JP2007233243A - Polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate which retains optical characteristics equal to those of the conventional polarizing plates, and moreover has high luminance. <P>SOLUTION: Fibers made by aligning thermoplastic resin filaments, impregnated with dichroic color material in a single direction and fibers having an optical interference function, are arranged in the same sheet-like direction, are contained in an optical transparent resin and are processed in a plate-like body, and thereby, the polarizing plate in which the improved luminance function is integrated is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polarizing plate having a function of increasing luminance, an optical member using the polarizing plate, a liquid crystal display device, and the like.

  As a polarizing plate used in a liquid crystal display device, a polyvinyl alcohol (hereinafter abbreviated as PVA) film that is usually colored with iodine and stretched uniaxially is used as a polarizer. Abbreviated as TAC) A method of bonding a film as a protective film of a polarizing plate, a method of providing a coating layer with an acrylic resin or the like on one side of a polarizer, or a phase difference film such as norbornene or polycarbonate on one side of a polarizer instead of TAC It is used to attach to. However, such a polarizing plate is classified as an absorption-type polarizing plate, which transmits only light in the transmission axis direction of the polarizing plate and absorbs light of the remaining components. Therefore, even under ideal conditions, 50% (inner surface reflection) The maximum light transmittance is 46% because it has 4%), and the effective use of the backlight and increasing the luminance are propositions of the liquid crystal display device.

  Applications of liquid crystal display devices range from small devices such as calculators, watches, mobile phones, and digital cameras to medium-sized devices such as PDAs, car navigation systems, and POS systems, as well as large liquid crystal display devices such as personal computer liquid crystal monitors and liquid crystal televisions. Products are applied to a wide variety of products, and there is an increasing demand for improving the quality and function of members used in liquid crystal display devices.

  As a polarizing plate having a function of increasing brightness, there is a reflective polarizing plate using optical interference. For example, Patent Documents 1 and 2 describe a polarizing element using interference of a multilayer film having birefringence, and polarization separation in an alignment multilayer film of two types of polymer films having different refractive indexes is described. A method of performing is disclosed. Non-Patent Document 1 also proposes a polarization separation method using a simple polymer blend, although the principle is the same as described above. Recently, Patent Document 3 reports a method using fibers instead of polymer blends. The reflection type polarizing plate in the polarization separation system has a characteristic of reflecting in a polarized component that does not transmit, and the reflected light is repeatedly reflected by a diffuse reflection film installed on the backlight side of the liquid crystal display device. Further, it is possible to take out the light that coincides with the light in the transmission axis direction of the polarizing plate once more, and it is possible to realize a transmittance of 60% or more. However, when the reflective polarizing plates are arranged before and after the liquid crystal cell, there is a problem that the color cannot be accurately displayed due to multiple reflection of light reflected in the liquid crystal cell. Limited to use only. In addition, as described in Patent Document 3 and Non-Patent Document 2, in order to realize a reflective polarizing plate, the refractive index of the polymer to be blended and the refractive index of the substrate serving as the bulk are strictly matched. It is necessary to strictly control the shape and arrangement of the blend polymer and fiber, and it is very difficult to obtain the same degree of polarization (99.9% or more) as the current polarizing plate. The current situation is that it cannot be kept good. For this reason, the present situation is that the reflective polarizing plate is used together with the absorptive polarizing plate in a form specialized only for its brightness increasing function. In this case, the reflective polarizing plate is not called a polarizing plate but is handled as a brightness enhancement film, and is actually commercially available as a product called D-BEF from 3M. However, even in D-BEF, since it is necessary to ensure polarization characteristics over a wide visible region, 400 to 800 layers are laminated as a whole. It is technically difficult to control the thickness and laminate several hundreds of polymer films, and to control the refractive index of each layer.

  In addition, the durability characteristics required for polarizing plates have become very high. Absorption-type polarizing plates using iodine do not have sufficient durability, particularly moisture and heat resistance, and the life of liquid crystal display devices using the same. Is limited by the characteristics of the polarizing plate.

  As an improvement in durability, Non-Patent Document 3 reports a dye-based polarizing plate using a dichroic dye as a polarizing element instead of iodine. However, the durability of the polarizer itself is obtained by adsorbing and orienting iodine. Although the TAC film, which is a protective film for the polarizing plate, is shrunk to give a shrinking stress to the liquid crystal panel, the image quality is lowered, and the TAC film itself is corroded.

US Pat. No. 3,610,729 US Pat. No. 5,486,949 International Publication No. 2005/8302 Journal of Applied Physics, 37, 1998, 4389 Monthly display April 2005, page 13 Monthly display April 2005, page 39

As described above, in order to improve the transmittance of the polarizing plate, the luminance of the liquid crystal display element is increased by using two absorption polarizing plates and two reflective polarizing plates (brightness increasing films). However, since it cannot have a polarizing function and has many technically difficult aspects, it is a high-cost member. For this reason, in the polarizing plate single-piece | unit, what expresses high polarization degree and high transmittance | permeability (it has a brightness increase function) is not obtained.
Moreover, when using a TAC film as a polarizing plate protective film, the improvement in the durable surface of a polarizing plate is not seen continuously.

An object of the present invention is to provide a polarizing plate having high luminance while maintaining optical properties equivalent to those of current polarizing plates.
A further object of the present invention is to provide a novel polarizing plate that realizes an improvement in durability, in particular heat and heat resistance, of a conventional polarizing plate by adopting a configuration in which a TAC film is not used as a polarizing plate protective film.

  In order to solve the above-mentioned problems, the present inventors have intensively studied a polymer material, a shape and the like for a polarizing plate. As a result, a fiber (A) in which thermoplastic resin fibers impregnated with a dichroic dye are arranged in a single direction and a fiber (B) having an optical interference function are arranged in the same direction and are encapsulated in an optical transparent resin. It has been found that by processing on a plate, a polarizing plate having not only a function of increasing brightness but also excellent temperature and humidity resistance in which light transmittance and polarization degree hardly change even under high temperature and high humidity can be produced. Invented.

That is, the present invention can be achieved by the following [1] to [13].
[1] (a) a thermoplastic resin fiber (A) on which a dichroic dye is adsorbed,
(B) A fiber composed of at least two types of thermoplastic resins and having an alternating layer-like cross-sectional structure, the alternating layer being 5 layers or more, and the thickness of each layer being in the range of 0.02 to 1.0 μm And at least the two types of thermoplastic resins are fibers (B) having an optical interference function in which a difference in refractive index at a wavelength of 589 nm in a cross-sectional direction with respect to the length direction of the fibers is 0.01 or less, and (c ) Optically transparent resin (C) having a refractive index that substantially matches the refractive index in the cross-sectional direction with respect to the length direction of the fiber (B),
The fibers (A) are arranged in a unidirectional plane, and the fibers (B) are on one side of the fibers (A) and arranged in the same direction as the fibers (A). A polarizing plate.
[2] The above polarizing plate in which the fibers (A) and (B) are encapsulated and fixed by an optical transparent resin (C).
[3] The polarizing plate as described above, wherein the fiber (A) is a fiber made of a polyvinyl alcohol resin.
[4] The polarizing plate as described above, wherein the polyvinyl alcohol-based resin has a degree of polymerization of 1,000 to 40,000 and a saponification degree of 80 to 100%.
[5] The polarizing plate described above, wherein the polyvinyl alcohol-based resin fiber has an average diameter of 0.7 μm or more and 100 μm or less.
[6] The polarizing plate as described above, wherein the dichroic dye is iodine.
[7] The polarizing plate as described above, wherein a difference in refractive index between at least two kinds of thermoplastic resins of the fiber (B) is 0.02 or more.
[8] The polarizing plate as described above, wherein an average diameter of the fibers (B) is 0.7 μm or more and 100 μm or less.
[9] The polarizing plate as described above, wherein the optically transparent resin (C) is a thermoplastic resin.
[10] The above polarizing plate, wherein the optically transparent resin (C) is a curable resin.
[11] An optical member comprising a laminate of the above polarizing plate and an optical layer exhibiting an optical function other than polarized light.
[12] The optical member as described above, wherein the optical layer is a retardation layer.
[13] A liquid crystal display device, wherein the fiber (A) constituting the polarizing plate in the optical member is disposed on one side or both sides of the liquid crystal cell so that the fiber (A) is on the liquid crystal cell side.

  As a result of diligent research, the present inventor has examined reconsidering the configuration in which the PVA film containing the dichroic dye is contained by the TAC film that has been conventionally used as a polarizing plate in order to improve the heat and moisture resistance. did. Since the TAC film itself is a material having high moisture permeability and large dimensional change, it was considered that a structure for reviewing or removing the material itself was indispensable. Therefore, by using the thermoplastic resin fiber (A) containing the dichroic dye as an alternative to the PVA film containing the dichroic dye and containing it in an optically transparent resin, the sandwiching configuration by TAC is achieved. It became unnecessary. In addition to the thermoplastic resin fiber, it is possible to add a brightness increasing function by arranging the fiber (B) having an optical interference function in the same direction plane as the fiber (A). As a result, it was possible to provide a single polarizing plate having a brightness increasing function and excellent in heat and moisture resistance.

  As described above, the polarizing plate of the present invention has a function of increasing luminance, and can achieve a polarizing function excellent in moisture and heat resistance with no change in transmittance and degree of polarization even under high temperature and high humidity.

  According to the present invention, a fiber (A) in which thermoplastic resin fibers impregnated with a dichroic dye are arranged in a single direction and a fiber (B) having an optical interference function are arranged in a plane in the same direction. By adopting a form encapsulated in an optically transparent resin such as the above, it becomes possible to easily obtain a polarizing plate having a brightness increasing function and excellent in heat-and-moisture resistance. Furthermore, the integration of the brightness enhancement film into the polarizing plate has been realized, and it has become unnecessary to use the TAC film as a protective film for the polarizing plate, thereby reducing the number of members and simplifying the processing process. Low cost can be realized in the polarizing plate.

  Such a polarizing plate having a function of increasing brightness can be combined with various retardation films and optical compensation films to provide a circularly polarizing film, an elliptically polarizing film, and a viewing angle widening polarizing film. In combination with a liquid crystal display device, a transmissive liquid crystal display device, or the like, it is possible to provide a liquid crystal display device that increases the luminance of the liquid crystal display device and does not impair the screen quality under an environment in a wide temperature and humidity range.

[Fibers made of thermoplastic resin fibers (A)]
The fiber (A) in the present invention is optically transparent and is preferably a fiber formed from a thermoplastic resin capable of adsorbing and orienting the dichroic dye. Examples of such thermoplastic resins include polyvinyl alcohol (hereinafter simply referred to as PVA), acrylic resin, nylon resin, polyolefin, polyester, polystyrene, polyether, polycarbonate, vinyl resin, polyurethane, polyamide, polyimide, and epoxy resin. Among these, PVA or a derivative thereof is particularly preferable. Derivatives of PVA include polyvinyl formal, polyvinyl acetal and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, alkyl esters thereof, acrylamide and the like. (Hereinafter, PVA or a derivative thereof may be referred to as a PVA resin). The polymerization degree of PVA or a derivative thereof is about 1000 to 40000, and the saponification degree is about 80 to 100 mol%. Here, in order to use it as a polarizer, an element having excellent durability is obtained when the degree of polymerization and saponification of PVA or a derivative thereof is higher. Therefore, the degree of polymerization is 1200 or more and 30000 or less, and the degree of saponification is 90 or more. PVA of 100 mol% or less or a derivative thereof is preferable, and a polymerization degree of 1500 to 20000 and a saponification degree of 98 to 100 mol% are more preferable.

Hereinafter, as a material of the thermoplastic resin fiber, a fiber made of PVA resin (hereinafter simply referred to as PVA resin fiber) will be described as an example.
A plasticizer etc. can also be mix | blended with the said PVA-type resin fiber. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but is preferably 20% by weight or less in the PVA resin. Moreover, additives, such as antioxidant, a ultraviolet absorber, a crosslinking agent, surfactant, can also be contained in PVA-type resin fiber.

  As a method (spinning method) for fiberizing the PVA-based resin, any commonly used method such as dry, wet, and dry wet can be employed. In these systems, the PVA resin can be produced (spun) using a solution dissolved in the following solvent. For example, water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, 1,3 dimethyl 2-imidazolidinone, ethylenediamine, diethylenetriamine, diethylenetriamine, glycerin, ethylene glycol, 3-methylpentane-1,3, Polyhydric alcohols such as 5-triol are used alone or in combination. Furthermore, any resin that dissolves the resin, such as an aqueous solution of an inorganic salt such as zinc chloride, magnesium chloride, rhodium calcium, or lithium bromide, or an aqueous solution of isopropanol can be used.

  The PVA-based resin fiber used in the present invention is a stretched product. This stretching process may be performed before dichroic dye dyeing, may be performed simultaneously with dyeing, or performed after dyeing. Also good. Of course, stretching may be performed in a plurality of stages. When the dichroic dye is dyed after drawing the fiber, the adsorbed dichroic dye is oriented along the drawing axis. At this dyeing stage, the dichroic dye is oriented and adsorbed along the drawing axis, while at the same time as the dichroic dye is dyed, or after dyeing, from the stretched spinning dope to immediately before dry heat drawing, or dry. You may impregnate a dichroic dye in any after hot-drawing. Examples of the method for applying the dichroic dye to the PVA fiber include a roller touch method, a dipping method, and a glass mouth contact method.

  The stretch ratio of the PVA resin fiber used in the present invention can be about 10 to 30 times as the maximum stretch ratio. At this time, the maximum draw ratio represents the ratio at which the fiber cuts during dry heat drawing. However, when the draw ratio is close to the maximum draw ratio, voids are generated inside the PVA-based resin fibers, whitening due to so-called irregular reflection of light is observed, and the transmittance and the degree of polarization are deteriorated. On the other hand, when the draw ratio is low, the orientation of the molecular chain and the dichroic dye is insufficient, and the strength and the degree of polarization are reduced. Therefore, the draw ratio of the PVA resin fiber is preferably 40% or more and 80% or less of the maximum draw ratio, more preferably 45% or more and 75% or less, and most preferably 50% or more and 70% or less. By this stretching process, a PVA resin fiber having a dichroic dye adsorbed and oriented is obtained.

  The thickness of the PVA-based resin fiber is preferably 0.7 μm or more and 100 μm or less, more preferably 0.8 μm or more and 80 μm or less, and further preferably 1 μm or more and 50 μm or less. If the fiber thickness is less than 0.7 μm, it is difficult to spin and stretch the fiber, and it is difficult to obtain a uniform color display due to surface scattering at a wavelength in the visible region depending on the fiber size. On the other hand, when the thickness of the fiber exceeds 100 μm, the fiber is too thick, and when a polarizing plate having a desired thickness is formed when arranged in one direction, a gap is generated, resulting in a light leakage defect. It is difficult to realize a high degree of polarization.

  As a PVA-based resin fiber that adsorbs and orients a dichroic dye, the thickness of the fiber does not need to be uniform, and if it achieves a high degree of polarization as a polarization function without gaps when arranged in one direction, A mixture of fine fibers and thick fibers may be used as an aggregate. The shape of the fiber is not limited to a circle, but may be an ellipse, triangle, quadrangle, pentagon, hexagon, or a polygon larger than that. As long as a high degree of polarization is achieved, the shape is not limited. Also, the shape of the aggregate fiber used for one PVA resin fiber does not need to be uniform, and may be a composite of various shaped fibers. This is preferable because it is not necessary to adjust them uniformly. The PVA-based resin fiber does not need to be an infinitely long fiber and includes a needle-like shape, and the aspect ratio is 10 or more, preferably 20 or more, more preferably the aspect ratio is 100 or more. . Here, the aspect ratio is the ratio of the length to the minor axis diameter. When the fiber shape is a polygon, the minor axis diameter is defined as the diameter of the circumscribed circle of the polygon. When the aspect ratio of the PVA-based resin fiber is less than 10, it is difficult to obtain a uniform alignment when aligning in the major axis direction. Although it is the maximum value of the aspect ratio, there is no upper limit as long as the PVA resin fiber is not cut.

The PVA resin fiber is used as an aggregate, that is, a bundle of fibers. Here, the number of fibers is not particularly limited depending on the thickness of the fibers and within a range in which the object and effect of the present invention can be achieved. For example, the density is 100 to 25 million fibers / cm ² .
For the purpose of improving the adhesion between the PVA-based resin fiber and the optical transparent resin, various different adhesion treatments such as corona treatment may be applied to the fiber surface.

  The PVA-based resin fibers are arranged in a plane in one direction. The arrangement is preferably such that the fibers are arranged in one direction in one or more layers. In the present invention, the state of one layer is also called a fiber. With regard to the optimum number of layers, it is possible to obtain relatively high polarization performance even with one layer, but it is a very difficult technique to arrange PVA resin fibers without gaps in one layer. When the PVA resin fibers are used, the number of laminated layers is preferably 2 or more and 100 or less, more preferably 3 or more and 100 or less, and most preferably 5 or more and 100 or less.

[Dichroic dye and dyeing method of thermoplastic resin fiber]
The fiber (A) made of the thermoplastic resin fiber has iodine or dichroic dye, which is a dichroic dye, adsorbed and oriented.

  When the thermoplastic resin fiber is a PVA-based resin fiber and the dichroic dye adsorbs iodine to it, an aqueous iodine solution can be used, and iodine ions are included as iodine and a dissolution aid, for example, potassium iodide. An aqueous solution is used. The iodine concentration is preferably about 0.01 to 0.5% by weight, and the potassium iodide concentration is preferably 0.01 to 10% by weight. In the iodine staining treatment, the temperature of the iodine solution is usually 20 to 50 ° C., and the immersion time is in the range of about 10 to 300 seconds. In addition, it is preferable to adjust the iodine content in the PVA-based resin fiber so that it is usually about 1 to 4% by weight so that the polarizer exhibits a good degree of polarization. In such iodine dyeing treatment, the iodine content in the PVA resin fiber is within the above range by adjusting the conditions such as the concentration of the iodine solution, the immersion temperature of the PVA resin fiber in the iodine solution, and the immersion time. Can be adjusted. Next, the PVA resin fiber subjected to iodine staining is subjected to boric acid treatment. The boric acid treatment is performed by immersing a PVA resin fiber dyed with iodine in an aqueous boric acid solution. The boric acid concentration in the boric acid aqueous solution is preferably about 2 to 15% by weight, the temperature of the boric acid aqueous solution is preferably in the range of 50 to 85 ° C., and the immersion time is preferably about 30 to 1000 seconds. The aqueous boric acid solution can contain iodine ions with potassium iodide. A boric acid aqueous solution containing potassium iodide can provide a polarizing plate with little coloration, that is, a so-called neutral gray polarizing plate having substantially constant absorbance over almost the entire wavelength range of visible light.

  When the dichroic dye is a dichroic dye, the dichroic dye is preferably a water-soluble dye such as an acid dye or a direct dye, and the structure thereof includes, for example, an azo dye, a stilbene dye, or an anthraquinone dye. Dyes, methine dyes, cyanine dyes and the like can be used. Specific examples include the disazo compounds described in JP-A-59-145255 and JP-A-60-156759, the trisazo compounds described in JP-A-3-78703, and the color index general name. CI Direct Yellow 12, CI Direct Yellow 44, CI Direct Orange 26, CI Direct Orange 39, CI Direct Red 2, CI Direct Red 23, CI Direct Red 31, CI Direct Red 79, CI Direct Red 81, CI Direct Vilet 9, CI DirectVilet 35, CI Direct Vilet 51, CI Direct Blue 15, CI Direct Blue 78, CI Direct Blue 90, CI Direct Blue 168, CI Direct Blue 202, CI Direct Blue 203, CI Direct Brown 2, CI Direct Black 17, CI Direct Black 19, CI Direct Black 118, CI Direct Black 132 and the like. These water-soluble dyes preferably have a pigment component content that can impart polarizing ability of 95%, more preferably 99% or more (both in weight ratio). Impurities other than the dye component are removed by a method such as an ion exchange membrane method or a recrystallization method. In actual use, since a single dye has a polarization characteristic only in a specific wavelength range, a polarizing element film having excellent polarization characteristics over the entire wavelength range of visible light of 400 to 700 nm, which is most commonly used, is used. In order to obtain it, it is preferable to use two or more water-soluble dyes having absorption characteristics in different ranges within this wavelength range. Examples of specific combinations include CI Direct Orange 39, CI Direct Red 81, green blue described in Example 23 of JP-A-59-145255, and blue of JP-A-3-78703. There are blends. As a dichroic dyeing method, an aqueous dye solution having a dye concentration of 0.02 to 0.1% by weight is used, and a PVA resin fiber is used at a temperature of 30 to 50 ° C. for about 100 to 600 seconds. Immerse. The dyed PVA resin fiber is preferably immersed in an aqueous boric acid solution having a boric acid concentration of about 2 to 15% by weight, as in the case of iodine.

[Fiber having optical interference function (B)]
The fiber having an optical interference function is one that interferes and develops the color of the wavelength in the visible light region by optical reflection and interference effects. Examples of fibers having an optical interference function are disclosed in Japanese Patent No. 3356438, Japanese Patent Application Laid-Open No. 11-124773, and Japanese Patent Application Laid-Open No. 2005-15962. The fiber having an optical interference function is a fiber having an alternating layered cross-sectional structure composed of two or more types of thermoplastic resin components, and the refractive index of the optical resin is different because the refractive index of the thermoplastic resin is different. And an interference effect due to the product of the thickness of each layer.
The optical interference effect is greatly influenced by the refractive index difference between the two thermoplastic resin layers, the optical distance of each layer (refractive index × the thickness of each layer), and the number of layers.

  First, regarding the two types of thermoplastic resins used for fibers having an optical interference function, the higher refractive index resin (sometimes referred to as a high refractive index resin) has a refractive index of 1.55 to 1.88. The resin having a lower refractive index (sometimes referred to as a low refractive resin) is preferably appropriately selected from those having a refractive index in the range of 1.35 to 1.55. In particular, the refractive index difference between the two thermoplastic resins is at least 0.02 or more, preferably 0.07 or more, and most preferably 0.15 or more. As for the combination of the thermoplastic resins, aromatic polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polycarbonate are preferable as the high refractive resin having a high refractive index and fiber forming property. The refractive indexes of these resins are as high as 1.58 for polyethylene terephthalate, 1.63 for polyethylene naphthalate, 1.55 for polybutylene terephthalate, 1.55, and 1.59 for polycarbonate, for example. Furthermore, when these resins are used to form fibers, high orientation occurs in the fiber axis direction, resulting in large birefringence. The birefringence has a high value such as 0.22 for polyethylene naphthalate, 0.153 for polyethylene naphthalate, and 0.20 for polycarbonate. On the other hand, as a low refractive resin, for example, methacrylates such as polymethyl methacrylate (refractive index 1.49), polyolefins such as polyethylene (1.51) and polypropylene, and aliphatic polyamides such as nylon 6 (1.53) are used. I can list them. Among these resins, polymethyl methacrylate has a birefringence of almost 0, and nylon 6 has a lower value than a highly refractive resin such as 0.08.

  Moreover, it is preferable that the thickness of the thermoplastic resin layer required for the cross-sectional structure of an alternating layer form is the range of 0.02-1.0 micrometer. When the thickness is less than 0.02 μm or exceeds 1.0 μm, it is difficult to obtain the expected optical interference effect in the visible light region. Furthermore, the thickness is preferably in the range of 0.05 to 0.15 μm. Further, when the optical distance between the two components, that is, the product of the layer thickness and the refractive index is equal, a higher optical interference effect can be obtained. In particular, when twice the sum of the two optical distances equal to the primary reflection is equal to the distance of the specific wavelength, the maximum interference effect at the specific wavelength can be obtained. In this case, it is necessary to adjust so as to obtain a uniform interference effect in the visible light region, particularly 400 to 700 nm, and it is difficult to obtain this characteristic with a monofilament. A fiber having an optical interference function having a maximum in the vicinity of 550 nm and 650 nm was combined, and a multifilament that obtains substantially uniform optical interference in the visible light region (400 to 700 nm) was used.

  Furthermore, the number of layers that require an alternate layered cross-sectional structure is preferably 5 to 120 layers. When the number of layers is less than 5, not only the interference effect is small, but also the interference color changes greatly depending on the viewing angle. On the other hand, when the number of layers exceeds 120, the die structure becomes complicated, and it becomes difficult to produce the yarn, and the laminar flow is liable to occur, resulting in a non-uniform layered structure. The alternating layered cross-sectional structure is more preferably 10 to 100 layers or less, and most preferably 10 to 80 layers or less.

  The cross-sectional shape of the fiber having an optical interference function is not particularly limited, but it is a flat structure, and it is preferable that the long axis of the cross-sectional structure of the alternate layer shape is arranged in parallel with the long-axis direction of the flat cross-section. When the fiber has a flat cross-sectional shape and has a long axis of a cross-sectional structure of alternating layers parallel to the long axis direction, the fiber is viewed from a direction perpendicular to the surface formed in the flat long axis direction and the fiber length direction. Sometimes, the reflected light due to optical coherence can be observed most strongly. At this time, when processing a fiber having an optical interference function consisting of a flat cross-sectional shape, the long axis of the flat cross-sectional shape is aligned in parallel to the stressed surface by external stress such as tension or friction force acting on the fiber. Orientation controllability can be expressed. At this time, the optical interference function can be maximized by adjusting the incident light so that the surface is formed in the flat major axis direction and the fiber length direction. In order to give the fiber self-orientation controllability, it is necessary that the flatness is 2 or more and 15 or less. For fibers with a flatness ratio of 2 or less, good self-orientation controllability cannot be obtained, and gathers in a close-packed shape in a fiber laminate due to external stresses such as tension and friction acting on the fibers, The orientation of the cross-sectional structure of the alternating layers of fibers that exhibit an optical interference function is a random arrangement, and a sufficient optical interference function cannot be obtained. On the other hand, if the flatness ratio exceeds 15, the shape becomes excessively thin, so that it becomes difficult to maintain the cross-sectional form, and defects such as a part of the cross-section being bent occur. The flatness of the fiber having an optical interference function is more preferably 2.5 or more and 13 or less, and most preferably 3 or more and 10 or less.

  Regarding the refractive index difference in the cross-sectional direction of each of the two or more kinds of thermoplastic resins in the optical interference fiber, 0.01 or less is preferable at a wavelength of 589 nm. When the refractive index difference in the cross-sectional direction of each of the two or more kinds of thermoplastic resins is large, when the fiber in the present invention is formed as a polarizing element, the transmission axis of the polarizing element and the cross-sectional direction of the fiber having an optical interference function are the same. However, when the refractive index in the cross-sectional direction of the cross-sectional structure of the alternating layer structure is different, the reflected light is generated due to the difference in refractive index between the layers, so that the amount of transmitted light is reduced and the polarization function as a polarizing element is reduced. It becomes. The difference in the refractive index at the wavelength 589 nm is minimized because the wavelength 589 nm corresponds to the NaD line, so that the refractive index can be easily observed with a light source using the NaD line, and the green color with high visibility is obtained. By adjusting the refractive index difference to the minimum at the wavelength to be exhibited, there is an effect of maintaining good polarization characteristics in visible light and minimizing the influence of visual tint. In the fiber having an optical interference function in the present invention, the difference in refractive index in the cross-sectional direction of each of the two or more thermoplastic resin components is an average refractive index difference of 0.01 or less in the wavelength range of 500 to 700 nm. More preferably, the average refractive index difference is 0.01 or less in the wavelength range of 400 to 700 nm. As a method of adjusting the difference in refractive index in the cross-sectional direction in each of two or more kinds of thermoplastic resin components, the refraction in the cross-sectional direction can be achieved by drawing a fiber having an optical interference function to a specific draw ratio. The ratio can be adjusted, and the draw ratio needs to be adjusted depending on the type of resin used. As a drawing process of a fiber having an optical interference function, the undrawn fiber is 2 to 20 times in a heating bath at a temperature higher than the glass transition temperature of the high refractive index resin and the low refractive index resin and lower than the crystal temperature. It is good to stretch. Regarding the draw ratio, if the draw ratio is less than 2 times, it is difficult to realize a predetermined layer thickness having optical interference, and if the draw ratio exceeds 20 times, fiber breakage or fiber voids are generated. , Scattering of light occurs, causing the characteristics of the polarizing element to deteriorate.

  The fiber diameter (or the length of the major axis of the cross section) having an optical interference function is preferably 1 μm or more and 50 μm or less. If the fiber diameter having an optical interference function is less than 1 μm, it becomes difficult to obtain an alternate layered cross-sectional structure necessary for the optical interference function, and if the fiber diameter exceeds 50 μm, it becomes difficult to control the resin discharge for fiber processing. Therefore, it becomes difficult to obtain a homogeneous fiber. More preferably, they are 2 micrometers or more and 40 micrometers or less, More preferably, they are 3 micrometers or more and 30 micrometers or less.

  Examples of the fiber having an optical interference function include the shapes shown in FIGS. 1- (a) to (d) as typical examples, but the layered structure is divided into two layers, and the layered structure among the fibers. Is divided into two or three, as long as it has an alternate layer structure having an optical interference function. 1- (a) shows a shape in which two types of resins having different refractive indexes are alternately laminated in the major axis direction of the flat cross section, and FIG. 1- (b) shows a flat cross-sectional shape laminated in a donut shape. FIG. 1- (c) shows a shape in which reinforcing portions made of the above-mentioned resin or other resin are interposed in the intermediate portion of the alternating lamination, and FIG. 1- (d) shows a reinforcing portion on the outer peripheral portion. Show shape.

  The fiber having the optical interference function is arranged in a plane in one direction. The arrangement is preferably such that the fibers are arranged in one direction in one or more layers. With regard to the optimum number of layers, it is possible to obtain a relatively high polarization performance even with one layer, but it is a very difficult technique to arrange fibers without gaps in one layer. When the fibers are used, the number of laminated layers is preferably 2 or more and 100 or less, more preferably 3 or more and 100 or less, and most preferably 5 or more and 100 or less. As a fiber having an optical interference function to be laminated, in order to obtain an optical interference function uniformly at a wavelength of visible light, a fiber having a maximum optical interference effect has a wavelength of 400 to 500 nm, a fiber of 500 to 600 nm, 600 to 700nm fibers may be combined and laminated, and if the effect of optical interference of visible light is obtained, there is no limitation on the type of fiber combination, but if the number of types increases, the number of layers increases too much, Since the amount of transmitted light is reduced, 10 or less types are preferable.

[Optical transparent resin (C)]
In the present invention, it is basically formed from a thermoplastic resin fiber (A) containing a dichroic dye, a fiber (B) having an optical interference function, and an optical transparent resin (C). For example, the thermoplastic resin fiber (A) and the fiber (B) having an optical interference function take the form of a plate or the like that is wrapped and fixed by the optical transparent resin (C). This is because the fiber (A) and the fiber (B) alone cannot maintain the state of being aligned in one direction, and the polarization performance cannot be continuously expressed, and the thermoplastic resin fiber as the fiber (A) is in the atmosphere. This is because the directly exposed form is remarkably affected by temperature and humidity, tends to cause shrinkage due to moisture absorption, disorder of orientation of the dichroic dye, etc., and cannot achieve high durability. The optically transparent resin (C) plays an important role as a function of suppressing deterioration of the polarizing plate while fixing and holding the fibers (A) and (B).

  As the optically transparent resin (C), the fiber (A) and the fiber (B) are arranged and finally fixed, and plays a role as a base material as a polarizing plate. Therefore, the optically transparent resin (C) is preferably one that has little or no absorption in the visible region and exhibits good adhesion to the fibers constituting the fibers (A) and (B). The optical transparent resin functions as a base material for the polarizing plate. Therefore, if the base material itself has birefringence, it can be a disadvantage of light penetration when the polarizing plate is arranged in a crossed Nicol state. Therefore, a material such as a thermoplastic resin, a heat or a photo-curing resin having low birefringence can be used. preferable. The optical transparent resin in the present invention is indispensable to be transparent in the visible region. Specifically, when the optical transparent resin is a film having a thickness of 50 μm at a wavelength of 400 nm to 800 nm, The measured light transmittance needs to be 80% or more, preferably 85% or more, and most preferably 90% or more.

Examples of the material of the optically transparent resin (C) are shown below.
Specific examples of the thermoplastic resin include acrylic resins such as poly (methyl methacrylate), polyolefins such as polyethylene, polyesters such as polyethylene terephthalate, polyethers such as polyphenylene oxide, vinyl resins such as polyvinyl alcohol, polyurethane, polyamide, Polyimide, epoxy resin, copolymer using two or more monomers constituting these, further poly (methyl methacrylate) and polyvinyl chloride weight ratio 82:18 mixture, poly (methyl methacrylate) and polyphenylene oxide weight Non-birefringent polymer blends such as a 65:35 ratio mixture and a 77:23 weight ratio of styrene / maleic anhydride copolymer and polycarbonate may be exemplified, but are not limited thereto.

  One example of the optically transparent resin is a curable resin. This is preferable as a material excellent in workability, for example, in that the resin (C) is rapidly cured after the resin is applied to the fibers (A) and (B). A representative example of the curable resin is a crosslinked resin obtained by curing through a crosslinking reaction or the like by external excitation energy. These are actinic radiation curable resins that are cured by irradiation with actinic rays such as ultraviolet rays and electron beams, and thermal crosslinkable resins that initiate a crosslinking reaction by heat.

  A typical example of the actinic radiation curable resin is an ultraviolet curable resin. Examples thereof include an ultraviolet curable polyester acrylate resin, an ultraviolet curable acrylic urethane resin, an ultraviolet curable methacrylate ester resin, an ultraviolet curable polyester acrylate resin, and an ultraviolet curable polyol acrylate resin. In particular, UV curable polyol acrylate resins are good, such as trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, alkyl-modified dipenta. Photopolymerizable monomer oligomers such as erythritol pentaerythritol are preferred.

  Examples of the electron beam curable resin are preferably those having an acrylate functional group, such as a polyester resin, polyether resin, acrylic resin, epoxy resin, urethane resin, alkyd resin, spiroacetal resin having a relatively low molecular weight. , Polybutadiene resin, polythiol polyene resin and the like.

  Examples of the thermosetting resin include epoxy resin, phenoxy resin, phenoxy ether resin, phenoxy ester resin, acrylic resin, melamine resin, phenol resin, and urethane resin, or a mixture thereof.

  In the present invention, any of the above-mentioned curable resins can be used suitably, but it is necessary to select an optical transparent resin having a refractive index that substantially matches the refractive index in the cross-sectional direction of the fiber (B). . Here, “substantially match” means that the difference from the value of the refractive index in the cross-sectional direction of the fiber (B) is within 0.01. Thus, a polarizing plate with a high transmittance can be obtained by using the optical transparent resin (C) having a refractive index that substantially matches the refractive index in the cross-sectional direction of the fiber (B).

(Retardation layer)
The polarizing plate of the present invention is useful as an optical member composed of a laminate with an optical layer having an optical function other than polarized light. For example, a retardation layer is an example of an optical layer that exhibits an optical function other than polarized light.
The retardation layer in the present invention is a layer which gives a retardation, and an example thereof is a retardation film obtained by stretching a transparent thermoplastic synthetic polymer film.

  The retardation film is preferably excellent in transparency, mechanical strength, thermal stability, moisture shielding property, isotropy and the like. Examples of the material that gives the retardation film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, acrylic polymers such as polymethyl methacrylate, styrene polymers such as polystyrene and acrylonitrile / styrene copolymer (AS resin), Examples thereof include polycarbonate polymers. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyethersulfone polymers, polyetheretherketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers, or blends of the above polymers A thing etc. are mentioned as an example of the polymer which forms the said retardation film. At this time, the retardation film is required to have a thin film and sufficient strength. Suitable materials in this respect include polycarbonate polymers, norbornene resin polymers, norbornene polymers, polyarylate polymers, polysulfone polymers. A polymer etc. are mentioned as a preferable thing.

The retardation film has good transparency, preferably a haze value of 5% or less and a total light transmittance of 85% or more. The glass transition temperature of the retardation film is usually 160 to 260 ° C., preferably 170 to 250 ° C., particularly preferably 180 to 240 ° C. At temperatures lower than that, the dimensional stability is poor and higher. At this temperature, it becomes very difficult to control the temperature of the stretching process, making it difficult to manufacture. The retardation film is a birefringent film having a retardation, and the birefringence that is an optical characteristic thereof is represented by a retardation value. In particular, in-plane retardation (R value) and retardation in the thickness direction (K value). ). These R value and K value are defined by the following formulas (a) and (b), respectively.
R = Δn · d = (nx−ny) · d (a)
K = ((nx + ny) / 2−nz) · d (b)
It is. The unit of R value and K value is nm. Here, nx, ny, and nz are defined as follows.
nx: maximum refractive index in the film plane ny: refractive index in the direction perpendicular to the direction showing the maximum refractive index in the film plane nz: refractive index in the film normal direction (stretching in the case of uniaxial stretching with the main stretching direction) In the case of direction and biaxial stretching, it means the direction of stretching so that the degree of orientation increases, and in terms of chemical structure, it refers to the orientation direction of the polymer main chain.)
The retardation film may be an optical uniaxial or biaxial film having a retardation.

  The other retardation layer is a layer having a refractive index anisotropy and having an optical axis in the normal direction of the layer surface, a retardation having a positive wavelength dispersion characteristic and a twist-oriented polymerizable chiral having a reflection wavelength in the ultraviolet region. A nematic (cholesteric) liquid crystal layer, a homeotropically oriented polymerizable discotic liquid crystal layer, or a coated layer made of a material that functions as having a phase difference in the normal direction to the layer when coated, or a thickness There is also a retardation layer having a hybrid structure in which refractive index ellipsoids are arranged radially in the thickness direction, but any of them may be used.

〔Polarizer〕
The thickness of the polarizing plate of the present invention is usually from 1 to 200 μm, preferably from 5 to 150 μm, and most preferably from 10 to 100 μm. If it is thinner than 1 μm, it will be difficult to secure a polarizing function as a polarizing plate, and it will be difficult from the viewpoint of handling. On the other hand, when the thickness is larger than 200 μm, there is a problem that the obtained polarizing plate is cracked with respect to bending, and there is a problem that it cannot be handled in a roll state and that it becomes very difficult to cut.

  When processing the polarizing plate of the present invention as a film, the orientation direction of the fibers (A) and (B) is not defined in the film transport direction, and is perpendicular to the transport direction or at a predetermined angle as necessary. The orientation can be fixed. When the polarizing plate is handled as a film, the film may be wound to form a roll, and the length and width of the roll film are not limited.

  As a manufacturing method of the polarizing plate of the present invention, as an example using a cured resin as an optical transparent resin, the cured resin is applied to the fibers (A) and (B) using a solvent or the like as necessary, cured, dried, etc. The method of manufacturing via is mentioned. In view of productivity, it is preferable to form a cured resin layer immediately after application, and an ultraviolet curable resin is more preferable in consideration of materials used for general purposes and processing equipment.

  Further, the fibers (A) and (B) can be stacked and arranged in a single row or multiple rows on a base material such as a polymer film or a glass substrate, and a curable resin can be applied thereto and then cured. In this case, the polarizing plate of the present invention may be used integrally with a polymer film or a glass substrate, but may be used by peeling off the polymer film or the glass substrate.

  A retardation film may be used as the base material for arranging the fibers (A) and (B), and it is not necessary to peel off the polarizing plate of the present invention from the retardation film. can do.

  The polarizing plate of the present invention may be subjected to a surface treatment. As the surface treatment, a surface which is not bonded to the liquid crystal cell may be subjected to a treatment for the purpose of hard coat layer, antireflection treatment, sticking prevention, diffusion or antiglare.

  The hard coat treatment is performed for the purpose of preventing the polarizing plate from being scratched. For example, the surface of the transparent protective film is coated with a cured film excellent in hardness and slipping properties by an appropriate ultraviolet curable resin such as acrylic or silicone. It can be formed by a method to be added to. Further, by using an appropriate ultraviolet curable resin itself such as acrylic or silicone with the crosslinkable resin of the present invention, a polarizing plate having a hard coat function may be used. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. The anti-sticking treatment is performed for the purpose of preventing adhesion with the adjacent layer.

  Anti-glare treatment is applied for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by sandblasting or embossing. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a method or a compounding method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing polarized transmitted light to expand a viewing angle or the like.

  The polarizing plate of the present invention is preferably subjected to a surface treatment before being bonded to the liquid crystal cell. Examples of the surface treatment include corona discharge treatment, ultraviolet irradiation treatment, and the like, and it is preferable that the surface state is preferably 65 ° or less, more preferably 60 ° or less, with a water droplet contact angle on the film surface.

  The polarizing plate of the present invention may be used simultaneously with an optical compensation film such as a retardation film or a viewing angle widening film. Furthermore, the polarizing plate of the present invention may be used for a liquid crystal display device using a ferroelectric liquid crystal or an antiferroelectric liquid crystal.

[Field of application of polarizing plate]
The polarizing plate of the present invention is used as a polarizing plate having an optical compensation function by laminating with a retardation film, and can form a liquid crystal display device having a wide viewing angle and excellent display quality such as contrast. Yes, it can be used for a TFT liquid crystal mode such as a twisted nematic mode, a vertical alignment mode, an OCB (Optically Compensated Bend) alignment mode, and an in-plane switching mode. In practical use, it can be used for all applications used as a polarizing plate. For example, in the case of a liquid crystal display device, a backlight, a reflector, or a transflective reflector is used in an illumination system. A mold, a reflection type, a transflective type, or the like can be formed. Examples of display devices using other polarizing plates include liquid crystal projectors, ferroelectric liquid crystals, those using antiferroelectric liquid crystals, and organic EL display devices. May be used for

  In the polarizing plate of the present invention, the pressure-sensitive adhesive layer is used to bond the liquid crystal panel, but the polarizing plate is provided with the pressure-sensitive adhesive layer, and on the surface where the pressure-sensitive adhesive layer is exposed, a separator is provided for the purpose of preventing contamination. It takes the form of being temporarily attached and covered.

  The adhesive layer is, for example, an adhesive such as a natural or synthetic resin, particularly a tackifier resin, a filler or pigment made of glass fiber, glass beads, metal powder, or other inorganic powder, a colorant, an antioxidant, or the like. You may contain the additive of being added to a layer. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient. Attachment of the adhesive layer to the polarizing plate can be performed by an appropriate method. As an example thereof, for example, an adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of an appropriate solvent alone or a mixture such as toluene and ethyl acetate is prepared. Examples thereof include a method in which an adhesive layer is formed on a polarizing plate or an optical film by an appropriate developing method such as a casting method or a coating method, and then transferred onto the polarizing plate or the optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 2 to 200 μm, particularly preferably 10 to 100 μm.

  As the separator of the adhesive layer, for example, a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foamed sheet or metal foil, an appropriate thin leaf body such as a laminate thereof, if necessary, a silicone type or a long mirror alkyl type, It is possible to have an appropriate one according to the prior art, such as one coated with an appropriate release agent such as fluorine-based or molybdenum sulfide.

  Examples of the present invention will be described below, but the present invention is not limited thereto. Moreover, the material characteristic value etc. which are described in this specification were obtained by the following evaluation methods.

(1) Measurement of light transmittance and degree of polarization The light transmittance T was calculated by the formula 1 from the spectral transmittance t (λ) obtained every 10 nm in the wavelength range of 400 to 700 nm. In the equation, P (λ) is a spectral distribution of standard light (C light source), and y (λ) is a color matching function based on the two-degree field of view X, Y, and Z systems. Spectral transmittance t (λ) was measured using a spectrophotometer (Hitachi Ltd., U-4000).

The degree of polarization P is defined as Tp (paranicol transmittance) when the two polarizing plates are stacked so that the absorption axis directions thereof are the same, and the absorption axes of the two polarizing plates are orthogonal to each other. Thus, the transmittance in the case of overlapping was defined as Tc (crossed Nicol transmittance), and calculated according to Equation 2.

(2) Thickness measurement Measured with an electronic micro manufactured by Anritsu Corporation.

(3) Measurement of birefringence (Δn) of fiber Using a polarizing microscope, an interference filter (589 nm) was installed in the light source and adjusted to be a linearly polarized light source.
The fiber was placed on a glass slide and installed so that linearly polarized light was parallel to the cross-sectional direction of the fiber.
Using the refraction adjusting liquid, from 1.500 to 1.600, at 0.002 STEP, while observing the microscope, it was observed that the outer shape of the fiber disappeared by dropping the refraction adjusting liquid sequentially. .

[Example 1]
PVA (Kuraray Co., Ltd., polymerization degree 4000, saponification degree 99.9%) was dissolved in dimethyl sulfoxide (hereinafter abbreviated as DMSO) as a solvent to prepare a spinning stock solution having a PVA concentration of 16% by weight. This spinning stock solution is dried and wet-spun with a spinning draft of 2.0 and an air gap of 30 mm in a coagulation bath made of methanol from a die having a pore size of 100 μm and a pore number of 300 at 100 ° C., and then DMSO is extracted with methanol in a methanol bath. Spinning and drawing were performed, followed by drying to obtain an undrawn PVA yarn (diameter 10 μm). This unstretched yarn was stretched 6.5 times using a heating roller at 110 ° C. to obtain a PVA fiber (diameter 2 μm). This PVA fiber was fixed in the length direction and immersed for 60 seconds in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.075 / 5/100. Next, it was immersed in a boric acid-containing aqueous solution at 65 ° C. in which the weight ratio of potassium iodide / boric acid / water was 6 / 7.5 / 100 for 300 seconds. This was pure and washed with water and dried to obtain PVA fibers (A).

  Next, polyethylene naphthalate copolymerized with 10 mol% of terephthalic acid and 1 mol% of sodium sulfoisophthalic acid (the intrinsic viscosity is 0.58; 89 mol% of naphthalenedicarboxylic acid, hereinafter referred to as copolymerized PEN) Nylon 6 (intrinsic viscosity 1.3) was melt-spun so that the number of layers of the alternating laminate portion was 61 and the surroundings were covered with copolymerized PEN, and wound at a speed of 1000 m / min. I took it. The obtained unstretched fiber was stretched 2.0 times with a roller stretching machine. The obtained fiber is a multi-fiber consisting of 12 filaments, and the cross-sectional shape thereof is as shown in FIG. 1- (d). The major axis length in the fiber section direction is 60 μm, the minor axis length is 19 μm, and the flat shape is flat. The thickness of the copolymer PEN layer was 0.09 μm and the thickness of the nylon layer was 0.10 μm. At this time, as an interference effect of the fiber having the optical interference function, a red to orange interference color having a maximum reflection characteristic at a wavelength of 640 nm was confirmed (optical interference fiber (red)). Similarly to the above, as a fiber having an optical interference function made of copolymerized PEN and nylon 6, a fiber having a maximum reflection characteristic at a wavelength of 530 nm with respect to a green color (major axis length 49 μm in the fiber cross-sectional direction, minor axis length 14 μm) The flatness is 3.5, and the layers of the alternately laminated portions have a maximum thickness of 0.07 μm for the copolymerized PEN layer, 0.08 μm for the nylon layer, an optical interference fiber (green), and a reflection characteristic with a wavelength of 460 nm for blue. The resulting fiber (major axis length 45 μm in the fiber cross-sectional direction, minor axis length 11 μm, flatness 4.1, between the layers of the alternately laminated portion, the copolymer PEN layer thickness 0.06 μm, nylon layer thickness 0.06 μm, Optical interference fiber (blue)) was obtained (all multifilaments consisting of 12 filaments). The refractive index in the cross-sectional direction at a wavelength of 589 nm of any of these fibers having an optical interference function was 1.526. Moreover, the refractive index of copolymer PEN is 1.62, the refractive index of nylon 6 is 1.53, and the refractive index difference between the two thermoplastic resins is 0.09.

  PVA fibers (A) impregnated with iodine are arranged on the glass plate with a thickness of 20 μm (about 10 layers as fiber layers) arranged in the longitudinal direction of the glass without gaps, and each optical interference that is a multifilament Each polyester fiber (B) of fibers (red, about 90 μm, blue, about 60 μm, green, about 70 μm, about 5 layers each, about 15 layers in total) is placed on the PVA fibers and PVA fibers Arranged in the same direction.

Next, BPEF-A: 66 parts by weight, UA: 434 parts by weight, toluene: 40 parts by weight as a diluent solvent, “Irgacure” 184: 15 parts by weight as a photoinitiator, and SH28PA: 0.18 parts by weight as a leveling agent Were sequentially added to prepare a solution that was stirred until uniform.
BPEF-A: Bisphenoxyethanol full orange acrylate (manufactured by Osaka Gas)
UA: urethane acrylate (“NK Oligo U-15HA” manufactured by Shin-Nakamura Chemical)
"Irgacure" 184 (Ciba Geigy)
SH28PA (Toray Dow Corning)

The prepared solution was evenly applied on the fiber (A) and (B) laminate prepared above to form a state in which the fibers (A) and (B) were encapsulated by the solution. . This was irradiated with ultraviolet light having an integrated light quantity of 700 mJ / cm ² with a high-pressure mercury lamp having a strength of 160 w, the solution was cured, and PVA fibers (A) and polyester fibers (B) were encapsulated by an optical transparent resin. The thickness was 240 μm. A polarizing plate was obtained. At this time, the refractive index of the optical transparent resin was 1.526.

  The polarizing plate thus obtained had a light transmittance of 45.0% and a degree of polarization of 99.9%. The polarizing plate was humidified in an atmosphere of 85 ° C. and 85% RH for 100 hours, and then the optical characteristics were measured. At this time, the transmittance of the polarizing plate was 44.9%, the degree of polarization was 99.9%, and it was confirmed that the polarizing plate had high wet heat resistance.

In addition, the polarizing plate obtained above was manufactured using a commercially available transflective liquid crystal display device, and a liquid crystal display device having the following configuration was prepared. When the increase in luminance at the time was measured, a luminance increase effect of 17% was confirmed.
Structure: (fiber (B) side) Polarizing plate (fiber (A) side) / retardation film / liquid crystal cell / retardation film / (fiber (A) side) polarizing plate (fiber (B) side) / backlight / Diffuse Reflective Film As a retardation film, “Pure Ace” WR-W142 manufactured by Teijin Chemicals Ltd. was used.

[Reference Example 1]
A PVA film (Kuraray Co., Ltd., polymerization degree 2400, saponification degree 99.9%, thickness 75 μm) was uniaxially stretched at a stretching temperature of 110 ° C. and a draw ratio of 5.0 times to obtain a polarizing substrate. The polarizing substrate was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.075 / 5/100 for 60 seconds while maintaining the tension during stretching. Next, it was immersed in a boric acid-containing aqueous solution at 65 ° C. in which the weight ratio of potassium iodide / boric acid / water was 6 / 7.5 / 100 for 300 seconds. This was pure and washed with water and dried. The film thickness of the PVA film impregnated with iodine thus obtained was 20 μm. A TAC film (Fuji Photo Film, Fuji TAC-UV80) was bonded to both surfaces of the dried film using a PVA adhesive. The polarizing plate thus obtained had a transmittance of 44.1% and a polarization degree of 99.9%. The polarizing plate was humidified in an atmosphere of 85 ° C. and 85% RH for 100 hours, and then the optical characteristics were measured. At this time, the transmittance of the polarizing plate was 58.3 and the degree of polarization was 52.1%. Moreover, corrosion was seen in the TAC film which bonded together in order to protect the PVA film which is a polarizer.

In addition, this polarizing plate is manufactured using a commercially available transflective liquid crystal display device, and a liquid crystal display device having the following configuration is manufactured and arranged so that the polarizing plate is crossed Nicol. When the increase was measured, the luminance was comparable to the initial value.
Configuration: Polarizing plate / retardation film / liquid crystal cell / retardation film / polarizing plate / backlight / diffuse reflection film In addition, “Pure Ace” WR-W142 manufactured by Teijin Chemicals Ltd. was used as the retardation film. .

  The polarizing plate of the present invention can be preferably used for a display of a liquid crystal display device that requires environmental resistance.

1A to 1D are conceptual diagrams showing fibers having an optical interference function in the present invention.

Claims (13)

(A) a thermoplastic resin fiber (A) on which a dichroic dye is adsorbed,
(B) A fiber composed of at least two types of thermoplastic resins and having an alternating layer-like cross-sectional structure, the alternating layer being 5 layers or more, and the thickness of each layer being in the range of 0.02 to 1.0 μm And at least the two types of thermoplastic resins are fibers (B) having an optical interference function in which a difference in refractive index at a wavelength of 589 nm in a cross-sectional direction with respect to the length direction of the fibers is 0.01 or less, and (c ) Optically transparent resin (C) having a refractive index that substantially matches the refractive index in the cross-sectional direction with respect to the length direction of the fiber (B),
The fibers (A) are arranged in a unidirectional plane, and the fibers (B) are on one side of the fibers (A) and arranged in the same direction as the fibers (A). A polarizing plate.   The polarizing plate according to claim 1, wherein the fibers (A) and (B) are encapsulated and fixed by the optically transparent resin (C).   The polarizing plate according to claim 1, wherein the fiber (A) is a fiber made of a polyvinyl alcohol-based resin.   The polarizing plate according to claim 3, wherein the polyvinyl alcohol-based resin has a degree of polymerization of 1000 or more and 40000 or less and a degree of saponification of 80 mol% or more and 100% or less.   The polarizing plate according to claim 3, wherein an average diameter of the polyvinyl alcohol-based resin fiber is 0.7 μm or more and 100 μm or less.   The polarizing plate according to claim 1, wherein the dichroic dye is iodine.   The polarizing plate according to claim 1, wherein a difference in refractive index between at least two thermoplastic resins of the fibers (B) is 0.02 or more.   The average diameter of the said fiber (B) is 0.7 micrometer or more and 100 micrometers or less, The polarizing plate in any one of Claims 1-7 characterized by the above-mentioned.   The polarizing plate according to claim 1, wherein the optically transparent resin (C) is a thermoplastic resin.   The polarizing plate according to claim 1, wherein the optically transparent resin (C) is a curable resin.   It consists of a laminated body of the polarizing plate in any one of Claims 1-10, and the optical layer which shows optical functions other than polarization | polarized-light, The optical member characterized by the above-mentioned.   The optical member according to claim 11, wherein the optical layer is a retardation layer.   13. A liquid crystal display device, wherein the fiber (A) constituting the polarizing plate in the optical member according to claim 11 or 12 is disposed on one side or both sides of the liquid crystal cell so as to be on the liquid crystal cell side.

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