JPH10170909A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a color liquid crystal display device that has a good visual angle characteristic and is a double refractive system, by combining a phase plate to the display device, which utilizes a comb-shaped electrode. SOLUTION: A lower polarizing plate 11 and a reflection plate 14 are joined to the outside of a first substrate 1 and a phase plate 13 and an upper polarizing plate 12 are joined to the outside of a second substrate 9. In order to avoid the reversed rotation of the liquid crystal molecules while a voltage is applied, the directions of the long axes of liquid crystal molecules 15 in a no voltage applied condition are set to a few degree clockwise rotation. The polarization axis of the plate 11 is arranged to make an approximately 45-degree angle with respect to the long axis direction of the molecules 15 and the polarization axis of the plate 12 is arranged to make an approximately 90-degree angle with respect to the ploarization axis of the plate 11. The stretching axis of the plate 13 is arranged to make an approximately 90-degree angle with respect 10 the long axis direction of the molecules 15. The molecules 15 are rotated while maintaining the directions that are approximately parallel to the substrate 1, the changes in the phase difference values by a visual angle are made small resulting in a less color change by a visual angle. Note that it is preferred to use the NRZ phase plate which is close to Nz=0.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention utilizes birefringence,
The present invention relates to a liquid crystal display device that performs color display without using a color filter, and more particularly to a liquid crystal display device that operates in a lateral electric field using a comb-shaped electrode having a wide viewing angle.

[0002]

2. Description of the Related Art In a conventional liquid crystal display device, electrodes for driving liquid crystals are formed on a first substrate and a second substrate, respectively, and an electric field in a direction perpendicular to the substrates is applied to the liquid crystal. The display is performed in a TN) mode or a super twisted nematic (STN) mode.

[0003] Further, as a color liquid crystal display device of a birefringence system which performs color display without using a color filter by utilizing the birefringence of liquid crystal, several systems have been proposed.

As a first conventional example, liquid crystal molecules are aligned in parallel between a first substrate and a second substrate, and a pair of polarizing plates is provided outside the first substrate and the second substrate. The birefringence of the liquid crystal cell is changed by placing the polarization axis of the polarizing plate at about 45 degrees with respect to the long axis of the liquid crystal molecules, and changing the way the liquid crystal molecules stand by voltage applied to the liquid crystal. There is a birefringence type color liquid crystal display device for performing display.

However, in this liquid crystal display device, when a voltage is applied between the first substrate and the second substrate to perform color display, the liquid crystal molecules are inclined obliquely. Since the birefringence of the liquid crystal cell fluctuates greatly depending on the angle, the color fluctuates depending on the viewing angle, and the liquid crystal cell has not been put to practical use.

As a second conventional example, an STN liquid crystal cell in which liquid crystal molecules of a first substrate and a second substrate are twisted by 180 to 270 degrees and aligned is used, and an STN liquid crystal cell is provided outside the first substrate and the second substrate. There is a birefringent color liquid crystal display device including a pair of polarizing plates and including at least one retardation plate between the polarizing plate and the substrate.

In this liquid crystal display device, since the liquid crystal molecules are greatly twisted, even when a voltage is applied to the liquid crystal cell and the liquid crystal molecules stand obliquely, the change in birefringence due to the viewing angle is relatively small, and the viewing angle is narrow. If it is within the range, no color change occurs,
Further, since a plurality of colors can be displayed by one pixel without using a color filter, it has recently been put to practical use in a small reflective color liquid crystal display device.

[0008]

However, in the color liquid crystal display device using the above STN liquid crystal cell, basically, electrodes for driving the liquid crystal cell are formed on the surfaces of the first substrate and the second substrate. The operation is performed by applying an electric field in a direction perpendicular to the substrate to the liquid crystal molecules.

Therefore, the liquid crystal molecules rise obliquely,
The display color and the background color change depending on the viewing angle, that is, there is a so-called viewing angle dependency of display quality, and a medium to large-sized color liquid crystal display device has not yet been realized.

As a method of improving the viewing angle dependency, a pair of comb-shaped electrodes are provided on a first substrate, and a voltage is applied between the comb-shaped electrodes to control the direction of liquid crystal molecules. There are means. This means will be described with reference to FIG. FIG.
Reference numeral 0 is a schematic enlarged view showing a planar shape of a pixel region of a liquid crystal display device using a comb-shaped electrode in a conventional example. As shown in FIG. 10, a first comb-shaped electrode 43 and a second
Are arranged at regular intervals.

The change in the magnitude of the voltage applied between the first comb-shaped electrode 43 and the second comb-shaped electrode 44 causes
The direction of the liquid crystal molecules 41 changes. When a liquid crystal material having a negative dielectric anisotropy is used, the state of the liquid crystal molecules 41 is maintained when a voltage lower than a predetermined voltage is applied. , And is held at the position of the liquid crystal molecule 42 indicated by the broken line. The liquid crystal molecules 41 and the liquid crystal molecules 42 move almost in parallel with the first substrate with almost no pretilt with the first substrate.

A pair of polarizing plates is provided outside the liquid crystal cell, and the polarizing plates are arranged so that the polarizing axes of the polarizing plates are orthogonal to each other and the polarizing axis of one of the polarizing plates is parallel to the liquid crystal molecules 41. The display is performed by changing the voltage applied to the first comb-shaped electrode 43 and the second comb-shaped electrode 44 to change the direction of the liquid crystal molecules. That is, at the position of the liquid crystal molecules 41, the incident polarized light goes straight as it is and is interrupted by the polarizing plate on the emission side, and black display is performed. On the other hand, at the position of the liquid crystal molecule 42 indicated by the dashed line, the incident polarized light enters the liquid crystal molecule 42 at an angle of about 45 degrees, so that a phase difference is generated, and this phase difference becomes の of the wavelength of visible light. Thus, by setting the birefringence Δn of the liquid crystal and the cell gap d, white display is achieved.

Since the liquid crystal molecules 42 move substantially parallel to the first substrate and do not rise obliquely as in a conventional liquid crystal display device, a liquid crystal display device having good viewing angle characteristics can be obtained.

However, the liquid crystal display device using the comb electrodes has a disadvantage that the aperture ratio is low because all the electrodes are provided on the first substrate. Therefore, in the case of a transmission type medium to large color display device having a color filter and illuminated by a backlight, it can be put to practical use by increasing the brightness of the backlight, but without a backlight, A reflective color liquid crystal display device that displays only external light cannot be realized.

An object of the present invention is to realize a bright birefringent color liquid crystal display device having good viewing angle characteristics by combining a display device using comb-shaped electrodes with a retardation plate. An object of the present invention is to provide a large reflective color liquid crystal display device.

[0016]

According to a first aspect of the present invention, there is provided a liquid crystal display device comprising: a first substrate; a second substrate; and a first substrate. A liquid crystal sandwiched between a pair of substrates including: a first substrate; a lower polarizer provided outside the first substrate; and an upper polarizer provided outside the second substrate. A pair of electrodes are arranged on the first substrate so as to form an electric field in a direction parallel to the substrate, and a major axis direction of the liquid crystal molecules is adjusted according to an electric field intensity according to a potential difference between the pair of electrodes. A liquid crystal display device that performs display while changing its direction while maintaining substantially parallel to a surface, and at least one of between a first substrate and a lower polarizer or between a second substrate and an upper polarizer. And a phase difference plate.

According to a second aspect of the present invention, there is provided a reflective liquid crystal display device comprising: a first substrate; a second substrate;
A liquid crystal sandwiched between a pair of substrates including the first substrate and the second substrate; a lower polarizing plate provided outside the first substrate; and a liquid crystal provided outside the second substrate. An upper polarizing plate, and a reflector provided outside the lower polarizing plate, a pair of electrodes is arranged on the first substrate so as to form an electric field in a direction parallel to the substrate, and between the pair of electrodes. A liquid crystal display device which performs a display by changing the direction of the long axis of liquid crystal molecules while keeping substantially parallel to the substrate surface in accordance with the electric field intensity according to the potential difference, wherein the first substrate and the lower polarizing plate are connected to each other. A phase difference plate is provided between at least one of the second substrate and the upper polarizing plate.

According to a third aspect of the present invention, there is provided a liquid crystal display device having the structure according to the first or second aspect, wherein a cell gap d is a gap between the first substrate and the second substrate. Δnd, which is the product of the liquid crystal and the birefringence Δn of the liquid crystal
Is 200 to 300 nm, the retardation value R of the retardation plate is 450 to 550 nm, and the crossing angle between the polarization axes of the upper and lower polarizers is about 90 degrees.

According to a fourth aspect of the present invention, a liquid crystal display device according to the fourth aspect includes the configuration according to the first or second aspect, and includes a cell gap d as a gap between the first substrate and the second substrate. Δnd, which is the product of the liquid crystal and the birefringence Δn of the liquid crystal
Is 700 to 800 nm, the retardation value R of the retardation plate is 150 to 250 nm, and the crossing angle of the polarization axes of the upper and lower polarizing plates is about 90 degrees.

According to a fifth aspect of the present invention, a liquid crystal display device according to the fifth aspect includes the configuration according to the first or second aspect, and includes a cell gap d as a gap between the first substrate and the second substrate. Δnd, which is the product of the liquid crystal and the birefringence Δn of the liquid crystal
Is about 350 to 450 nm, and the retardation value R of the retardation plate is
Is about 350 to 450 nm, and the crossing angle between the polarization axes of the upper and lower polarizing plates is about 0 degrees.

According to a sixth aspect of the present invention, a liquid crystal display device according to the sixth aspect includes the configuration according to the first, second, third, fourth, or fifth aspect, wherein the refractive index of the retardation plate in the extending direction is n.
x, the refractive index in the 90-degree direction with respect to the stretching direction is defined as ny, and the refractive index in the thickness direction of the retardation plate is defined as nz, and nx> nz
> Ny.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) The structure of a liquid crystal display device according to an embodiment of the present invention will be described below with reference to the drawings. First, the configuration of the liquid crystal display device according to the first embodiment of the present invention will be described with reference to FIGS.

FIG. 2 is a plan view showing one pixel of the liquid crystal display device according to the first embodiment of the present invention. FIG. 1 is a sectional view taken along line AA of FIG. Hereinafter, FIGS. 1 and 2
The configuration of the first exemplary embodiment of the present invention will be described with reference to FIGS.

A scanning electrode 3 made of an aluminum (Al) film and a counter electrode 6 made of Al are formed on a first substrate 1, and the surfaces of the scanning electrode 3 and the counter electrode 6 are made of an anodic oxide film of Al. Is coated with an aluminum oxide film (not shown). The gate silicon nitride (Si
N) film 7 and amorphous silicon (a-Si) film 4 are formed,
Impurities are implanted into the surface of the a-Si film 4 to form an n-type a-S
After the formation of the i film, the pixel electrode 5 and the signal electrode 2 made of Al are formed to form a thin film transistor structure.

The structure of the counter electrode 6 is T-shaped as shown in FIG. 2 and includes a connection wiring portion parallel to the scanning electrode 3 and a counter pixel portion parallel to the pixel electrode 5. The connection wiring portion between the scanning electrode 3 and the counter electrode 6 intersects with the signal electrode 2 via a gate SiN film 7 which is an insulating film.
A thin film transistor and all metal electrode groups are formed on the substrate 1 of FIG.

When a selection signal is applied to the scanning electrode 3 and the thin film transistor is turned on, the signal electrode 2 and the pixel electrode 5 are turned on.
Is reduced, an electric field is applied between the pixel electrode 5 and the counter electrode 6, and the liquid crystal molecules 15 rotate while being substantially parallel to the first substrate. Thereafter, when a non-selection signal is applied to the scanning electrode 3, the thin film transistor is turned off, the connection resistance between the signal electrode 2 and the pixel electrode 5 becomes very large, and the voltage applied to the pixel electrode 5 is maintained.

In the present embodiment, Al is used for the metal wiring on the first substrate. However, there is no particular limitation on the material as long as the metal wiring has a low electric resistance, and tantalum, chromium, or copper may be used. .

In order to protect the thin film transistor, Si
After forming the protective film 8 made of an N film, an alignment film 10 made of a polyimide film for aligning liquid crystal molecules is formed by a printing method.

An alignment film 10 made of a polyimide film is also printed on the second substrate 9. First substrate 1 and second substrate 9
Is rubbed so as to be substantially parallel to the pixel electrodes 5, and then a spacer (not shown) is sprayed so as to have a predetermined thickness between the substrates, and both substrates are spread with an epoxy-based adhesive (not shown). Glue. The liquid crystal 15 is injected and sealed to form a liquid crystal cell.

A lower polarizing plate 11 and a reflecting plate 14 are bonded outside the first substrate 1, and a retardation plate 13 and an upper polarizing plate 12 are bonded outside the second substrate 9. This adhesive is not shown in FIG. 1, and a portion corresponding to the adhesive is shown with a gap. In the present embodiment, the lower polarizing plate 11 and the reflecting plate 14 use a reflector integrated polarizing plate F3205G manufactured by Nitto Denko, and the upper polarizing plate 12 uses EG1225DU also manufactured by Nitto Denko.

As the retardation plate 13, an NRZ retardation plate having a retardation value R of 500 nm manufactured by Nitto Denko was used. This retardation plate has a refractive index in the stretching direction of nx, a refractive index in the stretching direction and 90 ° direction as ny, and a refractive index in the thickness direction as nz.
nx>nz> ny. Nz = (nx−nz)
As defined by / (nx-ny), Nz = 0.4.

FIG. 9 shows a change characteristic of the retardation value R when the retardation plate is inclined in the stretching direction. Curve 32 shows the characteristics of a normal retardation plate. An ordinary retardation plate has a relationship of nx> ny = nz
Nz = 1, and the phase difference value becomes smaller when tilted in the stretching direction. Curve 3 shows the characteristics of the retardation plate with Nz = 0.5
The curve 33 shows the characteristic when Nz = 0. Nz = 0.5
It can be seen that the phase difference value does not change at all even when tilted, and no color change occurs.

As the phase difference plate 13, a normal phase difference plate of Nz = 1 can be used, but a color change occurs when viewed in the right and left directions. In order to further improve the viewing angle characteristics, the above-mentioned NRZ retardation plate having Nz close to 0.5 was adopted. By employing this NRZ retardation plate, it is possible to realize a liquid crystal display device having good viewing angle characteristics with almost no color change when viewed from the front, rear, left and right directions.

First, the principle of color development of the liquid crystal display device of the present invention will be described. The polarization axes of the upper and lower polarizers are crossed at 90 degrees, a retardation plate having a retardation value R is provided between the polarizers, and
The transmitted light intensity Io when arranged at 5 degrees is Io = Ii / 2 × sin ² (πR / λ) with respect to the incident light intensity Ii and the wavelength λ. Therefore, R = λ × (1/2 + 0, 1, 2,...)
In the case of n), Io becomes the largest. Since Io changes for each wavelength λ, a color is generated. By changing the phase difference value R, various colors can be displayed. As described above, the color is changed by changing the retardation value R and Δnd which is the birefringence of the liquid crystal. When the polarization axes of the upper and lower polarizers are arranged in parallel, Io = Ii / 2 × sin ² (πR / λ + π / 2), and the color change is reversed. Becomes possible.

Next, the arrangement of the first embodiment of the present invention will be described. FIG. 3 is a plan view for explaining an arrangement relationship in the first embodiment of the present invention.

As the liquid crystal material, a P-type material having a birefringence anisotropy Δn of 0.1 and a positive dielectric anisotropy Δε is used.
The cell gap d which is a gap between the substrate 1 and the second substrate 9 is 2.5 μm. Therefore, Δnd = 250 nm representing the birefringence of the liquid crystal cell. The long axis direction of the liquid crystal molecules 15 in a state where no voltage is applied is oriented substantially in parallel with the pixel electrode 5. When a voltage is applied between the pixel electrode 5 and the counter electrode 6, the liquid crystal molecule 15 rotates in the direction of arrow 17 according to the voltage. Then, it reaches the liquid crystal molecules 16 indicated by the dotted line. Here, in order to avoid reverse rotation of the liquid crystal molecules when a voltage is applied, the liquid crystal molecules 15 in a state where no voltage is applied are used.
The direction of the long axis is set clockwise about several degrees.

The polarization axis of the lower polarizing plate 11 is arranged at an angle of about 45 degrees with the long axis direction of the liquid crystal molecules 15, and the polarization axis of the upper polarizing plate 12 is approximately equal to the polarizing axis of the lower polarizing plate 11. It is arranged so as to form an angle of 90 degrees. The stretching axis of the retardation plate 13 is arranged so as to make an angle of about 90 degrees with the long axis direction of the liquid crystal molecules 15.

FIG. 4 shows the color display characteristics of the color liquid crystal display device according to the first embodiment of the present invention. FIG.
In the chromaticity diagram by IE, the lower right indicates red, the lower left indicates blue, the upper center indicates green, and the center cross indicates white. When no voltage is applied, the major axis direction of the liquid crystal molecules 15 is 90 ° with respect to the stretching axis of the retardation plate 13.
Degree direction, the retardation value of the retardation plate R = 500 nm
Is subtracted from Δnd = 250 nm of the liquid crystal cell, and the phase difference value r of the liquid crystal display device is 250 nm, which is almost の of the wavelength of visible light.

When a voltage is applied to the liquid crystal, the liquid crystal molecules 15 rotate in the direction of arrow 17 and, when rotated exactly 45 degrees, become parallel to the upper polarizer 12, and no phase difference is caused by the liquid crystal molecules. The retardation value r of the device is
R = 500 nm only with the phase difference value R of 3;
The pink display shown by 1 is obtained.

Further, when the voltage applied to the liquid crystal is increased,
Since the liquid crystal moves to the position shown by the dotted line 16 and is in the same direction as the extending direction of the retardation plate, the retardation value of the retardation plate R = 5.
00 nm and Δnd = 250 nm of the liquid crystal are added, and the phase difference value r of the liquid crystal display device becomes 750 nm. Therefore, white →
Color display from pink to green is possible.

Since the liquid crystal molecules 15 rotate while being substantially parallel to the first substrate 1, there is little change in the phase difference value due to the viewing angle, so that there is little color change due to the viewing angle. Further, in the present embodiment, since the retardation plate 13 of Nz = 0.4 is employed, the viewing angle characteristics of the retardation plate 13 are also good, so that there is little color change in a very wide range and the viewing angle characteristics are good. A birefringent color liquid crystal display device can be realized.

In the first embodiment of the present invention, the number of pixels is 640 × 480, the pixel pitch is 200 μm in the horizontal direction (interval between signal electrodes 2), and 2 in the vertical direction (interval between scan electrodes 3).
A 6.3-inch reflective color liquid crystal display device of 00 μm is prepared. The line width between the counter electrode 6 and the pixel electrode 5 is 10 μm, the line width between the signal electrode 2 and the scan electrode 3 is 20 μm,
When the distance between the pixel electrode 5 and the counter electrode 6 is 10 μm and the distance between the signal electrode 2 and the counter electrode 6 is 10 μm, the distance between the pixel electrode 5 and the counter electrode 6 serving as a display unit is 140 μm, which is as high as about 55%. An aperture ratio can be secured.

By employing the above-described configuration, a birefringent color liquid crystal display device which is bright and has good viewing angle characteristics can be realized, and a medium to large reflective color liquid crystal display device can be provided.

In this embodiment, Δn of the liquid crystal cell
d = 250 nm, phase difference value R of the phase difference plate 13 = 500 n
FIG. 11 shows a chromaticity diagram showing a color change when Δnd and R are shifted in the first embodiment. The phase difference plate 13 is fixed at R = 500, and the Δ
An arrow 50 shows a change in white color when nd is increased from 250 nm. Since the phase difference value r of the liquid crystal display device is a difference between R of the phase difference plate and Δnd of the liquid crystal cell, the phase difference value r of the liquid crystal display device decreases with an increase of Δnd of the liquid crystal cell. And the display becomes dark. Conversely, when Δnd of the liquid crystal cell decreases, the phase difference value r of the liquid crystal display device increases, so that the liquid crystal cell becomes yellow as shown by the arrow 51. From the visual observation, the Δ
The appropriate nd is from 300 nm indicated by the mark 56 to 200 nm indicated by the mark 57.

On the other hand, a green color change when the liquid crystal cell is fixed at Δnd = 250 nm and R of the phase difference plate 13 is increased is shown by an arrow 52. Since the phase difference value r of the liquid crystal display device is the sum of the phase difference value R of the phase difference plate and Δnd of the liquid crystal cell,
As R increases, r also increases and becomes yellow. Conversely, when R decreases, r also decreases. That is, the case where r = Δnd + R = about 750 nm is optimal, and the Δnd of the liquid crystal cell is 200 to 300 nm, so that the retardation value R of the retardation plate is 450 to 550 nm.
It can be used in the range.

On the other hand, the pink display indicated by the mark 21 is determined only by the phase difference value R of the phase difference plate regardless of the Δnd of the liquid crystal cell. When R is increased, the display becomes blue as indicated by an arrow 54, and when R is decreased, the display is largely changed from a yellow display as indicated by an arrow 55. Therefore, when R = 450 nm, □
With the color of the mark 59, white → yellow → green is displayed, and R = 550.
In the case of nm, the liquid crystal display device displays white, blue, and green with the color of the mark 58.

In this embodiment, the first substrate 1 is located on the lower side and the reflector 14 is provided outside the lower polarizing plate 11, but the second substrate 9 is located on the lower side and the upper polarizing plate 12 is located on the lower side. It is also possible to provide a reflection plate 14 outside the. Also, the reflection plate 14
It is of course possible to provide a transmissive liquid crystal display device by removing the backlight and providing a backlight.

In the present embodiment, the phase difference plate 13
Is provided between the second substrate and the upper polarizing plate 12, but the first
Between the substrate 1 and the lower polarizing plate 11. It is obvious that the same effect can be obtained even if a plurality of retardation plates are arranged.

Further, in this embodiment, only the alignment film 10 is provided on the second substrate 9, but in order to protect the thin film transistor from light,
It is also possible to provide a black matrix with a metal such as chromium or a black pigment ink.

The liquid crystal 15 used in the present embodiment is
Used a material having a positive dielectric anisotropy Δε, but a material having a negative dielectric anisotropy Δε can also be used. In this case, the rubbing process is performed substantially in parallel with the scanning electrode 3 so that the position of the liquid crystal molecules when no voltage is applied becomes the dotted line 16. When a voltage is applied to the pixel electrode 5 and the counter electrode 6, the liquid crystal molecules rotate in a direction parallel to the pixel electrode.

In this embodiment, the case of active matrix driving in which a thin film transistor is provided for each pixel has been described. However, a thin film diode may be used instead of the thin film transistor, or the pixel electrode 5 may be directly connected to the outside. It is also possible to perform static driving.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
The configuration of the liquid crystal display device according to the embodiment is different from that of FIGS. 1 and 2 except that the arrangement relationship between the liquid crystal molecules 15 and the phase difference plate 13 and the difference Δnd of the liquid crystal cell and the phase difference value R of the phase difference plate differ.
This is the same configuration as the first embodiment shown in FIG.

FIG. 5 is a plan view for explaining an arrangement relationship of the second embodiment of the present invention. Hereinafter, FIGS. 1 and 2
The configuration of the second embodiment will be described with reference to FIG.

A lower polarizing plate 11 and a reflecting plate 14 are adhered outside the first substrate 1, and a retardation plate 13 and an upper polarizing plate 12 are arranged outside the second substrate 9. In the present embodiment,
The lower polarizing plate 11 and the reflecting plate 14 used a reflector integrated polarizing plate F3205G manufactured by Nitto Denko, and the upper polarizing plate 12 used EG1225DU also manufactured by Nitto Denko.

As the retardation plate 13, an NRZ retardation plate having a retardation value R = 200 nm manufactured by Nitto Denko was used. This retardation plate has a refractive index in the stretching direction of nx, a refractive index in the stretching direction and 90 ° direction as ny, and a refractive index in the thickness direction as nz.
nx>nz> ny. Nz = (nx−nz)
As defined by / (nx-ny), Nz = 0.4.

As the phase difference plate 13, the usual nx> ny
= Nz, and a retardation plate with Nz = 1 can be used, but a color change occurs when viewed obliquely in the left-right direction. To further improve the viewing angle characteristics, Nz is close to 0.5,
The NRZ retardation plate was used. By employing this NRZ retardation plate, it is possible to realize a liquid crystal display device having good viewing angle characteristics with almost no color change when viewed from the front, rear, left and right directions.

As the liquid crystal material, a P-type material having a birefringence anisotropy Δn of 0.1 and a positive dielectric anisotropy Δε is used.
The cell gap d which is a gap between the substrate 1 and the second substrate 9 is 7.5 μm. Therefore, Δnd = 750 nm indicating the birefringence of the liquid crystal cell. The long axis direction of the liquid crystal molecules 15 in a state where no voltage is applied is oriented substantially in parallel with the pixel electrode 5. When a voltage is applied between the pixel electrode 5 and the counter electrode 6, the liquid crystal molecule 15 rotates in the direction of arrow 17 according to the voltage. Then, it reaches the liquid crystal molecules 16 indicated by the dotted line. Here, in order to avoid reverse rotation at the time of applying a voltage, the major axis direction of the liquid crystal molecules 15 in a state where no voltage is applied is set clockwise by several degrees.

The polarization axis of the lower polarizing plate 11 is arranged so as to make an angle of about 45 degrees with the long axis direction of the liquid crystal molecules 15, and the polarization axis of the upper polarizing plate 12 is approximately equal to the polarizing axis of the lower polarizing plate 11. It is arranged so as to form an angle of 90 degrees. The stretching axis of the phase difference plate 13 is arranged so as to form an angle of about 0 degrees with the major axis direction of the liquid crystal molecules 15.

FIG. 6 shows the color display characteristics of the liquid crystal display device according to the second embodiment of the present invention. FIG. 6 is a chromaticity diagram based on CIE. When no voltage is applied, the major axis direction of the liquid crystal molecules 15 is parallel to the retardation plate 13, so that the retardation value R of the retardation plate is 750 nm and the Δnd of the liquid crystal is 200.
nm is added, and the phase difference value of the liquid crystal display device is r = 950n.
m, so that the mark 23 is displayed in orange.

When a voltage is applied to the liquid crystal cell, the liquid crystal molecules 1
5 rotates in the direction of arrow 17 and, when rotated just 45 degrees, becomes parallel to the polarization axis of the upper polarizer 12, does not cause a phase difference due to liquid crystal molecules, and has a phase difference value r of the liquid crystal display device.
Is only the phase difference value R of the phase difference plate 13, and r = 200 nm
, Which is almost １ ／ of the wavelength of visible light.
Is displayed in white.

Further, when the voltage applied to the liquid crystal is increased,
The liquid crystal molecules rotate to the position shown by the dotted line 16, and the retarder 1
3, the retardation value of the retardation plate R = 200 nm and the Δnd = 750 nm of the liquid crystal are subtracted, and the retardation value r of the liquid crystal display device is r = 550 nm. Display. Therefore, an orange->white-> blue color display is possible by changing the applied voltage.

Since the liquid crystal molecules 15 rotate while being substantially parallel to the first substrate 1, there is little change in the phase difference value due to the viewing angle, so that there is little color change due to the viewing angle. Further, in the present embodiment, since the retardation plate 13 of Nz = 0.4 is employed, the viewing angle characteristics of the retardation plate 13 are also good, so that there is little color change in a very wide range and the viewing angle characteristics are good. A birefringent color liquid crystal display device can be realized.

Also in the second embodiment of the present invention, the number of pixels is 640 × 480, the pixel pitch is 200 μm in the horizontal direction (the interval between signal electrodes 2), and 2 in the vertical direction (the interval between scan electrodes 3).
A 6.3-inch reflective color liquid crystal display device of 00 μm is prepared. The line width between the counter electrode 6 and the pixel electrode 5 is 10 μm, the line width between the signal electrode 2 and the scan electrode 3 is 20 μm,
When the distance between the pixel electrode 5 and the counter electrode 6 is 10 μm and the distance between the signal electrode 2 and the counter electrode 6 is 10 μm, the distance between the pixel electrode 5 and the counter electrode 6 serving as a display unit is 140 μm, which is as high as about 55%. An aperture ratio can be secured.

By adopting the configuration as described above, a birefringent color liquid crystal display device which is bright and has good viewing angle characteristics can be realized, and a medium to large reflective color display device can be provided.

In the present embodiment, Δn of the liquid crystal cell
d = 750 nm, phase difference value R of the phase difference plate 13 = 200n
FIG. 12 shows a chromaticity diagram showing a color change when Δnd and R are shifted in the second embodiment. The phase difference value R of the phase difference plate 13 is fixed to 200 nm,
When Δnd of the liquid crystal cell is reduced, r
The orange at 950 nm changes as indicated by arrow 62. That is, since the phase difference value r of the liquid crystal display device is the sum of the phase difference value R of the phase difference plate and Δnd of the liquid crystal cell, Δn
As d decreases, r also decreases and becomes yellow. Conversely, when Δnd increases, r also increases, so that the color becomes purple as indicated by an arrow 63, and at r = 1050 nm, the color becomes reddish purple as indicated by a square 69.
That is, it can be used in the range of r = Δnd + R = 950 nm to 1050 nm.

On the other hand, the blue display shown by the mark 25 is the difference between Δnd of the liquid crystal cell and the phase difference value R of the phase difference plate 13, where r = 55.
0 nm. When Δnd is increased, the phase difference value r of the liquid crystal display device is also increased, so that the display becomes light blue as indicated by an arrow 64, and at r = 650 nm, the light blue indicated by a mark 68. Conversely, when Δnd decreases, r decreases, and the display changes to purple as indicated by an arrow 65. That is, r = Δ
nd-R can be used in the range of 550 to 650 nm. Accordingly, as the phase difference value R of the phase difference plate, r = 950 to 1050 nm in orange display and r = 550 in blue display.
差 of the difference between ６650 nm is preferred, and R = 150〜2
50 nm, and therefore Δnd = 700-800 nm
It can be used in the range.

The white display shown by the mark 24 indicates the Δn of the liquid crystal cell.
Only the phase difference value R of the phase difference plate 13 can be determined without depending on d. Therefore, when R is reduced, as indicated by arrow 60,
It gradually becomes bluish and dark. Conversely, when R is increased, the color becomes yellow as indicated by an arrow 61. From the visual observation, the phase difference value R of the phase difference plate 13 is 150 nm
For example, the retardation value R of the retardation plate 13 may be set to 150 nm
Therefore, it becomes 250 nm shown by the mark 67.

In this embodiment, the first substrate 1 is located on the lower side and the reflector 14 is provided outside the lower polarizing plate 11, but the second substrate 9 is located on the lower side and the upper polarizing plate 12 is located on the lower side. It is also possible to provide a reflection plate 14 outside the. Also, the reflection plate 14
It is of course possible to provide a transmissive liquid crystal display device by removing the backlight and providing a backlight.

In the present embodiment, the phase difference plate 13
Is provided between the second substrate and the upper polarizing plate 12, but the first
Between the substrate 1 and the lower polarizing plate 11. It is obvious that the same effect can be obtained even if a plurality of retardation plates are arranged.

In this embodiment, only the alignment film 10 is provided on the second substrate 9. However, to protect the thin film transistor from light,
It is also possible to provide a black matrix with a metal such as chromium or a black pigment ink.

The liquid crystal 15 used in the present embodiment is
Used a material having a positive dielectric anisotropy Δε, but a material having a negative dielectric anisotropy Δε can also be used. In that case, the rubbing process is performed substantially in parallel with the scanning electrode 3 so that the position of the liquid crystal when no voltage is applied becomes the dotted line 16. When a voltage is applied to the pixel electrode 5 and the counter electrode 6, the liquid crystal molecules rotate in a direction parallel to the pixel electrode.

In this embodiment, the case of active matrix driving in which a thin film transistor is provided for each pixel has been described. However, a thin film diode may be used instead of the thin film transistor, or the pixel electrode 5 may be directly connected to an external device. It is also possible to perform static driving.

(Third Embodiment) Next, a third embodiment of the present invention will be described.
The configuration of the liquid crystal display device according to the first embodiment is different from that of the first embodiment shown in FIGS. 1 and 2 except that the crossing angle between the upper and lower polarizers, the Δnd of the liquid crystal cell and the phase difference value R of the phase difference plate are different. The configuration is the same as that of the embodiment.

FIG. 7 is a plan view for explaining an arrangement relationship of the third embodiment of the present invention. Hereinafter, FIGS. 1 and 2
The configuration of the third embodiment will be described with reference to FIG.

A lower polarizing plate 11 and a reflecting plate 14 are bonded outside the first substrate 1, and a retardation plate 13 and an upper polarizing plate 12 are disposed outside the second substrate 9. In the present embodiment,
The lower polarizing plate 11 and the reflecting plate 14 used a reflector integrated polarizing plate F3205G manufactured by Nitto Denko, and the upper polarizing plate 12 used EG1225DU also manufactured by Nitto Denko.

As the retardation plate 13, an NRZ retardation plate having a retardation value R = 380 nm manufactured by Nitto Denko was used. This retardation plate has a refractive index in the stretching direction of nx, a refractive index in the stretching direction and 90 ° direction as ny, and a refractive index in the thickness direction as nz.
nx>nz> ny. Nz = (nx−nz)
As defined by / (nx-ny), Nz = 0.4.

As the phase difference plate 13, the usual nx> ny
= Nz and a phase difference plate with Nz = 1 can be used,
A color change occurs when viewed from the left and right. In order to further improve the viewing angle characteristics, the above-mentioned NRZ retardation plate having Nz close to 0.5 was adopted. By employing this NRZ retardation plate, it is possible to realize a liquid crystal display device having good viewing angle characteristics with almost no color change when viewed from the front, rear, left and right directions.

As the liquid crystal material, a P-type material having a birefringence anisotropy Δn of 0.1 and a positive dielectric anisotropy Δε is used.
The cell gap d as a gap between the substrate 1 and the second substrate 9 is 3.8 μm. Therefore, Δnd = 380 nm indicating the birefringence of the liquid crystal cell. The long axis direction of the liquid crystal molecules 15 in a state where no voltage is applied is oriented substantially in parallel with the pixel electrode 5. When a voltage is applied between the pixel electrode 5 and the counter electrode 6, the liquid crystal molecule 15 rotates in the direction of arrow 17 according to the voltage. Then, it reaches the liquid crystal molecules 16 indicated by the dotted line. Here, in order to avoid reverse rotation at the time of applying a voltage, the major axis direction of the liquid crystal molecules 15 in a state where no voltage is applied is set clockwise by several degrees.

The polarization axis of the lower polarizing plate 11 is disposed so as to make an angle of about 45 degrees with the long axis direction of the liquid crystal molecules 15, and the polarization axis of the upper polarizing plate 12 is substantially equal to the polarizing axis of the lower polarizing plate 11. Place them in parallel. The stretching axis of the retardation plate 13 is arranged so as to make an angle of about 90 degrees with the long axis direction of the liquid crystal molecules 15.

FIG. 8 shows the color display characteristics of the liquid crystal display device according to the third embodiment of the present invention. FIG. 8 is a chromaticity diagram based on CIE. When no voltage is applied, the major axis direction of the liquid crystal molecules 15 is in a direction shifted by 90 degrees from the stretching direction of the retardation plate 13, so that the retardation value R of the retardation plate R = 380 nm and Δnd = 380 nm of the liquid crystal are subtracted. Then, the phase difference value r of the liquid crystal display device becomes 0 nm. Since the upper and lower polarizers are arranged almost in parallel, the incident light is transmitted as it is, and the white mark 26 is displayed.

When a voltage is applied to the liquid crystal cell, the liquid crystal molecules 1
5 is rotated in the direction of arrow 17 and when rotated exactly 45 degrees, the direction is shifted by 90 degrees from the polarization axis of the upper polarizer 12, and no phase difference due to liquid crystal molecules is generated. r is only the phase difference value R of the phase difference plate 13, and r =
It becomes 380 nm, and becomes blue display indicated by the mark 27.

When the voltage applied to the liquid crystal cell is further increased, the liquid crystal molecules rotate to the position indicated by the dotted line 16 and become parallel to the extending direction of the retardation plate.
= 380 nm and Δnd = 380 nm of the liquid crystal are added,
The phase difference value r of the liquid crystal display device was 760 nm,
The pink display shown in FIG. Therefore, a color display of white → blue → pink is possible by changing the applied voltage.

Since the liquid crystal molecules 15 rotate while being substantially parallel to the first substrate 1, a change in the phase difference value due to the viewing angle is small, and thus a color change due to the viewing angle is small. Further, in the present embodiment, since the retardation plate 13 of Nz = 0.4 is employed, the viewing angle characteristics of the retardation plate 13 are also good, so that there is little color change in a very wide range and the viewing angle characteristics are good. A birefringent color liquid crystal display device can be realized.

Also in the third embodiment of the present invention, the number of pixels is 640 × 480, the pixel pitch is 200 μm in the horizontal direction (interval between signal electrodes 2), and 2 in the vertical direction (interval between scanning electrodes 3).
A 6.3-inch reflective color liquid crystal display device of 00 μm is prepared. The line width between the counter electrode 6 and the pixel electrode 5 is 10 μm, the line width between the signal electrode 2 and the scan electrode 3 is 20 μm,
When the distance between the pixel electrode 5 and the counter electrode 6 is 10 μm and the distance between the signal electrode 2 and the counter electrode 6 is 10 μm, the distance between the pixel electrode 5 and the counter electrode 6 serving as a display unit is 140 μm, which is as high as about 55%. An aperture ratio can be secured.

By employing the configuration as described above, a birefringent color liquid crystal display device which is bright and has good viewing angle characteristics can be realized, and a medium to large reflective color display device can be provided.

In the present embodiment, Δn of the liquid crystal cell
d = 380 nm, phase difference value R of the phase difference plate 13 = 380n
FIG. 13 shows a chromaticity diagram showing a color change when Δnd and R are shifted in the third embodiment. The blue display indicated by the mark 27 is determined by only the phase difference value R of the phase difference plate regardless of the Δnd of the liquid crystal cell. When R is increased, light blue is displayed as indicated by an arrow 71, and when R is decreased, dark blue is displayed as indicated by an arrow 70. Here, since the crossing angles of the upper and lower polarizers are parallel unlike the second embodiment, the color change moves in reverse. Therefore, R = 35
In the case of 0 nm, it is a navy blue color indicated by □ mark 77, and R = 450 n
In the case of m, it becomes light blue indicated by the mark 76, but can be displayed as blue.

When the phase difference value R of the phase difference plate 13 is fixed at 380 nm and Δnd of the liquid crystal cell is increased, a circle 28 is obtained.
The arrow 72 shows the pink color change shown in FIG. The phase difference value r of the liquid crystal display device is obtained by dividing the phase difference value R of the phase difference plate by Δ
Since r is the sum of nd, r increases as Δnd increases and becomes blue-violet. Conversely, when Δnd decreases, r also decreases, so that the display becomes yellow as indicated by an arrow 73 and a large color change occurs. Here, since the crossing angles of the upper and lower polarizers are parallel unlike the first embodiment, the color change moves in reverse. That is, the case where r = Δnd + R = 750-800 nm is optimal, and since R = 350-450 nm, Δnd =
It can be used in the range of 350 to 450 nm.

On the other hand, the white display indicated by the mark 26 is most preferable when the phase difference value r of the liquid crystal display device is r = R−Δnd = 0, that is, the phase difference value R of the phase difference plate and the Δnd value of the liquid crystal cell are different.
Are equal. If R or Δnd deviates, r of the liquid crystal display device does not matter whether it is positive or negative, so | r |> 0, and as shown by the arrow 74, the color becomes yellow. In the result of the visual observation,
In the range of | r | <100 nm, it can be used.
R = 350-450 nm, Δnd = 350-450 nm
There is no problem in the range.

In the present embodiment, the first substrate 1 is located on the lower side and the reflector 14 is provided outside the lower polarizing plate 11, but the second substrate 9 is located on the lower side and the upper polarizing plate 12 is located on the lower side. It is also possible to provide a reflection plate 14 outside the. Also, the reflection plate 14
It is of course possible to provide a transmissive liquid crystal display device by removing the backlight and providing a backlight.

In the present embodiment, the phase difference plate 13
Is provided between the second substrate and the upper polarizing plate 12, but the first
Between the substrate 1 and the lower polarizing plate 11. It is obvious that the same effect can be obtained even if a plurality of retardation plates are arranged.

Further, in this embodiment, only the alignment film 10 is provided on the second substrate 9, but in order to protect the thin film transistor from light,
It is also possible to provide a black matrix with a metal such as chromium or a black pigment ink.

The liquid crystal 15 used in the present embodiment is
Used a material having a positive dielectric anisotropy Δε, but a material having a negative dielectric anisotropy Δε can also be used. In that case, the rubbing process is performed substantially in parallel with the scanning electrode 3 so that the position of the liquid crystal when no voltage is applied becomes the dotted line 16. When a voltage is applied to the pixel electrode 5 and the counter electrode 6, the liquid crystal molecules rotate in a direction parallel to the pixel electrode.

In this embodiment, the case of active matrix driving in which a thin film transistor is provided for each pixel has been described. However, a thin film diode may be used instead of the thin film transistor, or the pixel electrode 5 may be directly connected to the outside. It is also possible to perform static driving.

[0094]

As is apparent from the above description, according to the present invention, a display device using comb electrodes is combined with a retardation plate to optimize the Δnd of the liquid crystal cell and the retardation value R of the retardation plate. Thus, a color liquid crystal display device of a birefringence method having good viewing angle characteristics can be realized.

Further, according to the liquid crystal display device of the present invention, since it is bright and has a good viewing angle characteristic, it is possible to provide a medium to large reflective color liquid crystal display device.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a liquid crystal display device according to an embodiment of the present invention, and is a schematic enlarged view illustrating a cross-sectional shape taken along line AA of FIG.

FIG. 2 is a schematic enlarged view showing a planar shape of the liquid crystal display device according to the embodiment of the present invention.

FIG. 3 is a plan view for explaining an arrangement relationship of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 4 is a chromaticity diagram showing display colors of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 5 is a plan view illustrating an arrangement relationship of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 6 is a chromaticity diagram showing display colors of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 7 is a plan view illustrating an arrangement relationship of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 8 is a chromaticity diagram showing display colors of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 9 is a diagram illustrating viewing angle characteristics of a retardation plate used in the first embodiment of the present invention.

FIG. 10 is a schematic enlarged view showing a planar shape of a partial region of a liquid crystal display device using a comb-shaped electrode in a conventional example.

FIG. 11 is a chromaticity diagram showing a color change of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 12 is a chromaticity diagram illustrating a color change of the liquid crystal display device according to the second embodiment of the present invention.

FIG. 13 is a chromaticity diagram showing a color change of the liquid crystal display device according to the third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 first substrate 2 signal electrode 3 scanning electrode 4 amorphous silicon 5 pixel electrode 6 counter electrode 9 second substrate 11 lower polarizing plate (polarization axis) 12 upper polarizing plate (polarization axis) 13 retardation plate (stretching axis) ) 14 Reflector 15 Liquid crystal molecules

Claims (6)

[Claims] A first substrate, a second substrate, and the first substrate;
Liquid crystal sandwiched between a pair of substrates including the first substrate and the second substrate, a lower polarizing plate provided outside the first substrate, and an upper polarizing plate provided outside the second substrate A pair of electrodes are arranged on the first substrate so as to form an electric field in a direction parallel to the substrate, and a major axis direction of the liquid crystal molecules is changed according to an electric field intensity according to a potential difference between the pair of electrodes. Is a liquid crystal display device that changes the direction while maintaining substantially parallel to the substrate surface and thereby performs display, wherein the liquid crystal display device is between the first substrate and the lower polarizer or between the second substrate and the upper polarizer. A liquid crystal display device comprising a retardation plate on at least one side. 2. A first substrate, a second substrate, and the first substrate.
Liquid crystal sandwiched between a pair of substrates including the first substrate and the second substrate, a lower polarizing plate provided outside the first substrate, and an upper polarizing plate provided outside the second substrate And a reflector provided outside the lower polarizer, wherein a pair of electrodes are arranged on the first substrate so as to form an electric field in a direction parallel to the substrate, and a potential difference between the pair of electrodes is determined according to a potential difference between the pair of electrodes. The liquid crystal display device performs display by changing the direction of the major axis of the liquid crystal molecules while keeping substantially parallel to the substrate surface according to the applied electric field strength, thereby performing a display between the first substrate and the lower polarizing plate, or A liquid crystal display device comprising a phase difference plate on at least one of the second substrate and the upper polarizing plate. 3. A ΔΔ which is a product of a cell gap d which is a gap between the first substrate and the second substrate and a birefringence Δn of the liquid crystal.
The nd is 200 to 300 nm, the retardation value R of the retardation plate is 450 to 550 nm, and the crossing angle of the polarization axes of the upper and lower polarizers is about 90 degrees, The Claim 1 or Claim 2 characterized by the above-mentioned. The liquid crystal display device according to the above. 4. A product ΔΔ which is a product of a cell gap d which is a gap between the first substrate and the second substrate and a birefringence Δn of the liquid crystal.
2. The method according to claim 1, wherein nd is 700 to 800 nm, the retardation value R, which is the birefringence of the retardation plate, is 150 to 250 nm, and the crossing angle of the polarization axes of the upper and lower polarizing plates is about 90 degrees. 3. A liquid crystal display device according to claim 2. 5. A ΔΔ which is a product of a cell gap d which is a gap between the first substrate and the second substrate and a birefringence Δn of the liquid crystal.
The nd is about 350 to 450 nm, the retardation value R of the retardation plate is about 350 to 450 nm, and the crossing angle of the polarization axes of the upper and lower polarizers is about 0 degrees, or claim 1 or claim 2. Item 3. A liquid crystal display device according to item 2. 6. The refractive index in the stretching direction of the retardation plate is defined as nx, the refractive index in the 90-degree direction with respect to the stretching direction as ny, and the refractive index in the thickness direction of the retardation plate as nz, and nx>nz> 2. A retardation plate satisfying the relation of ny is used.
A liquid crystal display device according to claim 4 or claim 5.