JP3185784B2 - Liquid crystal display device - Google Patents

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 device.

[0002]

2. Description of the Related Art Conventional reflection type TN mode and reflection type STN
The mode is widely used in portable personal computers, word processors, and the like because it does not require a backlight and has low power consumption.

FIG. 27 is a sectional view of a conventional liquid crystal display device using a reflection type TN mode or a reflection type STN mode.
The conventional liquid crystal display element was composed of a liquid crystal cell 1, polarizing plates 2 and 3 disposed on both sides of the liquid crystal cell 1, and a reflecting plate 4 provided outside the polarizing plate 3.

[0004]

However, the conventional liquid crystal display device using the reflective TN mode or the reflective STN mode has a problem that the display is dark. In particular, in the case of the reflection type STN mode, coloring of display has also been a problem.

[0005] Furthermore, there is also a problem that the display appears double, which is peculiar to the reflection mode.

FIG. 28 shows the spectral characteristics of the conventional reflective STN liquid crystal display device when the electric field is turned off and when the electric field is turned on. 4 in the figure
Reference numeral 1 denotes a spectral characteristic when the electric field is off, and reference numeral 42 denotes a spectral characteristic when the electric field is on. However, the cell condition is such that the twist angle is 255 degrees, Δn ×
d is 0.85 μm, and the angle between the polarization axis direction and the rubbing direction is 45 degrees. In the STN mode, the display color is markedly yellow-green when turned off and blue when turned on, and the luminous reflectance is as low as 65%, degrading the visibility.

The present invention solves such a problem, and an object of the present invention is to provide a liquid crystal display device which is bright, has little coloring, and has good contrast by introducing a new reflective liquid crystal mode. Is to do.

[0008]

According to a first aspect of the present invention, a liquid crystal layer is sandwiched between a pair of substrates, and is formed on a polarizing means disposed on one of the substrates and on the other substrate. In the liquid crystal display device provided with the reflecting means, the light incident on the liquid crystal layer is converted into an elliptically polarized light state in the liquid crystal layer in a state where the electric field to the liquid crystal layer is turned off, and then converted into a substantially linearly polarized light state. The liquid crystal layer is set so as to reach the reflection surface of the reflection means, and the liquid crystal layer is set so that the contrast ratio of the liquid crystal display element becomes 1:10 or more when an electric field is applied to the liquid crystal layer. The twist angle of the liquid crystal molecules in the layer is set to not less than 0 degree and not more than 70 degrees, and the invention according to claim 2 is the liquid crystal display element according to claim 1, wherein The twist angle of the molecule is It is characterized in that less 0 degrees 70 degrees.

According to a third aspect of the present invention, a liquid crystal layer is sandwiched between a pair of substrates, and a polarizing means disposed on one of the substrates and a reflecting means formed on the other substrate are provided. In the liquid crystal display device provided with the electric field off to the liquid crystal layer, the light incident on the liquid crystal layer is converted into an elliptically polarized light state in the liquid crystal layer, and then converted into a substantially linearly polarized light state, and The liquid crystal layer is set so as to reach the reflection surface, and the twist of the liquid crystal molecules in the liquid crystal layer is adjusted so that the contrast ratio of the liquid crystal display element becomes 1:10 or more when the electric field is applied to the liquid crystal layer. The angle is set to 170 degrees or more and 265 degrees or less.

Further, in the liquid crystal display device according to the third aspect, the invention according to the fourth aspect is characterized in that the twist angle of the liquid crystal molecules is 170 degrees or more and 210 degrees or less. The invention described in Item 5 is characterized in that the twist angle of the liquid crystal molecules is not less than 250 degrees and not more than 265 degrees.

Further, of the two substrates of the liquid crystal cell,
A step of 0.1 μm is formed on the liquid crystal side surface of at least one of the substrates.
It is characterized by having irregularities of 2 μm or less.

[0012] Further, the reflection plate is provided on a liquid crystal side surface of the liquid crystal cell substrate.

The grounds for limiting the above numerical values are as follows:
This will be described in detail in the following operation section.

[0014]

In the liquid crystal display element of the present invention, the improvement in brightness is particularly emphasized, and the number of polarizing plates conventionally used in two is reduced to one. By using a single polarizing plate, the brightness is increased by at least the efficiency of the polarizing plate, and a brightness improvement of about 12% can be expected with this alone.

In order to obtain more ideal brightness, the linearly polarized light that has entered the liquid crystal cell through the polarizing plate causes the liquid crystal layer to have a brightness of 2 μm.
It is necessary to pass through the polarizing plate once and pass through the polarizing plate again in the same linearly polarized state. However, such a change in polarization occurs only under limited conditions. As a result of intensive examination of these conditions, it was found that various conditions of the liquid crystal cell should be adjusted so that light incident on the liquid crystal cell and reaching the reflection surface becomes linearly polarized light.

This will be described in detail with reference to FIG. FIG.
(A) is a diagram showing the orientation of liquid crystal molecules, wherein 2 is a polarizing plate, 11 is an upper substrate, 16 is liquid crystal molecules, and 4 is a reflector. On the other hand, FIG. 4B is a diagram illustrating a change in the polarization state. Light incident from the left becomes linearly polarized light by the polarizing plate 2. Next, while generating a phase difference due to the birefringence of the liquid crystal molecules, the light generally changes to elliptically polarized light. When this light reaches the reflector, if it is linearly polarized as shown in the figure, on the return path, which is reflected and travels to the left, it follows exactly the same polarization change as the outward path and returns to the original linearly polarized light. Can pass through the polarizing plate without loss of light quantity.

This phenomenon can be explained as follows. FIG.
The reflection type liquid crystal mode of the present invention shown in FIG.
It is optically equivalent to the transmission type liquid crystal mode of (b). In FIG. 5B, the liquid crystal molecules and the polarizing plate are arranged so as to be symmetric with respect to the surface 17 on which the reflecting plate exists.

By the way, when two retardation plates having the same retardation are superposed so that the optical abnormal axes are orthogonal to each other, the phenomenon that the retardation of the retardation plate is compensated has been well known for a long time. I have. An application of this principle to a liquid crystal display device is a new twisted nematic mode (hereinafter referred to as an NTN mode) proposed in Japanese Patent Publication No. 64-519 and the like. The NTN mode is a mode in which two liquid crystal cells having the same retardation and opposite twist directions are stacked. FIG. 5C is a diagram showing the liquid crystal molecule arrangement, in which a pair of liquid crystal molecules having a symmetrical positional relationship with the center plane 17 of the liquid crystal layer are orthogonal to each other.
Compensation is provided by exactly the above principle.

In order for the incident linearly polarized light to exit in the same linearly polarized light state in the reflection type liquid crystal display element,
It is necessary that the liquid crystal molecule arrangement shown in FIG. 3B performs the same function as that shown in FIG. The present inventor has found that this condition is satisfied when light is in a linearly polarized state at the center plane 17 of the liquid crystal layer. This can be easily confirmed from the fact that the optical characteristics do not change even when the pair of polarizing plates sandwiching the liquid crystal cell is rotated by 90 degrees.

There are not few cell conditions under which light incident on a liquid crystal cell and reaching a reflection surface becomes substantially linearly polarized light.
However, not all of the conditions can be used as a liquid crystal display, and the cell conditions under which a sufficient contrast ratio can be obtained when a voltage is applied are further limited.

For example, when the twist angle is 60 degrees, the range of the cell condition in which the light that has entered the liquid crystal cell and reached the reflecting surface is substantially linearly polarized is the area indicated by hatching in FIG. On the other hand, FIG. 12 is a diagram showing a range of cell conditions where a good contrast ratio is obtained when the twist angle is 60 degrees. However, the horizontal axis is retardation here.
nxd, and the vertical axis is the angle θ between the direction of the polarization axis of the polarizing plate and the orientation of the liquid crystal on the upper substrate. 51, 52, 5
Reference numeral 3 denotes regions where contrast ratios of 1:20, 1:10, and 1: 5 or more can be obtained. Here, the angle θ is 9
The same result can be obtained by adding an integer multiple of 0 degrees,
In these figures, it may be considered that 0 degrees and 90 degrees are continuous.

From FIG. 12, in the case of a twist of 60 degrees, the contrast ratio becomes maximum when Δn × d = 0.46 μm and θ = 4 degrees, and the cell condition under which a sufficient contrast ratio can be obtained is as follows. It turns out that it is limited to the vicinity.

As described above, the condition that the light incident on the liquid crystal cell and reaches the reflection surface becomes substantially linearly polarized light is not a sufficient condition for obtaining a good display, but it is a necessary condition. .

Similarly, at each twist angle from 0 ° to 270 °, the cell condition at which the contrast ratio is maximized was examined and summarized in FIG.

FIG. 7 summarizes the optical characteristics of the liquid crystal cell obtained under the conditions shown in FIG. The horizontal axis represents the twist angle of the liquid crystal, and the vertical axis represents the contrast ratio C.I.
R. , The off-state luminous reflectance Yoff, and the degree of coloring ΔE. In Yoff, the brightness of a reflector with a polarizing plate is 100%, but it is only about 85% at most due to surface reflection. $ E is CIE1
It is a value defined by the square root of a * ² + b * ² using a * and b * in the 976L * A * B * color system, and the smaller this value is, the smaller the degree of display coloring is. ing.

According to FIG. 7, in order to obtain a contrast ratio of 1:10 or more, which is sufficient for a high-quality display, the twist angle must be 0 to 70 degrees or 170 degrees or less.
It is necessary to be within the range of not less than 265 degrees. When the twist angle is 265 degrees or more and 270 degrees or less, the contrast ratio is reduced to about 1: 6. However, since the electro-optical characteristics are steep and suitable for a large-capacity display, they are sufficiently practical.

In addition, in particular, when the twist angle is 30 degrees or more and 70 degrees or less, or 175 degrees or more and 210 degrees or less,
When the angle is 50 degrees or more and 265 degrees or less, the coloring of the display is reduced, so that better display is possible.

In the claims and the means for solving the problems described above, along with the limitation of the twist angle range, the Δn × d value and the angle θ are also limited. The basis is shown in FIG. 6 which summarizes the cell conditions to be taken, and FIGS. 9 to 23 which show the range of cell conditions showing a good contrast ratio at each twist angle. 9 to 23, 51, 52, and 53 have isocontrast curves with contrast ratios of 1:20, 1:10, and 1: 5, respectively. It was determined that a contrast ratio of 1:10 or more was necessary for image quality display.

On the other hand, if irregularities are provided on the inner surface of the liquid crystal cell,
The coloring of the display can be further reduced. This is an effect that coloring is averaged by a change in the thickness of the liquid crystal layer. In addition, when a metal film having irregularities is provided on the inner surface of the cell, it can also serve as an omnidirectional reflector to solve the problem that the display looks double. However, when the unevenness is less than 0.1 μm, there is almost no effect of reducing the coloring of the display, and the metal film becomes a mirror surface without exhibiting non-directionality. Further, when the step exceeds 2 μm, the coloring of the liquid crystal is rather large, and the contrast ratio is significantly reduced. This is shown in FIG.
It can be easily understood by considering the ば ら つ き n × d value variation of 0.16 μm that occurs when a general liquid crystal of n = 0.08 is used. Hereinafter, the present invention will be described in detail with reference to examples.

[0030]

(Embodiment 1) FIG. 1 is a sectional view of a liquid crystal display device of the present invention. In the figure, 1 is a liquid crystal cell, 2 is a polarizing plate, and 4 is a reflecting plate. 11 is the upper substrate, 12
Is a lower substrate, 13 is a transparent electrode, and 15 is a liquid crystal. The liquid crystal is ZLI-4472 (Δn = 0.087) manufactured by Merck.
Using 1), a liquid crystal cell having a cell gap of 5.3 μm was twist-oriented. Retardation △ nxd is 0.46
μm.

FIG. 3 is a view showing the relationship between the respective axes of the liquid crystal display element of the present invention as viewed from the viewing direction. Reference numeral 21 denotes a polarization axis direction of the polarizing plate 2, 22 denotes a rubbing direction of the upper substrate, and 23 denotes a rubbing direction of the lower substrate. Reference numeral 31 denotes an angle θ between 21 and 22 (the twist direction of the liquid crystal is a positive value), and reference numeral 32 denotes a twist angle of the liquid crystal. Here, the angle θ is set to 4 degrees, and the twist angle is set to 60 degrees to the left.

FIG. 24 is a diagram showing the spectral characteristics of the liquid crystal display device manufactured under the above conditions. In the figure, reference numeral 41 denotes a spectral characteristic when the electric field is off, and reference numeral 42 denotes a spectral characteristic when the electric field is on. The off-axis luminous reflectance Yoff is as high as 81%, and its display color is close to white. Further, since the luminous reflectance at the time of ON is as low as 2.4%, the maximum contrast ratio C.I. R. Is
1:34.

Although the twist angle of the liquid crystal display device of this embodiment is as small as 60 degrees, the steepness of the voltage transmittance characteristic thereof is almost the same as that of a normal twisted nematic mode.
Multiplex drive of / 2 duty to 1/16 duty is also possible.

FIG. 12 shows a range of cell conditions in which a good display contrast can be obtained when the twist angle is 60 degrees, which is the same as in this embodiment. Note that the same result can be obtained by adding an integral multiple of 90 degrees to the angle θ. Therefore, θ =-
10 degrees is equivalent to the case where θ = 80 degrees or θ = 170 degrees. Reference numerals 51, 52, and 53 in the drawing denote isocontrast curves with contrast ratios of 1:20, 1:10, and 1: 5, respectively.

Good display can be expected inside these equal contrast curves. For example, △ n ×
When d = 0.60 μm and θ = 16 degrees, C.I. R. =
1:16, Yoff = 80%. Also, △ n × d =
When θ = −6 degrees at 0.34 μm, C.I. R. = 1: 1
0, Yoff = 71%. Also, Δn × d = 0.4
When θ = −6 degrees at 8 μm, C.I. R. = 1: 6, Yo
ff = 84%.

Conversely, good display cannot be made outside the curve. For example, when Δn × d = 0.28 μm and θ = −12 degrees, C.I. R. = 1: 3, Yoff = 62%. When Δn × d = 0.72 μm and θ = 4 degrees, C.I. R. = 1: 2, Yoff = 76%. When Δn × d = 0.40 μm and θ = 30 degrees,
C. R. = 1: 0.4, Yoff = 24%.

Therefore, when the twist angle is 60 degrees, it is necessary that the Δn × d value is at least 0.3 μm or more and 0.7 μm or less, and the angle θ is within the range of −13 degrees or more and 25 degrees or less.

(Embodiment 2) The liquid crystal display element of Embodiment 2 has the same configuration as that of Embodiment 1. However, the liquid crystal cell 1 of FIG. 1 has ZLI-4436 (Δn = 0.110) manufactured by Merck.
0) was used. The cell gap is 5.4 μm, and the retardation Δn × d is 0.59 μm.

In FIG. 3, the angle 31 (θ) is set to 6
0 degree and the twist angle 32 were set to 200 degrees to the left.

FIG. 25 is a diagram showing the spectral characteristics of the liquid crystal display device manufactured under the above conditions. The off-axis luminous reflectance Yoff is relatively high at 70%, and its display color is close to white. Further, since the luminous reflectance at the time of ON is as low as 3.3%, the maximum contrast ratio C.I. R. Is 1:21
It is.

The liquid crystal display device of the present embodiment is steeper than the liquid crystal display device of the first embodiment by a larger twist angle, and is suitable for multiplex driving.

FIG. 17 shows a range of cell conditions in which a good display contrast can be obtained when the twist angle is 200 degrees, which is the same as in this embodiment.

Good display can be expected inside each of the equal contrast curves 51, 52 and 53. For example, when Δn × d = 0.66 μm and θ = 64 degrees,
C. R. = 1: 11, Yoff = 75%.

Also, when Δn × d = 0.58 μm and θ = 52
At the time, C.I. R. = 1: 8, Yoff = 77%.

Conversely, good display cannot be performed outside the curve. For example, when Δn × d = 0.70 μm and θ = 46 degrees, C.I. R. = 1: 2, Yoff = 62%.
When Δn × d = 0.5 μ and θ = 90 degrees, C.I.
R. = 1: 0.3, Yoff = 19%.

Therefore, when the twist angle is 200 degrees,
At least Δn × d value is 0.48 μm or more and 0.72 μm
Below, the angle θ needs to be within the range of 48 degrees or more and 70 degrees or less.

(Embodiment 3) The liquid crystal display element of Embodiment 3 has the same configuration as that of Embodiment 1. However, the liquid crystal cell 1 of FIG. 1 has ZLI-4427 (Δn = 0.112) manufactured by Merck.
7) was used. The cell gap is 6.6 μm, and the retardation Δn × d is 0.74 μm. here,
For the alignment film, polyimide RN-721 manufactured by Nissan Chemical Industries, Ltd.
The liquid crystal was given a pretilt angle of about 10 degrees by rotating rubbing of a rayon flocking cloth. In FIG. 3, the angle 31 (θ) is 14 degrees, and the twist angle 32 is 25
Set to 5 degrees.

FIG. 26 is a diagram showing the spectral characteristics of the liquid crystal display device manufactured under the above conditions. The off-axis luminous reflectance Yoff is as high as 79%, and its display color is close to white. Further, since the luminous reflectance at the time of ON is as low as 3.2%, the maximum contrast ratio C.I. R. Is 1:25.

The liquid crystal display element of this embodiment has a large twist angle of 255 degrees and a very sharp voltage transmissivity characteristic. Therefore, the liquid crystal display element has a high ratio of 1:18 even when the multiplex drive of 1/480 duty is performed. Display contrast was obtained.

FIG. 20 shows the range of the cell conditions in which a good display contrast can be obtained when the twist angle is 255 degrees, which is the same as in this embodiment.

Good display can be expected inside each of the equal contrast curves 51, 52 and 53. For example, when Δn × d = 0.70 μm and θ = 5 degrees, C.I.
R. = 1: 11, Yoff = 78%. Also, △ n
× d = 0.90 μm and θ = 28 degrees, C.I. R. =
1: 9, Yoff = 71%.

Conversely, good display cannot be performed outside the curve. For example, when Δn × d = 0.50 μm and θ = 55 degrees, C.I. R. = 1: 1, Yoff = 81%.

When Δn × d = 1.1 μm and θ = 30 degrees, C.I. R. = 1: 3, Yoff = 63%.

Therefore, when the twist angle is 255 degrees,
At least Δn × d value is 0.52 μm or more and 0.98 μm
In the following, the angle θ needs to be within a range from −4 degrees to 32 degrees.

(Embodiment 4) FIG. 2 is a sectional view of a liquid crystal display device of this embodiment. In the figure, 1 is a liquid crystal cell, and 2 is a polarizing plate. Reference numeral 11 denotes an upper substrate, 12 denotes a lower substrate, 13 denotes a transparent electrode, 14 denotes a reflection film also serving as a pixel electrode, and 15 denotes a liquid crystal. The conditions of the liquid crystal cell were the same as in Example 1, using ZLI-4472 (Δn = 0.0871) as the liquid crystal, setting the average Δn × d to 0.46 μm, setting the twist angle to 60 degrees,
The angle θ was 4 degrees.

The reflection film 14 is formed by providing a metal aluminum thin film by sputtering on the surface of ground glass having a surface irregularity of 0.5 μm, and has a reflection characteristic with little directivity. The metal may be any material having a silvery white color such as nickel or chromium other than aluminum, and the surface irregularities may be provided by roughly polishing the surface of the metal or performing chemical treatment.

When the reflective film is patterned in a comb shape or the like, a method of directly patterning the metal thin film,
There is a method of providing a transparent electrode on a metal thin film via an insulator and patterning the transparent electrode. This insulation is
Since it has an effect of alleviating surface irregularities, it is effective when the twist angle is large and the d / p margin (d: cell gap, p: spontaneous pitch) is narrow.

As described above, by providing the reflection plate in the liquid crystal cell, a characteristic characteristic of the conventional reflection type liquid crystal display element can be obtained.
The problem that the display looks double can be solved. Further, a minute variation in the thickness of the liquid crystal also has a secondary effect of averaging display colors and reducing coloring. In this case, the dispersion of the liquid crystal thickness of 0.5 μm is represented by Δ
Although it is equivalent to the nxd value of 0.04 μm, the fact that this degree of variation hardly affects the contrast ratio is as follows.
It is clear from FIG.

Example 5 Example 5 was the same as Example 1 except that the twist angle was 0 degree, Δn × d was 0.28 μm, and the angle θ was 44 degrees. At this time, C. R. =
1:27, Yoff = 76%.

The liquid crystal display element of this embodiment is characterized in that the twist angle is 0 degree, and that the manufacture is easy.

FIG. 9 shows a range of cell conditions under which a good display contrast can be obtained when the twist angle is 0 degree. In this case, at least the Δn × d value is 0.22 μm.
It is indispensable for obtaining a good display that the angle θ falls within the range of m to 0.32 μm and the angle θ falls within the range of 34 to 55 degrees.

Example 6 Example 6 was the same as Example 1 except that the twist angle was 30 degrees, Δn × d was 0.30 μm, and the angle θ was 66 degrees. At this time, C. R.
= 1: 32, Yoff = 78%.

FIG. 10 shows a range of cell conditions that can provide a good display contrast when the twist angle is 30 degrees. In this case, at least the Δn × d value is equal to 0.
It is indispensable for obtaining a good display that the angle is within the range of 22 μm to 0.39 μm and the angle θ is within the range of 55 to 77 degrees.

Example 7 Example 7 was the same as Example 1 except that the twist angle was 45 degrees, Δn × d was 0.34 μm, and the angle θ was 76 degrees. At this time, C. R.
= 1: 34, Yoff = 80%.

FIG. 11 shows a range of cell conditions that can provide a good display contrast when the twist angle is 45 degrees. In this case, at least the Δn × d value is equal to 0.
It is indispensable for obtaining a good display that the angle θ be within the range of 25 μm to 0.50 μm and the angle θ be within the range of 64 degrees to 94 degrees.

Example 8 Example 8 was the same as Example 1 except that the twist angle was 70 degrees, Δn × d was 0.48 μm, and the angle θ was 8 degrees. At this time, C. R. =
1:10, Yoff = 81%.

FIG. 13 shows a range of cell conditions that can provide a good display contrast when the twist angle is 70 degrees. In this case, at least the Δn × d value is equal to 0.
It is indispensable for obtaining a good display that the angle θ is within the range of 36 to 0.61 μm and the angle θ is within the range of −6 to 21 degrees.

Example 9 In Example 2, the twist angle was 170 degrees, Δn × d was 0.72 μm, and the angle θ was 46.
The procedure was the same as in Example 2 except that the procedure was repeated. At this time, C.
R. = 1: 13, Yoff = 67%.

FIG. 14 shows a range of cell conditions that can provide a good display contrast when the twist angle is 170 degrees. In this case, at least the Δn × d value is equal to 0.
It is indispensable for obtaining a good display that the angle θ is within the range of 60 to 0.82 μm and the angle θ is within the range of 37 to 55 degrees.

(Embodiment 10) In Embodiment 2, the twist angle is 175 degrees, Δn × d is 0.70 μm, and the angle θ is 4
The procedure was the same as Example 2 except that the angle was changed to 8 degrees. At this time, C.
R. = 116. Yoff = 71%.

FIG. 15 shows a range of cell conditions that can provide a good display contrast when the twist angle is 175 degrees. In this case, at least the Δn × d value is equal to 0.
It is indispensable for obtaining a good display that the angle θ is within the range of 58 to 0.81 μm and the angle θ is within the range of 37 to 57 degrees.

Embodiment 11 In Embodiment 2, the twist angle is 180 degrees, Δn × d is 0.68 μm, and the angle θ is 5
The procedure was the same as in Example 2, except that the angle was 0 degrees. At this time, C.
R. = 1: 18, Yoff = 74%.

The liquid crystal display device of the present embodiment is superior to the liquid crystal display device of the second embodiment in that the display is less colored.

FIG. 16 shows a range of cell conditions that can provide a good display contrast when the twist angle is 180 degrees. In this case, at least the Δn × d value is equal to 0.
It is indispensable for obtaining a good display that the angle θ is within the range of 55 to 0.79 μm and the angle θ is within the range of 40 to 60 degrees.

Example 12 In Example 2, the twist angle was 190 degrees, Δn × d was 0.62 μm, and the angle θ was 5
The procedure was the same as Example 2 except that the temperature was changed to 4 degrees. At this time, C.
R. = 1: 21, Yoff = 74%.

Example 13 In Example 2, the twist angle was 210 degrees, Δn × d was 0.58 μm, and the angle θ was 6
The procedure was the same as in Example 2 except that the temperature was changed to 6 degrees. At this time, C.
R. = 1: 20, Yoff = 64%.

FIG. 18 shows a range of cell conditions that can provide a good display contrast when the twist angle is 210 degrees. In this case, at least the Δn × d value is equal to 0.
It is indispensable to obtain good display that the angle θ is within the range of 46 to 0.71 μm and the angle θ is within the range of 54 to 76 degrees.

Example 14 In Example 2, the twist angle was 225 degrees, Δn × d was 0.56 μm, and the angle θ was 7
The procedure was the same as in Example 2 except that the temperature was changed to 6 degrees. At this time, C.
R. = 1: 20, Yoff = 54%.

(Embodiment 15) In Embodiment 3, the twist angle is 240 degrees, Δn × d is 0.62 μm, and the angle θ is −.
The procedure was the same as in Example 2, except for twice. At this time, C.
R. = 1: 23, Yoff = 62%.

(Embodiment 16) In Embodiment 3, the twist angle is 250 degrees, Δn × d is 0.70 μm, and the angle θ is 8
The procedure was the same as in Example 3 except that the procedure was repeated. At this time, C.
R. = 1: 27, Yoff = 74%.

FIG. 19 shows a range of cell conditions that can provide a good display contrast when the twist angle is 250 degrees. In this case, at least the Δn × d value is equal to 0.
It is indispensable for obtaining a good display that the angle θ falls within the range of 51 μm to 1.05 μm and the angle θ falls within the range of −7 degrees to 35 degrees.

(Embodiment 17) In Embodiment 3, the twist angle is 260 degrees, Δn × d is 0.74 μm, and the angle θ is 1
The procedure was the same as Example 3 except that the temperature was changed to 6 degrees. At this time, C.
R. = 1: 16, Yoff = 80%.

The liquid crystal display device of the present embodiment is superior to the liquid crystal display device of the third embodiment in that the display is less colored.

FIG. 21 shows a range of cell conditions that can provide good display contrast when the twist angle is 260 degrees. In this case, at least Δn × d value is 05
5 to 0.96 μm, the angle θ is 0 to 32
It is indispensable for the display to be below the degree in order to obtain a good display.

(Embodiment 18) In Embodiment 3, the twist angle is 265 degrees, Δn × d is 0.74 μm, and the angle θ is 1
The procedure was the same as Example 3 except that the angle was changed to 8 degrees. At this time, C.
R. = 1:10, Yoff = 81%.

The liquid crystal display device of this embodiment is superior to the liquid crystal display devices of Embodiments 3 and 16 in that the display is less colored.

FIG. 22 shows a range of cell conditions that can provide a good display contrast when the twist angle is 265 degrees. In this case, at least the Δn × d value is equal to 0.
Angle θ is 4 degrees or more and 3 μm or more and 57 μm or more and 0.90 μm or less.
It is indispensable that the angle is less than 0 degrees in order to obtain a good display.

Example 19 In Example 3, the twist angle was 270 degrees, Δn × d was 0.70 μm, and the angle θ was 1
The procedure was the same as Example 3 except that the angle was changed to 8 degrees. At this time,
R. = 1: 6, Yoff = 80%.

The liquid crystal display device of this embodiment is superior to the liquid crystal display devices of Embodiments 3, 16 and 17 in that the steepness of the electro-optical characteristics is good.

FIG. 23 shows a range of cell conditions that can provide a good display contrast when the twist angle is 270 degrees. In this case, at least the Δn × d value is equal to 0.
It is indispensable for obtaining a good display that the angle θ is within the range of 64 to 0.81 μm and the angle θ is within the range of 12 to 26 degrees.

Comparative Example 1 The procedure of Example 1 was repeated except that the twist angle was 75 degrees, Δn × d was 0.48 μm, and the angle θ was 10 degrees. At this time, C. R.
= 1: 6, Yoff = 81%. This characteristic is the best that can be obtained at this twist angle, and the condition range where a contrast ratio of 1: 5 or more can be obtained is very narrow. This is outside the scope of the present invention, and satisfactory display cannot be performed under such conditions.

Comparative Example 2 In Example 2, the twist angle was 165 degrees, Δn × d was 0.76 μm, and the angle θ was 46.
The procedure was the same as in Example 2 except that the procedure was repeated. At this time,
R. = 1:10, Yoff = 61%. Further, the coloring of the display is remarkably large as compared with the tenth embodiment and the like. This is outside the scope of the present invention, and satisfactory display cannot be performed under such conditions.

Comparative Example 3 In Example 3, the twist angle was 285 degrees, Δn × d was 0.70 μm, and the angle θ was 20.
The procedure was the same as in Example 3 except that the procedure was repeated. At this time, C.
R. = 1: 2, Yoff = 82%. This characteristic is the best that can be obtained at this twist angle. This is outside the scope of the present invention, and satisfactory display cannot be performed under such conditions.

In the above embodiment, the twist angle has a discrete value in units of 5 degrees, but this is merely for the convenience of experiments. Since the characteristic change due to the twist angle is continuous, any value may be set within the twist angle range shown in the claims and the like.

[0095]

As described above, according to the present invention, by introducing a new reflective liquid crystal mode, a brighter liquid crystal mode can be obtained.
It is possible to provide a liquid crystal display element with little coloring and good contrast.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display device in Examples 1 to 3 and Examples 5 to 19 and Comparative Examples 1 to 3 of the present invention.

FIG. 2 is a sectional view of a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between axes of the liquid crystal display element of the present invention.

FIG. 4 shows the liquid crystal molecular orientation (a) of the liquid crystal display device of the present invention.
FIG. 4 is a diagram showing a change in polarization state (b).

FIG. 5 shows the liquid crystal molecular alignment (a) of the reflection type liquid crystal display device of the present invention, the transmission type liquid crystal molecule alignment optically equivalent thereto (b), and the conventional NTN mode liquid crystal molecular alignment (C). FIG.

FIG. 6 is a diagram showing a cell condition that maximizes a contrast ratio.

FIG. 7 is a diagram showing three optical characteristics (contrast ratio CR, luminous reflectance Yoff when turned on, and degree of coloring ΔE) of a liquid crystal cell obtained under a cell condition where the contrast ratio is maximized. is there.

FIG. 8 is a diagram showing a range of cell conditions in which when a twist angle is 60 degrees, light incident on a liquid crystal cell becomes substantially linearly polarized on a reflection surface and a high reflectance is obtained.

FIG. 9 is a diagram illustrating a range of cell conditions in which a good display contrast can be obtained when the twist angle is 0 degree.

FIG. 10 is a diagram showing a range of cell conditions in which a good display contrast can be obtained when the twist angle is 30 degrees.

FIG. 11 is a diagram showing a range of cell conditions where a good display contrast can be obtained when the twist angle is 45 degrees.

FIG. 12 is a diagram showing a range of cell conditions in which a good display contrast can be obtained when the twist angle is 60 degrees.

FIG. 13 is a diagram showing a range of cell conditions in which a good display contrast can be obtained when the twist angle is 70 degrees.

FIG. 14 is a diagram showing a range of cell conditions where a good display contrast can be obtained when the twist angle is 170 degrees.

FIG. 15 is a diagram showing a range of cell conditions in which good display contrast can be obtained when the twist angle is 175 degrees.

FIG. 16 is a diagram showing a range of cell conditions in which good display contrast can be obtained when the twist angle is 180 degrees.

FIG. 17 is a diagram showing a range of cell conditions in which good display contrast can be obtained when the twist angle is 200 degrees.

FIG. 18 is a diagram showing a range of cell conditions under which a good display contrast can be obtained when the twist angle is 210 degrees.

FIG. 19 is a diagram showing a range of cell conditions in which a good display contrast can be obtained when the twist angle is 250 degrees.

FIG. 20 is a diagram showing a range of cell conditions where a good display contrast is obtained when the twist angle is 255 degrees.

FIG. 21 is a diagram showing a range of cell conditions in which a good display contrast can be obtained when the twist angle is 260 degrees.

FIG. 22 is a diagram showing a range of cell conditions in which a good display contrast is obtained when the twist angle is 265 degrees.

FIG. 23 is a diagram showing a range of cell conditions in which good display contrast can be obtained when the twist angle is 270 degrees.

FIG. 24 is a diagram illustrating spectral characteristics of the liquid crystal display element according to Example 1 of the present invention when the electric field is off and when the electric field is on.

FIG. 25 is a diagram showing the spectral characteristics of the liquid crystal display element in Example 2 of the present invention when the electric field is off and when the electric field is on.

FIG. 26 is a diagram showing the spectral characteristics of the liquid crystal display element in Example 3 of the present invention when the electric field is off and when the electric field is on.

FIG. 27 is a sectional view of a conventional liquid crystal display device.

FIG. 28 is a diagram illustrating spectral characteristics of a conventional liquid crystal display element when an electric field is off and when an electric field is on.

[Explanation of symbols]

 1. Liquid crystal cell 2. 2. Polarizing plate (upper side) 3. Polarizing plate (lower side) Reflector plate 11. Upper substrate 12. Lower substrate 13. Transparent electrode 14. 14. Reflective film also serving as pixel electrode Liquid crystal 16. Liquid crystal molecules 17. Center plane of liquid crystal layer 21. 21. Polarization axis (absorption axis or transmission axis) direction of polarizing plate 2 22. Rubbing direction of upper substrate 11 (liquid crystal alignment direction) Rubbing direction of lower substrate 12 (liquid crystal alignment direction) 31. Twist angle of liquid crystal 15 41. 42. Spectral characteristics of reflected light when electric field is off 51. Spectral characteristics of reflected light when electric field is on 52. Isocontrast curve with contrast ratio of 1:20 Isocontrast curve with contrast ratio of 1:10 53. Isocontrast curve with contrast ratio 1: 5

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/133 500 G02F 1/1335 520 G09F 9/35 321

Claims (5)

(57) [Claims] 1. A liquid crystal display device comprising: a liquid crystal layer sandwiched between a pair of substrates; and a polarizing device disposed on one of the substrates, and a reflecting device formed on the other substrate. In a state where the electric field to the liquid crystal layer is off, the light incident on the liquid crystal layer is converted into an elliptically polarized state in the liquid crystal layer, and then converted into a substantially linearly polarized state so as to reach the reflection surface of the reflection means. A liquid crystal layer is set, and a twist angle of liquid crystal molecules in the liquid crystal layer is set to 0 degree or more and 70 degrees such that a contrast ratio of the liquid crystal display element becomes 1:10 or more when an electric field is applied to the liquid crystal layer. A liquid crystal display device characterized by the following settings. 2. The liquid crystal display device according to claim 1, wherein the twist angle of the liquid crystal molecules is 30 degrees or more and 70 degrees or less. 3. A liquid crystal display device comprising: a liquid crystal layer sandwiched between a pair of substrates; and a polarizing device disposed on one of the substrates, and a reflecting device formed on the other substrate. In a state where the electric field to the liquid crystal layer is off, the light incident on the liquid crystal layer is converted into an elliptically polarized state in the liquid crystal layer, and then converted into a substantially linearly polarized state so as to reach the reflection surface of the reflection means. A liquid crystal layer is set, and a twist angle of liquid crystal molecules in the liquid crystal layer is 170 degrees or more and 265 degrees so that a contrast ratio of the liquid crystal display element becomes 1:10 or more when an electric field is applied to the liquid crystal layer. A liquid crystal display device characterized by the following settings. 4. The liquid crystal display device according to claim 3, wherein the twist angle of the liquid crystal molecules is 170 degrees or more and 210 degrees or less. 5. The liquid crystal display device according to claim 3, wherein the twist angle of the liquid crystal molecules is not less than 250 degrees and not more than 265 degrees.