WO2012105428A1

WO2012105428A1 - Liquid crystal display device

Info

Publication number: WO2012105428A1
Application number: PCT/JP2012/051753
Authority: WO
Inventors: 坂井　彰; 一義櫻木; 雅浩長谷川
Original assignee: シャープ株式会社
Priority date: 2011-02-02
Filing date: 2012-01-27
Publication date: 2012-08-09

Abstract

The present invention provides a liquid crystal display device which is suppressed in light leakage and has improved CR. One embodiment of the present invention is a liquid crystal display device which is sequentially provided with a first polarizer, a first birefringent layer of a first type, a liquid crystal cell and a second polarizer in this order from the back surface side. The liquid crystal cell comprises a pair of substrates that face each other and a liquid crystal layer that is held between the substrates. The in-plane slow axis of the first birefringent layer of a first type is substantially parallel to the absorption axis of the second polarizer, and the absorption axis of the first polarizer is substantially perpendicular to the absorption axis of the second polarizer. When the NZ coefficient of the first birefringent layer of a first type is represented by NZ11 and the in-plane retardation is represented by R11, (1) 0 < NZ11 ≤ 0.5 and (2) 220 nm ≤ R11 ≤ 320 nm are satisfied.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device including a polarizer and a birefringent layer.

A liquid crystal display device is usually configured to include an optical element such as a polarizing plate and a retardation film (birefringent layer) together with a liquid crystal panel and a backlight. In the liquid crystal panel, a liquid crystal layer is sandwiched between upper and lower substrates on the viewer side and the back side, and optical elements for improving optical characteristics are placed on these substrates. Such liquid crystal display devices are widely used in electronic devices such as monitors, projectors, cellular phones, and personal digital assistants (PDAs) because of their excellent display characteristics.

In addition, among the substrates sandwiching the liquid crystal layer, a liquid crystal having a color filter on array (COA) structure in which a color filter and a thin film transistor (TFT: Thin Film Transistor) are provided on the back substrate. Display devices are known (for example, see Non-Patent Documents 1 and 2).

By the way, in a liquid crystal display device (liquid crystal panel), light leakage in black display and thereby a contrast ratio (hereinafter also referred to as “CR”. Unless otherwise specified, “CR” means “CR”. There is a problem that CR in the normal direction with respect to the substrate plane is low. The single CR (hereinafter also referred to as “native CR”) of the liquid crystal panel that has been commercialized is 3000 to 5000.

On the other hand, a dimming backlight that improves the CR (hereinafter also referred to as “dynamic CR”) of a liquid crystal display device by dynamically adjusting the brightness of the backlight brightness according to the brightness of the image is known. A liquid crystal display device having a dynamic CR of 10,000 or more is known.

However, the CR improvement effect due to the dimming backlight is limited depending on the type of video, or there is room for improvement in that no effect can be obtained. For example, when displaying a video with a mixture of pure black and pure white within the same frame, such as a starry sky, movie subtitles, and black and white checkered patterns, the white brightness of the white display is sacrificed and the backlight luminance cannot be reduced. . This problem is somewhat improved by the local dimming backlight that divides the backlight into multiple blocks whose brightness can be controlled independently, and dimming each block, but the above situation does not change inside the block, so it remains the same. It can be said that the effect is limited. Moreover, there was room for improvement in terms of cost increase by introducing dimming backlight. Under such circumstances, it is desired to improve the native CR of the liquid crystal panel.

The present invention has been made in view of the above situation, and an object of the present invention is to provide a liquid crystal display device capable of suppressing light leakage and improving CR.

As a result of examining the cause of the decrease in CR in the liquid crystal display device, the present inventors have found that (I) light leakage due to incomplete polarizing plate performance, and (II) the inside of the liquid crystal panel (lower substrate, liquid crystal It was found that light leakage due to light scattering of the layer and the upper substrate was the cause. However, since the CR of a typical polarizing plate used in a current liquid crystal panel is 10,000 to 30,000, it can be considered that the main factor that the CR of the liquid crystal panel is 3000 to 5000 is the above (II). .

Regarding the light leakage due to light scattering inside the liquid crystal panel of (II) above,

Non-Patent Documents

1 and 2 show that the light leakage observed in the normal direction of the panel due to light scattering is analyzed in detail, and is incident obliquely on the liquid crystal panel. It is shown that the light travels in the normal direction due to the internal scattering of the panel and is not absorbed sufficiently by the polarizer on the observation surface side, resulting in light leakage. This will be described more specifically with reference to FIG. As shown in (1) in FIG. 22, first, obliquely incident light on the liquid crystal panel (liquid crystal cell) 230 is modulated into elliptically polarized light by a retardation film or liquid crystal. Thereafter, as shown in (2), the traveling direction is changed to the normal direction by scattering (the polarization state hardly changes before and after scattering). Then, as shown in (3), since the light reaches the polarizing plate 211 and passes through the polarizing plate 211 as elliptically polarized light, light leakage is observed according to the ellipticity. In other words, the polarization state generally does not change before and after scattering, and the vertical alignment (VA: Vertical Alignment) mode liquid crystal layer and retardation film transmitted after scattering also change the polarization state completely for light traveling in the normal direction. Even if it is not changed or changed, the light leakage at the polarizer on the observation surface side is simply converted to another polarization state where the light leakage is exactly the same. Depends on the polarization state just before occurs. And the polarization state immediately before the scattering occurs depends on the configuration of the polarizing plate (polarizer) and the characteristic value of the retardation film.

In this regard,

Non-Patent Documents

1 and 2 describe the retardation value (| Rth |) of the retardation film on the back side (lower substrate side) of the VA mode liquid crystal panel having a color filter on array (COA) structure. ) Is adjusted to be smaller. As a result, even if light obliquely incident on the lower substrate changes its traveling direction in the normal direction due to scattering, most of the light is absorbed by the polarizer on the observation surface side (upper substrate side), so light leakage is unlikely. High CR can be obtained as compared with a conventional liquid crystal display device using a retardation film having a large retardation value on the lower substrate side. In the liquid crystal panel having the COA structure, a color filter that is a main cause of scattering of incident light is provided on the lower substrate side, and the scattering of incident light on the lower substrate is larger than the scattering on the upper substrate. However, in a liquid crystal panel in which scattering on the upper substrate is larger than that on the lower substrate, even if the retardation value of the retardation film is adjusted to be small, a sufficient CR improvement effect cannot be obtained. This is because the polarization state changes greatly before and after passing through the VA liquid crystal layer even if it is in a polarization state in which light does not leak even if it is scattered in the normal direction when the lower substrate is incident due to the polarizer. This is because, if the light is scattered in the linear direction, it changes to a polarization state that tends to cause light leakage. That is, light leakage due to lower substrate scattering is reduced as compared with the conventional case, but light leakage due to upper substrate scattering is increased as compared with the conventional case. In the panel where the scattering on the upper substrate is smaller than that on the lower substrate, the fact that the light is likely to leak from the polarizer on the upper substrate side when scattering occurs at the time of incidence on the upper substrate does not change, but in the first place Therefore, the total amount of light leakage from the upper substrate and light leakage from the lower substrate is reduced as compared with the conventional case.

When the present inventors scrutinized the liquid crystal display devices (liquid crystal panels) described in

Non-Patent Documents

1 and 2 above, CR was improved compared to the conventional configuration using a retardation film having a large retardation value on the lower side. However, leakage of light incident from an oblique direction and scattered in the normal direction is not sufficiently suppressed, and there is room for improvement in that light leakage occurs from the polarizer on the observation surface side. It has been found.

The inventors of the present invention have made further studies and found that the polarization state of the incident light from the oblique direction is different from the polarization state corresponding to the extinction position when the polarizer on the observation surface side is viewed from the normal direction. Accordingly, it has been found that light incident from an oblique direction and scattered in the normal direction of the polarizer on the observation surface side is emitted as light leakage. And the back side so that the polarization state of light obliquely incident on the lower substrate substantially coincides with the polarization state corresponding to the extinction position of the polarizer when the polarizer on the observation surface side is viewed from the normal direction By adjusting the retardation value of the retardation film (birefringent layer), even if the light obliquely incident on the lower substrate changes its traveling direction in the normal direction due to scattering, it is sufficiently absorbed by the polarizer on the observation surface side As a result, the inventors have arrived at the present invention by conceiving that the above problems can be solved brilliantly.

That is, one embodiment of the present invention is a liquid crystal display device including a first polarizer, one or more first birefringent layers (retardation film), a liquid crystal cell, and a second polarizer in this order from the back side. The liquid crystal cell includes a pair of opposing substrates (a lower substrate and an upper substrate) and a liquid crystal layer sandwiched between the substrates, and the absorption axis of the first polarizer is the second polarization When the liquid crystal display device includes two or more first birefringent layers substantially orthogonal to the absorption axis of the child, the two or more first birefringent layers have at least one of an NZ coefficient and a phase difference. A plurality of different birefringent layers are included, and the one or more first birefringent layers pass through the first polarizer, and the polarization state of light incident from an oblique direction is determined by the method of the second polarizer. A liquid crystal display device (hereinafter referred to as “the present invention”) that converts the polarization state to the extinction level when viewed from the line direction. The first liquid crystal display device of the "to be also referred to).

The “light incident from an oblique direction” specifically refers to an azimuth range of 45 ° ± 22.5 ° and an azimuth direction 135 when the absorption axis direction of the first polarizer is defined as azimuths of 0 ° and 180 °. The light is incident from the range of ± 22.5 ° and the direction of 225 ° ± 22.5 ° or the range of 315 ° ± 22.5 °.

In other words, “converting the polarization state of incident light into an extinction level when viewed from the normal direction of the second polarizer” means, in other words, converting the polarization state of incident light (polarized light) into linearly polarized light ( It can be said that the vibration direction is substantially matched with the absorption axis direction of the second polarizer. Here, “substantially coincide” refers to a state where the distance between two points on a Poincare sphere having a radius of 1 is 0.15 or less. Further, the polarization state of the light converted by the first birefringent layer may be elliptical polarization instead of perfect linear polarization.

The configuration of the first liquid crystal display device of the present invention is not particularly limited by other components as long as such components are essential.

As long as the above-described polarization conversion can be performed, the type (NZ coefficient), number, retardation value, material, and the like of the first birefringent layer can be appropriately selected. For example, the first birefringent layer May be a form consisting of only a single (one) birefringent layer, or may be a form consisting of only a plurality of birefringent layers having different NZ coefficients and phase differences from each other. Furthermore, a form (more specifically, including a plurality of birefringent layers having the same NZ coefficient and retardation, and at least one birefringent layer having at least one of the NZ coefficient and the phase difference different from the plurality of birefringent layers. May be, for example, a form including two identical positive C plates and one positive A plate). In particular, a form including a first birefringent layer, a form including a second birefringent layer and a fourth birefringent layer, a form including a third birefringent layer and a fifth birefringent layer A liquid crystal display device including such a birefringent layer is also an embodiment of the present invention. That is, another aspect of the present invention is a liquid crystal display device including a first polarizer, a first first-type birefringent layer, a liquid crystal cell (liquid crystal panel), and a second polarizer in this order from the back side. The liquid crystal cell includes a pair of opposing substrates (a lower substrate and an upper substrate) and a liquid crystal layer sandwiched between the substrates, and an in-plane retardation of the first first-type birefringent layer. The phase axis is substantially parallel to the absorption axis of the second polarizer, the absorption axis of the first polarizer is substantially orthogonal to the absorption axis of the second polarizer, and the first first When a NZ coefficient of a birefringent layer is NZ11 and an in-plane retardation is R11, a liquid crystal display device satisfying the following formulas (2-1) and (2-2) (hereinafter referred to as “second embodiment of the present invention”). It is also referred to as a “liquid crystal display device”.
0 <NZ11 ≦ 0.5 (2-1)
220 nm ≦ R11 ≦ 320 nm (2-2)

Even in the second liquid crystal display device of the present invention, similarly to the first liquid crystal display device of the present invention, even if light obliquely incident on the lower substrate changes its traveling direction in the normal direction due to scattering, It is sufficiently absorbed by the polarizer, and a large CR improvement effect is obtained. In addition, the manufacturing process can be simplified and the thickness can be reduced as compared with the case where a plurality of types of birefringent layers are combined. In addition, according to the form which combines multiple types of birefringent layers, each birefringent layer can be manufactured easily.

The configuration of the second liquid crystal display device of the present invention is not particularly limited by other components as long as such components are essential.

Still another embodiment of the present invention is a liquid crystal display device having a first polarizer, a first first-type birefringent layer, a liquid crystal cell (liquid crystal panel), and a second polarizer in this order from the back side. The liquid crystal cell includes a pair of opposing substrates (a lower substrate and an upper substrate) and a liquid crystal layer sandwiched between both substrates, and the in-plane of the first type birefringent layer. The slow axis is substantially perpendicular to the absorption axis of the second polarizer, the absorption axis of the first polarizer is substantially perpendicular to the absorption axis of the second polarizer, and the first first When a NZ coefficient of a birefringent layer is NZ11 and an in-plane retardation is R11, a liquid crystal display device satisfying the following formulas (3-1) and (3-2) (hereinafter referred to as “third embodiment of the present invention”). It is also referred to as a “liquid crystal display device”.
0.5 ≦ NZ11 <1.0 (3-1)
220 nm ≦ R11 ≦ 320 nm (3-2)

As with the first and second liquid crystal display devices of the present invention, the third liquid crystal display device of the present invention is also observed even when light obliquely incident on the lower substrate changes its traveling direction in the normal direction due to scattering. It is sufficiently absorbed by the surface-side polarizer, and a large CR improvement effect is obtained. In addition, the manufacturing process can be simplified and the thickness can be reduced as compared with the case where a plurality of types of birefringent layers are combined.

The configuration of the third liquid crystal display device of the present invention is not particularly limited by other components as long as such components are formed as essential.

Preferred embodiments of the first to third liquid crystal display devices of the present invention will be described in detail below.

The first liquid crystal display device of the present invention further includes one or two or more second birefringent layers between the liquid crystal cell and the second polarizer, and the liquid crystal display device has two or more second birefringent layers. When the birefringent layer is provided, the two or more second birefringent layers include a plurality of birefringent layers having different NZ coefficients and retardations, the liquid crystal layer, and the one or more birefringent layers. The second birefringent layer preferably does not substantially change the polarization state of light incident from the normal direction during black display. As a result, even if the light converted into the polarization state of the extinction position of the second polarizer is scattered in the normal direction inside the liquid crystal display device, it can be absorbed by the second polarizer. The improvement effect can be enhanced.

As long as the above-described characteristics can be exhibited, the type (NZ coefficient), number, retardation value, material, and the like of the second birefringent layer can be appropriately selected. For example, the second birefringent layer May be a form consisting of only a single (one) birefringent layer, or may be a form consisting of only a plurality of birefringent layers having different NZ coefficients and phase differences from each other. Furthermore, a form (more specifically, including a plurality of birefringent layers having the same NZ coefficient and retardation, and at least one birefringent layer having at least one of the NZ coefficient and the phase difference different from the plurality of birefringent layers. May be, for example, a form including two identical positive C plates and one positive A plate). In particular, a form including a first birefringent layer, a form including a second birefringent layer and a fourth birefringent layer, a form including a third birefringent layer and a fifth birefringent layer Is preferred.

In the second liquid crystal display device of the present invention, it is preferable that 0.15 ≦ NZ11 ≦ 0.35 and 250 nm ≦ R11 ≦ 290 nm are satisfied. As a result, even if light obliquely incident on the lower substrate changes its traveling direction in the normal direction due to scattering, it is sufficiently absorbed by the polarizer on the observation surface side, and a greater CR improvement effect is obtained.

The second liquid crystal display device of the present invention further includes a second type of birefringent layer and a second type of birefringent layer between the liquid crystal cell and the second polarizer. The liquid crystal molecules in the liquid crystal layer are substantially vertically aligned during black display, and the in-plane slow axis of the second first-type birefringent layer is the absorption of the second polarizer. It is substantially parallel to the axis, the NZ coefficient of the second type birefringent layer is NZ12, the in-plane retardation is R12, the thickness direction retardation of the second type birefringent layer is Rth2, black When the thickness direction retardation of the liquid crystal cell at the time of display is Rthlc, a form satisfying the following formulas (2-3) to (2-5) (hereinafter also referred to as “first form”) is preferable.
0.5 ≦ NZ12 <1.0 (2-3)
220 nm ≦ R12 ≦ 320 nm (2-4)
−50 nm ≦ Rth2 + Rthlc ≦ 50 nm (2-5)

In the present specification, “when displaying black” means displaying the lowest gradation.

Accordingly, light obliquely incident on the lower substrate and transmitted through the liquid crystal panel without being scattered can be absorbed by the polarizer (second polarizer) on the observation surface side. Can be reduced and the viewing angle can be expanded.

In the first embodiment, 0.65 ≦ NZ12 ≦ 0.85 and 250 nm ≦ R12 ≦ 290 nm are preferably satisfied, and −30 nm ≦ Rth2 + Rthlc ≦ 30 nm is preferably satisfied. Thereby, the light leakage from the oblique direction can be further reduced and the viewing angle can be expanded.

Further, when the NZ coefficient of the second birefringent layer is NZ2, it is preferable that 5 ≦ NZ2 is satisfied in the first embodiment, and it is more preferable that 10 ≦ NZ2 is satisfied. Thereby, the light leakage from the oblique direction can be further reduced and the viewing angle can be expanded.

In the third liquid crystal display device of the present invention, it is preferable that 0.65 ≦ NZ11 ≦ 0.85 and 250 nm ≦ R11 ≦ 290 nm are satisfied. As a result, even if light obliquely incident on the lower substrate changes its traveling direction in the normal direction due to scattering, it is sufficiently absorbed by the polarizer on the observation surface side, and a greater CR improvement effect is obtained.

The third liquid crystal display device of the present invention further includes a second birefringent layer and a second first birefringent layer between the liquid crystal cell and the second polarizer. The liquid crystal molecules in the liquid crystal layer are substantially vertically aligned during black display, and the in-plane slow axis of the second first-type birefringent layer is the absorption of the second polarizer. Substantially perpendicular to the axis, the NZ coefficient of the second birefringent layer of the second type is NZ12, the in-plane retardation is R12, the thickness direction retardation of the second birefringent layer is Rth2, black display When the thickness direction retardation of the liquid crystal cell at this time is Rthlc, a form satisfying the following formulas (3-3) to (3-5) (hereinafter also referred to as “second form”) is preferable.
0 <NZ12 ≦ 0.5 (3-3)
220 nm ≦ R12 ≦ 320 nm (3-4)
−50 nm ≦ Rth2 + Rthlc ≦ 50 nm (3-5)

In the second embodiment, 0.15 ≦ NZ12 ≦ 0.35 and 250 nm ≦ R12 ≦ 290 nm are preferably satisfied, and −30 nm ≦ Rth2 + Rthlc ≦ 30 nm is preferably satisfied. Thereby, the light leakage from the oblique direction can be further reduced and the viewing angle can be expanded.

Further, when the NZ coefficient of the second birefringent layer is NZ2, in the second embodiment, 5 ≦ NZ2 is preferably satisfied, and 10 ≦ NZ2 is more preferably satisfied. Thereby, the light leakage from the oblique direction can be further reduced and the viewing angle can be expanded.

From the viewpoint of enhancing the CR improvement effect of the present invention, in the first to third liquid crystal display devices of the present invention, when the back side of the pair of substrates is a lower substrate and the observation surface side is an upper substrate, the upper A form in which the scattering of the substrate is smaller than that of the lower substrate (hereinafter, also referred to as “third form”) is preferable. Here, the size of the scattering of the upper and lower substrates is determined by measuring the transmittance by sandwiching both of them between the same crossed Nicol polarizing plate and the parallel Nicol polarizing plate, and calculating the contrast. The higher one is discriminated as a substrate with less scattering.

From the viewpoint of realizing the third embodiment, the lower substrate preferably includes a color filter (CF) layer and a thin film transistor (TFT), and the liquid crystal cell preferably has a color filter on array (COA) structure. The liquid crystal cell preferably includes a dye-based color filter layer, and the liquid crystal cell preferably does not include a color filter layer. The TFT here means not only the TFT (transistor) itself but also a broad TFT including other materials and structures generally provided in the TFT substrate. For example, the gate wiring, the source wiring, Cs Including wiring (auxiliary capacitor), organic insulating film, transparent electrode (ITO), alignment film and the like. Currently, a pigment-based CF layer is generally used as the CF layer, and both the pigment-based CF layer and the TFT can be a major factor in the scattering of incident light. In addition, the scattering of the upper substrate can be made smaller than that of the lower substrate. Of the TFTs, the wirings exposed to the openings (regions through which incident light passes) particularly affect scattering. In particular, wiring extending in an orientation that is neither parallel nor orthogonal to the absorption axis or transmission axis of the polarizer causes scattering (may be diffraction). For example, in a liquid crystal display device in which the absorption axes of the first and second polarizers are 0 ° and 90 °, respectively, if there is a Cs wiring extending in the 45 ° azimuth, the edge portion of the Cs wiring appears to shine due to scattering or diffraction. Sometimes. In addition, the quality of the organic insulating film (the presence or absence of surface irregularities) and the like may affect the size of scattering. In addition, when a CF layer is provided on the upper substrate and a TFT is provided on the lower substrate, the scattering of the upper substrate is brought close to zero by making the CF layer a dye-based CF layer that has very little scattering. The scattering of the upper substrate can be made smaller than that of the lower substrate. Further, by providing the TFT on the lower substrate without providing the CF layer, the scattering of the upper substrate can be made close to zero and the scattering of the upper substrate can be made smaller than that of the lower substrate. The substrate including the CF layer may include a member such as a BM (black matrix) layer, an alignment film, and a transparent electrode (ITO), but scattering due to these is negligibly small compared to that of the pigment-based CF layer. .

According to the first, second and third liquid crystal display devices of the present invention, light leakage can be suppressed and CR can be improved.

1 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 1. FIG. FIG. 3 is a schematic cross-sectional view illustrating a state of light incident from an oblique direction in the liquid crystal display device according to the first embodiment. In the liquid crystal display device which concerns on Embodiment 1, it is a figure which shows the transition of a polarization state on the Poincare sphere when the light incident from an oblique direction is not scattered. In the liquid crystal display device according to Embodiment 1, the transition of the polarization state when light incident from an oblique direction is scattered in the direction perpendicular to the observation surface by the lower substrate is shown on the Poincare sphere. 6 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 2. FIG. In the liquid crystal display device which concerns on Embodiment 2, it is a cross-sectional schematic diagram which shows the mode of the light incident from the diagonal direction. In the liquid crystal display device which concerns on Embodiment 2, it is a figure which shows the transition of a polarization state when the light which enters from an oblique direction is not scattered on a Poincare sphere. In the liquid crystal display device which concerns on Embodiment 2, it is a figure which shows the transition of a polarization state on the Poincare sphere when the light which injected from an oblique direction is scattered in a perpendicular direction with respect to an observation surface by the lower board | substrate. 6 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 3. FIG. In the liquid crystal display device which concerns on Embodiment 3, it is a cross-sectional schematic diagram which shows the mode of the light which injects from the diagonal direction. In the liquid crystal display device which concerns on Embodiment 3, it is a figure which shows the transition of a polarization state when the light which enters from an oblique direction is not scattered on a Poincare sphere. In the liquid crystal display device which concerns on Embodiment 3, it is a figure which shows the transition of a polarization state on the Poincare sphere when the light which injected from an oblique direction is scattered in a perpendicular | vertical direction with respect to an observation surface by a lower board | substrate. In the liquid crystal display device which concerns on the comparative form 1, it is a cross-sectional schematic diagram which shows the mode of the light which injected from the diagonal direction. In the liquid crystal display device which concerns on the comparative form 1, it is a figure which shows the transition of a polarization state when the light which enters from an oblique direction is not scattered on a Poincare sphere. In the liquid crystal display device which concerns on the comparative form 1, it is a figure which shows the transition of a polarization state on the Poincare sphere when the light which injected from an oblique direction is scattered in a perpendicular direction with respect to an observation surface by a lower board | substrate. In the liquid crystal display device which concerns on the comparison form 2, it is a cross-sectional schematic diagram which shows the mode of the light which injects from the diagonal direction. In the liquid crystal display device which concerns on the comparative form 2, it is a figure which shows the transition of a polarization state when the light which enters from an oblique direction is not scattered on a Poincare sphere. In the liquid crystal display device which concerns on the comparative form 2, it is a figure which shows the transition of a polarization state on the Poincare sphere when the light which injected from an oblique direction is scattered in a perpendicular | vertical direction with respect to an observation surface by a lower board | substrate. In the liquid crystal display device which concerns on the comparative form 3, it is a cross-sectional schematic diagram which shows the mode of the light which injected from the diagonal direction. In the liquid crystal display device which concerns on the comparative form 3, it is a figure which shows the transition of a polarization state when the light which enters from an oblique direction is not scattered on a Poincare sphere. In the liquid crystal display device which concerns on the comparative form 3, it is a figure which shows the transition of a polarization state on the Poincare sphere when the light which injected from an oblique direction is scattered in a perpendicular direction with respect to an observation surface by a lower board | substrate. It is a schematic diagram which shows the scattering of the oblique incident light in a liquid crystal panel.

In this specification, a polarizer has a function of extracting polarized light (linearly polarized light) that vibrates only in a specific direction from non-polarized light (natural light), partially polarized light, or polarized light. Unless otherwise specified, the term “polarizer” in this specification refers to only a device having a polarizing function without including a protective film.

The in-plane retardation R is defined by R = (ns−nf) × d. The thickness direction retardation Rth is defined by Rth = (nz− (nx + ny) / 2) × d. The NZ coefficient (biaxial parameter) is defined by NZ = (ns−nz) / (ns−nf).

The ns is the larger of nx and ny, and the nf is the smaller of nx and ny. Further, nx and ny indicate the main refractive index in the in-plane direction of the birefringent layer (also applicable to a liquid crystal panel), and nz is the main refractive index in the out-of-plane direction, that is, in the direction perpendicular to the surface of the birefringent layer. D represents the thickness of the birefringent layer.

In this specification, the measurement wavelength of optical parameters such as the main refractive index, phase difference, and NZ coefficient is 550 nm unless otherwise specified.

In this specification, a birefringent layer (retardation film) is a layer (film) having optical anisotropy. The birefringent layer means that one of the in-plane retardation R and the absolute value of the thickness direction retardation Rth has a value of 10 nm or more, and preferably has a value of 20 nm or more. .

In this specification, the axis angle means the absorption axis of a polarizer or the slow axis of a birefringent layer unless otherwise specified.

Embodiments will be described below, and the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited only to these embodiments.

[Embodiment 1]
(Optical element and liquid crystal display device)
The liquid crystal display device 50 of the present embodiment is a transmissive liquid crystal display device, and as shown in FIG. 1, in order from the back side, a backlight (BL) unit 40, a first polarizer 10, and a first type of composite device. A liquid crystal cell 30 including a refractive layer 1 (corresponding to the first first-type birefringent layer), a liquid crystal layer 22 sandwiched between substrates 20 and 21 (upper and lower substrates), a second-type birefringent layer 2, a second This is a liquid crystal display device obtained by laminating a kind of birefringent layer 3 (corresponding to the second kind of birefringent layer) and a second polarizer 11 in this order. This embodiment is an embodiment according to the first and second liquid crystal display devices of the present invention.

Hereafter, each component which comprises a liquid crystal display device is explained in full detail.
(Birefringent layer)
The material of the birefringent layer used in Embodiment 1 is not particularly limited. For example, a stretched polymer film, a fixed liquid crystal material orientation, a thin plate made of an inorganic material, or the like can be used. . The method for forming the birefringent layer is not particularly limited. In the case of a birefringent layer formed from a polymer film, for example, a solvent casting method, a melt extrusion method, or the like can be used. A method of simultaneously forming a plurality of birefringent layers by a coextrusion method may be used. As long as the desired phase difference is expressed, the film may be unstretched or may be stretched. The stretching method is not particularly limited, and stretching is performed under the action of the shrinkage force of the heat-shrinkable film, in addition to the inter-roll tensile stretching method, the inter-roll compression stretching method, the tenter transverse uniaxial stretching method, the oblique stretching method, the longitudinal and transverse biaxial stretching method. A special stretching method or the like can be used. In the case of a birefringent layer formed of a liquid crystalline material, for example, a method of applying a liquid crystalline material on an orientation-treated base film and fixing the orientation can be used. As long as a desired phase difference is developed, a method of not performing a special orientation treatment on the base film, a method of removing the base film from the base film and transferring it to another film may be used. . Further, a method that does not fix the alignment of the liquid crystal material may be used. In the case of a birefringent layer formed from a non-liquid crystalline material, the same formation method as that for a birefringent layer formed from a liquid crystalline material may be used. Hereinafter, more specific description will be given for each type of birefringent layer.

(First birefringent layer)
In this specification, a birefringent layer (retardation film) of 0 <NZ <1 is referred to as a first type birefringent layer. A film obtained by stretching a film containing a material having a positive or negative intrinsic birefringence as a component under the action of the shrinkage force of a heat-shrinkable film can be appropriately used. For example, Japanese Patent No. 2818983 discloses a method for producing a birefringent layer that is stretched under the action of the shrinkage force of the heat-shrinkable film.

(Second birefringent layer)
In this specification, a birefringent layer (retardation film) of NZ >> 1 or a so-called negative C plate is referred to as a second type birefringent layer. As the second birefringent layer, a film containing a material having a positive intrinsic birefringence as a component is subjected to longitudinal and transverse biaxial stretching processing, or a liquid crystal material such as cholesteric (chiral nematic) liquid crystal or discotic liquid crystal is applied. In addition, a material coated with a non-liquid crystalline material containing polyimide, polyamide, or the like can be used as appropriate.

(Third kind of birefringent layer)
In this specification, a birefringent layer (retardation film) of NZ ≧ 1 is referred to as a third type birefringent layer. As the third birefringent layer, a film obtained by stretching a film containing a material having a positive intrinsic birefringence as a component can be appropriately used. Examples of the material having a positive intrinsic birefringence include polycarbonate, polysulfone, polyethersulfone, polyethylene terephthalate, polyethylene, polyvinyl alcohol, norbornene, triacetylcellulose, and diacylcellulose.

(Fourth birefringent layer)
In this specification, a birefringent layer (retardation film) of NZ ≦ 0 is referred to as a fourth type birefringent layer. The fourth kind of birefringent layer is a stretched film containing a material having a negative intrinsic birefringence as a component, and a film containing a material having a positive intrinsic birefringence as a component is acting on the shrinkage force of the heat shrinkable film What extended | stretched and processed below can be used suitably. Among these, from the viewpoint of simplifying the production method, a film obtained by stretching a film containing a material having a negative intrinsic birefringence as a component is preferable. Examples of the material having a negative intrinsic birefringence include a resin composition containing an acrylic resin and a styrene resin, polystyrene, polyvinyl naphthalene, polyvinyl biphenyl, polyvinyl pyridine, polymethyl methacrylate, polymethyl acrylate, and an N-substituted maleimide copolymer. , Polycarbonate having a fluorene skeleton, and triacetyl cellulose (particularly those having a low degree of acetylation). Among these, from the viewpoint of optical properties, productivity, and heat resistance, a resin composition containing an acrylic resin and a styrene resin is preferable. A method for producing a film containing such a resin composition as a component is disclosed in, for example, JP-A-2008-146003.

(Fifth birefringent layer)
In this specification, a birefringent layer (retardation film) of NZ << 0, a so-called positive C plate is referred to as a fourth type birefringent layer. As the fourth type of birefringent layer, a film containing a material having a negative intrinsic birefringence as a component and subjected to longitudinal and lateral biaxial stretching processing, a film coated with a liquid crystalline material such as a rod-like nematic liquid crystal, and the like can be used as appropriate. .

(Polarizer)
The polarizer used in Embodiment 1 is not particularly limited with respect to materials and optical performance. Specifically, a polarizer or the like in which an anisotropic material such as an iodine complex having dichroism is adsorbed and oriented on a polyvinyl alcohol (PVA) film can be appropriately used.

Moreover, in order to ensure mechanical strength and heat-and-moisture resistance, a protective film (not shown) such as a triacetyl cellulose (TAC) film may be laminated on both sides of the polarizer. The protective film is attached to the polarizer via any suitable adhesive layer (not shown). In addition, the birefringent layer may have the function of a protective film.

In this specification, the “adhesive layer” refers to a layer that joins surfaces of adjacent optical members and integrates them with practically sufficient adhesive force and adhesion time. Examples of the material for forming the adhesive layer include an adhesive and an anchor coat agent. The adhesive layer may have a multilayer structure in which an anchor coat layer is formed on the surface of an adherend and an adhesive layer is formed thereon. Further, it may be a thin layer that cannot be visually recognized.

(Liquid crystal cell)
The liquid crystal cell only needs to perform black display by aligning liquid crystal molecules in the liquid crystal layer substantially perpendicularly to the substrate surface, and may perform black display when a voltage is applied. It is also possible to perform black display when adding. As will be described later, since the

polarizers

10 and 11 are arranged in crossed Nicols, the liquid crystal display device of the present embodiment is driven in a normally white mode when black display is performed when a voltage is applied, and no voltage is applied. When black display is sometimes performed, it is driven in a normally black mode. As a display mode of a liquid crystal cell that performs black display when no voltage is applied, for example, a VA mode is exemplified. In addition to the TFT method (active matrix method), the liquid crystal cell may be driven by a simple matrix method (passive matrix method), a plasma address method, or the like. As a configuration of the liquid crystal cell, for example, a liquid crystal layer is sandwiched between a pair of substrates on which electrodes are formed, and display is performed by applying a voltage between the electrodes.

Examples of the VA mode include an MVA (Multi-domain Vertical Alignment) mode, a CPA (Continuous Pinwheel Alignment) mode, a PVA (Patterned Vertical Alignment) mode, a BVA (Biased Vertical Alignment) mode, and an RTN (Reverse Twisted Nematic) mode. UV2A (Ultra Violet Induced VA) mode, PSA (Polymer Sustained Alignment) mode, IPS-VA (In Plane Switching-Vertical Alignment) mode, TBA (Transverese Bend Alignment) mode, and the like. In the VA mode, the average pretilt angle of the liquid crystal molecules is preferably 80 ° or more (more preferably 85 ° or more).

As a display mode of a liquid crystal cell that performs black display when a voltage is applied, for example, a TN (TwistedwNematic) mode can be given.

Further, from the viewpoint of maximizing the CR improvement effect of the present invention, among the upper and lower substrates constituting the liquid crystal cell, the scattering of the upper substrate (observation surface side substrate) is more than the scattering of the lower substrate (non-observation surface side substrate). A small liquid crystal panel is more preferable. As such a liquid crystal panel, for example, a liquid crystal panel having a color filter on array (COA) structure in which a CF layer is provided on a lower substrate together with a TFT is more preferable. Both the CF layer and the TFT cause large scattering of incident light. However, since these are concentrated on the lower substrate, the scattering of the upper substrate can be surely made smaller than the scattering of the lower substrate. Examples of the liquid crystal panel having the COA structure include a liquid crystal panel mounted on a Samsung liquid crystal television (trade name: UN46C7000). In addition, for example, liquid crystal panels using a dye-based CF layer, which is considered to have little scattering, and black and white panels that do not include a CF layer can make the scattering of the upper substrate close to zero and smaller than the scattering of the lower substrate. Can be preferably used.

(Backlight unit)
The backlight (BL) unit is not particularly limited. For example, a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL), and a light emitting diode (LED). A light source including at least a light source such as can be used as appropriate. In general, it is more preferable to provide a diffusion layer such as a diffusion plate or a diffusion sheet in order to uniformize the light emitted from the light source that is a dot or a line in a planar shape. In addition, from the viewpoint of further improving CR or diverting the conventional BL unit without change, the BL unit itself includes an optical sheet such as a lens sheet or prism sheet, and has a collimating function. It may be.

In the liquid crystal display device of Embodiment 1, the first polarizer 10 and the second polarizer 11 are arranged so that their absorption axes are substantially orthogonal to each other. The term “substantially orthogonal” specifically means that the angle formed by the absorption axes of each other is within a range of 90 ± 3 ° (preferably 90 ± 1 °, more preferably 90 ± 0.5 °). That means.

The first type birefringent layer 1 is arranged so that the in-plane slow axis is substantially parallel to the absorption axis of the second polarizer 11, and the first type birefringent layer 3 is an in-plane slow phase. The axis is arranged so as to be substantially parallel to the absorption axis of the second polarizer 11. The term “substantially parallel” means that in any case, specifically, the angle formed by the in-plane slow layer axis and the absorption axis is 0 ± 3 ° (preferably 0 ± 1 °, more preferably 0 ± 0.5 °).

The NZ coefficient NZ11 of the first type birefringent layer 1 satisfies 0 <NZ11 ≦ 0.5, and the in-plane retardation R11 of the first type birefringent layer 1 satisfies 220 nm ≦ R11 ≦ 320 nm. The NZ coefficient NZ12 of the first type birefringent layer 3 satisfies 0.5 ≦ NZ12 <1.0, and the in-plane retardation R12 of the first type birefringent layer 3 satisfies 220 nm ≦ R12 ≦ 320 nm. Fulfill. Furthermore, the sum of the thickness direction retardation Rth2 of the second birefringent layer 2 and the thickness direction retardation Rthlc of the liquid crystal cell 30 during black display satisfies −50 nm ≦ Rth2 + Rthlc ≦ 50 nm.

According to the liquid crystal display device 50 of the first embodiment, light obliquely incident on the substrate 20 is absorbed by the second polarizer 11 even if the traveling direction is changed to the normal direction due to scattering, and thus light leakage is suppressed. A large CR improvement effect is obtained. In addition, light that is obliquely incident on the substrate 20 and is transmitted through the liquid crystal cell 30 without being scattered is also absorbed by the second polarizer 11, thereby reducing light leakage from the oblique direction. The viewing angle can be enlarged.

The technical reason why the liquid crystal display device 50 according to the first embodiment exhibits the above-described effect will be described with reference to FIGS. 2 to 4, a birefringent layer of R = 275 nm, Rth = 69 nm, and NZ = 0.25 is used as the first kind of birefringent layer 1, and there is no in-plane retardation as the liquid crystal layer 22. = VA nm VA liquid crystal layer was used. Further, as the second type birefringent layer 2, a birefringent layer having no in-plane retardation and Rth = −270 nm is used, and as the first type birefringent layer 3, R = 275 nm, Rth = −69 nm, NZ = 0.75 birefringent layer was used. Furthermore, the axial angles of the first polarizer 10 and the second polarizer 11 are set to 90 ° and 0 ° azimuth, respectively, and the in-plane slow axes of the

birefringent layers

1 and 2 are both set to 0 ° azimuth. did.

FIG. 2 is a schematic cross-sectional view showing a state in which light is incident on the liquid crystal display device of the first embodiment (no voltage applied, black display state) from an oblique direction of 45 ° polar angle and 60 °. In FIG. 2, (1) light that passes through the substrate 20 as it is and travels straight to the second polarizer 11, and (2) is scattered by the substrate 20, and the traveling direction is changed to the normal direction of the second polarizer 11. The light is shown. Since the second birefringent layer 2 and the VA liquid crystal layer have no in-plane anisotropy, the axis angle is not shown in FIG. Moreover, the arrow shown separately from what shows the advancing direction of light is for implying that a polarization state is linearly polarized light, and does not necessarily show a polarization state correctly. First, the change in the polarization state of the light (1) will be described using the Poincare sphere shown in FIG.

The concept of Poincare sphere is widely known in the field of crystal optics and the like as a useful technique for tracking the polarization state changing through the birefringent layer (for example, Hiroshi Takasaki, “Crystal optics”, Morikita Publishing, 1975, p.146-163). In the Poincare sphere, right-handed polarized light is represented in the upper hemisphere, left-handed polarized light is represented in the lower hemisphere, linearly polarized light is represented in the equator, and right circularly polarized light and left circularly polarized light are represented in the upper and lower poles. The two polarization states that are symmetric with respect to the center of the sphere form a pair of orthogonal polarization because the absolute values of the ellipticity angles are equal and the polarities are opposite. Also, the effect of the birefringent layer on the Poincare sphere is that the polarization state immediately before passing through the birefringent layer is expressed by the slow axis on the Poincare sphere (more precisely, the natural vibration of two birefringent layers). (2π) × (phase difference) / (wavelength) (unit: rad) centering on the line segment connecting the position of the point on the Poincare sphere representing the slower polarization state of the modes and the origin O of the Poincare sphere) ) Is converted into a point that is rotated counterclockwise by an angle determined in () (the same is true if it is rotated clockwise around the fast axis). The rotation center and rotation angle when observed from an oblique direction are determined by the slow axis (or fast axis) and the phase difference at the observation angle. Although detailed explanation is omitted, these can be calculated by, for example, solving Fresnel's wavefront normal equation and knowing the vibration direction and wave number vector of the natural vibration mode in the birefringent layer. The slow axis when observed from the oblique direction depends on the observation angle and the NZ coefficient, and the phase difference when observed from the oblique direction is the observation angle, the NZ coefficient and the in-plane retardation R (or the thickness direction retardation Rth). ).

The change in the polarization state of the light of (1) above is the polarization state each time the light emitted from the backlight unit 40 passes through the first polarizer 10, each birefringent layer, and the liquid crystal layer 22 (VA liquid crystal layer). When the points P0 to P4 representing are represented on the S1-S2 plane and the S1-S3 plane of the Poincare sphere, they are as shown in FIG. Point E is a point representing the polarization state of the extinction position (polarized light oscillating in the absorption axis direction) of the second polarizer 11 when viewed from an oblique direction of 45 ° azimuth and 60 ° polar angle. Although the points representing the respective polarization states are actually on the Poincare sphere, they are projected onto the S1-S2 plane and the S1-S3 plane for illustration. A point P0 representing the polarization state of the light after passing through the first polarizer 10 passes through the first-type birefringent layer 1 to P1, passes through the liquid crystal layer 22 to P2, and second-type birefringence. By passing through the layer 2, it is converted to P3, and by passing through the first kind birefringent layer 3, it is converted to P4. Since the point P4 representing this polarization state coincides with the point E representing the polarization state of the extinction position when viewed from the oblique direction of the 45 ° polar angle of the second polarizer 11 at 60 °, the polar angle is 45 °. Light incident from an oblique direction of 60 ° is finally absorbed by the second polarizer 11. That is, the original function of the retardation film, which reduces the light leakage from the oblique direction and expands the viewing angle, is working normally.

The description so far has been made in the case where light does not scatter inside the liquid crystal cell 30 and light incident from an oblique direction of 45 ° and polar angle of 60 ° passes through without changing the traveling direction. 4, using the Poincare sphere shown in FIG. 4, scattering occurs in the substrate 20, and the change in the polarization state when the incident light changes its traveling direction in the normal direction of the second polarizer 11, that is, (2 ) Will be described. The point P0 representing the polarization state of the light after passing through the first polarizer 10 is converted to P1 by passing through the first type birefringent layer 1, and then scattered by the lower substrate 20, whereby the law Although the traveling direction is changed to the linear direction, it may be considered that the polarization state hardly changes before and after the scattering (see, for example, Non-Patent Document 2), so even after the scattering progresses in the normal direction. The point representing the polarization state remains P1. Since the liquid crystal layer 22 and the second birefringent layer 2 (negative C plate) have no in-plane anisotropy (R = 0 nm), the polarization state conversion is not performed for the normal direction incidence. Points P2 and P3 representing the polarization state after passing through do not change from P1. By passing through the first kind of birefringent layer 3, P3 undergoes rotational movement around the slow axis on the Poincare sphere of the retardation film 3, but the slow axis of the retardation film 3 is Poincare sphere. The polarization state does not substantially change because P3 is already on the S2 axis. Therefore, the point P4 representing the polarization state of the light after passing through the first type birefringent layer 3 is the same as P3 (= P2 = P1). And since the point P4 representing this polarization state coincides with the point E ′ representing the polarization state of the extinction position in the normal direction of the second polarizer 11, it is incident from an oblique direction of 45 ° and polar angle of 60 °. Even when light travels in the normal direction due to scattering on the lower substrate of the liquid crystal panel, it is finally absorbed by the second polarizer 11. That is, since scattering at the lower substrate 20 is not observed as light leakage in the normal direction, a high CR can be obtained in the normal direction.

In addition, although the technical reason for suppressing light leakage has been described using light incident from an oblique direction with an azimuth of 45 ° and a polar angle of 60 ° as an example, the same reason applies to light incident from other oblique directions. Therefore, even if the traveling direction is changed to the normal direction of the second polarizer 11, the light is absorbed by the second polarizer 11, and thus light leakage is suppressed.

[Embodiment 2]
(Optical element and liquid crystal display device)
The liquid crystal display device 51 of the present embodiment is a transmissive liquid crystal display device, and as shown in FIG. 5, in order from the back side, a backlight (BL) unit 40, a first polarizer 10, and a first type of composite device. A refraction layer 4 (corresponding to the first first birefringent layer), a liquid crystal cell 30 including a liquid crystal layer 22 sandwiched between the

substrates

20 and 21, a second birefringent layer 2, a first birefringent layer. This is a liquid crystal display device obtained by laminating the refractive layer 6 (corresponding to the above-mentioned second type birefringent layer) and the second polarizer 11 in this order. Thus, instead of the first type birefringent layer 1 and the first type birefringent layer 3, the first type birefringent layer 4 and the first type birefringent layer 6 are provided. Except for this, the present embodiment is the same as the first embodiment. Therefore, in the following, items different from the first embodiment will be mainly described. This embodiment is an embodiment according to the first and third liquid crystal display devices of the present invention.

The NZ coefficient NZ11 of the first type birefringent layer 4 satisfies 0.5 ≦ NZ11 <1.0, and the in-plane retardation R11 of the first type birefringent layer 4 satisfies 220 nm ≦ R11 ≦ 320 nm. The NZ coefficient NZ12 of the first type birefringent layer 6 satisfies 0 <NZ12 ≦ 0.5, and the in-plane retardation R12 of the first type birefringent layer 6 satisfies 220 nm ≦ R12 ≦ 320 nm.

The first type birefringent layer 4 is disposed so that the in-plane slow axis is substantially parallel to the absorption axis of the second polarizer 11, and the first type birefringent layer 6 is provided with an in-plane slow phase. The axis is arranged so as to be substantially parallel to the absorption axis of the second polarizer 11. The term “substantially parallel” means that in any case, specifically, the angle formed by the in-plane slow layer axis and the absorption axis is 0 ± 3 ° (preferably 0 ± 1 °, more preferably 0 ± 0.5 °).

The various forms described in the first embodiment can be applied to this embodiment as appropriate.

According to the liquid crystal display device 51 of the second embodiment, light obliquely incident on the substrate 20 is absorbed by the second polarizer 11 even if the traveling direction is changed to the normal direction due to scattering, and thus light leakage is suppressed. A large CR improvement effect is obtained. In addition, light that is obliquely incident on the substrate 20 and is transmitted through the liquid crystal cell 30 without being scattered is also absorbed by the second polarizer 11, thereby reducing light leakage from the oblique direction. The viewing angle can be enlarged.

A technical reason why the liquid crystal display device 51 of the second embodiment has the above-described effect will be described with reference to FIGS. 6 to 8, a birefringent layer of R = 275 nm, Rth = −69 nm, NZ = 0.75 is used as the first type birefringent layer 4, and there is no in-plane retardation as the liquid crystal layer 22. A VA liquid crystal layer with Rth = 270 nm was used. Further, as the second type birefringent layer 2, a birefringent layer having no in-plane retardation and Rth = −270 nm is used, and as the first type birefringent layer 6, R = 275 nm, Rth = 69 nm, NZ = A birefringent layer of 0.25 was used. Further, the axial angles of the first polarizer 10 and the second polarizer 11 are set to 90 ° and 0 °, respectively, and the in-plane slow axes of the

birefringent layers

4 and 6 are both set to 90 °. did.

FIG. 6 is a schematic cross-sectional view showing a state in which light is incident on the liquid crystal display device of the second embodiment (no voltage applied, black display state) from an oblique direction of 45 ° polar angle and 60 °. In FIG. 6, (1) light that is transmitted through the substrate 20 as it is and travels straight to the second polarizer 11, and (2) is scattered by the substrate 20, and the traveling direction is changed to the normal direction of the second polarizer 11. The light is shown.

Similarly to the first embodiment, in the liquid crystal display device 50 of the second embodiment, as shown in FIG. 7, the polarization state P4 after passing through the first birefringent layer 6 of the light of (1) is the second. This coincides with the extinction position E of the polarizer 11. As shown in FIG. 8, the polarization state P4 of the light (2) after passing through the first-type birefringent layer 6 matches the extinction position E ′ of the second polarizer 11. That is, since scattering on the substrate 20 is not observed as light leakage in the normal direction, a high CR can be obtained in the normal direction.

[Embodiment 3]
(Optical element and liquid crystal display device)
The liquid crystal display device 52 of this embodiment is a transmissive liquid crystal display device. As shown in FIG. 9, the backlight (BL) unit 40, the first polarizer 10, and the fifth type of composite are sequentially arranged from the back side. Refractive layer 7 (positive C plate), third type birefringent layer 8 (third type of birefringent layer, Nz = 1, positive A plate), liquid crystal layer 22 sandwiched between

substrates

20 and 21 Liquid crystal cell 30, second birefringent layer 2, third birefringent layer 18 (third birefringent layer, Nz = 1, positive A plate), fifth birefringent layer 18 This is a liquid crystal display device obtained by laminating a birefringent layer 17 (positive C plate) and a second polarizer 11 in this order. Thus, instead of the first type birefringent layer 1, the fifth type birefringent layer 7 and the third type birefringent layer 8 are provided. The present embodiment is the same as the first embodiment except that the birefringent layer 18 and the fifth birefringent layer 17 are provided. Therefore, in the following, items different from the first embodiment will be mainly described. This embodiment is an embodiment according to the first liquid crystal display device of the present invention.

The third birefringent layer 8 is arranged so that the in-plane slow axis is substantially perpendicular to the absorption axis of the second polarizer 11, and the third birefringent layer 18 has an in-plane slow axis. It arrange | positions so that it may become substantially parallel with the absorption axis of the 2nd polarizer 11. FIG. The term “substantially parallel” means that in any case, specifically, the angle formed by the in-plane slow layer axis and the absorption axis is 0 ± 3 ° (preferably 0 ± 1 °, more preferably 0 ± 0.5 °).

According to the liquid crystal display device 52 of the third embodiment, light obliquely incident on the substrate 20 is absorbed by the second polarizer 11 even if the traveling direction is changed to the normal direction due to scattering, and thus light leakage is suppressed. A large CR improvement effect is obtained. In addition, light that is obliquely incident on the substrate 20 and is transmitted through the liquid crystal cell 30 without being scattered is also absorbed by the second polarizer 11, thereby reducing light leakage from the oblique direction. The viewing angle can be enlarged.

A technical reason why the liquid crystal display device 52 of the third embodiment has the above-described effect will be described with reference to FIGS. 10 to 12, a birefringent layer having no in-plane retardation and Rth = 45 nm is used as the fifth type birefringent layer 7, and R = 135 nm, NZ = as the third type birefringent layer 8. One birefringent layer was used. Then, a VA liquid crystal layer having no in-plane retardation and Rth = 270 nm is used as the liquid crystal layer 22, and a birefringent layer having no in-plane retardation and Rth = −270 nm is used as the second birefringent layer 2. Using. Further, a birefringent layer of R = 135 nm and NZ = 1 is used as the third birefringent layer 18, and a birefringent layer having no in-plane retardation and Rth = 45 nm is used as the fifth birefringent layer 17. Was used. Furthermore, the axial angles of the first polarizer 10 and the second polarizer 11 are set to 90 ° and 0 ° azimuth, respectively, and the in-plane slow axis of the third birefringent layer 8 is set to 90 ° azimuth. The in-plane slow axis of the third type birefringent layer 18 was set to 0 ° azimuth.

FIG. 10 is a schematic cross-sectional view showing a state in which light is incident on the liquid crystal display device of the third embodiment (no voltage applied, black display state) from an oblique direction of 45 ° polar angle and 60 °. In FIG. 10, (1) light that is transmitted through the substrate 20 as it is and travels straight to the second polarizer 11, and (2) is scattered by the substrate 20, and the traveling direction is changed to the normal direction of the second polarizer 11. The light is shown.

Similarly to the first embodiment, in the liquid crystal display device 52 of the third embodiment, as shown in FIG. 11, the polarization state P6 of the light (1) after passing through the fifth birefringent layer 17 is This coincides with the extinction position E of the two polarizers 11. As shown in FIG. 12, the polarization state P6 of the light (2) after passing through the fifth birefringent layer 17 coincides with the extinction position E ′ of the second polarizer 11. That is, since scattering on the substrate 20 is not observed as light leakage in the normal direction, a high CR can be obtained in the normal direction.

In the third embodiment, the fifth birefringent layer (positive C plate) and the third birefringent layer (positive A plate) satisfying NZ = 1 among the third birefringent layers are provided. Although used in combination, instead of these, among the second birefringent layer (negative C plate) and the fourth birefringent layer, the fourth birefringent layer (NZ = 0) (NZ = 0) A negative A plate) may be used in combination. Moreover, although it is necessary to adjust the phase difference value and the shaft angle optimally, the order of the birefringent layers may be changed. Furthermore, each birefringent layer does not necessarily have to be uniaxial (A plate, C plate), and may be a biaxial AC plate (third birefringent layer or fourth birefringent layer). Good.

[Comparison 1]
(Optical element and liquid crystal display device)
The liquid crystal display device 150 of the present embodiment is a transmissive liquid crystal display device, and as shown in FIG. 13, in order from the back side, a backlight (BL) unit 140, a first polarizer 110, R = 3 nm, Rth. = -45 nm, NZ = 16 birefringent layer 101, liquid crystal cell 130 including liquid crystal layer 122 sandwiched between

substrates

120 and 121, R = 55 nm, Rth = −200 nm, NZ = 4.1 birefringent layer 102, And it is the liquid crystal display device obtained by laminating | stacking the 2nd polarizer 111 in this order. The liquid crystal layer 122 is a VA liquid crystal layer having no in-plane retardation and Rth = 270 nm. Although not shown, the substrate 120 includes a thin film transistor (TFT) and a color filter layer.

In the liquid crystal display device of comparative form 1, the axial angles of the first polarizer 110 and the second polarizer 111 are set to 90 ° and 0 ° azimuth, respectively. The in-plane slow axes of the

birefringent layers

101 and 102 are both set to 90 ° azimuth.

In FIG. 13, when light is incident on the liquid crystal display device of comparative form 1 (no voltage applied, black display state) from an oblique direction of 45 ° polar angle 60 °, (1) the light passes through the substrate 120 as it is, Light that travels straight to the second polarizer 111 and (2) light that is scattered by the substrate 120 and whose traveling direction is changed to the normal direction of the second polarizer 111 are illustrated. First, the change in the polarization state of the light (1) will be described using the Poincare sphere shown in FIG.

A point P0 representing the polarization state of light after passing through the polarizer 1 passes through the birefringent layer 101, passes through the liquid crystal layer 122, passes through P2, and passes through the birefringent layer 102 through P3. Converted. The point P3 representing this polarization state coincides with the point E representing the polarization state of the extinction position when viewed from an oblique direction of 45 ° and polar angle 60 ° of the second polarizer 111. Light incident from an oblique direction with an angle of 60 ° is finally absorbed by the second polarizer 111. That is, the original function of the birefringent layer, which reduces the light leakage from the oblique direction and widens the viewing angle, is working normally.

The description so far has been for the case where light does not scatter inside the liquid crystal panel, and light incident from an oblique direction of 45 ° azimuth and 60 ° polar angle passes through without changing the traveling direction. Next, using the Poincare sphere shown in FIG. 15, scattering occurs in the lower substrate 120 of the liquid crystal cell 130, and the polarization state in the case where the incident light changes its traveling direction in the normal direction of the second polarizer 111. The change and the change in the polarization state of the light (2) will be described.

The point P0 representing the polarization state of the light after passing through the first polarizer 110 is converted to P1 by transmitting through the birefringent layer 101, and then scattered by the lower substrate 120, so that the traveling direction in the normal direction. However, since the polarization state hardly changes before and after the scattering, the point representing the polarization state remains P1 even after scattering and progressing in the normal direction. Since the liquid crystal layer 122 (VA liquid crystal layer) has no in-plane anisotropy (R = 0 nm), the polarization state conversion is not performed for the incidence in the normal direction, and thus the point P2 representing the polarization state after passing through it. Does not change from P1. Then, by passing through the birefringent layer 102, P2 undergoes rotational movement around the slow axis on the Poincare sphere of the retardation film 2 and moves to P3. Since the point P3 representing the polarization state does not coincide with the point E ′ representing the polarization state of the extinction position in the normal direction of the polarizer 2, light incident from an oblique direction of 45 ° and polar angle of 60 ° is liquid crystal. When the traveling direction is changed in the normal direction due to scattering on the lower substrate of the panel, it is not completely absorbed by the second polarizer 111, resulting in light leakage, and CR is lowered.

Note that the amount of light leakage increases as the distance between the point P3 and the point E ′ increases. More precisely, it is proportional to sin ² ((1/2) × ∠P3OE ′) (the point O represents the center of the Poincare sphere. Also, since P3 and E ′ are points on the Poincare sphere, Note that the angle must not be measured in a projection map such as in Fig. 15). Here, the slow axis on the Poincare sphere of the birefringent layer 102 coincides with the S2 axis, and the P2 (= P1) → P3 conversion is rotation about the S2 axis including the point O and the point E ′. Actually, ∠PnOE ′ is not changed before and after the conversion. That is, although the polarization state is different, the light is reached even if it reaches the second polarizer 111 in the polarization state represented by the point P2 (= P1) or reaches the second polarizer 111 in the polarization state represented by the point P3. The amount of leakage is the same. In general, the birefringent layer 102 and the comparative example 1 are not limited to the birefringent layer (retardation film) of the VA mode. Since it is arranged perpendicularly or parallel to the absorption axis of the child, the polarization conversion by the retardation film after the traveling direction has changed to the normal direction due to scattering is all rotational movement about the S2 axis on the Poincare sphere. . Therefore, the amount of light leakage from the second polarizer after scattering does not require an accurate determination of the polarization state Pn immediately before incidence on the second polarizer (P1 in the case of comparative form 1) If you know, you can estimate. It may be considered that the light leakage amount is small as P1 is close to E ′, and the light leakage amount is increased as P1 is separated from E ′. If P1 overlaps with E ′, the amount of light leakage is minimized.

[Comparison 2]
(Optical element and liquid crystal display device)
The liquid crystal display device 151 of the present embodiment is a transmissive liquid crystal display device, and as shown in FIG. 16, in order from the back side, a backlight (BL) unit 140, a first polarizer 110, R = 55 nm, Rth. = -200 nm, NZ = 4.1 birefringent layer 103, liquid crystal cell 130 including liquid crystal layer 122 sandwiched between

substrates

120 and 121, R = 3 nm, Rth = −45 nm, NZ = 16 birefringent layer 104, And it is the liquid crystal display device obtained by laminating | stacking the 2nd polarizer 111 in this order. The liquid crystal layer 122 is a VA liquid crystal layer having no in-plane retardation and Rth = 270 nm. Although not shown, the substrate 120 includes a thin film transistor (TFT) and a color filter layer.

In the liquid crystal display device of comparative form 2, the axial angles of the first polarizer 110 and the second polarizer 111 are set to 90 ° and 0 ° azimuth, respectively. The in-plane slow axis of the birefringent layer 103 is set to 90 ° azimuth, and the in-plane slow axis of the birefringent layer 104 is set to 0 ° azimuth.

In FIG. 16, when light is incident on the liquid crystal display device of comparative form 2 (no voltage applied, black display state) from an oblique direction of 45 ° polar angle 60 °, (1) is transmitted through the substrate 120 as it is, Light that travels straight to the second polarizer 111 and (2) light that is scattered by the substrate 120 and whose traveling direction is changed to the normal direction of the second polarizer 111 are illustrated. In the liquid crystal display device 151 of the comparative form 2, a change in the polarization state of light incident from an oblique direction will be described with reference to FIGS.

As shown in FIG. 17, in the liquid crystal display device of Comparative Example 2, as in Comparative Example 1, the light of the above (1) that is incident from an oblique direction with an azimuth of 45 ° and a polar angle of 60 ° and is not scattered inside. Since the point P3 indicating the polarization state coincides with the point E indicating the polarization state of the extinction position when viewed from an oblique direction of 45 ° azimuth and polar angle 60 ° of the second polarizer 111, the azimuth 45 ° and polar angle 60 The light incident from the oblique direction is finally absorbed by the second polarizer 111. That is, the original function of the birefringent layer, which reduces the light leakage from the oblique direction and widens the viewing angle, is working normally.

On the other hand, as shown in FIG. 18, the point P3 indicating the polarization state of the light of the above (2) scattered by the lower substrate 120 of the liquid crystal cell 130 and changing the traveling direction to the normal direction of the second polarizer 111 is Since it does not coincide with the point E ′ representing the polarization state of the extinction position in the normal direction of the second polarizer 111, light incident from an oblique direction of 45 ° and polar angle of 60 ° is scattered by the lower substrate of the liquid crystal panel. When the traveling direction is changed to the linear direction, the second polarizer 111 eventually leaks light. That is, the CR is lower than that of the liquid crystal display device of the embodiment. Further, even when compared with the liquid crystal display device of Comparative Example 1, the distance between P3 and E ′ is large and the CR is low.

[Comparison 3]
(Optical element and liquid crystal display device)
The liquid crystal display device 152 of the present embodiment is a transmissive liquid crystal display device. As shown in FIG. 19, in order from the back side, a backlight (BL) unit 140, a first polarizer 110, R = 50 nm, Rth = -120 nm, NZ = 2.9 birefringent layer 105, liquid crystal cell 130 including liquid crystal layer 122 sandwiched between

substrates

120 and 121, R = 50 nm, Rth = −120 nm, NZ = 2.9 birefringent layer 106 and a liquid crystal display device obtained by laminating the second polarizer 111 in this order. The liquid crystal layer 122 is a VA liquid crystal layer having no in-plane retardation and Rth = 270 nm. Although not shown, the substrate 120 includes a thin film transistor (TFT) and a color filter layer.

In the liquid crystal display device of comparative form 3, the axial angles of the first polarizer 110 and the second polarizer 111 are set to 90 ° and 0 ° azimuth, respectively. The in-plane slow axis of the birefringent layer 105 is set to 0 ° azimuth, and the in-plane slow axis of the birefringent layer 106 is set to 90 ° azimuth.

In FIG. 19, when light is incident on the liquid crystal display device of Comparative Example 3 (no voltage applied, black display state) from an oblique direction of 45 ° polar angle 60 °, (1) the light passes through the substrate 120 as it is, Light that travels straight to the second polarizer 111 and (2) light that is scattered by the substrate 120 and whose traveling direction is changed to the normal direction of the second polarizer 111 are illustrated. In the liquid crystal display device 152 of the comparative form 3, a change in the polarization state of light incident from an oblique direction will be described with reference to FIGS.

As shown in FIG. 20, in the liquid crystal display device of Comparative Example 3, as in Comparative Example 1, the light of the above (1) that is incident from an oblique direction with an azimuth of 45 ° and a polar angle of 60 ° and is not scattered inside. Since the point P3 indicating the polarization state coincides with the point E indicating the polarization state of the extinction position when viewed from an oblique direction of 45 ° azimuth and polar angle 60 ° of the second polarizer 111, the azimuth 45 ° and polar angle 60 The light incident from the oblique direction is finally absorbed by the second polarizer 111. That is, the original function of the birefringent layer, which reduces the light leakage from the oblique direction and widens the viewing angle, is working normally.

On the other hand, as shown in FIG. 21, the point P3 indicating the polarization state of the light of the above (2) scattered by the lower substrate 120 of the liquid crystal cell 130 and changing the traveling direction to the normal direction of the second polarizer 111 is Since it does not coincide with the point E ′ representing the polarization state of the extinction position in the normal direction of the second polarizer 111, light incident from an oblique direction of 45 ° and polar angle of 60 ° is scattered by the lower substrate of the liquid crystal panel. When the traveling direction is changed to the linear direction, the second polarizer 111 eventually leaks light. That is, the CR is lower than that of the liquid crystal display device of the embodiment. Further, even when compared with the liquid crystal display device of Comparative Example 1, the distance between P3 and E ′ is large and the CR is low.

Example 1
As the liquid crystal display device of Example 1, the liquid crystal display device 50 of Embodiment 1 was actually manufactured. As the first kind of birefringent layer 1, a birefringent layer of R = 275 nm, Rth = 69 nm, and NZ = 0.25 was used. As a material for the birefringent layer, norbornene (NB) was used. As the second type birefringent layer 2, a negative C plate having an Rth of −270 nm was used. Polyimide (PI) was used as a material for this birefringent layer. As the first type birefringent layer 3, a birefringent layer having R = 273 nm, Rth = −68 nm, and NZ = 0.75 was used. As a material for the birefringent layer, norbornene (NB) was used. As the liquid crystal cell 30, a liquid crystal cell mounted on a Samsung liquid crystal television (trade name: UN46C7000) having a COA structure was used. The Rth at the time of black display with no voltage applied to the liquid crystal cell was 272 nm.

(Examples 2 to 4 and Comparative Examples 1 to 3)
The liquid crystal display device of Example 1 except that at least one of the in-plane retardation (R), thickness direction retardation (Rth), and NZ coefficient (NZ) of the first type

birefringent layers

1 and 3 is changed. In the same manner, liquid crystal display devices of Examples 2 to 4 and Comparative Examples 1 to 3 were produced. In Example 2, a birefringent layer of R = 275 nm, Rth = 110 nm and NZ = 0.1 is used as the first type birefringent layer 1, and R = 273 nm, Rth as the first type birefringent layer 3. = −109.2 nm, NZ = 0.9 birefringent layer was used. In Comparative Example 1, a birefringent layer having R = 275 nm, Rth = 165 nm, and NZ = −0.1 is used as the first type birefringent layer 1, and R = 273 nm as the first type birefringent layer 3. A birefringent layer having Rth = -163.8 nm and NZ = 1.1 was used. In Example 3, a birefringent layer of R = 230 nm, Rth = 57.5 nm, and NZ = 0.25 is used as the first type birefringent layer 1, and R = 230 nm as the first type birefringent layer 3. A birefringent layer having Rth = −57.5 nm and NZ = 0.75 was used. In Comparative Example 2, a birefringent layer of R = 210 nm, Rth = 52.5 nm, and NZ = 0.25 is used as the first type birefringent layer 1, and R = 210 nm as the first type birefringent layer 3. , Rth = −52.5 nm, NZ = 0.75 birefringent layer was used. In Example 4, a birefringent layer of R = 310 nm, Rth = 77.5 nm, and NZ = 0.25 is used as the first type birefringent layer 1, and R = 310 nm as the first type birefringent layer 3. , Rth = −77.5 nm, NZ = 0.75 birefringent layer was used. In Comparative Example 3, a birefringent layer of R = 330 nm, Rth = 82.5 nm, and NZ = 0.25 is used as the first type birefringent layer 1, and R = 330 nm as the first type birefringent layer 3. Rth = −82.5 nm, NZ = 0.75 birefringent layer was used.

(Example 5)
As the liquid crystal display device of Example 5, the liquid crystal display device 51 of Embodiment 2 was actually manufactured. As the first type birefringent layer 4, a birefringent layer of R = 273 nm, Rth = −68 nm, and NZ = 0.75 was used. As a material for the birefringent layer, norbornene (NB) was used. As the first type birefringent layer 6, a birefringent layer of R = 275 nm, Rth = 69 nm, and NZ = 0.25 was used. As a material for the birefringent layer, norbornene (NB) was used. The rest is the same as the first embodiment.

(Examples 6 to 8 and Comparative Examples 4 to 6)
The liquid crystal display device of Example 5 except that at least one of the in-plane retardation (R), thickness direction retardation (Rth), and NZ coefficient (NZ) of the first type

birefringent layers

4 and 6 is changed. In the same manner, liquid crystal display devices of Examples 6 to 8 and Comparative Examples 4 to 6 were produced. In Example 6, a birefringent layer of R = 273 nm, Rth = −109.2 nm, and NZ = 0.9 is used as the first type birefringent layer 4, and R = A birefringent layer having 275 nm, Rth = 110 nm, and NZ = 0.1 was used. In Comparative Example 4, a birefringent layer of R = 273 nm, Rth = -163.8 nm, and NZ = 1.1 is used as the first type birefringent layer 4, and R = A birefringent layer having 275 nm, Rth = 165 nm, and NZ = −0.1 was used. In Example 7, a birefringent layer of R = 230 nm, Rth = −57.5 nm, NZ = 0.75 is used as the first type birefringent layer 4, and R = A birefringent layer having 230 nm, Rth = 57.5 nm, and NZ = 0.25 was used. In Comparative Example 5, a birefringent layer of R = 210 nm, Rth = −52.5 nm, NZ = 0.75 is used as the first type birefringent layer 4, and R = A birefringent layer having 210 nm, Rth = 52.5 nm, and NZ = 0.25 was used. In Example 8, a birefringent layer of R = 310 nm, Rth = −77.5 nm, NZ = 0.75 is used as the first type birefringent layer 4, and R = A birefringent layer of 310 nm, Rth = 77.5 nm, and NZ = 0.25 was used. In Comparative Example 6, a birefringent layer of R = 330 nm, Rth = −82.5 nm, NZ = 0.75 is used as the first type birefringent layer 4, and R = A birefringent layer having 330 nm, Rth = 82.5 nm, and NZ = 0.25 was used.

(Comparative Example 7)
As a liquid crystal display device of Comparative Example 7, a liquid crystal display device 150 of Comparative Example 1 was actually manufactured. As the birefringent layer 101, a birefringent layer having R = 2 nm, Rth = −43 nm, and NZ = 22 was used. As a material for this birefringent layer, triacetyl cellulose (TAC) was used. As the birefringent layer 102, a birefringent layer having R = 55 nm, Rth = −198 nm, and NZ = 4.1 was used. As a material for the birefringent layer, norbornene (NB) was used. The rest is the same as the first embodiment.

(Comparative Example 8)
As a liquid crystal display device of Comparative Example 8, a liquid crystal display device 151 of Comparative Example 2 was actually produced. As the birefringent layer 103, a birefringent layer having R = 55 nm, Rth = −198 nm, and NZ = 4.1 was used. As a material for the birefringent layer, norbornene (NB) was used. As the birefringent layer 104, a birefringent layer of R = 2 nm, Rth = −43 nm, and NZ = 22 was used. As a material for this birefringent layer, triacetyl cellulose (TAC) was used. The rest is the same as the first embodiment.

(Comparative Example 9)
As a liquid crystal display device of comparative example 9, a liquid crystal display device 152 of comparative form 3 was actually produced. As the birefringent layer 105 and the birefringent layer 106, birefringent layers of R = 50 nm, Rth = −121 nm, and NZ = 2.9 were used. As a material for this birefringent layer, triacetyl cellulose (TAC) was used. The rest is the same as the first embodiment.

The liquid crystal display devices according to Examples 1 to 8 and Comparative Examples 1 to 9 were evaluated for contrast ratio (CR). The evaluation results are shown in Tables 1 to 3 below.

(Measurement method of R, Rth, NZ coefficient, nx, ny, nz)
The measurement was performed using a dual retarder rotation type polarimeter (manufactured by Axometrics, trade name: Axo-scan). The in-plane retardation R was measured from the normal direction of the birefringent layer. The main refractive indexes nx, ny, nz, thickness direction retardation Rth and NZ coefficient are measured by measuring the phase difference from the normal direction of the birefringent layer and each oblique direction inclined by −50 ° to 50 ° from the normal direction. The refractive index ellipsoidal curve fitting was used. The tilt azimuth was such that the angle formed with the in-plane slow axis was 90 °. Further, nx, ny, nz, R and Nz depend on the average refractive index = (nx + ny + nz) / 3 given as the curve fitting calculation condition, but the average refractive index of each birefringent layer is unified to 1.5. Calculated. The birefringent layer having an actual average refractive index different from 1.5 was also converted assuming an average refractive index of 1.5.

(CR ratio measurement method for liquid crystal display devices)
The measurement was performed using an ultra-low luminance spectroradiometer (manufactured by TOPCON, trade name: SR-Ul1). The luminance of white display and black display in the normal direction was measured, and the ratio was taken as CR.

In all of the liquid crystal display devices of Examples 1 to 8 according to the present invention, the contrast ratio was 7000 or more. On the other hand, in all of the liquid crystal display devices of Comparative Examples 1 to 9, the contrast ratio was less than 7000. Visual evaluation also confirmed that the liquid crystal display devices of Examples 1 to 8 had higher CR than the liquid crystal display devices of Comparative Examples 1 to 9.

This application claims priority based on the Paris Convention or the laws and regulations in the country to which the transition is based on Japanese Patent Application No. 2011-021157 filed on February 2, 2011. The contents of the application are hereby incorporated by reference in their entirety.

1, 3, 4, 6: First birefringent layer 2: Second birefringent layer 7, 17: Fifth birefringent layer 8, 18: Third birefringent layer 10, 110: First polarizer 11, 111:

Second polarizer

20, 21, 120, 121: Substrate 22, 122:

Liquid crystal layer

30, 130, 230: Liquid crystal panel (liquid crystal cell)
40, 140: Backlight (BL)

units

50, 51, 52, 150, 151, 152: Liquid

crystal display devices

101, 102, 103, 104, 105, 106: Birefringent layer 211: Polarizing plate (polarizer)

Claims

A liquid crystal display device comprising a first polarizer, a first first-type birefringent layer, a liquid crystal cell, and a second polarizer in this order from the back side,
The liquid crystal cell includes a pair of opposing substrates, and a liquid crystal layer sandwiched between both substrates,
An in-plane slow axis of the first first-type birefringent layer is substantially parallel to an absorption axis of the second polarizer;
The absorption axis of the first polarizer is substantially perpendicular to the absorption axis of the second polarizer,
When the NZ coefficient of the first birefringent layer of the first type is NZ11 and the in-plane retardation is R11,
A liquid crystal display device satisfying the following formulas (1) and (2):
0 <NZ11 ≦ 0.5 (1)
220 nm ≦ R11 ≦ 320 nm (2)
2. The liquid crystal display device according to claim 1, wherein 0.15 ≦ NZ11 ≦ 0.35 and 250 nm ≦ R11 ≦ 290 nm are satisfied.
The liquid crystal display device further includes a second birefringent layer and a second first birefringent layer in this order from the liquid crystal cell side between the liquid crystal cell and the second polarizer. ,
During black display, the liquid crystal molecules in the liquid crystal layer are substantially vertically aligned,
An in-plane slow axis of the second first-type birefringent layer is substantially parallel to an absorption axis of the second polarizer;
The NZ coefficient of the second birefringent layer is NZ12, the in-plane retardation is R12, the thickness direction retardation of the second birefringent layer is Rth2, and the thickness direction of the liquid crystal cell during black display When the phase difference is Rthlc,
3. The liquid crystal display device according to claim 1, wherein the following formulas (3) to (5) are satisfied.
0.5 ≦ NZ12 <1.0 (3)
220 nm ≦ R12 ≦ 320 nm (4)
−50 nm ≦ Rth2 + Rthlc ≦ 50 nm (5)
4. The liquid crystal display device according to claim 3, wherein 0.65 ≦ NZ12 ≦ 0.85 and 250 nm ≦ R12 ≦ 290 nm are satisfied.
5. The liquid crystal display device according to claim 3, wherein −30 nm ≦ Rth2 + Rthlc ≦ 30 nm is satisfied.
When the back side of the pair of substrates is a lower substrate and the observation surface side is an upper substrate,
6. The liquid crystal display device according to claim 1, wherein scattering of the upper substrate is smaller than scattering of the lower substrate.
The liquid crystal display device according to claim 6, wherein the lower substrate includes a color filter layer and a thin film transistor, and the liquid crystal cell has a color filter-on-array structure.
The liquid crystal display device according to claim 6, wherein the liquid crystal cell includes a dye-based color filter layer.
The liquid crystal display device according to claim 6, wherein the liquid crystal cell does not include a color filter layer.
A liquid crystal display device having a first polarizer, a first first-type birefringent layer, a liquid crystal cell, and a second polarizer in this order from the back side,
The liquid crystal cell includes a pair of opposing substrates, and a liquid crystal layer sandwiched between both substrates,
The in-plane slow axis of the first first-type birefringent layer is substantially orthogonal to the absorption axis of the second polarizer,
The absorption axis of the first polarizer is substantially perpendicular to the absorption axis of the second polarizer,
When the NZ coefficient of the first birefringent layer of the first type is NZ11 and the in-plane retardation is R11,
A liquid crystal display device satisfying the following formulas (1) and (2):
0.5 ≦ NZ11 <1.0 (1)
220 nm ≦ R11 ≦ 320 nm (2)
The liquid crystal display device according to claim 10, wherein 0.65 ≦ NZ11 ≦ 0.85 and 250 nm ≦ R11 ≦ 290 nm are satisfied.
The liquid crystal display device further includes a second birefringent layer and a second first birefringent layer in this order from the liquid crystal cell side between the liquid crystal cell and the second polarizer. ,
During black display, the liquid crystal molecules in the liquid crystal layer are substantially vertically aligned,
The in-plane slow axis of the second first-type birefringent layer is substantially orthogonal to the absorption axis of the second polarizer,
The NZ coefficient of the second birefringent layer is NZ12, the in-plane retardation is R12, the thickness direction retardation of the second birefringent layer is Rth2, and the thickness direction of the liquid crystal cell during black display When the phase difference is Rthlc,
12. The liquid crystal display device according to claim 10, wherein the following formulas (3) to (5) are satisfied.
0 <NZ12 ≦ 0.5 (3)
220 nm ≦ R12 ≦ 320 nm (4)
−50 nm ≦ Rth2 + Rthlc ≦ 50 nm (5)
13. The liquid crystal display device according to claim 12, wherein 0.15 ≦ NZ12 ≦ 0.35 and 250 nm ≦ R12 ≦ 290 nm are satisfied.
14. The liquid crystal display device according to claim 12, wherein −30 nm ≦ Rth2 + Rthlc ≦ 30 nm is satisfied.
When the back side of the pair of substrates is a lower substrate and the observation surface side is an upper substrate,
15. The liquid crystal display device according to claim 10, wherein scattering of the upper substrate is smaller than scattering of the lower substrate.
16. The liquid crystal display device according to claim 15, wherein the lower substrate includes a color filter layer and a thin film transistor, and the liquid crystal cell has a color filter on array structure.
The liquid crystal display device according to claim 15, wherein the liquid crystal cell includes a dye-based color filter layer.
The liquid crystal display device according to claim 15, wherein the liquid crystal cell does not include a color filter layer.
A liquid crystal display device comprising a first polarizer, one or more first birefringent layers, a liquid crystal cell, and a second polarizer in this order from the back side,
The liquid crystal cell includes a pair of opposing substrates, and a liquid crystal layer sandwiched between both substrates,
The absorption axis of the first polarizer is substantially perpendicular to the absorption axis of the second polarizer,
When the liquid crystal display device includes two or more first birefringent layers, the two or more first birefringent layers include a plurality of birefringent layers having different NZ coefficients and phase differences from each other.
The one or more first birefringent layers pass through the first polarizer and have an extinction position when the polarization state of light incident from an oblique direction is viewed from the normal direction of the second polarizer. A liquid crystal display device characterized by converting into a polarization state.
The liquid crystal display device further includes one or more second birefringent layers between the liquid crystal cell and the second polarizer,
When the liquid crystal display device includes two or more second birefringent layers, the two or more second birefringent layers include a plurality of birefringent layers having different NZ coefficients and phase differences from each other.
20. The liquid crystal layer and the one or more second birefringent layers do not substantially change the polarization state of light incident from the normal direction during black display. Liquid crystal display device.
When the back side of the pair of substrates is a lower substrate and the observation surface side is an upper substrate,
21. The liquid crystal display device according to claim 19, wherein the scattering of the upper substrate is smaller than the scattering of the lower substrate.
The liquid crystal display device according to claim 21, wherein the lower substrate includes a color filter layer and a thin film transistor, and the liquid crystal cell has a color filter on array structure.
The liquid crystal display device according to claim 21, wherein the liquid crystal cell includes a dye-based color filter layer.
The liquid crystal display device according to claim 21, wherein the liquid crystal cell does not include a color filter layer.