JP2012008548A - Ips mode and ffs mode liquid crystal display devices - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a color shift and to improve contrast of viewing angle of an IPS mode liquid crystal display device and a FFS mode liquid crystal display device.SOLUTION: Provided is an IPS mode liquid crystal display device having a C-plate and a first optical film on the visible side of a liquid crystal cell, or a FFS mode liquid crystal display device having the C-plate and the first optical film on the backlight side of the liquid crystal cell. The liquid crystal display device is characterized in that the first optical film comprising a low substituted layer containing cellulose acylate as a main component that satisfies the following expression (1), or comprising the low substituted layer and a high substituted layer containing cellulose acylate as a main component that satisfies the following expression (2) on at least one surface of the low substituted layer. (1) 2.0<Z1<2.7, (2) 2.7<Z2.

Description

  The present invention relates to an IPS mode and FFS mode liquid crystal display device.

  In IPS (In-Plane Switching) mode and FFS (Fringe Field Switching) mode, an electric field is applied between the upper and lower substrates as in the TN (Twisted Nematic) mode, and the mode is not driven by the rise of liquid crystal molecules. In this mode, the liquid crystal molecules respond in the in-plane direction of the substrate by an electric field including substantially parallel components. Since it has excellent viewing angle characteristics, it is used in various applications such as TV applications. Conventionally, it has been proposed to use a C-plate and a uniaxial or biaxial optical member satisfying predetermined optical characteristics for the purpose of reducing light leakage occurring in an oblique direction during black display ( For example, Patent Document 1).

  On the other hand, as a protective film for a polarizing plate used in a liquid crystal display device or the like, it has been proposed to use cellulose acylate having a low degree of acyl substitution as a material (for example, Patent Document 2).

JP 2005-265889 A JP 2009-265598 A

In an aspect in which observation is performed from various angles by a plurality of observers such as TV applications in recent years, better viewing angle characteristics are required. It is also important to reduce the color shift when observed from an oblique direction during black display.
The present invention has been made in view of the above problems, and provides an IPS mode and FFS mode liquid crystal display device that has a high viewing angle contrast and reduces a color shift that occurs when observed from an oblique direction during black display. The task is to do.

Means for solving the above problems are as follows.
[1] A C-plate, a first optical film, and a first polarizer are provided on the viewing side of the liquid crystal cell, and a second optical film and a second polarization are provided on the backlight side of the liquid crystal cell. Have at least a child,
The first and second polarizers are arranged with their polarization axes orthogonal to each other,
The first optical film is composed of a low substitution layer containing, as a main component, cellulose acylate satisfying the following formula (1), or the following formula on at least one surface of the low substitution layer and the low substitution layer. Having a high substitution degree layer containing cellulose acylate satisfying (2) as a main component,
The IPS mode liquid crystal display device, wherein the second optical film satisfies the following formulas (I) to (IV).
(1) 2.0 <Z1 <2.7
(In formula (1), Z1 represents the total acyl substitution degree of the cellulose acylate of the low substitution degree layer.)
(2) 2.7 <Z2
(In formula (2), Z2 represents the total acyl substitution degree of the cellulose acylate of the high substitution degree layer.)
(I) 0 nm ≦ Re (550) ≦ 10 nm
(II) | Rth (550) | ≦ 25 nm
(III) | Re (630) -Re (450) | ≦ 10 nm
(IV) | Rth (630) −Rth (450) | ≦ 35 nm
(In the above formulas (I) to (IV), Re (λ) represents the front retardation value (nm) at the wavelength λnm, and Rth (λ) represents the retardation value in the film thickness direction at the wavelength λnm (nm). Represents.)
[2] The IPS mode liquid crystal display device of [1], wherein the first optical film satisfies the following formulas (V) and (VI).
(V) 70 nm ≦ Re (550) ≦ 140 nm
(VI) 40 nm ≦ Rth (550) ≦ 110 nm
[3] The second optical film is composed of a low substitution layer containing, as a main component, cellulose acylate satisfying the formula (1), or at least one surface of the low substitution layer and the low substitution layer The IPS mode liquid crystal display device according to [1] or [2], further comprising: a high substitution degree layer containing cellulose acylate satisfying the formula (2) as a main component.
[4] The IPS mode liquid crystal display device according to any one of [1] to [3], wherein the second optical film has a thickness of 30 to 130 μm.
[5] The IPS mode liquid crystal display device according to any one of [1] to [4], wherein the low substitution degree layer contains a non-phosphate ester compound.
[6] The high substitution degree layer contains a non-phosphate ester compound as an additive, and the ratio (part by mass) of the additive to the cellulose acylate contained in the high substitution degree layer is the low substitution degree. The IPS mode liquid crystal display device according to any one of [1] to [5], wherein the amount is less than the ratio (parts by mass) of the additive to the cellulose acylate contained in the layer.
[7] The IPS mode liquid crystal display device according to [5] or [6], wherein the non-phosphate ester compound is a polyester compound containing an aromatic ring.
[8] The IPS mode liquid crystal display device according to any one of [1] to [7], wherein the cellulose acylate contained in the low substitution degree layer satisfies the following formulas (3) to (5).
Formula (3) 1.0 <X1 <2.7
Formula (4) 0 <= Y1 <1.5
Formula (5) X1 + Y1 = Z1
(In the formulas (3), (4) and (5), X1 represents the degree of substitution of the acetyl group of the cellulose acylate of the low-substituted layer, and Y1 has 3 or more carbon atoms of the cellulose acylate of the low-substituted layer. The total substitution degree of acyl groups is represented, and Z1 represents the total acyl substitution degree of cellulose acylate in the low substitution layer.)
[9] The IPS mode liquid crystal display device according to any one of [1] to [8], wherein the cellulose acylate used in the high substitution degree layer satisfies the following formulas (6) to (8).
Formula (6) 1.2 <X2 <3.0
Formula (7) 0 <= Y2 <1.5
Formula (8) X2 + Y2 = Z2
(In the formulas (6), (7) and (8), X2 represents the substitution degree of the acetyl group of the cellulose acylate of the high substitution degree layer, and Y2 has 3 or more carbon atoms of the cellulose acylate of the high substitution degree layer. The total substitution degree of acyl groups is represented, and Z2 represents the total acyl substitution degree of cellulose acylate in the high substitution degree layer.
[10] The high substitution layer (however, the composition of each high substitution layer may be independent and the same) on both surfaces of the low substitution layer. The IPS mode liquid crystal display device according to any one of [1] to [9].
[11] Any one of [1] to [10], wherein the acyl group of the cellulose acylate contained in the low substitution layer and / or the high substitution layer has 2 to 4 carbon atoms. IPS mode liquid crystal display device.
[12] The IPS mode liquid crystal display device according to any one of [1] to [11], wherein the cellulose acylate contained in the low substitution degree layer and / or the high substitution degree layer is cellulose acetate.
[13] The average film thickness of the low substitution degree layer is 30 to 100 μm, and the average film thickness of at least one of the high substitution degree layers is 0.2% or more and less than 25% of the average film thickness of the low substitution degree layer. The IPS mode liquid crystal display device according to any one of [1] to [12].

[14] The C-plate, the first optical film, and the first polarizer are provided on the backlight side from the liquid crystal cell, and the second optical film and the second polarization are provided on the viewing side from the liquid crystal cell. Have at least a child,
The first and second polarizers are arranged with their polarization axes orthogonal to each other,
The first optical film is composed of a low substitution layer containing, as a main component, cellulose acylate satisfying the following formula (1), or the following formula on at least one surface of the low substitution layer and the low substitution layer. Having a high substitution degree layer containing cellulose acylate satisfying (2) as a main component,
The FFS mode liquid crystal display device, wherein the second optical film satisfies the following formulas (I) to (IV).
(1) 2.0 <Z1 <2.7
(In formula (1), Z1 represents the total acyl substitution degree of the cellulose acylate of the low substitution degree layer.)
(2) 2.7 <Z2
(In formula (2), Z2 represents the total acyl substitution degree of the cellulose acylate of the high substitution degree layer.)
(I) 0 nm ≦ Re (550) ≦ 10 nm
(II) | Rth (550) | ≦ 25 nm
(III) | Re (630) -Re (450) | ≦ 10 nm
(IV) | Rth (630) −Rth (450) | ≦ 35 nm
(In the above formulas (I) to (IV), Re (λ) represents the front retardation value (nm) at the wavelength λnm, and Rth (λ) represents the retardation value in the film thickness direction at the wavelength λnm (nm). Represents.)
[15] The FFS mode liquid crystal display device of [14], wherein the first optical film satisfies the following formulas (V) and (VI).
(V) 70 nm ≦ Re (550) ≦ 140 nm
(VI) 40 nm ≦ Rth (550) ≦ 110 nm
[16] The second optical film is composed of a low substitution layer containing, as a main component, cellulose acylate satisfying the formula (1), or at least one surface of the low substitution layer and the low substitution layer The FFS mode liquid crystal display device according to [14] or [15], further comprising a high-substitution layer containing, as a main component, cellulose acylate satisfying the formula (2).
[17] The FFS mode liquid crystal display device according to any one of [14] to [16], wherein the second optical film has a thickness of 30 to 130 μm.
[18] The FFS mode liquid crystal display device according to any one of [14] to [17], wherein the low substitution degree layer contains a non-phosphate ester compound.
[19] The high substitution degree layer contains a non-phosphate ester compound as an additive, and the ratio (part by mass) of the additive to the cellulose acylate contained in the high substitution degree layer is the low substitution degree. The FFS mode liquid crystal display device according to any one of [14] to [18], wherein the amount is less than the ratio (parts by mass) of the additive to the cellulose acylate contained in the layer.
[20] The FFS mode liquid crystal display device according to [18] or [19], wherein the non-phosphate compound is a polyester compound containing an aromatic ring.
[21] The FFS mode liquid crystal display device according to any one of [14] to [20], wherein the cellulose acylate contained in the low substitution degree layer satisfies the following formulas (3) to (5).
Formula (3) 1.0 <X1 <2.7
Formula (4) 0 <= Y1 <1.5
Formula (5) X1 + Y1 = Z1
(In the formulas (3), (4) and (5), X1 represents the degree of substitution of the acetyl group of the cellulose acylate of the low-substituted layer, and Y1 has 3 or more carbon atoms of the cellulose acylate of the low-substituted layer. The total substitution degree of acyl groups is represented, and Z1 represents the total acyl substitution degree of cellulose acylate in the low substitution layer.)
[22] The FFS mode liquid crystal display device according to any one of [14] to [21], wherein the cellulose acylate used in the high substitution degree layer satisfies the following formulas (6) to (8).
Formula (6) 1.2 <X2 <3.0
Formula (7) 0 <= Y2 <1.5
Formula (8) X2 + Y2 = Z2
(In the formulas (6), (7) and (8), X2 represents the substitution degree of the acetyl group of the cellulose acylate of the high substitution degree layer, and Y2 has 3 or more carbon atoms of the cellulose acylate of the high substitution degree layer. The total substitution degree of acyl groups is represented, and Z2 represents the total acyl substitution degree of cellulose acylate in the high substitution degree layer.
[23] The high substitution layer (however, the composition of each high substitution layer may be independent and the same) on both surfaces of the low substitution layer. The FFS mode liquid crystal display device according to any one of [14] to [22].
[24] Any one of [14] to [23], wherein the number of carbon atoms of the acyl group of the cellulose acylate contained in the low substitution degree layer and / or the high substitution degree layer is 2 to 4. FFS mode liquid crystal display device.
[25] The FFS mode liquid crystal display device according to any one of [14] to [24], wherein the cellulose acylate contained in the low substitution degree layer and / or the high substitution degree layer is cellulose acetate.
[26] The average film thickness of the low substitution degree layer is 30 to 100 μm, and the average film thickness of at least one of the high substitution degree layers is 0.2% or more and less than 25% of the average film thickness of the low substitution degree layer. The FFS mode liquid crystal display device according to any one of [14] to [25].

  According to the present invention, it is possible to provide an IPS mode and FFS mode liquid crystal display device with high viewing angle contrast and reduced color shift that occurs when viewing from an oblique direction during black display.

It is a schematic sectional drawing of an example of the IPS mode liquid crystal display device of this invention. It is a schematic sectional drawing of an example of the FFS mode liquid crystal display device of this invention. It is the figure which showed typically an example of the optical compensation effect | action of the IPS mode liquid crystal display device of this invention on a Poincare sphere. It is the figure which showed typically an example of the optical compensation effect | action of the FFS mode liquid crystal display device of this invention on the Poincare sphere. It is the schematic which shows an example when the low substitution degree cellulose acylate type | system | group film of a 3 layer structure is poured by simultaneous co-casting using a co-casting die.

Hereinafter, the present invention will be described in detail. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at the wavelength λ, respectively. Re (λ) is measured with KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments Co., Ltd.) by making light having a wavelength of λ nm incident in the normal direction of the film. In selecting the measurement wavelength λnm, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like. When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is the film surface when Re (λ) is used and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotation axis) (if there is no slow axis) Measurement is performed at a total of 6 points by injecting light of wavelength λ nm from each inclined direction in steps of 10 degrees from the normal direction to 50 ° on one side with respect to the film normal direction (with any rotation direction as the rotation axis). Then, KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed value of the average refractive index, and the input film thickness value. In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative. The retardation value is measured from two inclined directions with the slow axis as the tilt axis (rotation axis) (if there is no slow axis, the arbitrary direction in the film plane is the rotation axis). Rth can also be calculated from the following formula (A) and formula (III) based on the value, the assumed value of the average refractive index, and the input film thickness value.

なお、上記のＲｅ（θ）は法線方向から角度θ傾斜した方向におけるレターデーション値をあらわす。また、式（Ａ）におけるｎｘは、面内における遅相軸方向の屈折率を表し、ｎｙは、面内においてｎｘに直交する方向の屈折率を表し、ｎｚは、ｎｘ及びｎｙに直交する方向の屈折率を表す。
Ｒｔｈ＝｛（ｎｘ＋ｎｙ）／２−ｎｚ｝×ｄ・・・・・・・・・・・式（ＩＩＩ）

Note that Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. In the formula (A), nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction orthogonal to nx in the plane, and nz is the direction orthogonal to nx and ny. Represents the refractive index.
Rth = {(nx + ny) / 2−nz} × d (formula (III))

When the film to be measured is a film that cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film without a so-called optical axis, Rth (λ) is calculated by the following method. Rth (λ) is from −50 ° to the normal direction of the film, with Re (λ) being the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotary axis). Measured at 11 points by making light of wavelength λ nm incident in 10 ° steps up to + 50 °, and based on the measured retardation value, average refractive index assumption value and input film thickness value. KOBRA 21ADH or WR is calculated. In the above measurement, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. If the average refractive index is not known, it can be measured with an Abbe refractometer. Examples of the average refractive index values of main optical films are given below:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).
The KOBRA 21ADH or WR calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

The “slow axis” means the direction in which the refractive index is maximized, and the measurement wavelength of the refractive index is a value in the visible light region (λ = 550 nm) unless otherwise specified.
In addition, in this specification, numerical values, numerical ranges, and qualitative expressions (for example, expressions such as “equivalent” and “equal”) indicating the optical characteristics of each member such as an optical film and a liquid crystal layer are liquid crystal displays. It shall be construed to indicate numerical values, numerical ranges and properties including generally acceptable errors for the device and the components used therein.

  The present invention relates to an IPS mode and FFS mode liquid crystal display device using a uniaxial or biaxial optical film and a C-plate exhibiting predetermined optical characteristics for an optical compensation mechanism. In particular, in the present invention, the uniaxial or biaxial optical film is composed of a low-substitution layer containing, as a main component, a low-substitution cellulose acylate satisfying predetermined conditions, or the low-substitution layer. One feature is that at least one surface of the low substitution degree layer has a high substitution degree layer containing a cellulose acylate having a high substitution degree that satisfies a predetermined condition as a main component. As a result of studies by the present inventors, a uniaxial or biaxial optical film produced using a cellulose acylate having a predetermined low substitution degree as a main component is a cellulose acylate having a conventional high substitution degree as a main component. It was found that the haze is lower than that of the uniaxial or biaxial optical film produced by using the film, the reverse wavelength dispersion is achieved, and the film thickness can be further reduced. In the present invention, a uniaxial or biaxial optical film having such characteristics is used in an IPS mode and FFS mode liquid crystal display device together with a C-plate, so that a viewing angle contrast is high, and an oblique direction is displayed during black display. The color shift that occurs when observed is reduced.

FIG. 1 is a schematic cross-sectional view of an example of the IPS mode liquid crystal display device of the present invention. In FIG. 1, the upper side is the viewing side, and in FIG. 1, the lower side is the back side where the backlight 19 is arranged.
The IPS mode liquid crystal display device of FIG. 1 includes first and second polarizers 11 and 12 and an IPS mode liquid crystal cell 13 disposed therebetween. Between the liquid crystal cell 13 and the first polarizer 11, the first optical film 14 and the C-plate 15 are provided, and between the liquid crystal cell 13 and the second polarizer 12, the first optical film 14 and the C-plate 15 are provided. Two optical films 16 are respectively disposed. The first and second polarizers 11 and 12 are arranged with their polarization axes orthogonal to each other. The liquid crystal cell 13 is not a mode driven by rising of liquid crystal molecules, but is an IPS mode liquid crystal cell in which liquid crystal molecules respond in an in-plane direction of the substrate by an electric field including a component substantially parallel to the substrate surface. Outside protective films 17 and 18 made of a polymer film such as a cellulose acylate film are disposed outside the first and second polarizers 11 and 12, respectively.

FIG. 2 is a schematic cross-sectional view of an example of the FFS mode liquid crystal display device of the present invention. In FIG. 2, the upper side is the viewing side, and the lower side in FIG. 2 is the back side where the backlight 19 is disposed.
The FFS mode liquid crystal display device of FIG. 2 includes first and second polarizers 12 and 11 and an FFS mode liquid crystal cell 13 ′ disposed therebetween. Between the liquid crystal cell 13 ′ and the first polarizer 12, there is a first optical film 14 and a C-plate 15, and between the liquid crystal cell 13 ′ and the second polarizer 11. The second optical film 16 is disposed. The first and second polarizers 12 and 11 are arranged with their polarization axes orthogonal to each other. The liquid crystal cell 13 ′ is not a mode driven by the rising of liquid crystal molecules, but is an FFS mode liquid crystal cell in which liquid crystal molecules respond in the in-plane direction with an electric field including a component substantially parallel to the substrate surface. Outside protective films 18 and 17 made of a polymer film such as a cellulose acylate film are disposed outside the first and second polarizers 12 and 11, respectively.

In the liquid crystal display device of FIGS. 1 and 2, the absorption axes of the polarizers 11 and 12 are shifted from the orthogonal arrangement in the oblique direction by the uniaxial or biaxial first optical film 14 and the C-plate 15. , Light leakage occurring in an oblique direction during black display due to the off-axis arrangement is reduced. This compensation mechanism is described in detail in JP-A-11-133408 and can be referred to. The aspect in which the first optical film 14 satisfies the following formulas (V) and (VI) is preferable because the effect by the compensation mechanism is excellent.
(V) 70 nm ≦ Re (550) ≦ 140 nm
(VI) 40 nm ≦ Rth (550) ≦ 110 nm
More preferably, the embodiment satisfies the following formulas (V ′) and (VI).
(V ′) 90 nm ≦ Re (550) ≦ 120 nm
(VI ′) 60 nm ≦ Rth (550) ≦ 90 nm

In the present invention, the first optical film 14 is composed of a low substitution layer containing, as a main component, cellulose acylate satisfying the following formula (1), or at least one of the low substitution layer and the low substitution layer. And a high substitution degree layer containing cellulose acylate satisfying the following formula (2) as a main component.
(1) 2.0 <Z1 <2.7
(In formula (1), Z1 represents the total acyl substitution degree of the cellulose acylate of the low substitution degree layer.)
(2) 2.7 <Z2
(In formula (2), Z2 represents the total acyl substitution degree of the cellulose acylate of the high substitution degree layer.)
Since the first optical film 14 includes the predetermined low substitution layer, the first optical film 14 has a characteristic that wavelength dispersion is small. In the compensation mechanism, the smaller the wavelength dispersion of the uniaxial or biaxial film, the more the color shift that occurs in the oblique direction can be reduced. In the present invention, the first optical film includes the predetermined low substitution degree layer, thereby reducing the color shift that occurs when observed from an oblique direction during black display.

As described above, the first optical film 14 preferably has a small wavelength dispersibility, and specifically satisfies the following formulas (III) and (IV),
(III) | Re (630) -Re (450) | ≦ 10 nm
(IV) | Rth (630) −Rth (450) | ≦ 35 nm
It is more preferable that the following formulas (III ′) and (IV ′) are satisfied.
(III ′) | Re (630) −Re (450) | ≦ 5 nm
(IV ′) | Rth (630) −Rth (450) | ≦ 10 nm

The second optical film 16 preferably does not affect the optical compensation mechanism, that is, has a low phase difference and low wavelength dispersion. Specifically, the second optical film 16 preferably satisfies the following formulas (I) to (IV).
(I) 0 nm ≦ Re (550) ≦ 10 nm
(II) | Rth (550) | ≦ 25 nm
(III) | Re (630) -Re (450) | ≦ 10 nm
(IV) | Rth (630) −Rth (450) | ≦ 35 nm

In particular, the second optical film 16 is composed of a low substitution layer containing, as a main component, cellulose acylate satisfying the above formula (1), or at least one surface of the low substitution layer and the low substitution layer. It is preferable to have a high substitution degree layer containing a cellulose acylate satisfying the above formula (2) as a main component (more preferably, the thickness is in the above preferred range), since circular unevenness can be reduced. . Here, “circular unevenness” means that when a liquid crystal panel is displayed as an image, luminance unevenness having a circular shape is seen near the center of the panel. In the aspect in which the second optical film 16 has the predetermined low substitution degree layer, the distance from the light source can be taken as much as the thickness of the film can be reduced, so that circular unevenness can be reduced.
Further, in the embodiment in which the outer protective film 17 and / or 18 has the predetermined low substitution layer, the distance from the light source can be taken as much as the thickness of the film can be reduced. it can.

  In FIG. 1, the upper side is the viewing side, and in FIG. 1, the lower side is the back side where the backlight 19 is arranged. That is, in the IPS mode liquid crystal display device of the present invention, the C-plate 15 contributing to the optical compensation action and the uniaxial and biaxial first optical film 14 are arranged in this order on the viewing side of the liquid crystal cell 13. Be placed. Similarly, the upper side in FIG. 2 is the viewing side, and the lower side in FIG. 2 is the back side where the backlight 19 is disposed. That is, in the FFS mode liquid crystal display device of the present invention, the C-plate 15 contributing to the optical compensation action and the uniaxial and biaxial first optical film 14 are arranged on the backlight side surface of the liquid crystal cell 13 ′. Arranged in order. In order to obtain the effects of the present invention, the order of these is important. This reason can be explained by showing the polarization state of light passing through each optical element on the Poincare sphere. FIG. 3 schematically shows an example of the optical compensation function of the IPS mode liquid crystal display device of the present invention on the Poincare sphere, and FIG. 4 shows an example of the optical compensation function of the FFS mode liquid crystal display device of the present invention. A diagram schematically shown on a sphere is shown. In any embodiment, it can be understood that the second optical film does not contribute to optical compensation.

Hereinafter, various members usable for the liquid crystal display device of the present invention will be described.
First and second optical films:
The liquid crystal display device of the present invention is composed of a low substitution degree layer containing cellulose acylate satisfying the following formula (1) as a main component, or the following on at least one surface of the low substitution degree layer and the low substitution degree layer. A first optical film having a high substitution degree layer containing cellulose acylate satisfying the formula (2) as a main component.
(1) 2.0 <Z1 <2.7
(In formula (1), Z1 represents the total acyl substitution degree of the cellulose acylate of the low substitution degree layer.)
(2) 2.7 <Z2
(In formula (2), Z2 represents the total acyl substitution degree of the cellulose acylate of the high substitution degree layer.)
When the degree of substitution is small, the water absorption rate of cellulose acylate is large, which is not preferable because durability under high temperature and high humidity becomes a problem. Further, since the birefringence decreases as the degree of substitution increases, in order to develop birefringence, the layer must be thickened, and there is a problem that it takes time to dry during film formation, which is not preferable. . If the degree of substitution is within the range satisfying the above formula (1), any problem can be solved. As a result, a film satisfying the above formulas (II ′) and (IV ′) can be stably formed as a thin film by having a predetermined low substitution degree layer containing as a main component cellulose acylate satisfying the above formula (1). Can be produced.
In the present specification, “contains as a main component” means an ingredient having the highest mass fraction in an embodiment in which the component as a raw material is one kind, and an ingredient having two or more ingredients. To do.

The first optical film exhibits uniaxial or biaxial optical characteristics, and the C-plate exhibits characteristics that contribute to optical compensation of the IPS mode or FFS mode liquid crystal cell. Specifically, it is preferable to satisfy the following formulas (V) and (VI),
(V) 70 nm ≦ Re (550) ≦ 140 nm
(VI) 40 nm ≦ Rth (550) ≦ 110 nm
It is more preferable to satisfy the following formulas (V ′) and (VI).
(V ′) 90 nm ≦ Re (550) ≦ 120 nm
(VI ′) 60 nm ≦ Rth (550) ≦ 90 nm

Further, the first optical film preferably has a small wavelength dispersion, and specifically, preferably satisfies the following formulas (III) and (IV):
(III) | Re (630) -Re (450) | ≦ 10 nm
(IV) | Rth (630) −Rth (450) | ≦ 35 nm
It is more preferable that the following formulas (III ′) and (IV ′) are satisfied.
(III ′) | Re (630) −Re (450) | ≦ 5 nm
(IV ′) | Rth (630) −Rth (450) | ≦ 10 nm

  By including the low substitution layer that satisfies the above predetermined condition, an optical film that satisfies the characteristics required for the first optical film can be stably produced.

The liquid crystal display device of the present invention has a second optical film that satisfies the following formulas (I) to (IV). The second optical film preferably exhibits a lower phase difference so as not to affect the optical compensation mechanism between the first optical film and the C-plate.
(I) 0 nm ≦ Re (550) ≦ 10 nm
(II) | Rth (550) | ≦ 25 nm
(III) | Re (630) -Re (450) | ≦ 10 nm
(IV) | Rth (630) −Rth (450) | ≦ 35 nm
The material of the second optical film is not particularly limited, but is composed of a low substitution layer containing, as a main component, cellulose acylate satisfying the above formula (1), or the low substitution layer and the low substitution degree. An embodiment having a high substitution degree layer containing, as a main component, cellulose acylate satisfying the above formula (2) on at least one surface of the layer is preferable because circular unevenness can be reduced.

Hereinafter, a film having the predetermined low substitution layer and usable as the first or second optical film is referred to as a “low substitution cellulose acylate film”, and will be described in detail below.
(Cellulose acylate)
Examples of the cellulose acylate used for the production of the low-substituted cellulose acylate film include cotton linter and wood pulp (hardwood pulp, softwood pulp), and cellulose acylate obtained from any raw material cellulose can be used. You may mix and use depending on the case. Detailed descriptions of these raw material celluloses can be found, for example, by Marusawa and Uda, “Plastic Materials Course (17) Fibrous Resin”, published by Nikkan Kogyo Shimbun (published in 1970), and the Japan Institute of Invention and Technology Publication No. 2001 The cellulose described in No.-1745 (pages 7 to 8) can be used.

  The raw material cellulose acylate used for the production of the low-substituted cellulose acylate film is acylated with two or more types of acyl groups, even if it is acylated with one type of acyl group. May be. It is preferable to have an acyl group having 2 to 4 carbon atoms as a substituent. When two or more types of acyl groups are used, one of them is preferably an acetyl group, and the acyl group having 2 to 4 carbon atoms is preferably a propionyl group or a butyryl group. With these films, a solution having a preferable solubility can be prepared, and in particular, in a non-chlorine organic solvent, a good solution can be prepared. Furthermore, a solution having a low viscosity and good filterability can be prepared.

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by acylating part or all of these hydroxyl groups with an acyl group. The degree of acyl substitution means the sum of the ratios of acylation of the hydroxyl groups of cellulose located at the 2-position, 3-position and 6-position (100% acylation at each position is substitution degree 1).

  The acyl group having 2 or more carbon atoms may be an aliphatic group or an allyl group, and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. Preferred examples of these include acetyl group, propionyl group, butanoyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, isobutanoyl group Group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, an acetyl group, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a tert-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and an acetyl group is particularly preferable. A propionyl group and a butanoyl group (when the acyl group has 2 to 4 carbon atoms), more preferably an acetyl group (when the cellulose acylate is cellulose acetate).

  In the acylation of cellulose, when an acid anhydride or acid chloride is used as an acylating agent, an organic acid such as acetic acid or methylene chloride is used as an organic solvent as a reaction solvent.

As the catalyst, when the acylating agent is an acid anhydride, a protic catalyst such as sulfuric acid is preferably used, and when the acylating agent is an acid chloride (for example, CH ₃ CH ₂ COCl), Basic compounds are used.

  The most common industrial synthesis method of cellulose mixed fatty acid ester is to use cellulose corresponding to fatty acid corresponding to acetyl group and other acyl groups (acetic acid, propionic acid, valeric acid, etc.) or their anhydrides. This is a method of acylating with a mixed organic acid component.

In the present invention, it is from the viewpoint of retardation wavelength dispersion that the cellulose acylate film of the low-substituted cellulose acylate film satisfies the following formulas (3) and (4). preferable.
Formula (3) 1.0 <X1 <2.7
(In Formula (3), X1 represents the substitution degree of the acetyl group of the cellulose acylate in the low substitution degree layer.)
Formula (4) 0 <= Y1 <1.5
(In Formula (4), Y1 represents the total substitution degree of acyl groups having 3 or more carbon atoms in the cellulose acylate of the low substitution degree layer.)
Note that the relationship X1 + Y1 = Z1 holds between X1 and Y1 and Z1 in the formula (1).

The cellulose acylate used in the high substitution layer of the low substitution cellulose acylate film preferably satisfies the following formulas (6) and (7) from the viewpoint of retardation wavelength dispersion.
Formula (6) 1.2 <X2 <3.0
(In Formula (6), X2 represents the substitution degree of the acetyl group of the cellulose acylate of the high substitution degree layer.)
Formula (7) 0 <= Y2 <1.5
(In Formula (7), Y2 represents the total substitution degree of acyl groups having 3 or more carbon atoms in the cellulose acylate of the high substitution degree layer.)
Note that the relationship of X2 + Y2 = Z2 holds between X2 and Y2 and Z2 in the formula (2).

  The cellulose acylate used in the present invention can be synthesized, for example, by the method described in JP-A-10-45804.

(Non-phosphate compound)
The low-substituted cellulose acylate film preferably contains a non-phosphate ester compound in the low-substituted layer (more preferably in the high-substituted layer). By including such a non-phosphate ester compound, there is an effect of reducing the haze.
In the present specification, the “non-phosphate ester compound” refers to a “compound having an ester bond and the acid contributing to the ester bond other than phosphoric acid”. That is, the “non-phosphate ester compound” means a compound that does not contain phosphoric acid and is an ester compound.
Further, the non-phosphate ester compound may be a low molecular compound or a polymer (polymer compound). Hereinafter, a non-phosphate ester compound which is a polymer (polymer compound) is also referred to as a non-phosphate ester polymer.

  In the low substitution cellulose acylate film, the high substitution layer contains the non-phosphate ester compound as an additive, and the ratio of the additive to the cellulose acylate contained in the high substitution layer It is preferable from the viewpoint of low haze that (mass part) is less than the ratio (mass part) of the additive to the cellulose acylate contained in the low substitution degree layer. Hereinafter, the non-phosphate ester compounds that can be used in the present invention will be described.

  As the non-phosphate ester compound, known high molecular weight additives and low molecular weight additives can be widely employed as additives for cellulose acylate films. The content of the additive is preferably 1 to 35% by mass, more preferably 4 to 30% by mass, and still more preferably 10 to 25% by mass with respect to the cellulose acylate.

  The high molecular weight additive used as the non-phosphate ester compound in the low-substituted cellulose acylate film has a repeating unit in the compound, and preferably has a number average molecular weight of 700 to 10,000. The high molecular weight additive has a function of increasing the volatilization rate of the solvent and a function of reducing the residual solvent amount in the solution casting method. Furthermore, it exhibits useful effects from the viewpoint of film modification such as improvement in mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability.

Here, the number average molecular weight of the high molecular weight additive which is a non-phosphate ester compound in the present invention is more preferably a number average molecular weight of 700 to 8000, still more preferably a number average molecular weight of 700 to 5000, The number average molecular weight is preferably 1000 to 5000.
Hereinafter, the high molecular weight additive which is a non-phosphate ester compound that can be used in the present invention will be described in detail with specific examples. However, the high-phosphate additive that is a non-phosphate ester compound used in the present invention is described below. Needless to say, the molecular weight additives are not limited to these.
The non-phosphate ester compound is preferably a non-phosphate ester compound. However, the “non-phosphate ester-based compound” means a compound that does not contain a phosphate ester and is ester-based.

  Examples of the polymer additive that is a non-phosphate ester compound include polyester polymers (aliphatic polyester polymers, aromatic polyester polymers, etc.), copolymers of polyester components and other components, and the like. , Aliphatic polyester polymer, aromatic polyester polymer, polyester polymer (aliphatic polyester polymer, aromatic polyester polymer, etc.) and acrylic polymer and polyester polymer (aliphatic polyester polymer, aromatic A copolymer of an aromatic polyester polymer or the like) and a styrene polymer is preferable, and a polyester compound containing an aromatic ring as at least one of the copolymer components is more preferable.

  Examples of the aliphatic polyester-based polymer include at least one diol selected from aliphatic dicarboxylic acids having 2 to 20 carbon atoms, aliphatic diols having 2 to 12 carbon atoms, and alkyl ether diols having 4 to 20 carbon atoms. The both ends of the reaction product may be left as the reaction product, or the monocarboxylic acid, monoalcohol or phenol may be further reacted to carry out so-called end-capping. Good. It is effective in terms of storage stability that the end capping is performed in particular so as not to contain free carboxylic acids. The dicarboxylic acid used in the polyester polymer of the present invention is preferably an aliphatic dicarboxylic acid residue having 4 to 20 carbon atoms or an aromatic dicarboxylic acid residue having 8 to 20 carbon atoms.

  Examples of the aliphatic dicarboxylic acid having 2 to 20 carbon atoms preferably used in the present invention include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, and azelaic acid. , Sebacic acid, dodecanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid.

  Among these, preferable aliphatic dicarboxylic acids are malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, and 1,4-cyclohexanedicarboxylic acid. Particularly preferably, the aliphatic dicarboxylic acid component is succinic acid, glutaric acid, or adipic acid.

  The diol utilized for the high molecular weight additive is selected from, for example, an aliphatic diol having 2 to 20 carbon atoms and an alkyl ether diol having 4 to 20 carbon atoms.

  Examples of the aliphatic diol having 2 to 20 carbon atoms include alkyl diols and alicyclic diols, such as ethane diol, 1,2-propanediol, 1,3-propanediol, and 1,2-butane. Diol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol) ), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3 -Methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl 1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. Used as a mixture of two or more.

  Preferred aliphatic diols include ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1 , 4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, particularly preferred Is ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6- Hexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol.

  Preferred examples of the alkyl ether diol having 4 to 20 carbon atoms include polytetramethylene ether glycol, polyethylene ether glycol and polypropylene ether glycol, and combinations thereof. The average degree of polymerization is not particularly limited, but is preferably 2 to 20, more preferably 2 to 10, further 2 to 5, and particularly preferably 2 to 4. As examples of these, commercially useful polyether glycols typically include Carbowax resin, Pluronics resin and Niax resin.

In the present invention, a high molecular weight additive whose end is sealed with an alkyl group or an aromatic group is particularly preferable. This is because the terminal is protected with a hydrophobic functional group, which is effective against deterioration with time at high temperature and high humidity, and is due to the role of delaying hydrolysis of the ester group.
It is preferable to protect with a monoalcohol residue or a monocarboxylic acid residue so that both ends of the polyester additive of the present invention are not carboxylic acid or OH group.
In this case, the monoalcohol is preferably a substituted or unsubstituted monoalcohol having 1 to 30 carbon atoms, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol. , Octanol, isooctanol, 2-ethylhexyl alcohol, nonyl alcohol, isononyl alcohol, tert-nonyl alcohol, decanol, dodecanol, dodecahexanol, aliphatic alcohol such as dodecaoctanol, allyl alcohol, oleyl alcohol, benzyl alcohol, 3-phenyl Examples thereof include substituted alcohols such as propanol.

  End-capping alcohols that can be preferably used are methanol, ethanol, propanol, isopropanol, butanol, isobutanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol, isooctanol, 2-ethylhexyl alcohol, isononyl alcohol, oleyl alcohol Benzyl alcohol, in particular methanol, ethanol, propanol, isobutanol, cyclohexyl alcohol, 2-ethylhexyl alcohol, isononyl alcohol, benzyl alcohol.

  Moreover, when sealing with a monocarboxylic acid residue, the monocarboxylic acid used as a monocarboxylic acid residue is preferably a substituted or unsubstituted monocarboxylic acid having 1 to 30 carbon atoms. These may be aliphatic monocarboxylic acids or aromatic ring-containing carboxylic acids. Preferred aliphatic monocarboxylic acids are described, for example, acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, oleic acid, and examples of the aromatic ring-containing monocarboxylic acid include Benzoic acid, p-tert-butylbenzoic acid, p-tert-amylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal propylbenzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc. Yes, these can be used alone or in combination of two or more.

  The synthesis of the high molecular weight additive may be a hot melt condensation method using a polyesterification reaction or a transesterification reaction between the aliphatic dicarboxylic acid and a diol and / or a monocarboxylic acid or monoalcohol for end-capping by a conventional method. Alternatively, it can be easily synthesized by any of the interfacial condensation methods of acid chlorides of these acids and glycols. These polyester-based additives are described in detail in Koichi Murai, “Additives, Theory and Application” (Kokaibo Co., Ltd., first edition published on March 1, 1973). In addition, Japanese Patent Laid-Open Nos. 05-155809, 05-155810, Japanese Patent Laid-Open Nos. 05-97073, 2006-259494, 07-330670, 2006-342227, 2007-003679. The materials described in each publication can also be used.

The aromatic polyester polymer is obtained by copolymerizing a monomer having an aromatic ring with the polyester polymer. The monomer having an aromatic ring is at least one monomer selected from aromatic dicarboxylic acids having 8 to 20 carbon atoms and aromatic diols having 6 to 20 carbon atoms.
Examples of the aromatic dicarboxylic acid having 8 to 20 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,8- There are naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid. Among these, preferable aromatic dicarboxylic acids are phthalic acid, terephthalic acid, and isophthalic acid.

  Examples of the aromatic diol having 6 to 20 carbon atoms include, but are not limited to, bisphenol A, 1,2-hydroxybenzene, 1,3-hydroxybenzene, 1,4-hydroxybenzene, and 1,4-benzenedimethanol. Bisphenol A, 1,4-hydroxybenzene and 1,4-benzenedimethanol are preferred.

  In the present invention, the aromatic polyester-based polymer is used by combining at least one of each of aromatic dicarboxylic acid and aromatic diol with the above-mentioned polyester, but the combination is not particularly limited, and each component is not limited. There is no problem even if several types are combined. In the present invention, as described above, a high molecular weight additive whose end is sealed with an alkyl group or an aromatic group is particularly preferable, and the above-described method can be used for sealing.

<Other additives>
In the low substitution layer and the high substitution layer constituting the first and second optical films, as an additive other than the non-phosphate ester compound, a retardation adjusting agent (retardation agent and retardation) is used. Reducing agents); plasticizers such as phthalates and phosphates; ultraviolet absorbers; antioxidants; additives such as matting agents may be added.

  In the low-substituted cellulose acylate film, as a retardation reducing agent, a phosphoric acid ester compound or a compound other than a known non-phosphate ester compound as an additive for a cellulose acylate film Can be widely adopted.

  The polymer retardation reducing agent is selected from phosphoric acid-based polyester polymers, styrene polymers, acrylic polymers, and copolymers thereof, and acrylic polymers and styrene polymers are preferred. Moreover, it is preferable that at least one polymer having negative intrinsic birefringence, such as a styrene polymer and an acrylic polymer, is included.

  Examples of the low molecular weight retardation reducing agent which is a compound other than the non-phosphate ester compound include the following. These may be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of an ultraviolet absorbing material at 20 ° C. or lower and 20 ° C. or higher, and a mixture of deterioration preventing agents are also possible. Furthermore, infrared absorbing dyes are described, for example, in JP-A No. 2001-194522. Moreover, the addition time may be added at any time in the cellulose acylate solution (dope) preparation step, but it may be added by adding a preparation step to the final preparation step of the dope preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested.

  The low molecular weight retardation reducing agent which is a compound other than the non-phosphate ester compound is not particularly limited, but details are described in JP-A-2007-272177, [0066] to [0085].

The compound described as the general formula (1) in [0066] to [0085] of JP-A-2007-272177 can be prepared by the following method.
The compound of the general formula (1) of the publication can be obtained by a condensation reaction between a sulfonyl chloride derivative and an amine derivative.

  JP, 2007-272177, A The compound of general formula (2) is a dehydration condensation reaction of carboxylic acids and amines using a condensing agent (for example, dicyclohexylcarbodiimide (DCC) etc.), or a carboxylic acid chloride derivative, It can be obtained by a substitution reaction with an amine derivative.

  The retardation reducing agent may be an Rth reducing agent. Among the retardation reducing agents, examples of the Rth reducing agent include acrylic polymers and styrene polymers, and low molecular compounds of the general formulas (3) to (7). Among them, acrylic polymers and styrene polymers. Polymers are preferred, and acrylic polymers are more preferred.

The retardation reducing agent is preferably added in a proportion of 0.01 to 30% by mass, more preferably 0.1 to 20% by mass, more preferably 0.1 to 10%, based on cellulose acylate. It is particularly preferable to add at a ratio of mass%.
By making the said addition amount 30 mass% or less, compatibility with a cellulose acylate can be improved and whitening can be suppressed. When using two or more types of retardation reducing agents, the total amount is preferably within the above range.

(Plasticizer)
As the plasticizer used in the present invention, many compounds known as cellulose acylate plasticizers can be usefully used. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred.

(Retardation expression agent)
When producing the low substituted cellulose acylate film satisfying the optical properties required for the first optical film, at least one retardation is provided in the low substituted layer in order to express the retardation value. An expression agent may be added. Although there is no restriction | limiting in particular as said retardation developing agent, The compound which consists of a rod-shaped or a disk-shaped compound, and the compound which shows retardation expression among the said non-phosphate ester type compounds can be mentioned. As the rod-like or discotic compound, a compound having at least two aromatic rings can be preferably used as a retardation developer.
The addition amount of the retardation enhancer composed of the rod-shaped compound is preferably 0.1 to 30 parts by mass, and preferably 0.5 to 20 parts by mass with respect to 100 parts by mass of the polymer component containing cellulose acylate. Further preferred. The discotic compound contained in the retardation developer is preferably less than 3 parts by mass, more preferably less than 2 parts by mass, and less than 1 part by mass with respect to 100 parts by mass of the cellulose acylate. It is particularly preferred.
Since the discotic compound is superior to the rod-shaped compound in Rth retardation expression, it is preferably used when a particularly large Rth retardation is required. Two or more retardation developers may be used in combination.
The retardation developer preferably has a maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.

The discotic compound will be described. As the discotic compound, a compound having at least two aromatic rings can be used.
In the present specification, the “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring.
The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring).
The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.
As the aromatic ring, a benzene ring, a condensed benzene ring, and biphenyls are preferable. In particular, a 1,3,5-triazine ring is preferably used. Specifically, for example, compounds disclosed in JP-A No. 2001-166144 are preferably used.

The number of carbon atoms of the aromatic ring in the retardation enhancer is preferably 2-20, more preferably 2-12, still more preferably 2-8, and 2-6. Most preferred.
The bonding relationship between two aromatic rings can be classified into (a) when a condensed ring is formed, (b) when directly linked by a single bond, and (c) when linked via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c).

  Examples of the condensed ring (a condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, a naphthacene ring, Pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline Ring, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thiant It includes emissions ring. Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred.

  The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded with two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.

The linking group in (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof. Examples of linking groups composed of combinations are shown below. In addition, the relationship between the left and right in the following examples of the linking group may be reversed.
c1: -CO-O-
c2: —CO—NH—
c3: -alkylene-O-
c4: —NH—CO—NH—
c5: —NH—CO—O—
c6: —O—CO—O—
c7: -O-alkylene-O-
c8: -CO-alkenylene-
c9: -CO-alkenylene-NH-
c10: -CO-alkenylene-O-
c11: -alkylene-CO-O-alkylene-O-CO-alkylene-
c12: -O-alkylene-CO-O-alkylene-O-CO-alkylene-O-
c13: -O-CO-alkylene-CO-O-
c14: -NH-CO-alkenylene-
c15: -O-CO-alkenylene-

The aromatic ring and the linking group may have a substituent.
Examples of substituents include halogen atoms (F, Cl, Br, I), hydroxyl groups, carboxyl groups, cyano groups, amino groups, nitro groups, sulfo groups, carbamoyl groups, sulfamoyl groups, ureido groups, alkyl groups, alkenyls. Group, alkynyl group, aliphatic acyl group, aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group An aliphatic substituted carbamoyl group, an aliphatic substituted sulfamoyl group, an aliphatic substituted ureido group, and a non-aromatic heterocyclic group.

It is preferable that the alkyl group has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (for example, a hydroxy group, a carboxy group, an alkoxy group, an alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl, and 2- Each group of a diethylaminoethyl group is included.
The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable. The alkenyl group may further have a substituent. Examples of the alkenyl group include a vinyl group, an allyl group, and a 1-hexenyl group.
The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of the alkynyl group include ethynyl group, 1-butynyl group and 1-hexynyl group.

The number of carbon atoms in the aliphatic acyl group is preferably 1-10. Examples of the aliphatic acyl group include an acetyl group, a propanoyl group, and a butanoyl group.
The number of carbon atoms in the aliphatic acyloxy group is preferably 1-10. Examples of the aliphatic acyloxy group include an acetoxy group.
The number of carbon atoms of the alkoxy group is preferably 1-8. The alkoxy group may further have a substituent (for example, an alkoxy group). Examples of the alkoxy group (including a substituted alkoxy group) include a methoxy group, an ethoxy group, a butoxy group, and a methoxyethoxy group.
The number of carbon atoms of the alkoxycarbonyl group is preferably 2-10. Examples of the alkoxycarbonyl group include a methoxycarbonyl group and an ethoxycarbonyl group.
The number of carbon atoms of the alkoxycarbonylamino group is preferably 2-10. Examples of the alkoxycarbonylamino group include a methoxycarbonylamino group and an ethoxycarbonylamino group.

The alkylthio group preferably has 1 to 12 carbon atoms. Examples of the alkylthio group include a methylthio group, an ethylthio group, and an octylthio group.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include a methanesulfonyl group and an ethanesulfonyl group.
The number of carbon atoms in the aliphatic amide group is preferably 1-10. Examples of the aliphatic amide group include acetamide.
The number of carbon atoms of the aliphatic sulfonamide group is preferably 1-8. Examples of the aliphatic sulfonamido group include a methanesulfonamido group, a butanesulfonamido group and an n-octanesulfonamido group.
The number of carbon atoms of the aliphatic substituted amino group is preferably 1-10. Examples of the aliphatic substituted amino group include a dimethylamino group, a diethylamino group, and a 2-carboxyethylamino group.
The number of carbon atoms in the aliphatic substituted carbamoyl group is preferably 2-10. Examples of the aliphatic substituted carbamoyl group include a methylcarbamoyl group and a diethylcarbamoyl group.
The number of carbon atoms in the aliphatic substituted sulfamoyl group is preferably 1-8. Examples of the aliphatic substituted sulfamoyl group include a methylsulfamoyl group and a diethylsulfamoyl group.
The number of carbon atoms in the aliphatic substituted ureido group is preferably 2-10. Examples of the aliphatic substituted ureido group include a methylureido group.
Examples of the non-aromatic heterocyclic group include a piperidino group and a morpholino group.
The molecular weight of the retardation developer is preferably 300 to 800.

  As the discotic compound, a triazine compound represented by the following general formula (I) is preferably used.

In the above general formula (I):
R ²⁰¹ each independently represents an aromatic ring or a heterocyclic ring having a substituent in at least one of the ortho position, meta position and para position.
X ²⁰¹ each independently represents a single bond or —NR ²⁰² —. Here, each R ²⁰² independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an aryl group, or a heterocyclic group.

The aromatic ring represented by R ²⁰¹ is preferably phenyl or naphthyl, particularly preferably phenyl. The aromatic ring R ²⁰¹ represents may have at least one substituent at any substitutable position. Examples of the substituent include halogen atom, hydroxyl group, cyano group, nitro group, carboxyl group, alkyl group, alkenyl group, aryl group, alkoxy group, alkenyloxy group, aryloxy group, acyloxy group, alkoxycarbonyl group, Alkenyloxycarbonyl group, aryloxycarbonyl group, sulfamoyl group, alkyl-substituted sulfamoyl group, alkenyl-substituted sulfamoyl group, aryl-substituted sulfamoyl group, sulfonamide group, carbamoyl, alkyl-substituted carbamoyl group, alkenyl-substituted carbamoyl group, aryl-substituted carbamoyl group, amide Groups, alkylthio groups, alkenylthio groups, arylthio groups and acyl groups.

The heterocyclic group represented by ^R201 preferably has aromaticity. The heterocycle having aromaticity is generally an unsaturated heterocycle, preferably a heterocycle having the largest number of double bonds. The heterocyclic ring is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and most preferably a 6-membered ring. The hetero atom of the heterocyclic ring is preferably a nitrogen atom, a sulfur atom or an oxygen atom, and particularly preferably a nitrogen atom. As the heterocyclic ring having aromaticity, a pyridine ring (2-pyridyl or 4-pyridyl as the heterocyclic group) is particularly preferable. The heterocyclic group may have a substituent. Examples of the substituent of the heterocyclic group are the same as the examples of the substituent of the aryl moiety.
When X ²⁰¹ is a single bond, the heterocyclic group is preferably a heterocyclic group having a free valence on the nitrogen atom. The heterocyclic group having a free valence on the nitrogen atom is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and a 5-membered ring. Is most preferred. The heterocyclic group may have a plurality of nitrogen atoms. Further, the heterocyclic group may have a hetero atom other than the nitrogen atom (for example, O, S). Examples of heterocyclic groups having free valences on nitrogen atoms are shown below. Here, -C ₄ H ₉ ⁿ represents a n-C ₄ H _9.

The alkyl group represented by R ²⁰² may be a cyclic alkyl group or a chain alkyl group, but a chain alkyl group is preferable, and a linear alkyl group is more preferable than a branched chain alkyl group. preferable. The number of carbon atoms in the alkyl group is preferably 1-30, more preferably 1-20, further preferably 1-10, still more preferably 1-8, and 1-6. Most preferred. The alkyl group may have a substituent. Examples of the substituent include a halogen atom, an alkoxy group (for example, methoxy group, ethoxy group) and an acyloxy group (for example, acryloyloxy group, methacryloyloxy group).

The alkenyl group represented by R ²⁰² may be a cyclic alkenyl group or a chain alkenyl group, but is preferably a chain alkenyl group and is more preferably a linear alkenyl group than a branched chain alkenyl group. More preferably it represents a group. The number of carbon atoms in the alkenyl group is preferably 2 to 30, more preferably 2 to 20, still more preferably 2 to 10, still more preferably 2 to 8, 6 is most preferred. The alkenyl group may have a substituent. Examples of the substituent are the same as those of the alkyl group described above.
The aromatic ring group and heterocyclic group represented by R ²⁰² are the same as the aromatic ring and heterocyclic ring represented by R ²⁰¹ , and the preferred range is also the same. The aromatic ring group and the heterocyclic group may further have a substituent, and examples of the substituent are the same as those of the aromatic ring and heterocyclic ring of ^R201 .

  The compound represented by the general formula (I) can be synthesized by a known method such as the method described in JP-A-2003-344655. Details of the retardation enhancer are described on page 49 of published technical bulletin 2001-1745.

  As the retardation developer of the present invention, a polymer additive can be used as in the case of the low molecular compound. Here, in the present invention, the polymer used as the non-phosphate ester-based polymer may also function as a retardation developer. As the polymeric retardation developer which is also a non-phosphate ester polymer, the aromatic polyester polymer and copolymers of the aromatic polyester polymer and other resins are preferable.

  The retardation enhancer of the present invention is more preferably a Re enhancer from the viewpoint of efficiently expressing Re and realizing an appropriate Nz factor. Among the retardation developing agents, examples of the Re developing agent include a discotic compound and a rod-shaped compound.

  In the present invention, deterioration inhibitors, ultraviolet absorbers, peeling accelerators, matting agents, lubricants, the aforementioned plasticizers, and the like can be appropriately used as necessary.

(Deterioration inhibitor)
The low-substituted cellulose acylate film is a known deterioration (oxidation) inhibitor such as 2,6-di-tert-butyl-4-methylphenol, 4,4′-thiobis- (6-tert-butyl). -3-methylphenol), 1,1′-bis (4-hydroxyphenyl) cyclohexane, 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, A phenolic or hydroquinone antioxidant such as pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] can be added. Further, tris (4-methoxy-3,5-diphenyl) phosphite, tris (nonylphenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite, bis (2,6-di-tert) It is preferable to use a phosphorus-based antioxidant such as -butyl-4-methylphenyl) pentaerythritol diphosphite and bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite. The addition amount of the deterioration inhibitor is 0.05 to 5.0 parts by mass with respect to 100 parts by mass of the cellulose acylate.

(UV absorber)
The low-substituted cellulose acylate film may contain an ultraviolet absorber. As the ultraviolet absorber, those excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and having little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties. Specific examples of ultraviolet absorbers preferably used in the present invention include, for example, hindered phenol compounds, hydroxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds Etc. Examples of hindered phenol compounds include 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]. N, N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert) -Butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -isocyanurate and the like. Examples of benzotriazole compounds include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6 (2H-benzotriazol-2-yl) phenol), (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5- Triazine, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-tert-butyl-4- Hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole, (2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5 -Chlorobenzotriazole, 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and the like. The addition amount of these ultraviolet light inhibitors is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm by mass in the entire optical film.

(Peeling accelerator)
The low substitution cellulose acylate film may contain a peeling accelerator. For example, when the low-substituted cellulose acylate film is produced by a solution casting method, the peeling accelerator is added to make the peeling of the film from a support such as a band stable and easy. The release accelerator can be included at a ratio of 0.001 to 1% by weight, for example, and if it is added in an amount of 0.5% by weight or less, separation of the release agent from the film is less likely to occur. 005% by weight or more is preferable because a desired peeling reduction effect can be obtained. Therefore, it is preferably included at a rate of 0.005 to 0.5% by weight, and at a rate of 0.01 to 0.3% by weight. More preferably. As the peeling accelerator, known ones can be adopted, and organic and inorganic acidic compounds, surfactants, chelating agents and the like can be used. Among them, polyvalent carboxylic acids and esters thereof are effective, and in particular, ethyl esters of citric acid can be used effectively.
In the aspect in which the low-substituted cellulose acylate film has a high-substitution layer, it is preferable that the high-substitution layer is on the surface side of a support such as a band. Is preferably added.

(Matting agent)
In the low-substituted cellulose acylate film, it is preferable that at least one of the high-substituted layers contains a matting agent from the viewpoint of film slipperiness and stable production. The matting agent may be an inorganic compound matting agent or an organic compound matting agent.
Specific examples of the inorganic compound matting agent include silicon-containing inorganic compounds (for example, silicon dioxide, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, etc.), titanium oxide, and zinc oxide. , Aluminum oxide, barium oxide, zirconium oxide, strongtium oxide, antimony oxide, tin oxide, tin oxide / antimony, calcium carbonate, talc, clay, calcined kaolin, calcium phosphate, etc., more preferably silicon-containing inorganic compounds and oxides Although it is zirconium, since the turbidity of a cellulose acylate film can be reduced, silicon dioxide is particularly preferably used. As the silicon dioxide fine particles, for example, commercially available products having trade names such as Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.) can be used. As the zirconium oxide fine particles, for example, those commercially available under trade names such as Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) can be used.
Preferable specific examples of the organic compound matting agent include, for example, polymers such as silicone resin, fluorine resin and acrylic resin, and among them, silicone resin is preferably used. Of the silicone resins, those having a three-dimensional network structure are particularly preferable. A commercial product having a trade name can be used.

  When these matting agents are added to the cellulose acylate solution, the method is not particularly limited, and there is no problem as long as a desired cellulose acylate solution can be obtained by any method. For example, an additive may be contained at the stage of mixing cellulose acylate and a solvent, or an additive may be added after preparing a mixed solution with cellulose acylate and a solvent. Further, it may be added and mixed immediately before casting the dope, which is a so-called immediately preceding addition method, and the mixing is used by installing screw-type kneading online. Specifically, a static mixer such as an in-line mixer is preferable, and as the in-line mixer, for example, a static mixer SWJ (Toray Static In-Pipe Mixer Hi-Mixer) (manufactured by Toray Engineering) is used. Is preferred. In addition, regarding in-line addition, in order to eliminate density unevenness, particle aggregation, and the like, Japanese Patent Application Laid-Open No. 2003-053752 mixes additive liquids having different compositions into the main raw material dope in a method for producing a cellulose acylate film. An invention is described in which the distance L between the tip of the addition nozzle and the start end of the in-line mixer is 5 times or less the inner diameter d of the main raw material pipe, thereby eliminating concentration unevenness and aggregation of matte particles. As a more preferred embodiment, the distance (L) between the tip opening of the additive liquid supply nozzle having a composition different from that of the main raw material dope and the starting end of the in-line mixer is 10 times or less the inner diameter (d) of the supply nozzle tip opening. And that the in-line mixer is a static unstirred in-tube mixer or a dynamic agitated in-tube mixer. More specifically, it is disclosed that the flow rate ratio of the cellulose acylate film main raw material dope / in-line additive solution is 10/1 to 500/1, preferably 50/1 to 200/1. Furthermore, the additive is also added to Japanese Patent Application Laid-Open No. 2003-014933 of the invention which aims at a retardation film with little additive bleed-out, no delamination phenomenon, good slipperiness and excellent transparency. As a method to do this, it may be added to the melting pot, or a solution in which additives or additives are dissolved or dispersed between the melting pot and the co-casting die may be added to the dope being fed. However, in the latter case, it is described that it is preferable to provide a mixing means such as a static mixer in order to improve the mixing property.

In the aspect in which the low-substituted cellulose acylate film has a high-substituted layer, it is preferable that the low-substituted layer is a core layer, and a high-substituted layer is formed on both sides of the core layer. It is preferable to add the matting agent to any one of the layers from the viewpoints of scratch resistance due to reduction of the coefficient of friction of the film surface, prevention of scumming generated when a wide film is wound long, and prevention of film breakage. It is particularly preferable that a matting agent is contained in both the skin A layer and the skin B layer from the viewpoint of effectively reducing scratch resistance and creaking.
In the low-substituted cellulose acylate film, the matting agent does not increase the haze of the film unless it is added in a large amount. When actually used in an LCD, there are inconveniences such as a decrease in contrast and generation of bright spots. Hard to occur. If the amount is too small, the above-mentioned creaking and scratch resistance can be realized. From these viewpoints, it is preferably included in a proportion of 0.01 to 5.0% by weight, more preferably included in a proportion of 0.03 to 3.0% by weight, and a proportion of 0.05 to 1.0% by weight. It is particularly preferable to include

(Haze)
The low-substituted cellulose acylate film preferably has a haze of less than 0.20%, more preferably less than 0.15%, and particularly preferably less than 0.10%. By setting the haze to less than 0.2%, the contrast ratio when incorporated in a liquid crystal display device can be improved. In addition, there is an advantage that the transparency of the film becomes higher and it is easier to use as an optical film.

  The low-substituted cellulose acylate film preferably has an aspect in which the predetermined low-substituted layer and the predetermined high-substituted layer are laminated on at least one surface of the low-substituted layer. In addition, the acyl substitution degree of cellulose acylate in each layer may be uniform, or a plurality of cellulose acylates may be mixed in one layer, but the acyl substitution degree of cellulose acylate in each layer is all It is preferable that it is constant from the viewpoint of adjustment of optical characteristics.

  In the low-substituted cellulose acylate film, a layer in contact with the support (hereinafter also referred to as skin B layer) when produced by solution casting is the high-substitution layer, and the other layers are the low-substitution layers. The substitution degree layer is preferable from the viewpoint of further improving the peelability from the support during solution casting.

  The low-substituted cellulose acylate film preferably has a laminated structure of three or more layers from the viewpoint of dimensional stability and reduction of curling amount accompanying changes in environmental moisture and heat. Moreover, when it has the said high substitution degree layer on both surfaces of the said low substitution degree layer, it is preferable from a viewpoint of the freedom degree improvement in the process of implement | achieving the optical characteristic requested | required as a 1st and 2nd optical film. Further, the low-substituted cellulose acylate film has a laminated structure of three or more layers, and cellulose acylates contained in at least one inner layer all satisfy the formulas (3) and (4). More preferably, the cellulose acylate is an acylate and all the cellulose acylates contained in the surface layers on both sides satisfy the above formulas (5) and (6). The surface layer on the side not in contact with the support during film formation is also referred to as a skin A layer only when the low-substituted cellulose acylate film has a laminated structure of three or more layers.

The low-substituted cellulose acylate film preferably has a three-layer structure of skin B layer / core layer / skin A layer. When the low-substituted cellulose acylate film has a three-layer structure, the low-substitution layer / high-substitution layer / low-substitution layer even when the high-substitution layer / low-substitution layer / high-substitution layer are used. However, the high substitution layer / low substitution layer / high substitution layer configuration may improve the releasability from the support during solution casting and improve dimensional stability. It is preferable from the viewpoint.
When the low-substituted cellulose acylate film has a three-layer structure, the cellulose acylate contained in the surface layers on both sides uses the same acyl-substituted cellulose acylate. It is preferable from the viewpoint of reducing the curl amount accompanying the change.

(Film thickness)
In the low-substituted cellulose acylate film, the average film thickness of the low-substituted layer is preferably 30 to 100 μm, more preferably 30 to 80 μm, and further preferably 30 to 70 μm. By setting it to 30 μm or more, the handling property when producing a web-like film is improved, which is preferable. Moreover, by setting it as 70 micrometers or less, it is easy to respond to a humidity change and it is easy to maintain an optical characteristic.

  The low substitution cellulose acylate film has an average film thickness of at least one of the high substitution layers of 0.2% or more and less than 25% of the low substitution layer average film thickness of 0.2%. If it is above, the peelability is sufficient, streak-like unevenness, film thickness non-uniformity or optical characteristic non-uniformity is suppressed, and if it is less than 25%, the optical developability of the core layer can be used effectively. The laminated film is preferable from the viewpoint of obtaining sufficient optical characteristics. The average film thickness of at least one of the high substitution degree layers is more preferably from 0.5 to 15%, particularly preferably from 1.0 to 10%, of the low substitution degree layer average film thickness. Moreover, it is more preferable that the average film thicknesses of the skin A layer and the skin B layer are both 0.2% or more and less than 25% of the core layer average film thickness.

  The low-substituted cellulose acylate film has an average film thickness of the low-substituted layer of 30 to 100 μm, and an average film thickness of at least one of the high-substituted layers is the average film thickness of the low-substituted layer. Is preferably 0.2% or more and less than 25%, from the viewpoint of retardation wavelength dispersion. Furthermore, the average film thickness of the low substitution degree layer is 30 to 100 μm, and the average film thickness of both of the high substitution degree layers is 0.2% or more and less than 25% of the average thickness of the low substitution degree layer. Is more preferable.

When the low-substituted cellulose acylate film has a laminated structure of three or more layers, the film thickness of the low-substituted layer (preferably core layer) is preferably 30 to 70 μm, preferably 30 to 60 μm. More preferably, it is particularly preferably 30 to 50 μm.
When the film of the present invention has a laminated structure of three or more layers, it is more preferable that both the thicknesses of the high substitution degree layers (preferably the surface layers on both sides of the film) are 0.5 to 20 μm, It is particularly preferably 10 μm, and more preferably 0.5 to 3 μm.

  The low-substituted cellulose acylate film has a laminated structure of three layers, an inner layer (core layer) is the low-substituted layer, and a surface layer (skin B layer and skin A layer) is the high-substituted A layered structure that is a high layer can be mentioned. More preferably, the skin B layer and the skin A layer are thinner than the core layer. The preferable conditions for the film thickness of the surface layer are the same as in the case where the film of the present invention has a laminated structure of three or more layers.

(Film width)
The low-substituted cellulose acylate film preferably has a film width of 700 to 3000 mm, more preferably 1000 to 2800 mm, and particularly preferably 1500 to 2500 mm.
The low-substituted cellulose acylate film preferably has a film width of 700 to 3000 mm and ΔRe of 10 nm or less.

[Method for producing low-substituted cellulose acylate film]
An example of a method for producing a low-substituted cellulose acylate film satisfying the optical properties required for the first optical film is a cellulose acylate satisfying the above formula (1), and optionally a non-phosphate ester compound. A cellulose acylate solution for a low substitution layer containing a cellulose acylate solution and a cellulose acylate solution for a high substitution layer containing a cellulose acylate satisfying the following formula (2) are successively cast or simultaneously co-cast. A process for forming a rate laminated film, and a film formed in a film in a temperature range of 100 to 250 ° C. with a residual solvent in an amount of 5% by mass or more with respect to the mass of the entire film. And a step of stretching in the longitudinal direction while leaving the end portion in the direction (MD) as a free end (hereinafter, sometimes referred to as “MD stretching”).
An example of a method for producing a low-substituted cellulose acylate film satisfying the optical properties required for the second optical film is a cellulose acylate satisfying the above formula (1), and optionally a non-phosphate ester system. A cellulose acylate solution for a low-substituted layer containing the above compound and a cellulose acylate solution for a high-substituted layer containing a cellulose acylate satisfying the above formula (2) are sequentially cast or simultaneously co-casted. Then, the step of forming a cellulose acylate laminated film, and the film formed in the temperature range of 100 to 250 ° C., the width direction (TD) with the end in the longitudinal direction fixed to the film forming direction. (Hereinafter, it may be referred to as “TD stretching”).

  The cellulose acylate laminated film is preferably formed by a solvent cast method. About the manufacture example of the cellulose acylate film using a solvent cast method, U.S. Pat. Nos. 2,336,310, 2,367,603, 2,492,078, 2,492,977, 2,492,978, 2,607,704, 2,739,069 and 2,739,070, British Patent Nos. 640731 and 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, JP-A-60-203430, and JP-A-62-115035 can be referred to. The cellulose acylate film may be subjected to a stretching treatment. With respect to the stretching method and conditions, for example, refer to JP-A-62-115035, JP-A-4-152125, 4-284221, 4-298310, and 11-48271. can do.

  As a solution casting method, a method in which the prepared dope is uniformly extruded from a pressure die onto a metal support, and a method using a doctor blade in which the dope once cast on the metal support is adjusted with a blade is used. Although there is a method using a reverse roll coater that adjusts with a reverse rotating roll, a method using a pressure die is preferred. The pressure die includes a coat hanger type and a T die type, and any of them can be preferably used. In addition to the methods mentioned here, it can be carried out by various known methods for casting a cellulose triacetate solution, and each condition is set in consideration of differences in the boiling point of the solvent used. Thus, the same effects as those described in the respective publications can be obtained.

  The low-substituted cellulose acylate film comprises a cellulose acylate satisfying the formula (1) and, optionally, a non-phosphate ester-based compound, a cellulose acylate solution for a low-substituted layer (casting dope). And a step of casting a cellulose acylate solution for a high substitution degree layer containing cellulose acylate satisfying the formula (2) onto a support to form a film, and the obtained film is stretched under predetermined conditions. Manufactured in a process including steps.

  In the production method, the viscosity of the cellulose acylate solution for the low substitution layer at 25 ° C. is 10% or more higher than the viscosity at 25 ° C. of the cellulose acylate solution for the high substitution layer. From the viewpoint of the distribution in the width direction and the suitability for producing a laminated film.

In the formation of the low-substituted cellulose acylate film, it is preferable to use a lamination casting method such as a co-casting method, a sequential casting method, and a coating method. In particular, the simultaneous co-casting method is preferably used for stable production. It is particularly preferable from the viewpoint of reducing production costs.
When manufacturing by the co-casting method and the sequential casting method, first, a cellulose acetate solution (dope) for each layer is prepared. In the co-casting method (multi-layer simultaneous casting), a casting dope for each layer (which may be three layers or more) is simultaneously pressed from a separate slit or the like on a casting support (band or drum). This is a casting method in which a dope is extruded from a casting die to be cast, and each layer is cast simultaneously, peeled off from a support at an appropriate time, and dried to form a film. FIG. 5 is a cross-sectional view showing a state where three layers of the surface layer dope 1 and the core layer dope 2 are extruded simultaneously on the casting support 4 using the co-casting die 3 and cast.

  In the sequential casting method, a casting dope for a first layer is first extruded from a casting die on a casting support, cast, dried, or dried without drying. The dope for casting is extruded from the casting die, and if necessary, the dope is cast and laminated sequentially to the third layer or more, and then peeled off from the support at an appropriate time and dried. This is a casting method for forming a film. In general, the core layer film is formed into a film by a solution casting method to prepare a coating solution to be applied to the surface layer, and then applied to the film one side at a time or both sides simultaneously using an appropriate applicator. This is a method of forming a film having a laminated structure by applying and drying a liquid.

  The endlessly running metal support used to produce the low-substituted cellulose acylate film includes a drum whose surface is mirror-finished by chrome plating and a stainless steel belt (band) which is mirror-finished by surface polishing. May be used). One or more pressure dies may be installed above the metal support. Preferably 1 or 2 groups. When two or more are installed, the amount of dope to be cast may be divided into various ratios for each die, or the dope may be fed to the dies from each of a plurality of precision quantitative gear pumps. The temperature of the cellulose acylate solution used for casting is preferably −10 to 55 ° C., more preferably 25 to 50 ° C. In that case, all solution temperatures in the process may be the same or different at different points in the process. If they are different, the temperature may be a desired temperature just before casting.

Examples of methods for stretching in the width direction (TD stretching) include, for example, JP-A-62-115035, JP-A-4-152125, JP-A-4-284221, JP-A-4-298310, and JP-A-11-48271. It is described in. In the case of stretching in the width direction, the film can also be stretched by conveying the film while holding it with a tenter and gradually widening the tenter. After the film is dried, it can be stretched using a stretching machine (preferably uniaxial stretching using a long stretching machine). In the case of longitudinal stretching (MD stretching), for example, two pairs of nip rolls are installed, and the peripheral speed of the nip roll on the outlet side is made faster than the peripheral speed of the nip roll on the inlet side while heating between them. Under the present circumstances, the expression of the retardation of the thickness direction can be changed by changing the space | interval (L) between nip rolls, and the film width (W) before extending | stretching. When L / W exceeds 2 and is 50 or less (long span stretching), Rth can be decreased, and when L / W is 0.01 to 0.3 (short span stretching), Rth can be increased. In the present invention, any of a long span stretching, a short span stretching, and a region between them (intermediate stretching = L / W is more than 0.3 and 2 or less) may be used. Short span stretching is preferred. Further, when aiming at high Rth, it is more preferable to use short span stretching, and when aiming at low Rth, it is distinguished from long span stretching.
The preferred stretching temperature for these longitudinal stretching is (Tg-10 ° C) to (Tg + 50) ° C, more preferably (Tg-5 ° C) to (Tg + 40) ° C, and even more preferably (Tg + 5) to (Tg +). 30) ° C. The film is stretched by adjusting the speed of the film conveying roller so that the film winding speed is higher than the film peeling speed.

In MD stretching, the stretching ratio of the film is preferably 5% to 200%, more preferably 10% to 100%, and particularly preferably 20% to 50%.
In TD stretching, the stretching ratio of the film is preferably 5% to 200%, more preferably 10% to 100%, and particularly preferably 20% to 50%.
In addition, the draw ratio as used in the field of this invention is defined by a following formula.
Stretch ratio = {(Length after stretching) − (Length before stretching)} / (Length before stretching)

  When the first and second optical films made of the low-substituted cellulose acylate film produced by MD stretching and TD stretching are used as a protective film for a polarizer, the polarizing plate is viewed obliquely. In order to suppress light leakage, it is necessary to arrange the transmission axis of the polarizer and the slow axis in the plane of the cellulose acylate film in parallel. Since the transmission axis of the roll film-like polarizer produced continuously is generally parallel to the width direction of the roll film, it is composed of the roll film-like polarizer and the roll film-like cellulose acylate film. In order to continuously bond the protective film, the in-plane slow axis of the roll film-shaped protective film needs to be parallel to the width direction of the film. Therefore, it is preferable to stretch more in the width direction. In addition, the stretching treatment may be performed during the film forming process, or the raw film that has been formed and wound may be stretched, but in the production method of the present invention, the stretching is performed in a state containing a residual solvent. In order to carry out, it is preferable to extend | stretch in the middle of a film forming process.

  In MD stretching and TD stretching, it may include a step of drying the cellulose acylate laminated film after the stretching step, and a step of stretching the cellulose acylate laminated film after drying at a temperature of Tg-10 ° C or higher. It is preferable from the viewpoint of retardation development.

  In MD stretching and TD stretching, the dope drying on the metal support related to the production of the low-substituted cellulose acylate film is generally performed on the surface side of the metal support (drum or belt), that is, the metal. A method in which hot air is applied from the surface of the web on the support, a method in which hot air is applied from the back surface of the drum or belt, or a temperature-controlled liquid is contacted from the back surface on the opposite side of the belt or drum from which the dope is cast. There is a backside liquid heat transfer method in which the drum or belt is heated to control the surface temperature, and the backside liquid heat transfer method is preferred. The surface temperature of the metal support before casting may be any number as long as it is not higher than the boiling point of the solvent used for the dope. However, in order to promote drying and to lose fluidity on the metal support, the temperature should be set to 1 to 10 ° C. lower than the boiling point of the lowest boiling solvent. Is preferred. This is not the case when the cast dope is cooled and peeled off without drying.

  The film thickness may be adjusted by adjusting the solid content concentration contained in the dope, the slit gap of the die base, the extrusion pressure from the die, the metal support speed, and the like so as to obtain a desired thickness.

  The length of the low-substituted cellulose acylate film obtained as described above is preferably wound at 100 to 10,000 m per roll, more preferably 500 to 7000 m, and still more preferably 1000 to 10,000 m. 6000 m. When winding, it is preferable to give knurling to at least one end, the knurling width is preferably 3 mm to 50 mm, more preferably 5 mm to 30 mm, and the height is preferably 0.5 to 500 μm, more preferably 1 to 200 μm. is there. This may be a single push or a double push.

  Although there is no restriction | limiting in particular about the thickness of the said low substituted degree cellulose acylate film, The thinner one is preferable since a circular nonuniformity can be reduced. Specifically, the thickness of the low-substituted cellulose acylate film used as the first and second optical films is preferably 30 to 130 μm, and more preferably 30 to 50 μm.

  In addition, the second optical film satisfying the above formulas (I) to (IV) may be a film other than the low-substituted cellulose acylate film, and the raw material is not particularly limited. For example, a cellulose acylate film described in JP 2006-227606 A can be used. In addition, a cyclic olefin polymer film, a polyvinyl alcohol film, a polypropylene film, a polycarbonate film, a norbornene film, an acrylic film, a PET film, or the like can also be used. In the present invention, when the second optical film is the low-substituted cellulose acylate film (more preferably, the low-substituted cellulose acylate film having a thickness within the above preferred range), circular unevenness is reduced. It is preferable because it is possible.

  The first and second optical films are preferably arranged as a polarizer inner protective film (a polarizer protective film disposed between the liquid crystal cell and the polarizer). That is, only the pressure-sensitive adhesive layer for bonding exists between the first and second polarizers and the first and second optical films, and the retardation layer that affects optical compensation is disposed. Preferably not.

C-plate:
The liquid crystal display device of the present invention has a C-plate between the liquid crystal cell and the first polarizing plate. The C-plate includes a positive C-plate indicating nz> nx = ny and a negative C-plate indicating nz <nx = ny. “Nx = ny” includes not only the case where nx and ny are exactly equal, but also the case where nx and ny are substantially equal. “Substantially equal” means a range of −10 to 10 nm in terms of front retardation Re. In the present invention, a positive C-plate is preferably used. There is no restriction | limiting in particular about the material of C-plate used for this invention.
The retardation Rth in the thickness direction of the C-plate is preferably −150 to −90 nm. As the C-plate exhibiting such characteristics, an optically anisotropic layer formed by vertically aligning rod-like liquid crystal molecules is useful.

First and second polarizers:
In the present invention, the first and second polarizers are not particularly limited. A commonly used linear polarizing film can be used. The linear polarizing film is manufactured by Optiva Inc. And a polarizing film comprising a binder and iodine or a dichroic dye is preferable. The iodine and the dichroic dye in the linearly polarizing film exhibit polarizing performance by being oriented in the binder. It is preferable that the iodine and the dichroic dye are aligned along the binder molecule, or the dichroic dye is aligned in one direction by self-assembly such as liquid crystal. Currently, commercially available polarizers are made by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing iodine or dichroic dye to penetrate into the binder. Is common.

Outside protective film:
The liquid crystal display device of the present invention preferably has an outer protective film disposed on the outer side of the first and second polarizers. There is no restriction | limiting in particular about an outer side protective film. Cellulose acetate films, cyclic polyolefin polymer films, polyvinyl alcohol films, polypropylene films, polycarbonate films, norbornene films, acrylic films, PET films and the like can be used. A commercially available cellulose acetate film (for example, “TD80UL” manufactured by Fuji Film Co., Ltd.) can also be used.

  It is preferable that at least one of the two outer protective films is made of the low-substituted cellulose acylate film, since circular unevenness is reduced.

IPS mode or FFS mode liquid crystal cell:
There are no particular restrictions on the IPS mode and FFS mode liquid crystal cells. Various conventionally known configurations can be employed.
In the IPS mode, the liquid crystal molecules are switched so that the liquid crystal molecules are always horizontal with respect to the substrate, and the liquid crystal molecules are switched using a horizontal electric field in the horizontal direction with respect to the substrate. The shape of the electrode may be any of linear, mesh, spiral, dot, zigzag and the like. A desirable Δnd is about 300 nm.
The FFS mode is a mode in which liquid crystal molecules are always switched with respect to the substrate in a manner similar to IPS, and the liquid crystal molecules are switched using a horizontal electric field in the horizontal direction with respect to the substrate. In general, the FFS mode has a solid electrode, an interlayer insulating film, and a comb electrode, and the electric field direction is different from IPS. Desirable Δnd is about 350 nm.

  The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios of substances, operations, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples.

1. Preparation example of cellulose acylate film (Preparation of cellulose acylate)
Cellulose acylate was synthesized by the method described in JP-A-10-45804 and 08-231761, and the degree of substitution was measured. Specifically, sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, carboxylic acid serving as a raw material for the acyl substituent was added, and an acylation reaction was performed at 40 ° C. At this time, the kind and substitution degree of the acyl group were adjusted by adjusting the kind and amount of the carboxylic acid. In addition, aging was performed at 40 ° C. after acylation. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.

(Preparation of cellulose acylate solutions “C01” to “C08”)
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acylate solution. The amount of the solvent (methylene chloride and methanol) was appropriately adjusted so that the solid content concentration of each cellulose acylate solution would be the value described in Table 1 below.
-100.0 parts by mass of cellulose acetate having the substitution degree shown in the following table-Additives shown in the following table-Amounts shown in the following table-365.5 parts by mass of methylene chloride-54.6 parts by mass of methanol Shown in the following table As described above, other cellulose acylate solutions for a low substitution degree layer were prepared in the same manner as “C01” except that the acyl group type and substitution degree of cellulose acylate, the amount of additive, and the kind of additive were changed. The solid content concentration of the obtained cellulose acylate solution for the low substitution layer is shown in Table 1 below.

＊１：化合物Ａはテレフタル酸／コハク酸／プロピレンクリコール／エチレングリコール共重合体（共重合比[モル％]＝２７．５／２２．５／２５／２５）を表す。
＊２：化合物Ｂはテレフタル酸／フタル酸／アジピン酸／コハク酸／エチレングリコール共重合体（共重合比[モル％]＝２２．５／２．５／１０／１５／５０）を表す。
＊３：化合物Ｃはテレフタル酸／フタル酸／アジピン酸／エチレングリコール共重合体（共重合比[モル％]＝２２．５／２．５／２５／５０）を表す。
＊４：化合物Ｄはアジピン酸／コハク酸／エチレングリコール共重合体（共重合比[モル
％]＝２５／２５／５０）を表す。
＊５：化合物Ｅはテレフタル酸／フタル酸／コハク酸／プロピレンクリコール／エチレングリコール共重合体（共重合比[モル％]＝２２．５／２．５／２５／３７．５／１２．５）を表す。
なお、化合物Ａ〜Ｅはいずれも非リン酸エステル系の化合物であり、かつ、レターデーション発現剤でもある。化合物Ａ〜Ｄの末端はアセチル基で封止されており、化合物Ｅは末端が封止されていない。
＊６：化合物Ｆは、下記に示す化合物（特許４０５５８６１号公報に記載の（Ａ−１９））を使用した。

* 1: Compound A represents a terephthalic acid / succinic acid / propylene glycol / ethylene glycol copolymer (copolymerization ratio [mol%] = 27.5 / 22.5 / 25/25).
* 2: Compound B represents a terephthalic acid / phthalic acid / adipic acid / succinic acid / ethylene glycol copolymer (copolymerization ratio [mol%] = 22.5 / 2.5 / 10/15/50).
* 3: Compound C represents a terephthalic acid / phthalic acid / adipic acid / ethylene glycol copolymer (copolymerization ratio [mol%] = 22.5 / 2.5 / 25/50).
* 4: Compound D represents an adipic acid / succinic acid / ethylene glycol copolymer (copolymerization ratio [mol%] = 25/25/50).
* 5: Compound E is terephthalic acid / phthalic acid / succinic acid / propylene glycol / ethylene glycol copolymer (copolymerization ratio [mol%] = 22.5 / 2.5 / 25 / 37.5 / 12.5 ).
In addition, all of compounds A to E are non-phosphate ester compounds and are also retardation enhancers. The ends of the compounds A to D are sealed with an acetyl group, and the end of the compound E is not sealed.
* 6: As compound F, the following compound ((A-19) described in Japanese Patent No. 40558861) was used.

(Preparation of cellulose acylate solutions “S01” to “S05” for skin layers)
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acylate solution. The amount of the solvent (methylene chloride and methanol) was appropriately adjusted so that the solid content concentration of each cellulose acylate solution had the value described in Table 2 below.
-Cellulose acetate (substitution degree 2.79) 100.0 parts by mass-Additives described in the following table-Amounts described in the following table-Silica fine particles R972 (manufactured by Nippon Aerosil Co., Ltd.) 0.15 parts by mass-Methylene chloride 395.0 masses Parts / methanol 59.0 parts by weight Other cellulose acylates for skin layers in the same manner as “S01” except that the substitution degree of cellulose acylate, the amount of additive and the type of additive were changed as shown in Table 2 below. A rate solution was prepared. The solid content concentration of the obtained cellulose acylate solution for skin layer is shown in Table 2 below.

(Production of cellulose acylate film)
Production of films 1-12:
Regarding the films 1 to 11, the cellulose acylate solution for the high substitution degree layer is the film thickness described in the following table so that the cellulose acylate solution for the low substitution degree layer becomes a core layer having the film thickness described in the following table. The skin A layer and the skin B layer were cast respectively.
The obtained web (film) was peeled from the band, dried and wound up. At this time, the residual solvent amount with respect to the mass of the entire film was 0 to 0.5%. Subsequently, the film was fed out and TD stretched by a tenter under the conditions shown in the following table. Further, MD stretching was performed by making the peripheral speed of the nip roll on the outlet side faster than the peripheral speed of the nip roll on the inlet side while heating between the two nip rolls. At this time, the speed of the two nip rolls was adjusted so that the draw ratio shown in the following table was obtained.
For the film 12, only the cellulose acylate solution for the low substitution layer was subjected to TD stretching and MD stretching so as to satisfy the conditions shown in the following table.
The residual solvent amount was determined according to the following formula.
Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is a mass of the web at an arbitrary time point, and N is a mass when the web of which M is measured is dried at 120 ° C. for 2 hours.

Production of film 13:
Using the cellulose acylate solution of film 1, the cast film was peeled off from the band, and TD stretching with a tenter was performed in a state where the residual solvent content at the inlet of the tenter was 25%. At this time, the TD stretching conditions were a temperature of 160 ° C. and a stretching ratio of 0%. Subsequently, MD stretching was performed with a difference in peripheral speed between two pairs of nip rolls with a residual solvent content of 10%. At this time, MD stretching conditions were a peripheral speed difference at a stretching ratio of 50% at a temperature of 170 ° C., an interval (L) between nip rolls of 2000 mm, and a film width (W) before stretching of 950 mm. After stretching, the film was dried and wound up. The obtained film 13 exhibited optical properties equivalent to those of the film 1 as shown in the following table.
Thus, a low-substituted cellulose acylate film satisfying the formulas (V) and (VI) could be produced even in-line (free-end uniaxial stretching).

The optical characteristics of the produced films 1 to 13 are summarized in the following table.

2. Production Example of Polarizing Plate One of the cellulose acylate films 1 to 12 produced above is placed on one side, and a commercially available cellulose acetate film “TD80UL” (manufactured by Fuji Film) is placed on the opposite side, with a linear polarizing film sandwiched between them. The polarizing plate was produced by bonding to both sides. At this time, the absorption axis of the linear polarizing film and the slow axis of the films 1 to 12 were orthogonal to each other, and TD80UL had the absorption axis and the slow axis of the linear polarizing film parallel to each other. Moreover, regarding the film 5, the polarizing plate was produced by sandwiching the linearly polarizing film on both sides. In addition, the alkali saponification process was given to the bonding surface of each film. The linearly polarizing film is a 20 μm thick linearly polarizing film produced by continuously stretching a polyvinyl alcohol film having a thickness of 80 μm in an iodine aqueous solution 5 times and drying, and as an adhesive, A 3% aqueous solution of polyvinyl alcohol (PVA-117H manufactured by Kuraray) was used.
Moreover, about some polarizing plates produced as mentioned above, the rod-shaped liquid crystal composition was apply | coated to the surface of a protective film, and what formed the layer formed by carrying out the vertical alignment of a rod-shaped liquid crystal was bonded. The layer exhibited optical properties as a C-plate, with Re = 0 nm and Rth = −120 nm.

3. Examples of production of liquid crystal display device and evaluation results (1) IPS mode liquid crystal display device The polarizing plates on both sides are peeled off from a liquid crystal panel manufactured by Toshiba (37Z3500), and the polarizing plates produced above are arranged so that the polarizing plates are crossed Nicols. And pasted. At this time, bonding was performed with the absorption axis of the polarizing plate on the backlight side parallel to the slow axis of the liquid crystal cell. In addition, since the polarizing plate included in the product had the optical characteristics of the A plate, in the following table, this polarizing plate is used as it is in the comparative example having the A plate.
IPS mode liquid crystal display devices having the configurations shown in the following table were respectively produced.

(2) Production of FFS mode liquid crystal display device The polarizing plates on both sides were peeled off from a liquid crystal panel manufactured by Toshiba (37H3000), and produced in the same manner as the IPS mode liquid crystal display device. At this time, the polarizing plate on the viewing side was bonded in parallel with the slow axis of the liquid crystal cell. Moreover, in the following table | surface, in the comparative example which has A plate, the polarizing plate which has A plate contained in the liquid crystal panel made from Toshiba (37Z3500) was peeled off, and it bonded using the adhesive.
Each FFS mode liquid crystal display device having the configuration shown in the following table was produced.
(3) Evaluation of liquid crystal display devices

(Color shift evaluation)
About each of the produced IPS mode and FFS mode liquid crystal display devices, a backlight is installed, and using a measuring device (EZ-Contrast XL88, manufactured by ELDIM), from a polar angle of 60 degrees with respect to the front in black display. Observe and each of azimuth angle 0-90 degrees (first quadrant), 90-180 degrees (second quadrant), 180-270 degrees (third quadrant), 270-360 degrees (fourth quadrant) An index obtained by averaging the maximum ΔE of the elephant is defined as color shift and evaluated according to the following criteria.
○: Almost no color shift.
Δ: Color shift was observed, but no problem in practical use.
X: Color shift is observed, which is problematic in practical use.

(Viewing angle CR evaluation)
For each of the produced IPS mode and FFS mode liquid crystal display devices, a backlight is installed as shown in FIG. 1 and FIG. 2, and each of them is measured in a dark room using a measuring machine (EZ-Contrast XL88, manufactured by ELDIM). The luminance during display and white display was measured, and the average value of the minimum values of each quadrant in the direction of the polar angle of 60 degrees was defined as the viewing angle contrast (CR) and calculated.
The measurement results were evaluated according to the following criteria.
○: CR> 100, and there is no practical problem.
X: CR <100, which is problematic in practical use.

(Evaluation of circular unevenness)
The panel was observed from the front and diagonal directions, and it was visually evaluated whether circular unevenness occurred.
Evaluation was made according to the following criteria.
A: There is no unevenness (no problem in practical use).
○: Unevenness was observed, but there was no practical problem.
Δ: Unevenness and practical problems.

DESCRIPTION OF SYMBOLS 11, 12 Polarizer 13 IPS mode liquid crystal cell 13'FFS mode liquid crystal cell 14 1st optical film 15 C-plate 16 2nd optical film 17, 18 Outer protective film

Claims (26)

The liquid crystal cell has a C-plate, a first optical film, and a first polarizer on the viewing side, and at least a second optical film and a second polarizer on the backlight side of the liquid crystal cell. Have
The first and second polarizers are arranged with their polarization axes orthogonal to each other,
The first optical film is composed of a low substitution layer containing, as a main component, cellulose acylate satisfying the following formula (1), or the following formula on at least one surface of the low substitution layer and the low substitution layer. Having a high substitution degree layer containing cellulose acylate satisfying (2) as a main component,
An IPS mode liquid crystal display device in which the second optical film satisfies the following formulas (I) to (IV).
(1) 2.0 <Z1 <2.7
(In formula (1), Z1 represents the total acyl substitution degree of the cellulose acylate of the low substitution degree layer.)
(2) 2.7 <Z2
(In formula (2), Z2 represents the total acyl substitution degree of the cellulose acylate of the high substitution degree layer.)
(I) 0 nm ≦ Re (550) ≦ 10 nm
(II) | Rth (550) | ≦ 25 nm
(III) | Re (630) -Re (450) | ≦ 10 nm
(IV) | Rth (630) −Rth (450) | ≦ 35 nm
(In the above formulas (I) to (IV), Re (λ) represents the front retardation value (nm) at the wavelength λnm, and Rth (λ) represents the retardation value in the film thickness direction at the wavelength λnm (nm). Represents.) The IPS mode liquid crystal display device according to claim 1, wherein the first optical film satisfies the following formulas (V) and (VI).
(V) 70 nm ≦ Re (550) ≦ 140 nm
(VI) 40 nm ≦ Rth (550) ≦ 110 nm The second optical film is composed of a low substitution layer containing, as a main component, cellulose acylate satisfying the formula (1), or the formula on at least one surface of the low substitution layer and the low substitution layer. The IPS mode liquid crystal display device according to claim 1, further comprising a high substitution degree layer containing cellulose acylate satisfying (2) as a main component. The IPS mode liquid crystal display device according to claim 1, wherein the second optical film has a thickness of 30 to 130 μm. The IPS mode liquid crystal display device according to claim 1, wherein the low substitution degree layer contains a non-phosphate ester-based compound. The high substitution layer contains a non-phosphate ester compound as an additive, and the ratio (part by mass) of the additive to the cellulose acylate contained in the high substitution layer is contained in the low substitution layer The IPS mode liquid crystal display device according to claim 1, wherein the IPS mode liquid crystal display device is less than a ratio (parts by mass) of the additive to cellulose acylate. The IPS mode liquid crystal display device according to claim 5, wherein the non-phosphate ester compound is a polyester compound containing an aromatic ring. The IPS mode liquid crystal display device according to any one of claims 1 to 7, wherein the cellulose acylate contained in the low substitution degree layer satisfies the following formulas (3) to (5).
Formula (3) 1.0 <X1 <2.7
Formula (4) 0 <= Y1 <1.5
Formula (5) X1 + Y1 = Z1
(In the formulas (3), (4) and (5), X1 represents the degree of substitution of the acetyl group of the cellulose acylate of the low-substituted layer, and Y1 has 3 or more carbon atoms of the cellulose acylate of the low-substituted layer. The total substitution degree of acyl groups is represented, and Z1 represents the total acyl substitution degree of cellulose acylate in the low substitution layer.) The IPS mode liquid crystal display device according to claim 1, wherein the cellulose acylate used in the high substitution degree layer satisfies the following formulas (6) to (8).
Formula (6) 1.2 <X2 <3.0
Formula (7) 0 <= Y2 <1.5
Formula (8) X2 + Y2 = Z2
(In the formulas (6), (7) and (8), X2 represents the substitution degree of the acetyl group of the cellulose acylate of the high substitution degree layer, and Y2 has 3 or more carbon atoms of the cellulose acylate of the high substitution degree layer. The total substitution degree of acyl groups is represented, and Z2 represents the total acyl substitution degree of cellulose acylate in the high substitution degree layer. The high substitution layer (however, the composition of each high substitution layer may be independent and may be the same) on both sides of the low substitution layer. 2. The IPS mode liquid crystal display device according to item 1. The IPS mode liquid crystal display device according to any one of claims 1 to 10, wherein the acyl group of the cellulose acylate contained in the low substitution layer and / or the high substitution layer has 2 to 4 carbon atoms. . The IPS mode liquid crystal display device according to claim 1, wherein the cellulose acylate contained in the low substitution layer and / or the high substitution layer is cellulose acetate. The average film thickness of the low substitution degree layer is 30 to 100 µm, and the average film thickness of at least one of the high substitution degree layers is 0.2% or more and less than 25% of the average thickness of the low substitution degree layer. The IPS mode liquid crystal display device according to any one of 1 to 12. A C-plate, a first optical film, and a first polarizer are provided on the backlight side of the liquid crystal cell, and at least a second optical film and a second polarizer are provided on the viewing side of the liquid crystal cell. Have
The first and second polarizers are arranged with their polarization axes orthogonal to each other,
The first optical film is composed of a low substitution layer containing, as a main component, cellulose acylate satisfying the following formula (1), or the following formula on at least one surface of the low substitution layer and the low substitution layer. Having a high substitution degree layer containing cellulose acylate satisfying (2) as a main component,
An FFS mode liquid crystal display device in which the second optical film satisfies the following formulas (I) to (IV).
(1) 2.0 <Z1 <2.7
(In formula (1), Z1 represents the total acyl substitution degree of the cellulose acylate of the low substitution degree layer.)
(2) 2.7 <Z2
(In formula (2), Z2 represents the total acyl substitution degree of the cellulose acylate of the high substitution degree layer.)
(I) 0 nm ≦ Re (550) ≦ 10 nm
(II) | Rth (550) | ≦ 25 nm
(III) | Re (630) -Re (450) | ≦ 10 nm
(IV) | Rth (630) −Rth (450) | ≦ 35 nm
(In the above formulas (I) to (IV), Re (λ) represents the front retardation value (nm) at the wavelength λnm, and Rth (λ) represents the retardation value in the film thickness direction at the wavelength λnm (nm). Represents.) The FFS mode liquid crystal display device according to claim 14, wherein the first optical film satisfies the following formulas (V) and (VI).
(V) 70 nm ≦ Re (550) ≦ 140 nm
(VI) 40 nm ≦ Rth (550) ≦ 110 nm The second optical film is composed of a low substitution layer containing, as a main component, cellulose acylate satisfying the formula (1), or the formula on at least one surface of the low substitution layer and the low substitution layer. The FFS mode liquid crystal display device according to claim 14 or 15, further comprising a high substitution degree layer containing cellulose acylate satisfying (2) as a main component. 17. The FFS mode liquid crystal display device according to claim 14, wherein the second optical film has a thickness of 30 to 130 μm. The FFS mode liquid crystal display device according to any one of claims 14 to 17, wherein the low substitution degree layer contains a non-phosphate ester-based compound. The high substitution layer contains a non-phosphate ester compound as an additive, and the ratio (part by mass) of the additive to the cellulose acylate contained in the high substitution layer is contained in the low substitution layer 19. The FFS mode liquid crystal display device according to claim 14, wherein the FFS mode liquid crystal display device is less than a ratio (part by mass) of the additive to cellulose acylate. 20. The FFS mode liquid crystal display device according to claim 18, wherein the non-phosphate ester compound is a polyester compound containing an aromatic ring. The FFS mode liquid crystal display device according to any one of claims 14 to 20, wherein the cellulose acylate contained in the low substitution degree layer satisfies the following formulas (3) to (5).
Formula (3) 1.0 <X1 <2.7
Formula (4) 0 <= Y1 <1.5
Formula (5) X1 + Y1 = Z1
(In the formulas (3), (4) and (5), X1 represents the degree of substitution of the acetyl group of the cellulose acylate of the low-substituted layer, and Y1 has 3 or more carbon atoms of the cellulose acylate of the low-substituted layer. The total substitution degree of acyl groups is represented, and Z1 represents the total acyl substitution degree of cellulose acylate in the low substitution layer.) The FFS mode liquid crystal display device according to any one of claims 14 to 21, wherein the cellulose acylate used in the high substitution degree layer satisfies the following formulas (6) to (8).
Formula (6) 1.2 <X2 <3.0
Formula (7) 0 <= Y2 <1.5
Formula (8) X2 + Y2 = Z2
(In the formulas (6), (7) and (8), X2 represents the substitution degree of the acetyl group of the cellulose acylate of the high substitution degree layer, and Y2 has 3 or more carbon atoms of the cellulose acylate of the high substitution degree layer. The total substitution degree of acyl groups is represented, and Z2 represents the total acyl substitution degree of cellulose acylate in the high substitution degree layer. The high substitution layer (however, the composition of each high substitution layer may be independent and may be the same) on both sides of the low substitution layer. 2. An FFS mode liquid crystal display device according to item 1. 24. The FFS mode liquid crystal display device according to any one of claims 14 to 23, wherein the acyl group of the cellulose acylate contained in the low substitution layer and / or the high substitution layer has 2 to 4 carbon atoms. . The FFS mode liquid crystal display device according to any one of claims 14 to 24, wherein the cellulose acylate contained in the low substitution layer and / or the high substitution layer is cellulose acetate. The average film thickness of the low substitution degree layer is 30 to 100 µm, and the average film thickness of at least one of the high substitution degree layers is 0.2% or more and less than 25% of the average thickness of the low substitution degree layer. The FFS mode liquid crystal display device according to any one of 14 to 25.

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