JPH06343853A - Microcapsule and heat sensitive recording body using the same - Google Patents

Abstract

PURPOSE:To stably produce microcapsules having a specified average particle diameter and satisfactory particle diameter distribution and to provide a heat sensitive recording body applying the microcapsules and excellent in color developing property, surface stability and preservability, especially light and water resistance. CONSTITUTION:The microcapsules are produced using polyvinyl alcohol modified with acetoacetyl groups and having 92-98mol% degree of saponification as an emulsifier and have 0.1-3mum average particle diameter. The wall films of the microcapsules are made of polyurea or polyurethane/polyurea. The objective heat sensitive recording body has a heat sensitive recording layer and a protective layer successively formed on the substrate and the microcapsules are used in the protective layer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to microcapsules having a sharp particle size distribution and excellent production efficiency, and storage stability, particularly light resistance, using the microcapsules.
The present invention relates to a heat sensitive recording material having excellent water resistance.

[0002]

2. Description of the Related Art Wall membranes made of polyurea or polyurethane /
When preparing microcapsules made of polyurea, polyvinyl alcohol is generally used as an emulsifier, but depending on the type of polyvinyl alcohol, the particle size may be 3
It is difficult to stably obtain microcapsules having a size of μm or less, and there is a problem in water resistance of the obtained microcapsule dispersion. For this reason, the present inventors have found that microcapsule dispersions using an acetoacetyl group-modified polyvinyl alcohol as an emulsifier can easily impart water resistance and are preferably used, but saponification of such acetoacetyl group-modified polyvinyl alcohol is preferable. Regarding the degree, the effect on the obtained microcapsules is not a problem in the preparation of the table scale, but in the case of emulsification on the actual production scale, regardless of the emulsification method, it is conventionally used as a water resistant binder. Degree of saponification 99mo
When 1% or more of the polyvinyl alcohol is used as a raw material for modification, an emulsion having a target average particle size can be obtained in emulsification, but the protective colloid ability of the emulsifier may be insufficient, or the emulsifier may be insufficient during the reaction for forming the wall film. It was found that re-aggregation occurred, and as a result, microcapsules having the target average particle size and particle size distribution could not be obtained. Further, when acetoacetyl group-modified polyvinyl alcohol made from partially saponified polyvinyl alcohol (saponification degree 88 mol%) is used as an emulsifier, foaming due to stirring during emulsification is remarkable,
It became difficult to apply shear during emulsification, and the target average particle size and particle size distribution could not be obtained. Also,
A heat-sensitive recording material is well known in which microcapsules containing various compounds are used and a plurality of color-forming substances are brought into contact with each other by heat to obtain a recorded image. Since such a thermosensitive recording medium is relatively inexpensive, the recording device is compact, and its maintenance is easy, it is used not only as a recording medium for facsimiles and various computers but also in a wide range of fields.

One of the fields of use thereof is, for example, POS.
(Point of sales) Thermal recording labels for systems can be cited, but with the expansion of the systemization, it is attached to products for a long period of time in addition to the conventional food labels that end their mission in a short period of time. There is an increasing use as tag paper used, or as handy terminal paper for collection and delivery, which is often handled outdoors. However, in such applications, it is often exposed to room light or sunlight for a long period of time, which causes the background portion of the thermal recording material to turn yellow, resulting in a marked loss of product image.
Therefore, there is a strong demand for a thermosensitive recording medium that does not cause yellowing of the background portion even after being exposed to room light or sunlight for a long time.

Therefore, for the purpose of preventing yellowing of the background due to light, an inorganic pigment having an ultraviolet shielding effect such as zinc oxide or titanium oxide or a finely pulverized ultraviolet absorber is added to the heat-sensitive recording layer or the protective layer. The method of doing is proposed. However, inorganic pigments having a UV-shielding effect and finely pulverized UV absorbers have poor UV absorption efficiency, so sufficient effects cannot be obtained, and increasing the amount used causes background fog or decreases recording density. Etc. new arises.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above problems and to provide an average particle size of 0.1 to 3 μm.
In order to provide a heat-sensitive recording material having excellent color development, stability of the background portion, storage characteristics, particularly light resistance and water resistance, by producing microcapsules having a good particle size distribution. .

[0006]

Means for Solving the Problems The present inventors have found that an acetoacetyl group-modified polyvinyl alcohol having an saponification degree of 92 to 98 mol% as an emulsifier has an average particle size of 0.1 to 3 μm and a wall A microcapsule having a film made of polyurea or polyurethane / polyurea, and a thermosensitive recording medium in which a thermosensitive recording layer and a protective layer are sequentially provided on a support. The thermosensitive recording medium using the microcapsule in the protective layer provides the above-mentioned object. The inventors have found that the above is achieved and completed the present invention.

[0007]

The saponification degree of the acetoacetyl group-modified polyvinyl alcohol of the present invention means the saponification degree of the raw material to be modified with an acetoacetyl group. The acetoacetyl group-modified polyvinyl alcohol used as an emulsifier for producing the microcapsules of the present invention has a saponification degree of 92 to 9
Although 8 mol% of polyvinyl alcohol is used as a raw material, if the saponification degree exceeds 98%, re-aggregation occurs during the wall film forming reaction, probably due to lack of protective colloid ability of the emulsifier, resulting in the target average particle size. It was found that microcapsules having a size and a particle size distribution could not be obtained. When the degree of saponification is less than 92%, foaming due to stirring during emulsification is remarkable, and it becomes difficult for shearing to occur during emulsification, and the target average particle size and particle size distribution cannot be obtained. The degree of modification of the acetoacetyl group is not particularly limited, but it is preferably 1 to 10 mol%, more preferably 3 to 7 mol%. Also, the degree of polymerization is not particularly limited, and is, for example, 500 to 200.
0, preferably about 800 to 1800 is used. The amount of the emulsifier used is not particularly limited, but it should be in the range of 1 to 50% by weight, more preferably 3 to 30% by weight, based on the total amount of the microcapsule core substance and the wall membrane agent. It is desirable to adjust.

The microcapsules having a wall film made of polyurea resin or polyurethane / polyurea resin as a polymer substance forming the wall film of the microcapsules have excellent heat resistance, and therefore, when used in a thermal recording medium, the microcapsules are applied to a thermal head. It has an excellent accompanying effect that it also functions as an inorganic pigment added for the purpose of preventing sticking of, and has a lower refractive index than microcapsules composed of other wall films and ordinary pigments. In addition, since it has a spherical shape, even if it is mixed in a large amount in the protective layer, there is no fear of causing a reduction in the density of a recorded image (so-called whitening phenomenon) due to diffuse reflection of light, and therefore it is preferably used.

The microcapsules having a wall membrane made of polyurea or polyurethane / polyurea resin are cores for encapsulating a capsule wall membrane material such as a polyvalent isocyanate and a polyol that reacts with the polyisocyanate, or an adduct of the polyvalent isocyanate and the polyol. It is produced by mixing a substance into a substance, emulsifying and dispersing it in an aqueous medium in which a protective colloid substance such as polyvinyl alcohol is dissolved, and raising the liquid temperature to cause a polymer forming reaction at the oil drop interface.

Examples of the polyvalent isocyanate compound include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate,
2,4-tolylene diisocyanate, naphthalene-1,
4-diisocyanate, diphenylmethane-4,4'-
Diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4
-Diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1, Diisocyanates such as 4-diisocyanate, 4,4 ′, 4 ″ -triphenylmethane triisocyanate, triisocyanates such as toluene-2,4,6-triisocyanate, 4,4′-dimethyldiphenylmethane-2,2 ′ , 5,5'-Tetraisocyanate and other tetraisocyanates, addition product of hexamethylene diisocyanate and trimethylolpropane, addition of 2,4-tolylene diisocyanate and trimethylolpropane , An adduct of xylylene diisocyanate and trimethylolpropane, an adduct of triresin isocyanate and hexanetriol, an isocyanate prepolymer such as a trimer of hexamethylene diisocyanate, and the like. It is difficult to handle because it is high, and it is not preferable from the viewpoint of safety.Although oligomers and prepolymers of polyisocyanate compound are not highly reactive, the preparation of microcapsules is relatively easy,
When an aromatic isocyanate compound such as a tolylene diisocyanate derivative or a diphenylmethane diisocyanate derivative is used, the wall film itself tends to yellow due to light exposure, which is not preferable for applications where whiteness is important.

Further, a xylylene diisocyanate derivative having a property between an aromatic isocyanate and an aliphatic isocyanate generally requires a diluting solvent because of its high viscosity, and although it is problematic in terms of environment and disaster prevention, it is exposed to light. Since the wall film itself hardly yellows, it is preferably used as the wall film agent of the present invention. Furthermore, the aliphatic isocyanate derivative in which the wall film itself does not yellow due to light exposure deteriorates in compatibility with the ultraviolet absorber as its viscosity sounds high, and therefore, sufficient wall film strength of the microcapsule cannot be obtained. Problems such as precipitation of the ultraviolet absorber contained in the microcapsules occur. Therefore, as the aliphatic isocyanate derivative preferably used in the present invention,
It is a hexamethylene diisocyanate derivative having a viscosity at 25 ° C. measured by a B type viscometer of 1000 cps or less.

The hexamethylene diisocyanate derivative having a viscosity at 25 ° C. of 1000 cps or less, which is preferably used in the present invention, is, for example, isocyanurate type hexamethylene diisocyanate (hexamethylene diisocyanate trimer) or hexamethylene diisocyanate trimer. And a mixture of pentamers and pentamers, and burette type hexamethylene diisocyanate (trimer) are exemplified, and isocyanurate type hexamethylene diisocyanate is particularly preferable because the obtained microcapsules have excellent durability. Furthermore, in order to more positively improve the compatibility with the ultraviolet absorber, it is more preferable to use a reaction product of an isocyanurate compound and a monoalcohol as a wall film agent. Further, an aromatic isocyanate derivative may be used in combination within a range that does not impair the effects of the present invention.

Examples of the polyol compound used in combination with the above microcapsule wall film agent include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol. 1,7-heptanediol, 1,8-octanediol, propylene glycol, 2,3-dihydroxybutane, 1,2-dihydroxybutane, 1,3-dihydroxybutane, 2,2-dimethyl-1,3-propan Non-diol, 2,4-pentanediol, 2,5-hexanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, dihydroxycyclohexane, diethylene glycol, 1,2,6
-Trihydroxyhexane, phenylethylene glycol, 1,1,1-trimethylolpropane, hexanetriol, pentaerythritol, aliphatic polyols such as glycerin, 1,4-di (2-hydroxyethoxy)
Condensation products of aromatic polyhydric alcohols such as benzene and 1,3-di (2-hydroxyethoxy) benzene with alkylene oxides, p-xylylene glycol, m-xylylene glycol, α, α′-dihydroxy-p. -Diisopropylbenzene, 4,4'-dihydroxydiphenylmethane, 2- (p, p'-dihydroxydiphenylmethyl) benzyl alcohol, 4,4'-isopropylidenediphenol, 4,4'-dihydroxydiphenylsulfone, 4,4 ' -Dihydroxydiphenyl sulfide, ethylene oxide adduct of 4,4'-isopropylidene diphenol, propylene oxide adduct of 4,4'-isopropylidene diphenol and the like.

Of course, the polyisocyanate compound and the polyol compound are not limited to the above compounds, and two or more kinds may be used in combination, if necessary. Incidentally, the polyvalent isocyanate compound used in the present invention, or an adduct of a polyvalent isocyanate compound and a polyol compound, or even a reaction product of a polyvalent isocyanate compound and a polyol compound, three isocyanate groups in the molecule Those having the above are particularly preferable. In the present invention, the use ratio of the wall film agent of the microcapsule and the core substance is not particularly limited, but generally, the wall film agent is 1 to 1000 parts by weight relative to 100 parts by weight of the core substance.
It is desirable to use in an amount of about 5 parts by weight, preferably about 5 to 500 parts by weight.

As the ultraviolet absorber used in the present invention,
Although various known ones can be used, among them, a benzotriazole-based UV absorber is preferable in terms of UV absorption efficiency, and a liquid that is liquid at room temperature is particularly suitable for UV absorption when synthesizing oil-in-water type microcapsules. Since it is not necessary to dissolve the agent in an organic solvent, it can be contained in the microcapsule at a high concentration, and the ultraviolet absorbing ability is remarkably improved, so that it is more preferably used. Specific examples of the benzotriazole-based ultraviolet absorber that is liquid at room temperature include the following. 2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole, 2-
[2'-hydroxy-4 '-(2 "-ethylhexyl)
Oxyphenyl] benzotriazole, methyl-3-
[3-tert-Butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] propionate-condensate with polyethylene glycol (molecular weight about 300), 5-tert-butyl-3- (5- Chloro-2H-benzotriazol-2-yl) -4-hydroxybenzene-octyl propionate, 2- (2'-hydroxy-
3'-sec-butyl-5'-tert-butylphenyl)
-5-tert-butylbenzotriazole and the like.

The benzotriazole which is solid at room temperature includes 2- (2'-hydroxyphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole and 2- (2'-hydroxy). −
5'-tert-butylphenyl) benzotriazole, 2
-(2'-Hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5
-Chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-
3 ', 5'-di-tert-amylphenyl) benzotriazole, 2- (2'-hydroxy-3', 5'-di-te
rt-Butylphenyl) -5-tert-butylbenzotriazole, 2- (2'-hydroxy-3'-sec-butyl-5'-tert-butylphenyl) -5-tert-butylbenzotriazole, 2- (2 '-Hydroxy-3',
5'-di-tert-amylphenyl) -5-tert-amylbenzotriazole, 2- [2'-hydroxy-3'-
(3 ", 4", 5 ", 6" -tetrahydrophthalimido-methyl) -5'-methylphenyl] benzotriazole, 2- (2'-hydroxy-5'-tert-octylphenyl) benzotriazole, and the like. To be Other UV absorbers include phenyl salicylate, p-
Salicylic acid type ultraviolet absorbers such as tert-butylphenyl salicylate and p-octylphenyl salicylate, 2,
4-dihydroxybenzophenone, 2-hydroxy-4
-Methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-
Benzophenone-based UV absorbers such as 4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone and 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2-ethylhexyl-2-
Cyano-3,3'-diphenyl acrylate, ethyl-
Cyanoacrylate-based UV absorbers such as 2-cyano-3,3'-diphenylacrylate, bis (2,2,6,
6-Tetramethyl-4-piperidyl) sebacate, succinic acid-bis (2,2,6,6-tetramethyl-4-piperidyl) ester, 2- (3,5-di-tert-butyl)
Malonic acid-bis (1,2,2,6,6-pentamethyl-
Examples thereof include hindered amine UV absorbers such as 4-piperidyl) ester. Of course, it is not limited to these, and it is also possible to use two or more kinds in combination if necessary.

When a microcapsule filler containing an ultraviolet absorber is used in the protective layer of the thermal recording medium, the amount of the ultraviolet absorber used is 0.1 to 3.0 g / in the protective layer.
m ² is preferably present, more preferably 0.2 to
It is in the range of 2.0 g / m ² . If the amount of the ultraviolet absorber in the protective layer is less than 0.1 g / m ² , the effect of preventing yellowing of the background portion of the thermosensitive recording material is deteriorated. Also, 3.0 g / m
^{Since the} protective layer is inevitably thicker than ² , the recording sensitivity is lowered. Further, when the amount of the ultraviolet absorber is less than 10% by weight based on the total amount of the ultraviolet absorber, the microcapsule wall film material and the organic solvent which can be used together as necessary, the effect of preventing yellowing of the background portion of the thermosensitive recording medium is obtained. In order to exert the effect, the coating amount of the microcapsules must be increased, so that the protective layer inevitably becomes thick and the recording sensitivity is lowered.

The microcapsule used in the present invention has a molecular weight of 300 to 5,000, preferably 500 to 20.
It is also possible to include a medium molecular polymer of 00. Specific examples of such a medium-molecular polymer include the following, but are not limited to these, and two or more kinds may be used in combination as required. Low molecular weight polyethylenes; low molecular weight polypropylenes; liquid polybutenes; liquid polybutadienes [1,2-bond type, 1,4-bond type (including cis type, trans type) and their mixtures or in the same main chain Those having both 1,2-bonds and 1,4-bonds, those having hydroxyl groups or carboxyl groups introduced at their ends, those having isocyanate groups or maleic anhydride introduced, epoxy-modified types, hydrogenated types, etc. Including]; Liquid rubbers (liquid BR, liquid SBR, liquid NBR, liquid polychloroprene, liquid polysulfide, liquid polyisoprene, liquid polyisobutylene, liquid butyl rubber, etc.); Petroleum resins (C ₅ petroleum resin, C ₉ petroleum) resins, C ₅ and C ₉ copolymer petroleum resin, etc.); cyclopentadiene-based petroleum resins; low molecular weight polystyrene; polyhydroxy Po Olefin; thermosetting resin prepolymer; alpha-methylstyrene oligomer. Among these, liquid polybutenes and liquid polybutadienes are preferable, and liquid polybutadiene is more preferable.

The microcapsules used in the present invention may optionally contain an organic solvent.
The organic solvent is not particularly limited and can be appropriately selected and used from various high-boiling point hydrophobic media used in the field of pressure-sensitive copying paper, and specific examples include tricresyl phosphate and phosphorus. Phosphates such as octyl diphenyl acid, dibutyl phthalate, phthalates such as dioctyl phthalate, carboxylic esters such as butyl oleate, various fatty acid amides, diethylene glycol dibenzoate, monoisopropyl naphthalene, diisopropyl naphthalene, etc. Alkylated naphthalenes, 1-methyl-1-phenyl-1-tolylmethane, 1-methyl-1-phenyl-1-xylylmethane,
Alkylated benzenes such as 1-phenyl-1-tolylmethane, alkylated biphenyls such as isopropyl biphenyl, xenoxyalkanes such as o-phenylphenol glycidyl ether, acrylic acid esters such as trimethylolpropane triacrylate, polyvalent Ester of alcohol and unsaturated carboxylic acid, chlorinated paraffin,
And kerosene. Of course, these may be used in combination of two or more kinds. Also, in general, capsule wall membrane material,
The lower the viscosity of the mixture of the ultraviolet absorber and the organic solvent used as necessary, the smaller the particle size after emulsification, and the sharper the particle size distribution, so that the viscosity of the mixture may be reduced if necessary. A low boiling point solvent may be used in combination. Specific examples of such a low boiling point solvent include ethyl acetate, butyl acetate, methylene chloride and the like.

In the microcapsules used in the present invention, an antioxidant, an oil-soluble fluorescent dye, a release agent and the like can be added, if necessary, in addition to the ultraviolet absorber. Further, at the time of microencapsulation, a tin compound, a polyamide compound, an epoxy compound, a polyamine compound or the like can be used together as a reaction accelerator. When a polyamine compound is used, it is desirable to use an aliphatic polyamine compound from the viewpoint of light resistance.

The average particle diameter of the microcapsules used in the present invention is 0.1 to 3 μm, and preferably 0.1 to 3 μm, in consideration of the absorption efficiency of ultraviolet rays, the coating property of the coating liquid, the image quality of the recorded image and the like.
It is desirable to adjust the thickness in the range of about 3 to 2.5 μm.

The heat-sensitive recording system to which the present invention is applied includes, for example, a combination of a basic dye and a color former, a combination of a diazonium salt and a coupler, a combination of a chelate compound of a transition element such as iron and a color former, Examples include a combination of an aromatic isocyanate compound and an imino compound, but a combination of a basic dye and a colorant has a high color density, and is excellent in preservability of a background portion and a recorded image, and thus is preferably used. To be As the basic dye, various known colorless or pale basic dyes can be used, and examples thereof include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide and 3- (4-diethylamino-2). -Methylphenyl) -3- (4-dimethylaminophenyl) -6-dimethylaminophthalide, 3-
Diethylamino-7-dibenzylamino-benzo [a]
Blue coloring dye such as fluoran, 3- (N-ethyl-N-)
p-tolyl) amino-7-N-methylanilinofluorane, 3-diethylamino-7-anilinofluorane, 3
-Green-coloring dyes such as diethylamino-7-dibenzylaminofluorane, 3,6-bis (diethylamino) fluorane-γ-anilinolactam, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6
-Methyl-7-chlorofluorane, 3-diethylamino-7-chlorofluorane, rhodamine (o-chloroanilino) lactam, rhodamine (p-chloroanilino) lactam, 3-diethylamino-7,8-benzofluorane, 3- ( Red-coloring dyes such as N-ethyl-p-toluidino) -7-methylfluorane and 3-diethylamino-6,8-dimethylfluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl- 7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-
6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di (n-butyl) amino-6-methyl-7-anilinofluorane, 3-di (N-pentyl) amino-6-methyl-
7-anilinofluorane, 3-diethylamino-7-
(O-chlorophenylamino) fluorane, 3-di (n
-Butyl) amino-7- (o-chlorophenylamino)
Fluorane, 3-diethylamino-7- (o-fluorophenylamino) fluorane, 3-di (n-butyl) amino-7- (o-fluorophenylamino) fluorane, 3- (N-ethyl-p-toluidino)- 6-methyl-7-anilinofluorane, 3- (N-ethyl-p-toluidino) -6-methyl-7- (p-toluidino) fluorane, 3- (N-ethyl-N-tetrahydrofurfurylamino) -6-Methyl-7-anilinofluorane, 3
-Diethylamino-6-chloro-7-anilinofluorane, 3- (N-methyl-Nn-propylamino) -6
-Methyl-7-anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-m-toluidinofluorane, 3- (N- n-hexyl-N-ethyl) amino-6
-Methyl-7-anilinofluorane, 3- (N-ethyl-N-isobutyl) amino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-p
-Ethoxyanilinofluorane, 3-pyrrolidino-6-
Methyl-7-anilinofluorane, 3-piperidino-6
-Methyl-7-anilinofluorane, 2,2-bis {4
-[6 '-(N-cyclohexyl-N-methylamino)
3'-methylspiro [phthalide-3,9'-xanthen-2'-ylamino] phenyl} propane, 3-diethylamino-7- (3'-trifluoromethylphenyl) aminofluorane, etc. , 3-Bis [1- (4-methoxyphenyl) -1- (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6
7-Tetrachlorophthalide, 3,3-bis [1- (4-
Methoxyphenyl) -1- (4-pyrrolidinophenyl)
Ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6 , 7-
Tetrabromophthalide, 3-p- (p-dimethylaminoanilino) anilino-6-methyl-7-chlorofluorane, 3-p- (p-chloroanilino) anilino-6-methyl-7-chlorofluorane, Examples thereof include dyes having an absorption wavelength in the near infrared region, such as 3,6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide. Of course, it is not limited to these, and two or more kinds may be used in combination as required.

Various materials are known as a colorant used in combination with the basic dye as described above. For example, activated clay, attapulgite, colloidal silica, inorganic acidic substances such as aluminum silicate, 4,4'- Isopropylidene diphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4,4'-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, 4 -Benzyl hydroxybenzoate, 4,
4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4 '
-Isopropoxydiphenyl sulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenyl sulfone, 4-hydroxyphenyl-4'-benzyloxyphenyl sulfone,
3,4-dihydroxyphenyl-4'-methylphenyl sulfone, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, bis (p-hydroxyphenyl) Butyl acetate, methyl bis (p-hydroxyphenyl) acetate, 1,1-bis (4-hydroxyphenyl)-
1-phenylethane, 1,4-bis [α-methyl-α-
(4'-hydroxyphenyl) ethyl] benzene, 1,
3-bis [α-methyl-α- (4′-hydroxyphenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, 2,2′-thiobis (3-te
rt-octylphenol), 2,2'-thiobis (4-
tert-octylphenol) and other phenolic compounds,
Thiourea compounds such as N, N'-di-m-chlorophenylthiourea, p-chlorobenzoic acid, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4-
Aromatic carboxylic acids such as [3- (p-tolylsulfonyl) propyloxy] salicylic acid and 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid, and zinc, magnesium and aluminum of these aromatic carboxylic acids. , Salts with polyvalent metals such as calcium, titanium, manganese, tin and nickel, as well as organic acid substances such as antipyrine complexes of zinc thiocyanate and complex zinc salts of terephthalaldehyde acid with other aromatic carboxylic acids. It is illustrated. In particular, when 1,1-bis (4-hydroxyphenyl) cyclohexane, 4-hydroxy-4′-isopropoxydiphenylsulfone or bis (3-allyl-4-hydroxyphenyl) sulfone is used, the recorded image is generally preserved. It is preferably used because it has excellent properties.
The use ratio of the basic dye and the colorant is appropriately selected according to the type of the basic dye or the colorant used, and is not particularly limited, but generally 1 part by weight of the basic dye is used. On the other hand, about 1 to 50 parts by weight, preferably about 2 to 10 parts by weight, of the coloring agent is used.

A coating material for a heat-sensitive recording layer containing these substances is
Generally, water is used as a dispersion medium, and a ball mill, attritor,
It is prepared by dispersing the dye and the coloring agent together or separately by a stirring and crushing machine such as a sand mill. In the coating liquid, as a binder, starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, silicon modified polyvinyl alcohol, diisobutylene. Maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, urea resin, melamine resin, At least one kind of amide resin, polyurethane resin and the like is blended in the range of about 5 to 30% by weight based on the total solid content of the recording layer.

If desired, various auxiliary agents may be added to the coating liquid. For example, dispersants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts. , Zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, and other waxes,
An antifoaming agent, a coloring dye, etc. are added as appropriate. It is also possible to use various pigments in combination in the coating liquid, for example, kaolin, clay, calcium carbonate, calcined clay, calcined kaolin, titanium oxide, diatomaceous earth, fine anhydrous silica, inorganic clay such as activated clay and styrene. Examples thereof include microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and organic pigments such as raw starch particles.

Further, a sensitizer may be used in combination depending on the purpose. Specific examples of the sensitizer include stearic acid amide, methoxycarbonyl-N-stearic acid benzamide, N-benzoylstearic acid amide, N-eicosanoic acid amide, ethylenebisstearic acid amide, behenic acid amide, and methylenebisstearic acid amide. , N-
Methylol stearamide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate,
Benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthylbenzyl ether, m-terphenyl, dibenzyl oxalate, oxalate-di-p-methylbenzyl, oxalate-di-p- Chlorobenzyl, p-benzylbiphenyl, p-tolylbiphenyl ether, di (p-methoxyphenoxyethyl)
Ether, 1,2-di (3-methylphenoxy) ethane, 1,2-di (4-methylphenoxy) ethane, 1,
2-di (4-methoxyphenoxy) ethane, 1,2-di (4-chlorophenoxy) ethane, 1,2-diphenoxyethane, 1- (4-methoxyphenoxy) -2- (3
-Methylphenoxy) ethane, p-methylthiophenylbenzyl ether, 1,4-di (phenylthio) butane, p-acetotoluidide, p-acetophenetizide,
Examples include N-acetoacetyl-p-toluidine, di (β-biphenylethoxy) benzene, p-di (vinyloxyethoxy) benzene, 1-isopropylphenyl-2-phenylethane and the like. The amount of these sensitizers used is not particularly limited, but it is generally desirable to adjust the amount within the range of about 4 parts by weight or less relative to 1 part by weight of the color developing agent.

In the present invention, it is possible to add a storability improver in the heat-sensitive recording layer. Examples of such storability improvers include the following. 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,
2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-ethylidenebis (4,6-di-)
tert-butylphenol), 4,4'-thiobis (2-
Methyl-6-tert-butylphenol), 4,4′-butylidenebis (6-tert-butyl-m-cresol),
1- [α-methyl-α- (4'-hydroxyphenyl)
Ethyl] -4- [α ', α'-bis (4 "-hydroxyphenyl) ethyl] benzene, 1,1,3-tris (2
-Methyl-4-hydroxy-5-cyclohexylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,
4'-thiobis (3-methylphenol), 4,4'-
Dihydroxy-3,3 ', 5,5'-tetrabromodiphenyl sulfone, 4,4'-dihydroxy-3,3',
5,5'-tetramethyldiphenyl sulfone, 2,2-
Bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) Hindered phenol compounds such as propane, 1,4-diglycidyloxybenzene, 4,4'-diglycidyloxydiphenyl sulfone, 4-benzyloxy-4 '-(2-methylglycidyloxy) diphenyl sulfone, diglycidyl terephthalate, Epoxy compounds such as cresol novolac type epoxy resin, phenol novolac type epoxy resin, bisphenol A type epoxy resin, N, N'-di-2-naphthyl-p-phenylenediamine, 2,2'-methylenebis (4,6-di) -Tert-butylphenyl) phosphate sodium or Examples thereof include polyvalent metal salts and bis (4-ethyleneiminocarbonylaminophenyl) methane. Among them, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane is preferably used because it has an excellent effect on water resistance and does not easily cause background fog.

In the thermosensitive recording medium of the present invention, by providing a protective layer on the thermosensitive recording layer, the storability of a recorded image against a chemical such as a plasticizer is improved, and the protective layer is water-soluble or water-dispersible. It is also possible to add a binder made of a polymer compound. Specific examples of the binder include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxy modified polyvinyl alcohol, acetoacetyl group modified polyvinyl alcohol, silicon modified polyvinyl alcohol, and diisobutylene / anhydrous. Maleic acid copolymer salt, styrene
Maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt, styrene / acrylic acid copolymer salt, styrene /
Examples thereof include butadiene copolymer emulsion, urea resin, melamine resin, amide resin, polyurethane resin, etc. Among them, acetoacetyl group-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, and silicon-modified polyvinyl alcohol must form a strong film. It is particularly preferably used because it can be produced.

If desired, a pigment may be added to the protective layer in order to improve printability and sticking. Specific examples thereof include calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc,
Examples thereof include inorganic pigments such as kaolin, clay, calcined kaolin and colloidal silica, organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea / formalin resin filler, and raw starch particles.

The method for preparing the coating liquid for forming the protective layer is not particularly limited. Generally, water is used as a dispersion medium, and when microcapsules are added, microcapsules,
It is prepared by mixing an emulsifier, a binder, and a pigment added as necessary. Further, in the protective layer coating liquid, zinc stearate, calcium stearate, if necessary,
Lubricants such as polyethylene wax, carnauba wax, paraffin wax, ester wax, etc., surfactants such as sodium dioctylsulfosuccinate (dispersant, wetting agent),
Various anti-foaming agents and various auxiliaries such as water-soluble polyvalent metal salts such as potassium alum and aluminum acetate may be appropriately added.
In addition, glyoxal to further improve water resistance,
A curing agent such as boric acid, dialdehyde starch, or an epoxy compound can be used together.

The method for forming the heat-sensitive recording layer and the protective layer is not particularly limited, and suitable examples include air knife coating, varibar blade coating, pure blade coating, rod blade coating, short dwell coating, curtain coating and die coating. The coating liquid for recording layer is applied and dried on the support by the coating method, and then the coating liquid for protective layer is applied and dried on the recording layer. The support may be appropriately selected from paper, plastic film, synthetic paper, non-woven fabric, metal deposit, etc., and used.
The coating amount of the recording layer coating liquid is 2 to 12 g / dry weight.
m ² , preferably about 3 to 10 g / m ² , and the coating amount of the protective layer coating solution is adjusted to a dry weight of 0.1 to 20 g / m ² , preferably about 0.5 to 10 g / m ^2. It

If necessary, the microcapsules of the present invention can be added to a protective layer provided on the back side of the thermosensitive recording medium or an intermediate layer provided between the support and the thermosensitive recording layer, if necessary. . In addition, after applying each layer, smoothing treatment such as super calendering is applied, or the back surface of the recording material is treated with an adhesive to form an adhesive label, and a magnetic recording layer, a coating layer for printing, and a thermal transfer recording layer are formed. Various known techniques in the field of thermal recording material production, such as provision, can be added as necessary.

In the heat-sensitive recording material of the present invention, smoothing treatment after formation of the heat-sensitive recording layer or protective layer improves the color developing sensitivity and image quality of the recorded image, and the Beck (Bek) after the smoothing treatment is increased.
k) It is desirable that the smoothness (according to JIS P 8119) is 300 seconds or longer, preferably 500 seconds or longer.
As a smoothing device used at that time, a super calender or a gloss calender in which an elastic roll and a metal roll are combined is used.
It is preferable to use an elastic roll having a Shore D hardness defined by -2240 of 60 to 90 °, preferably 70 to 90 °. The nip linear pressure during the treatment should be appropriately selected according to the hardness of the elastic roll to be used and the desired smoothness, but it is preferably adjusted in the range of 30 to 300 kg / cm 2.

Examples of the material constituting the elastic layer of the elastic roll include natural rubber, styrene rubber, nitrile rubber, chloroprene rubber, chlorosulfonated ethylene rubber, butyl rubber, polysulfide rubber, silicone rubber, fluororubber, urethane rubber. Rubbers such as, various plastic resins,
Examples include cotton, paper, wool, tetron, nylon, or a mixture thereof. On the other hand, as the metal roll, a chilled roll, an alloy chilled roll, a steel roll, or a metal roll having a hard chrome plated surface is used. .

[0035]

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. In addition, unless otherwise indicated, the part and% in an example show a weight part and weight%, respectively.

Example 1 Preparation of Liquid A A heating device and a chores stirrer (model: J-25X, Mo
A tank with a bottom diameter of 800 mm equipped with a high share impeller (made by rehouse Industries, diameter 240 mm) has a polymerization degree of 1000 and a saponification degree of 96 mo.
Acetoacetyl group-modified polyvinyl alcohol using 1% polyvinyl alcohol as a raw material (modification degree 4.5 m
(120% of a 12.5% aqueous solution) was used as an aqueous medium for capsule production. Separately, 2- (2'-hydroxy-3'-dodecyl-5'-methylphenyl) benzotriazole (42 kg) and a hexamethylene diisocyanate derivative whose main component is a trimer of isocyanurate type hexamethylene diisocyanate (trade name: Takenate D −
170 HN, Takeda Yakuhin Kogyo Co., Ltd.) (18 kg) was heated to 40 ° C. and mixed and stirred to obtain a solution, which was then dispersed in the capsule-forming aqueous medium while cooling at 2400 rpm for 20 minutes using a Choles stirrer. The average particle size of the dispersion was 1.5 μm. Then, water 10
0 kg was added, and the mixture was reacted with stirring at 90 ° C. for 5 hours to prepare a microcapsule dispersion liquid having a wall film made of polyurea polyurethane resin. The average particle size of the dispersion after the reaction was 1.5 μm.

Preparation of Solution B A composition consisting of 10 parts of 3-diethylamino-7- (3′-trifluoromethylphenyl) aminofluorane, 5 parts of a 5% aqueous solution of methylcellulose and 40 parts of water and having an average particle size of 1 by a sand mill is used. It was pulverized to a size of 0.5 μm.

Preparation of Solution C A composition comprising 30 parts of 1,1-bis (4-hydroxyphenyl) cyclohexane, 5 parts of a 5% aqueous solution of methylcellulose, and 80 parts of water was sand-milled until the average particle size became 1.5 μm. Crushed.

Preparation of Liquid D A composition consisting of 20 parts of 1,2-di (3-methylphenoxy) ethane, 5 parts of a 5% aqueous solution of methylcellulose, and 55 parts of water was pulverized with a sand mill until the average particle diameter became 1.5 μm. did.

Formation of Recording Layer 55 parts of solution B, 115 parts of solution C, 80 parts of solution D, 80 parts of 10% aqueous solution of polyvinyl alcohol, and calcium carbonate 3
The coating liquid obtained by mixing and stirring 5 parts was applied and dried on one surface of a high-quality paper of 60 g / m ² so that the coating amount after drying was 6 g / m ² to form a heat-sensitive recording layer.

Formation of protective layer 220 parts of solution A, acetoacetyl group-modified polyvinyl alcohol (polymerization degree: 1000, saponification degree of raw material PVA: 99 mol)
% Or more) 10% aqueous solution 150 parts, kaolin [trade name:
UW-90, manufactured by EMC] 15 parts, a composition comprising 6 parts of a 30% dispersion of zinc stearate and 30 parts of water was mixed and stirred to obtain a coating liquid for a protective layer, which was dried on the recording layer. Was coated and dried to a coating amount of 6 g / m ^2, and then supercalendered to obtain a heat-sensitive recording material.

Example 2 In the preparation of solution A of Example 1, as the aqueous medium for producing capsules, the raw material PVA had a saponification degree of 94 mol% and a polymerization degree of 10.
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 120 kg of a 12.5% aqueous solution of acetoacetyl group-modified polyvinyl alcohol having a modification degree of 4.5 mol% was used.
The average particle size of the dispersion after emulsification and after the reaction was both 1.5 μm.

Comparative Example 1 In the preparation of solution A in Example 1, 12.5 of acetoacetyl group-modified polyvinyl alcohol having a saponification degree of the raw material PVA as the aqueous medium for capsule production of 99 mol% or more, a polymerization degree of 1000, and a modification degree of 5 mol% was used. % Aqueous solution was used to obtain a thermosensitive recording medium in the same manner as in Example 1.
The average particle size of the dispersion after emulsification and dispersion was 1.5 μm, but after the reaction, two peaks of 1.5 μm and 5.7 μm appeared and the average particle size was 4.5 μm. Also, during the super calender treatment, the surface of the chilled roll with which the protective layer surface was in contact was found to be contaminated due to the destruction of the microcapsules.

Comparative Example 2 In the preparation of solution A of Example 1, as the aqueous medium for capsule production, the raw material PVA had a saponification degree of 88 mol% and a polymerization degree of 10
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 120 kg of a 12.5% aqueous solution of acetoacetyl group-modified polyvinyl alcohol having a modification degree of 4.5 mol% was used.
The average particle diameter of the dispersion liquid after emulsification and dispersion for 20 minutes was 4.0 μm, and the average particle diameter of the dispersion liquid after emulsification and dispersion for 40 minutes was 3.8 μm. The average particle size of the dispersion after the reaction was 4.0 μm. Also,
During the super calendering process, the surface of the chilled roll contacting the protective layer surface was contaminated due to the destruction of the microcapsules.

The following evaluation tests were carried out on the four kinds of heat-sensitive recording materials thus obtained, and the results are shown in Table 1. [Evaluation] [Coloring property] A thermosensitive evaluation machine [trade name: TH-PMD, manufactured by Okura Electric Co., Ltd.] was used to color each thermosensitive recording medium at an applied energy of 0.45 mJ / dot, and the color density of the recorded image obtained. Was measured in a visual mode with a Macbeth densitometer [RD-914 type, manufactured by Macbeth Co.].

[Light Resistance] The initial density of the background portion of the thermal recording material after recording as described above and the density of the background portion after exposure to direct sunlight for 10 days were measured with a Macbeth densitometer (using a blue filter).

[Plasticizer resistance] A wrap film [trade name: KMA-W, manufactured by Mitsui Toatsu Chemicals, Inc.] was wound around a polycarbonate pipe (40 mmφ pipe) in three layers, and recorded by the above method. A thermosensitive recording medium was placed, and a wrap film was further wound around it in three layers, and the color density after standing at 40 ° C. for 24 hours was measured with a Macbeth densitometer (visual mode) to evaluate the plasticizer resistance. .

[High Temperature and High Humidity Resistance] The color density and background density of the thermosensitive recording material after recording as described above after being left at 50 ° C. and 75% RH for 24 hours are measured by a Macbeth densitometer (visual mode). Then, the high temperature and high humidity resistance was evaluated.

[Solvent Resistance] The surface of the recording paper was wiped with gauze soaked with ethanol, and the fog density was measured with a Macbeth densitometer (visual mode) to evaluate the solvent resistance.

[0050]

[Table 1]

[0051]

The average particle diameter of the microcapsule dispersion,
As is clear from the state of soiling of chilled rolls in the super calender treatment and the results in [Table 1], the average particle size of the microcapsules of the present invention was controlled to the target value even during production on a production scale. Further, the heat-sensitive recording material using the microcapsules did not cause any trouble even by smoothing treatment with a super calendar, and was excellent in color developability, light resistance on the background portion, and other storage characteristics.

Claims (5)

[Claims] 1. An emulsifier having a saponification degree of 92 to 98 mol.
% Of acetoacetyl group-modified polyvinyl alcohol having an average particle size of 0.1 to 3 μm and a wall film made of polyurea or polyurethane / polyurea. 2. A heat-sensitive recording material in which a heat-sensitive recording layer and a protective layer are sequentially provided on a support, wherein acetoacetyl group-modified polyvinyl alcohol having a saponification degree of 92 to 98 mol% is used as an emulsifier in the protective layer. A heat-sensitive recording material characterized in that the prepared average particle diameter is 0.1 to 3 μm, and the wall film contains microcapsules composed of polyurea or polyurethane / polyurea. 3. The thermosensitive recording medium according to claim 2, wherein the microcapsules contain an ultraviolet absorber. 4. The heat-sensitive recording material according to claim 3, wherein the ultraviolet absorber is benzotriazole which is liquid at room temperature. 5. The heat-sensitive recording material according to claim 2, wherein the heat-sensitive recording layer utilizes a coloring reaction between a colorless or light-colored basic dye and a coloring agent.