TW202234101A - Optical film production method thereof polarizer and image display device - Google Patents

Abstract

This optical film is provided with a slippery layer on the surface of a transparent film substrate. The slippery layer contains a binder resin and fine particles. The alkali component content of the slippery layer is 5-75 ppm. The slippery layer can be formed by applying a composition for forming the slippery layer which contains the binder resin or a precursor thereof, the fine particles, the alkali component, and a solvent onto the transparent film substrate, and heating the substrate. The optical film can be used as a polarizer protective film.

Description

Optical film and its manufacturing method, polarizing plate, and image display device

The present invention relates to an optical film provided with an easy-slip layer on the surface of a transparent film substrate and a manufacturing method thereof. Furthermore, the present invention relates to a polarizing plate in which an optical film provided with an easy-slip layer is bonded to the surface of a polarizer, and an image display device provided with the polarizing plate.

Background of the Invention Liquid crystal display devices and organic EL display devices have been widely used as various video display devices such as mobile devices, car navigation devices, monitors for personal computers, and televisions. Based on the display principle of the liquid crystal display device, a polarizing plate is arranged on the viewing side surface of the liquid crystal cell. In a transmissive liquid crystal display device, polarizers are arranged on both sides of the liquid crystal cell. In order to prevent external light from being reflected by the metal electrode (cathode) and appearing as a mirror surface, a circular polarizer (typically a laminate of a polarizer and a quarter-wave plate) is sometimes arranged on the viewing side surface of an organic EL display device.

The polarizer generally has a transparent film (polarizer protective film) on one side or both sides of the polarizer to protect the polarizer and the like. Nowadays, a polyvinyl alcohol (PVA)-based film that adsorbs iodine and orients molecules by stretching or the like is widely used as a polarizer.

As for the polarizer protective film attached to the surface of the polarizer, the polarizer attached with a low moisture permeability film made of acrylic, polyester, polycarbonate, cyclic polyolefin and other resin materials, even if exposed for a long time. In a high-humidity environment, the change in optical properties is still small, and the durability tends to be excellent. Patent Document 1 describes that an easy-slip layer containing fine particles and a binder resin is provided on the surface of an acrylic film to suppress sticking when the film is wound into a roll. An embodiment of Patent Document 1 discloses a polarizer protective film. The polarizer protective film is provided on the surface of the acrylic film with silica particles containing 1 to 7% by weight and an average thickness of 400 nm (thickness range of 300 to 500 nm). urethane resin layer.

prior art literature Patent Literature Patent Document 1: Japanese Patent No. 5354733

Summary of Invention The problem to be solved by the invention As image display devices progress toward larger size or higher brightness, the polarizing plate constituting the image display device is also required to have little change in optical properties even under severe environments (such as high temperature and high humidity conditions). . However, it has now been confirmed that there is a new problem: if the polarizing plate provided with the polarizer protective film disclosed in Patent Document 1 is exposed to a high humidity environment for a long time, optical defects such as rib-like unevenness will occur, resulting in a decrease in display characteristics. .

In view of the above-mentioned problems, an object of the present invention is to provide an optical film that does not easily cause sticking and that does not easily cause optical defects even when exposed to a high-temperature and high-humidity environment for a long time.

means of solving problems In view of the above problems, the inventors of the present invention have found that, as a result of studies, the alkali components such as ammonia and amines added to the composition for forming an easy-slip layer for the purpose of improving the dispersibility of fine particles and the like remain in the easy-bonding layer. It is one of the reasons for the decrease in durability in a wet environment, and it has been found that the above-mentioned problems can be solved by setting the alkali residual amount in the easy-slip layer within a predetermined range.

The present invention relates to an optical film provided with an easy-slip layer on the surface of a transparent film substrate and a manufacturing method thereof. The easy-slip layer contains binder resin and fine particles. The average primary particle size of the fine particles is, for example, 10 to 250 nm, preferably 10 to 100 nm. The alkali content of the easy-slip layer should be 5~75ppm. The thickness of the easy-slip layer is preferably 40-280 nm.

An acrylic film etc. can be used as a transparent film base material. For the adhesive resin of the easy-slip layer, urethane resin can be used. The content of fine particles in the easy-slip layer is preferably about 3 to 50% by weight, more preferably 10 to 50% by weight. The microparticles of the easy-slip layer can be embedded in the transparent film substrate.

The composition for forming an easy-slip layer is coated on the surface of the transparent film substrate and heated to form an easy-slip layer. The composition for forming an easy-slip layer contains a binder resin or a precursor thereof, fine particles, an alkali component, and a solvent. By containing an alkali component in the composition for forming an easy-slip layer, the dispersibility of the fine particles can be improved, and an optical film having excellent smoothness can be obtained. Moreover, the alkali component can also act as a catalyst for promoting the reaction of the binder resin (precursor). From the viewpoint of promoting volatilization of the alkali component by heating, the boiling point of the alkali component is preferably 150°C or lower. An amine, ammonia, etc. are mentioned as an alkali component.

By increasing the heating temperature after applying the composition for forming an easy-slip layer, the volatilization of the alkali component is accelerated, and an easy-slip layer with little residual alkali component can be formed. For example, the composition for forming an easy-slip layer can be heated at a temperature higher than the glass transition temperature of the transparent film substrate by 10° C. or more. By increasing the heating temperature, the microparticles that can easily form the easy-slip layer can be embedded in the area of the transparent film substrate, and the adhesion between the transparent film substrate and the easy-slip layer tends to improve.

After coating the composition for forming an easy-slip layer on the transparent film substrate, the transparent film substrate can be heated and extended. In particular, by heating the composition for forming an easy-slip layer at a temperature 10°C or more higher than the glass transition temperature of the transparent film substrate, and simultaneously extending the transparent film substrate, the transparent film substrate and the easy-slip layer can be formed. Tendency to increase in densities.

The easy-slip layer also helps to improve adhesion to other films or glass substrates. The optical film can be used, for example, as a polarizer protective film. For example, a polarizing plate can be produced by laminating an optical film on the surface of a polyvinyl alcohol-based polarizer through an adhesive layer. In the optical film, the polarizer can be bonded to either the easily bonding layer forming surface or the easily bonding layer non-forming surface. An image display device can be formed by disposing a polarizing plate on the surface of an image display unit such as a liquid crystal display unit or an organic EL unit.

Invention effect The optical film of the present invention has good adhesiveness, is not easy to produce adhesion, and is not easy to produce optical defects even if it is exposed to a high temperature and high humidity environment for a long time, and can be suitably used as a film for display devices such as a polarizer protective film.

Form for carrying out the invention FIG. 1 is a schematic cross-sectional view showing a configuration example of an optical film according to an embodiment of the present invention. The optical film 1 is provided with an easy-slip layer 15 on at least one side of the film substrate 11 . An easy-slip layer can also be provided on both sides of the film substrate. Optical films are used to bond with other films or glass substrates.

The use form of the optical film includes a polarizer protective film. 2A and 2B are cross-sectional views showing a configuration example of a polarizing plate including an optical film 1 as a polarizer protective film. The polarizing plate 100 shown in FIG. 2A and the polarizing plate 101 shown in FIG. 2B are provided with an optical film 1 on one surface (first main surface) of the polarizer 5 , and the optical film 1 is bonded through the adhesive layer 6 . In the polarizing plate 100 , the optical film 1 has an easy-slip layer 15 on the bonding surface of the optical film 1 and the polarizer 5 of the film substrate 11 . In the polarizing plate 101 shown in FIG. 2B , the polarizer 5 is attached to the surface of the optical film 1 on which the easy-slip layer 15 is not provided. In the polarizing plate 100 shown in FIG. 2A and the polarizing plate 101 shown in FIG. 2B , a transparent protective film 2 is attached to the other surface (second main surface) of the polarizer 5 through the adhesive layer 7 .

[Optical Film] The optical film 1 is provided with an easy-slip layer 15 on at least one side of the film substrate 11 .

<Film base material> The film substrate 11 is preferably a transparent film. The total light transmittance of the transparent film substrate is preferably above 80%, preferably above 85%, and more preferably above 90%. The resin material constituting the film base 11 includes acrylic resins, polyester resins, polycarbonate resins, polyolefin resins, cyclic polyolefin resins, polystyrene resins, polyamide resins, and polyamide resins. imide resin, etc. When the optical film is used as an optically isotropic polarizer protective film, the birefringence is small, so the resin material of the film substrate 11 is preferably acrylic resin or cyclic polyolefin resin, and acrylic resin is particularly preferred.

As a cyclic polyolefin resin, polynorbornene is mentioned, for example. Commercially available cyclic polyolefin-based resins include Zeonor and ZEONEX manufactured by ZEON Japan, ARTON manufactured by JSR, APEL manufactured by Mitsui Chemicals, and TOPAS manufactured by TOPAS ADVANCED POLYMERS. The cyclic polyolefin-based film preferably contains 50% by weight or more of the cyclic olefin-based resin.

Examples of acrylic resins include poly(meth)acrylates such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymers, methyl methacrylate-(meth)acrylate copolymers, Methyl methacrylate-acrylate-(meth)acrylic acid copolymer, methyl (meth)acrylate-styrene copolymer (MS resin, etc.), polymers with alicyclic hydrocarbon groups (such as methyl methacrylate) - cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.).

In this specification, "(meth)acrylic acid" means acrylic acid and/or methacrylic acid. The acrylic resin includes those having acrylic acid or its derivatives as constituent monomer components and those having methacrylic acid or its derivatives as constituent monomer components.

As the acrylic resin, acrylic resins having a glutaric anhydride structure described in Japanese Patent Laid-Open No. 2006-283013, Japanese Patent Laid-Open No. 2006-335902, Japanese Patent Laid-Open No. 2006-274118, etc.; Lactones described in Japanese Patent Laid-Open No. 2000-230016, Japanese Patent Laid-Open No. 2001-151814, Japanese Patent Laid-Open No. 2002-120326, Japanese Patent Laid-Open No. 2002-254544, Japanese Patent Laid-Open No. 2005-146084, etc. Ring-structured acrylic resin. Acrylic resins with a glutaric anhydride structure and acrylic resins with a lactone ring structure have high heat resistance, high transparency and high mechanical strength, so they are suitable for producing polarizing plates with high degree of polarization and excellent durability.

When the film substrate 11 is an acrylic film, the content of the acrylic resin in the film substrate is preferably more than 50% by weight, preferably 60-98% by weight, more preferably 70-97% by weight. The acrylic film may contain thermoplastic resins other than acrylic resins. For example, by blending other thermoplastic resins, the birefringence of the acrylic resin can be eliminated to obtain an acrylic film having excellent optical isotropy. Moreover, in order to improve the mechanical strength of a film, etc., you may mix|blend thermoplastic resin other than acrylic resin.

Examples of thermoplastic resins other than acrylic resins include olefin polymers, halogenated vinyl polymers, polystyrene, copolymers of styrene and acrylic monomers, polyesters, polyamides, polyacetals, polycarbonates, Polyphenylene ether, polyphenylene sulfide, polyether ether ketone, polystilbene, polyether slag, polyoxybenzylene, polyamide imide, rubber-based polymers, etc.

The film substrate 11 may also contain additives such as antioxidants, stabilizers, reinforcing materials, ultraviolet absorbers, flame retardants, antistatic agents, colorants, fillers, plasticizers, lubricants, and fillers. The resin material may be mixed with additives and the like, and the thermoplastic resin composition such as pellets may be prepared in advance, and then the film may be formed.

The thickness of the film substrate 11 is about 5 to 200 μm. From the viewpoints of mechanical strength, transparency, and handling properties, the thickness of the film substrate 11 is preferably 10 to 100 μm, preferably 15 to 60 μm.

The glass transition temperature Tg of the film substrate 11 is preferably 100°C or higher, preferably 110°C or higher. When the film substrate 11 is an acrylic film, as described above, by using an acrylic resin having a glutaric anhydride structure or an acrylic resin having a lactone ring structure as the acrylic resin, the Tg of the acrylic film can be increased, and the Tg of the acrylic film can be increased. Improve heat resistance. The upper limit of Tg of the film substrate 11 is not particularly limited, but is preferably 170° C. or lower from the viewpoint of formability and the like.

A solution casting method, a melt extrusion method, a calendering method, a compression molding method, etc. are mentioned as the manufacturing method of the film base material 11. The film substrate 11 may be either an unstretched film or a stretched film. When the film substrate 11 is an acrylic film, from the viewpoint of improving mechanical strength, the acrylic film is preferably a stretched film extending in at least one direction, and a biaxially stretched film is particularly preferred. By blending other thermoplastic resins to eliminate the birefringence of the acrylic resin, an acrylic film having a small retardation and excellent optical isotropy can be obtained even after extending it.

＜Slippery layer＞ The easy-slip layer 15 provided on the surface of the film base 11 contains a binder resin and fine particles. Since the easy-slip layer 15 contains fine particles, the surface of the easy-slip layer 15 can be formed with fine irregularities, thereby improving the smoothness of the film. Therefore, it is helpful to reduce damage when the optical film 1 is transported by a roll or to suppress sticking when it is wound into a roll.

唑啉基等交聯性官能基之丙烯酸樹脂等具有反應性基的樹脂(聚合物)。易滑層15之黏結劑樹脂以聚胺甲酸乙酯樹脂尤佳。含有聚胺甲酸乙酯樹脂黏結劑的易滑層15與薄膜基材11之密著性很高。 (Binder resin) From the viewpoint of excellent adhesion to film substrates such as acrylic films, as the binder resin, polyurethane resins, epoxy resins, isocyanate resins, polyester resins, and those containing Amine-based polymers, with

Resins (polymers) having reactive groups, such as acrylic resins with crosslinkable functional groups such as oxazoline groups. The adhesive resin of the easy-slip layer 15 is preferably polyurethane resin. The adhesion between the easy-slip layer 15 containing the polyurethane resin adhesive and the film substrate 11 is very high.

Urethane resins are representatively the reaction products of polyols and polyisocyanates. As the polyol component, polymer polyols such as polypropylene polyol, polyester polyol, and polyether polyol are preferably used.

Polypropylene polyols are typically obtained by polymerizing (meth)acrylates with hydroxyl-containing monomers. (Meth)acrylate, methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, etc. are mentioned, for example. Examples of hydroxyl-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate , Hydroxyalkyl esters of (meth)acrylic acid such as 4-hydroxybutyl (meth)acrylate and 2-hydroxypentyl (meth)acrylate; (meth)acrylic acid monoesters of polyols such as glycerol and trimethylolpropane ; N-methylol (meth) acrylamide and so on.

The polypropylene polyol may contain monomer components other than the above. Other monomer components include unsaturated monocarboxylic acids such as (meth)acrylic acid; unsaturated dicarboxylic acids such as maleic acid and their anhydrides and diesters; unsaturated nitriles such as (meth)acrylonitrile; ) unsaturated amides such as acrylamide and N-methylol(meth)acrylamide; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether; ethylene, α-olefins such as propylene; halogenated α,β-unsaturated aliphatic monomers such as vinyl chloride and vinylidene chloride; α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene, etc.

Polyester polyols are typically prepared by the reaction of polyacids and polyols. The polybasic acid includes phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, Aromatic dicarboxylic acids such as tetrahydrophthalic acid; oxalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, Dodecanedicarboxylic acid, octadecanedicarboxylic acid, tartaric acid, alkylsuccinic acid, hypolinoleic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, itonic acid and other aliphatic dicarboxylic acids; Alicyclic dicarboxylic acids such as hexahydrophthalic acid, tetrahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid; or their anhydrides, alkyl esters, Reactive derivatives such as halide, etc.

Examples of polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, and 1,6-hexanediol. Diol, 1,8-octanediol, 1,10-decanediol, 1-methyl-1,3-butanediol, 2-methyl-1,3-butanediol, 1-methyl- 1,4-pentanediol, 2-methyl-1,4-pentanediol, 1,2-dimethyl-neopentyl glycol, 2,3-dimethyl-neopentyl glycol, 1-methyl base-1,5-pentanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,2-dimethylbutanediol, 1,3 -Dimethylbutanediol, 2,3-dimethylbutanediol, 1,4-dimethylbutanediol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol , 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol, bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, etc.

Polyether polyols can be prepared by ring-opening polymerization of polyols to add alkylene oxides. As a polyhydric alcohol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerol, trimethylolpropane, etc. are mentioned, for example. As an alkylene oxide, ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, etc. are mentioned, for example.

Examples of polyisocyanates include tetramethylene diisocyanate, dodecylene diisocyanate, 1,4-butane diisocyanate, hexamethylene diisocyanate, and 2,2,4-trimethyl. Hexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane- Aliphatic diisocyanates such as 1,5-diisocyanate; isophorone diisocyanate, hydrogenated diisocyanate, 4,4'-cyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methyl ring Alicyclic diisocyanates such as hexylene diisocyanate and 1,3-bis(isocyanate methyl)cyclohexane; benzylidene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylene Methane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate , Aromatic diisocyanates such as stubble diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate; dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, Aromatic aliphatic diisocyanates such as α,α,α,α-tetramethyl diisocyanate, etc.

The urethane resin constituting the easy-slip layer 15 preferably has a carboxyl group. Since the urethane resin has a carboxyl group, a cross-linked structure can be introduced. The urethane resin having a carboxyl group can be prepared, for example, by reacting a polyol, a polyisocyanate and a chain extender having a free carboxyl group. The chain extender having a free carboxyl group includes dihydroxycarboxylic acid, dihydroxysuccinic acid, and the like. Dihydroxycarboxylic acids include dimethylolalkanoic acids (eg, dimethylolacetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, dimethylolbutanoic acid, dimethylolpentanoic acid) Dialkylol alkanoic acid, etc.

The production method of the urethane resin is not particularly limited, and may be any of a single-shot method in which the monomer components are reacted at one time and a multi-stage method in which the monomer components are reacted in stages. When a chain extender having a free carboxyl group is used to introduce the carboxyl group into the urethane resin, a multi-stage method is preferred. When manufacturing urethane resin, urethane reaction catalyst can also be used as required.

The number average molecular weight of the urethane resin is preferably 5,000-600,000, more preferably 10,000-400,000. The acid value of the urethane resin is preferably 10-50, preferably 20-45.

唑啉基、環氧基、碳二醯亞胺基等的交聯劑。該等中又以具有

唑啉基之交聯劑為宜。

唑啉基常溫下與羧基的反應性較小，所以與胺甲酸乙酯樹脂混合後的使用期限較長，可彈性應對步驟的前置時間。The urethane resin may also have a cross-linked structure. By introducing the urethane resin into the cross-linked structure, the adhesion between the easy-slip layer 15 and the film substrate 11 and the hardness of the easy-slip layer 15 tend to be improved. As the crosslinking agent, one that can react with the crosslinkable functional group of the urethane resin can be used without particular limitation. When the urethane resin has a carboxyl group, an amine group containing,

Crosslinking agent of oxazoline group, epoxy group, carbodiimide group, etc. Among these, there are also

An oxazoline-based crosslinking agent is suitable.

The oxazoline group has less reactivity with the carboxyl group at room temperature, so it has a longer service life after mixing with the urethane resin, and can flexibly cope with the lead time of the step.

唑啉基之丙烯酸系聚合物尤佳。The crosslinking agent may be a low molecular compound or a polymer. From the viewpoint of high solubility in water-based compositions and good compatibility with urethane resins, the crosslinking agent is preferably an acrylic polymer, and has

An oxazoline-based acrylic polymer is particularly preferred.

The usage amount of the crosslinking agent is preferably 1-30 parts by weight, preferably 3-20 parts by weight, relative to 100 parts by weight of the urethane resin.

(fine particles) Since the easy-slip layer 15 contains fine particles, fine concavo-convex shapes can be formed on the surface of the easy-slip layer, the smoothness of the optical film 1 is improved, and sticking can be suppressed. The particle size (average primary particle size) of the fine particles is preferably 10 nm or more, more preferably 15 nm or more, and more preferably 20 nm or more, from the viewpoint of forming irregularities that contribute to improving smoothness. The average primary particle size of the fine particles should be smaller than the thickness of the easy-slip layer. The particle size of the fine particles is smaller than the thickness of the easy-slip layer, thereby preventing the fine particles from falling off the easy-slip layer. The particle size of the fine particles is preferably 250 nm or less, and preferably 200 nm or less. In addition, by making the average primary particle size of the fine particles smaller than the wavelength of visible light, scattering of visible light at the interface between the binder resin and the fine particles can be suppressed. From the viewpoint of improving transparency, the particle diameter of the fine particles is preferably 100 nm or less, more preferably 80 nm or less, more preferably 60 nm or less, and particularly preferably 50 nm or less.

The microparticles of the easily bonding layer 15 may be any of inorganic microparticles and organic microparticles. From the viewpoint of excellent dispersibility and uniformity of particle size, the fine particles are preferably inorganic fine particles. Inorganic fine particles include inorganic oxides such as titanium dioxide, aluminum oxide, and zirconium dioxide; calcium carbonate, talc, clay, fired kaolin, fired calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, etc. . Of these, inorganic oxides are preferred. Examples of the organic fine particles include silicone resins, fluorine resins, acrylic resins, and the like. In order to suppress light scattering due to fine particles, the difference in refractive index between the binder resin (generally about 1.5 refractive index) and the fine particles should be small. From the viewpoint of having a small difference in refractive index with the binder resin and having excellent dispersibility, the fine particles of the easy-slip layer 15 are preferably silica particles.

When forming the easy-slip layer 15 from a water-based composition, fine particles with high water dispersibility are preferably used. Aqueous dispersions of microparticles can also be incorporated into the composition. In order to improve the dispersibility of the fine particles, an alkali component such as amine or ammonia is preferably added to make the easy-slip layer forming composition weakly alkaline.

The water-dispersible silica particles are preferably colloidal silica. The colloidal silica can also be used in the Quartron PL series manufactured by Fuso Chemical Industry Co., Ltd., the SNOWTEX series manufactured by Nissan Chemical Industry Co., Ltd., the AERODISP series and AEROSIL series manufactured by Japan Aerosil Co., Ltd., and the Seahostar KE series manufactured by Nippon Shokubai Co., Ltd. Sale.

The smoothness of the optical film 1 can be improved by forming concavities and convexities on the surface of the easy-slip layer 15. From this point of view, the content of fine particles in the easy-slip layer 15 is preferably 3 wt% or more, preferably 5 wt% or more. In particular, when the thickness of the easy-slip layer 15 is small (for example, below 280 nm), it is advisable to increase the content of fine particles to increase the amount of fine particles per unit area (number density), so as to form unevenness on the surface of the easy-slip layer 15 uniformly. The content of fine particles in the easy-slip layer 15 is preferably more than 8% by weight, preferably more than 10% by weight, more preferably more than 12% by weight. If the content of the microparticles in the easy-slip layer 15 is too large, it may lead to increased light scattering at the interface between the binder resin and the microparticles, resulting in a decrease in optical properties. In addition, as the content of fine particles increases, the relative content of the binder resin decreases, which may reduce the adhesion of the easy-slip layer. Therefore, the content of fine particles in the easy-slip layer 15 is preferably below 50% by weight, preferably below 40% by weight, more preferably below 30% by weight.

(Alkali Residual) If an alkali component such as amine or ammonia is used in order to improve the dispersibility of the fine particles, the alkali component will inevitably remain in the easy-slip layer. When the optical film 1 is used as a polarizer protective film, the residual alkali component of the easy-slip layer 15 may be dissolved into water, the alkali component that penetrates the film substrate 11 may deteriorate the polarizer and reduce the degree of polarization of the polarizer, or A case of optical defects such as rib-like unevenness.

Therefore, from the viewpoint of improving the humidification durability of the polarizing plate, the residual alkali content of the easy-slip layer 15 is preferably 75 ppm or less, preferably 70 ppm or less, more preferably 60 ppm or less, and particularly preferably 55 ppm or less. From the viewpoint of improving the humidification durability of the polarizing plate, the less alkali residue in the easy-slip layer 15 is, the better.

On the other hand, if the amount of alkali residue in the easy-slip layer 15 is too small, the dispersibility of the fine particles will be impaired, and the fine particles may agglomerate, resulting in poor appearance such as white turbidity. In addition, due to the decrease in dispersibility, the fine particles may aggregate or fall off from the easy-slip layer, so that proper unevenness cannot be formed on the surface of the easy-slip layer, and the smoothness of the optical film tends to decrease. Therefore, the residual alkali content of the easy-slip layer 15 is preferably 5 ppm or more, preferably 10 ppm or more, and more preferably 20 ppm or more.

Specific examples of the residual alkali component in the easy-slip layer include amine and ammonia, and the total content of the amine and ammonia in the easy-slip layer is preferably within the above range. The amount of alkali in the easy-slip layer can be quantified by liquid chromatography analysis or ion chromatography analysis according to the type of alkali components. The quantification of the base component can also be performed by an analytical method (eg, LC/MS) that combines chromatographic analysis and mass analysis (MS). When a plurality of alkali components are contained in the easy-slip layer, the total of each component is used as the alkali component content (residual amount) of the easy-slip layer.

<Forming an easy-slip layer> The formation method of forming the easy-slip layer 15 on the surface of the film substrate 11 is not particularly limited. Ideally, the easy-slip layer 15 is formed by applying a composition (coating liquid) for forming an easy-slip layer containing a binder resin and fine particles onto the film substrate 11 and heating it.

(Composition for forming an easy-slip layer) The composition for forming an easy-slip layer is preferably an aqueous composition using water as a solvent (and a dispersion medium for fine particles). The concentration of the solid content (nonvolatile matter) in the composition for forming an easy-slip layer is preferably 1 to 30% by weight, more preferably 2 to 20% by weight, and more preferably 3 to 15% by weight.

The composition for forming a water-based easy-slip layer contains water as a solvent (and a dispersion medium), a binder resin grease or its precursor, and fine particles. The composition for forming an easy-slip layer more preferably contains an alkali component. As described above, the alkali component has the effect of promoting the dispersion of fine particles. Fine particles with a small particle size tend to agglomerate easily, but when the composition for forming an easy-slip layer contains an alkali component such as ammonia or amine, the dispersibility of the fine particles can be improved, and an optical film with excellent appearance and smoothness can be obtained.

On the other hand, if the alkali contained in the composition for forming an easy-slip layer remains in the easy-slip layer, it may cause a decrease in the heat-and-moisture resistance of the polarizing plate. In particular, even a small amount of strong alkali such as caustic may cause deterioration of the polarizer. Therefore, the alkali component contained in the composition for forming an easy-slip layer is preferably a weak alkali component such as ammonia or amine. From the viewpoint of both improving the dispersibility of the fine particles and preventing the deterioration of the polarizer, the pH of the composition for forming an easy-slip layer (coating liquid) is preferably about 7.5 to 9.

From the viewpoint of improving the dispersibility of the fine particles, the amount of the alkali component contained in the easy-slip layer-forming composition is preferably 300 ppm or more, preferably 500 ppm or more, relative to the solid content of the easy-slip layer-forming composition. On the other hand, if the content of the alkali component is too large, it may become difficult to reduce the residual amount of alkali. Therefore, the amount of the alkali component contained in the composition for forming an easy-slip layer should preferably be relative to the solid content of the composition for forming an easy-slip layer. The component is 50,000 ppm or less, preferably 10,000 ppm or less, and more preferably 5,000 ppm or less. As described above, specific examples of the alkali component contained in the composition for forming an easy-slip layer include amine and ammonia, and the total content of these alkali components is preferably within the above-mentioned range.

The alkali component contained in the composition for forming an easy-slip layer may not only improve the dispersibility of the fine particles, but also have a catalytic effect. For example, when the binder resin is a urethane resin, the urethane catalyst serving as a polyurethane precursor (polyol, isocyanate, etc.) may also be included in the composition for forming an easy-slip layer. Tertiary amines such as triethylamine.

The composition for forming an easy-slip layer is coated on the film substrate and then heated to volatilize and remove the alkali component, thereby reducing the residual alkali component of the easy-slip layer 15 . From the viewpoint of promoting volatilization of the alkali component by heating, the boiling point of the alkali component contained in the composition for forming an easy-slip layer is preferably 150°C or lower. The boiling point of the alkali component is preferably 130°C or lower, more preferably 120°C or lower, and even more preferably 110°C or lower. The boiling point of the alkali component may be 100°C or lower or 90°C or lower. When the composition for forming an easy-slip layer contains a plurality of alkali components, the boiling point of at least one alkali component is preferably within the above range, and the boiling point of two or more alkali components is preferably within the above range. With respect to 100 parts by weight of the total amount of the alkali contained in the easy-slip layer, 50% by weight or more of the alkali component preferably has a boiling point within the above range. The boiling points of all the alkali components contained in the composition for forming an easy-slip layer are preferably within the above-mentioned range.

The composition for forming an easy-slip layer may contain a crosslinking agent in addition to the binder resin (or its precursor), fine particles, and an alkali component. The composition for forming an easy-slip layer may also contain a catalyst such as a crosslinking accelerator, an antioxidant, an ultraviolet absorber, a leveling agent, an anti-blocking agent, an antistatic agent, a dispersion stabilizer, a defoaming agent, a tackifier, Dispersants, surfactants, lubricants and other additives.

(Forming an easy-slip layer on the film substrate) Before coating the composition for forming an easy-slip layer on the film substrate 11, the surface treatment of the film substrate may be performed. By performing surface treatment, the wetting tension of the film substrate can be adjusted, and the adhesion between the film substrate and the easy-slip layer 15 can be improved. The surface treatment includes corona treatment, plasma treatment, ozone injection, ultraviolet irradiation, flame treatment, chemical treatment, and the like. Among these, corona treatment or plasma treatment is suitable.

The coating method of the composition for forming an easy-slip layer includes a bar coating method, a roll coating method, a gravure coating method, a rod coating method, a slit coating method, a curtain coating method, a fountain coating method, and the like. The easy-slip layer 15 can be formed by heating the coated composition for easy-slip layer forming to remove the solvent. The binder resin can also be cured by reacting with the precursor material by heating. For example, when the composition for forming an easy-slip layer contains a crosslinking agent, the crosslinking reaction can be accelerated by heating.

The heating temperature when forming the easy-slip layer is, for example, about 50 to 200°C. From the viewpoint of promoting the hardening reaction of the resin component of the composition for forming an easy-slip layer, and effectively volatilizing and removing the alkali component contained in the composition for forming an easy-slip layer, the heating temperature is preferably 100°C or higher and 120°C or higher Preferably, 130°C or higher is more preferable, and 135°C or higher is particularly preferable. Further, the heating temperature is preferably higher than the boiling point of the alkali component contained in the composition for forming an easy-slip layer.

The heating temperature for forming the easy-slip layer should be higher than the glass transition temperature (Tg) of the film substrate. By heating at a high temperature, the hardening reaction of the resin component of the composition for forming an easy-slip layer can be accelerated, and the alkali component contained in the composition for forming an easy-slip layer can be effectively volatilized and removed. The heating temperature is preferably a temperature higher than the Tg of the film substrate by 10°C or more.

We believe that by heating at a higher temperature than the Tg of the film substrate, the alkali volatilization removal efficiency in the easy-slip layer-forming composition can be improved, and the easy-slip layer-forming composition can more easily penetrate the film substrate. On the surface, the adhesion between the film substrate 11 and the easy-slip layer 15 is improved. From the viewpoint of improving the adhesion of the easy-slip layer, the heating temperature is preferably Tg+10°C or higher of the film substrate, more preferably Tg+15°C or higher, more preferably Tg+20°C or higher.

If the film base material is heated at a temperature above Tg+10°C, the film base material will change from a glass state to a rubber state, and the surface will become easily deformed, so a thin film is easily formed at the interface between the film base material 11 and the easy-slip layer 15 An interface layer in which the resin component of the base material and the constituent components of the easy-slip layer are mixed. By forming the interface layer, the adhesion between the film substrate 11 and the easy-slip layer 15 tends to be improved.

In particular, as shown in the cross-sectional observation image in FIG. 3 , when there is an area where the particles of the easy-slip layer 15 are embedded and embedded on the surface of the film substrate 11 , an optical film with high adhesion between the film substrate 11 and the easy-slip layer 15 can be obtained. film. We believe that if the microparticles are embedded in the film substrate in a rubber state in which the film substrate is heated to a temperature higher than Tg, and then the film substrate is returned to a glass state, the microparticles embedded on the surface of the film substrate and the presence of The surrounding adhesive resin will be fixed on the surface of the film substrate, so the adhesion between the film substrate 11 and the easy-slip layer 15 can be improved.

The easy-slip layer can also be formed in the manufacturing step of the film substrate. In addition, the easy-slip layer can also be formed by heating at the time of forming the film base material. For example, when the film substrate is a stretched film, the composition for forming an easy-slip layer can be coated on the surface of the film before stretching or on the surface of the film after longitudinal stretching, and use a tenter for lateral stretching or simultaneous biaxial stretching. heating to dry the solvent or harden the resin.

When the film base material is stretched after applying the composition for forming an easy-slip layer, the stretching ratio is preferably 5 times or less, more preferably 4 times or less, from the viewpoint of suppressing the occurrence of defects such as cracks in the easy-slip layer. , 3 times or less is better, and 2.5 times or less is even better. The lower limit of the stretching ratio is not particularly limited, but from the viewpoint of improving the strength of the film, the stretching ratio is preferably 1.3 times or more, more preferably 1.5 times or more. If the film substrate is an acrylic film, from the viewpoint of improving the strength of the film, it is preferable to carry out stretching at the above stretching ratios in the conveying direction (MD) and the width direction (TD), respectively.

When the film substrate is biaxially stretched, the biaxial stretching can be either successive biaxial stretching or simultaneous biaxial stretching. In addition, it can also be extended obliquely. In the case of successive biaxial stretching, the film can also be stretched in one direction (MD) by roll stretching as described above, and then the composition for forming an easy-slip layer can be coated on the film, and the easy-slip layer can be formed on the film during stretching by a tenter. The layer-forming composition is heated.

The extension temperature is the same as the above-mentioned heating temperature of the easy-slip layer, which is preferably higher than the Tg of the film substrate, and preferably above Tg+10°C, preferably above Tg+15°C, more preferably above Tg+20°C . In particular, after applying the composition for forming an easy-slip layer, it is preferable to extend in at least one direction at the above temperature. If the stretching is performed in a rubber state higher than the Tg of the film substrate, a region in which the fine particles of the composition for forming an easy-slip layer are embedded is easily formed on the surface of the film substrate, and the film substrate 11 and the easy-slip layer 15 The intimacy tends to increase. The reasons why it becomes easy to embed fine particles in the film base material by stretching at high temperature include: when stretching is carried out in a rubber state, the composition for forming an easy-slip layer tends to wet and diffuse when the film base material is deformed, so that it is easy to It becomes a state in which fine particles are embedded in the concave parts of the surface unevenness formed during deformation. Furthermore, we believe that if cooling is performed while releasing the stress after stretching, when the film substrate shrinks, the particles embedded in the surface of the film substrate will be fixed thereon, so that it is easy to form a region in which the microparticles are embedded in the film substrate.

The thickness of the easy-slip layer 15 can be adjusted by adjusting the solid content concentration and coating thickness of the composition for forming the easy-slip layer. The thickness of the easy-slip layer 15 can also be adjusted by the drawing ratio when the film substrate is stretched after applying the composition for forming an easy-slip layer.

The thickness of the easy-slip layer 15 is not particularly limited, but is preferably 280 nm or less, more preferably 250 nm or less, and more preferably 230 nm or less, from the viewpoint of promoting the removal of alkali components by heating. When the optical film 1 is used as a polarizer protective film, the smaller the thickness of the easy-slip layer 15 is, the higher the humidification durability of the polarizer tends to be.

When the composition for forming an easy-slip layer is heated and dried, if the alkali component is excessively removed, the dispersibility of the fine particles in the binder resin decreases, and the fine particles tend to agglomerate, or the resulting fine particles fall off the surface of the easy-slip layer. . Once the agglomeration or detachment of the fine particles occurs, the smoothness of the optical film is reduced, and it is easy to be damaged during transportation or to be stuck during winding. Therefore, the thickness of the easy-slip layer 15 is preferably more than 40 nm, preferably more than 50 nm, more preferably more than 80 nm, and more preferably more than 100 nm. The thickness of the easy-slip layer may also be 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, or 150 nm or more.

[polarizing plate] The polarizer can be provided with a transparent protective film only on one side of the polarizer, or can also be provided with a transparent protective film on both sides of the polarizer 5 as shown in FIG. 2A and FIG. 2B . By adhering the above-mentioned optical film as a polarizer protective film on one side of the polarizer, a polarizer with a transparent protective film only on one side of the polarizer can be formed. The polarizer having the polarizer protective film on both sides of the polarizer should just be attached with the above-mentioned optical film on at least one side of the polarizer. The polarizing plate may also be laminated with the above-mentioned optical films on both sides of the polarizer. The polarizer 5 and the optical film 1 can be pasted through the adhesive layer 6 .

＜Polarizer＞ As the polarizer 5, a polyvinyl alcohol-based film such as polyvinyl alcohol and partially formaldehyde polyvinyl alcohol can be used to adsorb a dichroic substance such as iodine or a dichroic dye on a polyvinyl alcohol-based film such that it is oriented in one direction (polyvinyl alcohol). PVA) is a polarizer. For example, a PVA-based polarizer can be produced by dyeing and stretching a polyvinyl alcohol-based film with iodine.

In the manufacturing steps of the polarizer 5, treatments such as water washing, swelling, and cross-linking may also be performed as required. The extension may optionally be performed before and after iodine staining, or may be performed concurrently with the dyeing. The stretching may be carried out in the air (dry stretching), or stretching in water or an aqueous solution containing boric acid, potassium iodide, etc. (wet stretching), or these may be used in combination. The film thickness of the polarizer 5 is not particularly limited, and is generally about 1 to 50 μm.

The polarizer 5 can also use a thin PVA-based polarizer with a thickness of 10 μm or less. As the thin polarizer, the thin polarizers described in Japanese Patent Laid-Open No. Sho 51-069644, Japanese Patent Laid-Open No. 2000-338329, Handbook WO2010/100917, Japanese Patent No. 4691205, and Japanese Patent No. 4751481 can be used. polarizer. These thin polarizers can be produced by a production method including a step of extending a PVA-based resin layer and a resin substrate for extending in a state of a laminate and a step of iodine dyeing. According to such a production method, even if the PVA-based resin layer is thin, it is supported by the resin base material for stretching, so that it can be stretched without problems such as breakage due to stretching.

＜Adhesive＞ The material of the adhesive layer 6 used to bond the polarizer 5 and the optical film 1 is not particularly limited as long as it is optically transparent, and examples include epoxy resin, polysiloxane resin, acrylic resin, and polyurethane. Ethyl ester, polyamide, polyether, polyvinyl alcohol, etc. The thickness of the adhesive layer 6 is, for example, about 0.01 to 20 μm, which can be appropriately set according to the type of the adherend or the material of the adhesive. When using a hardening type adhesive that exhibits adhesiveness by a cross-linking reaction after coating, the thickness of the adhesive layer 6 is preferably 0.01 to 5 μm, preferably 0.03 to 3 μm.

Various types of adhesives such as water-based adhesives, solvent-based adhesives, hot-melt adhesives, and active energy ray-curable adhesives can be used as the adhesive. Among these, from the viewpoint of reducing the thickness of the adhesive layer, a water-based adhesive or an active energy ray-curable adhesive is preferable.

The polymer component of the water-based adhesive includes vinyl polymers, gelatin, vinyl-based latex, polyurethane, polyester-based, epoxy, and the like. Among these, vinyl polymers are preferable, and polyvinyl alcohol-based resins are particularly preferable in terms of excellent adhesion to polarizers. Among the polyvinyl alcohol-based resins, polyvinyl alcohol containing an acetyl acetyl group is suitable.

From the viewpoint of adhesiveness, the average degree of polymerization of the polyvinyl alcohol-based resin is preferably about 100 to 5000, more preferably 1000 to 4000. The average degree of saponification of the polyvinyl alcohol-based resin is preferably 85 mol% or more, preferably 90 mol% or more.

The water-based adhesive composition (solution) may contain a polymer such as a polyvinyl alcohol-based resin and a crosslinking agent. The crosslinking agent can be used for a compound having at least two functional groups having a polymer constituting an adhesive and a reactive functional group in one molecule. Examples of crosslinking agents for polyvinyl alcohol-based resins include alkyl diamines; isocyanates; epoxy; aldehydes; amine-formaldehyde such as methylol urea and methylol melamine. Among these, amino-formaldehyde is again suitable. The amino-formaldehyde resin is preferably a compound having a methylol group, and methylol melamine is particularly preferred. The blending amount of the crosslinking agent in the adhesive composition is preferably about 10-60 parts by weight relative to 100 parts by weight of the polyvinyl alcohol-based resin, and preferably 20-50 parts by weight.

Active energy ray-curable adhesives are adhesives that can undergo radical polymerization, cationic polymerization, or anionic polymerization by irradiating active energy rays such as electron beams or ultraviolet rays. Among them, from the viewpoint of low-energy curing, a photo-radical polymerizable adhesive that initiates polymerization by ultraviolet irradiation, a photo-cationic polymerizable adhesive, or a hybrid-type adhesive that uses a combination of photo-cationic polymerization and photo-radical polymerization appropriate.

烷二醇二丙烯酸酯、EO改質二甘油四丙烯酸酯等多官能單體。 As a monomer of a radically polymerizable adhesive agent, the compound which has a (meth)acryloyl group, and the compound which has a vinyl group are mentioned. Among them, compounds having a (meth)acryloyl group are preferred. Examples of compounds having a (meth)acryloyl group include C _1-20 chain alkyl (meth)acrylates, alicyclic alkyl (meth)acrylates, and polycyclic alkyl (meth)acrylates Alkyl (meth)acrylates; hydroxyl-containing (meth)acrylates; epoxy-containing (meth)acrylates such as glycidyl (meth)acrylate and the like. The radically polymerizable adhesive may contain hydroxyethyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N- Nitrogen-containing monomers such as ethoxymethyl (meth)acrylamide, (meth)acrylamide, and (meth)acryloyl mofolin. The radical polymerizable adhesive may contain tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, and cyclic trimethylolpropane methyl acrylate as a crosslinking component Ester, Di

Multifunctional monomers such as alkanediol diacrylate and EO modified diglycerol tetraacrylate.

As a curable component of a cationically polymerizable adhesive agent, the compound which has an epoxy group or an oxetanyl group is mentioned, for example. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various generally known curable epoxy compounds can be used. Examples of ideal epoxy compounds include compounds having at least two epoxy groups and at least one aromatic ring in the molecule (aromatic epoxy compounds), or compounds having at least two epoxy groups in the molecule. And among them, at least one is a compound formed between two adjacent carbon atoms constituting an alicyclic ring (alicyclic epoxy compound). The cationic polymerizable adhesive may contain a radically polymerizable compound such as a compound having a (meth)acryloyl group, and a hybrid adhesive may also be used.

The photocurable adhesive preferably contains a photopolymerization initiator. The photopolymerization initiator may also be appropriately selected depending on the type of reaction. For example, a photo-radical generator that can generate radicals by light irradiation is suitable for blending a radical-polymerizable adhesive as a photopolymerization initiator. As a photopolymerization initiator, a photocationic polymerization initiator (photoacid generator) that is suitable for the cationic polymerizable adhesive to generate a cationic species or a Lewis acid by light irradiation can be used as the photopolymerization initiator. It is suitable for blending adhesive with photocationic polymerization initiator and photoradical generator.

The content of the polymerization initiator is usually about 0.1 to 10 parts by weight, preferably 0.5 to 3 parts by weight, relative to 100 parts by weight of the monomers. In addition, when the radically polymerizable adhesive is used as an electron beam curing type, there is no particular need for a photopolymerization initiator. In order to increase the curing speed or sensitivity, a photosensitizer may also be added to the active energy ray-curable adhesive as required. The usage amount of the photosensitizer is usually about 0.001 to 10 parts by weight, preferably 0.01 to 3 parts by weight, relative to 100 parts by weight of the monomer.

The subsequent agent may also contain suitable additives as required. Examples of additives include silane coupling agents, silane coupling agents such as titanium silane coupling agents, adhesion promoters such as ethylene oxide, ultraviolet absorbers, anti-deterioration agents, dyes, processing aids, ion scavengers, antioxidants, tackifiers Agents, fillers, plasticizers, leveling agents, foam inhibitors, antistatic agents, heat-resistant stabilizers, hydrolysis-resistant stabilizers, etc.

[Make a polarizer] The optical film 1 is attached to one surface (first main surface) of the polarizer 5 through the adhesive layer 6 to manufacture a polarizing plate. As shown in FIG. 2A, the optical film 1 can be attached to the polarizer 5 through the adhesive layer on the forming surface of the easy-slip layer; as shown in FIG. 2B, the non-formed surface of the easy-slip layer can pass through the adhesive layer and the polarizer 5. fit.

The easy-slip layer 15 can also function as an easy-bond layer. As shown in FIG. 2A , when the easy-slip layer 15 of the optical film 1 is formed and pasted to the polarizer 5 through the adhesive layer 6 , the easy-slip layer 15 helps to enhance the relationship between the polarizer and the polarizer protective film (optical film 1 ). Continuity. As shown in FIG. 2B , when the non-formed surface of the easy-slip layer is pasted with the polarizer 5 through the adhesive layer, the easy-slip layer 15 helps to lift other films, adhesive layers, glass substrates, etc. disposed on the optical film 1 . the continuity.

When laminating the polarizer 5 and the optical film 1, it is suitable to apply the adhesive composition to either or both of the polarizer 5 and the optical film 1, and then stick the polarizer 5 and the optical film 1 with a roll press or the like. Incorporation hardens the adhesive. The coating method for coating the adhesive composition on the polarizer 5 and/or the optical film 1 includes a roll coating method, a spray method, a dipping method, and the like. Before coating the adhesive composition on the surface of the polarizer 5 and/or the optical film 1, surface treatments such as corona treatment, plasma treatment, and saponification treatment can also be performed.

After the polarizer 5 and the optical film 1 are bonded together, the adhesive layer 6 can be formed by curing the adhesive according to the type of the adhesive. When a water-based adhesive is used, the adhesive can be hardened by heating and drying. When an active energy ray hardening type adhesive is used, the adhesive can be hardened by irradiating active energy rays such as electron beams or ultraviolet rays. If a photocationic polymerizable adhesive is provided on the easy-slip layer 15, photoactive species (cations or Lewis acids) are easily deactivated by the action of residual alkali components in the easy-slip layer, and polymerization may be hindered. Therefore, when a photocationic polymerizable adhesive or a photocationic/photoradical hybrid adhesive is used as the adhesive layer 6, as shown in FIG. fit.

＜Transparent protective film＞ The transparent protective film 2 can also be attached to the second main surface of the polarizer 5 through the adhesive layer 7 . As the transparent protective film 2, an arbitrary and appropriate transparent film can be used. The thickness of the transparent protective film 2 is about 5-200 μm. From the viewpoints of mechanical strength, transparency, and handling properties, the thickness of the transparent protective film 2 is preferably 10 to 100 μm, preferably 15 to 60 μm. The thicknesses of the optical film 1 and the transparent protective film 2 may be the same or different from each other.

The materials for forming the transparent protective film 2 include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); Cellulose-based polymers such as acyl cellulose or triacetyl cellulose; styrene-based polymers such as polystyrene or acrylonitrile-styrene copolymer; cyclic polyolefins such as polynorbornene; polycarbonate, etc.

The transparent protective film 2 may also have an easy-slip layer (not shown). The same easy-slip layer as the easy-slip layer 15 of the optical film 1 can also be provided on the transparent protective film 2 .

The adhesive layer 7 for bonding the polarizer 5 and the transparent protective film 2 can use various types of adhesives such as water-based adhesives, solvent-based adhesives, hot-melt adhesives, and active energy ray-curable adhesives. The same adhesive composition can also be used for the adhesive layer 6 and the adhesive layer 7 .

[Use of polarizing plate] An adhesive layer for bonding to a liquid crystal cell, an organic EL cell, etc. may also be provided on the polarizing plate. The adhesive for forming the adhesive layer can be suitably selected from acrylic polymer, polysiloxane polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer as the base polymer. Among them, acrylic adhesives are particularly suitable from the viewpoints of being excellent in optical transparency, exhibiting moderate wettability and cohesiveness, and being excellent in weather resistance, heat resistance, and the like.

Attaching the adhesive layer to the polarizing plate can be performed in a suitable manner. For example, a method of dissolving or dispersing a base polymer or the like in a solvent such as toluene or ethyl acetate to prepare an adhesive solution with a solid content concentration of about 10 to 40% by weight, and attaching it to a polarizing plate, or forming it on a polarizing plate can be used. The method of transferring the adhesive layer on the suitable substrate to the polarizing plate, etc.

Adhesive layers can also be provided on both sides of the polarizing plate. When the adhesive layers are arranged on both sides of the polarizing plate, the composition and thickness of the adhesive layers on the front and back can be the same or different from each other. The thickness of the adhesive layer is generally about 5 to 500 μm.

For the purpose of preventing the contamination of the adhesive layer, a separator can also be temporarily provided on the surface of the adhesive layer. Separation parts should be treated with release agents such as polysiloxane-based mold release agents, long-chain alkyl-based mold release agents, and fluorine-based mold release agents on the surface of plastic films.

The polarizing plate may also be a laminated polarizing plate laminated with other optics. Examples of the optical layer include retardation plates, viewing angle compensation films, and brightness enhancement films.

An image display device can be formed by attaching a polarizing plate to the surface of an image display unit such as a liquid crystal cell or an organic EL cell. The liquid crystal display device can be formed by appropriately assembling components such as a liquid crystal cell, a polarizer, and an illumination system as required, and incorporating a driving circuit and the like. In the organic EL display device, the circular polarizing plate formed by attaching the polarizing plate of the present invention and the retardation film (typically a 1/4 wavelength plate) to the surface of the organic EL unit can reduce the reflected light factor of external light. The metal electrode waits and then emits to improve the visibility. Example

The following examples are given to illustrate the present invention more specifically, but the present invention is not limited to these examples. The description of the symbol "%" below means % by weight unless otherwise specified.

唑啉之聚合物水溶液(日本觸媒製「Epocros WS-700」)5.2重量份、1重量%之氨水2.8重量份、平均一次粒徑35nm之膠質氧化矽的20%水分散液(扶桑化學工業製「Quartron PL-3」)7.5重量份及純水63.9重量份混合，而調製出易滑層形成用組成物。該組成物係相對於固體成分100重量份含有15.3重量份二氧化矽粒子之濃度9.8%的水溶液。在以下的實施例及比較例中，係使用該組成物來形成易滑層。 [Preparation of a composition for forming an easy-slip layer] A solid containing polyester urethane and isophorone diisocyanate as resin components and further containing triethylamine as a hardening catalyst and methyl ethyl ketone as a dispersing medium 20.6 parts by weight of water-based polyurethane ("SuperFlex 210R" manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) with a composition of 34% and a solid content of 25%

Aqueous polymer solution of oxazoline ("Epocros WS-700" manufactured by Nippon Shokubai Co., Ltd.) 5.2 parts by weight, 2.8 parts by weight of 1% by weight ammonia water, 20% aqueous dispersion of colloidal silica with an average primary particle size of 35nm (Fuso Chemical Industry Co., Ltd. 7.5 parts by weight of "Quartron PL-3") and 63.9 parts by weight of pure water were mixed to prepare a composition for forming an easy-slip layer. This composition is an aqueous solution with a concentration of 9.8% containing 15.3 parts by weight of silica particles with respect to 100 parts by weight of solid content. In the following Examples and Comparative Examples, the composition was used to form an easy-slip layer.

[Example 1] An optical film was produced using a film production apparatus equipped with a melt extrusion film forming apparatus, a gravure coater, a tenter-type simultaneous biaxial stretching apparatus, and a winding apparatus. As the acrylic resin, pellets of the same imidized MS resin (glass transition temperature: 120°C) as described in the Example of Japanese Patent Laid-Open No. 2017-26939 for producing the "transparent protective film 1A" were used . The acrylic resin was melted and extruded from a T-die, formed into a film with a thickness of 160 μm, and the above composition was coated on one side of the film with a wet thickness of about 9 μm using a gravure coater, and heated in a heating furnace with a temperature of 140 ° C. The long-side direction (MD) and the width-direction (TD) were respectively stretched twice by a simultaneous biaxial stretching tenter to obtain an optical film with an easy-slip layer with a thickness of 50 nm on one side of an acrylic film with a thickness of 40 μm.

[Examples 2 to 4 and Comparative Examples 1 and 2] An optical film was obtained in the same manner as in Example 1, except that the coating thickness of the composition for forming an easy-slip layer was changed. The thickness of the easy-slip layer (after extension) is shown in Table 2.

[Examples 5, 6 and Comparative Examples 3 to 5] The furnace temperature (stretching temperature) during stretching of the tenter was changed as shown in Table 2. An optical film was obtained in the same manner as in Example 1 except that the stretching temperature was changed.

[Make a polarizer] (Production of polarizer) A long roll of polyvinyl alcohol (PVA)-based resin film (“PE4500” manufactured by Kuraray Co., Ltd.) with a thickness of 45 μm was uniaxially stretched in the longitudinal direction with a roll stretcher so that the longitudinal direction was 5.9 times. At the same time, the swelling bath, dyeing bath, cross-linking bath 1, cross-linking bath 2 and cleaning bath shown in Table 1 were transported in sequence, and then dried at 70°C for 5 minutes to produce a polarizer with a thickness of 18 μm. The iodine concentration and potassium iodide concentration in the dye bath were adjusted so that the monomer transmittance of the polarizer was 43.4%.

[Table 1]

(Preparation of UV-curable adhesive) Prepared to contain 40 parts by weight of N-hydroxyethyl acrylate and 60 parts by weight of acryl molyfrin as curable components, and 2-methyl-1-(4-methylphenylthio) as a polymerization initiator )-2-Mofulinylpropan-1-one ("IRGACURE 819" manufactured by BASF) 3 parts by weight of UV-curable adhesive.

(Lamination of polarizer and polarizer protective film) As the polarizer protective film on one side, the optical films of the Examples and Comparative Examples were used, and the polarizer protective film on the other side was a biaxially stretched cyclic polyolefin film (Japan "ZeonorFilm ZF-14" manufactured by ZEON). The above-mentioned UV-curable adhesive was coated with a thickness of about 1 μm on the easy-slip layer-forming surface of the optical film and the surface of ZeonorFilm, and was attached to the polarizer by a roller press, and then irradiated with ultraviolet rays with a cumulative light intensity of 1000/mJ/cm ² . The adhesive was cured to obtain a polarizing plate having an acrylic film (optical film) on one side of the polarizer and ZeonorFilm on the other side.

[Evaluate] ＜Alkali residue in easy-slip layer＞ The amount of triethylamine and ammonia remaining in the easy-slip layer was quantified. The residual amount of triethylamine was quantified by the gas chromatography mass spectrometry (GC/MS) method of the solution after weighing and dissolving the powder of the easy-slip layer from the optical film surface and dissolving it in methanol. The residual amount of ammonia is obtained by immersing the optical film in pure water at 25°C, heating and extracting it in a dryer at 120°C for 60 minutes, and then quantitatively eluting ammonia in water by ion chromatography. The total of the amount of triethylamine and the amount of ammonia was defined as the alkali residual amount.

＜Adhesion of easy-slip layer＞ Crimp adhesive tape ("No.31B" manufactured by Nitto Denko) on the easy-slip layer forming surface of the optical film at a line pressure of 8kg/m and a crimping speed of 0.3m/min, and store it at 50°C for 48 hours before holding the adhesive. The front end of the tape was subjected to a 180° peel test at a tensile speed of 30 m/min, and the adhesion of the easily bonding layer was determined according to the following criteria. 〇: The easy-slip layer was not peeled off from the acrylic film but was peeled off at the interface between the adhesive tape and the easy-slip layer ×: Peeling occurred at the interface between the acrylic film and the easy-slip layer

＜Visual evaluation＞ The surface of the optical film was observed with the naked eye, and the presence or absence of local turbidity (increase in haze) caused by the aggregation of silica particles and the presence or absence of damage on the non-slippery layer non-formation surface were evaluated. 〇: No aggregation of silica particles, good in-plane uniformity, and no injuries were found △: No turbidity due to aggregation of silica particles, but damage with a depth of 1 μm or less was confirmed on the non-slippery layer non-formation surface ×: Cloudy due to aggregation of silica particles and damage to the non-formation surface of the easy-slip layer confirmed

<With or without interface layer> The cross section of the optical film was observed with a transmission electron microscope (TEM), and at the interface between the acrylic film and the easy-slip layer, it was confirmed whether or not particles in the easy-slip layer were embedded in the region (interface layer) of the acrylic film. FIG. 3 shows the TEM observation image of Example 3 (with the interface layer), and FIG. 4 shows the TEM observation image of the Comparative Example 4 (without the interface layer).

＜Wetting durability of polarizers＞ After cutting the polarizing plate into a size of 320 mm×240 mm, the surface on the side of the cyclic polyolefin film was pasted to the glass through an acrylic adhesive with a thickness of 20 μm. The sample was placed in a constant temperature and humidity tank with a temperature of 60°C and a relative humidity of 90% (condition 1), or a constant temperature and humidity tank with a temperature of 85°C and a relative humidity of 85% (condition 2), and kept for 500 hours to carry out heating, Humidification durability test.

The degree of polarization P ₀ before the durability test and the degree of polarization P after the durability test were measured, and the amount of change in the degree of polarization ΔP=|PP ₀ | was calculated. In addition, after the polarizing plate after the endurance test was arranged to be crossed polarized light, the presence or absence of rib-like unevenness was checked with the naked eye, and the evaluation was made according to the following criteria. ⊚: No uneven streak was observed in the samples after the durability test of Condition 1 and Condition 2. ○: No uneven streak was observed in the sample after the durability test of Condition 1, and the sample after the durability test of Condition 2 Slightly uneven streaks can be seen △: Slightly uneven streaks can be seen in the samples after the endurance test of Condition 1 and Condition 2 ×: The samples after the endurance test of Condition 1 and Condition 2 can be clearly seen uneven streaking

Table 2 shows the production conditions (stretching temperature and the thickness of the easy-slip layer after stretching) of the optical films of the Examples and Comparative Examples, the evaluation results of the optical films (the naked eye, the adhesion, the presence or absence of the interface layer), and the polarizing plates. Endurance test results (with or without uneven streaks and change in degree of polarization ΔP).

[Table 2]

The optical film of Comparative Example 2 with the easy-slip layer having a thickness of 350 nm has good adhesion between the acrylic film and the easy-slip layer, and the appearance of the optical film is also good. However, the polarization degree after the humidification endurance test of the polarizing plate using this optical film as a polarizer protective film was significantly decreased, and it was confirmed that there was a significant streak-like unevenness. In Comparative Examples 3 to 5, the elongation temperature (the heating temperature during the formation of the easy-slip layer) was 120° C. or lower, and the polarization degree decreased significantly after the humidification endurance test as in Comparative Example 2, and it was confirmed that there was a significant rib-like defect. all.

Examples 1 to 4 are optical thin films in which an easy-slip layer of 50 nm to 250 nm was formed at the stretching temperature of 140° C., and no cloudiness due to aggregation of fine particles was seen in the optical films, which showed good appearance. In addition, in the optical film of Example 1, fine damage was found on the non-slippery layer non-formation surface, but the damage was buried by an adhesive or an adhesive when it was bonded to other members, and did not constitute an optical defect. Furthermore, the polarizing plates using the optical films of Examples 1 to 4 were more excellent in humidification durability than the polarizing plates using the optical film of Comparative Example 2, and the occurrence of uneven streaks was suppressed.

In Comparative Example 1, an easy-slip layer with a thickness of 30 nm was formed, and the humidification durability of the polarizing plate of the optical film was good, but cloudiness caused by the aggregation of silica fine particles and damage to the non-formed surface of the easy-slip layer were confirmed, and the appearance was poor. . We believe that the damage occurs because the decrease in dispersibility causes the silica particles to fall off the surface of the easy-slip layer, resulting in a decrease in the smoothness of the optical film.

From the comparison of Examples 1 to 4 with Comparative Examples 1 and 2, it can be seen that the thickness of the easy-slip layer is small and the residual alkali component is less, the uneven streak after the humidification durability test can be suppressed, and the humidification durability can be obtained. Excellent polarizer. In addition, it is also known that when the thickness of the easy-slip layer is too small and the residual alkali component is too small, the dispersibility of the fine particles is lowered, and the appearance is poor or the smoothness is lowered.

Examples 5 and 6 formed an easy-slip layer with a thickness of 200 nm at the stretching temperature of 160° C. or 180° C., and were excellent in the appearance of the optical film and the humidification durability of the polarizing plate, as in Example 3. On the other hand, in Comparative Examples 3 to 5, an easy-slip layer with a thickness of 200 nm was formed at an extension temperature of 80 to 120°C, and the easy-slip layer had a large amount of alkali residue, and the same polarizing plate as in Comparative Example 2 was confirmed after the humidification durability test. There are obvious uneven streaks.

From these results, it was found that by reducing the alkali residue in the easy-slip layer within a range that does not reduce the dispersibility of the fine particles, an optical film excellent in humidification durability of the polarizing plate when used as a polarizer protective film can be obtained.

Comparative Examples 3 to 5 are stretched at low temperature, and compared with other examples, the adhesion between the acrylic film and the easy-slip layer is poor. In Example 3 and the like, an interface layer in which particles are embedded in the acrylic film is formed at the interface between the acrylic film and the easy-slip layer (see FIG. 3 ); on the other hand, in Comparative Examples 3 to 5, the interface layer was not formed. interface layer (see Figure 4). From these results, it can be seen that by increasing the heating temperature after applying the composition for forming an easy-slip layer, the alkali component in the composition for forming an easy-slip layer can be effectively volatilized to reduce the residual amount of alkali, and the film substrate can be improved. Adhesion to the interface of the slippery layer.

1: Optical film 2: Transparent protective film 5: Polarizer 6, 7: Adhesive layer 11: Film substrate 15: Easy slip layer 100, 101: polarizer

FIG. 1 is a cross-sectional view showing a configuration example of an optical film provided with an easy-slip layer. 2A is a cross-sectional view showing a configuration example of a polarizing plate. 2B is a cross-sectional view showing a configuration example of a polarizing plate. FIG. 3 is a cross-sectional TEM observation image of an optical film with an interface layer formed at the interface between the film substrate and the easy-slip layer. FIG. 4 is a cross-sectional TEM image of the optical film without forming an interface layer at the interface between the film substrate and the easy-slip layer.

1: Optical film

11: Film substrate

15: Easy slip layer

Claims (9)

A polarizing plate comprising a polyvinyl alcohol-based polarizer and an optical film, the polyvinyl alcohol-based polarizer having a first main surface and a second main surface, and the optical film is attached to the first main surface of the polarizer through an adhesive layer noodle, The aforementioned optical film has an easy-slip layer on the surface of the transparent film substrate, The aforementioned easy-slip layer contains binder resin and inorganic fine particles, The total content of amine and ammonia in the aforementioned easy-slip layer is 5 to 75 ppm, and The non-formed surface of the easy-slip layer of the optical film is attached to the first main surface of the polarizer. The polarizing plate of claim 1, wherein the non-slippery layer of the optical film is pasted on the first side of the polarizer through a photocationic polymerizable adhesive or a hybrid adhesive of photocationic polymerization and photoradical polymerization. a main side. The polarizing plate of claim 1 or 2, wherein the thickness of the aforementioned easy-slip layer is 40-280 nm. The polarizing plate of claim 1 or 2, wherein at the interface between the transparent film substrate and the easy-slip layer, there is a region in which the inorganic fine particles are embedded in the transparent film substrate. The polarizing plate of claim 1 or 2, wherein the average primary particle size of the inorganic fine particles is 10-250 nm. The polarizing plate according to claim 1 or 2, wherein the content of the inorganic fine particles in the easy-slip layer is 3 to 50% by weight. The polarizing plate according to claim 1 or 2, wherein the transparent film substrate is an acrylic film. The polarizing plate of claim 1 or 2, wherein the binder resin of the easy-slip layer is a urethane resin. An image display device has an image display unit and the polarizing plate according to any one of claims 1 to 8.

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