WO2005096039A1

WO2005096039A1 - Process for producing polarizing film, polarizing film obtained thereby and image display unit utilizing the same

Info

Publication number: WO2005096039A1
Application number: PCT/JP2005/005734
Authority: WO
Inventors: Hiroaki Mizushima; Morimasa Wada; Youichirou Sugino; Tadayuki Kameyama; Ken Aoki; Kenji Shimizu
Original assignee: Nitto Denko Corporation
Priority date: 2004-03-30
Filing date: 2005-03-28
Publication date: 2005-10-13
Also published as: JP2005284047A; TW200606470A

Abstract

A process for producing a polarizing film, in which a polarizing film excelling in optical properties and, even when being of large size, excelling in in-plane uniformity can be obtained. There is provided a process wherein in at least one step selected from the group consisting of swelling, dyeing, crosslinking, drawing and water washing steps, a TD-direction drawing operation comprising not only immersing a polymer film in a treating solution but also drawing the same in the TD direction is carried out, and wherein in the TD-direction drawing operation, the TD-direction drawing is performed by means of a crown roll of ≥3% curvature.

Description

Specification

Method for producing polarizing film, polarizing film obtained by the method, and image display device using the same

Technical field

The present invention relates to a method for producing a polarizing film, a polarizing film obtained by the method, and an image display device using the same.

Background art

[0002] A polarizing film used for an image display device (for example, a liquid crystal display device) needs to have high reproducibility of bright colors and to have high transmittance, high transmittance and high degree of polarization in order to provide an image. It has been. Conventionally, such a polarizing film is prepared by dyeing a polyvinyl alcohol (PVA) -based raw film with a dichroic substance such as iodine or dichroic dye having dichroism, and stretching it uniaxially in the MD direction. And manufactured. In the case of a long raw film (band-shaped raw film), the MD (Machinery Direction) direction refers to the longitudinal direction of the film, and the TD (Transverse Direction) direction refers to the film described above. In the width direction. The polarizing plate is obtained by laminating a transparent protective film on a polarizing film.

[0003] In recent years, with the improvement of functions, definition, and image quality of image display devices, a polarizing plate used therein has been required to have higher optical characteristics such as a degree of polarization and in-plane uniformity. The polarizing film used for the polarizing plate is produced by dyeing and uniaxially stretching the raw film, and the unevenness caused by stretching or dyeing causes deterioration of optical characteristics and in-plane uniformity, and the above-described image. When applied to a display device, the display of the screen becomes uneven, and various attempts have been made to eliminate the unevenness (for example, see Patent Document 1). The method for producing a polarizing film can be roughly classified into a wet method and a dry method.Furthermore, as a method for solving the above-mentioned problem, a method of stretching in the TD direction in a dry method (for example, see Patent Document 2) and a wet method In addition, a method has been proposed in which a spiral rubber roll is used to remove the bend (for example, see Patent Document 3). In addition, with the recent increase in the size of image display devices, it is necessary to increase the size of polarizing plates and polarizing films. However, as the size increases, it becomes more difficult to perform in-plane uniform stretching and dyeing. For this reason, there is a strong demand for the development of a technology for providing a large-size and in-plane uniform polarizing plate. Reference 1: JP 2001-290025

Patent Document 2: JP-A-11-183726

Patent Document 3: JP-A-2000-147252

Disclosure of the invention

Problems to be solved by the invention

[0004] In recent years, it has been found that such unevenness is dyeing unevenness caused by fine irregularities of the raw film. However, according to the method described above, the improvement of unevenness is still insufficient. Furthermore, in the dry method, since the film stretched in the TD direction in the air is dyed, if the stretched film is immersed in a solution, it shrinks instantaneously and a fold is formed. Is difficult. Further, as a method of stretching in the TD direction, a tenter stretching method in which the film is stretched in the TD direction across the edge of the film is generally known.However, it is difficult to obtain uniform stretching. It was difficult to use inside. Further, in Patent Document 3, although a spiral rubber roll is used, the effect of stretching in the direction of force is obtained, but no clear effect of stretching in the TD direction is obtained.

[0005] Accordingly, the present invention provides a method for producing a polarizing film, which has good in-plane uniformity and excellent optical properties without unevenness, and is effective in increasing the size, in a method for producing a polarizing film produced by a wet method. Further, it is another object of the present invention to provide a polarizing film obtained by the production method of the present invention, an optical film using the same, and an image display device using the polarizing film or the optical film. . Means for solving the problem

[0006] In order to achieve the above object, the production method of the present invention is a method for producing a polarizing film, which comprises a swelling step, a dyeing step, a crosslinking step, a stretching step, and a washing step. In at least one of the selected steps, a TD direction stretching step of immersing the polymer film in the treatment liquid and stretching in the TD direction is performed, and the TD direction stretching step has a curvature. This is a manufacturing method in which the film is stretched in the TD direction using a crown roll of 3% or more.

[0007] The polarizing film of the present invention is a polarizing film obtained by the production method of the present invention.

[0008] The optical film of the present invention is an optical film obtained by laminating at least one optical layer on the polarizing film of the present invention.

[0009] The image display device of the present invention is an image display device having the polarizing film of the present invention or the optical film of the present invention.

The invention's effect

[0010] According to the method for producing a polarizing film of the present invention, a polarizing film having good optical characteristics and no unevenness can be obtained, and further, a large-sized image display device having good display characteristics without uneven display. A suitable polarizing film can be provided.

Brief Description of Drawings

FIG. 1 is a cross-sectional view of an example of a crown roll used in the present invention.

Explanation of symbols

[0012] 1: Crown roll

D1: Crown roll end diameter

D2: Crown roll center diameter

L: Crown roll length

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the present invention will be described in detail.

[0014] As described above, in the method for producing a polarizing film of the present invention, in at least one of the steps selected from the group consisting of the swelling step, the dyeing step, the crosslinking step, the stretching step, and the washing step, A TD stretching step of stretching in the TD direction while being immersed in the treatment solution, wherein the TD stretching step is a step of stretching in the TD direction using a crown roll having a curvature of 3% or more. Is the way. More preferably, the curvature of the crown roll is 3% or more and 35% or less. [0015] For example, as shown in FIG. 1, the curvature (R) is as follows: D1 is the diameter of the end of the crown roll [mm], D2 is the diameter of the center of the crown roll [mm], and L is the roll length [mm]. ] Can be obtained by the following equation.

R [%] = ((D2-D1) / L) X 100

In the present invention, the curvature of the crown roll may be 3% or more, but from the viewpoint of the effect of stretching in the TD direction and the running property during film transport, it is preferably 3% or more and 35% or less. More preferably 3% or more and 30% or less, more preferably 5% or more and 25% or less, and still more preferably 7% or more and 22% or less. If the curvature force is less than S3%, the effect of suppressing shear bending can be obtained, but the effect of stretching in the TD direction may be insufficient. If it exceeds 35%, the running property is deteriorated, so that it is easy to meander, and the stretching at the center of the roll becomes strong, so that it is difficult to obtain a uniform stretching effect in the film plane. However, it is preferable that the curvature is appropriately adjusted according to the thickness and hardness of the film to be conveyed.

[0017] The stretching ratio in the TD direction at this time is, as in the swelling treatment step or another solution treatment step, that the film is stretched by a crown roll before and after the cross-linking treatment step in a state where the film is swollen and thin. When performing, it cannot be said unconditionally because it depends on the material of the film. For example, in the case of a polybutyl alcohol film, the width is increased by about 10% due to swelling. Therefore, the range of the stretching ratio is preferably 1.13 times or more and 1.40 times or less, more preferably 1.16 times or more and 1.35 times or less. If the stretching in the TD direction is less than 1.13 times, the stretching in the TD direction is insufficient and the effect of making the in-plane uniformity is not obtained. 1.When a crown roll exceeding 40 times is used On the contrary, it is not preferable because the possibility that the in-plane optical characteristic variation becomes large increases.

When the film is stretched in the TD direction by a crown roll in a state where the film is unlikely to swell, such as after the crosslinking step, the stretching ratio in the TD direction at this time is 1.03 times or more and 1.26 times. It is more preferably 1.06 times or more and 1.21 times or less. If the stretching in the TD direction is less than 1.03 times, stretching in the TD direction is inadequate and the effect of making the in-plane uniformity is difficult to obtain. 1.When a crown roll exceeding 26 times is used On the contrary, it is not preferable because the possibility of in-plane optical characteristic variation increases. The method for producing a polarizing film of the present invention includes a dyeing step of dyeing a raw film (a strip-shaped polymer film) and a stretching step of stretching the dyed film. The point is to have a stretching process in the TD direction. Therefore, the other steps, ie, the swelling step, the crosslinking step, and the washing step are optional steps. Further, the TD stretching step is performed in at least one of the above-described steps.

[0020] The thickness of the polarizing film is not particularly limited, but is generally about 5 to 40 / zm. As described above, a polarizing plate is obtained by laminating a transparent protective layer on one or both sides of a polarizing film.

The polymer film (raw film) is not particularly limited, and various types can be used. For example, PVA-based films, partially formalized PVA-based films, polyethylene terephthalate (PET) -based films, ethylene / butyl acetate copolymer-based films, and hydrophilic polymer films such as partially saponified films and cellulose-based films. And polyene-based oriented films such as PVA dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, it is preferable to use a PVA-based film because of its excellent dyeability with iodine. The thickness of the polymer film is preferably about 5 to 100 / ζπι.

[0022] The polymerization degree of the polymer as the material of the polymer film is generally 500 to 10,000, preferably in the range of 100 to 6000, more preferably in the range of 1400 to 4000. In the case of Sarakoko or Kenyidani film, the degree of saponification is preferably at least 75 mol%, more preferably at least 98 mol%, from the viewpoint of solubility in water. . and more preferably in the range of 8 mol ^_0/0.

When a PVA-based film is used as the polymer film, the PVA-based film may be produced by any method such as a casting method, a casting method, and an extrusion method of casting a stock solution dissolved in water or an organic solvent. Can be used as appropriate. The phase difference value at this time is preferably 5 nm to 100 nm. Further, in order to obtain an in-plane uniform polarizing film, the in-plane retardation variation of the PVA-based film as the raw film is preferably as small as possible. In m, it is preferably 10 nm or less, more preferably 5 nm or less.

[0024] The polarizing film according to the present invention preferably has a single transmittance power of at least 3.0% when measured with the polarizing film alone, and more preferably in the range of 43.0 to 45.0%. . The single transmittance can be measured by the method described in Examples below.

As a method for producing a polarizing film, a dry stretching method and a wet stretching method are generally used. In the present invention, a wet stretching method is used. As a process of manufacturing a polarizing film by a wet stretching method, an appropriate method can be used according to the conditions.For example, the polymer film as a raw film is swollen, dyed, crosslinked, stretched, washed with water, The drying process is generally performed by a series of manufacturing steps. In each of these treatment steps except for the drying treatment step, each treatment is performed while being immersed in a bath having various solution powers. The order, number of times, and whether or not each of the swelling, dyeing, cross-linking, stretching, washing, and drying treatments are performed in each treatment step are not particularly limited, and several treatments are performed simultaneously in one treatment step. Some of the processing need not be performed. For example, the stretching treatment may be performed after the dyeing treatment, or may be performed simultaneously with the swelling / dyeing treatment, or may be performed after the stretching treatment. The stretching process in the MD direction can be performed by any appropriate method without limitation. For example, in the case of roll stretching, a method of performing stretching by a difference in peripheral speed between rolls is used. Further, an additive such as boric acid, borax or potassium iodide may be appropriately added to each treatment. Therefore, the polarizing film according to the present invention may contain boric acid, zinc sulfate, zinc chloride, potassium iodide, and the like, if necessary. Further, in some of these treatments, a water washing treatment may be performed for each treatment which may be appropriately stretched in the MD or TD direction by a conventionally known method.

In the stretching in the TD direction according to the present invention, crowns such as a tapered crown shape and a radial crown shape (for example, see FIG. 1) whose diameter increases with the force S whose outer peripheral surface is directed from both ends toward the center portion are used. Use a roll. However, when used in pairs with these crown rolls, a crown roll whose diameter decreases toward the center, such as an inverted crown shape, may be used. The material of the crown roll is not particularly limited as long as it is not affected by the solution used and does not adversely affect the film to be conveyed. , A metal such as stainless steel, and a synthetic rubber material such as silicon and -tolylbutadiene rubber are preferably used. Further, the surface of the crown roll may be appropriately processed such as grooves and patterns for the purpose of preventing slippage. For example, it is effective to form a slit-shaped groove having a snail shape at an interval of 1 to 10 mm and a depth of 0.1 to 3 mm, or to use a knurling process when a metal crown roll is used. The roll length of the crown roll is preferably at least as long as the width of the film. For example, when the width of the film is 1000 mm or less, a force that is about 8 to 60% longer than the width of the film is preferably used.When the width of the film exceeds 1000 mm, the width of the film is about 100 mm more on each side than the width of the film. A roll having a length is preferably used. Specifically, in the case of a film width of 100 mm, for example, a roll having a length of about 108 to 160 mm is used, and in the case of a film width of 1200 mm, for example, a roll of about 1400 mm is used.

The stretching in the TD direction using the crown roll can be performed without limitation at each processing step, and may be performed at any step other than the swelling, dyeing, crosslinking, stretching, washing, and drying treatment steps. You may. In addition, the number of times is not limited, and a plurality of times may be performed. However, in order to obtain a polarizing film without unevenness as in the present invention as in the present invention, it is effective to perform stretching in the TD direction of the present invention before the crosslinking treatment step in which the polymer film is still highly flexible. However, it is particularly preferable to perform it in the swelling treatment step, which is more preferably performed before the dyeing treatment step. Stretching in the TD direction according to the present invention after the crosslinking treatment hardens the effect of expanding in the TD direction because the polymer film is cured by the crosslinking treatment.However, in order to prevent wrinkles and bending, It is valid. Further, the installation position of the crown roll in each processing step is not limited as long as it is appropriately installed at a position where the stretching in the TD direction can be performed efficiently. It is effective to provide it as a guide hole installed in the polymer film because the polymer film can be easily stretched at the time of immersion in a solution due to the characteristics of the polymer film.

[0028] The swelling step is performed, for example, by immersing the polymer film in a swelling bath filled with water. As a result, the polymer film is washed with water, so that dirt on the polymer film surface and an anti-blocking agent can be washed, and the effect of preventing unevenness such as uneven dyeing by swelling the polymer film can be expected. In this swelling bath, glycemic Phosphorus, potassium iodide and the like may be added as appropriate. The concentration of glycerin is preferably 5% by weight or less and potassium iodide is preferably 10% by weight or less. The temperature of the swelling bath is preferably in the range of 20-45 ° C, more preferably 25-40 ° C. The immersion time in the swelling bath is preferably from 2 to 300 seconds, more preferably from 10 to 180 seconds, particularly preferably from 60 to 150 seconds. The stretching ratio at which the polymer film can be stretched in this swelling bath is about 1.1 to 3.5 times in the MD direction.

In the dyeing step, for example, the polymer film is adsorbed on the polymer film by immersing the polymer film in a solution of the dichroic material in a dye bath containing a dichroic material such as iodine. It is a process.

[0030] As the dichroic substance, conventionally known substances can be used, and examples thereof include iodine and organic dyes. Organic dyes include, for example, Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue, Direct First Range S, First Black, etc. can be used.

[0031] These dichroic substances may be used alone or in combination of two or more. When the organic dye is used, it is preferable to combine two or more types from the viewpoint of, for example, reducing the amount of visible light in the visible light range. Specific examples include a combination of Congo I-Red and Supra Blue G, Supra Orange GL and Direct Sky Blue, or a combination of Direct Sky Venorey and First Black.

[0032] As the solution for the dye bath, a solution in which the dichroic substance is dissolved in a solvent can be used. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. The concentration of the dichroic substance is 0.010 to: preferably in the range of LO% by weight 0.02 to 5% by weight more preferably in the range of 0.020 to 7% by weight Especially preferred to be! / ,.

When iodine is used as the dichroic substance, the dyeing efficiency can be further improved. Therefore, it is preferable to further add iodide. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Titanium and the like can be mentioned. The proportion of these iodides to be added is preferably 0.01 to 10% by weight, more preferably 0.10 to 5% by weight, in the dyeing bath. Among these, the ratio of iodine to potassium iodide (weight ratio, iodine: potassium iodide) to which potassium iodide is preferably added is preferably in the range of 1: 5 to 1: 100. The magus is more preferably in the range of 1: 6 to 1:80, particularly preferably in the range of 1: 7 to 1:70.

[0034] The immersion time of the polymer film in the dyeing bath is not particularly limited, but is preferably 1 to 20 minutes, more preferably 2 to 10 minutes. . Further, the temperature of the dyeing bath is preferably in the range of 5 to 42 ° C, more preferably in the range of 10 to 35 ° C. In addition, when the polymer film is stretched in this dyeing bath, the total stretching ratio at that time is about 1.1 to 3.5 times in the MD direction.

[0035] The dyeing treatment may be, for example, a method of applying or spraying an aqueous solution containing a dichroic substance to the polymer film, in addition to the method of immersion in the dyeing bath as described above. A dichroic substance may be preliminarily mixed during the formation of the polymer film.

[0036] In the crosslinking step, for example, the polymer film is immersed in a bath containing a crosslinking agent to perform crosslinking. As the crosslinking agent, a conventionally known substance can be used. For example, boron compounds such as boric acid and borax, dalioxal, dartalaldehyde and the like can be mentioned. These may be used alone or in combination of two or more. When two or more kinds are used in combination, for example, a combination of boric acid and borax is preferred, and the addition ratio (molar ratio, boric acid: borax) is in the range of 4: 6 to 9: 1. Most preferably, the range of 5.5: 4.5.5-7: 3 is more preferably 6: 4.

[0037] As the solution of the crosslinking bath, a solution in which the crosslinking agent is dissolved in a solvent can be used. As the solvent, for example, water can be used, and it may further contain an organic solvent compatible with water. The concentration of the crosslinking agent in the solution is not limited to this, but is preferably in the range of 1 to 10% by weight, more preferably 2 to 6% by weight. [0038] An iodide may be added to the cross-linking bath from the viewpoint of obtaining in-plane uniform characteristics of the polarizing film. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Titanium chloride is included, and its content is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. Above all, the ratio of boric acid and potassium iodide (weight ratio, boric acid: potassium iodide) in which the combination of boric acid and potassium iodide is preferred is in the range of 1: 0.1 to 1: 3.5. More preferably, it is in the range of 1: 0.5 to 1: 2.5.

[0039] The temperature of the crosslinking bath is, for example, in the range of 20 to 70 ° C, and the immersion time of the polymer film is usually in the range of 1 second to 15 minutes, preferably 5 seconds to 10 minutes. In addition, the cross-linking treatment may be performed by applying or spraying a solution containing a cross-linking agent, as in the case of the dyeing treatment.The polymer film may be stretched in the MD direction in this cross-linking bath. Is about 1.1 to 3.5 times.

[0040] The solution of the stretching bath in the stretching step is not particularly limited, and for example, a solution to which various metal salts or compounds of iodine, boron or zinc are added can be used. As a solvent for this solution, water, ethanol, or various organic solvents are appropriately used. Among them, it is preferable to use a solution in which boric acid and Z or potassium iodide are added at about 2 to 18% by weight, respectively. When boric acid and potassium iodide are used at the same time, the content ratio (weight ratio, boric acid: potassium iodide) is about 1: 0.1 to 1: 4, more preferably 1: 0. It is preferable to use them at a ratio of about 5 to 1: 3.

[0041] The temperature of the stretching bath is, for example, preferably in the range of 40 to 67 ° C, more preferably 50 to 62 ° C. The total stretching ratio in the MD direction after this stretching process step is about 3 to 7 times.

[0042] In the washing step, for example, by immersing the polymer film in an aqueous solution of a washing bath, unnecessary residues such as boric acid adhered in the previous treatment can be washed away. To the aqueous solution, for example, sodium iodide or potassium iodide, to which iodide may be added, is preferably used. When potassium iodide is added to the water washing bath, its concentration is, for example, 0.1 to 10% by weight, and preferably 3 to 8% by weight. In addition, The temperature is preferably from 10 to 60 ° C, more preferably from 15 to 40 ° C. Further, the number of times of the water washing treatment is not particularly limited, and the type and concentration of the additive in each water washing bath may be changed.

When the polymer film is pulled out of each treatment bath, a known roll such as a pinch roll or the like may be used in order to prevent dripping, or an air knife may be used. Excess water may be removed by, for example, scraping off the water.

As the drying step, an appropriate method such as natural drying, air drying, and heat drying can be used, but usually, heat drying is preferably used. In the heat drying, for example, the heating temperature is preferably about 20 to 80 ° C, and the drying time is preferably about 1 to 10 minutes.

[0045] The final stretching ratio (total stretching ratio) of the polarizing film produced through the above-described processing steps is 3.0 to 7.0 times that of the polymer film before the above treatment. More preferably, it is more preferably 5.5 to 6.2 times. If the total stretching ratio is less than 3.0 times, it is difficult to obtain a polarizing film having a high degree of polarization. If it exceeds 7.0 times, the film is easily broken.

In the present invention, the polarizing film may be manufactured by using another manufacturing method without being limited to the above-described manufacturing method. For example, a polymer film such as polyethylene terephthalate (PET) into which a dichroic substance is kneaded, formed into a film, or stretched may be used, or a uniaxially oriented liquid crystal as a host and a dichroic dye as a guest. O-type (US Pat. No. 5,523,863, Japanese Patent Application Laid-Open No. 3-503322) and E-type using a dichroic lyo-pic pick-up liquid crystal (US Pat. , 049, 428)

[0047] The thickness of the polarizing film thus produced is not particularly limited, but is preferably 5 to 40 µm. When the thickness is 5 m or more, the mechanical strength does not decrease. When the thickness is 40 m or less, the optical characteristics do not decrease, and the thickness can be reduced even when applied to an image display device.

[0048] In the polarizing film according to the present invention, various optical layers can be laminated for practical use. The optical layer is not particularly limited as long as it satisfies the required optical characteristics.For example, a polarizing film may be provided on one or both sides of the polarizing film. Hard coat treatment, anti-reflection treatment, and anti-stating treatment on the transparent protective layer for the purpose of protecting the transparent protective layer, the surface opposite to the surface of the transparent protective layer adhered to the polarizing film, or one or both surfaces of the polarizing film itself. Or a method of applying a surface treatment for the purpose of diffusion or anti-glare, or a method of laminating an oriented liquid crystal layer for the purpose of compensating for a viewing angle or an adhesive layer for laminating another film. Furthermore, as an optical layer, a polarization conversion element, a reflection plate, a semi-transmission plate, a retardation plate (including a wavelength plate (λ plate) such as 1Z2 or 1Z4), an image display device such as a viewing angle compensation film, a brightness enhancement film, and the like. And those obtained by laminating one or two or more optical films used for forming the film. In particular, elliptically polarized light obtained by laminating a reflective polarizing plate or a transflective polarizing plate or a transflective polarizing plate obtained by laminating a reflecting plate or a transflective reflecting plate on a polarizing plate obtained by laminating the above polarizing film and a transparent protective layer. A plate or a circularly polarizing plate, a wide viewing angle polarizing plate in which a viewing angle compensation layer or a viewing angle compensation film is laminated, or a polarizing plate in which a brightness enhancement film is laminated is preferable. The timing of laminating the optical layer or the optical film with the transparent protective layer may be after lamination with the polarizing film or before lamination with the polarizing film.

As a material for forming the transparent protective layer provided on one or both surfaces of the polarizing film, a material having excellent transparency, mechanical strength, heat stability, moisture shielding property, isotropy and the like is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cenorellose polymers such as diacetinoresenorelose and triacetinoresenorelose, acrylic polymers such as polymethyl methacrylate, polystyrene and Atari mouth-tri- And styrene-based polymers such as styrene copolymer (AS resin) and polycarbonate-based polymers. Further, polyolefins such as polyethylene, polypropylene, polyolefins having a cyclo- or norbornene structure, polyolefin-based polymers such as ethylene-propylene copolymers, amide-based polymers, amide-based polymers such as nylon and aromatic polyamide, and imid-based polymers , Sunolefon-based polymer, polyethenoresnolefone-based polymer, polyetheneoleateno-leketone-based polymer, polyphenylene sulfide-based polymer, vinyl alcohol-based polymer, vinylidene chloride-based polymer, vinyl butyral-based polymer, arylate-based polymer, polyoxymethylene-based polymer , An epoxy-based polymer, or a blend of the above-mentioned polymers are also examples of the polymer forming the transparent protective layer. The transparent protective layer It can also be formed as a cured layer of a thermosetting or ultraviolet curable resin such as an acrylic, urethane, acrylic urethane, epoxy or silicone resin. Among these, as the transparent protective layer to be bonded to the polarizing film according to the present invention, a triacetyl cellulose film having a surface saponified with an alkali or the like is preferable.

As the transparent protective layer, a polymer film described in JP-A-2001-343529 (WO01Z37007), for example, (A) a thermoplastic resin having a substituted or Z or unsubstituted imide group in the side chain And a resin composition containing (B) a thermoplastic resin having a substituted or Z- or unsubstituted phenol group and a -tolyl group in the side chain. Specific examples thereof include isobutene and N- A film of a resin composition containing an alternating copolymer of methylmaleimide and an acrylonitrile-styrene copolymer is exemplified. As the film, a strong film such as a mixed extruded product of a resin composition can be used.

[0051] The thickness of the transparent protective layer is not particularly limited, but is, for example, 500 m or less, and preferably 1 to 300 Pm. In particular, the thickness is more preferably 5 to 200 μm. In addition, it is preferable that the surface of the transparent protective layer is subjected to a quenching treatment with an alkali or the like from the viewpoint of improving the polarization characteristics, durability, and adhesion characteristics.

[0052] Further, it is preferable that the transparent protective layer has as little coloring as possible. Therefore, Rth = [(nx + ny) / 2-nz]. D (where nx and ny are the main refractive indices in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness) Is 90ηπ! A transparent protective layer having a thickness of from +75 nm is preferably used, and by using this, the coloring (optical coloring) of the polarizing plate caused by the transparent protective layer can be almost completely eliminated. In addition, Rth is more preferably between 80 and +60 nm, particularly preferably between 70 nm and +45 nm! /.

[0053] When the transparent protective layer is laminated on both sides of the polarizing film, those having different characteristics for each one side may be used. The characteristics are not limited to these, but include, for example, thickness, material, light transmittance, tensile modulus, presence or absence of an optical layer, and the like.

The hard coat treatment is performed for the purpose of preventing the surface of a polarizing film or a polarizing plate on which a polarizing film and a transparent protective layer are laminated from being scratched. Alternatively, it can be formed by, for example, a method of adding a hardened film excellent in hardness and sliding properties with an appropriate ultraviolet curable resin such as a silicone resin to the surface of the transparent protective layer. The anti-reflection treatment is performed for the purpose of preventing reflection of external light on the polarizing plate surface, and can be achieved by forming an anti-reflection film or the like according to the related art. In addition, the anti-stating treatment is performed for the purpose of preventing adhesion to an adjacent layer.

The anti-glare treatment is performed for the purpose of preventing external light from being reflected on the surface of the polarizing plate and hindering the visibility of light transmitted through the polarizing plate. For example, the anti-glare treatment is performed by a sand blast method or an embossing method. The transparent protective layer can be formed by giving a fine uneven structure to the surface of the transparent protective layer by an appropriate method such as a surface roughening method or a method of blending transparent fine particles. Examples of the fine particles to be included in the formation of the above-mentioned surface fine uneven structure include silica, alumina, titania, zirco-a, tin oxide, indium oxide, cadmium oxide, and oxide having an average particle size of 0.5 to 50 μm. Transparent fine particles such as inorganic fine particles made of antimony and the like, which may have conductivity, and organic fine particles also having a crosslinked or uncrosslinked polymer and the like are used. When forming the fine surface uneven structure, the amount of the fine particles used is generally about 2 to 70 parts by weight, and 5 to 50 parts by weight based on 100 parts by weight of the transparent resin forming the fine surface uneven structure. Is preferred. The anti-glare layer may also serve as a diffusion layer (such as a viewing angle expanding function) for diffusing light transmitted through the polarizing plate to increase the viewing angle and the like.

The optical layers such as the anti-reflection layer, anti-staking layer, diffusion layer and anti-glare layer can be provided on the transparent protective layer itself, or separately provided separately from the transparent protective layer. Talk about this.

When the polarizing film and the transparent protective layer are bonded via an adhesive layer, the bonding treatment is not particularly limited. For example, an adhesive made of a vinyl polymer, or boric acid or borax is used. It can be carried out via an adhesive comprising at least a water-soluble crosslinking agent for a vinyl alcohol-based polymer such as glutaraldehyde, melamine, and oxalic acid. This adhesive layer can be formed as a layer for applying and drying an aqueous solution, but in the preparation of the aqueous solution, other additives and a catalyst such as an acid can be blended if necessary. . In particular, when a polyvinyl alcohol-based polymer film is used as the polarizing film, it is preferable to use an adhesive that also has a polyvinyl alcohol strength, because of its adhesive force. Also, The thickness of the adhesive layer is preferably 5 nm or more and 500 nm or less, and more preferably lOnm or more and 300 nm or less, determined by the balance between the adhesive effect and the thickness.

[0058] The reflective polarizing plate is provided with a reflective layer on the polarizing plate, and is used to form a liquid crystal display device or the like that reflects and reflects incident light from the viewing side (display side). In addition, there is an advantage that a built-in light source such as a backlight can be omitted, and the thickness of the liquid crystal display device can be easily reduced. The reflection type polarizing plate can be formed by an appropriate method such as a method in which a reflective layer having a strength such as a metal is provided on one side of the polarizing plate via a transparent protective layer or the like as necessary.

[0059] Specific examples of the reflective polarizing plate include, as necessary, a reflective layer formed by attaching a foil made of a reflective metal such as aluminum to one side of a matte-treated transparent protective layer and a vapor deposition film. Is raised. Further, there may be mentioned a transparent protective layer containing fine particles to form a fine surface unevenness structure, and a reflective layer having a fine unevenness structure formed thereon. The reflection layer having the fine uneven structure described above has an advantage that the incident light is diffused by irregular reflection to prevent a directional glare and to suppress uneven brightness. Further, the transparent protective layer containing fine particles has an advantage that the incident light and the reflected light are diffused when transmitting the light, and the unevenness of brightness and darkness can be further suppressed. The reflection layer having a fine uneven structure reflecting the fine uneven structure on the surface of the transparent protective layer is formed by an appropriate method such as an evaporation method such as a vacuum evaporation method, an ion plating method, or a sputtering method or a plating method. The method can be performed by directly attaching a metal to the surface of the transparent protective layer.

[0060] Instead of the method of directly applying the reflective plate to the transparent protective layer of the polarizing plate, the reflective plate can also be used as a reflective sheet or the like in which a reflective layer is provided on an appropriate film according to the transparent film. Since the reflective layer is usually made of metal, its use with its reflective surface covered with a transparent protective layer, a polarizing plate, etc. prevents the reduction of the reflectance due to oxidation and, consequently, maintains the initial reflectance for a long time. This is more preferable in terms of avoiding the additional attachment of the protective layer.

[0061] The transflective polarizing plate can be obtained by forming a transflective reflective layer such as a half mirror that reflects and transmits light on the reflective layer. The transflective polarizing plate is usually provided on the back side of the liquid crystal cell, and the liquid crystal display device is used in a relatively bright atmosphere. When used, an image is displayed by reflecting the incident light from the viewing side (display side), and the image is displayed on the back side of the transflective polarizing plate. A liquid crystal display device that displays images using a built-in light source such as a backlight can be formed.

. In other words, the transflective polarizing plate can save energy for using a light source such as a knock light in a bright atmosphere, and can be used for forming a liquid crystal display device of a type that can be used with a built-in light source even in a relatively bright atmosphere. Useful.

[0062] An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. When changing linearly polarized light to elliptically or circularly polarized light, elliptically or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light, a phase difference plate or the like is used. In particular, a so-called 1Z4 wavelength plate (also referred to as a λΖ4 plate) is used as a retardation plate that converts linearly polarized light into circularly polarized light or converts circularly polarized light into linearly polarized light. A 1Z2 wavelength plate (also referred to as a λΖ2 plate) is generally used to change the polarization direction of linearly polarized light.

The elliptically polarizing plate compensates (prevents) the coloring (blue or yellow) caused by the birefringence of the liquid crystal layer of the super twisted nematic (STN) type liquid crystal display device, and displays the colorless black and white. It is used effectively in such cases. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can also compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflection type liquid crystal display device that displays an image in color, and also has an antireflection function.

Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, an alignment film obtained by aligning a liquid crystal monomer and then crosslinking and polymerizing the alignment film, an alignment film of a liquid crystal polymer, And a film in which an alignment layer of a liquid crystal polymer is supported by a film. The stretching treatment can be performed by, for example, a roll stretching method, a long gap stretching method, a tenter stretching method, a tubular stretching method, or the like. The stretching ratio is generally about 1.1 to 3 times in the case of uniaxial stretching. The thickness of the retardation plate is not particularly limited either, but is generally 10 to 200 μm, preferably 20 to: LOO μm.

[0065] Examples of the polymer material include polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl atearylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methinoresenolerose, polycarbonate, and polyaryle. , Polysulfone, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, polyphenylene sulfide, polyphenylene oxide, polyallyl sulfone, polyvinyl alcohol, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulose polymer And various binary and ternary copolymers, graft copolymers and blends thereof. These polymer materials become oriented products (stretched films) by stretching or the like.

[0066] As the liquid crystal monomer, any of lyotropic and thermopick properties can be used. The workability is preferably a thermopick property. For example, an atalyloyl group, a vinyl group And those having a basic skeleton of a biphenyl derivative, a phenolbenzoate derivative, a stilbene derivative or the like into which a functional group such as an epoxy group is introduced. Such a liquid crystal monomer is aligned using a known method as appropriate, for example, a method using heat or light, a method for rubbing on a substrate, a method for adding an alignment aid, and then maintaining the alignment. A method of fixing the orientation by crosslinking and polymerizing with light, heat, an electron beam or the like is preferably used.

[0067] Examples of the liquid crystal polymer include various types of main chain and side chain in which a conjugated linear group (mesogen) for imparting liquid crystal orientation is introduced into the main chain or side chain of the polymer. And so on. Specific examples of the main chain type liquid crystal polymer include a structure in which a mesogen group is bonded at a spacer portion that imparts flexibility, such as a nematic-oriented polyester-based liquid crystal polymer, a discotic polymer, and a cholesteric polymer. And so on. Specific examples of the side-chain type liquid crystalline polymer include polysiloxane, polyacrylate, polymethacrylate or polymalonate as a main chain skeleton, and nematic alignment is provided through a spacer composed of a conjugated atomic group as a side chain. And the like having a mesogen portion that is a unitary force of a para-substituted cyclic compound. These liquid crystal polymers are, for example, those obtained by rubbing the surface of a thin film of polyimide or polyvinyl alcohol formed on a glass plate, or those obtained by obliquely depositing silicon oxide. This is done by developing the solution and heat-treating it.

[0068] The retardation plate may be a plate having an appropriate retardation according to the intended use, such as, for example, various wavelength plates or those for the purpose of compensating the viewing angle or the like due to birefringence of the liquid crystal layer. A device in which optical characteristics such as phase difference are controlled by laminating more than two kinds of phase difference plates may be used.

[0069] The elliptically polarizing plate and the reflection type elliptically polarizing plate are obtained by laminating a polarizing plate or a reflection type polarizing plate and a retardation plate in an appropriate combination. The strong elliptically polarizing plate or the like can also be formed by sequentially and separately laminating the (reflection type) polarizing plate and the retardation plate in the manufacturing process of the liquid crystal display device so as to form a combination. As described above, an optical film such as an elliptically polarizing plate is excellent in quality stability, laminating workability, and the like, and has an advantage that the production efficiency of a liquid crystal display device and the like can be improved.

[0070] The viewing angle compensation film is a film for widening the viewing angle so that the image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed in a direction not perpendicular to the screen but slightly oblique. As such a viewing angle compensating retardation plate, for example, a retardation plate, an alignment film such as a liquid crystal polymer, or a support in which an alignment layer such as a liquid crystal polymer is supported on a transparent base material can be used. A common retardation plate is a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film is a biaxially stretched biaxially stretched polymer film. Polymer films with refraction, biaxially stretched films such as uniaxially stretched in the plane direction and also in the thickness direction, birefringent polymers with controlled refractive index in the thickness direction, and bidirectionally stretched films such as obliquely oriented films Is used. Examples of the obliquely oriented film include, for example, a film obtained by bonding a heat shrink film to a polymer film and subjecting the polymer film to stretching or Z and shrinkage treatment under the action of the shrinkage force caused by heating, or an obliquely oriented liquid crystal polymer And the like. As the raw material polymer for the retardation plate, the same polymer as that described for the retardation plate is used, which prevents coloring etc. due to changes in the viewing angle based on the retardation of the liquid crystal cell and enlarges the viewing angle for good visibility. Appropriate ones for the purpose can be used.

[0071] Further, from the viewpoint of achieving a wide viewing angle with good visibility, an optically anisotropic layer composed of a liquid crystal polymer alignment layer, particularly a tilted alignment layer of discotic liquid crystal polymer, is formed of a triacetyl cellulose film. A supported optical compensation retardation plate can be preferably used.

Examples of the polarization conversion element include an anisotropic reflection-type polarization element and an anisotropic scattering-type polarization element. Cholesteric liquid crystal layers, especially A film that reflects either left-handed or right-handed circularly polarized light and transmits the other light, such as an oriented film of a steric liquid crystal polymer or one with its oriented liquid crystal layer supported on a film substrate. And at any wavelength in any of its reflection bands

0.2% linear polarization with a predetermined polarization axis, such as a composite with a retardation plate having a 25-fold retardation, or a multilayer laminate of dielectric thin films and thin films with different refractive index anisotropies. It is preferable to show a characteristic of transmitting other light and reflecting other light. Examples of the former include a PCF series manufactured by Nitto Denki, and examples of the latter include a DBEF series manufactured by 3M. Further, a reflective grid polarizer can be preferably used as the anisotropic reflective polarizer. Examples include Moxtek's Micro Wires. On the other hand, as the anisotropic scattering type polarizing element, for example, 3M DRPF and the like can be mentioned.

A polarizing plate obtained by laminating a polarizing plate and a brightness enhancement film is usually used by being provided on the back side of a liquid crystal cell. Brightness-enhancing films exhibit the property of reflecting linearly polarized light with a predetermined polarization axis or circularly polarized light in a predetermined direction when natural light enters due to reflection from the backlight or the back side of a liquid crystal display device, etc., and transmitting other light. The polarizing plate in which the brightness enhancement film is laminated with the polarizing plate receives light from a light source such as a backlight to obtain transmitted light in a predetermined polarization state, and reflects light other than the predetermined polarization state without transmitting. Is done. The light reflected from the surface of the brightness enhancement film is further inverted through a reflection layer or the like provided on the rear side thereof and re-incident on the brightness enhancement film, and a part or all of the light is transmitted as light in a predetermined polarization state, thereby obtaining brightness. In addition to increasing the amount of light transmitted through the enhancement film, the polarization film is supplied with polarized light that is hardly absorbed, thereby increasing the amount of light that can be used for liquid crystal image display and the like, thereby improving luminance. That is, when light is incident through a polarizing film on the back side of a liquid crystal cell with a backlight or the like without using a brightness enhancement film, light having a polarization direction that does not match the polarization axis of the polarizing film is Almost all light is absorbed by the polarizing film and does not pass through the polarizing film. That is, about 50% of the light, which varies depending on the characteristics of the polarizing film used, is absorbed by the polarizing film, and the amount of light available for liquid crystal image display and the like is reduced, and the image becomes darker. The brightness enhancement film enters the polarizing film with light having a polarization direction that is absorbed by the polarizing film. Instead of being reflected, the light is once reflected by the brightness enhancement film, then inverted through the reflective layer, etc., provided behind it, and then re-entered into the brightness enhancement film. Since only polarized light whose polarization direction is such that it can pass through a polarizing plate is transmitted and supplied to the polarizing film, light from a knock light or the like can be efficiently displayed on an image of a liquid crystal display device. It can be used and the screen can be brightened.

[0074] A diffusion plate may be provided between the brightness enhancement film and the above-mentioned reflection layer or the like. The light in the polarization state reflected by the brightness enhancement film goes to the reflection layer and the like, but the diffusion plate provided diffuses the passing light uniformly, and at the same time, eliminates the polarization state to make the light non-polarized. That is, it returns to the original natural light state. The light in the non-polarized state, that is, in the natural light state, repeatedly travels toward the reflection layer and the like, is reflected through the reflection layer and the like, passes through the diffusion plate again, and re-enters the brightness enhancement film. By providing the diffuser for returning to the original natural light state, the brightness of the display screen can be maintained, the unevenness of the brightness of the display screen can be reduced, and a uniform bright screen can be provided. By providing a diffuser to return to the original natural light state, the number of repetitions of the first incident light is increased moderately, and combined with the diffusion function of the diffuser, a uniform bright display screen can be provided. it is conceivable that.

[0075] As the brightness enhancement film, for example, linearly polarized light having a predetermined polarization axis is transmitted and other light is reflected, such as a multilayer thin film of a dielectric or a multilayer laminate of thin films having different refractive index anisotropy. Reflects either left-handed or right-handed circularly polarized light and transmits other light, such as those exhibiting characteristics, such as an alignment film made of cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate. Appropriate materials such as those exhibiting characteristics can be used.

Therefore, in the above-described brightness enhancement film that transmits linearly polarized light having a predetermined polarization axis, the transmitted light is directly incident on the polarizing plate with the polarization axis aligned, thereby suppressing absorption loss due to the polarizing plate. In addition, the light can be efficiently transmitted. On the other hand, a brightness enhancement film that transmits circularly polarized light, such as a cholesteric liquid crystal layer, can be directly incident on a polarizing film.However, in order to suppress absorption loss, the circularly polarized light is linearly transmitted through a phase difference plate. It is preferable that the light is polarized and incident on a polarizing plate. By using a 1Z4 wavelength plate as the retardation plate, circularly polarized light can be converted to linearly polarized light.

[0077] A retardation plate that functions as a 1Z4 wavelength plate in a wide wavelength range such as a visible light region is, for example, a wave plate. A phase difference layer functioning as a 1Z4 wavelength plate and a phase difference layer exhibiting other phase difference characteristics, for example, a method of superimposing a phase difference layer functioning as a 1Z2 wavelength plate on monochromatic light having a length of 550 nm can be obtained. it can. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

[0078] The cholesteric liquid crystal layer also has a structure in which two or three or more layers are overlapped by combining those having different reflection wavelengths to reflect circularly polarized light in a wide wavelength range such as a visible light region. Thus, it is possible to obtain the transmitted circularly polarized light in a wide wavelength range.

Further, the polarizing plate of the present invention may be formed by laminating a polarizing plate such as the above-mentioned polarized light separating type polarizing plate and two or three or more optical layers. Therefore, a reflective elliptically polarizing plate or a transflective elliptically polarizing plate obtained by combining the above-mentioned reflective polarizing plate, semi-transmissive polarizing plate, and retardation plate may be used.

[0080] The optical film in which the optical layer is laminated on a polarizing plate can also be formed by a method of sequentially laminating the optical film in the process of manufacturing a liquid crystal display device or the like. They are excellent in quality stability, assembling work, and the like, and have the advantage that the manufacturing process of a liquid crystal display device or the like can be improved. For the lamination, an appropriate adhesive means such as an adhesive layer is used. When bonding the above-mentioned polarizing plate and other optical layers, their optical axes can have an appropriate arrangement angle according to the target retardation characteristics and the like.

[0081] The polarizing film of the present invention and the laminated optical member may be provided with an adhesive layer for bonding to another member such as a liquid crystal cell. The pressure-sensitive adhesive layer is not particularly limited. For example, the pressure-sensitive adhesive layer can be formed of a conventional pressure-sensitive adhesive such as an acrylic, silicone, polyester, polyurethane, polyether, or rubber. . The pressure-sensitive adhesive is used to prevent foaming and peeling phenomena due to moisture absorption, to prevent deterioration of optical properties due to differences in thermal expansion, to prevent liquid crystal cells from warping, and to form image display devices with high quality and excellent durability. It is preferable that the adhesive layer has a low moisture absorption rate and excellent heat resistance because of its properties and the like.Moreover, in order to prevent changes in the optical properties of polarizing films, etc. It is preferable to use a material that does not require a long curing process or a long drying time. From such a viewpoint, in the present invention, an acrylic pressure-sensitive adhesive is preferably used. [0082] In addition, an adhesive layer or the like that contains fine particles and exhibits light diffusivity can also be used. The adhesive layer may be provided on a necessary surface as needed.For example, when referring to a polarizing plate comprising a polarizing film and a transparent protective layer as in the present invention, if necessary, one side of the protective layer or What is necessary is just to provide an adhesive layer on both surfaces.

[0083] The thickness of the adhesive layer is not particularly limited, but is preferably from 5 to 35 / zm, and more preferably from 15 to 25 Pm. By setting the thickness of the adhesive layer in this range, the stress accompanying the dimensional behavior of the polarizing film and the polarizing plate can be reduced.

When the adhesive layer is exposed on the surface, it is preferable to temporarily cover the adhesive layer with a separator for the purpose of preventing contamination until the adhesive layer is put into practical use. The separator is a system in which an appropriate release film such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum-sulfur-based release agent is provided on an appropriate film according to the transparent protective layer or the like. And the like.

[0085] The transparent protective layer, optical layer, adhesive layer, and other layers forming the above-mentioned polarizing plate and optical member are formed of, for example, a salicylate compound, a benzophenone compound, a benzotriazole compound, and a cyanoacrylate compound. Alternatively, a material having an ultraviolet absorbing ability by an appropriate method such as a method of treating with an ultraviolet ray absorbent such as a nickel complex salt-based compound may be used.

[0086] The polarizing film of the present invention is preferably used for forming an image display device such as a liquid crystal display device, an electroluminescent (EL) display device, a plasma display (PD), and a field emission display (FED). Can be.

[0087] The image display device of the present invention is, for example, a liquid crystal display device, an electroluminescent (EL) display device, a plasma display (PD), and a field emission display (FED).

[0088] The polarizing film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. For example, a reflective film or a polarizing plate in which a polarizing film or a polarizing plate is arranged on one side or both sides of a liquid crystal cell can be used. It can be used for a transflective or transmissive / reflective liquid crystal display device. The liquid crystal cell substrate may be either a plastic substrate or a glass substrate. The liquid crystal cell forming the liquid crystal display device is optional, for example, a thin film transistor type A liquid crystal cell of an appropriate type such as an active matrix driving type represented by a simple matrix driving type represented by a twist nematic type or a super twist nematic type may be used.

[0089] When polarizing plates and optical members are provided on both sides of the liquid crystal cell, they may be the same or different. Further, when forming the liquid crystal display device, one or more layers of appropriate components such as a prism array sheet, a lens array sheet, a light diffusing plate, and a backlight can be arranged at appropriate positions.

Next, an organic electroluminescence device (organic EL display device) will be described. In general, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially stacked on a transparent substrate to form a light emitting body (organic electroluminescent light emitting body). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative or the like and a light emitting layer of a fluorescent organic solid force such as anthracene, or A structure having various combinations such as a laminate of such a light-emitting layer and an electron injection layer having a perylene derivative or a hole injection layer, a light-emitting layer, and an electron injection layer. Is known.

[0091] In an organic EL display device, holes and electrons are injected into an organic luminescent layer by applying a voltage to a transparent electrode and a metal electrode, and energy generated by recombination of these holes and electrons is generated. Excites the fluorescent substance and emits light when the excited fluorescent substance returns to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be expected from this, the current and the emission intensity show a strong nonlinearity accompanying rectification with respect to the applied voltage.

[0092] In an organic EL display device, at least one electrode must be transparent in order to extract light emitted from the organic light emitting layer, and is usually formed of a transparent conductor such as indium tin oxide (ITO). The used transparent electrode is used as an anode. On the other hand, it is important to use a material with a small work function for the cathode in order to facilitate electron injection and increase the light emission efficiency, and metal electrodes such as Mg Ag and A1-Li are usually used.

[0093] In the organic EL display device having such a configuration, the organic light emitting layer is formed of an extremely thin film having a thickness of about lOnm. For this reason, the organic light-emitting layer almost completely emits light similarly to the transparent electrode. It is completely transparent. As a result, the light incident on the surface of the transparent substrate during non-light emission, transmitted through the transparent electrode and the organic light emitting layer, and reflected by the metal electrode was again emitted to the surface side of the transparent substrate, so that external force was also visually recognized. Sometimes, the display surface of the organic EL display device looks like a mirror surface.

[0094] In an organic EL display device including an organic electroluminescent luminous body having a transparent electrode on the front side of an organic luminescent layer that emits light by application of a voltage and a metal electrode on the back side of the organic luminescent layer, A polarizing plate can be provided on the surface side of the electrode, and a retardation film can be provided between the transparent electrode and the polarizing plate.

[0095] Since the retardation film and the polarizing film have a function of polarizing light incident from the outside and reflected on the metal electrode, there is an effect that a mirror surface of the metal electrode is not visually recognized from the outside by the polarizing function. In particular, if the retardation film is composed of a 1Z4 wavelength plate and the angle between the polarization directions of the polarizing plate and the retardation film is adjusted to πZ4, the mirror surface of the metal electrode can be completely shielded.

That is, only linearly polarized light components of the external light incident on the organic EL display device are transmitted by the polarizing plate. This linearly polarized light generally becomes elliptically polarized light by the retardation film, but it becomes circularly polarized light, especially when the retardation film is a 1Z4 wavelength plate and the angle between the polarization directions of the polarizing plate and the retardation film is π Ζ4. .

[0097] The circularly polarized light transmits through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, passes through the organic thin film, the transparent electrode, and the transparent substrate again, and becomes linearly polarized again by the retardation film. Become. The linearly polarized light is orthogonal to the polarization direction of the polarizing plate, and cannot be transmitted through the polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

[0098] The PD generates a discharge in a rare gas enclosed in the panel, especially a gas mainly composed of neon, and the vacuum ultraviolet rays generated at that time cause R, G, By generating the phosphor of B, an image can be displayed.

[0099] In the field of image display devices as described above, there is a demand for in-house manufacturing in which the processing steps from punching of the raw optical film to selection and bonding are consistently performed in order to reduce costs. I have. In the in-house manufacturing method, in which the post-processing (cutting) force of the optical film is also integrated until it is bonded to the cell, it is necessary to measure the defective area immediately. In the present invention, when the cut polarizing plate is used as it is for a display, a chip cut The size of the polarizing film is arbitrary. Generally, a film having a length of 10 cm to 130 cm and a width of 10 cm to 130 cm is used. In particular, there is no upper limit to the size of the display! / ヽ 1S It depends on the width of the base material for polarizing films such as transparent protective films and PVA films that can be made at present. Therefore, conventionally, an inspection process was required after the chip cut, and the power of eliminating defective products in the inspection process. In the present invention, the in-plane uniformity of the polarizing film was enhanced. It is possible to perform a single-line bonding and packaging process and a process of bonding to an image display device such as an EL display device without going through an unpacking process.

[0100] Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited by these Examples and Comparative Examples.

Example 1

[0101] Swelling, dyeing, cross-linking, stretching, washing with water, and drying using a polybutyl alcohol (PVA) film (thickness: 75 μm, raw film width: 200 mm, Kuraray Co., Ltd., degree of polymerization: 2400) After that, a polarizing film having a thickness of 25 μm was obtained.

The conditions in each process are as follows.

[0102] (Swelling treatment step)

Curvature R = 8.3% in pure water at 30 ° C with respect to the film (end diameter (Dl) = 55 mm, center diameter (D2) = 80 mm, length (L) = 300 mm) The crown roll was used as a roll near the outlet in the bath, and stretched 1.20 times in the TD direction and 2.5 times in the MD direction. The film width at the outlet of this processing step was 240 mm.

[0103] (Dyeing process)

The film is dyed in a 5% by weight iodine aqueous solution (IZKI (weight ratio) = 1Z10) at 30 ° C. for 120 seconds (the dyeing time is adjusted so that the single transmittance of the polarizing film becomes 43 ± 0.1%). It was adjusted.

[0104] (Cross-linking treatment step)

The film was immersed in a 3% by weight boric acid + 2% by weight KI aqueous solution (30 ° C.) for 60 seconds.

(Stretching process) The film was stretched in a 4% by weight boric acid + 3% by weight KI aqueous solution (60 ° C.) to a total stretch ratio of 5.5.

[0106] (Washing treatment step)

The film was immersed in a 5% by weight KI aqueous solution (25 ° C.) for 15 seconds.

(Drying process)

The film was dried at 50 ° C. for 1 minute while maintaining the tension.

[0108] The single film transmittance and the degree of polarization of the polarizing film (width 115 mm) thus obtained were measured to evaluate unevenness. The results of these measurements are shown in Table 1 below. The measurement of the single transmittance, the measurement of the degree of polarization, and the evaluation of unevenness (including other examples and comparative examples) were performed by the methods described below.

Example 2

[0109] In the swelling process of Example 1, a crown roll having a curvature of R = 15% (DlZD2 = 55mmZlOOmm, L = 300mm) was used in the same Cf standing as in Example 1, and stretched 1.26 times in the TD direction. Then, a polarizing film was obtained in the same manner as in Example 1, except that the film width was changed to 252 mm. The single transmittance and the degree of polarization of the obtained polarizing film (width 121 mm) were measured to evaluate unevenness. The results of these measurements are shown in Table 1 below.

Example 3

In the swelling process of Example 1, a crown roll having a curvature R = 21.7% (D1 / D2 = 70 mm / 140 mm, L = 300 mm) was used at the same position as in Example 1, and in the TD direction. A polarizing film was obtained in the same manner as in Example 1 except that the film was stretched 1.3 times and the film width became 265 mm. The single transmittance and degree of polarization of the obtained polarizing film (127 mm width) were measured to evaluate unevenness. The results of these measurements are shown in Table 1 below.

Example 4

[0111] In the swelling process of Example 1, a crown roll having a curvature R = 31.7% (D1 / D2 = 55mm / 150mm, L = 300mm) was used at the same position as in Example 1, and in the TD direction. A polarizing film was obtained in the same manner as in Example 1, except that the film was stretched 1.3 times and the film width became 275 mm. The single transmittance and the degree of polarization of the obtained polarizing film (132 mm width) were measured to evaluate unevenness. The results of these measurements are shown in Table 1 below. [0112] (Comparative Example 1)

In the swelling process of Example 1, a polarizing film was obtained in the same manner as in Example 1 except that the film was not stretched in the TD direction using a roll having a curvature of R = 0% (DlZD2 = 55 mmZ55 mm, L = 300 mm). Was. The film width after the swelling process was 220 mm. The single transmittance and the degree of polarization of the obtained polarizing film (106 mm in width) were measured to evaluate unevenness. The results of these measurements are shown in Table 1 below.

[0113] (Method of calculating curvature)

The curvature R of the crown roll was determined by the following equation.

R [%] = ((D2-D1) / L) X 100

In the above formula, D1 represents the diameter [mm] of the end, D2 represents the diameter [mm] of the center, and L represents the length [mm].

[0114] (Single transmittance, degree of polarization measurement method)

The polarizing film produced in the above example or comparative example was cut at a size of 50 mm × 25 mm at 45 ° with respect to the MD direction, and a spectrophotometer (Murakami Color Research Laboratory: DOT 3) was cut. Measure the single transmittance, parallel transmittance (H) and orthogonal transmittance (H) using

The degree of polarization was determined from the value by the following equation. Note that these transmittances are Y values obtained by performing visibility correction using a 2-degree visual field (C light source) of J1S Z8701.

Degree of polarization (%) = {(H—H) / (H + H)} ^{1 2} X 100

0 90 0 90

[0115] (Mura evaluation method)

An 80 μm-thick triacetylcellulose (TAC) film was adhered to both sides of the prepared polarizing film to form a polarizing plate, and two pieces of 50 mm × 50 mm were cut out. The polarizing plate on the superposed as MD direction perpendicular, placed on the backlight illuminance LOOOOcdZm ^2, to confirm the presence or absence of striped unevenness in frontal and oblique directions visually. As a result, X was given when there was unevenness, and Δ when there was no unevenness.

[0116] [Table 1]

[0117] From the results in Table 1 above, unevenness was confirmed in the conventional manufacturing method (Comparative Example 1). In contrast, in the example, the crown roll having a curvature of 3% or more was used. It can be seen that a wide polarizing film with good optical characteristics and no unevenness can be obtained.

Industrial applicability

[0118] The polarizing film obtained by the production method of the present invention has good in-plane uniformity and excellent optical characteristics without unevenness even if it is large in size. Therefore, the polarizing film obtained by the production method of the present invention is preferably used for various image display devices such as a liquid crystal display device, an EL display device, a PD and a FED, but its use is not limited and is widely used. Is performed.

Claims

The scope of the claims

[1] A method for producing a polarizing film, wherein a swelling step, a dyeing step, a cross-linking step, a stretching step, and a washing step are performed in at least one selected step. And a TD direction stretching step for stretching in the TD direction. The TD direction stretching step is a step of stretching in the TD direction using a crown roll having a curvature of 3% or more.

2. The production method according to claim 1, wherein the curvature of the crown roll is 3% or more and 35% or less.

[3] The production method according to claim 1, wherein the TD direction stretching step is performed at least in a step before the crosslinking step.

[4] The production method according to claim 1, wherein in the swelling step, the TD direction stretching step is performed.

[5] The production method according to claim 4, wherein the stretching ratio in the TD direction is in the range of 1.13 to L4 times.

[6] The method according to claim 1, wherein a crown roll having a roll length longer than the width of the polymer film is used.

[7] A polarizing film obtained by the production method according to claim 1.

[8] The polarizing film according to claim 7, wherein the degree of polarization is 99.80% or more.

[9] An optical film obtained by laminating at least one optical layer on the polarizing film according to claim 7.

[10] An image display device comprising the polarizing film according to claim 7 or the optical film according to claim 9.