TW202012979A - 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 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. In addition, the present invention relates to a polarizing plate having an optical film provided with an easy-slip layer 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 or organic EL display devices have been widely used as various image display devices such as mobile devices, car navigation devices, personal computer monitors, and televisions. Based on the display principle of the liquid crystal display device, a polarizing plate is arranged on the surface of the liquid crystal cell on the viewing side. In the transmissive liquid crystal display device, polarizing plates are arranged on both sides of the liquid crystal cell. In order to prevent external light from being reflected by a metal electrode (cathode) and appearing to be a mirror surface in an organic EL display device, a circular polarizing plate (typically a laminate of a polarizing plate and a 1/4 wavelength plate) is sometimes arranged on the surface on the viewing side.

The polarizing plate generally has a transparent film (polarizer protective film) on one or both sides of the polarizer, and its purpose is to protect the polarizer and the like. Nowadays, a polarizer is widely used in which polyvinyl alcohol (PVA) film adsorbs iodine and orients molecules by stretching or the like.

As for the polarizer protective film attached to the surface of the polarizer, a polarizer with a low moisture permeability film composed of resin materials such as acrylic, polyester, polycarbonate, cyclic polyolefin, etc., even if exposed for a long time In a high-humidity environment, the change in optical characteristics is still small, and tends to have excellent durability. Patent Document 1 describes that by providing a slippery layer containing fine particles and a binder resin on the surface of an acrylic film, it is possible to suppress adhesion when the film is wound into a roll. The embodiment of Patent Document 1 discloses a polarizer protective film, which is provided with silicon dioxide fine particles containing 1 to 7% by weight on the surface of the acrylic film and has an average thickness of 400 nm (thickness range 300 to 500 nm) Urethane resin layer.

Prior technical literature Patent Literature Patent Literature 1: Japanese Patent No. 5354733

Summary of the invention Problems to be solved by invention As the image display device progresses toward larger size or higher brightness, the polarizing plates constituting the image display device have also become required to have little change in optical characteristics even under severe environments (such as higher temperature and high humidity conditions) . However, it has been confirmed that there is a new problem: if a polarizing plate with a polarizer protective film disclosed in Patent Document 1 is exposed to a high humidity environment for a long period of time, it will produce optical defects such as ribs and unevenness, 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 is less likely to cause adhesion and hardly cause optical defects even when exposed to a high temperature and high humidity environment for a long time.

Means to solve the problem In view of the above-mentioned problems, the present inventors have studied and found that, for the purpose of improving the dispersibility of fine particles, etc., alkali components such as ammonia or amine added to the composition for forming an easy slip layer remain in the easy adhesion layer. One of the reasons for the decrease in durability in wet environments, and found that by setting the residual amount of alkali in the slippery layer within a predetermined range, the above-mentioned problems can be solved.

The 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 slippery layer contains binder resin and fine particles. The average primary particle size of the microparticles is, for example, 10 to 250 nm, preferably 10 to 100 nm. The content of alkali component of the easy-slip layer should be 5~75ppm. The thickness of the easy-slip layer should be 40~280nm.

As the transparent film substrate, an acrylic film or the like can be used. For the binder resin of the slippery layer, urethane resin can be used. The content of fine particles in the slippery layer is preferably about 3 to 50% by weight, and more preferably 10 to 50% by weight. The particles of the easy-slip layer can be buried in the transparent film substrate.

The composition for forming the slippery layer is coated on the surface of the transparent film substrate and heated to form the slippery layer. The composition for forming the slippery layer contains a binder resin or its precursor, fine particles, an alkali component, and a solvent. By containing the alkali component in the composition for forming the slippery layer, the dispersibility of the fine particles can be improved, and an optical film excellent in smoothness can be obtained. Moreover, the alkali component can also act as a catalyst to promote the reaction of the binder resin (precursor). From the viewpoint of using heat to promote volatilization of the alkali component, the boiling point of the alkali component is preferably 150°C or lower. Examples of the alkali component include amine and ammonia.

By increasing the heating temperature after applying the composition for forming the slippery layer, the volatilization of the alkali component can be promoted to form a slippery layer with little residual alkali component. For example, the composition for forming the slippery layer may 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 particles forming the slippery layer can be easily buried in the area of the transparent film substrate, and the adhesion between the transparent film substrate and the slippery layer tends to increase.

After the composition for forming an easy-slip layer is coated on the transparent film substrate, the transparent film substrate may be stretched while being heated. In particular, by heating the composition for forming the slippery layer at a temperature higher than the glass transition temperature of the transparent film substrate by 10° C. or more, the transparent film substrate is extended to allow the transparent film substrate and the slippery layer Tendency to improve the tightness.

The easy-slip layer also helps to improve adhesion to other films or glass substrates. The optical film can be used as a polarizer protective film, for example. For example, a polarizing plate can be produced by attaching an optical film to the surface of the polyvinyl alcohol polarizer through an adhesive layer. The optical film can bond any one of the easy-adhesive layer forming surface and the easy-adhesive layer non-forming surface to the polarizer. A polarizing plate is arranged on the surface of an image display unit such as a liquid crystal display unit or an organic EL unit to form an image display device.

Invention effect The optical film of the present invention has good adhesion, is not easy to cause adhesion, and is not easy to generate optical defects even when 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.

Forms 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 has 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. The optical film is used for bonding with other films or glass substrates.

As for the use form of the optical film, a polarizer protective film can be cited. 2A and 2B are cross-sectional views showing a configuration example of a polarizing plate provided with 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 principal 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 polarizer 5 of the film base 11. In the polarizing plate 101 shown in FIG. 2B, the polarizer 5 is attached to the surface of the optical film 1 where the slippery layer 15 is not provided. In the polarizing plate 100 shown in FIG. 2A and the polarizing plate 101 shown in FIG. 2B, the transparent protective film 2 is bonded to the other surface (second main surface) of the polarizer 5 through the adhesive layer 7.

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

>Film substrate> The film substrate 11 is preferably a transparent film. The total light transmittance of the transparent film substrate should be above 80%, preferably above 85%, and more preferably above 90%. Examples of the resin material constituting the film substrate 11 include acrylic resin, polyester resin, polycarbonate resin, polyolefin resin, cyclic polyolefin resin, polystyrene resin, polyamide resin, poly Acetyl imide resin, etc. When the optical film is used as a protective film for an optically isotropic polarizer, since the birefringence is small, the resin material of the film substrate 11 is preferably acrylic resin or cyclic polyolefin resin, and acrylic resin is particularly preferable.

Examples of the cyclic polyolefin resins include polynorcamene. Examples of commercially available cyclic polyolefin resins include Zeonor and ZEONEX manufactured by ZEON in 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 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.

For the acrylic resin, an acrylic resin 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. may be used; and/or Japan JP-A 2000-230016, JP-A 2001-151814, JP-A 2002-120326, JP-A 2002-254544, JP-A 2005-146084 and the like have lactones Acrylic resin with ring structure. Acrylic resins with glutaric anhydride structure and acrylic resins with lactone ring structure have high heat resistance, high transparency and high mechanical strength, so they are suitable for manufacturing 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 50% by weight or more, preferably 60 to 98% by weight, and more preferably 70 to 97% by weight. The acrylic film may contain a thermoplastic resin other than acrylic resin. For example, by blending other thermoplastic resins, the birefringence of the acrylic resin can be eliminated to obtain an acrylic film with excellent optical isotropy. In addition, in order to enhance the mechanical strength of the film, etc., thermoplastic resins other than acrylic resins may also be blended.

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, poly lanthanum, polyether lanolin, polyoxybenzylene (polyoxybenzylene), polyamidimide, 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, slip agents, fillers and the like. It is also possible to mix a resin material with additives, etc., and make a thermoplastic resin composition such as pellets in advance, and then thin the film.

The thickness of the film substrate 11 is about 5 to 200 μm. From the viewpoint of mechanical strength, transparency, and handleability, the thickness of the film substrate 11 is preferably 10 to 100 μm, and 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 Improve heat resistance. The upper limit of Tg of the film substrate 11 is not particularly limited, but from the viewpoint of formability and the like, it is preferably 170°C or lower.

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

<Easy slip layer> The easy-slip layer 15 provided on the surface of the film substrate 11 contains a binder resin and fine particles. Since the slippery layer 15 contains fine particles, fine irregularities can be formed on the surface of the slippery layer 15 to improve the smoothness of the film. Therefore, it helps to reduce the damage of the optical film 1 when it is transported by a roller 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, binder resins can be used polyurethane resins, epoxy resins, isocyanate resins, polyester resins, and molecules containing Amine-based polymers, with

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

Urethane resin represents the reaction product of polyol and polyisocyanate. For the polyol component, polymer polyols such as polypropylene polyol, polyester polyol, polyether polyol, etc. are preferably used.

Polypropylene acrylate polyol can be obtained by polymerizing (meth)acrylate and hydroxyl-containing monomer. Examples of (meth)acrylates include methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate. Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. , 4-hydroxybutyl (meth)acrylate, 2-hydroxypentyl (meth)acrylate and other hydroxyalkyl esters of (meth)acrylic acid; glycerin, trimethylolpropane and other polyols (meth)acrylic acid monoester ; N-hydroxymethyl (meth) acrylamide and so on.

The polypropylene polyol may also 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; (methyl ) 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.

Polyester polyol can be produced by the reaction of polyacid and polyhydric alcohol. The polybasic acid includes phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalene dicarboxylic acid, 2,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, biphenyl dicarboxylic 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, Aliphatic dicarboxylic acids such as dodecane dicarboxylic acid, octadecane dicarboxylic acid, tartaric acid, alkyl succinic acid, linolenic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, and itaconic acid; Alicyclic dicarboxylic acids such as hexahydrophthalic acid, tetrahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid; or anhydrides, alkyl esters, etc. Reactive derivatives such as acetyl halide.

Polyols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 1,6-hexane Glycol, 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 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 oxide. Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, and trimethylolpropane. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, benzene ethylene oxide, and tetrahydrofuran.

Examples of polyisocyanates include tetramethylene diisocyanate, dodecyl diisocyanate, 1,4-butane diisocyanate, hexamethylene diisocyanate, 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 stubble diisocyanate, 4,4′-cyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methyl ring Cyclohexyl diisocyanate, 1,3-bis(isocyanate methyl) cyclohexane and other alicyclic diisocyanates; benzylidene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenyl Methane diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 4,4′-dibenzyl diisocyanate, 1,5-naphthyl diisocyanate , Aromatic diisocyanates such as stubble diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate; dialkyl diphenylmethane diisocyanate, tetraalkyl diphenylmethane diisocyanate, α,α,α,α-Tetramethyl stubble diisocyanate and other aromatic aliphatic diisocyanate.

The urethane resin constituting the slippery 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 by, for example, reacting a polyol, polyisocyanate, and a chain extender having a free carboxyl group. Examples of the chain extender having a free carboxyl group include dihydroxycarboxylic acid and dihydroxysuccinic acid. Examples of dihydroxycarboxylic acids include dimethylol alkanoic acid (such as dimethylol acetic acid, dimethylol butanoic acid, dimethylol propionic acid, dimethylol butanoic acid, and dimethylol pentanoic acid) Such as dialkylol alkanoic acid (dialkylol alkanoic acid) and so on.

The production method of the urethane resin is not particularly limited, and may be any one of a single-shot method for reacting monomer components at one time and a multi-stage method for reacting monomer components in stages. When using a chain extender with a free carboxyl group 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 to 600,000, preferably 10,000 to 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. Since the urethane resin is introduced into the cross-linked structure, there is a tendency that the adhesion between the slippery layer 15 and the film substrate 11 and the hardness of the slippery layer 15 are improved. The cross-linking agent can be used without particular limitation to react with the cross-linkable functional group of the urethane resin. When the urethane resin has a carboxyl group, amine groups,

Crosslinking agents such as oxazoline, epoxy, carbodiimide, etc. Among these

A crosslinking agent of oxazoline is suitable.

The reactivity of the oxazoline group with the carboxyl group at room temperature is small, so the life span after mixing with the urethane resin is long, and the lead time of the step can be elastically handled.

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 cross-linking agent is preferably an acrylic polymer and has

The oxazoline-based acrylic polymer is particularly preferred.

The use amount of the crosslinking agent is preferably 1 to 30 parts by weight, and preferably 3 to 20 parts by weight with respect to 100 parts by weight of the urethane resin.

(Fine particles) Since the easy-slip layer 15 contains fine particles, a fine concave-convex shape 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. From the viewpoint of forming irregularities that contribute to improving smoothness, the particle diameter (average primary particle diameter) of the fine particles is preferably 10 nm or more, preferably 15 nm or more, and more preferably 20 nm or more. The average primary particle size of the microparticles should be less than the thickness of the slip layer. The particle size of the fine particles is smaller than the thickness of the slippery layer, thereby suppressing the shedding of fine particles from the slippery layer. The particle size of the fine particles is preferably 250 nm or less, and preferably 200 nm or less. Furthermore, by making the average primary particle diameter of the fine particles smaller than the wavelength of visible light, it is possible to suppress the scattering of visible light at the interface between the binder resin and the fine particles. From the viewpoint of improving transparency, the particle diameter of the fine particles is preferably 100 nm or less, preferably 80 nm or less, more preferably 60 nm or less, and particularly preferably 50 nm or less.

The fine particles of the easy-adhesion layer 15 may be either inorganic fine particles or organic fine particles. From the viewpoint of excellent dispersibility and uniformity of particle size, the fine particles are preferably inorganic fine particles. Examples of inorganic fine particles include inorganic oxides such as titanium dioxide, aluminum oxide, and zirconium dioxide; calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, etc. . Among these, inorganic oxides are preferred. Examples of the organic fine particles include polysiloxane resins, fluorine resins, and acrylic resins. In order to suppress the light scattering caused by the fine particles, the refractive index difference between the binder resin (generally, the refractive index is about 1.5) and the fine particles should be small. From the viewpoint of a small refractive index difference with the binder resin and excellent dispersibility, the fine particles of the slippery layer 15 are preferably silica particles.

When forming the slippery layer 15 from the water-based composition, it is preferable to use fine particles with high water dispersibility. The aqueous dispersion of fine particles can also be blended into the composition. In order to improve the dispersibility of the fine particles, it is preferable to add an alkali component such as amine or ammonia to make the composition for forming the slippery layer weakly alkaline.

Colloidal silica is suitable for water-dispersible silica particles. For colloidal silica, the Quartron PL series made by Fuso Chemical Industry Co., Ltd., SNOWTEX series made by Nissan Chemical Industry Co., Ltd., AERODISP series and AEROSIL series made by Japan Aerosil Co., Ltd., and Seahostar KE series made by Japan Catalyst Co., Ltd., etc. can also be used. Sale.

Since the surface of the slippery layer 15 is formed with irregularities, the smoothness of the optical film 1 can be improved. From this point of view, the content of fine particles in the slippery layer 15 is preferably 3% by weight or more, preferably 5% by weight or more. In particular, when the thickness of the easy-slip layer 15 is small (for example, when it is below 280 nm), it is preferable to increase the content of fine particles and the amount of fine particles per unit area (quantity density), so that unevenness is uniformly formed on the surface of the easy-slip layer 15. The content of fine particles in the slippery layer 15 is preferably at least 8% by weight, preferably at least 10% by weight, and more preferably at least 12% by weight. If the content of the fine particles in the slippery layer 15 is too large, there is a fear that the light scattering at the interface between the binder resin and the fine particles will increase and the optical characteristics will deteriorate. Moreover, as the content of fine particles increases, the relative content of the binder resin will shrink accordingly, which may reduce the adhesion of the slippery layer. Therefore, the content of fine particles in the slippery layer 15 is preferably 50% by weight or less, preferably 40% by weight or less, and more preferably 30% by weight or less.

(Residual amount of alkali) If an alkali component such as amine or ammonia is used to improve the dispersibility of the microparticles, it is inevitable that the alkali component will remain in the slippery layer. When the optical film 1 is used as a polarizer protective film, residual alkali components of the slippery layer 15 may be eluted into water, and the alkali components penetrating the film substrate 11 may deteriorate the polarizer and reduce the polarization degree of the polarizer, or The occurrence 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 slippery 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 the amount of alkali residue of the slippery layer 15 is, the better.

On the other hand, if the residual amount of alkali in the slippery layer 15 is too small, the dispersibility of the fine particles will be impaired, and the appearance of white turbidity and the like may be generated due to aggregation of the fine particles. In addition, the fine particles may aggregate or fall off from the slippery layer due to a decrease in dispersibility, and it may not be possible to form appropriate irregularities on the surface of the slippery layer, which tends to decrease the smoothness of the optical film. Therefore, the residual alkali content of the slippery 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 slippery layer include amine and ammonia, and the total content of the amine and ammonia in the slippery layer is preferably within the above range. The amount of alkali in the slippery layer can be quantified by liquid chromatography or ion chromatography according to the type of alkali component. The analysis method (such as LC/MS) combined with chromatography analysis and mass analysis (MS) can also be used to quantify the alkali content. When a plurality of alkali components are contained in the slippery layer, the total of each component is the alkali component content (residual amount) of the slippery layer.

<Forming a slippery layer> The method for forming the slippery layer 15 on the surface of the film substrate 11 is not particularly limited. Ideally, the composition (coating liquid) for forming the slippery layer containing the binder resin and the fine particles is applied to the film substrate 11 and heated to form the slippery layer 15.

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

The composition for forming an aqueous slippery layer contains water as a solvent (and dispersion medium), a binder resin resin or its precursor, and fine particles. The composition for forming the slippery layer 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 aggregate easily. However, by containing an alkaline component such as ammonia or amine, the composition for forming an easy-slip layer can improve the dispersibility of the fine particles and obtain an optical film excellent in appearance and smoothness.

On the other hand, if the alkali contained in the composition for forming the slippery layer remains in the slippery layer, it may cause a decrease in the moisture and heat resistance of the polarizing plate. In particular, only a small amount of strong alkalis such as causticity may cause deterioration of the polarizer. Therefore, the alkali component contained in the composition for forming the slippery layer is preferably a weak alkali component such as ammonia or amine. From the viewpoint of improving both the dispersibility of the fine particles and preventing the deterioration of the polarizer, the pH of the composition (coating liquid) for forming the slippery layer 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 composition for forming the slippery layer is preferably 300 ppm or more, preferably 500 ppm or more with respect to the solid content of the composition for slippage layer formation. 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, so the amount of the alkali component contained in the composition for forming the slippery layer should be relative to the solid content of the composition for forming the slippery layer The component is 50,000 ppm or less, preferably 10000 ppm or less, and more preferably 5000 ppm or less. As described above, specific examples of the alkali component contained in the composition for forming the slippery layer include amine and ammonia, and the total content of these alkali components is preferably within the above range.

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

After coating the composition for forming the slippery layer on the film substrate and heating, the alkali component is volatilized to remove the residual alkali component of the slippery layer 15. From the viewpoint of using heat to promote volatilization of the alkali component, the boiling point of the alkali component contained in the composition for forming the slippery 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 particularly 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 the slippery layer contains a plurality of alkali components, it is preferable that the boiling point of at least one alkali component is within the above range, and it is more preferable that the boiling point of two or more alkali components is within the above range. With respect to 100 parts by weight of the total amount of alkali contained in the slippery layer, it is preferable that the boiling point of the alkali component of 50% by weight or more is within the above range. The boiling point of all the alkali components contained in the composition for forming the slippery layer is preferably within the above range.

The composition for forming the slippery layer may contain a cross-linking agent in addition to the binder resin (or its precursor), fine particles, and alkali components. The composition for forming the slippery layer may also contain catalysts such as crosslinking accelerators, antioxidants, ultraviolet absorbers, leveling agents, anti-blocking agents, antistatic agents, dispersion stabilizers, defoamers, tackifiers, Additives such as dispersants, surfactants, slip agents.

(Forming an easy slip layer on the film substrate) Before coating the composition for forming the slip layer on the film substrate 11, the surface treatment of the film substrate may be performed. By performing surface treatment, the wet tension of the film substrate can be adjusted to improve its adhesion to the slippery layer 15. The surface treatment may include corona treatment, plasma treatment, ozone blowing, ultraviolet irradiation, flame treatment, chemical treatment, etc. Among them, corona treatment or plasma treatment is suitable.

The coating method of the composition for forming the slippery layer includes a bar coating method, a roll coating method, a gravure coating method, a bar coating method, a narrow hole coating method, a curtain coating method, a fountain coating method, and the like. The composition for forming the slippery layer after coating is heated to remove the solvent, whereby the slippery layer 15 can be formed. It is also possible to harden the binder resin by reacting it with heat by heating. For example, when the composition for forming the slippery layer contains a crosslinking agent, the crosslinking reaction can be promoted by heating.

The heating temperature when forming the slippery 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 the slippery layer and effectively evaporating and removing the alkali component contained in the composition for forming the slippery layer, the heating temperature is preferably 100°C or more and 120°C or more Preferably, it is more preferably 130°C or higher, and particularly preferably 135°C or higher. In addition, the heating temperature is preferably higher than the boiling point of the alkali component contained in the composition for forming the slippery layer.

The heating temperature when forming the slippery layer is preferably 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 the slippery layer can be promoted, and the alkali component contained in the composition for forming the slippery layer can be effectively volatilized. The heating temperature is preferably higher than the Tg of the film substrate by 10°C or higher.

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

If the film substrate is heated at a temperature of Tg+10°C or higher, the film substrate will change from a glass state to a rubber state, and the surface becomes easily deformed, so it is easy to form a film at the interface between the film substrate 11 and the slippery layer 15 An interface layer in which the resin component of the base material and the component of the slippery layer are mixed. By forming the interface layer, the adhesion between the film substrate 11 and the slippery layer 15 tends to be improved.

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

It is also possible to form an easy-slip layer in the manufacturing step of the film substrate. Alternatively, the slip layer may be formed by heating when forming the film substrate. For example, when the film substrate is a stretched film, a composition for forming an easy-slip layer may be coated on the surface of the film before stretching or the film after longitudinal stretching, and when using a tenter for lateral stretching or simultaneous biaxial stretching Heating it to dry the solvent or harden the resin.

When the film substrate is stretched after applying the composition for forming the slippery layer, the stretch ratio is preferably 5 times or less, and preferably 4 times or less from the viewpoint of suppressing the occurrence of cracks and the like in the slippery layer. , Better than 3 times, especially better than 2.5 times. The lower limit of the stretch ratio is not particularly limited. From the viewpoint of improving the strength of the film, the stretch ratio is preferably 1.3 times or 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 perform stretching in the conveying direction (MD) and the width direction (TD) at the above-mentioned stretching magnification.

When biaxial stretching of the film substrate is performed, the biaxial stretching can be biaxially stretched sequentially or simultaneously. It can also be extended diagonally. When performing biaxial sequential stretching, the film can also be stretched in one direction (MD) by roll stretching as described above, and a composition for forming an easy-slip layer can be coated on the film, and it can be easy to slip when stretched by a tenter The composition for layer formation is heated.

As for the heating temperature of the easy-slip layer, the elongation temperature should be higher than the Tg of the film substrate, and Tg+10°C or higher is better, Tg+15°C or higher is better, and Tg+20°C or higher is better . In particular, it is preferable to extend in at least one direction at the above-mentioned temperature after applying the composition for forming the slippery layer. If it is stretched in a rubber state higher than the Tg of the film substrate, it is easy to form an area on the surface of the film substrate where the particles in the composition for forming the slippery layer are buried, and the film substrate 11 and the slippery layer 15 The tightness has a tendency to improve. The reason why stretching at a high temperature makes it easy to embed fine particles in the film substrate may include: if stretching is performed in a rubber state, the composition for forming an easy-slip layer tends to wet and diffuse when the film substrate is deformed, which is easy It becomes a state in which fine particles are embedded in concave portions of the surface irregularities formed during deformation. Furthermore, we believe that if the film is cooled while releasing the stress after stretching, the particles embedded on the surface of the film substrate will be fixed when the film substrate shrinks, so it is easy to form an area in which the fine particles are embedded in the film substrate.

By adjusting the solid content concentration and coating thickness of the composition for forming the slippery layer, the thickness of the slippery layer 15 can be adjusted. When the film base material is stretched after applying the composition for forming the slippery layer, the thickness of the slippery layer 15 can also be adjusted by the stretch magnification.

The thickness of the easy-slip layer 15 is not particularly limited, but it is preferably 280 nm or less, 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 more the tendency to improve the humidification durability of the polarizing plate.

When the composition for forming the slippery layer is heated and dried, if the alkali component is excessively removed, the dispersibility of the fine particles in the binder resin is reduced, and the fine particles are easily aggregated, or the resulting fine particles fall off the surface of the slippery layer, etc. . Once the aggregation or shedding of fine particles occurs, the smoothness of the optical film will decrease, and it is easy to cause damage during transportation or adhesion during winding. Therefore, the thickness of the easy-slip layer 15 is preferably 40 nm or more, preferably 50 nm or more, more preferably 80 nm or more, and particularly preferably 100 nm or more. 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.

[Polarizer] The polarizing plate may be provided with a transparent protective film on only one side of the polarizer, or as shown in FIGS. 2A and 2B on both sides of the polarizer 5. By attaching the above-mentioned optical film as a polarizer protective film on one side of the polarizer, a polarizing plate having a transparent protective film on only one side of the polarizer can be formed. The polarizing plate having polarizer protective films on both sides of the polarizer only needs to be bonded with the optical film on at least one side of the polarizer. The polarizing plate may be bonded with the above-mentioned optical film on both sides of the polarizer. The polarizer 5 and the optical film 1 can be bonded through the adhesive layer 6.

>polarizer> As the polarizer 5, a polyvinyl alcohol which allows a polyvinyl alcohol-based film such as polyvinyl alcohol and partially formalized polyvinyl alcohol to adsorb a dichroic substance such as iodine or a dichroic dye and orient it in one direction ( PVA) is a polarizer. For example, a PVA-based polarizer can be produced by applying iodine dyeing and stretching to a polyvinyl alcohol-based film.

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

As the polarizer 5, a thin PVA polarizer having a thickness of 10 μm or less can be used. Examples of thin polarizers include those described in Japanese Unexamined Patent Publication No. 51-069644, Japanese Unexamined Patent Publication No. 2000-338329, WO2010/100917 manual, Japanese Patent No. 4691205 Specification, Japanese Patent No. 4751581 Specification, etc. Polarizer. These thin polarizers can be produced by a manufacturing method including a step of extending a PVA-based resin layer and a resin substrate for extension in a state of a laminate, and a step of iodine dyeing. According to such a manufacturing method, even if the PVA-based resin layer is very thin, it is supported by the resin substrate for stretching, and therefore it can be stretched without being broken due to stretching.

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

As the adhesive, various types of adhesives such as an aqueous adhesive, a solvent adhesive, a hot-melt adhesive adhesive, and an active energy ray hardening adhesive can be used. Among these, from the viewpoint of reducing the thickness of the adhesive layer, an aqueous adhesive or an active energy ray-curable adhesive is suitable.

Examples of the polymer component of the water-based adhesive include vinyl polymer, gelatin, vinyl latex, polyurethane, polyester, epoxy, and the like. Among these, from the viewpoint of excellent adhesion to polarizers, vinyl polymers are preferred, and polyvinyl alcohol-based resins are particularly preferred. Among the polyvinyl alcohol-based resins, polyvinyl alcohol containing acetylacetoyl groups is suitable.

From the viewpoint of adhesiveness, the average degree of polymerization of the polyvinyl alcohol-based resin is preferably about 100 to 5,000, preferably 1,000 to 4,000. The average saponification degree 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 cross-linking agent. The crosslinking agent can be used for compounds having at least two polymers and reactive functional groups constituting the adhesive in one molecule. Examples of crosslinking agents for polyvinyl alcohol-based resins include alkylene diamines; isocyanates; epoxy resins; aldehydes; amine-formaldehyde such as methylolurea and methylolmelamine. Among these, amino-formaldehyde is suitable. The amino-formaldehyde resin is preferably a compound having methylol groups, and methylolmelamine is particularly preferred. The blending amount of the crosslinking agent in the adhesive composition is preferably about 10 to 60 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol-based resin, and preferably 20 to 50 parts by weight.

The active energy ray hardening type adhesive agent is an adhesive agent capable of performing 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, a photo-cationic polymerizable adhesive, or a mixture of a photo-cationic polymerization and a photo-radical polymerization in combination to initiate polymerization by ultraviolet irradiation, or a mixed molding adhesive Is 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。Examples of the monomer of the radical polymerizable adhesive include compounds having a (meth)acryloyl group and compounds having a vinyl group. Among them, the compound having a (meth)acryloyl group is preferred. Examples of the compound having a (meth)acryloyl group include C _1-20 chain alkyl (meth)acrylates, alicyclic alkyl (meth)acrylates, and polycyclic alkyl (meth)acrylates. Alkyl (meth) acrylate; hydroxyl-containing (meth) acrylate; epoxy (meth) acrylate and other epoxy-containing (meth) acrylate. The radically polymerizable adhesive may also contain hydroxyethyl (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N- Nitrogen-containing monomers such as ethoxymethyl (meth) acrylamide, (meth) acrylamide, (meth) acryl morpholin, etc. The radically polymerizable adhesive may contain tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylolpropane methylal acrylic as a crosslinking component Ester, di

Alkylene glycol diacrylate, EO modified diglycerol tetraacrylate and other multifunctional monomers.

Examples of the hardening component of the cationic polymerizable adhesive include compounds having epoxy groups or oxetanyl groups. 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 hardenable epoxy compounds can be used. Examples of ideal epoxy compounds include compounds having at least 2 epoxy groups and at least one aromatic ring in the molecule (aromatic epoxy compounds), or at least 2 epoxy groups in the molecule. And at least one of the compounds formed between two adjacent carbon atoms constituting the alicyclic ring (alicyclic epoxy compound). The cationic polymerizable adhesive contains a radically polymerizable compound such as a compound having a (meth)acryloyl group, and can also be used as a mixed molding adhesive.

The photocurable adhesive preferably contains a photopolymerization initiator. The photopolymerization initiator can also be appropriately selected depending on the type of reaction. For example, it is suitable for the radical polymerizable adhesive to be blended with a photo radical generator that can generate radicals by light irradiation as a photopolymerization initiator. It is suitable for the cationic polymerizable adhesive to be blended with a photocationic polymerization initiator (photoacid generator) that can generate a cationic species or a Lewis acid by light irradiation as a photopolymerization initiator. It is suitable to mix molding 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 monomer. In addition, when a radically polymerizable adhesive is used as an electron beam curing type, there is no special need for a photopolymerization initiator. In order to increase the hardening speed or sensitivity, a photosensitizer may be added to the active energy ray hardening type adhesive as required. The use 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 follow-up agent may also contain suitable additives as required. Examples of additives include silane coupling agents such as silane coupling agents and titanium silane coupling agents, adhesion promoters such as ethylene oxide, ultraviolet absorbers, anti-deterioration agents, dyes, processing aids, ion trapping agents, antioxidants, and adhesion Agents, fillers, plasticizers, leveling agents, foam inhibitors, antistatic agents, heat stabilizers, hydrolysis stabilizers, etc.

[Make polarizer] A polarizing plate can be manufactured by laminating the optical film 1 through the adhesive layer 6 on one surface (first main surface) of the polarizer 5. As shown in FIG. 2A, the optical film 1 can pass the adhesive layer and the polarizer 5 through the adhesive layer forming surface; as shown in FIG. 2B, the adhesive layer and the polarizer 5 can be transmitted through the non-slip layer forming surface fit.

The easy slip layer 15 can also function as an easy adhesion layer. As shown in FIG. 2A, when the polarizer 5 is attached to the forming surface of the easy-slip layer 15 of the optical film 1 through the adhesive layer 6, the easy-slip layer 15 helps to enhance the polarizer and the polarizer protection film (optical film 1) Continuity. As shown in FIG. 2B, when the non-slip layer is formed with the adhesive layer and the polarizer 5, the slip layer 15 helps to lift the other film, adhesive layer, glass substrate, etc. provided on the optical film 1 Of continuity.

When bonding the polarizer 5 and the optical film 1, it is preferable 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 roller press or the like Combine to harden the adhesive. The coating method for applying the adhesive composition to the polarizer 5 and/or the optical film 1 may be a roll coating method, a spray method, a dipping method, or the like. Before coating the adhesive composition on the surface of the polarizer 5 and/or the optical film 1, surface treatment such as corona treatment, plasma treatment, saponification treatment, etc. may also be performed.

After the polarizer 5 and the optical film 1 are bonded, the adhesive layer 6 can be formed by hardening the adhesive according to the type of the adhesive. When using an aqueous adhesive, the adhesive can be hardened by heating and drying. When using an active energy ray hardening type adhesive, the adhesive can be hardened by irradiating active energy rays such as electron beams or ultraviolet rays. If a photocationically polymerizable adhesive is provided on the slippery layer 15, the photoactive species (cation or Lewis acid) may be easily deactivated by the residual alkali component of the slippery layer, which may cause polymerization inhibition. Therefore, when using a photocationic polymerizable adhesive or a photocationic/photoradical mixed molding adhesive as the adhesive layer 6, as shown in FIG. 2B, it is preferable to make the non-slip layer forming surface of the optical film 1 and the polarizer 5 fit.

>Transparent protective film> The transparent protective film 2 may be attached to the second main surface of the polarizer 5 through the adhesive layer 7. The transparent protective film 2 can be any suitable transparent film. The thickness of the transparent protective film 2 is about 5 to 200 μm. From the viewpoints of mechanical strength, transparency, and handleability, the thickness of the transparent protective film 2 is preferably 10 to 100 μm, preferably 15 to 60 μm. The thickness of the optical film 1 and the transparent protective film 2 may be the same or different from each other.

Materials forming the transparent protective film 2 may include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc.; diethylene Cellulose polymers such as acetyl cellulose or triethyl acetyl cellulose; styrene polymers such as polystyrene or acrylonitrile/styrene copolymer; cyclic polyolefins such as polynorcamene; polycarbonate, etc.

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

For the adhesive layer 7 for bonding the polarizer 5 and the transparent protective film 2, various types of adhesives such as an aqueous adhesive, a solvent adhesive, a hot-melt adhesive adhesive, and an active energy ray hardening adhesive can be used. The same adhesive composition may be used for the adhesive layer 6 and the adhesive layer 7.

[Use of polarizer] The polarizing plate may also be provided with an adhesive layer for bonding to a liquid crystal cell or an organic EL cell. The adhesive forming the adhesive layer can be suitably selected from acrylic polymers, polysiloxane polymers, polyesters, polyurethanes, polyamides, polyethers, fluorine-based or rubber-based polymers as the base Polymers. Among them, acrylic adhesives are particularly preferred from the viewpoints of excellent optical transparency, moderate wettability and agglomeration, and excellent weather resistance and heat resistance.

Attaching an adhesive layer to the polarizing plate can be performed in a suitable manner. For example, a method of dissolving or dispersing a base polymer and 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 The method of transferring the adhesive layer on a suitable substrate to the polarizing plate, etc.

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

For the purpose of preventing contamination of the adhesive layer, a separation member may be temporarily provided on the surface of the adhesive layer. The separator should be coated on the surface of the plastic film with a silicone silicone release agent, a long-chain alkyl release agent, or a fluorine release agent.

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

By attaching a polarizing plate to the surface of an image display unit such as a liquid crystal unit or an organic EL unit, an image display device can be formed. The formation of the liquid crystal display device can be formed by appropriately assembling the liquid crystal cell, the polarizing plate, and the lighting system as required, and incorporating it into a driving circuit. In the organic EL display device, the circular polarizing plate combined with the polarizing plate of the present invention and the retardation film (typically a 1/4 wavelength plate) on the surface of the organic EL unit can reduce the reflected light of external light. The metal electrode etc. are emitted again to improve visibility. Examples

The following examples illustrate the present invention more specifically, but the present invention is not limited to these examples. The description of the following symbol "%" refers to the 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 composition for forming slippery layer] A solid containing polyester urethane and isophorone diisocyanate as a resin component, and further containing triethylamine as a curing catalyst and methyl ethyl ketone as a dispersion medium 34% of water-based polyurethane ("SuperFlex 210R" manufactured by First Industrial Pharmaceuticals) 20.6 parts by weight, 25% of solid content

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

[Example 1] A thin film manufacturing apparatus equipped with a melt extrusion film forming apparatus, a gravure coater, a tenter type simultaneous biaxial stretching apparatus, and a take-up apparatus is used to produce an optical film. As the acrylic resin, pellets of the same imidized MS resin (glass transition temperature: 120°C) as those described in the examples of Japanese Patent Laid-Open No. 2017-26939 for producing the "transparent protective film 1A" are used. . After the acrylic resin was melt-extruded from the T-die and formed into a film with a thickness of 160 μm, the above composition was applied on one side of the film with a wet thickness of about 9 μm using a gravure coater, and heated at a temperature of 140° C. The simultaneous biaxial stretching tenter stretches twice in the longitudinal direction (MD) and the width direction (TD), respectively, to obtain an optical film having 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 the slip layer was changed. The thickness of the slip layer (after extension) is shown in Table 2.

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

[Make polarizer] (Production of polarizer) A long roll of polyvinyl alcohol (PVA) resin film ("PE4500" manufactured by Kuraray Co., Ltd.) with a thickness of 45 μm was uniaxially stretched in the long-side direction by a roller stretcher to make the long-side direction 5.9 times, At the same time, the swelling bath, dyeing bath, cross-linking bath 1, cross-linking bath 2 and washing bath shown in Table 1 were transported in sequence, and 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 dyeing bath have been adjusted so that the monomer transmittance of the polarizer is 43.4%.

[Table 1]

(Modulated ultraviolet curing adhesive) It contains 40 parts by weight of N-hydroxyethyl acrylate amide and 60 parts by weight of acryloyl morpholin as a hardening component, and also contains 2-methyl-1-(4-methylphenylthio) as a polymerization initiator )-2-morpholinyl propan-1-one ("IRGACURE 819" manufactured by BASF) 3 parts by weight of ultraviolet curing adhesive.

(Lamination of polarizer and polarizer protective film) As the single-sided polarizer protective film, the optical films of the examples and comparative examples were used, and on the other side, the polarizer protective film used a biaxially stretched cyclic polyolefin film (Japan "ZeonorFilm ZF-14" manufactured by ZEON). Apply the above UV-curable adhesive to the surface of the easy-slip layer of the optical film and the surface of ZeonorFilm to a thickness of about 1μm and apply it to the polarizer with a roller press, then irradiate the accumulated light of 1000/mJ/cm ² The agent is hardened to obtain a polarizing plate having an acrylic film (optical film) on one side and a Zeonor Film on the other side.

[Evaluation] <Residual alkali residue> Quantify the amount of triethylamine and ammonia remaining in the slippery layer. The residual amount of triethylamine is measured by weighing out the powder of the slippery layer cut from the surface of the optical film and dissolving it in methanol, and then quantifying it by gas chromatography mass analysis (GC/MS) method. The residual amount of ammonia is to immerse the optical film in pure water at 25°C, heat-extract with a dryer at 120°C for 60 minutes, and quantify the ammonia dissolved in the water by ion chromatography analysis. The sum of the amount of triethylamine and the amount of ammonia was determined as the residual amount of alkali.

＜Adhesion of slippery layer＞ Adhere adhesive tape ("No.31B" manufactured by Nitto Denko) on the surface of the easy-slip layer forming surface of the optical film at a line pressure of 8 kg/m and a crimping speed of 0.3 m/minute, and store at 50°C for 48 hours, then hold 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 easy-adhesive layer was determined according to the following criteria. 〇: The slippery layer is not peeled off from the acrylic film, but peeled off at the interface between the adhesive tape and the slippery layer ×: If peeling occurs at the interface between the acrylic film and the slip layer

>Visual assessment> Observe the surface of the optical film with the naked eye to evaluate whether there is local turbidity (rising of haze) due to aggregation of silica particles and damage on the non-slip layer-forming surface. 〇: No agglomeration of silica particles, good in-plane uniformity, and no injuries were found △: Although there is no turbidity due to the aggregation of silicon dioxide particles, it is confirmed that there is a damage with a depth of 1 μm or less on the non-slip layer non-forming surface ×: Those who caused turbidity due to the aggregation of silica particles and confirmed that there was damage to the non-forming surface of the slippery layer

>With or without interface layer> The cross section of the optical film was observed with a transmission electron microscope (TEM), and it was confirmed at the interface between the acrylic film and the slippery layer whether particles in the slippery layer were buried in the area (interface layer) of the acrylic film. FIG. 3 shows the TEM observation image of Example 3 (with interface layer), and FIG. 4 shows the TEM observation image of Comparative Example 4 (without interface layer).

>Humidity durability of polarizer> After cutting the polarizing plate to a size of 320 mm×240 mm, the surface on the side of the ring-shaped polyolefin film is pasted onto the glass through an acrylic adhesive with a thickness of 20 μm. Put the sample into a constant temperature and humidity tank at a temperature of 60°C and a relative humidity of 90% (condition 1) or a constant temperature and humidity tank at a temperature of 85°C and a relative humidity of 85% (condition 2), and hold for 500 hours for heating, Humidity durability test.

The degree of polarization P ₀ before the endurance test and the degree of polarization P after the endurance test were measured, and the amount of change in the degree of polarization ΔP=|PP ₀ | was calculated. In addition, after disposing other polarizing plates on the polarizing plate after the endurance test to be orthogonally polarized, visually observe whether there are any ribbed unevenness, and evaluate according to the following criteria. ◎: No uneven streaks were observed in the samples after the endurance test of Condition 1 and Condition 2: No uneven streaks were observed in the samples after the endurance test of Condition 1, the samples after the endurance test of Condition 2 Visible slight unevenness of traces △: All samples after the endurance test of condition 1 and condition 2 can be visually distinguished ×: All samples after endurance test of conditions 1 and 2 can be clearly seen Uneven streaks

Table 2 shows the manufacturing conditions (elongation temperature and 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 (naked eye, adhesion, presence or absence of interface layers), and the polarizing plate Durability test results (with or without streak unevenness and change in polarization ΔP).

[Table 2]

In the optical film of Comparative Example 2 provided with an easy-slip layer with a thickness of 350 nm, the adhesion between the acrylic film and the easy-slip layer is good, and the appearance of the optical film is also good. However, the polarizing plate using the optical film as a polarizer protective film showed a significant decrease in the degree of polarization after the humidification durability test, and it was confirmed that there were significant rib-like unevenness. In Comparative Examples 3 to 5, the elongation temperature (heating temperature at the time of forming the slippery layer) was 120°C or less, and the polarization degree after the humidification endurance test was significantly reduced as in Comparative Example 2, and it was confirmed that there were significant ribs all.

Examples 1 to 4 are optical films in which an easy-slip layer of 50 nm to 250 nm is formed at an extension temperature of 140° C. No turbidity due to aggregation of fine particles is observed, and a good appearance is shown. In addition, although the optical film of Example 1 was slightly damaged on the non-forming surface of the slippery layer, the degree of the damage was buried with adhesives or adhesives when it was bonded to other members, and did not constitute an optical defect. Moreover, the polarizing plates using the optical films of Examples 1 to 4 are superior to the polarizing plates using the optical film of Comparative Example 2 in humidification durability, and suppress the occurrence of unevenness of streaks.

In Comparative Example 1, an easy-slip layer with a thickness of 30 nm was formed, and the polarizing plate of the optical film had good humidification durability. However, it was confirmed that white turbidity due to the aggregation of silicon dioxide fine particles and damage to the non-slip layer formation surface were poor. . We believe that the damage occurs because the reduced dispersibility causes the silica particles to fall off the surface of the slippery layer, causing the smoothness of the optical film to decrease.

It can be seen from the comparison between Examples 1 to 4 and Comparative Examples 1 and 2 that the thickness of the easy-slip layer is small and the residual alkali component is less, which can suppress the unevenness of the streak after the humidification durability test and obtain the humidification durability Polarizer with excellent performance. It is also known that if the thickness of the easy-slip layer is too small and the residual alkali component is too small, the appearance of the particles or the smoothness may decrease due to the decrease in the dispersibility of the fine particles.

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

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

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

1: Optical film 2: Transparent protective film 5: polarizer 6, 7: Adhesive layer 11: film substrate 15: Easy to 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. 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 slip layer. FIG. 4 is a cross-sectional TEM observation image of an optical film without an interface layer formed at the interface between the film substrate and the slip layer.

1: Optical film

11: film substrate

15: Easy to slip layer

Claims (19)

An optical film with an easy-slip layer on the surface of a transparent film substrate; The aforementioned slippery layer contains binder resin and fine particles, and The alkali component content of the aforementioned slippery layer is 5 to 75 ppm. The optical film according to claim 1, wherein the thickness of the aforementioned slip layer is 40 to 280 nm. The optical film according to claim 1 or 2, wherein an area in which the fine particles are embedded in the transparent film substrate exists at the interface between the transparent film substrate and the easy-slip layer. The optical film according to claim 1 or 2, wherein the aforementioned fine particles are inorganic fine particles. The optical film according to claim 1 or 2, wherein the average primary particle diameter of the aforementioned fine particles is 10 to 250 nm. The optical film according to claim 1 or 2, wherein the content of the fine particles in the easy-slip layer is 3 to 50% by weight. The optical film according to claim 1 or 2, wherein the transparent film substrate is an acrylic film. The optical film according to claim 1 or 2, wherein the binder resin of the easy-slip layer is a urethane-based resin. A method for manufacturing an optical film, which is a method for manufacturing the optical film according to any one of claims 1 to 8; The manufacturing method is to apply a composition for forming an easy slip layer on the surface of a transparent film substrate, the composition for forming an easy slip layer containing a binder resin or its precursor, fine particles, an alkali component and a solvent, Then, the composition for forming the slippery layer is heated at a temperature higher than the glass transition temperature of the transparent film substrate by 10° C. or more to volatilize the solvent and the alkali component. The method for manufacturing an optical film according to claim 9, wherein the alkali component has a function of promoting dispersion of the fine particles. The method for manufacturing an optical film according to claim 9 or 10, wherein the composition for forming an easy-slip layer contains a polyurethane precursor as the binder resin precursor and a tertiary amine as the alkali component. The method for producing an optical film according to claim 9 or 10, wherein the composition for forming the slippery layer contains an amine having a boiling point of 150°C or less as the alkali component. The method for manufacturing an optical film according to claim 9 or 10, which heats the composition for forming an easy-slip layer at a temperature higher than the glass transition temperature of the transparent film substrate by 10° C. or more, and simultaneously coats the easy-slip layer The aforementioned transparent film substrate of the layer forming composition extends in at least one direction. A polarizing plate is provided with a polyvinyl alcohol polarizer having a first main surface and a second main surface and a transparent film, the transparent film is attached to the first main surface of the polarizer through an adhesive layer, and The aforementioned transparent film is the optical film according to any one of claims 1 to 8. The polarizing plate according to claim 14, wherein the non-slip surface of the optical film is formed on the first main surface of the polarizer. The polarizing plate according to claim 15, wherein the non-slip surface of the easy-slip layer of the optical film passes through the photo-cationic polymerizable adhesive, or a mixed molding adhesive of photo-cationic polymerization and photo-radical polymerization and is attached to the first part of the polarizer One main face. The polarizing plate according to claim 14, wherein the easy-slip layer forming surface of the optical film is attached to the first main surface of the polarizing member. The polarizing plate according to claim 17, wherein the non-slip layer forming surface of the optical film is bonded to the first main surface of the polarizing member through a light radical polymerizable adhesive. An image display device having an image display unit and a polarizing plate according to any one of claims 14 to 18.

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