KR20230033585A - Polarizing plate with retardation layer, and image display device - Google Patents

Abstract

The present invention provides a polarizing plate with a retardation layer and an image display device, capable of reducing black luminance in a slope direction in the image display device. The polarizing plate with a retardation layer according to the present invention comprises: a polarizing plate including a polarizer; and a retardation layer located adjacent to the polarizing plate and having a refractive index characteristic of which indicates the relationship nx > nz > ny. The absorption axis of the polarizer and the slow axis of the retardation layer are practically parallel or practically orthogonal. The polarizing plate with the retardation layer satisfies the relationship of formula (1) below. In formula (1), a to j represent the constant selected from the relationship between the absorption axis and the slow axis, R_0 represents the front phase difference of the retardation layer at a wavelength of 550 nm, and NZ represents the Nz coefficient of the retardation layer.

Description

Polarizing plate and image display device with retardation layer {POLARIZING PLATE WITH RETARDATION LAYER, AND IMAGE DISPLAY DEVICE}

The present invention relates to a polarizing plate with a retardation layer and an image display device.

BACKGROUND OF THE INVENTION In recent years, image display devices typified by liquid crystal display devices are rapidly spreading. As such an image display device, for example, a liquid crystal display device including an elliptically polarizing plate including a polarizing plate and a retardation plate and a liquid crystal cell is known (for example, Patent Document 1).

Such image display devices are used in various industrial products, and the required characteristics differ depending on the use, and visibility from an oblique direction is particularly required in some cases. However, in the image display device described in Patent Literature 1, there is a problem that the black luminance in the oblique direction is not sufficiently low (that is, the black display is not sufficiently black when viewed from the oblique direction).

Japanese Unexamined Patent Publication No. 5-157911

The present invention has been made to solve the above conventional problems, and its object is to provide a polarizing plate with a retardation layer capable of realizing an image display device having sufficiently low black luminance in an oblique direction.

A polarizing plate with a retardation layer of the present invention includes a polarizing plate containing a polarizer; and a retardation layer having a refractive index characteristic of nx>nz>ny, disposed adjacent to the polarizing plate. An absorption axis of the polarizer and a slow axis of the retardation layer are substantially parallel or substantially orthogonal. The said polarizing plate with a retardation layer satisfies the relationship of following formula (1).

(In Formula (1), a to j represent constants selected from the relationship between the absorption axis and the slow axis in any of Table 1 and Table 2 below. R ₀ is the front surface of the retardation layer at a wavelength of 550 nm represents a phase difference (NZ represents an Nz coefficient of the phase difference layer).

In one embodiment, the a to j represent constants selected from the relationship between the absorption axis and the slow axis in Table 1, the absorption axis of the polarizer and the slow axis of the retardation layer are substantially parallel, R ₀ of the retardation layer is 210 nm or more and 270 nm or less, and the Nz coefficient of the retardation layer is 0.38 or more and 0.53 or less.

In one embodiment, a to j represent constants selected from the relationship between the absorption axis and the slow axis in Table 1, and the absorption axis of the polarizer and the slow axis of the retardation layer are substantially orthogonal, R ₀ of the retardation layer is 270 nm or more and 360 nm or less, and the Nz coefficient of the retardation layer is 0.42 or more and 0.68 or less.

In one embodiment, a to j represent constants selected from the relationship between the absorption axis and the slow axis in Table 2, and the absorption axis of the polarizer and the slow axis of the retardation layer are substantially orthogonal, R ₀ of the retardation layer is 210 nm or more and 270 nm or less, and the Nz coefficient of the retardation layer is 0.42 or more and 0.53 or less.

In one embodiment, the a to j represent constants selected from the relationship between the absorption axis and the slow axis in Table 2, the absorption axis of the polarizer and the slow axis of the retardation layer are substantially parallel, R ₀ of the retardation layer is 270 nm or more and 360 nm or less, and the Nz coefficient of the retardation layer is 0.47 or more and 0.63 or less.

An image display device according to another aspect of the present invention includes an image display cell; The polarizing plate with the retardation layer disposed on the viewing side with respect to the image display cell is provided.

An image display device according to another aspect of the present invention includes an image display cell; The polarizing plate with the retardation layer disposed on the side opposite to the viewing side with respect to the image display cell is provided.

In one embodiment, the image display cell is a liquid crystal cell, and the drive mode of the liquid crystal cell is an IPS mode.

ADVANTAGE OF THE INVENTION According to embodiment of this invention, the polarizing plate with a retardation layer which can aim at the reduction of black luminance of an oblique direction in an image display apparatus can be realized.

1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention.
2 is a schematic cross-sectional view of an image display device according to one embodiment of the present invention.
3 is a schematic cross-sectional view of an image display device according to another embodiment of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, although embodiment of this invention is described with reference to drawings, this invention is not limited to these embodiment.

(Definition of Terms and Symbols)

Definitions of terms and symbols in this specification are as follows.

(1) Refractive index (nx, ny, nz)

'nx' is the refractive index in the direction in which the in-plane refractive index is maximized (ie, the slow axis direction), 'ny' is the refractive index in the direction orthogonal to the slow axis within the plane (ie, the fast axis direction), and 'nz' is is the refractive index in the thickness direction.

(2) In-plane retardation (Re) and face-to-face retardation (R ₀ )

'Re(λ)' is an in-plane retardation measured with light having a wavelength of λ nm at 23°C. For example, 'Re(550)' is an in-plane retardation (frontal retardation) measured with light having a wavelength of 550 nm at 23°C. In addition, in this specification, 'Re (550)' may be referred to as 'R ₀ '.

Re(λ) is obtained by the formula: Re=(nx-ny)×d when the thickness of the layer (film) is d(nm).

(3) Phase difference in thickness direction (Rth)

'Rth(λ)' is the phase difference in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, 'Rth(550)' is the phase difference in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) is obtained by the formula: Rth=(nx-nz)×d when the thickness of the layer (film) is d(nm).

(4) Nz factor

The Nz coefficient is obtained by Nz=Rth/Re.

(5) substantially orthogonal or parallel

The expressions 'substantially orthogonal' and 'approximately orthogonal' include the case where the angle formed by the two directions is 90°±10°, preferably 90°±7°, more preferably 90°±5 is ° The expressions 'substantially parallel' and 'approximately parallel' include the case where the angle formed by the two directions is 0°±10°, preferably 0°±7°, and more preferably 0°±5°. is ° In addition, when simply referring to 'orthogonal' or 'parallel' in this specification, a substantially orthogonal or substantially parallel state may be included.

A. Overall configuration of polarizing plate with retardation layer

1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. The polarizing plate 1 with the retardation layer in the illustrated example includes a polarizing plate 2 including a polarizer 21; A retardation layer (3) disposed adjacent to the polarizing plate (2) and exhibiting a relationship of refractive index characteristics of nx>nz>ny is provided. The absorption axis of the polarizer 21 and the slow axis of the retardation layer 3 are substantially parallel or substantially orthogonal. The polarizing plate 1 with the retardation layer satisfies the relationship of the following formula (1). The retardation layer 3 may be in direct contact with the polarizing plate 2 or may be affixed to the polarizing plate 2 via an adhesive or an adhesive.

(In Formula (1), a to j represent constants selected from the relationship between the absorption axis of the polarizer 21 and the slow axis of the retardation layer 3 in either Table 1 or Table 2 below. NZ is the phase difference represents the Nz coefficient of layer (3)).

[Table 1]

[Table 2]

If the polarizing plate with a retardation layer satisfies the relationship of the above formula (1), the black luminance in the oblique direction can be reduced in an image display device including the polarizing plate with a retardation layer.

In one embodiment, a to j in Equation (1) represent constants selected from the relationship between the absorption axis of the polarizer 21 and the slow axis of the retardation layer 3 in Table 1, and the polarizer 21 The absorption axis of and the slow axis of the retardation layer 3 are substantially parallel. In this case, R ₀ of the retardation layer 3 is typically 210 nm or more and 270 nm or less, preferably 250 nm or less. The Nz coefficient of the retardation layer 3 is typically 0.38 or more and 0.53 or less.

According to such a configuration, when the polarizing plate with the retardation layer is used in an O-mode liquid crystal display device described later, and the absorption axis of the polarizer 21 and the slow axis of the retardation layer 3 are substantially parallel, the oblique direction The black luminance can be stably reduced.

In one embodiment, a to j in Equation (1) represent constants selected from the relationship between the absorption axis of the polarizer 21 and the slow axis of the retardation layer 3 in Table 1, and the polarizer 21 The absorption axis of and the slow axis of the retardation layer 3 are substantially orthogonal. In this case, R ₀ of the retardation layer 3 is typically 270 nm or more, preferably 290 nm or more, and is typically 360 nm or less. The Nz coefficient of the retardation layer 3 is typically 0.42 or more and 0.68 or less.

According to such a configuration, when the polarizing plate with the retardation layer is used in an O-mode liquid crystal display device described later, and the absorption axis of the polarizer 21 and the slow axis of the retardation layer 3 are substantially orthogonal, the oblique direction The black luminance of can be stably reduced.

In one embodiment, a to j in Equation (1) represent constants selected from the relationship between the absorption axis of the polarizer 21 and the slow axis of the retardation layer 3 in Table 2, and the polarizer 21 The absorption axis of and the slow axis of the retardation layer 3 are substantially orthogonal. In this case, R ₀ of the retardation layer 3 is typically 210 nm or more, preferably 230 nm or more, and typically 270 nm or less. The Nz coefficient of the retardation layer 3 is typically 0.42 or more and 0.53 or less.

According to such a configuration, when the polarizing plate with the retardation layer is used for an E-mode liquid crystal display device described later, and the absorption axis of the polarizer 21 and the slow axis of the retardation layer 3 are substantially orthogonal, the oblique direction The black luminance of can be stably reduced.

In one embodiment, a to j in Equation (1) represent constants selected from the relationship between the absorption axis of the polarizer 21 and the slow axis of the retardation layer 3 in Table 2, and the polarizer 21 The absorption axis of and the slow axis of the retardation layer 3 are substantially parallel. In this case, R ₀ of the retardation layer 3 is typically 270 nm or more and 360 nm or less. The Nz coefficient of the retardation layer 3 is typically 0.47 or more and 0.63 or less.

According to such a configuration, when the polarizing plate with the retardation layer is used for an E-mode liquid crystal display device described later, and the absorption axis of the polarizer 21 and the slow axis of the retardation layer 3 are substantially parallel, the oblique direction The black luminance can be stably reduced.

B. Overall configuration of polarizing plate with retardation layer

2 is a schematic cross-sectional view of an image display device according to one embodiment of the present invention. The image display device 10 in the illustrated example includes an image display cell 6 and a polarizing plate with a retardation layer ( 1) is provided.

In this embodiment, preferably,

The absorption axis of the polarizer 21 of the first polarizing plate 2 and the slow axis of the retardation layer 3 are substantially parallel, R ₀ of the retardation layer 3 is 210 nm or more and 270 nm or less, and the retardation layer 3 The Nz coefficient of is 0.38 or more and 0.53 or less,

The absorption axis of the polarizer 21 of the first polarizing plate 2 and the slow axis of the retardation layer 3 are substantially orthogonal, R ₀ of the retardation layer 3 is 270 nm or more and 360 nm or less, and the retardation layer 3 ) has an Nz coefficient of 0.42 or more and 0.68 or less, or

The absorption axis of the polarizer 21 of the first polarizing plate 2 and the slow axis of the retardation layer 3 are substantially orthogonal, R ₀ of the retardation layer 3 is 210 nm or more and 270 nm or less, and the retardation layer 3 ) Nz coefficient of 0.42 or more and 0.53 or less.

The image display device 10 in the illustrated example further includes a second polarizing plate 4 disposed on the side opposite to the viewing side of the image display cell 6 (opposite side to the polarizing plate 1 with a retardation layer).

In addition, hereinafter, for convenience, the polarizing plate 2 is referred to as the first polarizing plate 2 and distinguished from the second polarizing plate 4. The second polarizing plate 4 includes a polarizer 41 . The direction of the absorption axis of the polarizer 21 included in the first polarizing plate 2 and the direction of the absorption axis of the polarizer 41 included in the second polarizing plate 4 are typically substantially orthogonal.

In practical terms, the image display device 10 (liquid crystal display device) further includes a backlight unit 9. The back light unit 9 includes a light source 7 and a light guide plate 8 . The back light unit 9 may further include any suitable other member (eg, a diffusion sheet, a prism sheet). In the illustrated example, the backlight unit 9 is of an edge light type, but any suitable other type (for example, a direct type) may be employed as the backlight unit 9 .

The image display cell 6 is typically a liquid crystal cell 6a, and the image display device 10 is typically a liquid crystal display device.

The liquid crystal display device may be a so-called O mode or a so-called E mode. 'O-mode liquid crystal display device' means that the direction of the absorption axis of the polarizer (in this embodiment, the polarizer 41) disposed on the opposite side (rear side) of the viewing side of the liquid crystal cell and the direction of the initial orientation of the liquid crystal cell are substantially says that it is parallel to 'E-mode liquid crystal display device' means that the absorption axis direction of a polarizer disposed on the opposite side (rear side) of the liquid crystal cell to the viewing side and the initial orientation direction of the liquid crystal cell are substantially orthogonal. The term 'initial alignment direction of the liquid crystal cell' refers to the direction in which the in-plane refractive index of the liquid crystal layer formed as a result of alignment of the liquid crystal molecules included in the liquid crystal layer to be described later is maximized (ie, the slow axis direction) in the absence of an electric field. say

When the liquid crystal display is in the O mode, a to j in Equation (1) are typically constants selected from the relationship between the absorption axis of the polarizer 21 and the slow axis of the retardation layer 3 in Table 1 above. In the case where the liquid crystal display device is in E mode, a to j in Equation (1) are typically from the relationship between the absorption axis of the polarizer 21 and the slow axis of the retardation layer 3 in Table 2 above. Indicates the selected constant.

In the image display device 10, the polarizing plate 1 with a retardation layer is arranged on the viewing side of the image display cell 6 (liquid crystal cell 6a), but the polarizing plate 1 with a retardation layer is It may be located on the side opposite to the viewing side with respect to (liquid crystal cell 6a).

3 is a schematic cross-sectional view of an image display device according to another embodiment of the present invention. The image display device 11 in the illustrated example includes an image display cell 6 and a polarizing plate 1 with a retardation layer disposed on the side opposite to the viewing side with respect to the image display cell 6 .

In this embodiment, preferably, the absorption axis of the polarizer 21 of the first polarizing plate 2 and the slow axis of the retardation layer 3 are substantially parallel, and R ₀ of the retardation layer 3 is 270 nm or more and 260 nm or less. , and the Nz coefficient of the retardation layer 3 is 0.47 or more and 0.63 or less.

Like the image display device 10, the image display device 11 is typically a liquid crystal display device. In this embodiment, the liquid crystal display device is preferably in E mode.

The image display device 11 (liquid crystal display device) further includes a second polarizing plate 4 disposed on the viewing side with respect to the image display cell 6 (liquid crystal cell 6a). In addition, the image display device 11 (liquid crystal display device), like the image display device 10, is practically further provided with a backlight unit 9.

The image display device (liquid crystal display device) may further include any appropriate other members. For example, another optical compensation layer (retardation layer) may be further disposed. The optical characteristics, number, combination, arrangement position, and the like of the different optical compensation layers can be appropriately selected depending on the purpose and desired optical characteristics and the like. Matters not described in this specification may employ a configuration of an image display device (liquid crystal display device) commonly used in the art.

Hereinafter, each member constituting the polarizing plate with the retardation layer and the image display device will be described.

C. Polarizer

C-1. polarizer

Arbitrary appropriate polarizers can be employed as the polarizer 21 included in the first polarizing plate 2 and the polarizer 41 included in the second polarizing plate 4 (hereinafter, collectively referred to simply as polarizers). For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

As a specific example of a polarizer composed of a single-layer resin film, iodine or dichroism (two-color性) Polyene-based oriented films such as those subjected to dyeing and stretching treatment with dichroic substances such as dyes, dehydrated PVA products and dehydrochlorinated polyvinyl chloride products, and the like. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching is used because of its excellent optical properties.

Dyeing with iodine is performed, for example, by immersing the PVA-based film in an aqueous solution of iodine. The draw ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after dyeing treatment or may be performed while dyeing. Moreover, you may dye after extending|stretching. Swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. are given to the PVA-based film as necessary. For example, by immersing and washing the PVA-based film in water before dyeing, it is possible not only to clean the surface of the PVA-based film from stains and antiblocking agents, but also to swell the PVA-based film to prevent staining and the like.

As a specific example of a polarizer obtained using a laminate, a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a layered product of and is mentioned. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer coated and formed on the resin substrate, for example, by applying a PVA-based resin solution to the resin substrate and drying it to form a PVA-based resin layer on the resin substrate, and obtaining a laminate of the PVA-based resin layer; It can be produced by: stretching and dyeing the layered product to make the PVA-based resin layer a polarizer. In this embodiment, extending|stretching typically includes extending|stretching by immersing a layered product in boric acid aqueous solution. Further, if necessary, the stretching may further include air-stretching the laminate at a high temperature (eg, 95° C. or higher) before stretching in a boric acid aqueous solution. The obtained laminate of the resin substrate/polarizer may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizer), and the resin substrate is peeled from the laminate of the resin substrate/polarizer, and the peel surface is used for the purpose. Any suitable protective layer according to the above may be laminated and used. The details of the manufacturing method of such a polarizer are described, for example in Unexamined-Japanese-Patent No. 2012-73580 and Unexamined-Japanese-Patent No. 6470455. These publications are incorporated herein by reference in their entirety.

The thickness of the polarizer is, for example, 1 μm to 80 μm, preferably 1 μm to 15 μm, more preferably 1 μm to 12 μm, still more preferably 3 μm to 12 μm, and particularly preferably 3 μm. ~8 μm. If the thickness of the polarizer is in such a range, curling at the time of heating can be favorably suppressed, and good appearance durability at the time of heating is obtained.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, still more preferably 99.9% or more.

C-2. protective layer

Each of the first polarizing plate 2 and the second polarizing plate 4 may further include a protective layer. The protective layer may be provided on at least one surface of the polarizer, or may be provided on both surfaces of the polarizer. In the image display device 10, the first polarizing plate 2 is provided with a protective layer 22 provided on the surface of the polarizer 21 on the viewing side, and the second polarizing plate 4 is on the viewing side of the polarizer 41. A protective layer 42 is provided on the surface on the opposite side. In addition, in the image display device 11, the protective layer 22 is provided on the surface opposite to the viewing side of the polarizer 21, and the protective layer 42 is provided on the viewing side of the polarizer 41. .

The protective layer is formed of any suitable film that can be used as a protective layer of a polarizer. Specific examples of the material serving as the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and transparent resins such as polysulfone, polystyrene, polynorbornene, polyolefin, (meth)acrylic, and acetate resins. Further, thermosetting resins such as (meth)acrylic, urethane-based, (meth)acrylurethane-based, epoxy-based, and silicone-based resins or ultraviolet curable resins may be used. In addition, glassy type polymers, such as a siloxane type polymer, are also mentioned, for example. Moreover, the polymer film of Unexamined-Japanese-Patent No. 2001-343529 (WO01/37007) can also be used. As a material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group on its side chain, a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group on its side chain can be used, for example, isobutene and N - A resin composition comprising an alternating copolymer of methyl maleimide and an acrylonitrile/styrene copolymer. The polymer film may be, for example, an extrusion molding of the resin composition.

When the polarizer disposed on the viewing side of the image display cell 6 has a protective layer located on the outermost surface of the image display device, the protective layer is optionally subjected to hard coat treatment, antireflection treatment, and anti-sticking treatment. , surface treatment such as antiglare treatment may be performed.

The thickness of the protective layer is typically 5 mm or less, preferably 1 mm or less, more preferably 1 μm to 500 μm, still more preferably 5 μm to 150 μm. In addition, when the surface treatment is performed, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer.

D. phase difference layer

As described above, the retardation layer 3 exhibits a refractive index characteristic of nx>nz>ny. Re (550) of the retardation layer 3 is typically 210 nm or more and 360 nm or less. When Re (550) of the retardation layer 3 is in this range, excellent color and luminance characteristics are realized because the moving distance on the Poincaré sphere is short, and shift due to the retardation component of the TFT (switching element) is reduced.

The retardation layer 3 may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases with the wavelength of the measurement light, or may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases with the wavelength of the measurement light. A flat wavelength dispersion characteristic that hardly changes even with the wavelength of the measurement light may be exhibited. The retardation layer 3 preferably exhibits flat wavelength dispersion characteristics.

The retardation layer 3 has a photoelastic coefficient of, for example, 10 × 10 ^-12 m ² /N or more, preferably 1.0 × 10 ^-12 m ² /N or more, and, for example, 100 × 10 ^-12 m ² /N or less, It is preferably 60×10 ^-12 m ² /N or less, more preferably 30×10 ^-12 m ² /N or less. When the photoelastic coefficient of the retardation layer 3 is equal to or less than the above upper limit, shift or variation in retardation values caused by shrinkage stress of the polarizer or heat of the backlight can be suppressed, and an image display device having good display uniformity (liquid crystal display device) ) can be obtained.

The thickness of the retardation layer 3 is typically 20 μm or more, preferably 30 μm or more, more preferably 40 μm or more, and typically 200 μm or less, preferably 150 μm or less.

The retardation layer 3 is typically a retardation film formed of any suitable resin capable of realizing the above characteristics. Examples of the resin forming the retardation layer 3 include polyarylate, polyamide, polyimide, polyester, polyaryl ether ketone, polyamideimide, polyesterimide, polyvinyl alcohol, polyfumaric acid ester, and polyethersulfone. , polysulfone, cycloolefin resin, polycarbonate resin, cellulose resin, and polyurethane. These resins may be used alone or in combination.

As the resin forming the retardation layer 3, preferably, a cycloolefin-based resin is used, and more preferably, a norbornene-based resin is used. Specific examples of the norbornene-based resin include "cycloolefin-based resin obtained by hydrogenating a ring-opening polymer of a norbornene-based monomer" described in Japanese Laid-Open Patent Publication No. 2006-208925.

The retardation layer 3 can be produced, for example, by bonding a highly shrinkable film (e.g., a polypropylene film) to both sides of a polymer film containing the above resin as a main component, and then heat-stretching using a longitudinal uniaxial stretching method in a roll stretching machine. can The high-shrinkability film is used to impart shrinkage force in a direction perpendicular to the stretching direction during heat stretching and to increase the refractive index (nz) of the retardation layer 3 in the thickness direction. The method of attaching the high-shrinkability film to both sides of the polymer film is not particularly limited, but a method of providing an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer and adhering the polymer film and the high-shrinkability film is an operation It is preferable in terms of excellent performance and economic feasibility.

In addition, by adjusting the thickness (original thickness) of the polymer film, the stretching temperature and the stretching ratio, the front retardation (R ₀ ) and the Nz coefficient of the retardation layer 3 can be adjusted within the above ranges.

The thickness (original thickness) of the polymer film is typically 80 µm or more, preferably 100 µm or more, and is typically 500 µm or less, preferably 400 µm or less, and more preferably 300 µm or less.

The stretching temperature is typically 120°C or higher, preferably 130°C or higher, and is typically 180°C or lower, preferably 170°C or lower.

The stretching ratio ((stretching direction dimension of retardation layer-stretching direction dimension of polymer film)/stretching direction dimension of polymer film × 100) is typically 0.1% or more, preferably 0.3% or more, and is typically 80% or less, preferably 70% or less.

E. liquid crystal cell

The liquid crystal cell 6a includes a first substrate 62 and a second substrate 63 and a liquid crystal layer 61 interposed therebetween and including liquid crystal molecules aligned in a homogeneous arrangement in the absence of an electric field. do. In a general configuration, a color filter and a black matrix are provided on one substrate (typically, the first substrate 62), and the other substrate (typically, the second substrate 63) controls the electro-optical characteristics of the liquid crystal. A switching element, a scan line for giving a gate signal to the switching element, a signal line for giving a source signal, a pixel electrode, and a counter electrode are provided. The distance between the substrates (cell gap) is controlled by a spacer or the like. An alignment layer made of, for example, polyimide may be provided on a side of the substrate in contact with the liquid crystal layer.

Rth (550) of the first substrate 62 and the second substrate 63 is -10 nm to 100 nm, respectively. In one embodiment, Rth (550) of at least one of the first substrate 62 and the second substrate 63 is preferably 8 nm to 90 nm, more preferably 15 nm to 80 nm, still more preferably 20 nm ~ 70 nm, particularly preferably 30 nm ~ 60 nm. In another embodiment, Rth (550) of at least one of the first substrate 62 and the second substrate 63 is preferably -0.1 nm or less, more preferably -5 nm to -50 nm. According to an embodiment of the present invention, when the substrate has such a phase difference in the thickness direction, black luminance in an oblique direction can be sufficiently reduced in a liquid crystal display device including liquid crystal cells of homogeneous alignment.

In one embodiment, at least one of the first substrate 62 and the second substrate 63 satisfies the relationship of Rth(450)>Rth(550), and preferably the first substrate 62 and the second substrate 62 Both sides of the substrate 63 satisfy the relationship of Rth(450)>Rth(550). More preferably, at least one of the first substrate 62 and the second substrate 63 further satisfies the relationship of Rth(550) > Rth(650), and still more preferably the first substrate 62 and the second substrate 63 Both of the two substrates 63 further satisfy the relationship of Rth(550)>Rth(650). According to an embodiment of the present invention, black luminance in an oblique direction can be sufficiently reduced in a liquid crystal display device including a liquid crystal cell of homogeneous alignment even when the substrate has such a wavelength dispersion characteristic.

As described above, the liquid crystal layer 61 includes liquid crystal molecules aligned in a homogeneous arrangement in the absence of an electric field. 'Liquid crystal molecules aligned in a homogeneous arrangement' refers to a state in which the orientation vector of the liquid crystal molecules is parallel and equally aligned with the plane of the substrate as a result of the interaction between the liquid crystal molecules and the substrate subjected to alignment treatment. Such a liquid crystal layer (result, a liquid crystal cell) typically exhibits a refractive index characteristic of nx > ny = nz. Here, 'ny = nz' includes not only the case where ny and nz are completely equal, but also the case where ny and nz are substantially equal. Re(550) of the liquid crystal layer may be, for example, 300 nm to 400 nm. The Nz coefficient of the liquid crystal layer may be, for example, 0.9 to 1.1.

In one embodiment, the liquid crystal molecules of the liquid crystal layer have a pre-tilt. That is, the orientation vector of the liquid crystal molecules is slightly inclined with respect to the substrate plane. The pre-tilt angle is preferably 0.1° to 1.0°, more preferably 0.2° to 0.7°.

As the driving mode of the liquid crystal cell 6a, for example, an in-plane switching (IPS) mode and a fringe field switching (FFS) mode are exemplified. In addition, the IPS mode includes a super-in-plane switching (S-IPS) mode and an advanced super-in-plane switching (AS-IPS) mode employing V-shaped electrodes or zigzag electrodes. Further, the FFS mode includes an advanced fringe field switching (A-FFS) mode and an ultra fringe field switching (U-FFS) mode employing V-shaped electrodes or zigzag electrodes. As the driving mode of the liquid crystal cell 6a, an in-plane switching (IPS) mode is preferably used.

When the driving mode of the liquid crystal cell 6a is the IPS mode, the visibility in the oblique direction of the liquid crystal display device can be improved.

F. Back light unit

The light source 7 is disposed at a position corresponding to the side surface of the light guide plate 8 . As the light source, for example, an LED light source configured by arranging a plurality of LEDs can be used. As the light guide plate 8, any suitable light guide plate can be used. For example, a light guide plate having a lens pattern formed on the back side and a light guide plate having a prism shape or the like formed on the rear side and/or the viewer side are used so that light from the horizontal direction can be deflected in the thickness direction. Preferably, a light guide plate in which prism shapes are formed on the rear side and the viewer side is used. In the light guide plate, the prism shape formed on the rear side and the prism shape formed on the viewer side preferably have orthogonal directions of ridge lines. If such a light guide plate is used, light that is more easily condensed can be made incident on a prism sheet (not shown).

[Example]

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited by these examples. Evaluation items in Examples are as follows.

(1) maximum black luminance

A black screen was displayed on the image display devices obtained in Examples and Comparative Examples, and a polar angle of 60 ° and an azimuth angle were circled using a luminance meter (manufactured by AUTONIC-MELCHERS, trade name 'Conoscope') The luminance of was obtained, and the maximum value thereof was taken as the maximum black luminance (unit: cd/m ² ).

[Production Example 1: Production of the first polarizing plate]

Corona treatment was performed on one side of the resin substrate using an amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a long shape and a Tg of about 75° C. as the thermoplastic resin substrate.

Polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name 'Gosephamer') mixed in a 9: 1 ratio of 100 parts by weight of a PVA-based resin 13 parts by weight of potassium iodide What was added was dissolved in water to prepare a PVA aqueous solution (coating liquid).

A PVA-based resin layer having a thickness of 13 μm was formed by applying the PVA aqueous solution to the corona-treated surface of the resin substrate and drying at 60° C. to prepare a laminate.

The obtained layered product was uniaxially stretched 2.4 times in the machine direction (longitudinal direction) in a 130°C oven (air assisted stretching treatment).

Next, the laminate was immersed in an insolubilization bath (boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insolubilization treatment).

Next, in a dyeing bath (100 parts by weight of water, an iodine aqueous solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ° C., the single transmittance (Ts) of the polarizer finally obtained is the desired value. It was immersed for 60 seconds while adjusting the concentration so as to be (dyeing treatment).

Next, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in an aqueous solution of boric acid at a liquid temperature of 70°C (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight), while the total draw ratio was 5.5 in the machine direction (longitudinal direction) between rolls having different circumferential speeds. Uniaxial stretching was performed so as to double (underwater stretching treatment).

Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20°C (washing treatment).

Thereafter, while drying in an oven maintained at about 90°C, it was brought into contact with a heating roll made of SUS whose surface temperature was maintained at about 75°C (dry shrinkage treatment).

In this way, a polarizer having a thickness of about 5 μm was formed on the resin substrate, and a laminate having a configuration of resin substrate/polarizer was obtained.

An HC-TAC film was bonded as a protective layer to the polarizer surface (the surface on the opposite side to the resin substrate) of the obtained laminate. Then, the resin substrate was peeled off to obtain a first polarizing plate having a configuration of a protective layer/polarizer.

[Production Example 2: Production of Second Polarizing Plate]

It carried out similarly to manufacture example 1, and obtained the laminated body which has a structure of resin base material/polarizer. A TAC film (thickness of 20 μm) was bonded as a protective layer to the polarizer surface (surface on the opposite side to the resin substrate) of the obtained laminate. Next, the resin substrate is peeled off, and a reflective polarizer (thickness: 26 μm) is bonded to the peeled surface with an adhesive layer (thickness: 12 μm) interposed therebetween to obtain a second polarizing plate having a configuration of a reflective polarizer/polarizer/protective layer. Got it.

[Production Example 3: Production of Phase Contrast Layer]

A cycloolefin (norbornene)-based resin film (trade name Arton3 manufactured by JSR) having a thickness (original thickness) shown in Table 3 was prepared. Next, a highly shrinkable polypropylene film was bonded to both sides of the cycloolefin (norbornene)-based resin film via an acrylic pressure-sensitive adhesive layer. Then, the longitudinal direction of the film was maintained with a roll stretching machine, and the film was stretched at the temperature and magnification shown in Table 3 to produce a retardation layer exhibiting refractive index characteristics of nx>nz>ny. Table 3 shows the correlation between the front retardation (R ₀ ) and Nz coefficient of the obtained retardation layer and the disk thickness, temperature, and magnification.

[Production Example 4: Preparation of Image Display Cell (Liquid Crystal Cell)]

A liquid crystal cell was taken out from an IPS mode liquid crystal display device (manufactured by Apple, trade name "iPad (registered trademark)"). The optical member attached to both surfaces of the said liquid crystal cell was removed, and the removal surface (outer surface of a board|substrate) was washed. This was used as an image display cell (liquid crystal cell). The first substrate of the liquid crystal cell is Rth(450)=32nm, Rth(550)=19nm, Rth(650)=23nm; The second substrate was Rth(450) = 9 nm, Rth(550) = 0.3 nm, and Rth(650) = -6 nm.

[Examples 1 to 6 and Comparative Examples 1 to 54: O mode]

The retardation layer of Production Example 3 and the first polarizing plate of Production Example 1 were laminated in this order on the viewing side of the liquid crystal cell of Production Example 4. Table 4 shows the front retardation (R ₀ ) and Nz coefficient of the retardation layer in each Example and each Comparative Example.

On the other hand, the second polarizing plate of Preparation Example 2 was laminated on the rear side of the liquid crystal cell. In the stacking, the absorption axis direction of the polarizer of the first polarizing plate and the absorption axis direction of the polarizer of the second polarizing plate are substantially orthogonal, the absorption axis direction of the polarizer of the first polarizing plate and the slow axis direction of the retardation layer are substantially parallel, It carried out so that the absorption axis direction of the polarizer of 2 polarizing plates and the initial stage orientation direction of a liquid crystal cell might become substantially parallel. In this way, an image display device (O mode liquid crystal display device) was produced. The value of said formula (1) in the obtained liquid crystal display device is shown in Table 4. In addition, the liquid crystal display device was subjected to evaluation of the maximum black luminance and evaluated according to the following criteria. The results are shown in Table 4.

○: less than 0.0072 cd/m ²

×: 0.0072 cd/m ² or more.

[Examples 7 to 23 and Comparative Examples 55 to 109: O mode]

An image display device (O-mode liquid crystal display device ) was produced. The value of said formula (1) in the obtained liquid crystal display device is shown in Table 5. In addition, the liquid crystal display device was subjected to evaluation of the maximum black luminance and evaluated according to the following criteria. The results are shown in Table 5.

○: less than 0.0127 cd/m ²

×: 0.0127 cd/m ² or more.

[Examples 24 to 35 and Comparative Examples 110 to 169: E mode]

The first polarizing plate of Production Example 1 was laminated on the viewing side of the liquid crystal cell of Production Example 4.

On the other hand, the retardation layer of Preparation Example 3 and the second polarizing plate of Preparation Example 2 were stacked in this order on the rear side of the liquid crystal cell. In the stacking, the direction of the absorption axis of the polarizer of the first polarizing plate and the direction of the absorption axis of the second polarizer are substantially orthogonal, the direction of the absorption axis of the polarizer of the first polarizing plate and the direction of the slow axis of the retardation layer are substantially parallel, and the second polarizing plate The direction of the absorption axis of the polarizer and the initial orientation direction of the liquid crystal cell were substantially orthogonal to each other. In this way, an image display device (E-mode liquid crystal display device) was produced. Table 6 shows the values of the above formula (1) in the obtained liquid crystal display device. In addition, the liquid crystal display device was subjected to evaluation of the maximum black luminance and evaluated according to the following criteria. The results are shown in Table 6.

○: less than 0.0138 cd/m ²

×: 0.0138 cd/m ² or more.

[Examples 36 to 38 and Comparative Examples 170 to 214: E mode]

An image display device (E-mode liquid crystal display device ) was produced. Table 7 shows the values of the above formula (1) in the obtained liquid crystal display device. In addition, the liquid crystal display device was subjected to evaluation of the maximum black luminance and evaluated according to the following criteria. The results are shown in Table 7.

○: less than 0.0064 cd/m ²

×: 0.0064 cd/m ² or more.

[evaluation]

As is clear from Tables 4 to 7, an image display device (liquid crystal display device) having a sufficiently small black luminance in an oblique direction can be realized by making the above equation (1) less than a predetermined value.

The polarizing plate and image display device with a retardation layer of the present invention are suitable for use in portable devices such as personal digital assistants (PDAs), mobile phones, watches, digital cameras, and portable game machines, OA devices such as PC monitors, notebook computers, copiers, video cameras, Household appliances such as LCD TVs and microwave ovens, vehicle equipment such as back monitors, car navigation system monitors, car audios, display equipment such as information monitors for commercial stores, security equipment such as monitoring monitors, nursing monitors, It can be used for various applications such as nursing/medical devices such as medical monitors.

1: Polarizing plate with retardation layer
2: polarizer
21: polarizer
3: phase difference layer
6: image display cell
10: image display device

Claims (9)

A polarizing plate including a polarizer;
A retardation layer having a refractive index characteristic exhibiting a relationship of nx>nz>ny, disposed adjacent to the polarizing plate,
The absorption axis of the polarizer and the slow axis of the retardation layer are substantially parallel or substantially orthogonal,
A polarizing plate with a retardation layer that satisfies the relationship of the following formula (1):

(In Formula (1), a to j represent constants selected from the relationship between the absorption axis and the slow axis in either Table 1 or Table 2 below. R ₀ is the retardation layer at a wavelength of 550 nm. represents the front phase difference. NZ represents the Nz coefficient of the phase difference layer)
[Table 1]

[Table 2]

. According to claim 1,
wherein a to j represent constants selected from the relationship between the absorption axis and the slow axis in Table 1;
The absorption axis of the polarizer and the slow axis of the retardation layer are substantially parallel,
R ₀ of the retardation layer is 210 nm or more and 270 nm or less,
The Nz coefficient of the said retardation layer is 0.38 or more and 0.53 or less, The polarizing plate with a retardation layer. According to claim 1,
wherein a to j represent constants selected from the relationship between the absorption axis and the slow axis in Table 1;
The absorption axis of the polarizer and the slow axis of the retardation layer are substantially orthogonal,
R ₀ of the retardation layer is 270 nm or more and 360 nm or less,
The Nz coefficient of the said retardation layer is 0.42 or more and 0.68 or less, The polarizing plate with a retardation layer. According to claim 1,
wherein a to j represent constants selected from the relationship between the absorption axis and the slow axis in Table 2;
The absorption axis of the polarizer and the slow axis of the retardation layer are substantially orthogonal,
R ₀ of the retardation layer is 210 nm or more and 270 nm or less,
The Nz coefficient of the retardation layer is 0.42 or more and 0.53 or less, a polarizing plate with a retardation layer. According to claim 1,
wherein a to j represent constants selected from the relationship between the absorption axis and the slow axis in Table 2;
The absorption axis of the polarizer and the slow axis of the retardation layer are substantially parallel,
R ₀ of the retardation layer is 270 nm or more and 360 nm or less,
The Nz coefficient of the retardation layer is 0.47 or more and 0.63 or less, a polarizing plate with a retardation layer. an image display cell;
The polarizing plate with a retardation layer according to any one of claims 2 to 4, which is disposed on the viewing side with respect to the image display cell.
An image display device comprising a. an image display cell;
The polarizing plate with a retardation layer according to claim 5, disposed on the side opposite to the viewing side with respect to the image display cell.
An image display device comprising a. According to claim 6,
The image display cell is a liquid crystal cell,
The driving mode of the liquid crystal cell is an IPS mode, an image display device. According to claim 7,
The image display cell is a liquid crystal cell,
The driving mode of the liquid crystal cell is an IPS mode, an image display device.

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