JP2012111843A - Ultraviolet curable resin composition for optical use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet curable resin composition which is a liquefied composition, and in which void caused by curing shrinkage is hardly generated, and furthermore, light transmittance, that is, optically excellent quality is stably maintained for a long period of time, and to provide a cured product of the ultraviolet curable resin composition.SOLUTION: The ultraviolet-curable resin composition for optical use contains (A) (meth)acrylic acid ester polymer having a radical polymer group and/or a cationic polymer group, and (B) a plasticizer. Furthermore, (C) a photo-polymerization initiator, and (D) a monomer containing a polymer group, which is polymerized with the (A) component, may be contained.

Description

  The present invention provides a space between a display panel of an image display device used in a mobile phone, a liquid crystal television, a plasma television, an electronic book, a touch panel, and the like and a protective plate installed on the display panel with a predetermined interval. The present invention relates to an optical ultraviolet curable resin composition filled in a liquid crystal, a cured product thereof, and a display device using the same.

  In flat panel displays such as liquid crystal display panels, when a shock is applied, a transparent protection consisting of a display panel and an acrylic plate or glass plate that protects the display panel so that the shock is not transmitted to the display panel A certain gap is provided between the plates.

  When this gap is an air layer, the loss of light due to the difference in refractive index between the material constituting the display panel and the protective plate and the air layer is large, and good visibility cannot be obtained. In recent years, a transparent substance is interposed in the gap. Transparent polymer materials such as transparent resin sheets, adhesive transparent gels, and curable adhesive resin compositions have been proposed as transparent substances.

  As the transparent resin sheet, for example, a (meth) acrylic pressure-sensitive adhesive having a gel fraction of 50 to 90% by weight and a storage elastic modulus of a predetermined value or less (JP 2009-263502 A (Patent Document 1) )), An acrylic acid alkyl ester, a copolymer of a polar monomer having a Tg of 50 ° C. or higher, and a hydrophilic monomer having an oxyalkylene group, and having a tan δ and a storage elastic modulus of a predetermined value or less 2010-163591 (Patent Document 2)) and the like have been proposed. In the pressure-sensitive adhesive sheet of Patent Document 2, the presence of a photopolymerization initiator for the above various monomers (acrylic acid alkyl ester, polar monomer having a homopolymer Tg of 50 ° C. or higher, and (meth) acrylic acid ester having an oxyalkylene group). By adding a cross-linking agent (1,6-hexanediol diacrylate) and an additional polymerization initiator to a viscous liquid obtained by partial polymerization by irradiating with ultraviolet light, and further curing by irradiation with light. (Example of paragraph number 0067).

  The transparent resin sheet has an advantage that it is easier for the user who assembles the display device than the gel or the like. Furthermore, in the case of a transparent sheet using a (meth) acrylic monomer as the main structural unit of the polymer, there is an advantage that it is excellent in adhesiveness as compared with silicone gel and other resins.

  On the other hand, with the increase in the size of television screens, the transparent resin sheets used in these must also be enlarged, but it is not easy to handle large sheets having viscoelasticity for ensuring predetermined adhesiveness and shock absorption. . Since it is necessary to attach the interface between the display panel and the protective plate so as not to generate bubbles and wrinkles, a high-level transparent resin sheet requires a high level of technology for the attaching operation. In particular, due to the demand for thin display devices, there is a strict demand for thinning the transparent resin sheet used therefor, and skilled techniques are required for its handling.

  In addition, anti-glare treatment is applied to the display panel and the protective plate, and a black printed layer is applied to the outer peripheral edge of the back surface of the protective plate (the surface on the side in contact with the sheet) to make the liquid crystal screen easier to see. There is. In these cases, since unevenness is formed on the adhesive surfaces of the display panel and the protective plate that are adherends, it is necessary to use a soft adhesive sheet that can absorb the level difference caused by the printing unit. This demands higher handling technology from users.

In this respect, since the curable resin composition is provided in a liquid state, it can be applied to various sizes of display screens and is excellent in versatility. In addition, since the work of curing after filling the space between the display panel and the protective plate does not depend on the size of the display screen, there is no problem of sophistication of work technology due to the enlargement of the screen. In addition, since the distance between the display panel and the protective plate varies depending on the type of user and product, in the case of a resin sheet, resin sheets with various thicknesses corresponding to the gap size are required. In the case of a thing, it can respond with one type of resin composition irrespective of the space | interval size with which it fills. Furthermore, there is an advantage that even a display device having an uneven surface can be filled without a gap.
On the other hand, in the case of a curable resin composition, since it hardens after filling, shrinkage due to curing becomes a problem.

  Examples of the curable resin composition used in the display device include, for example, JP 2009-186963 A (Patent Document 3), polymers such as polyisoprene acrylate, terpene hydrogenated resin, butadiene, and ultraviolet curable monomers. An ultraviolet curable resin composition containing the above has been proposed.

  In Patent Document 3, a cured product with less distortion is obtained by using a resin composition having a high elongation rate of the cured product. However, from the viewpoint of improving the clarity of display, further reduction of the shrinkage rate is required. It is done. Furthermore, rubber polymers such as polyisoprene-based and butadiene-based polymers contain many double bonds in the molecular chain, and these do not participate in the ultraviolet curing reaction, so that double bonds remain in the cured product. There is a risk. Residual double bonds cause a decrease in light resistance and heat resistance. Degradation and yellowing of rubber-based polymers under severe conditions under high temperature and high humidity not only deteriorate optical properties but also decrease elongation and viscoelastic properties. As a result, display panels and protective plates Bubbles and peeling may occur at the interface with each other, which may cause a reduction in display performance of the display device.

JP 2009-263502 A JP 2010-163591 A JP 2009-186963 A

  The present invention has been made in view of the above circumstances, and the object of the present invention is a liquid that can be applied to display devices of various sizes and display devices having irregularities on the adherend surface. UV curable resin composition that can reduce the generation of voids due to curing shrinkage and can stably maintain light transmittance, that is, optically excellent quality over a long period of time. To provide things.

  That is, the optical ultraviolet curable resin composition of the present invention is an ultraviolet curable resin composition used for laminating and integrating a display panel and a protective plate of a display device, and the ultraviolet curable resin composition (A) a (meth) acrylic acid ester polymer having a radical polymerizable group and / or a cationic polymerizable group (hereinafter referred to as “polymerizable group-containing (meth) acrylic polymer”), and (B) plastic It contains an agent.

  The (B) plasticizer is preferably a compound containing an oxyalkylene group. The (A) polymerizable group-containing (meth) acrylic polymer preferably contains an oxyalkylene group in the side chain.

  When the (A) polymerizable group-containing (meth) acrylic polymer is a radically polymerizable group-containing (meth) acrylic polymer, the (meth) acrylic polymer having a double bond in the side chain, The double bond equivalent is preferably 3000 to 30000. Moreover, in the case of a cationically polymerizable group-containing (meth) acrylic polymer, it is a (meth) acrylic polymer having an epoxy group in the side chain, and the epoxy equivalent is preferably 3000 to 30000.

  The ultraviolet resin curable resin composition for optics of the present invention may further contain (C) a photopolymerization initiator and can be polymerized with the (A) polymerizable group-containing (meth) acrylic polymer (D). A polymerizable group-containing monomer may be included.

  The (D) polymerizable group-containing monomer is an ethylenically unsaturated compound when the (A) polymerizable group-containing (meth) acrylic polymer is a radically polymerizable group-containing (meth) acrylic polymer. And preferably a compound having one double bond in one molecule. Further, an unsaturated compound having a hydroxyl group is preferable.

  The (D) polymerizable group-containing monomer is an epoxy group or vinyl ether group when the (A) polymerizable group-containing (meth) acrylic polymer is a cationic polymerizable group-containing (meth) acrylic polymer. It is preferable that it is a compound which has.

  The optical ultraviolet curable resin composition of the present invention is preferably a liquid composition containing no solvent.

  The present invention also includes a cured product obtained by curing the above-described optical ultraviolet curable resin composition of the present invention by ultraviolet irradiation, and also a display device having the cured product.

  In the present specification, acrylic and methacryl are collectively referred to as (meth) acryl when not particularly distinguished, and acrylate and methacrylate are collectively referred to as (meth) acrylate when not particularly distinguished.

  The UV curable resin composition for optical use of the present invention is a viscous liquid, and a three-dimensional cured product having a low crosslinking density and capable of incorporating a large amount of a plasticizer can be obtained by UV irradiation. Moreover, the ultraviolet curable resin composition for optics of the present invention can provide a cured product in which deterioration of optical properties against environmental changes due to high temperature, high humidity, light, etc. is suppressed. Therefore, it is suitable as a transparent polymer material filled in the display device.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a display device using the cured product of the present invention. FIG. 2 is a schematic cross-sectional view showing another embodiment of a display device using the cured product of the present invention.

  The description of the constituent requirements described below is an example (representative example) of an embodiment of the present invention, and is not limited to these contents.

<Optical UV curable resin composition>
First, the optical ultraviolet curable resin composition of the present invention will be described.
The UV curable resin composition for optical use of the present invention comprises (A) a (meth) acrylic polymer (hereinafter referred to as “polymerizable group”) having a radically polymerizable group and / or a cationically polymerizable group as a main component. And (B) a plasticizer. Here, the polymerizable group-containing (meth) acrylic polymer refers to a polymer in which 50% by mass or more of the constituent monomers are (meth) acrylate monomers.

[(A) Polymerizable group-containing (meth) acrylic polymer]
The (A) polymerizable group-containing (meth) acrylic polymer has a (meth) acrylic polymer ((meth) acrylic polymer (A _R )) having a radically polymerizable group and a cationic polymerizable group ( It is roughly classified into a (meth) acrylic polymer ((meth) acrylic polymer (Ac)), a (meth) acrylic polymer (Ap) having a radical polymerizable group and a cationic polymerizable group. Hereinafter, each will be described in order.

(1) (Meth) acrylic polymer (A _R ): side chain double bond-containing (meth) acrylic polymer (meth) acrylic polymer (A _R ) having a radical polymerizable group is specifically Is a polymer having a (meth) acrylic polymer chain as the main chain and a double bond in the side chain. Such a (meth) acrylic polymer (A _R ) has a reactive functional group-containing (meth) acrylic prepolymer having a functional group capable of reacting with the reactive functional group of the prepolymer and having an ethylenic non-reactive group. It is obtained by reacting a monomer having a saturated bond (hereinafter referred to as “double bond introducing vinyl monomer (d)”). The obtained polymer has a side chain double bond having the reactive functional group-containing (meth) acrylic prepolymer as a main chain and the reaction residue of the vinyl monomer for introducing a double bond (d) as a side chain. It is a contained (meth) acrylic polymer, that is, a (meth) acrylic polymer (A _R ) capable of radical polymerization by a double bond in a side chain.

(Reactive functional group-containing (meth) acrylic prepolymer)
Examples of the reactive functional group contained in the reactive functional group-containing (meth) acrylic prepolymer include a carboxyl group, an amino group, a cyano group, an epoxy group, a hydroxyl group, an aziridine group, and an amide group. Therefore, the reactive functional group-containing (meth) acrylic prepolymer has a (meth) acrylate and / or a functional group-containing (meth) acrylate so that the content of the (meth) acrylate monomer (a) is 50% by mass or more. It can be obtained by copolymerizing a vinyl monomer (b) other than the (meth) acrylate having a functional group with a (meth) acrylate having no functional group.

  As the (meth) acrylic monomer (a), a (meth) acrylic alkyl ester (a1) as a (meth) acrylate having no functional group, a terminal alkylated product of an alkylene oxide adduct of (meth) acrylic acid ( a2), (meth) acrylate (a3) having the above functional group, and the like can be used.

  As the alkyl ester (a1) of (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, t- Butyl (meth) acrylate, pentyl (meth) acrylate, neopentyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (Meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, isomyristyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meta) C 1-20 linear or branched alkyl ester such as alkyl (meth) acrylate such as acrylate, nonadecyl (meth) acrylate, eicodecyl (meth) acrylate, n-lauryl (meth) acrylate; cyclohexyl (meth) Alicyclic alkyl esters such as acrylate and dicyclopentenyloxyethyl (meth) acrylate; Aromatic alkyl esters such as phenyl (meth) acrylate and benzyl (meth) acrylate Le, and the like.

  As the alkylene oxide adduct (a2) of (meth) acrylic acid, methoxy-ethylene glycol (meth) acrylate, methoxy-diethylene glycol (meth) acrylate, methoxy-triethylene glycol (meth) acrylate, methoxy-polyethylene glycol (meth) Acrylate, ethoxy-ethylene glycol (meth) acrylate, ethoxy-diethylene glycol (meth) acrylate, ethoxy-triethylene glycol (meth) acrylate, ethoxy-polyethylene glycol (meth) acrylate, butoxy-ethylene glycol (meth) acrylate, butoxy-diethylene glycol (Meth) acrylate, butoxy-triethylene glycol (meth) acrylate, butoxy-polyethylene glycol With one end alkylated ethylene glycol or a polymer thereof such as styrene (meth) acrylate, phenoxy-ethylene glycol (meth) acrylate, phenoxy-diethylene glycol (meth) acrylate, phenoxy-triethylene glycol (meth) acrylate, etc. (Meth) acrylic acid ester; methoxy-propylene glycol (meth) acrylate, methoxy-dipropylene glycol (meth) acrylate, methoxy-tripropylene glycol (meth) acrylate, methoxy-polypropylene glycol (meth) acrylate, ethoxy-propylene glycol ( (Meth) acrylate, ethoxy-dipropylene glycol (meth) acrylate, ethoxy-tripropylene glycol (meth) acrylate, Xoxy-polypropylene glycol (meth) acrylate, butoxy-propylene glycol (meth) acrylate, butoxy-dipropylene glycol (meth) acrylate, butoxy-tripropylene glycol (meth) acrylate, butoxy-polypropylene glycol (meth) acrylate, phenoxy-propylene Propylene glycol with one terminal alkylated such as glycol (meth) acrylate, phenoxy-dipropylene glycol (meth) acrylate, phenoxy-tripropylene glycol (meth) acrylate, or a (meth) acrylic acid ester with a polymer thereof. Can be mentioned.

  Examples of the (meth) acrylate (a3) having a functional group include amino group-containing (meth) acrylates such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate; ethyl-2-cyano-3,5 -Cyano group-containing (meth) acrylate such as diphenyl acrylate; diethylene glycol (meth) acrylate, triethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, dipropylene glycol (meth) acrylate, tripropylene glycol (meth) acrylate, Alkylene oxide adducts of (meth) acrylic acid such as polypropylene glycol (meth) acrylate; 2-hydroxylmethyl (meth) acrylate, 2-hydroxylethyl (meth) a Hydroxyl group-containing (meth) acrylates other than those derived from alkylene oxide, such as relate and hydroxypropyl (meth) acrylate; aziridine group-containing (meth) acrylates such as 2- (1-aziridinyl) ethyl (meth) acrylate; (meth) acrylamide , Acrylamides such as N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide; glycidyl esters such as glycidyl (meth) acrylate, alicyclic epoxides such as 3,4-epoxycyclohexyl (meth) acrylate, etc. Epoxy group-containing (meth) acrylates; carboxyl group-containing (meth) acrylates such as 2-acryloyloxyethyl succinic acid.

  A vinyl monomer having a functional group (functional group-containing vinyl monomer (b)) other than the functional group-containing (meth) acrylate (a3) is typically a carboxyl group-containing vinyl monomer (b1). Specifically, unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, vinyl benzoic acid; unsaturated dicarboxylic acids such as itaconic acid, maleic acid, fumaric acid, phthalic acid, succinic acid, citraconic acid or the like Monoesters or acid anhydrides thereof can be used.

The (meth) acrylate monomer (a) and the functional group-containing vinyl monomer (b) can be used alone or in combination of two or more, and 50% by mass or more of the monomer constituting the prepolymer is A (meth) acrylate monomer (a) is used. Further, the (meth) acrylate monomer (a2) or (a3) of the alkylene oxide adduct is 10 to 80% by mass, preferably 20 to 70% by mass, more preferably, of the (meth) acrylate polymer (A _R ). It is preferable to contain 30-60 mass%. When the (meth) acrylic polymer has an oxyalkylene group in the side chain, a decrease in transparency under high temperature and high humidity can be suppressed.

  The monomer (a3 or b) having a functional group is a vinyl monomer (d) for introducing a double bond, which will be described later, from the relationship with the introduction of a double bond into the side chain of the reactive functional group-containing (meth) acrylic prepolymer The carboxyl group-containing vinyl monomer (b1) is preferably used, and (meth) acrylic acid is particularly preferably used from the viewpoint of the ease of the double bond introduction reaction.

  The monomer used for the synthesis of the reactive functional group-containing (meth) acrylic prepolymer is a monomer that can be copolymerized with the monomers (a) and (b) as long as the effects of the present invention are not impaired. A saturated monomer (hereinafter referred to as “other copolymerization monomer (c)”) can also be used. Examples of other copolymerization monomers (c) include styrenes such as styrene, α-methylstyrene, vinyltoluene, and chlorostyrene; vinyl esters such as vinyl acetate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, and butyl vinyl ether. Allyl compounds such as allyl alcohol, allyl glycidyl ether, ethylene glycol monoallyl ether and propylene glycol monoallyl ether; N-substituted maleimides such as N-phenylmaleimide, N-cyclohexylmaleimide and N-isopropylmaleimide; N- Examples thereof include N-vinyl compounds such as vinylpyrrolidone, N-vinylcaprolactam, N-vinyl-N-methylformamide, N-vinylimidazole and N-vinylacetamide.

  The other copolymerizable monomer (c) is preferably less than 50% by weight of the monomer constituting the (meth) acrylic prepolymer, more preferably less than 30% by weight, and even more preferably less than 20% by weight.

(Synthesis of reactive functional group-containing (meth) acrylic prepolymer)
By copolymerizing the above monomers ((meth) acrylate monomers (a), functional group-containing vinyl monomers (b), and other copolymerizable monomers (c) added as necessary), reactivity is achieved. A functional group-containing (meth) acrylic prepolymer can be synthesized.
Monomers to be used may be used in appropriate combination so that the glass transition temperature of the (meth) acrylic polymer (A _R ) to be synthesized falls within a predetermined range. The glass transition temperature of the (meth) acrylic polymer (A _R ) is preferably −80 to 25 ° C., more preferably −80 to 0 ° C., and further preferably −60 to −20 ° C.

  The glass transition temperature of the (meth) acrylic polymer (A) can be determined from Tg (K) of various homopolymers Tgn (K) and monomer mass fraction (Wn). The value described in various literatures (for example, polymer handbook etc.) should just be used for Tg (K) of a homopolymer.

  The copolymerization method is not particularly limited, and a known polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization or the like can be employed.

  In the copolymerization, it is desirable to use a polymerization initiator. Examples of the polymerization initiator include benzoyl peroxide, lauroyl peroxide, methyl ethyl ketone peroxide, t-butyl peroxy-2-ethyl hexanoate, t-butyl peroxy octoate, t-butyl peroxy benzoate, cumene hydro Organic peroxides such as peroxide, cyclohexanone peroxide, dicumyl peroxide, bis (4-t-butylcyclohexyl) peroxydicarbonate; 2,2′-azobisisobutyronitrile, 2-phenylazo-2, Examples include azo compounds such as 4-dimethyl-4-methoxyvaleronitrile, and these can be used alone or in combination.

  In order to adjust the average molecular weight of the (meth) acrylic prepolymer, it is preferable to carry out copolymerization in the presence of a chain transfer agent. Examples of the chain transfer agent include alkyl mercaptans such as t-butyl mercaptan, n-octyl mercaptan, and n-dodecyl mercaptan; aromatic mercaptans such as thiophenol and thionaphthol; thioglycolic acid; octyl thioglycolate, ethylene glycol dithiol. Thioglycolic acid alkyl esters such as glycolate, trimethylolpropane tris- (thioglycolate), pentaerythritol tetrakis- (thioglycolate); β-mercaptopropionic acid; octyl β-mercaptopropionic acid, 1,4-butanediol Β-mercaptopropionate such as di (β-thiopropionate), trimethylolpropane tris- (β-thiopropionate), pentaerythritol tetrakis- (β-thiopropionate) Such as glycol ester and the like, which may be used alone or in combination.

((D) Vinyl monomer for introducing double bond)
As the unsaturated monomer having a reactive functional group for introducing a double bond into the side chain of the (meth) acrylic prepolymer, that is, the vinyl monomer for introducing a double bond (d), the reactive functional group described above is used. Depending on the type of the functional group contained in the group-containing (meth) acrylic prepolymer, a vinyl compound having a functional group capable of reacting with the functional group can be used.

  As a combination of the functional group of the (meth) acrylic prepolymer and the functional group of the vinyl monomer for introducing a double bond (d), carboxyl group and epoxy group, carboxyl group and hydroxyl group, carboxyl group and amino group, carboxyl group and A combination of an oxazoline group, a hydroxyl group and an acid anhydride, a hydroxyl group and an isocyanate group, and the like can be given. Of these combinations, the combination of an epoxy group and a carboxyl group is preferred because there are no by-products and the control is easy due to irreversible reaction.

  Therefore, as the vinyl monomer for introducing a double bond (d), when the functional group contained in the (meth) acrylic prepolymer is a carboxyl group, a glycidyl ester such as glycidyl (meth) acrylate, or 3,4-epoxy Epoxy group-containing (meth) acrylates such as alicyclic epoxides such as cyclohexyl (meth) acrylate are preferably used. When the functional group contained in the (meth) acrylic prepolymer is an epoxy group, the vinyl monomer for introducing a double bond (d) may be an acrylic acid, methacrylic acid, crotonic acid, vinylbenzoic acid or the like. Saturated monocarboxylic acids; itaconic acid, maleic acid, fumaric acid, phthalic acid, succinic acid, citraconic acid and other unsaturated dicarboxylic acids or monoesters thereof or acid anhydrides thereof can be used.

(Double bond introduction reaction)
The reaction conditions for introducing a double bond into the side chain of the reactive functional group-containing (meth) acrylic prepolymer are the type of reactive functional group contained in the (meth) acrylic prepolymer, and the double bond. It is appropriately selected according to the type of functional group of the vinyl monomer for introduction (d).
In the case of an esterification reaction such as a carboxyl group and a hydroxyl group, or a carboxyl group and an epoxide, it is preferably carried out in the presence of an ester catalyst.

  Examples of esterification catalysts include zinc salts of carboxylic acids such as zinc octenoate, tin salts, zirconium salts; amines such as triethylamine; quaternary ammonium salts such as tetraethylammonium chloride; and phosphorus compounds such as triphenylphosphine. it can.

As described above, the side chain double bond used in the resin composition of the present invention (meta) is obtained by the reaction between the reactive functional group-containing (meth) acrylic prepolymer and the double bond-introducing vinyl monomer (d). ) An acrylic polymer, that is, a (meth) acrylic polymer (A _R ) having a radical polymerizable group is obtained. The number average molecular weight (Mn) in terms of polystyrene by gel permeation chromatography of the (meth) acrylic polymer (A _R ) is preferably 1000 to 50000, more preferably 3000 to 30000, still more preferably 3000. -10000.
Moreover, it is preferable that molecular weight distribution (Mw / Mn) is 1.0-4.0, More preferably, it is 1.0-3.0.

The polymerizable group equivalent (corresponding to the double bond equivalent) of the side chain double bond-containing (meth) acrylic polymer (A _R ), that is, the number average molecular weight per double bond is 3000 to 30000. Is more preferable, more preferably 3000 to 20000, and still more preferably 5000 to 20000. Therefore, the compounding amount of the vinyl monomer for introducing a double bond (d) is such that the double bond equivalent of the side chain double bond-containing (meth) acrylic polymer (A _R ) is within the above range. What is necessary is just to set suitably according to the average molecular weight of a functional group containing (meth) acrylic prepolymer, and the kind of vinyl monomer (d) for double bond introduction | transduction.

(2) (Meth) acrylic polymer (Ac): Cationic polymerizable group-containing (meth) acrylic polymer (Meth) acrylic polymer (Ac) has a polymerizable group that can be cationically polymerized by ultraviolet irradiation. (Meth) acrylic polymer. Cationic polymerization is a polymerization method in which cations generated by the action of an acidic compound such as a protonic acid or a Lewis acid proceed as growth ions. Examples of the functional group capable of generating a cation generated by the action of an acidic compound such as a protonic acid or a Lewis acid include an epoxy group, a vinyl ether group, a vinylamino group, and a vinylamide group, and among these, an epoxy group is preferable. .

  Therefore, the cationic polymerizable group-containing (meth) acrylic polymer (Ac) has a cationic polymerizable group as described above and can be copolymerized with a (meth) acrylate monomer (hereinafter referred to as “cationic polymerizable group”). Copolymerized vinyl monomer (e) ").

  As the cationic polymerizable group-containing vinyl monomer (e), a compound having an epoxy group and a vinyl group is preferable. Specifically, a glycidyl ester such as glycidyl (meth) acrylate, 3,4-epoxycyclohexyl (meth) acrylate, or the like. Epoxy group-containing (meth) acrylates such as alicyclic epoxides can be used. Of these, alicyclic epoxide-containing (meth) acrylates are preferably used from the viewpoint of cationic polymerization speed. From the viewpoint of curability (cationic polymerization) of the (meth) acrylic polymer (Ac), the cationically polymerizable group-containing vinyl monomer (e) is a monomer constituting the (meth) acrylic polymer (Ac). It is preferable that it is -80 mass%, More preferably, it is 20-70 mass%, More preferably, it is 30-60 mass%.

As the (meth) acrylate monomer copolymerized with the above cationic polymerizable group-containing vinyl monomer (e), one of the compounds listed in the above (meth) acrylate monomers (a1) and (a2) or Two or more kinds can be mixed and used. As in the case of the radical polymerizable group-containing (meth) acrylic polymer (A _R ), in order to enhance the durability of the optical properties of the cured product, an alkylene oxide adduct (a2) of (meth) acrylic acid is used. It is preferable to contain 10-80 mass% of the monomer used for the synthesis | combination of a (meth) acrylic-type polymer, More preferably, it is 20-70 mass%, More preferably, it is 30-60 mass%.

  The (meth) acrylic polymer (Ac) inhibits cationic polymerization initiated by light irradiation in addition to the above cationic polymerizable group-containing vinyl monomer (e) and (meth) acrylate monomer (a1) (a2). If it is in the range which does not carry out, a functional group containing (meth) acrylate (a3), a functional group containing vinyl compound (b), and another copolymerization monomer (c) can be used.

The monomers as described above may be used in appropriate combination so that the glass transition temperature of the (meth) acrylic polymer (Ac) to be synthesized is within a predetermined range. The glass transition temperature of the (meth) acrylic polymer (Ac) is preferably −80 to 25 ° C., more preferably −80 to 0 ° C., even more preferably, similarly to the (meth) acrylic polymer (A _R ). Is −60 to −20 ° C. Therefore, what is necessary is just to select suitably so that the glass transition temperature of a (meth) acrylic-type polymer (Ac) may become in the said range.

The copolymerization conditions and copolymerization method are the same as the polymerization conditions for the synthesis of the (meth) acrylic prepolymer of the side chain double bond-containing (meth) acrylic polymer ((meth) acrylic polymer (A _R )). Yes, the same polymerization initiators and chain transfer agents as those listed above can be used.

  The number average molecular weight (Mn) of the (meth) acrylic polymer (Ac) obtained as described above is preferably 3000 to 30000, more preferably 1000 to 50000, and still more preferably 3000 to 10000. . Moreover, it is preferable that molecular weight distribution (Mw / Mn) is 1.0-4.0, More preferably, it is 1.0-3.0.

  The polymerizable group equivalent of the (meth) acrylic polymer (Ac) (corresponding to the epoxy equivalent when an epoxy group-containing (meth) acrylate is used as the cationic polymerizable group-containing vinyl monomer (e)) is 3000 to 3000. It is preferable that it is 30000, More preferably, it is 3000-20000, More preferably, it is 5000-20000.

(3) (Meth) acrylic polymer (Ap): radically polymerizable and cationically polymerizable group-containing (meth) acrylic polymer (meth) acrylic polymer (Ap) is a radically polymerizable polymer as a polymerizable group. And a functional group having cationic polymerizability, or a (meth) acrylic polymer containing both a radical polymerizable group and a cationic polymerizable group.

  The former copolymerizes a compound having a functional group having radical polymerizability and cationic polymerizability and having a copolymerizable vinyl group (hereinafter, referred to as “radical / cation polymerizable group-containing vinyl monomer (f)”). Can be obtained. As the radical / cation polymerizable group-containing vinyl monomer (f), a compound having a vinyl ether group and an acryloyl group is preferable. For example, vinyloxyethoxyethyl acrylate (VEEA), vinyloxyethoxyethyl methacrylate (VEEM), or the like is used. be able to.

  In addition, as a monomer other than the radical / cation polymerizable group-containing vinyl monomer (f), (meth) acrylic monomers (a1) and (a2) having no reactive group functional group can be used. Furthermore, if it is in the range which does not inhibit radical polymerizability and cation polymerizability, a functional group containing (meth) acrylic monomer (a3), a functional group containing vinyl monomer (b), and other copolymerization monomers (c) are used. can do.

  In addition, as the latter, a compound having a radical polymerizable group is added to a (meth) acrylic prepolymer having a cationic polymerizable functional group in the side chain so that a part of the cationic polymerizable functional group remains. Is obtained. For example, when a (meth) acrylic prepolymer having an epoxy group in the side chain is used as the (meth) acrylic prepolymer having a cationic polymerizable functional group, for example, acrylic acid is used as the compound having a radical polymerizable group. When the addition reaction is performed, a (meth) acrylic polymer having a cationic polymerizable epoxy group and a radical polymerizable acryloyl group in the side chain is obtained.

<(B) Plasticizer>
The plasticizer used in the present invention refers to a compound having no polymerizability, and specifically refers to a compound having no vinyl group that undergoes vinyl polymerization.
Specifically, for example, phthalic acid such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, diisononyl phthalate, di-2-ethylhexyl phthalate, dibenzyl phthalate, diisodecyl phthalate, ditridecyl phthalate, diundecyl phthalate Esters; adipic acid esters such as di-n-butyl adipate, diisobutyl adipate, dibutoxyethyl adipate, di-n-octyl adipate, diisooctyl adipate, diisononyl adipate, bis-2-ethylhexyl adipate, diisodecyl adipate; Sebacic acid esters such as sebacate, dioctyl sebacate, di-2-ethylhexyl sebacate; dihexyl azelate, dioctyl Azelaic acid esters such as ruazelate; citric acid esters such as triethyl citrate, acetyl triethyl citrate, tri-n-butyl citrate; glycolic acid esters such as methyl phthalyl ethyl glycolate and ethyl phthalyl ethyl glycolate Trimellitic esters such as trioctyl trimellitate, tri-n-octyl-n-decyl trimellitate, trimellitic acid trialkyl (C4 to C11); methyl acetyl ricinolate, butyl acetyl ricinolate, glycerin monolysate Ricinoleic acid esters such as sinolate; maleic acid esters such as di-n-butyl malate; itaconic acid esters such as monobutyl itaconate; oleic acid esters such as butyl oleate; tricresyl phosphate, trioctyl In addition to phosphates such as phosphate, triphenyl phosphate, and trixylenyl phosphate, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, ethylene oxide / propylene oxide Oxyalkylene group-containing compounds such as polymers; polyolefin resins such as polyethylene, polypropylene, and polystyrene; (meth) acrylic heavy polymers that do not have polymerizable functional groups or double bonds in the side chains of polymethyl methacrylate, polyacrylic acid, etc. Polyester resin such as polyethylene terephthalate; Polyamide resin such as nylon 6,6; Rubber polymer such as polyisoprene and polybutadiene; Thermoplastic elastomer Can be used.

  The plasticizer is appropriately selected according to the type of (A) polymerizable group-containing (meth) acrylic polymer, the affinity with the (meth) acrylic polymer, the viscosity of the composition, and the like. Among the plasticizers, the highly hydrophilic oxyalkylene group-containing compound can prevent fogging due to moisture absorption and has a humidity control action, so that the optical properties of the cured product and the durability of transparency can be improved. From the point, it can be preferably used. In particular, when (A) a polymerizable group-containing (meth) acrylic polymer has a highly hydrophilic (meth) acrylic polymer such as having an oxyalkylene group, the oxyalkylene group used as a plasticizer The contained compound tends to be stably trapped in the three-dimensional network structure of the cured product, and as a result, there is a tendency for less leaching from the cured product.

  (B) The plasticizer is preferably blended in a proportion of 5 to 70% by mass of the entire composition excluding the photopolymerization initiator, more preferably 10 to 60% by mass, still more preferably 20 to 60% by mass, most preferably Preferably it is 49-60 mass%. By increasing the blending ratio of the (B) plasticizer in the resin composition, the curing shrinkage due to the double bond contained in the (A) polymerizable group-containing (meth) acrylic polymer can be reduced. . Moreover, the softness | flexibility of hardened | cured material can also be improved. On the other hand, if the blending amount of the plasticizer becomes too large, it becomes difficult for (A) the polymerizable group-containing (meth) acrylic polymer to be taken into the cured product, and as a result, excess plasticizer oozes out on the cured product surface. It will be in the state. Such bleeding of the plasticizer causes a decrease in adhesion to an adherend such as a display panel or a protective plate, and makes it difficult to obtain a soft cured product.

  Here, the (A) polymerizable group-containing (meth) acrylic polymer used in the present invention is an amount of a plasticizer incorporated into a network structure by enlarging the network of a three-dimensional cured product formed by curing. Can be increased. Therefore, in the optical ultraviolet curable resin composition of the present invention, as shown in the above range, the (A) polymerizable group-containing (meth) acrylic weight is relatively increased by increasing the plasticizer content than usual. The content ratio of the coalesced can be reduced to reduce the curing shrinkage rate. Moreover, it becomes easy to obtain a flexible cured product.

  Accordingly, the preferred content ratio (A: B) of (A) polymerizable group-containing (meth) acrylic polymer and (B) plasticizer is that of the polymerizable group-containing (meth) acrylic polymer and plasticizer. Depending on the type, it is preferably 1: 2 to 7: 2, more preferably 1: 2 to 5: 4.

[(C) Photopolymerization initiator]
The optical ultraviolet curable resin composition of the present invention preferably further contains a photopolymerization initiator. The photopolymerization initiator used in the present invention is a radical polymerization initiator that generates radicals when irradiated with ultraviolet rays, and that accelerates the initiation of polymerization, or a photoacid generator that generates cations (acids) when irradiated with ultraviolet rays. .

(A) When the polymerizable group-containing (meth) acrylic polymer is a radically polymerizable group-containing (meth) acrylic polymer (A _R ), a photopolymerization initiator (radical system) that generates radicals upon light irradiation. It is preferable to use a photopolymerization initiator (C1). In addition, when the (A) polymerizable group-containing (meth) acrylic polymer is a cationic polymerizable group-containing (meth) acrylic polymer (Ac), a photoacid generator (cation) that generates an acid upon irradiation with light. It is preferable to use a photopolymerization initiator (C2)).

(C1) Radical photopolymerization initiator As radical photopolymerization initiator, benzophenone, methylbenzophenone, trimethylbenzophenone, o-benzoylbenzoic acid, methyl o-benzoylbenzoate, 4-chlorobenzophenone, 4,4'-dichloro Benzophenones such as benzophenone, 4-fluorobenzophenone, 4,4′-difluorobenzophenone, tetra (t-butylperoxycarbonyl) benzophenone, [4- (methylphenylthio) phenyl] phenylmethanone; thioxanthone, 2,4- Hydrogen abstraction photopolymerization initiators such as thioxanthones such as diethylthioxanthone and 2-chlorothioxanthone, 3-ketocoumarin, 2-ethylanthraquinone, camphorquinone and Michlerketone; benzoin and benzoin isobuty Benzoins such as ether; acetophenones such as dimethylbenzyl ketal, 2,2-dimethoxyphenylacetophenone, 1-hydroxycyclohexylphenylketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one; bis (2, Self-cleaving polymerization initiators such as acylphosphine oxides such as 4,6-trimethylbenzoyl) -phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide can be used.
Commercially available products may be used, for example, Ciba Geigy's Irgacure series and Merck's Darocur series.

(C2) Cationic Photopolymerization Initiator As the cationic photopolymerization initiator, Lewis acid generating diazonium salt, Bronsted acid generating iodonium salt, sulfonium salt, bismuth compound (bismuthonium salt) can be used. . A commercial item may be used, for example, CPI-100P of San Apro Co., etc. can be used.

  Although the above photoinitiators are based on the kind of photoinitiator to be used, they are usually 0.1 to 100 mass% of (A) polymerizable group-containing (meth) acrylic polymer. It is preferable to use 10% by mass.

[(D) polymerizable group-containing monomer]
The (A) polymerizable group-containing (meth) acrylic polymer, which is the main component of the optical ultraviolet curable resin composition of the present invention, has a polymerizable group (side chain double bond, epoxy group, etc.) in the molecular chain. ) Can be crosslinked and cured by radical polymerization or cationic polymerization in the presence of a polymerization initiator. However, from the viewpoint of adjusting the viscosity of the resin composition and adjusting the hardness of the resulting cured product, (A) a polymerizable group-containing monomer that can participate in the crosslinking curing reaction of the polymerizable group-containing (meth) acrylic polymer. Further, it may be contained.

(D) As the polymerizable group-containing monomer, when (A) the polymerizable group-containing (meth) acrylic polymer is a radically polymerizable group-containing (meth) acrylic polymer (A _R ), ethylenically A compound having at least one saturated bond (ethylenically unsaturated monomer (D _R )) is used, and (A) a polymerizable group-containing (meth) acrylic polymer is a cationic polymerizable group-containing (meth) acrylic polymer In the case of (Ac), a compound containing a functional group capable of cationic polymerization (cationic polymerizable group-containing monomer (Dc)) is used.

The ethylenically unsaturated monomer (D _R ) may be a compound having one ethylenically unsaturated bond contained in one molecule (hereinafter referred to as “monofunctional unsaturated monomer (D _R 1)”). One or more ethylenically unsaturated bonds contained in one molecule (hereinafter referred to as “polyfunctional unsaturated monomer (D _R 2)”) may be used.

Examples of the monofunctional unsaturated monomer (D _R 1) include (A) (meth) acrylic acid alkyl esters (a1) and (meth) used in the synthesis of a polymerizable group-containing (meth) acrylic polymer. As appropriate, an alkylene oxide adduct (a2) of acrylic acid, a (meth) acrylate having a functional group (a3), a carboxyl group-containing vinyl monomer (b), a vinyl compound mentioned in the other copolymerization monomer (c), or the like is appropriately used. be able to.

Examples of the polyfunctional unsaturated monomer (D _R 2) include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and propylene glycol. Di (meth) acrylate, dipropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc. (Meth) acrylates of polyalcohols: ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, cyclo Examples include vinyl ethers of polyalcohols such as hexane dimethanol divinyl ether; compounds such as divinylbenzene, diallyl phthalate, diallyl isophthalate, triallyl cyanurate, triallyl isocyanurate.

As the (D) ethylenically unsaturated monomer (D _R ) used together with the side chain double bond-containing (meth) acrylic polymer (A _R ), a monofunctional unsaturated monomer (D _R 1) is preferably used. . Compared with the case of using a polyfunctional unsaturated monomer (D _R 2), the monofunctional unsaturated monomer (D _R 1) tends to have a lower crosslinking density of the cured product, and the cured product has Since the network size formed tends to be small, it tends to be advantageous in terms of the amount of plasticizer that can be incorporated into the cured product. Furthermore, since a hydrophilic group such as a hydroxyl group or a carboxyl group serves to improve the hydrophilicity of the cured product, a hydroxyl group-containing (meth) acrylate is most preferably used. Specifically, 2-hydroxylmethyl (meth) acrylate, 2-hydroxylethyl (meth) acrylate, hydroxypropyl (meth) acrylate and the like are preferably used.

  The cationic polymerizable group-containing monomer (Dc) used together with the cationic polymerizable group-containing (meth) acrylic polymer (Ac) is a functional group that can react with an acid or a cation to generate a cation (specifically, Are epoxy group-containing (meth) acrylates such as glycidyl esters such as glycidyl (meth) acrylate, alicyclic epoxides such as 3,4-epoxycyclohexyl (meth) acrylate, and the like. Vinyl glycidyl ether and the like.

  The (D) polymerizable group-containing monomer as described above is preferably blended in a proportion of 0 to 30% by mass, more preferably 0 to 20% by mass, further out of the entire composition excluding the photopolymerization initiator. Preferably it is 0-15 mass%. (D) If the amount of the polymerizable group-containing monomer is too large, the crosslinking density increases and the hardness tends to be too high.

[(E) Other ingredients]
Further, the ultraviolet curable resin composition of the present invention is imparted with a curing catalyst, an ultraviolet absorber, various thermal polymerization inhibitors, a leveling agent, a thickener, a thickener, and a thixotropy as long as the effects of the present invention are not impaired. Agents, matting agents, diluents, fillers, reinforcing materials and the like may also be included.

  Specific examples of the curing catalyst include benzoyl peroxide, lauroyl peroxide, methyl ethyl ketone peroxide, t-butyl peroxy-2-ethyl hexanoate, t-butyl peroxy octoate, and t-butyl. Organic peroxides such as peroxybenzoate, cumene hydroperoxide, cyclohexanone peroxide, dicumyl peroxide, bis (4-t-butylcyclohexyl) peroxydicarbonate; azobisisobutyronitrile, 2-phenylazo-2 An azo compound such as 4-dimethyl-4-methoxyvaleronitrile is not particularly limited. These curing catalysts may be used alone or in combination of two or more. The addition amount of the curing catalyst with respect to the monomer component is not particularly limited.

  A commercially available ultraviolet absorber may be used. For example, salicylic acid esters such as benzotriazoles, benzoates, cyanoacrylates, benzophenones, phenyl salicylate, pt-butylphenyl salicylate, p-octylphenyl salicylate; TINUVIN 770, 123, 144 622 (above, Ciba Geigy product name), SANOL LS-770,765,292, 2626 (above, Sankyo Co., Ltd. product name), Adekastab LA-52,57,62 (above, Asahi Denka Co., Ltd. product) Hindered amines such as name) can be used.

  (E) Other components as described above are preferably 0 to 30% by mass in the resin composition, more preferably 0 to 20% by mass, and still more preferably 0 to 10% by mass. .

(Preparation of resin composition)
The optical ultraviolet curable resin composition of the present invention can be prepared by mixing the above components. The optical ultraviolet curable resin composition of the present invention is usually in the form of a viscous liquid. Specifically, it is a liquid having a viscosity of 300 to 10000 mPa, preferably 300 to 5000 mPa. When the viscosity is too high, handling properties such as filling work are deteriorated.

The resin composition of the present invention is preferably solventless. This is because the diluting solvent needs to be volatilized after injection, and the residual solvent can cause a decrease in the photopolymerization speed, and can cause a decrease in the optical properties and durability of the resulting cured product.
Accordingly, when the (A) polymerizable group-containing (meth) acrylic polymer is obtained in a state containing a solvent by a synthesis method, the solvent is preferably removed by reduced pressure, distillation or the like.

<Hardened product>
The optical ultraviolet curable resin composition of the present invention having the above composition is a polymerizable group-containing (meth) acrylic polymer which is component A by ultraviolet irradiation, preferably in the presence of a photopolymerization initiator. Depending on the type of the polymerizable group contained in the polymer, radical polymerization or cationic polymerization is started and crosslinked to form a cured product having a three-dimensional network structure.

  Examples of the UV light source used for ultraviolet irradiation include black light, low-pressure mercury lamp, high-pressure mercury lamp, ultra-high pressure mercury lamp, metal halide lamp, and xenon lamp.

The UV irradiation intensity may be sufficient if the pressure-sensitive adhesive composition can be sufficiently cured. For example, the peak illuminance is preferably ²⁰ to 100 mW / cm ² . The irradiation dose of UV, for example, preferably UV irradiation integrated light quantity is 10 to 10000 mJ / cm ^2, more preferably 300~50000mJ / cm ^2, more preferably a 300~3000mJ / cm ^2. If the irradiation amount is too small, the curing may be insufficient and the high-speed adhesive force may be too high, and if too large, the conformability may be insufficient due to excessive curing. Further, the oxygen concentration in the irradiation atmosphere may be adjusted and cured.

  The obtained cured product seems to be in a state in which the plasticizer in the resin composition is incorporated into the three-dimensional network structure of the polymerizable group-containing (meth) acrylic polymer as the component A. Therefore, it is a soft cured product having a durometer C hardness meter of 3 to 50, preferably 3 to 30, more preferably 5 to 20, and is excellent in impact absorption. If the durometer C hardness is less than 3, the plasticizer acceptability is low, the stickiness is sticky, the visibility is poor, and the peelability is also poor. On the other hand, if the durometer C hardness exceeds 50, the cured product becomes too hard and the impact absorbability is poor.

  Moreover, it is excellent in transparency, and also has excellent optical properties such as moisture resistance, heat resistance, and light resistance. In particular, when the polymerizable group-containing (meth) acrylic polymer as the component A contains an oxyalkylene group, the moisture resistance is excellent. Furthermore, when an oxyalkylene group-containing compound, particularly polyalkylene oxide, is used as the plasticizer, the light resistance is excellent.

<Display device>
The ultraviolet curable resin composition for optical use of the present invention that can obtain the cured product as described above is a display unit and a protective plate of an image display device such as an electronic terminal such as a mobile phone, an electronic book, and a touch panel, a liquid crystal television, and a plasma television. It can be used as a filler for the space between. The optical ultraviolet curable resin composition of the present invention only needs to contain at least a display unit and a protective plate. For example, a touch panel or the like is further provided between the display unit and the protective plate in one layer or two or more layers. It can also be used for the provided image display device.

  Specifically, FIG. 1 is a schematic view of a liquid crystal display device in which a cured product 4 of the optical ultraviolet curable resin composition of the present invention is interposed between an image display unit 1 and a protective plate 2 (gap 3). It is sectional drawing. The cured product 4 adheres (adheres) to the image display unit 1 and the protection plate 2, and the image display unit 1 and the protection plate 2 are laminated and integrated. As the protective plate 2, a glass plate having the same size as the image display unit 1, a plastic plate such as (meth) acrylic resin (for example, PMMA), polycarbonate resin (PC), or triacetyl cellulose (TAC), a sheet, A film is used, and the protective plate 2 may further have black printing or the like on the outer peripheral portion, or may have an antireflection layer, a hard coat layer, or the like on the surface portion.

  The image display unit 1 is a liquid crystal display unit in the case of a liquid crystal display device, a plasma panel in the case of a plasma display device, and an organic EL panel in the case of an organic EL display device. In the case of the image display unit 1 in a liquid crystal display device, generally, a polarizing plate (polarizing filter) / transparent plate (glass plate, plastic plate) / liquid crystal material sandwiched between transparent electrodes / transparent plate (glass plate, plastic plate) / At least a laminated structure laminated in the order of polarizing plate (polarizing filter). The polarizing plate (polarizing filter) is usually formed by sandwiching polyvinyl alcohol (PVA) dyed with iodine between two pieces of triacetyl cellulose (TAC), and the TAC surface has no treatment and a hard coat treatment. Antireflection treatment, antistatic treatment, etc. are performed. The cured product 4 of the optical ultraviolet curable resin composition of the present invention can be adhered (adhered) to the polarizing plate (polarizing filter) in the outermost layer of the image display unit 1.

  FIG. 2 is a schematic cross-sectional view of a liquid crystal display device mounted with a touch panel using the cured product 4 of the optical ultraviolet curable resin composition of the present invention. In the liquid crystal display device, the touch panel 5 is disposed on the display surface of the image display unit 1 with a predetermined interval 6a, the protective plate 2 is disposed with a predetermined interval 6b, and formed with the predetermined intervals 6a and 6b. The resin composition of the present invention is injected into the space, and cured products (resin layers) 7 and 7 ′ are formed by ultraviolet curing, and the image display unit 1, the touch panel 5, and the protective plate 2 are laminated and integrated. . The touch panel 5 has a transparent conductive layer printed on the back surface (surface on the image display unit 1 side) of two transparent plates made of, for example, glass or polyethylene terephthalate. When the layers come into contact with each other, a conductive state is established. In the figure, reference numeral 8 denotes a black print layer printed on the outer peripheral edge of the protective plate 2. Similarly to FIG. 1, the protective plate 2 may have a functional layer such as an antireflection layer or a hard coat layer on the surface portion.

  As described above, the display device in which the cured product of the optical ultraviolet curable resin composition of the present invention is interposed is based on the characteristics of the resin composition of the present invention. Since it is filled and cured, there is very little display unevenness due to voids, irregularities and steps. Moreover, the cured product is soft, excellent in shock absorption, and can maintain excellent transparency against environmental changes such as high temperature, high humidity, and light. There is little reduction in definition.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to description of a following example.
In the examples, “part” means a weight basis unless otherwise specified.

〔Evaluation methods〕
(1) Viscosity The viscosity was measured using a B-type viscometer (RB-80L manufactured by TOKI).

(2) Polymerizable group equivalent Both double bond equivalent and epoxy equivalent contain polymerizable group from the number average molecular weight (Mn) of the polymerizable group-containing (meth) acrylic polymer measured by GPC (gel permeation chromatography). The polymerization chain length of the (meth) acrylic polymer is calculated, and the number of polymerizable group units (double bond or epoxy group) contained in the polymerizable group-containing (meth) acrylic polymer is calculated. The polymerizable group equivalent was determined by dividing the number average molecular weight of the polymerizable group-containing (meth) acrylic polymer by the number of polymerizable group-containing units.

(3) Glass transition point (Tg)
The glass transition point of the (meth) acrylic polymer as the component (A) was calculated from the glass transition point of the homopolymer of each monomer and the mass fraction of the monomer.

(4) Plasticizer acceptability A finger was placed on a sheet (thickness 1 mm) obtained by curing, and the evaluation was made in the following three stages according to the state in which an uncured product adhered to the fingertip.
○: No transfer of uncured material to the fingertip △: Uncured material has transferred to the fingertip, but not at a level that is a problem ×: Many uncured material adheres to the fingertip

(5) Hardness Based on JIS K7312, the hardness of the sheet (width 17 mm × length 45 mm × thickness 4 mm) obtained by curing was measured using a durometer C hardness meter manufactured by ASKER. The value after 15 seconds from the start of measurement was taken as the hardness value.

(6) Growth rate (%)
Using a sheet (width 4 mm × length 20 mm × thickness 1 mm) obtained by curing, a tensile test was performed at an atmospheric temperature of 25 ° C. and a tensile speed of 0.1 mm / s, and the elongation was calculated according to the following formula. In the formula, L is the displacement length until breakage, and L ₀ is the length of the sheet before the test.
Elongation rate (%) = L / L ₀ × 100

(7) Heat resistance The circular sheet | seat (diameter 30mm, thickness 1mm) obtained by hardening was heated for 100 hours in 100 degreeC oven with the state pinched | interposed into the glass plate. The discoloration after heating was visually confirmed and evaluated in the following three stages.
○: No discoloration △: Slight discoloration ×: Discoloration

(8) Light resistance Metalling weather meter (M6T, manufactured by Suga Test Instruments Co., Ltd., irradiation intensity 0.5 kW / m) with a circular sheet (diameter 30 mm, thickness 1 mm) obtained by curing sandwiched between glass plates ²⁾ was used to perform irradiation with light ^{100MJ / m 2, 300MJ / m} 2. The discoloration after irradiation was visually confirmed and evaluated in the following four stages.
(Double-circle): Even if it irradiated with the irradiation amount of 300 MJ / m < ² >, it did not discolor.
○: it was discolored by irradiation at dose 300 MJ / m ^2, did not change color in the irradiation with 100 MJ / m ^2.
Δ: Slightly discolored at an irradiation dose of 100 MJ / m ² .
X: Discolored at an irradiation dose of 100 MJ / m ² .

(9) Moisture resistance After the sheet (width 17 mm x length 45 mm x thickness 4 mm) obtained by curing is kept in a thermo-hygrostat (temperature 60 ° C., humidity 90% RH) for 70 hours, the turbidity of the sheet Was visually confirmed and evaluated in the following three stages.
○: No turbidity △: Slightly turbid ×: Turbid

[Production of (meth) acrylic polymer]
Side chain double bond-containing acrylic polymer A1-A7:
In a reactor equipped with a thermometer, a cooler, a gas introduction pipe, and a stirrer, acrylic monomers (a) shown in Table 1 (butyl acrylate, methyl acrylate, and light acrylate 130A manufactured by Kyoeisha Chemical Co., Ltd.) Acrylic acid as the carboxyl group-containing vinyl monomer (b) in the amount shown in Table 1 and 100 parts of toluene as a solvent were charged, and the inside of the reactor was purged with nitrogen gas. After the temperature was raised to 85 ° C. with stirring, 1 part of 2,2′-azobismethylbutyronitrile (hereinafter abbreviated as “ABNE”) as a polymerization initiator and β-mercapropion as a chain transfer agent 1 part of acid was added and the copolymerization reaction was carried out for 5 hours.

Subsequently, 0.1 parts of zinc octenoate as an esterification catalyst, and Antage W-400 (2,2′-methylenebis (4-methyl-6-tert-butylphenol) from Kawaguchi Chemical Co., Ltd. As the vinyl monomer (d) for introducing a heavy bond, glycidyl methacrylate was added in the amount shown in Table 1, the inside of the reactor was replaced with an air atmosphere, the temperature was raised to 100 ° C., and the esterification reaction was performed for 6 hours. It was.
Subsequently, toluene was distilled off under reduced pressure to obtain a side chain double bond-containing (meth) acrylic polymer A1-A7 as a colorless transparent viscous liquid.
Viscosity, glass transition temperature, number average molecular weight (Mn), molecular weight distribution (Mn / Mw), polymerizable group equivalent (corresponding to double bond equivalent) of the obtained (meth) acrylic polymer A1-A7, Also shown in FIG.

Cationic polymerizable group-containing acrylic polymer A8:
Acrylic monomer (a) (methyl acrylate, Kyoeisha Chemical's light acrylate 130A (trade name of methoxypolyethylene glycol acrylate), and epoxy group-containing methacrylate (e) as a cyclomer M100 (trade name: 3,4-epoxycyclohexylmethyl methacrylate) was used in the same manner as (meth) acrylic polymer A1, using the mixture shown in Table 1 and a mixture obtained by adding 100 parts of toluene as a solvent. went.
Subsequently, toluene was distilled off under reduced pressure to obtain a colorless and transparent viscous liquid (meth) acrylic polymer A8 having an epoxy group as a cationic polymerizable group.
Table 1 shows the viscosity, glass transition temperature, number average molecular weight (Mn), molecular weight distribution (Mn / Mw), and polymerizable group equivalent (corresponding to epoxy equivalent) of the obtained (meth) acrylic polymer A8. Show.

(Meth) acrylic polymer A9 having no polymerizable group:
A copolymerization reaction was carried out in the same manner as in the (meth) acrylic polymer A1, using the amounts of butyl acrylate and acrylic acid shown in Table 1 and a mixture obtained by adding 100 parts of toluene as a solvent.
Subsequently, toluene was distilled off under reduced pressure to obtain a colorless and transparent viscous liquid (meth) acrylic polymer A9 having no polymerizable group.
Table 1 shows the viscosity, glass transition temperature, number average molecular weight (Mn), and molecular weight distribution (Mn / Mw) of the obtained (meth) acrylic polymer A9.

[Preparation of UV-curable resin composition for optics and preparation of cured product]
Resin composition No. 1-7:
The radical polymerizable group-containing (meth) acrylic polymer (A1-A7) synthesized above is blended in the amounts shown in Table 2, and (D) a monofunctional unsaturated monomer (D) as the polymerizable group-containing monomer. _R 1) hydroxypropyl methacrylate (HPMA), a polymer of ethylene oxide and propylene oxide as a plasticizer (abbreviated as “p (EO / PO)”, PR-3007 (trade name) manufactured by Adeka), light Each of the radical generators (Irgacure 184D (trade name) of Ciba Specialty Chemicals) was blended in the amounts shown in Table 2, respectively. 1-7 were prepared.
Using the prepared composition, two glass plates were overlapped at a predetermined interval using a silicon spacer, and the resin composition was filled in a space surrounded by the glass plate and the spacer. Next, the sample was cured by light irradiation with a high-pressure mercury lamp for 1 minute to obtain a sample sheet of a predetermined size.
Using the prepared sample sheet, the viscosity, plasticizer acceptability, C hardness, elongation, heat resistance, light resistance, and moisture resistance were evaluated based on the evaluation measurement method. The evaluation results are shown in Table 2.

Resin composition No. 8:
The cation polymerizable group-containing (meth) acrylic polymer A8 synthesized above was blended in the amounts shown in Table 2, and further a plasticizer (PR-3007 (trade name) manufactured by Adeka), a photocation generator ( Sanapro Co., Ltd. CPI-100P (trade name)) was blended in the amounts shown in Table 2, respectively. 8 was prepared.
The prepared resin composition No. 8 and composition no. In the same manner as in No. 1, a sample sheet of a predetermined size was prepared. Using the prepared sample sheet, the viscosity, plasticizer acceptability, C hardness, elongation, heat resistance, light resistance, and moisture resistance were evaluated based on the evaluation measurement method. The evaluation results are shown in Table 2.

Resin composition No. 9:
50 parts of (meth) acrylic polymer A9 having no polymerizable group, (D) 9.2 parts by mass of HPMA as a monofunctional unsaturated monomer (D _R 1) as a polymerizable group-containing monomer, 0.8 mass part of 1,6-hexanediol diacrylate (1,6-Hx-DA) which is a functional unsaturated monomer (D _R 2) is blended, and further, a plasticizer (PR-3007 manufactured by Adeka). , A photo radical generator (Irgacure 184D (trade name) from Ciba Specialty Chemicals) was blended in the amounts shown in Table 2, respectively. 9 was prepared.
The prepared resin composition No. 9 and composition no. In the same manner as in No. 1, a sample sheet of a predetermined size was prepared. The prepared sample sheet was evaluated for viscosity, plasticizer acceptability, C hardness, elongation, heat resistance, light resistance, and moisture resistance based on the evaluation measurement method. The evaluation results are also shown in Table 2.

Resin composition No. 10:
(A) (meth) acrylic polymer is not blended, (D) 58.4 parts of HPMA as a polymerizable group-containing monomer, and 1,6-hexanediol diacrylate (1,6-Hx-DA) 1.6 parts are blended, and further, a plasticizer (PR-3007 manufactured by Adeka) and a photoradical generator (Irgacure 184D (trade name) from Ciba Specialty Chemicals) are blended in the amounts shown in Table 2, respectively. Curable resin composition No. 10 was prepared.
The prepared resin composition No. 10 and composition no. In the same manner as in No. 1, a sample sheet of a predetermined size was prepared. The prepared sample sheet was evaluated for viscosity, plasticizer acceptability, C hardness, elongation, heat resistance, light resistance, and moisture resistance based on the evaluation measurement method. The evaluation results are shown in Table 2.

Resin composition for reference:
As a commercially available non- (meth) acrylic polymer, an isoprene-based polymer (Kuraray US-203 (trade name of maleic anhydride adduct of polyisoprene and esterified product of 2-hydroxyethyl methacrylate)) is used (D ) HPAM as a polymerizable group-containing monomer was blended in the amounts shown in Table 2, and a plasticizer (PR-3007 manufactured by Adeka) and a photoradical generator (Irgacure 184D (trade name) from Ciba Specialty Chemicals) were added. These were blended in the amounts shown in Table 2 to prepare an ultraviolet curable resin composition (reference).
Using the prepared resin composition, composition no. In the same manner as in No. 1, a sample sheet of a predetermined size was prepared. The prepared sample sheet was evaluated for viscosity, plasticizer acceptability, C hardness, elongation, heat resistance, light resistance, and moisture resistance based on the evaluation measurement method. The evaluation results are shown in Table 2.

Resin composition No. using a (meth) acrylic polymer A9 having no polymerizable group. No. 9 is a resin composition No. 9 having a plasticizer acceptability using a polymerizable group-containing (meth) acrylic polymer A1-A8. It was inferior to 1-8. Resin composition No. In No. 9, the unsaturated monomer (D _R 1, D _R 2) as the component (D) does not form a crosslink with the (meth) acrylic polymer A9 having no polymerizable group by ultraviolet irradiation. Radical polymerization and curing. Therefore, no. In the cured product No. 9, the network structure into which the plasticizer can be taken in decreases, and the plasticizer that was not accepted seems to have exuded. Resin composition No. No. 9 has a moisture resistance of No. 9. It was inferior to 1-8. This is probably because the amount of moisture that was trapped in the cured product decreased because the amount of plasticizer with excellent hydrophilicity in the cured product was small, resulting in cloudiness.

Resin composition No. No. 10 is a (meth) acrylic polymer is not blended, and the cured product is a cured product of a polymerization reaction between unsaturated monomers (D _R 1 and D _R 2) as blended (D) components. Become. Therefore, the obtained cured product has a high crosslinking density and a smaller network size. As a result, a sufficient amount of the plasticizer cannot be taken into the network, so that the exudation of the plasticizer in the cured product seems to have increased. It is.

  In the resin composition for reference, since the rubber-based polymer is a main component, the heat resistance is inferior to other resin compositions having a (meth) acrylic polymer as a main component. Further, the plasticizer acceptability is such that the resin composition No. 1 containing a polymerizable group-containing (meth) acrylic polymer as a main component. Despite the same level as 1-8, the moisture resistance was poor. This is presumably because the rubber polymer is inferior in water affinity compared to the (meth) acrylic polymer.

[Types and optical properties of plasticizers]
Resin composition No. 11-17:
50 parts of side chain double bond-containing (meth) acrylic polymer A5, 10 parts by mass of HPMA as unsaturated monomer as component (D), photoradical generator (Irgacure 184D (trade name) from Ciba Specialty Chemicals) 1 part is blended, and the plasticizer shown in Table 3 is blended in the amount shown in Table 3 as a plasticizer. 11-17 was prepared. As plasticizers, DOA (trade name of dioctyl adipate) manufactured by Taoka Chemical Co., Ltd., PN-1030 (trade name of adipic acid ester) manufactured by Adeka Corporation, C-880 (trade name of trimellitic acid ester manufactured by Adeka Corporation) ), PR-3007 (trade name of polymer of ethylene oxide and propylene oxide), PEG400 (trade name of polymer of ethylene oxide (PEG)), P-400 (polymer of propylene oxide (PPG)) Product name).

  The prepared resin composition No. 11-17, composition No. In the same manner as in No. 1, a sample sheet of a predetermined size was prepared. The prepared sample sheet was evaluated for viscosity, plasticizer acceptability, C hardness, elongation, heat resistance, light resistance, and moisture resistance based on the evaluation measurement method. The evaluation results are shown in Table 3.

Resin composition No. using an ester plasticizer (abbreviated as Es1, 2, 3 in the table). 15-17 is a resin composition No. 15 using a plasticizer of an oxyalkylene group-containing compound. Compared to 11-14, the light resistance was inferior. Furthermore, resin composition No. using an oxyalkylene group-containing compound as a plasticizer. 11-14, especially resin composition No. using polyethylene glycol (PEG). Nos. 12 and 13 are resin composition Nos. Using a plasticizer (p (EO / PO) or PPG) containing propylene oxide as a constituent monomer of polyoxyalkylene. Light resistance was better than 11 and 14.
From these facts, it can be seen that the ether bond has a function of suppressing deterioration due to light, and the use of a plasticizer having a higher ether bond content reduces the light deterioration.

  Since the optical ultraviolet curable resin composition of the present invention is in a liquid state, it can be applied to display devices of various sizes, has excellent versatility, and is optical even against environmental changes such as light, heat, and moisture. Since the characteristics can be maintained, it is suitable as an ultraviolet curable resin composition used between a display panel and a protective plate of various display devices.

Claims (14)

An ultraviolet curable resin composition used for laminating and integrating a display panel and a protective plate of a display device, the ultraviolet curable resin composition,
(A) a (meth) acrylic acid ester polymer having a radical polymerizable group and / or a cationic polymerizable group (hereinafter referred to as “polymerizable group-containing (meth) acrylic polymer”), and (B) a plasticizer. An ultraviolet curable resin composition for optics, comprising: The optical ultraviolet curable resin composition according to claim 1, wherein the (B) plasticizer is a compound containing an oxyalkylene group. The optical ultraviolet curable resin composition according to claim 1 or 2, wherein the (A) polymerizable group-containing (meth) acrylic polymer contains an oxyalkylene group in a side chain. The (A) polymerizable group-containing (meth) acrylic polymer is a (meth) acrylic polymer having a double bond in a side chain, and the double bond equivalent is 3000 to 30000. The optical ultraviolet curable resin composition in any one of -3. The (A) polymerizable group-containing (meth) acrylic polymer is a (meth) acrylic polymer having an epoxy group in a side chain, and the epoxy equivalent is 3000 to 30000. The optical ultraviolet curable resin composition according to any one of the above. Furthermore, (C) The ultraviolet curable resin composition for optics in any one of Claims 1-5 containing a photoinitiator. Furthermore, any one of Claims 1-6 containing the monomer (henceforth "(D) polymeric group containing monomer") which has a polymeric group which can superpose | polymerize with said (A) polymeric group containing (meth) acrylic-type polymer. An ultraviolet curable resin composition for optical use as described above. The (A) polymerizable group-containing (meth) acrylic polymer is a radically polymerizable group-containing (meth) acrylic polymer, and the (D) polymerizable group-containing monomer is an ethylenically unsaturated compound. The optical ultraviolet curable resin composition according to claim 7. The optical ultraviolet curable resin composition according to claim 8, wherein the (D) polymerizable group-containing monomer is a compound having one double bond in one molecule. The optical UV-curable resin composition according to claim 8 or 9, wherein the (D) polymerizable group-containing monomer has a hydroxyl group. The (A) polymerizable group-containing (meth) acrylic polymer is a cationic polymerizable group-containing (meth) acrylic polymer, and the (D) polymerizable group-containing monomer has an epoxy group or a vinyl ether group. The optical ultraviolet curable resin composition according to claim 7, which is a compound. The ultraviolet curable resin composition for optics according to claims 1 to 11, which is a liquid composition containing no solvent. Hardened | cured material obtained by hardening | curing the ultraviolet curable resin composition for optics in any one of Claims 1-12 by ultraviolet irradiation. A display device comprising a cured product of the ultraviolet curable resin composition for optics according to claim 13.

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