JP2009079089A - Photocurable coating composition, overprint and method for producing the same - Google Patents

Abstract

Provided are a photocurable coating composition having excellent surface smoothness, an overprint excellent in non-tackiness and surface smoothness by applying and curing the photocurable coating composition, and a method for producing the same. thing.
A photocurable coating composition comprising an ethylenically unsaturated compound having a cyclic ether group and a photopolymerization initiator, and an overprint using the photocurable coating composition And its manufacturing method. Moreover, the photocurable coating composition of this invention can be used conveniently as a photocurable coating composition for the overprint of electrophotographic printed matter.
[Selection figure] None

Description

  The present invention relates to a photocurable coating composition, an overprint, and a method for producing the same. More specifically, the present invention relates to a photocurable coating composition that can be cured by irradiation with active radiation such as an electron beam and ultraviolet rays. In particular, light for coating an image created by arranging ink and / or toner on a printing substrate (image receiving substrate) by a method such as planographic printing, relief printing, intaglio printing, screen printing, ink jetting, and electrophotography. The present invention relates to a curable coating composition. More particularly, it relates to photocurable overprint compositions that can be used particularly suitably for coating toner-based prints printed by electrophotography.

In recent years, a large number of actinic radiation curable compositions that can be used for UV-curable printing inks, paints, and coatings have been developed and are now being popularized. However, it is difficult to obtain a photocurable composition that satisfies all of the curability, surface smoothness, strength, storage stability, and the like.
In particular, toner-based images such as electrophotography are more difficult to obtain the desired performance when a feather oil layer is present on the image surface.
In a conventional method for generating a toner-based image, such as electrophotography, an electrostatic charge is formed on the surface of the latent image carrier by uniformly charging the surface of the latent image carrier, for example, a photoreceptor. Let Then, the uniformly charged area is selectively released by the activation irradiation pattern corresponding to the image of the original. The latent image charge pattern remaining on the surface corresponds to the areas not exposed to irradiation. The photoreceptor is then passed through one or more development housings containing toner, so that the toner adheres in a charge pattern due to electrostatic attraction, thereby visualizing the latent image charge pattern. The developed image is then fixed to the imaging surface or transferred to a printing substrate, such as paper, and fixed to it by a suitable fixing technique to obtain an electrophotographic print, i.e. a toner-based print. .

As a known method for protecting a printed matter, it has been proposed to apply an overprint coating to the printed matter. For example, Patent Documents 1 and 2 propose a method of covering the surface by performing fixing after transferring a transparent toner onto a toner-based image, such as electrophotography.
Patent Document 3 proposes a method of performing overprint coating by applying a liquid film coating that can be cured by ultraviolet rays or the like, and polymerizing (crosslinking) the coating components with light.
In addition, Patent Document 4 discloses a polyfunctional alkoxylated acrylic monomer or polycrystal comprising a radiation curable oligomer selected from the group consisting of trifunctional unsaturated acrylic resins and one or more di-acrylates or tri-acrylates. An overprint composition comprising a radiation curable monomer selected from the group consisting of alkoxylated acrylic monomers, at least one photopolymerization initiator, and at least one surfactant is disclosed.

JP-A-11-70647 JP 2003-241414 A JP-A-61-210365 JP-A-2005-321882

  The problem to be solved by the present invention is a photocurable coating composition excellent in surface smoothness, and an overprint excellent in non-tackiness and surface smoothness by applying and curing the photocurable coating composition. And a method of manufacturing the same.

The above object has been achieved by <1>, <8> or <9> described below. It is described below together with <2> to <7> which are preferred embodiments.
<1> A photocurable coating composition comprising an ethylenically unsaturated compound having a cyclic ether group and a photopolymerization initiator,
<2> The ethylenically unsaturated compound having a cyclic ether group is an ethylenically unsaturated compound having a 1,3-dioxolane ring skeleton and / or a 1,3-dioxane ring skeleton, according to the above <1>. A photocurable coating composition,
<3> The photocurable coating composition according to <1> or <2> above, wherein the ethylenically unsaturated compound having a cyclic ether group is a monofunctional ethylenically unsaturated compound,
<4> The photocurable coating composition according to any one of <1> to <3> above, which contains a polyfunctional ethylenically unsaturated compound,
<5> The photocurable coating composition according to any one of <1> to <4>, which has substantially no absorption in a visible region,
<6> The photocurable coating composition according to any one of <1> to <5>, which is for overprinting,
<7> The photocurable coating composition according to any one of <1> to <6> above, which is for overprinting of an electrophotographic printed material,
<8> An overprint having an overprint layer obtained by photocuring the photocurable coating composition according to any one of <1> to <7> above on an electrophotographic printed material,
<9> A step of obtaining an electrophotographic printed material by electrophotographic printing on a printing substrate, and applying the photocurable coating composition according to any one of <1> to <7> above on the electrophotographic printed material. And a method of photocuring the photocurable coating composition.

  According to the present invention, a photocurable coating composition excellent in surface smoothness, an overprint excellent in non-tackiness and surface smoothness by applying and curing the photocurable coating composition, and a method for producing the same Could be provided.

The photocurable coating composition of the present invention comprises an ethylenically unsaturated compound having a cyclic ether group and a photopolymerization initiator.
The overprint of the present invention has an overprint layer obtained by photocuring the photocurable coating composition on an electrophotographic printed material.
The overprint production method of the present invention includes a step of electrophotographic printing on a printing substrate to obtain an electrophotographic printed matter, a step of applying the above-described photocurable coating composition on the electrophotographic printed matter, and the light Photocuring the curable coating composition.
Hereinafter, the present invention will be described in detail.

(Photocurable coating composition)
The photocurable coating composition of the present invention preferably has substantially no absorption in the visible range. “Substantially no absorption in the visible region” means that there is no absorption in the visible region of 400 to 700 nm, or there is absorption in the visible region only to the extent that there is no problem as a photocurable coating composition. It means not. Specifically, it means that the 5 μm optical path length transmittance of the coating composition is 70% or more, preferably 80% or more in the wavelength range of 400 to 700 nm.
The photocurable coating composition of the present invention can be suitably used for overprinting, and can be particularly suitably used for overprinting of electrophotographic prints.
The photocurable coating composition of the present invention is excellent in non-tackiness and surface smoothness, glossy and glossy even when an overprint layer is formed on an electrophotographic print having an image portion having a thickness equivalent to the toner. It gives a certain overprint and can visually give an impression close to that of a conventional silver halide photographic print.
In addition, the photocurable coating composition of the present invention is excellent in non-tackiness and surface smoothness, gloss, gloss, and flexibility with little warpage, even for a toner image having a feather oil layer on the image surface. Image prints rich in color, and an overprint visually close to a silver salt photographic print can be obtained.

<An ethylenically unsaturated compound having a cyclic ether group>
The photocurable coating composition of the present invention (hereinafter also simply referred to as “coating composition”) has an ethylenically unsaturated compound having a cyclic ether group (hereinafter also referred to as “specific cyclic monomer”) as an essential component. contains.
Hereinafter, the “ethylenically unsaturated compound having a cyclic ether group (specific cyclic monomer)” which is a characteristic component in the present invention will be described in detail.

The ethylenically unsaturated compound having a cyclic ether group used in the present invention is not particularly limited as long as it is a compound having one or more ethylenically unsaturated bonds and one or more cyclic ether groups in the molecule. That is, it may be monofunctional or polyfunctional.
The cyclic ether group may be a group obtained by removing one or more hydrogen atoms from the cyclic ether. The atoms forming the ring skeleton in the cyclic ether group are preferably only carbon atoms and oxygen atoms. The cyclic ether group preferably has no unsaturated bond in the ring skeleton.
As the cyclic ether group, the number of atoms forming the ring is preferably 3 to 12, more preferably 3 to 10, still more preferably 4 to 7, and further preferably 5 or 6. Particularly preferred.
Examples of the cyclic ether having one ether bond include oxirane, oxetane, oxolane, oxane, oxepane, oxocane, oxonan, oxecan and the like. Examples of the cyclic ether having two ether bonds include dioxolane, dioxane, dioxepane, dioxocane, dioxonan, dioxecan and the like.
The number of ether bonds that the cyclic ether group has in the ring skeleton is preferably 1 to 4, more preferably 1 to 3, further preferably 1 or 2, and particularly preferably 2. preferable.

  In the present invention, as the specific cyclic monomer, in particular, polymerization having a 1,3-dioxane ring skeleton represented by the following formula (I) and a 1,3-dioxolane ring skeleton represented by the following formula (II) Are preferred.

In the above formula, R ^{1 to} R ⁸ each independently represents a hydrogen atom or a hydrocarbon group. In the formula (I), at least one of R ^{1 to} R ⁸ , and in the formula (II), R ^{1 to} R 8 ^At least one of ⁶ has an ethylenically unsaturated bond. The compound represented by formula (I) or formula (II) preferably has an ethylenically unsaturated bond at the terminal.
As the hydrocarbon group when R ^{1 to} R ⁸ are hydrocarbon groups, a hydrocarbon group having about 1 to 18 carbon atoms is preferable. Specifically, an alkyl group, an aryl group, an aralkyl group, an alkenyl group, a cyclo group An alkyl group etc. are mentioned, Among these, an alkyl group is preferable.
A preferable alkyl group in the case where R ^{1 to} R ⁸ represent an alkyl group includes a linear or branched alkyl group having about 1 to 8 carbon atoms, and a linear alkyl group having 1 to 4 carbon atoms is more preferable. A methyl group or an ethyl group is preferable.

When R ^{1 to} R ⁸ are hydrocarbon groups, the hydrocarbon group may further have a substituent. The substituents that the hydrocarbon group may have include alkyl groups, hydroxy groups, cyano groups, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, iodine atoms), amino groups, carboxy groups, acyl groups, alkoxy groups. Examples thereof include a hydroxy group and a nitro group, and a hydroxy group is preferable.

The hydrocarbon group may have one or more divalent groups selected from the group consisting of —CO—, —S—, —NR ¹¹ —, and —O— in its structure. R ¹¹ represents a hydrogen atom or an alkyl group having 1 or more carbon atoms, preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 12 carbon atoms, More preferably, it is an alkyl group of 4. Specific examples of the alkyl group include a methyl group, an ethyl group, and a butyl group.
The hydrocarbon group may have two or more of the divalent linking groups, and these divalent linking groups are divalent linking groups configured by combining two or more types. There may be. Specifically, — (CO) O— and —NR ¹¹ CO— can be exemplified.

In the formula (I), at least one of R ^{1 to} R ⁸ and at least one of R ^{1 to} R ⁶ in the formula (II) may have an ethylenically unsaturated bond structure. Can be used without limitation. R ^{1 to} R ⁶ preferably have an ethylenically unsaturated bond at the terminal as a substituent, and the ethylenically unsaturated bond is preferably a radical polymerizable double bond.
Examples of the functional group containing an ethylenically unsaturated bond include a (meth) acryloyl group, an allyl group, a styryl group, a vinyloxy group, and the like, and a (meth) acryloyl group from the viewpoint of curing sensitivity of the photocurable coating composition. It is preferable that
From the viewpoint of surface smoothness, the viscosity of the compound is preferably low, and the number of ethylenically unsaturated bonds that the specific cyclic monomer has is preferably 1 to 3, more preferably 1 to 2, 1 is particularly preferred.
That is, the ethylenically unsaturated compound having a cyclic ether group is preferably a 1-3 functional ethylenically unsaturated compound, more preferably a monofunctional or bifunctional ethylenically unsaturated compound, and a monofunctional More preferably, it is an ethylenically unsaturated compound.

In Formula (I), at least one of R ^{1 to} R ⁸ , and in Formula (II), at least one of R ^{1 to} R ⁶ preferably has an ethylenically unsaturated bond as a substituent at the terminal. The structure of the ethylenically unsaturated bond at the terminal as a substituent is preferably a monovalent organic group represented by the following formula (III) or (IV).

In the formulas (III) and (IV), R ⁹ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, and is a hydrogen atom or a methyl group from the viewpoint of reactivity and flexibility of the polymer produced by the polymerization reaction. Preferably there is. R ¹⁰ has the same meaning as R ^{1 to} R ⁸ described above, but is preferably a hydrogen atom. In the above formula (III) and formula (IV), “*” means that R ^{1 to} R ^{8 in the} formula (I) and the formula (II) are bonded directly or through the above-described divalent linking group. It shows the position.
The structure derived from (meth) acrylic acid is preferably a monovalent organic group represented by the formula (III) from the viewpoint of the viscosity of the composition and the physical properties after curing.
The number of (meth) acrylic acid derivatives present as substituents at the ends of R ^{1 to} R ⁸ in formula (I) and R ^{1 to} R ⁶ in formula (II) is ¹ to 2 in one molecule. It is more preferable that it is one from the viewpoint of the viscosity of the compound itself and the physical properties after the composition is cured.
That is, the specific cyclic monomer is preferably a (meth) acrylate compound having a cyclic ether group, or a (meth) acrylamide compound having a cyclic ether group, and a monofunctional (meth) acrylate compound having a cyclic ether group, or More preferably, it is a monofunctional (meth) acrylamide compound having a cyclic ether group.
The (meth) acrylate represents acrylate or methacrylate, and (meth) acrylamide represents acrylamide or methacrylamide. In the present invention, for example, a monofunctional (meth) acrylate compound represents a compound having only one (meth) acryloxy group, and further has a functional group having an ethylenically unsaturated bond other than the acryloxy group. May be.
Among these, an ester or amide of (meth) acrylic acid having a 1,3-dioxane ring skeleton represented by the formula (I) is preferable from the viewpoint of curing speed, and particularly represented by the formula (I), A compound having one monovalent organic group represented by III) in the molecule is preferred.

Specific examples of the ethylenically unsaturated compound having a cyclic ether group that can be suitably used in the present invention [Exemplary compounds (B-1) to (B-23)] are shown below. It is not limited. Moreover, when a stereoisomer exists in each exemplary compound, any of them may be used, and a mixture of stereoisomers may be used.
In the present invention, the hydrocarbon chain of the compound or its partial structure may be described by a simplified structural formula in which symbols for carbon (C) and hydrogen (H) are omitted.

  Among these, (B-4), (B-6), (B-14), (B-15), (B-16) and (B-17) are preferable, and (B-6) is more preferable. It is.

The content of the specific cyclic monomer (preferably a polymerizable compound having a 1,3-dioxolane ring skeleton or a 1,3-dioxane ring skeleton) in the photocurable coating composition of the present invention is the surface smoothness (leveling property). From the viewpoint of imparting the suitability of non-tackiness (suppression of surface tackiness), it is preferably 10% by weight or more, and preferably in the range of 10 to 90% by weight with respect to the total weight of the photocurable coating composition. More preferably, the range is 10 to 60% by weight, still more preferably 30 to 60% by weight, and most preferably 40 to 60% by weight.
Furthermore, it is preferable that the specific cyclic monomer in the photocurable coating composition of the present invention accounts for 25% by weight or more based on the entire polymerizable monomer to be used.
Moreover, a specific cyclic monomer may be used individually by 1 type, and may use 2 or more types together.

  The specific cyclic monomer may have one cyclic ether group or two or more cyclic ether groups in its structure. It is preferable to have 1 to 3, more preferably 1 or 2, and still more preferably only one. When it has two or more cyclic ether groups, those cyclic ether groups may be directly bonded or may be bonded via a divalent linking group. Further, the cyclic ether group may share a part of the elements forming the ring, or may form a spiro ring.

<Other polymerizable compounds>
The photocurable coating composition of the present invention may contain other polymerizable compounds in addition to the ethylenically unsaturated compound (specific cyclic monomer) having a cyclic ether group.
Examples of other polymerizable compounds that can be used in the present invention include ethylenically unsaturated compounds (radical polymerizable compounds) that do not have a cyclic ether group, and cationic polymerizable compounds.

Other radical polymerizable compounds that can be used in the present invention are compounds having an ethylenically unsaturated bond capable of radical polymerization, preferably copolymerizable with a specific cyclic monomer, and having a cyclic ether structure. It may be any compound as long as it is a compound having at least one ethylenically unsaturated bond capable of radical polymerization in the molecule, and includes compounds having chemical forms such as monomers, oligomers and polymers.
Only one kind of the radically polymerizable compound having no cyclic ether group may be used, or two or more kinds thereof may be used in combination at an arbitrary ratio in order to improve the desired properties. It is preferable to use two or more kinds in combination for controlling performance such as reactivity and physical properties.

Examples of the polymerizable compound having an ethylenically unsaturated bond capable of radical polymerization include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and salts thereof, Examples thereof include radical polymerizable compounds such as anhydrides having a saturated group, (meth) acrylate, (meth) acrylamide, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes.
The (meth) acrylate represents acrylate or methacrylate, and (meth) acrylamide represents acrylamide or methacrylamide. In the present invention, for example, a monofunctional (meth) acrylate compound represents a compound having only one (meth) acryloxy group, and further has an ethylenically unsaturated bond other than the (meth) acryloxy group. Also good.

Specifically, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate, benzyl acrylate, bis (4-acryloxypolyethoxyphenyl) ) Propane, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, propylene glycol diacrylate, di Propylene glycol diacrylate, tripropylene glycol dia Lilate, tetrapropylene glycol diacrylate, polypropylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, oligoester acrylate, N-methylolacrylamide, Acrylic acid derivatives such as diacetone acrylamide, epoxy acrylate, lauryl acrylate, hexanediol diacrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate Rate, dimethylaminomethyl methacrylate, 1,6-hexanediol dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, 2 , Methacryl derivatives such as 2-bis (4-methacryloxypolyethoxyphenyl) propane, N-vinyl compounds such as N-vinyl pyrrolidone and N-vinyl caprolactam, allyl glycidyl ether, diallyl phthalate, triallyl trimellitate, etc. Derivatives of allyl compounds are mentioned. More specifically, Yamashita Shinzo, “Crosslinking agent handbook” (1981, Taiseisha); FUJI Kiyoshi, “UV / EB Curing Handbook (Raw Materials)” (1985, Polymer Publications); Radtech Research Group, “Application and Market of UV / EB Curing Technology”, p. 79, (1989, CMC); commercial products described in Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo Shimbun), etc., or radically polymerizable or cross-linkable monomers, oligomers and polymers known in the industry. Can be used.
Among these, it is preferable to use tripropylene glycol diacrylate, N-vinylcaprolactam, lauryl acrylate, and hexanediol diacrylate.

  Examples of the radical polymerizable compound include those disclosed in JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, JP-A-10-863, JP-A-9-134011, and the like. Photocurable polymeric compound materials used for the described photopolymerizable compositions are known and can also be applied to the coating compositions of the present invention.

Furthermore, it is also preferable to use a vinyl ether compound as the radically polymerizable compound used in combination. Suitable vinyl ether compounds include, for example, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, and cyclohexanedimethanol. Di- or trivinyl ether compounds such as divinyl ether and trimethylolpropane trivinyl ether; ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol monovinyl Monovinyl ether compounds such as ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl vinyl ether, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether, ethylene glycol monovinyl ether, triethylene glycol monovinyl ether, hydroxyethyl monovinyl ether, hydroxynonyl monovinyl ether, etc. Is mentioned.
Of these vinyl ether compounds, divinyl ether compounds and trivinyl ether compounds are preferable from the viewpoints of curability, adhesion, and surface hardness, and divinyl ether compounds are particularly preferable. A vinyl ether compound may be used individually by 1 type, and may be used in combination of 2 or more type as appropriate.

  Examples of other polymerizable compounds that can be used in the present invention include (meth) acrylic monomers or prepolymers, epoxy monomers or prepolymers, or (meth) acrylic acid esters such as urethane monomers or prepolymers (hereinafter referred to as “polymeric esters”). As appropriate, it is also referred to as an “acrylate compound”), and a compound having no cyclic ether group is preferably used. More preferably, they are the following compounds.

  That is, 2-ethylhexyl diglycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxybutyl acrylate, hydroxypivalate neopentyl glycol diacrylate, 2-acryloyloxyethyl phthalate, methoxypolyethylene glycol acrylate, tetramethylol Methane triacrylate, 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, dimethylol tricyclodecane diacrylate, ethoxylated phenyl acrylate, 2-acryloyloxyethyl succinic acid, nonylphenol ethylene oxide (EO) adduct acrylate, Modified glycerin triacrylate, bisphenol A diglycidyl ether acrylic acid adduct, modified bisphenol A diacrylate , Phenoxypolyethylene glycol acrylate, 2-acryloyloxyethyl hexahydrophthalic acid, propylene oxide (PO) adduct diacrylate of bisphenol A, EO adduct diacrylate of bisphenol A, dipentaerythritol hexaacrylate, pentaerythritol triacrylate Tolylene diisocyanate urethane prepolymer, lactone-modified flexible acrylate, butoxyethyl acrylate, propylene glycol diglycidyl ether acrylic acid adduct, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, 2-hydroxyethyl acrylate, methoxydi Propylene glycol acrylate, ditrimethylolpropane tetraacrylate, Data triacrylate, hexamethylene diisocyanate urethane prepolymer, stearyl acrylate, isoamyl acrylate, isomyristyl acrylate, isostearyl acrylate, lactone-modified acrylate.

  The acrylate compounds listed here have high reactivity, low viscosity, and excellent adhesion to a printing substrate.

The coating composition of the present invention preferably contains a polyfunctional ethylenically unsaturated compound as an ethylenically unsaturated compound having an essential cyclic ether group or other polymerizable compound that can optionally be used in combination.
Moreover, when using a polyfunctional ethylenically unsaturated compound, it is preferable that it is 5 to 40 weight% with respect to the total weight of a coating composition as content of a polyfunctional ethylenically unsaturated compound, 10-30 More preferably, it is% by weight. Within the above range, the non-tackiness is excellent, and the coating composition has an appropriate viscosity, so that good surface smoothness can be obtained.

  In the present invention, in order to improve non-tackiness (surface tackiness suppression) and surface smoothness, it is preferable to use a specific cyclic monomer in combination with a polyfunctional ethylenically unsaturated compound having no cyclic ether group. More preferably, the specific cyclic monomer and the polyfunctional (meth) acrylate monomer having no cyclic ether group are used in combination, and the monofunctional specific cyclic monomer and the polyfunctional acrylate monomer having no cyclic ether group are used in combination. More preferably.

  In addition, when a specific cyclic monomer and a polyfunctional ethylenically unsaturated compound having no cyclic ether group are used in combination, the content of the polyfunctional ethylenically unsaturated compound having no cyclic ether group is the total weight of the coating composition. The content is preferably 5 to 40% by weight, more preferably 10 to 30% by weight. Within the above range, non-tackiness is excellent and a viscosity suitable for the coating composition can be obtained.

  In the present invention, according to various purposes, in addition to a combination of a radical polymerizable compound and a radical photopolymerization initiator, together with these, a cationic polymerizable compound and a cationic polymerization initiator as shown below are used in combination. Alternatively, a radical-cation hybrid coating composition may be used.

The cationically polymerizable compound that can be used in the present invention is not particularly limited as long as it is a compound that initiates a polymerization reaction with an acid generated from a photoacid generator and cures, and various known compounds known as photocationically polymerizable monomers. Cationic polymerizable monomers can be used.
Examples of the cationic polymerizable monomer include JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, and 2001-2001. Examples thereof include epoxy compounds, vinyl ether compounds, oxetane compounds and the like described in each publication such as No. 220526.

  In addition, as the cationic polymerizable compound, for example, a polymerizable compound applied to a cationic polymerization type photocurable resin is known, and recently, a photo cationic polymerization type sensitized in a visible light wavelength region of 400 nm or more. Examples of the polymerizable compound applied to the photo-curable resin are disclosed in JP-A-6-43633 and JP-A-8-324137. These can also be applied to the coating composition of the present invention.

<Photopolymerization initiator>
The coating composition of the present invention contains a photopolymerization initiator.
A known photopolymerization initiator can be used as the photopolymerization initiator. In the present invention, it is preferable to use a radical photopolymerization initiator.
The photopolymerization initiator used in the coating composition of the present invention is a compound that generates a polymerization initiating species by absorbing external energy due to actinic radiation. Examples of the active radiation include γ rays, β rays, electron beams, ultraviolet rays, visible rays, and infrared rays. Although the wavelength to be used is not specifically limited, Preferably it is a 200-500 nm wavelength range, More preferably, it is a 200-450 nm wavelength range.

Examples of radical photopolymerization initiators that can be preferably used in the present invention include (a) aromatic ketones, (b) acylphosphine compounds, (c) aromatic onium salt compounds, (d) organic peroxides, (e) thios. Compound, (f) hexaarylbiimidazole compound, (g) ketoxime ester compound, (h) borate compound, (i) azinium compound, (j) metallocene compound, (k) active ester compound, (l) carbon halogen bond And (m) alkylamine compounds and the like.
A preferable photopolymerization initiator from the viewpoint of transparency is preferably a compound having an absorbance at a wavelength of 400 nm of 0.3 or less when the photopolymerization initiator is formed to a thickness of 3 g / cm ^2. More preferably, the compound is 2 or less, and further preferably 0.1 or less.
Among these, preferable photopolymerization initiators include (a) aromatic ketones, (b) acylphosphine compounds, and (c) aromatic onium salt compounds.
The photoinitiator in this invention may be used individually by 1 type, and may use 2 or more types together.

The content of the photopolymerization initiator in the present invention is preferably 0.01 to 35% by weight, preferably 0.1 to 30% by weight based on the total amount of the specific cyclic monomer and other polymerizable compound used in combination. %, More preferably 0.5 to 30% by weight.
Moreover, when using a sensitizer described later, the photopolymerization initiator is preferably 200: 1 to 1: 200 in a weight ratio of photopolymerization initiator: sensitizer with respect to the sensitizer. It is more preferably 50: 1 to 1:50, and further preferably 20: 1 to 1: 5.

In the present invention, as the cationic polymerization initiator (photoacid generator) used in combination with the above cationic polymerizable compound, for example, a chemical amplification type photoresist or a compound used for photocationic polymerization is used (for example, organic electronics). (Refer to Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), pages 187 to 192).
Examples of the cationic polymerization initiator suitable for the present invention are listed below.
That is, first, B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ salt of an aromatic onium compound such as diazonium, ammonium, iodonium, sulfonium or phosphonium. Can be mentioned. Secondly, sulfonated products that generate sulfonic acid can be mentioned. Thirdly, a halide that generates hydrogen halide by light can also be used. Fourthly, iron arene complexes can be mentioned.
The above cationic polymerization initiators may be used alone or in combination of two or more.

<Sensitizer>
A sensitizer can be added to the coating composition of the present invention in order to promote the decomposition of the photopolymerization initiator by irradiation with actinic radiation.
The sensitizer absorbs specific actinic radiation and enters an electronically excited state. The sensitizer in an electronically excited state comes into contact with the photopolymerization initiator to cause actions such as electron transfer, energy transfer, and heat generation, thereby causing a chemical change of the photopolymerization initiator, that is, decomposition, radical, acid. Or it promotes the production of bases.
In addition, the sensitizer that can be used in the present invention is preferably a compound or an amount having a small influence of coloring or the like when the coating composition of the present invention is used for overprinting.
The content of the sensitizer in the present invention is preferably 0.001 to 5% by weight, more preferably 0.01 to 3% by weight, based on the total weight of the coating composition. With this addition amount, curability is improved and the influence of coloring is small.

The sensitizer may be a compound corresponding to the wavelength of actinic radiation that generates an initiating species in the photopolymerization initiator to be used, but considering that it is used for a curing reaction of a general coating composition. Examples of preferred sensitizers include those belonging to the following compounds and having an absorption wavelength in the 350 nm to 450 nm region.
Polynuclear aromatics (eg, pyrene, perylene, triphenylene), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (eg, thiacarbocyanine, oxacarbocyanine), merocyanines (Eg, merocyanine, carbomerocyanine), thiazines (eg, thionine, methylene blue, toluidine blue), acridines (eg, acridine orange, chloroflavin, acriflavine), anthraquinones (eg, anthraquinone), squalium (eg, Squalium), coumarins (for example, 7-diethylamino-4-methylcoumarin), benzophenones (for example, benzophenone) and the like.

  More preferable examples of the sensitizer include compounds represented by the following formulas (II) to (VI).

In the formula (II), A ¹ represents a sulfur atom or NR ⁵⁰ , R ⁵⁰ represents an alkyl group or an aryl group, and L ² represents a non-nuclear group that forms a basic nucleus together with the adjacent A ¹ and the adjacent carbon atom. R ⁵¹ and R ⁵² each independently represent a hydrogen atom or a monovalent non-metal atomic group, and R ⁵¹ and R ⁵² may be bonded to each other to form an acidic nucleus. W represents an oxygen atom or a sulfur atom.

In formula (III), Ar ¹ and Ar ² each independently represent an aryl group, and are linked via a bond with —L ³ —. Here, L ³ represents —O— or —S—. W is synonymous with that shown in Formula (II).

In the formula (IV), A ² represents a sulfur atom or NR ⁵⁹ , L ⁴ represents a nonmetallic atomic group that forms a basic nucleus in combination with adjacent A ² and a carbon atom, R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ and R ⁵⁸ each independently represent a monovalent nonmetallic atomic group, and R ⁵⁹ represents an alkyl group or an aryl group.

In formula (V), A ³ and A ⁴ each independently represent —S— or —NR ⁶² — or —NR ⁶³ —, wherein R ⁶² and R ⁶³ each independently represent a substituted or unsubstituted alkyl group, substituted or Represents an unsubstituted aryl group, and L ⁵ and L ⁶ each independently represent a nonmetallic atomic group that forms a basic nucleus together with adjacent A ³ , A ^4, and adjacent carbon atoms, R ⁶⁰ , R Each ⁶¹ is independently a hydrogen atom or a monovalent nonmetallic atomic group, or can be bonded to each other to form an aliphatic or aromatic ring.

In the formula (VI), R ⁶⁶ represents an aromatic ring or a hetero ring which may have a substituent, and A ⁵ represents an oxygen atom, a sulfur atom or NR ⁶⁷ . R ⁶⁴ , R ⁶⁵ and R ⁶⁷ each independently represent a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁶⁷ and R ⁶⁴ , and R ⁶⁵ and R ⁶⁷ are each an aliphatic or aromatic ring. Can be combined to form

  Preferable specific examples of the compounds represented by formulas (II) to (VI) include those shown below.

<Co-sensitizer>
The coating composition of the present invention can also contain a co-sensitizer.
In the present invention, the co-sensitizer has functions such as further improving the sensitivity of the sensitizer to actinic radiation or suppressing polymerization inhibition of the polymerizable compound by oxygen.
Examples of such cosensitizers include amines such as M.I. R. Sander et al., “Journal of Polymer Society”, Vol. 10, 3173 (1972), Japanese Patent Publication No. 44-20189, Japanese Patent Publication No. 51-82102, Japanese Patent Publication No. 52-134692, Japanese Patent Publication No. 59-138205. And JP-A-60-84305, JP-A-62-18537, JP-A-64-33104, Research Disclosure 33825, and the like.
Specific examples include triethanolamine, p-dimethylaminobenzoic acid ethyl ester, p-formyldimethylaniline, p-methylthiodimethylaniline and the like.

Other examples of co-sensitizers include thiols and sulfides such as thiol compounds described in JP-A-53-702, JP-A-55-500806, and JP-A-5-142277, The disulfide compound of 56-75643 gazette etc. are mentioned.
Specific examples include 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzimidazole, 2-mercapto-4 (3H) -quinazoline, β-mercaptonaphthalene and the like.

  Other examples include amino acid compounds (for example, N-phenylglycine), organometallic compounds described in Japanese Patent Publication No. 48-42965 (for example, tributyltin acetate), and hydrogen described in Japanese Patent Publication No. 55-34414. Donors, sulfur compounds described in JP-A-6-308727 (for example, trithiane), phosphorus compounds described in JP-A-6-250387 (for example, diethyl phosphite), Si described in JP-A-8-54735 -H, Ge-H compounds and the like.

<Surfactant>
The coating composition of the present invention may contain a surfactant.
Examples of the surfactant include those described in JP-A Nos. 62-173463 and 62-183457. For example, anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene blocks Nonionic surfactants such as copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. Further, an organic fluoro compound or a polysiloxane compound may be used as the surfactant. The organic fluoro compound is preferably hydrophobic. Examples of the organic fluoro compounds include fluorine surfactants, oily fluorine compounds (eg, fluorine oil) and solid fluorine compound resins (eg, tetrafluoroethylene resin). No. (columns 8 to 17) and those described in JP-A Nos. 62-135826. Among these, as the surfactant, polydimethylsiloxane can be preferably exemplified.
These surfactants may be used alone or in combination of two or more.

<Other ingredients>
If necessary, other components can be added to the coating composition of the present invention. Examples of other components include a polymerization inhibitor, a solvent, inorganic particles, and organic particles.
A polymerization inhibitor may be added from the viewpoint of enhancing the storage stability. The polymerization inhibitor is preferably added in an amount of 200 to 20,000 ppm based on the total amount of the coating composition of the present invention.
Examples of the polymerization inhibitor include hydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, and cuperon Al.
Inorganic particles such as Aerosil (Degussa silicon dioxide particles) and organic particles such as crosslinked polymethylmethacrylate (PMMA) are added to the coating composition of the present invention to intentionally reduce the surface gloss. A print layer or overprint can be formed.

In view of the fact that the coating composition of the present invention is a radiation curable coating composition, it is preferable that the coating composition of the present invention does not contain a solvent so that it can react quickly and be cured after application. However, a predetermined solvent can be included as long as the curing rate of the coating composition is not affected.
In the present invention, an organic solvent can be used as the solvent, and it is preferable that water is not substantially added from the viewpoint of curing speed. An organic solvent can be added to improve adhesion to a printing substrate (image receiving substrate such as paper).
When using an organic solvent, the amount is preferably as small as possible, preferably 0.1 to 5% by weight, and preferably 0.1 to 3% by weight, based on the total weight of the coating composition of the present invention. Is more preferable.

In addition, known compounds can be added to the coating composition of the present invention as necessary.
For example, surfactants, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, waxes and the like are appropriately selected and added. be able to.

  Moreover, in order to improve the adhesiveness to printing base materials, such as polyolefin and a polyethylene terephthalate (PET), it is also preferable to contain the tackifier (tackifier) which does not inhibit superposition | polymerization. Specifically, a high molecular weight adhesive polymer described in JP-A-2001-49200, pages 5 to 6 (for example, (meth) acrylic acid and an alcohol having an alkyl group having 1 to 20 carbon atoms). Ester, (meth) acrylic acid and a C3-14 alicyclic alcohol ester, (meth) acrylic acid and a C6-14 aromatic alcohol ester copolymer), and polymerizability Examples thereof include a low molecular weight tackifying resin having an unsaturated bond.

<Properties of photocurable coating composition>
The preferred physical properties of the photocurable coating composition of the present invention will be described.
When used as a photocurable coating composition, the viscosity at 25 to 30 ° C. is preferably 5 to 100 mPa · s, more preferably 7 to 75 mPa · s in consideration of applicability.
It is preferable that the composition ratio of the photocurable coating composition of the present invention is appropriately adjusted so that the viscosity is in the above range.
By setting the viscosity at 25 to 30 ° C. to the above value, an overprint having an overprint layer excellent in non-tackiness (no surface stickiness) and excellent in surface smoothness can be obtained.
The surface tension of the photocurable coating composition of the present invention is preferably 16 to 40 mN / m, and more preferably 18 to 35 mN / m.

(Overprint and manufacturing method thereof)
The overprint of the present invention has an overprint layer obtained by photocuring the coating composition of the present invention on a printed material.
The overprint forms at least one overprint layer on the surface of a printed material obtained by a printing method such as electrophotographic printing, inkjet printing, screen printing, flexographic printing, planographic printing, intaglio printing, or relief printing. It is what.
The overprint layer in the overprint of the present invention may be formed on a part of the printed matter or on the entire surface of the printed matter. In the case of a double-sided printed matter, it is formed on the entire surface of both sides of the printing substrate. It is preferable. Needless to say, the overprint layer may be formed in a non-printed portion of the printed material.
The printed material used for the overprint of the present invention is preferably an electrophotographic printed material. By forming an overprint layer, which is a cured layer of the coating composition of the present invention, on an electrophotographic printed matter, it is excellent in non-tackiness, surface smoothness and gloss, and visually similar to a silver salt photographic print. Can be obtained.
The thickness of the overprint layer in the overprint of the present invention is preferably 1 to 10 μm, and more preferably 3 to 6 μm.

The overprint production method of the present invention includes a step of printing on a printing substrate to obtain a printed material, a step of applying the photocurable coating composition of the present invention on the printed material, and photocuring the coating composition. It is preferable to include the process to do.
The overprint manufacturing method of the present invention includes a step of generating an electrostatic latent image on a latent image carrier, a step of developing the electrostatic latent image with toner, and printing the developed electrostatic image. The method further includes a step of transferring to a substrate to obtain an electrophotographic printed material, a step of applying the photocurable coating composition of the present invention on the electrophotographic printed material, and a step of photocuring the coating composition. preferable.
The printing substrate is not particularly limited, and known materials can be used. However, image receiving paper is preferable, plain paper or coated paper is more preferable, and coated paper is further used. preferable. As the coated paper, a double-sided coated paper is preferable because a full color image can be printed on both sides beautifully. When the printing substrate is paper or double-side coated paper, the preferred basis weight is 20 to 200 g / m ² , and the more preferred basis weight is 40 to 160 g / m ² .

The method for developing an image in electrophotography is not particularly limited, and can be arbitrarily selected from methods known to those skilled in the art. For example, a cascade method, a touchdown method, a powder cloud method, a magnetic brush method, and the like can be given.
Examples of a method for transferring the developed image to the printing substrate include a method using a corotron or a bias roll.
A fixing step for fixing an image in the electrophotographic method can be performed by various appropriate methods. Examples thereof include flash fixing, heat fixing, pressure fixing, and vapor fixing.
The image forming method, apparatus, and system by electrophotography are not particularly limited, and known ones can be used. Specifically, as described in the following US patents.
US Pat. No. 4,585,884, US Pat. No. 4,584,253, US Pat. No. 4,563,408, US Pat. No. 4,265,990, US Pat. US Pat. No. 6,180,308, US Pat. No. 6,212,347, US Pat. No. 6,187,499, US Pat. No. 5,966,570, US Pat. No. 5,627,002, US Pat. No. 5,366,840; US Pat. No. 5,346,795, US Pat. No. 5,223,368, and US Pat. 826, 147 specification.

In order to apply the photocurable coating composition, a commonly used liquid film coating device can be used. Specifically, roll coaters, rod coaters, blades, wire bars, dipping, air knives, curtain coaters, slide coaters, doctor knives, screen coaters, gravure coaters, offset gravure coaters, slot coaters, extrusion coaters, etc. It can be illustrated. These devices can be used in the same way as usual, but for example, direct and reverse roll coating, blanket coating, dampner coating, There are curtain coating, lithographic coating, screen coating, and gravure coating. In a preferred embodiment, the coating composition of the present invention is applied and cured using two or three roll coaters and a UV curing station.
Moreover, you may heat as needed at the time of application | coating and hardening of the coating composition of this invention.
Typical levels of coating weight of the coating composition of the present invention, a weight per unit area is preferably in the range of 1 to 10 g / m ^2, and more to be 3 to 6 g / m ² preferable.
The formation amount of the overprint layer in the overprint of the present invention, per unit area, is preferably in the range of 1 to 10 g / m ^2, more preferably 3 to 6 g / m ^2.

The energy source used to initiate the polymerization of the polymerizable compound contained in the coating composition of the present invention may be actinic, for example, radiation having a spectral ultraviolet or visible wavelength. ) (Active radiation). Polymerization by irradiation with actinic radiation is excellent in initiating polymerization and adjusting the polymerization rate.
Suitable actinic radiation irradiation sources include, for example, mercury lamps, xenon lamps, carbon arc lamps, tungsten filament lamps, lasers, sunlight, and the like.

  Under ultraviolet irradiation (UV light irradiation), irradiation with a medium pressure mercury lamp using a high-speed conveyor (preferably 20 to 70 m / min) is preferable, in which case UV light irradiation has a wavelength of 200 to 500 nm. And preferably for less than 1 second. More preferably, the speed of the high-speed conveyor is 15 to 35 m / min, and UV light having a wavelength of 200 to 450 nm is irradiated for 10 to 50 milliseconds (ms). The emission spectrum of the UV light source usually overlaps with the absorption spectrum of the UV polymerization initiator. Curing equipment used in some cases includes a reflector that collects and diffuses UV light, and a cooling system for removing heat generated by the UV light source. It is not limited.

  The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the embodiments in these examples.

Example 1
The following components were stirred with a stirrer to obtain a photocurable coating composition.
・ Specific cyclic monomer shown in Table 1 50% by weight
Tripropylene glycol diacrylate (Aldrich) 20% by weight
・ N-vinylcaprolactam (Aldrich) 10% by weight
・ IRGACURE 907 (Ciba Specialty Chemicals) 15% by weight
・ Benzophenone (Tokyo Chemical Industry Co., Ltd.) 3% by weight
・ Polydimethylsiloxane (Aldrich) 2% by weight

  The obtained solventless photocurable coating composition of Example 1 was evaluated for performance by the following method.

<Evaluation of surface smoothness (leveling property)>
For electrophotographic prints output to double-sided coated paper with a digital printer (DC8000) manufactured by Fuji Xerox Co., Ltd., coated on one side with a film thickness of 5 g / m ² using a UV varnish coater (SG610V) manufactured by Shinano Kenshi Co., Ltd. Then, 120 mJ / cm ² exposure was performed at an illuminance of 1.0 W / cm ^2, an overprint sample was prepared, and the state of occurrence of vertical stripes on the surface of the coated printed material was visually evaluated. The evaluation criteria are shown below.
◎: No vertical stripes ○: Small vertical stripes are observed ×: Vertical stripes are observed

<Non-tackiness (surface stickiness suppression) evaluation>
It is obtained by applying a bar coating on one side of the electrophotographic printed matter outputted on a double-side coated paper with a digital printer (DC8000) manufactured by Fuji Xerox Co., Ltd. so that the coating composition has a film thickness of 5 g / m ^2. The coated film was exposed to 120 mJ / cm ² at an illuminance of 1.0 W / cm ² using a UV lamp (LC8) manufactured by Hamamatsu Photonics Co., Ltd., to prepare an overprint sample. The non-tackiness after exposure was evaluated by touch. The evaluation criteria are shown below.
◎: No stickiness ○: Almost no stickiness △: Slight stickiness ×: Uncured surface

  As a result of evaluation by the above method, the photocurable coating composition of Example 1 had a surface smoothness of ◯ and an overprint non-tackiness of ◯.

(Examples 2 to 18 and Comparative Examples 1 to 9)
A photocurable coating composition was prepared in the same manner as in Example 1 except that the specific cyclic monomer was changed to the monomer described in Table 1, and then this was used to make an overprint. Evaluation was performed. The evaluation results are summarized in Table 1.

Example 19
The following components were stirred with a stirrer to obtain a photocurable coating composition.
・ Specific cyclic monomers shown in Table 2 30% by weight
Tripropylene glycol diacrylate (Aldrich) 20% by weight
・ Lauryl acrylate 20% by weight
・ Hexanediol diacrylate (Aldrich) 10% by weight
・ IRGACURE 907 (Ciba Specialty Chemicals) 15% by weight
・ Benzophenone (Tokyo Chemical Industry Co., Ltd.) 3% by weight
・ Polydimethylsiloxane (Aldrich) 2% by weight

  The obtained photocurable coating composition of Example 19 and an overprint obtained using the same were produced, and performance evaluation was performed in the same manner as in Example 1. The evaluation results are shown in Table 2.

(Examples 20 to 36 and Comparative Examples 10 to 18)
A photocurable coating composition and an overprint using the same were prepared in the same manner as in Example 19 except that the specific cyclic monomer of the present invention was changed to the monomer described in Table 2, and performance evaluation of these was performed. Went. The evaluation results are shown in Table 2.

  In the table, OTA-480 and Blemmer PDT-800 are compounds having the structures shown below.

(Example 37)
Twenty printed materials were produced by electrophotographic printing full color images of several frames each on both sides of A4 size double side coated paper (basis weight 100 g / m ² ). The photocurable coating compositions prepared in Examples 1 to 36 were applied to both sides of these printed materials in the same manner as in Example 1 so that the application amount was 5 g / m ^{2 on} one side. Thereafter, ultraviolet light was irradiated to prepare a double-sided overprint. When these were bound and used as a photo album together with the cover, a photo album with the same visibility as a silver halide photo print was obtained.

(Example 38)
Ten printed materials were produced by electrophotographic printing full color images and text including menu photos on both sides of a B4 size double-side coated paper (basis weight 100 g / m ² ), and Example 1 was applied to both sides of the printed material. each photocurable coating composition prepared at ~ 36, in the same manner as in example 1 was applied so that the coating amount of the single-sided 5 g / m ^2, by irradiating ultraviolet rays produce a two-sided overprints did. When these were bound into a restaurant menu, a restaurant menu was obtained that had the same visibility as a silver halide photographic print.

Claims (9)

An ethylenically unsaturated compound having a cyclic ether group, and
A photocurable coating composition comprising a photopolymerization initiator.   The photocurable coating according to claim 1, wherein the ethylenically unsaturated compound having a cyclic ether group is an ethylenically unsaturated compound having a 1,3-dioxolane ring skeleton and / or a 1,3-dioxane ring skeleton. Composition.   The photocurable coating composition of Claim 1 or 2 whose ethylenically unsaturated compound which has the said cyclic ether group is a monofunctional ethylenically unsaturated compound.   The photocurable coating composition as described in any one of Claims 1-3 containing a polyfunctional ethylenically unsaturated compound.   The photocurable coating composition according to any one of claims 1 to 4, which has substantially no absorption in the visible region.   The photocurable coating composition according to any one of claims 1 to 5, which is used for overprinting.   The photocurable coating composition according to any one of claims 1 to 6, which is used for overprinting an electrophotographic printed material.   An overprint having an overprint layer obtained by photocuring the photocurable coating composition according to any one of claims 1 to 7 on an electrophotographic print. A step of obtaining an electrophotographic print by electrophotographic printing on a printing substrate;
Applying the photocurable coating composition according to any one of claims 1 to 7 on the electrophotographic printed material; and
A step of photocuring the photocurable coating composition.