JPH04179922A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To improve contrast and to allow bright black and white display by disposing uniaxial double refractive plates having the as Herent products of refractive index anisotropy and thickness of a liquid crystal layer on the inner side of a pair of polarizing plates on both outer side of the liquid crystal layer. CONSTITUTION:The product DELTAn1.d1 of the refractive index anisotropy DELTAn1 of the liquid crystal in the liquid crystal layer 3 and the thickness d1 of the liquid crystal layer 3 is specified to 0.4 to 1.5mum. Such double refractive plates 4A, 4B which are the uniaxial double refractive plates 4A, 4B having the different DELTAn21.d21, DELTAn22.d22 and have the relations of the double refractive plates 4A, 4B on the respective sides as shown by equation I to equation III are disposed on both outer sides of the liquid crystal layer 3 and the inner side of a pair of the polarizing plates 1, 2. The black and white display having the higher contrast ratio than the contrast ratio of the conventional supertwisted liquid crystal display element is attained in this way and the bright display of a positive type or negative type having the high display grade is obtd.

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, App
l, Phys, Lett, 50(5), 1
(987°p, 236) However, when this method was used, the display was dark and the maximum contrast was too large (and the display had a bluish tinge, 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. , (Haka Shinuchi, Television Society Technical Report, 11(27), p.
79. (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 inventionj] In the conventional method, 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 black and white display element with good contrast and can be produced at a high yield.

[Means for Solving the Problems 1] 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 Δn+ ' d+ of the refractive index anisotropy Δn1 of the liquid crystal in the liquid crystal layer and the thickness d of the liquid crystal layer is 0.4 to 1.5.
μm, and is a uniaxial birefringent plate having different Δn21・d21 and Δn22・d22 on the outside between the liquid crystal layers and inside a pair of polarizing plates. The relationship is 1.01X Δnz2・dzz<Δnzi'
d21<1.20X Δnzi・dzz, Δnx
' dz=Δn! 1・(121+Δnx*'dzz, then 0.7×Δn+ ” d+<Δnz・d2< 1.IX
The present invention provides a liquid crystal display element characterized in that birefringent plates are arranged such that Δn+'' (L).

In the present invention, at least one set of uniaxial birefringent plates is disposed on both outer sides of the liquid crystal layer and 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 means that if the angle is less than 160°, there will be little improvement in contrast when time-division driving is performed at a high duty rate, which requires a steep change in transmittance;
This is because if the angle exceeds 00°, hysteresis or domains that scatter light tend to occur.

Further, the product Δnl” 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
It is assumed to be 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 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+"d+ deviates from the above range, the display will be colored or the viewing angle characteristics will deteriorate.

ITO (In20) buttered in the desired pattern
3-Sn02), 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 5nOa 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'' is sandwiched between them.A typical example of this is a dot matrix liquid crystal display element in which many electrodes are formed in rows and columns, with 640 electrodes on one substrate. A stripe-shaped electrode is formed, and 400 stripe-shaped electrodes are formed perpendicularly to this on the other substrate, and a display like 640 x 400 dots is made. It is also possible to make a full-color display of 640 x 400 dots by arranging 1920 stripe-shaped electrodes, each consisting of three sets of electrodes, and arranging RGB color filters.

In addition, an insulating film such as Ti0z, SiO2, A11as, etc. may be provided between the electrode and the alignment control film to prevent short circuit between the substrates, or a low resistance lead electrode such as A1, Cr, Ti, etc. may be provided on the transparent electrode. , 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
The birefringent plate may be provided in a layer between the electrode and the substrate, the substrate itself may be a birefringent plate, the polarizing plate and the birefringent plate may be provided in a layer between the substrate and the polarizing plate, and the birefringent plate may be placed on the liquid crystal layer side. It is sufficient to use polarizing plates that are laminated in such a manner that they are integrated, or to provide a combination of them.

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, the Δnil・d21 of the birefringent plate above the liquid crystal layer and the Δn,・dat of the birefringent plate below the liquid crystal layer are adjusted and used. If adjustment is not possible, the same birefringent plate or a combination of a plurality of different birefringent plates may be used.

In order to perform a good black-and-white display, it is necessary to adjust the magnitude of Δnzl-d and ls Δn22・d22 of the −axial birefringent plate and their light for a liquid crystal layer with a certain twist angle and Δn1・dl. It is important to optimize the direction of the axis and also the direction of the polarization axes of the pair of polarizing plates.

The relationship between each birefringent plate placed on both sides is 1.01X
Δna.・dz2<Δn21・d21<1.20XΔ
It may be n22/d22. Outside this range,
Since the transmittance in the off state increases, the contrast ratio decreases.

Furthermore, a total of 6 birefringent plates arranged on both sides 2・d2
If the size is set approximately equal to or slightly smaller than the size of Δn1·d of the liquid crystal layer, it is easy to obtain a good black and white display. That is, specifically, 0.7×ΔnI−dI<Δnz'dz<1. IX△1
It may be set to 1+6 dl.

The total Δn2・d2 of this birefringent plate is 0.7XΔn,
If it is smaller than ++ d, the transmittance in the on state will be low and the display will be dark;
If it is larger than , the transmittance in the off state will increase, resulting in a decrease in the contrast ratio, so the above-mentioned range is set.

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; The optical axis is in the direction of the high principal refractive index.

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, 1.2 is a pair of polarizing plates, 3 is for displaying characters and figures, and Δnl*cL 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 birefringent plates laminated above and below, 5 is the polarization axis 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 birefringent plate, 9B is the lower birefringence The direction of the optical axis of the plate is shown.

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, θ1, 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
n and d are about 0.8 μm, and Δn21 and d21 of each of a pair of uniaxial birefringent plates placed above and below,
Δnza・dz□ is 0.41 μm.

If the thickness is about 0.39 μm, it is preferable that the polarizing axes of the pair of polarizing plates intersect at an angle of about 60 to 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@≦02≦14
By setting 0° and 40°≦04≦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, regarding θ1, θ2, θ8, and θ4, θ1 minus θ2
In this case, it is preferable that θ3<θ4, and θ1
When >θ2, it is preferable to set θ and >θ4.

In particular, 40°≦02≦140” large size 40″≦04≦1
A value of 40'' 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 θ2, θ
2, θ3. By setting θ4 counterclockwise and appropriately selecting it within the same range, a black and white display can be easily obtained 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
If it is set to °±30°, it becomes a negative type display, 0@±30″″
If this is done, a positive type display will be obtained, 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, a color polarizing plate may be used, a dye may be added to the liquid crystal, or illumination having a specific Φ 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 the displayed (not displayed) portion.

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. °, Δn1・dI is 0.4 to 1.5
A liquid crystal layer 11 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 11.
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, we get the result as shown in Figure 3 (B). When these circularly polarized lights, which have different shapes and directions, pass through the upper polarizing plate 11 on the output side, the intensity of the passing light differs depending on the red, green, and blue light, so that it appears 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 21 made of nematic liquid crystal having positive dielectric anisotropy with Δn+' dI of 0.4 to 1.5 μm, 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°, Δn1・d
l is 0.82 μm, and the crossing angle of the polarization axes of the pair of polarizing plates 21 and 22 arranged above and below is 90°. In this example, to simplify the explanation, uniaxial birefringent plates are used with one nuclide layer on each side of the liquid crystal layer, but it is also possible to use two or more uniaxial birefringent plates on each side. They may be used in a stacked manner.

When this -axial birefringent plate is sandwiched between polarizing plates, the -axial birefringent plate Δni+・d□, Δn
It has the property that incident linearly polarized light can be made into arbitrary elliptical polarized light, circularly polarized light, or returned to linearly polarized light depending on the value of z*4aa. Therefore, appropriate Δni+・d2
By overlapping birefringent plates of 8.Δn22·dI 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.

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 so that the polarization axes intersect by 90'', and the polarized light on the output side matches the absorption axis of the upper polarizing plate on the output side, the transmission The light 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 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・dI, △n21・d21, Δ of −axial birefringence plate
n22・d22, the angles between them and the polarizing plate θ1, θ2,
It changes by changing the configuration requirements such as θ8 and θ4.

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.

display becomes possible.

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 necessary to experimentally optimize Δn21, d28, Δn22, d22, the optical axis direction of the birefringent plate, the polarization axis direction of the polarizing plate, etc. using parameters such as the twist angle of the liquid crystal layer and Δn1・dl. is preferred. However, since a white state with high transmittance is brighter, clearer, easier to see, and suitable for color printing, it is preferable to give priority to white or black.

1 Example 1 Examples 1 to 4 As a first substrate, an ITO transparent electrode provided on a glass substrate was patterned into stripes, and an insulating film made of SiO□ for short circuit prevention was formed by vapor deposition. A polyimide overcoat 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 iOz was formed, and a polyimide overcoat 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, and uniaxial birefringent plates were laminated on both sides of this liquid crystal cell. .

The Δn-d of the liquid crystal layer of this liquid crystal cell and the Δn·d of the uniaxial birefringent plates disposed on both sides of the cell were varied as shown in Table 1.

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
r = 150°, θ2 = 85°, 0m = 120°
, θ4=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 arranged on the back side of this liquid crystal display element, and the element was driven at 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 90, 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.

Moreover, the contrast ratio of the liquid crystal display element of Example 2.3 (
When the pixel portion only) was measured, it was 60 or more in all cases.

Table 1 Comparative Examples 1 to 8 A liquid crystal display cell was manufactured in the same manner as in Example 1, and the Δn-d of the liquid crystal layer of this liquid crystal cell and the Δn-d of the uniaxial birefringent plates arranged on both sides of the cell were determined. The changes were made as shown in Table 2.

FIG. 5 shows the transmittance changes of Example 1 and Comparative Examples 1.2.

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).

In addition, Comparative Example 3.4 has a higher off transmittance than Example 1 (
, the contrast ratio was lower than that of Example 1.

Furthermore, Comparative Example 5 has a contrast ratio of 50, Comparative Examples 6 to 8
The contrast ratio remained at 40.

Example 5 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 the drawing]

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. 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. 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
．． 16.25.26 is the polarization axis, 7.8 is the long axis direction of the liquid crystal molecules, 9A, 9B is the optical axis direction of the birefringent plate 1'' - Figure 1 10 9A Figure 4 Figure 5

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 different Δn_2_1・d_2_1, Δn_
2_2・d_2_2, and the relationship between the birefringent plates on each side is 1.01×Δn_2_2・d_2_2<Δn_2_1・
d_2_1<1.20×Δn_2_2・d_2_2, and Δn_2・d_2=Δn_2_1・d_2_1+Δ
If n_2_2・d_2_2, then 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) θ_2 is the optical axis direction of the upper birefringent plate measured clockwise from the long axis direction of the liquid crystal molecules above the liquid crystal layer when viewed from the viewing direction. The liquid crystal according to claim 1, where θ_4 is the optical axis direction of the lower birefringent plate measured clockwise when viewed from the long axis direction, and 40°≦θ_2≦140° and 40°≦θ_4≦140°. display element. (3) When viewed from the viewing direction, the direction of the polarization axis of the upper polarizing plate measured clockwise from the long axis direction of the liquid crystal molecules above the liquid crystal layer is θ_1, the length of the liquid crystal molecules above the liquid crystal layer. θ_2 is the optical axis direction of the upper birefringent plate measured clockwise when viewed from the axial direction, and clockwise is the direction of the polarization axis of the lower polarizing plate when viewed from the long axis direction of the liquid crystal molecules below the liquid crystal layer. If θ_3 is the value measured at is θ_
If 3<θ_4 and θ_1>θ_2, then θ_3
3. The liquid crystal display element according to claim 1 or 2, wherein the angle θ_4 is satisfied.