JPH11179193A - Micro-capsule dispersion and pressure sensitive paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyurethane-urea wall micro-capsule dispersion coating liquid which can coat stably with a curtain coater and does not induce a V-cut phenomenon and pressure sensitive paper coated with it. SOLUTION: In a micro-capsule dispersion in which a polyurethane-urea wall micro-capsule containing at least a color coupler has micro-capsule protecting material particles, a binder, and a developer as desired, a micro-capsule dispersion in which the zeta potential of the micro-capsule is -60-10 mV is made a coating liquid. The zeta potential of the range is obtained by using an anionic polymer as an emulsifier in the preparation of the polyurethane-urea wall micro-capsule. The pressure sensitive paper obtained by applying the micro- capsule dispersion on a support is excellent in a printing aptitude and a pasting aptitude.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microcapsule dispersion containing polyurethane urea wall microcapsules as a main component and a pressure-sensitive copying paper coated with the dispersion, and more particularly, to a stable paper even at a lower flow rate. Microcapsule dispersion liquid for curtain coating and pressure-sensitive copying excellent in printability of microcapsule coated surface that enables stable free coating without breaking even under high-speed coating conditions. It is about paper.

[0002]

2. Description of the Related Art A recording material using a microcapsule containing a color former which chemically develops a color such as an electron-donating dye or a diazonium salt has been known for a long time and has been widely used. Such recording materials are roughly classified into pressure-sensitive recording materials and heat-sensitive recording materials. In particular, the pressure-sensitive recording material utilizes the fact that a microcapsule containing a color former is destroyed by pressure and a color-developed image is formed by reacting the color former with a developer. A type in which a color former layer comprising a capsule and a color developer layer containing a color developer are formed on the surface of separate supports, and the color former layer and the color developer layer are brought into pressure contact with each other, A self-coloring type in which microcapsules containing a coloring agent and a color developing agent on the same surface are laminated in the same layer or in separate layers is exemplified.

As a heat-sensitive recording material containing microcapsules, for example, a microcapsule containing a color former and a developer as described in JP-A-63-265682 and JP-A-1-1055782 are disclosed. There is a thermosensitive recording material in which a thermosensitive layer containing is formed on a support.

[0004] As a method for producing such a microcapsule containing a recording material, a coacervation method, an in-situ method, an interfacial polymerization method and the like utilizing the phase separation of gelatin are known. When a microcapsule having a polyurethane urea film is used as a microcapsule for a pressure-sensitive copying paper, the film has excellent flexibility, and thus a characteristic excellent in a balance between coloring and contamination can be obtained.

[0005] Such a recording material can be obtained by applying a coating solution containing microcapsules containing a color forming agent to a support and drying it. For coating such microcapsules, a non-contact metering type air knife coater is generally used in which the destruction of the microcapsules is suppressed in the liquid measurement after coating. As a coater
No. 16, JP-B-63-239, and JP-A-5
A curtain coating method as described in JP-A-7-39985 is also known.

[0006] The curtain coating method is a method of forming a free-fall vertical curtain of a coating liquid, coating the same on a support which is continuously running in a substantially horizontal direction, and forming a single-layer coating film. ,
Suitable for high-speed coating, it is a pre-metering method, and after a predetermined amount of coating liquid has been supplied in advance, there is no scraping step, so microcapsules are not broken, and changes in the coating liquid components do not occur. This is a coating method having advantages such as no coating.

The most important point to be noted for the coating liquid for curtain coating is that a substance such as an oil-soluble liquid that inhibits the formation of the curtain of the coating liquid is not mixed into the coating system. That is, when the oil-soluble inclusions are mixed into the coating liquid due to incomplete microcapsules or microcapsule breakage, the curtain breaks in an inverted V-shape from the lowermost portion of the curtain where the support comes into contact with the coating liquid. (Hereinafter, referred to as a V-shaped cut phenomenon). Generally, the free oil-soluble liquid that causes the V-shaped cut phenomenon is easily generated by the in-situ encapsulation method, and is less likely to be generated by the polyurethane urea capsule formed by the interfacial polymerization method, but is easily generated by the microparticles formed by the interfacial polymerization method. Even in the case of a capsule, a V-shaped cut phenomenon may easily occur when the microcapsule is unintentionally broken during coating, when the microcapsule particles aggregate or when the viscosity of the dispersion is low.

Japanese Patent Laid-Open No. 7-137439 discloses a measure against V-shaped cutting of a microcapsule dispersion for a curtain coater.
In the publication, the presence of a polyamine which is a material constituting the wall film is cited as a cause of the decrease in curtain stability of microcapsules having a polyurethane urea wall, and as a solution therefor, an alkali metal salt of an acrylic acid-based polymer is used. The method of adding is mentioned. However, in the experiments of the present inventors, V-shaped cuts may occur even in polyurethane urea microcapsules not using a polyvalent amine, and as a result of investigating the cause, the electric characteristics of the microcapsule surface were the largest. It turned out to be affecting. Due to the induction of the V-shaped cut phenomenon, not only unintended uncoated portions are generated, but also a large excess amount of coating is applied around the uncoated portions, which causes poor drying and wrinkles.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to induce a V-shaped cut phenomenon in a coating liquid for curtain coating using, as a main component, polyurethane urea wall microcapsules containing a coloring agent formed by an interfacial polymerization method. An object of the present invention is to provide a microcapsule dispersion for curtain coating, which forms a stable coating liquid curtain, and a pressure-sensitive copying paper coated with the dispersion.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present invention provides a high speed coating by setting at least a ζ potential of a polyurethane urea wall microcapsule containing a coloring agent in a specific range. V
It was found that a coating liquid capable of forming a stable curtain without generating a character cut phenomenon was obtained.

That is, in the first invention, the ウ potential of the polyurethane urea wall microcapsules containing the color former is −10.
It is a microcapsule dispersion liquid having a mV of not more than -60 mV or more.

Further, the second invention provides a polyurethane urea wall microcapsule containing at least a color former, microcapsule protective material particles, and a microcapsule in a coating solution comprising a binder having a ζ potential of -10 mV or less,
It is a microcapsule dispersion liquid characterized by being 60 mV or more. A sheet having a coating layer comprising at least these components is suitably used for a pressure-sensitive copying material in which both layers are opposed to a sheet having at least a layer containing a color developer.

In a third aspect of the present invention, a カ プ セ ル potential of a microcapsule in a coating solution comprising a polyurethane urea wall microcapsule containing at least a color former, a developer, a microcapsule protective material particle, and a binder is -10 mV.
The following is a microcapsule dispersion liquid characterized by having a voltage of -60 mV or more. A sheet having a coating layer comprising at least these components is suitably used for a self-coloring type pressure-sensitive copying material capable of forming an image with a single sheet.

Further, the fourth aspect of the present invention relates to the first to third aspects.
A pressure-sensitive copying paper in which the microcapsule dispersion according to the invention is applied to a support.

The ζ potential is a measure of the state of charge on the particle surface. Usually, an aqueous paper coating pigment or a water-insoluble binder-dispersed particle (a water-insoluble binder dispersion is referred to as a latex) is negatively charged. In many cases, the larger the absolute value of the ζ potential, the greater the repulsion between particles and the less likely they are to aggregate, so that stable coating is possible. It has been found that a number of factors such as the static and dynamic viscosities of coating liquids, thixotropic properties, and surface tension affect the curtain stability in curtain coating. At present, optimal conditions for obtaining a stable curtain are set while finely changing factors experimentally.

The present inventors have proposed a coating liquid using polyurethane urea wall microcapsules (hereinafter, unless otherwise specified, the term “microcapsules” means the polyurethane urea wall microcapsules according to the present invention). Attention was paid to ζ potential, which has not been considered so far, on a method of forming a stable curtain free from the V-shaped cut phenomenon, and the relationship between the value and the curtain stability was examined. It has been found that an extremely stable curtain can be obtained by setting the ζ potential of the microcapsules therein to −10 mV or less and −60 mV or more.

In the present invention, if the zeta potential of the microcapsules in the coating liquid exceeds -10 mV, a V-shaped cut phenomenon frequently occurs, and the amount of the liquid supplied to the coating head of the curtain coating apparatus in order to suppress this phenomenon. If the number is reduced, the curtain becomes more unstable, which is not preferable. On the other hand, even if the ζ potential of the microcapsules is less than −60 mV, the V-shaped cut phenomenon is not further improved, and it is substantially difficult in the range where existing materials are used. In the present invention, the ζ potential of the microcapsules is more preferably −20 mV or less and −60.
mV or more.

In the conventional microcapsule dispersion or coating solution containing microcapsules, the ζ potential of the microcapsules is not considered as described above,
For example, JP-A-4-265786 and JP-A-4-2
A coating liquid described in Examples in Japanese Patent No. 90538 was actually prepared, and a カ プ セ ル potential of microcapsules in this coating liquid was measured. In each case, a ζ potential of around +5 to -10 mV was obtained, and a curtain was formed. When a curtain is actually formed using a coating head of a curtain coating apparatus, a stable curtain cannot be obtained, and a V-shaped cut phenomenon is frequently induced, which is not suitable for stable coating. there were.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The components of the polyurethane urea wall microcapsule dispersion of the present invention and the method for producing the same will be described in detail below. A method for adjusting the potential within the range of the present invention and materials used for adjusting the ζ potential will be described.

Usually, the coating liquid containing microcapsules is
It is obtained by adding and mixing an additive such as a water-soluble binder, a latex, and particles of a microcapsule protective material to the microcapsule dispersion liquid. The value of ζ potential is different between the case where these additives are added to and mixed with microcapsules to form a coating liquid and the case where measurement is performed using the microcapsules alone. Represents the ζ potential of the microcapsules when a coating liquid is obtained by adding and mixing the same. Further, the カ プ セ ル potential of the microcapsules is 100
To 0.2 ml, a coating liquid serving as a sample is added in an amount of 0.2 ml, and a value obtained by measuring a well-dispersed sample is defined as the ζ potential of the microcapsule according to the present invention. The ζ potential according to the present invention is “LASER ZEE MODE” manufactured by PEN KEM, USA.
L501 "or the like.

As a method for adjusting the zeta potential of the microcapsules according to the present invention to the above range, an anionic compound is added as an emulsifier at the time of emulsifying and dispersing the oil-soluble liquid in the form of microdroplets in the microcapsule production step. A method of adjusting, a method of adjusting by adding an anionic compound before and after an additive at the time of adding and mixing various additives as desired after preparing microcapsules, adding and mixing all the constituent materials of the coating liquid Examples include a method of adding and adjusting an anionic compound to the obtained coating liquid, and a method of combining these. In the present invention, a method of adding and adjusting an anionic compound at the time of emulsifying and dispersing an oil-soluble liquid in the form of microdroplets when preparing microcapsules is preferable because the curtain-forming properties are the best.

The anionic compound according to the present invention includes fatty acid soap, metal soap, alkyl sulfate, polyoxyethylene alkyl ether sulfate, alkylbenzene sulfonate, dialkyl sulfosuccinate, or nonionic. And a polyfunctional anionic compound having a plurality of (many) anionic functional groups in the molecule.

Among these, in the present invention, when a compound having only one anionic functional group in a molecule is used as the anionic compound even if it is a monobasic acid or polybasic acid,
Although the ζ potential of the microcapsules decreases, the effect of suppressing the V-shaped cut phenomenon is insufficient, and the carboxyl group, sulfonic acid group, phosphoric acid, and phosphonic acid group are present in the molecule in preventing the V-shaped cut phenomenon. It is preferable to use a polyfunctional anionic compound having a large number of anionic functional groups such as

Therefore, in order to sufficiently achieve the effects of the present invention, a polyfunctional anion having a large number of anionic functional groups such as a carboxyl group, a sulfonic acid group, a phosphoric acid group, and a phosphonic acid group in a molecule. It is most preferable to use a water-soluble compound (hereinafter, referred to as an anionic polymer) as an emulsifier for emulsifying and dispersing an oil-soluble liquid in the form of fine droplets when preparing microcapsules.

Specific examples of the anionic polymer according to the present invention include poly (meth) acrylic acid, styrene-maleic anhydride copolymer hydrolyzate, α-alkylstyrene maleic anhydride copolymer hydrolyzate, methyl vinyl ether Maleic anhydride copolymer hydrolyzate, vinyl toluene maleic anhydride copolymer hydrolyzate, styrene benzyl methacrylate maleic anhydride copolymer hydrolyzate, ethylene maleic anhydride copolymer hydrolyzate, isobutylene maleic anhydride Copolymer hydrolyzate, vinyl acetate maleic anhydride copolymer hydrolyzate, vinyl acetate crotonic acid copolymer, (meth) acrylic acid (meth) acrylate copolymer, styrene (meth) acrylic acid (meth) ) Acrylic acid ester copolymer, polystyrenesulfonic acid, carboxymethyl Cellulose, alginic acid, carboxy-modified polyvinyl alcohol, sulfonated modified polyvinyl alcohol, and the like polyvinyl phosphoric acid, and alkali metal or ammonium salts. Those having a molecular weight of 5000 or more are preferred.

These anionic polymers are preferably used as emulsifiers when preparing microcapsules.
Simply mixing the anionic polymer in the coating liquid after microcapsulation is not sufficient. Although an effect is obtained when a dispersant having no ionic dissociation group such as polyvinyl alcohol and polyoxyethylene alkyl ether, which is usually called a nonionic dispersant, is used in combination with the anionic polymer according to the present invention. ,
When the nonionic dispersant is used alone, it does not exert a sufficient effect.

Next, the components constituting the microcapsules and the encapsulation method according to the present invention will be described. The microcapsule according to the present invention is a microcapsule having a polyurethane urea wall. Polyurethane urea wall microcapsules can be obtained by adding an oil-soluble liquid in which a polyvalent isocyanate, a color former and the like are dissolved, emulsifying and dispersing them in the form of microdroplets, and then reacting with a polyvalent amine or a polyhydric alcohol as desired. Specifically, in an aqueous solution containing an emulsifier, an oil-soluble liquid in which a polyvalent isocyanate, a color former, and the like are dissolved is added, and after emulsification and dispersion in the form of microdroplets using a known disperser, if necessary, Polyurethane urea wall microcapsules can be obtained by adding a polyamine or a polyhydric alcohol and stirring while heating.

As described above, the most suitable emulsifier used for producing the microcapsules according to the present invention is an anionic polymer. However, the anionic polymer does not necessarily have to be used alone, and at least 10% of the total emulsifier active ingredient is used. % By weight or more, preferably 30% by weight or more,
The effects of the present invention are sufficiently achieved. The concentration of the emulsifier component in the emulsifier aqueous solution containing the anionic polymer is 0.5 to
A range of 30% by weight, preferably 2-20% is preferred.

Specific examples of the polyvalent isocyanate used for the microcapsules according to the present invention include m-phenylene diisocyanate, 2,6-tolylene diisocyanate, naphthalene-1,4-diisocyanate, and 1,6-diisocyanate.
Hexamethylene diisocyanate, toluene-2,4
Isocyanate monomers such as 6-triisocyanate, adducts of hexamethylene diisocyanate and trimethylolpropane, adducts of tolylene diisocyanate and hexanetriol, polymethylene polyphenyl isocyanate, and buret adducts of hexamethylene diisocyanate. These are used alone or in combination.

Examples of the polyvalent amine which reacts with these polyvalent isocyanates to form a film include aliphatic amines such as ethylenediamine, diethylenetriamine, triethylenetetramine, and hexamethylenediamine, o-phenylenediamine, p-phenylenediamine, and the like. And aromatic amines such as diaminonaphthalene and xylenediamine. Examples of the polyhydric alcohol include ethylene glycol, glycerin, and pentaerythritol. When these polyhydric amines or polyhydric alcohols are used together with polyhydric isocyanates, 0.5 to 100% by weight, preferably 2 to 50% by weight, based on the polyhydric isocyanates.
%. These are used alone or in combination.

As the color former encapsulated in the microcapsule according to the present invention, a color former (also referred to as a dye precursor) which has been conventionally used for pressure-sensitive recording paper, heat-sensitive recording paper or the like can be used. Typical examples thereof include, but are not limited to, triarylmethane compounds, indolylphthalide compounds, diphenylmethane compounds, and anilinofluorane compounds. Specific examples include the following.

The triarylmethane compounds and indolylphthalide compounds include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (commonly called crystal violet lactone) and 3,3-bis ( p-dimethylaminophenylphthalide, 3- (p-
Dimethylaminophenyl) -3- (1,2-dimethylidondol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole-3-
Yl) phthalide, 3- (p-dimethylaminophenyl)
-3- (2-Phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-
Yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide,
3,3-bis (2-phenylindol-3-yl)-
5-dimethylaminophthalide and 3-p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl)
-6-dimethylaminophthalide and the like.

As the diphenylmethane-based compound, 4,
4'-bis (dimethylaminophenyl) benzhydryl benzyl ether, N-chlorophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine and the like.

As the anilinofluoran compound, 3
-Diethylamino-6-methyl-7-anilinofluoran, 3-piperidino-6-methyl-7-anilinofluoran 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-diethylamino-6- Methyl-7- (4-
Methylanilino) fluoran, 3-diethylamino-6
-Methyl-7- (4-n-butylanilino) fluoran, 3-diethylamino-6-methyl-7- (4-ethoxyanilino) fluoran, 3-pyrrolidino-6-methyl-7- (4-methylanilino) fluoran, 3-pyrrolidino-6-methyl-7- (4-n-butylanilino)
Fluoran, 3-pyrrolidino-6-methyl-7- (4-
Ethoxyanilino) fluoran, 3-di-n-propylamino-6-methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7-anilinofluoran, 3-di- n-pentylamino-6-methyl-7-
Anilinofluoran, 3- (N-methyl-NNn-propyl) amino-6-methyl-7-anilinofluoran,
3- (N-ethyl-NN-propyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N
-Isoamyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N-isobutyl) amino-
6-methyl-7-anilinofluoran, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-tetrahydrofuran-2-ylmethyl) Amino-6-methyl-7-
Anilinofluoran, 3- (N-ethyl-N-tetrahydrofurylmethyl) amino-6-methyl-7-anilinofluoran, 3- (N-methyl-N-tetrahydrofuran-2-yl) amino-6 Methyl-7-anilinofluoran, 3- (N-ethyl-N-tetrahydrofuryl)
Amino-6-methyl-7-anilinofluoran, 3-dimethylamino-6-methyl-7-anilinofluoran,
3- (N-methyl-N-ethyl) amino-6-methyl-
7-anilinofluoran, 3-isopentylamino-6
-Methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7- (2-fluoroanilino)
Fluoran, 3-dibutylamino-6-methoxy-7-
Anilinofluoran, 3-di-n-butylamino-6-
Methyl-7- (2,6-dimethylanilino) fluoran, 3- (N-ethyl-N-3-ethoxypropyl) amino-6-methyl-7-anilinofluoran, 3- (N
-Methyl-N-3-ethoxypropyl) amino-6-methyl-7-anilinofluoran, 3-diethylamino-
6-methyl-7- (3-trifluoromethylanilino)
Fluoran, 3-diethylamino-7- (3-trifluoromethylanilinofluoran, 3-diethylamino-
7- (2-chloroanilino) fluoran, 3-diethylamino-7- (3-chloroanilino) fluoran, 3-
Di-n-butylamino-7- (3-chloroanilino) fluoran, 3-diethylamino-7- (2-fluoroanilino) fluoran, 3-diethylamino-7- (2-
Methoxyanilino) fluoran, 3-pyrrolidino-7-
(2-chloroanilino) fluoran, 3-pyrrolidino-
7- (3-chloroanilino) fluoran, 3-pyrrolidino-7- (2-methoxyanilino) fluoran, 3-diethylamino-7- (2-isopentyloxycarbonylanilino) fluoran, and 3- (N-ethyl- N-
(p-tolyl) amino-6-methyl-7-anilinofluoran and the like.

In addition, xanthene compounds, spiropyran compounds, various diazonium salt compounds, and the like can be used as the color former according to the present invention. These can be used alone or in combination of two or more.

Examples of the oil-soluble liquid for dissolving the above color former include paraffin oil, cottonseed oil, soybean oil, corn oil, olive oil, castor oil, fish oil, lard oil, chlorinated paraffin, chlorinated diphenyl, dibutyl phthalate, dioctyl. Phthalate, tributyl phosphate, tricresyl phosphate, dibutyl maleate, o-dichlorobenzene, alkylated naphthalenes such as diisopropylnaphthalene, benzyl alcohol derivatives such as 1-phenyltrixylylethane, 1- (3,4-dimethylphenyl) ) -1-phenylethane and poly (1-4) isopropylnaphthalene.

The microcapsule protective material particles used in combination with the microcapsule dispersion liquid of the present invention are used to prevent the microcapsules from being destroyed when color development is not intended in the coating layer containing the microcapsules, ie, to protect the microcapsules. Particles. Therefore, it is important that the microcapsule protective material particles are at least larger than the diameter of the microcapsules according to the present invention and harder than the microcapsule particles (they are hardly deformed by pressing or the like). Specific examples of the microcapsule protective material particles according to the present invention include cellulose powder, starch particles, melamine particles, polyethylene particles, polystyrene particles, and talc, the maximum length of which is 5 μm or more, preferably 10 μm or more. Are preferred.

As the binder according to the present invention, conventionally known natural high molecular substances, modified natural polymers (semi-synthetic products) and synthetic products having binding ability and film forming ability can be used. Natural polymer substances used for the binder include sweet potato starch, potato starch, wheat starch, tapioca starch, starches such as corn starch, dextran, glucan, xanthan gum, and homopolysaccharides such as levan, and succinoglucan, pullulan, Microbial mucous such as heterosaccharides such as curdlan and xanthan gum; and proteins such as gelatin, casein, glue, and collagen.

Semi-synthetic products include propylene glycol alginate, viscose, methylcellulose, ethylcellulose, methylethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxypropylethylcellulose, carboxymethylhydroxyethylcellulose,
And cellulose derivatives such as hydroxypropylmethylcellulose phthalate, modified gums, processed starch and the like. Carboxymethyl guar gum for modified gum,
Hydroxypropyl guar gum, hydroxyethyl guar gum and the like. Processed starches include white dextrins, yellow dextrins, baked starches such as bridish gum, enzyme-modified dextrins such as enzyme dextrins and shardinger dextrins, acid-decomposed starches such as solubilized starch, and oxidized starches such as dialdehyde starch. Esterified starch such as pregelatinized starch, modified pregelatinized starch and unmodified pregelatinized starch, starch phosphate, fatty acid starch, sulfated starch, nitrate starch, xanthate starch, and carbamic acid starch, hydroxyalkyl starch, carboxyalkyl starch Etherified starch such as starch, sulfoalkyl starch, cyanoethyl starch, allyl starch, benzyl starch, carbamylethyl starch, and dialkylamino starch Methylol crosslinking starch, hydroxyalkyl crosslinked starch,
Crosslinked starch such as phosphoric acid crosslinked starch and dicarboxylic acid crosslinked starch, starch polyacrylamide copolymer, starch polyacrylonitrile copolymer, cationic starch polyacrylate copolymer, cationic starch vinyl polymer copolymer, starch polystyrene Examples include a maleic acid copolymer and a starch graft copolymer such as a starch polyethylene oxide copolymer.

Examples of the synthetic products include modified polyvinyl alcohols such as polyvinyl alcohol, partially acetalized polyvinyl alcohol, allyl-modified polyvinyl alcohol, polyvinyl methyl ether, polyvinyl ethyl ether, and polyvinyl isobutyl ether; poly (meth) acrylate; Poly (meth) acrylate partially saponified products, poly (meth) acrylic acid derivatives such as poly (meth) acrylamide, hydrophilic polymers such as polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, and vinylpyrrolidone vinyl acetate copolymer Or polyvinyl acetate, polyurethane, styrene-butadiene copolymer, carboxy-modified styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methylbutadiacrylate Emissions copolymer, and latices such as ethylene-vinyl acetate copolymer.

The anionic polymer can also be used in combination as the binder according to the present invention because of its excellent adhesion to the support. These binders can be used alone or in combination of two or more. The amount of the binder used is preferably in the range of 5 to 40% by weight based on the solid content of the microcapsules.

The color developing agent used in the present invention may be any compound capable of forming a color by reacting with the above color forming agent, such as a metal salt of a salicylic acid derivative, a phenol novolak resin, an inorganic solid acid, and the like. For example, combinations with couplers such as hydroxy aromatic compounds are known, and these combinations can be used alone or as a mixture.

If desired, inorganic or organic pigments may be added to and used in the microcapsule dispersion of the present invention. Specific examples thereof include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, calcium silicate, and the like. Examples include magnesium carbonate, basic magnesium carbonate, barium sulfate, titanium dioxide, zinc oxide, silicic acid, silicon dioxide, aluminum hydroxide, alumina, urea formalin resin, nylon resin, polyethylene resin, and polystyrene resin. Further, lubricants such as higher fatty acid metal salts such as zinc stearate and calcium stearate, and waxes such as paraffin, paraffin oxide, polyethylene, polyethylene oxide, stearamide, and caster wax may be used in combination.

Various materials constituting the microcapsule dispersion of the present invention and the coating liquid containing the microcapsules are stirred and mixed to form a uniform dispersion, and then the coating liquid for curtain coating described in the present invention. Are shared as The solid content of the coating solution is adjusted to 10 to 50%, preferably 20 to 40%, and applied. Further, the viscosity of the coating liquid is one of the conditions that give the stability of the curtain, and the B-type viscosity at 20 ° C. is preferably 5 to 500 cps, more preferably 50 to 300 cps.

The microcapsules obtained by the present invention are coated on high quality paper, synthetic paper, etc. together with additives to obtain pressure-sensitive copying paper. In addition, by coating with a color developing agent that forms a color forming agent or a microcapsule containing a color developing agent, a self-coloring type pressure-sensitive recording paper or heat-sensitive recording that can record an image with a single sheet by applying pressure or heating. Paper and the like are obtained.

[0046]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. Note that the ζ potential shown in the present invention is
"LASER ZEE MODEL" manufactured by EN KEM
501 ". The measurement conditions were as follows: 0.2 ml of the coating liquid serving as a sample in 100 ml of ion-exchanged water.
The sample was added and dispersed well to prepare a sample for measurement. The upper paper for pressure-sensitive copying paper in the examples means a sheet provided with a layer containing microcapsules on one side of a support, and a layer containing a color developer on one side of the support. Is referred to as a lower sheet.

Example 1 Sumidur N-3200 (manufactured by Sumitomo Bayer Urethane,
6 parts by weight of a burette type aliphatic isocyanate prepolymer) and 5 parts by weight of crystal violet lactone as a color former are dissolved by heating in 89 parts by weight of Hisol SAS-296 (manufactured by Nippon Petrochemical Co., Ltd., aromatic high boiling point solvent), 100 parts by weight of an oil-soluble liquid in which a color former was dissolved was obtained. This oil-soluble liquid is added to 100 parts by weight of an emulsifier aqueous solution in which 6 parts by weight of a sodium salt of a hydrolyzate of a styrene-maleic anhydride copolymer as an emulsifier is adjusted to pH 7 so that the volume average particle diameter becomes 8 μm. Vigorous stirring was performed. Then, while stirring this emulsion, 50 parts by weight of water was added.
The mixture was heated and stirred at 1 ° C. for 1 hour to obtain a polyurethane urea wall microcapsule dispersion.

With respect to 100 parts by weight in terms of dry weight of the obtained microcapsules, 30 parts by weight of wheat starch as microcapsule protective material particles, 15 parts by weight of a styrene butadiene latex as a binder, and polyvinyl alcohol (Kuraray, PVA) -110; 15 parts by weight of PVA-110 were used for "polyvinyl alcohol" shown below) and water, and a microcapsule dispersion coating solution for paper on a pressure-sensitive copying paper having a solid content concentration of 30% was prepared. Obtained.

The zeta potential of the microcapsules in the microcapsule dispersion coating solution was measured to be -55 mV. This coating liquid was applied to a head gap of 0.3 mm and a width of 1 m.
When a continuous coating was performed on one side of 40 g / m ^{2 high} quality paper at a flow rate of 9 liters / minute using a coating machine having a coating head of a curtain coating apparatus, a stable curtain was formed. Coating was possible at a speed of 800 m / min without any V-shaped cut. When a copy-forgery-inhibited pattern printing was performed on the microcapsule surface of the pressure-sensitive copying paper obtained by this coating using an offset printing machine, a printed matter having both good inking property and printing durability was obtained. When the upper and lower sheets of pressure-sensitive copying paper obtained by this coating were alternately overlapped and a latex-based adhesive was applied to the end, a form slip combined with an appropriate strength was obtained.

Example 2 10 parts by weight of Takenate 110N (manufactured by Takeda Pharmaceutical, aliphatic isocyanate prepolymer) and 10 parts by weight of crystal violet lactone were mixed with Hysol SAS-296.
The mixture was heated and dissolved in 80 parts by weight of an aromatic high boiling point solvent (manufactured by Nippon Petrochemical) to obtain 100 parts by weight of an oil-soluble liquid in which a color former was dissolved. 100 parts by weight of an emulsifier aqueous solution obtained by dissolving 1 part by weight of Sumirez Resin DS-40K (a styrene maleic anhydride resin manufactured by Sumitomo Chemical Co., Ltd.) as an emulsifier and 4 parts by weight of polyvinyl alcohol and adjusting the pH to 8 with this oil-soluble liquid. And stirred vigorously until the volume average particle diameter became 3.5 μm. Then, 50 parts by weight of water was added to the emulsion while stirring, and the mixture was heated and stirred at 60 ° C. for 1 hour to obtain a polyurethane urea wall microcapsule dispersion.

Salicylic acid developer 50 parts by weight, wheat starch 50 parts by weight, styrene butadiene latex 25 parts by weight, polyvinyl alcohol 15 parts by weight, and water Was added to obtain a self-coloring type microcapsule dispersion coating liquid for a pressure-sensitive copying paper having a solid content of 30%.

When the zeta potential of the microcapsules in the microcapsule dispersion coating liquid was measured, it was -35 mV. This coating liquid was applied to a head gap of 0.3 mm and a width of 1 m.
When a continuous coating was performed on one side of a 40 g / m ^{2 high-} quality paper at a flow rate of 13 liters / minute using a coating machine having a coating head of a curtain coating apparatus, a stable curtain was formed. Coating was possible at a processing speed of 800 m / min without any V-shaped cut.

Example 3 In Example 1, 4 parts by weight of a sodium salt of a styrene-maleic anhydride copolymer was replaced with 4 parts by weight of a sodium salt of a styrene-maleic anhydride copolymer hydrolyzate used as an emulsifier. Encapsulation was performed in the same manner as in Example 1 except that 100 parts by weight of an emulsifier aqueous solution in which 2 parts by weight of alcohol was dissolved and the pH was adjusted to 7 was used.
A polyurethane urea wall microcapsule dispersion was obtained.
Further, using this microcapsule dispersion, a microcapsule dispersion coating liquid for paper on pressure-sensitive copying paper was obtained in the same composition as in Example 1.

The カ プ セ ル potential of the microcapsules in the microcapsule dispersion coating solution was measured to be -48 mV. This coating liquid was applied to a head gap of 0.3 mm and a width of 1 m.
When a continuous coating was performed on one side of ^high- quality paper of 40 g / m ² at a flow rate of 9 liters / minute using a coating machine having a coating head of a curtain coating apparatus, a stable curtain was formed. Coating was possible at a processing speed of 800 m / min without any V-shaped cut, and a pressure-sensitive copying paper having good printability and good glueability was obtained.

Example 4 In Example 1, maleic acid-modified polyvinyl alcohol (Gosenal T350, manufactured by Nippon Synthetic Chemical Industry) was used in place of 6 parts by weight of the sodium salt of the hydrolyzate of styrene-maleic anhydride used as an emulsifier. Encapsulation was carried out in the same manner as in Example 1 except that 6 parts by weight of the emulsifier aqueous solution adjusted to pH 7 was adjusted to 7 to obtain a polyurethane urea wall microcapsule dispersion liquid. Further, using this microcapsule dispersion, a microcapsule dispersion coating liquid for paper on pressure-sensitive copying paper was obtained in the same composition as in Example 1.

The カ プ セ ル potential of the microcapsules in the microcapsule dispersion coating solution was measured to be -15 mV. This coating liquid was applied to a head gap of 0.3 mm and a width of 1 m.
When a continuous coating was performed on one side of ^high- quality paper of 40 g / m ² at a flow rate of 9 liters / minute using a coating machine having a coating head of a curtain coating apparatus, a stable curtain was formed. Coating was possible at a processing speed of 800 m / min without any V-shaped cut, and a pressure-sensitive copying paper having good printability and good glueability was obtained.

Example 5 Of the emulsifiers used in the microencapsulation step of Example 1, the sodium salt of the styrene-maleic anhydride copolymer hydrolyzate was replaced with the same amount of polyvinyl alcohol.
50 parts by weight of an aqueous solution obtained by dissolving 10 parts by weight of ethylene maleic anhydride copolymer (EMA-31, manufactured by Monsanto USA) in a polyurethane urea wall microcapsule dispersion prepared by using 6 parts by weight of polyvinyl alcohol alone as an emulsifier Was carried out in the same manner as in Example 1 except for adding, to obtain a polyurethane urea wall microcapsule dispersion liquid. Further, using this microcapsule dispersion liquid, a microcapsule dispersion coating liquid for pressure-sensitive copying paper was prepared in the same manner as in Example 1.

The zeta potential of the microcapsules in this microcapsule dispersion coating solution was measured to be -20 mV. This coating liquid was applied to a head gap of 0.3 mm and a width of 1 m.
When a continuous coating was performed on one side of ^high- quality paper of 40 g / m ² at a flow rate of 9 liters / minute using a coating machine having a coating head of a curtain coating apparatus, a stable curtain was formed. Coating was possible at a processing speed of 800 m / min without any V-shaped cut, and a pressure-sensitive copying paper having good printability and good glueability was obtained.

Comparative Example 1 Of the emulsifiers used in the microencapsulation step of Example 1, the sodium salt of the hydrolyzate of styrene-maleic anhydride copolymer was replaced with the same amount of polyvinyl alcohol. Encapsulation was performed in the same manner as in Example 1 except that 6 parts by weight were used, to obtain a polyurethane urea wall microcapsule dispersion liquid. Further, using this microcapsule dispersion liquid, a microcapsule dispersion coating liquid for pressure-sensitive copying paper was prepared in the same manner as in Example 1.

The カ プ セ ル potential of the microcapsules in the microcapsule dispersion coating solution was measured to be -2 mV. An attempt was made to apply this coating liquid using the same coating machine as in Example 1, but a stable curtain was not formed and continuous coating was difficult.

Comparative Example 2 Sumireze resin DS used in Example 2 was added to the polyurethane urea wall microcapsule dispersion obtained in Comparative Example 1.
A microcapsule-dispersed coating liquid for pressure-sensitive copying paper was obtained in the same manner as in Comparative Example 1 except that 5 parts by weight of -40 K was added.

The zeta potential of the microcapsules in the microcapsule dispersion coating solution was measured to be -8 mV. The application of this coating liquid was attempted using the same coating machine as in Example 1. However, a stable curtain was not formed and continuous coating was difficult, but the flow rate of the coating liquid was increased. Somehow, continuous coating was made possible and pressure-sensitive copying paper was obtained. When the same background pattern printing as in Example 1 was performed on the microcapsule surface of this pressure-sensitive copy paper, the ink inking property was poor and the reproducibility of the fine lines was poor.

Comparative Example 3 In the microencapsulation step of Example 1, 8 parts by weight of polyvinyl alcohol and 0.5 part by weight of sodium salt of carboxymethyl cellulose were dissolved by heating instead of the styrene-maleic anhydride copolymer as an aqueous emulsifier solution. Using 100 parts by weight of the aqueous solution, encapsulation was performed in the same manner as in Example 1 to obtain a polyurethane urea wall microcapsule dispersion liquid. Further, using this microcapsule dispersion liquid, a microcapsule dispersion coating liquid for pressure-sensitive copying paper was prepared in the same manner as in Example 1.

The カ プ セ ル potential of the microcapsules in this microcapsule dispersion coating solution was measured to be -5 mV. Further, this coating liquid was applied using the same coating machine as in Example 1, but a stable curtain was not formed and continuous coating was difficult.

[0065]

When the coating liquid containing the polyurethane urea wall microcapsules is applied using a curtain coating apparatus, the カ プ セ ル potential of the microcapsules in the coating liquid is -10 mV.
Hereinafter, by setting it to −60 mV or more, it became possible to obtain a microcapsule dispersion liquid for curtain coating suitable for high-speed coating without causing the V-shaped cut phenomenon. Further, using the microcapsule dispersion, a pressure-sensitive copying paper having good coloring properties, a middle sheet, and a self-coloring type pressure-sensitive copying paper were obtained by a curtain coating method. Also, it was excellent in suitability for high-speed printing on the surface to which microcapsules were applied, and extremely good in suitability for gluing the edges at the same time when creating a slip.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Noriyoshi Mori 3-4-2, Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Paper Mills Co., Ltd.

Claims (4)

[Claims] 1. A polyurethane urea wall microcapsule containing a color former has a ζ potential of −10 mV or less and −60 m or less.
V. The microcapsule dispersion for curtain coating. 2. The microcapsule in a coating liquid comprising at least a polyurethane urea wall microcapsule containing a color former, microcapsule protective material particles, and a binder, has a ζ potential of −10 mV or less and −60 mV or more. Microcapsule dispersion for curtain coating. 3. A urea potential of the microcapsules in a coating liquid comprising a polyurethane urea wall microcapsule containing at least a color former, a developer, a microcapsule protective material particle, and a binder is -10 mV or less, and -60 mV or more. A microcapsule dispersion for curtain coating. 4. A pressure-sensitive copying paper having the microcapsule dispersion liquid for curtain coating according to claim 1 applied to a support.