JP2010181710A - Polarizing plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate causing no dimensional change and having high optical performance even in a high temperature and high humidity environment, and superior in using efficiency of the light of a light source, and to provide a liquid crystal display device having the polarizing plate. <P>SOLUTION: This polarizing plate sequentially includes a circularly polarization separating element made of a resin layer having a cholesteric regularity, an optical compensation film, a linear polarization film, and a protective film having a predetermined water vapor permeability. The optical compensation film is a λ/4 plate including a layer made of resin whose specific birefringence value is negative. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polarizing plate and a liquid crystal display device.

  The liquid crystal display device includes a light source, an incident side polarizing plate, a liquid crystal cell, and an output side polarizing plate in this order. Each polarizing plate includes a polarizing film, a first protective film provided on one surface of the polarizing film, and a second protective film provided on the other surface of the polarizer. For each protective film, a triacetyl cellulose film (TAC film) is widely used in terms of excellent transparency and low birefringence.

  On the other hand, it is known that a display device such as a liquid crystal display device is provided with various optical members in order to improve its performance. For example, in a liquid crystal display device, it is known to provide a brightness enhancement film as a method for effectively using light from a light source to improve brightness and increase luminous efficiency. Proposed as such a brightness enhancement film are a circularly polarized light separating element that transmits predetermined circularly polarized light and reflects other polarized light, and a retardation film that converts circularly polarized light transmitted through the circularly polarized light separating element into linearly polarized light, and (For example, Patent Document 1).

  In recent years, attempts have been made to reduce the size and weight of such liquid crystal display devices by thinning the members (for example, the TAC film) or reducing the number of members. For example, Patent Document 2 proposes a thin polarizing plate including a polarizing film, a transparent substrate, a first optical compensation film, and a second optical compensation film.

JP 2002-341343 A JP 2007-286388 A

  However, in order to reduce the size and weight of the device, if the members are simply reduced and the members are made thin (especially, the TAC film is 40 μm or less), the display is caused by the deterioration of the polarizing film or the brightness enhancement film. It was found that there was a decrease in performance.

  An object of the present invention is to provide a polarizing plate and a liquid crystal display device including the polarizing plate that have high optical performance without dimensional change even in a high-temperature and high-humidity environment, and are excellent in light use efficiency of a light source. It is in.

  As a result of studies to solve the above problems, the present inventors have arranged a protective film made of an appropriate material as a protective film for a polarizing film at a predetermined position, and placed a specific brightness enhancement film at a predetermined position. It has been found that the above-mentioned problems can be solved by arranging them, and the present invention has been reached based on this finding.

The present invention provides the following [1] to [9].
[1] A circularly polarized light separating element, an optical compensation film, a linearly polarizing film, and a protective film are provided in this order, and the circularly polarized light separating element is formed of a resin layer having cholesteric regularity, It includes a layer made of a resin having a negative refraction value, and the retardation Re in the front direction is about 1/4 of the wavelength of transmitted light, and the protective film has a moisture permeability of 20 to 500 g / m ² · 24 h. There is a polarizing plate.
[2] The polarizing plate according to [1], wherein the optical compensation film has a moisture permeability of 10 to 100 g / m ² · 24 h.
[3] The polarizing plate according to [1] or [2], wherein the thickness of the optical compensation film is 5 to 40 μm.
[4] The polarizing plate according to any one of [1] to [3], wherein the protective film includes a layer made of an acrylic resin.
[5] The polarizing plate according to any one of [1] to [4], wherein the resin having a negative intrinsic birefringence value is a polystyrene resin.
[6] The polarizing plate according to any one of [1] to [5], wherein the optical compensation film has an Nz coefficient of less than 0.
[7] The polarizing plate according to any one of [1] to [6], wherein an in-plane slow axis of the optical compensation film intersects a transmission axis of the linearly polarizing film at about 45 °.
[8] The polarizing plate according to any one of [1] to [7], which is long.
[9] A liquid crystal display device comprising a light reflecting element, a light source, the polarizing plate according to any one of [1] to [7], a liquid crystal cell, and an analyzer in this order.

  The polarizing plate of the present invention can be reduced in thickness and area, has excellent manufacturing efficiency and durability, and has high light use efficiency when placed in a liquid crystal display device. Further, the liquid crystal display device of the present invention can be reduced in thickness and area, has excellent manufacturing efficiency and durability, has high luminance, and has little change in color tone depending on the viewing angle.

  The polarizing plate of the present invention comprises a circularly polarized light separating element, an optical compensation film, a linearly polarizing film, and a protective film in this order.

<Circularly polarized light separating element>
The circularly polarized light separating element has a function of transmitting left-rotated or right-rotated circularly polarized light in a specific wavelength region and reflecting other circularly polarized light.
The circularly polarized light separating element used in the present invention comprises a resin layer having cholesteric regularity (hereinafter sometimes referred to as “cholesteric resin layer”), and has a “base material layer” and an “alignment film” as necessary. .
Cholesteric regularity means that the molecular axes are aligned in a certain direction on one plane, but the direction of the molecular axis is slightly shifted on the next plane, and the angle is further shifted on the next plane. This is a structure in which the angle of the molecular axis is shifted (twisted) as it advances through a plane in which molecules are arranged in a certain direction. Thus, the structure in which the direction of the molecular axis is twisted becomes an optically chiral structure.

"Cholesteric resin layer"
The cholesteric resin layer used in the present invention is a layer formed by polymerizing the cholesteric liquid crystal composition (X). Such a layer becomes a non-liquid crystalline resin layer cured while exhibiting the molecular orientation of the liquid crystal.

The cholesteric liquid crystal composition (X) contains a compound represented by the following general formula (1) and a specific polymerizable rod-like liquid crystal compound.
R1X-A1X-B-A2X-R2X (1)

1. Compound (1) in cholesteric liquid crystal composition (X)
In the general formula (1), R1X and R2X are each independently a linear or branched alkyl group having 1 to 20 carbon atoms, or a linear or branched chain group having 1 to 20 carbon atoms. It is a group selected from the group consisting of an alkylene oxide group, a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a (meth) acryl group, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group. Here, (meth) acryl means acryl and methacryl.

  The alkyl group and alkylene oxide group may be unsubstituted or substituted with one or more halogen atoms. The halogen atom, hydroxyl group, carboxyl group, (meth) acryl group, epoxy group, mercapto group, isocyanate group, amino group, and cyano group are bonded to an alkyl group having 1 to 2 carbon atoms or an alkylene oxide group. May be.

Preferable examples of R1X and R2X include a halogen atom, a hydroxyl group, a carboxyl group, a (meth) acryl group, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group.
Moreover, it is preferable that at least one of R1X and R2X is a reactive group. By having a reactive group as R1X and / or R2X, the compound represented by the general formula (1) is fixed in the liquid crystal layer at the time of curing, and a stronger film can be formed. Here, examples of the reactive group include a carboxyl group, a (meth) acryl group, an epoxy group, a mercapto group, an isocyanate group, and an amino group.

  In the general formula (1), A1X and A2X are each independently 1,4-phenylene group, 1,4-cyclohexylene group, 1,4-cyclohexenyl group, 4,4′-biphenylene group, 4,4 ′. -Represents a group selected from the group consisting of a bicyclohexylene group and a 2,6-naphthylene group. The 1,4-phenylene group, 1,4-cyclohexylene group, 1,4-cyclohexenyl group, 4,4′-biphenylene group, 4,4′-bicyclohexylene group, and 2,6-naphthylene group are , It may be unsubstituted or substituted with one or more halogen atoms, hydroxyl groups, carboxyl groups, cyano groups, amino groups, alkyl groups having 1 to 10 carbon atoms, or halogenated alkyl groups. In each of A1X and A2X, when two or more substituents are present, they may be the same or different.

  Particularly preferred examples of A1X and A2X include groups selected from the group consisting of 1,4-phenylene group, 4,4'-biphenylene group, and 2,6-naphthylene group. These aromatic ring skeletons are relatively rigid as compared with the alicyclic skeletons, have high affinity with the mesogens of rod-like liquid crystalline compounds described later, and have higher alignment uniformity.

In the general formula (1), B is a single bond, —O—, —S—, —S—S—, —CO—, —CS—, —OCO—, —CH 2 —, —OCH 2 —, —CH═N. -N = CH-, -NHCO-, -OCOO-, -CH2COO-, and -CH2OCO-.
Particularly preferable examples of B include a single bond, —OCO—, and —CH═N—N═CH—.

  As for the compound of General formula (1), it is preferable that at least 1 type has liquid crystallinity, and it is preferable to have chirality. The cholesteric liquid crystal composition (X) preferably contains a mixture of a plurality of optical isomers as the compound of the general formula (1). For example, a mixture of plural kinds of enantiomers and / or diastereomers can be contained. At least one of the compounds of the general formula (1) preferably has a melting point in the range of 50 ° C to 150 ° C.

  When the compound of the general formula (1) has liquid crystallinity, a high Δn is preferable. By containing the high Δn liquid crystal, Δn as the cholesteric liquid crystal composition (X) can be improved, and a broadband circularly polarized light separating sheet can be produced. At least one Δn of the compound of the general formula (1) is preferably 0.18 or more, more preferably 0.22 or more.

2. Rod-like liquid crystal compound in cholesteric liquid crystal composition (X) In the present invention, the cholesteric liquid crystal composition (X) contains a rod-like liquid crystal compound having at least two or more reactive groups in one molecule.
Examples of the rod-like liquid crystalline compound include compounds represented by the formula (2).
R3X-C3X-D3X-C5X-M-C6X-D4X-C4X-R4X Formula (2)
(Wherein R3X and R4X are reactive groups, each independently (meth) acrylic group, (thio) epoxy group, oxetane group, thietanyl group, aziridinyl group, pyrrole group, vinyl group, allyl group, fumarate group) , A cinnamoyl group, an oxazoline group, a mercapto group, an iso (thio) cyanate group, an amino group, a hydroxyl group, a carboxyl group, and an alkoxysilyl group, wherein D3X and D4X are a single bond or a carbon atom. This represents a group selected from the group consisting of a linear or branched alkyl group having 1 to 20 carbon atoms and a linear or branched alkylene oxide group having 1 to 20 carbon atoms. C6X is a single bond, -O-, -S-, -SS-, -CO-, -CS-, -OCO-, -CH2-, -OCH2-, -CH = NN-CH-,- NH Represents a group selected from the group consisting of CO-, -OCOO-, -CH2COO-, and -CH2OCO-, wherein M represents a mesogenic group, specifically, may be unsubstituted or substituted. Azomethines, azoxys, phenyls, biphenyls, terphenyls, naphthalenes, anthracenes, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines , 2-4 skeletons selected from the group of phenyldioxanes, tolanes, alkenylcyclohexylbenzonitriles, -O-, -S-, -SS-, -CO-, -CS-, -OCO-, -CH2-, -OCH2-, -CH = NN-CH-, -NHCO-, -OCOO-,- H2COO-, and is formed are joined by a linking group such as -CH2OCO-.
Examples of the substituent that the mesogenic group M may have include a halogen atom, an optionally substituted alkyl group having 1 to 10 carbon atoms, a cyano group, a nitro group, —O—R 5 X, —O—C ( = O) -R5X, -C (= O) -O-R5X, -OC (= O) -O-R5X, -NR5X-C (= O) -R5X, -C (= O) -NR5XR7X, Or, -OC (= O) -NR5XR7X is represented. Here, R5X and R7X each represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. When the alkyl group is an alkyl group, -O-, -S-, -O-C (= O) -, -C (= O) -O-, -OC (= O) -O-, -NR6X-C (= O)-, -C (= O) -NR6X-, -NR6X-, or- C (= O)-may be present (except when two or more of -O- and -S- are present adjacent to each other). Here, R6X represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Examples of the substituent in the “optionally substituted alkyl group having 1 to 10 carbon atoms” include a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, an amino group, and an alkoxy group having 1 to 6 carbon atoms. Group, alkoxyalkoxy group having 2 to 8 carbon atoms, alkoxyalkoxyalkoxy group having 3 to 15 carbon atoms, alkoxycarbonyl group having 2 to 7 carbon atoms, alkylcarbonyloxy having 2 to 7 carbon atoms Group, an alkoxycarbonyloxy group having 2 to 7 carbon atoms, and the like.

  The rod-like liquid crystalline compound preferably has an asymmetric structure. Here, the asymmetric structure means a structure in which R3X-C3X-D3X-C5X- and -C6X-D4X-C4X-R4X are different from each other in the general formula (2) with the mesogenic group M as the center. By using a rod-like liquid crystal compound having an asymmetric structure, alignment uniformity can be further improved.

  The rod-like liquid crystal compound may have at least two reactive groups in one molecule. Specific examples of the reactive group include an epoxy group, a thioepoxy group, an oxetane group, a thietanyl group, an aziridinyl group, a pyrrole group, a fumarate group, a cinnamoyl group, an isocyanate group, an isothiocyanate group, an amino group, a hydroxyl group, and a carboxyl group. , Alkoxysilyl groups, oxazoline groups, mercapto groups, vinyl groups, allyl groups, methacryl groups, and acrylic groups. By having these reactive groups, a stable cured product can be obtained when the cholesteric liquid crystal composition is cured. When a compound having one or less reactive group in one molecule is used, when the cholesteric liquid crystal composition is cured, a crosslinked cured product cannot be obtained, so that there is a possibility that a film strength that can withstand practical use cannot be obtained. . Even when a cross-linking agent described later is used, the film strength is insufficient and practical use is difficult. The film strength that can be practically used is HB or more, preferably H or more, in pencil hardness (JIS K5400). If the film strength is lower than HB, the film is easily scratched and lacks handling properties. The upper limit of preferable pencil hardness is not particularly limited as long as it does not adversely affect the optical performance and durability test.

  The rod-like liquid crystalline compound preferably has a Δn value of 0.18 or more, and more preferably 0.22 or more. By having such a high Δn value, a circularly polarized light separating element having high optical performance (for example, circularly polarized light separation characteristics) can be provided.

  In the present invention, in the cholesteric liquid crystal composition (X), the weight ratio of (total weight of the compound of the general formula (1)) / (total weight of the rod-like liquid crystal compound) is 0.05 to 1. Preferably, it is 0.1 to 0.65, more preferably 0.15 to 0.45. When the weight ratio is less than 0.05, the alignment uniformity may be insufficient. On the other hand, when the weight ratio is more than 1, the alignment uniformity decreases, the stability of the liquid crystal phase decreases, and the liquid crystal composition As a result, the desired optical performance (for example, circularly polarized light separation characteristics) may not be obtained. The total weight indicates the weight when one kind is used and the total weight when one or more kinds are used.

  In the present invention, in the cholesteric liquid crystal composition (X), the compound of the general formula (1) preferably has a molecular weight of less than 600, and the rod-like liquid crystal compound has a molecular weight of 600 or more. When the molecular weight of the compound of the general formula (1) is less than 600, it can enter the gap between the rod-like liquid crystalline compounds having a larger molecular weight than that, and the alignment uniformity can be improved.

3. Arbitrary component in cholesteric liquid crystal composition (X) In the present invention, the cholesteric liquid crystal composition such as the cholesteric liquid crystal composition (X) optionally contains a crosslinking agent in order to improve film strength and durability after curing. Can be contained. The blending ratio of the crosslinking agent is preferably 0.1 to 15% by weight in a cured film obtained by curing the cholesteric liquid crystal composition. When the blending ratio of the crosslinking agent is less than 0.1% by weight, the effect of improving the crosslinking density cannot be obtained. Conversely, when the blending ratio is more than 15% by weight, the stability of the liquid crystal layer is lowered, which is not preferable.

In the present invention, the cholesteric liquid crystal composition (X) can optionally contain a photoinitiator. As the photoinitiator, known compounds that generate radicals or acids by ultraviolet rays or visible rays can be used. In addition, two or more compounds can be mixed depending on the desired physical properties, and if necessary, a known photosensitizer or a tertiary amine compound as a polymerization accelerator is added to control curability. You can also.
The blending ratio of the photoinitiator is preferably 0.03 to 7% by weight in the cholesteric liquid crystal composition. When the blending amount of the photoinitiator is less than 0.03% by weight, the degree of polymerization is lowered and the film strength may be lowered. On the other hand, if it is more than 7% by weight, the alignment of the liquid crystal is inhibited and the liquid crystal phase may become unstable.

In the present invention, the cholesteric liquid crystal composition (X) can optionally contain a surfactant. As the surfactant, those not inhibiting the orientation can be appropriately selected and used. As the surfactant, specifically, a nonionic surfactant containing siloxane or fluorinated alkyl group in the hydrophobic group portion can be preferably used, and an oligomer having two or more hydrophobic group portions in one molecule. Is particularly preferred.
The blending ratio of the surfactant is preferably 0.05% by weight to 3% by weight in the cured film obtained by curing the cholesteric liquid crystal composition. When the blending ratio of the surfactant is less than 0.05% by weight, the orientation regulating force at the air interface is lowered and an orientation defect may occur, which is not preferable. On the other hand, when the amount is more than 3% by weight, it is not preferable because an excessive surfactant may enter between liquid crystal molecules and lower the alignment uniformity.

In the present invention, the cholesteric liquid crystal composition (X) can optionally contain a chiral agent. Specific examples of the chiral agent include those disclosed in Japanese Patent No. 4054392, those disclosed in JP-A-9-31077, those disclosed in JP2000-309589, and JP2003. And those disclosed in Japanese Patent No. 137787/1990. Further, as a commercially available chiral agent, for example, LC756 of BASF Corporation Paliocolor can be obtained.
The chiral agent can be added within a range that does not deteriorate the desired optical performance.
The content ratio of the chiral agent is usually 1 to 60% by weight in the cholesteric liquid crystal composition.

  In the present invention, the cholesteric liquid crystal composition (X) can further contain other optional components as necessary. Examples of the other optional components include a solvent, a polymerization inhibitor for improving pot life, an antioxidant for improving durability, an ultraviolet absorber, and a light stabilizer. These optional components can be added as long as the desired optical performance is not deteriorated.

  The cholesteric resin layer used in the present invention preferably exhibits a circularly polarized light separating function over the entire wavelength region of visible light. For example, it is preferable to have a circularly polarized light separating function for light in any wavelength region of blue (wavelength 410 to 470 nm), green (wavelength 520 to 580 nm), and red (wavelength 600 to 660) nm.

Examples of the cholesteric resin layer include (i) a cholesteric resin layer in which the pitch of the chiral structure is changed stepwise, and (ii) a cholesteric resin layer in which the pitch of the chiral structure is continuously changed. Etc.
The pitch of the chiral structure is a distance in the plane normal direction until the angle of the molecular axis in the chiral structure gradually shifts as it advances along the plane and then returns to the original molecular axis direction again. By changing the pitch of this chiral structure, the wavelength at which the circularly polarized light separating function is exhibited can be changed.

(I) The cholesteric resin layer in which the pitch of the chiral structure is changed stepwise is, for example,
A cholesteric resin layer having a chiral pitch that exhibits a circularly polarized light separating function with light in the blue wavelength region, a cholesteric resin layer having a chiral structure pitch that exhibits a circularly polarized light separating function with light in the green wavelength region, and a red It can be obtained by laminating a cholesteric resin layer having a chiral pitch that exhibits a circularly polarized light separation function with light in the wavelength band. Further, cholesteric resin layers having a central wavelength of reflected circularly polarized light of 470 nm, 550 nm, 640 nm, and 770 nm are respectively produced, and these cholesteric resin layers are arbitrarily selected, and the order of the central wavelengths of reflected light is 3 to 3 It can be obtained by laminating seven layers. When the cholesteric resin layers having different chiral structure pitches are laminated, it is preferable that the rotation directions of the circularly polarized light reflected by the cholesteric resin layers are the same. In addition, in order to obtain a liquid crystal display device having a wide viewing angle, the stacking order of the cholesteric resin layers having different chiral structure pitches may be ascending or descending in order of the chiral structure pitch. preferable. The lamination of these cholesteric resin layers may be merely overlaid, or may be fixed via an adhesive or an adhesive.

  (Ii) The cholesteric resin layer in which the pitch of the chiral structure is continuously changed is not particularly limited by the manufacturing method, but a preferable example of the manufacturing method of such a cholesteric resin layer is to form a cholesteric resin layer. The cholesteric liquid crystal composition (X) is preferably applied on another layer such as an alignment film to obtain a cholesteric liquid crystal layer, and then the liquid crystal layer is formed by one or more light irradiation and / or heating treatments. The method of hardening is mentioned. The application can be carried out by a known method such as an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die coating method, or a bar coating method.

  Before the liquid crystal layer obtained by the application is cured, an alignment treatment can be performed as necessary. The alignment treatment can be performed, for example, by heating the liquid crystal layer at 50 to 150 ° C. for 0.5 to 10 minutes. By performing the alignment treatment, the cholesteric liquid crystal layer can be aligned well.

The curing step can be performed by a combination of one or more light irradiations and a heating treatment. Specifically, the heating condition is, for example, a temperature of 40 to 200 ° C, preferably 50 to 200 ° C,
More preferably, it is 50-140 degreeC, Time can be made into 1 second-3 minutes, Preferably it is 5-120 seconds. The light used for light irradiation in the present invention includes not only visible light but also ultraviolet rays and other electromagnetic waves. Specifically, the light irradiation can be performed by, for example, irradiating light having a wavelength of 200 to 500 nm for 0.01 second to 3 minutes. Further, for example, it is possible to obtain a circularly polarized light separating sheet having a wide reflection band by alternately repeating weak ultraviolet irradiation of 0.01 to 50 mJ / cm <2> and heating a plurality of times. After extending the reflection band by the above-mentioned weak ultraviolet irradiation, etc., a relatively strong ultraviolet ray of 50 to 10,000 mJ / cm @ 2 is irradiated to completely polymerize the liquid crystalline compound, whereby a cholesteric resin layer can be obtained. . The expansion of the reflection band and the irradiation with strong ultraviolet rays may be performed in the air, or a part or all of the process may be performed in an atmosphere in which the oxygen concentration is controlled (for example, in a nitrogen atmosphere). .

  In the present invention, the step of applying and curing the cholesteric liquid crystal composition on another layer such as an alignment film is not limited to one time, and the coating and curing are repeated a plurality of times to form two or more cholesteric resin layers. You can also. However, in the present invention, even when the cholesteric liquid crystal composition is applied and cured only once, a cholesteric resin layer having a well-oriented rod-like liquid crystalline compound having a Δn of 0.18 or more and a thickness of 5 μm or more can be easily formed. Can be formed.

  In the present invention, the dry film thickness of the cholesteric resin layer is preferably 3.0 μm to 10.0 μm, more preferably 3.5 to 8 μm. When the dry film thickness of the cholesteric resin layer is less than 3.0 μm, the reflectance decreases, and conversely, when thicker than 10.0 μm, the cholesteric resin layer is colored when observed from an oblique direction, Each is not preferred. The dry film thickness refers to the total film thickness of each layer when the cholesteric resin layer is two or more layers, and the film thickness when the cholesteric resin layer is one layer.

"Base material layer"
The said base material layer which is an arbitrary component of the circularly polarized light separation element used for this invention can be comprised with transparent resin.
The transparent resin is not particularly limited, and a resin having a thickness of 1 mm and a total light transmittance of 80% or more can be used. Specifically, alicyclic olefin polymers, chain olefin polymers such as polyethylene and polypropylene, triacetyl cellulose, polyvinyl alcohol, polyimide, polyarylate, polyester, polycarbonate, polysulfone, polyethersulfone, modified acrylic polymer, epoxy resin, Examples thereof include a single layer or laminated film made of a synthetic resin such as polystyrene or acrylic resin. Among these, an alicyclic olefin polymer or a chain olefin polymer is preferable, and an alicyclic olefin polymer is particularly preferable from the viewpoint of transparency, low hygroscopicity, dimensional stability, lightness, and the like.

`` Alignment film ''
The alignment film can be provided on the base material layer. By providing the alignment film, the cholesteric liquid crystal composition applied thereon can be suitably aligned in a desired direction. The alignment film is subjected to a corona discharge treatment, if necessary, on the surface of the substrate, and then a solution obtained by dissolving the alignment film material in water or a solvent, reverse gravure coating, direct gravure coating, die coating, It can be formed by applying and drying using a known method such as bar coating and then subjecting the dried coating film to a rubbing treatment. As the material for the alignment film, cellulose, silane coupling agent, polyimide, polyamide, polyvinyl alcohol, epoxy acrylate, silanol oligomer, polyacrylonitrile, phenol resin, polyoxazole, cyclized polyisoprene, etc. can be used. Polyamide is particularly preferred.
Examples of the modified polyamide include those obtained by modifying an aromatic polyamide or an aliphatic polyamide, and those obtained by modifying an aliphatic polyamide are preferred. Specifically, for example, modified to nylon-6, nylon-66, nylon-12, ternary to quaternary copolymer nylon, fatty acid polyamide, or fatty acid block copolymer (for example, polyether ester amide, polyester amide). Can be mentioned. Examples of the modification include terminal amino modification, carboxyl modification, hydroxyl modification and the like, and modification in which a part of the amide group is alkylaminated or N-alkoxyalkylated. Examples of the N-alkoxyalkylated modified polyamide include N-methoxymethylated part of the amide group of a copolymer nylon such as nylon-6, nylon-66, or nylon-12. The weight average molecular weight of the modified polyamide is preferably 5,000 to 500,000, more preferably 10,000 to 200,000.
The thickness of the alignment film may be any film thickness that provides the desired alignment uniformity of the liquid crystal layer, and is preferably 0.001 to 5 μm, and more preferably 0.01 to 2 μm.

  By providing a cholesteric resin layer on the alignment film by the method described above, a circularly polarized light separating element having a layer structure of base material layer / alignment film / cholesteric resin layer can be obtained. Such a circularly polarized light separating element composed of three layers is bonded through an adhesive layer or an adhesive layer, whereby a first base layer, a first alignment film, a first cholesteric resin layer, a second layer A circularly polarized light separating element having a base material layer, a second alignment film, and a second cholesteric resin layer in this order can be obtained.

  The circularly polarized light separating element used in the present invention is preferably long. The term “long” refers to one having a length of about 5 times or more, preferably 10 times or more, in the width direction of the element. Specifically, it has a length that can be stored in a roll and stored or transported.

<Optical compensation film>
The optical compensation film used in the present invention is a film capable of changing the phase of light, and includes a layer made of a resin having a negative intrinsic birefringence value.
Examples of the resin having a negative intrinsic birefringence value include polystyrene resins including homopolymers of styrene or styrene derivatives or copolymers with other monomers; polyacrylonitrile resins, polymethylmethacrylate resins, or multicomponent copolymers thereof. Etc. You may use these individually by 1 type or in combination of 2 or more types. Preferred examples of the other monomer used in the polystyrene resin include acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene. In the present invention, among these, from the viewpoint that the retardation development is high and the durability and display performance of the linearly polarizing film / circularly polarized light separating element and the display device can be further improved, Among them, a homopolymer of styrene or a styrene derivative is preferable, and a polystyrene resin is particularly preferable. The stereoregularity of the polystyrene-based resin may be an atactic structure or a syndiotactic structure, but is preferably a syndiotactic structure.

The molecular weight of the resin having a negative intrinsic birefringence value is appropriately selected according to the purpose of use, but is the weight average molecular weight (Mw) of polyisoprene measured by gel permeation chromatography using cyclohexane as a solvent, It is usually 10,000 to 300,000, preferably 15,000 to 250,000, more preferably 20,000 to 200,000.
Further, the intrinsic birefringence is negative resin has a glass transition temperature Tg _a of preferably 120 ° C. or higher, more preferably 120 to 200 [° C., particularly preferably from 120 to 140 ° C..

  To the resin having a negative intrinsic birefringence value, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, etc. are added for durability. May be.

  The resin having a negative intrinsic birefringence value is not particularly limited depending on its production method. For example, a resin having a negative intrinsic birefringence value can be obtained by a suspension polymerization method, an emulsion polymerization method, a bulk polymerization method, or the like. Can do.

  The layer made of a resin having a negative intrinsic birefringence value can be obtained by a cast molding method, an extrusion molding method, an inflation molding method, or the like. Among these, an extrusion method is preferable from the viewpoint of obtaining a film having excellent dimensional stability.

  The optical compensation film used in the present invention preferably has a laminated structure of a layer made of a resin having a negative intrinsic birefringence value and a layer containing another thermoplastic resin. By having the laminated structure, it is possible to obtain an element having both optical characteristics and appropriate moisture permeability due to a resin having a negative intrinsic birefringence value and mechanical strength due to another thermoplastic resin. Other thermoplastic resins include alicyclic resin, methacrylic resin, polycarbonate, acrylic ester-vinyl aromatic compound copolymer resin, methacrylic ester-vinyl aromatic compound copolymer resin, polyethersulfone. And so on. Among these, a methacrylic resin can be preferably used from the viewpoint of excellent adhesion to a resin having a negative intrinsic birefringence value (particularly polystyrene resin) and having appropriate moisture permeability and mechanical strength.

The methacrylic resin is a polymer resin containing a methacrylic acid alkyl ester as a main monomer unit. As the methacrylic resin, a homopolymer of an alkyl ester having 1 to 4 carbon atoms such as methyl methacrylate or ethyl methacrylate; a hydrogen of the alkyl group is a functional group such as OH group, COOH group or NH ₂ group. A homopolymer of a methacrylic acid alkyl ester having a C 1-4 alkyl group substituted by a group; or a methacrylic acid alkyl ester and styrene, vinyl acetate, α, β-monoethylenically unsaturated carboxylic acid, vinyltoluene , Α-methylstyrene, acrylonitrile, copolymers with ethylenically unsaturated monomers other than methacrylic acid alkyl esters such as alkyl acrylate. These can be used individually by 1 type or in combination of 2 or more types. Among these, acrylic acid alkyl esters are suitable for copolymerization with methacrylic acid alkyl esters. In a suitable methacrylic resin, the methacrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms which may be substituted with a functional group is preferably 50 to 100% by weight, more preferably 50 to 99.9% by weight, Preferably it contains 50-99.5 weight%, Preferably it is 0-50 weight% of acrylic acid alkylester, More preferably, it contains 0.1-50 weight%, More preferably, it contains 0.5-50 weight%.

  In order to give the other thermoplastic resin light resistance, heat resistance, etc., an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, a surfactant, rubber Particles or the like may be added.

The other thermoplastic resin preferably has a glass transition temperature Tg _b of 40 ° C. or higher, more preferably 60 ° C. or higher. Further, the glass transition temperature Tg _b is lower it is preferable than the glass transition temperature Tg _a of the resin having a negative intrinsic birefringence value, and more preferably less 20 ° C. or higher than Tg _b. With such a configuration, when a laminate of a layer made of a resin having a negative intrinsic birefringence value and a layer containing another thermoplastic resin is co-stretched as described later, the intrinsic birefringence value becomes negative. It is possible to efficiently develop the optical characteristics of the resin.

  The other thermoplastic resin is not particularly limited depending on its production method, and can be obtained by suspension polymerization, emulsion polymerization, bulk polymerization, or the like. In order to obtain a thermoplastic resin having a suitable glass transition temperature and excellent film formability, it is preferable to use a chain transfer agent during polymerization. The amount of the chain transfer agent is appropriately determined according to the type and composition of the monomer.

  A laminate of the layer made of a resin having a negative intrinsic birefringence value and the layer containing the other thermoplastic resin can be obtained by a cast molding method, an extrusion molding method, an inflation molding method, or the like. Among these, an extrusion method is preferable from the viewpoint of obtaining a film having excellent dimensional stability.

  In the optical compensation film used in the present invention, the retardation Re in the front direction (hereinafter sometimes abbreviated as “Re”) is about ¼ of the wavelength of the transmitted light, and the wavelength range of the transmitted light is from 400 nm to 400 nm. It can be 700 nm. Further, Re is about ¼ wavelength of transmitted light, that is, within a range of ¼ ± 65 nm, preferably ¼ ± 30 nm, more preferably ¼ ± 10 nm of the wavelength of transmitted light. Say. By setting Re within the above range, the luminance of the display device can be preferably increased. Re is an equation: Re = (nx−ny) × d (where nx is the refractive index in the slow axis direction in the film plane, and ny is orthogonal to the slow axis in the film plane in the plane) Is the refractive index in the direction of the film, and d is the thickness of the film.

  In the optical compensation film, the Nz coefficient represented by (nx−nz) / (nx−ny) is preferably less than 0, more preferably −2.7 to −0.1, and particularly preferably. -1.6 to -1.2. By setting the Nz coefficient in the above range, a change in color tone depending on the viewing angle of the display device can be suitably reduced. Nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the direction perpendicular to the slow axis in the film plane, and nz is in the thickness direction perpendicular to the film plane. Refractive index.

  The optical compensation film has a total light transmittance of visible light of preferably 85% or more, more preferably 90% or more. The total light transmittance is a value determined using a spectrophotometer (manufactured by JASCO Corporation, ultraviolet-visible near-infrared spectrophotometer “V570”) in accordance with JIS K0115.

  The optical compensation film has a haze of preferably 5% or less, more preferably 3% or less, and particularly preferably 1% or less. By setting the haze to a low value, the sharpness of the display image of the display device incorporating the optical compensation film of the present invention can be enhanced. In addition, haze is the average value calculated | required from five places using the Nippon Denshoku Industries Co., Ltd. "turbidimeter NDH-300A" based on JISK7361-1997.

  The optical compensation film preferably has a ΔYI of 5 or less, more preferably 3 or less. When this ΔYI is in the above range, there is no coloring and visibility is improved. ΔYI is determined as an arithmetic average value by performing the same measurement five times using “Spectral Color Difference Meter SE2000” manufactured by Nippon Denshoku Industries Co., Ltd. according to ASTM E313.

  The optical compensation film preferably has a JIS pencil hardness of H or higher. The adjustment of the JIS pencil hardness can be performed by changing the type of resin, changing the layer thickness of the resin, or the like. JIS pencil hardness is the hardness of a pencil that begins to scratch, scratching the surface of the film by tilting a pencil of various hardness by 45 °, applying a load of 500 g weight from the top, in accordance with JIS K5600-5-4. .

The optical compensation film has a moisture permeability of 10 to 100 g / m ² · 24 h, more preferably 30 to 60 g / m ² · 24 h at a thickness of 100 μm. By setting the moisture permeability to the above range, durability and display performance of the linearly polarizing film / circularly polarized light separating element and the display device can be further improved. The moisture permeability can be measured by the cup method described in JIS Z 0208 under the test conditions of leaving for 24 hours in an environment of 40 ° C. and 92% RH.

  The optical compensation film has a thickness (average thickness) of preferably 100 μm or less, more preferably 1 to 60 μm, further preferably 5 to 40 μm, and particularly preferably 10 to 10 μm from the viewpoint of having appropriate moisture permeability and mechanical strength. 30 μm. By making the thickness within the above range, the polarizing plate and the display device can be thinned.

  The optical compensation film is preferably long. The long length is a film having a length direction that is long (for example, a length of 10 times or more) with respect to the dimension in the width direction. Specifically, the film is wound or stored in a roll shape. It has the length of. Such a film can be obtained by continuously performing a production process in the length direction in a production line. In particular, when producing an optical compensation film used in the present invention in a process of preparing a pre-stretch film as a long film and further stretching the film, some or all of these processes are simply and efficiently performed inline. It is possible to do. In this case, from the viewpoint of further improving the display performance (luminance, etc.) of the display device, there is a slow axis of the optical compensation film in a direction inclined by about 45 ° from the longitudinal direction of the long film. preferable. In addition, about 45 ° means that it is in the range of 45 ° ± 3 °, preferably 45 ° ± 1 °, more preferably 45 ° ± 0.3 °.

  The optical compensation film used in the present invention is obtained by stretching a layer made of a resin having a negative intrinsic birefringence value, or a layer containing a layer made of a resin having a negative intrinsic birefringence value and the other thermoplastic resin. Can be obtained by co-stretching the laminate. Stretching is preferably performed by uniaxial stretching or oblique stretching, more preferably by uniaxial stretching or oblique stretching by a tenter, and from the viewpoint of obtaining a long polarizing plate that is a preferred embodiment of the present invention. It is particularly preferable that

<Linear polarizing film>
The linearly polarizing film used in the present invention transmits one of two linearly polarized lights that intersect at right angles. For example, a hydrophilic polymer film such as a polyvinyl alcohol film or an ethylene vinyl acetate partially saponified film adsorbed a dichroic substance such as iodine or a dichroic dye and uniaxially stretched, the hydrophilic polymer film Examples include uniaxially stretched and dichroic substances adsorbed, and polyene oriented films such as polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. The thickness of the linearly polarizing film is usually 5 to 80 μm. Moreover, it is preferable that the said linearly-polarizing film is elongate. In this case, the transmission axis of the linearly polarizing film (the axis through which one linearly polarized light is transmitted) is usually a direction parallel to the width direction of the long film.

<Protective film>
The protective film used in the present invention is a film for protecting the linearly polarizing film. The protective film preferably includes a layer made of a transparent material. The transparent material has a total light transmittance of 80% or more when a 1 mm thick film is used.
Transparent materials include norbornene resin, polyester resin, acetyl cellulose such as triacetyl cellulose, polyether sulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin such as polypropylene, acrylic resin, urethane resin, acrylic urethane resin, An epoxy resin, a silicone resin, etc. are mentioned. Among these, acetyl cellulose and acrylic resin are preferable, and acrylic resin is particularly preferable from the viewpoint of further improving durability and display performance of the linearly polarizing film, the circularly polarized light separating element and the display device. . The transparent material is preferably thermoplastic.

As the acrylic resin, homopolymers of (meth) acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate; the hydrogen of the alkyl group is OH group, COOH group, NH ₂ group or the like Homopolymer of (meth) acrylic acid alkyl ester substituted by a functional group; or (meth) acrylic acid alkyl ester and styrene, vinyl acetate, α, β-monoethylenically unsaturated carboxylic acid, vinyl toluene, α- Examples thereof include a copolymer with a vinyl monomer having an unsaturated bond such as methylstyrene. Of these, only one type may be used, or two or more types may be used in combination. More preferably, the acrylic resin contains polymethyl methacrylate and polybutyl methacrylate as monomer units. The acrylic resin preferably has a glass transition temperature Tg in the range of 80 to 120 ° C. Further, the acrylic resin has a high surface hardness when formed into a film, and specifically exceeds 2H in pencil hardness (according to JIS K5600-5-4 except that the test load is 500 g). Things are preferred

The protective film has a moisture permeability at a thickness of 100 μm of 20 to 500 g / m ² · 24 h, preferably 50 to 200 g / m ² · 24 h, more preferably 120 to 170 g / m ² · 24 h.

  The protective film has a thickness (average thickness) of preferably 100 μm or less, more preferably 1 to 60 μm, still more preferably 5 to 40 μm, and particularly preferably 10 to 35 μm. By making the thickness within the above range, the polarizing plate and the display device can be thinned. Moreover, it is preferable that the said protective film is elongate.

  From the viewpoint of improving the handleability of the polarizing plate of the present invention, the protective film used in the present invention preferably has a laminated structure of a layer made of the transparent material and a layer containing the other thermoplastic resin, It is more preferable to have a laminated structure of a layer made of an acrylic resin and a layer containing the other thermoplastic resin, a layer made of the acrylic resin, a layer containing the other thermoplastic resin, and elastic particles such as rubber, It is more preferable to have a laminated structure with a layer containing, and it is particularly preferred to have a laminated structure with a layer made of the acrylic resin and a layer containing the methacrylic resin and elastic particles such as rubber.

  In the polarizing plate of the present invention, it is preferable that a circularly polarized light separating element, an optical compensation film, a linearly polarizing film, and a protective film are integrated in this order. The polarizing plate and the display device can be thinned by integrating them without interposing other members. The method of integrating them is not particularly limited, and examples thereof include a method of bonding them using an adhesive or a pressure-sensitive adhesive, a method of bringing plasma into contact with these surfaces, and then press-bonding them. The adhesive or pressure-sensitive adhesive is preferably transparent to visible light, and preferably does not generate an unnecessary phase difference. When the optical compensation film and the linearly polarizing film are integrated, the optical compensation film also has a function of protecting the linearly polarizing film. Therefore, protection of the linearly polarizing film on the side close to the circularly polarized light separating element. The film can be omitted.

  In the polarizing plate of the present invention, it is preferable that the in-plane slow axis of the optical compensation film intersects the transmission axis of the linearly polarizing film at approximately 45 °. Thereby, the display performance (brightness etc.) of a display apparatus improves suitably. Note that “approximately 45 °” means that it is in the range of 45 ° ± 5 °, preferably 45 ° ± 2 °, more preferably 45 ° ± 0.5 °.

  The polarizing plate of the present invention is preferably long. When used in the liquid crystal display device described below, it becomes possible to efficiently cut out in the direction and shape according to the purpose, and the manufacturing efficiency of the polarizing plate and the display device of the present invention can be increased.

  The liquid crystal display device of the present invention comprises a light reflecting element, a light source, the polarizing plate, a liquid crystal cell, and an analyzer in this order.

  The light reflecting element is not particularly limited, and those employed in known liquid crystal display devices can be used. Specifically, a white plastic sheet having a cavity formed therein, a plastic sheet coated with a white pigment such as titanium oxide on the surface, and the like can be given.

  The light source is not particularly limited, and those employed in known liquid crystal display devices can be used. Specifically, a cold cathode tube, a light emitting diode, an electroluminescence lamp, and the like can be given.

  As the liquid crystal cell, a liquid crystal is inserted between a pair of glass substrates, and a known one is used. The driving method of the liquid crystal is not particularly limited. For example, in-plane switching (IPS) mode, vertical alignment (VA) mode, multi-domain vertical alignment (MVA) mode, continuous spin wheel alignment (CPA) mode, hybrid alignment nematic ( HAN) mode, twisted nematic (TN) mode, super twisted nematic (STN) mode, and optically compensated bend (OCB) mode.

  As said analyzer, what bonded the said protective film to both surfaces of the said linearly polarizing film can be used. The surface of the analyzer may be provided with an antireflection layer, an antifouling layer, an antiglare layer and the like.

  The liquid crystal display device of the present invention may include other members. For example, appropriate components such as a prism array sheet, a lens array sheet, a light diffusion plate, and a light guide plate can be arranged in one or more layers at appropriate positions.

  In the liquid crystal display device of the present invention, the polarizing plate of the present invention may be disposed between the light source and the liquid crystal cell, but the polarizing plate and the liquid crystal are located closer to the liquid crystal cell, that is, without interposing other members. It is preferable to arrange the cells in that the performance of the display device can be improved. In consideration of improving display performance of the display device, the polarizing plate of the present invention can be arranged so that the circularly polarized light separating element is close to the light source.

Hereinafter, the present invention will be described by way of examples. In addition, this invention is not limited by the following examples.
In addition, evaluation in a present Example is performed with the following method.

(Layer thickness of film)
After embedding the film in an epoxy resin, it was sliced using a microtome (product name “RUB-2100”, manufactured by Yamato Kogyo Co., Ltd.), and the cross section was observed and measured using a scanning electron microscope.

(Water permeability of film)
The measurement was performed by a method according to the cup method described in JIS Z 0208 under the test conditions of leaving for 24 hours in an environment of 40 ° C. and 92% RH. The unit of moisture permeability is g / m ² · 24h.

(Re and Nz coefficients of film)
Using an automatic birefringence meter (manufactured by Oji Scientific Instruments Co., Ltd., KOBRA-21ADH) at a wavelength of 550 nm, the measurement was performed at 50 mm intervals in the range of 50 mm in the width direction and 1000 mm in the flow direction. The in-plane direction retardation Re and the Nz coefficient were obtained by averaging all measurement results.

(Production Example 1)
<Preparation of cholesteric liquid crystal composition (X)>
7.31 parts by weight of a compound represented by the following formula (B1), 30 parts by weight of a rod-like liquid crystal compound (following formula (A2)), a photopolymerization initiator (“IRG907”, manufactured by Ciba Specialty Chemicals) 1.20 weights Parts, 2.22 parts by weight of chiral agent (“LC756”, manufactured by BASF), 0.04 parts by weight of surfactant (“KH40”, manufactured by Seimi Chemical), and 60.00 parts by weight of 2-butanone solvent. A cholesteric liquid crystal composition (X) was prepared.

(Production Example 2)
<Production of circularly polarized light separating element>
Long norbornene resin film: One side of a base material layer (“ZF14-100”, manufactured by Nippon Zeon Co., Ltd.) was subjected to corona discharge treatment. A polyvinyl alcohol aqueous solution was applied to the corona discharge treated surface, dried at 120 ° C. for 5 minutes, and the dry film was rubbed in one direction to obtain a long substrate 1 having an alignment film.
Next, the cholesteric liquid crystal composition (X) obtained in Production Example 1 was applied to the surface of the substrate 1 having the alignment film with a wire bar. The coating film is oriented at 100 ° C. for 5 minutes, irradiated with ultraviolet rays in a nitrogen atmosphere to broaden the reflection band, then cured by ultraviolet irradiation, and has a cholesteric resin layer having a dry film thickness of 5.3 μm. A scaled circularly polarized light separating element was obtained.

(Production Example 3)
<Preparation of optical compensation film 1>
Resin P1 having a negative intrinsic birefringence value (trade name “Dylark D332”, manufactured by Nova Chemical Japan, styrene-maleic anhydride copolymer, glass transition temperature 125 ° C.) and other thermoplastic resin P2 (product) The pellets of the name “SUMIPEX HT25X” (manufactured by Sumitomo Chemical Co., Ltd., methyl methacrylate polymer) are each melted by an extruder and fed to a die for coextrusion, and a P2 / P1 / P2 three-layer structure raw material Film 1 was formed.

Next, the original film 1 is stretched obliquely at a stretching temperature of 134 ° C. and a stretching ratio of 2.1 times so that the slow axis is inclined at 45 ° with respect to the longitudinal direction with a tenter stretching machine, and an optical compensation film 1 was obtained. A long optical compensation film 1 having a total thickness of 28 μm and a P1 layer thickness of 18 μm was obtained.
When the film cross section of the optical compensation film 1 was observed with a microscope, the average thickness of the P2 layer was 5 μm / the average thickness of the P1 layer was 18 μm / the average thickness of the P2 layer was 5 μm. Further, the slow axis was inclined 45 ° with respect to the MD direction. The characteristics of the obtained optical compensation film 1 are shown in Table 1.

(Production Example 4)
<Preparation of optical compensation film 2>
A monomer composition composed of 97.7% methyl methacrylate and 2.3% methyl acrylate was polymerized by a bulk polymerization method to obtain resin pellets.
On the other hand, rubber particles were produced according to Example 3 of JP-B-55-27576. This rubber particle has a spherical three-layer structure, the core inner layer is a cross-linked polymer of methyl methacrylate and a small amount of allyl methacrylate, and the inner layer is composed of butyl acrylate, styrene and a small amount of allyl acrylate as main components. Is a soft elastic copolymer obtained by crosslinking copolymerization, and the outer layer is a hard polymer of methyl methacrylate and a small amount of ethyl acrylate. The average particle size of the inner layer was 0.19 μm, and the particle size including the outer layer was 0.22 μm.
68 parts of the resin pellets and 32 parts of the rubber particles were mixed and melt kneaded with a twin screw extruder to obtain a thermoplastic resin P4 (glass transition temperature 104 ° C.).

  Next, the pellets of acrylic resin P3 (trade name “Delpet 980N”, manufactured by Asahi Kasei Co., Ltd.) and the thermoplastic resin P4 pellets are respectively melted by an extruder and supplied to a die for coextrusion. A raw film 2 having a three-layer structure of P3 / P4 was formed.

   Subsequently, the original film 2 is obliquely stretched with a tenter stretching machine at a stretching temperature of 144 ° C. and a stretching ratio of 2.6 times so that the slow axis is inclined at 45 ° with respect to the longitudinal direction. 2 was obtained. The characteristics of the obtained optical compensation film 2 are shown in Table 1.

(Production Example 5)
<Preparation of protective film 1>
Pellets of acrylic resin P3 (trade name “Delpet 980N”, manufactured by Asahi Kasei Co., Ltd.) and other thermoplastic resins P5 (trade name “SUMIPEX HT55X”, manufactured by Sumitomo Chemical Co., Ltd., methyl methacrylate polymer containing rubber particles) Each of the pellets was melted with an extruder and supplied to a die for coextrusion to obtain a long protective film 1 having a three-layer structure of P5 / P3 / P5. The properties of the protective film 1 obtained are shown in Table 1.

(Production Example 6)
<Preparation of protective film 2>
Triacetyl cellulose was dissolved in a solvent, and a single-layer protective film 2 was obtained by a cast molding method. The properties of the protective film 2 obtained are shown in Table 1.

(Example 1-1)
<Preparation of Polarizing Plate 1>
The long circularly polarized light separating element obtained in Production Example 2 and the optical compensation film 1 obtained in Production Example 3 were combined with a diffusing agent-containing adhesive composition (cross-linked acrylic powder “Chemisnow MX300” manufactured by Soken Chemical Co., Ltd.) Acrylic ester copolymer “SK Dyne 2094” made by Soken Chemical Co., Ltd.) is pasted by a roll-to-roll through a diffusion adhesive layer, and base material layer-alignment film-cholesteric resin layer-diffusion adhesive layer-optical compensation film A long laminate 1 having a layer configuration of 1 was produced.

  Next, the laminate 1, the long linear polarizing film having a transmission axis in the width direction (stretched by adsorbing iodine to a polyvinyl alcohol film), and the protective film 1 obtained in Production Example 5, A roll of polarizing plate having a layer structure of a circularly polarized light separating element-optical compensation film 1-linearly polarizing film-protective film 1 attached with an adhesive (manufactured by Sumitomo 3M, "8142") by roll-to-roll. Obtained.

(Example 2-1)
<Preparation of Polarizing Plate 2>
Except having replaced the protective film 1 with the protective film 2 obtained by manufacture example 6, it operated similarly to Example 1-1 and obtained the wound body of the polarizing plate.

(Example 1-2)
<Production of liquid crystal display device 1>
A commercially available liquid crystal display device (AQUAS 37 inch, manufactured by Sharp Corporation) was disassembled, and the polarizing plate 1 cut out from the wound body obtained in Example 1-1 was replaced with a polarizing plate on the backlight side, and circularly polarized light was separated. The liquid crystal display device 1 was obtained by reassembling the device so that the element was on the backlight side. This liquid crystal display device had a light reflecting element, a light source, a polarizing plate 1, a liquid crystal cell, and a polarizing plate (analyzer) in this order as main constituent members.

  With the backlight lamp of the obtained liquid crystal display device 1 turned on, a constant temperature and humidity test was conducted at 40 ° C. and 95% RH, and the display state of the display screen of the liquid crystal display device for 700 hours after the start of the test was visually observed. As a result, it was observed that uniform black display was possible. Further, when the display characteristics of the liquid crystal display device 1 were visually confirmed from the front direction or the oblique direction, color unevenness was not observed over the entire width, and the display was good. Further, even when observed from an oblique direction, there was almost no reduction in luminance. In addition, the brightness | luminance improvement was seen rather than the comparative control product (what replaced the laminated body 1 of the polarizing plate 1 with the protective film 2).

(Example 2-2)
<Production of liquid crystal display device 2>
A liquid crystal display device 2 was obtained in the same manner as in Example 1-2 except that the polarizing plate 1 was replaced with the polarizing plate 2 cut out from the wound body obtained in Example 2-1.
A constant temperature and humidity test was conducted at 40 ° C. and 95% RH with the backlight lamp of the obtained liquid crystal display device 2 turned on, and the display state of the display screen of the liquid crystal display device for 700 hours after the start of the test was visually observed. As a result of observation, a slight white spot was observed, but it was possible to confirm the image. Further, when the display characteristics of the liquid crystal display device 1 were visually confirmed from the front direction or the oblique direction, a slight decrease in luminance was observed in part. In addition, the brightness was improved over the comparative product.

(Comparative Example 1-1)
<Preparation of Polarizing Plate 3>
Except having replaced the optical compensation film 1 with the optical compensation film 2 obtained by manufacture example 4, it operated similarly to Example 2-1, and obtained the wound body of the polarizing plate.

(Comparative Example 1-2)
<Production of liquid crystal display device 3>
A liquid crystal display device 3 was obtained in the same manner as in Example 1-2 except that the polarizing plate 1 was replaced with the polarizing plate 3 cut out from the wound body obtained in Comparative Example 1-1.
With the backlight lamp of the obtained liquid crystal display device 3 turned on, a constant temperature and humidity test was conducted at 40 ° C. and 95% RH, and the display state of the display screen of the liquid crystal display device for 700 hours after the start of the test was visually observed. As a result, white spots were observed and it was difficult to confirm the image. Moreover, when the display characteristic of the liquid crystal display device 3 was confirmed visually from the front direction or the oblique direction, a decrease in luminance was observed as compared with the comparative product.

Claims (9)

A circularly polarized light separating element, an optical compensation film, a linearly polarizing film, and a protective film are provided in this order,
The circularly polarized light separating element is composed of a resin layer having cholesteric regularity,
The optical compensation film includes a layer made of a resin having a negative intrinsic birefringence value, and the retardation Re in the front direction is about 1/4 of the wavelength of transmitted light.
The protective film has a moisture permeability of 20 to 500 g / m ² · 24 h.
Polarizer. The polarizing plate according to claim 1, wherein the optical compensation film has a moisture permeability of 10 to 100 g / m ² · 24 h.   The polarizing plate according to claim 1 or 2, wherein the optical compensation film has a thickness of 5 to 40 µm.   The polarizing plate according to claim 1, wherein the protective film includes a layer made of an acrylic resin.   The polarizing plate according to claim 1, wherein the resin having a negative intrinsic birefringence value is a polystyrene-based resin.   The polarizing plate according to claim 1, wherein the optical compensation film has an Nz coefficient of less than 0.   The polarizing plate according to claim 1, wherein an in-plane slow axis of the optical compensation film intersects with a transmission axis of the linearly polarizing film at approximately 45 °.   The polarizing plate according to any one of claims 1 to 7, which is long.   A liquid crystal display device comprising a light reflecting element, a light source, a polarizing plate according to any one of claims 1 to 7, a liquid crystal cell, and an analyzer in this order.