JPH02503360A - ferroelectric liquid crystal device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] ferroelectric liquid crystal device The present invention relates to light transmission or light reflection systems using liquid crystal materials. .

A liquid crystal "screen" that can be selectively and electrically switched to transmit, reflect, or absorb light. 'Chatta' has many different uses.

Current clock and calculator display boards are common examples of the use of this type of shutter [ In G. J. Sprockel (ed.), Physics and Chemistry of Liquid Crystal Devices, Plenum Press. (1980)]. These devices use transparent electrodes to apply an electric field to the liquid crystal. The addition changes the orientation in the region between these electrodes.

This change in orientation results in a change in light appearance, which in turn This contrasts with the end switching area. Electrodes are generally on glass or plastic substrates. The two pieces, together with the liquid crystal sandwiched between them, form a device or forms a shutter. The most common forms of this type of equipment are polarizers and Twisted nematic display observing optical changes using an analyzer (Twisted Nematic Display). The following In other applications, two such devices are placed in front of each other and they are alternated. By switching to , a three-dimensional effect is produced for the user.

The principle of this type of device is summarized in British Patent No. 1,448,520.

Devices such as those described above incorporate liquid crystal materials in a "twisted" nematic phase. is known. These devices are known to have a relatively slow response, about 10 mm. It is not possible to switch from one state to another state faster than seconds.

It is an object of the present invention to provide a liquid crystal display that can be switched using convenient low voltages in less than 1 millisecond. The aim is to provide "shutter". Under suitable conditions, this time can be as short as 10 μs. It can be shortened by .

According to the invention, the A liquid that incorporates a ferroelectric liquid crystal phase that can be manipulated to transmit, reflect, or absorb light. A crystal device is provided.

The invention will now be described by way of example only with reference to the accompanying drawings, in which: FIG.

FIG. 1 is a cross-sectional view of a liquid crystal device made according to the present invention, and FIG. 2 is a non-light-transmitting 2 is a schematic diagram showing the molecular alignment of a liquid crystal material in the state, FIG. 3 is a similar drawing opened in a transparent state, and FIGS. 4.4a and 4b show the present invention. Single polarizer guest-host strong in absorption mode created according to is a schematic diagram of a dielectric device; Figure 5 shows the light transmission characteristics of the absorption mode single polarizer device shown in Figure 4. Figures 6a and 6b are graphs showing a polara made according to the present invention. 1 is a schematic diagram of a double guest-host ferroelectric device in absorption mode without an iser, Figures 78 and 7b show a single fluorescent mode structure made in accordance with the present invention. is a schematic diagram of a polarizer guest-host ferroelectric device; Figure 8 shows the light transmission characteristics of the fluorescence mode single polarizer device shown in Figure 7. Figures 98 and 9b are graphs showing a 1 is a schematic diagram of a guest-host ferroelectric device in fluorescence mode without an analyzer;

Figures 108 and 10b do not have polarizers made according to the invention. Abbreviation for double guest-host ferroelectric device that combines absorption and fluorescence modes. 11a to 11c are suitable polarizers made according to the present invention. 1 is a schematic diagram of a guest-host ferroelectric device in fluorescence or absorption mode with a ferroelectric device.

For example, chiral smectic C phase (Chiral SmeCtiCCphas Forming a rapid optical shutter using a material exhibiting a ferroelectric liquid crystal phase such as . Pulsed DC signals using low electric fields such as 20 volts per # or less. When driven by the signal, the device changes from the light transmitting state to the light absorbing state or from the light absorbing state. The speed at which the light emission state changes as described below is less than 1 millisecond, so This type of shutter can be powered using a simple battery pack.

Then, using this type of equipment, clock display boards and computer graphics Dotsutoma is an α-numeric suitable for a range of applications from small to large-area information panels. displaying visual information in the form of tricks, mean patterns or other forms; Can be done. Two shutter devices of this type operating in one of several absorption modes can be used together. Combined with a pair of glasses so that each device blocks one eye and is driven out of phase By observing suitable video images through two devices of this type, the switching speed is Cut between video frames to the extent that a three-dimensional image can be seen by the viewer without licker. The speed is such that a change occurs.

Can be created between two glass sheets 10 in a cell and connected to a power source Incorporating a transparent electrode for the purpose and providing an alignment layer 10 or grating surface to which the molecular atoms can be attached. The alignment can be coated. These layers glassen the smectic surface. vertically to the substrate, and these layers can be used to The average planar alignment direction can be adjusted. A ferroelectric liquid crystal is included between the glass layers 10. The medium 11 is placed and the entire system is placed between orthogonal polarizers 12 and 13. can be placed. A suitable spacing material is provided in the device to provide a defined liquid crystal media thickness @ can be maintained. In a simple transparent shutter device, the appropriate layer 14 is covered. producing a colored image or effect by using it as a color filter Alternatively, if this shutter is used for reflection or transmission-reflection, this layer has a high reflection. Provides radioactively colored or black or white or fluorescent surfaces for improved optical performance. Provides trust and/or brightness. Consisting of species single or zero polara In the analyzer device, as indicated by reference numeral 14, there is a The layer 14 can also be provided within a glass substrate.

The transmission of light through the cell is due to the molecular alignment in the liquid crystal material being one of the polarizer directions. This occurs in a birefringent mode that is not parallel to the If the molecule faces one of the polarizer directions When they become parallel, absorption of light occurs. Switching between these modes is , occurs in less than 1 ms upon application of a voltage pulse of less than 20 volts. Birefringence mode The maximum transmission at is when the molecules are switched at an angle of 45° to the polarizer direction. obtained in case.

To optimize the contrast ratio between absorption and transmission, use a suitable black, tinted or Fluorescent dyes can also be dissolved in the liquid crystal material.

A single polarizer device can be used as a shutter. this kind of In the arrangement, the absorption moment of the dye dissolved or included in the liquid-crystalline medium is Cooperatively align against a static polarizer via liquid crystal alignment. Figure 4a is Figure 4b shows the light absorption state in which the dye molecules are aligned with the polarizer direction, while Figure 4b shows the polarizer direction. It shows a non-absorbing state with molecular alignment perpendicular to the isa direction. Dye absorption mode The angle θ between the lens and the polarizer direction defines the degree of light transmission. This is the fifth The graph in the figure shows the angle θ with respect to the transmitted intensity.

In this guest-host arrangement, many of the limitations inherent in birefringent devices are overcome. Ru. For example, optics based on slight misalignment of ferroelectric domains or variations in sample thickness Defects are much less likely to appear. For example, a single polarizer arrangement like this For smell, contrast/1 degree ratio, LCD to polarizer in "off" state. It can be adjusted by manipulating the angle.

The theoretical maximum contrast and brightness is observed at θ = 9o°, but Changes in the iser angle are allowed at θ much smaller than this and typically around 45°. Provide acceptable contrast.

In other embodiments, both polarizers can be omitted and the absorbing guest-host A shutter with two superimposed "layers" of ferroelectric material that operates in a static relationship (described above) Create one of the layers to effectively replace a static polarizer. Figure 6a shows “o ffJ state, while Figure 6b shows the "On" or transparent state. . In this arrangement, the shutter switching is performed using the same liquid crystal material in the device, which also avoids birefringence. In fact, it can be more than twice as fast as a single polarizer cell. Because , each dye cell only needs to be rotated by about half a rotation for uniform optical contrast. It is. With this shutter arrangement, the maximum theoretical brightness and contrast is θ is 45° in opposite directions for two superimposed “layers” to create a single polarity of 90°. Obtained when applying equal total angles to the iser device.

In other embodiments, the light-absorbing dye can be fluorescent or luminescent. . For a single polarizer, the maximum absorption and intensity are This is obtained when the curve is parallel to the isa direction (Fig. 7a). The light thus absorbed is re-emitted at a different wavelength in the "on" state (Figure 7a). "off" state , the absorbed light and therefore the re-emitted fluorescent or luminescent light is reduced. , leaving only the transmitted low-intensity afterglow. Thus the optical contrast between the two states occurs, and the transmission characteristics are shown in the graph of FIG. By rotating the incident polarizer, The light levels of the two states can be reversed. colored polarizer or incident light Filters can be used to obtain different optical contrasts. For example, fireflies A filter of a different color than the photodye is used to form a switchable dichroic device. this Depending on the embodiment, e.g. direct sunlight or transmitted light with suitable background illumination. It can produce bright reflected light on the display.

In his example, a single-layer fluorescent guest-host device is created without a polarizer. It is also possible to do so (Figure 9). In this case, the incident light is directed along the layer direction (not through) In the “off” state (Figure 9a), the incident light is mainly absorbed by the absorption moment. Thus, little or no absorption occurs (Figure 9a). “O In the n' state, the dye rotates so that the direction of the incident light and absorption moment is no longer zero. and significant absorption and subsequent fluorescence can occur (Figure 9b). This example In this case, a contrast filter is used on the background as described above. Contrast is obtained (layer 14 in Figure 1). In this mode, It is also possible to match the “on” state to strong absorption and fluorescence due to the precession of the dye absorption axis with respect to the friction direction. do. Thus, the application of an electric field produces an "offJ" state, or Generate an intermediate “On” state as in Figure 9b to generate different light between the three states. can provide contrast.

Another embodiment of the present invention (FIG. 10) includes an absorption mode that does not include a polarizer. using the guest-host device, switch the light to the guest-host device in fluorescence mode. can be done.

[In the offJ state (Fig. 10a), the absorption direction of the "light-absorbing" first cell and The absorption direction of the second or fluorescent cell is parallel, resulting in a dark or tinged state. bring. In the "On" state (Fig. 10b), between the two absorption moments The angle is not O but 90°, resulting in a bright fluorescent state.

As in the double absorption mode device (Figure 6) no polarizer is required; Optimal light levels occur for each cell moving at 45°. The response time is at least can also be at least twice as fast as opening each guest-host device individually. Wear.

In a further embodiment of the invention (FIG. 11), different surface alignments agents can be used to provide "homeotropic" alignment. this place In this case, the smectic plane is parallel to the substrate. The precise screws required in this case The rotational pitch directs the molecules into a helix in the direction of propagation of the incident light. The dye contained is absorbed. If optical, the device appears dark due to absorption of unpolarized incident light. Contains fluorescent dye The device appears brighter due to the absorption/re-emission process described above. cell flat Applying an electric field along the plane (i.e. in the lateral direction) and between the inner and outer substrates If the electrodes are placed at , the dyes will realign to reduce absorption or fluorescence. Po If a polarizer is provided and aligned with the dye absorption direction, the polarizer direction can be defined. By doing so, the contrast can be optimized in either case. This implementation In examples, the apparatus may be used in transmission or reflection as described above, or with colored filters. Alternatively, it can be used with a colored polarizer. For other types of uses If the electrode arrangement of Figure 1 is used with the alignment described in this example, can be done.

In the various embodiments described above, the frequency of various switching states is changed within the cumulative time of the eye. By this, an optical gray scale can be produced. Thus, the dark state can be sensed more frequently than in the bright state, producing an intermediate gray color.

By simply varying the ratio of "on" and "off" times, grayscale The intensity changes. If the "OnJ" and "offJ" states have different colors, the color shading and complex colors using various primary colored filters, dyes or colored polarizers. , also in this case, it can be obtained by changing the time ratio between "on" and "off".

In this way, the entire color spectrum can be produced.

Switching speed, low drive voltage or high absorption contrast depending on liquid crystal composition and dye selection The device can be optimized according to operational requirements that prioritize the contrast ratio. These essentials Considering the above, any known ferroelectric liquid crystal phase can be used (e.g. Sc *, SL, J*, SG*, etc.).

*S The components of the liquid crystal mixture can have more than one function. For example, liquid crystal material The dye can be a dye, i.e. a ferroelectric dye, or the dye can be a natural color. A chiral phase can also be induced by this. These components have low molecular weight or high It can be a molecule. In the case of polymer liquid crystals, one of two or more functions It can be included in polymer molecules.

The dye can be dichroic, pleochroic, fluorescent or optically non-linear. Bicolor In the case of polychromatic or pleochroic dyes, they can absorb any color or combination of colors and produce a single color. It can appear as a color, multicolored or black.

Ferroelectric liquid crystals are made of a polymer or glass matrix placed between electrodes and a substrate. can be microencapsulated or dispersed within the voids of the customary using microencapsulation or dispersion techniques or photo-knitting of suitable polymers. can create these voids. Microencapsulation or dispersion If , the void can be shaped to produce a favorable alignment. Ru. In the case of photo-knitting methods, surface matching techniques known to those skilled in the art may be used. can. The glass substrate on which the electrodes are placed can equally be made of plastic; It can also be colored. In this way, lightweight and flexible displays can also be created. or create a shutter. In the case of embodiments with polarizers, forced One or both of the substrates containing the electrical material can be a polarizer.

For roughly three-dimensional viewing, the shutter can be used with standard plastic or glass glasses. It can be provided in the form of The support matrix can be equipped with special optics as required. It can be preformed or molded. For three-dimensional image applications, or In other embodiments, to switch the shutter so that the observer has a normal field of view There are two possibilities. First, the pitch of the chiral smectic C phase is When used in a bistable configuration that is larger than the thickness of the liquid crystal phase, a shutter glass is used. by simply switching both shutters to the transparent state and removing the drive voltage. A conventional image can be observed.

Alternatively, if the shutter glass is used in a non-bistable configuration, The relaxation of the molecules is moderated by leaving the driving voltage on both cells or removing the voltage from both cells. A conventional field of view is obtained by providing an intermediate state through which a permissible amount of light is transmitted. can be done. The liquid crystal shutter created in this way can be used for video displays. The infrared pulse from the unit is synchronized with the switching of the drive pulse. It can be used for. Alternatively, the synchronization may be electronic, optical, or by other means. It can also be achieved in stages.

By using suitable electrode patterns and materials, the video image itself can be transferred to the viewer. can be projected directly onto glasses.

In this case, synchronization is via infrared signals from the raster on the blank screen or Alternatively, it can be performed electronically or optically. In this kind of arrangement, the observed The images produced can be unique for each of many observers, even if they are all in the same room. Several people can watch different 3D video programs.

For display applications, e.g. alphanumeric, dot matrix and Conventional electrode arrangements, such as the pattern Can be used for either. Therefore, the display is flexible and lightweight. can be done. These are high speed applications in the automotive, aviation, maritime and space industries. It has many applications where light weight is important.

These shutters are designed with pattern recognition fiberglass and laser cavities and non- Rapid electro-optical with application in rQJ switching devices of linear optics It can equally be used as an optical moshulator.

Although the present invention has been described above with reference to Examples, the present invention is not limited to the above-mentioned Examples. It will be appreciated by those skilled in the art that many modifications may be made without departing from the scope of the invention. It will be.

A wide variety of ferroelectric liquid crystals were tested for use in the guest-host device. for Typical ferroelectric host materials are chiral fluoroesters, phenylpyryls, among others. It was based on midine and phenylpyridine. Pyridine and anthracite chiral 6 and non-chiral dyes based on azo dyes and anthraquinone dyes. The mixture was used to create colored and black dye compositions. fluorescent pyridine Similar to the materials, dinitrostilbene was also used in the fabrication of the device. These structures are Without implying any limitation, any material exhibiting the above ferroelectric phase and optical effects is suitable. However, when an electric field is applied, the direction of absorption or the direction of absorption and emission changes. shall be taken as a thing.

Copy and translation of written amendment) Submission form (Article 184-8 of the Patent Act) 1. Display of patent application PCT/GB88100320 2. Name of the invention t″i1M　M′σ 3. Patent applicant Address: UK, M139BL, Manchester, Oxford Row (no address) Name: The Victory University of Manchester - (Nationality) (UK) 4. Agent 6. List of attached documents (1) Copy of amendment R translation) 1 supplementary copy 　　　　　　　　　　　request　　　　　　　　　　　　　1　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　Equipped with ferroelectric liquid crystal material Polymers are also used in liquid crystal devices that can be operated to selectively transmit or absorb light. or a chiral smectic compound in the form of a polymeric compound. crystal device.

2. The chiral smectic has a low molecular weight with the polymer or high molecular compound 2. The liquid crystal device according to claim 1, wherein the liquid crystal device is composed of a mixture with a substance.

3. The ferroelectric liquid crystal material contains at least one fluorescent dye or luminescent dye. A liquid crystal device according to claim 1 or 2.

4. The ferroelectric liquid crystal material is composed of at least one kind of fluorescent dye or luminescent dye. A liquid crystal device according to claim 1.

5. The ferroelectric liquid crystal material contains at least one contrast-optimizing dye. A liquid crystal device according to claim 1.

6. When the device changes from light transmitting state to light absorbing state or vice versa, 20 volts per # Claim 1, which changes in a time of less than 1 millisecond when a driving electric field of less than or equal to The liquid crystal device described.

7. A ferroelectric material is placed between two sheets of substrate material, and at least one of the sheets is Claim 1, wherein the electrode is transparent and includes an electrode for connection to a power source. LCD device.

8. Coating the substrate with an alignment layer or grating surface to produce molecular alignment. A liquid crystal device according to claim 7.

9. The liquid crystal device according to claim 1, comprising a polarizer in the optical path.

10. Equipped with a colored filter or colored reflective or transmissive-reflective surface in the optical path. According to claim 1, the method further produces or enhances a colored image or effect. liquid crystal device.

11. The liquid crystal device according to claim 3, wherein the dye is dichroic or pleochroic. Place.

12. It is equipped with a single polarizer and uses light-absorbing dye as a ferroelectric material. 2. The liquid crystal device according to claim 1, wherein the liquid crystal device is provided inside a ferroelectric material or a ferroelectric material.

13. 2 of ferroelectric materials that operate in a light-absorbing guest-host relationship without a polarizer This arrangement has two superimposed layers compared to a single material layer in combination with a static polarizer. 2. A liquid crystal device as claimed in claim 1, which provides a faster switching speed.

14. Ferroelectric material containing fluorescent dye and superimposed single polarizer 1 with two layers arranged parallel to the incident polarizer direction for maximum absorption and intensity. The misalignment of the dye molecules with respect to the polarizer direction is The liquid crystal device according to claim 1, characterized by absorption and re-emission of light.

15. Two ferroelectric materials that operate in light-absorbing and fluorescent guest-host relationships, respectively. With superimposed layers, a material that operates in absorption mode can operate in fluorescence mode due to molecular alignment. Claim 1 which acts to switch the material between light absorbing and non-light absorbing. liquid crystal device.

16. With a single layer of fluorescent guest-host device, along the plane of the layer ( 2. The liquid crystal device according to claim 1, wherein the liquid crystal device receives input light that is incident thereon without passing through the liquid crystal device.

17. A horizontal plate placed between and cooperating with two substrates, at least one of which is transparent. along the plane of the device encapsulating the ferroelectric material (without passing through it). ) The liquid crystal device according to claim 1, wherein an electric field is applied.

18. Equipped with a means to adjust the frequency of the applied alternating electric field within the cumulative time of the eye, 2. The liquid crystal device according to claim 1, wherein the liquid crystal device is capable of forming a color and a gray scale.

19. The liquid crystal device according to claim 1, wherein the ferroelectric material is microencapsulated.

20. The ferroelectric material is a polymer or glass matrix placed between a pair of electrodes. 2. The liquid crystal device according to claim 1, wherein the liquid crystal device is dispersed in voids in a liquid crystal display.

21. Claim 20, wherein the void has a shape that produces suitable alignment. The liquid crystal device described.

22. Two devices are provided as a pair of glasses worn by the observer, and these two devices are Equipped with a means for producing a three-dimensional effect by alternately switching between different devices, this effect can be roughly achieved. The claim is that the device is equipped with a means for switching the device to remove the The liquid crystal device according to scope 1.

23. Ferroelectric materials can be selectively operated at normal ambient or other temperature levels. A liquid crystal device according to claim 1.

international search report 111--＾eye-mm, PCT/GB 88100320 International Search Report GB 8800320 S^　　　22034

Claims (22)

[Claims] 1. Ferroelectric liquid crystals exhibited by low molecular weight or high molecular weight compounds or mixtures thereof can be manipulated to selectively transmit or absorb light characterized by the incorporation of a phase liquid crystal device. 2. The liquid crystal according to claim 1, wherein the ferroelectric phase is a chiral smectic phase. Device. 3. 20 volts per μm when the device goes from a light transmitting state to a light absorbing state and vice versa. Claims that change in time less than 1 millisecond when applied with a driving field of less than or equal to The liquid crystal device according to item 1 or 2. 4. A ferroelectric material is disposed between two sheets of substrate material, and at least one of the sheets Claims 1 to 3 are transparent and include electrodes for connection to a power source. The liquid crystal device according to any one of Item 3. 5. The substrate is coated with an alignment layer or grating surface to create molecular alignment. 5. A liquid crystal device according to claim 4. 6. A polarizer is provided in the optical path according to any one of claims 1 to 5. liquid crystal device. 7. with a colored filter or colored reflective or transmissive-reflective surface in the optical path; Claims 1 to 6 which produce or enhance a colored image or effect. The liquid crystal device according to any one of the items. 8. Claim 1, wherein the ferroelectric material is composed of or contains a dye. 7. The liquid crystal device according to any one of items 7 to 7. 9. 9. The liquid crystal device according to claim 8, wherein the dye is dichroic or pleochroic. 10. 9. The liquid crystal device according to claim 8, wherein the dye is fluorescent or luminescent. . 11. In addition to having a single polarizer, it also uses light-absorbing dye as a ferroelectric material. The liquid according to any one of claims 1 to 9, which is contained inside the ferroelectric material. crystal device. 12. Two ferroelectric materials that operate in a light-absorbing guest-host relationship without a polarizer with superimposed layers of According to any one of claims 1 to 9, which provides an even faster switching speed. liquid crystal device. 13. A type of ferroelectric material that contains fluorescent dye and has a single polarizer superimposed on it. layers arranged parallel to the incident polarizer direction for maximum absorption and intensity. The misalignment of the dye molecules with respect to the polarizer direction is shown by the absorption direction. According to any one of claims 1 to 8, the method minimizes the absorption and re-release of LCD device. 14. Two types of ferroelectric materials that operate in light-absorbing and fluorescent guest-host relationships, respectively. With superimposed layers, a material that operates in absorption mode can operate in fluorescence mode due to molecular alignment. Claims 1 to 5 act to switch the material between light absorbing and non-light absorbing. Or the liquid crystal device according to any one of Item 7. 15. A single layer of fluorescent guest-host devices is provided along the plane of the layer. Claims 1 to 5 or 7 which accept incident input light The liquid crystal device according to any one of the items. 16. A lateral direction that is arranged and cooperates between two substrates, at least one of which is transparent. along the plane of a device that uses electrodes and encapsulates ferroelectric material. 2. The liquid crystal device according to claim 1, wherein an electric field is applied. 17. Different Any one of claims 1 to 16 that can form a color and a gray scale. The liquid crystal device according to item 1. 18. Any one of claims 1 to 17, wherein the ferroelectric material is microencapsulated. The liquid crystal device according to item (1). 19. The ferroelectric material is a polymer or glass matrix placed between a pair of electrodes. Claims 1 to 18 dispersed within the voids in the The liquid crystal device described. 20. Claim 19, wherein the void has a shape that produces suitable alignment. The liquid crystal device described. 21. The two devices are provided as a pair of glasses worn by the observer, and It is equipped with a means for producing a three-dimensional effect by alternately switching the devices, and furthermore, Claims comprising means for switching the device to remove and return to normal visual field. The liquid crystal device according to any one of items 1 to 20. 22. Ferroelectric materials may operate selectively at normal ambient or other temperature levels. A liquid crystal device according to any one of claims 1 to 21.