TWI487761B - Photo-curable adhesive and display device - Google Patents

Description

Photocurable adhesive and display element

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

In recent years, liquid crystal display panels have been used as a vehicle-mounted or portable information device, and the adhesive for bonding a polarizing plate constituting a liquid crystal display panel to an input member is strongly required to have excellent adhesive force and refractive index. Control or high transparency. In general, a method of manufacturing a display element and an input element includes a method of incorporating an input element into a display element (In-Cell), and a method of bonding an input element to a display element by bonding (external type ( On-Cell)). The former requires complicated steps or precise steps, and the latter has the advantage of saving production costs since only the input member and the display member are fabricated and the two are bonded together.

Currently, in order to bond an input member to a display element substrate, a double-sided tape or a photocurable adhesive is used. There is a method of fixing a transparent touch panel by providing a pad with a double-sided adhesive having a thickness of 0.3 mm to 1 mm on the outer periphery of the display element. Further, there is a method in which a touch panel is entirely attached to a display element by a photocurable adhesive. By fully fitting, the air layer between the display element and the touch panel or the cover is replaced by a photocurable adhesive, so that the reflection on the interface with the air layer is reduced and the image quality is improved.

The refractive index of the photocurable adhesive is preferably substantially the same as the refractive index of the touch panel or the cover. When a liquid adhesive is used as the photocurable adhesive, a method of applying a binder to a display member at a thickness of about 1 mm and then adhering it to a cover in a vacuum is known (for example, refer to Patent Document 1). ). A gel-like or rubber-like binder can also be used as the binder. In addition, a method in which a display element and a touch panel are bonded to the atmosphere in a manner that air bubbles are not mixed in the air is known (for example, see Patent Document 2).

Further, there is also a method of bonding with a transparent adhesive sheet without using a liquid adhesive. A method of laminating and bonding a display element and a touch panel with a volatile solvent and a 0.2 mm adhesive sheet so as not to allow air bubbles to enter the adhesive surface is known (for example, refer to Patent Document 3). Further, a transparent adhesive sheet having a three-layer structure in which a ruthenium rubber layer having a thickness of 0.1 mm is sandwiched by a ruthenium rubber layer having a thickness of 3 mm is known as a transparent adhesive sheet having repairability and impact absorption, and a display element is known. A method of bonding to a cover (for example, refer to Patent Document 4).

The photocurable adhesives to date have the disadvantage of not being able to repair (reattach) the bonding failure after bonding. Therefore, it has been strongly desired to develop a photocurable adhesive which is excellent in adhesion to a display element and an input element, and which is excellent in repairability. Further, similarly, a transparent adhesive film having the same refractive index as that of the material to be bonded is sought.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 07-114010

[Patent Document 2] Japanese Patent Laid-Open No. 09-274536

[Patent Document 3] Japanese Patent Laid-Open No. 06-75210

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2004-101636

The present invention provides a photocurable adhesive which can obtain an adhesive film having excellent transparency, adhesion to an adherend, and repairability.

The present inventors have found that the cellulose derivative (A) represented by the formula (I), the radical polymerizable monomer (B), the photopolymerization initiator (C), the filler (D), and the decane coupling agent are contained. (E) The photocurable adhesive of the surfactant (F) forms a highly transparent and adhered material only by photohardening when forming a cured film (for example, glass/glass or glass/triacetic acid) The film of the same degree of refractive index, adhesiveness, repairability, and the like of cellulose (Triacetyl Cellulose (TAC)) was completed according to the findings. The present invention encompasses the following items.

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

[Chemical 1]

In the formula (I), X is independently hydrogen or R, and R independently represents -(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 , n represents 10 to 20,000. Further, 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 contains a filler (D) as 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 comprising one or both of a decane coupling agent (E) and a surfactant (F).

[5] The photocurable adhesive according to any one of [1], wherein the radical polymerizable monomer (B) contains (meth)acrylic acid having one or more hydroxyl groups in one molecule. Ester compound.

[6] A display element which is a display element obtained by bonding two optical elements by a photocurable adhesive, and the photocurable adhesive is according to any one of [1] to [5]. Photocurable adhesive.

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

Effect of the invention

The photocurable adhesive of the present invention can form an adhesive film having excellent transparency, adhesion to an adherend, and repairability. In the present invention, since the adhesive film is formed by hardening by light irradiation, the adhesion is relatively easy. Further, in the present invention, the refractive index of the formed adhesive film can be adjusted by the type or composition of the photocurable medium.

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

The above described features and advantages of the present invention will be more apparent from the following description.

Photocuring adhesive of the invention

The photocurable adhesive of the present invention is a photocurable adhesive containing a cellulose derivative (A), a photocurable medium, and a photopolymerization initiator (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 which is dissolved in the photocurable medium in the present invention can be used. The cellulose derivative (A) may be one type or two or more types.

[Chemical 2]

In the formula (I), X is independently hydrogen or R, and R independently represents -(CH ₂ CH(CH ₃ )-O) _m H, -CH ₂ , -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 , n represents 10 to 20,000. Further, 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. From the viewpoint of improving the adhesion, the cellulose derivative (A) is preferably a cellulose derivative having a hydroxyalkyl group. Among them, hydroxypropylcellulose is particularly preferred.

The content of the cellulose derivative (A) based on the total amount of the photocurable binder of the present invention is preferably 0.01 wt% or more, more preferably 0.05 wt% or more, from the viewpoint of obtaining adhesiveness. Further, it is more preferably 1 wt% or more. The content of the cellulose derivative (A) is preferably 50% by weight or less, more preferably 30% by weight or less, and still more preferably 20% by weight or less from the viewpoint of easiness of handling of the photocurable adhesive.

The introduction ratio of R in the cellulose derivative (A) is preferably 13% or more, more preferably 15% to 80%, and still more preferably 40% to 80% from the viewpoint of solubility in a photocurable medium. %. The introduction ratio of R in the cellulose derivative (A) is represented by the percentage of the number of R in the cellulose derivative (A) to the number of hydrogen atoms of all the hydroxyl groups in the cellulose. That is, in the cellulose derivative (A), the introduction ratio of R = the number of R / (the number of R + the number of hydroxyl groups). The introduction rate can be determined by a general analysis machine such as ¹ H-NMR or elemental analysis. R in the cellulose derivative (A) can be uniformly introduced into the cellulose derivative (A), or can be introduced into the cellulose derivative (A) unevenly.

The cellulose derivative (A) can be obtained by a usual method of etherifying or esterifying a hydroxyl group of cellulose. Further, the cellulose derivative (A) can be obtained in the form of a commercially available product. Examples of commercially available products of the cellulose derivative (A) include HPC-SSL, HPC-SL, HPC-L, HPC-M, and HPC-H (Japan Soda Corporation, product name).

Photohardenable medium

The photocurable medium used in the present invention is a transparent liquid which has solubility in dissolving the cellulose derivative (A), the photopolymerization initiator (C), and other components added as needed, and is utilized. A material that is photopolymerized and hardened. 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), an oligomer having a radical polymerizable property or a photocrosslinkability, and a radical polymerizable property or Photocrosslinking polymer.

The radically polymerizable monomer (B) is not particularly limited as long as it contains an unsaturated double bond having a radical polymerizable property. The radically polymerizable monomer (B) may be one type or two or more types. Examples of the radical polymerizable monomer (B) include an acrylic monomer, a polymerizable monomer having an acid anhydride group, and another radical polymerizable monomer. The radical polymerizable group may be monofunctional or polyfunctional. For example, a monofunctional monomer and a polyfunctional monomer are mentioned as an acrylic monomer.

Examples of the acrylic monofunctional monomer include acrylic acid, methacrylic acid, methyl (meth)acrylate, methacryloylmorpholine, ethyl (meth)acrylate, and propyl (meth)acrylate. Isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, second butyl (meth)acrylate, tert-butyl (meth)acrylate, (methyl) Ethyl acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, (methyl) 2-ethylhexyl acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, 1-hydroxyethyl (meth) acrylate, (meth) acrylate 2-hydroxypropyl ester, 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 (meth)acrylic acid 2-hydroxyethyl ester.

Among these acrylic monofunctional monomers, a (meth) acrylate compound having one or more hydroxyl groups in one molecule, for example, a hydroxyl group-containing (meth) acrylate, is preferred from the viewpoint of improving the adhesion. Base ester. Examples of such a hydroxyl group-containing (meth)acrylic acid alkyl ester include 1-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate. Ester, 1-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, (methyl) 1-hydroxybutyl acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate.

In the photocurable adhesive, the alkyl (meth)acrylate containing a hydroxyl group not only imparts flexibility to the photopolymerized adhesive film, but also enhances the adhesion of the photocurable adhesive, and further serves as a photopolymerization initiator or The solvent of the cellulose derivative functions effectively. Further, among these hydroxyl group-containing alkyl (meth)acrylates, from the viewpoint of effectively acting as a solvent for the cellulose derivative, a hydroxyl group having 2 to 6 carbon atoms in the alkyl group is preferred. The alkyl (meth)acrylate is suitably combined.

Examples of the acrylic polyfunctional monomer include 1,4-butanediol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, and 1,6-hexanediol. (meth) acrylate, 1,9-nonanediol di(meth) acrylate, 1,10-nonanediol 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 addition bisphenol A di(methyl) Acrylate, ethylene oxide addition bisphenol A di(meth) acrylate, ethylene oxide addition bisphenol F di(meth) acrylate, dimethylol dicyclopentadienyl di(a) Acrylate, 1,3-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide modified diisocyanate di(meth)acrylate , 2-hydroxy-3-(meth) propylene methoxypropyl (meth) acrylate, carbonate diol di (methyl) Acrylate, polyether diol di(meth) acrylate, polyester diol di(meth) acrylate, polycaprolactone diol di(meth) acrylate, polybutadiene diol di Methyl)acrylate, bisphenol F ethylene oxide modified di(meth)acrylate, bisphenol A ethylene oxide modified di(meth)acrylate, isomeric cyanuric acid ethylene oxide 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 (Meth) acrylate, 1,9-nonanediol di(meth) acrylate, 1,4-cyclohexane dimethanol di(meth) acrylate, 2-n-butyl-2-ethyl- 1,3-propanediol di(meth)acrylate, trimethylolpropane di(meth)acrylate, dipentaerythritol di(meth)acrylate, modified iso-cyanuric acid ethylene oxide modified (meth) acrylate, pentaerythritol tri (meth) acrylate Ester, 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 (Meth) acrylate, epichlorohydrin modified glycerol tri(meth) acrylate, di-trimethylolpropane tetra (meth) acrylate, diglycerin tetra (meth) acrylate, caprolactone Dipentaerythritol hexa(meth) acrylate, ethylene oxide modified tris(meth) acrylate, tris[(methyl) propylene oxyethyl]isocyanate, caprolactone A tris[(meth)acrylomethoxyethyl]isocyanate, and a polyurethane (meth) acrylate.

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

Examples of the other radical polymerizable monomer include styrene, α-methylstyrene, vinyltoluene, vinyl acetate, allyl acetate, 2-alkylacrylic acid, acrylamide, and N-alkyl group. Acrylamide, dialkyl acrylamide, methacrylamide, N-alkyl methacrylamide, dialkyl methacrylamide, 4-vinyl pyridine, acrylonitrile, N-vinyl pyrrolidone , N-vinylimidazole, isoprene, divinylbenzene, diallyl phthalate, maleimide, N-methylbutyleneimine, N-ethyl Maleimide, N-cyclohexylmethyleneimine, and N-phenyl maleimide.

The content of the radical polymerizable monomer (B) based on the total amount of the photocurable binder of the present invention is preferably from 10% by weight to 90% by weight from the viewpoint of imparting flexibility to the polymerized adhesive film. More preferably, it is 15 wt% to 85 wt%, and still more preferably 20 wt% to 85 wt%.

In addition, the content of the acrylic monofunctional monomer relative to the total amount of the photocurable adhesive of the present invention is preferably from 0.5% by weight to 85 % by weight, from the viewpoint of imparting flexibility to the polymerized adhesive film. It is preferably from 1 wt% to 80 wt%, and still more preferably from 5 wt% to 75 wt%.

In addition, the content of the hydroxyl group-containing (meth)acrylic acid alkyl ester relative to the total amount of the photocurable binder of the present invention is from the viewpoint of the effectiveness of the solvent for the photopolymerization initiator or the cellulose derivative. Preferably, it is from 2 wt% to 90 wt%, more preferably from 5 wt% to 85 wt%, still more preferably from 10 wt% to 80 wt%.

In addition, the content of the acrylic polyfunctional monomer relative to the total amount of the photocurable binder of the present invention is preferably 0.01 wt% to 80 wt% from the viewpoint of imparting flexibility and controlling adhesion to the adhesive film. More preferably, it is 0.05 wt% to 60 wt%, and still more preferably 0.1 wt% to 50 wt%.

Further, the content of the polymerizable monomer having an acid anhydride group is preferably 0.01% by weight to 80% by weight based on the total amount of the photocurable adhesive of the present invention, from the viewpoint of imparting flexibility to the adhesive film. It is preferably from 0.05 wt% to 60 wt%, more preferably from 0.1 wt% to 50 wt%.

In addition, the content of the other radical polymerizable monomer in the total amount of the photocurable binder of the present invention is preferably 0.01 wt% to 80 wt%, more preferably from the viewpoint of imparting flexibility to the adhesive film. 1 wt% to 60 wt%, and more preferably 1 wt% to 50 wt%.

The filler (D) is a copolymer having a weight average molecular weight of 1,000 to 100,000. The filler (D) can be obtained by radical copolymerization of the radical polymerizable monomer (B). The filler (D) may be one type or two or more types. From the viewpoint of controlling the refractive index, the filler (D) is preferably contained.

The weight average molecular weight of the filler (D) can be determined by gel permeation Chromatography (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 Co., Ltd.) can be used as a standard polyethylene oxide, and Shodex KD-806M (manufactured by Showa Denko (manufactured)) can be used as a column. The measurement was carried out using dimethylformamide (DMF) as a mobile phase.

The content of the filler (D) based on the total amount of the photocurable binder of the present invention is preferably from 0.001% by weight to 80% by weight, more preferably from 0.005% by weight, from the viewpoint of control of the refractive index and solubility. ～60 wt%, and further preferably 0.1 wt% to 50 wt%.

An oligomer having a radical polymerizable property or a photocrosslinkability, and a polymer having a radical polymerizable property or a photocrosslinkability can be, for example, a radical polymerizable monomer containing a polyfunctional radical polymerizable monomer. Obtained by radical polymerization.

From the viewpoint of adjusting or improving the characteristics of the photocurable medium, it is preferred that the photocurable medium contains the two or more kinds of compounds. For example, from the viewpoint of imparting flexibility to the adhesive film and controlling the refractive index, the photocurable medium preferably contains a monomer (B) having a radical polymerizable property and a filler (D). In this case, the amount of the filler (D) to be used in terms of 100 parts by weight of the monomer (B) having a radical polymerizable property is preferably from 1 part by weight to 200 parts by weight, more preferably from the viewpoint of the above. 10 parts by weight to 150 parts by weight, and more preferably 20 parts by weight to 100 parts by weight.

Further, in the photocurable medium, the total content of the radical polymerizable monomer (B) and the filler (D) in the total amount of the photocurable binder of the present invention is It is preferably 50 wt% to 99.9 wt%, more preferably 70 wt% to 99 wt%, still more preferably 80 wt% to 98 wt%, and still more preferably 90 wt% to 98 wt%.

Photopolymerization initiator (C)

The photopolymerization initiator (C) is not particularly limited as long as it is a compound that generates a radical by irradiation with ultraviolet rays 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, oxonone, thioxanthone, and isophthalic acid. Propyl oxynone, 2,4-diethylthiazinone, 2-ethyl hydrazine, 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, benzoxanthone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinylpropan-1-one, 2-benzyl 2-dimethylamino-1-(4-morpholinylphenyl)-butanone-1, 4-dimethylaminobenzoic acid ethyl ester, 4-dimethylaminobenzoic acid isoamyl ester, 4, 4'-di(t-butylcarbonyl)benzophenone, 3,4,4'-tris(t-butylcarbonyl)benzophenone, 3,3',4,4'- Tetrakis(t-butylcarbonyl)benzophenone, 3,3',4,4'-tetra(t-butylhexylcarbonyl)benzophenone, 3,3'-bis(methoxycarbonyl) -4,4'-di(t-butylcarbonyl)benzophenone, 3,4'-bis(methoxycarbonyl)-4,3'-di(t-butylcarbonyl peroxide) Benzophenone, 4,4'-bis(methoxycarbonyl)-3,3'-di(t-butylperoxycarbonyl)benzophenone, 1,2-octanedione, 1-[4- (phenylthio)phenyl]-,2-(o-benzylidene fluorenyl), 2-(4'-methoxystyryl)-4,6-bis(trichloromethyl)-s-triazine , 2-(3',4'-dimethoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(2',4'-dimethoxystyrene -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-bis(trichloromethyl)-s-triazine, 1,3-bis(trichloromethyl)-5-(2'-chlorophenyl)-s-triazine, 1,3-bis(trichloro) Methyl)-5-(4'-methoxyphenyl)-s-triazine, 2-(p-dimethylaminostyryl)benzoxazole, 2-(p-dimethylaminostyryl) Benzothiazole, 2-mercaptobenzothiazole, 3,3'-carbonyl bis(7-diethylaminocoumarin), 2-(o-chlorophenyl)-4,4',5,5'-four Phenyl-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(2,4-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-dimethylamine Amidoxime, 3,6-bis(2-methyl-2-morpholinylpropanyl)-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- Trimethyl benzhydryl)phenylphosphine oxide and 2,4,6-trimethylbenzimidyldiphenylphosphine oxide.

The content of the photopolymerization initiator (C) based on the total amount of the photocurable binder of the present invention is preferably from 0.002 wt% to 20 wt% from the viewpoint of sensitivity to ultraviolet light or visible light irradiation. More preferably, it is 0.005 wt% to 15 wt%, and further preferably 0.01 wt% to 10 wt%.

In the range in which the effects of the present invention can be obtained, the photocurable adhesive of the present invention may further contain other components than the cellulose derivative (A), the photocurable medium, and the photopolymerization initiator (C). Examples of such other components include a decane coupling agent (E) and a surfactant (F).

Decane coupling agent (E)

The photocurable adhesive of the present invention may further contain a decane coupling agent (E) from the viewpoint of further enhancing the adhesion between the formed adhesive film and the substrate. From such a viewpoint, the content of the decane coupling agent (E) relative to the total amount of the photocurable binder of the present invention is preferably from 0.01% by weight to 20% by weight, more preferably from 0.05% by weight to 15% by weight, and further Preferably, it is from 0.1 wt% to 10 wt%. The decane coupling agent (E) may be one type or two or more types.

Examples of such a decane coupling agent (E) include 3-glycidoxypropyldimethylethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidol. Oxypropyltrimethoxydecane, and 3-methylpropenyloxypropyltrimethoxydecane.

Surfactant (F)

The photocurable adhesive of the present invention may further contain a surfactant (F) from the viewpoint of further improving coating uniformity. From this point of view, the content of the surfactant (F) relative to the total amount of the photocurable binder of the present invention is preferably from 0.01% by weight to 10% by weight, more preferably from 0.01% by weight to 8% by weight. Preferably, it is 0.01 wt% to 5 wt%. The surfactant (F) may be one type or two or more types.

Examples of the surfactant (F) include Polyflow No. 45, Polyflow KL-245, Polyflow No. 75, Polyflow No. 90, and Polyflow No. 95 (all of which are trademarks, manufactured by Kyoeisha Chemical Co., Ltd.). ), Disperbyk 161, Disperbyk 162, Disperbyk 163, Disperbyk 164, Disperbyk 166, Disperbyk 170, Disperbyk 180, Disperbyk 181, Disperbyk 182, BYK 300, BYK 306, BYK 310, BYK 320, BYK 330, BYK 344, BYK 346 ( All of the above are trademarks, manufactured by BYK-Chemie Japan Co., Ltd.), KP-341, KP-358, KP-368, KF-96-50CS, KF-50-100CS (all of which are trademarks, Shin-Etsu Chemical Co., Ltd. Manufacturing), Surflon SC-101, Surflon KH-40 (all of which are trademarks, manufactured by AGC Seimi Chemical Co., Ltd.), Ftergent 222F, Ftergent 251, FTX-218 (all of which are trademarks, manufactured by Neos Co., Ltd.), EFTOP EF-351, EFTOP EF-352, EFTOP EF-601, EFTOP EF-801, EFTOP EF-802 (all of which are trademarks, manufactured by Mitsubishi Materials, Inc.), Megafac F-171, Megafac F-177, Megafac F- 475, Megafac R-30, Megafac F-556, Megafac R-30 (all of which are trademarks, manufactured by DIC Corporation), fluoroalkylbenzenesulfonate, fluoroalkyl carboxylate, fluoroalkyl polyoxyethylene ether, fluoroalkylammonium iodide, fluoroalkyl beet Base, fluoroalkyl sulfonate, diglycerol tetrakis(fluoroalkyl polyoxyethylene ether), fluoroalkyl trimethyl ammonium salt, fluoroalkyl amine sulfonate, polyoxyethylene decyl phenyl ether, polyoxygen Ethylene octyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene tridecyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether , polyoxyethylene laurate, polyoxyethylene oleate, polyoxyethylene stearate, polyoxyethylene laurylamine, sorbitan laurate, sorbitan palmitate, sorbitan hard Fatty acid ester, sorbitan oleate, sorbitan fatty acid ester, polyoxyethylene sorbitan laurate, polyoxyethylene sorbitan palmitate, polyoxyethylene sorbitan hard Fatty acid esters, polyoxyethylene sorbitol oleate, polyoxyethylene naphthyl ether, alkylbenzene sulfonate, and alkyl diphenyl ether disulfonate.

The viscosity of the photocurable adhesive of the present invention can be determined in accordance with the coating method, and is preferably from 100 mPa ‧ to 40,000 mPa ‧ s. For example, when a coating film having a thickness of 20 μm to 50 μm is formed by a screen printing method, the viscosity is preferably from 100 mPa ‧ to 20,000 mPa ‧ from the viewpoint of satisfactory productivity. The viscosity of the photocurable adhesive can be adjusted, for example, by the content of the cellulose derivative (A) and the radical polymerizable monomer (B). In addition, the viscosity of the photocurable adhesive can be determined by measuring at 25 ° C using an E-type viscometer (Tokyo Keiki Co., Ltd., product name: VISCONIC EMD).

Applying the photocurable adhesive of the present invention to one or both of the two adherends including at least one of the transparent adherends, bonding the two adherends, and bonding them through the transparent The material is irradiated with light such as ultraviolet rays to cause photopolymerization, whereby the photocurable adhesive of the present invention can be used for bonding two bonded materials. The photocurable adhesive according to the present invention is applied to a primer layer (TAC film or glass) by a screen printing method, for example, and the upper layer is bonded to a binder (TAC film or glass) at 50 mJ. /cm ² to 3,000 mJ/cm ^{2 The} light-curable adhesive is cured by irradiation with light such as ultraviolet rays, whereby the adherend can be bonded.

In the present invention, since the photocurable medium dissolves other components, a photocurable adhesive containing no solvent can be obtained.

Further, since the photocurable adhesive of the present invention can be bonded to the adhesive by irradiation of light, the adhesive can be bonded with high workability.

Further, in the photocurable adhesive of the present invention, a release tape formed on the adherend can be removed using a release tape. Therefore, when the photocurable adhesive of the present invention is used, even when the bonding of the adherend fails, the adhesive film can be removed and reattached (repaired).

Further, in the photocurable adhesive of the present invention, an adhesive film having a refractive index similar to that of glass or TAC which is generally used for a display element can be formed. The photocurable adhesive of the present invention can be used as an interlayer adhesive for display elements.

As is apparent from the above description, the photocurable adhesive of the present invention has, for example, a preferred embodiment in which it is applied between a liquid crystal display element and a touch panel, and can be cured only by light irradiation. Further, it has high adhesion and a refractive index of about 1.5 and a transmittance of 95% or more, and can adjust the viscosity in accordance with various coating methods such as rotation, dispenser, screen printing, etc., and further has high adhesion to TAC. After the bonding, the adhesive is removed, and after the adhesive is peeled off, the adhesive film can be removed by using a release tape, and the repairing property is also possible.

The display element of the present invention is a display element obtained by bonding two optical elements by the photocurable adhesive of the present invention. The display element of the present invention may further have other constituent elements as long as it has an optical element bonded by the photocurable adhesive of the present invention.

The optical element is a member constituting the display element, and is a member that generates light of a specific optical characteristic, a member through which light passes, or a member that changes optical characteristics of light that passes therethrough. At least one of the two optical elements that are bonded is preferably transparent. Examples of such an optical element include an optical element including a glass substrate or an optical element including a TAC substrate or a TAC film. Examples of the optical element include members constituting the liquid crystal display element, and specific examples thereof include a display panel, an input element, a protective cover, and a color filter.

A display panel is a component that displays an image in a display element. Examples of such a display panel include a liquid crystal display element, a plasma display, an organic electroluminescence (EL), an inorganic EL, and a field emission display (FED). As the input element, for example, a transparent input element such as a touch panel can be cited.

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

The material of the adhesive surface of the optical element is preferably glass or TAC from the viewpoint of the function of the element such as transparency and mechanical strength, and the sufficient adhesiveness by the photocurable adhesive of the present invention.

[Example]

Hereinafter, the present invention will be further illustrated by examples, but the present invention is not limited by these examples.

[Example 1 to Example 53]

Each component of A to F described in Tables 1 and 2 was mixed and stirred in the blending amount (wt%) described in the above table to obtain a photocurable binder.

In addition, each component of A to F in Table 1 and Table 2 shows the following products or components.

A-1 Hydroxypropyl cellulose (Acros Organics, Hydroxypropyl cellulose, Average M.W. 100,000)

A-2 methyl cellulose (Wako Pure Chemical Industries, Ltd., Methyl cellulose 400)

A-3 Hydroxyethyl Cellulose (Hydroxyethyl cellulose)

B-1 Acid-modified epoxy acrylate (Nippon Chemical Co., Ltd., product name: KAYARD ZFR-1491)

B-2 Acid-modified epoxy acrylate (Nippon Chemical Co., Ltd., product name: KAYARD CCR-1285)

B-3 Acid-modified epoxy acrylate (Nippon Chemical Co., Ltd., product name: KAYARD CCR-1287)

B-4 Acid-modified epoxy acrylate (JAPAN U-PICA Co., Ltd., product name: Neopol 8477-350)

B-5 Dipentaerythritol hexaacrylate (East Asia Synthetic Co., Ltd., product name: Aronix M-402)

B-6 Difunctional acrylate (Kyoeisha Chemical Co., Ltd., product name: Epoxy Ester 80MFA)

B-7 Difunctional acrylate (Kyoeisha Chemical Co., Ltd., product name: Epoxy Ester 70PA)

B-8 Difunctional acrylate (Kyoeisha Chemical Co., Ltd., product name: Epoxy Ester 200PA)

B-9 4-Hydroxybutyl acrylate (Japan Chemical Industry 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., Ltd., product name: HEA)

C-1 2,4,6-trimethylbenzylidene-diphenyl-phosphine oxide (BASF, product name: DAROCUR TPO)

C-2 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinylpropan-1-one (BASF, product name: IRGACURE 907)

C-3 1-hydroxy-cyclohexyl-phenyl-one (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 butyl methacrylate (60) + hydroxyethyl methacrylate (40) copolymer (Mw: 15,000)

D-4 methyl methacrylate (16.5) + hydroxyethyl methacrylate (16.5) + butyl methacrylate (67) copolymer (Mw: 15,000)

E-1 3-methacryloxypropyltrimethoxydecane (Chisso Co., Ltd., product name: Sila-Ace, S710)

F-1 surfactant (DIC Co., Ltd., product name: Megafac F-556)

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

The viscosity of the photocurable adhesive was measured at 25 ° C using an E-type viscometer (Tokyo Keiki Co., Ltd., product name: VISCONIC EMD). The unit of viscosity is mPa‧s.

The light transmittance of the photocurable adhesive was measured by spreading a 50 μm glass spacer on a glass having a size of 4 cm × 4 cm × 0.05 cm, and then dropping about 0.1 on the glass. mL of photocurable adhesive, then a glass of 4 cm × 4 cm × 0.05 cm is attached to the surface of the glass to which the photocurable adhesive is added, and is crimped and exposed to ultraviolet light for exposure (full light) 1,000 mJ/cm ² , high pressure mercury lamp), the glass is bonded to the glass to prepare a sample, and then the sample is measured in a glass using an ultraviolet visible near-infrared spectrophotometer (Japan Spectrophoto Co., Ltd., product name: V-670). Light transmittance in the direction opposite to the glass. The light transmittance is the transmittance (T%) at 400 nm when the wavelength of 350 nm to 800 nm is measured.

The refractive index of the photocurable adhesive was measured by applying a photocurable adhesive to a glass by a spin coating method, and exposing the obtained coating film under a nitrogen atmosphere (total light of 1,000 mJ/cm ^{2 )} , high-pressure mercury lamp), thereby forming a film of a photocurable adhesive (film thickness: 7 μm to 10 μm), and then using a film reflective film thickness measuring device (Dayu Electronics Co., Ltd., product name: FE-3000) The film was measured. The refractive index is the refractive index of light having a wavelength of 589 nm.

Adhesion is measured by the following method.

The adhesion of the photocurable adhesive was evaluated by spreading a glass sphere of 50 μm on a glass of 1 cm × 4 cm, and then adding about 0.05 mL of the binder to the glass, followed by 1 cm × 4 The glass or TAC film of cm is attached to the surface of the glass to which the adhesive is added in a T-shape with respect to the underlying glass, and is crimped, and exposed to ultraviolet light for exposure (full light of 1,000 mJ/cm ² , high pressure) After the mercury lamp), the glass is bonded to the glass or the TAC film to form a T-shape, and then the glass bonded to each other in the T-shaped sample is peeled off from the glass or the TAC film by hand, and the photohardening is evaluated by the peeling condition. The adhesiveness of the adhesive. The evaluation criteria are as follows.

○: There is resistance when the sample is peeled off.

△: There was a slight resistance when the sample was peeled off.

×: There is no resistance when the sample is peeled off.

The repairability of the photocurable adhesive was evaluated by peeling off the glass bonded to each other in the T-shaped sample formed of the glass and the TAC film by hand, and then repeatedly attaching it. And a peeling adhesive tape (Sumitomo 3M Co., Ltd., electrical insulating tape polyester film tape No. 56) to remove the photocurable adhesive remaining on the peeling surface, and evaluate the photocurable adhesive by removing it. Repairability. The evaluation criteria are as follows.

○: The remaining photocurable adhesive can be removed by attaching and peeling the adhesive tape once or several times.

X: The remaining photocurable adhesive could not be removed by adhesion and peeling of the adhesive tape.

In Examples 1 to 52, the cellulose derivative (A), the radical polymerizable monomer (B), the photopolymerization initiator (C), the filler (D), the decane coupling agent (E), and the interfacial activity were used. The agent (F) is subjected to various combinations and evaluation, and various results in terms of viscosity, light transmittance, refractive index, adhesiveness, and repairability can be obtained as a result of the interlayer adhesive of the display element. In particular, the adhesion to the TAC film is good. It has been confirmed that if the cured product between the glass of Examples 1 to 34 and the TAC film is peeled off by hand, the cured product does not remain on the glass side but adheres to the TAC side. The cured film remaining on the TAC side can be removed by the polyester film tape to confirm the repairability.

In particular, in Examples 12 to 23, and Examples 35 to 50, a radical polymerizable monomer (B) and a filler of a photopolymer having a hardness generally higher than that of the radical polymerizable monomer (B) were used ( D) When used in combination, a higher refractive index than that in the case of using only the radical polymerizable monomer (B) containing the radical polymerizable monomer (B) or a radical is obtained Polymeric monomer (B) is a copolymer of similar monomers. Thus, it was confirmed that the refractive index was controlled by the use of the filler (D). Further, in Examples 12 to 23, and Examples 35 to 50, by using such a filler (D) in combination with a radical polymerizable monomer (B), it is also possible to obtain a free radical from a glass or a TAC film. The sufficient adhesiveness of the polymerizable monomer (B) is the same or higher than that of the adhesive.

[Comparative Example 1 to Comparative Example 28]

The components of B to F described in Table 5 were mixed and stirred in the same manner as in the examples, except that the cellulose derivative (component A) was used, in the same manner as in the examples. Thus, a comparative photocurable adhesive is obtained. Further, the viscosity, light transmittance, refractive index, adhesiveness, and repairability of the obtained photocurable adhesive were also evaluated in the same manner as in the examples. The evaluation results are shown in Tables 5 and 6.

In Comparative Example 1 to Comparative Example 28, satisfactory results as an interlayer adhesive of a display element were not obtained in terms of all properties of viscosity, light transmittance, refractive index, adhesiveness, and repairability. Further, in Comparative Examples 9 to 28, as in the results of the examples, it was confirmed that the refractive index was controlled by containing the filler (D).

Industrial availability

Various display elements such as liquid crystals are used for various purposes, and not only improvement in image quality but also improvement in productivity is required. In the present invention, in the manufacture of a display element requiring full adhesion of an optical element, an adhesive film having a refractive index substantially equal to that of a transparent member of a substrate or a mask generally used for an optical element can be formed without A decrease in image quality caused by a difference in refractive index is generated. Further, in the present invention, since such an adhesive film can be formed by a simple operation of light irradiation, the workability of the display element can be improved. Further, in the present invention, since the formed adhesive film can be peeled off from the optical element, the disposal of the defective product due to the failure of the attachment can be reduced, and the yield of the display element can be further improved. Thus, the present invention is expected to contribute greatly to the improvement in both quality and productivity in the production of display elements.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

Claims (6)

A photocurable adhesive containing a cellulose derivative (A) represented by the formula (I), a photocurable medium containing a radical polymerizable monomer (B) and cured by photopolymerization, and light Polymerization initiator (C), (In the formula (I), X is independently hydrogen or R, and R independently represents -(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 , n represents 10 to 20,000; in addition, in R, m represents 1~ An integer of 5). The photocurable adhesive according to claim 1, wherein the photocurable medium contains a filler (D) as a copolymer having a weight average molecular weight of 1,000 to 100,000. The photocurable adhesive according to claim 1, further comprising one or both of a decane coupling agent (E) and a surfactant (F). The photocurable adhesive according to the first aspect of the invention, wherein the radical polymerizable monomer (B) comprises a (meth) acrylate compound having one or more hydroxyl groups in one molecule. A display element which is a display element obtained by bonding two optical elements by a photocurable adhesive, wherein the photocurable adhesive is according to any one of items 1 to 4 of the patent application scope. The photocurable adhesive described. The display element of claim 5, wherein the two optical elements are a display panel and an input element.