JPH04182191A - Thermosensitive recording composition and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a heat-sensitive recording composition having high sensitivity and excellent chemical resistance, and a method for producing the same. Furthermore, the present invention relates to a heat-sensitive recording composition from which a low-gloss heat-sensitive recording material can be obtained, and a method for producing the same.

[Conventional technology]

A heat-sensitive recording material generally has a heat-sensitive recording layer on a base material, the main components of which are an electron-donating colorless dye precursor and an electron-accepting color developer. By heating the colorless dye precursor and the color developer, a recorded image can be obtained.
No. 60, Japanese Patent Publication No. 45-14039, etc. Such heat-sensitive recording materials have the advantages of being able to record with relatively simple equipment, being easy to maintain, and producing no noise. It is used in a wide range of fields such as automatic ticket vending machines, labels, and ticket vending machines. A heat-sensitive recording material using such an electron-donating colorless dye precursor and an electron-accepting color developer has a good appearance, a good feel,
Although it has excellent properties such as high color density and the ability to obtain various color hues, the heat-sensitive coloring part (recorded image part) comes into contact with plastics such as polyvinyl chloride, and the plasticity contained in the plastics It has the disadvantage of poor record keeping, such as being easily erased by agents or additives, or easily disappearing when it comes into contact with chemicals contained in food or cosmetics, or easily fading due to short-term exposure to sunlight. Due to this drawback, its use is currently subject to certain restrictions, and its improvement is strongly desired. In addition, as a heat-sensitive recording material in which two components react when heated and a recorded image with good storage stability is obtained, for example, JP-A-58-38733, JP-A-58-54085,
JP-A-58-104959, JP-A-58-14938
No. 8, JP-A-59-115887, JP-A-59-11
．． Publications No. 5888 and U.S. Patent No. 4,521,793
The specification discloses a heat-sensitive recording material whose two components are an imino compound and an isocyanate compound. In recent years, high-speed printing equipment that can print in a short time has been developed, and there is a need for highly sensitive thermal recording materials that have excellent thermal response and can produce sufficiently colored images even with low energy. It has become to. There has also been a demand for improvements in the above-mentioned color forming systems, ie, dye precursors and color developers, or aromatic isocyanate compounds and imino compounds, to increase their sensitivity. On the other hand, as a heat-sensitive recording material using microcapsules, the present inventors have previously filed an application in JP-A-59-191.
There is Publication No. 93 (Special Publication No. 2-2440). The publication describes ``thermal recording paper made by coating a support with microcapsules containing at least a color-forming colorless dye, a color developer, and a wax-like substance that is solid at room temperature and melts when heated.'' Disclosed. This relates to thermal recording paper that uses microcapsules containing colorless dyes, color developers, and wax-like substances (coloring aids).
The aim is to allow color to develop within the capsule without destroying it. Here, the following are examples of encapsulation methods. (1) Mix and melt a colorless dye or color developer and a color development aid,
A method of mixing and encapsulating a colorless dye-coloring aid emulsion and a color developer-coloring aid emulsion obtained by emulsification. This method has the drawback that the concentration of the colorless dye or color developer dissolved in the coloring aid is low, and if a large amount is melted, it will precipitate. Furthermore, when mixing emulsions, capsules are formed by each single emulsion particle, which is inefficient. (2) Mixing and melting a colorless dye or color developer and a color development aid,
Colorless dye obtained by emulsification - Emulsion of color development aid and color developer -
A method in which emulsions of color development aids are each pseudo-encapsulated (extremely thin film thickness), and each pseudo-capsule is mixed and encapsulated. (3) A method in which a finely dispersed colorless dye or color developer is pseudo-capsulated, and the pseudo-capsules are mixed and dispersed in a heated and melted coloring aid to be encapsulated. Methods (2) and (3) require a pseudo-encapsulation step and are inefficient.

[Problem to be solved by the invention]

As mentioned above, conventional heat-sensitive recording materials still have room for improvement in terms of higher sensitivity and chemical resistance of recorded images. Furthermore, the heat-sensitive recording paper previously filed by the present inventors had the above-mentioned drawbacks in its microencapsulation method. An object of the present invention is to solve these problems and provide a heat-sensitive recording composition that has high sensitivity and excellent chemical resistance, and a method for producing the same.

[Means to solve the problem]

As a result of extensive research, the present inventors have provided a heat-sensitive recording composition with high sensitivity and excellent chemical resistance, and a method for producing the same. Furthermore, the present invention provides a heat-sensitive recording composition from which a low-gloss heat-sensitive recording material can be obtained, and a method for producing the same. That is, the thermal recording composition provided by the present invention is
In a heat-sensitive recording composition consisting of a color-forming system of an aromatic isocyanate compound and an imino compound that develop color when they come into contact with each other during heating, the three components consisting of the aromatic isocyanate compound and the imino compound plus a sensitizer are used as essential components. It consists of microcapsules containing agglomerated particles obtained by agglomerating these particles using a cationic dispersant. The method for producing a heat-sensitive recording composition provided by the present invention consists of a color-forming system of an aromatic isocyanate compound and an imino compound that develop a color when they come into contact with each other during heating, and the aromatic isocyanate compound and the imino compound develop a color. In a method for producing a heat-sensitive recording composition comprising three components as essential components including a sensitizer, 1) the three components are mixed with an ionene condensate to form an average particle size of 0. Step 2: Monodisperse or co-disperse the aromatic isocyanate compound and the sensitizer or the imino compound and the sensitizer until the particle size is 5 to 1.0 μm. 2) Uniformly mix the dispersion of the three components. Step 3) Adding a cationic dispersant to the dispersion mixture under stirring to form aggregated particles of the three components. 4) Adding the aggregated particles to an anionic protective colloid substance and emulsifying and dispersing them. 5) A microcapsule containing aggregated particles of the three components is produced by a step of adding a microcapsule wall material to an emulsified dispersion and microcapsulating it. The microcapsules provided by the present invention have an average particle size of 2 to 30 μm1, preferably an average particle size of 3 to 20 μm1.
More preferably, the thickness is 5 to 10 μm. If the particle size of the microcapsules exceeds 30 μm, it is undesirable because it causes flaking of the coating layer, roughness of the coating surface, and color development due to scratching and frictional heat. On the other hand, if the average particle size is 2μ
If it is less than m, the effect cannot be fully exhibited. Note that the average particle size of the three-component agglomerated particles with respect to the microcapsules may be approximated to the average particle size of the Habo microcapsules. The cationic dispersant of the present invention is composed of a cationic surfactant or a cationic polymer. The cationic surfactant is at least one selected from amine salts, quaternary ammonium salts, phosphonium salts, and sulfonium salts. The cationic polymers include aminoalkyl methacrylate and its acrylamide copolymer, polyvinylpyridinium halide, polydiallylammonium halide, polyaminomethylacrylamide, polyvinylimidazoline, Mannich modified polyacrylamide, polyethyleneimine, polydiallylamine, polypyridinium halide, and chitosan. , cationized starch, cationized cellulose, cationized polyvinyl alcohol, ionene condensate, epoxyamine condensate, cationized polymethacrylic acid ester resin, and alkylene diamine-epichlorohydrin polycondensate. It is something. The wall of the microcapsule, which is the heat-sensitive recording composition of the present invention, is made of a melamine-formaldehyde polymer or a urea-formaldehyde polymer. In preparing the aggregated particles of the present invention that essentially contain the three components of an aromatic isocyanate compound, an imino compound, and a sensitizer, the mixing ratio of each component is as follows. The three components of the aromatic isocyanate compound, the imino compound, and the sensitizer are such that the imino compound is 50 to 300 parts by weight, preferably 100 to 200 parts by weight, and the sensitizer is 100 parts by weight. The amount is 10 to 300 parts by weight, preferably 30 to 200 parts by weight. Here, if the imino compound is less than 50 parts by weight, and if the unreacted aromatic isocyanate compound exceeds 300 parts by weight, a large amount of unreacted imino compound remains, which is uneconomical. Hereinafter, the heat-sensitive recording composition of the present invention and its manufacturing method will be specifically explained. A heat-sensitive recording material formed by coating a base material using the heat-sensitive recording composition of the present invention has a feature that the coated surface has low gloss (matte appearance). This is due to the fact that the heat-sensitive recording composition is agglomerated into three minute components, which easily scatters light, and the agglomerated particles themselves have large particle sizes and are scattered on the substrate. It is something. In general, heat-sensitive recording materials have the disadvantage that printed characters are difficult to read due to their high gloss. For this reason, recently, in order to prevent glare on the coated surface, a method has been adopted in which a matte layer made of a matting agent is coated on top of the heat-sensitive recording layer to give it a low gloss like that of plain paper. There is. The heat-sensitive recording composition of the present invention can obtain its effects simply by coating it on a substrate without applying such a matting layer. In the thermal recording composition of the present invention, the aggregated particles encapsulated in the microcapsules have an average particle size of 2 to 30 μm, preferably 3 to 20 μm, and more preferably 5 to 10 μm. Or, by co-dispersion (combination of aromatic isocyanate compound and sensitizer, or imino compound and sensitizer), the average particle size is 0.5 to 1 μm.
Use the one given below. The average particle size of the three components is 0.5~
A size of 1.0 μm is preferable because it is easy to control the formation of aggregated particles and from the efficiency of the dispersion process.
The average particle size exceeding this range may also be used. It is generally believed that the smaller these three components are, the higher the sensitivity will be. However, the surface of a substrate for heat-sensitive recording is not completely smooth, and irregularities due to pulp fibers are observed. The finely dispersed particles get into the irregularities of the pulp fibers, and the advantages of miniaturization are not fully utilized. On the other hand, when the heat-sensitive recording composition of the present invention is used, high sensitivity is achieved because the pulp fibers are arranged on the surface of the substrate while preventing them from entering into the uneven parts. . Furthermore, when the heat-sensitive recording composition of the present invention is used on a base material coated with an undercoat layer using an inorganic pigment or an organic pigment, the coated surface of the heat-sensitive recording layer becomes more uniform. This can have a further effect on increasing sensitivity. Since the three finely dispersed components exist in the microcapsule in close proximity as aggregated particles, they develop color when energy is applied by the thermal head, resulting in excellent thermal efficiency. Furthermore, since the microcapsule wall film is a thermosetting resin consisting of heavy melamine-formaldehyde or heavy urea-formaldehyde, the microcapsules will not be destroyed by the heat during printing and will not cause scum or sticking to the thermal head. Never. Printed images obtained using heat-sensitive recording materials coated with heat-sensitive recording compositions on the base material are isolated by microcapsule wall membranes even when they come into contact with chemicals such as organic solvents, so the printed images are desensitized. There is no discoloration such as fog or fog. Furthermore, the heat-sensitive recording material before use will not change color and will have excellent chemical resistance. In the method for producing a heat-sensitive recording composition of the present invention, the most important feature relates to the core material encapsulated in microcapsules. The core material, which has three essential components, has the form of agglomerated particles obtained by agglomerating each of the components previously dispersed with an ionene condensate using a cationic dispersant. The formed agglomerated particles are strongly agglomerated and stable over time, so they can be handled in the same way as ordinary emulsified particles. In the subsequent microencapsulation step, the formed aggregated particles are introduced into an anionic protective colloid substance and emulsified and dispersed. It is thought that the surface of the aggregated particles changes from a cationic state to an anionic state or a charge-neutralized state by a protective colloid substance. After this, a microcapsule wall material is added to perform microcapsulation. The formed microcapsules have a morphology similar to that of aggregated particles from the outside because the wall film covers the aggregated particles along the morphology. Since the core substance of microcapsules is a solid agglomerated particle, they will not be destroyed even when external pressure such as a supercalender is applied to a heat-sensitive recording material coated on a base material. This is because the agglomerated particles are strongly agglomerated at the manufacturing stage. In addition, completely coated microcapsules are
There is no possibility that organic solvents or the like will penetrate the wall membrane and color the core material. Furthermore, even if heat from a thermal head is applied, it will not melt. Microencapsulation methods include, for example, complex
Coacervation method, in situ method (in 5i
tu method), interfacial polymerization method, and other known methods may be used. However, preference is given to in situ methods. In the in-situ method, a method using melamine-formaldehyde weight or urea-formaldehyde weight as the wall material is particularly preferred. However, there is no restriction on the use of other wall materials. Examples of anionic protective colloid substances include carboxymethyl cellulose, sulfonated cellulose, sulfonated starch, carboxy-modified polyvinyl alcohol, polyacrylic acid, ethylene-maleic anhydride copolymer, methyl vinyl ether-maleic anhydride copolymer, vinyl Examples include acetate-maleic anhydride copolymer and styrene-maleic anhydride copolymer. As the coloring system of the present invention, an aromatic isocyanate compound and an imino compound of component B will be specifically exemplified. The aromatic isocyanate compound used in the present invention is a colorless or light-colored aromatic isocyanate compound or a heterocyclic isocyanate compound that is solid at room temperature, such as 2,6-dichlorophenyl in which one or more of the following is used. Isocyanate, p-chlorophenylisocyanate, 1
．． 3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1,3-dimethylbenzene-4゜6-diisocyanate, 1,4-dimethylbenzene-2
, 5-diisocyanate, 1-methoxybenzene-2,
4-diisocyanate, 1-methoxybenzene-2,5
-diisocyanate, 1-ethoxybenzene-2,4-
Diisocyanate, 2゜5-dimethoxybenzene-1,
4-diisocyanate, 2,5-jethoxybenzene-
1,4-diisocyanate, 2,5-dibutoxybenzene-1,4-cyisoanate, azobenzene-4,4'
-diisoanate, diphenyl ether-4゜4-diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate, naphthalene-2,7-
Diisocyanate, 3.3-dimethyl-biphenyl-
4,4'-diisocyanate, 3,3'dimethoxybiphenyl-4,4''-diisocyanate, diphenylmethane-4,4-1 diisocyanate, diphenyldimethylmethane-4,4'-diisocyanate, benzophenone -3,3'-diisocyanate, fluorene-2,7-
Diisocyanate, anthraquinone-2,6-diisocyanate, 9-ethylcarbazole-3,6-diisocyanate, pyrene-3,8-diisocyanate, naphthalene-13,7-) diisocyanate, biphenyl -2
゜4.4'-4-liisocyanate, 4.4-4'-triisocyanate-2,5-dimethoxytriphenylamine, p-dimethylaminophenyl isocyanate, tris(4-phenylisocyanate) thiophosphate, etc. There is. These isocyanate compounds may be used, if necessary, in the form of so-called blocked isocyanates, which are addition compounds with phenols, lactams, oximes, etc., or in the form of diisocyanate dimers, such as monomers. -methylbenzene-2,4-diisocyanate 2
It may be used in the form of isocyanurate, which is a mer or trimer, or it can also be used as a polyisocyanate adducted with various polyols. It is a colorless or light-colored compound that is solid at room temperature. A specific example is shown below. It is also possible to use two or more types of imino compounds in combination depending on the purpose. 3-iminoisoindolin-1-one, 3-imino-4
, 5,6,7-tetrachloroisoindolin-1-one, 3-imino-4,5,6,7-tetrabromoisoindolin-1-one, 3-imino-4,5,6,7-titra Fluoroisoindolin-1-one, 3-imino-5
,6-dichloroisoindolin-1-one, 3-imino-4゜5.7-)dichloro-6-methoxy-isoindolin-1-one, 3-imino-4,5,7-1lichloro-6-methyl mercaptoisoindolin-1-one,
3-imino-6-nitroisoindolin-1-one, 3
-imino-isoindoline-1-spiro-dioxolane, 1,1-dimethoxy-3-imino-isoindoline,
1,1-jethoxy-3-imino-4,5,6,7-titrachloroisoindoline, 1-ethoxy-3-imino-isoindoline, 1,3-diiminoisoindoline,
1,3-diimino-4,5,6,7-titrachloroisoindoline, 1,3-diimino-6-medoxyisoindoline, 1,3-diimino-6-cyanoisoindoline, 1,3-diimino -47-Sichia 5. 5. 6.
6-titrahydroisoindoline, 7-amino-2,
3-dimethyl-5-oxopyrrolo[:3,4b) pyrazine, 7-amino-2,3-diphenyl-5-oxopyrrolo[3゜4b) pyrazine, 1-iminodiphenic acid imide, 1-iminodiphenic acid imide, 1-phenyl Imino-3-iminoisoindoline, 1-(1-chlorophenylimino)-3-iminoisoindoline, 1-(2
", 5-dichlorophenylimino)-3-iminoisoindoline, 1-(2-,4-. 5'-trichlorophenylimino)-3-iminoisoindoline, 1-(2-cyano-4-m: trophenylimino)-3-iminoisoindoline, 1.-(2--
Chloro-5'-cyanophenylimino)-3-iminoisoindoline, 1-(2',6-dichloro4'-nitrophenylimino)-3-iminoisoindoline, 1
-(2-.5'-dimethoxyphenylimino)-3-iminoisoindoline, 1-(2'',5-jethoxyphenylimino)-3-iminoisoindoline, 1-(2-methyl-4' -nitrophenylimino)-3-iminoisoindoline, 1-(5-chloro-2'-phenoxyphenylimino)-3-iminoisoindoline, 1-(4
--N,N-dimethylaminophenylimino)-3-iminoisoindoline, 1-3--N,N-dimethylamino-4'-methoxyphenylimino)-3-iminoisoindoline, '1-(2- -methoxy-5--N-phenylcarbamoylphenylimino)-3-iminoisoindoline, 1-(2-chloro-5--1lifluoromethylphenylimino)-3-iminoisoindoline, 1
-(5-,6--dichlorobenzothiazolyl-2'-imino)-3-iminoisoindoline, 1. -(6--Methylbenzothiazolyl-2'-imino)-3-iminoisoindoline, 1-(4-phenylaminophenylimino)-3-iminoisoindoline, 1-(p-phenylazophenylimino) -3-iminoisoindoline 1-(naphthyl-1'-imino)-3-iminoisoindoline, 1-(anthraquinone-1'-imino)-3-
Iminoisoindoline, 1-(5--chloroanthraquinone-1'-imino)-3-iminoisoindoline, 1
-(N-ethylcarbazolyl-3'-imino)-3-iminoisoindoline, 1-(naphthoquinone-1'-imino)-3-iminoisoindoline, 1-(viridyl-4
'-imino)-3-iminoisoindoline, 1-(benzimidacylon-6'-imino)-3-iminoisoindoline, 1-(1'-methylbenzimidacylon-6'
-imino)-3-iminoisoindoline, 1-(7--
Chlorobenzimidazolone-5'-imino)-3-iminoisoindoline, 1-(benzimidazolyl-2'-
imino)-3-iminoisoindoline, 1-(benzimidazolyl-2'-imino)-3-imino-4,5,6
,7-titrachloroisoindoline, l (2”, 4-
-dinitrophenylhydrazone)-3-iminoisoindoline, 1-(intazolyl-3-imino)-3-iminoisoindoline, 1-(intazolyl-3'-imino)-3-imino-4,5,6, 7-titrabromoisoindoline, 1-(intazolyl-3'-imino)-3
-imino-4,5,6,7-titrafluoroisoindoline, 1-(benzimidazolyl-2--imino)-3
-imino-4,7-dithiatetrahydroisoindoline, 1-(4-.5'-dicyanoimidazolyl-2'-imino)=3-imino-56-dimethyl-4,7-pyradiisoindoline, 1-( cyanobenzoylmethylene)-3-iminoisoindoline, 1-(cyanocarbonamidomethylene)-
3-iminoisoindoline, 1-(cyanocarphomethoxymethylene)-3-iminoisoindoline, 1-(cyanocarphoethoxymethylene)-3-iminoisoindoline, 1-(cyano-N-phenylcarbamoylmethylene)- 3-iminoisoindoline, 1-[cyano-N-(
3″-methylphenyl)-rubamoylmethylene]-3
-iminoisoindoline, 1-[cyano-N-(4--
chlorophenyl)-carbamoylmethylene]-3-iminoisoindoline, 1-[cyano-N-(4-methoxyphenyl)-carbamoylmethylene]-3-iminoisoindoline, 1-[cyano-N-(3-chloro -4
-monomethylphenyl)-rubamoylmethylene]-3-
Iminoisoindoline, 1-(cyano-p-nitrophenylmethylene)-3-iminoisoindoline, 1-(dicyanomethylene)-3-iminoisoindoline, 1-(
Cyano-1", 2-. 4'-triazolyl-(3')-carbamoylmethylene)-3-iminoisoindoline, 1-(cyanothiazoyl-(2')carbamoylmethylene)-3-iminoisoindoline, 1-( Cyanobenzimidazolyl (2'
)-carbamoylmethylene)-3-iminoisoindoline, 1-(cyanobenzothiazolyl-(2')-carbamoylmethylene)-3-iminoisoindoline, 1-4
(cyanobenzimidazolyl-2')methylene]-3-
Iminoisoindoline, 1. -((cyanobenzimidazolyl-2')-methylene]-3-imino-4,5,6
, 7-titrachloroisointoline, 1-[(cyanobenzimidazolyl-2-)-methylene]-3-imino 5-methoxyisoindoline, 1-[(cyanobenzimidazolyl-2'-methylene]-3-imino -6-chloroisoindoline, 1-((1-phenyl-3'-methyl-5-oxo)-pyrazolithene-4']-3-iminoisoindoline, 1-[(cyanobenzimidazolyl-2')- Methylene]-3-imino-4゜7-dithiatetrahydroisoindoline, 1-[(cyanobenzimidazolyl-2')methylene-3-imino-5,6-dimethyl-4,7-pyradiisoindoline, 1- [(1-
monomethyl-3'-n-butyl)-barbic acid-51-
3-iminoisoindoline, 3-imino-1-sulfobenzoic acid imide, 3-imino-1-sulfo-6-chlorobenzoic acid imide, 3-imino-1-sulfo-5,6-dichlorobenzoic acid imide, 3 -imino-1-sulfo-4,5
, 6,7-tetrachlorobenzoic acid imide, 3-imino-
1-Sulfo-4,5゜6.7-tetrabromobenzoic acid imide, 3-imino-1-sulfo-4,5,6,7-tetrafluorobenzoic acid imide, 3-imino-1-sulfo-
6-nitrobenzoic acid imide, 3-imino-1-sulfo-
6-methoxybenzoic acid imide, 3-imino-1-sulfo-4,5,74lichloro-6-methylmercaptobenzoic acid imide, 3-imino-1-sulfonaphthoic acid imide,
Examples include 3-imino-1-sulfo-5-bromonaphthoic acid imide and 3-imino-2-methyl-4,5,6,7-tetrachloroisoindolin-1-one. Furthermore, in the case of color-forming systems using aromatic isocyanate compounds and imino compounds, commonly used electron-donating dye precursors and electron-accepting color developers may be mixed as necessary. Specific examples of the sensitizer of the present invention include N-hydroxymethylstearamide, stearamide,
Waxes such as palmitic acid amide, oleic acid amide, ethylene bisstearic acid amide, ricinoleic acid amide, paraffin wax, microcrystalline wax, polyethylene wax, rice wax, carnauba wax, naphthol derivatives such as 2-benzyloxynaphthalene, Biphenyl derivatives such as p-benzylbiphenyl and 4-allyloxybiphenyl, 1.2-bis(3-methylphenoxy)ethane, 2.2゛-bis(
4-methoxyphenoxy) diethyl ether, bis(4
- polyether compounds such as methoxyphenyl) ether, diphenyl carbonate, dibenzyl oxalate, di(
Examples include carbonic acid or oxalic acid diester derivatives such as p-florbenzyl) ester. These sensitizers can be used alone or in combination of two or more. A heat-sensitive recording material is manufactured by using the heat-sensitive recording composition of the present invention and coating a heat-sensitive recording layer on a substrate together with various materials. The various materials are as follows. As pigments, diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, etc. are used. In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, polyethylene oxide, stearic acid amide, and castor wax are used to prevent head wear and stickiness. A dispersant such as sodium sulfosuccinate, an ultraviolet absorber such as a benzophenone type or a benzotriazole type, a surfactant, a fluorescent dye, etc. are added as necessary. As the adhesive used for the heat-sensitive recording layer, various commonly used adhesives can be used. For example, starches, hydroquine ethylcellulose, methylcellulose, carboxydimethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol polyacrylic acid sorter, acrylamide/
``Acrylic ester copolymer, acrylic amide/acrylic ester/methacrylic acid ternary copolymer, alkali salt of styrene/maleic anhydride copolymer, alkali salt of ethylene/maleic anhydride copolymer, etc. Latex such as water-soluble adhesives, polyvinyl acetate, polyurethane, polyacrylic ester, styrene/butadiene copolymer, acrylonitrile/butadiene copolymer, methyl acrylate/butadiene copolymer, ethylene/vinyl acetate copolymer, etc. The base material used in the present invention is mainly paper, but nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., sheets coated with pigments, etc., or composite sheets combining these can also be optionally used. In addition, the above-mentioned base material may be coated with an undercoat layer made of an inorganic pigment or an organic pigment. By making it into an ink, it can also be used for partial printing using a printing machine.The heat-sensitive recording composition is coated with a core substance as microcapsules, so when it is made into an ink, it has chemical resistance and is effective. This is a typical use.

[Effect]

The heat-sensitive recording composition produced according to the present invention has three essential components: a color-forming component consisting of an aromatic isocyanate compound and an imino compound, and a sensitizer, and contains aggregated particles agglomerated by a cationic dispersant. It consists of microcapsules. Microcapsules containing these three components as core substances can efficiently transmit heat from the thermal head without penetrating into the irregularities of the pulp fibers of the base material, making it possible to obtain highly sensitive heat-sensitive recording materials. can. Furthermore, since the heat-sensitive recording composition itself is an aggregate of fine particles, the heat-sensitive recording material tends to cause light scattering and has low gloss. Microcapsules can have high sensitivity because the microparticles of the color-forming component made of an aromatic isocyanate compound and an imino compound are close to each other. Furthermore, since the coloring component is coated as microcapsules, it is not affected by chemicals such as organic solvents and has chemical resistance. For the above reasons, the heat-sensitive recording composition and the method for producing the same of the present invention have an effect not found in conventional techniques.

【Example】

The present invention will be specifically described below with reference to Examples. Example 1 Dispersion of 1.3 Components Mixtures having the following compositions were each pulverized and dispersed using a sand mill until the average particle size became approximately 0.7 μm. [Liquid A] Dispersion of aromatic isocyanate compound 4.4'
, 4”-triisocyanate-2,5-dimethoxyphenylamine 100 parts 2.5% polyvinyl alcohol aqueous solution 400 parts [Liquid B] Co-dispersion of imino compound and sensitizer 1
．． 3-diimino-4,5,6,7-titrachloroisoindoline 150 parts Benzyloxynaphthalene 150 parts 2.5% polyvinyl alcohol aqueous solution 700 parts Using an aqueous alcohol solution, mix the dispersions of liquids A and B obtained in step 1 above in the following ratio to obtain an average particle size of 1
Agglomerated particles of 0 μm were created. Solution A (20%) 2505 0 parts Solution B 30%) 500 parts Cationic dispersant 150 parts 3. Creation of microcapsules containing 3-component aggregated particles Styrene-maleic anhydride copolymer was dissolved with a small amount of sodium hydroxide. In 100 parts of a 5% aqueous solution at pH 4.0,
27% three-component aggregated particle dispersion 130 prepared in step 2 above.
portion was added little by little to disperse and emulsify. On the other hand, a mixed solution consisting of 10 parts of melamine, 25 parts of a 37% formaldehyde aqueous solution, and 65 parts of water was adjusted to pH 9.0 using sodium hydroxide, stirred and heated at 60°C to dissolve it, and a transparent melamine- A formaldehyde precondensate was prepared. 100 parts of melamine-formaldehyde initial condensate was added to 230 parts of the three-component emulsion, reacted with stirring in a constant temperature bath set at 60°C for 4 hours, and then cooled to room temperature to produce microcapsules. . The produced microcapsules had an average particle size of 10 μm, which is almost the same as the aggregated particles, and had a solid content of 18% as an aqueous microcapsule dispersion. 4. Preparation of heat-sensitive coating liquid Using the aqueous microcapsule dispersion having an average particle size of 10 μm obtained in 3 above, a heat-sensitive coating liquid was prepared according to the following formulation. Microcapsule (18%) 200 parts 10%
Polyvinyl alcohol aqueous solution 84 parts Calcium carbonate 20 parts Water
18 parts The 20% coating solution thus prepared was applied to base paper with a basis weight of 40 g/rrf using a Mayer bar to a coating weight (solid content) of 6 g/m, dried, and then super-coated. A heat-sensitive recording material was obtained by processing with a calendar. When the coated surface was observed using an optical microscope, it was found that the microcapsules were not damaged in any way by the pressure treatment of the supercalender. Regarding the heat-sensitive recording material created in this way, GmF
Color density was measured using an AX tester. The testing machine is made by Taishoku Denki (TH-PMD) and has a dot density of 8.
A thermal head with dots/mm, head resistance of 1300Ω, head voltage 22V, and current application time 1.0
Printed in ms. Regarding color density, Macbeth R
It was measured using a D-918 model reflection densitometer. Furthermore, the 75 degree glossiness of the coated surface of the heat-sensitive recording material was measured. Comparative Example 1 A heat-sensitive coating liquid was prepared as follows using the dispersion consisting of liquids A and B in Example 1 as is. Solution A (20%) 25 parts Solution B (30
%) 50 parts 10% polyvinyl alcohol aqueous solution 60 parts Calcium carbonate
20 parts water
75 parts of the 20% coating solution thus prepared was coated on base paper with a basis weight of 40 g/rd using a Mayer bar to a coating amount (solid content) of 6 g/rr! A heat-sensitive recording material was obtained by coating, drying, and treating with a super calender. The prepared heat-sensitive recording material was printed and evaluated in the same manner as in Example 1. Furthermore, the 75 degree glossiness of the coated surface of the heat-sensitive recording material was measured. Evaluation color density 75 degree glossiness Example 1 1.24 13 Comparative example 1 0.95 36 The results show that compared to the dispersion of Comparative Example 1 using microcapsules in Example 1, It showed high color density. Regarding the 75 degree glossiness, Example 1 was as low as 13, which was a low glossiness similar to that of plain paper. but,
Comparative Example 1 showed a high gloss level of 36. When the colored portion of the heat-sensitive recording material was observed using an optical microscope, it was confirmed that color was developed within the microcapsules in Example 1. - On the other hand, the colored part of Comparative Example 1 penetrated into the base material and was observed without any shading. As another evaluation, acetone was dropped onto the coated surfaces (unprinted areas) of the heat-sensitive recording materials prepared in Example 1 and Comparative Example 1, and the chemical resistance was observed. The results showed that in Example 1, there was no change in the coated surface and the white state was maintained. On the other hand, in Comparative Example 1, the color-forming component was dissolved by acetane, resulting in a blackish-brown state. From this, it was confirmed that in Example 1, the coloring component was coated with the microcapsule wall film. Comparative Example 2 In agglomerating the three components according to Example 1, the amount of 10% cationized polyvinyl alcohol aqueous solution used was increased,
Agglomerated particles having an average particle size of 33 μm were prepared, and microcapsules were prepared in the same manner as in the microencapsulation of Example 1. The obtained microcapsules were used to coat base paper with a basis weight of 40 g/rrf using a Mayer bar in the same manner as in Example 1. However, the surface of the coated layer after coating was observed to be loose due to microcapsules, making it unsuitable for use as a heat-sensitive recording material. Examples 2 to 4 and Comparative Examples 3 to 5 Heat-sensitive recording materials were obtained in the same manner as in Example 1, except that a 15% aqueous polyaminomethylacrylamide solution was used in place of the cationic dispersant used in Example 1. However, the quantitative ratios of the three components were changed as shown in Table 1. Here, Example 2~
4, the microcapsules were sequentially 5μm and 10μm125
μm, and Comparative Examples 3 to 5 were used as dispersions as they were. Color density and 75 degree gloss were measured in the same manner as in Example 1, and the results are listed in Table 1. Table 1 *A, B, and C in Table 1 are as follows. A: Aromatic isocyanate compound (parts by weight) B: Imino compound (·l) C: Sensitizer (〃) As is clear from Table 1, Examples 2 to 4 have high color density and high sensitivity. I understand that. Furthermore, the 75 degree glossiness also shows a low value. On the other hand, Comparative Examples 3 to 5 are Example 2
It can be seen whether the amount of each of the three components used in 4 to 4 corresponds to each other, or if the dispersion is used as it is, the color density is low and the sensitivity is poor. Moreover, the 75 degree glossiness also shows a high value.

【Effect of the invention】

The present invention provides a heat-sensitive recording composition comprising microcapsules in which three essential components of a coloring system consisting of an aromatic isocyanate compound and an imino compound and a sensitizer are agglomerated and the agglomerated particles are encapsulated as a core material. By using the heat-sensitive recording composition, a heat-sensitive recording material having unprecedented high sensitivity and chemical resistance can be produced. In addition, it is possible to produce a heat-sensitive recording material that provides low gloss. From the above, the thermal recording composition and the method for producing the same of the present invention have extremely high practical value.

Claims (1)

[Scope of Claims] 1. A heat-sensitive recording composition comprising a color-forming system of an aromatic isocyanate compound and an imino compound that develop color when they come into contact with each other when heated, wherein the aromatic isocyanate compound and the imino compound are provided with a sensitizer. A thermal recording composition comprising microcapsules containing agglomerated particles obtained by agglomerating these three components with a cationic dispersant as essential components. 2. The thermal recording composition according to claim 1, wherein the cationic dispersant comprises a cationic surfactant or a cationic polymer. 3. The heat-sensitive recording composition according to claim 2, wherein the cationic surfactant comprises at least one selected from amine salts, quaternary ammonium salts, phosphonium salts, and sulfonium salts. 4. The cationic polymer is aminoalkyl methacrylate and its acrylamide copolymer, polyvinylpyridinium halide, polydiallylammonium halide, polyaminomethylacrylamide, polyvinylimidazoline, Mannich modified polyacrylamide, polyethyleneimine, polydiallylamine, polypyridinium halide, Chitosan, cationized starch, cationized cellulose, cationized polyvinyl alcohol, ionene condensate, epoxyamine condensate, cationized polymethacrylate ester resin, alkylene diamine
4. The heat-sensitive recording composition according to claim 3, comprising at least one type of epichlorohydrin polycondensates. 5. The thermal recording composition according to claim 1, wherein the wall of the microcapsule is made of a melamine-formaldehyde polymer or a urea-formaldehyde polymer. 6. The heat-sensitive recording composition according to claim 1, wherein the microcapsules have an average particle size of 2 to 30 μm. 7. A thermosensitive recording comprising a color-forming system of an aromatic isocyanate compound and an imino compound that develop color when they come into contact with each other when heated, and the three essential components are the aromatic isocyanate compound and the imino compound plus a sensitizer. In the method for producing a composition for
A step of monodispersing or co-dispersing the aromatic isocyanate compound and the sensitizer or the imino compound and the sensitizer until the particle size reaches ~1.0 μm 2) A step of uniformly mixing the dispersion of the three components 3) Step of adding a cationic dispersant to the dispersion mixture under stirring to form aggregated particles of the three components 4) Step of adding aggregated particles to an anionic protective colloid substance and emulsifying and dispersing them 5 ) A method for producing a thermosensitive recording composition comprising microcapsules encapsulating aggregated particles of the three components, by introducing a microcapsule wall material into an emulsified dispersion and microcapsulating it. 8. The method for producing a heat-sensitive recording composition according to claim 7, wherein the cationic dispersant comprises a cationic surfactant or a cationic polymer. 9. The method for producing a heat-sensitive recording composition according to claim 8, wherein the cationic surfactant comprises at least one selected from amine salts, quaternary ammonium salts, phosphonium salts, and sulfonium salts. . 10, the cationic polymer is aminoalkyl methacrylate and its acrylamide copolymer, polyvinylpyridinium halide, polydiallylammonium halide, polyaminomethylacrylamide, polyvinylimidazoline, Mannich modified polyacrylamide, polyethyleneimine, polydiallylamine, polypyridinium halide, At least one of the following: chitosan, cationized starch, cationized cellulose, cationized polyvinyl alcohol, ionene condensate, epoxyamine condensate, cationized polymethacrylic acid ester resin, alkylene diamine-epichlorohydrin polycondensate 10. The method for producing a heat-sensitive recording composition according to claim 9. 11. The method for producing a heat-sensitive recording composition according to claim 7, wherein the wall of the microcapsule is made of a melamine-formaldehyde polymer or a urea-formaldehyde polymer. 12. The method for producing a heat-sensitive recording composition according to claim 7, wherein the microcapsules have an average particle size of 2 to 30 μm.