JPH11326897A - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize light from a light source and to control the decrease of a contrast due to external light in a liquid crystal display. SOLUTION: Unpolarized light from a light source device 12 is made incident on a liquid crystal cell 16 via a circularly polarized light separating layer 14. The liquid crystal cell 16 varies the direction of a director corresponding to the application of an electric field, transforming the direction of the axis of polarization of the circularly polarized incident light, making the resulting light incident on the dichroic linearly polarizing layer 18 on the surface and making only the component which coincides with its transmission axis exit outwards. The dichroic linearly polarizing layer 18 transmits 50% of the incident external light and absorbs the remainder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device using a polarization separation layer that transmits one polarized light component and reflects the other polarized light component, and a liquid crystal cell in which the direction of a liquid crystal director is changed by an electric field. About.

[0002]

2. Description of the Related Art A liquid crystal display device modulates polarized light obtained by transmitting light through a polarizing plate with a liquid crystal layer. For example, as shown in FIG. The display device 1 causes the light emitted from the light source device 2 to enter a dichroic linear polarizing plate 3 of a light absorption type, and causes the linearly polarized light obtained here to enter a liquid crystal cell 4.

In this liquid crystal display device 1, the liquid crystal cell 4
The polarized light that has entered and passed through is modulated by applying a voltage to the electrodes provided in the liquid crystal cell 4 and changing the liquid crystal layer in the cell with an electric field, or modulated without an electric field. Instead, the light is emitted from the liquid crystal cell 4 and only the polarized light in a specific direction is transmitted by the light-absorbing dichroic linear polarizing plate 5 disposed outside the liquid crystal cell 4.

[0004] The dichroic linear polarizing plate 3 of the light absorption type,
Numeral 5 transmits polarized light in the transmission axis direction and absorbs most of the polarized light in the direction perpendicular to the transmission axis. Therefore, about 50% of the light (non-polarized light) emitted from the light source device 2 is emitted. 2
The light is absorbed by the chromatic linearly polarizing plate 3, so that the light use efficiency of the liquid crystal display device 1 as a whole is lowered.
It was necessary to make the light enter the chromatic linear polarizing plate 3.

However, when the light emission amount of the light source device 2 is increased as described above, not only power consumption is increased, but also the heat generation amount of the light source device 2 is increased, which adversely affects the liquid crystal in the liquid crystal cell 4. The problem arises.

On the other hand, for example, Japanese Patent Application Laid-Open No. 4-502
As disclosed in JP-A-524-524 and JP-A-6-130424, the use of a cholesteric liquid crystal layer to transmit or reflect unpolarized light from a light source to circularly polarized light in the right or left turning direction. The circularly polarized light in one of the directions of rotation that has been separated and transmitted by the cholesteric liquid crystal layer is incident on the liquid crystal cell, and the reflected circularly polarizing plate in the other direction of rotation is reflected by the reflector, and the direction of rotation is reversed. There has been proposed a liquid crystal display device that transmits light and improves light use efficiency.

Further, as disclosed in Japanese Patent Publication No. 9-506985, unpolarized light from a light source is separated into two linearly polarized lights by transmission or reflection using a stretched multilayer film, and one of the transmitted ones is transmitted. Linearly polarized light is incident on the liquid crystal cell, and the reflected, linearly polarized light in the direction orthogonal to the above is changed in the polarization direction by a reflector, and then guided again to the stretched multilayer film so as to improve the light use efficiency. A liquid crystal display device has been proposed.

[0008] The liquid crystal layer in the liquid crystal display device disclosed in JP-A-4-502524 and JP-A-6-130424 has a light phase of π (λ / 2) when no electric field is applied. ) Or π / 2 (λ / 4) so that the phase of light is not shifted when an electric field is applied. Light emitted from this liquid crystal layer is a circularly polarizing plate disposed outside. , Where the light is transmitted or reflected depending on the degree of polarization of the incident light.

In the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 9-506985, one of the linearly polarized lights transmitted through the stretched multilayer film is incident on a liquid crystal cell. There is no disclosure of retardation.

[0010]

SUMMARY OF THE INVENTION The above-mentioned Japanese translation of PCT application No. Hei 4-502
The liquid crystal display devices disclosed in Japanese Patent Application Publication No. 524 and Japanese Patent Application Laid-Open No. Hei 6-130424 have extreme deterioration in the visibility of the liquid crystal display and a significant decrease in contrast due to the following reasons, and display quality is insufficient. There was a problem that it is.

That is, in the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 4-502524, a circularly polarizing plate disposed outside a liquid crystal layer and directly visible from the outside is formed of a low-pitch cholesteric coating film having wavelength selective reflection. As a result, about 50% of the external light incident on the circularly polarizing plate is reflected, which directly enters the observer's eyes, and extremely deteriorates the visibility.

Similarly, in the liquid crystal display device described in JP-A-6-130424, the color selection layer directly visible from the outside is a circular polarizing plate made of, for example, cholesteric liquid crystal. About 50% of the outside light
Is directly reflected, and the visibility is extremely reduced.

Further, the liquid crystal display devices disclosed in the above-mentioned JP-A-4-502524 and JP-A-6-130424 have
In both cases, since the control of the amount of phase shift of light in the cholesteric liquid crystal layer is not always as designed, a decrease in contrast is inevitable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has a simple structure without deterioration in visibility and a significant decrease in contrast due to external light. In the case of a display device, the use efficiency of light can be significantly improved, and in the case of a reflection type liquid crystal display device, a liquid crystal display device which has high contrast and can perform colorization using birefringence by a liquid crystal layer. The purpose is to provide.

[0015]

According to the present invention, a light source and a circularly polarized light component of one of right and left turning directions of light emitted from the light source are transmitted. It comprises a circularly polarized light separating layer for reflecting the other circularly polarized light component, a liquid crystal layer having a retardation value for substantially shifting the phase of transmitted light by π / 2, and an electrode for applying an electric field to the liquid crystal layer. Converting the circularly polarized light transmitted through the circularly polarized light separating layer into linearly polarized light until the circularly polarized light separating layer emits light in the opposite direction, and applying an electric field from the electrode to the liquid crystal layer. A liquid crystal cell that changes the direction of the director of the liquid crystal by applying the same, thereby changing the polarization axis of the linearly polarized light, and the liquid crystal cell is disposed on the side opposite to the circularly polarized light separating layer, and is incident from the liquid crystal cell. One of the linearly polarized light components Transmitted through, the liquid crystal display device which is characterized in that a this perpendicular direction light absorbing dichroic linear polarizing layer which absorbs linearly polarized light component of the is to achieve the above object.

According to a second aspect of the present invention, a light source,
Of the light emitted from the light source, a linearly polarized light separating layer that transmits one linearly polarized light component and reflects a linearly polarized light component in a direction orthogonal to the linearly polarized light component, and substantially shifts the phase of the transmitted light by π / 2. It comprises a liquid crystal layer having a retardation value and an electrode for applying an electric field to the liquid crystal layer, and emits linearly polarized light transmitted through and incident on the linearly polarized light separating layer in a direction opposite to the linearly polarized light separating layer. A liquid crystal cell that converts the direction of the director of liquid crystal by applying an electric field from the electrode to the liquid crystal layer, thereby changing the ellipticity of the circularly polarized light, The liquid crystal cell is disposed on the side opposite to the linearly polarized light separating layer, and among the circularly polarized light incident from the liquid crystal cell, transmits one circularly polarized light component in a right or left turning direction, and transmits the other circularly polarized light component. Absorbs light It is intended to achieve the above object by the liquid crystal display device characterized by comprising a color-circular polarization layer.

According to a third aspect of the present invention, there is provided a light-absorbing dichroic linear line which transmits one linearly polarized light component of external light and absorbs a linearly polarized light component in a direction orthogonal thereto. A polarizing layer, a liquid crystal layer having a retardation value for substantially shifting the phase of transmitted light by π / 2, and an electrode for applying an electric field to the liquid crystal layer. And converts the incident linearly polarized light into circularly polarized light until the light exits in the opposite direction to the dichroic linearly polarizing layer, and applies an electric field to the liquid crystal layer from the electrode to provide a liquid crystal director. And the liquid crystal cell so as to change the ellipticity of the circularly polarized light, thereby transmitting the circularly polarized light component in one of the right and left turning directions of the light transmitted through the liquid crystal cell and the other. Circularly polarized light separating layer that reflects the circularly polarized light component of A light absorbing layer disposed on the opposite side of the separated layer to the liquid crystal cell and absorbing light transmitted through the circularly polarized light separating layer, the above object is achieved by a liquid crystal display device. .

According to a fourth aspect of the present invention, there is provided a light absorbing type that transmits one circularly polarized light component in the right or left turning direction and absorbs the other circularly polarized light component of the external light. And the phase of transmitted light is substantially π / 2
A liquid crystal layer having a shifting retardation value; and an electrode for applying an electric field to the liquid crystal layer. The circularly polarized light transmitted through the dichroic circularly polarizing layer and incident thereon is converted into the dichroic circularly polarizing layer. Is converted to linearly polarized light until it is emitted in the opposite direction, and the direction of the director of the liquid crystal is changed by applying an electric field from the electrode to the liquid crystal layer, thereby changing the polarization axis of the linearly polarized light. A liquid crystal cell to be changed, a linearly polarized light separating layer that transmits one linearly polarized light component of light transmitted through the liquid crystal cell and reflects a linearly polarized light component in a direction orthogonal to the liquid crystal cell, and the liquid crystal of the linearly polarized light separating layer The above object is achieved by a liquid crystal display device comprising: a light absorption layer disposed on the side opposite to the cell and absorbing light transmitted through the linearly polarized light separation layer.

Further, the circularly polarized light separating layer may be constituted by an optical rotation selecting layer comprising a cholesteric liquid crystal layer.

Further, the linearly polarized light separating layer has a planar multilayer structure in which three or more birefringent films are laminated, and has a vibration direction perpendicular to each other in the plane of each layer.
Of the two lights, the difference in refractive index between layers adjacent in the thickness direction with respect to one light may be different from the difference in refractive index between layers adjacent in the thickness direction with respect to the other light.

Further, the circularly polarized light separating layer is formed by laminating a retardation layer having a retardation value for substantially shifting the phase of transmitted light by π / 2 and a birefringent film into three or more layers. Of two lights having vibration directions perpendicular to each other in the plane of each layer, a difference in refractive index between layers adjacent to each other in the thickness direction for one light, and a difference between the layers adjacent to each other in the thickness direction for the other light. A planar multilayer structure having a different refractive index may be used, and linearly polarized light transmitted through the planar multilayer structure may be converted into circularly polarized light.

Further, the linearly polarized light separating layer comprises a retardation layer having a retardation value for substantially shifting the phase of transmitted light by π / 2, and an optical rotation selecting layer comprising a cholesteric liquid crystal layer. The circularly polarized light transmitted through the cholesteric liquid crystal layer may be converted to linearly polarized light.

When the light incident on the liquid crystal layer is circularly polarized light, the direction of the director of the liquid crystal is changed to substantially -45 to 45 degrees with respect to the light transmission axis of the dichroic linearly polarizing layer. As described above, a circuit for controlling the voltage between the electrodes may be provided.

Further, when the light incident on the liquid crystal layer is circularly polarized, the direction of the director of the liquid crystal is changed to substantially -45 to 45 degrees with respect to the direction of the electric field vector of the incident linearly polarized light. And a circuit for controlling the voltage between the electrodes.

Further, in the liquid crystal cell, the liquid crystal layer is sandwiched between two substrates, the electrodes are formed on one of the electrodes, and the direction of the electric field when a voltage is applied to the electrodes is adjusted to the direction of the substrate surface. The liquid crystal layer may have a portion substantially parallel to the liquid crystal layer and rotate in a direction in which most of the directions of the liquid crystal molecules in the liquid crystal layer are substantially parallel to the substrate surface.

In the present invention, a dichroic polarizing plate of a light absorption type is used on the surface viewed from the outside, and the retardation value of the liquid crystal layer and the direction of the director of the liquid crystal are adjusted in accordance with the dichroic polarizing plate. Change, thereby preventing a significant decrease in contrast and visibility due to external light without lowering the light use efficiency, and keeping the birefringence of the liquid crystal layer substantially constant. By using it as it is, a color liquid crystal display device with good contrast can be obtained.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, a liquid crystal display device 10 according to a first embodiment of the present invention has a light source 12 that emits unpolarized light, and a light source 12 that emits unpolarized light. Circularly polarized light separating layer 1 that transmits one (elliptical) circularly polarized light component and reflects the other (elliptically) polarized light component in the right or left turning direction.
4 and a liquid crystal layer 22 (see FIG. 2) having a retardation value that substantially shifts the phase of transmitted light by π / 2, and pixel electrodes 24A and 24B for applying an electric field to the liquid crystal layer 22.
And converts the circularly polarized light entering through the circularly polarized light separating layer 14 into linearly polarized light before exiting in the opposite direction to the circularly polarized light separating layer 14, and the liquid crystal layer An electric field is applied to the pixel electrodes 24 from the pixel electrodes 24A and 24B to change the direction of the liquid crystal director, thereby changing the polarization axis of the linearly polarized light, and the circularly polarized light separating layer of the liquid crystal cell 16. And a light-absorbing dichroic linearly polarizing layer 18 that receives the linearly polarized light transmitted through the liquid crystal cell 16 and is disposed on the side opposite to the liquid crystal cell 16.

In FIG. 1, “← →” and “•” indicate electric field vibration vectors of linearly polarized light, respectively.
Is the direction in the plane of the paper, and “•” is the direction perpendicular to the paper.
“R” and “L” indicate right circularly polarized light and left circularly polarized light, respectively.

A reflection layer 12A is formed on the back surface (lower side surface in FIG. 1) of the light source device 12. Reflective layer 12
A reflects the polarized light component emitted from the light source device 12 and reflected by the circularly polarized light separating layer 14 again in the direction of the circularly polarized light separating layer 14, inverting the phase of the circularly polarized light component at this time, and It allows transmission.

The circularly polarized light separating layer 14 is composed of, for example, a cholesteric liquid crystal layer.
The chromatic linear polarization layer 18 transmits polarized light in the transmission axis direction,
It absorbs most of the polarized light in the direction perpendicular to the transmission axis. By immersing a PVA (polyvinyl alcohol) film in a potassium iodide-iodine aqueous solution, and then stretching the PVA film in one direction in a boric acid aqueous solution, And a dichroic polarizing material such as a so-called iodine-based polarizing plate in which iodine molecules absorbed in the PVA film are arranged in one direction and a protective film is laminated, or a dye-based polarizing plate.

The liquid crystal layer in the liquid crystal cell 16 makes the phase of transmitted light substantially π regardless of the application of an electric field.
It is adjusted so as to have a retardation value for shifting by ２.

This adjustment can be performed with various known liquid crystals, for example, a nematic (Nn) liquid crystal by controlling the birefringence and thickness of the liquid crystal layer.

A description will be given using a Poincare sphere.

The Poincare sphere is used to describe the polarization or to examine how the shape of the polarization changes when the phase changes. In FIG. 2, the upper and lower poles of the sphere are Each point represents left circularly polarized light and right circularly polarized light. Points on the equator indicate linearly polarized light, and the other points indicate elliptically polarized light.

An arbitrary point H on the equator indicates horizontal polarization, and a point V on the equator opposite to the diameter passing through the point H indicates vertical polarization. Polarizations perpendicular to each other will be represented by points at one end of a diameter, and generally assume that the radius of the sphere is 1, but may be proportional to the intensity of the light beam.

An arbitrary point P on the surface of a Poincare sphere having a unit radius is represented by a longitude 2λ and a latitude 2ω. However, -180 ° <2λ <180 °, -90 ° <
2ω <90 °.

The longitude is positive when measured clockwise from point H, and the latitude is positive when measured downward from the equator, that is, toward the pole representing right-handed circularly polarized light. Therefore, the coordinates of the point P in FIG. 2 are positive.

An arbitrary point P represents perfect elliptically polarized light having an azimuth angle λ of the ellipse and an ellipticity of tan | ω |. Further, whether the point P is counterclockwise or clockwise is determined depending on whether the point P is in the upper hemisphere or the lower hemisphere. In summary, the following equations (1) and (2) hold for the cross-sectional view of the elliptically polarized light represented by the point P.

Α = λ (1) b / a = tan | ω | (2)

The cross section of monochromatic light is generally elliptical,
This ellipse can be represented using the symbols shown in FIG. The angle α between the semi-major axis and the X axis is called the azimuth angle of the sectional view, and 90 ° ≧ α ≧ −90 °. Ratio of two half axes b
/ A is called ellipticity, and if tan ^-1 b / a = β, 90 °
≧ β ≧ −90 °.

The direction of polarized light is clockwise when 2ω is positive, and counterclockwise when 2ω is negative. Thus, each point on the Poincare sphere represents a different polarization shape. That is, one polarization shape can be represented by one point on the Poincare sphere.

Thus, for example, if the counterclockwise perfect circularly polarized light at the point of the upper pole of the Poincare sphere is shifted in the positive direction by π / 2 at the azimuth λ = 0, the point H on the equator in the Poincare sphere becomes To reach. That is, the circularly polarized light becomes horizontal linearly polarized light by being shifted by π / 2.

When the clockwise complete circularly polarized light at the lower pole position of the Poincare sphere is shifted by π / 2 at the azimuth λ = 0, it reaches the point V on the equator and becomes a vertical linearly polarized light.

The structure of the liquid crystal cell 16 will be described in more detail with reference to FIGS.

The liquid crystal cell 16 is, as shown in FIG.
A liquid crystal layer 22 sandwiched between two substrates 20A and 20B;
In FIG. 4, when a voltage is applied from the circuit 26 to the upper side surface of the lower substrate 20A, the pixel electrodes 24A and 24B are disposed apart from each other in a direction parallel to the lower surface of the substrate 20A. Is a direction in which the direction of the electric field is substantially parallel to the substrate surface and the direction of the director D of most of the liquid crystal molecules in the liquid crystal layer 22 is substantially parallel to the substrate surface (in general, IPS (In Plain)). Switching) mode.)

Further, the direction of the director D of the liquid crystal in the liquid crystal layer 22 will be described in detail. As shown in FIG. 5, when no electric field is applied between the pixel electrodes 24A and 24B, the direction of the director D of the liquid crystal is substantially perpendicular to the plane of the paper, as shown in FIG. When an electric field is applied between the pixel electrodes 24A and 24B, the director D of the liquid crystal moves in a direction substantially parallel to the paper surface.

FIG. 5 shows a case where the dielectric anisotropy Δε is positive for the liquid crystal, but when the dielectric anisotropy Δε is negative,
In the state where no electric field is applied between the pixel electrodes 24A and 24B, the direction of the director D of the liquid crystal is substantially parallel to the paper surface, and in the state where the electric field is applied between the pixel electrodes 24A and 24B. The liquid crystal director D is adapted to move in a direction substantially perpendicular to the plane of the paper.

In the example shown in FIG. 1, the change in the director D of the liquid crystal changes the linear polarization axis of the linearly polarized light when the polarization state of the circularly polarized light incident on the liquid crystal cell 16 is shifted to the linearly polarized light. Is the change in the azimuth angle λ direction on the sphere of Poincare in FIG. 2, that is, the longitude direction.

Therefore, for example, the horizontal linearly polarized light represented by the point H on the equator in the Poincare sphere has a tilt of the polarization axis as represented by the point moved on the equator by the change of the director D of the liquid crystal. Be changed.

With respect to the circularly polarized light, the polarization axis changes due to the change in the director D of the liquid crystal. For example, the left-handed circularly polarized light indicated by the upper pole point in the Poincare sphere is changed in the direction by the change in the director D of the liquid crystal. The angle λ changes,
It will be represented by a point on the equator that has moved in the latitude direction.

Here, the liquid crystal layer 22 is adjusted so as to have a retardation value that substantially shifts the phase of transmitted light by π / 2, and determines whether or not an electric field is applied between the pixel electrodes 24A and 24B. Regardless, the retardation values are almost the same. This adjustment can be performed with various known liquid crystals, for example, a nematic (Nn) liquid crystal by controlling the birefringence and thickness of the liquid crystal layer. The directions of the directors D of the liquid crystal are substantially the same as those of the substrates 20A, 2A and 2B.
It is parallel to 0B.

The term “substantially” in the above “substantially shift by π / 2” and “substantially parallel to the substrates 20A and 20B” means, for example, a pretilt angle of a liquid crystal,
It is meant to include a case where the ideal state slightly deviates due to various disturbances or the like.

Note that "R. Kiefer, B. Weber, F. Windscheid,
G. Baur, Proceedings of the 12th International D
isplay Reserch Conference, Japan Display '92 .547
(1992), there is a IPS mode. In this IPS mode, although the twist angle of the liquid crystal changes, the director of the liquid crystal retains the function of shifting the phase of light by π / 2. Direction has not changed.
Therefore, the IPS mode and the liquid crystal cell 16 have slightly different characteristics of the liquid crystal layer.

As described above, the circularly polarized light separating layer 14 is composed of, for example, a cholesteric liquid crystal layer. This cholesteric liquid crystal layer generally exhibits an optical rotation selection characteristic that separates an optical rotation component in one direction and an optical rotation component in the opposite direction based on a physical molecular arrangement, but has a helical axis in a planar arrangement. The incident light is a right-handed rotation light and a left-handed rotation light.
The light is split into two circularly polarized lights, one is transmitted and the other is reflected.

This phenomenon is known as circular dichroism,
When the optical rotation direction of the circularly polarized light is appropriately selected with respect to the incident light, the circularly polarized light having the same optical rotation direction as the helical axis direction of the cholesteric liquid crystal is selectively scattered and reflected.

The maximum optical rotation scattering in this case is expressed by the following (3)
It occurs at the wavelength λ0 in the equation.

Λ 0 = nav · p (3)

Here, p is a helical pitch, and nav is an average refractive index in a plane perpendicular to the helical axis.

At this time, the wavelength bandwidth Δλ of the reflected light is
It is expressed by the following equation (4).

Δλ = Δn · p (4)

Here, Δn = n (‖) -n (perpendicular), where n (‖) is the maximum refractive index in a plane perpendicular to the helical axis, and n (perpendicular) is in a plane parallel to the helical axis. Is the maximum refractive index.

As a method for broadening the wavelength bandwidth Δλ, a method of changing the helical pitch (for example,
US Pat. No. 5,691,789), several cholesteric liquid crystal layers having different p are stacked (for example, see Japanese Patent Application Laid-Open No. 9-30467).
0) and the like.

It is known that the wavelength λφ of the selectively scattered light of the light obliquely incident on the helical axis of the planar array shifts to a shorter wavelength side than λ0.

As a material of the cholesteric liquid crystal, an optically active 2-methylbutyl group, 2-methylbutoxy group or 4-methylhexyl group is bonded to a terminal group of a nematic liquid crystal compound such as a Schiff base, an azo type, an ester type or a biphenyl type. Preferred are chiral nematic liquid crystal compounds.

In general, a polymer liquid crystal is a polymer in which a mesogen group exhibiting a liquid crystal is introduced into a main chain, a side chain, or a position of a main chain and a side chain. A polymer cholesteric liquid crystal also has, for example, a cholesteryl group. It can be obtained by introduction into the side chain.

The polarization separation effect of the cholesteric liquid crystal is such that one circularly polarized light component (clockwise or counterclockwise) is transmitted by the cholesteric liquid crystal and the other circularly polarized light component is reflected. Upon reflection, right (left) circularly polarized light is reflected as it is right (left) circularly polarized light.

The light source device 12 is, for example, a transparent thin-film white light source made of thin-film electroluminescence sandwiched between transparent resin sheets having transparent electrodes, and is made of, for example, a metal thin film as described above. Reflective layer 12A
Is provided on the back.

The light source device 12 may be a so-called edge light type white surface light source in which a linear light source is disposed on a light guide plate, for example.

In the liquid crystal display device 10 as described above,
In the non-polarized light emitted from the light source device 12, only the circularly polarized light component in one of the turning directions of the light passes through the circularly polarized light separation layer 14 and reaches the liquid crystal cell 16.

For example, if only the left circularly polarized light component is set to be transmitted as shown in FIG. 1, the other right circularly polarized light component is reflected by the circularly polarized light separating layer 14 and
Circularly polarized light in the left-handed direction that transmits through the circularly polarized light separating layer 14 because the phase is inverted when reflected by the second reflective layer 12A or the light is transmitted through the circularly polarized light separating layer 14 because the phase is disturbed in the light source device (for example, by the light diffusion function). It becomes light and enters the liquid crystal cell 16.

The phase of the counterclockwise circularly polarized light passing through the liquid crystal cell 16 is substantially shifted by π / 2, regardless of whether or not an electric field is applied. Therefore, the liquid crystal cell 1
Circularly polarized light incident on the liquid crystal cell 6 becomes linearly polarized light.
6 out.

This will be described with reference to the Poincare sphere of FIG. 2. When the azimuth λ = 0 is shifted from the point of the upper pole of the Poincare sphere, for example, the left-handed circularly polarized light becomes horizontal linearly polarized light ( Point H), and when shifted at an azimuth angle λ = 90 °, the light becomes perpendicular linearly polarized light (point V).

As described above, the liquid crystal layer 2 in the liquid crystal cell 16
By applying a voltage to the pixel 2 from the pixel electrodes 24A and 24B, the polarization axis of the passing polarized light can be modulated by changing the direction of the director D of the liquid crystal while maintaining the retardation value.

On the Poincare sphere of FIG. 2, the phase is π /
As a result of the two shifts, the vertical linearly polarized light indicated by a point V on the equator becomes linearly polarized light having an inclination indicated by a point moved on the equator.

When circularly polarized light is incident on the liquid crystal layer 22, the direction of the director of the liquid crystal is changed to substantially -45 to 45 degrees with respect to the light transmission axis of the dichroic linearly polarizing layer. Preferably, a circuit 26 for controlling the voltage between the electrodes is provided.

The electric field applied to the liquid crystal layer 22 is controlled by the circuit 26 by setting the polarization transmission axis of the dichroic linear polarization layer 18 to coincide with or orthogonal to the polarization axis of the linearly polarized light emitted from the liquid crystal cell 16. In particular, by controlling the electric field so as to change the direction of the director of the liquid crystal substantially from -45 to 45 degrees with respect to the linearly polarized light transmission axis of the dichroic linearly polarizing plate 18, the dichroic linearly polarized light is controlled. The amount of light transmitted through the layer 18 can be adjusted from the maximum value to the minimum value, and a good liquid crystal display function, for example, a gradation display function can be provided.

This is expressed by the following equation (5).

I = I ₀ sin ² 2θ (V) sin ² (πdΔn / λ) (5)

Here, θ (V) is the rotation angle of the liquid crystal molecules, I
Is the intensity of light transmitted through the dichroic linear polarizing layer 18, I ₀ is the intensity of the incident light, θ is the angle between the long axis (optical axis) of the liquid crystal molecule and the incident polarization direction, and Δn and d are the multiples of the liquid crystal, respectively. The refractive index, cell thickness, and λ indicate the wavelength of the incident light.

FIG. 1 shows a so-called bright display in which the linearly polarized light is emitted from the dichroic linearly polarizing layer. As shown in FIG.
If the direction of the director D of the liquid crystal in the inside is set to the direction in which the polarization direction of the linearly polarized light emitted from the liquid crystal cell 16 is orthogonal to the case of FIG. 1, a so-called dark display is obtained.

Since the dichroic linear polarizing layer 18 is composed of a light absorbing type dichroic polarizing plate, external light (non-polarized light) is incident on the surface of the dichroic linear polarizing layer 18. Also, since 50% of the light is absorbed and the remaining 50% is transmitted, and there is almost no reflection component, a decrease in the contrast of the screen of the liquid crystal display device 10 can be significantly suppressed.

Since the birefringence of the liquid crystal layer 22 is used, a color liquid crystal display can be performed without providing a separate color filter.

Next, a liquid crystal display device 30 according to a second embodiment of the present invention shown in FIG. 8 will be described.

In FIG. 8, the same parts as those in the liquid crystal display device 10 shown in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and description thereof will be omitted.

The liquid crystal display device 30 includes the light source device 12
A linearly polarized light separating layer 32 that transmits one linearly polarized light component of the light emitted from the light source device 12 and reflects a linearly polarized light component in a direction perpendicular to the linearly polarized light component; a liquid crystal cell 16; And a light-absorbing dichroic circularly polarizing layer 34 for receiving polarized light transmitted therethrough.

The linearly polarized light separating layer 32 has a planar multilayer structure in which three or more birefringent films are laminated, and has a vibration direction perpendicular to each other in the plane of each layer.
Of the two lights, the difference in the refractive index between the layers adjacent in the thickness direction for one light is different from the difference in the refractive index between the layers adjacent in the thickness direction for the other light, The light is transmitted and the other light is reflected.

The film having birefringence as described above is disclosed in, for example, JP-A-3-75705, JP-T-Hei 9-5-5.
As disclosed in Japanese Patent Application Laid-Open No. 06837 and the like, in-plane birefringence (refractive index anisotropy) of polycarbonate resin, polyester resin (for example, crystalline naphthalenedicarboxylic acid polyester), polyvinyl alcohol resin, cellulose acetate resin, and the like. ) Can be obtained by a method such as stretching.

For example, adjacent birefringent layers (films)
Has a refractive index of substantially n for a light beam oscillating in the X-axis direction.
x, and the refractive index difference Δnx (= | nx−nx |) between adjacent layers in the X-axis direction is substantially zero.

On the other hand, for example, among the three birefringent layers, the refractive indices of the first layer and the third layer with respect to the light oscillating in the Y-axis direction are both ny ₁ and the refractive index of the second layer in the same direction is the same. Assuming that the refractive index is ny ₂ (≠ ny ₁ ), the refractive index Δny between adjacent layers in the Y-axis direction is not substantially zero.

The reflection of light oscillating in the direction with a large refractive index difference (Y-axis direction) is greater than the reflection of light oscillating in the direction with a small refractive index difference (X-axis direction). Light transmission is greater than light transmission in the Y-axis direction.

Therefore, even if the linearly polarized light separating layer 32 has a planar multilayer structure, the refractive index is substantially the same for the light oscillating in the X-axis direction. Only a slight surface reflection occurs at two points, the surface and the exit surface.

On the other hand, for the light oscillating in the Y-axis direction, the refractive index in the planar multilayer structure is different between the respective layers. Surface (interface) reflection occurs between the layers, and the greater the number of birefringent layers, the greater the number of times of reflection of light vibrating in the Y-axis direction.

The dichroic circularly polarizing layer 34 is the same as the dichroic linear polarizing layer 18 in the liquid crystal display device 10 shown in FIG.
The λ / 4 retardation layer (plate) 35 is placed on the liquid crystal cell 16 side such that linearly polarized light is incident at an angle of 45 degrees with respect to the slow axis or fast axis direction in the plane of the λ / 4 retardation layer 35. It is formed by a method such as lamination on the right, transmits one of the right or left-handed circularly polarized light components of the incident light, and almost absorbs the other.

The λ / 4 retardation layer (plate) 35 is
Any function that shifts the phase of light by λ / 4 is sufficient, and it may be formed from a liquid crystal material or an inorganic material.
Stretching a film made of a polymer such as CAB, PS, PMMA, norbornene resin (stretching ratio of 1.3 to 4 times)
It is preferable to use a stretched film obtained from the viewpoint of mass productivity.

In order to obtain a wide-band λ / 4 retardation plate that shifts the phase of light λ / 1 over the entire wavelength band of visible light, a λ / 4 retardation plate and a λ / 2 retardation plate are required. It is preferable to arrange the λ / 2 phase difference plate on the polarizing plate side by crossing the fast axis or the slow axis at an angle of 60 ° ± 10 °. At that time, the relationship between the transmission axis of the polarizing plate and the fast axis or slow axis of the λ / 2 phase difference plate is such that the amount of transmitted circularly polarized light incident on the λ / 4 phase difference plate is maximized, or It is appropriately adjusted so that the amount of transmitted circularly polarized light that is opposite to the circularly polarized light is minimized.

In the liquid crystal display device 30, one linearly polarized light component of the unpolarized light from the light source device 12 is transmitted through the linearly polarized light separating layer 32, and a linearly polarized light component in a direction orthogonal to this is reflected.

The reflected linearly polarized light component is
The phase is disturbed by being reflected in the reflection layer 12A or in the light source device (for example, by the light diffusion function), and the component transmitted through the linearly polarized light separating layer 32 increases.

When the direction of the electric field vector of the linearly polarized light in the liquid crystal layer 22 makes an angle of substantially 45 degrees with the direction of the director of the liquid crystal layer, the linearly polarized light incident on the linearly polarized light separating layer 32 (ie, When the linearly polarized light is incident at an angle of 45 degrees with respect to the slow axis direction or the fast axis direction of the liquid crystal layer), the phase thereof is substantially shifted by π / 2 to become circularly polarized light.

This will be described with reference to the Poincare sphere in FIG. 2. For example, a vertically linearly polarized light indicated by a point V on the equator is counterclockwise shifted by π / 2 positive direction. The horizontal linearly polarized light indicated by the point H on the equator is shifted by π / 2 in the positive direction, so that the clockwise circularly polarized light represented by the point on the lower pole of the sphere is obtained. It becomes light.

The angle at which linearly polarized light enters the liquid crystal layer with respect to the slow axis direction or the fast axis direction is changed by the electric field applied to the liquid crystal layer 22, and the ellipticity of the circularly polarized light is modulated. You. This will be described with reference to the Poincare sphere in FIG. 2. When the linearly polarized light changes to circularly polarized light, the light is modulated in the longitudinal direction on the Poincare sphere, and the ellipticity of the circularly polarized light changes. .

For example, when the angle at which the linearly polarized light enters the liquid crystal layer with respect to the slow axis direction or the fast axis direction is 0 degrees, the linearly polarized light incident on the liquid crystal layer remains linearly polarized light. When the angle at which the polarized light enters the liquid crystal layer with respect to the slow axis direction or the fast axis direction is -45 degrees, the linearly polarized light that has entered the liquid crystal layer is circularly polarized light that is opposite to the circularly polarized light.

That is, when linearly polarized light is incident on the liquid crystal layer 22, the circuit 26 changes the direction of the director of the liquid crystal to substantially -45 to 45 degrees with respect to the direction of the electric field vector of the incident linearly polarized light. In order to achieve this, it is preferable to control the voltage between the electrodes.

Accordingly, the pixel electrodes 24A,
By controlling the voltage applied from 24B, it is possible to adjust the amount of light transmitted through the dichroic circularly polarizing layer 34, thereby enabling gradation display. At this time, 2
Circularly polarized light that does not pass through the chromatic circularly polarized light layer 34, for example, counterclockwise circularly polarized light as shown in FIG. 8, is absorbed by this.

In this liquid crystal display device 30,
When no electric field is applied to the liquid crystal layer 22 in the liquid crystal cell 16, as shown in FIG. 9, linearly polarized light incident on the liquid crystal cell 16 is modulated into left-handed circularly polarized light, resulting in a so-called dark display.

Further, in the liquid crystal display device 30,
Even when external light that is unpolarized light is incident on the chromatic circularly polarizing layer 34, 50% of the light is absorbed, so that a decrease in screen contrast due to reflection can be suppressed.

Since the birefringence of the liquid crystal layer 22 is used, a color liquid crystal display can be performed without providing a separate color filter.

The liquid crystal display devices 10 and 30 are both transmissive types, but the present invention is not limited to this, and can be applied to a reflective type liquid crystal display device.

The liquid crystal display device 40 shown in FIG. 10 is a reflection type of the liquid crystal display device 10 shown in FIG. 1, and is provided with a light absorbing layer 36 instead of the light source device 12 shown in FIG.

Since the other structure is the same as that of the liquid crystal display device 10 of FIG. 1, the same portions are denoted by the same reference numerals and description thereof will be omitted.

Here, the light absorbing layer 36 is made of, for example, black paper, a resin plate, a film, a thin film, or the like, whose surface is matted to prevent reflection.

In the reflection type liquid crystal display device 40, only linearly polarized light components in one direction, for example, horizontal linearly polarized light, of the external light (non-polarized light) are transmitted through the dichroic linearly polarizing layer 18. Incident on the liquid crystal cell 16.

Of the external light, a vertical linearly polarized light component which cannot pass through the dichroic linearly polarizing layer 18 is absorbed by this.
Therefore, since no reflected light is generated, a decrease in contrast due to the reflected light can be suppressed.

The polarization axis of the linearly polarized light incident from the dichroic linearly polarizing layer 18 is modulated by a change in the electric field applied to the liquid crystal cell 16. On the other hand, since the liquid crystal layer 22 has a retardation value that substantially shifts the phase of transmitted light by π / 2 as described above, it has the function of shifting linearly polarized light to circularly polarized light.

The turning direction of the circularly polarized light is determined by the above-described modulation of the polarization axis. When the light enters the circularly polarized light separating layer 14, the light is reflected when the turning direction is left and transmitted when it is right. .

Explaining with reference to the Poincare sphere in FIG. 2, the incident horizontal linearly polarized light changes the director D of the liquid crystal by -45.
By changing it by ~ 45 degrees, from the point H on the equator,-
In the case of 45 to 0 degrees, the light moves from the upper pole point to the point H to change from counterclockwise circularly polarized light to linearly polarized light.
In the case of the degree, the light moves from the lower pole point to the point H and changes from clockwise circularly polarized light to linearly polarized light.

The counterclockwise circularly-polarized light L reflected by the circularly-polarized light separating layer 14 returns to the liquid crystal cell 16 in the opposite direction to that described above, and when transmitted through the liquid crystal cell 16, the liquid crystal display device 1 of FIG.
As in the case of 0, it is emitted as linearly polarized light,
The polarization axis is modulated by the direction of the director D of the liquid crystal and passes through the dichroic linear polarization layer 18 to become display light. Therefore, the amount of light reflected by the circularly polarized light separating layer 14 and transmitted through the liquid crystal cell 16 can be adjusted by the voltage applied to the liquid crystal layer 22. That is, gradation display can be performed.

In the case where the liquid crystal layer 22 produces clockwise circularly polarized light, the light is emitted from the liquid crystal layer 22, passes through the circularly polarized light separating layer 14, and is absorbed and removed by the light absorbing layer 36. As shown in FIG. For this reason, a display state with very good contrast can be obtained in comparison with the counterclockwise circularly polarized light L (display light) reflected by the circularly polarized light separating layer 14 and transmitted through the liquid crystal cell 16.

Since the birefringence of the liquid crystal layer 22 is used, a color liquid crystal display can be performed without providing a separate color filter.

Next, the reflection type liquid crystal display device 50 shown in FIG. 12 will be described.

The liquid crystal display device 50 is different from the liquid crystal display device 30 shown in FIG.
A light absorbing layer 36 similar to the above is disposed, and the dichroic circularly
4 is devised.

The dichroic circularly polarizing layer 34 is also provided with a λ on the reflection side of the dichroic linearly polarizing layer 34 of the liquid crystal display device 10 shown in FIG. /
The four phase difference layers are laminated such that the fast axis or the slow axis is at an angle of 45 degrees to the transmission axis of the dichroic linear polarizing plate.

In the liquid crystal display device 50, external light (non-polarized light) enters the dichroic circularly polarized light layer 34, and only clockwise circularly polarized light R enters the liquid crystal cell 16. Since the other counterclockwise circularly polarized light component L of the external light is absorbed by the dichroic circularly polarized light layer 34, the contrast of the screen is not reduced by the reflected light.

Clockwise circularly polarized light R incident on the liquid crystal layer 22
Since the liquid crystal layer 22 has a retardation value that substantially shifts the phase of light by π / 2, the electric field applied to the liquid crystal layer 22 in the Poincare sphere of FIG. By changing the direction,
The state is from the lower pole point to linearly polarized light indicated by point V or point H on the equator, and the ellipticity of circularly polarized light is modulated.

Accordingly, the linearly polarized light emitted from the liquid crystal cell 16 is reflected or transmitted by the linearly polarized light separating layer 32 depending on the polarization state.

In the example of FIG. 12, only the vertical linearly polarized light component is reflected by the linearly polarized light separating layer 32, enters the liquid crystal cell 16, and is converted into left-handed circularly polarized light by the liquid crystal layer. There is no bright indication because the light cannot pass through the layer 34.

As shown in FIG. 13, when only vertically linearly polarized light is emitted from the liquid crystal cell 16, all of the light passes through the linearly polarized light separating layer 32 and is absorbed by the absorbing layer 36, so that a dark display is obtained.

In the above embodiment, the light source device 12 is a transparent thin-film white surface light source made of thin-film electroluminescence and the like sandwiched between transparent resin sheets having transparent electrodes. However, the present invention is not limited to this, and the light source light incident from the side end surface of the light guide plate is emitted from one surface of the light guide plate. Or the like. In this case, a reflection layer made of a metal thin film or the like is provided on the other surface of the light guide plate.
(Polyethylene terephthalate) may be used.

Further, on the liquid crystal layer side of the circularly polarized light separating layer or the linearly polarized light separating layer, a retardation layer having a retardation value for substantially shifting the phase of transmitted light by π / 2 is laminated. You may make it have the same effect as a linearly polarized light separation layer or a circularly polarized light separation layer.

Generally, the mode of the liquid crystal panel is 2
Depending on the angle (azimuth) at which the transmission axis of the chromatic polarizer is arranged with respect to the liquid crystal, a "normally white" mode, in which light is transmitted when no voltage is applied to the liquid crystal, and a liquid crystal, There are two types of "normally black" mode, in which light does not pass when no voltage is applied,
The invention applies to both "normally white" mode and "normally black" mode.

[0131]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device 10 shown in FIG. 1 uses a cholesteric liquid crystal layer having a planar orientation as a circularly polarized light separating layer 14 and a liquid crystal cell 16 having a retardation value that substantially shifts the phase of light by π / 2; The light-absorbing type dichroic linear polarizing layer 18 was formed by lamination.

When the electric field was applied to the liquid crystal cell 16 and the director of the liquid crystal layer 22 was changed while the retardation value of the liquid crystal was kept constant, there was no significant decrease in contrast due to external light, and the light utilization efficiency was reduced. Could be improved.

The liquid crystal display device 30 shown in FIG. 8 uses a stretched multilayer as the linearly polarized light separating layer 32, and further has a liquid crystal cell 16 having a retardation value that substantially shifts the phase of light by π / 2, When the λ / 4 retardation layer is laminated on the light absorption type dichroic linear polarization layer as the circular polarization layer 34, similar to the above, there is no significant decrease in contrast due to external light, and The usage efficiency could be improved.

In the reflection type liquid crystal display device 40 shown in FIG. 10, a cholesteric liquid crystal layer is used as the circularly polarized light separating layer 14, the black light absorbing layer 36, and the phase of light are substantially shifted by π / 2. And a dichroic linearly polarizing layer 18 of a light absorption type. Also in this case, there was no significant decrease in contrast due to external light. In addition, since the polarized light component that has not been converted into perfect circularly polarized light after passing through the liquid crystal cell can be absorbed and removed by the black light absorbing layer 36, a display state with extremely high contrast is obtained.

The reflection type liquid crystal display device 5 shown in FIG.
In the case of 0, a dark display state with very good contrast could be obtained in the same manner.

[0136]

According to the present invention, the light utilization efficiency can be greatly improved, the contrast is not greatly reduced due to external light, and the birefringence of the liquid crystal layer is substantially reduced. In addition, there is an excellent effect that a display state with good contrast can be obtained by performing display while maintaining the same.

[Brief description of the drawings]

FIG. 1 is an exploded schematic sectional view showing a main part of a liquid crystal display device according to a first example of an embodiment of the present invention.

FIG. 2 is a diagram showing a Poincare sphere for explaining the relationship between various types of polarized light;

FIG. 3 is a diagram showing a symbol for describing elliptically polarized light and a cross section of elliptically polarized light.

FIG. 4 is an enlarged sectional view showing a liquid crystal cell in the liquid crystal display device.

FIG. 5 is an enlarged sectional view showing directions of directors of liquid crystal in the liquid crystal cell.

FIG. 6 is an enlarged sectional view showing a director of a liquid crystal when the same electric field is applied.

FIG. 7 is a diagram showing a dark display function of the liquid crystal display device.
Cross section similar to

FIG. 8 is an exploded schematic cross-sectional view showing a main part of a liquid crystal display device according to a second example of the embodiment of the present invention.

FIG. 9 is a sectional view similar to FIG. 7, showing a case of dark display in the liquid crystal display device.

FIG. 10 is an exploded schematic cross-sectional view showing a main part of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 11 shows a case of dark display in the liquid crystal display device.
Sectional view similar to 0

FIG. 12 is a sectional view similar to FIG. 6, illustrating a liquid crystal display device according to a fourth example of the embodiment.

FIG. 13 is a diagram showing a case of dark display on the liquid crystal display device.
Sectional view similar to 2

FIG. 14 is a sectional view similar to FIG. 1, showing a conventional liquid crystal display device;

[Explanation of symbols]

 10, 30, 40, 50: Liquid crystal display device 12: Light source device 12A: Reflective layer 14: Circularly polarized light separating layer 16: Liquid crystal cell 18: Dichroic linearly polarizing layer 20A, 20B: Substrate 22: Liquid crystal layers 24A, 24B ... Pixel electrode 26 ... Circuit 32 ... Linearly polarized light separating layer 34 ... Dichroic circularly polarizing layer 36 ... Light absorbing layer D ... Director

Claims (11)

[Claims] 1. A light source, a circularly polarized light separating layer that transmits one circularly polarized light component in the right or left turning direction and reflects the other circularly polarized light component of light emitted from the light source, That shifts the phase of the incident light substantially by π / 2.
A liquid crystal layer having a liquid crystal layer having an application value and an electrode for applying an electric field to the liquid crystal layer, until the circularly polarized light incident through the circularly polarized light separation layer is emitted in a direction opposite to the circularly polarized light separation layer. A liquid crystal cell which converts the direction of the director of the liquid crystal by changing the director of the liquid crystal by applying an electric field from the electrode to the liquid crystal layer, thereby changing the polarization axis of the linearly polarized light; A light-absorbing type that is disposed on the side opposite to the circularly polarized light separating layer of the cell and transmits one linearly polarized light component of the linearly polarized light incident from the liquid crystal cell and absorbs a linearly polarized light component in a direction orthogonal to this. A liquid crystal display device comprising: a dichroic linear polarizing layer. 2. A light source, a linearly polarized light separating layer that transmits one linearly polarized light component of the light emitted from the light source and reflects a linearly polarized light component in a direction perpendicular to the light, and a phase of the transmitted light. A liquid crystal layer having a retardation value for substantially shifting by π / 2, and an electrode for applying an electric field to the liquid crystal layer, wherein the linearly polarized light transmitted through the linearly polarized light separating layer and incident thereon is converted into the linearly polarized light. The light is converted into circularly polarized light before being emitted in the direction opposite to the separation layer, and the direction of the director of the liquid crystal is changed by applying an electric field from the electrode to the liquid crystal layer. A liquid crystal cell for changing the rate, disposed on the side of the liquid crystal cell opposite to the linearly polarized light separating layer, of the circularly polarized light incident from the liquid crystal cell,
A liquid crystal display device comprising: a light absorbing dichroic circularly polarizing layer that transmits one circularly polarized light component in the right or left turning direction and absorbs the other circularly polarized light component. 3. A light-absorbing dichroic linear polarization layer that transmits one linearly polarized light component and absorbs a linearly polarized light component in a direction perpendicular to the linearly polarized light component. A liquid crystal layer having a retardation value substantially shifted by π / 2, and an electrode for applying an electric field to the liquid crystal layer.
The light is converted into circularly polarized light before being emitted in the opposite direction to the dichroic linearly polarizing layer, and the direction of the director of the liquid crystal is changed by applying an electric field from the electrode to the liquid crystal layer. A liquid crystal cell that changes the ellipticity of circularly polarized light,
Among the light transmitted through the liquid crystal cell, a circularly polarized light separating layer that transmits one circularly polarized light component in one of the right and left turning directions and reflects the other circularly polarized light component, and the circularly polarized light separating layer is opposite to the liquid crystal cell. A light-absorbing layer disposed on the side and absorbing light transmitted through the circularly-polarized light separating layer. 4. A light-absorbing dichroic circularly polarizing layer that transmits one circularly polarized light component in the right or left turning direction and absorbs the other circularly polarized light component from outside light. A liquid crystal layer having a retardation value that substantially shifts the phase of the incident light by π / 2, and an electrode for applying an electric field to the liquid crystal layer. The polarized light is converted into linearly polarized light before being emitted in the opposite direction to the dichroic circularly polarizing layer, and an electric field is applied to the liquid crystal layer from the electrode to change the direction of the director of the liquid crystal. A liquid crystal cell for changing the polarization axis of the linearly polarized light, and a linearly polarized light separation for transmitting one linearly polarized light component of the light transmitted through the liquid crystal cell and reflecting a linearly polarized light component in a direction orthogonal to the liquid crystal cell. Layer, on the opposite side of the linearly polarized light separating layer from the liquid crystal cell. Is location, the liquid crystal display device characterized by comprising a light absorbing layer that absorbs light transmitted through the linear polarization separation layer. 5. A liquid crystal display device according to claim 1, wherein said circularly polarized light separating layer is constituted by an optical rotation selecting layer comprising a cholesteric liquid crystal layer. 6. The circularly polarized light separating layer according to claim 1, wherein the circularly polarized light separating layer comprises a retardation layer having a retardation value for substantially shifting the phase of transmitted light by π / 2, and a birefringent film. Of the two lights having the vibration directions perpendicular to each other in the plane of each layer, the difference in the refractive index between the layers adjacent to each other in the thickness direction for one light and the thickness for the other light A planar multilayer structure in which the difference in the refractive index between adjacent layers in the direction is different from each other, wherein linearly polarized light transmitted through the planar multilayer structure is converted into circularly polarized light. Liquid crystal display device. 7. The linearly polarized light separating layer according to claim 2, wherein the linearly polarized light separating layer has a planar multilayer structure in which three or more birefringent films are laminated, and vibration directions perpendicular to each other in the plane of each layer. The difference in the refractive index between the layers adjacent to each other in the thickness direction with respect to one of the two lights having a difference in the refractive index between the layers adjacent to each other in the thickness direction with respect to the other light. A liquid crystal display device characterized by the above-mentioned. 8. The optical rotation selecting layer according to claim 2, wherein the linearly polarized light separating layer comprises a retardation layer having a retardation value for substantially shifting the phase of transmitted light by π / 2, and a cholesteric liquid crystal layer. Wherein the circularly polarized light transmitted through the cholesteric liquid crystal layer is converted into linearly polarized light. 9. The liquid crystal display device according to claim 1, wherein the direction of the director of the liquid crystal is changed to substantially −45 to 45 degrees with respect to the light transmission axis of the dichroic linear polarizing layer. And a circuit for controlling a voltage between the electrodes. 10. The liquid crystal display device according to claim 2, wherein the direction of the director of the liquid crystal is changed from −45 ° to 45 ° with respect to the direction of the electric field vector of the incident linearly polarized light. A liquid crystal display device comprising a circuit for controlling a voltage between electrodes. 11. The method according to claim 1, wherein
In the liquid crystal cell, the liquid crystal layer is sandwiched between two substrates,
The electrode is formed on one of the electrodes, the direction of the electric field when a voltage is applied to the electrode has a portion substantially parallel to the substrate surface, and the direction of most of the liquid crystal molecules in the liquid crystal layer is The liquid crystal display device is in a mode of rotating while being substantially parallel to the substrate surface.