JP5184803B2 - Liquid crystal display device and color filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which has excellent color reproducibility at a wide viewing angle and is free from color shift even when being observed from oblique angles during black display. <P>SOLUTION: The liquid crystal display device includes: at least, a pair of substrates disposed so as to face each other, at least one of which has an electrode; a liquid crystal cell where an electric field having a component parallel with the substrate having the electrode is formed; and a pair of polarizing palates. The liquid crystal cell includes first, second, and third pixel regions and color filters disposed on respective pixel regions, and color filters disposed on at least two pixel regions are different in Rth, and &lambda;<SB>1</SB>&lt;&lambda;<SB>2</SB>&lt;&lambda;<SB>3</SB>is satisfied wherein &lambda;<SB>1</SB>, &lambda;<SB>2</SB>, and &lambda;<SB>3</SB>are principal wavelengths (nm) at which color filters disposed on the first, second, and third pixel regions take maximum transmittances respectively, and a retardation Rth(&lambda;<SB>1</SB>) in a perpendicular direction of color filters at the wavelength &lambda;<SB>1</SB>is equal to or smaller than 5 nm. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a liquid crystal display device having wide viewing angle characteristics, particularly excellent color reproducibility in a wide viewing angle. The present invention also relates to a color filter that contributes to an improvement in color reproducibility of a liquid crystal display device, particularly an IPS mode liquid crystal display device.

  Liquid crystal display elements (also referred to as liquid crystal display panels), electroluminescence elements (separated into organic and inorganic types depending on the fluorescent material used, hereinafter referred to as EL elements), field emission devices (hereinafter referred to as FED elements), electrophoresis A display device using an element or the like displays an image without providing a space (vacuum housing) for two-dimensionally scanning an electron beam on the back side of a display screen like a cathode ray tube (CRT). . Therefore, these display devices are characterized by being thinner and lighter and having lower power consumption than a cathode ray tube. These display devices are sometimes referred to as flat panel displays because of their appearance characteristics.

  A display device using a liquid crystal display element, an EL element, a field emission element, or the like is a display using a cathode ray tube in various applications such as notebook computers, OA devices such as personal computer monitors, portable terminals, and televisions because of the above-described advantages over the cathode ray tube. It is becoming widespread instead of devices. Technological innovations such as viewing angle characteristics of liquid crystal display elements and EL elements and image quality improvement such as expansion of the display color reproducibility area are behind the progress of replacement of CRTs with flat panel displays. Recently, with the widespread use of multimedia and the Internet, there has been an improvement in video display performance. Furthermore, there are some fields that cannot be realized with CRT, such as electronic paper, large public, and advertising information displays.

The liquid crystal display device usually includes a liquid crystal cell, a drive circuit that sends a display signal voltage to the liquid crystal cell, a backlight (back light source), and a signal control system that sends an input image signal to the drive circuit. Call.
A liquid crystal cell usually comprises liquid crystal molecules, two substrates for enclosing and sandwiching the liquid crystal molecules, and an electrode layer for applying a voltage to the liquid crystal molecules, and a polarizing plate is disposed on the outer side thereof. The polarizing plate is usually composed of a protective film and a polarizing film, and is obtained by dyeing a polarizing film made of a polyvinyl alcohol film with iodine, stretching, and laminating both surfaces with a protective film. In the transmissive liquid crystal display device, the polarizing plate is attached to both sides of the liquid crystal cell, and one or more optical compensation sheets may be disposed. In a reflective liquid crystal display device, usually, a reflector, a liquid crystal cell, one or more optical compensation sheets, and a polarizing plate are arranged in this order. The liquid crystal cell performs ON-OFF display depending on the alignment state of liquid crystal molecules, and can be applied to any of a transmission type, a reflection type, and a semi-transmission type.

By using an optical compensation sheet or the like whose optical properties are designed to an optimum value for each wavelength of light, a liquid crystal display device with little color change depending on the viewing angle can be provided. For example, in Patent Document 1, in-plane retardation at wavelengths of 450 nm and 550 nm has a predetermined relationship for the purpose of providing a polarizing film that prevents light leakage when observed from an oblique direction and the leakage light is not colored. A wide viewing angle polarizing film having a polymer oriented film satisfying the above has been proposed. Patent Document 2 discloses the value and direction of retardation on a color filter for the purpose of providing a color display element that optimizes the intensity balance of each color light from the tilt direction and improves display quality. Ferroelectric liquid crystal color filters have been proposed in which at least one of them has a transparent protective film different for each color.
JP 2002-221622 A JP-A-5-196931

However, in the liquid crystal display device, color reproducibility cannot be improved for all wavelengths in the visible light region, and coloring generated in an oblique direction cannot be improved. In particular, when observing obliquely during black display, the so-called color shift problem of coloring blue or red has not yet been solved.
Therefore, an object of the present invention is to provide a liquid crystal display device having excellent color reproducibility in a wide viewing angle.
It is another object of the present invention to provide a liquid crystal display device in which color shift is not observed or color shift is reduced even when observed obliquely during black display.
Another object of the present invention is to provide a color filter that contributes to an improvement in color reproducibility of a liquid crystal display device in a horizontal alignment mode.

  As a result of the study by the present inventors, in the liquid crystal display device in the horizontal alignment mode such as the IPS mode, when observed from an oblique direction, for example, in the aspect having the RGB color filter layer, among the main wavelengths taking the maximum transmittance, It has been found that there is a tendency to color the blue with the shortest wavelength. As a result of further intensive studies, it was found that the blue coloration in the oblique direction can be greatly reduced when the Rth in the thickness direction of the color filter at the wavelength of blue light satisfies a predetermined condition. Based on the above, the present invention has been completed.

That is, the means for solving the above problems are as follows.
[1] A pair of substrates, at least one of which has electrodes, and a liquid crystal layer which is disposed between the pair of substrates and whose orientation is controlled, are parallel to the substrate having the electrodes by the electrodes. A liquid crystal display device including at least a liquid crystal cell in which an electric field having various components is formed and a pair of polarizing plates arranged with the liquid crystal layer interposed therebetween, wherein the liquid crystal cell includes first, second and third liquid crystal cells. Rth of the color filters arranged on at least two of the pixel filters are different from each other, and the first, first, Λ ₁ <λ ₂ <λ ₃ , where λ ₁ , λ ₂ , and λ ₃ (unit: nm) are the main wavelengths taking the maximum transmittance of the color filters arranged on the second and third pixel regions, respectively. And the wavelength at wavelength λ ₁ A liquid crystal display device characterized in that the retardation Rth (λ ₁ ) in the thickness direction of the Lar filter satisfies the following formula (I):
Formula (I): Rth (λ ₁ ) ≦ 5 nm.
[2] The liquid crystal display device according to [1], wherein retardation Rth (λ ₂ ) in the thickness direction at a wavelength λ ₂ of the color filter satisfies the following formula (II):
Formula (II): −35 nm ≦ Rth (λ ₂ ) ≦ 25 nm.
[3] The liquid crystal display device of [1] or [2], wherein retardation Rth (λ ₃ ) in the thickness direction at a wavelength λ ₃ of the color filter satisfies the following formula (III):
Formula (III): −45 nm ≦ Rth (λ ₃ ) ≦ 0 nm.
[4] The liquid crystal display device according to any one of [1] to [3], wherein the parallel electric field is generated by a pixel electrode and a counter electrode arranged in different layers.
[5] Any one of [1] to [3], wherein the parallel electric field is generated by a pair of electrodes that are arranged in different layers and at least one of which is transparent, and an electrode to which no voltage is applied. Liquid crystal display device.
[6] At least one of the pair of polarizing plates has a polarizing film and a protective film, and the in-plane retardation Re (λ) and retardation Rth (λ) in the thickness direction of the protective film at a wavelength λnm. Satisfying all of the following formulas and disposed between the liquid crystal cell and the polarizing film: [1] to [5]
0 nm ≦ Re (630) ≦ 10 nm
| Rth (630) | ≦ 80nm
| Re (400) -Re (700) | ≦ 20 nm
| Rth (400) −Rth (700) | ≦ 45 nm.

[7] At least one of the pair of polarizing plates has a polarizing film and a protective film, and an in-plane retardation Re (λ) and a retardation Rth (λ) in the thickness direction of the protective film at a wavelength λnm. However, the liquid crystal display device according to [1], which satisfies all the following formulas and is disposed between the liquid crystal cell and the polarizing film:
0 nm ≦ Re (630) ≦ 10 nm
| Rth (630) | ≦ 25nm
| Re (400) -Re (700) | ≦ 10 nm
| Rth (400) −Rth (700) | ≦ 35 nm.
[8] The liquid crystal display device according to [7], wherein retardation Rth (λ ₂ ) in the thickness direction at a wavelength λ ₂ of the color filter satisfies the following formula (II) ′:
Formula (II) ′: −20 nm ≦ Rth (λ ₂ ) ≦ 10 nm.
[9] The liquid crystal display device according to [7] or [8], wherein retardation Rth (λ ₃ ) in the thickness direction at a wavelength λ ₃ of the color filter satisfies the following formula (III) ′:
Formula (III) ′: −15 nm ≦ Rth (λ ₃ ) ≦ 20 nm.

[10] A color filter layer including first, second and third colored regions, wherein Rth of at least two colored regions are different from each other, and maximum transmittance of the first, second and third colored regions Λ ₁ , λ ₂ , and λ ₃ (unit: nm), respectively, where λ ₁ <λ ₂ <λ ₃ holds, and the letter in the thickness direction of the color filter layer at wavelength λ ₁ A color filter characterized in that the foundation Rth (λ ₁ ) satisfies the following formula (I):
Formula (I): Rth (λ ₁ ) ≦ 5 nm.
[11] The color filter according to [10], wherein retardation Rth (λ ₂ ) in the thickness direction at a wavelength λ ₂ of the color filter layer satisfies the following formula (II):
Formula (II): −35 nm ≦ Rth (λ ₂ ) ≦ 25 nm.
[12] The color filter according to [10] or [11], wherein retardation Rth (λ ₃ ) in the thickness direction at a wavelength λ ₃ of the color filter layer satisfies the following formula (III):
Formula (III): −45 nm ≦ Rth (λ ₃ ) ≦ 0 nm.
[13] The color filter according to [10], wherein retardation Rth (λ ₂ ) in the thickness direction at a wavelength λ ₂ of the color filter layer satisfies the following formula (II) ′:
Formula (II) ′: −20 nm ≦ Rth (λ ₂ ) ≦ 10 nm.
[14] The color filter according to [10] or [13], wherein retardation Rth (λ ₃ ) in the thickness direction at a wavelength λ ₃ of the color filter layer satisfies the following formula (III) ′:
Formula (III) ′: −15 nm ≦ Rth (λ ₃ ) ≦ 20 nm.

  According to the present invention, a liquid crystal display device having excellent color reproducibility in a wide viewing angle can be provided. In addition, according to the present invention, it is possible to provide a liquid crystal display device in which color shift is not observed or color shift is reduced even when observed from an oblique direction during black display. In addition, according to the present invention, it is possible to provide a color filter that contributes to an improvement in color reproducibility of a liquid crystal display device.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.
In the present specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at the wavelength λ, respectively. Re (λ) is measured 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).
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis) (in the absence of the slow axis, any in-plane value) 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), Based on the value, the assumed value of the average refractive index, and the input film thickness value, Rth can also be calculated from the following equations (1) and (2).

注記：
式中、Ｒｅ（θ）は、法線方向から角度θ傾斜した方向におけるレターデーション値を表す。
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し、ｄは膜厚（ｎｍ）を表す。

Note:
In the formula, Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
In the formula, nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction orthogonal to nx in the plane, and nz represents the refractive index in the direction orthogonal to nx and ny. , D represents the film thickness (nm).

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 the above-mentioned Re (λ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotation axis) from −50 degrees to +50 degrees with respect to the film normal direction. The light of wavelength λ nm is incident from each inclined direction in 10 degree steps 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, the assumed value of the average refractive index may be a value in a polymer handbook (John Wiley & Sons, Inc.) or a catalog of various optical films. 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).
By inputting these assumed values of average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

In the present specification, regarding the angle, “+” means the counterclockwise direction, and “−” means the clockwise direction. Further, when the upper direction of the liquid crystal display device is 12 o'clock and the lower direction is 6 o'clock, the absolute value 0 ° direction in the angular direction means the 3 o'clock direction (right direction of the screen). Further, the “slow axis” means a direction in which the refractive index is maximized. The “visible light region” means 380 nm to 780 nm. Further, in this specification, the measurement wavelength such as the refractive index is a value at λ = 550 nm in the visible light region unless otherwise specified.
In addition, regarding the angle between each axis and direction, “parallel”, “vertical”, “45 °”, etc. means “approximately parallel”, “approximately vertical”, “approximately 45 °”, and is not exact. . Some deviation is allowed within the range to achieve each purpose. For example, “parallel” means that the crossing angle is approximately 0 °, and is −10 ° to 10 °, preferably −5 ° to 5 °, more preferably −3 ° to 3 °. “Vertical” means that the crossing angle is approximately 90 °, and is 80 ° to 100 °, preferably 85 ° to 95 °, more preferably 87 ° to 93 °. “45 °” means that the crossing angle is approximately 45 °, and is 35 ° to 55 °, preferably 40 ° to 50 °, more preferably 42 ° to 48 °.

  In this specification, “polarizing film (polarizing film)” and “polarizing film” are distinguished from each other. However, the “polarizing film” has a transparent protective film for protecting the polarizing film on at least one surface of the “polarizing film”. It shall mean a laminate.

The present invention includes a pair of opposed substrates, at least one of which has an electrode, and a liquid crystal layer that is disposed between the substrates and whose orientation is controlled, and is parallel to the substrate having the electrode by the electrode. A liquid crystal display device having at least a liquid crystal cell in which an electric field having a component is formed and a pair of polarizing plates arranged with the liquid crystal layer interposed therebetween, wherein the liquid crystal cell includes first, second and third liquid crystal cells. And a color filter disposed on each of the pixel regions, and among the color filters, Rth of color filters disposed on at least two of the pixel regions are different from each other, and the first and second And λ ₁ <λ ₂ <λ _3, where λ ₁ , λ ₂ , and λ ₃ (unit: nm) are the main wavelengths taking the maximum transmittance of the color filters arranged on the third pixel region, respectively. enacted, and color at a wavelength λ ₁ Filter thickness direction retardation Rth (λ ₁₎ is a liquid crystal display device characterized by satisfying the following formula (I).
Formula (I): Rth (λ ₁ ) ≦ 5 nm

In the case of using a so-called RGB color filter in which the first, second and third picture element regions are R, G and B in the liquid crystal display device of the present invention, λ ₁ is the wavelength of blue light, about 450 nm, As the RGB color filter, an RGB color filter satisfying Rth (450) ≦ 5 nm is used. The same applies to an RGBW color filter having a W layer as well as an RGB layer. In the aspect using the RGB color filter satisfying Rth (450) ≦ 5 nm, it is possible to reduce the tint when observed from an oblique direction, particularly the blue tint, and an excellent color over all wavelengths in the visible light range. Reproducibility can be realized.

Hereinafter, embodiments of the present invention using RGB color filters will be described with reference to the drawings.
The liquid crystal display device shown in FIG. 1 includes a liquid crystal cell (9 to 13), an upper polarizing plate 21 (1 to 6) and a lower polarizing plate 22 (14 to 19) disposed between the liquid crystal cells, and a lower side. A backlight unit 20 including a lamp 20 a serving as a light source is provided on the outer side of the polarizing plate 22. The liquid crystal cells (9 to 13) include a liquid crystal cell upper substrate 9, a liquid crystal cell lower substrate 12, and a liquid crystal layer 11 sandwiched therebetween. The lower substrate 12 has an electrode layer (not shown in FIG. 1) on its opposite surface, and the electrode layer is configured to be able to supply an electric field parallel to the surface of the substrate 12 to the liquid crystal layer. Yes. The electrode layer is usually made of transparent indium tin oxide (ITO). An alignment layer (not shown in FIG. 1) for controlling the alignment of the liquid crystal molecules 11 is formed on the electrode layer of the substrate 12 and on the opposite surface of the substrate 9, and is applied to the surface when no driving voltage is applied. The orientation direction of the liquid crystal molecules 11 is controlled by the rubbing treatment directions 10 and 13.

  The shape, configuration, etc. of the electrode are not particularly limited, and any may be used as long as an electric field parallel to the substrate of the liquid crystal cell can be formed. In general, electrode configurations used in IPS mode and FFS mode liquid crystal display devices can be used. For example, a pixel electrode and a counter electrode arranged in different layers may be used, or at least one of the electrodes arranged in different layers may be composed of a pair of transparent electrodes and an electrode to which no voltage is applied. May be.

FIG. 2 schematically shows an OFF state and an ON state of an example of an IPS mode liquid crystal display device. Note that FIG. 2 shows a part of one pixel of the liquid crystal display device, and the relative sizes and the like of the respective members do not necessarily coincide with the actual ones. The same applies to FIG. 3 described later. In FIG. 2, members corresponding to the members in FIG. The same applies to FIG. 3 described later.
In FIG. 2, the plurality of linear electrode layers 24 formed on the opposing surface of the substrate 12 form an electric field 23 including an electric field component parallel to the plane of the substrate 12 when a voltage is applied. When no voltage is applied or when a low voltage is applied (OFF state), the liquid crystal molecules 11 are aligned in the longitudinal direction of the linear electrode layer 24 by the rubbing axes (10 and 13 in FIG. 1) of the opposing surfaces of the substrates 9 and 12. The orientation is controlled so as to have a slight angle with respect to. In this case, the dielectric anisotropy of the liquid crystal is assumed to be positive. In a state in which a voltage is applied to the linear electrode layer 24 (ON state), an electric field 23 including a component parallel to the substrates 9 and 12 is formed, and the liquid crystalline molecules 11 are aligned with their major axes coinciding with the electric field direction. . The angle formed by the electric field direction 23 with respect to the surface of the substrate 12 is preferably 20 degrees or less, more preferably 10 degrees or less, that is, substantially parallel. Hereinafter, in the present invention, those below 20 degrees are generically expressed as a parallel electric field. Even if the linear electrode layer 24 is formed separately on the upper and lower substrates or formed only on one substrate, the effect does not change.

FIG. 3 schematically shows an OFF state and an ON state of an example of an FFS mode liquid crystal display device. In addition, the same number is attached | subjected to the member same as FIG. 2, and detailed description is abbreviate | omitted.
In FIG. 3, the electrode has a two-layer structure of an upper electrode layer 24 and a lower electrode layer 26, and the layers are arranged differently via an insulating layer 25. The electrode layer 26 may be an unpatterned electrode layer or an electrode layer patterned in a linear shape. The upper electrode layer 24 is preferably linear, but may be any of a mesh shape, a spiral shape, a dot shape, or the like as long as the electric field from the lower electrode layer 26 can pass therethrough. A floating electrode having a neutral potential may be further added. The insulating layer 25 may be a layer made of an inorganic material such as SiO or a nitride film, or a layer made of an organic material such as acrylic or epoxy. By applying a voltage to the upper electrode layer 24 and the lower electrode layer 26, an electric field 23 ′ including a component parallel to the substrate 8 is formed. In the OFF state, as in the IPS mode, the liquid crystalline molecules 11 are aligned with their long axes coinciding with the rubbing axes (10 and 13 in FIG. 1) of the opposing surfaces of the substrates 9 and 12. On the other hand, in the ON state, an electric field 23 ′ containing a component parallel to the substrates 9 and 2 is formed, and the liquid crystalline molecules 11 are aligned with their long axes coinciding with the electric field direction.

Although a detailed structure is not shown in FIG. 1, RGB color filters are arranged on the opposing surface of the upper substrate 9 or the lower substrate 12 of the liquid crystal cell, and the liquid crystal cell has an R layer, a G layer, and a B layer. It includes three arranged pixel regions. In this embodiment, among these three colored layers, Rth in the thickness direction of at least two colored layers, for example, the G layer and the R layer, or the G layer and the B layer are different from each other. More preferably, the three colored layers have different Rths. In the RGB color filter, the main wavelengths taking the maximum transmittance of the pixel region are the blue light wavelength λ _B , the green light wavelength λ _G and the red light wavelength λ _R in ascending order. In this embodiment, when the retardation in the thickness direction of the color filter in the R, G, and B layers is Rth (λ _B ), Rth (λ _G ), and Rth (λ _R ), in this embodiment, Rth (λ _B ) of the RGB color filter. Satisfies the following relational expression (I). In order to further improve color reproducibility, it is preferable to adjust Rth (λ _G ) and Rth (λ _R ), but the preferable range is the optical characteristics of the liquid crystal cell side protective films 5 and 14 for polarizing plates. Depends on.
For example, in FIG. 1, in the example using the polymer film which satisfy | fills following formula (2) -1-(2) -4 as the liquid crystal cell side protective film 5 and / or 14 (preferably 5 and 14) for polarizing plates in FIG. Furthermore, it is preferable that at least one of Rth (λ _G ) and Rth (λ _R ) of the RGB color filter satisfies each of the following formulas (II) and (III). ) And (III) are more preferable.
(I): Rth (λ _B ) ≦ 5 nm
(II): −35 nm ≦ Rth (λ _G ) ≦ 25 nm
(III): −45 nm ≦ Rth (λ _R ) ≦ 0 nm
(2) -10 0 nm ≦ Re (630) ≦ 10 nm
(2) -2 | Rth (630) | ≦ 80 nm
(2) -3 | Re (400) -Re (700) | ≦ 20 nm
(3) -4 | Rth (400) -Rth (700) | ≦ 45 nm.

  Examples of the polymer film satisfying the formulas (2) -1 to (2) -4 include a cellulose acylate film having an in-plane retardation Re of almost 0 and a thickness direction retardation Rth of about 40 nm. .

Moreover, as the liquid crystal cell side protective film 5 and / or 14 (preferably 5 and 14) for the polarizing plate in FIG. 1, a film satisfying all of the following formulas (3) -1 to (3) -4 (preferably In the example using the cellulose acylate film), Rth (λ _B ) satisfies the relational expression (I), and at least one of Rth (λ _G ) and Rth (λ _R ) of the RGB color filter is It is preferable that each of the following formulas (II) ′ and (III) ′ is satisfied, and it is more preferable that both satisfy the following formulas (II) ′ and (III) ′.
(II) ′: −20 nm ≦ Rth (λ _G ) ≦ 10 nm
(III) ′: −15 nm ≦ Rth (λ _R ) ≦ 20 nm
(3) -1: 0 nm ≦ Re (630) ≦ 10 nm
(3) -2: | Rth (630) | ≦ 25 nm
(3) -3: | Re (400) -Re (700) | ≦ 10 nm
(3) -4: | Rth (400) -Rth (700) | ≦ 35 nm

In order to satisfy this relational expression, for example, color filters having different R layer thickness (d _r ), G layer thickness (d _g ), and B layer thickness (d _b ) may be used.

  In FIG. 1 again, the liquid crystal cell is disposed between the upper polarizing plate 21 and the lower polarizing plate 22, and the upper polarizing plate 21 and the lower polarizing plate 22 are disposed with their absorption axes 4 and 17 orthogonal to each other. The When the upper polarizing plate 21 is a viewing side polarizing plate, the absorption axis 4 of the upper polarizing plate 21 is orthogonal to the extraordinary refractive index direction of the liquid crystalline molecules 11 in the liquid crystal cell when no voltage is applied (OFF state). It is preferable to laminate them as described above. The upper polarizing plate 21 includes the polarizing film 3 and the protective films 1 and 5 disposed on the surface thereof, and the lower polarizing plate 22 includes the polarizing film 16 and the protective films 14 and 18 disposed on the surface thereof. And have.

  The protective films 1, 5, 14, and 18 disposed on the surfaces of the polarizing films 3 and 16 are generally made of stretched films and have a delay that matches the MD (Mechanical direction) direction or TD (Tenter direction). Has a phase axis. The MD directions of the two protective films 1 and 5 (or 14, 18) arranged on the surface of one polarizing film 3 (or 6) are parallel to each other like the upper polarizing plate 21 in FIG. 2 and 6), and may be orthogonal to each other (15 and 19 in FIG. 1) like the lower polarizing plate 22 in FIG.

  In FIG. 1, consider a case where light is incident from a backlight unit 20 disposed outside the lower polarizing plate 22. In a non-driving state (OFF state) in which a driving voltage is not applied to the electrodes (not shown in FIG. 1), the liquid crystalline molecules 11 in the liquid crystal layer are substantially parallel to the surfaces of the substrates 9 and 12 and have their long axes. Are oriented substantially parallel to the rubbing axes 10 and 13. In this state, the light that is in a predetermined polarization state by the polarizing film 16 does not receive the birefringence effect of the liquid crystalline molecules 11 and is blocked by the absorption axis 4 of the polarizing film 3 as a result. At this time, the display is black. On the other hand, in a driving state (ON state) in which a driving voltage is applied to an electrode (not shown in FIG. 1), an electric field including a component parallel to the substrate is formed, and the liquid crystalline molecules 11 have their long axes. Oriented in accordance with the direction of the electric field. As a result, the light that has become a predetermined polarization state by the polarizing film 18 changes its polarization state due to the birefringence effect of the liquid crystalline molecules 11, and as a result, passes through the polarizing film 3. At this time, the display is white. In the present invention, since the retardation Rth in the thickness direction of the color filter is made different for each pixel region, good color reproducibility can be obtained with a wide viewing angle, and coloring during black display, so-called color shift, can be achieved. It has been reduced.

  In the IPS mode liquid crystal display device of FIG. 2, the alignment control direction of the liquid crystal layer (rubbing axes 10 and 13 in FIG. 1) is preferably arranged as the vertical direction of the display device, the 12 o'clock to 6 o'clock direction, The absorption axes 4 and 17 of the upper polarizing plate and the lower polarizing plate are also preferably arranged in the 12 o'clock to 6 o'clock direction and orthogonal to each other. Further, the slow axes 6 and 15 of the protective films 5 and 14 arranged between the polarizing films 3 and 16 and the liquid crystal layer are also arranged at 12 o'clock to 6 o'clock, and are arranged closer to each other. It is preferable to arrange them in parallel with the rubbing axis of the cell substrate. Such an arrangement is effective in reducing leakage light during black display and eliminating coloring in the viewing angle direction.

  Further, as shown in FIG. 1, the optically anisotropic layer 7 may be disposed between the liquid crystal cell side protective film 5 of the upper polarizing plate 21 and the liquid crystal layer 11. The retardation value of the optically anisotropic layer 7 is preferably set to not more than twice the value of Δn · d of the liquid crystal layer 11. 1 shows a configuration in which the optically anisotropic layer 7 is disposed between the protective film 5 of the upper polarizing plate 21 and the liquid crystal layer 11, the protective film 14 of the lower polarizing plate 22 and the liquid crystal layer. 11 may be arranged between the two or both. Further, if the retardation of the protective film 5 of the upper polarizing film 3 is greater than the retardation of the protective film 14 of the lower polarizing film 16 by Rth being 20 nm or more, light leakage during black display is reduced and coloring in the viewing angle direction is performed. It is effective in solving the problem.

  In the FFS mode liquid crystal display device shown in FIG. 3, the alignment control direction (rubbing axes 10 and 13 in FIG. 1) of the liquid crystal layer is preferably arranged as the horizontal direction of the display device, 3 o'clock to 9 o'clock. The absorption axes 4 and 17 of the polarizing plate and the lower polarizing plate are also preferably arranged in the 3 o'clock to 9 o'clock direction and orthogonal to each other. Further, the slow axes 6 and 11 of the protective films 5 and 14 arranged between the polarizing films 3 and 16 and the liquid crystal layer are also arranged at 3 o'clock to 9 o'clock, and the liquid crystal arranged at a closer position. It is preferable to arrange them in parallel with the rubbing axis of the cell substrate. Such an arrangement is effective in reducing leakage light during black display and eliminating coloring in the viewing angle direction. Further, as shown in FIG. 1, the optically anisotropic layer 7 may be disposed between the liquid crystal cell side protective film 5 of the upper polarizing plate 21 and the liquid crystal layer 11. The retardation value of the optically anisotropic layer 7 is preferably set to not more than twice the value of Δn · d of the liquid crystal layer 11. 1 shows a configuration in which the optically anisotropic layer 7 is disposed between the protective film 5 of the upper polarizing plate 21 and the liquid crystal layer 11, the protective film 14 of the lower polarizing plate 22 and the liquid crystal layer. 11 may be arranged between the two or both.

The shape and arrangement of the electrodes are not limited to the configurations shown in FIGS. 2 and 3, and any shape electrodes and configurations conventionally used in the IPS mode and the FFS mode can be used. For example, in order to obtain a wider viewing angle, linear electrodes (sometimes referred to as “comb electrodes”) may be arranged in a zigzag shape. However, in this case, the orientation of the liquid crystal molecules in the liquid crystal layer is disturbed at the bent portion of the electrode, and the contrast of the display device may be lowered. In order to reduce this decrease in contrast, the slow axis (6 and 15 in FIG. 1) of the protective film (5 and 14 in FIG. 1) made of a cellulose acylate film or the like of the polarizing film (3 and 16 in FIG. 1) or the like. ) With the average orientation control direction (10 and 13 in FIG. 1) of the liquid crystal layer 11 within 10 °. When arranged in this way, the retardation unevenness of the liquid crystal layer due to the alignment disorder can be compensated, and the display uniformity can be improved. In addition, brightness unevenness during black display due to disordered alignment of liquid crystal molecules due to rubbing treatment can be compensated by self-compensating for retardation unevenness by arranging a protective film with its slow axis intersecting the rubbing axis. Unevenness can be reduced.
The average direction of the alignment disorder of these liquid crystal molecules deviates from the original alignment control direction by about 5 to 15 °. Display unevenness can be reduced by compensating the retardation by crossing the slow axis of the protective film with the average orientation axis. As described above, when the protective film is arranged with its slow axis intersected, if the Re value of the protective film is large, even if the unevenness can be reduced, the black luminance absolute value increases and the contrast decreases. Since it may occur, for example, it is preferable to use a film having a small Re and almost zero, such as a cellulose acylate film described in JP-A-2005-138375.
Furthermore, as described above, an optically anisotropic layer is arranged, and unevenness can be similarly reduced by intersecting the slow axis, orientation control direction, and average orientation direction with the average orientation control direction of the liquid crystal layer within 10 °. can do.

In addition, the FFS mode has a tendency that the viewing angle tends to be narrower than that of the IPS mode, and the liquid crystal alignment disorder is large because a high electric field is applied at the electrode end. From these facts, the slow axis (6 and 15 in FIG. 1) of the protective film (5 and 14 in FIG. 1) made of a cellulose film or the like is the average orientation control direction of the liquid crystal layer 11 (10 and 13 in FIG. 1). ) And within 10 °, the effect of reducing unevenness is further increased.
In both the IPS mode and the FFS mode liquid crystal display device, the slow axis of the protective film and the absorption axis of the polarizing film are provided for both or one of the viewing-side and backlight-side polarizing plates. It is preferable that it is shifted within the above range, and it is more preferable that the slow axis of the protective film and the absorption axis of the polarizing film are shifted within the above range.

Hereafter, each member etc. which can be used for the liquid crystal display device of this invention are demonstrated in detail.
[Liquid crystal materials]
The liquid crystal material constituting the liquid crystal layer used in the liquid crystal display device of the present invention is not particularly limited. In the liquid crystal display device having the configuration shown in FIG. 1, for example, nematic liquid crystal having a positive dielectric anisotropy Δε may be used as the liquid crystal material. The thickness (gap) of the liquid crystal layer is preferably more than 2.8 μm and less than 4.5 μm. When the retardation (Δn · d) of the liquid crystal layer is more than 0.25 μm and less than 0.32 μm, a transmittance characteristic having almost no wavelength dependency within the visible light range can be obtained more easily. Maximum transmittance can be obtained when the liquid crystal molecules are rotated 45 degrees from the rubbing direction to the electric field direction. The thickness (gap) of the liquid crystal layer is controlled by polymer beads. Of course, the same gap can be obtained with glass bead fiber or resin columnar spacers. The liquid crystal material LC is not particularly limited as long as it is a nematic liquid crystal. As the value of the dielectric anisotropy Δε is larger, the driving voltage can be reduced, and as the refractive index anisotropy Δn is smaller, the thickness (gap) of the liquid crystal layer can be increased, and the liquid crystal sealing time is shortened. In addition, gap variation can be reduced.

[Liquid Crystal Cell]
The liquid crystal cell used in the liquid crystal display device of the present invention has a pair of substrates, at least one of which has electrodes, and a liquid crystal layer that is disposed between the substrates and the alignment of which is controlled. It is preferable to form an alignment film for aligning liquid crystal molecules on both inner surfaces of the liquid crystal cell substrate. Moreover, it is preferable to form a color filter on any one of the opposing surfaces. Furthermore, a polarizing film may be disposed inside the liquid crystal cell, or an optically anisotropic layer that contributes to optical compensation of retardation of the liquid crystal layer may be disposed. In general, a columnar or spherical spacer is disposed to maintain a distance (cell gap) between two substrates. In addition, a reflector, a condenser lens, a brightness enhancement film, a light emitting layer, a fluorescent layer, a phosphorescent layer, an antireflection film, an antifouling film, a hard coat film, and the like may be disposed in the cell.

  A transparent glass substrate is generally used as the substrate for the liquid crystal cell, but a silicon glass substrate that is harder and can withstand high temperatures may be used. Further, a plastic substrate having excellent heat resistance or a substrate made of a polymer material may be used. A flexible or reelable display using a substrate made of a deformable material is also effective. Further, in the reflective display device, one of the substrates may be transparent, and a metal substrate such as stainless steel may be used for the other.

In the present invention, the liquid crystal display device includes three picture element regions. For example, in a liquid crystal display device that has a color filter and performs color display, the sub-pixels (picture element regions) of the three primary colors of light, red, green, and blue form one set and usually form one pixel. In some cases, one pixel is formed by sub-pixels of three or more colors. As one aspect of the present invention, there is a multi-gap aspect in which the cell gap is different in each color sub-pixel constituting one pixel.
Further, a structure called a multi-domain in which one pixel is divided into a plurality of regions may be used to adjust the color balance and average the viewing angle characteristics.

[Color filter]
In the present invention, it is preferable to dispose a color filter on one opposing surface of the pair of substrates of the liquid crystal cell. Although it does not restrict | limit especially about a color filter, For example, it is preferable to arrange | position the color filter containing each layer of red (R), green (G), and blue (B).
As described above, in the liquid crystal display device of the present invention, it is preferable that the liquid crystal cell includes three picture element regions, and Rth of color filters arranged in at least two of these pixel regions are different from each other. . More preferably, the Rths of the color filters arranged in each of the three picture element regions are different from each other. One of the preferable means for achieving this configuration is that the thickness of the color filter arranged in at least two pixel regions is different from the thickness of the color filter arranged in each of the three pixel regions. There is a thing to do.
Accordingly, among the Rths of the color filters arranged in each of the three picture element regions, the Rths of the color filters arranged in each of the at least two picture element regions can be made different from each other. Can be achieved more effectively.

  The color filter can be produced, for example, by the following method. First, colored pixels, such as red, green, and blue, that match the purpose are formed on a transparent substrate. As a method of forming colored pixels such as red, green, and blue on a transparent substrate, the above-described staining method, printing method, or coloring resist method in which a colored photosensitive resin liquid is applied with a spin coater or the like and then patterned in a photolithography process. Furthermore, a laminating method or the like can be used as appropriate. For example, in a formation method including a coating process, a color filter having RGB layers having different thicknesses can be formed by adjusting the coating amount. In the case of using a laminate method, a color filter composed of RGB layers having different thicknesses can be formed by using transfer materials having different thicknesses.

When forming a black matrix using a black photosensitive resin, it is preferable to form it after forming the colored pixels. When a black matrix is first formed, only the resin surface is cured with a black photosensitive resin having a high optical density, so that the uncured resin is melted by the subsequent development process, particularly the repeated development process for forming colored pixels. This is because the formed matrix may be peeled off in an extreme case (referred to as side etching).
In contrast, if the black matrix is formed last, the periphery of the black matrix is surrounded by colored pixels, and the developer is difficult to penetrate from the cross section. There is a great advantage that it can be formed.
Furthermore, when the colored layer for forming the colored pixels is formed by the laminating method, if the black matrix is formed first, the place where the colored pixels are to be formed is closed in a substantially lattice pattern by the black matrix. Although there is a problem that air bubbles are sometimes easily involved, it is preferable to form a black matrix later because this problem does not occur.

  When the light transmittance of the colored pixel with respect to the photosensitive wavelength region of the black photosensitive resin exceeds 2%, it is preferable to add a light absorber or the like into the colored pixel in advance so that the transmittance is 2% or less. Various known compounds can be used as the light absorber used in this case. Examples include benzophenone derivatives (such as Michler's ketone), merocyanine compounds, metal oxides, benzotriazole compounds, and coumarin compounds. Among them, those that have good light absorption and retain 25% or more of light absorption performance even after heat treatment at 200 ° C. or higher are preferable. Specifically, titanium oxide, zinc oxide, benzotriazole compounds, coumarin compounds Compounds. Among these, coumarin compounds are particularly preferable from the viewpoints of both heat resistance and light absorption. The above-described heat treatment at 200 ° C. or higher is performed in order to further cure after forming each pixel.

  Next, a black photosensitive resin layer is provided on the entire surface of the transparent substrate so as to cover the pixel pattern. This is also a method of applying a black photosensitive resin liquid with a spin coater or a roll coater, or temporarily supporting the black photosensitive resin liquid in advance. An image forming material can be prepared by coating on the body, and the black photosensitive resin layer can be transferred onto the pixel pattern.

  Next, it exposes from the black photosensitive resin layer side through a photomask, and the black photosensitive resin layer of the light-shielding part (black matrix) in which a coloring pixel does not exist is hardened. The colored pixels are slightly misaligned due to the alignment error of the exposure tool and the thermal expansion of the substrate, the pixels themselves are thick and thin, and are not arranged at the designed dimensions. Is normal. This tendency is particularly strong for large-sized substrates. Therefore, when exposure is performed with a photomask according to the design pixel interval, a portion where the black matrix overlaps with the pixel or a portion where a gap is formed between the pixel is generated. Since the overlapped portion becomes a protrusion, and the portion where the gap is formed becomes light leakage, both are not preferable.

In the present invention, the color filter has a retardation Rth (λ ₁ ) in the thickness direction of the color filter at the wavelength λ ₁ among the _three main wavelengths (λ ₁ <λ ₂ <λ ₃ ) having the maximum transmittance. The following formula (I) is satisfied.
Formula (I): Rth (λ ₁ ) ≦ 5 nm.
If Rth (λ ₁ ) is 5 nm or less, it may be a negative value, and the lower limit is not particularly limited, but considering the range that can be produced using existing materials, the lower limit is −65 nm. Degree. Rth (λ ₁ ) is preferably −30 nm to −50 nm.
As a protective film on the liquid crystal cell side for a polarizing plate, a polymer film satisfying all of the above formulas (2) -1 to (2) -4 (for example, the in-plane retardation Re is almost zero and the thickness direction letter is In order to further improve color reproducibility in a liquid crystal display device including a cellulose acylate film having a foundation Rth of about 40 nm, Rth (λ ₂ ) of the color filter is −35 to 25 nm. Preferably, it is -27 nm-22 nm. From the same viewpoint, Rth (λ ₃ ) is preferably −45 to 0 nm, and more preferably −38 nm to −1 nm.
Moreover, in order to improve color reproducibility more in the liquid crystal display device provided with the polymer film which satisfies the optical characteristic of said Formula (3) -1-(3) -4 as a liquid crystal cell side protective film for polarizing plates. In the color filter, Rth (λ ₂ ) is preferably −20 to 10 nm, and more preferably −15 nm to 5 nm. From the same viewpoint, Rth (λ ₃ ) is preferably −15 to 20 nm, and more preferably −10 nm to 15 nm.

The retardation of the color filter is adjusted, for example, by adding a retardation increasing agent or reducing agent to the photosensitive layer or the colored layer, which is a constituent layer of the transfer material, when the color filter is prepared using a transfer material. Also good.
Representative examples of the retardation increasing agent include compounds represented by the following general formula (X) and compounds similar thereto.

  Examples of the retardation reducing agent include compounds represented by the following general formula (XI).

In the general formula (XI), R ¹¹ represents an alkyl group or an aryl group, and R ¹² and R ¹³ each independently represent a hydrogen atom, an alkyl group, or an aryl group. Further, it is particularly preferable that the total number of carbon atoms of R ¹¹ , R ¹² and R ¹³ is 10 or more. R ¹¹ , R ¹² and R ¹³ may have a substituent, and the substituent is preferably a fluorine atom, an alkyl group, an aryl group, an alkoxy group, a sulfone group or a sulfonamide group, an alkyl group, an aryl group, Alkoxy groups, sulfone groups and sulfonamido groups are particularly preferred. Further, the alkyl group may be linear, branched or cyclic, and preferably has 1 to 25 carbon atoms, more preferably 6 to 25, and more preferably 6 to 20 (For example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, amyl, isoamyl, t-amyl, hexyl, cyclohexyl, heptyl, octyl, bicyclo Octyl, nonyl, adamantyl, decyl, t-octyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, didecyl) are particularly preferred . As the aryl group, those having 6 to 30 carbon atoms are preferable, and those having 6 to 24 carbon atoms (for example, phenyl group, biphenyl group, terphenyl group, naphthyl group, binaphthyl group, triphenylphenyl group) are particularly preferable.

[Optical compensation sheet]
The liquid crystal display device of the present invention may have an optical compensation sheet. Optical compensation sheets are used in various liquid crystal display devices in order to eliminate image coloring and expand the viewing angle. As an optical compensation sheet, a stretched birefringent polymer film has been conventionally used. Use of an optical compensation sheet having an optically anisotropic layer formed from a low-molecular or high-molecular liquid crystalline compound on a transparent support instead of an optical compensation sheet comprising a stretched birefringent film, or from a stretched birefringent film In addition to the optical compensation sheet, it has been proposed to use an optical compensation sheet having an optically anisotropic layer formed from a low-molecular or high-molecular liquid crystalline compound. Since liquid crystalline compounds have various alignment forms, it has become possible to realize optical properties that cannot be obtained only with conventional stretched birefringent polymer films by using liquid crystalline compounds. Furthermore, it can also function as a protective film for a polarizing plate. The present optical compensation sheet itself can be used as a substrate for a liquid crystal cell, and a plastic substrate can also serve as an optical compensation sheet. It is also possible to form this optical compensation sheet inside the liquid crystal cell.

  The optical properties of the optical compensation sheet are determined according to the optical properties of the liquid crystal cell, specifically, the display mode differences as described above. When a liquid crystal compound is used, optical compensation sheets having various optical properties corresponding to various display modes of the liquid crystal cell can be produced. Various optical compensation sheets using liquid crystal compounds in the form of rods, spheroids, or disks corresponding to various display modes have already been proposed. For example, the IPS mode optical compensation sheet can compensate for the viewing angle dependency of the polarizing plate to reduce the luminance of black display in all directions and improve the viewing angle characteristic of contrast. Furthermore, the optical property of the optical compensation sheet is designed to be an optimum value for each wavelength of light, thereby providing a liquid crystal display device having a wide visual field characteristic with little color change. It is particularly effective when combined with multi-gap and multi-domain. In addition, the viewing angle can be narrowed so that the display can be observed only from a specific direction, instead of enlarging the viewing angle.

Hereinafter, as an optical compensation sheet that can be used in the present invention, an optical compensation sheet having an optically anisotropic layer formed from a composition containing a liquid crystal compound on a support made of a polymer film or the like will be described in detail. .
<< Optically anisotropic layer >>
The optically anisotropic layer is formed by disposing a composition containing a liquid crystalline compound on a surface, for example, a surface subjected to rubbing treatment along a predetermined rubbing axis or the like, and depending on the rubbing axis, molecules of the liquid crystalline compound Can be oriented and fixed in the oriented state. Examples of the liquid crystalline compound used for forming the optically anisotropic layer include both a rod-like liquid crystalline compound and a discotic liquid crystalline compound. The rod-like liquid crystal compound and the discotic liquid crystal compound may be a polymer liquid crystal or a low-molecular liquid crystal, and further include those in which the low-molecular liquid crystal is cross-linked and no longer exhibits liquid crystallinity.

《Bar-shaped liquid crystalline molecules》
Examples of rod-like liquid crystalline molecules include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.
The rod-like liquid crystalline molecule includes a metal complex. In addition, a liquid crystal polymer containing a rod-like liquid crystalline molecule in a repeating unit can also be used as the rod-like liquid crystalline molecule. In other words, the rod-like liquid crystal molecule may be bonded to a (liquid crystal) polymer.
For rod-like liquid crystalline molecules, see Chapter 4, Chapter 7 and Chapter 11 in the Chemistry of the Quarterly Chemical Review Vol. Described in Chapter 3. The birefringence of the rod-like liquid crystal molecule is preferably in the range of 0.001 to 0.7.

  The rod-like liquid crystalline molecule preferably has a polymerizable group in order to fix its alignment state. The polymerizable group is preferably a radically polymerizable unsaturated group or a cationically polymerizable group. Specifically, for example, the polymerizable groups described in paragraphs [0064] to [0086] of JP-A-2002-62427 are described. Group and a polymerizable liquid crystal compound.

《Discotic liquid crystalline compound》
The discotic liquid crystalline compound is aligned substantially perpendicular to the polymer film surface. Discotic liquid crystalline compounds are disclosed in various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by The Chemical Society of Japan, Quarterly Chemical Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J Am. Chem. Soc., Vol. 116, page 2655 (1994)) can be widely used.

The discotic liquid crystalline compound preferably has a polymerizable group, for example, as described in JP-A-8-27284 so that it can be fixed by polymerization. For example, a structure in which a polymerizable group is bonded as a substituent to the discotic core of a discotic liquid crystalline compound can be considered, but if a polymerizable group is directly connected to the discotic core, the alignment state can be maintained in the polymerization reaction. It becomes difficult. Therefore, a structure having a linking group between the discotic core and the polymerizable group is preferable. That is, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following formula (III).
Formula (III) D (-LP) _n
In formula (III), D is a discotic core, L is a divalent linking group, P is a polymerizable group, and n is an integer of 4 to 12.

  Preferred specific examples of the discotic core (D), the divalent linking group (L), and the polymerizable group (P) in the formula (III) are (D1) described in JP-A No. 2001-4837, respectively. To (D15), (L1) to (L25), and (P1) to (P18), and the contents described in the publication can be preferably used.

  In the optically anisotropic layer, the molecules of the liquid crystalline compound are preferably aligned substantially perpendicular to the layer surface. The rod-like liquid crystalline molecules are preferably oriented with their major axes being substantially perpendicular to the layer surface, and the discotic liquid crystalline molecules are oriented with their disc surfaces substantially perpendicular to the layer surface. preferable. The term “substantially perpendicular” means that the average angle (average inclination angle) between the major axis of the rod-like liquid crystal compound or the disc surface of the discotic liquid crystal molecule and the layer surface is in the range of 70 ° to 90 °. . The liquid crystalline molecules are preferably substantially uniformly aligned, more preferably fixed in a substantially uniformly aligned state, and the liquid crystalline compound is fixed by a polymerization reaction. Most preferably.

  The optically anisotropic layer is preferably formed by disposing a liquid crystal compound and, if desired, a composition containing the following polymerization initiator and other additives on the alignment film. The composition may be prepared as a coating solution. 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), 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. The coating liquid can be applied by a known method (eg, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

<Immobilization of alignment state of liquid crystalline compounds>
The aligned liquid crystal compound molecules are preferably fixed while maintaining the alignment state. The immobilization is preferably carried out by a polymerization reaction of a polymerizable group introduced into the liquid crystal compound. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator, and a photopolymerization reaction is more preferable. Examples of photopolymerization initiators 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 substitution. Aromatic acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US Patent No. 3549367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (US Pat. No. 4,221,970) Is included.

The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. Light irradiation for the polymerization of the liquid crystalline compound is preferably performed using ultraviolet rays. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , further preferably 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

<< Vertical alignment film >>
In order to align the liquid crystalline compound vertically on the alignment film side, it is important to reduce the surface energy of the alignment film. Specifically, the surface energy of the alignment film is lowered by the functional group of the polymer, thereby bringing the liquid crystalline compound into a standing state. As the functional group for reducing the surface energy of the alignment film, a hydrocarbon group having 10 or more fluorine atoms and carbon atoms is effective. In order to make a fluorine atom or a hydrocarbon group exist on the surface of the alignment film, it is preferable to introduce a fluorine atom or a hydrocarbon group into the side chain rather than the main chain of the polymer. The fluoropolymer preferably contains fluorine atoms in a proportion of 0.05 to 80% by mass, more preferably in a proportion of 0.1 to 70% by mass, and in a proportion of 0.5 to 65% by mass. More preferably, it is most preferable to contain in the ratio of 1-60 mass%. The hydrocarbon group is an aliphatic group, an aromatic group or a combination thereof. The aliphatic group may be cyclic, branched or linear. The aliphatic group is preferably an alkyl group (may be a cycloalkyl group) or an alkenyl group (may be a cycloalkenyl group). The hydrocarbon group may have a substituent that does not exhibit strong hydrophilicity, such as a halogen atom. The number of carbon atoms of the hydrocarbon group is preferably 10 to 100, more preferably 10 to 60, and most preferably 10 to 40. The main chain of the polymer preferably has a polyimide structure or a polyvinyl alcohol structure.

  Polyimide is generally synthesized by a condensation reaction of tetracarboxylic acid and diamine. A polyimide corresponding to a copolymer may be synthesized using two or more kinds of tetracarboxylic acids or two or more kinds of diamines. The fluorine atom or hydrocarbon group may be present in the repeating unit derived from tetracarboxylic acid, may be present in the repeating unit derived from diamine, or may be present in both repeating units. When introducing a hydrocarbon group into polyimide, it is particularly preferable to form a steroid structure in the main chain or side chain of the polyimide. The steroid structure present in the side chain corresponds to a hydrocarbon group having 10 or more carbon atoms, and has a function of vertically aligning the liquid crystalline compound. In this specification, the steroid structure is a cyclopentanohydrophenanthrene ring structure or a ring structure in which a part of the ring bond is a double bond in the range of an aliphatic ring (a range that does not form an aromatic ring). means.

  Further, as a means for vertically aligning the molecules of the liquid crystal compound, a method of mixing an organic acid with a polymer of polyvinyl alcohol or polyimide can be suitably used. As the acid to be mixed, carboxylic acid, sulfonic acid and amino acid are preferably used. You may use what shows the acidity among the below-mentioned air interface aligning agent. The mixing amount is preferably 0.1% by mass to 20% by mass and more preferably 0.5% by mass to 10% by mass with respect to the polymer.

  For uniform alignment of the molecules of the discotic liquid crystalline compound, it is preferable to control the alignment direction by rubbing the vertical alignment film. The rubbing treatment may be performed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. On the other hand, the molecules of the rod-like liquid crystal compound can be aligned without performing rubbing treatment. In any alignment film, the alignment film preferably has a polymerizable group for the purpose of improving the adhesion between the optically anisotropic layer and the transparent support. The polymerizable group can be introduced by introducing a repeating unit having a polymerizable group in the side chain or as a substituent of a cyclic group. It is more preferable to use an alignment film that forms a chemical bond with the molecules of the liquid crystal compound at the interface. Such an alignment film is described in JP-A-9-152509. The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 1 μm. In addition, after aligning the molecules of the liquid crystalline compound using the alignment film, the molecules of the liquid crystalline compound are fixed in the aligned state to form an optically anisotropic layer, and only the optically anisotropic layer is formed as a polymer film. The image may be transferred onto a support such as.

<Air interface alignment agent>
Ordinary liquid crystal compound molecules have the property of being tilted and aligned on the air interface side, so in order to obtain a uniformly vertically aligned state, the liquid crystal compound molecules are also vertically aligned on the air interface side. It is necessary. For this purpose, the composition (coating liquid) contains a compound that is unevenly distributed on the air interface side and acts to vertically align the molecules of the liquid crystalline compound by its excluded volume effect or electrostatic effect. . The action of vertically aligning the molecules of the liquid crystal compound corresponds to the action of reducing the tilt angle of the director, that is, the angle formed by the director and the air side surface, in the molecule of the discotic liquid crystal compound. Compounds that reduce the angle of inclination of the director of the discotic liquid crystalline molecule include those in which a plurality of F atoms are bonded in order to be unevenly distributed on the air interface side, and those in which a sulfonyl group or a carboxyl group is bonded. In addition, a compound in which a rigid structural unit that gives an excluded volume effect such that the liquid crystal molecules are aligned perpendicularly is bonded preferably.

  In addition to the exemplified compounds, compounds described in JP-A Nos. 2002-20363 and 2002-129162 can be used as the air interface alignment agent. In addition, paragraph numbers 0072 to 0075 of Japanese Patent Application Laid-Open No. 2004-53981, paragraph numbers 0038 to 0048 and 0048 to 0049 of Japanese Patent Application No. 2002-243600, paragraph numbers 0037 to 0039 of Japanese Patent Application No. 2002-262239, The matters described in paragraph Nos. 0071 to 0078 of JP 2004-4688 A can also be applied to the present invention as appropriate.

  When using an air interface alignment agent, it is preferable that the addition amount of the air interface alignment agent in the composition for optically anisotropic layer formation is 0.05 mass%-5 mass%. Moreover, when using a fluorine saturation type | system | group air interface aligning agent, it is preferable that it is 1 mass% or less.

  The in-plane retardation (Re) of the entire optical compensation sheet is preferably 20 to 200 nm. The thickness direction retardation (Rth) of the entire optical compensation sheet is preferably 50 to 500 nm.

The optical compensation sheet may have a support made of a polymer film that supports the optically anisotropic layer. The polymer film used for the support is not particularly limited, and films such as cellulose acylate, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, norbornene resin are used. These polymer films may be stretched polymer films or a combination of a coating-type polymer layer and a polymer film. These polymer films are preferably manufactured in the same direction (roll-to-roll) in the longitudinal direction of the film at the time of manufacture in order to improve productivity and shape stability when temperature and humidity change.
In the embodiment in which the support of the optically anisotropic layer also serves as a protective film for the polarizing plate, the support is preferably a cellulose acylate film described later.

  Since the liquid crystal compound has various alignment forms, the optically anisotropic layer formed using the liquid crystal compound exhibits a desired optical property by a single layer or a laminate of a plurality of layers. That is, the optical compensation sheet may be an aspect that satisfies the optical characteristics required for the optical compensation sheet in the whole of the support, one or more optically anisotropic layers formed on the support, and the laminate. Good. In such an embodiment, the retardation of the entire optical compensation sheet can be adjusted by both the optical characteristics of the optically anisotropic layer and the optical characteristics of the support made of the polymer film.

  In the liquid crystal display device of the present invention, an optical compensation sheet made of a stretched birefringent polymer film may be used. By adjusting the stretching conditions and the like, a stretched birefringent polymer film that satisfies the optical properties required for the optical compensation sheet can be produced.

[Polarizer]
In the present invention, a polarizing plate having a polarizing film and a pair of protective films sandwiching the polarizing film, or a polarizing film and a protective film provided on at least one side of the polarizing film may be used. For example, a polarizing film obtained by dyeing a polarizing film made of a polyvinyl alcohol film or the like with iodine, stretching, and laminating both surfaces with a protective film can be used. A polarizing film may be disposed inside the liquid crystal cell. In the liquid crystal display device of the present invention, it is preferable that a pair of polarizing plates each having a polarizing film and a pair of protective films sandwiching the polarizing film are disposed with a liquid crystal cell interposed therebetween.

《Polarizing film》
Examples of polarizing films (sometimes referred to as “linearly polarizing films”) include iodine-based polarizing films, dye-based polarizing films using dichroic dyes, and polyene-based polarizing films. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film.

  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 deflection 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.

  A commercially available polarizing film has iodine or dichroic dye distributed about 4 μm (about 8 μm on both sides) from the polymer surface, and a thickness of at least 10 μm is necessary to obtain sufficient polarizing performance. The penetrability can be controlled by the solution concentration of iodine or dichroic dye, the temperature of the bath, and the immersion time. As described above, the lower limit of the binder thickness is preferably 10 μm. The upper limit of the thickness is preferably as thin as possible from the viewpoint of light leakage of the liquid crystal display device. It is preferably not more than a commercially available polarizing plate (about 30 μm), preferably 25 μm or less, and more preferably 20 μm or less. When the thickness is 20 μm or less, the light leakage phenomenon is not observed on a 17-inch liquid crystal display device.

  The binder of the polarizing film may be cross-linked. As the crosslinked binder, a polymer that can be crosslinked per se can be used. A polarizing film can be formed by reacting a polymer having a functional group or a binder obtained by introducing a functional group into a polymer between the binders by light, heat, or pH change. Moreover, you may introduce | transduce a crosslinked structure into a polymer with a crosslinking agent. Crosslinking is generally performed by applying a coating liquid containing a polymer or a mixture of a polymer and a crosslinking agent to the surface and then heating. Since it is only necessary to ensure durability at the stage of the final product, the crosslinking treatment may be performed at any stage until the final polarizing plate is obtained.

  As the binder of the polarizing film, either a polymer that can be crosslinked per se or a polymer that is crosslinked by a crosslinking agent can be used. Most preferred are polyvinyl alcohol and modified polyvinyl alcohol. The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509, and JP-A-9-316127. Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination.

  In the polarizing film, the addition amount of the binder crosslinking agent is preferably 0.1 to 20% by mass with respect to the binder. The orientation of the polarizing element and the wet heat resistance of the polarizing film are improved.

The alignment film contains a certain amount of a crosslinking agent that has not reacted even after the crosslinking reaction has been completed. However, the amount of the remaining crosslinking agent is preferably 1.0% by mass or less and more preferably 0.5% by mass or less in the alignment film. By doing so, the polarization degree does not decrease even when the polarizing film is incorporated in a liquid crystal display device and used for a long time or left in a high temperature and high humidity atmosphere for a long time.
The crosslinking agent is described in US Reissue Patent 23297. Boron compounds (eg, boric acid, borax) can also be used as a crosslinking agent.

As the dichroic dye, an azo dye, stilbene dye, pyrazolone dye, triphenylmethane dye, quinoline dye, oxazine dye, thiazine dye or anthraquinone dye is used. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl).
As an example of a dichroic dye, the compound as described in page 58 of the said technical number 2001-1745 is mentioned, for example.

  When the polarizing film is produced by a stretching method, the stretching ratio is preferably 2.5 to 30.0 times, and more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. Moreover, you may implement wet extending | stretching in the state immersed in water. The stretch ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretch ratio of wet stretching is preferably 3.0 to 10.0 times. The stretching step may be performed in several steps including oblique stretching. By dividing into several times, it is possible to stretch more uniformly even at high magnification. Before the oblique stretching, a slight stretching (a degree to prevent shrinkage in the width direction) may be performed horizontally or vertically. Stretching can be performed by performing tenter stretching in biaxial stretching in different steps. The biaxial stretching is the same as the stretching method performed in normal film formation. In biaxial stretching, stretching is performed at different speeds on the left and right, so that the thickness of the binder film before stretching needs to be different on the left and right. In casting film formation, the flow rate of the binder solution can be differentiated between the left and right sides by tapering the die.

  When the polarizing film is produced by a rubbing method, a rubbing treatment method widely adopted as a liquid crystal alignment treatment step for LCD can be applied. That is, orientation is obtained by rubbing the surface of the film in a certain direction using paper, gauze, felt, rubber, nylon, or polyester fiber. Generally, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are planted on average. It is preferable to carry out using a rubbing roll in which the roundness, cylindricity, and deflection (eccentricity) of the roll itself are 30 μm or less. The film wrap angle on the rubbing roll is preferably 0.1 to 90 °. However, as described in JP-A-8-160430, a stable rubbing treatment can be obtained by winding 360 ° or more.

  When the process of rubbing a long film is included, the film is preferably transported at a speed of 1 to 100 m / min in a constant tension state by a transport device. The rubbing roll is preferably rotatable in the horizontal direction with respect to the film traveling direction for setting an arbitrary rubbing angle. It is preferable to select an appropriate rubbing angle in the range of 0 to 60 °.

  The polarizing film used in the present invention preferably has an absorption axis having a predetermined angle with respect to the longitudinal direction. When the absorption axis of the polarizing film has a predetermined angle with respect to the longitudinal direction, it can be easily pasted with a roll-to-roll when pasting with a protective film whose slow axis coincides with the longitudinal direction. it can. For example, as described in JP-A-2003-207628, a pair of protective films prepared in a long shape is bonded to both sides of a polarizing film prepared in a long shape, and a long laminate is obtained. Through a process of cutting (punching) into a desired size, a single plate polarizing plate can be obtained with high yield.

  The moisture permeability of the protective film is important for improving the productivity of the polarizing plate. That is, the polarizing film and the protective film are bonded together with an aqueous adhesive, and the adhesive solvent is dried by diffusing in the protective film. The higher the moisture permeability of the protective film, the faster the drying and the higher the productivity. However, if the protective film is too high, moisture will enter the polarizing film depending on the usage environment (high humidity) of the liquid crystal display device. There is a tendency for the polarization ability to decrease.

"Protective film"
As the protective film, a protective film (protective film disposed on the liquid crystal cell side) provided on at least one surface of the polarizing film satisfies the following conditions (3) and (4). Is preferred.
(3) Film satisfying all of the following formulas (3) -1 to (3) -4:
(3) -1: 0 nm ≦ Re (630) ≦ 10 nm
(3) -2: | Rth (630) | ≦ 25 nm
(3) -3: | Re (400) -Re (700) | ≦ 10 nm
(3) -4: | Rth (400) -Rth (700) | ≦ 35 nm
(4) Film in which Rth in the film thickness direction of the protective film satisfies all of the following formulas (4) -1 and (4) -2 (4) -1: (Rth _(A) -Rth ₍₀₎ ) / A ≦ −1.0
(4) -2: 0.01 ≦ A ≦ 30
In the above formula, Rth _(A) represents Rth (unit: nm) of a protective film containing a compound that lowers Rth, and Rth ₍₀₎ is the protective film, a compound that lowers Rth. R represents the Rth (nm) of a film containing no A, and A represents the mass (%) of a compound that reduces Rht when the mass of the film raw material polymer is 100.
The above formulas (4) -1 and (4) -2 are: (4) ′-1: (Rth _(A) −Rth ₍₀₎ ) /A≦−2.0
(4) '-2: 0.1 ≦ A ≦ 20
More preferably.
Here, the polymer of the film raw material refers to the raw material polymer of the main component constituting the film, and examples thereof include cellulose acylate.

  Examples of cellulose as a cellulose acylate raw material include cotton linter and wood pulp (hardwood pulp, conifer pulp). Cellulose acylate obtained from any raw material cellulose can be used, and in some cases, a mixture may be used. . Detailed descriptions of these raw material celluloses can be found in, for example, Plastic Materials Course (17) Fibrous Resin (Maruzawa, Uda, Nikkan Kogyo Shimbun, published in 1970) and Invention Association Open Technical Report 2001-1745 (page 7). To page 8) can be used, and the cellulose is not particularly limited.

  The cellulose acylate that can be used in the present invention is, for example, one obtained by acylating a hydroxyl group of cellulose, and the substituent can be any acetyl group having 2 to 22 carbon atoms of the acyl group. The degree of substitution of the cellulose acylate that can be used in the present invention with the hydroxyl group of the 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 replace the cellulose with a hydroxyl group is measured, The degree of substitution is obtained by calculation. As a measuring method, it can carry out according to ASTM D-817-91.

  In the cellulose acylate, the degree of substitution of the cellulose with a hydroxyl group is not particularly limited, but the degree of acyl substitution with the hydroxyl group of cellulose is preferably 2.50 to 3.00. Furthermore, the substitution degree is more preferably 2.75 to 3.00, and further preferably 2.85 to 3.00.

  Among the acetic acid and / or fatty acid having 3 to 22 carbon atoms substituted for the hydroxyl group of cellulose, the acyl group having 2 to 22 carbon atoms may be an aliphatic group or an allyl group, and may be a single or a mixture of two or more types. Good. Examples thereof include cellulose alkylcarbonyl ester, alkenylcarbonyl ester, aromatic carbonyl ester and aromatic alkylcarbonyl ester. Each of these may further have a substituted group. These preferred acyl groups include acetyl group, propionyl group, butanoyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group , Iso-butanoyl group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, acetyl group, propionyl group, butanoyl group, dodecanoyl group, octadecanoyl group, tert-butanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like are preferable, and acetyl group, propionyl group, butanoyl group are preferable. Groups are more preferred.

  Among the acyl substituents substituted on the hydroxyl group of cellulose described above, in the case of substantially consisting of at least two kinds of acetyl group, propionyl group and butanoyl group, the total substitution degree is 2.50 to 3.00 In particular, the optical anisotropy of the cellulose acylate film can be lowered, which is preferable. The degree of acyl substitution is more preferably 2.60 to 3.00, still more preferably 2.65 to 3.00.

  The degree of polymerization of cellulose acylate preferably used in the present invention is 180 to 700 in terms of viscosity average polymerization degree, and in cellulose acetate, 180 to 550 is more preferable, 180 to 400 is more preferable, and 180 to 350 is particularly preferable. . By making the degree of polymerization below a certain level, the viscosity of the cellulose acylate dope solution becomes high, and it is possible to more effectively prevent film production from becoming difficult due to casting. By setting the degree of polymerization to a certain level or more, it is possible to more effectively prevent the strength of the produced film from being lowered. The average degree of polymerization can be measured, for example, by the intrinsic viscosity method of Uda et al. (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962). This method is described in detail in JP-A-9-95538.

  Further, the molecular weight distribution of cellulose acylate preferably used in the present invention is evaluated by gel permeation chromatography, and its polydispersity index Mw / Mn (Mw is mass average molecular weight, Mn is number average molecular weight) is small, and molecular weight distribution. Is preferably narrow. The specific value of Mw / Mn is preferably 1.0 to 3.0, more preferably 1.0 to 2.0, and most preferably 1.0 to 1.6. preferable.

  When the low molecular component is removed, the average molecular weight (degree of polymerization) increases, but the viscosity becomes lower than that of normal cellulose acylate, which is useful. Cellulose acylate having a small amount of low molecular components can be obtained by removing low molecular components from cellulose acylate synthesized by a usual method. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent. In addition, when manufacturing a cellulose acylate with few low molecular components, it is preferable to adjust the sulfuric acid catalyst amount in an acetylation reaction to 0.5-25 mass parts with respect to 100 mass parts of cellulose. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate that is preferable in terms of molecular weight distribution (uniform molecular weight distribution) can be synthesized. When used in the production of cellulose acylate that can be used in the present invention, the water content is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly 0.7% by mass. It is a cellulose acylate having a moisture content of not more than%. In general, cellulose acylate contains water and is known to be 2.5 to 5% by mass. In order to make the moisture content of a cellulose acylate into the said range, it is necessary to dry, and the method will not be specifically limited if it becomes the target moisture content. As for the raw material cotton of cellulose acylate and the synthesis method satisfying the above-mentioned various characteristics, pages 7 to 12 are disclosed in JIII Journal of Technical Disclosure (Publication No. 2001-1745, published on March 15, 2001, Invention Association). It is described in detail on the page.

  As a raw material of the cellulose acylate film, a mixture of two or more different types of cellulose acylates having the above-mentioned ranges such as a substituent, a substitution degree, a polymerization degree, and a molecular weight distribution can be preferably used.

  The cellulose acylate solution (dope) that can be used for producing the cellulose acylate film has various additives (for example, a compound that reduces optical anisotropy, a wavelength dispersion adjusting agent) according to the use in each preparation step. UV inhibitors, plasticizers, deterioration inhibitors, fine particles, optical property modifiers, etc.), which will be described below. Further, the addition may be performed at any time in the dope preparation step, but may be performed by adding a preparation step by adding an additive to the final preparation step of the dope preparation step.

First, a compound that lowers the optical anisotropy of a cellulose acylate film, which is one of the additives that can be added to the dope, will be described.
The compound is a compound that inhibits the cellulose acylate in the film from being oriented in the plane and in the film thickness direction, and the optical anisotropy of the film is obtained by adding the compound to the dope to produce a film. Is sufficiently reduced, Re is zero, and Rth is close to zero. Here, being close to zero means, for example, ± 2 nm or less at an arbitrary wavelength. For this purpose, it is advantageous that the compound for reducing the optical anisotropy is sufficiently compatible with cellulose acylate, and the compound itself does not have a rod-like structure or a planar structure. Specifically, when a plurality of planar functional groups such as aromatic groups are provided, a structure having these functional groups in a non-planar rather than the same plane is advantageous.

Among the compounds that reduce the optical anisotropy by inhibiting the cellulose acylate in the film from being oriented in the plane and in the film thickness direction as described above, the octanol-water partition coefficient (log P value) is 0 to 7 It is preferred to use certain compounds. By adopting a compound having a log P value of 7 or less, compatibility with cellulose acylate is improved, and the cloudiness and powder blowing of the film can be more effectively prevented. Moreover, since the hydrophilicity is high by adopting a compound having a log P value of 0 or more, it is possible to more effectively prevent the water resistance of the cellulose acetate film from deteriorating. A more preferable range for the logP value is 1 to 6, and a particularly preferable range is 1.5 to 5.
The octanol-water partition coefficient (log P value) can be measured by a flask immersion method described in JIS Japanese Industrial Standard Z7260-107 (2000). Further, the octanol-water partition coefficient (log P value) can be estimated by a computational chemical method or an empirical method instead of the actual measurement. As a calculation method, Crippen's fragmentation method (J. Chem. Inf. Comput. Sci., 27, 21 (1987)), Viswanadhan's fragmentation method (J. Chem. Inf. Comput. Sci., 29,). 163 (1989).), Broto's fragmentation method (Eur. J. Med. Chem.-Chim. Theor., 19, 71 (1984).) And the like are preferably used, but the Crippen's fragmentation method (J. Chem. Inf. Comput. Sci., 27, 21 (1987). When the log P value of a certain compound varies depending on the measurement method or calculation method, it is preferable to determine whether or not the compound is within the scope of the present invention by the Crippen's fragmentation method.

The compound that reduces optical anisotropy may or may not contain an aromatic group. In addition, the compound that decreases the optical anisotropy preferably has a molecular weight of 150 to 3000, more preferably 170 to 2000, and even more preferably 200 to 1000. A specific monomer structure may be used as long as these molecular weights are within the range, and an oligomer structure or a polymer structure in which a plurality of the monomer units are bonded may be used.
The compound that reduces optical anisotropy is preferably a liquid at 25 ° or a solid having a melting point of 25 to 250 °, more preferably a liquid at 25 ° or a melting point of 25 to 200 °. It is a solid. Moreover, it is preferable that the compound which reduces optical anisotropy does not volatilize in the process of dope casting for cellulose acylate film production and drying.

The addition amount of the compound that decreases the optical anisotropy is preferably 0.01 to 30% by mass of the cellulose acylate, more preferably 1 to 25% by mass, and 5 to 20% by mass. Is particularly preferred.
The compound that decreases the optical anisotropy may be used alone, or two or more compounds may be mixed and used in an arbitrary ratio.
The timing for adding the compound for reducing the optical anisotropy may be any time during the dope preparation process, or may be performed at the end of the dope preparation process.

  The compound that reduces the optical anisotropy is such that the average content of the compound in the portion from the surface on at least one side to 10% of the total film thickness is the average content of the compound in the central portion of the cellulose acylate film. It is preferable that it exists so that it may become 80 to 99% of. The amount of the compound that reduces the optical anisotropy can be determined by measuring the amount of the compound at the surface and in the central portion, for example, by a method using an infrared absorption spectrum described in JP-A-8-57879.

  Specific examples of the compound that reduces the optical anisotropy of the cellulose acylate film are described in JP-A-2005-309382, [0081] to [0214], and can be used in the present invention. It is not limited.

  Regarding the cellulose acylate film satisfying the formulas (3) -1 to (3) -4, the raw materials and the production method are described in detail in JP-A-2006-30937, and the polarizing plate of the present invention It can be used for the production of a protective film. Moreover, since the cellulose acylate film satisfying the above formulas (3) -1 to (3) -4 is also marketed as “ZRF80s” manufactured by Fuji Film, it is of course possible to use this commercially available product.

  Moreover, you may use the various cellulose acylate film marketed as a protective film of the liquid crystal cell side or outer side of a polarizing plate. Among them, it is preferable to use a commercially available product such as “Fujitac TD80UL” manufactured by Fuji Film Co., Ltd., which has an in-plane retardation of about 0 and a thickness direction retardation of about 40 nm.

  In addition, the thickness of the protective film on the liquid crystal cell side or the outer side of the polarizing plate is important to reduce the thickness from the viewpoint of preventing stress due to temperature and humidity changes or the accompanying light leakage, and is preferably 1 μm to 100 μm, preferably 5 μm to 80 μm. Further preferred.

"adhesive"
The adhesive between the polarizing film and the protective film is not particularly limited, and examples thereof include PVA-based resins (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. PVA resin is preferable. The thickness of the adhesive layer is preferably 0.01 to 10 μm, and particularly preferably 0.05 to 5 μm after drying.

《Integrated manufacturing process of polarizing film and protective film》
The polarizing plate used in the present invention usually has a drying step in which the polarizing film is stretched and then contracted to reduce the volatile content rate, but after drying or after a protective film is bonded to at least one side during drying, It is preferable to have a heating step. In an aspect in which the protective film also serves as a support for an optical compensation film functioning as an optical compensation layer, heating is performed after laminating a transparent support having a protective film on one side and an optical compensation film on the opposite side. preferable. As a specific application method, during the film drying process, a protective film is applied to the polarizing film with an adhesive while holding both ends, and then both ends are cut off, or after drying, polarized from the both ends holding part. There is a method of releasing a film for a film, cutting off both ends of the film, and then attaching a protective film. As a method for cutting off the ears, general techniques such as a method of cutting with a cutter such as a blade or a method of using a laser can be used. After bonding, it is preferable to heat in order to dry the adhesive and improve the polarization performance. The heating condition varies depending on the adhesive, but in the case of an aqueous system, it is preferably 30 ° or more, more preferably 40 to 100 °, and further preferably 50 to 90 °. It is more preferable in terms of performance and production efficiency that these processes are manufactured in a consistent line.

<Performance of polarizing plate>
In order to increase the contrast ratio of the liquid crystal display device of the present invention, it is preferable that the polarizing plate used has a higher transmittance and a higher degree of polarization. The transmittance of the polarizing plate is preferably in the range of 30 to 50%, more preferably in the range of 35 to 50%, and most preferably in the range of 40 to 50% in light having a wavelength of 550 nm. . The degree of polarization is preferably in the range of 90 to 100%, more preferably in the range of 95 to 100%, and most preferably in the range of 99 to 100% in light having a wavelength of 550 nm.
In particular, the optical properties and durability (short-term and long-term storage stability) of the polarizing plate are equivalent to or better than those of commercially available super high contrast products (for example, HLC2-5618 manufactured by Sanlitz Co., Ltd.). It is preferable. Specifically, the visible light transmittance is 42.5% or more, and the degree of polarization {(Tp−Tc) / (Tp + Tc)} ^1/2 ≧ 0.9995 (where Tp is parallel transmittance and Tc is orthogonal transmission) The change rate of the light transmittance before and after being left in a 60 °, 90% humidity RH atmosphere for 500 hours and 80 ° in a dry atmosphere for 500 hours is 3% or less based on the absolute value, Further, it is preferably 1% or less, and the rate of change in polarization degree is preferably 1% or less, more preferably 0.1% or less, based on the absolute value.

  The polarizing plate used in the present invention may have an antireflection film whose outermost surface has antifouling properties and scratch resistance. Any conventionally known antireflection film can be used.

[Elliptically polarizing plate]
In the present invention, an elliptically polarizing plate having an optically anisotropic layer may be used. For example, an elliptically polarizing plate in which a protective film, a polarizing film, and the optical compensation sheet are laminated in this order may be disposed in the liquid crystal display device with the optical compensation sheet facing the liquid crystal cell. In the elliptically polarizing plate having such a configuration, the support (polymer film) of the optical compensation sheet also serves as a protective film for the polarizing film. The elliptically polarizing plate is preferably molded into a shape substantially the same as that of the pair of substrates constituting the liquid crystal cell so that it can be incorporated into a liquid crystal display device as it is (for example, if the liquid crystal cell is rectangular, the elliptically polarizing plate). The plate is also preferably molded into the same rectangular shape).

[Backlight]
The liquid crystal display device performs display by turning on and off the light passing through the liquid crystal cell, but when used as a transmission type, a cold cathode or a hot cathode fluorescent tube, or a light emitting diode, a field emission element, an electroluminescent element By arranging a backlight having a light source on the back surface, a bright and vivid display device is obtained.
There are two types of backlights: side-edge type backlights used for display devices used in portable terminals and notebook computers, and direct type backlights used for display devices such as televisions. The side edge type has a shape in which one or two fluorescent lamps are arranged at the end of the light guide plate, and has an advantage that the thickness of the backlight device can be reduced. On the other hand, in the direct backlight, the number of fluorescent lamps can be increased according to the required luminance, and high luminance can be easily obtained. A structure using a light emitting diode, a field emission element, an electroluminescent element or the like instead of the fluorescent lamp in the side edge type and direct type backlights is also effective.
Furthermore, in order to increase the luminous efficiency of the backlight, a prismatic or lens-shaped condensing brightness enhancement sheet (film) is laminated, or a polarization reflection type brightness enhancement sheet (film) that improves light loss due to absorption of the polarizing plate. ) May be laminated between the backlight and the liquid crystal cell. In addition, a diffusion sheet (film) for making the light source of the backlight uniform may be laminated, and conversely, a sheet (film) formed by printing a reflection or diffusion pattern for giving an in-plane distribution to the light source. You may laminate. In addition to the backlight that is always lit, there are a backlight that is intermittently lit and a backlight that is divided into a plurality of regions to emit light. It is also possible to adjust the light emission method in association with the image. The backlight may be divided into a plurality of regions, and each may emit different light (brightness and color).

[application]
The liquid crystal display device of the present invention includes an image direct view type, an image projection type, and a light modulation type. The image direct view type is effective for small display devices such as notebook computers, OA devices such as monitors for personal computers, multimedia displays such as televisions, car navigation systems, mobile phones, portable terminals, clock-type terminals, and wearable displays. Furthermore, it is also effective for display devices for amusement devices and large display devices for vertical or floor use for meetings.
The image projection type includes a front projector type that projects directly onto the screen and a rear projector type that projects from the back of the screen. It is also effective for a portable projector using an LED light source or the like.
The light modulation type is effective for a display device called a three-dimensional display or a highly realistic display. For example, it is effective for a three-dimensional display using two liquid crystal cells and a cylindrical three-dimensional display composed of a plurality of rear projectors.

The present invention also includes a color filter layer including first, second, and third colored regions, wherein Rth of the color filter layers of at least two colored regions are different from each other, and the first, second, and third colors Λ ₁ <λ ₂ <λ ₃ and λ ₁ <λ ₂ <λ ₃ and the color filter at wavelength λ ₁ , where λ ₁ , λ ₂ , and λ ₃ (unit: nm) are the main wavelengths taking the maximum transmittance of the colored region The present invention also relates to a color filter characterized in that the retardation Rth (λ ₁ ) in the thickness direction of the layer satisfies the formula (I).
One aspect of the color filter of the present invention is an RGB color filter in which the first, second, and third colored regions are R, G, and B colored regions. In this embodiment, λ ₁ is the wavelength of B light, λ ₂ is the wavelength of G light, and λ ₃ is the wavelength of R light. That is, when Rth at the wavelength of the B light is Rth (B), Rth (λ _B ) ≦ 5 nm is established in this aspect. The lower limit is not particularly limited, but the lower limit is about −65 nm in consideration of the range that can be produced using existing materials. Rth (λ _B ) is preferably −30 nm to −50 nm.

In an example of the color filter of the present invention that can further improve color reproducibility, Rth (λ _G ) is preferably −35 to 25 nm, and more preferably −27 nm to 22 nm. From the same viewpoint, Rth (λ _R ) is preferably −45 to 0 nm, and more preferably −38 nm to −1 nm.
In another example of the color filter of the present invention that can further improve color reproducibility, Rth (λ _G ) is preferably −20 to 10 nm, and more preferably −15 nm to 5 nm. From the same viewpoint, Rth (λ _R ) is preferably −15 to 20 nm, and more preferably −10 nm to 15 nm.

  The color filter layer including the first, second, and third colored regions may be formed on a substrate. The material of the substrate is not particularly limited, and any glass plate, transparent polymer film, and the like can be used. In addition, the color filter of the present invention may have a black matrix that separates the first, second, and third colored regions, and a transparent electrode layer, an alignment layer, or the like above or below the color filter layer. Other layers may be included.

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

[Example 1: Production of IPS mode liquid crystal display device]
The effect of the present invention was confirmed for the IPS mode liquid crystal display device.
First, an IPS mode liquid crystal cell having a liquid crystal layer between two glass substrates and a substrate gap (gap; d) of 3.4 μm was produced. The Δn of the liquid crystal layer was 0.08765, and the value of d · Δn of the liquid crystal layer was 298 nm. In addition, it set so that the rubbing direction of two glass substrates might become parallel. Various RGB color filter layers having different values of Rth (450) were formed on the inner surface of the liquid crystal cell on the viewing side, and seven types of IPS mode liquid crystal cells were produced. The Rth value can be adjusted by adjusting the thickness of the color filter layer, or by forming a retardation increasing agent (for example, a compound of the general formula (X)) or a reducing agent (for example, the general formula (X The compound (XI)) was added or the amount added was adjusted.

A polarizing plate produced by the following method was produced on the outer surface of the produced liquid crystal cell substrate.
A commercially available cellulose acylate film “TD80UL” (manufactured by Fuji Film, Re = 3.0 nm, Rth = 45 nm) was bonded to both surfaces of the polyvinyl alcohol polarizing film. Bonding was performed so that the slow axis of the cellulose acylate film and the absorption axis of the polarizing film were in parallel for both the viewing side and the backlight side polarizing plates. Here, the parallel state means that the crossing angle is within ± 2 °.

The produced polarizing plate was bonded to the outer surface on both sides of each IPS mode liquid crystal cell produced above.
The polarizing plate on the viewing side (upper polarizing plate) was laminated so that the extraordinary refractive index direction of the liquid crystal composition in the liquid crystal cell and the absorption axis of the polarizing plate were orthogonal when no voltage was applied. Further, the absorption axes of polarizing plates on the viewing side and the backlight side were arranged to be orthogonal to each other.
In this manner, seven types of liquid crystal display devices each having the above seven types of liquid crystal cells were produced.

[Optical performance of liquid crystal display]
The prepared seven types of liquid crystal display devices were respectively placed on a diffusion light source, and the maximum transmittance of blue light at a polar angle of 60 ° and an azimuth angle of 0 to 360 ° during black display was measured. The results are shown in FIG. FIG. 4 shows the maximum transmittance of blue light at a polar angle of 60 ° and an azimuth angle of 0 to 360 ° with the horizontal axis representing the Rth (450) value of the color filter for the seven types of liquid crystal display devices produced. As a plotted graph.

  From the results shown in FIG. 4, when the Rth (450) of the color filter is 5 nm or less, the transmittance of blue light at the time of black display is remarkably reduced, that is, the blue tint when observed from an oblique direction. Can be reduced.

Next, from the viewpoint of color reproducibility, an attempt was made to optimize Rth (550) and Rth (550) of the RGB color filter.
The value of Rth (550) of the RGB color filter was varied as a parameter, and the maximum transmittance of green light at a polar angle of 60 ° and an azimuth angle of 0 to 360 ° during black display was obtained by simulation calculation. The results are shown in FIG. FIG. 5 shows the red color at a polar angle of 60 ° and an azimuth angle of 0 to 360 ° obtained by simulation, with the horizontal axis representing the Rth (550) value of the color filter for the seven types of liquid crystal display models. It is the graph plotted as the maximum transmittance of light.

  From the results shown in FIG. 5, when the Rth (550) of the color filter is −35 to 25 nm, the transmittance of green light during black display is remarkably reduced, that is, the green color when observed from an oblique direction. It is also considered that the color tone can be reduced, the three primary colors are balanced, and the color reproducibility is further improved.

  Further, the Rth (650) value of the RGB color filter was varied as a parameter, and the maximum transmittance of red light at a polar angle of 60 ° and an azimuth angle of 0 to 360 ° during black display was obtained by simulation calculation. The results are shown in FIG. FIG. 6 shows the red color at a polar angle of 60 ° and an azimuth angle of 0 to 360 ° obtained by simulation, with the horizontal axis representing the Rth (650) value of the color filter for the seven types of liquid crystal display models. It is the graph plotted as the maximum transmittance of light.

  From the results shown in FIG. 6, when the Rth (650) of the color filter is −45 to 0 nm, the red light transmittance at the time of black display is remarkably reduced, that is, the red color when observed from an oblique direction. It is also considered that the color tone can be reduced, the three primary colors are balanced, and the color reproducibility is further improved.

  Considering the results shown in FIG. 4 to FIG. 6, considering that the characteristic when Rth is 0 is equivalent to the case where the color filter is not laminated, the RGB color filter is particularly blue in terms of the result shown in the above graph. It can be understood that the transmittance in the oblique direction at the time of black display of light and green light is large, that is, light leaks and coloration occurs.

[Example 2: Production of IPS mode liquid crystal display device]
In the production of the liquid crystal display device, a commercially available cellulose acylate film “ZRF80s” (manufactured by FUJIFILM, Re = 1.5 nm, Rth = −12.2 nm) is formed on one side of a polyvinyl alcohol polarizing film as upper and lower polarizing plates. Each IPS mode liquid crystal cell was prepared by bonding a commercially available cellulose acylate film “TD80UL” (Fuji Film, Re = 3.0 nm, Rth = 45 nm) to the other side. A liquid crystal display device was produced in the same manner as described above except that “ZRF80s” was attached to the cell side on both side outer surfaces, and optical performance was similarly evaluated.
The results are shown in FIG. From the results shown in FIG. 7, even in the liquid crystal display device of this example, when the Rth (450) of the color filter is 5 nm or less, the transmittance of blue light during black display is remarkably reduced, that is, from an oblique direction. It can be understood that the blue tint when observed can be reduced.

  Next, with regard to the liquid crystal display device of this example, optimization of Rth (550) and Rth (550) of the RGB color filter was attempted in the same manner as described above from the viewpoint of color reproducibility. The results are shown in FIGS. FIG. 8 shows the red color at a polar angle of 60 ° and an azimuth angle of 0 to 360 ° obtained by simulation, with the horizontal axis representing the Rth (550) value of the color filter for the seven types of liquid crystal display models. It is the graph plotted as the maximum transmittance of light. FIG. 9 shows the red color at a polar angle of 60 ° and an azimuth angle of 0 to 360 ° obtained by simulation, with the horizontal axis representing the Rth (650) value of the color filter for the seven types of liquid crystal display models. It is the graph plotted as the maximum transmittance of light.

From the results shown in FIG. 8, in this example, when the Rth (550) of the color filter is -20 to 20 nm, the transmittance of green light during black display is remarkably reduced, that is, observed from an oblique direction. In this case, the green color can be reduced, and the three primary colors are balanced, and the color reproducibility is further improved.
Further, from the result shown in FIG. 9, in this embodiment, when the Rth (650) of the color filter is −15 to 20 nm, the transmittance of red light at the time of black display is remarkably reduced, that is, in the oblique direction. It can be considered that the red tint when observed from above can be reduced, the three primary colors are balanced, and the color reproducibility is further improved.

[Example 3: Production of IPS mode liquid crystal display device]
(Preparation of cellulose acylate film)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acylate solution A.
<Composition of cellulose acylate solution A>
Cellulose acetate having a substitution degree of 2.86 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first solvent) 300 parts by weight Methanol (second solvent) ) 54 parts by mass 1-butanol 11 parts by mass

The following composition was charged into another mixing tank, stirred while heating to dissolve each component, and an additive solution B-6 was prepared.
<Additive solution B-6 composition>
Methylene chloride 80 parts by weight Methanol 20 parts by weight Optical anisotropy reducing agent (following formula A-19) 40 parts by weight Wavelength dispersion adjusting agent (following formula UV-102) 4 parts by weight

<Preparation of Cellulose Acetate Film Sample 001>
40 parts by mass of additive solution B-6 was added to 477 parts by mass of cellulose acylate solution A, and the mixture was sufficiently stirred to prepare a dope. The dope was cast from a casting port onto a drum cooled to 0 degrees. The film is peeled off at a solvent content of 70% by mass, and both ends in the width direction of the film are fixed with a pin tenter (a pin tenter described in FIG. 3 of JP-A-4-1009), and the solvent content is 3 to 5% by mass. Then, it was dried while maintaining an interval at which the stretching ratio in the transverse direction (direction perpendicular to the machine direction) was 3%. Then, it dried further by conveying between the rolls of the heat processing apparatus, and produced the cellulose acetate film sample 105 with a thickness of 40 micrometers.

In the production of the liquid crystal display device, a cellulose acetate film sample 105 (Re = 0.5 nm, Rth = −2.8 nm) is bonded to one side of a polyvinyl alcohol polarizing film as upper and lower polarizing plates, and the other side is used. A polarizing plate produced by bonding a commercially available cellulose acylate film “T40U” (manufactured by Fuji Film, Re = 0.4 nm, Rth = 29.3 nm) is formed on each outer surface of each IPS mode liquid crystal cell with cellulose acetate. A liquid crystal display device was prepared in the same manner as described above except that the film sample 105 was bonded to the cell side, and the optical performance was similarly evaluated.
The results are shown in FIG. From the results shown in FIG. 10, even in the liquid crystal display device of this example, when the Rth (450) of the color filter is 5 nm or less, the transmittance of blue light during black display is remarkably reduced, that is, from an oblique direction. It can be understood that the blue tint when observed can be reduced.

  Next, with regard to the liquid crystal display device of this example, optimization of Rth (550) and Rth (550) of the RGB color filter was attempted in the same manner as described above from the viewpoint of color reproducibility. The results are shown in FIGS. FIG. 11 shows the red color at a polar angle of 60 ° and an azimuth angle of 0 to 360 ° obtained by simulation, with the horizontal axis representing the Rth (550) value of the color filter and the vertical axis representing the seven types of liquid crystal display models. It is the graph plotted as the maximum transmittance of light. FIG. 12 shows the red color at a polar angle of 60 ° and an azimuth angle of 0 to 360 ° obtained by simulation, with the horizontal axis representing the Rth (650) value of the color filter for the seven types of liquid crystal display models. It is the graph plotted as the maximum transmittance of light.

From the results shown in FIG. 11, in this example, when the Rth (550) of the color filter is −20 to 20 nm, the transmittance of green light during black display is remarkably reduced, that is, observed from an oblique direction. In this case, the green color can be reduced, and the three primary colors are balanced, and the color reproducibility is further improved.
Further, from the results shown in FIG. 12, in this embodiment, when the Rth (650) of the color filter is −15 to 20 nm, the transmittance of red light during black display is remarkably reduced, that is, in the oblique direction. It can be considered that the red tint when observed from above can be reduced, the three primary colors are balanced, and the color reproducibility is further improved.

It is the schematic which shows an example of the liquid crystal display device of this invention. It is a schematic sectional drawing which shows an example of the liquid crystal display device of this invention. It is a schematic sectional drawing which shows an example of the liquid crystal display device of this invention. About the liquid crystal display device produced in Example 1, the horizontal axis is the value of Rth (450) of the color filter, the vertical axis is the maximum transmittance of blue light at a polar angle of 60 °, and an azimuth angle of 0 to 360 °. It is a graph. FIG. 6 is a graph showing the results calculated in Example 1, and for a liquid crystal display device, the horizontal axis is the Rth (550) value of the color filter, the vertical axis is the polar angle 60 °, and the azimuth angle is 0 to 360 °. It is the graph which plotted as the maximum transmittance of. FIG. 4 is a graph showing the results calculated in Example 1, and for a liquid crystal display device, the horizontal axis is the value of Rth (650) of the color filter, the vertical axis is the polar angle 60 °, and the azimuth angle is 0 to 360 °. It is the graph which plotted as the maximum transmittance of. About the liquid crystal display device produced in Example 2, the horizontal axis is the Rth (450) value of the color filter, and the vertical axis is the maximum transmittance of blue light at a polar angle of 60 ° and an azimuth angle of 0 to 360 °. It is a graph. FIG. 10 is a graph showing the results calculated in Example 2, and for a liquid crystal display device, the horizontal axis is the value of Rth (550) of the color filter, the vertical axis is the polar angle 60 °, and the azimuth angle is 0 to 360 °. It is the graph which plotted as the maximum transmittance of. FIG. 10 is a graph showing the results calculated in Example 2, and for a liquid crystal display device, the horizontal axis is the value of Rth (650) of the color filter, the vertical axis is the polar angle 60 °, and the azimuth angle is 0 to 360 °. It is the graph which plotted as the maximum transmittance of. About the liquid crystal display device produced in Example 3, the horizontal axis is the Rth (450) value of the color filter, and the vertical axis is the maximum transmittance of blue light at a polar angle of 60 ° and an azimuth angle of 0 to 360 °. It is a graph. FIG. 10 is a graph showing the results calculated in Example 3, and for a liquid crystal display device, the horizontal axis is the value of Rth (550) of the color filter, the vertical axis is the polar angle 60 °, and the azimuth angle is 0 to 360 °. It is the graph which plotted as the maximum transmittance of. FIG. 10 is a graph showing the results calculated in Example 3, and for a liquid crystal display device, the horizontal axis is the Rth (650) value of the color filter, the vertical axis is the polar angle of 60 °, and the azimuth angle is 0 to 360 °. It is the graph which plotted as the maximum transmittance of.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper polarizing plate protective film 2 Upper polarizing plate protective film MD direction 3 Upper polarizing plate polarizing film 4 Upper polarizing plate polarizing film absorption axis 5 Upper polarizing plate liquid crystal cell side protective film 6 Upper polarizing plate liquid crystal cell side protective film MD direction (slow Phase axis direction)
7 optical anisotropic film 8 optical anisotropic film slow axis 9 liquid crystal cell upper substrate 10 upper substrate rubbing direction 11 for liquid crystal alignment liquid crystal molecule (liquid crystal layer)
12 Liquid crystal cell lower substrate 13 Lower substrate Liquid crystal alignment rubbing direction 14 Lower polarizer liquid crystal cell side protective film 15 Lower polarizer liquid crystal cell side protective film MD direction (slow axis direction)
16 Lower polarizing plate polarizing film 17 Absorption axis 18 of lower polarizing plate polarizing film Lower polarizing plate protective film 19 Lower polarizing plate protective film MD direction 20 Backlight unit 20a Light source lamp 21 Upper polarizing plate 22 Lower polarizing plate 23 , 23 'Applied electric field direction 24 Linear electrode 25 Insulating layer 26 Electrode

Claims (6)

A pair of substrates, at least one of which has an electrode, and a liquid crystal layer that is arranged between the pair of substrates and is controlled in alignment; A liquid crystal display device having at least a liquid crystal cell in which an electric field is formed and a pair of polarizing plates arranged with the liquid crystal layer interposed therebetween, wherein the liquid crystal cell includes first, second and third picture elements. A color filter disposed on each of the pixel regions, and among the color filters, Rth of color filters disposed on at least two of the pixel regions are different from each other, and the first, second and second Λ ₁ <λ ₂ <λ ₃ is established, where λ ₁ , λ ₂ , and λ ₃ (unit: nm) are the main wavelengths that take the maximum transmittance of the color filters arranged on the three pixel regions, respectively. , color filter at a wavelength λ ₁ Filled thickness direction retardation Rth (λ ₁₎ satisfies the following formula (I), and a color filter in the thickness direction retardation Rth (λ ₃₎ is at the wavelength lambda _3, the following formula (III) satisfies the,
Formula (I): Rth (λ ₁ ) ≦ 5 nm
Formula (III): −45 nm ≦ Rth (λ ₃ ) ≦ 0 nm;
At least one of the pair of polarizing plates has a polarizing film and a protective film, and the in-plane retardation Re (λ) and the thickness direction retardation Rth (λ) at the wavelength λ nm of the protective film are as follows. A liquid crystal display device satisfying all of the formulas and disposed between the liquid crystal cell and the polarizing film:
0 nm ≦ Re (630) ≦ 10 nm
| Rth (630) | ≦ 80nm
| Re (400) -Re (700) | ≦ 20 nm
| Rth (400) −Rth (700) | ≦ 45 nm. _2. The liquid crystal display device according to claim 1, wherein a retardation Rth (λ ₂ ) in the thickness direction at a wavelength λ ₂ of the color filter satisfies the following formula (II):
Formula (II): −35 nm ≦ Rth (λ ₂ ) ≦ 25 nm. The liquid crystal display device according to claim 1, wherein Rth (λ ₁ ) of the color filter satisfies the following formula.
−50 nm ≦ Rth (λ ₁ ) ≦ −30 nm The liquid crystal display device according to claim 1, wherein the parallel electric field is generated by a pixel electrode and a counter electrode that are arranged in different layers. The parallel electric field is generated by a pair of electrodes that are arranged in different layers and at least one of which is transparent, and an electrode to which no voltage is applied. Liquid crystal display device. The in-plane retardation Re (λ) and retardation Rth (λ) in the thickness direction of the protective film at a wavelength λ nm of the at least one polarizing plate satisfy all of the following formulas: The liquid crystal display device of any one of -5:
0 nm ≦ Re (630) ≦ 10 nm
| Rth (630) | ≦ 25nm
| Re (400) -Re (700) | ≦ 10 nm
| Rth (400) −Rth (700) | ≦ 35 nm.

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