JP6568666B1 - Easy-adhesive film and method for producing the same, polarizing plate, and image display device - Google Patents

Abstract

An easy-adhesive film that exhibits high adhesiveness to a film such as a polarizer, is less likely to block, and is excellent in uniformity and durability. An easily adhesive film (1) includes an easily adhesive layer (15) on the surface of a transparent film substrate (11). The easy adhesion layer (15) contains a binder resin and inorganic fine particles having an average primary particle diameter of 10 to 100 nm. Content of the alkali component of an easily bonding layer (15) is 5-75 ppm. An easy-adhesion layer can be formed by applying an easy-adhesion composition containing a binder resin or a precursor thereof, inorganic fine particles, an alkali component and a solvent on a transparent film substrate and heating. [Selection] Figure 1

Description

  The present invention relates to an easy-adhesion film comprising an easy-adhesion 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 easily adhesive film is bonded 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, personal computer monitors, and televisions. In the liquid crystal display device, a polarizing plate is disposed on the viewing side surface of the liquid crystal cell because of its display principle. In the transmissive liquid crystal display device, polarizing plates are arranged on both surfaces of the liquid crystal cell. In an organic EL display device, in order to prevent external light from being reflected by a metal electrode (cathode) and viewed like a mirror surface, a circularly polarizing plate (typically, a polarizing plate and 1 / There are cases where a laminate of four-wave plates is disposed.

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

  Cellulose-based films such as cellulose acetate are widely used as the polarizer protective film bonded to the surface of the polarizer because of its excellent adhesiveness with PVA-based polarizers. As the transparent protective film, a film made of a resin material such as acrylic, polyester, polycarbonate, or cyclic polyolefin is also used. Films made of these resin materials have low moisture permeability compared to cellulosic films, and polarizing plates with a low moisture permeability resin film bonded to the surface of a polarizer are exposed to a high humidity environment for a long time. However, the change in optical properties is small and the durability tends to be excellent.

  On the other hand, a film made of a resin material such as acrylic, polyester, polycarbonate, or cyclic polyolefin tends to have lower adhesion to a PVA polarizer than a cellulose film. Therefore, a method has been proposed in which an easy-adhesion layer is provided on the surface of a transparent film used as a polarizer protective film to improve adhesion with the polarizer.

  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 is excellent in adhesiveness with a polarizer, and when the film is wound into a roll shape It is described that blocking can be suppressed. In the Example of Patent Document 1, an easy-adhesive film comprising a urethane easy-adhesive layer having an average thickness of 400 nm (thickness range of 300-500 nm) containing 1 to 7% by weight of silica fine particles on the surface of an acrylic film is a polarizer protective film. The example used as is shown.

Japanese Patent No. 5354733

  As the size and brightness of image display devices increase, the polarizing plate constituting the image display device has a small change in optical characteristics even in a harsher environment (for example, higher temperature and higher humidity conditions). It has come to be required. The polarizing plate using the easy-adhesion film described in Patent Document 1 as a polarizer protective film is excellent in adhesion between the polarizer and the polarizer protective film, and has high adhesion reliability. However, the polarizing plate using the easy-adhesion film disclosed in Patent Document 1 as a polarizer protective film is likely to cause streaky unevenness when exposed to a high humidity environment for a long time, resulting in deterioration of display characteristics. A new issue has been identified.

  In view of the above problems, the present invention is excellent in adhesiveness with a polarizer or the like, is not easily blocked, and has optical defects such as streaky irregularities even when exposed to a high temperature and high humidity environment for a long time. The purpose is to provide a difficult-to-adhere adhesive film.

  As a result of the study by the present inventors in view of the above problems, alkali components such as ammonia and amine added to the easy-adhesion composition for the purpose of improving the dispersibility of the inorganic fine particles remain in the easy-adhesion layer. However, it has been found that this is a cause of a decrease in durability in a humidified environment, and that the above problem can be solved by setting the residual alkali amount in the easy-adhesive layer within a predetermined range.

  The present invention relates to an easy-adhesion film comprising 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 inorganic fine particles having an average primary particle diameter of 10 to 100 nm. As for content of the alkali component of an easily bonding layer, 5-75 ppm is preferable. The thickness of the easy adhesion layer is preferably 40 to 280 nm.

  An acrylic film or the like is used as the transparent film substrate. Urethane resin or the like is used as the binder resin for the easy adhesion layer. The content of inorganic fine particles in the easy-adhesion layer is preferably about 8 to 50% by weight. The inorganic fine particles of the easy adhesion layer may be embedded in the transparent film substrate.

  An easy-adhesion layer is formed by apply | coating an easily bonding composition to the surface of a transparent film base material, and heating. The easy-adhesion composition contains a binder resin or a precursor thereof, inorganic fine particles having an average primary particle size of 10 to 100 nm, an alkali component, and a solvent. By including an alkali component in the easy-adhesive composition, the dispersibility of the inorganic fine particles is improved, and an easy-adhesive film excellent in slipperiness is obtained. The alkaline component can also act as a catalyst for promoting the reaction of the binder resin (precursor). From the viewpoint of promoting volatilization of the alkali component by heating, the boiling point of the alkali component is preferably 150 ° C. or less. Examples of the alkali component include amines and ammonia.

  By increasing the heating temperature after application of the easy-adhesion composition, volatilization of the alkali component can be 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 that is 10 ° C. or more higher than the glass transition temperature of the transparent film substrate. By increasing the heating temperature, a region in which the inorganic fine particles of the easy adhesion layer are embedded in the transparent film substrate is easily formed, and the adhesion between the transparent film substrate and the easy adhesion layer tends to be improved.

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

  Said easily adhesive film is excellent in adhesiveness with another film, a glass substrate, etc. The easily adhesive film can be used as a polarizer protective film, for example. For example, a polarizing plate can be obtained by attaching an easy-adhesion film to the surface of a polyvinyl alcohol 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-adhesive film of the present invention is excellent in adhesiveness, is less likely to block, and is less susceptible to optical defects even when exposed to a high temperature and high humidity environment for a long time. It is suitably used as a film.

It is sectional drawing which shows the structural example of an easily bonding film. It is sectional drawing which shows the structural example of a polarizing plate. It is a cross-sectional TEM observation image of the easily bonding film in which the interface layer is formed in the interface of a film base material and an easily bonding layer. It is a cross-sectional TEM observation image of the easily bonding film in which the interface layer is not formed in the interface of a film base material and an easily bonding 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 illustrating a configuration example of an easy-adhesion film according to an embodiment of the present invention. The easy adhesion film 1 is provided with an easy adhesion layer 15 on at least one surface of the film substrate 11. Easy adhesion layers may be provided on both sides of the film substrate. The easily adhesive film is used by being bonded to another film, a glass substrate, or the like.

  A polarizer protective film is mentioned as a usage form of an easily bonding 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 an easy-adhesive film 1 bonded 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 an easy-adhesion layer 15 on the bonding surface of the film substrate 11 with 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 via the adhesive layer 7.

[Easily adhesive film]
The easy adhesion film 1 includes an easy adhesion layer 15 on at least one surface of the film substrate 11.

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

  Examples of the cyclic polyolefin resin include polynorbornene. Examples of commercially available cyclic polyolefin-based resins include ZEONOR and ZEONEX manufactured by Nippon Zeon, Arton manufactured by JSR, Appel manufactured by Mitsui Chemicals, and TOPAS ADVANCED POLYMERS. The cyclic polyolefin film preferably contains 50% by weight or more of a cyclic olefin resin.

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

  In this specification, “(meth) acryl” means acrylic and / or methacrylic. 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 the like; Acrylic resins having a lactone ring structure described in JP 2000-230016 A, JP 2001-151814 A, JP 2002-120326 A, JP 2002-254544 A, JP 2005-146084 A, etc. It may be used. Acrylic resin having a glutaric anhydride structure and an 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 base 11 is an acrylic film, the content of the acrylic resin in the film base is preferably 50% by weight or more, more preferably 60 to 98% by weight, and still 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, an acrylic film excellent in optical isotropy can be obtained by canceling the birefringence of the acrylic resin. Moreover, you may mix | blend thermoplastic resins other than an acrylic resin for the purpose of the mechanical strength improvement of a film, etc.

  Examples of thermoplastic resins other than acrylic resins include olefin polymers, vinyl halide polymers, polystyrene, copolymers of styrene and acrylic monomers, polyester, polyamide, polyacetal, polycarbonate, polyphenylene oxide, polyphenylene sulfide, poly Examples include ether ether ketone, polysulfone, polyether sulfone, polyoxybenzylene, polyamideimide, and rubber-based polymer.

  The film substrate 11 may contain additives such as an antioxidant, a stabilizer, a reinforcing material, an ultraviolet absorber, a flame retardant, an antistatic agent, a colorant, a filler, a plasticizer, a lubricant, and a filler. A resin material and an additive may be mixed to form a thermoplastic resin composition such as a pellet in advance before forming a film.

  The thickness of the film substrate 11 is about 5 to 200 μm. From the viewpoint of mechanical strength, transparency, handling properties, 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, and 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. Although the upper limit of Tg of the film base material 11 is not specifically limited, 170 degreeC or less is preferable from viewpoints of a moldability etc.

  Examples of the method for producing the film substrate 11 include a solution casting method, a melt extrusion method, a calendar method, and a compression molding method. The film substrate 11 may be 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 a biaxially stretched film is particularly preferred 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 can be obtained even when stretched.

<Easily adhesive layer>
The easy adhesion layer 15 provided on the surface of the film substrate 11 includes a binder resin and fine particles. By providing the easy-adhesion layer 15, it is possible to improve the adhesion to a film such as a polarizer or a glass substrate. 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 at the time of roll conveyance of the easy-adhesion film 1, and the blocking suppression at the time of winding up in roll shape.

(Binder resin)
As binder resin, it has excellent adhesion to film substrates such as acrylic film, so it can be crosslinked with polyurethane resin, epoxy resin, isocyanate resin, polyester resin, polymers containing amino group in the molecule, oxazoline group, etc. 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 a polyurethane resin binder has high adhesion to the film substrate 11. Moreover, the easy-adhesion film 1 in which the easy-adhesion layer 15 contains a polyurethane resin binder tends to exhibit high adhesiveness when a film such as a polarizer is laminated via an 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) acrylic acid ester and a hydroxyl group-containing monomer. Examples of the (meth) acrylic acid ester include methyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, (meth) Hydroxyalkyl esters of (meth) acrylic acid such as 4-hydroxybutyl acrylate and 2-hydroxypentyl (meth) acrylate; (meth) acrylic monoesters of polyhydric alcohols such as glycerin and trimethylolpropane; N-methylol (Meth) acrylamide etc. are mentioned.

  The polyacryl polyol may contain monomer components other than those described above. Other monomer components include unsaturated monocarboxylic acids such as (meth) acrylic acid; unsaturated dicarboxylic acids such as maleic acid and anhydrides and diesters thereof; 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 Halogenated α, β-unsaturated aliphatic monomers such as α; β-unsaturated aromatic monomers such as styrene and α-methylstyrene.

  The polyester polyol is typically obtained by a reaction between a polybasic acid and a polyol. Polybasic acids include aromatics such as orthophthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, tetrahydrophthalic acid, etc. Dicarboxylic acid; oxalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, octadecanedicarboxylic acid, tartaric acid, alkylsuccinic acid, linolenic acid Aliphatic dicarboxylic acids such as maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid; alicyclic rings such as hexahydrophthalic acid, tetrahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, 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, , 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-penty Lenglycol, 3-methyl-1,5-pentylene glycol, 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 an alkylene oxide to a polyhydric alcohol by ring-opening polymerization. Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, trimethylolpropane, and the like. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, styrene oxide, and tetrahydrofuran.

  Examples of polyisocyanates include tetramethylene diisocyanate, dodecamethylene diisocyanate, 1,4-butane diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2 -Aliphatic diisocyanates such as methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate; isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-cyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate Alicyclic diisocyanates such as methylcyclohexylene diisocyanate and 1,3-bis (isocyanatomethyl) cyclohexane Tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1 , 5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate and other aromatic diisocyanates; dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, α, α, α, α-tetramethylxylylene Examples include aromatic aliphatic diisocyanates such as range isocyanate.

  The urethane resin constituting the easy-adhesion layer 15 preferably has a carboxy group. When the urethane resin has a carboxy group, a cross-linked structure can be introduced, and the adhesion durability between the easy-adhesive film 1 and the polarizer tends to be improved. The urethane resin having a carboxy group can be 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 and dihydroxysuccinic acid. Examples of the dihydroxycarboxylic acid include dialkylolalkanoic acids such as dimethylolalkanoic acid (for example, dimethylolacetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, dimethylolbutyric acid, dimethylolpentanoic acid).

  The method for producing the urethane resin is not particularly limited, and any one of a one-shot method in which monomer components are reacted at a time and a multistage method in which stepwise reaction is performed may be used. When introducing a carboxy group into a urethane resin using a chain extender having a free carboxy group, a multistage 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 5,000 to 600,000, and more preferably 10,000 to 400,000. 10-50 are preferable and, as for the acid value of a urethane resin, 20-45 are more preferable.

  The urethane resin may have a crosslinked structure. By introducing a cross-linked structure into the urethane resin, the adhesion durability between the easy-adhesive film 1 and the polarizer tends to be improved. As the crosslinking agent, those capable of reacting with the crosslinkable 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. Since the oxazoline group has low reactivity with the carboxy group at room temperature, the pot life when mixed with a urethane resin is long, and the lead time of the process can be flexibly handled.

  The crosslinking agent may be a low molecular compound or a polymer. An acrylic polymer is preferred as the cross-linking agent because of its high solubility in aqueous compositions and excellent compatibility with urethane resins. In particular, when an acrylic polymer having an oxazoline group is used as a crosslinking agent, the adhesion between the easy-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 and more preferably 3 to 20 parts by weight with respect to 100 parts by weight of the urethane resin.

(Fine particles)
By including fine particles in the easy-adhesion layer 15, a fine uneven shape is 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 irregularities that contribute to the improvement of 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 further preferably 20 nm or more. When the average primary particle diameter of the fine particles is smaller than the visible light wavelength, scattering of visible light at the interface between the binder resin and the fine particles is suppressed, and an easily adhesive film having high transparency can be obtained. Therefore, the particle diameter of the fine particles is preferably 100 nm or less, more preferably 80 nm or less, still more preferably 60 nm or less, and particularly preferably 50 nm or less.

  Inorganic particles are preferred as the fine particles of the easy-adhesion layer 15 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. Among these, inorganic oxides are preferable. In order to suppress light scattering caused by the fine particles, it is preferable that the refractive index difference between the binder resin (generally having a refractive index of about 1.5) and the fine particles is small. Silica particles are preferred as the fine particles of the easy-adhesion layer 15 because the difference in refractive index from the binder resin is small and the dispersibility is excellent.

  When the easy-adhesion layer 15 is formed from an aqueous composition, it is preferable to use fine particles with high water dispersibility. You may mix | blend the fine particle aqueous dispersion in a composition. In order to improve the dispersibility of the inorganic fine particles, it is preferable to add an alkali component such as amine or ammonia to make the easily adhesive composition weakly alkaline.

  As the water-dispersible silica particles, colloidal silica is preferably used. As the colloidal silica, commercially available products such as Quartron PL series manufactured by Fuso Chemical Industry Co., Ltd., Snowtex series manufactured by Nissan Chemical Industry Co., Ltd., Aeroerosp series produced by Nippon Aerosil Co., Ltd., and AEROSIL series may be used.

  From the viewpoint of enhancing the slipperiness of the easy-adhesive film 1 by forming irregularities on the surface of the easy-adhesive layer 15, the content of fine particles in the easy-adhesive layer 15 is preferably 8% by weight or more, more preferably 10% by weight or more. 12% by weight or more is more preferable. In particular, when the thickness of the easy-adhesion layer 15 is 280 nm or less, by increasing the content of fine particles to increase the amount of fine particles per unit area (number density), unevenness is uniformly formed in the surface of the easy-adhesion layer 15. Is preferably formed. If the content of the fine particles in the easy-adhesion layer 15 is excessively large, optical characteristics may be deteriorated due to an increase in light scattering at the interface between the binder resin and the fine particles. Moreover, since the relative content of the binder resin decreases as the fine particle content increases, the adhesion of the easy-adhesion layer may decrease. Therefore, the content of fine particles in the easy-adhesion layer 15 is preferably 50% by weight or less, more preferably 40% by weight or less, and further preferably 30% by weight or less.

(Residual alkali amount)
If an alkali component such as amine or ammonia is used to improve the dispersibility of the inorganic fine particles, the alkali component inevitably remains in the easy-adhesion layer. When the easy-adhesive film 1 is used as a polarizer protective film, if the residual alkali component of the easy-adhesive layer 15 is eluted by moisture or the like, the polarizer is deteriorated, and the degree of polarization of the polarizing plate is reduced, stripe-like unevenness, etc. An optical defect may occur.

  From the viewpoint of enhancing the humidification durability of the polarizing plate, the residual alkali amount of the easy-adhesion layer 15 is preferably 75 ppm or less, more preferably 70 ppm or less, further preferably 60 ppm or less, and particularly preferably 55 ppm or less. From the viewpoint of improving the humidification durability of the polarizing plate, the smaller the residual alkali amount in the easy-adhesion layer 15, the better.

  On the other hand, if the residual alkali amount of the easy-adhesion layer 15 is too small, the dispersibility of the fine particles is impaired, and appearance defects such as white turbidity due to the aggregation of the fine particles may occur. In addition, due to aggregation of fine particles due to a decrease in dispersibility and falling off from the easy-adhesion layer, appropriate unevenness is 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 further preferably 20 ppm or more.

  The amount of alkali in the easy-adhesion layer can be quantified by liquid chromatography, ion chromatography, or the like depending on the type of alkali component. The alkali component may be quantified by an analysis 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 (residual amount) of the easy-adhesion layer.

<Formation of easy adhesion layer>
The formation method of the easily bonding layer 15 to the surface of the film base material 11 is not specifically limited. Preferably, the easy-adhesion layer 15 is formed by apply | coating the easily bonding composition (coating liquid) containing binder resin and microparticles | fine-particles on the film base material 11, and heating.

(Easily adhesive composition)
The easy-adhesion composition is preferably an aqueous composition using water as a solvent (and a dispersion medium for fine particles). 1-30 weight% is preferable, as for the density | concentration of solid content (nonvolatile component) in an easily bonding composition, 2-20 weight% is more preferable, and 3-15 weight% is further more preferable.

  The water-based easy-adhesion composition includes water as a solvent (and a dispersion medium), a binder resin fat or a precursor thereof, and inorganic fine particles. The easy-adhesion composition preferably further contains an alkali component. As described above, the alkali component has an action of promoting the dispersion of the inorganic fine particles. Therefore, when the easy-adhesion composition contains an alkali component, an easy-adhesion film that improves the dispersibility of the inorganic fine particles and is excellent in appearance and slipperiness can be obtained.

  On the other hand, when the alkali contained in the easy-adhesive composition remains in the easy-adhesive layer, it may cause a decrease in the wet heat resistance of the polarizing plate. In particular, strong alkali such as caustic can cause the polarizer to deteriorate even in a small amount. Therefore, as the alkali component contained in the easy-adhesion composition, weak alkali components such as ammonia and amines are preferable. The pH of the easy-adhesive composition (coating liquid) is preferably about 7.5 to 9 from the viewpoint of achieving both improved dispersibility of the inorganic fine particles and prevention of deterioration of the polarizer.

  From the viewpoint of improving the dispersibility of the inorganic 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 residual alkali amount. Therefore, the amount of the alkali component contained in the easy-adhesion composition is based on the solid content of the easy-adhesion composition. On the other hand, 50000 ppm or less is preferable, 10000 ppm or less is more preferable, and 5000 ppm or less is more preferable.

  The alkali component contained in the easy-adhesion composition may have a catalytic action or the like in addition to the improvement in dispersibility of the inorganic fine particles. For example, when the binder resin is a urethane-based resin, a tertiary amine such as triethylamine may be included in the easy-adhesion composition as a urethanization catalyst for a polyurethane precursor (polyol, isocyanate, etc.).

  By heating after applying an easily bonding composition on a film base material, an alkali component can be volatilized and removed, and the remaining alkali component of the easily bonding 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 less, further preferably 120 ° C. or less, and particularly preferably 110 ° C. or less. 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 points of two or more alkali components are preferably in the above range. The boiling point of the alkali component of 50% by weight or more is preferably in the above range with respect to 100 parts by weight of the total amount of alkali contained in the easy-adhesion layer. Ideally, the boiling points of all alkali components contained in the easy-adhesion composition are in the above range.

  The easy-adhesion composition may contain a crosslinking agent in addition to the binder resin (or its precursor), the inorganic fine particles, and the alkali component. Easy-adhesion compositions include cross-linking accelerators, catalysts, antioxidants, UV absorbers, leveling agents, anti-blocking agents, antistatic agents, dispersion stabilizers, antifoaming agents, thickeners, dispersants, and surfactants. In addition, additives such as a lubricant may be included.

(Formation of easy adhesion layer on film substrate)
Before applying the easy-adhesion composition on 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 with 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 easy-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 layer 15 is formed by heating the easy-adhesion composition after application | coating and removing a solvent. The precursor of the binder resin may be reacted and cured by heating. For example, when the easy-adhesion composition contains a crosslinking agent, the crosslinking reaction can be accelerated by heating.

  The heating temperature when forming the easy-adhesion layer is, for example, about 50 to 200 ° C. From the viewpoint of promoting the curing reaction of the resin component in the easy-adhesive composition and efficiently volatilizing and removing the alkali component contained in the easy-adhesive composition, the heating temperature is preferably 100 ° C or higher, more preferably 120 ° C or higher, 130 degreeC or more is further more preferable, and 135 degreeC or more is especially preferable. Moreover, it is preferable that heating temperature is higher than the boiling point of the alkali component contained in an easily bonding composition.

  The heating temperature at the time of forming 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 is promoted, and the alkali component contained in the easy-adhesion composition can be efficiently volatilized and removed. The heating temperature is preferably a temperature that is 10 ° C. or more higher than the Tg of the film substrate.

  By heating at a temperature higher than the Tg of the film substrate, the volatilization removal efficiency of the alkali in the easy-adhesive composition is enhanced, and the easy-adhesive composition easily penetrates into the surface of the film substrate. It is considered that the adhesion between the adhesive layer 15 and the easy adhesion 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 further preferably Tg + 20 ° C. or higher.

  When the film substrate is heated at a temperature of Tg + 10 ° C. or higher, the film substrate is changed from a glass state to a rubber state, and the surface is easily deformed. Therefore, at the interface between the film substrate 11 and the easy adhesion layer 15, the resin of the film substrate An interface layer in which components and constituent components of the easy-adhesion layer are mixed is easily formed. By forming the interface layer, the adhesion between the film substrate 11 and the easy adhesion layer 15 tends to be improved.

  In particular, as shown in the cross-sectional observation image of FIG. 3, when there is a region where fine particles of the easy-adhesion layer 15 are embedded in the surface of the film base 11, the film base 11 and the easy-adhesion layer 15 An easy-adhesion film with high adhesion is obtained. When the film substrate is heated to a temperature higher than Tg and the fine particles are embedded in the film substrate, and then the film substrate returns to the glass state, the fine particles embedded in the surface of the film substrate and the surroundings are present. It is considered that the adhesion between the film base material 11 and the easy-adhesion layer 15 is improved because the binder resin to be fixed adheres to the surface of the film base material.

  You may form an easily bonding layer in the manufacturing process of a film base material. Moreover, you may form an easily bonding 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-adhesive composition is applied to the surface of the film before stretching or the film after longitudinal stretching, and heating during transverse stretching with a tenter or simultaneous biaxial stretching is used. Then, the solvent can be dried and the resin can be cured.

  When the film substrate is stretched after the easy-adhesive composition is applied, the stretch ratio is preferably 5 times or less, more preferably 4 times or less, from the viewpoint of suppressing problems such as generation of cracks in the easy-adhesion layer. The ratio is further preferably 2 times or less and particularly preferably 2.5 times or less. Although the minimum of a draw ratio is not specifically limited, From a viewpoint of film strength improvement, 1.3 times or more are preferable and, as for a draw ratio, 1.5 times or more are more preferable. When a film base material is an acrylic film, it is preferable to implement extending | stretching by said draw ratio to each of a conveyance direction (MD) and the width direction (TD) from a viewpoint of film strength improvement.

  When biaxial stretching of the film substrate is performed, 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, after stretching the film in one direction (MD) by roll stretching, the easy-adhesive composition is applied on the film, and the easy-adhesive composition is heated during stretching by the 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. In particular, it is preferable to perform stretching in at least one direction at the above temperature after applying the easy-adhesive composition. When stretching is performed in a rubber state at a temperature higher than Tg of the film base, a region in which the fine particles in the easy-adhesive composition are embedded is easily formed on the surface of the film base, and the film base 11 and the easy-adhesion layer 15 are formed. There is a tendency for adhesion to improve. The reason why fine particles are easily embedded in the film substrate by stretching at a high temperature is that when the film substrate is stretched, the easy-adhesive composition easily spreads when the film substrate is deformed. It is mentioned that it is easy to be in a state where fine particles are fitted in the recess. In addition, when cooling is performed while releasing the stress after stretching, when the film base contracts, the particles fitted on the surface of the film base are fixed, so that a region where fine particles are embedded in the film base 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 coating thickness of the easy adhesion composition. When extending | stretching a film base material after apply | coating an easily bonding composition, the thickness of the easily bonding layer 15 can be adjusted also with a draw 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 further preferably 230 nm or less from the viewpoint of promoting the removal of the alkali component by heating. When the easy-adhesive film 1 is used as a polarizer protective film, as the thickness of the easy-adhesive layer 15 is smaller, the humidification durability of the polarizing plate is improved, and the occurrence of optical defects such as streaky unevenness tends to be reduced. There is. Moreover, there exists a tendency for the fall of the polarization degree when a polarizing plate is exposed to a humid environment, so that the thickness of the easily bonding layer 15 is small.

  When the alkali component is excessively removed during the heat-drying of the easy-adhesive composition, the dispersibility of the fine particles in the binder resin is reduced, and the fine particles are aggregated and the fine particles from the surface of the easy-adhesive layer. Is likely to fall off. When the fine particles are aggregated or dropped, the slipping property of the easy-adhesive film is lowered, and damage during transportation 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. Moreover, it is preferable that the thickness of the easy-adhesion layer 15 is the said range also from a viewpoint of making the adhesive improvement effect by the easy-adhesion layer 15 express appropriately.

[Polarizer]
The polarizing plate may be provided with a transparent protective film only on one surface of the polarizer, or may be provided with a transparent protective film on both surfaces of the polarizer 5 as shown in FIG. A polarizing plate having a transparent protective film only on one surface of the polarizer is formed by bonding the above-mentioned easy-adhesion film as a polarizer protective film to one surface of the polarizer. In the polarizing plate having the polarizer protective film on both surfaces of the polarizer, the above-mentioned easy-adhesion film may be bonded to at least one surface of the polarizer. The polarizing plate may be one in which the above-mentioned easy-adhesion film is bonded to both sides of a polarizer. The polarizer 5 and the easy-adhesive film 1 are bonded together via the adhesive layer 6.

<Polarizer>
As the polarizer 5, polyvinyl alcohol (PVA) in which a dichroic substance such as iodine or a dichroic dye is adsorbed on a polyvinyl alcohol film such as polyvinyl alcohol or partially formalized polyvinyl alcohol and oriented in one direction. A system polarizer is used. For example, a PVA polarizer can be obtained by subjecting a polyvinyl alcohol film to iodine staining and stretching.

  In the manufacturing process of the polarizer 5, treatments 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. Stretching may be either stretching in the air (dry stretching) or stretching in water or an aqueous solution containing boric acid, potassium iodide, etc. (wet stretching), and these 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 polarizer having a thickness of 10 μm or less can be used. Thin polarizers are described in, for example, JP-A-51-069644, JP-A-2000-338329, WO2010 / 100917, Patent No. 4691205, Patent No. 4751481, and the like. A thin polarizer may be mentioned. These thin polarizers are obtained by a production method including a step of stretching a PVA-based resin layer and a stretching resin base material in the state of a laminate, and a step of iodine staining. With this manufacturing method, even if the PVA-based resin layer is thin, it is supported by the stretching resin base material, so that it can be stretched without problems such as breakage due to stretching.

<Adhesive>
The material of the adhesive layer 6 used for bonding the polarizer 5 and the easy-adhesive 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 adherend and the material of the adhesive. When using the curable adhesive which shows adhesiveness by the crosslinking reaction after application | coating, 0.01-5 micrometers is preferable and, as for the thickness of the adhesive bond layer 6, 0.03-3 micrometers is more preferable.

  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 water-based adhesive include vinyl polymer, gelatin, vinyl latex, polyurethane, polyester, and epoxy. Among these, since it is excellent in the adhesiveness of an easily bonding film and a polarizer, a vinyl polymer is preferable and a polyvinyl alcohol-type resin is especially preferable. Among the 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, and more preferably 1000 to 4000, from the viewpoint of adhesiveness. The average saponification degree of the polyvinyl alcohol-based resin is preferably 85 mol% or more, and more preferably 90 mol% or more.

  The aqueous adhesive composition (solution) may contain a crosslinking agent in addition to a polymer such as a polyvinyl alcohol resin. As the crosslinking agent, a compound having at least two functional groups having reactivity with the polymer constituting the adhesive is used. Examples of the crosslinking agent for the polyvinyl alcohol 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. About 10-60 weight part is preferable with respect to 100 weight part of polyvinyl alcohol-type resin, and, as for the compounding quantity of the crosslinking agent in adhesive composition, 20-50 weight part is more preferable.

  The active energy ray-curable adhesive is an adhesive capable of radical polymerization, cationic polymerization, or anion polymerization by irradiation with active energy rays such as electron beams and ultraviolet rays. Among these, a photo-radical polymerizable adhesive that initiates radical polymerization upon irradiation with ultraviolet rays is preferable because it can be cured with low energy.

Examples of the monomer for the radical polymerizable adhesive include a compound having a (meth) acryloyl group and a compound having a vinyl group. Among these, a compound having a (meth) acryloyl group is preferable. Examples of the compound having a (meth) acryloyl group include C _1-20 chain alkyl (meth) acrylate, alicyclic alkyl (meth) acrylate, polycyclic alkyl (meth) acrylate and other alkyl (meth) acrylates; hydroxyl group Containing (meth) acrylate; Epoxy group-containing (meth) acrylate such as glycidyl (meth) acrylate and the like. Radical polymerizable adhesives are hydroxyethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, (meth) acrylamide, (meth) acryloylmorpholine Nitrogen-containing monomers such as Radical polymerizable adhesives include tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate, EO-modified di-acid as a crosslinking component. A polyfunctional monomer such as glycerin tetraacrylate may be included.

  Photocurable adhesives such as photoradical polymerizable adhesives preferably contain a photopolymerization initiator. What is necessary is just to select a photoinitiator suitably according to a reaction seed | species. For example, the radical polymerizable adhesive preferably contains a photo radical generator that generates radicals upon light irradiation as a photo polymerization initiator. The content of the photo radical generator is usually about 0.1 to 10 parts by weight, preferably 0.5 to 3 parts by weight with respect to 100 parts by weight of the monomer. In addition, when using a radically polymerizable adhesive as an electron beam curable type, 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. The photosensitizer is used for increasing the curing rate and sensitivity of the electron beam. The usage-amount of a photosensitizer is about 0.001-10 weight part normally with respect to 100 weight part of monomers, Preferably, it is 0.01-3 weight part.

  The adhesive may contain an appropriate additive as required. Examples of additives include coupling agents such as silane coupling agents and titanium coupling agents, adhesion promoters such as ethylene oxide, ultraviolet absorbers, deterioration inhibitors, dyes, processing aids, ion trap 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-adhesive film 1 may have an easy-adhesive layer forming surface bonded to the polarizer 5 via an adhesive layer, and an easy-adhesive layer non-formed surface bonded to the polarizer 5 via an adhesive layer. It may be. As shown in FIG. 2, the polarizer and the polarizer protective film (easily adhesive film 1) are bonded by attaching the polarizer 5 to the surface of the easily adhesive film 1 on which the easy adhesive layer 15 is formed via the adhesive layer 6. A polarizing plate having high adhesiveness and excellent mechanical strength and durability can be obtained. When the non-adhesive layer non-forming surface is bonded to the polarizer 5 through the adhesive layer, the adhesion to other films, pressure-sensitive adhesive layers, glass substrates and the like provided on the easy-adhesive film can be improved. .

  In laminating the polarizer 5 and the easy-adhesive film 1, after applying an adhesive composition to one or both of the polarizer 5 and the easy-adhesive film 1, the polarizer 5 and the easy-adhesive film 1 are bonded. It is preferable that the adhesive is cured by laminating with a roll laminator or the like. Examples of the method for applying the adhesive composition to the polarizer 5 and / or the easy-adhesion film 1 include a roll method, a spray method, and an immersion method. Before applying the adhesive composition to the surface of the polarizer 5 and / or the easy-adhesion film 1, surface treatment such as corona treatment, plasma treatment, and saponification treatment may be performed.

  After bonding the polarizer 5 and the easy-adhesive film 1, the adhesive layer 6 is formed by curing the adhesive according to the type of the adhesive. When an aqueous adhesive is used, the adhesive is cured by heat 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 ultraviolet rays.

<Transparent protective film>
The transparent protective film 2 may be bonded to the second main surface of the polarizer 5 via the adhesive layer 7. Any appropriate transparent film can be adopted as the transparent protective film 2. The thickness of the transparent protective film 2 is about 5 to 200 μm. From the viewpoint of mechanical strength, transparency, handling properties, 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 easy-adhesion film 1 and the transparent protective film 2 may be the same or different.

  Examples of the 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 -Styrenic polymers such as styrene copolymers; cyclic polyolefins such as polynorbornene; polycarbonates and the like.

  The transparent protective film 2 may include an easy-adhesion layer (not shown) on the bonding surface with 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.

  Examples of the adhesive layer 7 used for bonding the polarizer 5 and the transparent protective film 2 include various forms such as a water-based adhesive, a solvent-based adhesive, a hot-melt adhesive, and a radical polymerization curable adhesive. 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 forming the pressure-sensitive adhesive layer, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected and used. Can do. In particular, an acrylic pressure-sensitive adhesive is preferable because it is excellent in optical transparency, exhibits appropriate wettability and cohesiveness, 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 method of preparing a pressure-sensitive adhesive solution having a solid content concentration 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, and being attached on a polarizing plate, or on an appropriate substrate And a method of transferring the pressure-sensitive adhesive layer formed on the polarizing plate.

  You may provide an adhesive layer on both surfaces of a polarizing plate. When providing an adhesive layer on both surfaces of a polarizing plate, the composition and thickness of the adhesive layers on the front and back sides may be the same or different. The thickness of the 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, a plastic film whose surface is coated with a release agent such as a silicone release agent, a long-chain alkyl release agent, or a fluorine 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, a polarizing plate, and an illumination system as necessary, and incorporating a drive circuit. In an organic EL display device, a metal electrode or the like is bonded to the surface of an organic EL cell with a circularly polarizing plate that is a combination of the polarizing plate of the present invention and a retardation film (typically a quarter wave plate). Visibility can be improved by reducing re-emission of reflected light of external light due to.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not limited to these Examples. The following description of “%” is by weight unless otherwise specified.

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

[Example 1]
An easy-adhesion film was produced using a film production apparatus equipped with a melt extrusion film forming apparatus, a gravure coater, a tenter type simultaneous biaxial stretching apparatus, and a winding apparatus. As the acrylic resin, pellets of the same imidized MS resin (glass transition temperature: 120 ° C.) used for 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-mentioned easy-adhesion composition is applied to one surface of the film with a gravure coater with a wet thickness of about 9 μm. The film is stretched twice in the longitudinal direction (MD) and the width direction (TD) by a simultaneous biaxial stretching tenter, and has an easy-adhesion layer having a thickness of 50 nm on one surface of an acrylic film having a thickness of 40 μm. Got.

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

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

[Preparation of polarizing plate]
(Production of polarizer)
A long roll of polyvinyl alcohol (PVA) -based resin film (“Kuraray“ PE4500 ”) having a thickness of 45 μm is stretched uniaxially in the longitudinal direction so as to be 5.9 times in the longitudinal direction by a roll stretching machine. The shown swelling bath, dyeing bath, crosslinking bath 1, crosslinking bath 2, and washing bath were conveyed in 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 staining bath were adjusted so 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. An ultraviolet curable adhesive containing 3 parts by weight of “Irgacure 819” (manufactured “Irgacure 819”) was prepared.

(Bonding of polarizer and polarizer protective film)
As the polarizer protective film on one side, the easy-adhesive films of the examples and comparative examples are used, and as the polarizer protective film on the other side, a biaxially stretched cyclic polyolefin film (“Zeonor film ZF-14” manufactured by Nippon Zeon Co., Ltd.) is used. It was. The above-mentioned UV curable adhesive is applied to the surface of the easy-adhesive film and the surface of the ZEONOR film with a thickness of about 1 μm, and after being attached to the polarizer with a roll laminator, the integrated light quantity is 1000 / mJ / cm. ^The adhesive was cured by irradiating the ultraviolet rays of No. 2 to obtain a polarizing plate having an acrylic film (an easy-adhesion film) on one side of the polarizer and a ZEONOR film on the other side.

[Evaluation]
<Remaining alkali amount of easy-adhesion layer>
The amount of triethylamine and ammonia remaining in the easy-adhesion layer was quantified. The residual amount of triethylamine was quantified by gas chromatography mass spectrometry (GC / MS) of the solution after weighing out the powder obtained by scraping the easy-adhesion layer from the surface of the easy-adhesion film and dissolving it in methanol. The residual amount of ammonia was determined by immersing the easy-adhesive film in pure water at 25 ° C., followed by heat extraction for 60 minutes with a dryer at 120 ° C., and quantifying the ammonia eluted in the water by ion chromatography. The total amount of triethylamine and ammonia was defined as the residual alkali amount.

<Adhesiveness of easy adhesion layer>
After the pressure-sensitive adhesive tape (“No. 31B” manufactured by Nitto Denko) was pressure-bonded to the surface of the easy-adhesive film with 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 adhesive tape was held and a 180 ° peel test was conducted at a tensile speed of 30 m / min, and the adhesion of the easy-adhesion layer was determined according to the following criteria.
◯: The easy adhesion layer did not peel from the acrylic film and peeled at the interface between the pressure-sensitive adhesive tape and the easy adhesion layer. X: The peeling occurred at the interface between the acrylic film and the easy adhesion 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 aggregation of silica particles and the presence or absence of scratches on the surface where the easy-adhesion layer was not formed were evaluated.
◯: Silica particles are not agglomerated and in-plane uniformity is good, and no flaws are observed. The following scratches were observed. X: Turbidity due to aggregation of silica particles, and scratches on the non-adhesive layer formed surface were observed.

<Presence / absence of interface layer>
The cross section of the easy-adhesive film is observed with a transmission electron microscope (TEM), and at the interface between the acrylic film and the easy-adhesive layer, the region (interface layer) where the particles in the easy-adhesive layer are embedded in the acrylic film. The presence or absence was confirmed. A TEM observation image of Example 3 (with an interface layer) is shown in FIG. 3, and a TEM observation image of Comparative Example 4 (without an interface layer) is shown in FIG.

<Humidation durability of polarizing plate>
The polarizing plate was cut out to a size of 320 mm × 240 mm, and the surface on the side of the cyclic polyolefin film was bonded onto the glass via an acrylic adhesive having a thickness of 20 μm. This sample is placed in a constant temperature and humidity chamber at a temperature of 60 ° C. and a relative humidity of 90% (condition 1) or a constant temperature and humidity chamber at a temperature of 85 ° C. and a relative humidity of 85% (condition 2). A humidification endurance test was conducted.

The degree of polarization P ₀ before the endurance test and the degree of polarization P after the endurance test were measured, and the amount of change ΔP = | P−P ₀ | of the degree of polarization was calculated. Moreover, another polarizing plate was arrange | positioned by crossed Nicol on the polarizing plate after an endurance test, the presence or absence of a stripe-shaped nonuniformity was confirmed by visual observation, and the following references | standards evaluated.
◎: No streak is observed in any of the samples after the endurance test of condition 1 or 2; ○: No streak is observed in the sample after the endurance test of condition 1; △: Slight unevenness is visually recognized in both samples after the durability test of Condition 1 and Condition 2 ×: Straight unevenness is clearly visible in both samples after the durability test of Condition 1 and Condition 2

  Observation photographs (taken with “EYESCALE-4W” manufactured by iSystem, a low luminance unevenness measurement system) before and after the endurance 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 easy-adhesion layer after stretching) of easy-adhesive films of Examples and Comparative Examples, evaluation results of easy-adhesive films (visual observation, adhesion, presence / absence of interface layer), and durability test of polarizing plate Table 2 shows the results (presence / absence of uneven stripes and amount of change ΔP in polarization degree).

  In the polarizing plate using the acrylic film of Comparative Example 6 in which no easy-adhesion layer was formed, no streaks were observed even after the humidification durability test, and the decrease in the degree of polarization was small and good optical characteristics were exhibited. However, the 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 provided with an easy-adhesion layer having a thickness of 350 nm had good adhesion between the acrylic film and the easy-adhesion layer, and the appearance of the easy-adhesion film was also good. However, the polarizing plate using this easy-adhesive film as a polarizer protective film has a large decrease in the degree of polarization after the humidification durability test, and significant stripe-like unevenness was confirmed. In Comparative Examples 3 to 5 where the stretching temperature (heating temperature at the time of forming the easy-adhesion layer) is 120 ° C. or less, as in Comparative Example 2, the decrease in the degree of polarization after the humidification durability test is large, and remarkable streak-like unevenness is confirmed. It was done.

  The easy-adhesion films of Examples 1 to 4 in which an easy-adhesion layer 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 exhibited a good appearance. The easy-adhesion film of Example 1 had fine scratches on the surface where the easy-adhesion layer was not formed, but was optically filled with a pressure-sensitive adhesive or an adhesive when bonded to another member. It was a level of scratch that would not be a fault. Moreover, the polarizing plate using the easily adhesive film of Examples 1-4 was excellent in humidification durability compared with the polarizing plate using the easily adhesive film of the comparative example 2, and generation | occurrence | production of the uneven stripe was suppressed.

  The easy-adhesion film of Comparative Example 1 in which an easy-adhesion layer having a thickness of 30 nm was formed had good humidification durability of the polarizing plate, but white turbidity due to aggregation of silica fine particles and scratches on the surface where the easy-adhesion layer was not formed were observed. The appearance was inferior. The occurrence of scratches is considered to be caused by the fact that the silica fine particles dropped 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 of Examples 1 to 4 and Comparative Examples 1 and 2, as the thickness of the easy-adhesion layer is small and the remaining alkali component is small, the occurrence of uneven stripes after the humidification durability test is suppressed, and the polarizing plate is excellent in humidification durability. You can see that 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 understood that the appearance defect and the slipperiness are deteriorated due to the decrease in the dispersibility of the fine particles.

  In Example 5 and Example 6 in which an easy-adhesion layer having a thickness of 200 nm 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 an easy-adhesion layer having a thickness of 200 nm was formed at a stretching temperature of 80 to 120 ° C., the residual alkali amount of the easy-adhesion layer was large. Was confirmed.

  From these results, an adhesive film excellent in the humidification durability of the polarizing plate when used as a polarizer protective film by reducing the residual alkali amount of the easy adhesion layer within a range that does not reduce the dispersibility of the inorganic fine particles. You can see that

  In Comparative Examples 3 to 5 in which stretching was performed at a low temperature, the adhesion between the acrylic film and the easy-adhesion layer was inferior compared to the other examples. In Example 3 and the like, an interface layer (see FIG. 3) in which particles were embedded in the acrylic film was formed at the interface between the acrylic film and the easy adhesion layer, whereas Comparative Examples 3 to 5 were formed. Then, the interface layer was not formed (see FIG. 4). From these results, in addition to the ability to efficiently volatilize the alkali component in the easy-adhesive composition and reduce the residual alkali amount by increasing the heating temperature after application of the easy-adhesive composition, It turns out that the adhesiveness in an interface with an easily bonding layer can be improved.

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 Polarizing plate

Claims (13)

An easy-adhesion film comprising an easy-adhesion layer on the surface of a transparent film substrate
The easy adhesion layer contains a binder resin and inorganic fine particles having an average primary particle size of 10 to 100 nm,
The easy-adhesion film whose total of the content of the amine and ammonia of the said easy-adhesion layer is 5-75 ppm.   The easy-adhesion film of Claim 1 whose thickness of the said easy-adhesion layer is 40-280 nm.   The easy-adhesion film according to claim 1 or 2, wherein the content of the inorganic fine particles in the easy-adhesion layer is 8 to 50% by weight.   The easy-adhesion film of any one of Claims 1-3 whose said transparent film base material is an acrylic film.   The easily-adhesive film of any one of Claims 1-4 whose said binder resin of the said easily-adhesive layer is urethane type resin.   The easily-adhesive film of any one of Claims 1-5 in which the area | region where the said inorganic fine particle is embed | buried under the said transparent film base material exists in the interface of the said transparent film base material and the said easily-adhesive layer. . A method for producing the easy-adhesive film according to any one of claims 1 to 6,
Easy adhesion containing at least one alkali component selected from the group consisting of a binder resin or a precursor thereof, inorganic fine particles having an average primary particle size of 10 to 100 nm, amine and ammonia on the surface of the transparent film substrate and a solvent Apply the composition,
The manufacturing method of an easily bonding film which heats the said easily bonding composition at the temperature 10 degreeC or more higher than the glass transition temperature of the said transparent film base material, and volatilizes the said solvent and the said alkali component.   The method for producing an easy-adhesion film according to claim 7, wherein the alkali component has a function of promoting dispersion of the inorganic fine particles.   The method for producing an easy-adhesive film according to claim 7 or 8, wherein the easy-adhesive composition contains a polyurethane precursor as a precursor of the binder resin and a tertiary amine as the alkali component. The manufacturing method of the easily bonding film of any one of Claims 7-9 in which the said easily bonding composition contains the amine whose boiling point is 150 degrees C or less as said alkaline component.   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 that is 10 ° C or higher than the glass transition temperature of the transparent film substrate. The manufacturing method of the easily-adhesive film of any one of 7-10. 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,
The polarizing plate whose said transparent film is an easily bonding film of any one of Claims 1-6.   An image display device comprising an image display cell and the polarizing plate according to claim 12.