JP5261346B2 - Liquid crystal panel and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal panel and a liquid crystal display device, which hardly cause light leakage at a corner of the liquid crystal display device on black display even when being used in a high-temperature and high-humidity environment. <P>SOLUTION: The liquid crystal panel includes: a liquid crystal cell 10 provided with a liquid crystal layer including liquid crystal molecules aligned in homogeneous alignment in such a state that an electric field is not present; a first polarizer 21 arranged on one side surface of the liquid crystal cell; a second polarizer 22 arranged on the other side surface of the liquid crystal cell; a first retardation plate 30 which is arranged between the liquid crystal cell and the first polarizer and satisfies the relation of nx<SB>1</SB>&gt;nz<SB>1</SB>&gt;ny<SB>1</SB>; and a second retardation plate 40 which is arranged between the liquid crystal cell and the second polarizer and satisfies the relation of nx<SB>2</SB>&gt;ny<SB>2</SB>&ap;nz<SB>2</SB>, wherein the optical element is arranged in the prescribed direction. Preferably, an absolute value of in-plane retardation Re<SB>0</SB>with respect to light of wavelength 550 nm of the optical element in which the liquid crystal cell, the first retardation plate and the second retardation plate are regarded as one body is (190 nm to 360 nm)&times;(2m+1). <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a liquid crystal cell including a liquid crystal layer including liquid crystal molecules aligned in a homogeneous arrangement in the absence of an electric field, a liquid crystal panel including a pair of polarizers, and a retardation plate. The present invention also relates to a liquid crystal display device using the liquid crystal panel.

  In a liquid crystal display device having an in-plane switching (IPS) type liquid crystal cell, when no electric field is applied, liquid crystal molecules aligned in a substantially horizontal direction are rotated about 45 degrees by applying a horizontal electric field. This controls the transmission (white display) and shielding (black display). A liquid crystal display device having a conventional IPS mode liquid crystal cell viewed the screen from an oblique direction at angles of 45 degrees (azimuth angles of 45 degrees, 135 degrees, 225 degrees, and 315 degrees) with respect to the absorption axis of the polarizing plate. In some cases, there is a problem that the contrast is lowered and a phenomenon (also referred to as color shift) that varies depending on the viewing angle of the display color becomes large. In order to solve this problem, for the purpose of improving contrast and reducing color shift, it has been proposed to dispose an optical compensation layer (retardation plate) having predetermined optical characteristics between a liquid crystal cell and a polarizer (for example, Patent Document 1).

  The above-described problem of image quality deterioration in the oblique direction occurs even in an initial state where the liquid crystal panel is not used. On the other hand, in a liquid crystal display device in which a liquid crystal panel is mounted in combination with a backlight or the like, although it does not exist in the initial state, light leakage occurs at the corner of the liquid crystal display device during black display with use. The occurrence of “unevenness” is a problem. As a cause of such corner unevenness, a dimensional change or a change in optical characteristics due to inferior heat resistance and humidification resistance of the optical compensation layer or the polarizer is considered. Further, in a normal liquid crystal panel, a liquid crystal cell and an optical film such as a polarizer and an optical compensation layer are laminated via an adhesive layer such as an adhesive, but the display surface side (viewing side) of the liquid crystal display device It is also considered that the liquid crystal panel is warped due to the difference in temperature and humidity between the backlight and the backlight side.

  From the viewpoint of solving the problem of such corner unevenness, a method using an optical compensation layer having a predetermined tensile elastic modulus and optical characteristics (for example, Patent Document 2), a method using a polarizer protective film having a predetermined thickness (for example, Patent documents 3, 4) and the like have been proposed.

JP 2006-72309 A JP 2008-217021 A JP 2007-292917 A JP 2009-69720 A

  As described above, it is presumed that a plurality of factors are involved in the occurrence of corner unevenness. Therefore, even by the methods described in Patent Documents 2 to 4, if the liquid crystal panel is left at room temperature after being exposed to a high temperature and high humidity environment, corner unevenness still tends to occur. The present invention has been made to solve such a problem, and an object of the present invention is to provide a liquid crystal panel in which light leakage is unlikely to occur at the corner of the liquid crystal display device during black display even when used in a high temperature and high humidity environment. A liquid crystal display device is provided.

As a result of intensive studies to solve the above problems, the present inventors have arranged a retardation plate having predetermined optical characteristics as in Patent Document 1 between one polarizer and a liquid crystal cell, and It has been found that the occurrence of corner unevenness is eliminated by arranging the A plate between the other polarizer and the liquid crystal cell.

That is, the present invention provides a liquid crystal cell including a liquid crystal layer containing liquid crystal molecules aligned in a homogeneous arrangement in the absence of an electric field, a first polarizer disposed on one side of the liquid crystal cell, and the other of the liquid crystal cell. A second polarizer disposed on the first side, a first retardation plate disposed between the liquid crystal cell and the first polarizer and satisfying nx ₁ > nz ₁ > ny ₁ , and a liquid crystal cell, The present invention relates to a liquid crystal panel including: a second retardation plate that is disposed between the second polarizer and satisfies nx ₂ > ny ₂ ≈nz ₂ . Note that nx ₁ , ny ₁ , and nz ₁ are the refractive index in the slow axis direction in the plane of the first retardation plate, the refractive index in the fast axis direction in the plane, and the refractive index in the thickness direction, respectively. Nx ₂ , ny ₂ , and nz ₂ represent the refractive index in the slow axis direction in the plane of the second retardation plate, the refractive index in the fast axis direction in the plane, and the thickness direction, respectively. Represents the refractive index.

  In the liquid crystal panel of the present invention, the absorption axis direction of the first polarizer and the absorption axis direction of the second polarizer are orthogonal to each other, and the initial alignment direction of the liquid crystal cell and the retardation of the first retardation plate are delayed. The phase axis direction is parallel or orthogonal, and the initial alignment direction of the liquid crystal cell, the slow axis direction of the second retardation plate, and the absorption axis direction of the second polarizer are parallel to each other. is there.

In the liquid crystal panel of the present invention, the absolute value of the in-plane retardation Re ₀ with respect to light having a wavelength of 550 nm of an optical element in which the liquid crystal cell, the first retardation plate, and the second retardation plate are regarded as an integral unit is ( 190 nm to 360 nm) × (2 m + 1) is preferable. However, m represents an integer of 0 or more.

In the first embodiment of the present invention in which the initial alignment direction of the liquid crystal cell and the slow axis direction of the first retardation plate are orthogonal, the liquid crystal cell, the first retardation plate, and the second retardation The absolute value | Re ₀ | of the in-plane retardation with respect to light having a wavelength of 550 nm of the optical element in which the plate is regarded as an integral unit is represented by | Re ₀ | = | Re _cell −Re ₁ + Re ₂ |. On the other hand, in the second embodiment of the present invention in which the initial alignment direction of the liquid crystal cell and the slow axis direction of the first retardation plate are parallel to each other, | Re ₀ | = | Re _cell + Re ₁ + Re ₂ | Is done. Re _cell , Re ₁ , and Re ₂ represent in-plane retardation for light having a wavelength of 550 nm of the liquid crystal cell, the first retardation plate, and the second retardation plate, respectively.

In the liquid crystal panel of the present invention, the liquid crystal cell is preferably in an IPS mode, an FFS mode, or an FLC mode, and more preferably in an IPS mode. It is preferable that the photoelastic coefficient of the first retardation plate is less 2 × ¹⁰ -11 ^m 2 / N, the photoelastic coefficient of the second retardation plate is 2 × ¹⁰ -11 ^m 2 / N or less It is preferable that

  Furthermore, this invention relates to a liquid crystal display device provided with the said liquid crystal panel.

  Since the liquid crystal panel of the present invention includes the second retardation plate (A plate) in addition to the first retardation plate having predetermined optical characteristics, even when used in a high temperature / high humidity environment. In the black display, light leakage hardly occurs at the corners of the liquid crystal display device.

It is a schematic sectional drawing of the liquid crystal panel by one Embodiment of this invention. 1 is a schematic perspective view of a liquid crystal panel according to a first embodiment of the present invention. It is a schematic perspective view of the liquid crystal panel by the 2nd Embodiment of this invention. It is a schematic sectional drawing of the liquid crystal display device by one Embodiment of this invention. It is a figure showing the viewing angle distribution of the black luminance of the liquid crystal panel of Example 14. It is a figure showing the viewing angle distribution of the black luminance of the liquid crystal panel of the comparative example 12.

[Overview of the entire LCD panel]

  FIG. 1 is a schematic cross-sectional view of a liquid crystal panel 100 according to an embodiment of the present invention. FIG. 2A is a schematic perspective view of the liquid crystal panel of the first embodiment of the present invention, and FIG. 2B is a schematic perspective view of the liquid crystal panel of the second embodiment of the present invention. In addition, the aspect ratio of each structural member in these figures and the ratio of thickness are shown differently from the actual thing for the sake of simplicity.

  The liquid crystal panel 100 includes a liquid crystal cell 10, a first polarizer 21 disposed on one side of the liquid crystal cell 10, a second polarizer 22 disposed on the other side of the liquid crystal cell 10, and a liquid crystal cell. 10 and a first retardation plate 30 disposed between the first polarizer 21 and a second retardation plate 40 disposed between the liquid crystal cell 10 and the second polarizer 22. Prepare.

  In the liquid crystal panel of the present invention, the absorption axis direction 21a of the first polarizer and the absorption axis direction 22a of the second polarizer are orthogonal to each other. The initial alignment direction 10n of the liquid crystal cell, the slow axis direction 40e of the second retardation plate, and the absorption axis direction 22a of the second polarizer are parallel to each other. The initial alignment direction 10n of the liquid crystal cell and the slow axis direction 30e of the first retardation plate are parallel or orthogonal. The term “parallel” includes not only completely parallel but also substantially parallel, and the angle is generally within ± 2 °, preferably within ± 1 °, more preferably Within ± 0.5 °. The term “orthogonal” includes not only completely orthogonal but also substantially orthogonal, and the angle is generally in the range of 90 ± 2 °, preferably 90 ± 1 °, more preferably The range is 90 ± 0.5.

  In the first embodiment shown in FIG. 2A, the initial alignment direction 10n of the liquid crystal cell and the slow axis direction 30e of the first retardation plate are perpendicular to each other. In the second embodiment shown in FIG. 2B, The initial alignment direction 10n of the liquid crystal cell and the slow axis direction 30e of the first retardation plate are parallel to each other.

  In practice, any appropriate protective layer is preferably disposed outside the polarizers 21 and 22. Moreover, in another embodiment, another structural member can also be arrange | positioned between each structural member shown in FIG.

  The liquid crystal panel of the present invention may be a so-called O mode or a so-called E mode. The “O-mode liquid crystal panel” refers to a panel in which the absorption axis direction of a polarizer disposed on the light source side of the liquid crystal cell is parallel to the initial alignment direction of the liquid crystal cell. The “E mode liquid crystal panel” refers to a liquid crystal panel in which the absorption axis direction of a polarizer disposed on the light source side of the liquid crystal cell is orthogonal to the initial alignment direction of the liquid crystal cell.

  In both of the first embodiment shown in FIG. 2A and the first embodiment shown in FIG. 2B, when the first polarizer 21 is a light source side polarizer, the initial alignment direction 10n of the liquid crystal cell Since the absorption axis direction 21a of the first polarizer disposed on the light source side is orthogonal, the “E-mode liquid crystal panel” is formed. On the other hand, when the first polarizer 21 is a viewing-side polarizer, the initial alignment direction 10n of the liquid crystal cell 10 and the absorption axis direction 22a of the second polarizer disposed on the light source side are parallel to each other. Therefore, it becomes an “O-mode liquid crystal panel”.

  Hereinafter, the liquid crystal cell, the polarizer, the first retardation plate, and the second retardation plate constituting the liquid crystal panel of the present invention will be sequentially described.

[Liquid Crystal Cell]
Referring to FIG. 1, a liquid crystal cell 10 used in the liquid crystal panel of the present invention has a pair of substrates 11 and 11 ′ and a liquid crystal layer 12 as a display medium sandwiched between the substrates 11 and 11 ′. In a general configuration, one substrate 11 is provided with a color filter and a black matrix, and the other substrate 11 ′ has a switching element for controlling the electro-optical characteristics of the liquid crystal and a gate signal to this switching element. A scanning line to be supplied, a signal line to supply a source signal, a pixel electrode, and a counter electrode are provided. The distance (cell gap) between the substrates 11 and 11 ′ can be controlled by a spacer or the like. For example, an alignment film made of polyimide or the like can be provided on the side of the substrates 11 and 11 ′ in contact with the liquid crystal layer 12.

The liquid crystal layer 12 includes liquid crystal molecules aligned in a homogeneous arrangement in the absence of an electric field. Such a liquid crystal layer (as a result, a liquid crystal cell) is typical when the refractive index in the slow axis direction, the fast axis direction, and the thickness direction of the liquid crystal layer is nx _cell , ny _cell , and nz _cell , respectively. Shows a refractive index distribution of nx _cell > ny _cell ≈ nz _cell .

  Note that ny≈nz includes not only the case where ny and nz are completely the same, but also the case where ny and nz are substantially the same. Specifically, the NZ coefficient represented by NZ = (nx−nz) / (nx−ny) is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. preferable. The same applies to a second retardation plate described later.

  The “initial alignment direction of the liquid crystal cell” refers to the direction in which the in-plane refractive index of the liquid crystal layer resulting from the alignment of the liquid crystal molecules contained in the liquid crystal layer is maximized in the absence of an electric field, The slow axis direction.

  Typical examples of driving modes using a liquid crystal layer exhibiting such a refractive index distribution include an in-plane switching (IPS) mode, a fringe field switching (FFS) mode, and a ferroelectric liquid crystal (FLC) mode. Specific examples of the liquid crystal used in such a drive mode include nematic liquid crystal and smectic liquid crystal. In general, a nematic liquid crystal is used for the IPS mode and the FFS mode, and a smectic liquid crystal is used for the FLC mode. In the liquid crystal panel of the present invention, among the above, an IPS mode liquid crystal cell is preferably used.

  The IPS mode uses a voltage-controlled birefringence (ECB) effect to generate liquid crystal molecules that are homogeneously aligned in the absence of an electric field, for example, between a counter electrode and a pixel electrode formed of metal. The substrate is made to respond with an electric field (also referred to as a transverse electric field) parallel to the substrate. More specifically, for example, Techno Times Publishing “Monthly Display July” p. 83-p. 88 (1997 edition) and “Liquid Crystal vol. 2 No. 4” published by the Japanese Liquid Crystal Society. 303-p. 316 (1998 edition), in the normally black mode, the alignment direction of the liquid crystal cell when no electric field is applied is aligned with the absorption axis of the polarizer on one side so that the upper and lower polarizing plates are If they are arranged orthogonally, the display is completely black without an electric field. When an electric field is present, the transmittance according to the rotation angle can be obtained by rotating the liquid crystal molecules while keeping them parallel to the substrate. The IPS mode includes a super-in-plane switching (S-IPS) mode and an advanced super-in-plane switching (AS-IPS) mode using a V-shaped electrode or a zigzag electrode.

Since the liquid crystal layer 12 includes a liquid crystal component aligned in a homogeneous arrangement, assuming that the thickness of the liquid crystal layer is d _cell , the in-plane retardation Re _cell of the liquid crystal cell 10 with respect to light having a wavelength of 550 nm is Re _cell = (nx _cell − ny _cell ) × d. As described above, the value of Re _cell can be appropriately set within the range in which bright and dark display can be obtained by the rotation operation of liquid crystal molecules, but generally takes a value slightly larger than 275 nm which is a half wavelength (λ / 2), The range is from 300 nm to 400 nm.

[Polarizer]
A polarizer refers to what converts natural light or predetermined polarized light into linearly polarized light. Examples of the first polarizer 21 and the second polarizer 22 of the present invention include high hydrophilicity such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film. Examples of the molecular film include a uniaxially stretched film obtained by adsorbing a dichroic substance such as iodine or a dichroic dye, a polyene-based oriented film such as a dehydrated polyvinyl alcohol product or a dehydrochlorinated polyvinyl chloride product. Among these, a polarizer obtained by adsorbing a dichroic substance such as iodine on a polyvinyl alcohol film and uniaxially stretching is particularly preferable because of its high polarization dichroic ratio. The thickness of these polarizers is not particularly limited, but is generally about 1 to 80 μm.

  In the liquid crystal panel of the present invention, the first polarizer 21 and the second polarizer 22 may be the same or different from each other.

[First retardation plate]
(In-plane retardation)
In the liquid crystal panel of the present invention, the first retardation plate 30 is disposed between the liquid crystal cell 10 and the first polarizer 21. The first retardation plate satisfies nx ₁ > nz ₁ > ny ₁ . nx ₁ , ny ₁ , and nz _{1 respectively} represent the refractive index in the slow axis direction, the refractive index in the fast axis direction, and the refractive index in the thickness direction in the plane of the first retardation plate. Represent.

The first retardation plate preferably satisfies the following formulas (1) and (2).
100 nm ≦ (nx ₁ −ny ₁ ) · d ≦ 350 nm (1)
_{0.1 ≦ (nx 1 -nz 1)} / (nx 1 -ny 1) ≦ 0.9 ··· (2)
However, d ₁ is the thickness of the first retardation plate.

The formula (1) indicates in-plane retardation Re ₁ for light having a wavelength of 550 nm, and Re ₁ = (nx ₁ −ny ₁ ) × d ₁ . Further, the formula (2) shows a NZ coefficient NZ ₁ wavelength 550nm to _light, NZ ₁ = a _{(nx 1 -nz 1) / (} nx 1 -ny 1). Re ₁ is more preferably 120 nm to 330 nm, and further preferably 150 nm to 300 nm. Further, NZ ₁ is more preferably 0.1 to 0.7, and further preferably 0.2 to 0.6.

(material)
Although the material which forms the 1st phase difference plate 30 is not specifically limited, The absolute value of a photoelastic coefficient is 2 * 10 < ^-11 > m < ² > / N or less suitably. The absolute value of photoelastic coefficient, 2 × ¹⁰ -13 ^m, more preferably from ^{2 / N~1 × 10 -11 m 2} / N, 1 × 10 -12 m 2 / N~1 × 10 -11 m ² / N is more preferable. When the absolute value of the photoelastic coefficient is in such a range, a phase difference change is unlikely to occur when a shrinkage stress is generated during heating. Therefore, a change in the optical characteristics of the liquid crystal panel is suppressed. If the photoelastic coefficient is excessively small, the expression of retardation tends to be small, and it may be difficult to make the in-plane retardation Re ₁ within a desired range. The photoelastic coefficient is a value intrinsic to a chemical structure such as a resin. However, the photoelastic coefficient can be suppressed low by copolymerizing or mixing a plurality of components having different signs (positive and negative) of the photoelastic coefficient. Is possible.

  Typical examples of resins that can satisfy such a photoelastic coefficient include cyclic polyolefin resins and cellulose resins, and cyclic polyolefin resins are particularly preferable. The cyclic polyolefin resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers). And graft modified products in which these are modified with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

  Examples of the norbornene-based monomer include norbornene and alkyl and / or alkylidene substituted products thereof such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, and 5-butyl. 2-Norbornene, 5-ethylidene-2-norbornene, and the like, polar substituents such as halogens thereof; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc .; dimethanooctahydronaphthalene, its alkyl and / or alkylidene Substituents and polar group substituents such as halogen such as 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6- Ethyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-oct Hydronaphthalene, 6-ethylidene-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4: 5,8-dimethano -1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a -Octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4: 5 8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene and the like; 3-pentamer of cyclopentadiene, for example, 4,9: 5,8-dimethano-3a, 4 4a, 5,8,8a, 9,9a-octahydro-1H-benzoin 4,11: 5,10: 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a, 10,10a, 11,11a-dodecahydro-1H-cyclopentanthracene and the like. It is done.

  Further, as the cyclic polyolefin-based resin, other cyclic olefins other than those described above capable of ring-opening polymerization can be used in combination as long as the object of the present invention is not impaired. Specific examples of such cyclic olefins include compounds having one reactive double bond such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene.

  The cyclic polyolefin resin has a number average molecular weight (Mn) measured by a gel permeation chromatograph (GPC) method using a toluene solvent, preferably 25,000 to 200,000, more preferably 30,000 to 100,000. 000, most preferably 40,000-80,000. When the number average molecular weight is in the above range, a material having excellent mechanical strength, good solubility, moldability, and casting operability can be obtained.

  When the cyclic polyolefin resin is obtained by hydrogenating a ring-opening polymer of a norbornene monomer, the hydrogenation rate is preferably 90% or more, more preferably 95% or more, Preferably it is 99% or more. Within such a range, the heat deterioration resistance and light deterioration resistance are excellent.

  Various products are commercially available as such cyclic polyolefin resins. Specific examples include trade names “Zeonex” and “Zeonor” manufactured by Zeon Corporation, trade names “Arton” manufactured by JSR Corporation, and product names “Topas” manufactured by TICONA Corporation. ", Trade name" Apel "manufactured by Mitsui Chemicals.

(Formation method)
The first retardation plate is generally obtained by stretching a film formed from a material such as a resin. Any appropriate forming method can be adopted as a method of forming the film. In addition, since many film products are marketed, the said cyclic polyolefin resin, the said cellulose resin, etc. may use the said commercial film as it is for a extending | stretching process.

Any appropriate stretching method may be adopted as the stretching method. From the viewpoint of obtaining a film satisfying the optical properties of nx ₁ > nz ₁ > ny ₁ , a shrinkable film is bonded to one or both sides of the film. A method of stretching is preferably employed. In particular, when a cyclic polyolefin-based resin is used, as described in JP-A-2006-72309, a method of stretching by attaching a shrinkable film having a predetermined shrinkage rate to one or both sides of the film is preferable. Adopted.

[Second retardation plate]
(In-plane retardation)
In the liquid crystal panel of the present invention, the second retardation plate 40 is disposed between the liquid crystal cell 10 and the second polarizer 22. The second retardation plate is a positive A plate that satisfies nx ₂ > ny ₂ ≈nz ₂ . nx ₂ , ny ₂ , and nz ₂ are the refractive index in the slow axis direction in the plane of the second retardation plate, the refractive index in the fast axis direction in the plane, and the refractive index in the thickness direction, respectively. Represent.

The in-plane retardation Re ₂ of the _second retardation plate 40 is represented by Re ₂ = (nx ₂ −ny ₂ ) × d ₂ . However, d ₂ is the thickness of the second retardation plate. Re ₂ indicates that the absolute value of the in-plane retardation Re ₀ with respect to light having a wavelength of 550 nm of an optical element in which the liquid crystal cell, the first retardation plate, and the second retardation plate are integrated, is a half wavelength (λ / It is preferably set to be an odd multiple of 2), that is, within a range of (190 nm to 360 nm) × (2m + 1). However, m is an integer greater than or equal to 0. | Re ₀ | is more preferably in the range of (200 nm to 350 nm) × (2m + 1), and more preferably in the range of (230 nm to 320 nm) × (2m + 1).

In the first embodiment of the present invention in which the initial alignment direction 10n of the liquid crystal cell and the slow axis direction 30e of the first retardation plate are orthogonal, the liquid crystal cell 10 and the first retardation plate 30 are The absolute value of in-plane retardation with respect to light having a wavelength of 550 nm of an optical element in which the second retardation plate 40 is regarded as an integral unit is represented by | Re ₀ | = | Re _cell −Re ₁ + Re ₂ |. On the other hand, in the second embodiment of the present invention in which the initial alignment direction 10n of the liquid crystal cell and the slow axis direction 30e of the first retardation plate are parallel, the liquid crystal cell 10 and the first retardation plate 30 are provided. The absolute value of in-plane retardation with respect to light having a wavelength of 550 nm of an optical element in which the first and second retardation plates 40 are regarded as an integral unit is represented by | Re ₀ | = | Re _cell + Re ₁ + Re ₂ |.

Therefore, when the initial alignment direction 10n of the liquid crystal cell and the slow axis direction 30e of the first retardation plate are orthogonal, | Re _cell -Re ₁ + Re ₂ | is (190 nm to 360 nm) × (2 m +1), preferably (200 nm to 350 nm) × (2 m + 1), more preferably (230 nm to 320 nm) × (2 m + 1). Is more preferable. Further, as described above, in consideration of the fact that Re _cell generally takes a value slightly larger than a half wavelength and a preferable range of in-plane retardation Re ₁ of the _first retardation plate, m = 0. preferable.

On the other hand, when the initial alignment direction 10n of the liquid crystal cell and the slow axis direction 30e of the first retardation plate are parallel, | Re _cell + Re ₁ + Re ₂ | is (190 nm to 360 nm) × (2 m + 1). ), Preferably (200 nm to 350 nm) × (2 m + 1), more preferably (230 nm to 320 nm) × (2 m + 1). preferable. Further, considering that Re _cell generally takes a value slightly larger than a half wavelength and a preferable range of in-plane retardation Re ₁ of the _first retardation plate, m is generally 1 or more. In consideration of the range of retardation values that can be taken by the second retardation plate, it is preferable that m = 1.

  By setting the in-plane retardation of the second retardation plate 40 within the above range, even when the liquid crystal panel is returned to room temperature after being exposed to a high temperature / high humidity environment, light leakage occurs at the corner of the panel during black display ( The occurrence of so-called “corner unevenness” is more effectively suppressed. Although it is not clear why corner unevenness is suppressed by having the first retardation plate 30 having a predetermined in-plane retardation between the second polarizer 22 and the liquid crystal cell 10, during black display, In other words, compensating the deviation from the half-wavelength of the in-plane retardation in the initial alignment state of the liquid crystal cell by the A plate, and making the in-plane retardation of the liquid crystal panel as a whole half-wave contributes to the suppression of corner unevenness. It is estimated that

According to the study of the present inventors, instead of using the A plate having the characteristics of nx _2> ny ₂ ≒ nz ₂ as the second phase difference plate 40, as shown in Examples and Comparative Examples described later The occurrence of corner unevenness is also suppressed by using an optical compensation layer (biaxial plate) having optical characteristics such as nx ₂ > ny ₂ > nz ₂ . However, when such an optical compensation layer is used as the second retardation plate, the viewing angle characteristics in the initial state before heating and humidification are not sufficient as compared with the case where the A plate is used. From this point of _{view, (nx 2 -nz 2) /} (nx 2 -ny 2) NZ coefficient NZ ₂ of the second phase difference plate 40, represented by is preferably 0.8 to 1.2, It is more preferable that it is 0.9-1.1.

(Photoelastic coefficient)
As the second retardation plate 40, one having an absolute value of the photoelastic coefficient of 2 × 10 ⁻¹¹ m ² / N or less is preferably used. The absolute value of photoelastic coefficient, 2 × ¹⁰ -13 ^m, more preferably from ^{2 / N~1 × 10 -11 m 2} / N, 1 × 10 -12 m 2 / N~1 × 10 -11 m ² / N is more preferable. When the absolute value of the photoelastic coefficient is in such a range, a phase difference change is unlikely to occur when a shrinkage stress is generated during heating. Therefore, a change in the optical characteristics of the liquid crystal panel is suppressed. If the photoelastic coefficient is excessively small, the expression of retardation tends to be small, and it may be difficult to set the in-plane retardation Re ₂ within the above range. The photoelastic coefficient is a value intrinsic to a chemical structure such as a resin. However, the photoelastic coefficient can be suppressed low by copolymerizing or mixing a plurality of components having different signs (positive and negative) of the photoelastic coefficient. Is possible.

(Material and forming method)
As a material that can satisfy such a photoelastic coefficient, the same materials as those described above for the first retardation plate can be suitably used. As for the film forming method, any appropriate method can be adopted in the same manner as described above with respect to the first retardation plate. Moreover, any appropriate stretching method can be adopted as the stretching method.

[Arrangement of optical members]
Hereinafter, in the liquid crystal panel 100 of the present invention, the arrangement of the liquid crystal cell 10, the first and second polarizers 21 and 22, the first retardation plate 30, the second retardation plate 40, and other optical elements, and A lamination method will be described.

(Arranging means for first polarizer and first retardation plate)
Referring to FIGS. 1, 2 </ b> A, and 2 </ b> B, the first retardation plate 30 is disposed between the first polarizer 21 and the liquid crystal cell 10. The first retardation plate 30 and the first polarizer 21 may be directly laminated, or may be laminated via a polarizer protective film (not shown).

  In the case where the first retardation plate 30 and the first polarizer 21 are directly laminated, it is preferable that the two are laminated and integrated by an adhesive layer or an adhesive layer. By adopting such a configuration, the first retardation plate 30 can also serve as a polarizer protective film for the first polarizer 21, so that the total number of optical films used in the liquid crystal panel can be reduced and reduced. Cost can be reduced.

  On the other hand, when laminating the first retardation plate 30 and the first polarizer 21 via the polarizer protective film, the polarizer and the polarizer protective film, the polarizer protective film and the first retardation plate are These are preferably laminated and integrated through an adhesive layer or a pressure-sensitive adhesive layer, respectively.

  As the polarizer protective film, a film that is excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, and the like and is less likely to cause optical unevenness due to strain is preferably used. Moreover, when it has a polarizer protective film between the 1st phase difference plate 30 and the 1st polarizer 21, the said polarizer protective film is an optically isotropic layer which does not have birefringence substantially. Preferably there is.

  As a material constituting the polarizer protective film having optical isotropy, polycarbonate resin, polyvinyl alcohol resin, cellulose resin, polyester resin, polyarylate resin, polyimide resin, cyclic polyolefin resin, polysulfone resin Examples thereof include resins, polyethersulfone resins, polyolefin resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. Further, a thermosetting resin such as urethane, acrylic urethane, epoxy, or silicone, or an ultraviolet curable resin can also be used.

Any appropriate adhesive or pressure-sensitive adhesive can be adopted as the adhesive or pressure-sensitive adhesive forming the adhesive or pressure-sensitive adhesive layer. For example, acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate / vinyl chloride copolymers, modified polyolefins, epoxy-based, fluorine-based, natural rubber-based, rubber-based polymers such as synthetic rubber, etc. A base polymer can be appropriately selected and used. In particular, a water-based adhesive is preferably used for laminating the polarizer protective film and the first polarizer,
Among them, those mainly composed of polyvinyl alcohol resin are used. In addition, the same adhesive is also preferably used when directly laminating the first retardation plate and the first polarizer.

  An adhesive is preferably used for laminating the polarizer protective film and the first retardation plate. The pressure-sensitive adhesive is not particularly limited, but for example, an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer may be appropriately selected and used. it can. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  In addition to the above, in terms of prevention of foaming and peeling phenomena due to moisture absorption, deterioration of optical properties and liquid crystal cell warpage due to differences in thermal expansion, etc., as well as formability of liquid crystal display devices with high quality and excellent durability An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The adhesive layer is, for example, natural or synthetic resins, in particular, tackifier resins, fillers or pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, antioxidants, etc. It may contain an additive to be added to the adhesive layer. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

(Arrangement means for the first retardation plate and the liquid crystal cell)
Referring to FIG. 1, the first retardation plate 30 is laminated with the substrate 11 of the liquid crystal cell. The first retardation plate and the substrate of the liquid crystal cell are preferably laminated and integrated via an adhesive layer or a pressure-sensitive adhesive layer, and particularly preferably laminated via a pressure-sensitive adhesive layer. As the pressure-sensitive adhesive layer, the same ones as described above can be preferably used. In addition, other optical layers may be disposed between the first retardation plate 30 and the substrate 11 of the liquid crystal cell. In that case, the optical layer is preferably optically isotropic.

(Arranging means for second polarizer and second retardation plate)
Referring to FIGS. 1, 2 </ b> A, and 2 </ b> B, the second retardation plate 40 is disposed between the second polarizer 22 and the liquid crystal cell 10. The second retardation plate 40 and the first polarizer 21 may be directly laminated as described above with respect to the lamination of the first retardation plate 30 and the first polarizer 21. It can also laminate | stack through a child protective film (not shown). When a polarizer protective film is provided between the second retardation plate 40 and the second polarizer 22, the polarizer protective film is an optically isotropic layer that has substantially no birefringence. Is preferred. Regarding the formation of the adhesive layer and the pressure-sensitive adhesive layer used for the lamination, the same adhesives and pressure-sensitive adhesives as described above can be suitably used.

(Arrangement means for second retardation plate and liquid crystal cell)
Referring to FIG. 1, the second retardation plate 40 is laminated with the substrate 11 ′ of the liquid crystal cell. The second retardation plate and the liquid crystal cell substrate are preferably laminated and integrated via an adhesive layer or an adhesive layer, and particularly preferably laminated via an adhesive layer. As the pressure-sensitive adhesive layer, the same ones as described above can be preferably used. In addition, another optical layer can be disposed between the second retardation plate 40 and the substrate 11 ′ of the liquid crystal cell. In that case, the optical layer is preferably optically isotropic.

As described above, the liquid crystal panel of the present invention includes the polarization cell in addition to the liquid crystal cell 10, the first polarizer 21, the second polarizer 22, the first retardation plate 30, and the second retardation plate 40. Although it can also have a child protective film, an adhesive layer, an adhesive layer, etc., it is preferable that these are all optically isotropic. In other words, it is preferable that all optical layers other than the first retardation plate 30 disposed between the first polarizer 21 and the liquid crystal cell 10 are optically isotropic. All of the optical layers other than the second retardation plate 40 disposed between the element 22 and the liquid crystal cell 10 are preferably optically isotropic. Thus, by reducing the birefringence of the optical layer other than the retardation plate disposed between the polarizer and the liquid crystal cell, the liquid crystal cell, the first retardation plate, and the second retardation plate can be reduced. Since not only the in-plane retardation Re _{0 of} the optical element regarded as an integral, but also the in-plane retardation when the entire liquid crystal panel is regarded as an integral is an odd multiple of a half wavelength, corner unevenness can be suppressed.

  Note that the term “optical isotropic” means a characteristic that does not substantially change the polarization state of light transmitted through the normal direction of the liquid crystal panel. More specifically, “optical isotropy” refers to the refractive index in the slow axis direction in the plane of the optical element nx, the refractive index in the fast axis direction in the plane ny, and the refractive index in the thickness direction. When nz and thickness are d, the in-plane retardation represented by (nx−ny) × d is preferably 15 nm or less, and more preferably 10 nm or less.

[Formation of liquid crystal panel]
As described above, in the liquid crystal panel of the present invention, the liquid crystal cell 10, the first polarizer 21, the second polarizer 22, the first retardation plate 30, and the second retardation plate 40 are arranged. Can be obtained. In the manufacturing process, the members can be formed by sequentially laminating the members separately, or a member obtained by laminating several members in advance can be used. Further, the stacking order is not particularly limited.

  In particular, in the liquid crystal panel of the present invention, the first polarizer 21, the first retardation plate 30, and a first polarizing plate in which a polarizer protective film is laminated as necessary, a second polarizer 22, A second retardation plate 40 and a second polarizing plate on which a polarizer protective film is laminated as necessary are prepared in advance, and these are laminated with the liquid crystal cell 10 to thereby ensure quality stability and assembly work. It can be made excellent in properties.

  The liquid crystal panel of the present invention can also include optical layers other than those described above and other members. Examples thereof include surface treatment layers such as antireflection layers, antisticking layers, diffusion layers and antiglare layers, and brightness enhancement films. The brightness enhancement film is not particularly limited. For example, it transmits linearly polarized light having a predetermined polarization axis, such as a dielectric multilayer thin film or a multilayer laminate of thin film films having different refractive index anisotropy, and the like. Those exhibiting the characteristic of reflecting light can be used.

[Liquid Crystal Display]
The liquid crystal panel is preferably used for a liquid crystal display device such as a personal computer, a liquid crystal television, a mobile phone, and a personal digital assistant (PDA).

  FIG. 3 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. The liquid crystal display device includes a liquid crystal panel 100, a prism sheet 110, a light guide plate 120, and a light source 130. Moreover, in another embodiment, as long as the optical member illustrated in FIG. 3 satisfies the present invention, a part of the optical member is omitted depending on the driving mode and use of the liquid crystal cell to be used. The optical member can be replaced.

  As described above, in the liquid crystal panel constituting the liquid crystal display device of the present invention, since the in-plane retardation when the entire liquid crystal panel is regarded as an integral body is adjusted to a predetermined range, corner unevenness is suppressed. More specifically, in the liquid crystal display device of the present invention, the difference between the black luminance at the center of the screen and the black luminance at the corners of the screen (four corners) after the heating test at 95 ° C. × 24 hours can be kept small. . The difference in black luminance between the center portion of the screen and the corner portion is preferably 1 / 100,000 (10 ppm) or less, more preferably 1 / 200,000 (5 ppm) or less with respect to the luminance of the backlight.

  The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to these examples. The measurement methods used in the examples are as follows.

[Retardation value, three-dimensional refractive index]
The retardation value was measured with light having a wavelength of 550 nm using a phase difference meter (product name “KOBRA-WPR” manufactured by Oji Scientific Instruments) based on the parallel Nicol rotation method. Retardation is measured when the film is tilted by 40 ° in the front (normal) direction and the center of the slow axis. From these values, the direction in which the in-plane refractive index is maximum, the direction perpendicular thereto, the thickness of the film Refractive indexes nx, ny and nz in each direction were calculated by a program attached to the apparatus. From these values and thickness d, in-plane retardation: Re = (nx−ny) × d, and NZ coefficient: (nx−nz) / (nx−ny) were determined.
The thickness of the film required for calculating the three-dimensional refractive index was measured using a digital micrometer “KC-351C type” manufactured by Anritsu Corporation. The refractive index was measured using an Abbe refractometer [product name “DR-M4” manufactured by Atago Co., Ltd.].

[Black brightness of liquid crystal display]
A luminance measuring device (TOPCON BM-5A) was used for measuring the luminance. The liquid crystal panel is placed on a high-brightness backlight having a luminance of about 10000 cd / m ² , for each of the initial state before use of the liquid crystal panel and after being left at room temperature for 15 minutes after being placed in a heating test for 24 hours. Then, in the dark room at 23 ° C., black luminance measurement in the front direction was performed for each of the center and four corners of the screen with the black image displayed.

[Comparative Example 1]
(Preparation of first retardation plate)
Using a norbornene-based resin film (manufactured by JSR: Arton FLZU130D0, thickness 130 μm), the retardation of light having a wavelength of 550 nm is 270 nm, and the NZ coefficient is 0.00 by the method described in Example 16 of JP-A-2006-72309. 5 retardation plates were obtained.

(Production of second retardation plate)
A norbornene-based resin film (manufactured by Nippon Zeon Co., Ltd .: ZEONOR thickness 60 μm) is uniaxially stretched at a free end by a roll stretching machine, and has a retardation with respect to light having a wavelength of 550 nm of 30 nm and a NZ coefficient of 1.0 (A plate) Got.
(Polarizer)
A polarizing plate (NPF-CWQ1463CU manufactured by Nitto Denko Corporation) having a polarizer protective film on both surfaces of a polarizer made of a polyvinyl alcohol film uniaxially stretched by adsorbing iodine was used. In addition, when bonding to the liquid crystal cell, the surface on which the polarizer protective film having both in-plane retardation and thickness direction retardation was substantially zero was bonded to the liquid crystal cell side.

(Polarizing plate with compensation layer)
The first retardation plate and the polarizing plate are punched with a continuous punching machine so that the slow axis direction of the first retardation plate and the absorption axis direction of the polarizing plate are parallel to each other. Using, the 1st polarizing plate with a compensation layer with which the 1st phase difference plate was bonded together to the polarizing plate through the acrylic adhesive was obtained. Similarly, the second retardation plate and the polarizing plate are bonded together so that the slow axis direction of the second retardation plate and the absorption axis direction of the polarizing plate are parallel to each other. An attached polarizing plate was obtained.

(Liquid crystal cell)
An IPS mode liquid crystal cell having a retardation value of 370 nm with respect to light having a wavelength of 550 nm was used.

(Production of liquid crystal panel)
The polarizing plate with the first compensation layer is disposed on the viewing side surface of the liquid crystal cell so that the absorption axis direction of the polarizer is orthogonal to the initial alignment direction of the liquid crystal cell and the retardation plate faces the liquid crystal cell. And an acrylic pressure-sensitive adhesive (thickness: 20 μm). Next, the polarizing plate with the second compensation layer is arranged on the light source side surface of the liquid crystal cell, the absorption axis direction of the polarizer and the initial alignment direction of the liquid crystal cell are parallel, and the retardation plate is the liquid crystal cell. A liquid crystal panel was produced by laminating with an acrylic pressure-sensitive adhesive (thickness 20 μm) so as to face the substrate.

[Examples 1-5, Comparative Examples 2-5]
A liquid crystal panel was produced in the same manner as in Comparative Example 1 except that the A plate having the retardation shown in Table 1 was used as the second retardation plate in Comparative Example 1.

[Comparative Example 6]
In the comparative example 1, as a polarizing plate on the light source side, instead of using a polarizing plate with a second compensation layer to which a second retardation plate is bonded, a polarizing plate having no optical compensation layer (Nitto Denko Corporation) A liquid crystal panel was produced in the same manner as in Comparative Example 1 except that NPF-CWQ1463CU) was used.

[Examples 6 to 8]
In Comparative Example 1, an IPS mode liquid crystal cell having a retardation value of 370 nm with respect to light having a wavelength of 550 nm is used as the liquid crystal cell, and an A plate having the retardation shown in Table 1 is used as the second retardation plate. A liquid crystal panel was produced in the same manner as in Comparative Example 1 except that.

[Examples 9 to 11]
(Preparation of first retardation plate)
A norbornene-based resin film (manufactured by JSR: Arton FLZU130D0, thickness 130 μm) is used, and the retardation of light having a wavelength of 550 nm is 180 nm and the NZ coefficient is 0.00 by the method described in Example 20 of JP-A-2006-72309. A phase difference plate of 4 was obtained.

(Production of liquid crystal panel)
In the comparative example 1, a retardation plate having a retardation of 180 nm and a NZ coefficient of 0.4 with respect to the light having the wavelength of 550 nm is used as the first retardation plate, and the second retardation plate is shown in Table 1. A liquid crystal panel was produced in the same manner as in Comparative Example 1 except that an A plate having retardation was used.

[Comparative Example 7]
(Polarizing plate with compensation layer)
In Comparative Example 1, the same procedure as in Comparative Example 1 was repeated except that the slow axis direction of the first retardation plate and the absorption axis direction of the polarizing plate were laminated so that they were orthogonal to each other instead of being parallel. A polarizing plate with a compensation layer 1 was obtained. As the second polarizing plate with a compensation layer, the same polarizing plate with a compensation layer as used in Comparative Example 1 was used.

(Liquid crystal cell)
As in Comparative Example 1, an IPS mode liquid crystal cell having a retardation value of 370 nm with respect to light having a wavelength of 550 nm was used.

(Production of liquid crystal panel)
A polarizing plate with a first compensation layer is provided on the viewing side surface of the liquid crystal cell so that the absorption axis direction of the polarizer is orthogonal to the initial alignment direction of the liquid crystal cell and the retardation plate faces the liquid crystal cell. And an acrylic pressure-sensitive adhesive (thickness 20 μm). Next, the polarizing plate with the second compensation layer is arranged on the light source side surface of the liquid crystal cell, the absorption axis direction of the polarizer and the initial alignment direction of the liquid crystal cell are parallel, and the retardation plate is the liquid crystal cell. A liquid crystal panel was produced by laminating with an acrylic pressure-sensitive adhesive (thickness 20 μm) so as to face the substrate.

[Examples 12 to 16, Comparative Examples 8 to 11]
In Comparative Example 7, a liquid crystal panel was produced in the same manner as Comparative Example 7 except that the A plate having the retardation shown in Table 2 was used as the second retardation plate.

[Comparative Example 12]
In Comparative Example 7, a norbornene resin film (manufactured by Nippon Zeon Co., Ltd .: ZEONOR thickness 60 μm) was sequentially biaxially stretched as the second retardation plate, the retardation for light having a wavelength of 550 nm was 170 nm, and the NZ coefficient was 2. A liquid crystal panel was produced in the same manner as in Comparative Example 7 except that a 0.0 biaxial plate was used.

[Comparative Example 13]
In Comparative Example 7, a polarizing plate having no optical compensation layer (Nitto Denko Corporation) is used as the polarizing plate on the light source side instead of using the polarizing plate with the second compensation layer to which the second retardation plate is bonded. A liquid crystal panel was produced in the same manner as in Comparative Example 7 except that NPF-CWQ1463CU) was used.

[Examples 17 to 19]
In Comparative Example 7, an IPS mode liquid crystal cell having a retardation value of 370 nm with respect to light having a wavelength of 550 nm was used as the liquid crystal cell, and an A plate having the retardation shown in Table 2 was used as the second retardation plate. A liquid crystal panel was produced in the same manner as in Comparative Example 7 except that.

[Examples 20 to 22]
In the comparative example 7, as the first retardation plate, a retardation plate having a retardation with respect to light having a wavelength of 550 nm of 180 nm and an NZ coefficient of 0.4 is used as in the case of the embodiments 9 to 11, and the second retardation plate is used. A liquid crystal panel was produced in the same manner as in Comparative Example 7 except that an A plate having the retardation shown in Table 2 was used as the retardation plate.

Optical characteristics of the first retardation plate and the second retardation plate used in the liquid crystal panels of Examples and Comparative Examples, retardation value of the liquid crystal cell, initial alignment direction of the liquid crystal cell, and slow axis direction of each retardation plate Table 1 and Table 2 show the positional relationship between and the black luminance measurement results. In Tables 1 and 2, the unit of retardation is nm, and the unit of luminance is cd / m ² . Moreover, the viewing angle distribution of the black luminance in the screen center part before the heating test of the liquid crystal panel of Example 14 and Comparative Example 12 is shown in FIGS. 4 and 5, respectively. 4 and 5, the radial direction represents a polar angle, and the circumferential direction represents an azimuth angle.

As is clear from the comparison between each example and Comparative Examples 6 and 13, the liquid crystal display device of the present invention including the A plate having a predetermined retardation as the second retardation plate is used even after the heating test. It can be seen that the difference in black luminance between the center of the screen and the four corners of the screen is small, and the occurrence of corner unevenness is suppressed. Further, from the comparison between each example and each comparative example, in-plane retardation Re ₀ for light having a wavelength of 550 nm of an optical element in which the liquid crystal cell, the first retardation plate, and the second retardation plate are regarded as one body. It can be seen that the closer the absolute value of is to an odd multiple of the half wavelength, the smaller the change in the black luminance at the edge after the heating test.

In Comparative Example 12 using a biaxial plate of NZ ₂ = 2.0 as the second retardation plate, the difference in black luminance between the screen center and the four corners after the heating test is small, and the corner unevenness It can be said that the occurrence is suppressed. However, in Comparative Example 12, as shown in FIG. 5, the black luminance in the oblique direction, particularly in the direction of the azimuth angle of 45 degrees is increased, and the visibility is decreased. On the other hand, as shown in FIG. 4, in Example 14, the black luminance in the oblique direction is also suppressed.

DESCRIPTION OF SYMBOLS 10 Liquid crystal cell 10n Initial alignment direction 11, 11 'Substrate 12 Liquid crystal layer 21, 22 Polarizer 21a, 22a Absorption axis direction 30, 40 Phase difference plate 30e, 40e Slow axis direction 100 Liquid crystal panel
110 Prism sheet 120 Light guide plate 130 Light source 200 Liquid crystal display device

Claims (7)

A liquid crystal cell comprising a liquid crystal layer comprising liquid crystal molecules aligned in a homogeneous arrangement in the absence of an electric field;
A first polarizer disposed on one side of the liquid crystal cell;
A second polarizer disposed on the other side of the liquid crystal cell;
A first retardation plate that is disposed between the liquid crystal cell and the first polarizer and satisfies nx ₁ > nz ₁ > ny ₁ ;
A second retardation plate disposed between the liquid crystal cell and the second polarizer and satisfying nx ₂ > ny ₂ ≈nz ₂ ,
The absorption axis direction of the first polarizer and the absorption axis direction of the second polarizer are orthogonal to each other,
The initial alignment direction of the liquid crystal cell and the slow axis direction of the first retardation plate are parallel or orthogonal,
The initial alignment direction of the liquid crystal cell, the slow axis direction of the second retardation plate, and the absorption axis direction of the second polarizer are parallel to each other,
The absolute value of the in-plane retardation Re ₀ for light having a wavelength of 550 nm of an optical element in which the liquid crystal cell, the first retardation plate, and the second retardation plate are regarded as an integral unit is ( 230 nm to 320 nm ) × (2 m + 1) is a liquid crystal panel (however, nx ₁ , ny ₁ , nz ₁ are respectively the refractive index in the slow axis direction in the plane of the first retardation plate and the fast axis direction in the plane) The refractive index represents the refractive index in the thickness direction, and nx ₂ , ny ₂ , and nz ₂ represent the refractive index in the slow axis direction in the plane of the second retardation plate and the fast axis direction in the plane, respectively. And the refractive index in the thickness direction, m represents an integer of 0 or more). The initial alignment direction of the liquid crystal cell and the slow axis direction of the first retardation plate are orthogonal to each other, and | Re _cell −Re ₁ + Re ₂ | is in the range of ( 230 nm to 320 nm ) × (2m + 1). The liquid crystal panel according to claim 1, wherein Re _cell , Re ₁ , and Re ₂ are for the light of wavelength 550 nm of the liquid crystal cell, the first retardation plate, and the second retardation plate, respectively. Represents in-plane retardation). The initial alignment direction of the liquid crystal cell and the slow axis direction of the first retardation plate are parallel, and | Re _cell + Re ₁ + Re ₂ | is in the range of ( 230 nm to 320 nm ) × (2m + 1). The liquid crystal panel according to claim 1, wherein Re _cell , Re ₁ , and Re ₂ are in-plane with respect to light having a wavelength of 550 nm of the liquid crystal cell, the first retardation plate, and the second retardation plate, respectively. Represents retardation).   The liquid crystal panel according to claim 1, wherein the liquid crystal cell is one of an IPS mode, an FFS mode, and an FLC mode. The liquid crystal panel according to claim 1, wherein the photoelastic coefficient of the second retardation plate is 2 × 10 ⁻¹¹ m ² / N or less. The liquid crystal panel according to claim 1, wherein the photoelastic coefficient of the first retardation plate is 2 × 10 ⁻¹¹ m ² / N or less.   A liquid crystal display provided with the liquid crystal panel in any one of Claims 1-6.

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