JP2008129175A - Elliptical polarizing plate and vertically aligned liquid crystal display apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an elliptical polarizing plate that is superior in viewing angle characteristics, and to provide a vertically aligned liquid crystal display apparatus that uses the same. <P>SOLUTION: The elliptical polarizing plate is constituted by laminating at least a first polarizing plate, a first optically anisotropic layer, a second optical anisotropic layer, a third optical anisotropic layer and a fourth optical anisotropic layer, in this order. The first optically anisotropic layer satisfies Expression [1], the second anisotropic layer satisfies Expressions [2],[3], the third optically anisotropic layer satisfies Expression [4] and the fourth optical anisotropic layer satisfies Expressions [5],[6]. The expressions are [1] 50≤Re1≤300, [2] 0≤Re2≤20, [3] -500≤Rth2≤-30, [4] 100≤Re3≤180, [5] 0≤Re4≤20, [6] 100≤Rth4≤400, where Re denotes an in-plane retardation value of each optical anisotropic layer, and Rth denotes the retardation value in the thickness direction of each optically anisotropic layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an elliptically polarizing plate and a liquid crystal display device excellent in viewing angle characteristics, and more particularly to a vertical alignment type liquid crystal display device in which liquid crystal molecules are aligned perpendicularly to a substrate when no voltage is applied.

As one of display modes in the liquid crystal display device, there is a vertical alignment mode in which liquid crystal molecules in the liquid crystal cell are aligned perpendicularly to the substrate surface in the initial state. When no voltage is applied, the liquid crystal molecules are aligned perpendicular to the substrate surface, and a black display can be obtained by arranging linearly polarizing plates orthogonally on both sides of the liquid crystal cell.
The optical characteristics in the liquid crystal cell are isotropic in the in-plane direction, and ideal viewing angle compensation is easily possible. In order to compensate for positive uniaxial optical anisotropy in the thickness direction of the liquid crystal cell, an optical element having negative uniaxial optical anisotropy in the thickness direction is interposed between one or both surfaces of the liquid crystal cell and the linear polarizing plate. If it is inserted into, a very good black display viewing angle characteristic can be obtained.
When a voltage is applied, the orientation of liquid crystal molecules changes from a direction perpendicular to the substrate surface to a direction parallel to the substrate surface. At this time, it is difficult to make the liquid crystal alignment uniform. When the rubbing process for the substrate surface, which is a normal alignment process, is used, the display quality is significantly lowered.
In order to make the liquid crystal alignment uniform when a voltage is applied, there are proposals such as devising the electrode shape on the substrate, generating an oblique electric field in the liquid crystal layer, and obtaining uniform alignment. According to this method, a uniform liquid crystal alignment can be obtained, but a microscopic non-uniform alignment region is generated, and this region becomes a dark region when a voltage is applied. Therefore, the transmittance of the liquid crystal display device is reduced.

  According to Patent Document 1, a configuration is proposed in which linearly polarizing plates disposed on both sides of a liquid crystal element having a liquid crystal layer including a randomly aligned state are replaced with circularly polarizing plates. By replacing the linearly polarizing plate with a circularly polarizing plate that combines a linearly polarizing plate and a quarter-wave plate, a dark region at the time of voltage application can be eliminated and a high transmittance liquid crystal display device can be realized. However, a vertical alignment type liquid crystal display device using a circularly polarizing plate has a problem that viewing angle characteristics are narrower than that of a vertical alignment type liquid crystal display device using a linear polarizing plate. According to Patent Document 2, an optical anisotropic element having a negative uniaxial optical anisotropy or a biaxial optical anisotropic material is proposed as a viewing angle compensation of a vertical alignment type liquid crystal display device using a circularly polarizing plate. Has been. However, an optical anisotropic element having negative uniaxial optical anisotropy can compensate for positive uniaxial optical anisotropy in the thickness direction of the liquid crystal cell, but cannot compensate the viewing angle characteristics of the quarter-wave plate. A sufficient viewing angle characteristic cannot be obtained. Also, when producing a biaxial optically anisotropic material, when the in-plane main refractive index of the resulting retardation plate is nx, ny, the refractive index in the thickness direction is nz, and nx> ny Nz defined by Nz = (nx−nz) / (nx−ny) is −1.0 <Nz <0.1, and there is a limit to stretching in the thickness direction. Can not be controlled. Moreover, in the said manufacturing method, since the elongate film is heat-shrinked with the heat shrink film and it is extended | stretched in the thickness direction, thickness of the obtained phase difference plate increases rather than a elongate film. The thickness of the retardation plate obtained by the manufacturing method is about 50 to 100 μm, which is not sufficient for thinning required for a liquid crystal display device or the like.

According to Patent Documents 3 and 4, as a viewing angle compensation of a vertical alignment type liquid crystal display device using a circularly polarizing plate, an optical anisotropic element having negative uniaxial optical anisotropy as compensation of a liquid crystal cell, As a viewing angle compensation for a four-wavelength plate, a configuration combining a compensation layer having a large refractive index in the thickness direction and a polarizing plate compensation film has been proposed. However, these three types of films are used on both sides of the vertical alignment type liquid crystal display device, so that a total of six films are used, and further, a λ / 4 plate is used on both sides to provide a circularly polarizing plate function. For this reason, a total of 8 films are used, and although the viewing angle is greatly improved, it is not realistic in terms of both price and thickness.
Japanese Patent Laid-Open No. 2002-40428 JP 2003-207782 A JP 2002-55342 A JP 2006-85203 A

  An object of the present invention is to provide an elliptically polarizing plate for a vertical alignment type liquid crystal display device and a vertical alignment type liquid crystal display device which can be reduced in price and have excellent viewing angle characteristics.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by the elliptically polarizing plate shown below and a vertical alignment type liquid crystal display device using the same, thereby completing the present invention. It came.

That is, the present invention includes at least the first polarizing plate, the first optical anisotropic layer, the second optical anisotropic layer, the third optical anisotropic layer, and the fourth optical anisotropic layer. It is an elliptically polarizing plate laminated in order,
The first optically anisotropic layer satisfies the following [1],
[1] 50 ≦ Re1 ≦ 300
(Here, Re1 means an in-plane retardation value of the first optically anisotropic layer. Re1 is Re1 = (Nx1−Ny1) × d1 [nm], where d1 is The thickness of the first optically anisotropic layer, Nx1 and Ny1 are the main refractive index in the plane of the first optically anisotropic layer with respect to light having a wavelength of 550 nm, and Nz1 is the main refraction in the thickness direction with respect to light having a wavelength of 550 nm. (Nx1> Nz1 ≧ Ny1)
The second optically anisotropic layer satisfies the following [2] and [3],
[2] 0 ≦ Re2 ≦ 20
[3] −500 ≦ Rth2 ≦ −30
(Here, Re2 means an in-plane retardation value of the second optical anisotropic layer, and Rth2 means a retardation value in the thickness direction of the second optical anisotropic layer.) Re2 and Rth2 are respectively Re2 = (Nx2−Ny2) × d2 [nm] and Rth2 = {(Nx2 + Ny2) / 2−Nz2} × d2 [nm], where d2 is the second optical element. The thickness of the anisotropic layer, Nx2, Ny2 is the main refractive index in the plane of the second optical anisotropic layer for light having a wavelength of 550 nm, Nz2 is the main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nz2 > Nx2 ≧ Ny2.)
The third optically anisotropic layer satisfies the following [4],
[4] 100 ≦ Re3 ≦ 180
(Here, Re3 means an in-plane retardation value of the third optically anisotropic layer. Re3 is Re3 = (Nx3−Ny3) × d3 [nm], where d3 is The thickness of the third optically anisotropic layer, Nx3 and Ny3 are the main refractive index in the plane of the third optically anisotropic layer with respect to light having a wavelength of 550 nm, and Nz3 is the main refraction in the thickness direction with respect to light having a wavelength of 550 nm. (Nx3> Ny3 = Nz3)
The fourth optically anisotropic layer relates to an elliptically polarizing plate characterized by satisfying the following [5] and [6].
[5] 0 ≦ Re4 ≦ 20
[6] 100 ≦ Rth4 ≦ 400
(Here, Re4 means an in-plane retardation value of the fourth optically anisotropic layer, and Rth4 means a retardation value in the thickness direction of the fourth optically anisotropic layer.) Re4 and Rth4 are Re4 = (Nx4-Ny4) × d4 [nm] and Rth4 = {(Nx4 + Ny4) / 2−Nz4} × d4 [nm], respectively, where d4 is the fourth optical anisotropic. Nx4 is a main refractive index in the plane of the fourth optical anisotropic layer for light having a wavelength of 550 nm, Nz4 is a main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nx4 ≧ Ny4 > Nz4.)

The present invention also provides at least a first polarizing plate, a first optical anisotropic layer, a second optical anisotropic layer, a third optical anisotropic layer, a fourth optical anisotropic layer, and an electrode. A vertically aligned liquid crystal cell including liquid crystal molecules that are vertically aligned with respect to the substrate surface when no voltage is applied, a fifth optically anisotropic layer, and a second polarizing plate are arranged in this order between a pair of substrates including Vertical alignment type liquid crystal display device,
The first optically anisotropic layer satisfies the following [1],
[1] 50 ≦ Re1 ≦ 300
(Here, Re1 means an in-plane retardation value of the first optically anisotropic layer. Re1 is Re1 = (Nx1−Ny1) × d1 [nm], where d1 is The thickness of the first optically anisotropic layer, Nx1 and Ny1 are the main refractive index in the plane of the first optically anisotropic layer with respect to light having a wavelength of 550 nm, and Nz1 is the main refraction in the thickness direction with respect to light having a wavelength of 550 nm. (Nx1> Nz1 ≧ Ny1)
The second optically anisotropic layer satisfies the following [2] and [3],
[2] 0 ≦ Re2 ≦ 20
[3] −500 ≦ Rth2 ≦ −30
(Here, Re2 means an in-plane retardation value of the second optical anisotropic layer, and Rth2 means a retardation value in the thickness direction of the second optical anisotropic layer.) Re2 and Rth2 are respectively Re2 = (Nx2−Ny2) × d2 [nm] and Rth2 = {(Nx2 + Ny2) / 2−Nz2} × d2 [nm], where d2 is the second optical element. The thickness of the anisotropic layer, Nx2, Ny2 is the main refractive index in the plane of the second optical anisotropic layer for light having a wavelength of 550 nm, Nz2 is the main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nz2 > Nx2 ≧ Ny2.)
The third optically anisotropic layer satisfies the following [4],
[4] 100 ≦ Re3 ≦ 180
(Here, Re3 means an in-plane retardation value of the third optically anisotropic layer. Re3 is Re3 = (Nx3−Ny3) × d3 [nm], where d3 is The thickness of the third optically anisotropic layer, Nx3 and Ny3 are the main refractive index in the plane of the third optically anisotropic layer with respect to light having a wavelength of 550 nm, and Nz3 is the main refraction in the thickness direction with respect to light having a wavelength of 550 nm. (Nx3> Ny3 = Nz3)
The fourth optically anisotropic layer satisfies the following [5] and [6],
[5] 0 ≦ Re4 ≦ 20
[6] 100 ≦ Rth4 ≦ 400
(Here, Re4 means an in-plane retardation value of the fourth optically anisotropic layer, and Rth4 means a retardation value in the thickness direction of the fourth optically anisotropic layer.) Re4 and Rth4 are Re4 = (Nx4-Ny4) × d4 [nm] and Rth4 = {(Nx4 + Ny4) / 2−Nz4} × d4 [nm], respectively, where d4 is the fourth optical anisotropic. Nx4 is a main refractive index in the plane of the fourth optical anisotropic layer for light having a wavelength of 550 nm, Nz4 is a main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nx4 ≧ Ny4 > Nz4.)
The fifth optically anisotropic layer satisfies the following [7], and relates to a vertical alignment type liquid crystal display device.
[7] 100 ≦ Re5 ≦ 180
(Here, Re5 means an in-plane retardation value of the fifth optically anisotropic layer. Re5 is Re5 = (Nx5-Ny5) × d5 [nm], where d5 is The thickness of the fifth optically anisotropic layer, Nx5 and Ny5 are the main refractive indices in the plane of the fifth optically anisotropic layer for light with a wavelength of 550 nm, and Nz5 is the main refraction in the thickness direction for light with a wavelength of 550 nm. (Nx5> Ny5 = Nz5)

In addition, the present invention provides at least a pair of substrates including a first polarizing plate, a second optical anisotropic layer, a third optical anisotropic layer, a fourth optical anisotropic layer, and an electrode. A vertically aligned liquid crystal cell containing liquid crystal molecules that are aligned vertically with respect to the substrate surface when no voltage is applied, a fifth optically anisotropic layer, a first optically anisotropic layer, and a second polarizing plate are arranged in this order. Vertical alignment type liquid crystal display device,
The first optically anisotropic layer satisfies the following [1],
[1] 50 ≦ Re1 ≦ 300
(Here, Re1 means an in-plane retardation value of the first optically anisotropic layer. Re1 is Re1 = (Nx1−Ny1) × d1 [nm], where d1 is The thickness of the first optically anisotropic layer, Nx1 and Ny1 are the main refractive index in the plane of the first optically anisotropic layer with respect to light having a wavelength of 550 nm, and Nz1 is the main refraction in the thickness direction with respect to light having a wavelength of 550 nm. (Nx1> Nz1 ≧ Ny1)
The second optically anisotropic layer satisfies the following [2] and [3],
[2] 0 ≦ Re2 ≦ 20
[3] −500 ≦ Rth2 ≦ −30
(Here, Re2 means an in-plane retardation value of the second optical anisotropic layer, and Rth2 means a retardation value in the thickness direction of the second optical anisotropic layer.) Re2 and Rth2 are respectively Re2 = (Nx2−Ny2) × d2 [nm] and Rth2 = {(Nx2 + Ny2) / 2−Nz2} × d2 [nm], where d2 is the second optical element. The thickness of the anisotropic layer, Nx2, Ny2 is the main refractive index in the plane of the second optical anisotropic layer for light having a wavelength of 550 nm, Nz2 is the main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nz2 > Nx2 ≧ Ny2.)
The third optically anisotropic layer satisfies the following [4],
[4] 100 ≦ Re3 ≦ 180
(Here, Re3 means an in-plane retardation value of the third optically anisotropic layer. Re3 is Re3 = (Nx3−Ny3) × d3 [nm], where d3 is The thickness of the third optically anisotropic layer, Nx3 and Ny3 are the main refractive index in the plane of the third optically anisotropic layer with respect to light having a wavelength of 550 nm, and Nz3 is the main refraction in the thickness direction with respect to light having a wavelength of 550 nm. (Nx3> Ny3 = Nz3)
The fourth optically anisotropic layer satisfies the following [5] and [6],
[5] 0 ≦ Re4 ≦ 20
[6] 100 ≦ Rth4 ≦ 400
(Here, Re4 means an in-plane retardation value of the fourth optically anisotropic layer, and Rth4 means a retardation value in the thickness direction of the fourth optically anisotropic layer.) Re4 and Rth4 are Re4 = (Nx4-Ny4) × d4 [nm] and Rth4 = {(Nx4 + Ny4) / 2−Nz4} × d4 [nm], respectively, where d4 is the fourth optical element. The thickness of the anisotropic layer, Nx4 and Ny4 are the main refractive index in the plane of the fourth optical anisotropic layer for light having a wavelength of 550 nm, Nz4 is the main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nx4 ≧ Ny4> Nz4.)
The fifth optically anisotropic layer satisfies the following [7], and relates to a vertical alignment type liquid crystal display device.
[7] 100 ≦ Re5 ≦ 180
(Here, Re5 means an in-plane retardation value of the fifth optically anisotropic layer. Re5 is Re5 = (Nx5-Ny5) × d5 [nm], where d5 is The thickness of the fifth optically anisotropic layer, Nx5 and Ny5 are the main refractive indices in the plane of the fifth optically anisotropic layer for light with a wavelength of 550 nm, and Nz5 is the main refraction in the thickness direction for light with a wavelength of 550 nm. (Nx5> Ny5 = Nz5)

In addition, the present invention provides a sixth optical difference satisfying the following [8] and [9] between the vertical alignment liquid crystal cell and the fifth optical anisotropic layer of the vertical alignment liquid crystal display device. The present invention relates to the vertical alignment type liquid crystal display device having an isotropic layer.
[8] 0 ≦ Re6 ≦ 20
[9] 100 ≦ Rth6 ≦ 400
(Here, Re6 means the in-plane retardation value of the sixth optically anisotropic layer, and Rth6 means the retardation value in the thickness direction of the sixth optically anisotropic layer.) Re6 and Rth6 are Re6 = (Nx6-Ny6) × d6 [nm] and Rth6 = {(Nx6 + Ny6) / 2−Nz6} × d6 [nm], respectively, where d6 is the sixth optical element. The thickness of the anisotropic layer, Nx6, Ny6 is the main refractive index in the surface of the sixth optical anisotropic layer for light having a wavelength of 550 nm, Nz6 is the main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nx6 ≧ Ny6> Nz6.)

  The vertical alignment type liquid crystal display device of the present invention has a bright display and can display with high contrast in all directions.

Hereinafter, the present invention will be described in detail.
The elliptically polarizing plate of the present invention includes at least a first polarizing plate, a first optically anisotropic layer, a second optically anisotropic layer, a third optically anisotropic layer, a fourth layer as shown in FIG. These are elliptically polarizing plates in which the optically anisotropic layers are laminated in this order.
The vertical alignment type liquid crystal display device of the present invention is composed of the following two types, and members such as a light diffusion layer, a light control film, a light guide plate, and a prism sheet are further added as necessary. In the present invention, there is no particular limitation except that a second optically anisotropic layer made of a homeotropic alignment liquid crystal film is used. Any of the configurations (1) to (2) may be used in terms of obtaining optical characteristics with little viewing angle dependency.

(1) First polarizing plate / first optical anisotropic layer / second optical anisotropic layer / third optical anisotropic layer / fourth optical anisotropic layer / vertical alignment liquid crystal cell / 5th optical anisotropic layer / second polarizing plate / backlight (2) first polarizing plate / second optical anisotropic layer / third optical anisotropic layer / fourth optical anisotropy Layer / liquid crystal cell / fifth optical anisotropic layer / first optical anisotropic layer / second polarizing plate / backlight

Further, a sixth optical anisotropic layer is inserted between the vertical alignment liquid crystal cell and the fifth optical anisotropic layer of the vertical alignment liquid crystal display devices (1) and (2), The configurations of 3) to (4) can also be used.
(3) First polarizing plate / first optical anisotropic layer / second optical anisotropic layer / third optical anisotropic layer / fourth optical anisotropic layer / vertical alignment liquid crystal cell / (6) first optical anisotropic layer / fifth optical anisotropic layer / second polarizing plate / backlight (4) first polarizing plate / second optical anisotropic layer / third optical anisotropy Layer / fourth optical anisotropic layer / liquid crystal cell / sixth optical anisotropic layer / fifth optical anisotropic layer / first optical anisotropic layer / second polarizing plate / backlight By reducing the configuration of the eight films proposed in Patent Documents 3 and 4 to five or six films, the cost can be reduced while maintaining wide viewing angle characteristics.

Hereinafter, the constituent members used in the present invention will be described in order.
First, the vertical alignment type liquid crystal cell used in the present invention will be described.
Although there is no restriction | limiting in particular as a liquid crystal cell, Various liquid crystal cells of a transmissive type, a reflective type, and a semi-transmissive type can be mentioned. The driving method of the liquid crystal cell is not particularly limited, and is a passive matrix method used for STN-LCDs, an active matrix method using active electrodes such as TFT (Thin Film Transistor) electrodes, TFD (Thin Film Diode) electrodes, and a plasma addressing method. Any driving method may be used.

  The transparent substrate constituting the liquid crystal cell is not particularly limited as long as the liquid crystal material constituting the liquid crystal layer is aligned in a specific alignment direction. Specifically, a transparent substrate having the property of aligning the liquid crystal itself, a substrate itself lacking alignment ability, but a transparent substrate provided with an alignment film having the property of aligning liquid crystal, etc. Can also be used. Moreover, well-known things, such as ITO, can be used for the electrode of a liquid crystal cell. The electrode can usually be provided on the surface of the transparent substrate with which the liquid crystal layer is in contact. When a substrate having an alignment film is used, it can be provided between the substrate and the alignment film.

  The material exhibiting liquid crystallinity for forming the liquid crystal layer is not particularly limited as long as it has a negative dielectric anisotropy, and various ordinary low-molecular liquid crystal substances and polymer liquid crystals capable of constituting various liquid crystal cells. Materials and mixtures thereof. In addition, a dye, a chiral agent, a non-liquid crystal substance, or the like can be added to these as long as liquid crystallinity is not impaired. If a chiral agent is added to a vertically aligned liquid crystal layer using a liquid crystal material exhibiting negative dielectric anisotropy and the liquid crystal molecules are rotated when voltage is applied, the rotation of the liquid crystal molecules when voltage is applied should be stabilized. Can do. Furthermore, when the rubbing directions of the upper and lower substrates are other than the same direction, the trace of the alignment process is not the same direction, so that the streak is less noticeable. In addition, if the liquid crystal layer is twisted by 90 degrees, retardation occurs in the tilt direction of the liquid crystal molecules when tilted by several degrees with respect to the substrate to prevent disclination when a voltage is applied. Since the directions in which the liquid crystal molecules in the vicinity are inclined at an angle of 90 degrees in the vicinity of the upper and lower substrates, the generated retardation can be canceled and a black display with less leakage light can be obtained.

In addition, a transflective vertical alignment type liquid crystal cell can be obtained by using one substrate of the vertical alignment type liquid crystal cell as a substrate having a region having a reflection function and a region having a transmission function.
A region having a reflection function (hereinafter sometimes referred to as a reflective layer) included in the transflective electrode used in the transflective vertical alignment type liquid crystal cell is not particularly limited, and may be aluminum, silver, gold Examples thereof include metals such as chromium and platinum, alloys containing them, oxides such as magnesium oxide, dielectric multilayer films, liquid crystals exhibiting selective reflection, or combinations thereof. These reflective layers may be flat or curved. Furthermore, the reflective layer is processed to have a surface shape such as an uneven shape to give diffuse reflection, to the electrode on the electrode substrate opposite to the viewer side of the liquid crystal cell, or a combination thereof It may be.

  The vertical alignment type liquid crystal cell of the present invention can be provided with other constituent members in addition to the constituent members described above. For example, by attaching a color filter to the liquid crystal display device of the present invention, a color liquid crystal display device capable of performing multicolor or full color display with high color purity can be manufactured.

Next, the optically anisotropic layer used in the present invention will be described in order.
First, the first, third, and fifth optical anisotropic layers will be described.
As the optically anisotropic layer, for example, a film made of an appropriate polymer such as polycarbonate, norbornene resin, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, or polyamide is uniaxially or biaxially stretched. A birefringent film, a liquid crystal polymer, etc. produced by a method of processing, a method of heat shrinking the width direction of a long film with a heat shrink film as shown in JP-A-5-157911, and increasing the phase difference in the thickness direction And an alignment film made of the above liquid crystal material, and an alignment layer of the liquid crystal material supported by the film.
As said optically anisotropic layer, a polycarbonate and a norbornene-type resin are preferable.

  When the x and y directions are taken in the in-plane direction and the thickness direction is the z direction, the positive uniaxial optically anisotropic layer has a relationship of nx> ny = nz as a refractive index. The positive biaxial optically anisotropic layer has a relationship of nx> nz> ny as a refractive index. The negative uniaxial optically anisotropic layer has a relationship of nx = ny> nz as a refractive index. The negative biaxial optically anisotropic layer has a relationship of nx> ny> nz as a refractive index.

The first optical anisotropic layer has a thickness d1 of the first optical anisotropic layer, Nx1 and Ny1 main refractive indexes in the first optical anisotropic layer surface, and a main refractive index in the thickness direction. When Nz1 and Nx1> Nz1 ≧ Ny1 and an in-plane retardation value for light having a wavelength of 550 nm (Re1 = (Nx1−Ny1) × d1 [nm]), the following equation [1] is satisfied.
[1] 50 ≦ Re1 ≦ 300
The first optically anisotropic layer contributes to the viewing angle compensation of the polarizing plate, and the retardation value (Re1) in the first optically anisotropic layer surface is usually 50 nm to 550 nm for light of 550 nm. It is in the range of 300 nm, preferably 80 nm to 200 nm, more preferably 100 nm to 140 nm. When the Re1 value is out of the above range, a sufficient viewing angle improvement effect may not be obtained, or unnecessary coloring may occur when viewed from an oblique direction.

The third and fifth optically anisotropic layers preferably exhibit a quarter wavelength retardation in the plane, and the thicknesses of the third and fifth optically anisotropic layers are d3, d5, and third. Nx3, Nx5 and Ny3, Ny5, the main refractive indexes in the thickness direction are Nz3, Nz5, and Nx3> Ny3 = Nz3, Nx5> Ny5 = Nz5, When the in-plane retardation value in light with a wavelength of 550 nm (Re3 = (Nx3-Ny3) × d3 [nm], Re5 = (Nx5-Ny5) × d5 [nm]), the following [4], [ 7] Expression is satisfied.
[4] 100 ≦ Re3 ≦ 180
[7] 100 ≦ Re5 ≦ 180

  The third and fifth optically anisotropic layers exhibit retardation values in the planes of the third and fifth optically anisotropic layers with respect to 550 nm light in that they exhibit a phase difference of ¼ wavelength. Re3, Re5) are usually in the range of 100 nm to 180 nm, preferably 120 nm to 160 nm, more preferably 130 nm to 150 nm. When the Re3 and Re5 values are out of the above ranges, the circular polarization when combined with the polarizing plate cannot be sufficiently obtained, and the display characteristics when viewed from the front may be deteriorated.

The angle formed by the slow axis of the third optically anisotropic layer and the slow axis of the fifth optically anisotropic layer is usually 80 to 100 degrees, preferably 85 to 95 degrees, more preferably about 90 degrees. (Orthogonal) range. When outside the above range, the contrast when viewed from the front may be lowered.
The in-plane retardation values of the third and fifth optically anisotropic layers with wavelengths of 450 nm and 590 nm are respectively Re3 (450), Re3 (590), Re5 (450), and Re5 (590). The following equations [10] and [11] are satisfied.
[10] 0.7 ≦ Re3 (450) / Re3 (590) ≦ 1.05
[11] 0.7 ≦ Re5 (450) / Re5 (590) ≦ 1.05

  In terms of improving the contrast characteristics at the time of reflection of the transflective vertical alignment type liquid crystal display device, the dependence of the retardation value of the quarter-wave plate on the wavelength increases as the wavelength increases. Alternatively, it is preferably close to constant, and the ratio of the phase difference values of the third and fifth optically anisotropic layers with respect to 450 nm light and 590 nm light (the above [10] and [11]) is usually 0.7 to 1.05, preferably in the range of 0.75 to 1.0. If it is out of the above range, the display characteristics may be deteriorated such that the black display upon reflection becomes a bluish color.

The circularly polarizing plate has a function of changing linearly polarized light into circularly polarized light or changing circularly polarized light into linearly polarized light with a quarter wave plate, and has linearly polarizing plates on both sides of the vertical alignment type liquid crystal cell. By having the third and fifth optically anisotropic layers having a phase difference of ¼ wavelength in the plane between the liquid crystal cell and the vertical alignment type liquid crystal cell, the phase difference in the observation direction of the liquid crystal layer can be reduced when no voltage is applied. Since the upper and lower polarizing plates are orthogonal to each other because of 0, dark display becomes possible, and when a voltage is applied, a phase difference in the observation direction occurs and bright display becomes possible. The angle formed between the absorption axis of the first polarizing plate and the slow axis of the third optically anisotropic layer is that a circularly polarizing plate is formed by combining a linear polarizing plate with a quarter wave plate. When p is set, it is usually in the range of 40 ° to 50 °, preferably 42 to 48 °, more preferably about 45 °.
Similarly, when the angle formed by the absorption axis of the second polarizing plate and the slow axis of the fifth optically anisotropic layer is q, 40 ° to 50 °, preferably 42 to 48 °, More preferably, it is a range of about 45 °. In a range other than the above, there is a risk of image quality deterioration due to a decrease in front contrast.

Next, the second optical anisotropic layer will be described.
The second optically anisotropic layer of the present invention is composed of a homeotropic alignment liquid crystal film in which a liquid crystal material exhibiting positive uniaxial property is homeotropically aligned in a liquid crystal state and then fixed in alignment. In the present invention, selection of a liquid crystal material and an alignment substrate is extremely important for obtaining a liquid crystal film in which the homeotropic alignment of the liquid crystal material is fixed.
The liquid crystal material used in the present invention contains at least a side chain type liquid crystalline polymer such as poly (meth) acrylate or polysiloxane as a main constituent component.
Further, the side chain type liquid crystal polymer used in the present invention has a polymerizable oxetanyl group at the terminal. More specifically, the side chain obtained by homopolymerizing the (meth) acrylic moiety of the (meth) acrylic compound having an oxetanyl group represented by the formula (1) or copolymerizing with another (meth) acrylic compound. A preferred example is a liquid crystalline polymer material.

In the above formula (1), R ₁ represents hydrogen or a methyl group, R ₂ represents hydrogen, a methyl group or an ethyl group, and L ₁ and L ₂ each independently represent a single bond, —O—, —O—CO. -Represents either-or -CO-O-, M represents Formula (2), Formula (3) or Formula (4), and n and m each independently represent an integer of 0 to 10.
-P ₁ -L ₃ -P ₂ -L ₄ -P _3- (2)
-P ₁ -L ₃ -P _3- (3)
-P _3- (4)

In formulas (2) to (4), P ₁ and P ₂ each independently represent a group selected from formula (5), P ₃ represents a group selected from formula (6), and L ₃ and L ₄ are Each represents a single bond, —CH═CH—, —C≡C—, —O—, —O—CO— or —CO—O—.

  The method for synthesizing these (meth) acrylic compounds having an oxetanyl group is not particularly limited, and can be synthesized by applying a method used in an ordinary organic chemical synthesis method. For example, by combining a site having an oxetanyl group and a site having a (meth) acrylic group by means such as Williamson's ether synthesis or ester synthesis using a condensing agent, oxetanyl group and (meth) acrylic group 2 A (meth) acrylic compound having an oxetanyl group having two reactive functional groups can be synthesized.

  It is represented by the following formula (7) by homopolymerizing the (meth) acrylic group of the (meth) acrylic compound having an oxetanyl group represented by the formula (1) or copolymerizing with another (meth) acrylic compound. A side-chain liquid crystalline polymer substance containing units can be obtained. The polymerization conditions are not particularly limited, and normal radical polymerization or anionic polymerization conditions can be employed.

  As an example of radical polymerization, a (meth) acrylic compound is dissolved in a solvent such as dimethylformamide (DMF), and 2,2′-azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), or the like is used as an initiator. The method of making it react at 60-120 degreeC for several hours is mentioned. Moreover, in order to make the liquid crystal phase appear stably, copper bromide (I) / 2,2′-bipyridyl series, 2,2,6,6-tetramethylpiperidinooxy free radical (TEMPO) series, etc. are used. A method of controlling the molecular weight distribution by conducting living radical polymerization as an initiator is also effective. These radical polymerizations are preferably performed under deoxygenation conditions.

  Examples of anionic polymerization include a method in which a (meth) acrylic compound is dissolved in a solvent such as tetrahydrofuran (THF) and reacted with a strong base such as an organic lithium compound, an organic sodium compound, or a Grignard reagent as an initiator. In addition, the molecular weight distribution can be controlled by optimizing the initiator and the reaction temperature for living anionic polymerization. These anionic polymerizations must be performed strictly under dehydration and deoxygenation conditions.

  In addition, the (meth) acryl compound to be copolymerized at this time is not particularly limited and may be anything as long as the synthesized polymer substance exhibits liquid crystallinity, but in order to increase the liquid crystallinity of the synthesized polymer substance, A (meth) acrylic compound having a mesogenic group is preferred. For example, a (meth) acrylic compound represented by the following formula can be exemplified as a preferred compound.

Here, R represents hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a cyano group.
The side chain type liquid crystalline polymer substance preferably contains 5 to 100 mol% of the unit represented by the formula (7), and particularly preferably contains 10 to 100 mol%. The side chain type liquid crystalline polymer substance preferably has a weight average molecular weight of 2,000 to 100,000, particularly preferably 5,000 to 50,000.

  The liquid crystal material used in the present invention may contain various compounds that can be mixed without impairing liquid crystallinity, in addition to the side-chain liquid crystalline polymer substance. Examples of compounds that can be contained include compounds having a cationic polymerizable functional group such as an oxetanyl group, an epoxy group, and a vinyl ether group, various polymer substances having film-forming ability, and various low-molecular liquid crystal compounds exhibiting liquid crystallinity. And polymer liquid crystalline compounds. When the side chain liquid crystalline polymer substance is used as a composition, the proportion of the side chain liquid crystalline polymer substance in the entire composition is 10% by mass or more, preferably 30% by mass or more, and more preferably. Is 50 mass% or more. If the content of the side chain type liquid crystalline polymer substance is less than 10% by mass, the concentration of the polymerizable group in the composition becomes low, and the mechanical strength after polymerization becomes insufficient.

  In addition, the liquid crystal material is subjected to alignment treatment, and then the oxetanyl group is cationically polymerized to crosslink to fix the liquid crystal state. For this reason, it is preferable that the liquid crystal material contains a photocation generator and / or a thermal cation generator that generates cations by an external stimulus such as light or heat. If necessary, various sensitizers may be used in combination.

The photo cation generator means a compound capable of generating a cation by irradiating with light having an appropriate wavelength, and examples thereof include organic sulfonium salt systems, iodonium salt systems, and phosphonium salt systems. Antimonates, phosphates, borates and the like are preferably used as counter ions of these compounds. Specific examples of the compound include Ar ₃ S ⁺ SbF ₆ ⁻ , Ar ₃ P ⁺ BF ₄ ⁻ , Ar ₂ I ⁺ PF ₆ ⁻ (wherein Ar represents a phenyl group or a substituted phenyl group), and the like. In addition, sulfonate esters, triazines, diazomethanes, β-ketosulfone, iminosulfonate, benzoinsulfonate, and the like can also be used.

  The thermal cation generator is a compound capable of generating a cation when heated to an appropriate temperature, for example, benzylsulfonium salts, benzylammonium salts, benzylpyridinium salts, benzylphosphonium salts, hydrazinium salts, carboxylic acid esters, Examples thereof include sulfonic acid esters, amine imides, antimony pentachloride-acetyl chloride complexes, diaryliodonium salts-dibenzyloxycopper, and boron halide-tertiary amine adducts.

  The amount of these cation generators added to the liquid crystal material varies depending on the structure of the mesogenic part and spacer part, the oxetanyl group equivalent, the alignment condition of the liquid crystal, etc. constituting the side chain type liquid crystalline polymer material to be used. Although it cannot be said, it is usually 100 mass ppm to 20 mass%, preferably 1000 mass ppm to 10 mass%, more preferably 0.2 mass% to 7 mass%, most preferably based on the side chain type liquid crystalline polymer substance. Is in the range of 0.5% to 5% by weight. If the amount is less than 100 mass ppm, the amount of cations generated may not be sufficient and polymerization may not proceed. If the amount is more than 20 mass%, the remaining cation generator remains in the liquid crystal film. It is not preferable because there is a risk that the light resistance and the like may deteriorate due to an increase in the number of objects.

Next, the alignment substrate will be described.
As the alignment substrate, a substrate having a smooth plane is preferable, and examples thereof include a film or sheet made of an organic polymer material, a glass plate, and a metal plate. From the viewpoint of cost and continuous productivity, it is preferable to use a material made of an organic polymer. Examples of organic polymer materials include polyvinyl alcohol, polyimide, polyphenylene oxide, polyether ketone, polyether ether ketone, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, Examples include films made of transparent polymers such as polycarbonate polymers and acrylic polymers such as polymethyl methacrylate. Also, styrene polymers such as polystyrene, acrylonitrile / styrene copolymer, olefin polymers such as polyethylene, polypropylene, ethylene / propylene copolymer, cyclopolyolefins having cyclic or norbornene structure, vinyl chloride polymers, nylon and aromatic polyamides. Examples thereof include a film made of a transparent polymer such as an amide polymer. Furthermore, imide polymers, sulfone polymers, polyether sulfone polymers, polyether ether ketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers Examples thereof include a film made of a transparent polymer such as a polymer, an epoxy-based polymer, and a blend of the above polymers. Among these, plastic films such as triacetyl cellulose, polycarbonate, norbornene polyolefin and the like used as optical films are awarded. Examples of organic polymer film include norbornene such as ZEONOR (trade name, manufactured by ZEON CORPORATION), ZEONEX (trade name, manufactured by ZEON CORPORATION), Arton (trade name, manufactured by JSR Corporation), etc. A plastic film made of a polymer material having a structure is preferable because it has excellent optical properties. Moreover, as a metal film, the said film formed from aluminum etc. is mentioned, for example.

  In order to obtain homeotropic alignment stably using the liquid crystal material described above, the material constituting these substrates has a long chain (usually 4 or more carbon atoms, preferably 8 or more) alkyl group, More preferably, the substrate surface has a compound layer having a long-chain alkyl group. Among them, it is preferable to form a layer made of polyvinyl alcohol having a long-chain alkyl group because the formation method is easy. These organic polymer materials may be used alone as a substrate, or may be formed as a thin film on another substrate. In the field of liquid crystal, rubbing treatment with a cloth or the like is generally performed on a substrate, but the homeotropic alignment liquid crystal film of the present invention is an alignment in which in-plane anisotropy basically does not occur. Because of the structure, rubbing is not necessarily required. However, it is more preferable to apply a weak rubbing treatment from the viewpoint of suppressing repelling when a liquid crystal material is applied. An important setting value that defines the rubbing condition is a peripheral speed ratio. This represents the ratio between the movement speed of the cloth and the movement speed of the substrate when the rubbing cloth is wound around a roll and rubbed while the substrate is rubbed. In the present invention, the weak rubbing treatment usually has a peripheral speed ratio of 50 or less, more preferably 25 or less, and particularly preferably 10 or less. When the peripheral speed ratio is greater than 50, the effect of rubbing is too strong, and the liquid crystal material cannot be completely aligned vertically, and there is a possibility that the alignment is tilted in the in-plane direction from the vertical direction.

Next, the manufacturing method of the homeotropic alignment liquid crystal film of this invention is demonstrated.
Although the method for producing the liquid crystal film is not limited to these, the above-mentioned liquid crystal material is spread on the above-mentioned alignment substrate, and after aligning the liquid crystal material, light irradiation and / or heat treatment is performed. It can manufacture by fixing the said orientation state.
The liquid crystal material is spread on the alignment substrate to form the liquid crystal material layer. The liquid crystal material is applied directly on the alignment substrate in a molten state, or the liquid crystal material solution is applied on the alignment substrate, and then the coating film is applied. And drying the solvent to distill off the solvent.

  The solvent used for preparing the solution is not particularly limited as long as it can dissolve the liquid crystal material of the present invention and can be distilled off under suitable conditions. Generally, ketones such as acetone, methyl ethyl ketone, isophorone, and cyclohexanone, butoxyethyl Ethers such as alcohol, hexyloxyethyl alcohol, methoxy-2-propanol, glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, esters such as ethyl acetate and ethyl lactate, phenols such as phenol and chlorophenol, N Amides such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, halogens such as chloroform, tetrachloroethane, dichlorobenzene, etc. Mixing system is preferably used. Further, in order to form a uniform coating film on the alignment substrate, a surfactant, an antifoaming agent, a leveling agent, or the like may be added to the solution.

Regardless of the method of directly applying the liquid crystal material or the method of applying the solution, the application method is not particularly limited as long as the uniformity of the coating film is ensured, and a known method may be adopted. it can. Examples thereof include spin coating, die coating, curtain coating, dip coating, and roll coating.
In the method of applying a liquid crystal material solution, it is preferable to include a drying step for removing the solvent after the application. As long as the uniformity of a coating film is maintained, this drying process can employ | adopt a well-known method, without being specifically limited. For example, a method such as a heater (furnace) or hot air blowing may be used.

  The film thickness of the liquid crystal film cannot be generally described because it depends on the type of the liquid crystal display device and various optical parameters, but is usually 0.2 μm to 10 μm, preferably 0.3 μm to 5 μm, more preferably 0.5 μm. ~ 2 μm. When the film thickness is thinner than 0.2 μm, there is a possibility that a sufficient viewing angle improvement or brightness enhancement effect cannot be obtained. If it exceeds 10 μm, the liquid crystal display device may be unnecessarily colored.

Subsequently, the liquid crystal material layer formed on the alignment substrate is liquid crystal aligned by a method such as heat treatment, and is cured and fixed by light irradiation and / or heat treatment. In the first heat treatment, the liquid crystal is aligned by the self-alignment ability inherent in the liquid crystal material by heating to the liquid crystal phase expression temperature range of the used liquid crystal material. As conditions for the heat treatment, the optimum conditions and limit values differ depending on the liquid crystal phase behavior temperature (transition temperature) of the liquid crystal material to be used, but it cannot be generally stated, but usually in the range of 10 to 250 ° C., preferably 30 to 160 ° C. In addition, it is preferable to perform heat treatment at a temperature equal to or higher than the glass transition point (Tg) of the liquid crystal material, more preferably at a temperature higher by 10 ° C. than Tg. If the temperature is too low, the liquid crystal alignment may not proceed sufficiently, and if the temperature is high, the cationic polymerizable reactive group in the liquid crystal material and the alignment substrate may be adversely affected. Moreover, about heat processing time, it is 3 seconds-30 minutes normally, Preferably it is the range of 10 seconds-10 minutes. If the heat treatment time is shorter than 3 seconds, the liquid crystal alignment may not be completed sufficiently, and if the heat treatment time exceeds 30 minutes, the productivity is deteriorated.
After the liquid crystal material layer is formed into a liquid crystal alignment by a method such as heat treatment, the liquid crystal material is cured by a polymerization reaction of oxetanyl groups in the composition while maintaining the liquid crystal alignment state. The curing step is aimed at fixing the liquid crystal alignment state of the completed liquid crystal alignment by a curing (crosslinking) reaction and modifying it into a stronger film.

Since the liquid crystal material of the present invention has a polymerizable oxetanyl group, as described above, it is preferable to use a cationic polymerization initiator (cation generator) for the polymerization (crosslinking) of the reactive group. As the polymerization initiator, it is preferable to use a photo cation generator rather than a thermal cation generator.
When a photo cation generator is used, the liquid crystal material can be obtained by adding the photo cation generator to the heat treatment for aligning the liquid crystal under dark conditions (light blocking conditions that do not cause the photo cation generator to dissociate). The liquid crystal can be aligned with sufficient fluidity without curing until the alignment stage. Thereafter, the liquid crystal material layer is cured by generating cations by irradiating light from a light source that emits light of an appropriate wavelength.

As a light irradiation method, a photocation is generated by irradiating light from a light source such as a metal halide lamp, a high pressure mercury lamp, a low pressure mercury lamp, a xenon lamp, an arc lamp, or a laser having a spectrum in the absorption wavelength region of the photocation generator used. Cleave the generator. The dose per square centimeter is usually in the range of 1 to 2000 mJ, preferably 10 to 1000 mJ as the cumulative dose. However, this is not the case when the absorption region of the photocation generator and the spectrum of the light source are remarkably different, or when the liquid crystal material itself has the ability to absorb the light source wavelength. In these cases, it is possible to adopt a method such as using a suitable photosensitizer or a mixture of two or more photocation generators having different absorption wavelengths.
The temperature at the time of light irradiation needs to be within a temperature range in which the liquid crystal material takes liquid crystal alignment. In order to sufficiently enhance the curing effect, it is preferable to perform light irradiation at a temperature equal to or higher than Tg of the liquid crystal material.

The liquid crystal material layer produced by the above process is a sufficiently strong film. Specifically, the mesogens are three-dimensionally bonded by the curing reaction, and not only the heat resistance (the upper limit temperature for maintaining the liquid crystal alignment) is improved as compared to before curing, but also scratch resistance, abrasion resistance, crack resistance. The mechanical strength such as property is also greatly improved.
As the alignment substrate, it is not optically isotropic, or the liquid crystal film to be obtained is finally opaque in the intended use wavelength region, or the alignment substrate is too thick, resulting in problems in actual use. When there is a problem such as, a form transferred from a form formed on an alignment substrate to a stretched film having a retardation function may be used. As a transfer method, a known method can be adopted. For example, as described in JP-A-4-57017 and JP-A-5-333313, a liquid crystal film layer is laminated on a substrate different from the alignment substrate via an adhesive or an adhesive, and then if necessary. Examples thereof include a method of transferring only a liquid crystal film by performing a surface curing treatment using an adhesive or an adhesive and peeling the alignment substrate from the laminate.
The pressure-sensitive adhesive or adhesive used for transfer is not particularly limited as long as it is of optical grade, and generally used ones such as acrylic, epoxy, and urethane can be used.

  The homeotropic alignment liquid crystal layer obtained as described above can be quantified by measuring the optical phase difference of the liquid crystal layer at an angle inclined from the normal incidence. In the case of homeotropic alignment liquid crystal layers, this retardation value is symmetric with respect to normal incidence. Several methods can be used for measuring the optical phase difference. For example, an automatic birefringence measuring apparatus (manufactured by Oji Scientific Instruments) and a polarizing microscope can be used. This homeotropic alignment liquid crystal layer appears black between the crossed Nicol polarizers. Thus, homeotropic orientation was evaluated.

The homeotropic alignment liquid crystal film used in the present invention has a thickness d2 of the liquid crystal film, Nx2 and Ny2 as the main refractive index in the liquid crystal film plane, Nz2 as the main refractive index in the thickness direction, and Nz2> Nx2 ≧ When Ny2, the in-plane retardation value (Re2 = (Nx2-Ny2) × d2 [nm]) and the retardation value in the thickness direction (Rth2 = (Nx2-Nz2) × d2 [nm]) The following [2] and [3] are satisfied.
[2] 0 nm ≦ Re2 ≦ 20 nm
[3] −500 nm ≦ Rth2 ≦ −30 nm

  Although the Re2 and Rth2 values, which are optical parameters of the homeotropic alignment liquid crystal film, depend on the type of the liquid crystal display device and various optical parameters, it cannot be generally stated, but the homeotropic alignment for monochromatic light of 550 nm The retardation value (Re2) in the plane of the liquid crystal film is usually in the range of 0 nm to 20 nm, preferably 0 nm to 10 nm, more preferably 0 nm to 5 nm, and the retardation value (Rth2) in the thickness direction is usually It is controlled to −500 to −30 nm, preferably −400 to −50 nm, and more preferably −400 to −100 nm.

  By setting the Re2 value and the Rth2 value in the above ranges, the viewing angle improving film of the liquid crystal display device can widen the viewing angle while correcting the color tone of the liquid crystal display. When the Re2 value is larger than 20 nm, the front characteristics of the liquid crystal display element may be deteriorated due to the large front phase difference value. Further, when the Rth2 value is larger than −30 nm or smaller than −500 nm, a sufficient viewing angle improvement effect cannot be obtained, or unnecessary coloring may occur when viewed from an oblique direction.

Next, the fourth and sixth optical anisotropic layers will be described.
The fourth and sixth optically anisotropic layers are not particularly limited, but non-liquid crystal materials have excellent heat resistance, chemical resistance, transparency, and high rigidity. Polyolefins such as rate, ZEONEX, ZEONOR (both manufactured by ZEON Corporation), ARTON (manufactured by JSR Corporation), polyamide, polyimide, polyester, polyetherketone, polyaryletherketone, polyamideimide, polyesterimide, etc. The polymer is preferred. Any one of these polymers may be used alone, or a mixture of two or more kinds having different functional groups such as a mixture of polyaryletherketone and polyamide may be used. Among such polymers, polyimide is particularly preferable because of its high transparency and high orientation. Examples of the liquid crystal material include a cholesteric alignment film made of a liquid crystal material such as a cholesteric liquid crystal polymer, and a film in which a cholesteric alignment layer of the liquid crystal material is supported by a film.

The fourth and sixth optically anisotropic layers compensate the viewing angle of the vertically aligned liquid crystal layer of the vertically aligned liquid crystal cell, and the thicknesses of the fourth and sixth optically anisotropic layers are d4 and d6. , Nx4, Nx6 and Ny4, Ny6, the main refractive indexes in the thickness direction are Nz4, Nz6, and Nx4 ≧ Ny4> Nz4, Nx6 ≧ Ny6>. Nz6, in-plane retardation value in light with a wavelength of 550 nm (Re4 = (Nx4-Ny4) × d4 [nm], Rth4 = {(Nx4 + Ny4) / 2−Nz4} × d4 [nm], Re6 = (Nx6- Ny6) × d6 [nm], Rth6 = {(Nx6 + Ny6) / 2−Nz6} × d6 [nm]), the following equations [5], [6], [8], and [9] are satisfied. .
[5] 0 ≦ Re4 ≦ 20
[6] 100 ≦ Rth4 ≦ 400
[8] 0 ≦ Re6 ≦ 20
[9] 100 ≦ Rth6 ≦ 400

  Although the fourth and sixth optically anisotropic layers depend on the optical film thickness of the vertical alignment liquid crystal cell and the birefringence value Δn of the liquid crystal material used in the vertical alignment liquid crystal cell, they cannot be generally described. The retardation values (Re4, Re6) in the plane of the sixth optically anisotropic layer are usually in the range of 0 nm to 20 nm, preferably 0 nm to 10 nm, more preferably 0 nm to 5 nm. When the Re4 and Re6 values are out of the above range, there is a risk of a decrease in contrast when viewed from the front. The retardation values (Rth4, Rth6) in the fourth and sixth thickness directions are generally 200 to 400 nm because the retardation value in the thickness direction of the vertical alignment type liquid crystal cell is usually 200 to 400 nm. When only the isotropic layer is used, it is usually in the range of 150 nm to 400 nm, preferably 180 nm to 360 nm, and more preferably 200 nm to 300 nm. When the fourth optical anisotropic layer and the sixth optical anisotropic layer are used in combination, the total of Re4 value and Re6 value is usually 150 to 400 nm, preferably 180 to 360 nm, more preferably 200 to 300 nm. Therefore, when viewed as a single-layer optically anisotropic layer, the thickness is usually 75 to 200 nm, preferably 90 to 180 nm, and more preferably 100 to 150 nm. When outside the above range, a sufficient viewing angle improvement effect may not be obtained, or unnecessary coloring may occur when viewed from an oblique direction.

  As the linear polarizing plate used in the present invention, one having a protective film on one side or both sides of a polarizer is usually used. The polarizer is not particularly limited, and various types can be used. For example, for a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, an ethylene / vinyl acetate copolymer partially saponified film. And polyene-based oriented films such as those obtained by adsorbing dichroic substances such as iodine and dichroic dyes and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, those obtained by stretching a polyvinyl alcohol film and adsorbing and orienting a dichroic material (iodine, dye) are preferably used. The thickness of the polarizer is not particularly limited, but is generally about 5 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  The protective film provided on one side or both sides of the polarizer preferably has excellent transparency, mechanical strength, thermal stability, moisture shielding properties, isotropic properties, and the like. Examples of the material for the protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile / styrene copolymer, and the like. Examples thereof include styrene polymers such as coalesced (AS resin), polycarbonate polymers, and the like. Also, polyolefin polymers such as polyethylene, polypropylene, ethylene / propylene copolymers, polyolefins having cycloolefin or norbornene structures, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfones Polymer, polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or Examples of the polymer that forms the protective film include blends of the aforementioned polymers. Other examples include films made of thermosetting or ultraviolet curable resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone. Generally the thickness of a protective film is 500 micrometers or less, and 1-300 micrometers is preferable. In particular, the thickness is preferably 5 to 200 μm.

The protective film is preferably an optically isotropic substrate, for example, a triacetyl cellulose (TAC) film such as Fujitac (product of Fuji Photo Film) or Konicatak (product of Konica Minolta Opto), Arton film (product of JSR) ), ZEONOR film, ZEONEX film (product of Nippon Zeon Co., Ltd.), etc., TPX film (product of Mitsui Chemicals), acrylprene film (product of Mitsubishi Rayon Co., Ltd.), etc. From the viewpoint of flatness, heat resistance and moisture resistance, triacetyl cellulose and cycloolefin polymers are preferred.
In addition, when providing a protective film in the both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used. The polarizer and the protective film are usually in close contact with each other through an aqueous adhesive or the like. Examples of aqueous adhesives include polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, aqueous polyurethanes, aqueous polyesters, and the like.

As the protective film, a hard coat layer, an antireflection treatment, an anti-sticking treatment, or a treatment subjected to diffusion or anti-glare treatment can be used.
Hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film having excellent hardness and slipping properties with an appropriate ultraviolet curable resin such as acrylic or silicone is applied to the protective film. It can be formed by a method of adding to the surface. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

Anti-glare treatment is applied for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, roughening by sandblasting or embossing. It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a method or a compounding method of transparent fine particles. Examples of the fine particles to be included in the formation of the surface fine concavo-convex structure include conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like having an average particle diameter of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.
The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the protective film itself, or can be provided separately from the transparent protective layer as an optical layer.

  The first, second, third, third, fourth, fifth and sixth optically anisotropic layers and the polarizing plate can be produced by sticking each other through an adhesive layer. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or rubber-based polymer is appropriately used as a base polymer. Can be selected and used. 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.

The pressure-sensitive adhesive layer can be formed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of an appropriate solvent alone or a mixture such as toluene and ethyl acetate is prepared. , A method in which it is directly attached on the liquid crystal layer by an appropriate development method such as a casting method or a coating method, or an adhesive layer is formed on the separator according to the above and transferred onto the liquid crystal layer Examples include methods. The pressure-sensitive adhesive layer includes, for example, natural and synthetic resins, in particular, tackifier resins, glass fibers, glass beads, metal powder, fillers made of other inorganic powders, pigments, colorants, You may contain the additive added to adhesion layers, such as antioxidant. Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.
In addition, when bonding each optically anisotropic layer mutually through an adhesive layer, the film surface can be surface-treated and adhesiveness with an adhesive layer can be improved. The surface treatment means is not particularly limited, and a surface treatment method such as corona discharge treatment, sputtering treatment, low-pressure UV irradiation, or plasma treatment that can maintain the transparency of each optically anisotropic layer can be suitably employed. Among these surface treatment methods, corona discharge treatment is good.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
In addition, each analysis method used in the Example is as follows.
⁽¹⁾ Measurement compound of 1 H-NMR was dissolved in deuterated chloroform and measured by ¹ H-NMR of 400 MHz (Variant Co. INOVA-400).
(2) Measurement of GPC The compound was dissolved in tetrahydrofuran, and TSK-GEL SuperH1000, SuperH2000, SuperH3000, and SuperH4000 were connected in series with an 8020 GPC system manufactured by Tosoh Corporation and measured using tetrahydrofuran as an eluent. Polystyrene standards were used for molecular weight calibration.
(3) Microscope observation The alignment state of the liquid crystal was observed with an Olympus BH2 polarizing microscope.
(4) Parameter measurement of liquid crystal film Obi Scientific Instruments Co., Ltd. automatic birefringence meter KOBRA21ADH was used.

[Example 1]
A liquid crystalline polymer represented by the following formula (8) was synthesized. The molecular weight was Mn = 8000 and Mw = 15000 in terms of polystyrene. In addition, although Formula (8) is described with the structure of a block polymer, it represents the component ratio of a monomer.

After dissolving 1.0 g of the polymer of the formula (8) in 9 ml of cyclohexanone and adding 0.1 g of a triallylsulfonium hexafluoroantimonate 50% propylene carbonate solution (manufactured by Aldrich) in the dark, A solution of liquid crystal material was prepared by filtering insoluble matter with a 0.45 μm polytetrafluoroethylene filter.
The alignment substrate was prepared as follows. A 38 μm-thick polyethylene naphthalate film (manufactured by Teijin Limited) was cut into a 15 cm square, and a 5 wt% solution of alkyl-modified polyvinyl alcohol (PVA: Kuraray Co., Ltd., MP-203) (the solvent was water and isopropyl). (A mixed solvent of alcohol in a weight ratio of 1: 1) was applied by spin coating, dried on a hot plate at 50 ° C. for 30 minutes, and then heated in an oven at 120 ° C. for 10 minutes. Subsequently, it was rubbed with a rayon rubbing cloth. The film thickness of the obtained PVA layer was 1.2 μm. The peripheral speed ratio during rubbing (moving speed of rubbing cloth / moving speed of substrate film) was 4.
The liquid crystal material solution described above was applied to the alignment substrate thus obtained by spin coating. Next, it was dried on a hot plate at 60 ° C. for 10 minutes and heat-treated in an oven at 150 ° C. for 2 minutes to align the liquid crystal material. Next, the sample is placed in close contact with an aluminum plate heated to 60 ° C., and then a 600 mJ / cm ² ultraviolet light (however, measured at 365 nm) is irradiated with a high-pressure mercury lamp lamp to cure the liquid crystal material. It was.

Since the polyethylene naphthalate film used as the substrate has a large birefringence and is not preferable as an optical film, the obtained liquid crystalline film on the alignment substrate is converted to a triacetyl cellulose (TAC) film via an ultraviolet curable adhesive. Transcribed to. That is, on the cured liquid crystal material layer on the polyethylene naphthalate film, an adhesive is applied to a thickness of 5 μm, laminated with a TAC film, and irradiated with ultraviolet rays from the TAC film side to cure the adhesive. After that, the polyethylene naphthalate film was peeled off.
When the obtained optical film (PVA layer / liquid crystal layer / adhesive layer / TAC film) is observed under a polarizing microscope, there is no disclination and the monodomain has a uniform orientation. It was found that the homeotropic orientation has a structure. The retardation (Re1) in the in-plane direction combining the TAC film and the liquid crystal layer measured using KOBRA21ADH was 0.5 nm, and the retardation (Rth1) in the thickness direction was −230 nm. In addition, since the TAC film alone was negative uniaxial, the in-plane retardation was 0.5 nm, and the retardation in the thickness direction was +35 nm, the retardation of the liquid crystal layer alone was Re 0 nm and Rth -195 nm was estimated. When pasting to the vertical alignment type liquid crystal display device in Example 3 or later, the TAC film of the substrate was removed and only the homeotropic alignment liquid crystal layer was taken out and used.

[Example 2]
In Example 1, an optical film was produced in the same manner as in Example 1 except that the thickness of the homeotropic alignment liquid crystal film was 1.0 μm. The in-plane retardation (Re2) of the TAC film and the liquid crystal layer measured using KOBRA21ADH was 0.5 nm, and the retardation in the thickness direction (Rth2) was -125 nm. In addition, since the TAC film alone was negative uniaxial, the in-plane retardation was 0.5 nm, and the retardation in the thickness direction was +35 nm, the retardation of the liquid crystal layer alone was Re1 of 0 nm and Rth1 of Estimated -90 nm.

[Example 3]
A vertical alignment type liquid crystal display device of Example 3 will be described with reference to FIGS.
A transparent electrode 10 is formed of a material having a high transmittance made of an ITO layer or the like on the substrate 8, a counter electrode 9 is formed on the substrate 7, and exhibits a negative dielectric anisotropy between the transparent electrode 10 and the counter electrode 9. A liquid crystal layer 11 made of a liquid crystal material is sandwiched.
A vertical alignment film (not shown) is formed on the surface of the transparent electrode 10 and the counter electrode 9 in contact with the liquid crystal layer 11. After the alignment film is applied, alignment such as rubbing is performed on at least one alignment film. Processing is in progress.
The liquid crystal molecules of the liquid crystal layer 11 have a tilt angle of 1 ° with respect to the vertical direction of the substrate surface by an alignment treatment such as rubbing on the vertical alignment film.
Since a liquid crystal material exhibiting negative dielectric anisotropy is used for the liquid crystal layer 11, when a voltage is applied between the transparent electrode 10 and the counter electrode 9, the liquid crystal molecules are inclined in a direction parallel to the substrate surface. .
As the liquid crystal material of the liquid crystal layer 11, Ne (refractive index for extraordinary light) = 1.561, No (refractive index for normal light) = 1.478, ΔN (Ne−No) = 0.083 A cell gap was set to 4.7 μm.

  A linearly polarizing plate 1 (thickness of about 105 μm; SQW-062 manufactured by Sumitomo Chemical Co., Ltd.) is disposed on the display surface side (upper side of the figure) of the vertical alignment type liquid crystal cell 6, and between the upper side linearly polarizing plate 1 and the liquid crystal cell 6. 1st optically anisotropic layer 2 (Zeonor manufactured by Nippon Zeon Co., Ltd.), 2nd optically anisotropic layer 3 made of homeotropic alignment liquid crystal film prepared in Example 1, and 3rd optical anisotropy Layer 4 (ZEONOR manufactured by Nippon Zeon Co., Ltd.) and fourth optically anisotropic layer 5 (ARTON manufactured by JSR Corporation) were disposed. A linearly polarizing plate 13 (thickness: about 105 μm; SQW-062 manufactured by Sumitomo Chemical Co., Ltd.) is disposed on the back side of the vertical alignment type liquid crystal cell 6 (the lower side in the figure). A fifth optically anisotropic layer 12 (Zeonor manufactured by Nippon Zeon Co., Ltd.) was disposed therebetween. It was Rth = 35 nm of the triacetyl cellulose used for the support substrate of the linear polarizing plate (Sumitomo Chemical Co., Ltd. SQW-062).

The first, third, and fifth optically anisotropic layers 2, 4, and 12 are formed of optical elements having an in-plane optical axis and positive uniaxial optical anisotropy. The orientations of the absorption axes of the linearly polarizing plates 1 and 13 indicated by arrows in FIG. 3 were 90 degrees and 0 degrees in the plane, respectively. The slow axis orientation of the first optically anisotropic layer 2 indicated by an arrow in FIG. 3 is 0 degree, and Re1 indicates a phase difference of 105 nm. The slow axis orientations of the third and fifth optically anisotropic layers 4 and 12 indicated by arrows in FIG. 3 are 45 degrees and 135 degrees, respectively, and Re3 and Re5 have a phase difference of 137.5 nm.
The fourth optically anisotropic layer 5 exhibits a phase difference in which Re4 is approximately 0 nm and Rth4 is 280 nm.
The second optically anisotropic layer 3 made of a homeotropic alignment liquid crystal film exhibits a phase difference in which Re2 is 0 nm and Rth2 is -195 nm.
FIG. 4 shows the contrast ratio from all directions, where the transmittance ratio (white display) / (black display) of black display 0V and white display 5V is used as the contrast ratio. Contrast contour lines were set to 100, 500, 200, 100, 50 in order from the inside. The concentric circles indicate an angle of 20 degrees from the center. Therefore, the outermost circle shows 80 degrees from the center (the same applies to the following figures).

[Example 4]
A vertical alignment type liquid crystal display device of Example 4 will be described with reference to FIGS.
Using the second optically anisotropic layer 3 made of the homeotropic alignment liquid crystal film produced in Example 1, the first optically anisotropic layer 2 of Example 1 was combined with the linearly polarizing plate 1 and the second optically anisotropic layer. Moving from the isotropic layer 3 to the fifth optically anisotropic layer 12 and the linearly polarizing plate 13 so that the direction of the slow axis of the first optically anisotropic layer 2 is 90 degrees. A vertical alignment type liquid crystal display device was produced in the same manner as in Example 3 except that.
FIG. 7 shows the contrast ratio from all directions, with the transmittance ratio (white display) / (black display) of black display 0V and white display 5V as the contrast ratio.

[Example 5]
The semi-transparent vertical alignment type liquid crystal display device shown below and the third and fifth optically anisotropic layers 4 and 12 were transferred from Nippon Zeon Co., Ltd. ZEONOR to Teijin Co., Ltd. Pure Ace WRF-W. A transflective vertical alignment type liquid crystal display device was produced in the same manner as in Example 1 except that it was used in the same manner as in Example 1.
A transflective vertical liquid crystal display device will be described with reference to FIGS.
The substrate 8 is provided with a reflective electrode 15 made of a material having a high reflectance made of an Al layer, and a transparent electrode 10 made of a material having a high transmittance made of an ITO layer, and the substrate 7 is provided with a counter electrode 9. 15, a liquid crystal layer 11 made of a liquid crystal material exhibiting negative dielectric anisotropy is sandwiched between the transparent electrode 10 and the counter electrode 9.
A vertical alignment film (not shown) is formed on the surface of the reflective electrode 15, the transparent electrode 10, and the counter electrode 9 in contact with the liquid crystal layer 11. After the alignment film is applied, at least one of the alignment films is formed. Alignment treatment such as rubbing is performed.
The liquid crystal molecules of the liquid crystal layer 11 have a tilt angle of 1 ° with respect to the vertical direction of the substrate surface by an alignment treatment such as rubbing on the vertical alignment film.
Since a liquid crystal material exhibiting negative dielectric anisotropy is used for the liquid crystal layer 11, when a voltage is applied between the reflective electrode 15, the transparent electrode 10 and the counter electrode 9, the liquid crystal molecules are parallel to the substrate surface. Tilt toward.
The liquid crystal material of the liquid crystal layer 11 was the same material as in Example 3, and the cell gap was set to 2.4 μm for the reflective electrode portion and 4.7 μm for the transparent electrode portion.
The third and fifth optically anisotropic layers 4 and 12 are Teijin's Pure Ace WRF-W slow axis orientations of 45 degrees and 135 degrees, respectively, and Re3 and Re5 are 137.5 nm retardation values. This is the same as in Example 3.
FIG. 10 shows the contrast ratio from all directions, where the transmittance ratio (white display) / (black display) of black display 0V and white display 5V is used as the contrast ratio.

[Example 6]
A vertical alignment type liquid crystal display device of Example 6 will be described with reference to FIGS.
Using the second optically anisotropic layer 3 made of the homeotropic alignment liquid crystal film produced in Example 1, yet another fourth optically anisotropic layer 5 of Example 3, a vertically aligned liquid crystal cell A vertical alignment type liquid crystal display device was produced in the same manner as in Example 3 except that the liquid crystal display device was arranged between the sixth optical anisotropic layer 12 and the fifth optically anisotropic layer 12. At this time, the two fourth optical anisotropic layers 5 had a phase difference in which Re4 was approximately 0 nm and Rth4 was 140 nm.
FIG. 13 shows the contrast ratio from all directions, where the transmittance ratio (white display) / (black display) of black display 0V and white display 5V is used as the contrast ratio.

[Comparative Example 1]
A vertical alignment type liquid crystal display device shown in FIG. 14 was produced in the same manner as in Example 3 except that the first optically anisotropic layer 2 in Example 3 was omitted.
FIG. 15 shows the angular relationship between the constituent members. The Re3 and Re5 of the third and fifth optical anisotropic layers 4 and 12 are 137.5 nm, and the Rth2 and Rth4 values of the second and fourth optical anisotropic layers 3 and 5 are the widest viewing angle characteristics. The optimization was performed to obtain −90 nm and 130 nm, respectively. As the second optically anisotropic layer 3, the homeotropic alignment liquid crystal film produced in Example 2 was used.
FIG. 16 shows the contrast ratio from all directions, where the transmittance ratio (white display) / (black display) of black display 0V and white display 5V is used as the contrast ratio.
Comparing the omnidirectional isocontrast curves in FIGS. 4, 7 and 16, it can be seen that the viewing angle characteristics are greatly improved by adding the first optically anisotropic layer 2.

[Comparative Example 2]
A vertical alignment type liquid crystal display device shown in FIG. 17 was produced in the same manner as in Example 3 except that the second optically anisotropic layer 3 made of the homeotropic alignment liquid crystal film of Example 3 was omitted.
FIG. 18 shows the angular relationship between the constituent members. Re3 and Re5 of the third and fifth optical anisotropic layers are set to 137.5 nm, and the Re1 and Rth4 values of the first and fourth optical anisotropic layers are optimized so as to have the widest viewing angle characteristics. To 115 nm and 205 nm, respectively.
FIG. 19 shows the contrast ratio from all directions, where the transmittance ratio (white display) / (black display) of black display 0V and white display 5V is used as the contrast ratio.
Comparing the omnidirectional isocontrast curves in FIGS. 4, 7 and 19, it can be seen that the viewing angle characteristics are greatly improved by using the homeotropic alignment liquid crystal film.

[Comparative Example 3]
A vertical alignment type liquid crystal display device of Comparative Example 3 will be described with reference to FIGS.
As the vertical alignment type liquid crystal cell 6, the same cell as in Example 3 was used.
A linearly polarizing plate 1 (thickness: about 105 μm; SQW-062 manufactured by Sumitomo Chemical Co., Ltd.) is disposed on the display surface side (upper side of the drawing) of the vertical alignment type liquid crystal cell 6, and between the upper linear polarizing plate 1 and the liquid crystal cell 6. 1st optically anisotropic layer 2 (Zeonor manufactured by Nippon Zeon Co., Ltd.), 2nd optically anisotropic layer 3 made of homeotropic alignment liquid crystal film produced in Example 2, and 3rd optical anisotropy Layer 4 (ZEONOR manufactured by Nippon Zeon Co., Ltd.) and fourth optically anisotropic layer 5 (ARTON manufactured by JSR Corporation) were disposed. A linearly polarizing plate 13 (thickness: about 105 μm; SQW-062 manufactured by Sumitomo Chemical Co., Ltd.) is disposed on the back side of the vertical alignment type liquid crystal cell 6 (the lower side in the figure). Between the first optically anisotropic layer 2 (Zeonor manufactured by Nippon Zeon Co., Ltd.), the second optically anisotropic layer 3 comprising the homeotropic alignment liquid crystal film produced in Example 2, and the fifth optically anisotropic The layer 12 (ZEONOR manufactured by Nippon Zeon Co., Ltd.) and the fourth optically anisotropic layer 5 (ARTON manufactured by JSR Corporation) were disposed.
The first, third, and fifth optically anisotropic layers 2, 4, and 12 are formed of optical elements having an in-plane optical axis and positive uniaxial optical anisotropy. The directions of the absorption axes of the linearly polarizing plates 1 and 13 indicated by arrows in FIG. 21 were 90 degrees and 0 degrees, respectively. The slow axis orientation of the first optically anisotropic layer 2 indicated by an arrow in FIG. 21 is 0 degree, and Re1 indicates a phase difference of 105 nm. The slow axis orientations of the third and fifth optical anisotropic layers 4 and 12 indicated by arrows in FIG. 21 are 45 degrees and 135 degrees, respectively, and Re3 and Re5 indicate a phase difference of 137.5 nm.
The fourth optical anisotropic layer 5 exhibits a phase difference in which Re4 is approximately 0 nm and Rth4 is 140 nm.
The second optically anisotropic layer 3 made of a homeotropic alignment liquid crystal film exhibits a phase difference in which Re2 is 0 nm and Rth2 is −90 nm.
FIG. 22 shows the contrast ratio from all directions, where the transmittance ratio (white display) / (black display) of black display 0V and white display 5V is used as the contrast ratio.
When comparing the omnidirectional isocontrast curves in FIGS. 4, 7 and 22, almost the same viewing angle characteristics are obtained. By changing to the configuration of the present invention, the viewing angle characteristics are maintained, At the same time, it can be seen that both the thickness and the price can be reduced by reducing the number of films.

It is a cross-sectional schematic diagram of the elliptically polarizing plate of this invention. 6 is a schematic cross-sectional view of a vertical alignment type liquid crystal display device used in Example 3. FIG. FIG. 6 is a plan view showing the angular relationship of each component of the vertical alignment type liquid crystal display device used in Example 3. It is a figure which shows contrast ratio when the vertical alignment type liquid crystal display device in Example 3 is seen from all directions. Note that concentric circles indicate every 20 degrees (hereinafter the same). 6 is a schematic cross-sectional view of a vertical alignment type liquid crystal display device used in Example 4. FIG. FIG. 6 is a plan view showing the angular relationship of each component of the vertical alignment type liquid crystal display device used in Example 4. It is a figure which shows contrast ratio when the vertical alignment type liquid crystal display device in Example 4 is seen from all directions. 6 is a schematic cross-sectional view of a transflective vertical alignment liquid crystal display device used in Example 5. FIG. FIG. 10 is a plan view showing the angular relationship of each component of the transflective vertical alignment type liquid crystal display device used in Example 5. FIG. 10 is a diagram showing a contrast ratio when the transflective vertical alignment type liquid crystal display device in Example 5 is viewed from all directions. 6 is a schematic cross-sectional view of a transflective vertical alignment liquid crystal display device used in Example 6. FIG. FIG. 10 is a plan view showing the angular relationship of each component of the transflective vertical alignment type liquid crystal display device used in Example 6. It is a figure which shows the contrast ratio when the transflective vertical alignment liquid crystal display device in Example 6 is viewed from all directions. 6 is a schematic cross-sectional view of a vertical alignment type liquid crystal display device used in Comparative Example 1. FIG. 6 is a plan view showing the angular relationship of each component of the vertical alignment type liquid crystal display device used in Comparative Example 1. FIG. It is a figure which shows the contrast ratio when the vertical alignment type liquid crystal display device in Comparative Example 1 is viewed from all directions. 6 is a schematic cross-sectional view of a vertical alignment type liquid crystal display device used in Comparative Example 2. FIG. FIG. 10 is a plan view showing the angular relationship between the constituent members of the vertical alignment type liquid crystal display device used in Comparative Example 2. It is a figure which shows the contrast ratio when the vertical alignment type liquid crystal display device in Comparative Example 2 is viewed from all directions. 10 is a schematic cross-sectional view of a vertical alignment type liquid crystal display device used in Comparative Example 3. FIG. FIG. 10 is a plan view showing the angular relationship of each component of the vertical alignment type liquid crystal display device used in Comparative Example 3. It is a figure which shows the contrast ratio when the vertical alignment type liquid crystal display device in Comparative Example 3 is viewed from all directions.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 13 Linearly-polarizing plate 2 1st optical anisotropic layer 3 2nd optical anisotropic layer 4 3rd optical anisotropic layer 5 4th optical anisotropic layer 12 5th optical anisotropy Layers 7 and 8 Substrate 10 Transparent electrode 9 Counter electrode 15 Reflective electrode 11 Liquid crystal layer (vertical alignment)
6 Vertical alignment type liquid crystal cell 14 Transflective vertical alignment type liquid crystal cell

Claims (21)

Elliptical polarized light in which at least a first polarizing plate, a first optical anisotropic layer, a second optical anisotropic layer, a third optical anisotropic layer, and a fourth optical anisotropic layer are laminated in this order A board,
The first optically anisotropic layer satisfies the following [1],
[1] 50 ≦ Re1 ≦ 300
(Here, Re1 means an in-plane retardation value of the first optically anisotropic layer. Re1 is Re1 = (Nx1−Ny1) × d1 [nm], where d1 is The thickness of the first optically anisotropic layer, Nx1 and Ny1 are the main refractive index in the plane of the first optically anisotropic layer with respect to light having a wavelength of 550 nm, and Nz1 is the main refraction in the thickness direction with respect to light having a wavelength of 550 nm. (Nx1> Nz1 ≧ Ny1)
The second optically anisotropic layer satisfies the following [2] and [3],
[2] 0 ≦ Re2 ≦ 20
[3] −500 ≦ Rth2 ≦ −30
(Here, Re2 means an in-plane retardation value of the second optical anisotropic layer, and Rth2 means a retardation value in the thickness direction of the second optical anisotropic layer.) Re2 and Rth2 are respectively Re2 = (Nx2−Ny2) × d2 [nm] and Rth2 = {(Nx2 + Ny2) / 2−Nz2} × d2 [nm], where d2 is the second optical element. The thickness of the anisotropic layer, Nx2, Ny2 is the main refractive index in the plane of the second optical anisotropic layer for light having a wavelength of 550 nm, Nz2 is the main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nz2 > Nx2 ≧ Ny2.)
The third optically anisotropic layer satisfies the following [4],
[4] 100 ≦ Re3 ≦ 180
(Here, Re3 means an in-plane retardation value of the third optically anisotropic layer. Re3 is Re3 = (Nx3−Ny3) × d3 [nm], where d3 is The thickness of the third optically anisotropic layer, Nx3 and Ny3 are the main refractive index in the plane of the third optically anisotropic layer with respect to light having a wavelength of 550 nm, and Nz3 is the main refraction in the thickness direction with respect to light having a wavelength of 550 nm. (Nx3> Ny3 = Nz3)
The elliptically polarizing plate, wherein the fourth optically anisotropic layer satisfies the following [5] and [6].
[5] 0 ≦ Re4 ≦ 20
[6] 100 ≦ Rth4 ≦ 400
(Here, Re4 means an in-plane retardation value of the fourth optically anisotropic layer, and Rth4 means a retardation value in the thickness direction of the fourth optically anisotropic layer.) Re4 and Rth4 are Re4 = (Nx4-Ny4) × d4 [nm] and Rth4 = {(Nx4 + Ny4) / 2−Nz4} × d4 [nm], respectively, where d4 is the fourth optical anisotropic. Nx4 is a main refractive index in the plane of the fourth optical anisotropic layer for light having a wavelength of 550 nm, Nz4 is a main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nx4 ≧ Ny4 > Nz4.)   The second optically anisotropic layer is composed of a homeotropic alignment liquid crystal film obtained by homeotropic alignment of a liquid crystalline composition exhibiting positive uniaxiality in a liquid crystal state and then fixing the alignment. 2. The elliptically polarizing plate according to 1.   3. The elliptically polarizing plate according to claim 2, wherein the liquid crystalline composition exhibiting positive uniaxiality includes a side chain type liquid crystalline polymer having an oxetanyl group.   The elliptically polarizing plate according to claim 1, wherein the first and third optically anisotropic layers contain a thermoplastic polymer containing a polycarbonate resin or a cyclic polyolefin resin.   The fourth optically anisotropic layer is selected from polymers such as liquid crystalline compounds, triacetylcellulose, cyclic polyolefin, polyolefins, polyamide, polyimide, polyester, polyetherketone, polyaryletherketone, polyamideimide, and polyesterimide. The elliptically polarizing plate according to claim 1, wherein the elliptically polarizing plate is a layer formed of at least one kind of material. The elliptically polarizing plate according to any one of claims 1 to 5, wherein the third optically anisotropic layer further satisfies the following [10].
[10] 0.7 ≦ Re3 (450) / Re3 (590) ≦ 1.05
(Here, Re3 (450) and Re3 (590) mean in-plane retardation values of the third optically anisotropic layer in the light of wavelengths 450 nm and 590 nm).   The laminated structure is such that the absorption axis of the first polarizing plate and the slow axis of the first optically anisotropic layer are orthogonal or parallel to each other. The elliptically polarizing plate described. A pair comprising at least a first polarizing plate, a first optical anisotropic layer, a second optical anisotropic layer, a third optical anisotropic layer, a fourth optical anisotropic layer, and an electrode Vertical alignment type liquid crystal display in which a vertical alignment type liquid crystal cell including liquid crystal molecules which are aligned vertically with respect to the substrate surface when no voltage is applied between the substrates, a fifth optical anisotropic layer, and a second polarizing plate are arranged in this order. A device,
The first optically anisotropic layer satisfies the following [1],
[1] 50 ≦ Re1 ≦ 300
(Here, Re1 means an in-plane retardation value of the first optically anisotropic layer. Re1 is Re1 = (Nx1−Ny1) × d1 [nm], where d1 is The thickness of the first optically anisotropic layer, Nx1 and Ny1 are the main refractive index in the plane of the first optically anisotropic layer with respect to light having a wavelength of 550 nm, and Nz1 is the main refraction in the thickness direction with respect to light having a wavelength of 550 nm. (Nx1> Nz1 ≧ Ny1)
The second optically anisotropic layer satisfies the following [2] and [3],
[2] 0 ≦ Re2 ≦ 20
[3] −500 ≦ Rth2 ≦ −30
(Here, Re2 means an in-plane retardation value of the second optical anisotropic layer, and Rth2 means a retardation value in the thickness direction of the second optical anisotropic layer.) Re2 and Rth2 are respectively Re2 = (Nx2−Ny2) × d2 [nm] and Rth2 = {(Nx2 + Ny2) / 2−Nz2} × d2 [nm], where d2 is the second optical element. The thickness of the anisotropic layer, Nx2, Ny2 is the main refractive index in the plane of the second optical anisotropic layer for light having a wavelength of 550 nm, Nz2 is the main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nz2 > Nx2 ≧ Ny2.)
The third optically anisotropic layer satisfies the following [4],
[4] 100 ≦ Re3 ≦ 180
(Here, Re3 means an in-plane retardation value of the third optically anisotropic layer. Re3 is Re3 = (Nx3−Ny3) × d3 [nm], where d3 is The thickness of the third optically anisotropic layer, Nx3 and Ny3 are the main refractive index in the plane of the third optically anisotropic layer with respect to light having a wavelength of 550 nm, and Nz3 is the main refraction in the thickness direction with respect to light having a wavelength of 550 nm. (Nx3> Ny3 = Nz3)
The fourth optically anisotropic layer satisfies the following [5] and [6],
[5] 0 ≦ Re4 ≦ 20
[6] 100 ≦ Rth4 ≦ 400
(Here, Re4 means an in-plane retardation value of the fourth optically anisotropic layer, and Rth4 means a retardation value in the thickness direction of the fourth optically anisotropic layer.) Re4 and Rth4 are Re4 = (Nx4-Ny4) × d4 [nm] and Rth4 = {(Nx4 + Ny4) / 2−Nz4} × d4 [nm], respectively, where d4 is the fourth optical anisotropic. Nx4 is a main refractive index in the plane of the fourth optical anisotropic layer for light having a wavelength of 550 nm, Nz4 is a main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nx4 ≧ Ny4 > Nz4.)
The fifth optically anisotropic layer satisfies the following [7]: A vertical alignment type liquid crystal display device.
[7] 100 ≦ Re5 ≦ 180
(Here, Re5 means an in-plane retardation value of the fifth optically anisotropic layer. Re5 is Re5 = (Nx5-Ny5) × d5 [nm], where d5 is The thickness of the fifth optically anisotropic layer, Nx5 and Ny5 are the main refractive indices in the plane of the fifth optically anisotropic layer for light with a wavelength of 550 nm, and Nz5 is the main refraction in the thickness direction for light with a wavelength of 550 nm. (Nx5> Ny5 = Nz5) Substrate surface when no voltage is applied between a pair of substrates including at least a first polarizing plate, a second optically anisotropic layer, a third optically anisotropic layer, a fourth optically anisotropic layer, and an electrode Vertical alignment type liquid crystal display in which a vertical alignment type liquid crystal cell containing liquid crystal molecules vertically aligned with respect to the liquid crystal, a fifth optical anisotropic layer, a first optical anisotropic layer, and a second polarizing plate are arranged in this order A device,
The first optically anisotropic layer satisfies the following [1],
[1] 50 ≦ Re1 ≦ 300
(Here, Re1 means an in-plane retardation value of the first optically anisotropic layer. Re1 is Re1 = (Nx1−Ny1) × d1 [nm], where d1 is The thickness of the first optically anisotropic layer, Nx1 and Ny1 are the main refractive index in the plane of the first optically anisotropic layer with respect to light having a wavelength of 550 nm, and Nz1 is the main refraction in the thickness direction with respect to light having a wavelength of 550 nm. (Nx1> Nz1 ≧ Ny1)
The second optically anisotropic layer satisfies the following [2] and [3],
[2] 0 ≦ Re2 ≦ 20
[3] −500 ≦ Rth2 ≦ −30
(Here, Re2 means an in-plane retardation value of the second optical anisotropic layer, and Rth2 means a retardation value in the thickness direction of the second optical anisotropic layer.) Re2 and Rth2 are respectively Re2 = (Nx2−Ny2) × d2 [nm] and Rth2 = {(Nx2 + Ny2) / 2−Nz2} × d2 [nm], where d2 is the second optical element. The thickness of the anisotropic layer, Nx2, Ny2 is the main refractive index in the plane of the second optical anisotropic layer for light having a wavelength of 550 nm, Nz2 is the main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nz2 > Nx2 ≧ Ny2.)
The third optically anisotropic layer satisfies the following [4],
[4] 100 ≦ Re3 ≦ 180
(Here, Re3 means an in-plane retardation value of the third optically anisotropic layer. Re3 is Re3 = (Nx3−Ny3) × d3 [nm], where d3 is The thickness of the third optically anisotropic layer, Nx3 and Ny3 are the main refractive index in the plane of the third optically anisotropic layer with respect to light having a wavelength of 550 nm, and Nz3 is the main refraction in the thickness direction with respect to light having a wavelength of 550 nm. (Nx3> Ny3 = Nz3)
The fourth optically anisotropic layer satisfies the following [5] and [6],
[5] 0 ≦ Re4 ≦ 20
[6] 100 ≦ Rth4 ≦ 400
(Here, Re4 means an in-plane retardation value of the fourth optically anisotropic layer, and Rth4 means a retardation value in the thickness direction of the fourth optically anisotropic layer.) Re4 and Rth4 are Re4 = (Nx4-Ny4) × d4 [nm] and Rth4 = {(Nx4 + Ny4) / 2−Nz4} × d4 [nm], respectively, where d4 is the fourth optical element. The thickness of the anisotropic layer, Nx4 and Ny4 are the main refractive index in the plane of the fourth optical anisotropic layer for light having a wavelength of 550 nm, Nz4 is the main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nx4 ≧ Ny4> Nz4.)
The fifth optically anisotropic layer satisfies the following [7]: A vertical alignment type liquid crystal display device.
[7] 100 ≦ Re5 ≦ 180
(Here, Re5 means an in-plane retardation value of the fifth optically anisotropic layer. Re5 is Re5 = (Nx5-Ny5) × d5 [nm], where d5 is The thickness of the fifth optically anisotropic layer, Nx5 and Ny5 are the main refractive indices in the plane of the fifth optically anisotropic layer for light with a wavelength of 550 nm, and Nz5 is the main refraction in the thickness direction for light with a wavelength of 550 nm. (Nx5> Ny5 = Nz5) A sixth optical anisotropic layer satisfying the following [8] and [9] is further provided between the vertical alignment liquid crystal cell and the fifth optical anisotropic layer of the vertical alignment liquid crystal display device. The vertical alignment type liquid crystal display device according to claim 8 or 9, wherein:
[8] 0 ≦ Re6 ≦ 20
[9] 100 ≦ Rth6 ≦ 400
(Here, Re6 means the in-plane retardation value of the sixth optically anisotropic layer, and Rth6 means the retardation value in the thickness direction of the sixth optically anisotropic layer.) Re6 and Rth6 are Re6 = (Nx6-Ny6) × d6 [nm] and Rth6 = {(Nx6 + Ny6) / 2−Nz6} × d6 [nm], respectively, where d6 is the sixth optical element. The thickness of the anisotropic layer, Nx6, Ny6 is the main refractive index in the surface of the sixth optical anisotropic layer for light having a wavelength of 550 nm, Nz6 is the main refractive index in the thickness direction for light having a wavelength of 550 nm, and Nx6 ≧ Ny6> Nz6.)   The second optically anisotropic layer is composed of a homeotropic alignment liquid crystal film obtained by homeotropic alignment of a liquid crystalline composition exhibiting positive uniaxiality in a liquid crystal state and then fixing the alignment. The vertical alignment type liquid crystal display device according to any one of 8 to 10.   The vertical alignment liquid crystal display device according to claim 11, wherein the liquid crystalline composition exhibiting positive uniaxiality includes a side-chain liquid crystalline polymer having an oxetanyl group.   The vertical alignment according to any one of claims 8 to 12, wherein the first, third, and fifth optically anisotropic layers contain a thermoplastic polymer containing a polycarbonate resin or a cyclic polyolefin resin. Type liquid crystal display device.   The fourth optically anisotropic layer is selected from polymers such as liquid crystalline compounds, triacetylcellulose, cyclic polyolefin, polyolefins, polyamide, polyimide, polyester, polyetherketone, polyaryletherketone, polyamideimide, and polyesterimide. The vertical alignment type liquid crystal display device according to claim 8, wherein the vertical alignment type liquid crystal display device is a layer formed of at least one kind of material. The vertical alignment type liquid crystal display device according to claim 8, wherein the third optically anisotropic layer further satisfies the following [10].
[10] 0.7 ≦ Re3 (450) / Re3 (590) ≦ 1.05
(Here, Re3 (450) and Re3 (590) mean in-plane retardation values of the third optically anisotropic layer in the light of wavelengths 450 nm and 590 nm). The vertical alignment type liquid crystal display device according to any one of claims 8 to 15, wherein the fifth optically anisotropic layer further satisfies the following [11].
[11] 0.7 ≦ Re5 (450) / Re5 (590) ≦ 1.05
(Here, Re5 (450) and Re5 (590) mean in-plane retardation values of the fifth optically anisotropic layer in the light of wavelengths 450 nm and 590 nm).   The laminated structure is such that the absorption axis of the first polarizing plate and the slow axis of the first optically anisotropic layer are perpendicular or parallel to each other. The vertical alignment type liquid crystal display device described.   The laminated structure is such that the slow axis of the third optical anisotropic layer and the slow axis of the fifth optical anisotropic layer are perpendicular to each other. 4. A vertical alignment type liquid crystal display device according to 1.   The angle formed by the absorption axis of the first polarizing plate and the slow axis of the third optical anisotropic layer is p, the absorption axis of the second polarizing plate and the fifth optical anisotropic layer The vertical alignment type according to any one of claims 8 to 18, wherein when the angle formed with the slow axis is q, 40 ° ≤p≤50 ° and 40 ° ≤q≤50 ° are satisfied. Liquid crystal display device.   20. The vertical alignment type liquid crystal display device according to claim 8, wherein the first and second polarizing plates have a support layer having a retardation Rth in the thickness direction larger than 0.   21. The vertical alignment type liquid crystal display device according to claim 8, wherein one substrate of the vertical alignment type liquid crystal cell is a substrate having a region having a reflection function and a region having a transmission function. .

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