JP2001272699A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type liquid crystal display device using a bistable nematic liquid crystal device, in which a bright screen is obtained. SOLUTION: The bistable nematic liquid crystal device 1 has a liquid crystal layer 10 consisting of a nematic liquid crystal with addition of a chiral agent held between a pair of substrates 2, 3 having electrodes 4, 5 and alignment films 7, 8 which are subjected to aligning treatment. A polarizing plate 11 is disposed on the outer face of the substrate 2, and a reflection means 12 is formed in the back side from the alignment film 8 of the back substrate 2 of the liquid crystal display device 1, for example, on the outer face of the back substrate 2 so that the light entering from the front side and transmitting through the polarizing plate 11 and the liquid crystal layer 10 of the liquid crystal device 1 is reflected by the reflection means 12 and the polarized component of the reflected light transmitting the polarizing plate 11 is made to exit to the front face as the image light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display using a bistable nematic liquid crystal element.

[0002]

2. Description of the Related Art A liquid crystal element of a bistable nematic system is:
An electrode is formed on each of the opposing inner surfaces, and a liquid crystal layer made of a nematic liquid crystal to which a chiral agent is added is sandwiched between a pair of substrates on which an alignment treatment is performed, and the liquid crystal molecules are After the application of the reset voltage having a sufficiently high value, the first selection voltage having a predetermined value lower than the reset voltage or the second selection voltage having another predetermined value lower than the reset voltage is applied. It has the property of being oriented to either the first or second metastable state.

Conventionally, a liquid crystal display device using a bistable nematic liquid crystal element has a pair of polarizing plates on an outer surface of a front substrate which is a display observation side substrate and an outer surface of a rear substrate with the liquid crystal element interposed therebetween. Are arranged with their respective absorption axes oriented in a predetermined direction.

In this liquid crystal display device, the orientation state of the liquid crystal molecules of the liquid crystal element is switched between a first metastable state and a second metastable state for display. The switching is performed by applying the reset voltage (for example, a voltage at which liquid crystal molecules rise and orient substantially perpendicularly to the substrate surface) between the electrodes of the pair of substrates, and then switches the first voltage between the electrodes.
And the second selection voltage is applied.

The direction of the absorption axis of each of the pair of polarizers is determined by the direction of the liquid crystal molecules of the liquid crystal element.
The liquid crystal display device has the highest transmittance of light when aligned in one of the metastable states, and the transmittance is set to be lowest when aligned in the other metastable state, Therefore, when the liquid crystal molecules are oriented in one metastable state by applying one of the first and second selection voltages after the application of the reset voltage, the display in that region becomes bright, and the display of the reset voltage becomes low. When the liquid crystal molecules are aligned in the other metastable state by applying the other selection voltage after the application, the display in that region becomes a dark display.

The liquid crystal molecules aligned in the first or second metastable state maintain the alignment state after the application of the selection voltage until the next reset voltage is applied. .

That is, the bistable nematic liquid crystal element has a memory property in the alignment state of liquid crystal molecules, and therefore has a self-memory property in the written state that maintains the written state of the pixel without applying a voltage. ing.

Therefore, the bistable nematic liquid crystal element holds the voltage between the electrodes for each pixel like an active matrix liquid crystal element used in a general TN (twisted nematic) liquid crystal display device. There is no need to provide a switching element (for example, a TFT), and therefore, it can be manufactured at low cost.

A liquid crystal display device using the bistable nematic liquid crystal element includes a transmissive liquid crystal display device that performs transmissive display using illumination light from a backlight, and a liquid crystal display device that emits light in an environment in which the liquid crystal display device is used. There is a reflection type that performs reflection display using light, and a reflection type liquid crystal display device is conventionally, of a pair of polarizing plates disposed with the liquid crystal element interposed therebetween, behind a rear polarizing plate, It is configured by disposing a reflection plate.

[0010]

However, in a conventional reflective liquid crystal display device in which a pair of polarizing plates are arranged with a bistable nematic liquid crystal element interposed therebetween and a reflecting plate is arranged behind a polarizing plate on the rear side, a screen is not provided. Has the problem of darkness.

That is, in the conventional reflection type liquid crystal display device, light enters from the front side (viewing side of display), passes through the front polarizer disposed on the outer surface of the front substrate of the liquid crystal element, and enters the liquid crystal element. In the process of passing through the liquid crystal layer of the liquid crystal element, the light (linearly polarized light) undergoes a birefringence effect according to the alignment state of the liquid crystal molecules to change the polarization state, and of the light emitted to the rear surface of the liquid crystal element, The light of the polarization component transmitted through the rear polarizer disposed on the outer surface of the rear substrate of the liquid crystal element is transmitted through the rear polarizer to become image light, and the image light is reflected by the reflector, and The light passes through the side polarizing plate, the liquid crystal element, and the front polarizing plate in order and is emitted to the front.

Therefore, in this liquid crystal display device, the light that has passed through the front polarizer, the liquid crystal element, and the rear polarizer and has become image light is reflected by the reflector and emitted to the front, and the light is transmitted through the rear polarizer. Absorbed by the side polarizer and the front polarizer,
As a result, the intensity of the light emitted to the front decreases, and the screen becomes darker.

An object of the present invention is to provide a reflection type liquid crystal display device using a bistable nematic liquid crystal element which can provide a bright screen.

[0014]

According to a liquid crystal display device of the present invention, a nematic material having a chiral agent added between a pair of substrates having electrodes formed on opposing inner surfaces and having been subjected to an alignment treatment thereon. A liquid crystal layer made of liquid crystal is sandwiched, and after applying a reset voltage having a sufficiently high value, the liquid crystal molecules have a first selection voltage having a predetermined value lower than the reset voltage or another predetermined voltage lower than the reset voltage. Application of a second selection voltage of the first or second value.
A bistable nematic liquid crystal element oriented in a metastable state; and a liquid crystal element disposed on the outer surface of a front substrate, which is a substrate on the display observation side of the liquid crystal element, with an absorption axis directed in a predetermined direction. A polarizing plate, and a reflecting means provided on the rear side of the alignment-processed surface of the rear substrate of the liquid crystal element and reflecting light incident from the front side and transmitted through the polarizing plate and the liquid crystal layer of the liquid crystal element. It is characterized by having.

This liquid crystal display device performs reflection display using external light, and has a front side (a display observation side).
From the liquid crystal element, the light transmitted through the polarizing plate and the liquid crystal layer of the liquid crystal element disposed on the outer surface of the front substrate of the liquid crystal element,
The liquid crystal element is reflected by the reflection unit provided on the rear side of the alignment processing surface of the rear substrate of the liquid crystal element, and of the reflected light, the light of the polarization component transmitted through the polarizing plate is emitted to the front as image light. Display by

That is, in this liquid crystal display device,
The light (linearly polarized light) incident from the front side, transmitted through the polarizing plate and incident on the liquid crystal element, is birefringent in the liquid crystal according to the alignment state of the liquid crystal molecules in the process of transmitting through the liquid crystal layer of the liquid crystal element. The polarization state is changed by the action, and the light is reflected by the reflection means, passes through the liquid crystal layer again, and is emitted to the front surface of the liquid crystal element. Of the light, the light of the polarization component transmitted through the polarizing plate is Then, the light passes through the polarizing plate to become image light and is emitted to the front.

Therefore, according to this liquid crystal display device, the light is absorbed only by the polarizing plate at the time of incidence and at the time of emission by the polarizing plate disposed on the outer surface of the front substrate of the liquid crystal element. And therefore emits light of sufficient intensity to the front,
A bright screen can be obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a liquid crystal display device according to the present invention, as described above, one polarizing plate is disposed on the outer surface of a front substrate of a bistable nematic liquid crystal device, and the alignment of a rear substrate of the liquid crystal device is performed. By providing the reflecting means behind the processing surface, the light incident from the front side and transmitted through the polarizing plate and the liquid crystal layer of the liquid crystal element is reflected by the reflecting means, and the polarized light of the reflected light is reflected. The light of the polarization component transmitted through the plate is emitted to the front as image light, thereby obtaining a bright screen.

In the liquid crystal display device according to the present invention, the liquid crystal element of the liquid crystal element preferably has a state in which the initial alignment state of the liquid crystal molecules is twisted at a twist angle of about 180 ° in one direction with respect to the alignment processing direction of one of the substrates. Wherein the liquid crystal molecules are applied by applying a first selection voltage after applying a reset voltage.
A first metastable state is obtained in which the one substrate is twist-oriented in one direction with a twist angle of about 360 ° in one direction with respect to the orientation processing direction of the one substrate, and the second selection voltage is applied after the reset voltage is applied. Is in a second metastable state in which non-twist alignment is performed along the alignment processing direction of the substrate, and the value of the product Δnd of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal element and the liquid crystal layer thickness d is 900 to 900. 1900 nm, 370
0 to 4700 nm or 6600 to 7300 nm, and the absorption axis of the polarizing plate disposed on the outer surface of the front substrate of the liquid crystal element is aligned with the alignment processing direction of the one substrate of the liquid crystal element. It is preferable to have a configuration in which they intersect at an angle of approximately 45 °. With such a configuration, an image with a brighter screen and sufficient contrast can be displayed.

[0020]

1 to 3 show an embodiment of the present invention. FIG. 1 is a sectional view of a liquid crystal display device.

The liquid crystal display of this embodiment has a liquid crystal element 1
And a front substrate 2 which is a substrate on the display observation side of the liquid crystal element 1.
And a reflector 12 disposed behind the liquid crystal element 1 and opposed to the outer surface of the substrate.

The liquid crystal element 1 is of a bistable nematic type. As shown in FIG. 1, a pair of transparent electrodes 4 and 5 are formed on opposing inner surfaces and an alignment process is performed thereon. A liquid crystal layer 10 made of a nematic liquid crystal to which a chiral agent is added is sandwiched between the transparent substrates 2 and 3.

The liquid crystal element 1 used in this embodiment is:
One of the substrates, for example, the electrodes 4 on the inner surface of the front substrate 2 are a plurality of scanning electrodes parallel to each other along the row direction (the left-right direction in FIG. 1), and the electrodes on the inner surface of the rear substrate 3. Reference numeral 5 denotes a plurality of signal electrodes parallel to each other along a column direction (a direction perpendicular to the plane of FIG. 1).

The liquid crystal element 1 is for displaying a multicolor image, and the plurality of scanning electrodes 4 and signal electrodes 5 are provided on one of the substrates, for example, on the inner surface of the front substrate.
And a plurality of colors corresponding to a plurality of pixels facing each other, for example, three color filters 6R,
6G and 6B. The color filter 6
The electrodes 4 on the inner surface of the front substrate 3 on which R, 6G, 6B are formed
It is formed on the color filters 6R, 6G, 6B.

Further, horizontal alignment films 7 and 8 made of polyimide or the like are provided on the inner surfaces of the pair of substrates 2 and 3 so as to cover the electrodes 4 and 5, respectively. An alignment process is performed by rubbing the film surface.

The pair of substrates 2 and 3 are joined at their peripheral edges via a frame-shaped sealing material 9, and a region surrounded by the sealing material 9 between these substrates 2 and 3 is formed. And a liquid crystal layer 10 made of a nematic liquid crystal to which the chiral agent is added.

In the bistable nematic liquid crystal element 1, after the liquid crystal molecules of the liquid crystal layer 10 are applied with a sufficiently high reset voltage, the first selection voltage or the reset voltage having a predetermined value lower than the reset voltage is applied. It has a characteristic of being oriented to either the first or second metastable state by application of any one of the second predetermined selection voltages lower than the predetermined value.

The polarizing plate 11 disposed on the outer surface of the front substrate 2 of the liquid crystal element 1 is provided with its absorption axis directed in a predetermined direction. When the liquid crystal molecules of (a) are aligned in one of the first and second metastable states, the transmittance of light of the liquid crystal display device becomes the highest, and when the liquid crystal molecules are aligned in the other metastable state, the transmittance becomes It is set to be the lowest.

FIG. 2 shows a pair of substrates 2 of the liquid crystal element 1.
3 shows the alignment treatment direction (rubbing direction of the alignment films 7 and 8) applied to the inner surface of the liquid crystal element 3 and the direction of the absorption axis of the polarizing plate 11. In FIG. The processing direction 3a indicates the orientation processing direction of the rear substrate 3.

As shown in FIG. 2, in this embodiment, the alignment direction 2a of the front substrate 2 of the liquid crystal element 1 is set to the horizontal axis O of the screen.
At an intersection angle of approximately 90 ° from the upper edge to the lower edge of the screen, and the orientation processing direction 3a of the rear substrate 3 is set at the lower edge of the screen at an intersection angle of approximately 90 ° with respect to the horizontal axis O. To the upper edge.

That is, in this embodiment, the alignment processing directions 2a and 3a of the pair of substrates 2 and 3 of the liquid crystal element 1 are substantially parallel and opposite to each other, and the initial alignment state of the liquid crystal molecules of the liquid crystal layer 10 is changed. (The orientation state when no voltage is applied between the electrodes 3 and 4) is a twist orientation with a twist angle of about 180 °. In this initial alignment state, the liquid crystal molecules are twisted at an angle of about 180 ° with respect to the alignment direction of one of the substrates, for example, the twist direction given by the chiral agent with respect to the alignment direction 3a of the rear substrate 3. This is a splay alignment state in which twist alignment is performed.

The initial alignment state is a state not used for display, and the liquid crystal element 1 switches the alignment state of liquid crystal molecules between a first metastable state and a second metastable state to display. Driven.

In the first metastable state and the second metastable state, the twist angle of the liquid crystal molecules is substantially 1 from the initial alignment state.
This is a state in which the splay distortion is eliminated by changing by 80 °. In this embodiment, the initial alignment state of the liquid crystal molecules is changed by almost 180 °.
Since the twist orientation of the torsion angle is, for example, with respect to the orientation processing direction 3a of the rear substrate 3, the torsion angle in the torsion direction given by the chiral agent is +, and the torsion angle given by the chiral agent is +. Is the twist angle in the opposite direction (the direction to untwist due to the chiral agent)
, The first metastable state is a twist alignment state in which the twist angle has changed by + 180 ° with respect to the initial alignment state, and the second metastable state has a twist angle of − in the initial alignment state. It is a non-twist alignment state (homogeneous alignment state) changed by 180 °.

FIGS. 3A and 3B are schematic views, as viewed from the front side, showing the alignment state of the liquid crystal molecules in the initial alignment state and the first and second metastable states. FIG.
(B) shows the alignment state in the first metastable state, and (b) shows the alignment state in the second metastable state.

The alignment state shown in FIG. 3 is an example when a nematic liquid crystal to which a chiral agent having a counterclockwise twist alignment is added as viewed from the front side is used. The liquid crystal molecules 10a in the metastable state are twisted counterclockwise as viewed from the front side.

The switching of the alignment state from the initial alignment state to the first and second metastable states is performed by first setting a sufficiently high reset voltage (for example, a liquid crystal) between the electrodes 4 and 5 of the pair of substrates 2 and 3. A voltage at which the molecule 10a rises and orients substantially perpendicularly to the surfaces of the substrates 2 and 3), and thereafter, one of the first and second selection voltages is applied between the electrodes 4 and 5. Done.

The first and second selection voltages are sufficiently lower than the reset voltage, and their values (absolute values) are determined by the characteristics of the nematic liquid crystal and the chiral agent and the amount of the chiral agent added. Depends on, for example, the first
The selection voltage is approximately 0 V, and the second selection voltage is a low voltage value at which most of the liquid crystal molecules 10a are oriented at an inclination angle substantially equal to or close to the pretilt angle with respect to the substrates 2 and 3.

That is, when the first selection voltage is applied after the reset voltage is applied, the liquid crystal molecules 10a
Is a twist angle (180 ° + 180 ° = 36) obtained by adding a twist of approximately 180 ° to the twist angle in the initial orientation state.
At 0 °), the film is oriented in a twisted state to eliminate the splay distortion, and enters the first metastable state shown in FIG. 3B. The first metastable state is maintained even after the application of the first selection voltage is stopped until the next reset voltage is applied.

When a second selection voltage having another predetermined value lower than the reset voltage is applied after the reset voltage is applied, the liquid crystal molecules 10a are shifted from the twist angle in the initial alignment state by about 180 °. FIG. 3 shows a state in which the twist is subtracted and the twist angle is almost 0 ° (180 ° −180 ° = 0 °), that is, the twist orientation in the initial orientation state is untwisted and the splay distortion is eliminated. The second metastable state shown in FIG. This second metastable state is maintained even after the application of the second selection voltage is stopped until the next reset voltage is applied.

On the other hand, in FIG. 2, reference numeral 11a denotes an absorption axis of the polarizing plate 11. In this embodiment, the direction of the absorption axis 11a of the polarizing plate 11 is changed to the direction of the one substrate 3 of the liquid crystal element 1. Is set in a direction crossing clockwise at an angle of approximately 45 ° with respect to the orientation processing direction 3a of
When the liquid crystal molecules 10a are aligned in the first metastable state shown in FIG. 3B, the light transmittance of the liquid crystal display device becomes the highest, and the liquid crystal molecules 10a are shifted to the state shown in FIG. When the liquid crystal display device is oriented in the second metastable state as shown, the light transmittance of the liquid crystal display device is set to be the lowest.

In this embodiment, the value of the product Δnd of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal element 1 and the thickness d of the liquid crystal layer is 900 to 1900 nm, 3700 to 4700 nm,
It is set to any range from 6600 to 7300 nm.

This liquid crystal display device performs reflection display using external light, and has a front side (a display observation side).
From the liquid crystal element 1 and transmitted through the polarizing plate 11 disposed on the outer surface of the front substrate 2 of the liquid crystal element 1 and the liquid crystal layer 10 of the liquid crystal element 1, the light is opposed to the outer surface of the rear substrate 4 of the liquid crystal element 1. The light is reflected by the reflecting plate 12 arranged in such a manner, and of the reflected light, the light of the polarized light component transmitted through the polarizing plate 11 is emitted to the front as image light for display.

That is, in this liquid crystal display device,
The light (linearly polarized light) incident from the front side and transmitted through the polarizing plate 11 and incident on the liquid crystal element 1 is transmitted through the liquid crystal layer 10 of the liquid crystal element 1 according to the alignment state of the liquid crystal molecules 10a. Changes the polarization state by the birefringence of the liquid crystal,
The light is reflected by the reflection plate 12 so that the liquid crystal layer 1
0 again, exits to the front of the liquid crystal element 1, and out of the light, the polarized component light transmitted through the polarizing plate 11 is:
The light passes through the polarizing plate 11 to become image light and is emitted to the front.

Therefore, according to this liquid crystal display device, the absorption of the light by the polarizing plate is caused by the absorption by the polarizing plate 11 arranged on the outer surface of the front substrate 2 of the liquid crystal element 1 at the time of incidence and at the time of emission. Therefore, although reflective display using external light is performed, light of sufficient intensity is emitted to the front, and a bright screen can be obtained.

Moreover, in the liquid crystal display device of this embodiment, as described above, the initial alignment state of the liquid crystal molecules 10a of the liquid crystal element 1 is adjusted by the alignment treatment of one of the substrates (the rear substrate in this embodiment) 3. A state in which the liquid crystal molecules are twist-oriented with a twist angle of about 180 ° in one direction based on the direction 3a,
The application of the first selection voltage after the application of the reset voltage causes the liquid crystal molecules 10 a to move in the alignment processing direction 3 of the one substrate 3.
a in a first metastable state in which the substrate is twisted in one direction at a twist angle of about 360 ° in one direction, and the orientation of the one substrate 3 is adjusted by applying a second selection voltage after applying the reset voltage. Non-twist oriented along the second
And a Δnd of the liquid crystal element 1
Is 900 to 1900 nm, 3700 to 4700 n
m is set to any range of 6600 to 7300 nm, and the absorption axis 11a of the polarizing plate 11 arranged on the outer surface of the front substrate 3 of the liquid crystal element 1 is aligned with the one substrate 3 of the liquid crystal element 1. Since the configuration intersects the direction 3a at an angle of approximately 45 °, an image with a brighter screen and sufficient contrast can be displayed.

For example, a liquid crystal element 1 having no color filters 6R, 6G, 6B is used, the value of Δnd of the liquid crystal element 1 is 1400 nm, and the initial alignment state of the liquid crystal element 1 and the first and second , The orientation of the liquid crystal molecules 10a in the metastable state, the direction of the absorption axis 11a of the polarizing plate 11, and the light emission rate of the liquid crystal display device set as described above (the intensity of incident light from the front surface to the front surface The ratio of the intensity of the emitted light) is about 33.7% in a bright display in which the liquid crystal molecules 10a are aligned in the first metastable state, and is a dark display in which the liquid crystal molecules 10a are aligned in the second metastable state. Therefore, the brightness of the bright display is sufficient, and the contrast is as high as about 54.

The chromaticity of the bright display and the dark display on the CIE chromaticity diagram is x coordinate = 0.3 at the time of bright display.
2, y coordinate = 0.33, thus:
The bright display is a white display close to an achromatic point. on the other hand,
The chromaticity at the time of dark display is x coordinate = 0.19,
Although y coordinate is 0.09, the dark display takes on a color. However, since the emission ratio at the time of dark display is as low as about 0.6% as described above, the dark display is almost black.

The emission ratio and the contrast are values when the value of Δnd of the liquid crystal element 1 is 1400 nm, and the value of Δnd of the liquid crystal element 1 is 900 to 190.
0 nm, 3700-4700 nm, 6600-7300
In any range of nm, almost the same emission rate and contrast can be obtained.

A conventional reflection-type liquid crystal display device in which a pair of polarizing plates is disposed on the liquid crystal display device with a bistable nematic liquid crystal element interposed therebetween, and a reflecting plate is disposed behind a polarizing plate on the rear side, for example, The alignment state of the liquid crystal molecules in the initial alignment state and the first and second metastable states is the same as in the above embodiment, the value of Δnd of the liquid crystal element is 2800 nm, and the direction of the absorption axis of the front polarizing plate is the rear direction of the liquid crystal element. In the case where the direction of the alignment processing direction of the substrate is approximately 45 ° and the direction of the absorption axis of the rear polarizing plate is approximately 135 ° with respect to the alignment processing direction of the rear substrate, a color filter is used as the liquid crystal element. The emission rate when using the one that does not have the
About 23.4 at the time of bright display oriented in the metastable state of
% In a dark display in which the liquid crystal molecules are aligned in the second metastable state, which is about 0.1%. The brightness of the bright display is not sufficient, and the screen is dark.

As described above, the liquid crystal display device of the above embodiment has a sufficient bright display brightness as compared with the conventional liquid crystal display device, and therefore can obtain a bright screen.

In the liquid crystal display of the above embodiment, the liquid crystal element 1 includes a plurality of scanning electrodes 4 formed on the inner surface of the front substrate 2 and a plurality of signal electrodes 5 formed on the inner surface of the rear substrate 3. Are provided with three color filters 6R, 6G, and 6B of red, green, and blue respectively corresponding to a plurality of pixels facing each other.
R, 6G, 6B absorbs the wavelength light in the absorption wavelength band and emits red, green, and blue colored light colored to the color filters 6R, 6G, 6B to display a multicolor image. However, a much brighter color image can be displayed as compared with a case where a liquid crystal element having a color filter is used in a conventional liquid crystal display device.

However, the color filters 6R, 6G,
6B is preferably formed as thin as possible within a range in which colored light of a sufficient color can be obtained. By doing so, light absorption by the color filters 6R, 6G, and 6B is reduced, and sufficient brightness is obtained. A color image can be displayed.

In the above embodiment, the color filter 6
Although the liquid crystal element 1 including R, 6G, and 6B is used, the present invention can be applied to a liquid crystal display device that displays a monochrome image using a bistable nematic liquid crystal element without a color filter.

The liquid crystal element 1 is of a simple matrix type. In the liquid crystal element, a segment electrode having a shape corresponding to a display pattern is formed on the inner surface of one substrate.
A segment type bistable nematic liquid crystal element in which a common electrode corresponding to the segment electrode is formed on the inner surface of the other substrate may be used.

Further, in the above embodiment, the reflection plate 12 is used as reflection means for reflecting light transmitted through the polarizing plate 11 disposed on the outer surface of the front substrate of the liquid crystal element 1 and the liquid crystal layer of the liquid crystal element 1. Although the reflection plate 12 is disposed behind the liquid crystal element 1, the reflection unit may be provided on the rear side of the alignment processing surface (alignment film 8) of the rear substrate 3 of the liquid crystal element 1.
It may be provided on the inner surface of the rear substrate 3.

That is, the reflecting means is provided on the rear substrate 3.
A high-reflectance metal film such as aluminum may be formed on the inner surface of the substrate by sputtering, vapor deposition, or plating. In this case, the metal film is covered with a transparent insulating film, and an electrode provided on the inner surface of the rear substrate 3 thereon 5 may be formed.

When the reflecting means is provided on the inner surface of the rear substrate 3, an electrode 5 formed on the inner surface of the rear substrate 3 may be used.
May be formed of a high-reflectance metal, and this electrode 5 may also serve as a reflection means.

[0058]

According to the liquid crystal display device of the present invention, one polarizing plate is arranged on the outer surface of the front substrate of the bistable nematic liquid crystal element, and the liquid crystal element is disposed on the rear side of the alignment treatment surface of the rear substrate of the liquid crystal element. By providing the reflecting means, the light incident from the front side and transmitted through the polarizing plate and the liquid crystal layer of the liquid crystal element is reflected by the reflecting means, and of the reflected light of the polarized light component transmitted through the polarizing plate. Since light is emitted to the front as image light, reflective display using external light is performed, but a bright screen can be obtained.

In the liquid crystal display device according to the present invention, the liquid crystal element in the liquid crystal element preferably has an initial alignment state in which one of the substrates is twisted at a twist angle of approximately 180 ° in one direction with respect to the alignment processing direction of one of the substrates. Wherein the liquid crystal molecules are applied by applying a first selection voltage after applying a reset voltage.
A first metastable state is obtained in which the one substrate is twist-oriented in one direction with a twist angle of about 360 ° in one direction with respect to the orientation processing direction of the one substrate, and the second selection voltage is applied after the reset voltage is applied. Is in a second metastable state in which non-twist alignment is performed along the alignment processing direction of the substrate, and the value of the product Δnd of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal element and the liquid crystal layer thickness d is 900 to 900. 1900 nm, 370
0 to 4700 nm or 6600 to 7300 nm, and the absorption axis of the polarizing plate disposed on the outer surface of the front substrate of the liquid crystal element is aligned with the alignment processing direction of the one substrate of the liquid crystal element. It is preferable to have a configuration in which they intersect at an angle of approximately 45 °. With such a configuration, an image with a brighter screen and sufficient contrast can be displayed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a view showing an orientation processing direction of a pair of substrates of a liquid crystal element and a direction of an absorption axis of a polarizing plate in the liquid crystal display device.

FIG. 3 shows an initial alignment state of the liquid crystal element and first and second alignment states.
FIG. 3 is a schematic diagram showing the alignment state of liquid crystal molecules in a metastable state of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Bistable nematic liquid crystal element 2,3 ... Substrate 2a, 3a ... Orientation processing direction 4,5 ... Electrode 6R, 6G, 6B ... Color filter 7,8 ... Alignment film 10 ... Nematic liquid crystal added chiral agent Liquid crystal layer 10a: liquid crystal molecules 11: polarizing plate 11a: absorption axis 12: reflector

Claims (2)

[Claims] An electrode is formed on each of opposing inner surfaces, and a pair of substrates on which an alignment treatment is performed is provided.
A liquid crystal layer made of a nematic liquid crystal to which a chiral agent is added is sandwiched, and after applying a reset voltage having a sufficiently high value, the liquid crystal molecules have a first selection voltage having a predetermined value lower than the reset voltage or the reset voltage. A liquid crystal element which is oriented in either the first or second metastable state by application of any one of a second selection voltage having a lower predetermined value, and a substrate on a display observation side of the liquid crystal element. One polarizing plate having an absorption axis directed in a predetermined direction on an outer surface of the substrate; and a polarizing plate provided on the rear side of the alignment-processed surface of the rear substrate of the liquid crystal element, the polarizing plate being incident on the front side and receiving the liquid crystal element. And a reflection means for reflecting light transmitted through the liquid crystal layer of the liquid crystal element. 2. An initial alignment state of liquid crystal molecules of a liquid crystal element is a state in which the liquid crystal molecules are twist-aligned with a twist angle of about 180 ° in one direction with respect to the alignment processing direction of one of the substrates. By applying the first selection voltage after the application of the reset voltage, a first metastable state in which the one substrate is twist-oriented with a twist angle of approximately 360 ° in one direction with respect to the orientation processing direction of the one substrate, By the application of the second selection voltage after the voltage is applied, the one substrate becomes a second metastable state in which non-twist alignment is performed along the alignment processing direction, and the refractive index anisotropy Δn of the liquid crystal of the liquid crystal element and The value of the product Δnd with the liquid crystal layer thickness d is 900 to 1900 nm, 3700 to
4700 nm, set to any range of 6600 to 7300 nm, and the absorption axis of the polarizing plate disposed on the outer surface of the front substrate of the liquid crystal element is substantially 45 degrees with respect to the alignment processing direction of the one substrate of the liquid crystal element. The liquid crystal display device according to claim 1, wherein the liquid crystal display devices intersect at an angle of °.