Optical film and method for manufacturing the same

Abstract

The present invention provides an acrylic resin film that constitutes an optical film, and an optical film that has high adhesion to a polarizer and excellent optical properties. [Solution] An optical film comprising an acrylic resin film 11 mainly containing a first acrylic resin, and an easy-adhesion layer 12 laminated on one surface of the acrylic resin film 11, wherein the easy-adhesion layer 12 is formed from an easy-adhesion composition comprising a second acrylic resin and fine particles, and the second acrylic resin is a core-shell type resin composition comprising an alkali-soluble copolymer (A) of a monomer mixture containing (meth)acrylic acid and an alicyclic alkyl group-containing ethylenically unsaturated monomer as the shell part, and a copolymer (B) of a monomer mixture containing diacetone (meth)acrylamide and an ethylenically unsaturated monomer as the core part.

Description

[Technical Field]

[0001] The present invention relates to an optical film having an acrylic resin film mainly composed of a (meth)acrylic resin and an easy-adhesion layer laminated on one surface thereof, and a method for manufacturing the same. [Background technology]

[0002] Acrylic resin films, formed from (meth)acrylic polymers such as polymethyl methacrylate (PMMA), are known to have excellent optical properties, including light transmittance, as well as a good balance of mechanical strength and moldability. For this reason, acrylic resin films have recently been used in optical applications, and their application as optical films incorporated into image display devices such as liquid crystal displays (LCDs), plasma display panels (PDPs), and organic light-emitting diodes (OLEDs) is progressing.

[0003] Optical films are usually used in a laminated state with other functional films. For example, a polarizer protective film, which is a type of optical film, is used in image display devices in the form of a polarizer plate laminated with a polarizer and an adhesive layer made of a hydrophilic adhesive or an ultraviolet-curing adhesive on at least one surface of the polarizer. Therefore, good adhesion between the laminated polarizer (and the adhesive layer) and the polarizer is necessary.

[0004] However, acrylic resin films have a problem in that they have poor adhesion to hydrophilic adhesives and UV-curing adhesives, and do not adhere sufficiently to polarizers. Therefore, a method has been proposed to impart easy adhesion to acrylic resin films by providing an easy-adhesion layer on the surface of the acrylic resin film, mainly composed of an adhesive-supporting resin (binder resin) such as polyester, acrylic, or urethane.

[0005] For example, Patent Document 1 discloses a laminate in which a hard coat layer for protecting a display contains an acrylic resin, and an easy-adhesion layer contains an acrylic resin or a polyester resin.

[0006] Furthermore, Patent Document 2 discloses an optical film in which an easily adhesive layer is formed on an acrylic resin film, the layer being made of an easily adhesive composition containing a polyurethane polymer with a weight-average molecular weight of 10,000 to 100,000 obtained by reacting a polycarbonate diol and an isocyanate, and that by using the polyurethane polymer as the easily adhesive composition, an optical film with excellent adhesion can be obtained.

[0007] Furthermore, Patent Document 3 discloses an optical film having an easily adhesive layer formed from an easily adhesive composition mainly containing a polycarbonate-based polyurethane having a weight-average molecular weight of 200,000 to 2,500,000, and whose shear loss tangent temperature curve (-50 to 160°C, 1 Hz) obtained in a dynamic viscoelasticity test exhibits multiple maximum values, and that by using the polyurethane polymer as the easily adhesive composition, an optical film with even better adhesion can be obtained. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2014 / 148594 [Patent Document 2] Japanese Patent Publication No. 2010-63773 [Patent Document 3] International Publication No. 2024 / 095968 [Overview of the project] [Problems that the invention aims to solve]

[0009] Conventionally, optical films have been proposed in which an easily adhesive layer mainly composed of polyester resin, acrylic resin, or urethane resin is provided on the surface of an acrylic resin film. However, there is a demand for optical films with even higher adhesion to polarizers. Furthermore, in the manufacturing process of optical films in which an easily adhesive layer is formed on an acrylic resin film, a stretching process is performed in which the optical film with the easily adhesive layer laminated is stretched several times to the target thickness. However, this stretching process can cause whitening (white dot-like unevenness) or optical transparency defects that appear as grains or holes in the easily adhesive layer, and there is a demand for optical films with excellent optical properties.

[0010] The present invention aims to provide an acrylic resin film that constitutes an optical film, and an optical film that has high adhesion to a polarizer and excellent optical properties. [Means for solving the problem]

[0011] The present invention is essentially an optical film as described in any of the following (1) to (7). (1) An optical film comprising an acrylic resin film mainly containing a first acrylic resin, and an easy-adhesion layer laminated on one surface of the acrylic resin film, wherein the easy-adhesion layer is formed from an easy-adhesion composition comprising a second acrylic resin and fine particles, and the second acrylic resin is a core-shell type resin composition comprising an alkali-soluble copolymer (A) of a monomer mixture containing (meth)acrylic acid and an alicyclic alkyl group-containing ethylenically unsaturated monomer as the shell part, and a copolymer (B) of a monomer mixture containing diacetone (meth)acrylamide and an ethylenically unsaturated monomer as the core part. (2) The optical film according to (1) above, wherein the easy-adhesion layer further contains a hydrazide compound, and the diacetone (meth)acrylamide is crosslinked by a crosslinking reaction between the keto group derived from the diacetone (meth)acrylamide skeleton of the core and the hydrazide compound. (3) The optical film according to (1) above, wherein the fine particles are silica with an average primary particle size of 50 to 400 nm. (4) The optical film according to (1) above, wherein the alicyclic alkyl group-containing ethylenically unsaturated monomer is one or more selected from (meth)acrylate cyclopentyl, (meth)acrylate cyclohexyl, and (meth)acrylate cyclooctyl. (5) The optical film according to (1) above, wherein the ethylenically unsaturated monomer is a (meth)acrylic acid ester. (6) The optical film according to (1) above, wherein the content of diacetone (meth)acrylamide in the copolymer (B) is 1 to 20% by mass relative to the total of the alkali-soluble copolymer (A) and the copolymer (B), and the mass ratio of the alkali-soluble copolymer (A) to the copolymer (B) is (A):(B) = 20:80 to 60:40. Furthermore, the present invention is essentially based on the method for manufacturing an optical film described in (7) below. (7) A method for producing an optical film, comprising: emulsion polymerization of a monomer mixture containing diacetone (meth)acrylamide and an ethylenically unsaturated monomer in the presence of an alkali-soluble copolymer (A) of a monomer mixture containing an alicyclic alkyl group-containing ethylenically unsaturated monomer to obtain a copolymer (B); then adding a hydrazide compound (C) to produce a resin dispersion for aqueous ink; adding fine particles to the resin dispersion for aqueous ink to produce an ink composition; and applying the ink composition to one side of an acrylic resin film. [Effects of the Invention]

[0012] According to the present invention, in an optical film having an acrylic resin film and an easy-adhesion layer, the easy-adhesion layer contains an alkali-soluble copolymer (A) of a monomer mixture containing (meth)acrylic acid and an alicyclic alkyl group-containing ethylenically unsaturated monomer as a shell part, and a copolymer (B) of a monomer mixture containing diacetone (meth)acrylamide and an ethylenically unsaturated monomer as a core part. By including the core-shell type resin composition, an optical film with high adhesion to an acrylic resin film, an adhesion layer, and a polarizer and excellent optical properties can be provided.

Brief Description of Drawings

[0013] [Figure 1] It is a cross-sectional view showing a polarizing plate according to this embodiment. [Figure 2] It is a diagram for explaining a transparent defect.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the optical film according to the present invention will be described. In this embodiment, as shown in FIG. 1, as the optical film 10 according to the present invention, a polarizer protection film that adheres to a polarizer 30 and protects the polarizer 30 will be exemplified and described. Note that FIG. 1 is a configuration diagram of a polarizing plate 1 according to this embodiment. Hereinafter, each component constituting the polarizing plate 1 will be described.

[0015] [Optical Film 10] In this embodiment, as shown in FIG. 1, in order to protect the polarizer 30, the optical film 10 is adhered to the polarizer 30 via an adhesive layer 20. Further, as shown in FIG. 1, the optical film 10 according to this embodiment has an easy-adhesion layer 12 containing a second acrylic resin composition and fine particles on one surface of an acrylic resin film 11 containing a first acrylic resin as a main component.

[0016] [Acrylic Resin Film 11] The acrylic resin film 11 is made of a thermoplastic resin containing a first acrylic resin as its main component. Here, "main component" means that the main component makes up 50% by weight or more of the components constituting the acrylic resin film 11, preferably 60% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more.

[0017] Any suitable acrylic resin can be used as the first acrylic resin. Typically, the first acrylic resin contains alkyl (meth)acrylate as the main component as monomer units. In this specification, "(meth)acrylic" means acrylic and / or methacrylic. Examples of alkyl (meth)acrylates constituting the main skeleton of the (meth)acrylic resin include linear or branched alkyl groups having 1 to 18 carbon atoms. These can be used alone or in combination. Furthermore, any suitable copolymer monomer may be introduced into the (meth)acrylic resin by copolymerization. The type, number, copolymerization ratio, etc., of such copolymer monomers can be appropriately set depending on the purpose.

[0018] The first acrylic resin may preferably have at least one selected from glutarimide units, lactone ring units, maleic anhydride units, maleimide units, and glutaric anhydride units. An acrylic resin having lactone ring units is described, for example, in Japanese Patent Application Publication No. 2008-181078, the description of which is incorporated herein by reference. The glutarimide unit is preferably represented by the following general formula (1). [ka]

[0019] In general formula (1), R 1 and R 2 Each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, R 3represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 10 carbon atoms. In General Formula (1), preferably, R 1 and R 2 are each independently a hydrogen atom or a methyl group, and R 3 is a hydrogen atom, a methyl group, a butyl group, or a cyclohexyl group. More preferably, R 1 is a methyl group, R 2 is a hydrogen atom, and R 3 is a methyl group.

[0020] Alkyl (meth)acrylate is typically represented by the following General Formula (2). [Chemical Formula]

[0021] In General Formula (2), R 4 represents a hydrogen atom or a methyl group, and R 5 represents a hydrogen atom or an optionally substituted aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms. Examples of the substituent include a halogen and a hydroxyl group. Specific examples of alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth)acrylate, and 2,3,4,5-tetrahydroxypentyl (meth)acrylate. In General Formula (2), R 5 is preferably a hydrogen atom or a methyl group. Therefore, particularly preferred alkyl (meth)acrylate is methyl acrylate or methyl methacrylate.

[0022] The first acrylic resin may contain only a single glutarimide unit, or R in the general formula (1) above. 1 , R 2 and R 3 The resin may contain multiple glutarimide units of different types. The glutarimide unit content in the first acrylic resin is preferably 2 mol% to 50 mol%, more preferably 2 mol% to 45 mol%, even more preferably 2 mol% to 40 mol%, particularly preferably 2 mol% to 35 mol%, and most preferably 3 mol% to 30 mol%. If the content is less than 2 mol%, the effects derived from the glutarimide units (e.g., high optical properties, high mechanical strength, excellent adhesion to the polarizer 30, thinning) may not be fully realized. If the content exceeds 50 mol%, for example, heat resistance and transparency may be insufficient.

[0023] The first acrylic resin may contain only a single alkyl (meth)acrylate unit, or R in the general formula (2) above. 4 and R 5 The resin may contain multiple alkyl (meth)acrylate units of different types. The content of alkyl (meth)acrylate units in the first acrylic resin is preferably 50 mol% to 98 mol%, more preferably 55 mol% to 98 mol%, even more preferably 60 mol% to 98 mol%, particularly preferably 65 mol% to 98 mol%, and most preferably 70 mol% to 97 mol%. If the content is less than 50 mol%, the effects derived from the alkyl (meth)acrylate units (e.g., high heat resistance, high transparency) may not be fully exhibited. If the content is more than 98 mol%, the resin may become brittle and prone to cracking, and high mechanical strength may not be fully exhibited, potentially resulting in poor productivity.

[0024] The first acrylic resin may contain units other than glutarimide units and alkyl (meth)acrylate units. In one embodiment, the first acrylic resin may contain, for example, 0 to 10% by weight of unsaturated carboxylic acid units that are not involved in the intramolecular imidation reaction described later. The content of unsaturated carboxylic acid units is preferably 0 to 5% by weight, and more preferably 0 to 1% by weight. Transparency, retention stability, and moisture resistance can be maintained within this content range.

[0025] In one embodiment, the first acrylic resin may contain copolymerizable vinyl monomer units other than those mentioned above (other vinyl monomer units). Examples of other vinyl monomers include acrylonitrile, methacrylonitrile, ethacrylonitrile, allyl glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N-methylallylamine, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acroyl-oxazoline, N-phenylmaleimide, phenylaminoethyl methacrylate, styrene, α-methylstyrene, p-glycidylstyrene, p-aminostyrene, and 2-styryl-oxazoline. These may be used alone or in combination. Preferably, they are styrene monomers such as styrene and α-methylstyrene. The content of other vinyl monomer units is preferably 0 to 5% by weight, more preferably 0 to 1% by weight, and even more preferably 0 to 0.1% by weight. Within this range, the appearance of undesirable phase differences and a decrease in transparency can be suppressed.

[0026] The imidization rate in the first acrylic resin is preferably 2.5% to 20.0%. Within this range, a resin with excellent heat resistance, transparency, and moldability can be obtained, and charring and a decrease in mechanical strength during film molding can be prevented. In the first acrylic resin described above, the imidization rate is expressed as the ratio of glutarimide units to alkyl (meth)acrylate units. This ratio can be obtained, for example, from the NMR spectrum, IR spectrum, etc., of the first acrylic resin. In this embodiment, the imidization rate is, 1 Using 1H NMR BRUKER Avance III (400 MHz), the resin 1 This can be determined by 1H-NMR measurement. More specifically, if A is the peak area derived from the O-CH3 proton of alkyl (meth)acrylate around 3.5 to 3.8 ppm, and B is the peak area derived from the N-CH3 proton of glutarimide around 3.0 to 3.3 ppm, it can be determined by the following formula. Imidization rate Im(%) = {B / (A+B)} × 100

[0027] The acid value of the first acrylic resin is preferably 0.10 mmol / g to 0.50 mmol / g. Within this range, a resin with an excellent balance of heat resistance, mechanical properties, and moldability can be obtained. If the acid value is too low, problems may arise such as increased costs due to the use of modifiers to adjust the acid value to the desired level, and the generation of gel-like substances due to residual modifiers. If the acid value is too high, foaming is more likely to occur during film molding (e.g., during melt extrusion), leading to a decrease in the productivity of molded products. In the first acrylic resin described above, the acid value is the content of carboxylic acid units and carboxylic acid anhydride units in the first acrylic resin. In this embodiment, the acid value can be calculated, for example, by the titration method described in WO2005 / 054311 or Japanese Patent Publication No. 2005-23272.

[0028] The weight-average molecular weight of the first acrylic resin is preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, even more preferably 10,000 to 500,000, particularly preferably 50,000 to 500,000, and most preferably 60,000 to 150,000. The weight-average molecular weight can be determined, for example, by using a gel permeation chromatograph (GPC system, manufactured by Tosoh Corporation) and calculating it on a polystyrene basis. Tetrahydrofuran may be used as the solvent.

[0029] The glass transition temperature (Tg) of the first acrylic resin is preferably 110°C or higher, more preferably 115°C or higher, even more preferably 120°C or higher, particularly preferably 125°C or higher, and most preferably 130°C or higher. If the Tg is 110°C or higher, polarizing plates containing a base film obtained from such a resin tend to have excellent durability. The upper limit of the glass transition temperature (Tg) is preferably 300°C or lower, more preferably 290°C or lower, even more preferably 285°C or lower, particularly preferably 200°C or lower, and most preferably 160°C or lower. If the glass transition temperature (Tg) is within this range, excellent moldability can be achieved.

[0030] The first acrylic resin can be produced, for example, by the following method. This method may include (I) copolymerizing an alkyl (meth)acrylate monomer corresponding to an alkyl (meth)acrylate unit represented by general formula (2) with an unsaturated carboxylic acid monomer and / or its precursor monomer to obtain a copolymer (a); and (II) treating the copolymer (a) with an imidizing agent to carry out an intramolecular imidation reaction between the alkyl (meth)acrylate monomer unit and the unsaturated carboxylic acid monomer and / or its precursor monomer unit in the copolymer (a), thereby introducing a glutarimide unit represented by general formula (1) into the copolymer.

[0031] Examples of unsaturated carboxylic acid monomers include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, and α-substituted methacrylic acid. Examples of precursor monomers include acrylamide and methacrylamide. These may be used alone or in combination. Preferred unsaturated carboxylic acid monomers are acrylic acid or methacrylic acid, and preferred precursor monomers are acrylamide.

[0032] Any suitable method can be used to treat copolymer (a) with an imidizing agent. Specific examples include a method using an extruder and a method using a batch-type reaction vessel (pressure vessel). The method using an extruder involves heating and melting copolymer (a) using an extruder and treating it with an imidizing agent. In this case, any suitable extruder can be used. Specific examples include a single-screw extruder, a twin-screw extruder, and a multi-screw extruder. In the method using a batch-type reaction vessel (pressure vessel), any suitable batch-type reaction vessel (pressure vessel) can be used.

[0033] As the imidizing agent, any suitable compound can be used as long as it can generate glutarimide units represented by the above general formula (1). Specific examples of imidizing agents include aliphatic hydrocarbon group-containing amines such as methylamine, ethylamine, n-propylamine, i-propylamine, n-butylamine, i-butylamine, tert-butylamine, and n-hexylamine; aromatic hydrocarbon group-containing amines such as aniline, benzylamine, toluidine, and trichloroaniline; and alicyclic hydrocarbon group-containing amines such as cyclohexylamine. Furthermore, urea-based compounds that generate such amines by heating, for example, can also be used. Examples of urea compounds include urea, 1,3-dimethylurea, 1,3-diethylurea, and 1,3-dipropylurea. The imidizing agent is preferably methylamine, ammonia, or cyclohexylamine, and more preferably methylamine. In imidation, in addition to the above imidizing agent, a ring-closing accelerator may be added as needed.

[0034] The amount of imidizing agent used in imidization is preferably 0.5 to 10 parts by weight, and more preferably 0.5 to 6 parts by weight, per 100 parts by weight of copolymer (a). If the amount of imidizing agent used is less than 0.5 parts by weight, the desired imidization rate is often not achieved. As a result, the heat resistance of the resulting resin becomes extremely insufficient, which may induce appearance defects such as charring after molding. If the amount of imidizing agent used exceeds 10 parts by weight, residual imidizing agent remains in the resin, which may induce appearance defects such as charring and foaming after molding.

[0035] The first method for producing the acrylic resin may, if necessary, include treatment with an esterifying agent in addition to the imidization described above. Examples of esterifying agents include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyltoluene sulfonate, methyltrifluoromethanesulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethylcarbodiimide, dimethyl-t-butylsilyl chloride, isopropenyl acetate, dimethylurea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-N-butoxysilane, dimethyl(trimethylsilane) phosphite, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2-ethylhexylglycidyl ether, phenylglycidyl ether, and benzylglycidyl ether. Among these, dimethyl carbonate is preferred from the viewpoint of cost and reactivity. The amount of esterifying agent added can be set so that the acid value of the first acrylic resin reaches a desired value.

[0036] The acrylic resin film 11 may be made by combining the first acrylic resin with other resins. That is, monomer components constituting the first acrylic resin may be copolymerized with monomer components constituting the other resin, and the copolymer may be used for film formation as described later, or a blend of the first acrylic resin and other resins may be used for film formation. Examples of other resins include other thermoplastic resins such as styrene resins, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, and polyetherimide, as well as thermosetting resins such as phenolic resins, melamine resins, polyester resins, silicone resins, and epoxy resins. The type and amount of resins used in combination can be appropriately set according to the purpose and the desired properties of the resulting film. For example, styrene resins (preferably acrylonitrile-styrene copolymers) can be used in combination as a phase difference control agent. When the first acrylic resin is used in combination with other resins, the content of the first acrylic resin in the blend of the first acrylic resin and other resins is preferably 50% to 100% by weight, more preferably 60% to 100% by weight, even more preferably 70% to 100% by weight, and particularly preferably 80% to 100% by weight. If the content is less than 50% by weight, the high heat resistance and high transparency inherent in the first acrylic resin may not be fully reflected.

[0037] The acrylic resin film 11 may be a first acrylic resin blended with core-shell type particles, preferably in an amount of 5 to 50 parts by weight, more preferably 5 to 40 parts by weight, per 100 parts by weight of the first acrylic resin. The core-shell type particles typically have a core made of a rubbery polymer and a coating layer made of a glassy polymer that covers the core. The core-shell type particles may also have one or more layers made of a glassy polymer as the innermost or intermediate layer.

[0038] Details regarding the rubbery polymer constituting the core of the core-shell type particle, the glassy polymer (rigid polymer) constituting the coating layer, the polymerization methods for these polymers, and other components are described, for example, in Japanese Patent Application Publication No. 2016-33552. The description in this publication is incorporated herein by reference.

[0039] The thickness of the acrylic resin film 11 is preferably 5 μm or more, more preferably 8 μm or more, even more preferably 10 μm or more, preferably 200 μm or less, more preferably 100 μm or less, even more preferably 70 μm or less, and particularly preferably 60 μm or less. By making the thickness of the resin film above the lower limit of the above range, the mechanical strength of the resin film can be increased. Conversely, by making it below the upper limit, the thickness of the acrylic resin film 11 can be reduced.

[0040] Any suitable method can be used to form the acrylic resin film 11. Specific examples include cast coating (e.g., casting), extrusion molding, injection molding, compression molding, transfer molding, blow molding, powder molding, FRP molding, calendering, and hot pressing. Extrusion molding or cast coating is preferred because it enhances the smoothness of the resulting film and provides good optical uniformity. Extrusion molding is particularly preferred. Among these, extrusion molding using a T-die is preferred from the viewpoint of film productivity and ease of subsequent stretching. Molding conditions can be appropriately set according to the composition and type of resin used, the desired properties of the resulting film, and other factors.

[0041] Any suitable stretching method and conditions (e.g., stretching temperature, stretching ratio, stretching speed, stretching direction) can be used. Specific examples of stretching methods include free-end stretching, fixed-end stretching, free-end shrinking, and fixed-end shrinking. These may be used individually, simultaneously, or sequentially.

[0042] The stretching direction can be an appropriate direction depending on the purpose. Specifically, this includes the length direction, width direction, thickness direction, and oblique direction. The stretching direction may be uniaxial (uniaxial stretching), biaxial (biaxial stretching), or three or more directions. In this embodiment, typically, uniaxial stretching in the length direction, simultaneous biaxial stretching in the length and width directions, and sequential biaxial stretching in the length and width directions can be employed. Preferably, biaxial stretching (simultaneous or sequential) is used, as it allows for easy control of the in-plane phase difference and facilitates the achievement of optical isotropy.

[0043] The stretching temperature can vary depending on the desired optical properties, mechanical properties, and thickness of the base film, the type of resin used, the thickness of the film used, the stretching method (uniaxial stretching or biaxial stretching), the stretching ratio, and the stretching speed. Specifically, the stretching temperature is preferably Tg to Tg+50°C, more preferably Tg+15°C to Tg+50°C, and most preferably Tg+35°C to Tg+50°C. By stretching at such temperatures, a base film with appropriate properties can be obtained.

[0044] The stretching ratio, like the stretching temperature, can vary depending on the optical properties, mechanical properties and thickness, the type of resin used, the thickness of the film used, the stretching method (uniaxial stretching or biaxial stretching), the stretching temperature, the stretching speed, etc. When biaxial stretching is used, the ratio of the stretching ratio in the width direction (TD) to the stretching ratio in the length direction (MD) (TD / MD) is preferably 1.0 to 1.5, more preferably 1.0 to 1.4, and even more preferably 1.0 to 1.3. Also, when biaxial stretching is used, the surface magnification (product of the stretching ratio in the length direction and the stretching ratio in the width direction) is preferably 2.0 to 6.0, more preferably 3.0 to 5.5, and even more preferably 3.5 to 5.2.

[0045] The stretching speed, like the stretching temperature, can vary depending on the optical properties, mechanical properties and thickness, the type of resin used, the thickness of the film used, the stretching method (uniaxial stretching or biaxial stretching), the stretching temperature, the stretching ratio, etc. The stretching speed is preferably 3% / sec to 20% / sec, more preferably 3% / sec to 15% / sec, and even more preferably 3% / sec to 10% / sec. When biaxial stretching is employed, the stretching speed in one direction and the stretching speed in the other direction may be the same or different.

[0046] [Easy adhesive layer 12] The easy-adhesion layer 12 is formed on one side of the acrylic resin film 11 and has the function of properly bonding the acrylic resin film 11 and the polarizer 30 via the adhesive layer 20. In this embodiment, the easy-adhesion layer 12 is characterized by containing a second acrylic resin different from the first acrylic resin contained in the acrylic resin film 11, and fine particles.

[0047] The second acrylic resin is a core-shell type resin composition comprising an alkali-soluble copolymer (A) of a monomer mixture containing (meth)acrylic acid and an alicyclic alkyl group-containing ethylenically unsaturated monomer as the shell part, and a copolymer (B) of a monomer mixture containing diacetone (meth)acrylamide and an ethylenically unsaturated monomer as the core part.

[0048] The alkali-soluble copolymer (A) of a monomer mixture containing (meth)acrylic acid and an alicyclic alkyl group-containing ethylenically unsaturated monomer is a copolymer of a monomer mixture having (meth)acrylic acid and at least one alicyclic alkyl group-containing ethylenically unsaturated monomer as essential components, and refers to a water-soluble polymer that is completely or partially neutralized by adding 90 to 100% equivalent amounts of a basic compound to the acid groups of the alkali-soluble copolymer (A) and dissolving it at 80 to 90°C for 3 hours. The pH of the solution obtained by solubilizing the alkali-soluble copolymer (A) in water with a basic compound is preferably 7.5 to 9.0.

[0049] In the alkali-soluble copolymer (A), at least one monomer selected from acrylic acid and methacrylic acid can preferably be used as (meth)acrylic acid. It is preferable that (meth)acrylic acid is present in the monomer mixture used for copolymerization of the alkali-soluble copolymer (A) at a concentration of 6 to 23% by mass, such that the alkali-soluble copolymer (A) becomes soluble in water when neutralized with a basic compound.

[0050] Furthermore, in the alkali-soluble copolymer (A), examples of alicyclic alkyl group-containing ethylenically unsaturated monomers include (meth)acrylic acid esters such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and cyclooctyl (meth)acrylate, and one or more of these can be selected. From the viewpoint of adhesion to acrylic resin films 11 and the like, the alicyclic alkyl group-containing ethylenically unsaturated monomer is preferably contained in the monomer mixture used for copolymerization of the alkali-soluble copolymer (A) in an amount of 10 to 30% by mass, and more preferably in an amount of 20 to 30% by mass.

[0051] Other monomer components that can be used in copolymerization of the alkali-soluble copolymer (A) include styrenes such as styrene and α-methylstyrene; and (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and benzyl (meth)acrylate. One or more of these can be selected. Among these, (meth)acrylic acid esters are preferred from the viewpoint of adhesion. The skeletons derived from these monomers are preferably present in the monomer mixture used in copolymerization of the alkali-soluble copolymer (A) in an amount of 47 to 84% by mass, and more preferably in an amount of 47 to 74% by mass.

[0052] When copolymerizing the alkali-soluble copolymer (A), the preferred ratio of each monomer by mass is (meth)acrylic acid: alicyclic alkyl group-containing ethylenically unsaturated monomer: other monomers = 6-23:10-30:47-84 (%), and more preferably (meth)acrylic acid: alicyclic alkyl group-containing ethylenically unsaturated monomer: other monomers = 6-23:20-30:47-74 (%).

[0053] Furthermore, in the copolymerization of the alkali-soluble copolymer (A), in addition to some of the other monomer components, one or more of the following can be optionally used, as long as they do not impair the effects of the present invention: hydroxyl group-containing ethylenically unsaturated monomers such as hydroxyethyl (meth)acrylate; monoalkoxyalkylene glycol (meth)acrylates such as 2-methoxyethyl (meth)acrylate; (meth)acrylamide; N-substituted (meth)acrylamides such as N,N-dimethyl(meth)acrylamide and diacetone(meth)acrylamide; and dicarboxylic acid monomers such as itaconic acid and maleic acid, and their anhydrides or derivatives. These can usually be used up to a maximum of 10% by mass of the monomer mixture used in the copolymerization of the alkali-soluble copolymer (A).

[0054] Next, copolymer (B), which constitutes the second acrylic resin, will be described. Copolymer (B) is obtained by copolymerizing diacetone (meth)acrylamide with a monomer mixture containing an ethylenically unsaturated monomer.

[0055] The ethylenically unsaturated monomers used in the copolymerization of copolymer (B) are preferably those that do not have ionic properties. Examples include styrenes such as styrene and α-methylstyrene; and (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, and benzyl (meth)acrylate. One or more of these can be selected. Among these, (meth)acrylic acid esters are preferred from the viewpoint of adhesion to acrylic resin film 11, and in particular, a combination of monomers that increase the glass transition temperature, such as methyl methacrylate, and monomers that decrease the glass transition temperature, such as butyl acrylate and 2-ethylhexyl acrylate, is more preferred from the viewpoint of adhesion of the easily bondable layer.

[0056] The amount of ethylenically unsaturated monomer used for copolymerization of copolymer (B) is determined by the conditions described later. <ii>and conditions <iii>You just need to adjust it to satisfy that requirement.

[0057] In this embodiment, alkali-soluble copolymer (A) and copolymer (B) are as follows: ~ <iii>It is preferable that the following conditions be satisfied. Alkali-soluble copolymer (A) has an acid value of 5-75 mg KOH / g <ii>The proportion of diacetone (meth)acrylamide-derived material in copolymer (B) is 1 to 20% by mass relative to the total of alkali-soluble copolymer (A) and copolymer (B). <iii>The mass ratio of alkali-soluble copolymer (A) to copolymer (B) is (A):(B) = 20:80 to 60:40 The following are the conditions ~ <iii>This explains the details.

[0058] conditions The alkali-soluble copolymer (A) preferably has an acid value of 5 to 75 mgKOH / g. In the ink composition for forming the easy-adhesion layer 12, the core-shell type resin composition of copolymer (A) and copolymer (B) exists in the solvent as an emulsion, but if the acid value is less than 5 mgKOH / g, the storage stability of the emulsion decreases. Furthermore, if the acid value exceeds 75 mgKOH / g, the stretchability of the coating film decreases, and whitening may occur when stretched. The acid value is more preferably 10 to 60 mgKOH / g, and even more preferably 15 to 50 mgKOH / g.

[0059] conditions <ii> In copolymer (B) of a monomer mixture containing diacetone (meth)acrylamide and ethylenically unsaturated monomers, the content of the diacetone (meth)acrylamide-derived skeleton is preferably 1 to 20% by mass relative to the total of the alkali-soluble copolymer (A) and copolymer (B), from the viewpoint of adhesion and optical properties. If it is less than 1% by mass, the effect of adhesion due to crosslinking cannot be confirmed in the easily adhering layer, and there is a risk of transparency defects occurring upon stretching. If it exceeds 20% by mass, there is a risk of reduced adhesion to the acrylic resin film. A content of 2 to 15% by mass is more preferable. Furthermore, the above is also preferable for the content of the diacetone (meth)acrylamide-derived skeleton contained in both the alkali-soluble copolymer (A) and copolymer (B).

[0060] conditions <iii> The alkali-soluble copolymer (A) and copolymer (B) preferably have a mass ratio of (A):(B) = 20:80 to 60:40. If the mass ratio of (A) is less than 20, polymerization of the emulsion will not occur sufficiently or the stability of the emulsion will decrease, and if it exceeds 60, the adhesion to the acrylic resin film will be poor. A more preferable ratio is (A):(B) = 30:70 to 60:40.

[0061] Also, the above conditions ~ <iii>In addition, the polystyrene-equivalent weight-average molecular weight of the alkali-soluble copolymer (A) in gel permeation chromatography (GPC) is preferably 6,000 to 20,000 from the viewpoint of adhesion and storage stability of the emulsion, and more preferably 8,000 to 20,000.

[0062] Furthermore, the overall glass transition temperature (Tg) of the alkali-soluble copolymer (A) and copolymer (B) is preferably -5 to 30°C from the viewpoint of ink film-forming properties, adhesion, and blocking resistance. In particular, adhesion tends to be good when the glass transition temperature (Tg) is 30°C or lower, while adhesion does not change much even when it is lowered below -5°C, and conversely, blocking resistance tends to decrease. For this reason, the overall glass transition temperature (Tg) of the alkali-soluble copolymer (A) and copolymer (B) is preferably 0 to 20°C, and more preferably 5 to 15°C. The overall glass transition temperature of the alkali-soluble copolymer (A) and copolymer (B) can be designed based on the FOX formula, which is calculated from the glass transition temperature of each homopolymer and the weight fraction of each monomer, and may be a theoretical value calculated from the FOX formula.

[0063] Furthermore, in this embodiment, the second acrylic resin is preferably configured to contain a hydrazide compound (C). The hydrazide compound (C) is a hydrazide compound containing two or more hydrazide groups in its molecule, and it is acceptable as long as it crosslinks with the keto groups derived from the diacetone (meth)acrylamide skeleton in the copolymer (B). Examples include aliphatic dihydrazides such as adipic acid dihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, and sebacate dihydrazide, as well as polyhydrazides of carbonate, aliphatic, alicyclic, aromatic bissemicarbazides, aromatic dicarboxylic acid dihydrazides, polyhydrazides of polyacrylic acid, dihydrazides of aromatic hydrocarbons, hydrazine-pyridine derivatives, and dihydrazides of unsaturated dicarboxylic acids such as maleic acid dihydrazide. Preferably, it is adipic acid dihydrazide.

[0064] Furthermore, the hydrazide compound (C) is preferably blended in a ratio of 0.1 to 1.2 molar equivalents per molar equivalent of keto groups derived from diacetone (meth)acrylamide in the copolymer (B), more preferably in a ratio of 0.5 to 1.2 molar equivalents, and even more preferably in a ratio of 0.8 to 1.2 molar equivalents. By including the hydrazide compound (C) within the above range, the diacetone (meth)acrylamide contained in the core of one core shell can be appropriately crosslinked with the diacetone (meth)acrylamide contained in the core of another core shell, forming an easily adhesive layer with excellent adhesion. On the other hand, if the amount of hydrazide compound blended exceeds 1.2 molar equivalents, hydrazide compounds that do not bond with diacetone (meth)acrylamide will remain, and these remaining hydrazide compounds may degrade the polarizer.

[0065] In this embodiment, an easy-to-adhere layer 12 is formed by applying an ink composition containing an aqueous resin dispersion liquid containing a core-shell type emulsion, which has an alkali-soluble copolymer (A) of a monomer mixture containing (meth)acrylic acid and an alicyclic alkyl group-containing ethylenically unsaturated monomer as the shell part and a copolymer (B) of a monomer mixture containing diacetone (meth)acrylamide and an ethylenically unsaturated monomer as the core part, and fine particles such as silica, to one side of an acrylic resin film 11.

[0066] The above-mentioned resin dispersion for aqueous ink will now be described. The above-mentioned resin dispersion for aqueous ink is obtained by emulsion polymerization of a monomer mixture containing diacetone (meth)acrylamide and an ethylenically unsaturated monomer in the presence of an alkali-soluble copolymer (A) of a monomer mixture containing (meth)acrylic acid and an alicyclic alkyl group-containing ethylenically unsaturated monomer to obtain a copolymer (B), and then adding a hydrazide compound (C) as needed.

[0067] When emulsion polymerization is carried out using a monomer mixture containing diacetone (meth)acrylamide and ethylenically unsaturated monomers, the alkali-soluble copolymer (A) is neutralized with a basic compound and used as an aqueous solution. Suitable basic substances for neutralization include ammonia; alkylamines such as trimethylamine, triethylamine, and butylamine; alcoholamines such as dimethylaminoethanol, diethanolamine, triethanolamine, and aminomethylpropanol; and bases such as morpholine. In this case, the pH after neutralization does not necessarily need to be around 7. That is, there are no particular restrictions on the degree of neutralization; the alkali-soluble copolymer (A) only needs to function as a polymer emulsifier when forming a core-shell emulsion.

[0068] By emulsion polymerization of a monomer mixture containing diacetone (meth)acrylamide and ethylenically unsaturated monomers using an alkali-soluble copolymer (A) as a polymer emulsifier, a core-shell type emulsion can be obtained in which the alkali-soluble copolymer (A) forms the shell and copolymer (B) forms the core.

[0069] By adding a hydrazide compound (C) to the core-shell emulsion obtained in this way, if necessary, a resin dispersion for aqueous ink according to this embodiment can be prepared.

[0070] Furthermore, pigments, solvents, and other additives can be added to the above-mentioned resin dispersion for aqueous ink.

[0071] As the solvent mentioned above, water and small amounts of water-soluble organic solvents may be used. Examples of such solvents include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and n-propyl alcohol; glycols such as ethylene glycol and propylene glycol; and glycol ethers such as butyl cellosolve, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether. Here, "small amount" refers to the minimum necessary amount considering environmental emissions and drying time.

[0072] Furthermore, in this embodiment, the easy-adhesion layer 12 contains fine particles in addition to the second acrylic resin. If the easy-adhesion layer is composed only of the second acrylic resin, the slipperiness is low, and blocking may occur when the optical film 10 is used as a roll. In this embodiment, in order to prevent such blocking, the easy-adhesion layer 12 contains fine particles. In this embodiment, an ink composition is prepared by adding a solvent such as water or ethanol and fine particles to the above-mentioned aqueous ink resin dispersion containing the second acrylic resin, and the prepared ink composition is applied to the acrylic resin film 11 and dried to form an easy-adhesion layer 12 containing fine particles in addition to the second acrylic resin.

[0073] The above-mentioned fine particles can include any fine particles that have the function of preventing blocking, but water-dispersible fine particles are preferred. The fine particles may be inorganic or organic. Examples of inorganic fine particles include inorganic oxides such as silica, titania, alumina, and zirconia, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Examples of organic fine particles include silicone resins, fluororesins, (meth)acrylic resins, (meth)acrylonitrile resins, and urethane resins. Among these, silica is preferred. This is because silica-based fine particles have excellent blocking suppression ability, excellent transparency, do not produce haze, and do not discolor, thus reducing the influence of the easy-adhesion layer 12 on the optical properties. Furthermore, from the viewpoint of recycling, organic fine particles made of (meth)acrylic resin may be used as fine particles, for example, those with a size of 100 to 400 nm can be used. The (meth)acrylic resin may be crosslinked or not, but from the viewpoint of lubricity, it is preferable that it be crosslinked.

[0074] The average particle size of the fine particles is not particularly limited, but from the viewpoint of maintaining the transparency of the easy-adhesion layer 12, it is preferably 1 to 500 nm, more preferably 10 to 450 nm, even more preferably 50 to 400 nm, and particularly preferably 70 to 200 nm. By using fine particles of such particle size, it is possible to appropriately form irregularities on the surface of the easy-adhesion layer 12, thereby effectively reducing the frictional force at the contact surface between the acrylic resin film 11 and the easy-adhesion layer 12 and / or between the easy-adhesion layers 12 themselves, and suppressing blocking.

[0075] Furthermore, the easy-adhesion layer 12 may contain other crosslinking agents to improve its heat and humidity resistance under high temperature and high humidity conditions. Any suitable crosslinking agent can be used, such as urea compounds, epoxy compounds, melamine compounds, isocyanate compounds, oxazoline compounds, silanol compounds, and carbodiimide compounds. These can be used alone or in combination of two or more. The amount of crosslinking agent is not particularly limited, but it is preferably 0.1 parts by weight or more and 35 parts by weight or less per 100 parts by weight of the total of the second acrylic resin and fine particles, in terms of solid content. The lower limit is more preferably 0.5 parts by weight or more, even more preferably 3 parts by weight or more, and particularly preferably 5 parts by weight or more. The upper limit is more preferably 30 parts by weight or less, even more preferably 25 parts by weight or less, and particularly preferably 20 parts by weight or less. If resin components other than the second acrylic resin and fine particles are included, the crosslinking agent should be blended with 100 parts by weight of solid content including the other resin components.

[0076] Furthermore, the easy-adhesion layer 12 may further contain any suitable additives. Examples of additives include dispersion stabilizers, thixotropes, antioxidants, UV absorbers, defoamers, thickeners, dispersants, surfactants, catalysts, lubricants, and antistatic agents.

[0077] The thickness of the easy-adhesion layer 12 is not particularly limited, but is preferably, for example, 0.01 μm or more and 10 μm or less. The lower limit is more preferably 0.03 μm or more, even more preferably 0.05 μm or more, particularly preferably 0.1 μm or more, and most preferably 0.15 μm or more. The upper limit is more preferably 3 μm or less, even more preferably 2 μm or less, particularly preferably 1 μm or less, and most preferably 0.5 μm or less. By setting the thickness of the easy-adhesion layer 12 within the above range, the adhesion to the acrylic resin film 11 and the polarizer 30 can be effectively improved. In this embodiment, the acrylic resin film 11 can also be stretched while the easy-adhesion layer 12 is laminated on the acrylic resin film 11, and in this case, it is preferable that the thickness of the easy-adhesion layer 12 falls within the above thickness range after stretching.

[0078] The easy-adhesion layer 12 according to this embodiment is characterized by high adhesion to the acrylic resin film 11, polarizer 30, or adhesive layer 20, and high optical properties. In particular, in terms of optical properties, in addition to not whitening even when stretched, when the acrylic easy-adhesion layer 12 is stretched, holes or granular transparent defects may occur as shown in Figure 2(B), but the easy-adhesion layer 12 is characterized by not producing such transparent defects even when stretched. Transparent defects in the easy-adhesion layer may cause light leakage or loss when used as an optical film such as a polarizer protective film in an image display device such as a display, potentially reducing contrast. Figure 2 is a diagram to explain transparent defects, where (A) shows an easy-adhesion layer without transparent defects and (B) shows an easy-adhesion layer with transparent defects, and the size of the transparent defects is about 1 to 10 mm. In this embodiment, the easy-adhesion layer 12 is a thin film of 300 nm or less, and it is difficult to see the cross-section, so it has not been determined whether the transparent defects are holes or granules.

[0079] [Optical film 10] As shown in Figure 1, the optical film 10 according to this embodiment has an easy-adhesion layer 12 containing a second acrylic resin and fine particles on one surface of an acrylic resin film 11 mainly containing a first acrylic resin. The easy-adhesion layer 12 only needs to be formed on at least one surface of the acrylic resin film 11, and may be formed on both surfaces of the acrylic resin film 11.

[0080] From the viewpoint of ensuring that the optical film 10 stably exhibits its function as an optical component, the total light transmittance is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The light transmittance can be measured using a spectrophotometer (UV-Vis-Near-Infrared Spectrophotometer "V-570" manufactured by JASCO Corporation) in accordance with JIS K0115.

[0081] The haze of the optical film 10 is not particularly limited, but is preferably 2.0% or less, more preferably 1.0% or less, even more preferably 0.8% or less, and especially preferably 0.5% or less. The haze can be measured using a "turbidity meter NDH-300A" manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K7361-1997.

[0082] The total thickness of the optical film 10 is preferably 5 μm or more, more preferably 8 μm or more, even more preferably 10 μm or more, preferably 200 μm or less, more preferably 100 μm or less, and particularly preferably 70 μm or less. By making the total thickness of the optical film 10 above the lower limit, the mechanical strength of the optical film 10 can be increased. Conversely, by making it below the upper limit, the overall thickness of the optical film 10 can be reduced.

[0083] Various functional layers may be formed on the surface of the optical film 10 opposite to the surface on which the easy-adhesion layer 12 is formed, as needed. Examples of functional layers include antistatic layers, adhesive layers, adhesive layers, easy-adhesion layers, anti-glare (non-glare) layers, anti-fouling layers such as photocatalytic layers, anti-reflective layers, hard coat layers, ultraviolet shielding layers, heat shielding layers, electromagnetic wave shielding layers, and gas barrier layers.

[0084] The optical film 10 is not limited to a polarizer protective film, but can be, for example, a phase difference film, a viewing angle compensation film, a light diffusion film, a reflective film, an anti-reflective film, an anti-glare film, a brightness enhancement film, a conductive film for touch panels, and the like. Furthermore, the optical film 10 may be an optically isotropic film or an optically anisotropic film (for example, a film that exhibits birefringence such as phase difference).

[0085] [Method for manufacturing optical film 10] The method for manufacturing the optical film 10 is not particularly limited, but it includes the steps of: applying an ink composition containing an aqueous solvent such as water or ethanol, a second acrylic resin, and fine particles to at least one surface of an acrylic resin film 11 mainly containing a first acrylic resin to form a coating film; and drying or curing the coating film to form an easy-adhesion layer 12. Among these, the following manufacturing method is preferred.

[0086] A preferred method for producing an optical film in the present invention comprises the steps of: applying an ink composition containing an aqueous solvent, a second acrylic resin, and fine particles to at least one surface of an acrylic resin film 11 before stretching, which is made of a thermoplastic resin mainly containing a first acrylic resin, to form a coating film; drying or curing the coating film to form an easy-adhesion layer 12; and stretching the acrylic resin film 11 before stretching to obtain a stretched film.

[0087] In the method for manufacturing an optical film of the present invention, the first step is to prepare an acrylic resin film 11 before stretching. The acrylic resin film 11 before stretching is a raw film that will become a stretched film when subjected to a stretching treatment, and is made of a thermoplastic resin mainly containing a first acrylic resin. Note that the "acrylic resin film" of the present invention includes both an unstretched acrylic resin film 11 and a stretched acrylic resin film 11.

[0088] The surface of the acrylic resin film 11 before stretching, on which the coating film is formed, may be subjected to a surface modification treatment to improve the adhesion between the acrylic resin film 11 and the easy-adhesion layer 12. In the surface modification treatment, the hydrophilicity of the treated surface is usually improved to bring the average water contact angle and the standard deviation of the water contact angle of the surface into a desired range. The desired range of the average water contact angle is preferably 20° to 80°, more preferably 20° to 75°, and even more preferably 20° to 50°. Examples of surface modification treatments include energy ray irradiation treatment and chemical treatment. Examples of energy ray irradiation treatments include corona discharge treatment, plasma treatment, electron beam irradiation treatment, and ultraviolet irradiation treatment, with corona discharge treatment and plasma treatment being preferred from the viewpoint of treatment efficiency, and corona discharge treatment being particularly preferred. Examples of chemical treatments include saponification treatment and treatment in which the film is immersed in an aqueous solution of an oxidizing agent such as potassium dichromate solution and concentrated sulfuric acid, and then washed with water.

[0089] Next, an ink composition containing an aqueous solvent, a second acrylic resin, and fine particles is applied to at least one surface of the acrylic resin film 11 before stretching to form a coating film. The method for forming the coating film on the acrylic resin film before stretching is not particularly limited, but examples of application methods include wire bar coating, dip coating, spray coating, spin coating, roll coating, gravure coating, air knife coating, curtain coating, slide coating, and extrusion coating.

[0090] Next, a coating film is formed on the surface of the resin film before stretching, and then this coating film is dried or cured to obtain an easy-adhesion layer 12. Typically, the coating film is cured by drying the solvent contained in the ink composition. At this time, it is preferable to perform a heat treatment from the viewpoint of rapidly promoting reactions such as crosslinking reactions in the coating film. The heating temperature and heating time should be appropriately set within a range that allows the desired reactions, such as processing reactions, to proceed.

[0091] Then, after forming an easy-adhesion layer 12 on the surface of the acrylic resin film 11 before stretching, the acrylic resin film 11 is stretched to obtain a stretched film. The stretching method described above can be used.

[0092] In the above manufacturing method, the step of drying or curing the coating film to obtain the easy-adhesion layer 12 and the step of stretching the acrylic resin film 11 before stretching to obtain a stretched film may be performed in either order, or both steps may be performed simultaneously. From the viewpoint of improving the adhesion between the stretched film and the easy-adhesion layer 12, it is preferable that the step of drying or curing the coating film to obtain the easy-adhesion layer 12 and the step of stretching the acrylic resin film 11 before stretching to obtain a stretched film be performed continuously (apparently simultaneously). Specifically, this is because the coating film is heated before stretching by the preheating applied when stretching the acrylic resin film 11 before stretching, and the drying or curing of the coating layer of the ink composition proceeds. By performing the above steps, an optical film 10 is obtained comprising a stretched film and an easy-adhesion layer 12 provided on at least one surface of the stretched film.

[0093] From the viewpoint of improving the manufacturing efficiency of the optical film 10, it is preferable to manufacture the optical film 10 as a long film. When manufacturing the optical film 10 as a long film, it is preferable to prepare a long acrylic resin film 11 before stretching, and while conveying the acrylic resin film 11 before stretching in the longitudinal direction, apply an ink composition containing a second acrylic resin and fine particles to the surface of the acrylic resin film 11 before stretching, and dry or cure it to continuously form an easy-adhesion layer 12. For example, it is preferable to apply an ink composition for forming an easy-adhesion layer 12 to the surface of the acrylic resin film 11 before stretching just before the continuously conveyed long acrylic resin film 11 before stretching is supplied to the stretching device, and to continuously dry the coating and stretch the acrylic resin film 11 before stretching in the preheating zone and stretching zone of the stretching device.

[0094] [Polarizing plate 1] Next, a polarizing plate 1 will be described as an example of an optical component of the present invention. Figure 1 is a cross-sectional view showing a polarizing plate 1 according to this embodiment. As shown in Figure 1, the polarizing plate 1 has a structure in which a polarizer 30 is laminated on the surface of the optical film 10 according to this embodiment on the side with the easy-adhesion layer 12, via an adhesive layer 20. Although not shown, the polarizing plate 1 may also have other polarizer protective films or phase difference films laminated via adhesive on the side of the polarizer 30 opposite to the optical film 10. The easy-adhesion layer 12 formed on the optical film 10 according to this embodiment has excellent strength and ease of adhesion, so a polarizing plate 1 can be made with excellent adhesion between the polarizer 30 and the optical film 10.

[0095] As the polarizer 30, any suitable polarizer can be used depending on the purpose. For example, hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and partially saponified ethylene-vinyl acetate copolymer films can be uniaxially stretched after adsorbing dichroic substances such as iodine or dichroic dyes, or polyene-based oriented films such as dehydrated polyvinyl alcohol or dehydrochlorinated polyvinyl chloride. Among these, polarizers made by uniaxially stretching a polyvinyl alcohol-based film after adsorbing dichroic substances such as iodine are particularly preferred because they have a high dichroic ratio of polarization. The thickness of these polarizers is not particularly limited, but is generally about 1 to 80 μm.

[0096] Any suitable adhesive can be used to form the adhesive layer 20. Preferably, the adhesive layer 20 is formed from a hydrophilic adhesive composition containing a polyvinyl alcohol-based resin or an ultraviolet-curable adhesive composition containing an acrylic resin. The easy-adhesion layer 12 of the optical film 10 according to this embodiment can adhere to both the hydrophilic adhesive composition and the ultraviolet-curable adhesive composition with higher adhesive strength than conventional methods. [Examples]

[0097] The following describes examples of the optical film 10 according to this embodiment. In this embodiment, the optical films according to Examples 1-3 and Comparative Examples 1-2 were manufactured as follows. Specifically, pellets of the first acrylic resin [Tg: 122°C, melt viscosity: 1000 Pa·s (temperature 260°C, shear rate 100 (1 / sec))] were melt-extruded at 260°C using a single-screw extruder (φ=40.0 mm, L / D=32) and a coat hanger type T die (width 500 mm), and the molten resin was discharged onto a cooling roll held at 100°C to form an acrylic resin film 11 with a thickness of 100 μm. Next, one surface of the acrylic resin film 11 was treated with a heat treatment of 40 Wmin / m 2 Corona treatment was performed, and the film was dried at 100°C for 3 minutes. Then, an ink composition for forming an easy-adhesion layer was applied to the surface of the corona-treated acrylic resin film 11 using a bar coater, and the film was placed in a hot air dryer and dried at 100°C for 180 seconds. The film was then uniaxially stretched at the fixed end using a table stretcher (stretching temperature: 145°C, stretching ratio: 3.0 times) to produce optical films according to Examples 1-3 and Comparative Examples 1-2, which had an easy-adhesion layer with a thickness of 0.3 μm on the surface of the 40 μm thick acrylic resin film 11.

[0098] In this example, the easily adhering layers according to Examples 1-3 and Comparative Example 1-2 were prepared as follows. First, an ink composition for forming the easily adhering layers according to Examples 1-3 and Comparative Example 1-2 was prepared. Specifically, 100 parts by weight of propylene glycol monomethyl ether acetate (PGMAc) as a solvent was charged into a four-necked separatory flask equipped with a stirrer, thermometer, cooler, and nitrogen inlet tube, and after creating a nitrogen atmosphere, the internal temperature was set to 145°C. Next, while introducing nitrogen gas, 100 parts of a monomer mixture shown in Table 1 and 4 parts of di-t-butyl peroxide (DTBP) as a polymerization initiator were added dropwise over 3 hours using a metering pump. After the addition was complete, the mixture was kept warm at the same temperature for 2 hours to allow the copolymerization reaction to proceed. The obtained copolymer liquid was heated to 180°C and distilled at atmospheric pressure. When the amount of effluent decreased, PGMAc was removed by vacuum distillation to obtain alkali-soluble copolymers A-1 and A-2 shown in Table 1.

[0099] [Table 1]

[0100] In Table 1 above, MAA represents methacrylic acid, MMA represents methyl methacrylate, BA represents butyl acrylate, and CHA represents cyclohexyl acrylate. In Table 1 above, the content of each component is shown in parts by weight. Thus, alkali-soluble copolymer A-1 contains cyclohexyl acrylate (CHA), while alkali-soluble copolymer A-2 does not contain cyclohexyl acrylate (CHA).

[0101] Next, in a four-necked separatory flask equipped with a stirrer, thermometer, cooler, and nitrogen inlet tube, alkali-soluble copolymers A-1 and A-2 (hereinafter also referred to as alkali-soluble copolymer (A)) as shown in Table 1, and 25% aqueous ammonia as a basic compound for neutralization were charged in an amount equivalent to the acid value of the alkali-soluble copolymer (A) to be used. The mixture was heated to 80°C and kept warm for 3 hours to dissolve and obtain an aqueous solution. Then, while maintaining the temperature at 80°C and introducing nitrogen gas, the monomers of copolymer (B) in the amount shown in Table 2 and 0.5 parts by weight of 10% ammonium persulfate aqueous solution were added dropwise over 3 hours using a metering pump to the aqueous solution containing 40 parts by weight of alkali-soluble copolymer (A), as shown in Table 2. After the addition was completed, the mixture was kept warm at 80°C for another 2 hours to polymerize the remaining monomers. Then, the amount of dihydrazide adipic acid (ADH) shown in Table 2 was added as hydrazide compound (C), and the mixture was stirred at 60-70°C for 30 minutes to dissolve. Subsequently, an appropriate amount of water was added to the water-based ink resin dispersion so that its viscosity at 25°C was approximately 1000 mPa·s, and the mixture was cooled to obtain the water-based ink resin dispersions for Examples 1-3 and Comparative Examples 1-2 shown in Table 2 below. The non-volatile content shown in Table 2 below represents the percentage of non-volatile content relative to the water-based ink resin dispersion when 2 g of the water-based ink resin dispersion is dried in a dryer at 180°C for 1 hour.

[0102] [Table 2]

[0103] In Table 2 above, MMA represents methyl methacrylate, EHA represents 2-ethylhexyl acrylate, DAAM represents diacetone acrylamide, and ADH represents dihydrazide adipate. Also in Table 2 above, the content of each component is expressed in parts by weight.

[0104] As a result, the aqueous ink resin dispersion according to Example 1 contains a core-shell type resin composition in which an alkali-soluble copolymer (A) of a monomer mixture containing methacrylic acid (meth) and cyclohexyl acrylate (an alicyclic alkyl group-containing ethylenically unsaturated monomer) serves as the shell portion, and a copolymer (B) of a monomer mixture containing diacetone acrylamide and methyl methacrylate and 2-ethylhexyl acrylate (both ethylenically unsaturated monomers) serves as the core portion. Furthermore, the aqueous ink resin dispersion according to Example 2 contains the same types of components as in Example 1, but the amount of methyl methacrylate and 2-ethylhexyl acrylate, which are ethylenically unsaturated monomers, in the core component copolymer (B) differs from that of Example 1. The aqueous ink resin dispersion according to Example 3 contains the same types of components as in Example 1, but the core component copolymer (B) contains less diacetone acrylamide, at 2 parts by weight. Comparative Example 1 differs from Example 1 in that the alkali-soluble copolymer (A), which is the shell component, does not contain an alicyclic alkyl group-containing ethylenically unsaturated monomer. Comparative Example 2, a resin dispersion for aqueous ink, differs from Example 1 in that the core component copolymer (B) does not contain diacetone acrylamide.

[0105] In this example, an ink composition was prepared containing the aqueous ink resin dispersion according to Examples 1-3 and Comparative Example 1-2 shown in Table 2, along with fine particles. As described above, an easy-adhesion layer according to Example 1-3 and Comparative Example 1-2 was formed on one surface of an acrylic resin film, respectively. In this example, in both Example 1-3 and Comparative Example 1-2, 5% by weight of silica with an average primary particle size of 90 nm was added as fine particles, and the concentration was adjusted with deionized water to a total solid content of 13.5%. Optical properties (total light transmittance Tt, number of transparency defects), peel strength, and slipperiness were measured for the optical films having the easy-adhesion layers according to Example 1-3 and Comparative Example 1-2.

[0106] Furthermore, in this example, as Reference Example 1, an optical film was manufactured by forming an easily adhesive layer from an ink composition prepared by using a water-dispersible urethane resin emulsion (polyester-based polyurethane, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Superflex® 210, solid content 35% by weight) as a resin dispersion for aqueous ink, and adding silica with an average primary particle size of 35 nm to a non-volatile content of 5% by weight. The optical properties (total light transmittance Tt, number of transparent defects), peel strength, and slipperiness of the optical film of Reference Example 1 were also measured. The measurement results of the optical properties (total light transmittance Tt, number of transparent defects), peel strength, and slipperiness of the optical films according to Examples 1-3, Comparative Examples 1-2, and Reference Example 1 are shown below. [Table 3]

[0107] Furthermore, the transparency defects, which are an indicator of optical properties in Table 3 above, are pores or particles that may occur in the easily adhering layer when the acrylic resin film 11 is stretched, as shown in Figure 2(B), and were confirmed visually. In this example, any 10 cm 2 The number of transparent defects present in the specified region is counted and displayed. The total light transmittance Tt was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7361.

[0108] Furthermore, the peel strength of the optical film was measured by applying an ultraviolet-curable acrylic adhesive composition to the easy-adhesion layer side of the optical film having an easy-adhesion layer according to Examples 1-3, Comparative Examples 1-2, and Reference Example 1. A 60 μm thick iodine-based polarizer was then laminated via the adhesive composition, and the laminate was dried in a hot air dryer (80 °C) for 1 minute. Subsequently, the dried coating film was cured by irradiating it with ultraviolet light from a high-pressure mercury lamp, thereby obtaining a laminate in which the optical film and polarizer were bonded together. A sample piece measuring 25 mm × 250 mm was cut from the obtained laminate, adhesive processing was applied to the surface of the optical film, and it was attached to a glass plate. Then, the polarizer of the laminate was grasped, and the peel strength at 90 degrees was measured according to the floating roller method of the Japanese Adhesive Industry Standard JAI 13-1996. The unit of peel strength is expressed as (N / 25 mm).

[0109] Furthermore, in this embodiment, the slipperiness of the optical films according to Examples 1-3, Comparative Examples 1-2, and Reference Example 1 was also confirmed. The slipperiness was evaluated relatively compared to Reference Example 1 to determine if there was any decrease in slipperiness, and if there was no decrease in slipperiness, it was evaluated as having "good" slipperiness. When the slipperiness is "good", the optical film can be wound onto a roll without the interposition of a protective film, and the wound optical film can be pulled out from the roll without blocking.

[0110] As shown in Table 3 above, in Comparative Example 2, the number of transparent defects, as shown in Figure 2(B), was 30 per 10 cm. 2 The observed optical properties were inferior. Transparent defects in the easily adhering layer were not observed in the unstretched state but occurred after stretching. The cause of the transparent defects is not clear, but for example, if the resin microparticles are cross-linked at cross-linking points due to the cross-linking reaction between the keto groups derived from the diacetone acrylamide skeleton of the core and the hydrazide compound, the stress is likely to be applied uniformly during stretching. However, in Comparative Example 2, the resin microparticles are not cross-linked, so the stress during stretching tends to be uneven, and it is presumed that the areas that are difficult to stretch occur as transparent defects. In addition, in Comparative Example 1, the entire surface of the easily adhering layer turned white after stretching, and white dot-like unevenness was observed, resulting in inferior optical properties. The whitening in the easily adhering layer was not observed in the unstretched state but occurred after stretching. Although the cause of whitening is unclear, Comparative Example 1 contained butyl acrylate instead of cyclohexyl acrylate. While butyl acrylate is considered to have superior flexibility compared to cyclohexyl acrylate, which has a cyclic cyclohexyl group, whitening occurred. In easily bondable layers that undergo a stretching process, using an acrylic acid ester with an alicyclic alkyl group that has not only flexibility but also a certain degree of rigidity in the shell portion can be said to result in superior optical properties. On the other hand, Examples 1-3 showed no transparency defects or whitening, and the optical properties were good. Furthermore, while the peel strength in Comparative Examples 1-2 and Reference Example 1 was 0.64 N / 15 mm or less, the peel strength in Example 1-3 was higher at 0.72 N / 15 mm or more. In addition, the optical film according to Example 1-3 also showed good total light transmittance Tt and slipperiness. In the optical film according to Reference Example 1, separation occurred at the interface between the optical film and the UV-curable acrylic adhesive when the optical film was peeled from the polarizer 30. However, in the optical films according to Examples 1-3, the UV-curable acrylic adhesive fractured and separated when the optical film was peeled from the polarizer 30. This also indicates that the easy-adhesion layer of the optical film according to Examples 1-3 has high adhesive strength to the UV-curable acrylic adhesive.

[0111] From these findings, it was found that by incorporating a core-shell type resin composition in the easy-adhesion layer 12, in which an alkali-soluble copolymer (A) of a monomer mixture containing (meth)acrylic acid and an alicyclic alkyl group-containing ethylenically unsaturated monomer serves as the shell portion and a copolymer (B) of a monomer mixture containing diacetone acrylamide and an ethylenically unsaturated monomer serves as the core portion, an easy-adhesion composition can be obtained that has excellent optical properties, good slipperiness, and higher adhesion to the acrylic resin film 11 and polarizer 30 (adhesive layer 20) than conventional urethane-based adhesive compositions. In particular, regarding adhesion, the adhesion was higher in Examples 1-3, which contain an alicyclic alkyl group-containing ethylenically unsaturated monomer and diacetone acrylamide, compared to Comparative Example 1, which does not contain an alicyclic alkyl group-containing ethylenically unsaturated monomer, and Comparative Example 2, which does not contain diacetone acrylamide. Therefore, it is inferred that the alicyclic alkyl group-containing ethylenically unsaturated monomer and diacetone acrylamide particularly contribute to the improvement of adhesion.

[0112] As described above, in this embodiment, in an optical film 10 having an acrylic resin film 11 mainly containing a first acrylic resin and an easy-adhesion layer 12 laminated on one surface of the acrylic resin film 11, the easy-adhesion layer 12 is formed from an easy-adhesion composition containing a second acrylic resin and fine particles, and by using a core-shell type resin composition as the second acrylic resin, in which an alkali-soluble copolymer (A) of a monomer mixture containing (meth)acrylic acid and an alicyclic alkyl group-containing ethylenically unsaturated monomer is used as the shell part and a copolymer (B) of a monomer mixture containing diacetone acrylamide and an ethylenically unsaturated monomer is used as the core part, it is possible to provide an adhesive composition that has good slipperiness, excellent optical properties, and high adhesion to the acrylic resin film 11 and the polarizer 30 (adhesive layer 20).

[0113] Although preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the embodiments described above. Various modifications and improvements can be made to the above embodiments, and such modified or improved forms are also included in the technical scope of the present invention. [Explanation of symbols]

[0114] 1…Polarizing plate 10…Optical film 11…Acrylic resin film 12…Easy adhesion layer 20...Adhesive layer 30… Polarizer< / iii> < / iii> < / ii> < / iii> < / iii> < / ii> < / iii> < / iii> < / ii>

Claims

1. An optical film comprising an acrylic resin film containing a first acrylic resin as its main component, and an easy-adhesion layer laminated on one surface of the acrylic resin film, The aforementioned easy-adhesion layer is formed from an easy-adhesion composition comprising a second acrylic resin and fine particles. The second acrylic resin is a core-shell type resin composition comprising an alkali-soluble copolymer (A) of a monomer mixture containing (meth)acrylic acid and an alicyclic alkyl group-containing ethylenically unsaturated monomer as the shell portion, and a copolymer (B) of a monomer mixture containing diacetone (meth)acrylamide and an ethylenically unsaturated monomer as the core portion, for use as an optical film.

2. The aforementioned easy-adhesion layer further contains a hydrazide compound, The optical film according to claim 1, wherein the diacetone (meth)acrylamide is crosslinked by a crosslinking reaction between the keto group derived from the diacetone (meth)acrylamide skeleton of the core portion and the hydrazide compound.

3. The optical film according to claim 1, wherein the fine particles are silica with an average primary particle size of 50 to 400 nm.

4. The optical film according to claim 1, wherein the alicyclic alkyl group-containing ethylenically unsaturated monomer is one or more selected from cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and cyclooctyl (meth)acrylate.

5. The optical film according to claim 1, wherein the ethylenically unsaturated monomer is a (meth)acrylic acid ester.

6. The proportion of diacetone (meth)acrylamide-derived material in the copolymer (B) is 1 to 20% by mass relative to the total of the alkali-soluble copolymer (A) and copolymer (B). The optical film according to claim 1, wherein the mass ratio of the alkali-soluble copolymer (A) to the copolymer (B) is (A):(B) = 20:80 to 60:

40.

7. A polymer (B) is obtained by emulsion polymerization of a monomer mixture containing diacetone (meth)acrylamide and an ethylenically unsaturated monomer in the presence of an alkali-soluble copolymer (A) containing (meth)acrylic acid and an alicyclic alkyl group-containing ethylenically unsaturated monomer, and then a resin dispersion for aqueous ink is prepared by adding a hydrazide compound (C). Fine particles are added to the aforementioned aqueous ink resin dispersion to prepare an ink composition. A method for manufacturing an optical film, comprising applying the aforementioned ink composition to one side of an acrylic resin film.

Images