JP2006235576A - Liquid crystal display apparatus and polarizing plate set useful therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an IPS (In-Plane Switching) mode liquid crystal display apparatus having a wide viewing angle with equal contrast and little color shift depending on a viewing angle, and to provide a polarizing plate set effective to enhance the viewing angle by disposing in both sides of a liquid crystal cell of an IPS mode liquid crystal display apparatus. <P>SOLUTION: The liquid crystal display apparatus is equipped with an IPS mode liquid crystal cell 50 and a first polarizing plate 10 and a second polarizing plate 20 disposed to sandwich the liquid crystal cell, wherein a retardation plate 30 is disposed between the first polarizing plate 10 and the liquid crystal cell 50. The sum of retardation Rth in the thickness direction of birefringent layers (a protective layer 12 and the retardation plate 30) present between a polarizer 11 constituting the first polarizing plate 10 and the above retardation plate 30 ranges from -40 nm to +40 nm, and the sum of retardation R<SB>0</SB>in the plane of the above layers ranges from 100 nm to 200 nm. The second polarizing plate 20 includes transparent protective layers 22, 23 applied on both sides of a polarizer 21, wherein the retardation Rth in the thickness direction of the transparent protective layer 22 placed in the liquid crystal cell side of the polarizer 21 ranges from -10 nm to +40 nm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device that is in an in-plane switching (IPS) mode and enables a wide viewing angle. The present invention also relates to a set of polarizing plates useful for the liquid crystal display device.

  In recent years, due to various advantages such as low power consumption, low voltage operation, light weight, and thinness, liquid crystal display devices (LCDs) are used for information such as mobile phones, personal digital assistants (PDAs), personal computers and televisions. Applications as display devices are increasing rapidly. With the development of LCD technology, LCDs in various modes have been proposed, and LCD problems such as response speed, contrast, and narrow viewing angle are being solved. Further, the viewing angle has been further improved by sandwiching the retardation plate between the polarizing plate and the glass substrate.

  Among these liquid crystal display devices, an IPS mode liquid crystal display device includes a liquid crystal cell having a pair of transparent substrates that sandwich the liquid crystal, and a pair of polarizing plates that are disposed on both sides of the cell. Are parallel to the substrate surface and oriented in substantially the same direction, and a comb-like electrode parallel to the inner side (liquid crystal layer side) of at least one of the pair of transparent substrates is arranged between the electrodes. By changing the applied voltage, the direction of the molecular long axis of the liquid crystal is changed in a plane parallel to the substrate, and light passing through the front-side polarizing plate is controlled to perform display.

  In order to improve the viewing angle by compensating the birefringence of such an IPS mode liquid crystal display device, for example, as described in SID 00 DIGEST, p.1094-1097 (Non-patent Document 1), the thickness is oriented. It is known that a retardation plate is effective. As one method of manufacturing a thickness-oriented retardation film, Japanese Patent Application Laid-Open No. 7-230007 (Patent Document 1) discloses that a thermoplastic resin film made of uniaxially stretched polycarbonate is subjected to heat shrinkage in a predetermined form. A method of waking is disclosed. Such a retardation plate oriented in the thickness direction has a transmission axis and a phase difference between adjacent polarizing plates between one of the two polarizing plates arranged with the liquid crystal cell sandwiched therebetween and the liquid crystal cell substrate. Arranging the plates so that their slow axes are parallel is effective in compensating the birefringence of the liquid crystal cell and expanding the viewing angle.

Japanese Patent Laid-Open No. 10-54982 (Patent Document 2) discloses a retardation plate (optical compensation sheet) having negative uniaxiality between a cell substrate and at least one polarizing plate in an IPS mode liquid crystal display device. It is described that the viewing angle characteristics can be improved by arranging. Also Japanese Patent 2002-258041 (Patent Document 3), absorbing polarizer on one or both sides of the polarizer transparent protective layer is provided on both sides of the photon, the refractive indices n _x and the thickness direction of the slow axis direction In which a retardation plate (optical compensation film) having substantially the same refractive index _nz is laminated.

In the above embodiment of the Patent Document 3, by biaxial stretching of polycarbonate having a positive intrinsic birefringence, but n _x and n _z is obtained substantially equal retardation plate, such n _x and n _z is approximately equal position The phase difference plate is advantageously manufactured by uniaxial stretching of a polymer film having negative intrinsic birefringence. Various proposals have also been made for materials for retardation plates having negative intrinsic birefringence. For example, JP 2003-207640 A (Patent Document 4) discloses an acyclic olefin monomer, a cyclic olefin monomer, and an aromatic. It is described that a ternary copolymer with a vinyl monomer is used as a retardation plate. JP-A-2004-214325 (Patent Document 5) discloses a copolymer comprising an α-olefin unit and an N-phenylmaleimide unit and having negative intrinsic birefringence as an optical compensator or a retardation plate. It is described to do.

  Even when the configurations described in Patent Document 2 and Patent Document 3 are adopted, there is still a problem that there is a limit to the expansion of the viewing angle showing equicontrast or the color shift due to the viewing angle is large, Further improvements are desired.

  The present inventor, in Japanese Patent Application Laid-Open Publication No. 2005-221532 (Patent Document 6, Japanese Patent Application No. 2004-26444), uses a single retardation film having negative uniaxiality and adjoins the slow axis of this retardation film. It has been proposed to improve the viewing angle characteristics by arranging it in parallel with the transmission axis of the polarizing plate and the major axis direction of the liquid crystal molecules on the adjacent cell substrate side. Such a negative uniaxial retardation plate is easier to produce than a retardation plate oriented in the thickness direction, and high heat resistance can be obtained by selecting the type of polymer. Furthermore, Japanese Patent Application No. 2004-126387 proposes further improvement of the viewing angle characteristics by using two retardation films having negative uniaxiality.

JP-A-7-230007 (Claim 1) JP-A-10-54982 (Claim 1, FIG. 3) JP 2002-258041 A (Claim 1) JP 2003-207640 A (Claim 1) JP-A-2004-214325 (Claims 1, 5, 6) JP-A-2005-221532 (Claim 1) T. Ishinabe et al., ‘Novel Wide Viewing Angle Polarizer with High Achromaticity’, SID 00 DIGEST, p.1094-1097 (2000) (Table 1)

  The inventor of the present invention has continued to study the IPS mode liquid crystal display device in order to further improve the viewing angle. SUMMARY OF THE INVENTION An object of the present invention is to provide an IPS mode liquid crystal display device having a wide viewing angle exhibiting equal contrast and a small color shift due to the viewing angle. Another object of the present invention is to provide a set of polarizing plates effective for enlarging the viewing angle by being arranged on both sides of the liquid crystal cell of the IPS mode liquid crystal display device.

In order to achieve the above object, according to the present invention, a liquid crystal is sealed between a pair of transparent substrates parallel to each other, and the liquid crystal is aligned in parallel and substantially in the same direction with the substrate. A first polarizing plate and a second polarizing plate arranged with a liquid crystal cell interposed therebetween, and the direction of the molecular long axis of the liquid crystal changes in a plane parallel to the substrate due to a change in voltage applied to the liquid crystal cell. A liquid crystal display device configured to perform display,
Birefringence including at least one retardation plate between the first polarizing plate and the liquid crystal cell and including the retardation plate existing from the polarizer constituting the first polarizing plate to the retardation plate The sum of the thickness direction retardation Rth of the layers is in the range of −40 nm to +40 nm, and the sum of the plane retardations R ₀ is in the range of 100 nm to 200 nm, and the second polarizing plate is formed on both sides of the polarizer. A transparent protective layer is provided, and a liquid crystal display device in which the thickness direction retardation Rth of the transparent protective layer located on the liquid crystal cell side of the polarizer is in the range of −10 nm to +40 nm is provided.

  In this liquid crystal display device, the transparent protective layer located on the liquid crystal cell side of the second polarizing plate where no retardation plate is disposed is advantageously composed of a thermoplastic cyclic polyolefin resin film. If the transparent protective layer is formed of such a thermoplastic cyclic polyolefin-based resin film, the thickness direction retardation Rth can be set in the range of −10 nm to +10 nm.

Further, the retardation plate disposed between the first polarizing plate and the liquid crystal cell preferably has a planar retardation R _{0 in} the range of 100 nm to 200 nm, and further has an Nz coefficient defined later of −0. It is preferably in the range of 0.5 to +0.5.

Here, the plane retardation of the transparent protective layer and a retardation plate R _0, the thickness direction retardation Rth, and the Nz coefficient is in each of the film, the refractive index in a slow axis direction in a plane n _x, in the plane the refractive index n _y in the direction perpendicular to the slow axis, the refractive index in the thickness direction n _z, and the thickness is taken as d, those defined by the following equation, respectively (1) to (3) is there.

_{R 0 = (n x -n y} ) × d (1)
_{Rth = [(n x + n} y) / 2-n z] × d (2)
_{Nz = (n x -n z)} / (n x -n y) (3)

In other words, the plane retardation R ₀ is a value obtained by multiplying the in-plane refractive index difference by the film thickness, and the thickness direction phase difference Rth is the difference between the in-plane average refractive index and the thickness direction refractive index. The Nz coefficient is the ratio of the difference between the in-plane maximum refractive index (slow axis direction refractive index) and the thickness direction refractive index to the in-plane refractive index difference, and is the ratio in the thickness direction. It is an index representing the degree of orientation. For example, the positive optical axis is in the plane in uniaxial film if _{(n x> n y ≒ n} z), Nz ≒ 1 , and the optical axis is in the plane with a negative uniaxial film (n _x If ≈n _z > _ny ), Nz≈0.

When the birefringent layer existing from the polarizer constituting the first polarizing plate to the retardation plate is only the retardation plate, the retardation plate has the above-described thickness direction retardation Rth and planar retardation R. _It is sufficient to satisfy ₀ . On the other hand, when the birefringent layer is a transparent protective layer and a retardation plate of a polarizing plate, a subscript 1 is attached to each value of the transparent protective layer on the retardation plate side, and attached to each value of the retardation plate. When the letter 2 is added, the sum of the thickness direction retardations of the transparent protective layer and the retardation plate is set to a range represented by the following formula (4).

−40 nm ≦ Rth ₁ + Rth ₂ ≦ + 40 nm (4)
However,
Rth ₁ = [(n _x1 + _{ny 1} ) / 2−n _z1 ] × d ₁
Rth ₂ = [(n _x2 + _ny 2) / 2−n _z2 ] × d ₂

  Further, in this liquid crystal display device, the retardation plate disposed between the first polarizing plate and the liquid crystal cell is preferably disposed so that the slow axis thereof is substantially perpendicular to the absorption axis of the first polarizing plate. . Furthermore, it is preferable that the retardation plate is arranged so that the slow axis thereof is substantially parallel to the major axis direction when no voltage is applied to the liquid crystal molecules located on the adjacent transparent substrate surface.

According to the present invention, a set of polarizing plates for a liquid crystal display device comprising the following combinations is also provided.
Birefringence comprising the first polarizing plate and at least one retardation plate disposed on one side thereof, and including the retardation plate existing from the polarizer constituting the first polarizing plate to the retardation plate A composite polarizing plate in which the sum of thickness direction retardations Rth is in the range of −40 nm to +40 nm and the sum of the plane retardations R ₀ is in the range of 100 nm to 200 nm, and transparent protection is provided on both sides of the polarizer. A combination of second polarizing plates in which a layer is provided, and the thickness direction retardation Rth of at least one of the transparent protective layers is in the range of −10 nm to +40 nm.

  On one side of the IPS mode liquid crystal cell, the composite polarizing plate of the set of polarizing plates is arranged so that the retardation plate side faces the liquid crystal cell, and the second polarizing plate is placed on the other side of the liquid crystal cell. If the plate is arranged so that the transparent protective layer having a thickness direction retardation Rth in the range of −10 nm to +40 nm faces the liquid crystal cell, an IPS mode liquid crystal display device with improved viewing angle characteristics can be obtained. .

  Since the liquid crystal display device according to the present invention can highly compensate for the phase difference caused by the liquid crystal layer and the polarizing plate as compared with a liquid crystal display device having a conventional configuration, light leakage due to the viewing angle is suppressed and the contrast viewing angle is widened. Also, color shift due to viewing angle can be suppressed.

  Hereinafter, the present invention will be described in detail with appropriate reference to the accompanying drawings. 1A and 1B show an example of a liquid crystal display device according to the present invention, in which FIG. 1A is a schematic longitudinal sectional view showing a layer structure, and FIG. 1B is a perspective view for explaining an axial relationship. . This liquid crystal display device is mainly composed of an IPS mode liquid crystal cell 50. As described above, the IPS mode liquid crystal cell has a pair of transparent substrates 51 and 52 sandwiching the liquid crystal layer 53, and the liquid crystal is aligned in substantially the same direction parallel to the substrate surface. A comb-like electrode (not shown) parallel to the inner side (liquid crystal layer side) of at least one of the pair of transparent substrates 51 and 52 is disposed, and the liquid crystal is changed by a change in voltage applied between the electrodes. The direction of the molecular long axis is changed in a plane parallel to the substrate.

  The first polarizing plate 10 is disposed outside one substrate 51, and the second polarizing plate 20 is disposed outside the other substrate 52. The absorption axis 15 of the first polarizing plate 10 and the absorption axis 25 of the second polarizing plate 20 are generally arranged in a substantially orthogonal relationship and are normally black, but both absorption axes are substantially parallel. It is also possible to arrange normally and make it normally white. In addition, the absorption axis of one polarizing plate is substantially parallel to the major axis direction 55 of the liquid crystal molecules in the liquid crystal cell 50 when no voltage is applied, so that the absorption axis of one polarizing plate is substantially orthogonal. Are arranged as follows. In FIG. 1B, the major axis direction 55 of the liquid crystal molecules is shown by a white solid line arrow and a white broken line arrow orthogonal thereto, which means that the liquid crystal molecules are arranged in either direction. To do.

  In the present invention, the retardation plate 30 is disposed between the first polarizing plate 10 and the liquid crystal cell 50. The composite polarizing plate 40 is configured with the retardation plate 30 bonded to the first polarizing plate 10. For bonding the first polarizing plate 10 and the phase difference plate 30, a normal adhesive or a pressure-sensitive adhesive (adhesive) can be used.

  Each of the first polarizing plate 10 and the second polarizing plate 20 may transmit linearly polarized light that vibrates in one direction orthogonal to each other in the film plane and absorb linearly polarized light that vibrates in the other direction. In the first polarizing plate 10, transparent protective layers 12 and 13 are provided on both sides of the polarizer 11. The second polarizing plate 20 is also configured by providing transparent protective layers 22 and 23 on both sides of the polarizer 21.

Specifically, the polarizers 11 and 21 may be an iodine polarizing film in which iodine is adsorbed and oriented on a polyvinyl alcohol film, or a dye polarizing film in which a dichroic organic dye is adsorbed and oriented on a polyvinyl alcohol film. The transparent protective layers 12, 13, 22, and 23 are generally made of a polymer material, and are, for example, known cellulose-based materials such as saponified triacetyl cellulose (TAC), diacetyl cellulose (DAC), and cellulose propionate. A film can be used. Such a polymer protective film, generally little plane retardation (n _x ≒ n _y), a negative uniaxial slightly smaller than the principal refractive indices n _x and n _y in the refractive index n _z in the thickness direction surface The optical axis appears in the normal direction. That is, the transparent protective layers 12, 13, 22, and 23 are in a so-called C-plate state. The thickness direction retardation Rth of such a polymer protective film is usually in the range of about 10 to 500 nm. In particular, the thickness direction retardation Rth of the transparent protective layer 12 on the side where the retardation plate 30 is disposed is 50 to 120 nm. In this range, color shift due to viewing angle can be suppressed when applied to an IPS mode liquid crystal display device.

A retardation plate 30 is disposed between the first polarizing plate 10 and the liquid crystal cell 50, and the retardation plate existing from the polarizer 11 to the retardation plate 30 constituting the first polarizing plate 10. The sum of the thickness direction retardations Rth of the birefringent layers including s is in the range of −40 nm to +40 nm, and the sum of the planar retardations R ₀ is in the range of 100 nm to 200 nm. When these birefringent layers are only the retardation plate 30, that is, when the cell-side transparent protective layer 12 of the first polarizing plate 10 is omitted and the retardation plate 30 is directly attached to the polarizer 11, The phase difference plate 30 should just satisfy said phase difference value. However, since it is generally advantageous to dispose the cell-side transparent protective layer 12 on the first polarizing plate 10, in that case, the sum of the thickness direction retardation Rth of the transparent protective layer 12 adjacent to the retardation plate 30 and The sum of the plane phase difference sums R ₀ satisfies each of the above values. The sum of Rth is more preferably in the range of −20 nm to +20 nm, while the sum of R ₀ is more preferably 130 nm or more and 180 nm or less. If the sum of Rth exceeds ± 40 nm, the color shift due to the viewing angle increases, which is not preferable. If the sum of _R0 exceeds the above range, both the luminance and the color shift due to the viewing angle deteriorate, which is not preferable.

A preferable film configuration for the viewing angle compensation of the liquid crystal cell 50 in the IPS mode is that the cell-side transparent protective layer 12 of the first polarizing plate 10 is composed of Rth of about 50 to 110 nm, and is adjacent to the transparent protective layer. The arranged retardation plate 30 is composed of negative uniaxiality, having R ₀ of 130 to 150 nm, Nz coefficient of −0.3 to +0.3, and a slow axis 35 of the retardation plate 30. Are arranged so as to be substantially perpendicular to the absorption axis 15 of the adjacent first polarizing plate 10 and substantially parallel to the major axis direction 55 of the liquid crystal molecules in the state where no voltage is applied. For the transparent protective layer 22 located on the liquid crystal cell side of the second polarizing plate 20, it is preferable to use a substantially non-oriented film (Rth≈0) or a thin-walled cellulose film (Rth = 20 to 40 nm). . Such a configuration is advantageous in terms of cost and optical characteristics.

The substantially non-oriented film is intended refractive index n _z in the thickness direction is substantially equal to the principal refractive indices n _x and n _y in a plane, for example, a thickness direction retardation Rth is as long as 10nm or less It can be said that it is substantially non-oriented. Such a substantially non-oriented transparent protective film can be made of, for example, a cyclic polyolefin resin having a cyclic olefin such as norbornene as a monomer. If it is a cellulosic film, thickness direction phase difference Rth can be made small by making the film thickness comparatively thin.

Usually, a transparent protective layer of the polarizing plate, because the plane phase difference R ₀ is a small value, the phase difference plate 30, plane retardation R ₀ expressed by the above equation (1) is a range of 100nm to 200nm What should I do. Further, it is more preferably 120 nm or more and 180 nm or less. The Nz coefficient represented by the above formula (3) is preferably in the range of −0.5 to +0.5, and more preferably in the range of −0.3 to +0.3.

  The retardation plate 30 is preferably arranged so that the slow axis 35 thereof is substantially orthogonal to the absorption axis 15 of the polarizing plate 10 from the viewpoint of optical compensation in an IPS mode liquid crystal cell. FIG. 1B shows a state where the absorption axis 15 of the polarizing plate 10 and the slow axis 35 of the phase difference plate 30 are arranged so as to be substantially orthogonal to each other. Further, the relationship between the phase difference plate 30 and the liquid crystal cell 50 is that the former slow axis 35 is substantially parallel or substantially orthogonal to the major axis direction 55 in the voltage-free state of liquid crystal molecules located on the adjacent transparent substrate surface. It is sufficient that they are in a relationship, but preferably they are arranged so that they are substantially parallel. In this specification, “substantially” when saying “substantially parallel” or “substantially orthogonal” means that an angle of about ± 10 ° is allowed around the arrangement (parallel or orthogonal) described there. .

  Preferred forms of the retardation film 30 include a film in which a polymer having negative intrinsic birefringence is uniaxially stretched, and a film in which a layer of a liquid crystalline discotic compound exhibiting negative uniaxiality is formed. Both are negative uniaxial retardation plates in which the Nz coefficient is almost zero. Especially, since it is easy to control Nz coefficient, the film in which the polymer which has a negative intrinsic birefringence was uniaxially stretched is preferable.

FIG. 2 shows a state in which the phase difference plate 30 having negative uniaxiality and having an optical axis in the in-plane direction is represented by a refractive index ellipsoid. 2A shows a state in which the slow axis 35 in the refractive index ellipsoid is taken in the horizontal direction, and FIG. 2B shows an axis (fast axis) orthogonal to the slow axis 35 in the plane. Is in the state of taking in the horizontal direction. Has a negative uniaxial optical axis thereof and the retardation in the plane direction, as shown in FIG. 2, but the refractive index structure, comprising a relation of n _z ≒ n _x> n _y There, the smallest n _y direction refractive index (fast axis direction) is the optical axis.

Examples of the polymer used when uniaxially stretching a polymer having negative intrinsic birefringence to form the retardation plate include a styrene polymer, an acrylate ester polymer, a methacrylate ester polymer, an acrylonitrile polymer, Methacrylonitrile polymer, vinyl naphthalene polymer, vinyl pyridine polymer, vinyl carbazole polymer, phenyl acrylamide polymer, vinyl biphenyl polymer, vinyl anthracene polymer, acenaphthylene polymer, phenyl carbonyl Oxynorbornene polymers, biphenylcarbonyloxynorbornene polymers, naphthylcarbonyloxynorbornene polymers, anthracenylcarbonyloxynorbornene polymers, phenylcarbonyloxytetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene polymer, biphenylcarbonyloxytetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene polymer, naphthylcarbonyloxytetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene polymer, anthracenylcarbonyloxytetracyclo [4.4.0.1 ^2,5 . 1 ^{7, 10} ] -3-dodecene polymer, α-olefin / N-phenylmaleimide copolymer, and the like, but are not limited thereto. Here, tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene has the following structure and is also called dimethanooctahydronaphthalene.

  In addition, the above-mentioned polymers can be mixed with other polymers or copolymerized with other monomers so that the negative intrinsic birefringence is not impaired. Functions such as elasticity may be added.

The polymer used for producing the retardation plate is preferably composed of a copolymer having a glass transition temperature of usually 120 ° C. or higher and heat resistance in consideration of the use environment. The glass transition temperature of this copolymer is particularly preferably 130 ° C. or higher. The polymer preferably has a photoelastic coefficient of 10 × 10 ⁻⁵ mm ² kg ⁻¹ or less. Photoelasticity is a phenomenon in which, when an external force is applied to an isotropic substance to cause an internal stress, it exhibits optical anisotropy and exhibits birefringence. When the stress (force per unit area) acting on the substance is σ and the birefringence is Δn, the stress σ and the birefringence Δn are theoretically proportional and can be expressed as Δn = Cσ. This C is the photoelastic coefficient. In other words, if the stress σ acting on the substance is taken on the horizontal axis and the birefringence Δn when the stress is applied on the vertical axis, the relationship between them is theoretically a straight line, and the gradient of this straight line is the photoelasticity. It is a coefficient.

  In view of the high glass transition temperature and low photoelasticity, preferred polymers having negative intrinsic birefringence include acyclic olefin monomers selected from ethylene and α-olefin compounds having 3 to 20 carbon atoms, and cyclic olefins. Examples thereof include terpolymers in which at least one cyclic olefin monomer selected from compounds and an aromatic vinyl monomer selected from vinyl compounds having an aromatic hydrocarbon ring are used.

  Next, each monomer component which comprises this ternary copolymer is demonstrated. The acyclic olefin monomer is selected from ethylene and an α-olefin compound having 3 to 20 carbon atoms. Here, examples of the α-olefin compound having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1- C3-C20 linear α-olefin such as hexadecene, 1-octadecene, 1-eicosene, 4-methyl-1-pentene, 3-methyl-1-pentene, 3-methyl-1-butene And branched α-olefins having 4 to 20 carbon atoms. Among these, ethylene having 2 carbon atoms and propylene or 1-butene, which is a linear α-olefin having 3 or 4 carbon atoms, is obtained when the resulting copolymer is formed into a film. In view of flexibility, ethylene is particularly preferable for the same reason. The above ethylene and α-olefin may be used alone or in combination of two or more.

The cyclic olefin monomer is a compound having a polymerizable carbon-carbon double bond in a carbocycle, and when copolymerized, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring in the main chain of the copolymer, A monomer capable of introducing an alicyclic ring such as one or more bonded rings. Specifically, bicyclo [2.2.1] hept-2-ene, which is usually called norbornene, 6-alkylbicyclo [2.2.1] hept-2-ene, 5,6-dialkylbicyclo Such as [2.2.1] hept-2-ene, 1-alkylbicyclo [2.2.1] hept-2-ene, 7-alkylbicyclo [2.2.1] hept-2-ene, Tetracyclo [4.4.0.1 ^2,5 .Norbonene derivatives into which an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, or a butyl group is introduced, or dimethanooctahydronaphthalene. 1 ^7,10 ] -3-dodecene and 8-alkyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene, 8,9-dialkyltetracyclo [4.4.0.1 ^2,5 . ^{Dimethanooctahydronaphthalene} derivative in which an alkyl group having 3 or more carbon atoms is introduced into the 8-position and / or 9-position of dimethanooctahydronaphthalene, such as 1 ^7,10 ] -3-dodecene, Examples thereof include norbornene derivatives in which one or more halogens are introduced, and dimethanooctahydronaphthalene derivatives in which halogens are introduced at the 8th and / or 9th positions. These cyclic olefins may be used alone or in combination of two or more.

  Aromatic vinyl monomers include styrene and its derivatives. Styrene derivatives are compounds in which other groups are bonded to styrene, such as o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, o-ethylstyrene, p-ethyl. Alkyl styrene such as styrene, hydroxy styrene, tert-butoxy styrene, vinyl benzoic acid, vinyl benzyl acetate, o-chloro styrene, p-chloro styrene, benzene nucleus of styrene with hydroxyl group, alkoxy group, carboxyl group, Substituted styrene having an acyloxy group and halogen introduced therein, vinylbiphenyl compounds such as 4-vinylbiphenyl and 4-hydroxy-4'-vinylbiphenyl, and vinyls such as 1-vinylnaphthalene and 2-vinylnaphthalene And naphthalene compounds.

  Regarding the amount of each monomer, when the amount of the aromatic vinyl monomer is too small, it is not preferable because it has positive intrinsic birefringence, and conversely, when the amount is too large, the photoelastic coefficient is Is unfavorable because of the increase. Further, when the amount of the cyclic olefin monomer is too small, the glass transition temperature is low, which is not preferable. On the other hand, when the amount is too large, the copolymer becomes brittle, which is also not preferable. Therefore, it is suitable to copolymerize the aromatic vinyl monomer at a ratio of about 5 to 50 mol% and the total of the acyclic olefin monomer and the cyclic olefin monomer to be about 50 to 95 mol%. A terpolymer having such a copolymerization ratio is particularly advantageous from the viewpoint of the heat resistance of the retardation plate.

More specifically, for example, the acyclic olefin monomer is ethylene, the aromatic vinyl monomer is styrene, and the cyclic olefin monomer is tetracyclo [4.4.0.1 ^2,5 . In the ternary copolymer composed of ^1,7,10 ] -3-dodecene, 15 to 25 mol% of styrene and tetracyclo [4.4.0.1 ^2,5 . It is particularly preferable that the content of 1 ^7,10 ] -3-dodecene is 25 to 35 mol%, since the resin exhibits negative birefringence, a high glass transition temperature, and a low photoelasticity.

  In addition, in consideration of the high glass transition temperature and low photoelasticity, another preferred polymer having negative intrinsic birefringence includes a copolymer containing an α-olefin unit and an N-phenylmaleimide unit. It is done. Specifically, this copolymer can have units of the following formulas (I) and (II).

In formula (I), R ₁ , R ₂ and R ₃ each independently represent hydrogen or an alkyl group having 1 to 6 carbon atoms;
In the formula (II), R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ and R ₁₀ each independently represent hydrogen, halogen, a carboxyl group or an alkyl group having 1 to 8 carbon atoms.

Formula (I) represents an α-olefin unit, and R ₁ , R ₂ and R ₃ appearing therein are each independently hydrogen or an alkyl group having 1 to 6 carbon atoms. When any of R _{1 to} R ₃ is an alkyl group, the alkyl group may be linear, and when it has 3 or more carbon atoms, isopropyl, isobutyl, sec-butyl, tert-butyl, etc. It may be branched. Among the α-olefins that give the unit of formula (I), those having 4 or more carbon atoms and R ₂ and R ₃ being an alkyl group are preferred.

Formula (II) represents an N-phenylmaleimide unit, and R ₄ , R ₅ , R ₆ , R ₇ and R ₈ appearing on the benzene ring are each independently hydrogen, halogen, a carboxyl group (—COOH) or It is a C1-C8 alkyl group. When any of these is halogen, examples of the halogen include fluorine, chlorine, bromine and iodine. When any of R _{4 to} R ₈ is an alkyl group, the carbon number thereof is 1 to 8, which may be linear, and when it has 3 or more carbon atoms, isopropyl, isobutyl, sec-butyl , Tert-butyl and the like may be branched. Of the groups R ₄ , R ₅ , R ₆ , R ₇ and R ₈ on the benzene ring, at least one of them is preferably a group other than hydrogen, especially one or two are alkyl groups and the rest Is preferably hydrogen. In particular, it is preferable that R ₄ located at the 2-position and / or R ₈ located at the 6-position is an alkyl group.

In the formula (II), R ₉ and R ₁₀ appearing on the carbon atom of maleimide are each independently hydrogen, halogen, a carboxyl group (—COOH 3) or an alkyl group having 1 to 8 carbon atoms. The same explanation as described above applies to the halogen and alkyl groups in this case. These R ₉ and R ₁₀ appearing on the carbon atom of the maleimide are generally advantageously hydrogen, but on the other hand, it is also effective to use a polar halogen or carboxyl group.

  Examples of the compound giving an α-olefin unit of the formula (I) include isobutene, 2-methyl-1-butene, 2-methyl-1-pentene, 2-methyl-1-hexene, 2-methyl-1-heptene. 2-methyl-1-octene, 2-ethyl-1-pentene, 2-methyl-2-butene, 2-methyl-2-pentene, 2-methyl-2-hexene, ethylene, propylene, 1-butene, 2 -Butene, 1-hexene and the like. These can be used alone or in combination of two or more for polymerization.

  Examples of the compound giving an N-phenylmaleimide unit of the formula (II) include N-phenylmaleimide, N- (2-methylphenyl) maleimide, N- (2-ethylphenyl) maleimide, N- (2-isopropylphenyl) ) Maleimide, N- (3-methylphenyl) maleimide, N- (3-ethylphenyl) maleimide, N- (4-methylphenyl) maleimide, N- (4-ethylphenyl) maleimide, N- (2,6- Dimethylphenyl) maleimide, N- (2,6-diethylphenyl) maleimide, N- (2,6-diisopropylphenyl) maleimide, N- (2,4,6-trimethylphenyl) maleimide, N- (2-, 3 -Or 4-carboxyphenyl) maleimide, N- (2,4-dimethylphenyl) maleimide and the like. . These can also be used for polymerization individually or in combination of two or more.

  As described above, the compound that gives the α-olefin unit of the formula (I) and the compound that gives the N-phenylmaleimide unit of the formula (II) are polymerized by a known method, thereby producing light in a negative uniaxial manner. An α-olefin / N-phenylmaleimide copolymer used for a retardation plate having an axis in the in-plane direction can be produced. At this time, if desired, other vinyl monomers can be copolymerized in a small amount within a range not damaging negative uniaxiality, heat resistance and photoelasticity. Examples of other vinyl monomers include styrene, α-methylstyrene, and vinyl toluene.

  The amount of each monomer in the α-olefin / N-phenylmaleimide copolymer will be described. When the amount of N-phenylmaleimide is too small, positive intrinsic birefringence is exhibited and the glass transition temperature is low. On the other hand, if the amount is too large, the photoelastic coefficient is increased and the copolymer becomes brittle. Therefore, a copolymer obtained by copolymerization in such a proportion that the α-olefin unit is about 50 to 95 mol% and the N-phenylmaleimide unit is about 5 to 50 mol% is suitable. In order to prevent the glass transition temperature from being lowered, N-alkylmaleimide may be used as a monomer to the extent that the optical properties of the polymer are not impaired.

  A retardation plate can be obtained by forming a polymer as described above into a film and stretching it by an appropriate method. In order to obtain a retardation plate with small variations in retardation, it is important to use an optically uniform film for stretching. There are various known methods for forming a film, such as a melt extrusion method, a solvent casting method, and an inflation method. However, the film thickness variation is small, the retardation is small, and an optically isotropic film is obtained. Any method can be applied as long as it is.

  The film thus obtained can be subjected to an orientation treatment by a known stretching method to give a uniform retardation. As the stretching method, a uniaxial or biaxial thermal stretching method can be employed. When optical uniaxiality is important, free end longitudinal uniaxial stretching can be cited as a preferred stretching method.

  The retardation plate thus obtained exhibits negative uniaxiality and can be preferably used for compensation of viewing angle characteristics of a liquid crystal display device using the IPS liquid crystal operation mode.

  When producing a phase difference plate having an optical axis in the in-plane direction and exhibiting negative uniaxiality, a stretched film obtained by adopting a method in which a polymer having negative intrinsic birefringence is subjected to free end longitudinal uniaxial stretching ( In the retardation plate), the stretching direction is the fast axis, and the direction orthogonal thereto is the slow axis. On the other hand, in the polarizing plate, the stretching direction is the absorption axis, and the direction orthogonal thereto is the transmission axis. Then, if the retardation plate and polarizing plate obtained in this way are bonded by a roll-to-roll, a composite polarizing plate in which the slow axis of the retardation plate and the absorption axis of the polarizing plate are orthogonal is obtained. As a result, the number of manufacturing steps is reduced, and the target composite polarizing plate can be efficiently manufactured.

  Next, a mode in which a layer of a liquid crystalline discotic compound exhibiting negative uniaxiality is formed to form a retardation plate having negative uniaxiality and an optical axis in-plane will be described. A liquid crystal discotic compound is a compound that exhibits liquid crystallinity and has a discotic molecular structure. In such a state that such a compound is melted or dissolved in an appropriate solvent, it is applied onto a transparent plastic film so that the disk surface is in a predetermined direction parallel to the film surface. By aligning the disk surface upright on the film surface so that the disk surface is in a predetermined orientation and solidifying while maintaining the orientation, or removing the solvent, the resulting liquid crystal discotic compound layer is negative. Uniaxiality is exhibited, and the optical axis (fast axis) is in the plane. A retardation film having a refractive index ellipsoidal structure as shown in FIG. 2 can also be manufactured by such a method. In order to align the liquid crystalline discotic compound, a general method such as use of an alignment film, rubbing, addition of a chiral dopant, or light irradiation can be used. Further, after aligning the liquid crystalline discotic compound, it is possible to cure the liquid crystalline compound in order to fix the alignment.

As described above, by uniaxial stretching of a polymer having negative intrinsic birefringence or by aligning a disc of a liquid crystalline discotic compound exhibiting negative uniaxiality so as to stand upright on the substrate film, the above formula (3 A phase difference plate having a substantially zero Nz coefficient can be produced, but at the time of stretching, for example, fixed-end longitudinal uniaxial stretching or tenter lateral uniaxial stretching should be used to give some biaxiality. _{in, n z> n x> n} y next, Nz coefficient in the case a negative retardation film (Nz = -0.5~0) obtained. That is, a negative uniaxial retardation plate having an Nz coefficient in the range of −0.5 to 0 can be produced, for example, by uniaxially stretching a polymer having negative intrinsic birefringence. The polymer having a negative intrinsic birefringence has an acyclic olefin monomer selected from ethylene and an α-olefin compound having 3 to 20 carbon atoms, a cyclic olefin monomer selected from a cyclic olefin compound, and an aromatic hydrocarbon ring. A copolymer obtained by polymerizing an aromatic vinyl monomer selected from vinyl compounds at a ratio of 5 to 50 mol% of the aromatic vinyl monomer and 50 to 95 mol% of the total of the acyclic olefin monomer and the cyclic olefin monomer. Is preferable from the viewpoint of the heat resistance of the retardation plate.

On the other hand, by processing a polymer having positive intrinsic birefringence according to the method described in Patent Document 1, _nx > _nz > ny is _satisfied , and in this case, the Nz coefficient is 0 to +0.9. A thickness-oriented retardation plate is obtained. Of these, in order to obtain a retardation plate that can be employed in the present invention, the Nz coefficient may be set to 0 to +0.5. That is, a thickness-oriented retardation plate having an Nz coefficient in the range of 0 to +0.5 is uniaxially stretched with a polymer having positive intrinsic birefringence in accordance with the method described in Patent Document 1 described above. It can be produced by heat shrinking in a predetermined form.

  As shown in FIG. 1, the set of polarizing plates according to the present invention includes a composite polarizing plate 40 including a first polarizing plate 10 and a retardation plate 30 disposed on one side thereof, and a second polarizing plate 20. In combination, they are bonded to the front and back of the liquid crystal cell. About each optical characteristic, the explanation so far is applied. The composite polarizing plate 40 is arranged on one side of the IPS mode liquid crystal cell so that the phase difference plate 30 side faces the liquid crystal cell, and the second polarizing plate 20 is arranged in the thickness direction on the other side of the liquid crystal cell. If the transparent protective layer 22 having the phase difference Rth in the range of −10 nm to +40 nm is disposed so as to face the liquid crystal cell, an IPS mode liquid crystal display device with improved viewing angle characteristics can be obtained.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples.

Comparative Example 1
A linear polarizing plate “SRW842A” (manufactured by Sumitomo Chemical Co., Ltd.) was prepared, in which a transparent protective film made of triacetylcellulose was bonded to both sides of a polarizer in which iodine was adsorbed and oriented on polyvinyl alcohol. In this linear polarizing plate, Rth on one side of the transparent protective layer is 55 nm, R ₀ is 1 nm, and the slow axis of the transparent protective layer is arranged parallel to the absorption axis of the polyvinyl alcohol-iodine polarizer. An IPS mode liquid crystal cell ("WOOO 3000" manufactured by Hitachi, Ltd.) has only the above-described linear polarizing plate "SRW842A" on both sides, and a liquid crystal display device having no retardation plate is manufactured. did. At this time, on the front side (viewing side), the absorption axis of the linear polarizing plate is arranged so as to be orthogonal to the major axis direction (alignment direction) of the liquid crystal molecules when no voltage is applied, and the front side linear polarizing plate and the back side straight line are arranged. The polarizing plate was arrange | positioned so that each absorption axis might orthogonally cross. The layer configuration and the axial relationship of the liquid crystal display device manufactured here are as shown in FIG. 3 is the same as that in FIG. 1, and FIG. 3 is that the retardation plate 30 is not disposed and that the major axis direction 55 of the liquid crystal molecules is fixed in the direction of the white arrow. It is only different from FIG. When the backlight was turned on from the back side of the liquid crystal display device and the color shift and the luminance change depending on the viewing angle were visually observed, the luminance change due to the viewing angle was large and the viewing angle dependency was high.

Example 1
(A) Preparation of composite polarizing plate A straight line in which transparent protective films (one Rth is 65 nm, _R0 is 1 nm) bonded to both sides of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol. A polarizing plate was prepared. On one side of the protective film, a retardation film having a negative intrinsic birefringence and having a free intrinsic vertical refraction of polystyrene having a R ₀ of 140 nm and an Nz coefficient of 0.0 is disposed on the absorption axis of the linear polarizing plate. Were bonded via a polyvinyl alcohol-based adhesive so that the slow axes of the retardation plates were orthogonal to each other to obtain a composite polarizing plate.

(B) Production and Evaluation of Liquid Crystal Display Device The composite polarizing plate produced in (a) above was placed on the front side (viewing side) of the same IPS mode liquid crystal cell “WOOO 3000” used in Comparative Example 1 on the cell substrate side. Laminated with an acrylic pressure-sensitive adhesive in order from the phase difference plate to the linear polarizing plate, and only the iodine linear polarizing plate on the back side (backlight side), again acrylic pressure-sensitive adhesive Laminated. The linear polarizing plate used on the back side is a non-oriented protective film made of norbornene-based resin on one side of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol ("ZEONOR" manufactured by Optes, Rth is 4 nm). Is bonded with a protective film made of triacetyl cellulose on the other side, and on the protective film side made of norbornene resin, it is attached to the cell substrate via an acrylic pressure sensitive adhesive. Pasted together. At this time, on the front side, the retardation plate was arranged so that the slow axis of the retardation plate was parallel to the major axis direction (alignment direction) of the liquid crystal molecules when no voltage was applied. Further, the front-side linear polarizing plate and the back-side linear polarizing plate were arranged so that their absorption axes were orthogonal to each other. The layer configuration and the axial relationship of the liquid crystal display device manufactured here are as shown in FIG. 4 has the same meaning as in FIG. 1, and FIG. 4 is different from FIG. 1 only in that the major axis direction 55 of the liquid crystal molecules is fixed in the direction of the solid line arrow. When the backlight was turned on from the back side of the liquid crystal display device and the color shift and the luminance change depending on the viewing angle were visually observed, it was confirmed that both the color shift and the luminance change were small as compared with Comparative Example 1.

Example 2
Evaluation was performed in the same manner as in Example 1 except that the retardation plate was changed to a free-end longitudinally uniaxially stretched polystyrene film having R ₀ of 130 nm and an Nz coefficient of 0.0. As a result, it was confirmed that there was little color shift and luminance change depending on the viewing angle, and it was almost the same level as in Example 1.

Example 3
Evaluation was performed in the same manner as in Example 1 except that the back side polarizing plate was changed to “SRW042A” (Rth of the transparent protective layer on one side was 34 nm) manufactured by Sumitomo Chemical Co., Ltd. As a result, it was confirmed that both the color shift and the luminance change depending on the viewing angle were small.

Example 4
Linearly polarized light manufactured by Sumitomo Chemical Co., Ltd., in which transparent protective films (one Rth is 110 nm, _R0 is 7 nm) bonded to both sides of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol. One side of the protective film of the plate “SR2042A” is a free-end longitudinally uniaxially stretched film of polystyrene having negative intrinsic birefringence, and a retardation plate having an R ₀ of 160 nm is connected to the absorption axis of the linearly polarizing plate. The plate was bonded via a polyvinyl alcohol-based adhesive so that the slow axes of the plates were orthogonal to form a composite polarizing plate. Evaluation was performed in the same manner as in Example 1 except that the composite polarizing plate disposed on the front side of the liquid crystal cell was changed to the one prepared here. As a result, it was confirmed that both the color shift and the luminance change depending on the viewing angle were small.

Example 5
Ethylene, styrene and tetracyclo [4.4.0.1 ^2,5 . A copolymer having a molar ratio of 1 ^{7, 10} ] -3-dodecene and a molar ratio of 50:20:30 (abbreviated as ESD) was formed into a film having a thickness of 100 μm by press molding. This film was uniaxially stretched by an autograph to produce a retardation plate exhibiting negative birefringence, a plane retardation R ₀ of 140 nm, and an Nz coefficient of 0.0. A composite polarizing plate was produced in the same manner as in Example 1 except that this retardation plate was used instead of the uniaxially stretched polystyrene film, and a liquid crystal display device was further produced. When this liquid crystal display device was evaluated by the same method as in Example 1, the same result as in Example 1 was obtained, and it was confirmed that there was little luminance change and color shift in both the front direction and the oblique direction.

Comparative Example 2
The retardation plate “SEZ270135” manufactured by Sumitomo Chemical Co., Ltd. is made of polycarbonate and has a thickness orientation, R ₀ is 135 nm, Rth is −41 nm, and the Nz coefficient is 0.2. On the one protective film side of the same linear polarizing plate “SRW842A” as used in Comparative Example 1 (Rth on one side of the transparent protective layer is 55 nm, _R0 is 1 nm), the above thickness-oriented retardation plate “SEZ270135” is placed. The composite polarizing plate was prepared by pasting with an acrylic pressure-sensitive adhesive so that the absorption axis of the linear polarizing plate and the slow axis of the retardation plate were orthogonal to each other. This composite polarizing plate is arranged on the front side (viewing side) of the liquid crystal cell, and the same linear polarizing plate “SRW842A” (Rth on one side of the transparent protective layer is 55 nm) used in Comparative Example 1 is provided on the back side of the liquid crystal cell. A liquid crystal display device was produced in the same manner as in Example 1 except for the arrangement. When this liquid crystal display device was evaluated by the same method as in Example 1, there was little change in luminance depending on the viewing angle, but the color shift was significant compared to Comparative Example 1.

  The main conditions and the results obtained in the above Comparative Example 1, Examples 1 to 5 and Comparative Example 2 are summarized in Table 1.

[Table 1]
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Comparative Example Example Comparative Example
1 1 2 3 4 5 2
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Front side Polarizer Cell side protective layer Rth 55 nm 65 nm 65 nm 65 nm 110 nm 65 nm 55 nm
Cell side protective layer R ₀ 1 nm 1 nm 1 nm 1 nm 7 nm 1 nm 1 nm
Phase plate Material ^{* 1} None PS PS PS PS PS ESD PC
Rth − −70 nm −65 nm −70 nm −80 nm −70 nm −41 nm
R ₀ − 140 nm 130 nm 140 nm 160 nm 140 nm 135 nm
Nz coefficient − 0.0 0.0 0.0 0.0 0.0 0.2
Cell side protective layer and retardation plate Sum of Rth 55 nm -5 nm 0 nm -5 nm 30 nm -5 nm 14 nm
Sum of R ₀ 1 nm 141 nm 131 nm 141 nm 167 nm 141 nm 136 nm
───────────────────────────────────────
Back side polarizing plate Cell side protective layer Rth 55 nm 4 nm 4 nm 34 nm 4 nm 4 nm 55 nm
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Light leakage ^{* 2} × ◎ ◎ ○ ○ ◎ △
───────────────────────────────────────
Color shift ^{* 3} △ ◎ ◎ ◎ ◎ ◎ ×
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
^{* 1} Material PS: Polystyrene.
ESD: ethylene, styrene, and tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] −
A terpolymer having a molar ratio of 3-dodecene of 50:20:30.
PC: Polycarbonate.
^{* 2} Light leakage ◎: Good.
○: Slight light leakage in an oblique direction is observed, but almost good.
Δ: Light leaks in an oblique direction.
X: Large amount of light leaks in an oblique direction
^{* 3} color shift A: Good.
Δ: There is a color shift in an oblique direction.
X: Large color shift in an oblique direction.

Comparative Example 3
(A) Preparation of composite polarizing plate A straight line in which transparent protective films (one Rth is 52 nm and _R0 is 1 nm) are bonded to both sides of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol. A polarizing plate was prepared. On one side of the protective film, a polycarbonate thickness-thick retardation plate having R ₀ of 135 nm, Rth of −27 nm and Nz coefficient of 0.3 is used. These were laminated via an acrylic pressure-sensitive adhesive so that their slow axes were orthogonal to each other to obtain a composite polarizing plate.

(B) Production and Evaluation of Liquid Crystal Display Device The composite polarizing plate produced in (a) above was placed on the front side (viewing side) of an IPS mode liquid crystal cell [“WOOO 5000” manufactured by Hitachi, Ltd.] on the cell substrate side. Are laminated via an acrylic pressure-sensitive adhesive so as to be in the order of a retardation plate and a linear polarizing plate, and on the back (backlight side), the linear polarizing plate before pasting the retardation plate in (a) above Only (with a transparent protective film having Rth of 52 nm and _R0 of 1 nm on both sides) was laminated with an acrylic pressure-sensitive adhesive. On the front side, the retardation plate was arranged so that the slow axis of the retardation plate was parallel to the major axis direction (alignment direction) when no voltage was applied to the liquid crystal molecules in the liquid crystal cell. Further, the front-side linear polarizing plate and the back-side linear polarizing plate were arranged so that their absorption axes were orthogonal to each other. The layer configuration and the axial relationship of the liquid crystal display device manufactured here are as shown in FIG. The backlight was turned on from the back side of this liquid crystal display device, and the contrast change and color shift depending on the viewing angle were measured with an ELDIM liquid crystal viewing angle / chromaticity characteristic measuring device “EZ Contrast”.

  FIG. 5 shows an isocontrast curve at this time. In this isocontrast curve, the right direction of the screen is 0 °, the counterclockwise direction is positive, and the azimuth angle is displayed (numbers are displayed every 45 ° from 0 ° to 315 °). “10”, “20”..., “70” means an inclination angle (elevation angle) from the normal line at each azimuth angle. For example, the right end of the circle means the contrast in the direction with the azimuth angle of 0 ° (right side of the screen) and the elevation angle of 80 °, and the center of the circle means the elevation angle of 0 °, that is, the contrast in the normal direction of the screen. . “CR = 200” is displayed on the curve having the contrast of 200, and the contrast curves of the contrast 400, 600, and 800 are sequentially formed toward the inner side. Since the figure showing the isocontrast curve shown below has the same meaning, detailed description will be omitted when the figure of the isocontrast curve comes out below. Here, the contrast is the ratio of the luminance at the time of white display (voltage application to the liquid crystal cell) to the luminance at the time of black display (no voltage application to the liquid crystal cell).

  FIG. 6 is an x, y chromaticity diagram according to the viewing angle measured in this example. The outer closed curve is a monochromatic light locus representing the stimulus value of monochromatic light. The largest point of x at the right end is the wavelength of 780 nm, the largest point of y is near the wavelength of 520 nm, and the smallest point of y is the lower left. This corresponds to a wavelength of 380 nm. The vicinity of (x = 0.33, y = 0.33) corresponds to white, and generally the lower right side in the outer closed curve corresponds to red, the upper side corresponds to green, and the lower left side corresponds to blue. The inner closed curve is the actual measurement data, and the elevation angle is fixed at 60 °, and the chromaticity when the azimuth is rotated sequentially from 0 ° to 360 ° during black display (no voltage applied to the liquid crystal cell) It represents a locus, and the smaller the area of this closed curve, the smaller the color shift due to the viewing angle. Since the x and y chromaticity diagrams shown below have the same meaning, the detailed description will be omitted when the x and y chromaticity diagrams appear below.

  5 and 6, the liquid crystal display device of Comparative Example 3 has a particularly large color shift depending on the viewing angle.

Example 6
(A) Preparation of composite polarizing plate A straight line in which transparent protective films (one Rth is 65 nm, _R0 is 1 nm) bonded to both sides of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol. A polarizing plate was prepared. On one side of the protective film, a retardation film having a negative intrinsic birefringence and having a free intrinsic vertical refraction of polystyrene having a R ₀ of 140 nm and an Nz coefficient of 0.0 is disposed on the absorption axis of the linear polarizing plate. Were bonded via a polyvinyl alcohol-based adhesive so that the slow axes of the retardation plates were orthogonal to each other to obtain a composite polarizing plate.

(B) Production and Evaluation of Liquid Crystal Display Device The composite polarizing plate produced in (a) above was placed on the front side (viewing side) of the same IPS mode liquid crystal cell “WOOO 5000” used in Comparative Example 3 on the cell substrate side. Laminated with an acrylic pressure-sensitive adhesive in order from the phase difference plate to the linear polarizing plate, and only the iodine linear polarizing plate on the back side (backlight side), again acrylic pressure-sensitive adhesive Laminated. The linear polarizing plate used on the back side is a non-oriented protective film made of norbornene-based resin on one side of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol ("ZEONOR" manufactured by Optes, Rth is 4 nm). Was bonded to the cell substrate, and the protective film made of triacetylcellulose was bonded to the other surface, and was bonded to the cell substrate on the protective film side made of the norbornene resin. On the front side, the retardation plate was arranged so that the slow axis of the retardation plate was parallel to the major axis direction (alignment direction) when no voltage was applied to the liquid crystal molecules in the liquid crystal cell. Further, the front-side linear polarizing plate and the back-side linear polarizing plate were arranged so that their absorption axes were orthogonal to each other. The layer configuration and the axial relationship of the liquid crystal display device manufactured here are the same as those in FIG. The backlight was turned on from the back side of the liquid crystal display device, and the contrast change and color shift depending on the viewing angle were measured with “EZ Contrast” manufactured by ELDIM as in Comparative Example 3. An isocontrast curve is shown in FIG. 7, and an x, y chromaticity diagram is shown in FIG. In the liquid crystal display device manufactured in this example, the isocontrast curve spreads to the wide viewing angle side and the color shift due to the viewing angle is smaller than that in Comparative Example 3.

Example 7
Evaluation was performed in the same manner as in Example 6 except that the back side polarizing plate was changed to “SRW042A” (Rth of the transparent protective layer on one side was 34 nm) manufactured by Sumitomo Chemical Co., Ltd. An isocontrast curve is shown in FIG. 9, and an x, y chromaticity diagram is shown in FIG. The liquid crystal display device produced in this example also had good contrast viewing angle and color shift due to viewing angle.

  With respect to the above Comparative Example 3 and Examples 6 and 7, the inclination angle (elevation angle) at which the contrast 200 was obtained was read from the isocontrast curve at every azimuth angle of 45 °, and the results are shown in Table 2. As compared with the comparative example, it can be seen that the viewing angles in the azimuth angle 45 ° -225 ° direction and the 135 ° -315 ° direction are broadened.

[Table 2]
Tilt angle at which contrast 200 can be obtained ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Azimuth 0 ° 45 ° 90 ° 135 ° 180 ° 225 ° 270 ° 315 °
Right upper right upper left upper left lower left lower right lower
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Comparative Example 3 79 ° 44 ° 78 ° 41 °> 80 ° 66 °> 80 ° 68 °
────────────────────────────────────
Example 6> 80 ° 50 ° 75 ° 47 °> 80 °> 80 °> 80 °> 80 °
Example 7> 80 ° 47 ° 76 ° 41 °> 80 ° 73 °> 80 ° 77 °
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Table 3 summarizes the main conditions and the results obtained in Comparative Example 3 and Examples 6 and 7.

[Table 3]
━━━━━━━━━━━━━━━━━━━━━━━━
Comparison example
3 6 7
━━━━━━━━━━━━━━━━━━━━━━━━
Front side Polarizer Cell side protective layer Rth 52 nm 65 nm 65 nm
Cell side protective layer R ₀ 1 nm 1 nm 1 nm
Retardation plate material ^{* 1} PC PS PS
Rth -27 nm -70 nm -70 nm
R ₀ 135 nm 140 nm 140 nm
Nz coefficient 0.3 0.0 0.0
Cell side protective layer and retardation plate Sum of Rth 25 nm -5 nm -5 nm
Sum of R ₀ 136 nm 141 nm 141 nm
────────────────────────
Back side polarizer Cell side protective layer Rth 52 nm 4 nm 34 nm
━━━━━━━━━━━━━━━━━━━━━━━━
Contrast ^{* 2} ◎ ◎ ◎
────────────────────────
Color shift ^{* 3} × ◎ ◎
━━━━━━━━━━━━━━━━━━━━━━━━
^{* 1} Material PS: Polystyrene.
PC: Polycarbonate.
^{* 2} Contrast A: Good.
^{* 3} color shift A: Good.
X: Large color shift in an oblique direction.

Comparative Example 4
(A) Preparation of composite polarizing plate A straight line in which transparent protective films (one Rth is 65 nm, _R0 is 1 nm) bonded to both sides of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol. A polarizing plate was prepared. On one side of the protective film, a retardation film having a negative intrinsic birefringence and having a free intrinsic vertical refraction of polystyrene having a R ₀ of 140 nm and an Nz coefficient of 0.0 is disposed on the absorption axis of the linear polarizing plate. Were bonded via a polyvinyl alcohol-based adhesive so that the slow axes of the retardation plates were orthogonal to each other to obtain a composite polarizing plate.

(B) Fabrication and evaluation of liquid crystal display device IPS mode liquid crystal cell ["WOOO 7000" manufactured by Hitachi, Ltd.] is laminated on the front surface (viewing side) only with an acrylic pressure-sensitive adhesive. On the back (backlight) side, the composite polarizing plate produced in the above (a) is also passed through an acrylic pressure-sensitive adhesive so that the retardation plate and the linear polarizing plate are arranged in this order from the cell substrate side. And laminated. The linear polarizing plate used on the front side is obtained by bonding protective films made of triacetyl cellulose (one Rth is 51 nm) on both sides of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol. The rear retardation plate was arranged so that its slow axis was parallel to the major axis direction (alignment direction) of the liquid crystal molecules when no voltage was applied. Further, the front-side linear polarizing plate and the back-side linear polarizing plate were arranged so that their absorption axes were orthogonal to each other. The layer configuration and the axial relationship of the liquid crystal display device manufactured here are as shown in FIG. 11 has the same meaning as in FIG. 1, and FIG. 11 shows that the upper and lower sides are inverted and the major axis direction 55 of the liquid crystal molecules is fixed in the direction of the white solid arrow. It is only different from. The backlight was turned on from the back of the liquid crystal display device, and the contrast change and color shift depending on the viewing angle were measured with the liquid crystal viewing angle / chromaticity characteristic measuring device “EZ Contrast” manufactured by ELDIM as in Comparative Example 3. . An isocontrast curve is shown in FIG. 12, and an x, y chromaticity diagram according to the viewing angle is shown in FIG. Neither contrast change nor color shift due to viewing angle was sufficient.

Comparative Example 5
(A) Preparation of composite polarizing plate A straight line in which transparent protective films (one Rth is 51 nm, _R0 is 1 nm) bonded to both sides of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol. A polarizing plate was prepared. On one side of the protective film, a polycarbonate thickness-thick retardation plate having R ₀ of 180 nm, Rth of −36 nm and Nz coefficient of 0.3 is used. These were laminated via an acrylic pressure-sensitive adhesive so that their slow axes were orthogonal to each other to obtain a composite polarizing plate.

(B) Production and Evaluation of Liquid Crystal Display Device The same IPS mode liquid crystal cell “WOOO 7000” used in Comparative Example 4 was laminated on the front surface (viewing side) only with a linear polarizing plate via an acrylic pressure-sensitive adhesive. On the back surface (backlight side), the composite polarizing plate produced in the above (a) is also passed through an acrylic pressure-sensitive adhesive so that the retardation plate and the linear polarizing plate are arranged in this order from the cell substrate side. And laminated. The linear polarizing plate used on the front side is obtained by bonding protective films made of triacetyl cellulose (one Rth is 51 nm) on both sides of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol. The rear retardation plate was arranged so that its slow axis was parallel to the major axis direction (alignment direction) of the liquid crystal molecules when no voltage was applied. Further, the front-side linear polarizing plate and the back-side linear polarizing plate were arranged so that their absorption axes were orthogonal to each other. The layer configuration and axial relationship of the liquid crystal display device manufactured here are also as shown in FIG. The backlight was turned on from the back side of the liquid crystal display device, and the contrast change and the color shift depending on the viewing angle were measured by “EZ Contrast” manufactured by ELDIM as in Comparative Example 4. FIG. 14 shows an isocontrast curve, and FIG. 15 shows an x, y chromaticity diagram according to the viewing angle. The color shift shown in FIG. 15 was a good result, but the contrast change due to the viewing angle shown in FIG. 14 was not sufficient.

Example 8
The same IPS mode liquid crystal cell “WOOO 7000” used in Comparative Example 4 was laminated on the front side (viewing side) only with a linear polarizing plate via an acrylic pressure-sensitive adhesive, and on the back side (backlight side). The composite polarizing plate produced in the same manner as in (a) of Comparative Example 4 was laminated with an acrylic pressure-sensitive adhesive again in the order of the retardation plate and the linear polarizing plate from the cell substrate side. The linear polarizing plate used on the front side is a non-oriented protective film made of norbornene resin on one side of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol ["ZEONOR" manufactured by Optes Co., Ltd.,
Rth is 4 nm], and a protective film made of triacetylcellulose is attached to the other surface, and the protective film made of norbornene resin was attached to the cell substrate. The rear retardation plate was arranged so that its slow axis was parallel to the major axis direction (alignment direction) of the liquid crystal molecules when no voltage was applied. Further, the front-side linear polarizing plate and the back-side linear polarizing plate were arranged so that their absorption axes were orthogonal to each other. The layer configuration and axial relationship of the liquid crystal display device manufactured here are also as shown in FIG. The backlight was turned on from the back side of the liquid crystal display device, and the contrast change and color shift depending on the viewing angle were measured by “EZ Contrast” manufactured by ELDIM as in Comparative Example 4. FIG. 16 shows an isocontrast curve, and FIG. 17 shows an x, y chromaticity diagram according to viewing angles. Compared to Comparative Example 4, the isocontrast curve with a contrast of 200 was widened, and the color shift was small.

Example 9
(A) Preparation of composite polarizing plate Sumitomo, in which transparent protective films (one Rth is 96 nm, _R0 is 7 nm) bonded to both sides of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol A linear polarizing plate “SR2042A” manufactured by Chemical Co., Ltd. was prepared. On one side of the protective film, a polystyrene fixed-end lateral uniaxially stretched film having negative intrinsic birefringence, having a R ₀ of 140 nm, an Rth of −92 nm, and an Nz coefficient of −0.2, The composite polarizing plate was obtained by pasting via an acrylic pressure-sensitive adhesive so that the absorption axis of the linear polarizing plate and the slow axis of the retardation plate were orthogonal to each other.

(B) Production and Evaluation of Liquid Crystal Display Device Evaluation was performed in the same manner as in Example 8 except that the composite polarizing plate on the back side was changed to that produced in (a) above. FIG. 18 shows an isocontrast curve, and FIG. 19 shows an x, y chromaticity diagram according to viewing angles. Also in this example, the contrast change and the color shift depending on the viewing angle were good.

Example 10
(A) Preparation of composite polarizing plate A straight line in which transparent protective films (one Rth is 51 nm, _R0 is 1 nm) bonded to both sides of a polarizer in which iodine is adsorbed and oriented on polyvinyl alcohol. A polarizing plate was prepared. On one side of the protective film, a polycarbonate thickness-thick retardation plate having R ₀ of 180 nm, Rth of −36 nm and Nz coefficient of 0.3 is used. These were laminated via an acrylic pressure-sensitive adhesive so that their slow axes were orthogonal to each other to obtain a composite polarizing plate.

(B) Production and Evaluation of Liquid Crystal Display Device Evaluation was performed in the same manner as in Example 8 except that the composite polarizing plate on the back side was changed to that produced in (a) above. An isocontrast curve is shown in FIG. 20, and an x, y chromaticity diagram according to the viewing angle is shown in FIG. Compared with Comparative Example 5, the isocontrast curve with a contrast of 200 was greatly expanded.

  For the above Comparative Examples 4 and 5 and Examples 8 to 10, the inclination angle (elevation angle) at which the contrast 200 was obtained from the isocontrast curve was read every 45 ° azimuth, and the results are shown in Table 4. As compared with the comparative example, it can be seen that the viewing angles in the azimuth angle 45 ° -225 ° direction and the 135 ° -315 ° direction are broadened.

[Table 4]
Tilt angle at which contrast 200 can be obtained ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Azimuth 0 ° 45 ° 90 ° 135 ° 180 ° 225 ° 270 ° 315 °
Right upper right upper left upper left lower left lower right lower
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Comparative Example 4 78 ° 47 °> 80 ° 54 ° 75 ° 57 °> 80 ° 55 °
Comparative Example 5> 80 ° 47 ° 79 ° 48 ° 80 ° 48 °> 80 ° 55 °
────────────────────────────────────
Example 8> 80 ° 47 ° 78 ° 80 °> 80 °> 80 °> 80 ° 57 °
Example 9> 80 ° 47 ° 79 °> 80 °> 80 °> 80 °> 80 ° 67 °
Example 10> 80 ° 79 ° 78 ° 76 °> 80 ° 79 °> 80 °> 80 °
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  Table 5 summarizes the main conditions and the results obtained in Comparative Examples 4 and 5 and Examples 8 to 10 described above.

[Table 5]
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Comparative Example implementation example
4 5 8 9 10
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Front side Polarizing plate Cell side protective layer Rth 51 nm 51 nm 4 nm 4 nm 4 nm
Cell side protective layer R ₀ 1 nm 1 nm 0 nm 0 nm 0 nm
────────────────────────────────
Back side Polarizing plate Cell side protective layer Rth 65 nm 51 nm 65 nm 96 nm 51 nm
Cell side protective layer R ₀ 1 nm 1 nm 1 nm 7 nm 1 nm
Phase difference plate material ^{* 1} PS PC PS PS PC
Rth -70 nm -36 nm -70 nm -92 nm -36 nm
R ₀ 140 nm 180 nm 140 nm 140 nm 180 nm
Nz coefficient 0.0 0.3 0.0 -0.2 0.3
Cell side protective layer and retardation plate Sum of Rth -5 nm 15 nm -5 nm 4 nm 15 nm
Sum of R ₀ 141 nm 181 nm 141 nm 147 nm 181 nm
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Contrast ^{* 2} △ △ ◎ ◎ ◎
────────────────────────────────
Color shift ^{* 3} × ◎ ◎ ◎ ◎
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
^{* 1} Material PS: Polystyrene.
PC: Polycarbonate.
^{* 2} Contrast A: Good.
Δ: Light leaks in an oblique direction.
^{* 3} color shift A: Good.
X: Large color shift in an oblique direction.

An example of the liquid crystal display device concerning the present invention is shown, (A) is a longitudinal section mimetic diagram showing a layer composition roughly, and (B) is a perspective view for explaining an axial relation. a negative uniaxial retardation plate satisfying n _z ≒ n _x> n _y the relationship a perspective view showing a refractive index ellipsoid, (A) is taken slow axis of the refractive index ellipsoid in the lateral direction (B) is a state in which an axis (fast axis) orthogonal to the slow axis in the plane is taken in the lateral direction. It is the liquid crystal display device produced by the comparative example 1, Comprising: (A) is a longitudinal cross-sectional schematic diagram which shows a layer structure schematically, (B) is a perspective view for demonstrating an axial relationship. It is the liquid crystal display device produced in Examples 1-5, Comparative Example 2, Comparative Example 3, and Example 6 and 7, Comprising: (A) is a longitudinal cross-sectional schematic diagram which shows a layer structure schematically, (B) is an axis | shaft. It is a perspective view for demonstrating a relationship. It is a figure which shows the isocontrast curve of the liquid crystal display device produced in the comparative example 3. FIG. 14 is an x, y chromaticity diagram when the azimuth angle is changed at an elevation angle of 60 ° during black display for the liquid crystal display device manufactured in Comparative Example 3. FIG. 10 is a diagram showing isocontrast curves of the liquid crystal display device manufactured in Example 6. FIG. 10 is an x, y chromaticity diagram when the azimuth angle is changed at an elevation angle of 60 ° during black display for the liquid crystal display device manufactured in Example 6. FIG. 10 is a diagram showing isocontrast curves of a liquid crystal display device manufactured in Example 7. FIG. 14 is an x, y chromaticity diagram when the azimuth angle is changed at an elevation angle of 60 ° during black display for the liquid crystal display device fabricated in Example 7. It is the liquid crystal display device produced by Comparative Examples 4 and 5 and Examples 8-10, Comprising: (A) is a longitudinal cross-sectional schematic diagram which shows a layer structure schematically, (B) is a perspective view for demonstrating an axial relationship. It is. It is a figure which shows the isocontrast curve of the liquid crystal display device produced in the comparative example 4. It is an x, y chromaticity diagram when changing the azimuth at an elevation angle of 60 ° during black display for the liquid crystal display device manufactured in Comparative Example 4. It is a figure which shows the isocontrast curve of the liquid crystal display device produced in the comparative example 5. FIG. 14 is an x, y chromaticity diagram when the azimuth angle is changed at an elevation angle of 60 ° during black display for the liquid crystal display device manufactured in Comparative Example 5. FIG. 10 is a diagram showing isocontrast curves of the liquid crystal display device manufactured in Example 8. FIG. 14 is an x, y chromaticity diagram when the azimuth angle is changed at an elevation angle of 60 ° during black display for the liquid crystal display device fabricated in Example 8. FIG. 10 is a diagram showing isocontrast curves of the liquid crystal display device manufactured in Example 9. FIG. 14 is an x, y chromaticity diagram when the azimuth angle is changed at an elevation angle of 60 ° during black display for the liquid crystal display device manufactured in Example 9. FIG. 11 is a diagram showing isocontrast curves of the liquid crystal display device produced in Example 10. FIG. 16 is an x, y chromaticity diagram when the azimuth angle is changed at an elevation angle of 60 ° during black display for the liquid crystal display device fabricated in Example 10.

Explanation of symbols

10 …… First polarizing plate,
11 ... Polarizer,
12, 13 ... Transparent protective layer,
15: Absorption axis of the first polarizing plate,
20 …… Second polarizing plate,
21 …… Polarizer,
22, 23 ... Transparent protective layer,
25 …… The absorption axis of the second polarizing plate,
30 ... retardation plate,
35 …… Slow axis of retardation plate,
40 …… Composite polarizing plate,
50 …… IPS mode liquid crystal cell,
51, 52 ... Liquid crystal cell substrate,
53 …… Liquid crystal layer,
55: Long axis direction of liquid crystal molecules.

Claims (6)

A liquid crystal cell in which liquid crystal is sealed between a pair of transparent substrates parallel to each other, the liquid crystal is aligned in parallel and substantially in the same direction, and a first polarizing plate disposed with the liquid crystal cell interposed therebetween And a second polarizing plate, wherein the liquid crystal display is configured to change the orientation of the molecular major axis in a plane parallel to the substrate by changing the voltage applied to the liquid crystal cell. A device,
Birefringence including at least one retardation plate between the first polarizing plate and the liquid crystal cell and including the retardation plate existing from the polarizer constituting the first polarizing plate to the retardation plate The sum of the thickness direction retardation Rth of the layers is in the range of −40 nm to +40 nm, and the sum of the plane retardations R ₀ is in the range of 100 nm to 200 nm, and the second polarizing plate is formed on both sides of the polarizer. A transparent protective layer is provided, and the thickness direction retardation Rth of the transparent protective layer located on the liquid crystal cell side of the polarizer is in the range of −10 nm to +40 nm. A liquid crystal display device.   2. The liquid crystal display according to claim 1, wherein the transparent protective layer located on the liquid crystal cell side of the second polarizing plate is made of a thermoplastic cyclic polyolefin resin film and has a thickness direction retardation Rth in the range of −10 nm to +10 nm. apparatus. Retardation plate is located from the plane phase difference R ₀ 100 nm in the range of 200 nm, a slow axis direction of the refractive index n _x in the plane, the refractive index in a direction perpendicular to the slow axis in the plane n _y, and the refractive index in the thickness direction is taken as _{n z, (n x -n z} ) / claims (n _x -n _y) Nz coefficient expressed by is in the range of -0.5 to +0.5 3. A liquid crystal display device according to 1 or 2.   The liquid crystal display device according to claim 1, wherein the retardation plate is disposed so that a slow axis thereof is substantially orthogonal to an absorption axis of the first polarizing plate.   5. The liquid crystal display according to claim 1, wherein the retardation plate is disposed substantially parallel to a major axis direction when no voltage is applied to liquid crystal molecules positioned on the adjacent transparent substrate surface. apparatus. Birefringence comprising the first polarizing plate and at least one retardation plate disposed on one side thereof, and including the retardation plate existing from the polarizer constituting the first polarizing plate to the retardation plate A composite polarizing plate in which the sum of thickness direction retardations Rth is in the range of −40 nm to +40 nm and the sum of the planar retardations R ₀ is in the range of 100 nm to 200 nm, and a transparent protective layer on both sides of the polarizer And a second polarizing plate having a thickness direction retardation Rth of -10 nm to +40 nm in at least one of the transparent protective layers.

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