TWI598642B - Manufacturing method of polarizing plate - Google Patents

Description

Method for manufacturing polarizing plate

The present invention relates to a method of producing a polarizing plate having a polarizing film and a transparent resin film and an adhesive layer in this order.

The polarizing plate is a constituent member of a useful liquid crystal display device, and its demand is rapidly increasing with the spread of liquid crystal display devices. Further, as a large-sized television or the like which is applied to a liquid crystal display device, the polarizing plate maintains or improves its performance, and pursues a further improvement in durability, thinning, and low cost.

A general polarizing plate has a structure in which at least one surface of a polarizing film having a function of selectively penetrating linearly polarized light in a certain direction derived from natural light is applied, and a transparent protective film is usually bonded to both surfaces. In the protective film of the polarizing plate, a cellulose acetate-based resin film typified by cellulose triacetate has been conventionally used, and the thickness thereof is conventionally about 40 to 120 μm. In the bonding of the polarizing film of the cellulose acetate-based resin film, an adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin is often used. However, a polarizing film composed of an aqueous solution of a polyvinyl alcohol-based resin is laminated with a protective film made of a cellulose acetate-based resin, and a polarizing plate comprising a protective film made of a cellulose acetate-based resin is used in a damp heat condition. When used for a long period of time, there is a problem that the polarizing performance is low and the protective film is peeled off from the polarizing film.

Further, when the protective film is composed of a cellulose acetate-based resin, as described above, the thickness thereof must be at least about 40 μm. If it is thinner, the cellulose acetate-based resin film is cracked in the production step of the polarizing plate. The problem of the handling of the rupture. Further, since the cellulose acetate resin is formed by a solvent casting method, there is a limit in cost reduction.

Therefore, at least one of the protective films bonded to both surfaces of the polarizing film is attempted to be composed of a resin other than the cellulose acetate resin. For example, a polarizing plate having a protective film on both areas of a polarizing plate is disclosed in Japanese Laid-Open Patent Publication No. Hei 8-43812, and at least one of the protective films is composed of a thermoplastic norbornene-based resin having a retardation film function. . In JP-A-2002-174729, a surface of one side of a polarizing film which is formed by adsorbing a polyvinyl alcohol-based resin having an iodine or a dichroic dye, and an amorphous polyolefin resin are described. A polarizing plate in which a protective film composed of a resin different from an amorphous polyolefin resin such as a cellulose acetate resin or the like is bonded to the surface of the polarizing film, and the protective film is bonded to the other side of the polarizing film. . The amorphous polyolefin-based resin, which is also a cycloolefin-based resin, is also called a cycloolefin-based resin, and is excellent in heat resistance and moisture resistance, excellent in transparency, and can be extended by uniaxial or biaxial stretching. A moderate phase difference is given, and it is widely used because of appropriate viewing angle compensation or phase difference compensation of the liquid crystal cell.

Attempts have been made to apply a resin other than an amorphous polyolefin resin to a protective film. For example, JP-A-2007-334295 discloses a protective film bonded to both surfaces of a polarizing plate, and at least one of the protective films is a polarizing plate made of a polypropylene resin. Japanese Laid-Open Patent Publication No. 2007-316603 discloses a polarizing plate using a retardation film made of a polypropylene resin as a protective film. Since the polypropylene resin film can be obtained at a low price, the cost advantage of using such a polarizing plate is large. Further, since the phase difference by the elongation is high, the retardation film can be made thinner by using a polypropylene-based resin, and the polarizing film can be made thin.

On the other hand, the use of a non-aqueous adhesive is reviewed in place of the conventional polyvinyl alcohol-based resin aqueous solution used for bonding the polarizing film and the protective film. For example, JP-A-2004-257925 and JP-A-2008-257199 propose to cure an adhesive by irradiation with an active energy ray by using an adhesive mainly composed of a specific epoxy compound. Then the technology of the polarizing film and the protective film.

In order to achieve further reduction in cost and thickness of the polarizing plate, the inventors of the present invention have formed a protective film-based amorphous polyolefin resin or polypropylene resin laminated on at least one side of the polarizing film. The polarizer is reviewed. As a result, when a resin having a weak tensile modulus such as an amorphous polyolefin resin or a polypropylene resin is used, or when a material having a high tensile modulus is a film, the transparent resin film is clarified. It is very rigid, that is, it does not have "elasticity". Therefore, in the bonding step (polarizing plate step) of the surface of the polarizing film through the transparent resin film, the transparent resin film cannot withstand the tension applied to itself, and is easy to produce. Problems such as elongation and cracking.

When the transparent resin film having insufficient rigidity is supplied to the polarizing plate forming step by the protective film of the reinforcing material, the elongation, cracking, and the like of the transparent resin film in the polarizing plate forming step can be solved. However, in this method, after the polarizing plate step, when the adhesive layer for laminating the liquid crystal cell is laminated on the outer surface of the transparent resin film (the bonding surface with the protective film), the step of peeling off the protective film must be performed, resulting in production. A new problem of low sexuality. In addition, when the peeled protective film has to be discarded, the cost will increase.

In view of the above, an object of the present invention is to provide a method for producing a polarizing plate comprising a polarizing film and a transparent resin film and an adhesive layer in this order, wherein the transparent resin film does not elongate even when a transparent resin film having a relatively low rigidity is used. , rupture, etc., without increasing the number of manufacturing steps, can be manufactured efficiently and at low cost.

The present inventors have continuously studied to solve the above problems, and as a result, it has been found that a transparent resin film having an adhesive layer with a transparent resin film, an adhesive layer, and a separator film is prepared in advance, by using the separator as a transparent film. The reinforcing material of the resin film is provided to the polarizing plate step of the transparent resin film with the adhesive layer, without requiring an additional reinforcing material and a reinforcing material peeling step, and the transparent resin film does not cause elongation, cracking, etc., but may have A polarizing plate with an adhesive layer is manufactured efficiently and inexpensively.

In other words, the present invention encompasses the following.

[1] A method for producing a polarizing plate, comprising: a step (A) of forming a transparent resin film with an adhesive layer by separating a film on a transparent resin film via an adhesive layer; and attaching an adhesive a surface of the transparent resin film of the transparent resin film of the agent layer is subjected to a surface activation treatment step (B); and a surface of the transparent resin film subjected to the surface activation treatment is attached to the surface of the transparent resin film via a first adhesive Step (C).

[2] The method for producing a polarizing plate according to the above aspect, wherein the step (C) of bonding the polarizing film is included on a side opposite to a surface of the polarizing film to which the transparent resin film having the adhesive layer is attached The step of bonding the protective film through the second adhesive.

[3] The method for producing a polarizing plate according to Item 1, wherein the first adhesive is composed of an active energy ray-curable composition, and the step (C) of bonding the polarizing film includes The step of irradiating the active energy ray from the side of the separation membrane.

[4] The method for producing a polarizing plate according to the item 2, wherein the second adhesive for bonding the protective film and the polarizing film is composed of an active energy ray-curable composition, and the step of bonding the polarizing film (C) includes a step of irradiating the active energy ray from the side of the separator, and the second adhesive is cured by irradiating the active energy ray to have a thickness of 8 μm or less.

[5] The method for producing a polarizing plate according to any one of the preceding claims, wherein the surface activation treatment of the step (B) of the surface activation treatment is a corona discharge treatment.

[6] The method of producing a polarizing plate according to any one of the first aspect, wherein the transparent resin film has a Gurley method having a bending resistance of 350 mgf or less.

The method for producing a polarizing plate according to any one of the first aspect, wherein the transparent resin film is composed of a polypropylene resin.

[8] The method for producing a polarizing plate according to Item 7, wherein the polypropylene resin is substantially composed of a single polymer of propylene.

[9] The method for producing a polarizing plate according to Item 7, wherein the polypropylene resin is composed of a copolymer of propylene and ethylene containing 10% by weight or less of ethylene units.

[10] The method of producing a polarizing plate according to any one of the first aspect, wherein the in-plane retardation value R ₀ of the transparent resin film is 20 nm or less.

[11] The method for producing a polarizing plate according to any one of the preceding claims, wherein the in-plane phase difference value R ₀ of the transparent resin film is in a range of 30 to 500 nm, and a phase difference in the thickness direction The value R _th is in the range of 20 to 500 nm.

According to the present invention, even when a transparent resin film having a relatively low rigidity such as a resin film of a film or a film having a low elastic modulus is used, a polarizing film and a polarizing plate of a transparent resin film and an adhesive layer are sequentially provided. The transparent resin film does not cause elongation or cracking, and can be produced efficiently and at low cost without increasing the number of manufacturing steps. According to the present invention, it is possible to further reduce the thickness of the polarizing plate, improve productivity, and reduce cost.

In the method for producing a polarizing plate of the present invention, the transparent resin film is formed by laminating a separator film via an adhesive layer, and a step (A) of producing a transparent resin film with an adhesive layer; and an adhesive layer is attached thereto. Step (B) of applying a surface activation treatment to the surface of the transparent resin film of the transparent resin film; and a step of adhering the polarizing film to the surface of the transparent resin film subjected to the surface activation treatment via the first adhesive ( C). Hereinafter, each step of the present invention will be described in detail with reference to Fig. 1. Fig. 1 is a schematic flow chart showing a preferred embodiment of the production method of the present invention, showing the intermediate product of each step and the obtained polarizing plate in a schematic sectional view.

[Step (A) of manufacturing transparent resin film with adhesive layer]

In this step, a transparent resin film is used to laminate the separator film via the adhesive layer, and a transparent resin film 17 having the adhesive layer provided with the transparent resin film 10 and the adhesive layer 11 and the separator film 12 in this order is produced. (Refer to Figure 1 (a)). The transparent resin film 17 to which the adhesive layer is attached can be formed into an adhesive layer 11 by, for example, applying an adhesive composition (typically a solvent-containing adhesive solution) to the transparent resin film 10 and drying it. Thereafter, a method of laminating the separator film 12 is carried out thereon; by applying a pressure-sensitive adhesive composition (typically a solvent-containing adhesive solution) to the surface of the separator film 12 subjected to the release treatment and drying it, etc. After the adhesive layer 11 is formed, the separator film with the pressure-sensitive adhesive layer is formed by bonding the adhesive layer side as a bonding surface to the surface of the transparent resin film 10.

In the latter method, a double-sided separator film type adhesive sheet obtained by laminating a sheet of a separator film on the pressure-sensitive adhesive layer 11 may be used after the pressure-sensitive adhesive layer 11 is formed on the separator film 12. Such a double-sided separation film type adhesive sheet can be peeled off to the one side of the separation film and bonded to the transparent resin film 10 as necessary.

Examples of the double-sided separator film type adhesive sheet include commercially available products, and the respective product names are: "LUCIACS" sold by Nitto Denko Co., Ltd., "Noncareer" sold by Lintec Co., Ltd., and Rising Sun "Optical Substrate-Free Double-Sided Adhesive Tape MHM-F25" sold by Processing Co., Ltd., "Optical Adhesive Sheet FS800" sold by Toyo Ink Co., Ltd., and sold by Synthetic Chemical Co., Ltd. "Optical double-sided tape SK" and the like.

It is preferable that the bonding surface of the transparent resin film 10 and the adhesive layer 11 and/or the bonding surface of the adhesive layer 11 and the transparent resin film 10 are surface-activated in advance. Thereby, the adhesion of the transparent resin film 10 and the adhesive layer 11 can be improved.

The surface activation treatment method may suitably employ an apparatus and method for improving the adhesion of the transparent resin film 10 and the adhesive layer 11. Examples of the surface activation treatment include corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, and electron beam irradiation treatment. Among them, it is preferable to use corona discharge treatment from the viewpoint of simplicity and versatility of the device. The corona discharge treatment is a treatment in which a discharge is performed at a high voltage between electrodes, and a resin film disposed between the electrodes is activated. The effect of the corona discharge treatment differs depending on the type of the electrode, the electrode interval, the voltage, the humidity, and the type of the resin film used. Therefore, the treatment conditions depend on the corona discharge treatment conditions in consideration of the surface activation effect of the treated film. Sexuality and productivity, etc., and it is better to make appropriate settings. In addition, the transparent resin film 10 and the adhesive layer 11 may be subjected to a cleaning process of the bonding surface and a subsequent drying process before the surface activation treatment, or may be applied by coating. Surface treatment of the bonding surface of the agent or surface modifier, and subsequent drying treatment.

Hereinafter, the transparent resin film 10, the adhesive layer 11, and the separator film 12 will be described in more detail.

[Transparent resin film]

The transparent resin film 10 is not particularly limited as long as it is composed of a resin having excellent transparency. The transparent resin constituting the transparent resin film 10 may, for example, be a (meth)acrylic resin such as a methyl methacrylate resin [(meth)acrylic resin means a methacrylic resin or an acrylic resin], An olefin resin, a polyvinyl chloride resin, a cellulose resin, a styrene resin, an acrylonitrile/butadiene/styrene copolymer resin, an acrylonitrile/styrene copolymer resin, a polyvinyl acetate resin, Polyvinylidene chloride resin, polyamido resin, polyacetal resin, polycarbonate resin, modified polyphenylene ether resin, polyester resin (for example, polybutylene terephthalate) Diester, polyethylene terephthalate resin, etc., polyfluorene-based resin, polyether oxime resin, polyarylate resin, polyamidamine resin, polyimide resin, ring An oxygen resin or an oxetane resin. These resins may contain additives insofar as they do not impede transparency or adhesion to the polarizing film.

In the present invention, as the transparent resin film 10, a transparent resin film having a bending resistance of 350 mgf or less according to the Glory method measured in accordance with JIS L 1096 is preferably used. According to the method of the present invention, even when a transparent resin film having a relatively low rigidity is used, the transparent resin film does not cause elongation, cracking, or the like, and the polarizing plate can be efficiently produced. The transparent resin film 10 may have a flexural resistance of 250 mgf or less, and may be a film having a rigidity of less than 150 mgf. When the transparent resin film having a bending resistance of more than 350 mgf is used, the advantage of the method of the present invention is weak, and if the rigidity is too high, the handleability is impaired. Further, from the viewpoint of the rationality of providing the adhesive layer 11 on the transparent resin film 10, the flexural resistance of the transparent resin film 10 is preferably 1 mgf or more.

The transparent resin film 10 may be a protective film (hereinafter referred to as a "protective film") having substantially no phase difference function, or may be a protective film (hereinafter referred to as a "retardation film") having a phase difference function. When the transparent resin film 10 is a protective film, the in-plane retardation value R _{0 of the} transparent resin film 10 at a wavelength of 590 nm is preferably 20 nm or less, more preferably 10 nm or less, and still more preferably 5 nm or less. When the transparent resin film 10 is used as described above, when the in-plane retardation value R _{0 is} more than 20 nm, the light leakage when the liquid crystal display device displays black becomes large, and the contrast is lowered. When the function as a protective film is exhibited, if there is an excessive in-plane retardation value R ₀ , the viewing angle characteristics of the liquid crystal display device may be adversely affected.

Further, when the transparent resin film 10 is a protective film, the angle θ between the MD (machine direction) and the slow axis of the transparent resin film 10 is preferably ±5° or less and ±3° or less. Better. When the angle θ is larger than ±5°, the light leakage when the liquid crystal display device displays black becomes large, and the contrast is remarkably lowered.

Further, the refractive index in the slow axis direction of the film is n _x , the in-plane fast axis direction (the direction in which the slow axis intersects the in-plane perpendicular direction) is n _y , and the refractive index in the thickness direction is n. _z . When the thickness is set to d, the in-plane phase difference value R ₀ and the thickness direction phase difference value R _th are defined by the following formulas (I) and (II), respectively.

R ₀ =(n _x -n _y )×d (I)

R _th =[(n _x +n _y )/2-n _z ]×d (II)

Further, when the transparent resin film 10 is a protective film, the transmittance parameter calculated by the in-plane phase difference R ₀ and the angle θ between the MD and the slow axis is preferably 0.03% or less, and 0.007% or less. Good, 0.001% or less is better. When the transmittance parameter is more than 0.03%, the light leakage when the liquid crystal display device displays black becomes large, and the contrast is lowered. Here, the penetration parameter is defined by the following formula:

Penetration parameter = sin ² 2θ × sin ² (π × R ₀ /590)

On the other hand, when the transparent resin film 10 is a retardation film, the in-plane retardation value R ₀ of the transparent resin film 10 is in the range of 30 to 500 nm, and the phase difference R _th in the thickness direction is 20 to 500 nm. The range is better. In this range, it is sufficient to appropriately select the characteristics required for the liquid crystal display device to be applied. The in-plane phase difference R ₀ is preferably 100 nm or less, and the phase difference R _{th in the} thickness direction is preferably 80 nm or more, and is preferably 300 nm or less. When the transparent resin film 10 as the retardation film is bonded to the polarizing film 16, the angle between the absorption axis of the polarizing film 16 and the slow axis of the transparent resin film 10 can be appropriately selected depending on the application. For example, when used as a wave plate, the absorption axis of the polarizing film 16 and the slow axis of the transparent resin film 10 are at an angle of 5 to 85°, and when used as a viewing angle compensation film, the absorption axis of the polarizing film 16 and the transparent resin film 10 are used. The angle of the slow axis is substantially 0° or 90°.

The transparent resin film 10 may have a thickness of the above-mentioned preferred range, and the thickness of the transparent resin film 10 is preferably about 3 to 150 μm, for example, when the transparent resin film 10 is made of a polypropylene resin. It is more preferably about 100 μm.

(1) Transparent resin film composed of a polypropylene resin

In the above, the transparent resin film 10 is preferably composed of a polypropylene resin, from the viewpoints of the bending resistance of the Gourd method, the thinning of the polarizing plate, the ease of the phase difference, and the low cost. The polypropylene resin constituting the transparent resin film 10 may be a resin consisting essentially of a single polymer of propylene, or a resin composed of a copolymer of propylene and another copolymerizable comonomer. Compared with the copolymer of propylene and other copolymerizable comonomers, the crystallization degree of the individual polymer of propylene is high, so that the heat resistance of the film can be high. On the other hand, the copolymer of propylene and another copolymerizable comonomer has a low degree of crystallization, so that the transparency and the operability of the production step of the stretched film can be improved more than the propylene alone polymer resin.

Here, the "substantially propylene-based polymer" contains an ethylene unit in the range of about 0.6% by weight or less for the purpose of improving the productivity of the unstretched film, etc., in addition to the polymer having a propylene unit content of 100% by weight. Propylene/ethylene copolymers are also included.

When the polypropylene-based resin constituting the transparent resin film 10 is composed of a copolymer of propylene and another copolymerizable monomer, the polypropylene-based resin is mainly composed of propylene and one or more kinds of copolymerizable polymers. A small amount of copolymerization of the co-monomer is preferred. Specifically, the polypropylene-based resin composed of such a copolymer may have a comonomer unit contained in the resin in an amount of 20% by weight or less, preferably 10% by weight or less, and preferably 7% by weight or less. Better. The content of the comonomer unit of the copolymer is at least more than 0.6% by weight, preferably 1% by weight or more, more preferably 3% by weight or more. When the content of the comonomer unit is 1% by weight or more, workability and transparency can be remarkably improved. On the other hand, when the content of the comonomer unit is more than 20% by weight, the melting point of the polypropylene resin is lowered, and the heat resistance tends to be lowered. Further, when it is a copolymer of two or more kinds of comonomers and propylene, the total content of the units derived from all the comonomers contained in the copolymer is preferably in the above range.

The co-monomer copolymerized with propylene may be, for example, ethylene or an α-olefin having 4 to 20 carbon atoms. Specifically, the α-olefin is exemplified by the following. 1-butene, 2-methyl-1-propene (above C ₄ ); 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene (above C ₅ ); -hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl 1-pentene, 3,3-dimethyl-1-butene (above C ₆ ); 1-heptene, 2-methyl-1-hexene, 2,3-dimethyl-1- Pentene, 2-ethyl-1-pentene, 2-methyl-3-ethyl-1-butene (above C ₇ ); 1-octene, 5-methyl-1-heptene, 2- Ethyl-1-hexene, 3,3-dimethyl-1-hexene, 2-methyl-3-ethyl-1-pentene, 2,3,4-trimethyl-1-pentene , 2-propyl-1-pentene, 2,3-diethyl-1-butene (above C ₈ ); 1-decene (C ₉ ); 1-decene (C ₁₀ ); 1-ten Monoolefin (C ₁₁ ); 1-dodecene (C ₁₂ ); 1-tridecene (C ₁₃ ); 1-tetradecene (C ₁₄ ); 1-pentadecene (C ₁₅ ); 1-ten Hexene (C ₁₆ ); 1-heptadecen (C ₁₇ ); 1-octadecene (C ₁₈ ); 1-nonenylene (C ₁₉ ) and the like.

Among the above α-olefins, an α-olefin having 4 to 12 carbon atoms is preferred, and specific examples thereof include 1-butene and 2-methyl-1-propene; 1-pentene and 2-methyl. 1-butene, 3-methyl-1-butene; 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1 -pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene; 1-heptene, 2-methyl-1-hexyl Alkene, 2,3-dimethyl-1-pentene, 2-ethyl-1-pentene, 2-methyl-3-ethyl-1-butene; 1-octene, 5-methyl- 1-heptene, 2-ethyl-1-hexene, 3,3-dimethyl-1-hexene, 2-methyl-3-ethyl-1-pentene, 2,3,4-tri Methyl-1-pentene, 2-propyl-1-pentene, 2,3-diethyl-1-butene; 1-decene; 1-decene; 1-undecene; 1-ten Diene, etc. From the viewpoint of copolymerizability, 1-butene, 1-pentene, 1-hexene and 1-octene are preferred, and 1-butene and 1-hexene are more preferred.

The copolymer may be a random copolymer or a block copolymer. Preferred examples of the copolymer include a propylene/ethylene copolymer or a propylene/1-butene copolymer. In the propylene/ethylene copolymer or the propylene/1-butene copolymer, the content of the ethylene unit or the content of the 1-butene unit can be, for example, in the "Handbook of Polymer Analysis" (released by Kiyokiya Bookstore, 1995). The method described on page 616 is obtained by infrared (IR) spectrometry.

From the viewpoint of improving transparency and processability, the copolymer is preferably propylene and ethylene mainly composed of propylene or a random copolymer with the above α-olefin, more preferably random copolymerization of propylene and ethylene. Things. The content of the ethylene unit of the propylene/ethylene copolymer is preferably from 1 to 20% by weight, preferably from 1 to 10% by weight, more preferably from 3 to 7% by weight, as described above.

The polypropylene-based resin used in the present invention is preferably in the range of 0.1 to 200 g/10 minutes at a temperature of 230 ° C and a load of 21.18 N in accordance with JIS K 7210. It is preferably in the range of 50 g/10 minutes, more preferably in the range of 0.5 to 15 g/10 minutes. By using a polypropylene-based resin having an MFR within this range, a uniform polypropylene-based resin film can be obtained without causing a large load on the extruder.

The polypropylene resin can be produced by a method of polymerizing propylene alone or a method of copolymerizing propylene with another copolymerizable comonomer by using a known catalyst for polymerization. Examples of the catalyst for polymerization include the following.

(a) a Ti-Mg catalyst composed of a solid catalyst component containing magnesium, titanium, and halogen as essential components;

(b) a catalyst system in which a solid catalyst component containing magnesium, titanium, and halogen as essential components, and an organoaluminum compound, and a third component such as an electron-donating compound required;

(c) Metallocene is a catalyst or the like.

The solid catalyst component of the above-mentioned (a) and (b) is described in, for example, JP-A-61-218606, JP-A-61-287904, JP-A-7-216017, and the like. Media. Further, the organoaluminum compound of the catalyst system of the above (b) is preferable, and examples thereof include triethyl aluminum, triisobutyl aluminum, a mixture of triethyl aluminum and diethyl aluminum chloride, and tetraethyl group. A tetraethyl dialuminoxane or the like, and preferred examples of the electron-donating compound include, for example, cyclohexylethyldimethoxydecane, tert-butylpropyldimethoxydecane, and tert-butylethyldimethoxy. Decane, dicyclopentyldimethoxydecane, and the like.

In addition, as the metal-based catalyst of the above-mentioned (c), a catalyst system such as those described in Japanese Patent No. 2,587, 251, Japanese Patent No. 2,627, 669, and Japanese Patent No. 2,668,732 is exemplified.

Among them, the polymerization reaction is also easily carried out because it is easy to obtain, and it is preferable to use a metal aromatic catalyst.

The polypropylene resin can be polymerized by, for example, a solution using an inert solvent represented by a hydrocarbon compound of hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, benzene, toluene or xylene. In the bulk polymerization method in which a liquid monomer is used as a solvent, a gas phase polymerization method in which a monomer of a gas is directly polymerized is produced. The polymerization system by such methods can be carried out batchwise or continuously.

A known additive can also be blended in the polypropylene resin. Examples of the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, an antifogging agent, an anti-caking agent, and the like.

Examples of the antioxidant include a phenol antioxidant, a phosphorus antioxidant, a sulfur antioxidant, a hindered amine light stabilizer, and the like, and may be used in one molecule, for example, having a phenolic resistance. A composite antioxidant of an oxidation mechanism and a unit of a phosphorus-based antioxidant mechanism.

Examples of the ultraviolet absorber include a UV absorber such as 2-hydroxybenzophenone or hydroxyphenylbenzotriazole, and a benzoate-based ultraviolet absorber.

The antistatic agent may be any of a polymer type, an oligomer type, and a monomer type.

Examples of the lubricant include higher fatty acid amines such as erucic acid amines and oleic acid amines; higher fatty acids such as stearic acid; and salts thereof.

As the anti-caking agent, a spherical shape or a microparticle having a shape similar to this shape may be used, either inorganic or organic.

The nucleating agent may be any of an inorganic nucleating agent and an organic nucleating agent. Examples of the inorganic nucleating agent include talc, clay, and calcium carbonate. Further, examples of the organic nucleating agent include metal salts such as metal salts of aromatic carboxylic acids and metal salts of aromatic phosphoric acids; high-density polyethylene, poly-3-methylbutene-1, and polycyclic rings. Pentene, polyethylene cyclohexane, and the like. Among these, an organic nucleating agent is preferred, and the above metal salts and high density polyethylene are more preferred. The nucleating agent is preferably added in an amount of 0.01 to 3% by weight, more preferably 0.05 to 1.5% by weight, based on the polypropylene resin.

A plurality of the above additives may also be used in combination.

(2) Method for producing transparent resin film composed of polypropylene resin

The transparent resin film 10 which is a protective film made of a polypropylene resin can be obtained by forming a film made of a polypropylene resin. The film forming method of the polypropylene resin is not particularly limited, and examples thereof include a solvent casting method in which a resin dissolved in an organic solvent is spread on a flat plate by a extrusion molding method of a molten resin, and a solvent is removed to form a film. By such a film forming method, a polypropylene resin film having substantially no in-plane retardation can be obtained.

A method of producing a polypropylene resin film by extrusion molding will be described in detail. In the extrusion molding, the polypropylene resin was melted in the extruder by the rotation of the screw, and was extruded in a sheet form from the T-die. The temperature of the extruded molten flakes is about 180 to 300 °C. When the temperature of the melted sheet is less than 180 ° C at this time, the ductility is insufficient, and the obtained film thickness becomes uneven, which may cause a film having a phase difference. Further, when the temperature exceeds 300 ° C, deterioration or decomposition of the resin is likely to occur, and bubbles or carbides are generated in the molten sheet.

The extruder can be a single screw extruder or a twin screw extruder. For example, when a single-axis extruder is used, the ratio L/D of the length L to the diameter D of the screw is about 24 to 36, the space volume V ₁ of the screw groove of the resin supply portion, and the space volume V of the screw of the resin weighing portion. ₂ is a ratio of a compression ratio V ₁ / V ₂ is about 1.5 to 4, but may use the full flight type, barrier type or a type having Margolis kneading type screw such portion. From the viewpoint of suppressing the deterioration or decomposition of the polypropylene-based resin and uniformly melting the yttrium, it is preferable to use a barrier-type screw having an L/D of 28 to 36 and a compression ratio of V ₁ /V ₂ of 2.5 to 3.5.

Further, in order to suppress deterioration and decomposition of the polypropylene resin as much as possible, it is preferred that the extruder be in a nitrogen atmosphere or a vacuum. Further, in order to remove the volatile gas generated by the degradation of the polypropylene resin, an orifice of 1 mm Φ or more and 5 mm Φ or less is provided at the tip end of the extruder to increase the resin pressure at the tip end portion of the extruder. good. Increasing the resin pressure at the front end portion of the extruder by providing the orifice means increasing the back pressure of the front end portion, thereby improving the stability of the extrusion. The diameter of the orifice used is preferably 2 mm Φ or more and 4 mm Φ or less.

The T-shaped mold used for extrusion is preferably such that there is no slight drop or scratch on the surface of the flow path of the resin, and the lip portion is plated with a material having a small friction coefficient with the polypropylene resin. It is preferred to apply and sharpen the front end of the lip to a sharp edge of 0.3 mm or less. Examples of the material having a small friction coefficient include tungsten carbide (Tungsten Carbide) or fluorine-based special plating. By using such a T-shaped mold, generation of plugging holes can be suppressed, and at the same time, mold lines can be suppressed, and a resin mold excellent in appearance uniformity can be obtained. This T-shaped mold is in the shape of a manifold or a hanger, and it is preferable to satisfy the following conditions (i) or (ii), and it is more preferable to satisfy the condition (iii) or (iv).

(i) When the lip width of the T-shaped mold is less than 1500 mm: the length direction of the T-shaped mold is >180 mm;

(ii) When the lip width of the T-shaped mold is 1500 mm or more: the length direction of the T-shaped mold is >220 mm;

(iii) when the lip width of the T-shaped mold is less than 1500 mm: the length direction of the T-shaped mold is >250 mm;

(iv) When the lip width of the T-shaped mold is 1500 mm or more: the length of the T-shaped mold in the height direction is >280 mm.

By using a T-shaped mold that satisfies such conditions, the flow of the molten polypropylene-based resin inside the T-shaped mold can be rectified, and the thickness of the lip portion can be suppressed while being extruded, so that thickness precision can be obtained. A protective film made of a polypropylene resin which is more excellent in phase difference and more uniform in phase difference.

Further, from the viewpoint of suppressing the extrusion variation of the polypropylene resin, it is preferred that a gear pump is attached between the extruder and the T-die with the adapter interposed therebetween. Further, in order to remove foreign matter in the polypropylene resin, it is preferred to attach a leaf disk filter.

The desired polypropylene resin film can be crimped to a metal cooling roll (also referred to as a chill roll or a mold roll) by crimping the melted sheet extruded from the T-die. The contact rolls of the elastic body which are rotated in the direction around the metal cooling roll are cooled and solidified. In this case, the contact roller may directly be an elastomer such as rubber, or the outer cylinder of the metal sleeve may be coated on the surface of the elastic roller. When the surface of the elastomer roll is covered with a contact roll made of a metal sleeve, it is usually cooled between a metal cooling roll and a contact roll by a melted sheet of a polypropylene resin. On the other hand, when a contact roll having an elastic surface is used, the biaxially stretched film of the thermoplastic resin may be pressed between the molten sheet of the polypropylene resin and the contact roll.

When the melted sheet of the polypropylene resin is caught by the cooling roll and the contact roll and cooled and solidified as described above, it is preferable that the surface temperature of the cooling roll and the contact roll is low, and the melted sheet is rapidly cooled. For example, it is preferred to adjust the surface temperature of the two rolls to a range of from 0 ° C to 30 ° C. When the surface temperature exceeds 30 ° C, the cooling and solidification of the molten sheet becomes time consuming, and the crystal component in the polypropylene resin grows, so that the transparency of the obtained film is deteriorated. On the other hand, when the surface temperature of the roll is less than 0 ° C, the surface of the metal cooling roll is dew condensation and water droplets adhere thereto, and the appearance of the obtained film tends to be deteriorated.

The metal cooling roll used is transferred to the surface of the polypropylene resin film because of its surface state, and when the surface has irregularities, the thickness precision of the obtained polypropylene resin film may become low. Therefore, the surface of the metal cooling roll is preferably as mirror-like as possible. Specifically, the surface roughness of the metal cooling roll is expressed by a standard number of maximum heights, preferably 0.4 S or less, more preferably 0.05 S to 0.2 S.

The contact roller which forms the nip portion with the metal chill roll has a surface hardness of 65 to 80 in terms of the surface hardness of the elastic body as measured by a spring type hardness test (type A) prescribed in JIS K 6301. It is better to use 70 to 80. By using such a surface-hardness contact roll, the linear pressure applied to the molten sheet becomes easy to maintain uniform, and the molten sheet between the metal cooling roll and the contact roll does not cause stacking (resin deposition) and is easy. Film formation.

The pressure (linear pressure) at the time of pinching the melted sheet depends on the pressure at which the contact roller applies pressure to the metal cooling roll. The linear pressure is preferably 50 N/cm or more and 300 N/cm or less, and more preferably 100 N/cm or more and 250 N/cm or less. By the linear pressure being in the above range without stacking, it becomes easy to manufacture a polypropylene-based resin film while maintaining a constant linear pressure.

When a molten sheet of a polypropylene resin and a biaxially stretched film of a thermoplastic resin are sandwiched between a metal cooling roll and a contact roll, the thermoplastic resin constituting the biaxially stretched film may be a polypropylene resin. Specific examples of the solid heat-soluble ones include polyester, polyamide, polyvinyl chloride, polyvinyl alcohol, Ethylene-vinyl alcohol copolymer, and polyacrylonitrile. Among these, polyester having the smallest dimensional change due to humidity or heat is preferred. The thickness of the biaxially stretched film is usually about 5 to 50 μm, preferably 10 to 30 μm.

The distance (air gap) from the lip of the T-shaped mold to the pressing of the metal cooling roll and the contact roll is preferably 200 mm or less, and preferably 160 mm or less. The molten sheet extruded from the T-shaped mold is stretched from the lip to the roll, and orientation tends to occur easily. Further, as described above, the voids are shortened, and a film having a smaller orientation can be obtained. The lower limit of the void is determined by the diameter of the metal cooling roll to be used, the diameter of the contact roll, and the shape of the outlet end used, and is usually 50 mm or more.

The processing speed at the time of producing a polypropylene resin film is determined by the time required for the cooling of the melted sheet. When the diameter of the metal cooling roll to be used is increased, the contact distance between the molten sheet and the cooling roll becomes long, so that it can be produced at a relatively high speed. Specifically, when a 600 mm Φ metal cooling roll is used, the processing speed is at most about 5 to 20 m/min.

The molten sheet sandwiched between the metal cooling roll and the contact roll is cooled and solidified by contact with the roll. Further, after the end portion is cut as required, the film is taken up by a winder to form a roll-shaped polypropylene resin film. As described above, a protective mold composed of a polypropylene resin film can be produced.

In addition, the transparent resin film 10 which is a retardation film which consists of a polypropylene resin film can be made into a raw material film, and can be uniaxial after the film formation of the polypropylene resin in the same thing as the manufacturing method of the above-mentioned protective film. Extending or biaxial stretching is obtained by visualizing the phase difference. In particular, the retardation film used in the present invention preferably exhibits birefringence in the biaxial direction by biaxial stretching. In this case, in the longitudinal direction and the lateral direction, the direction in which the slow axis appears (the direction in which the stretching ratio is large is the direction of the slow axis) is about 1.1 to 10 times, which is the direction of the fast axis intersecting perpendicularly (the stretching ratio) The small direction is about 1.1 to 7 times the direction of the fast axis, so the appropriate phase difference can be appropriately selected. It is also possible to visualize the slow axis in the transverse direction of the film or to visualize the slow axis in the longitudinal direction.

The transparent resin film 10 (protective film or retardation film) composed of a polypropylene resin preferably has a haze value of 0.5% or less, preferably 0.3% or less, and the haze value here is preferably (Diffraction transmittance / total light transmittance) × 100 (%) The value defined by JIS K 7105. When the transparent resin film 10 is a protective film, as a method for suppressing the haze value to 0.5% or less, (a) a random copolymer of propylene and another copolymerizable comonomer may be used. a method of adding a polypropylene resin; (b) a method of adding a nucleating agent to a polypropylene resin; (c) improving a cooling efficiency of a metal cooling roll (casting roll) and a contact roll during extrusion molding, and a polypropylene system A method of forming a resin film; (d) a method of thinning a film thickness of a molten sheet; and combining two or more of these.

As the random copolymer of the above method (a), there may be mentioned, for example, a propylene/ethylene random copolymer, a propylene/1-butene random copolymer, a propylene/1-hexene random copolymer, and propylene. / ethylene / 1-octene random copolymer, propylene / ethylene / 1-butene random copolymer, etc., especially in the copolymer with ethylene is preferred. The content of the comonomer unit of the random copolymer is preferably from 1 to 20% by weight, preferably from 1 to 10% by weight, more preferably from 3 to 7% by weight, as described above. When two or more kinds of comonomers and propylene are copolymerized, the total content of the units derived from all the comonomers contained in the copolymer is preferably in the above range. By adjusting the content of the comonomer unit to the above range, a polypropylene-based resin film excellent in transparency can be obtained. When the content of the comonomer unit exceeds 20% by weight, the melting point of the polypropylene resin decreases, and the heat resistance tends to decrease.

The nucleating agent of the above method (b) may, for example, be as described above, and the preferred addition amount thereof is as described above. The method of adding the nucleating agent may be uniformly dispersed, and is not particularly limited. For example, in the polymerization step of producing a polypropylene resin, the polymerization mixture may be added to the polymerization reaction during the polymerization reaction or immediately after the completion of the polymerization reaction. Nuclear agent. The nucleating agent may be added as a solution after being dissolved in a solvent, or may be pulverized into a powder which is easily dispersed, and then added as a dispersing agent, or may be added in a molten state after heating.

In the above method (c), when the melted sheet of the polypropylene resin is sandwiched between the cooling roll and the contact roll to be cooled and solidified, the surface temperature of the cooling roll and the contact roll is lowered to rapidly cool the melted sheet. The surface temperature of the two rolls is as described above, and is preferably 0 ° C or more and 30 ° C or less.

The method (d) is a method of reducing the film thickness of the melt-formed sheet to be extruded, whereby the effect of reducing the haze value is obtained by thinning, and the cooling efficiency of the cooling roll and the contact roll is improved. Reduce the effect of the haze value. The amount of extrusion of the melted sheet can be arbitrarily selected.

Further, when the transparent resin film 10 is a retardation film, as a method of suppressing the haze value to 0.5% or less, the raw material film (unstretched film) is applied in addition to the methods (a) to (d) above or In addition to the methods of combining such methods, (e) a thin raw material film or a method of increasing the thickness of the retardation film by increasing the stretching ratio, (f) extending the ambient temperature, the stretching speed, and the stretching ratio The method of optimizing the extension conditions, etc.

[Adhesive layer]

The adhesive layer 11 laminated on one side of the transparent resin film 10 is typically used for bonding a polarizing plate to a liquid crystal cell. Examples of the adhesive for forming the adhesive layer 11 include an acrylic polymer, a cerium oxide polymer, a polyester, a polyurethane, a polyether, and the like as a base polymer. Among them, an acrylic adhesive having an acrylic polymer as a base polymer is excellent in optical transparency, maintains appropriate wettability or cohesive force, and is excellent in weather resistance and heat resistance, even in heating or humidifying conditions. The separation problem such as embossing or peeling is less likely to occur, and thus it is suitable for use.

The acrylic base polymer constituting the acrylic adhesive is preferably a methyl group, an ethyl group, a butyl group, or an alkyl acrylate having an alkyl group having a carbon number of 20 or less, such as 2-ethylhexyl group. An acrylic copolymer with a (meth)acrylic monomer containing a functional group such as (meth)acrylic acid or 2-hydroxyethyl (meth)acrylate. When the adhesive layer containing such an acrylic copolymer is peeled off if it has to be peeled off after bonding to a liquid crystal cell, it is easy to peel off without generating residual glue on a glass substrate. The acrylic copolymer used for the adhesive preferably has a glass transition temperature of 25 ° C or lower and more preferably 0 ° C or less. Further, the acrylic copolymer usually has a weight average molecular weight of 100,000 or more.

As the adhesive forming the adhesive layer, a diffusion adhesive in which a light diffusing agent is dispersed may be used. The light diffusing agent imparts light diffusibility to the adhesive layer. The light diffusing agent may be fine particles having a refractive index different from that of the base polymer constituting the adhesive layer, and fine particles composed of inorganic compounds or fine organic compounds (polymers) may be used. In the acrylic base polymer, the refractive index of the base polymer constituting the adhesive layer is usually about 1.4, and the light diffusing agent may be appropriately selected from the refractive index of about 1 to 2. The difference in refractive index between the base polymer constituting the adhesive layer and the light diffusing agent is usually 0.01 or more, and from the viewpoint of maintaining the brightness or visibility of the liquid crystal display device, it is preferably 0.01 or more and 0.5 or less. The fine particles used as the light diffusing agent are preferably spherical or nearly monodisperse. For example, fine particles having an average particle diameter of about 2 to 6 μm can be suitably used.

Examples of the fine particles composed of the inorganic compound include alumina (refractive index: 1.76), cerium oxide (refractive index: 1.45), and the like. Further, examples of the fine particles composed of the organic compound (polymer) include melamine resin beads (refractive index of 1.57), polymethyl methacrylate beads (refractive index of 1.49), and methyl methacrylate/styrene. Polymer resin beads (refractive index 1.50 to 1.59), polycarbonate beads (refractive index 1.55), polyethylene beads (refractive index 1.53), polystyrene beads (refractive index 1.6), polyvinyl chloride beads (refractive index 1.46) , silicone resin beads (refractive index 1.46) and the like.

The blending amount of the light diffusing agent can be appropriately determined in consideration of the haze value required for the dispersed adhesive layer, or the brightness of the liquid crystal display device to be applied, and the like, and usually constitutes an adhesive layer with respect to 100 parts by weight. The base polymer is about 3 to 30 parts by weight.

The haze value of the adhesive layer in which the light diffusing agent is dispersed is used to ensure the brightness of the liquid crystal display device to which the polarizing plate having the adhesive layer is applied, and to prevent the occurrence of burrs or hysteresis of the displayed image. It is preferably in the range of 20 to 80%. The haze value here is a value defined by (diffusion transmittance / total light transmittance) × 100 (%), and is measured in accordance with JIS K 7105.

Each component (base polymer, light diffusing agent, crosslinking agent, etc.) constituting a transparent adhesive or a diffusion adhesive is dissolved in a suitable solvent such as ethyl acetate to form an adhesive composition. However, a component which is insoluble in a solvent such as a light diffusing agent is in a dispersed state. This adhesive composition is applied onto the transparent resin film 10 or the separator film 12 to form an adhesive layer after drying.

In order to remove static electricity from the polarizing plate, the adhesive layer 11 preferably has antistatic properties. In the polarizing plate manufactured by the method of the present invention, when the separator film 12 laminated on the pressure-sensitive adhesive layer 11 is peeled off to adhere to the liquid crystal cell or the like, although the static electricity is applied, the adhesive layer 11 has antistatic properties. The static electricity is quickly removed to suppress the display circuit of the liquid crystal cell from being damaged, disturbing the orientation of the liquid crystal molecules, and the like.

The method of providing the antistatic property of the adhesive layer 11 is, for example, a method of containing metal fine particles, metal oxide fine particles, or fine particles coated with a metal or the like in the adhesive composition; A method of ionic conductive composition composed of organopolysiloxane; a method of formulating an organic salt-based antistatic agent, and the like. The holding time of the antistatic property required is at least about 6 months from the viewpoint of general polarizing plate production, distribution, and storage time.

The adhesive layer 11 is irradiated with an active energy ray in order to cure the first adhesive 14 and the second adhesive 15 which will be described later. Therefore, it is preferred that the spectral region of the active energy line has a high transmittance. Further, it is preferred that the characteristics of the adhesive are not changed by irradiating the active energy ray.

The adhesive layer 11 can be aged for about 3 to 20 days under an environment of, for example, a temperature of 23 ° C and a relative humidity of 65%, and after the reaction of the crosslinking agent is sufficiently performed, it can be bonded to the liquid crystal cell.

The thickness of the adhesive layer 11 can be appropriately determined depending on the adhesion force or the like, and is usually about 1 to 40 μm. In order to obtain a thin polarizing plate having properties such as non-destructive workability or durability, the thickness of the adhesive layer 11 is preferably from about 3 to 25 μm. Further, when the adhesive layer in which the light diffusing agent is dispersed is used, the thickness of the adhesive layer 11 is such a range that the brightness of the liquid crystal display device can be maintained from the front or from the oblique angle, and the display image is less likely to be generated. Raw edges or blurry.

[separator film]

The separator 12 can generally be used for forming a peelable layer for a transparent substrate film and imparting releasability to the self-adhesive layer 11. The transparent substrate film may, for example, be polyethylene terephthalate or polyethylene naphthalate; an extruded film of a thermoplastic resin such as polyethylene or polypropylene; a coextruded film in combination; A film that is uniaxially or biaxially stretched, and the like.

The flexural resistance of the septum 12 is preferably 20 mgf or more, more preferably 70 mgf or more. If the bending resistance of the Gourd method is less than 20 mgf, the rigidity of the separation film 12 is too small, and it is not sufficient as a reinforcing material for the transparent resin film 10.

[Surfacting step (B)]

In this step, the surface of the transparent resin film (the surface on the opposite side of the adhesive layer 11 of the transparent resin film 10 and the bonding surface with the polarizing film 16) of the transparent resin film 17 to which the adhesive layer is attached is applied. Activation treatment (refer to Fig. 1 (b)). By applying the surface activation treatment, the surface is easily adhered, and the adhesion of the transparent resin film 17 with the adhesive layer and the polarizing film 16 can be improved.

The surface activation treatment method may suitably employ an apparatus and method for improving the adhesion of the transparent resin film 17 with the adhesive layer and the polarizing film 16. Examples of the surface activation treatment include corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, and electron beam irradiation treatment. Among them, from the viewpoint of simplicity and versatility of the device, it is preferred to use a corona discharge treatment. The conditions of the corona discharge treatment are preferably set as appropriate in consideration of the corona discharge treatment condition dependency and productivity of the surface activation effect of the treated film. In addition, the transparent resin film 17 and the polarizing film 16 with the adhesive layer may be subjected to a cleaning process of the bonding surface and subsequent drying treatment before the surface activation treatment, or may be coated by coating. It is easy to follow the surface treatment of the bonding surface of the treating agent or the surface modifying agent and its subsequent drying treatment.

[Polarizing film bonding step (C)]

In this step, the surface of the transparent resin film subjected to the surface activation treatment of the adhesive resin layer-attached transparent resin film 17 obtained in the above step (B) is bonded to the polarizing film 16 via the first adhesive 15, A polarizing plate is obtained. Further, as shown in FIG. 1(c), this step may include a surface on the opposite side of the surface to which the transparent resin film 17 of the polarizing film 16 to which the adhesive layer is attached, via the second adhesive 14 The step of bonding the protective film 13 is carried out. At this time, the polarizing plate 1 having the protective film 13 in the single-layer layer of the polarizing film 16 and the transparent resin film 17 having the adhesive layer on the other surface layer can be obtained. The protective film 13 is bonded to the polarizing film 16 via the second adhesive 14 before or after the surface of the surface-activated transparent resin film 17 is adhered to the polarizing film 16 via the first adhesive 15 or You can combine the stickers on both sides or at the same time. Further, in the following description, the adhesive layer formed of the first adhesive 15 is referred to as "first adhesive layer 15", and the adhesive layer formed of the second adhesive 14 is referred to as "second adhesive layer 14". "."

The bonding surface of the protective film 13 and the polarizing film 16 and/or the bonding surface of the polarizing film 16 and the protective film 13 may be subjected to a surface activation treatment in advance. Thereby, the adhesion of the protective film 13 and the polarizing film 16 can be improved.

Examples of the surface activation treatment include corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, and electron beam irradiation treatment. Among them, from the viewpoint of simplicity and versatility of the device, it is preferred to use a corona discharge treatment. In addition, the protective film 13 and the polarizing film 16 may be subjected to a cleaning treatment of the bonding surface and a subsequent drying treatment before the surface activation treatment, or may be performed by applying an easy-to-treat treatment agent or surface modification. Surface treatment of the bonding surface of the agent and the like and subsequent drying treatment thereof.

The first adhesive layer 15 may be formed on the transparent resin film 10 of the transparent resin film 17 to which the adhesive layer is attached, or may be formed on the polarizing film 16, but is usually formed on the transparent resin film 10. Further, the second adhesive layer 14 may be formed on the protective film 13, or may be formed on the polarizing film 16, and is usually formed on the protective film 13.

The method of forming the subsequent agent layers 14 and 15 is not particularly limited, and a device and a method capable of uniformly applying a necessary amount of the adhesive agent may be employed. Various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be employed.

The method of bonding the protective film 13 to the transparent resin film 17 with the adhesive layer on the polarizing film 16 via the adhesive layers 14 and 15 is not particularly limited, and it is considered that the uniformity and productivity are considered. Choose as appropriate. The transparent resin film 17 with the adhesive layer formed thereon and the second adhesive layer 14 are formed by forming the first adhesive layer 15 supplied from both sides thereof as the polarizing film 16 is sandwiched, and the protective film 13 is formed, respectively. A first bonding roller that is in contact with the outer side of the transparent resin film 17 to which the adhesive layer is attached, and a second bonding roller that is in contact with the outer side of the protective film 13 are used for bonding.

Hereinafter, the polarizing film 16, the adhesive layers 14, 15 and the protective film 13 will be described in further detail.

[Polarizing film]

The polarizing film 16 used in the present invention is not particularly limited as long as it has a function of selectively penetrating linearly polarized light from a certain direction of natural light, and may be exemplified by adsorption of iodine on a polyvinyl alcohol film. a polarizing film; a dye-based polarizing film that adsorbs a dichroic dye on a polyvinyl alcohol film; and a coated polarized film that is coated, oriented, and immobilized in a lyotropic liquid crystal state. Membrane and the like. These iodine-based polarizing films, dye-based polarizing films, and coating-type polarizing films are called absorption by having a function of selectively penetrating linearly polarized light from a certain direction of natural light and absorbing linear polarization in other directions. Type polarizing film. In addition, in addition to the absorbing polarizing film, the polarizing film 16 also has a function of selectively penetrating linearly polarized light from a certain direction of natural light to reflect or scatter linear light in other directions, and is called a scattering type polarized light. Membrane. Among these polarizing films, an absorbing polarizing film having excellent visibility is preferably used, and an iodine-based polarizing film or a dye-based polarizing film is preferably used, and an iodine-based polarizing film excellent in polarization degree and transmittance is particularly used. For the best.

The iodine-based polarizing film or the dye-based polarizing film is usually a step of uniaxially stretching a polyvinyl alcohol-based resin film; and the polyvinyl alcohol-based resin film is a dichroic dye (iodine or a dichroic organic dye). a step of dyeing to adsorb a dichroic dye; a step of treating a polyvinyl alcohol-based resin film having a dichroic dye adsorbed thereon with a boric acid aqueous solution; and a water washing step after treating with a boric acid aqueous solution.

The polyvinyl alcohol-based resin can be produced by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate-based resin may be a copolymer of vinyl acetate and other monomers copolymerizable therewith, in addition to the polyvinyl acetate of the individual polymer of vinyl acetate. Examples of the monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, an aldehyde-modified polyethylene formaldehyde or a polyvinyl acetal may be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually from about 1,000 to 10,000, preferably from about 1,500 to 5,000.

The film formed of such a polyvinyl alcohol-based resin can be used as a raw material film of a polarizing film. The method for forming a film of a polyvinyl alcohol-based resin is not particularly limited, and a film can be formed by a known method. The film thickness of the polyvinyl alcohol-based resin raw material film is, for example, about 10 to 150 μm, preferably about 10 to 100 μm.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be carried out before dyeing with a dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxially stretching after dyeing, the uniaxial stretching can be carried out before the boric acid treatment or in the boric acid treatment. Of course, uniaxial stretching can also be performed at the plural stages shown here. The uniaxial extension system may be a method of performing uniaxial stretching between rolls having different rotational speeds, or a method of extending a single shaft by using a heat roller. Further, the uniaxial stretching may be a dry stretching in which air is stretched, or may be a wet stretching in which the polyvinyl alcohol resin film is swollen and stretched using a solvent such as water. The stretching ratio is usually about 3 to 8 times.

The polyvinyl alcohol-based resin film is dyed with a dichroic dye, and can be, for example, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing a dichroic dye. As the dichroic dye, specifically, iodine or a dichroic organic dye can be used. Further, the polyvinyl alcohol-based resin film is preferably a treatment which is immersed in water and swelled before the dyeing treatment.

When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing iodine and potassium iodide is usually used for dyeing. The iodine content of the aqueous solution is usually about 0.01 to 1 part by weight with respect to 100 parts by weight of water; and the content of potassium iodide is usually about 0.5 to 20 parts by weight with respect to 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 °C. Further, the immersion time (dyeing time) of the aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing a water-soluble dichroic organic dye to perform dyeing is usually employed. The content of the dichroic organic dye of the aqueous solution is usually from about 1 × 10 ^-4 to 10 parts by weight, preferably from 1 × 10 ^-3 to 1 part by weight, per 100 parts by weight of water. The aqueous dye solution may also contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the aqueous solution of the dichroic organic dye used for dyeing is usually about 20 to 80 °C. Further, the soaking time (dyeing time) of the aqueous solution is usually about 10 to 1,800 seconds.

The boric acid treatment after dyeing with a dichroic dye can be carried out by immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid. The boric acid content of the aqueous solution containing boric acid is usually about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, the aqueous solution containing boric acid preferably contains potassium iodide. The potassium iodide content of the aqueous solution containing boric acid is usually about 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. The time of immersion in the aqueous solution containing boric acid is usually about 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is usually 50 ° C or more, preferably 50 to 85 ° C, and more preferably 60 to 80 ° C.

The polyvinyl alcohol-based resin film treated with boric acid is usually washed with water. The water washing treatment can be carried out, for example, by immersing a boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of the water to be washed is usually about 5 to 40 °C. Further, the immersion time is usually about 1 to 120 seconds.

After washing with water, drying treatment is carried out to obtain a polarizing film. The drying treatment can be carried out using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually about 30 to 100 ° C, preferably 50 to 80 ° C. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. By drying, the water content can be reduced to a practical level. The water content is usually from about 5 to 20% by weight, preferably from 8 to 15% by weight. When the water content is less than 5% by weight, the polarizing film loses flexibility and may be damaged or broken after drying. Further, when the water content exceeds 20% by weight, the thermal stability tends to be insufficient.

As described above, it is possible to produce a polarizing film in which a polyvinyl alcohol-based resin film is adsorbed with a dichroic dye and oriented. The thickness of the obtained polarizing film can be, for example, about 2 to 40 μm.

In the present invention, it is preferred that the polarizing film 16 is continuously produced, and the obtained polarizing film 16 is directly supplied to the above-described polarizing film bonding step (C). Thereby, the polarizing plate can be continuously produced.

[adhesive layer]

The first and second adhesives 15 and 14 are not particularly limited as long as the polarizing film 16 and the transparent resin film 17 with the adhesive layer and the polarizing film 16 and the protective film 13 are sufficiently strong to be used. A curable adhesive composition which is cured by irradiation with an active energy ray, heating, drying, or the like is preferably used. The curable adhesive composition may, for example, be a cationically polymerizable compound such as a glycidyl ether epoxy compound, an alicyclic epoxy compound or a propylene oxide compound, or a cation formed by a photocationic polymerization initiator. A polymerizable active energy ray-curable adhesive composition; in a radically polymerizable compound such as an acrylic compound, a radical polymerizable active energy ray-curable adhesive composed of a photoradical polymerization initiator a thermosetting adhesive composition formed by dissolving a thermal polymerization initiator, that is, a thermal cation generator or a thermal radical generator, in the cationically polymerizable or radically polymerizable compound as described above; In the water-soluble or hydrophilic cross-linking epoxy compound or the amine ester compound, an aqueous solution or an aqueous dispersion of a water-soluble resin having a reactive group such as a polyvinyl alcohol-based resin is prepared as needed. Composition, etc. The adhesive composition forming the first adhesive layer 15 and the adhesive composition forming the second adhesive layer 14 may be the same or different.

Among them, a cationically polymerizable active energy ray-curable adhesive composition comprising an epoxy compound and a photocationic polymerization initiator is particularly preferred. Further, the adhesive composition is preferably a user which can be used without a solvent. In other words, the photo-cation-curable epoxy compound is selected to have a moderate fluidity when no solvent is present, and can impart an appropriate hardening strength and an active energy ray hardening property by blending a suitable cationic polymerization initiator. In the subsequent composition, the drying apparatus of the hardening step can be omitted, and the polypropylene-based resin film which is hardened by ordinary active energy rays and which is hard to be cured by heat can be adhered to the polarizing film 16 with a good adhesion. In addition, irradiation with a suitable active energy ray can promote the rate of hardening and increase the production speed.

Examples of the epoxy compound which can be used for such a cationically polymerizable active energy ray-curable adhesive composition include, for example, an epoxy compound having a hydroxyl group or a glycidyl ether compound of a chain compound; a compound having an amine group; Epoxypropylamine; an epoxide of a chain compound having a CC double bond; bonded to a saturated carbocyclic ring directly or via an alkyl group with a epoxypropyloxy group or an epoxy group, or An alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated carbocyclic ring. These epoxy compounds may be used singly or in combination of plural kinds. Among them, the alicyclic epoxy compound is suitable for use because it has excellent cationic polymerizability.

The epoxy propyl etherate of the aromatic compound or the chain compound having a hydroxyl group can be condensed by epichlorohydrin at a hydroxyl group of the aromatic compound or the chain compound under basic conditions, for example. The method is obtained. Examples thereof include a bisphenol type epoxy resin, a polyaromatic ring type epoxy resin, and an alkylene glycol type epoxy resin.

The bisphenol type epoxy resin may, for example, be a epoxidized ether ether of bisphenol A and an oligomer thereof, a epoxidized propyl ether of bisphenol F and an oligomer thereof, 3, 3', 5, 5' - a glycidyl etherate of tetramethyl-4,4'-bisphenol, an oligomer thereof, and the like.

The polyaromatic ring type epoxy resin may, for example, be a phenolic novolac resin epoxidized propyl etherate, a cresol novolac resin, a propylene propyl ether compound, or an aralkyl phenol resin. The epoxy propyl etherate, the epoxy propyl ether compound of the aralkyl naphthol resin, the epoxy propyl ether compound of the dicyclopentadiene phenol resin, and the like. The phenolic epoxypropyl etherate and its oligomers are also polyaromatic ring-type epoxy resins.

Examples of the alkylene glycol type epoxy resin include a epoxypropyl etherate of ethylene glycol, a glycidyl etherate of diethylene glycol, and a glycidyl etherate of 1,4-butanediol. A propylene oxide etherate of 1,6-hexanediol or the like.

The epoxypropylamine of the compound having an amine group can be obtained by subjecting epichlorohydrin to condensation condensation under basic conditions on the amine group of the compound. The compound having an amine group may also have a hydroxyl group. Examples of the epoxypropylamine of the compound having an amine group include a glycidylamine of 1,3-phenylenediamine and an oligomer thereof, and a glycidylamine of 1,4-phenylenediamine; Its oligomer, epoxypropyl amination of 3-aminophenol and epoxy propyl etherate and oligomers thereof, epoxypropyl amination of 4-aminophenol and epoxy propyl etherate and their oligomers Polymer, etc.

An epoxide of a chain compound having a C-C double bond can be obtained by a method of epoxidizing a C-C double bond of the chain compound using a peroxide under basic conditions. Examples of the chain compound having a C-C double bond include butadiene, polybutadiene, isoprene, pentadiene, and hexadiene. Further, a terpene having a double bond can also be used as an epoxidation raw material, and an acyclic monoterpene is exemplified as a linalool or the like. Examples of the peroxide which can be used for the epoxidation include hydrogen peroxide, peracetic acid, tert-butyl hydroperoxide, and the like.

An alicyclic epoxy compound having a glycidyloxy group or an epoxyethyl group bonded to a saturated carbocyclic ring directly or via an alkyl group, which may be a representative example of the previously disclosed bisphenols. a glycidyl etherate of a hydrogenated cyclic polyhydroxy compound obtained by hydrogenation of an aromatic ring of a compound, a glycidyl etherate of a saturated cyclic compound having a hydroxyl group, a saturated cyclic compound having a vinyl group Epoxide and the like.

The epoxy compound as described above can be easily obtained. For example, in the case of a commercial product, "Epicoat" sold by Japan Epoxy Resins Co., Ltd., "Epiclon" sold by DIC Co., Ltd., and "Epotote" sold by Dongdu Chemical Co., Ltd. "Adeka Resin" sold by ADEKA Co., Ltd., "Denacol" sold by Nagase ChemteX Co., Ltd., "Dow epoxy" sold by Dow Chemical Co., Ltd., and Nissan Chemical Industry Co., Ltd. "Tepic" sold, etc.

On the other hand, an alicyclic epoxy compound having an epoxy group directly bonded to a saturated carbocyclic ring can be subjected to basic conditions by, for example, a CC double bond of a non-aromatic cyclic compound having a CC double bond in the ring. It is obtained by a method of peroxide epoxidation. The non-aromatic cyclic compound having a CC double bond in the ring may, for example, be a compound having a cyclopentene ring, a compound having a cyclohexane ring, or at least two carbon atoms in a cyclopentene ring or a cyclohexane ring. A polycyclic compound or the like which forms an additional ring. Such a non-aromatic cyclic compound having a C-C double bond in the ring may have other C-C double bonds outside the ring. Examples of the non-aromatic cyclic compound having a CC double bond in the ring include cyclohexene, 4-ethylenecyclohexene, limonene of monocyclic monoterpene, and alpine-pinene (pinene). .

An alicyclic epoxy compound having an epoxy group directly bonded to a saturated carbocyclic ring, or an alicyclic structure having an epoxy group directly bonded to the ring as described above, formed in the molecule via a suitable linking group At least 2 compounds. The linking group referred to herein includes, for example, a group having an ester bond, an ether bond, an alkyl group bond, and the like.

The alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated carbocyclic ring can be exemplified as follows.

3,4-Epoxycyclohexanemethyl 3,4-epoxycyclohexylmethyl, 1,2-epoxy-4-vinylcyclohexane, 1,2-epoxy-4- Epoxyethylcyclohexane, 1,2-epoxy-1-methyl-4-(1-methylepoxyethyl)cyclohexane, 3,4-epoxy (meth)acrylate Addition of cyclohexylmethyl ester, 2,2-bis(hydroxymethyl)-1-butanol to 4-epoxyethyl-1,2-epoxycyclohexane, ethylene double (3, 4-epoxycyclohexanecarboxylate), oxydiethylene bis(3,4-epoxycyclohexanecarboxylate), 1,4-cyclohexanedimethylbis (3,4- Epoxycyclohexanecarboxylate), 3-(3,4-epoxycyclohexylmethoxycarbonyl)propyl 3,4-epoxycyclohexanecarboxylate, and the like.

As described above, an alicyclic epoxy compound in which a saturated carbon ring is directly bonded to an epoxy group can be easily obtained as a commercially available product. For example, commercially available products include "CELLOXIDE" and "CYCLOMER" sold by Daicel Chemical Industry Co., Ltd., and "Cyracure" sold by Dow Chemical Co., Ltd., respectively.

The active energy ray-curable adhesive composition containing an epoxy compound may contain an active energy ray-curable compound other than the epoxy compound. Examples of the active energy ray-curable compound other than the epoxy compound include a propylene oxide compound and an acrylic compound. Among them, since the curing rate can be increased by cationic polymerization, it is preferred to use a propylene oxide compound in combination.

The propylene oxide compound is a compound having a four-membered cyclic ether in the molecule, and examples thereof include the following compounds.

1,4-bis[(3-ethylepoxypropan-3-yl)methoxymethyl]benzene, 3-ethyl-3-(2-ethylhexyloxymethyl) propylene oxide, double (3-ethyl-epoxypropylmethyl)ether, 3-ethyl-3-(phenoxymethyl) propylene oxide, 3-ethyl-3-(cyclohexyloxymethyl)epoxy Propane, phenol novolac oxetane, 1,3-bis[(3-ethyl propylene oxide-3-yl)methoxy]benzene, and the like.

A propylene oxide compound can also be easily obtained as a commercial product. For example, "ARON OXETANE" sold by Toagosei Co., Ltd., and "ETERNACOLL" sold by Ube Industries Co., Ltd., etc., are available as the commercial products.

The curable compound containing an epoxy compound or a propylene oxide compound is preferably a solvent-free adhesive composition, and it is preferably used without dilution with an organic solvent. Further, the photocationic polymerization initiator or the small component containing the sensitizer, or a compound dissolved in the organic solvent, which constitutes the active energy ray-curable adhesive composition described later, is a compound which uses the removed/dried organic solvent. A separate powder or liquid is preferred.

The photocationic polymerization initiator may be a cationic species which is irradiated with an active energy ray, for example, ultraviolet rays, and which is required to have a bonding strength and a curing rate required for the active energy ray-curable adhesive composition to be formulated. The photocationic polymerization initiator may, for example, be an aromatic diazonium salt; for example, an anthracene salt of an aromatic onium salt or an aromatic onium salt; an iron-propadiene complex or the like. These photocationic polymerization initiators may be used singly or in combination of plural kinds.

The aromatic diazonium salt may, for example, be the following compounds.

Diazobenzene hexafluoroantimonate, diazobenzene hexafluorophosphate, diazobenzene hexafluoroborate, and the like.

Examples of the aromatic onium salt include the following compounds.

Diphenyl hydrazine (pentafluorophenyl) borate, diphenyl hydrazine hexafluorophosphate, diphenyl hydrazine hexafluoroantimonate, bis(4-mercaptophenyl) iodine hexafluorophosphate, and the like.

Examples of the aromatic onium salt include the following compounds.

Triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium (pentafluorophenyl) borate, diphenyl (4-phenylthiophenyl)phosphonium hexafluoroantimonate, 4 , 4'-bis(diphenylfluorene)diphenyl sulfide dihexafluorophosphate, 4,4'-bis[bis(β-hydroxyethoxyphenyl)indolyl]diphenyl sulfide dihexafluoroantimony Acid salt, 4,4'-bis[bis(β-hydroxyethoxyphenyl)indenyl]diphenyl sulfide dihexafluorophosphate, 7-[bis(p-tolylyl) Thiophenethone hexafluoroantimonate, 7-[bis(p-tolylmethylhydrazino)-2-isopropylthioxanthone oxime (pentafluorophenyl) Borate, 4-phenylcarbonyl-4'-diphenyldecyldiphenyl sulfide hexafluorophosphate 4-(p-t-butylphenylcarbonyl)-4'-diphenyldecyldiphenyl Thioether hexafluoroantimonate 4-(p-t-butylphenylcarbonyl)-4'-bis(p-tolylmethyl) fluorenyl-diphenyl sulfide quinone (pentafluorophenyl) borate .

The iron-propadiene complex compound may, for example, be the following compounds.

Xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate

Xylene-cyclopentadienyl iron (II) tris(trifluoromethylsulfonyl)methanide or the like.

Among the photocationic polymerization initiators, the aromatic onium salt has ultraviolet absorption characteristics in a wavelength region of 300 nm or more, and is excellent in curability, and can supply an adhesive layer having good mechanical strength and adhesion strength. Suitable for use.

Commercially available products can also be easily obtained by photocationic polymerization initiators. For example, in the case of a commercial product, the product name is sold by "KAYARAD" sold by Nippon Kayaku Co., Ltd., "Cyracure" sold by Union Carbide Co., Ltd., and San-apro Co., Ltd. Photoacid generator "CPI", light acid generator "TAZ", "BBI" and "DTS" sold by Midori Chemical Co., Ltd.; "ADEKA OPTOMER" sold by ADEKA Co., Ltd.; RHODIA company "RHODOSIL" sold, etc.

The compounding amount of the photocationic polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 to 15 parts by weight, based on 100 parts by weight of the total amount of the active energy ray-curable adhesive composition. If the amount is less than 0.5 part by weight, the hardening becomes insufficient, and the mechanical strength or the subsequent strength of the adhesive layer may be lowered. In addition, when the amount is more than 20 parts by weight, the ionic substance in the adhesive layer is increased to increase the hygroscopicity of the adhesive layer, and the durability of the obtained polarizing plate can be lowered.

The active energy ray-curable adhesive composition may contain a photosensitizer as needed. By using a photosensitizer, the reactivity can be improved, and the mechanical strength and the subsequent strength of the adhesive layer can be further improved. Examples of the photosensitizer include a carbonyl compound, an organic sulfur compound, a persulfide compound, a redox compound, an azo compound, a diazo compound, a halogen compound, and a photoreductive dye.

Examples of the carbonyl compound which can be a photosensitizer include benzoin methyl ether, benzoin isopropyl ether and benzoin derivatives such as α,α-dimethoxy-α-phenylacetophenone; for example, 9,10 a hydrazine compound such as dibutoxy hydrazine; such as diphenyl ketone, 2,4-dichlorodiphenyl ketone, methyl o-benzhydryl benzoate, 4,4'-bis(dimethyl Diphenyl ketones such as amino)diphenyl ketone and 4,4'-bis(diethylamino)diphenyl ketone and derivatives thereof; such as 2-chloropurine (anthraquinone) and 2-methyl Anthracene derivatives such as guanidine; acridone derivatives such as N-methylacridone and N-butylacridone; such as α,α-diethoxyacetophenone An acetophenone derivative; a xanthone derivative; a fluorene derivative or the like. Examples of the organic sulfur compound which can be a photosensitizer include thioxanthone derivatives of 2-chlorothioxanthone and 2-isopropylthioxanthone. In addition to this, a benzyl compound or a uranyl compound or the like can also be used as a photosensitizer. These photosensitizers may be used singly or in combination of plural kinds.

When the photosensitizer is blended, the blending amount is preferably from 0.1 to 20 parts by weight based on 100 parts by weight of the total amount of the active energy ray-curable adhesive composition.

The active energy ray-curable adhesive composition can be formulated with various additives within a range that does not impair the effect thereof. Examples of the additive include an ion trapping agent, an antioxidant, a chain transfer agent, an adhesion-imparting agent, a thermoplastic resin, a filler, a flow regulating agent, a plasticizer, and an antifoaming agent.

The active energy ray-curable adhesive composition may have a viscosity which can be applied to the film by a suitable method, and the viscosity at 25 ° C is preferably in the range of 10 to 30,000 mPa ‧ sec, and is 50 to 6,000 mPa ‧ sec The range is better. If the viscosity is too low, the coating device can be limited, and it becomes difficult to obtain a uniform coating film without unevenness even after coating is completed. On the other hand, if the viscosity is too high, the flow becomes difficult, and similarly, the apparatus which can be applied is limited, and it is difficult to obtain a homogeneous coating film having no unevenness. Here, the viscosity is a value measured at 60 rpm after the composition is adjusted to 25 ° C using a B-type viscometer.

When an active energy ray-curable adhesive composition is used as an adhesive for forming the adhesive layers 14 and 15, the polarizing film bonding step (C) includes a step of curing the adhesive layers 14 and 15 with active energy rays to harden them. . The curing of the adhesive layers 14 and 15 by the irradiation of the active energy rays may be performed by laminating the protective film 13 and the transparent resin film 17 with the adhesive layer interposed therebetween via the adhesive layers 14 and 15, respectively. Work with the fit. The active energy ray is preferably irradiated from the side of the separator film 12.

The active energy ray which can be used for adhesion hardening, for example, may be X-rays having a wavelength of 1 pm to 10 nm, ultraviolet rays having a wavelength of 10 to 400 nm, visible light having a wavelength of 400 to 800 nm, or the like. Among them, ultraviolet light is preferably used from the viewpoints of ease of handling, ease of preparation of the active energy ray-curable adhesive composition, safety, and hardenability. For the ultraviolet light source, for example, a light-emitting distribution having a wavelength of 400 nm or less, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black lamp, a microwave-excited mercury lamp, a metal halide lamp, or the like can be used. .

The irradiation intensity of the ultraviolet ray is not particularly limited as long as it depends on the kind of the adhesive or the irradiation time. For example, the irradiation intensity in the wavelength region effective for activation of the photocationic polymerization initiator is set to 0.1 to 300 mW/cm ^{2 .} Preferably, it is more preferably set to 1 to 200 mW/cm ² . When the light irradiation intensity of the active energy ray-curable adhesive composition is too small, the curing reaction time becomes long, and the irradiation time is not prolonged without prolonging the irradiation time, which is disadvantageous in terms of productivity. On the other hand, if the light irradiation intensity is too large, the active energy ray-curable adhesive composition yellow is generated due to the heat energy radiated from the lamp and the heat generation of the active energy ray-curable adhesive composition during polymerization. Degradation of the polarizing film or the polarizing film.

The irradiation time of the ultraviolet ray is also not particularly limited depending on the type of the adhesive or the irradiation intensity. For example, the integrated light amount expressed by the product of the irradiation intensity and the irradiation time is preferably set to 10 to 5,000 mJ/cm ² . Further, it is more preferably set to 50 to 1,000 mJ/cm ² . When the integrated light amount of the active energy ray-curable adhesive composition is too small, the generation of the active species derived from the photocationic polymerization initiator is insufficient, and the hardening of the obtained adhesive layer tends to be insufficient. . On the other hand, when the amount of integrated light is too large, the irradiation time becomes extremely long, which is disadvantageous in terms of productivity.

The thickness of the adhesive layer obtained by the irradiation of the active energy ray is usually 1 μm or more and 20 μm or less. However, from the viewpoint of maintaining an appropriate adhesion and a thin polarizing plate, it is preferably 10 μm or less. More preferably 8 μm.

In particular, when the second adhesive layer 14 of the protective film 13 and the polarizing film 16 is formed of an active energy ray-curable composition, the second adhesive layer 14 is cured by irradiation with an active energy ray. It is preferably 8 μm or less. That is, as shown in the later-described embodiment, when the polarizing plate obtained by the method of the present invention is subjected to a damp heat test under high temperature and high humidity conditions, when the second adhesive layer 14 is thick, the polarizing plate (polarizing film) Will produce discoloration. This is because the irradiation of the active energy ray is performed by the side of the separation film 12, and if the second adhesive layer 14 farther from the place is thick, the active energy ray cannot be sufficiently penetrated, and it is presumed that the cause of the reaction rate is insufficient. . By the thickness of the second adhesive layer 14 being 8 μm or less, such discoloration can be prevented. In order to more effectively prevent discoloration due to the damp heat test, the thickness of the second adhesive layer 14 is preferably 5 μm or less. Of course, when the first adhesive layer 15 of the transparent resin film 10 and the polarizing film 16 is formed of an active energy ray-curable composition, the thickness thereof is preferably 8 μm or less and more preferably 5 μm or less.

[protective film]

The protective film 13 is not particularly limited as long as it is a film made of a transparent resin film. The transparent resin may, for example, be a (meth)acrylic resin such as a methyl methacrylate resin, an olefin resin, a polyvinyl chloride resin, a cellulose resin, a styrene resin, or an acrylonitrile/butadiene/ Styrene-based copolymer resin, acrylonitrile/styrene copolymer resin, polyvinyl acetate resin, polydichloroethylene resin, polyamine resin, polyacetal resin, polycarbonate resin, modified Polyphenylene ether resin, polyester resin (for example, polybutylene terephthalate resin, polyethylene terephthalate resin, etc.), polyfluorene resin, polyether oxime resin, poly aryl An ester resin, a polyamidoximine resin, a polyimide resin, an epoxy resin, or a propylene oxide resin. These resins may contain additives insofar as they do not impede transparency or adhesion to the polarizing film.

The above transparent resin may be formed into a film shape and subjected to an extension treatment as a protective film. The extension processing system can extend the uniaxial extension for MD (flow direction) or TD (direction perpendicular to the flow direction), the biaxial extension for extending both MD and TD, and extend in the direction of non-MD or non-TD. It is carried out by several methods such as oblique extension. By applying the stretching treatment, a protective film having high mechanical strength can be obtained.

The (meth)acrylic resin is a polymer obtained by using (meth) acrylate as a main monomer component, such as methyl (meth) acrylate. The (meth)acrylic resin may be a material in which rubber fine particles are blended as needed. The toughness of the (meth)acrylic resin in which the rubber fine particles are blended is improved, and the mechanical properties of the polarizing plate can be further improved when the polarizing plate is formed.

The polyethylene terephthalate-based resin means a resin composed of ethylene terephthalate in an amount of 80 mol% or more of the repeating unit, and may also include a constituent unit derived from another copolymerized component. Other copolymerization components may, for example, be isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxydiphenyl ketone, bis(4-carboxyphenyl)ethane, adipic acid, a dicarboxylic acid component such as sebacic acid, sodium 5-sulfonate isophthalate or 1,4-dicarboxycyclohexane; propylene glycol, butylene glycol, neopentyl glycol, diethylene glycol, cyclohexanediol, An ethylene oxide adduct of bisphenol A, a glycol component such as polyethylene glycol, polypropylene glycol, or tetramethylene glycol. These dicarboxylic acid components or diol components can be used in combination of two or more kinds as needed. Further, the carboxylic acid component or the diol component may be used in combination with a hydroxycarboxylic acid such as p-hydroxybenzoic acid or p-β-hydroxyethoxybenzoic acid. As the other copolymerization component, a dicarboxylic acid component and/or a glycol containing a small amount of a guanamine bond, an amine ester bond, an ether bond, or a carbonate bond may be used.

After the polyethylene terephthalate resin is formed into a film, the laminate is subjected to the above-mentioned elongation treatment as a protective film, thereby obtaining mechanical properties, solvent resistance, scratch resistance, cost, and the like. Excellent, simultaneously thinned polarizing plate.

The cellulose-based resin may, for example, be a part or all of a hydrogen atom of a hydroxyl group of cellulose which is available from a raw material such as cotton linter or wood pulp (a broad-leaved wood pulp or coniferous wood pulp). The sulfhydryl group and/or the butyl group are substituted, and are referred to as a cellulose organic acid ester or a cellulose mixed organic acid ester. Examples thereof include those composed of cellulose acetate, propionate, butyrate, and a mixed ester thereof. Among them, cellulose triacetate, cellulose diacetate, cellulose acetate propionate or cellulose acetate butyrate are suitably used.

The polyolefin-based resin may, for example, be a cyclic olefin-based resin obtained by polymerizing a cyclic olefin monomer such as norbornene or another cyclopentadiene derivative with a catalyst for polymerization, or ethylene or propylene. The chain olefin monomer is a chain olefin resin polymerized by a polymerization catalyst.

The cyclic olefin-based resin may, for example, be a monomer obtained by using a cyclodecene obtained from a cyclopentadiene and an olefin by a Diels-Alder reaction or a derivative thereof. a ring-opening metathesis polymerization reaction, and a resin obtained by subsequent hydrogenation; a tetracyclic ring obtained by reacting dicyclopentadiene with an olefin or a methacrylate by a Dickens-Alder reaction a resin obtained by subjecting dodecene or a derivative thereof as a monomer, a ring-opening metathesis polymerization reaction, and a subsequent hydrogenation; and using two or more kinds of the above-described norbornene, the above tetracyclododecene, and the like Derivatives and other cyclic olefin monomers, similarly subjected to ring-opening metathesis polymerization, and resins obtained by subsequent hydrogenation; the above-mentioned norbornene, the above tetracyclododecene or derivatives thereof A resin obtained by subjecting an aromatic compound having a vinyl group or the like to addition polymerization.

The chain olefin resin is, for example, a polyethylene resin or a polypropylene resin. As the polypropylene resin, a polypropylene resin described as a resin constituting the transparent resin film 10 can be used.

The thickness of the protective film 13 is usually 20 to 200 μm, preferably 20 to 120 μm. When the thickness of the protective film 13 is less than 20 μm, it tends to be difficult to handle, and if the thickness exceeds 120 μm, the thickness of the polarizing plate is disadvantageous.

A surface treatment layer such as a hard coat layer, an antireflection layer, an antiglare layer or an antistatic layer may be formed on the surface of the protective film 13 opposite to the polarizing film 16; or a liquid crystal compound or a high molecular weight compound thereof may be formed. A coating layer is formed; other optical films such as a brightness enhancement film may be laminated. However, the antistatic function may be imparted to other portions of the polarizing plate such as the adhesive layer or the adhesive layer instead of the protective film 13. When the surface treatment layer is formed on the surface of the protective film 13 opposite to the polarizing film 16, a protective film having a surface treatment layer is usually prepared in advance and supplied to the polarizing film bonding step (C).

Further, on the side of the adhesive layer 11 of the obtained polarizing plate 1, a polymer film having a negative original birefringence may be bonded to be uniaxially or biaxially formed by lateral stretching or successive stretching. Phase difference film.

(Example)

Hereinafter, the present invention will be more specifically described by way of examples, but the invention is not limited to the embodiments. In the following examples, the part indicating the amount of use is based on the weight basis unless otherwise specified.

(Production Example 1: Production of Transparent Resin Film)

A polypropylene-based resin (a single polymer of propylene produced by a continuous gas phase polymerization method using a Ziegler-Natta catalyst having a solid as an essential component of magnesium, titanium, and halogen: from The ratio of the constituent unit of propylene was 99.8% by weight or more, the melting point was 153 ° C, and the degree of crystallization was 52%.) A 90 mm Φ extruder having a roll temperature of 250 ° C was used to carry out melt kneading by mounting on an extruder. Extruded by a T-shaped mold with a width of 1250 mm. The extruded molten polypropylene resin was cooled by a casting roll (void 90 mm) adjusted to a temperature of 10 ° C to obtain a thickness of 50 μm, and the in-plane phase difference R ₀ was 11.9 nm, and haze. A polypropylene resin film having a transparency of 0.3% and excellent in transparency. The polypropylene resin film had a Gore test bending resistance of 40 mgf. The film's Gloria resistance is based on the method specified in JIS L 1096 "Bending Resilience A Method", using a temperature tester (manufactured by Kumagai Rico Industrial Co., Ltd.) to The measurement was carried out under the conditions of 22 ° C and a relative humidity of 53%. Further, the haze value was measured in accordance with JIS K 7105.

(Production Example 2: Production of ultraviolet curable adhesive)

The trade name "Epicoat (registered trademark) YX8000" (dihydroxyepoxy ether of nuclear hydrogenated bisphenol A, having an epoxy equivalent of about 205 g / equivalent) of 10 parts of hydrogenated epoxy resin manufactured by Japan Epoxy Resins Co., Ltd. 4 parts of the product name "CI5102" manufactured by Japan Soda Co., Ltd. and the product name "CS7001" of the photo-sensitizer manufactured by Japan Soda Co., Ltd. were mixed, and after defoaming, preparation was carried out. It is an adhesive consisting of an ultraviolet curable resin composition containing an epoxy resin.

[Example 1]

(1) Step of producing a transparent resin film with an adhesive layer

The double-sided separation film type adhesive sheet sandwiched between the two acrylic adhesive layers is prepared, and the separator film on one side is peeled off, and then the surface of the adhesive layer exposed by peeling off the separation film is subjected to corona discharge. At the same time, one side of the polypropylene resin film obtained in Production Example 1 was subjected to corona discharge treatment. The corona discharge-treated surfaces were bonded together to form an adhesive layer on the polypropylene resin film within 5 minutes after the corona discharge treatment to obtain a polypropylene resin film/adhesive layer/minute. A transparent resin film having an adhesive layer formed of a separator.

(2) Surface activation step

The surface of the polypropylene resin film side of the adhesive resin layer with the adhesive layer obtained in the above (1) was subjected to a corona discharge treatment.

(3) Polarizing film bonding step

First, a polyester-based resin film having an anti-glare layer formed on one side thereof is prepared, and a surface on which the anti-glare layer is not formed is subjected to a corona discharge treatment. Next, a corona discharge of a transparent resin film with an adhesive layer attached thereto was applied to a single surface of a polarizing film in which iodine was adsorbed on a polyvinyl alcohol resin film, and a UV curable adhesive obtained in the second embodiment. The surface to be treated was bonded to the other surface of the polarizing film, and the surface of the polyester resin film which was subjected to the corona discharge treatment was bonded to each other via the ultraviolet curable adhesive obtained in Production Example 2. Thereafter, an ultraviolet irradiation system (manufactured by Fusion UV System Co., Ltd.) was used to irradiate ultraviolet rays from the side of the separation film of the transparent resin film to which the adhesive layer was attached to cure the adhesive. In this way, a transparent resin film made of a polypropylene resin having an adhesive layer on one surface of the polarizing film and a polyester resin film (protective film) having an antiglare treatment on the other surface are obtained. A polarizing plate with an adhesive layer laminated with an ultraviolet curable adhesive.

[Comparative Example 1]

A polarizing plate was produced in the same manner as in Example 1 except that the polypropylene resin film (non-adhesive layer and separator film) produced in Production Example 1 was used instead of the transparent resin film with the adhesive layer attached thereto. When the rigidity of the polypropylene resin film is low, as a result, elongation occurs in the bonding of the polarizing film, and bubbles or embossing are generated between the polypropylene resin film and the polarizing film.

[Comparative Example 2]

First, on one surface of the polypropylene resin film obtained in Production Example 1, a protective film of a weakly adhesive acrylic pressure-sensitive adhesive layer and a biaxially oriented polyethylene terephthalate film having a thickness of 60 μm was laminated. A polypropylene resin film reinforced with a protective film was obtained. Then, in the same manner as (2) and (3) of Example 1, except that the reinforcing polypropylene resin film was used, a protective film/polypropylene resin film/adhesive layer/polarizing film was obtained. / Polarizing plate composed of an adhesive layer/polyester resin film.

Next, the same double-sided separator film type adhesive sheet as that shown in (1) of Example 1 was prepared, and after the one side separator film was peeled off, the surface of the adhesive layer exposed by peeling off the separator film was subjected to corona. In the discharge treatment, the protective film is peeled off from the polarizing plate, and the surface of the polypropylene resin film exposed by peeling off the protective film is subjected to corona discharge treatment. These corona discharge-treated surfaces were bonded together within 5 minutes after the corona discharge treatment, and the same separator/adhesive layer/polypropylene-based resin film/adhesive agent as in Example 1 was obtained. A polarizing plate with an adhesive layer formed of a layer/polarizing film/adhesive layer/polyester resin film.

In the method of Comparative Example 2, since the protective film was additionally required, the step of peeling off the protective film was required, and the productivity was lowered. Further, in the bonding step of the adhesive layer and the polypropylene resin film, there is a fear that bubbles or foreign matter are mixed in the interface.

[Embodiment 2]

(1) Step of producing a transparent resin film with an adhesive layer

An acrylic adhesive layer having a thickness of 20 μm was prepared, and a double-sided separator film type adhesive sheet sandwiched between two separator films made of polyethylene terephthalate was used to peel off the one-sided separator film. Thereafter, the surface of the adhesive layer exposed by peeling off the separator film was subjected to corona discharge treatment. Further, a single surface of the polypropylene resin film obtained in Production Example 1 was also subjected to a corona discharge treatment. Each of the corona discharge-treated surfaces was bonded together to form an adhesive layer on the polypropylene resin film within 5 minutes after the corona discharge treatment, and a polypropylene resin film/adhesive layer was formed. / A transparent resin film with an adhesive layer formed of a separator film.

(2) Surface activation step

The surface of the polypropylene resin film side of the transparent resin film with an adhesive layer produced by the above (1) was subjected to a corona discharge treatment. Further, a polypropylene resin film having an antiglare layer formed on one side and having a thickness of about 86 μm was prepared, and a surface on which the antiglare layer was not formed was also subjected to corona discharge treatment.

(3) Polarizing film bonding step

A polarizing film in which iodine is oriented is adsorbed on the polyvinyl alcohol-based resin film. The one surface of one end in the longitudinal direction is produced by the above (1), and the corona discharge treated surface (polypropylene) of the transparent resin film with the adhesive layer applied by the corona discharge treatment of the above (2) is superposed. One end in the longitudinal direction of the resin film surface), and the other side of the same position of the polarizing film is superposed on the longitudinal direction of the corona discharge treated surface of the propylene resin film subjected to the corona discharge treatment of the above (2) One end. Subsequently, an epoxy-based ultraviolet curable adhesive is supplied between the polypropylene resin film and the polarizing film, and another epoxy-based ultraviolet curable adhesive is supplied between the propylene resin film and the polarizing film, and the first overlapping end is used. The order was passed through a Roll-type laminating machine ("Lamipacker" manufactured by Fujipla Co., Ltd.). In this case, the transparent resin film with the adhesive layer on one side of the polarizing film is made of the polypropylene resin film side, and the propylene resin film having the antiglare layer is provided on the other side of the polarizing film. The glare layer side was bonded to each other via an epoxy-based ultraviolet curable adhesive. Then, the ultraviolet ray irradiation system (manufactured by Nippon Battery Co., Ltd.) was irradiated with ultraviolet rays containing a metal halide lamp as a light source from the side of the separation film of the transparent resin film to which the pressure-sensitive adhesive layer was attached, and the adhesive was cured.

At this time, the thickness of the adhesive layer is adjusted by changing the gap of the nip of the bonding machine. Then, the cross section of the polarizing plate obtained by curing the adhesive by ultraviolet irradiation was observed, and four types of polarizing plates having a thickness of the adhesive layer on the side of the propylene resin film of 3.4 μm, 4.5 μm, 6.1 μm, and 8.7 μm were obtained. In the case of any of the polarizing films, the operability of the adhesive resin layer and the separator film provided with the adhesive layer on the single side of the polypropylene resin film is good; a transparent resin film comprising a polypropylene resin having a separator film having an adhesive layer; and a propylene resin film (protective film) having an antiglare layer on the other surface, which are laminated via an ultraviolet curable adhesive. A polarizing plate with an adhesive layer is formed. The polarizing plate produced was also confirmed to have no bubbles or embossing.

(4) Damp heat test of polarizing plate

The four types of polarizing plates obtained above were subjected to a damp heat test at a temperature of 60 ° C and a relative humidity of 90% for 1500 hours, and the polarizing plate after the test was observed. As a result, the polarizing plate having the thickness of the adhesive layer on the side of the propylene resin film side of 3.4 μm and 4.5 μm was not changed, and the polarizing plate having a thickness of the adhesive layer of 6.1 μm was confirmed in some cases. There was a slight discoloration, but in order not to hinder the use of the polarizing plate, it was confirmed that the polarizing plate having a thickness of the adhesive layer of 8.7 μm was significantly decolored.

1. . . Polarizer

10. . . Transparent resin film

11. . . Adhesive layer

12. . . Separator

13. . . Protective film

14. . . Second adhesive

15. . . First adhesive

16. . . Polarizing film

17. . . Transparent resin film with adhesive layer

1(a) to (c) are schematic flow charts showing a preferred example of the manufacturing method of the present invention.

1. . . Polarizer

10. . . Transparent resin film

11. . . Adhesive layer

12. . . Separator

13. . . Protective film

14. . . Second adhesive

15. . . First adhesive

16. . . Polarizing film

17. . . Transparent resin film with adhesive layer

Claims (16)

A method for producing a polarizing plate, comprising: preparing a transparent resin film; and laminating a separator film having a peeling property from an adhesive layer via an adhesive layer prepared thereon a step of a transparent resin film of the adhesive layer; a step of applying a surface activation treatment on the surface of the transparent resin film with the adhesive layer-attached transparent resin film; and a surface of the transparent resin film subjected to the surface activation treatment, a step of bonding a polarizing film via a first adhesive, wherein the transparent resin film with the adhesive layer is bonded to the bonding surface of the transparent resin film and the adhesive layer and/or the adhesive layer The bonding surface of the transparent resin film is subjected to a surface activation treatment. The method for producing a polarizing plate according to claim 1, wherein the step of bonding the polarizing film comprises: bonding a surface of the polarizing film to the transparent resin film with the adhesive layer; The surface on the opposite side is a step of bonding a protective film via a second adhesive. The method for producing a polarizing plate according to claim 1, wherein the first adhesive is composed of an active energy ray-curable composition, and the step of bonding the polarizing film includes irradiation from the separation film side. The step of the active energy line. The method for producing a polarizing plate according to claim 2, wherein the second adhesive agent for bonding the protective film and the polarizing film is composed of an active energy ray-curable composition; The step of bonding the polarizing film includes a step of irradiating the active energy ray from the side of the separation film; and the adhesive layer obtained by curing the second adhesive by irradiation with the active energy ray has a thickness of 8 μm or less. The method for producing a polarizing plate according to the first aspect of the invention, wherein the surface of the transparent resin film coated with the transparent resin film with the adhesive layer is surface-activated by a corona discharge treatment. The method for producing a polarizing plate according to the first aspect of the invention, wherein the transparent resin film has a Gurley resistance of 350 mgf or less. The method for producing a polarizing plate according to the first aspect of the invention, wherein the transparent resin film is composed of a polypropylene resin. The method for producing a polarizing plate according to claim 7, wherein the polypropylene resin is substantially composed of a single polymer of propylene. The method for producing a polarizing plate according to claim 7, wherein the polypropylene resin is composed of a copolymer of propylene and ethylene containing 10% by weight or less of an ethylene unit. The method for producing a polarizing plate according to claim 1, wherein the in-plane retardation value of the transparent resin film is 20 nm or less. The method for producing a polarizing plate according to claim 1, wherein the in-plane retardation value of the transparent resin film is in the range of 30 to 500 nm, and the phase difference in the thickness direction is in the range of 20 to 500 nm. By. The method for producing a polarizing plate according to claim 1, wherein the separator film is a film made of polyethylene terephthalate. The method for producing a polarizing plate according to claim 1, wherein the separator film has a release treatment surface. The method for producing a polarizing plate according to claim 1, wherein the transparent resin film with an adhesive layer is formed by forming an adhesive layer on the separation film, and the adhesive layer side and the transparent resin. The film is bonded to the maker. The method for producing a polarizing plate according to the first aspect of the invention, wherein the transparent resin film with an adhesive layer is formed by laminating the adhesive layer layer after forming an adhesive layer on the transparent resin film. Producer of the diaphragm. The method for producing a polarizing plate according to claim 1, wherein at least one of a surface of the transparent resin film and the adhesive layer and a surface of the adhesive layer and the transparent resin film layer is used. Surface activation treatment.