FI89311B - SPRIDNING CONDITIONING AND ENCLOSURE INK CAPS CRYSTALS - Google Patents

Description

! 8 9 31Ί

This invention relates generally to liquid crystal technology, and more particularly to a liquid crystal device, a liquid crystal structure and their use, and a method of displaying bright marks or the like against a dark background using a liquid crystal material located in the enclosure. The invention further relates to the use of such scattering in a liquid crystal display device to form a white or bright mark and in optical shutter devices, for example brightness control, to improve the light output / contrast of a liquid crystal device, especially in a type using an encapsulated liquid crystal or a liquid crystal material. for manufacture and use.

The invention also relates, in another embodiment, to the use of a pleochromatic dye in a liquid crystal to absorb light entering it, and to similar methods for making and using such liquid crystals.

Liquid crystal material is now used in many different devices, such as optical devices as display terminals. One property of liquid crystals that allows their use in display terminals is the ability to scatter and / or absorb (especially if a pleochro dye is mixed with the liquid crystal) light when the liquid crystals are randomly oriented, and the ability to transmit light when the liquid crystals are sequentially oriented.

A display terminal that uses liquid crystals often shows dark marks on a gray or relatively light background. However, in many circumstances, it would be desirable to display relatively bright characters or other information, etc., on a relatively dark background when using a liquid crystal material. It may also be desirable to improve the effective contrast between the displayed character and the background of the display itself.

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An example of an electrically sensitive liquid crystal material and its use can be found in U.S. Patent 3,322,485. Certain types of liquid crystal material are sensitive to temperature, altering optical properties such as random or ordered orientation of the liquid crystal material in response to temperature.

Today, there are three classes of liquid crystal materials, namely cholesteric, nematic and smectic. The various principles of the invention may be used in conjunction with one or more different types of liquid crystal materials or combinations thereof. In the present invention, a nematic liquid crystal material or a combination of a nematic and a cholesteric type is preferably used. More specifically, the liquid crystal material is preferably functionally nematic, i.e., it behaves like a nematic material, and not like other types. Functionally nematic means that in the absence of external fields, the structural distortion of the liquid crystal is dominated by the orientation of the liquid crystal at its boundaries instead of material phenomena such as very strong distortions, such as in cholesteric materials, or deposition, such as in smectic material. Therefore, they would be helical, components that cause a tendency to twist but cannot exceed the effect of boundary alignment could still be functionally nematic. Such materials should have positive dielectric anisotropy. In particular, nematic liquid crystal materials have been found to be reversible, while a cholesteric material is not usually reversible.

Pleochroic dyes are mixed with the liquid crystal material to form a solution with it. Usually, the pleochromatic dye is exposed to the liquid crystal material. Therefore, such pleochromatic dyes tend to act optically in the same way as a liquid crystal material in response to a variable parameter, such as the use or non-use of an electric field. Examples of the use of pleochroic dyes in connection with a liquid crystal material are described in U.S. Patents 3,499,702 and 3,551,026. One advantage of using a pleochro dye with a £ 3,911 liquid crystal material is that no polarizer is required. However, the contrast of the pleochroic device in the nematic form is relatively low. Previously, a cholesteric material could be added to a nematic material along with a dye to improve the contrast ratio. See, e.g., White and others in Journal of Applied Physics, Volume 45, No. 11, November 1974, p. 4718-4723. However, although the nematic material is, depending on whether or not it is crossed by an electric field, reversible, the cholesteric material usually tends to its original zero field shape when the electric field is removed. Another drawback when using a pleochronous dye in solution together with a liquid crystal material is that the dye absorption is not zero when the field is coupled, but the absorption follows the sequence parameter when the field is coupled, which is proportional to or a function of the relative alignment of the dyes.

The liquid crystal material is usually anisotropic both optically (birefringence) and, for example, in the case of a nematic material, electrically. Optical anisotropy is indicated by the scattering of light when the liquid crystal material is randomly aligned and the passage of light through the liquid crystal material when it is aligned in an ordered manner. Electrical anisotropy can be the ratio of the dielectric constant or dielectric constant to the alignment of the liquid crystal material.

In the past, devices that used liquid crystals, such as display terminals, have been relatively small. One reason is the fluidity of the liquid crystals (the liquid crystal material may tend to drain so that areas of different thicknesses appear on the screen). As a result, the optical properties of the display may not be uniform, the contrast characteristics of different parts of the display may vary, etc., and variations in thickness may in turn cause changes or gradations in the optical properties of the liquid crystal device. In addition, 4 69311 causes variation in the thickness of the liquid crystal layer to vary in the electrical properties of the liquid crystal layer, such as capacitance and impedance, which further impairs the uniformity of a large-sized liquid crystal device. The varying properties of the liquid crystal layer may then also cause a corresponding change in the effective electric field across the liquid crystal material and / or react differently in response to a constant electric field in those regions of the liquid crystal of different thickness.

To overcome such problems, the thickness of the liquid crystal should be as uniform as possible. (As used herein, the term "liquid crystal material" means the liquid crystals themselves and, depending on the context, the pleochro dye in solution therewith). The distance between the electrodes at which the electric field is provided in the electrode material should also be as favorable as possible. In order to maintain such an optimal thickness and spacing, the tolerances must be quite small. Maintaining small tolerances limits the size of the device when using such liquid crystals, as it is quite difficult to maintain narrow tolerances, for example on large surfaces.

The use of encapsulated liquid crystals disclosed in accordance with the present invention has made it possible to use liquid crystals on relatively large screens such as bulletin boards, etc., and another large (or small) use may be an optical shutter to monitor light flow from one area to another, e.g. surface. The present invention relates to improvements in such encapsulated liquid crystals as well as to the light scattering properties of the liquid crystal material as opposed to, for example, its light absorption properties (usually in combination with a pleochro dye). The invention also relates to the use of such a material and such properties, for example, to provide a relatively bright mark or information on a relatively dark or colored background on both large and small screens, as an optical shutter, etc. Such large screens or shutters may have a surface area of about 0.1 m or more. According to the present invention, the liquid crystal is preferably of the encapsulated type. The invention is characterized by what is stated in the characterizing parts of claims 1, 44-46 and 50.

As used herein, in connection with the present invention, encapsulated liquid crystal material means liquid crystal material in a substantially enclosed protective material, such as separate housings or cells, and is preferably in the form of a liquid crystal material and a protective material. Such an emulsion must be stable. Various methods for making and using an encapsulated liquid crystal material and associated equipment are set forth below.

A typical prior art display may comprise a carrier and a liquid crystal material supported thereon. The display is relatively flat and is viewed from the direction from which the so-called front surface is viewed. The back surface of the support may have a light reflective coating that tends to make this relatively bright compared to the relatively dark marks formed in areas with liquid crystal material. (Rear, front, top, bottom, etc. are terms used only for convenience, and nothing forces the view direction to be used, for example, as shown, only from above, etc.) When the liquid crystal material is sequentially oriented, the light passes through the liquid crystal material to the light-reflecting coating and, even in the absence of liquid crystal material, passes directly to the light-reflecting coating, and no sign of the viewing direction is observed. However, when the liquid crystal material is randomly oriented, it absorbs a portion and scatters a portion of the incoming light so as to form a relatively dark mark on a relatively light-colored background, such as gray, depending on the light-reflecting surface. In this type of display, it is not desired for the liquid crystal material to scatter light because some of that scattered light is directed back in the viewing direction, thereby reducing the darkness or contrast of the mark with respect to the background of the display. 6 S 9 31Ί pleochro dye is often added to the liquid crystal material to improve the absorbance and, if the liquid crystal material is randomly oriented, the contrast.

Briefly, in one aspect of the invention, the liquid crystal material is encapsulated, in another aspect, the encapsulated liquid crystal material is used in liquid crystal devices, such as relatively large display terminals and optical shutters, and in other aspects, methods are provided for encapsulating the liquid crystal material and encapsulating such liquid crystal material.

In one embodiment of the invention, it can be broadly said that a liquid crystal scatters or absorbs light without a predetermined supply, such as an electric field, and under the influence of such a supply, scattering or absorption is reduced. The absorption is increased if such a feed is not affected if a pleochro dye is mixed into the liquid crystal.

In another embodiment, which may comprise, but preferably does not comprise, a pleochro dye, the invention briefly relates to the isotropic scattering of light by a liquid crystal material and the use of such isotropic light to produce a white or bright shape, mark, information, etc., especially against a background of liquid crystal material. in a fieldless or distortedly aligned state, or in a colored or dark form, for example, the same as the background when the liquid crystal material is in a state of parallel or ordered alignment under the action of a field. Preferably, the liquid crystal material decomposes almost completely isotropically when it is bent. Isotropic scattering means that when a light beam enters a liquid crystal material, there is virtually no way to predict the angle of exit of the scattered light. In this embodiment, a pleochro dye is not preferred because the dye would absorb light and reduce brightness when scattering and brightening are intended.

7,093,11 As used herein, in connection with the invention, the terms distorted alignment, random alignment, and fieldless state mean essentially the same thing, namely, that the orientation of liquid crystal molecules is effectively distorted into a curved shape. Such twisting is caused, for example, by the wall of the housings. The specific distorted alignment of the liquid crystal material in a particular housing is usually substantially the same when the electric field is unaffected. On the other hand, in the context of the present invention, the terms parallel alignment, ordered alignment and field space mean that the liquid crystal material in the housing is generally oriented with respect to an electric field acting from the outside. Functionally nematic is defined above.

Enclosure refers to the protective structure or material that surrounds the amount of liquid crystal material, and "encapsulant" or "material" is the material or material from which such enclosures are made. "Encapsulated liquid crystal" or "encapsulated liquid crystal material" means an amount of liquid crystal material enclosed in separate volumes or incorporated into an encapsulant, such as a solid as separate enclosures or dry stable emulsions.

The housings of the present invention are generally approximately spherical in shape (although this is not in itself a requirement of the invention) having a diameter of about 0.3 to 100 microns, preferably 0.1 to 30 microns, especially 3 to 15 microns, for example 5 to 15 microns.

In the context of this invention, encapsulation and related terms refer not only to the formation of products commonly referred to as enclosures, but also to the formation of stable emulsions or dispersions of a liquid crystal material in a material (encapsulant) resulting in stable, preferably uniformly sized, particles in a uniform surrounding material. Encapsulation methods, commonly referred to as microencapsulation, due to the size of the enclosure, are well known in the art (see, e.g., Asaji Kondon's "Microcapsule Processing and Technology" published by Marcel Dekker, Inc.) and to 8,893,111, having regard to this disclosure. , to define suitable encapsulants and methods for liquid crystal materials.

A liquid crystal device is a device formed of a liquid crystal material.

The present invention provides devices made of encapsulated liquid crystals capable of the type of liquid crystal material typically accustomed to, such as a display terminal or an optical shutter that, in response to electric field switching or removal, affects the selected attenuation, preferably including attenuation of optical radiation.

One method of making encapsulated liquid crystals is to mix a liquid crystal material and an encapsulant in which the liquid crystal material is insoluble and to form separate enclosures containing the liquid crystal material.

One method of making a liquid crystal device having such encapsulated liquid crystals comprises, for example, placing such an encapsulated liquid crystal material on a substrate. In addition, such a method may comprise means for applying an electric field to the liquid crystal material to change its properties.

According to another aspect of the invention, a functionally nematic material in which a pleochro dye is dissolved is placed in a generally spherical housing. When the electric field is not affected, the wall of the housing twists the structure of the liquid crystal so that it and the toner tend to absorb light regardless of its polarization direction. When a suitable electric field is directed across such a crystal, for example across its axis, the liquid crystal material tends to be parallel to a field from which the absorption properties of such a material of the conductors decrease to the assumed value? g τ i -j

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when the liquid crystal material is planar. To facilitate ensuring that a sufficient electric field is directed across the liquid crystal material in the housing, and not just the encapsulant, and in fact that the voltage drop across the enclosure walls is minimized, the dielectric constant of the encapsulant is at least equal to the lower dielectric constant of the liquid crystal material. On the other hand. Ideally, the dielectric constant of the encapsulant should be close to the higher dielectric constant of the liquid crystal.

The contrast of a liquid crystal device using encapsulated liquid crystals can be improved by selecting an encapsulant having a refractive index corresponding to the usual refractive index of the liquid crystal material (i.e., the refractive index along the optical axis of the crystal). See. e.g., Borne & Wolf's "Optics" or Hartshore & Stewart in "Crystals and the Polarizing Microscope." In addition to encapsulating the liquid crystal material, the encapsulant can be used to attach the enclosures to the substrate supporting them. Alternatively, another binder may be used to hold the liquid crystal enclosures relative to the substrate. In the latter case, however, the refractive index of the additional binder is preferably suitable over the refractive index of the encapsulating wave in order to maintain the improved contrast property described above. Since the refractive index of a substance is generally voltage-dependent and the stress can be applied to the encapsulant, for example, it may be necessary to take this effect into account by matching the refractive indices of the liquid crystal, the encapsulant and any binder. In addition, if iridescence is to be avoided, it may be desirable to adjust the refractive indices instead of just one wavelength to the entire wavelength range, if possible.

According to the present invention, one feature of a spherical or otherwise curved housing having a liquid crystal material is that the liquid crystal material tends to follow a curvature or otherwise align with the curved surfaces of the housing.

Accordingly, the liquid crystal material tends to be depressed or distorted into a particular shape, folded in a sense over itself as it follows the housing wall, so that the optical properties of a particular housing containing the liquid crystal material are such that substantially all of the light is exposed to light, e.g. no) or absorbed (if a phleochromatic dye is present) if an electric field is not used, regardless of the polarization direction of the incoming light. This effect may cause scattering and thus opacity even without toner.

Another feature is the ability to adjust the effective thickness of the liquid crystal material in the housing by adjusting the inside diameter of such a housing. Such diameter adjustment can be accomplished by a size separation process during the production of encapsulated liquid crystals using any of a number of conventional or novel sorting methods and by controlling the mixing process, the number of ingredients, and / or the nature of the ingredients added during mixing. By monitoring such a tolerance parameter with relatively narrow tolerances, subsequent tolerance requirements when the final liquid crystal device is fabricated using encapsulated liquid crystals are not as critical as required in former devices with unencapsulated liquid crystals.

However, another and very significant feature of the present invention is that there does not appear to be a limit on the size of a high quality liquid crystal device made using the encapsulated liquid crystals of the present invention. More specifically, enclosing separate amounts of liquid crystal material in, for example, the described housings overcomes the problems that previously prevented the use of liquid crystal material in large devices, since each housing can in fact still function as an independent liquid crystal device. In addition, the physical properties of each housing preferably allow it to still be installed in virtually any environment, including one in which a plurality of other such liquid crystal enclosures are attached to a substrate or otherwise supported for use in responding to and removing some type of excitation source, such as electric or magnetic. This feature also makes it possible to place the liquid crystal material only in selected areas of the optical device, such as large screens (e.g. bulletin boards), optical shutters, etc.

Important considerations in accordance with the invention and the inventor's invention are that an encapsulant having electrical properties predetermined to the electrical properties of the liquid crystal material encapsulated therein, and further preferably optically matched to the optical properties of such liquid crystal material, enables efficient and high performance of the liquid crystal material. stimulus or lack of stimulus, and that the interaction of the encapsulant with the liquid crystal material distorts the latter in a predetermined manner, changing the mode of operation of the liquid crystal material. In view of the latter, liquid crystals absorb or block light instead of transmitting it if they are forced to twist in a generally parallel or conforming alignment with the housing wall if they are not subjected to an electric field and operate with any incoming light, regardless of the direction of possible incoming polarization.

According to one aspect of the present invention, the liquid crystal display may provide relatively bright or white marks, information, etc., on a relatively dark background, the bright mark being provided by a liquid crystal material that is randomly oriented (preferably without a pleochro dye that would absorb and reduce scatter); for example, an ordered oriented liquid crystal material and therefore optically translucent and / or areas of the display where there is no liquid crystal material. When the liquid crystal material 12 '' 3 9 3 1 1 is oriented parallel or sequentially, only a relatively dark background, such as an absorber, is visible. The above is accomplished by using relatively low power requirements, minimal liquid crystal material, and lighting coming from either the viewing side or direction, or from behind or outside the viewing side of the screen. The principles of the invention can also be used, for example, in an optical shutter or a lighting control device for adjusting brightness.

Briefly, the liquid crystal device comprises selectively scattering or transmitting light from the liquid crystal material in response to a predetermined feed, and a support for holding the liquid crystal material therein. In a preferred embodiment, the liquid crystal material is of an encapsulated type which causes the light entering it to dissipate substantially isotropically, which comprises some of such light dissipating back towards the viewing direction, for example to the eye of the observer. Such a liquid crystal is preferably functionally nematic, has a positive dielectric anisotropy, and has a standard refractive index substantially suitable for its protective or encapsulating agent.

In one embodiment, the support internally reflects much of the light scattered by the liquid crystal material completely back into the liquid crystal material, illuminating it and causing further isotropic scattering and brightening of the appearance of the liquid crystal material, e.g., to the eye of an observer. The internal reflection property of the support may be provided by the interface of such a backing surface with another substance, such as a solid, liquid or gas, even air, provided that the refractive index of the support is higher than that of such another substance. The carrier may be formed from a number of components, which may include, for example, a protective / encapsulating agent (or an agent with which the liquid crystal material forms an emulsion), additional amounts of such! 3 9931 1 casing or other material, adhesive such as plastic film or glass, etc., each of which is explained below.

The back side of the support may be optically transmissive so that light that encounters such a surface in a substantially perpendicular manner transmits it. The light absorbing black or colored material beyond such back surface can help darken the side or color the apparent background on which the nestekidemateriaa-signal generated characters appear. The ordered alignment of the liquid crystal material eliminates at least substantially isotropic scattering so that substantially all of the light passing through the liquid crystal material also passes through the back surface of the support.

In an alternative embodiment, a dielectric coating tuned by the evaporation method, for example, may be coated on the back surface of the support to provide selective constructive and destructive optical interference. The thickness of such a tuned dielectric coating is a function of lambda (λ) divided by two, where lambda is the wavelength of the light used in the device. Constructive interference improves internal reflection, in particular by reducing the spatial angle at which light is not fully reflected internally to the support, so that such interference further brightens the marks of liquid crystal materials.

In the liquid crystal display according to the invention, light can come from the front or the viewing side. Alternatively, the light may come from the back, preferably through a mask or rectifier, to direct light completely transmitted by the liquid crystal material out of the field or from the viewing angle on the viewing side. However, the light scattered by the liquid crystal material, which is in the viewing angle, is visible.

In addition, a cholesteric material may be added to the nematic liquid crystal material to cause the former to return to a distorted alignment pattern that generally follows the housing or cell wall when the electric field is disconnected, especially if the housings are relatively large. If desired, a viscosity adjusting additive can also be mixed into the 14,593,3 liquid crystal. In addition, an additive can be used in the liquid crystal to help force the liquid crystal structure in the housing into popular alignment.

These and other embodiments of the invention will become apparent as the following description proceeds.

The following description and the accompanying drawings detail certain illustrative embodiments of the invention, which, however, refer to. just a few of the several principles by which the principles of the invention may be practiced.

In the accompanying drawings:

Figure 1 is a schematic representation of a liquid crystal device according to the present invention.

Figures 2 and 3 are enlarged schematic views of a liquid crystal housing of the present invention, in a fieldless or field-disconnected state, and an electric field in a switched-on or field state. Figures 4 and 5 are schematic representations of a liquid crystal device according to an embodiment of the present invention, in the fieldless and field state, respectively.

Figure 6 is a schematic representation of a liquid crystal device according to another embodiment of the present invention using an air gap to provide complete internal reflection. Figures 7 and 8 are schematic representations of a liquid crystal device according to another embodiment of the present invention, which uses optical interference principles in the fieldless and field states, respectively.

Figure 9 is an isometric view of a liquid crystal display device according to the present invention that may be formed from any of the embodiments disclosed herein.

Figure 10 is a partial schematic elevational view of another embodiment of a liquid crystal device using continuous layers of liquid crystal material and truncated electrodes.

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Fig. 11 is a schematic isometric view of the embodiment of Fig. 10 with part removed.

Fig. 12 is a schematic view of an approximately proportional liquid crystal display according to the invention, showing in more detail the representative aspect ratio of the carrier layers and the encapsulated liquid crystal layer for several embodiments described herein.

Figure 13 is a schematic view of a nematic liquid crystal housing having a cholesteric additive that can be used in several of the embodiments disclosed herein.

Figures 14 and 15 are schematic views of yet another embodiment of a liquid crystal device having a light control film controller into which the illumination enters from the non-viewing side, in the field state and the field field, respectively.

Fig. 16 is a view similar to Figs. 14 and 15, but with the light control film guide glued to the support. Fig. 17 is a schematic view similar to Figs. 2 and 3 showing an alternative embodiment of an encapsulated liquid crystal.

Fig. 18 is a schematic representation of a liquid crystal device according to the invention, in which a liquid crystal dye is used.

Fig. 19 is an enlarged fragmentary view of the liquid crystal display device of Fig. 9, with a portion removed, but with a pleochro dye, as in the embodiment shown in Fig. 18, for example. Fig. 20 shows an electrical circuit diagram of a liquid crystal housing according to the invention with the field connected.

Referring to Figures 1, 2 and 3, there is shown a liquid crystal material used in accordance with the present invention. Figure 1 shows a liquid crystal device 10 according to the present invention. The device 10 comprises an encapsulated liquid crystal material 11, which is shown in Figures 1-3 by a single housing. Although the housings are shown in the drawings in two dimensions and therefore in planar form, it is clear that the housings are three-dimensional, preferably spherical.

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The housing 11 is preferably shown attached to a transparent support material 12 having upper and lower portions 12a, 12b, which may have a common structure. The device 10 also comprises a pair of electrodes 13, 14 for directing an electric field across the liquid crystal material when the switch 15 is closed to magnetize the electrodes from a conventional voltage source 16.

The main feature of the present invention is that such an encapsulated liquid crystal material isotropically diffuses the light impinging upon it when the crystal is in a fieldless, randomly directed state, and in an ordered field state such a substance is substantially optically transmissive.

The housing 11 may be one of a plurality of housings formed separately, or preferably formed by mixing a liquid crystal material with a so-called encapsulating material or protective agent to form an emulsion which is preferably stable. The emulsion can be attached to the support components 12a, 12b or placed between them and the electrodes 13, 14, as shown. If desired, the carrier 12 and the so-called encapsulant or protective agent may be of the same material. Alternatively, the top and bottom of the support material or one of them may be of a plastic-like, glass or similar, preferably transparent, fastening material. In the latter case, the electrodes can be attached to such an adhesive, and an encapsulated liquid crystal material / emulsion comprising a plurality of enclosures 11 can, for example, be interposed between such an adhesive 12a, 12b to form a device 10, as will be explained in more detail below.

The reflector 18 forms an interface 19 with the support portion 12b to provide the desired internal total reflection function. Due to the use of the total reflection principle, incoming light from the liquid crystal material in the housing 11, represented by a light beam 17, is scattered isotropically in the device 10 so that 17 $ 9311 from the viewing area 20, beyond the support top 12a, appears as white or relatively bright , for example switch 15 is open. The principle of total internal reflection of the present invention enhances the scattering, and therefore brightens the visual / optical appearance of the marks formed by the liquid crystal material of the housings. A light absorbing layer 21 made of black or colored material can be attached to the bottom of the reflecting surface 18, at a distance from the intermediate surface 19, to absorb light entering the layer 21.

The electrode 13 may be tin oxide vacuum coated on the lower part 12b of the support and the electrode 14 may be an electrically conductive printing ink applied directly to the liquid crystal material, or it may be similar to the electrode 13. Other electrode material and its attachment methods can also be used for each electrode. Examples include tin oxide and tin oxide doped with antimony. The electrodes are preferably relatively thin, for example about 200 Angstroms thick, and transparent so as not to significantly affect the optics of the liquid crystal device 10.

The encapsulated liquid crystal material 11 comprises a liquid crystal 30 stored in the interior 31 of the housing 32. Each housing 32 may be separate or alternatively the liquid crystal may be stored in a stable emulsion 33 of a preservative or so-called encapsulating material which tends to form a plurality of encapsulating media. To simplify the presentation, the housings 32 are shown as separate housings in a protective material or encapsulation material 33, the total amount of which is preferably formed. Preferably, the housing 32 is generally spherical in shape, and the liquid crystal 30 is a nematic or functionally nematic liquid crystal material having a positive dielectric anisotropy. However, the principles of the invention apply even if the housing 32 is non-spherical in shape, as long as such shape provides the desired optical and electrical properties that work satisfactorily with properties of the liquid crystal material 30, such as refractive index, and allows a sufficient portion of the electric field to act across the liquid crystal. 30 itself in order to obtain the desired ordered or parallel alignment of the liquid crystal when it is desired in the field space. The shape should also tend to distort the liquid crystal material when in a fieldless or randomly aligned state. A particular advantage of the preferred spherical shape of the housing 32 is the distortion it causes in the liquid crystal 30 when in the fieldless state. This distortion is due, at least in part, to the relative sizes of the housings and the slope of the liquid crystal, which should preferably be approximately the same or at least of the same order of magnitude. In addition, the nematic liquid crystal material has liquid-like properties that facilitate its adaptation or distortion to the shape of the housing wall in the absence of an electric field. On the other hand, when the electric field acts, such a nematic material changes to a relatively easily ordered alignment with respect to such a field.

A type of liquid crystal material other than nematic or different types of combinations of liquid crystal materials and / or other additives may be used in conjunction with or instead of the popular liquid crystal material as long as the encapsulated liquid crystal is functionally nematic. Cholesteric and smectic liquid crystal materials are usually total magnetizable.

It is more difficult to break their overall structure to accommodate the shape of the housing wall and the energy considerations of the housing.

Referring to Figures 2 and 3, there is shown a schematic illustration of a single housing containing a liquid crystal 30 in a fieldless state and a field state, respectively. The housings 32 have a generally smooth curved inner wall surface 50 which forms a boundary in place of 31. The actual measurement parameters of the wall surface 50 and the entire housing 32 relate to the amount of liquid crystal 30 in the housing and possibly other properties of the individual liquid crystal material therein. In addition, the housing 32 applies a force to the liquid crystals 30 in an effort to pressurize the space 31, or at least to keep the pressure therein substantially constant. As a result of the former, and due to the wetting nature of the liquid crystal surface, the liquid crystals, which would normally tend to be parallel in the free state, although perhaps randomly distributed, curve in a direction generally parallel to the relatively close portion of the inner wall surface 50. Due to such distortion storing 'liquid crystals' elastic energy. To simplify the description, a liquid crystal molecular layer 51 is shown closest to the inner wall surface 50, the direction of which is represented by corresponding dashed lines 52. The direction of the liquid crystal molecules 52 is distorted into an arc parallel to the region near the wall surface 50. Reference numeral 53 shows a directional pattern of those in the housing away from the boundary layer 52. The direction of the liquid crystal molecules is shown layer by layer, but it is clear that the molecules themselves are not limited to such layers. Therefore, the organization of the wall structure 52 predetermines the organization in a single housing that is permanent if not affected by external forces, such as an electric field. When the electric field is removed, the trend returns to the original, shown in Figure 2.

The nematic-type material usually settles in a parallel shape and is usually sensitive to the optical polarization direction. However, since the material 52 in the encapsulated liquid crystal 11 is distorted or forced into a curved shape in all three dimensions of the housing 32, such a nematic liquid crystal material in such a housing assumes an improved property while being insensitive to the optical polarization of incoming light. It has now further been found that when a pleochro dye, which would normally also be expected to be sensitive to optical polarization, is dissolved in the liquid crystal material 30 in the housing 32, it is no longer present because the dye tends to follow the curved orientation or distortion of the individual liquid crystal molecules 52.

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Due to the inability of the liquid crystal to align uniformly in the direction of the wall 50 and the minimum elastic energy requirement, there is a discontinuity 55 in the generally spherical orientation of the liquid crystal 30 in the housing 32. Such a discontinuity is three dimensional and useful in further distorting the liquid crystal direction, would decrease. The discontinuity protrusion 55 would tend to cause scattering and absorption in the housing, and tangential and parallel alignment of the liquid crystal molecules with respect to some portions of the housing inner wall surface 50 both cause scattering and absorption in the housing 32. When, for example, optical transmittance when the encapsulated liquid crystal 11 is in a field or focused state.

Although the above discussion is based on the homogeneous orientation of the liquid crystal material (parallel to the housing wall), it is not a prerequisite for the invention. The only requirement is that the action between the wall and the liquid crystal provides a generally uniform and continuous continuous orientation in the liquid crystal near the wall, so that the average spatial orientation of the liquid crystal material across the housing volume is strongly curved and the liquid crystal structure has no parallel direction when the electric field Absent. It is this strongly curved tendency that causes numbness and polarization, which is a feature of the present invention.

In a field state or any other state that causes the liquid crystal to be in an ordered or parallel alignment, as shown in Figure 3, the encapsulated liquid crystal 11 transmits substantially all of its incoming light and tends to be invisible in the support 12. On the other hand, some incoming light is absorbed disintegrate 21,693,11 isotropically into the support 12 in an uncoated state when the liquid crystal is distorted, sometimes referred to as random alignment, as shown in Figure 2, for example. By using internal total reflection, such isotropically scattered light can be redirected to the encapsulated liquid crystal, thus brightening it and tending to make it appear white to the viewer or viewing device.

The refractive index of the housing material 32 and the ordinary refractive index of the liquid crystal should be matched as well as possible when in the field or the liquid crystal is in an orderly orientation to avoid optical distortion due to refraction of incoming light as it passes through. However, when the liquid crystal material is distorted or randomly exposed, i. there is no field, there is a difference in the refractive indices at the boundary of the liquid crystal 30 and the wall of the housing 32, so that the specific refractive index of the liquid crystal is higher than the refractive index of the encapsulant. This causes refraction of light at that interface or boundary between the liquid crystal material and the protective or encapsulating agent, and thus increases scattering. The light, thus further scattered, is reflected internally to further brighten the appearance of the liquid crystal. Such manifestation of different refractive indices is called birefringence. The principles of birefringence are explained in Sears' "Optics" and Hartshorne and Stewart's "Crystals and the Polarizing Microscope," the relevant representations of which are incorporated herein by reference. Refractive indices of the encapsulant or protective agent 32 and the support agent 12. are preferably the same so that they behave optically as the same material, so as to avoid an additional optical interface.

As long as the ordinary refractive index of the liquid crystal material is closer to the refractive index of the so-called encapsulant than the special refractive index, there is a change in scattering when moving from the field state to the field state and vice versa. The result is maximum contrast when the standard refractive index matches the refractive index of the medium. The proximity of the coefficients to match depends on the desired degree of contrast and transmittance of the device, but the standard refractive index of the crystal and the coefficient of the medium preferably differ by no more than 0.1, more preferably 0.03, more preferably 0.01, especially 0.001. The allowable difference depends on the size of the housing.

The electric field shown in Figure 3 is desirably applied to most of the liquid crystal in the housing 32, rather than being disintegrated or substantially lowered into the housing material. The voltage drop should not be significant across or through the material from which the wall 54 of the housing 32 is formed, but should instead occur across the liquid crystal 30 in the space 31 of the housing 32.

The electrical impedance of the encapsulant should preferably be so high in relation to the electrical impedance of the liquid crystal in the encapsulated liquid crystal 11 that the short circuit does not occur exclusively through the wall 54, for example from point A only through the wall to point B, bypassing the liquid crystal. Therefore, for example, the effective impedance for the induced or offset current flowing only through or through wall 54 from point A to point B must be greater than the impedance encountered on the track from point A to point A 'inside the inner wall surface 50, through liquid crystal material 30, to point B' still in state 31. and finally again to point B. This condition ensures that there is a potential difference between point A and point B. Such a potential difference should be large enough to generate an electric field across the liquid crystal material that tends to align this. It is clear that due to geometrical considerations, namely only through the wall from point A to point B, such a condition can be met even if the actual impedance of the wall material is lower than the actual impedance of the liquid crystal material inside the wall.

23 0 93ΊΊ

The dielectric constants (coefficients) of the material from which the encapsulant is made and from which the liquid crystal material is formed, and the effective capacitance value of the housing wall 54, especially in the radial direction and the effective capacitance value of the liquid crystal through which the electric field E passes 32 54 does not significantly reduce the strength of the electric field. Ideally, the entire layer 61 of the encapsulated liquid layer material (Figure 4) should be substantially the same for the field space.

The value of the dielectric constant of the liquid crystal material 30 is anisotropic. The dielectric constant (coefficient) of the wall 54 is preferably at least equal to the dielectric constant (coefficient) of the anisotropic liquid crystal material to make it easier to meet the above conditions for optimum operation. It is desirable that the positive dielectric anisotropy be relatively large in order to have lower voltage requirements for the electric field E. The difference between the liquid crystal dielectric constant (coefficient) when the electric field is disconnected, which should be quite small, and the liquid crystal dielectric constant (coefficient) when it is subjected to the electric field, which should be relatively large, should be as large as possible. In particular, it should be noted that the critical relationship between the dielectric values and the electric field used should be such that the field directed across the liquid crystal material in the housing or housings is sufficient to align the liquid crystal structure with respect to the field. Commonly used liquid crystals have lower di-electrical values ranging from as low as about 3.5 to as high as about 8.

The sizes of the housings 32 may vary. However, the smaller the size, the higher the electric field requirements for aligning the liquid crystal in the housing. However, the size parameters of the housings should be uniform so that the optical and electrical properties of a device such as a monitor using an encapsulated liquid crystal are substantially uniform. In addition, the housings 32 should have a diameter of at least 1 micron so that they are visible as separate housings with respect to the incoming light beam, as the smaller diameter would result in the light beam "seeing" them as a continuous homogeneous layer without the required isotropic scattering.

A preferred liquid crystal material according to the best practice of the invention is the nematic material NM-8250, an ester sold by American Liquid Xtal Chemical Corp., Kent, Ohio, USA. Other examples may be ester combinations, diphenyl and / or diphenyl combinations and the like.

Several other types of liquid crystal materials useful in the present invention include the following four examples, each of which is a manufacturing instruction for liquid crystal materials. The so-called 10% material has about 10% 4-cyano-substituted materials, 20% the material has 20% 4-cyano-substituted materials, and so on.

10% Material

Pentylphenylmethoxybenzoate 54 g

Pentylphenylpentyloxybenzoate 36 g

Cyanophenyl pentyl benzoate 2.6 g

Cyanophenylheptyl benzoate 3.9 g

Cyanophenylpentyloxybenzoate 1.2 g

Cyanophenylheptyloxybenzoate 1.1 g

Cyanophenyloctyloxybenzoate 9.94 g

Cyanophenylmethoxybenzoate 0.35 g 20% material

Pentylphenylmethoxybenzoate 48 g

Pentylphenylpentyloxybenzoate 32 g

Cyanophenyl pentyl benzoate 5.17 g

Cyanophenylheptyl benzoate 7.75 g

Cyanophenylpentyloxybenzoate 2.35 g

Cyanophenylheptyloxybenzoate 2.12 g

Cyanophenyloctyloxybenzoate 1.88 g

Cyanophenylmethoxybenzoate 0.705 g 25 8931 1 40% material

Pentylphenylmethoxybenzoate 36 g

Pentylphenylpentyloxybenzoate 24 g

Cyanophenyl pentyl benzoate 10.35 g

Cyanophenylheptyl benzoate 15.52 g

Cyanophenylpentyloxybenzoate 4.7 g

Cyanophenylheptyloxybenzoate 4.23 g

Cyanophenyloctyloxybenzoate 3.76 g

Cyanophenylmethoxybenzoate 1.41 g

40% MOD

Pentylphenylmethoxybenzoate 36 g

Pentylphenylpentyloxybenzoate 24 g

Cyanophenyl pentyl benzoate 16 g

Cyanophenylheptyl benzoate 24 g

The encapsulant forming the housings 32 should be of such a type that it and the liquid crystal material do not have a substantial effect on each other. Various resins and / or polymers can be used as the encapsulant. One popular encapsulant is polyvinyl alcohol (PVA), which has a good, relatively high, dielectric constant and a refractive index that is relatively closely matched to the refractive index of a popular liquid crystal material. An example of a preferred PVA is about 84% hydrolyzed resin having a molecular weight of at least about 1000. The use of PVA manufactured by Monsanto Company under the name Gelvatol 20/30 represents best practice of the invention.

The method of making emulsified or encapsulated liquid crystals may comprise mixing a protective or encapsulating agent, a liquid crystal material, and perhaps a carrier such as water. The mixing can take place in several different mixing devices, such as a mixing tap, a colloid mill, which is the most popular, or the like. During such mixing, the ingredients form an emulsion which can then be dried by removing a carrier such as water and satisfactorily curing the encapsulant such as PVA. Although the housing of all the encapsulated liquid crystals 11 thus prepared may not be a complete ball, each housing is substantially spherical in shape because the ball is the lowest free energy state of the individual droplets, spheres, and housings of the emulsion, both initially formed and after drying or curing. .

The size (diameter) of the housing in the emulsion should be uniform so that the operation is uniform in terms of the effect on the incoming light and the reaction with respect to the electric field. An exemplary housing size may be about 0.3 to 100 microns, preferably 0.3 to 30 microns, especially 3 to 15 microns, for example 5 to 15 microns.

Various methods can be used to prepare the support material 12, which may be the same or a similar material as the encapsulating or protective material. For example, the lower support 12b can be prepared by casting. The electrode 13 and the liquid crystal material can be attached to support that material 12b. The electrode 14 can be attached, for example, by pressing. The top 12a of the support can then be molded in place to complete the encapsulation of the encapsulated liquid crystal material and electrodes. Alternatively, the support components 12a, 12b may be a substantially transparent plastic-like film or glass sheet, as described, for example, in Example 1.

If the reflective material 18 is solid, it can also be attached to the support member 12b by casting, and the lower coating 21, which is a dark or colored light absorbing material, can be attached to the back surface of the reflective material 18, i. to a surface remote from the interface between it and the lower portion 12b of the support. Alternatively, the reflector may be an air or other flowing medium gap between the support member 12b and the absorber 21, or the tuned dielectric layer may be attached by a standard evaporation technique directly to the bottom surface of the support member 12b instead of the reflector 18, as will be explained below.

27 8931 1

The following are several examples of materials and methods for making the liquid crystal display devices of the present invention, as well as their functional properties.

Example 1

An example of an isotropically degradable material was prepared by mixing about 2 g of nematic liquid crystal 8250 (an ester of American Liquid Xtal) with about 4 grams of a 20% solution of Airco 405 polyvinyl alcohol (the remaining 80% of the solution was water). The material was mixed in a small homogenizer to form an emulsion. Using a scraper at a setting of about 0.127 mm, the emulsion was applied to an electrode made of Intrex material, which was already in place on a polyester film substrate about 0.127 mm thick. Such a film is known as Mylar. A second sheet of such a film with such electrodes was placed on the encapsulated liquid crystal layer so that this remained between both electrodes and the films. The individual encapsulated, functionally nematic, liquid crystal enclosures or particles had a diameter of about 4-5 microns and the total thickness of the layer of encapsulated liquid crystal material was about 20-30 microns.

The device made according to Example 1 was tested. The resulting material scattered light when in a state where the electric field was zero (hereinafter, the state is commonly referred to as a zero-field or non-field state). At 10 volts, the scatter was reduced and at 40 volts, the scatter was completely eliminated.

Although a homogenizer was used herein, other types of mixers can be used to perform the desired mixing.

Example 2

An example of an isotropically degradable material was prepared by mixing about 2 g of a nematic liquid crystal with about 4 grams of a 22% (78% water) Gelvatol 20/30 (Monsanto) polyvinyl alcohol solution. The material was mixed in a small 28,631 L homogenizer with a small cut to an emulsion. The emulsion was applied to the Intrex film electrode and Mylar film polyester substrate as in Example 1 with a scraper set at 0.127 mm and the layer structure was completed as in Example 1. The diameter of the nematic housings or particles was about 3-4 microns and the layer of encapsulated liquid crystals the thickness was about 25 microns.

The device made according to Example 2 was tested. The resulting material scattered light in the fieldless state. At 10 volts, the scatter was reduced and at 40 volts, the scatter was completely eliminated.

Example 3

An example of an isotropically degradable material was prepared by mixing about 2 g of nematic liquid crystal E-63 (a diphenyl manufactured by British DrugHouse, a subsidiary of West German E. Merck) with about four grams of a 22% solution of Gelvatol 20/30 (Monsanto) polyvinyl alcohol. The material was mixed in a small homogenizer with a small cut to an emulsion. The emulsion was applied to the Intrex film electrode and Mylar film-polyester substrate with a scraper set at 0.127 mm and the layer structure was completed as above. The layer of encapsulated liquid crystals had a thickness of about 25 microns and the diameter of the nematic enclosures or particles was about 4-5 microns.

The device made according to Example 3 was tested. The resulting material scattered light in the fieldless state. In the 7-volt field, the scatter was reduced and at 35 volts the scatter was completely eliminated.

Example 4

An example of an isotropically degradable material was prepared by mixing about 2 g of liquid crystal 8250 with about four grams of a 22% solution of Gelvatol 20/30 polyvinyl alcohol. The material was mixed in a small homogenizer with a small cut to an emulsion. The emulsion was applied to an Intrex film electrode and a Mylar film-polyester substrate with a scraper set at 0.127 mm, and the layer structure was completed as above. The layer of encapsulated liquid crystals was about 25 microns thick and the diameter of the nematic enclosures or particles was about 4-5 mm.

To improve the stability of the emulsion and the uniformity of the coating, 0.001% nonionic detergent GAF LO 630 was added before the mixing step. It was found that the instability of the emulsion performance and the coating of the emulsion on the electrode and the polyester film substrate were improved. The functional results were otherwise substantially similar to those described above in connection with Example 1.

Therefore, it is clear that according to the invention, a detergent, preferably a nonionic detergent, or the like can be mixed with the encapsulated liquid crystal material before being deposited on the electrode-coated film, as just described above.

Example 5

The steps of Example 1 were followed using the same materials as in Example 1 except that the Mylar film was replaced with a 3.175 mm glass plate. The operation was essentially the same as described in connection with Example 1.

Example 6

A mixture of nematic liquid crystal 8250 and a solution of 15% AN169 Gantrezri in 85% water was made. Such Gantrez is a poly (methyl vinyl ether maleic anhydride), a polymaleic acid product produced by GAF Corporation. The mixture comprised 15% liquid crystal and 85% Gantrezri as a preservative.

The mixture was homogenized by small shear into an emulsion which was applied to an electrode and a support film as above, and the thickness of the support film was about 0.03 mm. After the emulsion was dried, the resulting liquid crystal emulsion generally reacted to an electric field as above, decomposing in the fieldless state, starting from Q 3 1 1 30 w "° * 1, reducing the scattering at the 7 volt threshold and saturating at about 45 volts, eliminating substantial scattering. occurred.

Another example of an acid-base preservative useful in the invention is carbopol (a carboxypolymethylene polymer from B.F. Goodrich Chemical Company) or a poly acid.

Other types of carrier 12 that can be used include polyesters and polycarbonate such as Kodel film. A Tedlar film, which is highly inert, can also be used if adequate adhesion of the electrode can be achieved. Such a material 12 should preferably be optically substantially transparent.

Table I below lists several different useful polymeric preservatives. The table also shows several properties of different polymers.

Table I

Preservative and Viscosity- Hydrolysis- Molecule- Temperature & Producer_take %_Weight_Solution -% _

20/30 4-6 CPS 88.7 - 85.5 10,000 4% 20 ° C

Gelvatol

Monsanto Co.

40/20 2.4-3 CPS 77-72.9 3,000 4% 20 ° C

Gelvatol

Monsanto Co.

523 21-25 87-89 - 4% 20 ° C

Air Products & Chemicals,

Inc.

72/60 55-60 99-100 - 4% 20 ° C

Elvanol,

DuPont Co.

405 2 - 4 CPS 80 - 82 - 4% 20 ° C

Poval

Kurashiki 31 ti 9 3 Π

Other Gelvatol PVA materials that may be used include. those denoted by Monsanto as 20-90, 9000, 20-60, 6000, 3000, and 40-10.

The preferred ratio of liquid crystal material to preservative is about one part by weight of liquid crystal material to about three parts by weight of preservative. An acceptable encapsulated liquid crystal emulsion that can be used in accordance with the invention can also be obtained by using a ratio of about one part by weight of liquid crystal material to about two parts by weight of a preservative, for example Gelvatol-PVA. Also, while a 1: 1 ratio also works, it usually doesn’t work quite as well as material with a ratio of about 1: 2 to 1: 3.

Referring now to Figures 4 and 5, there is shown a portion 60 of a liquid crystal display device according to the present invention. The portion or device 60 is a completion of the liquid crystal device 10 described above with reference to Figure 1, in which a plurality of encapsulated liquid crystals 11 are stored in a support 12. The dimensions, thicknesses, diameters, etc. of the many parts shown in Fig. 5 are not necessarily to scale, but are such as are necessary to describe the parts and their operation.

The electrodes 13 and 14 are used to provide the desired electric field for selectively orienting the liquid crystal material in a manner shown, for example, in Figure 3. Means other than the electrodes may be used to direct some type of feed to the display device 60 to direct the liquid crystal in an ordered or random direction.

The encapsulated liquid crystals 11 are arranged in a plurality of layers 61 in the display portion 60. The layers 61 may be divided into a plurality of portions representing different characters or character portions to be displayed on the display 60. For example, those shown in Figure 4

32 a 9 31 I

the longer left portion 61L of the layers 61 may show a sectional view of a portion of the well-known 7-segment display pattern, and the relatively short right portion 61R of the layers 61 shown in Figure 4 may show a portion of another 7-segment character display. According to the present invention, different patterns of the liquid crystal material can be used. The zone 62 of the support material 12 fills the area between the liquid crystal layer portions 61L and 62R. When reference is subsequently made to layer 61, it occurs collectively, i. so that layer 61 means the number of layers that make it up. By way of example, the combined thickness of such a layer 61 may be about 8-254 microns, preferably of uniform thickness to respond uniformly to electric field, scattering, etc.

An arrangement or design of the portions 6IL and 62R of the encapsulated liquid crystal material layers in which the support 12 or other material separates them at zone 62 is facilitated or even made possible by encapsulating or enclosing the liquid crystal in a separate protective agent formed by a preferred stable emulsion. Therefore, especially in relatively large devices such as a display, a bulletin board, an optical shutter, etc., the encapsulated liquid crystal material can be placed in the support 12 only where it is needed to provide the selectable optical properties. Such a pattern can reduce the amount of such material required for a particular application. In addition, such a pattern has become possible, due to the desired functional use, which will be explained in detail below.

For example, the display 60 may be used in ambient air, indicated by reference numeral 63, and the air forms a dividing surface 64 on the viewing side or from the viewing direction 20 with the support 12. The refractive index of the external medium 63 differs from the refractive index N 'of the support 12, which is usually higher. As a result, the light beam 65, which generally arrives from the viewing direction 20 and passes through the dividing surface 64 to the support material 12, folds towards the normal imaginary line 66 perpendicular to that dividing surface 64. That light beam 65a is closer to normal within the support 12 than the incoming beam 65, fulfilling the equation N sin-θ— = N 'sin O-', where -Θ- is the angle of the incoming light beam 65 with respect to normal and - © 'is the angle of light beam 65a with respect to normal . The following mathematical equation holds for the distribution surface 19: N 'sin -Θ-' = N "sin-ö-". In order to achieve the desired total refractive index according to the invention, the refractive index N "of the reflective material 18 is smaller than the refractive index N 'of the support material 12. Accordingly, if the light beam 65a could and would pass through the dividing surface 19, it would fold away from the normal angle Θ-" . In fact, since the light beam 65, 65a is of course not scattered by the liquid crystal material in the layers 61, i. since it passes through zone 62, it is indeed likely to exit through the dividing surface 19.

During operation of the liquid crystal display 60 (Fig. 4), the functionally nematic liquid crystal 30 is distorted or randomly aligned due to the fieldless state. The incoming light beam 70 enters the support 12 at the dividing surface 64 and refracts into a light beam 70a which impinges on the layer 61 of liquid crystals encapsulated as incoming light. The incident light is distorted isotropically by a randomly or distortedly oriented liquid crystal material. Therefore, there are several possibilities for such an incident light beam 70a to scatter.

A. One possibility is that the incoming light beam is directed along the dotted line 70b towards the dividing surface 19. The angle at which the light beam 70b impinges on the dividing surface 19 is at the space angle α shown in the so-called illumination cone (shown in the plane direction by dashed lines 71). Light incident at such a space angle α or illumination cone is at an angle too small to normal in the dividing surface 19 to be fully reflected in that dividing surface, causing the light beam 70b to pass through the dividing surface 19 34 8 931 1 while refracting away from the normal to form the light beam 70c. The light beam 70c passes to the reflective material 18 and is absorbed by the layer 21.

B. Another possibility is that the light beam 70a is isotropically scattered in the direction of the light beam 70d outside the cone angle α. A complete internal reflection occurs at the distribution surface 19, which causes the light beam 70d to be reflected as a light beam 70e back to the layer 61 formed by the encapsulated liquid crystal material, where it is treated like any single incoming light beam, just like the light beam 70a it is a derivative of. Therefore, the light beam 70e is scattered isotropically again, as explained herein.

C. Alternatively, an incoming light beam 70a or a derivative thereof, such as a light beam 70e, is isotropically scattered toward the dividing surface 64 at an angle so close to normal at that dividing surface 64 that the light beam passes through the dividing surface 64 to a "medium" 63, such as air. for viewing by an observer or attention device. The space angle α 'of the illumination cone, which is similar to the previously mentioned cone angle α and within which such a scattered light beam 70e must be to pass through the dividing surface 64, is shown by dotted lines 72. The light beam 70f represents a light beam thus emitted from the display 60. light, for example the light rays 70f thus emanating from the dividing surface 64, make the layer 61 of encapsulated liquid crystals 11 appear as a white or bright mark when viewed from the viewing direction 20.

D. Yet another possibility is that the light beam 70a may be scattered isotropically in the direction of the light beam 70g. The light beam 70g is outside the cone angle α 'and is therefore completely reflected internally in the dividing surface 64, after which the reflected beam 70h bounces back on the layer 61 as a truly independent incoming light beam, similar to the above-mentioned beam 70e with similar effects.

35 Β931Ί

The refractive index of the electrodes 13, 14 is usually higher than the refractive index (s) of the protective agent and the support agent, and the refractive indices of the protective and supporting agents are preferably at least approximately the same. Therefore, the light flowing from the protective material to the electrode material is refracted towards normal and the light flowing from the electrode to the support is refracted away from normal so that the effect of the electrode is zero or substantially negligible. Accordingly, most of the total internal reflection occurs at the dividing surfaces 19 and 64.

Viewed from the viewing direction 20, the zone appears black or colored depending on the composition of the absorbent layer 21. This is because the light beam 65, 65a, 65b, which represents most of the light passing through the zone 62, tends to pass through the dividing surface 64, the support 12, the dividing surface 19 and the reflective 18, thus folding towards or away from the normal at each dividing surface, and finally layer 21 substantially absorbs it.

Referring briefly to Figure 5, the state and operation of the field or ordered alignment of the layer 61 of encapsulated liquid crystals in the display device 60 is shown. The encapsulated liquid crystals in the layer 61 of Figure 5 are similar to those seen in Figure 3. Therefore, in the same way as light beam 65, 65a, 65b , which passes through the zone 62 and is absorbed by the layer 21, follows a similar path of the light beam 70, 70a, 70i and also passes through the aligned and therefore effectively transparent or non-diffusing layer 61. At the dividing surface 19, the beam 70a folds away from normal and then absorbs the layer 21 light beam 70i. Accordingly, regardless of the visual shape the light beam seeks to provide relative to the observer at the viewing point, the light beam 70 provides the same effect as it passes through the ordered encapsulated liquid crystal material. Therefore, when the display 60, and in particular the encapsulated liquid crystal material therein, is in an orderly aligned or field state, 36 c · 9311 shows the area in which the liquid crystal is located substantially the same as the zone 62.

It is noted that if either the incident beam 65 or 70 arrived at the support surface 12 at such an angle to the normal at the dividing surface 64, and therefore finally collide with the dividing surface 19 at an angle greater than the angle inside the so-called light cone angle, such beam would be fully reflected internally at the dividing surface. 19. However, such reflected light would likely remain in the support 12 due to subsequent passage through the liquid crystal material layer 61 and subsequent complete internal reflection in the interface 64, etc.

Figure 6 shows a popular reflection medium 80, air. In Fig. 6, reference numbers with a comma denote parts corresponding to parts denoted by the same reference numerals without a comma in Figs. 4 and 5. The display 60 'has a dividing surface 19' formed by air 80. In order to absorb the light transmitted by the dividing surface 19 'and the medium 80, a black or colored absorbent can be placed separately from the dividing surface 19'. A preferred absorber is carbon black, which can be attached to a support surface generally positioned as shown in Figure 6. The preferred liquid crystal is NM-8250, the popular preservative is PVA and the popular support 12 is polyester. In addition, it is preferred that the refractive indices of the support material 12a, 12b and the liquid crystal shielding agent be at least substantially the same, which helps to ensure that internal full reflection occurs mainly at the interface 19 ', 64' and not at all, if at all, between the guard and the support. the optical distortion becomes as small as possible and the contrast as large as possible. The display 60 'operates in substantially the same manner as the display 60 described above, referring to Figures 4 and 5.

37 1 '9 311

Referring now to Figures 7 and 8, the modified liquid crystal display 90 comprises a support material 12 having a layer 61 of encapsulated liquid crystal material, as above. However, a dielectric interference layer 91 is tuned on the distribution surface 19. The thickness of the dielectric layer 91 exaggerated in the drawings is preferably an odd integer function or a multiple of lambda divided by two, such as 3A / 2, 5X / 2, etc., where A is the wavelength of light in the support display. 60. The tuned dielectric interference layer 91 can be attached to the back surface of the support 12 by a conventional evaporation technique. Such a dielectric layer may be formed of barium oxide (BaO), lithium fluoride (LiF), or other material that provides the desired optical interference function. The refractive index of such a layer is preferably lower than that of the material 12 in order to provide a dividing surface 19 in which the light inside the cone angle is completely reflected internally. An extensive description of optical interference can be found in Born &

Wolf's "Optics", Resnick's and Halliday's "Fundamentals of Physics" 2nd edition, p. 731-735, and from the publication "University Physics" by Sears and Zemansky, the relevant teachings of which are incorporated herein by reference.

In the fieldless / random liquid crystal alignment mode shown in Fig. 7, the display 90 operates in substantially the same manner as the display 60 described above in that a) a layer 61 of encapsulated liquid crystals scatter isotropically, b) light outside the space angle cone a is fully reflected internally. from the dividing surface 19 (or a 'in the case of light isotropically scattered at the dividing surface 64) and c) light such as the light beam 70f emits towards the viewing direction 20 to display a white mark on a relatively dark background.

By using the excited dielectric interference layer 91 and the optical interference in the fieldless state, the illumination provided by the layer 61 b 9 3 1 f provided by the encapsulated liquid crystals is further improved. In particular, the effective light cone angle α decreases to the angle ¢ shown in Fig. 7. Generally, the incoming light beam impinging on the dividing surface 64 is refracted into a light beam 92a, which then enters the layer 61. If the light beam 92a were scattered isotropically, such as a beam 92b at an angle outside the original angle α, full internal reflection described above occurs. However, if the light beam 92a is isotropically scattered, such as the light beam 92c, at an angle inside the light cone but outside the light cone φ, it is actually reflected and constructive optical interference occurs to further improve the illumination of the layer 61 of encapsulated liquid crystals.

More specifically, when the light beam 92c enters the tuned di-electrical interference layer 91, at least a portion 92d is actually reflected back toward the dividing surface 19. The dividing surface 19 undergoes constructive interference with the second incoming light beam 93, increasing the effective intensity in the internally reflected resultant beam 94 a layer 61 of liquid crystals, increasing its illumination. As a result of such constructive interference, the display 90 produces more light rays scattered or reflected up to the layer 61 than the display 60. However, the downside is that the effective viewing angle of the display 90 is smaller than that of the display 60. In particular, incoming light enters the support at an angle 64 is equal to or less than the angle α to be fully reflected because the back of the tuned dielectric interference layer 91 tends to act as a mirror so that some of the contrast is lost in the display 90. The angle α, if any, tends to be less than the angle 90 of the display 60. .

The light beams 95 and 96 (Fig. 7) passing through the zone 62 of the display 90 and the light beams 92 '(Fig. 8) passing through the aligned (field) liquid crystal layer 61 39 O 9 311 and falling inside the cone angle, are subjected to destructive optical interference. question. Therefore, the zone 62 and the area in which the liquid crystal is arranged in an orderly manner appear relatively dark from the viewing area, i. on a dark background compared to the white or brightly lit part of the liquid crystal layer 61 which is fieldless and disintegrates. If desired, an absorbent (black or colored) may be used behind the layer 91. The background color can also be changed as a function of the thickness of the layer 91.

Referring now to Figure 9, there is shown a liquid crystal device 100 according to the invention in the form of a liquid crystal display device shown as a rectangular octagon 101 in a substrate or support 12, which in this case is preferably plastic such as Mylar, or may alternatively be other material such as glass. The shaded area shown in Figure 9, which forms a rectangular octagon, comprises one or more layers 61 of encapsulated liquid crystals 11 disposed as one or more layers on the substrate 12 and adhered thereto. Figure 4 shows a partial sectional view of the rectangular octagon 101 as a display 60, 60 'or 90 described above with reference to Figures 4-8. Each of the seven segments of the octagon 101 may be selectively magnetized or non-magnetized so that different numerals can be generated. Magnetization here means putting different segments in a state where they look bright compared to the background. Therefore, magnetization means, for example, the fieldless or randomly aligned state of the segments 101a and 101b if it is desired to display "1" while the other segments are aligned.

Figures 10 and 11 illustrate, respectively, a partial sectional view and a partial isometric view of an embodiment of the invention showing the preferred placement of the liquid crystal layer 61 "and the electrodes 13", 14 "in the support 12". In Figs. 10 and 11, reference numerals with two dots denote parts in which the reference numerals in Figs. 4 and 5 had no commas at all and in the reference numerals in Fig. 6 there was one comma. In particular, according to the example of Figures 10 and 11, it is preferred that the display device 60 "have a layer 61" and that the electrode 13 "be substantially continuous across the entire display device or at least a relatively large portion thereof. The electrode 14 "may be divided into a plurality of electrically insulated electrode portions, such as 14a and 14b, each of which may be selectively connected to an electric potential source to provide an electric field across the liquid crystal material between the magnetized electrode portion 14a or 14b and the second electrode 13". Therefore, an electric field can be conducted across the electrodes 14a and 13 ", whereby the encapsulated liquid crystal material substantially directly between them becomes organized and therefore optically efficiently transparent in the manner described above. At the same time, the electrode 14b may not be connected to an electric potential source. the liquid crystal material between the electrode 14b and the electrode 13 "is distorted or randomly aligned and therefore appears relatively bright from the viewing direction 20". The narrow gap 120 between the electrodes 14a and 14b forms an electrical insulation between them so that they can or may not be magnetized separately, such as just explained.

Referring briefly to Figure 12, there is shown a preferred embodiment of the present invention and best practice in the form of a display 60 ". In Figure 12, parts denoted by three-dot reference numerals correspond to parts denoted by the same reference numerals as described above. The display device 60" is generally made in accordance with the above numbering. Specifically, the lower support 12 "is made of a Mylar film with an indium-doped tin oxide Intrex electrode on it, and a layer of encapsulated liquid crystal material ei'1 'was attached to the surface covered by the electrode, as shown. A plurality of subelectrodes 14a '' ', 14b'1', etc. with a gap 120 '' '41 & 9311 between them were attached either directly to the surface of the layer 61' '' on the opposite side of the support 12b '' 'or to the support 12a'and the latter was attached as shown in Fig. 12 to supplement the layer structure of the display device 60'1 '.

In addition, there is a reflective medium 80 '' 'of air, and a carbon black absorber 21' * * attached to the support shown in Fig. 12 was placed on the opposite side of such an air gap δΟ1 '' from the support 12b1'1, as can be seen in the figure. The operation of the display device 60 "'is in accordance with the operation described above, for example with reference to Figs. 4-6 and 10.

Referring to Fig. 13, there is schematically shown an encapsulated liquid crystal 130 of the type described below in Example 7. Such a housing 130 comprises a spherical housing wall 131 made of a protective material 132, a functionally nematic liquid crystal material 133 within the housing, and a cholesteric helical additive 134. 133, although the additive is shown in the middle of Fig. 13 because its operation is primarily related to the liquid crystal material remote from the housing wall, as will be explained below. The housing 130 is shown in a field-free, distorted state in which the liquid crystal material is distorted in the manner described above with reference to Fig. 2. The liquid crystal material closest to the wall 131 tends to deflect the arc of the wall and the discontinuity 135 is analogous to the discontinuity 55 in Fig. 2.

Example 7

The steps of Example 1 were followed using the same materials and steps as in Example 1, except that 3% cholesterol oleate (helical additive), a cholesteric material, was added prior to the mixing step, and then mixing was performed with very little shear. The resulting housings were somewhat larger than those made in Example 1. The encapsulated liquid crystal material was still functionally nematic.

42 b 9 311

In operation of the material made in Example 7, it was found that the helical additive improved (shortened) the reaction time of the functionally nematic encapsulated liquid crystal material, especially returning to a distorted alignment that generally followed the shape of the individual enclosure walls immediately after transitioning from field to field.

When such relatively large, say at least 8 microns in total diameter, enter a fieldless state, it is common for a liquid crystal material near the housing wall to return to a distorted alignment of the housing shape and curvature faster than a liquid crystal material closer to the center of the housing. However, the thread additive causes the structure to tend to twist. This effect on the nematic material is most pronounced away from the housing wall and thus accelerates the return of a relatively distant material to a distorted alignment that is preferably affected by the shape of the housing wall. The amount of such helical additive may be about 0.1-8% of the liquid crystal material, and preferably about 2-5%. The amount may vary depending on the additive and the liquid crystal and may even be outside said range, as long as the housing remains functionally nematic.

It will be appreciated that the encapsulated liquid crystal 130 of Figure 13 may be used in various embodiments of the invention described herein in place of or in conjunction with the encapsulated liquid crystal materials otherwise described herein. The operation should generally follow the guidelines explained in Example 7.

Another additive may also be used to reduce and / or otherwise control the viscosity of the liquid crystal, for example, during the manufacture of the device 60. The reduced viscosity may have a positive effect on emulsion formation and / or the process of attaching the emulsion to the electrode-coated support 12. One example of such an additive 43 1--9311 may be chloroform, which is water soluble and leaves the emulsion during drying.

Example 8

An emulsion was prepared using about 15 grams of 22% (remaining water) low viscosity, medium hydrolysis PVA, about 5 grams (American Liquid Xtal) of liquid crystal 8250 containing about 3% (percent by weight of liquid crystal). ) cholesterol oleate, about 0.1% 1% (the rest was water) detergent LO 630 and 15% chloroform.

Such material was mixed with a large shear for about 3 minutes. The casings produced had a diameter of about 1-2 microns. A layer of such encapsulated liquid crystals was applied to the electrode-covered support using a scraper with a gap setting of 5. The material was dried and used in general as the materials described above.

Figures 14 and 15 show schematically a modified liquid crystal device 140 according to the present invention. The device 140 provides main illumination from a light source 141 on the so-called back or non-viewing side 142. The display device 140 comprises a layer 61 of encapsulated liquid crystal layer 61, top and bottom between the electrodes 13 and 14 supported by them 12a, 12b, generally in the same way as above, for example with reference to Fig. 12, was shown. The reflective medium 80 is an air gap, as described above in connection with the preferred embodiment.

143 is a light control film (VSK) sold by 3M Company with the popular type designation LCFS-ABR0-30 ° -0B-60o-CLEAR-GL0S-.030. The light control film is preferably a thin plastic film made of a black, substantially light-absorbing material with black microcracks 144 which pass through the film from its back surface 145 towards its front surface 146. Such a film or similar material may be used in various embodiments of the invention; 9 311 forms. Such a film may, in fact, tend to collinate the light passing through it to impinge on the liquid crystal material.

The microcrack acts as a louver to direct light, for example light rays 150, 151 to and through the display device 140, and in particular through the support 12 and the liquid crystal layer 61, at an angle generally away from the viewing direction 20 of the viewer's 140 viewing angle when the liquid crystal is aligned or optically substantially transparent. Such an aligned field space is shown in Figure 14, where light beams 150, 151 pass substantially through the display device 140 outside the line of sight. In addition, light, such as a light beam 152, entering the display device 140 from the viewing direction 20, generally passes through the support 12 and the aligned liquid crystal layer, after which it is absorbed by a black film 143 acting like an absorber 21, f.

However, as seen in Fig. 15, when the liquid crystal layer 61 is in a fieldless state, i. the liquid crystal is distorted or randomly oriented, the liquid crystal material layer 61 isotropically scattering the light rays 150, 151 from the source 141, causing complete internal reflection and clarification of the liquid crystal material as described above. Thus, for example, the beam 151 is shown to be isotropically scattered into a beam 151a, internally reflected to a beam 151b and further scattered isotropically to a beam 151c directed out through the dividing surface 64 in the viewing direction 20. The display device 140 of Figures 14 and 15 is particularly useful in situations where light -Viewing-side. However, such a display device also operates as described above, for example with reference to the display device 60 '' 'of Fig. 12, even if the light source 141 is not in the background, as long as sufficient light comes from the viewing direction 20.

Therefore, the device 140 can be used in daylight with or without a light source 141, for example by illuminating it with ambient light on one or both sides, and at night or in other conditions where ambient light is insufficient for the desired brightness, e.g. illumination.

The display device 160 in Fig. 16 is similar to the display device 140, except that the light control film 161 is glued directly to the support material 12b at 162 or otherwise placed against it. Fully internal reflection occurs as described above when the display device 160 is illuminated by light from the viewing direction 20, which is mainly due to the interface 64 of the support material 12a with the air.

There may also be some complete internal reflection at the interface 162. However, since the VSK film is attached directly to the support 12b, the black film absorbs a relatively large amount of light reaching the distribution surface 162. Therefore, it is particularly desirable to use a background light source 141 in the display device 160 to ensure adequate illumination of the liquid crystal material in the layer 61 so as to achieve the desired bright mark display function of the invention.

Referring briefly to Figure 17, there is shown an alternative embodiment 200 of an encapsulated liquid crystal material that can replace various other embodiments of the present invention. The encapsulated liquid crystal material 200 comprises a functionally nematic liquid crystal material 201 housed in a housing whose wall 203 is preferably spherical. In Fig. 17, the material 200 is in a fieldless state, and in that state the structure 204 of the liquid crystal molecules is oriented perpendicular or substantially perpendicular to the wall 203 at the dividing surface 205. Therefore, the structure 204 at the dividing surface 205 is oriented in the radial direction, taking into account the geometry of the housing 202. Closer to the center of the housing 202, the orientation of the structure 204, or at least some of the liquid crystal molecules, tends to curve in order to take advantage, i. to fill, 46 k 9 311 the space 202 of the housing with the substantially lowest free energy arrangement of the liquid crystal in the housing, for example, as seen in the drawing.

Such alignment is believed to result from the addition of an additive to the liquid crystal material 201 that reacts with the support to form normally oriented steryl or alkyl groups at the inner wall of the housing. More specifically, such an additive may be a chromeryleryl complex or a Werner complex that reacts with the PVA of the support 12 to form a housing wall 203 to form a relatively rigid shell or wall with a steryl group or portion that tends to penetrate radially into the liquid crystal material itself. Such penetration tends to affect the observed radial or normal alignment of the liquid crystal structure. In addition, such alignment of the liquid crystal material still follows the above-mentioned strongly curved distortion of the liquid crystal material in the fieldless state, because the derivatives taken at right angles to the general direction of the molecules are not zero.

An example of such a material 200 is shown below. Example 9 To a 5 gram sample of a nematic liquid crystal was added 0.005 g of a 10% solution of Quilon Μ, a chromisteryl complex prepared by DuPont, together with 3 grams of chloroform. The resulting material was homogenized at low viscosity with 15 grams of a 22% Gelvatol 20/30 aqueous PVA solution (the remaining 78% Gelvatol solution was water).

The result was an encapsulated liquid crystal in which the enclosure wall reacted with ς) ιιϊ1οη M to form an insoluble shell.

Examination with polarized light revealed that the wall of the housing aligned the liquid crystal in the radial direction.

47 b 9311

A film was applied to the Mylar support, which already had an Intrex electrode, as above, using a scraper with a gap setting of 0.127 mm. The thickness of the resulting film when dry was 0.025 mm. An auxiliary electrode was attached. The material in the housing began to orient at 10 volts and was fully oriented at 40 volts. The trend was as in Figure 3 above.

The invention can be used in many different ways to display data, characters, data, images, etc. on both large and small scale. According to a preferred embodiment of the invention and best practice, the liquid crystal material is placed in the support material 12 only in those areas where the marks, etc. are to be formed. Alternatively, the layer 61 may extend across the entire support 12 and only those areas where the indicia are to be displayed have electrodes to control this space in the portions near the liquid crystal layer 61. As an optical shutter, the invention can be used to adjust the effective and / or visible brightness of the light seen from the viewing side. If desired, many other structures can also be used that take advantage of the principles of enhanced scattering and / or optical interference provided by the complete internal reflection of this invention.

Referring now to Figure 18, there is shown a liquid crystal device 310 in accordance with the present invention. The device 310 comprises an encapsulated liquid crystal 311 supported by a mounting substrate across which an electric field can be guided through electrodes 313 and 314.

For example, the electrode 313 may be a quantity of indium tin oxide vacuum coated on the substrate 312 and the electrode 314 may be, for example, an electrically conductive ink. A protective layer or coating 315 may be placed over the electrode 314 for protection purposes, but such a layer 315 is not usually necessary to support or limit the encapsulated liquid crystal 311 or the electrode 314. Voltage may be applied to the electrodes 313 and 314 from an AC or DC voltage source 316 via a selectively closed switch 317 and electrical leads 318 and 319 to generate an electric field across the encapsulated pin crystal 311 when the switch 317 is closed.

The encapsulated liquid crystal 311 comprises a liquid crystal material 320 stored within the interior 321 of the housing 322. According to a preferred embodiment and best practice of the present invention, the housing is generally spherical. However, the principles of the invention apply even if the housing 322 is non-spherical. Such a shape should provide those desired optical and electrical properties, such as refractive index, that satisfactorily match the optical properties of the liquid crystal 320, and allow a sufficient portion of the electric field to pass across the liquid crystal material 320 itself to achieve the desired alignment of the liquid crystal when in the field. A particular advantage of the preferred spherical shape of the housing 322 is explained below in view of its effect on the distortion of the liquid crystal structure.

The mounting substrate 312, the electrodes 313 and 314, and the protective coating 315 may be optically transmissive so that the liquid crystal device 310 can control the passage of light therethrough in response to whether or not an electric field is connected across the electrodes and therefore across the encapsulated liquid crystal 311. Alternatively, the mounting substrate may be optically reflective or may have an optically reflective coating thereon, such that such reflective coating reflects light coming through the protective coating 315 depending on whether or not an electric field passes through the encapsulated liquid crystal 311.

According to a preferred embodiment of the invention and best practice, a plurality of encapsulated liquid crystals 311 are placed on the attachment substrate 312 so that the encapsulated liquid crystals adhere to the attachment substrate 312 or a sharing surface material such as an electrode 313 so that the attachment substrate 312 supports and holds them in place. The encapsulant from which the housing 322 is made is also suitable for binding or otherwise adhering the capsule 322 to the substrate 312. Alternatively, another binder (not shown) may be used to adhere the encapsulated liquid crystals 311 to the substrate 312. Since the housings 322 are adhered to the substrate 312 and since each housing provides the necessary attachment to the liquid crystal material 320, the second attachment substrate typically required in prior art liquid crystal devices is not usually necessary. However, in order to protect the electrode from scratches, electrochemical wear, e.g., oxidation, or the like, a protective coating 315 may be placed on the side of the liquid crystal device 310 opposite the mounting substrate 312, the mounting substrate 312 providing a desired physical protection. 310.

Because the encapsulated liquid crystals 311 adhere relatively securely to the substrate 312 and because, as mentioned above, no additional substrate is usually required, the electrode 314 can be attached directly to the encapsulated liquid crystals 321.

Fig. 19 is an enlarged partial sectional view of a portion 322 on a liquid crystal display, e.g., as an octagon 101 and a substrate 12 in Fig. 9. As seen in Fig. 19, a 200 Angstrom thick electrode layer 333 is coated on a surface of a substrate 12 (312 in Fig. 19). , which may be indium tin oxide or other suitable electrode material such as gold, aluminum, tin oxide, antimony tin oxide, etc. One or more layers 334 having a plurality of encapsulated liquid crystals 311 are directly placed and adhered to the electrode surface 333. According to a preferred embodiment and best practice with the encapsulant forming the various housings 322, although, as mentioned above, an additional adhesive or bonding agent may be used for such adhesion purposes. The thickness of the layer 334 may be, for example, about 8-254 microns, preferably 18-102 microns, more preferably 50 b 9 311 20-30 microns, especially 25 microns. Other thicknesses can also be used, depending on, among other things, the ability to make a thin film and the puncture properties of the film. The second electrode layer 335 is coated on the layer 334 either directly on the material from which the housings 322 are made or alternatively on the additional bonding material used to bond the individual encapsulated liquid crystals 311 to each other and the attachment substrate 312. The electrode layer 335 may be about 13 microns thick and electrically conductive. printing ink or materials mentioned above for layer 333. As shown in Figure 19, the display may have a protective layer 336 for the purposes described above in connection with the coating 15 in Figure 18.

One feature of this invention using encapsulated liquid crystals 311 is that the multi-purpose substrate can be made to display virtually any display as a function of selective segments of electrically conductive printing electrodes printed only on the liquid crystal material.

In this case, the entire surface 331 of the substrate 312 may be coated with an electrode material 333, and even the entire surface of that electrode material may be coated with a layer 334 of substantially associated encapsulated liquid crystals 311. Thereafter, the electrode segment pattern may be printed with electrically conductive printing ink 335. may connect the surface 331 to a voltage source, and the respective electrical wires may connect the respective segments of the electrically conductive printing ink via respective controlled switches to such a voltage source. Alternatively, the encapsulated liquid crystals 311 and / or the electrode material 333 may be placed on the surface 331 only in those areas where the display segments are desired. The ability to place the encapsulated liquid crystal only in the desired area or in several areas such as display segments by substantially conventional methods (such as screen printing or other printing methods) is particularly attractive compared to the prior art which has the problem of storing liquid crystals between flat plates.

51 8 9 31 1

The function of the liquid crystals in the layer 334 is to attenuate or not to attenuate the light entering them depending on whether or not an electric field passes across them. The liquid crystal material preferably contains a piezocratic dye in solution to provide substantial absorption attenuation in the "fieldless" state, but to be sufficiently transparent in the "field" state. Said electric field may, for example, be one which is generated when the electrode layer portions 333 and 335 are connected to an electric voltage source in a single segment of the liquid crystal device 10 ', such as segment 101a. The magnitude of the electric field required to connect the encapsulated liquid crystals 311 from the non-field (magnetized) state to the field (magnetized) state may be a function of several parameters including, for example, the diameter of the individual enclosures and the thickness of layer 334, which in turn may depend on the diameter of individual enclosures 322. in the thickness direction of layer 334.

It will be appreciated that because the liquid crystal material is enclosed in the respective housings 322 and because the individual encapsulated liquid crystals 311 are attached to the substrate 312, the size of the liquid crystal device 10 'or any liquid crystal device using the encapsulated liquid crystals of this invention is substantially unlimited. Areas intended to effect a change in the optical properties of the encapsulated liquid crystals of such a device in response to a field or field space must, of course, have electrodes or other means for applying a suitable electric field to such liquid crystals.

The electrode layer 333 can be attached to the substrate 312 by evaporation, vacuum coating, metallization, pressing, or some other conventional technique. In addition, the layer 334 formed of encapsulated liquid crystals 311 can be attached by, for example, web or gravure roll or reversing roll printing methods. The electrode layer 335 can also be attached by various printing, jet printing or other methods. If desired, the electrode layer 333 may be made as a full coating of the substrate 312 52 1/9311, such as Mylar, as described above, as part of the process in which the Mylar film material is made, and also the layer 334 may be attached as part of such a manufacturing process.

It has now further been found that when a pleochro dye is dissolved in the liquid crystal material 30 in the housing 32 (Fig. 2), a dye which is also normally expected to be sensitive to optical polarization is no longer polar sensitive because the dye tends to follow the same curved orientation or distortion. the liquid crystal structure has. Here, it has been found that the discontinuity point 55 in the housing 32 further distorts the liquid crystal structure, which in turn further reduces the possibility that the liquid crystal material 30 would be sensitive to the optical polarization of the incoming light. When the liquid crystal structure and the pleochro dye are sufficiently distorted to fold on themselves generally, for example as shown in Figure 2, the encapsulated liquid crystal usually absorbs light or prevents it from passing through when the encapsulated liquid crystal, and in particular its liquid crystal material, is not affected by an electric field.

However, when an electric field acts on the encapsulated liquid crystal as shown in Fig. 3, the liquid crystal and the pleochro dye in solution therewith are exposed to the electric field as shown in the figure. Such alignment allows light to pass through the encapsulated liquid crystal 11.

In order to optimize the contrast properties of a liquid crystal device such as that shown in Fig. 9 comprising encapsulated liquid crystals 11 having a pleochro dye, and more specifically from the encapsulant to the liquid crystal material, and vice versa, that they are as much as possible the same. The proximity of the 53 £ 9311 compatibility factors depends on the desired degree of contrast and permeability of the device, but the standard refractive index of the crystal and the material factor preferably differ by no more than 0.1, more preferably 0.01, especially 0.001. The permissible difference depends on the size of the housing and the intended use of the device. Sears ’publication,“ Optics, ”published by Addison-Wesley, contains an in-depth review of the two-folds relevant to the above, and the relevant parts of its text are enclosed with reference.

However, when the field is not affected, there is a difference in the refractive indices at the boundary between the liquid crystal and the housing wall, due to the fact that the specific refractive index of the liquid crystal is higher than that of the encapsulant. This causes refraction at that interface or boundary and thus increases scattering and is the reason why the nematic encapsulated liquid crystal material of this invention works particularly to prevent light transmission even when no pleochro dye is used, although such dye absorbs considerable light scatter in the housing.

Typically, the encapsulated liquid crystals 311 are placed on the substrate 312 such that the individual encapsulated liquid crystals 311 are relatively randomly aligned, and preferably a plurality of enclosures thickly, to provide a sufficient amount of liquid crystal material to provide the desired level of light retention and / or transmission properties.

In a liquid crystal device, such as the device 100 shown in Fig. 9, which consists of a liquid crystal material 320 containing pleochro dye to form encapsulated liquid crystals 311 of the invention (Fig. 18), it has been found that the degree of optical absorption is at least approximately equal to that of relatively free (unencapsulated) pleoc dye-containing liquid crystal material. Unexpectedly, it has also been observed

54 «« H

that when the electric field is switched on, for example as shown in Fig. 3, the translucency or lack of opacity of the encapsulated liquid crystal material containing the pleochro dye is at least approximately the same as in the conventional case of a prior art device in which the dye is in solution with a relatively free liquid crystal material.

Fig. 20 is a circuit diagram showing a circuit across which the electric field E of Fig. 3 is generated. The electric field is conducted from the voltage source 316 when the switch 317 is closed. Capacitor 370 shows the capacitance of the liquid crystal material 30, 320 in the encapsulated liquid crystal 11, 311 when such an electric field is connected as shown in Fig. 3. Capacitor 371 shows the capacitance of the housing wall 54 in the upper region (direction suitably refers to the drawing, but otherwise has no particular significance). Capacitor 372 similarly shows the capacitance of the lower part of the housing, which is exposed to the electric field E. The magnitude of the capacitance of each capacitor 370-372 is a function of the dielectric constant (coefficient) of the material from which each capacitor is made and the distance between their effective plates. It is desirable that the voltage drop in capacitors 371 and 372 be less than the voltage drop in capacitor 370, with the result that most of the electric field E affects the liquid crystal material 30 in the encapsulated liquid crystal 11, 311 for the best possible result, i. to achieve alignment of its liquid crystal structure with the minimum energy consumption of the voltage source 316.

However, it is possible that the voltage drop in one or both capacitors 371, 372 exceeds the voltage drop in capacitor 370, which is functionally acceptable as long as the loss in the capacitor (liquid crystal material) is large enough to produce an electric field toward the liquid crystal material, e.g.

55 89311

For example, with respect to capacitor 371, the dielectric material is that of which wall 54 is made relatively close to the top of housing 32, 322. The effective plates of such a capacitor are the outer and inner surfaces of the housing wall, and the same is true of the capacitor 372 at the bottom of the housing. By making the wall 54 as thin as possible while still maintaining sufficient strength to protect the liquid crystal material, the size of the capacitors 371 and 372 can be maximized, especially compared to the rather thick or long distance between the top and bottom of the liquid crystal material in the housing.

The value of the dielectric constant of the liquid crystal material 320 is anisotropic, which is why such a value is also called the dielectric constant. It is preferred that the dielectric constant of the wall 54 be not less than the lower dielectric constant of the anisotropic liquid crystal material 20 to facilitate meeting the above conditions. Since the liquid crystal material typically has a lower dielectric constant of about 6, this indicates that the encapsulant material preferably has a dielectric constant of at least about 6. Such a value can vary widely depending on the liquid crystal material used, and can be as low as about 3.5 and as high as about 8 commonly used liquid crystals. .

The encapsulated liquid crystal 311 has such features that since the liquid crystal structure is distorted and the pleochro dye is similarly distorted, the absorption or blocking of light passing through the encapsulated liquid crystals is very effective when the electric field E is not connected across them. On the other hand, due both to the efficient use of the electric field across the liquid crystal material 320 encapsulated in the encapsulated liquid crystals 311 to align the liquid crystal molecules and the dye therewith and to the above-described preferred when the electric field is connected, the encapsulated liquid crystal 311 has optical transmission properties. good.

Since multiple encapsulated liquid crystals 11, 311 are usually required to construct a final liquid crystal device, such as device 100 of Figure 9, and since those encapsulated liquid crystals generally exist in multiple layers, it is desirable that the dielectric anisotropy of the liquid crystal material be relatively high to reduce the electric field E voltage requirement. More specifically, the difference between the dielectric constant of the liquid crystal material in the fieldless state, which must be quite small, and the dielectric constant of the liquid crystal material subjected to the electric field, which must be relatively large, must be as large as possible corresponding to the dielectric constant of the encapsulant.

As stated above, the smaller the size of the housings, the smaller the electric field required to cause the liquid crystal molecules in the housings to align. However, the larger the ball, the longer the reaction time. One skilled in the art will have no difficulty, in view of this presentation, in determining the appropriate optimum enclosure size for a particular application.

The encapsulant from which the enclosures are made should be of a type that is not substantially affected by, reacted with or otherwise chemically affected by the liquid crystal material or the pleochro dye. The toner should dissolve in the liquid crystal material and should not be absorbed by the encapsulant. In addition, in order to achieve the desired relatively high impedance of the encapsulant, such material must be relatively pure. In particular, when the encapsulant is prepared as an aqueous dispersion or ion polymerization, etc., it is important that the amount of (electrically conductive) ionic impurities be as small as possible.

Examples of pleochroic dyes suitable for use in the encapsulated liquid crystals 57 8 931 1 11 of this invention include indophenol blue, Sudan black B, Sudan 3, Sudan 2, D-37, D-43 and D-85, manufactured by E. Merck, identified above.

Example 10 0.45% of the pleochro dye Sudan Black B was dissolved in a liquid crystal formed of aromatic esters. Such a material mixture is sold by American Liquid Xtal Chemical Corp., Kent, Ohio under the trade name NMB250.

Such material was mixed with 7% polyvinyl alcohol, purified to remove all salts. The solution was also made using ASTM-100 water. The resulting mixture was placed in a colloid mill with a cone gap setting of 0.1 mm, and the material was ground for four minutes to make the particle suspension size fairly uniform.

The result was a stable emulsion with a suspension particle size of about 3 microns. The emulsion was cast on a Mylar film 2 precoated with a 31 ohm / cm layer of indiuratin oxide electrode purchased from Sierracin. A scraper was used to apply the emulsion material to the electrode coated side of the Mylar film.

A 178 micron layer of emulsion material was placed on such an electrode and allowed to dry to a total thickness of 20 microns. A second layer of the same emulsion was then applied to the first, resulting in a 40 micron composite layer with small liquid droplets in the polyvinyl alcohol matrix. The encapsulated liquid crystals may preferably be lowered as a single layer having a thickness of one or more enclosures.

The liquid crystal device thus made, comprising a Mylar layer, an electrode, and encapsulated liquid crystals, was then tested by applying an electric field, after which the material changed from black to almost completely transparent. Material viewing angle, i.e. the angle at which the light transmitted was very large, and the contrast ratio of 58,893,11 in a 50-volt electric field was 7: 1. The switching speed was about 2 milliseconds closed and about 4 milliseconds open.

Example 11

In the example, 900 g of 7% high viscosity, fully hydrolyzed polymer (American Liquid Xtal Chemical Corporation SA-72), 100 g of nematic liquid material 8250 from the same manufacturer, 0.45 g of C26510 Sudan Black B and 0.15 g of C26100 Sudan three (the latter two ingredients were pleochromatic dyes). The polymer was weighed in a beaker. The liquid crystal was weighed, placed on a hot plate and heated slowly. The dye was weighed on a scale and added very slowly to the liquid crystal, which was stirred until all the dye had dissolved.

The liquid crystal and dye solution was then filtered through a standard Millipore filtration system using 8 m of filter paper. The filtered liquid crystal and dye solution was stirred into the polymer using a Teflon stick. Such a mixture was encapsulated by placing it in a colloid mill which was operated for five minutes. The emulsion film was then drawn onto an electrically conductive polyester sheet.

In use, the liquid crystal structure of such an example began to be subjected to an electric field of 10 volts, and at 40 volts it reached the saturation point as well as the maximum optical transmittance.

Example 12

The procedure of Example 11 was performed using the same ingredients and steps, except that the 7% polymer of Example 11 was replaced with a 5% high viscosity, fully hydrolyzed polymer such as SA-72. The functional results were the same as in Example 2.

Example 13

The process of Example 11 was performed to make an emulsion using 4 g of a 20% medium viscous, partially hydrolyzed polymer (as 405 in Table I above), 2 g of nematic liquid crystal material 8250 with 0.08% purple pleochro dye D-37 ( E. Merck, an exclusive pleochro dye manufactured by West Germany) in solution with a liquid crystal.

Using a Teflon swab, a slide was taken, and the inspection revealed an average casing diameter of about 3-4 microns. The material was filtered through a Millipore sieve filter and a second slide was taken, at which point the inspection revealed that there had been very little change in the housing size since the first inspection.

The emulsion was drawn on an electrically conductive polyester backing film as in Example 11 using a scraper with a gap setting of 0.127 mm. In use, the encapsulated liquid crystal material began to subject to an electric field of 10 volts and was saturated at 40 to 60 volts.

Example 14 Using a glass rod purified and washed with deionized ASTM-100 water, 2 grams of 40% nematic liquid crystal material 8250 in which 0.08% of pleochro dye D-37 was dissolved in 4 grams of unsalted liquid was stirred very carefully for about 15 minutes. 20% by weight of a semi-hydrolysed medium viscous polymer. The material was then passed through a Millipore filter of about 4 microns. After the bubbles had disappeared, a slide plate was taken.

The film was then drawn with a gap setting of 0.127 mm onto an electrically conductive Intrex electrode film placed on a Mylar polyester support material. In use, it became apparent that the liquid crystal material began to subject in a 5 volt electric field. The contrast was good and the liquid crystal material was saturated in a 40 volt electric field.

60 b 9 31 1

Example 15 In this example, 8 grams of pleochro dye D-85 dissolved in diphenyl liquid crystal E-63 was used. British Drug House, a subsidiary of E. Merck in West Germany, sells such material pre-mixed. In the example, 16 grams of 20% medium viscosity semi-hydrolyzed PVA polymer was also used as the encapsulant. The liquid crystal and polymer solution was thoroughly mixed into the polymer by hand slowly. The combined material was then sieved at low viscosity. A slide was taken, which on examination showed a housing size of about 3 microns. A film of such an emulsion was drawn on an electrically conductive polyester sheet as above using a 0.127 mm setting. The liquid crystal structure of the film began to subject to an electric field of about 6 volts and was saturated at about 24 volts.

Example 16

A mixture of a nematic liquid crystal 8250 with 0.08% pleochro dye D-37 dissolved and a solution of 15% Gantrez AN16 in 85% water was made. The mixture was 15% liquid crystal and 85% Gantrez preservative. The mixture was homogenized at low viscosity to an emulsion which was coated, as above, on an electrode / support film having a thickness of 0.030 mm. After the emulsion was dried, the resulting liquid crystal emulsion generally reacted to the electric field as above, absorbing substantially or at least not significantly transmitting light when in the fieldless state, so that the transmission threshold was about 7 volts and the maximum transmission saturation limit was about 45 volts.

According to the present invention, the properties of the ingredients used for the preparation of the encapsulated liquid crystals 11, for example as described above, may be as follows.

The liquid crystal material. This material may be about 5-20% and preferably about 50% (and in some cases more, not 8931 1 depending on the nature of the encapsulant) including a pleochromatic dye, 25% by volume (when using Gelvatol as an encapsulant) in a mixing device such as a colloid mill. of the total volume of solution. Generally, the actual amount of liquid crystal material used should exceed the volume of encapsulant, e.g., PVA, to optimize the enclosure size.

PVA. The amount of PVA in the solution should be on the order of about 5-50%, and possibly more, depending on the hydrolysis and molecular weight of the PVA, and preferably, as explained above, about 22%. For example, if the molecular weight of PVA is too high, the resulting material will become glass-like, especially if too much PVA is used in the solution. On the other hand, if the molecular weight of PVA is too low, too little use of PVA causes the viscosity of the material to be too low, and the resulting emulsion does not retain well and the small droplets of the emulsion do not solidify sufficiently into the desired spherical liquid crystals.

The carrier material. The remainder of the solution should be water or another, preferably volatile, carrier, as described above, with which the emulsion can be made and applied appropriately to a substrate, electrode, or the like.

It will be appreciated that since uncured enclosures or small droplets are liquid supported, various conventional or other methods may be used to sort the enclosures by size so that the enclosures can be freed from undesired size by re-feeding them through a mixing device and the end-use enclosures. reasons for the desired consistency.

Although the encapsulation technique has been described in detail with reference to emulsification because the fact that the encapsulation and binder are the same makes the manufacture of liquid crystal devices 62 b 9 31 1 easy, the production of separate liquid crystals from liquid crystal material can sometimes be advantageous, and the use of such separate enclosures within the scope of the present invention.

Although the invention of the present invention functions in response to the activation and removal of an electric field, operation can also be accomplished by activating and removing the magnetic field.

Among other things, the invention can be used to provide a controlled optical display.

Claims (52)

Liquid crystal apparatus (10), characterized in that it comprises liquid crystal means (30) for primarily selective light scattering and, in response to an exposed input, light transmitting, wherein the liquid crystal means comprises an operational nematic liquid crystal material having a pos. carrier medium (11; 12; 32) for supporting said liquid crystal member, said carrier medium including a protective medium for pouring said liquid crystal member (30) into a plurality of volumes, said protective medium comprising a surface for directing said liquid crystal member (30) and receiving ice liquid. 1 light scattering in the absence of an exposed entrance, and the reflector (18, 19) for streamlining internal reflection of the light scattered by the liquid crystal member (30). Apparatus according to claim 1, characterized in that said liquid crystal means and protective medium comprise a layer of encapsulated liquid crystal and furthermore an electrode member (13, 14) located between said carrier medium and said layer of encapsulated liquid crystal for providing an electric field. and direction of said liquid; crystal in relation thereto. Apparatus according to claim 1 or 2, characterized in that the liquid crystal means comprises operationally nematic liquid crystal material, wherein the liquid crystal material has a normal refractive index adapted to the carrier medium in the presence of an electric field, and an abnormal refractive index. 74 B 9 311 refractive index for achieving substantially isotropic scattering in the absence of an electric field. 4. Apparatus according to any one of claims 1-3, characterized in that said carrier medium has a face side and an opposite side, corresponding media on said viewing and opposite side, and the refractive index of said carrier medium is greater than the index of refraction. of the medium on the view and the opposite side, said reflection means comprising an interface with the medium of that of said sides, which provides total internal reflection in said carrier medium of such light entering at such an interface at an angle exceeding an exposed light angle cone at which light could be transmitted through such an interface. 5. Apparatus according to claim 4, characterized in that said liquid crystal means operates in the absence of an electric field for spreading a substantial amount of light at an angle exceeding the total internal reflection angle of said carrier medium at such an interface. 6. Apparatus according to claim 5, characterized in that said carrier medium further comprises a carrier for supporting said volumes of liquid crystal means in said protective medium. 7. Apparatus according to claim 5, characterized in that the refractive index of the carrier medium is higher than the median refractive index on both the view and the opposite side and said reflection means comprise the interfaces between said sides and such media, that total internal reflection is achieved. Apparatus according to claims 1-7, characterized in that it further comprises a directing means (143) for directing incoming light to said carrier medium at said opposite side, said directing means including means for directing incoming light in said carrier arm. 1 dium in a direction substantially outside the normal line of view from said face. Apparatus according to claim 8, characterized in that said reflection means comprises a gap (80) between said carrier medium and said directing means for providing a total internal reflection interface between said carrier medium and the gap. Apparatus according to claim 9, characterized in that said directional means comprises a light-controlling film with light transmitting and light absorbing parts, the absorption part being in relation to said interface such that it absorbs at least part of the light transmitted through the interface. 11. Apparatus according to claims 1-4, characterized in that said liquid crystal means comprises operationally nematic liquid crystal material and said protective medium pour the operational nematic liquid crystal material in the form of separate amounts, said liquid crystal material rotates in a non-parallel direction in a non-parallel direction. -rich field, and allows a generally parallel direction of them in the presence of an electric field. 12. Apparatus according to claim 11, characterized in that it further comprises additives (134) in said operationally nematic liquid crystal material for accelerating such distortion and reversing in random direction upon franking of such an electric field. 13. Apparatus according to claim 11, characterized in that such an additive comprises a chiral additive. Apparatus according to claims 1-13, characterized in that said carrier medium has a viewing side (20) for emitting at least part of the light isotropically scattered by said liquid crystal means, and said carrier medium has an in relation to said carrier medium. opposite side, and further includes optical absorption means (81) for absorbing light transmitted through said opposite side of the carrier medium. Apparatus according to claims 1-14, characterized in that said surface impacts the natural structure of said liquid crystal means by inducing a twisted direction thereof in the absence of an exposed entrance and further comprising means for forcing at least part of the at least some of the liquid crystal means. a direction substantially perpendicular to said surface-defining means in the absence of such exposed entrance. Apparatus according to claims 1-15, characterized in that said reflection means comprise means for reflecting light, scattered by said liquid crystal means, back to said liquid crystal means for displaying relatively clear signs or the like on a relatively dark background. Liquid crystal structure, characterized in that it comprises an operational nematic liquid crystal material with a tendency to be oriented in a direction and allow light to pass therethrough, at an exposed entrance, and a means defining a non-planar surface, which means affecting the liquid crystal member. natural structure by inducing a distorted direction thereof in the absence of an exposed input, the optical transmission of the liquid crystal material substantially decreasing due to the dispersion or absorption. 18. Apparatus according to claim 17, characterized in that the surface defining means comprises an encapsulating medium (32) which rotates the structure of the liquid crystal material in the absence of an electric field, the encapsulating medium comprising a dried stable emulsion. 19. Apparatus according to claim 17, characterized in that the surface-defining means comprises protective means for protecting the liquid crystal material and providing such a distorted direction, the crystal material and the protective medium forming a dispersion thereof. Apparatus according to claims 17-19, characterized in that the liquid crystal material is optically anisotropic and that the difference between the ordinary refractive index of said liquid crystal material and the refractive index of said surface defining material is at most about 0.3. Apparatus according to any one of claims 17-20, characterized in that the liquid crystal material comprises an optically anisotropic liquid crystal material which is poured into a protective means provided with means for defining a non-planar surface, and which in the presence of an electric field has a water level. a refractive index, which is substantially the same as the refractive index of said guard, for maximizing the optical transmission. Apparatus according to claim 21, characterized in that the liquid crystal material has a fringe of the normal deviating refractive index which deviates from the refractive index of the surface defining means. Apparatus according to claims 19-22, characterized in that it contains a substrate (12) for supporting a layer of said liquid crystal material and protective means, the layer being from 0.076 to 0.254 mm thick. Apparatus according to claims 19-23, characterized in that the protective means forms capsular-like volumes containing liquid crystal material and that the size of the capsular-like volumes is about 0.3-100 microns. 25. Apparatus according to claims 17-24, characterized in that the liquid crystal material has positive dielectric anisotropy and that the surface-defined means influence the natural structure of the liquid crystal material to provide a 78 b 9 51 in the distorted direction thereof in the absence of an electric field for reduction. of the optical transmission independently of polarization, said crystal material responding to the presence of an electric field to increase such optical transmission. Apparatus according to claims 17-25, characterized in that the liquid crystal material comprises an operational nematic liquid dielectric material with positive dielectric anisotropy and the surface defining means comprises a plurality of protective means with curved surfaces for providing a twisted direction of said liquid crystal material. such rotation either spreads or absorbs light if the pleochroic dye is present in the liquid crystal material and p.g.a. an electric field in the form of such an exposed input reduces the amount of such scattering or absorption at least in the direction of the applied electric field. 27. Apparatus according to claims 17-26, characterized in that the surface defining means form curved volumes (31) containing liquid crystal material and said twisted direction comprises a direction at least partially parallel to the curvature of such volumes. 28. Apparatus according to claim 27, characterized in that the curved volumes contain discrete curved volumes containing discrete quantities of liquid crystal material. 29. Apparatus according to claims 17-28, characterized in that the surface-defined members are selected from the group of resin, polymer, gelatin, Carbopole and Gantrez, polyvinyl alcohol, carboxypolymethylene polymer and polymethylvinyl ether / maleic anhydride. 30. Apparatus according to claims 17-29, characterized in that it further comprises substrate means (12) for the support of the combination of said liquid crystal material and surface defining means. Apparatus according to claims 1-30, characterized in that it further comprises means (13-16) for applying the electric field through said liquid crystal material for effecting its direction and providing light absorption or scattering. Apparatus according to claim 31, characterized in that it is provided with electrode means (13, 14) for applying an electric field over the liquid crystal material. Apparatus according to claim 32, characterized in that the electrode means comprise electrically conductive ink. Apparatus according to claim 33, characterized in that the electrically conductive ink is optically reflective. 35. Apparatus according to claim 32, characterized in that the electrode means are applied according to any of the following methods: evaporation, vacuum coating, sputtering, printing, disc roll printing, roll depth printing, counter roll printing, stencil printing, silk screen printing or ordinary printing. 36. Apparatus according to claim 32, characterized in that said electrode comprises at least one material component of the group consisting of indium tin oxide, gold, aluminum, tin oxide and antimony tin oxide. Apparatus according to claim 32, characterized in that a number of volumes of liquid crystal material in a protective member cover a substantial part of the carrier medium. Apparatus according to claim 37, characterized in that it further comprises a plurality of electrode means for applying an electric field to selected parts of said liquid crystal material, said electrode means comprising a plurality of 80 3 9 31 electrodes distributed over a smaller range of said carrier medium. and liquid crystal material than the size of the portion of the liquid crystal material covering said carrier medium. 39. Apparatus according to claim 38, characterized in that one of the electrode members comprises a sheet-shaped electrode which covers a substantial surface portion of said protective medium. Apparatus according to claims 32-39, characterized in that it further has circuit means (15, 16} for applying electrical energy to said electrode means for providing an electric field. 41. Apparatus according to claims 1-40, characterized in that the liquid crystal material has a positive dielectric anisotropy and the lower dielectric constant of the liquid crystal material is between about 3.5 and about 8. 42. Liquid crystal structure, characterized in that it includes an operational nematic liquid crystal material (30) in a protective medium (11, 12, 32) which tends to distort said material in a direction relative to a wall (50) thereof, the substance in the absence of an electric field is generally randomly directed, whereby its light transmission decreases, and the liquid crystal material reacts to an electric field and strives to be directed relative to the light transmission field, and an additive (134) in said liquid crystal material removing the seed distortion and bending in a random direction upon the cessation of such an electric field. 43. A structure according to claim 42, characterized in that the additive comprises a chiral additive. 44. Liquid crystal apparatus, characterized in that it comprises a liquid crystal means (30) for selective, mainly isotropic scattering of light or transmission of light which is respected at an exposed entrance, said liquid crystal apparatus comprising an operational nematic material liquid crystal. positive dielectric anisotropy, a first media means (11, 12, 32) for preserving said liquid crystal means, said first media means consisting of a surface means for providing non-linear direction of the liquid crystal structure and thereby a diffusion of light in the absence of such exposed input, and a second media means (18, 19) for cooperation with said first media means for providing total internal reflection of light scattered by said liquid crystal means. A liquid crystal apparatus for displaying clear signs or the like on a dark background, characterized in that it comprises liquid crystal means (30) for substantially isotropic scattering of light entering therein, said liquid crystal means including a plurality of volumes of liquid crystal with positive dielectric anisotropy in a protective medium (11, 12, 32), and said volumes are defined by walls (50) of the protective medium, which walls are operational in the absence of an electric field for interaction with said liquid crystal material for scattering light, and said liquid crystal material. responds to the provision of an electric field for directing in relation thereto and simultaneously reducing such scattering, and a reflection means for reflecting light, which is in such a way isotropically scattered by the liquid crystal means, back to the liquid crystal means for further spreading thereof. 46. Liquid crystal apparatus for displaying clear signs or the like on a dark background, comprising liquid crystal means (30) for substantial isotropic scattering of light entering therein, and reflection means (18, 19) for reflection of light, which is in such a manner dispersed by said liquid crystal , back to said liquid crystal means for further diffusion thereof, characterized in that said reflection means comprises a carrier medium (12) for supporting 82 '' 931 I of said liquid crystal means and providing total internal reflection of light therein, and said carrier medium ( 64) through which light isotropically scattered by said liquid crystal means can be transmitted within an exposed angle to produce such clear signs, and said carrier medium has a region in which light is not reflected through said viewing surface to thereby produce a relatively dark background, said region comprising an o is closest to the liquid crystal member and is substantially optically transmissive, and said liquid crystal member comprises at least one layer (61) of encapsulated operational nematic liquid crystal material in said carrier medium, and the optical beam mission in the presence of an electric field and the creation of substantial isotropic scattering in the absence of an electric field. Apparatus according to claim 46, characterized in that it further comprises optically absorbent means (21) for absorbing light transmitted through said liquid crystal material and the medium which is away from the front of the apparatus. Use of an apparatus according to claims 1-47 as an electro-optical display. Use of an apparatus according to claims 1-47 as a bulletin board. 50. A method for displaying a clear sign or the like against a relatively dark background using liquid crystal material preserved in volumes formed in a protective medium, characterized in that the liquid crystal material is operationally nematic and has a positive dielectric anisotropy and a standard deviation refractive index, which differs from the refractive index of the protective medium and a normal refractive index substantially adapted to the refractive index of the protective medium, the natural structure of such a liquid crystal material being distorted to provide substantially isotropic scattering of light, on the liquid crystal material, reflection of at least a portion of the sealed scattered light back into said volumes of liquid crystal material for further diffusion, said dispersion comprising total internal reflection of isotropic scattered light back into liquid crystal. the transmitting material for clarity, and transmitting to a viewing area at least a portion of the light scattered by said liquid crystal material to form such a sign or other information. 51. A method according to claim 50, characterized in that it further comprises selectively applying an electric field to such liquid crystal material for directing it for transparency and providing a relatively dark background. 52. A method according to claim 51, characterized in that it further comprises absorbing at least a portion of the light transmitted by such a liquid crystal material.