JPH0247625A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To produce a bright black-and-white display element with good black- and-white contrast 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 uniaxial birefringent plates which are colored on at least one of the liquid crystal layer and a polarizing plate. CONSTITUTION:A couple of polarizing plates 1 and 2 are installed outside the liquid crystal layer 3. 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 set to 0.4-1.5mum and the uniaxial birefringent plates 4A and 4B which are colored are arranged on at least either of the liquid crystal layer 3 and polarizing plates 1 and 2. Further, the uniaxial birefringent plates 4A and 4B have their maximum absorption wavelength between 470 and 600nm so as to absorb, specially, yellow. Consequently, the bright liquid crystal display element which has the good black-and-white contrast can be produced at high yield.

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 liquid crystal molecules between both 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 refractive index anisotropy 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 (specifically 1986-
No. 10720), good contrast was obtained only with specific combinations of hues, such as yellow-green and dark blue, bluish-violet and pale yellow, as display colors.

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, by using a similar method and setting the product Δn-d of the refractive index anisotropy Δn and the thickness d of the liquid crystal to a small value of around 0.6 μm, a display that is almost white and black can be obtained. Proposed.

(M, 5chadtet at, Appl,
Phys, Lett, 50(5), 1987
．． (p. 236) However, when this method was used, the display was dark, the maximum contrast was not very thick, 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. (Shiso et al., Technical Report of the Televising Society, 11(27), p. 7
9. (1987)) However, with this method, the matching of Δn-d in a two-layer cell is extremely difficult, making it difficult to improve yield, and because it requires two layers of liquid crystal cells, it sacrifices the thin and light characteristics of liquid crystal cells. It had its drawbacks.

It has also been proposed that in a two-layer cell, one liquid crystal cell used as an optical compensator is replaced with a uniaxial birefringent plate, so that there is only one layer of the liquid crystal cell.

Although this method also provides a display that is close to black and white, it is difficult to obtain a display with good black and white accuracy.

[Problems to be Solved by the Invention 1] With these conventional methods, it is difficult to produce bright liquid crystal display elements with good black and white clarity at a high 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, light, and has low power consumption.

For this reason, there has been a desire for a liquid crystal display element that can produce black-and-white display elements with good contrast, brightness, and black-and-white accuracy 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 Δn1·dl of the refractive index anisotropy Δold 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, and at least one of the liquid crystal layer and the polarizing plate is colored. A liquid crystal display element characterized in that a uniaxial birefringent plate is arranged, and the product Δn1·cL 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. ~1.5
μm, and a pair of birefringent plates, one of which is colored, are arranged on both sides of a liquid crystal layer and inside a pair of polarizing plates, and their liquid crystal The present invention provides a liquid crystal display element characterized in that a colored birefringent plate has a maximum absorption wavelength of 470 to 600 nm.

In the present invention, a colored uniaxial birefringent plate having a maximum absorption wavelength of 470 to 600 na+, which absorbs yellow color, is disposed at least on one side between the liquid crystal layer and the polarizing plate.

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

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

Specifically, a nematic liquid crystal with positive dielectric anisotropy containing an optically active substance is sandwiched between a pair of transparent electrode substrates arranged almost in parallel, and the twist angle of the liquid crystal molecules between the two electrodes is set to 1.
The angle may be 60 to 300°. This is due to the ability to improve contrast when performing time-division driving at a high duty rate, where a steep change in transmittance is required when the angle is less than 160° (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 Δn+'d+h' of the refractive index anisotropy Δn1 of the liquid crystal of the liquid crystal layer and the thickness d of the liquid crystal layer is 0.4 to 1.
It is assumed to be 5 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 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 Δn1·dl of the liquid crystal layer is 0.5 to 1.0 μm.

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

ITOuntos patterned into 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 Snow is provided, and this surface is rubbed or coated with 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 Ties, SiO□, or AhOl may be provided between the electrode and the alignment control film to prevent short circuits between the substrates, or a low-resistance lead electrode such as A1, Cr, or Ti may be provided on the transparent electrode. Alternatively, 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 colored 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 preferable to arrange them on both sides because it is less likely to cause unreasonable compensation for Δn−d 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, as a layer between a substrate and a polarizing plate, or as a combination of these.

As this birefringent plate, any transparent plate that exhibits -axial birefringence can be used, and plastic films, inorganic crystal plates, etc. can be used. To obtain the desired birefringence effect,
Product Δ of the refractive index anisotropy Δn= of the birefringent plate and its thickness d
Although n and d are adjusted and used, if the adjustment cannot be made with a single plate, the same birefringent plate or a plurality of different birefringent plates may be used in combination. In this case, Δn2・d2
is the sum of 6 ports/d of multiple birefringent plates, that is,
Let it represent the sum total of a plurality of birefringent plates.

In the present invention, at least one of the birefringent plates is colored, and when a plurality of birefringent plates are used, some of them may be colored, or all of them may be colored. It may also be a birefringent plate. As such a colored birefringent plate, a plastic film containing a pigment, dyed, or printed with a color, a colored inorganic crystal plate, etc. can be used.

In order to perform a good black and white display, it is necessary to adjust the size of Δn8・d2 of the -axial birefringent plate, the coloring absorption characteristics, and the light absorption characteristics of the 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.

When a simple birefringent plate is used, the displayed color of the white level of a super twist liquid crystal display element using this plate is completely white (
It often shows a pale yellow-green to yellow color. For this reason, it is preferable that the colored birefringent plate has absorption characteristics that correct these yellowish hues and bring it closer to white display.Specifically, the maximum absorption wavelength of the colored birefringent plate is 470 ~ Preferably, a birefringent plate such as that at 600 nm is used.

The size of the birefringent plate glue tarp John Δn8・d2 is
If the value 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. Specifically, the thickness may be approximately 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 Figure 1, 1.2 is a pair of polarizing plates, 3 is for displaying characters and figures, and Δn+jd is 0.4 to 1.
．． A liquid crystal layer with a twist angle of 160 to 300' made of nematic liquid crystal with a positive dielectric anisotropy of 5 μm, 4A and 4B are birefringent plates laminated above and below the layer, 5 is a polarizing 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, and 9B is the lower birefringent plate. It shows the optical axis direction of the refracting plate. In the present invention, one of the birefringent plates 4A and 4B is colored, and the hue of this element itself is corrected to obtain a display with better black and white accuracy.

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. The value measured clockwise is 03, and the value 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 is 04.

In the present invention, these θ1, θ2, θ8, and θ4 may be optimized so that black and white display is achieved.

When using the liquid crystal display element of the present invention in a negative type display, for example, the twist angle of the liquid crystal layer is about 240°, and the Δ
n, d is about 0.8 μm, and the total Δn2 d of the pair of uniaxial birefringent plates placed above and below is 0.8 μm.
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°. is preferred. 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 this case, especially for negative display, 5°≦02≦14
By setting 0° and 40°≦04≦170@,
This is preferable because a display having a sufficient contrast ratio with low off-state transmittance (and high on-state transmittance) can be realized.

Also, regarding θ1, θ2, θ3, and θ4, θ1 minus θ2
When θ1<θ4, it is preferable that θ1<θ4, and when θ,>θ, it is preferable that θ,>e4.

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, 40'≦8. ≦140” Tekatsu 40°≦0
By setting 4≦140°, -20°≦θ, ≦20@ and -20°≦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 2, θ3, and θ, a monochrome display can be easily obtained as in the above example.

In this case, since the present invention uses a birefringent plate that has a color that corrects the color of the element itself, coloring caused by the element itself is suppressed, making it possible to display with better black and white accuracy. .

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, it does not cause deviation depending on the viewing angle (and enables more precise color display. Specifically, it may be formed on the underside of the electrode, or it may be formed on the bottom of the electrode. It may be formed on the upper side.

Furthermore, 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 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 comparable to those of the super twist liquid crystal display element, and as mentioned above, it is possible to display bright (clear and black and white with high black-and-white) display, so it is possible to display the fine power of the three primary colors of red, edge, and blue. By arranging a filter on the inner surface of the cell, it is also possible to obtain a high-density multicolor liquid crystal display element.

The liquid crystal display element of the present invention can be used as a personal combinator,
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. °, Δnl + dl is 0.4 to 1
．． A liquid crystal layer 13 made of nematic liquid crystal having a positive dielectric anisotropy of 5 gm, and a pair of polarizing plates 1 disposed above and below the liquid crystal layer 13.
1.12. 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.

On the other hand, a method has been proposed in which a monoaxial birefringent plate having no absorption property for visible light is used to display black and white, and the device configuration thereof is shown in FIG. 4(A). This liquid crystal display element has a twist angle of 160 to 300° and Δn+ ”
A liquid crystal layer 23 made of a nematic liquid crystal having positive dielectric anisotropy with a dl of 0.4 to 1.5 μm, uniaxial birefringent plates 24A and 24B placed on top of the liquid crystal layer 23, and a pair of birefringent plates placed above and below the liquid crystal layer 23. It is composed of polarizing plates 21 and 22.

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 -axial birefringent plates are stacked on one side, but it is also possible to use one or more uniaxial birefringent plates on one side, or use a liquid crystal layer as described above. A pair of one or more uniaxial birefringent plates may be provided above and below.

When this -axial birefringent plate is sandwiched between polarizing plates, it can convert incident linearly polarized light into arbitrary elliptically polarized light or circularly polarized light depending on the value of Δn2・dt of the -axial birefringent plate. , or it has the property of being able to return to linearly polarized light. Therefore, by superimposing a birefringent plate with a certain value of Δn2·d 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 layer 23, it becomes an elliptical polarized state. This elliptically polarized light is further processed by a birefringent plate 2.
4A and 24B, the elliptical polarized light may be returned to a state close to linearly polarized light depending on the conditions.

If we consider light by dividing it into the three primary colors of red, green, and blue, this becomes as shown in Figure 4 (CB). As in this example, when the directions of the red, green, and blue polarization axes are almost the same and return to linear polarization,
Regardless of the direction of the polarization axis on the output side, wavelength dependence of the intensity of the passing light can be eliminated. That is, the color can be made considerably achromatic.

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

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

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

Note that negative and positive display values are determined by the twist angle of the liquid crystal layer and its Δ
The values of n, ·d, - the value of the total flux Δnyo ·d2 of the axial birefringent plate, and the angle θ1 between them and the polarizing plate.
, θ2, θ3, θ4, and the like.

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 was 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 elliptically polarized light and creates a black or white state when no voltage is applied, it does not necessarily mean that the state will be white or black even when a voltage is applied. Not exclusively.

Therefore, in the present invention, a colored uniaxial birefringent plate that has visible light absorption properties is used as the -axial birefringent plate,
Display with high black and white accuracy is achieved both in a state where no voltage is applied and a state where a voltage is applied.

The absorption characteristics required of this colored uniaxial birefringent plate are as follows: It is desirable to correct the colored white state and make the spectral transmittance flat. Since the color changes from pale yellow-green to yellow, it is best to use a birefringent plate colored in reddish-purple color that can absorb this. Specifically, the maximum absorption wavelength of the colored birefringent plate is 470 to 600 nm. It is sufficient to use a birefringent plate that has the following properties.It is sufficient to select a birefringent plate such that the absorption strength, that is, the color density, is corrected so that its spectral transmittance becomes approximately flat.

That is, depending on parameters such as the twist angle of the liquid crystal layer and Δn1・d+, the absorption characteristics of the colored birefringent plate and Δn2・d
2. It is preferable to experimentally optimize the optical axis direction, the polarization axis direction of the polarizing plate, etc. to obtain a whitish display.

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 a polyimide film was formed. The 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 inches was formed, and an overcoat of polyimide was applied. was rubbed at an angle of intersection of 60° with the rubbing direction of the first substrate to prepare a substrate on which an alignment control film was formed.

The peripheries of these two substrates are sealed with a sealing material to form a liquid crystal cell, and a nematic liquid crystal with positive dielectric anisotropy is injected into this liquid crystal cell to form a liquid crystal layer twisted at 240 degrees. The injection port was sealed. In this liquid crystal layer, 01・dl
was 0.82 μm.

On both sides of this liquid crystal cell, the retardation is 0.
．． One uniaxial birefringent plate colored reddish-purple having a maximum absorption at 520 nm at 40 μm was laminated, and a pair of polarizing plates were further laminated above and below the plate.

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=856θs = 120°, θ
, =95″″.

As a result of applying a voltage to this liquid crystal display element and examining the degree of transmission, it was found that good threshold voltage characteristics were obtained as shown in Figure 5, 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.

In FIG. 6, O indicates the hue of the on state (white) of this example, . indicates the hue of the off state (black) of this example, and △ indicates the colored birefringent plate of this example. The figure shows the hue of the comparative example in the on state (white) using a non-birefringent plate, and M indicates the hue of the comparative example in the off state (black). In addition, X in the figure indicates the hue of the C light source. .

As is clear from this result, the example element has a higher white level when turned on than the comparative example element, which uses a conventional non-colored uniaxial birefringent plate that does not have absorption characteristics for visible light. was obtained, which was slightly yellowish in the off state, but because the transmittance was low, a negative black-and-white display that appeared sufficiently black was obtained.

When we measured the contrast ratio of this liquid crystal display element, we found that
The contrast ratio was approximately 50, and a much higher contrast ratio was obtained than that of a conventional simple super twist liquid crystal display element.

Moreover, a transmittance of about 25% can be obtained when the O
Since it was brighter than an MI element, it was also possible to use it as a reflective type.

Example 2 In the liquid crystal display element of Example 1, 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 reddish-purple colored birefringent plate having maximum absorption at 520 nm. A liquid crystal display element was created by changing only the following. That is, θ+
=60', θ2=115@, θ8=301, θ4
=65'.

When this liquid crystal display element was driven at 1/200 duty and l/15 bias 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, full color gradation driving was possible.

Example 4 In the liquid crystal display element of Example 1, 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 reddish-purple colored birefringent plate having maximum absorption at 520 nm. A liquid crystal display element was created by changing only the following. That is, θ1
=lO°, θ8=120°, θ, =45°5 θ4 =
It was set to 125'.

This liquid crystal display element was driven at 1/200 duty and 1/15 bias as in Example 1.

A positive display with a good white level when turned off and slightly bluish when turned on, but with a low transmittance that appears sufficiently black, was obtained. Contrast ratio of this liquid crystal display element (pixel part only)
When measured, it was about 30.

[Effects of the Invention] As explained above, the present invention has a better contrast ratio than the conventional super twist liquid crystal display element, and enables black and white display with good black and white accuracy, resulting in clear and high display quality. Highly positive or negative type display can be 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 it is possible to display a display that is closer to black and white, by combining it with a color filter, a colorful display is possible.In particular, by arranging red, green, and blue color filters for each pixel, multicolor and full color It has also been recognized that it is effective in displaying images, opening up more diverse applications.

Particularly, in the present invention, although black and white display is possible, bright display is possible, and not only transmissive type display but also reflective type display is possible, and the range of application thereof is wide.

Furthermore, according to the present invention, by simply arranging a colored birefringent plate, bright black-and-white display is possible without providing a second liquid crystal layer, and a thin, lightweight, and highly reliable liquid crystal display element can be created. It also has the advantage of being highly productive (manufacturable).

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 a liquid crystal display element using a -axial birefringent plate, and a plan view 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 and Comparative Example. 1.2.11.12.21.22 is a polarizing plate, 3.13.
23 is a liquid crystal layer, 4A, 4B, 24 are birefringent plates, 5.6.15.16.25.26 are polarization axes, 7.8 is the long axis direction of liquid crystal molecules, 9A, 9B are the lights of the birefringent plates Axial direction 1 diagram Title of the invention: Liquid crystal display device 3; Relationship with the amended case

Claims (3)

[Claims] (1) A nematic liquid crystal with positive dielectric anisotropy containing an optically active substance sandwiched between a pair of substrates with transparent electrodes arranged almost in parallel and having an alignment control film has a twist angle of 16
It has a liquid crystal layer of 0 to 300° and a driving means for applying a voltage between transparent electrodes of upper and lower substrates sandwiching this liquid crystal layer,
In a liquid crystal display element in which a pair of polarizing plates is installed outside the liquid crystal layer, the product Δn_1·d_1 of the refractive index anisotropy Δn_1 of the liquid crystal in the liquid crystal layer and the thickness d_1 of the liquid crystal layer is 0.4 to
1. A liquid crystal display element having a diameter of 1.5 μm and comprising a colored uniaxial birefringent plate arranged 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. A liquid crystal display element characterized in that a pair of birefringent plates, at least one of which is colored, are disposed on both sides of a liquid crystal layer and inside a pair of polarizing plates. (3) The liquid crystal display element according to claim 1 or 2, wherein the colored birefringent plate has a maximum absorption wavelength of 470 to 600 nm.