JP5062261B2 - Vertical alignment type liquid crystal panel, vertical alignment type liquid crystal display device - Google Patents

Description

  The present invention relates to a vertical alignment type liquid crystal panel and a vertical alignment type liquid crystal display device which are excellent in viewing angle characteristics and have reduced tint change when observed from an oblique direction.

  As a liquid crystal display device, a twisted nematic type (hereinafter referred to as TN mode) liquid crystal display device is widely known. Further, in recent years, vertical alignment type (also referred to as VA, MVA, PVA, hereinafter abbreviated as VA mode) liquid crystal in which liquid crystal molecules are aligned in a direction parallel to the homeotropic direction (the thickness direction of the liquid crystal cell) when no voltage is applied. A liquid crystal display device using this is also known. The VA liquid crystal display device has a higher response speed than the TN method, has a high contrast and a wide viewing angle, and has little change in color when the viewing angle is changed, so that it can be used for TV applications. Many.

  However, the viewing angle characteristics of a conventional VA liquid crystal display device cannot be said to be sufficient, and particularly for TV applications, a liquid crystal display device capable of obtaining good contrast from a wider viewing angle is desired.

  On the other hand, as a liquid crystal display device having a wide viewing angle, a liquid crystal display device called an in-plane switching method represented by the IPS method is known. However, in-plane switching type liquid crystal display devices tend to have lower contrast when viewed from the front as compared to the VA method, so the viewing angle characteristics are improved with the VA type liquid crystal display device having excellent contrast from the front. It was hoped to do.

  As a technique for improving viewing angle characteristics in a VA liquid crystal display device, for example, Patent Document 1 discloses that a viewing angle in a VA liquid crystal display device is set by using a negative uniaxial film as a birefringence compensation medium. An expanding technique is described. As a negative uniaxial film, Patent Document 2 also discloses a negative uniaxial film made of cholesteric liquid crystal. However, these methods also have a narrower viewing angle than the in-plane switching method, and further improvements have been demanded.

In Patent Document 3, in a VA liquid crystal display device, an in-plane retardation of a light beam having a wavelength of 550 nm is 30 nm to 150 nm, and a thickness direction retardation is −50 nm to −500 nm (according to the definition of the present invention, 50 nm to A technique for improving the contrast from the front and the tilt angle using a biaxial optical compensation film of about 500 nm) is described. As such an optical compensation film, for example, Patent Document 4 discloses a method for producing a retardation film by coating and stretching a non-liquid crystalline birefringence-expressing compound on a triacetyl cellulose film, and Patent Document 5 describes. Has proposed a retardation film using a cycloolefin-based material. All of these have been required to be improved because there is a problem with the color when viewed from an oblique direction, particularly the color when displaying black. Patent Document 6 describes optical compensation in which an in-plane retardation in a light beam having a wavelength of 590 nm is in a range of 15 nm to 70 nm and a retardation in a thickness direction is in a range of 80 nm to 350 nm. A technique for disposing a film between a liquid crystal cell and a polarizing plate is disclosed. Further, Patent Document 7 proposes a configuration using a circularly polarizing plate in the VA method, but it still does not reach a sufficient viewing angle characteristic and needs to be improved.
U.S. Pat. No. 4,889,412 JP 2002-533784 A JP-T-2006-515686 Japanese Patent No. 3735361 Japanese Patent Laid-Open No. 2005-43740 JP 2004-151640 A JP 2006-154436 A

  Accordingly, an object of the present invention is to provide a vertical alignment type liquid crystal panel and a vertical alignment type liquid crystal which are excellent in viewing angle characteristics while using a vertical alignment type liquid crystal excellent in front contrast and reduced in color change when observed from an oblique direction. It is to provide a display device.

  The above object of the present invention is achieved by the following configurations.

1. A vertical alignment type liquid crystal panel having a first polarizer, a second polarizer, and a vertical alignment type liquid crystal cell provided between the first polarizer and the second polarizer,
The vertical alignment type liquid crystal panel includes a retardation region A provided between the first polarizer and the vertical alignment type liquid crystal cell, and between the second polarizer and the vertical alignment type liquid crystal cell. Having a phase difference region B provided;
In-plane direction retardation R0 _{A (590)} and thickness direction retardation Rt _{A (590)} for the light of wavelength 590 nm in the retardation region A satisfy the following relationships (1) and (2):
The plane retardation for light of wavelength 590nm of the retardation regions B _{R0 B (590)} and the thickness direction retardation _{Rt B (590)} is meet the following relationship (3) and (4),
The phase difference region A further satisfies the following relationships (5) and (6): A vertical alignment type liquid crystal panel.
45 nm ≦ R0 _{A (590)} ≦ 100 nm (1)
−50 nm ≦ Rt _{A (590)} ≦ 20 nm (2)
0 nm ≦ R0 _{B (590)} ≦ 20 nm (3)
200 nm ≦ Rt _{B (590)} ≦ 500 nm (4)
0.7 ≦ D (R40 _A ) 1 ≦ 0.95 (5)
−15 nm ≦ D (R40 _A ) 2 ≦ −3 nm (6)
_{D (R40 A) 1 = R40} A (480) / R40 A (630)
_{D (R40 A) 2 = R40} A (480) -R40 A (630)
However, R40 _{A (480)} is a retardation for a light beam having a wavelength of 480 nm when measured from a direction inclined by 40 ° from the normal direction of the phase difference region A with the fast axis of the phase difference region A as an inclination axis. R40 _{A (630)} represents a wavelength of 630 nm when measured from a direction inclined by 40 ° from the normal direction of the phase difference region A with the fast axis of the phase difference region A as an inclination axis. Retardation (nm) with respect to the light beam.
2. 2. The vertical alignment type liquid crystal panel according to 1 above, wherein the retardation region A satisfies the following relationships (7) and (8).
0.3 ≦ D (Rt _A ) 1 ≦ 0.9 (7)
−70 nm ≦ D (Rt _A ) 2 ≦ −10 nm (8)
D (Rt _A ) 1 = | Rt _{A (630)} / Rt _{A (480)} |
D (Rt _A ) 2: Rt _{A (480)} −Rt _{A (630)}
However, Rt _{A (480)} represents retardation (nm) in the thickness direction with respect to a light beam having a wavelength of 480 nm in the retardation region A, and Rt _{A (630)} represents a thickness direction with respect to a light beam with a wavelength of 630 nm in the retardation region A. Retardation of (nm).

3. 3. The vertical alignment type liquid crystal panel according to 1 or 2 above, wherein the retardation region B satisfies the following relationships (9) and (10).
0.85 ≦ D (Rt _B ) 1 ≦ 1.00 (9)
10 nm ≦ D (Rt _B ) 2 ≦ 100 nm (10)
D (Rt _B ) 1 = Rt _{B (480)} / Rt _{B (630)}
D (Rt _B ) 2 = Rt _{B (630)} −Rt _{B (480)}

However, Rt _{B (480)} represents the retardation (nm) in the thickness direction with respect to the light beam having a wavelength of 480 nm in the retardation region B, and Rt _{B (630)} represents the thickness direction with respect to the light beam with a wavelength of 630 nm in the retardation region B. Retardation of (nm).

4). 4. The vertically aligned liquid crystal according to any one of 1 to 3, wherein the retardation region A has an in-plane slow axis in a direction orthogonal to the absorption axis of the first polarizer. panel.

5. The retardation region A is provided on the viewing side with respect to the vertical alignment type liquid crystal cell, and the retardation region B is provided on the opposite side of the retardation region A with respect to the vertical alignment type liquid crystal cell. 5. The vertical alignment type liquid crystal panel according to any one of 1 to 4 above.

6). The retardation region B is provided on the viewing side with respect to the vertical alignment type liquid crystal cell, and the retardation region A is provided on the opposite side of the retardation region B with respect to the vertical alignment type liquid crystal cell. 5. The vertical alignment type liquid crystal panel according to any one of 1 to 4 above.

7). A vertical alignment type liquid crystal panel having a first polarizer, a second polarizer, and a vertical alignment type liquid crystal cell provided between the first polarizer and the second polarizer,
The vertical alignment type liquid crystal panel includes a retardation region A provided between the first polarizer and the vertical alignment type liquid crystal cell, and between the second polarizer and the vertical alignment type liquid crystal cell. Having a phase difference region B provided;
In-plane direction retardation R0 _{A (590)} and thickness direction retardation Rt _{A (590)} for the light of wavelength 590 nm in the retardation region A satisfy the following relationships (1) and (2):
In-plane retardation R0 _{B (590)} and thickness direction retardation Rt _{B (590)} for the light of wavelength 590 nm in the retardation region B satisfy the following relationships (3) and (4):
The retardation region A includes at least an optically biaxial layer a that satisfies the following relationships (11) to (13), and an optically positive uniaxial layer that satisfies the following relationships (14) and (15): A vertical alignment type liquid crystal panel, wherein the layer b is laminated.
45 nm ≦ R0 _{A (590)} ≦ 100 nm (1)
−50 nm ≦ Rt _{A (590)} ≦ 20 nm (2)
0 nm ≦ R0 _{B (590)} ≦ 20 nm (3)
200 nm ≦ Rt _{B (590)} ≦ 500 nm (4)
nx _{a (590)} > ny _{a (590)} > nz _{a (590)} (11)
45 nm ≦ R0 _{a (590)} ≦ 100 nm (12)
70 nm ≦ Rta ₍₅₉₀₎ ≦ 300 nm (13)
0 nm ≦ R0 _{b (590)} ≦ 5 nm (14)
−300 nm ≦ Rt _{b (590)} ≦ −70 nm (15)
However, nx _{a (590)} represents a refractive index with respect to a light beam having a wavelength of 590 nm in the slow axis direction in the plane of the optically biaxial layer a, and ny _{a (590)} is optically biaxial. Represents a refractive index with respect to a light beam having a wavelength of 590 nm in a direction perpendicular to the slow axis direction of the layer a, and nz _{a (590)} represents a light beam with a wavelength of 590 nm in the thickness direction of the optically biaxial layer a. R0 _{a (590)} represents the in-plane retardation of the optically biaxial layer a with respect to light having a wavelength of 590 nm, and Rta ₍₅₉₀₎ represents the optically biaxial layer a. Represents a retardation in the thickness direction with respect to a light beam having a wavelength of 590 nm, and R0 _{b (590)} represents an in-plane retardation with respect to a light beam with a wavelength of 590 nm of the optically positive uniaxial layer b, and Rt _{b ( 590)} represents retardation in the thickness direction of the optically positive uniaxial layer b with respect to light having a wavelength of 590 nm.

8). The retardation region A includes at least an optically biaxial layer a that satisfies the following relationships (11) to (13), and an optically positive uniaxial layer that satisfies the following relationships (14) and (15): 6. The vertical alignment type liquid crystal panel according to any one of 1 to 5 , wherein a layer b is laminated.
nx _{a (590)} > ny _{a (590)} > nz _{a (590)} (11)
45 nm ≦ R0 _{a (590)} ≦ 100 nm (12)
70 nm ≦ Rta ₍₅₉₀₎ ≦ 300 nm (13)
0 nm ≦ R0 _{b (590)} ≦ 5 nm (14)
−300 nm ≦ Rt _{b (590)} ≦ −70 nm (15)
However, nx _{a (590)} represents a refractive index with respect to a light beam having a wavelength of 590 nm in the slow axis direction in the plane of the optically biaxial layer a, and ny _{a (590)} is optically biaxial. Represents a refractive index with respect to a light beam having a wavelength of 590 nm in a direction perpendicular to the slow axis direction of the layer a, and nz _{a (590)} represents a light beam with a wavelength of 590 nm in the thickness direction of the optically biaxial layer a. R0 _{a (590)} represents the in-plane retardation of the optically biaxial layer a with respect to light having a wavelength of 590 nm, and Rta ₍₅₉₀₎ represents the optically biaxial layer a. Represents a retardation in the thickness direction with respect to a light beam having a wavelength of 590 nm, and R0 _{b (590)} represents an in-plane retardation with respect to a light beam with a wavelength of 590 nm of the optically positive uniaxial layer b, and Rt _{b ( 590)} represents retardation in the thickness direction of the optically positive uniaxial layer b with respect to light having a wavelength of 590 nm.

9. 9. The vertical alignment type liquid crystal panel according to 7 or 8 , wherein the optically biaxial layer a is provided closer to the first polarizer than the optically positive uniaxial layer b. .

10. 10. The vertical alignment type liquid crystal panel according to any one of 7 to 9, wherein the optically biaxial layer a satisfies the following relationship (16).
1.0 ≦ Rt _{a (590)} / R0 _{a (590)} ≦ 6.0 (16)
11. The retardation region A, the 7, characterized in that it comprises a layer c is optically isotropic, between the layer and the optically positive uniaxial layers of said optically biaxial 11. The vertical alignment type liquid crystal panel according to any one of 10 above.

  12 12. The vertical alignment type liquid crystal panel as described in 11 above, wherein the optically isotropic layer c has a thickness in the range of 0.01 μm to 5 μm.

13. 11 or 12, wherein the optically biaxial layer a, the optically positive uniaxial layer b, and the optically isotropic layer c satisfy the following relationship (17): The vertical alignment type liquid crystal panel described.
n _{a (ave)} <nc _(ave) < _{nb (ave)} (17)
Where n _{a (ave)} represents the average refractive index of the optically biaxial layer a, _{nb (ave)} represents the average refractive index of the optically positive uniaxial layer b, and n _{c (ave)} represents the average refractive index of the optically isotropic layer c.

14 Said optically biaxial layer a is a layer having a cellulose ester, the degree of substitution of the cellulose ester satisfies the following (18), any one of the 7-13, characterized in that satisfy (19) A vertical alignment type liquid crystal panel as described in 1.
2.0 ≦ X + Y <3.0 (18)
0.5 <Y <1.6 (19)
45 nm ≦ R0 _{A (590)} ≦ 100 nm (1)
However, X represents an acetyl group substitution degree, and Y represents a substitution degree of a substituent selected from propionyl and butyryl groups.

  15. 15. A vertical alignment type liquid crystal display device comprising the vertical alignment type liquid crystal panel according to any one of 1 to 14 and a backlight on one side of the vertical alignment type liquid crystal panel.

  According to the present invention, a vertical alignment type liquid crystal panel and a vertical alignment type liquid crystal display device which have excellent viewing angle characteristics and reduced color change when observed from an oblique direction while using a vertical alignment type liquid crystal having excellent front contrast. Can be provided.

It is the schematic which shows the structure of the liquid crystal display panel which concerns on this invention. This is a preferred embodiment of the retardation region A according to the present invention.

Explanation of symbols

1 Protective film on viewing side 2 Phase difference area A
3 Phase difference area B
4 BL side protective film 5 1st polarizer 6 2nd polarizer 7 Vertical alignment type liquid crystal cell 8, 9 Glass substrate a Absorption axis of 1st polarizer b Slow axis of retardation region A c Liquid crystal cell Orientation direction 10 Optical biaxial layer a
11 Optically isotropic layer c
12 Optically positive uniaxial layer b

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  As a result of intensive studies on the above problems, the present inventors have separated the component that compensates for the birefringence of the liquid crystal cell and the component that suppresses light leakage due to the change in the angle of the polarizing plate in a vertically aligned liquid crystal panel. The present inventors have found that a vertical alignment type liquid crystal panel can be obtained in which a viewing angle characteristic equivalent to that of the IPS method is obtained in the VA method having excellent front contrast, and the color change when observed from an oblique direction is reduced.

That is, the vertical alignment type liquid crystal panel of the present invention includes the first polarizer, the second polarizer, and a vertical alignment type liquid crystal cell provided between the first polarizer and the second polarizer. A vertically aligned liquid crystal panel having
The vertical alignment type liquid crystal panel includes a retardation region A provided between the first polarizer and the vertical alignment type liquid crystal cell, and between the second polarizer and the vertical alignment type liquid crystal cell. Having a phase difference region B provided;
In-plane direction retardation R0 _{A (590)} and thickness direction retardation Rt _{A (590)} for the light of wavelength 590 nm in the retardation region A satisfy the following relationships (1) and (2):
The plane retardation for light of wavelength 590nm of the retardation regions B _{R0 B (590)} and the thickness direction retardation _{Rt B (590)} is meet the following relationship (3) and (4),
The phase difference region A further satisfies the following relationships (5) and (6) .
45 nm ≦ R0 _{A (590)} ≦ 100 nm (1)
−50 nm ≦ Rt _{A (590)} ≦ 20 nm (2)
0 nm ≦ R0 _{B (590)} ≦ 20 nm (3)
200 nm ≦ Rt _{B (590)} ≦ 500 nm (4)
0.7 ≦ D (R40 _A ) 1 ≦ 0.95 (5)
−15 nm ≦ D (R40 _A ) 2 ≦ −3 nm (6)
_{D (R40 A) 1 = R40} A (480) / R40 A (630)
_{D (R40 A) 2 = R40} A (480) -R40 A (630)
In the present invention, when the term “retardation region provided between a polarizer and a vertical alignment type liquid crystal cell” is used, one or all of a plurality of layers existing between the polarizer and the liquid crystal cell are combined into one. It shall be regarded as a phase difference region.

In the present invention, “in-plane direction retardation R0 _{A (λ) with} respect to a light beam having a wavelength of λ nm in the phase difference region A” is
R0 _{A (λ)} = (nx _{A (λ)} −ny _{A (λ)} ) × d _A
Nx _{A (λ)} represents a refractive index with respect to a light beam having a wavelength λ nm in the in-plane slow axis direction of the retardation region A, and ny _{A (λ)} represents the slow phase of the retardation region A. The refractive index for a light beam having a wavelength λ nm in a direction perpendicular to the axial direction is represented, and d _A represents the thickness (nm) of the retardation region A.

In the present invention, “a retardation Rt _{A (λ) in the} thickness direction with respect to a light beam having a wavelength λ nm in the retardation region A” is:
Rt _{A (λ)} = ((nx _{A (λ)} + ny _{A (λ)} ) / 2-nz _{A (λ)} ) × d _A
Nx _{A (λ)} represents a refractive index with respect to a light beam having a wavelength λ nm in the in-plane slow axis direction of the retardation region A, and ny _{A (λ)} represents the slow phase of the retardation region A. The refractive index with respect to a light beam having a wavelength λ nm in a direction perpendicular to the axial direction is represented, nz _{A (λ)} represents the refractive index with respect to a light beam with a wavelength λ nm in the thickness direction of the retardation region A, and d _A is The thickness (nm) of the retardation region A is represented.

Similarly, the in-plane retardation with respect to the light of wavelength λ nm in the retardation region B is
R0 _{B (λ)} = (nx _{B (λ)} −ny _{B (λ)} ) × d _B
Nx _{B (λ)} represents a refractive index with respect to a light beam having a wavelength λ nm in the in-plane slow axis direction of the retardation region B, and ny _{B (λ)} represents the slow phase of the retardation region B. axially with respect to the refractive index for light of wavelength λnm in a direction perpendicular, d _B represents the thickness (nm) of the retardation region B.

The retardation in the thickness direction is
Rt _{B (λ)} = ((nx _{B (λ)} + ny _{B (λ)} ) / 2-nz _{B (λ)} ) × d _B
Nx _{B (λ)} represents a refractive index with respect to a light beam having a wavelength λ nm in the in-plane slow axis direction of the retardation region B, and ny _{B (λ)} represents the slow phase of the retardation region B. The refractive index for a light beam having a wavelength of λ nm in a direction perpendicular to the axial direction is represented, nz _{B (λ)} represents the refractive index for a light beam having a wavelength of λ nm in the thickness direction of the retardation region B, and d _B is The thickness (nm) of the retardation region B is represented.

  In order to make the optical characteristics of the retardation region A and the retardation region B within the above numerical range, when a thermoplastic resin film was used for the retardation region A and the retardation region B, the film was heated. It is preferable to perform the stretching treatment in a state. Further, in order to make the retardation region A in the above range, it is also preferable to provide a retardation layer having a vertically aligned liquid crystal on the film, and control the thickness of the retardation layer, the temperature during UV curing, the tilt It is preferable to perform angle control and control of the pretilt angle at the support / air interface. In particular, the film thickness control and the curing temperature have a great influence on the retardation control.

  In order to make the retardation in the state where the optically biaxial layer a and the retardation layer are laminated within the above numerical range, R0 of the optically biaxial layer a is set by the above means. This can be achieved by controlling the retardation of the optically biaxial layer a and the retardation layer as viewed from an oblique direction.

_{Furthermore, D (R40 A) 1,} D (R40 A) 2, D (Rt A) 1, D (Rt A) 2, D (Rt B) 1, D (Rt B) retardation region represented by 2 As means for controlling the wavelength dispersion of A or the phase difference region B, it is preferable to appropriately select materials and manufacturing methods of the phase difference region A and the phase difference region B.

  In the present invention, the retardation of the retardation region A and the retardation region B is controlled within a specific range, and the wavelength dispersion of the retardation is further controlled, thereby using a vertically aligned liquid crystal excellent in front contrast. A vertical alignment type liquid crystal panel having excellent viewing angle characteristics and reduced tint change when observed from an oblique direction is obtained.

  Hereinafter, the present invention will be described in detail for each element.

(Measurement of retardation)
As an example, the retardation measurement according to the present invention can be performed in an environment of 23 ° C. and 55% RH using KOBRA 21ADH manufactured by Oji Scientific Instruments. Moreover, when calculating the retardation in the thickness direction, a value obtained by measuring the refractive index of the corresponding wavelength of each layer using an Abbe refractometer is used. Moreover, in the case of a laminated body, the average value of the refractive indexes of each layer is used.

  In the case where the retardation in the thickness direction of the retardation region in the present invention is a negative value, when calculating the retardation, the in-plane phase axis of the retardation region is set as the tilt axis, and the sample is tilted by 40 degrees. Retardation was measured and used for calculation.

(Configuration of LCD panel)
The configuration of the liquid crystal display panel of the present invention will be described with reference to the drawings.

  FIG. 1A is a schematic diagram showing a configuration of a liquid crystal display panel according to the present invention.

  A viewing-side polarizing plate is constituted by the protective film 1 on the viewing side from the viewing side, the first polarizer 5 and the retardation region A2, and the polarizing plate is a vertical alignment type sandwiched between two glass substrates 8 and 9. The liquid crystal cell 7 is bonded. Further, a polarizing plate including the retardation region B3, the second polarizer 6, and the backlight (BL) side protective film 4 is disposed on the surface opposite to the liquid crystal cell.

  1B, the retardation region B3 is provided on the viewing side with respect to the vertical alignment type liquid crystal cell 7, and the retardation region A2 is positioned with respect to the vertical alignment type liquid crystal cell 7. The structure provided in the other side of phase difference area | region B3 may be sufficient.

  The retardation region A2 preferably has an in-plane slow axis b in a direction orthogonal to the absorption axis a of the first polarizer 5, and the in-plane slow axis and the alignment direction c of the liquid crystal cell. Are preferably parallel.

  FIG. 2 is a preferred embodiment of the phase difference region A according to the present invention.

  2A shows an optically biaxial layer a10 that satisfies the relationships (11) to (13) and an optically positive uniaxial layer b12 that satisfies the relationships (14) and (15). It is a schematic diagram of the phase difference area | region A where these are laminated | stacked.

  FIG. 2B shows another configuration in which an optically isotropic layer c11 is laminated between the optically biaxial layer a10 and the optically positive uniaxial layer b12. 3 is a schematic diagram of a phase difference region A. FIG.

  In any case, the optically biaxial layer a10 is preferably provided on the first polarizer 5 side.

(Phase difference area A, Phase difference area B)
The optical influence on the effect of the present invention in the phase difference region A and the phase difference region B, and the formation method thereof will be described in more detail.

The retardation of the phase difference region A and the phase difference region B is 45 nm ≦ R0 _{A (590)} ≦ 100 nm (1) which is the range of the first claim.
−50 nm ≦ Rt _{A (590)} ≦ 20 nm (2)
0 nm ≦ R0 _{B (590)} ≦ 20 nm (3)
200 nm ≦ Rt _{B (590)} ≦ 500 nm (4)
By doing so, light leakage when viewed from an oblique direction in black display of the liquid crystal display device can be minimized, and the contrast viewing angle can be sufficiently widened. If this R0 _A is outside this lower limit, the contrast viewing angle becomes extremely narrow, and if it is outside the upper limit, the contrast viewing angle does not become extremely narrow, but the amount by which the color change changes depending on the observation angle becomes large. In addition, there arises a problem that the yield is greatly reduced.

  This value can be controlled by the stretching conditions and the film thickness of the stretched layer constituting the retardation region A. In the case of a material that increases the refractive index in the stretching direction, the value can be increased by increasing the stretching ratio.

When R0 _B exceeds the upper limit, the amount of color change when the observation direction is changed increases. This value largely depends on the stretching ratio at the time of manufacturing the layer constituting the phase difference region B. For example, it can be within this range by bringing the stretching ratio in the transport direction and the direction orthogonal to the transport direction close to each other during production. Yes, but often depends on the temperature during stretching.

When the range of Rt _{A and} the range of Rt _B are out of this range, the contrast viewing angle becomes extremely narrow. Rt _A can be controlled by controlling the stretching conditions, or in the case of a laminated type, by the film thickness of each layer. Stretching conditions can be controlled within the above range by using free-end uniaxial stretching or a heat-shrinkable film. In the case of a laminated type, for example, when aligning and fixing a vertical alignment type liquid crystal, it depends on the film thickness. Control is active. In addition, there is a method of laminating layers having different refractive index directions with respect to the stretching direction. In this case, both film thickness control and stretching condition control are effective control means. The value of Rt _B can be controlled by stretching conditions or film thickness. Simultaneous or sequential biaxial stretching is a very effective method. Further, although the above method is effective even in the case of lamination, it is preferable that the method can be controlled by controlling the film thickness in view of the time and labor required for production.

Each preferable range is as described above, but (1) is more preferably 50 nm ≦ R0 _{A (590)} ≦ 80 nm, (3) is more preferably 5 nm ≦ R0 _{B (590)} ≦ 15 nm, and (4) is 250 nm. ≦ Rt _{B (590)} ≦ 400 nm is more preferable.

Next, a preferable range of wavelength dispersion of the phase difference region A is
0.7 ≦ D (R40 _A ) 1 ≦ 0.95 (5)
−15 nm ≦ D (R40 _A ) 2 ≦ −3 nm (6)
By doing so, the color change due to the observation angle can be minimized. The color change due to the observation angle becomes large. In particular, when the upper limit is removed, it deteriorates rapidly. This value can be controlled to some extent by the stretching method when it is created by stretching, but the part that depends on the material itself is very large, and for easy control, the film thickness or retardation can be changed to a laminated type. It can be controlled by changing the balance. In particular, when a laminate type of a stretched film and a vertical alignment type liquid crystal is used, it can be controlled by the thickness of the layer in which the stretching condition of the stretched film and the alignment of the vertical alignment type liquid crystal are fixed.

Similarly, the wavelength dispersion of Rt in the phase difference region A is set to 0.3 ≦ D (Rt _A ) 1 ≦ 0.9 (7)
−70 nm ≦ D (Rt _A ) 2 ≦ −10 nm (8)
Thus, the above effect can be further enhanced. These control methods can be performed in the same manner as described above.

Further, the wavelength dispersion of the phase difference region B is set to 0.85 ≦ D (Rt _B ) 1 ≦ 1.00 (9)
10 nm ≦ D (Rt _B ) 2 ≦ 100 nm (10)
By doing so, the effect of the present invention can be further enhanced, and if it is out of the range, the color change becomes large. When this value is created by stretching, it can be controlled slightly depending on the stretching conditions, but the portion depending on the material itself is very large, such as it is difficult to cut 1.00 with a cycloolefin-based material. When cellulose ester is used, it can be controlled by changing the degree of substitution and substituent of cellulose ester. Specifically, the higher the degree of substitution, the smaller the value, and the substituent changes from acetyl to propionyl, butyryl, etc. By making it, the value can be reduced.

As in claim 8, the retardation region A of the present invention includes at least an optically biaxial layer a satisfying the following relationships (11) to (13), and the following (14) and (15): It is preferable that an optically positive uniaxial layer b satisfying the relationship
nx _{a (590)} > ny _{a (590)} > nz _{a (590)} (11)
45 nm ≦ R0 _{a (590)} ≦ 100 nm (12)
70 nm ≦ Rta ₍₅₉₀₎ ≦ 300 nm (13)
0 nm ≦ R0 _{b (590)} ≦ 5 nm (14)
−300 nm ≦ Rt _{b (590)} ≦ −70 nm (15)
Satisfying this further enhances the effect of the present invention. Also when the Rt _a and Rt _b to outside the above, the change in color increases by observation direction, so that red is conspicuous especially during black display. (11) to (13) can be controlled by stretching conditions, and (14) and (15) can be controlled by the film thickness of the layer.

Furthermore, the relationship between the optically retardation _{R0 a} biaxial layer _{a (590), Rt a (} 590),
1.0 ≦ Rta ₍₅₉₀₎ / R0a ₍₅₉₀₎ ≦ 6.0 (16)
It is preferable that This largely depends on the material that forms the optically biaxial layer a. This value can be controlled somewhat depending on the stretching conditions when the optically biaxial layer a is formed by stretching, but it is difficult to cut 1.0 with a cycloolefin-based material. The part that depends on is very large. When cellulose ester is used, it can be controlled by changing the degree of substitution of the cellulose ester and the substituent. Specifically, the higher the degree of substitution, the smaller the value, and the substituent from acetyl to propionyl, butyryl, etc. By changing to, the value can be reduced.

  First, the retardation layer used for the optically positive uniaxial layer b preferable for constituting the retardation region A of the present invention will be described.

(Retardation layer)
In the retardation region A of the present invention, the liquid crystal (or liquid crystal solution) is preferably applied to the optically biaxial layer a which is a base material, dried and heat-treated (also referred to as an alignment treatment) to be vertically aligned. It is preferable to fix the alignment of the liquid crystal by ultraviolet curing or thermal polymerization and to have an optically positive uniaxial layer b made of substantially vertically aligned rod-like liquid crystal, and the layer b includes the following (14), ( It is preferable to satisfy the relationship of 15).
0 nm ≦ R0 _{b (590)} ≦ 5 nm (14)
−300 nm ≦ Rt _{b (590)} ≦ −70 nm (15)
Where R0 _{b (590)} represents the in-plane retardation of the optically positive uniaxial layer b with respect to a light beam having a wavelength of 590 nm, and Rt _{b (590)} represents the optically positive uniaxial layer b of the optically uniaxial layer b. Represents retardation in the thickness direction with respect to light having a wavelength of 590 nm.

  The term “vertical alignment” as used herein refers to black when a retardation layer is sandwiched between crossed Nicol polarizers when evaluated using a polarizing microscope in order to evaluate the optical retardation of the obtained retardation layer. Those that appear and appear white when the retardation layer is tilted between crossed Nicol polarizers are defined as being vertically aligned.

When forming the retardation layer, a vertical alignment film is preferably used as the optically isotropic layer c if necessary. In that case, the average refractive index of each layer is preferably in the following relationship.
n _{a (ave)} <nc _(ave) < _{nb (ave)} (17)
Where n _{a (ave)} represents the average refractive index of the optically biaxial layer a, _{nb (ave)} represents the average refractive index of the optically positive uniaxial layer b, and n _{c (ave)} represents the average refractive index of the optically isotropic layer c. For the average refractive index, the average refractive index at 589 nm is measured using an Abbe refractometer (1T) and a spectral light source. A polarizing unit is used for the eyepiece, and for the optically biaxial layer a, the stretching direction in the film plane, the direction perpendicular to the stretching direction, and the refractive index in the thickness direction are measured, and these values are averaged. Ask. For the retardation layer (optically positive uniaxial layer b) and optically isotropic layer c, the refractive index is measured in one direction, the direction perpendicular thereto, and the thickness direction, and the values are averaged. Can be obtained.

  In addition, the thickness of the optically isotropic layer c is preferably in the range of 0.01 μm to 5 μm.

  There is no particular limitation on the vertical alignment film, but when the liquid crystal material itself is vertically aligned at the air interface and the alignment regulating force extends to the interface opposite to the air interface, the alignment film is not particularly necessary and the configuration is not limited. This is also preferable from the viewpoint of simplification. When using a vertical alignment film, it is also preferable to use an alignment film made of a cross-linked product of a block polymer composition containing a (meth) acrylic block polymer described in JP-A-2005-148473.

  The optically positive uniaxial layer b used in the present invention preferably satisfies the above relationships (14) and (15). In order to make the layer b within the above range, it is preferable to carry out by controlling the thickness of the retardation layer, controlling the temperature during UV curing, controlling the tilt angle, and controlling the pretilt angle at the interface between the support and the air.

  The optically positive uniaxial layer b is formed by curing a liquid crystal material capable of forming a liquid crystal phase at a predetermined temperature with a predetermined liquid crystal regularity. The upper limit of the temperature showing the liquid crystal phase is not particularly limited as long as it is a temperature at which the optically biaxial layer a of the substrate is not damaged. Specifically, a temperature of 120 ° C. or lower is preferable from the viewpoint of easy control of process temperature and maintenance of dimensional accuracy, and a liquid crystal material that becomes a liquid crystal phase at a temperature of 100 ° C. or lower is preferably used. On the other hand, the lower limit of the temperature showing the liquid crystal phase can be said to be a temperature at which the liquid crystal material can maintain the alignment state when used as the retardation region A.

  As the liquid crystal material used for the optically positive uniaxial layer b of the present invention, a polymerizable liquid crystal material is preferably used. The polymerizable liquid crystal material can be used by being polymerized by irradiating with predetermined actinic radiation. Since the alignment state is fixed in the polymerized state, the liquid crystal phase is used when the polymerizable liquid crystal material is used. The lower limit of the temperature is not particularly limited.

  As the polymerizable liquid crystal material, any of a polymerizable liquid crystal monomer, a polymerizable liquid crystal oligomer, and a polymerizable liquid crystal polymer can be used, and they can also be mixed with each other. Since the polymerizable liquid crystal material can fix the alignment state, the alignment of the liquid crystal can be easily performed at a low temperature, and the alignment state is fixed at the time of use. Can be used regardless of the usage conditions.

  Of the above, a polymerizable liquid crystal monomer is particularly preferably used as the polymerizable liquid crystal material. This is because the polymerizable liquid crystal monomer can be aligned at a lower temperature than the polymerizable liquid crystal oligomer and the polymerizable liquid crystal polymer and has high sensitivity at the time of alignment, so that it can be easily aligned.

  Specific examples of the polymerizable liquid crystal monomer include a rod-like liquid crystal compound (I) represented by the following general formula (1) and a rod-like liquid crystal compound (II) represented by the following general formula (2). be able to. As the compound (I), two or more compounds included in the general formula (1) can be mixed and used. Similarly, the compound (II) is included in the general formula (2). Two or more kinds of compounds may be mixed and used. Moreover, 1 type or more and 1 or more types of compounds can also be used for compound (I).

In the general formula (1) representing the compound (I), R ¹ and R ² each represent hydrogen or a methyl group, but R ¹ and R ² are both hydrogen due to the wide temperature range showing the liquid crystal phase. preferable. X may be hydrogen, chlorine, bromine, iodine, an alkyl group having 1 to 4 carbon atoms, a methoxy group, a cyano group, or a nitro group, but is preferably chlorine or a methyl group. Moreover, a and b which show the chain length of the (meth) acryloyloxy group of the molecular chain both ends of compound (I), and the alkylene group which is a spacer with an aromatic ring are respectively arbitrary integers in the range of 2-12. Although it can take, it is preferable that it is the range of 4-10, and it is more preferable that it is the range of 6-9. The compound of the general formula (1) in which a = b = 0 is poor in stability, easily subjected to hydrolysis, and the compound itself has high crystallinity. In addition, the compound of the general formula (1) in which a and b are each 13 or more has a low isotropic transition temperature (TI). For this reason, both of these compounds are not preferred because the temperature range showing liquid crystallinity is narrow.

  Compound (I) can be synthesized by any method. For example, compound (I) wherein X is a methyl group can be obtained by an esterification reaction of 1 equivalent of methylhydroquinone and 2 equivalents of 4- (m- (meth) acryloyloxyalkoxy) benzoic acid. In the esterification reaction, the benzoic acid is usually activated with an acid chloride or a sulfonic anhydride, and this is reacted with methylhydroquinone. In addition, a carboxylic acid unit and methylhydroquinone can be reacted directly using a condensing agent such as DCC (dicyclohexylcarbodiimide). As other methods, esterification reaction of 1 equivalent of methylhydroquinone and 2 equivalents of 4- (m-benzyloxyalkoxy) benzoic acid is first performed, and then the resulting ester is debenzylated by hydrogenation reaction or the like. Then, compound (I) can also be synthesized by a method in which the molecular terminal is acryloylated. When performing esterification reaction of methylhydroquinone and 4- (m-benzyloxyalkoxy) benzoic acid, methylhydroquinone is introduced into diacetate and then reacted with the above benzoic acid in a molten state to obtain an ester directly. It is also possible. The compound (I) in the case where X in the general formula (1) is not a methyl group can also be obtained by performing the same reaction as above using hydroquinone having a corresponding substituent instead of methylhydroquinone.

In the general formula (2) representing the compound (II), R ³ represents hydrogen or a methyl group, but R ³ is preferably hydrogen because of the wide temperature range showing the liquid crystal phase. As for c indicating the chain length of the alkylene group, the compound (II) having this value of 2 to 12 does not exhibit liquid crystallinity. However, considering the compatibility with the compound (I) having liquid crystallinity, c is preferably in the range of 4 to 10, and more preferably in the range of 6 to 9. Compound (II) can also be synthesized by any method. For example, compound (II) can be synthesized by esterification reaction of 1 equivalent of 4-cyanophenol and 1 equivalent of 4- (n- (meth) acryloyloxyalkoxy) benzoic acid. II) can be synthesized. In the esterification reaction, the benzoic acid is generally activated with an acid chloride or a sulfonic acid anhydride and reacted with 4-cyanophenol, as in the case of synthesizing the compound (I). Moreover, you may make the said benzoic acid and 4-cyanophenol react using condensing agents, such as DCC (dicyclohexyl carbodiimide).

  In addition to the above, in the present invention, a polymerizable liquid crystal oligomer, a polymerizable liquid crystal polymer, or the like can be used. As such a polymerizable liquid crystal oligomer and a polymerizable liquid crystal polymer, those conventionally proposed can be appropriately selected and used.

  In the present invention, a photopolymerization initiator may be used as necessary in addition to the polymerizable liquid crystal material. When polymerizing a polymerizable liquid crystal material by electron beam irradiation, a photopolymerization initiator may not be necessary. However, in the case of curing by, for example, ultraviolet (UV) irradiation, which is generally used, photopolymerization is usually performed. This is because the initiator is used for promoting the polymerization.

  Photopolymerization initiators include benzyl (also called bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoyl benzoic acid, methyl benzoyl benzoate, 4-benzoyl-4'-methyldiphenyl sulfide, benzyl methyl ketal, dimethylamino Methylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3′-dimethyl-4-methoxybenzophenone, methylobenzoylformate, 2-methyl-1- (4 -(Methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 1- (4-dodecylphenyl) -2- Droxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2- Examples include methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, or 1-chloro-4-propoxythioxanthone. it can. In general, the addition amount of the photopolymerization initiator is preferably 0.01% to 20%, more preferably 0.1% to 10%, and still more preferably 0.5% to 5%. Can be added to the polymerizable liquid crystal material of the present invention. In addition to the photopolymerization initiator, a sensitizer can be added as long as the object of the present invention is not impaired.

  The thickness of the retardation layer in the present invention is preferably in the range of 0.1 μm to 20 μm, and more preferably in the range of 0.2 to 10 μm. When the retardation layer of the present invention is thicker than the above range, an optical anisotropy more than necessary occurs, and when it is thinner than the above range, a predetermined optical anisotropy may not be obtained. Therefore, the thickness of the retardation layer may be determined according to the required optical anisotropy.

  The polymerizable liquid crystal material is prepared by using a photopolymerization initiator, a sensitizer, and the like as necessary to prepare a composition for forming a retardation layer, coating the substrate, and forming a retardation layer forming layer. Form. Examples of the method for forming the phase difference layer forming layer include a method of previously forming a dry film or the like and laminating the layer as the phase difference layer forming layer on the substrate, or a phase difference layer forming composition. In the present invention, a solvent is added as a retardation layer forming composition, and other components are dissolved in the coating composition. It is preferable to form the phase difference layer forming layer by coating on the alignment film using the composition and removing the solvent. This is simple in terms of process as compared with other methods.

  The solvent is not particularly limited as long as it is a solvent capable of dissolving the above-described polymerizable liquid crystal material and the like and does not deteriorate the properties of the transparent resin film. Specifically, benzene, Hydrocarbons such as toluene, xylene, n-butylbenzene, diethylbenzene, tetralin; ethers such as methoxybenzene, 1,2-dimethoxybenzene, diethylene glycol dimethyl ether; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or 2,4- Ketones such as pentanedione; ethyl acetate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, or γ-butyrolactone Amides solvents such as 2-pyrrolidone, N-methyl-2-pyrrolidone, dimethylformamide or dimethylacetamide; chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, tritrichloroethylene, tetrachloroethylene, chlorobenzene, or orthodichlorobenzene Halogen solvents such as t-butyl alcohol, diacetone alcohol, glycerin, monoacetin, ethylene glycol, triethylene glycol, hexylene glycol, ethylene glycol monomethyl ether, ethyl cellosolve, or butyl cellosolve; phenols, One or more of phenols such as parachlorophenol can be used.

  If only a single type of solvent is used, the solubility of the polymerizable liquid crystal material or the like may be insufficient, or the substrate may be eroded as described above. However, this inconvenience can be avoided by using a mixture of two or more solvents. Of the above-mentioned solvents, preferred as a single solvent are a hydrocarbon solvent and a glycol monoether acetate solvent, and a preferred mixed solvent is a mixed system of ethers or ketones and glycols. It is. The concentration of the solution depends on the solubility of the polymerizable liquid crystal material or the like and the film thickness of the retardation layer to be produced, and thus cannot be defined unconditionally, but is usually preferably 1% to 60%, more preferably 3%. It is adjusted within a range of ˜40%.

  Compounds other than those described above can be added to the composition for forming a retardation layer used in the present invention within a range not impairing the object of the present invention. Examples of compounds that can be added include polyester (meth) acrylate obtained by reacting (meth) acrylic acid with a polyester prepolymer obtained by condensing polyhydric alcohol and monobasic acid or polybasic acid; A polyurethane (meth) acrylate obtained by reacting a compound having two isocyanate groups with each other and then reacting the reaction product with (meth) acrylic acid; bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak Type epoxy resin, polycarboxylic acid polyglycidyl ester, polyol polyglycidyl ether, aliphatic or cycloaliphatic epoxy resin, amine epoxy resin, triphenolmethane type epoxy resin, dihydroxybenzene type epoxy resin and the like (meth) Ak Photopolymerizable compounds such as epoxy (meth) acrylate obtained by reacting le acid, or a photopolymerizable liquid crystal compound, and the like having an acrylic group or methacrylic group. The amount of these compounds added to the retardation layer forming composition used in the present invention is selected within a range that does not impair the object of the present invention, and is generally a retardation layer forming composition used in the present invention. Is preferably 40% or less, more preferably 20% or less. Addition of these compounds improves the curability of the liquid crystal material in the present invention, increases the mechanical strength of the resulting retardation layer, and improves its stability.

  In addition, a surfactant or the like can be added to the retardation layer forming composition containing a solvent in order to facilitate coating. Examples of surfactants that can be added include cationic surfactants such as imidazoline, quaternary ammonium salts, alkylamine oxides and polyamine derivatives; polyoxyethylene-polyoxypropylene condensates, primary or secondary Alcohol ethoxylate, alkylphenol ethoxylate, polyethylene glycol and its ester, sodium lauryl sulfate, ammonium lauryl sulfate, lauryl sulfate amines, alkyl-substituted aromatic sulfonate, alkyl phosphate, aliphatic or aromatic sulfonic acid formalin condensate, etc. Anionic surfactants; amphoteric surfactants such as laurylamidopropylbetaine and laurylaminoacetic acid betaine; nonionic systems such as polyethylene glycol fatty acid esters and polyoxyethylene alkylamine Surfactant: Perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl trimethyl ammonium salt, perfluoroalkyl group / hydrophilic group-containing oligomer, perfluoroalkyl / lipophilic group Fluorosurfactants such as containing oligomer perfluoroalkyl group-containing urethanes. The amount of surfactant added depends on the type of surfactant, the type of liquid crystal material, the type of solvent, and the type of alignment film on which the solution is applied. 10 ppm to 10% is preferable, more preferably 100 ppm to 5%, and still more preferably 0.1 to 1%.

  As a method for coating the composition for forming a retardation layer, a spin coating method, a roll coating method, a printing method, a dip pulling method, a die coating method, a casting method, a bar coating method, a blade coating method, a spray coating method, a gravure coating Method, reverse coating method, extrusion coating method and the like. As a method for removing the solvent after coating the phase difference layer forming composition, for example, air drying, heat removal, or reduced pressure removal, and a combination of these methods are performed. By removing the solvent, a retardation layer forming layer is formed.

  In the step of curing the polymerizable liquid crystal material, energy for curing the polymerizable liquid crystal material is given, and thermal energy may be used, but it is usually performed by irradiation with ionizing radiation capable of causing polymerization. If necessary, a polymerization initiator may be contained in the polymerizable liquid crystal material. The ionizing radiation is not particularly limited as long as it is a radiation capable of polymerizing the polymerizable liquid crystal material, but usually ultraviolet light or visible light is used from the viewpoint of the ease of the apparatus, and the wavelength. Is preferably from 150 to 500 nm, more preferably from 250 to 450 nm, and even more preferably from 300 to 400 nm.

  In the present invention, a method of performing radical polymerization by irradiating ultraviolet rays (UV) as actinic radiation and generating radicals from the polymerization initiator with ultraviolet rays is preferable. This is because the method using UV as the actinic radiation is an established technique, and therefore it is easy to apply to the present invention including the polymerization initiator to be used.

  As a light source for irradiating ultraviolet rays, a low-pressure mercury lamp (sterilization lamp, fluorescent chemical lamp, black light), a high-pressure discharge lamp (high-pressure mercury lamp, metal halide lamp), or a short arc discharge lamp (ultra-high-pressure mercury lamp, xenon) Lamp, mercury xenon lamp) and the like. In particular, the use of metal halide lamps, xenon lamps, high-pressure mercury lamps, etc. is recommended. The irradiation intensity may be appropriately adjusted depending on the composition of the polymerizable liquid crystal material forming the retardation layer and the amount of the photopolymerization initiator.

  The alignment fixing step by irradiation with actinic radiation may be performed at the processing temperature in the step of forming the retardation layer forming layer described above, that is, the temperature condition in which the polymerizable liquid crystal material becomes a liquid crystal phase, or becomes a liquid crystal phase. The temperature may be lower than the temperature. The polymerizable liquid crystal material once in a liquid crystal phase does not suddenly disturb the alignment state even if the temperature is lowered thereafter.

(Base material)
As the base material used for the optically biaxial layer a and the retardation region B in the retardation region A according to the present invention, it is preferable that it is easy to manufacture, optically transparent, etc. It is preferable that it is a transparent thermoplastic resin film.

  The term “transparent” as used in the present invention means that the visible light transmittance is 60% or more, preferably 80% or more, and particularly preferably 90% or more.

  Although it will not specifically limit if it has said property, For example, cellulose ester-type films, such as a cellulose diacetate film, a cellulose triacetate film, a cellulose acetate propionate film, a cellulose acetate butyrate film, a polyester-type film, a polycarbonate Film, polyarylate film, polysulfone (including polyethersulfone) film, polyester film such as polyethylene terephthalate and polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, polyvinylidene chloride film, polyvinyl alcohol film, ethylene vinyl alcohol Film, syndiotactic polystyrene film, polycarbonate film, nor Runen resin film, a polymethylpentene film, a polyether ketone film, polyether ketone imide film, a polyamide film, a fluororesin film, a nylon film, polymethyl methacrylate film, acrylic film or a glass plate or the like. Of these, norbornene resin films and cellulose ester films are preferred.

  The norbornene-based resin film preferably used in the present invention is an amorphous polyolefin film having a norbornene structure. For example, APO manufactured by Mitsui Petrochemical Co., Ltd., ZEONEX manufactured by Nippon Zeon Co., Ltd., manufactured by JSR Co., Ltd. There is ARTON.

  In the optically biaxial layer a and the retardation region B in the retardation region A of the present invention, among these, it is preferable to use a cellulose ester film, and in particular, the optically biaxial layer in the retardation region A. The base material of the layer a is preferably a cellulose ester film mainly containing a specific cellulose ester described later. As the cellulose ester, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate phthalate are preferable, and among these, cellulose acetate and cellulose acetate propionate are preferably used. Examples of commercially available cellulose ester films include Konica Minoltak KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC12UR, KC4FR (manufactured by Konica Minolta Opto Co., Ltd. It can use preferably from viewpoints, such as transparency and adhesiveness. These films may be films produced by melt casting film formation or films produced by solution casting film formation.

<Cellulose ester>
The cellulose ester used in the present invention will be described in detail.

  The cellulose ester used in the present invention is preferably an aliphatic carboxylic acid ester having about 2 to 22 carbon atoms, an aromatic carboxylic acid ester, or a mixed ester of an aliphatic carboxylic acid ester and an aromatic carboxylic acid ester. A lower fatty acid ester is preferred. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. Specifically, it is described in cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate phthalate, etc., JP-A Nos. 10-45804, 8-231761, U.S. Pat. No. 2,319,052, and the like. And mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate. Among the above descriptions, the lower fatty acid ester of cellulose particularly preferably used is cellulose acetate propionate.

The cellulose ester has an acyl group having 2 to 22 carbon atoms as a substituent, the substitution degree of an acetyl group is X, and the substitution degree of a substituent selected from a propionyl group and a butyryl group is Y. It is a cellulose ester which satisfies (18) and (19) simultaneously.
2.0 ≦ X + Y <3.0 (18)
0.5 <Y <1.6 (19)
However, X represents an acetyl group substitution degree, and Y represents a substitution degree of a substituent selected from propionyl and butyryl groups.

  Among them, 2.30 ≦ X + Y ≦ 2.70 is preferable, and 2.40 ≦ X + Y ≦ 2.60 is more preferable. Moreover, 0.50 <Y <0.90 is preferable, and 0.70 ≦ Y ≦ 0.90 is more preferable.

  The portion not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods. Moreover, these acyl group substitution degrees can be measured according to the method prescribed | regulated to ASTM-D817-96.

  As the cellulose ester, a cellulose ester synthesized using cotton linter, wood pulp, kenaf or the like as a raw material can be used alone or in combination. In particular, it is preferable to use a cotton linter (hereinafter sometimes simply referred to as a linter) or a cellulose ester synthesized from wood pulp alone or in combination.

  Moreover, the cellulose ester obtained from these can be mixed and used in arbitrary ratios, respectively. These cellulose esters are prepared by using an organic acid such as acetic acid or an organic solvent such as methylene chloride when sulfuric acid is used as the acylating agent (acetic anhydride, propionic anhydride, butyric anhydride). It can obtain by making it react by a conventional method using a protic catalyst like.

  In the case of acetylcellulose, it is necessary to extend the time for the acetylation reaction in order to increase the acetylation rate. However, if the reaction time is too long, the decomposition proceeds at the same time, and the polymer chain is broken and the acetyl group is decomposed, resulting in undesirable results. Therefore, it is necessary to set the reaction time within a certain range in order to increase the degree of acetylation and suppress decomposition to some extent. It is not appropriate to define the reaction time because the reaction conditions are various and greatly change depending on the reaction apparatus, equipment and other conditions. As the decomposition of the polymer progresses, the molecular weight distribution becomes wider. Therefore, in the case of cellulose ester, the degree of decomposition can be defined by the value of weight average molecular weight (Mw) / number average molecular weight (Mn) that is usually used. That is, in the process of acetylation of cellulose triacetate, the weight average molecular weight is used as one index of the reaction degree for allowing the acetylation reaction to be carried out for a sufficient time for acetylation without being too long and being decomposed too much. The value of (Mw) / number average molecular weight (Mn) can be used.

  The ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose ester used in the present invention is preferably 1.4 to 3.0. In the present invention, the cellulose ester film may contain, as a material, a cellulose ester having a Mw / Mn value of 1.4 to 3.0, but the cellulose ester contained in the film (preferably cellulose triacetate). Or the value of Mw / Mn of cellulose acetate propionate) is more preferably in the range of 1.4 to 3.0. In the process of synthesizing cellulose ester, it is difficult to make it less than 1.4, and cellulose ester having a uniform molecular weight can be obtained by fractionation by gel filtration or the like. However, this method is very expensive. Moreover, it is preferable that it is 3.0 or less because the flatness is easily maintained. In addition, More preferably, it is 1.7-2.2.

  The molecular weight of the cellulose ester used in the present invention is preferably a number average molecular weight (Mn) of 80,000 to 200,000. More preferred are 100,000 to 200,000, particularly preferably 150,000 to 200,000.

  The average molecular weight and molecular weight distribution of the cellulose ester can be measured by a known method using high performance liquid chromatography. Using this, the number average molecular weight and the weight average molecular weight can be calculated, and the ratio (Mw / Mn) can be calculated.

The measurement conditions are as follows.
Solvent: Methylene chloride column: Shodex K806, K805, K803G (used by connecting 3 products manufactured by Showa Denko KK)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000-500 calibration curves with 13 samples were used. It is preferable to obtain 13 samples at approximately equal intervals.

  The method for producing cellulose ester can be obtained by the method described in JP-A-10-45804.

  Cellulose esters are also affected by trace metal components in cellulose esters. These are considered to be related to water used in the production process, but it is preferable that there are few components that can become insoluble nuclei, and metal ions such as iron, calcium, and magnesium contain organic acidic groups. Insoluble matter may be formed by salt formation with a polymer degradation product or the like that may be present, and it is preferable that the amount is small. The iron (Fe) component is preferably 1 ppm or less. About calcium (Ca) component, it is contained in a lot of ground water and river water, etc., and it becomes hard water, and it is unsuitable as drinking water. Coordination compounds with ligands, that is, complexes are easily formed, and scum (insoluble starch, turbidity) derived from many insoluble calcium is formed.

  The calcium (Ca) component is 60 ppm or less, preferably 0 to 30 ppm. The magnesium (Mg) component is preferably in the range of 0 to 70 ppm, particularly preferably 0 to 20 ppm, since too much will cause insoluble matter. Metal components such as iron (Fe) content, calcium (Ca) content, magnesium (Mg) content, etc. are pre-processed by completely digesting cellulose ester with micro digest wet cracking equipment (sulfuric acid decomposition) and alkali melting. After performing, it can obtain | require by performing an analysis using ICP-AES (inductively coupled plasma optical emission spectrometry).

  The refractive index of the optically biaxial layer a using the cellulose ester and the retardation region B is preferably 1.45 to 1.60 at 550 nm. As a method for measuring the refractive index of the film, an Abbe refractometer is used, and measurement is performed based on Japanese Industrial Standard JIS K 7105.

<Additive>
The cellulose ester film used in the present invention may contain additives such as a plasticizer, an ultraviolet absorber, an antioxidant, and a matting agent.

  As described above, the cellulose ester film used in the optically biaxial layer a and the retardation region B of the present invention is melted in order to adjust the retardation so as to satisfy the relationships (1) to (13). It is preferable to produce by film formation, or to stretch or hold the width by solution film formation, or to add an additive having birefringence expression opposite to that of cellulose ester. Especially, in order to adjust retardation within the said range, it is preferable to contain the following acrylic polymer.

<Acrylic polymer>
The cellulose ester film used for the optically biaxial layer a according to the present invention may contain an acrylic polymer having a weight average molecular weight of 500 or more and 30000 or less that exhibits negative orientation birefringence with respect to the stretching direction. Preferably, the acrylic polymer is an acrylic polymer having an aromatic ring in the side chain or an acrylic polymer having a cyclohexyl group in the side chain.

  By controlling the composition of the polymer so that the weight average molecular weight of the polymer is 500 or more and 30000 or less, the compatibility between the cellulose ester and the polymer can be improved.

  In particular, for an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or an acrylic polymer having a cyclohexyl group in the side chain, if the weight average molecular weight is preferably 500 or more and 10,000 or less, in addition to the above, The cellulose ester film has excellent transparency and extremely low moisture permeability, and exhibits excellent performance as a protective film for polarizing plates.

  Since the polymer has a weight average molecular weight of 500 or more and 30000 or less, it is considered to be between the oligomer and the low molecular weight polymer. In order to synthesize such a polymer, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible by a method that does not increase the molecular weight too much.

  Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Although used, the method described in the publication is particularly preferable.

  Although the monomer as a monomer unit which comprises the polymer useful for this invention is mentioned below, it is not limited to this.

  The ethylenically unsaturated monomer unit constituting the polymer obtained by polymerizing the ethylenically unsaturated monomer is as a vinyl ester, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, caproic acid. Vinyl, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl benzoate, vinyl cinnamate Etc .; As acrylate ester, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n -, I-, s-), hexyl acrylate (n I-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic Cyclohexyl acid, acrylic acid (2-ethylhexyl), benzyl acrylate, phenethyl acrylate, acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3- Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, etc .; The above acrylic acid ester is changed to methacrylic acid ester; Examples thereof include acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, itaconic acid and the like. The polymer composed of the above monomers may be a copolymer or a homopolymer, and is preferably a vinyl ester homopolymer, a vinyl ester copolymer, or a copolymer of vinyl ester and acrylic acid or methacrylic acid ester.

  In the present invention, an acrylic polymer (simply referred to as an acrylic polymer) refers to a homopolymer or copolymer of acrylic acid or methacrylic acid alkyl ester having no monomer unit having an aromatic ring or a cyclohexyl group. An acrylic polymer having an aromatic ring in the side chain is an acrylic polymer that always contains an acrylic acid or methacrylic acid ester monomer unit having an aromatic ring.

  The acrylic polymer having a cyclohexyl group in the side chain is an acrylic polymer containing an acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group.

  Examples of the acrylate monomer having no aromatic ring and cyclohexyl group include, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-) , Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid 2-methoxy-ethyl), acrylic acid (2-ethoxyethyl), or the acrylic acid ester may include those obtained by changing the methacrylic acid ester.

  The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomers, but the acrylic acid methyl ester monomer unit preferably has 30% by mass or more, and the methacrylic acid methyl ester monomer unit has 40% by mass or more. preferable. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferred.

  Examples of acrylic acid or methacrylic acid ester monomers having an aromatic ring include phenyl acrylate, phenyl methacrylate, acrylic acid (2 or 4-chlorophenyl), methacrylic acid (2 or 4-chlorophenyl), and acrylic acid (2 or 3 Or 4-ethoxycarbonylphenyl), methacrylic acid (2 or 3 or 4-ethoxycarbonylphenyl), acrylic acid (o or m or p-tolyl), methacrylic acid (o or m or p-tolyl), benzyl acrylate, Benzyl methacrylate, phenethyl acrylate, phenethyl methacrylate, acrylic acid (2-naphthyl) and the like can be mentioned, but benzyl acrylate, benzyl methacrylate, phenethyl acrylate, and phenethyl methacrylate are preferably used. That.

  Among acrylic polymers having an aromatic ring in the side chain, the acrylic acid or methacrylic acid ester monomer unit having an aromatic ring has 20 to 40% by mass, and the acrylic acid or methacrylic acid methyl ester monomer unit is 50 to 80% by mass. % Is preferable. The polymer preferably has 2 to 20% by mass of acrylic acid or methacrylic acid ester monomer units having a hydroxyl group.

  Examples of the acrylate monomer having a cyclohexyl group include cyclohexyl acrylate, cyclohexyl methacrylate, acrylic acid (4-methylcyclohexyl), methacrylic acid (4-methylcyclohexyl), acrylic acid (4-ethylcyclohexyl), and methacrylic acid. (4-ethylcyclohexyl) and the like can be mentioned, but cyclohexyl acrylate and cyclohexyl methacrylate can be preferably used.

  In the acrylic polymer having a cyclohexyl group in the side chain, the acrylic acid or methacrylic acid ester monomer unit having a cyclohexyl group has 20 to 40% by mass and preferably 50 to 80% by mass. Moreover, it is preferable to have 2-20 mass% of acrylic acid or methacrylic acid ester monomer units having a hydroxyl group in the polymer.

  A polymer obtained by polymerizing the above ethylenically unsaturated monomer, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, and an acrylic polymer having a cyclohexyl group in the side chain are all excellent in compatibility with the cellulose resin.

  In the case of an acrylic acid or methacrylic acid ester monomer having these hydroxyl groups, it is not a homopolymer but a structural unit of a copolymer. In this case, it is preferable that the acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group is contained in the acrylic polymer in an amount of 2 to 20% by mass.

  In the present invention, a polymer having a hydroxyl group in the side chain can also be preferably used. The monomer unit having a hydroxyl group is the same as the monomer described above, but acrylic acid or methacrylic acid ester is preferable. For example, acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3 -Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, or these acrylic acids. The thing replaced by methacrylic acid can be mentioned, Preferably, it is 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. The acrylic acid ester or methacrylic acid ester monomer unit having a hydroxyl group in the polymer is preferably contained in the polymer in an amount of 2 to 20% by mass, more preferably 2 to 10% by mass.

  A polymer containing 2 to 20% by mass of the above-mentioned monomer unit having a hydroxyl group, of course, is excellent in compatibility with cellulose ester, retention, dimensional stability, low moisture permeability, and polarized light. It is particularly excellent in adhesiveness with a polarizer as a plate protective film, and has the effect of improving the durability of the polarizing plate.

  The method of having a hydroxyl group at at least one terminal of the main chain of the acrylic polymer is not particularly limited as long as it has a hydroxyl group at the terminal of the main chain, but azobis (2-hydroxyethylbutyrate) A method using a radical polymerization initiator having such a hydroxyl group, a method using a chain transfer agent having a hydroxyl group such as 2-mercaptoethanol, a method using a polymerization terminator having a hydroxyl group, and terminating a hydroxyl group by living ion polymerization. A compound having one thiol group and a secondary hydroxyl group as described in JP-A No. 2000-128911 or 2000-344823, or a polymerization catalyst using the compound and an organometallic compound in combination The method described in the above publication is particularly preferred.

  The polymer produced by the method related to the description in this publication is commercially available as Act Flow Series manufactured by Soken Chemical Co., Ltd., and can be preferably used. In the present invention, the polymer having a hydroxyl group at the terminal and / or the polymer having a hydroxyl group in a side chain has an effect of significantly improving the compatibility and transparency of the polymer.

  Furthermore, a polymer using styrene as an ethylenically unsaturated monomer exhibiting negative orientation birefringence with respect to the stretching direction is preferred in order to develop negative refraction. Examples of styrenes include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, chloromethyl styrene, methoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, and vinyl benzoic acid methyl ester. Although it is mentioned, it is not a thing limited to these.

  It may be copolymerized with the exemplified monomers listed as the unsaturated ethylenic monomer, or may be used by being dissolved in a cellulose ester using two or more kinds of the above polymers for the purpose of controlling birefringence.

  Further, the cellulose ester film used in the present invention is composed of an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in the molecule and an ethylenically unsaturated group having no hydrophilic ring and having a hydrophilic group in the molecule. A weight average molecular weight of 500 or more obtained by polymerizing a polymer X having a weight average molecular weight of 5000 or more and 30000 or less obtained by copolymerization with the monomer Xb, and more preferably an ethylenically unsaturated monomer Ya having no aromatic ring. It is preferable to contain 3000 or less polymer Y.

(Polymer X, Polymer Y)
The polymer X used in the present invention comprises an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in the molecule and an ethylenically unsaturated monomer Xb having no aromatic ring and having a hydrophilic group in the molecule. It is a polymer having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization. Preferably, Xa is an acrylic or methacrylic monomer that does not have an aromatic ring and a hydrophilic group in the molecule, and Xb is an acrylic or methacrylic monomer that does not have an aromatic ring in the molecule and has a hydrophilic group.

  The polymer X used in the present invention is represented by the following general formula (X).

Formula (X)
-(Xa) m- (Xb) n- (Xc) p-
More preferably, it is a polymer represented by the following general formula (X-1).

Formula (X-1)
_{- [CH 2 -C (-R1)} (- CO 2 R2)] m- [CH 2 -C (-R3) (- CO 2 R4-OH) -] n- [Xc] p-
(In the formula, R 1, R ₃ and R 5 represent H or CH _3. R ₂ represents an alkyl group having 1 to 12 carbon atoms and a cycloalkyl group. R 4 and R 6 represent —CH ₂ — and —C ₂ H ₄ —. Or -C ₃ H _6- , Xc represents a monomer unit that can be polymerized to Xa and Xb, m, n and p represent molar composition ratios, where m ≠ 0, n ≠ 0, m + n + p = 100 .)
Although the monomer as a monomer unit which comprises the polymer X used for this invention is mentioned below, it is not limited to this.

  In X, the hydrophilic group means a group having a hydroxyl group or an ethylene oxide chain.

  Examples of the ethylenically unsaturated monomer Xa having no aromatic ring and no hydrophilic group in the molecule include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), and butyl acrylate (n-, i- , S-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n- I-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-ethoxyethyl) ) Or the like, or those obtained by replacing the acrylic ester with a methacrylic ester. Among these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

  The ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a hydrophilic group is preferably acrylic acid or methacrylic acid ester as a monomer unit having a hydroxyl group. For example, acrylic acid (2-hydroxyethyl), List acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or those in which these acrylic acids are replaced by methacrylic acid. Acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl) are preferable.

  Xc is not particularly limited as long as it is an ethylenically unsaturated monomer other than Xa and Xb and copolymerizable, but preferably has no aromatic ring.

  The molar composition ratio m: n of Xa, Xb and Xc is preferably in the range of 99: 1 to 65:35, more preferably in the range of 95: 5 to 75:25. P of Xc is 0-10. Xc may be a plurality of monomer units.

  When the molar composition ratio of Xa is large, compatibility with the cellulose ester is improved, but the retardation value Rt in the film thickness direction is increased. When the molar composition ratio of Xb is large, the compatibility is deteriorated, but the effect of reducing Rt is high. Further, if the molar composition ratio of Xb exceeds the above range, haze tends to occur during film formation, and it is preferable to optimize these and determine the molar composition ratio of Xa and Xb.

  As for the molecular weight of the polymer X, the weight average molecular weight is from 5,000 to 30,000, more preferably from 8,000 to 25,000.

  By setting the weight average molecular weight to 5,000 or more, it is preferable because the cellulose ester film has advantages such as less dimensional change under high temperature and high humidity and less curling as a polarizing plate protective film. When the weight average molecular weight is 30000 or less, the compatibility with the cellulose ester is further improved, and bleeding out under high temperature and high humidity, and further haze generation immediately after film formation is suppressed.

  The weight average molecular weight of the polymer X used in the present invention can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like. The polymerization temperature is usually room temperature to 130 ° C., preferably 50 ° C. to 100 ° C., and this temperature or the polymerization reaction time can be adjusted.

  The measuring method of a weight average molecular weight can be based on the following method.

(Weight average molecular weight measurement method)
The weight average molecular weight Mw was measured using gel permeation chromatography.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000-500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  The polymer Y used in the present invention is a polymer having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring.

  A weight average molecular weight of 500 or more is preferable because the residual monomer of the polymer is reduced. Moreover, it is preferable to set it as 3000 or less in order to maintain retardation value Rt fall performance.

  Ya is preferably an acrylic or methacrylic monomer having no aromatic ring.

  The polymer Y used in the present invention is represented by the following general formula (Y).

General formula (Y)
-(Ya) k- (Yb) q-
More preferably, it is a polymer represented by the following general formula (Y-1).

General formula (Y-1)
_{- [CH 2 -C (-R5)} (- CO 2 R6)] k- [Yb] q-
(Wherein, R5 is, .Yb .R6 representing H or CH ₃ is representing an alkyl group or a cycloalkyl group having 1 to 12 carbon atoms, .k and q represents the Ya and copolymerizable monomer units, This represents the molar composition ratio, where k ≠ 0 and k + q = 100.)
Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Yb may be plural. k + q = 100, q is preferably 0-30.

  The ethylenically unsaturated monomer Ya constituting the polymer Y obtained by polymerizing an ethylenically unsaturated monomer having no aromatic ring is, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i- , N-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (N-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid (2- Ethyl hexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropiyl) ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), methacrylic acid ester, the above acrylic acid ester changed to methacrylic acid ester; unsaturated acid, for example, acrylic acid, methacrylic acid And maleic anhydride, crotonic acid, itaconic acid and the like.

  Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, and vinyl caproate. Vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate and the like are preferred. Yb may be plural.

  In order to synthesize the polymers X and Y, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can make the molecular weights as uniform as possible without increasing the molecular weight. Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. In particular, a polymerization method using a compound having a thiol group and a secondary hydroxyl group in the molecule as a chain transfer agent. It is preferred.

  In this case, the terminal of the polymer X and the polymer Y has a hydroxyl group and a thioether resulting from the polymerization catalyst and the chain transfer agent. By this terminal residue, the compatibility between the polymers X and Y and the cellulose ester can be adjusted.

  The hydroxyl values of the polymers X and Y are preferably 30 to 150 [mg KOH / g].

(Measurement method of hydroxyl value)
This measurement conforms to JIS K 0070 (1992). This hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated. Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 ml of an acetylating reagent (a solution obtained by adding pyridine to 20 ml of acetic anhydride to 400 ml) is accurately added thereto. An air cooling tube is attached to the mouth of the flask and heated in a glycerin bath at 95-100 ° C.

  After 1 hour and 30 minutes, the mixture is cooled, 1 ml of purified water is added from an air condenser, and acetic anhydride is decomposed into acetic acid. Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point. Further, as a blank test, titration is performed without a sample, and an inflection point of the titration curve is obtained.

  The hydroxyl value is calculated by the following formula.

Hydroxyl value = {(BC) × f × 28.05 / X} + D
(Wherein B is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test (ml), and C is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the titration (ml). F is a factor of 0.5 mol / L potassium hydroxide ethanol solution, D is an acid value, and 28.05 is 1/2 of 1 mol amount of potassium hydroxide 56.11)
All of the above-mentioned X polymer polymers Y have excellent compatibility with cellulose esters, excellent productivity without evaporation and volatilization, good retention as a protective film for polarizing plates, low moisture permeability, and excellent dimensional stability. ing.

The content of the polymer X and the polymer Y in the cellulose ester film is preferably in a range satisfying the following formulas (i) and (ii). When the content of the polymer X is Xg (mass% = the mass of the polymer X / the mass of the cellulose ester × 100) and the content of the polymer Y is Yg (mass%),
Formula (i) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (ii) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
A preferable range of the formula (i) is 10 to 25% by mass.

  If the total amount of the polymer X and the polymer Y is 5% by mass or more, the polymer X and the polymer Y act sufficiently to reduce the retardation value Rt. Moreover, if it is 35 mass% or less as a total amount, adhesiveness with polarizer PVA is favorable.

  The polymer X and the polymer Y can be directly added and dissolved as a material constituting the dope liquid described later, or can be added to the dope liquid after being previously dissolved in an organic solvent for dissolving the cellulose ester.

<Other additives>
The cellulose ester film used in the present invention may contain an additive that can be added to a normal cellulose ester film.

  Examples of these additives include plasticizers, ultraviolet absorbers, and fine particles.

  The present invention preferably contains the following plasticizer. Examples of plasticizers include phosphate ester plasticizers, phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, glycolate plasticizers, citrate ester plasticizers, and polyesters. A plasticizer, a polyhydric alcohol ester plasticizer, and the like can be preferably used.

  For phosphate plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenylbiphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. For phthalate ester plasticizers, diethyl phthalate, dimethoxy Ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, butyl benzyl phthalate, diphenyl phthalate, dicyclohexyl phthalate, and other trimellitic acid plasticizers include tributyl trimellitate, triphenyl trimellitate, triethyl For pyromellitic acid ester plasticizers such as trimellitate, tetrabutylpyromellitate, In the case of glycolate plasticizers such as lupyromelitate and tetraethylpyromellitate, triacetin, tributyrin, ethylphthalylethyl glycolate, methylphthalylethylglycolate, butylphthalylbutylglycolate, etc. Citrate, tri-n-butyl citrate, acetyl triethyl citrate, acetyl tri-n-butyl citrate, acetyl tri-n- (2-ethylhexyl) citrate and the like can be preferably used. Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters.

  As the polyester plasticizer, a copolymer of a dibasic acid and a glycol such as an aliphatic dibasic acid, an alicyclic dibasic acid, or an aromatic dibasic acid can be used. The aliphatic dibasic acid is not particularly limited, and adipic acid, sebacic acid, phthalic acid, terephthalic acid, 1,4-cyclohexyl dicarboxylic acid, and the like can be used. As glycol, ethylene glycol, diethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol and the like can be used. These dibasic acids and glycols may be used alone or in combination of two or more.

  The polyhydric alcohol ester plasticizer comprises an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid. Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, 2-n-butyl-2-ethyl-1,3- Propanediol, galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol, and the like can be raised. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable. There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto. As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid. Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid, olein Unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid can be raised. Examples of preferable alicyclic monocarboxylic acid include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof. Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. Aromatic monocarboxylic acids or derivatives thereof can be raised. Particularly preferred is benzoic acid. The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably in the range of 300 to 1500, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose ester.

  The carboxylic acid used in the polyhydric alcohol ester used in the present invention may be one kind or a mixture of two or more kinds. Further, all of the OH groups in the polyhydric alcohol may be esterified with carboxylic acid, or a part of the OH groups may be left as they are.

  These plasticizers are preferably used alone or in combination.

  The amount of these plasticizers used is preferably from 1 to 20% by mass, particularly preferably from 3 to 13% by mass, based on the cellulose ester, in terms of film performance, processability and the like.

  The ultraviolet absorber that can be used in the present invention aims to improve durability by absorbing ultraviolet rays of 400 nm or less, and preferably has a transmittance of 10% or less at a wavelength of 370 nm. More preferably, it is 5% or less, and further preferably 2% or less.

  Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body. It is good also as a polymer type ultraviolet absorber.

  It is preferable to use fine particles for the cellulose ester film used in the present invention. As the fine particles, both inorganic compounds and organic compounds can be used. Examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate And calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle size of the fine particles is preferably 5 to 50 nm, and more preferably 7 to 20 nm. These are preferably contained mainly as secondary aggregates having a particle size of 0.05 to 0.3 μm. The content of these fine particles in the cellulose ester film is preferably 0.05 to 1% by mass, particularly preferably 0.1 to 0.5% by mass. In the case of a cellulose ester film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.). it can.

  Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Examples of the polymer include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the cellulose ester film low.

<Method for producing cellulose ester film>
Next, the manufacturing method of the cellulose ester film used for this invention is demonstrated.

  The cellulose ester film used in the present invention is preferably a cellulose ester film produced by a solution casting method or melt casting.

  The cellulose ester film used in the present invention was produced by dissolving a cellulose ester and an additive in a solvent to prepare a dope, casting a dope onto an endless metal support, and casting the dope. It is performed by a step of drying the dope as a web, a step of peeling from the metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

  The process for preparing the dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The solvent used in the dope may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester.

  The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent.

  Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2.4), cellulose Acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

  Although the good solvent used for this invention is not specifically limited, Organic halogen compounds, such as a methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. are mentioned. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although the poor solvent used for this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water contains in dope. Moreover, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again.

  A general method can be used as a dissolution method of the cellulose ester when preparing the dope described above. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure. It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamaco. Moreover, after mixing a cellulose ester with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.

  The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature with the addition of a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates. A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

  Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

  Next, this cellulose ester solution is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is easily clogged if the absolute filtration accuracy is too small. For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is still more preferable.

  There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable. It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

The bright spot foreign matter was placed in a crossed Nicols state with two polarizing plates, a rolled cellulose ester was placed between them, and light was applied from the side of one polarizing plate, and observed from the side of the other polarizing plate. It is a point (foreign matter) where light from the opposite side sometimes leaks, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less. More preferably, it is 100 pieces / cm < ² > or less, More preferably, it is 50 pieces / m < ² > or less, More preferably, it is 0-10 pieces / cm < ² > or less. Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

  The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable. A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

  A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

  Here, the dope casting will be described.

  The metal support in the casting (casting) step preferably has a mirror-finished surface. As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used. The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. May deteriorate. A preferable support body temperature is 0-40 degreeC, and 5-30 degreeC is still more preferable.

  Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

  In order for the roll cellulose ester to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. %, Particularly preferably 20 to 30% by mass or 70 to 120% by mass.

  In the drying step of the roll cellulose ester, the web is peeled off from the metal support and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less. Particularly preferably, it is 0 to 0.01% by mass or less.

  In the film drying process, generally, a roll drying method (a method in which a plurality of rolls arranged on the upper and lower sides are alternately passed through and dried) or a method of drying while transporting the web by a tenter method is adopted.

  In order to produce the cellulose ester film used in the present invention, the web is stretched in the transport direction (= long direction) where the amount of residual solvent of the web immediately after peeling from the metal support is large, and both ends of the web are further clipped. It is preferable to perform stretching in the width direction by a gripping tenter method.

  The stretching operation may be performed in multiple stages, and biaxial stretching is preferably performed in the casting direction and the width direction. Also, when biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise. In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible.

  A preferable draw ratio is 1.05 to 2 times, preferably 1.1 to 1.5 times. In the case of simultaneous biaxial stretching, the film may be contracted in the longitudinal direction, or may be contracted so as to be 0.8 to 0.99, preferably 0.9 to 0.99. Preferably, the area is preferably 1.12 times to 1.44 times, more preferably 1.15 times to 1.32 times, due to transverse stretching and longitudinal stretching or shrinkage. This can be determined by the draw ratio in the longitudinal direction × the draw ratio in the transverse direction.

  Further, the “stretch direction” in the present invention is usually used to mean a direction in which a stretching stress is directly applied when performing a stretching operation, but in the case of being biaxially stretched in multiple stages, In some cases, it is used in the sense of the one having a higher draw ratio (that is, the direction usually serving as the slow axis).

The retardation of the optically biaxial layer a according to the present invention preferably satisfies the following.
, Nx _{a (590)} > ny _{a (590)} > nz _{a (590)} (11)
45 nm ≦ R0 _{a (590)} ≦ 100 nm (12)
70 nm ≦ Rta ₍₅₉₀₎ ≦ 300 nm (13)
However, nx _{a (590)} represents a refractive index with respect to a light beam having a wavelength of 590 nm in the slow axis direction in the plane of the optically biaxial layer a, and ny _{a (590)} is optically biaxial. Represents a refractive index with respect to a light beam having a wavelength of 590 nm in a direction perpendicular to the slow axis direction of the layer a, and nz _{a (590)} represents a light beam with a wavelength of 590 nm in the thickness direction of the optically biaxial layer a. R0 _{a (590)} represents the in-plane retardation of the optically biaxial layer a with respect to light having a wavelength of 590 nm, and Rta ₍₅₉₀₎ represents the optically biaxial layer a. Represents the retardation in the thickness direction with respect to the light having a wavelength of 590 nm.

It is also a preferable aspect that the optically biaxial layer a satisfies the following relationship (16).
1.0 ≦ Rta ₍₅₉₀₎ / R0a ₍₅₉₀₎ ≦ 6.0 (16)
In addition to appropriately selecting the cellulose ester material, the retardation is adjusted in the range of about 1.1 to 1.5 times in the direction perpendicular to the conveying direction, particularly within the range of the glass transition point of the cellulose ester ± 10 ° C. Or by stretching the film produced by solution casting about 1.1 to 1.7 times in the direction perpendicular to the transport direction with the residual solvent amount remaining about 2 to 100% by mass. , And can fall within the above retardation range.

  For this purpose, it is preferable to precisely control the balance between the stretching temperature and the stretching ratio and to independently control the stretched portion (such as a tenter clip) on both sides of the protective film. This can be achieved by adjusting the stretching temperature and the stretching ratio with respect to the clip position and the stress of the clip.

  The film thickness of the cellulose ester film used in the retardation region A and the retardation region B according to the present invention is preferably in the range of 20 to 200 μm, more preferably 20 to 100 μm, and more preferably 20 to 80 μm. More preferably. In particular, the cellulose ester film used for the retardation region A is preferably 20 to 45 μm in order to obtain the effects of the present invention.

(Polarizer)
The polarizing plate can be produced by a general method. On the at least one surface of the polarizing film prepared by subjecting the back side of the cellulose ester film used in the retardation region A and retardation region B of the present invention to alkali saponification treatment and immersion drawing in an iodine solution, a completely saponified type It is preferable to bond using an aqueous polyvinyl alcohol solution. The film may be used on the other surface, or another polarizing plate protective film may be used. Commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC12UR, KC4FR,
KC8UY-HA, KC8UX-RHA, manufactured by Konica Minolta Opto Co., Ltd.) are also preferably used.

  The polarizing film, which is the main component of the polarizing plate, is an element that transmits only light having a polarization plane in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol film. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed. As the polarizing film, a polyvinyl alcohol aqueous solution is formed and dyed by uniaxial stretching or dyed, or uniaxially stretched after dyeing, and then preferably subjected to a durability treatment with a boron compound.

(Liquid crystal display device)
By incorporating the polarizing plate of the present invention into a display device, the liquid crystal display device of the present invention having various visibility can be manufactured. In particular, it is preferably applied to a VA type (MVA type, PVA type) liquid crystal display device.

  The liquid crystal display device using the polarizing plate of the present invention is particularly effective for use in a multi-domain liquid crystal display device, more preferably a multi-domain liquid crystal display device with a birefringence mode. I can do it.

  Multi-domain is a method of dividing a liquid crystal cell that constitutes one pixel into a plurality of parts, and is also suitable for improving viewing angle dependency and improving symmetry of image display. Various methods have been reported. “Okita, Yamauchi: Liquid Crystal, 6 (3), 303 (2002)”. The liquid crystal display cell is also shown in “Yamada, Yamabara: Liquid Crystal, 7 (2), 184 (2003)”, but is not limited thereto.

  The display quality of the display cell is preferably symmetrical with respect to human observation. Therefore, when the display cell is a liquid crystal display cell, the domains can be multiplied substantially giving priority to the symmetry on the observation side. A known method can be used to divide the domain, and can be determined by taking into account the properties of the known liquid crystal mode by a two-division method, more preferably a four-division method.

  The polarizing plate of the present invention can be effectively used in an MVA (Multi-domain Vertical Alignment) mode typified by a vertical alignment mode and a known PVA (Patterned Vertical Alignment) mode multi-domained by electrode arrangement.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<< Measurement of retardation and wavelength dispersion >>
In the examples, retardation measurement was performed in an environment of 23 ° C. and 55% RH using KOBRA 21ADH manufactured by Oji Scientific Instruments. When calculating the retardation in the thickness direction, a value obtained by measuring the refractive index of the corresponding wavelength of each layer using an Abbe refractometer (4T) was used. When the phase difference region A is a laminate, the average value of the refractive indexes of the respective layers is used. The following formula was used for the calculation of retardation.

  Further, in the sample in which the retardation in the thickness direction of the retardation region A and the retardation region B in the present invention is a negative value, when calculating the retardation, the in-plane fast axis of the laminate is the tilt axis. The retardation when tilted by 40 degrees was measured and used for the calculation.

In the example, “in-plane direction retardation R0 _{A (λ)} for a light beam having a wavelength of λ nm in the phase difference region A” is
R0 _{A (λ)} = (nx _{A (λ)} −ny _{A (λ)} ) × d _A
The following formula was used. nx _{A (λ)} represents a refractive index with respect to a light beam having a wavelength of λ nm in the in-plane slow axis direction of the retardation region A, and ny _{A (λ)} is in the slow axis direction of the retardation region A. The refractive index with respect to a light beam having a wavelength of λ nm in a direction perpendicular to each other is represented, and d _A represents the thickness (nm) of the retardation region A.

Further, in the example, “a retardation Rt _{A (λ) in the} thickness direction with respect to a light beam having a wavelength λ nm in the retardation region A” is:
Rt _{A (λ)} = ((nx _{A (λ)} + ny _{A (λ)} ) / 2-nz _{A (λ)} ) × d _A
The following formula was used. nx _{A (λ)} represents a refractive index with respect to a light beam having a wavelength of λ nm in the in-plane slow axis direction of the retardation region A, and ny _{A (λ)} is in the slow axis direction of the retardation region A. The refractive index with respect to a light beam having a wavelength λ nm in a direction perpendicular to each other, nz _{A (λ)} represents the refractive index with respect to a light beam with a wavelength λ nm in the thickness direction of the retardation region A, and d _A represents the retardation region A. Represents the thickness (nm).

Similarly, retardation in the in-plane and thickness direction of the retardation region B is
R0 _{B (λ)} = (nx _{B (λ)} −ny _{B (λ)} ) × d _B
The following formula was used. nx _{B (λ)} represents a refractive index with respect to a light beam having a wavelength of λ nm in the in-plane slow axis direction of the retardation region B, and ny _{B (λ)} is in the slow axis direction of the retardation region B. It represents a refractive index with respect to light having a wavelength λnm in a direction perpendicular, d _B represents the thickness (nm) of the retardation region B.
Rt _{B (λ)} = ((nx _{B (λ)} + ny _{B (λ)} ) / 2-nz _{B (λ)} ) × d _B
The following formula was used. nx _{B (λ)} represents a refractive index with respect to a light beam having a wavelength of λ nm in the in-plane slow axis direction of the retardation region B, and ny _{B (λ)} is in the slow axis direction of the retardation region B. The refractive index with respect to a light beam having a wavelength λ nm in a direction perpendicular to each other, nz _{B (λ)} represents the refractive index with respect to a light beam with a wavelength λ nm in the thickness direction of the retardation region B, and d _B represents the retardation region B Represents the thickness (nm).

_{D (R40 A) 1, D} (R40 A) 2 which represents the wavelength dispersion property was calculated by the following equation.
_{D (R40 A) 1 = R40} A (480) / R40 A (630)
_{D (R40 A) 2 = R40} A (480) -R40 A (630)
However, R40 _{A (480)} is a retardation for a light beam having a wavelength of 480 nm when measured from a direction inclined by 40 ° from the normal direction of the phase difference region A with the fast axis of the phase difference region A as an inclination axis. R40 _{A (630)} represents a wavelength of 630 nm when measured from a direction inclined by 40 ° from the normal direction of the phase difference region A with the fast axis of the phase difference region A as an inclination axis. Retardation (nm) with respect to the light beam.

Similarly, D (Rt _A ) 1 and D (Rt _A ) 2 were also determined by the following formula.
D (Rt _A ) 1 = | Rt _{A (630)} / Rt _{A (480)} |
D (Rt _A ) 2: Rt _{A (480)} −Rt _{A (630)}
However, Rt _{A (480)} represents retardation (nm) in the thickness direction with respect to a light beam having a wavelength of 480 nm in the retardation region A, and Rt _{A (630)} represents a thickness direction with respect to a light beam with a wavelength of 630 nm in the retardation region A. Retardation of (nm).

Further, D (Rt _B ) 1 and D (Rt _B ) 2 were similarly determined by the following formula.
D (Rt _B ) 1 = Rt _{B (480)} / Rt _{B (630)}
D (Rt _B ) 2 = Rt _{B (630)} −Rt _{B (480)}
However, Rt _{B (480)} represents the retardation (nm) in the thickness direction with respect to the light beam having a wavelength of 480 nm in the retardation region B, and Rt _{B (630)} represents the thickness direction with respect to the light beam with a wavelength of 630 nm in the retardation region B. Retardation of (nm).

Example 1
<Preparation of optically biaxial layer a (biaxial transparent film) 1>
(Synthesis of polymer X1)
Bulk polymerization was performed by the polymerization method described in JP-A No. 2000-344823. That is, the contents were heated to 70 ° C. while introducing the following methyl acrylate and ruthenocene into a flask equipped with a stirrer, a nitrogen gas inlet tube, a thermometer, an inlet, and a reflux condenser.

  Next, half of the following β-mercaptopropionic acid which had been sufficiently purged with nitrogen gas was added to the flask under stirring. After the addition of β-mercaptopropionic acid, the contents in the stirring flask were maintained at 70 ° C. and polymerization was carried out for 2 hours.

  Further, after adding the other half of β-mercaptopropionic acid substituted with nitrogen gas, the temperature of the content being stirred was maintained at 70 ° C., and polymerization was carried out for 4 hours. The temperature of the reaction product was returned to room temperature, and 20 parts by mass of a 5% by mass benzoquinone tetrahydrofuran solution was added to the reaction product to stop the polymerization.

  While gradually heating the polymer to 80 ° C. under reduced pressure with an evaporator, tetrahydrofuran, residual monomer and residual thiol compound were removed to obtain polymer X1. The weight average molecular weight was 1000.

Methyl acrylate 100 parts by mass Ruthenocene (metal catalyst) 0.05 parts by mass β-mercaptopropionic acid 12 parts by mass (additive solution A)
Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass (average diameter of primary particles 12 nm, apparent specific gravity 100 g / liter)
18 parts by mass or more of ethanol was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. The liquid turbidity after dispersion was 100 ppm. 18 parts by mass of methylene chloride was added to the silicon dioxide dispersion while stirring, and the mixture was stirred and mixed with a dissolver for 30 minutes to prepare an additive liquid A as a silicon dioxide dispersion dilution.

(Dope solution A for cellulose ester)
Cellulose ester (total substitution degree 2.48, acetyl group substitution degree 1.66, propionyl substitution degree 0.82) 100 parts by mass Polymer X1 2.5 parts by mass The following sugar ester compound 10 parts by mass Methylene chloride 400 parts by mass Ethanol 62 parts by mass Part Additive Solution A 2 parts by mass

  The above was put into an airtight container, heated, stirred and completely dissolved, and Azumi Filter Paper No. 24, and the dope liquid A was prepared. The dope solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film production line. The dope liquid whose temperature was adjusted to 33 ° C. was fed to a die and uniformly cast from a die slit onto a stainless steel belt. The cast part of the stainless steel belt was heated from the back with hot water of 37 ° C. After casting, the dope film (referred to as a web after casting on a stainless steel belt) on a metal support was dried by applying hot air of 44 ° C., and peeling was performed at a residual solvent amount of 120% by mass. The film was stretched so as to have a stretching ratio of 1.1 times in the casting direction by applying tension at the time of peeling.

  The film thickness was adjusted by adjusting the flow rate of the dope, and the residual dissolution was 120% by mass by controlling the air flow on the stainless steel belt.

  Next, after preheating at 140 ° C. for 2 seconds, a stretching process of 1.28 times in the width direction is performed at 145 ° C., and after the stretching, the width is maintained for 5 seconds, and then the width is maintained by relaxing the tension in the width direction. Was released and dried at 120 ° C. The optically biaxial layer a (biaxial transparent film) 1 having a thickness of 35 μm and a width of 1.5 m produced as described above was wound up.

<Production of optically biaxial layer a (biaxial transparent film) 2>
After the dope flow rate adjustment, the film prepared and peeled as described above was preheated at 155 ° C. for 2 seconds and then stretched at 1.35 times at 160 ° C. After being stretched and held for 5 seconds while maintaining its width, The tension in the width direction was relaxed to release the width retention, and the film was dried at 120 ° C. The optically biaxial layer a (biaxial transparent film) 2 having a thickness of 44 μm and a width of 1.5 m produced as described above was wound up. The average refractive index of this film was 1.488 as measured by the following method.

  Next, on the optically biaxial layer a2, a solid content of 25% by mass is dissolved using PGME (propylene glycol monomethyl ether) / IPA (isopropanol) = 3/7 of UV-7510B (Nippon Synthetic Chemical) as a solvent. An optically biaxial layer a (two layers) having a layer c that is optically isotropic is cured after being applied with a wire bar # 3, dried at 80 ° C. for 30 seconds, cured by irradiation with ultraviolet rays of 120 mJ. Axial transparent film) 2 was obtained.

  When the refractive index of the cured layer c was measured in the same manner, it was confirmed that it was optically isotropic, the refractive index at a wavelength of 589 nm was 1.511, and the dry film thickness was 0.7 μm. It was.

[Refractive index measurement]
Average refractive index measurement of optically biaxial layer a, retardation layer, and optically isotropic layer c: The average refractive index at 589 nm was measured using an Abbe refractometer (1T) and a spectral light source. . A polarizing unit was used for the eyepiece, and for the optically biaxial layer a, the stretching direction in the film plane, the direction perpendicular to the stretching direction, and the refractive index in the thickness direction were measured, and those values were averaged. . For the phase difference layer and the optically isotropic layer c, the refractive indexes in one direction, the direction perpendicular thereto and the thickness direction were measured and the values were averaged.

<Production of optically biaxial layer a (biaxial transparent film) 3>
After the dope flow rate adjustment and the film prepared and peeled in the same manner as described above, the film was preheated at 155 ° C. for 2 seconds and then subjected to a stretching process of 1.41 times at 163 ° C. The tension in the width direction was relaxed to release the width retention, and the film was dried at 120 ° C. The optically biaxial layer a (biaxial transparent film) 3 having a film thickness of 60 μm and a width of 1.5 m produced as described above was wound up.

<Production of optically biaxial layer a (biaxial transparent film) 4>
After the dope flow rate adjustment, the film prepared and peeled in the same manner as described above was subjected to a 1.26 times stretching treatment at 140 ° C. after preheating at 140 ° C. for 2 seconds, and after maintaining the width for 5 seconds after stretching, The tension in the width direction was relaxed to release the width retention, and the film was dried at 120 ° C. The optically biaxial layer a (biaxial transparent film) 4 having a film thickness of 45 μm and a width of 1.5 m produced as described above was wound up.

<Preparation of optically biaxial layer a (biaxial transparent film) 5>
The film prepared and peeled in the same manner as described above after adjusting the dope flow rate was subjected to a 1.67-fold stretching treatment at 170 ° C. after preheating at 140 ° C. for 2 seconds, and after maintaining the width for 5 seconds after stretching, The tension in the width direction was relaxed to release the width retention, and the film was dried at 120 ° C. The optically biaxial layer a (biaxial transparent film) 5 having a film thickness of 65 μm and a width of 1.5 m produced as described above was wound up.

<Production of optically biaxial layer a (biaxial transparent film) 6>
After the dope flow rate adjustment and the film prepared and peeled in the same manner as described above, after preheating at 151 ° C. for 2 seconds, subjecting the film to 1.37 times stretching at 158 ° C., and maintaining the width after stretching for 5 seconds, The tension in the width direction was relaxed to release the width retention, and the film was dried at 120 ° C. The optically biaxial layer a (biaxial transparent film) 6 having a film thickness of 44 μm and a width of 1.5 m produced as described above was wound up. The average refractive index of this film was 1.488 as a result of measurement.

  Next, on the optically biaxial layer a, 3% by mass of Irgacure 500 (manufactured by Ciba Specialty Chemicals) is dissolved in UCECOAT7772 manufactured by Daicel Cytec Co., Ltd., so that the dry film thickness becomes 0.5 μm with wire bar # 3. The film was dried at 100 ° C. for 30 seconds and cured by irradiation with 100 mJ of ultraviolet light to obtain an optically biaxial layer a (biaxial transparent film) 6 having an optically isotropic layer c. The optically isotropic layer c had an average refractive index of 1.485.

<Preparation of optically biaxial layer a (biaxial transparent film) 7>
After adjusting the dope flow rate and producing the peeled film in the same manner as described above, the film was preheated at 145 ° C. for 2 seconds, subjected to a stretching treatment of 1.37 times at 148 ° C., and held for 5 seconds while maintaining its width after stretching. The tension in the width direction was relaxed to release the width retention, and the film was dried at 120 ° C. The optically biaxial layer a (biaxial transparent film) 7 having a film thickness of 44 μm and a width of 1.5 m produced as described above was wound up.

<Production of optically biaxial layer a (biaxial transparent film) 8>
After the dope flow rate adjustment, the film prepared and peeled in the same manner as described above was preheated at 145 ° C. for 2 seconds and then subjected to a stretching process of 1.41 times at 183 ° C. The tension in the width direction was relaxed to release the width retention, and the film was dried at 120 ° C. The optically biaxial layer a (biaxial transparent film) 8 having a film thickness of 65 μm and a width of 1.5 m produced as described above was wound up.

<Production of optically biaxial layer a (biaxial transparent film) 9>
The film prepared and peeled in the same manner as described above after adjusting the dope flow rate was subjected to a 1.37-fold stretching treatment at 143 ° C. after preheating at 140 ° C. for 2 seconds, and after maintaining the width for 5 seconds after stretching, The tension in the width direction was relaxed to release the width retention, and the film was dried at 120 ° C. The optically biaxial layer a (biaxial transparent film) 9 having a thickness of 95 μm and a width of 1.5 m produced as described above was wound up.

<Production of optically biaxial layer a (biaxial transparent film) 10>
After adjusting the dope flow rate, the stretching due to the tension at the time of peeling is 1.01 times, and the film prepared and peeled in the same manner as described above is preheated at 160 ° C. for 2 seconds, and then the speed at the time of stretching is reduced by 6% while reducing the speed at 188 ° C. After stretching, the film was held for 5 seconds while maintaining its width after stretching, then the tension in the width direction was relaxed to release the width and dried at 120 ° C. The optically biaxial layer a (biaxial transparent film) 10 having a thickness of 95 μm and a width of 1.5 m produced as described above was wound up.

<Preparation of optically biaxial layer a (biaxial transparent film) 11>
After adjusting the dope flow rate, the stretching by the tension at the time of peeling is 1.15 times, and the film prepared and peeled in the same manner as the manufacturing method of 1 is 1.36 times at 140 ° C. after preheating at 140 ° C. for 2 seconds. The film was stretched and held for 5 seconds while maintaining its width after stretching, and the tension in the width direction was relaxed to release the width and dried at 120 ° C. The optically biaxial layer a (biaxial transparent film) 11 having a film thickness of 60 μm and a width of 1.5 m produced as described above was wound up.

<Production of optically biaxial layer a (biaxial transparent film) 12>
After adjusting the dope flow rate, the stretching by the tension at the time of peeling is 1.05 times, and the film prepared and peeled in the same manner as in the manufacturing method of 1 is 1.41 times at 170 ° C. after preheating at 150 ° C. for 2 seconds. The film was stretched and held for 5 seconds while maintaining its width after stretching, and the tension in the width direction was relaxed to release the width and dried at 120 ° C. The optically biaxial layer a (biaxial transparent film) 12 having a film thickness of 41 μm and a width of 1.5 m produced as described above was wound up.

<Production of optically biaxial layer a (biaxial transparent film) 13>
After adjusting the dope flow rate, the film prepared and peeled in the same manner as in the production method 1 was preheated at 155 ° C. for 2 seconds, and then subjected to a stretching treatment of 1.40 times at 167 ° C. After holding, the tension in the width direction was relaxed to release the width holding and drying at 120 ° C. The optically biaxial layer a (biaxial transparent film) 13 having a film thickness of 52 μm and a width of 1.5 m produced as described above was wound up.

<Production of optically biaxial layer a (biaxial transparent film) 14>
Cellulose ester (acetyl group substitution degree 1.90, propionyl group substitution degree 0.70, total acyl group substitution degree 2.60) 100 parts by mass Trimethylolpropane tribenzoate 5 parts by mass Ethylphthalylethyl glycolate 5 parts by mass A 10 parts by mass Methylene chloride 430 parts by mass Ethanol 40 parts by mass The above dope composition was put into a sealed container, heated to 70 ° C, and stirred to completely dissolve the cellulose ester to obtain a dope solution. Next, after the dope solution was filtered, the dope solution whose temperature was adjusted to 33 ° C. was fed to the die and uniformly cast with a width of 2.0 m from the die slit onto the stainless steel belt. The cast part of the stainless steel belt was heated from the back with hot water of 37 ° C. After casting, the dope film on the metal support (which is called a web after casting on the stainless steel belt) is dried by applying hot air of 44 ° C., and the residual solvent in the peeling is peeled off at 120 mass%. Then, the film was stretched to a longitudinal stretching ratio of 1.1 times by applying a tension of 1.5%, and then preheated at 105 ° C. for 5 seconds with a residual solvent amount of 24%, gripped at the web edge with a tenter, and wide at 130 ° C. It extended | stretched so that it might become a draw ratio of 1.63 times in the direction. After stretching, the film was held for several seconds while maintaining its width, then the tension in the width direction was relaxed, and the film was dried at 120 ° C. after releasing the width. The optically biaxial layer a (biaxial transparent film) 14 having a film thickness of 52 μm produced as described above was wound up with a width of 2.65 m and a length of 7500 m.

<Preparation of optically biaxial layer a (biaxial transparent film) 15>
(Dope solution B)
Cellulose ester (cellulose triacetate synthesized from linter cotton)
100 parts by mass (Mn = 148000, Mw = 310000, Mw / Mn = 2.1)
Triphenyl phosphate 9.5 parts by mass Ethylphthalyl ethyl glycolate 2.2 parts by mass Methylene chloride 440 parts by mass Ethanol 40 parts by mass Azumi filter paper No. 1 manufactured by Filter Paper Co., Ltd. 24, and the dope liquid B was prepared. The dope solution B was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film production line. (A part of the dope solution B was also used for preparing the following in-line additive solution B.)
(Silicon dioxide dispersion B)
Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass (average diameter of primary particles 12 nm, apparent specific gravity 100 g / liter)
18 parts by mass or more of ethanol was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. The liquid turbidity after dispersion was 100 ppm. 18 parts by mass of methylene chloride was added to the silicon dioxide dispersion while stirring, and the mixture was stirred and mixed for 30 minutes with a dissolver to prepare silicon dioxide dispersion dilution B.

(Preparation of inline additive solution B)
Methylene chloride 100 parts by weight Dope solution B 34 parts by weight Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 5 parts by weight Tinuvin 171 (manufactured by Ciba Specialty Chemicals) 5 parts by weight Tinuvin 326 (manufactured by Ciba Specialty Chemicals) 3 parts by mass or more was put into a closed container, heated, stirred and completely dissolved and filtered.

  To this, 20 parts by mass of silicon dioxide dispersion diluent B was added with stirring, and the mixture was further stirred for 60 minutes, followed by filtration with Advantech Toyo Co., Ltd. polypropylene wind cartridge filter TCW-PPS-1N. Was prepared.

  In-line additive solution B was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the in-line additive solution line. Add 2.5 parts by weight of the filtered inline additive B to 100 parts by weight of the filtered dope liquid B, mix thoroughly with an inline mixer (Toray static in-pipe mixer Hi-Mixer, SWJ), and then belt Using a casting apparatus, casting was uniformly performed on a stainless steel band support at a temperature of 35 ° C. and a width of 2.5 m. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and then peeled off from the stainless steel band support. At the time of peeling, tension was applied in the casting direction, the film was stretched 1.3 times, then preheated at 105 ° C. for 5 seconds with a residual solvent amount of 24%, the web edge was gripped with a tenter, and the width direction was 110 ° C. The film was stretched to a stretching ratio of 1.70 times. After stretching, the film was held for several seconds while maintaining its width, then the tension in the width direction was relaxed, and the film was dried at 120 ° C. after releasing the width. The optically biaxial layer a (biaxial transparent film) 15 having a film thickness of 200 μm produced as described above was wound up.

<Production of optically biaxial layer a (biaxial transparent film) 16>
After peeling off from the stainless steel band support with the same formulation as above, it was dried at a drying temperature of 130 ° C. while being stretched 1.1 times in the width direction with a tenter. The optically biaxial layer a (biaxial transparent film) 16 having a film thickness of 52 μm produced as described above was wound up.

<Production of optically biaxial layer a (biaxial transparent film) 20>
(Dope solution for cellulose ester)
Cellulose ester (total substitution degree 2.58, acetyl group substitution degree 1.48, propionyl substitution degree 1.10) 100 parts by mass Sugar ester compound 10 parts by mass Methylene chloride 400 parts by mass Ethanol 62 parts by mass Additive liquid A 2 parts by mass
The above was put into an airtight container, heated, stirred and completely dissolved, and Azumi Filter Paper No. 24, and the dope liquid A was prepared. The dope solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film production line. The dope liquid whose temperature was adjusted to 33 ° C. was fed to a die and uniformly cast from a die slit onto a stainless steel belt. The cast part of the stainless steel belt was heated from the back with hot water of 37 ° C. After casting, the dope film (referred to as a web after casting on a stainless steel belt) on a metal support was dried by applying hot air of 44 ° C., and peeling was performed at a residual solvent amount of 120% by mass. The film was stretched to a stretching ratio of 1.6 times in the casting direction by applying a tension at the time of peeling, then preheated at 135 ° C. for 5 seconds at a residual solvent amount of 24%, and the web end was gripped with a tenter. It extended | stretched so that it might become a draw ratio of 1.70 times in the width direction at ° C. After stretching, the film was held for several seconds while maintaining its width, then the tension in the width direction was relaxed, and the film was dried at 120 ° C. after releasing the width. The optically biaxial layer a (biaxial transparent film) 20 having a film thickness of 148 μm produced as described above was wound up.

<21 Production of Optically Biaxial Layer a (Biaxial Transparent Film)>
Cellulose ester (total substitution degree 2.46, acetyl group substitution degree 1.46, propionyl substitution degree 1.10) was used, and the tension during peeling was controlled and stretched 1.50 times in the casting direction, 130 ° C. After preheating, optically similar to the biaxial layer a (biaxial transparent film) 20 except that the film was stretched 1.46 times in the width direction at 148 ° C. and adjusted to a film thickness of 100 μm. Thus, a biaxial layer a (biaxial transparent film) 21 was produced.

<Production of optically biaxial layer a (biaxial transparent film) 22>
Cellulose ester (total substitution degree 2.41, acetyl group substitution degree 1.43, propionyl substitution degree 0.98) was used, and the tension during peeling was controlled and stretched 1.60 times in the casting direction, 135 ° C. After preheating, it is optically similar to the biaxial layer a (biaxial transparent film) 20 except that the film is stretched 1.48 times in the width direction at 160 ° C. and adjusted to a film thickness of 125 μm. Thus, a biaxial layer a (biaxial transparent film) 22 was produced.

<23 production of optically biaxial layer a (biaxial transparent film)>
Using cellulose ester (total substitution degree 2.89, acetyl group substitution degree 2.25, propionyl substitution degree 0.64), the tension during peeling was controlled, and the film was stretched 1.60 times in the casting direction, 110 ° C. After preheating, the film is optically similar to the biaxial layer a (biaxial transparent film) 20 except that the film is stretched 1.43 times in the width direction at 120 ° C. and adjusted to a film thickness of 115 μm. Thus, a biaxial layer a (biaxial transparent film) 23 was produced.

<24 Production of Optically Biaxial Layer a (Biaxial Transparent Film)>
Cellulose ester (total substitution degree 2.24, acetyl group substitution degree 1.13, propionyl substitution degree 1.11) was used and stretched 1.58 times in the casting direction by controlling the tension during peeling, 140 ° C After preheating, the film is stretched 1.53 times in the width direction at 160 ° C., and optically similar to the biaxial layer a (biaxial transparent film) 20 except that the film thickness is adjusted to 86 μm. Specifically, a biaxial layer a (biaxial transparent film) 24 was produced.

<25 production of optically biaxial layer a (biaxial transparent film)>
A cellulose ester film was prepared according to the following.

(Preparation of dope solution B)
Cellulose ester (cellulose triacetate synthesized from linter cotton)
100 parts by mass (Mn = 148000, Mw = 310000, Mw / Mn = 2.1)
Triphenyl phosphate 9.5 parts by mass Ethylphthalyl ethyl glycolate 2.2 parts by mass Methylene chloride 440 parts by mass Ethanol 40 parts by mass Azumi filter paper No. 1 manufactured by Filter Paper Co., Ltd. 24, and the dope liquid B was prepared. The dope solution B was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film production line. (A part of the dope solution B was also used for preparing the following in-line additive solution B.)
(Silicon dioxide dispersion B)
Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass (average diameter of primary particles 12 nm, apparent specific gravity 100 g / liter)
18 parts by mass or more of ethanol was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. The liquid turbidity after dispersion was 100 ppm. 18 parts by mass of methylene chloride was added to the silicon dioxide dispersion while stirring, and the mixture was stirred and mixed for 30 minutes with a dissolver to prepare silicon dioxide dispersion dilution B.

(Preparation of inline additive solution B)
Methylene chloride 100 parts by weight Dope solution B 34 parts by weight Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 5 parts by weight Tinuvin 171 (manufactured by Ciba Specialty Chemicals) 5 parts by weight Tinuvin 326 (manufactured by Ciba Specialty Chemicals) 3 parts by mass or more was put into a closed container, heated, stirred and completely dissolved and filtered.

  To this, 20 parts by mass of silicon dioxide dispersion diluent B was added with stirring, and the mixture was further stirred for 60 minutes, followed by filtration with Advantech Toyo Co., Ltd. polypropylene wind cartridge filter TCW-PPS-1N. Was prepared.

  In-line additive solution B was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the in-line additive solution line. Add 2.5 parts by weight of the filtered inline additive B to 100 parts by weight of the filtered dope liquid B, mix thoroughly with an inline mixer (Toray static in-pipe mixer Hi-Mixer, SWJ), and then belt Using a casting apparatus, casting was uniformly performed on a stainless steel band support at a temperature of 35 ° C. and a width of 2.5 m. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and then peeled off from the stainless steel band support. The peeled cellulose ester web was evaporated at 35 ° C., and then dried at a drying temperature of 130 ° C. while being stretched 1.2 times in the width direction with a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 11%. After that, drying is completed while transporting the drying zone at 120 ° C. and 110 ° C. with a number of rolls, slitting to 2.6 m width, and knurling with a width of 15 mm and an average height of 10 μm is applied to both ends of the film. An optically biaxial layer a (biaxial transparent film) 25 having a film thickness of 80 μm and a length of 7500 m was produced by winding it around a 6-inch inner diameter core with a tension of 220 N / m and a final tension of 110 N / m.

<Preparation of optically biaxial layer a (biaxial transparent film) 26>
Cellulose ester (total substitution degree 2.17, acetyl group substitution degree 1.06, propionyl substitution degree 1.11) was used, the tension during peeling was controlled, and the film was stretched 1.72 times in the casting direction. After preheating, optically in the same manner as the biaxial layer a (biaxial transparent film) 20 except that the film was stretched 1.80 times in the width direction at 128 ° C. and adjusted to a film thickness of 119 μm. Thus, a biaxial layer a (biaxial transparent film) was produced.

  Furthermore, a polyimide synthesized from 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane and 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl on the film. The solution prepared at 15% by mass using cyclohexanone as a solvent was applied with a die coater. Thereafter, the film was dried at 100 ° C. for 10 minutes to obtain a thin film having a residual solvent amount of 7% and a thickness of 5.6 μm. Thereafter, the thin film formed on the film was horizontally stretched 11% at a temperature of 160 ° C. together with the base material to obtain an optically biaxial layer a (biaxial transparent film) 26. R0 = 24 nm, Rth = 506 nm, d = 41.8 μm.

<Preparation of optically biaxial layer a (biaxial transparent film) 27>
Cellulose ester (total substitution degree 2.41, acetyl group substitution degree 1.43, propionyl substitution degree 0.98) was used, and the tension during peeling was controlled and stretched 1.40 times in the casting direction. After preheating, the film was optically similar to the biaxial layer a (biaxial transparent film) 20 except that the film was stretched 1.37 times in the width direction at 160 ° C. and adjusted to a film thickness of 58 μm. Thus, a biaxial layer a (biaxial transparent film) 27 was produced.

<Application of retardation layer>
Next, Dainippon Ink vertical alignment type liquid crystal (UCL-018) was applied and dried on the obtained optically biaxial layers a (biaxial transparent films) 1 to 6 and 9 to 16 in the following manner. Then, the alignment was fixed and a retardation layer (optically positive uniaxial layer b referred to in the present invention) was provided.

  The liquid preparation method was 99.7% by mass of the above liquid crystal composition, 0.2% by mass of a photopolymerization initiator Lucillin TPO (manufactured by Basf), and 0.1% of hindered amine LS-765 (manufactured by Sankyo Lifetech Co., Ltd.). A polymerizable liquid crystal composition (H1) added by mass% was prepared. Next, a PGMEA solution containing 20% by mass of the polymerizable liquid crystal composition (H1) was prepared. This solution was applied with a thickness of 5 to 8 μm on the biaxial transparent film by a die coater. The coated film was irradiated with UV light of 250 mJ / mm for 10 seconds at an oxygen concentration of 0.2% and a temperature of 38 ° C. to cure the polymerizable liquid crystal composition (H1), and a biaxial transparent film with a retardation layer ( Phase difference region A) 1H to 6H, 9H to 16H were prepared.

  The average refractive index of the retardation layer was 1.611 as measured by the above method.

  Optically biaxial layers a (biaxial transparent films) 1 to 16, 20 to 27 and biaxial films with retardation layers (retardation region A) 1H to 6H, 9H to 16H at 590 nm Table 1 shows the results of retardation measurement by retardation, retardation of the retardation layer, and retardation measurement of the retardation region A in which the optically biaxial layer a and the retardation layer are laminated.

<Production of polarizing plate>
Biaxial transparent film with retardation layer (retardation region A) 1H to 6H, 9H to 16H, biaxial transparent film without retardation layer (retardation region B) 7, 8, 20 to 27 Was subjected to alkali treatment with a 2.5 mol / L sodium hydroxide aqueous solution at 40 ° C. for 60 seconds, washed with water for 3 minutes and saponified to obtain an alkali-treated film.

  Next, a 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizer.

  Biaxial transparent films with retardation layers 1H to 6H, 9H to 9 as a retardation region A having a composition shown in Table 2, Table 3, Table 4, and Table 5 using a 5% aqueous solution of saponified polyvinyl alcohol as an adhesive. 16H or biaxial transparent films 7 and 8 not provided with a retardation layer, a first polarizer, and Konica Minolta Tack KC4UY (manufactured by Konica Minolta Opto Co., Ltd.) are laminated in this order to be polarized on the viewing side. Each plate was made.

  Similarly, the biaxial transparent film 8, 20 to 27, in which no retardation layer is provided as the retardation region B, the second polarizer, and Konica Minolta Tack KC4UY (manufactured by Konica Minolta Opto). Each of the polarizing plates on the backlight side (BL side) was prepared by laminating.

<Production of liquid crystal display device>
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

  The 40-inch BRAVIA KDL40W5000 (VA mode type liquid crystal display device) made by SONY is peeled off from the viewing side and the BL-side polarizing plate, and the viewing-side and BL-side polarizing plates prepared above are liquid crystal in the configuration of FIG. It bonded on the glass surface of the cell and produced VA mode type liquid crystal display devices 1-9 of the composition of Table 2. The in-plane slow axis of the retardation region A of the polarizing plate and the alignment direction of the liquid crystal cell were substantially parallel.

<Evaluation of liquid crystal display device>
(Viewing angle)
The viewing angle of the produced liquid crystal display device was measured by EZ-contrast manufactured by ELDIM. As the viewing angle, the contrast between the white display and the black display of the liquid crystal cell was calculated, and the angle at which the contrast was 100 in the oblique direction was defined as the viewing angle.

(Color)
Color measurement at the time of black display was performed with Topcon SR-3A.

Tint measurement was performed between the front and an inclination angle of 60 ° (front reference) at an obliquely upward (azimuth angle of 45 degrees), and ((x−x ′) ² + (y−y ′) ² ) ^1/2 was evaluated. .

  * In the formula, front: (x, y), diagonal: (x ', y').

  The obtained results are shown in Table 2.

In this measurement, it can be seen that the liquid crystal display device 2 of the present invention has a viewing angle (contrast of 100 or more) exceeding 50 degrees and smaller than 0.09 in color change, which is superior to the comparison. .

Further, optically biaxial layer a, the phase difference layer (layer b of optically positive uniaxial), the refractive index of the layer c of optically isotropic _{is, n a (ave) <n} c (ave ₎ < _{Nb (ave)} (No. 17) satisfying (17). _2, the liquid crystal display device is a _{n c (ave) <n a} (ave) <n b (ave) No. The front contrast of No. 6 was evaluated according to the following method. 2 is 2600, no. 6 is 1800. 2 was found to be excellent.

(Front contrast)
The measurement was performed after the backlight of each liquid crystal display device was lit continuously for one week in an environment of 23 ° C. and 55% RH. For measurement, EZ-Contrast 160D manufactured by ELDIM was used to measure the luminance from the normal direction of the display screen of white display and black display with a liquid crystal display device, and the ratio was defined as the front contrast.

Front contrast = (brightness of white display measured from the normal direction of the display device)
/ (Luminance of black display measured from normal direction of display device)
Example 2
Using the viewing-side polarizing plate and the BL-side polarizing plate prepared in Example 1, liquid crystal display devices 10 to 14 were prepared with the configuration shown in Table 3, and the viewing angle and color change were evaluated in the same manner as in Example 1. The results are shown in Table 3.

From the results in the above table, it was found that excellent evaluation can be obtained when the relationship of claim 1 is satisfied.

Example 3
Using the viewing-side polarizing plate and the BL-side polarizing plate prepared in Example 1, liquid crystal display devices 15 to 19 were prepared with the configuration shown in Table 4, and the viewing angle and color change were evaluated in the same manner as in Example 1. The results are shown in Table 4.

From the results in the above table, it was found that excellent evaluation can be obtained when the relationship of claim 2 is satisfied.

Example 4
Using the viewing-side polarizing plate and the BL-side polarizing plate prepared in Example 1, liquid crystal display devices 20 to 24 were prepared with the configuration shown in Table 5, and the viewing angle and color change were evaluated in the same manner as in Example 1. The results are shown in Table 5.

From the results in the above table, it was found that excellent evaluation can be obtained when the relationship of claim 3 is satisfied.

Claims (15)

A vertical alignment type liquid crystal panel having a first polarizer, a second polarizer, and a vertical alignment type liquid crystal cell provided between the first polarizer and the second polarizer,
The vertical alignment type liquid crystal panel includes a retardation region A provided between the first polarizer and the vertical alignment type liquid crystal cell, and between the second polarizer and the vertical alignment type liquid crystal cell. Having a phase difference region B provided;
In-plane direction retardation R0 _{A (590)} and thickness direction retardation Rt _{A (590)} for the light of wavelength 590 nm in the retardation region A satisfy the following relationships (1) and (2):
The plane retardation for light of wavelength 590nm of the retardation regions B _{R0 B (590)} and the thickness direction retardation _{Rt B (590)} is meet the following relationship (3) and (4),
The phase difference region A further satisfies the following relationships (5) and (6): A vertical alignment type liquid crystal panel.
45 nm ≦ R0 _{A (590)} ≦ 100 nm (1)
−50 nm ≦ Rt _{A (590)} ≦ 20 nm (2)
0 nm ≦ R0 _{B (590)} ≦ 20 nm (3)
200 nm ≦ Rt _{B (590)} ≦ 500 nm (4)
0.7 ≦ D (R40 _A ) 1 ≦ 0.95 (5)
−15 nm ≦ D (R40 _A ) 2 ≦ −3 nm (6)
_{D (R40 A) 1 = R40} A (480) / R40 A (630)
_{D (R40 A) 2 = R40} A (480) -R40 A (630)
However, R40 _{A (480)} is a retardation for a light beam having a wavelength of 480 nm when measured from a direction inclined by 40 ° from the normal direction of the phase difference region A with the fast axis of the phase difference region A as an inclination axis. R40 _{A (630)} represents a wavelength of 630 nm when measured from a direction inclined by 40 ° from the normal direction of the phase difference region A with the fast axis of the phase difference region A as an inclination axis. Retardation (nm) with respect to the light beam. The vertical alignment type liquid crystal panel according to claim 1, wherein the retardation region A satisfies the following relationships (7) and (8).
0.3 ≦ D (Rt _A 1 ≦ 0.9 (7)
−70 nm ≦ D (Rt _A ) 2 ≦ −10 nm (8)
D (Rt _A 1 = | Rt _{A (630)} / Rt _{A (480)} ｜
D (Rt _A ) 2: Rt _{A (480)} -Rt _{A (630)}
However, Rt _{A (480)} Represents the retardation (nm) in the thickness direction with respect to the light having a wavelength of 480 nm in the retardation region A, and Rt _{A (630)} Represents retardation (nm) in the thickness direction with respect to a light beam having a wavelength of 630 nm in the retardation region A. The vertical alignment liquid crystal panel according to claim 1, wherein the retardation region B satisfies the following relationships (9) and (10).
0.85 ≦ D (Rt _B ) 1 ≦ 1.00 (9)
10 nm ≦ D (Rt _B 2 ≦ 100 nm (10)
D (Rt _B ) 1 = Rt _{B (480)} / Rt _{B (630)}
D (Rt _B ) 2 = Rt _{B (630)} -Rt _{B (480)}
However, Rt _{B (480)} Represents retardation (nm) in the thickness direction with respect to a light beam having a wavelength of 480 nm in the retardation region B, and Rt _{B (630)} Represents retardation (nm) in the thickness direction with respect to a light beam having a wavelength of 630 nm in the retardation region B. The vertical alignment type according to any one of claims 1 to 3, wherein the retardation region A has an in-plane slow axis in a direction orthogonal to the absorption axis of the first polarizer. LCD panel. The retardation region A is provided on the viewing side with respect to the vertical alignment type liquid crystal cell, and the retardation region B is provided on the opposite side of the retardation region A with respect to the vertical alignment type liquid crystal cell. The vertical alignment type liquid crystal panel according to claim 1, wherein: The retardation region B is provided on the viewing side with respect to the vertical alignment type liquid crystal cell, and the retardation region A is provided on the opposite side of the retardation region B with respect to the vertical alignment type liquid crystal cell. The vertical alignment type liquid crystal panel according to claim 1, wherein: A vertical alignment type liquid crystal panel having a first polarizer, a second polarizer, and a vertical alignment type liquid crystal cell provided between the first polarizer and the second polarizer,
The vertical alignment type liquid crystal panel includes a retardation region A provided between the first polarizer and the vertical alignment type liquid crystal cell, and between the second polarizer and the vertical alignment type liquid crystal cell. Having a phase difference region B provided;
In-plane direction retardation R0 with respect to a light beam having a wavelength of 590 nm in the retardation region A _{A (590)} And retardation Rt in the thickness direction _{A (590)} Satisfies the relationship (1) and (2) below,
In-plane retardation R0 for the light having a wavelength of 590 nm in the retardation region B _{B (590)} And retardation Rt in the thickness direction _{B (590)} Satisfies the relationship (3) and (4) below,
The retardation region A includes at least an optically biaxial layer a that satisfies the following relationships (11) to (13), and an optically positive uniaxial layer that satisfies the following relationships (14) and (15): A vertical alignment type liquid crystal panel, wherein the layer b is laminated.
45nm ≦ R0 _{A (590)} ≦ 100 nm (1)
−50 nm ≦ Rt _{A (590)} ≦ 20nm (2)
0nm ≦ R0 _{B (590)} ≦ 20nm (3)
200 nm ≦ Rt _{B (590)} ≦ 500nm (4)
nx _{a (590)} > Ny _{a (590)} > Nz _{a (590)}   (11)
45nm ≦ R0 _{a (590)} ≦ 100 nm (12)
70 nm ≦ Rt _{a (590)} ≦ 300 nm (13)
0nm ≦ R0 _{b (590)} ≦ 5nm (14)
−300 nm ≦ Rt _{b (590)} ≦ −70 nm (15)
However, nx _{a (590)} Represents the refractive index for light with a wavelength of 590 nm in the slow axis direction in the plane of the optically biaxial layer a, ny _{a (590)} Represents a refractive index for a light beam having a wavelength of 590 nm in a direction perpendicular to the slow axis direction of the optically biaxial layer a, and nz _{a (590)} Represents a refractive index with respect to a light beam having a wavelength of 590 nm in the thickness direction of the optically biaxial layer a, and R0 _{a (590)} Represents the in-plane retardation of the optically biaxial layer a with respect to light having a wavelength of 590 nm, and Rt _{a (590)} Represents retardation in the thickness direction of the optically biaxial layer a with respect to a light beam having a wavelength of 590 nm, and R0 _{b (590)} Represents the in-plane retardation for the light of wavelength 590 nm of the optically positive uniaxial layer b, Rt _{b (590)} Represents the retardation in the thickness direction of the optically positive uniaxial layer b with respect to light having a wavelength of 590 nm. The retardation region A includes at least an optically biaxial layer a that satisfies the following relationships (11) to (13), and an optically positive uniaxial layer that satisfies the following relationships (14) and (15): The vertically aligned liquid crystal panel according to claim 1 , wherein the layer b is laminated.
nx _{a (590)} > ny _{a (590)} > nz _{a (590)} (11)
45 nm ≦ R0 _{a (590)} ≦ 100 nm (12)
70 nm ≦ Rta ₍₅₉₀₎ ≦ 300 nm (13)
0 nm ≦ R0 _{b (590)} ≦ 5 nm (14)
−300 nm ≦ Rt _{b (590)} ≦ −70 nm (15)
However, nx _{a (590)} represents a refractive index with respect to a light beam having a wavelength of 590 nm in the slow axis direction in the plane of the optically biaxial layer a, and ny _{a (590)} is optically biaxial. Represents a refractive index with respect to a light beam having a wavelength of 590 nm in a direction perpendicular to the slow axis direction of the layer a, and nz _{a (590)} represents a light beam with a wavelength of 590 nm in the thickness direction of the optically biaxial layer a. R0 _{a (590)} represents the in-plane retardation of the optically biaxial layer a with respect to light having a wavelength of 590 nm, and Rta ₍₅₉₀₎ represents the optically biaxial layer a. Represents a retardation in the thickness direction with respect to a light beam having a wavelength of 590 nm, and R0 _{b (590)} represents an in-plane retardation with respect to a light beam with a wavelength of 590 nm of the optically positive uniaxial layer b, and Rt _{b ( 590)} represents retardation in the thickness direction of the optically positive uniaxial layer b with respect to light having a wavelength of 590 nm. 9. The vertically aligned liquid crystal according to claim 7 , wherein the optically biaxial layer a is provided on the first polarizer side with respect to the optically positive uniaxial layer b. panel. The vertical alignment type liquid crystal panel according to any one of claims 7 to 9, wherein the optically biaxial layer a satisfies the following relationship (16).
1.0 ≦ Rt _{a (590)} / R0 _{a (590)} ≦ 6.0 (16) The retardation region A, according to claim characterized by having a layer c is optically isotropic, between the layer and the optically positive uniaxial layers of said optically biaxial 7 10. The vertical alignment type liquid crystal panel according to any one of 10 to 10 . 12. The vertical alignment type liquid crystal panel according to claim 11 , wherein the thickness of the optically isotropic layer c is in the range of 0.01 [mu] m to 5 [mu] m. It said optically biaxial layers a, claim 11 or 12 wherein the optically positive uniaxial layer b and said optically isotropic layer c is characterized by satisfying the following relationship (17) A vertical alignment type liquid crystal panel as described in 1.
n _{a (ave)} <nc _(ave) < _{nb (ave)} (17)
Where n _{a (ave)} represents the average refractive index of the optically biaxial layer a, _{nb (ave)} represents the average refractive index of the optically positive uniaxial layer b, and n _{c (ave)} represents the average refractive index of the optically isotropic layer c. Said optically biaxial layer a is a layer having a cellulose ester, the degree of substitution of the cellulose ester satisfies the following (18), any one of claims 7 to 13, characterized in that satisfy (19) The vertical alignment type liquid crystal panel according to item .
2.0 ≦ X + Y <3.0 (18)
0.5 <Y <1.6 (19)
45 nm ≦ R0 _{A (590)} ≦ 100 nm (1)
However, X represents an acetyl group substitution degree, and Y represents a substitution degree of a substituent selected from propionyl and butyryl groups. 15. A vertical alignment type liquid crystal display device comprising: the vertical alignment type liquid crystal panel according to claim 1; and a backlight on either side of the vertical alignment type liquid crystal panel.

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