer applied to the support is not particularly limited, and is usually 2 to 12
g/I, preferably adjusted in the range of about 3 to 10 g/%.

The heat-sensitive recording material of the present invention thus obtained has high sensitivity and high whiteness, and remains white even when stored under high temperature conditions, because a specific coloring agent and thermofusible substance are selectively used. It does not easily cause a drop in hardness, and also exhibits excellent properties in terms of preventing debris from adhering to the recording head (piling).

Note that it is also possible to provide an overcoat layer on the recording layer for the purpose of protecting the recording layer, and it is of course also possible to provide a protective layer on the back side of the support or an undercoat layer on the support. In addition, 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 Oki m-line formation.

Firing Ray (Product name: Ansilex, apparent specific gravity:
0.22 g/cJ, manufactured by Engelhard) 100 parts styrene-butadiene copolymer latex (solid content: 5
0%) 15 parts polyvinyl alcohol 10% aqueous solution 30 parts water
A coating solution for an intermediate layer was prepared by mixing 200 parts of the above composition.

The obtained coating liquid was applied to a high-quality paper of 50 g/I so that the coating amount after drying was 10 g/rrf, and dried to form an intermediate layer.

Comprehensive Dictionary of Tinghuang■Star Alliance■Liquid Preparation 3-(N-ethyl-N-isopentylamino)-6-methyl-7~phenylaminofluorane
10 parts Benzyl-4-methylthiophenyl ether 20 parts Methylcellulose 5% aqueous solution 15 parts Water
120 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ Preparation of B solution 4-hydroxy-4'-isopropyloxydiphenylsulfone 30 parts Methylcellulose 5
% aqueous solution 30 parts water
70 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ Formation of recording layer 165 parts of liquid A, 130 parts of liquid B, silicon oxide pigment (oil absorption 1
80 m1/100 g), 150 parts of a 20% oxidized starch aqueous solution, and 55 parts of water were mixed and stirred to prepare a recording layer coating liquid. The resulting coating liquid was applied onto the intermediate layer with a dry weight of 5.0 g.
/nf was coated and dried to obtain heat-sensitive recording paper.

Examples 2 to 5 In the preparation of Example 1 OB liquid, 4-hydroxy-4'-
Instead of isopropyloxydiphenyl sulfone,
4.4'-(1,3-dimethylbutylidene)bisphenol (Example 2), 4,4'-(1-phenylethylidene)bisphenol (Example 3), 4.4'-(p
-phenylene diisopropylidene) bisphenol (Example 4), s.

4'-(m-phenylene diisopropylidene) bisphenol (Example 5) was used in the same manner.
Various types of thermal recording paper were obtained.

Examples 6-10 Same as Examples 1-5 except that 4-chlorobenzyl-4'-methylthiophenyl ether was used instead of benzyl-4-methylthiophenyl ether in Afi preparation of Examples 1-5. Five types of thermal recording paper were obtained.

Comparative Example 1 In preparing liquid B of Example 1, 4-hydroxy-4'-
Instead of isopropyloxydiphenyl sulfone,
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that bisphenol A was used.

Comparative Example 2 Stearic acid amide was used in place of benzyl-4-methylthiophenyl ether in the preparation of liquid A in Example 1, and bisphenol A was used in place of 4-hydroxy-4'-isopropyloxydiphenyl sulfone in the preparation of lacquer B. A thermosensitive recording paper was obtained in the same manner as in Example 1 except for the following.

The 12 types of thermal recording paper thus obtained were placed in a Kyocera simulator (voltage: 15V, pulse cycle: 5m5).
ec) with a pulse width of 0.30 m sec and a pulse width of 0.30 m sec.
Recording was performed at 45 m sec, and the color density was measured using a Macpass quadmeter (model RD-100R, using an amber filter), and the results are shown in Table 1.

In addition, the whiteness of the recording layer before recording was measured using a Hunter whiteness meter, and the thermal recording paper was placed in an atmosphere of 60°C for 2 hours.
After standing for 4 hours, the whiteness was measured again in the same manner, and the results are shown in Table 1.

"Effect" As is clear from the results in Table 1, the heat-sensitive recording material of the present invention is an excellent recording material that has high sensitivity and high whiteness, and does not cause a decrease in whiteness even when exposed to high temperature conditions. Met.

Claims (1)

[Scope of Claims] A thermosensitive recording material in which a recording layer containing a colorless or light-colored basic dye and a coloring agent that develops a color upon contact with the dye is provided on a support, wherein as the coloring agent, 4 -Hydroxy-4
'-Isopropyloxydiphenyl sulfone, 4,4
'-(1,3-dimethylbutylidene)bisphenol,
At least one selected from 4,4'-(1-phenylethylidene) bisphenol, 4,4'-(p-phenylene diisopropylidene) bisphenol, and 4,4'-(m-phenylene diisopropylidene) bisphenol is used. A heat-sensitive recording material characterized by containing a thermofusible substance represented by the following general formula [I]. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [I] [In the formula, X is a hydrogen atom, a halogen atom, C_1_～_4
represents an alkyl group or an alkoxyl group of C_1_ to_4. ]