JPH0248433B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a heat-sensitive recording medium, and particularly to a highly sensitive heat-sensitive recording medium with excellent storage stability. ``Prior art'' Conventionally, a coloring reaction between a coloring agent and a coloring agent that develops color upon contact with the coloring agent is used to obtain a colored image by bringing both coloring substances into contact with each other using heat. Thermosensitive recording media are well known. Such thermosensitive recording media are relatively inexpensive, the recording equipment is compact, and maintenance is relatively easy, so they are used not only as recording media for facsimile machines and various computers, but also in a wide range of fields. One of its applications is retail stores, etc.
With the expansion of POS (point of sales) systemization,
Its use as a label is increasing. However, such heat-sensitive recording materials generally have water resistance,
Because it has poor oil resistance and plasticizer resistance, for example, if water, oil, oil, or plasticizers contained in plastic film come into contact with the print after coloring, the print density will drop significantly, and it may be difficult to handle the print. However, when you touch the heat-sensitive recording layer with your hand, it has the disadvantage of causing a fingerprint-like fog. As a method to eliminate such drawbacks, for example, a method of containing a 4-hydroxydiphenyl sulfone derivative as a coloring agent (Japanese Patent Application Laid-Open No. 57-210886)
etc. have been proposed. However, although these coloring agents are generally effective in improving moisture resistance,
A satisfactory improvement effect on oil resistance and plasticizer resistance cannot necessarily be obtained, and recording sensitivity is also insufficient. "Problems to be Solved by the Invention" The purpose of the present invention is to provide a high-sensitivity print that has excellent printing stability such as water resistance, oil resistance, and plasticizer resistance, has no color fog, and has excellent high-speed recording suitability. The object is to provide a heat-sensitive recording material, and this object is achieved by selectively combining 4-hydroxy-4'-isopropoxydiphenyl sulfone with a specific sensitizer. "Means for Solving the Problem" The present invention provides a heat-sensitive recording material provided with a heat-sensitive recording layer containing at least a color former and a color former that develops a color when in contact with the color former. A heat-sensitive recording material containing hydroxy-4'-isopropoxydiphenyl sulfone and at least one compound represented by the following general formula [] as a sensitizer. [In the formula, X represents -O- or -CO-O-,
R ₁ to _{R 6} each represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aralkyl group. Note that the substituents R ₁ to _{R 6} may be bonded to each other to form an aromatic ring. n represents an integer from 1 to 10. [Function] In the present invention, examples of the color former contained in the recording layer include various known colorless or light-colored basic dyes. Examples of such basic dyes include 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethyl aminophenyl)-3-(1,2-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindole-
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-(1-methylpyrrole-
Triallylmethane dyes such as 3-yl)-6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoolamine, N-2,4,5
- Diphenylmethane dyes such as trichlorophenyl leuco auramine, thiazine dyes such as benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, 3-methyl-spiro-
dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3
Spiro dyes such as -methyl-naphtho-(6'-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine (p-nitroanilino)lactam, rhodamine (o-chloroanilino) Lactam dyes such as 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-toluidino)-7-methylfluorane, 3-diethylamino-7-N-acetyl-
N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane,
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)fluoran, 3-
(N-cyclopentyl-N-ethylamino)-6-
Methyl-7-anilinofluorane, 3-diethylamino-4-methyl-7-phenylaminofluorane, 3-diethylamino-7-(2-carbomethoxy-phenylamino)fluorane, 3-(N
-ethyl-N-isoamylamino)-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-pyrrolidino-
6-Methyl-7-p-butylphenylaminofluorane, 3-(N-methyl-N-n-amyl)amino-6-methyl-7-phenylaminofluorane, ,-(N-ethyl-N -n-amyl)amino-
6-methyl-7-phenylaminofluorane, 3
-(N-ethyl-N-iso-amyl)amino-6-
Methyl-7-phenylaminofluorane, 3-
(N-methyl-N-n-hexyl)amino-6-
Methyl-7-phenylaminofluorane, 3-
(N-ethyl-N-n-hexyl)amino-6-
Methyl-7-phenylaminofluorane, 3-
Examples include fluoran dyes such as (N-ethyl-N-β-ethylhexyl)amino-6-methyl-7-phenylaminofluoran. In the present invention, 4-hydroxy-
Although 4'-isopropoxydiphenyl sulfone is selectively used, it is also possible to use various other coloring agents in combination if necessary. However, in order to obtain the desired effect of the present invention, it is recommended to use 4-hydroxy-4'-isopropoxydiphenyl sulfone in an amount of at least 40% by weight, preferably 70% by weight or more based on the total coloring agent. desirable. Note that the ratio of the coloring agent and coloring agent used in the recording layer is appropriately selected depending on the type of coloring agent and coloring agent used, and is not particularly limited.
Generally 0.5 to 20 parts by weight per 1 part by weight of color former,
Preferably 1 to 10 parts by weight of color former are used. As mentioned above, the heat-sensitive recording material of the present invention is characterized in that 4-hydroxy-4'-isopropoxydiphenyl sulfone as a coloring agent and a sensitizer represented by the following general formula [] are selectively used together. It has important characteristics. [In the formula, X represents -O- or -CO-O-,
R ₁ to _{R 6} each represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aralkyl group. Note that the substituents R ₁ to _{R 6} may be bonded to each other to form an aromatic ring. n represents an integer from 1 to 10. ] Examples of the compound represented by the general formula [ ] include the following compounds. 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, 1-phenoxy-6
-naphthoxy(2)-hexane, 1-(2-phenylphenoxy)-2-phenoxyethane, 1-(4
-phenylphenoxy)-2-(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-phenoxy-2-(4-tert
-butylphenoxy)ethane, 1,2-diphenoxyethane, 1-(4-methylphenoxy)-2-
Phenoxyethane, 1-(2,3-dimethylphenoxy)-2-phenoxyethane, 1-(3,4-
dimethylphenoxy)-2-phenoxyethane,
1-(4-ethylphenoxy)-2-phenoxyethane, 1-(4-isopropylphenoxy)-2-
Phenoxyethane, 1,2-di(2-methylphenoxy)ethane, 1-(4-methylphenoxy)-
2-(2-methylphenoxy)ethane, 1-(4-
tert-butylphenoxy)-2-(2-methylphenoxy)ethane, 1,2-di-(3-methylphenoxy)ethane, 1-(4-methylphenoxy)-
2-(3-methylphenoxy)ethane, 1-(4-
Ethylphenoxy)-2-(3-methylphenoxy)ethane, 1,2-di(4-methylphenoxy)ethane, 1-(2,3-dimethylphenoxy)
-2-(4-methylphenoxy)ethane, 1-
(2,5-dimethylphenoxy)-2-(4-methylphenoxy)ethane, phenoxyacetic acid β-naphthol ester, 2-naphthoxyacetic acid p-cresol ester, 2-naphthoxyacetic acid m-cresol ester, etc. Among the compounds represented by the above general formula [], compounds in which X is -O- are preferred, particularly
R ₁ and R ₆ are hydrogen atoms or alkyl groups having 1 to 4 carbon atoms, R ₂ to _{R 5} are hydrogen atoms, and n is 1
Compounds that are an integer of ~4 are 4-hydroxy-
It is more preferably used in combination with 4'-isopropoxydiphenyl sulfone because a highly sensitive thermosensitive recording material with particularly excellent print storage stability can be obtained. The amount of the sensitizer added is not particularly limited, and it is generally desirable to adjust the amount to about 4 parts by weight or less per 1 part by weight of the coloring agent. A coating solution containing these substances is generally prepared by using water as a dispersion medium and dispersing the coloring agent, coloring agent, and sensitizer together or separately using a ball mill, attritor, sand mill, etc., stirring or grinding machine. It is prepared by Such coating liquids usually contain starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, diisobutylene/maleic anhydride copolymer salt, and styrene as binders.・Maleic anhydride copolymer salt, ethylene/acrylic acid copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion, urea resin, melamine resin, amide resin, etc. have a total solid content of 10 ~70% by weight,
It is preferably used in an amount of about 15 to 50% by weight. Furthermore, various auxiliary agents can be added to the coating solution, such as dispersants such as sodium dioctyl sulfosuccinate, sodium dotecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, etc. , ultraviolet absorbers such as benzophenone, antifoaming agents, fluorescent dyes, and colored dyes. In addition, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, kaolin, clay, talc,
Inorganic pigments such as calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, particulate anhydrous silica, and activated clay may 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 techniques, such as air knife coating, blade coating, etc. It is formed by applying and drying. Further, the amount of the coating liquid to be applied is not particularly limited, and is usually adjusted in the range of about 2 to 12 g/m ² in terms of dry weight, preferably about 3 to 10 g/m ² . The support on which such a recording layer is formed is generally paper, but synthetic resin films, laminated papers, synthetic fiber sheets, nonwoven fabric sheets, etc. can also be used. As mentioned above, the heat-sensitive recording material of the present invention exhibits excellent print storage stability because it combines a specific coloring agent and a sensitizer. A resin layer containing a water-soluble polymer compound as a main component can also be provided on the recording layer. Examples of such water-soluble polymer compounds include:
Polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, hydroxyethyl cellulose,
Examples include methylcellulose, carboxymethylcellulose, starch and its derivatives, casein, sodium alginate, polyvinylpyrrolidone, polyacrylamide, styrene-maleic acid copolymer salt, polyurethane resin, urea resin, and melamine resin. Among these water-soluble polymer compounds,
In particular, acetoacetyl group-modified polyvinyl alcohol is preferably used because it provides a heat-sensitive recording material with particularly excellent printing stability. Incidentally, a pigment may be added to the resin layer as necessary in order to improve printability and staking. Specifically, such pigments include calcium carbonate, zinc oxide, aluminum oxide,
Titanium dioxide, silicon dioxide, talc, kaolin,
Examples include inorganic pigments such as clay, calcined clay, and colloidal silica, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea/formalin resin filler, and raw starch. In addition, the amount used is generally determined by the resin component.
It is desirable that the amount is in the range of 5 to 500 parts by weight per 100 parts by weight. Furthermore, in the coating liquid, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, and surfactants (dispersants, wetting agents, etc.) such as sodium dioctyl sulfosuccinate are added as necessary. ), various auxiliary agents such as antifoaming agents can also be added as appropriate. In the present invention, the coating liquid forming the resin layer is generally prepared as an aqueous coating liquid, and is thoroughly mixed and dispersed using a mixing/stirring machine such as a mixer, attritor, ball mill, or roll mill as necessary. It is applied onto the heat-sensitive recording layer using a known coating device. The amount of the resin layer coating liquid is not particularly limited, but if it is ^less than 0.1 g/m2, the desired effect cannot be obtained sufficiently, and if it exceeds 20 g/ ^m2 , the heat-sensitive recording material will deteriorate. Generally, the dry weight is 0.1 to 20g/ ^m2 , as it may significantly reduce recording sensitivity.
Preferably, it is adjusted within a range of about 0.5 to 10 g/m ² . The thus obtained heat-sensitive recording material of the present invention selectively uses a specific coloring agent and sensitizer, so that it does not cause color fogging and has excellent high-speed recording suitability. It exhibits excellent print storage stability even under harsh conditions. In addition,
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, by providing an undercoat layer on the support,
Various known techniques in the field of heat-sensitive recording material manufacturing may be added as necessary, such as applying an adhesive treatment to the back surface of the recording material and processing it into an adhesive label. "Example" The present invention will be described in more detail with reference to Examples below, but it 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-cyclohexyl-N-methylamino)
-6-methyl-7-phenylaminofluorane
10 parts Methylcellulose 5% aqueous solution 5 parts Water 40 parts This composition was ground to an average particle size of 3 μm using a sand mill. Preparation of Solution B 20 parts of 4-hydroxy-4'-isopropoxydiphenylsulfone 5 parts of 5% aqueous solution of methylcellulose 55 parts of water This composition was ground with a sand mill to an average particle size of 3 μm. Preparation of Solution C 1,2-diphenoxyethane 20 parts Methylcellulose 5% aqueous solution 5 parts Water 55 parts This composition was ground with a sand mill to an average particle size of 3 μm. Formation of Recording Layer 55 parts of liquid A, 80 parts of liquid B, 80 parts of liquid C, 50 parts of a 15% aqueous polyvinyl alcohol solution, and 10 parts of calcium carbonate were mixed and stirred to prepare a coating liquid. 50g/of the obtained coating liquid
A thermosensitive recording paper was obtained by coating and drying the coating onto m ² base paper so that the coating amount after drying was 6 g/m ² . Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 80 parts of liquid C was not used in forming the recording layer. Comparative Example 2 In the preparation of liquid B, 4,
A thermosensitive recording paper was obtained in exactly the same manner as in Example 1 except that 4'-isopropylidene diphenol was used. In order to evaluate the degree of color fog on the three types of heat-sensitive recording papers thus obtained, the whiteness of the recording layer was measured using a Hunter whiteness meter, and the results are shown in Table 1. In addition, thermal recording paper was printed using a thermal printer, and the printed color density was measured using a Macbeth densitometer (manufactured by Macbeth, Model RD-100R).
The results are shown in Table 1. Furthermore, the plasticizer resistance and water resistance of the thermal recording paper after printing were evaluated by the following methods, and the results are also listed in Table 1. [Plasticizer resistance] Vinyl chloride wrap film (manufactured by Mitsui Toatsu Co., Ltd.) is wrapped three times around a polypropylene pipe (40mmφ pipe), and a thermal recording paper with colored print is placed on top of it, with the colored side facing out. Then wrap the vinyl chloride wrap film three times over the scissors.
Plasticizer resistance was evaluated from the print density after being left at room temperature for 12 hours. ○: Good ×: Poor [Water resistance] After printing, the thermal recording paper was left in water for 12 hours, dried, and water resistance was evaluated from the change in print density. ○: Good ×: Poor

[Plasticizer resistance]

Wrap vinyl chloride wrap film (manufactured by Mitsui Toatsu Co., Ltd.) three times around a polypropylene pipe (40mmφ pipe), sandwich thermal recording paper with colored print on it so that the colored side of the print is on the outside, and then Wrap vinyl chloride wrap film three times from above.
Plasticizer resistance was evaluated from the print density after being left at 40°C for 24 hours. ◎: Very good ○: Good △: Slightly poor ×: Poor [Water resistance] After printing, the thermal recording paper was left in water for 24 hours, dried, and the water resistance was evaluated from the change in print density. ◎: Extremely good ○Good △Slightly poor ×: Poor

[Table] "Effect" As is clear from the results in Tables 1 and 2,
The heat-sensitive recording material according to the present invention was a highly sensitive recording material that did not cause color fog and had excellent printing stability.

Claims (1)

[Scope of Claims] 1. In a heat-sensitive recording material provided with a heat-sensitive recording layer containing at least a color former and a color former that develops a color when in contact with the color former, 4-hydroxy-
A heat-sensitive recording material comprising 4'-isopropoxydiphenyl sulfone and at least one compound represented by the following general formula [] as a sensitizer. [In the formula, X represents -O- or -CO-O-,
R ₁ to _{R 6} each represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aralkyl group. Note that the substituents R ₁ to _{R 6} may be bonded to each other to form an aromatic ring. n represents an integer from 1 to 10. 2. The heat-sensitive recording material according to claim 1, which has a resin layer containing a water-soluble polymer compound as a main component on the heat-sensitive recording layer.