JPH11231305A - Reflection liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an achromatic reflection liquid crystal display device free from coloring. SOLUTION: In this device, a liquid crystal display element 20 for driving having a liquid crystal layer 29 of twist orientation is arranged between a polarizing plate 31 and a reflection plate 32. In this case, a color compensation element 14 is arranged between the polarizing plate 31 and the liquid crystal display element 20 for driving. The color compensation element 10 includes a chiral nematic liquid crystal layer 18 whose twist direction is opposite to that of the liquid crystal layer 29 and angle of twist and value obtained by multiplying the refractive index anisotropy and the layer thickness are approximately equal to those of the liquid crystal layer 29.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reflection type liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been used in notebook computers,
Monitor, car navigation, scientific calculator, small and medium TV
It is applied to various fields. Above all, reflection type liquid crystal display devices have been studied for application to displays for portable devices in order to take advantage of low power consumption, thinness and light weight because no backlight is required.

In a reflection type liquid crystal display device, two polarizing plates are used.
There are three types of display modes other than the TN mode using a single sheet, which are broadly classified into a GH (guest host) mode, a polymer dispersion mode, and a single polarizing plate mode. GH (guest host)
The mode has a feature that a bright display can be obtained since the light absorption is relatively small. However, since the two-color ratio of the material cannot be sufficiently obtained, there is a disadvantage that the contrast is low. The polymer dispersion mode has a feature that a wide viewing angle is obtained since sufficient diffusivity is obtained. However, it has a drawback of low reflectivity and contrast and has not been put to practical use.

In the one-polarizer mode, although sufficient brightness cannot be obtained due to light absorption by the polarizer, a high contrast is obtained because the polarizer is used. It is becoming mainstream. Polarizing plate 1
The configuration example of the sheet mode is, as an example, viewed from the observation side, a polarizing plate, for example, a front substrate made of glass, a driving liquid crystal layer made of a twisted orientated chiral nematic liquid crystal, for example, a rear substrate made of glass, a reflector and a reflection plate. It is composed of electrodes.

[0005] The incident light passes through the liquid crystal layer and the polarizing plate twice through the reflecting layer at the time of incidence and at the time of emission, so that the function of both the polarizer and the analyzer is obtained by one polarizing plate. is there. Therefore, compared to the conventional reflective TN mode using two polarizing plates used in calculators, watches, etc., the same control effect is obtained in that the number of polarizing plates is one, which is brighter and uses a polarizer. Therefore, the contrast is high enough.

The relative reflectance in the single-polarizer mode is obtained as follows. In the case of the LTN mode which is designed so that the polarization state of the light incident on the liquid crystal layer is shifted by 層 wavelength and has a twist angle of 63 °, the reflectance R is

(Equation 1) Becomes Here, I0 is the light intensity, Δn is the anisotropy of the refractive index of the liquid crystal, d is the thickness of the liquid crystal layer, and λ is the light wavelength. FIG. 5 shows a graph of the retardation Δnd dependency at that time.

In the MTN mode when the twist angle is 90 ° (Shin-Tson Wu et al., APL 68 (11), P1
455-1457), the reflectance R is

(Equation 2) And the graph of the Δnd dependency is as shown in FIG.

From FIGS. 5 and 6, it can be seen that the reflectance R also depends on the wavelength, and the reflectance differs depending on the wavelength at any Δnd value, and the coloring cannot be eliminated.

As a method for reducing the coloring, there is a method using a compensation film. In order to perform sufficient color compensation, the wavelength dispersion of the refractive index anisotropy of the liquid crystal layer and the compensation film must be equal. However, while the Δn of the liquid crystal is 0.07 to 0.25, the Δn of a general plastic film is 0.001 to 0.005.
And the chromatic dispersions do not completely match. As described above, when the wavelength dispersion is different, optical compensation cannot be performed in the entire visible light range, and therefore, with the conventional technology, sufficient color compensation cannot be performed, and an achromatic reflective liquid crystal display device cannot be realized. Was.

[0010]

As described above, the conventional reflection type liquid crystal display device has a problem that coloring occurs. The present invention solves this problem with a new configuration,
It is an object of the present invention to provide a method for realizing an achromatic reflective liquid crystal display device in which coloring does not occur.

[0011]

According to the present invention, there is provided at least a front substrate with electrodes on the observation side, a rear substrate with electrodes disposed behind the substrate, and a chiral nematic liquid crystal twisted and aligned sandwiched between the substrates. A driving liquid crystal layer, a light reflecting layer provided behind the liquid crystal layer when viewed from the viewing side, and a single polarizing plate provided before the liquid crystal layer when viewed from the viewing side. In a reflection type liquid crystal display device including a single-plate reflection type liquid crystal display element and a color compensation element provided between the polarizing plate and the reflection layer, the color compensation element has a twisting direction opposite to that of the liquid crystal layer. And a reflection type liquid crystal display device comprising a chiral nematic liquid crystal layer having a twisted orientation substantially equal to a value obtained by multiplying a twist angle, a refractive index anisotropy and a layer thickness. As a result, an achromatic reflective liquid crystal display device without coloring can be realized.

Further, the liquid crystal molecule alignment direction of the color compensating element composed of the driving liquid crystal layer and the twisted orientated chiral nematic liquid crystal layer is orthogonal to the molecular alignment direction at the interface between the opposing surfaces. And a reflection type liquid crystal display device characterized by the following.

Further, the present invention provides a liquid crystal display device wherein the color compensating element is a liquid crystal polymer film.

Further, the present invention provides a reflection type liquid crystal display device, wherein the driving liquid crystal layer is a twisted nematic liquid crystal layer which obtains a phase difference of about a quarter wavelength in one way. 4. The reflection type liquid crystal display device according to claim 1, wherein an electrode of said rear substrate also functions as said reflection layer. With this structure, it is possible to realize an achromatic color liquid crystal display device that is easy to see and that does not cause shading of characters.

Further, the reflection layer is a smooth reflection surface whose surface obtains specular reflection, and is provided with a light diffusion layer for diffusing light to the observer side from the driving liquid crystal layer. Item 6. The reflective liquid crystal display device according to item 1 or 5.
With this structure, it is possible to realize an achromatic reflective liquid crystal display device having a wide viewing angle and obtaining more whiteness.

4. The reflection type liquid crystal display device according to claim 1, further comprising a color filter having three colors of yellow, magenta and cyan. With this structure, a bright achromatic reflective liquid crystal display device capable of displaying color can be realized.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a liquid crystal display device according to the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIGS. 1 to 3 show a liquid crystal display device according to a first embodiment of the present invention. Two glass substrates having a thickness of 0.7 mm were used.
A direction 3 in which polyimide (AL-1051, manufactured by Nippon Synthetic Rubber Co., Ltd.) is printed and baked in the effective display area as 3 and tilted 31.5 degrees from the horizontal axis x of the observed effective display area 13
The upper substrate 11 is formed by rubbing the substrate a. Next, polyimide (AL) is formed on the other glass substrate 15 as an alignment film 16.
-1051, manufactured by Nippon Synthetic Rubber Co., Ltd.) is printed on the effective display area, baked, and rubbed in the direction 16a in which the direction is 63 ° opposite to that of the upper substrate 11, thereby forming the lower substrate 11.

Thereafter, a peripheral seal 17 having an opening of 5 mm width around the effective display area of the upper substrate 11 was formed by a screen printing method. The sealing material used here is a one-part epoxy resin (XN-21, manufactured by Mitsui Toatsu Chemicals, Inc.). Thereafter, a substrate gap material (not shown) is provided on the upper substrate 11.
3μm spacer material (trade name Micropearl S
P, Sekisui Fine Chemical Co., Ltd.) spray density 100
Sprayed at Ke / mm ^2, and the upper substrate 11 and lower substrate 14 overlaid as oriented plane faces, while pressurizing to substrate gap becomes equal to the diameter of the substrate Question gap material 180
It is baked at 2 ° C. for 2 hours to obtain an empty cell of the color compensation element used in the liquid crystal display device of the present embodiment.

Thereafter, a chiral material S811 (manufactured by Merck Japan Ltd.) as a liquid crystal material is added to the empty cell for 0.0%.
A nematic liquid crystal material (ZLI-1695, manufactured by Merck Japan Ltd.) having a positive dielectric anisotropy added with 7 wt% is injected by a vacuum injection method to form a liquid crystal layer 18, and an opening of the peripheral seal 17 is provided. UV curable resin UV-100
0 (manufactured by Sony Chemical Co., Ltd.) to obtain an optical member 10 for color compensation used in the liquid crystal display device of the present embodiment. At this time, it is desirable that the molecular arrangement direction of the interface of the alignment film of the optical member 10 for color compensation is orthogonal to the molecular arrangement direction of the interface of each layer on the opposing surface.

Next, an ITO film having a thickness of 2000 A is formed on a substrate 22 on the observation side made of glass having a thickness of 0.7 mm, a counter electrode 23 is formed, and polyimide (AL-1051) is used as an alignment film 24. Is printed on the effective display area, baked, and rubbed in a direction 24a inclined at 31.5 degrees with respect to the vertical axis y of the effective display area to be observed, to form a counter substrate 21 which is a front substrate on the observation side.

Next, on a glass substrate 26 having a thickness of 0.7 mm,
A gate line electrode made of MoW, a signal line electrode made of Mo / Al / Mo, a storage capacitor Cs electrode made of MoW, TF
A T element and a pixel electrode 27 are formed, and then polyimide (AL-1051) is printed as an alignment film 28 in the effective display area.
Direction 28 in which the direction is 63 ° opposite to that of front substrate 21 after firing
The substrate is rubbed to form a matrix array substrate 25 as a rear substrate, and is held at a distance of, for example, 3 μm from the counter substrate 21. At this interval, the chiral material S811
The liquid crystal ZLI1695 (manufactured by Merck Japan KK) to which 0.07 wt% (manufactured by Merck Japan KK) is added is injected to form the driving liquid crystal layer 29, and the driving liquid crystal element 20 in the LTN mode is obtained. At this time, it is desirable that the driving liquid crystal layer 29 be formed so as to obtain a phase difference of about a quarter wavelength in one way with no driving voltage applied.

Further, a polarizing plate 31 is bonded on the upper substrate 12 of the color compensating element 10, and a reflective plate 32 having diffusivity is bonded below the rear substrate 25 of the driving liquid crystal element 20. Thus, according to the first embodiment of the present invention, for example, 800
A liquid crystal display device of 11.3 × 600 dots is formed.

In this embodiment, the reflection plate is provided outside the driving liquid crystal layer. However, by forming the pixel electrode 29 as a reflection electrode made of, for example, an Al electrode, the shadow of characters does not occur.
An achromatic liquid crystal display device that is easy to see can be realized.

Further, a thin achromatic liquid crystal display device can be realized by forming a film made of a liquid crystal polymer as an optical member for color compensation instead of the optical member 10 for color compensation of the present embodiment. It is.

Next, a method for controlling incident light by the liquid crystal display device of the present invention will be described with reference to FIG.

When the driving liquid crystal layer is in an OFF state (voltage is not applied), the incident light 40 becomes linearly polarized light 41 by passing through the polarizing plate 31. Next, the color compensation element 10 converts the light into elliptically polarized light 42. Subsequently, when passing through the driving liquid crystal layer 29, the elliptically polarized light becomes the linearly polarized light 43. Next, the linearly polarized light reflected by the reflection plate 32 enters the driving liquid crystal layer 29. In the driving liquid crystal layer, the linearly polarized light is changed to elliptically polarized light 42.
a, and becomes linearly polarized light 41a by the color compensating element. At this time, the polarization axis direction is parallel to the polarization axis 31a of the polarization plate 31, so that the light passes through the polarization plate and becomes OFF (white) display (NW
mode).

Next, when the driving liquid crystal layer is in the ON state (voltage applied state), the incident light 40 becomes linearly polarized light by passing through the polarizing plate 31. Next, the light is converted into elliptically polarized light 42 by the color compensation element. Next, when passing through the driving liquid crystal layer 29, the elliptically polarized light passes as it is. Next, the reflection plate 32
The light is reflected by and becomes elliptically polarized light 42b in the opposite direction, and passes through the driving liquid crystal layer as it is. Next, the linearly polarized light 4
1b, and the polarization axis direction at this time is the polarization axis 31 of the polarizing plate.
Since it is orthogonal to a, it is absorbed by the polarizing plate 31 and is turned on.
(Black) display.

In this embodiment, the reflection plate also has a diffusive property, but the reflection plate is a smooth reflection surface for obtaining specular reflection, and diffuses light from the driving liquid crystal layer to the observer side. Needless to say, a similar effect can be obtained even in a structure provided with a light diffusion layer.

In the present embodiment, the reflection type liquid crystal display device for monochrome display has been described. However, by forming yellow, magenta, and cyan color filters on the front substrate 21 of the present embodiment, the color display is realized. A displayable bright and achromatic reflective liquid crystal display device can be realized. At this time, a color filter layer can be provided on the rear substrate.

[Embodiment 2] FIG. 4 shows an embodiment in which the present invention is applied to an MTN mode liquid crystal display device. One polarizing plate 50, a color compensating element 60, a driving liquid crystal element 70, a color filter 8
0, a reflection plate 90 is disposed, with respect to the horizontal x and vertical y axes of the effective display area, the polarization axis 50a of the polarizing plate, the liquid crystal alignment (rubbing) directions 60a and 60b of the color compensation element, and the driving liquid crystal element. Liquid crystal alignment (rubbing) directions 70a, 70b
Are inclined at an angle of 45 degrees, and the orientation direction of each element is 9
The liquid crystal molecules of each liquid crystal layer intersect at 0 degrees to form a 90-degree twisted arrangement. The twist arrangement of the two elements 60, 70 is reversed. Orientation direction 60a of upper substrate of color compensating element 60
And the orientation direction 70a of the driving element on the observation side is made coincident, and the orientation direction 60b of the lower substrate of the color compensation element 60 and the orientation direction 70b of the rear substrate of the driving element 70 are reversed.

According to the present embodiment, the coloring of the driving element is eliminated to make it achromatic, and the color display by the color filter 80 is displayed without turbidity.

[0033]

According to the present invention, an achromatic reflection type liquid crystal display device without coloring can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of Embodiment 1 of the present invention;

FIG. 2 is a diagram illustrating an operation of the first embodiment.

FIG. 3 is a schematic perspective view showing each part of the first embodiment in an unfolded state.

FIG. 4 is a schematic exploded perspective view of Embodiment 2 of the present invention,

FIG. 5 shows Δ of a conventional LTN mode reflective liquid crystal display device.
curve diagram showing nd-relative reflectance;

FIG. 6 shows Δ of a conventional MTN mode reflective liquid crystal display device.
FIG. 4 is a curve diagram showing nd-relative reflectance.

[Explanation of symbols]

 10: Color compensating element 18: Iral nematic liquid crystal layer 20: Driving liquid crystal display element 21: Front substrate 25: Back substrate 29: Driving liquid crystal layer 31: Polarizer 32: Reflector

Claims (7)

[Claims] 1. A front substrate with electrodes on at least an observation side, a rear substrate with electrodes disposed behind the front substrate, a driving liquid crystal layer made of a twisted orientated chiral nematic liquid crystal sandwiched between the substrates, A single-polarizer-type reflective liquid crystal display having a light-reflecting layer provided behind the liquid crystal layer as viewed from the side and a single polarizing plate provided forward of the liquid crystal layer as viewed from the observation side; In a reflection type liquid crystal display device comprising an element and a color compensation element provided between the polarizing plate and the reflection layer, the color compensation element has a twisting direction opposite to that of the liquid crystal layer, and a twist angle and a refractive index difference. A reflection type liquid crystal display device comprising a twisted orientated chiral nematic liquid crystal layer having substantially equal values obtained by multiplying anisotropy and a layer thickness. 2. A liquid crystal molecule arrangement direction of a color compensating element composed of the driving liquid crystal layer and the twist-aligned chiral nematic liquid crystal layer is orthogonal to a molecular arrangement direction of an interface of each of the opposing surfaces. The reflective liquid crystal display device according to claim 1, wherein: 3. The reflection type liquid crystal display device according to claim 1, wherein said color compensation element is a liquid crystal polymer film. 4. The reflection type liquid crystal layer according to claim 1, wherein the driving liquid crystal layer is a twisted nematic liquid crystal layer that obtains a phase difference of approximately a quarter wavelength in one way. Liquid crystal display. 5. The reflection type liquid crystal display device according to claim 1, wherein an electrode of said rear substrate also functions as said reflection layer. 6. The reflection layer, wherein the surface is a smooth reflection surface for obtaining specular reflection, and a light diffusion layer for diffusing light toward the observer from the driving liquid crystal layer is provided. Item 6. The reflective liquid crystal display device according to item 1 or 5. 7. The reflection type liquid crystal display device according to claim 1, further comprising a color filter composed of three colors of yellow, magenta and cyan.