JPS60247592A - Thermal recording body - Google Patents

Abstract

PURPOSE:To obtain a thermal recording body excellent in the preservability of a printed character and generating no fogging even under such a condition that both of temp. and humidity are acted, by using 1,1-bis(4-hydroxyphenyl)-1-phenylethane as a coupler developing a color upon the contact with a basic colorless dye. CONSTITUTION:In a thermal recording body wherein a protective layer is provided on a recording layer containing a colorless or light-colored basic dye and a coupler capable of developing a color upon the contact with said dye, at least 1,1-bis(4-hydroxyphenyl)-1-phenylethane is used as said coupler. In order to improve the printability or sticking of the protective layer, if necessary, pigment is added to the above specific protective layer. By this method, the thermal recording body improved in background fogging under a high temp. and high humidity condition and excellent in the preservability of a printed character is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material with excellent storage stability.

Conventionally, heat-sensitive recording materials have been well known, which utilize a coloring reaction between a coloring agent and a coloring agent that develops color when they come into contact with the coloring agent, and bring both coloring materials into contact with each other using heat to obtain a colored image. ing. Such thermal recording media are relatively inexpensive, and the recording devices are compact and relatively easy to maintain, so they are used not only as recording media for facsimiles and various point counting machines, but also in a wide range of fields. .

One of the fields of use is POS (PoS) in retail stores etc.
(int of 5ales) With the expansion of systemization, the use as labels is increasing.

However, such heat-sensitive recording materials generally have water resistance, oil resistance,
Because of its poor plasticizer resistance, for example, if water, oil, oil, or plasticizers contained in plastic films come into contact with the colored print, the print density will drop significantly, and heat-sensitive recording may occur during handling. There is a drawback that when the layer is touched with the hand, a fingerprint-like fog appears.

As a method to eliminate such drawbacks, there is a method of coating an aqueous emulsion of a resin having film-forming ability and chemical resistance on the heat-sensitive recording layer (Japanese Patent Application Laid-open No. 128347-1982).
, a method of applying a water-soluble polymer compound such as polyvinyl alcohol (Utility Model Application Publication No. 56-125354), and the like have been proposed.

However, in a heat-sensitive recording material using a phenol compound such as 4,4'-isopropylidenediphenol (bisphenol A) as a coloring agent, even if a protective layer is provided on the recording layer, humidity and When a recording medium is placed in an environment where both temperature and temperature are affected, there is a problem in that fogging occurs on the surface of the recording medium.

In view of the current situation, the present inventor has developed a thermal recording medium that has excellent printing stability and does not cause fogging even under conditions where both temperature and humidity act (hereinafter simply referred to as temperature and humidity conditions). As a result of extensive research into the field of coloring agents for human bodies, we have completed the present invention.

The present invention provides a thermal recording material in which a protective layer is provided on a recording layer containing a colorless or light-colored basic dye and a coloring agent capable of forming a color when it comes into contact with the dye. .1-bis(4-hydroxyphenyl)-1-
This is a heat-sensitive recording material characterized by using phenylethane.

Various types of colorless to light-colored basic dyes are known to be contained in the recording layer in the present invention, and the following are exemplified.

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. s-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-(1-methylvirol-3-yl)-6-dimethylaminophthalide, etc. triallyl Methane dye, 4,
4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoolamine, N-2
, 4,5-) diphenylmethane dyes such as dichlorophenyl leuco auramine, thiazine dyes such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue, 3-methyl-spiro-dinaphthopyran,
3-ethyl-spiro-dinaphthopyran, 3-phenyl-
Spiro dyes such as spiro-dinaphthopyran, 3-hensyl-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(0-chloroanilino)lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-methoxy, fluoran, 3
-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-(N -Ethyl-p-toluidino)-7-methylfluorophone, 3
-thiethylano-7-, N-acetyl-N-methylaminofluorane, 3-dinitylamino-'1-N-methylaminofluorane, 3-diethylamino-7-dihendylaminofluorane, 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-1-luidino)-6-methyl-7=(p-
) luidino) fluoran, 3-diethylamino-6-methyl-7-phenylaminofluoran, 3-diethylamine-7-(2-carbomethoxy-phenylamino)fluoran, 3-(N-ethyl-N-4so-amylamino) -6-methyl-7-phenylaminofluorane, 1
-(N-cyclohexyl-N-methylamino)-6-methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylamino Fluoran, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(0-chlorophenylamino)fluoran, 3-dibutylamino-7-(
Fluoran dyes such as o-chlorophenylamino)fluoran, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, etc.

The present invention has an important feature in that 1,1-bis(4-hydroxyphenyl)-1-phenylethane is used as a coloring agent that develops color when it comes into contact with the above-mentioned basic colorless dye. However, other phenolic compounds can be used in combination as necessary. Various compounds are known as such phenolic compounds, but in the present invention, it is particularly preferable to use compounds such as those exemplified below, since a heat-sensitive recording material with even better print resistance to plasticizers can be obtained.

4.4'-isopropylidenediphenol; 1°1-di(4-hydroxyphenyl)cyclohexane, 1l-(
4-hydroxyphenyl)-1-(3-methyl-4-hydroxyphenyl)cyclohexane, 1-(4-hydroxyphenyl)-1-(3,5-dimethyl-4-hydroxyphenyl)cyclohexane, 1=(4 -hydroxyphenyl)-1-(3-ethyl-4-hydroxyphenyl)cyclohexane, 1-(4-hydroxyphenyl)
, -1-(3-isopropyl-4-hydroxyphenyl)cyclohexane, 1-(4-hydroxyphenyl)-
1-(3-tert-butyl-4-hydroxyphenyl)cyclohexane and 1-(4-hydroxyphenyl)
-214 1,1-di(4-hydroxyphenyl)cyclohexane such as 1-(3-cyclohexyl-4-hydroxyphenyl)cyclohexane; 4-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2°4.4'- Trihydroxybenzophenone and 2゜2'
, 4.4'-Tetrahydroxybenzoic acid and other hydroxybenzophenone compounds; methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-5ec
-Butyl, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, hensyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, 4-hydroxybenzoate phenethyl acid, 4
-4-hydroxybenzoic acid esters such as p-chlorohensyl hydroxybenzoate and p-methoxybenzyl 4-hydroxybenzoate; 4-hydroxydiphenylsulfone, 4゜4'-dihydroxydiphenylsulfone, methyl-4-hydroxyphenyl Sulfone, ethyl
4-hydroxyphenyl sulfone, cyclohexyl-4
-Hydroxyphenylsulfone, Hensyl-4-hydroxyphenylsulfone, 4'-chloro-4-hydroxydiphenylsulfone, 4-'-fluoro-4-hydroxydiphenylsulfone, 4-methyl-4-hydroxydiphenylsulfone, 4-hydroxydiphenyl Sulfone, 2-hydroxydiphenylsulfone, 3', '4'-
Dimethyl a4-hydroxydiphenyl sulfone and “4
4-hydroxydiphenylsulfone derivatives such as '-methoxy-4-hydroxydiphenylsulfone.

In addition, 1,1-bis(4-hydroxyphenyl)=1-
The blending ratio when phenylethane and other phenol+'l compounds are used together should be selected appropriately depending on the quality objective, type of phenolic compound, etc.
(2) It is desirable to use 1-bis(4-hydroxyphenyl)-1-phenylethane in an amount of at least 5% by weight, preferably 30% by weight or more based on the total color former.

In addition, the ratio of the basic colorless dye and coloring agent used in the recording layer is appropriately selected depending on the type of basic dye and coloring agent used, and is not particularly limited. 1 to 50 parts by weight, preferably 2 to 10 parts by weight of coloring agent are used per 1 part by weight of dye.

In the heat-sensitive recording material of the present invention, a sensitizer may be added to the recording layer as necessary. Although various substances are known as sensitizers, it is preferable to use the substances exemplified below in the present invention.

Dimethyl terephthalate, dicyclohexyl phthalate, diphenyl phthalate, dibenzylisophthalate,
2-(2'-hydroxy-5'-methylphenyl)hencytriazole, 2-(2'-hydroxy-5'-t
ert-octylphenyl)benzotriazole, 2-
(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 1-
(2'-hydroxy-3'-tert-butyl-5'
-methylphenyl)-5-chlorobenzotriazole,
2-(2'-hydroxy-3',5'-tert-
amyl phenyl)benzotriazole, 1-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-5'
-tert-butylphenyl)benzotriazole,
1-phenoxy-2-naphthoxy(1)-ethane, 1-
Phenoxy-4-naphthoxy(2)-butane, 1-(
2-isopropylphenoxy)-2-naphthoxy (2)
-ethane, 1-(4-methylphenoxy)-3-naphthoxy(2)-propane, 1-(2-methylphenoxy)
-2-naphthoxy(2)-ethane, 1-(3-methylphenoxy)-2-naphthoxy(2)-ethane, 1-phenoxy-2-naphthoxy(2)-ethane, l-phenoxy-6-naphthoxy(2)-ethane )-hexane, 1-(2-phenylphenoxy)-2-phenoxyethane, 1-(4-
phenylphenoxy)-1-(2-methylphenoxy)
Ethane, 1.4-diphenoxybutane, 1.4-di(
4-methylphenoxy)butane, 1,2-di(3,4-
dimethylphenoxy)ethane, 1-(4-phenylphenoxy)-3-phenoxypropane, 1-phenoxy2
(4tert-butylphenoxy)ethane, etc.

The amount of the sensitizer added is not particularly limited, and is generally 0.05 to 5 parts by weight per 1 part by weight of the basic dye.
It is used in an amount of 0 parts by weight, preferably in the range of 0.2 to 5 parts by weight.

To prepare a coating solution containing these substances, the coloring agent and the coloring agent are generally dispersed together or separately using water as a dispersion medium, stirring with a ball mill, attritor, sand grinder, etc., or using a pulverizer, and then coating. Prepared as a liquid. Such coating liquids usually contain starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene/maleic anhydride copolymer salt, styrene/maleic anhydride copolymer as binders. salts, ethylene/acrylic acid copolymer salts, styrene/acrylic acid copolymer salts, styrene/butadiene copolymer emulsions, etc. in an amount of 10 to 70% by weight of the total solids, preferably 1
It is used in an amount of 5 to 50% 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 benzophenone, other antifoaming agents, fluorescent dyes, Examples include colored dyes.

In addition, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine particle state star silica, and active Inorganic pigments such as white clay can also be added.

In the heat-sensitive recording material of the present invention, there are no particular limitations on the method of forming the recording layer, and the recording layer can be formed according to conventionally well-known and commonly used techniques, such as applying a coating liquid by air knife coating, blade coating, etc. - Formed by drying methods, etc. There is also no particular limitation on the amount of coating liquid applied, but it is usually between 12g/n and 12g/n in terms of dry weight. , preferably 3 to Lo
g/d range.

As described above, the heat-sensitive recording material of the present invention is provided with a protective layer on the recording layer thus formed, and the protective layer is mainly made of a water-soluble polymer, such as polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol. , acetoacetyl group it1 polyvinyl alcohol, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, starch and its derivatives, casein, sodium alginate, polyvinylpyrrolidone, polyacrylamide,
Styrene-maleic acid copolymer salt, polyurethane resin,
It is formed from urea resin, melamine resin, etc.

Incidentally, a pigment may be added to the above-mentioned specific protective layer in the present invention, if necessary, in order to improve the printability and sticking of the protective layer.

Specific examples of such pigments include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc,
Examples include inorganic pigments such as olefin, clay, calcined clay, colloidal silica, styrene microballs, nylon powder, polyethylene powder urea/formalin resin filler, and organic pigments such as raw starch granules. Generally, it is desirable that the amount is blended in the range of 5 to 500 parts by weight per 100 parts by weight of the resin component.

Furthermore, in the coating solution, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, surfactants (dispersants, Various auxiliary agents such as a wetting agent) and an antifoaming agent can also be added as appropriate.

In the present invention, the coating liquid forming the protective layer is generally prepared as an aqueous coating liquid, and if necessary, it is thoroughly mixed and dispersed using a mixing/stirring machine such as a mixer, attritor, ball mill, or roll mill. It is applied onto the heat-sensitive recording layer by a device.

The coating amount of the protective layer coating liquid is not particularly limited, but if it is less than 0.1 g/ITr, the desired effect of the present invention cannot be sufficiently obtained, and if it exceeds 20 g/'of, it will not be heat sensitive. Doing so may significantly reduce the recording sensitivity of the recording medium.
Generally 0.1 to 20 g/M in dry weight, preferably 0
．． It is desirable to adjust it within the range of 5 to Log/rrr.

Thus, according to the present invention, it is possible to obtain a heat-sensitive recording material in which background fogging under temperature and humidity conditions is improved and print storage stability is excellent.

Note that, if necessary, it is also possible to further improve the storage stability by providing a protective layer on the back side of the heat-sensitive recording material. Furthermore, various known techniques in the field of heat-sensitive recording material production may be added as necessary, such as providing an undercoat layer on the support, applying an adhesive treatment to the back surface of the recording material, and processing it into an adhesive label.

The present invention will be described in more detail with reference to Examples below, but it is of course not limited thereto.

Note that parts and % in the examples indicate parts by weight and % by weight, respectively, unless otherwise specified.

Example 1 ■ Solution A opening 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-phenylaminofluorane 10 parts Methyl cellulose 5% aqueous solution 5 parts Water 40 parts This composition was ground with a sand grinder to an average particle size of 3 μm.

(2) Preparation of Solution B 1. 1-bis(4-hydroxyphenyl)=1-phenylethane 20 parts Methyl cellulose 5% water iS solution 5 parts Water 755 parts This composition was ground with a sand grinder to an average particle size of 3 μm.

(2) Formation of Recording Layer 55 parts of liquid A, 80 parts of liquid B, 50 parts of a 20% oxidized starch aqueous solution, and 10 parts of water were mixed and stirred to prepare a coating liquid. The obtained coating liquid was applied to a 50 g/% base paper with a coating amount of 6 g/r+f after drying.
A heat-sensitive recording paper was obtained by coating and drying so as to obtain the following.

(2) Formation of a protective layer 100 parts of a 10% aqueous polyvinyl alcohol solution, 20 parts of calcium carbonate, and 50 parts of water were mixed and stirred to prepare a coating solution. The obtained coating liquid was applied onto the recording layer of the heat-sensitive recording paper so that the coating amount after drying was 6 g/cd, and dried to form a protective layer.

Example 2 In Example 1, B liquid 8 was used as the coating liquid for forming the recording layer.
A thermosensitive recording paper having a protective layer was obtained in the same manner as in Example 1, except that 80 parts of a mixture of liquid B and liquid C below was used instead of 0 part.

(2) Cil'& Kaisei 4.4'-Isopropylidenediphenol 20 parts Methyl cellulose 5% aqueous solution 5 parts Water 55 parts This composition was ground with a sand grinder to an average particle size of 3 μm.

Example 3 A thermosensitive recording paper having a protective layer was obtained in the same manner as in Example 1, except that 40 parts of the following liquid was further added as a coating liquid for forming a recording layer.

(2) Preparation of Solution D 2-(2'-Hydroxy-5'-methylphenyl)benzotriazole 10 parts Methylcellulose 5% aqueous solution 5 parts Water 25 parts This composition was ground with a sand grinder to an average particle size of 3 μm.

Example 4 In Example 1, B liquid 8 was used as the coating liquid for forming the recording layer.
Instead of 0 parts, use 80 parts of a mixed solution of liquid B and liquid E below,
Furthermore, a thermosensitive recording paper having a protective layer was obtained in the same manner as in Example 1, except that 40 parts of Liquid D obtained in the same manner as in Example 3 was added.

(2) Solution E Opening 4.4'-Cyclohexylidene diphenol 20 parts Methyl cellulose 5% aqueous solution 5 parts Water 55 parts This composition was ground with a sand grinder to an average particle size of 3 μm.

Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that a protective layer was not provided on the recording layer.

Comparative Example 2 In Example 1, B liquid 8 was used as the coating liquid for forming the recording layer.
A thermosensitive recording paper having a protective layer was obtained in the same manner as in Example 1, except that 80 parts of Liquid C obtained in the same manner as in Example 2 was used instead of 0 parts.

Comparative Example 3 In Example 1, B liquid 8 was used as the coating liquid for forming the recording layer.
A protective layer was prepared in the same manner as in Example 1, except that 80 parts of Solution E obtained in the same manner as in Example 4 was used instead of 0 parts, and 40 parts of Solution D obtained in the same manner as in Example 3 were added. A thermosensitive recording paper having the following properties was obtained.

Comparative Example 4 In Example 1, B liquid 8 was used as the coating liquid for forming the recording layer.
Instead of 0 parts, 80 parts of a mixture of liquids C and E obtained in the same manner as in Examples 2 and 4 was used, and 40 parts of liquid D obtained in the same manner as in Example 3 was added. A thermal recording paper having a protective layer was obtained in the same manner as in Example 1.

The eight types of thermal recording paper obtained in this way were printed using a thermal printer, and the color density of the print was measured using a Macbeth density needle (
The results are shown in Table 1.

Next, plasticizer resistance and temperature/humidity suitability were evaluated using the following methods, and the results are listed in Table 1.

Plasticizer resistance: Wrap a polypropylene pipe (40mmφ tube) in three layers with a vinyl chloride lamp film (manufactured by San-・Jitoatsusha), and then place a colored thermal recording paper on top of it, with the colored side facing out. Then, a vinyl chloride lamp film was wrapped three times over the paper, and the print density was evaluated after 72 hours.

◎: Very good ○: Good △: Slightly poor ×: Poor temperature and humidity suitability 2 Unprinted thermal recording paper was heated at 50°C and 90% RH.
The recording layer was left in an atmosphere for 24 hours, and the degree of fog on the recording layer was evaluated.

○: Almost no fog is observed △: Fog is observed ×: Significant fog is observed Table 1 As is clear from the results in Table 1, the thermal recording material according to the present invention has poor print storage stability. It was an extremely excellent recording material that was excellent in temperature and humidity, and did not cause fogging even under conditions of temperature and humidity.

Patent applicant Kanzaki Paper Co., Ltd.

Claims (1)

[Claims] (1) In a thermosensitive recording material in which a protective layer is provided on a recording layer containing a colorless or light-colored basic dye and a coloring agent capable of forming a color when it comes into contact with the dye, at least one coloring agent is used as the coloring agent. A heat-sensitive recording material characterized by using 1-bis(4-hydroxyphenyl)-1-phenylethane.