JP4918499B2 - Optical pressure-sensitive adhesive composition and optical functional film - Google Patents

Description

  The present invention relates to an optical pressure-sensitive adhesive composition used for adhering an optical functional film such as a polarizing plate or a retardation plate to an optical component such as a liquid crystal cell of a liquid crystal display device, and an adhesive formed from the composition. The present invention relates to an optical functional film having an agent layer.

  A liquid crystal cell constituting a liquid crystal display device includes a liquid crystal component oriented in a predetermined direction sandwiched between two glass substrates, and an adhesive layer formed from an optical adhesive composition on the outside of these glass substrates. An optical functional film such as a polarizing plate or a laminate of a polarizing plate and a retardation plate is attached. In recent years, liquid crystal display devices have been widely used due to the reduction in weight and thickness of displays for vehicles, outdoor instruments, displays such as personal computers, and televisions, and the demand for such devices has been increasing. As a result, the usage environment of liquid crystal display devices has become extremely harsh, both indoors and outdoors.

  A polarizing plate used in a liquid crystal display device has a three-layer structure in which both surfaces of a polyvinyl alcohol polarizer are sandwiched between triacetyl cellulose protective films, but has poor dimensional stability due to the characteristics of these materials. In addition, since an optical functional film such as a polarizing plate is formed by stretching, it tends to expand and contract over time. For this reason, in the liquid crystal display device, the internal stress generated by the expansion and contraction of the optical functional film cannot be absorbed and relaxed by the adhesive layer, and the distribution of residual stress acting on the optical functional film becomes non-uniform, In particular, stress concentrates on the peripheral edge. As a result, the peripheral portion of the liquid crystal display device becomes brighter or darker than the center, which causes color unevenness and white blurring in the liquid crystal display device.

  Further, as another factor that causes uneven color / whitening phenomenon in the liquid crystal display device, a difference in refractive index between the glass substrate, the optical functional film, and the pressure-sensitive adhesive layer is considered.

  Many means have been studied to solve the above problems. For example, in Patent Document 1, the outline is “100% by mass of a high molecular weight (meth) acrylic copolymer having a weight average molecular weight of 1,000,000 or more, and a low molecular weight (meth) acrylic system having a weight average molecular weight of 30,000 or less. An invention of “adhesive composition for polarizing plate comprising 20 to 200% by mass of a copolymer and 0.005 to 5% by mass of a polyfunctional compound” is disclosed. The invention describes that a pressure-sensitive adhesive layer that can follow the dimensional change of the polarizing plate is formed, and color unevenness and white spotting phenomenon hardly occur in the liquid crystal element. However, as a result of investigations by the present inventors, the addition amount of the polyfunctional compound disclosed by the invention is wide, and in order to make it difficult for color unevenness and white spot phenomenon to occur, the addition amount of the polyfunctional compound is Therefore, it is difficult to produce an optical functional film having a stable pressure-sensitive adhesive layer.

  Patent Document 2 uses a non-birefringent optical resin material to which a low-molecular substance exhibiting orientation birefringence that tends to cancel the orientation birefringence of the pressure-sensitive adhesive layer is added, and the resin material. An adhesive featuring the above is disclosed. However, this Patent Document 2 does not describe that the adhesive is used for an optical functional film to prevent color unevenness and white blurring of a liquid crystal display device and improve its optical characteristics.

Japanese Patent No. 3533589 Japanese Patent No. 3696649

  An object of the present invention is an adhesive used for a liquid crystal cell constituting a liquid crystal display device, which absorbs internal stress caused by expansion and contraction of an optical functional film, and causes color unevenness and white spotting phenomenon of the liquid crystal display device. It is providing the optical adhesive composition for forming the adhesive layer which can prevent.

  In order to solve the above-mentioned problems, the present inventors have conducted extensive research, and as a result, have a compound having at least two benzene rings in the molecule and a molecular weight of 150 to 1,000 (hereinafter referred to as “rod-like compound”). In some cases, the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition containing the liquid crystal cell of the liquid crystal display device is used for the pressure-sensitive adhesive layer between the glass substrate and the optical functional film. The pressure-sensitive adhesive layer can follow the expansion and contraction of the optical functional film and the refractive index of the pressure-sensitive adhesive layer itself is increased, so that the color unevenness / whitening phenomenon that is peculiar to liquid crystal display devices does not occur. The invention has been completed.

That is, the present invention is an optical pressure-sensitive adhesive composition containing at least a compound having at least two benzene rings in the molecule and a molecular weight of 150 to 1,000, a pressure-sensitive resin, and a crosslinking agent, The content of the compound is 0.1 to 15 parts by mass per 100 parts by mass of the adhesive resin, and the adhesive resin is a (meth) acrylic acid alkyl ester monomer unit (a ) And a copolymerizable monomer unit (b) containing a carboxyl group and / or a hydroxyl group and having a weight average molecular weight of 1,000,000 to 2,000,000, the copolymer (A) The coalescence (A) further contains a copolymerizable monomer unit (c) containing an aromatic group occupying 20 to 60% by mass of the total amount of the copolymer, and is formed from the above composition. The viscosity coefficient of the layer at 90 ° C is 0.5 Providing the optical pressure-sensitive adhesive composition according to ^{10 7 ~10 × 10 7 Pa ·} s der wherein Rukoto.

In the optical pressure-sensitive adhesive composition, the rod-shaped compound is trans-stilbene, fluorene, diphenyl sulfide, benzyl benzoate, benzoin and is at least one selected from the group consisting of diphenyl acetylene; content before Symbol crosslinking agent but the this the tacky resin 0.01 parts by weight per 100 parts by weight is preferred.

  In the optical pressure-sensitive adhesive composition, the silane compound (C) containing a mercaptoalkyl group and an alkoxy group in the molecule is further contained in an amount of 0.01 to 2 parts by mass per 100 parts by mass of the adhesive resin. Further, a low molecular weight (co) polymer (D) composed of an alkyl ester of (meth) acrylic acid having 1 to 18 carbon atoms is added in an amount of 1 to 50 parts by mass per 100 parts by mass of the copolymer (A). The (co) polymer (D) has a weight average molecular weight of 1,000 to 50,000, a dispersity (MW / MN) of 1.0 to 2.5, and It is preferable that it is compatible with the coalescence (A).

  Moreover, this invention provides the optical functional film characterized by having the adhesive layer formed from the optical adhesive composition of the said invention on the surface.

  The pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention has an appropriate pressure-sensitive adhesive force and good adhesion to an optical functional film, and the pressure-sensitive adhesive layer is used as a liquid crystal cell constituting a liquid crystal display device. When used, it can absorb the stress caused by the expansion and contraction of the optical functional film, and can prevent the occurrence of uneven color and white spots in the liquid crystal display device.

  Next, the present invention will be described in more detail with reference to the best mode for carrying out the invention. The optical pressure-sensitive adhesive composition of the present invention is characterized by containing the rod-shaped compound. When the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention is contained in the pressure-sensitive adhesive layer of the liquid crystal cell constituting the liquid crystal display device by containing the rod-like compound, the glass substrate, the optical function Since the difference in refractive index between the adhesive film and the pressure-sensitive adhesive layer becomes as small as possible, even if a dimensional change occurs in the optical functional film, it is possible to prevent the occurrence of uneven color and white spots in the liquid crystal display device. it can.

  The rod-like compound used in the present invention has a molecular weight of 150 to 1,000, preferably 150 to 500. The “benzene ring” of the rod-like compound includes a benzene ring forming a condensed ring. That is, naphthalene has two benzene rings and anthracene has three benzene rings. A rod-like compound having a molecular weight of less than 150 is used in the optical pressure-sensitive adhesive composition of the present invention, and when the pressure-sensitive adhesive layer formed from the composition is used in a liquid crystal cell, the size of the optical functional film changes. Is not preferable because the refractive index of the pressure-sensitive adhesive layer does not increase. On the other hand, a rod-like compound having a molecular weight exceeding 1,000 has almost the same compatibility as the adhesive resin. However, when used in the optical pressure-sensitive adhesive composition of the present invention, the rod-like compound tends to have an aggregated structure. The uniformity of the refractive index of the pressure-sensitive adhesive layer to be formed is lowered, which causes undesirable color unevenness and white spots in a liquid crystal display device.

  The optical pressure-sensitive adhesive composition of the present invention contains 0.1 to 15 parts by mass of the rod-shaped compound per 100 parts by mass of the adhesive resin. When the content of the rod-shaped compound is less than 0.1 parts by mass, the refractive index of the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention is low, and color unevenness when used in a liquid crystal display device.・ It may cause white spot phenomenon. On the other hand, when the amount of the rod-shaped compound is more than 15 parts by mass, the rod-shaped compound is not completely dissolved in the optical pressure-sensitive adhesive composition and is precipitated, which causes a bleed phenomenon.

Furthermore, the optical pressure-sensitive adhesive composition of the present invention has a viscosity coefficient at 90 ° C. of the pressure-sensitive adhesive layer formed from the composition of 0.5 × 10 ⁷ to 10 × 10 ⁷ Pa · s, It is preferably 1 × 10 ^{7 to} 5 × 10 ⁷ Pa · s. Within this viscosity coefficient range, the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention is less likely to cause foaming or peeling when used in a liquid crystal cell, and is composed of the liquid crystal cell. The liquid crystal display device is less likely to cause uneven color and white spots.

In addition, the viscosity coefficient of an adhesive layer can be calculated | required by the method according to the holding power measuring method of JISZ-0237. In this measurement method, an optical functional film having an adhesive layer is attached to a glass plate, a test sample is prepared, a load is applied to the test sample, and the amount of deviation after being kept in a 90 ° C. atmosphere for a certain period of time. The viscosity coefficient (Pa · s) of the pressure-sensitive adhesive layer can be calculated from the amount of deviation according to the following [Equation 1].
[Formula 1]
Viscosity coefficient (Pa · s) = deviation stress / deviation speed
Misalignment stress (N / m ² ) = Load (N) / Adhesion area (m ² )
And
Deviation speed (1 / s) = deviation amount (m) / test time (seconds) / adhesive layer thickness (m)
It is.

  As the rod-shaped compound used in the optical pressure-sensitive adhesive composition of the present invention, those having good compatibility with the pressure-sensitive resin are preferable. Specific examples include biphenyl, diphenylsulfone, 4-phenylphenol, benzoin, and diphenyl sulfide. Diphenyl ether, 4-hydroxybiphenyl-4′-carboxylic acid, 4,4′-biphenol, 4,4′-dihydroxydiphenylmethane, 4-α-cumylphenol, diphenylacetylene, azobenzene, dibenzofuran, diphenylmethane, benzyl benzoate, Diphenyl phthalate, N- (4-methoxybenzylidene) -4-acetoxyaniline, 4-[(methoxybenzylidene) amino] azobenzene, 4,4′-sulfonyldiphenol, 4-phenoxyphenol, 4′-methoxybenzylyl Naminostilbene, bisphenol A, benzylidenephenylamine, N, N′-dibenzylidenehydrazine, transstilbene, p-dianisalbenzidine, terephthalbis- (p-phenetidine), carbazole, 1,4-diphenyl-1,3 -At least one selected from the group consisting of butadiene, 1,4-diphenyl-1,3,5-hexadiene, fluorene and dibenzothiophene can be used, but is not limited thereto. Among these compounds, it is more preferable to use at least one selected from the group consisting of transstilbene, fluorene, diphenyl sulfide, benzyl benzoate, benzoin, and diphenylacetylene.

For example, the rod-like compound is represented by the following structural formula.

  The pressure-sensitive adhesive resin used in the optical pressure-sensitive adhesive composition of the present invention can be copolymerized with a (meth) acrylic acid alkyl ester monomer unit (a) having a carboxyl group and / or a hydroxyl group. It is preferable that the copolymer (A) contains at least a monomer unit (b) and has a weight average molecular weight (MW) of 1,000,000 to 2,000,000.

  In addition, the weight average molecular weight in this invention is a polystyrene conversion molecular weight measured by gel permeation chromatography. Specifically, the coating film obtained by drying the (co) polymer at room temperature was dissolved in tetrahydrofuran, and a high performance liquid chromatograph (manufactured by Shimadzu Corporation, LC-10ADvp, column; KF-G + KF-806). × 2) was used to measure the retention time, and the weight average molecular weight (MW) was determined in terms of polystyrene.

  In the present invention, “(meth) acrylic acid” means both “acrylic acid” and “methacrylic acid”.

  Specific examples of the monomer unit (a) constituting the copolymer (A) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl ( Mention may be made of (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, and at least one of these is used. can do.

  The proportion of the monomer unit (a) in the copolymer (A) is such that the copolymer (A) is composed only of the monomer unit (a) and the monomer unit (b). When the copolymer (A) is 100% by mass, the content is 90 to 99.8% by mass. Preferably it is 93-99.5 mass%. When the proportion of the monomer unit (a) is less than 90% by mass, the adhesiveness of the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention to the optical functional film is lowered. On the other hand, when the proportion of the monomer unit (a) exceeds 99.8% by mass, the proportion of the monomer unit (b) below becomes relatively low, which depends on the crosslinking agent of the copolymer (A). This is not preferable because the degree of crosslinking decreases and the viscosity of the optical pressure-sensitive adhesive composition of the present invention decreases.

  Among the monomer units (b), examples of the copolymerizable monomer unit (b1) containing a carboxyl group include (meth) acrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, Mention may be made of fumaric anhydride and carboxyethyl acrylate. (Meth) acrylic acid or carboxyethyl acrylate is preferred. On the other hand, as the copolymerizable monomer unit (b2) containing a hydroxyl group, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, caprolactone-modified ( Mention may be made of (meth) acrylates, polyethylene glycol (meth) acrylates and polypropylene glycol (meth) acrylates. As the monomer unit of the copolymer (A), the monomer unit (b1) and the monomer unit (b2) may be used alone or in combination.

  The copolymer (A) preferably has a weight average molecular weight of 1,000,000 to 2,000,000. When the copolymer (A) having a weight average molecular weight of less than 1,000,000 is used in the optical pressure-sensitive adhesive composition of the present invention, the cohesive force of the pressure-sensitive adhesive layer formed from the composition is insufficient, and the pressure-sensitive adhesive layer Foaming occurs and the optical functional film is easily peeled off. On the other hand, when the copolymer (A) having a weight average molecular weight exceeding 2 million is used in the optical pressure-sensitive adhesive composition of the present invention, the viscosity of the composition becomes too high and workability is lowered. In addition, the pressure-sensitive adhesive layer formed from the composition cannot sufficiently absorb and relax the stress caused by the expansion and contraction of the optical functional film.

  The proportion of the monomer unit (b) in the copolymer (A) is such that the copolymer (A) consists only of the monomer unit (a) and the monomer unit (b). When the copolymer (A) is 100% by mass, the content is preferably 0.2 to 10% by mass. More preferably, it is 0.5-7 mass%. When the proportion of the monomer unit (b) is less than 0.2% by mass, the degree of cross-linking of the copolymer (A) by the cross-linking agent is reduced, and when the pressure-sensitive adhesive layer is formed, the viscosity is preferably reduced. Absent. On the other hand, when the proportion of the monomer unit (b) exceeds 10% by mass, the crosslinking density of the copolymer (A) by the crosslinking agent becomes too high, and the formed pressure-sensitive adhesive layer expands and contracts the optical functional film. This is not preferable because the ability to absorb and relieve the stress is reduced.

  The copolymer (A) can be produced by bulk polymerization or solution polymerization. Solution polymerization is preferred. As a solvent used for the solution polymerization, an organic solvent usually used for a solution polymerization reaction such as ethyl acetate, toluene, n-hexane, acetone, methyl ethyl ketone and the like can be used. As polymerization initiators used for polymerization, peroxides such as benzoyl peroxide and lauryl peroxide, azobis compounds such as azobisisobutyronitrile and azobisvaleronitrile, or polymer azo polymerization initiators are used alone. Or it can use together.

  The crosslinking agent used in the optical pressure-sensitive adhesive composition of the present invention is a compound that is necessary for increasing the cohesive force of the pressure-sensitive resin and reacts with the carboxyl group and / or hydroxyl group of the monomer unit (b). It is preferable. The usage-amount should just be 0.01-1 mass part per 100 mass parts of said adhesive resin, Preferably, it is 0.05-0.5 mass part. When the amount used is less than 0.01 parts by mass, the cohesive force of the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition containing the crosslinking agent is low, which causes foaming or peeling of the pressure-sensitive adhesive layer. This is not preferable. On the other hand, when the amount used exceeds 1 part by mass, it becomes difficult for the pressure-sensitive adhesive layer to sufficiently absorb and relax the stress caused by the expansion and contraction of the optical functional film.

  The crosslinking agent that can be used in the optical pressure-sensitive adhesive composition of the present invention includes a glycidyl compound having at least two glycidyl groups in one molecule, an isocyanate compound having two or more isocyanate groups in one molecule, and aziridinyl in one molecule. Examples thereof include an aziridine compound having at least two groups, an oxazoline compound having an oxazoline group in a molecule, a metal chelate compound, and a butylated melamine compound. Preferred are a glycidyl compound having at least two glycidyl groups in one molecule, an isocyanate compound having two or more isocyanate groups in one molecule, and an aziridine compound having at least two aziridinyl groups in one molecule.

  Examples of the glycidyl compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol. Diglycidyl ether, N, N, N ′, N′-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl And polyfunctional glycidyl compounds such as ether, polyglycerol polyglycidyl ether and sorbitol polyglycidyl ether, At least one of which can be used.

  Examples of the isocyanate compound include tolylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and prepolymers modified from these, and at least one of these can be used.

  Examples of the aziridine compound include 1,1 ′-(methylene-di-p-phenylene) bis-3,3-aziridylurea, 1,1 ′-(hexamethylene) bis-3,3-aziridylurea, ethylene Bis- (2-aziridinylpropionate), tris (1-aziridinyl) phosphine oxide, 2,4,6-triaziridinyl-1,3,5-triazine and trimethylolpropane-tris- (2-aziridinyl) Propionate) and the like, and at least one of them can be used.

  The copolymer (A) may further contain a copolymerizable monomer unit (c) having an aromatic group. Specific examples of the monomer unit (c) include 2-phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, styrene, and α-methylstyrene, and at least one of these is used. be able to. Preferred monomer units (c) are 2-phenoxyethyl (meth) acrylate and benzyl (meth) acrylate. The proportion of the monomer unit (c) is 20 to 60% by mass, preferably 30 to 50% by mass, when the total amount of the copolymer (A) is 100% by mass. When the proportion is less than 20% by mass or exceeds 60% by mass, even if an adhesive layer formed from the optical adhesive composition containing the copolymer (A) is used in a liquid crystal cell, This is not preferable because the occurrence of uneven color and white spots in the liquid crystal display device cannot be suppressed. When the copolymer (A) is composed of the monomer unit (a), the monomer unit (b) and the monomer unit (c), the total amount of the copolymer (A) is 100% by mass. , The proportion of the monomer unit (a) is 39.8 to 79.8% by mass, preferably 43 to 69.5% by mass. The ratio for which a monomer unit (b) accounts is 0.2-10 mass%, Preferably it is 0.5-7 mass%.

  The optical pressure-sensitive adhesive composition of the present invention may further contain a silane compound (C) containing a mercaptoalkyl group and an alkoxy group in the molecule. By containing the silane compound (C), the pressure-sensitive adhesive layer formed from the composition further improves the adhesion with the glass substrate surface that is the adherend in the liquid crystal cell.

  When using the said silane compound (C) for the optical adhesive composition of this invention, it is preferable that it is 0.01-2 mass parts per 100 mass parts of copolymers (A). If the amount used exceeds 2 parts by mass, the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition tends to peel off, which is not preferable.

  Specific examples of the silane compound (C) include γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptobutyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, and mercapto group-containing alkoxysilane oligomer. And at least one of these can be used.

  The optical pressure-sensitive adhesive composition of the present invention has a low molecular weight composed of an alkyl ester having 1 to 18 carbon atoms of (meth) acrylic acid at a ratio of 1 to 50 parts by mass per 100 parts by mass of the copolymer (A). A (co) polymer (D) can be used. The (co) polymer (D) has a weight average molecular weight of 1,000 to 50,000, a dispersity (MW / MN) of 1.0 to 2.5, and the copolymer (A) It is preferable that they are compatible. The (meth) acrylic acid alkyl ester monomer unit constituting the (co) polymer (D) is the same as the monomer unit (a) in the copolymer (A). In the present invention, the term “(co) polymer” means to include both a homopolymer and a copolymer. When the (co) polymer (D) is a copolymer, the proportion of the monomer unit (a) in the copolymer (D) is when the copolymer (D) is 100% by mass. 98 to 99.9% by mass is preferable. Moreover, as a monomer unit other than the (meth) acrylic acid alkyl ester, a copolymerizable monomer unit (c) containing an aromatic group, except for the monomer unit (b) containing a functional group. May be included.

  When the weight average molecular weight of the (co) polymer (D) is less than 1,000, the viscosity of the pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition decreases, and the pressure-sensitive adhesive when used in a liquid crystal cell. It is not preferable because it causes bleeding of the agent layer and lowering of adhesiveness and color unevenness and white spotting phenomenon of the liquid crystal display device. On the other hand, when the weight average molecular weight exceeds 50,000, the (co) polymer (D) in the optical pressure-sensitive adhesive composition enters between the cross-linked structures formed by the copolymer (A). Becomes difficult, and the elasticity and flexibility of the pressure-sensitive adhesive layer formed from the composition are reduced. For this reason, even if the pressure-sensitive adhesive layer is used in a liquid crystal display device, the effect of preventing uneven color and white spots cannot be expected. In addition, when the (co) polymer (D) having a dispersity exceeding 2.5 is used in the optical pressure-sensitive adhesive composition of the present invention, the cohesive force of the pressure-sensitive adhesive layer formed from the composition decreases. This is not preferable because it causes foaming and peeling of the pressure-sensitive adhesive layer.

  In the optical pressure-sensitive adhesive composition of the present invention, when the (co) polymer (D) is used, it may be 1 to 50 parts by mass, preferably 5 to 40 parts per 100 parts by mass of the copolymer (A). It is a mass part, More preferably, it is 10-30 mass parts. By using the (co) polymer (D) in the optical pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive layer formed from the composition has a stress caused by expansion and contraction of the optical functional film in the liquid crystal cell. This increases the effect of preventing foaming and peeling of the pressure-sensitive adhesive layer. This is because the (co) polymer (D) has a small weight average molecular weight and does not contain a functional group, so it does not contribute to the formation of a crosslinked structure by the crosslinking agent, and the pressure-sensitive adhesive layer formed from the composition. This is thought to be due to the high flexibility.

  However, when the amount used exceeds 50 parts by mass, the cohesive force of the pressure-sensitive adhesive layer is reduced, which causes foaming or peeling of the pressure-sensitive adhesive layer.

  The (co) polymer (D) can be produced by the same method as the copolymer (A) described above.

  Moreover, in manufacture of the optical adhesive composition of this invention, you may mix | blend various additives as needed for the purpose of adjusting the adhesiveness of a copolymer (A). Specific examples of such additives include terpene-based, terpene-phenol-based, coumarone indene-based, styrene-based, rosin-based, xylene-based, phenol-based and petroleum-based tackifier resins, antioxidants, ultraviolet absorption, etc. Agents, fillers and pigments.

  The optical functional film of the present invention has a pressure-sensitive adhesive layer formed from the optical pressure-sensitive adhesive composition of the present invention on the surface of an optical functional film as a substrate. Examples of the optical functional film as the substrate include a film light guide plate, an antireflection film, a conductive film, a viewing angle widening film, a retardation film, and a polarizing plate. By using the optical functional film of the present invention for the production of a liquid crystal cell, to provide a liquid crystal cell having good optical functionality and causing no uneven color and white blurring in a liquid crystal display device. Can do.

  The optical functional film of the present invention is applied to the optical functional film as a base material using a commonly used coating apparatus, for example, a roll coating apparatus, and then dried. And it can obtain by forming an adhesive layer by carrying out heat bridge | crosslinking as needed, or making it harden | cure by light, such as an ultraviolet-ray. The thickness of the pressure-sensitive adhesive layer in the optical functional film of the present invention is usually preferably about 10 to 50 μm.

The color unevenness / white spot test of the optical functional film of the present invention is performed for all points of the optical functional film of the present invention using visual observation and a haze meter (for example, NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.). The light transmittance (%) is measured, and the difference Δ of the total light transmittance is calculated from the following [Equation 2] from the maximum total light transmittance and the minimum total light transmittance of the obtained total light transmittance. be able to.
[Formula 2]
Difference in total light transmittance Δ = maximum total light transmittance−minimum total light transmittance

  The difference Δ in the total light transmittance of the optical functional film of the present invention is preferably 0.1 or less, more preferably 0.05 or less. When an optical functional film having Δ greater than 0.1 is used in a liquid crystal display device, uneven color and white spots may become a problem.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited by these Examples. In the following text, “parts” and “%” are based on mass unless otherwise specified.

[Production Example 1 (Copolymer A-1)]
After nitrogen gas is sealed in a reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen introduction tube, 100 parts of ethyl acetate, 98 parts of butyl acrylate, 2 parts of acrylic acid and a polymerization initiator (azobisisobutyronitrile) ) 0.1 part was charged and a polymerization reaction was carried out at 68 ° C. for 8 hours in a nitrogen gas stream while stirring. After completion of the reaction, 300 parts of ethyl acetate was added, and the contents were cooled at room temperature to obtain a solution of copolymer A-1 having a viscosity of 2,000 mPa · s, a solid content of 20%, and a weight average molecular weight of 1.3 million. It was.

[Production Example 2 (Copolymer A-2)]
Polymerization was conducted in the same manner as in Production Example 1 except that 98 parts of butyl acrylate in Production Example 1 were replaced with 58 parts of butyl acrylate and 40 parts of phenoxyethyl acrylate, and the viscosity was 1,800 mPa · s, the solid content was 20%, and the weight average molecular weight. A solution of 1.22 million copolymer A-2 was obtained.

[Production Example 3 (Copolymer A-3)]
Polymerization was conducted in the same manner as in Production Example 1 except that 2 parts of acrylic acid in Production Example 1 was changed to 2 parts of hydroxyethyl acrylate, and the viscosity was 1,900 mPa · s, the solid content was 20%, and the weight average molecular weight was 1.32 million. A solution of polymer A-3 was obtained.

[Production Example 4 (Copolymer A-4)]
Polymerization was conducted in the same manner as in Production Example 1 except that 98 parts of butyl acrylate in Production Example 1 were replaced with 48 parts of butyl acrylate, 15 parts of phenoxyethyl acrylate, and 35 parts of benzyl acrylate, and the viscosity was 2,000 mPa · s and the solid content was 20 %, A solution of copolymer A-4 having a weight average molecular weight of 1,220,000 was obtained.

[Production Example 5 (Copolymer D-1)]
After nitrogen gas is sealed in a reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen introduction tube, 20 parts of ethyl acetate, 60 parts of toluene, 5 parts of α-methylstyrene dimer, 60 parts of butyl acrylate, phenoxyethyl acrylate 40 parts and 0.5 parts of a polymerization initiator (azobisisobutyronitrile) were charged and reacted for 8 hours at a reflux temperature in a nitrogen gas stream while stirring. After completion of the reaction, 20 parts of ethyl acetate was added, the contents were cooled at room temperature, viscosity 20 mPa · s, solid content 50%, weight average molecular weight 10,000, number average molecular weight 5,900, dispersity 1.7. A solution of copolymer D-1 was obtained.

[ Reference Example 1]
For 100 parts of solid content in the solution of copolymer A-1 obtained in Production Example 1, 0.5 part of transstilbene (rod compound) (molecular weight 180), polyisocyanate (trade name; Coronate L, 0.2 parts of Nippon Polyurethane Industry Co., Ltd.) and 0.1 part of silane coupling agent (trade name: KBM-803, γ-mercaptopropylmethyltrimethoxysilane, Shin-Etsu Chemical Co., Ltd.) are added. mixture to obtain a light chemical pressure-sensitive adhesive composition.

  The obtained optical pressure-sensitive adhesive composition was applied onto a silicon-coated polyethylene terephthalate film (PET film) so that the thickness after drying was 25 μm, and the solvent was removed at 90 ° C., followed by drying and a crosslinking reaction. Thus, an adhesive layer was formed. A polarizing film having a thickness of 250 μm, which is an optical functional film as a base material, was bonded to the obtained pressure-sensitive adhesive layer to produce an optical functional film of the present invention. The optical functional film of the present invention was cured at 23 ° C. and 50% relative humidity (hereinafter abbreviated as “RH”) for 7 days, and then the durability, adhesive strength, holding power, viscosity coefficient and white spots (described later) The measurement was evaluated according to the test method. All the results were good. The results are shown in Table 2.

[ Reference Examples 2 to 4, 7, and 8 Examples 5 and 6 ]
As shown in Table 1, adhesive resins, except changing the kind and amount of the rod-like compound and a crosslinking agent was prepared in the same manner as the optical science PSA composition及beauty light chemical functional film as in Reference Example 1, durability And so on. All the results were good. The results are shown in Table 2.

[Examples 9 and 10]
In Example 9, 10 parts of the copolymer D-1 obtained in Production Example 5 and 7 parts of transstilbene were obtained with respect to 100 parts of the solid content in the solution of the copolymer A-2 obtained in Production Example 2. , 0.2 parts of polyisocyanate (trade name; Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) and silane coupling agent (trade name: KBM-803, γ-mercaptopropylmethyltrimethoxysilane, Shin-Etsu Chemical Co., Ltd.) 0.1 part) was added, and the optical pressure-sensitive adhesive composition of the present invention and the optical functional film of the present invention were prepared in the same manner as in Reference Example 1, and the durability and the like were evaluated. Example 10 produced the optical pressure-sensitive adhesive composition of the present invention and the optical functional film of the present invention in the same manner as Example 9 except that the copolymer D-1 of Example 9 was changed to 30 parts, and was durable. Sexuality was evaluated. The results were all good. The results are shown in Table 2.

[ Reference Example 11]
Reference Example 11 except for not using the silane coupling agent to produce an optical chemical adhesive composition for及beauty light chemical functional film in the same manner as in Reference Example 2, was evaluated and durability. All the results were good. The results are shown in Table 2.

[Comparative Example 1]
Comparative Example 1, except that the rod-shaped compound added 20 parts to prepare a light chemical adhesive composition for及beauty light chemical functional film in the same manner as in Reference Example 1 to evaluate durability. As a result, the pressure-sensitive adhesive layer foamed in the durability test, and the white spot evaluation was poor. The results are shown in Table 2.

[Comparative Example 2]
Comparative Example 2, except for not using a crosslinking agent, Reference Example 2 and was prepared in the same manner as the optical science PSA composition及beauty light chemical functional film was evaluated and durability. The results were poor in durability and holding power, but the white spots were good. The results are shown in Table 2.

[Comparative Example 3]
Comparative Example 3 does not use the rod-like compound, except that the amount of crosslinking agent in 1.0 parts was prepared in the same manner as the optical science PSA composition及beauty light chemical functional film as in Reference Example 1, Durability was evaluated. As a result, the durability was good, but the viscosity coefficient and white spots were bad. The results are shown in Table 2.

Specify the abbreviations and product names listed in Table 1.
Rod-shaped compound A: transstilbene (molecular weight: 180)
B: Fluorene (molecular weight: 166)
C: Benzoin (molecular weight: 212)
D: Diphenyl sulfide (molecular weight: 186)
E: Benzyl benzoate (molecular weight: 212)
F: Diphenylacetylene (molecular weight: 178)
Cross-linking agent Coronate L: Polyisocyanate, Nippon Polyurethane Industry Co., Ltd. Takenate D-110N: Polyisocyanate, Mitsui Takeda Chemical Co., Ltd. Takenate D-160N: Polyisocyanate, Mitsui Takeda Chemical Co., Ltd. Tetrad X: Multifunctional Glycidyl compound, silane coupling agent manufactured by Mitsubishi Gas Chemical Co., Ltd. KBM-803: γ-mercaptopropylmethyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd. X-41-1805: mercapto group-substituted alkoxy oligomer, Shin-Etsu Chemical ( X-41-1810: Mercapto group-substituted alkoxy oligomer, manufactured by Shin-Etsu Chemical Co., Ltd. KBM-802: γ-mercaptopropylmethyldimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.

[Test method]
1. Durability The optical functional films of Examples , Reference Examples and Comparative Examples were each cut to 90 mm × 150 mm, and after peeling the PET film, the optical functional film was attached to a glass plate, and this was placed in an autoclave at 50 ° C. For test samples that were held at 5 kg / cm ² for 18 minutes and then allowed to stand at 80 ° C. for 500 hours, or test samples that had been left to stand in an environment of 60 ° C. and 95% RH for 500 hours. The foam generated in the agent layer and the state of peeling of the optical functional film as the substrate were visually observed, and durability was evaluated according to the following criteria.

<Evaluation criteria>
[Foaming]
A: No foaming was confirmed in the pressure-sensitive adhesive layer.
(Triangle | delta): Foaming was confirmed slightly in the adhesive layer.
X: Foaming was confirmed in the pressure-sensitive adhesive layer.
[Peeling]
◯: No peeling occurred on the optical functional film as the substrate.
Δ: Slight peeling was confirmed on the optical functional film as the substrate.
X: Peeling was confirmed on the optical functional film as the substrate.

2. Adhesive strength About the optical functional films of Examples , Reference Examples and Comparative Examples, 180 ° peeling adhesive strength was measured according to JIS Z-0237. A glass plate was used as the adherend.

3. Holding power The viscosity coefficient of the pressure-sensitive adhesive layer was determined by the following method according to the holding power measuring method of JIS Z-0237. The long side of the optical functional film (polarizing film) of Examples , Reference Examples and Comparative Examples having an adhesive layer is cut to a size of 25 mm × 55 mm with a cutting line that is 90 ° with respect to the absorption axis of the polarizing film. Cut. The cut polarizing film was attached to a glass plate so that the adhesion area was 25 mm × 10 mm, and this was held in an autoclave at 50 ° C. and 5 kg / cm ² for 18 minutes to prepare a test sample. A load (9.8 N) was applied to the lower end of the polarizing film of the test sample, and after holding for 1 hour in an atmosphere at 90 ° C., the distance (displacement amount) by which the polarizing film adhered to the glass plate was shifted downward was measured. The holding power was expressed by this amount of deviation.

4). Viscosity coefficient 3. The viscosity coefficient (Pa · s) of the pressure-sensitive adhesive layer was calculated according to the above [Equation 1] from the amount of deviation obtained by holding force measurement.
In this example, in [Formula 1],
Displacement stress (N / m ² ) = Load / Adhesion area = 9.8 N / (0.025 m × 0.01 m)
And
Deviation speed (1 / s) = deviation amount / test time / pressure-sensitive adhesive layer thickness = deviation amount (m) / 3600 seconds / 0.000025 m
It is.

5. Evaluation of white spots (1) Visual observation In the “1. Durability test”, two optical functional films of the same type after being left at 80 ° C. for 500 hours were bonded together in crossed Nicols, and this was attached to the backlight of the LCD monitor. It was placed on top and the state of white spots was visually observed and evaluated according to the following criteria.
<Evaluation criteria>
◯: No white spots were found on the optical functional film.
Δ: Slight white spots were confirmed on the optical functional film.
X: White spots were confirmed on the optical functional film.

(2) Total Light Transmittance Evaluation Using the hazemeter (Nippon Denshoku Industries Co., Ltd., NDH2000), the total light transmittance (%) of 35 points was measured using the haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.). The difference Δ of the total light transmittance was calculated from the above [Equation 2] from the maximum total light transmittance and the minimum total light transmittance among the 35 points.

  ADVANTAGE OF THE INVENTION According to this invention, in the liquid crystal cell which comprises a liquid crystal display device, the optical adhesive composition which forms the adhesive layer for adhere | attaching a glass substrate and an optical functional film is provided. The pressure-sensitive adhesive layer has an appropriate adhesive force, has good adhesion to the optical functional film, and can absorb the stress caused by the expansion and contraction of the optical functional film, which has been difficult to improve with the conventional pressure-sensitive adhesive. In addition, it is possible to suppress the occurrence of uneven color and white spots in the liquid crystal display device.

Claims (6)

An optical pressure-sensitive adhesive composition comprising at least a compound having at least two benzene rings in the molecule and a molecular weight of 150 to 1,000, an adhesive resin and a crosslinking agent,
The content of the compound is 0.1 to 15 parts by mass per 100 parts by mass of the adhesive resin,
The adhesive resin comprises (meth) acrylic acid alkyl ester monomer unit (a) having 1 to 18 carbon atoms and copolymerizable monomer unit (b) containing a carboxyl group and / or a hydroxyl group. The copolymer (A) contains at least a weight average molecular weight of 1,000,000 to 2,000,000, and the copolymer (A) further comprises an aromatic group occupying 20 to 60% by mass of the total amount of the copolymer. Containing a copolymerizable monomer unit (c) ,
Optical adhesive composition viscosity at 90 ° C. of the pressure-sensitive adhesive layer formed from the above composition and wherein ^{0.5 × 10 7 ~10 × 10 7} Pa · s der Rukoto.   The compound having at least two benzene rings in the molecule and having a molecular weight of 150 to 1,000 is at least one selected from the group consisting of transstilbene, fluorene, diphenyl sulfide, benzyl benzoate, benzoin, and diphenylacetylene. The optical pressure-sensitive adhesive composition according to claim 1. The optical pressure-sensitive adhesive composition according to claim 1 or 2 , wherein the content of the crosslinking agent is 0.01 to 1 part by mass per 100 parts by mass of the adhesive resin. Silane compounds containing a mercapto group and alkoxy group in the molecule (C), in any one of claims 1 to 3, further containing the 0.01 to 2 parts by weight per 100 parts by weight adhesive resin The optical pressure-sensitive adhesive composition according to the description. Furthermore, the low molecular weight (co) polymer (D) which consists of a C1-C18 alkylester of (meth) acrylic acid is included in the ratio of 1-50 mass parts per 100 mass parts of said copolymers (A). The (co) polymer (D) has a weight average molecular weight of 1,000 to 50,000, a dispersity (MW / MN) of 1.0 to 2.5, and the copolymer (A) The optical pressure-sensitive adhesive composition according to claim 1, which is compatible with It has the adhesive layer formed from the optical adhesive composition of any one of Claims 1-5 on the surface, The optical functional film characterized by the above-mentioned.