JP4827226B2 - Manufacturing method of polarizing plate, polarizing plate and image display apparatus using the same - Google Patents

Description

  The present invention relates to a method for producing a polarizing plate, a polarizing plate, and an image display device using the same. More specifically, the present invention is free from problems such as peeling, curling, cracking, blocking, etc., and has excellent productivity. A method for manufacturing a polarizing plate, and excellent polarizing properties and durability obtained by such a manufacturing method. The present invention relates to a polarizing plate having a liquid crystal display and an image display device using such a polarizing plate.

  A polarizing plate used for an image display device (particularly, a liquid crystal display device) is a step of bonding a polarizer and a protective layer made of a transparent protective film such as a triacetyl cellulose (TAC) film. It is manufactured by the manufacturing method containing these. The process of forming a polarizer includes, for example, a dyeing process for dyeing a polyvinyl alcohol (PVA) film with iodine or dichroic dye having dichroism, a crosslinking process for crosslinking with boric acid or borax, and the like. A stretching process for stretching and a drying process for drying the stretched film are included. In addition, each process of dyeing | staining, bridge | crosslinking, and extending | stretching does not necessarily need to be performed separately, you may perform several processes simultaneously, and the order of each process is not prescribed | regulated especially strictly. Generally manufactured polarizing plates have a TAC film bonded to both sides of the polarizer using an adhesive, so that the appearance and curl of the polarizer and two protective films can be bonded simultaneously. It can be manufactured without causing any problems in the characteristics.

  However, since the TAC film has insufficient heat-and-moisture resistance, when a polarizing plate using the TAC film as a protective film is used at high temperature or high humidity, there is a disadvantage that the performance of the polarizing plate such as the degree of polarization and hue deteriorates. is there.

  In order to solve such a problem, a method of using a transparent film made of a resin having a low moisture permeability (for example, a cyclic olefin resin) as a protective film on at least one surface of a polarizer has been proposed. When using such a protective film having a low water vapor transmission rate, a protective material having a low water vapor transmission rate is usually provided on one surface of the polarizer in order to facilitate drying of the adhesive used for bonding the polarizer and the protective film. A polarizing plate is manufactured by attaching a film and attaching a protective film having a relatively high moisture permeability to the other surface.

  However, when the physical properties and thickness of the protective film to be bonded on both sides are different, the three films (that is, the polarizer, the protective film with a low moisture permeability and the protective film with a relatively high moisture permeability) are bonded together. Sometimes peeling or curling often occurs. As a result, there is a problem that not only the problem relating to the appearance and the problem of reduction in work efficiency are caused, but also the polarization performance of the obtained polarizing plate is lowered. In order to avoid such a problem, conventionally, a method of reducing the thickness of the protective film has been employed (see, for example, Patent Document 1).

Alternatively, a method has been proposed in which a first protective film is bonded to one surface of a polarizer and wound, and then a second protective film is bonded to the surface of the polarizer to which the first protective film is not bonded ( For example, see Patent Document 2). According to this method, there is a possibility that blocking or cracking of the film taken up in the middle of the polarizing plate production process may occur, resulting in a decrease in productivity.
JP 2001-235625 A JP 2002-196132 A

  The present invention has been made in order to solve the above-described conventional problems. The object of the present invention is to produce a polarizing plate having excellent productivity without problems such as peeling, curling, cracking, and blocking. Is to provide. Another object of the present invention is to provide a polarizing plate obtained by such a production method and having excellent polarization characteristics and durability. Still another object of the present invention is to provide an optical film in which at least one optical layer is laminated on such a polarizing plate, and an image display device using the polarizing plate and / or the optical film. .

Method for producing a polarizing plate of the present invention, after forming the first transparent protective film bonded to one surface of the polarizer a laminate having the following moisture permeability 200g / m 2 / ^24h, the laminate A step of bonding a second transparent protective film having a higher water vapor transmission rate than the first transparent protective film to the other surface of the polarizer without winding is included.

  In preferable embodiment, the said manufacturing method bonds together the said polarizer and the said 1st transparent protective film in the state which provided tension | tensile_strength to this polarizer and this 1st transparent protective film. In another preferred embodiment, in the manufacturing method, the laminate and the second transparent protective film are bonded together in a state where tension is applied to the laminate and the second transparent protective film.

  In a preferred embodiment, the curl amount of the laminate is 5 mm or less. In another preferred embodiment, the obtained polarizing plate has a curl amount of 5 mm or less.

  In a preferred embodiment, the first transparent protective film is made of an amorphous polyolefin resin.

  In a preferred embodiment, the second transparent protective film is made of triacetyl cellulose.

  In preferable embodiment, the said manufacturing method further includes the process of drying the said laminated body, before bonding the said 2nd transparent protective film.

  According to another aspect of the present invention, a polarizing plate is provided. This polarizing plate is obtained by the manufacturing method described above.

  According to still another aspect of the present invention, an optical element is provided. This optical element is formed by laminating at least one optical layer on the polarizing plate.

  According to still another aspect of the present invention, an image display device is provided. The image display device includes the polarizing plate and / or the optical element. Examples of such an image display device include a liquid crystal display device, an electroluminescence (EL) display device, a plasma display (PD), and a field emission display (FED).

  According to the present invention, a transparent protective film having a relatively low moisture permeability is bonded to a polarizer to form a laminate, and then the laminate is wound up without taking up the laminate. By laminating a transparent protective film to produce a polarizing plate, peeling and curling at the time of laminating are prevented. As a result, a polarizing plate having excellent durability and polarization characteristics can be obtained with excellent productivity. Furthermore, according to this invention, problems, such as a crack resulting from temporary winding of a laminated body and blocking, do not arise. That is, according to the present invention, the thickness of the transparent protective film is reduced due to problems caused by sticking transparent protective films having different characteristics (for example, elastic modulus) and thickness on both sides of the polarizer. It can be solved without any problems. This is considered to be one of the factors that enabled drying so that moisture and the like can be appropriately removed in the drying step after the protective film is bonded. For example, when moisture or the like cannot be appropriately removed from the polarizing plate, a color loss phenomenon such as red discoloration, a light leakage phenomenon, or a phenomenon in which the transmittance increases and the degree of polarization decreases. It was actually confirmed that this phenomenon does not appear.

A. Polarizing plate A polarizing plate according to a preferred embodiment of the present invention includes a polarizer, a first transparent protective film provided on one surface of the polarizer, and a second provided on the other surface of the polarizer. And a transparent protective film.

  Any appropriate polarizer may be adopted as the polarizer depending on the purpose. For example, dichroic substances such as iodine and dichroic dyes are adsorbed on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. And polyene-based oriented films such as a uniaxially stretched product, a polyvinyl alcohol dehydrated product and a polyvinyl chloride dehydrochlorinated product. Among these, a uniaxially stretched polarizer obtained by adsorbing a dichroic substance such as iodine on a polyvinyl alcohol film is particularly preferable because of its high polarization dichroic ratio. The polarizer may contain boric acid, zinc sulfate, zinc chloride or the like as necessary. The thickness of the polarizer is not particularly limited, but is generally about 5 to 80 μm.

The first transparent protective film, the moisture permeability is 200g ^/ m 2 ^/ 24h or less, preferably 0~100g ^/ m 2 ^/ 24h. The moisture permeability is a measured value at 40 ° C. and 92% RH in accordance with JIS Z 0280. A typical material for forming a film having such moisture permeability includes amorphous polyolefin resin. Examples of the amorphous polyolefin resin include a resin having a polymerization unit of a cyclic olefin such as norbornene or a polycyclic norbornene monomer, and a resin made of a copolymer of a cyclic olefin and a chain olefin.

  The first transparent protective film comprises a resin composition containing a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted and / or unsubstituted phenyl group in the side chain. It may be a formed film. The resin composition may have an olefin component. Specific examples include a polymer film of a resin composition containing a glutarimide copolymer composed of N-methylglutarimide and methylmethacrylate and an acrylonitrile / styrene copolymer, and an alternating copolymer composed of isobutylene and N-methylmaleimide. Examples thereof include a polymer film of a resin composition containing a combination and an acrylonitrile / styrene copolymer.

  The adhesive surface with the polarizer of the first transparent protective film may be subjected to a treatment for improving the adhesive force as necessary. Typical examples of such treatment include dry treatment and easy adhesion treatment. Specific examples of the dry treatment include corona treatment, gas corona treatment, plasma treatment, and low-pressure UV treatment. As a specific example of the easy adhesion treatment, application of an easy adhesion treatment material can be mentioned. Examples of the easy adhesion treatment material include cellulose resin, urethane resin, silane coupling agent, silicon primer, PVA, nylon, styrene resin, and the like. Dry treatment and easy adhesion treatment can be used in combination. Alternatively, the adhesive strength can be improved by performing a saponification treatment with an aqueous sodium hydroxide solution. The saponification treatment can be used in combination with the easy adhesion treatment.

  In one embodiment, the first transparent protective film can also function as a retardation film. When the first transparent protective film is used as a retardation film, the first transparent protective film may be stretched. The stretching conditions (for example, the stretching ratio, the stretching direction, and the stretching temperature) can be appropriately set according to the purpose and the desired phase difference.

  Any appropriate transparent film can be adopted as the second transparent protective film as long as it has a moisture permeability higher than that of the first transparent protective film. Two kinds of films having different moisture permeability are selected from those listed as the first transparent protective film, a film having lower moisture permeability is used as the first transparent protective film, and a film having higher moisture permeability is used as the second film. It may be used as a transparent protective film. Alternatively, a transparent film other than those listed as the first transparent protective film may be used as the second transparent protective film.

  Examples of the transparent film other than those listed as the first transparent protective film include a cellulose resin film. More specifically, cellulose acetate type resin films such as a triacetyl cellulose film and a diacetyl cellulose film can be mentioned. Triacetyl cellulose is preferable, and a saponified triacetyl cellulose film is more preferable.

The second transparent protective film, the moisture permeability is preferably from 200 to 1000 g ^/ m 2 / 24h, more preferably 300~900 ^/ m 2 ^/ 24h.

  The thicknesses of the first transparent protective film and the second transparent protective film are not particularly limited. The thicknesses of the first transparent protective film and the second transparent protective film are each independently typically 500 μm or less, preferably 1 to 300 μm, more preferably 5 to 200 μm, Most preferably, it is 5-100 micrometers. Thus, even if the thickness of the transparent protective film is increased to about 500 μm at the maximum, curling and peeling are one of the major features of the present invention. Since it becomes possible to use a thick transparent protective film, it becomes possible to produce a polarizing plate having excellent durability (for example, heat resistance and moisture resistance). On the other hand, even when the image display apparatus is used for applications that require a reduction in thickness, the transparent protective film used in the present invention can be thinned to about 1 μm, and can be adequately handled.

  It is preferable that neither the first transparent protective film nor the second transparent protective film is colored as much as possible. Accordingly, the thickness direction retardation Rth of the first transparent protective film and the second transparent protective film is preferably independently from −90 nm to +75 nm, more preferably from −80 to +60 nm, and most preferably. Is -70 nm to +45 nm. By using the film having Rth in such a range, the coloring (optical coloring) of the polarizing plate due to the transparent protective film can be substantially eliminated. The thickness direction retardation Rth is expressed as Rth = [(nx + ny) / 2−nz] · d. Here, 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.

B. Hereinafter, a preferable example of the method for producing a polarizing plate of the present invention will be described. First, the manufacturing method of a polarizer is demonstrated. Here, the manufacturing method of the polarizer which made the polyvinyl alcohol-type film adsorb | suck dichroic substances, such as iodine, and was uniaxially stretched is demonstrated. Such a polarizer is manufactured, for example, by a manufacturing method including a swelling process, a dyeing process, a crosslinking process, and a stretching process. In the swelling step, the polyvinyl alcohol film is immersed in water to swell the film. By immersing in water and washing with water, stains on the surface of the polyvinyl alcohol film and an anti-blocking agent can be washed. Furthermore, by swelling the polyvinyl alcohol film, there is an effect of preventing unevenness such as uneven dyeing. In the dyeing step, the polyvinyl alcohol film is dyed in a bath containing a dichroic substance such as iodine or a dye such as a dichroic dye. In the crosslinking step, the polyvinyl alcohol film is crosslinked in a bath containing a crosslinking agent such as boric acid or borax. In the stretching step, the polyvinyl alcohol film is stretched 3 to 7 times the original length. The order of these steps is not particularly limited, and several steps may be performed simultaneously. For example, the stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be performed with dyeing after iodine. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  Next, a polarizer and a transparent protective film are bonded together. In the production method of the present invention, the first transparent protective film and the second transparent protective film are separately bonded to each side of the polarizer. Since the first transparent protective film and the second transparent protective film have different properties (for example, elastic modulus and moisture permeability), if a polarizer and two protective films are bonded together, the curl This is because peeling may occur. Furthermore, in the manufacturing method of the present invention, for example, as shown in FIG. 1, after the first transparent protective film 32 is bonded to one surface of the polarizer 31 to form the laminate 35, the laminate 35 is then used. Without winding up, the second transparent protective film 33 is bonded to the other surface of the polarizer 31 to obtain the polarizing plate 30. In this way, blocking and cracking are prevented by sticking the second transparent protective film 33 without winding up the laminate 35 of the polarizer 31 and the first transparent protective film 32, and the obtained polarized light. Degradation of the optical properties of the plate can be prevented. Furthermore, the installation space of the manufacturing apparatus can be made very small, and there is no time loss due to the winding process, so that the production efficiency can be greatly improved and the manufacturing cost can be greatly reduced.

  The lamination step of the laminate and the second transparent protective film may be performed continuously from the lamination step of the polarizer and the first transparent protective film as shown in FIG. You may perform after performing other operation (For example, the process which improves the adhesive force, for example) to the laminated body 35. When the second protective film is continuously bonded, a polarizing plate can be obtained with extremely excellent productivity. In the case where other operations are performed on the laminated body 35, a polarizing plate having more excellent characteristics depending on the purpose can be obtained. In one embodiment, the bonding process of the laminate and the second transparent protective film is performed after the laminate is subjected to a drying process. By performing the drying process, excess water can be removed very well, so it is possible to remarkably prevent the phenomenon of color loss such as red discoloration, light leakage, or the phenomenon that the transmittance increases and the degree of polarization decreases. obtain. Conditions for the drying treatment (for example, drying temperature, drying time, drying method) can be appropriately set according to the purpose. For example, the drying temperature is 40 to 90 ° C., and the drying time is 1 to 10 minutes.

  The order of laminating the transparent protective film is as follows: first the first transparent protective film (film having relatively low moisture permeability) is bonded to the polarizer, and then the second transparent protective film (film having relatively high moisture permeability). ). By pasting together in this order, excess moisture can be removed very well if drying is performed at an appropriate time as described above. As a result, a polarizing plate having very excellent polarization characteristics and display characteristics can be obtained.

  Preferably, the bonding between the polarizer and the first transparent protective film and the bonding between the laminate and the second transparent protective film are performed such that the state after the bonding becomes flat. While done. In the present invention, whether the state after bonding is flat or not is determined based on the curl amount. In this specification, “curl amount” means a sample obtained by punching a laminate or polarizing plate obtained by bonding into a size of 100 mm × 100 mm in a direction of 45 ° with respect to the absorption axis of the polarizer. Is the spatial distance P lifted from the flat surface. The curl amount of the laminate or polarizing plate is preferably as small as possible after the pasting is flat. Specifically, the curl amount is preferably 5 mm or less, and more preferably 3 mm or less.

  As a representative example of the treatment for flattening the state after the bonding, the polarizer and the first transparent protective film are bonded together with tension applied to the polarizer and the first transparent protective film. Is mentioned. This method is similarly applied to bonding of the laminate and the second transparent protective film. Examples of a method for applying tension include a method using a difference in peripheral speed between guide rollers that convey a polarizer and a transparent protective film. More specifically, for example, when the polarizer and the first transparent protective film are bonded together, the rotational speed of the take-up roll 36 in FIG. 1 may be faster than the rotational speed of the feed roll 37. . The rotation speed of the roll can be appropriately set according to the purpose and desired tension.

  The bonding between the polarizer and the first or second transparent protective film is typically performed using an adhesive. Any appropriate adhesive having good adhesion to the polarizer and the transparent protective film can be adopted as the adhesive. For example, when the polarizer is a polyvinyl alcohol (PVA) film, an adhesive containing a PVA resin is preferable. This is because it is particularly excellent in adhesiveness with a polarizer. Any appropriate PVA-based resin can be adopted as the PVA-based resin. Representative examples include unsubstituted PVA and PVA having a highly reactive functional group. PVA having a highly reactive functional group is particularly preferred. This is because the durability of the resulting polarizing plate can be significantly improved. Specific examples of PVA having a highly reactive functional group include acetoacetyl-modified PVA resins. The polymerization degree of the binder resin (for example, PVA resin) of the adhesive is preferably 100 to 3000. By having a polymerization degree in such a range, the adhesion to the polarizer and the transparent protective film can be particularly good. Although the thickness of an adhesive bond layer can be suitably set according to the objective and use of the image display apparatus in which a polarizing plate is used, Preferably it is 30-300 nm, More preferably, it is 50-150 nm. The adhesive layer is formed by applying and drying an adhesive aqueous solution.

  Preferably, the adhesive may further contain a cross-linking agent. The cross-linking agent is preferably a water-soluble cross-linking agent. Specific examples of the water-soluble crosslinking agent include boric acid, borax, glutaraldehyde, melamine, oxalic acid and the like. If desired, the adhesive may further contain any suitable additive (eg, antioxidant, UV absorber) and / or catalyst (eg, acid).

C. Optical Element According to another aspect of the present invention, an optical element is provided. This optical element is formed by laminating an optical layer on the polarizing plate. Any appropriate optical layer may be employed as the optical layer depending on the purpose. More specifically, examples of the optical layer include various optical films that can improve display accuracy and / or visibility of the image display device. Specific examples of such an optical layer include an alignment liquid crystal layer, a reflection plate, a transflective plate, a retardation plate (for example, λ / 2 plate, λ / 4 plate), a viewing angle compensation film, a brightness enhancement film, and the like. . Specific examples of optical elements that combine a polarizing plate and an optical layer include a reflective polarizing plate (a combination of a polarizing plate and a reflective plate), a semi-transmissive polarizing plate (a combination of a polarizing plate and a semi-transmissive reflective plate), Polarizing plate with retardation plate (combination of polarizing plate and retardation plate), elliptical polarizing plate or circular polarizing plate (combination of polarizing plate and λ / 4 plate), wide viewing angle polarizing plate (polarizing plate and viewing angle compensation layer or And a polarizing plate with a brightness enhancement film (a combination of a polarizing plate and a brightness enhancement film). Furthermore, in this specification, the “optical layer” includes a surface-treated portion (surface-treated layer) applied to the surface of the transparent protective film on which the polarizer is not bonded. Specific examples of such surface treatment include hard coat treatment, antireflection treatment, antisticking treatment, diffusion or antiglare treatment.

  The optical layer may be a single layer or two or more layers. When there are two or more optical layers, the respective layers may be the same, or the above various optical layers may be appropriately combined. Typically, an image display device having better display accuracy and / or visibility can be obtained by combining optical layers having different characteristics. The stacking position (substantially the stacking order) of the optical layers can be appropriately set according to the purpose. For example, the optical layer may be bonded to the polarizer before the polarizer and the transparent protective film are bonded, or may be bonded to the transparent protective film. For example, after laminating a polarizer and a transparent protective film, the obtained laminate or polarizing plate may be laminated. Further, for example, the polarizer, the transparent protective film, and the optical layer may be bonded at the same time. Furthermore, the polarizer and the optical layer can be stacked such that their optical axes (for example, the absorption axis of the polarizer and the slow axis of the optical layer) define an appropriate angle depending on the purpose. In addition, arbitrary appropriate adhesives can be used for lamination | stacking (bonding) of a polarizing plate and an optical layer.

C-1. Surface treatment layer The hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. The hard coat treatment is performed, for example, by forming a cured film having excellent hardness and slipperiness. The cured film is typically formed using an ultraviolet curable resin (for example, an acrylic resin or a silicone resin). The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate. The antireflection treatment is performed by forming any appropriate antireflection film. The anti-sticking treatment is performed for the purpose of preventing adhesion with 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 viewing of the light transmitted through the polarizing plate. The antiglare treatment is typically performed by providing a fine uneven structure on the surface of the transparent protective film. Specific examples of means for imparting a fine concavo-convex structure include roughening by sandblasting or embossing, and formation of concavo-convex by transparent fine particles. Concavity and convexity formation with transparent fine particles is performed by applying and drying a composition containing a transparent resin and transparent fine particles on the surface of the transparent protective film. The transparent fine particles used for forming irregularities include inorganic fine particles that can be conductive, such as silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide, and organic materials such as crosslinked or uncrosslinked polymers. System fine particles. The average particle diameter of the transparent fine particles is preferably 0.5 to 50 μm. The amount of the transparent fine particles to be used is preferably about 2 to 70 parts by weight, more preferably 5 to 50 parts by weight with respect to 100 parts by weight of the transparent resin. The antiglare layer formed by the antiglare treatment may also serve as a diffusion layer that diffuses the polarizing plate transmission light and expands the viewing angle or the like (that is, has a viewing angle expanding function).

  The surface treatment layer as described above may be formed on the transparent protective film itself by subjecting the transparent protective film to surface treatment, or a separate and independent film may be laminated on the transparent protective film surface.

C-2. Reflective Polarizing Plate A reflective polarizing plate is configured by providing a reflective plate (reflective layer) made of metal or the like on one surface of a polarizing plate. A transparent protective layer or the like is provided between the polarizing plate and the reflective film as necessary. The transparent protective layer is subjected to mat treatment or the like as necessary. The reflective polarizing plate is suitably used for a reflective liquid crystal display device (a liquid crystal display device that reflects incident light from the viewing side (display side)). By using the reflective polarizing plate, there is no need to incorporate a light source such as a backlight in the liquid crystal display device, so that the liquid crystal display device can be advantageously thinned.

  A typical example of the material constituting the reflective layer is a reflective metal such as aluminum. The reflective layer may be formed by attaching such a reflective metal foil to a transparent protective film, or may be formed by vapor deposition. The reflective layer may have a fine uneven structure on the surface. Such a reflective layer can be obtained, for example, by incorporating fine particles into a transparent protective film when forming a protective film, forming a fine concavo-convex structure on the surface, and forming a reflective metal layer thereon. That is, such a reflective layer is formed reflecting the fine uneven structure on the surface of the transparent protective film. By forming a reflective layer having a fine concavo-convex structure, incident light can be diffused by irregular reflection to prevent directivity and glaring appearance, and uneven brightness can be suppressed. Moreover, since the fine particle-containing transparent protective film itself has a function of diffusing incident light and its reflected light when passing through it, unevenness in brightness and darkness can be further suppressed. The reflective layer reflecting the surface fine concavo-convex structure of the transparent protective film is formed by, for example, a vapor deposition method such as vacuum vapor deposition, ion plating, sputtering, or a plating method. Alternatively, instead of directly forming the reflective layer on the surface of the transparent protective film, a reflective plate in which the reflective layer is provided on an appropriate base film can be used. In addition, since a reflective layer is normally comprised from a metal, it is preferable to use in the state in which the reflective surface was coat | covered with the transparent protective film, the polarizing plate, etc. This is because the decrease in reflectance due to oxidation is prevented, so that the initial reflectance can be maintained for a long time and it is not necessary to separately form a protective layer.

C-3. Transflective Polarizing Plate A transflective polarizing plate is configured by providing a transflective reflector (reflective layer) on one side of a polarizing plate. The semi-transmissive reflective layer is typically a half mirror that reflects and transmits light. The transflective polarizing plate is applied to a transflective liquid crystal display device. In the transflective liquid crystal display device, the transflective polarizing plate is usually provided on the back side of the liquid crystal cell. A transflective liquid crystal display device displays an image by reflecting incident light from the viewing side (display side) when used in a relatively bright environment, and back when used in a relatively dark environment. An image is displayed using a built-in light source such as a light. Therefore, by using a transflective polarizing plate, it is possible to save energy by using a light source such as a backlight in a bright environment, so that power saving is realized. In addition, since light from the light source is used even in a relatively dark environment, display is possible. The advantage of easy viewing is obtained.

C-4. Polarizing plate with retardation plate A polarizing plate with a retardation plate is formed by laminating a retardation plate on a polarizing plate. As the phase difference plate, a phase difference plate having any appropriate optical characteristic can be adopted depending on the purpose. For example, when changing the polarization direction of linearly polarized light, a λ / 2 plate is used as a retardation plate. Further, for example, when changing linearly polarized light to elliptically polarized light or circularly polarized light, or changing elliptically polarized light or circularly polarized light to linearly polarized light, a λ / 4 plate is used as a retardation plate (such a polarization plate with a retardation plate). The plate is called an elliptically polarizing plate or a circularly polarizing plate). The elliptically polarizing plate is effective when compensating for (preventing) coloring (blue or yellow) caused by birefringence in the liquid crystal layer of a super twist nematic (STN) type liquid crystal display device to achieve black and white display without coloring. Used for. Furthermore, an elliptically polarizing plate whose refractive index is controlled three-dimensionally is particularly preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. In one embodiment, the λ / 4 plate may constitute a reflective elliptical polarizing plate in combination with a reflective polarizing plate. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has an antireflection function. In addition to the λ / 2 plate and λ / 4 plate, a retardation plate having a refractive index distribution that compensates for coloring and viewing angle characteristics caused by the birefringence of the liquid crystal layer of the liquid crystal display device, and various wavelengths are supported. A phase difference plate having a phase difference is used. The retardation plate can be used alone or in combination of two or more having different characteristics.

  Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, a liquid crystal polymer alignment film, and a liquid crystal polymer alignment layer 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. In the case of uniaxial stretching, the stretching ratio is generally about 1.1 to 3 times. The thickness of the retardation plate is not particularly limited, but is generally 10 to 200 μm, preferably 20 to 100 μm.

  Examples of the polymer material include polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate, and polyether sulfone. , Polyphenylene sulfide, polyphenylene oxide, polyallylsulfone, polyvinyl alcohol, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulosic polymers, or binary, ternary various copolymers, graft copolymers, Examples include blends. Birefringence (phase difference) is imparted by subjecting films formed from these polymer materials to stretching treatment or the like.

  Examples of the liquid crystal polymer include a main chain type liquid crystal polymer in which a conjugated rigid atomic group (mesogen) capable of exhibiting liquid crystallinity is introduced into the main chain of the polymer, and a side chain type in which mesogen is introduced into the side chain. A liquid crystal polymer is mentioned. More specifically, the main chain type liquid crystal polymer has a structure in which mesogenic groups are bonded via a spacer portion that imparts flexibility. Specific examples of the main chain type liquid crystal polymer include, for example, a nematic alignment type polyester liquid crystal polymer, a discotic polymer, and a cholesteric polymer. Specific examples of the side chain type liquid crystal polymer include polysiloxane, polyacrylate, polymethacrylate or polymalonate as a main chain skeleton, and a para-substituted cyclic having a nematic orientation imparting property via a spacer portion composed of a conjugated atomic group as a side chain. Examples thereof include a polymer having a mesogenic part composed of compound units. An alignment film of a liquid crystal polymer is prepared by, for example, applying a solution containing these liquid crystal polymers on an alignment-treated substrate, heat-treating the liquid crystal polymer at a temperature at which the liquid crystal phase develops, and fixing the liquid crystal phase. It is formed. Specific examples of the alignment-treated substrate include those obtained by rubbing the surface of a thin film such as polyimide or polyvinyl alcohol formed on a glass plate, or those obtained by obliquely depositing silicon oxide.

  The polarizing plate with a retardation plate can be formed by sequentially laminating a polarizing plate and a retardation plate in the manufacturing process of the liquid crystal display device. However, the polarizing plate with an integrated retardation plate in which the polarizing plate and the retardation plate are laminated in advance. It is preferable to use it as a plate. This is because the production efficiency of the liquid crystal display device and the like can be improved because the quality stability and the laminating workability are excellent.

C-5. Wide viewing angle polarizing plate The viewing angle compensation film used for the wide viewing angle polarizing plate has a field of view so that the image can be seen clearly even when the screen of an image display device (typically a liquid crystal display device) is viewed from an oblique direction. A film for widening the corners. Examples of such viewing angle compensation films include alignment films such as retardation plates and liquid crystal polymers, or films in which an alignment layer such as a liquid crystal polymer is supported on a transparent substrate. A retardation plate used as a viewing angle compensation film is a birefringent polymer film stretched biaxially in the plane direction, a refractive index in the thickness direction stretched uniaxially in the plane direction and stretched in the thickness direction. Examples include a polymer film having controlled birefringence, or a bi-directionally stretched film such as a tilted orientation film. Examples of the tilted alignment film include a film obtained by bonding a heat-shrinkable film to a polymer film and stretching and / or shrinking the polymer film under the action of the contraction force by heating, a film obtained by obliquely aligning a liquid crystal polymer, etc. Is mentioned. As a polymer material constituting a retardation plate used as a viewing angle compensation film, a visual field that prevents coloring due to a change in viewing angle due to the birefringence of a liquid crystal cell (liquid crystal layer) and obtains good visibility. Any suitable polymeric material that enlarges the corners can be used. Specifically, the same polymer material as that described for the normal retardation plate is used. Further, specific examples of the viewing angle compensation film in which an alignment layer such as a liquid crystal polymer is supported on a transparent substrate include a viewing angle compensation film in which a tilt alignment layer of a discotic liquid crystal polymer is supported on a triacetyl cellulose film substrate. . Such a viewing angle compensation film can greatly expand the viewing angle at which good visibility is obtained.

C-6. A polarizing plate with a brightness enhancement film A polarizing plate with a brightness enhancement film is usually provided on the back side of a liquid crystal cell. When natural light is incident, the brightness enhancement film reflects linearly polarized light having a predetermined polarization direction or circularly polarized light having a predetermined rotation direction, and transmits other light. Therefore, when the light from a light source such as a backlight is incident on the polarizing plate with the brightness enhancement film, only the polarized light in a predetermined polarization state is transmitted from the incident light, and the other light is reflected. By reversing the reflected light through a reflective layer or the like provided on the back side of the brightness enhancement film and re-entering the brightness enhancement film, and transmitting part or all of the reflected light as polarized light in a predetermined polarization state. The amount of light that can be used for liquid crystal image display can be increased by increasing the amount of light transmitted through the brightness enhancement film and supplying polarized light that is not easily absorbed by the polarizer. As a result, the luminance of the liquid crystal display device can be improved. In other words, if the brightness enhancement film is not used, when light from the light source is incident on the back side of the liquid crystal cell through the polarizer, substantially all of the light having a polarization direction that does not coincide with the polarization axis of the polarizer is used. It is absorbed by the polarizer and does not pass through the polarizer. As a result, about 50% of the light from the light source is absorbed by the polarizer, so that the amount of light that can be used for liquid crystal image display or the like is reduced and the image becomes dark. The brightness enhancement film is reflected once by the brightness enhancement film without being incident on the polarizer with light having a polarization direction that is absorbed by the polarizer, and then inverted through a reflective layer or the like provided behind the brightness enhancement film. The polarization is changed so that the polarization direction of the light reflected and inverted between the brightness enhancement film and the reflective layer can pass through the polarizer by repeating the incident on the brightness enhancement film. Since only the light is transmitted to the polarizer, the light from the light source can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

  A diffusion plate may be provided between the brightness enhancement film and the reflective layer. As described above, the polarized light reflected by the brightness enhancement film travels to the reflective layer. By providing a diffusion plate in the light path, the light passing through the path is uniformly diffused, and at the same time, the polarization state is canceled and the light is returned to the non-polarized state (ie, the original natural light state). The light in the non-polarized state (natural light state) is inverted through the reflective layer and the like, and is repeatedly passed through the diffuser plate and re-incident on the brightness enhancement film. As a result, while maintaining the brightness of the display screen, it is possible to provide a bright uniform screen with less uneven brightness. This is considered to be because the number of times the first incident light is repeatedly reflected and inverted is appropriately increased by providing the diffusion plate, and both brightness and uniformity are improved by a synergistic effect with the diffusion function of the diffusion plate.

  As a specific example of the brightness enhancement film, the film has a characteristic of transmitting only linearly polarized light having a predetermined polarization direction and reflecting other light (for example, dielectric multilayer thin film, refractive index anisotropy is different) Multilayer laminate of thin film), which shows the property of reflecting either left-handed or right-handed circularly polarized light and transmitting the other (for example, a cholesteric liquid crystal polymer alignment film, a cholesteric alignment liquid crystal layer as a film base material) Those supported above).

  According to the brightness enhancement film of the type that transmits only linearly polarized light having a predetermined polarization direction as described above, the transmitted light and the polarization axis of the polarizing plate are aligned with each other, and the transmitted light is directly incident on the polarizing plate. Thus, loss due to absorption by the polarizing plate can be suppressed, and the polarizing plate can be transmitted efficiently. On the other hand, according to a brightness enhancement film of a type that transmits circularly polarized light having a predetermined rotation direction, such as a cholesteric liquid crystal layer, it is preferable to convert the transmitted circularly polarized light into linearly polarized light before entering the polarizing plate. This is to suppress loss due to absorption by the polarizing plate. A phase difference plate (typically a λ / 4 plate) is used for conversion from circularly polarized light to linearly polarized light. Such a retardation plate may be a single-layer λ / 4 plate or a laminate including a λ / 4 plate. For example, as a retardation plate that functions as a λ / 4 plate in a wide wavelength range (for example, the entire visible light region), a retardation layer that functions as a λ / 4 plate for monochromatic light with a wavelength of 550 nm, and other retardation characteristics A retardation plate formed by laminating a retardation layer (for example, a retardation layer functioning as a λ / 2 plate) is preferably used. As for the cholesteric liquid crystal layer, by using a combination of two or more layers having different reflection wavelengths, a brightness enhancement film that reflects circularly polarized light in a very wide wavelength range (for example, the entire visible light region) can be obtained. By using such a brightness enhancement film, transmitted circularly polarized light applicable to a wide wavelength range can be obtained.

C-7. Others As described above, the optical layer used in the optical element of the present invention is used in appropriate combination depending on the purpose. For example, the optical element of the present invention includes a reflective elliptical polarizing plate combining a reflective polarizing plate (above C-2) and a retardation plate, or a transflective polarizing plate (above C-3) and a retardation. It may be a transflective elliptically polarizing plate combined with a plate.

  The optical element of the present invention may be formed by sequentially laminating a polarizing plate and an optical layer when manufacturing an image display device, or may be used as an integrated optical element in which a polarizing plate and an optical layer are laminated in advance. Good. An integral type is preferred. This is because it is excellent in stability of quality, assembly work, and the like, and the manufacturing efficiency of the image display device can be improved.

  In the polarizing plate and the optical element of the present invention, a pressure-sensitive adhesive layer for bonding with other members (for example, a liquid crystal cell) of the image display device may be formed practically. The pressure-sensitive adhesive layer preferably has a low moisture absorption rate and excellent heat resistance. This is because the foaming phenomenon and the peeling phenomenon due to moisture absorption are prevented, and the optical characteristics are prevented from being lowered and the liquid crystal cell is warped due to a difference in thermal expansion, so that an image display device having high quality and excellent durability can be obtained. The pressure-sensitive adhesive layer can be formed from, for example, an acrylic pressure-sensitive adhesive. If necessary, the pressure-sensitive adhesive layer contains fine particles and may have light diffusibility. The pressure-sensitive adhesive layer can be formed at any appropriate location depending on the purpose. For example, in a polarizing plate having a polarizer and protective films on both sides thereof, an adhesive layer may be provided on either protective film surface, or an adhesive layer may be provided on both protective film surfaces.

  When the pressure-sensitive adhesive layer is exposed on the surface of the polarizing plate or optical element, a temporary cover should be provided with a separator for the purpose of preventing the pressure-sensitive adhesive layer from being contaminated before practical use. Is preferred. The separator is formed by providing a release coat on an appropriate thin film formed from the material used for the transparent protective film, if necessary. The release coat is typically composed of a release agent layer such as silicone, long chain alkyl, fluorine, or molybdenum sulfide.

  In addition, each layer (specifically, a polarizer, a transparent protective film, an optical layer, and an adhesive layer) constituting the polarizing plate and / or the optical element of the present invention is provided with an ultraviolet absorbing ability as necessary. Also good. The ultraviolet absorbing ability is imparted, for example, by introducing an ultraviolet absorber into the layer. Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds.

D. Image display device D-1. Liquid Crystal Display Device FIG. 2 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. In the illustrated example, a transmissive liquid crystal display device will be described, but it goes without saying that the present invention is also applied to a reflective liquid crystal display device and the like.

  The liquid crystal display device 100 includes a liquid crystal cell 10, phase difference plates 20 and 20 ′ disposed across the liquid crystal cell 10, and polarizing plates 30 and 30 ′ disposed outside the phase difference plates 20 and 20 ′. A light guide plate 40, a light source 50, and a reflector 60 are provided. The polarizing plates 30 and 30 ′ are typically arranged so that the polarization axes of the polarizers are orthogonal to each other. The polarizing plates 30, 30 'are the polarizing plates of the present invention described above. When the polarizing plates 30 and 30 'are the optical element of the present invention (that is, a combination of a polarizing plate and various optical layers), the retardation plates 20 and 20' can be omitted. The liquid crystal cell 10 includes a pair of substrates (glass substrate or plastic substrate) 11 and 11 ′, and a liquid crystal layer 12 as a display medium disposed between the substrates. One substrate 11 is provided with a switching element (typically a TFT) for controlling the electro-optical characteristics of the liquid crystal, a scanning line for supplying a gate signal to the switching element, and a signal line for supplying a source signal ( Neither is shown). The other substrate 11 ′ is provided with a color layer constituting a color filter and a light shielding layer (black matrix layer) (none of them are shown). The distance (cell gap) between the substrates 11 and 11 ′ is controlled by the spacer 13.

  As a display mode of the liquid crystal cell 10, any appropriate display mode can be adopted as long as the effects of the present invention can be obtained. Typically, VA (Vertical Alignment) mode, OCB (Optically Compensated Birefringence) mode, twisted nematic (TN) mode, super twisted nematic (STN) mode, horizontal alignment (ECB) mode, in-plane switching (IPS) mode, Examples thereof include a ferroelectric liquid crystal (SSFLC) mode and an antiferroelectric liquid crystal (AFLC) mode. Hereinafter, the VA mode will be described as an example.

  FIG. 3 is a schematic cross-sectional view illustrating the alignment state of liquid crystal molecules in the VA mode. As shown in FIG. 3A, when no voltage is applied, the liquid crystal molecules are aligned perpendicular to the surfaces of the substrates 11 and 11 '. Such vertical alignment can be realized by arranging a nematic liquid crystal having negative dielectric anisotropy between substrates on which a vertical alignment film (not shown) is formed. When light is incident from the surface of one substrate 11 in such a state, the linearly polarized light that has passed through the polarizing plate 30 and entered the liquid crystal layer 12 is directed in the direction of the major axis of the vertically aligned liquid crystal molecules. Proceed along. Since birefringence does not occur in the major axis direction of the liquid crystal molecules, incident light travels without changing the polarization direction and is absorbed by the polarizing plate 30 ′ having an absorption axis orthogonal to the polarizing plate 30. This provides a dark display when no voltage is applied (normally black mode). As shown in FIG. 3B, when a voltage is applied between the electrodes, the long axes of the liquid crystal molecules are aligned parallel to the substrate surface. Liquid crystal molecules exhibit birefringence with respect to linearly polarized light incident on the liquid crystal layer 12 in this state, and the polarization state of incident light changes according to the inclination of the liquid crystal molecules. Light that passes through the liquid crystal layer when a predetermined maximum voltage is applied becomes, for example, linearly polarized light whose polarization direction is rotated by 90 °, and therefore is transmitted through the polarizing plate 30 ′ to obtain a bright display. When the voltage is not applied again, the display can be returned to the dark state by the orientation regulating force. Further, gradation display can be performed by changing the intensity of transmitted light from the polarizing plate 30 ′ by changing the applied voltage to control the inclination of the liquid crystal molecules.

D-2. Self-luminous display device The present invention is applicable not only to liquid crystal display devices but also to self-luminous display devices such as electroluminescence (EL) displays, plasma displays (PD), and field emission displays (FEDs). Can be done. Here, an organic electroluminescence (EL) display device will be described as an example.

  FIG. 4 is a schematic cross-sectional view of an organic electroluminescence (EL) display device according to a preferred embodiment of the present invention. The organic EL display device 600 includes a transparent substrate 610, a transparent electrode 620, an organic light emitting layer 630, and a counter electrode 640 that are sequentially formed on the transparent substrate 610, an inorganic protective film 660 and a resin disposed so as to cover them. A protective film 670. The transparent electrode 620, the organic light emitting layer 630, and the counter electrode 640 in a region where the transparent electrode 620 and the counter electrode 640 overlap with each other serve as the pixel 650.

  In the organic EL display device, at least one electrode needs to be transparent in order to extract light emitted from the organic light emitting layer 630. Therefore, typically, the transparent electrode 620 is composed of an ITO (Indium Tin Oxide) film, which is a transparent conductive film, and is used as an anode. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a low work function for the cathode. Therefore, typically, the counter electrode 640 is made of a metal film such as Mg—Ag or Al—Li and used as a cathode.

  The organic light emitting layer 630 is a laminate of various organic thin films. In the illustrated example, the organic light emitting layer 630 is made of a hole injecting organic material (for example, a triphenylamine derivative), and has a hole injecting layer 631 provided to improve the hole injecting efficiency from the anode, and a light emitting property. A light emitting layer 632 made of an organic substance (eg, anthracene) and an electron injection layer 632 made of an electron injecting material (eg, a perylene derivative) and provided to improve the electron injection efficiency from the cathode. The organic light emitting layer 630 is not limited to the illustrated example, and any suitable combination of organic thin films capable of causing light emission by recombination of electrons and holes in the light emitting layer 632 can be adopted.

  When a voltage equal to or higher than the threshold value is applied between the transparent electrode and the counter electrode, holes are supplied from the anode and reach the light emitting layer 632 through the hole injection layer 631. On the other hand, electrons are supplied from the cathode and reach the light emitting layer 632 through the electron injection layer 633. Energy generated by recombination of holes and electrons in the light emitting layer 632 excites the light emitting organic material in the light emitting layer, and emits light when the excited light emitting organic material returns to the ground state. Emits light. Image display is possible by applying a voltage to each desired pixel to cause the organic light emitting layer to emit light. In the case of performing color display, for example, the light emitting layers of three adjacent pixels may be made of a light emitting organic material that emits red (R), green (G), and blue (B) light, respectively. A suitable color filter may be provided on the light emitting layer.

  In such an organic EL display device, the thickness of the organic light emitting layer 630 is preferably as thin as possible. This is because it is preferable to transmit the emitted light as much as possible. The organic light emitting layer 630 can be formed of a very thin film having a thickness of about 10 nm, for example. As a result, when no light is emitted (black state), the light incident from the surface of the transparent substrate 610, transmitted through the transparent electrode 620 and the organic light emitting layer 630, and reflected by the counter electrode 640 is again on the surface side of the transparent substrate 610. Go out. For this reason, when viewed from the outside, the display surface of the organic EL display device often looks like a mirror surface. From the viewpoint of preventing such reflection in the black state, it is preferable to dispose the polarizing plate and the retardation plate on the surface of the transparent electrode 620. Since the polarizing plate has a function of polarizing the light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the display surface is not visually recognized from the outside by the polarization function. In particular, the angle formed between the slow axis of the retardation plate and the absorption axis of the polarizing plate is adjusted to π / 4, and the entire retardation of the retardation plate is adjusted to ¼ of the visible wavelength. As a result, the mirror surface of the display surface can be substantially completely shielded. Specifically, in an organic EL display device in which such a polarizing plate and a retardation plate are arranged, only the linearly polarized light component of the incident external light is transmitted by the polarizing plate. Linearly polarized light is generally elliptically polarized by the retardation plate, but the overall retardation of the retardation plate is ¼ of the visible wavelength, and the slow axis of the retardation plate and the absorption axis of the polarizing plate When the angle formed by is π / 4, circularly polarized light is obtained. This circularly polarized light is transmitted through the transparent substrate 610, the transparent electrode 620, and the organic light emitting layer 630, reflected by the counter electrode 640, and again transmitted through the organic light emitting layer 630, the transparent electrode 620, and the transparent substrate 610, and the above retardation plate. It becomes linearly polarized light again. Since this linearly polarized light is orthogonal to the polarization direction of the polarizing plate, it cannot pass through the polarizing plate. As a result, the mirror surface of the display surface can be substantially completely shielded.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples. In addition, the evaluation items in the examples are as follows.

(1) Adhesion test The polarizing plate was cut into 25 × 50 mm, and it was tested whether the polarizer and the transparent protective film could be peeled by hand at room temperature.
(2) 60 degreeC warm water immersion test The polarizing plate was cut into 25x50 mm, immersed in 60 degreeC warm water, and the time until the protective film of a polarizing plate peeled was measured.
(3) Durability test at 90 ° C. Two polarizing plates are bonded to a glass plate so that the absorption axes of the polarizers are orthogonal to each other, left in an oven at 90 ° C. for 120 hours, and then lighted on the backlight. The leak was observed.

[Preparation of transparent protective film a]
One side of a norbornene-based film (manufactured by Nippon Zeon Co., Ltd., trade name “ZEONOR”, 40 μm) was corona treated with a discharge amount of 200 w · min / m ² . Then, a silicon primer on its treated surface after casting the (Nippon Unica Co., Ltd., trade name "APZ-6601" 5 wt%), and heated at 120 ° C. 30 minutes, moisture permeability 0.6g ^/ m 2 ^/ 24h A transparent protective film a was obtained.

[Preparation of transparent protective film b]
65 parts by weight of a gluterimide copolymer comprising N-methylglutarimide and methyl methacrylate (N-methylglutarimide content 75% by weight, acid content 0.01 meq / g or less, glass transition temperature 147 ° C.), acrylonitrile And 35 parts by weight of acrylonitrile-styrene copolymer having a styrene content of 28% by weight and 72% by weight, respectively. The resin composition obtained by melt kneading these was extruded with a T-die melt extruder to obtain a film having a thickness of 135 μm. This film was stretched 1.7 times in the MD direction at 160 ° C., and then stretched 1.8 times in the TD direction at 160 ° C. The thickness of the obtained biaxially stretched transparent film was 50 μm. One side of the transparent protective film was subjected to corona treatment with a discharge amount of ²⁰⁰ w · min / m ² . Then, the silicon primer treated surface after casting the (Nippon Unica Co., Ltd., trade name "APZ-6601" 5 wt%), and heated at 120 ° C. 30 minutes, the moisture permeability ^87g / m 2 / 24h transparent A protective film b was obtained.

[Preparation of transparent protective film c]
Thickness using a triacetyl cellulose film moisture permeability 900g ^/ m 2 ^/ 24h subjected to saponification treatment of 40 [mu] m.

[Example 1]
Polyvinyl alcohol having a thickness of 75 μm and a polymerization degree of 2400 was stretched 2.5 times while immersed in pure water at 30 ° C. for 1 minute. Next, the film was stretched 1.2 times while being immersed in a dyeing bath containing iodine and potassium iodide at 30 ° C. for 1 minute. Next, the film was stretched twice while immersed in a boric acid bath at 60 ° C. for 2 minutes. Furthermore, after being immersed in an aqueous solution having a potassium iodide concentration of 5% at 30 ° C. for 5 seconds, it was dried at 35 ° C. for 5 minutes to obtain a polarizer. A transparent protective film a was bonded to one surface of this polarizer using a PVA adhesive to form a laminate. At the time of bonding, the tension was controlled so that the resulting laminate was flat. The obtained laminate was dried at 50 ° C. for 5 minutes, and subsequently (that is, without winding up and storing the laminate), the other surface of the polarizer was transparent using a PVA adhesive. The protective film c was bonded and dried at 60 ° C. for 5 minutes and at 70 ° C. for 5 minutes to obtain a polarizing plate. At the time of pasting, the tension was controlled so that the resulting polarizing plate was flat. The obtained polarizing plate was subjected to an adhesion test, a 60 ° C. hot water immersion test, and a 90 ° C. durability test. The results are shown in Table 1 below.

[Example 2]
A polarizing plate was produced in the same manner as in Example 1 except that the transparent protective film b was used instead of the transparent protective film a. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
A polarizer was prepared in the same manner as in Example 1, and a transparent protective film c was simultaneously bonded to both sides using a PVA adhesive, and dried at 60 ° C. for 5 minutes and at 70 ° C. for 5 minutes to obtain a polarizing plate. It was. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
A polarizer was produced in the same manner as in Example 1, and a transparent protective film a was simultaneously laminated on both sides using a PVA adhesive, and dried at 50 ° C. for 5 minutes, 60 ° C. for 5 minutes, and 70 ° C. for 5 minutes. Thus, a polarizing plate was obtained. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
A polarizer was prepared in the same manner as in Example 1, and a transparent protective film a and a transparent protective film c were simultaneously bonded using a PVA adhesive, and the mixture was bonded at 50 ° C. for 5 minutes, 60 ° C. for 5 minutes, and 70 ° C. for 5 minutes. It dried for minutes and obtained the polarizing plate. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 4]
A polarizer was obtained in the same manner as in Example 1. A transparent protective film c was bonded to one side of this polarizer using a PVA adhesive to form a laminate. At the time of bonding, the tension was controlled so that the resulting laminate was flat. The obtained laminate was dried at 50 ° C. for 5 minutes, and subsequently (that is, without winding up and storing the laminate), the other surface of the polarizer was transparent using a PVA adhesive. The protective film a was bonded and dried at 60 ° C. for 5 minutes and at 70 ° C. for 5 minutes to obtain a polarizing plate. At the time of pasting, the tension was controlled so that the resulting polarizing plate was flat. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

As is clear from Table 1, it can be seen that the polarizing plates of the examples of the present invention are superior in adhesiveness even under high temperature and high humidity, and no light leakage is observed, as compared with the polarizing plates of the comparative examples. That is, after forming the first transparent protective film bonded to one surface laminate polarizer having the moisture permeability 200g / m 2 / ^24h, without winding up the laminate, the first By sticking a second transparent protective film having a moisture permeability higher than that of the transparent protective film to the other surface of the polarizer, peeling and curling at the time of bonding are prevented, and the polarizer and the transparent protective film It turns out that the polarizing plate excellent in adhesiveness is obtained. Further, as is clear when comparing Example 1 and Comparative Example 4, after pasting together a relatively protective film having a relatively low moisture permeability, by bonding a transparent protective film having a relatively large moisture permeability, It can be seen that light leakage is improved.

  The polarizing plate of the present invention can be suitably used for flat panel displays such as liquid crystal display devices and self-luminous display devices (for example, organic EL display devices).

It is the schematic explaining the manufacturing method of the polarizing plate by preferable embodiment of this invention. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. When the liquid crystal display device of this invention employ | adopts a VA mode liquid crystal cell, it is a schematic sectional drawing explaining the orientation state of the liquid crystal molecule of a liquid crystal layer. 1 is a schematic cross-sectional view of an organic EL display device according to a preferred embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal cell 11, 11 'Substrate 12 Liquid crystal layer 20, 20' Phase difference plate 30, 30 'Polarizing plate 40 Light guide plate 50 Light source 60 Reflector 100 Liquid crystal display device 600 Organic EL display device 610 Transparent substrate 620 Transparent electrode 630 Organic light emitting layer 631 Hole injection layer 632 Light emitting layer 633 Electron injection layer 640 Counter electrode 650 Pixel

Claims (7)

After the first transparent protective film having the moisture permeability 200g / m 2 / ^24h to form a bonded to one surface laminate of a polarizer, without winding up the laminate, the first transparent Bonding a second transparent protective film having a moisture permeability higher than that of the protective film to the other surface of the polarizer,
Further including a step of drying the laminate before bonding the second transparent protective film;
Manufacturing method of polarizing plate.   The manufacturing method according to claim 1, wherein the polarizer and the first transparent protective film are bonded together in a state where tension is applied to the polarizer and the first transparent protective film.   The manufacturing method of Claim 1 or 2 which bonds the said laminated body and said 2nd transparent protective film in the state which provided the tension | tensile_strength to this laminated body and this 2nd transparent protective film.   The manufacturing method in any one of Claim 1 to 3 whose curl amount of the said laminated body is 5 mm or less.   The manufacturing method in any one of Claim 1 to 4 whose curl amount of the polarizing plate obtained is 5 mm or less.   The manufacturing method according to claim 1, wherein the first transparent protective film is made of an amorphous polyolefin resin. The manufacturing method according to claim 6, wherein the second transparent protective film is made of triacetyl cellulose.

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