Liquid crystal panel and polarizing laminate for use in the liquid crystal panel

Abstract

A liquid crystal panel which is capable of significantly reducing a thickness thereof as compared to conventional liquid crystal panels, and, when used in a liquid crystal display device using a liquid crystal cell such as an IPS-type liquid crystal cell, reducing oblique light leakage in a black state of the liquid crystal display device to enhance contrast.

Claims

1. A liquid crystal panel comprising: a liquid crystal cell having a liquid crystal layer containing liquid crystal molecules oriented in one direction in a plane thereof in an electric field-off state; a first polarizer disposed on a side of the liquid crystal cell; a second polarizer disposed on a side of the liquid crystal cell opposite to the side of the liquid crystal cell having the first polarizer, the second polarizer having an absorption axis that orthogonally intersects an absorption axis of the first polarizer; and a first retardation layer and a second retardation layer between the first polarizer and the liquid crystal cell and arranged in this order from a side of the first polarizer, wherein the second retardation layer is laminated to the liquid crystal cell through a light-sensitive adhesive layer, the light-sensitive adhesive layer having a storage elastic modulus of 310.sup.5 to 110.sup.8 Pa (25 C.), the first retardation layer is configured to satisfy the relationship of nx1>ny1>nz1, where: nx1 represents a refractive index in an in-plane slow axis direction, ny1 represents a refractive index in an in-plane fast axis direction, and nz1 represents a refractive index in a thickness-wise direction, the second retardation layer is configured to satisfy the relationship of nz2>nx2>ny2, where nx2 represents a refractive index in the in-plane slow axis direction, ny2 represents a refractive index in the in-plane fast axis direction, and nz2 represents a refractive index in the thickness-wise direction, the slow axis of the first retardation layer is parallel to the slow axis of the second retardation layer, each of the first polarizer and the second polarizer have a thickness of 10 m or less, with optical properties including a single transmittance of 40.0% or more and a polarization degree of 99.8% or more, the second polarizer is directly bonded to the liquid crystal cell through a pressure-sensitive adhesive layer with the absorption axis thereof being parallel to an orientation direction of the liquid crystal molecules of the liquid crystal cell in the electric field-off state, the second polarizer has a first protective layer laminated thereto at a side opposite to the liquid crystal cell, through a pressure-sensitive adhesive layer, the first protective layer has a thickness of 10 to 50 m, with a moisture permeability of 200 g/m.sup.2 or less, the first retardation layer has a thickness of 25 m or less, with a moisture permeability of 200 g/m.sup.2 or less, wherein a value of nxy1 and a value of nxz1 are, respectively, 0.0036 or more, and 0.0041 or more, and Re and Rth are, respectively, in the range of 90 nm to 140 nm and the range of 100 nm to 240 nm, where nxy1 represents a difference between the refractive index nx1 in the slow axis direction and the refractive index ny1 in the fast axis direction, nxz1 represents a difference between the refractive index nx1 in the slow axis direction and the refractive index nz1 in the thickness direction, Re represents an in-plane retardation, and Rth represents a thicknesswise retardation expressed in the formula Rth=(nx1nz1)d1, where d1 represents a thickness of the first retardation layer, the second retardation layer has a thickness of 20 m or less, wherein a value of nxy2 and a value of nxz2 are, respectively, 0.0008 or more, and 0.0030 or less, and Re and Rth are, respectively, in the range of 15 nm to 50 nm and the range of 110 nm to 60 nm, where nxy2 represents a difference between the refractive index nx2 in the slow axis direction and the refractive index ny2 in the fast axis direction, nxz2 represents a difference between the refractive index nx2 in the slow axis direction and the refractive index nz2 in the thickness direction, Re represents an in-plane retardation, and Rth represents a thicknesswise retardation expressed in the formula Rth=(nx2nz2)d2, where d2 represents a thickness of the second retardation layer, the first polarizer has a second protective layer laminated thereto at a side opposite to the first retardation layer, the second protective layer has a thickness of 50 m or and a moisture permeability of 200 g/m.sup.2 or less, and the thickness of the first retardation layer is greater than the thickness of the second retardation layer.

2. A laminate of polarizer and retardation layers configured to be used in a liquid crystal panel which comprises a liquid crystal cell having a liquid crystal layer containing liquid crystal molecules oriented in one direction in a plane thereof in an electric field-off state, and a pair of polarizers disposed, respectively, on opposite sides of the liquid crystal cell with absorption axes thereof orthogonally intersecting each other, wherein the laminate is between the liquid crystal cell and one of the polarizers of the pair of polarizers, the laminate includes a first retardation layer disposed adjacent to the one polarizer, and a second retardation layer laminated to the first retardation layer through a light-sensitive adhesive layer, the light-sensitive adhesive layer having a storage elastic modulus of 310.sup.5 to 110.sup.8 Pa (25 C.), the first retardation layer is configured to satisfy the relationship of nx1>ny1>nz1, where nx1 represents a refractive index in an in-plane slow axis direction, ny1 represents a refractive index in an in-plane fast axis direction, and nz1 represents a refractive index in a thickness-wise direction, the second retardation layer is configured to satisfy the relationship of nz2>nx2>ny2, where nx2 represents a refractive index in the in-plane slow axis direction, ny2 represents a refractive index in the in-plane fast axis direction, and nz2 represents a refractive index in the thickness-wise direction, a slow axis of the first retardation layer is parallel to a slow axis of the second retardation layer, the first retardation layer has a thickness of 25 m or less, with a moisture permeability of 200 g/m.sup.2 or less, wherein a value of nxy1 and a value of nxz1 are, respectively, 0.0036 or more, and 0.0041 or more, and Re and Rth are, respectively, in the range of 90 nm to 140 nm and the range of 100 nm to 240 nm, where nxy1 represents a difference between the refractive index nx1 in the slow axis direction and the refractive index ny1 in the fast axis direction; nxz1 represents a difference between the refractive index nx1 in the slow axis direction and the refractive index nz1 in the thickness (z-axis) direction, and Re represents an in-plane retardation, and Rth represents a thicknesswise retardation expressed in the formula Rth=(nx1nz1)d1, where d1 represents a thickness of the first retardation layer, the second retardation layer has a thickness of 20 m or less, wherein a value of nxy2 and a value of nxz2 are, respectively, 0.0008 or more, and 0.0030 or less, and Re and Rth are, respectively, in the range of 15 nm to 50 nm and the range of 110 nm to 60 nm, where nxy2 represents a difference between the refractive index nx2 in the slow axis direction and the refractive index ny2 in the fast axis direction, nxz2 represents a difference between the refractive index nx2 in the slow axis direction and the refractive index nz2 in the thickness-wise direction; Re represents an in-plane retardation, and Rth represents a thicknesswise retardation expressed in the formula Rth=(nx2nz2)d2, where d2 represents a thickness of the second retardation layer, and the thickness of the first retardation layer is greater than the thickness of the second retardation layer.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a fragmentally cross-sectional view illustrating a liquid crystal panel according to one embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

(2) FIG. 1 is a sectional view illustrating a liquid crystal panel according to one embodiment of the present invention. In this FIGURE, the liquid crystal panel 1 comprises an IPS-type liquid crystal cell 10. A first polarizer 11 and a second polarizer 21 are disposed, respectively, on the opposite sides of the liquid crystal cell 10. A first retardation layer 12 and a second retardation layer 13 are disposed between the first polarizer 11 and the liquid crystal cell 10, and arranged in this order from the side of the first polarizer 11.

(3) Each of the first polarizer 11 and the second polarizer 21 is a type obtained by impregnating a stretched polyvinyl alcohol-based resin layer with iodine, wherein each of them has a thickness of 10 m or less, typically, 5 m. As the first polarizer 11, a type exhibiting optical properties including a single transmittance of 40.8% and a polarization degree of 99.99% or more is typically used. As the second polarizer 21, a type exhibiting optical properties including a single transmittance of 42.8% and a polarization degree of 99.95% or more is typically used.

(4) The first retardation layer 12 may be formed using any one of the materials presented as examples suitable for the first retardation layer-forming material. It has a thickness, typically, of 25 m. The first retardation layer 12 is configured to satisfy optical properties including the aforementioned moisture permeability and refractive index, and bonded to a surface of the first polarizer 11.

(5) The second retardation layer 13 may be formed using any one of the materials presented as examples suitable for the second retardation layer-forming material. It has a thickness, typically, of 20 m. The second retardation layer 13 is configured to satisfy optical properties including the aforementioned refractive index, and bonded to a surface of the first retardation layer 12 on a side opposite to the first polarizer 11 through a pressure-sensitive adhesive layer or adhesive layer 14. Further, the second retardation layer 13 is bonded to one of opposite surfaces of the liquid crystal cell 10 through a pressure-sensitive adhesive layer or adhesive layer 15.

(6) For reducing the thickness of the laminate including the polarizer, it is preferable that each of the first retardation layer 12 and the second retardation layer 13 is laminated to the liquid crystal cell through an adhesive layer using a light-curable adhesive. In this case, preferably, the adhesive layer has a storage elastic modulus of 310.sup.5 to 110.sup.8 Pa (25 C.). If the storage elastic modulus is less than 310.sup.5 Pa (25 C.), peeling is likely to occur due to poor adhesive force. On the other hand, if the storage elastic modulus is greater than 110.sup.8 Pa (25 C.), peeling is likely to occur due to poor shock resistance.

(7) The adhesive layer has a thickness, preferably, of 0.1 m to 5.0 m, more preferably, of 0.2 m to 2.0 m. If the thickness is less than 0.1 m, peeling is likely to occur due to poor shock resistance.

(8) The adhesive layer has a peel force (90), preferably, of 0.5 N/15 mm width or more, more preferably, of 1.0 N/15 mm width or more. If the peel force is less than 0.5 N/15 mm width, peeling of the adhesive layer is likely to occur when a surface protective layer is peeled.

(9) As a light-curable adhesive, it is possible to use a type obtained by irradiating with an activation energy ray a composition containing a radical polymerizable compound or an optical radical polymerization initiator, substantially without containing any organic solvent, and having a liquid viscosity of 1 to 100 cp/25 C.

(10) As the radical polymerizable compound, it is possible to use a compound containing an N-vinyl compound and an acrylamide derivative, a (meth)acrylate compound having one (meth)acryloyl group, a (meth)acrylate compound having two or more (meth)acryloyl groups, or the like.

(11) As the optical radical polymerization initiator, it is possible to use an initiator containing a thioxanthone-based initiator.

(12) The above composition may further contain a silane coupling agent having at least one organic group selected from the group consisting of an amino group, an acid anhydride, an epoxy group, a triazine ring and a (meth)acryloyl group.

(13) A protective layer 16 is bonded to a surface of the first polarizer 11 on a side opposite to the first retardation layer 12. The protective layer 16 has a thickness of 40 m, and exhibits a moisture permeability, typically, of 80 g/m.sup.2. An anti-reflection layer 17 is provided on an outer surface of the protective layer 16. The anti-reflection layer 17 has a thickness of 7 m. Specifically, as the protective layer 16 with the anti-reflection layer 17, an acrylic-based protective film with anti-reflection function (DSG 11 produced by Dai Nippon Printing Co., Ltd., thickness: 47 m) may be used. Instead of or in addition to the anti-reflection layer 17, an optical film such as a brightness-enhancing film may be used.

(14) The second polarizer 21 is bonded to the other surface of the liquid crystal cell 10 through a pressure-sensitive adhesive layer 22. A protective layer 23 is bonded to a surface of the second polarizer 21 on a side opposite to the liquid crystal cell 10. The protective layer 23 may have the same configuration as that of the protective layer 16. A brightness-enhancing film 25 is bonded to an outer surface of the protective layer 23 through a pressure-sensitive adhesive layer 24.

(15) When the liquid crystal panel having the above configuration is used in the O-mode, a side of the brightness-enhancing film 25 is positioned on a light source side, and a side of the anti-reflection layer 17 is positioned on a viewing side. On the other hand, when used in the E-mode, the side of the brightness-enhancing film 25 is positioned on the viewing side, and the side of the anti-reflection layer 17 is positioned on the light source side.

EXAMPLES

(16) An example of production of a liquid crystal panel according to the present invention and an evaluation method for the liquid crystal will be described below.

(17) [Measurement of Transmittance and Polarization Degree of Polarizer]

(18) A single transmittance T, a parallel transmittance Tp and a crossed transmittance Tc of a polarizer was measured using a UV-visible spectrophotometer (V7100 produced by JASCO Corporation). As used therein, the term parallel transmittance means a transmittance measured when two polarizers having the same configuration are laminated to allow absorption axes thereof to become parallel to each other, and the term crossed transmittance means a transmittance measured when the two polarizers having the same configuration are laminated to allow the absorption axes thereof to orthogonally intersect each other. On the other hand, the term single transmittance means a transmittance of a single polarizer. Each value of T, Tp and Tc is a Y value measured by the 2-degree visual field (C light source) of JIS Z8701 and corrected for spectral luminous efficacy. The measurement was performed in a state in which a protective layer (acrylic-based resin film or cycloolefin-based resin film) was laminated to the polarizer in order to facilitate handling of the polarizer. Light absorption of the protective layer is negligibly small as compared to light absorption of the polarizer. Thus, a transmittance of a laminate obtained by laminating the protective layer to the polarizer was determined as a transmittance of the polarizer.

(19) The polarization degree P is derived from the following formula by using the above parallel transmittance and crossed transmittance.
Polarization degree P={(TpTc)/(Tp+Tc)}.sup.1/2100
[Measurement of Thickness]

(20) A thickness of each of the polarizer and the protective layer was measured using a digital micrometer (KC-351C produced by Anritsu Corporation).

(21) [Measurement of Moisture Permeability]

(22) Moisture permeability was measured based on the moisture permeability test method for moisture-proof packaging material (cup method) described in JIS Z 0208.

(23) [Production of First Polarizer]

(24) An amorphous-polyethylene terephthalate (A-PET) film (produced by Mitsubishi Plastics, Inc., trade name: NOVACLEAR SH046, thickness: 200 m) was preliminarily prepared as a substrate, and a surface thereof was subjected to a corona treatment (58 W/m.sup.2/min) Further, PVA (polymerization degree: 4,200, saponification degree: 99.2%) added with 1 wt % of an acetoacetyl-modified PVA (produced by The Nippon Synthetic Chemical Industry Co., Ltd., trade name GOHSEFIMER Z200 (polymerization degree: 1,200, saponification degree: 99.0% or more, acetoacetyl modification degree: 4.6%)) was preliminarily prepared, and applied to the corona-treated surface of the substrate to form a film thereon in such a manner as to allow the film to have a thickness of 12 m after drying. Then, the film was dried by hot air in an atmosphere at 60 C. for 10 minutes to prepare a laminate of the substrate and a PVA-based resin layer provided on the substrate.

(25) Subsequently, the laminate was stretched in air at 130 C., at a stretching ratio of 2.0 times, to form a stretched laminate. Then, a step of immersing the stretched laminate in an insolubilizing aqueous boric acid solution at a solution temperature of 30 C. for 30 seconds to insolubilize a PVA layer comprised in the stretched laminate and containing oriented PVA molecules was performed. The insolubilizing aqueous boric acid solution in this step contained 3 weight parts of boric acid with respect to 100 weight parts of water. The stretched laminate after the insolubilization step was dyed to form a dyed laminate. This dyed laminate was obtained by immersing the stretched laminate in a dyeing solution to adsorb iodine to the PVA layer comprised in the stretched laminate. The dyeing solution contained iodine and potassium iodide. A solution temperature of the dyeing solution was set at 30 C., and an iodine concentration and a potassium iodide were set, respectively, in the range of 0.08 to 0.25 weight % and in the range of 0.56 to 1.75 weight %, using water as a solvent. A concentration ratio of iodine to potassium iodide was set to 1:7. As dyeing conditions, the iodine concentration and an immersion time were set to allow a single transmittance of a PVA-based resin layer constituting a polarizer to become 40.9%.

(26) Subsequently, a step of immersing the dyed laminate in a cross-linking aqueous boric acid solution at 30 C. for 60 minutes to subject PVA molecules of the PVA layer having iodine adsorbed thereto to a cross-linking treatment. The cross-linking aqueous boric acid solution in this cross-linking step contained 3 weight parts of boric acid with respect to 100 weight parts of water, and 3 weight parts of potassium iodide with respect to 100 weight parts of water. Then, the obtained dyed laminate was further stretched in an aqueous boric acid solution at a stretching temperature of 70 C., in the same direction as that in the previous in-air stretching, at a stretching ratio of 2.7 times to attain an ultimate total stretching ratio of 5.4 times, thereby obtaining an optical film laminate comprising a polarizer for test sample. The aqueous boric acid solution used in this stretching step contained 4.0 weight parts of boric acid with respect to 100 weight parts of water, and 5 weight parts of potassium iodide with respect to 100 weight parts of water. The obtained optical film laminate was taken out from the aqueous boric acid solution, and boric acid adhering onto a surface of the PVA layer was washed away by an aqueous solution containing 4 weight parts of potassium iodide with respect to 100 weight parts of water. The washed optical film laminate was dried through a drying step using a hot air at 60 C. to obtain a 5 m-thick polarizer laminated to the PET film.

(27) [Production of Second Polarizer]

(28) Except that the iodine concentration of the dyeing solution or bath and the immersion time were changed to allow a PVA layer constituting a finally-formed polarizer to have a single transmittance of 42.8%, a second polarizer was prepared in the same manner as that for the first polarizer.

(29) [Production of Protective Layer]

(30) Methacrylic resin pellets having a glutarimide ring unit were dried under 100.5 kPa at 100 C. for 12 hours, and extruded from a T-die at a die temperature of 270 C. by using a single-screw extruder to form a film. Then, this film was stretched in a conveyance direction thereof (hereinafter referred to as the MD direction) in an atmosphere at a temperature higher than a glass transition temperature Tg of the resin by 10 C., and further stretched in a direction perpendicular to the MD direction (this direction will hereinafter be referred to as the TD direction) in an atmosphere at a temperature higher than the glass transition temperature Tg of the resin by 7 C., to obtain a 40 m-thick acrylic-based protective film.

(31) [Protective Film of First Polarizer]

(32) An acrylic-based protective film with anti-reflection function (DSG 11 produced by Dai Nippon Printing Co., Ltd., thickness: 47 m) was used.

Production Examples

Example of Production of First Retardation Layer

Production Example N-1

(33) A commercially-available polymer film consisting mainly of a cyclic polyolefin-based polymer (produced by LSR Corporation, trade name ARTON FILM FEKP 100 (thickness: 100 m)) was subjected to fixed-end uniaxial stretching using a tenter stretching machine, in a width direction (TD direction) at 147 C., in such a manner as to have a film width 4.3 times greater than its original film width (transverse stretching step). The obtained film had a thickness of 23 m, and was a negative biaxial plate having a fast axis in the MD direction (nx>ny>nz).

Production Example N-2

(34) A commercially-available polymer film consisting mainly of a cyclic polyolefin-based polymer (produced by LSR Corporation, trade name ARTON FILM FEKP 130 (thickness: 130 m)) was subjected to fixed-end uniaxial stretching using a tenter stretching machine, in a width direction at 145 C., in such a manner as to have a film width 3.0 times greater than its original film width (transverse stretching step). The obtained film had a thickness of 20 m, and was a negative biaxial plate having a fast axis in the MD direction (nx>ny>nz).

Production Example N-3

(35) A composition obtained by melting and mixing a cyclic olefin-based resin (ZEONOR 1420R produced by ZEON Corporation) using a twin-screw melt extruder was extruded using a single-screw extruder having a T-die attached thereto to obtain a 30 m-thick cyclic olefin-based resin film.

(36) The obtained film was subjected to fixed-end uniaxial stretching using a tenter stretching machine, in a width direction at 145 C., in such a manner as to have a film width 4.3 times greater than its original film width (transverse stretching step). The obtained film had a thickness of 7 m, and was a negative biaxial plate having a fast axis in the MD direction (nx>ny>nz).

Production Example N-4

(37) A commercially-available polymer film consisting mainly of a cyclic polyolefin-based polymer (produced by LSR Corporation, trade name ARTON FILM FEKP 100 (thickness: 130 m)) was subjected to fixed-end uniaxial stretching using a tenter stretching machine, in a width direction at 147 C., in such a manner as to have a film width 3.4 times greater than its original film width (transverse stretching step). The obtained film had a thickness of 38 m, and was a negative biaxial plate having a fast axis in the MD direction (nx>ny>nz).

(38) [Example of Production of Second Retardation Layer]

(39) (Synthesis of Fumarate-Based Resin)

(40) 48 g of hydroxypropyl methylcellulose (produced by Shin-Etsu Chemical Co., Ltd., trade name: METOLOSE 60SH-50), 15601 g of distilled water, 8161 g of fumaric acid diisopropyl ester, 240 g of methacrylic acid (3-ethyl-3-oxetanyl)methyl ester and 45 g of t-butyl peroxypivalate serving as a polymerization initiator were put in a 30-L autoclave equipped with a stirrer, a cooling tube, a nitrogen inlet tube and a thermometer. Subsequently, the mixture was subjected to nitrogen bubbling for one hour, and then held at 49 C. for 24 hours under stirring at 200 rpm to induce radical suspension polymerization. Then, the solution was cooled to room temperature, and a suspension containing created polymer particles was centrifugally separated. The obtained polymer particles was washed twice by distilled water and twice by methanol, and then dried under reduced pressure at 80 C. (yield: 80%).

Production Example P-1

(41) The obtained fumarate-based resin was dissolved in a toluene-methyl ethyl ketone mixed solution (toluene/methyl ethyl ketone: 50 weight %/50 weight %) to form a 20% solution thereof, and then 5 weight parts of tributyl trimellitate serving as a plasticizer was added with respect to 100 weight parts of the fumarate-based resin. The obtained solution was casted on a support substrate of a solution casting apparatus by a T-die method, and dried at 80 C. for 4 minutes and at 130 C. for 4 minutes to obtain a film having a width of 250 mm and a thickness of 18 m. The obtained film was subjected to free-end uniaxial stretching using a roll stretching machine, in the MD direction at 150 C. and at a stretching ratio of 1.04 times (longitudinal stretching step). The obtained film had a thickness of 18 m, and was a positive biaxial plate having a fast axis in the MD direction (nz>nx>ny).

Synthesis of Poly(nitrostyrene)

(42) A solvent-based mixture of nitrobenzene (900 g) and 1,2-dichloroethane (300 g) was put in a three-neck round-bottom flask equipped with a mechanical stirrer, and polystyrene (50.0 g) was dissolved in the mixture under stirring. An acid mixture consisting of nitric acid (86.0 g) and concentrated sulfuric acid (100.0 g) (nitro/styrene equivalent ratio=2/1) was dripped into and added to the stirred mixture for 30 minutes. The obtained mixture was subjected to reaction under nitrogen at room temperature for a total time of 22 hours. The resulting yellow mixture was poured into sodium hydroxide diluted with water to separate an organic layer, and then the organic layer was precipitated in methanol to provide a piece of solid substance. The solid was solved in N,N-dimethylformamide (DMF), and re-precipitated in methanol. The obtained precipitate was subjected to stirring for 2 hours, filtering, repetitive washing with methanol, and drying under vacuum to obtain a slightly yellowish fibrous powder. A yield was 95% or more in total.

Production Example P-2

(43) The obtained poly(nitrostyrene)-based resin was dissolved in cyclopentanone to form a 20% solution thereof, and the solution was casted on a support substrate of a solution casting apparatus by a T-die method. Then, the cast solution was dried at 40 C. for 4 minutes and at 130 C. for 4 minutes, and further dried under vacuum to obtain a film having a width of 250 mm and a thickness of 3 m. The obtained film was subjected to free-end uniaxial stretching using a roll stretching machine, in the MD direction at 184 C. and at a stretching ratio of 1.06 times (longitudinal stretching step). The obtained film had a thickness of 3 m, and was a positive biaxial plate having a fast axis in the MD direction (nz>nx>ny).

Production Example P-3

(44) A pellet-shaped resin of polystyrene resin (XAREC 130ZC produced by Idemitsu Kosan Co., Ltd.) was extruded at 290 C. using a single-screw extruder and a T-die, and a resulting sheet-shaped molten resin was cooled by a cooling drum to obtain a 20 m-thick film. This film was subjected to free-end uniaxial stretching using a roll stretching machine, in the MD direction at 125 C. and at a stretching ratio of 1.5 times to obtain a retardation film having a fast axis in the MD direction (longitudinal stretching step). The obtained film was further subjected to fixed-end uniaxial stretching using a tenter stretching machine, in a width direction at 130 C., in such a manner as to have a film width 1.6 times greater than a film width just after the above longitudinal stretching, thereby obtaining a 10 m-thick biaxially-stretched film (transverse stretching step). The obtained film was a positive biaxial plate having a fast axis in the MD direction (nz>nx>ny).

Production Example P-4

(45) A pellet-shaped resin of styrene-maleic anhydride polymer (DYLARK D232 produced by NOVA Chemicals Japan Ltd.) was extruded at 270 C. using a single-screw extruder and a T-die, and a resulting sheet-shaped molten resin was cooled by a cooling drum to obtain a 77 m-thick film. This film was subjected to free-end uniaxial stretching using a roll stretching machine, in the MD direction at 125 C. and at a stretching ratio of 1.7 times to obtain a retardation film having a fast axis in the MD direction (longitudinal stretching step). The obtained film was further subjected to fixed-end uniaxial stretching using a tenter stretching machine, in a width direction at 135 C., in such a manner as to have a film width 1.8 times greater than a film width just after the above longitudinal stretching, thereby obtaining a 33 m-thick biaxially-stretched film (transverse stretching step). The obtained film was a positive biaxial plate having a fast axis in the MD direction (nz>nx>ny).

(46) [Production of Laminate Consisting of First Polarizer, First Retardation Layer, Second Retardation Layer and Protective Layer]

(47) The first retardation layer N-1 prepared in the above manner was laminated to the 5 m-thick polarizer comprised in the laminate prepared in the example of production of the first polarizer, specifically, to a surface of the 5 m-thick polarizer on a side opposite to the PET film of the laminate, through a UV-curable adhesive. Subsequently, after the PET film was peeled from the laminate, the acrylic-based protective film with anti-reflection function was laminated to the polarizer through a UV-curable adhesive. Then, the second retardation layer P-1 was further laminated to a surface of the resulting laminate on the side of the first retardation layer N-1, through an acrylic-based pressure-sensitive adhesive (thickness: 5 m), in a roll-to-roll manner, i.e., under a condition that they are conveyed parallel to each other, thereby obtaining a first polarizing laminate.

(48) [Production of Laminate Consisting of Second Polarizer and Protective Film]

(49) The 40 m-thick acrylic-based protective film was laminated to the 5 m-thick polarizer comprised in the laminate prepared in the example of production of the second polarizer, specifically, to a surface of the 5 m-thick polarizer on a side opposite to the PET film of the laminate, through a UV-curable adhesive. Subsequently, the PET film was peeled from the laminate to obtain a second polarizing plate (second polarizing laminate) laminated to the acrylic-based protective film.

(50) [Production of Liquid Crystal Panel]

Example 1

(51) From a slate type PC equipped with an IPS type liquid crystal cell (iPad Retina Display Model produced by Apple Inc.), the liquid crystal cell was taken out, and polarizing plates disposed on the top and bottom sides of the liquid crystal cell were removed. Then, opposite glass surfaces of the liquid crystal cell were cleaned by washing. Subsequently, the first polarizing plate produced in the above manner was laminated to the viewing-side surface of the liquid crystal cell with the absorption axis of the polarizer of the first polarizing laminate oriented in a direction perpendicular to the initial orientation direction of the liquid crystal cell, through an acrylic-based pressure-sensitive adhesive (thickness: 15 m). Then, the second polarizing plate produced in the above manner was laminated to the illumination light source-side surface of the liquid crystal cell with the absorption axis of the polarizer of the second polarizing laminate oriented in a direction parallel to the initial orientation direction of the liquid crystal cell, through an acrylic-based pressure-sensitive adhesive (thickness: 15 m).

Examples 2 to 3

(52) In the example of production of a first polarizing plate, two different types of first polarizing plates were obtained using: the first retardation layer N-2 and the second retardation film P-2; and the first retardation layer N-3 and the second retardation film P-3, instead of the first retardation layer N-1 and the second retardation film P-1. Then, a liquid crystal panel was produced in the same manner as that in Example 1, using each of the obtained first polarizing plates.

Example 4

(53) Except that, in the example of production of a first polarizing plate, each of the first retardation layer N-1 and the second retardation film P-1 was laminated through a light-curable adhesive (storage elastic modulus: 2.610.sup.6, thickness: 2 m), a liquid crystal panel was produced in the same manner as that in Example 1.

Example 5

(54) Except that, in the example of production of a first polarizing plate, each of the first retardation layer N-2 and the second retardation film P-2 was laminated through a light-curable adhesive (storage elastic modulus: 4.010.sup.5, thickness: 2 m), a liquid crystal panel was produced in the same manner as that in Example 1.

Example 6

(55) Except that, in the example of production of a first polarizing plate, each of the first retardation layer N-3 and the second retardation film P-3 was laminated through a light-curable adhesive (storage elastic modulus: 9.010.sup.7, thickness: 2 m), a liquid crystal panel was produced in the same manner as that in Example 1.

(56) [Black-State Brightness]

(57) A block image was displayed on a liquid crystal display device in a dark room at a room temperature of 23, brightness (Y value in an XYZ color coordinate system) was measured using EZContrast 160D (product name) produced by ELDIM SA, and an average of black-state brightness in an azimuth range of 0 to 360 at a polar angle of 60 was calculated. A result of the calculation is presented in Table 2. In Table 2, the term polar angle means an inclination angle with respect to a normal line perpendicular to a screen of the liquid crystal display device, and the term azimuth means a counterclockwise angle with respect to a direction corresponding to three o'clock of a clock dial when viewing the screen from a front side thereof.

(58) TABLE-US-00002 TABLE 2 First retardation layer Average of black- Negative B plate state bright- Mate- moisture ness rial Thickness nxy nxz permeability (cd/cm.sup.2) Example 1 N-1 23 0.0048 0.0052 85 0.73 Example 2 N-2 20 0.0068 0.0095 98 0.74 Example 3 N-3 7 0.0129 0.0206 60 0.75 Con- N-4 38 0.0033 0.0039 78 0.75 parative Exampke 1 Average of black- state Second retardation layer bright- Mate- Positive B plate ness rial Thickness nxy nxz (cd/cm.sup.2) Example 1 P-1 18 0.0014 0.0043 0.73 Example 2 P-2 3 0.0050 0.0217 0.74 Example 3 P-3 10 0.0045 0.0067 0.75 Com- P-4 33 0.0007 0.0026 0.75 parative Example 1

(59) In Examples, the iPad having a brightness-enhancing film was used as a liquid crystal panel for evaluation. Thus, as regards Examples in the Patent Document 3 using a TV panel as a liquid crystal panel, black-state brightness values in the above Table 2 are higher than those presented in Table 3 of the Patent Document 3. However, such black-state brightness values in the above Table 2 are at a sufficiently satisfactory level. The result also shows that the present invention can achieve a totally satisfying compensation effect, despite a reduction in thickness of the retardation layers. Each of the retardation layers in Examples (Inventive Examples) 1 to 3 has a thickness less than that of Comparative Example 1, and exhibits a black-state value less than, or, even at worst, equal to that of Comparative Example 1.

(60) [Thickness of Polarizing Laminate]

(61) The polarizing laminate comprising the protective layer, the polarizer, the first retardation layer and the second retardation layer which are laminated together was measured in thickness using a digital micrometer (KC-351C produced by Anritsu Corporation).

(62) TABLE-US-00003 TABLE 3 First Second Retardation Retardation Thickness of Layer Layer Pressure-sensitive adhesive/Adhesive Polarizing plate Material Material Material Thickness (laminate) Example 1 N-1 P-1 Acrylic-based 5 113 pressure-sensitive adhesive Example 2 N-2 P-2 Acrylic-based 5 95 pressure-sensitive adhesive Example 3 N-3 P-3 Acrylic-based 5 89 pressure-sensitive adhesive Example 4 N-1 P-1 Light-curable adhesive 2 110 Example 5 N-2 P-2 Light-curable adhesive 2 92 Example 6 N-3 P-3 Light-curable adhesive 2 86 Comparative N-4 P-4 Acrylic-based 5 143 Example 1 pressure-sensitive adhesive

(63) It has been verified that the polarizing laminate comprising the first retardation layer and the second retardation layer each laminated using a light-curable adhesive can achieve thickness reduction.

LIST OF REFERENCE SIGNS

(64) 1: liquid crystal panel 10: liquid crystal cell 11: first polarizer 12: first retardation layer 13: second retardation layer 14, 15: pressure-sensitive adhesive layer 16: protective layer 17: anti-reflection layer 21: second polarizer 22, 24: pressure-sensitive adhesive layer 23: protective layer 25: brightness-enhancing film