JP2019215574A - Method of performing activation treatment on and manufacturing method for optical film, optical film, and image display device - Google Patents

Abstract

To provide a method of performing activation treatment on a laminated optical film with which an adhesive property can be improved and the occurrence of appearance defects can be prevented, and a manufacturing method for the optical film.SOLUTION: In a method of conveying an optical film along a roll and performing activation treatment on the optical film on the opposite side of the roll, the activation treatment is performed while the roll is cooled. The activation treatment is preferably at least one of corona discharge treatment, plasma treatment, and glow discharge treatment, and the optical film is preferably at least one of a polarizer and a transparent protective film.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for activating an optical film and a method for producing the same. The invention also relates to an optical film obtained by the method. The optical film can be used alone or by laminating it to form an image display device such as a liquid crystal display (LCD), an organic EL display, a CRT, or a PDP.

  The liquid crystal display device visualizes the polarization state by switching of liquid crystal, and from the display principle, an optical film such as a polarizing film in which a transparent protective film is bonded to both surfaces of a polarizer with an adhesive layer is used. I have. As a polarizer, for example, an iodine-based polarizer having a structure in which iodine is adsorbed on polyvinyl alcohol and stretched has a high transmittance and a high degree of polarization, and thus is widely used as the most general polarizer. As the transparent protective film, triacetyl cellulose having high moisture permeability is used.

  As the adhesive used for forming the adhesive layer, for example, a so-called water-based adhesive obtained by dissolving a polyvinyl alcohol-based material in water is used. However, when the polyvinyl alcohol-based adhesive is left under a high temperature and high humidity for a long time, the film absorbs moisture and the adhesive strength is reduced, so that the film is easily peeled or the dimensional stability of the polarizing film is reduced. There is a problem that a hue change of the liquid crystal display occurs. To solve the above problem, it has been proposed that the surface of a triacetyl cellulose film used as a transparent protective film is saponified to improve the adhesive strength between the adhesive and the transparent protective film (Patent Document 1). As the adhesive, an adhesive containing a polyvinyl alcohol-based resin containing an acetoacetyl group and a crosslinking agent has been proposed (Patent Document 2).

  On the other hand, it has been proposed to use a curable adhesive such as a thermosetting type or an active energy ray-curing type instead of the water-based adhesive (Patent Document 3). However, even when these curable adhesives were used, the adhesive strength between the polarizer and the transparent protective film was not sufficient.

  Further, Patent Document 4 described below describes a method for producing a polarizing film in which the occurrence of reverse curl and wave curl is suppressed by curing an adhesive while being in close contact with an opposing roll heated to 40 ° C. during UV treatment. Have been. However, such a method does not anticipate the occurrence of foreign matter defects, nor does it describe or suggest a method of preventing the occurrence.

JP-A-56-50301 JP-A-7-198945 Patent No. 3511111 JP 2009-134190 A

  When two or more optical films are laminated via an adhesive layer, it is important to improve the adhesive strength. In particular, when the optical film is a polarizing film, it is required to further improve the adhesive strength between the polarizer and the transparent protective film. Activation methods such as corona discharge treatment, plasma treatment and glow discharge treatment may be mentioned as methods for improving the adhesiveness of the optical film.However, depending on the treatment conditions, appearance defects may occur on the optical film after the activation treatment. Occurred in some cases. In other words, although the activation treatment is indispensable for improving the adhesiveness of the optical film, appearance defects are caused by the activation treatment, and it is difficult to achieve both improvement of the adhesion of the optical film and prevention of appearance defects. It was a fact.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for activating an optical film and a method for manufacturing the same, which are capable of achieving both improved adhesion and prevention of appearance defects in a laminated optical film.

  Another object of the present invention is to provide an optical film obtained by the production method. Further, another object of the present invention is to provide an image display device such as a liquid crystal display device using the optical film.

In order to solve the above-mentioned problems, the present inventors have first conducted intensive studies on the mechanism of appearance defects occurring when activating an optical film. as a result,
(1) High energy electrons and ions collide with the surface of the optical film due to the discharge for the activation treatment, and radicals and ions are generated on the surface of the optical film.
(2) These react with surrounding N ₂ , O ₂ , H _{2 and the} like to introduce polar reactive groups such as a carboxyl group, a hydroxyl group, a cyano group and the like, and at the same time, an oxalate (ammonium oxalate ((NH ₄ ) ₂ C ₂ O ₂ )) are also produced.
(3) The inventors have found that the generation of oxalate and the like is a cause of depositing on the optical film and causing appearance defects. Based on these findings, further investigations revealed that by performing the activation treatment while cooling the optical film, it is possible to prevent the occurrence and accumulation of appearance defects such as oxalate caused by the above. did. The present invention has been obtained as a result of such findings.

  That is, the present invention is a method of carrying an optical film along a roll and performing an activation process on the optical film from the opposite side of the roll, wherein the activation process is performed while cooling the roll. And an activation method for an optical film.

  In the method for activating an optical film, it is preferable that the activation treatment is at least one of a corona discharge treatment, a plasma treatment, and a glow discharge treatment.

  In the method for activating an optical film, the optical film is preferably at least one of a polarizer and a transparent protective film.

In the above-mentioned method for activating an optical film, it is preferable that a discharge amount of the activation treatment is 100 to 2000 W · min / m ² .

  In the method for activating an optical film, it is preferable that the roll is cooled by passing a cooling medium through the roll.

  Further, the present invention is a method for producing an optical film in which another optical film is laminated via an adhesive layer on at least one surface of the optical film, wherein the optical film has a side on which the adhesive layer is laminated. An activation treatment step of performing the activation treatment method according to any of the above, and a coating step of applying an adhesive to the surface of the optical film on which the activation treatment has been performed and laminating an adhesive layer. And a laminating step of laminating the optical film on which the adhesive layer is laminated and the other optical film via the adhesive layer.

  In the method for producing an optical film, the optical film is a polarizing film provided with a transparent protective film on at least one surface of a polarizer via an adhesive layer, and at least one of the polarizer and the transparent protective film. On the other hand, an activation treatment step of performing the activation treatment method according to any one of the above, and an adhesive on the activated surface of the polarizer or the activated surface of the transparent protective film, It is preferable to have a coating step of applying and laminating an adhesive layer, and a laminating step of bonding the polarizer and the transparent protective film via the adhesive layer.

  Further, the present invention relates to an optical film obtained by the above-mentioned manufacturing method, and an image forming apparatus using the optical film.

  In the present invention, along with the outer peripheral surface of the roll, when performing the activation process while closely contacting the optical film, by performing the activation process of the optical film while cooling the roll, generated and deposited on the optical film And appearance defects due to oxalate and the like can be prevented.

  In general, when a discharge treatment is employed as the activation treatment method, when the discharge treatment amount during the activation treatment is increased, the amount of functional groups such as hydroxyl groups introduced on the optical film and contributing to the improvement of the adhesiveness increases. Therefore, the adhesiveness with another optical film via the adhesive layer is improved. However, as the amount of discharge treatment at the time of the activation treatment is increased, the amount of oxalate or the like that causes appearance defects also increases, so that both improvement in the adhesiveness of the optical film and prevention of appearance defects can be achieved. The difficulty is as described above. However, in the present invention, even if the discharge treatment amount during the activation treatment is increased in order to improve the adhesiveness of the optical film, the amount of oxalate and the like can be significantly reduced. It is possible to achieve both the prevention of the occurrence of the noise.

  The method for activating an optical film according to the present invention is useful when activating a polarizer and / or a transparent protective film among optical films. Generally, when an optical film is activated, the lower the moisture content of the optical film, the smaller the amount of functional groups such as hydroxyl groups that can be introduced onto the optical film, and the smaller the degree of improvement in adhesiveness. However, when the discharge treatment amount at the time of the activation treatment is increased, the amount of the functional group introduced onto the optical film increases, and the adhesiveness is improved even when the moisture content of the optical film is low. Therefore, the method for activating an optical film according to the present invention is extremely useful when activating an optical film having a low moisture content, particularly a polarizer and / or a transparent protective film.

  In the method for producing an optical film having the activation treatment method for an optical film according to the present invention as an activation treatment step, an optical film having excellent adhesion between laminated optical films and having significantly reduced appearance defects is produced. can do.

  In particular, in a method for producing a polarizing film as an optical film, a polarizing film having significantly reduced appearance defects can be produced while enhancing the adhesion between the polarizer and the transparent protective film.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows one Embodiment of the activation processing method of the optical film which concerns on this invention. Schematic showing another embodiment of the method for activating the optical film according to the present invention.

  In the method for activating an optical film according to the present invention, when performing the activation process while closely contacting the optical film along the outer peripheral surface of the roll, the activation process of the optical film is performed while cooling the roll. In particular, the present invention is useful as an activation treatment method for an optical film having a low water content and requiring an increased discharge treatment amount when performing an activation treatment, specifically, for example, a polarizer or a transparent protective film.

<Polarizer>
The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include, for example, a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, a hydrophilic polymer film such as an ethylene-vinyl acetate copolymer-based partially saponified film, and dichroic properties of iodine and a dichroic dye. Examples thereof include a uniaxially stretched film obtained by adsorbing a substance, and a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrochlorinated product of polyvinyl chloride. Among these, a polarizer composed 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 10 to 80 μm. The moisture content of a polarizer having a general thickness is about 10 to 30% within one hour after drying. The thickness of the polarizer is preferably from 10 to 30 μm, and most preferably from 15 to 25 μm. The water content of the polarizer is preferably 10 to 25%, most preferably 15 to 20%.

  The moisture content of the polarizer can be adjusted in any suitable way. For example, there is a method of controlling by adjusting the conditions of the drying step in the manufacturing process of the polarizer.

  The water content of the polarizer is measured by the following method. That is, the polarizer was cut into a size of 100 × 100 mm, and the initial weight of the sample was measured. Subsequently, the sample was dried at 120 ° C. for 2 hours, the dry weight was measured, and the moisture content was measured by the following equation. Moisture percentage (% by weight) = {(initial weight−dry weight) / initial weight} × 100. The weight was measured three times each, and the average value was used.

  A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching can be produced by, for example, dyeing polyvinyl alcohol by immersing it in an aqueous solution of iodine, and stretching the film to 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. By washing the polyvinyl alcohol-based film with water, dirt on the surface of the polyvinyl alcohol-based film and an anti-blocking agent can be washed, and by swelling the polyvinyl alcohol-based film, the effect of preventing unevenness such as uneven dyeing can be obtained. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be stretched and then dyed with iodine. Stretching can be performed in an aqueous solution of 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. Such a thin polarizer preferably has less thickness unevenness, is excellent in visibility, is excellent in durability due to small dimensional change, and can be made thinner as a polarizing film.

  Note that the thin polarizer has a lower moisture content than a polarizer having a general thickness, and is about 0 to 10% within one hour after drying. Therefore, when an activation treatment is applied to a thin polarizer to improve the adhesiveness, it is necessary to necessarily increase the discharge treatment amount. Therefore, the activation treatment method according to the present invention is particularly useful as an activation treatment method for a thin polarizer. The thickness of the thin polarizer is preferably 1 to 7 μm, most preferably 2 to 6 μm. The water content of the polarizer is preferably 1 to 5%, and most preferably 1 to 3%.

  Representative examples of the thin polarizer include Japanese Patent Application Laid-Open Nos. 51-069694 and 2000-338329, WO2010 / 100917, pamphlet of PCT / JP2010 / 001460, and Japanese Patent Application No. 2010-001460. Thin polarizing films described in Japanese Patent Application No. 269002 and Japanese Patent Application No. 2010-263892 can be exemplified. These thin polarizing films can be obtained by a production method including a step of stretching a polyvinyl alcohol-based resin (hereinafter, also referred to as a PVA-based resin) layer and a resin substrate for stretching in a laminated state and a step of dyeing. According to this production method, even if the PVA-based resin layer is thin, it can be stretched without any trouble such as breakage due to stretching, because it is supported by the stretching resin base material.

  WO 2010/100917 pamphlet, PCT / PCT, and the like. As for the thin polarizing film, WO2010 / 100917, PCT / JP 2010/001460, or those obtained by a production method including a step of stretching in an aqueous boric acid solution as described in Japanese Patent Application No. 2010-269002 or Japanese Patent Application No. 2010-263892 are preferable, and particularly preferable. What is obtained by the manufacturing method including the process of auxiliary | assistant air drawing before extending | stretching in a boric-acid aqueous solution as described in Japanese Patent Application No. 2010-269002 or Japanese Patent Application No. 2010-263692 is preferable.

  The thin high-performance polarizing film described in the specification of PCT / JP2010 / 001460 described above is a thin type having a thickness of 7 μm or less made of a PVA-based resin in which a dichroic substance is oriented and formed integrally with a resin base material. It is a high-performance polarizing film having optical characteristics such that a single transmittance is 42.0% or more and a degree of polarization is 99.95% or more.

  The thin high-performance polarizing film forms a PVA-based resin layer by coating and drying a PVA-based resin on a resin base material having a thickness of at least 20 μm, and dyes the generated PVA-based resin layer with a dichroic material. The dichroic substance is adsorbed on the PVA-based resin layer by dipping in the liquid, and the PVA-based resin layer adsorbed on the dichroic substance is integrated with the resin base material in a boric acid aqueous solution to obtain a total stretching ratio based on the total stretch ratio. It can be manufactured by stretching so as to be at least 5 times the length.

  Also, a method for producing a laminated film including a thin high-performance polarizing film in which dichroic substances are oriented, comprising a resin base material having a thickness of at least 20 μm and a PVA-based resin on one surface of the resin base material A step of producing a laminate film including a PVA-based resin layer formed by applying and drying an aqueous solution, and the lamination including a resin substrate and a PVA-based resin layer formed on one surface of the resin substrate. A step of immersing the body film in a dye solution containing a dichroic substance to adsorb the dichroic substance to the PVA-based resin layer contained in the laminated film; and a step of adsorbing the dichroic substance to the PVA-based resin layer. Stretching the laminate film including the resin layer in a boric acid aqueous solution so that the total stretching ratio becomes 5 times or more of the original length; and forming the PVA-based resin layer adsorbing the dichroic substance on the resin base. Stretched together with the material As a result, on one side of the resin substrate, a PVA-based resin layer in which a dichroic substance is oriented, the thickness is 7 μm or less, the single transmittance is 42.0% or more, and the degree of polarization is 99.95% or more. The thin high-performance polarizing film can be manufactured by including a step of manufacturing a laminated film in which a thin high-performance polarizing film having the above optical characteristics is formed.

  In the present invention, as a polarizer having a thickness of 10 μm or less, a continuous web polarizing film made of a PVA-based resin in which a dichroic substance is oriented, and a polyvinyl alcohol-based resin layer formed on a thermoplastic resin substrate Can be used as obtained by stretching a laminate containing the above in a two-stage stretching step consisting of auxiliary stretching in air and stretching in boric acid in water. As the thermoplastic resin substrate, an amorphous ester-based thermoplastic resin substrate or a crystalline ester-based thermoplastic resin substrate is preferable.

The thin polarizing film disclosed in the above-mentioned Japanese Patent Application No. 2010-269002 or 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 has an amorphous property. The laminate including the PVA-based resin layer formed on the ester-based thermoplastic resin base material was stretched in a two-stage stretching step including an aerial auxiliary stretching and a boric acid in-water stretching to have a thickness of 10 μm or less. Things. When such a thin polarizing film has a single transmittance of T and a polarization degree of P, P>-(10 ^0.929T-42.4 -1) × 100 (where T <42.3), and P ≧ It is preferable to have optical characteristics satisfying the condition of 99.9 (where T ≧ 42.3).

  Specifically, the thin polarizing film is formed by stretching a PVA-based resin layer formed on an amorphous ester-based thermoplastic resin substrate of a continuous web in the air at a high temperature in the air. A step of producing a product, and a coloring intermediate formation comprising a PVA-based resin layer in which a dichroic substance (preferably iodine or a mixture of iodine and an organic dye) is oriented by adsorbing the dichroic substance on the stretched intermediate product Thin film comprising: a step of forming a product; and a step of forming a polarizing film having a thickness of 10 μm or less, comprising a PVA-based resin layer in which a dichroic substance is oriented, by stretching a colored intermediate product in boric acid in water. It can be manufactured by the manufacturing method described above.

In this production method, the total stretch ratio of the PVA-based resin layer formed on the amorphous ester-based thermoplastic resin base material by the high-temperature stretching in air and the stretching in boric acid in water is set to be 5 times or more. desirable. The liquid temperature of the boric acid aqueous solution for drawing in boric acid in water can be 60 ° C. or higher. Before stretching the colored intermediate product in an aqueous boric acid solution, it is preferable to perform an insolubilization treatment on the colored intermediate product. In this case, the colored intermediate product is added to an aqueous boric acid solution having a liquid temperature not exceeding 40 ° C. Is desirably carried out by immersion. The non-crystalline ester-based thermoplastic resin base material is non-crystalline polyethylene containing copolymerized polyethylene terephthalate obtained by copolymerizing isophthalic acid, copolymerized polyethylene terephthalate obtained by copolymerizing cyclohexane dimethanol, or other copolymerized polyethylene terephthalate. It can be terephthalate and is preferably made of a transparent resin, and its thickness can be at least seven times the thickness of the PVA-based resin layer to be formed. Further, the stretching ratio in the high-temperature in-air stretching is preferably 3.5 times or less, and the stretching temperature in the high-temperature in-air stretching 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 performing high-temperature stretching in the air 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. . In the case where the high-temperature in-air stretching is performed by fixed-end uniaxial stretching, 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 preferred.
More specifically, a thin polarizing film can be manufactured by the following method.

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

  An amorphous PET substrate having a thickness of 200 μm and a 4 to 5% aqueous PVA 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 200 μm-thick amorphous PET substrate is coated with an aqueous PVA solution, dried at a temperature of 50 to 60 ° C., and a 7 μm-thick PVA layer is formed on the amorphous PET substrate. obtain.

  A 3 μm-thick thin high-performance polarizing film is manufactured from the laminate including the 7 μm-thick PVA layer through the following steps including a two-stage stretching step of auxiliary in-air stretching and stretching in boric acid in water. In the first-stage auxiliary aerial stretching step, the laminate including the 7 μm-thick PVA layer is integrally stretched with the amorphous PET base material to produce a stretched laminate including the 5 μm-thick PVA layer. Specifically, this stretched laminate is subjected to a stretching device provided in an oven set to a stretching temperature environment of 130 ° C. by applying a laminate including a 7 μm-thick PVA layer so that the stretching ratio becomes 1.8 times. The free end is uniaxially stretched. By this stretching treatment, the PVA layer included in the stretched laminate is changed into a 5 μm-thick PVA layer in which PVA molecules are oriented.

  Next, by a dyeing process, a colored laminate in which iodine is adsorbed on a 5 μm-thick PVA layer in which PVA molecules are oriented is generated. Specifically, this colored laminate is prepared by adding the stretched laminate to a dye solution containing iodine and potassium iodide at a liquid temperature of 30 ° C., and transmitting the single transmittance of the PVA layer constituting the high-performance polarizing film finally produced. The iodine is adsorbed on the PVA layer contained in the stretched laminate by immersing it for an arbitrary time so as to be 40 to 44%. In this step, the dyeing solution has water as a solvent, the iodine concentration is in the range of 0.12 to 0.30% by weight, and the potassium iodide concentration is in the range of 0.7 to 2.1% by weight. The ratio between the concentrations of iodine and potassium iodide is 1: 7. Incidentally, potassium iodide is required to dissolve iodine in water. More specifically, the stretched laminate is immersed 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, so that a 5 μm-thick PVA layer in which PVA molecules are oriented is formed. To produce a colored laminate to which is adsorbed.

  Further, the colored laminate is further stretched integrally with the amorphous PET substrate by the second stage of boric acid in water stretching step to produce an optical film laminate including a PVA layer constituting a high-performance polarizing film having a thickness of 3 μm. I do. Specifically, this optical film laminate is subjected to a stretching device provided 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, and the colored laminate is stretched. The film is uniaxially stretched at the free end so that the magnification becomes 3.3 times. More specifically, the temperature of the boric acid aqueous solution is 65 ° C. It also has a boric acid content of 4 parts by weight per 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 the adjusted iodine adsorption amount is first immersed in a boric acid aqueous solution for 5 to 10 seconds. Thereafter, the colored laminate is passed as it is between a plurality of sets of rolls having different peripheral speeds, which are stretching apparatuses provided in the processing apparatus, and freely stretched to have a stretching ratio of 3.3 times in 30 to 90 seconds. The film is uniaxially stretched. By this stretching treatment, the PVA layer contained in the colored laminate is changed into a 3 μm-thick PVA layer in which adsorbed iodine is unidirectionally oriented as a polyiodide ion complex in one direction. This PVA layer constitutes a high-performance polarizing film of the optical film laminate.

  Although not an essential step in the production of the optical film laminate, the washing step removed the optical film laminate from the aqueous boric acid solution and attached it to the surface of the 3 μm thick PVA layer formed on the amorphous PET substrate. Preferably, boric acid is washed with an aqueous solution of potassium iodide. Thereafter, the washed optical film laminate is dried by a drying process using hot air at 60 ° C. The washing step is a step for eliminating appearance defects such as boric acid precipitation.

  Similarly, it is not an essential step for the production of an optical film laminate, but 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 step. Then, after laminating the 80 μm-thick triacetyl cellulose film, the amorphous PET base material is peeled off, and the 3 μm-thick PVA layer can be transferred to the 80 μm-thick triacetyl cellulose film.

[Other steps]
The above method for producing a thin polarizing film may include other steps in addition to the above steps. Other steps include, for example, an insolubilization step, a cross-linking step, a drying (adjustment of moisture content) step, and the like. Other steps can be performed at any appropriate timing.
The insolubilization step is typically performed by immersing the PVA-based resin layer in a boric acid aqueous solution. By performing 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 based on 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 production of the laminate and before the dyeing step or the underwater stretching step.
The cross-linking step is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing the crosslinking treatment, the PVA-based resin layer can be provided with water resistance. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 4 parts by weight based on 100 parts by weight of water. When the crosslinking step is performed after the dyeing step, an iodide is preferably further added. By blending iodide, elution of iodine adsorbed on the PVA-based resin layer can be suppressed. The amount of iodide is preferably 1 to 5 parts by weight based on 100 parts by weight of water. Specific examples of iodide are as described above. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably from 20C to 50C. Preferably, the cross-linking step is performed before the second boric acid aqueous stretching step. In a preferred embodiment, the dyeing step, the cross-linking step, and the second drawing step in boric acid in water are performed in this order.

<Transparent protective film>
The material constituting the transparent protective film is not particularly limited, but a material having excellent transparency, mechanical strength, heat stability, moisture barrier properties, isotropy, and the like is 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; styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin) Polymers, polycarbonate polymers, and the like. In addition, polyethylene, polypropylene, polyolefin having a cyclo- or norbornene structure, polyolefin polymers such as ethylene-propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, and sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Blends of polymers and the like are also examples of the polymer forming the transparent protective film. The transparent protective film may contain one or more arbitrary appropriate additives. Examples of the additives include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. 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 moisture content of a general transparent protective film is about 0 to 7%, but in the activation treatment method according to the present invention, the transparent protective film having a low moisture rate, specifically, having a moisture rate of 0 to 1%. It is particularly useful as a method for activating certain transparent protective films.

  The method for activating the optical film according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing one embodiment of a method for activating an optical film according to the present invention. In the embodiment illustrated in FIG. 1, the optical film 3 is activated from the opposite side of the roll 1 while the optical film 3 is transported along the roll 1 disposed between the two guide rolls 21 and 22. At this time, the optical film is activated while the roll 1 is cooled.

  As a method of cooling the roll 1, for example, a method of circulating a coolant such as water in the roll 1 while passing the same is exemplified. As the refrigerant, not only water but also a refrigerant known to those skilled in the art can be used. In general, when performing the activation treatment, the surface of the roll 1 is heated up to about 80 to 100 ° C. because the surface of the roll 1 generates heat due to the discharge irradiation. In the present invention, the surface temperature of the roll 1 is cooled to 80 ° C. or less. Is preferably cooled to 50 ° C. or lower, more preferably 30 ° C. or lower. When the surface temperature of the roll 1 is cooled, the temperature of the optical film 3 becomes substantially the same as the surface temperature of the roll 1 because the optical film 3 is conveyed while being closely adhered along the outer peripheral surface of the roll 1. That is, by cooling the roll 1, the temperature of the optical film 3 is also cooled, and as a result, appearance defects on the optical film 3 are prevented from occurring. When water is passed as the refrigerant, the temperature of the water is not particularly limited, but is, for example, about 20 to 30 ° C.

Examples of the activation treatment method include a corona discharge treatment, a plasma treatment, a glow discharge treatment, an ozone treatment, and an itro treatment. In the case of corona discharge treatment, the roll 1 acts as a dielectric (earth) roll in FIG. Among the corona discharge treatments, an atmospheric pressure corona discharge treatment in which the external atmosphere indicated by 5 is an air atmosphere is preferable. In the case of the plasma processing, the roll 1 functions as a dielectric (earth) roll in FIG. Among the plasma treatments, the atmospheric pressure plasma treatment in which the external atmosphere indicated by 5 is the atmosphere (including N ₂ , O ₂ , Ar, etc.) is preferable. In the case of the glow discharge treatment, the roll 1 in FIG. 1 functions as a dielectric (earth) roll, and performs the glow discharge treatment from the treatment electrode 4 in an external atmosphere indicated by 5 in a vacuum.

  In the case of the intro processing, the roll 1 in FIG. 1 acts as a transport roll, and performs the intro processing from the flame source 4 under the atmosphere indicated by 5. In the case of the ozone treatment, the roll 1 acts as a transport roll in FIG. 1 and performs the ozone treatment from the ozone source 4 under the atmosphere indicated by 5.

Among the activation treatment methods, corona discharge treatment, plasma treatment, and / or glow discharge treatment, which can improve the adhesion improving effect and the appearance preventing effect in a good balance, are preferable. The discharge amount when the corona discharge treatment, the plasma treatment and / or the glow discharge treatment is employed is preferably a high discharge amount in order to improve the adhesiveness, and specifically, is 100 W · min / m ² or more. It is more preferably set to 400 W · min / m ² or more, and further preferably set to 1000 W · min / m ² or more. On the other hand, in order to effectively prevent appearance defects occurring on the optical film 3, the discharge amount during the activation treatment is preferably set to 2000 W · min / m ² or less, and 1500 W · min / m ^2. It is more preferably set to 1250 W · min / m ² or less. Further, among corona discharge treatment, plasma treatment or glow discharge treatment, from the viewpoint of productivity and equipment design, corona discharge treatment or plasma treatment is preferable, and furthermore, atmospheric pressure corona discharge treatment which can be carried out under atmospheric pressure, Atmospheric pressure plasma treatment is more preferred.

  FIG. 1 shows an embodiment in which the activation process is performed using the processing electrode 4. However, as shown in FIG. 2, the activation process may be performed by a discharge irradiated from the electrode roll 6 facing the roll 1. .

  The method for producing an optical film according to the present invention is a method for producing an optical film in which another optical film is laminated on at least one surface of the optical film via an adhesive layer, wherein the adhesive layer of the optical film is provided. An activation treatment step of performing the activation treatment method according to any one of claims 1 to 4, and an adhesive is applied to the surface on which the activation treatment of the optical film has been performed. And a laminating step of laminating the optical film on which the adhesive layer is laminated and the other optical film via the adhesive layer. As the optical film, a polarizer and / or a transparent protective film can be suitably used. In the present invention, in particular, the optical film is provided with a transparent protective film on at least one surface of the polarizer via an adhesive layer. A polarizing film, wherein at least one of a polarizer and a transparent protective film, an activation treatment step of performing the activation treatment method described above, and activation of a surface or a transparent protective film on which the activation treatment of the polarizer has been performed. An optical film having a coating step of applying an adhesive and laminating an adhesive layer on the treated surface, and a laminating step of bonding a polarizer and a transparent protective film through an adhesive layer. (Polarizing film) is useful as a production method.

  In the adhesive coating step, the coating method is appropriately selected depending on the viscosity of the adhesive 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.

  The optical films, especially the polarizer and the transparent protective film, are bonded together via the adhesive applied as described above. These laminations can be performed by a roll laminator or the like.

  After the bonding step, an adhesive layer is formed. The formation of the adhesive layer is performed according to the type of the adhesive. In particular, in the present invention, the adhesive includes an active energy ray-curable adhesive. The active energy ray-curable adhesive is an adhesive whose curing proceeds by an active energy ray such as an electron beam or an ultraviolet ray, and can be used in, for example, an electron beam-curable or ultraviolet-curable mode. The active energy ray-curable adhesive includes a cationic photopolymerization type and a photoradical polymerization type. Among them, the photocationic type can be suitably used in the present invention. When a photo-radical polymerization type active energy ray-curable adhesive is used as an ultraviolet ray-curable adhesive, the adhesive contains (A) a radical polymerizable compound and (B) a photo radical 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 or more carbon-carbon double bonds, a (meth) acryloyl group, or the like. In the present invention, among the (A) radically polymerizable compounds, the following general formula (1): CH ₂ ＣC (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 represents a — (CH ₂ ) _n —H group (where n is 0, 1 Or 2), and m represents 1 or 2).

  Specific examples of the N-substituted amide-based monomer represented by the general formula (1) include, for example, N-hydroxyethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide and the like can be mentioned. One of these N-substituted amide monomers can be used alone, or two or more can be used in combination.

  As the N-substituted amide-based monomer represented by the general formula (1), commercially available products can also be suitably used. Specifically, for example, N-hydroxyethyl acrylamide (trade name "HEAA", manufactured by Kojin Co., Ltd.), N-methoxymethyl acrylamide (trade name "NMMA", manufactured by MRC Unitech), N-butoxymethyl acrylamide (trade name) "NBMA" (manufactured by MRC Unitech), N-methoxymethyl methacrylamide (trade name "Wasmer 2MA", manufactured by Kasano Kosan Co., Ltd.) and the like.

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

  The active energy ray-curable adhesive comprises, as a radically polymerizable compound (A), an N-substituted amide monomer other than that represented by the general formula (1), a monofunctional monomer having various aromatic rings and a hydroxy group. It may contain (meth) acrylate, urethane (meth) acrylate, polyester (meth) acrylate, compounds having various (meth) acryloyl groups, and the like. However, in consideration of the adhesiveness and water resistance of the adhesive layer, the ratio of the N-substituted amide-based monomer represented by the general formula (1) to the total amount of the (A) radically polymerizable compound is 50 to 99. % By mass, more preferably 60 to 90% by mass.

  Examples of N-substituted amide monomers other than those represented by the general formula (1) include N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide , N-isopropylacrylamide, N-butyl (meth) acrylamide, N-hexyl (meth) acrylamide, aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide, mercaptomethyl (meth) acrylamide, mercaptoethyl (meth) acrylamide , N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine 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 be present as a substituent on the aromatic ring, but in the present invention, the hydroxy group is present as an organic group (a hydrocarbon group, particularly one bonded to an alkylene group) that bonds the aromatic ring to the (meth) acrylate. Are preferred.

  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 phenyl glycidyl ether, t-butylphenyl glycidyl ether, phenyl polyethylene glycol glycidyl ether, and the like. Specific examples of the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group include, for example, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-hydroxy-3-t-butylphenoxypropyl (meth) Acrylate and 2-hydroxy-3-phenyl polyethylene glycol propyl (meth) acrylate.

  Examples of the urethane (meth) acrylate include 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, or a polyalkylene glycol such as polyethylene glycol or polypropylene glycol. And the like.

  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. And alkyl (meth) acrylates having 1 to 12 carbon atoms, such as lauryl (meth) acrylate; alkoxyalkyl (meth) acrylate monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; ) 2-hydroxyethyl acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, (meth) ) Acrylic acid Hydroxyl-containing monomers such as 0-hydroxydecyl, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate; monomers containing acid anhydride groups such as maleic anhydride and itaconic anhydride; acrylic acid Adduct of caprolactone; styrenesulfonic acid, allylsulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, (meth) acrylamidopropanesulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalenesulfonic acid And sulfonic acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate. Also, (meth) acrylamide; maleimide, N-cyclohexylmaleimide, N-phenylmaleimide, etc .; aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyloxymethylene succinimide, and t-butylaminoethyl (meth) acrylate and 3- (3-pyridinyl) propyl (meth) acrylate. Nitrogen-containing monomers such as succinimide-based monomers such as (meth) acryloyl-6-oxyhexamethylene succinimide and N- (meth) acryloyl-8-oxyoctamethylene succinimide.

  The active energy ray-curable adhesive further comprises (C) a monomer having two or more carbon-carbon double bonds, particularly preferably a polyfunctional (meth) acrylate monomer, as the (A) radical polymerizable compound. When it is contained, it is preferable because the water resistance of the adhesive layer is improved. In consideration of the water resistance of the adhesive layer, the monomer having two or more carbon-carbon double bonds is more preferably hydrophobic. Monomers having two or more hydrophobic carbon-carbon double bonds, in particular, hydrophobic polyfunctional (meth) acrylate monomers include, for example, tricyclodecane dimethanol 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) acryl 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- (2-vinyloxyethoxy) ethyl (meth) acrylate, bisphenol A-EO adduct di (meth) acrylate, trimethylolpropane tri (meth) acrylate, neopentyl glycol hydroxypivalate (meth) Acrylic acid adduct, EO-modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, iso Anuric acid EO modified di (meth) acrylate, isocyanuric acid EO modified tri (meth) acrylate, ε-caprolactone modified tris ((meth) acryloxyethyl) isocyanurate, 1,1-bis ((meth) acryloyloxymethyl) ethyl Examples include isocyanate, a polymer of 2-hydroxyethyl (meth) acrylate and 1,6-diisocyanatehexane, 9,9-bis [4- (2- (meth) acryloyloxyethoxy) phenyl] fluorene, and the like.

  (A) The proportion of the monomer having two or more carbon-carbon double bonds to the total amount of the radically polymerizable compound is preferably 5 to 50% by mass, more preferably 9 to 40% by mass. . If this proportion 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 photo-radical generator generates a radical by irradiation with an active energy ray. (B) Examples of the photo radical generator include a hydrogen abstraction type photo radical generator and a cleavage type photo radical 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-iodonaphthalene. , 2-iodonaphthalene, 1-naphthol, 2-naphthol, 1-methoxynaphthalene, 2-methoxynaphthalene, naphthalene derivatives such as 1,4-dicyanonaphthalene, 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-prop-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-carbazolemethanol, 9-carbazolepropionic acid, 9-carbazolepropionitrile, 9-ethyl-3,6 -Dinitro-9H-carbazole, 9-ethyl-3-nitrocarbazole, 9-ethylcarbazole, 9-isopropylcarbazole, 9- (ethoxycarbonylmethyl) carbazole, 9- (morpholinomethyl) carbazole, 9-acetylcarbazole, 9- Allyl Lubazole, 9-benzyl-9H-carbazole, 9-carbazoleacetic acid, 9- (2-nitrophenyl) carbazole, 9- (4-methoxyphenyl) carbazole, 9- (1-ethoxy-2-methyl-propyl) -9H Carbazole, 3-nitrocarbazole, 4-hydroxycarbazole, 3,6-dinitro-9H-carbazole, 3,6-diphenyl-9H-carbazole, 2-hydroxycarbazole, 3,6-diacetyl-9-ethylcarbazole and the like Carbazole derivatives, benzophenone, 4-phenylbenzophenone, 4,4'-bis (dimethoxy) benzophenone, 4,4'-bis (dimethylamino) benzophenone, 4,4'-bis (diethylamino) benzophenone, methyl 2-benzoylbenzoate 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- Thioxanthone derivatives such as chloro-4-propoxythioxanthone and coumarin derivatives are exemplified.

  The cleavage type photoradical generator is a type of photoradical generator in which the compound is cleaved by irradiation with active energy rays to generate a radical. Specific examples thereof include arylalkyl such as benzoin ether derivatives and acetophenone derivatives. Examples include, but are not limited to, ketones, oxime ketones, acylphosphine oxides, S-phenyl thiobenzoates, titanocenes, and derivatives obtained by increasing the molecular weight thereof. Commercially available cleavage photoradical generators include 1- (4-dodecylbenzoyl) -1-hydroxy-1-methylethane, 1- (4-isopropylbenzoyl) -1-hydroxy-1-methylethane, 1-benzoyl -1-Hydroxy-1-methylethane, 1- [4- (2-hydroxyethoxy) -benzoyl] -1-hydroxy-1-methylethane, 1- [4- (acryloyloxyethoxy) -benzoyl] -1-hydroxy- 1-methylethane, diphenyl ketone, phenyl-1-hydroxy-cyclohexyl ketone, benzyldimethyl ketal, bis (cyclopentadienyl) -bis (2,6-difluoro-3-pyryl-phenyl) titanium, (η6-isopropylbenzene) -(Η5-cyclopentadienyl) -iron (II) hexaf Fluorophosphate, 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-1-dimethylaminopropane, 4- (methylthiobenzoyl) -1 -Methyl-1-morpholinoethane; and the like, but is not limited thereto.

  (B) The photoradical generator, that is, the hydrogen abstraction type or the cleavage type photoradical generator, can be used alone or in combination of two or more. Also, more preferable in terms of the curability of the composition in the present invention are one or more combinations of cleavage type photoradical generators. Among the cleavage-type photoradical generators, acylphosphine oxides are preferable, and more specifically, trimethylbenzoyldiphenylphosphine oxide (trade name “DAROCURE TPO”; manufactured by Ciba Japan), 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) is preferable.

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

  When the active energy ray-curable adhesive according to the present invention is used in an electron beam-curable adhesive, the adhesive (B) may be any of the photoradical generators. Further, a sensitizer may be added to increase the curing speed and sensitivity by an electron beam represented by a carbonyl compound or the like.

  Examples of the sensitizer include anthracene, phenothiazene, perylene, thioxanthone, and benzophenone thioxanthone. Further, as sensitizing dyes, thiopyrylium salt dyes, merocyanine dyes, quinoline dyes, styrylquinoline dyes, ketocoumarin dyes, thioxanthene dyes, xanthene dyes, oxonol dyes, cyanine dyes, rhodamine dyes And pyrylium salt-based dyes.

  As specific anthracene compounds, dibutoxyanthracene, dipropoxyanthraquinone (Anthracure UVS-1331, 1221 manufactured by Kawasaki Kasei Co., Ltd.) and the like are effective.

  When a sensitizer is added, its content 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 particularly preferably 0.1 to 3 parts by mass.

  The active energy ray-curable adhesive may contain various additives as other optional components as long as the objects and effects of the present invention are not impaired. Examples of such additives include polyamide, polyamide imide, polyurethane, polybutadiene, polychloroprene, polyether, polyester, styrene-butadiene block copolymer, petroleum resin, xylene resin, ketone resin, cellulose resin, fluorine-based oligomer, and silicone-based oligomer. , A polymer or oligomer such as a polysulfide oligomer; a polymerization inhibitor such as phenothiazine and 2,6-di-t-butyl-4-methylphenol; a polymerization initiation auxiliary agent; a leveling agent; a wettability improver; a surfactant; Agents; ultraviolet absorbers; silane coupling agents; inorganic fillers; pigments; However, in the active energy ray-curable adhesive, the content of the above-mentioned additive is preferably 0.005 to 20 parts by mass, preferably 0.01 to 10 parts by mass, based on the total amount of the active energy ray-curable adhesive. Is more preferably 0.1 to 5 parts by mass.

  The viscosity of the active energy ray-curable adhesive is preferably 10 to 300 cps (25 ° C.), more preferably 20 to 300 cps (25 ° C.), and further preferably 40 to 150 cps (25 ° C.). If the viscosity is 10 cps or less, the viscosity becomes too low, and the applied adhesive is applied to the back side of the film (single protective polarizing film), and the thickness of the adhesive layer is difficult to design. Further, if the viscosity exceeds 300 cps, the viscosity becomes too high, and if the line speed is increased, the application of the adhesive cannot be sufficiently performed, or the coating streaks are easily generated, which is preferable in terms of productivity. Absent.

  When the optical film is a polarizing film in which a polarizer and a transparent protective film are laminated with an adhesive layer interposed therebetween, when bonding the polarizer and the transparent protective film, there is an easy gap between the transparent protective film and the adhesive layer. An adhesive layer can be provided. The easy-adhesion layer can be formed of, for example, various resins having a polyester skeleton, polyether skeleton, polycarbonate skeleton, polyurethane skeleton, silicone, polyamide skeleton, polyimide skeleton, polyvinyl alcohol skeleton, and the like. These polymer resins can be used alone or in combination of two or more. Further, other additives may be added to the formation of the easily adhesive layer. Specifically, stabilizers such as tackifiers, ultraviolet absorbers, antioxidants, and heat stabilizers may be used.

  The easy-adhesion layer is usually provided in advance on the transparent protection film, and the easy-adhesion layer side of the transparent protection film and the polarizer are bonded to each other with an adhesive layer. The easy-adhesion layer is formed by applying and drying a material for forming the easy-adhesion layer on a transparent protective film by a known technique. The material for forming the easily adhesive 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 easily adhesive layer after drying is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm, and still more preferably 0.05 to 1 μm. Note that a plurality of easy-adhesion layers can be provided. In this case, it is preferable that the total thickness of the easy-adhesion layers be in the above range.

  When the polarizing film is manufactured 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 still more preferably 10 to 100 m / min. If the line speed is too low, the productivity is poor, or the damage to the transparent protective film is too large, and a polarizing film that can withstand a durability test or the like cannot be produced. If the line speed is too high, the curing of the adhesive becomes insufficient, and the desired adhesiveness may not be obtained.

  As described above, a polarizing film having a transparent protective film on at least one side of the polarizer is obtained.However, a hard coat layer, an antireflection layer, an anti-sticking layer, A functional layer such as a layer or an antiglare layer can be provided. The functional layers such as the hard coat layer, the antireflection layer, the anti-sticking layer, the diffusion layer and the antiglare layer can be provided on the transparent protective film itself, or separately provided separately from the transparent protective film. You can also.

  A polarizing film, which is a kind of optical film, can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, it is used for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including a wavelength plate such as や or や), a viewing angle compensation film, and the like. One or more optical layers that may be used may be used. In particular, as the polarizing film, a reflective polarizing film or a transflective polarizing film in which a reflecting plate or a transflective reflecting plate is further laminated, an elliptically polarizing film or a circularly polarizing film in which a retardation plate is further laminated on a polarizing film A wide viewing angle polarizing film in which a viewing angle compensation film is further laminated on a polarizing film, or a polarizing film in which a brightness enhancement film is further laminated on a polarizing film is preferable.

  An optical film obtained by laminating the above-mentioned optical layer on a polarizing film can also be formed by a method of sequentially laminating the optical film in a manufacturing process of a liquid crystal display device or the like. It is excellent in stability, assembling work, and the like, and has an advantage that a manufacturing process of a liquid crystal display device or the like can be improved. Appropriate bonding means such as an adhesive layer can be used for lamination. In bonding the above-mentioned polarizing film and other optical films, their optical axes can be arranged at an appropriate angle depending on the intended retardation characteristics and the like.

  The above-mentioned polarizing film or the optical film in which at least one polarizing film is laminated may be provided with an adhesive layer for bonding to another member such as a liquid crystal cell. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and for example, an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, and a polymer having a fluorine-based or rubber-based polymer as a base polymer are appropriately selected. Can be used. In particular, an acrylic adhesive having excellent optical transparency, exhibiting appropriate wettability, cohesiveness and adhesive adhesive properties and having excellent weather resistance and heat resistance can be preferably used.

  The pressure-sensitive adhesive layer may be provided on one side or both sides of a polarizing film or an optical film as a superposed layer of different compositions or types. When provided on both sides, it is also possible to form an adhesive layer having a different composition, type or thickness on the front and back of the polarizing film or optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined depending on the purpose of use, adhesive strength, and the like, and is generally 1 to 500 μm, preferably 1 to 200 μm, and particularly preferably 1 to 100 μm.

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

  The polarizing film or the optical film can be preferably used for forming various devices such as a liquid crystal display device. The formation of the liquid crystal display device can be performed according to a conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing film or an optical film, and an illumination system as necessary, and incorporating a driving circuit. There is no particular limitation except that a polarizing film or an optical film according to the present invention is used, and it can be in accordance with the conventional one. As for 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 or both sides of a liquid crystal cell, or a lighting system using a backlight or a reflector can be formed. In that case, the polarizing film or the optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When a polarizing film or an optical film is provided on both sides, they may be the same or different. Further, when forming the liquid crystal display device, for example, a suitable component such as a diffusion plate, an anti-glare layer, an antireflection film, a protection plate, a prism array, a lens array sheet, a light diffusion plate, a backlight, etc. Two or more layers can be arranged.

  Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. In addition, all parts and% in each example are based on weight.

<Preparation of polarizing film>
In order to produce a thin polarizing film, first, a laminate in which a 9 μm-thick PVA layer was formed on an amorphous PET base material was subjected to auxiliary stretching in the air at a stretching temperature of 130 ° C. to form a stretched laminate. A colored laminate is produced by dyeing the laminate, and the colored laminate is further stretched integrally with an amorphous PET substrate by stretching in a boric acid solution at a stretching temperature of 65 ° C. so that the total stretching ratio becomes 5.9 times. An optical film laminate comprising a 4 μm thick PVA layer was produced. By such two-stage stretching, the PVA molecules of the PVA layer formed on the amorphous PET substrate are highly oriented, and the iodine adsorbed by the dyeing is oriented unidirectionally as a polyiodide ion complex in one direction. An optical film laminate including a PVA layer having a thickness of 4 μm, which constitutes a highly functional polarizing film, could be produced. The moisture content of the PVA layer (thin polarizer) was 1.7% within one hour after drying.

  An active energy ray-curable adhesive composition (hydroxyethyl acrylamide (HEAA)) comprising a 4 μm thick optical film laminate including a PVA layer and a ZEONOR film (60 μm thick, manufactured by Zeon Corporation) as a compensator -50 parts, acryloylmorpholine (ACMO) -40 parts, New Frontier PGA-10 parts, Irgacure 907-2 parts as a polymerization initiator, and diethylthioxanthone (DETX) -0.9 parts as a photosensitizer. After bonding through the obtained adhesive layer, the amorphous PET base material was peeled off to produce an optical film in which a thin polarizer was laminated on a compensator.

Example 1
Using the apparatus shown in FIG. 1, using an optical film 3 laminated such that the thin polarizer is on the front side (the side where the compensator is in contact with the ground roll 1), and along the outer peripheral surface of the ground roll 1 The corona discharge treatment was performed using the treatment electrode 4 while the optical film 3 was transported while being in close contact with the optical film 3. The surface temperature of the earth roll 1 was cooled to 25 ° C., and the discharge amount during corona discharge was (250) W / m ² .

Examples 2 to 5
The activation treatment was performed in the same manner as in Example 1, except that the discharge treatment amount during the corona discharge treatment was changed to the amount shown in Table 1.

Example 6
The activation treatment was performed in the same manner as in Example 1, except that the corona discharge treatment was changed to the atmospheric pressure plasma treatment (discharge amount 250 W · min / m ² ).

  When performing the corona discharge treatment, the activation treatment was performed in the same manner as in Example 1 except that the earth roll 1 was not cooled.

  The appearance characteristics generated on the surfaces of the optical films activated by the activation treatment methods of Examples 1 to 6 and Comparative Example 1 were measured by the following methods. The results are shown in Table 1.

<Evaluation Method for Appearance Characteristics> Appearance Observation The optical film surfaces of the activated surfaces of Examples 1 to 6 and Comparative Example 1 were visually observed. In the case where there is at least one defect per 1 m ² , the result is indicated by x, and the results are shown in Table 1.

<Method of evaluating adhesive properties>
In the case where the adhesive was forcibly peeled off, the state where the adhesive and the optical film were not peeled off was evaluated as ○, and the state where the adhesive was peeled off at the interface between the adhesive and the optical film was evaluated as x.

From the results in Table 1, it can be seen that the optical films on which the activation treatment methods according to Examples 1 to 6 had good adhesive properties, hardly caused any appearance defects, and had good appearance properties. . On the other hand, it can be seen that in the optical film on which the activation treatment method according to Comparative Example 1 was performed, many appearance defects occurred, and the appearance characteristics deteriorated.

Claims (9)

Conveying the optical film along the roll, a method of performing an activation process of the optical film from the opposite side of the roll,
An activation treatment method for an optical film, wherein the activation treatment is performed while cooling the roll.   The activation treatment method for an optical film according to claim 1, wherein the activation treatment is at least one of a corona discharge treatment, a plasma treatment, and a glow discharge treatment.   The method for activating an optical film according to claim 1, wherein the optical film is at least one of a polarizer and a transparent protective film. The method for activating an optical film according to claim ² , wherein a discharge amount of the activation processing is 100 to 2000 W · min / m ² .   The method for activating an optical film according to claim 1, wherein the roll is cooled by passing a cooling medium through the roll. A method for producing an optical film in which another optical film is laminated via an adhesive layer on at least one surface of the optical film,
An activation treatment step of performing the activation treatment method according to any one of claims 1 to 4, on a surface of the optical film on which the adhesive layer is laminated,
On the surface on which the activation treatment of the optical film has been performed, a coating step of coating an adhesive and laminating an adhesive layer,
A laminating step of laminating the optical film on which the adhesive layer is laminated and the other optical film via the adhesive layer. The optical film is a polarizing film provided with a transparent protective film via an adhesive layer on at least one surface of the polarizer,
An activation treatment step of performing the activation treatment method according to any one of claims 1 to 4, on at least one of the polarizer and the transparent protective film, and a surface or the transparent surface on which the activation treatment of the polarizer is performed. On the activated surface of the protective film, a coating step of applying an adhesive and laminating an adhesive layer, and bonding the polarizer and the transparent protective film via the adhesive layer. The method for producing an optical film according to claim 6, comprising a laminating step.   An optical film obtained by the method according to claim 6.   An image forming apparatus comprising the optical film according to claim 8.

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