JP6947870B2 - Method of manufacturing polarizing film - Google Patents

Description

The present invention relates to a method for producing a polarizing film. The polarizing film obtained by the production method can form an image display device such as a liquid crystal display (LCD), an organic EL display device, a CRT, or a PDP as an optical film obtained by itself or laminated.

LCD display devices are rapidly expanding into the market for watches, mobile phones, PDAs, laptop computers, personal computer monitors, DVD players, TVs, and the like. The liquid crystal display device visualizes the polarization state due to the switching of the liquid crystal, and a polarizer is used because of the display principle. In particular, applications such as TVs are required to have higher brightness, higher contrast, and a wider viewing angle, and polarizing films are also required to have higher transmittance, higher degree of polarization, and higher color reproducibility.

As the polarizer, since it has high transmittance and high degree of polarization, for example, an iodine-based polarizer having a structure in which iodine is adsorbed on polyvinyl alcohol and stretched is most widely used. Such a polarizer has an extremely weak mechanical strength, and has a disadvantage that it shrinks due to heat or moisture and the polarization function is significantly reduced. Therefore, usually, the obtained polarizing element is immediately coated with a water-based adhesive, and the transparent protective film is simultaneously attached to both sides of the polarizer via this adhesive as a polarizing film. As the transparent protective film, triacetyl cellulose having high moisture permeability or the like is used. On the other hand, in order to suppress the dimensional change, the moisture content of the polarizer can be lowered, or a transparent protective film having low moisture permeability can be used.

However, when a water-based adhesive is used in manufacturing a polarizing film (so-called wet lamination), high productivity cannot be expected because a drying step is required after the polarizing element and the transparent protective film are bonded together. .. Further, when a transparent protective film having a low moisture permeability is used, the drying efficiency is further deteriorated, and high productivity cannot be expected.

In order to solve the above-mentioned problems in wet lamination, active energy ray-curable adhesives containing no water or organic solvent have been proposed (Patent Documents 1 and 2). The active energy ray-curable adhesive is roughly classified into a photocationic polymerization type and a photoradical polymerization type. Since the active energy ray-curable adhesive does not require a drying step like a water-based adhesive, the productivity of the polarizing film can be increased even when a transparent protective film having low moisture permeability is used.

Japanese Unexamined Patent Publication No. 2010-286754 Japanese Unexamined Patent Publication No. 2008-23874

In the wet lamination using the water-based adhesive, there was no particular problem in terms of appearance with respect to the polarizing film obtained by laminating the polarizer and the transparent protective film. That is, when a water-based adhesive is used, the polarizer and the transparent protective film are bonded together with a wet adhesive, and then the adhesive is dried to gradually remove water. For this reason, it is difficult for air bubbles to get caught in the bonded surface, and there is no problem of appearance caused by these air bubbles. However, when the active energy ray-curable adhesive is used, the obtained polarizing film is inferior in appearance, which is a new problem.

The present invention is a method for manufacturing a polarizing film in which transparent protective films are provided on both sides of the polarizer, even when the polarizer and the transparent protective film are bonded together using an active energy ray-curable adhesive. It is an object of the present invention to provide a method capable of producing a polarizing film having a good appearance.

As a result of diligent studies to solve the above problems, the present inventors have found the following method for producing a polarizing film and the like, and have completed the present invention.

That is, the present invention is a method for manufacturing a polarizing film in which first and second transparent protective films are provided on the first and second surfaces, which are both sides of the polarizing element.
A step (1) of applying an active energy ray-curable adhesive to the second surface of the polarizing element in the single-sided protective polarizing film in which the first transparent protective film is provided on the first surface of the polarizing element.
The step (2) of laminating the second transparent protective film via the active energy ray-curable adhesive, and
The present invention relates to a method for producing a polarizing film, which comprises a step (3) of irradiating the active energy ray-curable adhesive with active energy rays to form an adhesive layer.

In the method for producing the polarizing film, the polarizing element is a continuous web polarizing film made of a polyvinyl alcohol-based resin in which a dichroic substance is oriented, and the one-sided protective polarizing film is a thermoplastic resin base material. It can be suitably applied to the case where the laminate containing the polyvinyl alcohol-based resin layer formed in the above film is obtained by stretching in a two-step stretching step consisting of auxiliary stretching in the air and stretching in water boric acid.

The method for producing the polarizing film is described in the step (1), after 2 seconds or more have passed after applying the active energy ray-curable adhesive to the second surface of the polarizer in the single-protective polarizing film. It is preferable to carry out the step (2).

In the method for producing a polarizing film, the viscosity of the active energy ray-curable adhesive is preferably 10 to 350 cps (25 ° C.).

In the method for producing a polarizing film, the active energy ray-curable adhesive preferably contains a radically polymerizable compound.

In the method for producing a polarizing film, in the step (1), the second surface of the polarizer in the one-side protection polarizing film is dried before the active energy ray-curable adhesive is applied. It is preferable to include a step of performing the treatment.

In the method for producing a polarizing film, it is preferable to irradiate the active energy rays in the step (3) from the side of the second transparent protective film.

In the method for producing a polarizing film, the thickness of the adhesive layer formed by the step (3) is preferably 300 nm to 1.3 μm.

In the production of polarizing films, it is very difficult to handle the polarizer due to the problem of strength. For this reason, when using an active energy ray-curable adhesive (hereinafter, may be simply referred to as an adhesive), the adhesive is applied not to the polarizer side but to the transparent protective film side, and the polarizer and the transparent protective film are applied. It is considered preferable to bond the two. However, since the surface of the polarizer has streaks with a pitch of several μm and irregularities on the level of several hundred nm, the adhesive is applied to the transparent protective film side, which has a relatively smooth surface, and then attached to the polarizer. When combined, it was found that the irregularities and streaks on the surface of the polarizer could hardly be filled with the adhesive. Therefore, it has been found that a large number of bubbles are generated in the obtained polarizing film, resulting in poor appearance. That is, it was found that when the polarizing element and the transparent protective film are bonded to each other by the active energy ray-curable adhesive, the surface roughness of the polarizing element has an influence on the cause of the biting of the bubbles.

Therefore, in the present invention, the active energy ray-curable adhesive is applied not to the transparent protective film side but to the polarizer side. Generally, the surface roughness of the polarizer is larger than the surface roughness of the transparent protective film. Therefore, rather than applying the active energy ray-curable adhesive to the transparent protective film and bonding it, applying the adhesive to the polarizer side and pasting it dramatically creates bubbles that bite into the bonding surface. Can be reduced. That is, by applying an adhesive to the polarizer side, it is possible to bond it to the transparent protective film in a state where the unevenness of the surface of the polarizer is filled to some extent with the adhesive, so that the generation of air bubbles to be caught is suppressed. The appearance can be improved.

As mentioned above, the polarizer is very difficult to handle, and there is a risk that the production line will be stopped when the adhesive is applied directly to the polarizer. In particular, when the polarizer obtained through the stretching step is bonded to the transparent protective film in a continuous line, it is the most dangerous and difficult, and is not suitable for production. In the present invention, when applying an adhesive, a single protective polarizing film in which a first transparent protective film is already provided on the first surface of the polarizer on the side opposite to the second surface of the polarizer to be coated is provided. I am using it. Since the single-protective polarizer is durable, the adhesive is applied directly to the second surface of the single-protective polarizer by applying the adhesive directly to a single polarizer without transparent protective films on both sides of the polarizer. It is possible to realize a stable coating as compared with the case where the coating is performed.

The method for producing the polarizing film of the present invention will be described below. In the polarizing film of the present invention, a first transparent protective film is provided on one side (first surface) of the polarizer, and a second transparent protective film is provided on the other side (second surface). The polarizing film of the present invention can be obtained by sequentially performing steps (1) to (3).

<Process (1)>
In the step (1), the active energy ray-curable adhesive is applied to the second surface of the polarizing element in the one-sided protective polarizing film provided with the first transparent protective film on the first surface of the polarizing element.

<One-sided protective polarizing film>
In the single protective polarizing film, the first transparent protective film is provided only on the first surface of the polarizer, but the first surface of the polarizer and the first transparent protective film are attached via an adhesive layer. It may be combined.

Examples of the adhesive used for the bonding treatment between the first surface of the polarizer and the first transparent protective film include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based adhesives, and water-based polyesters. It can be exemplified. The adhesive is usually used as an adhesive consisting of an aqueous solution, and usually contains 0.5 to 60% by weight of a solid content. In addition to the above, examples of the adhesive between the polarizer and the transparent protective film include an active energy ray-curable adhesive such as an ultraviolet curable adhesive and an electron beam-curable adhesive. Further, the adhesive used in the present invention may contain a metal compound filler.

When a water-based adhesive is used as the adhesive, the thickness of the adhesive layer is preferably about 10 to 300 nm. The thickness of the adhesive layer is more preferably 10 to 200 nm, and particularly preferably 20 to 150 nm, from the viewpoint of obtaining a uniform in-plane thickness and obtaining sufficient adhesive strength. When an active energy ray-curable adhesive is used as the adhesive, the thickness of the adhesive layer is preferably controlled within the same range as the thickness of the adhesive layer related to the second surface, which will be described later.

When the first transparent protective film is provided on the first surface of the polarizer alone, it is difficult to directly apply the adhesive to the polarizer alone. In this case, the adhesive is applied to the first transparent protective film. It is preferable to work. On the other hand, as described in the thin polarizing element described later, a thin high-performance polarizing film integrally formed with a resin base material has good handleability. Therefore, when using a thin, high-performance polarizing film integrally formed with a resin base material, applying an adhesive directly to the first surface of the polarizer has a larger surface roughness than the surface protective film. It is good for suppressing the biting of air bubbles by the polarizing element having.

<Polarizer>
The polarizer is not particularly limited, and various polarizers can be used. Examples of the polarizer include a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, and an ethylene-vinyl acetate copolymerization system partially saponified film, and a bicolor property of iodine or a bicolor dye. Examples thereof include a uniaxially stretched film by adsorbing a substance, a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrogenated product of polyvinyl chloride. Among these, a polarizer made of a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 1 to 80 μm.

A polarizing element obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching it can be prepared, for example, by dyeing polyvinyl alcohol by immersing it in an aqueous solution of iodine and stretching it 3 to 7 times its original length. If necessary, it can be immersed in an aqueous solution of potassium iodide or the like, which may contain boric acid, zinc sulfate, zinc chloride or the like. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. In addition to being able to clean the surface of the polyvinyl alcohol film and blocking inhibitors by washing the polyvinyl alcohol film with water, it also has the effect of preventing non-uniformity such as uneven dyeing by swelling the polyvinyl alcohol film. be. Stretching may be performed after dyeing with iodine, stretching while dyeing, or stretching and then dyeing with iodine. It can be stretched even in an aqueous solution such as boric acid or potassium iodide or in a water bath.

≪Thin Polarizer≫
As the polarizer, a thin polarizer having a thickness of 10 μm or less can be used. From the viewpoint of thinning, the thickness is preferably 1 to 7 μm. It is preferable that such a thin polarizing element has less uneven thickness, excellent visibility, excellent durability because there is little dimensional change, and the thickness of the polarizing film can be reduced.

Typical examples of the thin polarizing element include JP-A-51-069644, JP-A-2000-338329, WO2010 / 100917 pamphlet, PCT / JP2010 / 00146, or Japanese Patent Application No. 2010-. Examples thereof include the thin polarizing film described in the specification of No. 269002 and the specification of Japanese Patent Application No. 2010-263692. These thin polarizing films can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol-based resin (hereinafter, also referred to as PVA-based resin) layer and a resin base material for stretching in a laminated state and a step of dyeing. With this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without problems such as breakage due to stretching because it is supported by the stretching resin base material.

Among the manufacturing methods including a step of stretching in a laminated state and a step of dyeing, the thin polarizing film can be stretched at a high magnification and the polarization performance can be improved. It is preferably obtained by a production method including a step of stretching in an aqueous boric acid solution as described in JP2010 / 00460, or in Japanese Patent Application No. 2010-269002 and Japanese Patent Application No. 2010-263692, particularly preferably. It is preferably obtained by a production method including a step of auxiliary stretching in the air before stretching in the boric acid aqueous solution described in Japanese Patent Application No. 2010-269002 and Japanese Patent Application No. 2010-263692.

The thin and high-performance polarizing film described in the above description of PCT / JP2010 / 00160 is a thin thin film having a thickness of 7 μm or less made of a PVA-based resin in which a dichroic substance is oriented, which is integrally formed on a resin substrate. It is a high-performance polarizing film and has optical characteristics such as a single transmittance of 42.0% or more and a degree of polarization of 99.95% or more.

In the thin high-performance polarizing film, a PVA-based resin layer is formed on a resin base material having a thickness of at least 20 μm by coating and drying a PVA-based resin, and the generated PVA-based resin layer is dyed with a bicolor substance. The PVA-based resin layer, which is immersed in a liquid to adsorb a bicolor substance on the PVA-based resin layer and has the bicolor substance adsorbed, is integrated with the resin base material in a boric acid aqueous solution based on the total draw ratio. It can be produced by stretching it to be 5 times or more the length.

Further, it is a method for producing a laminated film containing a thin and highly functional polarizing film in which a bicolor substance is oriented, and contains a resin base material having a thickness of at least 20 μm and a PVA-based resin on one side of the resin base material. The step of producing a laminate film containing a PVA-based resin layer formed by coating and drying an aqueous solution, and the laminate including a resin base material and a PVA-based resin layer formed on one side of the resin base material. A step of adsorbing a bicolor substance on a PVA-based resin layer contained in a laminated film by immersing the body film in a dyeing solution containing a bicolor substance, and a PVA system in which the bicolor substance is adsorbed. The step of stretching the laminated film containing the resin layer in an aqueous boric acid solution so that the total draw ratio is 5 times or more of the original length, and the PVA-based resin layer on which a bicolor substance is adsorbed are resin groups. By being stretched integrally with the material, it is composed of a PVA-based resin layer in which a bicolor substance is oriented on one side of a resin base material, has a thickness of 7 μm or less, a single unit permeability of 42.0% or more, and a degree of polarization. The thin and highly functional polarizing film can be produced by including the step of producing a laminated film obtained by forming a thin and highly functional polarizing film having 99.95% or more optical characteristics.

In the present invention, a polyvinyl alcohol-based resin layer formed on a thermoplastic resin base material, which is a continuous web polarizing film made of a PVA-based resin in which a dichroic substance is oriented as a polarizer having a thickness of 10 μm or less. It is possible to use a laminate obtained by stretching a laminate containing As the thermoplastic resin base material, an amorphous ester-based thermoplastic resin base material or a crystalline ester-based thermoplastic resin base material is preferable.

The thin polarizing film of Japanese Patent Application No. 2010-269002 and Japanese Patent Application No. 2010-263692 is a continuous web polarizing film made of a PVA-based resin in which a dichroic substance is oriented, and is amorphous. The laminate containing the PVA-based resin layer formed on the ester-based thermoplastic resin base material was stretched in a two-step stretching step consisting of aerial auxiliary stretching and boric acid water stretching to obtain a thickness of 10 μm or less. It is a thing. In such a thin polarizing film, when the simple substance transmittance is T and the degree of polarization is P, P>-(10 ^{0.929T-42.4-1} ) × 100 (where T <42.3), and P ≧ It is preferable that the material has optical characteristics that satisfy the condition of 99.9 (however, T ≧ 42.3).

Specifically, the thin polarizing film is a stretching intermediate composed of a PVA-based resin layer oriented by high-temperature stretching in the air with respect to a PVA-based resin layer formed on a continuous web amorphous ester-based thermoplastic resin base material. Colored intermediate formation consisting of a PVA-based resin layer in which a dichroic substance (preferably iodine or a mixture of iodine and an organic dye) is oriented by a step of producing a product and adsorption of the dichroic substance to the stretching intermediate product. A thin polarizing film including a step of producing a substance and a step of forming a polarizing film having a thickness of 10 μm or less composed of a PVA-based resin layer in which a dichroic substance is oriented by stretching in boric acid with respect to a colored intermediate product. It can be manufactured by the manufacturing method of.

In this production method, the total draw ratio of the PVA-based resin layer formed on the amorphous ester-based thermoplastic resin base material by high-temperature stretching in the air and stretching in water boric acid is set to 5 times or more. desirable. The liquid temperature of the boric acid aqueous solution for stretching in boric acid water can be 60 ° C. or higher. Before stretching the colored intermediate product in the boric acid aqueous solution, it is desirable to insolubilize the colored intermediate product. In that case, the colored intermediate product is added to the boric acid aqueous solution whose liquid temperature does not exceed 40 ° C. It is desirable to do this by immersing. The amorphous ester-based thermoplastic resin base material is an amorphous polyethylene containing copolymerized polyethylene terephthalate copolymerized with isophthalic acid, copolymerized polyethylene terephthalate copolymerized with cyclohexanedimethanol, or other copolymerized polyethylene terephthalate. It can be made of terephthalate, preferably made of a transparent resin, and its thickness can be 7 times or more the thickness of the PVA-based resin layer to be formed. The stretching ratio of the high-temperature stretching in the air is preferably 3.5 times or less, and the stretching temperature of the high-temperature stretching in the air is preferably equal to or higher than the glass transition temperature of the PVA-based resin, specifically in the range of 95 ° C to 150 ° C. When high-temperature stretching in the air is performed by free-end uniaxial stretching, the total stretching ratio of the PVA-based resin layer formed on the amorphous ester-based thermoplastic resin base material is preferably 5 times or more and 7.5 times or less. .. Further, when high-temperature stretching in the air is performed by uniaxial stretching at a fixed end, the total stretching ratio of the PVA-based resin layer formed on the amorphous ester-based thermoplastic resin base material is 5 times or more and 8.5 times or less. Is preferable.
More specifically, a thin polarizing film can be manufactured by the following method.

A continuous web substrate of isophthalic acid copolymerized polyethylene terephthalate (amorphous PET) obtained by copolymerizing 6 mol% of isophthalic acid is prepared. The glass transition temperature of amorphous PET is 75 ° C. A laminate composed of an amorphous PET substrate of a continuous web and a polyvinyl alcohol (PVA) layer is prepared as follows. Incidentally, the glass transition temperature of PVA is 80 ° C.

A 200 μm-thick amorphous PET substrate and a 4 to 5% concentrated PVA aqueous solution prepared by dissolving PVA powder having a degree of polymerization of 1000 or more and a degree of saponification of 99% or more in water are prepared. Next, a PVA aqueous solution was applied to a 200 μm-thick amorphous PET base material, dried at a temperature of 50 to 60 ° C., and a laminate in which a 7 μm-thick PVA layer was formed on the amorphous PET base material was formed. obtain.

A thin, high-performance polarizing film having a thickness of 3 μm is produced from a laminate containing a PVA layer having a thickness of 7 μm through the following steps including a two-step stretching step of auxiliary stretching in the air and stretching in boric acid in water. By the first-stage aerial auxiliary stretching step, the laminated body containing the PVA layer having a thickness of 7 μm is stretched integrally with the amorphous PET substrate to produce a stretched laminated body containing the PVA layer having a thickness of 5 μm. Specifically, this stretched laminate is subjected to a stretching device equipped in an oven set to a stretching temperature environment of 130 ° C. to obtain a stretching ratio of 1.8 times. It is stretched uniaxially at the free end. By this stretching treatment, the PVA layer contained in the stretched laminate is changed into a 5 μm-thick PVA layer in which PVA molecules are oriented.

Next, the dyeing step produces a colored laminate in which iodine is adsorbed on a 5 μm-thick PVA layer in which PVA molecules are oriented. Specifically, in this colored laminate, the stretched laminate is mixed with a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ° C., and the single transmittance of the PVA layer constituting the highly functional polarizing film finally produced is obtained. Iodine is adsorbed on the PVA layer contained in the stretched laminate by immersing it for an arbitrary time so that the content is 40 to 44%. In this step, the dyeing solution uses water as a solvent and has an iodine concentration in the range of 0.12 to 0.30% by weight and a potassium iodide concentration in the range of 0.7 to 2.1% by weight. The ratio of iodine to potassium iodide concentrations is 1: 7. By the way, potassium iodide is required to dissolve iodine in water. More specifically, by immersing the stretched laminate in a dyeing solution having an iodine concentration of 0.30% by weight and a potassium iodide concentration of 2.1% by weight for 60 seconds, iodine is applied to a 5 μm-thick PVA layer in which PVA molecules are oriented. To produce a colored laminate in which iodine is adsorbed.

Further, by the second step of stretching in boric acid in water, the colored laminate is further stretched integrally with the amorphous PET substrate to generate an optical film laminate containing a PVA layer constituting a high-performance polarizing film having a thickness of 3 μm. do. Specifically, this optical film laminate is stretched by subjecting the colored laminate to a stretching device installed in a processing device set in a boric acid aqueous solution having a liquid temperature range of 60 to 85 ° C. containing boric acid and potassium iodide. It is stretched uniaxially at the free end so that the magnification is 3.3 times. More specifically, the liquid temperature of the boric acid aqueous solution is 65 ° C. It also has a boric acid content of 4 parts by weight with respect to 100 parts by weight of water and a potassium iodide content of 5 parts by weight with respect to 100 parts by weight of water. In this step, the colored laminate having an adjusted iodine adsorption amount is first immersed in a boric acid aqueous solution for 5 to 10 seconds. After that, the colored laminate is passed as it is between a plurality of sets of rolls having different peripheral speeds, which is a stretching device deployed in the processing device, and the stretching ratio is freely increased to 3.3 times over 30 to 90 seconds. Stretch uniaxially. By this stretching treatment, the PVA layer contained in the colored laminate is changed into a 3 μm-thick PVA layer in which the adsorbed iodine is highly oriented in one direction as a polyiodine ion complex. This PVA layer constitutes a high-performance polarizing film of an optical film laminate.

Although not an essential step in the production of the optical film laminate, the optical film laminate was taken out from the boric acid aqueous solution by the cleaning step and adhered to the surface of the 3 μm-thick PVA layer formed on the amorphous PET substrate. It is preferable to wash boric acid with an aqueous solution of potassium iodide. After that, the washed optical film laminate is dried by a drying step with warm air at 60 ° C. The cleaning step is a step for eliminating appearance defects such as boric acid precipitation.

Similarly, although it is not an essential process for producing an optical film laminate, an adhesive is applied to the surface of a 3 μm-thick PVA layer formed on an amorphous PET substrate by a bonding and / or transfer process. At the same time, after the 80 μm-thick triacetyl cellulose film is attached, the amorphous PET substrate can be peeled off and the 3 μm-thick PVA layer can be transferred to the 80 μm-thick triacetyl cellulose film.

[Other processes]
The method for producing a thin polarizing film may include other steps in addition to the above steps. Examples of other steps include an insolubilization step, a cross-linking step, a drying (adjustment of water content) step, and the like. Other steps can be performed at any suitable timing.
The insolubilization step is typically performed by immersing a PVA-based resin layer in an aqueous boric acid solution. By applying the insolubilization treatment, water resistance can be imparted to the PVA-based resin layer. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 4 parts by weight with respect to 100 parts by weight of water. The liquid temperature of the insolubilizing bath (boric acid aqueous solution) is preferably 20 ° C to 50 ° C. Preferably, the insolubilization step is performed after the laminate is prepared and before the dyeing step and the underwater stretching step.
The above-mentioned cross-linking step is typically performed by immersing a PVA-based resin layer in an aqueous boric acid solution. Water resistance can be imparted to the PVA-based resin layer by subjecting it to a cross-linking treatment. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 4 parts by weight with respect to 100 parts by weight of water. Further, when the cross-linking step is performed after the dyeing step, it is preferable to further add iodide. By blending iodide, the elution of iodine adsorbed on the PVA-based resin layer can be suppressed. The blending amount of iodide is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. Specific examples of iodide are as described above. The liquid temperature of the crosslinked bath (boric acid aqueous solution) is preferably 20 ° C. to 50 ° C. Preferably, the cross-linking step is performed before the second boric acid water stretching step. In a preferred embodiment, the dyeing step, the cross-linking step, and the second boric acid water stretching step are performed in this order.

<1st transparent protective film>
As the material constituting the first transparent protective film, those having excellent transparency, mechanical strength, thermal stability, moisture blocking property, isotropic property and the like are preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, and styrene such as polystyrene and acrylonitrile-styrene copolymer (AS resin). Examples thereof include based polymers and polystyrene polymers. In addition, polyethylene, polypropylene, polyolefins having a cyclo- or norbornene structure, polyolefin-based polymers such as ethylene / propylene copolymers, vinyl chloride-based polymers, amide-based polymers such as nylon and aromatic polyamide, imide-based polymers, and sulfone-based polymers. , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, allylate polymer, polyoxymethylene polymer, epoxy polymer, or the above. Polymer blends and the like are also examples of polymers that form the transparent protective film. The transparent protective film may contain one or more of any suitable additives. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, an antioxidant, a flame retardant, a nucleating agent, an antistatic agent, a pigment, a coloring agent and the like. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by mass, more preferably 50 to 99% by mass, still more preferably 60 to 98% by mass, and particularly preferably 70 to 97% by mass. .. When the content of the thermoplastic resin in the transparent protective film is 50% by mass or less, the high transparency inherent in the thermoplastic resin may not be sufficiently exhibited. The first transparent protective film can be appropriately selected and used.

The thickness of the first transparent protective film can be appropriately determined, but is generally about 1 to 500 μm in terms of workability such as strength and handleability, and thin layer property. In particular, 1 to 300 μm is preferable, and 5 to 200 μm is more preferable.

<Active energy ray-curable adhesive>
The active energy ray-curable adhesive according to the present invention is an adhesive whose curing progresses by active energy rays such as an electron beam and ultraviolet rays, and can be used in, for example, an electron beam curable type or an ultraviolet curable type. As the active energy ray-curable adhesive in the present invention, the ultraviolet curable adhesive is preferable in that it can be easily tested with general-purpose equipment. On the other hand, since the electron beam curable adhesive does not use a light initiator, it can be used even with a material that does not transmit light (metal film or high-concentration pigment), and has the feature of improving adhesion, but it is an ultraviolet curable type. There are equipment restrictions compared to adhesives.

Further, the active energy ray-curable adhesive used in the present invention can be either a photocationic polymerization type or a photoradical polymerization type, but the active energy ray-curable adhesive of the present invention is a photoradical polymerization type. Adhesives are preferably used because they cure faster and are more suitable for high-speed production.

When a photoradical polymerization type active energy ray-curable adhesive is used as an ultraviolet curable type, the adhesive contains (A) a radically polymerizable compound and (B) a photoradical generator.

<< (A) Radical Polymerizable Compound >>
The radically polymerizable compound (A) can be used without particular limitation as long as it is a compound having a vinyl group containing at least one carbon-carbon double bond, a (meth) acryloyl group, and the like. In the present invention, among the radically polymerizable compounds (A), the following general formula (1):
CH ₂ = C (R ¹ ) -CONH _2-m- (X-O-R ² ) _m (1)
(R ¹ represents a hydrogen atom or a methyl group, X represents a −CH ₂ − group or −CH ₂ CH ₂ − group, and R ² is a − (CH ₂ ) _n −H group (where n is 0,1). Alternatively, an N-substituted amide-based monomer represented by 2) and m indicating 1 or 2) is preferable.

Specific examples of the N-substituted amide-based monomer represented by the general formula (1) include N-hydroxyethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, and the like. Examples thereof include N-ethoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, and N-ethoxyethyl (meth) acrylamide. These N-substituted amide-based monomers may be used alone or in combination of two or more.

As the N-substituted amide-based monomer represented by the general formula (1), a commercially available product can also be preferably used. Specifically, for example, N-hydroxyethylacrylamide (trade name "HEAA", manufactured by Kojinsha), N-methoxymethylacrylamide (trade name "NMMA", manufactured by MRC Unitech), N-butoxymethylacrylamide (trade name). Examples thereof include "NBMA" (manufactured by MRC Unitech) and N-methoxymethylmethacrylamide (trade name "Wasmer 2MA", manufactured by Kasano Kosan Co., Ltd.).

As the N-substituted amide-based monomer represented by the general formula (1), N-hydroxyethyl (meth) acrylamide is suitable. The N-substituted amide-based monomer shows good adhesiveness to a polarizer having a low water content and a transparent protective film using a material having a low moisture permeability, and among the monomers exemplified above, N- Hydroxyethyl acrylamide shows particularly good adhesion.

The active energy ray-curable adhesive is a monofunctional monofunctional compound (A) having an N-substituted amide-based monomer other than that represented by the general formula (1), various aromatic rings, and a hydroxy group as a radically polymerizable compound. It may contain (meth) acrylate, urethane (meth) acrylate, polyester (meth) acrylate, compounds having various (meth) acryloyl groups, and the like. However, when the adhesiveness and water resistance of the adhesive layer are taken into consideration, the ratio of the N-substituted amide-based monomer represented by the above general formula (1) to the total amount of the (A) radically polymerizable compound is 30 to 95. It is preferably by mass%, more preferably 35 to 90% by mass.

Examples of N-substituted amide-based monomers other than those represented by the above general formula (1) include N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, and N, N-diethyl (meth) acrylamide. , N-isopropylacrylamide, N-butyl (meth) acrylamide, N-hexyl (meth) acrylamide, aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide, mercaaptomethyl (meth) acrylamide, mercaptoethyl (meth) acrylamide , N-acrylamide morpholine, N-acrylamide piperidine, N-methacrylamide piperidine, N-acrylamide pyrrolidine and the like.

As the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group, various monofunctional (meth) acrylates having an aromatic ring and a hydroxy group can be used. The hydroxy group may exist as a substituent of the aromatic ring, but in the present invention, it exists as an organic group (hydrocarbon group, particularly one bonded to an alkylene group) that binds the aromatic ring and the (meth) acrylate. Is preferable.

Examples of the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group include a reaction product of a monofunctional epoxy compound having an aromatic ring and (meth) acrylic acid. Examples of the monofunctional epoxy compound having an aromatic ring include phenylglycidyl ether, t-butylphenylglycidyl ether, and phenylpolyethylene glycol glycidyl ether. Specific examples of the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group include, for example, 2-hydroxy-3-phenoxypropyl (meth) acrylate and 2-hydroxy-3-t-butylphenoxypropyl (meth). Examples thereof include acrylate and 2-hydroxy-3-phenylpolyethylene glycol propyl (meth) acrylate.

The urethane (meth) acrylate includes a (meth) acrylate having an isocyanate group and a hydroxyl group at one end of a diol compound such as a polyurethane diol, a polyester diol, a polyether diol, a polyethylene glycol, or a polyalkylene glycol such as polypropylene glycol. Examples include the reaction product with.

Examples of the compound having a (meth) acryloyl group include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, and isononyl (meth) acrylate. Alkyl (meth) acrylates having 1 to 12 carbon atoms such as lauryl (meth) acrylate; (meth) alkoxyalkyl-based monomers acrylate such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; (meth). ) 2-Hydroxyethyl acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, (meth) ) Hydroxyl group-containing monomers such as 10-hydroxydecyl acrylate, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methylacrylate; Acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride. Caprolactone adduct of acrylic acid; styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxy Examples thereof include sulfonic acid group-containing monomers such as naphthalene sulfonic acid; and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate. Also, (meth) acrylamide; maleimide, N-cyclohexyl maleimide, N-phenylmaleimide, etc .; aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate. Alkylaminoalkyl (meth) acrylate monomers such as t-butylaminoethyl (meth) acrylate, 3- (3-pyrinidyl) propyl (meth) acrylate; N- (meth) acryloyloxymethylene succinimide and N-( Examples thereof include nitrogen-containing monomers such as succinimide-based monomers such as meta) acryloyl-6-oxyhexamethylene succinimide and N- (meth) acryloyl-8-oxyoctamethylene succinimide.

When the active energy ray-curable adhesive further contains, as (A) a radically polymerizable compound, a monomer having two or more carbon-carbon double bonds, particularly preferably a polyfunctional (meth) acrylate-based monomer. , It is preferable because the water resistance of the adhesive layer is improved. Considering the water resistance of the adhesive layer, it is more preferable that the monomer having two or more carbon-carbon double bonds is hydrophobic. Monomers having two or more hydrophobic carbon-carbon double bonds, particularly hydrophobic polyfunctional (meth) acrylate-based monomers include, for example, tricyclodecanedimethanol diacrylate, divinylbenzene, N, N'-methylene. Bisacrylamide, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) Acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) Acrylate, 1,9-nonanediol glycol di (meth) acrylate, glycerin di (meth) acrylate, EO-modified glycerin tri (meth) acrylate, EO-modified diglycerin tetra (meth) acrylate, 2- (meth) acrylic acid 2- (2) -Vinyloxyethoxy) ethyl, bisphenol A-EO adduct Di (meth) acrylate, trimethyl propantri (meth) acrylate, neopentyl glycol (meth) acrylic acid adduct, EO-modified trimethyl propanthry (meth) ) Acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, isocyanuric acid EO-modified di (meth) acrylate, isocyanuric acid EO-modified tri (meth) acrylate, ε- Caprolactone-modified tris ((meth) acloxyethyl) isocyanurate, 1,1-bis ((meth) acryloyloxymethyl) ethyl isocyanate, polymer of 2-hydroxyethyl (meth) acrylate and 1,6-diisocyanate hexane, Examples thereof include 9,9-bis [4- (2- (meth) acryloyloxyethoxy) phenyl] fluorene.

The ratio of the monomer having two or more carbon-carbon double bonds to the total amount of the radically polymerizable compound (A) is preferably 5 to 70% by mass, more preferably 10 to 65% by mass. .. If this ratio is less than 5% by mass, sufficient water resistance may not be obtained, while if it exceeds 50% by mass, sufficient adhesiveness may not be obtained.

≪ (B) Photo-radical generator ≫
(B) The photoradical generator generates radicals by irradiating with active energy rays. Examples of the photoradical generator (B) include a hydrogen abstraction type photoradical generator and a cleavage type photoradical generator.

Examples of the hydrogen abstraction type photoradical generator include 1-methylnaphthalene, 2-methylnaphthalene, 1-fluoronaphthalene, 1-chloronaphthalene, 2-chloronaphthalene, 1-bromonaphthalene, 2-bromonaphthalene and 1-iodonnaphthalene. , 2-Iodonaphthalene, 1-naphthol, 2-naphthol, 1-methoxynaphthalene, 2-methoxynaphthalene, 1,4-dicyanonaphthalene and other naphthalene derivatives, anthracene, 1,2-benzanthracene, 9,10-dichloroanthracene , 9,10-Dibromoanthracene, 9,10-diphenylanthracene, 9-cyanoanthracene, 9,10-dicyanoanthracene, 2,6,9,10-tetracyanoanthracene and other anthracene derivatives, pyrene derivatives, carbazole, 9- Methylcarbazole, 9-phenylcarbazole, 9-prope-2-ynyl-9H-carbazole, 9-propyl-9H-carbazole, 9-vinylcarbazole, 9H-carbazole-9-ethanol, 9-methyl-3-nitro-9H -Carbazole, 9-methyl-3,6-dinitro-9H-carbazole, 9-octanoylcarbazole, 9-carbazole methanol, 9-carbazole propionic acid, 9-carbazole propionitrile, 9-ethyl-3,6-dinitro -9H-carbazole, 9-ethyl-3-nitrocarbazole, 9-ethylcarbazole, 9-isopropylcarbazole, 9- (ethoxycarbonylmethyl) carbazole, 9- (morpholinomethyl) carbazole, 9-acetylcarbazole, 9-allylcarbazole , 9-benzyl-9H-carbazole, 9-carbazole acetic acid, 9- (2-nitrophenyl) carbazole, 9- (4-methoxyphenyl) carbazole, 9- (1-ethoxy-2-methyl-propyl) -9H- Carbazole such as carbazole, 3-nitrocarbazole, 4-hydroxycarbazole, 3,6-dinitro-9H-carbazole, 3,6-diphenyl-9H-carbazole, 2-hydroxycarbazole, 3,6-diacetyl-9-ethylcarbazole Derivatives, benzophenone, 4-phenylbenzophenone, 4,4'-bis (dimethoxy) benzophenone, 4,4'-bis (dimethylamino) benzophenone, 4,4'-bis (diethylamino) benzophenone, 2-benzoyl benzoate methyl ester , 2- Benzophenone derivatives such as methylbenzophenone, 3-methylbenzophenone, 4-methylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 2,4,6-trimethylbenzophenone, aromatic carbonyl compounds, [4- (4-methyl Phenylthio) phenyl] -phenylmethanone, xanthone, thioxanthone, 2-chlorothioxanthone, 4-chlorothioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 1- Examples thereof include thioxanthone derivatives such as chloro-4-propoxythioxanthone and coumarin derivatives.

Cleavage-type photoradical generators are photoradical generators of the type in which the compound is cleaved to generate radicals by irradiating with active energy rays, and specific examples thereof are arylalkyls such as benzoin ether derivatives and acetophenone derivatives. Examples thereof include, but are not limited to, ketones, oxime ketones, acylphosphine oxides, S-phenyl thiobenzoates, titanosenes, and high molecular weight derivatives thereof. Commercially available cleavage-type photoradical generators include 1- (4-dodecylbenzoyl) -1-hydroxy-1-methylethane, 1- (4-isopropylbenzoyl) -1-hydroxy-1-methylethane, and 1-benzoyl. -1-Hydroxy-1-methylethane, 1- [4- (2-hydroxyethoxy) -benzoyl] -1-hydroxy-1-methylethane, 1- [4- (acryloyloxyethoxy) -benzoyl] -1-hydroxy- 1-Methylethane, diphenylketone, phenyl-1-hydroxy-cyclohexylketone, benzyldimethylketal, bis (cyclopentadienyl) -bis (2,6-difluoro-3-pyrryl-phenyl) titanium, (η6-isopropylbenzene) -(Η5-Cyclopentadienyl) -iron (II) hexafluorophosphate, trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxy-benzoyl)-(2,4,4-trimethyl-pentyl) -phosphine oxide, Bis (2,4,6-trimethylbenzoyl) -2,4-dipentoxyphenylphosphine oxide or bis (2,4,6-trimethylbenzoyl) phenyl-phosphine oxide, (4-morpholinobenzoyl) -1-benzyl- Examples thereof include, but are not limited to, 1-dimethylaminopropane and 4- (methylthiobenzoyl) -1-methyl-1-morpholinoetan.

(B) The photoradical generator, that is, the hydrogen abstraction type or cleaved type photoradical generator, can be used individually or in combination of two or more, but the stability of the photoradical generator alone. Further, more preferable in terms of curability of the composition in the present invention is a combination of one or more cleaving type photoradical generators. Acylphosphine oxides are preferable among the cleavage-type photoradical generators, and more specifically, trimethylbenzoyldiphenylphosphine oxide (trade name "DAROCURE TPO"; manufactured by Ciba Japan Co., Ltd.), bis (2,6-dimethoxy-benzoyl). )-(2,4,4-trimethyl-pentyl) -phosphine oxide (trade name "CGI 403"; manufactured by Ciba Japan) or bis (2,4,6-trimethylbenzoyl) -2,4-dipen Toxiphenylphosphine oxide (trade name "IRGACURE819"; manufactured by Ciba Japan Co., Ltd.) is preferable.

The content of the photoradical generator (B) is preferably 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, based on the total amount of the active energy ray-curable adhesive. It is more preferably 0.1 to 3 parts by mass, and particularly preferably 0.1 to 3 parts by mass.

Further, when the active energy ray-curable adhesive according to the present invention is used in an electron beam-curable type, the above-mentioned (B) photoradical generator can be arbitrarily used as the adhesive. Further, a sensitizer that increases the curing speed and sensitivity by an electron beam typified by a carbonyl compound may be added.

Examples of the sensitizer include anthracene, phenothiazene, perylene, thioxanthone, benzophenone thioxanthone and the like. Further, as the sensitizing pigment, thiopyrylium salt-based pigment, merocyanine-based pigment, quinoline-based pigment, styrylquinolin-based pigment, ketocoumarin-based pigment, thioxanthene-based pigment, xanthene-based pigment, oxonol-based pigment, cyanine-based pigment, rhodamine-based pigment. , Pyrylium salt-based pigments and the like are exemplified.

As specific anthracene compounds, dibutoxyanthracene, dipropoxyanthraquinone (Anthraquin UVS-1331, 1221 manufactured by Kawasaki Kasei Chemicals, Inc.) and the like are effective.

When a sensitizer is added, the content thereof is preferably 0.01 to 20 parts by mass, more preferably 0.01 to 10 parts by mass, based on the total amount of the active energy ray-curable adhesive. It is preferably 0.1 to 3 parts by mass, and particularly preferably 0.1 to 3 parts by mass.

In addition, various additives can be added to the active energy ray-curable adhesive as other optional components as long as the object and effect of the present invention are not impaired. Examples of such additives include polyamide, polyamideimide, polyurethane, polybutadiene, polychloroprene, polyether, polyester, styrene-butadiene block copolymer, petroleum resin, xylene resin, ketone resin, cellulose resin, fluorine-based oligomer, and silicone-based oligomer. , Polymers or oligomers such as polysulfide oligomers; polymerization inhibitors such as phenothiazine, 2,6-di-t-butyl-4-methylphenol; polymerization initiators; leveling agents; wettability improvers; surfactants; plastics Agents; UV absorbers; Silane coupling agents; Inorganic fillers; Pigments; Dyes and the like. However, the content of the above-mentioned additives in the active energy ray-curable adhesive is preferably 0.005 to 20 parts by mass, and 0.01 to 10 parts by mass, based on the total amount of the active energy ray-curable adhesive. It is more preferably parts, and particularly preferably 0.1 to 5 parts by mass.

As the photocationic polymerization type active energy ray-curable adhesive, for example, a composition containing a compound having an epoxy group and a photoacid generator can be used.

The viscosity of the active energy ray-curable adhesive is preferably 10 to 350 cps (25 ° C.), more preferably 20 to 300 cps (25 ° C.), and further preferably 40 to 150 cps (25 ° C.). When the viscosity is 10 cps or less, the viscosity becomes too low, and the applied adhesive turns to the back side of the film (single protective polarizing film), and it becomes difficult to design the thickness of the adhesive layer. Further, if the viscosity exceeds 300 cps, the viscosity becomes too high, and if the line speed is increased, the adhesive cannot be sufficiently applied or coating streaks are likely to appear, which is preferable in terms of productivity. No.

The method for applying the active energy ray-curable adhesive to the second surface of the polarizer in the one-sided protective polarizing film is appropriately selected depending on the viscosity of the composition and the desired thickness. Examples of the coating method include a reverse coater, a gravure coater (direct, reverse and offset), a bar reverse coater, a roll coater, a die coater, a bar coater, a rod coater and the like. In addition, a method such as a dipping method can be appropriately used for coating.

Further, the coating of the adhesive improves the adhesiveness between the second transparent protective film and the polarizing element from the viewpoint of filling the streaks and irregularities on the surface of the polarizer to prevent air bubbles from getting caught in the bonded surface. From this point of view, it is preferable that the thickness of the adhesive layer finally formed is 300 nm or more. On the other hand, it is considered that the thicker the adhesive layer is, the more air bubbles can be reduced during bonding. However, if the adhesive layer is too thick, it is not preferable in terms of water resistance. Therefore, the thickness of the adhesive layer is preferably 1.3 μm or less, more preferably 1.2 μm or less, and further preferably 1 μm or less. The thickness of the adhesive layer is preferably controlled to be 300 nm to 1 μm, more preferably 350 to 900 nm, and further preferably 400 to 800 nm.

<Process (2)>
After the step (1) is performed, the second transparent protective film is bonded to the second transparent protective film by the step (2) via the active energy ray-curable adhesive. The bonding of the step (2) can be performed by a roll laminator or the like.

Further, in the step (2), after 2 seconds or more have passed after applying the active energy ray-curable adhesive to the second surface of the polarizer in the one-sided protective polarizing film in the step (1), It is preferable to apply. Although it depends on the type and viscosity of the active energy ray-curable adhesive, the adhesive was applied to the second surface of the polarizer in order to apply the adhesive to the second surface of the polarizer with many streaks and irregularities. It is preferable to attach the second transparent protective film after a while. By setting the time after application of the adhesive to 2 seconds or more, it is possible to apply the adhesive to the polarizing element surface of the adhesive more than immediately after application, and to prevent air bubbles from being caught when the second transparent protective film is attached. It can be further reduced. The elapsed time is more preferably 4 seconds or more, and further preferably 6 seconds or more. If the elapsed time is too long, the coating liquid permeates the substrate too much and the adhesive single layer becomes thin, so that the adhesive cannot be removed. Therefore, the elapsed time is preferably 30 seconds or less.

As the second transparent protective film, the same material exemplified in the first transparent protective film can be used, and a film having the same thickness can be used. Further, as the second transparent protective film, one having the same material and thickness as the first transparent protective film may be used, or one having a different material and thickness may be used. The second transparent protective film can be appropriately selected and used.

<Process (3)>
Next, after the step (2) is performed, the active energy ray-curable adhesive is irradiated with active energy rays to form an adhesive layer in the step (3). Examples of the active energy ray include ultraviolet rays and electron beams.

When the ultraviolet curable adhesive is adopted, any appropriate ultraviolet irradiation condition can be adopted as long as the adhesive can be cured. The dose of ultraviolet rays is preferably from 100 to 500 mJ / cm ² in accumulated light quantity, and even more preferably 200 to 400 mJ / cm ^2.

When the electron beam curable adhesive is adopted, any appropriate conditions can be adopted as the electron beam irradiation conditions as long as the adhesive can be cured. For example, in electron beam irradiation, the acceleration voltage is preferably 5 kV to 300 kV, and more preferably 10 kV to 250 kV. If the acceleration voltage is less than 5 kV, the electron beam may not reach the adhesive and curing may be insufficient. If the acceleration voltage exceeds 300 kV, the penetrating force through the sample is too strong and the electron beam bounces off, and a transparent protective film or There is a risk of damaging the polarizer. The irradiation dose is 5 to 100 kGy, more preferably 10 to 75 kGy.

The electron beam irradiation is usually performed in an inert gas, but if necessary, it may be performed in the atmosphere or under conditions in which a small amount of oxygen is introduced. Depending on the material of the transparent protective film, by appropriately introducing oxygen, oxygen inhibition can be caused on the surface of the transparent protective film that is first hit by the electron beam, and damage to the transparent protective film can be prevented, only for the adhesive. The electron beam can be efficiently irradiated.

The irradiation direction of the active energy rays in the step (3) can be any appropriate direction, but the irradiation from the first transparent protective film side is extra because the light is absorbed by the polarizer. Since irradiation is required, it is preferable to irradiate from the second transparent protective film side from the viewpoint of effective irradiation light.

The method for producing a polarizing film of the present invention includes the steps (1) to (3), but can include steps other than the above steps. For example, in the step (1), a step of performing a dry treatment on the second surface of the polarizer before applying the active energy ray-curable adhesive to the second surface of the polarizer in the one-side protection polarizing film. Can be provided. Specific examples of the dry treatment include corona treatment and plasma treatment. By performing the dry treatment, the surface modification treatment of the second surface of the polarizer is performed, which is preferable in improving the wettability and adhesiveness of the adhesive.

Further, when the polarizer (for both the first surface and the second surface) and the transparent protective film are bonded together, an easy-adhesion layer can be provided between the transparent protective film and the adhesive layer. The easy-adhesion layer can be formed of, for example, various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone-based material, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, and the like. These polymer resins may be used alone or in combination of two or more. Further, other additives may be added to form the easy-adhesion layer. Specifically, a tackifier, an ultraviolet absorber, an antioxidant, a stabilizer such as a heat-resistant stabilizer, or the like may be used.

The easy-adhesion layer is usually provided in advance on the transparent protective film, and the easy-adhesion layer side of the transparent protective film and the polarizer are bonded to each other by an adhesive layer. The easy-adhesive layer is formed by applying a material for forming the easy-adhesive layer onto a transparent protective film by a known technique and drying it. The material for forming the easy-adhesion layer is usually adjusted as a solution diluted to an appropriate concentration in consideration of the thickness after drying, the smoothness of coating, and the like. The thickness of the easy-adhesion layer after drying is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm, and further preferably 0.05 to 1 μm. A plurality of easy-adhesive layers can be provided, but even in this case, it is preferable that the total thickness of the easy-adhesive layers is within the above range.

When the polarizing film of the present invention is produced in a continuous line, the line speed depends on the curing time of the adhesive, but is preferably 1 to 500 m / min, more preferably 5 to 300 m / min, and further preferably 10 to 100 m / min. Is. If the line speed is too low, the productivity is poor, or the damage to the transparent protective film is too great, and a polarizing film that can withstand durability tests cannot be produced. If the line speed is too high, the adhesive may not be sufficiently cured and the desired adhesiveness may not be obtained.

As described above, a polarizing film having a first transparent protective film and a second transparent protective film on both sides of the polarizing element can be obtained, but a hard coat layer and antireflection are provided on the surface of the transparent protective film to which the polarizer is not adhered. A functional layer such as a layer, an anti-sticking layer, a diffusion layer or an anti-glare layer can be provided. The functional layers such as the hard coat layer, the antireflection layer, the sticking prevention layer, the diffusion layer and the antiglare layer can be provided on the transparent protective film itself, and are separately provided separately from the transparent protective film. You can also do it.

The polarizing film of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited, but is used for forming, for example, a reflecting plate, a transflective plate, a retardation plate (including a wave plate such as 1/2 or 1/4), a liquid crystal display device such as a viewing angle compensation film, and the like. One or two or more optical layers that may be used can be used. In particular, a reflective polarizing film or a semi-transmissive polarizing film in which a reflecting plate or a semi-transmissive reflecting plate is further laminated on the polarizing film of the present invention, an elliptically polarizing film or a circularly polarized light in which a retardation plate is further laminated on a polarizing film. A wide viewing angle polarizing film in which a viewing angle compensating film is further laminated on a film or a polarizing film, or a polarizing film in which a brightness improving film is further laminated on a polarizing film is preferable.

An optical film in which the above optical layer is laminated on a polarizing film can also be formed by a method of sequentially and separately laminating in a manufacturing process of a liquid crystal display device or the like, but a pre-laminated optical film is of good quality. It is excellent in stability and assembly work, and has an advantage that the manufacturing process of a liquid crystal display device and the like can be improved. An appropriate adhesive means such as an adhesive layer may be used for laminating. When adhering the above-mentioned polarizing film and other optical films, their optical axes can be arranged at an appropriate arrangement angle according to a target phase difference characteristic or the like.

An adhesive layer for adhering to other members such as a liquid crystal cell may be provided on the above-mentioned polarizing film or an optical film in which at least one polarizing film is laminated. The pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer is not particularly limited, and for example, a polymer based on an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer, a rubber-based polymer, or the like is appropriately selected. Can be used. In particular, an acrylic pressure-sensitive adhesive that has excellent optical transparency, exhibits appropriate wettability, cohesiveness, and adhesiveness, and has excellent weather resistance and heat resistance can be preferably used.

The adhesive layer may be provided on one side or both sides of a polarizing film or an optical film as a superimposing layer having a different composition or type. Further, when provided on both sides, adhesive layers having different compositions, types and thicknesses can be formed on the front and back surfaces of the polarizing film or the optical film. The thickness of the adhesive layer can be appropriately determined according to the purpose of use, adhesive strength, etc., and is generally 1 to 500 μm, preferably 1 to 200 μm, and particularly preferably 1 to 100 μm.

The exposed surface of the adhesive layer is temporarily covered with a separator for the purpose of preventing contamination until it is put into practical use. As a result, it is possible to prevent the adhesive layer from coming into contact with the adhesive layer in the usual handling state. Except for the above thickness conditions, the separator may be a suitable thin leaf such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet or metal leaf, or a laminate thereof, and if necessary, a silicone-based separator or the like. Appropriate conventional ones such as those coated with an appropriate release agent such as long-chain alkyl type, fluorine type and molybdenum sulfide can be used.

The polarizing film or optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, the liquid crystal display device is generally formed by appropriately assembling a liquid crystal cell, a polarizing film or an optical film, and if necessary, components such as a lighting system, and incorporating a drive circuit. There is no particular limitation except that the polarizing film or the optical film according to the invention is used, and the conventional method can be applied. As the liquid crystal cell, any type such as TN type, STN type, and π type can be used.

An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing film or an optical film is arranged on one side or both sides of the liquid crystal cell, or a lighting system using a backlight or a reflector can be formed. In that case, the polarizing film or optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When polarizing films or optical films are provided on both sides, they may be the same or different. Further, when forming the liquid crystal display device, for example, an appropriate component such as a diffuser plate, an anti-glare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffuser plate, and a backlight is placed in one layer or at an appropriate position. Two or more layers can be arranged.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. In addition, each part and% in each example is based on weight.
A protective polarizing film was produced.

<Preparation of single-sided protective polarizing film (1)>
In order to produce a thin polarizing film, first, a laminated body in which a 9 μm-thick PVA layer is formed on an amorphous PET substrate is subjected to aerial auxiliary stretching at a stretching temperature of 130 ° C. to produce a stretched laminated body, and then stretching. A colored laminate is produced by dyeing the laminate, and the colored laminate is further stretched integrally with the amorphous PET substrate by stretching in boric acid water at a stretching temperature of 65 ° C. so that the total stretching ratio becomes 5.94 times. An optical film laminate containing a PVA layer having a thickness of 4 μm was produced. The PVA molecules in the PVA layer formed on the amorphous PET substrate by such two-step stretching are highly oriented, and the iodine adsorbed by dyeing is highly oriented in one direction as a polyiodine ion complex. It was possible to produce an optical film laminate containing a PVA layer having a thickness of 4 μm, which constitutes a high-performance polarizing film. Further, while applying a polyvinyl alcohol-based adhesive to the surface (first surface) of the polarizing film of the optical film laminate, a saponified 40 μm-thick triacetyl cellulose film (first transparent protective film) was attached. After that, the amorphous PET base material was peeled off. Hereinafter, this is referred to as a thin single-protective polarizing film (1).

<Second transparent protective film>
A 60 μm-thick Zeonoa film (manufactured by ZEON Corporation) treated with corona was used.

(Adjustment of active energy ray-curable adhesive)
Each of the following components is mixed at a ratio of 40 parts of compound (a), 20 parts of compound (b), 40 parts of compound (c) and 3 parts of a photopolymerization initiator, and stirred at 50 ° C. for 1 hour to cure active energy rays. A mold adhesive was obtained.
Radical Polymerizable Compound (a): HEAA (Hydroxyethyl acrylamide), manufactured by Kojinsha;
Radical polymerizable compound (b): Light acrylate BP-4EAL (EP adduct diacrylate of bisphenol A), manufactured by Kyoei Chemical Co., Ltd .;
Radical Polymerizable Compound (c): ACMO (Acryloyl Morpholine), manufactured by Kojinsha;
Photopolymerization Initiator: IRGACURE819 (bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide), manufactured by BASF.

<Measurement of adhesive viscosity>
The viscosity of the adhesive was measured with a precision rotary viscometer.

Example 1
(Step 1)
The thickness of the final adhesive layer is applied to the second surface of the single protective polarizing film (1) by using a microgravure coater (gravure roll: # 180, rotation speed 140% / line speed). Was applied so that the thickness was 600 nm.

(Step 2)
Then, after 10 seconds had passed after applying the adhesive, the second transparent protective film was bonded with a roll machine via the adhesive.

(Step 3)
Next, ultraviolet rays were irradiated from the bonded second transparent protective film side to obtain a polarizing film having transparent protective films on both sides. The line speed was 20 m / min, and the irradiation amount of ultraviolet rays was 700 mJ / cm ² in total light intensity.

Examples 2-5 and Comparative Example 1
Examples 1 except that the coated surface of the adhesive, the thickness of the adhesive layer, the time until bonding after coating, the ratio of each compound of the adhesive, and the viscosity were changed as shown in Table 1. A polarizing film was produced in the same manner as in 1.

[evaluation]
The polarizing films obtained in Examples and Comparative Examples were evaluated as follows. The results are shown in Table 1.

<Appearance evaluation>
The appearance of the obtained polarizing film was observed with an optical microscope, and bubbles having a maximum diameter of 5 μm to 200 μm were counted. The results are shown in Table 1.

Claims (5)

A method for manufacturing a polarizing film in which first and second transparent protective films are provided on the first and second surfaces, which are both sides of a polarizing element.
The polarizer is a polyvinyl alcohol-based resin.
The thickness of the second transparent protective film is 5 to 200 μm.
A step (1) of applying an active energy ray-curable adhesive to the second surface of the polarizing element in the single-sided protective polarizing film in which the first transparent protective film is provided on the first surface of the polarizing element.
The step (2) of laminating the second transparent protective film via the active energy ray-curable adhesive, and
With respect to the active energy ray-curable adhesive, and an active energy ray, forming an adhesive layer (3), only it contains,
The polarizer is a continuous web polarizing film made of a polyvinyl alcohol-based resin in which a bicolor substance is oriented, and the one-sided protective polarizing film is a polyvinyl alcohol-based film formed on a thermoplastic resin base material. A laminate containing a resin layer is stretched in a two-step stretching step consisting of auxiliary stretching in the air and stretching in water borate, and is obtained by stretching the surface of the polarizing film of the optical film laminate via a polyvinyl alcohol-based adhesive layer. After the first transparent protective film is attached, the thermoplastic resin base material is peeled off.
In the step (1), after applying the active energy ray-curable adhesive to the second surface of the polarizer in the one-side protective polarizing film, the step (2) is performed after 2 seconds or more have passed. A characteristic method for manufacturing a polarizing film. The method for producing a polarizing film according to claim 1, wherein the active energy ray-curable adhesive has a viscosity of 10 to 350 cps (25 ° C.). The step (1) includes a step of applying a dry treatment to the second surface of the polarizing element before applying the active energy ray-curable adhesive to the second surface of the polarizing element in the one-side protection polarizing film. The method for producing a polarizing film according to claim 1 or 2. The method for producing a polarizing film according to any one of claims 1 to 3 , wherein the irradiation of the active energy rays in the step (3) is performed from the side of the second transparent protective film. The method for producing a polarizing film according to any one of claims 1 to 4 , wherein the thickness of the adhesive layer formed by the step (3) is 300 nm to 1.3 μm.