JP2007179024A - Wide viewing angle polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wide viewing angle polarizing plate which reduces a leak of light to the oblique direction and improves a change of a color easily when used in a liquid crystal display device, particularly, in the liquid crystal display device of an IPS or FFS mode. <P>SOLUTION: The wide viewing angle polarizing plate has a polarizing film and protective films on both sides of the polarizing film. One of the protective films has a phase difference region satisfying expression (1): 0.4<Nz<0.6 and expression (2): 0.4<(Re(λ)/λ)<0.6 (wherein Nz and (Re(λ)/λ) are values when the measured wavelength λ is within 400-700 nm and Nz=Rth/Re+0.5). The lag-axis of the phase difference region is layered in a state almost perpendicular or almost parallel to the absorption axis of the polarizing film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technical field of a liquid crystal display device, and more particularly, to an IPS mode or FFS mode liquid crystal display device that performs display by applying a horizontal electric field to liquid crystal molecules aligned in a horizontal direction. Furthermore, the present invention relates to a wide viewing angle polarizing plate that contributes to an improvement in color change in an oblique direction of a liquid crystal display device, particularly a liquid crystal display device in an IPS mode or an FFS mode.

  As a liquid crystal display device, a so-called TN mode is widely used in which a liquid crystal layer in which nematic liquid crystal is twisted is sandwiched between two orthogonal polarizing plates and an electric field is applied in a direction perpendicular to the substrate. In this system, since the liquid crystal rises with respect to the substrate during black display, birefringence occurs due to liquid crystal molecules when viewed from an oblique direction, and light leakage occurs. To solve this problem, a system for optically compensating the liquid crystal cell and preventing this light leakage by using a film in which liquid crystal molecules are hybrid-aligned has been put into practical use. However, even if liquid crystal molecules are used, it is very difficult to completely optically compensate the liquid crystal cell without any problem, resulting in a problem that gradation reversal in the lower direction of the screen cannot be suppressed.

  In order to solve such problems, a so-called in-plane switching (IPS) mode or FFS mode liquid crystal display device in which a lateral electric field is applied to the liquid crystal, or a liquid crystal having a negative dielectric anisotropy is vertically aligned in the panel. A vertical alignment (VA) mode in which alignment is divided by protrusions and slit electrodes formed on the substrate is proposed and put into practical use. In recent years, these panels have been developed not only for monitor applications but also for TV applications, and screen brightness has been greatly improved accordingly. For this reason, slight light leakage in the diagonally oblique incidence direction during black display, which has not been considered as a problem in these operation modes, has become apparent as a cause of deterioration in display quality.

As one means for improving the viewing angle and color tone of this black display, disposing an optical compensation material having birefringence characteristics between the liquid crystal layer and the polarizing plate has been studied also in the IPS and FFS modes. For example, by arranging a birefringent medium having an optical axis orthogonal to each other to compensate for the increase / decrease in retardation of the liquid crystal layer during tilting, a white display or a halftone display is diagonally arranged between the substrate and the polarizing plate. It is disclosed that coloring can be improved when viewing directly from (see Patent Document 1). In addition, a technique using an optical compensation film made of a styrene-based polymer having a negative intrinsic birefringence or a discotic liquid crystalline compound (see Patent Documents 2, 3, and 4) or an optical compensation film having a positive birefringence and an optical axis A technique that combines a film in the plane of the film with a film having a positive birefringence and an optical axis in the normal direction of the film (see Patent Document 5), biaxial optical compensation with a retardation of half wavelength A technique using a film (see Patent Document 6), a technique using a film having a negative retardation as a protective film of a polarizing plate, and a technique of providing an optical compensation layer having a positive retardation on this surface (see Patent Document 7) Proposed.
Japanese Patent Laid-Open No. 9-80424 Japanese Patent Laid-Open No. 10-54982 JP-A-11-202323 Japanese Patent Laid-Open No. 9-292522 JP 11-133408 A JP-A-11-305217 JP-A-10-307291

  However, when optically compensating an IPS or FFS mode liquid crystal cell using an optical compensation film, especially when the liquid crystal display device is observed from an oblique direction during black display, the color changes compared to the front observation. End up.

  The present invention has been made in view of the above-mentioned problems. In a liquid crystal display device, particularly a liquid crystal display device in IPS or FFS mode, the present invention is a wide-ranging device that easily reduces light leakage in an oblique direction and changes color tone. It is an object to provide a viewing angle polarizing plate.

  It is considered that the color change in the oblique direction that occurs particularly during black display when optical compensation is performed using the optical compensation film described above is due to the wavelength dependence of the optical characteristics of the optical compensation film. In many systems, since a plurality of optical compensation sheets are used, it is difficult to balance the chromatic dispersion and suppress the color change.

  In addition to the above-mentioned patent documents, there is JP-A-2002-156528 as a technique for defining wavelength dependency. When this technique is used, the color is slightly improved due to the wide band, but the color change remains. This change in color is considered to be due to the optical characteristics of the protective film included between the polarizing film and the retardation region. In addition, the increase in the number of times of bonding increases the cost and the yield, which is not necessarily suitable for manufacturing.

  The above problem has been solved by the following configuration. Furthermore, by adopting the following constitution, it was possible not only to solve the above-mentioned problems, but also to provide a wide viewing angle polarizing plate suitable for production suitability at low cost.

1. A polarizing plate and a polarizing plate having a protective film on both sides thereof,
One of the protective films is a retardation region that satisfies the following formulas (1) and (2):
A wide viewing angle polarizing plate, wherein a slow axis of the retardation region is laminated substantially orthogonally or substantially parallel to an absorption axis of a polarizing film.
0.4 <Nz <0.6 (1)
0.4 <(Re (λ) / λ) <0.6 (2)
Here, Nz and (Re (λ) / λ) are values at the measurement wavelength λ (400 nm to 700 nm), and Nz = Rth / Re + 0.5.
2. The cellulose acylate further comprises a retardation region containing cellulose acylate between the retardation region satisfying the formulas (1) and (2) and the polarizing film, which the wide viewing angle polarizing plate of 1 has. A wide viewing angle polarizing plate characterized in that a retardation region containing a rate satisfies the following formulas (3) and (4).
0 ≦ Re <30 (3)
−20 <Rth <20 (4)
3. 3. The wide viewing angle polarizing plate as described in 1 or 2 above, wherein the retardation region satisfying the formulas (1) and (2) is produced by stretching.
4). 4. The wide viewing angle polarizing plate as described in any one of 1 to 3 above, wherein the retardation region satisfying the formulas (1) and (2) comprises polycarbonate.
5. 4. The wide viewing angle polarizing plate as described in any one of 1 to 3 above, wherein the retardation region satisfying the formulas (1) and (2) comprises a cyclic polyolefin.
6). 6. A liquid crystal display device having a liquid crystal panel that sandwiches a liquid crystal layer between a pair of substrates and a pair of polarizing plates that sandwich the liquid crystal panel, wherein the polarizing plate is a wide film according to any one of 1 to 5 above. A liquid crystal display device characterized by being a viewing angle polarizing plate.
7). 7. The liquid crystal display device according to 6, wherein
Of the pair of polarizing plates sandwiching the liquid crystal panel, one polarizing plate is the wide viewing angle polarizing plate according to any one of 1 to 5, and the other polarizing plate has a polarizing film and protective films on both sides thereof. And one of the protective films includes a retardation region containing cellulose acylate, and the retardation region containing cellulose acylate satisfies the following formulas (3) and (4): A liquid crystal display device.
0 ≦ Re <30 (3)
−20 <Rth <20 (4)

  In the present specification, “substantially parallel”, “substantially orthogonal”, “parallel”, and “orthogonal” mean that the angle is within a range of strictly less than ± 10 °. In this range, an error from a strict angle is preferably less than ± 5 °, and more preferably less than ± 2 °. Further, “substantially” means within a range of less than ± 20 ° from a strict angle. In this range, an error from a strict angle is preferably less than ± 15 °, and more preferably less than ± 10 °. Further, the “slow axis” means a direction in which the refractive index is maximized. Further, the measurement wavelength of the refractive index is a value at λ = 550 nm in the visible light region unless otherwise specified.

  In this specification, unless otherwise specified, the term “polarizing plate” is cut into a size to be incorporated into a long polarizing plate and a liquid crystal display device (in this specification, “cutting” includes “punching” and “ It is also used in the sense of including both of the polarizing plates. In this specification, “polarizing film” and “polarizing plate” are distinguished from each other. “Polarizing plate” means a laminate having a transparent protective film for protecting the polarizing film on at least one side of the “polarizing film”. It shall be.

In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at a wavelength λ, respectively. Re (λ) is measured in KOBRA 21ADH (manufactured by Oji Scientific Instruments) by making light having a wavelength of λ nm incident in the normal direction of the film. Rth (λ) is a light having a wavelength of λ nm from the direction inclined by + 40 ° with respect to the normal direction of the film, using Re (λ) and the in-plane slow axis (determined by KOBRA 21ADH) as the tilt axis (rotation axis). And a retardation value measured by making light of wavelength λ nm incident from a direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). KOBRA 21ADH is calculated based on retardation values measured in three directions in total. As the wavelength λ, a value in the range of 450 to 750 nm is usually used. In the present application, a value of 589 nm is used unless otherwise specified. Here, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. Examples of the average refractive index values of main optical films are given below:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).

  The KOBRA 21ADH calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. In addition, the sign of Rth is when the retardation measured by injecting light having a wavelength of 550 nm from the direction inclined + 20 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis) exceeds Re Is positive and negative is below Re. However, in the sample with | Rth / Re | of 9 or more, it was tilted by + 40 ° with respect to the film normal direction with the in-plane fast axis as the tilt axis (rotation axis) using a polarizing microscope with a free rotation base. In the state, the case where the slow axis of the sample which can be determined using the polarizing plate inspection plate is parallel to the film plane is positive, and the case where the slow axis is in the thickness direction of the film is negative.

  According to the present invention, in a liquid crystal display device, in particular, an IPS or FFS mode liquid crystal display device, it is possible to reduce the change in color between the front and the diagonal direction during black display. Furthermore, it is possible to provide a wide viewing angle polarizing plate suitable for production suitability at low cost.

  Hereinafter, an embodiment of the liquid crystal display device of the present invention and its constituent members will be described in order. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

The wide viewing angle polarizing plate of the present invention has a polarizing film and protective films on both sides thereof, and one of the protective films is a retardation region that satisfies a specific formula.
Hereinafter, the phase difference region used in the present invention will be described.

[Phase difference area]
The retardation region of the present invention is a retardation region in which Nz and (Re (λ) / λ) satisfy the following expressions (1) and (2) at a measurement wavelength λ (400 nm to 700 nm).
0.4 <Nz <0.6 (1)
0.4 <Re (λ) / λ <0.6 (2)
(However, Nz = Rth / Re + 0.5)
That is, a wide viewing angle polarizing plate characterized in that a retardation region satisfying the above formulas (1) and (2) and a polarizing film are laminated so that their optical axes are orthogonal or parallel to each other. is there.
A specific material of the retardation region that satisfies the above characteristics will be described below.

  The retardation region used in the present invention is preferably a polymer alignment film formed of a polymer material. The polymer material of the polymer oriented film has a glass transition temperature of 120 ° C. or higher, preferably 140 ° C. or higher. If it is less than 120 ° C., problems such as orientation relaxation may occur depending on the use conditions of the display device. The water absorption is preferably 1% by mass or less from the viewpoint of practical durability. The film material is preferably selected so that the water absorption rate of the film satisfies the condition of 1% by mass or less, preferably 0.5% by mass or less.

  The polymer material used in the present invention may be a blend polymer or a copolymer.

  The polymer material constituting the polymer oriented film used in the present invention is not particularly limited, and has excellent heat resistance, good optical performance, and can be formed into a solution, such as polyarylate, polyester, polycarbonate, polyolefin, poly A thermoplastic polymer such as ether, polysulfine copolymer, polysulfone, or polyethersulfone is preferred.

The polymer material applied to the retardation region used in the present invention is, in particular, when the retardation region is used in a single layer, the main chain direction of the polymer structure and the main chain in the plane of the layer. It is preferable that the difference in refractive index component between the direction perpendicular to the direction (not the thickness direction) is large.
The reason is that the structure having the above characteristics forms a state in which the difference between the refractive index in the slow axis direction and the refractive index in the fast axis direction is large in the phase difference region, and the absorption wavelength peak in each direction. This is because it is estimated that the wavelength dispersion characteristic is affected.

  Further, in the IPS mode and the FFS mode, the polymer material is suitable because the thickness direction retardation can be obtained from the characteristics of the cell.

  When this thermoplastic polymer is used, it is a blend polymer composed of a polymer having a positive refractive index anisotropy and a polymer having a negative refractive index anisotropy, and a high polymer having a positive refractive index anisotropy. A copolymer comprising a monomer unit of a molecule and a polymer monomer unit having a negative refractive index anisotropy is more preferable. Two or more kinds thereof may be combined, or one or more kinds of blend polymers and one or more kinds of copolymers may be used in combination.

  In the case of a blend polymer, in order to obtain optical transparency, it is preferable that the compatible blend or the refractive index of each polymer is substantially equal. As specific combinations of blend polymers, for example, poly (methyl methacrylate) as a polymer having negative optical anisotropy, poly (vinylidene fluoride), poly ( A combination of at least one polymer selected from the group consisting of (ethylene oxide) and poly (vinylidene fluoride-co-trifluoroethylene), poly (phenylene oxide) as a polymer having positive optical anisotropy, and negative At least one selected from the group consisting of polystyrene, poly (styrene-co-lauroylmaleimide), poly (styrene-co-cyclohexylmaleimide) and poly (styrene-co-phenylmaleimide) In combination with other polymers, poly (s) with negative optical anisotropy (Lene-co-maleic anhydride) and a polycarbonate having positive optical anisotropy, poly (acrylonitrile-co-butadiene) having positive optical anisotropy and poly (acrylic-co-butadiene) having negative optical anisotropy A combination of (acrylonitrile-co-styrene) and a combination of a polycarbonate having a positive optical anisotropy and a polycarbonate having a negative optical anisotropy can be suitably exemplified, but the invention is not limited thereto. In particular, from the viewpoint of transparency, blend polymers obtained by combining polystyrene and poly (phenylene oxide) such as poly (2,6-dimethyl-1,4-phenylene oxide), polycarbonate having positive optical anisotropy, and negative A blend obtained by combining a polycarbonate having optical anisotropy of 5 is preferred. In the former case, it is preferable that the ratio of the polystyrene occupies 67% by mass or more and 75% by mass or less of the whole.

  Examples of the copolymer include poly (butadiene-co-polystyrene), poly (ethylene-co-polystyrene), poly (acrylonitrile-co-butadiene), poly (acrylonitrile-co-butadiene-co-styrene), and polycarbonate. A polymer, a polyester copolymer, a polyester carbonate copolymer, a polyarylate copolymer, or the like can be used. In particular, since a segment having a fluorene skeleton can have negative optical anisotropy, a polycarbonate copolymer, a polyester copolymer, a polyester carbonate copolymer, a polyarylate copolymer, and the like having a fluorene skeleton are more preferably used.

  The polymer material may be a blend of two or more types of copolymers, or may be a blend of one or more types of copolymers and the blend or other polymer, or two or more types of blends. Or a blend of other polymers or copolymers. A polycarbonate copolymer produced by reacting a bisphenol with a carbonate ester-forming compound such as phosgene or diphenyl carbonate is excellent in transparency, heat resistance and productivity, and can be particularly preferably used. The polycarbonate copolymer is preferably a copolymer having a structure having a fluorene skeleton. The component having a fluorene skeleton is preferably a repeating unit represented by the following formula (A), and preferably 1 to 99 mol% of the entire repeating unit.

  Formula (A)

In the formula (A), R _{1 to} R ₈ are each independently at least one selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 6 carbon atoms, and X is represented by the following structural formula.

  Specifically, the repeating unit a represented by the above formula (A) is 30 to 90 mol%, and the polycarbonate copolymer in which the repeating unit b represented by the following formula (B) accounts for 70 to 10 mol% of the whole and And / or blends.

  Formula (B)

In the formula (B), R _{9 to} R ₁₆ are each independently at least one selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 22 carbon atoms, and Y is at least 1 selected from the following formula group. It is a seed.

Here, R _{17 to} R ₁₉ , R ₂₁ and R ₂₂ in Y are each independently a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms, and R ₂₀ and R ₂₃ are each independently one having 1 carbon atom. is selected from a hydrocarbon group of to _20, Ar 1 to Ar ₃ is at least one group selected from an aryl group having 6 to 10 carbon atoms.

In the above formula (A), R _{1 to} R ₈ are each independently selected from a hydrogen atom, a halogen atom, and a hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group having 1 to 6 carbon atoms include alkyl groups such as methyl group, ethyl group, isopropyl group, and cyclohexyl group, and aryl groups such as phenyl group. Among these, a hydrogen atom and a methyl group are preferable.

In the formula (B), R _{9 to} R ₁₆ are each independently selected from a hydrogen atom, a halon atom, and a hydrocarbon group having 1 to 22 carbon atoms. Examples of the hydrocarbon group having 1 to 22 carbon atoms include alkyl groups having 1 to 9 carbon atoms such as a methyl group, an ethyl group, an isopropyl group, and a cyclohexyl group, and aryl groups such as a phenyl group, a biphenyl group, and a terphenyl group. It is done. Among these, a hydrogen atom and a methyl group are preferable.

In Y of the above formula (B), R _{17 to} R ₁₉ , R ₂₁ and R ₂₂ are each independently at least one group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms. Examples of the hydrocarbon group are the same as those described above. R ₂₀ and R ₂₃ are each independently selected from hydrocarbon groups having 1 to 22 carbon atoms, and examples of such hydrocarbon groups include the same ones as described above. Ar _{1 to} Ar ₃ are aryl groups having 6 to 10 carbon atoms such as a phenyl group and a naphthyl group.

  The polymer oriented film used in the present invention is preferably one using a polycarbonate having a fluorene skeleton. Examples of the polycarbonate having a fluorene skeleton include a polycarbonate copolymer comprising a repeating unit represented by the above formula (A) and a repeating unit represented by the above formula (B), and a repeating unit represented by the above formula (A). A blend of the polycarbonate and the polycarbonate composed of the repeating unit represented by the above formula (B) is good. The content of the above formula (A), that is, the copolymer composition in the case of the copolymer, the blend composition ratio in the case of the blend is 30 to 90 mol% of the whole polycarbonate is preferable. Although the composition ratio is different from the copolymer having the repeating units of the above formulas (A) and (B), the copolymer having the repeating units of the above formulas (A) and (B) may be blended. Moreover, 35-85 mol% of the whole polycarbonate is more preferable, and, as for the content rate of the said formula (A), 45-80 mol% is further more preferable.

  The copolymer may be a combination of two or more repeating units represented by the above formulas (A) and (B). In the case of a blend, two or more of the repeating units may be combined.

  Here, the molar ratio can be obtained for the entire polycarbonate bulk constituting the polymer oriented film, for example, by a nuclear magnetic resonance (NMR) apparatus, regardless of the copolymer or blend.

  The above copolymer and / or blend can be produced by a known method. As the polycarbonate, a method by polycondensation of a dihydroxy compound and phosgene, a melt polycondensation method or the like is preferably used. In the case of a blend, a compatible blend is preferable, but even if it is not completely compatible, light scattering between components can be suppressed and transparency can be improved by adjusting the refractive index between components.

  The intrinsic viscosity of the polycarbonate is preferably 0.3 to 2.0 dl / g. If it is less than 0.3, there is a problem that it becomes brittle and the mechanical strength cannot be maintained, and if it exceeds 3.0, the solution viscosity becomes too high, so problems such as die line formation in solution casting, and purification at the end of polymerization are difficult. There is a problem of becoming.

The polymeric material may be a cyclic polyolefin.
In the case where the retardation region is a region composed only of a cyclic polyolefin resin, it is desirable that the structure has a characteristic that the refractive index component in the direction perpendicular to the main chain is large as described above. Further, when the retardation region is composed of a plurality of layers of a cyclic polyolefin resin and a resin other than a cyclic polyolefin such as polyimide, the present invention can be achieved by adjusting the wavelength dispersion characteristics of the entire plurality of layers. It is possible to realize the optical characteristics that are features of the above.

  As the cyclic polyolefin resin, the following norbornene-based ring-opening polymer can be used. Although the structural unit (C) is included as an essential structural unit, the following general formula (D):

[Wherein, a is an integer of 0 to 2, X is a group represented by the formula: —CH═CH— or a group represented by the formula: —CH ₂ CH ₂ —, and R ^{1 to} R ^6] Are independently a hydrogen atom; a halogen atom; a substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms, which may have a linking group containing an oxygen atom, a sulfur atom, a nitrogen atom or a silicon atom; or A group consisting of a group having an aromatic ring represented by the following general formula (C1) and a group having an aromatic ring represented by the general formula (C2), wherein at least one of R ^{3 to} R ⁶ is a polar group Is a group selected from ]
And a plurality of Xs present the same or different norbornene-based ring-opening polymers.

[Wherein Ar independently represents the following structural formula:

R ^{7 to} R ¹⁵ are independently a hydrogen atom; a halogen atom; a linking group containing an oxygen atom, a sulfur atom, a nitrogen atom or a silicon atom. A substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms; or a polar group, and b and c are each independently an integer of 0 to 3, provided that b = c = 0 In this case, R ⁸ and R ¹¹ , and / or R ¹⁵ and R ¹¹ may be bonded to each other to form a carbocyclic or heterocyclic ring (these carbocyclic or heterocyclic rings may have a monocyclic structure, and other rings may be condensed). A polycyclic structure may be formed). ]

[Wherein Ar is as defined above with respect to general formula (C1), and R ^{16 to} R ²⁴ independently represent a hydrogen atom; a halogen atom; a linking group containing an oxygen atom, a sulfur atom, a nitrogen atom or a silicon atom. A substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms; or a polar group, and d is an integer of 0 to 3. ]

[Wherein, e and f are independently 0 or 1, provided that at least one of them is 1, g and h are each independently an integer of 0 to 2, and Y is a group represented by the formula: —CH═CH— Or a group represented by the formula: —CH ₂ CH ₂ —, wherein R ^{25 to} R ³⁴ are independently a hydrogen atom; a halogen atom; an aromatic ring represented by the general formula (C1). A substituted or unsubstituted carbon atom which may have a linking group containing an oxygen atom, a sulfur atom, a nitrogen atom or a silicon atom other than the group having an aromatic ring and the group having an aromatic ring represented by formula (C2) Or a polar group, and R ³¹ and R ³² , and / or R ³³ and R ³⁴ may be combined to form a divalent hydrocarbon group, R ³¹ or R ³² When, R ³³ or carbocyclic or heterocyclic ring (these carbocyclic or double bonded to each other and R ³⁴ Ring may be a single ring structures, another ring may form a condensed polycyclic structure.) May be formed. ]
Or a structural unit other than the structural unit (D) may be included.

  In addition to the norbornene ring-opening polymer, the following norbornene ring-opening polymer can be used as the cyclic polyolefin resin.

[In Formula (E), m is an integer of 1 or more, p is 0 or an integer of 1 or more, and D is a group independently represented by —CH═CH— or —CH ₂ CH ₂ —. Each of R ^{1 to} R ⁴ independently has a hydrogen atom; a halogen atom; a substituted or unsubstituted carbon atom that may have a linking group containing an oxygen atom, a sulfur atom, a nitrogen atom, or a silicon atom; Or a polar group, and R ¹ and R ² and / or R ³ and R ⁴ may be combined to form a divalent hydrocarbon group, R ¹ or R ² and R ³ or R ⁴ may be bonded to each other to form a carbocyclic or heterocyclic ring, and the carbocyclic or heterocyclic ring may be a monocyclic structure or a polycyclic structure. ]

[In Formula (F), E is a group independently represented by —CH═CH— or —CH ₂ CH ₂ —, and R ^{5 to} R ⁸ each independently represent a hydrogen atom; a halogen atom; an oxygen atom. Represents a substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms which may have a linking group containing a sulfur atom, a nitrogen atom or a silicon atom; or represents a polar group, and R ⁵ and R ⁶ and / or R ⁷ and R ⁸ may be combined to form a divalent hydrocarbon group, and R ⁵ or R ⁶ and R ⁷ or R ⁸ are bonded to each other to form a carbocyclic or heterocyclic ring. The carbocyclic or heterocyclic ring may be a monocyclic structure or a polycyclic structure. ]

  In addition, the norbornene-based ring-opening polymer can be laminated with a polymer having negative birefringence having a fluorene skeleton to form a multi-layer retardation region. A polyimide having a repeating unit represented by (G) can be used.

[In Formula (G), X is a tetravalent organic group having an alicyclic structure, and Y is a divalent organic group having a fluorene skeleton. ]

  The polymer oriented film described above is preferably transparent, and preferably has a haze value of 3% or less and a total light transmittance of 85% or more.

  Furthermore, you may add ultraviolet absorbers, such as a phenyl salicylic acid, 2-hydroxybenzophenone, and a triphenyl phosphate, a bluing agent for changing a color, antioxidant.

  The retardation region used in the present invention is preferably composed of a polymer oriented film in which an unstretched film such as the polycarbonate is stretched to align polymer chains. As a method for producing such a film, a known melt extrusion method, solution casting method, or the like is used, and the solution casting method is more preferably used from the viewpoint of film thickness unevenness, appearance, and the like. As the solvent in the solution casting method, methylene chloride, dioxolane and the like are preferably used.

  Moreover, although a well-known extending | stretching method can be used also for the extending | stretching method, Preferably it is vertical or horizontal uniaxial stretching. In the film, for the purpose of improving stretchability, phthalates such as dimethyl phthalate, diethyl phthalate and dibutyl phthalate which are known plasticizers, phosphate esters such as tributyl phosphate, aliphatic dibasic esters, glycerin derivatives, A glycol derivative or the like may be contained. At the time of stretching, the organic solvent used at the time of film formation described above may remain in the film for stretching. The amount of the organic solvent is preferably 1 to 20% by mass relative to the polymer solid content.

  Further, the additives such as the plasticizer and the liquid crystal can change the retardation wavelength dispersion of the polymer oriented film used in the present invention, but the addition amount is preferably 10% by mass or less relative to the polymer solid content, and 3% by mass. % Or less is more preferable.

  The film thickness of the polymer oriented film is preferably 1 μm to 150 μm. In addition, although expressed as a polymer oriented film in the present invention, it is meant to include any material commonly referred to as “film” or “sheet”.

Further, as in the above formula (2), the larger the measurement wavelength, the larger Re, and the smaller the measurement wavelength, the smaller Re is called “broadband”. Conversely, the smaller the measurement wavelength, the smaller Re, and the smaller the measurement wavelength, the larger Re is called “narrowband”.
As described above, in order to broaden the retardation of the polymer oriented film as shown in the above formula (2), the chemical structure of the polymer constituting the polymer oriented film is important. It should be noted that a considerable part is determined by the chemical structure, but also varies depending on film forming conditions, additives, stretching conditions, blending conditions, molecular weight, and the like.

The wide viewing angle polarizing plate of the present invention comprises a retardation region and a polarizing film satisfying the above formulas (1) and (2), and the optical axis of the retardation region and the optical axis of the polarizing film are orthogonal or parallel. It is laminated so that As such a phase difference region, one having a phase difference of Re (550) of 5 to 500 nm, preferably 100 to 450 nm is used, and Nz and (Re (λ) at a measurement wavelength λ (400 nm to 700 nm) of the phase difference region are used. ) / Λ) preferably satisfies the above formula (1) and the following formula (2-2), and more preferably satisfies the above formula (1) and the following formula (2-3). is there.
0.425 <(Re (λ) / λ) <0.575 (2-2)
0.45 <(Re (λ) / λ) <0.55 (2-3)

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a pixel region of the liquid crystal display device of the present invention. 2 and 3 are schematic views of an embodiment of the liquid crystal display device of the present invention. Either light may be incident from below or light may be incident from above.

[Liquid Crystal Display]
The liquid crystal display device shown in FIG. 2 has polarizing films 9 and 16, a retardation region 14, substrates 12a and 12b, and a liquid crystal layer 18 sandwiched between the substrates. The polarizing films 9 and 16 are sandwiched between protective films 7 and 10 and 17 and 19, respectively. The phase difference region 14 represents a phase difference region that satisfies the above expressions (1) and (2).

  In the liquid crystal display device of FIG. 2, a liquid crystal panel (also referred to as a liquid crystal cell) includes substrates 12a and 12b and a liquid crystal layer 18 sandwiched between them. The product Δn · d of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn is optimal in the range of 0.2 to 0.4 μm for the IPS type having no twisted structure in the transmission mode. In this range, the white display luminance is high and the black display luminance is small, so that a bright and high-contrast display device can be obtained. An alignment film (not shown) is formed on the surfaces of the substrates 12a and 12b that are in contact with the liquid crystal layer 18, and the liquid crystal molecules are aligned substantially parallel to the surface of the substrate and are rubbed on the alignment film. The alignment direction of liquid crystal molecules in a state where no voltage is applied or in a state where a voltage is not applied is controlled by the processing direction (not shown in FIG. 2). Further, an electrode (not shown in FIG. 2) capable of applying a voltage to liquid crystal molecules is formed on the inner surface of the substrate 12a or 12b.

  FIG. 1 schematically shows the orientation of liquid crystal molecules in one pixel region of the liquid crystal layer 18. FIG. 1 shows the alignment of liquid crystal molecules in a very small area corresponding to one pixel of the liquid crystal layer 18, the rubbing direction 4 of the alignment film formed on the inner surfaces of the substrates 12a and 12b, and the substrates 12a and 12b. It is the schematic diagram shown with the electrodes 2 and 3 which can apply a voltage to the liquid crystal molecule formed in the inner surface. When active driving is performed using a nematic liquid crystal having positive dielectric anisotropy as a field effect liquid crystal, the liquid crystal molecule alignment directions in a no voltage application state or a low application state are 5a and 5b. A display is obtained. When applied between the electrodes 2 and 3, the liquid crystal molecules change their alignment direction in the directions of 6 a and 6 b in accordance with the voltage. Usually, bright display is performed in this state.

In FIG. 2 again, the absorption axis 8 of the polarizing film 9 and the absorption axis 15 of the polarizing film 16 are arranged orthogonally. The slow axis 13 of the retardation region 14 is orthogonal to the absorption axis 8 of the polarizing film 9 and the slow axis direction 11 of the liquid crystal molecules in the liquid crystal layer 18 during black display, but may be parallel.
In the liquid crystal display device shown in FIG. 2, the polarizing film 16 is sandwiched between the two protective films 17 and 19, but the protective film 19 may be omitted. When the protective film 19 is provided, the protective film 19 is preferably a retardation region that satisfies the following formulas (3) and (4).
0 ≦ Re <30 (3)
−20 <Rth <20 (4)
More preferably, the retardation region contains cellulose acylate.

In the liquid crystal display device shown in FIG. 2, the polarizing film 9 is sandwiched between the two protective films 7 and 10, but the protective film 10 is not necessary. When the protective film 10 is provided, the protective film 10 is preferably a retardation region that satisfies the following formulas (3) and (4).
0 ≦ Re <30 (3)
−20 <Rth <20 (4)
More preferably, the retardation region contains cellulose acylate.

  Another embodiment of the present invention is shown in FIG. In the liquid crystal display device of FIG. 3, the directions of the absorption axes 8 and 15 of the polarizing films 9 and 16 are different from those of FIG. Further, the slow axis direction 13 of the retardation region 14 is orthogonal to the absorption axis 8 of the polarizing film 9 and parallel to the slow axis direction 11 of the liquid crystal molecules in the liquid crystal layer 18 during black display. Further, it may be parallel to the absorption axis 8 and orthogonal to the slow axis direction 11.

  2 and 3 show a mode of a transmissive mode display device including an upper polarizing plate and a lower polarizing plate, the present invention is a mode of a reflective mode including only one polarizing plate. In such a case, since the optical path in the liquid crystal cell is doubled, the optimum value of Δn · d is about the above half value. The liquid crystal cell used in the present invention is not limited to the IPS mode, and any liquid crystal display device in which liquid crystal molecules are aligned substantially parallel to the surfaces of the pair of substrates during black display can be used. It can be used suitably. Examples thereof include a ferroelectric liquid crystal display device, an antiferroelectric liquid crystal display device, and an ECB type liquid crystal display device.

  The liquid crystal display device of the present invention is not limited to the configuration shown in FIGS. 1 to 3 and may include other members. For example, a color filter may be disposed between the liquid crystal layer and the polarizing film. Further, an antireflection treatment or a hard coat may be applied to the surface of the protective film of the polarizing film. Moreover, you may use what gave electroconductivity to the structural member. In the case of use as a transmission type, a cold cathode or a hot cathode fluorescent tube, or a backlight having a light emitting diode, a field emission element, or an electroluminescent element as a light source can be disposed on the back surface. In this case, the arrangement of the backlight may be on the upper side or the lower side in FIGS. In addition, a reflective polarizing plate, a diffusion plate, a prism sheet, or a light guide plate can be disposed between the liquid crystal layer and the backlight. In addition, as described above, the liquid crystal display device of the present invention may be of a reflective type. In such a case, only one polarizing plate may be disposed on the observation side, and the back side of the liquid crystal cell or the lower side of the liquid crystal cell. A reflective film is disposed on the inner surface of the substrate. Of course, it is also possible to provide a front light using the light source on the liquid crystal cell observation side.

  The liquid crystal display device of the present invention includes an image direct view type, an image projection type, and a light modulation type. The present invention is particularly effective when applied to an active matrix liquid crystal display device using a three-terminal or two-terminal semiconductor element such as TFT or MIM. Of course, a mode applied to a passive matrix liquid crystal display device called time-division driving is also effective.

  Hereinafter, preferred optical characteristics of various members usable in the liquid crystal display device of the present invention, materials used for the members, manufacturing methods thereof, and the like will be described in detail.

[Protective film for polarizing film]
As the first and second protective films for the polarizing film, those having no absorption in the visible light region, a light transmittance of 80% or more, and a retardation based on birefringence are preferable. The in-plane retardation is preferably in the range of 0 ≦ Re ≦ 30, more preferably 0 ≦ Re <30, still more preferably 0 ≦ Re ≦ 15, and most preferably 0 ≦ Re ≦ 5. Further, the retardation in the thickness direction is preferably in the range of −20 ≦ Rth ≦ 20, more preferably −20 <Rth <20, further preferably −10 ≦ Rth ≦ 10, and −5 ≦ Rth ≦ 5. Most preferred. The unit of the retardation value is nm. The protective film for the polarizing film can be suitably used without particular limitation as long as it is a film having the above optical characteristics, but from the viewpoint of durability of the polarizing film, a cellulose acylate or norbornene film is more preferable. Examples of a method for reducing Rth of the cellulose acylate film include methods described in JP-A Nos. 11-246704, 2001-247717, and Japanese Patent Application No. 2003-379975. Rth can also be reduced by reducing the thickness of the cellulose acylate film. The thickness of the cellulose sylate film as the protective film for the first and second polarizing films is preferably 10 to 100 μm, more preferably 10 to 60 μm, and still more preferably 20 to 45 μm. By using the protective film for polarizing film having such characteristics, it is possible to increase the contrast while suppressing the luminance when observed from the polar angle direction of 60 ° during the black display of the liquid crystal panel. Further, it is possible to suppress a change in color when the azimuth angle direction is swung in the polar angle direction of 60 °. In particular, it is preferable to apply a cellulose acylate film satisfying the above Re and Rth to the protective film 19. It is also a preferable aspect to apply a cellulose acylate film satisfying the above Re and Rth to the protective film 10. However, the polarizing film protective film on the side opposite to the liquid crystal cell has little influence on the color, and the optical characteristics are not limited to this.

[Wide viewing angle polarizing plate]
A polarizing film is directly bonded to the retardation region satisfying the above formulas (1) and (2) used in the present invention, or a protective film is further provided between the retardation region and the polarizing film, As a protective film, a cellulose acylate film, which is a retardation region satisfying the above formulas (3) and (4), is used as a wide viewing angle polarizing plate of the present invention and used in a liquid crystal display device. . In a normal polarizing plate, protective films having large optical properties are bonded to both sides of the polarizing film. By using the wide viewing angle polarizing plate of the present invention, it is possible to significantly suppress color change. The polarizing film will be described below.

[Polarizing film]
Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Preparation of IPS mode liquid crystal cell 1>
As shown in FIG. 1, electrodes (2 and 3 in FIG. 1) are arranged on one glass substrate so that the distance between adjacent electrodes is 20 μm, and a polyimide film is used as an alignment film on it. A rubbing process was performed. The rubbing process was performed in the direction 4 shown in FIG. A polyimide film was provided on one surface of a separately prepared glass substrate, and a rubbing treatment was performed to obtain an alignment film. The two glass substrates are stacked and bonded so that the alignment films face each other, the distance between the substrates (gap; d) is 3.9 μm, and the rubbing directions of the two glass substrates are parallel. A nematic liquid crystal composition having a refractive index anisotropy (Δn) of 0.0769 and a dielectric anisotropy (Δε) of 4.5 was enclosed. The value of d · Δn of the liquid crystal layer was 300 nm.

  The monomer structures of the polycarbonates used in the following examples and comparative examples are shown below.

<Production of Phase Difference Regions 1A to 1C and Phase Difference Regions 2A and 2C>
A reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser was charged with an aqueous sodium hydroxide solution and ion-exchanged water, and the monomers [X] and [Y] having the above structure were dissolved in the molar ratio shown in Table 1 and a small amount. Of hydrosulfite was added. Next, methylene chloride was added thereto, and phosgene was blown in at about 20 ° C. over about 60 minutes. Further, p-tert-butylphenol was added for emulsification, and then triethylamine was added and stirred at 30 ° C. for about 3 hours to complete the reaction. After completion of the reaction, the organic phase was collected, and methylene chloride was evaporated to obtain a polycarbonate copolymer. The composition ratio of the obtained copolymer was almost the same as the monomer charge ratio.

  This copolymer was dissolved in methylene chloride to prepare a dope solution having a solid concentration of 19% by mass. A cast film was prepared from this dope solution, and stretched by the method described in JP 2002-156528 A, etc. to obtain a polymer oriented film. In addition, even if the monomer charge ratio is the same, it is possible to obtain retardation regions having different optical characteristics by changing the stretching ratio, stretching temperature, etc. The stretching ratio is generally 1.05 times or more and 5 It is preferable that the film is stretched at a stretching temperature of 100 ° C. or higher and lower than 350 ° C.

  Table 1 summarizes the measurement results. This film was confirmed to have a smaller retardation and a positive refractive index anisotropy as the measurement wavelength was shorter. This was designated as a phase difference region 1A.

  Further, even when the monomer charge ratio was the same, the retardation regions 1B and 1C having different optical characteristics were obtained by changing the draw ratio.

  A polycarbonate homopolymer was obtained in the same manner as in the retardation region 1 except that the monomers listed in Table 1 were used. The composition ratio of the obtained homopolymer was almost the same as the monomer charge ratio. A film was formed in the same manner as in Example 1, and stretched by a known method to obtain a polymer oriented film. Table 1 summarizes the measurement results. It was confirmed that this polymer oriented film had a larger retardation with an absolute value as the measurement wavelength was shorter. This was designated as a phase difference region 2A.

  Further, even when the monomer charge ratio was the same, the retardation region 2B having different optical characteristics was obtained by decreasing the draw ratio. Table 1 shows values of optical characteristics of the obtained phase difference regions.

Table 1

<Preparation of protective film 1 for polarizing plate>
The following composition was put into a mixing tank, stirred while heating to dissolve each component, and a cellulose acetate solution A was prepared.

(Cellulose acetate solution A composition)
Cellulose acetate having a substitution degree of 2.86 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first solvent) 300 parts by weight Methanol (second solvent) ) 54 parts by mass 1-butanol 11 parts by mass

  The following composition was charged into another mixing tank, stirred while heating to dissolve each component, and an additive solution B-1 was prepared.

(Additive solution B-1 composition)
Methylene chloride 80 parts by mass Methanol 20 parts by mass The following retardation reducing agent 40 parts by mass

  40 parts by mass of the additive solution B-1 was added to 477 parts by mass of the cellulose acetate solution A, and the dope was prepared by sufficiently stirring. The dope was cast from a casting port onto a drum cooled to 0 ° C. The film is peeled off at a solvent content of 70% by mass, and both ends in the width direction of the film are fixed with a pin tenter (the pin tenter described in FIG. 3 of JP-A-4-1009), and the solvent content is 3-5% by mass. In this state, the film was dried while maintaining an interval at which the stretching ratio in the transverse direction (direction perpendicular to the machine direction) was 3%. Then, it dried further by conveying between the rolls of a heat processing apparatus, and produced the protective film 1 for polarizing plates of thickness 80 micrometers.

  Using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments Co., Ltd.), the light incident angle dependence of Re was measured, and the optical characteristics were calculated. Re was 1 nm and Rth was 0.5 nm. It was confirmed that.

<Preparation of polarizing plate A>
Next, iodine is adsorbed on the stretched polyvinyl alcohol film to produce a polarizing film, and a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd., Re = 3 nm, Rth = 45 nm) is subjected to saponification treatment. A polarizing plate A was formed using a polyvinyl alcohol-based adhesive and pasted on both surfaces of the polarizing film.

<Preparation of polarizing plate B>
A polarizing film was produced in the same manner, and a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was subjected to saponification treatment and attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive. . Further, similarly, the polarizing plate protective film 1 manufactured as described above was attached to the other surface of the polarizing film to form a polarizing plate B.

<Preparation of Polarizing Plates 1A-1C (Examples 1-3, Wide Viewing Angle Polarizing Plate of the Present Invention)>
A polarizing film was produced in the same manner, and a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was subjected to saponification treatment and attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive. . Further, the manufactured retardation region 1A is attached to the other surface of the polarizing film with a known adhesive or adhesive so that the slow axis is parallel to the absorption axis of the polarizing film, and the polarizing plate 1A Formed. Further, a polarizing plate 1B was formed in the same manner except that 1B was used instead of the retardation region 1A in the polarizing plate 1A. Furthermore, a known pressure-sensitive adhesive material or adhesive is applied to the polarizing plate B on the polarizing plate protective film 1 side so that the retardation region 1C of the production is parallel to the absorption axis of the polarizing film. Using this, the polarizing plate 1C was formed.

<Preparation of polarizing plates 2A and 2B (polarizing plates of Comparative Examples 2 and 3)>
A polarizing film was produced in the same manner, and a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was subjected to saponification treatment and attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive. . Furthermore, the retardation regions 2A and 2B of the production are attached to the other surface of the polarizing film with a known adhesive or adhesive so that the slow axis is parallel to the absorption axis of the polarizing film, Plates 2A and 2B were formed.

<Preparation of retardation region 3>
After saponifying the surface of a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.), an alignment film coating solution having the following composition was applied onto the film with a wire bar coater at 20 ml / m ² . The film was formed by drying with warm air of 60 ° C. for 60 seconds and further with warm air of 100 ° C. for 120 seconds. Next, the formed film was rubbed in a direction parallel to the slow axis direction of the film to form an alignment film.

(Composition of alignment film coating solution)
The following modified polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde 0.5 parts by weight Compound B 0.2 parts by weight

  Next, a coating solution having the following composition was applied on the alignment film rubbed with each strength so that the front retardation after curing was 250 nm with a wire bar.

(Coating solution composition)
Discotic liquid crystalline compound 1.8g
Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 0.2g
Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 0.06 g
Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.02g
Air interface side alignment agent (compound A below) 0.01 g
Methyl ethyl ketone 3.9g

  This was attached to a metal frame and heated in a thermostatic bath at 125 ° C. for 3 minutes to align the discotic liquid crystal compound. Next, using a 120 W / cm high-pressure mercury lamp, UV irradiation was performed for 30 seconds to crosslink the discotic liquid crystal compound. The temperature at the time of UV curing was set to 80 ° C., and then allowed to cool to room temperature. In this way, the phase difference region 3 was manufactured.

  Using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments Co., Ltd.), the light incident angle dependence of Re in the retardation region 3 was measured, and the cellulose acetate film (Re = 5 nm) measured in advance The optical characteristics of only the discotic liquid crystal phase difference layer were calculated by subtracting the contribution of. The front Re was 250 nm. Moreover, Re of the whole laminated body of a cellulose acetate film, alignment film, and retardation region 3 was 255 nm. Further, the tilt angle of the liquid crystal was 90.0 °, and it was confirmed that the discotic liquid crystal was aligned with the optical axis aligned parallel to the substrate with respect to the film surface. The slow axis direction was parallel to the rubbing direction of the alignment film. The optical properties are shown in Table 1.

[Comparative Example 1]
The polarizing plate A was attached to one side of the IPS mode liquid crystal cell 1 so that the absorption axis of the polarizing plate and the slow axis of the rod-shaped liquid crystal in the liquid crystal cell were parallel. Subsequently, the cellulose acetate film of the other polarizing plate A and the cellulose acetate film of the laminate of the cellulose acetate film, the alignment film, and the retardation region 3 were bonded together, and the IPS mode liquid crystal cell was placed on the retardation region 3 side. A liquid crystal display device was manufactured by pasting on the other side of 1.
At this time, the light leakage in the direction of 45 ° azimuth was large, and the change in color when the azimuth was 360 ° at the polar angle of 60 ° was greatly changed compared to the color in front.

[Example 1]
The polarizing plate B is placed on one side of the IPS mode liquid crystal cell 1, the polarizing plate protective film 1 is on the liquid crystal cell side, and the absorption axis of the polarizing film is parallel to the slow axis of the rod-like liquid crystal in the liquid crystal cell. Pasted. Subsequently, the wide viewing angle polarizing plate 1A is arranged on the other side of the IPS mode liquid crystal cell 1, so that the retardation region 1A is on the liquid crystal cell side, and the polarizing plate B is arranged in a crossed Nicols arrangement. A liquid crystal display device was manufactured by pasting.
The light leakage in the direction of 45 ° azimuth was small, and the change in color when the azimuth was 360 ° at a polar angle of 60 ° was almost unchanged compared to the color in front.

[Example 2]
The polarizing plate B is placed on one side of the IPS mode liquid crystal cell 1, the polarizing plate protective film 1 is on the liquid crystal cell side, and the absorption axis of the polarizing film is parallel to the slow axis of the rod-like liquid crystal in the liquid crystal cell. Pasted.
Subsequently, the wide viewing angle polarizing plate 1B is arranged on the other side of the IPS mode liquid crystal cell 1, so that the retardation region 1B is on the liquid crystal cell side, and the polarizing plate B is arranged in a crossed Nicols arrangement. A liquid crystal display device was manufactured by pasting.
The light leakage in the direction of 45 ° azimuth was small, and the change in color when the azimuth was 360 ° at a polar angle of 60 ° was almost unchanged compared to the color in front.

[Example 3]
The polarizing plate B is placed on one side of the IPS mode liquid crystal cell 1, the polarizing plate protective film 1 is on the liquid crystal cell side, and the absorption axis of the polarizing film is parallel to the slow axis of the rod-like liquid crystal in the liquid crystal cell. Pasted.
Subsequently, the wide viewing angle polarizing plate 1C is arranged on the other side of the IPS mode liquid crystal cell 1, so that the retardation region 1C is on the liquid crystal cell side, and the polarizing plate B is in a crossed Nicols arrangement. A liquid crystal display device was manufactured by pasting.
The light leakage in the direction of 45 ° azimuth was small, and the change in color when the azimuth was 360 ° at a polar angle of 60 ° was almost unchanged compared to the color in front.

[Comparative Example 2]
The polarizing plate A was attached to one of the IPS mode liquid crystal cells 1 so that the absorption axis of the polarizing film and the slow axis of the rod-like liquid crystal in the liquid crystal cell were parallel.
Subsequently, a commercially available polycarbonate retardation film (TR film) manufactured by Nitto Denko was bonded to the other side of the IPS mode liquid crystal cell 1, and a polarizing plate A was bonded thereon to produce a liquid crystal display device.
The light leakage in the azimuth angle of 45 degrees was large, and the color change when the azimuth angle was 360 degrees at the polar angle of 60 degrees was larger than the color in front.

[Comparative Example 3]
In Example 1, a liquid crystal display device was produced in the same manner except that the polarizing plate A was used instead of the polarizing plate B, and the polarizing plate 2A was used instead of the polarizing plate 1A.
The light leakage in the direction of 45 ° azimuth was small, but the change in color when the azimuth was swung 360 ° at the polar angle of 60 ° was shifted compared to the color in front.

[Comparative Example 4]
A liquid crystal display device was produced in the same manner as in Example 1, except that the polarizing plate A was used instead of the polarizing plate B, and the polarizing plate 2B was used instead of the polarizing plate 1A.
The light leakage in the direction of 45 ° azimuth was small, but the change in color when the azimuth was swung 360 ° at the polar angle of 60 ° was greatly deviated from the color in front.

[Comparative Example 5]
In Example 1, a liquid crystal display device was produced in the same manner except that the polarizing plate 2A was used instead of the polarizing plate 1A.
The light leakage in the direction of 45 ° azimuth was small, but the change in color when the azimuth was swung 360 ° at the polar angle of 60 ° was shifted compared to the color in front.

[Table 2] shows the presence or absence of a protective film between the retardation region and the polarizing film, and the Rth (nm) of the protective film when the protective film is provided.
Further, the retardation region also indicates Rth (nm) of the protective film on the side opposite to the liquid crystal cell in the polarizing plate on the opposite side across the liquid crystal cell.

The summary of evaluation is shown in [Table 2].
For light leakage in the direction of 45 ° azimuth, the following index was used for evaluating the maximum luminance within 60 ° polar angle with respect to the front black luminance.
○ Less than 20 times the front black brightness,
△ 20 times or more and less than 100 times the front black luminance,
× More than 100 times the front black brightness.
The following indices were used for the change in color between the polar angle of 60 degrees and the front.
◎ There is almost no deviation compared to the color in front.
○ There is a slight shift compared to the color in front.
× The range where the deviation is large compared to the color of the front and cannot be put to practical use.

Table 2

<Production of Phase Difference Regions 4 and 5>

  In a reaction vessel purged with nitrogen, 80 g (0.471 mol) of 5-phenyl-bicyclo [2.2.1] hept-2-ene, 8.85 g of 1-hexene as a molecular weight regulator, and 160 g of toluene as a solvent. Charged and heated to 80 ° C. As a polymerization catalyst, 0.63 mL of a toluene solution of triethylaluminum (concentration: 0.6 mol / L) and 1.88 mL of a toluene solution of methanol-modified tungsten hexachloride (concentration: 0.025 mol / L) were added, By reacting at 80 ° C. for 4 hours, a polymer solution containing a ring-opening polymer was obtained.

The obtained polymer solution was put in an autoclave, and 300 g of toluene was further added. Next, RuHCl (CO) [P (C ₆ H ₅ ) ₃ ] ₃ as a hydrogenation catalyst is added to the charged amount of monomer (5-phenyl-bicyclo [2.2.1] hept-2-ene). An amount of 500 ppm was added, and a hydrogenation reaction was performed under the conditions of hydrogen gas pressure: 9 to 10 MPa, reaction temperature: 160 to 165 ° C., and reaction time: 4 hours. After the reaction was completed, the obtained reaction solution was poured into a large amount of methanol and precipitated to obtain a hydrogenated ring-opening polymer. This hydrogenated ring-opening polymer is referred to as “polymer P1”.

The polymer P1 has a weight average molecular weight (Mw): 8.46 × 10 ⁴ , a number average molecular weight (Mn): 2.01 × 10 ⁴ , a molecular weight distribution (Mw / Mn): 4.21, an intrinsic viscosity [η ]: 0.59, Glass transition temperature (Tg): 69 ° C.

  After dissolving 15.0 g (phenyl group content: 0.029 mol) of the polymer P in 20 mL of nitrobenzene, 7.5 g (0.043 mol) of phenylsulfonyl chloride was added and stirred. To this solution, 3.8 g (0.029 mol) of aluminum chloride was added and reacted at 50 ° C. for 3 hours. The reaction mixture was precipitated in isopropanol, redissolved in methylene chloride, and filtered through celite. Subsequently, 2.0 g of light yellow solid polymer was obtained by reprecipitation in methanol. This polymer is referred to as “polymer P2”.

The polymer P2 has a weight average molecular weight (Mw): 7.47 × 10 ⁴ , a number average molecular weight (Mn): 1.97 × 10 ⁴ , a molecular weight distribution (Mw / Mn): 3.80, a glass transition temperature ( Tg): 119 ° C. Further, this polymer P2 was analyzed by ¹ H-NMR, and from the integral ratio of the signal at 6.8 ppm to 8.2 ppm derived from the benzene ring, among the phenyl groups of the polymer P1 side chain, As a result of calculating the ratio of phenylsulfonyl group substitution (phenylsulfonylation rate) by the above reaction, it was 31 mol%.

In addition, since a signal was observed at 7.81 ppm, it was confirmed that the substitution position of the phenylsulfonyl group with respect to the phenyl group of the polymer P1 side chain was the para position or the ortho position. (A signal was not observed in the vicinity of 7.7 ppm, so it was confirmed that there was almost no substitution at the meta position.
The obtained polymer P2 was dissolved in methylene chloride (concentration: 25% by weight) and cast on a flat glass plate to obtain a film having a dry film thickness of 100 μm, and further, at 60 ° C. under vacuum for 12 hours. Allowed to dry.
The obtained film was held at a temperature of glass transition temperature + 10 ° C. for 5 minutes using a tensile testing machine with a thermostatic bath (manufactured by Instron, model MODEL5567), and then uniaxially stretched under the same temperature condition. . The draw ratio was 2.0 times.
As described above, the phase difference region 4 was created, and its optical characteristics are shown in Table 3.

<Synthesis Example 1> Synthesis of Cyclic Olefin Resin (Resin A1) 8-Methyl-8-methoxycarbonyltetracyclo [4.4.0.1 _2,5 . 1 _7,10 ] -3-dodecene (specific monomer) 250 parts, 1-hexene (molecular weight regulator) 18 parts, toluene (ring-opening polymerization reaction solvent) 750 parts in a nitrogen-substituted reaction vessel Charge and heat the solution to 60 ° C. Next, 0.62 parts of a toluene solution of triethylaluminum (1.5 mol / l) as a polymerization catalyst and tungsten hexachloride modified with t-butanol and methanol (t-butanol: methanol: tungsten) were added to the solution in the reaction vessel. = 0.35 mol: 0.3 mol: 1 mol) of a toluene solution (concentration 0.05 mol / l) 3.7 parts was added, and the system was heated and stirred at 80 ° C. for 3 hours to open the ring. Polymerization reaction was performed to obtain a ring-opening polymer solution. The polymerization conversion rate in this polymerization reaction was 97%, and the intrinsic viscosity (ηinh) of the obtained ring-opened polymer measured in chloroform at 30 ° C. was 0.75 dl / g.

The autoclave was charged with 4,000 parts of the ring-opening polymer solution thus obtained, and 0.48 part of RuHCl (CO) [P (C ₆ H ₅ ) ₃ ] ₃ was added to the ring-opening polymer solution. Then, the hydrogenation reaction was performed by heating and stirring for 3 hours under the conditions of a hydrogen gas pressure of 100 kg / cm ² and a reaction temperature of 165 ° C.

  After cooling the obtained reaction solution (hydrogenated polymer solution), the hydrogen gas was released. This reaction solution was poured into a large amount of methanol to separate and recover the coagulated product, and dried to obtain a hydrogenated polymer (hereinafter referred to as “resin A1”).

<Synthesis Example 3> Synthesis of negative birefringent polymer (resin B) 2,95,541 g of 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 30.4259 g of 9,9-bis (4-aminophenyl) fluorene Was dissolved in 1000 g of N-methyl-2-pyrrolidone and reacted at room temperature for 6 hours. The obtained reaction product liquid was poured into a large excess of methyl alcohol to precipitate polyamic acid, then washed with methyl alcohol, and dried under reduced pressure at 40 ° C. for 15 hours to obtain a logarithmic viscosity of 1.44 dl / g. 60.2 g of polymer was obtained. 30.0 g of this polymer was dissolved in 570 g of γ-butyrolactone, 21.6 g of pyridine and 16.74 g of acetic anhydride were added to this solution, and imidation treatment was carried out at 120 ° C. for 3 hours. By pouring into methyl alcohol and precipitation, a polymer having a logarithmic viscosity of 1.35 dl / g (hereinafter referred to as “resin B”) was obtained.

  When this resin B is formed into a film by the method described later and uniaxially stretched 1.1 times at 200 ° C. in a state of residual solvent of 20 wt%, the refractive index in the direction perpendicular to the refractive index in the stretching direction becomes larger. The resin B was confirmed to be a negative birefringent polymer.

<Production Example 1> Resin film (a1-1)
Resin A1 is dissolved in toluene so as to have a concentration of 30% (solution viscosity at room temperature is 30,000 mPa · s), and pentaerythrityl tetrakis [3- (3,5-di-t-butyl) is used as an antioxidant. -4-hydroxyphenyl) propionate] is added in an amount of 0.1 part by weight based on 100 parts by weight of the polymer, and a differential pressure is within 0.4 MPa using a metal fiber sintered filter having a pore diameter of 5 μm manufactured by Nippon Pole. The solution was filtered while controlling the flow rate of the solution.
The obtained polymer solution was treated with an acrylic acid-based INVEX lab coater installed in a Class 1000 clean room and made hydrophilic (easy-to-adhesive) surface treatment with a 100 μm thick PET film (Toray Industries, Inc.) The film thickness after drying was applied to 200 μm on Lumirror U94 manufactured by Co., Ltd., and this was subjected to primary drying at 50 ° C. and then secondary drying at 90 ° C. The resin film peeled off from the PET film was designated as (a1-1). The residual solvent amount of the obtained film was 0.5%, and the total light transmittance was 93%.

<Production Example 3> Resin film (b-1)
A resin film (b-1) having a thickness of 15 μm was prepared in the same manner as in Production Example 1 except that resin B was used instead of resin A1, and γ-butyrolactone was used instead of toluene to make the concentration 10%. Obtained. The residual solvent amount of the obtained film was 20%, and the total light transmittance was 91%.

  A polyester film having a stretching temperature of 180 ° C. (Tg + 10 ° C.) and a shrinkage of 30% is attached to the surface of the resin film (a1-1) with an adhesive so that the shrinking direction is perpendicular to the stretching direction. The film was stretched 2.0 times at a stretching speed of 300% / min. Next, it is cooled while maintaining this state for 1 minute in an atmosphere of 150 ° C. (Tg−20 ° C.), further cooled to room temperature and taken out, and the polyester film is peeled off to obtain a retardation film (a1-2). Obtained.

  Next, the polyester film was similarly applied to the surface of the resin film (b-1), and stretched 2.0 times at a stretching temperature of 180 ° C. and a stretching speed of 300% / min. Subsequently, it was cooled while maintaining this state for 1 minute in an atmosphere of 150 ° C., further cooled to room temperature and taken out. After the polyester film was peeled off, the amount of residual solvent was reduced to 0.00 in a 100 ° C. vacuum dryer. The film was allowed to stand at 5% or less and dried to obtain a retardation film (b-2).

  While adjusting the retardation films (a1-2) and (b-2) thus obtained using an acrylic UV adhesive so that the adhesive layer thickness is 5 μm or less, the respective stretching directions Were laminated so that the two were parallel to each other to obtain a retardation region 5. Table 3 shows the optical characteristics of the obtained retardation region 5.

<Preparation of polarizing plates 4A and 5A (polarizing plates of Reference Examples 1 and 2)>
A polarizing film was produced in the same manner, and a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was subjected to saponification treatment and attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive. . Further, the manufactured retardation regions 4 and 5 are attached to the other surface of the polarizing film with a known pressure-sensitive adhesive or adhesive so that the slow axis is parallel to the absorption axis of the polarizing film. Plates 4A and 5A were formed.

[Example 4]
The polarizing plate B is placed on one side of the IPS mode liquid crystal cell 1, the polarizing plate protective film 1 is on the liquid crystal cell side, and the absorption axis of the polarizing film is parallel to the slow axis of the rod-like liquid crystal in the liquid crystal cell. Pasted. Subsequently, a wide viewing angle polarizing plate 4A is arranged on the other side of the IPS mode liquid crystal cell 1, so that the phase difference region 4A is on the liquid crystal cell side, and the polarizing plate B is arranged in a crossed Nicols arrangement. A liquid crystal display device was manufactured by pasting.
The light leakage in the direction of 45 ° azimuth was small, and the change in color when the azimuth was 360 ° at a polar angle of 60 ° was almost unchanged compared to the color in front.
The display characteristics are shown in Table 4.

[Example 5]
The polarizing plate B is placed on one side of the IPS mode liquid crystal cell 1, the polarizing plate protective film 1 is on the liquid crystal cell side, and the absorption axis of the polarizing film is parallel to the slow axis of the rod-like liquid crystal in the liquid crystal cell. Pasted.
Subsequently, the wide viewing angle polarizing plate 5A is arranged on the other side of the IPS mode liquid crystal cell 1, so that the retardation region 5A is on the liquid crystal cell side, and the polarizing plate B is arranged in a crossed Nicols arrangement. A liquid crystal display device was manufactured by pasting.
The light leakage in the direction of 45 ° azimuth was small, and the change in color when the azimuth was 360 ° at a polar angle of 60 ° was almost unchanged compared to the color in front.
The display characteristics are shown in Table 4.

Table 3

Table 4

It is the schematic which shows the pixel area example of the liquid crystal display device of this invention. It is the schematic which shows the example of the liquid crystal display device of this invention. It is the schematic which shows the example of the liquid crystal display device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal element pixel area 2 Pixel electrode 3 Display electrode 4 Rubbing direction 5a, 5b Director of liquid crystal compound at the time of black display 6a, 6b Director of liquid crystal compound at the time of white display 7 Protective film of the first polarizing film 8 First polarized light Polarization absorption axis of the film 9 First polarizing film 10 Protective film of the first polarizing film 11 Slow axis 12a, 12b of liquid crystal cell when displaying black 13 Slow axis 14 of phase difference region 14 Phase difference region 15 Polarization absorption axis of two polarizing film 16 Second polarizing film 17 Outer protective film of second polarizing film 18 Liquid crystal layer 19 Liquid crystal cell side protective film of second polarizing film

Claims (7)

A polarizing plate and a polarizing plate having a protective film on both sides thereof,
One of the protective films is a retardation region that satisfies the following formulas (1) and (2):
A wide viewing angle polarizing plate, wherein a slow axis of the retardation region is laminated substantially orthogonally or substantially parallel to an absorption axis of a polarizing film.
0.4 <Nz <0.6 (1)
0.4 <(Re (λ) / λ) <0.6 (2)
Here, Nz and (Re (λ) / λ) are values at the measurement wavelength λ (400 nm to 700 nm), and Nz = Rth / Re + 0.5. A retardation region containing cellulose acylate is further included between the retardation region satisfying the formulas (1) and (2) and the polarizing film of the wide viewing angle polarizing plate according to claim 1, A wide viewing angle polarizing plate characterized in that a retardation region containing an acylate satisfies the following formulas (3) and (4).
0 ≦ Re <30 (3)
−20 <Rth <20 (4)   The wide viewing angle polarizing plate according to claim 1 or 2, wherein a retardation region satisfying the formulas (1) and (2) is produced by stretching.   The wide viewing angle polarizing plate according to any one of claims 1 to 3, wherein the retardation region satisfying the formulas (1) and (2) comprises polycarbonate.   The wide viewing angle polarizing plate according to any one of claims 1 to 3, wherein the retardation region satisfying the formulas (1) and (2) comprises a cyclic polyolefin.   A liquid crystal display device comprising: a liquid crystal panel that sandwiches a liquid crystal layer between a pair of substrates; and a pair of polarizing plates that sandwich the liquid crystal panel, wherein the polarizing plates are according to claim 1. A liquid crystal display device characterized by being a wide viewing angle polarizing plate. The liquid crystal display device according to claim 6.
One polarizing plate of the pair of polarizing plates sandwiching the liquid crystal panel is the wide viewing angle polarizing plate according to any one of claims 1 to 5, and the other polarizing plate is protected on the polarizing film and both sides thereof. A polarizing plate having a film, wherein one of the protective films includes a retardation region containing cellulose acylate, and the retardation region containing the cellulose acylate satisfies the following formulas (3) and (4): A liquid crystal display device characterized by the above.
0 ≦ Re <30 (3)
−20 <Rth <20 (4)

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