JPH02821A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To produce the liquid crystal display element which is bright and has a good black-and-white extent at high yield by specifying the product of the refractive index anisotropy of the liquid crystal in a liquid crystal layer and the thickness of the liquid crystal layer and arranging an uniaxial birefringent plate between the liquid crystal layer and a polarizing plate. 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 3 is set to 0.4-1.5mum and uniaxial birefringent plates 4A and 4B are arranged between the liquid crystal and at least either of deflecting plates 1 and 2. Only one liquid crystal layer 3 is required and no 2nd liquid crystal layer which easily causes deterioration in productivity and a color irregularity is not necessary. Consequently, a black-and-white display which has a higher contrast ratio than a conventional supertwist liquid crystal display element can be obtained and a sharp positive or negative display of high display quality is realized.

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 (7,
J, 5chefferand J, Nehring.
, Appl, , Phys, , Lett, 45
(1011021-1023 (1984) l was known.

However, in this method, the value of Δn-d between 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. 60-1(
Good contrast was obtained only with specific combinations of hues, such as +72 (+?f), FE light blue L/T, yellow-green and dark blue, and bluish-purple 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 Δnod of the birefringence index and the thickness of the liquid crystal to a small value of around 0.6 μm, thereby obtaining a display that is almost white and black. (M, 5chadtet al, App
l, Phys, Lett, 50(5), 1
(987°p, 236) However, when this method was used, the display was dark, the maximum contrast was not very high, 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, a method is used in which two layers of liquid crystal cells are arranged in opposite spirals, and a voltage is applied to only one cell, while the other cell is used simply as an optical compensation plate. is proposed. (Haka Koshimura, Television Society Technical Report, H(27), p. 79
．． (1987)) However, this method is
N-D matching is very severe, making it difficult to improve yield, and since two layers of liquid crystal cells are required, the advantages of thin and light liquid crystal cells are sacrificed.

(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.

Bright black-and-white display elements are not only easy to see without any distinctive coloring, but also have color filters formed inside or outside the cells, unlike conventional twisted nematic (TN) elements with a 90° twist. It is expected that the market will expand dramatically as it can realize mono-color, multi-color, or full-color display, 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
In a liquid crystal display element that has a liquid crystal layer of ~30G'' and a driving means for applying 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 refractive index anisotropy of the liquid crystal in the liquid crystal layer, and the thickness d1 of the liquid crystal layer, Δn0・d, are 0.4 to 1.5 μm, and a uniaxial polarizer is formed on at least one side between the liquid crystal layer and the polarizing plate. The liquid crystal display element is characterized in that a birefringent plate having a polarity is arranged, and the refractive index anisotropy Δnl of the liquid crystal in the liquid crystal layer and the thickness d1 Δn, 6 d of the liquid crystal layer are 0.4 to 1. 5 μm, and a pair of birefringent plates are arranged on both sides of a liquid crystal layer and inside a pair of polarizing plates.

In the present invention, a uniaxial birefringent plate is disposed at least on one side between the liquid crystal layer and the polarizing plate.

Therefore, only one piece of the liquid crystal layer is required, and a liquid crystal display element with a bright monochrome 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 electroplating substrates arranged almost parallel to each other, and the twist angle of the liquid crystal molecules between the two electrodes is set to 1.
The angle should be between 60 and 300 degrees. This means that if it is less than 180", 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. On the other hand, if it exceeds 300 degrees, This is because hysteresis and domains that scatter light are likely to occur.

In addition, the product Δn1・d of the refractive index anisotropy (Δn+) of the liquid crystal in the liquid crystal layer and the thickness (d, ) of the liquid crystal layer is 0.4 to 1.5.
It is assumed to be μm.

This is because 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,·d of the liquid crystal layer is 0.5 to 1.0 μm.

Note that this range of Δn8·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,·d8 deviates from the above range, the display may become colored or the viewing angle characteristics may deteriorate.

ITO (In*0) patterned into the desired pattern
A film of polyimide, polyamide, etc. is provided on the surface of a substrate such as plastic or glass on which a transparent electrode of s-3nO, SnO, etc. is provided, and this surface is rubbed or SiO
A substrate with transparent electrodes on which an orientation-controlling W film is formed by diagonally vapor-depositing or the like is prepared, and between the substrates with transparent electrodes, the above-mentioned nematic liquid crystal with positive dielectric anisotropy is placed.
A liquid crystal layer with a twist of 60 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 striped electrodes formed on one substrate and perpendicular to these on the other substrate. 400 striped electrodes are formed on the screen, and a display like 640 x 400 dots is created. Further, each of these 640 striped electrodes can be made into a set of 3 to form 1920 striped electrodes, and RGB color filters can be arranged to display a full color display of 640×400 dots.

In addition, an insulating film such as Tie, 5ift, Al2oz, 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 AI, (:r, Ti) may be provided on the transparent electrode. A color filter may be provided side by side, 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 birefringent plate is laminated adjacent to the liquid crystal layer. This birefringent plate may be provided between the liquid crystal layer and the polarizing plate, and may be provided on only one side of the liquid crystal layer or on both sides. However, it is better to provide it on both sides to compensate for Δn-d. This is preferable because it is less likely to cause distortion and enables black and white display with less color unevenness.

Further, 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 electrode, or it may be provided in a layer between the electrode and the substrate, or the substrate itself may be provided as a layer. It may be provided as a refractive plate, provided in a layer between a substrate and a polarizing plate, or provided in combination.

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, Δn, d2 is adjusted and used, but if adjustment is not possible with a single plate, the same or 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 Δn, dl, the magnitude of Δn2 d2 of the -axial birefringent plate and the direction of their optical axes, Furthermore, it is important to optimize the direction of the polarization axes of the pair of polarizing plates.

The size of Δn3・d of the birefringent plate is roughly equal to Δn of the liquid crystal layer.
, * If the size is set to be approximately equal to or slightly smaller than d, it is easy to obtain a good black and white display. Specifically, it may be set to about 0.3 to 1.5 μm.

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 ΔnIad 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 polarizing axis of the upper polarizing plate, 6 is the lower 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 birefringence plate.

In Fig. 2, 01 is the total length 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 01 is the length 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 axial direction, and 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 under the liquid crystal layer. was measured clockwise. It is assumed that the value is 03, and the value measured clockwise in the optical axis direction 9B of the lower birefringent plate as viewed from the long sleeve direction of the liquid crystal molecules 8 on the lower side of the liquid crystal layer is 04.

In the present invention, these θ1, θ2.03, and θ may be optimized 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 2400, then Δ
n, dl is 0.8 μm culm, and the sum of Δn, d of a pair of uniaxial birefringent plates placed above and below 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, 5°≦0,≦1
By setting 40@, 40°≦θ, ≦170”,
This is preferable because a display with sufficient contrast can be realized with low transmittance in the off state and high transmittance in the on state.

Also, regarding θ4, θ3, Os, θ4, θ1 × θ2
In this case, it is preferable to set θ, <θ, and Ol
When >OR, it is preferable to set θ, >04.

As a result, this liquid crystal display element is capable of black and white display with excellent viewing angle characteristics and a high contrast ratio.

In particular, 4G@≦θ, ≦140° and 40m≦04≦1
406 or -20°≦02≦20° 20
By setting °≦04≦20°, the off-state transmittance is low and a sufficient contrast ratio can be obtained, which is preferable.

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 appropriately selecting 3, θ1, and θ4, a monochrome display can be easily obtained as in the above example.

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 as a transmissive type, but since it is bright, it can also be used as a reflective type.

When used as a transmissive type, the back 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,
It is suitable as a display element for word processors, workstations, etc., but it is also suitable for external liquid hole TVs, fish finders,
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 ~
A liquid crystal J'W13 made of a nematic liquid crystal having a positive dielectric anisotropy of 1.5 μm and a pair of polarizing plates 11 and 12 disposed above and below the liquid crystal J'W13 are 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
It is set to 0.

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 twist angle is 160 to 300'', as shown in a schematic diagram seen from the side in FIG. 4(A).
A liquid crystal M23 made of a nematic liquid crystal having positive dielectric anisotropy with Δnt T d of 0.4 to 1.5 μm, and two uniaxial birefringent plates 24A and 24B disposed thereon.
, and a pair of polarizing plates 21 and 22 arranged above and below the polarizing plates 21 and 22.
It shows.

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, two uniaxial birefringent plates are stacked on one side to simplify the explanation, but one or more uniaxial birefringent plates may be used on one side, or As described above, a pair of one or more uniaxial birefringent plates may be provided above and below the liquid crystal layer.

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 overlaying a birefringent plate with an appropriate value of Δn2·d2 on 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, the light that is almost completely linearly polarized through the lower polarizing plate 22 on the incident side is When the light passes through the liquid crystal J123, it becomes an elliptical polarized state. By further passing this elliptically polarized light through the birefringent plates 24A and 24B, 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 red, green, and blue polarization axes are almost the same and the polarization returns to almost linear polarization, the wavelength dependence of the intensity of the passing light can be eliminated regardless of the direction of the polarization axis on the output side. I can do it. In other words, it is possible to make the color achromatic.

As in this example, if a polarizing plate is installed so that the polarizing 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 transmitted light The intensity is the lowest and it appears black, resulting 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
It can be changed by changing the structural conditions such as n, dl, Δn2 d2 of the -axial birefringent plate, and the angles θ1, θ2, θ3.04 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, 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. Therefore, depending on parameters such as the twist angle of the liquid crystal layer, Δn1 and d8, Δn2 and d2 of the birefringent plate, its leading axis direction, and the direction of the polarization axis of the polarizing plate can be determined experimentally! & It is preferable to optimize.

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.

This effect of the birefringent plate works similarly even if the birefringent plate is placed on the incident side of the liquid crystal layer.

[Example 1 Example 1 As a first substrate, an ITO transparent electrode provided on a glass substrate was patterned into stripes, an insulating film made of SiO□ for short circuit prevention was formed by vapor deposition, and an overlay of polyimide 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 is patterned into stripes perpendicular to the first substrate, an SiO2 insulating film is formed, and a polyimide overcoat is applied. A substrate on which an alignment control film was formed was prepared by rubbing so that the angle of intersection with the rubbing direction of the first substrate was 60°.

The periphery of these two substrates is 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 240" twisted liquid crystal layer. The injection port was sealed.In this liquid crystal layer, Δn,・dl
was 0.82 μm.

Uniaxial birefringent plates with Δn2·d of 0.40 μm were laminated on both sides of this liquid crystal cell, and a pair of polarizing plates were further placed above and below the a layer.

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''', θ, = I15''θ, = 120'
, θ, = 95 @ closed.

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

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 was obtained when the switch was on, and a negative black and white display that appeared to be sufficiently black was obtained when the switch was off, although slightly yellowish due to the low transmittance.

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.

Example 2 A liquid crystal display element was created 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 in the liquid crystal display element of Example 1. . That is, e, = 60" θt = 115", θ, = 30"
θ, = 65°.

When this liquid crystal display element was driven at 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 3 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, a full-color llj? Adjustable drive was possible.

Example 4 A liquid crystal display element was created 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 in the liquid crystal display element of Example 1. . That is, θ,=lO1(3x=120@, O:+=45@
, 04=125°.

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 good white level was obtained when the display was turned on, and a positive image that appeared slightly bluish when turned on, but was sufficiently black due to the low transmittance. A type indication was obtained.

The contrast ratio (pixel portion only) of this liquid crystal display element was measured and found to be approximately 30.

[Effects of the Invention] As explained in F-F, the present invention enables a black and white display with a better contrast ratio than the conventional super twist liquid crystal display element, and provides a clear and high quality positive or negative display. You will get an indication of the type.

In addition, the time-division display characteristics and viewing angle characteristics are 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 the threshold voltage characteristics of Example 1. FIG. 6 is a hue diagram showing hues in the on and off states of Example 1. 1.2.11.12, 21.22 are polarizing plates, 3.13.
23 is a liquid crystal layer, 4A, 411.24Δ, 24B is a birefringent plate, 5.6.1
5.16.25.26 is the polarization axis, 7.8 is the long sleeve direction of liquid crystal molecules, 9A and 9B are the optical axis directions of the birefringent plate.

Claims (2)

[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 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 Δn_1·d_1 is 0.4 to 1.
5 μm, and a uniaxial birefringent plate is disposed at least on one side between a liquid crystal layer and a polarizing plate. (2) A twist angle of 16 by a nematic liquid crystal with positive dielectric anisotropy containing an optically active substance and sandwiched between a pair of substrates with transparent electrodes arranged almost in parallel and having alignment control films.
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
1.5 μm, and a pair of birefringent plates are arranged on both sides of a liquid crystal layer and inside a pair of polarizing plates.