JPH02275412A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain a good-contrast, bright black-and-white display element by setting the product of the refractive index anisotropy of the liquid crystal of a liquid crystal layer and the thickness of the liquid crystal layer to 0.4 - 1.5mum and arranging a couple of uniaxial birefringent plates of nearly the same size on both sides of the liquid crystal layer and inside a couple of polarizing plates. CONSTITUTION:The product DELTAn1.d1 of the refractive index anisotropy DELTAn1 of the liquid crystal at a liquid crystal layer and the thickness d1 of the liquid crystal of such a layer is set to 0.4 - 1.5mum, and the couple of birefringent plates of nearly the same DELTAn.d2 which satisfy an inequality I are arranged on both sides of the liquid crystal layer and inside the couple of polarizing plates. Consequently, only one liquid crystal layer is needed and a 2nd liquid crystal layer which lowers the productivity and easily causes color slurring need not be provided. Consequently, a black-and-white display which has a superior contrast ratio as compared with a supertwisted liquid crystal display element can be made, and a sharp display of high display quality is obtained.

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, the twist angle of the liquid crystal molecules between the two electrodes was increased (by
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 in which a similar method is used, and by setting the product Δn-d of the liquid crystal's birefringence and thickness to a small value of around 0.6 μm, a display that is close to white and black can be obtained. (M, 5chadtet al, App
l, Phys, Lett, 50(5), 1
(987p, 236) However, when this method is used, the display is dark, the maximum contrast is not very high, 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. (Reality Idiot, 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 the liquid crystal cell requires 2N, it sacrifices the thin and light characteristics of the liquid crystal cell. There was a drawback.

[Problem to be solved by the invention 1 In the conventional method, a liquid crystal display element with good brightness (black and white),
Good yield (it was difficult to produce).

A bright black and white display element is not only easy to see without any distinctive coloration (it is conventionally realized with a normal twisted nematic (TN) element with a 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 black and white display element with good contrast and can be produced at a high yield.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems. The twist angle of the nematic liquid crystal with positive dielectric anisotropy containing a polar substance is 160
In a liquid crystal display element that has a liquid crystal layer with an angle of ~300° and 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 is installed on the outside of this liquid crystal layer. , the product ΔndI of the refractive index anisotropy Δnl of the liquid crystal in the liquid crystal layer and the thickness dl of the liquid crystal layer is 0.4 to 1.5 μm. At least one set of uniaxial birefringent plates having the same Δn2·d2, where Δn2·d2 of the birefringent plate on each side
The present invention provides a liquid crystal display element characterized in that a birefringent plate is arranged.

In the present invention, the liquid crystal layer is amphoteric, and at least one set of uniaxial birefringent plates is arranged between a pair of polarizing plates.

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 lowering 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 when the angle is less than 160°, there is little improvement in contrast when performing time-division driving at a high duty rate, which requires a steep change in transmittance (on the contrary, when the angle exceeds 300°, hysteresis and domains that scatter light are generated). This is because it is easy to occur.

Further, the product Δaux・d+ 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 to 1.
It is assumed to be 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 1, the hue when turned on changes from yellow to red, and the display becomes black and white.

In particular, in applications where achromatic display colors are strictly required,
It is preferable that Δn,·dl of the liquid crystal layer be 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. Due to extreme performance requirements, only in a portion of the operating temperature range,
It is possible that this relationship may be satisfied. In this case, in a temperature range in which the range of Δn,·dl deviates from the above range, the display may become colored or the viewing angle characteristics may deteriorate.

ITO (InlO) buttered in the desired pattern
A film of polyimide, polyamide, etc. is provided on the surface of a substrate made of plastic, glass, etc. on which a transparent electrode such as 1-3nO, 5n02, 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. 400 stripe-shaped electrodes are formed, and a display like 640 x 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 TiO□, SiO□, A1□01, 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, birefringent plates are laminated adjacent to both sides of the liquid crystal layer. This birefringent plate may be provided 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 electrodes, or
A birefringent plate may be provided between the electrode and the substrate, the birefringent plate may be attached to the substrate itself, a birefringent plate may be provided between the substrate and a polarizing plate, or the polarizing plate and the birefringent plate may be placed on the liquid crystal layer side. Polarizing plates laminated and integrated in this manner may be used, or they may be combined.

As this birefringent plate, any transparent plate exhibiting uniaxial birefringence can be used, and plastic films, inorganic crystal plates, etc. can be used. In order to obtain the desired birefringence effect, Δn2·d2 is adjusted and used; however, if adjustment cannot be achieved with a single plate, the same birefringence plate or a plurality of different birefringence plates may be used in combination.

In order to perform a good black and white display, for a liquid crystal layer with a certain twist angle and Δnl j a+, the magnitude of Δn,·d2 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 Δn2・d2 of the birefringent plates arranged on both sides 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, Δn*' d of the birefringent plate on each side
Since the magnitudes of 2 are approximately equal, approximately Δ of the liquid crystal layer
It is set approximately equal to half the size of the old dl, or slightly smaller than that half. Specifically, it may be set as follows.

Δn2・d2 of this birefringent plate is 0.35XΔn1・d
.

If it is smaller than 0.55 range.

Incidentally, when a combination of two or more birefringent plates arranged on both sides is used, the total Δn2·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 birefringent plate, the long axis direction of the liquid crystal molecules above the liquid crystal layer, and , is a plan view showing the relative positions of the polarization axis direction of the lower polarizing plate, the optical axis direction of the birefringent 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 Δn, d, is 0.4 to 1.5μ.
A liquid crystal layer with a twist angle of 160 to 300° made of nematic liquid crystal with positive dielectric anisotropy of m, 4A and 4B are birefringent plates laminated above and below it, 5 is the polarization axis of the upper polarizing plate, 6 is the lower one The polarization axis of the polarizing plate on the side, 7 is the liquid crystal molecule on the upper side of the liquid crystal layer,
Reference numeral 8 indicates the liquid crystal molecules on the lower side of the liquid crystal layer, 9A indicates the optical axis direction of the upper birefringent plate, and 9B indicates the optical axis direction of the lower birefringent plate.

In FIG. 2, 01 is the direction of the polarization axis 5 of the upper polarizing plate when viewed from the long axis direction of the liquid crystal molecules 7 above the liquid crystal layer, and 01 is the long axis of the liquid crystal molecules 7 above the liquid crystal layer. 02 is the optical axis direction 9A of the upper birefringent plate measured clockwise when viewed from the direction, and 02 is the direction of the polarization axis 6 of the lower polarizing plate when viewed from the long axis direction of the liquid crystal molecules 8 below the liquid crystal layer. It is assumed that θ1 is measured clockwise, and 04 is measured clockwise in the optical axis direction 9B of the lower birefringent plate viewed from the long axis direction of the liquid crystal molecules 8 below the liquid crystal layer.

In the present invention, these θ1, θ2, θ3, and θ4 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 pair of uniaxial birefringent plates placed above and below it is 0.4.
If it is about μm, the polarization axis of a pair of polarizing plates is approximately 60~
It is preferable to arrange them so that they 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°. is preferred. As a result, this liquid crystal display element is capable of high-contrast black-and-white display with excellent viewing angle characteristics.

In this case, especially for negative display, 5゜≦θ2≦1
By setting 40', 40°≦θ, and ≦170°, it is possible to realize a display having sufficient contrast with low off-state transmittance and high on-state transmittance, which is preferable.

Also, θ3, θ2. Regarding θ3 and θ, θ1<θ2
In this case, it is preferable that θ<θ4, and θ1
>θ2, it is preferable that θ1>θ4.

In particular, 40@≦02≦140° and 40°≦θ4≦
A value of 140° is preferable because off-state transmittance is low and 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 θ1, θ
By setting 2, θ8, and θ4 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 cloth spiral example.

In the present invention, the crossing angle of the polarization axes of a pair of polarizing plates is approximately 90
@ ±30° will result in negative type display, 0° ±30°
Although this will result in a positive type display, it is preferable to use a negative type display with a backlight in terms 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 super twist liquid crystal display elements, and as mentioned above, bright and clear black and white display is possible. 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. ', 5Δn1・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 ii arranged 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
When light that has become almost completely linearly polarized through the liquid crystal layer 13 passes through the liquid crystal layer 13, it becomes elliptically polarized. The shape and direction of this elliptical polarization differ depending on the wavelength of the light, and it divides light into three colors: red, green, and blue.
If we consider the primary colors separately, the result will be as shown in Figure 3 (B). These shapes and directions are different. However, when circularly polarized light passes through the upper polarizing plate 11 on the output side, the red, green, and blue light passes through the polarizing plate 11. They have different intensities, so they appear colored in a specific color. In addition, in Fig. 3 (B), 15.16
indicate the polarization axes of the polarizing plates 11 and 12, respectively.

In contrast, in the present invention, the torsion angle is 160 to 300@, as shown in a schematic diagram seen from the side in FIG.
A liquid crystal layer 23 made of a nematic liquid crystal having positive dielectric anisotropy with Δn+'' d+ of 0.4 to 1.5 gm, and two uniaxial birefringent plates 24A and 24 disposed on both sides thereof.
B, and a pair of polarizing plates 21.2 arranged above and below it.
2.

In this example, the twist angle of the liquid crystal layer is 240°Δn+”d+
is 0.82 μm, and a pair of polarizing plates 2 are arranged above and below.
1.22, the crossing angle of the polarization axes is 90°. In addition,
In this example, one uniaxial birefringent plate is laminated on each side of the liquid crystal layer to simplify the explanation, but two or more uniaxial birefringent plates are laminated on each side of the liquid crystal layer. It may also be used.

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 Δn2・d2 of the -axial birefringence plate. , or it has the property of being able to return to linearly polarized light. Therefore, by overlapping birefringent plates with appropriate values of Δn and d2 on both sides 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 becomes double light. The refracting plate 24B brings the light into an elliptical polarization state. The light then passes through the liquid crystal layer 23 and becomes a different circularly polarized state. This elliptically polarized light is further processed by a birefringent plate 2.
Depending on the conditions, the elliptical polarized light may be returned to a state close to linearly polarized light by passing through 4A.

This means that when 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, the directions of the polarization axes of red, green, and blue are almost the same, and the light is almost linearly polarized. If it returns, the wavelength dependence of the transmitted light intensity can be eliminated regardless of the direction of the polarization axis on the exit side. 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 black is visible. 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 almost parallel to the polarizing axis of the lower polarizing plate, these intensities will be large and white (white) will be visible, 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
This can be changed by changing the configuration conditions such as n1, dl1, Δn2 and d2 of the axial birefringent plate, and the angles θ5, θ2, θ1, θ4 between them and the 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, by inserting a birefringent plate, although the shape and direction of the elliptical polarized light are aligned and a black or white state is created when no voltage is applied, it does not necessarily become white or black when a voltage is applied. For this reason, it is necessary to experimentally optimize the Δn2 and d2 of the birefringent plate, its front axis direction, the polarization axis direction of the polarizing plate, etc., using parameters such as the twist angle of the liquid crystal layer and Δn1 and dl. is preferred.

However, since the white state, which has a high transmittance, is brighter (clearer and easier to see) and suitable for colorization, it is preferable to give priority to white or black.

[Example 1 Example 1 As a first substrate, an ITO transparent electrode provided on a glass substrate was patterned into stripes, an insulating film for short circuit prevention of 5 inches was formed by vapor deposition, and a polyimide overlay was formed. The coat was spin-coded and rubbed to create a substrate on which an alignment control film was formed.

As a second substrate, an ITO transparent electrode provided on a glass substrate was patterned into stripes perpendicular to the first substrate, an insulating film of 5 iOa was formed, and an overcoat of polyimide was applied. A substrate was prepared on which an alignment control film was formed by rubbing so that the angle of intersection with the rubbing direction of the first substrate was 60°.

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, Δn1・dl
is 0.82 μm.

Uniaxial birefringent plates with Δn2·d of 0.38 μm were laminated on both sides 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
, = 150°, θ2=85°θ, = 120°
, θ, = 90°.

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 disposed on the back side of this liquid crystal display element, and the device was driven with a duty of 1/200 and a bias of 1/15, 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 display was on, and because the transmittance was low when the display was off, a negative black and white display that appeared sufficiently black 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 27%, and since it was brighter than the OMI element, it was possible to use it as a reflective type.

Comparative Example 1.2 Comparative Example 1 is the birefringent plate of Example 1 in which Δn2·d2 is 0.28 μm, and Comparative Example 2 is that the birefringent plate is 0.46 μm. We investigated the changes.

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
, and distributed on both sides! A liquid crystal display element was prepared by setting the 80 y d2 of each of the birefringent plates as shown in Table 1.

These liquid crystal display elements were prepared at 1/200 scale as in Example 1.
When driven at duty and l/15 bias, negative black and white display almost equivalent to 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, = 60° θ2 = 85°, θ3 = 30@, θ4 =
It was set at 90°.

When this liquid crystal display element was driven with a duty of 1/200 and a bias of 1/15 in the same manner 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 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] 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 displays. 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 the birefringent plate,
Bright black and white display is possible without providing a second liquid crystal layer, and the liquid crystal display element has the advantage of extremely high productivity.

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) are plan views showing the relative positions of the long axis directions of the upper and lower liquid crystal molecules, the polarization axis direction of the polarizing plate, and the optical axis direction of the birefringent plate, respectively, when viewed from above. It is. Figure 3 (A) iB) is just a super rice)-'t
FIG. 1 is a schematic diagram showing the configuration of a 11-product 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 the threshold f1α 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. 1, 2.11.12.21.22 is a polarizing plate, 3.13.
23 is a liquid crystal layer, 4A, 4B, 24A, 24B are birefringent plates, 5.6.15
．． 1B, 25.26 are the polarization axes, 7.8 is the long axis direction of the liquid crystal molecules, 9A, 9B are the optical axis directions of the birefringent plate. Na- Funeral diagram 1.5 2,0 2.5 Applied voltage (V) 3.0 To NoC- End

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 with an angle of 0 to 300 degrees, and a driving means for applying a voltage between transparent electrodes of upper and lower substrates that sandwich 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
1.5 μm, and at least one set of uniaxial birefringent plates having substantially the same Δn_2 and d_2 on both sides of the liquid crystal layer and inside the pair of polarizing plates, the birefringent plates on each side Δn_2・d_2 is (0.7×Δn_1・d_1)/2<Δn_2・d_2
A liquid crystal display element characterized by disposing a birefringent plate with <(1.1×Δn_1·d_1)/2. (2) The liquid crystal display element according to claim 1, wherein the intersecting angles between the liquid crystal molecular axis and the optical axis of the birefringent plate are 40°≦θ_2≦140° and 40°≦θ_4≦140°. (3) Regarding θ_1, θ_2, θ_3, θ_4, θ_1
If <θ_2, then θ_3<θ_4, and θ_1>
3. The liquid crystal display element according to claim 1, wherein when θ_2, θ_3>θ_4.