JP5632605B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a TN (Twisted Nematic) type, ECB (Electrically Controlled Birefringence) type, or OCB (Optically Compensated Bend) type liquid crystal display device with improved front contrast.

  In recent years, the contrast in the normal direction of a display image (hereinafter referred to as “front contrast (front CR)”) has been rapidly improved in various modes of liquid crystal display devices. The same applies to TN type, ECB type, and OCB type liquid crystal display devices. This is because the particle size of the pigment used for forming the color filter is reduced, the black matrix is thinned, the TFT array is improved, and the like. The front CR is an index that clearly represents the performance of the liquid crystal display device as described in the catalog. Therefore, in order to improve the front CR even a little, improvement of various members related to the liquid crystal display device has been studied, and various proposals have been made by academic conference presentations, papers, patent publications, and the like. In the TN type, ECB type, and OCB type liquid crystal display devices, the front CR will be improved more and more in the future.

For example, there is a color filter on array (COA) structure as one means for increasing the transmittance (for example, Patent Documents 1, 2, and 3). According to the COA structure, since the aperture ratio can be increased, the transmittance during white display can be increased. At present, there is a high interest in environmental problems, and adopting a COA structure to improve the transmittance contributes to the reduction of power consumption and is preferable from the viewpoint of the environment.
By the way, the front CR is determined by two transmittances (white luminance and black luminance) at the time of white display and black display, and therefore cannot be achieved only by increasing the transmittance. Even if the transmittance at the time of white display can be increased, the transmittance at the time of black display also increases, so that a high CR cannot be achieved. In order to increase the front CR by adopting a structure capable of improving the transmittance during white display, it is important to suppress an increase in black transmittance due to the adoption of the structure.

On the other hand, for a liquid crystal display device, it is important that not only the front CR is high, but also the CR in the oblique direction (hereinafter sometimes referred to as “viewing angle CR”) is high. With respect to the TN type or OCB type liquid crystal display device, optical compensation is achieved by symmetrically arranging the same retardation films on the front side and the rear side with the liquid crystal cell as the center (for example, Patent Document 4).
Conventionally, the influence of these retardation films on the front CR has been studied mainly from the viewpoint that the front CR is lowered due to the axial shift and haze of the retardation film, and there is a technique for reducing these effects. Various proposals have been made.

JP 2005-99499 A JP 2005-258004 A JP 2005-3733 A Japanese Patent No. 2587398

When the present inventor tried to improve the front CR by adopting the COA structure in the TN type, ECB type and OCB type liquid crystal display devices, it was found that the improvement of the front CR could not be achieved. As a result of further investigation, it was found that the cause was due to the presence of a retardation film for viewing angle compensation. In particular, in a TN type, ECB type, or OCB type liquid crystal display device in which a retardation film having a large phase difference is arranged on the rear side, when the COA structure is adopted, the front CR is not improved, but rather it is decreased. It was. In the TN type, ECB type, or OCB type liquid crystal display device having a retardation film, it can be said that the problem of adopting the COA structure has not been known so far as far as the present inventors know.
That is, an object of the present invention is to solve the problem of adopting the COA structure in TN type, ECB type and OCB type liquid crystal display devices having a retardation film, which has not been conventionally known. Specifically, an object of the present invention is to provide a TN type, ECB type, or OCB type liquid crystal display device having a COA structure with improved front contrast.

  As described above, as a result of the study by the present inventors, when the COA structure is adopted, the aperture ratio is increased, so that the transmittance at the time of white display is increased, but the light leakage at the time of black display is also increased. I understood. In particular, when a COA structure is adopted in a TN type, ECB type, or OCB type liquid crystal display device in which a retardation film having a large retardation is arranged on the rear side, the front CR is not improved, and the COA structure is adopted. It turned out that the front CR would be lower than the one without it. As a result of various studies in order to solve this problem, the present inventor found that the total Rth of the retardation films arranged on the rear side is within a predetermined range, and that the TN type, ECB type, or The knowledge that the front CR of the OCB type liquid crystal display device can be remarkably improved has been obtained, and the present invention has been completed.

That is, the means for solving the above problems are as follows.
[1] Front-side polarizer, rear-side polarizer, liquid crystal layer disposed between the front-side polarizer and the rear-side polarizer, and a color filter disposed between the liquid-crystal layer and the rear-side polarizer A rear-side retardation region (hereinafter, rear-side polarizer and color) composed of one or more retardation layers disposed between the rear-side polarizer and the color filter layer. The entire retardation layer or two or more retardation layers disposed between the filter layers is referred to as a “rear retardation region”; and 1 disposed between the front polarizer and the liquid crystal layer. Front side retardation region composed of one or two or more retardation layers (hereinafter referred to as “front layer of one or more retardation layers arranged between the front polarizer and the liquid crystal layer” TN, ECB or OCB type liquid crystal display having a "side retardation region" A device,
The rear side retardation region is composed of one or more polymer films having optical anisotropy, and the following formula (I)
(I): | Rth (550) | ≦ 140 nm
Where Rth (λ) means a retardation in the thickness direction at a wavelength λnm (nm); and an array in which the liquid crystal layer includes the color filter layer A TN, ECB or OCB type liquid crystal display device which is sandwiched between a rear side substrate which is a substrate and a front side substrate which is a counter substrate disposed to face the array substrate.
[2] Front side polarizer, rear side polarizer, liquid crystal layer disposed between the front side polarizer and the rear side polarizer, and a color filter disposed between the liquid crystal layer and the rear side polarizer A rear-side retardation region (hereinafter, rear-side polarizer and color) composed of one or more retardation layers disposed between the rear-side polarizer and the color filter layer. The entire retardation layer or two or more retardation layers disposed between the filter layers is referred to as a “rear retardation region”; and 1 disposed between the front polarizer and the liquid crystal layer. Front side retardation region composed of one or two or more retardation layers (hereinafter referred to as “front layer of one or more retardation layers arranged between the front polarizer and the liquid crystal layer” A liquid crystal display device having a side retardation region),
The rear side retardation region is composed of one or more polymer films having optical anisotropy, and has the following formula (II)
(II): | Rth (550) | ≦ 100 nm
A first retardation layer that satisfies
Retardation R2 [+ 40 °] at a wavelength of 550 nm measured from a direction tilted + 40 ° from the normal to the tilt azimuth in the plane including the tilt azimuth and the normal, and opposite to the normal The ratio of retardation R2 [−40 °] (provided that R2 [−40 °] <R2 [+ 40 °]) at a wavelength of 550 nm measured from a direction inclined by 40 ° to the following formula (III)
(III): 1 <R2 [+ 40 °] / R2 [−40 °]
However, Re (λ) means an in-plane retardation (nm) at a wavelength λnm, and a second retardation layer that satisfies the following; and an array in which the liquid crystal layer includes the color filter layer A liquid crystal display device, wherein the liquid crystal display device is sandwiched between a rear substrate as a substrate and a front substrate as a counter substrate disposed to face the array substrate.

[3] The second retardation layer has the following formula (IIIa)
(IIIa): 3 ≦ R2 [+ 40 °] / R2 [−40 °]
[2] The liquid crystal display device according to [2].
[4] The first retardation layer has the following formula (IV):
(IV): 0 ≦ Re (550) ≦ 500 nm
The liquid crystal display device according to any one of [1] to [3], wherein:
[5] The front side retardation region is composed of one or more polymer films having optical anisotropy, and the following formulas (V) and (VI):
(V): 0 ≦ Re (550) ≦ 500 nm
(VI): −100 nm ≦ Rth (550) ≦ 1000 nm
The liquid crystal display device according to any one of [1] to [4], comprising a third retardation layer satisfying
[6] The front side retardation region is composed of one or more optically anisotropic polymer films, and the following formulas (V) and (VI):
(V): 0 ≦ Re (550) ≦ 500 nm
(VI): −100 nm ≦ Rth (550) ≦ 1000 nm
A third retardation layer satisfying
Retardation R4 [+ 40 °] at a wavelength of 550 nm measured from a direction tilted + 40 ° from the normal to the tilt azimuth in the plane including the tilt azimuth and the normal, and opposite to the normal The ratio of retardation R4 [−40 °] (provided that R4 [−40 °] <R4 [+ 40 °]) at a wavelength of 550 nm measured from a direction inclined at 40 ° to the following formula (VII)
(VII): 1 <R4 [+ 40 °] / R4 [−40 °]
However, Re (λ) means an in-plane retardation (nm) at a wavelength λnm; and any one of [1] to [4], wherein the fourth retardation layer is satisfied. Liquid crystal display device.
[7] The fourth retardation layer has the following formula (VIIa)
(VIIa): 3 ≦ R4 [+ 40 °] / R4 [−40 °]
[6] The liquid crystal display device according to [6].
[8] A TN liquid crystal display device in which the liquid crystal layer is aligned parallel to the substrate surface when no voltage is applied and at a twist angle of 45 ° to 135 ° between the substrates;
The third retardation layer has the following formulas (Va) and (VIa)
(Va): 0 ≦ Re (550) ≦ 400 nm
(VIa): −100 nm ≦ Rth (550) ≦ 300 nm
The liquid crystal display device according to any one of [1] to [7], wherein:
[9] A TN liquid crystal display device in which the liquid crystal layer is aligned parallel to the substrate surface when no voltage is applied and at a twist angle of 90 ° between the substrates;
The third retardation layer has the following formulas (Vb) and (VIb)
(Vb): 0 ≦ Re (550) ≦ 300 nm
(VIb): 50 nm ≦ Rth (550) ≦ 300 nm
[8] The liquid crystal display device according to [8].
[10] A liquid crystal display device in which the liquid crystal layer is aligned parallel to the substrate surface when no voltage is applied and at a twist angle of 0 ° to 45 ° between the substrates;
The third retardation layer has the following formulas (Vc) and (VIc)
(Vc): 70 nm <Re (550) ≦ 400 nm
(VIc): −100 nm ≦ Rth (550) ≦ 250 nm
The liquid crystal display device according to any one of [1] to [7], wherein:
[11] The liquid crystal display device in which the liquid crystal layer is bend-aligned between the substrates parallel to the substrate surface when no voltage is applied;
The third retardation layer has the following formulas (Vd) and (VId)
(Vd): 0 ≦ Re (550) ≦ 100 nm
(VId): 200 nm ≦ Rth (550) ≦ 1000 nm
The liquid crystal display device according to any one of [1] to [7], wherein:
[12] The liquid crystal display device according to any one of [1] to [11], wherein the array substrate is an array substrate having a black matrix that partitions pixels provided with the color filter layer.

  According to the present invention, it is possible to provide a TN type, ECB type, and OCB type liquid crystal display device having a high front contrast and a COA structure.

It is a cross-sectional schematic diagram of an example of the liquid crystal display device of this invention. It is the schematic diagram used in order to demonstrate the effect | action of this invention. It is the schematic diagram used in order to demonstrate the effect | action of the conventional common liquid crystal cell used for reference. It is the schematic diagram used in order to demonstrate the optical characteristic of the 2nd and 4th phase difference layer.

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

注記：上記のＲ［(］は法線方向から角度θ傾斜した方向におけるレターデーション値をあらわす。また、式中、ｎｘは面内における遅相軸方向の屈折率を表し、ｎｙは面内においてｎｘに直交する方向の屈折率を表し、ｎｚはｎｘ及びｎｙに直交する方向の屈折率を表す。ｄは膜厚を表す。

Note: R [(] above represents the retardation value in the direction inclined at an angle θ from the normal direction, where nx represents the refractive index in the slow axis direction in the plane, and ny represents the in-plane direction. The refractive index in the direction perpendicular to nx is represented, nz represents the refractive index in the direction perpendicular to nx and ny, and d represents the film thickness.

In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is from −50 degrees to +50 degrees with respect to the normal direction of the film, with Re (λ) being the in-plane slow axis (determined by KOBRA 21ADH or WR) and the tilt axis (rotating axis). In each of the 10 degree steps, light of wavelength λ nm is incident from the inclined direction and measured at 11 points. Based on the measured retardation value, the assumed average refractive index, and the input film thickness value, KOBRA 21ADH or WR is calculated.
In the above measurement, as the assumed value of the average refractive index, the values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. Examples of the average refractive index values of main optical films are given below:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).
The KOBRA 21ADH or WR calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

In this specification, the values of Re (λ) and Rth (λ) such as Re (450), Re (550), Re (650), Rth (450), Rth (550), Rth (650) are , Re and Rth are measured for three or more different wavelengths (for example, λ = 479.2, 546.3, 632.8, and 745.3 nm) by a measuring device, and calculated from these values. Specifically, these measured values are approximated by Cauchy's equation (up to the third term, Re = A + B / λ ² + C / λ ⁴ ), and values A, B, and C are obtained, respectively. From the above, Re and Rth at the wavelength λ can be plotted again, and Re (λ) and Rth (λ) at each wavelength λ can be obtained therefrom.

In the present specification, the “slow axis” of a retardation film or the like means a direction in which the refractive index is maximized. The “visible light region” means 380 nm to 780 nm. Moreover, in this specification, when there is no special mention about a measurement wavelength, a measurement wavelength is 550 nm.
Further, in this specification, numerical values, numerical ranges, and qualitative expressions (for example, “equivalent”, “equal”, etc.) indicating optical characteristics of each member such as a retardation region, a retardation film, and a liquid crystal layer are used. ) Is interpreted to indicate numerical values, numerical ranges and properties including generally allowable errors for liquid crystal display devices and members used therefor.

  In this specification, the angle of the optical axis of an optical member such as a liquid crystal layer or a retardation layer (for example, an angle such as “45 °”) and the relationship thereof (for example, “orthogonal”, “parallel”, and “45 ° The term “intersection” or the like) includes a range of errors allowed in the technical field of liquid crystal display devices. For example, it means that the angle is within the range of strict angle ± 5 °, and the error from the strict angle is preferably less than 4 °, more preferably less than 3 °. In the TN type, ECB type, and OCB type liquid crystal display devices, the liquid crystal layer usually has a pretilt, and the pretilt is less than about 10 °. In this specification, “the liquid crystal layer” is “parallel to the substrate surface” is assumed to be included in an allowable error of the tilt due to the pretilt.

In this specification, the retardation film means a self-supporting film disposed between the liquid crystal cell and the polarizer. (It does not matter whether the retardation is large or small.) The retardation film, the retardation layer, and the retardation film are synonymous. The retardation region is located between the liquid crystal cell and the polarizer 1
It is a general term for a retardation film having two or more layers.
In this specification, “front side” means the display surface side, and “rear side” means the backlight side. In this specification, “front” means a normal direction with respect to the display surface, and “front contrast (CR)” is calculated from white luminance and black luminance measured in the normal direction of the display surface. The viewing angle contrast (CR) is an oblique direction inclined from the normal direction of the display surface (for example, a direction defined by an azimuth angle direction of 45 degrees and a polar angle direction of 60 degrees with respect to the display surface). ) Means the contrast calculated from the white luminance and the black luminance measured.

The present invention relates to a TN type, ECB type, or OCB type liquid crystal display device having a COA structure. A schematic cross-sectional view of an example of the liquid crystal display device of the present invention is shown in FIG.
The TN-type, ECB-type, or OCB-type liquid crystal display device of the present invention shown in FIG. A liquid crystal layer 10, a color filter layer 12 disposed between the liquid crystal layer 10 and the rear side polarizer 24, a rear side retardation region 20 disposed between the rear side polarizer 24 and the color filter layer 12, and The front side retardation region 22 is disposed between the front side polarizer 26 and the liquid crystal layer 10. In the liquid crystal cell LC included in the TN type, ECB type, or OCB type liquid crystal display device shown in FIG. This is a COA-structured liquid crystal cell disposed on the same substrate, the rear substrate 16. The liquid crystal cell LC may have a black matrix (not shown), and the position may be on the rear substrate 16 or the front substrate 18.

  The liquid crystal layer 10 is aligned parallel to the surfaces of the rear side substrate 16 and the front side substrate 18 when no voltage is applied, and is TN type, ECB type, and OCB type depending on the presence / absence of twist orientation (that is, the range of the twist angle). Each is classified. For example, when no voltage is applied, the orientation is parallel to the substrate and twisted, specifically, the twist angle is about 45 to 135 ° (generally about 90 °). A mode of the mold, which is parallel to the substrate when no voltage is applied and is not twisted, specifically, oriented at a twist angle of less than 45 °, is an ECB type. Further, the mode in which the bend orientation is parallel to the substrate surface when no voltage is applied is an OCB type mode.

The TN type, ECB type, or OCB type liquid crystal display device of the present invention is characterized in that the rear side retardation region 20 located on the rear side of the liquid crystal cell LC has a low phase difference.
In the conventional liquid crystal display device, the phase difference required for viewing angle compensation is generally assigned equally to the phase difference in the front side phase difference region and the phase difference in the rear side phase difference region. However, in recent years, with respect to liquid crystal cells, even when only the color filter layer is taken as an example, the particle size of the pigment used for forming the RGB colored layer has been miniaturized, and the multiple scattering of light generated in the liquid crystal cell has been significantly reduced. As a result, higher contrast is being promoted. As a result of intensive studies by the present inventors, it has been found that in such a high-contrast liquid crystal cell, the polarization state when incident on the liquid crystal cell is not lost due to scattering and affects the contrast in the front direction. Note that the front contrast greatly depends on light leakage during black display. The lower the brightness during black display, the higher the front contrast. As far as the present inventor knows, it can be said that no study has been made on the influence of the retardation of a retardation film or the like disposed outside the liquid crystal cell on the front CR.

Usually, from the backlight unit of the TN type, ECB type, or OCB type liquid crystal display device, light having directivity is incident on the rear side polarizer, but the light incident from an oblique direction is the rear side retardation film. Ellipsoidal polarization is performed by the retardation (hereinafter referred to as “Ret rear”) of the rear side phase difference region in which etc. are arranged. After that, the elliptically polarized light is incident on the liquid crystal cell, and the present inventors diligently studied to find that the elliptically polarized light is converted into each member (liquid crystal, color filter, black matrix) in the liquid crystal cell. When the light is incident on the array substrate structure, the protrusion structure of the counter substrate, the slit on the common electrode on the counter substrate, etc., the light is scattered in the front due to optical phenomena such as scattering and diffraction in each member. Was found to be reduced. That is, the present inventor has found that the amount of reduction in the front CR is determined by the relationship between the Ret rear and the optical phenomenon of each member of the liquid crystal cell. As a result of further investigation based on this knowledge, in a TN type, ECB type, or OCB type liquid crystal display device having a liquid crystal cell with a COA structure, a rear side retardation region (in FIG. 1) through which light passes before entering the liquid crystal cell. 20) is an optically anisotropic one or two or more polymer films (hereinafter sometimes referred to as “first aspect”), the following formula (I)
(I): | Rth (550) | ≦ 140 nm
In addition, as another aspect, the rear side retardation region (20 in FIG. 1) is formed of a first film composed of one or more polymer films having optical anisotropy. A phase difference layer and a second phase difference layer having an asymmetry centering on the normal direction (polar angle 0 °) (hereinafter, referred to as “second mode”). ), The first retardation layer is represented by the following formula (II), the second retardation layer is represented by the following formula (III),
(II): | Rth (550) | ≦ 100 nm
(III): 1 <R2 [+ 40 °] / R2 [−40 °]
(However, R2 [+ 40 °]> R2 [−40 °])
It has been found that the front CR is remarkably improved by satisfying.
The phase difference of the entire rear side retardation region through which light passes before entering the liquid crystal cell is the above formula (I) in the first mode, or the above formulas (II) and (III) in the second mode. As long as the above condition is satisfied, even if light incident from an oblique direction is diffused or diffracted by the array member and the color filter layer in the liquid crystal cell and then travels in the normal direction, the front direction when displaying black Compared with a TN type, ECB type, or OCB type liquid crystal display device having a general configuration in which liquid crystal cells having a non-COA structure are arranged, the front CR can be remarkably improved. it can.

In addition, the formula (III) (the same applies to the formula (VII) described later) is a direction (incident direction 1) inclined from the normal to the tilt azimuth side in a plane including the tilt azimuth and normal. ) Measured from a retardation R [+ 40 °] having a wavelength of 550 nm and R [−40 °] measured from a direction (incident direction 2) inclined 40 ° to the opposite side of the tilt direction with respect to the normal line, It is requested from. This optical characteristic is a characteristic that cannot be achieved by the first retardation layer composed of one or more optically anisotropic polymer films.
Here, in this specification, the “direction inclined by θ ° from the retardation layer” is defined as a direction inclined in the layer surface direction by θ ° in the inclination direction from the normal direction. That is, the normal direction of the layer surface is a direction with an inclination angle of 0 °, and an arbitrary direction within the layer surface is a direction with an inclination angle of 90 °.

FIG. 4 is a schematic diagram illustrating an example of the relationship between the tilt direction of the retardation layer, the incident surface, and the incident direction when measuring R [+ 40 °] and R [−40 °]. The measurement of R [+ 40 °] and R [−40 °] may be in any of the incident directions 1 and 2, and is determined so as to satisfy the relationship of R [+ 40 °]> R [−40 °]. .
In the present specification, R [0 °] = Re, R [+ 40 °], and R [−40 °] of the retardation layer are the normal lines in the plane including the following tilt direction and normal of the retardation layer. Retardation value measured at a direction (at an inclination angle of 0 °) at a wavelength of 550 nm, retardation value measured at a direction inclined by 40 ° toward the inclination direction with respect to the normal line (at an inclination angle of 40 degrees), and It means a retardation value (at an inclination angle of −40 degrees) measured from a direction inclined by 40 ° to the opposite side of the inclination direction with respect to the normal line. In the present specification, the numeral “2” in R2 [+ 40 °] and R2 [−40 °] is added to indicate the characteristics of the second retardation layer. That is, R2 [+ 40 °] and R2 [−40 °] indicate R [+ 40 °] and R [−40 °] of the second retardation layer.
Similarly, the numeral “4” in R4 [+ 40 °] and R4 [−40 °], which will be described later, is appended to indicate the characteristics of the fourth retardation layer, and R4 [+ 40 °]. And R4 [−40 °] indicate R [+ 40 °] and R [−40 °] of the fourth retardation layer.

Here, the tilt direction is determined by the following method.
(1) The slow axis orientation in the plane of the retardation layer is 0 °, and the fast axis orientation in the plane of the retardation layer is 90 °, and the preliminary tilt is in increments of 0.1 ° between 0 ° and 90 °. Set the direction.
(2) R [+ 40 °] and R [−40 °] are measured in a plane including each provisional tilt direction and the normal of the retardation layer, and | R [+ 40 °] −R [−40 °] | Ask.
(3) The direction in which | R [+ 40 °] −R [−40 °] | is maximized is determined as the tilt direction.
In this specification, Rth of the retardation layer is calculated by KOBRA21ADH or WR in the tilt direction.
In addition, variations in Re, R [+ 40 °] and R [−40 °] can be measured by the following method. Sampling is performed at any 10 or more positions at 2 mm or more apart from each other in the center of the retardation layer (for example, film), and Re, R [+ 40 °] and R [−40 °] are measured by the above method. The difference between the maximum value and the minimum value is the variation of Re, R [+ 40 °] and R [−40 °]. In the present invention, the average value of the above 10 points is Re, R [+ 40 °], and R [−40 °].
Further, the slow axis and the aforementioned variation in Rth are also measured in the same manner.

R [+ 40 °] / R [−40 °] indicates the degree of asymmetry of the polar angle dependency of retardation. The larger this ratio, the more the degree of asymmetry of the polar angle dependency of retardation. It means big. In the present invention, it is preferable to use a member having a large degree of asymmetry of the polar angle dependence of retardation as the second retardation layer, and the second retardation layer comprises:
3 ≦ R2 [+ 40 °] / R2 [−40 °]
It is preferable to satisfy
5 ≦ R2 [+ 40 °] / R2 [−40 °]
Is more preferable.

  The reason why the front CR is improved in the liquid crystal display device of the present invention shown in FIG. 1 as compared with the conventional liquid crystal display device is summarized as shown in FIGS. 2 shows the liquid crystal display device of the present invention shown in FIG. 1, and FIG. 3 shows the position of each rear side retardation region (20 in FIG. 1) of the conventional liquid crystal display device having a non-COA liquid crystal cell. The tendency of the influence of each member arranged in each of the COA structure liquid crystal cell LC and the non-COA structure liquid crystal cell LC ′ in the front CR direction when the phase difference becomes large and the strength of the influence are summarized. Is. In FIG. 2B and FIG. 3B, “↑” indicates the action of increasing the front CR, and “↓” indicates the action of lowering the front CR. The number of arrows is a measure of the strength of the action, and the greater the number, the stronger the action. In FIGS. 2 and 3, in order to simplify the description, the description will be made by paying attention to three of the CF member (color filter and black matrix), the liquid crystal layer, and the array member (TFT array).

One feature of the liquid crystal display device of the present invention is that a color filter on array (COA) substrate is arranged as a rear substrate between the rear polarizer and the liquid crystal layer.
The dependency of incident light on the incident polarization state of light leakage during black display due to the optical phenomenon in the color filter, black matrix, and TFT array shows the same tendency, but the contribution of the black matrix is relatively small. The position of the black matrix in the liquid crystal display device may be anywhere in the liquid crystal cell, but is preferably located between the rear polarizer and the liquid crystal layer.

  As summarized in FIG. 3B, in the conventional liquid crystal display measure having a general structure, the relationship between the CF member and the array member, and the Ret rear, which have a large influence on the front CR, is opposite to each other. When the Ret rear becomes smaller, the optical phenomenon due to the array member acts in the direction of increasing the front CR, whereas the optical phenomenon due to the CF member acts in the direction of lowering the front CR, so that the mutual action is offset, and the front side It was not recognized as an impact on CR.

  On the other hand, in the liquid crystal cell of FIG. 2 (a) which is an example of the present invention, as summarized in FIG. 2 (b), the relationship between the CF member and the array member, which has a large influence on the front CR, and the Ret rear are equal to each other. That is, when the Ret rear is reduced, the optical phenomenon due to the CF member and the array member both acts in the direction of increasing the front CR. Therefore, when the Ret rear is increased, the optical phenomenon of both the CF member and the array member is caused by the optical phenomenon. CR is improved. As a result, compared with the liquid crystal cell LC ′ having the normal structure shown in FIG. 3A, the front CR is remarkably improved in the liquid crystal display device of the present invention.

The reason why the optical phenomenon of each member in the liquid crystal cell has an influence on the front CR depending on its arrangement is as follows.
The degree of scattering that occurs in the array member and the CF member is mainly determined by the ellipticity of the incident polarized light immediately before scattering occurs in the array member and the CF member, and the incident polarized light having a smaller ellipticity is scattered by being incident on the member. The degree of becomes smaller. If the amount of scattering is small, light leakage during black display can be reduced, and as a result, the front CR is increased. In the member in which light is incident before entering the liquid crystal layer, for example, the array member 54 in FIG. 3A, the ellipticity of the polarized light incident on the array member 54 becomes smaller as the Ret rear becomes smaller. The optical phenomenon caused by 54 acts in the direction of increasing the front CR. However, in a member in which light enters after passing through the liquid crystal layer, not only Ret rear but also Δnd (λ) of the liquid crystal (d is the thickness (nm) of the liquid crystal layer, and Δn (λ) is a compound at the wavelength λ of the liquid crystal layer. Is the refractive index, and Δnd (λ) is the product of Δn (λ) and d.) Also affects the ellipticity of the incident polarization. In the TN type, Δnd (550) of the liquid crystal layer is about 300 to 500 nm, in the ECB type, Δnd (550) of the liquid crystal layer is about 250 to 350 nm, and in the OCB type, Δnd (550) of the liquid crystal layer is 500 to 1300 nm. As a result, the smaller the Ret rear, the greater the ellipticity of the polarized light that enters the member after passing through the liquid crystal layer. Therefore, in the member in which light enters after entering the liquid crystal layer, for example, the color filter 52 in FIG. 3A, the smaller the Ret rear, the greater the ellipticity of the polarized light that enters after passing through the liquid crystal layer. Any optical phenomenon caused by these members acts in the direction of lowering the front CR.

That is, in the liquid crystal cell LC ′ having the conventional general configuration shown in FIG. 3A, even if the Ret rear is made small, the action due to the optical phenomenon of the array member 54 is canceled by the action due to the optical phenomenon of the CF member 52. Therefore, the front CR cannot be greatly improved.
On the other hand, in the liquid crystal cell LC of FIG. 2A according to the present invention, when the Ret rear is reduced, the optical phenomena of the color filter 12 and the array member 14 both act in the direction of increasing the front CR. Compared with the liquid crystal display device, the front CR can be remarkably improved.
In the table, the degree of action of the array member is indicated by three “↑” and the degree of action of the CF member is indicated by two “↑”. For example, the degree of action due to scattering of the liquid crystal layer is relative. It is small and will be shown by one “↑”. 2 and 3, the scattering action by the liquid crystal layer acts in the direction of lowering the front CR as the elliptical polarization rate of obliquely incident light is smaller, that is, as the Ret rear is smaller, It acts in the direction of lowering the front CR.

  The influence of the Ret rear on the front CR is almost negligible in a low front CR liquid crystal display device. However, this influence cannot be ignored in order to further improve the front CR of a liquid crystal display device with a high front CR (for example, the front CR is 1000 or more) that has been provided in recent years. The present invention is particularly useful for further improving the front CR for a liquid crystal display device having a front CR of 1000 or more.

  As described above, the front CR improvement effect of the present invention is not the effect of increasing the aperture ratio by adopting a COA-structured liquid crystal cell, but making the rear side retardation region of the COA-structured liquid crystal cell have a low phase difference. This is because the scattering of polarized light entering the liquid crystal cell is reduced, and as a result, the front black luminance is lowered. The effect of the present invention can also be explained by the locus of the polarization on the Poincare sphere, assuming that the polarization state is substantially maintained after the polarized light incident on the liquid crystal cell is scattered by the internal members. On the other hand, conventionally, when polarized light is scattered, it was not thought that the polarization state is maintained. Therefore, the effect of the present invention that solves the reduction of the front CR due to scattering in the liquid crystal cell is effective on the Poincare sphere. What can be explained by the trajectory of polarization was unexpected.

In addition, reducing the phase difference region on the rear side of the liquid crystal cell having a COA structure contributes not only to the front-side CR but also to the contrast in the oblique direction (hereinafter sometimes referred to as “viewing angle CR”). To do. For example, even if a liquid crystal cell having a COA structure is employed, neither the front CR nor the viewing angle CR can be improved if the rear phase difference region has a high phase difference as in the prior art. That is, this viewing angle CR improvement effect of the present invention is also an effect brought about by reducing the light leakage that fluctuates due to the polarized light incident on the liquid crystal cell. By adopting a liquid crystal cell with a COA structure, the aperture ratio is increased. This effect cannot be obtained only by
Further, the effect of improving the viewing angle CR is distinguished by the front side phase difference region described later.
As with the front CR improvement effect, the viewing angle CR improvement effect of the present invention is also assumed to be on the Poincare sphere, assuming that the polarization state that is incident on the liquid crystal cell is substantially maintained after being scattered by the internal members. This can also be explained by the locus of polarization.

As a result of intensive studies by the present inventors, a rear side phase difference region (20 in FIG. 1) through which light passes before entering the liquid crystal cell having the COA structure is
In the first embodiment comprising one or two or more polymer films having optical anisotropy, the following formula (I)
(I): | Rth (550) | ≦ 140 nm
In addition, as another aspect, the rear side retardation region (20 in FIG. 1) is formed of a first film composed of one or more polymer films having optical anisotropy. In the second mode comprising the phase difference layer and the second phase difference layer in which the polar angle dependency of retardation has asymmetry centering on the normal direction (polar angle 0 °), the first phase difference layer is: Formula (II), the second retardation layer is represented by the following formula (III),
(II): | Rth (550) | ≦ 100 nm
(III): 1 <R2 [+ 40 °] / R2 [−40 °]
(However, R2 [+ 40 °]> R2 [−40 °])
Surprisingly, it has been found that the above problems can be solved by satisfying the above. In the first aspect, as long as the phase difference of the entire rear-side retardation region that passes before the light enters the liquid crystal cell LC having the COA structure satisfies the above formula (I), and in the second aspect, As long as the expressions (II) and (III) are satisfied, the light incident from the oblique direction is then scattered or diffracted by the array member 14 and the color filter layer 12 in the liquid crystal cell and travels in the normal direction. TN type using a liquid crystal cell with a non-COA structure without excessively increasing the light leakage in the front direction during black display even under the influence of fluctuations of liquid crystal molecules in the liquid crystal layer, Compared with an ECB type or OCB type liquid crystal display device, the front CR can be remarkably improved. The effect of the present invention is an effect that cannot be obtained only by adopting the COA structure and enlarging the aperture ratio. The COA structure is adopted, and the rear-side phase difference region in the first aspect has the above formula ( In the second embodiment, the effect obtained only by satisfying I) and satisfying the above formulas (II) and (III) is obtained.

Other members (for example, black matrix) not shown in FIG. 1 are the same as the color filter layer and the array member described above. That is, the member through which light passes before entering the liquid crystal layer is the same as the non-COA structure array member in the above table, and the member through which light passes after entering the liquid crystal layer has the non-COA structure color filter in the above table It becomes the same as a member.
As described above, the incident light polarization state dependence of light leakage at the time of black display due to the optical phenomenon in the color filter, black matrix, and array member shows the same tendency, but the contribution of the black matrix is relatively Since it is small, the position of the black matrix in the liquid crystal display device with the COA structure may be anywhere in the liquid crystal cell, but it is preferably located between the rear-side polarizer and the liquid crystal layer in order to obtain a high front CR.

Δn · d (λ) (Δnd (λ)), which is a product of the thickness d of the liquid crystal layer 10 and the birefringence index Δn at the wavelength λ, is generally 300 to 500 nm in the aspect of the TN liquid crystal display device. Preferably, it is about 380 to 450 nm. In general, in the TN type liquid crystal display device, the twist angle of the liquid crystal layer between the substrates is mainly 90 °, but various TN mode liquid crystal cells in which the twist angle is increased or decreased from 90 ° are also proposed. In the liquid crystal display device shown in FIG. 1, the twist angle of the liquid crystal layer 10 between the front and rear substrates 18 and 16 can be set to about 45 to 135 °.
As another embodiment, in the ECB type liquid crystal display device, the liquid crystal layer 10 is aligned with a twist angle of 45 ° or less between the front side and rear side substrates 18 and 16, and Δnd (λ) is about 250 to 350 nm (more Preferably, it is about 280-320 nm. In the OCB type liquid crystal display device, the liquid crystal layer 10 is bend-oriented between the front side and rear side substrates 18 and 16, and Δnd (λ) is about 500 to 1300 nm (more preferably about 800 to 1300 nm).

The liquid crystal layer 10 may be a multi-gap liquid crystal layer having different thicknesses between the RGB sub-pixel regions. For example, the thickness of the color filter is not uniform, and the thickness of the R subpixel, the G subpixel, and the B subpixel can be changed to form a multi-gap liquid crystal layer. As an example, Δnd (R) of the liquid crystal layer corresponding to the R subpixel, Δnd (G) of the liquid crystal layer corresponding to the G subpixel, and Δnd (B) of the liquid crystal layer corresponding to the B subpixel are Δnd (B ) <Δnd (G) <Δnd (R). According to this example, a color image with high contrast and color reproducibility can be displayed over a wide viewing angle.
On the other hand, as a liquid crystal material, Δn (λ) has a wavelength dependency, and Δn (R) for R light, Δn (G) for G light, and Δn (B) for B light satisfy Δn (B) <Δn ( G) By using a liquid crystal material that satisfies the relationship <Δn (R), the same effect can be obtained even if the thickness of the color filter is uniform.

  The liquid crystal display device shown in FIG. 1 is in a normally white mode, and the pair of front-side polarizer 26 and rear-side polarizer 24 are arranged with their absorption axes (not shown) substantially orthogonal to each other. ing. The front-side retardation region 22 and the rear-side retardation region 20 can be bonded to the front-side polarizer 26 and the rear-side polarizer 24, respectively, and used as a protective film. That is, in the said aspect, polarizing plate PL1 and PL2 in FIG. 1 can be manufactured, it can be bonded to liquid crystal cell LC, and a liquid crystal display device can be manufactured.

The liquid crystal display device shown in FIG. 1 has a rear-side retardation region composed of a first retardation layer composed of one or more optically anisotropic polymer films satisfying the above formula (I). 20 or a first retardation layer comprising one or more optically anisotropic polymer films satisfying the above formula (II) and a second retardation satisfying the above formula (III) It has a rear side retardation region composed of layers.
The rear side retardation region 20 in FIG. 1 may have a single-layer structure or a laminate composed of two or more layers. The aspect in which the rear side retardation region 20 has a single layer structure is the first aspect, that is, the single layer needs to satisfy the formula (I). The aspect of the laminate having two or more layers can be either the first aspect or the second aspect, and in the first aspect, the laminate needs to satisfy the formula (I) as a whole; In the embodiment, one or two layers constituting the laminate must satisfy the formula (II) as a whole, and other layers must satisfy the formula (III).
In order to obtain a higher front CR, the haze of the film disposed as the rear side retardation region 20 in FIG. 1 is preferably 0.5 or less, more preferably 0.3 or less, and 0.2 or less. Is more preferable. In addition, in this specification, the measuring method of the haze of a film is as follows. A film sample of 40 mm × 80 mm is prepared and measured according to JIS K-6714 with a haze meter (NDH-2000, manufactured by Nippon Denshoku Industries Co., Ltd.) in an environment of 25 ° C. and 60% RH.

In one example of the first and second aspects, the first retardation layer made of one or more optically anisotropic polymer films is represented by the following formula (IV):
(IV): 0 ≦ Re (550) ≦ 500 nm
Satisfied. Even if Re of the first retardation layer composed of one or two or more optically anisotropic polymer films is high, Rth of the first retardation layer is the above formula (I) in the first aspect. ) And in the second embodiment, the effect of the present invention can be obtained as long as the above formula (II) is satisfied.

The front side retardation region 22 in FIG. 1 may also have a single-layer structure or a laminate composed of two or more layers. It is preferable that the front side phase difference region 22 has a phase difference that contributes to the improvement of the viewing angle CR, since not only the effect of the present invention, that is, the improvement of the front CR, but also the viewing angle CR can be achieved. As described above, Δnd (λ) of the liquid crystal layer of the liquid crystal cell LC is generally about 300 to 500 nm for the TN type, about 250 to 350 nm for the ECB type, and about 500 to 1300 nm for the OCB type. However, the preferable range of retardation of the front side retardation region 22 varies depending on the retardation of the rear side retardation region 20, the value of Δnd (λ) of the liquid crystal layer, and the mode of the liquid crystal cell. In order to improve the oblique CR, various publications describe preferred combinations of the front side retardation region and the rear side retardation region with respect to Δnd (λ) of the liquid crystal layer.
In this respect, the front side retardation region 22 is composed of one or more optically anisotropic polymer films, and the following formulas (V) and (VI),
(V): 0 ≦ Re (550) ≦ 500 nm
(VI): −100 nm ≦ Rth (550) ≦ 1000 nm
It is preferable that the third retardation layer satisfies the above.
As another aspect, the front side retardation region 22 is made of one or more polymer films having optical anisotropy, and satisfies the above formulas (V) and (VI). The following formula (VII) where the polar angle dependence of retardation layer and retardation has asymmetry around the normal direction (polar angle 0 °),
(VII): 1 <R4 [+ 40 °] / R4 [−40 °]
(However, R4 [+ 40 °]> R4 [−40 °])
It is preferable that the fourth retardation layer is satisfied.
A third retardation layer composed of one or more optically anisotropic polymer films satisfying the above formulas (V) and (VI), or the above formula in addition to the third retardation layer By including the front side retardation region composed of the fourth retardation layer that satisfies (VII), the front side retardation region is used to suppress the decrease in contrast depending on the viewing angle. It is preferable because the viewing angle dependency of display characteristics such as contrast can be reduced and the viewing angle characteristics can be improved.
The fourth retardation layer is preferably a member having a large degree of asymmetry in the polar angle dependence of retardation, and the fourth retardation layer is
3 ≦ R4 [+ 40 °] / R4 [−40 °]
It is preferable to satisfy
5 ≦ R4 [+ 40 °] / R4 [−40 °]
Is more preferable.

As an aspect of the present invention, as described above,
A first aspect in which the rear side retardation region is composed of one or more optically anisotropic polymer films and satisfies the above formula (I); and the rear side retardation region is optically The first retardation layer consisting of one or more polymer films having anisotropy and satisfying the above formula (II), and the polar angle dependence of the retardation is in the normal direction (polar angle 0 °) A second embodiment comprising a second retardation layer having an asymmetric structure at the center and satisfying the above formula (III);
Is mentioned.
The first aspect includes an aspect in which the front side retardation region is composed only of the third retardation layer, and the front side retardation region is the third retardation layer and the fourth retardation layer. And the second mode includes a mode in which the front side phase difference region is composed only of the third phase difference layer, and a front side phase difference region is the third phase difference layer. And a mode comprising the fourth retardation layer.

The first retardation layer and the third retardation layer used in the present invention are composed of one or more optically uniaxial or biaxial polymer films, each having the above characteristics. Satisfied. The above characteristics can be achieved by, for example, one or more stretched or unstretched polymer films. By selecting a draw ratio and a polymer material, a uniaxial or biaxial polymer film satisfying the above characteristics can be produced with one sheet or two or more sheets.
The optical characteristics required for the second retardation layer and the fourth retardation layer used in the present invention are formed by bringing the curable liquid crystal composition into a desired alignment state and then curing it. This can also be achieved by a retardation layer. Specifically, a retardation layer formed by fixing the discotic liquid crystal composition in a so-called hybrid alignment state can be mentioned. A method for producing a retardation layer comprising a curable liquid crystal composition that can be used for the second retardation layer and the fourth retardation layer will be described later. Alternatively, the optical characteristics required for the second retardation layer and the fourth retardation layer are obtained by melt-extruding a positive intrinsic birefringent amorphous thermoplastic resin into a film, and then It can be achieved by a film formed by passing between rolls with different speeds. A method for producing this polymer film will also be described later.

A preferred aspect of the optical axis relationship of the liquid crystal display device will be described.
In the embodiment in which the liquid crystal display device shown in FIG. 1 is a TN type liquid crystal display device, the alignment treatment direction (usually the rubbing axis) of the alignment film formed on the facing surface of the front substrate 18 is the right and left of the screen of the liquid crystal display device. The orientation processing direction of the alignment film formed on the opposite surface of the rear substrate 16 is the direction of the screen of the liquid crystal display device. It is preferably in a direction rotated 45 ° clockwise as viewed from the observer side (upper side of the drawing) with respect to the left-right direction. When no voltage is applied, the liquid crystal molecules in the vicinity of the alignment film interface are aligned with the major axis direction aligned with the alignment treatment direction, and thus are substantially twist aligned with a twist angle of 90 °.

  The rear-side polarizer 24 is arranged with its absorption axis parallel to the alignment treatment direction of the alignment film formed on the opposing surface of the rear-side substrate 16 and is the rear-side retardation region 20 or one of them. It is preferable that the first retardation layer, which is a part, is arranged with its in-plane slow axis substantially orthogonal to the absorption axis of the rear polarizer 24. However, the same effect can be obtained even if the absorption axis of the rear polarizer 24 and the in-plane slow axis of the first retardation layer forming the rear retardation region 20 are substantially parallel. In the second mode in which the rear-side retardation region 20 includes the second retardation layer, the tilt direction of the main axis of the second retardation layer and the alignment film formed on the opposing surface of the rear-side substrate 16. It is preferable to arrange in parallel or orthogonal to the orientation treatment direction.

  The front-side polarizer 26 is disposed with its absorption axis parallel to the alignment treatment direction of the alignment film formed on the facing surface of the front-side substrate 18 and is the front-side retardation region 22 or The third retardation layer that is a part of the third retardation layer is preferably disposed with its in-plane slow axis substantially orthogonal to the absorption axis of the front polarizer 26. However, the same effect can be obtained even if the absorption axis of the front polarizer 26 and the in-plane slow axis of the third retardation layer forming the front retardation region 22 are substantially parallel. Moreover, in the aspect in which the front side retardation region 22 includes the fourth retardation layer, the tilt direction of the main axis of the fourth retardation layer and the orientation treatment of the orientation film formed on the facing surface of the front side substrate 18 are performed. The direction is preferably parallel or orthogonal. Arranging in this relationship is preferable because the viewing angle is enlarged.

In the aspect in which the rear-side retardation region 20 includes the second retardation layer, and the second retardation layer is a layer made of a curable liquid crystal composition, one or two sheets that are the first retardation layer Using the above polymer film as a support, the curable liquid crystal composition can be coated thereon to form a retardation layer that satisfies the optical properties required for the second retardation layer. A polarizing plate PL1 in which the produced laminate is bonded as a protective film to a polarizer (the rear-side polarizer 24 in FIG. 1) can also be incorporated into a liquid crystal display device.
Similarly, in an aspect in which the front side retardation region 22 includes a fourth retardation layer, and the fourth retardation layer is a layer made of a curable liquid crystal composition, one sheet that is the third retardation layer. Alternatively, two or more polymer films may be used as a support, and the curable liquid crystal composition may be applied thereon to form a retardation layer that satisfies the optical characteristics required for the fourth retardation layer. it can. A polarizing plate PL2 in which the produced laminate is bonded to a polarizer (front-side polarizer 26 in FIG. 1) as a protective film can be incorporated into a liquid crystal display device.

  In the embodiment in which the liquid crystal display device shown in FIG. 1 is an ECB type or OCB type liquid crystal display device, the directions of the alignment treatment applied to the inner surfaces of the front substrate 18 and the rear substrate 16 are parallel or antiparallel to each other. It is preferable that the liquid crystal layer 10 is not substantially crossed, that is, when the electric field is not applied, the liquid crystal layer 10 is not substantially twisted. In the ECB type aspect, the rubbing direction differs by 180 ° between the front side substrate 18 and the rear side substrate 16, and in the OCB type aspect, the front side substrate 18 and the rear side substrate 16 are the same. For example, in an aspect in which the liquid crystal cell LC is an ECB type, the liquid crystal layer 10 is aligned with a twist angle of 45 ° or less between the front side substrate 18 and the rear side substrate 16, and Δnd (λ) is as described above. Thus, it is about 250 to 350 nm (more preferably, about 280 to 320 nm). On the other hand, in the aspect in which the liquid crystal cell LC is an OCB type, the liquid crystal layer 10 is bend-aligned between the front side substrate 18 and the rear side substrate 16, and Δnd (λ) is about 500 to 1300 nm as described above (more preferably). Is about 800 to 1300 nm.

  In the ECB-type or OCB-type liquid crystal display device, the front-side polarizer 26 and the rear-side polarizer 24 are arranged with their absorption axes orthogonal to each other, and the liquid crystal cell is arranged with the absorption axes closer to each other. It is arranged at 45 ° with respect to the alignment treatment direction (generally the rubbing direction) applied to the inner surface of each of the substrates 18 and 16. In an embodiment in which the rear-side retardation region 20 includes the second retardation layer, the tilt direction of the main axis of the second retardation layer and the alignment treatment direction of the alignment film formed on the opposing surface of the rear-side substrate 16 Are preferably arranged parallel or orthogonal. Moreover, in the aspect in which the front side retardation region 22 includes the fourth retardation layer, the tilt direction of the main axis of the fourth retardation layer and the orientation treatment of the orientation film formed on the facing surface of the front side substrate 18 are performed. The direction is preferably parallel or orthogonal.

In the TN liquid crystal display device, Re (550) and Rth (550) of the third retardation layer which is the front-side retardation region or a part thereof are represented by the following formulas (Va) and (VIa),
(Va): 0 ≦ Re (550) ≦ 400 nm
(VIa): −100 nm ≦ Rth (550) ≦ 300 nm
It is preferable to satisfy In particular, in an embodiment in which the twist angle between the substrates of the TN liquid crystal cell LC is 90 °, Re (550) and Rth (550) of the third retardation layer are represented by the following formulas (Vb) and (VIb),
(Vb): 0 ≦ Re (550) ≦ 300 nm
(VIb): 50 nm ≦ Rth (550) ≦ 300 nm
Preferably satisfying the following formula:
0 nm ≦ Re (550) ≦ 200 nm
50 nm ≦ Rth (550) ≦ 250 nm
It is more preferable to satisfy the following formula:
100 nm ≦ Re (550) ≦ 150 nm
130 nm ≦ Rth (550) ≦ 150 nm
Is more preferable.
On the other hand, in an embodiment in which the twist angle between the substrates of the TN type liquid crystal cell LC is about 45 °, Re (550) and Rth (550) of the third retardation layer are expressed by the following formulas (Ve) and (VIe),
(Ve): 30 nm ≦ Re (550) ≦ 400 nm
(VIe): −100 nm ≦ Rth (550) ≦ 300 nm
It is preferable to satisfy
150 nm ≦ Re (550) ≦ 230 nm
40 nm ≦ Rth (550) ≦ 150 nm
It is more preferable to satisfy

In the ECB type liquid crystal display device in which the liquid crystal layer 10 of the liquid crystal cell LC is aligned in parallel with the substrate surface and with a twist angle of 0 ° to 45 ° between the substrates when no voltage is applied, the front side retardation region is provided. Alternatively, Re (550) and Rth (550) of the third retardation layer which is a part of the third retardation layer are represented by the following formulas (Vc) and (VIc)
(Vc): 70 nm <Re (550) ≦ 400 nm
(VIc): −100 nm ≦ Rth (550) ≦ 250 nm
It is preferable to satisfy the following formula: 150 nm ≦ Re (550) ≦ 200 nm
50 nm ≦ Rth (550) ≦ 100 nm
It is more preferable to satisfy

In the OCB mode in which the liquid crystal layer 10 of the liquid crystal cell LC is bend-aligned between the substrates parallel to the substrate surface when no voltage is applied, the third phase which is the front-side retardation region or a part thereof. Re (550) and Rth (550) of the retardation layer of the following formulas (Vd) and (VId):
(Vd): 0 ≦ Re (550) ≦ 100 nm
(VId): 200 nm ≦ Rth (550) ≦ 1000 nm
It is preferable to satisfy

In FIG. 1 again, “COA” of the COA structure of the liquid crystal cell LC in FIG. 1 is an abbreviation for color filter on array, and a structure in which a color filter is formed on an active matrix substrate is called a COA structure. . Initially, the COA structure was only for forming a color film on a normal TFT substrate, but recently, in order to improve display characteristics, a pixel electrode is formed on the upper side of the color film, and a small hole called a contact hole is formed. A structure in which the pixel electrode and the TFT are connected to each other is generally used. Any structure may be used in the present invention. In the COA structure, the thickness of the color filter layer is thicker than that of a conventional color film layer (about 1 to 2 μm), and generally about 2 to 4 μm. This is to suppress parasitic capacitance generated between the end of the pixel electrode and the wiring. The color filter layer of the liquid crystal display device of the present invention preferably has a thickness of about 2 to 4 μm, but is not limited to this range. Further, in manufacturing a liquid crystal cell having a COA structure, it is necessary to pattern the pixel electrode on the color filter layer, and resistance to an etching solution or a stripping solution is required. For this purpose, a color filter material (colored photosensitive composition) whose film thickness is adjusted to be thick is used, but a two-layer structure of color filter layer + overcoat layer formed of a normal color filter material may be used. Any configuration may be used in the present invention.
The COA structure is also described in JP-A-2007-240544, JP-A-2004-163979, etc. in addition to the above-mentioned Patent Documents 1 and 2, and any configuration is adopted in the present invention. Can do.

  Further, the color filter of the liquid crystal display device of the present invention has a plurality of different colors (for example, three primary colors of red, green, and blue light, transparent, Yellow, cyan, etc.). There are various preparation methods, for example, using a coloring material (organic pigment, dye, carbon black, etc.) to prepare a colored photosensitive composition (which may be colorless) called a color resist. In general, a layer is formed by coating on a substrate, and a pattern is formed by photolithography. There are also various methods for applying the colored photosensitive composition on the substrate. For example, the spin coater method is employed in the initial stage, and the slit & spin type coater method is employed from the viewpoint of liquid saving. The slit coater method is generally adopted. Other methods include roll coating, bar coating, and die coating. In recent years, after forming a pattern called a separation wall by photolithography, a pixel color is also formed by an inkjet method. In addition, methods using a combination of a colored non-photosensitive composition and a photosensitive positive resist, a printing method, an electrodeposition method, and a film transfer method are known. The color filter used in the present invention may be produced by any method.

  There are no particular restrictions on the material for forming the color filter. As the coloring material, any of dyes, organic pigments, inorganic pigments and the like can be used. Dyes have been studied because of the demand for higher contrast, but in recent years, organic pigment dispersion technology has advanced, and breakdown pigments that have been finely crushed by the salt milling method, finer pigments by the build-up method, etc. Used for contrast. Any coloring material may be used in the present invention.

  In FIG. 1, all or part of the rear-side retardation region 20 and the front-side retardation region 22 may function as protective films for the rear-side polarizer 24 and the front-side polarizer 26, respectively. Although omitted in FIG. 1, the rear polarizer 24 has a functional film such as a protective film, an antifouling film, an anti-reflection film, an anti-glare film, and an anti-static film on the surface on the backlight 28 side. Similarly, the front-side polarizer has a functional film such as a protective film, an antifouling film, an anti-reflection film, an anti-glare film, or an anti-static film on its display surface side surface. You may do it.

  The effect of improving the front contrast of the present invention may be further improved by adjusting the angle profile of the light emitted from the backlight. Specifically, when a backlight having a higher light collecting property is used, the absolute value of the front contrast is increased, so that the increase in the absolute value of the front CR shown in the present invention is also increased. The light collecting index is represented by, for example, a ratio I (0 °) / I (45 °) of the outgoing light intensity I (45 °) at a polar angle of 45 degrees with respect to the outgoing light intensity I (0 °) at the front. The larger the value, the stronger the light collection. As a backlight having a high light collecting property, it is desirable to provide a prism film (prism layer) having a light collecting function between the diffusion film and the liquid crystal panel. This prism film collects the light emitted from the light exit surface of the light guide plate and diffused by the diffusion film with high efficiency on the effective display area of the liquid crystal panel. A liquid crystal display device equipped with a general direct type backlight has, for example, a color filter sandwiched between a transparent substrate and a polarizing plate at the top, a liquid crystal panel composed of a liquid crystal layer, and a backlight on the lower surface side. It has been. A brightness enhancement film (Brightness Enhancement Film: BEF), which is a registered trademark of 3M USA, is a representative example. BEF is a film in which unit prisms having a triangular cross section are periodically arranged in one direction on a film substrate, and the prism has a size (pitch) larger than the wavelength of light. The BEF collects light from “off-axis” and directs this light to the viewer “on-axis” or “recycle”. To do. Patent documents that disclose that a luminance control member having a repetitive array structure of prisms represented by BEF is adopted for a display include Japanese Patent Publication No. 1-37801, Japanese Patent Laid-Open No. Hei 6-102506, and Special Tables. Many examples are known as exemplified in Japanese Patent Laid-Open No. 10-506500.

  It is also desirable to use a lens array sheet in order to improve the light collecting property. The lens array sheet has a lens surface in which a plurality of unit lenses formed in a convex shape at a predetermined pitch are two-dimensionally arranged. A lens array sheet in which the opposite side of the lens surface is a flat surface and a light reflecting layer for reflecting light rays on the non-light-condensing surface region of the lens is formed on the flat surface is preferable. Further, a lenticular lens surface in which a plurality of convex cylindrical lenses formed at a predetermined pitch are arranged in parallel, and a side opposite to the lens surface is a flat surface, and the convex surface has the convex surface. A lens array sheet in which a light reflecting layer for reflecting light beams in the longitudinal direction is formed on the non-light-condensing surface region of the cylindrical lens is also preferable. Further, for example, a lenticular lens array sheet in which unit lenses composed of cylindrical curved surfaces are arranged in one plane in a plane, or a dome-shaped curved surface having a bottom surface shape such as a circle, a rectangle, or a hexagon. A lens array sheet in which unit lenses are two-dimensionally arranged in a plane can also be used. Regarding these lens array sheets, JP-A-10-241434, JP-A-2001-201611, JP-A-2007-256575, JP-A-2006-106197, JP-A-2006-208930, JP-A-2007-213035, And can be referred to in JP-A 2007-41172.

  The present invention is also effective in a display mode in which the color reproduction range is widened by adjusting the emission light spectrum of the backlight and the transmission spectrum of the color filter. Specifically, it is desirable to use a white backlight in which a red LED, a green LED, and a blue LED are mixed and mixed as the backlight. Moreover, it is preferable that the half value width of the emitted light peak of red LED, green LED, and blue LED is small. In the case of LED, the half-value wavelength width is as small as about 20 nm as compared with CCFL, and the peak wavelength is R (red) is 610 nm or more, G (green) is 530 nm, and B (blue) is 480 nm or less. The color purity of the light source itself can be increased.

  Further, it has been reported that the color reproducibility is further improved by suppressing the spectral transmittance of the color filter as small as possible except for the peak wavelength of the LED, and the NTSC ratio is 100%. For example, there is description in JP-A-2004-78102. The red color filter desirably has a small transmittance at the peak positions of the green LED and the blue LED, the green color filter desirably has a small transmittance at the peak position of the blue LED and the red LED, and the blue color filter has a red color. It is desirable that the transmittance at the peak position of the LED and the green LED is small. Specifically, both of these transmittances are desirably 0.1 or less, more preferably 0.03 or less, and still more preferably 0.01 or less. The relationship between the backlight and the color filter is described in, for example, Japanese Patent Application Laid-Open No. 2009-192661, and can be referred to.

  It is also preferable to use a laser light source for the backlight in order to widen the color reproduction range. The peak wavelengths of the red, green, and blue laser light sources are preferably 430 to 480 nm, 520 to 550 nm, and 620 to 660 nm, respectively. The backlight of the laser light source is described in JP2009-14892A, and can be referred to.

Hereinafter, various members used in the TN type, ECB type, or OCB type liquid crystal display device of the present invention will be described in detail.
1. Rear side phase difference region and front side phase difference region In the present invention, one or two or more layers disposed between a rear side polarizer and a color filter layer in a TN type, ECB type, or OCB type liquid crystal cell. The entire phase difference layer is referred to as a “rear phase difference region”. In the first aspect, the rear-side retardation region is composed of a first retardation layer made of one or more optically anisotropic polymer films. The phase difference layer satisfies the above formula (I). In the second aspect, the rear side retardation region has polar retardation dependence on the first retardation layer made of one or more optically anisotropic polymer films. A second retardation layer having asymmetry about the normal direction (polar angle 0 °), and in this embodiment, the first retardation layer satisfies the above formula (II), and the second retardation layer The phase difference layer satisfies the above formula (III). It is preferable that the above formula (IV) is further satisfied.

In the first aspect, the first retardation layer preferably satisfies the above formulas (I) and (IV), more preferably,
0 nm ≦ Re (550) ≦ 300 nm and | Rth (550) | ≦ 140 nm
More preferably,
0 nm ≦ Re (550) ≦ 200 nm and | Rth (550) | ≦ 120 nm
More preferably, the following formula:
0 nm ≦ Re (550) ≦ 120 nm and | Rth (550) | ≦ 105 nm
Satisfied.

In the second aspect, in the rear side retardation region, the first retardation layer preferably satisfies the above formulas (II) and (IV), more preferably,
0 nm ≦ Re (550) ≦ 300 nm and 20 nm <Rth (550) ≦ 100 nm
More preferably,
0 nm ≦ Re (550) ≦ 200 nm and 30 nm ≦ Rth (550) ≦ 95 nm
More preferably, the following formula:
0 nm ≦ Re (550) ≦ 120 nm and 40 nm ≦ Rth (550) ≦ 90 nm
Satisfied.

In the present invention, the entire retardation layer of one layer or two or more layers disposed between the front side polarizer and the liquid crystal layer in the TN type, ECB type, or OCB type liquid crystal cell is referred to as “front side position”. It is called “phase difference region”. The front side phase difference region preferably has a phase difference that contributes to the improvement of the viewing angle CR in relation to the whole and the phase difference of the rear side phase difference region.
Specifically, in the aspect in which the front side retardation region is composed of a third retardation layer composed of one or more optically anisotropic polymer films, from the viewpoint of viewing angle compensation, It is preferable that the formulas (V) and (VI) are satisfied. In another aspect, the front side retardation region has a third retardation layer, and a retardation whose polar angle dependence is asymmetric with respect to the normal direction (polar angle 0 °). From the viewpoint of viewing angle compensation, it is preferable that the third retardation layer satisfies the above formulas (V) and (VI) and the fourth retardation layer satisfies the above formula (VII). In the TN type liquid crystal display device, the third retardation layer constituting the front side retardation region preferably satisfies the above formulas (Va) and (VIa). In particular, in the aspect where the twist angle is about 90 °, It is preferable that the formulas (Vb) and (VIb) are satisfied, and it is preferable that the above formulas (Ve) and (VIe) are satisfied, particularly in an embodiment having a twist angle of about 45 °. The ECB type liquid crystal display device preferably satisfies the above formulas (Vc) and (VIc), and the OCB type liquid crystal display device preferably satisfies the above formulas (Vd) and (VId).

1-1. The first retardation layer in the rear side retardation region and the third retardation layer in the front side retardation region:
In the present invention, the material of each layer constituting the first retardation layer in the rear side retardation region and the third retardation layer in the front side retardation region is not particularly limited. The first retardation layer satisfying the formula (I) or (II) and (IV), or the third retardation layer satisfying the formulas (V) and (VI) is one sheet or two or more sheets. A biaxial film can be used, or a combination of two or more uniaxial films, such as a combination of a C plate and an A plate. Of course, it can also be configured by combining one or more biaxial films and one or more uniaxial films. From the viewpoint of cost reduction, it is preferable that one of the rear-side retardation region and the front-side retardation region is constituted by one film, and more preferably both are constituted by one film.

In any of the above aspects, the wavelength dispersion of the in-plane retardation Re of the first retardation layer in the rear-side retardation region and the third retardation layer in the front-side retardation region is in the visible light region. It is preferable to exhibit the so-called reverse dispersion property that the wavelength increases as the wavelength increases. That is, it is preferable to satisfy Re (450) <Re (550) <Re (650). The reason for this is that if the Re in the phase difference region is inverse wavelength dispersive, the optical wavelength is optimized at the center wavelength of about 550 nm in the visible light region, and there is a tendency to be optimized over the entire visible light region. Most preferably, Re is reversely dispersible, and it is also preferred that it be constant regardless of wavelength. The same applies to Rth in the rear-side retardation region, and it is preferable that Rth exhibits reverse wavelength dispersion or is constant regardless of the wavelength in the visible light region. More preferred is reverse wavelength dispersion. The reverse wavelength dispersion or constant regardless of the wavelength is, for example, the following two formulas for Rth:
(Rth (450) (/ (Rth (550) (≦ 1, and 1 ≦ (Rth (650) (/ (Rth (550) (
Is equivalent to satisfying

In order to obtain a higher front CR, the haze of the retardation film constituting the rear side and front side retardation regions is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.2 or less. .
In addition, in this specification, the measuring method of the haze of retardation film is as follows. A retardation film sample of 40 mm × 80 mm is prepared and measured according to JIS K-6714 with a haze meter (NDH-2000, manufactured by Nippon Denshoku Industries Co., Ltd.) in an environment of 25 ° C. and 60% RH.

  There are no particular restrictions on the materials constituting the first retardation layer in the rear-side retardation region and the third retardation layer in the front-side retardation region. Various polymer films such as cellulose acylate, polycarbonate polymer, polyester polymer such as polyethylene terephthalate and polyethylene naphthalate, acrylic polymer such as polymethyl methacrylate, polystyrene, acrylonitrile / styrene copolymer (AS resin), etc. Styrene polymers and the like can be used. Polyolefins such as polyethylene and polypropylene, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers, polyethersulfone polymers , Polyether ether ketone polymer, polyphenylene sulfide polymer, vinylidene chloride polymer, vinyl alcohol polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or polymer mixed with the above polymers, etc. One or two or more polymers are selected from the above, and a polymer film is produced using the polymer as a main component, and the first retardation layer in the rear side retardation region, and a combination satisfying the above characteristics, and And the third retardation layer in the front side retardation region can be used.

As a retardation film satisfying the above formulas (I) or (II) and (IV), or a retardation film satisfying the above formulas (V) and (VI) as a single layer or as a plurality of layers as a whole, cellulose An acylate film, an acrylic polymer film, and a cyclic olefin polymer film are preferred.
Cellulose acylate film:
In the present specification, the “cellulose acylate film” refers to a film containing cellulose acylate as a main component (50% by mass or more of all components). The cellulose acylate used for producing the film is obtained by substituting the hydrogen atom of the hydroxyl group of cellulose with an acyl group. The cellulose acylate is obtained by acylating a hydroxyl group of cellulose, and the substituent can be any from an acetyl group having 2 carbon atoms to an acyl group having 22 carbon atoms. In the cellulose acylate used in the present invention, the degree of substitution with a hydroxyl group of cellulose is not particularly limited, but the degree of binding of acetic acid and / or a fatty acid having 3 to 22 carbon atoms to be substituted with a hydroxyl group of cellulose is measured, The degree of substitution can be obtained by calculation. As a measuring method, it can carry out according to ASTM D-817-91.

Although the substitution degree of the cellulose acylate is not particularly limited, it is desirable that the acyl substitution degree of the cellulose is 2.30 to 3.00. Moreover, in order to obtain a retardation film having a low haze, the acyl substitution degree is preferably low, and the acyl substitution degree is preferably 2.30 to 2.65, and preferably 2.35 to 2.60. Is more preferable, and it is still more preferable that it is 2.40-2.60. On the other hand, in order for the retardation film to exhibit reverse wavelength dispersion, it is preferable that the acyl substitution degree is high, and specifically, it is preferably 2.65 to 3.00, and 2.75 to 3.00. More preferably, it is more preferably 2.80 to 3.00.
The cellulose acylate is preferably cellulose acetate, but may be substituted with an acyl group other than the acetyl group instead of or together with the acetyl group. Among these, cellulose acylate having at least one acyl group selected from acetyl, propionyl and butyryl groups is preferable, and cellulose acylate having at least two acyl groups selected from acetyl, propionyl and butyryl groups is more preferable. Further, a cellulose acylate having an acetyl group and a propionyl and / or butyryl group is preferable, the substitution degree of the acetyl group is 1.0 to 2.97, and the substitution degree of the propionyl and / or butyryl group is 0.2 to A cellulose acylate of 2.5 is more preferred.

  The cellulose acylate preferably has a mass average degree of polymerization of 200 to 800, more preferably 250 to 550. The cellulose acylate used in the present invention preferably has a number average molecular weight of 70000 to 230,000, more preferably 75000 to 230,000, and more preferably 78000 to 120,000. Further preferred.

  Examples of cellulose acylate that can be used for film production include cellulose acylate described in detail in JP-A-2006-184640, [0019] to [0025].

  The cellulose acylate film is preferably produced by a solution casting method. In this method, a film can be produced using a solution (dope) obtained by dissolving cellulose acylate in an organic solvent. When using the said additive, you may add an additive at any timing of dope preparation.

A retardation developer may be used for the production of the first retardation layer in the rear retardation region and the third retardation layer in the front retardation region. Examples of the retardation developing agent that can be used include a discotic compound, a rod-shaped compound, and a positive birefringent compound. As the discotic compound or rod, a compound having at least two aromatic rings can be preferably used as a retardation developer. The addition amount of the retardation developer composed of the rod-shaped compound is preferably 0.1 to 30 parts by mass, and 0.5 to 20 parts by mass with respect to 100 parts by mass of the polymer component containing cellulose acylate. Is more preferable. The discotic retardation enhancer is preferably used in a range of 0.05 to 20 parts by mass, and in a range of 0.1 to 15 parts by mass, with respect to 100 parts by mass of the cellulose acylate resin. It is more preferable to use in the range of 0.1 to 10 parts by mass.
Since the discotic compound is superior to the rod-like compound in Rth retardation expression, it is preferably used when a particularly large Rth retardation is required. Two or more retardation developers may be used in combination.
The retardation developer preferably has a maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.

Examples of the retardation developer include the following compounds (1) to (3).
(1) Discotic compound The discotic compound will be described. As the discotic compound, a compound having at least two aromatic rings can be used.
In the present specification, the “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring. Examples of the discotic compound that can be used in the present invention include compounds described in JP-A 2008-181105, [0038] to [0046].

  Examples of the discotic compound include compounds represented by the following general formula (I).

In the formula, X ¹ is a single bond, —NR ⁴ —, —O— or S—; X ² is a single bond, —NR ⁵ —, —O— or S—; X ³ is a single bond A bond, —NR ⁶ —, —O— or S—. R ¹ , R ² , and R ³ are each independently an alkyl group, an alkenyl group, an aromatic ring group, or a heterocyclic group; R ⁴ , R ^5, and R ⁶ are each independently a hydrogen atom , An alkyl group, an alkenyl group, an aryl group or a heterocyclic group.

  Preferred examples (I- (1) to IV- (10)) of the compounds represented by the general formula (I) are shown below, but the present invention is not limited to these specific examples.

(2) Rod-shaped compound In the present invention, a rod-shaped compound having a linear molecular structure can be preferably used in addition to the aforementioned disk-shaped compound. Examples of the rod-like compound that can be used in the present invention include compounds described in [0053] to [0095] of JP-A-2007-268898.

(3) Positive birefringent compound A positive birefringent compound is a compound in which light is incident on a layer formed by uniaxial orientation of molecules, and the refractive index of light in the orientation direction is the orientation direction. A polymer that is larger than the refractive index of light in a direction orthogonal to the.
Such a positive birefringent compound is not particularly limited, and examples thereof include polymers having a positive intrinsic birefringence value such as polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide. Ketones and polyester polymers are preferred, and polyester polymers are more preferred.

  The polyester polymer includes a mixture of an aliphatic dicarboxylic acid having 2 to 20 carbon atoms and an aromatic dicarboxylic acid having 8 to 20 carbon atoms, an aliphatic diol having 2 to 12 carbon atoms, and an alkyl ether diol having 4 to 20 carbon atoms. And at least one kind of diol selected from aromatic diols having 6 to 20 carbon atoms, and both ends of the reaction product may remain as the reaction product. Alcohols or phenols may be reacted to perform so-called end sealing. It is effective in terms of storage stability that the end capping is performed in particular so as not to contain free carboxylic acids. The dicarboxylic acid used in the polyester polymer of the present invention is preferably an aliphatic dicarboxylic acid residue having 4 to 20 carbon atoms or an aromatic dicarboxylic acid residue having 8 to 20 carbon atoms.

Examples of the aliphatic dicarboxylic acid having 2 to 20 carbon atoms preferably used include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. , Dodecanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid.
Examples of the aromatic dicarboxylic acid having 8 to 20 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,8 -Naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid.

  Among these, preferable aliphatic dicarboxylic acids are malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, and 1,4-cyclohexanedicarboxylic acid, and aromatic dicarboxylic acid is phthalic acid. Acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid. Particularly preferably, the aliphatic dicarboxylic acid component is succinic acid, glutaric acid, and adipic acid, and the aromatic dicarboxylic acid is phthalic acid, terephthalic acid, and isophthalic acid.

  Although at least one of each of the aforementioned aliphatic dicarboxylic acids and aromatic dicarboxylic acids is used in combination, the combination is not particularly limited, and there is no problem even if several types of each component are combined.

  Examples of the diol or aromatic ring-containing diol used in the positive birefringent compound include an aliphatic diol having 2 to 20 carbon atoms, an alkyl ether diol having 4 to 20 carbon atoms, and an aromatic having 6 to 20 carbon atoms. It is selected from ring-containing diols.

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

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

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

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

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

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

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

The positive birefringent compound may be synthesized by a hot melt condensation method using a polyesterification reaction or a transesterification reaction between the dicarboxylic acid and a diol and / or a monocarboxylic acid or monoalcohol for end-capping, according to a conventional method. Alternatively, it can be easily synthesized by any of the interfacial condensation methods of acid chlorides of these acids and glycols. These polyester-based additives are described in detail in Koichi Murai, “Additives, Theory and Application” (Kokaibo Co., Ltd., first edition published on March 1, 1973). In addition, Japanese Patent Laid-Open Nos. 05-155809, 05-155810, Japanese Patent Laid-Open Nos. 05-97073, 2006-259494, 07-330670, 2006-342227, 2007-003679. The materials described in each publication can also be used.
Specific examples of the positive birefringent compound are described below, but the positive birefringent compound that can be used in the present invention is not limited thereto.

  In Tables 2 and 3, PA is phthalic acid, TPA is terephthalic acid, IPA is isophthalic acid, AA is adipic acid, SA is succinic acid, 2,6-NPA is 2,6-naphthalenedicarboxylic acid 2,8-NPA is 2,8-naphthalenedicarboxylic acid, 1,5-NPA is 1,5-naphthalenedicarboxylic acid, 1,4-NPA is 1,4-naphthalenedicarboxylic acid, 1,8 -NPA represents 1,8-naphthalenedicarboxylic acid, respectively.

  The addition amount of the positive birefringent compound is preferably 1 to 30 parts by mass, more preferably 4 to 25 parts by mass with respect to 100 parts by mass of the cellulose acylate resin. It is especially preferable that it is -20 mass parts.

  The cellulose acylate film for the first retardation layer in the rear-side retardation region and the third retardation layer in the front-side retardation region may be used together with or in place of the retardation developer. These additives may be added. Examples of other additives include an antioxidant, an ultraviolet absorber, a peeling accelerator, a plasticizer, a wavelength dispersion adjusting agent, fine particles, and an optical property adjusting agent, all of which are known additives. it can.

  The cellulose acylate film for the first retardation layer in the rear-side retardation region and the third retardation layer in the front-side retardation region is used for improving the mechanical properties of the film obtained, or A plasticizer can be added to improve the drying rate. Examples of the plasticizer that can be used in the present invention include compounds described in JP-A-2008-181105, [0067].

Acrylic polymer film:
The acrylic polymer film is a film mainly composed of an acrylic polymer having a repeating unit derived from at least one of (meth) acrylic acid esters. A preferable example of the acrylic polymer film is an acrylic polymer containing at least one unit selected from a lactone ring unit, a maleic anhydride unit, and a glutaric anhydride unit together with a repeating unit derived from a (meth) acrylic ester. Based polymer. The acrylic polymer is described in detail in Japanese Patent Application Laid-Open No. 2008-9378 and can be referred to.

  In addition, when a cellulose polymer is added to the acrylic polymer film as a polymer other than the acrylic polymer, the physical properties of the acrylic and the cellulose act in a complementary manner, resulting in a material having desired characteristics. preferable. The addition amount of the cellulose polymer is preferably about 5 to 40% by mass (ratio to the whole polymer). For example, an acrylic polymer film has low moisture permeability, so that residual moisture after polarizing plate processing is difficult to escape, but by adding a cellulose polymer, appropriate moisture permeability can be given. As a specific example, a film to which 10% by mass of cellulose acylate (CTA described in Table 4) is added and a film to which 30% by mass of cellulose acylate propionate (CAP482-20 (manufactured by Eastman Chemical Co.)) are added Is mentioned.

Cyclic olefin polymer film:
The raw material of the cyclic olefin-based polymer film, the production method thereof, and the production method of the film using the raw material are described in detail in [0098] to [0193] of JP-A-2006-293342. You can refer to it. Examples of cyclic olefin-based polymer films that can be used as the retardation film constituting the first retardation layer in the rear-side retardation region and the third retardation layer in the front-side retardation region include a norbornene-based polymer film In the case of commercially available polymers, Arton (manufactured by JSR), ZEONOR (manufactured by Nippon Zeon) and the like can be used.

  Various polymer films used as retardation films for the first retardation layer in the rear retardation region and the third retardation layer in the front retardation region can be produced by various methods. Examples thereof include a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Of these film forming methods, the solution casting method (solution casting method) and the melt extrusion method are particularly preferable. In addition, various polymer films used as a retardation film for the first retardation layer in the rear retardation region and the third retardation layer in the front retardation region are formed and then stretched. It may be a film manufactured through the process. The film may be stretched uniaxially or biaxially. It is preferable to perform biaxial stretching treatment simultaneously or sequentially. In order to achieve a large optical anisotropy, it is necessary to stretch the film at a high stretch ratio. For example, the film is preferably stretched in the width direction of the film and in the longitudinal direction (flow direction) of the film. The draw ratio is preferably about 3 to 100%. The stretching process can be performed using a tenter. Further, longitudinal stretching may be performed between the rolls.

  In addition, the first retardation layer in the rear side retardation region and the third retardation layer in the front side retardation region are formed by setting the liquid crystal composition in a desired alignment state and then fixing the alignment state. The laminated body which has the polymer film which supports the said layer with the said layer may be sufficient. In the latter embodiment, the polymer film can be used as a protective film for a polarizer. Examples of liquid crystals that can be used to fabricate the first retardation layer in the rear-side retardation region and the third retardation layer in the front-side retardation region include various materials such as a rod-like liquid crystal, a disk-like liquid crystal, and a cholesteric liquid crystal. The liquid crystal is included.

As the solution casting method, a lamination casting method such as a co-casting method, a sequential casting method, and a coating method can also be used. When manufacturing by the co-casting method and the sequential casting method, first, a cellulose acetate solution (dope) for each layer is prepared. In the co-casting method (multi-layer simultaneous casting), the dope for casting of each layer (which may be three layers or more) is simultaneously pressed from another slit or the like on a casting support (band or drum). This is a casting method in which the dope is extruded from the casting gies to be cast, and each layer is cast at the same time, peeled off from the support at an appropriate time, and dried to form a film.
In the sequential casting method, the casting dope for the first layer is first extruded from the casting giusa on the casting support, cast, and dried on the second layer without drying or drying. Extrude the casting dope for casting from the casting gieser, cast the dope sequentially to the third layer or more, if necessary, peel it off from the support at an appropriate time, and dry it. This is a casting method for forming a film.
In general, the core layer film is formed into a film by a solution casting method to prepare a coating solution to be applied to the surface layer, and then applied to the film one side at a time or both sides simultaneously using an appropriate applicator. This is a method of forming a film having a laminated structure by applying and drying a liquid.

  The thickness of the first retardation layer in the rear side retardation region and the third retardation layer in the front side retardation region is preferably 20 μm or more and 200 μm or less from the viewpoint of manufacturing suitability.

1-2. The second retardation layer in the rear side retardation region and the fourth retardation layer in the front side retardation region:
In the present invention, the second retardation layer and the fourth retardation layer satisfy the optical characteristics of the above formulas (III) and (VII), respectively, that is, at least one incident surface including the normal of the layer surface. It is a phase difference layer in which the polar angle dependency of retardation with respect to incident light has an asymmetry around the normal direction (polar angle 0 °). Furthermore, it is preferable that the retardation layer satisfy all of the following optical properties (1) to (3). The preferred optical characteristics of the second and fourth retardation layers are substantially the same for the TN, ECB, and OCB mode liquid crystal display devices described above.
(1) In-plane retardation Re (550) at a wavelength of 550 nm is 20 nm to 120 nm (more preferably, Re (550) is 25 to 50 nm);
(2) R [40 °] having a wavelength of 550 nm measured from a direction tilted by 40 ° from the normal to the tilt azimuth side in a plane including the tilt azimuth and normal of the second and fourth retardation layers. 0 nm to 300 nm (more preferably 0 to 190 nm); and (3) 40 ° from the normal to the tilt azimuth side in the plane including the tilt azimuth and normal of the second and fourth retardation layers. Measured from a tilted direction (incident direction 1), a retardation R [+ 40 °] with a wavelength of 550 nm, and a direction tilted 40 ° to the opposite side of the tilt direction with respect to the normal (incident direction 2). R [−40 °] is represented by the following formula (III) in the second retardation layer constituting the rear-side retardation region.
1 <R2 [+ 40 °] / R2 [−40 °] (III)
And the fourth retardation layer constituting the front side retardation region satisfies the following formula (VII)
1 <R4 [+ 40 °] / R4 [−40 °] (VII)
Is preferable.
As for the characteristic (2), R [40 °] means both R [+ 40 °] and R [−40 °], and R [40 °] is 0 nm to 300 nm. , R [+ 40 °] and R [−40 °] both are in the range of 0-300 nm.
Note that the polar angle dependence of retardation has asymmetry about the normal direction (polar angle 0 °) with respect to incident light on at least one incident surface including the normal of the layer surface. As long as it is not used in combination with the first and third retardation layers whose optical characteristics do not satisfy the formulas (I) or (II) and (IV) even if the retardation layer of TN, ECB and OCB are used, Even if it is used for optical compensation of any type of liquid crystal display device, the remarkable front contrast improvement effect of the present invention cannot be obtained.

  An example of the second and fourth retardation layers is a retardation layer formed by fixing discotic liquid crystal molecules in a so-called hybrid alignment state. When the hybrid orientation of discotic liquid crystal molecules is used, second and fourth retardation layers having R [+ 40 °] / R [−40 °] of about 5 to 20 (more preferably about 8 to 15) are obtained. It is done. In the hybrid alignment, the angle between the major axis (disk surface) of the discotic liquid crystalline molecule and the layer surface increases or decreases in the depth direction of the layer and with an increase in the distance from the alignment film surface. The angle preferably decreases with increasing distance. Further, the change in angle can be a continuous increase, a continuous decrease, an intermittent increase, an intermittent decrease, a change including a continuous increase and a continuous decrease, or an intermittent change including an increase and a decrease. The intermittent change includes a region where the angle does not change in the middle of the thickness direction. In the present specification, “hybrid orientation” includes an orientation state in which the angle does not change, or the orientation state increases or decreases as a whole. Hybrid orientation in which the angle continuously changes is preferable.

  Examples of discotic liquid crystal compounds that can be used for the production of the second and fourth retardation layers include C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), azacrown type and phenylacetylene type macrocycles are included.

  As a molecule of the discotic liquid crystal compound, it exhibits liquid crystallinity in which a linear alkyl group, an alkoxy group, and a substituted benzoyloxy group are radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule. Also included are compounds. The molecule or the assembly of molecules is preferably a compound having rotational symmetry and imparting a certain orientation. A retardation layer formed from a composition containing a discotic liquid crystal compound does not need to exhibit liquid crystallinity when finally contained in the retardation layer. For example, if a low molecular weight discotic liquid crystalline molecule having a group that reacts with heat or light is polymerized by heating or light irradiation to increase the molecular weight, the liquid crystallinity is lost. Of course, a retardation layer containing can also be used in the present invention. Preferable examples of the discotic liquid crystal compound include compounds described in JP-A-8-50206. The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284.

  In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. A compound in which the discotic core and the polymerizable group are bonded via a linking group is preferable, whereby the orientation state can be maintained even in the polymerization reaction. Examples thereof include compounds described in paragraphs [0151] to “0168” in JP-A No. 2000-155216.

In forming the second and fourth retardation layers, additives such as a plasticizer, a surfactant, and a polymerizable monomer may be used in combination with the liquid crystal compound. These additives will be added for various purposes such as improving the uniformity of the coating film, the strength of the film, the orientation of the liquid crystal molecules, and the like.
Examples of the polymerizable monomer include radically polymerizable or cationically polymerizable compounds. Preferably, it is a polyfunctional radically polymerizable monomer and is preferably copolymerizable with the above-described polymerizable group-containing liquid crystal compound. Examples thereof include those described in paragraph numbers [0018] to [0020] in JP-A No. 2002-296423. The amount of the compound added is generally in the range of 1 to 50% by mass and preferably in the range of 5 to 30% by mass with respect to the liquid crystal compound.
Examples of the surfactant include conventionally known compounds, and fluorine compounds are particularly preferable. Specific examples include compounds described in paragraph numbers [0028] to [0056] in JP-A-2001-330725.
Examples of polymers that can be used include cellulose esters. Preferable examples of the cellulose ester include those described in paragraph [0178] of JP-A No. 2000-155216. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass, and in the range of 0.1 to 8% by mass with respect to the liquid crystal molecule so as not to inhibit the alignment of the liquid crystal molecules. It is more preferable.
The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline molecules is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

The second and fourth retardation layers are prepared by applying a coating liquid containing a liquid crystalline compound and, if necessary, a polymerization initiator or an optional additive described later on the surface of the support (preferably on the support surface). An alignment film can be formed and applied to the surface of the alignment film. As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.
Application | coating of a coating liquid can be implemented by a conventionally well-known method, and the thing of the content as described in the said oriented film is mentioned.
The thickness of the second and fourth retardation layers is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and still more preferably 1 to 10 μm.

The aligned liquid crystal molecules can be fixed while maintaining the alignment state. The alignment state is preferably fixed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred.
Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).

The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.
It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules.
The irradiation energy is preferably in the range of ^{20mJ / cm 2 ~50J / cm 2} , more preferably in the range of 20~5000mJ / cm ^2, more preferably in the range of 100 to 800 mJ / cm ² . In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.

  The major axis (disk surface) direction of the liquid crystal molecules on the surface side (air side) in the second and fourth retardation layers is generally the additive used together with the liquid crystal molecules used for forming the retardation layer (for example, , Plasticizers, surfactants, polymerizable monomers, polymers, etc.). The degree of change in the orientation direction of the major axis can also be adjusted by selecting liquid crystalline molecules and additives as described above.

  Another example of the second and fourth retardation layers is a film whose principal axis is inclined in the thickness direction. Here, the “main axis” of the film means the main refractive index nz of the refractive index ellipsoid calculated by KOBRA 21ADH or WR, and the main refractive index nz in the film thickness direction at nx, ny, and nz. Further, “inclined in the thickness direction” means an angle θt ° (provided that 0 ° <θt < 90 ° is satisfied, which means that θt is inclined by “inclination angle”). The retardation layer preferably has an inclination angle of 47 ° or less and a R [+ 40 °] / R [−40 °] of 5 or more with respect to the normal direction of the film surface (more preferably an inclination angle of 9 to 47 °). R [+ 40 °] / R [−40 °] is 8 or more, and more preferably, the inclination angle is 20 to 47 ° and R [+ 40 °] / R [−40 °] is in the range of 8 to 15. And a layer made of a polymer film or a liquid crystal composition having a main axis in the direction of In any of the TN, ECB, and OCB modes, the inclination angle θt is more preferably 47 ° or less, further preferably 9 to 47 °, and more preferably 20 to 47 °. Further preferred.

In addition, the inclination angle with respect to the film surface of the main axis of the film can be measured by the following method. In addition, the tolerance | permissible_error in the following measuring methods will be accept | permitted also about the inclination-angle of the main axis | shaft of the film used for this invention.
The tilt angle of the main axis of the film is measured using KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments) with the width direction (TD direction) of the film as the tilt axis, and the phase difference at the tilt angle of 40 degrees and The tilt angle of the main axis is measured from the phase difference at the tilt angle of -40 degrees. The measurement wavelength is 550 nm.
Further, the variation in the inclination angle of the main shaft can be measured by the following method.
Sampling is performed at 10 points in the width direction of the film and 10 points in the transport direction at equal intervals, and the tilt angle of the main shaft is measured by the above method, and the difference between the maximum value and the minimum value is defined as the variation in the tilt angle of the main shaft. be able to.
The slow axis angle can be determined by the above-described measurement of Re, and the variation is also the maximum value when measurement is performed at equal intervals of 10 points in the width direction of the film and 10 points in the transport direction. It can be determined by the difference between the minimum values.

The second and fourth retardation layers of the above aspect can be produced, for example, by the following method.
The film-like melt of the composition containing the thermoplastic resin can be produced by a method including passing between two rolls having different peripheral speeds and further stretching as required. By this method, a polymer film satisfying the optical properties (1) to (3) can be stably and easily produced. More specifically, by passing between two rolls having different peripheral speeds in a melted state, there is no or small variation in optical characteristics, and stable generation without causing defects such as contact scratches on the film surface. A polymer film satisfying the optical properties (1) to (3) can be produced. Films produced by the following method are described in JP-A-7-333437 and JP-A-6-222213 in that there is no or little variation in optical properties and there are no defects such as contact scratches on the film surface. The film is different from a film in which the optical axis is inclined by passing a non-melted film between rolls having different peripheral speeds.
Hereinafter, this manufacturing method will be described in detail.

In the method, a composition containing a thermoplastic resin (sometimes referred to as a “thermoplastic resin composition”) is melt-extruded. Prior to melt extrusion, the thermoplastic resin composition is preferably pelletized. Pelletization can be made by drying the thermoplastic resin composition, melting it at 150 ° C. to 300 ° C. using a twin-screw kneading extruder, and then solidifying and cutting the extruded noodle in air or water. . Further, after melting by an extruder, it can be pelletized by an underwater cutting method in which it is cut while being directly extruded from a die into water. Extruders used for pelletization include single screw extruders, non-meshing different direction rotating twin screw extruders, meshing different direction rotating twin screw extruders, and meshing same direction rotating twin screw extruders. Etc. can be used. The number of revolutions of the extruder is preferably 10 rpm to 1000 rpm, more preferably 20 rpm to 700 rpm. The extrusion residence time is 10 seconds to 10 minutes, more preferably 20 seconds to 5 minutes.
No particular limitation is imposed on the size of the pellets is generally about 10mm ³ ~1000mm ^3, more preferably about 30 mm ³ 500 mm ^3.

  It is preferred to reduce the moisture in the pellets prior to melt extrusion. A preferable drying temperature is 40 to 200 ° C, more preferably 60 to 150 ° C. Thereby, the moisture content is preferably 1.0% by mass or less, and more preferably 0.1% by mass or less. Drying may be performed in air, nitrogen, or vacuum.

  Next, the dried pellets are supplied into the cylinder through the supply port of the extruder, and are kneaded and melted. The inside of the cylinder is composed of, for example, a supply unit, a compression unit, and a measurement unit in order from the supply port side. The screw compression ratio of the extruder is preferably 1.5 to 4.5, the ratio of the cylinder length to the cylinder inner diameter (L / D) is preferably 20 to 70, and the cylinder inner diameter is preferably 30 mm to 150 mm. The extrusion temperature is determined according to the melting temperature of the thermoplastic resin, but generally about 190 to 300 ° C is preferable. Furthermore, in order to prevent the molten resin from being oxidized by residual oxygen, it is also preferable to carry out the inside of the extruder in an inert (nitrogen or the like) air flow or while evacuating using an extruder with a vent.

  It is preferable to provide a filtration apparatus incorporating a breaker plate type filtration or a leaf type disk filter for filtering foreign matter in the thermoplastic resin composition. Filtration may be performed in one stage or may be performed in multistage filtration. The filtration accuracy is preferably 15 μm to 3 μm, more preferably 10 μm to 3 μm. It is desirable to use stainless steel as the filter medium. As the configuration of the filter medium, a knitted wire, a sintered metal fiber or metal powder (sintered filter medium) can be used, and among them, a sintered filter medium is preferable.

  In order to reduce the fluctuation of the discharge amount and improve the thickness accuracy, it is preferable to provide a gear pump between the extruder and the die. Thereby, the resin pressure fluctuation width in the die can be within ± 1%. In order to improve the quantitative supply performance by the gear pump, a method of controlling the pressure before the gear pump to be constant by changing the number of rotations of the screw can also be used.

The molten resin is melted by the extruder configured as described above, and the molten resin is continuously fed to the die via a filter and a gear pump as necessary. The die may be any of a T die, a fish tail die, and a hanger coat die. It is also preferable to insert a static mixer immediately before the die to increase the uniformity of the resin temperature. The clearance of the T-die exit portion is generally 1.0 to 10 times the film thickness, preferably 1.2 to 5 times.
The die is preferably adjustable in thickness at intervals of 5 to 50 mm. An automatic thickness adjustment die that calculates downstream film thickness and thickness deviation and feeds back the results to die thickness adjustment is also effective.
In addition to the single layer film forming apparatus, it is also possible to manufacture using a multilayer film forming apparatus.
Thus, the residence time from when the resin enters the extruder through the supply port until it exits from the die is preferably 3 minutes to 40 minutes, and more preferably 4 minutes to 30 minutes.

Next, the melt of the thermoplastic resin is extruded from the die into a film, passed between two rolls (for example, a touch roll and a casting roll), and cooled and solidified (touch roll method) to obtain a film. In the method, the film-like melt is passed between two rolls rotating at different peripheral speeds, so that the film is sheared to satisfy the relational expression (III) (the main axis is a normal line). Polymer films can be made that are tilted with respect to the direction. When a roll having a large diameter is used, the shear applied to the film increases, and the value of R [+ 40 °] / R [−40 °] tends to increase (the inclination angle of the main shaft increases). It is preferable to use two rolls (for example, a touching roll and a casting roll) having a diameter of 350 to 600 nm (more preferably 350 to 500 nm). When a roll with a large diameter is used, the contact area between the film-like melt and the roll becomes wide, and the time for shearing becomes longer. Can be produced while suppressing the variation. In the method of the present invention, the diameters of the two rolls may be the same or different. Moreover, since the biting property of the film is improved, the film can be manufactured more stably. On the other hand, if the temperature distribution in the width direction of the film-like melt is remarkable, it becomes difficult to maintain uniformity. Until then, it is preferable to reduce the temperature distribution in the width direction of the melt, and specifically, the temperature distribution in the width direction is preferably within 5 ° C. In order to reduce the temperature distribution, a member having a heat insulating function or a heat reflecting function is arranged in at least a part of the passage between the melt die and the two rolls to shield the melt from the outside air. Is preferred. Thus, by arranging the heat insulating member in the passage and shielding it from the outside air, it is possible to suppress the influence of the external environment, for example, wind, and to suppress the temperature distribution in the width direction of the film. The temperature distribution in the width direction of the film-like melt is more preferably within ± 3 ° C, and still more preferably within ± 1 ° C. Thus, the variation which makes uniform the temperature of the width direction of a film-form melt can be suppressed until just before passing between rolls.
The temperature distribution of the film-like melt can be measured with a contact-type thermometer or a non-contact type thermometer, and in particular, can be measured with a non-contact-type infrared thermometer.

  As a method of eliminating the variation, there is a method of increasing the adhesion when the film-like melt comes into contact with the casting roll. Specifically, the adhesion can be improved by combining electrostatic application method, air knife method, air chamber method, vacuum nozzle method and the like. Such an adhesion improving method may be performed on the entire surface of the film-like melt or may be partially performed.

  Moreover, it is preferable to apply a pressure of 5 to 500 MPa between the rolls in addition to a conventional method in which the melt of the supplied thermoplastic resin composition is continuously sandwiched between two roll surfaces to form a film. A more preferable pressure is 20 to 300 MPa, still more preferably 25 to 200 MPa, and particularly preferably 30 to 150 MPa.

In the present invention, the material of the two rolls is preferably a metal, more preferably stainless steel, and a roll whose surface is plated is also preferred. On the other hand, it is preferable not to use a rubber roll or a metal roll lined with rubber because the surface has large irregularities and the film surface is easily damaged.
As for the touch roll, for example, JP-A-11-314263, JP-A-2002-36332, JP-A-11-235747, WO97 / 28950, JP-A-2004-216717, JP2003. -145609 can be used.

  In addition to two rolls (for example, a casting roll and a touch roll) that allow the film-like melt to pass through, it is preferable to use one or more casting rolls to cool the film. The touch roll is usually arranged so as to touch the first casting roll on the most upstream side (closer to the die). In general, it is relatively common to use three cooling rolls, but this is not a limitation. The distance between the plurality of casting rolls is preferably 0.3 mm to 300 mm, more preferably 1 mm to 100 mm, and still more preferably 3 mm to 30 mm between the surfaces.

  The surface of the touch roll or casting roll has an arithmetic average height Ra of usually 100 nm or less, preferably 50 nm or less, more preferably 25 nm or less.

Here, the peripheral speed ratio of the two rolls means the ratio of the peripheral speeds of the two rolls (the peripheral speed of the first roll / the peripheral speed of the second roll). However, the peripheral speed of the first roll <the peripheral speed of the second roll. The larger the peripheral speed difference between the two rolls, that is, the smaller the peripheral speed ratio, the larger the R [+ 40 °] / R [−40 °] value of the film obtained (the inclination angle of the main shaft becomes larger). On the other hand, if the peripheral speed difference is too large, the surface of the obtained film is easily scratched. Specifically, when producing a polymer film having a large value of R [+ 40 °] / R [−40 °] (a major axis inclination angle β, for example, 20 ° or more), the circumference of two rolls The speed ratio is preferably 0.55 to 0.80, and more preferably 0.55 to 0.74. However, it is preferable to satisfy the following conditions (i) to (iii) so as not to be scratched.
(I) Temperature range where the viscoelasticity of the melt of the thermoplastic resin composition immediately before contacting at least one of the two rolls shows loss elastic modulus> storage elastic modulus (specifically, Tg + 50 ° C. to Tg + 70 ° C. or more ( Tg is the glass transition point of the thermoplastic resin)),
(Ii) The temperature distribution in the width direction of the melt is within ± 5 ° C. until just before the film-like melt melt-extruded from the die comes into contact with at least one of the two rolls.
(Iii) As the two rolls, use is made of a roll having a metal surface at least.

  The two rolls may be driven or driven independently, but in order to control the variation in the optical axis, it is preferable that the two rolls be driven independently. In the present invention, the two rolls are driven at different peripheral speeds as described above. However, the surface temperatures of the two rolls may be further differentiated. A preferable temperature difference is 5 ° C to 80 ° C, more preferably 20 ° C to 80 ° C, and further preferably 20 ° C to 60 ° C. In that case, the temperature of two rolls becomes like this. Preferably it sets to 60 to 160 degreeC, More preferably, it is 70 to 150 degreeC, More preferably, it sets to 80 to 140 degreeC. Such temperature control can be achieved by passing a temperature-controlled liquid or gas through the touch roll.

It is preferable to trim both ends after the melt is formed into a film. The portion cut off by trimming may be crushed and used again as a raw material.
Further, it is also preferable to perform a thickness increasing process (knurling process) on one or both ends. The height of the unevenness due to the thickness increasing process is preferably 1 μm to 50 μm, more preferably 3 μm to 20 μm. Thickening processing may be convex on both sides or convex on one side. The width of the thickness increasing process is preferably 1 mm to 50 mm, more preferably 3 mm to 30 mm. Extrusion can be performed at room temperature to 300 ° C. It is also preferable to attach a lami film on one side or both sides before winding. The thickness of the laminated film is preferably 5 μm to 100 μm, more preferably 10 μm to 50 μm. The material is not particularly limited, such as polyethylene, polyester, and polypropylene.
The winding tension is preferably 2 kg / m width to 50 kg / width, more preferably 5 kg / m width to 30 kg / width.

In order to produce a polymer film that satisfies the properties required for the retardation layer, stretching and / or relaxation treatment may be performed after the film is formed. For example, each step can be performed by the following combinations (a) to (i).
(A) transverse stretching (b) transverse stretching → relaxation treatment (c) longitudinal stretching → lateral stretching (d) longitudinal stretching → lateral stretching → relaxation treatment (e) longitudinal stretching → relaxation treatment → lateral stretching → relaxation treatment (f) Stretching → Longitudinal stretching → Relaxation treatment (g) Transverse stretching → Relaxation treatment → Longitudinal stretching → Relaxation treatment (h) Longitudinal stretching → Transverse stretching → Longitudinal stretching (i) Longitudinal stretching → Transverse stretching → Longitudinal stretching → Relaxation treatment Among these What is particularly required is the transverse stretching step (a).

The transverse stretching can be performed using a tenter. That is, the film is stretched by holding both ends in the width direction with clips and widening the film in the lateral direction. At this time, the stretching temperature can be controlled by sending wind at a desired temperature into the tenter. In the present specification, the “stretching temperature” (hereinafter also referred to as “lateral stretching temperature”) is specified by the film film surface temperature (in the present specification, the stretching temperature is also the film in each stretching step other than the lateral stretching). Specified by the film surface temperature). The stretching temperature is preferably controlled so as to be Tg−40 ° C. to Tg + 40 ° C. That is, the transverse stretching temperature in the transverse stretching step is preferably Tg-40 ° C to Tg + 40 ° C, more preferably Tg-20 ° C to Tg + 20 ° C, and still more preferably Tg-10 ° C to Tg + 10 ° C. Here, the transverse stretching temperature in the transverse stretching step means an average temperature from the stretching start point to the stretching end point.
The stretching time in the transverse stretching step is preferably 1 second to 10 minutes, more preferably 2 seconds to 5 minutes, and even more preferably 5 seconds to 3 minutes. By controlling the stretching temperature and the stretching time within the above ranges, it is difficult to relax the tilt structure in the thickness direction in the film formed in the melt clamping step, and the tilt structure of the film after stretching can be largely maintained. In addition, R [+ 40 °] / R [−40 °] within the preferred range of the present invention can be formed. The stretching temperature in the transverse stretching process can be controlled by sending wind at a desired temperature into the tenter.
Moreover, a preferable lateral stretch ratio is 1.01 to 4 times, more preferably 1.03 to 3.5 times, and still more preferably 1.1 to 3.0 times. The transverse draw ratio is particularly preferably 1.51 to 3.0 times.

  The transverse stretching may be performed in accordance with a normal transverse stretching method in which the clip is widened in the width direction in the tenter, and may also be performed in accordance with the following stretching method in which the clip is held and widened. .

(Simultaneous biaxial stretching)
Like the normal transverse stretching method, the clip is widened in the transverse direction, but at the same time, it is stretched and contracted in the longitudinal direction. Specifically, Japanese Utility Model Laid-Open Nos. 55-93520, 63-247021, 6-271026, 6-278204, 2000-334832, 2004-106434, JP-A-2004-195712, JP-A-2006-142595, JP-A-2007-210306, JP-A-2005-22087, JP-T-2006-517608, JP-A-2007-210306 Reference can also be made to the method described in the publication.

(Diagonal stretching)
Similar to the normal lateral stretching method, the clip is widened in the lateral direction, but is stretched in an oblique direction by changing the conveying speed of the left and right clips. Thereby, the film can be stretched from 30 ° to 150 °, more preferably from 40 ° to 140 °, and still more preferably from 50 ° to 130 ° from the MD direction. Specifically, JP 2002-22944, JP 2002 JP-A-86554, JP-A-2004-325561, JP-A-2008-23775, JP-A-2008-110573, JP-A-2000-9912, JP-A-2003-342384, JP-A-2004-20701, JP-A-2004-2004. 258508, JP-A-2006-224618, JP-A-2006-255589, JP-A-2008-2221834, JP-A-2003-342384, and International Publication No. WO2003 / 102639 Reference can also be made to these methods.

By performing preheating before stretching and heat setting after stretching, the Re and Rth distribution after stretching can be reduced, and the variation in orientation angle associated with bowing can be reduced. Either preheating or heat setting may be performed, but both are more preferable. These preheating and heat setting are preferably performed by holding with a clip, that is, preferably performed continuously with stretching.
Preheating can be performed at a temperature about 1 ° C. to 50 ° C. higher than the stretching temperature, preferably 2 ° C. to 40 ° C. or less, more preferably 3 ° C. or more and 30 ° C. or less. The preheating time is preferably 1 second or longer and 10 minutes or shorter, more preferably 5 seconds or longer and 4 minutes or shorter, and even more preferably 10 seconds or longer and 2 minutes or shorter. During preheating, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to ± 10% of the width of the unstretched film.
The heat setting can be performed at a temperature 1 ° C. or more and 50 ° C. or less lower than the stretching temperature, more preferably 2 ° C. or more and 40 ° C. or less, and further preferably 3 ° C. or more and 30 ° C. or less. More preferably, it is less than the stretching temperature and less than Tg. The preheating time is preferably 1 second or longer and 10 minutes or shorter, more preferably 5 seconds or longer and 4 minutes or shorter, and even more preferably 10 seconds or longer and 2 minutes or shorter. During the heat setting, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to 0% (the same width as the tenter width after stretching) to −10% (shrinking by 10% from the tenter width after stretching = reduced width) of the tenter width after stretching. If the width is wider than the stretched width, residual strain is likely to occur in the film, and it is not preferable because it is likely to increase the variation with time of Re and Rth.

The reason why the variation in orientation angle and Re and Rth can be reduced by such preheating and heat setting is as follows.
(I) The film is stretched in the width direction and tends to become thin in the orthogonal direction (longitudinal direction) (necking phenomenon). For this reason, the film before and after transverse stretching is pulled and stress is generated. However, both ends in the width direction are fixed by a chuck and are not easily deformed by stress, and the central portion in the width direction is easily deformed. As a result, the stress due to necking is deformed into a bow shape and bowing occurs. As a result, in-plane Re and Rth unevenness and distribution of orientation axes occur.
(ii) To suppress this, if the temperature on the preheating side (before stretching) is increased and the temperature on the heat treatment (after stretching) is decreased, neck-in occurs on the high temperature side (preheating) with a lower elastic modulus, It is difficult to generate by heat treatment (after stretching). As a result, bowing after stretching can be suppressed.

By such stretching, variations in the width direction and the longitudinal direction of Re and Rth can both be 5% or less, more preferably 4% or less, and even more preferably 3% or less. Further, the orientation angle can be 90 ° ± 5 ° or less or 0 ° ± 5 ° or less, more preferably 90 ° ± 3 ° or less, or 0 ° ± 3 ° or less, and further preferably 90 ° ± 1 ° or less or It can be 0 ° ± 1 ° or less.
A high-speed stretching process may be performed, and the stretching process can be performed preferably at 20 m / min or more, more preferably 25 m / min or more, and further preferably 30 m / min or more.

  A film that can be used as a retardation layer contains a thermoplastic resin exhibiting positive intrinsic birefringence. The thermoplastic resin is preferably amorphous. The intrinsic birefringence of various resins is described in MSDS, resin specification table, polymer database, etc., and can be referred to. Moreover, when it is not described in any book etc., it can measure according to the prism coupling method. In the present invention, “amorphous resin” refers to a resin having no crystal melting peak when a thermal analysis measurement is performed on a film on which the resin is formed. As long as the above properties are satisfied, the type of resin is not particularly limited. Examples of thermoplastic resins include cyclic olefin copolymers, cellulose acylates, polyesters, and polycarbonates. In the case of producing using a melt extrusion method, it is preferable to use a material having good melt extrusion moldability. From this viewpoint, it is preferable to select cyclic olefin copolymers and cellulose acylates. One kind of the resin may be contained, or two or more kinds of the resins different from each other may be contained. Of these, cellulose acylates and cyclic olefin resins obtained by addition polymerization are preferred.

Examples of the cyclic olefin copolymers include a resin obtained by polymerization of a norbornene compound. It may be a resin obtained by any polymerization method of ring-opening polymerization and addition polymerization.
Examples of the addition polymerization and the resin obtained thereby include, for example, Japanese Patent No. 3517471, Japanese Patent No. 3559360, Japanese Patent No. 3867178, Japanese Patent No. 3871721, Japanese Patent No. 3907908, Japanese Patent No. 3945598, and Japanese Translation of PCT International Publication No. 2005-527696. JP-A-2006-28993, JP-A-2006-11361, International Publication WO 2006/004376, International Publication WO 2006/0307077, and the like. Among these, those described in Japanese Patent No. 3517471 are particularly preferable.
Examples of the ring-opening polymerization and the resin obtained thereby include WO 98/144499, pamphlet, patent 30605532, patent 3220478, patent 373046, patent 334027, patent 3428176, patent. Examples are described in Japanese Patent No. 3687231, Japanese Patent No. 3873934, and Japanese Patent No. 3912159. Of these, those described in International Publication WO 98- / 14499 pamphlet and Japanese Patent No. 30605532 are particularly preferable.
Of these cyclic olefins, addition polymerization is more preferable. A commercially available product may be used, and in particular, “TOPAS # 6013” (manufactured by Polyplastics Co., Ltd.) that can easily suppress gel generated during extrusion molding can be used.

  Examples of the cellulose acylates include any cellulose acylate in which at least a part of three hydroxyl groups in the cellulose unit is substituted with an acyl group. The acyl group (preferably an acyl group having 3 to 22 carbon atoms) may be either an aliphatic acyl group or an aromatic acyl group. Among them, cellulose acylate having an aliphatic acyl group is preferable, those having an aliphatic acyl group having 3 to 7 carbon atoms are more preferable, those having an aliphatic acyl group having 3 to 6 carbon atoms are more preferable, and carbon number More preferably has 3 to 5 aliphatic acyl groups. A plurality of these acyl groups may be present in one molecule. Examples of preferred acyl groups include acetyl, propionyl, butyryl, pentanoyl, hexanoyl and the like. Among these, cellulose acylate having one or more selected from acetyl group, propionyl group and butyryl group is more preferable, and more preferable one has both acetyl group and propionyl group. Cellulose acylate (CAP). CAP is preferable in terms of easy resin synthesis and high stability of extrusion molding.

When producing a film by the melt extrusion method, it is preferable that the cellulose acylate to be used satisfies the following formulas (S-1) and (S-2). Cellulose acylate satisfying the following formula has a low melting temperature and improved meltability, and is therefore excellent in melt extrusion film formation.
Formula (S-1) 2.5 ≦ X + Y ≦ 3.0
Formula (S-2) 1.25 ≦ Y ≦ 3.0
In the formula, X represents the degree of substitution of the acetyl group with respect to the hydroxyl group of cellulose, and Y represents the sum of the degree of substitution of the acyl group with respect to the hydroxyl group of cellulose. The “degree of substitution” in the present specification means the total of the ratio of substitution of hydrogen atoms of hydroxyl groups at the 2-position, 3-position and 6-position of cellulose. When the hydrogen atoms of all hydroxyl groups at the 2nd, 3rd and 6th positions are substituted with acyl groups, the degree of substitution is 3.
Furthermore, it is more preferable to use a cellulose acylate that satisfies the following formula:
2.6 ≦ X + Y ≦ 2.95
2.0 ≦ Y ≦ 2.95
It is more preferable to use a cellulose acylate that satisfies the following formula.
2.7 ≦ X + Y ≦ 2.95 2.3 ≦ Y ≦ 2.9

  There is no restriction | limiting in particular about the mass average polymerization degree and number average molecular weight of cellulose acylates. In general, the mass average degree of polymerization is about 350 to 800, and the number average molecular weight is about 70000 to 230,000. The cellulose acylates can be synthesized using acid anhydrides or acid chlorides as acylating agents. In the industrially most general synthesis method, cellulose obtained from cotton linter, wood pulp, etc. is converted into organic acids (acetic acid, propionic acid, butyric acid) corresponding to acetyl groups and other acyl groups, or their acid anhydrides (anhydrous anhydride). A cellulose ester is synthesized by esterification with a mixed organic acid component containing acetic acid, propionic anhydride, and butyric anhydride). As a method for synthesizing cellulose acylate satisfying the above formulas (S-1) and (S-2), the Technical Report of the Japan Society of Invention (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention) 7 Pp. 12 to 12, JP-A-2006-45500, JP-A-2006-241433, JP-A-2007-138141, JP-A-2001-188128, JP-A-2006-142800, JP-A-2007. Reference can be made to the method described in Japanese Patent No. 98917.

  Examples of the polyester include a polyester resin which is a diol unit having a cyclic acetal skeleton, and in particular, a diol unit containing a dicarboxylic acid unit and a diol unit, wherein 1 to 80 mol% of the diol unit has a cyclic acetal skeleton. A polyester resin having a small birefringence is preferably used in the present invention.

  The polymer film used for the retardation layer may contain a material other than the thermoplastic resin, but one or more of the thermoplastic resins as a main component (in all the materials in the composition, It means a material with the highest content ratio, and in an embodiment containing two or more of the resins, it means that the total content ratio is higher than the content ratio of each of the other materials) Is preferred. In order to enhance the front contrast ratio characteristic when the polymer film is used in a liquid crystal display, it is more preferable to use only one kind of the thermoplastic resin. In this embodiment, “use only one kind” means “use only one kind of polymer material as a main raw material”, and even if one or more of the following additives are added, this embodiment Is not excluded.

Examples of materials other than the thermoplastic resin include various additives, and examples thereof include a stabilizer, an ultraviolet absorber, a light stabilizer, a plasticizer, fine particles, and an optical adjusting agent.
Stabilizer:
The optical film of the present invention may contain at least one stabilizer. The stabilizer is preferably added before or when the thermoplastic resin is heated and melted. The stabilizer has effects such as preventing oxidation of the film constituting material, capturing an acid generated by decomposition, and suppressing or inhibiting a decomposition reaction caused by radical species caused by light or heat. Stabilizers are useful for suppressing the occurrence of alterations such as coloring and molecular weight reduction and the generation of volatile components due to various decomposition reactions including unresolved decomposition reactions. Even at the melting temperature for forming a resin film, the stabilizer itself is required to function without being decomposed. Typical examples of stabilizers include phenol-based stabilizers, phosphorous acid-based stabilizers (phosphite-based), thioether-based stabilizers, amine-based stabilizers, epoxy-based stabilizers, and lactone-based stabilizers. Stabilizers, amine stabilizers, metal deactivators (tin stabilizers) and the like are included. These are described in JP-A-3-199201, JP-A-5-1907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, and the like. Then, it is preferable to use at least one or more of a phenol-based or phosphorous acid-based stabilizer. Among phenolic stabilizers, it is particularly preferable to add a phenolic stabilizer having a molecular weight of 500 or more. Preferable phenolic stabilizers include hindered phenolic stabilizers.

These materials are readily available as commercial products and are sold by the following manufacturers. From Ciba Specialty Chemicals, Irganox 1076, Irganox 1010, Irganox 3113, Irganox 245, Irganox 1135, Irganox 1330, Irganox 259, Irganox 565, Irganx 565, Irganx 565, Ir35x10 Moreover, it can obtain from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-50, ADK STAB AO-60, ADK STAB AO-20, ADK STAB AO-70, and ADK STAB AO-80. Furthermore, it can be obtained from Sumitomo Chemical Co., Ltd. as Sumilizer BP-76, Sumilizer BP-101, Sumilizer GA-80. In addition, it is also possible to obtain as Sinox 326M and Sinox 336B from Sipro Kasei Corporation.

  Moreover, as said phosphorous acid type stabilizer, the compound as described in [0023]-[0039] of Unexamined-Japanese-Patent No. 2004-182979 can be used more preferably. Specific examples of the phosphite ester stabilizer include JP-A-51-70316, JP-A-10-306175, JP-A-57-78431, JP-A-54-157159, Examples thereof include compounds described in Japanese Utility Model Laid-Open No. 55-13765. Furthermore, as other stabilizers, the materials described in detail on pages 17 to 22 of the Japan Institute of Invention Disclosure Bulletin (Public Technical No. 2001-1745, issued March 15, 2001, Japan Society of Invention) are preferably used. be able to.

  The phosphite stabilizer is useful to have a high molecular weight in order to maintain stability at high temperature, has a molecular weight of 500 or more, more preferably a molecular weight of 550 or more, and particularly a molecular weight of 600 or more. Is preferred. Furthermore, at least one substituent is preferably an aromatic ester group. The phosphite ester stabilizer is preferably a triester, and is desirably free of impurities such as phosphoric acid, monoester and diester. When these impurities are present, the content is preferably 5% by mass or less, more preferably 3% by mass or less, and particularly 2% by mass or less. These include compounds described in [0023] to [0039] of JP-A No. 2004-182979, JP-A-51-70316, JP-A-10-306175, JP-A-57. The compounds described in JP-A-78431, JP-A-54-157159, and JP-A-55-13765 can also be mentioned. Preferable specific examples of the phosphite ester stabilizer include the following compounds, but the phosphite ester stabilizer that can be used in the present invention is not limited thereto.

  These are commercially available from Asahi Denka Kogyo Co., Ltd. as ADK STAB 1178, 2112, PEP-8, PEP-24G, PEP-36G, and HP-10, and Sandostab P-EPQ from Clariant. Is possible. Furthermore, a stabilizer having phenol and phosphite in the same molecule is also preferably used. These compounds are further described in detail in JP-A-10-273494. Examples of the compounds are included in the examples of the stabilizer, but are not limited thereto. As a typical commercial product, Sumitizer GP is available from Sumitomo Chemical Co., Ltd. These are commercially available from Sumitomo Chemical Co., Ltd. as Sumilizer TPL, TPM, TPS, TDP. It is also available from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-412S.

  The stabilizers can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention. Preferably, the addition amount of the stabilizer is preferably 0.001 to 5% by mass, more preferably 0.005 to 3% by mass, and still more preferably 0.01 to 0% with respect to the mass of the thermoplastic resin. 0.8% by mass.

UV absorber:
The optical film of the present invention may contain one type or two or more types of ultraviolet absorbers. From the viewpoint of preventing deterioration, the ultraviolet absorbent is preferably excellent in the ability to absorb ultraviolet light having a wavelength of 380 nm or less and has little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of transparency. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Particularly preferred ultraviolet absorbers are benzotriazole compounds and benzophenone compounds. Among these, a benzotriazole-based compound is preferable because unnecessary coloring with respect to the cellulose mixed ester is small. These are disclosed in JP-A-60-235852, JP-A-3-199201, 5-1907073, 5-194789, 5-271471, 6-107854, 6-118233, 6 -148430, 7-11056, 7-11055, 7-11056, 8-29619, 8-239509, and JP-A-2000-204173.
The addition amount of the ultraviolet absorber is preferably 0.01 to 2% by mass of the thermoplastic resin, and more preferably 0.01 to 1.5% by mass.

Light stabilizer:
The optical film of the present invention may contain one or more light stabilizers. Light stabilizers include hindered amine light stabilizer (HALS) compounds, more specifically, US Pat. No. 4,619,956, columns 5-11 and US Pat. No. 4,839. 2,405, 2,2,6,6-tetraalkylpiperidine compounds, or their acid addition salts or complexes of them with metal compounds. These are commercially available from Asahi Denka as ADK STAB LA-57, LA-52, LA-67, LA-62, LA-77, and TINUVIN 765, 144 from Ciba Specialty Chemicals. .

  These hindered amine light stabilizers can be used alone or in combination of two or more. Of course, these hindered amine light stabilizers may be used in combination with additives such as plasticizers, stabilizers, UV absorbers, etc., and are introduced into a part of the molecular structure of these additives. Also good. The blending amount is determined within a range not impairing the effects of the present invention, and is generally about 0.01 to 20 parts by mass, preferably 0.02 to 15 parts per 100 parts by mass of the thermoplastic resin. About mass parts, and particularly preferably about 0.05 to 10 mass parts. The light stabilizer may be added at any stage of preparing the melt of the thermoplastic resin composition, for example, at the end of the melt preparation process.

Plasticizer:
The optical film of the present invention may contain a plasticizer. The addition of a plasticizer is preferable from the viewpoint of film modification such as improvement of mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability. Further, when the optical film of the present invention is produced by a melt film-forming method, the purpose is to lower the melting temperature of the film constituting material by adding a plasticizer rather than the glass transition temperature of the thermoplastic resin to be used. It will be added for the purpose of lowering the viscosity at the same heating temperature than the added thermoplastic resin. For the optical film of the present invention, for example, a plasticizer selected from a phosphoric acid ester derivative and a carboxylic acid ester derivative is preferably used. Further, a polymer obtained by polymerizing an ethylenically unsaturated monomer having a weight average molecular weight of 500 to 10,000 described in JP-A-2003-12859, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or cyclohexyl An acrylic polymer having a group in the side chain is also preferably used.

Fine particles:
The optical film of the present invention may contain fine particles. Examples of the fine particles include fine particles of inorganic compounds and fine particles of organic compounds, and any of them may be used. The average primary particle size of the fine particles contained in the thermoplastic resin in the present invention is preferably 5 nm to 3 μm, more preferably 5 nm to 2.5 μm, more preferably 10 nm to 2.0 μm from the viewpoint of keeping haze low. More preferably. Here, the average primary particle size of the fine particles is determined by observing the thermoplastic resin with a transmission electron microscope (magnification of 500,000 to 1,000,000 times) and determining the average value of the primary particle sizes of 100 particles. The addition amount of the fine particles is preferably 0.005 to 1.0% by mass with respect to the thermoplastic resin, more preferably 0.01 to 0.8% by mass, and further preferably 0.02 to 0%. 4% by mass.

Optical modifier:
The optical film of the present invention may contain an optical adjusting agent. Examples of the optical adjusting agent include a retardation adjusting agent, for example, those described in JP-A Nos. 2001-166144, 2003-344655, 2003-248117, and 2003-66230. Can be used. By adding an optical adjusting agent, in-plane retardation (Re) and thickness direction retardation (Rth) can be controlled. A preferable addition amount is 0 to 10% by mass, more preferably 0 to 8% by mass, and further preferably 0 to 6% by mass.

2. Polarizer There is no particular limitation on the polarizer disposed on the front side and the rear side. A commonly used linear polarizing film can be used. The linear polarizing film is manufactured by Optiva Inc. And a polarizing film comprising a binder and iodine or a dichroic dye is preferable. The iodine and the dichroic dye in the linearly polarizing film exhibit polarizing performance by being oriented in the binder. It is preferable that the iodine and the dichroic dye are aligned along the binder molecule, or the dichroic dye is aligned in one direction by self-assembly such as liquid crystal. Currently, commercially available polarizers are made by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing iodine or dichroic dye to penetrate into the binder. Is common.

3. Protective film It is preferable that the protective film is bonded to both surfaces of the front-side polarizer and the rear-side polarizer. However, the protective film disposed on the liquid crystal cell side constitutes a part of the rear-side retardation region and the front-side retardation region, respectively, and the former has the above formula (I) or (II) and ( It is required to satisfy IV). The latter also constitutes a part of the front-side retardation region, and depending on the mode, it is required to show optical characteristics that contribute to the improvement of the viewing angle CR alone or in combination with other layers.

  There is no restriction | limiting in particular about the protective film arrange | positioned on the outer side of a front side polarizer and a rear side polarizer. Various polymer films can be used. This is the same as the example of the polymer film that can constitute the front side retardation region. For example, cellulose acylates (eg, films of cellulose acetate, cellulose propionate, cellulose butyrate, etc.), polyolefins (eg, norbornene polymers, polypropylene), poly (meth) acrylates (eg, polymethyl methacrylate) Examples thereof include, but are not limited to, films mainly composed of polycarbonate, polyester, or polysulfone. Commercially available polymer films ("Fujitac TD80UL" (manufactured by Fujifilm) for cellulose acylates), Arton (manufactured by JSR), ZEONOR (manufactured by ZEON Corporation) and the like for norbornene polymers can also be used.

  Hereinafter, the present invention will be described in more detail based on examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

1. Production and Evaluation of TN Type Liquid Crystal Display Device (1) Preparation of TN Type Liquid Crystal Cells 1 and 2 TN type liquid crystal cell 1 having the same COA configuration as that shown in FIGS. 1 and 2, and the configuration shown in FIG. A TN type liquid crystal cell 2 having the same non-COA configuration was produced. The liquid crystal cells 1 and 2 are liquid crystal cells manufactured by the same method except that the positions of the color filters are different.
In addition, the color filter is composed of a colored photosensitive composition prepared as described in Examples 17, 18 and 19 in JP-A-2009-144126, and an organic developer CD2000 (Fuji Film Electromaterial). Manufactured by the same company). For the liquid crystal layer, a liquid crystal having positive dielectric anisotropy, refractive index anisotropy Δn = 0.0854 (589 nm, 20 ° C.), Δε = + 8.5 (for example, MLC-9100 manufactured by Merck) is used. used. Also, the inner surfaces of the upper and lower substrates were rubbed, and the liquid crystal layer was twisted and aligned with a twist angle of 90 ° between the upper and lower substrates when no voltage was applied. Δnd (550) of the produced liquid crystal cells 1 and 2 was 400 nm.

  As a rear side polarizing plate (PL1 in FIG. 1), a polarizing film and a polarizing plate having an optical compensation film on one surface thereof, the optical compensation film (rear side retardation region 20 in FIG. 1) is used. The liquid crystal cell was placed on the side. The optical compensation film is made of a material shown in the following table, an optical compensation film made of a polymer film showing the optical properties shown in the following table, or a curable discotic on a polymer film showing the optical properties shown in the following table. An optical compensation film comprising a liquid crystal composition and having a retardation layer having optical characteristics shown in the following table. The polymer film is used as a first retardation layer in the rear retardation region, and a retardation layer composed of a curable discotic liquid crystal composition, or a melt inclined position composed of a thermoplastic resin composition formed by the melt extrusion. The retardation film was disposed as a second retardation layer in the rear side retardation region. In the second retardation layer, it was confirmed from measurement of optical properties that the discotic liquid crystal molecules were fixed in a hybrid alignment state and that the main axis of the melt-formed thermoplastic film was inclined. . The optical properties of the polymer film used as the first retardation layer are adjusted by selecting the material of the polymer film, stretching conditions, additives, etc., and the optical properties of the second retardation layer are as follows: It adjusted by etc. When the polymer film used as the first retardation layer has an in-plane slow axis, the in-plane slow axis is orthogonal to the absorption axis of the rear polarizer (24 in FIG. 1) or Parallel. A commercially available cellulose acylate film, trade name “Fujitac TD80UL” (manufactured by FUJIFILM Corporation) was bonded to the other surface of the polarizing film.

  As a front side polarizing plate (PL2 in FIG. 1), a polarizing film and a polarizing plate having an optical compensation film on one surface thereof, the optical compensation film (front side retardation region 22 in FIG. 1) is used. The liquid crystal cell was placed on the side. The optical compensation film is made of a material shown in the following table, an optical compensation film made of a polymer film showing the optical properties shown in the following table, or a curable discotic on a polymer film showing the optical properties shown in the following table. An optical compensation film comprising a liquid crystal composition and having a retardation layer having optical characteristics shown in the following table. The polymer film is used as a third retardation layer in the front side retardation region, and a retardation layer composed of a curable discotic liquid crystal composition, or a melt inclined position composed of a thermoplastic resin composition formed by the melt extrusion. The retardation film was disposed as a fourth retardation layer in the front side retardation region. In the fourth retardation layer, it was confirmed from the measurement of optical properties that the discotic liquid crystal molecules were fixed in a hybrid alignment state and that the main axis of the melt-formed thermoplastic film was inclined. . The optical properties of the polymer film used as the third retardation layer are adjusted by selecting the material of the polymer film, stretching conditions, additives, etc., and the optical properties of the fourth retardation layer are It adjusted by etc. When the polymer film used as the third retardation layer has an in-plane slow axis, the in-plane slow axis is orthogonal to the absorption axis of the front polarizer (26 in FIG. 1) or Parallel. A commercially available cellulose acylate film, trade name “Fujitac TD80UL” (manufactured by FUJIFILM Corporation) was bonded to the other surface of the polarizing film.

  Further, when the front side polarizer and the rear side polarizer were bonded to the liquid crystal cell, the front side and rear side substrate rubbing directions of the liquid crystal cell were used as the first retardation layer in the rear side retardation region. It was made to become substantially parallel or substantially orthogonal to the in-plane slow axis of the polymer film. The same applies to the case where the polymer film used as the third retardation layer in the front retardation region has an in-plane slow axis. The absorption axis of the front side polarizer and the rear side polarizer is substantially parallel to the liquid crystal cell alignment direction (the rubbing direction of the front side substrate or the rear side substrate), and the intersection of the absorption axes of the front side polarizer and the rear side polarizer. The angle was approximately 90 ° orthogonal Nicol.

(2) Evaluation of TN-type liquid crystal display device The following evaluation was performed on each of the manufactured liquid crystal display devices.
(2-1) Front contrast ratio Using a measuring device (BM5A, manufactured by TOPCON), the brightness value of black display and white display in the panel normal direction is measured in a dark room, and the front contrast (white brightness / black brightness) is measured. Was calculated.
At this time, the distance between the measuring instrument and the panel was set to 700 mm.
Subsequently, the front contrast ratio was calculated by the following formula based on the front contrast ratio in the reference form.
Front contrast ratio = Front contrast in the embodiment / Front contrast in the reference form The reference form in each form is shown in the table below.
(2-2) Contrast viewing angle characteristics Using a measuring instrument (BM5A, manufactured by TOPCON), luminance values of black display and white display were measured in a dark room, and contrast (white luminance / black luminance) was calculated. The viewing angle of each liquid crystal display device was normalized and evaluated with reference to a viewing angle at which the contrast of each liquid crystal display device in the vertical and horizontal directions exceeded 10.
“◎” means. The total of the vertical and horizontal viewing angles (CR> 10) is 240 ° or more,
“O” means that the total of the viewing angles (CR> 10) is 180 ° or more and less than 240 °,
“X” means that the total of the viewing angles (CR> 10) is less than 180 °,
Means.
The results are shown in the following table.
In the table below, “TAC” means triacetyl cellulose, but cellulose acylates in which part of the acetyl group is substituted with a propionyl group, a butyryl group, a pentanoyl group, or a hexanoyl group should be used. You can also. Further, cellulose acylates in which hydrogen atoms remain in a predetermined ratio can be used in addition to those in which all the hydrogen atoms of three hydroxyl groups in one unit of cellulose are substituted with acyl groups such as acetyl groups.
In the following table, “norbornene” means a cyclic olefin copolymer, and means that “TOPAS # 6013” pellets manufactured by Polyplastics were used.
In the table below, “DLC” means a retardation layer made of a curable discotic liquid crystal composition, and “melting gradient” means a retardation film made of a thermoplastic resin composition formed by melt extrusion. To do.
These meanings are the same in any of the following tables.

From the above results, the TN liquid crystals of Examples 1 to 4, 11 and 12 of the first embodiment in which the retardation film satisfying the above formula (I) is disposed between the rear-side polarizer and the liquid crystal cell having the COA structure. All of the display devices had a front CR compared to the TN type liquid crystal display devices (Comparative Examples 3, 6-8, 17 and 18) having the same configuration except that a non-COA liquid crystal cell was used. I can understand that it is expensive.
Similarly, a retardation film satisfying the above formula (II) and a retardation layer satisfying the above formula (III) (a layer made of a DLC composition or a retardation film prepared by a melting gradient method) are rear-side polarized light. The TN type liquid crystal display devices of Examples 5 to 10, 13 and 14 of the second embodiment arranged between the child and the liquid crystal cell of the COA structure are the same except that the liquid crystal cell of the non-COA structure is used. It can be understood that the front CR is higher than the TN type liquid crystal display device (Comparative Examples 11, 14 to 16, 19 and 20) of the comparative example of the configuration.

Further, referring to Comparative Examples 1 and 2 and Comparative Examples 4 and 5, these are TN type liquid crystal display devices having the same configuration except that the liquid crystal cell has a COA structure or a non-COA structure. The relationship between Example 1 and Comparative Example 3 is the same. However, in Comparative Examples 1 and 2, Rth (550) in the rear side retardation region does not satisfy the formula (I), and therefore, the front CR is rather lowered as compared with Comparative Examples 4 and 5.
Similarly, referring to Comparative Examples 9 and 10 and Comparative Examples 12 and 13, these are TN liquid crystal display devices having the same configuration except that the liquid crystal cell has a COA structure or a non-COA structure. The relationship between Example 5 and Comparative Example 11 is the same. However, in Comparative Examples 9 and 10, Rth (550) in the rear side retardation region does not satisfy the formula (II), and therefore, the front CR is rather lowered as compared with Comparative Examples 12 and 13.
From this, the effect of the present invention is that the COA structure is adopted, and in the first aspect, the rear side phase difference region is obtained only when the formula (I) is satisfied; Then, the rear side retardation region can be obtained only when the first retardation layer satisfying the formula (II) and the second retardation layer satisfying the formula (III) are obtained. It is.

2. Preparation and evaluation of ECB type liquid crystal display device (2) Preparation of ECB type liquid crystal cells 3 and 4 ECB type liquid crystal cell 3 having a COA configuration similar to the configuration shown in FIGS. 1 and 2, and the configuration shown in FIG. An ECB type liquid crystal cell 4 having a similar non-COA configuration was produced. The liquid crystal cells 3 and 4 are liquid crystal cells manufactured by the same method except that the positions of the color filters are different. The cell gap of the liquid crystal cell was 3.5 μm. For the liquid crystal layer, a liquid crystal having positive dielectric anisotropy, refractive index anisotropy Δn = 0.0854 (589 nm, 20 ° C.), Δε = + 8.5 (for example, MLC-9100 manufactured by Merck) is used. used. Also, the inner surfaces of the upper and lower substrates were rubbed, and the liquid crystal layer was aligned at a crossing angle of 0 ° without twisting between the upper and lower substrates when no voltage was applied. Δnd (550) of the produced liquid crystal cells 3 and 4 was 300 nm.

  As a rear side polarizing plate (PL1 in FIG. 1), a polarizing film and a polarizing plate having an optical compensation film on one surface thereof, the optical compensation film (rear side retardation region 20 in FIG. 1) is used. The liquid crystal cell was placed on the side. The optical compensation film is made of a material shown in the following table, an optical compensation film made of a polymer film showing the optical properties shown in the following table, or a curable discotic on a polymer film showing the optical properties shown in the following table. An optical compensation film comprising a liquid crystal composition and having a retardation layer having optical characteristics shown in the following table. The polymer film is used as a first retardation layer in the rear retardation region, and a retardation layer composed of a curable discotic liquid crystal composition, and a melt inclined position composed of a thermoplastic resin composition formed by the melt extrusion. The retardation film was disposed as a second retardation layer in the rear side retardation region. In the second retardation layer, it was confirmed from measurement of optical properties that the discotic liquid crystal molecules were fixed in a hybrid alignment state and that the main axis of the melt-formed thermoplastic film was inclined. . The optical properties of the polymer film used as the first retardation layer are adjusted by selecting the material of the polymer film, stretching conditions, additives, etc., and the optical properties of the second retardation layer are as follows: It adjusted by etc. When the polymer film used as the first retardation layer has an in-plane slow axis, the in-plane slow axis is orthogonal to the absorption axis of the rear polarizer (24 in FIG. 1) or Parallel. A commercially available cellulose acylate film, trade name “Fujitac TD80UL” (manufactured by FUJIFILM Corporation) was bonded to the other surface of the polarizing film.

  As a front side polarizing plate (PL2 in FIG. 1), a polarizing film and a polarizing plate having an optical compensation film on one surface thereof, the optical compensation film (front side retardation region 22 in FIG. 1) is used. The liquid crystal cell was placed on the side. The optical compensation film is made of a material shown in the following table, an optical compensation film made of a polymer film showing the optical properties shown in the following table, or a curable discotic on a polymer film showing the optical properties shown in the following table. An optical compensation film comprising a liquid crystal composition and having a retardation layer having optical characteristics shown in the following table. The polymer film is used as a third retardation layer in the front retardation region, a retardation layer made of a curable discotic liquid crystal composition, and a melt inclined position made of a thermoplastic resin composition formed by the melt extrusion. The retardation film was disposed as a fourth retardation layer in the front side retardation region. In the fourth retardation layer, it was confirmed from the measurement of optical properties that the discotic liquid crystal molecules were fixed in a hybrid alignment state and that the main axis of the melt-formed thermoplastic film was inclined. . The optical properties of the polymer film used as the third retardation layer are adjusted by selecting the material of the polymer film, stretching conditions, additives, etc., and the optical properties of the fourth retardation layer are It adjusted by etc. When the polymer film used as the third retardation layer has an in-plane slow axis, the in-plane slow axis is orthogonal to the absorption axis of the front polarizer (26 in FIG. 1) or Parallel. A commercially available cellulose acylate film, trade name “Fujitac TD80UL” (manufactured by FUJIFILM Corporation) was bonded to the other surface of the polarizing film.

  Further, when the front side polarizer and the rear side polarizer were bonded to the liquid crystal cell, the front side and rear side substrate rubbing directions of the liquid crystal cell were used as the first retardation layer in the rear side retardation region. It intersected with the in-plane slow axis of the polymer film at about 45 °. The same applies to the case where the polymer film used as the third retardation layer in the front retardation region has an in-plane slow axis. The absorption axis of the front side polarizer and the rear side polarizer intersects the liquid crystal cell alignment direction (the rubbing direction of the front side substrate or the rear side substrate) at about 45 °, and the absorption of the front side polarizer and the rear side polarizer. The crossing angle of the axes was approximately 90 ° orthogonal Nicol.

(2) Evaluation of ECB type liquid crystal display device The front contrast ratio and contrast viewing angle characteristics were evaluated in the same manner as in the TN mode liquid crystal display device. The results are shown in the following table. In addition, the meanings of “TAC” and “norbornene” in the following table are as described above.

From the above results, the ECB type liquid crystal display devices of Examples 20 and 21 of the first aspect in which the retardation film satisfying the above formula (I) is disposed between the rear-side polarizer and the liquid crystal cell having the COA structure are used. However, it can be understood that the front CR is higher than that of the comparative ECB type liquid crystal display device (Comparative Examples 28 and 29) having the same configuration except that a liquid crystal cell having a non-COA structure is used.
Similarly, a retardation film satisfying the above formula (II) and a retardation layer satisfying the above formula (III) (a layer made of a DLC composition or a retardation film prepared by a melting gradient method) are rear-side polarized light. The ECB type liquid crystal display devices of Examples 15 to 19, 22 and 23 of the second embodiment arranged between the child and the COA structure liquid crystal cell are the same except that the non-COA structure liquid crystal cell is used. It can be understood that the front CR is higher than that of the ECB type liquid crystal display device of the comparative example of the configuration (Comparative Examples 23, 26, 27, 30 and 31).

Further, referring to Comparative Examples 21 and 22 and Comparative Examples 24 and 25, these are ECB type liquid crystal display devices having the same configuration except that the liquid crystal cell has a difference in COA structure or non-COA structure. The relationship between Example 15 and Comparative Example 23 is the same. However, in Comparative Examples 21 and 22, Rth (550) in the rear side phase difference region does not satisfy Formula (II), and therefore, the front CR is rather lowered as compared with Comparative Examples 24 and 25.
From this, the effect of the present invention is that the COA structure is adopted, and in the first aspect, the rear side phase difference region is obtained only when the formula (I) is satisfied; Then, the rear side retardation region can be obtained only when the first retardation layer satisfying the formula (II) and the second retardation layer satisfying the formula (III) are obtained. It is.

3. Production and Evaluation of OCB Type Liquid Crystal Display Device (1) Preparation of OCB Type Liquid Crystal Cells 5 and 6 OCB Type Liquid Crystal Cell 5 having the same COA configuration as shown in FIGS. 1 and 2, and the configuration shown in FIG. An OCB type liquid crystal cell 6 having the same non-COA configuration was produced. The liquid crystal cells 5 and 6 are liquid crystal cells manufactured by the same method except that the positions of the color filters are different.
In addition, the color filter is composed of a colored photosensitive composition prepared as described in Examples 17, 18 and 19 in JP-A-2009-144126, and an organic developer CD2000 (Fuji Film Electromaterial). Manufactured by the same company). The liquid crystal cell has a cell gap of 6.8 μm, and the liquid crystal layer has a positive dielectric anisotropy and a refractive index anisotropy Δn = 0.1396 (589 nm, 20 ° C.) (for example, ZLI1132 manufactured by Merck). ) To produce a bend-aligned liquid crystal cell. Δnd (550) of the produced liquid crystal cells 5 and 6 was 950 nm.

  As a rear side polarizing plate (PL1 in FIG. 1), a polarizing film and a polarizing plate having an optical compensation film on one surface thereof, the optical compensation film (rear side retardation region 20 in FIG. 1) is used. The liquid crystal cell was placed on the side. The optical compensation film is made of a material shown in the following table, a polymer film showing the optical properties shown in the following table, a curable discotic liquid crystal composition, and a retardation layer showing the optical properties shown in the following table. This is an optical compensation film formed. The polymer film was disposed as the first retardation layer in the rear side retardation region, and the retardation layer composed of the curable discotic liquid crystal composition was disposed as the second retardation layer in the rear side retardation region. In the second retardation layer, it was confirmed from the measurement of optical characteristics that the discotic liquid crystal molecules were fixed in a hybrid alignment state. The optical properties of the polymer film used as the first retardation layer are adjusted by selecting the material of the polymer film, stretching conditions, additives, etc., and the optical properties of the second retardation layer are as follows: It adjusted by etc. When the polymer film used as the first retardation layer has an in-plane slow axis, the in-plane slow axis is orthogonal to the absorption axis of the rear polarizer (24 in FIG. 1) or Parallel. A commercially available cellulose acylate film, trade name “Fujitac TD80UL” (manufactured by FUJIFILM Corporation) was bonded to the other surface of the polarizing film.

  As a front side polarizing plate (PL2 in FIG. 1), a polarizing film and a polarizing plate having an optical compensation film on one surface thereof, the optical compensation film (front side retardation region 22 in FIG. 1) is used. The liquid crystal cell was placed on the side. The said optical compensation film is an optical compensation film which consists of a material shown to the following table | surface, and consists of a polymer film which shows the optical characteristic shown to the following table | surface. The polymer film was arranged as a third retardation layer in the front side retardation region. The optical properties of the polymer film used as the third retardation layer were adjusted by selecting the polymer film material, stretching conditions, additives, and the like. When the polymer film used as the third retardation layer has an in-plane slow axis, the in-plane slow axis is orthogonal to the absorption axis of the front polarizer (26 in FIG. 1) or Parallel. A commercially available cellulose acylate film, trade name “Fujitac TD80UL” (manufactured by FUJIFILM Corporation) was bonded to the other surface of the polarizing film.

  Further, when the front side polarizer and the rear side polarizer were bonded to the liquid crystal cell, the front side and rear side substrate rubbing directions of the liquid crystal cell were used as the first retardation layer in the rear side retardation region. It intersected with the in-plane slow axis of the polymer film at about 45 °. The same applies to the case where the polymer film used as the third retardation layer in the front retardation region has an in-plane slow axis. The absorption axis of the front side polarizer and the rear side polarizer intersects the liquid crystal cell alignment direction (the rubbing direction of the front side substrate or the rear side substrate) at about 45 °, and the absorption of the front side polarizer and the rear side polarizer. The crossing angle of the axes was approximately 90 ° orthogonal Nicol.

(2) Evaluation of OCB type liquid crystal display device The front contrast ratio and contrast viewing angle characteristics were evaluated in the same manner as in the TN mode liquid crystal display device. The results are shown in the following table. In addition, the meanings of “TAC” and “norbornene” in the following table are as described above.

  From the above results, a retardation film satisfying the above formula (II) and a retardation layer satisfying the above formula (III) (a layer made of a DLC composition) are composed of a rear side polarizer and a liquid crystal cell having a COA structure. The OCB type liquid crystal display device of Example 24 of the present invention disposed in between is compared with the OCB type liquid crystal display device of comparative example (Comparative Example 32) having the same configuration except that a liquid crystal cell having a non-COA structure is used. It can be understood that the front CR is high.

DESCRIPTION OF SYMBOLS 10 Liquid crystal layer 12 Color filter layer 14 Array member 16 Rear side substrate 18 Front side substrate 20 Rear side phase difference area 22 Front side phase difference area 24 Rear side polarizer 26 Front side polarizer 28 Backlight unit LC Liquid crystal cell of COA structure PL1 Rear side polarizing plate PL2 Front side polarizing plate

Claims (12)

A front side polarizer, a rear side polarizer, a liquid crystal layer disposed between the front side polarizer and the rear side polarizer, and a color filter layer disposed between the liquid crystal layer and the rear side polarizer. And a rear-side retardation region (hereinafter referred to as a rear-side polarizer and a color filter layer) composed of one or more retardation layers disposed between the rear-side polarizer and the color filter layer. 1 layer or the whole of the two or more retardation layers disposed between the two layers is referred to as a “rear-side retardation region”); and one layer or two disposed between the front-side polarizer and the liquid crystal layer. A front side retardation region (hereinafter referred to as one or more retardation layers arranged between a front side polarizer and a liquid crystal layer) is composed of a front side retardation layer composed of a retardation layer of at least one layer. A liquid crystal display device having a region)
The rear side retardation region is composed of one or more polymer films having optical anisotropy, and has the following formula (II)
(II): | Rth (550) | ≦ 100 nm
Where Rth (λ) means retardation in the thickness direction at a wavelength λnm (nm);
Retardation R2 [+ 40 °] at a wavelength of 550 nm measured from a direction tilted + 40 ° from the normal to the tilt azimuth in the plane including the tilt azimuth and the normal, and opposite to the normal The ratio of retardation R2 [−40 °] (provided that R2 [−40 °] <R2 [+ 40 °]) at a wavelength of 550 nm measured from a direction inclined by 40 ° to the following formula (III)
(III): 1 <R2 [+ 40 °] / R2 [−40 ° ]
Is composed of a second retardation layer satisfies a; and the liquid crystal layer, and a rear-side substrate is an array substrate provided with the color filter layer, it is a counter substrate disposed to face the array substrate A liquid crystal display device which is sandwiched between a front substrate and a liquid crystal display device. The second retardation layer has the following formula (IIIa)
(IIIa): 3 ≦ R2 [+ 40 °] / R2 [−40 °]
The liquid crystal display device according to claim 1, wherein: The first retardation layer has the following formula (IV)
(IV): 0 ≦ Re (550) ≦ 500 nm
The liquid crystal display device according to claim 1, wherein: The front side retardation region is made of one or more polymer films having optical anisotropy, and has the following formulas (V) and (VI)
(V): 0 ≦ Re (550) ≦ 500 nm
(VI): −100 nm ≦ Rth (550) ≦ 1000 nm
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is configured by a third retardation layer that satisfies the above. The front side retardation region is made of one or more polymer films having optical anisotropy, and has the following formulas (V) and (VI)
(V): 0 ≦ Re (550) ≦ 500 nm
(VI): −100 nm ≦ Rth (550) ≦ 1000 nm
A third retardation layer satisfying
Retardation R4 [+ 40 °] at a wavelength of 550 nm measured from a direction tilted + 40 ° from the normal to the tilt azimuth in the plane including the tilt azimuth and the normal, and opposite to the normal The ratio of retardation R4 [−40 °] (provided that R4 [−40 °] <R4 [+ 40 °]) at a wavelength of 550 nm measured from a direction inclined at 40 ° to the following formula (VII)
(VII): 1 <R4 [+ 40 °] / R4 [−40 °]
However, Re ((lambda)) means in-plane retardation (nm) in wavelength (lambda) nm; It is comprised from the 4th phase difference layer satisfying; The liquid crystal display device according to item. The fourth retardation layer has the following formula (VIIa)
(VIIa): 3 ≦ R4 [+ 40 °] / R4 [−40 °]
The liquid crystal display device according to claim 5, wherein: A TN type liquid crystal display device in which the liquid crystal layer is aligned parallel to the substrate surface when no voltage is applied and at a twist angle of 45 ° to 135 ° between the substrates;
The third retardation layer has the following formulas (Va) and (VIa)
(Va): 0 ≦ Re (550) ≦ 400 nm
(VIa): −100 nm ≦ Rth (550) ≦ 300 nm
The liquid crystal display device according to claim 1, wherein: A TN type liquid crystal display device in which the liquid crystal layer is aligned parallel to the substrate surface when no voltage is applied and at a twist angle of 90 ° between the substrates;
The third retardation layer has the following formulas (Vb) and (VIb)
(Vb): 0 ≦ Re (550) ≦ 300 nm
(VIb): 50 nm ≦ Rth (550) ≦ 300 nm
The liquid crystal display device according to claim 7, wherein: A liquid crystal display device in which the liquid crystal layer is aligned parallel to the substrate surface when no voltage is applied and at a twist angle of 0 ° to 45 ° between the substrates;
The third retardation layer has the following formulas (Vc) and (VIc)
(Vc): 70 nm <Re (550) ≦ 400 nm
(VIc): −100 nm ≦ Rth (550) ≦ 250 nm
The liquid crystal display device according to claim 1, wherein: A liquid crystal display device in which the liquid crystal layer is bend-aligned between substrates parallel to the substrate surface when no voltage is applied;
The third retardation layer has the following formulas (Vd) and (VId)
(Vd): 0 ≦ Re (550) ≦ 100 nm
(VId): 200 nm ≦ Rth (550) ≦ 1000 nm
The liquid crystal display device according to claim 1, wherein: The liquid crystal display device according to claim 1, wherein the array substrate is an array substrate having a black matrix that partitions pixels provided with the color filter layer. The liquid crystal display according to claim 1, wherein the second retardation layer satisfies the following expression 4.3 ≦ R2 [+ 40 °] / R2 [−40 °]. apparatus.

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