WO2012090769A1 - Optical element and liquid crystal display device - Google Patents

Abstract

The present invention provides: an optical element which has excellent productivity and is capable of providing high CR; and a liquid crystal display device. The present invention is an optical element which is provided with a first polarizer, a birefringent layer and a second polarizer. The first polarizer, the birefringent layer and the second polarizer are sequentially laminated in this order, and the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other. The biaxiality parameter NZ of the birefringent layer satisfies 10 ≤ NZ or NZ ≤ -9, and the absolute value |Rth| of the retardation of the birefringent layer in the thickness direction satisfies |Rth| ≥ 200 nm.

Description

Optical element and liquid crystal display device

The present invention relates to an optical element and a liquid crystal display device. More specifically, the present invention relates to an optical element in which a polarizing plate and a birefringent layer are laminated, and a liquid crystal display device including the optical element.

The liquid crystal display device is usually configured to include an optical element such as a polarizing plate and a retardation film together with a liquid crystal panel and a backlight. Liquid crystal display devices are widely used in electronic devices such as monitors, projectors, mobile phones, and personal digital assistants (PDAs) because of their excellent display characteristics. In addition, a technique using a condensing element is known in order to control the viewing angle of a display such as a liquid crystal display device.

Specifically, for example, at least a first polarizer, a liquid crystal cell having a liquid crystal layer between the first substrate and the second substrate, an optical compensation element, a second polarizer, and a condensing backlight A liquid crystal display device provided in this order from the viewing side is known (for example, see Patent Document 1).

Also known are light-collecting sheets having an absorption linear polarizing layer, a negative birefringent layer, and a reflective linear polarizing layer, and a light control film having a sandwich structure in which a birefringent film is disposed between polarizing films. (For example, refer to Patent Documents 2 and 3.)

JP 2010-15038 A JP 2009-265124 A Japanese Patent No. 2561483

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, dimming backlights that improve 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 are known. A liquid crystal display device having a dynamic CR of 10,000 or more is known.

However, the CR improvement effect by 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 the effect remains the same. It can be said that it is limited. In addition, there is room for improvement in terms of cost increase by introducing a dimming backlight. Under such circumstances, it is desired to improve the native CR of the liquid crystal panel.

With regard to this point, Patent Document 1 discloses that a collimated backlight having a luminance half-value angle of 3 to 30 ° reduces the amount of light incident obliquely on the liquid crystal panel, thereby reducing the amount of light leakage in the normal direction and CR. A condensing-diffusion-type liquid crystal display device has been disclosed that improves and distributes light in the front direction in an oblique direction and expands the viewing angle by providing a diffusing element on the viewing side of the viewing side polarizer. .

However, the liquid crystal display device described in Patent Document 1 aims to reduce the luminance half-value angle (isotropically collimate) in all azimuth angles, as described in paragraph [0030]. As described in paragraph [0047], there is a side effect that luminance in an oblique direction is reduced, and it is necessary to provide a diffusing element as a countermeasure. That is, since it is necessary to diffuse the collimated light again in order to improve the viewing angle characteristics, there is room for improvement in that the system is complex and wasteful. Further, it is technically difficult to diffuse collimated light isotropically, and it is technically difficult to collimate light isotropically in the first place. And if these technologies are adopted, it will lead to cost increase.

Furthermore, the light-condensing sheet described in Patent Document 2 and the light control film described in Patent Document 3 are also laminated so that the birefringent layer and the polarizer form an angle of 45 ° or 135 °, which is neither orthogonal nor parallel. The objective is to perform isotropic collimation to reduce the transmittance at oblique viewing angles in all directions. Therefore, the condensing sheet described in Patent Document 2 and the light control film described in Patent Document 3 also have room for improvement, similar to the liquid crystal display device described in Patent Document 1.

In addition, lenses and micro blind films are conventionally known as light condensing elements, but these light condensing elements are difficult to apply to large liquid crystal display devices, and the liquid crystal display devices are thinned. There was room for improvement in that it would be difficult.

The present invention has been made in view of the above-described present situation, and an object thereof is to provide an optical element and a liquid crystal display device that are excellent in productivity and can realize a high 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). .

Light leakage due to light scattering inside the liquid crystal panel (II) will be described with reference to FIG. As shown in (1) in FIG. 57, first, obliquely incident light on the liquid crystal panel is modulated into elliptically polarized light by a birefringent layer (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), the light reaches the polarizing plate while being elliptically polarized and passes through the polarizing plate, so that light leakage is observed according to the ellipticity.

As described above, the light leakage due to the light scattering is light that is obliquely incident on the liquid crystal panel, changes its traveling direction to the normal direction due to internal scattering, and leaks from the observation surface side polarizing plate. CR can be improved by limiting the amount of obliquely incident light on the panel. As a result of further diligent investigations on the relationship between the light leakage and the oblique incident light, the present inventors have found that light leakage due to panel internal scattering, which causes a decrease in CR of the liquid crystal panel, is caused by oblique incident light in a specific direction. On the other hand, it has been found that it is remarkable, and it has been found that a CR improving effect can be obtained by a collimated backlight that limits the incidence in this direction. The second polarizer is arranged on the back side (outside) of the back side polarizer (first polarizer) so that the two polarizers are in a parallel Nicol relationship, and the first polarizer and the second polarizer are arranged. Between the polarizers, (1) a so-called C plate having a small in-plane retardation, that is, a birefringent layer satisfying NZ ≦ -9 or 10 ≦ NZ, is arranged, and the absolute value of the thickness direction retardation of the birefringent layer | Rth | is set to 200 nm or more, or (2) a birefringent layer in which the in-plane retardation is not small, particularly a birefringent layer satisfying 2 ≦ NZ <10 or −9 <NZ ≦ −1. By arranging the angle between the transmission axis of the first polarizer and the in-plane slow axis of the birefringent layer not to be 45 ° or 135 °, the outgoing light in the oblique direction is limited in all directions. Anisotropic rather than isotropic collimation, which restricts incident light in an oblique direction in a specific direction where light leakage is noticeable It is possible to effectively collimate, effectively suppress light leakage due to internal scattering of liquid crystal panels, improve CR, and find that polarizing films and retardation films with excellent productivity can be used. The present inventors have arrived at the present invention.

That is, the present invention is an optical element comprising a first polarizer, a birefringent layer and a second polarizer, wherein the first polarizer, the birefringent layer and the second polarizer are laminated in this order, The transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other, and the biaxial parameter NZ of the birefringent layer satisfies 10 ≦ NZ or NZ ≦ −9. The absolute value | Rth | of the thickness direction retardation of the birefringent layer is an optical element satisfying | Rth | ≧ 200 nm (hereinafter also referred to as “first optical element of the present invention”).

The configuration of the first optical element of the present invention is not particularly limited by other components as long as such components are formed as essential.

The present invention is also an optical element comprising a first polarizer, a birefringent layer and a second polarizer, wherein the first polarizer, the birefringent layer and the second polarizer are laminated in this order, The transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other, and the biaxial parameter NZ of the birefringent layer is 2 ≦ NZ <10 or −9 <NZ ≦ -1 and an optical element whose angle between the transmission axis of the first polarizer and the in-plane slow axis of the birefringent layer is not 45 ° or 135 ° (hereinafter referred to as “second invention It is also referred to as an “optical element”.

The configuration of the second optical element of the present invention is not particularly limited by other components as long as such components are formed as essential.

In the first and second optical elements of the present invention, the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other. The transmission axes of the two polarizers do not necessarily have to be strictly parallel to each other. More specifically, the angle formed by both transmission axes is preferably 0 ± 10 ° (more preferably 0 ± 5 °). Set within range. If it is set outside the preferred range, the transmittance in the normal direction may decrease.

According to the optical element of the present invention, the following effects can be obtained. Hereinafter, for the sake of convenience, the case where the backlight is disposed so as to face the second polarizer and the absorption axis or reflection axis of the first and second polarizers is set to an azimuth of 90 ° will be described. The effects of the invention can also be achieved in other cases.

First, the first optical element of the present invention will be described. The birefringent layer is used for incidence from the normal direction, incidence from an oblique direction from the direction parallel to the transmission axis, and incidence from an oblique direction from the direction parallel to the absorption axis or reflection axis. Since the polarization state after passing through the two polarizers is hardly changed, a high transmittance close to the parallel Nicol transmittance of the first polarizer and the second polarizer is observed. On the other hand, with respect to incidence from other directions typified by an azimuth of 45 °, a low transmittance is observed because the birefringent layer changes the polarization state after passing through the second polarizer.

Next, the second optical element of the present invention will be described. The birefringent layer is used for incidence from the normal direction, incidence from an oblique direction from the direction parallel to the transmission axis, and incidence from an oblique direction from the direction parallel to the absorption axis or reflection axis. Since it is difficult to change the polarization state after passing through the two polarizers, a relatively high transmittance is observed. On the other hand, a relatively low transmittance is observed for incident light from other directions typified by a 45 ° azimuth direction because the birefringent layer changes the polarization state after passing through the second polarizer. .

As described above, according to the present invention, collimation can be performed so that the distribution of light emitted from the backlight is selectively concentrated in the normal direction, the transmission axis direction, and the absorption axis or reflection axis direction (cross-shaped). Light distribution). The light leakage due to the scattering is particularly conspicuous with respect to obliquely incident light having an azimuth angle of 45 °. Therefore, anisotropic collimation as in the present invention has a sufficient light leakage reducing effect, and a CR improving effect can be obtained.

Further, according to the present invention, since a bright display can be obtained in a plurality of directions other than the normal direction without providing a diffusing element on the observation surface side of the polarizer on the observation surface side, the diffusion function can be omitted, or Simplification is possible. A condensing-non-diffusing method other than the condensing-diffusing method is also possible. For example, even when anisotropic collimation is performed to limit oblique emission light to azimuths of 45 °, 135 °, 225 °, and 315 °, the other azimuths of 0 °, 90 °, 180 °, In addition, since there is obliquely emitted light to 270 °, that is, obliquely emitted light vertically and horizontally, bright display can be obtained in the normal direction and vertically and horizontally without depending on the diffusion function of the diffusing element. This is very different from isotropic collimation in which a bright display is obtained only in the normal direction when no diffusing element is provided. Of course, even in the case of using the present invention, it is more preferable to provide a diffusing element from the viewpoint of obtaining bright display other than in the vertical and horizontal directions, but a diffusing element having a low diffusing ability as compared with conventional isotropic collimation. Is superior in that it can be used.

On the other hand, if the isotropic collimation is performed as described in Patent Document 1, the viewpoint is limited to only one point when the diffusion element is not used. Therefore, a diffusing element has been essential.

Furthermore, optical members such as a polarizer and a birefringent layer can be easily increased in size, and current technology can be used for mass production of large displays such as 60 to 100 inches. In addition, these optical elements have a thickness on the order of several hundred micrometers to several millimeters, and do not require a large spatial distance as in the case of collimation using a lens or a point light source. Light weight and thickness can be reduced.

In addition, the 1st optical element of this invention has a light leak reduction effect more compared with the 2nd optical element of this invention, and can improve CR more. On the other hand, since the second optical element can use a biaxial film that has already been mass-produced, it is more productive than the first optical element of the present invention.

As the application of the first and second optical elements of the present invention, a liquid crystal display device is suitable, and in particular, a liquid crystal display device provided with a backlight is particularly suitable.

Thus, a liquid crystal display device including the first or second optical element of the present invention and a backlight (hereinafter also referred to as “first liquid crystal display device of the present invention”) is also one aspect of the present invention. One. Thereby, a liquid crystal display device having excellent productivity and high CR can be obtained.

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.

The present invention further provides a liquid crystal display device comprising a liquid crystal panel, a first polarizer, a birefringent layer, a second polarizer and a backlight, wherein the first polarizer, the birefringent layer and the second polarizer are The liquid crystal panel and the backlight are arranged in this order, and the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other, and the two axes of the birefringent layer The liquidity display device NZ satisfies 10 ≦ NZ or NZ ≦ −9, and the absolute value | Rth | of the thickness direction retardation of the birefringent layer is a liquid crystal display device satisfying | Rth | ≧ 200 nm (hereinafter, “ It is also referred to as a “second liquid crystal display device of the present invention”.

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.

The present invention is a liquid crystal display device comprising a liquid crystal panel, a first polarizer, a birefringent layer, a second polarizer and a backlight, wherein the first polarizer, the birefringent layer and the second polarizer are The liquid crystal panel and the backlight are arranged in this order, and the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other, and the two axes of the birefringent layer The property parameter NZ satisfies 2 ≦ NZ <10 or −9 <NZ ≦ −1, and the angle formed by the transmission axis of the first polarizer and the in-plane slow axis of the birefringent layer is 45 °. Or a liquid crystal display device that is not 135 ° (hereinafter also referred to as “third liquid crystal display device of the present invention”).

In the second and third liquid crystal display devices of the present invention, the first polarizer, the birefringent layer, and the second polarizer may be arranged in this order from the liquid crystal panel side, or the back They may be arranged in this order from the light side.

In the second and third liquid crystal display devices of the present invention, an air layer may be provided between at least one of the members, for example, between the liquid crystal panel and the first polarizer, There is an air layer between at least one of the first polarizer and the birefringent layer, between the birefringent layer and the second polarizer, and between the second polarizer and the backlight. May be provided.

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.

In the second and third liquid crystal display devices of the present invention, the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other. The transmission axes of the second polarizer do not necessarily have to be strictly parallel to each other. More specifically, the angle formed by both transmission axes is preferably 0 ± 10 ° (more preferably 0 ± 5 °). ). If it is set outside the preferred range, the transmittance in the normal direction may decrease.

According to the second and third liquid crystal display devices of the present invention, the same effects as the optical element of the present invention can be achieved.

Preferred embodiments of the first and second optical elements of the present invention and the first, second and third liquid crystal display devices of the present invention will be described in detail below.

At least one of the first polarizer and the second polarizer may be a reflective polarizer or a composite polarizer in which an absorptive polarizer and a reflective polarizer are stacked. Thereby, the light absorption loss by the absorption polarizer is reduced, and the reflected light is returned to the backlight and reused, whereby the light can be effectively used.

Each of the first polarizer and the second polarizer is an absorptive polarizer or a composite polarizer in which an absorptive polarizer and a reflective polarizer are laminated, and the first polarizer has a single transmittance. May be different from the second polarizer. In general, in an absorptive polarizer, the single transmittance and the contrast of the polarizer are in a trade-off relationship. Meanwhile, since the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other, the first and second polarizers function to complement each other's contrast of the polarizer. To do. Therefore, even if the single transmittance of one of the first and second polarizers is increased, it is possible to suppress a decrease in the contrast of the polarizer. As a result, in the entire system (for example, a liquid crystal display device) including the first and second polarizers, the transmittance, that is, the light use efficiency can be improved while maintaining the contrast.

In the present specification, the single transmittance and contrast of a composite polarizer mean the single transmittance and contrast of a single absorption polarizer included in the composite polarizer, respectively.

The absolute value (ΔT1 = | T1-T2 |) of the difference between the single transmittance (T1) of the first polarizer and the single transmittance (T2) of the second polarizer is preferably 0.2 to 3 0.0%, more preferably 0.5 to 2.0%. When ΔT1 is less than 0.2%, the effect of improving the transmittance of the entire system may not be sufficiently obtained. On the other hand, when ΔT1 exceeds 3.0%, the contrast in the entire system may be lowered.

The contrast (CR1) of the first polarizer and the contrast (CR2) of the second polarizer are not particularly limited and can be set as appropriate. As described above, in the absorption polarizer, in general, the single transmittance and the contrast of the polarizer are in a trade-off relationship. However, when the contrast can be adjusted independently of the single transmittance, both CR1 and CR2 are Higher is preferable.

The first optical element of the present invention preferably comprises a plurality of the birefringent layers, and the first polarizer, the plurality of birefringent layers, and the second polarizer are laminated in this order. The second liquid crystal display device of the present invention preferably includes a plurality of the birefringent layers, and the first polarizer, the plurality of birefringent layers, and the second polarizer are stacked in this order. Thereby, a plurality of inexpensive birefringent layers can be stacked to produce a desired in-plane retardation. When a plurality of birefringent layers have minute in-plane anisotropic properties, the axial angles of the birefringent layers can be appropriately set independently of each other. Are preferably orthogonal to each other or parallel to each other. For example, when there are three birefringent layers, the in-plane slow axes may be laminated in the order of 90 °, 90 °, and 0 °, that is, birefringence in which the in-plane slow axes are orthogonal to each other. Birefringent layers that are parallel to each other may be mixed.

From the same viewpoint, the second optical element of the present invention includes a plurality of the birefringent layers, and the first polarizer, the plurality of birefringent layers, and the second polarizer are stacked in this order, The in-plane slow axes of the plurality of birefringent layers are preferably orthogonal to each other or parallel to each other. The third liquid crystal display device of the present invention includes a plurality of the birefringent layers, and the first polarizer, the plurality of birefringent layers, and the second polarizer are arranged in this order, and the plurality of birefringent layers are arranged. The in-plane slow axes of the refractive layer are preferably orthogonal to each other or parallel to each other. Thereby, a plurality of inexpensive birefringent layers can be stacked to produce a desired in-plane retardation. For example, when there are three birefringent layers, the in-plane slow axes may be laminated in the order of 90 °, 90 °, and 0 °, that is, birefringence in which the in-plane slow axes are orthogonal to each other. Birefringent layers that are parallel to each other may be mixed.

Note that the in-plane slow axes of the plurality of birefringent layers are orthogonal to each other or parallel to each other, the angle formed by the in-plane slow axes of the plurality of birefringent layers is strictly 90 °, or The angle is not limited to 0 °, and may be slightly shifted from 90 ° or 0 °. More specifically, the angle formed by the in-plane slow axes of the plurality of birefringent layers is preferably 90 ± 10 ° (more preferably 90 ± 5 °), or 0 ± 10 ° ( More preferably, it is set within a range of 0 ± 5 °. When it is set outside the preferable range, there is a risk that the transmittance in the normal direction or in an oblique direction with an azimuth of 0 ° or 90 ° may decrease.

In the second optical element of the present invention and the third liquid crystal display device of the present invention, the angle formed by the transmission axis of the first polarizer and the in-plane slow axis of the birefringent layer is 90 Preferably, the transmission axis of the first polarizer and the in-plane slow axis of the birefringent layer are orthogonal to each other, or are mutually within a range of ± 20 ° or 0 ± 20 °. More preferably, the transmission axis of the first polarizer and the in-plane slow axis of the birefringent layer are more preferably parallel to each other. That is, the absorption axis (or reflection axis) of the first polarizer and the in-plane slow axis of the birefringent layer are more preferably orthogonal to each other. Thus, the transmittance with respect to the incident from other directions represented by the azimuth 45 ° oblique direction can be obtained without sacrificing the transmittance with respect to the normal direction, the azimuth 0 ° oblique direction, and the azimuth 90 ° oblique direction. It can be further reduced.

The transmission axis of the first polarizer and the in-plane slow axis of the birefringent layer are orthogonal to each other or parallel to each other. The angle formed with the inner slow axis is not limited to being strictly 90 ° or 0 °, and may be slightly shifted from 90 ° or 0 °. More specifically, the angle formed by the transmission axis of the first polarizer and the in-plane slow axis of the birefringent layer is within a range of 90 ± 10 ° or 0 ± 10 ° (preferably 90 ± 5 ° or within a range of 0 ± 5 °). When it is set outside the preferable range, there is a risk that the transmittance in the normal direction or in an oblique direction with an azimuth of 0 ° or 90 ° may decrease.

In the first optical element of the present invention and the second liquid crystal display device of the present invention, the absolute value | Rth | of the birefringent layer in the thickness direction is preferably 400 nm or more, and 600 nm or more. It is more preferable that Thereby, the transmittance | permeability with respect to the incident from the other direction represented by the 45 degrees azimuth | direction diagonal direction can be reduced more.

In the second optical element of the present invention and the third liquid crystal display device of the present invention, the absolute value | Rth | of the birefringent layer in the thickness direction is preferably 200 nm or more, and preferably 400 nm or more. It is more preferable that it is 600 nm or more. Thereby, the transmittance | permeability with respect to the incident from an unnecessary direction can be reduced more.

From the viewpoint of reducing the transmittance with respect to incidence from other directions represented by the oblique direction in a wide range, the following forms (1) and (2) are preferable in the first optical element of the present invention.

In the form (1), the first optical element of the present invention further includes a second birefringent layer and a third polarizer, and the first polarizer, the birefringent layer, the second polarizer, and the first polarizer. The second birefringent layer and the third polarizer are stacked in this order, and the transmission axis of the second polarizer and the transmission axis of the third polarizer are parallel to each other, and the second birefringent layer The biaxial parameter NZ satisfies 10 ≦ NZ or NZ ≦ −9, and the absolute value | Rth | of the thickness direction retardation of the second birefringent layer satisfies | Rth | ≧ 200 nm. The value is different from the absolute value of the thickness direction retardation of the refractive layer.

In the form (2), the first optical element of the present invention further includes a second birefringent layer and a third polarizer, and the first polarizer, the birefringent layer, the second polarizer, and the first polarizer. The second birefringent layer and the third polarizer are stacked in this order, and the transmission axis of the second polarizer and the transmission axis of the third polarizer are parallel to each other, and the second birefringent layer The biaxial parameter NZ satisfies 2 ≦ NZ <10 or −9 <NZ ≦ −1, and is formed by the transmission axis of the second polarizer and the in-plane slow axis of the second birefringent layer. The angle is not 45 ° or 135 °, and the absolute value | Rth | of the thickness direction retardation of the second birefringent layer is different from the absolute value of the thickness direction retardation of the birefringent layer.

From the same viewpoint, in the second liquid crystal display device of the present invention, the following forms (3) and (4) are preferable.

In the form (3), the second liquid crystal display device of the present invention further comprises a second birefringent layer and a third polarizer, and the first polarizer, the birefringent layer, the second polarizer, The second birefringent layer and the third polarizer are arranged in this order between the liquid crystal panel and the backlight, and the transmission axis of the second polarizer and the transmission axis of the third polarizer are: The biaxiality parameter NZ of the second birefringent layer satisfies 10 ≦ NZ or NZ ≦ −9, and the absolute value | Rth | of the thickness direction retardation of the second birefringent layer is , | Rth | ≧ 200 nm, and a value different from the absolute value of the thickness direction retardation of the birefringent layer.

In the form (4), the second liquid crystal display device of the present invention further comprises a second birefringent layer and a third polarizer, and the first polarizer, the birefringent layer, the second polarizer, The second birefringent layer and the third polarizer are arranged in this order between the liquid crystal panel and the backlight, and the transmission axis of the second polarizer and the transmission axis of the third polarizer are: The biaxiality parameter NZ of the second birefringent layer satisfies 2 ≦ NZ <10 or −9 <NZ ≦ −1, the transmission axis of the second polarizer, and the second birefringence layer are parallel to each other. The angle formed by the in-plane slow axis of the birefringent layer is not 45 ° or 135 °, and the absolute value | Rth | of the thickness direction retardation of the second birefringent layer is the thickness direction of the birefringent layer The value is different from the absolute value of the phase difference.

From the same viewpoint, in the second optical element of the present invention, the following form (5) is preferable.

In form (5), the second optical element of the present invention further comprises a second birefringent layer and a third polarizer, and the first polarizer, the birefringent layer, the second polarizer, and the first polarizer. The second birefringent layer and the third polarizer are stacked in this order, and the transmission axis of the second polarizer and the transmission axis of the third polarizer are parallel to each other, and the second birefringent layer The biaxial parameter NZ satisfies 2 ≦ NZ <10 or −9 <NZ ≦ −1, and is formed by the transmission axis of the second polarizer and the in-plane slow axis of the second birefringent layer. The angle is not 45 ° or 135 °, and the absolute value | Rth | of the thickness direction retardation of the second birefringent layer is different from the absolute value of the thickness direction retardation of the birefringent layer.

From the same viewpoint, in the third liquid crystal display device of the present invention, the following mode (6) is preferable.

In the form (6), the third liquid crystal display device of the present invention further includes a second birefringent layer and a third polarizer, and the first polarizer, the birefringent layer, the second polarizer, The second birefringent layer and the third polarizer are arranged in this order between the liquid crystal panel and the backlight, and the transmission axis of the second polarizer and the transmission axis of the third polarizer Are parallel to each other, and the biaxial parameter NZ of the second birefringent layer satisfies 2 ≦ NZ <10 or −9 <NZ ≦ −1, the transmission axis of the second polarizer, The angle formed by the in-plane slow axis of the second birefringent layer is not 45 ° or 135 °, and the absolute value | Rth | of the thickness direction retardation of the second birefringent layer is the value of the birefringent layer. The value is different from the absolute value of the thickness direction retardation.

In the above embodiments (1) to (6), the transmission axis of the second polarizer and the transmission axis of the third polarizer are parallel to each other. The transmission axis of the child does not necessarily have to be strictly parallel, and more specifically, the angle formed by both transmission axes is preferably within a range of 0 ± 10 ° (more preferably 0 ± 5 °). Set to If it is set outside the preferred range, the transmittance in the normal direction may decrease.

Moreover, in the said form (3), (4), (6), said 1st polarizer, said birefringent layer, said 2nd polarizer, said 2nd birefringent layer, and said 3rd polarizer are said liquid crystals. It may be arranged in this order from the panel side, or may be arranged in this order from the backlight side.

Moreover, in said form (3), (4), (6), between said 2nd polarizer and said 2nd birefringent layer, between said 2nd birefringent layer and said 3rd polarizer, An air layer may be provided between at least one of the third polarizer and the backlight.

From the same point of view as described above, preferred forms in the above forms (1) to (6) include the following forms.

In the embodiments (1) to (6), at least one of the first polarizer, the second polarizer, and the third polarizer is a reflective polarizer, or an absorption polarizer and a reflective polarizer. It is preferable that the composite polarizer is laminated.

In the above-described embodiments (1) to (6), the first polarizer, the second polarizer, and the third polarizer are each an absorption polarizer, or an absorption polarizer and a reflection polarizer. It is preferable that at least one of the first polarizer, the second polarizer, and the third polarizer has a single transmittance different from that of the other polarizers.

At this time, if the maximum value is Tmax1 and the minimum value is Tmin1 among the single transmittances of the first polarizer, the second polarizer, and the third polarizer, the absolute value of the difference (ΔT2 = | Tmax1- Tmin1 |) is preferably 0.2 to 3.0%, more preferably 0.5 to 2.0%. When ΔT2 is less than 0.2%, the effect of improving the transmittance of the entire system may not be sufficiently obtained. On the other hand, if ΔT2 exceeds 3.0%, the contrast of the entire system may be lowered.

At this time, the contrast (CR1) of the first polarizer, the contrast (CR2) of the second polarizer, and the contrast (CR3) of the third polarizer are not particularly limited, Can be set. If the contrast can be adjusted independently of the single transmittance, the higher CR1, CR2 and CR3 are preferable.

In the mode (1), the first optical element of the present invention includes a plurality of the second birefringent layers, and the second polarizer, the plurality of second birefringent layers, and the third polarizer A form in which the layers are sequentially laminated (hereinafter also referred to as form (1-1)) is preferable.

In the mode (3), the second liquid crystal display device of the present invention includes a plurality of the second birefringent layers, and the second polarizer, the plurality of second birefringent layers, and the third polarizer are A form in which the layers are laminated in this order (hereinafter also referred to as form (3-1)) is preferable.

In the above embodiments (1-1) and (3-1), when the plurality of second birefringent layers have minute in-plane different directions, the axial angles of the second birefringent layers are independent of each other. The in-plane slow layer axes are preferably perpendicular to each other or parallel to each other. The in-plane slow axes of the plurality of second birefringent layers being orthogonal to each other or parallel to each other means that the angle formed by the in-plane slow axes of the plurality of second birefringent layers is exactly 90. The angle is not limited to 0 ° or 0 °, and may be slightly shifted from 90 ° or 0 °. More specifically, the angle formed by the in-plane slow axes of the plurality of second birefringent layers is preferably 90 ± 10 ° (more preferably 90 ± 5 °), or 0 ± 10. It is set within the range of ° (more preferably 0 ± 5 °). When it is set outside the preferable range, there is a risk that the transmittance in the normal direction or in an oblique direction with an azimuth of 0 ° or 90 ° may decrease.

In the mode (2), the first optical element of the present invention includes a plurality of the second birefringent layers, and the second polarizer, the plurality of second birefringent layers, and the third polarizer It is preferable that the in-plane slow axes of the plurality of birefringent layers are laminated in order and are orthogonal to each other or parallel to each other (hereinafter also referred to as “form (2-1)”).

In the aspect (4), the second liquid crystal display device of the present invention includes a plurality of the second birefringent layers, and the second polarizer, the plurality of second birefringent layers, and the third polarizer are The in-plane slow axes of the plurality of birefringent layers stacked in this order are preferably orthogonal to each other or parallel to each other (hereinafter also referred to as mode (4-1)).

In the aspect (5), the second optical element of the present invention includes a plurality of the second birefringent layers, and the second polarizer, the plurality of second birefringent layers, and the third polarizer It is preferable that the in-plane slow axes of the plurality of birefringent layers are stacked in order and are orthogonal to each other or parallel to each other (hereinafter also referred to as “form (5-1)”).

In the mode (6), the third liquid crystal display device of the present invention includes a plurality of the second birefringent layers, and the second polarizer, the plurality of second birefringent layers, and the third polarizer are The in-plane slow axes of the plurality of birefringent layers stacked in this order are preferably orthogonal to each other or parallel to each other (hereinafter also referred to as mode (6-1)).

In the above embodiments (2-1), (4-1), (5-1), and (6-1), the in-plane slow axes of the plurality of birefringent layers are orthogonal to each other or parallel to each other. Is not strictly limited to the angle formed by the in-plane slow axes of the plurality of birefringent layers being 90 ° or 0 °, and may be slightly shifted from 90 ° or 0 °. . More specifically, the angle formed by the in-plane slow axes of the plurality of birefringent layers is preferably 90 ± 10 ° (more preferably 90 ± 5 °), or 0 ± 10 ° ( More preferably, it is set within a range of 0 ± 5 °. When it is set outside the preferable range, there is a risk that the transmittance in the normal direction or in an oblique direction with an azimuth of 0 ° or 90 ° may decrease.

In the above forms (2), (4), (5), and (6), the angle formed by the transmission axis of the second polarizer and the in-plane slow axis of the second birefringent layer is 90 ± 20. Or within the range of 0 ± 20 °, and the transmission axis of the second polarizer and the in-plane slow axis of the second birefringent layer are orthogonal to each other or mutually More preferably, the transmission axis of the second polarizer and the in-plane slow axis of the second birefringent layer are more preferably parallel to each other. That is, it is more preferable that the absorption axis (or reflection axis) of the second polarizer and the in-plane slow axis of the second birefringent layer are orthogonal to each other.

Note that the transmission axis of the second polarizer and the in-plane slow axis of the second birefringent layer are orthogonal to each other or parallel to each other. The angle formed with the in-plane slow axis of the refracting layer is not limited to being strictly 90 ° or 0 °, and may be slightly shifted from 90 ° or 0 °. More specifically, the angle formed by the transmission axis of the second polarizer and the in-plane slow axis of the second birefringent layer is within a range of 90 ± 10 ° or 0 ± 10 ° (preferably Within the range of 90 ± 5 ° or 0 ± 5 °). When it is set outside the preferable range, there is a risk that the transmittance in the normal direction or in an oblique direction with an azimuth of 0 ° or 90 ° may decrease.

In the above forms (1) and (3), the absolute value | Rth | of the thickness direction retardation of the second birefringent layer is preferably 400 nm or more, and more preferably 600 nm or more.

In the above forms (2), (4), (5), and (6), the absolute value | Rth | of the thickness direction retardation of the second birefringent layer is preferably 200 nm or more, and preferably 400 nm or more. It is more preferable that the thickness is 600 nm or more.

The display modes of the first, second and third liquid crystal display devices of the present invention are preferably vertical alignment modes. At this time, light leakage is particularly suppressed, and a very high CR can be obtained.

In the first liquid crystal display device of the present invention, the first or second optical element of the present invention is disposed on the observation surface side of the backlight, and the first liquid crystal display device of the present invention is the first liquid crystal display device of the present invention. A liquid crystal panel disposed on the observation surface side of the first or second optical element; and a fourth polarizer disposed on the observation surface side of the liquid crystal panel, the first polarizer and the second polarizer. And each of the fourth polarizers is an absorptive polarizer or a composite polarizer in which an absorptive polarizer and a reflective polarizer are laminated, and at least one of the first polarizer and the second polarizer is The single transmittance is preferably larger than that of the fourth polarizer. In general, in an absorptive polarizer, the single transmittance and the contrast of the polarizer are in a trade-off relationship. Meanwhile, since the transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other, the first and second polarizers function to complement each other's contrast of the polarizer. To do. As a result of the study by the present inventors, it is found that the transmittance of the polarizer and the transmittance of the liquid crystal display device are correlated, and the contrast of the polarizer and the CR of the liquid crystal display device are also correlated. ing. Therefore, if the single transmittance of at least one of the first and second polarizers is made higher than the single transmittance of the fourth polarizer, the single transmittances of the first, second, and fourth polarizers are all the same. Compared with a certain liquid crystal display device, it is possible to improve the transmittance, that is, the light utilization efficiency, while suppressing the decrease in CR. When the single transmittance of only one of the first and second polarizers is made larger than the single transmittance of the fourth polarizer, the single transmittance of either polarizer may be increased. Further, when the single transmittance of only one polarizer is larger than the single transmittance of the fourth polarizer, the single transmittance of the other polarizer is substantially equal to the single transmittance of the fourth polarizer. It may be smaller or smaller. Further, from the viewpoint of manufacturing efficiency of the liquid crystal display device, the first polarizer and the second polarizer arranged on the backlight side have a single transmittance larger than that of the fourth polarizer. It is preferable. Thereby, the manufacturing process of the conventional liquid crystal display device having only one polarizer on the backlight side of the liquid crystal panel can be easily used. That is, the above-described embodiment can be realized by adding a polarizer whose single transmittance is adjusted to be larger than that of the fourth polarizer to such a conventional liquid crystal display device. On the other hand, from the viewpoint of further improving the transmittance (light utilization efficiency), it is more preferable that each of the first and second polarizers has a single transmittance greater than that of the fourth polarizer. At this time, the first and second polarizers may have the same single transmittance or may be different from each other.

As described above, from the viewpoint of improving the transmittance while suppressing the reduction in CR, the second and third liquid crystal display devices of the present invention include a fourth polarizer disposed on the observation surface side of the liquid crystal panel. Further, the first polarizer, the second polarizer and the fourth polarizer are each an absorption polarizer, or a composite polarizer in which an absorption polarizer and a reflection polarizer are laminated, It is preferable that at least one of the first polarizer and the second polarizer has a single transmittance larger than that of the fourth polarizer. When the single transmittance of only one of the first and second polarizers is made larger than the single transmittance of the fourth polarizer, the single transmittance of either polarizer may be increased. Further, when the single transmittance of only one polarizer is larger than the single transmittance of the fourth polarizer, the single transmittance of the other polarizer is substantially equal to the single transmittance of the fourth polarizer. It may be smaller or smaller. Further, from the viewpoint of manufacturing efficiency of the liquid crystal display device, the first polarizer and the second polarizer arranged on the backlight side have a single transmittance larger than that of the fourth polarizer. More preferably, from the viewpoint of further improving the transmittance (light utilization efficiency), it is more preferable that the first and second polarizers both have a single transmittance greater than that of the fourth polarizer.

In these forms, if the maximum value is Tmax2 and the minimum value is Tmin2 among the single transmittances of the first polarizer, the second polarizer, and the fourth polarizer, the absolute value of the difference (ΔT3 = | Tmax2-Tmin2 |) is preferably 0.2 to 3.0%, more preferably 0.5 to 2.0%. When ΔT3 is less than 0.2%, the effect of improving the transmittance of the entire system may not be sufficiently obtained. On the other hand, when ΔT3 exceeds 3.0%, the contrast in the entire system may be lowered.

In these embodiments, the contrast (CR1) of the first polarizer, the contrast (CR2) of the second polarizer, and the contrast (CR4) of the fourth polarizer are not particularly limited, Can be set as appropriate. If the contrast can be adjusted independently of the single transmittance, the higher CR1, CR2 and CR4 are all the higher.

Moreover, when the 1st liquid crystal display device of this invention contains the 1st optical element of this invention, the following forms are suitable. That is, the first optical element of the present invention has the above-described form (1) or (2) and is disposed on the observation surface side of the backlight. The liquid crystal panel arranged on the observation surface side of the first optical element of the invention, and the fourth polarizer arranged on the observation surface side of the liquid crystal panel, further comprising the first polarizer and the second polarizer The third polarizer and the fourth polarizer are each an absorption polarizer or a composite polarizer in which an absorption polarizer and a reflection polarizer are laminated, and the first polarizer and the second polarizer. At least one of the polarizer and the third polarizer preferably has a single transmittance larger than that of the fourth polarizer. Since the transmission axis of the third polarizer is parallel to the transmission axis of the second polarizer (and the first polarizer), the first, second, and third polarizers are in contrast with each other. Functions to complement each other. As a result, if at least one single transmittance of the first, second and third polarizers is higher than a single transmittance of the fourth polarizer, the first, second, third and fourth polarizers Compared with a liquid crystal display device that has the same single transmittance, the transmittance (light utilization efficiency) can be improved while suppressing a decrease in CR. At this time, the single transmittance of any one of the first, second, and third polarizers may be larger than the single transmittance of the fourth polarizer. Further, among the first, second and third polarizers, there may be a polarizer whose single transmittance is substantially equal to the single transmittance of the fourth polarizer, or the single polarizer of the fourth polarizer. There may be a polarizer smaller than the transmittance. Further, from the viewpoint of manufacturing efficiency of the liquid crystal display device, among the first, second and third polarizers, the polarizer disposed on the backlight side and / or the single transmittance of the second polarizer is More preferably, it is larger than the fourth polarizer. Thereby, the manufacturing process of the conventional liquid crystal display device having only one polarizer on the backlight side of the liquid crystal panel can be easily used. That is, the above-described embodiment can be realized by adding two polarizers in which at least one single transmittance is adjusted to be larger than that of the fourth polarizer to such a conventional liquid crystal display device. On the other hand, from the viewpoint of further improving the transmittance (light utilization efficiency), it is more preferable that at least two of the first, second and third polarizers have a single transmittance larger than that of the fourth polarizer. The first polarizer, the second polarizer, and the third polarizer all preferably have a single transmittance larger than that of the fourth polarizer. At this time, the polarizers having a single transmittance greater than that of the fourth polarizer may have the same or different single transmittance.

From the viewpoint of improving the transmittance while suppressing the decrease in CR as described above, when the first liquid crystal display device of the present invention includes the second optical element of the present invention, the following modes are preferable. That is, the second optical element of the present invention has the above-described form (5) and is arranged on the observation surface side of the backlight, and the first liquid crystal display device of the present invention is the second liquid crystal display of the present invention. A liquid crystal panel disposed on the observation surface side of the optical element, and a fourth polarizer disposed on the observation surface side of the liquid crystal panel, wherein the first polarizer, the second polarizer, and the third polarizer Each of the polarizer and the fourth polarizer is an absorptive polarizer, or a composite polarizer in which an absorptive polarizer and a reflective polarizer are laminated, and the first polarizer, the second polarizer, and the fourth polarizer. At least one of the three polarizers preferably has a single transmittance greater than that of the fourth polarizer. At this time, the single transmittance of any one of the first, second, and third polarizers may be larger than the single transmittance of the fourth polarizer. Further, among the first, second and third polarizers, there may be a polarizer whose single transmittance is substantially equal to the single transmittance of the fourth polarizer, or the single polarizer of the fourth polarizer. There may be a polarizer smaller than the transmittance. Further, from the viewpoint of manufacturing efficiency, among the first, second and third polarizers, the polarizer disposed on the backlight side and / or the single transmittance of the second polarizer is the fourth polarization. It is preferably larger than the child. On the other hand, from the viewpoint of further improving the transmittance (light utilization efficiency), it is more preferable that at least two of the first, second and third polarizers have a single transmittance larger than that of the fourth polarizer. The first polarizer, the second polarizer, and the third polarizer all preferably have a single transmittance larger than that of the fourth polarizer. At this time, the polarizers having a single transmittance greater than that of the fourth polarizer may have the same or different single transmittance.

In addition, from the viewpoint of improving the transmittance while suppressing a decrease in CR, the second liquid crystal display device of the present invention has the above-described form (3) or (4) and is on the observation surface side of the liquid crystal panel. The first polarizer, the second polarizer, the third polarizer, and the fourth polarizer are each an absorption polarizer or an absorption polarizer. A composite polarizer in which a reflective polarizer is laminated, and at least one of the first polarizer, the second polarizer, and the third polarizer has a single transmittance greater than that of the fourth polarizer. preferable. At this time, the single transmittance of any one of the first, second, and third polarizers may be larger than the single transmittance of the fourth polarizer. Further, among the first, second and third polarizers, there may be a polarizer whose single transmittance is substantially equal to the single transmittance of the fourth polarizer, or the single polarizer of the fourth polarizer. There may be a polarizer smaller than the transmittance. Further, from the viewpoint of manufacturing efficiency, among the first, second and third polarizers, the polarizer disposed on the backlight side and / or the single transmittance of the second polarizer is the fourth polarization. It is preferably larger than the child. On the other hand, from the viewpoint of further improving the transmittance (light utilization efficiency), it is more preferable that at least two of the first, second and third polarizers have a single transmittance larger than that of the fourth polarizer. In any case, it is particularly preferable that the single transmittance is larger than that of the fourth polarizer. At this time, the polarizers having a single transmittance greater than that of the fourth polarizer may have the same or different single transmittance.

Furthermore, from the viewpoint of improving the transmittance while suppressing a decrease in CR, the third liquid crystal display device of the present invention has the above-described form (6) and is disposed on the observation surface side of the liquid crystal panel. The first polarizer, the second polarizer, the third polarizer, and the fourth polarizer are each an absorption polarizer, or an absorption polarizer and a reflection polarizer. It is preferable that at least one of the first polarizer, the second polarizer, and the third polarizer has a single transmittance greater than that of the fourth polarizer. At this time, the single transmittance of any one of the first, second, and third polarizers may be larger than the single transmittance of the fourth polarizer. Further, among the first, second and third polarizers, there may be a polarizer whose single transmittance is substantially equal to the single transmittance of the fourth polarizer, or the single polarizer of the fourth polarizer. There may be a polarizer smaller than the transmittance. Further, from the viewpoint of manufacturing efficiency, among the first, second and third polarizers, the polarizer disposed on the backlight side and / or the single transmittance of the second polarizer is the fourth polarization. It is preferably larger than the child. On the other hand, from the viewpoint of further improving the transmittance (light utilization efficiency), it is more preferable that at least two of the first, second and third polarizers have a single transmittance larger than that of the fourth polarizer. The first polarizer, the second polarizer, and the third polarizer all preferably have a single transmittance larger than that of the fourth polarizer. At this time, the polarizers having a single transmittance greater than that of the fourth polarizer may have the same or different single transmittance.

In these forms, if the maximum value is Tmax3 and the minimum value is Tmin3 among the single transmittances of the first polarizer, the second polarizer, the third polarizer, and the fourth polarizer, The absolute value (ΔT4 = | Tmax3−Tmin3 |) is preferably 0.2 to 3.0%, more preferably 0.5 to 2.0%. If ΔT4 is less than 0.2%, the effect of improving the transmittance of the entire system may not be sufficiently obtained. On the other hand, when ΔT4 exceeds 3.0%, the contrast of the entire system may be lowered.

In these embodiments, the first polarizer contrast (CR1), the second polarizer contrast (CR2), the third polarizer contrast (CR3), and the fourth polarizer contrast. (CR4) is not particularly limited, and can be set as appropriate. When the contrast can be adjusted independently of the single transmittance, the higher CR1, CR2, CR3, and CR4 are preferable.

According to the first and second optical elements of the present invention and the first, second and third liquid crystal display devices of the present invention, productivity can be improved and high CR can be realized.

1 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 1. FIG. 6 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 2. FIG. 6 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 3. FIG. 10 is a contour diagram and a graph showing calculation results for viewing angle characteristics of an optical element according to Embodiment 3. FIG. It is the contour figure and graph which show the calculation result of the viewing angle characteristic of the transmittance | permeability of a polarizer. It is the contour figure and graph which show the calculation result of the viewing angle characteristic of the transmittance | permeability of two polarizers. 6 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 4. FIG. It is a contour figure and graph which show the calculation result about the viewing angle characteristic of the optical element concerning Embodiment 4. 6 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 5. FIG. 10 is a contour diagram and a graph showing calculation results for viewing angle characteristics of an optical element according to Embodiment 5. FIG. 7 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 6. FIG. It is a contour figure and a graph which show the calculation result about the viewing angle characteristic of the optical element concerning Embodiment 6. 10 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 7. FIG. It is a contour figure and graph which show the calculation result about the viewing angle characteristic of the optical element concerning Embodiment 7. 10 is a graph showing calculation results of transmittance of optical elements according to Embodiments 5 to 7. It is a graph which shows the calculation result about the viewing angle characteristic when the value of Rth of a 1st birefringent layer is changed from 0 nm to -1000 nm. FIG. 6 is a contour diagram showing calculation results for viewing angle characteristics when the Rth value of the first birefringent layer is changed from 0 nm to −1000 nm. FIG. 10 is a schematic cross-sectional view of a liquid crystal display device according to an eighth embodiment. It is the contour figure and graph which show the calculation result about the viewing angle characteristic of the optical element which concerns on Embodiment 8. 10 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 9. FIG. It is the contour figure and graph which show the calculation result about the viewing angle characteristic of the optical element which concerns on Embodiment 9. FIG. It is a figure which shows transition of the polarization state on the Poincare sphere in the optical element which concerns on Embodiment 8. FIG. It is a figure which shows the transition of the polarization state on the Poincare sphere in the optical element which concerns on Embodiment 9. FIG. It is a figure which shows transition of the polarization state on the Poincare sphere in an optical element when NZ is changed. It is a contour figure which shows the calculation result about the viewing angle characteristic of the optical element when NZ is changed. It is a graph which shows the relationship between NZ and the transmittance | permeability T (45, 60). FIG. 10 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 10. It is the contour figure and graph which show the calculation result about the viewing angle characteristic of the optical element which concerns on Embodiment 10. FIG. 14 is a schematic cross-sectional view of a liquid crystal display device according to Embodiment 11. FIG. It is the contour figure and graph which show the calculation result about the viewing angle characteristic of the optical element which concerns on Embodiment 11. FIG. FIG. 6 is a contour diagram and a graph showing calculation results for viewing angle characteristics of an optical element when the axial angle direction of a birefringent layer is −45 °. FIG. 10 is a contour diagram and a graph showing calculation results for viewing angle characteristics of an optical element when the axial angle direction of a birefringent layer is −25 °. FIG. 6 is a contour diagram and a graph showing calculation results for viewing angle characteristics of an optical element when the axial angle direction of a birefringent layer is −20 °. FIG. 10 is a contour diagram and a graph showing calculation results for viewing angle characteristics of an optical element when the axial angle direction of a birefringent layer is −15 °. FIG. 6 is a contour diagram and a graph showing calculation results for viewing angle characteristics of an optical element when the axial angle direction of a birefringent layer is −10 °. It is a contour figure and a graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 0 degrees. It is a contour figure and graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 10 degrees. It is a contour figure and graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 15 degrees. It is a contour figure and graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 20 degrees. It is a contour figure and a graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 25 degrees. It is a contour figure and graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 45 degrees. It is a contour figure and a graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 65 degrees. It is a contour figure and graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 70 degrees. It is a contour figure and a graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 75 degrees. It is a contour figure and a graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 80 degrees. It is a contour figure and graph which show the calculation result about the viewing angle characteristic of an optical element in case the axial angle of both a polarizer and a birefringent layer is 90 degrees. It is a contour figure and a graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 100 degrees. It is a contour figure and a graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 105 degrees. It is a contour figure and graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 110 degrees. It is a contour figure and graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 115 degrees. It is a contour figure and graph which show the calculation result about the viewing angle characteristic of an optical element when the direction of the axis angle of a birefringent layer is 135 degrees. It is a cross-sectional schematic diagram of an optical element. FIG. 53 is a contour diagram and a graph showing calculation results for viewing angle characteristics in the optical element of FIG. 52. It is a cross-sectional schematic diagram of the liquid crystal display device which concerns on the comparative form 1. It is a cross-sectional schematic diagram of the liquid crystal display device which concerns on the comparative form 2. It is the contour figure and graph which show the calculation result about the viewing angle characteristic of the optical element which concerns on the comparative form 2. 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 absorptive polarizer has a function of absorbing light that vibrates in a specific direction and transmitting polarized light (linearly polarized light) that vibrates in a direction perpendicular thereto. The reflective polarizer has a function of reflecting light that vibrates in a specific direction and transmitting polarized light (linearly polarized light) that vibrates in a direction perpendicular thereto.

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

In the present specification, the measurement wavelength of optical parameters such as the main refractive index, the phase difference, and the 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. .

The isotropic film means that both the in-plane retardation R and the absolute value of the thickness direction retardation Rth have a value of 10 nm or less, preferably 5 nm or less. Means.

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

Further, in this specification, the single transmittance (T) of a polarizer is a transmittance when a single polarizer is used, and is obtained from the formula: (k1 + k2) / 2.

k1 and k2 are referred to as main transmittance, and the main transmittance k1 refers to the transmittance when linearly polarized light that vibrates in a direction parallel to the transmission axis is incident on the polarizer. The main transmittance k2 refers to the transmittance when linearly polarized light that vibrates in a direction perpendicular to the transmission axis is incident on the polarizer.

Examples of the measuring device for the main transmittance k1 and the main transmittance k2 include an ultraviolet-visible spectrophotometer (trade name “V-7100” manufactured by JASCO Corporation). In order to make the measurement light (light incident on the polarizer sample) linearly polarized light, an ideal polarizing element such as a Glan-Thompson prism or a Gran Taylor prism, which is prepared as an option of the measurement device, may be used. The spectral transmittance in the visible wavelength region (wavelength 380 nm to 780 nm) is measured, and the Y value that has been corrected for visibility with the two-degree field of view (C light source) defined in JIS Z8701-1982 is defined as the transmittance.

The parallel transmittance (Tp) is a value of transmittance when two polarizers of the same type are stacked and used so that their absorption axes are parallel to each other, and the formula: (k1 ² + k2 ² ) Calculated from / 2.

The orthogonal transmittance (Tc) is a transmittance value when two polarizers of the same type are stacked and used so that their absorption axes are orthogonal to each other, and is obtained from the equation: k1 × k2.

The contrast of the polarizer is obtained from the formula: Tp / Tc by measuring the parallel transmittance (Tp) and orthogonal transmittance (Tc) of the polarizer.

In addition, even if these characteristics of a polarizer are measured using what is called a polarizing plate containing members, such as a protective film and a birefringent layer, the same result as the case where it measures with a polarizer single-piece | unit can be obtained.

In addition, these characteristics of a composite polarizer in which a reflective polarizer and an absorption polarizer are stacked mean a measurement result of the absorption polarizer alone.

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 30 of the present embodiment is a transmissive liquid crystal display device. As shown in FIG. 1, a polarizer 24, a birefringent layer 23, a liquid crystal panel 22 including a liquid crystal layer, This is a liquid crystal display device obtained by laminating the refractive layer 21, the polarizer 2, the birefringent layer 3, the polarizer 1, and the backlight (BL) unit 25 in this order. The polarizer 2, the birefringent layer 3, and the polarizer 1 constitute an optical element 10. One of the polarizers 1 and 2 corresponds to the first polarizer in the present invention, and the other is the second polarizer in the present invention. The birefringent layer 3 corresponds to the birefringent layer in the present invention. The polarizers 1 and 2 are arranged in parallel Nicols. The biaxial parameter of the birefringent layer 3 satisfies NZ ≦ -9 or 10 ≦ NZ, and the absolute value | Rth | of the thickness direction retardation Rth of the birefringent layer 3 satisfies | Rth | ≧ 200 nm.

According to the optical element 10, birefringence is applied to light incident from the normal direction of the liquid crystal panel 22, the polarization axis directions of the polarizers 1 and 2, and the absorption axis or reflection axis direction of the polarizers 1 and 2. Since the layer 3 does not function substantially, a high transmittance is observed. On the other hand, the birefringent layer 3 functions effectively for light incident obliquely with respect to the axes of the polarizers 1 and 2 and obliquely with respect to the surface of the polarizer 1. Rate is observed. As a result, the emitted light from the backlight (BL) unit 25 can be selectively collimated (parallelized), and a cross-shaped light distribution can be realized. Further, as described above, light leakage due to scattering inside the liquid crystal panel 22 is significant for obliquely incident light in a specific direction. Therefore, by arranging the optical element 10 so that a low transmittance is obtained in an orientation in which light leakage is likely to occur and a high transmittance is obtained in an orientation in which light leakage is unlikely to occur, the optical element 10 is scattered due to scattering inside the liquid crystal panel 22. Light leakage can be sufficiently reduced, and as a result, CR can be effectively improved.

The polarizers 1 and 2 are arranged in parallel Nicols, and the polarizers 2 and 24 are arranged in crossed Nicols. More specifically, the angle formed by the absorption axes or reflection axes of the polarizers 1 and 2 is set within a range of 0 ± 10 ° (preferably within a range of 0 ± 5 °). The angle formed by the absorption axis or the reflection axis is set within a range of 90 ± 3 ° (preferably within a range of 90 ± 1 °).

The polarizers 2 and 24 may be arranged in parallel Nicols, but are preferably arranged in crossed Nicols from the viewpoint of obtaining high CR.

The axial angles of the polarizers 1 and 2 can be set as appropriate, but the axial angles of the polarizers 1 and 2 are preferably set to an orientation within a range of 0 ± 10 ° or 90 ± 10 °. It is more preferable to set the azimuth within a range of ± 5 ° or 90 ± 5 °, and it is particularly preferable that the azimuth is set to substantially 0 ° or 90 °. Thereby, a bright display can be obtained in the normal direction and in the vertical and horizontal directions. Here, the substantially 0 ° or 90 ° azimuth is an orientation that can be achieved when the liquid crystal display device of this embodiment is designed and manufactured to be 0 ° or 90 ° azimuth. And may include errors that may occur in the manufacturing process.

| Rth | of the birefringent layer 3 is preferably | Rth | ≧ 400 nm, and more preferably | Rth | ≧ 600 nm. Thereby, the transmittance | permeability with respect to the light which slanted with respect to the axis | shaft of the polarizers 1 and 2 and entered from the diagonal direction with respect to the surface of the polarizer 1 can be reduced more.

The birefringent layer 3 preferably satisfies NZ ≦ −19.5 or 20.5 ≦ NZ, and more preferably satisfies NZ ≦ −39.5 or 40.5 ≦ NZ. Thereby, the in-plane retardation R of the birefringent layer 3 can be made 10 nm or less (preferably 5 nm or less), and substantially the same effect as a birefringent layer having no in-plane anisotropy is expected. be able to. Since the in-plane anisotropy is substantially eliminated, the degree of freedom in designing the axial angle can be increased.

In FIG. 1, the birefringent layer 3 is illustrated as being composed of a single birefringent layer, but the birefringent layer 3 may be composed of a plurality of birefringent layers. For example, three birefringent layers may be stacked to function as one birefringent layer as a total. This makes it possible to use a large-area and inexpensive birefringent layer that is widely used as a conventional optical compensation film for liquid crystal display devices.

In the liquid crystal display device 30 of this embodiment, a birefringent layer similar to the birefringent layer 3 and a polarizer similar to the polarizer 1 are disposed on the polarizer 1 side on the backlight (BL) unit 25 side of the polarizer 1. May be laminated in this order. Thereby, the transmittance | permeability with respect to the light which injected into the diagonal azimuth | direction with respect to the axis | shaft of the polarizers 1 and 2 and diagonally with respect to the surface of the polarizer 1 can be reduced especially effectively.

Hereafter, each component which comprises an optical element and 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 2 ≦ NZ <10 is referred to as a first type birefringent layer. As the first kind of 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.

(Second birefringent layer)
In this specification, a birefringent layer (retardation film) of −9 <NZ ≦ 1 is referred to as a second type birefringent layer. The second 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.

(Third kind of birefringent layer)
In this specification, a birefringent layer (retardation film) of 10 ≦ NZ, a so-called negative C plate is referred to as a third type birefringent layer. As the third birefringent layer, a film containing a material having a positive intrinsic birefringence as a component is subjected to a longitudinal and lateral biaxial stretching process, and a liquid crystal material such as a cholesteric (chiral nematic) liquid crystal or a 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.

(Fourth birefringent layer)
In the present specification, a birefringent layer (retardation film) of NZ ≦ −9, 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. .

As described above, in the first embodiment, the birefringent layer 3 is a third birefringent layer or a fourth birefringent layer. On the other hand, the material, characteristics, axial angle, and the like of the birefringent layers 21 and 23 can be appropriately set in consideration of the liquid crystal mode of the liquid crystal panel 22 and the like.

(Polarizer)
The polarizer used in Embodiment 1 is not particularly limited in terms of materials and optical performance, and for example, an absorbing polarizer, a reflective polarizer, or the like can be used as appropriate. Specifically, a co-extruded film made of two types of resins is uniaxially stretched in addition to an absorbing polarizer in which an anisotropic material such as an iodine complex having dichroism is adsorbed and oriented on a polyvinyl alcohol (PVA) film. A reflective polarizer (for example, DBEF manufactured by 3M), a reflective polarizer in which fine wires of metal wires are periodically arranged (so-called wire grid polarizer), and the like can be used as appropriate. Moreover, the thing which laminated | stacked the absorption type polarizer and the reflection type polarizer can also be used.

(When using absorption polarizer or composite polarizer)
When using only an absorptive polarizer, oblique incident light in a specific orientation is absorbed by the polarizer, limiting transmission and providing a light collimation effect. This reduces the amount of light incident on the liquid crystal panel (light Loss). Therefore, when only the absorption type polarizer is used, the liquid crystal panel is compared with a conventional configuration that does not perform light collimation (for example, a liquid crystal display device that does not include the polarizer 1 and includes only the polarizer 2 and the polarizer 24). The amount of incident light decreases. Therefore, when only an absorption polarizer is used, at least one of the polarizers 1 and 2 is preferably set to have a large single transmittance, and more preferably set to be larger than that of the polarizer 24. The single transmittance of the polarizers 1 and 2 is more preferably larger than that of the polarizer 24. In general, the single transmittance of the absorption polarizer and the contrast (polarization degree) of the polarizer are in a trade-off relationship. Therefore, if the single transmittance is set large, the contrast of the polarizer is lowered. However, in the optical element and the liquid crystal display device of the present embodiment, since the transmission axes (absorption axes) of the polarizer 1 and the polarizer 2 are parallel to each other, the polarizer 1 and the polarizer 2 have a polarizer contrast with each other. Functions to complement each other. Accordingly, as long as the polarizer 1 and the polarizer 2 are considered as a single body, the CR of the entire liquid crystal display device can be sufficiently secured as long as the contrast of the polarizer is sufficient. On the other hand, lowering the contrast of the polarizer 24 directly leads to lowering of the CR of the liquid crystal display device, so it is not preferable to set the single transmittance of the polarizer 24 large.

On the other hand, when using a composite polarizer in which an absorption polarizer and a reflection polarizer are laminated, that is, when using only a composite polarizer, or when using a combination of an absorption polarizer and a composite polarizer, reflection If the polarizing polarizer is placed on the backlight side of the absorptive polarizer, and the reflective polarizer has perfect polarization performance, the absorption by the absorptive polarizer (light loss) is complete. Can be eliminated. However, in reality, the polarization performance of the reflective polarizer is not perfect, so part of the light that you want to be completely reflected is transmitted through the reflective polarizer, and part of it is the next absorption-type polarized light. Since the light is absorbed by the optical element, an optical loss occurs even when the composite polarizer is used. If the polarization performance of the reflective polarizer is perfect, sufficient performance can be obtained with the reflective polarizer itself, so there is little significance in stacking with an absorptive polarizer and using it as a composite polarizer. In other words, when it is used as a composite polarizer in which a reflective polarizer and an absorption polarizer are laminated, it is almost limited to the case where the performance of the reflective polarizer is insufficient. It can be said that light loss occurs in the later absorption polarizer. Therefore, even if it is a configuration that uses a reflective polarizer, if it is used as a laminate with an absorptive polarizer, only the absorptive polarizer is used from the viewpoint of minimizing optical loss. As in the design concept, at least one of the polarizers 1 and 2 is preferably set to have a large single transmittance, and more preferably set to be larger than that of the polarizer 24. The single transmittance of the polarizers 1 and 2 is more preferably larger than that of the polarizer 24.

The relationship between the single transmittance of each of the polarizers 1, 2, and 24 and the contrast of the polarizer will be described using specific calculation results. When the polarizer 24, the polarizer 2, and the polarizer 1 are selected from the polarizers A to D shown in Table 1, the parallel transmittance, the orthogonal transmittance, and the contrast of the polarizer are simulated. It is shown in 2. Since the polarizer 2 and the polarizer 1 are used so that their transmission axes (absorption axes) are parallel to each other, it is considered that the two polarizers function as a single polarizer II. The parallel transmittance and orthogonal transmittance when the polarizer I (corresponding to the polarizer 24) and the polarizer II were combined were calculated.

In order to simplify the simulation, this simulation does not include a liquid crystal cell or a birefringent layer. However, as a result of the study by the present inventors, the transmittance of the polarizer alone and the transmittance of the liquid crystal display device are small. It is known that there is also a correlation between the magnitude of the contrast of the polarizer and the magnitude of the contrast (CR) of the liquid crystal display device. As shown in Table 2, in the polarizer 2 and the polarizer 1, the contrast of the entire system (combination of the polarizers I and II) can be achieved even if the single transmittance is set large instead of sacrificing the contrast to some extent. Has little effect. At this time, high transmittance can be achieved while maintaining high CR of the liquid crystal display device. On the other hand, if the single transmittance is set large while sacrificing the contrast of the polarizer I (polarizer 24), the contrast of the entire system is large even if the contrast of the polarizer II (polarizer 2 and polarizer 1) is sufficient. As a result, the CR of the liquid crystal display device is greatly reduced.

As described above, the light use efficiency is improved by positively adjusting at least one of the polarizer 1 and the polarizer 2 to high transmittance. Since there are a total of two polarizers, a polarizer 1 and a polarizer 2, on the back side of the liquid crystal panel, if a sufficient degree of polarization can be secured with these two sheets, the decrease in the CR of the liquid crystal display device is suppressed, and the light is reduced. Utilization efficiency can be improved.

When the single transmittance of only one of the polarizers 1 and 2 is made higher than the single transmittance of the polarizer 24, the single transmittance of either polarizer may be increased. When the single transmittance of only one polarizer is higher than the single transmittance of the polarizer 24, the single transmittance of the other polarizer may be substantially equal to the single transmittance of the polarizer 24. Or smaller. From the viewpoint of manufacturing efficiency of the liquid crystal display device, it is preferable that the single transmittance of the polarizer 1 is larger than the single transmittance of the polarizer 24. As a result, the production line of the conventional liquid crystal display device can be diverted. On the other hand, from the viewpoint of further improving the transmittance (light utilization efficiency), it is preferable to make the single transmittance of both the polarizers 1 and 2 larger than the single transmittance of the polarizer 24. At this time, the polarizers 1 and 2 may have the same single transmittance or may be different from each other.

(When using a reflective polarizer)
On the other hand, when a reflective polarizer is used instead of an absorptive polarizer, or an absorptive polarizer and a reflective polarizer are laminated so that the reflective polarizer is closer to the BL side than the absorptive polarizer. When combined and used, obliquely incident light in a specific direction is reflected by the polarizer so that transmission is limited, and a light collimation effect is obtained. Since the reflected light is returned to the BL unit and is reflected and reused in the BL unit, a substantial decrease in the amount of incident light on the liquid crystal panel can be minimized. From such a viewpoint, it is more preferable to use a reflective polarizer, and from the viewpoint of obtaining high contrast when using a reflective polarizer, at least one of the polarizer 24 and the polarizers 1 and 2 is used. Preferably includes an absorptive polarizer, and the polarizer 24 and one of the polarizers 1 and 2 more preferably include an absorptive polarizer.

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.

(LCD panel)
The liquid crystal mode of the liquid crystal panel is not particularly limited, and the liquid crystal mode may be such that black display is performed by aligning the liquid crystal molecules in the liquid crystal layer perpendicularly to the substrate surface, or the liquid crystal molecules in the liquid crystal layer are horizontal to the substrate surface. Alternatively, black display may be performed by orientation in a direction that is neither vertical nor horizontal. From the viewpoint of obtaining a high CR, a vertical alignment (VA) mode that performs black display by aligning liquid crystal molecules in the liquid crystal layer substantially perpendicularly to the substrate surface is more preferable. That is, the display mode of the liquid crystal display device 30 is preferably a vertical alignment mode. In addition to the TFT method (active matrix method), the liquid crystal panel 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 panel, for example, a liquid crystal layer is sandwiched between a pair of substrates each having an electrode formed thereon, and display is performed by applying a voltage between the electrodes.

As the VA mode, for example, an MVA (Multi-domain Vertical Alignment) mode, a CPA (Continuous Pinheal Alignment) mode, a PVA (Patterned Vertical Alignment) mode, and a BVA (Beared VT) mode. , UV2A (Ultra Violet Induced VA) mode, PSA (Polymer Sustained Alignment) mode, IPS-VA (In Plane Switching-Vertical Alignment) mode, TBA (Transverse B) nd 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).

(Backlight unit)
The backlight (BL) unit 25 is not particularly limited, and, for example, a cold cathode fluorescent lamp (CCFL), a hot cathode tube (HCFL), a light emitting diode (LED: Light Emitting Diode). A light source including at least a light source such as 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 the first embodiment, collimation (condensation) of incident light to the liquid crystal panel is performed by the polarizer 1 and the birefringent layer 3 (including the polarizer 2) included between the polarizer 2 and the BL unit 25. Therefore, the BL unit itself does not necessarily have a collimating function. However, from the viewpoint of collimating the incident light on the liquid crystal panel to increase the brightness in the normal direction, further improving the CR, or diverting the conventional BL unit without change, the BL unit itself It may include an optical sheet such as a lens sheet or a prism sheet, and may have a collimating function to some extent.

(Other)
In the present embodiment, a bright display can be obtained in the normal direction and four directions (preferably in the vertical and horizontal directions) without providing a diffusing element. However, from the viewpoint of obtaining bright display in directions other than these, a diffusing element may be further provided on the observation surface side of the polarizer 24.

In the first embodiment, the birefringent layer 3 and the polarizer 1 are attached to the liquid crystal panel 22 side. For example, only the polarizer 1 or the polarizer 1 and the birefringent layer 3 are attached to the BL unit 25. It may be done. Although not shown, an isotropic film may be inserted between the members. Alternatively, an air layer may be used.

[Embodiment 2]
(Optical element and liquid crystal display device)
The liquid crystal display device 31 of the present embodiment is a transmissive liquid crystal display device. As shown in FIG. 2, a polarizer 24, a birefringent layer 23, a liquid crystal panel 22 including a liquid crystal layer, This is a liquid crystal display device obtained by laminating the refractive layer 21, the polarizer 2, the birefringent layer 4, the polarizer 1, and the backlight (BL) unit 25 in this order. The polarizer 2, the birefringent layer 4, and the polarizer 1 constitute an optical element 11. Thus, the configuration of the liquid crystal display device 31 according to the second embodiment is the same as the configuration of the liquid crystal display device 30 according to the first embodiment, except that the birefringent layer 4 is used instead of the birefringent layer 3. is there.

As the birefringent layer 4, a first type birefringent layer or a second type birefringent layer is used. That is, the birefringent layer 4 satisfies 2 ≦ NZ <10 or −9 <NZ ≦ −1. The birefringent layer 4 is arranged so that the angle formed by the transmission axis of the polarizer 1 and the in-plane slow layer axis of the birefringent layer 4 is not 45 °.

According to the optical element 11, birefringence is applied to light incident from the normal direction of the liquid crystal panel 22, the polarization axis directions of the polarizers 1 and 2, and the absorption axis or reflection axis direction of the polarizers 1 and 2. High transmission is observed because layer 3 does not function effectively. On the other hand, the birefringent layer 3 functions effectively for light incident obliquely with respect to the axes of the polarizers 1 and 2 and obliquely with respect to the surface of the polarizer 1. Rate is observed. As a result, the emitted light from the BL unit 25 can be selectively collimated (parallelized), and a cross-shaped light distribution can be realized. Accordingly, similarly to the case of the first embodiment, light leakage due to scattering inside the liquid crystal panel 22 can be sufficiently reduced, and as a result, CR can be effectively improved.

The angle formed between the transmission axis of the polarizer 1 and the in-plane slow layer axis of the birefringent layer 4 is preferably in the range of 90 ± 20 ° or 0 ± 20 °. And the in-plane slow layer axis of the birefringent layer 4 are preferably orthogonal to each other, more preferably parallel to each other, and still more preferably orthogonal to each other. Thereby, the transmittance | permeability with respect to the light which slanted with respect to the axis | shaft of the polarizers 1 and 2 and entered from the diagonal direction with respect to the surface of the polarizer 1 can be reduced more.

The absolute value | Rth | of the thickness direction retardation of the birefringent layer 4 is preferably | Rth | ≧ 200 nm, more preferably | Rth | ≧ 400 nm, and more preferably | Rth | ≧ 600 nm. Thereby, the transmittance | permeability with respect to the light which slanted with respect to the axis | shaft of the polarizers 1 and 2 and entered from the diagonal direction with respect to the surface of the polarizer 1 can be reduced more.

The birefringent layer 4 preferably satisfies NZ ≦ −2 or 3 ≦ NZ, and more preferably satisfies NZ ≦ −3 or 4 ≦ NZ. Thereby, the transmittance | permeability with respect to the light which slanted with respect to the axis | shaft of the polarizers 1 and 2 and entered from the diagonal direction with respect to the surface of the polarizer 1 can be reduced more.

In FIG. 2, the birefringent layer 4 is illustrated as being composed of a single birefringent layer, but the birefringent layer 4 may be composed of a plurality of birefringent layers. For example, three birefringent layers may be stacked to function as one birefringent layer as a total. This makes it possible to use a large-area and inexpensive birefringent layer that is widely used as a conventional optical compensation film for liquid crystal display devices.

In the liquid crystal display device 31 of this embodiment, a birefringent layer similar to the birefringent layer 4 and a polarizer similar to the polarizer 1 are disposed on the polarizer 1 side on the backlight (BL) unit 25 side of the polarizer 1. May be laminated in this order. Thereby, the transmittance | permeability with respect to the light which injected into the diagonal azimuth | direction with respect to the axis | shaft of the polarizers 1 and 2 and diagonally with respect to the surface of the polarizer 1 can be reduced especially effectively.

In the second embodiment, the birefringent layer 4 and the polarizer 1 are attached to the liquid crystal panel 22 side. For example, only the polarizer 1 or the polarizer 1 and the birefringent layer 4 are provided in the BL unit 25. It may be attached to.

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

In the following, axial angles and phase difference values of the respective polarizers, birefringent layers, and VA mode liquid crystal layers in the respective embodiments are shown in the corresponding drawings. Note that the VA liquid crystal layer (a kind of the fourth birefringent layer when no voltage is applied) has no in-plane anisotropy, and therefore does not indicate an axial angle. Further, in the technical field of the present invention, the C plate (third birefringent layer, fourth birefringent layer) is also treated as having no in-plane anisotropy, so the axial angle is not shown, or the axial angle It is shown as 0 ° or 90 °. The meaning of describing the axis angle is different from an ideal C plate in which the in-plane anisotropy is completely zero, and an actually manufactured C plate may have a minute in-plane anisotropy. Therefore, it indicates the axial angle in that case. Only in the case of the C plate, the axis angle represents a more preferable axis angle, and the effect of the present invention is not limited to the axis angle. In addition, since NZ cannot be defined in the VA mode liquid crystal layer of (ns−nf) = 0 or (ns−nf) ≈0 and the C plate, it is not shown or, for convenience, NZ = + It is indicated as ∞ (third birefringent layer) or −∞ (fourth birefringent layer).

[Embodiment 3]
(Optical element and liquid crystal display device)
The liquid crystal display device 32 of this embodiment is a transmissive liquid crystal display device, and includes a polarizer 24, a birefringent layer 23, and a VA mode liquid crystal layer in this order from the viewing surface side, as shown in FIG. 22 is a liquid crystal display device obtained by laminating the birefringent layer 21, the polarizer 2, the birefringent layer 5, the polarizer 1, and the backlight (BL) unit 25 in this order. The polarizer 2, the birefringent layer 5, and the polarizer 1 constitute an optical element 12, and the birefringent layer 5 corresponds to the birefringent layer of the present invention.

The birefringent layer 5 is a third birefringent layer (negative C plate) having R = 0 nm and Rth = −600 nm.

FIG. 4 shows a simulation result regarding the viewing angle characteristics of the optical element 12 according to the third embodiment. That is, when a negative C plate of R = 0 nm and Rth = −600 nm is inserted as the birefringent layer 5 between the polarizers 1 and 2 and illuminated with a BL unit assuming Lambertian, The calculation result of the viewing angle characteristic of the transmittance observed at the position is shown. A liquid crystal optical simulator LCD Master (manufactured by Shintech) was used for the calculation. 4 is a contour diagram showing the relationship between polar angle (theta) and azimuth angle (phi) and transmittance, and the lower side of FIG. 4 is the polar at azimuth 0 °, azimuth 45 °, azimuth 90 °, and azimuth 135 °. It is a graph which shows the relationship between an angle | corner and the transmittance | permeability. For comparison, FIG. 5 shows a calculation result of transmittance viewing angle characteristics of one polarizer having an absorption axis azimuth 90 ° (transmission axis azimuth 0 °), and another polarizer having an absorption axis azimuth 90 °. FIG. 6 shows the calculation result of the viewing angle characteristic of the transmittance when the sheets are stacked (two polarizers arranged in parallel Nicols).

As shown in FIG. 4, in the liquid crystal display device (optical element) of Embodiment 3, the transmittance at azimuths of 45 ° and 135 ° is higher than the transmittance at azimuths of 0 ° and 90 ° at oblique viewing angles having large polar angles. It is low. The transmittance in the normal direction (polar angle 0 °) and oblique viewing angles of 0 ° and 90 ° azimuth is completely the same as the calculation result in the case of only two polarizers (polarizers 1 and 2). is there. That is, by inserting the birefringent layer 5, the transmittance of the oblique viewing angle at 45 ° and 135 ° can be increased without affecting the transmittance of the oblique viewing angle at the normal direction and the orientations of 0 ° and 90 °. Can be reduced. By arranging an optical element composed of such a polarizer and a birefringent layer on the BL unit, the light distribution of the light emitted from the BL unit is changed, and the light distribution of the incident light to the liquid crystal panel is changed. Anisotropic collimation that selectively concentrates in the normal direction and the oblique directions of azimuths of 0 ° and 90 ° is possible. The operation principle will be described in detail as follows.

Since the birefringent layer 5, that is, the negative C plate has R = 0 nm, it does not function as a birefringent layer with respect to incidence from the normal direction. Therefore, in the normal direction, the same transmittance as that obtained when the birefringent layer 5 is not present, that is, when only two polarizers shown in FIG. 6 are obtained can be obtained. On the other hand, in the case of incidence from an oblique viewing angle, the birefringent layer 5 has a non-zero phase difference (birefringence) and functions as a birefringent layer. However, when observed from an oblique viewing angle of 0 °, the effective slow axis of the birefringent layer 5 is parallel to the absorption axis of the polarizer 1. Accordingly, also in this case, the birefringent layer 5 does not substantially change the polarization state of the light after passing through the polarizer 1, and the same transmittance as that obtained with only two polarizers is obtained. When observed from an oblique viewing angle with an azimuth angle of 90 °, the effective slow axis of the birefringent layer 5 is orthogonal to the absorption axis of the polarizer 1. The polarization state of the light after passing through the polarizer 1 is not changed, and the same transmittance as in the case of using only two polarizers is obtained. On the other hand, when observed from oblique viewing angles of 45 ° and 135 °, the effective slow axis of the birefringent layer 5 is neither parallel nor orthogonal to the absorption axis of the polarizer 1. The layer 5 changes the polarization state of the light after passing through the polarizer 1. Therefore, the transmittance is lower than in the case of using only two polarizers. From the above, it is possible to reduce the transmittance of the oblique viewing angles of 45 ° and 135 ° without affecting the normal direction and the transmittance of the oblique viewing angles of 0 ° and 90 °.

[Embodiment 4]
(Optical element and liquid crystal display device)
The liquid crystal display device 33 of the present embodiment is a transmissive liquid crystal display device, and includes a polarizer 24, a birefringent layer 23, and a VA mode liquid crystal layer in this order from the viewing surface side, as shown in FIG. 22 is a liquid crystal display device obtained by laminating the birefringent layer 21, the polarizer 2, the birefringent layer 6, the polarizer 1, and the backlight (BL) unit 25 in this order. The polarizer 2, the birefringent layer 6, and the polarizer 1 constitute an optical element 13, and the birefringent layer 6 corresponds to the birefringent layer of the present invention.

The birefringent layer 6 is a fourth birefringent layer (positive C plate) having R = 0 nm and Rth = + 600 nm.

FIG. 8 shows a simulation result regarding the viewing angle characteristics of the optical element 13 according to the fourth embodiment. That is, when a positive C plate with R = 0 nm and Rth = + 600 nm is inserted between the polarizers 1 and 2 as the birefringent layer 6 and illuminated with a BL unit assuming Lambertian, The calculation result of the viewing angle characteristic of the transmittance observed at the position is shown. As shown in FIG. 8, the transmittance at the azimuths of 45 ° and 135 ° is lower than the transmittance at the azimuths of 0 ° and 90 ° at an oblique viewing angle having a large polar angle. By arranging an optical element composed of such a polarizer and a birefringent layer on the BL unit, the light distribution of the light emitted from the BL unit is changed, and the light distribution of the incident light on the liquid crystal panel is changed. Anisotropic collimation that selectively concentrates in the normal direction and the oblique directions of azimuths of 0 ° and 90 ° is possible. This viewing angle characteristic calculation result is exactly the same as the calculation result of the third embodiment, which differs only in the sign of the phase difference Rth.

[Embodiment 5]
(Optical element and liquid crystal display device)
The liquid crystal display device 34 of this embodiment is a transmissive liquid crystal display device, and as shown in FIG. 9, a liquid crystal panel including a polarizer 24, a birefringent layer 23, and a VA mode liquid crystal layer in this order from the viewing surface side. 22 is a liquid crystal display device obtained by laminating the birefringent layer 21, the polarizer 2, the birefringent layer 7, the polarizer 1, and the backlight (BL) unit 25 in this order. The polarizer 2, the birefringent layer 7, and the polarizer 1 constitute an optical element 14, and the birefringent layer 7 corresponds to the birefringent layer of the present invention.

As the birefringent layer 7, a fourth birefringent layer (negative C plate) having R = 0 nm and Rth = −1000 nm is used.

FIG. 10 shows a simulation result regarding the viewing angle characteristics of the optical element 14 according to the fifth embodiment. That is, when a negative C plate with R = 0 nm and Rth = −1000 nm is inserted as the birefringent layer 7 between the polarizers 1 and 2 and illuminated with a BL unit assuming Lambertian, The calculation result of the viewing angle characteristic of the transmittance observed at the position is shown. As shown in FIG. 10, the transmittance at the azimuths of 45 ° and 135 ° is lower than the transmittance at the azimuths of 0 ° and 90 ° at an oblique viewing angle having a large polar angle. By arranging an optical element composed of such a polarizer and a birefringent layer on the BL unit, the light distribution of the light emitted from the BL unit is changed, and the light distribution of the incident light on the liquid crystal panel is changed. Anisotropic collimation that selectively concentrates in the normal direction and the oblique directions of azimuths of 0 ° and 90 ° is possible.

In FIG. 10, an increase in transmittance (inverted bump) was observed near the polar angle of 70 ° at azimuths of 45 ° and 135 °. However, the transmittance is higher than that in the case of only the polarizers 1 and 2 (FIG. 6). However, there is no problem because light leakage reduction effect is obtained.

[Embodiment 6]
(Optical element and liquid crystal display device)
The liquid crystal display device 35 of this embodiment is a transmissive liquid crystal display device, and as shown in FIG. 11, a liquid crystal panel including a polarizer 24, a birefringent layer 23, and a VA mode liquid crystal layer in this order from the viewing surface side. 22 is a liquid crystal display device obtained by laminating the birefringent layer 21, the polarizer 2, the birefringent layer 8, the polarizer 1, and the backlight (BL) unit 25 in this order. The polarizer 2, the birefringent layer 8, and the polarizer 1 constitute an optical element 15, and the birefringent layer 8 corresponds to the birefringent layer of the present invention.

As the birefringent layer 8, a fourth type birefringent layer (negative C plate) of R = 0 nm and Rth = −2000 nm is used.

FIG. 12 shows a simulation result regarding the viewing angle characteristics of the optical element 15 according to the sixth embodiment. That is, when a negative C plate of R = 0 nm and Rth = −2000 nm is inserted as the birefringent layer 8 between the polarizers 1 and 2 and illuminated with a BL unit assuming Lambertian, The calculation result of the viewing angle characteristic of the transmittance observed at the position is shown. As shown in FIG. 12, the transmittance at the azimuths of 45 ° and 135 ° is lower than the transmittance at the azimuths of 0 ° and 90 ° at an oblique viewing angle having a large polar angle. By arranging an optical element composed of such a polarizer and a birefringent layer on the BL unit, the light distribution of the light emitted from the BL unit is changed, and the light distribution of the incident light on the liquid crystal panel is changed. Anisotropic collimation that selectively concentrates in the normal direction and the oblique directions of azimuths of 0 ° and 90 ° is possible.

In FIG. 12, two inverted bumps were observed at azimuths of 45 ° and 135 °, but the transmittance is not higher than in the case of only polarizers 1 and 2 (FIG. 6). There is no problem because the light leakage reduction effect can be obtained.

[Embodiment 7]
(Optical element and liquid crystal display device)
The liquid crystal display device 36 of this embodiment is a transmissive liquid crystal display device, and includes a polarizer 24, a birefringent layer 23, and a VA mode liquid crystal layer in this order from the viewing surface side, as shown in FIG. 22, a liquid crystal display device obtained by laminating a birefringent layer 21, a polarizer 2, a birefringent layer 7, a polarizer 1, a birefringent layer 8, a polarizer 50, and a backlight (BL) unit 25 in this order. is there. The polarizer 2, the birefringent layer 7, the polarizer 1, the birefringent layer 8, and the polarizer 50 constitute an optical element 16, and the birefringent layers 7 and 8 correspond to the birefringent layer of the present invention.

The birefringent layer 7 is the fourth birefringent layer (negative C plate) of R = 0 nm and Rth = −1000 nm used in the fifth embodiment, and the birefringent layer 8 is used in the sixth embodiment. A fourth birefringent layer (negative C plate) having R = 0 nm and Rth = −2000 nm.

FIG. 14 shows a simulation result regarding the viewing angle characteristics of the optical element 16 according to the seventh embodiment. That is, a negative C plate with R = 0 nm and Rth = −2000 nm is inserted between the polarizers 1 and 2, and further, a negative C plate with R = 0 nm and Rth = −1000 nm and the polarizer 50 are placed outside thereof. FIG. 14 shows the calculation result of the viewing angle characteristic of the transmittance observed at the position of * in FIG. 13 when stacked and illuminated with a BL unit assuming Lambertian. As shown in FIG. 14, at an oblique viewing angle having a large polar angle, the transmittance at azimuths of 45 ° and 135 ° is lower than the transmittance at azimuths of 0 ° and 90 °. By arranging an optical element composed of such a polarizer and a birefringent layer on the BL unit, the light distribution of the light emitted from the BL unit is changed, and the light distribution of the incident light on the liquid crystal panel is changed. Anisotropic collimation that selectively concentrates in the normal direction and the oblique directions of azimuths of 0 ° and 90 ° is possible.

In Embodiment 7, the valley (minimum point) of the transmittance viewing angle characteristics of the optical element of Embodiment 5 (Rth = −1000 nm) in the azimuth 45 ° and 135 ° between the polar angles 40 ° to 60 °, It was made by paying attention to the fact that the peak (maximum point) of the transmittance viewing angle characteristics of the optical element of Embodiment 6 (Rth = −2000 nm) overlapped. Furthermore, in the optical element of Embodiment 5, there is a maximum point in the vicinity of the polar angle of 70 °, while in the optical element of Embodiment 6, the transmittance in the vicinity of the polar angle of 70 ° is lower than that in Example 2. It was made paying attention to. That is, as shown in FIG. 15, the seventh embodiment is designed for the purpose of obtaining a viewing angle characteristic that suppresses the transmittance at a polar angle of 40 ° to 60 ° and also suppresses the transmittance at around a polar angle of 70 °. It is a thing.

In the present embodiment, either one of the birefringent layers 7 and 8 may be the first type birefringent layer, or both the birefringent layers 7 and 8 may be the first type birefringent layers. It may be a layer. At this time, the first birefringent layer and the absorption axis of the polarizer adjacent to the first birefringent layer are laminated so as to be 90 ° or 0 °.

In Embodiment 7, it is preferable that at least one of the polarizers 1, 2, and 50 has a single transmittance larger than that of the polarizer 24. At this time, the single transmittance of any one of the polarizers 1, 2, and 50 may be larger than the single transmittance of the polarizer 24. Of the polarizers 1, 2, and 50, there may be a polarizer having a single transmittance substantially equal to the single transmittance of the polarizer 24, or a polarizer smaller than the single transmittance of the polarizer 24. There may be. From the viewpoint of manufacturing efficiency of the liquid crystal display device, it is more preferable that the single transmittance of the polarizer 1 and / or the polarizer 50 is larger than the single transmittance of the polarizer 24. On the other hand, from the viewpoint of further improving the transmittance (light utilization efficiency), it is more preferable that at least two of the polarizers 1, 2, and 50 have a single transmittance larger than that of the polarizer 24, and all three simplexes. It is particularly preferable that the transmittance is larger than that of the polarizer 24. At this time, the polarizers (two or three of the polarizers 1, 2 and 50) having a single transmittance larger than that of the polarizer 24 may have the same single transmittance or different from each other. Also good.

When the C plate is used for the birefringent layer between the polarizer 1 and the polarizer 2 (hereinafter also referred to as the first birefringent layer) using FIGS. The relationship between the Rth of the first birefringent layer and the change in transmittance will be described.

FIG. 16 shows the calculation result of the change in viewing angle characteristics when the Rth value of the first birefringent layer is changed from 0 nm to −1000 nm. Regardless of the magnitude of Rth, the transmissivity at the azimuths of 0 ° and 90 ° is the same as in the case without the first birefringent layer, and the transmissivity at the azimuth of 45 ° and the transmissivity at the azimuth of 135 °. Since the rate is always the same, the graph in FIG. 16 shows only the relationship between the polar angle and the transmittance at an azimuth of 45 °. The case where the first birefringent layer with Rth = 0 nm is inserted is substantially the same as the case where the first birefringent layer is not inserted, that is, the case where only two polarizers are used. As shown in FIG. 17, as the absolute value of Rth increases, the transmittance at an oblique viewing angle of less than 40 ° polar angle decreases. The decrease in transmittance was clearly confirmed at 400 nm or more, and the decrease in transmittance was confirmed more remarkably at 600 nm or more. On the other hand, when the absolute value of Rth exceeds 600 nm, there is an inversion region (inversion bump) where the transmittance starts increasing again with an increase in the polar angle at an oblique viewing angle of less than 40 °. Since the transmittance at an azimuth of 45 ° is kept lower than when the first birefringent layer is not inserted (when Rth = 0 nm), an effect of reducing light leakage in black display can be obtained. In the case of a liquid crystal panel in which incident light with a polar angle of 40 ° or more is unlikely to leak, better results can be obtained by allowing this inversion bump and selecting -1000 nm. On the other hand, when -1000 nm is selected on a liquid crystal panel in which incident light with a polar angle of 40 ° or more is likely to leak, the transmittance with a polar angle of less than 40 ° is lower than when -600 nm is selected. Since both the reduction of the light leakage due to the increase and the increase of the light leakage due to the increase in the transmittance of the polar angle of 40 ° or more are observed, good results are not necessarily obtained. As described above, it is dependent on the viewing angle characteristics of the liquid crystal panel which of the Rth first birefringent layers can provide a greater light leakage reduction effect. From the above, the optimum Rth of the first birefringent layer is determined according to the properties of the liquid crystal panel and the usage pattern. In the third embodiment, Rth = −600 nm, which is the last Rth that does not cause inversion bumps, is employed.

Further, as shown in FIG. 15, even in the case of the first birefringent layer in which the inversion bump is observed, the transmittance can be increased over a wide polar angle range by using a combination of the first birefringent layers having different Rths. It can also be kept low.

[Embodiment 8]
(Optical element and liquid crystal display device)
The liquid crystal display device 37 of this embodiment is a transmissive liquid crystal display device, and includes a polarizer 24, a birefringent layer 23, and a VA mode liquid crystal layer in this order from the viewing surface side, as shown in FIG. 22 is a liquid crystal display device obtained by laminating the birefringent layer 21, the polarizer 2, the birefringent layer 9, the polarizer 1, and the backlight (BL) unit 25 in this order. The polarizer 2, the birefringent layer 9, and the polarizer 1 constitute an optical element 17, and the birefringent layer 9 corresponds to the birefringent layer of the present invention.

As the birefringent layer 9, a first type birefringent layer of R = 165 nm, Rth = −600 nm, and NZ = 4.1 is used. Further, the polarizer 1 and the birefringent layer 9 are laminated so that the angle formed by the absorption axis of the polarizer 1 and the in-plane slow layer axis of the birefringent layer 9 is 90 °.

FIG. 19 shows a simulation result regarding the viewing angle characteristics of the optical element 17 according to the eighth embodiment. In other words, as a birefringent layer 9 between the polarizers 1 and 2, a first birefringent layer of R = 165 nm, Rth = −600 nm, NZ = 4.1 is inserted, and a BL unit assuming Lambertian is used. 18 shows the calculation result of the viewing angle characteristic of the transmittance observed at the position of ★ in FIG. 18 when illuminated. As shown in FIG. 19, at an oblique viewing angle having a large polar angle, the transmittance at azimuths of 45 ° and 135 ° is lower than the transmittance at azimuths of 0 ° and 90 °. By arranging an optical element composed of such a polarizer and a birefringent layer on the BL unit, the light distribution of the light emitted from the BL unit is changed, and the light distribution of the incident light on the liquid crystal panel is changed. Anisotropic collimation that selectively concentrates in the normal direction and the oblique directions of azimuths of 0 ° and 90 ° is possible.

By selecting the birefringent layer 9 with R = 165 nm, Rth = −600 nm, and NZ = 4.1, the emitted light from the BL unit can be collimated anisotropically and incident on the liquid crystal panel. The reason is the same as in the first embodiment in which the negative C plate is selected. That is, the birefringent layer 9 has R ≠ 0 nm, but its in-plane slow axis is set to be parallel to the absorption axis of the polarizer 1 or at a relative angle orthogonal (in the case of the eighth embodiment, orthogonal). In this case, the birefringent layer 9 does not substantially function as a birefringent layer with respect to incidence from the normal direction. Therefore, in the normal direction, substantially the same transmittance can be obtained as in the case where there is no birefringent layer 9, that is, only two polarizers. When observed from an oblique viewing angle at an azimuth of 0 °, the effective slow axis of the birefringent layer 9 is orthogonal or parallel to the absorption axis of the polarizer 1 (or orthogonal in the case of Embodiment 8). However, the birefringent layer 9 does not substantially change the polarization state of the light after passing through the polarizer 1, and the same transmittance as in the case of using only two polarizers is obtained. Similarly, when observed from an oblique viewing angle of 90 °, the effective slow axis of the birefringent layer 9 is orthogonal or parallel to the absorption axis of the polarizer 1 (or orthogonal in the case of Embodiment 8). Also in this case, the birefringent layer 9 does not substantially change the polarization state of the light after passing through the polarizer 1, and the same transmittance as in the case of using only two polarizers is obtained. On the other hand, when observed from an oblique viewing angle at azimuths of 45 ° and 135 °, the effective slow axis of the birefringent layer 9 is neither parallel nor orthogonal to the absorption axis of the polarizer 1, and in this case, the polarizer 1 Changes the polarization state of the light after passing through the polarizer 1. Therefore, the transmittance is lower than in the case of using only two polarizers. From the above, it is possible to reduce the transmittance of the oblique viewing angles of 45 ° and 135 ° without affecting the normal direction and the transmittance of the oblique viewing angles of 0 ° and 90 °.

[Embodiment 9]
(Optical element and liquid crystal display device)
The liquid crystal display device 38 of this embodiment is a transmissive liquid crystal display device, and includes a polarizer 24, a birefringent layer 23, and a VA mode liquid crystal layer in this order from the viewing surface side, as shown in FIG. 22 is a liquid crystal display device obtained by laminating the birefringent layer 21, the polarizer 2, the birefringent layer 9, the polarizer 1, and the backlight (BL) unit 25 in this order. The polarizer 2, the birefringent layer 9, and the polarizer 1 constitute an optical element 18, and the birefringent layer 9 corresponds to the birefringent layer of the present invention.

As the birefringent layer 9, a first type birefringent layer of R = 165 nm, Rth = −600 nm, and NZ = 4.1 is used. Further, the polarizer 1 and the birefringent layer 9 are stacked so that the angle formed by the absorption axis of the polarizer 1 and the in-plane slow layer axis of the birefringent layer 9 is 0 °.

FIG. 21 shows a simulation result regarding the viewing angle characteristics of the optical element 18 according to the ninth embodiment. In other words, as a birefringent layer 9 between the polarizers 1 and 2, a first birefringent layer of R = 165 nm, Rth = −600 nm, NZ = 4.1 is inserted, and a BL unit assuming Lambertian is used. FIG. 21 shows the calculation result of the viewing angle characteristic of the transmittance observed at the position of ★ in FIG. 20 when illuminated. As shown in FIG. 21, the transmittance at the azimuths of 45 ° and 135 ° is lower than the transmittance at the azimuths of 0 ° and 90 ° at an oblique viewing angle having a large polar angle. By arranging an optical element composed of such a polarizer and a birefringent layer on the BL unit, the light distribution of the light emitted from the BL unit is changed, and the light distribution of the incident light on the liquid crystal panel is changed. Anisotropic collimation that selectively concentrates in the normal direction and the oblique directions of azimuths of 0 ° and 90 ° is possible.

However, the effect is limited as compared with the case of the eighth embodiment using the birefringent layer 9 having the same retardation value. That is, it can be seen that the in-plane slow axis of the birefringent layer 9 is more preferably orthogonal to the absorption axis of the polarizer 1. The reason is analyzed in detail and shown below.

22 and 23 show the collimating optical elements (second polarizer 2, first birefringent layer 6, and first polarizer 1) of Embodiments 8 and 9, respectively, with an azimuth of 45 ° and a polar angle of 60 °. It is a figure which shows transition of a polarization state on the Poincare sphere at the time of observing from the diagonal viewing angle.

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 have the same absolute value of the ellipticity angle and the opposite polarities, so that a pair of polarized light whose angle between the polarization axes of each other is 90 °. It is made. 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). A rotation center and a rotation angle when observed from an oblique direction are determined by a slow axis (or a fast axis) and a 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). ).

Considering the case where light is incident on the optical element 17 of Embodiment 8 from an oblique direction with an azimuth angle of 45 ° and a polar angle of 60 °, polarized light every time the light emitted from the BL unit passes through the polarizer 1 and the birefringent layer 9. Points P0 and P1 representing the state are illustrated on the S1-S2 plane of the Poincare sphere 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 polarizer 2 when viewed from an oblique direction with an azimuth of 45 ° and a polar angle of 60 °. Although the points representing the respective polarization states are actually on the Poincare sphere, they are projected onto the S1-S2 plane for illustration. The point P0 representing the polarization state of the light after passing through the polarizer 1 connects the point R3 representing the slow axis of the birefringent layer 9 on the Poincare sphere by passing through the birefringent layer 9 and the center O of the Poincare sphere. The line segment R3O is rotated counterclockwise and converted into P1, and then enters the polarizer 2. At this time, light is transmitted according to the distance between the point P1 representing the polarization state and the point E representing the polarization state of the extinction position of the polarizer 2. More precisely, the transmittance is proportional to sin ² ((1/2) × ∠P1OE).

The case where light enters the optical element 18 of the ninth embodiment from an oblique direction with an azimuth angle of 45 ° and a polar angle of 60 ° is as shown in FIG. The point P0 representing the polarization state of the light after passing through the polarizer 1 passes through the birefringent layer 9, thereby causing the point R3 representing the slow axis of the birefringent layer 9 on the Poincare sphere and the center of the Poincare sphere. It receives a rotational movement counterclockwise around the line connecting O and is converted into P1, and then enters the polarizer 2. In the case of the ninth embodiment, the angle formed by the slow axis of the birefringent layer 9 and the absorption axis of the polarizer 2 is 0 ° (when observed from the normal direction). However, the points R3 and E are close to each other. For this reason, even if rotational movement about the line segment R3O is performed, the point P1 cannot reach the vicinity of the point E, and the transmittance is not so small. On the other hand, in the case of the eighth embodiment described above, the angle formed by the slow axis of the birefringent layer 9 and the absorption axis of the polarizer 2 is 90 °. E is away. Therefore, by performing rotational movement around the line segment R3O, the point P1 can reach close to the point E, and low transmission can be realized as compared with the case of the eighth embodiment.

Note that the position of the point R3 representing the slow axis when the birefringent layer 9 is observed from an oblique direction with an azimuth of 45 ° and a polar angle of 60 ° depends on the NZ coefficient. When the NZ coefficient is increased, the birefringent layer 9 approaches the third type of birefringent layer (negative C plate), and therefore the angle formed by the slow axis of the birefringent layer 9 and the absorption axis of the polarizer 2 is 0 °. Even when the angle is 90 °, the point R3 approaches the + S1 axis, and in the limit of 1 << NZ (NZ → + ∞), the birefringent layer 9 becomes a completely negative C plate, and the point R3 coincides with the + S1 axis. On the contrary, when the NZ coefficient is reduced, the birefringent layer 9 approaches the positive C plate, so the angle formed by the slow axis of the birefringent layer 9 and the absorption axis of the polarizer 2 is 0 ° or 90 °. However, the point R3 approaches the -S1 axis.

In order to confirm the operation principle for each NZ coefficient, in addition to the case of NZ = 4.1 described above, the transition of the polarization state in the case of NZ = 1.0, NZ = 10.5, NZ = + ∞ is described. The angle formed by the slow axis of the first birefringent layer and the absorption axis of the polarizer 2 is divided into the case of 0 ° and the case of 90 ° as shown in FIG. 24 on the Poincare sphere (in the case of NZ = + ∞) There is no distinction between 0 ° and 90 °, so there is only one type.) In addition, a contour diagram showing calculation results for each viewing angle characteristic is shown in FIG. In each case, Rth was fixed at −600 nm.

As shown in FIG. 24, when the angle formed by the slow axis of the first birefringent layer and the absorption axis of the polarizer 2 is 0 °, the point P1 cannot approach the point E compared to the case of 90 °. Therefore, sufficient transmittance reduction and collimating effect cannot be obtained. In particular, when NZ = 1, since the point P0 overlaps the line segment R3O that is the rotation center axis, no collimating effect is obtained. Therefore, when using the first birefringent layer whose in-plane retardation is not zero, it is more preferable to arrange the slow axis of the first birefringent layer and the absorption axis of the polarizer 2 to be orthogonal. However, as can be seen from the result of NZ = 10.5, as the NZ increases, the first birefringent layer approaches the negative C plate, so that the transmittance in the oblique direction is sufficiently lowered in both the orthogonal arrangement and the parallel arrangement. Thus, a collimating effect can be obtained in the optical element. When NZ exceeds 10, it may be either orthogonal arrangement or parallel arrangement. In the case of NZ = 1, even if they are arranged so as to be orthogonal, the point P0 and the point R3 are too close, so that the point P1 is close to the point E by performing rotational movement around the line segment R3O. It can also be seen that almost no collimating effect can be obtained. Regardless of how the phase difference value is adjusted, the point P1 can exist only on the line segment P0P1 (on the S1-S2 plane of the Poincare sphere) or its extension line, and a sufficient collimating effect cannot be obtained.

Summarizing the above results, in order to obtain a sufficient collimating effect, (1) the slow axis of the first birefringent layer and the absorption axis of the polarizer 2 are arranged orthogonally (however, 10 < In the case of NZ, it is preferable to satisfy the condition that it may be either orthogonal or parallel, and (2) the NZ coefficient is as large as possible.

Next, a preferable value of the NZ coefficient of the first birefringent layer will be described. In FIG. 26, the in-plane retardation R is scanned for each NZ coefficient, and the design guideline of minimizing the transmittance T (45, 60) at an azimuth of 45 ° and a polar angle of 60 ° is used. The result of optimization is shown. T (45, 60) at the time of selecting the optimum R is shown as a function of the NZ coefficient. In FIG. 26, numbers obtained by normalizing T (45, 60) with values in the case of no first birefringent layer are used. As shown in FIG. 26, T (45, 60) can be kept low as NZ increases. According to the results of separate investigations by the inventors, it is necessary to make T (45, 60) less than half that of the case without the first birefringent layer in order to obtain the light leakage reduction effect. I understood. From such a viewpoint, it is preferable that the NZ coefficient of the first birefringent layer satisfies 2 <NZ.

[Embodiment 10]
(Optical element and liquid crystal display device)
The liquid crystal display device 39 of this embodiment is a transmissive liquid crystal display device, and as shown in FIG. 27, a liquid crystal panel including a polarizer 24, a birefringent layer 23, and a VA mode liquid crystal layer in this order from the viewing surface side. 22 is a liquid crystal display device obtained by laminating the birefringent layer 21, the polarizer 2, the birefringent layer 29, the polarizer 1, and the backlight (BL) unit 25 in this order. The polarizer 2, the birefringent layer 29, and the polarizer 1 constitute an optical element 19, and the birefringent layer 29 corresponds to the birefringent layer of the present invention.

As the birefringent layer 29, a second birefringent layer of R = 165 nm, Rth = + 595 nm, and NZ = −3.1 is used. Further, the polarizer 1 is laminated so that the angle formed by the absorption axis of the polarizer 1 and the in-plane slow layer axis of the birefringent layer 9 is 0 °.

Although detailed description is omitted, as a result of the study by the present inventors, a slow axis angle α °, an in-plane phase difference R, and a NZ coefficient = NZ are obtained between two polarizers having an absorption axis angle of 90 °. The transmittance viewing angle characteristic of an optical element sandwiched between two birefringent layers and a fast axis angle α ° (= slow axis angle α ° + 90 °) between two polarizers having an absorption axis angle of 90 °. It is known that the transmittance viewing angle characteristic of the optical element in which the first-type birefringent layer having in-plane retardation R and NZ coefficient = 1-NZ is sandwiched is almost the same. Therefore, the liquid crystal display device 39 (optical element 19) of the present embodiment and the liquid crystal display device 37 (optical element 17) of the eighth embodiment are expected to exhibit the same viewing angle characteristics.

FIG. 28 shows a simulation result regarding the viewing angle characteristics of the optical element 19 according to the tenth embodiment. That is, as the birefringent layer 29 between the polarizers 1 and 2, the second birefringent layer of R = 165 nm, Rth = + 595 nm, NZ = −3.1 is used as the absorption axis of the polarizer 1 and the birefringent layer 29. 27 is inserted at an angle of 0 ° with the in-plane slow layer axis and illuminated with a BL unit assuming Lambertian, and the viewing angle characteristics of the transmittance observed at the position of ★ in FIG. The calculation result of is shown. As shown in FIG. 28, the transmittance at the azimuths of 45 ° and 135 ° is lower than the transmittance at the azimuths of 0 ° and 90 ° at an oblique viewing angle with a large polar angle. By arranging an optical element composed of such a polarizer and a birefringent layer on the BL unit, the light distribution of the light emitted from the BL unit is changed, and the light distribution of the incident light on the liquid crystal panel is changed. Anisotropic collimation that selectively concentrates in the normal direction and the oblique directions of azimuths of 0 ° and 90 ° is possible.

As expected, the liquid crystal display device 39 (optical element 19) of the present embodiment and the liquid crystal display device 37 (optical element 17) of the eighth embodiment showed the same viewing angle characteristics (FIGS. 19 and 19). 28).

[Embodiment 11]
(Optical element and liquid crystal display device)
The liquid crystal display device 40 of this embodiment is a transmissive liquid crystal display device, and as shown in FIG. 29, a liquid crystal panel including a polarizer 24, a birefringent layer 23, and a VA mode liquid crystal layer in this order from the viewing surface side. 22 is a liquid crystal display device obtained by laminating the birefringent layer 21, the polarizer 2, the birefringent layer 29, the polarizer 1, and the backlight (BL) unit 25 in this order. The polarizer 2, the birefringent layer 29, and the polarizer 1 constitute the optical element 20, and the birefringent layer 29 corresponds to the birefringent layer of the present invention.

As the birefringent layer 29, a second birefringent layer of R = 165 nm, Rth = + 595 nm, and NZ = −3.1 is used. Further, the polarizer 1 and the birefringent layer 29 are laminated so that the angle formed by the absorption axis of the polarizer 1 and the in-plane slow layer axis of the birefringent layer 29 is 90 °.

The liquid crystal display device 40 (optical element 20) of the present embodiment and the liquid crystal display device 38 (optical element 18) of the ninth embodiment are expected to exhibit the same viewing angle characteristics.

FIG. 30 shows a simulation result regarding the viewing angle characteristics of the optical element 20 according to the eleventh embodiment. That is, as the birefringent layer 29 between the polarizers 1 and 2, the second birefringent layer of R = 165 nm, Rth = + 595 nm, NZ = −3.1 is used as the absorption axis of the polarizer 1 and the birefringent layer 29. 29 is inserted at an angle of 90 ° with the in-plane slow layer axis and illuminated with a BL unit assuming Lambertian, and the viewing angle characteristics of the transmittance observed at the position of ★ in FIG. The calculation result of is shown.

As expected, the liquid crystal display device 40 (optical element 20) of the present embodiment and the liquid crystal display device 38 (optical element 18) of the ninth embodiment showed the same viewing angle characteristics (FIGS. 21 and 29). .

Next, with reference to FIGS. 31 to 41, when the first type birefringent layer or the second type birefringent layer is used as the birefringent layer, the absorption axis of the polarizer and the in-plane of the birefringent layer are used. The relationship between the angle formed by the slow axis and the transmittance will be described. 31 to 41 show a birefringent layer of R = 165 nm, Rth = −600 nm, and NZ = 4.1 as a birefringent layer between polarizers 1 and 2 having an absorption axis direction of 90 °. It is the calculation result of the transmittance | permeability viewing angle characteristic at the time of inserting so that it may become 0 +/- 45 degrees.

When the first-type birefringent layer or the second-type birefringent layer whose in-plane retardation is not 0 is used, if the axial angle is not 0 °, the transmittance in the normal direction is reduced or the orientation The transmittance in the oblique direction of 0 ° or 90 ° may be higher than the transmittance in the oblique direction of 45 ° or 135 °, which is not preferable. It was found from FIG. 31 to FIG. 41 that the allowable shaft angle is 0 ± 20 °. When the deviation is outside the optimum value beyond the range, in addition to the decrease in the transmittance in the normal direction, for example, the azimuth angle 45 ° or 135 °, such as the axial angle 0 ± 25 ° shown in FIGS. The polar angle range in which the transmittance in the oblique direction exceeds the transmittance in the azimuth 0 ° or 90 ° becomes wider than the lower polar angle range, and the CR improvement effect may be limited. It has also been found that the allowable shaft angle is more preferably 0 ± 10 °. As shown in FIGS. 35 to 37, the transmittance in the oblique direction of 45 ° or 135 ° does not exceed the transmittance of 0 ° or 90 ° in any polar angle within this range. Therefore, a high CR improvement effect can be obtained.

In the case of using the first type birefringent layer or the second type birefringent layer, the allowable axis angle when the axis angle deviates from 90 ° was also examined. FIGS. 41 to 51 show a first birefringent layer of R = 165 nm, Rth = −600 nm, and NZ = 4.1 as a birefringent layer between polarizers 1 and 2 having an absorption axis orientation of 90 °. It is the calculation result of the transmittance | permeability viewing angle characteristic at the time of inserting so that it may become 90 +/- 45 degrees. As a result, it was found that the allowable angle was 90 ± 20 ° as in the case where the shaft angle deviated from 0 °. When the deviation is outside the optimum value beyond the range, in addition to the decrease in the transmittance in the normal direction, for example, the azimuth 45 ° or 135 °, such as the axial angle 90 ± 25 ° shown in FIGS. The polar angle range in which the transmittance in the oblique direction exceeds the transmittance in the azimuth 0 ° or 90 ° becomes wider than the lower polar angle range, and the CR improvement effect may be limited. It has also been found that the allowable shaft angle is more preferably 0 ± 10 °. As shown in FIGS. 45 to 47, the transmittance in the oblique direction of 45 ° or 135 ° does not exceed the transmittance of 0 ° or 90 ° in any polar angle within this range. Therefore, a high CR improvement effect can be obtained.

In order to prevent only a decrease in the transmittance in the normal direction, a plurality of birefringences are laminated so that the angle formed between the slow axes of each other is 0 ° or 90 °, and the effective position as a laminate is obtained. A method of setting the phase difference to 0 is conceivable. As shown in FIG. 52, the simplest configuration is a method of laminating two birefringent layers 103 and 104 having the same in-plane retardation R so that the angle formed between the axes is 90 °. . For normal incidence, two birefringent layers having the same in-plane phase difference and an angle of 90 ° between each other act to compensate for each other's phase difference. Since the effective phase difference of the birefringent layer is 0, the transmittance does not decrease with respect to incidence in the normal direction. However, the effective phase difference is not zero because the angle formed by the effective axis of each birefringent layer is not 90 ° with respect to the incidence from the oblique direction at 0 ° or 90 °. So-called elliptical birefringence related to optical rotation (a phenomenon of rotating the direction of polarized light) remains. As a result, as shown in FIG. 53, the transmittance is reduced with respect to incidence from an oblique direction at an azimuth of 0 ° or 90 ° as compared to the case where there is no birefringent layer or the case of the eighth embodiment. Therefore, this method also has a problem from the viewpoint of realizing cross-shaped collimation that does not reduce the transmittance with respect to the normal direction and the oblique direction at 0 ° or 90 ° in the azimuth direction. The same can be said for Comparative Example 2 described later.

[Comparison 1]
The liquid crystal display device 130 of the present embodiment is a transmissive liquid crystal display device, and as shown in FIG. 54, a liquid crystal panel including a polarizer 24, a birefringent layer 23, and a VA mode liquid crystal layer in order from the observation surface side. 22 is a liquid crystal display device obtained by laminating the birefringent layer 21, the polarizer 2, and the backlight (BL) unit 25 in this order. Except for not having the birefringent layer 5 and the polarizer 1, it is the same as the liquid crystal display device of the third embodiment.

[Comparison 2]
The liquid crystal display device 131 of this embodiment is a transmissive liquid crystal display device, and as shown in FIG. 55, a liquid crystal panel including a polarizer 24, a birefringent layer 23, and a VA mode liquid crystal layer in order from the viewing surface side. 22 is a liquid crystal display device obtained by laminating a birefringent layer 21, a polarizer 2, two birefringent layers 9, a polarizer 1, and a backlight (BL) unit 25 in this order. The two birefringent layers 9 are inserted so that the axial angles are 45 ° and 135 °, respectively.

In FIG. 56, the simulation result regarding the viewing angle characteristic of the optical element which concerns on the comparative form 2 is shown. That is, two birefringent layers of R = 165 nm, Rth = −600 nm, and NZ = 4.1 are used as the birefringent layer 9 between the polarizers 1 and 2, and the axial angles are 45 ° and 135 °, respectively. FIG. 55 shows the calculation result of the viewing angle characteristic of the transmittance observed at the position of * in FIG. 55 when it is inserted so as to be at 0 ° and illuminated with a BL unit assuming Lambertian. As shown in FIG. 56, regardless of the azimuth angle, the transmittance is low compared to the case where there is no birefringent layer at an oblique viewing angle with a large polar angle (see, for example, FIG. 6). It can be said that the optical element composed of such a combination of a polarizer and a birefringent layer aims at isotropic collimation that selectively concentrates the light distribution of incident light on the liquid crystal panel in the normal direction. Unlike Embodiments 1 to 11 of the present invention, the transmittance decreases even when the orientation is 0 ° and 90 ° because the slow axis of the birefringent layer 9 is neither parallel nor orthogonal to the absorption axis of the first polarizer 1. Even when observed from oblique viewing angles of 0 ° and 90 °, the effective slow axis of the birefringent layer 9 is neither parallel nor orthogonal to the absorption axis of the polarizer 1, and the birefringent layer 9 passes through the polarizer 1. This is to change the polarization state of the later light. The two birefringent layers 9 are laminated at an angle of 45 ° and 135 °, respectively, and the angle formed by the two slow axes is 90 °, and the in-plane retardation R is equal, so that when observing from the normal direction, The effective phase difference is zero, and the same transmittance as in the case where there is no birefringent layer in the normal direction, that is, only two polarizers, is obtained. On the other hand, in the oblique direction, the laminate of the two birefringent layers 9 functions as a birefringent layer regardless of the viewing direction, and thus the transmittance is lower than that in the case where there is no birefringent layer.

Example 1
As the liquid crystal display device of Example 1, the liquid crystal display device 32 of Embodiment 3 was actually manufactured. As the birefringent layer 5, a stack of six birefringent layers having R = 1 nm and Rth = −99 nm was used. As a material for these birefringent layers, norbornene (NB) was used. As a material of the birefringent layer 21 and the birefringent layer 23, triacetyl cellulose (TAC) was used. For each polarizer, an absorptive polarizer in which a dichroic iodine complex was adsorbed and oriented on a polyvinyl alcohol (PVA) film was used. The characteristics of each polarizer (single transmittance, parallel transmittance (Tp), orthogonal transmittance (Tc), and contrast of the polarizer) were set to be A in Table 1 above. A TAC film (R = 0 nm, Rth = 52 nm) was attached to both surfaces of each polarizer. As the backlight unit 25, a backlight unit mounted on a Sharp liquid crystal television (trade name: LC40-SE1) was used. The configuration of the backlight unit was an LED light source, a diffusion plate, a diffusion sheet, and a lens sheet laminated in this order.

(Example 2)
As the liquid crystal display device of Example 2, the liquid crystal display device 34 of Embodiment 5 was actually manufactured. As the birefringent layer 6, a stack of 10 birefringent layers having R = 1 nm and Rth = −99 nm was used. As a material for these birefringent layers, norbornene (NB) was used. The rest is the same as the first embodiment.

(Example 3)
As the liquid crystal display device of Example 3, the liquid crystal display device 35 of Embodiment 6 was actually manufactured. As the birefringent layer 8, a layer in which ten birefringent layers having R = 1 nm and Rth = −202 nm were stacked was used. As a material for these birefringent layers, norbornene (NB) was used. The rest is the same as the first embodiment.

Example 4
As the liquid crystal display device of Example 4, the liquid crystal display device 36 of Embodiment 7 was actually manufactured. As the birefringent layer 8, a stack of 10 birefringent layers having R = 1 nm and Rth = −99 nm was used. As the material of the birefringent layer 8, norbornene (NB) was used. Further, as the birefringent layer 9, a layer in which ten birefringent layers having R = 0 nm and Rth = −202 nm were stacked was used. As a material for the birefringent layer 9, cholesteric liquid crystal (ChLC) was used. The rest is the same as the first embodiment.

(Example 5)
As the liquid crystal display device of Example 5, the liquid crystal display device 37 of Embodiment 8 was actually manufactured. As the birefringent layer 9, a laminate of three birefringent layers with R = 55 nm and Rth = −198 nm was used. Triacetyl cellulose (TAC) was used as a material for these birefringent layers. The rest is the same as the first embodiment.

(Examples 5-1 to 5-6)
Example 5 is the same as Example 5 except that the characteristics (single transmittance, parallel transmittance (Tp), orthogonal transmittance (Tc), and contrast of the polarizer) of each polarizer are changed.

(Example 6)
As the liquid crystal display device of Example 6, the liquid crystal display device 38 of Embodiment 9 was actually manufactured. As the birefringent layer 9, the same layer as that obtained by laminating three birefringent layers of R = 55 nm and Rth = −198 nm used in Example 5 was used. Other than that is the same as Example 5.

(Example 7)
As a liquid crystal display device of Example 7, a liquid crystal display device 37 of Embodiment 8 was actually manufactured. The birefringent layer was the same as that obtained by laminating three birefringent layers of R = 55 nm and Rth = −198 nm used in Example 5, and the characteristics of each polarizer were changed, except that the characteristics of each polarizer were changed. Is the same.

(Comparative Example 1)
As a liquid crystal display device of comparative example 1, a liquid crystal display device of comparative form 1 was actually made. Except for not having the birefringent layer 5, it is the same as the liquid crystal display device of Example 1.

(Comparative Example 2)
As a liquid crystal display device of Comparative Example 2, a liquid crystal display device of Comparative Example 2 was actually produced. As the birefringent layer 9, two birefringent layers 9 used in Example 5 were inserted between the polarizer 1 and the polarizer 2 so that the axial angles were 45 ° and 135 °, respectively. The rest is the same as the liquid crystal display device of Example 5.

Regarding the liquid crystal display devices according to Examples 1 to 7, Comparative Example 1 and Comparative Example 2, CR evaluation and visual evaluation of viewing angle were performed. The results are shown in Table 3.

(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 R0 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.

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

In each of the liquid crystal display devices of Examples 1 to 7 according to the present invention, a high CR was obtained as compared with Comparative Example 1, and high CR and an excellent display characteristic were confirmed by visual subjective evaluation. In addition, when visual subjective evaluation focusing on viewing angle characteristics is performed, the liquid crystal display devices of Examples 1 to 7 of the present invention do not include a diffusing element outside the viewing side of the third polarizer 24. Bright display was obtained even from oblique viewing angles of 0 ° and 90 ° (up, down, left and right), and sufficient viewing angle characteristics were obtained for practical use, confirming the effect of anisotropic collimation. Further, in the liquid crystal display devices of Examples 5-1 to 5-6, high white luminance was obtained as compared with Example 5 while high CR was obtained as in Example 5. Similarly, in Example 7, high CR and high white luminance were obtained while high CR was obtained as in Example 5. Further, when an anti-glare (AG) film having a haze of 41% is provided as a diffusing element outside the viewing side of the polarizer 1 of the liquid crystal display devices of Examples 1 to 7, bright display can be obtained even at azimuths of 45 ° and 135 °. A viewing angle characteristic comparable to that of the liquid crystal display device of Comparative Example 1 in which the incident light on the liquid crystal panel was not collimated was obtained.

On the other hand, in the liquid crystal display device of Comparative Example 2, although high CR was observed due to the effect of isotropic collimation, the display was dark at all oblique viewing angles other than the normal direction, and a practically sufficient viewing angle characteristic was obtained. It wasn't. Further, when an AG film having a haze of 41% was provided as a diffusing element on the outside of the viewing side of the third polarizer 24 of the liquid crystal display device of Comparative Example 2, a slight viewing angle improvement effect was confirmed, but Comparative Example 1 A viewing angle comparable to that of the liquid crystal display device was not obtained.

The present application is based on Japanese Patent Application 2010-293849 filed on December 28, 2010 and Japanese Patent Application 2011-096525 filed on April 22, 2011. Or claim priority based on laws and regulations in the country of transition. The contents of the application are hereby incorporated by reference in their entirety.

1, 2, 24, 50: Polarizers 3, 4, 5, 6, 7, 8, 9, 21, 23, 29: Birefringent layers 10, 11, 12, 13, 14, 15, 16, 17, 18 19, 20: Optical element 22: Liquid crystal panel 25: Backlight (BL) units 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 130, 131: Liquid crystal display device

Claims (26)

1. An optical element comprising a first polarizer, a birefringent layer and a second polarizer,
   The first polarizer, the birefringent layer, and the second polarizer are laminated in this order,
   The transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other,
   The biaxial parameter NZ of the birefringent layer satisfies 10 ≦ NZ or NZ ≦ −9,
   The optical element characterized in that the absolute value | Rth | of the thickness direction retardation of the birefringent layer satisfies | Rth | ≧ 200 nm.
2. The at least one of the first polarizer and the second polarizer is a reflective polarizer, or a composite polarizer in which an absorption polarizer and a reflective polarizer are stacked. Optical elements.
3. Each of the first polarizer and the second polarizer is an absorptive polarizer, or a composite polarizer in which an absorptive polarizer and a reflective polarizer are laminated,
   The optical element according to claim 1, wherein the first polarizer has a single transmittance different from that of the second polarizer.
4. The optical element includes a plurality of the birefringent layers, and the first polarizer, the plurality of birefringent layers, and the second polarizer are stacked in this order. An optical element according to any one of the above.
5. 5. The optical element according to claim 1, wherein the absolute value | Rth | of the thickness direction retardation of the birefringent layer satisfies | Rth | ≧ 400 nm.
6. 6. The optical element according to claim 5, wherein the absolute value | Rth | of the thickness direction retardation of the birefringent layer satisfies | Rth | ≧ 600 nm.
7. The optical element further includes a second birefringent layer and a third polarizer,
   The first polarizer, the birefringent layer, the second polarizer, the second birefringent layer, and the third polarizer are laminated in this order,
   The transmission axis of the second polarizer and the transmission axis of the third polarizer are parallel to each other,
   The biaxial parameter NZ of the second birefringent layer satisfies 10 ≦ NZ or NZ ≦ −9,
   The absolute value | Rth | of the thickness direction retardation of the second birefringent layer satisfies | Rth | ≧ 200 nm and is different from the absolute value of the thickness direction retardation of the birefringent layer. The optical element according to any one of claims 1 to 6.
8. The optical element further includes a second birefringent layer and a third polarizer,
   The first polarizer, the birefringent layer, the second polarizer, the second birefringent layer, and the third polarizer are laminated in this order,
   The transmission axis of the second polarizer and the transmission axis of the third polarizer are parallel to each other,
   The biaxial parameter NZ of the second birefringent layer satisfies 2 ≦ NZ <10 or −9 <NZ ≦ −1,
   The angle formed by the transmission axis of the second polarizer and the in-plane slow axis of the second birefringent layer is not 45 ° or 135 °,
   7. The absolute value | Rth | of the thickness direction retardation of the second birefringent layer is different from the absolute value of the thickness direction retardation of the birefringent layer. The optical element described.
9. An optical element comprising a first polarizer, a birefringent layer and a second polarizer,
   The first polarizer, the birefringent layer, and the second polarizer are laminated in this order,
   The transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other,
   The biaxial parameter NZ of the birefringent layer satisfies 2 ≦ NZ <10 or −9 <NZ ≦ −1,
   An optical element, wherein an angle formed between a transmission axis of the first polarizer and an in-plane slow axis of the birefringent layer is not 45 ° or 135 °.
10. The angle formed by the transmission axis of the first polarizer and the in-plane slow axis of the birefringent layer is in the range of 90 ± 20 ° or 0 ± 20 °. The optical element described.
11. The optical element according to claim 10, wherein a transmission axis of the first polarizer and an in-plane slow axis of the birefringent layer are orthogonal to each other or parallel to each other.
12. The optical element according to claim 11, wherein a transmission axis of the first polarizer and an in-plane slow axis of the birefringent layer are parallel to each other.
13. 10. The at least one of the first polarizer and the second polarizer is a reflective polarizer or a composite polarizer in which an absorption polarizer and a reflective polarizer are laminated. 12. The optical element according to any one of 12.
14. Each of the first polarizer and the second polarizer is an absorptive polarizer, or a composite polarizer in which an absorptive polarizer and a reflective polarizer are laminated,
    The optical element according to any one of claims 9 to 12, wherein the first polarizer has a single transmittance different from that of the second polarizer.
15. The optical element includes a plurality of the birefringent layers,
    The first polarizer, the plurality of birefringent layers, and the second polarizer are laminated in this order,
    The optical element according to any one of claims 9 to 14, wherein in-plane slow axes of the plurality of birefringent layers are orthogonal to each other or parallel to each other.
16. 16. The optical element according to claim 9, wherein the absolute value | Rth | of the thickness direction retardation of the birefringent layer satisfies | Rth | ≧ 200 nm.
17. 17. The optical element according to claim 16, wherein the absolute value | Rth | of the thickness direction retardation of the birefringent layer satisfies | Rth | ≧ 400 nm.
18. 18. The optical element according to claim 17, wherein the absolute value | Rth | of the thickness direction retardation of the birefringent layer satisfies | Rth | ≧ 600 nm.
19. The optical element further includes a second birefringent layer and a third polarizer,
    The first polarizer, the birefringent layer, the second polarizer, the second birefringent layer, and the third polarizer are laminated in this order,
    The transmission axis of the second polarizer and the transmission axis of the third polarizer are parallel to each other,
    The biaxial parameter NZ of the second birefringent layer satisfies 2 ≦ NZ <10 or −9 <NZ ≦ −1,
    The angle formed by the transmission axis of the second polarizer and the in-plane slow axis of the second birefringent layer is not 45 ° or 135 °,
    The absolute value | Rth | of the thickness direction retardation of the second birefringent layer is different from the absolute value of the thickness direction retardation of the birefringent layer. The optical element described.
20. A liquid crystal display device comprising the optical element according to any one of claims 1 to 19 and a backlight.
21. The liquid crystal display device according to claim 20, wherein the display mode of the liquid crystal display device is a vertical alignment mode.
22. The optical element is disposed on the observation surface side of the backlight,
    The liquid crystal display device further includes a liquid crystal panel disposed on the observation surface side of the optical element, and a fourth polarizer disposed on the observation surface side of the liquid crystal panel,
    Each of the first polarizer, the second polarizer, and the fourth polarizer is an absorptive polarizer, or a composite polarizer in which an absorptive polarizer and a reflective polarizer are laminated,
    The liquid crystal display device according to claim 20 or 21, wherein at least one of the first polarizer and the second polarizer has a single transmittance larger than that of the fourth polarizer.
23. 23. The liquid crystal display device according to claim 22, wherein one of the first polarizer and the second polarizer disposed on the backlight side has a single transmittance larger than that of the fourth polarizer. .
24. 23. The liquid crystal display device according to claim 22, wherein each of the first polarizer and the second polarizer has a single transmittance greater than that of the fourth polarizer.
25. A liquid crystal display device comprising a liquid crystal panel, a first polarizer, a birefringent layer, a second polarizer and a backlight,
    The first polarizer, the birefringent layer, and the second polarizer are arranged in this order between the liquid crystal panel and the backlight,
    The transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other,
    The biaxial parameter NZ of the birefringent layer satisfies 10 ≦ NZ or NZ ≦ −9,
    The absolute value | Rth | of the thickness direction retardation of the birefringent layer satisfies | Rth | ≧ 200 nm.
26. A liquid crystal display device comprising a liquid crystal panel, a first polarizer, a birefringent layer, a second polarizer and a backlight,
    The first polarizer, the birefringent layer, and the second polarizer are arranged in this order between the liquid crystal panel and the backlight,
    The transmission axis of the first polarizer and the transmission axis of the second polarizer are parallel to each other,
    The biaxial parameter NZ of the birefringent layer satisfies 2 ≦ NZ <10 or −9 <NZ ≦ −1,
    The liquid crystal display device, wherein an angle formed between a transmission axis of the first polarizer and an in-plane slow axis of the birefringent layer is not 45 ° or 135 °.

Images