WO2004059376A1 - Cholesteric phase liquid crystal display with the property of nematic phase - Google Patents

Abstract

A Cholesteric phase liquid crystal display with the property of nematic phase, comprises a liquid crystal cell which contains two parallel transparent substrates, and a transparent electrode and an aligning layer provided on the inner surface of the transparent substrates in this order. A seal ring is provided around the liquid crystal cell. The character is that the cholesteric phase liquid crystal domain of the cholesteric phase liquid crystal in the liquid crystal cell, has the property of nematic phase liquid crystal domain. The helix pitch P, domain length S of the said cholesteric phase liquid crystal domain and light wavelength /λ are followed the relationships: P1 4 ≤ λ and S > λ. The extraordinary refractive index and the ordinary refractive index of the cholesteric phase liquid crystal domain are '= no and no'= (no + ne )/ 2 respectively. A voltage is applied to the liquid crystal cell so that the cholesteric phase liquid crystal with the property of nematic phase could change its state: make a pixel appearing light or dark state.

Description

 Cholesteric liquid crystal display with nematic characteristics

 The present invention relates to a cholesteric liquid crystal display having nematic phase characteristics. The cholesteric liquid crystal in the display has the characteristics of nematic liquid crystal under certain conditions. The core technology of the present invention is to make the pitch P, crystal domain S, and wavelength A of the cholesteric liquid crystal satisfy the conditions: // 4 和 S> L. In this way, the liquid crystal in a planar texture can be regarded as a homogeneous medium; The cone-textured liquid crystal can be regarded as a single crystal domain retarder with electronically controllable light retardation. Using a special liquid crystal cell structure and driving method, it controls the transition of liquid crystal state and changes in light retardation to display images.

 Background technique

 Liquid crystal displays have become the mainstream of today's high-information flat panel displays, and their main representatives are STN-LCD and TFT-LCD. Neither type of display has a zero-field memory function. It also consumes power in static and quasi-static displays, and has a slow response speed. When it comes to color display, it has to use 3 times the pixels and expensive color filters. Light utilization is also low (about 5%).

 It is generally believed that cholesteric phase liquid crystals have two zero-field steady states and many intermediate states, which are planar texture and focal cone texture. The liquid crystal in the plane texture state has Bragg reflection to a certain band of co-rotation light, and the 'liquid crystal in the focal cone texture state has certain light scattering. The reflective bistable and multistable liquid crystal displays that have been made by using these characteristics , Significantly reduced power consumption, and first applied to e-books. However, the response speed of the zero-field steady-state liquid crystal display is slow, the brightness and contrast of the black and white display are poor, and full-color display is not yet available. Therefore, liquid crystal displays based on existing display technologies cannot meet people's requirements for a display that is fast, memorable, power-saving, inexpensive, high-contrast, high-brightness, full-color, and high-quality.

 Summary of the Invention

 The object of the present invention is to provide a cholesteric liquid crystal display with nematic phase characteristics. The pitch of the cholesteric liquid crystal domain used in the display, the domain length S and the wavelength A of the light wave are in accordance with the relationship 4 A and S> λ. It has the characteristics of nematic liquid crystal. In this way, the liquid crystal layer in the planar texture state can be regarded as a homogeneous medium; the liquid crystal in the focal cone texture state can be regarded as a single crystal domain retarder. Based on this knowledge, a zero-field steady state is designed. Of various bile-phase liquid crystal displays with nematic characteristics, which are both fast, fast response, or zero-field steady-state and fast response, which solves the slow response speed, low light utilization, and brightness of all current liquid crystal displays. Technical problems such as insufficient, poor contrast, and high cost of color display. ...

The object of the present invention is achieved by the following technical solution: A cholesteric liquid crystal display with nematic phase characteristics has a liquid crystal cell. The liquid crystal cell is provided with two parallel transparent substrates. A transparent electrode is provided on the surface, and an alignment layer is provided on the inner surface of the transparent electrode to set a pretilt angle. A sealing ring is arranged around the liquid crystal cell, which is characterized in that: the liquid crystal cell is filled with cholesteric liquid crystal, and the cholesteric liquid crystal domain in the cholesteric liquid crystal has a uniform spiral texture and has nematic liquid crystal domain characteristics. , The pitch parameter ^{5 of} the cholesteric liquid crystal domain, the length parameter S of the crystalline domain and the wavelength parameter of the light wave, accord with the relationship ^^ and ^>A; the extraordinary optical refractive index of the cholesteric liquid crystal domain; = n ₀ ; Its ordinary light refractive index „<= (« o + «e 12; a retarder and a polarizer are provided on the outer surface of the upper substrate of the liquid crystal cell, and a reflector is provided on the outer surface of the lower substrate of the liquid crystal cell. A driving voltage is applied to the cell to change the state of the cholesteric liquid crystal with nematic liquid crystal characteristics to a bright state and a dark state of the pixel.

 The present invention is realized by making a series of liquid crystal displays through technical solutions such as the structural design of the liquid crystal cell and the display, a fast driving scheme, and reducing the influence of scattering, based on the flexible application of the newly discovered bile-phase liquid crystal characteristics.

 1. Newly discovered cholesteric liquid crystal characteristics

 In a liquid crystal cell composed of two parallel substrates, under a zero-field condition where no power is applied, a cholesteric liquid crystal having a spiral texture has two stable states, a planar texture state and a focal cone texture state. When the pitch parameter, crystal domain length parameter S, and light wavelength parameter ^ I of a cholesteric liquid crystal domain conform to the relations P / 4 i and>, this cholesteric liquid crystal domain can be regarded as a nematic with a zero field steady state. Phase liquid crystal domain, whose director is the axis of helical symmetry of the cholesteric domain; extraordinary light refractive index; 7 =; ordinary light refractive index,

12, of which, ". The extraordinary light and ordinary light refractive indices of cholesteric liquid crystals, respectively. The crystal domain length parameter refers to a shape parameter with the largest crystal domain. .

 The plane-textured liquid crystal layer has a spiral symmetry axis that is perpendicular or approximately perpendicular to the substrate. When light is irradiated, the anti-rotational component will be transmitted through, and only the co-rotational component will generate Bragg reflection, and it can only reflect a certain wavelength A and a certain Light with bandwidth Δ Λ

 厶 = Ίη cos Θ or Δ = An, P cos Θ

 By changing the formula of the liquid crystal to change the “ο ′ and”, the wavelengths I and Δ A of the reflected light can fall outside the visible spectrum region. For visible light, the liquid crystal layer in the plane texture state can be regarded as a homogeneous medium.

The liquid crystal in the focal cone texture state has a two-dimensional disorder or a one-dimensional order in the plane of the spiral symmetry axis. For incident light, it is equivalent to a retarder, and its retardation varies with voltage. Refractive index difference between two polarization directions'-"o, =" o- (" _e +" o) / 2 =-(" _e -Mo) / 2; optical retardation R = n, d =-n _e -n ₀ d / 2, where is the thickness of the domain. For a thin liquid crystal cell, ^ is equal to the cell thickness. By changing the liquid crystal formulation and cell thickness to make the light retardation R equal to 1/2 or 1/4, etc., it can be made into 1 / 2 retarder, or 1/4 retarder, etc.

2. LCD structural design The principle of the liquid crystal display is to display the image by changing the state of the liquid crystal to make the pixels appear bright and dark. When designing a liquid crystal cell, the cholesteric liquid crystal should satisfy the conditions P / 4 A and S> A, and the liquid crystal alignment layer be specially treated. In this way, the liquid crystal layer in a planar texture state can be regarded as a uniform material that does not affect light. Hook medium; the liquid crystal layer in a focal cone texture state is used as a retarder whose retardation varies with the applied voltage. At the same time, according to the use requirements of the display, combined with the driving method, it is combined with a polarizer, a retarder, a reflector, and a backlight to form various liquid crystal displays.

 3. Fast driving scheme

 The purpose of adopting the fast driving scheme is to make the liquid crystal switch rapidly between the plane texture state and the focal cone texture state, and to change the light retardation amount quickly when it is in a one-dimensional ordered focal cone state.

The dc-optical characteristic curve of cholesteric liquid crystal is shown in Fig. 1. In the figure, L is the relative transmittance and V is the applied voltage. The general driving method is to apply a DC voltage V to the bile-phase liquid crystal layer, so that the director of the liquid crystal tends to be parallel to the direction of the applied electric field, and then gradually increase the voltage. When the voltage is greater than v _B , the unwinding is started; when the voltage is greater than v _c At this time, the liquid crystal layer enters the field nematic phase, and the director is completely parallel to the direction of the electric field. At this time, if the power is suddenly cut off, the liquid crystal will become a plane texture. If the voltage is slowly reduced to less than Vc :, the liquid crystal will show "Pseudo-field-induced nematic phase"; when the voltage drops to Vc ', the liquid crystal starts to form a focal conic texture with the increase of the pitch as the voltage increases; when the voltage drops to less than V _A , the liquid crystal is completely conical Configuration. With this driving method, the response speed is too slow.

In order to speed up the conversion speed, we use the pulse sequence shown in Figure 2 instead of the DC electric field. First, a liquid crystal is driven to a field nematic phase by applying a pulse voltage τ having an amplitude much larger than V _c . During a short period of τ ₂ , the liquid crystal is in a planar texture state. Then, a pulse voltage τ _{3 having} an amplitude V ₂ is applied. Here, V _A <

After V ₂ <V _B and τ ₃ , the liquid crystal has a two-dimensional disordered focal cone texture. Adjust V ,, ¥ ₂ and "^ + 1 _3" to make the total driving time τ = τ ₁₊ τ ₂ + τ _{3 the} shortest, and realize fast conversion.

In order to obtain a one-dimensional ordered focal cone texture with a spiral axis orientation, a program step wave pulse voltage as shown in FIG. 3 is used instead of a DC voltage. First, the liquid crystal layer is driven to a field nematic phase with a pulse of amplitude V ₁ >> V _C , and then a pulse τ _{2 of} amplitude V ₂ (slightly less than V _c ') is used to cause the liquid crystal layer to begin to develop a focal cone with a gradually increasing pitch. Configuration, and then use two or three step pulses with amplitudes V ₃ , V ₄ .... which are smaller but larger than V _A to make the liquid crystal layer directly transition from the "pseudo-field nematic phase" to the spiral axis orientation. -Dimensional ordered focal cone texture. Adjust the amplitude and duration of each step pulse to achieve fast conversion.

 The plane texture state and the focal cone texture state are both zero-field stable states. Because driving the plane texture state is faster than driving the focal cone texture state, when designing, first drive all the liquid crystals as pixels into focus. The cone texture state, and then progressive scanning drives the pixels to be converted into a plane texture state, so that the frame driving can be completed quickly.

4.Reduce the effects of scattering In fact, the cholesteric liquid crystal in the liquid crystal cell is composed of many crystal domains with a diameter of several micrometers to several tens of micrometers, especially in the focal cone texture state, the spiral axis orientation is usually two-dimensional disordered. The length parameter S> A, when the light is irradiated, Mie scattering occurs, which deviates the light from the original propagation direction, and depolarizes part of the polarized light into unpolarized light, which reduces the contrast and affects the display quality.

 In order to reduce the scattering and improve the contrast, for the plane texture state, the method of rubbing the upper and lower surfaces can be used to make the domains larger and reduce the scattering. For the focal cone texture state, the antiparallel orientation of the upper and lower surfaces is used and the most suitable pretilt angle is selected, including the pretilt angle that is parallel to one side and perpendicular to the other to make the domains larger and reduce scattering. In addition, changing the orientation of the spiral axis from a two-dimensional disorder to a substantially one-dimensional order, forming large domains, making the liquid crystal layer an ideal retarder, and reducing the effects of scattering.

 Compared with the prior art, the present invention has the following advantages:

 1. Since the present invention utilizes the electro-optical characteristics of cholesteric liquid crystal and nematic liquid crystal, and adopts a special driving method, the liquid crystal can be quickly switched between the plane texture state and the focal cone texture state, and the liquid crystal can also be driven. It is a focal cone texture state, and its light delay is controlled by an applied voltage. Therefore, the liquid crystal display provided by the present invention has a memory function represented by a zero-field steady state, is very power-saving, and has a fast response capability;

 2. Since the present invention can use a special driving method to make the liquid crystal always work in a one-dimensional ordered focal cone texture state, the light delay can be quickly changed by changing the applied voltage, so the response speed is much faster than TN .. STN liquid crystals Is sufficient for animation display, and by controlling the voltage, the light delay can be continuously changed between λ / 2 and 0 to generate different gray levels to achieve multi-gray level display;

 3. 'Since the response speed of the present invention is very fast, a time-series color scheme can be adopted, and only 1/3 of the pixels of an existing color liquid crystal display can be used to obtain the same definition, so 2/3 of the driving circuit is saved. , Eliminating the need for expensive color filters, reducing costs and improving light utilization;

 4. Since the display principle of the present invention uses light to display a bright state, but the light pass does not display a dark state to display an image, it is displayed in black and white under natural light and is used as an e-book, suitable for people's reading habits;

5. Since the present invention adopts technical measures to reduce the influence of scattering, the scattering is reduced, and the liquid crystal layer in the plane texture state is equivalent to a homogeneous medium, showing a good dark state in the entire spectral range, so the contrast ratio is relatively High

 6. The present invention is a principle invention. As long as ^^ and ^^> 1 are satisfied, an appropriate driving scheme can be selected according to the use requirements, with a polarizer, a retarder, a mirror, a backlight, an active matrix, etc. Designed as a reflective or transmissive display, a display that can be used day and night, a memory display, a full-color display, etc., and can have multiple functions on one display at the same time.

The picture says.

The invention is further described below with reference to the drawings and embodiments. Figure 1. DC photoelectric characteristic curve of cholesteric liquid crystal

 Figure 2.The driving pulse sequence of the present invention

 Figure 3.Driver step wave of the present invention

 Fig. 4. Reflective zero-field steady-state liquid crystal display of the present invention (two-dimensional disorder with spiral axis orientation) Fig. 5. Transmissive and reflective zero-field stable liquid crystal display of the present invention (two-dimensional disorder with spiral axis orientation) Fig. 6 1. The transmissive liquid crystal display of the present invention displaying a color animation (two-dimensional disorder of spiral axis orientation). FIG. 7. The reflective zero-field steady-state fast liquid crystal display of the present invention (spiral axis orientation-one-dimensional order). Invented reflective high-contrast zero-field steady-state display (spiral axis orientation-one-dimensional ordered) Figure 9. Transmissive and reflective zero-field steady-state liquid crystal display of the present invention (spiral-axis orientation--dimensional ordered) Fig. 10, The reflective fast liquid crystal display of the present invention (one-dimensional order of spiral axis orientation) Figure 1 1. The transmissive display of the present invention displaying a color animation (one-dimensional order of spiral axis orientation) Fig. 12. The color animation of the present invention display Transmissive display (one-dimensional order of spiral axis orientation)

 According to the orientation of the helix axis of the focal cone texture state, there are two-dimensional disorder and one-dimensional order in the plane. Two types of displays are designed.

 First, the spiral axis orientation is two-dimensional disordered in the plane

 The advantage of this type of display is that the alignment layer in the liquid crystal cell is easy to make and the driving waveform is simple; the disadvantage is that the scattering caused by the liquid crystal domain will reduce the image contrast and the structure of the liquid crystal cell is relatively complicated.

 1.1 Reflective Zero-Field Steady-State Liquid Crystal Display

Referring to FIG. 4, in this embodiment, there is a liquid crystal cell having a thickness of 3 micrometers. The liquid crystal cell is provided with two parallel transparent substrates above and below, and a transparent electrode made of a material such as IT0 is provided on the inner surface of the transparent substrate. An alignment layer with a pretilt angle is provided on the inner surface of the if electrode, and the function of the alignment layer is to make the surface liquid crystal layer have a certain orientation and a pretilt angle, and the pretilt angle is 6 °. A sealing ring is arranged around the liquid crystal cell, which is characterized in that: the liquid crystal cell is filled with biliary liquid crystal LC, and its spiral symmetry axis is substantially parallel to the liquid crystal cell substrate, and is distributed two-dimensionally in the plane of the liquid crystal cell substrate. The cholesteric liquid crystal domain in the cholesteric liquid crystal exhibits a uniform spiral texture and has the characteristics of a nematic liquid crystal domain, the pitch parameter of the cholesteric liquid crystal domain, the crystal domain length parameter S, and the light wavelength parameter, It is in accordance with the meanings of relationship 4 A and S>; the extraordinary light refractive index of the cholesteric liquid crystal domain " _e '= n _Q ; its ordinary light refractive index" _Q ' = (n ₀ + «e) 12; said A broadband λ / 4 retarder is provided on the outer surface of the upper substrate of the liquid crystal cell, and its optical retardation is λ / 4. A polarizer PZ is affixed to the other side of the λ / 4 retarder, and its polarization direction is parallel to the substrate of the liquid crystal cell. A reflector M made of aluminum or other materials is provided on the outside of the lower substrate of the liquid crystal cell. A driving voltage is applied to the liquid crystal cell to change the state of the cholesteric liquid crystal with nematic liquid crystal characteristics. Phenomenon light and dark states. The driving voltage described in this embodiment is a pulse voltage without a DC component. When the liquid crystal is driven into a plane texture state that has no effect on light: incident natural light passes through a polarizer and becomes linearly polarized light, and becomes circularly polarized light through a λ / 4 retarder. The change, after specular reflection, propagates upward. With respect to the direction of light propagation, the circularly polarized light reverses rotation, and then passes through the liquid crystal in a plane texture state. There is no change. After passing through the λ / 4 retarder, the circularly polarized light reverses rotation, and the outgoing polarized light and incoming polarized light are polarized. It is vertical and cannot pass through the polarizer and appears dark.

 When the liquid crystal is driven to a focal cone texture state that retards light by λ / 4: incident natural light passes through the polarizer and the / 4 retarder to become circularly polarized light, and the liquid crystal is delayed by the focal cone texture liquid crystal λ / 4, becomes linearly polarized light, and after specular reflection, it propagates upward. Then, the light is delayed by λ / 4 through the liquid crystal to become co-rotating circularly polarized light. After passing through the λ / 4 retarder, it becomes linearly polarized light. The polarization direction is the same as that of the polarizer, and the light passes through the polarizer and appears bright.

 Although the texture of this liquid crystal cell is simple, the two-dimensional disorder of the spiral axis orientation requires that the incident light and the reflected light must be in the same liquid crystal domain, which requires the liquid crystal domain to be large and the reflective surface to be close to the liquid crystal.

 1.2 Transflective, reflective zero-field steady-state LCD (see Figure 5)

 It consists of a polarizer PZ1, a λ / 4 retarder λ / 41, a liquid crystal LC, a λ / 4 retarder λ / 42, and a polarizer. The polarization directions of the polarizer PZ1 and the polarizer PZ2 are perpendicular to each other. The liquid crystal can drive a pair of light. Inactive planar texture, or a focal cone texture that is driven to retard light by λ / 2

 When the liquid crystal is driven into a plane texture state that has no effect on light: the incident natural light passes through the polarizer PZ1 and the λ / 4 retarder λ / 41 and becomes circularly polarized light. The liquid crystal in the plane texture state does not change. By entering the / 4 retarder λ / 42, since the optical axis of λ / 42 is perpendicular to the optical axis of λ / 41, their effects are cancelled out, and the outgoing light is still linearly polarized in the original polarization direction. The light passes through the polarizer PZ2, showing Bright state.

 When the liquid crystal is driven into a focal cone texture state that retards light by λ / 2: Natural light passes through the polarizer PZ1 and I / 4 retarder λ / 41 to become circularly polarized light. Textured liquid crystals become reversed circularly polarized light and pass through the λ / 4 retarder λ / 42. Because the optical axis of λ / 42 is perpendicular to the optical axis of λ / 41, their effects cancel out and become linearly polarized light. It is perpendicular to the polarization direction of the polarizing plate PZ2, and the light cannot pass through, and is in a dark state. '

 If the polarization direction of the polarizer PZ2 is changed to be perpendicular to the polarization direction of the polarizer PZ1, then when the light passes through the polarizer PZ2, the light from the plane texture cannot pass through, and the light is dark, and the light from the focal cone texture. Can pass, bright. Since the liquid crystal in the plane texture state is equivalent to a homogeneous medium, it has a good dark state in the entire spectral range, so the contrast is better.

If a reflector M is added under the polarizer PZ2, it becomes a reflective display; a transflective mirror and a backlight are used, and the reflective zero field steady-state display is used when the environment is bright to save power; it is turned on when the environment is dark With backlight, available day and night.

 1.3 Transmissive LCD with color animation (see Figure 6)

 It consists of a polarizing plate PZ1, a λ / 4 retarder λ / 41, a liquid crystal LC, a λ / 4 retarder λ / 42, and a polarizing plate PZ2. The polarization directions of the polarizing plate PZ1 and the polarizing plate PZ2 are perpendicular to each other. When the liquid crystal in the liquid crystal cell is in a cone-cone texture, the amount of light retardation changes with the applied voltage. When the power is not applied, the amount of light retardation is λ / 2. When the voltage is applied to close to the unwinding voltage, it starts to show nematic characteristics. The amount of optical retardation is close to zero.

 When power is applied, the liquid crystal in the liquid crystal cell begins to exhibit nematic characteristics, and the optical retardation is close to zero: the incident natural light passes through the polarizer PZ1 and the λ / 4 retarder λ / 41 and becomes circularly polarized light. The liquid crystal in the column phase has an optical retardation close to zero. After passing through the λ / 4 retarder λ / 42, it becomes linearly polarized light. The light does not pass through the polarizer PZ2, and no light is emitted, and it is in a dark state.

 When the power is not applied, the light retardation of the liquid crystal in the liquid crystal cell is λ / 2: the incident natural light passes through the polarizer PZ1 and the λ / 4 retarder λ / 41 and becomes circularly polarized light. The liquid crystal delays the light into / 2, and turns it into a circularly polarized light of reverse rotation, and passes through a λ / 4 retarder λ / 42. Because the optical axis of λ / 42 is perpendicular to the optical axis of λ / 41, their effects cancel each other out and become linearly polarized light, which is the same as the polarization direction of the polarizer PZ2, and the light passes through and appears bright.

 Since the liquid crystal works near the nematic phase and the focal cone texture state, the response speed is fast enough for animation display. In addition, by controlling the voltage, the delay amount can be continuously changed from λ / 2 to 0, and different gray levels can be generated to realize multi-gray level display. If three sets of red, green and blue light sources are irradiated in synchronization with red, green and blue images and driven by a TFT circuit, a color display can be made. Only 1/3 of the pixels of the existing color liquid crystal display can be obtained. Same clarity. Since two-thirds of the driving circuit is saved, and expensive color filters are eliminated, the cost is greatly reduced, and the light utilization ratio is greatly improved.

 If a reflector is added under the polarizer PZ2, it becomes a reflective display; if a transflective mirror and a backlight are added, it is used as a reflective zero-field steady-state display when the environment is bright and saves power; when the environment is dark, it is enabled Backlight, available day and night. In this way, using the same display not only has memory function, saves power, does not flicker, but also has fast response characteristics, and can see color animation.

 Second, the spiral axis orientation is one-dimensionally ordered in the plane

 The advantages of this type of display are the simple structure of the liquid crystal cell, which can form large domains, reduce scattering, and improve contrast. However, the surface of the liquid crystal cell needs to be anti-parallel aligned and a suitable pretilt angle selected, including selecting a pretilt angle that is parallel to the other side and perpendicular to the other. It is also necessary to design a special driving waveform to make the liquid crystal enter the one-dimensional ordered focal cone texture state quickly.

 2.1 Reflective Zero-Field Steady-State Fast LCD (see Figure 7)

Consists of a polarizer PZ, liquid crystal LC, and mirror M. The liquid crystal can be driven to have no effect on light. Planar texture state; or one-dimensional ordered focal cone texture state which drives light retardation λ / 4, and its spiral axis orientation is at an angle of 45 ° with the polarizer direction.

 When the liquid crystal is driven into a plane texture state that has no effect on light: the incident natural light passes through the polarizer and becomes linearly polarized light. It does not change through the liquid crystal layer in the plane texture state, and after mirror reflection, it propagates upward. After passing through the liquid crystal in a planar texture state, the light passes through the polarizer and remains bright. · '

 When the liquid crystal is driven into a one-dimensional ordered focal cone texture state that retards light by λ / 4, and its spiral axis orientation is at an angle of 45 ° with the polarizer direction: the incident natural light passes through the polarizer and becomes linearly polarized light, The retardation of the liquid crystal layer in the focal cone texture state by λ / 4 becomes circularly polarized light, which is specularly reflected and propagates upward. With respect to the direction of propagation, it becomes circularly circularly polarized light, and then passes through the liquid crystal retardation λ / 4 in the focal cone texture state, and becomes linearly polarized light with a polarization direction perpendicular to the polarization direction of the polarizer. It cannot pass through the polarizer and is in a dark state. .

 2.2 Reflective high-contrast zero-field steady-state LCD (see Figure 8)

 Consists of a polarizer PZ, a λ / 4 retarder, a liquid crystal LC, and a mirror M. The liquid crystal layer can be driven into a planar texture state that does not affect light; or a one-dimensional ordered focus that retards light by λ / 4 In the cone texture state, the orientation of the spiral axis is perpendicular to the optical axis of the λ / 4 retarder.

 When the liquid crystal is driven into a plane texture state that has no effect on light: the incident natural light passes through the polarizing plate PZ and becomes linearly polarized light. It passes through the liquid crystal LC and the λ / 4 retarder in a plane texture state before and after reflection It becomes linearly polarized light whose polarization direction is perpendicular to the paper surface, and cannot pass through the polarizing plate PZ, and appears dark.

 When the liquid crystal is driven in a one-dimensional ordered focal cone texture state that retards light λ / 4, and its spiral axis is oriented perpendicular to the optical axis of the retardation plate: linearly polarized light generated by the polarizer passes through In the focal cone texture state, the liquid crystal layer retards λ / 4. Since the spiral axis of the focal cone texture is perpendicular to the optical axis of the λ / 4 retarder, their retardation effects cancel out and have no effect on light. After reflection, the polarization direction does not change, and it can pass through the polarizing plate again to be bright.

 Since the plane texture state has no effect on light, a broad-spectrum λ / 4 retarder is used, and the dark state is better. Moreover, the one-dimensional ordered focal cone texture state has large liquid crystal domains and weak scattering, so the contrast is high.

 2.3 Transflective, reflective zero-field steady-state liquid crystal display (see Figure 9)

 It is composed of a polarizer PZ1, a liquid crystal LC, and a polarizer PZ2. The polarization directions of the polarizer P1 and the polarizer P2 are the same. The liquid crystal can be driven into a plane texture that does not affect light, or a one-dimensional ordered focal cone texture that delays light into / 2, and its spiral axis is at an angle of 45 ° to the polarization direction of polarizer P1 ,.

 When the liquid crystal is driven into a plane-textured state that has no effect on light: Incident natural light passes through the polarizer PZ1 and becomes linearly polarized light. After the plane-textured liquid-crystal has no effect on light, the polarization direction does not change. The polarizing plate PZ2 is bright.

When the liquid crystal is driven in a one-dimensional ordered focal cone texture state that retards light by λ / 2, and its spiral axis is at an angle of 45 ° with the polarization direction of the polarizer P1: the incident natural light passes through the polarizer PZ1 and becomes linearly polarized Light, The liquid crystal in a one-dimensional ordered focal cone texture state is delayed by λ / 2, and the polarization direction of the polarized light is rotated by 90 °, and cannot pass through the polarizing plate PZ2, and is in a dark state.

 If the polarizing direction of the polarizing plate PZ2 is perpendicular to the polarizing direction of the polarizing plate PZ1, the liquid crystal is dark when the plane texture is in the state, and the liquid crystal is bright when it is in the focal cone texture. The contrast is high because it is dark in the plane texture state.

 If a reflector is added under the polarizer PZ2, it becomes a reflective display; if a half-transmissive mirror and a backlight are added under the polarizer PZ2, it can be used as a zero-field steady-state display when the environment is bright, saving power; environment Backlight is enabled during dark, available day and night.

 2.4, reflective fast LCD (see Figure 10)

 Consists of polarizer PZ, liquid crystal LC, and mirror M. The liquid crystal always has a one-dimensional ordered focal cone texture. Its spiral axis is oriented at a 45 ° angle to the polarization direction of polarizer PZ. The response speed is faster than TN and STN. To display animation. When power is not applied, the retardation of the liquid crystal is λ / 2; when power is applied, the retardation of the liquid crystal is λ / 4 (right).

 When no power is applied, the retardation of the liquid crystal is λ / 2: natural light becomes linearly polarized light through the polarizer PZ, and is delayed by λ / 2 through the liquid crystal LC to become linearly polarized light whose polarization direction is perpendicular to the original polarization direction. After reflection, it passes through the liquid crystal LC, retards λ / 2, and becomes polarized light in the same polarization direction as the incident polarized light. It passes through the polarizer and appears bright.

At power-on, the retardation of the liquid crystal is λ / 4 _: natural light is converted to linearly polarized light by the polarizer PZ, and the light is delayed by λ / 4 through the liquid crystal LC to become circularly polarized light. After reflection by M, it passes through the liquid crystal LC. So that the light is delayed by λ / 4 and becomes polarized light perpendicular to the polarization direction of the incident polarized light, which cannot pass through the polarizer and is in a dark state.

 If a λ / 4 retarder is added between the polarizer PZ and the liquid crystal LC, its optical axis is at an angle of 45 ° to the polarization direction of the polarizer PZ, and at an angle of 90 ° to the direction of the spiral axis of the liquid crystal LC. The liquid crystal retards light by λ / 4 and appears in a dark state; when the power is not applied, the liquid crystal retards light by λ / 2 and appears in a bright state.

 2.5 Transmissive LCD with color animation (see Figure 11)

 It consists of a polarizing plate PZ1, a 3λ / 4 retarder, a liquid crystal LC, and a polarizing plate PZ2. The polarization directions of the two polarizers are the same. The optical axis of the 3λ / 4 retarder is 45 ° to the polarization direction, and the spiral axis direction is perpendicular to the optical axis direction of the retarder. When power is not applied, the liquid crystal delays light by 3λ / 4; when power is applied, the liquid crystal delays light by 1/4 in. Because the liquid crystal always works in a one-dimensional ordered focal cone texture, the response speed is faster than TN and STN. Can be used for animation and time-series full-color display.

When no power is applied, the liquid crystal retards the light by 3λ / 4: the light retardation (3λ / 4) of the one-dimensional ordered focal-cone-textured liquid crystal layer LC cancels the effect of the 3λ / 4 retarder, and the light passes through the polarizer P2 Is bright. When power is applied, the liquid crystal delays the light by 1 / 4λ: the light delay of the dimensional ordered focal cone-shaped liquid crystal LC is λ / 4, and the total effect with the 3 / 4λ retardation sheet is equivalent to the light delay λ / 2, polarization The polarization direction of the light was changed by 90 °, and the light could not pass through the polarizer P2 and appeared in a dark state.

 If the polarization directions of the polarizer PZ1 and the polarizer PZ2 are made perpendicular, the liquid crystal retards the light by 3λ / 4 and becomes dark when the power is not applied. When the power is applied, the liquid crystal retards the light by λ / 4 and becomes the bright state.

 If a reflector is added under the polarizer PZ2, it becomes a reflective display; if a half mirror and a backlight are added, it can be made to be a display that can be used day and night; if the backlight is illuminated in red, green and blue in turn Synchronized with red, green, and blue images, a time-series full-color display capable of displaying animation can be made.

 2. 6 Transmissive LCD with color animation (see Figure 12)

 The liquid crystal always works in a one-dimensional ordered focal cone texture state. When the liquid crystal is not powered, the light delay of the liquid crystal is λ / 2. When the liquid crystal is powered, the liquid crystal is approximately a field nematic phase, and the light delay is close to 0. Into a fast-response display; if two sets of programmed step-wave drive voltages (see Figures 2 and 3) are added to this textured liquid crystal, and equipped with red, green, and blue light sources, they can be used for zero The field-stable display saves power and can be used for sequential full-color animation display.

Claims

Rights request 1. A bile-phase liquid crystal display with nematic characteristics, which has a liquid crystal cell. The liquid crystal cell is provided with two parallel transparent substrates on the top and bottom. The transparent substrate is provided with a transparent electrode on the inner surface, and the inner surface of the transparent electrode is provided. An alignment layer with a pretilt angle is provided, and a seal ring is provided around the liquid crystal cell, which is characterized in that: the liquid crystal cell is filled with a cholesteric liquid crystal, and the cholesteric liquid crystal domain in the cholesteric liquid crystal is expressed as Uniform spiral texture with nematic liquid crystal domain characteristics, the pitch parameter of the cholesteric liquid crystal domain ^, the crystal domain length parameter S, and the wavelength of the light wave ^, which are in accordance with the relationship of the formula / 4 1 and> A _; the cholesterol The extraordinary light refractive index of the liquid crystal domain of the phase " _e '= n ₀ ; its ordinary light refractive index = C n _Q + n _e ) 12; a retardation plate and a polarizing plate are provided on the outer surface of the upper substrate of said liquid crystal cell, The outer surface of the lower substrate of the liquid crystal cell is provided with a mirror, and a driving voltage is applied to the liquid crystal cell to change a bile phase liquid crystal having a nematic liquid crystal characteristic to a light state and a dark state of the pixel.  2. The cholesteric liquid crystal display according to claim 1, characterized in that: the alignment layer of the liquid crystal cell is an anti-parallel alignment layer, or an alignment layer having a parallel surface and a vertical surface, and the thickness of the liquid crystal cell is 0.5 to 1.0. Micrometer, the pitch of the cholesteric liquid crystal domain is less than 3 micrometers, a zero-field stable one-dimensional oriented focal cone texture can be obtained, and the helical symmetry axis of the cholesteric liquid crystal domain is perpendicular to the orientation layer direction, which is equivalent to incident light For delay films.  3. The cholesteric liquid crystal display according to claim 1, characterized in that: a polarizer is provided on the outer surface of the upper substrate of the liquid crystal cell, and a reflector is provided on the outer surface of the lower substrate of the liquid crystal cell. Step wave pulse voltage drives the bile-phase liquid crystal into a plane texture state that does not work with light, or drives one-dimensionally to retard light λ / 4, the orientation of the spiral axis and the polarization direction of the polarizer at an angle of 45 ° The ordered focal cone texture state constitutes a reflective zero-field steady-state fast liquid crystal display.  4. The cholesteric liquid crystal display according to claim 1, wherein: a polarizer is provided on the outer surface of the upper substrate of the liquid crystal cell, and a reflector is provided on the outer surface of the lower substrate of the liquid crystal cell; Steroid liquid crystals always work in a one-dimensional ordered focal cone texture. Its spiral axis orientation is at an angle of 45 ° to the polarization direction of the polarizer. The optical delay is λ / 2 when no driving voltage is applied. 4, constitute a reflective fast liquid crystal display. 5. The cholesteric liquid crystal display according to claim 1, wherein: a 3 λ / 4 retarder is disposed on an outer surface of the upper substrate of the liquid crystal cell, and a polarizer is disposed on the retarder, A polarizer is provided on the outer surface of the lower substrate of the liquid crystal cell. The polarization directions of the two polarizers are the same. The optical axis of the retarder and the polarization direction of the polarizer are at an angle of 45 °. The cholesteric liquid crystal always works at The one-dimensional ordered focal cone texture has a spiral axis direction that is perpendicular to the direction of the optical axis of the retarder. When no driving voltage is applied, the optical delay is 3 λ / 4, and when a driving voltage is applied, the optical delay is λ / 4. Steroid liquid crystal always works With a one-dimensional ordered focal cone texture, the light delay can continuously change with the driving voltage, presenting multi-level grayscale, and the response speed is fast. It can be used for animation and time-series full-color display. If the polarization directions of the two polarizers are perpendicular to each other, the display image is inverted, that is, the light state and the dark state are interchanged.  6. The cholesteric liquid crystal display according to claim 1, characterized in that: an outer surface of the upper substrate of the liquid crystal cell is provided with a λ / 4 retarder, and a polarizer is disposed on the retarder, and The outer surface of the lower substrate of the liquid crystal cell is provided with a reflecting mirror, and the lambda value is 550 nanometers, which ensures that incident light and reflected light pass through the same focal cone domain. The cholesteric liquid crystal can be driven into a planar texture state that does not affect light, or a two-dimensional disordered focal cone texture state that retards light by λ / 4 to form a reflective zero-field steady-state liquid crystal display. .  7. The cholesteric liquid crystal display according to claim 1, wherein a polarizer is provided on each of the outer surfaces of the upper and lower substrates of the liquid crystal cell, and the polarizing directions of the two polarizers are the same, and the cholesteric phase When the liquid crystal is in a focal cone texture state, the light retardation is λ / 2, and the λ value is 550 nm. The cholesteric liquid crystal can be driven into a planar texture state that does not affect light, or can be driven so that A one-dimensional ordered focal cone texture with a light retardation of λ / 2, the spiral axis of which is at an angle of 45 ° with the polarization direction of the polarizer, thereby forming a transmission-type zero-field steady-state liquid crystal display; When driven into a field nematic phase, the light delay is close to zero, which has no effect on light and has a faster response speed. When two sets of program step wave driving voltages are applied to the liquid crystal at the same time, they are matched with red, The green and blue three-color light source, the display can be used for both zero-field steady-state display and time-series full-color animation display. When the applied electric field causes the optical delay of the focal cone domain to continuously change between / 2 and 0 Can realize multi-gray scale display .  8. The cholesteric liquid crystal display according to claim 1, characterized in that: an external surface of each of the upper and lower substrates of the liquid crystal cell is provided with a λ / 4 retarder, and each of the other surfaces of the retarder is provided with One polarizer, the polarization directions of the two polarizers are the same, the optical axes of the two retarders are perpendicular to each other, and the light retardation when the cholesteric liquid crystal is in a focal cone texture state is λ / 2, and the λ value is 550 nanometers, the cholesteric liquid crystal can be driven into a planar texture state that has no effect on light, or can be driven into a focal cone texture state that retards light by λ / 2, thereby constituting a transmissive zero-field steady-state liquid crystal Display; when a reflector is provided under the lower polarizer, it becomes a reflective display; when a transflective mirror and a backlight are provided under the lower polarizer, a transmissive and reflective type can be formed Zero-field steady-state LCD. 9. The liquid crystal display according to claim 8, characterized in that: when the liquid crystal layer of the liquid crystal display is in a cone-cone texture state, the amount of light retardation changes with the applied voltage, and when the applied voltage is close to the unwinding voltage, it starts to appear. The characteristic of nematic phase is that the amount of optical retardation is close to zero. Since the liquid crystal works near the nematic phase and the focal cone texture state, the response speed is very fast. The retardation can be controlled to be in the range of / 2 to 0 by controlling the voltage. Change to achieve multi-grayscale display; if three sets of red, green and blue light sources are used to synchronize with red, green and blue images In turn, combined with the active matrix, a transmissive liquid crystal display capable of displaying color animation can be made. 10. The cholesteric liquid crystal display according to claim 1, wherein: the driving voltage has two groups; one is a program pulse voltage for driving the cholesteric liquid crystal into a two-dimensional disordered focal cone texture state: first A pulse voltage with a pulse width much larger than the untwisting voltage and a pulse width of less than 5ms is added. At the end of the pulse width, the cholesteric liquid crystal is driven to the field nematic phase in a planar texture state, and then a pulse width smaller than the untwisting voltage is added. The pulse voltage with a slightly wider pulse width makes the bile phase liquid crystal in a two-dimensional disordered focal cone texture. Adjusting the voltage and pulse width can achieve fast conversion; the other group is to drive the bile phase liquid crystal into one-dimensional order. The program step pulse pulse voltage of the focal cone texture state: First, a step pulse pulse voltage with an amplitude greater than the untwisting voltage and a pulse width less than 5 ms is added. At the end of the pulse width, the cholesteric liquid crystal enters the field nematic phase, and then the amplitude is added. Slightly smaller than the minimum voltage that can maintain the pseudo-field nematic phase, and the pulse width is appropriate. At the end of the pulse width, the cholesteric liquid crystal part enters the one-dimensional distortion zoom cone texture, and then add one or two. Narrow pulse staircase wave pulse voltage, it quickly enters a focal conic texture dimensional ordered state.