TW201446477A - Method for manufacturing polarizing plate, polarizing plate, optical film and image display device - Google Patents

Abstract

The purpose of the present invention is to provide a method for manufacturing polarizing plate, which is capable of inhibiting the generation of bubbles when active energy ray curing adhesive is used to adhere a polarizing element to a transparent protection film so as to manufacture a polarizing plate. In addition, another purpose of the present invention is to provide an optical film including the polarizing plate obtained by the manufacturing method. The method for manufacturing polarizing plate in accordance with the present invention is characterized in comprising: a step of at least performing a dying process, a crosslinking process, and an extending process to a polyvinyl alcohol series film, and then performing a drying process so as to manufacture a polarizing element; and a step of laminating a transparent protection film on at least one surface of the polarizing element by using an active energy ray curing adhesive layer. The drying process is provided to transport the polyvinyl alcohol series film that has been at least performed with the dying process, the crosslinking process and the extending process by a plurality of rollers toward a predetermined direction, and perform a heating process at the same time. The ratio (L1/W1) of the distance L1 between rollers to the width W1 of the polyvinyl alcohol series film to be performed with the heating process is less than 0.4.

Description

Method for manufacturing polarizing plate, polarizing plate, optical film and image display device

The present invention relates to a method for producing a polarizing plate, a polarizing plate obtained by the manufacturing method, an optical film in which the polarizing plate is laminated, and an image display device including the optical film.

A polarizing plate widely used in an image display device such as a liquid crystal display device or an organic EL display device is usually produced by laminating a transparent protective film on at least one surface of a polarizing element. Further, the polarizing element is produced by aligning a dichroic substance such as dioxane or a dichroic dye in a polyvinyl alcohol (PVA) film.

In recent years, with the increase in size, function, and brightness of liquid crystal display devices, the polarizing plates used in these applications have also been required to be enlarged, and optical characteristics and in-plane uniformity have been required to be improved. However, in order to obtain a large-sized polarizing plate, it is necessary to uniformly uniaxially extend the wide-width film of the above-mentioned PVA-based film, and this treatment is actually very difficult, and there is a tendency that the in-plane uniformity and optical characteristics are simultaneously deteriorated.

Various methods have been proposed as the method of manufacturing the above polarizing element. For example, there is known a method of manufacturing a polarizing film (polarizing element) including a wet stretching step of a film which is carried by a pair of conveying rollers while being conveyed in a predetermined direction, between the pair of conveying rollers A guide roller for changing the conveyance direction of the film in the bath is provided, and a ratio (L ₁ /W) of the distance L ₁ between the guide rolls to the width W of the film immediately before the extension is set to 1.2 or less ( For example, refer to Patent Document 1). According to Patent Document 1, by setting the ratio between the distance between the guide rolls and the width of the film immediately before the stretching to a specific range, it is possible to satisfactorily maintain the optical characteristics of the polarizing film and to manufacture a wide-width optical film. .

Further, a method for producing a polarizing element is disclosed in which a drying step is performed after at least a dyeing step, a crosslinking step, and an extending step are performed on a PVA film, and the drying step has a specific rapid drying stage ( For example, refer to Patent Document 2). Patent Document 2 discloses that a urethane complex can be stably immobilized in a molecular chain of PVA by a specific rapid drying step to obtain a good durable polarizing element.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-15277

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-163202

However, in the case of the optical film (polarizing element) obtained by the method of the above-mentioned Patent Documents 1 and 2, when the transparent protective film is bonded to the optical film (polarizing element) via the active energy ray-curable adhesive layer, Sometimes bubbles are generated.

When a water-based adhesive such as a PVA-based adhesive which is conventionally used for a polarizing element and a transparent protective film is used, it takes a certain length of time from the application of the adhesive to hardening, so that even in the polarizing element A little wrinkle, during which the folds are also moderated. However, the active energy ray-curable adhesive such as an ultraviolet curable adhesive has a short period of time from the start of coating to hardening, and is not moderated by the above-described water-based adhesive. Therefore, the polarizing element and the transparent member are made transparent. When the protective film is bonded, there is a problem that bubbles are generated (the appearance is poor).

Therefore, an object of the present invention is to provide a method for producing a polarizing plate which can suppress generation of bubbles when a polarizing element is bonded to a transparent protective film via an active energy ray-curable adhesive layer to form a polarizing plate. Further, it is an object of the invention to provide an optical film comprising a polarizing plate obtained by the production method.

The inventors of the present invention have conducted intensive studies in order to solve the above problems, and as a result, have found that the above object can be attained by the production method shown below, and the present invention is completed.

That is, the present invention relates to a method for producing a polarizing plate, comprising the steps of: performing a dyeing treatment, a crosslinking treatment, and an extension treatment on at least a polyvinyl alcohol-based film, and then performing a drying treatment to produce a polarizing element; a step of laminating a transparent protective film on at least one surface of the polarizing element via an active energy ray-curable adhesive layer; and the drying treatment is performed by using at least a polyvinyl alcohol-based film having a dyeing treatment, a crosslinking treatment, and an elongation treatment The root roller is heated while being conveyed in a predetermined direction, and the ratio (L ₁ /W ₁ ) of the distance L ₁ between the rolls to the width W ₁ of the polyvinyl alcohol film immediately before the drying process is 0.4 or less.

The active energy ray-curable adhesive is preferably a radical-curable adhesive, more preferably a photopolymerization initiator, and an N-hydroxyethyl acrylamide and/or an N-propenyl morpholine binder. .

The transparent protective film preferably contains at least one selected from the group consisting of a cellulose resin, a (meth)acrylic resin, a cyclic olefin resin, a polyolefin resin, and a polyester resin.

Furthermore, the present invention relates to a polarizing plate which is obtained by the above-described manufacturing method; the present invention also relates to an optical film characterized in that at least one of the above polarizing plates is laminated; An image display device comprising the above optical film.

In the method for producing a polarizing plate of the present invention, the distance between the rolls is made smaller than the width of the polarizing element in the drying process of the polarizing element, whereby the PVA film during drying can be suppressed. When the polarizing element and the transparent protective film are bonded together via the active energy ray-curable adhesive layer to form a polarizing plate, generation of bubbles can be suppressed.

1‧‧‧PVA film

2‧‧‧heating furnace

3‧‧‧film

4‧‧‧Pinch roller

5‧‧‧guide roller

6‧‧‧Swelling treatment steps

7‧‧‧Staining process steps

8‧‧‧ Crosslinking process steps

9‧‧‧Drying process steps

10‧‧‧Polarized components

R1~R5‧‧‧ Roll

L ₁ , L ₁₁ , L ₁₂ ‧‧ ‧ distance between rolls

d ₁ ‧‧‧PVA film leaving the position of the roller R1

d ₂ ‧‧‧PVA film is initially connected to roller R2

Fig. 1(a) is a conceptual view showing one aspect of the drying process of the polarizing element in the manufacturing step of the present invention. Fig. 1(b) is a conceptual view showing one aspect of the drying process of the polarizing element in the manufacturing step of the present invention.

Fig. 2 is a conceptual diagram showing an aspect of the manufacturing method of the present invention.

The method for producing a polarizing plate according to the present invention includes the steps of: performing a dyeing treatment, a crosslinking treatment, and an elongation treatment on at least a polyvinyl alcohol (PVA) film to produce a polarizing element, and the polarizing element a step of laminating a transparent protective film on at least one side of the device via an active energy ray-curable adhesive layer; and the drying treatment is performed by using a plurality of rolls of a polyvinyl alcohol-based film having at least a dyeing treatment, a crosslinking treatment, and an elongation treatment The process of heating is carried out in a predetermined direction, and the ratio (L ₁ /W ₁ ) of the distance L ₁ between the rolls to the width W ₁ of the polyvinyl alcohol film immediately before the drying process is 0.4 or less.

Polarized component

The PVA-based film used for the polarizing element used in the production method of the present invention can be used without any particular limitation in a PVA system having a light-transmitting property in the visible light region and dispersing and adsorbing a dichroic substance such as iodine or a dichroic dye. membrane. Usually, the PVA film used as the original film is a PVA film having a thickness of about 10 to 300 μm, preferably about 20 to 100 μm. The width of the PVA film used as the original film is usually about 100 to 5000 mm.

As the PVA-based film, for example, a PVA-based film conventionally used for a polarizing element is preferably used. Examples of the material of the PVA-based film include PVA or a derivative thereof. Examples of the derivative of PVA include polyvinyl acetal and polyvinyl acetal, and examples thereof include an olefin such as ethylene or propylene, an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid, and an alkane thereof. Modified by a base ester, acrylamide or the like. The degree of polymerization of PVA is preferably from about 100 to 10,000, more preferably from 1,000 to 10,000. Usually, the degree of saponification is about 80 to 100 mol%.

In addition to the above, examples of the PVA-based film include a hydrophilic polymer film such as an ethylene-vinyl acetate copolymer-based partial saponified film, a dehydrated product of PVA, or a polyene-based alignment film such as a dechlorination-treated product of polyvinyl chloride. .

The PVA film may further contain an additive such as a plasticizer or a surfactant. Examples of the plasticizer include a polyhydric alcohol and a condensate thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer or the like to be used is not particularly limited, but is preferably 20% by weight or less in the PVA film.

In the present invention, at least the dyeing treatment, the crosslinking treatment, and the stretching treatment are performed on the PVA film.

The dyeing treatment is carried out by adsorbing and aligning the iodine or the dichroic dye to the PVA-based film. The dyeing treatment can be carried out together with the stretching treatment. Dyeing is usually carried out by immersing the above film in a dyeing solution. As the dyeing solution, it is usually an iodine solution. As the iodine solution, an aqueous solution containing iodine and an iodide compound as a dissolution aid and containing an iodide ion can be used. As the iodinated compound, for example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, titanium iodide, etc. can be used. . As the iodinated compound, potassium iodide is preferred. When the iodinated compound used in the present invention is used in other treatments, it is also the same as described above.

The iodine concentration in the iodine solution is not particularly limited, and is, for example, preferably about 0.01 to 1% by weight, more preferably 0.01 to 0.5% by weight. The concentration of the iodinated compound is not particularly limited, and is, for example, preferably about 0.1 to 10% by weight, more preferably 0.2 to 8% by weight. In the iodine dyeing, the temperature of the iodine solution is usually preferably about 20 to 50 ° C, more preferably 25 to 40 ° C. Impregnation The time is usually preferably about 10 to 300 seconds, more preferably 20 to 240 seconds.

The crosslinking treatment is usually carried out using a boron compound as a crosslinking agent. The order of the crosslinking treatment is not particularly limited. The crosslinking treatment can be carried out together with the elongation treatment. The cross-linking process can be performed plural times. Examples of the boron compound include boric acid, borax, and the like. The boron compound is usually used in the form of an aqueous solution or a water-organic solvent mixed solution. An aqueous boric acid solution is usually used. The boric acid concentration of the aqueous boric acid solution is preferably from about 2 to 15% by weight, more preferably from 3 to 13% by weight. When the heat resistance is imparted by the degree of crosslinking, the boric acid concentration is preferably used. The boric acid aqueous solution or the like may contain an iodinated compound such as potassium iodide. When the boric acid aqueous solution contains an iodinated compound, the concentration of the iodinated compound is preferably about 0.1 to 10% by weight, and further preferably 0.2 to 5% by weight.

The crosslinking treatment can be carried out by immersing the PVA-based film in a boric acid aqueous solution or the like. In addition, a boron compound or the like can be used for the PVA film by a coating method, a spray method, or the like. The treatment temperature of the crosslinking treatment is usually preferably 25 ° C or higher, more preferably 30 to 85 ° C, and still more preferably 30 to 70 ° C. The processing time is usually 5 to 800 seconds, more preferably 8 to 500 seconds.

The stretching process is usually performed by performing uniaxial stretching. This stretching method can be carried out together with the dyeing treatment and the crosslinking treatment. The stretching method may employ any one of a wet stretching method and a dry stretching method, but in the present invention, a wet stretching method is preferably used. As the wet stretching method, for example, stretching is usually carried out after the dyeing treatment is carried out. Further, it can be extended together with the crosslinking treatment. On the other hand, in the case of dry stretching, examples of the stretching method include a roll stretching method, a heating roll stretching method, a compression stretching method, and the like. In the above extension method, the unstretched film is usually in a heated state. The stretching process can also be carried out in multiple stages.

The treatment liquid used in the wet stretching method can contain an iodinated compound. When the treatment liquid contains an iodinated compound, the concentration of the iodinated compound is preferably from about 0.1 to 10% by weight, more preferably from 0.2 to 5% by weight. The processing temperature of the wet stretching method is usually preferably 25 ° C or more, more preferably 30 to 85 ° C, and further preferably 30 to 60 ° C. Further, the immersion time is preferably from 10 to 800 seconds, more preferably from 30 to 500 seconds.

In the stretching treatment, it is preferred that the total stretching ratio is in the range of 3 to 17 times the total stretching ratio with respect to the original length of the PVA film, more preferably 4 to 10 times, and still more preferably 4 ~8 times. In other words, the total stretch ratio refers to a cumulative stretch ratio which is extended in the processes, such as the swelling treatment, the dyeing treatment, or the cross-linking treatment described later, in addition to the stretching treatment. When the total stretching ratio is low, the alignment is insufficient, and there is a tendency that it is difficult to obtain a polarizing element having high optical characteristics (polarizability). On the other hand, if the total stretching ratio is too high, elongation cracking is likely to occur, and the polarizing element is changed. It is too thin, and there is a drop in the processability in the subsequent steps.

Further, in the wet stretching treatment of the film, for example, as described in Japanese Laid-Open Patent Publication No. 2009-15277, the distance L ₀ between the guide rolls in the bath and the film width W ₀ immediately before the extension can be made. The ratio (L ₀ /W ₀ ) is set to 1.2 or less. Thereby, shrinkage in the width direction of the film can be suppressed, and therefore, it is preferable from the viewpoint of maintaining the optical characteristics of the polarizing film satisfactorily and producing a wide polarizing film.

In the method for producing a polarizing plate of the present invention, the PVA film is subjected to at least the dyeing treatment, the crosslinking treatment, and the stretching treatment, and the swelling treatment may be performed before the dyeing treatment. By the swelling treatment, the dirt or the anti-blocking agent on the surface of the PVA film can be cleaned, and the PVA film is swollen, which also has the effect of preventing unevenness in dyeing.

As the treatment liquid for the swelling treatment, water, distilled water, or pure water can be usually used. When the main component of the treatment liquid is water, an additive such as an iodinated compound or a surfactant, or an alcohol may be added in a small amount. Further, when the treatment liquid contains an iodinated compound, the concentration of the iodinated compound is preferably from about 0.1 to 10% by weight, more preferably from 0.2 to 5% by weight.

The treatment temperature of the swelling treatment is usually preferably adjusted to about 20 to 45 ° C, more preferably 25 to 40 ° C. Further, if there is uneven swelling, the portion may be unevenly dyed in the dyeing step, and thus uneven swelling may be avoided. The immersion time is preferably about 10 to 300 seconds. More preferably 20 to 240 seconds. Further, in the swelling treatment, stretching can be suitably performed, and the stretching ratio is usually 6.5 times or less with respect to the original length of the PVA film.

In the method for producing a polarizing plate of the present invention, in addition to the above treatment, metal ion treatment may be performed. The metal ion treatment is carried out by immersing the PVA-based film in an aqueous solution containing a metal salt. The metal ion treatment can cause various metal ions to be contained in the PVA film.

Further, in the method for producing a polarizing plate of the present invention, as described above, the cleaning treatment can be carried out after the above treatment is carried out. As the washing treatment, a water washing treatment can be performed. The water washing treatment is usually carried out by immersing the PVA-based membrane in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually 5 to 50 ° C, and the immersion time is usually 10 to 300 seconds. Further, the order of the cleaning treatment is not particularly limited as long as it is before the drying treatment.

The PVA-based film subjected to each of the above treatments was subjected to a drying treatment to produce a polarizing element. In the drying step, at least the PVA-based film subjected to the dyeing treatment, the crosslinking treatment, and the stretching treatment is heated while being conveyed in a predetermined direction by a plurality of rolls, and the distance between the rolls L ₁ and the drying process is about to be performed. The ratio (L ₁ /W ₁ ) of the width W ₁ of the former polyvinyl alcohol-based film is 0.4 or less. When L ₁ /W ₁ is 0.4 or less, the shrinkage during drying can be suppressed and wrinkles are not easily generated in the polarizing element, and as a result, the polarizing element and the transparent protective film are made via the active energy ray-curable adhesive layer. When the polarizing plate is bonded and formed, the generation of bubbles can be suppressed.

The ratio (L ₁ /W ₁ ) of the distance L ₁ between the rolls to the width W ₁ of the PVA film immediately before the drying treatment is preferably 0.3 or less, more preferably 0.2 or less. In addition, the lower limit of the ratio (L ₁ /W ₁ ) of the distance L ₁ between the rolls and the width W ₁ of the polarizing element immediately before the drying process is not particularly limited, and may be, for example, about 0.01 or more. The distance L ₁ between the rolls refers to the distance from the position where the PVA-based film is separated from the upstream side of the roll to the position where the PVA-based film first contacts the downstream side roll ( FIG. 1 ). In addition, the width W ₁ of the polarizing element immediately before the drying treatment is a PVA system which is subjected to the above-described dyeing treatment, crosslinking treatment, and elongation treatment, and if necessary, after the above-described swelling treatment or the like, immediately before the heat drying treatment The width of the film.

The drying treatment in the present invention will be described more specifically with reference to the drawings. For example, as shown in Fig. 1(a), when there are two rolls in the heating furnace 2 such as an oven, the distance L ₁ between the rolls is from the position d ₁ of the roll R1 which is separated from the upstream side of the PVA film 1 The distance from the position d ₂ at which the PVA film 1 first contacts the downstream roller R2 is the distance L ₁ between the rolls. Further, for example, as shown in FIG. 1(b), in the case where three rolls are continuously disposed in the heating furnace 2, the inter-roll distance L ₁₁ between the rolls R3 and R4 and the rolls R4 and R5 are Any one of the inter-roller distances L ₁₂ may be L ₁ /W ₁ ≦ 0.4, and it is preferable that the inter-roller distance L ₁₁ between the rolls R3 and R4 satisfies the above relationship, and more preferably L ₁₁ and Both of L ₁₂ satisfy the above relationship. Further, in the above-described FIGS. 1(a) and 1(b), two or three rolls are provided in the heating furnace 2, but the number of the rolls is not particularly limited as long as it is plural. The rolls are usually preferably from about 2 to about 40, more preferably from 4 to 30. Further, in order to uniformly dry both surfaces of the film, the number of rolls is preferably an even number. Further, having a plurality of rolls, and there is a case where the distance L from _a plurality of rollers, as long as the distance L between the rolls ₁ is any one of L ₁ / W ₁ ≦ 0.4 can, preferably the most upstream side between the roll (i.e., the distance between the first roll and the second roll in the oven) satisfies the above relationship, and it is more preferable that all L ₁ satisfy the above relationship.

The above roller has a roll shape that is free to rotate. Further, the diameter thereof is not particularly limited, and is, for example, preferably 50 to 300 mm, more preferably 100 to 200 mm. The diameters of the plurality of rollers may be the same or different. Further, the rotation speed of the roller is not particularly limited, and is, for example, preferably from 3 to 100 m/min, more preferably from 6 to 100 m/min.

The distance L ₁ between the rolls is not particularly limited, but is preferably 2000 mm or less, more preferably 500 mm or less, still more preferably 150 mm or less. Further, the lower limit value is not particularly limited, and an optimum condition can be selected depending on the diameter of the roll or the like, and is, for example, 10 mm or more. From the viewpoint of reducing bubbles, it is preferred that L ₁ is in the above range.

The width W ₁ of the PVA film immediately before the drying treatment is not particularly limited, and is determined according to the width of the PVA film used as the original sheet. For example, it is preferably about 40 to 60% of the width of the original PVA film used as the original sheet (the width of the original PVA film). That is, the width of the PVA-based film used as the original sheet is usually about 100 to 5,000 mm as described above. Therefore, the width W ₁ of the PVA-based film immediately before the drying treatment is about 40 to 3,000 mm.

The drying temperature at the time of the drying treatment can be appropriately set, and is, for example, preferably 20 to 100 ° C, more preferably 50 to 90 ° C. Further, the above roller may be a heat roller. In the case of a hot roll, the temperature is preferably set to be higher than the temperature of the dry atmosphere.

The time of the above drying treatment is not particularly limited, and is, for example, preferably about 10 to 240 seconds, more preferably 15 to 110 seconds, still more preferably 20 to 100 seconds.

Further, it is preferable that the inner wall of the heating furnace is provided with a plurality of hot air ports which can blow hot air toward the surface of the PVA film passing between the rolls. The air blowing mechanism is not particularly limited, and those generally used for heating furnaces and the like can be used without limitation.

Further, in the above drying treatment, the above respective treatments are usually carried out in a series of successive steps, and therefore the drying treatment may be carried out in the form of a continuous step following the above respective treatments. For example, in the present invention, as shown in FIG. 2, a series of successive steps including a swelling treatment step 6, a dyeing treatment step 7, a crosslinking treatment step 8, and a drying treatment step 9 can be performed by the above-described dyeing treatment step 7. And the continuous step of performing the elongation processing in the crosslinking treatment step 8 is performed. Specifically, the PVA-based film which is successively fed from the green film 3 of the PVA-based film is conveyed by the pinch roller 4 and the guide roller 5, and is subjected to a swelling treatment step 6, a dyeing treatment step 7, a crosslinking treatment step 8, and a drying treatment step. 9. Finally, the polarizing element 10 is obtained. In FIG. 2, the roller of the polarizing element 10 is provided. However, the polarizing plate may be continuously manufactured by directly transferring the polarizing element 10 to the bonding step with the transparent protective film without taking up the polarizing element 10. Further, an extension processing step (not shown) may be additionally provided after the crosslinking treatment step 8, and the cleaning processing step (not shown) may be appropriately provided.

The thickness of the polarizing element obtained by the above method is not particularly limited, but is preferably 2 to 50 μm, more preferably 10 to 30 μm.

In the production method of the present invention, the specific drying treatment is carried out, so that the shrinkage during drying can be suppressed, and wrinkles are less likely to occur in the polarizing element, and as a result, the polarizing element can be made via an active energy ray-curable adhesive to be described later. When a polarizing plate is bonded to a transparent protective film, generation of bubbles can be suppressed.

2. Transparent protective film

The polarizing plate of the present invention is obtained by laminating a transparent protective film on at least one surface of the polarizing element obtained above via an active energy ray-curable adhesive.

Examples of the material constituting the transparent protective film include thermoplastic resins excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy. Specific examples of the thermoplastic resin include a cellulose resin such as triethylene fluorene cellulose, a polyester resin such as polyethylene terephthalate (PET), a polyether oxime resin, and a polyfluorene resin. a polycarbonate resin, a polyamide resin, a polyimide resin, a polyolefin resin, a cyclic olefin resin, a (meth)acrylic resin, a polyarylate resin, a polystyrene resin, A mixture of PVA-based resins, and the like. Further, a thermosetting resin such as a (meth)acrylic resin, a urethane resin, an urethane urethane resin, an epoxy resin, or a polyoxyxylene resin, or an ultraviolet curable resin may be used. . Among these, it is preferably at least one selected from the group consisting of a cellulose resin, a (meth)acrylic resin, a cyclic olefin resin, and a polyester resin, and more preferably a cellulose system. Resin or (meth)acrylic resin.

Further, one or more optional additives may be contained in the transparent protective film. Examples of the additive include a UV absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, a colorant, and the like. In the transparent protective film, the content of the thermoplastic resin is preferably from 50 to 100% by weight, more preferably from 50 to 99% by weight, still more preferably from 60 to 98% by weight, particularly preferably from 70 to 97% by weight. When the content of the thermoplastic resin in the transparent protective film is 50% by weight or less, the high transparency and the like which the thermoplastic resin originally has may not be sufficiently exhibited.

The thickness of the transparent protective film can be appropriately determined. Generally, it is about 1 to 500 μm, preferably 1 to 300 μm, and more preferably 5 to 200 μm in terms of workability and thinness such as strength and handleability. , especially good for 5~150μm.

Further, when a transparent protective film is provided on both sides of the polarizing element, a protective film made of the same resin material may be used on the front surface and the back surface, and a protective film made of a different resin material or the like may be used.

The transparent protective film of the present invention preferably comprises a film selected from at least one of a cellulose resin, a polycarbonate resin, a cyclic polyolefin resin, and a (meth)acrylic resin.

Cellulose resins are esters of cellulose and fatty acids. Specific examples of such a cellulose ester-based resin include triacetonitrile cellulose, diacetyl cellulose, tripropylene cellulose, and dipropylene cellulose. Among these, it is particularly preferred to be triacetyl cellulose. Triacetyl cellulose is commercially available in a large number of products, which is advantageous in terms of availability or cost. As an example of the commercial product of the triacetone cellulose, the product names "UV-50", "UV-80", "SH-80", "TD-80U", and "TD" manufactured by Fujifilm Co., Ltd. -60UL", "TD-TAC", "UZ-TAC" or "KC Series" made by KONICA.

As a specific example of the cyclic polyolefin resin, it is preferred to lower An olefinic resin. The cyclic olefin-based resin is a general term for a resin obtained by polymerizing a cyclic olefin as a polymerization unit, and examples thereof include a Japanese Patent Laid-Open No. Hei No. 1-240517, Japanese Patent Laid-Open No. Hei No. Hei No. Hei No. Hei No. Hei No. Hei No. Hei. The resin described in the publication No. 122137 or the like. Specific examples thereof include a ring-opening (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and an α-olefin such as ethylene or propylene (representatively random) a copolymer), a graft polymer obtained by modifying the unsaturated carboxylic acid or a derivative thereof, a hydrogenated product thereof, and the like. Specific examples of the cyclic olefin include a descending An olefinic monomer.

As the cyclic polyolefin resin, various products are commercially available. As a specific example, it can be listed Manufactured under the trade name "ZEONX" by the ZEON Co., Ltd., "ZEONOR", the product name "ARTON" made by JSR (share), the product name "TOPAS" made by TICONA, and the product name of Mitsui Chemicals Co., Ltd. "APEL".

On the other hand, as the transparent protective film, a phase difference plate having a front phase difference of 40 nm or more and/or a thickness direction retardation of 80 nm or more can be used. The front phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When a retardation film is used as the transparent protective film, the retardation film also functions as a transparent protective film, so that it can be made thinner.

Examples of the phase difference plate include a birefringent film obtained by subjecting a polymer material to uniaxial or biaxial stretching treatment, an alignment film of a liquid crystal polymer, and a film obtained by supporting a film for an alignment layer of a liquid crystal polymer. . The thickness of the phase difference plate is not particularly limited and is usually about 20 to 150 μm.

Examples of the polymer material include PVA, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, and poly. Carbonate, polyacrylate, polyfluorene, polyethylene terephthalate, polyethylene naphthalate, polyether oxime, polyphenylene sulfide, polyphenylene ether, polyallyl fluorene, polyamine, Polyimine, polyolefin, polyvinyl chloride, cellulose resin, cyclic polyolefin resin An olefin resin, or a binary system or a ternary copolymer, a graft copolymer, a blend, or the like. These polymer raw materials can be oriented (stretched film) by stretching or the like.

Further, the film having the retardation may be bonded to a transparent protective film having no phase difference to impart the above-described function.

Further, the transparent protective film may be subjected to a hard coating treatment, an anti-reflection treatment, an anti-sticking treatment, a brightness enhancement treatment, a treatment for diffusion or anti-glare, or may be applied to the surface of the transparent protective film. Further, it is provided as an optical layer in a form independent of the transparent protective film.

The transparent protective film may also be subjected to a surface modification treatment before the application of the adhesive. Specific examples of the treatment include corona treatment, plasma treatment, primer treatment, and saponification treatment.

3. Active energy ray hardening type adhesive

The polarizing element and the transparent protective film are laminated via an active energy ray-curable adhesive layer. The active energy ray-curable type is an adhesive which is cured by an active energy ray such as an electron beam or an ultraviolet ray, and can be used, for example, in an electron beam curing type or an ultraviolet curing type. The active energy ray-curable adhesive used in the present invention is preferably an ultraviolet curable adhesive.

Further, the active energy ray-curable adhesive used in the present invention may be either a cationic curing type or a radical curing type, but is preferably a radical curing type.

Examples of the curable component of the radical curing adhesive include a compound having a (meth)acryl fluorenyl group and a compound having a vinyl group. As the curable component, either monofunctional or difunctional or more can be used. In addition, these curable components may be used alone or in combination of two or more. As such a curable component, for example, a compound having a (meth) acrylonitrile group is preferable.

Specific examples of the compound having a (meth)acryl fluorenyl group include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and (meth)acrylic acid. Isopropyl ester, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, second butyl (meth)acrylate, Tert-butyl (meth)acrylate, n-amyl (meth)acrylate, third amyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,2-dimethyl (meth)acrylate Butyl butyl ester, n-hexyl (meth) acrylate, cetyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylate (Meth)acrylic acid (having 1 to 20 carbon atoms) alkyl esters such as 4-methyl-2-propylpentyl ester and n-octadecyl (meth)acrylate.

Moreover, examples of the compound having a (meth)acryl fluorenyl group include a cycloalkyl (meth)acrylate (for example, cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, etc.) ( Alkyl methacrylate (for example, benzyl (meth) acrylate, etc.), polycyclic (meth) acrylate (for example, 2-iso(meth)acrylate Ester, 2-(meth)acrylic acid Methyl ester, (meth)acrylic acid 5-nor Alk-2-yl-methyl ester, 3-methyl-2-methyl (meth)acrylate a methyl ester or the like), a hydroxyl group-containing (meth) acrylate (for example, hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2, 3 (meth) methacrylate -dihydroxypropylmethyl-butyl ester, etc.), alkoxy or phenoxy-containing (meth) acrylates (2-methoxyethyl (meth) acrylate, (meth) acrylate 2-ethoxyethyl ester, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylic acid Ester, phenoxyethyl (meth) acrylate, etc.), epoxy group-containing (meth) acrylate (for example, glycidyl (meth) acrylate), halogen-containing (meth) acrylate Classes (for example, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, Hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptafluorodecyl (meth)acrylate, etc., alkylaminoalkyl (meth)acrylate (for example) (Methylaminoethyl methacrylate), etc.).

Further, examples of the compound having a (meth) acrylonitrile group other than the above include N-hydroxyethyl acrylamide, N-methylol acrylamide, N-methoxymethyl propylene amide, and N. - a mercapto group-containing monomer such as ethoxymethyl acrylamide or (meth) acrylamide. Further, examples thereof include nitrogen-containing monomers such as acryloylmorpholine.

In addition, as the curable component of the radical-curable adhesive, a compound having a plurality of polymerizable double bonds such as a (meth)acryl fluorenyl group or a vinyl group may be exemplified, and the compound may be mixed as a crosslinking component. In the ingredients. Examples of the curable component to be the crosslinking component include tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, and cyclic trimethylolpropane. Acetal acrylate, two Alkylene glycol diacrylate, EO modified diglycerin tetraacrylate, ARONIX M-220 (manufactured by Toagosei Co., Ltd.), Light acrylate 1,9ND-A (manufactured by Kyoeisha Chemical Co., Ltd.), Light acrylate DGE -4A (manufactured by Kyoeisha Chemical Co., Ltd.), Light acrylate DCP-A (manufactured by Kyoeisha Chemical Co., Ltd.), SR-531 (manufactured by Sartomer Co., Ltd.), CD-536 (manufactured by Sartomer Co., Ltd.), and the like. Further, various (meth)acrylic acid epoxy esters, (meth)acrylic acid urethanes, (meth)acrylic polyesters, or various (meth)acrylic monomers may be mentioned as needed.

The radical curing adhesive contains the curable component. However, in addition to the above components, a radical polymerization initiator may be added depending on the type of curing. When the above-mentioned adhesive is used in the electron beam curing type, it is not particularly necessary to use the above-mentioned adhesive agent to contain a radical polymerization initiator, but in the case of using the above-mentioned adhesive agent in an ultraviolet curing type, a photopolymerization initiator is used. . The amount of the photopolymerization initiator to be used is usually from 0.1 to 10 parts by weight, preferably from 0.5 to 5 parts by weight, per 100 parts by weight of the curable component. Further, in the radical polymerization-type adhesive, a photosensitizer which is improved by the curing speed or sensitivity of the electron beam, such as a carbonyl compound, may be added as needed. The amount of the photosensitizer to be used is usually about 0.001 to 10 parts by weight, preferably 0.01 to 3 parts by weight, per 100 parts by weight of the curable component.

Examples of the curable component of the cation hardening type adhesive include a compound having an epoxy group or an oxetanyl group. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various curable epoxy compounds generally known can be used. The preferred epoxy compound is exemplified by a compound having at least two epoxy groups and at least one aromatic ring in the molecule, or at least two epoxy groups in the molecule, and at least one of them is formed. A compound between two adjacent carbon atoms constituting an alicyclic ring.

The active energy ray-curable adhesive used in the present invention is, for example, preferably an active energy ray-curable type containing a photopolymerization initiator, and N-hydroxyethyl acrylamide and/or N-propenyl morpholine. The subsequent composition, more preferably an active energy ray-curable adhesive combination containing a photopolymerization initiator, and N-hydroxyethyl acrylamide and N-propenyl morpholine Things.

The adhesive forming the above-mentioned adhesive layer may contain an additive as needed. Examples of the additive include a coupling agent such as a decane coupling agent and a titanium coupling agent, an adhesion promoter represented by ethylene oxide, an additive for improving the wettability with a transparent film, and an acryl oxide compound or a hydrocarbon. Additives, ultraviolet absorbers, anti-aging agents, dyes, processing aids, ion trapping agents, antioxidants, adhesion-imparting agents, fillers (such as natural, synthetic resins) and the like to improve mechanical strength or processability ( Stabilizers such as plasticizers, plasticizers, leveling agents, foaming inhibitors, antistatic agents, heat stabilizers, and hydrolysis stabilizers.

The thickness of the adhesive layer composed of the active energy ray-curable adhesive is not particularly limited, but is preferably 0.01 to 7 μm, more preferably 0.01 to 5 μm, still more preferably 0.01 to 2 μm, and particularly preferably 0.01 to 0.01. 1 μm. When the thickness of the adhesive layer is thinner than 0.01 μm, the cohesive force of the adhesion force itself cannot be obtained, and the adhesive strength cannot be obtained. On the other hand, if the thickness of the adhesive layer exceeds 7 μm, the polarizing plate cannot satisfy the durability.

4. Polarizer

In the method for producing a polarizing plate of the present invention, the method may include the step of applying an active energy ray-curable type to the surface of the polarizing element on which the adhesive layer is formed and/or the surface of the transparent protective film forming the adhesive layer. And a step of bonding the polarizing element to the transparent protective film; and then, the active energy ray-curable adhesive is cured by irradiation of the active energy ray to form an adhesive layer.

The coating method of the active energy ray-curable adhesive can be appropriately selected depending on the viscosity of the composition or the target thickness. Examples of the coating method include a reverse coater, a gravure coater (direct gravure coater, reverse gravure coater, or gravure coater), a bar reverse coater, and a roll coater. , die coater, bar coater, rod coater, etc. In addition to this, the coating may be suitably used, such as a dipping method.

The polarizing element is bonded to the transparent protective film via an adhesive applied as described above. Partial The bonding of the optical element and the transparent protective film can be performed by a roll laminator or the like.

After bonding the polarizing element to the transparent protective film, an active energy ray (electron beam, ultraviolet light, or the like) is irradiated to cure the active energy ray-curable adhesive to form an adhesive layer. The irradiation direction of the active energy ray (electron beam, ultraviolet ray, etc.) can be irradiated from any suitable direction. It is preferred to irradiate from the side of the transparent protective film. When the light is emitted from the side of the polarizing element, the polarizing element is deteriorated by active energy rays (electron beam, ultraviolet light, or the like).

Further, in the polarizing plate obtained by the production method of the present invention, the polarizing element and the transparent protective film are bonded via the adhesive layer formed of the cured layer of the active energy ray-curable adhesive, but the transparent protective film is An easy adhesion layer can be disposed between the layers of the agent. The easy-adhesion layer may be, for example, a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a polyoxane-based, a polyamide-based skeleton, a polyimine skeleton, a polyvinyl alcohol skeleton, or the like. Formed from a resin. These polymer resins may be used alone or in combination of two or more. Further, when the layer is easily formed, other additives may be added. Specifically, a stabilizer such as an adhesion-imparting agent, an ultraviolet absorber, an antioxidant, or a heat-resistant stabilizer can be further used.

5. Optical film

The optical film of the present invention can be obtained by laminating a polarizing plate obtained by the above-described production method of the present invention with other optical layers in actual use. The optical layer is not particularly limited, and for example, one or two or more layers such as a reflecting plate or a semi-transmissive plate, a phase difference plate (including 1/2 and 1/4 wavelength plates), and a liquid crystal display such as a viewing angle compensation film can be used. An optical layer used in the formation of a device or the like. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a reflecting plate or a semi-transmissive reflecting plate is laminated on a polarizing plate obtained by the manufacturing method of the present invention, and an elliptically polarizing plate formed by laminating a phase difference plate on a polarizing plate It is preferable to use a circular polarizing plate, a wide viewing angle polarizing plate in which a viewing angle compensation film is laminated on a polarizing plate, or a polarizing plate in which a brightness improving film is laminated on a polarizing plate.

The polarizing plate or the optical film obtained by the production method of the present invention can be preferably used for formation of various devices such as a liquid crystal display device. The formation of the liquid crystal display device can be carried out in accordance with the convention. In other words, the liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate, an optical film, and an illumination system as needed, and assembling them into a driving circuit or the like, except that the polarizing plate obtained by the manufacturing method of the present invention is used. Other than the optical film, it is not particularly limited and can be carried out in accordance with the conventional practice. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples and comparative examples, but the present invention is not limited by the examples and comparative examples.

<Measurement of glass transition temperature>

The glass transition temperature (Tg) was measured by the dynamic viscoelasticity measuring apparatus RSAIII (made by TA INSTRUMENTS) under the following measurement conditions.

Sample size: width 10mm, length 30mm, fixture distance: 20mm,

Measurement mode: stretching, frequency: 1 Hz, heating rate: 5 ° C / min

The dynamic viscoelasticity was measured by using the peak top temperature of tan δ as the Tg.

Production Example 1 Production of Active Energy Ray Hardening Type Binder Composition

38.3 parts of N-hydroxyethyl acrylamide (trade name: HEAA, manufactured by Xingren Co., Ltd.), 19.3 parts of tripropylene glycol diacrylate (trade name: ARONIX M-220, manufactured by Toagosei Co., Ltd.), propylene fluorenyl group Morpholine (trade name: ACMO, manufactured by Xingren Co., Ltd.) 38.3 parts, diethyl 9-oxosulfur as a photopolymerization initiator (trade name: KAYACURE DETX-S, manufactured by Nippon Kayaku Co., Ltd.) 1.4 parts, 2-methyl-1-(4-methylphenylthio)-2-morpholinylpropan-1-one (trade name) 2.9 parts of IRGACURE 907, manufactured by BASF Corporation, and the mixture was stirred at 50 ° C for 1 hour to obtain an active energy ray-curable adhesive composition.

Example 1

(Manufacture of polarizing elements)

A PVA film (thickness: 75 μm, width: 2900 mm) having an average degree of polymerization of 2,400 and a degree of saponification of 99.9 mol% was immersed in warm water of 30 ° C for 60 seconds to swell.

Then, immersing in a dye bath filled with an aqueous solution of iodine/potassium iodide (weight ratio = 0.5/8) at a concentration of 0.3% in an aqueous solution of iodine (30 ° C) for 120 seconds, uniaxially extending to a relative length with respect to the original length The stretching ratio was 3.5 times while the film was dyed.

Then, uniaxial stretching was carried out while immersing in a crosslinking bath filled with a 3.25% aqueous boric acid ester solution at 60 ° C for 20 seconds while the total stretching ratio was 6 times with respect to the original length. Further, the ratio (L ₀ /W ₀ ) of the distance L ₀ between the guide rolls in the bath to the film width W ₀ immediately before the extension is 3.

Then, the PVA film (W ₁ : 1500 mm) treated as described above was dried using a heating furnace (oven) shown in Fig. 1 . As in the case of Fig. 1 (b), 14 rolls (roll diameter: 100 mm, rotation speed: 20 m/min) were arranged in a staggered manner. The distance L ₁ between the rolls was 300 mm, and L ₁ /W ₁ = 0.2. Further, in the oven, the air was blown while being blown by a wind blower at a temperature of 50 ° C and a wind speed of 15 m/s. The temperature in the oven was 50 ° C and the drying time was 117 seconds. The obtained polarizing element had a thickness of 20 μm.

(Manufacture of polarizing plate)

It is coated with MCD on a cyclic polyolefin resin film (trade name: ZEONOR, manufactured by Japan ZEON Co., Ltd.) having a thickness of 60 μm and a TAC film (trade name: TD-60UL, manufactured by Fujifilm Co., Ltd.) having a thickness of 60 μm. The machine (mesh shape: honeycomb, gravure roll line number: 1000 pieces/inch, rotation speed 140%/pair speed, manufactured by Fuji Machinery Co., Ltd.) was applied in the manner of thickness of 0.7 μm. Active energy ray hardening type adhesive composition. The surface of the TAC film coated with the active energy ray-curable adhesive composition is bonded to one surface of the polarizing element by a roll machine, and the cyclic polyolefin resin film is coated with an active energy ray-curable adhesive. The surface of the composition is bonded to the other side of the above polarizing element. Then, from the side of the transparent protective film (on both sides), use an IR heater to heat to 50 ° C, and both sides The active energy ray-curable adhesive composition was cured by irradiation with ultraviolet rays under the following conditions, and then dried by hot air at 70 ° C for 3 minutes to obtain a polarizing plate having a transparent protective film on both sides of the polarizing element.

<Active energy ray>

As the active energy ray, an ultraviolet ray (metal halide lamp enclosed with gallium) irradiation device (product name: Light HAMMER 10, lamp tube: V-shaped tube, peak illuminance: 1600 mW/cm ² , cumulative irradiation amount: 1000/mJ/) Cm ² (wavelength: 380 to 440 nm), manufactured by Fusion UV Systems, Inc.). Further, the illuminance of the ultraviolet ray was measured using a Sola-Check system manufactured by Solatell.

Examples 2 to 4 and Comparative Examples 1 to 3

The inter-roller distance L ₀ , the film width W ₀ , and the heating temperature in the drying process, the inter-roller distance L ₁ , and the film width W _{1 were} changed to the values shown in Table 1, and the examples were carried out. 1 The same operation was performed to manufacture a polarizing plate.

<Appearance>

The polarizing plates obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were visually confirmed for the presence or absence of bubbles, and evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1.

○: No air bubbles were observed by visual observation under reflection or reflection, and no air bubbles were observed when the panel was mounted.

×: The bubbles were confirmed by visual observation under reflection and reflection, and bubbles were also observed when the panel was displayed.

As can be seen from the above Table 1, in the examples, a polarizing plate which ensures a sufficient width and a good appearance can be obtained. On the other hand, in the comparative example, many bubbles were generated, and the function as a polarizing plate was not exhibited.

1‧‧‧PVA film

2‧‧‧heating furnace

R1~R5‧‧‧ Roll

L ₁ , L ₁₁ , L ₁₂ ‧‧ ‧ distance between rolls

d ₁ ‧‧‧PVA film leaving the position of the roller R1

d ₂ ‧‧‧PVA film is initially connected to roller R2

Claims (7)

A method for producing a polarizing plate, comprising the steps of: performing a dyeing treatment, a crosslinking treatment, and an elongation treatment on at least a polyvinyl alcohol-based film, and performing a drying treatment to produce a polarizing element, and the polarizing element; a step of laminating a transparent protective film on at least one side of the device via an active energy ray-curable adhesive layer; and the drying treatment is performed by using a plurality of rolls of a polyvinyl alcohol-based film having at least a dyeing treatment, a crosslinking treatment, and an elongation treatment The process of heating is carried out in a predetermined direction, and the ratio (L ₁ /W ₁ ) of the distance L ₁ between the rolls to the width W ₁ of the polyvinyl alcohol film immediately before the drying process is 0.4 or less. The method of producing a polarizing plate according to claim 1, wherein the active energy ray-curable adhesive is a radical-curable adhesive. The method for producing a polarizing plate according to claim 1, wherein the active energy ray-curable adhesive contains a photopolymerization initiator, and N-hydroxyethyl acrylamide and/or N-propylene decylmorpholine. The method for producing a polarizing plate according to any one of claims 1 to 3, wherein the transparent protective film comprises a cellulose resin, a (meth)acrylic resin, a cyclic olefin resin, a polyolefin resin, and At least one of the group consisting of polyester resins. A polarizing plate obtained by the manufacturing method according to any one of claims 1 to 4. An optical film characterized in that at least one of the polarizing plates of claim 5 is laminated. An image display device comprising the optical film of claim 6.