GB2257153A - Microcapsule ink composition - Google Patents

Description

22371 4

MICROCAPSULE INK COMPOSITION FIELD OF THE INVENTION

The present invention relates to a microcapsule ink composition and more particularly to a Uv-curing type 5 microcapsule ink composition.

PRIOR ART

Microcapsules, varying in particle size from several microns to tens microns, comprise an internal phase covered with a natural or synthetic polymer film, the internal phase including, e.g., pharmaceuticals, agricultural chemicals, perfumes, dyes, liquid crystals, thermochromic materials. adhesivesf etc. Microcapsules have great advantages of, among others, being capable of chemically or physically protecting the internal phase and enabling is handling liquids as solids. For these advantages, microcapsules are widely used in the fields of pressure sensitive recording media or sheets and other products.

Well known is a pressure sensitive recording medium or sheet utilizing the color-forming reaction between an electron donating chromogenic material such as crystal violet lactone, benzoylleucomethylene blue or the like and an electron accepting color developer such as activated clay, phenolic resin, a polyvalent metal salt of salicylic acid derivative or the like.

Such a pressure sensitive recording medium generally comprises (a) a top sheet prepared by coating the bottom side of a support sheet with a dispersion of microcapsules each containing a chromogenic material in the core as prepared by coacervation, interfacial polymerization, insitu polymerization or the like technique, (b) an under sheet prepared by coating the top side of a support sheet with a color developer, and if desired (c) a middle sheet prepared by coating one side of a support sheet with said dispersion of microcapsules and the other side with said color developer.

Further known is a so-called self-contained type pressure-sensitive recording sheet comprising discrete layers or a mixed layer of said microcapsules and color developer composition on the same side of a support as well as a system wherein a microcapsule layer is formed over the rear (non-coated) side of said self-contained type pressure sensitive recording paper. These sheets are used either independently or in combination with the aforesaid top sheet, middle sheet and/or under sheet.

The microcapsule layer of such a pressure sensitive recording sheet is generally formed by coating a support sheet with an aqueous dispersion of microcapsuies using a large-sized coating machine (hereinafter referred to as "coating process"). There is also known a group of processes wherein a microcapsule ink composition is printed on a substrate sheet by means of a printing machine for, for example, flexographic printing, gravure printing, screen printing, letterpress printing, offset printing or the like (hereinafter referred to collectively as "printing process").

The printing process is more suitable than the coating process for the production of a diversity of recording media in small amounts because it entails little losses even when the lot size is small. For example, the printing process is suited for the production of a pressure sensitive recording sheet designed to form an extraordinary color (red, for example), which is usually produced in small lots.

Furthermore, the printing process allows the microcapsule coating to be applied exclusively to selected areas on the support sheet so that it is more economical than the coating process which applies an expensive microcapsule coating composition to the entire surface of a support. A pressure sensitive recording sheet (a top sheet or a middle sheet) having a plurality of areas, each of which is designed to form a different color, can be manufactured by printing back side of a wood-free paper sheet or back side of an under sheet (bottom sheet), with microcapsule inks adapted to yield different colors in a predetermined pattern, or also manufactured by partially printing on a microcapsule layer of a top sheet or middle sheet coated all over (with a microcapsule composition) by a coating process with a microcapsule ink composition for a color different from the color given by the coated microcapsule layer on which it is superimposed, as described in Japanese Unexamined Patent Publication (Kokai) No. 3 01360/1989. Thus, this process enables production of a variety of characteristic products.

While the printing process is, thus, a production system having many such beneficial features, letterpress and offset printing processes pose the problems that oil is released from microcapsules with a lower efficiency because of hindrance from other components than microcapsules which are contained with a low content relative to the solids content (all the solids after drying and curing of the ink), resulting in poor color forming property. Particularly when a UV-curing type microcapsule ink composition is used in letterpress or offset printing process, this tendency is made conspicuous. Therefore UVtype microcapsule ink compositions suitable f or use have not been developed hitherto.

SUMMARY OF THE INVENTION

To obviate these problems, the present inventors have 25 conducted extensive research and found that when a UV- 1 curing type microcapsule ink composition contains a specific ethylenically unsaturated compound, the composition provides a sheet having a high quality conventionally not achieved.

The present invention provides a microcapsule ink composition comprising microcapsules, anethylenically unsaturated compound and a photo polymerization initiator, the composition comprising, as the ethylenically unsaturated compound, at least one member se lected from the group consisting of:

(a) a liquid polybutadiene (neth)acrylate, (b) a liquid hydrogenated polybutadiene (meth)acrylate, (c) a compound represented by the formula W 0 X Y j 11 1 1 CH 2 =C-C O-CH-CH 0 - Z ( 1) is wherein W represents a hydrogen atom or a methyl group, X and Y are the same and each represents a hydrogen atom, or one of X and Y represents a hydrogen atom and the other representp a methyl group, Z is an unsdbstituted or substituted aryl group, and n is an integer of 1 or more, and, (d) a compound represented by the formula X 1 0 OH 1 11 1 1 CH 2 = C - C - 0 - C H 2 - C H - C H 2 0 - Y ( II) wherein X 1 represents a hydrogen atom or a methyl group, Y 1 is an unsubstituted or substituted aryl or alkyl group having not more than 34 carbon atoms.

The microcapsule ink composition of the invention has an excellent colorforming property. The microcapsule ink composition can be used in flexographic printing, gravure printing, screen printing, letterpress printing, of f set printing and other printing processes, and can exhibit pronouncedly improved properties such as color-forming ability particularly when used in letterpress printing and offset printing processes.

DETAILED DESCRIPTION OF THE INVENTION

According to one preferred embodiment of the invention, the microcapsule ink composition of the invention comprises, as the ethylenically unsaturated compound, at least one of (a) a liquid polybutadiene (meth)acrylate and (b) a liquid hydrogenated polybutadiene (meth)acrylate.

According to another embodiment of the invention, the microcapsule ink composition comprises, as the ethylenically unsaturated compound, at least one of (c) the compound of the f ormula (I) and (d) the compound of the formula (II).

There are two types of polybutadienes, one being 1,2linkage type and the other being 1, 4-linkage type. The liquid polybutadiene (meth) acrylate (a) is prepared by chemically modifying a functional group- containing liquid polybutadiene with (meth) acryloyl group, and the liquid hydrogenated polybutadiene (meth-)acrylate (b) is prepared by chemically modifying a functionalgroup-containing liquid hydrogenated polybutadiene (which is prepared by hydrogenating a liquid polybutadiene) with (meth)acryloyl group. The functional group-containing liquid polybutadiene or liquid hydrogenated polybutadiene can be prepared by adding a functional group to a liquid polybutadiene or liquid hydrogenated polybutadiene by various conventional methods. For example, when maleic anhydride is added by ene addition reaction, a maleinized liquid polybutadiene is prepared. Upon reaction with an is epoxidizing agent, an epoxidized liquid polybutadiene or an epoxidized liquid hydrogenated polybutadiene is prepared.

The method of addition of functional groups are not particularly limited and various conventional methods are used. As the liquid hydrogenated polybutadiene (meth)acrylates, liquid hydrogenated 1,2-polybutadiene (ineth)acrylates are preferred.

Preferable examples of the liquid polybutadiene (meth)acrylate and the liquid hydrogenated polybutadiene (meth)acrylate usable as the components (a) and (b) respectively include:

a liquid polybutadiene (meth)acrylate prepared by subjecting to urethane addition reaction 2-hydroxyethyl (meth)acrylate and the hydroxyl group of a hydroxyl- containing liquid polybutadiene via 2,4-tolylene diisocyanate; ii) a liquid polybutadiene (meth)acrylate prepared by esterifying 2hydroxyethyl (meth)acrylate and maleinized polybutadiene wherein maleic anhydride is added to the polybutadiene chain by ene addition reaction; iii) a liquid polybutadiene (meth)acrylate prepared by subjecting the carboxyl group of a carboxyl-containing liquid polybutadiene and glycidyl acrylate to epoxy esterification; iv) a liquid polybutadiene (meth)acrylate prepared by 15 esterifying (meth)acrylic acid and an expoxidized polybutadiene produced by causing an expoxidizing agent to act on a liquid polybutadiene; v) a liquid polybutadiene (meth)acrylate prepared by reaction for removal of hydrochloric acid between a hydroxyl-containing liquid polybutadiene and (meth)acrylic acid chloride; and vi) a liquid hydrogenated 1,2 polybutadiene (meth)acrylate prepared by subjecting to urethane addition reaction 2hydroxyethyl (meth)acrylate and the hydroxy group of liquid hydrogenated 1,2 polybutadiene glycol via 2,4-tolylene 1 -g- diisocyanate.

The liquid polybutadiene (meth) acrylates and liquid hydrogenated polybutadiene (meth)acrylate as described above are known per se and commercially available, and any 5 of those as disclosed by Shigeru NAKAMURA, "Application and Market of UV-EB curing technique", published on September 29, 1989, Kabushiki Kaisha CMC, pp. 46-55, under. the supervision of Yoneho TABATA, is usable. Among the liquid polybutadiene (meth)acrylates and liquid hydrogenated polybutadiene (meth) acrylates, it is pref erable to use those having a number average molecular weight of about 500 to about 10,000, preferably about 500 to about 5,000, and having a viscosity of about 1,000 to about 100,000 cps, particularly about 1,000 to about 10,000 cps. Furthermore, it is preferable to use those containing 1.5 to 3 (meth)acryloyl groups on the average per molecule. Generally, the liquid polybutadiene acrylates and liquid hydrogenated polybutadiene acrylates have ability to be cured more rapidly upon UV-irradiation than the corresponding methacrylates, and therefore are preferred.

In the compound of the f ormula (I) useful as the component (C) in the present invention, preferable examples of unsubstituted aryl group represented by Z are a phenyl group, a naphthyl group and the like. Preferable examples of the substituted aryl group are a phenyl group, a naphthyl group and the like, each having 1 to 3 substitutents, pref erably one substituent. Examples of such substitutent are C i-C 20 alkyl group (preferably C i-C 12 alkyl group), halogen atom, hydroxyl group or the like. It is preferable that n is an integer of 1 to 20, preferably 1 to 10.

Examples of preferred compounds of the formula (I) are 2-phenoxyethyl (ineth)acrylate, 2-(nonylphenoxy)ethyl acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene bromophenoxydiethylene butylphenoxydiethylene butylphenoxydipropylene hexylphenoxydiethylene is hexylphenoxydipropylene glycol octylphenoxydiethylene glycol octylphenoxydipropylene nonylphenoxydiethylene nonylphenoxydipropylene 20 dodecylphenoxydiethylene glycol glycol glycol glycol glycol (meth) acrylate, (meth) acrylate, (meth)acrylate, (meth)acrylate, (meth) acrylate, (meth)acrylate, (raeth)acrylate, glycol (meth)acrylate, glycol (meth)acrylate, glycol (meth)acrylate, glycol dodecylphenoxydipropylene glycol naphthoxydiethylene glycol naphthoxydipropylene glycol butylnaphthoxydiethylene glycol bromonaphthoxydiethylene glycol (meth)acrylate, (meth)acrylate, (meth) acrylate, (meth) acrylate, (meth)acrylate, (meth)acrylate, hydroxyphenoxypolyethylene glycol (meth)acrylate, chlorophenoxypolypropylene glycol (meth)acrylate, butylphenoxypolyethylene glycol (meth)acrylate, butylphenoxypolypropylene glycol (meth)acrylate, hexylphenoxypolyethylene glycol (meth)acrylate, hexylphenoxypolypropylene glycol (meth)acrylate, octylphenoxypolyethylene glycol (meth)acrylate, octylphenoxypolypropylene glycol (meth)acrylate, nonylphenoxypolyethylene glycol (meth)acrylate, nonylphenoxypolypropylene glycol (meth)acrylate, dodecylphenoxypolyethylene glycol (meth)acrylate, dodecylphenoxypolypropylene glycol (meth)acrylate, naphthoxypolypropylene glycol (meth)acrylate, etc. Among these examples, those containing a polyethylene glycol moiety or propylene glycol moiety are preferably 1 to 20, more preferably 1 to 10 in the polymerization degree of ethylene glycol or propylene glycol.

In the compound of the formula (II) useful as the component (d) in the present invention, preferable examples of unsubstituted ary group represented by Y 1 are a phenyl group, a naphthyl group and the like. Preferable substituted aryl groups are C 6- C34 substituted aryl groups, such as a phenyl group, a naphthyl group and the like each of which is substituted with 1 to 3, preferably 1 to 2, substituents selected from C 1-C 20 alkyl groups (preferably -12c I-C 12 alkyl groups), halogen atoms and the like. Preferable substituted or unsubstituted alkyl groups represented by Y1 and having 34 carbon atoms or less are unsubstituted alkyl groups having 1 to 34 carbon atoms, more preferably 2 to 12 carbon atoms, and alkyl groups having 1 to 34 carbon atoms, more preferably 2 to 12 carbon atoms, and substituted with 1 to 3 halogen atoms, more preferably one halogen atom.

Desirable as the compound of the formula (II) are 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-hydroxy-3-(p bromophenoxy)propyl (meth)acrylate, 2-hydroxy-3-(o- methylphenoxy)propyl methylphenoxy)propyl ethylphenoxy)propyl propylphenoxy)propyl butylphenoxy)propyl dimethylphenoxy)propyl hexylphenoxy)propyl octylphenoxy)propyl nonylphenoxy)propyl (meth)acrylate, (meth)acrylate, (meth)acrylate, 2-hydroxy-3-(p 2-hydroxy-3-(p 2-hydroxy-3-(p (meth)acrylate, 2-hydroxy-3-(p (meth)acrylate, 2-hydroxy-3(o,p (meth)acrylate, 2-hydroxy-3-(p (meth)acrylate, 2-hydroxy-3-(p (meth)acrylate, 2-hydroxy-3-(p (neth) acrylate, dodecylphenoxy)propyl (meth)acrylate, naphthoxypropyl (neth)acrylate, (butylnaphthoxy)propyl (neth)acrylate, 2-hydroxy-3-(p 2-hydroxy-3 2-hydroxy-3 2-hydroxy-3 ethoxypropyl (neth)acrylate, 2-hydroxy-3-propoxypropyl (meth)acrylate, 2-hydroxy-3-butoxypropyl (meth)acrylate, 2- 1 hydrOXy-3-dodecyloxypropyl (meth)acrylate, 2-hydroxy-3-(4chlorobutoxy) propyl (meth) acrylate, etc. among which the acrylates are preferable.

Another ethylenically unsaturated compound which is conventional in the art may be used conjointly with at least one of the components (a) to (d) in the present invention. Examples of such conventional ethylenically unsaturated compounds include photopolymerizable monomers and photopolymerizable prepolymers. Examples of photopolymerizable monomers are methyl methacrylate, butyl methacrylate, 2-ethoxyethyl acrylate, cyclohexyl methacrylate, benzyl methacrylate, trifluoroethyl methacrylate, 3-sulfopropyl methacrylate potassium salt, N (3-sulfopropyl)-N-methacryloylamidopropyl-N,N-dimeth- ylammonium betaine, glycidyl methacrylate, allyl methacrylate, dimethylaminoethyl methacrylate, 3-chloro-2 hydroxypropyl methacrylate, benzyl acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, 1 methoxycyclododecadienyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2,6 dibromo-4-t butylphenyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethoxydiethylene glycol acrylate, propylene glycol diacrylate, propylene glycol diraethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, 1,2-butanediol diacrylate, 1,2-butanediol-dimethacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol diacrylate, 1, 6-hexanediol dimethacrylate, neopentyl glycol diacrylate, glycerol dimethacrylate, glycerol methacrylate acrylate, trimethylolpropane diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol 10 tetraacrylate, hydroxypivalic acid neopentyl glycol ester diacrylate, 2,2-bis[4-(acryloyloxydiethoxy)phenyl]propane, hydroxypivalic acid neopentyl glycol ester-caprolactone adduct diacrylate, hydroxypivaldehyde-trimethylolpropane acetal diacrylate, diallyloxydiacryloyloxycyclohexane, 15 trimethylolpropane-propylene oxide adduct triacrylate, dipentaerythritol lower f atty acid and acrylic acid esters, dipentaerythritol-caprolactone adduct acrylate, dioctyl-2 acryloyloxyethyl phosphate, diphenyl-2-acryloyloxyethyl phosphate and the like. Examples of useful photopolymerizable prepolymers are polyester acrylate, polyurethane acrylate, epoxyacrylate, polyether acrylate, oligoacrylate, alkyd acrylate, polyol acrylate and the like.

The polyester acrylates can be prepared by f irst 25 providing a polyester and then acrylating the polyester.

Examples of the polyhydric alcohol that can constitute said polyester are ethylene glycol, 1,4-butanediol, 1,6hexanediol, diethylene glycol, trimethylolpropane, dipropylene glycol, polyethylene glycol (preferably having a molecular weight of about 400), polypropylene glycol (preferably having a molecular weight of about 400), pentaerythritol, dipentaerythritol or the like. Examples of the polybasic acid to be reacted with the polyvalent alcohol are phthalic acid, adipic acid, maleic acid, trimellitic acid, itaconic acid, succinic acid, terephthalic acid, alkenylsuccinic acid or the like.

The polyurethane acrylates can be prepared by reacting an isocyanate group-containing compound such as tolylene diisocyanate with a hydroxy group-containing acrylate such as 2-hydroxyethyl acrylate. In this case, it is possible to use an isocyanate group-containing compound which has a polyester structure in the center of the molecule and isocyanate groups in the terminal ends, which is acrylated.

The epoxy acrylates can be classified into a bisphenol A type, novolac type and alicyclic type, and basically prepared by esterifying the epoxy groups of epoxy resin with acrylic acid to form acryloyl groups.

The photopolymer iz able prepolymers on their own can form a film upon ultraviolet curing and generally have a viscosity of about 500 to about 200,000 cps. The photopolymerizable monomers are often used as admixed with said phtopolymerizable prepolymer so as to dilute the prepolymer for reducing the viscosity thereof. The photopolymerizable monomers generally have a viscosity of about I to about 500 cps.

The photopolymerizable prepolymers have a greater effect on the properties of the cured ink composition.. The photopolymerizable monomers have the advantage of reducing the viscosity of ultraviolet-curable composition to thereby facilitate the coating operation.

When the components (a) to (d) are used in combination with another ethylenically unsaturated compound conventional in the art, a ratio of the f ormer to the latter can be selected from a wide range and the ratio by weight ranges usually from 95: 5 to 15: 85, preferably from 90: 10 to 30: 70.

The ethylenically unsaturated compound comprising at least one of the components (a) to (d) is used preferably in an amount of about 9 to about 95% by weight, more preferably about 30 to about 90% by weight, based on the microcapsule ink composition. The ethylenically unsaturated compound comprising at least one of the components (a) and (b) is used in an amount of preferably about 30 to about 95% by weight, more preferably about 30 to about 90% by weight, based on the microcapsule ink -17 composition. The ethylenically unsaturatedcompound comprising at least one of the components (c) and (d) is used in an amount of about 9 to about 94% by weight, preferably about 30 to about 90% by weight, based on the microcapsule ink composition.

The ethylenically unsaturated compound comprising at least one of the components (a) to (d) can be used singly or a mixture of such compounds can be used, optionally in combination with the above another ethylenically unsaturated compound conventional in the art. In any case, the viscosity of the ethylenically unsaturated compound or a mixture of the ethylenically unsaturated compounds is preferably in the range of about 1 to about 10,000 cps, more preferably in the range of about I to about 5, 000 cps, as determined by Brookfield viscometer at 25C and 60 rpm. If the above compound or a mixture of the compounds having a viscosity of over 10,000 cps is used, the resulting ink permeates a substrate to a lesser degree and the resulting color will tend to be poor.

The photo polymerization initiator useful in the invention may be conventional one, and includes, inter alia, aromatic ketones, quinones, ethers and nitro compounds, such as benzoquinone, phenanthrenequinone, naphthoquinone, diisopropylphenanthrenequinone, benzoisobutyl ether, benzoin, benzoin methyl ether, furoin butyl -is- ether, Michler's ketone, Michlerys thioketone, fluorenone., trinitrof luorenone, fl-benzoylaminonaphthalene and so on. The photo polymerization initiator is used in an amount of about I to about 20 parts by weight, preferably about 1 to about 10 parts by weight, per 100 parts by weight of the ethylenically unsaturated compound.

A sensitizer may be used to accelerate the polymerization. Useful sensitizers include, inter alia, triethanolamine, N-methyldiethanolamine, N,N- dimethylethanolamine, N-methylmorpholine and so on. The sensitizer is used in an amount of about 0 to about 10 parts by weight per 100 parts by weight of the ethylenically unsaturated compound.

When the microcapsule ink composition of the present invention is used for preparing pressure sensitive recording sheets, an electron donating chromogenic material is usually microencapsulated.

Useful electron donating chromogenic materials include a variety of wellknown ones, namely triarylmethane-based dyes such as 3,3-bis(p-dimethylaminophenyl)-6dimethylaminophthalide, 3-(pdimethylaminophenyl)-3-(1,2dimethylindol-3-yl)phthalide, 3,3-bis(1,2dimethylindol-3yl)-5-dinethylaminophthalide, 3,3-bis(9-ethylcarbazol-3yl)6-dimethylaminophthalide, etc.; diphenylmethane-based dyes such as 4,4-bis-dimethylaminobenzhydryl benzyl ether, N-halophenylleucoauramines, N-2,4,5 trichlorophenylleucoauramine, etc.; thiazine-based dyes such as benzoylleucomethylene blue, p- nitrobenzoylleucomethylene blue, etc.; spiro-based dyes such as 3-methylspirodinaphthopyran, 3-phenylspirodi naphthopyran, 3-propylspirodibenzopyran, etc.; lactam-based dyes such as rhodamine-B-anilinolactam, rhodamine(o chloroanilino)lactam, etc.; fluorane-based dyes such as 3 dimethylamino-7-methoxyf luorane,3-diethylamino-6-methyl-7- chlorofluorane, 3-(N-ethyl-p-toluidino)-7-methylfluorane, 3-diethylamino7-N-methylaminofluorane, 3-diethylamino-7dibenzylaminofluorane, 3-(Nethyl-p-toluidino)-6-methyl-7phenylaminofluorane, 3-diethylamino-6-methyl7phenylaminofluorane, 3-(N-cyclohexyl-N-methylamino)-6methyl-7-phenylaminofluorane, 3-piperidino-methyl-7phenylaminofluorane, 3diethylamino-6-methyl-7xylidinofluorane, etc.; and infrared series dyes such as 3,3-bis[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethylene-2yl]-4,5,6,7-tetrachlorophthalide and so on. These dyes can be used alone or in combination.

Generally, any of these electron donating chromogenic materials is dissolved in an oil and then microencapsulated. As examples of such oil, there can be mentioned the following known substances.

Vegetable oils such as cottonseed oil; mineral oils -20such as kerosene, paraffin, naphthene, chlorinated paraffin, etc.; aromatic hydrocarbons such as alkylated biphenyls, alkylated terphenyls, alkylated naphthalenes, diarylethanes, triarylmethanes, diphenylalkanes, etc.; esters such as dimethyl phthalate, diethyl phthalate, di-nbutyl phthalate, dioctyl phthalate, diethyl adipate, dipropyl adipate, di-n- butyl adipate, dioctyl adipate, etc.; and mixtures of these oils.

The electron donating chromogen is generally added to the oil in an amount of generally about 2 to 80 parts by weight, preferably about 5 to 50 parts by weight, per 100 parts by weight of the oil.

The method for microencapsulation may be selected from among various known processes such as coacervation, interfacial polymerization, in-situ polymerization and so on. While there are various microencapsulation methods, microcapsules having a capsule wall films of a synthetic resin are preferred from the viewpoints of capsule strength, ease of preparation of such capsules, etc.

Examples of the resins forming microcapsule wall are aminoaldehyde resin, polyurea resin, polyurethane resin, polyamide resin, etc., among which the amino-aldehyde resin is preferred.

The microcapsules having amino-aldehyde resin wall film are prepared by in-situ polymerization method with use of at least one amine compound such as urea, thiourea, alkylurea, ethylene urea, acetoguanamine, benzoguanamine, melamine, guanidine, biuret and cyanamide and at least one aldehyde compound such as formaldehyde, acetaldehyde, paraformaldehyde, hexamethylenetetramine, glutaraldehyde, glyoxal and furfural, or with use of pre-condensates of said amine compound and aldehyde compound. Microcapsules comprising melamine-f ormaldehyde resin as a wall f orming material (as disclosed in U.S. Patent No. 4,100,103, the disclosure of which is incorporated herein by reference) is particularly preferred because they are resistant to solvents and because an aqueous dispersion of such microcapsules can readily give a powdery microcapsules upon removal of an aqueous medium therefrom. The average particle size of microcapsules depends on the material used and the thickness of the wall structure but is generally about 1 to about 10 pm. Where necessary, an antioxidant, ultraviolet absorber, perfume, etc. can also be incorporated in the microcapsule. 20 The microcapsules prepared as above generally are in the form of an aqueous dispersion. The microcapsules, either in semi-dry condition subsequent to filtration or in dry condition subsequent to air drying, surface drying, fluidized drying, air suspension drying, spray drying, vacuum drying, freeze drying, infrared drying, dielectric -22 drying, ultrasonic drying, pulverization drying or the like, are dispersed in a nonaqueous vehicle and, where necessary, supplemented with various auxiliary agents to give a finished microcapsule ink composition. The nicrocapsules can also be dispersed in such a nonaqueous vehicle by either mixing said aqueous dispersion of microcapsules with the nonaqueous vehicle and removing water under reduced pressure as described in Japanese Unexamined Patent Publication (Kokai) No. 135718/1978 or filtering said dispersion of microcapsules and washing them with a water- miscible nonaqueous vehicle for replacement.

The amount of microcapsules in the microcapsule ink composition is generally about 5 to about 80% by weight, preferably about 10 to about 40% by weight, based on the ink composition. When the ethylenically unsaturated compound comprises at least one of the components (a) and (b), the amount of microcapsules is preferably about-5 to about 60% by weight, more preferably about 10 to about 40% by weight, based on the ink composition. When the ethylenically unsaturated compound comprises atleast one of the components (c) and (d), the amount of microcapsules is preferably about 5 to about 80% by weight, more preferably about 10 to about 40% by weight, based on the ink composition.

As the ink vehicle for use in the microcapsule ink composition of this invention, not only the above-mentioned ethylenically unsaturated compound but, optionally, various other substances such as high-boiling point or low-boiling point solvents, resins, waxes and oils can be additionally 5 employed either singly or in admixture.

Examples of useful high-boiling point solvents are ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol (preferably having a molecular weight of about 400), propylene glycol, dipropylene glycol, 2,3- butylene glycol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol and so on. The high-boiling solvent is used preferably in an amount of 0 to about 40% by weight based on the ink composition.

Examples of useful low-boiling point solvents are methanol, ethanol, n-propanol, iso-propanol, n-butanol, ethyl acetate, propyl acetate, butyl acetate,acetone, methyl ethyl ketone, benzene, toluene, xylene, etc. The low-boiling point solvent is used preferably in an amount of 0 to about 40% by weight based on the ink composition.

The resins mentioned above include. inter alia, gum rosin, wood rosin, shellac, ester gum/ rosin pentaerythritol ester, polymerized rosin pentaerythritol ester, maleic acid resin, maleinized rosin pentaerythritol ester, dimer rosin, rosin-modif ied phenolic resin, butanol modified urea resin, butanol-modified melamine resin, terpene resin, terpene-phenolic resin, soybean oil-modif ied alkyd resin, polyamide resin, polyvinyl acetate, acrylic resin, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, ethylene-maleic anhydride copolymer, styrene- maleic anhydride copolymer, methyl vinyl ether-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, modified polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, ethylcellulose, nitrocellulose, hydroxypropylcellulose, cellulose acetate propionate, cellulose acetate butyrate and so on. The resin is used preferably in an amount of 0 to 40 % by weight based on the ink composition.

Among the waxes mentioned above are beeswax, spermaceti, lanolin, candelilla wax, carnauba wax, wood wax, rice wax, Montan wax, ozokerite, paraffin wax, microcrystalline wax, Montan wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives, castor wax, opal wax, low molecular weight polyethylene, distearyl ketone, caprylic. acid amide, stearic acid amide, ethylene- bis-stearic acid amide, stearic acid, behenic acid, stearyl alcohol, distearyl phosphate and so on. The wax is used preferably in an amount of 0 to 20% by weight based on the ink composition.

Among the oils mentioned above are various vegetable oils such as linseed oil, safflower oil, soybean oil, -25castor oil, etc.; processed oils such as dehydrated castor oil, polymerized oil, maleinized oil, vinyl oil, urethane oil, etc.; and mineral oils such as machine oil, spindle oil and so on. The oil is used preferably in an amount of 0 to about 40% by weight based on the ink composition.

The ink vehicle for use herein which contains the ethylenically unsaturated compound comprising at least.one of the components (a) to (d) and optionally high-boiling or low-boiling point solvents, resins, waxes, oils and the like is used in an amount of about 9 to about 95 parts by weight, preferably about 30 to about 90 parts by weight, per 100 parts by weight of the ink composition.

The microcapsule ink composition of the invention.may, where necessary, contain stilt materials such as is cellulose powder, starch particles, synthetic resin particles, etc.; white pigments such as titanium oxide, surface-treated titanium oxide, zinc oxide, calcium carbonate, aluminum hydroxide, etc.; thixotropic agents such as colloidal silica, metal soap (aluminum stearate, aluminum octanoate, etc.), sodium palmitate, aluminum chelate (aluminum diisopropoxide monoacetoacetate ethyl, etc.), organic amine-modified bentonite, thixotropic polyamide resin, etc.; color desensitizers for suppressing color forming reaction and like desensitizers, antioxidants, fluorescent brighteners, plasticizers, -26coloring dyes, and so on. Among these substances, titanium oxide or surface-treated titanium oxide is preferable to use because they can prevent the printed portion from becoming transparent. Further, the addition of the thixotropic agent such as colloidal silica is particularly preferred in order to prevent sagging (i.e., oozing of ink from an ink reservoir of a letterpress) and ink mist..

When at least one of liquid polybutadiene (meth) acrylate and liquid hydrogenated polybutadiene acrylate is (are) used as the ethylenically unsaturated compound, it is preferable to use at least one of these acrylates in combination with an ethylenically unsaturated compound of the lower viscosity or in combination with a high- or low-boiling point solvent, oil or the like, rather than to use at least one of the (meth) acrylates singly used as the ink vehicle, because the resulting ink composition exhibits a higher color forming ability when used as an ink composition for a pressure-sensitive recording sheet. It is generally preferable to combine at least one of liquid polybutadiene (meth) acrylate and liquid hydrogenated polybutadiene (meth)acrylate with at least one ethylenically unsaturated compound or with a high- or low boiling point solvent, oil or the like so that the resulting mixture will have a viscosity of about 1 to about 5,000 cps.

The microcapsule ink composition of the invention is prepared usually by incorporating microcapsules and other auxiliaries into an ink vehicle and fully stirring the mixture by a propeller mixer, supersonic mill, ball mill, three-roll mill or the like.

A suitable viscosity of the ink composition is in the range of at least 3000 cps (25C), preferably about 5,000 to about 30,000 cps, as determined by Brookfield viscometer at 25C and 60 rpm. The viscosity of less than 3000 cps (25C) results in a tendency to induce sagging (i.e., oozing of ink from an ink reservoir) in letterpress printing process and ink mist in offset printing process, and might lead to a difficulty in stably conducting the operation.

The microcapsule ink composition thus obtained is applied to a support sheet by letterpress or offset printing method, generally in an amount of I to 10 g/m 2 and preferably in an amount of 2 to 6 g/m 2, on a dry weight basis. The ink composition of the present invention can also be used as a printing ink f or screen printing and other printing methods.

The support sheet f or such printing includes, inter alia, wood free paper, synthetic paper, film, art paper, coated paper, cast-coated paper, light weight coated paper, pressure sensitive recording paper (top, middle and bottom -28sheets, self-contained type paper) and so on.

The microcapsule ink composition of the invention printed on the support sheet is irradiated with ultraviolet light by means conventionally used in the art to achieve curing. While the conditions of UV irradiation are not specifically limited insofar as the printed microcapsule ink composition is cured, it is preferred to conduct UV irrad iation with use of a high-pressure mercury lamp, metal halide lamp or the like.

The support sheet having the microcapsule ink composition printed and cured thereon in this manner can be advantageously used as the top sheet or middle sheet for a pressure sensitive recording material. The middle sheet comprises a layer of the microcapsule ink composition of the invention on one side of a support sheet and an electron accepting color developer layer on the other side of the support sheet.

Sheets coated with an electron accepting color developer (i.e., acceptor) to be used in combination with said top sheet or said middle sheet are various and include a wide range of conventional ones which are not specifically limited. Preferred embodiments of such sheets will be described below.

The color developer (acceptor) layer to be described below can also be used f or preparing the middle sheet 1 -29comprising a layer of the microcapsule ink composition of the invention on one side and such acceptor layer on the other side.

The coating composition for forming an acceptor layer contains an acceptor, an adhesive and if desired additives.

Examples of useful adhesives are starch, casein, gum arabic, carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene copolymer latex, vinyl acetate-based latex, etc. Useful additives include zinc oxide, magnesium oxide, titanium oxide, aluminum hydroxide, calcium carbonate, magnesium sulfate, calcium sulfate and like inorganic pigments, plastic pigments, binder pigments and like organic pigments, and auxiliary agents conventionally used in the art of pressure sensitive recording sheets.

The coating composition for forming an acceptor layer may further contain microcapsules (i.e., oil microcapsules) containing a hydrophobic liquid but not containing a dye.

Useful acceptors include inorganic acceptors such as acid clay, activated clay, attapulgite, zeolite, bentonite, silica, aluminum silicate, etc. and organic acceptors such as phenolic polymers such as phenol-aldehyde polymers and phenol-acetylene polymers, aromatic carboxylic acid derivatives, etc. The organic acceptors are superior to the inorganic acceptors in fastness to light such as sunlight.

Examples of the organic acceptor are salicylic acid, 3-phenylsalicylic acid, 3-cyclohexylsalicylic acid, 3-tert butyl-S-methylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-methyl-5-benzylsalicylic acid, 3-phenyl-5-(a,a dimethylbenzyl)salicylic acid, 3-(a,a-dimethylbenzyl)-5 methylsalicylic acid, 3,5-di-cyclohexylsalicylic acid, 3,5 di-(a-methylbenzyl)salicylic acid, 3,5-di-(a,a dimethylbenzy1) salicylic acid, 3- (a-methylbenzy1) -5- (a, a dimethylbenzyl)salicylic acid, 4-methyl-S cyclohexylsalicylic acid, 2-hydroxy-l-benzyl-3-naphthoic acid, 3-hydroxy-5-cyclohexyl-2-naphthoic acid, 3-methyl5 (iso)nonylsalicylic acid, 3-methyl-5-(iso)dodecylsalicylic acid, 3-methyl-5- (iso) pentadecylsalicylic acid, 3-.methyl-5 (a-methylbenzyl)salicylic acid, 3-methyl-S-(a,a dimetnylbenzyl)salicylic acid, 3,5-di-sec-butylsalicylic acid, 3,5-di-tert-butyl-6-methylsalicylic acid, 3 cyclohexyl-5- (iso) nonylsalicylic acid, 3- (a-methylbenzyl) - 5-(iso)nonylsalicylic acid, 3-isopropyl-5 (iso)nonylsalicylic acid, 3-(iso)nonylsalicylic acid, 3 (iso)nonyl-S-methylsalicylic acid, 3-(iso)nonyl-5- cyclohexylsalicylic acid, 3-(iso)nonyl-S-(a methylbenzy1)salicylic acid, 3-(iso)nonyl-S-(4,a dimethylbenzy1)salicylic acid, 3-(iso)nonyl-S-(a,a dimethylbenzy1)salicylic acid, 3-(a,a-dimethylbenzyl)-5 (iso)nonylsalicylic acid, 5-(iso)nonylsalicylic acid, 3(iso)nonyl-6-methylsalicylic acid, 3-tert-butyl-5 (iso)nonylsalicylic acid, 3,5-di(iso)nonylsalicylic acid, 3-(iso)dodecylsalicylic acid, 3-(iso)dodecyl-5 inethylsalicylic acid, 3-(iso)dodecyl-6-methylsalicylic acid, 3-isopropyl-5-(iso)dodecylsalicylic acid, 3 (iso)dodecyl-5-ethylsalicylic acid, 5 (iso)pentadecylsalicylic acid, 3-cyclohexyl-5-(a methylbenzyl)salicylic acid, 3-phenyl-5-(a inethylbenzyl) salicylic acid, 3- (a-methylbenzy1) salicylic acid, 3-(a-methylbenzyl)5-Tnethylsalicylic acid, 3- (anethylbenzyl)-6methylsalicylic acid, 3-(a,4dinethylbenzyl)-5-raethylsalicylic acid, 3,5di(a,4dimethylbenzy1)salicylic acid, 3-(a,a-diTnethylbenzyl)6nethylsalicylic acid, 3,5-di(a,a-dimethylbenzyl)salicylic is acid, 5(4-mesitylmethylbenzy1) salicylic acid, 2-hydroxy-3(a,adimethylbenzyl)-1-naphthoic acid, 3-hydroxy-7-(a,adimethylbenzyl)-2naphthoic acid and like aromatic carboxylic acids and the corresponding salts of polyvalent metals. Examples of polyvalent metals are magnesium, calcium, zinc, aluminum, iron, cobalt, nickel, etc. These acceptors can be used singly or in combination.

Also usable as acceptors are those disclosed in Japanese Examined Patent Publications Nos.9309/1965 and 2014411967 and Japanese Unexamined Patent Publication No.1440911973, such as 6,61-methylenebis(4-chloro-m-cresol) -32and like phenolic compounds; phenolic resins, e.g., pphenylphenol formaldehyde resin and like phenol-aldehyde resins, p-tert-butylphenolacetylene resin and like phenolacetylene resins, and the corresponding polyvalent metal salts of such phenolic resins; acidic polymers such as maleic acid-rosin resin, copolymers of styrene, ethylene or vinyl methyl ether with maleic anhydride; and those disclosed in Japanese Examined Patent Publications Nos. 821511973, 821611973 and 132611977, i.e., polymers of aromatic carboxylic acids with aldehyde or acetylene and polyvalent metal salts thereof.

Preferred among these organic acceptors are polyvalent metal salts of aromatic carboxylic acids. These acceptors may be used in combination.

is The coating composition for forming the acceptor layer can be prepared usually by dispersing the acceptor and other component(s) conjointly or separately with an agitating or pulverizing means such as a sand mill, ball mill, attritor or the like using water as a dispersing medium or by disolving them in an organic solvent and emulsifying the solution in water with an emulsifying or dispersing medium such as polyvinyl alcohol and evaporating off the organic solvent by steam distillation, followed by adding a pigment, binder, immobilizing agent, etc. The coating composition for forming the acceptor layer is -33applied to a support sheet in an amount which is not specifically limited. The amount is usually in the range of about 2 to about 8 g/m 2 on dry weight basis.

The coating composition for forming the acceptor layer is applied to a support sheet such as wood free paper, coated paper, synthetic paper, film or the like with an air-knife coater, blade coater, roll coater, size press coater, curtain coater, short dwell coater or like conventional coaters to give a finished color developing 10 sheet for pressure sensitive recording sheets.

The substances which can be encapsulated in microcapsules in the microcapsule ink composition of the invention are not limited to the constituent materials of a pressure sensitive recording sheet but may include is perfumes, liquid crystals, thermochromic materials, antirust agents, mothproofing agents, rodenticides, tackifiers, adhesives and so on.

The following examples and comparative examples are intended to illustrate the invention in further detail and should by no means be construed as defining the scope of the invention.

It should be understood that, in all the examples and comparative examples, parts and percentages are all by weight unless otherwise indicated. Furthermore, in all the examples and comparative examples, ratios are all by weight unless otherwise indicated.

ExamiDle 1-1 Preparation of microcapsules containing electron donating chromocrenic materials In 75 parts of benzyltoluene was dissolved 25 parts of 3,3-bis(2-methyl-l-octyl-3-indolyl)phthalide with heating to give an inner-phase solution. This solution -was emulsified in 200 parts of a 3% aqueous solution of ethylene-maleic anhydride copolymer (tradename "EMA 3111, product of Monsanto Co.) adjusted to pH 6.0, and the system was heated to 55C.

Separately, 15 parts of melanine was added to 45 parts of a 37% aqueous solution of formaldehyde and the reaction was conducted at 60C for 15 minutes to give an aqueous prepolymer solution.

This prepolymer solution was added dropwise to the above emulsion and the mixture was adjusted to pH 5.3 by dropwise addition of 0.1N hydrochloric acid with stirring. The system was then heated to 80C and stirred for 1 hour.

Then, 0.2N hydrochloric acid was added dropwise to bring the pH of the system to 3.5 and the mixture was further stirred for 3 hours. on cooling, there was obtained a dispersion of microcapsules with an average particle size of 3.8 Am.

This dispersion was filter-pressed and dried to give 1 -35powdery microcapsules. Preparation of a microcansule ink composition A microcapsule ink composition was preparedby admixing the following components.

- Microcapsules containing electron donating chromogenic materials 100 parts - An ethylenically unsaturated compound composition [a liquid polybutadiene acrylate prepared by subjecting 2 hydroxyethyl acrylate and hydroxyl group of a liquid polybutadiene to urethane addition reaction via 2,4 tolylenediisocyanate (hereinafter referred to as "liquid polybutadiene acrylate All; viscosity=5200 cps, average number of acryloyl groups per molecule=1.8): dipropylene glycol diacrylate = 1:1] 300 parts - Photo polymerization initiator (benzoin methyl ether) parts Preparation of a toD sheet Using a letterpress printing method, a base paper sheet weighing 40 g/m 2 was printed with the above microcapsule ink composition (in an amount of 5. 0 g/m 2) which was then cured with an ultraviolet irradiator equipped with a 6 kw high-pressure mercury lamp to give a top sheet. Preparation of oil microcaDsules for bottom sheet One-hundred parts of alkyldiphenyl ethane, as an inner- -36phase oil, was emulsified in 200 parts of a 3% aqueous solution of ethylene-maleic anhydride copolymer (tradename "EMA-3111, product of Monsanto Co.) adjusted to pH 6.0 and the resulting emulsion was heated to 550C.

Separately, 15 parts of melamine was added to 45 parts of a 37% aqueous solution of formaldehyde and the reaction was conducted at 600C for 15 minutes to give an aqueous prepolymer solution.

This aqueous prepolymer solution was added dropwise to the above emulsion and the mixture was adjusted to pH 5.3 by dropwise addition of 0.1N hydrochloric acid with stirring. The system was then heated to 800C and stirred at that temperature for 1 hour. Thereafter, 0. 2 N hydrochloric acid was added dropwise to bring the pH of the system to 3.5 and the mixture was further stirred for 3 hours. On cooling, there was obtained a dispersion of microcapsules having an average particle size of 5.0 gm.

Preparation of a bottom sheet In 300 parts of a 0.2% aqueous solution of polyvinyl alcohol were dispersed 60 parts of precipitated calcium carbonate, 10 parts of zinc oxide, 10 parts of a co-melt of zinc 3,5-di(amethylbenzyl)salicylate and a-methylstyrenestyrene copolymer (80:20), 10 parts of the above-prepared oil microcapsules, and 10 parts of pulp powder, followed by addition of 10 parts (calculated as solids) of glutinized starch and 15 parts (calculated as solids) of carboxymodified styrene- butadiene latex. The mixture was diluted to give a 30 wt. % color developer coating composition. This coating composition was applied, with an air-knife coater, to a base paper sheet weighing 40 g/m 2 in an amount of 7 g/m 2 on a dry weight basis to give a bottom sheet.

Evaluation The top sheet prepared in the above manner and the bottom sheet were superimposed and images were formed thereon with use of an electric typewriter which has a square-shaped flat type designed to give a squareshaped color image on the recording paper, wherein the flat type strikes the recording paper at a constant pressure. The typewriter used in the following Examples and Comparative Examples were the same as this typewriter. As a result, very distinct color images were obtained on the bottom sheet.

Example 1-2

The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared with use of 300 parts of an ethylenically unsaturated compound composition [a liquid polybutadiene acrylate prepared by esterifying 2hydroxyethyl acrylate and a maleinized polybutadiene wherein maleic anhydride is added to the polybutadiene chain by ene addition reaction (hereinafter referred to as "liquid polybutadiene acrylate B11; viscosity=3800 cps, average number of acryloyl groups per molecule=1.8): dipropylene glycol diacrylate=1:1] in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1. In the same manner as in Example I-1, a top sheet was prepared and images were f ormed on the bottom sheet and evaluated. The color images obtained were very distinct.

ExamDle 1-3 The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared with use of 300 parts of an ethylenically unsaturated compound composition [a liquid polybutadiene acrylate prepared by subjecting acrylic chloride and a liquid polybutadiene containing hydroxyl groups to a reaction for removing hydrogen chloride (hereinafter referred to as "liquid polybutadiene acrylate C11; viscosity=4200 cps, average number of acryloyl groups per molecule=2.0): dipropylene glycol diacrylate=1:1] in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1. In the same manner as in Example I-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

Example 1-4

The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared using 300 parts of an ethylenically unsaturated compound composition [liquid polybutadiene acrylate A: 2-(pnonylphenoxy)ethyl acrylate=1:1] in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1, and further adding thereto 5 parts of colloidal silica (tradename IIAEROSIL 20011, product of Nippon Aerosil Co., Ltd.). In the same manner as in Example I-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The images obtained were very distinct. No sagging (i.e., oozing of ink from an ink reservoir) occurred during printing.

ExamDle 1-5 The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared with use of 300 parts of an ethylenically unsaturated compound composition [liquid polybutadiene acrylate A: 1, 6-hexanediol diacrylate =1:1] in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1. In the same manner as in Example I-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The images obtained were very distinct.

Example 1-6

The procedure of Example I-1 was repeated except that -40a microcapsule. ink composition was prepared with use of 300 parts of an ethylenically unsaturated compound composition (liquid polybutadiene acrylate A: dipropylene glycol diacrylate: 2-(p-nonylphenoxy) ethyl acrylate=1:1:1] in lieu of 300 parts of ethylenically unsaturated compound composition used in Example 1-1. In the same manner as in Example I-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

Example 1-7

The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared with use of 300 parts of polybutadiene acrylate A in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1. In the same manner as in Example I-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were distinct.

Example 1-8

The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared using 240 parts of liquid polybutadiene acrylate A in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1, and further adding thereto 80 parts of ethanol and 5 parts of colloidal silica (tradename "AEROSIL 20011, Nippon Aerosil Co., Ltd.). In the same manner as in Example 1-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

Example 1-9

The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared using 200 parts of liquid polybutadiene acrylate A in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1, and further adding thereto 80 parts of ethyl cellosolve and 50 parts of pentaerythritol ester of rosin. In the same manner as in Example 1-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

ExamiDle I-10 The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared using 220 parts of liquid polybutadiene acrylate B in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1, and further adding thereto 100 parts of ethylene glycol. In the same manner as in Example I-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

Example I-11

The procedure of Example 1-1 was repeated except that a microcapsule ink composition was prepared with use of 300 parts of an ethylenically unsaturated compound composition [liquid hydrogenated 1, 2-polybutadiene acrylate prepared by 5 subjecting to urethane addition reaction 2hydroxyethyl acrylate and a liquid hydrogenated 1,2-polybutadiene glycol via 2,4-tolylene diisocyanate (hereinafter referred to as "liqu id hydrogenated 1,2-polybutadiene acrylate D"; viscosity=4900 cps, average number of acryloyl groups per molecule=1. 9): dipropylene glycol diacrylate=l: 1] in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I- 1. In the same manner as in Example I-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

ExamiDle 1-12 The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared by using 170 parts of liquid hydrogenated 1,2- polybutadiene acrylate D in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1, and further adding thereto 80 parts of propylene glycol and 50 parts of pentaerythritol ester of rosin. In the same manner as in Example 1-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images -43obtained were very distinct. Example 1-13 The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared with use of 300 parts of liquid hydrogenated 1,2polybutadine acrylate D in lieu of said ethylenically unsaturated compound composition used in Example I-1. In the same manner as in Example I-1, a top sheet was prepared and images were f ormed on the bottom sheet and evaluated. The color images obtained were distinct.

Example 1-14 Preparation of a top sheet Using an of f set printing method, a base paper sheet weighing 40 g/m 2 was printed twice with the microcapsule ink composition prepared in the same manner as in Example I1 (in an amount of 4.0 g/m 2), which was then cured with an ultraviolet irradiator equipped with a 6 kw highpressure mercury lamp to give a top sheet. Evaluation 20 When the top sheet prepared in the above manner was superimposed on the bottom sheet prepared in the same manner as in Example I-1, and images were f ormed thereon with use of a typewriter, very distinct color images were obtained on the bottom sheet. Comparative ExamiDle I-1 The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared with use of 300 parts of an ethylenically unsaturated compound composition [pentaerythritol triacrylate:pentaerythritol tetraacrylate=1:1] in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example 1-1. In the same manner as in Example I-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were so inferior that they were of no practical use. ComDarative Example 1-2 The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared with use of 300 parts of an ethylenically unsaturated compound composition (pentaerythritol triacrylate: pentaerythritol tetraacrylate: dipropylene glycol diacrylate=1:1:1] in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1. In the same manner as in Example I-1, a top sheet wasprepared and images were formed on the bottom sheet and evaluated. The color images obtained were so inferior that they were of no practical use.

ComDarative Example 1-3 The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared with use of 300 -45 parts of an ethylenically unsaturated compound composition [trimethylolpropane triacrylate: trimethylolpropane diacrylate=1:1] in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1. In the same manner as in Example 1-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were so inferior that they were of no practical use.

Comparative ExamDle 1-4 The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared with use of 300 parts of an ethylenically unsaturated compound composition (trimethylolpropane triacrylate: trimetylolpropane diacrylate:dipropylene glycol diacrylate=1:1:1] in lieu of 300 parts of ethylenically unsaturated compound composition used in Example I-1. In the same manner as in Example I-1, a top sheet was prepared and images were f ormed on the bottom sheet and evaluated. The color images obtained were so inferior that they were of no practical use.

Comparative Examnle 1-5 The procedure of Example I-1 was repeated except that a microcapsule ink composition was prepared with use of 300 parts of 1,6-hexanediol diacrylate in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1. In the same manner as in Example I-1, a top -46sheet was prepared and images were f ormed on the bottom sheet and evaluated. The color images obtained were so inferior that they were of no practical use.

Comparative ExamiDle 1-6 The procedure of Example 1-1 was repeated except that a microcapsule ink composition was prepared with use of 300 parts of dipropylene glycol diacrylate in lieu of 300 parts of said ethylenically unsaturated compound composition used in Example I-1. In the same manner as in Example I-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were so inferior that they were of no practical use.

Example II-1 Preparation of a microcapsule ink composition In 75 parts of benzy1toluene was dissolved 25 parts of 3,3-bis(2-methyl-l-octyl-3-indolyl)phthalide with heating to give an inner-phase solution. This solution was emulsified in 200 parts of a 3% aqueous solution of ethylene-maleic anhydride copolymer (tradename "EMA 3111, product of Monsanto Co.) adjusted to pH 6.0, and the system was heated to 550C.

Separately, 15 parts of melamine was added to 45 parts of a 37% aqueous solution of formaldehyde and the reaction was conducted at 600C for 15 minutes to give an aqueous prepolymer solution.

This prepolymer solution was added dropwise to the above emulsion and the mixture was adjusted to pH 5.3 by dropwise addition of 0.1 N hydrochloric acid with stirring. The system was then heated to 800C and stirred for I hour.

Then, 0.2N hydrochloric acid was added dropwise to bring the pH of the system to 3.5 and the mixture was further stirred for 3 hours. On cooling, there was obtained a dispersion of microcapsules with an average particle size of 3.8 gm.

This dispersion was then filter-pressed and dried to give powdery microcapsules. A microcapsule ink composition was prepared by admixing 100 parts of the microcapsules, 400 parts of an ethylenically unsaturated compound composition [2-(p-nonylphenoxy)ethyl acrylate:

pentaerythritol triacrylate =7:3), 10 parts of photo polymerization initiator (benzoin methyl ether), and 20 parts of titanium oxide.

Preparation of a top sheet Using a letterpress printing method, a base paper sheet weighing 40 g/m 2 was printed with the above microcapsule ink composition (in an amount 'of 5.0 g/m 2) which was then cured with an ultraviolet irradiator equipped with a 6 kw high-pressure mercury lamp to give a top sheet.

Evaluation When the top sheet prepared in the above manner and a bottom sheet prepared in the same manner as in Example I-1 were superimposed and images were formed thereon with use of an electric typewriter, very distinct color images were 5 obtained on the bottom sheet.

Example 11-2 Preparation of a toD sheet Using an of f set printing method, a base paper sheet weighing 40 g/m 2 was printed with the microcapsule ink 10 composition prepared in the same manner as in Example II-1 (in an amount of 3.0 g/m 2) which was then cured with an ultraviolet irradiator equipped with a 6 kw high-pressure mercury lamp to give a top sheet.

Evaluation When the top sheet prepared in the above manner was superimposed on the bottom sheet prepared in the same manner as in Example I-1 and images were f ormed thereon with use of an electric typewriter, very distinct color images were obtained on the bottom sheet.

Example 11-3

The procedure of Example II-1 was repeated except that a microcapsule ink composition was prepared with use of 400 parts of an ethylenically unsaturated compound composition (p-nonylphenoxy diethylene glycol acrylate:1,6-hexanediol diacrylate=5:5) in lieu of 400 parts of said ethylenically -49unsaturated compound composition used in Example II-1. In the same manner as in Example II-1, a top sheet was prepared and images were f ormed on the bottom sheet and evaluated. The color images obtained were very distinct.

Example 11-4

The procedure of Example II-1 was repeated except that a microcapsule ink composition was prepared with use of 400 parts of an ethylenically unsaturated compound composition [ 2 - (p-nonylphenoxy) ethyl acrylate: 1, 6-hexanediol diacrylate =6:4] in lieu of 400 parts of said ethylenically unsaturated compound composition used in Example II-1. In the same manner as in Example II-1, a top sheet was prepared and images were f ormed on the bottom sheet and evaluated. The color images obtained were quite distinct.

Example 11-5

The procedure of Example II-1 was repeated except that a microcapsule ink composition was prepared with use of 400 parts of an ethylenically unsaturated compound composition (p-butylphenoxy polypropylene glycol acrylate: 1,6 hexanediol diacrylate=5:5) in lieu of 400 parts of said ethylenically unsaturated compound composition used in Example II-1. In the same manner as in Example II-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

Example 11-6

The procedure of Example II-1 was repeated except that a microcapsule ink composition was prepared with use of an ethylenically unsaturated compound composition (p-nonyl phenoxydipropylene glycol acrylate: p- nonylphenoxy propylene glycol acrylate: polypropylene glycol dimethacrylate--4:3:3) in lieu of 400 parts of said ethylenically unsaturated compound composition used in Example II-1. In the same manner as in Example II-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

Example 11-7

The procedure of Example II-1 was repeated except that a microcapsule ink composition was prepared with use of an ethylenically unsaturated compound composition [2-(pnonylphenoxy) ethyl acrylate: liquid polybutadiene acrylate B = 6:4] in lieu of 400 parts of said ethylenically unsaturated compound composition used in Example II-1. In the same manner as in Example II-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

Comparative Example II-1 The Procedure of Example II-1 was repeated except that a microcapsule was prepared with use of 400 parts of 7 pentaerythritol triacrylate in lieu of 400 parts of said ethylenically unsaturated compound composition used in Example II-1. In the same manner as in Example II-1, a top paper was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were quite inferior.

ExamDle III-1 Preparation of a microcapsule ink composition In 75 parts of benzy1toluene was dissolved 25 parts of 3,3-bis(2-methyl-l-octyl-3-indolyl)phthalide with heating to give an inner-phase solution. This solution was emulsified in 200 parts of a 3% aqueous solution of ethylene-maleic anhydride copolymer (tradename "EMA 3111, product of Monsanto Co.) adjusted to pH 6.0, and the system was heated to 550C.

Separately, 15 parts of melamine was added to 45 parts of a 37% aqueous solution of formaldehyde and the reaction was conducted at 600C for 15 minutes to give an aqueous prepolymer solution.

This prepolymer solution was added dropwise to the above emulsion and the mixture was adjusted to pH 5.3 by dropwise addition of O.IN hydrochloric acid with stirring.

The system was then heated to 800C and stirred for 1 hour.

Then, 0.2N hydrochloric acid was added dropwise to bring the pH of the system to 3.5 and the mixture was further is stirred f or 3 hours. On cooling, there was obtained a dispersion of microcapsules with an average particle size of 3. 8 Am.

This dispersion was then filter-pressed and dried to give powdery microcapsules. A microcapsule ink composition was prepared by admixing 100 parts of the microcapsules, 400 parts of an ethylenically unsaturated compound composition (2-hydroxy-3-phenoxypropyl acrylate: pentaerythritol triacrylate=7:3), 10 parts of a photo polymerization initiator (benzoin methyl ether) and 20 parts of titanium oxide.

Preparation of a top sheet Using a letterpress printing method, a base paper sheet weighing 40 g/m 2 was printed with the above microcapsule ink composition (in an amount of 5. 0 g/m 2) which was then cured with a 6 kw high-pressure mercury lamp to give a top sheet.

Evaluation When the top sheet prepared in the above manner and a bottom sheet prepared in the same manner as in Example I-1 were superimposed and images were formed thereon with use of an electric typewriter, very distinct color images were obtained on the bottom sheet.

Example 111-2

Preparation of a top sheet Using an of f set printing method, a base paper sheet weighing 40 g/m 2 was printed with the microcapsule ink composition prepared in the same manner as in Example III-1 (in an amount of 3.0 g/m 2) which was then cured with a 6 kw high-pressure mercury lamp to give a top sheet.

Evaluation When the top sheet prepared in the above mannerwas superimposed on the bottom sheet prepared in the same manner as in Example 1-1 and images were formed thereon with use of an electric typewriter, very distinct color images were obtained on the bottom sheet.

Example 111-3

The procedure of Example III-1 was repeated except that a microcapsule ink composition was prepared with use of 400 parts of an ethylenically unsaturated compound composition [2-hydroxy-3-(p-nonylphenoxy)propyl acrylate: 1,6-hexanediol diacrylate =5:5] in lieu of 400 parts of said ethylenically unsaturated compound composition used in Example III-1. In the same manner as in Example III-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

Example 111-4

The procedure of Example III-1 was repeated except that a microcapsule ink composition was prepared with use -54of 400 parts of an ethylenically unsaturated compound composition (2- hydroxy-3-dodecyloxypropyl acrylate:1,6hexanediol diacrylate=6:4) in lieu of 400 parts of said ethylenically unsaturated compound composition used in Example III-1. In the same manner as in Example III-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were quite distinct.

Example 111-5

The procedure of Example III-1 was repeated except that a microcapsule ink composition was prepared with use of 400 parts of an ethylenically unsaturated compound composition [2-hydroxy-3-(p-butylphenoxy)propyl acrylate: 1,6-hexanediol diacrylate=5:5] in lieu of 400 parts of ethylenically unsaturated compound composition used in Example III-1. In the same manner as in Example III-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

-Example 111-6 The procedure of Example III-1 was repeated except that a microcapsule ink composition was prepared with use of 400 parts of an ethylenically unsaturated compound composition (2-hydroxy-3-phenoxypropyl acrylate: P_ nonylphenoxypropylene glycol acrylate: polypropylene glycol dimethacrylate=4:3:3) in lieu of 400 parts of said ethylenically unsaturated compound composition used in Example III-1. In the same manner as in Example III-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

Example 111-7

The procedure of Example III-1 was repeated except that a microcapsule ink composition was prepared with use of 400 parts of an ethylenically unsaturated compound composition (2- hydroxy-3-phenoxypropyl acrylate:liquid polybutadiene acrylate A=6:4) in lieu of 400 parts of said ethylenically unsaturated compound composition used in Example III-1. In the same manner as in Example III-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were quite distinct.

Example 111-8

The procedure of Example III-1 was repeated except that a microcapsule ink composition was prepared with use of 400 parts of an ethylenically unsaturated compound composition [2-hydroxy-3- phenoxypropyl acrylate: 2-(pnonylphenoxy)ethyl acrylate: liquid polybutadiene acrylate A =4:4:2] in lieu of 400 parts of said ethylenically unsaturated compound composition used in Example III-1. In -56the same manner as in Example III-1, a top sheet was prepared and images were formed on the bottom sheet and evaluated. The color images obtained were very distinct.

The color density of the images formed on the entire surface of the under sheet each of the pressure sensitive recording sheets (comprising the top sheet and the bottom sheet) prepared in the foregoing examples and comparative examples were measured by Macbeth densitometer of RD-914 type (product of Macbeth Company). The results are shown in Table 1 below.

Table 1 also shows the viscosity of the ethylenically unsaturated compound composition comprising at least one of components (a) to (d) optionally in combination with other ethylenically unsaturated compound or other ink vehicle (e.g., ethanol, ethyl cellosolve), as determined by Brookfield viscometer at 250C and 60 rpm

Table 1

9 viscosity Color (cps) density Example 1-1 3000 0.60 Example 1-2 2700 0.58 Example 1-3 2200 0.58 Example 1-4 4500 0.60 Example 1-5 3200 0.57 Example 1-6 1500 0.58 Example 1-7 5200 0.48 Example 1-8 4300 0.55 Example 1-9 4100 0.56 Example 1-10 2950 0.57 Example 1-11 2800 0.60 Example 1-12 1900 0.59 Example 1-13 4900 0.45 Example 1-14 3000 0.54 Comp. Ex. 1-1 3800 0.29 Comp. Ex. 1-2 2900 0.30 Comp. Ex. 1-3 1900 0.30 Comp. Ex. 1-4 3500 0.29 Comp. Ex. 1-5 10 0.32 Comp. Ex. 1-6 15 0.29 Table 1 (continued) viscosity Color (cps) density Example 11-1 1250 0.59 Example 11-2 1250 0.50 Example 11-3 1650 0.60 Example 11-4 950 0.55 Example 11-5 2300 0.60 Example 11-6 1700 0.60 Example 11-7 2900 0.59 Comp. Ex. 11-1 1200 0.30 Example 111-1 1750 0.60 Example 111-2 1750 0.50 Example 111-3 1350 0.59 Example 111-4 1700 0.54 Example 111-5 950 0.60 Example 111-6 1550 0.59 Example 111-7 3500 0.60 Example 111-8 4600 0.59 -59

Claims (12)

CLAIMS:

1. A microcapsule ink composition comprising microcapsules, an ethylenically unsaturated compound and a photo polymerization initiator, the composition comprising, as the ethylenically unsaturated compound, at least one member selected from the group consisting of:

(a) a liquid polybutadiene (meth)acrylate, (b) a liquid hydrogenated polybutadiene (meth) acrylate, (c) a compound represented by the formula W 0 X Y 1 11 1 1 C H 2 =C-C O-CH-CH n --o-z wherein W represents a hydrogen atom or a methyl group, X and Y are the same and each represents a hydrogen atom, or one of X and Y represents a hydrogen atom and the other represents a methyl group, Z is an unsubstituted or is substituted aryl group, and n is an integer of 1 or more, and, c H, 2 '= c - (d) a compound represented by the formula X 1 0 0 H 1 11 1 1 C-O-CH 2- CH-CH 2- O-Y (E) wherein X' represents a hydrogen atom or a methyl group, Y 1 is an unsubstituted or substituted aryl or alkyl group -60having not more than 34 carbon atoms.

2. A microcapsule ink composition according to claim 1 which comprises, as the ethylenically unsaturated compound, at least one member selected from the group consisting of:

(a) a liquid polybutadiene (meth)acrylate, and (b) a liquid hydrogenated polybutadiene (meth) acrylate.

3. A microcapsule ink composition according to claim 2 wherein the liquid hydrogenated polybutadiene (meth)acrylate is a liquid hydrogenated 1,2polybutadiene (meth)acrylate.

4. A microcapsule ink composition according to claim I which comprises, as the ethylenically unsaturated is compound, at least one member selected from the group consisting of:

(c) a compound represented by the formula (I) and (d) a compound represented by the formula (II).

5. A microcapsule ink composition according to claim 1 which comprises, as said ethylenically unsaturated compound, not only at least one of the components (a) to (d) but also another ethylenically unsaturated compound comprising at least one member selected from the group consisting of photopolymerizable monomers and photopolymerizable prepolymers.

1 -61

6. A microcapsule ink composition according to claim 2 wherein said ethylenically unsaturated compound is used in an amount of about 30 to about 95% by weight based on the ink composition.

7. A microcapsule ink composition according to claim 4 wherein said ethylenically unsaturated compound is used in an amount of about 9 to about 94% by weight based on- the ink composition.

8. A microcapsule ink composition according to claim 2 wherein the microcapsules are used in an amount of about 5 to about 60% by weight based on the ink composition.

9. A microcapsule ink composition according to claim 4 wherein the microcapsules are used in an amount of about 5 to about 80% by weight based on the ink composition.

10. A microcapsule ink composition according to claim 1 wherein the ethylenically unsaturated compound has a viscosity of about 1 to about 10,000 cps as determined at 25C.

11. A microcapsule ink composition according to claim 1 wherein the photo polymerization initiator is used in an amount of about 1 to about 20 parts by weight per 100 parts by weight of the ethylenicaly unsaturated compound.

12. A microcapsule ink composition according to claim 1 which further contains at least one ink vehicle selected from the group consisting of high-boiling point solvents, low-boiling point solvents, resins, waxes and oils.