JP5793855B2 - Photo-curable adhesive and display element - Google Patents

Description

  The present invention relates to a photocurable adhesive suitable for bonding a display screen and a translucent member disposed on the display screen.

  In recent years, liquid crystal display panels are often used for in-vehicle and portable information devices, and the adhesive that bonds the polarizing plate and the input element constituting the liquid crystal display panel has excellent adhesive force and refractive index control. High transparency is strongly demanded. Generally, a method for manufacturing a display element and an input element includes a method in which the input element is built in the display element (in-cell) and a method in which the input element and the display element are bonded together (on-cell). The former requires a complicated process and a precise process, but the latter only produces input elements and display elements, and these are bonded together, so the latter has the advantage of saving manufacturing costs. There is.

  Currently, a double-sided tape or a photocurable adhesive is used to bond the input element and the display element substrate. There is a method of fixing a transparent touch panel by providing a double-sided adhesive cushion having a thickness of 0.3 to 1 mm on the outer periphery of the display element. There is also a method in which a touch panel is attached to the entire surface with a photo-curable adhesive on the display element. By laminating the entire surface, the air layer between the display element and the touch panel or cover plate replaces the photo-curing adhesive, so that reflection at the interface with the air layer is reduced and image quality is improved.

  The refractive index of the photo-curable adhesive is desirably substantially the same as the refractive index of the touch panel or cover plate. In the case of using a liquid adhesive as the photocurable adhesive, a method is known in which an adhesive is applied to the display element with a thickness of about 1 mm and bonded to a cover plate in a vacuum (see, for example, Patent Document 1). .) The adhesive may be a gel or rubber. Similarly, a method is known in which a liquid adhesive is used to bond a display element and a touch panel in the air so that air bubbles are not mixed in the air (see, for example, Patent Document 2).

  There is also a method of bonding with a transparent adhesive sheet without using a liquid adhesive. A method is known in which a display element and a touch panel are laminated and bonded together using a volatile solvent and a 0.2 mm adhesive sheet so that air bubbles do not enter the adhesive surface (see, for example, Patent Document 3). Further, as a transparent adhesive sheet having a repair property and a shock absorption property, a display element and a cover plate are formed with a three-layer transparent adhesive sheet in which a silicone gel layer of 3 mm thickness is sandwiched between a silicone rubber layer of 0.1 mm thickness. A method of bonding is known (for example, see Patent Document 4).

  Conventional photo-curing adhesives have a drawback that they cannot be repaired (re-attached) to bonding errors after bonding. Therefore, development of a photo-curing adhesive having high transparency, excellent adhesiveness between the display element and the input element, and repairability is strongly desired. Similarly, there is a need for a transparent adhesive film having the same refractive index as the material to be adhered.

JP 07-1114010 A JP 09-274536 A Japanese Patent Laid-Open No. 06-75210 JP 2004-101636 A

  The present invention provides a photocurable adhesive from which an adhesive film excellent in transparency, adhesion to an adherend, and repairability can be obtained.

  The present inventors represent a cellulose derivative (A), a radical polymerizable monomer (B), a photopolymerization initiator (C), a filler (D), and a silane coupling agent (E) represented by the formula (I). The photo-curable adhesive containing the surfactant (F) is highly transparent only in photo-curing in the formation of the cured film, for example, between glass / glass or glass / TAC (triacetyl cellulose). The present invention has been completed based on this finding, and the present invention includes the following items: a film having the same refractive index, adhesiveness, repairability, and the like.

[1] A photocurable adhesive containing a cellulose derivative (A) represented by the formula (I), a photocurable medium cured by photopolymerization, and a photopolymerization initiator (C).

In the formula (I), X is independently hydrogen or R, and R is independently — (CH ₂ CH (CH ₃ ) —O) _m H, —CH ₃ , —CH ₂ CH ₃ , —COCH _3. Represents —CH ₂ CH ₂ OH, —CH ₂ CH ₂ CH ₃ , —CH ₂ CH ₂ OCH ₂ CH ₃ , or —CH ₂ CH (CH ₃ ) —OCH ₃ , and n represents 10 to 20,000. . In R, m represents an integer of 1 to 5.

[2] The photocurable adhesive according to [1], wherein the photocurable medium contains a radical polymerizable monomer (B).

[3] The photocurable adhesive according to [1] or [2], wherein the photocurable medium includes a filler (D) which is a copolymer having a weight average molecular weight of 1,000 to 100,000.

[4] The photocurable adhesive according to any one of [1] to [3], further including one or both of a silane coupling agent (E) and a surfactant (F).

[5] The photocurable adhesive according to any one of [1] to [4], wherein the radical polymerizable monomer (B) includes a (meth) acrylate compound having one or more hydroxyl groups in one molecule. .

[6] In a display element in which two optical elements are bonded by a photocurable adhesive, the photocurable adhesive is the photocurable adhesive according to any one of [1] to [5]. Display element.

[7] The display element according to [6], wherein the two optical elements are a display panel and an input element.

  The photocurable adhesive of the present invention can form an adhesive film that is excellent in transparency, adhesion to an adherend, and repairability. In the present invention, since the adhesive film is formed by curing by light irradiation, the bonding operation is easy. Furthermore, in this invention, it is possible to adjust the refractive index of the adhesive film formed with the kind and composition of a photocurable medium.

  In addition, in this specification, in order to show both an acrylate and a methacrylate, it may describe as "(meth) acrylate".

The photocurable adhesive of this invention The photocurable adhesive of this invention is a photocurable adhesive containing a cellulose derivative (A), a photocurable medium, and a photoinitiator (C).

Cellulose derivative (A)
The cellulose derivative (A) used in the present invention is represented by the formula (I). As the cellulose derivative (A), a compound that is soluble in the photocurable medium in the present invention can be used. The cellulose derivative (A) may be one type or two or more types.

In the formula (I), X is independently hydrogen or R, and R is independently — (CH ₂ CH (CH ₃ ) —O) _m H, —CH ₃ , —CH ₂ CH ₃ , —COCH _3. Represents —CH ₂ CH ₂ OH, —CH ₂ CH ₂ CH ₃ , —CH ₂ CH ₂ OCH ₂ CH ₃ , or —CH ₂ CH (CH ₃ ) —OCH ₃ , and n represents 10 to 20,000. . In R, m represents an integer of 1 to 5.

  Specific examples of the cellulose derivative (A) include hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, methyl cellulose, methyl hydroxypropyl cellulose, and hydroxypropyl cellulose. The cellulose derivative (A) is preferably a cellulose derivative having a hydroxyalkyl in terms of enhancing adhesiveness. Of these, hydroxypropylcellulose is particularly preferred.

  The content of the cellulose derivative (A) with respect to the total amount of the photocurable adhesive of the present invention is preferably 0.01% by weight or more, more preferably 0.05% by weight or more from the viewpoint of obtaining adhesiveness. More preferably, it is 1% by weight or more. The content of the cellulose derivative (A) is preferably 50% by weight or less, more preferably 30% by weight or less, and more preferably 20% by weight or less, from the viewpoint of easy handling of the photocurable adhesive. More preferably it is.

The introduction rate of R in the cellulose derivative (A) is preferably 13% or more, more preferably 15 to 80%, and more preferably 40 to 80% from the viewpoint of solubility in the photocurable medium. More preferably. The introduction rate of R in the cellulose derivative (A) is expressed as a percentage of the number of R in the cellulose derivative (A) with respect to the number of hydrogen atoms of all hydroxyl groups in the cellulose. That is, in the cellulose derivative (A), the introduction rate of R = the number of R / (the number of R + the number of hydroxyl groups). The introduction rate can be determined by, for example, a normal analytical instrument such as ¹ H-NMR or elemental analysis. R in the cellulose derivative (A) may be introduced uniformly or may be introduced unevenly in the cellulose derivative (A).

  A cellulose derivative (A) is obtained by manufacturing by the normal method of etherifying and esterifying the hydroxyl group of a cellulose. Moreover, a cellulose derivative (A) is obtained as a commercial item. As a commercial item of a cellulose derivative (A), Nippon Soda Co., Ltd., product name: HPC-SSL, HPC-SL, HPC-L, HPC-M, and HPC-H are mentioned, for example.

Photocurable medium The photocurable medium used in the present invention is a transparent liquid, and dissolves the cellulose derivative (A) and the photopolymerization initiator (C), and other components that are added as necessary. It is a material that has the solubility to be cured and is cured by photopolymerization. The photocurable medium may be one type or two or more types. Examples of such a photocurable medium include a radical polymerizable monomer (B), a filler (D), a radical polymerizable or photocrosslinkable oligomer, and a radical polymerizable or photocrosslinkable polymer. Can be mentioned.

  The radical polymerizable monomer (B) is not particularly limited as long as it has an unsaturated double bond having radical polymerizability. The radical polymerizable monomer (B) may be one type or two or more types. Examples of the radical polymerizable monomer (B) include acrylic monomers, polymerizable monomers having an acid anhydride group, and other radical polymerizable monomers. The radical polymerizable group may be monofunctional or polyfunctional. For example, examples of the acrylic monomer include a monofunctional monomer and a polyfunctional monomer.

  Examples of the acrylic monofunctional monomer include acrylic acid, methacrylic acid, methyl (meth) acrylate, methacryloylmorpholine, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl (meth) acrylate. , Isobutyl (meth) acrylate, secondary butyl (meth) acrylate, tertiary butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) Acrylate, nonyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate 1-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 1-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (Meth) acrylate, 2-hydroxybutyl (meth) acrylate, 1-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 2-hydroxyethyl (meth) acrylate Is mentioned.

  Among these, a (meth) acrylate compound having one or more hydroxyl groups in one molecule, for example, an alkyl (meth) acrylate containing a hydroxy group is preferable from the viewpoint of improving adhesiveness. Examples of such an alkyl (meth) acrylate containing a hydroxy group include 1-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 1-hydroxypropyl ( (Meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 1-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6 -Hydroxyhexyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate are mentioned.

  Hydroxy group-containing alkyl (meth) acrylate not only gives flexibility to an adhesive film by photopolymerization in a photocurable adhesive, but also enhances the adhesive strength of the photocurable adhesive, and further includes a photopolymerization initiator and It effectively acts as a solvent for cellulose derivatives. Furthermore, among these hydroxy group-containing alkyl (meth) acrylates, it is preferable from the viewpoint of effectively acting as a solvent for the cellulose derivative to appropriately combine hydroxy group-containing alkyl (meth) acrylates having 2 to 6 carbon atoms in the alkyl group. .

  Examples of the acrylic polyfunctional monomer include 1,4-butanediol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9- Nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di (meth) acrylate, dipropylene glycol di (meth) acrylate , Tripropylene glycol di (meth) acrylate, polypropylene glycol (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate Propylene oxide added bisphenol A di (meth) acrylate, ethylene oxide added bisphenol A di (meth) acrylate, ethylene oxide added bisphenol F di (meth) acrylate, dimethylol dicyclopentadienyl di (meth) acrylate, 1,3- Butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene oxide-modified isocyanuric acid di (meth) acrylate, 2-hydroxy-3- (meth) acryloyloxypropyl (meth) acrylate, carbonate diol di (meth) ) Acrylate, polyether diol di (meth) acrylate, polyester diol di (meth) acrylate, polycaprolactone diol di (meth) acrylate, polybutadiene Diol di (meth) acrylate, bisphenol F ethylene oxide modified di (meth) acrylate, bisphenol A ethylene oxide modified di (meth) acrylate, isocyanuric acid ethylene oxide modified di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) Acrylate, pentaerythritol di (meth) acrylate, dipentaerythritol di (meth) acrylate, pentaerythritol di (meth) acrylate monostearate, trimethylolpropane di (meth) acrylate, 1,4-butanediol di (meth) acrylate 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,4-cyclohexanedi Methanol di (meth) acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di (meth) acrylate, trimethylolpropane di (meth) acrylate, dipentaerythritol di (meth) acrylate, modified isocyanuric acid Ethylene oxide modified di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate , Dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate , Propylene oxide modified trimethylolpropane tri (meth) acrylate, epichlorohydrin modified trimethylolpropane tri (meth) acrylate, glycerol tri (meth) acrylate, ethylene oxide modified glycerol tri (meth) acrylate, propylene oxide modified glycerol tri (meth) acrylate , Epichlorohydrin modified glycerol tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, diglycerol tetra (meth) acrylate, caprolactone modified dipentaerythritol hexa (meth) acrylate, ethylene oxide modified tri (meth) acrylate phosphate, tris [ (Meth) acryloxyethyl] isocyanurate, caprolactone-modified tris [(meth) acryloxy Chill] isocyanurate, and a urethane (meth) acrylate.

  Examples of the polymerizable monomer having an acid anhydride group include maleic anhydride, itaconic anhydride, and citraconic anhydride.

  Examples of other radical polymerizable monomers include styrene, α-methyl styrene, vinyl toluene, vinyl acetate, allyl acetate, 2-alkylpropenoic acid, acrylamide, N-alkyl acrylamide, dialkyl acrylamide, methacrylamide, and N-alkyl methacryl. Amide, dialkylmethacrylamide, 4-vinylpyridine, acrylonitrile, N-vinylpyrrolidone, N-vinylimidazole, isoprene, divinylbenzene, diallyl phthalate, maleimide, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, and N-phenylmaleimide may be mentioned.

  The content of the radical polymerizable monomer (B) with respect to the total amount of the photocurable adhesive of the present invention is preferably 10 to 90% by weight from the viewpoint of imparting flexibility to the adhesive film by polymerization. It is more preferably 85% by weight, and further preferably 20 to 85% by weight.

  Further, the content of the acrylic monofunctional monomer with respect to the total amount of the photocurable adhesive of the present invention is preferably 0.5 to 85% by weight from the viewpoint of imparting flexibility to the adhesive film by polymerization. It is more preferably ˜80 wt%, and further preferably 5 to 75 wt%.

  Moreover, content of the alkyl (meth) acrylate containing a hydroxy group with respect to the total amount of the photocurable adhesive of the present invention is 2 to 90% by weight from the viewpoint of effectiveness as a solvent for the photopolymerization initiator and the cellulose derivative. It is preferably 5 to 85% by weight, more preferably 10 to 80% by weight.

  In addition, the content of the acrylic polyfunctional monomer with respect to the total amount of the photocurable adhesive of the present invention is 0.01 to 80% by weight from the viewpoint of imparting flexibility to the adhesive film and controlling the adhesive force. Is preferable, 0.05 to 60% by weight is more preferable, and 0.1 to 50% by weight is further preferable.

  The content of the polymerizable monomer having an acid anhydride group is 0.01 to 80% by weight with respect to the total amount of the photocurable adhesive of the present invention from the viewpoint of imparting flexibility to the adhesive film. Is preferable, 0.05 to 60% by weight is more preferable, and 0.1 to 50% by weight is further preferable.

  The content of the other radical polymerizable monomer with respect to the total amount of the photocurable adhesive of the present invention is preferably 0.01 to 80% by weight from the viewpoint of imparting flexibility to the adhesive film. More preferably, it is 60 weight%, and it is further more preferable that it is 1-50 weight%.

  The filler (D) is a copolymer having a weight average molecule of 1,000 to 100,000. The filler (D) is obtained by radical copolymerization of the aforementioned monomer (B) having radical polymerizability. The filler (D) may be one type or two or more types. The inclusion of the filler (D) is preferable from the viewpoint of controlling the refractive index.

  The weight average molecular weight of the filler (D) can be determined by GPC analysis using polyethylene oxide as a standard. Polyethylene oxide having a molecular weight of 1,000 to 510,000 (for example, TSK standard manufactured by Tosoh Corporation) is used for the standard polyethylene oxide, and Shodex KD-806M (made by Showa Denko KK) is used for the column. It can be measured under conditions using DMF as the mobile phase.

  The content of the filler (D) with respect to the total amount of the photocurable adhesive of the present invention is preferably 0.001 to 80% by weight, and preferably 0.005 to 60% by weight from the viewpoints of refractive index control and solubility. % Is more preferable, and 0.1 to 50% by weight is further preferable.

  The oligomer having radical polymerizability or photocrosslinkability and the polymer having radical polymerizability or photocrosslinkability can be obtained, for example, by radical polymerization of a radically polymerizable monomer containing a polyfunctional radically polymerizable monomer.

  The photocurable medium is preferably composed of two or more kinds of compounds from the viewpoint of adjusting and improving the characteristics of the photocurable medium. For example, it is preferable that the photocurable medium contains a monomer (B) having a radical polymerization property and a filler (D) from the viewpoints of imparting flexibility to the adhesive film and controlling the refractive index. In this case, the amount of the filler (D) used relative to 100 parts by weight of the radically polymerizable monomer (B) is preferably 1 to 200 parts by weight, and 10 to 150 parts by weight from the above viewpoint. Is more preferable, and it is further more preferable that it is 20-100 weight part.

  Moreover, the photocurable medium has a total content of the monomer (B) having a radical polymerizability and the filler (D) with respect to the total amount of the photocurable adhesive of the present invention, from the above viewpoint, from 50 to 99. 0.9% by weight, more preferably 70 to 99% by weight, still more preferably 80 to 98% by weight, and still more preferably 90 to 98% by weight.

Photopolymerization initiator (C)
A photoinitiator (C) will not be specifically limited if it is a compound which generate | occur | produces a radical by irradiation of an ultraviolet-ray or visible light. The photopolymerization initiator (C) may be one type or two or more types. Examples of the photopolymerization initiator (C) include benzophenone, Michler's ketone, 4,4′-bis (diethylamino) benzophenone, xanthone, thioxanthone, isopropylxanthone, 2,4-diethylthioxanthone, 2-ethylanthraquinone, acetophenone, 2- Hydroxy-2-methylpropiophenone, 2-hydroxy-2-methyl-4′-isopropylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, isopropyl benzoin ether, isobutyl benzoin ether, 2,2-diethoxyacetophenone, 2, 2-dimethoxy-2-phenylacetophenone, camphorquinone, benzanthrone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzi 2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 4,4′-di (t-butylperoxycarbonyl) benzophenone, 3,4,4′-tri (t-butylperoxycarbonyl) benzophenone, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 3,3 ′, 4,4′-tetra (t -Hexylperoxycarbonyl) benzophenone, 3,3'-di (methoxycarbonyl) -4,4'-di (t-butylperoxycarbonyl) benzophenone, 3,4'-di (methoxycarbonyl) -4,3'-di (T-butylperoxycarbonyl) benzophenone, 4,4′-di (methoxycarbonyl) -3,3′-di (t-butylpe) Ruoxycarbonyl) benzophenone, 1,2-octanedione, 1- [4- (phenylthio) phenyl]-, 2- (o-benzoyloxime), 2- (4′-methoxystyryl) -4,6-bis ( Trichloromethyl) -s-triazine, 2- (3 ′, 4′-dimethoxystyryl) -4,6-bis (trichloromethyl) -s-triazine, 2- (2 ′, 4′-dimethoxystyryl) -4, 6-bis (trichloromethyl) -s-triazine, 2- (2′-methoxystyryl) -4,6-bis (trichloromethyl) -s-triazine, 2- (4′-pentyloxystyryl) -4,6 -Bis (trichloromethyl) -s-triazine, 4- [p-N, N-di (ethoxycarbonylmethyl)]-2,6-di (trichloromethyl) -s-triazine, 1,3-bis (Trichloromethyl) -5- (2′-chlorophenyl) -s-triazine, 1,3-bis (trichloromethyl) -5- (4′-methoxyphenyl) -s-triazine, 2- (p-dimethylaminostyryl) ) Benzoxazole, 2- (p-dimethylaminostyryl) benzthiazole, 2-mercaptobenzothiazole, 3,3′-carbonylbis (7-diethylaminocoumarin), 2- (o-chlorophenyl) -4,4 ′, 5 , 5′-tetraphenyl-1,2′-biimidazole, 2,2′-bis (2-chlorophenyl) -4,4 ′, 5,5′-tetrakis (4-ethoxycarbonylphenyl) -1,2 ′ -Biimidazole, 2,2'-bis (2,4-dichlorophenyl) -4,4 ', 5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis ( , 4-dibromophenyl) -4,4 ′, 5,5′-tetraphenyl-1,2′-biimidazole, 2,2′-bis (2,4,6-trichlorophenyl) -4,4 ′, 5,5′-tetraphenyl-1,2′-biimidazole, 3- (2-methyl-2-dimethylaminopropionyl) carbazole, 3,6-bis (2-methyl-2-morpholinopropionyl) -9-n -Dodecylcarbazole, 1-hydroxycyclohexyl phenyl ketone, bis (η ⁵ -2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) -phenyl) Titanium, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide It is.

  The content of the photopolymerization initiator (C) with respect to the total amount of the photocurable adhesive of the present invention is preferably 0.002 to 20% by weight from the viewpoint of sensitivity to irradiation with ultraviolet light or visible light, and is 0.005. It is more preferably ˜15% by weight, and further preferably 0.01˜10% by weight.

  The photocurable adhesive of the present invention further contains components other than the cellulose derivative (A), the photocurable medium, and the photopolymerization initiator (C) as long as the effects of the present invention are obtained. Also good. Examples of such other components include a silane coupling agent (E) and a surfactant (F).

Silane cup linking agent (E)
The photocurable adhesive of the present invention may further contain a silane coupling agent (E) from the viewpoint of further improving the adhesion between the formed adhesive film and the substrate. From such a viewpoint, the content of the silane coupling agent (E) with respect to the total amount of the photocurable adhesive of the present invention is preferably 0.01 to 20% by weight, and 0.05 to 15% by weight. It is more preferable that the content is 0.1 to 10% by weight. The silane coupling agent (E) may be one type or two or more types.

  Examples of such silane coupling agents (E) include 3-glycidoxypropyldimethylethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-methacrylic acid. Roxypropyltrimethoxysilane is mentioned.

Surfactant (F)
The photocurable adhesive of the present invention may further contain a surfactant (F) from the viewpoint of further improving the coating uniformity. From such a viewpoint, the content of the surfactant (F) with respect to the total amount of the photocurable adhesive of the present invention is preferably 0.01 to 10% by weight, and preferably 0.01 to 8% by weight. Is more preferable, and it is still more preferable that it is 0.01 to 5 weight%. The surfactant (F) may be one kind or two or more kinds.

  As the surfactant (F), for example, Polyflow No. 45, polyflow KL-245, polyflow no. 75, Polyflow No. 90, polyflow no. 95 (all are trademarks, manufactured by Kyoeisha Chemical Co., Ltd.), Disperbak 161, Disperse Bake 162, Disperse Bake 163, Disperse Bake 164, Disperse Bake 166, Disperse Bake 170, Disperse Bake 180, Disperse Bake 181 and Disper Bake 182, BYK300, BYK306, BYK310, BYK320, BYK330, BYK344, BYK346 (all of which are trademarks, manufactured by BYK Japan), KP-341, KP-358, KP-368, KF-96-50CS, KF- 50-100CS (all are trademarks, manufactured by Shin-Etsu Chemical Co., Ltd.), Surflon SC-101, Surflon KH-40 (all are trademarks, manufactured by AGC Seimi Chemical Co., Ltd.) Aftergent 222F, Aftergent 251, FTX-218 (all are trademarks, manufactured by Neos Co., Ltd.), EFTOP EF-351, EFTOP EF-352, EFTOP EF-601, EFTOP EF-801, EFTOP EF-802 (all above) Trademark, manufactured by Mitsubishi Materials Corporation), Megafuck F-171, Megafuck F-177, Megafuck F-475, Megafuck R-30, Megafuck F-556, Megafuck R-30 (all are trademarks) Manufactured by DIC Corporation), fluoroalkylbenzenesulfonate, fluoroalkylcarboxylate, fluoroalkylpolyoxyethylene ether, fluoroalkylammonium iodide, fluoroalkylbetaine, fluoroalkylsulfonate, diglyce Tetrakis (fluoroalkyl polyoxyethylene ether), fluoroalkyltrimethylammonium salt, fluoroalkylaminosulfonate, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene lauryl ether, poly Oxyethylene oleyl ether, polyoxyethylene tridecyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene laurate, polyoxyethylene oleate, polyoxyethylene stearate, polyoxyethylene laurylamine, sorbitan laur Rate, sorbitan palmitate, sorbitan stearate, sorbitan oleate, sol Tan fatty acid ester, polyoxyethylene sorbitan laurate, polyoxyethylene sorbitan palmitate, polyoxyethylene sorbitan stearate, polyoxyethylene sorbitan oleate, polyoxyethylene naphthyl ether, alkylbenzene sulfonate, and alkyl diphenyl ether disulfonate Is mentioned.

  The viscosity of the photocurable adhesive of the present invention can be determined according to the coating method, and is preferably 100 to 40,000 mPa · s. For example, when a coating film having a thickness of 20 to 50 μm is formed using a screen printing method, the viscosity is preferably 100 to 20,000 mPa · s from the viewpoint of coating with good productivity. The viscosity of a photocurable adhesive agent can be adjusted with content of a cellulose derivative (A) and a radically polymerizable monomer (B), for example. Moreover, the viscosity of a photocurable adhesive agent can be calculated | required by the measurement in 25 degreeC using an E-type viscosity meter (Tokyo Keiki Co., Ltd., product name: VISCONIC EMD).

The photo-curable adhesive of the present invention is obtained by applying the photo-curable adhesive of the present invention to one or both of two adherends including at least one transparent adherend, and bonding the two adherends together By irradiating the adhesive surface with light that causes photopolymerization such as ultraviolet rays through the transparent adherend, it can be used for adhering the two adherends. According to the photocurable adhesive of the present invention, for example, after being applied to a base material to be bonded (TAC film or glass) by a screen printing method and pasting the upper plate material to be bonded (TAC film or glass), ultraviolet light is applied. The above-mentioned adherend can be adhered by irradiating light containing, for example, 50 to 3,000 mJ / cm ² to cure the photocurable adhesive.

  In this invention, since a photocurable medium melt | dissolves another component, the photocurable adhesive agent which does not contain a solvent can be obtained.

  In addition, since the curable adhesive of the present invention can adhere the adherend by light irradiation, it can adhere the adherend with high workability.

  Furthermore, in the photocurable adhesive of this invention, the adhesive film formed on a to-be-adhered material can be removed using a peeling tape. Therefore, if the photocurable adhesive of the present invention is used, even when the bonding of the adherends fails, the adhesive film can be removed and the bonding can be performed again (repaired).

  Furthermore, the photocurable adhesive of the present invention can form an adhesive film having the same refractive index as that of glass or TAC generally used for display elements. The photocurable adhesive of the present invention can be used as an interlayer adhesive for display elements.

  As is clear from the above description, the photocurable adhesive of the present invention can be applied between a liquid crystal display element and a touch panel, for example, in a preferred embodiment, and can be cured only by light irradiation, and has higher adhesiveness. It has a refractive index of about 1.5 and a transmittance of 95% or more, and can adjust the viscosity corresponding to various application methods such as spin, dispenser, screen printing, etc. Although it has high adhesiveness, it is possible to remove these materials with a peeling tape after the material to be bonded is removed against bonding mistakes after bonding. It is.

  The display element of the present invention is a display element in which two optical elements are bonded with the photocurable adhesive of the present invention. The display element of the present invention may further have other components as long as it has an optical element bonded with the photocurable adhesive of the present invention.

  The optical element is a member that constitutes the display element, and is a member that generates light having a specific optical characteristic, a member through which light passes, or a member that changes the optical characteristics of light passing through. It is preferable that at least one of the two optical elements to be bonded is transparent. Examples of such an optical element include an optical element including a glass substrate and an optical element including a TAC substrate or a TAC film. As an optical element, each member which comprises a liquid crystal display element is mentioned, for example, Specifically, a display panel, an input element, a protective cover, and a color filter are mentioned.

  The display panel is a member that displays an image on the display element. Examples of such a display panel include a liquid crystal display element, a plasma display, an organic EL, an inorganic EL, and an FED. As an input element, transparent input elements, such as a touch panel, are mentioned, for example.

  The bonding surface of the optical element in the display element of the present invention may be a part (dot or line) of the surface of the optical element or the whole. In the display element of the present invention, since the refractive index of the adhesive film is approximately the same as the refractive index of the substrate, the adhesive surface of the optical element includes the entire image display area of the display panel. This is preferable from the viewpoint of image quality.

  The material of the adhesive surface in the optical element is glass or TAC from the viewpoint of enhancement of functions as an element such as transparency and mechanical strength, and from the viewpoint of sufficient adhesiveness by the photocurable adhesive of the present invention. Is preferred.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited by these.

[Examples 1 to 53]
The components A to F described in Table 1 and Table 2 were mixed at the blending amounts (% by weight) described in these tables and stirred to obtain a photocurable adhesive.

In addition, the display of each component of A-F in Table 1 and 2 represents the following products or components.
A-1 Hydroxypropyl cellulose (Acros Organics, Hydroxypropyl cellulose, Average MW 100,000)
A-2 Methylcellulose (Wako Pure Chemical Industries, Ltd., Methylcellulose 400)
A-3 Hydroxyethylcellulose (Wako Pure Chemical Industries, Ltd., hydroxyethylcellulose)
B-1 Acid-modified epoxy acrylate (Nippon Kayaku Co., Ltd., product name: KAYARD ZFR-1491)
B-2 Acid-modified epoxy acrylate (Nippon Kayaku Co., Ltd., product name: KAYARD CCR-1285)
B-3 Acid-modified epoxy acrylate (Nippon Kayaku Co., Ltd., product name: KAYARD CCR-1287)
B-4 Acid-modified epoxy acrylate (Nippon Iupika Co., Ltd., product name: Neopol 8477-350)
B-5 Dipentaerythritol hexaacrylate (Toagosei Co., Ltd., product name: Aronix M-402)
B-6 Bifunctional acrylate (Kyoeisha Chemical Co., Ltd., product name: epoxy ester 80MFA)
B-7 Bifunctional acrylate (Kyoeisha Chemical Co., Ltd., product name: epoxy ester 70PA)
B-8 Bifunctional acrylate (Kyoeisha Chemical Co., Ltd., product name: Epoxy ester 200PA)
B-9 4-hydroxybutyl acrylate (Nippon Kasei Co., Ltd., product name: 4-HBA) B-10 2-hydroxyethyl methacrylate (Kanto Chemical Co., Ltd., product name: HEMA)
B-11 2-hydroxyethyl acrylate (Kanto Chemical Co., Inc., product name: HEA)
C-1, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (BASF, product name: DAROCUR TPO)
C-2 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one (BASF, product name: IRGACURE 907)
C-3 1-hydroxy-cyclohexyl-phenyl-ketone (BASF, product name: IRGACURE 184)
D-1 Methyl methacrylate (60) + butyl methacrylate (40) copolymer (Mw: 10,000)
D-2 Methyl methacrylate (20) + butyl methacrylate (80) copolymer (Mw: 10,000)
D-3 Copolymer (Mw: 15,000) of butyl methacrylate (60) + hydroxyethyl methacrylate (40)
D-4 Methyl methacrylate (16.5) + hydroxyethyl methacrylate (16.5) + butyl methacrylate (67) copolymer (Mw: 15,000)
E-1 3-methacryloxypropyltrimethoxysilane (Chisso Corporation, product name: Silers, S710)
F-1 Surfactant (DIC Corporation, product name: MegaFuck F-556)

  About the obtained photocurable adhesive agent, viscosity, light transmittance, refractive index, adhesiveness, and repair property were evaluated. The evaluation results are shown in Tables 3 and 4.

The viscosity of the photo-curable adhesive is an E-type viscometer (Tokyo Keiki Co., Ltd., product name: VISCONIC).
EMD) at 25 ° C. The unit of viscosity is mPa · s.

The light transmittance of the photocurable adhesive was measured by spreading 50 μm bead spacers on a glass of 4 cm × 4 cm × 0.05 cm size, dropping about 0.1 mL of the photocurable adhesive on the glass, A glass having a size of 4 cm × 4 cm × 0.05 cm is bonded to the surface of the glass on which the curable adhesive has been dropped, and is pressed and exposed to ultraviolet rays for exposure (all lines 1,000 mJ / cm ² , high pressure mercury lamp). A specimen is prepared by bonding glass and glass, and light transmittance measurement of the specimen in the opposite direction of the glass is performed using an ultraviolet-visible near-infrared spectrophotometer (JASCO Corporation, product name: V-670). It measured using. The light transmittance is a light transmittance (T%) at 400 nm when a wavelength of 350 nm to 800 nm is measured.

The refractive index of the photocurable adhesive is such that the photocurable adhesive is applied onto glass by spin coating, and the resulting coating film is exposed under a nitrogen atmosphere (all lines 1,000 mJ / cm ² , high pressure mercury lamp). Thus, a photo-curable adhesive film (film thickness: 7 to 10 μm) was formed, and this film was measured using a thin film reflection type film thickness measuring instrument (Otsuka Electronics Co., Ltd., product name: FE-3000). . The refractive index is a refractive index with light having a wavelength of 589 nm.

The adhesion was measured by the following method.
The adhesiveness of the photo-curing adhesive is that a 50 μm bead spacer is dispersed on 1 cm × 4 cm glass, about 0.05 mL of the adhesive is dropped on the glass, and the surface of the glass on which the adhesive is dropped is 1 cm × 4 cm. A glass or TAC film is bonded to a lower glass so as to form a T-shape, pressed, exposed to ultraviolet rays and exposed (all lines 1,000 mJ / cm ² , high-pressure mercury lamp), and glass and glass or The TAC film was adhered to a T-shape, and the glass and the glass or TAC film adhered to each other in this T-shaped specimen were peeled by hand, and evaluation was performed according to the state at the time of peeling. The evaluation criteria are as follows.
○: There is resistance when the specimen is peeled off.
Δ: There is a little resistance when the specimen is peeled off.
X: No resistance when peeling the specimen.

The repairability of the photocurable adhesive is that the glass and TAC film adhered to each other in the T-shaped specimen made of glass and TAC film are peeled off by hand, and the photocurable adhesive remaining on the peeled surface is adhered. It evaluated by the mode when it removed by repetition of pasting and peeling of a tape (Sumitomo 3M Co., Ltd., electrical insulation tape polyester film tape No. 56). The evaluation criteria are as follows.
◯: The remaining photocurable adhesive could be removed by applying and peeling the adhesive tape once to several times.
X: The remaining photocurable adhesive cannot be removed by sticking and peeling of the pressure-sensitive adhesive tape.

  In Examples 1 to 52, the cellulose derivative (A), the radical polymerizable monomer (B), the photopolymerization initiator (C), the filler (D), the silane coupling agent (E), and the surfactant (F) are added. When evaluated in various combinations, satisfactory results were obtained as interlayer adhesives for display elements in all properties of viscosity, light transmittance, refractive index, adhesiveness, and repairability. In particular, the adhesion to the TAC film was good. When the hardened | cured material between the glass of Examples 1-34 and a TAC film was peeled by hand, it did not remain on the glass side but adhesion to the TAC side was confirmed. The cured product remaining on the TAC side could be removed with the polyester film tape, and repairability was confirmed.

  Particularly in Examples 12 to 23 and 35 to 50, the radical polymerizable monomer (B) and the filler (D) which is a copolymer of a monomer containing or similar to the radical polymerizable monomer (B). Further, by using together with a filler (D) whose hardness is generally higher than that of the photopolymerized product of the radical polymerizable monomer (B), the refractive index is higher than when only the radical polymerizable monomer (B) is used. The rate was obtained. Thus, it was confirmed that the refractive index was controlled by using the filler (D). Moreover, in Examples 12-23, 35-50, by using such a filler (D) together with a radical polymerizable monomer (B), it is based on a radical polymerizable monomer (B) with respect to glass or a TAC film. Adhesiveness equal to or better than sufficient adhesiveness was also obtained.

[Comparative Examples 1 to 28]
In the same manner as in the examples except that the cellulose derivative (component A) was not used, the components BF described in Table 5 were mixed in the blending amounts (% by weight) described in this table and stirred. As a result, a comparative photocurable adhesive was obtained. Moreover, also about the obtained photocurable adhesive agent, the viscosity, light transmittance, refractive index, adhesiveness, and repair property were evaluated similarly to the Example. The evaluation results are shown in Tables 5 and 6.

  In Comparative Examples 1 to 28, the results satisfying all the properties of viscosity, light transmittance, refractive index, adhesiveness, and repairability as interlayer adhesives for display elements were not obtained. In Comparative Examples 9 to 28, it was confirmed that the refractive index was controlled by containing the filler (D), as in the results of Examples.

  Various display elements such as liquid crystal are used for various purposes, and not only an improvement in image quality but also an improvement in productivity is required. In the present invention, in the manufacture of a display element that requires the entire surface of an optical element to be bonded, an adhesive film having substantially the same refractive index as that of a transparent member usually used for a substrate or cover of the optical element can be formed. There is no deterioration in image quality due to the difference in rate. Moreover, in this invention, since such an adhesive film can be formed by simple operation called light irradiation, the workability | operativity of a display element can be improved. Furthermore, in the present invention, since the formed adhesive film can be peeled off from the optical element, it is possible to reduce the discard of defective products due to a failure in attachment and further improve the yield of display elements. As described above, the present invention is expected to greatly contribute to improvement in both quality and productivity in the manufacture of display elements.

Claims (6)

A photocurable adhesive comprising cellulose represented by formula (I) and / or a cellulose derivative (A), a photocurable medium cured by photopolymerization, and a photopolymerization initiator (C) ,
A photocurable adhesive, wherein the curable medium contains a (meth) acrylate compound having one or more hydroxyl groups in one molecule .

(In the formula (I), X is independently hydrogen or R, and R is independently — (CH ₂ CH (CH ₃ ) —O) _m H, —CH ₃ , —CH ₂ CH ₃ , —COCH. ₃ , —CH ₂ CH ₂ OH, —CH ₂ CH ₂ CH ₃ , —CH ₂ CH ₂ OCH ₂ CH ₃ , or —CH ₂ CH (CH ₃ ) —OCH ₃ ;
Represents 20,000. In R, m represents an integer of 1 to 5. ) The photocurable adhesive according to claim 1, wherein an introduction rate of R in the cellulose derivative (A) (R introduction rate = number of R / (number of R + number of hydroxyl groups)) is 13% or more. The photocurable adhesive according to claim 1 or 2 , wherein the photocurable medium contains a filler (D) which is a copolymer having a weight average molecular weight of 1,000 to 100,000. Furthermore, the photocurable adhesive agent as described in any one of Claims 1-3 containing one or both of a silane coupling agent (E) and surfactant (F). The display element by which two optical elements are adhere | attached with a photocurable adhesive agent, The display element whose photocurable adhesive agent is a photocurable adhesive agent as described in any one of Claims 1-4 . The display element according to claim 5 , wherein the two optical elements are a display panel and an input element.