JP2020023171A - Optical film, manufacturing method thereof, polarizing plate and picture display unit - Google Patents

Abstract

To provide an optical film hardly causing blocking and excellent in homogeneity and durability.SOLUTION: An optical film (1) includes a slippery layer (15) on a surface of a transparent film base material (11). The slippery layer (15) contains a binder resin and fine particles. A content of an alkaline component of the slippery layer (15) is 5-75 ppm. A slippery layer can be formed by coating a transparent film base material with a slipper layer formation composition containing a binder resin or a precursor thereof, fine particles, an alkaline component and a solvent, and then applying heat.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical film having a lubricating layer on the surface of a transparent film substrate and a method for producing the same. Furthermore, the present invention relates to a polarizing plate in which an optical film having a lubricating layer is attached to the surface of a polarizer, and an image display device including the polarizing plate.

  Liquid crystal display devices and organic EL display devices are widely used as various image display devices such as mobile devices, car navigation devices, monitors for personal computers, and televisions. In the liquid crystal display device, a polarizing plate is disposed on the viewing side surface of the liquid crystal cell from the display principle. In a transmission type liquid crystal display device, polarizing plates are arranged on both sides of a liquid crystal cell. In the organic EL display device, in order to prevent external light from being reflected by the metal electrode (cathode) and being viewed like a mirror, a circularly polarizing plate (typically, 1 / (A laminate of four wavelength plates).

  The polarizing plate generally includes a transparent film (polarizer protective film) for protecting the polarizer on one or both sides of the polarizer. As the polarizer, a polarizer in which iodine is adsorbed on a polyvinyl alcohol (PVA) -based film and molecules are oriented by stretching or the like is widely used.

  As a polarizer protective film to be bonded to the surface of the polarizer, a polarizing plate to which a low moisture-permeable film made of a resin material such as acrylic, polyester, polycarbonate, or cyclic polyolefin was bonded was exposed to a high-humidity environment for a long time. Even in such a case, there is a tendency that the change in optical characteristics is small and the durability is excellent. Patent Literature 1 describes that by providing a smooth layer containing fine particles and a binder resin on the surface of an acrylic film, blocking when the film is wound into a roll can be suppressed. The example of Patent Document 1 discloses a polarizer protective film in which a urethane resin layer having an average thickness of 400 nm (thickness range of 300 to 500 nm) containing 1 to 7% by weight of silica fine particles is provided on the surface of an acrylic film. I have.

Patent No. 5354733

  As image display devices become larger and have higher brightness, the polarizers that make up the image display devices have less change in optical characteristics even in more severe environments (for example, higher temperature and higher humidity conditions). As required. The polarizing plate provided with the polarizer protective film disclosed in Patent Document 1 has a problem that, when exposed to a high-humidity environment for a long time, optical defects such as streak-like unevenness may occur and display characteristics may be deteriorated. Newly found out.

  In view of the above-mentioned problems, an object of the present invention is to provide an optical film that is unlikely to cause blocking and hardly causes optical defects even when exposed to a high-temperature and high-humidity environment for a long time.

  In light of the above problems, as a result of investigations by the present inventors, alkali components such as ammonia and amine added to the slippery layer forming composition for the purpose of improving the dispersibility of fine particles remain in the slippery layer. Has been found to be one of the causes of the decrease in durability in a humid environment, and it has been found that the above problem can be solved by keeping the amount of alkali remaining in the easy sliding layer in a predetermined range.

  The present invention relates to an optical film having a lubricating layer on the surface of a transparent film substrate and a method for producing the same. The slippery layer contains a binder resin and fine particles. The average primary particle diameter of the fine particles is, for example, 10 to 250 nm, and preferably 10 to 100 nm. The content of the alkali component in the slippery layer is preferably from 5 to 75 ppm. The thickness of the slippery layer is preferably from 40 to 280 nm.

  An acrylic film or the like is used as the transparent film substrate. A urethane-based resin or the like is used as the binder resin for the slippery layer. The content of the fine particles in the slippery layer is preferably about 3 to 50% by weight, and more preferably 10 to 50% by weight. The fine particles of the slippery layer may be embedded in the transparent film substrate.

  A composition for forming a slippery layer is applied to the surface of a transparent film substrate and heated to form a slippery layer. The composition for forming a slippery layer contains a binder resin or a precursor thereof, fine particles, an alkali component, and a solvent. When the composition for forming a slippery layer contains an alkali component, the dispersibility of the fine particles is improved, and an optical film having excellent slipperiness can be obtained. Further, the alkali component can also act as a catalyst for accelerating the reaction of the binder resin (precursor). From the viewpoint of promoting the volatilization of the alkali component by heating, 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 the application of the composition for forming a slippery layer, volatilization of an alkali component is promoted, and a slippery layer with less residual alkali component can be formed. For example, the composition for forming a 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, a region in which the fine particles of the slippery layer are embedded in the transparent film substrate is likely to be formed, and the adhesiveness between the transparent film substrate and the slippery layer tends to be improved.

  After applying the composition for forming a slippery layer on a transparent film substrate, stretching may be performed while heating the transparent film substrate. In particular, by stretching the transparent film substrate while heating the composition for forming a lubricating layer at a temperature higher than the glass transition temperature of the transparent film substrate by 10 ° C. or more, the adhesion between the transparent film substrate and the lubricating layer is improved. Properties tend to improve.

  The slippery layer can also contribute to improving the adhesion to other films, glass substrates, and the like. The optical film can be used, for example, as a polarizer protective film. For example, a polarizing plate can be obtained by attaching an optical film to the surface of a polyvinyl alcohol-based polarizer via an adhesive layer. In the optical film, any surface of the surface on which the easy-adhesion layer is formed and the surface on which the easy-adhesion layer is not formed may be bonded to the polarizer. An image display device can be formed by disposing a polarizing plate on the surface of an image display cell such as a liquid crystal display cell or an organic EL cell.

  The optical film of the present invention is excellent in adhesiveness, hardly causes blocking, and even when exposed to a high-temperature and high-humidity environment for a long time, optical defects hardly occur. It is preferably used as

It is sectional drawing which shows the example of a structure of the optical film provided with a lubricity layer. It is sectional drawing which shows the example of a structure of a polarizing plate. It is sectional drawing which shows the example of a structure of a polarizing plate. It is a cross-sectional TEM observation image of the optical film in which the interface layer is formed in the interface of a film base material and a lubricity layer. It is a cross-sectional TEM observation image of the optical film in which the interface layer is not formed in the interface of a film base material and a lubricity layer.

  FIG. 1 is a schematic cross-sectional view illustrating a configuration example of an optical film according to an embodiment of the present invention. The optical film 1 includes an easy-slip layer 15 on at least one surface of the film substrate 11. A lubricating layer may be provided on both sides of the film substrate. The optical film is used by being bonded to another film, a glass substrate, or the like.

  Examples of usage of the optical film include a polarizer protective film. 2A and 2B are cross-sectional views illustrating a configuration example of a polarizing plate including the 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 include the optical film 1 bonded to one surface (first main surface) of the polarizer 5 with an adhesive layer 6 interposed therebetween. In the polarizing plate 100, the optical film 1 has the easy-slip layer 15 on the surface of the film substrate 11 to be bonded to the polarizer 5. In the polarizing plate 101 shown in FIG. 2B, the polarizer 5 is bonded 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 with an adhesive layer 7 interposed therebetween.

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

<Film substrate>
As the film substrate 11, a transparent film is preferable. The total light transmittance of the transparent film substrate is preferably at least 80%, more preferably at least 85%, even more preferably at least 90%. Examples of the resin material constituting the film substrate 11 include an acrylic resin, a polyester resin, a polycarbonate resin, a polyolefin resin, a cyclic polyolefin resin, a polystyrene resin, a polyamide resin, and a polyimide resin. When the optical film is used as an optically isotropic polarizer protective film, since the birefringence is small, an acrylic resin or a cyclic polyolefin resin is preferable as the resin material of the film substrate 11, and an acrylic resin is particularly preferable. preferable.

  Examples of the cyclic polyolefin-based resin include polynorbornene. Commercial products of the cyclic polyolefin-based resin include ZEONOR and ZEONEX manufactured by Zeon Corporation, ARTON manufactured by JSR, APPEL manufactured by Mitsui Chemicals, and TOPAS manufactured by TOPAS ADVANCED POLYMERS. The cyclic polyolefin-based film preferably contains at least 50% by weight of the cyclic olefin-based resin.

  Examples of the acrylic resin include poly (meth) acrylates such as polymethyl methacrylate, methyl methacrylate- (meth) acrylate copolymer, methyl methacrylate- (meth) acrylate copolymer, methyl methacrylate -Acrylic acid ester- (meth) acrylic acid copolymer, (meth) acrylic acid methyl-styrene copolymer (MS resin or the like), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-methacrylic acid) Cyclohexyl copolymer, methyl methacrylate-norbornyl (meth) acrylate copolymer, etc.).

  In the present specification, “(meth) acryl” means acryl and / or methacryl. Acrylic resins include those containing acrylic acid or a derivative thereof as a constituent monomer component and those containing methacrylic acid or a derivative thereof as a constituent monomer component.

  As the acrylic resin, an acrylic resin having a glutaric anhydride structure described in JP-A-2006-283013, JP-A-2006-335902, JP-A-2006-274118, and / or the like; JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, JP-A-2005-146084 and the like have an acrylic resin having a lactone ring structure. May be used. Acrylic resin having a glutaric anhydride structure and acrylic resin having a lactone ring structure have high heat resistance, high transparency, and high mechanical strength, and therefore have a high degree of polarization and excellent durability. Suitable for manufacturing.

  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, more preferably 60 to 98% by weight, and even more preferably 70 to 97% by weight. The acrylic film may contain a thermoplastic resin other than the acrylic resin. For example, by blending another thermoplastic resin, the birefringence of the acrylic resin is canceled, and an acrylic film having excellent optical isotropy can be obtained. Further, a thermoplastic resin other than the acrylic resin may be blended for the purpose of improving the mechanical strength of the film.

  Thermoplastic resins other than acrylic resins include olefin polymers, vinyl halide polymers, polystyrene, copolymers of styrene and acrylic monomers, polyesters, polyamides, polyacetals, polycarbonates, polyphenylene oxides, polyphenylene sulfides, and polyphenylene sulfides. Examples include ether ether ketone, polysulfone, polyethersulfone, polyoxybenzylene, polyamideimide, and rubber-based polymers.

  The film substrate 11 may include additives such as an antioxidant, a stabilizer, a reinforcing material, an ultraviolet absorber, a flame retardant, an antistatic agent, a coloring agent, a filler, a plasticizer, a lubricant, and a filler. A film may be formed by mixing a resin material and an additive and forming a thermoplastic resin composition such as a pellet in advance.

  The thickness of the film substrate 11 is about 5 to 200 μm. In light of mechanical strength, transparency, handleability, and the like, the thickness of the film substrate 11 is preferably 10 to 100 μm, and more preferably 15 to 60 μm.

  The glass transition temperature Tg of the film substrate 11 is preferably 100 ° C. or higher, more 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, Tg can be increased and heat resistance can be improved. The upper limit of the Tg of the film substrate 11 is not particularly limited, but is preferably 170 ° C. or lower from the viewpoint of moldability and the like.

  Examples of the method for producing the film substrate 11 include a solution casting method, a melt extrusion method, a calendering method, and a compression molding method. The film substrate 11 may be either an unstretched film or a stretched film. When the film substrate 11 is an acrylic film, the acrylic film is preferably a stretched film stretched in at least one direction, and particularly preferably a biaxially stretched film, from the viewpoint of improving mechanical strength. By blending another thermoplastic resin so as to cancel the birefringence of the acrylic resin, an acrylic film having small retardation and excellent optical isotropy even when stretched can be obtained.

<Easy layer>
The slippery layer 15 provided on the surface of the film substrate 11 contains a binder resin and fine particles. When the slippery layer 15 contains fine particles, fine irregularities are formed on the surface of the slippery layer 15, and the slipperiness of the film is improved. Therefore, it contributes to the reduction of scratches during the transport of the optical film 1 during roll transport and the suppression of blocking when the optical film 1 is wound up in a roll shape.

(Binder resin)
As the binder resin, polyurethane resin, epoxy resin, isocyanate resin, polyester resin, polymers containing amino groups in the molecule, crosslinkability of oxazoline groups, etc., because of their excellent adhesion to film bases such as acrylic films A resin (polymer) having a reactive group such as an acrylic resin having a functional group is used. As the binder resin of the slippery layer 15, a polyurethane resin is particularly preferable. The lubricious layer 15 containing the polyurethane resin binder has high adhesion to the film substrate 11.

  The urethane resin is typically a reaction product of a polyol and a polyisocyanate. As the polyol component, polymer polyols such as polyacryl polyol, polyester polyol and polyether polyol are preferably used.

  The polyacryl polyol is typically obtained by polymerization of a (meth) acrylate and a hydroxyl group-containing monomer. Examples of the (meth) acrylate include methyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and cyclohexyl (meth) acrylate. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and (meth) acrylate. Hydroxyalkyl esters of (meth) acrylic acid such as 4-hydroxybutyl acrylate and 2-hydroxypentyl (meth) acrylate; monoesters of polyhydric alcohols such as glycerin and trimethylolpropane; N-methylol (Meth) acrylamide and the like.

  The polyacryl polyol may contain a monomer component other than the above. Other monomer components include unsaturated monocarboxylic acids such as (meth) acrylic acid; unsaturated dicarboxylic acids such as maleic acid and 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; α-olefins such as ethylene and propylene; vinyl chloride and vinylidene chloride And the like, and α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene.

  The polyester polyol is typically obtained by reacting a polybasic acid with a polyol. Examples of the polybasic acid include aromatic acids such as orthophthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and tetrahydrophthalic acid. Dicarboxylic acids: 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, linoleic acid Aliphatic dicarboxylic acids such as maleic acid, fumaric acid, fumaric acid, mesaconic acid, citraconic acid and itaconic acid; alicyclic rings such as hexahydrophthalic acid, tetrahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid Formula dicarboxylic acid; or These acid anhydrides, alkyl esters, reactive derivatives such as acid halides and the like.

  Examples of the polyol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1-methyl-1,3-butylene glycol, 2-methyl-1,3-butylene glycol, 1-methyl-1,4-pentylene glycol, 2-methyl -1,4-pentylene glycol, 1,2-dimethyl-neopentyl glycol, 2,3-dimethyl-neopentyl glycol, 1-methyl-1,5-pentylene glycol, 2-methyl-1,5-pentylene Lenglycol, 3-methyl-1,5-pentyleneglycol, 1,2-dimethylbutyleneglycol 1,3-dimethylbutylene glycol, 2,3-dimethylbutylene glycol, 1,4-dimethylbutylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, 1,4-cyclohexanedimethanol, , 4-cyclohexanediol, bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, and the like.

  The polyether polyol is typically obtained by adding a polyhydric alcohol to an alkylene oxide by ring-opening polymerization. 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, styrene oxide, tetrahydrofuran and the like.

  Examples of the polyisocyanate include tetramethylene diisocyanate, dodecamethylene diisocyanate, 1,4-butane diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, Aliphatic diisocyanates such as -methylpentane-1,5-diisocyanate and 3-methylpentane-1,5-diisocyanate; isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-cyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate , Cycloaliphatic diisocyanates such as methylcyclohexylene diisocyanate and 1,3-bis (isocyanatomethyl) cyclohexane G; tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, Aromatic diisocyanates such as 1,5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate; dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, α, α, α, α-tetramethylxylylene An araliphatic diisocyanate such as a diisocyanate is exemplified.

  The urethane resin forming the easy sliding layer 15 preferably has a carboxy group. When the urethane resin has a carboxy group, it becomes possible to introduce a crosslinked structure. The urethane resin having a carboxy group is obtained, for example, by reacting a chain extender having a free carboxy group in addition to a polyol and a polyisocyanate. Examples of the chain extender having a free carboxy group include dihydroxycarboxylic acid, dihydroxysuccinic acid and the like. Examples of the dihydroxycarboxylic acid include dialkylolalkanoic acids such as dimethylolalkanoic acid (for example, dimethylolacetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, dimethylolbutyric acid, and dimethylolpentanoic acid).

  The method for producing the urethane resin is not particularly limited, and may be either a one-shot method in which the monomer components are reacted at one time or a multi-stage method in which the monomer components are reacted stepwise. When a carboxy group is introduced into a urethane resin using a chain extender having a free carboxy group, a multi-step method is preferred. In producing the urethane resin, a urethane reaction catalyst may be used as necessary.

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

  The urethane resin may have a crosslinked structure. The introduction of the crosslinked structure into the urethane resin tends to improve the adhesion between the lubricious layer 15 and the film substrate 11 and the hardness of the lubricious layer 15. As the crosslinking agent, those capable of reacting with the crosslinking functional group of the urethane resin can be used without particular limitation. When the urethane resin has a carboxy group, a crosslinking agent containing an amino group, an oxazoline group, an epoxy group, a carbodiimide group or the like is used. Among these, a crosslinking agent having an oxazoline group is preferable. The oxazoline group has a low reactivity with the carboxy group at room temperature, so that the oxazoline group has a long pot life when mixed with the urethane resin, and can flexibly cope with the lead time of the process.

  The crosslinking agent may be a low molecular compound or a polymer. An acrylic polymer is preferable as the crosslinking agent, and an acrylic polymer having an oxazoline group is particularly preferable, since it has high solubility in an aqueous composition and excellent compatibility with a urethane resin.

  The amount of the crosslinking agent used is preferably 1 to 30 parts by weight, more preferably 3 to 20 parts by weight, based on 100 parts by weight of the urethane resin.

(Fine particles)
The inclusion of the fine particles in the slippery layer 15 forms fine irregularities on the surface of the slippery layer, improves the slipperiness of the optical film 1, and suppresses blocking. From the viewpoint of forming unevenness that contributes to the improvement of the slipperiness, the particle diameter (average primary particle diameter) of the fine particles is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. The average primary particle diameter of the fine particles is preferably smaller than the thickness of the lubricating layer. When the particle diameter of the fine particles is smaller than the thickness of the slippery layer, the fine particles can be prevented from falling off the slippery layer. The particle diameter of the fine particles is preferably 250 nm or less, more preferably 200 nm or less. Further, since the average primary particle diameter of the fine particles is 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, further 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. As the fine particles, inorganic fine particles are preferable because of excellent dispersibility and uniformity of particle diameter. Examples of the inorganic fine particles include inorganic oxides such as titania, alumina and zirconia; calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate and the like. Of these, inorganic oxides are preferred. Examples of the organic fine particles include a silicone resin, a fluorine resin, and an acrylic resin. In order to suppress light scattering caused by the fine particles, it is preferable that the difference in the refractive index between the binder resin (generally, the refractive index is about 1.5) and the fine particles is small. Since the difference in refractive index from the binder resin is small and the dispersibility is excellent, silica particles are preferable as the fine particles of the slippery layer 15.

  When the easy-slip layer 15 is formed from an aqueous composition, it is preferable to use fine particles having high water dispersibility. An aqueous dispersion of fine particles may be incorporated into the composition. In order to enhance the dispersibility of the fine particles, it is preferable to add an alkali component such as an amine or ammonia to make the composition for forming a slippery layer weakly alkaline.

  Colloidal silica is preferably used as the water-dispersible silica particles. Examples of the colloidal silica include Quartron PL series manufactured by Fuso Chemical Industry Co., Ltd., Snowtex Series manufactured by Nissan Chemical Industry Co., Ltd., AERODISP Series and AEROSIL Series manufactured by Nippon Aerosil Co., Ltd. Commercial products such as the KE series may be used.

  From the viewpoint of enhancing the slipperiness of the optical film 1 by forming irregularities on the surface of the easy sliding layer 15, the content of the fine particles in the easy sliding layer 15 is preferably 3% by weight or more, more preferably 5% by weight or more. In particular, when the thickness of the slippery layer 15 is small (for example, 280 nm or less), the surface of the slippery layer 15 is increased by increasing the content of the fine particles to increase the amount (number density) of the fine particles per unit area. It is preferable to form unevenness uniformly in the inside. The content of the fine particles in the slippery layer 15 is preferably 8% by weight or more, more preferably 10% by weight or more, and further preferably 12% by weight or more. If the content of the fine particles in the slippery layer 15 is excessively large, the optical characteristics may be deteriorated due to an increase in light scattering at the interface between the binder resin and the fine particles. Further, as the content of the fine particles increases, the relative content of the binder resin decreases, so that the adhesiveness of the easy-slip layer may decrease. Therefore, the content of the fine particles in the easy sliding layer 15 is preferably 50% by weight or less, more preferably 40% by weight or less, and further preferably 30% by weight or less.

(Remaining alkali amount)
When an alkali component such as amine or ammonia is used to enhance the dispersibility of the fine particles, the alkali component inevitably remains in the slippery layer. When the optical film 1 is used as a polarizer protective film, the remaining alkali component of the easy-to-be-smooth layer 15 is eluted into water, and the alkali component that has passed through the film substrate 11 deteriorates the polarizer, and the degree of polarization of the polarizing plate is reduced. And optical defects such as streak-like unevenness may occur.

  In light of enhancing the humidification durability of the polarizing plate, the amount of residual alkali in the easy-slip layer 15 is preferably equal to or less than 75 ppm, more preferably equal to or less than 70 ppm, still more preferably equal to or less than 60 ppm, and particularly preferably equal to or less than 55 ppm. From the viewpoint of improving the humidification durability of the polarizing plate, the smaller the amount of alkali remaining in the slippery layer 15, the better.

  On the other hand, if the amount of residual alkali in the slippery layer 15 is excessively small, the dispersibility of the fine particles is impaired, and appearance defects such as cloudiness due to aggregation of the fine particles may occur. In addition, due to aggregation of fine particles due to a decrease in dispersibility and dropping out of the slippery layer, appropriate unevenness is not formed on the surface of the slippery layer, and the slipperiness of the optical film tends to decrease. Therefore, the amount of residual alkali in the easy sliding layer 15 is preferably 5 ppm or more, more preferably 10 ppm or more, and even 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 determined by liquid chromatography, ion chromatography, or the like, depending on the type of alkali component. The quantification of the alkali component may be performed by an analytical method (for example, LC / MS) that combines chromatography and mass spectrometry (MS). When a plurality of alkali components are contained in the slippery layer, the total of each component is defined as the alkali component content (remaining amount) of the slippery layer.

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

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

  The water-based composition for forming a slippery layer contains water as a solvent (and a dispersion medium), a binder resin or a precursor thereof, and fine particles. It is preferable that the composition for forming a slippery layer further contains an alkali component. As described above, the alkali component has an effect of promoting the dispersion of the fine particles. Although the fine particles having a small particle diameter tend to be easily aggregated, the composition for forming a slippery layer contains an alkali component such as ammonia or an amine, so that the dispersibility of the fine particles is improved, and the optical film is excellent in appearance and slipperiness. Is obtained.

  On the other hand, if the alkali contained in the composition for forming a slippery layer remains in the slippery layer, it may cause the wet heat resistance of the polarizing plate to decrease. In particular, strong alkali such as caustic may cause the polarizer to deteriorate even in a small amount. Therefore, as the alkali component contained in the composition for forming a slippery layer, a weak alkali component such as ammonia or an amine is preferable. From the viewpoint of improving the dispersibility of the fine particles and preventing the polarizer from deteriorating, the pH of the composition (coating liquid) for forming a 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 a smooth layer is preferably 300 ppm or more, more preferably 500 ppm or more, based on the solid content of the composition for forming a smooth layer. On the other hand, if the content of the alkali component is excessively large, it may be difficult to reduce the amount of the remaining alkali, and therefore, the amount of the alkali component contained in the composition for forming a slippery layer may be reduced. It is preferably 50,000 ppm or less, more preferably 10,000 ppm or less, still more preferably 5,000 ppm or less, based on the solid content of the composition. As described above, specific examples of the alkali component contained in the composition for forming a 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 a slippery layer may have a catalytic action or the like in addition to improving the dispersibility of the fine particles. For example, when the binder resin is a urethane-based resin, a tertiary amine such as triethylamine may be included in the composition for forming a slippery layer as a catalyst for urethanizing a polyurethane precursor (polyol, isocyanate, or the like). .

  By heating after applying the composition for forming a slippery layer on the film substrate, the alkali component is volatilized and removed, and the remaining alkali component of the slippery layer 15 can be reduced. From the viewpoint of promoting the volatilization of the alkali component by heating, the alkali component contained in the composition for forming a slippery layer preferably has a boiling point of 150 ° C. or lower. The boiling point of the alkali component is more preferably 130 ° C or lower, further 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 a slippery layer contains a plurality of alkali components, the boiling point of at least one alkali component is preferably in the above range, and the boiling points of two or more alkali components are preferably in the above range. It is preferable that the boiling point of 50% by weight or more of the alkali component is in the above range based on 100 parts by weight of the total amount of the alkali contained in the lubricating layer. Ideally, the boiling points of all the alkali components contained in the composition for forming a slippery layer are within the above range.

  The composition for forming a slippery layer may include a crosslinking agent in addition to the binder resin (or a precursor thereof), fine particles, and an alkali component. The composition for forming a slippery layer includes a catalyst such as a crosslinking accelerator, an antioxidant, an ultraviolet absorber, a leveling agent, an antiblocking agent, an antistatic agent, a dispersion stabilizer, an antifoaming agent, a thickener, a dispersant, It may contain additives such as surfactants and lubricants.

(Formation of slippery layer on film substrate)
Before applying the composition for forming a slippery layer onto the film substrate 11, the film substrate may be subjected to a surface treatment. By performing the surface treatment, the wetting tension of the film substrate can be adjusted, and the adhesion to the lubricating layer 15 can be improved. Examples of the surface treatment include corona treatment, plasma treatment, ozone spraying, ultraviolet irradiation, flame treatment, and chemical treatment. Among these, corona treatment or plasma treatment is preferable.

  Examples of a method for applying the composition for forming a slippery layer include a bar coating method, a roll coating method, a gravure coating method, a rod coating method, a slot orifice coating method, a curtain coating method, and a fountain coating method. The lubricating layer 15 is formed by heating the composition for forming the lubricating layer after application and removing the solvent. The precursor of the binder resin may be reacted and cured by heating. For example, when the composition for forming a slippery layer contains a crosslinking agent, the crosslinking reaction can be promoted by heating.

  The heating temperature at the time of forming the slippery layer is, for example, about 50 to 200 ° C. From the viewpoint of accelerating the curing reaction of the resin component in the composition for forming a slippery layer and efficiently volatilizing and removing the alkali component contained in the composition for forming a slippery layer, the heating temperature is preferably 100 ° C or higher, and 120 ° C or higher. C. or higher is more preferable, 130 C. or higher is more preferable, and 135 C. or higher is particularly preferable. The heating temperature is preferably higher than the boiling point of the alkali component contained in the composition for forming a slippery layer.

  The heating temperature at the time of forming the slippery layer is preferably higher than the glass transition temperature (Tg) of the film substrate. By heating at a high temperature, the curing reaction of the resin component in the composition for forming a slippery layer can be promoted, and the alkali component contained in the composition for forming a slippery layer can be efficiently volatilized and removed. The heating temperature is preferably at least 10 ° C. higher than the Tg of the film substrate.

  By heating at a temperature higher than the Tg of the film substrate, the efficiency of volatilization and removal of alkali in the composition for forming a smooth layer is increased, and the composition for forming a smooth layer is easily penetrated into the surface of the film substrate. It is considered that the adhesion between the film substrate 11 and the lubricating layer 15 is improved. From the viewpoint of improving the adhesion of the slippery layer, the heating temperature is preferably Tg + 10 ° C. or higher, more preferably Tg + 15 ° C. or higher, and even more preferably Tg + 20 ° C. or higher.

  When heated at a temperature of Tg + 10 ° C. or more of the film base, the film base is changed from a glass state to a rubber state, and the surface is easily deformed. An interface layer in which the component and the component of the easy-slip layer are mixed is easily formed. The formation of the interface layer tends to improve the adhesion between the film substrate 11 and the slippery layer 15.

  In particular, as shown in the cross-sectional observation image of FIG. 3, when there is a region in which fine particles of the slippery layer 15 are embedded and embedded on the surface of the film base 11, the film base 11 and the slippery layer 15 An optical film having high adhesion can be obtained. When the film substrate is heated to a temperature higher than Tg and rubber particles are buried in the film substrate, and then the film substrate returns to the glass state, the fine particles buried on the surface of the film substrate and present around the particles It is considered that the adhesiveness between the film substrate 11 and the easy-slip layer 15 is improved because the binder resin adheres to the surface of the film substrate.

  A lubricious layer may be formed in the production process of the film substrate. Further, the lubricating layer may be formed by utilizing the heating during the formation of the film substrate. For example, when the film substrate is a stretched film, the composition for easy layer formation is applied to the surface of the film before stretching or the film after longitudinal stretching, and is used for transverse stretching or simultaneous biaxial stretching by a tenter. Using the heating, drying of the solvent and curing of the resin can be performed.

  When stretching the film substrate after applying the composition for forming a slippery layer, the draw ratio is preferably 5 times or less, more preferably 4 times or less, from the viewpoint of suppressing problems such as crack generation in the slippery layer. It is preferably 3 times or less, more preferably 2.5 times or less. The lower limit of the stretching ratio is not particularly limited, but from the viewpoint of improving the film strength, the stretching ratio is preferably 1.3 times or more, more preferably 1.5 times or more. When the film substrate is an acrylic film, it is preferable to perform stretching at the above-described stretching ratio in each of the transport direction (MD) and the width direction (TD) from the viewpoint of improving the film strength.

  When performing biaxial stretching of the film substrate, the biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching. Further, oblique stretching may be performed. In the case where sequential biaxial stretching is performed, as described above, the film is stretched in one direction (MD) by roll stretching, and then the composition for forming a smooth layer is applied on the film. The composition for forming may be heated.

  As described above, the stretching temperature is preferably higher than the Tg of the film substrate, preferably Tg + 10 ° C. or higher, more preferably Tg + 15 ° C. or higher, and still more preferably Tg + 20 ° C. or higher, as described above as the heating temperature of the easy-smooth layer. In particular, it is preferable to perform stretching in at least one direction at the above temperature after applying the composition for forming a slippery layer. When the film is stretched in a rubber state at a temperature higher than the Tg of the film base, a region in which the fine particles in the composition for forming a slippery layer are embedded is easily formed on the surface of the film base, and the film base 11 and the slippery layer are formed. 15 tends to be improved. The reason that the fine particles are easily buried in the film substrate by stretching at a high temperature is that when the film is stretched in a rubber state, the composition for forming a smooth layer easily spreads when the film substrate is deformed, and is formed at the time of deformation. That is, the fine particles are likely to be fitted in the concave portions of the surface irregularities. Further, if cooling is performed while releasing the stress after stretching, when the film substrate contracts, the particles fitted on the surface of the film substrate are fixed, so that a region in which the fine particles are embedded in the film substrate is formed. It is considered easy.

  By adjusting the solid concentration and the applied thickness of the composition for forming a slippery layer, the thickness of the slippery layer 15 can be adjusted. In the case where the film base material is stretched after the application of the composition for forming a slippery layer, the thickness of the slippery layer 15 can be adjusted by the stretching ratio.

  The thickness of the slippery layer 15 is not particularly limited, but is preferably 280 nm or less, more preferably 250 nm or less, and still more preferably 230 nm or less from the viewpoint of promoting removal of the alkali component by heating. When the optical film 1 is used as a polarizer protective film, the humidification durability of the polarizing plate tends to improve as the thickness of the slippery layer 15 decreases.

  When the alkali component is excessively removed during the heating and drying of the composition for forming a slippery layer, the dispersibility of the fine particles in the binder resin is reduced, and the aggregation of the fine particles and the accompanying surface of the slippery layer are reduced. It is easy for fine particles to fall off from the surface. When the aggregation or falling off of the fine particles occurs, the slipperiness of the optical film is reduced, so that the optical film is likely to be damaged at the time of transport and blocking at the time of winding. Therefore, the thickness of the slippery layer 15 is preferably 40 nm or more, more preferably 50 nm or more, further preferably 80 nm or more, and particularly preferably 100 nm or more. The thickness of the slippery layer may 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 have a transparent protective film on only one surface of the polarizer, or may have a transparent protective film on both surfaces of the polarizer 5 as shown in FIGS. 2A and 2B. By bonding the above-mentioned optical film as a polarizer protective film to one surface of the polarizer, a polarizing plate having a transparent protective film only on one surface of the polarizer is formed. The polarizing plate having the polarizer protective films on both surfaces of the polarizer may be any one as long as the optical film is attached to at least one surface of the polarizer. The polarizing plate may have a structure in which the above-described optical film is bonded to both surfaces of a polarizer. The polarizer 5 and the optical film 1 are bonded via an adhesive layer 6.

<Polarizer>
As the polarizer 5, polyvinyl alcohol (PVA), which is unidirectionally oriented by adsorbing a dichroic substance such as iodine or a dichroic dye on a polyvinyl alcohol-based film such as polyvinyl alcohol or partially formalized polyvinyl alcohol, is used. A system polarizer is used. For example, a PVA-based polarizer can be obtained by performing iodine dyeing and stretching on a polyvinyl alcohol-based film.

  In the manufacturing process of the polarizer 5, processes such as washing with water, swelling, and crosslinking may be performed as necessary. Stretching may be performed before or after iodine dyeing, or may be performed while dyeing. The stretching may be any of stretching in the air (dry stretching) or stretching in water or an aqueous solution containing boric acid, potassium iodide, or the like (wet stretching), and may be used in combination. The thickness of the polarizer 5 is not particularly limited, but is generally about 1 to 50 μm.

  As the polarizer 5, a thin PVA-based polarizer having a thickness of 10 μm or less can be used. Examples of the thin polarizer include those described in, for example, JP-A-51-069694, JP-A-2000-338329, WO2010 / 100917, pamphlet No. 4691205, Japanese Patent No. 4751481, and the like. Thin polarizers. These thin polarizers are obtained by a manufacturing method including a step of stretching a PVA-based resin layer and a resin substrate for stretching in a laminate state, and a step of iodine dyeing. According to this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without any trouble such as breakage due to stretching because it is supported by the stretching resin base material.

<Adhesive>
The material of the adhesive layer 6 used for bonding the polarizer 5 and the optical film 1 is not particularly limited as long as it is optically transparent, and may be an epoxy resin, a silicone resin, an acrylic resin, a polyurethane, Examples include polyamide, polyether, and polyvinyl alcohol. The thickness of the adhesive layer 6 is, for example, about 0.01 to 20 μm, and is appropriately set according to the type of the adherend, the material of the adhesive, and the like. In the case of using a curable adhesive that exhibits adhesiveness by a crosslinking reaction after coating, the thickness of the adhesive layer 6 is preferably 0.01 to 5 μm, more preferably 0.03 to 3 μm.

  As the adhesive, various forms such as a water-based adhesive, a solvent-based adhesive, a hot-melt adhesive, and an active energy ray-curable adhesive are used. Among these, a water-based adhesive or an active energy ray-curable adhesive is preferable because the thickness of the adhesive layer can be reduced.

  Examples of the polymer component of the aqueous adhesive include vinyl polymer, gelatin, vinyl latex, polyurethane, polyester, epoxy and the like. Among these, a vinyl polymer is preferable, and a polyvinyl alcohol-based resin is particularly preferable because of its excellent adhesiveness to a polarizer. Among polyvinyl alcohol resins, acetoacetyl group-containing polyvinyl alcohol is preferable.

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

  The aqueous adhesive composition (solution) may include a crosslinking agent in addition to a polymer such as a polyvinyl alcohol-based resin. As the cross-linking agent, a compound having at least two functional groups in one molecule having reactivity with the polymer constituting the adhesive is used. Examples of the crosslinking agent for the polyvinyl alcohol-based resin include alkylene diamines; isocyanates; epoxies; aldehydes; and amino-formaldehyde such as methylol urea and methylol melamine. Of these, amino-formaldehyde is preferred. As the amino-formaldehyde resin, a compound having a methylol group is preferable, and methylol melamine is particularly preferable. The blending amount of the crosslinking agent in the adhesive composition is preferably about 10 to 60 parts by weight, more preferably 20 to 50 parts by weight, based on 100 parts by weight of the polyvinyl alcohol-based resin.

  The active energy ray-curable adhesive is an adhesive capable of undergoing radical polymerization, cationic polymerization, or anionic polymerization by irradiation with an active energy ray such as an electron beam or an ultraviolet ray. Above all, a photo-radical polymerizable adhesive whose polymerization is initiated by irradiation with ultraviolet light, a photo-cationic polymerizable adhesive, or a hybrid type adhesive that uses a combination of photo-cation polymerization and photo-radical polymerization is preferable because it can be cured with low energy. .

Examples of the monomer of the radical polymerizable adhesive include a compound having a (meth) acryloyl group and a compound having a vinyl group. Among them, compounds having a (meth) acryloyl group are preferred. Examples of the compound having a (meth) acryloyl group include alkyl (meth) acrylates such as _C1-20 chain alkyl (meth) acrylate, alicyclic alkyl (meth) acrylate, and polycyclic alkyl (meth) acrylate; (Meth) acrylate containing epoxy group-containing (meth) acrylate such as glycidyl (meth) acrylate. Radical polymerizable adhesives include hydroxyethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, (meth) acrylamide, (meth) acryloylmorpholine And the like. Radical polymerizable adhesives include, as crosslinking components, tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate, and EO-modified diacrylate. It may contain a polyfunctional monomer such as glycerin tetraacrylate.

  Examples of the curable component of the cationically polymerizable adhesive include compounds having an epoxy group or an oxetanyl group. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in a molecule, and various curable epoxy compounds generally known are used. Preferred epoxy compounds include compounds having at least two epoxy groups and at least one aromatic ring in the molecule (aromatic epoxy compounds), and those having at least two epoxy groups in the molecule and at least one of them. Is a compound formed between two adjacent carbon atoms constituting an alicyclic ring (an alicyclic epoxy compound). A hybrid adhesive can be obtained by adding a radically polymerizable compound such as a compound having a (meth) acryloyl group to the cationically polymerizable adhesive.

  The photocurable adhesive preferably contains a photopolymerization initiator. The photopolymerization initiator may be appropriately selected according to the reaction species. For example, it is preferable to mix a radically polymerizable adhesive with a photoradical generator that generates radicals by light irradiation as a photopolymerization initiator. It is preferable that a cationic photopolymerization initiator (photoacid generator) that generates a cationic species or a Lewis acid upon irradiation with light is added to the cationic polymerizable adhesive as a photopolymerization initiator. It is preferable to mix a photocationic polymerization initiator and a photoradical generator in the hybrid adhesive.

  The content of the polymerization initiator is usually about 0.1 to 10 parts by weight, preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the monomer. When the radical polymerizable adhesive is used as an electron beam curable adhesive, a photopolymerization initiator is not particularly required. If necessary, a photosensitizer can be added to the active energy ray-curable adhesive in order to increase the curing speed and sensitivity. The amount of the photosensitizer to be used is generally about 0.001 to 10 parts by weight, preferably 0.01 to 3 parts by weight, based on 100 parts by weight of the monomer.

  The adhesive may contain an appropriate additive as needed. Examples of additives include silane coupling agents, coupling agents such as titanium coupling agents, adhesion promoters such as ethylene oxide, ultraviolet absorbers, deterioration inhibitors, dyes, processing aids, ion trapping agents, and antioxidants. , Tackifiers, fillers, plasticizers, leveling agents, foam inhibitors, antistatic agents, heat stabilizers, hydrolysis stabilizers and the like.

[Preparation of polarizing plate]
A polarizing plate is manufactured by attaching the optical film 1 to one surface (first main surface) of the polarizer 5 with the adhesive layer 6 interposed therebetween. As shown in FIG. 2A, the optical film 1 may have a surface on which a slippery layer is formed bonded to the polarizer 5 via an adhesive layer, and as shown in FIG. It may be bonded to the polarizer 5 via an adhesive layer.

  The easy sliding layer 15 can also function as an easy adhesion layer. As shown in FIG. 2A, when the polarizer 5 is attached to the surface of the optical film 1 on which the slippery layer 15 is formed via the adhesive layer 6, the slippery layer 15 includes the polarizer and the polarizer protective film (the optical film 1). ) Can be improved. As shown in FIG. 2B, when the surface on which the easy-slip layer is not formed is bonded to the polarizer 5 with the adhesive layer interposed therebetween, the easy-slip layer 15 may be provided on another film provided on the optical film 1. It can contribute to the adhesiveness to the agent layer, the glass substrate and the like.

  In laminating the polarizer 5 and the optical film 1, after applying the adhesive composition to one or both of the polarizer 5 and the optical film 1, the polarizer 5 and the optical film 1 are bonded to a roll laminator or the like. It is preferable to bond together and cure the adhesive. Examples of a method for applying the adhesive composition to the polarizer 5 and / or the optical film 1 include a roll method, a spray method, and a dipping method. Before applying the adhesive composition to the surface of the polarizer 5 and / or the optical film 1, a surface treatment such as a corona treatment, a plasma treatment, or a saponification treatment may be performed.

  After bonding the polarizer 5 and the optical film 1, the adhesive is cured according to the type of the adhesive, whereby the adhesive layer 6 is formed. When an aqueous adhesive is used, the adhesive is cured by heating and drying. When an active energy ray-curable adhesive is used, the adhesive is cured by irradiation with an active energy ray such as an electron beam or an ultraviolet ray. 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 action of the remaining alkali component of the slippery layer, which may cause polymerization inhibition. Therefore, when a photocationically polymerizable adhesive or a photocation / photoradical hybrid type adhesive is used as the adhesive layer 6, as shown in FIG. It is preferable to bond with No. 5.

<Transparent protective film>
The transparent protective film 2 may be bonded to the second main surface of the polarizer 5 via an adhesive layer 7. As the transparent protective film 2, any appropriate transparent film can be adopted. The thickness of the transparent protective film 2 is about 5 to 200 μm. In light of mechanical strength, transparency, handleability, and the like, the thickness of the transparent protective film 2 is preferably 10 to 100 μm, and more preferably 15 to 60 μm. The thicknesses of the optical film 1 and the transparent protective film 2 may be the same or different.

  Examples of a material for forming the transparent protective film 2 include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); cellulose polymers such as diacetyl cellulose and triacetyl cellulose; polystyrene and acrylonitrile -Styrene-based polymers such as styrene copolymers; cyclic polyolefins such as polynorbornene; polycarbonates;

  The transparent protective film 2 may have a lubricating layer (not shown). The transparent protective film 2 may be provided with a slippery layer similar to the slippery layer 15 of the optical film 1.

  The adhesive layer 7 used for bonding the polarizer 5 and the transparent protective film 2 includes various forms such as an aqueous adhesive, a solvent adhesive, a hot melt adhesive, and an active energy ray-curable adhesive. Is used. The same adhesive composition may be used for the adhesive layer 6 and the adhesive layer 7.

[Use of polarizing plate]
The polarizing plate may be provided with an adhesive layer for bonding to a liquid crystal cell, an organic EL cell, or the like. As the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer, an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or rubber-based polymer or the like as a base polymer is appropriately selected and used. Can be. In particular, an acrylic pressure-sensitive adhesive is preferable because it is excellent in optical transparency, exhibits appropriate wettability and cohesion, and is excellent in weather resistance, heat resistance, and the like.

  The attachment of the pressure-sensitive adhesive layer to the polarizing plate can be performed by an appropriate method. For example, a pressure-sensitive adhesive solution having a solid content of about 10 to 40% by weight in which a base polymer or the like is dissolved or dispersed in a solvent such as toluene or ethyl acetate is prepared and attached on a polarizing plate, or on a suitable base material. And a method of transferring the pressure-sensitive adhesive layer formed on the polarizing plate onto the polarizing plate.

  An adhesive layer may be provided on both surfaces of the polarizing plate. When the pressure-sensitive adhesive layers are provided on both surfaces of the polarizing plate, the compositions and thicknesses of the front and back pressure-sensitive adhesive layers may be the same or different. The thickness of the pressure-sensitive adhesive layer is generally about 5 to 500 μm.

  A separator may be temporarily attached to the surface of the pressure-sensitive adhesive layer for the purpose of preventing contamination of the pressure-sensitive adhesive layer. As the separator, one obtained by coating the surface of a plastic film with a release agent such as a silicone-based release agent, a long-chain alkyl-based release agent, or a fluorine-based release agent is preferably used.

  The polarizing plate may be a laminated polarizing plate laminated with another optical layer. Examples of the optical layer include a retardation plate, a viewing angle compensation film, and a brightness enhancement film.

  An image display device can be formed by attaching a polarizing plate to the surface of an image display cell such as a liquid crystal cell or an organic EL cell. The liquid crystal display device is formed by appropriately assembling components such as a liquid crystal cell and a polarizing plate and, if necessary, a lighting system and incorporating a driving circuit. In an organic EL display device, a metal electrode or the like is formed by adhering a surface of an organic EL cell to a circularly polarizing plate obtained by combining the polarizing plate of the present invention and a retardation film (typically a 波長 wavelength plate). , The re-emission of the reflected light of the external light due to the above can be reduced, and the visibility can be improved.

  Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples. The description of “%” below is% by weight unless otherwise specified.

[Preparation of composition for easy slip layer formation]
20.6 parts by weight of a 34% solids aqueous polyurethane ("Superflex 210R" manufactured by Daiichi Kogyo Seiyaku) 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; Oxazoline-containing polymer aqueous solution having a solid content of 25% (Nippon Shokubai "Epocross WS-700") 5.2 parts by weight, 1% by weight of ammonia water 2.8 parts by weight, 20% water of colloidal silica having an average primary particle diameter of 35 nm 7.5 parts by weight of a dispersion liquid (“Quatron PL-3” manufactured by Fuso Chemical Co., Ltd.) and 63.9 parts by weight of pure water were mixed to prepare a composition for forming a slippery layer. This composition was a 9.8% aqueous solution containing 15.3 parts by weight of silica particles with respect to 100 parts by weight of solids. In the following Examples and Comparative Examples, a slippery layer was formed using this composition.

[Example 1]
An optical film was produced using a film manufacturing apparatus including a melt extrusion film forming apparatus, a gravure coater, a tenter type simultaneous biaxial stretching apparatus, and a winding apparatus. As the acrylic resin, the same pellets of imidized MS resin (glass transition temperature: 120 ° C.) as those used in the production of “Transparent protective film 1A” described in Examples of JP-A-2017-26939 were used. Acrylic resin is melt-extruded from a T-die to form a film with a thickness of 160 μm, and the above composition is applied to one surface of the film with a gravure coater at a wet thickness of about 9 μm, and heated in a heating furnace at a temperature of 140 ° C. The film was stretched twice in the longitudinal direction (MD) and in the width direction (TD) by a simultaneous biaxial stretching tenter to obtain an optical film having a 50-nm-thick smooth layer on one surface of an acrylic film having 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 a slippery layer was changed. The thickness (after stretching) of the slippery layer was as shown in Table 2.

[Examples 5 and 6 and Comparative Examples 3 to 5]
The furnace temperature (stretching temperature) during tenter stretching 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.

[Preparation of polarizing plate]
(Preparation of polarizer)
Table 1 shows that a long roll of a 45 μm-thick polyvinyl alcohol (PVA) -based resin film (“PE4500” manufactured by Kuraray) was uniaxially stretched in the longitudinal direction by a roll stretching machine so as to be 5.9 times longer in the longitudinal direction. The swelling bath, the dyeing bath, the cross-linking bath 1, the cross-linking bath 2, and the washing bath were conveyed in this order and dried at 70 ° C. for 5 minutes to produce a polarizer having a thickness of 18 μm. The iodine concentration and potassium iodide concentration in the dyeing bath were adjusted such that the single transmittance of the polarizer was 43.4%.

(Preparation of UV curable adhesive)
It contains 40 parts by weight of N-hydroxyethylacrylamide and 60 parts by weight of acryloylmorpholine as a curable component, and further contains 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one (BASF) as a polymerization initiator. (Irgacure 819), 3 parts by weight was prepared.

(Lamination of polarizer and polarizer protective film)
As the polarizer protective film on one side, the optical films of Examples and Comparative Examples were used, and as the polarizer protective film on the other side, a biaxially stretched cyclic polyolefin film ("Zeonor Film ZF-14" manufactured by Zeon Corporation) was used. . The UV curable adhesive described above is applied to a thickness of about 1 μm on the surface on which the smooth layer is formed on the optical film and on the surface of the Zeonor film, and is adhered to a polarizer with a roll laminator, and then the integrated light amount is 1000 / mJ / cm ^2. To cure the adhesive, to obtain a polarizing plate having an acrylic film (optical film) on one surface of the polarizer and a Zeonor film on the other surface.

[Evaluation]
<Remaining alkali amount of the lubricating layer>
The amounts of triethylamine and ammonia remaining in the slippery layer were determined. The remaining amount of triethylamine was determined by weighing powder obtained by shaving a smooth layer from the surface of an optical film, dissolving the powder in methanol, and quantifying the solution by gas chromatography-mass spectrometry (GC / MS). The remaining amount of ammonia was determined by immersing the optical film in pure water at 25 ° C., performing heat extraction with a dryer at 120 ° C. for 60 minutes, and quantifying the ammonia eluted in the water by ion chromatography. The total of the amount of triethylamine and the amount of ammonia was defined as the amount of residual alkali.

<Adhesion of lubricious layer>
An adhesive tape (“No. 31B” manufactured by Nitto Denko Corporation) is pressure-bonded to the surface of the optical film on which the slippery layer is formed, at a linear pressure of 8 kg / m and a pressure bonding speed of 0.3 m / min. The tip of the tape was gripped and a 180 ° peel test was performed at a pulling speed of 30 m / min, and the adhesion of the slippery layer was determined according to the following criteria.
〇: Peeling off at the interface between the adhesive tape and the lubricating layer without peeling of the lubricating layer from the acrylic film ×: Peeling off at the interface between the acrylic film and the lubricating layer

<Visual evaluation>
The surface of the optical film was visually observed to evaluate the presence or absence of local turbidity (haze increase) due to the aggregation of silica particles and the presence or absence of flaws on the surface where the smooth layer was not formed.
〇: Good in-plane uniformity without aggregation of silica particles and no scratches Δ: No turbidity due to aggregation of silica particles was observed, but a depth of 1 μm on the non-smooth layer-forming surface The following scratches were observed. ×: Turbidity due to aggregation of silica particles and scratches on the surface on which the smooth layer was not formed were observed.

<Presence of interface layer>
The cross section of the optical film is observed with a transmission electron microscope (TEM). At the interface between the acrylic film and the slippery layer, the presence or absence of a region (interface layer) in which particles in the slippery layer are embedded in the acrylic film. It was confirmed. FIG. 3 shows a TEM observation image of Example 3 (with an interface layer), and FIG. 4 shows a TEM observation image of Comparative Example 4 (without an interface layer).

<Humidification durability of polarizing plate>
The polarizing plate was cut into a size of 320 mm × 240 mm, and the surface on the side of the cyclic polyolefin film was bonded to glass via an acrylic adhesive having a thickness of 20 μm. This sample is placed in a thermo-hygrostat at a temperature of 60 ° C. and a relative humidity of 90% (condition 1) or a thermo-hygrostat at a temperature of 85 ° C. and a relative humidity of 85% (condition 2), and held for 500 hours for heating and heating. A humidification durability test was performed.

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 ΔP = | P−P ₀ | of the degree of polarization was calculated. Further, another polarizing plate was arranged in crossed Nicols on the polarizing plate after the durability test, and the presence or absence of streak-like unevenness was confirmed by visual observation, and evaluated according to the following criteria.
：: No linear streaks were observed in any of the samples after the durability test under the conditions 1 and 2 〇: No linear streaks were observed in the sample after the durability test under the condition 1 and slight linear streaks were observed in the sample after the durability test under the condition 2 Δ: Slight streaks are visually recognized in both samples after the durability test under the conditions 1 and 2 ×: Streaks are clearly visible in both samples after the durability tests under the conditions 1 and 2

  Preparation conditions of optical films of Examples and Comparative Examples (stretching temperature and thickness of easily slippery layer after stretching), evaluation results of optical films (visual observation, adhesion, presence / absence of interface layer), and durability test results of polarizing plate ( Table 2 shows the presence or absence of uneven streaks and the amount of change ΔP in the degree of polarization.

  The optical film of Comparative Example 2 including the 350-nm-thick lubricating layer had good adhesion between the acrylic film and the lubricating layer, and also had good appearance of the optical film. However, in the polarizing plate using this optical film as a polarizer protective film, the degree of polarization after the humidification durability test was largely reduced, and remarkable streak-like unevenness was confirmed. Also in Comparative Examples 3 to 5 in which the stretching temperature (heating temperature at the time of forming the easy-smooth layer) is 120 ° C. or less, the degree of polarization after the humidification durability test is largely reduced and remarkable streak-like unevenness is confirmed, as in Comparative Example 2. Was done.

  The optical films of Examples 1 to 4 in which a smooth layer having a thickness of 50 nm to 250 nm was formed at a stretching temperature of 140 ° C. did not show white turbidity due to aggregation of fine particles and showed a good appearance. Although the optical film of Example 1 had fine scratches on the surface where the easy-slip layer was not formed, the optical film was buried with an adhesive or an adhesive at the time of lamination with another member, resulting in an optical defect. It was a level of scratch that did not happen. Further, the polarizing plates using the optical films of Examples 1 to 4 were superior to the polarizing plate using the optical film of Comparative Example 2 in humidification durability, and generation of streaks was suppressed.

  The optical film of Comparative Example 1 in which a 30-nm-thick smooth layer was formed had good humidification durability of the polarizing plate, but cloudiness due to aggregation of silica fine particles and damage to the surface on which the smooth layer was not formed were observed. The appearance was poor. It is considered that the generation of the scratches is caused by the silica fine particles falling off the surface of the slippery layer due to the decrease in dispersibility, and the slipperiness of the optical film being lowered.

  From the comparison between Examples 1 to 4 and Comparative Examples 1 and 2, as the thickness of the slippery layer is smaller and the residual alkali component is smaller, the occurrence of uneven streaks after the humidification durability test is suppressed, and a polarizing plate having excellent humidification durability is obtained. It can be seen that it can be obtained. On the other hand, if the thickness of the slippery layer is excessively small and the residual alkali component is excessively small, it is found that poor appearance and reduced slipperiness are caused due to reduced dispersibility of the fine particles.

  In Examples 5 and 6, in which a 200-nm-thick smooth layer was formed at a stretching 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, in Comparative Examples 3 to 5 in which a 200-nm-thick smooth layer was formed at a stretching temperature of 80 to 120 ° C., the amount of alkali remaining in the easy-slip layer was large. Was confirmed.

  From these results, an optical film having excellent humidification durability of a polarizing plate when used as a polarizer protective film is obtained by reducing the amount of residual alkali in the easy-to-be-smooth layer within a range that does not reduce the dispersibility of the fine particles. You can see that.

  In Comparative Examples 3 to 5 in which the stretching was performed at a low temperature, the adhesion between the acrylic film and the lubricating layer was inferior to those of the other examples. In Example 3 and the like, at the interface between the acrylic film and the lubricious layer, an interface layer (see FIG. 3) in which the particles were embedded in the acrylic film was formed, whereas Comparative Examples 3 to 5 were formed. No interface layer was formed (see FIG. 4). From these results, by increasing the heating temperature after application of the composition for forming a slippery layer, it is possible to efficiently volatilize an alkali component in the composition for forming a slippery layer and reduce the amount of residual alkali. Thus, it can be seen that the adhesion at the interface between the film substrate and the lubricating layer can be improved.

DESCRIPTION OF SYMBOLS 1 Optical film 11 Film base material 15 Lubricant layer 2 Transparent film 5 Polarizer 6,7 Adhesive layer 100,101 Polarizing plate

Claims (19)

An optical film having a lubricating layer on the surface of a transparent film substrate,
The slippery layer contains a binder resin and fine particles,
An optical film, wherein the content of the alkali component in the easy-slip layer is 5 to 75 ppm.   The optical film according to claim 1, wherein the thickness of the easy-slip layer is 40 to 280 nm.   3. The optical film according to claim 1, wherein an area in which the fine particles are embedded in the transparent film base exists at an interface between the transparent film base and the lubricating layer. 4.   The optical film according to any one of claims 1 to 3, wherein the fine particles are inorganic fine particles.   The optical film according to any one of claims 1 to 4, wherein the fine particles have an average primary particle diameter of 10 to 250 nm.   The optical film according to any one of claims 1 to 5, wherein the content of the fine particles in the slippery layer is 3 to 50% by weight.   The optical film according to any one of claims 1 to 6, wherein the transparent film substrate is an acrylic film.   The optical film according to any one of claims 1 to 7, wherein the binder resin of the slippery layer is a urethane-based resin. A method for producing an optical film according to any one of claims 1 to 6,
On the surface of the transparent film substrate, a binder resin or a precursor thereof, fine particles, a composition for forming a slippery layer containing an alkali component and a solvent is applied,
A method for producing an optical film, comprising heating the composition for forming a slippery layer 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 producing an optical film according to claim 9, wherein the alkali component has a function of accelerating dispersion of the fine particles.   The method for producing an optical film according to claim 9, wherein the composition for forming a slippery layer contains a polyurethane precursor as a precursor of the binder resin, and contains a tertiary amine as the alkali component.   The method for producing an optical film according to any one of claims 9 to 11, wherein the composition for forming a slippery layer contains an amine having a boiling point of 150 ° C or less as the alkali component.   While heating the composition for forming a 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 coated with the composition for forming a slippery layer may be heated in at least one direction. The method for producing an optical film according to any one of claims 9 to 12, wherein the film is stretched. A polyvinyl alcohol-based polarizer having a first main surface and a second main surface, and a transparent film bonded to the first main surface of the polarizer via an adhesive layer,
A polarizing plate, wherein the transparent film is the optical film according to any one of claims 1 to 8.   The polarizing plate according to claim 14, wherein the surface of the optical film on which the slippery layer is not formed is bonded to the first main surface of the polarizer.   The non-smooth layer forming surface of the optical film is bonded to the first principal surface of the polarizer through a photo-cationically polymerizable adhesive or a hybrid type of photo-cation polymerization and photo-radical polymerization. The polarizing plate according to claim 15, wherein   The polarizing plate according to claim 14, wherein a surface on which the smooth layer is formed of the optical film is bonded to a first main surface of the polarizer.   The polarizing plate according to claim 17, wherein the surface of the optical film on which the smooth layer is not formed is bonded to the first main surface of the polarizer via a photo-radical polymerizable adhesive.   An image display device comprising: an image display cell; and the polarizing plate according to claim 14.