JP2020023170A - Easy adhesion film, manufacturing method thereof, polarizing plate and picture display unit - Google Patents

Abstract

To provide an easy adhesion film exhibiting high adhesiveness against a film such as a polarizer, hardly causing blocking and excellent in homogeneity and durability.SOLUTION: An easy adhesion film (1) includes an easy adhesion layer (15) on a surface of a transparent film base material (11). The easy adhesion layer (15) contains a binder resin and fine particles. A content of an alkaline component of the easy adhesion layer (15) is 5-75 ppm. An easy adhesion layer can be formed by coating a transparent film base material with an easy adhesion 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 easy-adhesion film having an easy-adhesion layer on the surface of a transparent film substrate, and a method for producing the same. Further, the present invention relates to a polarizing plate in which an easy-adhesion film is bonded to a 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 the polarizer protective film to be bonded to the surface of the polarizer, a cellulose-based film such as cellulose acetate is widely used because of its excellent adhesion to a PVA-based polarizer. As the transparent protective film, a film made of a resin material such as acrylic, polyester, polycarbonate, and cyclic polyolefin has been used. Films made of these resin materials have lower moisture permeability than cellulosic films, and a polarizing plate in which a low moisture-permeable resin film is bonded to the surface of a polarizer is exposed to a high-humidity environment for a long time. However, there is a tendency that the change in optical characteristics is small and the durability is excellent.

  On the other hand, a film made of a resin material such as acryl, polyester, polycarbonate, or cyclic polyolefin tends to have lower adhesiveness to a PVA-based polarizer than a cellulose-based film. Therefore, there has been proposed a method of improving the adhesiveness with a polarizer by providing an easy-adhesion layer on the surface of a transparent film used as a polarizer protective film.

  For example, in Patent Document 1, an easy-adhesion film in which an easy-adhesion layer containing fine particles and a binder resin is provided on the surface of an acrylic film has excellent adhesiveness to a polarizer, and is used when the film is wound into a roll. It describes that blocking can be suppressed. In the example of Patent Document 1, a polarizer protective film is formed by providing an urethane easy-adhesion layer having an average thickness of 400 nm (thickness range: 300 to 500 nm) containing 1 to 7% by weight of silica fine particles on the surface of an acrylic film. Is shown.

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. A polarizing plate using the easy-adhesion film described in Patent Literature 1 as a polarizer protective film has excellent adhesion between the polarizer and the polarizer protective film, and has high adhesion reliability. However, when a polarizing plate using the easy-adhesion film disclosed in Patent Document 1 as a polarizer protective film is exposed to a high-humidity environment for a long time, streak-like unevenness may occur and display characteristics may be degraded. The challenge has been newly identified.

  In view of the above problems, the present invention is excellent in adhesion to a polarizer or the like, hardly causes blocking, and even when exposed to a high temperature and high humidity environment for a long time, optical defects such as streak-like unevenness occur. It is intended to provide an easily adhesive film which is difficult.

  In view of the above problems, the present inventors have studied and found that alkali components such as ammonia and amine added to the easy-adhesion composition for the purpose of improving the dispersibility of the fine particles remain in the easy-adhesion layer. It has been found that this is one of the causes of a decrease in durability in a humid environment, and that the above problem can be solved by setting the amount of alkali remaining in the easily adhesive layer to a predetermined range.

  The present invention relates to an easy-adhesion film having an easy-adhesion layer on the surface of a transparent film substrate, and a method for producing the same. The easy-adhesion layer contains a binder resin and fine particles. The content of the alkali component in the easy-adhesion layer is preferably from 5 to 75 ppm, and the total content of amine and ammonia is preferably from 5 to 75 ppm. The thickness of the easily adhesive 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 a binder resin for the easy-adhesion layer. The content of the fine particles in the easy-adhesion layer is preferably about 8 to 50% by weight. The fine particles of the easy adhesion layer may be embedded in the transparent film substrate.

  An easy-adhesion composition is applied to the surface of the transparent film substrate and heated to form an easy-adhesion layer. The easily adhesive composition contains a binder resin or a precursor thereof, fine particles, an alkali component, and a solvent. When the alkali component is contained in the easy-adhesion composition, the dispersibility of the fine particles is improved, and an easy-adhesion film excellent in slipperiness is 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 easy-adhesion composition, the volatilization of the alkali component is promoted, and an easy-adhesion layer with little residual alkali component can be formed. For example, the easy-adhesion composition may be heated at a temperature higher by at least 10 ° C. than the glass transition temperature of the transparent film substrate. By increasing the heating temperature, a region in which the fine particles of the easy-adhesion layer are buried in the transparent film substrate is likely to be formed, and the adhesion between the transparent film substrate and the easy-adhesion layer tends to be improved.

  After applying the easily adhesive composition on the transparent film substrate, stretching may be performed while heating the transparent film substrate. In particular, the adhesion between the transparent film substrate and the easy-adhesion layer is improved by stretching the transparent film substrate while heating the easy-adhesion composition at a temperature higher than the glass transition temperature of the transparent film substrate by 10 ° C. or more. Tend to.

  The above-mentioned easy-adhesion film is excellent in adhesion to other films, glass substrates, and the like. The easily adhesive film can be used, for example, as a polarizer protective film. For example, a polarizing plate can be obtained by attaching an easily adhesive film to the surface of a polyvinyl alcohol-based polarizer via an adhesive layer. 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 easy-adhesion 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, does not easily cause optical defects. It is suitably used as a film.

It is sectional drawing which shows the example of a structure of an easily bonding film. 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 easy adhesion film in which the interface layer is formed in the interface of the film base material and the easy adhesion layer. It is a cross-sectional TEM observation image of the easy-adhesion film in which the interface layer is not formed at the interface between the film substrate and the easy-adhesion layer. It is a cross Nicol observation photograph before and after the durability test of the polarizing plate

  FIG. 1 is a schematic cross-sectional view showing a configuration example of an easily adhesive film according to one embodiment of the present invention. The easy-adhesion film 1 is provided with the easy-adhesion layer 15 on at least one surface of the film substrate 11. An easy adhesion layer may be provided on both surfaces of the film substrate. The easily adhesive film is used by being bonded to another film, a glass substrate, or the like.

  Examples of the mode of use of the easily adhesive film include a polarizer protective film. FIG. 2 is a cross-sectional view illustrating a configuration example of a polarizing plate including the easy-adhesion film 1 as a polarizer protective film. The polarizing plate 100 includes the easy-adhesion film 1 attached to one surface (first main surface) of the polarizer 5 via an adhesive layer 6. In the polarizing plate 100 shown in FIG. 2, the easy-adhesion film 1 has the easy-adhesion layer 15 on the surface of the film substrate 11 to be bonded to the polarizer 5. An easy adhesion layer may be provided on the surface where the polarizer 5 is not bonded. In the polarizing plate 100 shown in FIG. 2, 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.

[Easy adhesive film]
The easy-adhesion film 1 includes an easy-adhesion 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 easily adhesive 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 preferable. Particularly preferred.

  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 adhesion layer>
The easy-adhesion layer 15 provided on the surface of the film substrate 11 contains a binder resin and fine particles. The provision of the easy-adhesion layer 15 can improve the adhesion to a film such as a polarizer, a glass substrate, or the like. When the easy-adhesion layer 15 contains fine particles, fine irregularities are formed on the surface of the easy-adhesion layer 15, and the slipperiness of the film is improved. Therefore, it contributes to the reduction of the damage when the easy-adhesive film 1 is transported in the roll and the suppression of blocking when the film is wound into a roll.

(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 easy-adhesion layer 15, a polyurethane resin is particularly preferable. The easy-adhesion layer 15 containing the polyurethane resin binder has high adhesion to the film substrate 11. Further, the easy-adhesion film 1 in which the easy-adhesion layer 15 contains a polyurethane resin binder tends to show high adhesiveness when a film such as a polarizer is laminated via the adhesive layer.

  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 constituting the easy-adhesion layer 15 preferably has a carboxy group. When the urethane resin has a carboxy group, a crosslinked structure can be introduced, and the adhesion durability between the easily adhesive film 1 and a polarizer or the like tends to be improved. 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. Introducing a crosslinked structure into the urethane resin tends to improve the adhesion durability between the easily adhesive film 1 and a polarizer or the like. 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. Acrylic polymers are preferred as the crosslinking agent because they have high solubility in the aqueous composition and have excellent compatibility with the urethane resin. In particular, when an acrylic polymer having an oxazoline group is used as a cross-linking agent, the adhesiveness between the easily adhesive film 1 and a film such as a polarizer tends to be improved.

  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)
By including fine particles in the easy-adhesion layer 15, fine irregularities are formed on the surface of the easy-adhesion layer, the slipperiness of the easy-adhesion film 1 is improved, and blocking can be suppressed. 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 easily adhesive layer. When the particle diameter of the fine particles is smaller than the thickness of the easy-adhesion layer, the fine particles can be prevented from falling off from the easy-adhesion 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 easy-adhesion layer 15.

  When forming the adhesive layer 15 from the composition of the aqueous system, it is preferable to use a highly water-dispersible particulates. 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 easily adhesive composition 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 easy-adhesion film 1 by forming irregularities on the surface of the easy-adhesion layer 15, the content of the fine particles in the easy-adhesion layer 15 is preferably 3% by weight or more, more preferably 5% by weight or more. In particular, when the thickness of the easy-adhesion layer 15 is small (for example, 280 nm or less), the surface of the easy-adhesion 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 easy adhesion 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 easy-adhesion 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 easily adhesive layer may decrease. Therefore, the content of the fine particles in the easy-adhesion layer 15 is preferably equal to or less than 50% by weight, more preferably equal to or less than 40% by weight, and still more preferably equal to or less than 30% by weight.

(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 easy-adhesion layer. When the easy-adhesion film 1 is used as a polarizer protective film, when the remaining alkali component of the easy-adhesion layer 15 is eluted by moisture or the like, the polarizer is degraded, the degree of polarization of the polarizing plate is reduced, and streak-like unevenness is caused. Optical defects may occur.

  In light of enhancing the humidification durability of the polarizing plate, the amount of residual alkali in the easy-adhesion 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 easily adhesive layer 15, the more preferable.

  On the other hand, if the amount of the remaining alkali in the easy-adhesion layer 15 is excessively small, the dispersibility of the fine particles is impaired, and poor appearance 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 easy-adhesion layer, appropriate irregularities are not formed on the surface of the easy-adhesion layer, and the slipperiness of the easy-adhesion film tends to decrease. Therefore, the residual alkali amount of the easy-adhesion 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 remaining alkali component in the easy-adhesion layer include amine and ammonia, and the total content of the amine and ammonia in the easy-adhesion layer is preferably within the above range. The amount of alkali in the easy-adhesion 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 easy-adhesion layer, the total of each component is defined as the alkali component content (remaining amount) of the easy-adhesion layer.

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

(Easy adhesive composition)
The easily adhesive composition 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 easily adhesive composition 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 easy-adhesion composition contains water as a solvent (and a dispersion medium), a binder resin or a precursor thereof, and fine particles. The easily adhesive composition preferably further contains an alkali component. As described above, the alkali component has an effect of promoting the dispersion of the fine particles. Fine particles having a small particle diameter tend to agglomerate easily.However, the easy-adhesion composition contains an alkali component such as ammonia or an amine, thereby improving the dispersibility of the fine particles and obtaining an easily-adhesive film having excellent appearance and slipperiness. Can be

  On the other hand, if the alkali contained in the easy-adhesion composition remains in the easy-adhesion layer, it may cause the moist 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 easy-adhesion composition, 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 deterioration of the polarizer, the pH of the easily adhesive composition (coating solution) is preferably about 7.5 to 9.

  From the viewpoint of improving the dispersibility of the fine particles, the amount of the alkali component contained in the easy-adhesion composition is preferably 300 ppm or more, more preferably 500 ppm or more, based on the solid content of the easy-adhesion composition. 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 easy-adhesion composition is determined by the solid content of the easy-adhesion composition. On the other hand, 50,000 ppm or less is preferable, 10,000 ppm or less is more preferable, and 5000 ppm or less is further preferable. As described above, specific examples of the alkali component contained in the easy-adhesion composition include amine and ammonia, and the total content of these alkali components is preferably within the above range.

  The alkali component contained in the easy-adhesion composition 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 easily adhesive composition as a catalyst for urethanizing a polyurethane precursor (polyol, isocyanate, or the like).

  By heating after applying the easy-adhesion composition on the film substrate, the alkali component is volatilized and removed, and the remaining alkali component of the easy-adhesion layer 15 can be reduced. From the viewpoint of promoting the volatilization of the alkali component by heating, the alkali component contained in the easy-adhesion composition 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 a plurality of alkali components are contained in the easy-adhesion composition, the boiling point of at least one alkali component is preferably in the above range, and the boiling point of two or more alkali components is preferably in the above range. It is preferable that the boiling point of the alkali component of 50% by weight or more with respect to the total amount of the alkali contained in the easy-adhesion layer is within the above range. It is ideal boiling point of all the alkaline component contained in the easy-adhesion composition is in the above range. For example, when the alkali components are amine and ammonia, the amine preferably has a boiling point within the above range.

  The easy-adhesion composition may include a crosslinking agent in addition to the binder resin (or a precursor thereof), fine particles, and an alkali component. The easily adhesive composition 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, and a surfactant. And additives such as lubricants.

(Formation of easy adhesion layer on film substrate)
Before applying the easy-adhesion composition onto the film substrate 11, the surface treatment of the film substrate may be performed. By performing the surface treatment, the wetting tension of the film substrate can be adjusted, and the adhesion to the easy-adhesion 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 the method for applying the easily adhesive composition 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 easy-adhesion composition 15 after application is heated and the solvent is removed to form the easy-adhesion layer 15. The precursor of the binder resin may be reacted and cured by heating. For example, when the easily adhesive composition contains a crosslinking agent, the crosslinking reaction can be promoted by heating.

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

  The heating temperature during the formation of the easy-adhesion 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 easy-adhesion composition can be promoted, and the alkali component contained in the easy-adhesion composition 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 easy-adhesion composition is increased, and the easy-adhesion composition easily penetrates into the surface of the film substrate. It is considered that the adhesion between the adhesive layer 15 and the adhesive layer 15 is improved. From the viewpoint of improving the adhesion of the easy-adhesion layer, the heating temperature is preferably Tg + 10 ° C. or higher, more preferably Tg + 15 ° C. or higher, and still 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-adhesion layer are mixed is easily formed. The formation of the interface layer tends to improve the adhesion between the film substrate 11 and the easy-adhesion 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 easy-adhesion layer 15 are embedded and embedded in the surface of the film substrate 11, the film base 11 and the easy-adhesion layer 15 An easily adhesive 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 since the binder resin adheres to the surface of the film substrate, the adhesion between the film substrate 11 and the easily adhesive layer 15 is improved.

  You may form an easy adhesion layer in the manufacturing process of a film base material. Moreover, you may form the easy-adhesion layer using the heating at the time of formation of a film base material. For example, when the film substrate is a stretched film, the easy-adhesion composition is applied to the surface of the film before stretching or the film after longitudinal stretching, and heat is applied during transverse stretching or simultaneous biaxial stretching by a tenter. Thus, drying of the solvent and curing of the resin can be performed.

  When the film substrate is stretched after application of the easy-adhesion composition, the stretching ratio is preferably 5 times or less, more preferably 4 times or less, and 3 times or less, from the viewpoint of suppressing problems such as cracks in the easy-adhesion layer. It is more preferably at most 2.5 times, particularly preferably at most 2.5 times. 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. When performing sequential biaxial stretching, as described above, the film is stretched in one direction (MD) by roll stretching, then the easy-adhesion composition is applied onto the film, and the easy-adhesion composition is heated during stretching by a tenter. May be performed.

  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 further preferably Tg + 20 ° C. or higher, as described above as the heating temperature of the easy-adhesion layer. In particular, it is preferable to perform stretching in at least one direction at the above temperature after the application of the easy-adhesion composition. 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 easy-adhesion composition are embedded is easily formed on the surface of the film base, and the film base 11 and the easy-adhesion layer 15 Adhesion tends to improve. As a reason that the fine particles are easily embedded in the film substrate by stretching at a high temperature, when the stretching is performed in a rubber state, the easy-adhesion composition easily spreads when the film substrate is deformed, and the surface unevenness formed at the time of deformation is reduced. That is, the fine particles are likely to be fitted in the concave portions. 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.

  The thickness of the easy-adhesion layer 15 can be adjusted by adjusting the solid content concentration and the application thickness of the easy-adhesion composition. In the case where the film substrate is stretched after the application of the easy-adhesion composition, the thickness of the easy-adhesion layer 15 can also be adjusted by the stretching ratio.

  The thickness of the easy-adhesion 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 easy-adhesive film 1 is used as a polarizer protective film, the smaller the thickness of the easy-adhesive layer 15 is, the more the humidification durability of the polarizing plate is improved, and the occurrence of optical defects such as streak-like unevenness tends to be reduced. There is. Further, as the thickness of the easy-adhesion layer 15 is smaller, a decrease in the degree of polarization when the polarizing plate is exposed to a humid environment tends to be suppressed.

  When the alkali component is excessively removed during the heating and drying of the easy-adhesion composition, the dispersibility of the fine particles in the binder resin is reduced, and the aggregation of the fine particles and the fine particles from the surface of the easy-adhesion layer accompanying this are reduced. Easily fall off. When the aggregation or falling off of the fine particles occurs, the slipperiness of the easily adhesive film is reduced, so that damage during transport and blocking during winding are likely to occur. Therefore, the thickness of the easy adhesion 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 easy adhesion layer may be 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, or 150 nm or more. The thickness of the easy-adhesion layer 15 is preferably in the above range from the viewpoint of appropriately exhibiting the effect of improving the adhesion by the easy-adhesion layer 15.

[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 FIG. By attaching the above-mentioned easy-adhesive film as a polarizer protective film to one surface of the polarizer, a polarizing plate having a transparent protective film on only 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 above-mentioned easy-adhesion film is attached to at least one surface of the polarizer. The polarizing plate may be one in which the above-mentioned easy-adhesive film is bonded to both surfaces of a polarizer. The polarizer 5 and the easy-adhesion film 1 are bonded together 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 easy-adhesion film 1 is not particularly limited as long as it is optically transparent. Epoxy resin, silicone resin, acrylic resin, polyurethane , Polyamide, polyether, polyvinyl alcohol and the like. 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, since the adhesiveness between the easily adhesive film and the polarizer is excellent. 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 radical polymerization starts by irradiation with ultraviolet rays 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.

  The photocurable adhesive such as a photoradical polymerizable 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. The content of the photoradical generator 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 represented by a carbonyl compound or the like can be added to the radical polymerizable adhesive. A photosensitizer is used to increase the curing speed and sensitivity by an electron beam. 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 easy-adhesion film 1 to one surface (first main surface) of the polarizer 5 via the adhesive layer 6. The easy-adhesion film 1 may have an easy-adhesion layer-forming surface bonded to the polarizer 5 via an adhesive layer, or a non-easy-adhesion layer-forming surface bonded to the polarizer 5 via an adhesive layer. It may be. As shown in FIG. 2, the polarizer 5 is attached to the surface of the easy-adhesion film 1 on which the easy-adhesion layer 15 is formed via the adhesive layer 6, so that the polarizer and the polarizer protective film (the easy-adhesion film 1) are bonded together. A polarizing plate having high adhesiveness and excellent mechanical strength and durability can be obtained. When the surface on which the easy-adhesion layer is not formed is bonded to the polarizer 5 via the adhesive layer, the adhesiveness with another film, an adhesive layer, a glass substrate, or the like provided on the easy-adhesion film can be improved. .

  In bonding the polarizer 5 and the easy-adhesion film 1, the adhesive composition is applied to one or both of the polarizer 5 and the easy-adhesion film 1, and then the polarizer 5 and the easy-adhesion film 1 are bonded together. It is preferable that the adhesive is cured by laminating with a roll laminator or the like. Examples of a method for applying the adhesive composition to the polarizer 5 and / or the easily adhesive 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 adhesive 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 easy-adhesive 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.

<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 thickness of the easily adhesive 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 an easy-adhesion layer (not shown) on the surface to be bonded to the polarizer 5. The transparent protective film 2 may be provided with an easy adhesion layer similar to the easy adhesion layer 15 of the easy adhesion 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 easy-adhesion composition]
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 an easily adhesive composition. This easily adhesive 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, an easy-adhesion layer was formed using this easy-adhesion composition.

[Example 1]
An easily adhesive 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. An acrylic resin is melt-extruded from a T-die to form a film with a thickness of 160 μm, and the above-mentioned easy-adhesion composition is applied to one surface of the film with a gravure coater at a wet thickness of about 9 μm, and a heating furnace at a temperature of 140 ° C. The film is stretched twice in the longitudinal direction (MD) and the width direction (TD) by a simultaneous biaxial stretching tenter, and an easy-adhesion film having an easy-adhesion layer having a thickness of 50 nm on one surface of an acrylic film having a thickness of 40 μm. I got

[Examples 2 to 4 and Comparative Examples 1 and 2]
An easy-adhesion film was obtained in the same manner as in Example 1, except that the coating thickness of the easy-adhesion composition was changed. The thickness (after stretching) of the easily adhesive 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 easily adhesive film was obtained in the same manner as in Example 1 except that the stretching temperature was changed.

[Comparative Example 6]
The coating of the easy-adhesion composition with a gravure coater was not performed, and an acrylic film having a thickness of 40 μm without an easy-adhesion layer was obtained.

[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)
A biaxially stretched cyclic polyolefin film ("Zeonor Film ZF-14" manufactured by Zeon Corporation) was used as a polarizer protective film on one side using the easy-adhesive film of each Example and Comparative Example as a polarizer protective film on the other side. Was. The above-mentioned ultraviolet-curable adhesive is applied to a thickness of about 1 μm on the surface of the easy-adhesion film on which the easy-adhesion layer is formed and the surface of the Zeonor film, and is adhered to a polarizer with a roll laminator. ^The adhesive was cured by irradiating ultraviolet light of No. 2 to obtain a polarizing plate having an acrylic film (easy adhesion film) on one surface of the polarizer and a Zeonor film on the other surface.

[Evaluation]
<Remaining alkali amount of easy adhesion layer>
The amounts of triethylamine and ammonia remaining in the easily adhesive layer were quantified. The remaining amount of triethylamine was determined by weighing a powder obtained by shaving the easily adhesive layer from the surface of the easily adhesive 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 easily adhesive 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 easy adhesion layer>
An adhesive tape (Nitto Denko “No. 31B”) was pressure-bonded to the surface of the easy-adhesion film on which the easy-adhesion layer was formed at a linear pressure of 8 kg / m and a pressure bonding speed of 0.3 m / min, and stored at 50 ° C. for 48 hours. The tip of the pressure-sensitive adhesive tape was gripped and a 180 ° peel test was performed at a pulling speed of 30 m / min, and the adhesion of the easily adhesive layer was determined according to the following criteria.
〇: Peeling off at the interface between the adhesive tape and the adhesive layer without peeling of the adhesive layer from the acrylic film ×: Peeling off at the interface between the acrylic film and the adhesive layer

<Visual evaluation>
The surface of the easy-adhesion film was visually observed, and the presence or absence of local turbidity (haze increase) due to the aggregation of silica particles and the presence or absence of scratches on the surface on which the easy-adhesion layer was not formed were evaluated.
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 was formed on the surface where the easily adhesive layer was not formed. The following scratches were observed. ×: Turbidity due to aggregation of silica particles and scratches on the surface on which the easily adhesive layer was not formed were observed.

<Presence of interface layer>
The cross section of the easy-adhesion film was observed with a transmission electron microscope (TEM), and at the interface between the acrylic film and the easy-adhesion layer, a region (interface layer) in which particles in the easy-adhesion layer were embedded in the acrylic film. The presence was checked. 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

  Cross Nicols observation photograph (taken with “EYESCALE-4W” manufactured by Eye System, a low-luminance unevenness measurement system) before and after the durability test (60 ° C., 90% Rh, 500 hours) of the polarizing plates of Example 1 and Comparative Example 2. As shown in FIG.

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

  In the polarizing plate using the acrylic film of Comparative Example 6 in which the easy-adhesion layer was not formed, no linear streaks were observed even after the humidification durability test, and the optical properties were small with a small decrease in the degree of polarization. However, adhesion between the acrylic film and the polarizer was low, and peeling of the acrylic film from the polarizer was observed at the end of the polarizing plate after the humidification durability test.

  The easy-adhesion film of Comparative Example 2 including the easy-adhesion layer having a thickness of 350 nm had good adhesion between the acrylic film and the easy-adhesion layer, and also had a good appearance. However, in the polarizing plate using this easy-adhesion film as the 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 easily adhesive layer) was 120 ° C. or less, the degree of polarization after the humidification durability test was significantly reduced and remarkable streak-like unevenness was confirmed, similarly to Comparative Example 2. Was done.

  The easy-adhesion films of Examples 1 to 4 in which an easy-adhesion 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 the fine particles and had a good appearance. Although the easy-adhesion film of Example 1 had fine scratches on the surface on which the easy-adhesion layer was not formed, the film was buried with an adhesive or an adhesive at the time of lamination with another member, and optically. It was a level of scratch that would not be a disadvantage. Further, the polarizing plates using the easy-adhesive films of Examples 1 to 4 were superior to the polarizing plate using the easy-adhesive film of Comparative Example 2 in humidification durability, and generation of streaks was suppressed.

  In the easy-adhesion film of Comparative Example 1 in which the easy-adhesion layer having a thickness of 30 nm was formed, the humidification durability of the polarizing plate was good, but cloudiness due to aggregation of silica fine particles and damage to the surface on which the easy-adhesion layer was not formed were observed. , Appearance was poor. It is considered that the generation of the scratches is caused by the fact that the silica fine particles fell off from the surface of the easy-adhesion layer due to the decrease in dispersibility, and the slipperiness of the easy-adhesion film was reduced.

  From the comparison between Examples 1 to 4 and Comparative Examples 1 and 2, as the thickness of the easy-adhesion 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 excellent in humidification durability is obtained. It can be seen that it can be obtained. On the other hand, when the thickness of the easy-adhesion layer is excessively small and the residual alkali component is excessively small, it is found that poor appearance and a decrease in slipperiness occur due to a decrease in the dispersibility of the fine particles.

  In Examples 5 and 6, in which a 200-nm-thick easy-adhesion layer was formed at a stretching temperature of 160 ° C. or 180 ° C., as in Example 3, the appearance of the easy-adhesion 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 easy-adhesion layer was formed at a stretching temperature of 80 to 120 ° C., the amount of alkali remaining in the easy-adhesion layer was large, and, as in Comparative Example 2, a remarkable uneven streaks after the humidification durability test of the polarizing plate. Was confirmed.

  From these results, as long as the dispersibility of the fine particles is not reduced, by reducing the amount of alkali remaining in the easy-adhesion layer, an easily-adhesive film having excellent humidification durability of the polarizing plate when used as a polarizer protective film is obtained. It is understood that it can be done.

  In Comparative Examples 3 to 5 in which the stretching was performed at a low temperature, the adhesion between the acrylic film and the easily adhesive layer was inferior to those of the other examples. In Example 3 and the like, at the interface between the acrylic film and the easily-adhesive layer, an interface layer (see FIG. 3) in which the particles were embedded in the acrylic film was formed. No interface layer was formed (see FIG. 4). From these results, by increasing the heating temperature after application of the easy-adhesion composition, in addition to being able to efficiently volatilize the alkali component in the easy-adhesion composition and reduce the amount of residual alkali, the film base and it can be seen that can improve the adhesion at the interface between the adhesive layer.

DESCRIPTION OF SYMBOLS 1 Easy-adhesion film 11 Film base material 15 Easy-adhesion layer 2 Transparent film 5 Polarizer 6,7 Adhesive layer 100 Polarizer

Claims (13)

An easy-adhesion film including an easy-adhesion layer on the surface of the transparent film substrate,
The easy adhesion layer contains a binder resin and fine particles,
The easy-adhesion film, wherein the content of the alkali component in the easy-adhesion layer is 5 to 75 ppm.   The easy-adhesion film according to claim 1, wherein the thickness of the easy-adhesion layer is 40 to 280 nm.   The easy adhesion film according to claim 1, wherein the content of the fine particles in the easy adhesion layer is 8 to 50% by weight.   The easy-adhesion film according to any one of claims 1 to 3, wherein the transparent film substrate is an acrylic film.   The easy-adhesion film according to any one of claims 1 to 4, wherein the binder resin of the easy-adhesion layer is a urethane-based resin.   The easy-adhesion film according to any one of claims 1 to 5, wherein, at an interface between the transparent film substrate and the easy-adhesion layer, there is a region where the fine particles are embedded in the transparent film substrate. A method for producing an easily adhesive 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, an easy-adhesive composition containing an alkali component and a solvent is applied,
A method for producing an easy-adhesion film, wherein the easy-adhesion composition is heated at a temperature higher than the glass transition temperature of the transparent film substrate by 10 ° C. or more to evaporate the solvent and the alkali component.   The method for producing an easily adhesive film according to claim 7, wherein the alkali component has a function of accelerating dispersion of the fine particles.   9. The method for producing an easy-adhesion film according to claim 7, wherein the easy-adhesion composition contains a polyurethane precursor as a precursor of the binder resin, and contains a tertiary amine as the alkali component. 10.   The method for producing an easy-adhesion film according to any one of claims 7 to 9, wherein the easy-adhesion composition includes, as the alkali component, an alkali component having a boiling point of 150 ° C or lower.   The transparent film substrate coated with the easy-adhesion composition is stretched in at least one direction while heating the easy-adhesion composition at a temperature higher by 10 ° C. or more than the glass transition temperature of the transparent film substrate. The method for producing an easily adhesive film according to any one of 7 to 10. 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 easy-adhesion film according to any one of claims 1 to 6.   An image display device, comprising: an image display cell; and the polarizing plate according to claim 12.