JP2003222725A - Polarization element and liquid crystal display provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarization element and a liquid crystal display which is excellent in efficiency for utilizing a light and adaptability to environment. <P>SOLUTION: The polarization element 10C of the liquid crystal display 20C is provided with circular polarization separating layers 13-15. The circular polarization separating layer 13 reflects a light with a predetermined wavelength region included in an external light at each pixel. The circular polarization separating layer 14 transmits a backlight in a state of not being polarized as a clockwise circular polarization. The circular polarization separating layer 15 selectively reflects the clockwise circular polarization at each pixel in a wavelength region other than the predetermined wavelength region reflected by the circular polarization separating layer 13. Absorbing linear polarization layers 11, 12 are respectively provided on a back side and an observed side of the circular polarization separating layer 13. A 1/4 wavelength wave plate layer 16 is provided so as to transmit the backlight emitted from the circular polarization separating layers 14, 15 to the observed side without a loss. 1/4 wavelength wave plate layers 17, 18 are also respectively provided on the back side and the observed side of the circular polarization separating layer 13 so as to arbitrarily set the efficiency for utilizing the external light and the backlight. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing element preferably used in a transflective liquid crystal display device and the like, and more particularly, to display an image or the like by efficiently utilizing both external light and backlight light. The present invention relates to a polarizing element and a liquid crystal display device including the polarizing element.

[0002]

2. Description of the Related Art Conventionally, a transflective liquid crystal display device has been known as a liquid crystal display device that displays an image and the like by utilizing both external light and backlight light. recent years,
Such a transflective liquid crystal display device is used in a mobile phone or a P
It is drawing attention as a display for mobile terminals such as DAs (personal digital assistants).

In such a transflective liquid crystal display device, in general, the light in a specific wavelength region of the external light incident from the viewing side is reflected at a predetermined ratio, and the light from the backlight provided on the back side is reflected. A semi-transmissive reflective layer that transmits light (backlight light) at a predetermined ratio is provided, and both external light and backlight light are used efficiently, and in bright places, mainly external light is used for display. In a dark place, it is possible to display mainly by using the backlight light.

By the way, as a semi-transmissive reflective layer used in such a transflective liquid crystal display device, a polarized light separating layer which selectively reflects light in a specific wavelength region of a specific polarization state is used. Many. Such a polarization separation layer is composed of a cholesteric liquid crystal layer or the like, and based on the physical molecular arrangement (planar arrangement) of the cholesteric liquid crystal layer, a circular polarization component in one direction and a circular polarization component in the opposite direction are generated. Due to the polarization separation property of separation, the incident light incident on the helical axis of the planar array is separated into the right circularly polarized light component and the left circularly polarized light component, one circularly polarized light component is reflected, and the other circularly polarized light component is transmitted. . This phenomenon is widely known as circular dichroism, and by appropriately selecting the optical rotation direction of the circularly polarized light component with respect to the incident light, a circular polarization direction that is the same as the direction of the helical axis of the cholesteric liquid crystal layer is obtained. The polarized component is selectively reflected or transmitted. In this specification, the term “liquid crystal layer” is used to mean a film that retains the properties (particularly optical properties) of liquid crystal in a certain portion, and refers to a state of a liquid crystal phase in a physical sense. Not of. For example, a liquid crystal layer referred to here is a film that is solidified while maintaining the molecular alignment of the liquid crystal phase (for example, cholesteric phase) even if it has no fluidity.

Since such a polarization separation layer has a function of selectively reflecting light in a specific wavelength region, it also functions as a color filter for reflective display when external light is reflected to perform display. By combining with an absorption color filter such as a pigment dispersion type, it is possible to realize color display in both reflective display using external light and transmissive display using backlight light.

[0006]

However, in the above-mentioned conventional transflective liquid crystal display device, a color filter for reflective display using external light is realized by the polarization separation layer having excellent light utilization efficiency. However, since an absorption color filter such as a pigment dispersion type is used as a color filter for transmissive display using backlight light, the light utilization efficiency is reduced by the amount of light absorbed by the color filter. There is a problem of doing.

Further, in the above-mentioned conventional transflective liquid crystal display device, the utilization efficiency of the external light and the backlight light is set in advance, and even if the use environment of the display device is changed, the utilization efficiency of them is reduced. There is a problem that the ratio cannot be changed.

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a polarizing element and a liquid crystal display device which are not required to use an absorption type color filter and have excellent light utilization efficiency. And

The present invention is also capable of arbitrarily setting the utilization efficiency of external light and backlight light in accordance with the environment in which the display is used, and has excellent adaptability to the environment and a liquid crystal display. The purpose is to provide a device.

[0010]

As a first feature of the present invention, either the right circularly polarized light component or the left circularly polarized light component is selected in a predetermined wavelength region included in the visible light region. First circularly polarized light separating layer that reflects light selectively, and an absorption-type first circularly polarized light separating layer provided on the back side of the first circularly polarized light separating layer.
A linear polarizing layer, and an absorptive second linear polarizing layer provided on the observation side of the first circularly polarized light separating layer and arranged so that the optical axis is orthogonal to the first linear polarizing layer, A circular polarization component having the same optical rotation direction as the one circular polarization component provided on the back side of the first linear polarization layer and selectively reflected by the first circular polarization separation layer is set to the first circle. Between a second circularly polarized light separating layer that selectively reflects in the visible light region including the predetermined wavelength region that is reflected by the polarized light separating layer, and the first linearly polarizing layer and the second circularly polarized light separating layer And the first circularly polarized light separating layer in the visible light region reflects a circularly polarized light component having a different optical rotation direction from the one circularly polarized light component selectively reflected by the second circularly polarized light separating layer. A third circularly polarized light separating layer that selectively reflects in a wavelength region other than the predetermined wavelength region, and A first quarter-wave retardation layer provided between the first linearly polarizing layer and the third circularly polarized light separating layer, wherein the first linearly polarizing layer has an optical axis, It is arranged so as to match the amplitude direction of the linearly polarized light formed by passing through the second circularly polarized light separating layer and the first quarter-wave retardation layer.
A polarizing element is provided.

According to the first aspect of the present invention, a second quarter-wave retardation layer provided between the first circularly polarized light separating layer and the first linearly polarizing layer, Provided between the first circularly polarized light separating layer and the second linearly polarizing layer,
It is preferable to further include a second quarter-wave retardation layer and a third quarter-wave retardation layer arranged such that their optical axes are orthogonal to each other.

The second and third quarter-wave retardation layers are preferably retardation layers whose optical axis changes in response to an applied voltage.

At least one of the first to third quarter-wave retardation layers is preferably a broadband quarter-wave retardation layer.

Further, the second circularly polarized light separating layer is 400
It is preferable to selectively reflect light in the wavelength region of ˜750 nm.

Further, the first circularly polarized light separating layer has a plurality of divided areas divided in the layer plane, and in each of the divided areas, light of different wavelength regions (red, green, or blue wavelength regions). Light) is preferably reflected selectively,
The third circularly polarized light separating layer has a plurality of divided regions corresponding to the divided regions of the first circularly polarized light separating layer, and in each of the divided regions, the first circle of the visible light region is included. It is preferable to selectively reflect light in a wavelength region other than the wavelength region reflected by each of the divided regions of the polarization separation layer. In addition,
The third circularly polarized light separating layer has, in each of the divided regions,
It is preferable to selectively reflect at least two kinds of light in different wavelength regions (light in blue and green wavelength regions, light in green and red wavelength regions, or light in blue and red wavelength regions).

It is preferable that at least one of the first to third circularly polarized light separating layers is a cholesteric liquid crystal layer.

Further, the third circularly polarized light separating layer selectively reflects a circularly polarized light component having the same optical rotation direction as the one circularly polarized light component selectively reflected by the second circularly polarized light separating layer. It is preferable to have a cholesteric liquid crystal layer and a pair of half-wave retardation layers sandwiching the cholesteric liquid crystal layer.

The polarizing element according to the first feature described above can be used in a liquid crystal display device. The liquid crystal display device in this case is provided on the observation side of the polarizing element,
A liquid crystal drive cell that performs light / dark control by changing the polarization state of light according to an applied voltage, and a backlight that is provided on the back side of the polarizing element and irradiates the liquid crystal drive cell with white light. ing.

As a second feature of the present invention, one of the right-handed circularly polarized light component and the left-handed circularly polarized light component is
A first circularly polarized light separating layer that selectively reflects light in a predetermined wavelength range included in the visible light region; and an absorption-type first linearly polarizing layer provided on the back side of the first circularly polarized light separating layer. ,
The first circularly polarized light separating layer is provided on the observation side, and
A linear absorption layer disposed between the first circularly polarized light separating layer and the first linearly polarizing layer, and an absorption type second linearly polarizing layer arranged so that its optical axis is orthogonal to the linearly polarizing layer. 2 quarter-wave retardation layer, and provided between the first circularly polarized light separation layer and the second linear polarization layer, and the optical axis is orthogonal to the second quarter-wave retardation layer. Third quarter arranged to
Provided is a polarizing element having a wavelength retardation layer.

In a second aspect of the present invention, the second aspect
The third quarter-wave retardation layer is preferably a retardation layer whose optical axis changes according to an applied voltage.

At least one of the first to third quarter-wave retardation layers is preferably a broadband quarter-wave retardation layer.

Further, a circular polarization component having the same optical rotation direction as the one circular polarization component provided on the back side of the first linear polarization layer and selectively reflected by the first circular polarization separation layer, At least a second circularly polarized light separating layer that selectively reflects in the predetermined wavelength range that is reflected by the first circularly polarized light separating layer, a first linearly polarizing layer, and a second circularly polarized light separating layer And a first quarter-wave retardation layer provided between the first linear polarization layer and the first linear polarization layer.
It is preferably arranged so as to match the amplitude direction of the linearly polarized light formed by passing through the second circularly polarized light separating layer and the first quarter-wave retardation layer.

Further, the first circularly polarized light separating layer has a plurality of divided areas divided in the layer plane, and in each of the divided areas, light of different wavelength regions (red, green or blue wavelength regions are divided). It is preferable to selectively reflect (light).

Furthermore, at least one of the first and third circularly polarized light separating layers is preferably a cholesteric liquid crystal layer.

The polarizing element according to the second feature described above can be used in a liquid crystal display device. The liquid crystal display device in this case is provided on the observation side of the polarizing element,
A liquid crystal drive cell that controls light and darkness by changing the polarization state of light according to an applied voltage, and a first circularly polarized light separating layer that is provided on the back side of the polarizing element and is reflected by the liquid crystal drive cell. And a backlight that emits colored light in the same wavelength range as the predetermined wavelength range. An electroluminescence light source can be used for the backlight.

According to the first feature of the present invention, the polarizing element provided between the liquid crystal driving cell and the backlight includes the first to third circularly polarized light separating layers, and the first circularly polarized light separating layer. In the second circularly polarized light separating layer, while transmitting light in a predetermined wavelength range included in outside light, the non-polarized backlight light is transmitted as circularly polarized light in one optical rotation direction, and In the circularly polarized light separating layer, the circularly polarized light in one optical rotation direction is selectively reflected in a wavelength region other than the predetermined wavelength region reflected by the first circularly polarized light separating layer. Here, with respect to external light, the absorption-type first linear polarization layer and the absorption-type second linear polarization layer arranged so that their optical axes are orthogonal to each other on the back side and the observation side of the first circularly polarized light separating layer. Since the linearly polarizing layer is provided, the emission of light in the extra wavelength region of external light is suppressed, and only light of a desired color can be efficiently extracted. On the other hand, regarding the backlight light, in the second circularly polarized light separating layer, the backlight light in the non-polarized state is almost 10 due to the light recycling effect.
It transmits as circularly polarized light with 0% intensity. Also, the first 1 /
The fourth circularly polarized light separating layer and the third
The light emitted from the circularly-polarized light separating layer can be converted into linearly polarized light having an amplitude direction that matches the optical axis of the absorption-type first linearly polarizing layer, and the backlight light can be sent to the observing side without loss. Therefore, according to such a polarizing element, it is possible to efficiently extract light in a specific wavelength region having a specific polarization state from outside light and backlight light. Further, a liquid crystal display device including such a polarizing element can display an image or the like by efficiently using both external light and backlight light without using an absorption color filter. It is possible to obtain a display with high light utilization efficiency.

According to the first feature of the present invention, the first
By providing the second and third quarter-wave retardation layers on the back side and the observation side of the circularly polarized light separating layer, respectively, the optical axes of the second and third quarter-wave retardation layers are By simply changing the angle, the utilization efficiency of outside light and backlight light can be set arbitrarily. Therefore, a liquid crystal display device including such a polarizing element can display images and the like by most efficiently utilizing both external light and backlight light according to the environment in which it is used. Thus, it is possible to obtain a display with high light utilization efficiency.
Further, it is also possible to control the light utilization efficiency by dividing it within the plane of the display, and in this case, it is possible to effectively prevent a reduction in visibility due to reflection of light in a specific portion. it can. Particularly, by arranging the second and third quarter-wave retardation layers so that their optical axes are orthogonal to each other, emission of light in an extra wavelength region of external light is suppressed,
Only light of a desired color can be efficiently extracted.

According to the first feature of the present invention, the second
By making the third quarter-wave retardation layer a retardation layer whose optical axis changes according to the applied voltage, the user himself / herself can control the utilization efficiency of outside light and backlight light by electrical control. It can be set arbitrarily.

Further, according to the first feature of the present invention, the first to third quarter-wave retardation layers have a 1 / th of a wide band.
By using the 4-wavelength retardation layer, good color purity, contrast and light utilization efficiency can be obtained.

Further, according to the first feature of the present invention, the second circularly polarized light separating layer selectively reflects light in the wavelength region of 400 to 750 nm, and thus it can be suitably used for a display. it can. Further, in the first circularly polarized light separating layer, light of different wavelength regions (light of red, green or blue wavelength regions) in a plurality of divided regions divided in the layer plane corresponding to each pixel of the liquid crystal drive cell. Of the first circularly polarized light separating layer,
In each of the divided regions corresponding to the divided region of the circularly polarized light separating layer, light in a wavelength region other than the wavelength region reflected by each divided region of the first circularly polarized light separating layer in the visible light region (blue and green wavelength regions Light, light in the wavelength regions of green and red, or light in the wavelength regions of blue and red) can be suitably used for a color display such as a liquid crystal display device.

Further, according to the first feature of the present invention, by using the cholesteric liquid crystal layer as the first to third circularly polarized light separating layers, it is possible to control the wavelength range of reflected light even in a thin layer, and thus to reduce the thickness. The polarizing element and the liquid crystal display device can be obtained.

Further, according to the first feature of the present invention, as the third circularly polarized light separating layer, the second circularly polarized light separating layer selectively reflects the one circularly polarized light component of the same circular polarization direction. By using a cholesteric liquid crystal layer that selectively reflects a polarization component and a pair of half-wave retardation layers that sandwich the cholesteric liquid crystal layer, the second and third circularly polarized light separating layers are made the same. Of the cholesteric liquid crystal layer, and by unifying the physical properties such as the refractive index, hardness, heat resistance, and solvent resistance, the device design becomes easy and the reliability is also improved.

According to the second feature of the present invention, with respect to external light, the absorption-type second optical elements are arranged on the back side and the observation side of the first circularly polarized light separating layer so that their optical axes are orthogonal to each other. Since the first linear polarization layer and the absorption-type second linear polarization layer are provided, the emission of light in an extra wavelength region of external light is suppressed for each pixel, and only light of a desired color corresponding to the pixel is provided. Can be taken out efficiently. On the other hand, as for the backlight light, light in a specific wavelength region emitted from the electroluminescent light source of the backlight can be sent to the observation side through the absorption-type first linear polarization layer. Therefore, according to such a polarizing element, it is possible to efficiently extract light in a specific wavelength region having a specific polarization state from outside light and backlight light. Further, a liquid crystal display device including such a polarizing element can display an image or the like by efficiently using both external light and backlight light without using an absorption color filter.
It is possible to obtain a display with high light utilization efficiency.

Further, since the second and third quarter-wave retardation layers are provided on the back side and the observation side of the first circularly polarized light separating layer, respectively, these second and third layers are provided.
By changing the angle of the optical axis of the 1/4 wavelength retardation layer of
The utilization efficiency of outside light and backlight light can be set arbitrarily. Therefore, a liquid crystal display device including such a polarizing element can display images and the like by most efficiently utilizing both external light and backlight light according to the environment in which it is used. Thus, it is possible to obtain a display with high light utilization efficiency. Further, it is also possible to control the light utilization efficiency by dividing it within the plane of the display, and in this case, it is possible to effectively prevent a reduction in visibility due to reflection of light in a specific portion. it can.

Further, since the second and third quarter-wave retardation layers are arranged so that their optical axes are orthogonal to each other, the emission of light in the extra wavelength region of external light is suppressed, Only light of a desired color corresponding to the pixel can be efficiently extracted.

According to the second feature of the present invention, the second
By making the third quarter-wave retardation layer a retardation layer whose optical axis changes according to the applied voltage, the user himself / herself can control the utilization efficiency of outside light and backlight light by electrical control. It can be set arbitrarily.

According to the second aspect of the present invention, the first
Through the third quarter-wave retardation layer, the quarter-wave of the broadband
By using the wavelength retardation layer, good color purity, contrast and light utilization efficiency can be obtained.

Further, according to the second feature of the present invention, the one circularly polarized light component provided on the back side of the first linearly polarizing layer and selectively reflected by the first circularly polarized light separating layer. A second circularly polarized light separating layer which selectively reflects a circularly polarized light component having the same optical rotation direction as at least in the predetermined wavelength region in which the first circularly polarized light separating layer reflects, and the first linearly polarizing layer. By further providing a first quarter-wave retardation layer provided between the second circularly polarized light separating layer and the second circularly polarized light separating layer,
An image or the like can be displayed by more efficiently utilizing both the external light and the backlight light, and a display display with high light utilization efficiency can be obtained.

Further, according to the second feature of the present invention, in the first circularly polarized light separating layer, different wavelength regions are provided in a plurality of divided regions divided in the layer plane corresponding to each pixel of the liquid crystal driving cell. By selectively reflecting the light (light in the wavelength region of red, green or blue), it can be suitably used for a color display such as a liquid crystal display device.

Further, according to the second aspect of the present invention, by using the cholesteric liquid crystal layer as the first and second circularly polarized light separating layers, it becomes possible to control the wavelength range of reflected light even in a thin layer, and thus the thin layer can be obtained. The polarizing element and the liquid crystal display device can be obtained.

Definition of Optical System In the present specification, the optical system is defined as follows unless otherwise specified.

(1) Optical axis In a linearly polarizing layer, it means the transmission axis of linearly polarized light (amplitude direction (vibration direction) of the electric field vector of linearly polarized light), and in the 1/4 wavelength phase difference layer, it is in the Nx direction (however, Nx> Ny = Nz)
Means

(2) Coordinate system The clockwise direction as viewed from the observation side is the positive direction.

(3) Optical rotation direction of circularly polarized light When the direction of rotation of the electric field vector of light coming toward the observing side is right-handed, it is right-handed circularly polarized light.

[0045]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment First, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. The polarizing element according to the first embodiment of the present invention is preferably used in a transflective liquid crystal display device provided with a backlight that emits white light.

As shown in FIG. 1, the liquid crystal display device 20A according to the first embodiment of the present invention includes a liquid crystal drive cell 21.
And an absorption type observation side linear polarization layer 22 provided on the viewing side of the liquid crystal driving cell 21, and a red, green and blue color for the liquid crystal driving cell 21 provided on the back side of the liquid crystal driving cell 21. The backlight 23 irradiates non-polarized white light including light. The backlight 23
As the light source, a surface light source including a linear light source that illuminates white light and a light guide plate can be used, and L that illuminates white light can be used.
A surface light source including an ED element, an electroluminescence element, or the like can be used. A diffuse reflection plate is appropriately provided on the back side of the backlight 23.

Further, the liquid crystal driving cell 21 and the backlight 2
A polarizing element 10A is provided between the light source 3 and the light source 3, and reflects light in a specific wavelength region among external light entering from the observation side at a predetermined ratio, and from a backlight 23 provided on the back surface side. Light (backlight light) can be transmitted at a predetermined ratio.

Here, the polarizing element 10A has either one of the right-handed circularly polarized light component and the left-handed circularly polarized light component (for example, the right-handed circularly polarized light component) in a predetermined wavelength region (for example, right circularly polarized light component) included in the visible light region. Almost 100% in the green wavelength range)
The first circularly polarized light separating layer 13 that selectively reflects, the absorption-type first linearly polarizing layer 11 provided on the back side of the first circularly polarized light separating layer 13, and the first circularly polarized light separating layer 13 The first linearly polarizing layer 11 and the absorption type second linearly polarizing layer 12 arranged so that their optical axes are orthogonal to each other are provided on the observation side of.

The polarization element 10A is provided on the back side of the first linear polarization layer 11 and has the same circular polarization direction as the one circular polarization component selectively reflected by the first circular polarization separation layer 13. A second circle that selectively reflects a polarized light component (for example, right circularly polarized light component) almost 100% in a visible light region (for example, 400 to 750 nm) including a predetermined wavelength region that is reflected by the first circularly polarized light separating layer 13. It is provided between the polarized light separating layer 14 and the first linearly polarized light layer 11 and the second circularly polarized light separating layer 14, and is different from one circularly polarized light component which is selectively reflected by the second circularly polarized light separating layer 14. The circularly polarized light component in the optical rotation direction (for example, the left circularly polarized light component) is converted into the first circularly polarized light separation layer 1 in the visible light region.
The third circularly polarized light separating layer 15 that selectively reflects almost 100% in a wavelength range (for example, a blue and red wavelength range) other than the predetermined wavelength range in which 3 reflects, the first linear polarization layer 11 and the third It has a first quarter-wave retardation layer 16 provided between the circularly polarized light separating layer 15 and the circularly polarized light separating layer 15. The first
Of the linearly polarizing layer 11 so that the optical axis thereof coincides with the amplitude direction of the linearly polarized light formed by passing through the second circularly polarized light separating layer 14 and the first quarter-wave retardation layer 16. It is arranged.

The first circularly polarized light separating layer 13 has a plurality of segmented regions segmented in the layer plane corresponding to each pixel of the liquid crystal driving cell 21, and each segmented region has a different wavelength region. It is preferable to selectively reflect light (for example, light in the red, green, or blue wavelength range).
Further, the third circularly polarized light separating layer 15 has a plurality of divided regions corresponding to the divided regions of the first circularly polarized light separating layer 13, and in each of the divided regions, the first circularly polarized light in the visible light region is included. Light in at least two kinds of different wavelength regions (light in blue and green wavelength regions, light in green and red wavelength regions, or blue and red wavelengths) other than the wavelength region in which each segmented region of the separation layer 13 reflects. It is preferable to selectively reflect the light of the area). The first to third circularly polarized light separating layers 13 to 15 are preferably made of cholesteric liquid crystal layers.

The liquid crystal drive cell 21 controls the brightness by changing the polarization state of light according to the applied voltage. The liquid crystal mode is TN (twisted nematic) mode and STN (twisted nematic) mode. Any liquid crystal mode such as a super twisted nematic mode, a VA (vertical alignment) mode and a TFD (Thin Film Diode) mode can be used. In the twisted nematic (TN) mode, for example, the optical axis of the observation side linear polarization layer 22 and the optical axis of the second linear polarization layer 12 of the polarization element 10A are arranged so as to be orthogonal to each other, and liquid crystal driving is performed. The cell 21 may be controlled to rotate the linearly polarized light by 90 °.

Next, the operation state of the liquid crystal display device 20A shown in FIG. 1 will be described with reference to FIG. 2 by taking as an example the case where the optical axes and optical rotation selection characteristics of the respective layers which are the constituent elements are set as shown. . Although only the behavior of the light in the portion corresponding to the green pixel will be described here, the behavior of the light in the portion corresponding to the other red and blue pixels is the wavelength range of the reflected and transmitted light. Except for the differences, the other parts are the same as those shown in FIG. 2, and therefore detailed description will be omitted here.

Here, FIGS. 2 (a) (b) (c) (d) show the case where the polarization state of light is changed by the liquid crystal drive cell 21 and the portion corresponding to the green pixel is displayed brightly. It is a thing. Of these, FIGS. 2 (a) and 2 (b) respectively show optical paths of external light and backlight light in a wavelength region (blue and red wavelength regions) other than the green wavelength region, together with the polarization state of light and utilization efficiency. 2 (c) and 2 (d) respectively show the optical paths of the external light and the backlight light in the green wavelength region together with the polarization state of the light and the utilization efficiency.

2 (a) (b) (c) (d), the meanings of the symbols attached to the respective constituent elements are as shown in Table 1 below.
Here, the numbers in parentheses after the symbols mean the angles of the respective optical axes.

[Table 1]

2 (a) (b) (c) (d), the polarization state and the optical path of light are shown in accordance with the notation in Table 2 below.

[Table 2]

Further, the number attached in the vicinity of the optical path of light indicates the light utilization efficiency. In the case of external light, for example, in the portion corresponding to the green pixel, the white external light other than the green light is absorbed. Therefore, the intensity of external light is divided into three equal parts, red light, green light, and blue light, and each becomes 33.3%. On the other hand, in the case of backlight light, for example, in the portion corresponding to the green pixel, the green light reflected and recycled in the peripheral portion can also be used, while the light corresponding to the green pixel is reflected. The red light and the blue light that are generated are used in a portion corresponding to pixels of another color in the peripheral portion. Therefore, the intensity of the backlight light is 100% for each of red light, green light, and blue light. The intensity obtained by the light recycling effect is shown in parentheses.

The above notation method is commonly used not only in FIG. 2 but also in FIGS. 4 to 6, 8 and 10.

First, with reference to FIGS. 2 (a) and 2 (b), the behavior of light other than green light (blue light and red light (hereinafter also referred to as "blue-red light")) of the ambient light and the backlight light will be described. To do.

As shown in FIG. 2A, the bluish red light contained in the outside light is incident on the absorption type observation side linear polarization layer 22 having an optical axis angle of −45 ° in a non-polarized state. The observation-side linearly polarizing layer 22 transmits only linearly polarized light of which the electric field vector has an amplitude direction of −45 ° among unpolarized blue-red light. Such linearly polarized light is converted into linearly polarized light whose electric field vector has an amplitude direction of 45 ° by passing through the liquid crystal driving cell 21, and the absorption-type second linearly polarizing layer whose optical axis angle is 45 °. 12 is 100% transparent. Here, since this linearly polarized light is bluish red light, it is transmitted through the first circularly polarized light separation layer 13 that reflects green right circularly polarized light, and the first absorption type first circularly polarized light is obtained.
Reaching the linearly polarizing layer 11. However, since the first linear polarizing layer 11 is arranged so that the optical axis thereof is orthogonal to the second linear polarizing layer 12, and the angle of the optical axis is −45 °, the first linear polarizing layer 11 is At, the bluish red light contained in the outside light is completely absorbed.

On the other hand, as shown in FIG. 2B, the bluish red light contained in the backlight is incident on the second circularly polarized light separating layer 14 which reflects the white right circularly polarized light in a non-polarized state. Second
The circularly polarized light separating layer 14 transmits only the left circularly polarized light component of the unpolarized blue-red light. Here, since the right circularly polarized light component reflected by the second circularly polarized light separating layer 14 is returned to the backlight 23 and recycled, as a result, from the observation side of the second circularly polarized light separating layer 14, the left circularly polarized light component is left. Circularly polarized blue-red light is emitted with 100% intensity. Such bluish red light in the left circularly polarized state reaches the third circularly polarized light separating layer 15. However, since the third circularly polarized light separation layer 15 reflects bluish red left-handed circularly polarized light, the bluish red light included in the backlight light is emitted from the observation side of the third circularly polarized light separation layer 15. There is no.

Next, with reference to FIGS. 2 (c) and 2 (d), the behavior of the green light of the external light and the backlight will be described.

As shown in FIG. 2C, the green light contained in the external light is incident on the absorption type observation side linear polarization layer 22 having an optical axis angle of −45 ° in a non-polarized state. The observation-side linearly polarizing layer 22 transmits only linearly polarized light of which the electric field vector has an amplitude direction of −45 ° among unpolarized green light. Such linearly polarized light is converted into linearly polarized light whose electric field vector has an amplitude direction of 45 ° by passing through the liquid crystal driving cell 21, and the absorption-type second linearly polarizing layer whose optical axis angle is 45 °. 100% of light is transmitted through the first circularly polarized light separating layer 13
To reach. Here, since this linearly polarized light is green light, the right circularly polarized light component is reflected and the left circularly polarized light component is transmitted in the first circularly polarized light separating layer 13 that reflects green right circularly polarized light. . Of these, the first circularly polarized light separation layer 13
The green right-handed circularly polarized light reflected by is sequentially transmitted through the second linear polarization layer 12, the liquid crystal driving cell 21 and the observation side linear polarization layer 22 in the optical path and polarization state as shown in the figure, and is emitted from the observation side. . On the other hand, the green left circularly polarized light transmitted through the first circularly polarized light separating layer 13 reaches the absorption type first linearly polarizing layer 11. Here, the first linear polarizing layer 11 is arranged so that the optical axis thereof is orthogonal to the second linear polarizing layer 12, and the angle of the optical axis is −45 °. At 11, half of the green light is absorbed and the other half is converted into linearly polarized light with the electric field vector having an amplitude direction of −45 °. After that, the linearly polarized light is converted into left circularly polarized light by passing through the first quarter-wave retardation layer 16 having an optical axis angle of 0 °, and the third circularly polarized light that reflects blue-red left circularly polarized light is reflected. The circularly polarized light separating layer 15 and the second circularly polarized light separating layer 14 that reflects the white right-handed circularly polarized light are sequentially transmitted by 100%,
It is returned to the backlight 23 as green left circularly polarized light. This green left circularly polarized light is reflected by the backlight 23 and has the second circularly polarized light separating layer 14, the third circularly polarized light separating layer 15 and the first 1/4 with the optical path and the polarization state as shown in the figure.
After sequentially passing through the wavelength phase difference layer 16 and the first linear polarization layer 11, only green left circularly polarized light is transmitted through the first circularly polarized light separating layer 13, and the second linearly polarizing layer 12 and the liquid crystal driving cell 21 and the linear polarization layer 22 on the observation side are sequentially transmitted and emitted from the observation side. In the process of exiting from the observation side in this way, the green right circularly polarized light will be returned to the backlight 23 side again in the first circularly polarized light separating layer 13, but it was returned in this way. The light also finally exits from the observation side through the optical path and polarization state as shown in the figure.

As a result, as shown in FIG. 2C, the green light contained in the external light is emitted from the observation side at a rate of about 6% of the total.

On the other hand, as shown in FIG. 2D, the green light included in the backlight light is incident on the second circularly polarized light separating layer 14 which reflects the white right circularly polarized light in a non-polarized state. The second circularly polarized light separating layer 14 transmits only the left circularly polarized light component of the unpolarized green light. Here, the second circularly polarized light separating layer 1
Since the right-handed circularly polarized light component reflected at 4 is returned to the backlight 23 and recycled, the left-handed circularly polarized light is seen from the observation side of the second circularly polarized light separating layer 14 as in the case shown in FIG. 2 (b). Ideally, the polarized green light is emitted with an intensity of 100%.
Further, such left circularly polarized green light is transmitted through the third circularly polarized light separating layer 15 which reflects the bluish red left circularly polarized light.
At this time, the portion of the third circularly polarized light separating layer 15 corresponding to, for example, the green pixel naturally contains blue light and red light in the left circularly polarized state in addition to green light in the left circularly polarized state. However, in the case of a display such as a liquid crystal display device, since red, green and blue pixels are formed in a fine pattern and are close to each other, they are reflected at the portions corresponding to these green pixels. The blue light and the red light are returned to the backlight 23 and recycled, and are used in the portion corresponding to the pixel of another color in the peripheral portion. Similarly, the green light reflected at the peripheral portions corresponding to the blue and red pixels is used at the portions corresponding to the green pixels. Therefore, the second and third circularly polarized light separating layers 14, 1
From the observation side of 5, the left circularly polarized green light ideally exits with 100% intensity.

After that, the green left-handed circularly polarized light transmitted through the third circularly polarized light separating layer 15 has a first 1/1/0 angle of the optical axis of 0 °.
By passing through the four-wavelength phase difference layer 16, the amplitude direction of the electric field vector is converted into linearly polarized light of −45 °, and the absorption-type first linearly polarizing layer 11 having an optical axis angle of −45 °.
Of 100% to reach the first circularly polarized light separating layer 13. Here, since this linearly polarized light is green light,
In the first circularly polarized light separating layer 13 which reflects green right circularly polarized light, the right circularly polarized light component is reflected and the left circularly polarized light component is transmitted. Among these, the green left-handed circularly polarized light that has passed through the first circularly polarized light separating layer 13 reaches the absorptive second linearly polarizing layer 12. Here, the second linear polarizing layer 12 is arranged such that the optical axis thereof is orthogonal to the second linear polarizing layer 11, and the angle of the optical axis is 45 °, so that the second linear polarizing layer 12 is formed. At, half of the green light is absorbed and the other half is converted into linearly polarized light with the electric field vector having an amplitude direction of 45 °. After that, such linearly polarized light is converted into linearly polarized light whose electric field vector has an amplitude direction of −45 ° by passing through the liquid crystal drive cell 21, and the angle of the optical axis is −45.
100% of light is transmitted through the absorption-type second linearly polarizing layer 12 having an angle of °, and the light is emitted from the observation side. On the other hand, the first circularly polarized light separating layer 1
The green right-handed circularly polarized light reflected by 3 is backlit again.
The light is returned to the third side, and a part of the light passes through the optical path and the polarization state as shown in the figure and is emitted from the observation side.

As a result, as shown in FIG. 2D, the green light contained in the backlight is emitted from the observation side at a rate of about 33% of the whole.

To summarize the above, as shown in FIGS. 2 (a) (b) (c) (d), in the portion corresponding to the green pixel, the light other than the green light in the outside light and the backlight light is (Blue-red light) does not leak out, green light included in outside light is emitted from the observation side at a ratio of about 6% of the whole, and green light included in backlight light is a ratio of about 33% of the whole. The light is emitted from the observation side. Note that this ratio is the same in the portions corresponding to other red pixels and blue pixels.

As described above, according to the first embodiment of the present invention, the polarizing element 10A provided between the liquid crystal driving cell 21 and the backlight 23 includes the first to third circularly polarized light separating layers 13 to. 15 is provided, in the first circularly polarized light separating layer 13,
While reflecting the light in the predetermined wavelength range included in the outside light for each pixel, the second circularly polarized light separating layer 14 transmits the backlight light in the non-polarized state as the right circularly polarized light and the third circular light. In the polarized light separating layer 15, the right circularly polarized light is selectively reflected for each pixel in a wavelength region other than the predetermined wavelength region in which the first circularly polarized light separating layer 13 reflects. Here, as for external light, the first circularly polarized light separating layer 13
Since the absorption-type first and second linear polarization layers 11 and 12 arranged so that their optical axes are orthogonal to each other are provided on the back side and the observation side, respectively, an extra wavelength of external light is provided for each pixel. Emission of light in a region (for example, blue light and red light in a portion corresponding to a green pixel) is suppressed, and only light of a desired color corresponding to the pixel can be efficiently extracted. On the other hand, with respect to the backlight light, in the second circularly polarized light separating layer 14, the unpolarized backlight light is transmitted as left circularly polarized light having an intensity of almost 100% for each pixel, and at the same time, the third circularly polarized light separating layer is provided. Also in No. 15, due to the above-described light recycling effect, the light is transmitted as left circularly polarized light having an intensity of almost 100%. In addition, the first quarter-wave retardation layer 16 allows the second and third circularly polarized light separation layers 1 to be formed.
The light emitted from 4, 15 can be converted into linearly polarized light having an amplitude direction that coincides with the optical axis of the absorption-type first linearly polarizing layer 11, and the backlight light can be sent to the observation side without loss. Therefore, according to such a polarizing element 10A, it is possible to efficiently extract light in a specific wavelength region having a specific polarization state from outside light and backlight light. Further, a liquid crystal display device 2 including such a polarizing element 10A
0A can display images and the like by efficiently using both external light and backlight light without using an absorption type color filter, and can obtain a display display with high light utilization efficiency. it can.

Further, according to the first embodiment of the present invention, in the second circularly polarized light separating layer 14, 400 to 750 is used.
Since the light in the wavelength region of nm is selectively reflected, it can be suitably used for a display.
In addition, in the first circularly polarized light separating layer 13, light of different wavelength regions (red, green, or blue light) is emitted in a plurality of divided regions divided in the layer plane corresponding to each pixel of the liquid crystal drive cell 21. In the third circularly polarized light separating layer 15, the first circularly polarized light separating layer 13 of the visible light region is selectively reflected, and in each divided region corresponding to the divided region of the first circularly polarized light separating layer 13. Selectively reflects light in a wavelength range other than the wavelength range reflected by each section area (light in the blue and green wavelength ranges, light in the green and red wavelength ranges, or light in the blue and red wavelength ranges) I am doing so
It can be suitably used for a color display such as a liquid crystal display.

Further, according to the first embodiment of the present invention, since the cholesteric liquid crystal layer is used as the first to third circularly polarized light separating layers 13 to 15, even if it is a thin layer, the wavelength range of the reflected light is reduced. It becomes possible to control, and it is possible to obtain a thin polarizing element and a liquid crystal display device.

In the above-described first embodiment, the third circularly polarized light separating layer 15 has the same optical rotation direction as one circularly polarized light component selectively reflected by the second circularly polarized light separating layer 14. It is also possible to use a cholesteric liquid crystal layer that selectively reflects the circularly polarized light component of, and a pair of half-wave retardation layers that sandwich the cholesteric liquid crystal layer. As a result, the second and third circularly polarized light separation layers 14 and 15 can be composed of the same cholesteric liquid crystal layer, and the physical properties such as the refractive index, hardness, heat resistance, and solvent resistance are unified, The device can be easily designed and the reliability is improved.

Further, in the above-described first embodiment, a wide band ¼ wavelength phase difference layer may be used as the first ¼ wavelength phase difference layer 16. In addition,
As such a wideband quarter-wave retardation layer, a combination of a quarter-wave retardation layer and a half-wave retardation layer can be used in addition to one that achieves the function alone. In the latter case, the half-wave retardation layer is arranged on the side where linearly polarized light is incident. Thereby, good color purity, contrast, and light utilization efficiency can be obtained.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment of the present invention is different from the first circularly polarized light separating layer of the polarizing element except that second and third quarter-wave retardation layers are provided on the back side and the observing side, respectively. Other than that, it is almost the same as the first embodiment shown in FIGS. In the second embodiment of the present invention, the same parts as those of the first embodiment shown in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 3, in the liquid crystal display device 20B according to the second embodiment of the present invention, the polarizing element 10B is provided between the liquid crystal drive cell 21 and the backlight 23.

Here, in addition to the configuration of the polarizing element 10A shown in FIG. 1, the polarizing element 10B includes a first circularly polarized light separating layer 13
And the second 1 / that is provided between the first linear polarization layer 11 and
The four-wavelength phase difference layer 17, the first circularly polarized light separating layer 13 and the second
The third quarter-wavelength retardation layer 17, which is provided between the second quarter-wave retardation layer 17 and the linearly polarizing layer 12 of FIG.
1/4 wavelength retardation layer 18 of

Here, the angle θ of the optical axis of the second quarter-wave retardation layer 17 is, for example, 0 ° to 180 ° with reference to the optical axis of the first quarter-wave retardation layer 16. It can be set arbitrarily within the range, whereby the utilization efficiency of external light and backlight light can be changed. At this time, the angle of the optical axis of the third quarter-wave retardation layer 18 is
The angle is set to be orthogonal to the optical axis of the second quarter-wave retardation layer 17.

As the second and third quarter-wave retardation layers 17 and 18, retardation layers whose optical axis changes in accordance with the applied voltage can be used. Specifically, for example,
A drive cell that imparts a phase difference with nematic liquid crystal or smectic liquid crystal can be used. Further, the second and third quarter-wave retardation layers 17 and 18 themselves are arranged so as to be rotatable in a plane orthogonal to the traveling direction of light, and the second Also, the angle θ of the optical axes of the third quarter-wave retardation layers 17 and 18 may be changed.

Next, referring to FIG. 4, FIG. 5 and FIG.
In the operating state of the liquid crystal display device 20B shown in FIG. 2, the angle θ of the optical axis of the second quarter-wave retardation layer 17 is 0 °, 45.
An example will be described in which the angle is set to either 90 ° or 90 °, and the optical axes and optical rotation selection characteristics of the other layers, which are the constituent elements, are set as illustrated. Note that here, as in the case of the above-described first embodiment, only the behavior of light in the portion corresponding to the green pixel will be described, but the light in the portions corresponding to the other red and blue pixels will be described. The behavior of is the same as that shown in FIGS. 4, 5 and 6 except that the wavelength regions of reflected and transmitted light are different, and therefore detailed description thereof is omitted here. Note that the notational methods in FIGS. 4, 5, and 6 are the same as those shown in FIG.

First, referring to FIGS. 4 (a) (b) (c) (d), as the first operation state of the liquid crystal display device 20B shown in FIG. 3, the optical characteristics of the second quarter-wave retardation layer 17 are set. An operation state when the axis angle θ is 0 ° will be described.

First, with reference to FIGS. 4A and 4B, the behavior of the bluish red light other than the green light among the external light and the backlight will be described.

As shown in FIG. 4 (a), the bluish red light contained in the external light is incident on the absorption type observation side linear polarization layer 22 having an optical axis angle of −45 ° in a non-polarized state. The observation-side linearly polarizing layer 22 transmits only linearly polarized light of which the electric field vector has an amplitude direction of −45 ° among unpolarized blue-red light. Such linearly polarized light is converted into linearly polarized light whose electric field vector has an amplitude direction of 45 ° by passing through the liquid crystal driving cell 21, and the absorption-type second linearly polarizing layer whose optical axis angle is 45 °. 12 is 100% transparent. Next, this linearly polarized light is converted into left circularly polarized light by passing through the third quarter-wave retardation layer 18 having an optical axis angle of 90 °,
1 for the first circularly polarized light separating layer 13 that reflects the right circularly polarized light of green
00% transparent. Further, the bluish red left-handed circularly polarized light is converted into linearly polarized light whose electric field vector has an amplitude direction of 45 ° by passing through the second quarter-wave retardation layer 17 whose optical axis angle is 0 °. , Reaches the absorption-type first linearly polarizing layer 11. However, since the first linear polarizing layer 11 is arranged so that the optical axis thereof is orthogonal to the second linear polarizing layer 12, and the angle of the optical axis is −45 °, the first linear polarizing layer 11 is At, the bluish red light contained in the outside light is completely absorbed.

On the other hand, as shown in FIG. 4B, the bluish red light contained in the backlight light is incident on the second circularly polarized light separating layer 14 which reflects the white right circularly polarized light in a non-polarized state. Second
The circularly polarized light separating layer 14 transmits only the left circularly polarized light component of the unpolarized blue-red light. Here, the right circularly polarized light component reflected by the second circularly polarized light separating layer 14 is returned to the backlight 23 and recycled, so that the second circularly polarized light separating component is recycled as in the first embodiment. From the observation side of the layer 14, bluish red light in the left circularly polarized state is emitted with 100% intensity. Such bluish red light in the left circularly polarized state reaches the third circularly polarized light separating layer 15. However, since the third circularly polarized light separation layer 15 reflects bluish red left-handed circularly polarized light, the bluish red light included in the backlight light is emitted from the observation side of the third circularly polarized light separation layer 15. There is no.

Next, with reference to FIGS. 4 (c) and 4 (d), the behavior of the green light of the outside light and the backlight will be described.

As shown in FIG. 4 (c), the green light contained in the outside light is incident on the absorption type observation side linear polarization layer 22 having an optical axis angle of −45 ° in a non-polarized state. The observation-side linearly polarizing layer 22 transmits only linearly polarized light of which the electric field vector has an amplitude direction of −45 ° among unpolarized green light. Such linearly polarized light is converted into linearly polarized light whose electric field vector has an amplitude direction of 45 ° by passing through the liquid crystal driving cell 21, and the absorption-type second linearly polarizing layer whose optical axis angle is 45 °. 12 is 100% transparent. Next, this linearly polarized light is converted into left circularly polarized light by passing through the third quarter-wave retardation layer 18 having an optical axis angle of 90 °, and the first circularly polarized light that reflects green right circularly polarized light is reflected. The circularly polarized light separation layer 13 is 100
%To Penetrate. Further, this green left-handed circularly polarized light is converted into linearly polarized light having an amplitude direction of the electric field vector of 45 ° by passing through the second quarter-wave retardation layer 17 having an optical axis angle of 0 °. The first linear polarization layer 11 of absorption type is reached. However, since the first linear polarizing layer 11 is arranged so that the optical axis thereof is orthogonal to the second linear polarizing layer 12, and the angle of the optical axis is −45 °, the first linear polarizing layer 11 is At, the green light is completely absorbed.

On the other hand, as shown in FIG. 4D, the green light contained in the backlight light is incident on the second circularly polarized light separating layer 14 which reflects the white right-handed circularly polarized light in a non-polarized state. The second circularly polarized light separating layer 14 transmits only the left circularly polarized light component of the unpolarized green light. Here, the second circularly polarized light separating layer 1
Since the right-handed circularly polarized light component reflected at 4 is returned to the backlight 23 and recycled, the left-handed circularly polarized light is seen from the observation side of the second circularly polarized light separating layer 14 as in the first embodiment described above. Ideally, the polarized green light is emitted with an intensity of 100%. Further, such left circularly polarized green light is transmitted through the third circularly polarized light separating layer 15 which reflects the bluish red left circularly polarized light.

After that, the green left-handed circularly polarized light transmitted through the third circularly polarized light separating layer 15 has a first 1/0 angle of which the optical axis angle is 0 °.
By passing through the four-wavelength phase difference layer 16, the amplitude direction of the electric field vector is converted into linearly polarized light of −45 °, and the absorption-type first linearly polarizing layer 11 having an optical axis angle of −45 °.
Is 100% transparent. Next, this linearly polarized light is converted into right circularly polarized light by passing through the second quarter-wave retardation layer 17 having an optical axis angle of 0 °, and reaches the first circularly polarized light separating layer 13. . However, this first circularly polarized light separation layer 1
Since 3 reflects green right circularly polarized light, green light is not emitted from the observation side of the first circularly polarized light separating layer 13.

To summarize the above, as shown in FIGS. 4 (a) (b) (c) (d), when the angle θ of the optical axis of the second quarter-wave retardation layer 17 is 0 °, In the portion corresponding to the green pixel, not only the light other than the green light (blue-red light) among the external light and the backlight light, but also the green light itself is not emitted at all. Note that such an operation state is the same in the portions corresponding to other red pixels and blue pixels.

Next, referring to FIGS. 5 (a) (b) (c) (d), the second 1/4 wavelength retardation layer 17 of the liquid crystal display device 20B shown in FIG. The operation state when the angle θ of the optical axis is 45 ° will be described.

First, with reference to FIGS. 5A and 5B, the behavior of the bluish red light other than the green light among the external light and the backlight will be described.

As shown in FIG. 5A, the bluish-red light contained in the external light is incident on the absorption-type observation-side linear polarization layer 22 having an optical axis angle of −45 ° in a non-polarized state. The observation-side linearly polarizing layer 22 transmits only linearly polarized light of which the electric field vector has an amplitude direction of −45 ° among unpolarized blue-red light. Such linearly polarized light is converted into linearly polarized light whose electric field vector has an amplitude direction of 45 ° by passing through the liquid crystal driving cell 21, and the absorption-type second linearly polarizing layer whose optical axis angle is 45 °. 12 is 100% transparent. Next, this linearly polarized light is 100% transmitted through the third quarter-wave retardation layer 18 having an optical axis angle of 135 °, and the first circularly polarized light separation layer 13 that reflects green right circularly polarized light, and The angle of the optical axis is 45
The second quarter-wave retardation layer 17 of 100 ° also transmits 100% and reaches the absorption-type first linear polarization layer 11. However, this first linearly polarizing layer 11 is the second linearly polarizing layer 12
Are arranged so that the optical axes thereof are orthogonal to each other, and the angle of the optical axes is −45 °, so that the blue-red light contained in the external light is completely absorbed in the first linear polarization layer 11.

On the other hand, as shown in FIG. 5B, the bluish red light included in the backlight light behaves similarly to the case shown in FIG. No bluish red light is emitted from the observation side.

Next, with reference to FIGS. 5 (c) and 5 (d), the behavior of the green light of the outside light and the backlight will be described.

As shown in FIG. 5 (c), the green light contained in the external light is incident on the absorption type observation side linear polarization layer 22 having an optical axis angle of −45 ° in a non-polarized state. The observation-side linearly polarizing layer 22 transmits only linearly polarized light of which the electric field vector has an amplitude direction of −45 ° among unpolarized green light. Such linearly polarized light is converted into linearly polarized light whose electric field vector has an amplitude direction of 45 ° by passing through the liquid crystal driving cell 21, and the absorption-type second linearly polarizing layer whose optical axis angle is 45 °. 12 is 100% transparent. Next, this linearly polarized light 100% passes through the third quarter-wave retardation layer 18 having an optical axis angle of 135 ° and reaches the first circularly polarized light separation layer 13. Here, since this linearly polarized light is green light, the first circularly polarized light separation layer 13 that reflects green right circularly polarized light.
At, the right circularly polarized light component is reflected and the left circularly polarized light component is transmitted. Among these, the green right circularly polarized light reflected by the first circularly polarized light separating layer 13 has a third ¼ wavelength phase difference layer 18 and a second linearly polarizing layer with an optical path and a polarization state as shown in the drawing. 12, the liquid crystal driving cell 21 and the observation side linear polarization layer 22 are sequentially transmitted, and emitted from the observation side. On the other hand, the first
The green left-handed circularly polarized light transmitted through the circularly polarized light separating layer 13 is transmitted through the second quarter-wave retardation layer 17 having an optical axis angle of 45 °, so that the amplitude direction of the electric field vector is 90 °. It is converted into linearly polarized light and reaches the absorption-type first linearly polarizing layer 11. Here, the first linear polarizing layer 11 is arranged so that the optical axis thereof is orthogonal to the second linear polarizing layer 12, and the angle of the optical axis is −45 °. At 11, half of the green light is absorbed and the other half is converted into linearly polarized light with the electric field vector having an amplitude direction of −45 °. After that, the linearly polarized light is converted into left circularly polarized light by passing through the first quarter-wave retardation layer 16 having an optical axis angle of 0 °, and the third circularly polarized light that reflects blue-red left circularly polarized light is reflected. The circularly polarized light separating layer 15 and the second circularly polarized light separating layer 14 that reflects the white right-handed circularly polarized light are sequentially transmitted by 100%,
It is returned to the backlight 23 as green left circularly polarized light. This green left circularly polarized light is reflected by the backlight 23 and has the second circularly polarized light separating layer 14, the third circularly polarized light separating layer 15 and the first 1/4 with the optical path and the polarization state as shown in the figure.
After passing through the wavelength phase difference layer 16, the first linear polarization layer 11 and the second quarter wavelength phase difference layer 17 sequentially, only the green left circularly polarized light is transmitted through the first circularly polarized light separating layer 13. , The second linear polarization layer 12, the liquid crystal driving cell 21, and the observation-side linear polarization layer 22 are sequentially transmitted and emitted from the observation side. In the process of exiting from the observation side in this way, the green right circularly polarized light will be returned to the backlight 23 side again in the first circularly polarized light separating layer 13, but it was returned in this way. The light also finally exits from the observation side through the optical path and polarization state as shown in the figure.

As a result, as shown in FIG. 5C, the green light contained in the external light is emitted from the observation side at a rate of about 6% of the whole.

On the other hand, as shown in FIG. 5D, the green light included in the backlight is incident on the second circularly polarized light separating layer 14 which reflects the white right-handed circularly polarized light in a non-polarized state. The second circularly polarized light separating layer 14 transmits only the left circularly polarized light component of the unpolarized green light. Here, the second circularly polarized light separating layer 1
Since the right-handed circularly polarized light component reflected at 4 is returned to the backlight 23 and recycled, the left-handed circularly polarized light is seen from the observation side of the second circularly polarized light separating layer 14 as in the first embodiment described above. Ideally, the polarized green light is emitted with an intensity of 100%. Further, such left circularly polarized green light is transmitted through the third circularly polarized light separating layer 15 which reflects the bluish red left circularly polarized light. At this time, in the portion of the third circularly polarized light separating layer 15 corresponding to, for example, the green pixel, as in the above-described first embodiment, it is reflected by the peripheral portions corresponding to the blue and red pixels. Green light is used in the portion corresponding to the green pixel, and the second and third circularly polarized light separating layers 1
From the observation side of 4 and 15, the green light in the left circularly polarized state ideally exits with 100% intensity.

After that, the green left-handed circularly polarized light transmitted through the third circularly polarized light separating layer 15 has a first 1/1/0 angle of the optical axis of 0 °.
By passing through the four-wavelength phase difference layer 16, the amplitude direction of the electric field vector is converted into linearly polarized light of −45 °, and the absorption-type first linearly polarizing layer 11 having an optical axis angle of −45 °.
Is 100% transparent. Next, this linearly polarized light passes through the second quarter-wave retardation layer 17 having an optical axis angle of 45 ° and reaches the first circularly polarized light separating layer 13. Here, since this linearly polarized light is green light, the right circularly polarized light component is reflected and the left circularly polarized light component is transmitted in the first circularly polarized light separating layer 13 that reflects green right circularly polarized light. . Of these, the green left-handed circularly polarized light that has passed through the first circularly polarized light separating layer 13 passes through the third quarter-wave retardation layer 18 having an optical axis angle of 135 °, and thus the amplitude of the electric field vector is increased. The light is converted into linearly polarized light having a direction of 90 ° and reaches the absorption-type second linearly polarizing layer 12. Here, this second linear polarization layer 1
2 is arranged so that the optical axis is orthogonal to the second linear polarization layer 11, and the angle of the optical axis is 45 °, so that half of the green light is absorbed in the second linear polarization layer 12. The other half is converted into linearly polarized light whose electric field vector has an amplitude direction of 45 °. After that, such linearly polarized light
By passing through the liquid crystal driving cell 21, the amplitude direction of the electric field vector is converted into linearly polarized light of −45 °, and 100% is transmitted through the absorption-type second linearly polarizing layer 12 having an optical axis angle of −45 °. Then, the light is emitted from the observation side. On the other hand, the green right circularly polarized light reflected by the first circularly polarized light separating layer 13 is returned to the backlight 23 side again, and a part of the right circularly polarized light is emitted from the observation side through the optical path and the polarization state as shown in the figure. To do.

As a result, as shown in FIG. 5D, the green light contained in the backlight is emitted from the observation side at a rate of about 33% of the whole.

In summary, as shown in FIGS. 5 (a) (b) (c) (d), when the angle θ of the optical axis of the second quarter-wave retardation layer 17 is 45 °, In the portion corresponding to the green pixel, light other than green light (blue-red light) out of the external light and the backlight does not leak out, and the green light included in the external light accounts for about 6% of the whole. Percentage of green light emitted from the observation side and contained in the backlight is about 33% of the total.
The light is emitted from the observation side at a rate of. Note that this ratio is the same in the portions corresponding to other red pixels and blue pixels.

Next, referring to FIGS. 6 (a) (b) (c) (d), as the third operating state of the liquid crystal display device 20B shown in FIG. The operation state when the angle θ of the optical axis is 90 ° will be described.

First, with reference to FIGS. 6 (a) and 6 (b), the behavior of the bluish red light other than the green light among the outside light and the backlight will be described.

As shown in FIG. 6A, the bluish red light contained in the external light is incident on the absorption type observation side linear polarization layer 22 having an optical axis angle of −45 ° in a non-polarized state. The observation-side linearly polarizing layer 22 transmits only linearly polarized light of which the electric field vector has an amplitude direction of −45 ° among unpolarized blue-red light. Such linearly polarized light is converted into linearly polarized light whose electric field vector has an amplitude direction of 45 ° by passing through the liquid crystal driving cell 21, and the absorption-type second linearly polarizing layer whose optical axis angle is 45 °. 12 is 100% transparent. Next, this linearly polarized light is converted into right circularly polarized light by passing through the third quarter-wave retardation layer 18 having an optical axis angle of 180 °, and the first circularly polarized light that reflects green right circularly polarized light is reflected. Circularly polarized light separating layer 13
Is 100% transparent. Further, the blue-red left-handed circularly polarized light is converted into linearly polarized light having an electric field vector amplitude direction of 45 ° by passing through the second quarter-wave retardation layer 17 having an optical axis angle of 90 °. , Reaches the absorption-type first linearly polarizing layer 11. However, this first linear polarization layer 11
Is arranged so that the optical axis is orthogonal to the second linear polarization layer 12, and the angle of the optical axis is −45 °, so that blue-red light is completely absorbed in the first linear polarization layer 11. It

On the other hand, as shown in FIG. 6B, the bluish red light contained in the backlight light behaves similarly to the case shown in FIG. No bluish red light is emitted from the observation side.

Next, with reference to FIGS. 6 (c) and 6 (d), the behavior of the green light of the external light and the backlight will be described.

As shown in FIG. 6 (c), the green light contained in the outside light is incident on the absorption type observation side linear polarization layer 22 having an optical axis angle of −45 ° in a non-polarized state. The observation-side linearly polarizing layer 22 transmits only linearly polarized light of which the electric field vector has an amplitude direction of −45 ° among unpolarized green light. Such linearly polarized light is converted into linearly polarized light whose electric field vector has an amplitude direction of 45 ° by passing through the liquid crystal driving cell 21, and the absorption-type second linearly polarizing layer whose optical axis angle is 45 °. 12 is 100% transparent. Next, this linearly polarized light is converted into right circularly polarized light by passing through the third quarter-wave retardation layer 18 having an optical axis angle of 180 °, and the first circularly polarized light that reflects green right circularly polarized light is reflected. Circularly polarized light separation layer 13 10
It is reflected by 0%. Thereafter, the green right circularly polarized light reflected by the first circularly polarized light separating layer 13 has the optical path and the polarization state as shown in the figure, and the third quarter wavelength retardation layer 18 and the second linear polarizing layer 12 are provided. , The liquid crystal driving cell 21 and the observation-side linear polarization layer 22 are sequentially transmitted, and emitted from the observation side.

As a result, as shown in FIG. 6C, the green light contained in the external light is emitted from the observation side at a rate of about 17% of the whole.

On the other hand, as shown in FIG. 6D, the green light included in the backlight light is incident on the second circularly polarized light separating layer 14 which reflects the white right-handed circularly polarized light in a non-polarized state. The second circularly polarized light separating layer 14 transmits only the left circularly polarized light component of the unpolarized green light. Here, the second circularly polarized light separating layer 1
Since the right-handed circularly polarized light component reflected at 4 is returned to the backlight 23 and recycled, the left-handed circularly polarized light is seen from the observation side of the second circularly polarized light separating layer 14 as in the first embodiment described above. Ideally, the polarized green light is emitted with an intensity of 100%. Further, such left circularly polarized green light is transmitted through the third circularly polarized light separating layer 15 which reflects the bluish red left circularly polarized light. At this time, in the portion of the third circularly polarized light separating layer 15 corresponding to, for example, the green pixel, as in the above-described first embodiment, it is reflected by the peripheral portions corresponding to the blue and red pixels. Green light is used in the portion corresponding to the green pixel, and the second and third circularly polarized light separating layers 1
From the observation side of 4 and 15, the green light in the left circularly polarized state ideally exits with 100% intensity.

After that, the green left-handed circularly polarized light transmitted through the third circularly polarized light separating layer 15 has a first 1/1/0 angle of the optical axis.
By passing through the four-wavelength phase difference layer 16, the amplitude direction of the electric field vector is converted into linearly polarized light of −45 °, and the absorption-type first linearly polarizing layer 11 having an optical axis angle of −45 °.
Is 100% transparent. Next, this linearly polarized light is converted into left circularly polarized light by passing through the second quarter-wave retardation layer 17 having an optical axis angle of 90 °, and the first circularly polarized light that reflects green right circularly polarized light is reflected. The circularly polarized light separating layer 13 is 100% transmitted. After that, the green left-handed circularly polarized light transmitted through the first circularly polarized light separating layer 13 has a third 1 / th of which the optical axis angle is 180 °.
By passing through the four-wavelength phase difference layer 18, the amplitude direction of the electric field vector is converted into linearly polarized light of −45 °, and reaches the absorption-type second linearly polarizing layer 12. Where this second
The linear polarizing layer 12 of is arranged so that the optical axis thereof is orthogonal to the second linear polarizing layer 11, and the angle of the optical axis is 45 °. Is absorbed by.

Summarizing the above, as shown in FIGS. 6A, 6B, 6C and 6D, when the angle θ of the optical axis of the second quarter-wave retardation layer 17 is 90 °, In the part corresponding to the green pixel, light other than green light (blue-red light) out of the external light and the backlight does not leak out, and the green light included in the external light accounts for about 17% of the whole. The green light included in the backlight is emitted from the observation side at a ratio of about 0% of the whole. Note that this ratio is the same in the portions corresponding to other red pixels and blue pixels.

In the above description, the angle θ of the optical axis of the second quarter-wave retardation layer 17 is 0 °, 45 ° and 9 °.
Although only the case of setting to 0 ° has been described, the angle θ of the optical axis of the second quarter-wave retardation layer 17 can naturally take other values.

As described above, according to the second embodiment of the present invention, the polarizing element 10A according to the above-described first embodiment.
In addition to the above configuration, the second and third quarter-wave retardation layers 17 and 18 are provided on the back side and the observation side of the first circularly polarized light separating layer 13, respectively. Also, by simply changing the angles of the optical axes of the third quarter-wave retardation layers 17 and 18, the utilization efficiency of external light and backlight light can be set arbitrarily. Therefore, the liquid crystal display device 20B including such a polarizing element 10B is
Depending on the environment in which it is used, both external light and backlight light can be used most efficiently to display images and the like, and a display display with high light utilization efficiency can be obtained. Further, it is also possible to control the light utilization efficiency by dividing it within the plane of the display, and in this case, it is possible to effectively prevent a reduction in visibility due to reflection of light in a specific portion. it can.

Further, according to the second embodiment of the present invention, since the second and third quarter-wave retardation layers 17 and 18 are arranged so that their optical axes are orthogonal to each other,
Emission of light in an extra wavelength region of external light (for example, blue light and red light in the portion corresponding to the green pixel) is suppressed for each pixel, and only light of a desired color corresponding to the pixel is efficiently emitted. You can take it out.

Furthermore, according to the second embodiment of the present invention, the second and third quarter-wave retardation layers 17, 18 are provided.
Is a retardation layer whose optical axis changes in accordance with the applied voltage, so that the user can arbitrarily set the utilization efficiency of outside light and backlight light by electrical control.

In the above-described second embodiment, wideband quarter-wave retardation layers may be used as the second and third quarter-wave retardation layers 17 and 18. . In addition, as such a wideband 1/4 wavelength phase difference layer, in addition to the one that realizes the function independently,
A combination of a 4-wavelength retardation layer and a 1 / 2-wave retardation layer can be used. In the latter case,
The ½ wavelength retardation layer is arranged on the side where linearly polarized light is incident. Thereby, good color purity, contrast, and light utilization efficiency can be obtained.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. 7 and 8. The third embodiment of the present invention is preferably used in a transflective liquid crystal display device or the like having a backlight that emits colored light, and has a configuration on the back surface side of a polarizing element (first embodiment). 1/4 wavelength retardation layer, second
The third embodiment is almost the same as the second embodiment shown in FIGS. 3 to 6 except that the third circularly polarized light separating layer) is omitted. In the third embodiment of the present invention, the same parts as those in the second embodiment shown in FIGS. 3 to 6 are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 7, the liquid crystal display device 20C according to the third embodiment of the present invention includes a liquid crystal drive cell 21.
And an absorption-type linear polarization layer 22 on the observation side of the liquid crystal driving cell 21, and on the back side of the liquid crystal driving cell 21, the liquid crystal driving cell 21 is irradiated with unpolarized colored light. And a backlight 40 that operates. As the backlight 40, a surface light source including an electroluminescent light source 41 that emits colored light of each color of red, green, and blue for each pixel and a reflection plate 42 can be used. Instead of the electroluminescence light source 41, it is of course possible to use an LED element that emits colored light of each color of red, green and blue for each pixel.

Further, the liquid crystal driving cell 21 and the backlight 2
A polarization element 10C is provided between the back light 23 and the back light 23 provided on the back side while reflecting the light in a specific wavelength region of the external light incident from the observation side at a predetermined ratio. Light (backlight light) can be transmitted at a predetermined ratio.

Here, the polarizing element 10C is configured so that either the right circularly polarized light component or the left circularly polarized light component (for example, the right circularly polarized light component) has a predetermined wavelength region (for example, green light) included in the visible light region. The first circularly polarized light separating layer 13 that selectively reflects almost 100% in a wavelength region), and the absorption-type first linearly polarizing layer 11 provided on the back side of the first circularly polarized light separating layer 13. It is provided on the observation side of the first circularly polarized light separating layer 13 and has the first linear polarizing layer 11 and an absorptive second linear polarizing layer 12 arranged so that their optical axes are orthogonal to each other.

The polarizing element 10C includes the second quarter-wave retardation layer 17 provided between the first circularly polarized light separating layer 13 and the first linearly polarizing layer 11, and the first circularly polarized light phase difference layer 17. Polarization separation layer 1
3 between the second linearly polarizing layer 12 and the second linear polarizing layer 12.
It has a quarter-wave retardation layer 17 and a third quarter-wave retardation layer 18 arranged so that their optical axes are orthogonal to each other.

The first circularly polarized light separating layer 13 has a plurality of divided areas divided in the layer plane corresponding to each pixel of the liquid crystal drive cell 21, and the backlight 40 has a divided area in each divided area. It is preferable to selectively reflect light of different wavelength regions (for example, light of red, green, or blue wavelength regions) emitted by the electroluminescent light source 41 for each pixel. Further, the first circularly polarized light separating layer 13 is preferably made of a cholesteric liquid crystal layer.

As the second and third quarter-wave retardation layers 17 and 18, retardation layers whose optical axis changes according to the applied voltage can be used. Specifically, for example,
A drive cell that imparts a phase difference with nematic liquid crystal, smectic liquid crystal, or the like can be used. Further, the second and third quarter-wave retardation layers 17 and 18 themselves are arranged so as to be rotatable in a plane orthogonal to the traveling direction of light, and the second And the angle θ of the optical axes of the third quarter-wave retardation layers 17 and 18 may be changed. Next, referring to FIG. 8, the operation state of the liquid crystal display device 20C shown in FIG. An example is described in which the angle θ of the optical axis of the ¼ wavelength retardation layer 17 is set to 45 °, and the optical axes and optical rotation selection characteristics of the other layers that are the constituent elements are set as illustrated. To do. Note that, here, as in the case of the above-described second embodiment, only the behavior of light in the portion corresponding to the green pixel will be described, but the light in the portions corresponding to the other red and blue pixels will be described. The behavior of is the same as that shown in FIG. 8 except that the wavelength regions of reflected and transmitted light are different, and therefore detailed description thereof is omitted here. The notation method of FIG. 8 is the same as that shown in FIG.

First, with reference to FIGS. 8A and 8B, the behavior of bluish red light other than green light among outside light and backlight will be described.

As shown in FIG. 8A, the bluish-red light contained in the external light is incident on the absorption-type observation side linear polarization layer 22 having an optical axis angle of −45 ° in a non-polarized state. The observation-side linearly polarizing layer 22 transmits only linearly polarized light of which the electric field vector has an amplitude direction of −45 ° among unpolarized blue-red light. Such linearly polarized light is converted into linearly polarized light whose electric field vector has an amplitude direction of 45 ° by passing through the liquid crystal driving cell 21, and the absorption-type second linearly polarizing layer whose optical axis angle is 45 °. 12 is 100% transparent. Next, this linearly polarized light is 100% transmitted through the third quarter-wave retardation layer 18 having an optical axis angle of 135 °, and the first circularly polarized light separation layer 13 that reflects green right circularly polarized light, and The angle of the optical axis is 45
The second quarter-wave retardation layer 17 of 100 ° also transmits 100% and reaches the absorption-type first linear polarization layer 11. However, this first linearly polarizing layer 11 is the second linearly polarizing layer 12
And the optical axis are orthogonal to each other, and the angle of the optical axis is −45 °, so that the blue-red light is completely absorbed in the first linear polarization layer 11.

On the other hand, as shown in FIG. 8B, only the green light is emitted from the electroluminescence light source 41 of the backlight 40 in the portion corresponding to the green pixel.
No blue-red light is emitted from this portion.

Next, with reference to FIGS. 8 (c) and 8 (d), the behavior of the green light of the external light and the backlight will be described.

As shown in FIG. 8C, the green light contained in the external light is incident on the absorption type linear polarization layer 22 on the observation side having an optical axis of −45 ° in a non-polarized state. The observation-side linearly polarizing layer 22 transmits only linearly polarized light of which the electric field vector has an amplitude direction of −45 ° among unpolarized green light. Such linearly polarized light is converted into linearly polarized light whose electric field vector has an amplitude direction of 45 ° by passing through the liquid crystal driving cell 21, and the absorption-type second linearly polarizing layer whose optical axis angle is 45 °. 12 is 100% transparent. Next, this linearly polarized light 100% passes through the third quarter-wave retardation layer 18 having an optical axis angle of 135 ° and reaches the first circularly polarized light separation layer 13. Here, since this linearly polarized light is green light, the first circularly polarized light separation layer 13 that reflects green right circularly polarized light.
At, the right circularly polarized light component is reflected and the left circularly polarized light component is transmitted. Among these, the green right circularly polarized light reflected by the first circularly polarized light separating layer 13 has a third ¼ wavelength phase difference layer 18 and a second linearly polarizing layer with an optical path and a polarization state as shown in the drawing. 12, the liquid crystal driving cell 21 and the observation side linear polarization layer 22 are sequentially transmitted, and emitted from the observation side. On the other hand, the first
The green left-handed circularly polarized light transmitted through the circularly polarized light separating layer 13 is transmitted through the second quarter-wave retardation layer 17 having an optical axis angle of 45 °, so that the amplitude direction of the electric field vector is 90 °. It is converted into linearly polarized light and reaches the absorption-type first linearly polarizing layer 11. Here, the first linear polarizing layer 11 is arranged so that the optical axis thereof is orthogonal to the second linear polarizing layer 12, and the angle of the optical axis is −45 °. At 11, half of the green light is absorbed and the other half is converted into linearly polarized light with the electric field vector having an amplitude direction of −45 °. After that, this linearly polarized light is reflected by the backlight 4.
0 is reflected by the reflection plate 42, and is sequentially transmitted through the first linear polarization layer 11 and the second quarter-wave retardation layer 17 in the optical path and the polarization state as shown in the figure, and then the first circularly polarized light is separated. Only the left-handed circularly polarized light of green is transmitted through the layer 13, the second linear polarization layer 12, the liquid crystal drive cell 21, and the observation side linear polarization layer 22 are sequentially transmitted and emitted from the observation side. In the process of exiting from the observation side in this way, the green right circularly polarized light will be returned to the backlight 23 side again in the first circularly polarized light separating layer 13, but it was returned in this way. The light also finally exits from the observation side through the optical path and polarization state as shown in the figure.

As a result, as shown in FIG. 8C, the green light contained in the external light is emitted from the observation side at a rate of about 6% of the whole.

On the other hand, as shown in FIG. 8 (d), the green light emitted from the electroluminescent light source 41 of the backlight 40 is the first absorption type linearly polarized light having an optical axis angle of −45 °. It is incident on the layer 11 in a non-polarized state. The first linearly polarizing layer 11 transmits only linearly polarized light having an electric field vector of −45 ° out of unpolarized green light. This linearly polarized light is then converted into a second linearly polarized light with an optical axis angle of 45 °.
The first circularly polarized light separating layer 1 which is transmitted through the / 4 wavelength retardation layer 17
Reach 3. Here, since this linearly polarized light is green light, the right circularly polarized light component is reflected and the left circularly polarized light component is transmitted in the first circularly polarized light separating layer 13 that reflects green right circularly polarized light. . Of these, the first circularly polarized light separation layer 1
The green left circularly polarized light transmitted through 3 has an optical axis angle of 135
By passing through the third quarter-wave retardation layer 18 of 90 °, the electric field vector is converted into linearly polarized light of 90 ° in the amplitude direction, and reaches the absorption-type second linearly polarizing layer 12. Here, the second linear polarization layer 12 is the second linear polarization layer 11
And the optical axis are orthogonal to each other, and the angle of the optical axis is 45 °, half of the green light is absorbed in the second linear polarization layer 12, and the other half is in the amplitude direction of the electric field vector. Is converted to 45 ° linearly polarized light. After that, such linearly polarized light passes through the liquid crystal drive cell 21 to be converted into linearly polarized light whose electric field vector has an amplitude direction of −45 °, and the absorption-type second polarized light whose optical axis angle is −45 °. 100% of light is transmitted through the linear polarization layer 12 and is emitted from the observation side. On the other hand, the green right circularly polarized light reflected by the first circularly polarized light separating layer 13 is returned to the backlight 23 side again, and a part of the right circularly polarized light is emitted from the observation side through the optical path and the polarization state as shown in the figure. To do.

As a result, as shown in FIG. 8D, the backlight light (green light) is emitted from the observation side at a rate of about 17% of the whole.

To summarize the above, as shown in FIGS. 8 (a) (b) (c) (d), when the angle θ of the optical axis of the second quarter-wave retardation layer 17 is 45 °, In the portion corresponding to the green pixel, light other than green light (blue-red light) out of the external light and the backlight does not leak out, and the green light included in the external light accounts for about 6% of the whole. About 17% of the total green light emitted from the observation side and contained in the backlight light
The light is emitted from the observation side at a rate of. Note that this ratio is the same in the portions corresponding to other red pixels and blue pixels.

In the above description, only the case where the angle θ of the optical axis of the second quarter-wave retardation layer 17 is set to 45 ° has been described.
Naturally, the angle θ of the optical axis of 7 can take other values. For example, when the angle θ of the optical axis of the second quarter-wave retardation layer 17 is set to 0 °, the external light and the external light are emitted in the portion corresponding to the green pixel as in the second embodiment described above. Not only the light other than green light (blue-red light) of the backlight light, but also the green light itself is not emitted at all. Further, when the angle θ of the optical axis of the second quarter-wave retardation layer 17 is set to 90 °, in the portion corresponding to the green pixel, as in the above-described second embodiment,
Light other than green light (blue-red light) out of the external light and the backlight does not leak out, and the green light included in the external light is emitted from the observation side at a rate of about 17% of the total, and the backlight light is emitted. (Green light) is emitted from the observation side at a rate of about 0% of the whole.

As described above, according to the third embodiment of the present invention, as with the above-described first and second embodiments, with respect to outside light, the first circularly polarized light separating layer 13 is provided. Absorption-type first and second linear polarization layers 1 arranged so that their optical axes are orthogonal to each other on the back side and the observation side of the
Since 1 and 12 are provided, emission of light in an extra wavelength region of external light (for example, blue light and red light in a portion corresponding to a green pixel) is suppressed for each pixel, and a desired light corresponding to the pixel is provided. Only the light of the color can be extracted efficiently.
On the other hand, as for the backlight light, the light (for example, green light) in a specific wavelength range emitted from the electroluminescent light source 41 of the backlight 40 is observed through the absorption-type first linear polarization layer 11 on the observation side. Can be sent to. Therefore, according to such a polarization element 10C, it is possible to efficiently extract light in a specific wavelength region having a specific polarization state from outside light and backlight light. Further, the liquid crystal display device 20C including such a polarizing element 10C can display images and the like by efficiently using both external light and backlight light without using an absorption type color filter. It is possible to obtain a display with high light utilization efficiency.

According to the third embodiment of the present invention, the second and third quarter-wave retardation layers 17 and 18 are provided on the back side and the observation side of the first circularly polarized light separating layer 13, respectively.
Therefore, the second and third of these are provided.
The utilization efficiency of outside light and backlight light can be arbitrarily set only by changing the angles of the optical axes of the quarter-wave retardation layers 17 and 18. Therefore, the liquid crystal display device 20C including such a polarization element 10C is required to display an image or the like by most efficiently using both external light and backlight light according to the environment in which it is used. Therefore, a display with high light utilization efficiency can be obtained. Further, it is also possible to control the light utilization efficiency by dividing it within the plane of the display, and in this case, it is possible to effectively prevent a reduction in visibility due to reflection of light in a specific portion. it can.

Further, according to the third embodiment of the present invention, since the second and third quarter-wave retardation layers 17 and 18 are arranged so that their optical axes are orthogonal to each other,
Emission of light in an extra wavelength region of external light (for example, blue light and red light in the portion corresponding to the green pixel) is suppressed for each pixel, and only light of a desired color corresponding to the pixel is efficiently emitted. You can take it out.

Furthermore, according to the third embodiment of the present invention, the second and third quarter-wave retardation layers 17, 1 are provided.
By using 8 as a retardation layer whose optical axis changes according to the applied voltage, the user can set the utilization efficiency of outside light and backlight light arbitrarily by electrical control.

In the above third embodiment, as the first to third quarter-wave retardation layers 16 to 18, broadband quarter-wave retardation layers may be used. . In addition, as such a wideband quarter-wave retardation layer, one that realizes the function independently,
A combination of the wavelength retardation layer and the 1/2 wavelength retardation layer can be used. In the latter case, the half-wave retardation layer is arranged on the side where linearly polarized light is incident. Thereby, good color purity, contrast, and light utilization efficiency can be obtained.

Fourth Embodiment Next, a fourth embodiment of the present invention will be described with reference to FIGS. 9 and 10. In the fourth embodiment of the present invention, a first quarter-wave retardation layer and a second circularly polarized light separating layer are provided between the absorption type first linear polarizing layer and the backlight. Other than the above, the others are the third shown in FIG. 7 and FIG.
This is almost the same as the embodiment of. In the fourth embodiment of the present invention, the same parts as those of the third embodiment shown in FIGS. 7 and 8 are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 9, in the liquid crystal display device 20D according to the fourth embodiment of the present invention, a polarizing element 10D is provided between the liquid crystal drive cell 21 and the backlight 23.

Here, in addition to the configuration of the polarizing element 10C shown in FIG. 7, the polarizing element 10D is provided on the back side of the absorption type first linear polarizing layer 11, and the first circularly polarized light separating layer 13 is provided. At least the first circularly polarized light component having the same optical rotation direction as the circularly polarized light component selectively reflected (for example, the right circularly polarized light component)
In a predetermined wavelength range (for example, a green wavelength range or a white wavelength range) reflected by the circularly polarized light separating layer 13 of
A second circularly polarized light separating layer 14 that selectively reflects 100%, and a first quarter-wave retardation layer provided between the first linearly polarizing layer 11 and the second circularly polarized light separating layer 14. 16 and 16 are further included. The optical axis of the first linear polarization layer 11 is the same as the amplitude direction of linear polarization formed by passing through the second circularly polarized light separation layer 14 and the first quarter-wave retardation layer 16. It is arranged to match.

Next, referring to FIG. 10, regarding the operating state of the liquid crystal display device 20D shown in FIG. 9, the angle θ of the optical axis of the second quarter-wave retardation layer 17 is set to 45 °, and the constituent elements are set. An example will be described in which the optical axes and optical rotation selection characteristics of certain other layers are set as illustrated. Note that here, as in the case of the above-described first embodiment, only the behavior of light in the portion corresponding to the green pixel will be described, but the light in the portions corresponding to the other red and blue pixels will be described. The behavior of is the same as that shown in FIG. 10 except that the wavelength regions of reflected and transmitted light are different, and therefore detailed description thereof is omitted here. The notation method in FIG. 10 is the same as that shown in FIG.

First, with reference to FIGS. 10A and 10B, the behavior of bluish red light other than green light among the outside light and the backlight will be described.

As shown in FIG. 10 (a), the bluish red light contained in the external light behaves similarly to the case shown in FIG. 8 (a),
In the first linear polarization layer 11, the bluish red light included in the outside light is completely absorbed.

On the other hand, as shown in FIG. 10 (b), only green light is emitted from the electroluminescence light source 41 of the backlight 40 in the portion corresponding to the green pixel. Will not be emitted.

Next, with reference to FIGS. 10 (c) and 10 (d), the behavior of the green light of the outside light and the backlight will be described.

As shown in FIG. 10 (c), the green light contained in the outside light behaves in substantially the same manner as the case shown in FIG. 8 (c).

However, the green left-handed circularly polarized light transmitted through the first circularly polarized light separating layer 13 is transmitted through the second quarter-wave retardation layer 17 and the absorption-type first linear polarizing layer 11 to generate an electric field. After the vector amplitude direction is converted to -45 ° linearly polarized light,
The second circularly polarized light separating layer 14 that is converted into left circularly polarized light by transmitting through the first quarter-wave retardation layer 16 having an optical axis angle of 0 ° and reflects green or white right circularly polarized light 1
00% transmission, and backlight 23 as green left circularly polarized light
Returned to.

As a result, as shown in FIG. 10 (c), the green light contained in the external light is as in the case shown in FIG. 8 (c).
The light is emitted from the observation side at a rate of about 6% of the whole.

On the other hand, as shown in FIG. 10 (d), the green light emitted from the electroluminescent light source 41 of the backlight 40 behaves in a manner substantially similar to that shown in FIG. 8 (d).

However, the green light emitted from the backlight 40 enters the second circularly polarized light separating layer 14 which reflects the white right circularly polarized light in a non-polarized state. Second circularly polarized light separating layer 1
Reference numeral 4 transmits only the left-handed circularly polarized light component of the unpolarized green light. Here, since the right-handed circularly polarized light component reflected by the second circularly polarized light separating layer 14 is returned to the backlight 23 and recycled, the second circularly polarized light component is recycled as in the first embodiment described above.
From the observation side of the circularly polarized light separating layer 14, the green light in the left circularly polarized state is ideally emitted with an intensity of 100%.

Thereafter, the green left-handed circularly polarized light transmitted through the second circularly polarized light separating layer 14 has a first 1/1/0 angle of the optical axis of 0 °.
By passing through the four-wavelength phase difference layer 16, the amplitude direction of the electric field vector is converted into linearly polarized light of −45 °, and the absorption-type first linearly polarizing layer 11 having an optical axis angle of −45 °.
Is 100% transparent.

As a result, the backlight light (green light)
Differs from the case shown in FIG. 8 (d) in the first linearly polarizing layer 1
Since the loss at 1 is eliminated, as shown in FIG.
The light is emitted from the observation side at a rate of about 33% of the whole.

To summarize the above, as shown in FIGS. 10 (a) (b) (c) (d), when the angle θ of the optical axis of the second quarter-wave retardation layer 17 is 45 °. In the portion corresponding to the green pixel, light other than green light (blue-red light) out of the external light and the backlight does not leak out, and the green light included in the external light accounts for about 6% of the whole. Percentage of green light emitted from the observation side and contained in the backlight is about 33% of the total.
The light is emitted from the observation side at a rate of. Note that this ratio is the same in the portions corresponding to other red pixels and blue pixels.

In the above description, only the case where the angle θ of the optical axis of the second quarter-wave retardation layer 17 is set to 45 ° has been described.
Naturally, the angle θ of the optical axis of 7 can take other values. For example, when the angle θ of the optical axis of the second quarter-wave retardation layer 17 is set to 0 °, the external light and the external light are emitted in the portion corresponding to the green pixel as in the second embodiment described above. Not only the light other than green light (blue-red light) of the backlight light, but also the green light itself is not emitted at all. Further, when the angle θ of the optical axis of the second quarter-wave retardation layer 17 is set to 90 °, in the portion corresponding to the green pixel, as in the above-described second embodiment,
Light other than green light (blue-red light) out of the external light and the backlight does not leak out, and the green light included in the external light is emitted from the observation side at a rate of about 17% of the total, and the backlight light is emitted. The green light contained in is emitted from the observation side at a rate of about 0% of the whole.

As described above, according to the fourth embodiment of the present invention, the polarization element 10C according to the above-described third embodiment.
In addition to the above configuration, the first quarter-wave retardation layer 16 is provided between the absorption-type first linear polarization layer 11 and the backlight 40.
Further, since the second circularly polarized light separating layer 14 is provided, in the liquid crystal display device 20D including such a polarizing element 10D, both external light and backlight light can be used more efficiently to obtain an image or the like. Can be displayed, and a display with high light utilization efficiency can be obtained.

[0155]

EXAMPLES Next, specific examples of the above-described embodiment will be described. The present example corresponds to the above-described second embodiment.

In this embodiment, as shown in FIG.
Observation-side linear polarization layer 22, liquid crystal drive cell 21, polarization element 1
0B and the backlight 23 were arranged in this order from the observation side to prepare a liquid crystal display device 20B.

As the polarizing element 10B, as shown in FIG. 3, the second linear polarizing layer 12, the third ¼ wavelength retardation layer 18, the first circularly polarized light separating layer 13, and the second 1 The quarter-wave retardation layer 17, the first linear polarization layer 11, the first quarter-wave retardation layer 16, the third circularly polarized light separating layer 15 and the second circularly polarized light separating layer 14 are arranged from the observation side. They are arranged in order.

However, in the polarizing element 10B according to the present embodiment, the first circularly polarized light separating layer 13 and the third circularly polarized light separating layer 15 are not divided in the plane of the layer, and in the first circularly polarized light separating layer 13 Selectively reflects light in the green wavelength region,
The circularly polarized light separating layer 15 is configured to selectively reflect light in the blue-red wavelength range. It should be noted that such a configuration corresponds to a portion corresponding to a green pixel in the liquid crystal display device.

Here, as the liquid crystal mode of the liquid crystal drive cell 21, a TN (twisted nematic) mode was used. As the backlight 23, a surface light source including a linear light source that emits white light and a light guide plate is used. Further, as the observation side linear polarization layer 22, an absorption type was used, and the angle of its optical axis was set to −45 °.

As the first circularly polarized light separating layer 13,
A cholesteric liquid crystal layer that selectively reflects almost 100% of right circularly polarized light having a center wavelength of 500 nm was used. Also,
The second circularly polarized light separating layer 14 is 400 nm to 700 nm.
A cholesteric liquid crystal layer that reflects almost 100% of right circularly polarized light of nm was used. Further, as the third circularly polarized light separating layer 15, approximately 10 circularly polarized left circularly polarized light having a center wavelength of 410 nm is used.
A cholesteric liquid crystal layer that selectively reflects 0% and 590
A laminate with a cholesteric liquid crystal layer that selectively reflects almost 100% of left-handed circularly polarized light having a center wavelength of nm was used.

Furthermore, the first and second linear polarizing layers 1
Absorption type is used as 1 and 12, specifically, TE
A CH SPEC (trademark) polarizing film (manufactured by Edmond) was used. Here, the optical axis of the observation side linear polarization layer 22 and the optical axis of the second linear polarization layer 12 were arranged so as to be orthogonal to each other. Further, the optical axis of the second linear polarizing layer 12 and the optical axis of the first linear polarizing layer 11 were arranged so as to be orthogonal to each other. That is, the first and second linear polarization layers 11 and 12
Respectively set the angles of their optical axes to -45 ° and 45 °.

Further, as the first to third quarter-wave retardation layers 16 to 18, COMMERCIAL 1 / 4λ retardation films (made by Polaroid) were used. Here, the first quarter-wave retardation layer 16 has an amplitude direction of linearly polarized light formed by passing through the second circularly polarized light separation layer 14 and the first quarter-wave retardation layer 16. First linear polarization layer 1
They are arranged in such a relationship that they coincide with the optical axis of 1. As described above, since the angle of the optical axis of the first linear polarization layer 11 is −45 °, the first quarter-wave retardation layer 1
The angle of the optical axis of 6 was set to 0 degree. The second and third quarter-wave retardation layers 17 and 18 are arranged so that their optical axes are orthogonal to each other, but their angles (for example, the second
The angle θ of the optical axis of the quarter-wave retardation layer 17 of
It was arbitrarily set in the range of 0 ° to 180 °.

(Evaluation Results) First, when the angle θ of the optical axis of the second quarter-wave retardation film 17 is set to 45 ° (second to the optical axis of the first linear polarizing layer 11). 1 /
When the optical axes of the four-wavelength phase difference layer 17 are orthogonal to each other), it was confirmed that when the backlight 23 was turned on in a dark room, it looked green. Moreover, it was confirmed that even when the backlight 23 was turned off, it looked green under the illumination of a fluorescent lamp. Furthermore, it was confirmed that when the backlight 23 was turned on in that state, the green color became brighter.

Next, the light utilization efficiency was measured when the angles of the optical axes of the second and third quarter-wave retardation films 17 and 18 were changed. A Goniometer (made by Apex) was used for the measurement.

Regarding the utilization efficiency of external light, the unpolarized white light was irradiated and the intensity of the reflected light at an incident angle of 5 ° was measured. In this case, the utilization efficiency is 410nm, 500nm
And the wavelength of 590 nm were calculated by (intensity of incident light at a specific wavelength) / (intensity of reflected light at a specific wavelength).

On the other hand, regarding the utilization efficiency of the backlight light, after removing the backlight 23, the left circularly polarized white light is made incident on the second circularly polarized light separating layer 14, and the efficiency is 0 °. The intensity of the transmitted light at the angle of incidence was measured. In addition,
This case corresponds to a state in which the light emitted from the backlight 23 is first recycled 100%, but the amount of repeated internal recycling is not taken into consideration. In this case, the utilization efficiency is 410nm, 500nm
And (590 nm) respectively, it was calculated by (intensity of incident light at a specific wavelength) / (intensity of transmitted light at a specific wavelength).

The measurement results of this example are shown in Table 3 below.

[Table 3]

With respect to Table 3 above, in the case of outside light, a portion other than green light is absorbed in the portion corresponding to the green pixel in the white outside light as a color display, so that the outside light is absorbed. The intensity of was divided into three parts by red light, green light and blue light, and the measurement result was multiplied by 1/3.

Further, θ in Table 3 represents the angle of the optical axis of the second quarter-wave retardation film 17.

As shown in Table 3 above, the wavelength is 410 nm.
It can be seen that the blue light and the red light having a wavelength of 590 nm have a utilization efficiency of almost 0% at any angle θ. Further, the utilization efficiency of green light having a wavelength of 500 nm changed with the change of the angle θ.

FIG. 11 shows the calculation results obtained by numerical calculation of the change in utilization efficiency with respect to green light in this example. It can be confirmed that the measurement results in Table 3 above are similar to these calculation results. (In the measurement results of Table 3 above, the intensity of the backlight does not include the internally recycled component, but if this recycled component is included, it is expected that the numerical value will increase.) As can be seen from Table 3 and FIG. 11, it is preferable to use a large amount of external light in a bright place such as in the midday on a sunny day, and when the external light is used to the maximum, a second 1/4 The angle θ of the optical axis of the wavelength retardation layer 17 may be set to 90 °, and in this case, 17% of outside light can be used. On the other hand, in a dark place such as a dark room, it is preferable to use the backlight light to the maximum extent. When the angle θ of the optical axis of the second quarter-wave retardation layer 17 is set to 40 °, the backlight light is reduced to 35 degrees. % Can be used (5% of external light is used). Regarding the utilization efficiency of the backlight light, even if the conventional transmissive liquid crystal display device is ideal,
There is only% utilization efficiency. It should be noted that under room illumination, the brightness is only a few percent of that in a clear day at noon, but the brightness can be kept high by using it together with the backlight light. For example, the ratio of utilization efficiency of external light and backlight light is set to 8: 2.
If desired, the angle θ of the optical axis of the second quarter-wave retardation layer 17 may be set to around 50 °. Further, when it is desired to set the ratio of the utilization efficiency of the external light and the backlight light to 8: 2, the angle θ of the optical axis of the second ¼ wavelength phase difference layer 17 may be set to around 70 °.

[0172]

As described above, according to the present invention, it is possible to provide a polarizing element and a liquid crystal display device which do not need to use an absorption type color filter and have excellent light utilization efficiency. Further, it is possible to provide a polarizing element and a liquid crystal display device which are capable of arbitrarily setting the utilization efficiency of external light and backlight light according to the environment in which the display is used, and which are excellent in environmental compatibility. .

[Brief description of drawings]

FIG. 1 shows a polarizing element according to a first embodiment of the present invention,
The schematic diagram which shows the said polarization element in the state incorporated in the liquid crystal display device.

FIG. 2 is an optical path diagram for explaining an operating state of the liquid crystal display device shown in FIG.

FIG. 3 shows a polarizing element according to a second embodiment of the present invention,
The schematic diagram which shows the said polarization element in the state incorporated in the liquid crystal display device.

FIG. 4 is an optical path diagram for explaining a first operation state of the liquid crystal display device shown in FIG.

5 is an optical path diagram for explaining a second operation state of the liquid crystal display device shown in FIG.

6 is an optical path diagram for explaining a third operation state of the liquid crystal display device shown in FIG.

FIG. 7 shows a polarizing element according to a third embodiment of the present invention,
The schematic diagram which shows the said polarization element in the state incorporated in the liquid crystal display device.

FIG. 8 is an optical path diagram for explaining an operating state of the liquid crystal display device shown in FIG.

FIG. 9 shows a polarizing element according to a fourth embodiment of the present invention,
The schematic diagram which shows the said polarization element in the state incorporated in the liquid crystal display device.

10 is an optical path diagram for explaining an operating state of the liquid crystal display device shown in FIG.

11 is a diagram showing calculated values of light use efficiency (use efficiency of external light and backlight light) in the liquid crystal display device shown in FIG.

[Explanation of symbols]

10A, 10B, 10C, 10D Polarizing element 11 First linearly polarizing layer 12 Second linearly polarizing layer 13 First circularly polarized light separating layer 14 Second circularly polarized light separating layer 15 Third circularly polarized light separating layer 16 First Quarter Wave Phase Difference Layer 17 Second quarter-wave retardation layer 18 Third quarter-wave retardation layer 20A, 20B, 20C, 20D Liquid crystal display device 21 LCD drive cell 22 Observation side linear polarization layer 23,40 backlight 41 Electroluminescent light source (colored light source) 42 Reflector

Claims (21)

[Claims] 1. A first circularly polarized light separating layer which selectively reflects either one of the right circularly polarized light component and the left circularly polarized light component in a predetermined wavelength region included in a visible light region, and An absorption-type first linear polarization layer provided on the back side of the first circularly polarized light separating layer, and an absorption type first linearly polarizing layer provided on the observation side of the first circularly polarized light separating layer,
An absorptive second linearly polarizing layer arranged so that its optical axis is orthogonal to the linearly polarizing layer, and the first circularly polarized light separating layer is provided on the back side of the first linearly polarizing layer. A second circularly polarized light component that selectively reflects a circularly polarized light component having the same optical rotation direction as the first circularly polarized light component that is selectively reflected in a visible light region including the predetermined wavelength region that is reflected by the first circularly polarized light separating layer. Circularly polarized light separating layer, and the one circularly polarized light component which is provided between the first linearly polarizing layer and the second circularly polarized light separating layer and which is selectively reflected by the second circularly polarized light separating layer. And a third circularly polarized light separating layer that selectively reflects a circularly polarized light component having a different optical rotation direction in a wavelength region other than the predetermined wavelength region in which the first circularly polarized light separating layer reflects in the visible light region, A first linear polarization layer provided between the first linear polarization layer and the third circular polarization separation layer; A 1/4 wavelength retardation layer, wherein the optical axis of the first linearly polarizing layer passes through the second circularly polarized light separation layer and the first 1/4 wavelength retardation layer. A polarizing element, wherein the polarizing element is arranged so as to match the amplitude direction of the formed linearly polarized light. 2. A second quarter-wave retardation layer provided between the first circularly polarized light separating layer and the first linearly polarizing layer, the first circularly polarized light separating layer and the first circularly polarized light separating layer. It further comprises a third quarter-wave retardation layer provided between the second linear polarization layer and the second quarter-wave retardation layer arranged so that the optical axis thereof is orthogonal to the second quarter-wave retardation layer. The polarizing element according to claim 1, wherein: 3. The polarizing element according to claim 2, wherein the second and third quarter-wave retardation layers are retardation layers whose optical axes change according to an applied voltage. 4. The polarized light according to claim 2, wherein at least one of the first to third quarter-wave retardation layers is a broadband quarter-wave retardation layer. element. 5. The second circularly polarized light separating layer is 400 to 750.
5. The polarizing element according to claim 1, which selectively reflects light in the wavelength region of nm. 6. The first circularly polarized light separating layer has a plurality of segmented regions that are segmented within a layer surface, and selectively reflects light in different wavelength regions in each of the segmented regions. The polarizing element according to any one of claims 1 to 5. 7. The third circularly polarized light separating layer has a plurality of divided areas corresponding to the divided areas of the first circularly polarized light separating layer, and in each of the divided areas, the 7. The polarizing element according to claim 6, wherein light of a wavelength region other than the wavelength region reflected by each of the divided regions of the circularly polarized light separating layer of No. 1 is selectively reflected. 8. The polarizing element according to claim 7, wherein the third circularly polarized light separating layer selectively reflects at least two kinds of light in different wavelength regions in each of the divided regions. . 9. The first circularly polarized light separating layer selectively reflects light in the wavelength region of red, green or blue in each of the divided regions, and the third circularly polarized light separating layer has each of the respective regions. 9. The polarizing element according to claim 8, wherein light in the blue and green wavelength regions, light in the green and red wavelength regions, or light in the blue and red wavelength regions is selectively reflected in the divided regions. . 10. The polarizing element according to claim 1, wherein at least one of the first to third circularly polarized light separating layers is a cholesteric liquid crystal layer. 11. The third circularly polarized light separating layer selectively reflects a circularly polarized light component having the same optical rotation direction as the one circularly polarized light component selectively reflected by the second circularly polarized light separating layer. 11. The polarizing element according to claim 1, comprising a cholesteric liquid crystal layer and a pair of half-wave retardation layers sandwiching the cholesteric liquid crystal layer. 12. A first circularly polarized light separating layer which selectively reflects either one of the right circularly polarized light component and the left circularly polarized light component in a predetermined wavelength region included in a visible light region, An absorption-type first linear polarization layer provided on the back side of the first circularly polarized light separating layer, and an absorption type first linearly polarizing layer provided on the observation side of the first circularly polarized light separating layer,
An absorptive second linearly polarizing layer arranged so that its optical axis is orthogonal to the linearly polarizing layer, and a first circularly polarized light separating layer and a first linearly polarizing layer provided between the first circularly polarized light separating layer and the first linearly polarizing layer. 2 ¼ wavelength retardation layer, provided between the first circularly polarized light separation layer and the second linear polarization layer, and the optical axis is orthogonal to the second ¼ wavelength retardation layer. And a third quarter-wave retardation layer arranged so as to provide a polarizing element. 13. The polarizing element according to claim 12, wherein the second and third quarter-wave retardation layers are retardation layers whose optical axes change according to an applied voltage. 14. The polarized light according to claim 12, wherein at least one of the first to third quarter-wave retardation layers is a broadband quarter-wave retardation layer. element. 15. A circularly polarized light component having the same optical rotation direction as the one circularly polarized light component provided on the back side of the first linearly polarized light layer and selectively reflected by the first circularly polarized light separating layer, At least a second circularly polarized light separating layer that selectively reflects in the predetermined wavelength region that is reflected by the first circularly polarized light separating layer; and a first linearly polarizing layer and a second circularly polarized light separating layer A first quarter-wave retardation layer provided between the first linear polarization layer and the first linear polarization layer, and the optical axes of the first linear polarization layer are the second circular polarization separation layer and the first quarter wavelength. 13. The structure is arranged so as to coincide with the amplitude direction of the linearly polarized light formed by passing through the wavelength phase difference layer.
15. The polarizing element according to any one of 14 to 14. 16. The first circularly polarized light separating layer has a plurality of divided regions divided in a layer surface, and selectively reflects light in different wavelength regions in each divided region. The polarizing element according to claim 12, wherein 17. The polarizing element according to claim 16, wherein the first circularly polarized light separating layer selectively reflects light in a wavelength region of red, green or blue in each divided region thereof. . 18. The polarizing element according to claim 12, wherein at least one of the first and second circularly polarized light separating layers is a cholesteric liquid crystal layer. 19. A polarizing element according to any one of claims 1 to 11, and a liquid crystal drive cell provided on the viewing side of said polarizing element, for controlling light and darkness by changing the polarization state of light according to an applied voltage. And a backlight provided on the back side of the polarizing element for irradiating the liquid crystal driving cell with white light, a liquid crystal display device. 20. A polarizing element according to any one of claims 12 to 18, and a liquid crystal driving cell provided on the viewing side of the polarizing element, for controlling light and darkness by changing the polarization state of light according to an applied voltage. And a backlight provided on the back side of the polarizing element and irradiating the liquid crystal driving cell with colored light in the same wavelength region as the predetermined wavelength region reflected by the first circularly polarized light separating layer. A liquid crystal display device characterized by being provided. 21. The liquid crystal display device according to claim 20, wherein the backlight is an electroluminescent light source.