JP2004205784A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display capable of performing display by efficiently utilizing light from a surface light source. <P>SOLUTION: The surface light source 10 which consists of, a light guide plate 11 guiding and emitting light from a light emitting elements 13 to a liquid crystal element 1 and transmitting light made incident from the front and the rear sides, a reflection plate 14 disposed in the rear side of the light guide plate 14, and a λ/4 retardation plate 15 disposed between the light guide plate 11 and the reflection plate 14, is arranged on the rear side of a liquid crystal element 1 which is composed of a liquid crystal cell 2 and absorbing polarization plate 7 and 8 disposed in the front side and rear side of the liquid crystal cell 2, respectively. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device having a surface light source.
[0002]
[Prior art]
As a liquid crystal display device, a liquid crystal provided with a liquid crystal layer that controls the polarization state of transmitted light according to an electric field applied between a front substrate that is a display observation side and a rear substrate that faces the front substrate. A cell, an absorption polarizer disposed on the front side of the liquid crystal cell and absorbing one of the two linearly polarized light components of the incident light orthogonal to each other and transmitting the other polarized light component; and The liquid crystal element is disposed on the rear side of a liquid crystal element comprising a reflective polarizer that is disposed on the rear side and reflects one of two linearly polarized light components of the incident light and transmits the other polarized light component. There is one in which a surface light source that emits light toward an element is arranged (see Patent Document 1).
[0003]
This liquid crystal display device performs both a transmissive display using light from the surface light source and a reflective display using external light that is light of an external environment, and performs a transmissive display using light from the surface light source. Is performed, light emitted from the surface light source and incident on the liquid crystal element from the rear side is incident on the liquid crystal cell as linearly polarized light by the reflective polarizer, and the polarization state is controlled according to the electric field applied to the liquid crystal layer. Then, of the light emitted to the front side of the liquid crystal cell, one linearly polarized light component is absorbed by the absorbing polarizer, and the other linearly polarized light component is transmitted through the absorbing polarizer and emitted to the front side for display.
[0004]
When performing reflective display using external light, light incident on the liquid crystal element from the front side, which is the display observation side, is incident on the liquid crystal cell as linearly polarized light by the absorbing polarizer, and is applied to the liquid crystal layer. Of the light emitted to the rear side of the liquid crystal cell whose polarization state is controlled in accordance with the electric field, one linearly polarized light component is reflected by the reflective polarizer and emitted to the front side, and the other linearly polarized light component is reflected. The light is transmitted through the rear side of the polarizing plate for display.
[0005]
[Patent Document 1]
JP 2002-47195 A
[Problems to be solved by the invention]
However, in the above liquid crystal display device, of the light emitted from the surface light source and incident on the liquid crystal element from the rear side, a linearly polarized light component parallel to the transmission axis of the reflective polarizing plate is transmitted through the reflective polarizing plate, and And the linearly polarized light component parallel to the reflection axis of the reflective polarizer is reflected by the reflective polarizer, so that the utilization efficiency of light from the surface light source is poor.
[0007]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal display device capable of performing display by efficiently using light from a surface light source.
[0008]
[Means for Solving the Problems]
In the liquid crystal display device of the present invention, a liquid crystal layer that controls the polarization state of transmitted light according to an applied electric field is provided between a front substrate that is a display observation side and a rear substrate that faces the front substrate. The liquid crystal cell provided is disposed at least on the front side of the liquid crystal cell, has a transmission axis and an absorption axis in directions orthogonal to each other, and is parallel to the absorption axis among two linear polarization components of the incident light orthogonal to each other. A liquid crystal element comprising an absorbing polarizer that absorbs one polarized component and transmits the other polarized component parallel to the transmission axis;
A light guide plate disposed on the rear side of the liquid crystal element, for guiding light from the light emitting element and emitting toward the liquid crystal element, and transmitting light incident from the front side and the rear side, and a rear side of the light guide plate. A reflector that reflects the light emitted to the rear side of the light guide plate, and is disposed between the light guide plate and the reflector, and has a quarter wavelength between the ordinary light and the extraordinary light of the transmitted light. A surface light source comprising a λ / 4 retardation plate providing a phase difference;
One of the two linearly polarized light components of the incident light, which are disposed between the liquid crystal element and the surface light source, have a transmission axis and a reflection axis in directions orthogonal to each other, and are parallel to the reflection axis. And a reflective polarizing plate that reflects the polarized light component and transmits the other polarized light component parallel to the transmission axis.
[0009]
According to this liquid crystal display device, of the light emitted from the light guide plate of the surface light source, a linearly polarized light component parallel to the transmission axis of the reflective polarizer is transmitted through the reflective polarizer and incident on the liquid crystal element. The light reflected by the reflective polarizing plate, that is, the linearly polarized light component parallel to the reflection axis of the reflective polarizing plate is transmitted through a λ / 4 retardation plate disposed on the rear side of the light guide plate, and is reflected by the reflecting plate. While being reflected and transmitted again through the λ / 4 retardation plate and exiting to the front side of the light guide plate, the reflected light is converted into linearly polarized light parallel to the transmission axis of the reflective polarizer and re-entered into the reflective polarizer, Since the light can also be transmitted through the reflective polarizing plate and enter the liquid crystal element, display can be performed by efficiently using the light from the surface light source.
[0010]
As described above, the liquid crystal display device of the present invention guides light from the light emitting element to the rear side of the liquid crystal element including the liquid crystal cell and the absorption polarizer disposed at least in front of the liquid crystal cell and emits the light toward the liquid crystal element. A light guide plate for transmitting light incident from the front side and the rear side; a reflection plate disposed on the rear side of the light guide plate; and a λ / 4 position disposed between the light guide plate and the reflection plate. By arranging a surface light source including a phase difference plate and further arranging a reflective polarizer between the liquid crystal element and the surface light source, it is possible to efficiently use light from the surface light source for display. It was made.
[0011]
In the liquid crystal display device of the present invention, the liquid crystal molecules of the liquid crystal cell of the liquid crystal element are twist-aligned at a twist angle of substantially 90 ° between the front and rear substrates, and the absorption polarization disposed at the front side of the liquid crystal cell. It is desirable that the transmission axis of the plate and the transmission axis of the reflective polarizer between the liquid crystal element and the surface light source be substantially orthogonal to each other.
[0012]
Further, in this liquid crystal display device, the liquid crystal element is provided with two absorbing polarizers respectively disposed on the front side and the rear side of the liquid crystal cell, and the reflective polarizer between the liquid crystal element and the surface light source is provided. Is preferably arranged such that the transmission axis is substantially parallel to the transmission axis of the absorption polarizer on the rear side of the liquid crystal element.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 3 show an embodiment of the present invention. FIG. 1 is an exploded perspective view of a liquid crystal display device, and FIG. 2 is an emission of light at the time of transmissive display using light from a surface light source of the liquid crystal display device. FIG. 3 is a cross-sectional view of the liquid crystal display device in which hatching is omitted and hatching indicating a light emission path in a reflective display using external light is omitted.
[0014]
As shown in FIGS. 1 to 3, the liquid crystal display device has a liquid crystal element 1, a surface light source 10 disposed on the rear side of the liquid crystal element 1, and a liquid crystal element 1 and the surface light source 10. And a reflection polarizing plate 9 disposed.
[0015]
The liquid crystal element 1 includes a liquid crystal cell 2 and two polarizing plates 7 and 8 arranged on the front and rear sides of the liquid crystal cell 2, respectively.
[0016]
The liquid crystal cell 2 changes a polarization state of transmitted light between a front transparent substrate 3 which is a display observation side and a rear transparent substrate 4 opposed to the front substrate 3 in accordance with an applied electric field. A liquid crystal layer 6 to be controlled is provided, and the front substrate 3 and the rear substrate 4 are joined via a frame-shaped sealing material 5 and surrounded by the sealing material 5 between these substrates 3 and 4. The liquid crystal layer 6 is provided in the region which is located.
[0017]
Although not shown in the drawing, transparent electrodes forming a plurality of pixels arranged in a matrix by opposing regions are provided on opposing inner surfaces of the substrates 3 and 4 before and after the liquid crystal cell 2, An alignment film for defining the alignment direction of the liquid crystal molecules of the liquid crystal layer 6 in the vicinity of each of the substrates 3 and 4 is provided thereon.
[0018]
Further, the two polarizing plates 7, 8 disposed on the front side and the rear side of the liquid crystal cell 2, respectively, have transmission axes 7a, 8a and an absorption axis (not shown) in directions orthogonal to each other. Is an absorption polarizer that absorbs one of the two linearly polarized light components orthogonal to each other and that is parallel to the absorption axis and transmits the other polarized light component parallel to the transmission axes 7a and 8a.
[0019]
The liquid crystal element 1 is of a TN (twisted nematic) type, and the liquid crystal layer 6 of the liquid crystal cell 2 has liquid crystal molecules twist-oriented at a twist angle of substantially 90 ° between the front and rear substrates 3 and 4. It consists of a nematic liquid crystal having a positive dielectric anisotropy.
[0020]
In FIG. 1, an arrow 3a indicates a liquid crystal molecule alignment direction in the vicinity of the front substrate 3 of the liquid crystal cell 2, and an arrow 4a indicates a liquid crystal molecule alignment direction in the vicinity of the rear substrate 4. The molecular alignment direction 3a is substantially 45 ° in one direction with respect to the horizontal axis x of the screen of the liquid crystal display device, and the liquid crystal molecular alignment direction 4a near the rear substrate 4 is relative to the horizontal axis x. And the liquid crystal molecules of the liquid crystal layer 6 move from the rear substrate 4 toward the front substrate 3 substantially in the twist direction indicated by the broken arrow in FIG. It is twist-oriented at a twist angle of 90 °.
[0021]
Further, the liquid crystal element 1 is of a normally white mode, and the absorption polarizer 7 on the front side of the liquid crystal cell 2 has its transmission axis 7a oriented in the liquid crystal molecule alignment direction 3a near the front substrate 3 of the liquid crystal cell 2. The liquid crystal cell 2 is affixed to the outer surface of the front substrate 3 of the liquid crystal cell 2 substantially parallel or orthogonal (in FIG. 1, orthogonal), and the rear absorption polarizer 8 has its transmission axis 8a set to the front absorption polarizer 7. The liquid crystal cell 2 is affixed to the outer surface of the rear substrate 4 so as to be substantially perpendicular to the transmission axis 7a.
[0022]
On the other hand, the reflective polarizing plate 9 disposed between the liquid crystal element 1 and the surface light source 10 has a transmission axis 9a and a reflection axis 9b in directions orthogonal to each other, and two orthogonal linear polarization components of incident light. Among them, one of the polarization components parallel to the reflection axis 9b is reflected, and the other polarization component parallel to the transmission axis 9a is transmitted.
[0023]
The reflective polarizing plate 9 has its transmission axis 9a substantially orthogonal to the transmission axis 7a of the absorption polarizing plate 7 on the front side of the liquid crystal element 1, and the transmission axis of the absorption polarizing plate 8 on the rear side of the liquid crystal element 1. 8a, and is adhered to the rear surface of the rear absorbing polarizing plate 8 substantially parallel to 8a.
[0024]
Also, the surface light source 10 guides light from the light emitting element 13 and emits the light toward the liquid crystal element 1 and transmits light incident from the front side and the rear side; The light guide plate 11 includes a reflector 14 that reflects light emitted to the rear side of the light guide plate 11, and a retardation plate 15 disposed between the light guide plate 11 and the reflector 14.
[0025]
The light guide plate 11 has an incident end face on which light is incident on one end face, a front face formed on a flat exit face, and a light incident on the rear face from the incident end face to be guided through the light guide plate 11. Acrylic resin in which a plurality of groove-shaped recesses 12 are formed in parallel with the incident end face to reflect the light from the front face of the light guide plate (outgoing face) in a direction in which the angle with respect to the normal to the front face becomes smaller. It is made of a transparent plate such as a plate.
[0026]
The light guide plate 11 guides light incident from the incident end face and emits most of the light from the front face, and transmits the light incident from the incident end face to the interface between the front and rear faces of the light guide plate 11 and the air layer which is the outside air. In the process, the light reflected by the plurality of groove-shaped recesses 12 on the rear surface of the light guide plate in the direction in which the angle with respect to the normal to the front surface of the light guide plate becomes smaller is transmitted to the front surface of the light guide plate by air. The light passes through the interface with the layer and is emitted to the front side.
[0027]
The light guide plate 11 transmits light incident from the front surface in the thickness direction and emits the light from the rear surface, and transmits light incident from the rear surface in the thickness direction and emits the light from the front surface.
[0028]
The light guide plate 11 is arranged such that an air layer is provided between the light guide plate 11 and the reflective polarizer 9 on the rear side of the reflective polarizer 9 with its front surface (emission surface) facing the liquid crystal element 1. A light-emitting element 13 is arranged on the side of the light-guiding plate 11 so as to face the incident end face of the light guide plate 11.
[0029]
The light-emitting element 13 is a solid-state light-emitting element composed of, for example, an LED (light-emitting diode). In this embodiment, a plurality of solid-state light-emitting elements 13 are arranged so as to face the incident end face of the light guide plate 11. The light emitting element may be a straight tube cold cathode tube or the like.
[0030]
The phase difference plate 15 disposed between the light guide plate 11 and the reflection plate 14 is a λ / 4 phase difference plate that gives a phase difference of 1/4 wavelength between the ordinary light and the extraordinary light of the transmitted light. The λ / 4 retardation plate 15 has its slow axis 15 a crossing the transmission axis 9 a of the reflective polarizing plate 9 at an angle of substantially 45 °, so that the reflection surface of the (The surface facing the light plate 11).
[0031]
Then, the reflection plate 14 and the λ / 4 phase difference plate 15 stuck on the reflection surface are provided between the light guide plate 11 and the λ / 4 phase difference plate 15 on the rear side of the light guide plate 11. Is provided with an air layer.
[0032]
The liquid crystal display device performs both a transmissive display using light from the surface light source 10 and a reflective display using external light that is light of an external environment. Is turned off when performing reflective display in an environment where external light of sufficient brightness can be obtained, and is turned on when performing transmissive display.
[0033]
First, transmission display using light from the surface light source 10 will be described. In this transmission display, light (non-polarized light) emitted from the light emitting element 13 enters the light guide plate 11 from an end face thereof and the light guide plate Most of the light is guided from inside the light guide plate 11 to the front side as shown by the arrow in FIG.
[0034]
The light emitted to the front side of the light guide plate 11 is incident on the reflective polarizer 9 disposed between the light guide plate 11 and the liquid crystal element from the rear side. A linearly polarized component parallel to the axis 9a passes through the reflective polarizing plate 9 and enters the liquid crystal element 1 from behind.
[0035]
On the other hand, among the light emitted to the front side of the light guide plate 11 and incident on the reflective polarizing plate 9 from the rear side, a linearly polarized component parallel to the reflection axis 9b of the reflective polarizing plate 9 is converted by the reflective polarizing plate 9. It is reflected back.
[0036]
The light reflected rearward by the reflective polarizing plate 9, that is, linearly polarized light parallel to the reflection axis 9 b of the reflective polarizing plate 9 passes through the light guide plate 11 and enters the λ / 4 phase difference plate 15. The light is converted into circularly polarized light by the λ / 4 phase difference plate 15 and reflected by the reflection plate 14.
[0037]
The circularly polarized light reflected by the reflection plate 14 is transmitted through the λ / 4 retardation plate 15 again, and is linearly polarized light in which the plane of polarization of the linearly polarized light reflected by the reflection polarization plate 9 is substantially rotated by 90 °. That is, the light becomes a linearly polarized light parallel to the transmission axis 9a of the reflective polarizing plate 9, and the light is transmitted again through the light guide plate 11 and re-enters the reflective polarizing plate 9, and transmitted through the reflective polarizing plate 9 to form the liquid crystal. The light enters the element 1 from the rear side.
[0038]
That is, the liquid crystal display device transmits the linearly polarized light component parallel to the transmission axis 9a of the reflective polarizing plate 9 out of the light emitted from the light guide plate 11 of the surface light source 10 While being incident on the element 1, the light reflected by the reflective polarizing plate 9, that is, the linearly polarized light component parallel to the reflection axis 9 b of the reflective polarizing plate 9, is reflected by the λ / 4 disposed on the rear side of the light guide plate 11. The light passes through the phase difference plate 15 and is reflected by the reflection plate 14, passes through the λ / 4 phase difference plate 15 again, and is emitted to the front side of the light guide plate 11 while being parallel to the transmission axis 9 a of the reflection polarization plate 9. Is converted into a linearly polarized light, and is re-incident on the reflective polarizer 9. The light is also transmitted through the reflective polarizer 9 and is incident on the liquid crystal element 1. Most of the light The light can be incident on the liquid crystal element 1 as linearly polarized light parallel to the transmission axis 9 a of the light plate 9.
[0039]
In addition, out of the light emitted from the light emitting element 13 and incident on the light guide plate 11 from the end face thereof, and a part of the light guided in the light guide plate 11, some of the light is as shown by broken lines in FIG. The light leaks to the rear side of the light guide plate 11, and the leaked light passes through the λ / 4 phase difference plate 15 without changing the polarization state, is reflected by the reflection plate 14, and passes through the λ / 4 phase difference plate 15. The light is transmitted again without changing the polarization state, and further transmitted through the light guide plate 11 to enter the reflective polarizing plate 9 from the rear side.
[0040]
Then, of the light incident on the reflective polarizer 9 from the rear side, a linearly polarized component parallel to the transmission axis 9a of the reflective polarizer 9 is transmitted through the reflective polarizer 9 and is incident on the liquid crystal element 1, The linearly polarized light component parallel to the reflection axis 9b of the reflection polarizing plate 9 is reflected by the reflection polarizing plate 9 to the rear side, and this light also passes through the λ / 4 phase difference plate 15 again and is reflected by the reflection plate 14. And is transmitted through the λ / 4 retardation plate 15 to become linearly polarized light parallel to the transmission axis 9 a of the reflective polarizing plate 9, re-enters the reflective polarizing plate 9, and And is incident on the liquid crystal element 1.
[0041]
Therefore, according to this liquid crystal display device, almost all of the light leaked to the rear side of the light guide plate 11 is incident on the liquid crystal element 1 as linearly polarized light parallel to the transmission axis 9a of the reflective polarizer 9. Can be.
[0042]
Light emitted from the surface light source 10, transmitted through the reflective polarizer 9, and incident on the liquid crystal element 1 from behind is transmitted through the absorption polarizer 8 on the rear side of the liquid crystal element 1 and has a high degree of polarization. The light enters the liquid crystal cell 2 as linearly polarized light.
[0043]
Since the reflective polarizing plate 9 is disposed with its transmission axis 9a substantially parallel to the transmission axis 8a of the absorption polarizing plate 8 on the rear side of the liquid crystal element 1, the reflective polarizing plate 9 transmits through the reflective polarizing plate 9. Then, the light incident on the liquid crystal element 1 from the rear side passes through the absorbing polarizer 8 on the rear side of the liquid crystal element 1 with a high transmittance and is incident on the liquid crystal cell 2.
[0044]
Light incident on the liquid crystal cell 2 from the rear side (linearly polarized light parallel to the transmission axis 9a of the reflective polarizer 9 and the transmission axis 8a of the rear absorption polarizer 8) is applied between the electrodes of each pixel. The birefringent action of the liquid crystal layer 6 according to the orientation state of the liquid crystal molecules changed by the electric field causes the liquid crystal cell 2 to emit to the front side of the liquid crystal cell 2, and out of the light, the light is parallel to the transmission axis 7 a of the absorption polarizer 7 on the front side. The linearly polarized light component passes through the absorbing polarizer 7 and is emitted to the front side, and the linearly polarized light component parallel to the absorption axis of the front absorbing polarizer 7 is absorbed by the absorbing polarizer 7.
[0045]
That is, of the light incident on the liquid crystal cell 2 from the rear side, the light incident on the non-electric field pixel in which the liquid crystal molecules are in the initial twist alignment state is substantially rotated by 90 ° by the liquid crystal layer 6 and absorbed on the front side. Light that is emitted as linearly polarized light parallel to the transmission axis 7a of the polarizing plate 7 and is emitted to the front side of the liquid crystal cell 2 and is incident on an electric field application pixel in which liquid crystal molecules rise substantially vertically to the substrates 3 and 4 and are aligned. Emits to the front side of the liquid crystal cell 2 without being subjected to the birefringence action of the liquid crystal layer 6.
[0046]
Therefore, in this transmissive display, the light transmitted through the non-electric field pixel of the liquid crystal cell 2 passes through the front absorption polarizer 7 and is emitted to the front side, and the area becomes a bright display. The light transmitted through the electric field application pixel is absorbed by the absorption polarizer 7 on the front side, and the area becomes dark.
[0047]
Then, as described above, this liquid crystal display device can make most of the light from the surface light source 10 enter the liquid crystal element 1 as linearly polarized light parallel to the transmission axis 9a of the reflective polarizing plate 9. The display from the surface light source 10 can be efficiently utilized.
[0048]
Further, in this embodiment, the liquid crystal element 1 is provided with two absorbing polarizers 7 and 8 arranged on the front side and the rear side of the liquid crystal cell 2, respectively. Since the reflection polarizing plate 9 is disposed with its transmission axis 9a substantially parallel to the transmission axis 8a of the absorption polarizing plate 8 on the rear side of the liquid crystal element 1, light is emitted from the surface light source 10. The linearly polarized light transmitted through the reflective polarizing plate 9 is made to enter the liquid crystal cell 2 as linearly polarized light having a high degree of polarization by the rear absorbing polarizing plate 8, so that a high-contrast image can be displayed on the liquid crystal element 1. .
[0049]
Next, a description will be given of a reflective display using external light. In the case of the reflective display, as shown by an arrow in FIG. The light is converted into linearly polarized light parallel to the transmission axis 7a by the absorption polarizing plate 7 on the front side and enters the liquid crystal cell 2 from the front side.
[0050]
Then, of the light incident on the liquid crystal cell 2 from the front side, the light incident on the non-electric field pixel in which the liquid crystal molecules are in the initial twist alignment state is substantially rotated by 90 ° by the liquid crystal layer 6 and absorbed on the rear side. The light becomes linearly polarized light parallel to the transmission axis 8a of the polarizing plate 8 and is emitted to the rear side of the liquid crystal cell 2.
[0051]
The light emitted to the rear side of the liquid crystal cell 2 is transmitted through the absorption polarizer 8 on the rear side, further transmitted through the reflective polarizer 9 and emitted to the rear side.
[0052]
Light transmitted through the reflective polarizer 9 and emitted to the rear side (linearly polarized light parallel to the transmission axis 8a of the absorption polarizer 8 on the rear side of the liquid crystal element 1 and the transmission axis 9a of the reflective polarizer 9) is incident on the surface. The light passes through the light guide plate 11 of the light source 10, is converted into circularly polarized light by the λ / 4 retardation plate 15, is reflected by the reflection plate 14, passes through the λ / 4 retardation plate 15 again, and passes through the reflection polarizing plate 9. The light is emitted to the front side of the light guide plate 11 and is reflected to the rear side by the reflection polarizing plate 9.
[0053]
The light reflected rearward by the reflective polarizing plate 9 passes through the λ / 4 phase difference plate 15 again, is reflected by the reflection plate 14, and passes through the λ / 4 phase difference plate 15 again. The polarization plane is further rotated by 90 ° while being emitted to the front side of the light guide plate 11, becomes linearly polarized light parallel to the transmission axis 9 a of the reflection polarization plate 9, and re-enters the reflection polarization plate 9. The light passes through the plate 9, passes through the absorption polarizer 8 on the rear side of the liquid crystal element 1, the liquid crystal cell 2, and the absorption polarizer 7 on the front side, and is emitted to the front side.
[0054]
Also, of the light incident on the liquid crystal cell 2 from the front side, the light incident on the electric field application pixel in which the liquid crystal molecules rise substantially perpendicularly to the surfaces of the substrates 3 and 4 is incident on the liquid crystal layer 6. The light is emitted to the rear side of the liquid crystal cell 2 without being affected, and is absorbed by the rear absorption polarizer 8.
[0055]
Therefore, in the case of this reflective display, the light transmitted through the non-electric field pixels of the liquid crystal cell 2, transmitted through the rear absorbing polarizing plate 8 and emitted to the rear side of the liquid crystal element 1 is reflected by the reflecting plate of the surface light source 10. The liquid crystal cell 2 reflects the light toward the front side and emits light in the area, and the area becomes a bright display. The light transmitted through the electric field application pixel of the liquid crystal cell 2 is absorbed by the rear absorbing polarizing plate 8 and the area becomes a dark display. .
[0056]
In this embodiment, the liquid crystal element 1 is provided with two absorbing polarizers 7 and 8 arranged on the front side and the rear side of the liquid crystal cell 2 respectively. Since the reflection polarizing plate 9 is disposed with its transmission axis 9a substantially parallel to the transmission axis 8a of the absorption polarizing plate 8 on the rear side of the liquid crystal element 1, the light enters from the front side during the reflective display. Then, the linearly polarized light transmitted through the rear absorption polarizer 8 on the rear side of the liquid crystal element 1 and emitted to the rear side is transmitted through the reflective polarizer 9 with a high transmittance and is incident on the surface light source 10, and The linearly polarized light reflected by the reflector 14 of the light source 10 and transmitted through the reflective polarizer 9 and emitted to the front side thereof is transmitted through the absorbing polarizer 8 on the rear side of the liquid crystal element 1 with a high transmittance and the liquid crystal cell 2 , So that the bright display is sufficiently bright Preparative it is, because the degree of polarization of the absorption polarizer 7,8 is higher than that of the reflective polarizer 9, even when the reflective display, it is possible to display a good image contrast in the liquid crystal device 1.
[0057]
In the above-described embodiment, the liquid crystal element 1 has a configuration in which the absorbing polarizers 7 and 8 are disposed on the front side and the rear side of the liquid crystal cell 2, respectively. The reflective polarizer 9 may also serve as the rear polarizer of the liquid crystal element 1.
[0058]
Further, the liquid crystal display device of the above embodiment is provided with the TN type liquid crystal element 1. The liquid crystal element is arranged such that the liquid crystal molecules of the liquid crystal layer of the liquid crystal cell are 180 ° to 270 ° (preferably between the front and rear substrates). The liquid crystal element may be an STN-type liquid crystal element in which the liquid crystal molecules are twist-aligned at a twist angle of 200 ° to 250 °, or a homogeneously-aligned liquid crystal element in which liquid crystal molecules are homogeneously aligned with their molecular long axes aligned in one direction.
[0059]
【The invention's effect】
The liquid crystal display device according to the present invention is a liquid crystal display device comprising: a liquid crystal element comprising a liquid crystal cell and an absorbing polarizer disposed at least in front of the liquid crystal cell; And a light guide plate for transmitting light incident from the rear side, a reflector disposed on the rear side of the light guide plate, and a λ / 4 phase difference plate disposed between the light guide plate and the reflector. Since a surface light source is disposed and a reflective polarizing plate is disposed between the liquid crystal element and the surface light source, display can be performed by efficiently using light from the surface light source.
[0060]
In the liquid crystal display device of the present invention, the liquid crystal molecules of the liquid crystal cell of the liquid crystal element are twist-aligned at a twist angle of substantially 90 ° between the front and rear substrates, and the absorption polarization disposed at the front side of the liquid crystal cell. It is desirable that the transmission axis of the plate and the transmission axis of the reflective polarizing plate between the liquid crystal element and the surface light source be substantially orthogonal to each other. Can do it.
[0061]
Further, in this liquid crystal display device, the liquid crystal element is provided with two absorbing polarizers respectively disposed on the front side and the rear side of the liquid crystal cell, and the reflective polarizer between the liquid crystal element and the surface light source is provided. It is preferable that the transmission axis is arranged substantially in parallel with the transmission axis of the absorbing polarizer on the rear side of the liquid crystal element. The linearly polarized light transmitted through the reflective polarizing plate is incident on the liquid crystal cell as linearly polarized light having a high degree of polarization by the rear absorbing polarizing plate, so that an image with good contrast can be displayed on the liquid crystal element.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a liquid crystal display device according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the liquid crystal display device, in which hatching is omitted, showing light emission paths in a transmissive display using light from a surface light source.
FIG. 3 is a cross-sectional view of the liquid crystal display device, without hatching, showing a light emission path in a reflective display using external light.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Liquid crystal element, 2 ... Liquid crystal cell, 3, 4 ... Substrate, 6 ... Liquid crystal layer, 7, 8 ... Absorption polarizing plate, 7a, 8a ... Transmission axis, 9 ... Reflection polarizing plate, 9a ... Transmission axis, 9b ... Reflection Axis: 10: Surface light source, 11: Light guide plate, 13: Light emitting element, 14: Reflector, 15: λ / 4 phase plate, 15a: Slow axis.

Claims (3)

A liquid crystal cell provided with a liquid crystal layer for controlling a polarization state of transmitted light according to an applied electric field between a front substrate that is a display observation side and a rear substrate facing the front substrate; It is disposed at least on the front side of the liquid crystal cell, has a transmission axis and an absorption axis in directions orthogonal to each other, and absorbs one of the two linear polarization components of the incident light orthogonal to each other, which is parallel to the absorption axis. A liquid crystal element comprising: an absorption polarizer that transmits the other polarization component parallel to the transmission axis;
A light guide plate disposed on the rear side of the liquid crystal element, for guiding light from the light emitting element and emitting toward the liquid crystal element, and transmitting light incident from the front side and the rear side, and a rear side of the light guide plate. A reflector that reflects the light emitted to the rear side of the light guide plate, and is disposed between the light guide plate and the reflector, and has a quarter wavelength between the ordinary light and the extraordinary light of the transmitted light. A surface light source comprising a λ / 4 retardation plate providing a phase difference;
One of the two linearly polarized light components of the incident light, which are disposed between the liquid crystal element and the surface light source, have a transmission axis and a reflection axis in directions orthogonal to each other, and are parallel to the reflection axis. A reflective polarizer that reflects a polarized light component and transmits the other polarized light component parallel to the transmission axis,
A liquid crystal display device comprising: The liquid crystal molecules of the liquid crystal layer of the liquid crystal cell of the liquid crystal element are twist-oriented at a twist angle of substantially 90 ° between the front and rear substrates, and the transmission axis of an absorbing polarizer disposed on the front side of the liquid crystal cell; 2. The liquid crystal display device according to claim 1, wherein a transmission axis of the reflective polarizing plate between the liquid crystal element and the surface light source is substantially orthogonal. The liquid crystal element includes two absorption polarizers disposed on the front side and the rear side of the liquid crystal cell, respectively, and the reflection polarizer between the liquid crystal element and the surface light source has a transmission axis corresponding to the liquid crystal element. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is arranged substantially parallel to a transmission axis of a rear absorption polarizing plate.

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