JPH02278228A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To produce the element being bright and good in the degree of black and white with high yield by setting the product of a refractive index anisotropy of a liquid crystal in a liquid crystal layer and the thickness of the liquid crystal layer to 0.4 - 1.5mum, and specifying a double refraction plate. CONSTITUTION:The product DELTAn1.d1 of a refractive index anisotropy DELTAn1 of a liquid crystal in a liquid crystal layer 3 and thickness d1 of the liquid crystal layer 3 is set to 0.4 - 1.5mum, and double refraction plates 4A, 4B which are plural uniaxial double refraction plates having almost the same DELTAn2.d2 in one between the liquid crystal layer 3 and a polarizing plate 1, and in which DELTAn2.d2 of the total double refraction plates comes to 0.7XDELTAn1.d1<DELTAn2.d2<1.1XDELTAn1.d1 are placed. In such a case, by only placing plural pieces of double refraction plates on one face of the liquid crystal layer, bright black-and-white display is capable without providing a second liquid crystal layer, and the productivity of the liquid crystal display element is extremely high.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display element suitable for high-density display.

[Conventional technology] Conventionally, by increasing the twist angle of liquid crystal molecules between both electrodes,
A super twist element (T,
J, 5chefferand J, Nehri
ng, Appl, Phys, Lett.
45(10) 1021-1023 (1984))
was known.

However, in this method, the value of the product Δn-d of the birefringence Δn of the liquid crystal of the liquid crystal display element used and the thickness d of the liquid crystal layer is substantially between 0.8 and 1.2 μm (Japanese Patent Application Laid-Open No. 60-10
No. 720), good contrast was obtained only with specific combinations of display colors, such as yellow-green and dark blue, bluish-violet and light yellow.

As described above, since this liquid crystal display element could not perform black and white display, it had the disadvantage that it could not perform multicolor or full color display when combined with a microcolor filter.

On the other hand, a method has been proposed that uses a similar method and sets the product Δn-d of the liquid crystal's birefringence and thickness to a small value of around 0.6 μm, thereby obtaining a nearly black and white display. . (M, 5chadtet al, A
ppl, Phys, Lett, 50(5),
19g? .

9.236) However, when this method is used, the display is dark, the maximum contrast is not very thick, and the display is bluish, resulting in a lack of clarity.

In addition, as a liquid crystal display element with black and white display and high contrast, there is a method in which two layers of liquid crystal cells with opposite spirals are stacked, a voltage is applied to only one cell, and the other cell is used simply as an optical compensation plate. Proposed. (Baka Okumura, Television Society Technical Report, 11(27), p. 7
9. (1987)) However, with this method, the matching of Δn-d in a two-layer cell is extremely difficult, making it difficult to improve yield, and because it requires two layers of liquid crystal cells, it sacrifices the thin and light characteristics of liquid crystal cells. It had its drawbacks.

[Problem to be solved by the invention 1] In the conventional system, a bright liquid crystal display element with good black and white
It was difficult to produce with good yield.

A bright black and white display element is not only easy to see without any distinctive coloration (it was previously realized with a twisted nematic (TN) element of 90@twist by forming a color filter inside or outside the cell). It is expected that the market will expand dramatically as it can realize various mono-color, multi-color, or full-color displays, and is thin, lightweight, and has low power consumption.

For this reason, there has been a desire for a liquid crystal display element that is a bright monochrome display element with good contrast and can be produced with high yield.

[Means for Solving the Problems 1] The present invention has been made to solve the above-mentioned problems, and is directed to an optical rotation device sandwiched between a pair of substrates with transparent electrodes arranged substantially parallel to each other and having alignment control films. The twist angle of the nematic liquid crystal with positive dielectric anisotropy containing a polar substance is 160
A liquid crystal display element that has a liquid crystal layer with an angle of ~300°, a driving means that applies a voltage between transparent electrodes of upper and lower substrates that sandwich this liquid crystal layer, and a pair of polarizing plates installed on the outside of this liquid crystal layer. , the product Δn+・d of the refractive index anisotropy Δn of the liquid crystal in the liquid crystal layer and the thickness dl of the liquid crystal layer is 0.4 to 1.5 μ.
m, and almost the same Δ between the liquid crystal layer and the polarizing plate.
A plurality of uniaxial birefringent plates having n8 and d3,
The total birefringent plate Δn*”dm is 0.7xΔn+
The present invention provides a liquid crystal display element characterized in that a birefringent plate is arranged such that 'd+<Δnz''di<1, lXΔn1·dl.

In the present invention, a plurality of uniaxial birefringent plates are arranged on one side of the liquid crystal layer and between the liquid crystal layer and the polarizing plate.

Therefore, only one liquid crystal layer is required, and a liquid crystal display element with bright black and white display can be easily obtained without reducing productivity or providing a second liquid crystal layer that tends to cause color unevenness.

This liquid crystal layer has the same structure as the liquid crystal layer of a conventional super twist liquid crystal display element, and has electrode groups facing each other, thereby making it possible to control on/off for each dot. The twist angle of this liquid crystal layer is about 160 to 300 degrees.

Specifically, a nematic liquid crystal with positive dielectric anisotropy containing an optically active substance is sandwiched between a pair of transparent electrode substrates arranged almost in parallel, and the twist angle of the liquid crystal molecules between the two electrodes is set to 1.
The angle may be 60 to 300°. This is because if it is less than 160", there will be little improvement in contrast when performing time-division driving at a high duty rate that requires a steep change in transmittance, and if it exceeds 300 degrees, hysteresis or domains that scatter light will occur. This is because it is easy.

Further, the product Δnl*dt of the refractive index anisotropy (Δn+) of the liquid crystal of the liquid crystal layer and the thickness (dl) of the liquid crystal layer is 0.4
~1.5 μm.

This means that when the thickness is less than 0.4 μm, the transmittance when on is low (,
The display color tends to be bluish, and the thickness of 1.5 μm
If the value exceeds , the hue when turned on changes from yellow to red, making it difficult to display black and white.

In particular, in applications where achromatic display colors are strictly required,
It is preferable that Δnl # dt of the liquid crystal layer is 0.5 to 1.0 μm.

Note that this range of Δn1·dl is preferably satisfied within the operating temperature range of the liquid crystal display element, and a beautiful display can be obtained within the operating temperature range. However, due to extreme performance requirements, only in a portion of the operating temperature range,
It is possible that this relationship will be satisfied. In this case, in a temperature range in which the range of Δn+'' dt deviates from the above range, the display becomes colored and the viewing angle characteristics deteriorate.

ITO (IntO) buttered in the desired pattern
A film of polyimide, polyamide, etc. is provided on the surface of a substrate such as plastic-glass on which a transparent electrode of s-SnO*), 5nOs, etc. is provided, and this surface is rubbed or SiO
A substrate with transparent electrodes on which an alignment control film is formed by obliquely vapor-depositing the above-mentioned nematic liquid crystal with positive dielectric anisotropy is placed between the substrates with transparent electrodes.
A liquid crystal layer with a twist of 0 to 300 degrees is sandwiched therebetween. A typical example of this is a dot matrix liquid crystal display device in which a large number of electrodes are formed in rows and columns, with 640 stripe-like electrodes formed on one substrate and stripes perpendicular to these electrodes on the other substrate. Thus, 400 strip-shaped electrodes are formed, and a display like 640×400 dots is made. Further, each of these 640 stripe-shaped electrodes can be arranged in groups of 3 to form 1920 stripe-shaped electrodes, and RGB color filters can be arranged to display a full color display of 640×400 dots.

Note that an insulating film such as Ties, SiO□, Altos, etc. may be provided between the electrode and the alignment control film to prevent short circuit between the substrates, or A1. A lead electrode of low resistance such as Cr or Ti may also be provided, or a color filter may be laminated above or below the electrode.

A pair of polarizing plates is placed on both sides of this liquid crystal layer. This polarizing plate itself is generally placed outside the substrate that makes up the cell, but if performance permits, the substrate itself may be made up of a polarizing plate, or it may be provided as a polarizing layer between the substrate and the electrode. Good too.

In the present invention, a plurality of birefringent plates are stacked adjacent to one side of the liquid crystal layer. This birefringent plate may be provided on one side of the liquid crystal layer between the liquid crystal layer and the polarizing plate. For example, it may be provided in a layer between the liquid crystal layer and the electrode, between the electrode and the substrate, or in a layer between the electrode and the substrate. A polarizing plate that can be used as a birefringent plate itself, or provided as a layer between a substrate and a polarizing plate, or integrated by laminating a polarizing plate and a birefringent plate with the birefringent plate facing the liquid crystal layer. or a combination of them may be used.

As this birefringent plate, any transparent plate that exhibits -axial birefringence can be used, and plastic films, inorganic crystal plates, etc. can be used. In order to obtain the desired birefringence effect, Δn8·d2 is adjusted and used.

In order to perform a good black and white display, the magnitude of Δn2・d8 of the -axial birefringent plate and the direction of their optical axis, Furthermore, it is important to optimize the direction of the polarization axes of the pair of polarizing plates.

If the total size of Δn,・d8 of the birefringent plates arranged on one side is approximately equal to or slightly smaller than the size of Δn,・d of the liquid crystal layer, good black and white display can be achieved. Easy to obtain, that is, the total Δn3・d of multiple birefringent plates
8 is 0.7xΔn,・dl Δn8・dt<1. I
XΔrl+” dt may be changed.

The total Δn2・d2 of this birefringent plate is 0.7×Δn1
・When it is smaller than dl, the transmittance when on is low and the display becomes dark, and when it is larger than 1.1×Δn+'' d+, the transmittance when off is high.
Since the contrast ratio will be lowered, it is set within the above-mentioned range.

Specifically, when using two birefringent plates stacked together,
Since the magnitudes of Δn8・d are approximately equal,
It is set approximately equal to half of the size of Δn1·d of the liquid crystal layer, or slightly smaller than that half.

It is sufficient if it is taken as.

Note that when three or more birefringent plates are arranged on one side, the total Δn snow·d2 may be set as described above.

In addition, a birefringent plate has a high principal refractive index in a specific direction within the plane, and a low principal refractive index in the direction perpendicular to the plane; Since it is almost the same as the principal refractive index of

The present invention will be explained in more detail below with reference to the drawings.

FIG. 1 is a perspective view schematically showing a liquid crystal display element according to the present invention. Figures 2 (A) and (B) show the polarization axis direction of the upper polarizing plate in Figure 1, the optical axis direction of the two birefringent plates, and the long axis of the liquid crystal molecule on the upper side of the liquid crystal layer, respectively, when viewed from above. FIG. 3 is a plan view showing the direction and the relative position of the polarization axis direction of the lower polarizing plate and the long axis direction of the liquid crystal molecules under the liquid crystal layer.

In Fig. 1, 1 and 2 are a pair of polarizing plates, and 3 is a pair of polarizing plates for displaying characters and figures, and Δn1・d is 0.4 to 1.5.
A liquid crystal layer with a twist angle of 160 to 300° made of nematic liquid crystal with positive dielectric anisotropy in μm, 4A and 4B are two birefringent plates laminated on the liquid crystal layer, and 5 is the polarized light of the upper polarizing plate. 6 is the polarization axis of the lower polarizing plate, 7 is the liquid crystal molecule above the liquid crystal layer, 8 is the liquid crystal molecule below the liquid crystal layer, 9A is the optical axis direction of the upper stacked birefringent plate, 9B indicates the optical axis direction of the lower laminated birefringent plate.

In FIG. 2, θ3 is the direction of the polarization axis 5 of the upper polarizing plate viewed from the long axis direction of the liquid crystal molecules 7 above the liquid crystal layer, and θ3 is the long axis of the liquid crystal molecules 7 above the liquid crystal layer. Optical axis direction 9 of birefringent plate 4A on the upper side (polarizing plate side) as seen from the direction
The value of A measured clockwise is θ□, and the value measured clockwise in the optical axis direction 9B of the lower birefringent plate 4B (on the liquid crystal layer side) when viewed from the long axis direction of the liquid crystal molecules 7 on the upper side of the liquid crystal layer. 028,
Let θ be the direction of the polarization axis 6 of the lower polarizing plate measured clockwise when viewed from the long axis direction of the liquid crystal molecules 8 under the liquid crystal layer.

In the present invention, these θ1, θ31, θ1, and θ may be optimized so as to display black and white.

When using the liquid crystal display element of the present invention in negative type display,
For example, if the twist angle of the liquid crystal layer is about 240°, the Δ
n1・d is about 0.8 μm, and Δn2・d2 of each of the two uniaxial birefringent plates arranged on one side is 0.4.
If it is about μm, the polarization axis of a pair of polarizing plates is approximately 60~
Preferably, they are arranged so as to intersect at an angle of about 120°.

In addition, when using the same liquid crystal layer and a uniaxial birefringent plate for positive display, the pair of polarizing plates should be arranged so that their polarization axes intersect at an angle of approximately ±30°. It is preferable that the liquid crystal display element is capable of displaying black and white with excellent viewing angle characteristics and high contrast.

In this case, especially for negative display, 60@≦θ, l≦
180°, 50°≦θ, ≦1301, and θ, ≦θ
This is preferable because it is possible to realize a display having sufficient contrast with low off-state transmittance and high on-state transmittance.

Furthermore, for positive display, 40°≦θ, 1≦
200°, 40@≦θ, ≦140°, and θ22≦
It is preferable to set θ and I because a sufficient contrast ratio can be obtained.

In the above example, the liquid crystal layer is a left-handed spiral, but even if the spiral is reversed, the direction of the long axis of the liquid crystal molecules in the liquid crystal layer, the direction of the polarization axis of the polarizing plate, and the optical axis direction of the birefringent plate Relationship θ3, θ
By setting O1, θ22, and θ counterclockwise and appropriately selecting them within the same range, a black-and-white display can be easily obtained in the same way as in the left-hand spiral example.

In the present invention, the crossing angle of the polarization axes of a pair of polarizing plates is approximately 90
Setting the angle to 0°±30° results in a negative type display, and setting the angle to 0°±30° results in a positive type display, but a negative type display provided with a backlight is preferable from the viewpoint of appearance.

Note that in the present invention, since a display close to a black and white display can be obtained, a colorful display can be achieved by using a color filter in combination. In particular, even with high-duty driving, a high contrast ratio can be achieved, so full-color gradation display is possible, and it can also be used in LCD televisions.

By forming this color filter on the inner surface of the cell, more precise color display is possible without causing deviation due to viewing angle. Specifically, it may be formed below the electrode or above the electrode.

Also, if you need to make the colors completely black and white,
A color filter for color correction or a color polarizing plate may also be used, a dye may be added to the liquid crystal, or illumination having a specific wavelength distribution may be used.

In the present invention, a driving means for applying a voltage to the electrodes is connected to the liquid crystal cell having such a configuration, and the liquid crystal cell is driven.

In particular, since the present invention enables bright display, it can be applied to either a transmissive type or a reflective type, and has a wide range of applications.

Note that when using a transmission type, a light source is placed on the back side. Of course, a light guide, a color filter, etc. may be used in combination with this.

The liquid crystal display element of the present invention is often used in a transmissive type, but since it is bright, it can also be used in a reflective type.

When using a transmissive type, the background portion other than the pixels can be covered with a light-shielding film by printing or the like. Further, in addition to using a light-shielding film, it is also possible to perform reverse driving such that a selection voltage is applied to a portion that is not desired to be displayed.

In addition to this, the present invention includes, within the scope that does not impair the effects of the present invention,
Various techniques used in ordinary liquid crystal display elements can be applied.

In the present invention, the time division characteristics are on the same level as those of super twist liquid crystal display elements, and as mentioned above, bright and clear black and white display is possible. Therefore, fine color filters of the three primary colors of red, green, and blue are installed on the inner surface of the cell, etc. By arranging them, it is possible to obtain a high-density multicolor liquid crystal display element.

The liquid crystal display element of the present invention can be used for personal computers,
Suitable as a display element for word processors, workstations, etc., but also for LCD TVs, fish finders, etc.
It can be used for a variety of purposes, including radars, oscilloscopes, and various consumer dot matrix display devices, regardless of black and white display or color display.

[Operation 1] Although the principle of operation of the present invention is not necessarily clear, it can be estimated as follows.

FIG. 3(A) is a schematic side view showing the structure of a super-twist liquid crystal display element that does not use only a birefringent plate in comparison with the liquid crystal display element of the present invention, and shows a twist angle of 160 to 300. ”, Δn, d+ is 0.4 to 1.5
A liquid crystal layer 13 made of nematic liquid crystal having a positive dielectric anisotropy of μm, and a pair of polarizing plates 11 disposed above and below the liquid crystal layer 13.
12 is shown. In this example, the crossing angle of the polarization axes of the pair of polarizing plates 11 and 12 arranged above and below is 90''.

In the case of a liquid crystal display element having such a configuration, when no voltage is applied to the liquid crystal layer or a low voltage such as a non-selection voltage is applied, the lower polarizing plate 1 on the incident side
Almost completely fixed through 2! j! When polarized light passes through this liquid crystal, 11F13, it becomes an elliptical polarized state.

The shape and direction of this elliptical polarized light depend on the wavelength of the light, and if we divide light into the three primary colors of red, green, and blue, we get circularly polarized light with different shapes and directions, as shown in Figure 3 (B). When the light passes through the upper polarizing plate 11 on the emission side, the intensity of the red, green, and blue light that passes through the light is different, so that the light appears colored in a specific color. In addition, in FIG. 3(B), 15 and 16 indicate the polarization axes of the polarizing plates 11 and 12, respectively.

In contrast, in the present invention, the twist angle is 160 to 300 degrees, as shown in a schematic diagram seen from the side in FIG. 4(A).
A liquid crystal layer 23 made of a nematic liquid crystal having positive dielectric anisotropy with Δn,*d of 0.4 to 1.5 μm, and two uniaxial birefringent plates 24A and 24 laminated on one side of the liquid crystal layer 23.
B1 and a pair of polarizing plates 21.2 placed above and below B1
2.

In this example, the twist angle of the liquid crystal layer is 240°Δn+”
dl is 0.85 μm, and the crossing angle of the polarization axes of the pair of polarizing plates 21 and 22 arranged above and below is 90°.

When this -axial birefringent plate is sandwiched between polarizing plates, it can convert incident linearly polarized light into arbitrary elliptical polarization or circularly polarized light depending on the value of Δn,・d, of the -axial birefringent plate. It has the property of being able to polarize light or return it to linearly polarized light. Therefore, by stacking a plurality of birefringent plates having an appropriate value of Δn2·da on one side of the liquid crystal layer, the structure shown in FIG. 4(B) can be obtained.

That is, in a state where no voltage is applied to the liquid crystal layer or a low voltage such as a non-selective voltage is applied, light that is almost completely linearly polarized through the lower polarizing plate 22 on the incident side passes through the liquid crystal layer. The light passes through the layer 23 and becomes an elliptical polarized state. By further passing this elliptical polarized light through the birefringent plates 24B and 24A, the elliptical polarized light may be returned to a state close to linearly polarized light depending on the conditions.

If we consider that light is divided into the three primary colors of red, green, and blue, it becomes as shown in Figure 4 (B). As in this example, when the directions of the polarization axes of red, green, and blue are almost the same, and the polarization returns to almost linear polarization, the wavelength dependence of the intensity of the light passing through the light is independent of the direction of the polarization axis on the output side. It can be eliminated. In other words, it is possible to make the color achromatic.

As in this example, if a polarizing plate is installed with the polarization axes intersecting 90 degrees and the polarized light on the output side matches the absorption axis of the upper polarizing plate on the output side, the transmitted light The intensity is the lowest and it appears black. This results in a negative display.

In addition, in FIG. 4(B), 25 and 26 are the polarizing plates 2, respectively.
1.22 polarization axis is shown.

Conversely, if the polarizing axis of the upper polarizing plate is made substantially parallel to the polarizing axis of the lower polarizing plate, these intensities will be large, resulting in a white appearance, resulting in a positive display.

Note that negative and positive display values are determined by the twist angle of the liquid crystal layer and its Δ
n1·d l This can be changed by changing the structural conditions such as Δn,·d3 of the s-axis birefringent plate, and the angles θ1, θ81, θ38, θ8 with respect to the upper polarizing plate.

On the other hand, if a sufficient voltage is applied to the liquid crystal layer with this configuration, the shape and direction of the circularly polarized light transmitted through the liquid crystal layer will be different from before the voltage is applied.

Therefore, the state of elliptical polarization after passing through the birefringent plate is also different, which changes the transmittance and enables display.

However, although the insertion of a birefringent plate successfully aligns the shape and direction of the elliptical polarized light and creates a black or white state when no voltage is applied, this does not necessarily mean that the state becomes white or black when a voltage is applied. is not limited. For this reason, it is preferable to experimentally optimize Δnl·d8 of the birefringent plate, its optical axis direction, the polarizing axis direction of the polarizing plate, etc. using parameters such as the twist angle of the liquid crystal layer, Δn1·d, and the like.

However, since white state, which is a state with high transmittance, is brighter, clearer, easier to see, and suitable for colorization, it is preferable to prioritize white or black.

[Example 1 Example 1 ITO provided on a glass substrate as the first substrate
A substrate was prepared by patterning a transparent electrode into stripes, forming an insulating film of 5iOi to prevent short circuits by vapor deposition, applying a spin code as an overcoat of polyimide, and rubbing this to form an alignment control film.

As a second substrate, an ITO transparent electrode provided on a glass substrate is patterned into stripes perpendicular to the first substrate, an insulating film of SiO□ is formed, and an overcoat of polyimide is applied. This was rubbed so that the angle of intersection with the rubbing direction of the first substrate was 60° to create a substrate on which an alignment control film was formed.

The peripheries of these two substrates are sealed with a sealing material to form a liquid crystal cell, and a nematic liquid crystal with positive dielectric anisotropy is injected into this liquid crystal cell to form a liquid crystal layer twisted at 240 degrees. The injection port was sealed. In this liquid crystal layer, Δnl ”
dl was 0.85 μm.

Two uniaxial birefringent plates with Δn8·d of 0.40 am were laminated on one side of this liquid crystal cell, and a pair of polarizing plates were further laminated above and below the birefringent plates.

The relative relationship between the long axis direction of the liquid crystal molecules of this liquid crystal display element, the polarization axis direction of the polarizing plate, and the optical axis direction of the birefringent plate is θ,
= 160°, θ, = 120°θ. =85@, θ
, =: 135°.

As a result of applying a voltage to this liquid crystal display element and examining its transmittance change, it was found that good threshold voltage characteristics were obtained as shown by the solid line A in Figure 5, and good contrast was obtained when multiplex driving was performed. It was found that the ratio can be obtained.

A backlight of a C light source was placed on the back side of this liquid crystal display element, and the device was driven at 1/200 duty and 1/15 bias, and the hue in the on and off states was observed. The results are shown in FIG. As is clear from these results, a good white level with a slightly yellow-greenish color was obtained when the switch was on, and because the transmittance was low when the switch was off, a negative black and white display with sufficient black (visible) was obtained.

When the contrast ratio (pixel portion only) of this liquid crystal display element was measured, it was approximately 50, which was much higher than that of a conventional simple super twist liquid crystal display element. Furthermore, the transmittance in the ON state was about double circle, and it was brighter than the OMI element, so it was fully possible to use it as a reflective type.

Comparative Example 1.2 The birefringent plate of Example 1 had Δn, d2 of 0.28 μm as Comparative Example 1, and that of 0.46 μm as Comparative Example 2. The rate change was examined.

The results are shown in FIG.

Comparative Example 1 is shown by broken line B, but the on-state transmittance was only about half that of Example 1, and the display was dark. Further, Comparative Example 2 is indicated by a broken line C, but the off-state transmittance was three times higher than that of Example 1, and a sufficient contrast ratio could not be obtained.

Examples 2 to 5 In the liquid crystal display element of Example 1, Δn1·d of the liquid crystal layer
A liquid crystal display element was prepared with Δn3·d2 of the birefringent plates disposed on both sides as shown in Table 1.

These liquid crystal display elements were prepared at 1/200 scale as in Example 1.
When driven at 1/15 bias, a negative black and white display almost the same as in Example 1 was obtained in both cases.
The contrast ratio (pixel portion only) was also approximately 40.

Table 1 Example 6 The liquid crystal display element of Example 1 was modified by changing only the relative relationship between the long axis direction of the liquid crystal molecules, the polarization axis direction of the polarizing plate, and the optical axis direction of the birefringent plate. It was created. That is, θ, = 70° θml = 120° θ, = 858 θ
m=45@closed.

When this liquid crystal display element was driven at 1/200 duty and 1/15 bias as in Example 1, a negative black and white display almost equivalent to that in Example 1 was obtained, and the contrast ratio (pixel portion only) was approximately It was 50.

Example 7 In the liquid crystal display element of Example 1, Δ of the liquid crystal layer of the liquid crystal layer
n+ ” d+ is 0.88 μm, Δn8 of the birefringent plate
- A liquid crystal display element was created by setting d2 to 0.36 μm and changing only the relative relationship between the long axis direction of the liquid crystal molecules, the polarization axis direction of the polarizing plate, and the optical axis direction of the birefringent plate. That is, θ
t=165°, θ22=135", θ**=80"
s θ, = 30 @ closed.

When this liquid crystal display element was driven at 1/200 duty and 1/15 bias in the same manner as in Example 1, a good white level with a slightly yellow-greenish color was obtained when it was off, and a sufficiently black level was obtained because the transmittance was low when it was on. A visible positive black and white display was obtained. The contrast ratio (pixel portion only) of this liquid crystal display element was measured and was approximately 40.

Example 8 When three color filter layers were formed in stripes on the electrodes of the liquid crystal display element of Example 1 and the device was driven, full color gradation driving was possible.

[Effects of the Invention J As explained above, the present invention enables black-and-white display with a better contrast ratio than conventional super-twist liquid crystal display elements, and enables clear and high-quality positive or negative type display elements. Display is obtained.

In addition, it has excellent effects such as time division display characteristics and viewing angle characteristics comparable to those of conventional super twist liquid crystal display elements.

In addition, since the display is close to black and white, it is possible to display colorful displays by combining it with color filters.In particular, by arranging red, green, and blue color filters for each pixel, multi-color and full-color displays can be achieved. It has also been recognized that the method can be used to realize even more diverse applications.

In particular, although the present invention enables black-and-white display, bright display is possible, and not only transmissive type display but also reflective type display is possible, and its application range is wide.

Furthermore, in the present invention, by simply arranging a plurality of birefringent plates on one side of the liquid crystal layer, a bright black and white display is possible without providing a second liquid crystal layer, which improves the productivity of the liquid crystal display element. It also has the advantage of being extremely high.

The present invention can be applied in various ways in the future without detracting from the effects of the present invention.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing a liquid crystal display element according to the present invention. Figures 2 (A) and (B) show the upper and lower sides (viewed from above), respectively.
1) It is a plan view showing the relative positions of the long axis direction of the J-product molecule, the polarization axis direction of the polarizing plate, and the optical axis direction of the birefringent plate. FIGS. 3A and 3B are schematic diagrams showing the structure of a simple super-twist liquid crystal display element, and a plan view illustrating the state of polarization thereof. FIGS. 4(A) and 4(B) are schematic diagrams showing the structure of the liquid crystal display element of the present invention and plan views illustrating the state of polarization thereof. FIG. 5 is a graph showing threshold voltage characteristics of Example 1 and Comparative Examples 1.2. FIG. 6 is a hue diagram showing hues in the on and off states of Example 1; l, 2.11.12.21.22 are polarizing plates. 3.13.23 is a liquid crystal layer, 4A, 4B, 24A, 24B are birefringent plates, 5.6.1
5.16.25.26 is the polarization axis, 7.8 is the long axis direction of the liquid crystal molecules, 9A and 9B are the optical axis directions of the birefringent plate.

Claims (3)

[Claims] (1) A nematic liquid crystal with positive dielectric anisotropy containing an optically active substance sandwiched between a pair of substrates with transparent electrodes arranged almost in parallel and having an alignment control film has a twist angle of 16
It has a liquid crystal layer of 0 to 300° and a driving means for applying a voltage between transparent electrodes of upper and lower substrates sandwiching this liquid crystal layer,
In a liquid crystal display element in which a pair of polarizing plates is installed outside the liquid crystal layer, the product Δn_1·d_1 of the refractive index anisotropy Δn_1 of the liquid crystal in the liquid crystal layer and the thickness d_1 of the liquid crystal layer is 0.4 to
A plurality of uniaxial birefringent plates having a thickness of 1.5 μm and having almost the same Δn_2·d_2 on one side between the liquid crystal layer and the polarizing plate, where the total birefringent plate Δn_2·d_2 is 0.
．． 7×Δn_1・d_1<Δn_2・d_2<1.1×
A liquid crystal display element characterized in that a birefringent plate is arranged such that Δn_1·d_1. (2) The liquid crystal display element according to claim 1, wherein two uniaxial birefringent plates having substantially the same Δn_2 and d_2 are used. (3) The intersection angle between the liquid crystal molecular axis and the optical axis of the birefringent plate is 40°.
≦θ_2_1≦200° and 40°≦θ_2_2≦14
Claim 1: 0° and θ_2_2≦θ_2_1
or the liquid crystal display element according to 2.