WO1999020671A1

WO1999020671A1 - Radiation curable resin composition

Info

Publication number: WO1999020671A1
Application number: PCT/NL1998/000612
Authority: WO
Inventors: Tsuyoshi Watanabe; Ryoji Furuta; Takashi Ukachi
Original assignee: Dsm N.V.; Jsr Corporation; Japan Fine Coatings Co., Ltd.
Priority date: 1997-10-23
Filing date: 1998-10-23
Publication date: 1999-04-29
Also published as: JPH11124514A; JP3756643B2

Abstract

A radiation curable resin composition comprising (A) a (meth)acrylate of bisphenol diglycidyl ether compound, (B) a branched (meth)acryloyl group containing compound, (C) a radiation polymerization initiator, (D) inorganic particles and (E) a terminal reactive polydimethyl siloxane compound. The composition is suitable for use as a printable heat-resistant protective coat which is used for information recording media such as thermosensible recording cards and thermosensible photographic printing paper.

Description

RADIATION CURABLE RESIN COMPOSITION

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a radiation curable resin composition which has light resistance, heat resistance, high temperature marring resistance, fingerprint attachment resistance and excellent characteristics for adhering to substrates, characteristics for avoiding damage when scratched, for instance by a nail, steel, wool or the like,

(hereinafter referred to as "scratch resistance"), and printing aptitude, and, more particularly, to a radiation curable resin composition suitable for use as a printable heat-resistant protective coat which is used for information recording media in particular thermorecordable media such as thermosensible recording cards and thermosensible photographic printing paper. The heat resistant protective coat made from the photo- curable resin composition prevents the thermo recordable media or the like from being bruised when coming into contact with a thermal head (hereinafter referred to as anti-bruising characteristics) , ensures that the cards are conveyed with slight noise, and protects the thermal head from attracting extraneous material (i.e. minimizes adhesion or attraction) of undesirable particles which may interfere with the recording, reading and/or erasing of such media) , thereby improving durability of the cards or the like in a repeated printing-erasing operation. Description of related Art

A protective coating layer is provided in order to improve heat resistance and resistance to marring on the surface of recording media such as rewritable-type thermosensible recording cards and thermosensible photographic printing paper. A UV-curable type acrylate resin composition conventionally used for surface protection of plastic boards and as a protective coat for optical disks has been also used as the material for forming such a protective coating layer. Japanese Patent Application Laid-open No. 4-149280 proposes an overcoating composition for optical disks which comprises tripropylene glycol diacrylate, 2- (2-ethoxyethoxy) ethyl acrylate, and a photopolymerization initiator. The overcoating composition disclosed here exhibits low irritation to skin, has a low viscosity, and when used as an overcoating for optical disks, possesses sufficient coated film hardness and superior resistance to marring. Although such an overcoating material excels in mar resistance at normal temperatures, the material has poor shock resistance when subjected to thermal head contact when used as a protective coat for thermosensible record cards. Thus, mar resistance at high temperatures is a problem of this composition which must be solved. In addition, the protective coating surface produced by this overcoating composition shows inferior resistance to fingerprint attachment. When touched by a finger, a fingerprint trace is easily attached, which not only results in impaired surface transparency, but also makes it difficult to identify the character information and the like recorded in a lower layer of the protective coat layer .

A multi-layer coating of thermosetting resin consisting of a combination of a specific primer material containing an unsaturated double bond and an organopolysiloxane hard coating was proposed in Japanese Patent Application Laid-open No. 4-106161. The articles coated by this material are characterized in their possession of excellent mar resistance, abrasion resistance, and surface glossiness, as well as superb weather resistance of their adhesion characteristics. The organopolysiloxane hard coat disclosed here forms a coating film containing siloxane bonds when hardened. It is expected that the hard coat will exhibit superior mar resistance at high temperatures. This patent further proposes an addition of fine particles of an inorganic oxide to surface coating films in order to improve the surface hardness of the coating film. However, because the hardening is performed by heat, the addition of fine particles of inorganic oxide not only lengthens the hardening time and thereby decreases the productivity, but also a thermosensible layer is caused to deteriorate if used as the thermosensible recording media. Thus, the material is not practical. Moreover, although the overcoat layer with a polysiloxane structure formed possesses superior mar resistance and heat resistance, the coating film has only poor flexibility. If used on a rewriting type thermosensible record card or on thermosensible record paper, cracks are easily produced. In addition, the surface of the overcoating produced in this manner easily repels printing ink and makes favorable printing difficult.

Japanese Patent Application Laid-Open No. 103328/1995 discloses a radiation curable coating composition comprising, 100 parts by weight (hereinafter simply referred to as parts) of polymerizable compounds consisting of :

(A) 20 to 80 parts of an acrylated bisphenol-A epoxy resin wherein the resin comprises 1 to 3 bisphenol-A moieties in average,

(B) 5 to 50 parts of a compound comprising a acrylated dipentaeritrylol derivative that may comprise polymerised caprolacton and hydrogenated acrylic acid groups,

(C) 0 to 40 parts of a compound comprising two acrylate groups and a 1,3-dioxane moiety, and

(D) 0 to 40 parts of monomers or prepolymers which are copolymerizable with the compounds (A) , (B) , and (C) ;

0-10 parts of a photopolymerization initiator; and

0-150 parts of an organic solvent. The inventors of the invention of this laid-open patent application claim that this composition has a low viscosity, is easy to apply, and is hardened in a short period of time by irradiation using ultraviolet rays or electronic beams, has excellent processability such as superior adhesion to a substrate and superb bending characteristics, and produces products with a favorable gloss. However, the coating film produced from this composition, when used as a heat resistant protective coating, has inferior scratch resistance and fingerprint attachment resistance.

An object of the present invention is to provide a radiation curable resin composition which is suitable for producing a printable heat resistant protective coating used for thermosensible type information recording media such as a thermosensible recording card and a thermosensible printing photographic paper.

SUMMARY OF THE INVENTION

This object has been achieved in the present invention by a radiation curable resin composition comprising (A) a (meth) acrylate of a bisphenol diglycidyl ether compound, (B) a branched (meth) acryloyl group-containing compound, (C) a radiation polymerization initiator, (D) inorganic particles, and (E) terminal reactive polydialkyl siloxane.

More in particular the radiation curable resin composition comprises as components (A) and (B) : (A) a (meth) acrylate of a bisphenol diglycidyl ether compound represented by the following formula (1) ,

CH₂=C(R¹) -CO-O-X¹- (-X²-Ar-Y-Ar-0-)_n-X -χ¹-_CO-c(R¹)=CH₂ (1)

wherein R¹ is a hydrogen atom or a methyl group, X¹ represents a bond or a group represented by the following formula (2) ,

-(R²-0)_!-

wherein R² denotes an alkylene group having 2 to 6 carbon atoms and 1 is a value from 1 to 5; X² is a group represented by the following formula (3),

OH

I

-(-CH₂CHCH₂0-)_m- (3) wherein m is a value from 0 to 1; Ar represents a divalent aromatic hydrocarbon group such as a phenylene group, bisphenylene group, or naphthylene group, Y is a divalent organic group, and n is a value from 1 to 35; provided that 1 + m is 1 or more;

(B) a branched (meth) acryloyl grou -containing compound selected from compounds comprising a pentaeritrytol or dipentaeritrytol derivative having at least one of an (meth) acryloyl, alkoxylated (meth) acryloyl, and/or

(poly) caprolacton (meth) acryloyl group .

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

(A) A (meth) acrylate of a bisphenol diglycidyl ether compound

The (meth) acrylate of a bisphenol diglycidyl ether compound preferably includes (meth) acryaltes of bisphenol-A, -F, and -S diglycidyl ether polymer and more preferably those represented by the above formula (1) in particular those wherein "n" is less than 5.

Given as specific compounds for component (A) are a bisphenol A diglycidyl ether polymer with (meth) acrylic acids added to both ends of the molecule (in formula (1) when 1=0, m≠O) , a bisphenol A propylene oxide polymer with (meth) acrylic acids added to both ends (in formula (1) when m=0, R²=propylene group) , and bisphenol A ethylene oxide polymer with (meth) acrylic acids add to both ends (in formula (1) when m=0,

R²=ethylene group) and mixtures of such compounds. As commercially available products of these polymers, given as examples of the (meth) acrylic acid addition bisphenol A-diglycidyl ether polymer are SP-1506, SP-1509SP-1519-1, SP-1563, SP-2500, VR-77, VR-60, and VR-90 (trademarks, manufactured by Showa Highpolymer Co., Ltd.), Viscoat 540 (trademarks, manufactured by Osaka Organic Chemical Industry, Ltd.), epoxy ester 3000A, 3000M (trademarks, manufactured by Kyoeisha Chemical Co., Ltd.); as examples of the (meth) acrylic acid addition bisphenol A propylene oxide polymer are BP-4PA, BP-2PA, epoxy ester 3002A, 3002M (trademarks, manufactured by Kyoeisha Chemical Co., Ltd.); and as examples of the (meth) acrylic acid addition bisphenol A ethylene oxide polymer are SR-349, SR-640, R-712 (trademarks, manufactured by Nippon Kayaku Co., Ltd.), and BPE-10 (trademark, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). Among these, particularly preferred polymers for component (A) include (meth) acrylic acid addition bisphenol A diglycidyl ether polymer, and mixtures of such compounds .

The proportion of (meth) acrylate of a bisphenol diglycidyl ether comounds (the component (A) ) relative to the total amount of the components (A) plus (B) which make up the larger part of composition of the present invention is preferably 10 to 50 wt%, and more preferably 10 to 40 wt% and more preferably 15 to 35 wt.%

(B) a branched (meth) acryloyl group-containing compounds

The branched (meth) acryloyl group-containing compound used in the present invention is a compound having a branched structure and at least one (meth) acryloyl group. A branched structure means that the compound comprises a derivative from a poly-hydroxy compound, which has three or more hydroxy groups, preferably four to 10 hydroxy groups. More in particular, the compound comprises a pentaeritrytol or dipentaeritrytol derivative having at least one of an (meth) acryloyl, alkoxylated (meth) acryoyl and/or (poly) caprolacton (meth) acryloyl group. These branched (meth) acryloyl group-containing compounds have at least one (meth) acryloyl group in a molecule, and preferably at least about 3. Given as specific examples of these compounds are pentaerythritol tetra (meth) acrylate an ethylene oxide addition product of pentaerythritol esterified with tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate and the (meth) acrylate of a copoly er of dipentaerythritol and ε-caprolactone. Preferably, component (B) comprises on average about 4 or more (meth) acryloyl groups per molecule, in particular dipenta erythritol monohydroxypentaacrylate .

As commercially available products of these compounds, given as examples of the pentaerythritol tetra (meth) acrylate are KAYARAD PET-30, PET-40 (trademarks, manufactured by Nippon Kayaku Co., Ltd.),

PE-4E (trademark, manufactured by Kyoeisha Chemical Co., Ltd.), Viscoat #400 (trademark, manufactured by Osaka Organic Chemical Industry, Ltd.); as an example of the of ethylene oxide addition product of pentaerythritol esterified with (meth) acrylate to obtain a tetra (meth) acrylate is KAYARAD RP-1040 (trademark, manufactured by Nippon Kayaku Co., Ltd.); as an example of the dipentaerythritol penta (meth) acrylate is SR-399 (trademark, manufactured by Nippon Kayaku Co., Ltd.); and as examples of the dipentaerythritol hexa (meth) acrylate are KAYARAD DPHA, DPHA-2C, DPHA-21 (trademarks, manufactured by Nippon Kayaku Co., Ltd.), DPE-6A (trademark, manufactured by Kyoeisha Chemical Co., Ltd.); and as examples of the (meth) acrylate of copolymer of dipentaerythritol and ε-caprolactone are KAYARAD D-310, DPCA-20, DPCA-30, DPCA-60, DPCA-120 (trademarks, manufactured by Nippon Kayaku Co., Ltd.). Among these, the penta (meth) acrylate of dipentaerythritol and the

(meth) acrylate of dipentaerythritol and ε-caprolactone are preferred.

The amount of the component (B) , in terms of the proportion of this component relative to the total amount of the components (A) - (B) , is preferably from 50 to 90 parts by weight, more preferably from 60 to 90 parts by weight, and particularly preferably from 65 to 85 parts by weight, for 100 parts by weight of the total amount of the component (A) and component (B) . If more than 90 parts by weight, the coating film produced from the composition easily cracks, if less than 50 parts by weight, surface hardness of the coating film after curing decreases, allowing the coating to be easily bruised.

(C) Radiation polymerization initiator

The radiation polymerization initiator which is the component (C) used in the present invention may be any compound which is decomposed by irradiation and produces radicals to initiate polymerization.

A photosensitizer may be used in combination if necessary. Here, "radiation" means ultraviolet rays, visible rays, infrared rays, X-rays, electron beam, α-rays, β-rays, and γ-rays. UV or UV/Vis light is preferred.

Given as examples of such radiation polymerization initiators are acetophenone, acetophenone benzyl ketal, anthraquinone, 1-hydroxycyclohexylphenyl ketone, 2, 2-dimethoxy-2-phenylacetophenone, xanthone compounds, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4 ' -dimethoxybenzophenone, 4,4' -diaminobenzophenone, 2 -hydroxy-2 -methyl-l-phenylpropan-1-one,

1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-l-one, 1, 1-dimethoxydeoxybenzoin, 3,3' -dimethyl-4-methoxybenzophenone, diethylthioxanthone , 2-isopropylthioxanthone, 2-chlorothioxanthone,

1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-l-one, 2-methyl-l- [4- (methylthio) phenyl] -2-morpholinopropan-l- one, triphenylamine, 2 , 4, 6-trimethylbenzoyl diphenylphosphine oxides, bis- (2 , 6-dimethoxy- benzoyl) -2,4,4 -trimethylpentylphosphine oxide , bisacylphosphine oxide, benzyl methyl ketal, 2 -hydroxy-2 -methyl-1-phenylpropan-l-one, fluorenone, fluorene, benzaldehyde, benzoin ethyl ether, benzoin propyl ether, benzophenone , Michler's ketone, 2-benzyl-2-dimethylamino-l- (4-morpholinophenyl) -butan-1 -one, 3-methylacetophenone,

3 , 3 ' , 4 , 4 ' -tetra (t-butylperoxycarbonyl) benzophenone (BTTB) , and a combination of BTTB and a coloring matter sensitizer such as xanthene, thioxanthene, cumarin, or ketocumarin, as well as the compound represented by the following formula (4) ,

CH₃

I -(-C-CHa-)r-

I Ar

I

C=0 (4)

R³-C-R⁴

OH wherein R³ and R⁴ are individually an alkyl group having 1 to 5 carbon atoms and Ar stands for a divalent aromatic hydrocarbon group such as a phenylene group, biphenylene group, or naphthylene group, and r is a value from 2 to 50.

Examples of preferred alkyl groups having 1 to 5 carbon atoms in the compound of the formula (4) are a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, t-butyl group, n-pentyl group, and i-pentyl group. Of these, alkyl groups having 1 to 3 carbon atoms are particularly preferred. The value from 2 to 20 for r is preferred.

Among the above compounds, particularly preferred compounds are benzyl methyl ketal, 1-hydroxycyclohexylphenyl ketone, 2,4, 6-trimethylbenzoyl diphenylphosphine oxides, bis- (2 , 6-dimethoxy- benzoyl) -2 , 4, 4-triτnethylpentylphosphine oxide, and 2-benzyl-2-dimethylamino-l- (4-morpholinophenyl) -butan-1 -one. In addition, Irgacure 184, 651, 500, 907, 369, 784, 2959 (trademarks, manufactured by Ciba Geigy) , Lucirin TPO (trademark, manufactured by BASF) , Darocurlllδ, 1173 (trademarks, manufactured by Merck Co.), Ubecryl P36 (trademark, manufactured by UCB Co.), ESCACURE KIP150, ESCACURE KIP100F (trademarks, manufactured by Lamberti Co.) can be given as commercially available products . Given as examples of the photosensitizers are triethylamine, diethylamine, N-methyldiethanoleamine, ethanolamine, 4-dimethylaminobenzoic acids, 4-methyl dimethylaminobenzoate, 4-ethyl dimethylaminobenzoate, 4-isoamyl dimethylaminobenzoate, and commercially available products such as Ubecryl P102, 103, 104, and 105 (trademarks, manufactured by UCB Co.) . The proportion of the above-mentioned radiation polymerization initiator, which is the component (C) , relative to the total amount of the components (A) to (E) which constitutes the composition of the present invention is preferably 0.1 to 10 wt%, more preferably 0.5 to 7 wt%, and particularly preferably 1 to 5 wt%. When the amount exceeds 10 wt%, this sometimes adversely affects the curing characteristics of the resinous liquid, the properties of cured products, and handling of the composition. If less than 0.1 wt%, the curing rate may be decreased.

(D) Inorganic Particles

The component (D) used in the present invention is made up of inorganic particles. The average particle diameter of the inorganic particles is preferably from 0.1 to 10 μm, and more preferably from 0.2 to 5 μm. If the average particle diameter is smaller than 0.1 μm, the mar resistance and surface sliding characteristics of the coating film are not sufficient, if more than 10 μm, transparency of the coating film may be conspicuously impaired.

Specific examples of the inorganic particles include silica particles, glass particles, alumina, magnesium carbonate, calcium carbonate, calcium phosphate, aluminum hydroxide, talc, and titanium oxide. Among these, silica particles, glass particles, calcium carbonate, and talc are desirable. Silica particles are commercially available under the trademarks NipsilE220A, E220, K300, E1011, HD, E743, SS-10F, SS-178B (manufactured by Nippon Silica Industrial Co., Ltd.), Sildex H31, H32, L-31 (manufactured by Asahi Glass Co., Ltd.), or SO-E2, S0- E3 , SO-E5 (manufactured by Admatechs Co., Ltd.). Talc is commercially available under trademarks such as LMS-300, LMS-200, LMS-100, LMP-100, LMG-100, LMR-100, PKP-53 (manufactured by Fuji Talc Industry Co., Ltd.). Calcium carbonate is commercially available under trademarks such as Calcies, Calcies-P, PL,-X, Star Brand Light Calcium Carbonate (manufactured by KONOSHIMA CHEMICALS Co., Ltd.) and light calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) .

These inorganic particles may be used either individually or in combinations of two types or more .

The amount of the component (D) , in terms of the proportion of this component relative to the total amount of the components (A) and (E) , is preferably from 0.1-30 wt.%, more preferably from 0.2- 20 wt.% parts by weight, and particularly preferably from 0.3-18 wt.%. If this amount of the inorganic particles is less than 0.1 wt.%, the fingerprint resistance and surface sliding characteristics of the coating film tend to be insufficient; if more than 30 wt.%, transparency and mar resistance of the coating film are adversely affected.

(E) Terminal reactive polydialkylsiloxane The component (E) used in the present invention is a terminal reactive polydialkylsiloxane and is insoluble or sparingly soluble in a mixture of the above-mentioned components (A) , (B) , (C) , and (D) . The component (E) is preferably stably dispersed in the state of micro liquid droplets. The diameters of these dispersed micro liquid droplets are preferably 0.1-10 μm, and more preferably 0.2-5 μm. If the diameters of the dispersed micro liquid droplets are smaller than 0.1 μm, surface sliding characteristics are insufficient, which causes high conveyance noise, while exhibiting poor durability in repeated printing. On the other hand, if the diameter of the dispersion micro liquid droplets exceeds 10 μm, the dispersion tends to be instable, which not only causes phase separation during storage, but also produces uneven coating when applied.

The preferred terminal reactive polydialkylsiloxane of the present invention is represented by the following formula (5) ,

R¹ R⁴ R⁴

CH₂=C-C- (0-R²)_k- (Si-0) i-Si-R³ (5) II I I

0 R⁴ R⁴

wherein R¹ is a hydrogen atom or a methyl group, R² is an alkylene group having 2-8 carbon atoms, R³ is an alkyl group having 1-8 carbon atoms, R⁴ is an alkyl group having 1-8 carbon atoms, k denotes an integer from 1-10, and 1 denotes an integer from 1-200.

In the formula (2) , it is preferable that R^: be an alkylene group having 2-5 carbon atoms; R³, an alkyl group having 1-5 carbon atoms; R⁴ a methyl group; k, an integer from 1-5; and 1, an integer from 1-100. As commercially available products of a terminal reactive polydimethylsiloxane, Silaplene FM- 0711, FM-0721, FM-0725 (manufactured by Chisso Corp.) and AK-5 (manufactured by Toagosei Co., Ltd.) can be given.

The amount of the polydialkylsiloxane having a polymerizable reactive group used as the component (E) , relative to the total amount of the components (A) , (B) , (C) , and (D) , is preferably 0.1- 10 parts by weight, more preferably 0.2-7 parts by weight, and particularly preferably 0.3-5 parts by weight, for 100 parts by weight of the total amount of components (A) , (B) , (C) , and (D) . If the amount of the polydimethylsiloxane having a polymerizable reactive group is less than 0.1 parts by weight, surface sliding characteristics of the coating film are insufficient, which causes high conveyance noise, if the proportion exceeds 10 parts by weight, stability of a liquid resin and transparency and mar resistance of the coating film tend to be impaired.

In addition to the component (A) , component (B) , component (C) , component (D) , and component (E) one or more reactive diluents such as mono-functional monomers and poly-functional monomers other than the component (A) and the component (B) can be used as an optional component in the composition of the present invention. Given as examples of the mono-functional monomer are compounds such as acrylamide, 7-amino-3 , 7-dimethyloctyl (meth) acrylate, isobutoxymethyl (meth) acrylamide, isobornyloxyethyl (meth) acrylate, isobornyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ethyldiethylene glycol (meth) acrylate, t-octyl (meth) acrylamide, diacetone (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate and lauryl (meth) acrylate, dicyclopentadiene (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentenyl (meth) acrylate, N,N-dimethyl (meth) acrylamide, tetrachlorophenyl (meth) acrylate,

2-tetrachlorophenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, tetrabromophenyl (meth) acrylate, 2-tetrabromophenoxyethyl (meth) acrylate, 2-trichlorophenoxyethyl (meth) acrylate, tribromophenyl (meth) acrylate, 2-tribromophenoxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, phenoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, pentachlorophenyl

(meth) acrylate, pentabromophenyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, bornyl (meth) acrylate, methyltriethylene diglycol (meth) acrylate, and (meth) acryloyl group- containing monomers represented by the following formulas (6) to (8) ,

CH₂=C(R¹) -CO-O- (-R⁵-0)_s-Ar-R^s (6)

wherein R¹ is a hydrogen atom or a methyl group, R⁵ is an alkylene group having 2 to 6, preferably 2 to 4, carbon atoms, R⁶ is a hydrogen atom or an alkyl group having 1 to 12, preferably 1 to 9, carbon atoms, Ar stands for a divalent aromatic hydrocarbon group such as phenylene group, biphenylene group, or naphthylene group, and s is a value from 1 to 12, preferably 1 to 8;

CH₂=C(R¹) -CO- (0R⁷-C0-)_t-0-CH₂-S (7)

wherein R¹ is a hydrogen atom or a methyl group, R⁷ is an alkylene group having 2 to 8 , preferably 2 to 5, carbon atoms, t is a value from 1 to 8, preferably 1 to 4, and S is a tetrahydrofuryl group; R⁹

O-CH R⁹

/ \ / CH₂=C(R¹) -CO- (-OR⁸-CO-)_u-0-CH₂-C(CH₃)₂-CH C (8) \ / \

O-CH R⁹

I

R⁹ wherein R¹ is a hydrogen atom or a methyl group, R⁸ is an alkylene group having 2 to 8, preferably 2 to 5, carbon atoms, R⁹ is a hydrogen atom or a methyl group, and u is a value from 1 to 8, preferably 1 to 4; and vinyl group-containing monomers such as N-vinyl carbazole N-vinyl pyrrolidone and N-vinyl caprolactam.

Of these compounds, isobornyl (meth) acrylate, phenoxyethyl (meth) acrylate, N-vinylcarbazole, are particularly preferred.

These mono-functional monomers are commercially available under the trademarks of Aronix M-lll, M-113, M-117 (trademarks, manufactured by Toagosei Chemical Industry Co., Ltd.), KAYARAD TC110S, R-629, R-644 (trademarks, manufactured by Nippon Kayaku Co., Ltd.), and Viscoat 3700 (trademarks, manufactured by Osaka Organic Chemical Industry, Ltd.) .

The following (meth) acryloyl group containing monomers can be given as examples of the poly-functional monomer: ethylene glycol di (meth) acrylate, dicyclopentenyl di (meth) acrylate, triethylene glycol diacrylate, tetra ethylene glycol di (meth) acrylate, tricyclodecanediyldimethylene di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane trioxyethyl (meth) acrylate, tripropylene diacrylate, neopentylglycol di (meth) acrylate, bisphenol A-diglycidyl ether with (meth) acrylic acid added in both terminals, 1,4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, polyester di (meth) acrylate, and polyethylene glycol di (meth) acrylate .

As examples of poly-functional monomers, (meth) acryloyl group-containing monomers such as ethylene glycol di (meth) acrylate, dicyclopentenyl di (meth) acrylate, triethylene glycol diacrylate, tetraethylene glycol di (meth) acrylate, tricyclodecanediyldimethylene di (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, PO-modified trimethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, pentaerythritol tri (meth) acrylate, polyester di (meth) acrylate, polyethylene glycol di (meth) acrylate , and tris [ (meth) acryloxyethyl] - isocyanurate, and (meth) acryloyl group-containing monomers represented by the following formula (9) ,

R¹0 OH OH 0 R¹

I II I I II I

CH₂=C-CO- (CH₂CHCH₂0)_p-X- (0CH₂CHCH₂) _q-OC-C=C (9)

wherein R¹ is a hydrogen atom or a methyl group, X is a divalent group having 2-26, preferably 2-14 carbon atoms, such as an alkylene group, phenylene group, biphenylene group, or naphthylene group, and p and q respectively denote an integer from 1-10, preferably 1- 5, can be given.

Of these, tris [ (meth) acryloxyethyl] - isocyanurate, trimethylolpropane triacrylate, EO- modified trimethylolpropane triacrylate, tricyclo- decanediyldimethylene di (meth) acrylate, tetraethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and (meth) acryloyl group-containing monomers represented by the formula (9) are preferable. These poly-functional monomers are commercially available under trademarks such as Yupimer UV, SA1002 (manufactured by Mitsubishi Chemical Corp.), Viscoat 700 (manufactured by Osaka Organic Chemical Industry Co., Ltd.), KAYARAD R-604, D-310, D-330

(manufactured by Nippon Kayaku Co., Ltd.), Aronix M- 210, M-315 (manufactured by Toagosei Co., Ltd.), and Epoxy ester 40EM, 70PA, 200PA, 1600A, 80MFA, 3002M, 3002A, 3000M, 3000A, 200EA, 400EA (manufactured by Kyoeisha Chemical Co., Ltd.)

The above mono-functional and poly- functional monomers may be used either individually or in combinations of two or more and preferably formulated in the composition of the present invention in an amount of 30 wt% or less, preferably 20 wt% or less. If the amount exceeds 30 wt%, anti-bruising characteristics and durability in repeated printing of the cured product tend to be impaired.

Various additives can be used in the composition of the present invention as required.

Antioxidants, photostabilizers, silane coupling agents, thermal polymerization inhibitors, leveling agents, surfactants, preservatives, coloring agents, UV absorbers, plasticizers, lubricants, inorganic fillers, organic fillers, wettability improvers, coating surface improvers, and the like are included in such additives.

As commercially available antioxidants, Irganox 1010, 1035, 1076, 1222 (trademarks, manufactured by Ciba Geigy) Antigene W, S, P, 3C, 6C, RD-G, FR, AW (trademarks, manufactured by Sumitomo

Chemical Industries Co., Ltd.) and the like are given. Tinuvin P, 234, 320, 326, 327, 328, 213 (trademarks, manufactured by Ciba Geigy), Sumisorb 110, 130, 140, 220, 250, 300, 320, 340, 350, 400 (trademarks, manufactured by Sumitomo Chemical Industries Co., Ltd.) , and the like are given as examples of the UV absorbers. As commercially available photostabilizers, Tinuvin 292, 144, 622LD (trademarks, manufactured by Ciba Geigy), Sanol LS-770, 765, 292, 2626, 1114, 744 (trademarks, manufactured by Sankyo Chemical Co.), and the like are given. As examples of the silane coupling agent, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-acryloxypropyltri-methoxysilane are given, and SH6062, SZ6030 (trademarks, manufactured by Toray-Dow Corning

Silicone Co.), KBE903, KBM803 (trademarks, manufactured by Shin-Etsu Silicone Co., Ltd.), and the like are given as examples of commercially available silane coupling agents. Other additives which can be added to the composition of the present invention include epoxy resin; polymerizable compounds such as urethane acrylate, vinyl ether, propenyl ether, and maleic acid derivatives; polymer or oligomers such as polyamide, polyimide, polyamideimide, polyurethane, polybutadiene, chloroprene, polyether, polyester, pentadiene derivatives, styrene/butadiene/styrene block copolymer, styrene/ethylene/butene/styrene block copolymer, styrene/isoprene/styrene block copolymer, petroleum resin, xylene resin, ketone resin, fluorine-containing oligomer, silicon-containing oligomer, and polysulfide oligomer.

In addition, a dilution solvent can be used in the composition of the present invention. Given as examples of such a dilution solvent are alcohols such as methanol, ethanol, isopropyl alcohol, butanol, and cyclohexanol; esters such as ethyl acetate, butyl acetate, isoamyl acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone; aromatic hydrocarbons such as benzene, toluene, and xylene; and mixed solvents consisting of two or more of the solvents selected from these solvents. Of these dilution solvents, preferred are ethanol, isopropyl alcohol, or butanol; and mixed solvents consisting of one of these alcoholic solvents, an ester solvent such as ethyl acetate or butyl acetate, and a ketone solvent such as methyl ethyl ketone or methyl isobutyl ketone . The amount of the dilution solvent used in the composition of the present invention differs greatly depending on the coating method. Usually, 0 to 2000 parts by weight is preferably used for 100 parts by weight of the total amount of the composition of the present invention comprising the components (A) to (E) and the additives. More preferably, the amount is 50- 500 parts by weight of solvent relative to 100 parts by weight of the total composition.

The order in which various components of the composition of the present invention are mixed is not critical. Usually, from the viewpoint of ease in carrying out the blending and ease of causing the inorganic particles which form the component (D) to uniformly disperse, the component (D) is added to a mixture comprising the components (A) , (B) , (C) , (E) , and the above-mentioned optional components, and the mixture is stirred until the inorganic particles are uniformly dispersed to obtain the composition of the present invention. Viscosity of the resulting composition is usually 1 to 100,000 mPa.s, 5-50,000 mPa.s, at 25°C. The composition of the present invention can be coated on substrates by commonly used methods . Such coating methods include, for example, dip coating, spray coating, flow coating, roll coating, and screen printing. The thickness of coating films obtained by these coating operations is usually 0.1 to 50μm, and preferably 1 to lOμm. After the composition of the present invention has been applied, volatile components are removed at a temperature of 0 to 200°C, preferably 20 to 100°C, and more preferably 40 to 70°, for 1 second to 24 hours, preferably 10 seconds to 1 hour, as required, and then the coatings are cured by irradiation. Preferably, the cured conting is transparent . Ultraviolet rays are preferably used for curing the composition of the present invention. The ultraviolet rays used should include light with a wave length of 400 nm or below. A metal halide lamp or a mercury lamp (high pressure, medium pressure, or low pressure) can be used as a light source at a dose usually of 0.01 to 10 J/cm², preferably of 0.1 to 3 J/cm².

Examples

The present invention will be explained in more detail by way of examples, which are not intended to be limiting of the present invention. In the examples below, part(s) indicates part(s) by weight unless otherwise indicated.

1. Preparation of compositions Example 1

17 parts of acrylate of bisphenol A diglycidyl ether polymer (Lipoxy VR-90, manufactured by Showa Highpolymer Co., Ltd.) as the component (A), 51 parts of dipentaerythritol monohydroxy pentaacrylate as the component (B) , 3 parts of 1-hydroxycyclohexyl phenyl ketone and 1 part of 2-methyl-1-4- (methylthio)phenyl-2-morpholinopropan-l-one as the component (C) , 2 parts of polydimethylsiloxane with a methacryloyl-modified terminal (Silaplene FM-0721, manufactured by Chisso Corp.) as the component (E) , and as optional components, 8 parts of EO-modified trimethylolpropane triacrylate (manufactured by Shin- Nakamura Kogyo Co., Ltd.) and 9 parts of tris [ (meth) acryloxyethyl] isocyanurate (Aronix M-315, manufactured by Toagosei Co., Ltd.) were placed in a glass vessel equipped with a stirrer. After the mixture was stirred for about 3 hours at 70°C, 9 parts of silica particles (Nipsil E220A, secondary particles diameter of 1-2 μm by the Coulter counter average diameter method, manufactured by Nippon Silica Industrial Co., Ltd.) was added as the component (D) . The resulting mixture was stirred for about 10 minutes using a homogenizer (TK Homodisper 2.5 type, manufactured by Tokushu Kika Industry Ltd.) until silica particles in the liquid resin were uniformly dispersed to provide the composition of Example 1 shown in Table 1.

Examples 2-4 and Comparative Examples 1-5

The compositions of Examples 2-4 and Comparative Examples 1-5 were prepared using formulations shown in Table 1 according to the same operations as in Example 1. Components described in Table 1 are as follows.

Component (A) A-l: Acrylate of bisphenol A diglycidyl ether polymer

(Lipoxy VR-90, molecular weight 1100, manufactured by

Showa Highpolymer Co., Ltd.)

A-2 : Acrylate of bisphenol A diglycidyl ether polymers

(Lipoxy VR-77, molecular weight 510, manufactured by Showa Highpolymer Co., Ltd.)

Component (B) : Dipentaerythritolmonohydroxy pentaacrylate

Component (C)

C-l: l-hydroxycyclohexylphenyl ketone

C-2 : 2-methyl-l [-4- (methylthio) phenyl] -2- morpholinopropan-1-one

Component (D)

D-l: Nipsil E220A (manufactured by Nippon Silica Industrial Co., Ltd., secondary particles diameter 1-2 μ ) D-2 : Light calcium carbonate (manufactured by Maruo Calcium Co., Ltd.)

D-3: Talc LMS-300 (manufactured by Fuji Talc Industrial Co., Ltd.)

Component (E)

E-l: Polydimethylsiloxane with a methacryloyl-modified terminal (Silaplene FM-0721, manufactured by Chisso Corp . )

Other components

F-l: EO-modified trimethylolpropane triacrylate

F-2 : Tris [ (meth) acryloxyethyl] isocyanurate

F-3: N-vinyl caprolactam

F-4 : Acryloyl morpholine F-5: Non-reactive polydimethylsiloxane (DC-57, manufactured by Dow-Corning Co.) Table 1

2. Application and curing of compositions

A sample of each composition was applied to a film substrate made from a vinyl chloride-vinyl acetate copolymer resin or a glass plate using a No. 6 bar-coater so as to form a film with a thickness of about 5 μm. The coated film was cured by exposure to atmospheric conducting to ultraviolet radiation, at a dose of 1.0 J/cm² (using ultraviolet irradiation apparatus type: UBX0311-00, light source: metal halide lamp of 120 W/cm, manufactured by Eye Graphics Co., Ltd. ) .

3. Evaluation of cured coating

Test specimens of the above cured coating film were evaluated according to the following methods. The results are shown in Table 1.

(1) Pencil hardness: Pencil hardness was evaluated using a cured coating film prepared by on a glass plate

(in accordance with 2 above) according to the pencil hardness test JIS K5400.

(2) Adhesion to a substrate: According to JIS K5400, ten cross-cut notches in length and breadth were formed at intervals of 1 mm on the cured coating film obtained by coating a film made fromed at a vinyl chloride- vinyl acetate copolymer resin (in accordance with 2 above) to perform a peeling test using a cellophane tape. The case where peeling of the cured film was not observed was rated as O and the case where peeling of the cured film was observed was rated as X. (3) Anti-bruising characteristics: Using the cured coating film obtained by coating a polyester film, a record printing-erasing operation with a thermal head having the temperature of 350°C was repeated 500 times to observe bruising of the surface of cured coating film by the thermal head. The case where the surface of the cured coating film was scarcely bruised was rated as O and the case where the surface of cured coating film was obviously bruised was rated as X. (4) Conveyance noise: Using the cured coating film obtained by coating a polyester film, a record printing-erasing operation with a thermal head having a temperature of 350°C was repeated 500 times. During these operations, the case where mechanical noise occurring from around the thermal head was small was rated as O and the case where mechanical noise was large was rated as X.

(5) Printing test: Using the cured coating film obtained by coating a polyester film, a record printing-erasing operation with a thermal head having a temperature of 350°C was repeated 500 times to observe the printing surface. The case where acceptable printing was achieved was rated as O and the case where printing was inacceptable obviously occurred was rated as X.

By using the photo-curable resin composition of the present invention, it is possible to form a hard coat having superb characteristics such as high hardness, superior adhesion to a substrate, mar resistance, light resistance, heat resistance, and a good appearance of the cured coating surface. In particular, when used as a surface protective coat for a thermosensible type information recording carrier, the photo-curable resin composition exhibits superb characteristics such as superior anti-bruising characteristics, slight conveyance noise in a printing- erasing operation, and high durability in a repeated printing operation.

Claims

WHAT IS CLAIMED IS:

1. A radiation curable resin composition comprising (A) a (meth) acrylate of a bisphenol diglycidyl ether compound,

(B) a branched (meth) acrylol group-containg compound,

(C) a radiation polymerization initatiator (D) inorganic particles, and

(E) a terminal reactive polydialkyl siloxane.

2) Radidation curable resin composition according to claim 1, in which the (meth) acrylate of a bisphenol diglycidyl ether compound (A) is represented by the following formula (1) :

CH₂=C(R¹) -CO-O-X¹- (-X²-Ar-Y-Ar-0-)_n-X²-X¹-C0-C(R¹)=CH₂ (1)

wherein R¹ represents a hydrogen atom or a methyl group, X¹ represents a bond or a group represented by the following formula (2) ,

-(R²-0)╬╣-

wherein R² denotes an alkylene group having 2 to 6 carbon atoms and 1 is a value from 1 to 5; X² is a group represented by the following formula (3) ,

OH

I (-CH₂CHCH₂0-)_m- (3) wherein m is a value from 0 to 1; Ar represents a divalent aromatic hydrocarbon group such as a phenylene group, bisphenylene group, or naphthylene group, Y is a divalent organic group, and n is a value from 1 to 35; provided that 1 + m is 1 or more;

3. Radiation curable resin composition according to any one of claims 1-2, in which the branched (meth) acryloyl group-containing compound (B) is selected from compounds comprising a pentaeritrytol or dipentaeritrytol derivative having at least one of an (meth) acryloyl, alkoxylated (meth) acryloyl, and/or (poly) caprolacton (meth) acryloyl group.

4. Radiation curable resin composition according to claims 1-3 wherein component (A) comprises groups derived from bisphenol-A.

5. Radiation curable resin composition according to claims 1-4, wherein component (A) is present in 10-50 wt.% relative to components A-B.

6. Radiation curable resin composition according to claims 1-5, wherein component (B) comprises at least 4 (meth) acryloyl groups .

7. Radiation curable resin composition according to claims 1-6, wherein component (B) is present in an amount of 50-90 wt.% relative to components A-B.

8. Radiation curable resin composition according to claim 1-7, wherein the terminal reactive polydialkylsiloxane is represented by the following formula (5) : R¹ R⁴ R⁴

CH₂=C ¹-C- (0-R²)_k- (S Ii-OJiS Ii-R³ (5) 0 R⁴ R⁴

wherein R¹ is a hydrogen atom or a methyl group, R² is an alkylene group having 2-8 carbon atoms, R³ is an alkyl group having 1-8 carbon atoms, R⁴ is an alkyl grop having 1-8 carbon atoms k denotes an integer from 1-10, and 1 denotes an integer from 1-200.

9. Radiation curable resin composition according to claims 1-8, wherein the inorganic particles have an average particle diameter of 0.1-10 ╬╝m.

10. Radiation curable resin composition according to claims 1-9, wherein component (D) is present in an amount of 0.01-30 wt.% relative to component A-C.

11. Radiation curable resin composition according to claims 1-10, wherein the composition further comprises one or more reactive diluents in an amount of less than 30 wt.% relative to components A-E.

12. Radiation curable resin composition according to claims 1-11, wherein the composition further comprises one or more of an antioxidant, UV absorber, silane coupling agent, inhibitor, or coloring agent .

13. Radiation curable resin composition according to claims 1-12, wherein the composition further comprises 0-2000 parts by weight of a non-reactive solvent relative to 100 parts by weight of the total composition of components A-E and the additives.

14. Radiation curable resin composition according to claims 1-13, wherein the composition has a viscosity of (1-10,000 mPa.s) at 25┬░C.

15. Protective coating, being a cured resin composition of any one of claims 1-14.

16. Coating according to claims 1-15, wherein the coating is printable and heat resistant.

17. Coating according to any one of claims 15-16, wherein the coating is transparent.

18. Thermo-recordable media at least partially covered with the coating according anyone of claims 15-17.

19. The thermo-recordable media of claim 18 wherein the media is a card or photographic paper.

20. Process for preparing a radiation curable resin composition comprising:

I) mixing a (meth) acrylate of a bisphenol diglycidyl ether compound, a branhced (meth) acrylol group-containing compound, a radiation polymerization initaitor, and a terminal reactive polydialkyl siloxane, and ii) admixing inorganic particles.