JPH06255259A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material having a remarkably small deterioration of a brightness and a recording density even under exposure to a high temperature environment as high as 100 deg.C and having favorable properties for adhesion of scum. CONSTITUTION:In a thermal recording material provided with a recording layer containing a basic dye and a color developer on a substrate, 3- diethylamino-7-(o-chlorophenylamino) fluorane and/or 3-di(n-butyl)amino-7-(o- chlorophenylamino) fluorane is used as the basic dye, 2,4'-dihydroxydiphenyl sulfone is used as the color developer, and bis(3,5-dimethyl-4-hydroxyphenyl) sulfone is incorporated in the recording layer.

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 in particular, it has excellent background fog and storability of recorded images in a high temperature environment.
Moreover, the present invention relates to a heat-sensitive recording material with less dust deposit.

[0002]

2. Description of the Related Art Heretofore, a heat-sensitive recording material has been well known which utilizes a reaction between a colorless or light-colored basic dye and a coloring agent to react both color-forming substances by heat to obtain a recorded image. . Such a thermosensitive recording medium is relatively inexpensive, and the recording device is compact and maintenance-free, and is used in a wide range of fields.

For example, POS (Point of Sales) label systems have come to be used in various manufacturing processes,
Along with this, there has been a demand for a thermal recording material that is free from background fog even when used in a place where the environmental temperature is 100 ° C. and has excellent preservability of recorded images. The thermal recording material generally has a problem in storage stability of a recorded image, and particularly has a defect that the recorded image is discolored within a relatively short time under high temperature conditions. For the purpose of improving the storage stability of such a recorded image, a method of using various storage stability improving agents has been proposed, but the previously proposed storage stability improving agents cannot provide sufficient effects, or Satisfactory results have not been obtained due to new defects such as a decrease in whiteness even though they are effective in improving the storability of recorded images under high temperature conditions.

Therefore, the inventors of the present invention can obtain a thermosensitive recording medium having a small decrease in whiteness and recording density even when exposed to a high temperature environment, by using a specific basic dye and a color former in combination. This was found, and it was previously proposed as JP-A-4-216993. However, even in a heat-sensitive recording material in which such a specific basic dye and a coloring agent are combined, in order to further enhance the storage stability of the recorded image, phenols in which the ortho position of the hydroxyl group is substituted with a tert-butyl group, It has been clarified that when a so-called hindered phenol compound is used in combination, the storage stability of a recorded image is further improved, but a new problem arises in that deposition of dust on the thermal head is increased. Therefore, there is a strong demand for a thermosensitive recording medium in which the whiteness of the recording layer does not decrease even when exposed to a high temperature environment, the recorded image can be stably maintained, and less dust is attached.

[0005]

In view of the present situation, the present inventors have further studied a method for further improving the excellent properties of the previously proposed color developing system comprising a basic dye and a color former. . As a result, when a specific sulfone compound is used in combination with such a color-developing system, even if exposed to a high temperature environment of 100 ° C., the decrease in whiteness and recording density is extremely small
Moreover, they have found that a heat-sensitive recording material can be obtained which is sufficiently satisfactory in terms of dust adhesion, and has completed the present invention.

[0006]

SUMMARY OF THE INVENTION The present invention comprises:
In a thermosensitive recording medium provided with a recording layer containing a colorless or light-colored basic dye and a coloring agent, 3-
Diethylamino-7- (o-chlorophenylamino) fluorane and / or 3-di (n-butyl) amino-7-
(O-chlorophenylamino) fluorane was included as a colorant in each of 2,4'-dihydroxydiphenylsulfone, and further bis (3,5-dimethyl-4-hydroxyphenyl) sulfone was included in the recording layer. Is a thermosensitive recording medium.

[0007]

In the present invention, 3-diethylamino-7- (o-chlorophenylamino) fluorane and 3-di (n-butyl) amino-7- (o-chlorophenylamino) fluorane are used as the basic dye. The basic dye has a very small decrease in whiteness in a white paper portion under a high temperature environment, but has a serious drawback that the fading of a recorded image is large. However, as a coloring agent for such a basic dye, 2,
Combining 4'-dihydroxydiphenyl sulfone,
Further, when bis (3,5-dimethyl-4-hydroxyphenyl) sulfone is used in combination, the fading of the recorded image is remarkably improved while maintaining the advantages of the basic dye even under a high temperature environment of 100 ° C. It has been found that a heat-sensitive recording material with less dust deposit can be obtained.

The use ratio of the basic dye and the color developing agent is not particularly limited, but generally 50 to 1000 parts by weight, preferably 150 to 700 parts by weight, relative to 100 parts by weight of the basic dye. It is desirable to adjust the range. The amount of bis (3,5-dimethyl-4-hydroxyphenyl) sulfone used is not particularly limited, but it is 5 per 100 parts by weight of the basic dye.
It is desirable to add the compound in an amount of ˜1000 parts by weight, preferably 30 to 700 parts by weight.

As described above, the heat-sensitive recording material of the present invention has a significant feature in that a specific basic dye and a coloring agent are selectively used and a specific sulfone compound is used in combination therewith. However, if necessary, the basic dyes and colorants listed in JP-A-4-216993 can be used in combination,
It is also possible to mix in the range which does not inhibit the desired effect of this invention.

Further, in the present invention, various known heat-fusible substances may be used in combination for the purpose of improving recording sensitivity. Examples of such heat-fusible substances include stearic acid amide, stearic acid methylenebisamide,
Stearic acid ethylenebisamide, stearic acid methylolamide, oleic acid amide, palmitic acid amide,
Fatty acid amides such as coconut fatty acid amide, p-benzylbiphenyl, 1,2-bis (phenoxy) ethane, 1,2
-Bis (4-methylphenoxy) ethane, 1,2- (3
-Methylphenoxy) ethane, 2-naphtholbenzyl ether, ethers such as benzyl-4-methylthiophenyl ether, dibenzyl terephthalate, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid di (p-methylbenzyl) ester, Esters such as oxalic acid di (p-chlorobenzyl) ester, 2- (2'-
Examples thereof include ultraviolet absorbers such as hydroxy-5'-methylphenyl) benzotriazole and 2-hydroxy-4-benzyloxybenzophenone.

The coating liquid containing them is generally prepared by using water as a dispersion medium and an agitator / pulverizer such as a ball mill, attritor, vertical or horizontal sand mill, and colloid mill.
It is prepared by dispersing the above-mentioned specific basic dye, color former, sulfone compound or the like together or separately. In such a coating liquid, starch as a binder, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy group-modified polyvinyl alcohol, sulfone group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, 2 to 40% by weight of the total solid content of various modified polyvinyl alcohols such as silicone modified polyvinyl alcohol, styrene / maleic anhydride copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion,
Preferably about 5 to 25% by weight is blended. Of course, these binders may be used in combination of two or more.

Further, various auxiliaries can be added to the coating solution, for example, 2,2'-methylenebis (4,6-
Mixture of sodium salt of di-tert-butylphenyl) phosphate and magnesium silicate, dispersant such as sodium salt of dioctyl sulfosuccinate and metal salt of fatty acid, UV absorber such as benzophenone type, cyanoacrylate type and hydroxybenzoate type , Other defoaming agents, fluorescent dyes, coloring dyes and the like.

Further, stearic acid ester wax, polyethylene wax, carnauba wax, microcrystalline wax, so as to prevent the thermal recording material from sticking due to contact with a recording device or recording head.
It is also possible to add a dispersion liquid or emulsion of carboxy-modified paraffin wax, zinc stearate, calcium stearate or the like.

In addition, kaolin, clay, talc, calcium carbonate,
Magnesium carbonate, calcined clay, aluminum hydroxide,
It is also possible to add inorganic pigments such as titanium oxide, diatomaceous earth, particulate anhydrous silica, activated clay and the like, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch granules.

In the thermosensitive recording medium of the present invention, the method for forming the recording layer is not particularly limited, and the recording layer can be formed according to a conventionally known and commonly used technique. For example, the coating liquid for the heat-sensitive recording layer is coated on a support with an appropriate coating device such as an air knife coater, a blade coater, a bar coater, a gravure coater, a curtain coater and a lip coater, and dried to form a recording layer.

The coating amount of the coating liquid is not particularly limited, and generally 1.0 to 12 g / m 2 as dry weight.
² , preferably in the range of 1.5 to 10 g / m ² . As the support, paper, plastic film, synthetic paper or the like is used, but paper is most preferably used in terms of cost and coating suitability.

The thermal recording material of the present invention thus obtained is
Even when it is exposed to a high temperature environment, the whiteness and recording density are not significantly reduced, and less dust is attached, which is an excellent characteristic. In the present invention, it is of course possible to provide a protective layer on the front surface and / or the back surface of the thermosensitive recording medium, or to provide an intermediate layer between the support and the thermosensitive recording layer, if necessary. Various known techniques in the field of manufacturing a thermal recording material such as adhesion processing can be added.

[0018]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, parts and% in the examples represent parts by weight and% by weight, respectively.

Example 1 Formation of Intermediate Layer Calcined clay (trade name: Ansilex, manufactured by EMC) 1
00 parts, styrene-butadiene copolymer latex (solid
Form: 50%) 15 parts, 10% polyvinyl alcohol water
Mix a composition consisting of 30 parts of the solution and 200 parts of water,
To prepare a coating liquid for the intermediate layer. 50 g / m of the obtained coating liquid
²Coating amount after drying on high quality paper is 7g / m ²So that
It was applied and dried to form an intermediate layer.

Preparation of Solution A A composition consisting of 10 parts of 3-di (n-butyl) amino-7- (o-chlorophenylamino) fluorane, 10 parts of a 5% methylcellulose aqueous solution, and 5 parts of water was used to measure an average particle diameter in a horizontal sand mill. Was pulverized to 0.5 μm. Preparation of solution B 2,4'-dihydroxydiphenyl sulfone 50 parts, 5
% Methylcellulose aqueous solution and 40 parts of water were used to prepare a composition with a horizontal sand mill having an average particle size of 1.0 μm.
It was crushed until it became.

Preparation of Solution C A composition comprising 50 parts of bis (3,5-dimethyl-4-hydroxyphenyl) sulfone, 50 parts of a 5% aqueous solution of methylcellulose, and 25 parts of water was used in a horizontal sand mill to have an average particle size of 1.0 μm. Crushed until Formation of thermosensitive recording layer 25 parts of solution A, 140 parts of solution B, 125 parts of solution C, 200 parts of 10% silicon-modified polyvinyl alcohol aqueous solution, 30 parts of light calcium carbonate, and 170 parts of water were mixed and stirred to form a coating for the thermosensitive recording layer. A liquid was obtained. The obtained coating liquid was applied and dried on the above-mentioned intermediate layer so that the dry weight was 7 g / m ² .

Formation of Protective Layer Acetoacetyl group-modified polyvinyl alcohol (trade name:
Gocefimer Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 1
200 parts of 0% aqueous solution, kaolin (trade name: UW-90,
EMC part) 60 parts, 30% zinc stearate dispersion liquid 1
5 parts and 140 parts of water were mixed and stirred to obtain a coating liquid for the protective layer. The resulting coating liquid was applied and dried on the thermosensitive recording layer so that the coating amount after drying was 6 g / m ^2, and then supercalendered to obtain a thermosensitive recording material having a protective layer.

Example 2 In preparation of solution A, 3-di (n-butyl) amino-7-
3 instead of (o-chlorophenylamino) fluorane
-Diethylamino-7- (o-chlorophenylamino)
A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 1 except that fluoran was used.

Comparative Example 1 A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 1 except that the liquid C was not added in the formation of the thermosensitive recording layer.

Comparative Example 2 In the preparation of solution A, 3-di (n-butyl) amino-7-
3 instead of (o-chlorophenylamino) fluorane
A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 1 except that -di (n-butyl) amino-6-methyl-7-phenylaminofluorane was used.

Comparative Example 3 A heat-sensitive material having a protective layer in the same manner as in Example 1 except that 4-hydroxy-4'-isopropyloxydiphenylsulfone was used in place of 2,4'-dihydroxydiphenylsulfone in the preparation of solution B. I got a record.

Comparative Example 4 In the preparation of solution C, 1,1,3-tris (5-cyclohexyl-4-hydroxy-2-methylphenyl) butane was used instead of bis (3,5-dimethyl-4-hydroxyphenyl) sulfone. A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 1 except that was used.

Comparative Example 5 In the preparation of solution C, 1,1,3-tris (5-tert-butyl-4-hydroxy-2-methylphenyl) was used instead of bis (3,5-dimethyl-4-hydroxyphenyl) sulfone. ) A thermosensitive recording medium having a protective layer was obtained in the same manner as in Example 1 except that butane was used.

[Evaluation] The seven types of heat-sensitive recording materials thus obtained were used as the Matsushita Simulator MF-1 (applied voltage: 16 V,
The pulse width was 3 ms). The recorded density of the obtained image and the background density of the white paper portion were measured with a Macbeth densitometer (RD-9
14 type, manufactured by Macbeth), and the results are shown in [Table 1]. Then, the thermal recording material after recording is heated to 100 ° C.
After being kept in the hot air dryer for 5 hours, the recording density of the image and the background density of the white paper portion were measured again with a Macbeth reflection densitometer to evaluate the storability of the recorded image under high temperature conditions and the background fog, The results are also shown in [Table 1].

Also, a thermosensitive recording medium is used as a Matsushita Simulator M.
After printing for 5 m with F-1 (applied voltage 16 V, pulse width 3.5 ms, printing rate 50%), the amount of dust adhering to the thermal head was visually evaluated, and the results are also shown in [Table 1]. .

[Table 1]

[0031]

As is clear from the results of [Table 1], the thermal recording material of the present invention is excellent in that the whiteness and the recording density are not significantly reduced even when exposed to a high temperature environment, and the amount of dust is small. It was a thermosensitive recording medium.

Claims (1)

[Claims] 1. A thermosensitive recording medium comprising a support and a recording layer containing a colorless or light-colored basic dye and a coloring agent, wherein 3-diethylamino-7- (o-
Chlorophenylamino) fluorane and / or 3-di (n-butyl) amino-7- (o-chlorophenylamino) fluorane were added to each of 2,4'-dihydroxydiphenylsulfone as a colorant, and the recording layer was further added. A heat-sensitive recording material containing bis (3,5-dimethyl-4-hydroxyphenyl) sulfone.