TWI763976B - Easy-adhesive film and method for producing the same, polarizing plate, and image display device - Google Patents

Abstract

An object of the present invention is to provide an easy-adhesive film which exhibits a high degree of adhesion to films such as polarizers, does not easily cause sticking, and is excellent in uniformity and durability. The solution is an easy-bonding film, which is provided with an easy-bonding layer on the surface of the transparent film substrate. The easily bonding layer contains a binder resin and inorganic fine particles with an average primary particle size of 10-100 nm. The alkali content of the easy-bond layer is 5-75 ppm. An easily bonding layer can be formed by applying an easily bonding composition containing a binder resin or its precursor, inorganic fine particles, an alkali component and a solvent on a transparent film substrate and heating it.

Description

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

The present invention relates to an easy-adhesive film having an easy-adhesive layer on the surface of a transparent film substrate and a method for producing the same. In addition, the present invention also relates to a polarizing plate with an easily adhesive film attached to the surface of the polarizer, and an image display device provided with the polarizing plate.

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

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

As the polarizer protective film to be bonded on the surface of the polarizer, cellulose-based films such as cellulose acetate are widely used from the viewpoint of excellent adhesion to the PVA-based polarizer. As transparent protective films, films made of resin materials such as acrylic, polyester, polycarbonate, and cyclic polyolefin are also used. Compared with cellulose-based films, the films made of these resin materials have lower moisture permeability, and the polarizing plate with the low-moisture-permeable resin film attached to the surface of the polarizer will change its optical properties even if it is placed in a high-humidity environment for a long time. It is still small and tends to be excellent in durability.

On the other hand, films made of resin materials such as acrylic, polyester, polycarbonate, and cyclic polyolefin tend to have lower adhesion to PVA-based polarizers than cellulose-based films. Therefore, some documents propose a method of providing an easy-adhesion layer on the surface of a transparent film used as a polarizer protective film to improve the adhesion to the polarizer.

For example, it is described in Patent Document 1 that an easily-bondable film in which an easily-bonded layer containing fine particles and a binder resin is sprayed on the surface of an acrylic film is excellent in adhesion to a polarizer, and it is possible to prevent the film from being wound into a roll. of bonding. The example of Patent Document 1 shows an example of using an easily-bonded film as the polarizer protective film. The easily-bonded film contains 1-7 wt% of silica fine particles on the surface of the acrylic film and has an average thickness of 400 nm (thickness range 300~500nm) urethane easy bonding layer.

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

Summary of Invention The problem to be solved by the invention As image display devices progress toward larger size or higher brightness, the polarizing plate constituting the image display device is also required to have little change in optical properties even under severe environments (such as high temperature and high humidity conditions). . The polarizing plate using the easy-bonding film described in Patent Document 1 as the polarizer protective film has excellent adhesion between the polarizer and the polarizer protective film, and the adhesion reliability is also high. However, a new problem has now been identified: if a polarizing plate using the easy-adhesive film disclosed in Patent Document 1 as a polarizer protective film is exposed to a high humidity environment for a long time, rib-like unevenness occurs, resulting in a decrease in display characteristics. Happening.

In view of the above problems, an object of the present invention is to provide an easy-to-bond film, which is excellent in adhesion to polarizers and the like, is less likely to cause adhesion, and is less likely to generate optical defects such as rib-like unevenness even if it is exposed to a high temperature and high humidity environment for a long time. .

means of solving problems In view of the above problems, the inventors of the present invention, as a result of studies, found that the case where alkali components such as ammonia or amines added to the easily bonding composition for the purpose of improving the dispersibility of the inorganic fine particles and the like remain in the easily bonding layer is a humidified environment. It is one of the reasons why the lower durability is lowered, and it has been found that the above-mentioned problems can be solved by setting the alkali residual amount in the easily bonding layer within a predetermined range.

The present invention relates to an easy-adhesive film having an easy-adhesive layer on the surface of a transparent film substrate and a method for producing the same. The easily bonding layer contains a binder resin and inorganic fine particles with an average primary particle size of 10-100 nm. The content of the alkali component in the easy-bonding layer is preferably 5-75 ppm. The thickness of the easy bonding layer is preferably 40-280 nm.

An acrylic film etc. can be used as a transparent film base material. As the adhesive resin of the easy-bonding layer, urethane resin or the like can be used. The content of the inorganic fine particles in the easily bonding layer is preferably about 8 to 50% by weight. The inorganic fine particles of the easily bonding layer can be embedded in the transparent film substrate.

The easy-adhesive layer can be formed by coating the easy-adhesive composition on the surface of the transparent film substrate and heating. The easy-bond composition contains a binder resin or its precursor, inorganic fine particles with an average primary particle size of 10 to 100 nm, an alkali component and a solvent. By containing an alkali component in the easily bonding composition, the dispersibility of the inorganic fine particles can be improved, and an easily bonding film excellent in smoothness can be obtained. Moreover, the alkali component can also act as a catalyst for promoting the reaction of the binder resin (precursor). From the viewpoint of promoting volatilization of the alkali component by heating, the boiling point of the alkali component is preferably 150°C or lower. An amine, ammonia, etc. are mentioned as an alkali component.

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

After coating the easy-adhesion composition on the transparent film substrate, the transparent film substrate can be heated and extended. In particular, by heating the easily bondable composition at a temperature 10°C or more higher than the glass transition temperature of the transparent film base material, the transparent film base material is stretched, and the adhesion between the transparent film base material and the easily bondable layer is improved. tendency to increase.

The above-mentioned easily adhesive 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 produced by laminating an easily adhesive film on the surface of a polyvinyl alcohol-based polarizer through an adhesive layer. An image display device can be formed by disposing a polarizing plate on the surface of an image display unit such as a liquid crystal display unit or an organic EL unit.

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

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

As the usage form of the easily adhesive film, a polarizer protective film is mentioned. FIG. 2 is a cross-sectional view showing a configuration example of a polarizing plate provided with an easily bonding film 1 as a polarizer protective film. The polarizing plate 100 is provided with the easily-bondable film 1 on one surface (the first main surface) of the polarizer 5 , and the easily-bonded film 1 is bonded through the adhesive layer 6 . In the polarizing plate 100 shown in FIG. 2 , the easily bonding film 1 has the easily bonding layer 15 on the bonding surface with the polarizer 5 of the film substrate 11 . An easy-bonding layer may also be provided on the surface not attached to the polarizer 5 . In the polarizing plate 100 shown in FIG. 2 , the transparent protective film 2 is attached to the other surface (second main surface) of the polarizer 5 through the adhesive layer 7 .

[Easy Bonding Film] The easily adhesive film 1 is provided with an easily adhesive layer 15 on at least one side of the film substrate 11 .

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

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

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

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

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

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

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

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

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

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

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

＜Easy bonding layer＞ The easily bonding layer 15 provided on the surface of the film base 11 contains a binder resin and fine particles. By providing the easy-adhesion layer 15, the adhesiveness of the polarizer and the like to a film, a glass substrate, or the like can be improved. The easily bonding layer 15 contains fine particles, and fine irregularities can be formed on the surface of the easily bonding layer 15 to improve the smoothness of the film. Therefore, it is helpful to reduce the damage of the easy-bond film 1 when it is transported by a roll or to suppress sticking when it is wound into a roll.

唑啉基等交聯性官能基之丙烯酸樹脂等具有反應性基的樹脂(聚合物)。易接著層15之黏結劑樹脂以聚胺甲酸乙酯樹脂尤佳。含有聚胺甲酸乙酯樹脂黏結劑的易接著層15與薄膜基材11之密著性很高。而且，易接著層15含有聚胺甲酸乙酯樹脂黏結劑的易接著薄膜1透過接著劑層積層偏光件等薄膜時，有展現高接著性之傾向。(Binder resin) From the viewpoint of excellent adhesion to film substrates such as acrylic films, as the binder resin, polyurethane resins, epoxy resins, isocyanate resins, polyester resins, and those containing Amine-based polymers, with

Resins (polymers) having reactive groups, such as acrylic resins with crosslinkable functional groups such as oxazoline groups. The adhesive resin of the easy-bonding layer 15 is preferably a polyurethane resin. The adhesion between the easily bonding layer 15 containing the polyurethane resin adhesive and the film substrate 11 is high. In addition, the easily adhesive film 1 in which the easily adhesive layer 15 contains a polyurethane resin adhesive tends to exhibit high adhesiveness when a film such as a polarizer is laminated through the adhesive.

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

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

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

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

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

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

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

The urethane resin constituting the easily bonding layer 15 preferably has a carboxyl group. Since the urethane resin has a carboxyl group, a cross-linked structure can be introduced, so that the adhesion durability of the easy-bond film 1 to a polarizer and the like tends to be improved. The urethane resin having a carboxyl group can be prepared, for example, by reacting a polyol, a polyisocyanate and a chain extender having a free carboxyl group. The chain extender having a free carboxyl group includes dihydroxycarboxylic acid, dihydroxysuccinic acid, and the like. Dihydroxycarboxylic acids include dimethylolalkanoic acids (eg, dimethylolacetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, dimethylolbutanoic acid, dimethylolpentanoic acid) Dialkylol alkanoic acid, etc.

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

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

唑啉基、環氧基、碳二醯亞胺基等的交聯劑。該等中又以具有

唑啉基之交聯劑為宜。

唑啉基常溫下與羧基的反應性較小，所以與胺甲酸乙酯樹脂混合後的使用期限較長，可彈性應對步驟的前置時間。The urethane resin may also have a cross-linked structure. By introducing a crosslinked structure to the urethane resin, the adhesion durability of the easily bonding film 1 to a polarizer and the like tends to be improved. As the crosslinking agent, one that can react with the crosslinkable functional group of the urethane resin can be used without particular limitation. When the urethane resin has a carboxyl group, an amine group containing,

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

An oxazoline-based crosslinking agent is suitable.

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

唑啉基之丙烯酸系聚合物作為交聯劑時，有提升易接著薄膜1與偏光件等薄膜之接著性的傾向。The crosslinking agent may be a low molecular compound or a polymer. The crosslinking agent is preferably an acrylic polymer from the viewpoint of high solubility in water-based compositions and good compatibility with urethane resins. In particular, using

When the oxazoline-based acrylic polymer is used as a crosslinking agent, the adhesiveness of the easily adhesive film 1 to films such as polarizers tends to be improved.

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

(fine particles) Since the easily bonding layer 15 contains fine particles, fine concavo-convex shapes can be formed on the surface of the easily bonding layer, the smoothness of the easily bonding film 1 is improved, and sticking can be suppressed. The particle size (average primary particle size) of the fine particles is preferably 10 nm or more, more preferably 15 nm or more, and more preferably 20 nm or more, from the viewpoint of forming irregularities that contribute to improving smoothness. By making the average primary particle size of the microparticles smaller than the wavelength of visible light, scattering of visible light at the interface between the binder resin and the microparticles can be suppressed, and an easy-to-bond film with high transparency can be obtained. Therefore, the particle size of the fine particles is preferably 100 nm or less, more preferably 80 nm or less, more preferably 60 nm or less, and still more preferably 50 nm or less.

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

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

The water-dispersible silica particles are preferably colloidal silica. 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., AERODISP series and AEROSIL series manufactured by Japan Aerosil Co., Ltd. can also be used.

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

(Alkali Residual) If an alkali component such as amine or ammonia is used in order to improve the dispersibility of the inorganic fine particles, the alkali component will inevitably remain in the easily bonding layer. When the easy-bond film 1 is used as a polarizer protective film, once the residual alkali component of the easily-bonded layer 15 is eluted by moisture, etc., it may deteriorate the polarizer, reduce the polarization degree of the polarizer, or produce optical defects such as rib-like unevenness. .

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

On the other hand, if the alkali residue in the easily bonding layer 15 is too small, the dispersibility of the fine particles will be impaired, and the fine particles may aggregate and cause poor appearance such as cloudiness. In addition, due to the decrease in dispersibility, the fine particles may aggregate or fall off from the easily bonding layer, so that proper unevenness cannot be formed on the surface of the easily bonding layer, and the smoothness of the easily bonding film tends to decrease. Therefore, the alkali residue in the easily bonding layer 15 is preferably 5 ppm or more, preferably 10 ppm or more, and more preferably 20 ppm or more.

The amount of alkali in the easily bondable layer can be quantified by liquid chromatography analysis or ion chromatography analysis according to the type of the alkali component. The quantification of the base component can also be performed by an analytical method (eg, LC/MS) that combines chromatographic analysis and mass analysis (MS). When a plurality of alkali components are contained in the easily bonding layer, the total of each component is used as the alkali component content (residual amount) of the easily bonding layer.

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

(Easy Adhesion Composition) The easily bonded 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 content) in the easy-to-bond composition is preferably 1 to 30% by weight, preferably 2 to 20% by weight, and more preferably 3 to 15% by weight.

The water-based easy-adhesive composition contains water as a solvent (and dispersion medium), a binder resin grease or its precursor, and inorganic fine particles. The easy-bonding composition preferably contains an alkali component. As described above, the alkali component has the effect of promoting the dispersion of the inorganic fine particles. Therefore, when the easy-bonding composition contains an alkali component, the dispersibility of the inorganic fine particles can be improved, and an easy-bonding film excellent in appearance and smoothness can be obtained.

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

From the viewpoint of improving the dispersibility of the inorganic fine particles, the amount of the alkali component contained in the easily bonding composition is preferably 300 ppm or more, preferably 500 ppm or more, relative to the solid content of the easily bonding composition. On the other hand, if the content of the alkali component is too large, it may become difficult to reduce the residual alkali content. Therefore, the amount of the alkali component contained in the easy-bonding composition is preferably 50,000 ppm or less and 10,000 ppm relative to the solid content of the easy-bonding composition. The following is preferable, and 5000 ppm or less is more preferable.

In addition to improving the dispersibility of the inorganic fine particles, the alkali component contained in the easy-bonding composition may also have a catalytic effect. For example, when the binder resin is a urethane resin, as a urethane catalyst for the polyurethane precursor (polyol, isocyanate, etc.), triethylamine can also be included in the easy-to-bond composition. and other tertiary amines.

After coating the easily bonding composition on the film substrate, heating is performed to volatilize and remove the alkali component, which can reduce the residual alkali component of the easily bonding layer 15 . From the viewpoint of promoting volatilization of the alkali component by heating, the boiling point of the alkali component contained in the easily bonding composition is preferably 150°C or lower. The boiling point of the alkali component is preferably 130°C or lower, more preferably 120°C or lower, and even more preferably 110°C or lower. The boiling point of the alkali component may be 100°C or lower or 90°C or lower. When the easily bonding composition contains a plurality of alkali components, the boiling point of at least one alkali component is preferably within the above range, and the boiling point of two or more alkali components is more preferably within the above range. With respect to 100 parts by weight of the total amount of the alkali contained in the easily bonding layer, 50% by weight or more of the alkali component preferably has a boiling point within the above range. It is preferable that the boiling points of all the alkali components contained in the easy-bonding composition are within the above-mentioned range.

The easily bonding composition may contain a crosslinking agent in addition to the binder resin (or its precursor), inorganic fine particles, and an alkali component. The easy-adhesive composition may also contain catalysts such as cross-linking accelerators, antioxidants, ultraviolet absorbers, leveling agents, anti-blocking agents, antistatic agents, dispersion stabilizers, defoaming agents, tackifiers, dispersants, Additives such as surfactants and lubricants.

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

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

The heating temperature at the time of forming the easily bonding layer is, for example, about 50 to 200°C. The heating temperature is preferably 100°C or higher, more preferably 120°C or higher, and 130°C or higher from the viewpoint of promoting the hardening reaction of the resin component of the easily bonding composition and effectively volatilizing and removing the alkali component contained in the easily bonding composition. More preferably, above 135°C is particularly preferred. Further, the heating temperature is preferably higher than the boiling point of the alkali component contained in the easy-bonding composition.

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

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

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

In particular, as shown in the cross-sectional observation image of FIG. 3 , when the surface of the film substrate 11 has a region where the microparticles of the easily bonding layer 15 are embedded and embedded, a high adhesion between the film substrate 11 and the easily bonding layer 15 can be obtained. Then the film. We believe that if the microparticles are embedded in the film substrate in a rubber state in which the film substrate is heated to a temperature higher than Tg, and then the film substrate is returned to a glass state, the microparticles embedded on the surface of the film substrate and the presence of The adhesive resin around it will be fixed on the surface of the film base material, so the adhesion between the film base material 11 and the easily adhesive layer 15 can be improved.

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

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

When the film substrate is biaxially stretched, the biaxial stretching can be either successive biaxial stretching or simultaneous biaxial stretching. In addition, it can also be extended obliquely. In the case of successive biaxial stretching, the film can also be stretched in one direction (MD) by means of roll stretching as described above, and then the easily bonding composition can be coated on the film, and the easily bonding composition can be heated during stretching with a tenter. .

The extension temperature is the same as the above-mentioned heating temperature of the easy-bond layer, and it is preferably a temperature higher than the Tg of the film substrate, and preferably above Tg+10°C, preferably above Tg+15°C, more preferably above Tg+20°C . In particular, it is preferable to extend in at least one direction at the above-mentioned temperature after applying the easily adhesive composition. If the stretching is performed in a rubber state higher than the Tg of the film substrate, a region in which the fine particles of the easily bonding composition are embedded is easily formed on the surface of the film substrate, and the film substrate 11 and the easily bonding layer 15 adhere to each other. Sex has a tendency to improve. The reasons why it becomes easier to embed fine particles in the film substrate by stretching at a high temperature include: if the stretching is performed in a rubber state, when the film substrate is deformed, the adhesive composition tends to wet and diffuse, so that the fine particles are easily embedded. The state in the concave portion of the surface unevenness formed during deformation. Furthermore, we believe that if cooling is performed while releasing the stress after stretching, when the film substrate shrinks, the particles embedded in the surface of the film substrate will be fixed thereon, so that it is easy to form a region in which the microparticles are embedded in the film substrate.

The thickness of the easily bonding layer 15 can be adjusted by adjusting the solid content concentration and coating thickness of the easily bonding composition. When the film substrate is stretched after applying the easily bonding composition, the thickness of the easily bonding layer 15 can also be adjusted by the stretching ratio.

The thickness of the easily bonding layer 15 is not particularly limited, but is preferably 280 nm or less, more preferably 250 nm or less, and more preferably 230 nm or less, from the viewpoint of promoting the removal of the alkali component by heating. When the easy-bond film 1 is used as a polarizer protective film, the smaller the thickness of the easily-bonded layer 15 is, the better the humidification durability of the polarizer can be improved, and the occurrence of optical defects such as rib-like unevenness tends to be reduced. In addition, the smaller the thickness of the easy-bond layer 15 is, the more likely it is that the decrease in the degree of polarization can be suppressed when the polarizing plate is exposed to a humidified environment.

When the easily bonding composition is heated and dried, if the alkali component is excessively removed, the dispersibility of the fine particles in the binder resin decreases, and the fine particles tend to agglomerate or the resulting fine particles fall off the surface of the easily bonding layer. Once the agglomeration or detachment of the fine particles occurs, the smoothness of the easy-to-bond film is reduced, and it is likely to be damaged during transportation or sticking during winding. Therefore, the thickness of the easy-bonding layer 15 is preferably 40 nm or more, preferably 50 nm or more, more preferably 80 nm or more, and particularly preferably 100 nm or more. Also, the thickness of the easily-bondable layer 15 is preferably within the above-mentioned range from the viewpoint that the adhesion-improving effect of the easily-bonded layer 15 can be appropriately exhibited.

[polarizing plate] The polarizer can be provided with a transparent protective film only on one side of the polarizer, or can also be provided with a transparent protective film on both sides of the polarizer 5 as shown in FIG. 2 . By attaching the above-mentioned easy-bond film as a polarizer protective film on one side of the polarizer, a polarizer with a transparent protective film only on one side of the polarizer can be formed. The polarizer having the polarizer protective film on both sides of the polarizer only needs to be bonded with the above-mentioned easy-bonding film on at least one side of the polarizer. The polarizing plate may also be laminated with the above-mentioned easy-bonding films on both sides of the polarizer. The polarizer 5 and the easily adhesive film 1 can be pasted through the adhesive layer 6 .

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

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

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

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

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

The polymer component of the water-based adhesive includes vinyl polymers, gelatin, vinyl-based latex, polyurethane, polyester-based, epoxy, and the like. Among these, vinyl polymers are preferable, and polyvinyl alcohol-based resins are especially preferable in view of excellent adhesion between the easily adhesive film and the polarizer. Among the polyvinyl alcohol-based resins, polyvinyl alcohol containing an acetyl acetyl group is suitable.

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

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

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

啉等含氮單體。自由基聚合性接著劑中作為交聯成分可含有三丙二醇二丙烯酸酯、1,9‐壬二醇二丙烯酸酯、三環癸烷二甲醇二丙烯酸酯、環狀三羥甲丙烷甲縮醛丙烯酸酯、二

烷二醇二丙烯酸酯、EO改質二甘油四丙烯酸酯等多官能單體。As a monomer of a radically polymerizable adhesive agent, the compound which has a (meth)acryloyl group, and the compound which has a vinyl group are mentioned. Among them, compounds having a (meth)acryloyl group are preferred. Examples of compounds having a (meth)acryloyl group include C _1-20 chain alkyl (meth)acrylates, alicyclic alkyl (meth)acrylates, and polycyclic alkyl (meth)acrylates Alkyl (meth)acrylates; hydroxyl-containing (meth)acrylates; epoxy-containing (meth)acrylates such as glycidyl (meth)acrylate and the like. The radically polymerizable adhesive may contain hydroxyethyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N- Ethoxymethyl (meth)acrylamide, (meth)acrylamide, (meth)acrylamide

Nitrogen-containing monomers such as phenoline. The radical polymerizable adhesive may contain tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, and cyclic trimethylolpropane methyl acrylate as a crosslinking component Ester, Di

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

The photocurable adhesive such as a photoradical polymerizable adhesive preferably contains a photopolymerization initiator. The photopolymerization initiator may also be appropriately selected depending on the type of reaction. For example, a photo-radical generator that can generate radicals by light irradiation is suitable for blending a radical-polymerizable adhesive as a photopolymerization initiator. Specific examples of the photoradical generator will be described later. The content of the photoradical generator is usually about 0.1 to 10 parts by weight, preferably 0.5 to 3 parts by weight, relative to 100 parts by weight of the monomer. In addition, when the radically polymerizable adhesive is used as an electron beam curing type, there is no particular need for a photopolymerization initiator. A photosensitizer represented by a carbonyl compound and the like can also be added to the radically polymerizable adhesive as required. The photosensitizer is used to increase the hardening speed and sensitivity of electron beam. The usage amount of the photosensitizer is usually about 0.001 to 10 parts by weight, preferably 0.01 to 3 parts by weight, relative to 100 parts by weight of the monomer.

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

[Make a polarizer] The easy-bond film 1 is attached to one surface (first main surface) of the polarizer 5 through the adhesive layer 6 to manufacture a polarizing plate. The easily bonding film 1 may be bonded to the polarizer 5 through the adhesive layer on the easily bonding layer-forming surface, or may be bonded to the polarizer 5 through the adhesive layer on the non-forming surface of the easily bonding layer. As shown in FIG. 2 , by attaching the polarizer 5 through the adhesive layer 6 on the formation surface of the easily bondable layer 15 of the easily bondable film 1 , the adhesion between the polarizer and the polarizer protective film (the easily bondable film 1 ) is high, Polarizing plates with excellent mechanical strength and durability can be obtained. When the non-formed surface of the easily bonding layer is bonded to the polarizer 5 through the adhesive layer, the adhesiveness to other films, adhesive layers, glass substrates, etc. provided on the easily bonding film can be improved.

When laminating the polarizer 5 and the easy-bond film, it is suitable to apply an adhesive composition to either or both of the polarizer 5 and the easy-to-bond film 1, and then use a roll press or the like to separate the polarizer 5 and the easy-to-bond film. 1Attach and harden the adhesive. The coating method of applying the adhesive composition to the polarizer 5 and/or the easily adhesive film 1 includes a roll coating method, a spray method, a dipping method, and the like. Before coating the adhesive composition on the surface of the polarizer 5 and/or the easily adhesive film 1 , surface treatments such as corona treatment, plasma treatment, and saponification treatment can also be performed.

After the polarizer 5 and the easily adhesive film 1 are bonded together, the adhesive layer 6 can be formed by curing the adhesive according to the type of the adhesive. When a water-based adhesive is used, the adhesive can be hardened by heating and drying. When an active energy ray hardening type adhesive is used, the adhesive can be hardened by irradiating active energy rays such as electron beams or ultraviolet rays.

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

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

The transparent protective film 2 may also be provided with an easy-bonding layer (not shown) on the bonding surface with the polarizer 5 . The same easy-bonding layer as the easy-bonding layer 15 of the easy-bonding film 1 can also be provided on the transparent protective film 2 .

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

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

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

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

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

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

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

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

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

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

[Example 1] The easily adhesive film was produced using a film production apparatus equipped with a melt extrusion film forming apparatus, a gravure coater, a tenter-type simultaneous biaxial stretching apparatus, and a winding apparatus. As the acrylic resin, pellets of the same imidized MS resin (glass transition temperature: 120°C) as described in the Example of Japanese Patent Laid-Open No. 2017-26939 for producing the "transparent protective film 1A" were used . The acrylic resin was melted and extruded from the T-die, and the film was formed with a thickness of 160 μm. Then, the above-mentioned easy-adhesive composition was applied on one side of the film with a wet thickness of about 9 μm by a gravure coater, and the temperature was 140 ° C. In the heating furnace, a simultaneous biaxial stretching tenter was used to extend 2 times in the longitudinal direction (MD) and the width direction (TD), respectively, to obtain an easy-bonding layer with a thickness of 200 nm on one side of an acrylic film with a thickness of 40 μm. film.

[Examples 2 to 4 and Comparative Examples 1 and 2] An easily adhesive film was obtained in the same manner as in Example 1 except that the coating thickness of the easily adhesive composition was changed. The thickness of the easily bonding layer (after stretching) is shown in Table 2.

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

[Comparative Example 6] An acrylic film having a thickness of 40 μm without an easily bonding layer was obtained without applying the easily bonding composition with a gravure coater.

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

[Table 1]

啉60重量份作為硬化性成分，更含有作為聚合引發劑之2-甲基-1-(4-甲基苯硫基)-2-

啉基丙-1-酮(BASF製「IRGACURE 819」)3重量份的紫外線硬化型接著劑。(Preparation of UV-curable adhesive) Preparation containing 40 parts by weight of N-hydroxyethyl acrylate and acrylamide

60 parts by weight of phenoline as a sclerosing component, further containing 2-methyl-1-(4-methylphenylthio)-2- as a polymerization initiator

Linopropan-1-one ("IRGACURE 819" manufactured by BASF) is a UV-curable adhesive of 3 parts by weight.

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

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

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

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

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

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

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

Figure 5 shows the observation photographs of the polarizing plates of Example 1 and Comparative Example 2 before and after the durability test (60° C. 90%Rh for 500 hours) under crossed polarized light (using an uneven measurement system for low brightness, manufactured by I System Co. "EYESCALE-4W" shooting).

Table 2 shows the fabrication conditions (stretching temperature and the thickness of the easily-bonded layer after stretching), the evaluation results of the easily-bonded films (the naked eye, the adhesion, the presence or absence of an interface layer), and the polarized light of the easily-bonded films of the Examples and Comparative Examples. The results of the durability test of the board (with or without uneven streaks and the amount of change in the degree of polarization ΔP).

[Table 2]

In the polarizing plate using the acrylic film of Comparative Example 6 without forming an easy-bond layer, no uneven streak was observed after the humidification durability test, and the degree of polarization was less decreased, showing good optical properties. However, the adhesion between the acrylic film and the polarizer was low, and the acrylic film was found to be peeled from the polarizer at the end of the polarizing plate after the humidification durability test.

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

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

In Comparative Example 1, an easily bonding layer with a thickness of 30 nm was formed, and the polarizing plate of the easily bonding film had good humidification durability, but cloudiness caused by the aggregation of silica fine particles and damage to the non-forming surface of the easily bonding layer were confirmed. bad. We believe that the damage occurred because the decrease in dispersibility caused the silica particles to fall off the surface of the easily bonded layer, resulting in a decrease in the smoothness of the easily bonded film.

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

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

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

In Comparative Examples 3 to 5, the stretching was performed at a low temperature, and the adhesion between the acrylic film and the easily bonding layer was poor compared to the other examples. In Example 3 and the like, an interface layer in which particles are embedded in the acrylic thin film is formed at the interface between the acrylic thin film and the easily bonding layer (see FIG. 3 ); on the other hand, in Comparative Examples 3 to 5, the interface layer was not formed. interface layer (see Figure 4). From these results, it can be seen that by increasing the heating temperature after coating the easy-bond composition, the alkali component in the easy-bond composition can be effectively volatilized to reduce the residual amount of alkali, and the interface between the film substrate and the easily-bonded layer can be improved. the tightness.

1‧‧‧Easy Bonding Film 2‧‧‧Transparent protective film 5‧‧‧Polarizer 6.7‧‧‧Adhesive layer 11‧‧‧Film substrate 15‧‧‧Easy bonding layer 100‧‧‧Polarizer

FIG. 1 is a cross-sectional view showing a configuration example of an easily adhesive film. FIG. 2 is a cross-sectional view showing a configuration example of a polarizing plate. FIG. 3 is a cross-sectional TEM observation image of the easy-bond film with an interface layer formed at the interface between the film substrate and the easily-bonded layer. FIG. 4 is a cross-sectional TEM observation image of the easy-bond film with no interface layer formed at the interface between the film substrate and the easily-bonded layer. FIG. 5 is a photograph of the cross-polarized light observation of the polarizing plate before and after the durability test.

1‧‧‧Easy Bonding Film

11‧‧‧Film substrate

15‧‧‧Easy bonding layer

Claims (12)

An easy-adhesive film is provided with an easy-adhesive layer on the surface of a transparent film substrate; the easy-adhesive layer contains a binder resin and a colloidal silicon oxide with an average primary particle size of 10-100 nm, and the above-mentioned colloidal oxide in the easy-adhesive layer is oxidized The silicon content is 10 to 50 wt %, the thickness of the easily bonded layer is 150 to 280 nm, and the total content of amine and ammonia in the easily bonded layer is 20 to 75 ppm. The easily bonding film according to claim 1, wherein the content of the aforementioned colloidal silicon oxide in the aforementioned easily bonding layer is 12-30 wt %. The easily adhesive film according to claim 1 or 2, wherein the transparent film substrate is an acrylic film. The easily bonding film according to claim 1 or 2, wherein the aforementioned binder resin of the aforementioned easily bonding layer is a urethane resin. The easily bonding film according to claim 1 or 2, wherein there is a region in which the colloidal silicon oxide is embedded in the transparent film substrate at the interface between the transparent film substrate and the easily bonding layer. A method for producing an easy-bond film, which is used to produce the easy-bond film as claimed in any one of claims 1 to 5. The method comprises a colloid containing a binder resin or its precursor and an average primary particle size of 10 to 100 nm. An easily bonding composition comprising silicon oxide, one or more alkali components selected from the group consisting of amines and ammonia, and a solvent is coated on the surface of the transparent film substrate at a temperature higher than the glass transition temperature of the transparent film substrate. The easily bonding composition is heated at a temperature higher than 10° C. to volatilize the solvent and the alkali component. The method for producing an easily bonded thin film according to claim 6, wherein the alkali component has the effect of promoting the dispersion of the colloidal silica. The method for producing an easily bondable film according to claim 6 or 7, wherein the easily bondable composition contains a polyurethane precursor as the binder resin precursor and a tertiary amine as the alkali component. The method for producing an easily bondable film according to claim 6 or 7, wherein the easily bondable composition contains an amine having a boiling point of 150° C. or less as the base component. The method for producing an easily-bondable film according to claim 6 or 7, wherein the easily-bonded composition is heated at a temperature 10° C. or more higher than the glass transition temperature of the transparent film substrate, and the easily-bonded film is coated at the same time. The aforementioned transparent film substrate of the composition extends in at least one direction. A polarizing plate, comprising a polyvinyl alcohol-based polarizer having a first main surface and a second main surface, and a transparent film, and the transparent film is attached to the first main surface of the polarizer through an adhesive layer; and the above-mentioned The transparent film is an easily adhesive film as claimed in any one of claims 1 to 5. An image display device has an image display unit and a polarizing plate as claimed in item 11.

Images