JPH10251591A - Aqueous resin dispersion for thermosensitive recording material, production of the dispersion and thermosensitive recording material by using the dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject dispersion capable of forming a high performance coloring layer or protecting layer, and further providing a thermosensitive recording material excellent in light resistance, etc., by using an emulsion polymerization product comprising a polymerizable monomer containing a ultraviolet-absorbing group, and a (meth)acrylic ester-based monomer introduced therein. SOLUTION: The objective dispersion contains a copolymer obtained by carrying out an emulsion polymerization of monomers consisting essentially of (A) a polymerizable monomer containing a ultraviolet-absorbing group [preferably, 2-(2'- hydroxy-5'-methacryloyloxyethylphenyl)-2H-benzotriazol] and (B) a (meth)acrylic ester- based monomer [e.g. methyl (meth)acrylate]. A modified or unmodified polyvinyl alcohol having 550-2400 degree of polymerization of 20-200wt.% based on the total amount of components A and B is preferably used as the emulsifier when producing the objective dispersion. The emulsion polymerization is preferably carried out by a two step polymerization comprising the foregoing step for polymerizing a polymerizable polyfunctional monomer and the component A, and the latter step for polymerizing monomer components containing the component B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin dispersion for a heat-sensitive recording material and to a heat-sensitive recording material using the same which is excellent in light resistance.

[0002]

2. Description of the Related Art Thermosensitive recording materials having a dye-based thermosensitive coloring layer formed of a combination of a leuco dye and a phenolic acid substance are known as facsimile, medical output, POS system,
Widely used for output paper of various thermal printers such as handy terminals, ticketing systems, measuring instruments, etc.

Under such a background, various proposals have been made for a binder resin for a heat-sensitive coloring layer, a resin for forming a protective layer, and the like. For example, the applicant of the present application has proposed a method of performing two-stage polymerization using a specific emulsifier. A heat-sensitive recording material using an aqueous resin containing crosslinked fine particles obtained as described above as a binder resin or a resin for a protective layer has already been disclosed (Japanese Patent Laid-Open No. 6-2).
27124). This heat-sensitive recording material is excellent in ground color development, water resistance, sticking resistance, print color development, plasticizer migration resistance, and the like.

[0004] The above-described heat-sensitive recording material is susceptible to ultraviolet rays, and has a problem that, when exposed to a fluorescent lamp or sunlight for a long time, a background color (yellowing, etc.) is caused or a color-developed part is discolored. For this reason, attempts have been made to improve the light resistance by blending an ultraviolet absorber in the thermosensitive coloring layer or the protective layer. However, the mere addition of a low-molecular ultraviolet absorber is insufficient in the effect of improving light resistance, and when used in a large amount in order to obtain a satisfactory effect, other properties as a heat-sensitive recording material are inferior. Therefore, instead of blending a low-molecular ultraviolet absorber, a proposal has been made to add a UV-absorbing substituent to the resin for a heat-sensitive recording material and to impart UV-absorbing properties to the resin (for example, JP-A-7-179046 and Japanese Unexamined Patent Publication (Kokai) No. 7-156548) and a proposal of using an ultraviolet-absorbing polymer as a resin for a coloring layer and a protective layer of a heat-sensitive recording material (Japanese Patent Application Laid-Open No. 7-137453) have been made. Ground color development that is important as a material,
At present, no heat-sensitive recording material has been obtained that satisfies all of the properties such as water resistance, sticking resistance, printing color development property, and plasticizer migration resistance.

[0005]

SUMMARY OF THE INVENTION The present invention has found an aqueous resin dispersion for a heat-sensitive recording material capable of providing a high-performance color-forming layer or a protective layer, and uses the dispersion to obtain ground color-forming properties, water resistance and water resistance. An object of the present invention is to provide a thermosensitive recording material having good properties such as sticking property, printing color development property, and migration property of a plasticizer, and exhibiting excellent light resistance.

[0006]

According to the present invention, an aqueous resin dispersion for a heat-sensitive recording material comprises a polymerizable monomer having an ultraviolet absorbing group and a (meth) acrylate monomer as essential components. The gist lies in having a copolymer obtained by emulsion polymerization of a monomer component. By introducing a polymerizable monomer having an ultraviolet absorbing group and a (meth) acrylate monomer into an emulsion polymer, a heat-sensitive recording material having excellent light resistance can be provided.

The ultraviolet-absorbing group-containing polymerizable monomer is a benzotriazole group-containing polymerizable monomer,
-(2'-Hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole is preferred.

An emulsion polymer is obtained by polymerizing a polymerizable monomer component A containing a polymerizable polyfunctional monomer and a polymerizable monomer having an ultraviolet absorbing group as essential monomers at a stage prior to the emulsion polymerization reaction. A heat-sensitive recording material which is obtained by polymerizing a polymerizable monomer component B containing a polymerizable monomer having an ultraviolet absorbing group in the subsequent stage, which is excellent not only in light resistance but also in various properties. Can be obtained. The amount of the UV-absorbing group-containing polymerizable monomer in the polymerizable monomer component A is 1 to 20.
When the amount of the UV-absorbing group-containing polymerizable monomer in the polymerizable monomer component B is 1 to 20% by weight, the light resistance is effectively improved.

When the emulsion polymer in the aqueous resin dispersion is observed with a transmission electron microscope, an inner core that appears darker to allow passage of an electron beam and a lighter color that is easier to pass an electron beam than the inner core. If the visible outer shell is a two-layer structured particle whose density difference is recognized discontinuously, it is possible to obtain a heat-sensitive recording material having excellent heat resistance, sticking resistance, etc. Can be.

According to the present invention, there is provided a heat-sensitive recording material having a structure in which a heat-sensitive coloring layer using the aqueous resin dispersion for a heat-sensitive recording material as a binder is provided on a substrate, and a heat-sensitive coloring layer is provided on the substrate. A heat-sensitive recording material having a structure in which a protective layer containing an aqueous resin dispersion for a heat-sensitive recording material is provided on the heat-sensitive coloring layer is also included.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have attempted to introduce various ultraviolet absorbing compounds into an aqueous resin for a heat-sensitive recording material, and as a result, have found that a polymerizable monomer having an ultraviolet absorbing group, particularly a benzotriazole group, It has been found that the use of a polymer obtained by emulsion polymerization using the contained monomer is most effective for improving light resistance, and that it does not degrade the necessary properties as a heat-sensitive recording material, to complete the present invention. Reached. Hereinafter, the present invention will be described in detail.

The UV-absorbing group-containing polymerizable monomer, which is an essential component in the present invention, is used for the purpose of improving light resistance, and may be any compound having a UV-absorbing group and radical emulsion polymerizability. In particular, a benzotriazole group-containing polymerizable monomer is preferably used. Among the ultraviolet absorbing group-containing monomers other than the benzotriazole-based monomer, for example, a benzophenone-based monomer makes it difficult to balance the effect of improving the light resistance and the necessary properties as a heat-sensitive recording material. Specific examples of the benzotriazole group-containing polymerizable monomer include 2-
(2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole and the like.

The (meth) acrylic acid ester-based monomer, which is another essential component, has an effect of further improving light resistance when used in combination with a monomer having an ultraviolet absorbing group. In addition, since the copolymerizable with the UV-absorbing group-containing monomer is good, the charged UV-absorbing group-containing monomer can be introduced into the polymer without waste. Specific examples of the (meth) acrylic acid ester monomer, (meth) acrylate, (meth) acrylate, (meth) and butyl acrylate (meth) acrylic acid with C ₁ -C ₁₈ (Meth) acrylates which are esters of alcohols;
Examples thereof include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and hydroxyl group-containing (meth) acrylates such as a monoester of (meth) acrylic acid and polypropylene glycol.

In the present invention, when producing an aqueous resin dispersion for a heat-sensitive recording material, emulsion polymerization is carried out. As the emulsion polymerization method, a known method can be employed. At this time, as the emulsifier, a polyvinyl alcohol having a polymerization degree of 300 to 2400 or a modified polyvinyl alcohol [hereinafter, both may be collectively referred to as (modified) polyvinyl alcohol] may be used. It is recommended to use. Many emulsifiers used in the production of general emulsions have a hydrophilic group part such as a carboxyl group or a sulfonic acid group, or polyethylene glycol, and have a molecular weight of several hundred to several thousand. May cause ground color. On the other hand, polyvinyl alcohol is generally used as a resin for thermal recording, and hardly causes ground coloration.
This polyvinyl alcohol is known to have a weak but emulsifying activity, but if it is a vinyl alcohol having the following degree of polymerization and saponification degree, by using it as an emulsifier, it has good polymerization stability and causes ground coloration. A difficult aqueous resin can be obtained.

First, the degree of polymerization of the (modified) polyvinyl alcohol is preferably in the range of 300 to 2400. If the degree of polymerization is less than 300, the protective layer and the coloring layer of the heat-sensitive recording material obtained by using the above dispersion may have poor heat resistance. The use of (modified) polyvinyl alcohol having a degree of polymerization of 550 or more results in good sticking resistance and is more preferable. However, when the degree of polymerization is 240
If it is larger than 0, the viscosity during the polymerization becomes so high that gelation occurs, which is not preferable.

The (modified) polyvinyl alcohol having a saponification degree of 80% or more is preferably used. Saponification degree 80
%, The viscosity increases during polymerization and gelation occurs. A more preferred saponification degree is 88% or more.

In the present invention, it is recommended that the (modified) polyvinyl alcohol be used as an emulsifier in the production of the emulsion polymer in an amount of 10 to 250% by weight based on the total amount of the polymerizable monomer components A and B. Is done. If the amount of the emulsifier used is less than 10% by weight of the total amount of the monomers, a large number of suspension polymers having large particles are generated and precipitated in an aqueous medium, which is not preferable as an aqueous resin dispersion for a thermosensitive recording material.
If the emulsifier is used in an amount exceeding 250% by weight, the sticking resistance may decrease. A more preferred amount is 20 to 200% by weight of the total amount of the monomers. When used in this range, an aqueous resin dispersion for a heat-sensitive recording material having a good balance of physical properties for a heat-sensitive recording material can be obtained.

In order to obtain an emulsion polymer, it is preferable to carry out two-stage polymerization. First, in the first stage, a polymerizable monomer containing an ultraviolet absorbing group-containing monomer, a (meth) acrylate monomer and a polymerizable polyfunctional monomer, and optionally containing other monomers Highly crosslinked fine particles (core) are obtained by polymerizing component A. The highly crosslinked fine particles have excellent heat resistance and do not show a sharp endothermic peak in glass transition point measurement using a thermal compensation type differential scanning calorimeter. By using such highly crosslinked fine particles as the core of the core-shell structured particles, it has a function of improving the sticking resistance of the coloring layer and the protective layer of the thermosensitive recording material. In the polymerizable monomer component A, the polymerizable polyfunctional monomer is in the range of 15 to 70% by weight, the UV-absorbing group-containing monomer is in the range of 1 to 20% by weight, and the (meth) acrylate is It is preferable to use 5% by weight or more of the system monomer. When the amount of the polymerizable polyfunctional monomer is less than 15% by weight, the effect of improving the sticking resistance is small, and when the amount exceeds 70% by weight, the polymerization stability tends to be poor. If the amount of the UV-absorbing group-containing monomer is less than 1% by weight, the effect of improving light resistance is hardly observed, and
If it is used in excess of% by weight, the polymerization stability is undesirably deteriorated. 5 (meth) acrylate monomers
If the amount is less than 10% by weight, the effect of improving the light resistance and the effect of improving the copolymerizability when used in combination with the monomer having an ultraviolet absorbing group become insufficient.

Examples of the polymerizable polyfunctional monomer which can be used as a monomer of the polymerizable monomer component A include (meth) acrylic acid and ethylene glycol, 1,3-butylene glycol, diethylene glycol, 1,6 -Hexanediol, neopentyl glycol, polyethylene glycol, propylene glycol, polypropylene glycol, trimethylolpropane, pentaerythritol,
Polyfunctional (meth) acrylates having two or more polymerizable unsaturated groups in the molecule, such as esterified products with polyhydric alcohols such as dipentaerythritol; and polymerizable non-polymerizable compounds in the molecule such as methylenebis (meth) acrylamide. Polyfunctional (meth) acrylamides having two or more saturated groups; polyfunctional allyl compounds having two or more polymerizable unsaturated groups in a molecule such as diallyl phthalate, diallyl maleate, and diallyl fumarate; (meth) acrylic acid Allyl, divinylbenzene and the like can be mentioned, and one or more of these can be used as a mixture.

In addition to the above monomers, those which can be used as other polymerizable monomers constituting the polymerizable monomer component A include styrene, vinyltoluene, α-methylstyrene,
Styrene derivatives such as chloromethylstyrene; (meth) acrylamide, N-monomethyl (meth) acrylamide, N-monoethyl (meth) acrylamide, N,
(Meth) acrylamide derivatives such as N-dimethyl (meth) acrylamide; vinyl acetate, (meth) acrylonitrile and the like; dimethylaminoethyl (meth) acrylate,
Basic polymerizable monomers such as dimethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, vinylpyridine, vinylimidazole, vinylpyrrolidone; N-methylol (meth) acrylamide, N-butoxymethyl (meth) Crosslinkable (meth) acrylamides such as acrylamide; to silicon atoms such as vinyltrimethoxysilane, vinyltriethoxysilane, γ- (meth) acryloylpropyltrimethoxysilane, vinyltris (2-methoxyethoxy) silane and allyltriethoxysilane A polymerizable monomer having a hydrolyzable silicon group directly bonded thereto; an epoxy group-containing polymerizable monomer such as glycidyl (meth) acrylate or acrylglycidyl ether; 2-isopropenyl-2-oxazoline, 2-vinyloxazoline etc Oxazoline group-containing polymerizable monomers, (meth) -2-aziridinyl ethyl acrylate,
An aziridine group-containing polymerizable monomer such as (meth) acryloylaziridine; and vinyl fluoride, vinylidene fluoride,
Vinyl chloride, vinylidene chloride and the like can be mentioned, and one kind or a mixture of two or more kinds can be used.

However, in order to obtain highly crosslinked fine particles having substantially no glass transition point, a polymerizable monomer component other than a polymerizable polyfunctional monomer ｛a UV-absorbing group-containing polymerizable monomer, It is preferable that the polymerizable monomer component is selected so that the glass transition temperature when the polymer is formed from the (meth) acrylate monomer and the other polymerizable monomer｝ is 70 ° C. or higher. It is more preferably at least 90 ° C. If the glass transition point of the polymer comprising the polymerizable monomer component is less than 70 ° C., even when the above-described polymerizable polyfunctional monomer is added and polymerized, it has substantially no glass transition point, that is, It is not preferable because highly heat-resistant highly crosslinkable fine particles may not be obtained.

Next, as a subsequent stage, the polymerizable monomer component B is polymerized. The essential components of the polymerizable monomer component B are a UV-absorbing group-containing polymerizable monomer and a (meth) acrylate monomer, the former being in the range of 1 to 20% by weight, and the latter being 5% by weight.
Preferably, it is used in an amount of at least% by weight. The reason for the amount limitation and the specific examples are the same as those described in the previous section of the polymerization. Further, since it is preferable that the ultraviolet-absorbing group is contained in both phases of the core-shell of the obtained emulsion polymer particles without much difference from the viewpoint of improving light resistance, the ultraviolet-absorbing group-containing polymerizable monomer is a single monomer. It is recommended to use the same amount in the monomer component A and the monomer component B.

As the polymerizable monomer component B, in addition to the above-mentioned polymerizable monomer having an ultraviolet absorbing group, a film-forming property of the aqueous resin dispersion for a heat-sensitive recording material of the present invention, It is preferable to include a monomer which plays an effective role in improving the water resistance, flexibility and smoothness of the polymer. Since the minimum film forming temperature of the aqueous resin dispersion for a heat-sensitive recording material of the present invention is preferably 80 ° C. or lower, the monomer component B may be selected so that the glass transition temperature after polymerization is 90 ° C. or lower. A more preferred glass transition temperature is 70 ° C. or lower. When the glass transition temperature of the monomer component B after polymerization is 90 ° C. or higher, the minimum film-forming temperature of the aqueous resin dispersion for heat-sensitive recording materials may exceed 80 ° C.

Specific examples of the polymerizable monomer component B other than the UV-absorbing group-containing polymerizable monomer include those other than the polymerizable polyfunctional monomer in the description of the polymerizable monomer component A described above. Examples of the monomer that can be used are the same as those exemplified above, and one or a mixture of two or more thereof can be used. In addition, the above-mentioned polymerizable polyfunctional monomer also has a minimum film-forming temperature of the aqueous resin dispersion for heat-sensitive recording material of 8 or less.
They can be used together within a range not exceeding 0 ° C.

The method of adding the polymerizable monomer components A and B to the polymerization reaction system is not particularly limited. For both the first and second stages of polymerization, batch addition, monomer dropping, pre-emulsion method, power feed method, seed method , Multi-stage addition and the like.

As the polymerization catalyst used in the emulsion polymerization in the present invention, conventionally known polymerization catalysts can be used. For example, potassium persulfate, ammonium persulfate, and the like which are decomposed by heat to generate molecules having radicals can be used. Persulfates such as sodium persulfate; water-soluble azo compounds such as 2,2'-azobis (2-amidinopropane) dihydrochloride and 4,4'-azobis (4-cyanopentanoic acid); hydrogen peroxide and the like Redox systems such as ascorbic acid and hydrogen peroxide, sodium sulfoxylate and t-butyl hydroperoxide, potassium persulfate and metal salts, which generate radical-containing molecules in a redox reaction by combining an oxidizing agent and a reducing agent. Examples thereof include a polymerization initiator, and one or more of these can be used as a mixture. The polymerization temperature is 0 to 100 ° C, preferably 50 to 80 ° C,
The polymerization time is 1 to 15 hours. At the time of emulsion polymerization, it is possible to add a hydrophilic solvent or an additive within a range that does not adversely affect the physical properties of the aqueous resin dispersion for a heat-sensitive recording material of the present invention.

The preferred form of the emulsion polymer in the aqueous resin dispersion for a heat-sensitive recording material of the present invention is that the high cross-linking degree portion composed of the monomer component A is obtained by employing the above-mentioned two-stage polymerization method of the first and second stages. The core has a core-shell structure which is a shell composed of the monomer component B. In the present invention, it is not always necessary to take a core-shell structure, but if a polymer having a core-shell structure is used, various properties of the coating film, particularly transparency,
It is preferable because the film formability is improved. This is because the core-shell structure makes the interface between the core portion and the shell portion unclear and eliminates irregular reflection of light at this portion, thereby increasing transparency. In addition, the binder component of the shell efficiently acts on the core particles that do not form a film, thereby improving the film forming property.

When the emulsion polymer particles are observed with a transmission electron microscope, a core (inner core) that appears darker to allow the passage of electron beams and a shell that appears easier and more light-permeable than the inner core. The outer shell is preferably a particle having a two-layer structure that exists so that the difference in density is recognized discontinuously. FIG. 1 is a drawing-substitute photograph obtained by observing such a core-shell type emulsion polymer having a two-layer structure with a transmission electron microscope, and FIG. 2 is an explanatory view of this photograph.

The observation method using a transmission electron microscope is as follows. Emulsion obtained by polymerization (Normally, non-volatile content is 10
程度 50%) is diluted about 100,000 to 1,000,000 times with distilled water. One drop of the emulsion diluted is placed on a transmission electron microscope cell on which a collodion film is provided. Gently put the cell into a test tube, and quench the entire test tube with dry ice. When the emulsion (water droplets) in the cell freezes, the test tube is sealed, and the pressure is reduced while cooling. After visually confirming that the ice in the cell in the test tube has completely sublimated, the pressure is released and the emulsion polymer particles in the cell are observed with a transmission electron microscope.

1 and 2, it can be seen that the core of the emulsion polymer particles looks darker and the shell is lighter than the core, and the boundary between the core and the shell can be clearly seen. On the other hand, FIG. 3 shows a photograph as a substitute of a drawing in which a normal emulsion polymer was observed with a transmission electron microscope. In FIG.
The central portion of the emulsion polymer particles looks darker and gradually fades in color toward the outside of the particles, but the boundaries between the core and shell as seen in FIG. 1 are not observed.

The reason why the core looks dark as shown in FIG. 1 by observation with a transmission electron microscope is that the core component is hard to pass an electron beam. In particular, when an aromatic polymerizable polyfunctional monomer such as divinylbenzene is used as a component of the core, the difference in shading between the core and the shell becomes clearer. Either the molecular chains of the polymer in the emulsion polymer particles are difficult to move and the electron beam is difficult to pass through, or the polymer molecules are concentrated in the core and the electron orbits in the molecule approach to increase the electron density It is thought that it would be difficult to pass the electron beam.

The average particle size of the emulsion polymer in the aqueous resin dispersion is preferably 500 nm or less, more preferably 300 nm or less from the viewpoint of transparency. If it exceeds 500 nm, the coating film becomes cloudy and opaque, which is not preferable. Next, a heat-sensitive recording material using the above-described aqueous resin dispersion for a heat-sensitive recording material will be described.

The heat-sensitive recording material of the present invention is of a type in which an aqueous resin dispersion for a heat-sensitive recording material containing an emulsion polymer obtained by the above-mentioned emulsion polymerization is used as a binder for a heat-sensitive color-forming layer. And a type provided with a protective layer using an aqueous resin dispersion for heat-sensitive recording materials.

First, the first type is a heat-sensitive recording material having a heat-sensitive coloring layer provided on a base material. This heat-sensitive coloring layer is composed of a known leuco dye, a developer, and an aqueous resin for a heat-sensitive recording material of the present invention. A dispersion obtained by adding a known additive, an auxiliary agent, and the like described below as necessary, including a minimum of a dispersion liquid, and coating and drying the resultant on a substrate such as paper, plastic film, or synthetic paper. is there.

As the leuco dye, known leuco compounds of dyes such as triphenylmethane, fluoran, phenothiazine, auramine, spiropyran and indolinophthalide can be used. Specific examples of such leuco dyes include, for example, 3,3-bis (p-
Dimethylaminophenyl) phthalide, 3,3-bis (p
-Dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3
-Bis (p-dimethylaminophenyl) -5-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3- (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino -6-chlorofluoran, 3-dimethylamino-5
7-dimethylfluorane, 3-dimethylamino-7-chlorofluorane, 3-dimethylamino-7,8-benzfluorane, 3-dimethylamino-6-methyl-7-chlorofluorane, 3- (N- p-tolyl-N-ethylamino) -6-methyl-7-anilinofluoran, 3-pyridino-6-methyl-7-anilinofluoran, 2-
(N- (3'trifluoromethylphenyl) amino)-
6-diethylaminofluoran, 2- (3,6-bis (diethylamino) -9 (o-chloroanilino) xanthylbenzoate lactam), 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluoran, 3-dimethylamino-7- (o-chloroanilino)
Fluoran, 3-dibutylamino-7- (o-chloroanilino) fluoran, 3-N-methyl-N-amylamino-6-methyl-7-anilinofluoran, 3-N-methyl-N-cyclohexylamino-6 Methyl-7-anilinofluoran, 3-diethylamino-6-methyl-
7-anilinofluoran, 3- (N, N-diethylamino) -5-methyl-7- (N, N-dibenzylamino)
Fluoran, benzoyl leucomethylene blue, 6'-
Chloro-4'-methoxy-benzoindolino-pyrirospiropyran, 5'-bromo-3'-methoxy-benzoindolino-pyrirospiropyran, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3 -(2'-methoxy-5'-chlorophenyl) phthalide, 3- (2 '
-Hydroxy-4'-dimethylaminophenyl) -3-
(2′-methoxy-5′-nitrophenyl) phthalide,
3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl)
Phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-methylphenyl) phthalide, 3-morpholino-
7- (N-propyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7-trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-
7- (N-benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluoran, 3-diethylamino-
5-chloro-7- (α-phenylethylamino) fluoran, 3- (N-ethyl-p-toluidino) -7- (α
-Phenylethylamino) fluoran, 3-diethylamino-7- (α-methoxycarbonylphenylamino)
Fluoran, 3-diethylamino-5-methyl-7-
(Α-phenylethylamino) fluoran, 3-diethylamino-7-piperidinofluoran, 2-chloro-3
-(N-methyltoluidino) -7- (pn-butylanilino) fluoran, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4′-bromofluoran , 3-diethylamino-6-methyl-7-mesitidino-4 ', 5'-benzofluoran.

The color developer is a compound that reacts with the leuco dye upon heating to form a color, and may be a phenolic substance, an organic or inorganic acidic substance, or an ester or salt thereof. Acid, salicylic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 3 ′, 5-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,
4′-isopropylidene diphenol, 4,4′-isopropylidene bis (2,6-dibromophenol),
4,4'-isopropylidenebis (2,6-dichlorophenol), 4,4'-isopropylidenebis (2-methylphenol), 4,4'-isopropylidenebis (2,8-dimethylphenol), 4 , 4'-isopropylidenebis (2-tert-butylphenol),
4,4'-sec-butylidene diphenol, 4,4 '
-Cyclohexylidenebisphenol, 4,4'-cyclohexylidenebisphenol, 4,4'-cyclohexylidenebis (2-methylphenol), 4-tert
-Butylphenol, 4-hydroxydiphenoxide,
α-naphthol, β-naphthol, 3,5-xylenol, thymol, methyl-4-hydroxybenzoate,
4-hydroxyacetophenone, novolak-type phenol resin, 2,2′-thiobis (4,6-dichlorophenol), catechol, resorcin, hydroquinone, pyrogallol, phloroglysin, phloroglysin carboxylic acid, 4-tert-octyl catechol, 2, 2'-methylenebis (4-chlorophenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2'-dihydroxydiphenyl, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate Butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-chlorobenzyl p-hydroxybenzoate, o-chlorobenzyl p-hydroxybenzoate, p-methylbenzyl p-hydroxybenzoate, p
-Hydroxybenzoic acid-n-octyl, benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-5-naphthoic acid, zinc 2-hydroxy-6-naphthoate, 4-hydroxydiphenylsulfone,
-Hydroxy-4'-chlorodiphenylsulfone, bis (4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, zinc 3,5-di-tert-butylsalicylate, 3,5-di-tert-butylsalicylic acid Examples include tin, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, and thiourea derivatives.

Further, a leuco dye,
Developer, if necessary with the aqueous resin dispersion for a heat-sensitive recording material of the present invention, conventional additives, for example, sensitizers, pigments,
A lubricant, a water-soluble or aqueous resin, a surfactant, a waterproofing agent (crosslinking agent), an ultraviolet absorber, an antioxidant and the like can be used in combination.

As the sensitizer, various heat-fusible substances can be used. Examples thereof include higher fatty acids such as stearic acid and behenic acid and esters, amides and metal salts thereof, and aromatic carboxylic acids and amines. Phenyl benzoate, p-benzylbisphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, β-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid Phenyl ester, 1-hydroxy-2-naphthoic acid methyl ester, diphenyl carbonate, terephthalic acid dimethyl ester, 1,4-diethoxynaphthalene, 1,4-benzyloxynaphthalene, 1,2-bis (phenoxy) ethane, 1 , 2-bis (3-methylphenoxy) ethane, 1 , 2-bis (4-methylphenoxy) ethane, 1,4-bis (phenoxy) butane, 1,
4-bis (phenoxy) -2-butene, 1,2-bis (4-methoxyphenylthio) ethane, benzoylmethane, 1,4-bis (phenylthio) -2-butene, 1,
2-bis (4-methoxyphenylthio) ethane, 1,3
-Bis (2-vinyloxyethoxy) benzene, 1,4
-Bis (2-vinyloxyethoxy) benzene, p-
(2-vinyloxyethoxy) biphenyl, p-allyloxybiphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, 1,3-dibenzoyloxypropane, dibenzyl sulfide, 1,1-diphenylethanol, 1,1- Diphenylpropanol,
p- (benzyloxy) benzyl alcohol, 1,3-
Diphenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-
5 such as octadecylcarbamoylbenzene, higher linear glycol, dialkyl 3,4-epoxy-hexahydrophthalate, higher ketone, and other heat-fusible organic compounds;
Those having a melting point of about 0 to 200 ° C can be mentioned.

As the pigment, for example, calcium carbonate,
Silica, zinc oxide, titanium oxide, aluminum hydroxide,
In addition to inorganic fine powders such as zinc hydroxide, barium sulfate, clay, talc, surface-treated calcium and silica, urea-formalin resin, styrene / methacrylic acid copolymer,
An organic fine powder such as a polystyrene resin can be used.

Examples of the lubricant include various waxes such as carnauba, paraffin, and polyethylene, alkyl phosphates, silicones, higher fatty acids such as stearic acid and behenic acid, and esters, amides or metal salts thereof, and polyacrylic acid. Long-chain alkyl esters of (meth) acrylic acid such as stearyl are exemplified.

As the water-soluble resin or the aqueous resin, a resin generally used as a binder can be used. For example, polyvinyl alcohol, starch and derivatives thereof, methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, carboxymethylcellulose, methylcellulose, Cellulose derivatives such as ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / (meth) acrylate copolymer, acrylamide / (meth) acrylate / (meth) acrylate terpolymer, Styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, acrylic emulsion polymer Styrene / acrylic copolymer emulsion copolymer, styrene / vinyl acetate copolymer emulsion polymers, it may be mentioned styrene / butadiene / styrene (SBS) emulsion polymers, and the like.

The heat-sensitive recording material thus obtained is
The use of a pigment such as calcium carbonate at all, or the use of a small amount, satisfies the basic physical properties of a thermosensitive recording paper with excellent sticking resistance, and the transparency of the resin coating film itself is high. As compared with the recording material, an image having excellent surface gloss, high print density, and high print quality can be obtained. In addition, if an emulsion polymerization method in which an emulsifier is (modified) polyvinyl alcohol is employed, it is possible to almost completely prevent ground color formation caused by the emulsifier when an emulsion polymer using a general emulsifier is used. Further, since an ultraviolet-absorbing group-containing compound effective for improving light resistance is introduced, inconvenience such as discoloration after exposure to light is eliminated.

The second type is a heat-sensitive recording material in which a protective layer containing the above-mentioned aqueous resin dispersion for a heat-sensitive recording material is provided on the heat-sensitive coloring layer of the heat-sensitive recording material. It is divided into a case where the protective layer is formed only from the aqueous resin dispersion for the material, and a case where the protective layer containing the dispersion and other components is formed. In any case, the substrate in the second type is the same as that in the first type, and the heat-sensitive coloring layer may be the first type described above, or any other known heat-sensitive coloring layer may be used. Although it is possible, it is preferable to use the above-mentioned first type of heat-sensitive coloring layer, since it is needless to say that the light-resistant layer is excellent, the printing density is high, and the printing quality is high. In addition, the known thermosensitive coloring layer, the leuco dye, the above-described developer, the above-mentioned additives and an auxiliary agent using a water-soluble resin or an aqueous resin as a binder,
It is obtained by coating and drying.

The protective layer formed on the heat-sensitive coloring layer is basically formed by applying and drying the above-mentioned aqueous resin dispersion for a heat-sensitive recording material by a known method and, if necessary, by subjecting it to a calender treatment. can get. If necessary in the aqueous resin dispersion for a heat-sensitive recording material, the pigments, lubricants, water-soluble or aqueous resins, surfactants, water-proofing agents (crosslinked ), A heat-fusible substance, a pH adjuster, a viscosity adjuster, an ultraviolet absorber, an antioxidant, and other additives within a range that does not adversely affect the performance of the protective layer. It can also be used. The thickness of the protective layer is not particularly limited, but is preferably in the range of 0.5 to 10 μm, more preferably in the range of 1 to 5 μm in consideration of the effects and economy of the present invention.

[0045]

EXAMPLES Examples of the present invention will be shown below, but these are given for illustrative purposes and do not limit the scope of the present invention. In the following, parts and% are parts by weight, respectively.
It represents% by weight.

Example 1 A flask equipped with a dropping funnel, a stirrer, a nitrogen inlet tube, a thermometer and a cooler was charged with 790 parts of ion-exchanged water and a polymerization degree of 1.
750, 50 parts of polyvinyl alcohol PVA-CST manufactured by Kuraray Co., Ltd. having a saponification degree of 96.0% were charged, and 8 parts were stirred.
The mixture was heated to 0 to 90 ° C. to completely dissolve the polyvinyl alcohol. After the internal temperature was cooled to 75 ° C., 5 parts of a 5% aqueous solution of potassium persulfate was added, and then the solution was dropped from a dropping funnel.
66 parts of methyl methacrylate previously prepared, 30 parts of divinylbenzene and 2- (2'-hydroxy-5 ')
-Methacryloxyethylphenyl) -2H-benzotriazole (trade name "NORBLOC7966"; NOR in the United States)
AMCO) (4 parts) was added dropwise over 3 hours. After the completion of dropping, potassium persulfate was added as a post-addition catalyst.
% Aqueous solution, and then 21 parts of methyl methacrylate, 23 parts of butyl acrylate, γ-
1 part of (methacryloxypropyl) trimethoxysilane,
1 part of trimethylolpropane trimethacrylate, 1 part of hydroxyethyl methacrylate, 2- (2'-hydroxy-5'-methacryloxyethylphenyl) -2H-
A mixture of 3 parts of benzotriazole was added dropwise over 1 hour. After completion of the dropwise addition, the temperature was raised to 85 ° C., and stirring was continued for 1 hour.
A 0.0% aqueous resin dispersion (1) for a heat-sensitive recording material was obtained. During the polymerization, no problems such as aggregation occurred. The transmission-type microphotograph of FIG. 1 is that of the aqueous resin dispersion obtained in Example 1.

Example 2 A flask equipped with a dropping funnel, a stirrer, a nitrogen inlet tube, a thermometer and a cooler was charged with 790 parts of ion-exchanged water and a polymerization degree of 5
60, 80 parts of Kuraray Co., Ltd. polyvinyl alcohol PVA-105 having a saponification degree of 98.5% was charged, and 80 parts were stirred.
The mixture was heated to ９０90 ° C. to completely dissolve the polyvinyl alcohol. After cooling the internal temperature to 70 ° C., a 5% aqueous solution of 2,2′-azobis (2-amidinopropane) dihydrochloride 5
Then, from a dropping funnel, 63 parts of methyl methacrylate prepared in advance, 15 parts of ethylene glycol dimethacrylate, 2- (2'-hydroxy-5'-
A mixture of 2 parts of (methacryloxyethylphenyl) -2H-benzotriazole was added dropwise over 3 hours. After completion of the dropwise addition, 5 parts of a 2% aqueous solution of 2,2′-azobis (2-amidinopropane) dihydrochloride was added as a post-addition catalyst,
Subsequently, 23 parts of methyl methacrylate prepared in advance,
14 parts of ethyl acrylate, glycidyl methacrylate 1
Part, 1 part of vinyltrimethoxysilane and 2- (2′-
Hydroxy-5'-methacryloxyethylphenyl)-
A mixture consisting of 1 part of 2H-benzotriazole was added dropwise over 1 hour. After completion of the dropwise addition, the temperature was raised to 85 ° C., and stirring was continued for 1 hour, followed by cooling to complete the polymerization. The aqueous resin dispersion for a heat-sensitive recording material having a nonvolatile content of 19.9% (2)
I got During the polymerization, no problems such as aggregation occurred.

Example 3 A flask equipped with a dropping funnel, a stirrer, a nitrogen inlet tube, a thermometer and a cooler was charged with 790 parts of ion-exchanged water and a polymerization degree of 2.
40, 40 parts of polyvinyl alcohol PVA-224 manufactured by Kuraray Co., Ltd. having a saponification degree of 88.0% were charged, and 8 parts were stirred.
The mixture was heated to 0 to 90 ° C. to completely dissolve the polyvinyl alcohol. After the internal temperature was cooled to 80 ° C., 5 parts of a 5% aqueous solution of 4,4′-azobis (4-cyanovaleric acid) neutralized with aqueous ammonia was added, and the mixture was previously prepared from a dropping funnel. 74 parts of styrene, 40 parts of trimethylolpropane trimethacrylate and 2-
A mixture of 6 parts of (2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzotriazole was added dropwise over 3 hours. After completion of the dropping, 5 parts of a 2% aqueous solution of 4,4'-azobis (4-cyanovaleric acid) neutralized with aqueous ammonia was added as a post-addition catalyst, and 20 parts of styrene and acrylic prepared in advance were added. 12 parts of butyl acrylate, 4 parts of glycidyl methacrylate, 2- (2′-
Hydroxy-5'-methacryloxyethylphenyl)-
A mixture of 4 parts of 2H-benzotriazole was added dropwise over 1 hour. After completion of the dropwise addition, the temperature was raised to 85 ° C., and stirring was continued for 1 hour.
Thus, a 9.8% aqueous resin dispersion (3) for a heat-sensitive recording material was obtained. During the polymerization, no problems such as aggregation occurred.

Comparative Example 1 95 parts of calcium carbonate and 2- (2'-hydroxy-5'-methylphenyl) were added to 100 parts of a 3% aqueous solution of polyvinyl alcohol PVA-CST having a degree of polymerization of 1750 and a degree of saponification of 96.0%. ) -2H-benzotriazole (trade name “TI
(NUVIN P); Ciba-Geigy; ultraviolet absorber not a monomer) (5 parts) was added, and the mixture was dispersed using a sand mill until the particle diameter became 1 μm. In addition, 12.1
% PVA-CST aqueous solution was added to obtain a comparative pigment-dispersed resin liquid (1 ′) having a nonvolatile content of 20.0%.

Comparative Example 2 In a flask equipped with a dropping funnel, a stirrer, a nitrogen inlet tube, a thermometer and a cooler, 790 parts of ion-exchanged water, polyethylene glycol nonyl phenyl ether sulfonic acid manufactured by Daiichi Kogyo Seiyaku Co., Ltd. After 6 parts of ammonium emulsifier Hytenol N-08 was charged and the internal temperature was brought to 75 ° C., 5 parts of a 5% aqueous solution of potassium persulfate was added, and then methacrylic acid prepared in advance from a dropping funnel. Methyl 81
Part, butyl acrylate 87 parts, γ- (methacryloxypropyl) trimethoxysilane 6 parts, 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H—
A mixture of 12 parts of benzotriazole was added dropwise over 2 hours. After completion of the dropwise addition, stirring was continued for 1 hour and then the mixture was cooled to complete the polymerization. However, during the polymerization, a large number of aggregates were generated, which revealed that the polymerization stability was poor. The mixture was filtered through a 300-mesh wire net to obtain an aqueous resin dispersion having a nonvolatile content of 20.1%.

100 parts of kaolin clay was added to 100 parts of a 3% aqueous solution of polyvinyl alcohol PVA-CST having a degree of polymerization of 1750 and a degree of saponification of 96.0%, and the mixture was dispersed using a sand mill until the particle diameter became 1 μm. 20 parts of this dispersion and 100 parts of the aqueous resin dispersion were mixed, and prepared with ion-exchanged water so as to have a nonvolatile content of 20.0% to obtain a pigment dispersion resin liquid for comparison (2 ′). Dispersibility was good.

Comparative Example 3 A flask equipped with a dropping funnel, a stirrer, a nitrogen inlet tube, a thermometer and a cooler was charged with 790 parts of ion-exchanged water and a polymerization degree of 1.
750, polyvinyl alcohol PV having a saponification degree of 96.0%
A-CST (50 parts) was charged and heated to 80 to 90 ° C. with stirring to completely dissolve the polyvinyl alcohol. After cooling the internal temperature to 75 ° C., 5 parts of a 5% aqueous solution of potassium persulfate was added, and then 70 parts of methyl methacrylate and 30 parts of divinylbenzene prepared in advance from a dropping funnel.
Parts of the mixture were added dropwise over 3 hours. After dropping,
5 parts of a 2% aqueous solution of potassium persulfate was added as a post-addition catalyst, and methyl methacrylate 2 prepared in advance was added.
A mixture of 2 parts, 25 parts of butyl acrylate, 1 part of γ- (methacryloxypropyl) trimethoxysilane, 1 part of trimethylolpropane trimethacrylate, and 1 part of hydroxyethyl methacrylate was added dropwise over 1 hour.
After completion of the dropwise addition, the temperature was increased to 85 ° C., and stirring was continued for 1 hour.
Thereafter, the mixture was cooled to complete the polymerization, and the non-volatile content concentration was 19.9%.
To obtain a comparative aqueous resin dispersion (3 ′). During the polymerization, no problems such as aggregation occurred.

Comparative Example 4 2- (2 ′) was added to 50 parts of a 3% aqueous solution of polyvinyl alcohol PVA-CST having a polymerization degree of 1750 and a saponification degree of 96.0%.
-Hydroxy-5'-methylphenyl) -2H-benzotriazole (10 parts) was added, and the mixture was dispersed using a sand mill until the particle diameter became 1 µm. 20 parts of this dispersion and 100 parts of the comparative aqueous resin dispersion (3 ′) obtained in Comparative Reference Example 3 were mixed, and the mixture was prepared with ion-exchanged water so as to have a nonvolatile content of 20.0%. An aqueous resin dispersion (4 ') was obtained.

Comparative Example 5 A flask equipped with a dropping funnel, a stirrer, a nitrogen inlet tube, a thermometer and a cooler was charged with 790 parts of ion-exchanged water and a polymerization degree of 1.
750, polyvinyl alcohol PV having a saponification degree of 96.0%
50 parts of A-CST is charged and heated to 80 to 90 ° C.
Stirring was continued for an hour to completely dissolve the polyvinyl alcohol. After cooling the internal temperature to 75 ° C, 5% potassium persulfate was added.
% Aqueous solution, and then 69.5 parts of methyl methacrylate prepared in advance, 30 parts of divinylbenzene and 2- (2'-hydroxy-5'-methacryloxyethylphenyl) -2H from a dropping funnel. -A mixture of 0.5 parts of benzotriazole was added dropwise over 3 hours. After dropping, 5 parts of a 2% aqueous solution of potassium persulfate was added as a post-addition catalyst, and 22.7 parts of methyl methacrylate, 24 parts of butyl acrylate, and γ- (methacryloxypropyl) were prepared in advance. A mixture of 1 part of trimethoxysilane, 1 part of trimethylolpropane trimethacrylate, 1 part of hydroxyethyl methacrylate, and 0.25 part of 2- (2′-hydroxy-5′-methacryloxyethylphenyl) -2H-benzotriazole was added for 1 hour. The solution was dropped. After completion of the dropwise addition, the temperature was raised to 85 ° C., stirring was continued for 1 hour, and then the polymerization was completed by cooling, whereby a comparative aqueous resin dispersion (5 ′) having a nonvolatile content of 20.0% was obtained. During the polymerization, no problems such as aggregation occurred.

Comparative Example 6 A flask equipped with a dropping funnel, a stirrer, a nitrogen inlet tube, a thermometer and a cooler was charged with 790 parts of ion-exchanged water and a polymerization degree of 1.
750, polyvinyl alcohol PV having a saponification degree of 96.0%
50 parts of A-CST is charged and heated to 80 to 90 ° C.
Stirring was continued for an hour to completely dissolve the polyvinyl alcohol. After cooling the internal temperature to 75 ° C, 5% potassium persulfate was added.
5 parts of an aqueous solution, and 30 parts of methyl methacrylate, 30 parts of divinylbenzene and 2- (2'-hydroxy-5'-methacryloxyethylphenyl) -2H-benzo prepared in advance from a dropping funnel. Triazole 4
0 parts of the mixture were added dropwise over 3 hours. After completion of the dropwise addition, 5 parts of a 2% aqueous solution of potassium persulfate was added as a post-addition catalyst, and 13 parts of methyl methacrylate, 14 parts of butyl acrylate, and γ- (methacryloxypropyl) trimethoxy were prepared in advance. 1 part of silane, 1 part of trimethylolpropane trimethacrylate, 1 part of hydroxyethyl methacrylate, 2- (2′-hydroxy-5′-
A mixture of 20 parts of (methacryloxyethylphenyl) -2H-benzotriazole was added dropwise over 1 hour. After the completion of the dropwise addition, the temperature was raised to 85 ° C. and stirring was continued for 1 hour, and then the polymerization was completed by cooling. However, a large number of aggregates were generated and the polymerization stability was extremely poor. Filtration was not possible due to too much agglomerates and subsequent evaluation was abandoned.

The results of polymerization or dispersion in Examples 1 to 3 and Comparative Examples 1 to 5, the obtained aqueous resin dispersions (1) to (3) for thermosensitive recording materials, and the pigment dispersion resin for comparison Alternatively, Table 1 shows the measurement results of the nonvolatile components of the comparative aqueous resin dispersions (1 ′) to (5 ′). The non-volatile content was calculated by taking 1 g of a sample in an aluminum dish, drying it using a hot air drier, and changing the weight before and after the drying. Each product name in the table is as follows. -Highenol N-08: emulsifier based on ammonium polyethylene glycol nonyl phenyl ether sulfonate; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.-NORBLOC 7966-2- (2'-hydroxy-)
5'-methacryloxyethylphenyl) -2H-benzotriazole; manufactured by NORAMCO USA TINVIN P ... 2- (2'-hydroxy-5 ')
-Methylphenyl) -2H-benzotriazole; manufactured by Ciba-Geigy

[0057]

[Table 1]

—Preparation and Evaluation of Thermosensitive Recording Material— [A Solution] 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluoran 30 parts 2% polyvinyl alcohol PVA-CST aqueous solution 70 Part [b liquid] bisphenol A 30 parts 2% polyvinyl alcohol PVA-CST aqueous solution 70 parts [liquid c] calcium carbonate 30 parts 2% polyvinyl alcohol PVA-CST aqueous solution 70 parts

Each of the above compositions was dispersed using a sand mill until the particle diameter became 1 μm or less to obtain liquids a to c. Next, 20 parts of the liquid a, 40 parts of the liquid b, 50 parts of the liquid c and 37 parts of 12% polyvinyl alcohol PVA-CST were mixed to prepare a coating liquid for a thermosensitive coloring layer. This is the basis weight 5
0 g / m ² of high-quality paper with a coating amount of 5 g / m on one side after drying
^The resultant was coated and dried to obtain a base ^2, and a base thermosensitive recording paper was obtained.

The aqueous resin dispersions (1) to (3) for heat-sensitive recording materials obtained in Examples 1 to 3 and Comparative Examples 1 to 5, the pigment dispersion resin liquid for comparison or the aqueous resin dispersion liquid for comparison (1 ′) ) ~
Glyoxal as a crosslinking agent was added to (5 ′) in an amount of 3% in terms of nonvolatile content to prepare a coating liquid for a protective layer. This protective layer coating solution was applied onto the surface of the thermosensitive coloring layer of the base thermosensitive recording paper so that the coated amount after drying was 3 g / m ^2.
After drying to form a protective layer, the surface smoothness was adjusted to 30 using a super calender 30FC-200E manufactured by Kumagaya Riki Kogyo Co., Ltd.
Processing was performed for at least 00 seconds to obtain a heat-sensitive recording material.

With respect to the base thermosensitive recording paper having no protective layer and the thermosensitive recording materials of Examples and Comparative Examples, whiteness, surface gloss, water resistance, sticking resistance and printing color density during and after exposure of the protective layer were applied. The transferability of the plasticizer was measured using the following apparatus and conditions, and the results are shown in Table 2.

Surface gloss: Measured at an incident angle of 75 ° using a gloss meter VG-1D manufactured by Nippon Denshoku Industries Co., Ltd.・ Whiteness during coating: Nippon Denshoku Industries Co., Ltd. Colorimeter ND-1
It was calculated using the following equation from the value measured using 001. Whiteness = 100-[(100-L) ² + a ² + b ² ] ^0.5. Whiteness after exposure (lightfastness): Brightness after 3 days and 7 days after exposure to direct sunlight for an average of 8 hours a day Was measured by the above method. Water resistance: The number of rubs until a drop of water was dropped on the surface of the heat-sensitive coloring layer and lightly rubbed with the pad of a finger until the surface of the heat-sensitive coloring layer began to peel off was indicated. -Sticking resistance: Printing was performed at each printing energy using a thermal paper printing apparatus of Okura Electric Co., Ltd., and the printing energy at the point where sticking began to occur was regarded as sticking energy.・ Printing color density: Using a thermal paper printing device manufactured by Okura Electric Co., Ltd., the printing color density when printing at a printing energy of 0.5 mJ / dot was measured using the Macbeth reflection densitometer RD-9 from Kollmorgen Co.
It measured using 14. -Plasticizer transfer resistance: One drop of dibutyl phthalate as a plasticizer was dropped on the printed surface, and the time when decolorization started was measured.

[0063]

[Table 2]

[0064]

The aqueous resin dispersion for a heat-sensitive recording material of the present invention contains a polymer obtained by emulsion copolymerization of a monomer having an ultraviolet absorbing group, and exhibits good light fastness. In particular, when a monomer component containing a benzotriazole group-containing monomer is used, the effect of improving light resistance is remarkable. An aqueous resin dispersion containing core-shell type particles composed of a highly cross-linked core and a shell having properties such as film-forming properties improves the properties required as a heat-sensitive recording material and has an ultraviolet absorbing group. It is contained at the same level in both the core and the shell, and has even better lightfastness.
When a two-stage polymerization method using polyvinyl alcohol as an emulsifier is employed, a monomer component containing an ultraviolet-absorbing group-containing monomer, which is an essential component for improving light resistance, can be stably subjected to two-stage polymerization. There is also an advantage.

Therefore, when this aqueous resin dispersion is used as a binder resin for a thermosensitive coloring layer, or a thermosensitive recording material having a protective layer formed thereon satisfies the basic physical properties of thermosensitive recording paper such as sticking resistance. Can be
In addition, the light resistance was good, and inconveniences such as yellowing after light exposure could be prevented as much as possible.

Since the heat-sensitive recording material of the present invention has high transparency of the resin coating film itself, it has excellent surface gloss, high print density, and high print quality as compared with conventional heat-sensitive recording materials. The heat-sensitive recording material having a protective layer formed using the aqueous resin dispersion of the present invention is not only excellent in transparency and glossiness but also excellent in sticking resistance, and when polyvinyl alcohol is used as an emulsifier, polyvinyl alcohol is simply used as a general emulsion. Since polyvinyl alcohol exists more efficiently on the surface of the emulsion particles than when alcohol is blended and used, it exhibits plasticizer transfer resistance comparable to polyvinyl alcohol.

The heat-sensitive recording material of the present invention has light resistance and
It has special features such as surface gloss, print density, and plasticizer migration resistance, so it can be used for special applications such as labels such as POS, prepaid cards, tickets, and general computers and word processors.
It can be widely and suitably used as an output paper of a thermal printer for various outputs such as a facsimile, a handy terminal, an image output, various measuring instruments, and a cash dispenser.

[Brief description of the drawings]

FIG. 1 is a transmission electron micrograph instead of a drawing of a core-shell emulsion.

FIG. 2 is an explanatory view simulating a drawing substitute photograph of FIG. 1;

FIG. 3 is a transmission electron micrograph instead of a drawing of a general emulsion.

Claims (7)

[Claims] 1. A copolymer obtained by emulsion polymerization of a monomer component having a UV-absorbing group-containing polymerizable monomer and a (meth) acrylate monomer as essential components. Aqueous resin dispersion for heat-sensitive recording materials. 2. A polymerizable monomer component A containing a polymerizable polyfunctional monomer and a UV-absorbing group-containing polymerizable monomer as essential monomers in the first stage of the emulsion polymerization reaction, and in the second stage, An aqueous resin dispersion for a heat-sensitive recording material, obtained by polymerizing a polymerizable monomer component B containing a polymerizable monomer having an ultraviolet absorbing group. 3. The aqueous resin dispersion for a thermosensitive recording material according to claim 1, wherein polyvinyl alcohol or modified polyvinyl alcohol is used as the emulsifier used in the emulsion polymerization. 4. The polymerizable monomer containing an ultraviolet absorbing group is a polymerizable monomer containing a benzotriazole group.
The aqueous resin dispersion for a heat-sensitive recording material according to any one of the above. 5. When an emulsion polymer is observed with a transmission electron microscope, an inner core that appears darker to allow passage of electron beams and an outer shell that appears more light and easier to pass electron beams than the inner core are: The aqueous resin dispersion for a heat-sensitive recording material according to any one of claims 1 to 4, wherein particles having a two-layer structure are present such that the difference in density is discontinuously recognized. 6. A heat-sensitive recording material comprising a heat-sensitive coloring layer using the aqueous resin dispersion for a heat-sensitive recording material according to claim 1 as a binder. 7. A thermosensitive coloring layer provided on a substrate, and a protective layer containing the aqueous resin dispersion for a thermosensitive recording material according to claim 1 provided on the thermosensitive coloring layer. A heat-sensitive recording material characterized by the following.