US3647279A - Color display devices - Google Patents

Abstract

A display device for exhibiting a color pattern, said device comprising container means having a light-transmitting section and a juxtaposed darker hued or opaque section, a quantity of liquid crystalline material interposed between said container sections and encapsulated within said container means, said material having a characteristic of selective light scattering to exhibit color patterns within a range of temperatures at which said display device is normally utilized, and means for peripherally sealing one of said container sections to the other. Means can also be provided for applying deformational stress to the liquid crystal to vary its color pattern.

Description

United States Patent Sharpless et al.

[ Mar. 7, 1972 [54] COLOR DISPLAY DEVICES [72] Inventors: Edward N. Shnrpless, Pitcairn; Frederick [2! 1 Appl. No.: 40,925

[52] US. Cl ..350/l60, 40/ I30, 356/32 [5 l] Int. Cl. ..G02t H40 [58] Field of Search ..356/32; 350/160; 40/130 [56] References Cited UNITED STATES PATENTS 3,441,513 4/ 1969 Woodmansee ..350/ 160 LC OTHER PUBLICATIONS Product Engineering, Dec. 21, 1964, Vol. 35, pp. 56 57. Ferguson, Liquid Crystals, Scientific American, Vol. 21], 8/64, pp. 76- 85.

Wysooki et al., Molecular Crystals & Liq. Crystals, Vol. 8, 8/6 p 47 l- 488.

Adams et al., Molecular Crystals & Liq. Crystals, Vol. 8, 8/68, pp. 9- l8.

Klein et 21]., Rev. of Sci. lnstr., Vol. 41, No. 2, 2/70, pp. 238 239.

Garn, J. of Amer. Chem. Soc., Vol. 91, No. 19, 9/69, p. 5382. Lehmann, Thermodynamics, Vol. I, 1966, pp. 2- 5.

Fergason et al., Electro- Technology, l/70, pp. 41- 50.

Primary Examiner-Ronald L. Wibert Assistant Examiner.l. Rothenberg Attorney-Donn J. Smith [57 ABSTRACT A display device for exhibiting a color pattern, said device comprising container means having a light-transmitting section and a juxtaposed darker hued or opaque section, a quantity of liquid crystalline material interposed between said container sections and encapsulated within said container means, said material having a characteristic of selective light scattering to exhibit color patterns within a range of temperatures at which said display device is normally utilized, and means for peripherally sealing 'one of said container sections to the other. Means can also be provided for applying deformational stress to the liquid crystal to vary its color pattern.

20 Claims, 54 Drawing Figures PATENTEUMAR 71912 3, 647, 279

sum 2 [IF 8 PAIENIEUMAR 7 I972 3,647, 279

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rang aw mavzn" COLOR DISPLAY DEVICES The present invention relates to variable color display or aesthetic devices and to means for enhancing the variable color patterns produced by the device for entertainment, advertising, aesthetic or decorative effects or purposes.

Devices for displaying color patterns for various purposes are legion. These devices usually employ various colored materials or surfaces, color filters or simply lights of various colors. Many of these devices are capable only of displaying colors or color patterns of a fixed or invarying nature, and their usefulness is thereby limited. Particularly in displays for decorative or aesthetic purposes, the novelty wears off" all too soon.

Color display devices in the form of various kinds of lightprojecting machines are likewise available for use in advertising, entertainment and in the purely decorative field. For the most part, these machines rely on solid crystalline or plastic colored materials, photographic slides, systems of mirrors with color filters attached, movable arrays of color filters, or simply lights of various colors which may be movably disposed or otherwise sequenced to illuminate the object or area with the intended color pattern or patterns. While some of these machines work reasonably well in a limited range of applications and furnish a number of fixed color patterns, the machines usually are complex in construction owing to mechanical repetition of various components. The total number of available color patterns or color variation is severely limited in most cases and the sense of variety is soon lost. The colors or color patterns are usually overly brilliant, cold, or otherwise unnatural in their hues and intensities.

In many color display devices there is the frequent requirement that several such devices or systems be used to approach the desired aesthetic or decorative effects. The number of moving components of these systems are thereby multiplied, leading to maintenance problems. When several. such light systems are utilized, a time synchronization is often required, particularly when one attempts to associate music with a changing color display or an analogous dynamic lighting system. This objective is difficult to accomplish with conventional systems owing to large numbers of moving parts and other practical difficulties. Moreover, the potential variation in color patterns has been severely limited for the reasons pointed out above.

In many other fields of endeavor, it is desired to illuminate relatively large areas in varying color patterns. For example, in the fields of theatrical and nightclub lighting, various means have been utilized for providing colored illuminational patterns, for backdrop or other environmental effects. Frequently, a subdued character is desired of these environmental effects. This is accomplished by rather complex lighting systems, as alluded to above, requiring, where moving patterns are desired, the services of a skilled operator to arrange the necessary combination of lighting components, to achieve a desired sequence of colors or color patterns. Conventionally theatrical lighting systems for this purpose include a light source with a plurality of solenoid-operated color filters for selective orientation in front of the light source for varying the color saturation with which the stage is illuminated. Such equipment may require several hundred color panels, and numerous light sources, all of which must be operated by skilled personnel. Other arrangements involve complicated arrays of mirrors and/or projectors, none of which is capable of changing color patterns with smooth transitions between colors and hues.

Certain of these problems have been alleviated to some extent by projection and display devices disclosed in the U5. Pats. to Clark, 111 No. 3,431,044; Lane et al. No. 3,3l5,39l; and Billings No. 2,600,962. The Clark device inherently involves a number of moving parts but limited color variation.

1 The potential color variations achieved by the Clark device A similar arrangement is shown in the Lane et al. reference in which the intermediate solid member is additionally deformed to simulate motion. The Billings device is analogous, except that a stress-responsive birefringent crystal is employed. The Billings arrangement, moreover, is not directed to the problem of aesthetic or decorative lighting, as it is arranged to pass very narrow optical bands.

in general, the variety of color patterns attainable with devices such as disclosed by Lane et al. and Clark is limited, owing to the employment of birefringent solid members. The cited references require the use of various light polarizing structures, which are not essential to our invention. Our color display device, which can be more or less permanently and directly applied to large surface areas, such as walls, ceilings, stage backdrop, and furniture surfaces, in many cases obviates the need for colored lights or the optical projection of color patterns.

We overcome these disadvantages of the prior art by providing a unique optical display device capable of producing an infinite variety of color variations and patterns. The solution of this perennial problem is realized by introducing a liquid crystalline material into a display device of novel construction. Desirably the liquid crystalline material is selected which has a characteristic of variable light scattering at room temperature or at least at those environmental temperatures under which the device is employed. For example, a liquid crystalline material can be selected, which is capable of variable light scattering at operating temperatures in the region of an illuminating light source, for example one utilized in an advertising sign, area lighting, or other display arrangement. The selected liquid crystalline material desirably but not necessarily exhibits a variable scattering characteristic which is further modified when subjected to mechanical deformation, such as occasioned by shear or flow stresses.

Accordingly, our novel display device or liquid crystal cell is provided firstly with a light transmitting wall to permit viewing of the contained liquid crystalline material. Secondly, the liquid crystalline cell is desirably associated with means for inducing deformational stresses within the contained liquid crystalline material. This can be accomplished in a variety of ways: For examples, the liquid crystalline cell can be constructed with means permitting the displacement of one wall structure thereof relative to another. Various mechanical means can be associated with the cell or display device for inducing flow and attendant shear stresses within the liquid crystalline material.

Our display device as thus far described is capable of a large number of applications, for example as an aesthetic novelty, decorative wall, floor and ceiling panels, backdrops for stages and other illuminated areas, toys, book and album covers, place mats, paper weights, clock faces, displays for table tops and other furniture surfaces, and numerous analogous applications. For many of these applications a subdued background or environmental illumination is sufficient for viewing the infinite variety of color patterns resulting from a stress manipulation of my display device. Deformational stresses can be applied manually or through the operation of suitable mechanical, electromechanical, or electrohydraulic means. Owing to the pressure sensitivity of many liquid crystalline materials, useful in our invention, stresses can be applied by vibratory or minor shock energies. For example, certain forms of the .display device can be suspended or stretched over loudspeaker, or the like, such that color pattern changes are effected by sonic vibrations. An analogous application involves incorporation of my display device on piano tops or in connection with other musical instruments.

In many other applications, our liquid crystal display devices find utilization where it is desirable to show visually strain patterns, or patterns of stress application. For example, components of our display devices can be applied to such items as glass or metal sheets to demonstrate physical stresses therein.

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minim Conventionally, the usefulness of cholesteric liquid crystaltine materials has been severely limited owing to their ,greaselike nature. There has been no adequate conventional means for protecting the liquid crystalline material from a hostile environment such as dirt, dust, oil and accidental removal of the material from the surface to which it is applied. Various means for encapsulating liquid crystals have been proposed from time to time. According to one such attempt, the liquid crystalline material is encapsulated as minute balls or droplets in a gelatin matrix. The form of encapsulation, however, does not permit the visual stress phenomenon to be observed and greatly diminishes the light-scattering characteristic of the liquid crystal. Other attempts, involving a simple overlay with a protective material, have met with failure in the absence of an adequate sealing means for excluding elements of a hostile environment.

With the application of deformational stresses to the liquid crystalline material, a distinct and abrupt change in the color of the selectively scattered light is observed. The greatest color change is observable in the area of greatest mechanical force. A deformational force as small as 0.5 gram per square centimeter can be registered as shear phenomenon by appropriate liquid crystalline materials. The sensitivity of these materials is illustrated by the fact that a liquid crystal encapsulation according to our invention and of suitable length tseveral feet, for example) can be used to register a sound wave.

The color patterns produced by the deformational stresses have a relaxation time, that is to say the time for the visible effects of the deformation to return to their relaxed" form after the deformational stress is removed. The deformational stress is most advantageously applied normally of the liquid crystal encapsulation. The pressure can be applied for a smaller or greater interval of time, but preferably for a minimum of 0.2 second. The deformation stresses can be applied by means of an auxiliary member either incorporated in or separate from the encapsulation and having a message. aesthetic design, or the like embossed thereon. A plurality of such auxiliary members can be provided, if desired, for use with a single encapsullation to provide a variety of messages or designs. By pressing the design or message member against a flexible portion of the liquid crystal encapsulation the message or design is delineated by lines or areas of darker color in the ensuing color pattern.

The clear or transparent member of the encapsulation can be made from two or more associated materials of differing refractive indicies for a further enhancement and a variety of the color pattern display.

Therefore, we also contemplate the use of various novel container means to enhance or modify the color patterns and to protect the liquid crystalline material from hostile environments. At least one section of the container is light-transmitting for viewing purposes and a second container section is secured thereto to enclose a quantity of the liquid crystal. The second container section desirably is closely disposed to the first-mentioned container section to conserve liquid crystalline material, which in most applications can be utilized in the context of film thicknesses. The liquid crystal container can be substantially flat, or otherwise as described more fully below, and can be made sufficiently large to cover entire desk or table top surfaces or wall and ceiling surfaces, for example. The liquid crystalling areas of such panels can be continuous or discontinuous depending on the application and character of the container. Light-absorbing means are associated with the liquid crystal material to absorb transmitted light, which would otherwise substantially mask that light which is also variably scattered from the liquid crystal. The light absorber can be incorporated directly in the liquid crystal as a dark dye or suspended material. Alternatively, the second container section can be dark opaque or otherwise dark hued to absorb part or all of the transmitted light to enhance the light scattering characteristic of the liquid crystalline material. Optimally the light absorber is black for maximum enhancement. At

least one of the container sections desirably is flexible or resilient so that the aforementioned deformational stresses can be applied to the liquid crystal externally of the package. Alternatively, deformational stresses can be applied internally of the container, for example in accordance with certain modifications of the invention described and claimed in a copending, coassigned application of Edward N. Sharpless entitled Variable Color Display Device and Projection Means Therefor," Ser. No. 40,899, filed concurrently herewith.

Desirably, the light-transmitting section is of a certain minimal thickness to enhance an illusion of depth in the color pattern of the liquid crystal. In such case, the light-transmitting panel preferably is transparent. The use of a relatively thick light-transmitting section for enhancement purposes is particularly desirable in relatively small decorative objects or panels, which may be viewed from a number of angles or positions. We also contemplate the formation of the liquid crystal container in a variety of shapes and forms, for example as a cube, parallelopipedon, prism, various types of pyramidal forms, hemisphere, hexahedron, octahedron, and other geometric forms. In the multifaceted fonns, we contemplate further the application of liquid crystalline material and corresponding second container sections of two or more faces or facets of the form. Obviously, the invention is equally applicable of nongeometric or random shapes which may be faceted or nonfaceted.

The aforementioned forms and shapes desirably are of lighttransmitting and preferably transparent material so that an in teresting array of reflections and refractions of color patterns are seen within the shape. An unexpected feature of this form of the invention is the fact that the various reflections or refractions may be of widely differing basic colors, as the viewing angle is effectively different for each reflection or refraction of the liquid crystal surface. Our invention utilizes, therefore, in an unobvious manner, another aspect of the selective scattering characteristic of the liquid crystalline material.

ln the latter feature of our invention the forms or shapes can be molded from a transparent plastic and various types of coins, models, fossils, precious and semiprecious stones and the like can be molded within the plastic and viewed against the variable and colored background of the encapsulated liquid crystalline material. The last-mentioned display devices can be utilized as various decorative objects for desk and table tops or as part of ink stands, pen and calendar holders and similar utilitarian articles.

in another arrangement of our invention, a synchronous motor can be provided for operating the aforementioned stress-varying means in accordance with a timed or rythmic sequence for synchronizing our color display device with music or other rythmic operation. Our novel display device is capable of an infinitely variable sequence of color patterns for aesthetic, decorative, and entertainment purposes. A large number of applications of our inventions in the advertising field for various types of eye-catching signs and displays will become readily apparent.

Our display device is capable of producing nonrepetitive color patterns which are a mixture of natural hues and intensities. The effects achieved are warm, relaxed, and psychologically subdued and are therefore particularly desirable for decorative and other aesthetic purposes.

Besides its aesthetic values, our display device is useful in depicting, as a color display, relative motions between or among a number of objects. Such relative motions can be comparatively slight and even of a vibratory nature. 0f greater significance is the capability of simultaneous indication of a number of forces applied externally to our display device at a given time.

We are aware, of course, of a number of United States Patents relating to various applications of liquid crystalline materials. For example, Fergason et al., US. Pat. No. 3,l 14,836 depicts an imaging device, which exhibits a color pattern on a film of liquid crystal upon focusing a heat or thermal pattern thereon. Fergason US. Pat. No. 3,409,404 discloses a liquid crystalline device in which variation in selective scattering of liquid crystalline materials is employed for identifying unknown materials. Williams US. Pat. NO. 3,322,485 utilizes a threshold characteristic of liquid crystalline material to scatter light selectively in the presence of a given electric field. Freund et al. US. Pat. No. 3,364,433 employs a frequency-shifting characteristic of liquid crystalline materials in the presence of an electric and/or magnetic field. None of these references, however, discloses a color display device utilizing liquid crystalline materials in which an infinite or non-repetitive pattern is exhibited by a liquid crystalline material applied by attendant variation in applied mechanical stresses.

We accomplish these desirable results by providing a display device for exhibiting a color pattern, said device comprising container means having a light-transmitting section and a juxtaposed opaque section, a quantity of liquid crystalline material interposed between said container sections and encapsulated within said container means, said material having a characteristic of selective light scattering within a range of temperatures at which said display device is normally utilized, and means for peripherally sealing one of said container sections to the other.

We also desirably provide a similar display device wherein said material has an additional characteristic of a selective light scattering which is variable in accordance with applied deformational stresses, and means are provided for the application of said deformational stress to said material.

We also desirably provide a similar display device wherein flow effecting means include means for displacing at least one of said container sections relative to the other of said sections to effect flow of said material within said container.

We also desirably provide a similar display device wherein the juxtaposed surface of said opaque section is provided with a dark color.

We also desirably provide a similar display device wherein said light-transmitting member is a transparent hemispheroidal member, and said opaque container section is peripherally joined and sealed to a substantially flat surface of said hemispheroidal member, at least some of the faces of said multifaceted member are disposed for reflection and/or refraction of the color pattern of said liquid crystal.

We also desirably provide a similar display device wherein said light-transmitting section is a transparent multifaceted member having container means encapsulating a quantity of liquid crystalline material and secured to at least one face of said multifaceted member.

We also desirably provide a similar display device wherein said light-transmitting section is a substantially flat transparent member of about one-eighth inch in thickness.

We also desirably provide a similar display device wherein said light-transmitting section in a transparent member and said opaque section is peripherally sealed to a surface of said transparent member to encapsulate said liquid crystalline material, a stand is provided for said display device, said stand being shaped to receive at least those portions of said transparent member adjacent said surface, said opaque section is relatively flexible, and said stand includes indicia means engageable with said opaque section when said device is seated in said stand for applying deformational stress to said opaque section to outline said indicia within a color pattern of said material which is visible through said transparent member.

During the foregoing discussion, various objects, features and advantages of the invention have been set forth, or alluded to. These and other objects, features and advantages of the invention together with structural details thereof will be elaborated upon during the forthcoming description of certain presently preferred embodiments of the invention and presently preferred methods of practicing the same.

In the accompanying drawings we have shown certain presently preferred embodiments of the invention and have illustrated certain presently preferred methods of practicing the same, wherein:

FIG. 1 is an isometric view, partially broken away, of one form of liquid crystal display device arranged in accordance with our invention;

FIG. 2 is a cross-sectional view of the device as shown in FIG. I and taken along reference line II-II thereof;

FIG. 3 is a partial isometric view of another form of our novel display device in conjunction with mechanical means for the application of deformational stresses;

FIG. 4 is an isometric view of still another form of our display device configured in the context of a common geometric form. Illustrated also are pressure-sensitive means for applying indicia to the liquid crystal;

FIG. 5 is an isometric view of still another form of our display device showing a multifaceted and multicontainer geometric form;

FIGS. 6-8 are isometric views representing the incorporation of our novel display device as still other geometric forms. FIGS. 7 and 8 show the incorporation of other decorative objects within the liquid crystal container structure;

FIG. 9 is a similar view of another form of our novel display device configured nongeometrically;

FIG. 10 is an isometric view of our novel display device incorporated in a surface of an article of furniture or the like;

FIG. 10A is an enlarged partial, isometric view showing a modified form of the light-transmitting member shown in FIG. 10;

FIG. 11 is a partial isometric view of one form of wall structure incorporating our novel display device;

FIG. 12 is an isometric view of another form of our novel display device;

FIG. 13 is a cross-sectional view of the display device of FIG. 12 and taken along reference line XIII-XIII thereof;

FIG. 14 is an isometric view of still another form of our novel display device;

FIG. 15 is a similar view of still another modification of our display device;

FIGS. 16 and 16A are top plan views of an advertising novelty arranged in accordance with our invention;

FIG. 17 is an isometric view of a further modification of our display device, arranged here as a paper weight or the like;

FIG. 18 is an isometric view of the modified form of the invention as shown previously in FIG. 15;

FIG. 18A is a cross-sectional view of the display device shown in FIG. 18 and taken along reference line XVIIIA- XVIIIA thereof;

FIG. 19 is a similar view of another form of the novel display device;

FIG. 19A is a cross-sectional view of the device as shown in FIG. 19 and taken along reference line XIXAXIXA thereof;

FIG. 20 is an isometric view of a further modification of the display device of our invention;

FIG. 20A is a cross-sectional view of the device as shown in FIG. 20 and taken along reference line XXAXXA thereof;

FIG. 21 is a similar view of a further modification of our novel display device;

FIG. 21A is a cross-sectional view of the device as shown in FIG. 21 and taken substantially along reference line XXIA XXIA thereof;

FIG. 22 is an isometric view of still another modification of our invention, presented here as a display device capable of exhibiting color patterns on both sides thereof;

FIG. 22A is a cross-sectional view of the display device of FIG. 22 and taken along reference line XXIIA-XXIIA thereof;

FIG. 22B is a similar view of a modified form of the device as shown in FIGS. 22 and 22A, but incorporating novel message means;

FIG. 22C is a similar view of our novel display device but incorporating modified light absorption means, in which the color pattern is visible through a flexible section of the display device container;

FIG. 22D is a cross-sectional view similar to FIG. 13 but illustrating a sheet form modification of our invention, in which the display device container is completely flexible;

FIG. 23 is a side elevational view of a further modification of our novel display device and incorporating another form of deformation producing means according to our invention;

FIG. 23A is a cross-sectional view of the device as shown in FIG. 23 and taken along reference line XXIIIA XXIIIA thereof;

FIG. 24 is an exploded isometric vrew of still another modification of our novel display device;

FIG. 24A is an assembled isometric view of the display device shown in FIG. 24;

FIG. 24B is a cross-sectional view of the display device as shown in FIG. 24A and taken along reference line XXIVB- KXIVB thereof;

FIG. 24C is an isometric view similar to FIG. 22 and to others of the preceding Figures. but illustrating the use of multiple encapsulations;

FIG. 24D is a cross-sectional view of the display device shown in FIG. 24C and taken along reference line XXIVD- XXIVD thereof;

FIG. 25 is an isometric view of a modification of our novel display device similar to that illustrated previously in FIG. 4;

FIG. 25A is a cross-sectional view of the display device as shown in FIG. 25 and taken along reference line XXVA- IKXVA thereof;

FIG. 25B is a similar view of a modified form of the display device as shown in FIGS. 25 and 25A;

FIG. 25C is a similar view of a modified form of the display device as shown in FIGS. 25 and 25A;

FIG. 25D is a similar view of a modified form of the display device as shown in FIGS. 25 and 25A;

FIG. 26 is an isometric view of still another modification of our novel display device;

FIG. 26A is a cross-sectional view of the display device of FIG. 26 and taken along reference line XXVIA-XXVIA thereof;

FIG. 27 is an isometric view of still another form of our hovel display device;

FIG. 27A is a cross-sectional view of the display device as shown in FIG. 27 and taken along reference line XXVIIA- KXVIIA thereof;

FIG. 28 is an isometric view of still another form of our novel display device;

FIG. 28A is a cross-sectional view of the display device as shown in FIG. 28 and taken along reference line XXVIIIA- KXVIIIA thereof;

FIG. 29 is a bottom plan view of a further modification of our novel display device incorporating another form of our deformational means;

FIG. 29A is an elevational view, partly in section, of the display device of FIG. 29;

FIG. 30 is an isometric view of still another form of our novel display device, incorporating in this case novel illumination means therefor; and

FIG. 30A is a cross-sectional view of the display device as shown in FIG. 30 and taken along reference line XXXA- .KXXA thereof.

With reference now to FIG. I of the drawings, a display device I in the fonn of a liquid crystalline support 12 is illustrated therein. In this arrangement, the support 12 in the form of a flat container having opposed container wall sections or structures 14,16 of any suitable size and shape. In the arrangement shown, the wall sections l4, 16 are substantially coextensive although this is not an essential requirement. In point of fact, one of the wall structures 14, 16 can be significantly smaller than the other wall structure (FIG. 3), as long as one wall structure is joined about its periphery to the other wall structure, for example in the manner described below. Likewise, the wall structures l4, 16 need not be of flat configuration as illustrated but can be of some other configuration for example parallelopipedon or hemispherical as illustrated in FIGS. 4 and 5. It is contemplated however, that any geometrical or nongeometrical, symmetrical or nonsymmetrical shape or form can be employed for either or both of the wall structures l4, 16. As noted previously, the wall structures 14,

16 need not be coterminus. Further, the wall structures I4, 16 need not be planar as shown in FIGS. 1 and 2 but instead one or both sides thereof can be dished as indicated in the aforementioned copending application, or they can be otherwise configured as described below.

Depending on the manner in which the wall structures l4, 16 are joined, the resilience and hence the thickness of either or both of the wall structures l4, 16 may or may not be critical. Such criticality, whether encountered depends on the manner in which deformational stresses are to be applied to a liquid crystalline material 18 confined between the wall structures 14, 16. In the arrangement ofour novel display device as illustrated in FIGS. 1 and 2, at least one of the wall structures l4, 16 is sufficiently thin or is made of a suitably plastic material as to lend a resilient or flexible character to the wall structure. Thus, the wall structure, such as the wall structure 16 can be bent or otherwise deformed toward the wall structure 14 when a force is applied more or less transversely thereto as denoted by arrow 20. Such force can be applied at various locations on the wall 16 as denoted by dashed arrows 21.

By thus bending one of the wall structures l4, 16 relative to the other, the liquid crystalline material 18, which is supported, in this example, between the wall structures 14, 16 in filmlike form, is caused to flow generally away from the region of applied force (arrows 20, 21) to other regions of the volume confined within the liquid crystal container 12. The application of the force 20 and the resultant flow of the liquid crystal l8 develops shear and other deformational stresses within the liquid crystal 18. Such stresses modify the light scattering and attendant transmittance characteristics of the liquid crystal material 18 and result in an endless variety of color changes and patterns.

In order to observe these aesthetic color changes one of the container sections, for example the section 14, is light transmitting, and desirably transparent, to permit the display device 10 to be observed from a side away from the application of deformational forces 20 or 21. The clear container section 14 can be fabricated from polyacrylic, polycarbonate, polybutyrate, glass or other suitable material.

At least a portion of the other wall structure l6 can be made dark opaque or of a more or less transparent but darker hued material for optimum visual characteristics, which result from viewing only the light scattered from the display device 10, in particular from its liquid crystal layer I8. The darker hued container section 16 may be a buff gray or other neutral color although desirably a darker coloration will make the color patterns of a liquid crystal more obvious. A particular color may be selected or several colors can be provided on that side of the container section 16 facing the liquid crystalline material 18. Use of such coloring, particularly a darker color or mixture of colors, lends an interesting and subtle shading to the color patterns produced in the liquid crystals. For maximum light-scattering characteristics of the liquid crystal, the background coloration" desirably is black, which, as in the case of the aforementioned colors can be coated at 17 on the container section 16 or incorporated therein. The terms dark-opaque" or dark-hued" are inclusive of black for the purposes of this specification and claims. Similarly, "darkhued" is inclusive of colored but transparent or translucent materials of low light transmittance. Desirably, whatever coloration is provided for the container section 16 is made at least coextensive with the area of the liquid crystalline material 18. The dark colored, black and/or dark opaque layer can be applied at the interface of the liquid crystal 18 and container section 16 as shown or alternatively on the juxtaposed outer surface of the container section 16, if the container section 16 is otherwise clear or transparent. Alternatively the light-absorbing means can be physically incorporated in the liquid crystal 18, as described below in reference to FIG. 22A.

As noted previously, at least one of the container sections l4, 16 is joined about its periphery to a surface of the other wall structure. In the FIG. I arrangement, such joining means are further arranged to peripherally seal one wall structure to a surface of the other. In the display device 10, such joining and sealing means include a pressure-sensitive tape 22, which is compatible with the material of the wall structures l4, l6 and covers their coextensive peripheral edges. The liquid crystal 18 is thereby sealed in the context of film thicknesses within the space defined by the slightly separated wall structures 14, 16 and the peripheral tape 22. It will be understood, of course, that the separation between the wall structures l4, 16 can be different from that illustrated, depending upon the relative quantity of liquid crystal 18 which is used, the desired intensity of color patterns, and the background coloration of the dark-opaque or dark-hued container section 16. Generally, a relatively thin film of liquid crystal 18 should be enclosed between the wall structures 14, 16 in conservation of the liquid crystalline material.

In those cases wherein the joining and sealing tape 22 is quite flexible and more or less loosely applied at the wall edges or is at least somewhat elastic, one or both of the wall structures 14, 16 can be made thicker and hence less resilient. In such cases, an eccentric application of the deformational force 20 will cause one of the wall structures to become slightly canted or angulated or otherwise displaced relative to the other in order to induce deformational flows in the liquid crystalline material. Such deformational flows are, of course, aided by the elasticity and/or edge slackness of the joining and sealing tape.

In any event it is desirable to provide the light transmitting section 14, particularly when transparent, with appreciable thickness to enhance the variable color patterns of the liquid crystal l8 and to create an illusion of depth. When the display device is substantially planar as in FIGS. 1, 2, l and 11, the

, container section 14 should be in the neighborhood of about one-eighth inch or more in thickness although such thickness is not essential to the invention and can be varied depending upon a specific application of the display device. When the device is incorporated into a relatively small decorative ob ject, a transparent container section of at least this thickness is desirable as the object is more readily viewed from different angles or positions. When supplied in greater thicknesses or when multifaced or faceted, the variable color display is even further enhanced as described below.

The liquid crystalline material 18 is selected from one or more of those materials which exhibit variation in light-scattering and attendant transmittance characteristics under 'deformational stresses. Desirably, such variations are within the visible range at room temperatures or at whatever ambient temperature conditions prevailing in the area of utilization of the display device 10. As an example of the latter situation, the liquid crystalline material 18 can be one of those which exhibit visual stress variation in the aforementioned characteristics at or near body temperature, and is therefore useful when the display device is held in the observer's hand. Larger display devices 10 can of course be bathed with infrared radiation, if their liquid crystals are not of the room-temperaturevisual variety. o

On the other hand, display devices for outdoor use, as for signs and other advertising situations, require liquid crystalline materials exhibiting stress indicia at correspondingly lower temperatures.

There are a considerable number of substances which exhibit the characteristics required of the liquid crystalline material 18. In general the category of materials known as cholesteric liquid crystals are suitable for use with my invention and exhibit an optical phenomenon known as selective scattering of white light. The appellation of this'categorization of liquid crystals originates in the frequent use of cholesterol as the starting material in synthesizing these organic substances. The derivatives of cholesterol usually are liquid crystalline in character and demonstrate the characteristic of selective light scattering. Liquid crystalline substances fall additionally into the general chemical classifications of esters, carbonic esters, ethers, schiff bases, and related classes.

Nominally, the cholesteric liquid crystals are not limited to the use of cholesterol as a base material. Many steroids exhibit similar optical characteristics when synthesized into the general classifications of organic compounds, as mentioned above. These and other cholesteric" liquid crystals are useful for the purposes of our invention as long as their molecular arrangement exhibits the necessary anisotropic and optical characteristics.

For the purposes of our invention, we employ a cholesteric liquid crystalline material which exhibits a relative optical phenomenon attendant to the selective scattering characteristic of this category of liquid crystal. The latter characteristic is the stress or shear sensitivity of certain cholesteric materials whereby the selective (light frequency) scattering characteristic is varied upon the application of deformational stresses.

Cholesteric materials will selectively and visibly scatter white light, at or near room temperature conditions, when two or more of these substances are admixed in proper proportions. Mixtures of liquid crystals can be selected or varied to obtain visual responses at other temperatures for the purposes mentioned previously. It is observed that a physical deformation of the liquid crystal will shift the frequency of the observed cholesteric color display or pattern, when viewed at a given angle, toward the blue or shorter wave length end of the visible spectrum. The amount of color shift, measured in wave length units, can be employed to indicate quantitatively the physical stress applied to the cholesteric material, when a given liquid crystalline material has been properly calibrated.

A constant pressure applied to the liquid crystalline material will not, after its initial application, thereafter appreciably effect the then observed color patterns. Instead, the great variety of color changes or patterns exhibited by our display device are produced by changes in applied forces and attendant deformational stresses. With acceleration of changing deformational stresses, in either direction, changes in the observed color patterns become more pronounced.

It has also been observed that the application of a constant deformational stress over a significant period of time will initially induce an observable change in the cholesteric color pattern, which despite continued stress, will revert to the unstressed or original cholesteric color in time. That is to say, there is a relaxational effect in the liquid crystalline structure, owing to its nature.

It is contemplated that the liquid crystalline material may have a single basic color or that a mixture of liquid crystalline materials having differing basic colors can be employed. For example, liquid crystalline materials I, V, and/or Vl, tabulated below, can be employed in the package 10 or in others of the packages described below. It is also contemplated that liquid crystalline materials of differing basic coloration can be employed in differing areas of the package 10 but within the same liquid crystalline layer 18 to enhance the variety of color patterns. Owing to the viscous nature of the liquid crystals, the differing colored materials will not readily admix although the flexible or resilient backing layer (if used) of the package is manipulated a relatively large number of times.

It will be understood herein that a cholesteric substance is one which exists in the cholesteric state at a certain temperature. The cholesteric state of such mesomorphic substance exists in the region between the temperature at which the substance behaves as a true liquid and the temperature at which the substance is a solid. In the cholesteric state, the substance is optically negative, has a strong rotatory power, selectively scatters light to give vivid colors (or monochromatic light to give areas of darkness and brightness), and exhibits circular dichorism. Such a physical state is especially notable in derivatives of cholesterol and like materials, although a relatively few other substances such as optically active amylcyanobenzylidineaminocinnamate and the aforementioned steriods exhibit the cholesteric state.

The liquid crystalline substances herein contemplated will be in the cholesteric state within at least a certain temperature Alan Ill

range, but as the temperature is raised above or depressed below this range the substances will pass into another mesomorphic state or into a normal liquid or solid state. Thus, the cholesteric substance will be in the cholesteric state at a first temperature and will change its phase into some other state at a second temperature. The range of temperatures within which a visible color display is exhibited as a result of scattering of white light can be determined by a proper selection of cholesteric substances and will be referred to as the color play range.

Cholesteric substances used according to the present invention can be chosen from a wide range of compounds exhibiting the cholesteric phase. Derivatives of cyclopentanophenanthrene are desirably used. There are a number of factors to be considered in selecting such derivatives: All of the ring systems should be in the trans configuration, the 3- :substituent (on the A ring) should be in the Bconfiguration, and there should be no more than two axial methyl groups. Unsaturation at the 5, 6 carbon atom bond can have an effect on the melting point, but otherwise has little effect on the formation of the cholesteric phase. Thus, derivatives of such cyclopentanophenanthrenes as cholesterol, compesterol, ergosterol, B-sitosterol, stigmasterol, and like materials can be used.

llt is preferred in the present invention to utilize alkyl and aryl derivatives of the cyclopentanophenanthrene materials, particularly those derivatives which are esters of alkanoic or .aralkanoic acids, or mixed alkyl esters of the cyclopentanophenanthrene material and carbonic acid. The alkanoic acids used can contain from one to 24 or more carbon atoms in the molecule, and can be saturated or unsaturated and straight or branched chain. It is preferred to utilize esters comprising higher fatty acids, containing from nine to 22 carbon atoms or lower saturated or unsaturated phenalkanoic acids having one to three carbon atoms. Mixed carbonate esters comprising alkanols having from one to 22 carbon atoms and cholesterol are also among the preferred cholesteric substances.

Such derivatives of cholesterol are presently preferred in certain aspects of the invention. Thus, useful cholesteric substances include cholesteryl nonanoate. cholesteryl caprylate, cholesteryl laurate, cholesteryl palmitate, cholesteryl stearate, cholesteryl arachidate, cholesteryl behenate, cholesteryl ioleate, cholesteryl linoleate, and cholesteryl linolenate, cholesteryl benzoate, cholesteryl cinnamate, cholesteryl idihydrocinnamate, and the like. Carbonate esters such as oleyl cholesteryl carbonate, stearyl cholesteryl carbonate, methyl cholesteryl carbonate, ethyl cholesteryl carbonate, pentyl cholesteryl carbonate, and the like carbonates are very useful in the present invention.

it will be appreciated by those skilled in the art that a pure cholesteric substance may have only a very limited color play range. However, where this color change does not occur at the temperature of interest, several stratagems permit coverage of a broad range of temperatures from C., and cven down to 40 C., up to and above 250 C. One method of varying the color play temperature range is to prepare a substance at a desired purity level, as increased impurities usually lower the temperature range. One convenient method of carrying out this adjustment is to admix a plurality of chemically distinct cholesteric substances having different color play temperature ranges until the desired temperature range is obtained. Another method of adjusting the color play range is to prepare the substance in a highly purified form and to admix enough of a less refined aliquot or aliquots of the substance with the purer material until the desired change of color play range is obtained. For instance, in this latter aspect, a 99.99% pure cholesteryl oleyl carbonate can be prepared and admixed with less refined material. Those skilled in the art will have no difficulty in providing a desired transition temperature for use in the compositions and articles of the present invention. All parts, proportions, percentages and ratios herein are by weight unless otherwise stated.

The following tabulation will exemplify a few of the many color play regions obtained with the cholesteric substance or substances:

90 0 10% cholesteryl benzoate Cholesteryl butyl carbonate- 20% cholesteryl dlhydroc1nnamate. cholesteryl nonanoate It will accordingly be appreciated that one, two or more cholesteric substances can be mixed to obtain the requisite color play temperature range, and that both the temperature and the range of temperatures can be widely varied. It is desirable that the cholesteric substance(s) not crystallize at the lowest temperature at which they are held before use.

As disclosed above. a desired melting range can also be obtained by varying the purity of cholesteric substances. It is usually found that increasing the purity raises the temperature of the color play region and a narrowing of the range is also frequently obtained. It will, of course be appreciated that the presence of excessive quantities of impurities will ultimately entirely prevent obtaining of the cholesteric phase, especially if the impurities themselves are not cholesteric substances. The cholesteric substance(s) can also comprise up to 5 percent or so of miscible materials such as fatty acid triglycerides to lower the range. As disclosed hereinafter, it is most desira ble to protect the cholesteric substance from the milieu to obviate the inhibition of impurities by the cholesteric substances and thereby to maintain the desired color play temperature.

As an illustration, cholesteryl oleyl carbonate is prepared as described in Detection of Liquid Crystals," AD 620 940, U.S. Department of Commerce Aug. 1965). A portion of the cholesteryl derivative is purified by solvent extraction and washed with methanol. The purified cholesteryl material is found to have a color play temperature of 2 l-22 C. Admixing 80 parts of this material with 20 parts of an unpurified material provides a color play temperature of 15 1 6 C.

The cholesteric materials for use with this invention can also include a cholesteryl halide. Although cholesteryl fluoride can be prepared, the desired halides for use herein are cholesteryl chloride, cholesteryl bromide, cholesteryl iodide, and mixtures of these halides. The preferred halide for use herein is cholesteryl chloride.

The cholesteryl halide serves-to provide a uniform color over a broad range of temperatures in which the cholesteric substance or substances are in the cholesteric phase. Thus, in such case, our novel display device shows a single color below transition to the condition wherein the liquid crystal does not scatter visible light, i.e., the condition in which it becomes colorless. The color below the transition point can be selected according to the amount of cholesteryl halide used. As the quantity of halide is increased from about 15 percent of the composition up to above 40 percent, the color usually varies from deep violet to deep red. The quantity of halide used will also vary according to the particular cholesteric substances utilized.

These halides are conveniently prepared by refluxing the cholesterol with an excess (twice or more, stoichiometrically) of a thionyl halide for 48-72 hours and distilling the mixture thereafter to remove unreacted material. Generally, the purity of the halides is sufficient to permit the desired change of phase from the cholesteric. It is preferred that the halides be at least 90 percent pure. Such halides usually have a tendency to broaden the color play temperature range of the cholesteric substance(s).

Depending upon a particular application of our display device a cholesterol halide may or may not be used depending on whether a single or multiple color display is desired.

Specific examples of liquid crystalline compositions useful for our present invention appear below, wherein all amounts are in parts, ChCl is cholesteryl chloride melting at 9495 C.; High ChOlC" is cholesteryl oleyl carbonate showing a color play at 20-22 C.; Low ChOlC" is cholesteryl oleyl carbonate showing a color play at -6 C.; ChNo" is cholesteryl nonanoate; and the upper temperatures are those at which the compositions become colorless.

Color play High Low Example ChCI ChOlC ChOlC ChNo Color Range (0.")

Other alkanoic esters of cholesterol or alkyl carbonate esters of cholesterol can be used in the foregoing Examples to provide a broad variety of temperatures and temperature ranges for the liquid crystalline material 18. Likewise, other cholesteric materials such as corresponding derivatives of B- sitosterol, stigmasterol, ergosterol, and the like can be substituted with comparable results.

In the display device of FIGS. 1 and 2 it is contemplated that the forces 20, 21 can be applied manually, for example by pressing or stroking the container section 16 with the fingers. A single force can be applied as designated by arrow or alternatively multiple forces can be applied as desired as denoted by arrows 21. The edge-sealing tape 22 can be of the pressure-sensitive variety, desirably of the light-transmitting or transparent type, in the illustrate embodiment. It will be understood, of course, that other means can be utilized for joining and sealing the container section 16 to the container section 14. For example the joining means illustrated in the aforementioned copending application or herein in subsequent figures can be utilized, depending upon the application of the invention.

Alternatively the container sections can be joined as illustrated in FIG. 3. The latter arrangement of our invention demonstrates also that the container sections need not be coterminus. In the container 12' of the display device 10 of FIG. 3, container section 16' is of appreciably smaller area than that of the container section 14'. In this example the section 14 is relatively rigid and light-transmitting or transparent in contrast to the resiliency and opaqueness of the section 16' for the reasons set forth above. Where the joining and sealing tape 24 is of a character, for example, inherent elasticity, to permit, of itself, relative displacement of the container'sections 14', 16', the container section 16' can also be made rigid. The container sections 14', 16' enclose a quantity of liquid crystalline material 18' therebetween, and the periphery of the smaller container section 16' (in this case) is sealed and joined to the juxtaposed surface of the larger container section 14', by means of the aforementioned tape 24. The tape 24 also is of the pressure-sensitive variety, and can be light-transmitting or transparent to render its presence less obvious. The structure of FIG. 3 exhibits the practical ad vantage of an inobvious joining means, when the display device 10' is viewed from its light-transmitting surface.

The color patterns of the liquid crystal 18' can be varied manually in the manner set forth above with respect to the display device 10 of FIGS. 1 and 2. Alternatively, various mechanical means can be provided in conjunction with the display device 10' for the application of deformational stress of the liquid crystal 18'. One form of such means includes contacting means 26 including in this example roller 28 positioned to engage the external surface of the opaque wall structure 16'. Means are provided for reciprocating the contacting device 26-28 across the exposed surface of the container section 16'. One arrangement of such means includes a link 30 pivoted at 32 to the contacting means 26 and to crank 34. Although the crank 34 is illustrated for manual actuation by hand wheel 36, suitable motive means (not shown) can be substituted. The roller 28 of the contacting device is held in bearing engagement with the container section I6 by means of a pair of slotted brackets 38, 40 which engage the projecting ends 42 of the roller axle.

The varying color patterns of the display device 10' can be set to music or other rhythmic activity by rotation of the crank 34 in accordance with a predetermined timed sequence, as by use of a synchronous drive motor (not shown) and suitable gearing or other transmission, arrangements of which are disclosed in the aforementioned copending application.

The force applying arrangement of FIG. 3 is particularly useful for varying the color patterns of large-area devices such as the wall panel illustrated in FIG. 11 or other relatively nonportable display devices.

xsbdiiiiea' out in the description of FIGS. 1 and 2 and previously it is contemplated that the light-transmitting or transparent container section can be provided with appreciable thickness to enhance the variable color display made possible by our device. For example display device 44 of FIG. 4 is furnished in the form of a container 46 including in this example a hemispheroidal container section 48 and a substantially flat container section 50 adhered to the flat face 52 of the container section 48. In the modification of FIG. 4 the substantially flat container section 50 can be applied as shown in FIG. 3 except that the container section 50 desirably is made circular. The hemispheroidal container section 48 provides an interesting magnification and refraction of color patterns 54 of the liquid crystalline material enclosed between the fiat face 52 of the hemispheroidal section 48 and the flat container section 50.

The display device 44 can be utilized, for example, as an entertaining and ornamental novelty for a table or desk top. A relatively slight pressure upon the rounded surface of the hemispheroidal container section 48 will apply compressional forces to the resilient or displaceable container section 50 resting, for example, directly upon the table or desk top. This in turn will cause various flow patterns within the liquid crystal 54 depending upon the magnitude and location of the applied forces. As a result an interesting and entirely unexpected variable color display is produced.

We contemplate also that localized forces can be applied to the external surface of the container section 50. One arrangement for effecting such force application includes a stand 56 adapted for the display serve 44 and likewise shown in FIG. 4. The stand 56 in this example includes a retaining rim 58, shaped to receive the peripheral surface of the display device 44 adjacent its flat face 52. The bottom of the stand 56 desirably includes a number of contact surfaces arranged in the form of a design, message, various geometrical configurations, or other indicia. For example, the bottom area 60 of the stand 56 may incorporate the owners initials denoted in this example by reference numeral 62. The design, message item, or indicia 62 can be fabricated from any suitable structural material, plastic or metallic, and desirably are arranged such that their undersurfaces seat flushly against the table or desk top. The upper surfaces of the design or message items 62 project sufficiently above the remainder of the bottom structure 60 and are supported in this example by connecting links 64. In consequence onlythe message items 62 are engaged by the container section 50 when the display device 44 is seated in the stand 58. When so arranged the message items or indicia 62 depress the flexible container section 50 at their top surface areas with the result that the items appear as a discrete and contrasting coloration within the color pattern 54 of the liquid crystal. A variety of stands 58 can be furnished with a tingle display device 44 to display a variety of message or design motifs of this character. When the several stands, similar to the stand 56. are thus changed corresponding changes in the overall color patterns of the liquid crystal patterns likewise occur owing to difiering distribution of applied base or bottom forces at the flexible container section 50.

Other geometric shapes can be utilized in addition to the hemisphere or hemispheroid of FIG. 4. For example, FIG. illustrates another geometric. transparent member 66, exemplarily in the form of a cube, forming part of display device 68. One or more faces of the cube 66 can be utilized as a component container section of a corresponding number of liquid crystal containers or cells. In the illustrated display device 68 two such cells 70 are afforded, although obviously a different number can be furnished. Each of the cells 70 include, in this example, a substantially flat container section or structure 72 of about the same size as the adjacent face of the cubic member 66. The container structures 72 can be secured to the corresponding face of the member 66 by means of pressuresensitive tape 74, after the manner of FIG. 3 or FIG. I depending upon whether the container structure 72 is desired to be of the same size (FIG. I) or correspondingly smaller than the juxtaposed face of the cubic member 66 (FIG. 3). Quantities 76 of liquid crystal enclosed between the container sections 72 and the juxtaposed faces of the cubic member 66 are visible within the transparent cubic member 66. The facets or faces of the cubic member 66 provide an interesting array of reflections and refractions of the variable color patterns of the liquid crystal portions 76. With only a liquid crystal encapsulation at only one cubic face. for example. up to about I3 reflections and refractions (including secondary images) can be seen. An endless variety of color patterns, therefore. can be obtained by application of forces to the container sections 72 after the manner of FIG. 2 or FIG. 3. or as set forth in the aforesaid copending application. and/or by changing viewing angles.

Similar geometric shapes are illustrated in FIGS. 6. 7 and 8 which respectively show parallelopiped. pyramidal, and prismatic shapes. The transparent members 78. 80 and 82 of these figures each have liquid crystalline material 84. 86 or 88 confined against one face thereof after the manner of FIG. 4 pr FIG. 5. Liquid crystalline material (not shown) similarly can be applied to additional faces of each transparent member 78. 80 or 82 if desired. The display devices 90. 92, 94 of FIGS. 6-8 provide interesting and respective arrays of reflections and refractions of the color patterns of the contained liquid crystalline material. For example in FIG. 6 the several refractions and reflections of the liquid crystal patterns are denoted by the reference characters 84' and will of course vary depending upon the direction from which the display device 90 is viewed. Similarly, refractions and reflections 86' appear in the display device 92 of FIG. 7 and a reflection 88' in the display device 94 of FIG. 8. These and additional reflections and refractions will appear or disappear depending upon the viewing angle, all of which heightens the interest engendered by the display devices. Moreover. the basic color of the associated liquid crystal pattern and its reflections and/or refractions will vary depending on the viewing angle. Of equal importance, the several reflections and/or refractions will differ in color from each other and from that of the liquid crystal itself, as the viewing angle is effectively different for each reflection or refraction, although the display device is viewed from a single position.

The aforementioned liquid crystal color patterns (which can be varied by the application of deformational stress as described previously or as set forth in the aforementioned copending application) can be employed as unexpectedly decorative and entertaining backgrounds for items such as coins, models, fossils. precious and semiprecious stones. specimens and the like embedded in the transparent member. In furtherance of this purpose a molded plastic such as plexiglass or one of the polyacrylic resin is employed for the transparent member. In the display devices 92 and 94 (FIGS. 7 and )8) coins 96 and 98 are so used. Other items (not shown) can be employed with or substituted for the coins 96, 98. In FIG. 7. one such coin 96 has been molded within the transparent member 80. while several coins, in differing positions have been so included in FIG. 8. A reflection 96 (FIG. 7) or reflections of these items may appear depending again on the viewing angle.

The display devices according to this feature of our invention are not limited, of course, to geometric shapes. For example display device I00 of FIG. 9 incorporates a faceted but nongeometric or irregular transparent solid 102 against at least one face or facet of which is contained a quantity of liquid crystalline material. The last-mentioned liquid crystalline material preferably is encapsulated against the juxtaposed facet of the transparent member 102 in the manner described previously. A color pattern 104 of the liquid crystal appears in a number of additional faces 104 of the transparent member I02. The shaded facets 106 denote areas of mirror-type reflections. which, when combined with the liquid crystal color pattern I04 and its various reflections or refractions 104', again provide an unexpected decorative and entertaining display.

The display devices of FIGS. 4-9, as in the case of the devices 10 and 10 of FIGS. 1-3 are made of any convenient or suitable size. Primarily. the display devices of FIGS. 4-9 are intended for relatively small ornamental items for various decorative purposes.

In FIG. 10, however. the adaption of our novel display device to relatively large surface areas is exemplified. The latter form of our display device 108 is incorporated in an article of furniture. in this example table 110. For maximum effect the display device 108 is applied to top structure 112 of the table 110. The display device 108 further includes a lighttransmitting member 114 which conforms in contour and extent to the shape of the table top I12. The table top 112 and the light-transmitting member 114 are flat although this is not necessarily the case.

A quantity of liquid crystal 115 is enclosed between the light-transmitting member or sheet 114 serving as one container component and a preferably opaque structure including sheet I16 which serves as the other liquid crystal component. The sheet 116 is adhered about its peripheral edges to the undersurface or periphery of the light-transmitting member I I4. The sheet 116 can of itself be opaque, or if transparent, the table top 112 preferably is opaque.

The container components 114, 116 can be secured and sealed together after the manner of FIGS. 1 or 3. Desirably also the light-transmitting or transparent member 114 is relatively thin such that forces applied to the upper surfaces thereof. either manually as by individuals utilizing the table for various purposes or by various utilitarian objects placed upon the light-transmitting member 114, produce an endless and unexpected variety of color patterns within the liquid crystalline material as a result of its variable lightscattering and pressure-sensitive characteristics.

To heighten the observers interest still further a lens or refractive configuration I18 can be molded in the light-transmitting sheet 114 of the display device 108', as shown alternatively in FIG. 10A.

The display arrangement 108 or 108' can, as noted previously, be applied to other furniture surfaces. disposed either vertically or horizontally or at some other inclination as desired. An interesting application of this arrangement of our invention is to a piano top (not shown) or other surface subject to sonic vibrations. Alternatively, a display device, such as the device 108 or 108' can be stretched over a loudspeaker cone (not shown) in an analogous arrangement. In this latter application the display device including its container components desirably is made relatively thin for maximum sensitivity of the liquid crystal contained therebetween to sonic vibrations. Other applications subject to vibratory forces will suggest themselves.

The display device as shown in FIG. 10 or 10A can likewise be applied to room surfaces and for this purpose can be furnished in the form of conveniently sized panels fabricated after the manner of the display panel 108 or 108' in FIG. or 10A. These can be applied to floor, wall, ceiling and/or door surfaces of a conventional room or as a stage or auditorium backdrop. One arrangement of such panels is illustrated in FIG. 11, where display device 120 is shown as a wall panel and will be presently described. Deformational forces can be applied to the aforementioned panels by manual pressures exerted against the accessible surfaces of the panel, or by mechanical means such as illustrated in FIG. 3 in this application or in various Figures of the aforementioned copending application With the incorporation of display device 120 in a room structure as shown in FIG. 11, the device 120 desirably includes light-transmitting sheet 122 which preferably faces the interior 124 of the room structure 126. The sheet 122 can be provided with cove I28, baseboard 130 and base shoe 132 moldings where appropriate to conform to conventional wall structures which may be used elsewhere in the room. The light-transmitting panel 122 can be secured to studs 134 or other structural members conventionally used in bearing and nonbearing walls as the case may be.

The rear of the light-transmitting panel 122, i.e., the side away from the interior 124 of the room structure 126, is substantially covered by encapsulating means for retaining a relatively thin layer of liquid crystal against the rear surface. In the illustrated arrangement the encapsulating means are extended generally between adjacent pairs of the studs 134 or other wall support members. One form of such encapsulating means includes one or more container sections 136 secured to the rear surfaces of the light-transmitting panels 122 and disposed between each associated pair of the studs 134. In the illustrated example three such container sections 136 are utilized between each pair of studs, although a different number can be employed.

The container sections 136 desirably are relatively stiff but resilient plastic sheets adhered about their peripheries to the juxtaposed surfaces of the light-transmitting panel 122 after the manner of FIGS. 1 and 3 and related figures described above, or after the manner of FIGS. 12-16 described below. The container sections 136 can be colored or coated as described previously and each encloses a quantity of liquid crystal against the adjacent surface of the light-transmitting panel 122. Any rear surfaces of the light-transmitting panel 122 which are not covered by the container sections 136 can be suitably masked by various types or colors of coatings. For example, the masked areas, such as denoted by reference characters 130, can be colored to blend more or less with the color patterns produced by the several liquid crystalline areas as defined by the container section 136 and visible through the front surfaces of the light-transmitting Another arrangement of our novel display device is exemplified by display container 140 of FIGS. l2, 13. The display container 140 or aesthetic novelty includes a light-transmitting member 142, which can be fabricated from a polyacrylic resin in sufficient thickness to give the aesthetic novelty 142 sufficient rigidity or structural strength. For example, if the aesthetic novelty 140 is of the order of about 4 inches square, the light-transmitting member 142 can be of the order of about one-eighth inch in thickness, although a greater or lesser thickness can be employed as evident from FIGS. 16, 16A described below. Desirably, the light-transmitting member 142 is fabricated from a fully transparent polyacrylic resin to enhance the color patterns of the liquid crystal material 144 encased between the light-transmitting member 142 and a desirably darker-hued or dark-opaque film or sheet 148 adhered to the upper surface (as viewed in FIGS. 12 and 13) of the flexible film 146. Other light-absorbing means can be substituted such as described with reference to FIG. 22A and other figures hereof. In this arrangement, the film 146 can be formed from a sheet of PVC plastic or the like to which a coating of pressure sensitive adhesive is applied entirely over one surface thereof. The PVC sheet or film 146 and the application of the adhesive thereto can be formed by conventional techniques.

The area occupied by the liquid crystalline material 144 can be demarcated by a sheet of heavy paper or cardboard or by a second plastic film or sheet 148, which can be pressed into adhesive engagement with the central area of the adhesive film 146. Use of the film layer 148 prevents the juxtaposed surfaces of the film 146 from adhering to the underside of the light-transmitting member 142 and thus delineates a shallow pocket for the liquid crystalline material 144.

The film layer 148 can be coated or formed from a material having a dark or other contrasting color relative to the predominating color of the liquid crystalline material 144. Printed messages (not shown) or various designs, e.g., the design 150 (FIG. 12) or 152 (FIG. 14) or 154 (FIG. 15), can be applied to the film or sheet layer 148. Such designs, for example the designs 150, 152 can be printed in darker colors or shades upon a light background or alternatively as evident from the design 154 in FIG. 15, the design can be delineated in lighter colors against a darker background. Also, the designs can be more or less geometrical as shown in FIG. 12 or random as shown in FIG. 14 or pictorial as shown in FIG. 15. The unique cooperation of the contrasting colors of the film layer 148, when provided with a design of some sort such as those described above, is evident when the flexible film 146 is depressed in the area of the film layer 148 to apply deformational stresses to the liquid crystalline material 144. The alternate thinning and thickening of the liquid crystalline layer considerably enhances the varying color patterns resulting from deformational flows in the liquid crystal. Interest in the liquid crystalline patterns is heightened, with the variation in thickness or depth of the liquid crystalline material above the various contrasting colors or shades of the designs imparted to the film layer 148.

The area of contained liquid crystal, such as the area 156 in FIGS. 12, 13 can be similar in shape to that of the light-transmitting member 142 or can be of a different shape or series of shapes (not shown) as denoted by the liquid crystal areas 158 of FIG. 14 or 160 of FIG. 15. Similarly, the light-transmitting member 142 of FIGS. 12-14 can be of geometrical contour or can be of some other contour as denoted by the light-transmitting member 162 of FIG. 15. The film 164 adhered to the light-transmitting member 162 desirably is of similar shape.

It is contemplated that the film layer 148 can be omitted, and that the aforementioned pressuresensitive adhesive layer can be confined to the peripheral areas of the film 146 or 164 to delineate the container sections or areas 156, 158, 160 of FIGS. 12-15 respectively. In such case, the designs 150, 152 and 154 can be printed or embossed directly upon the uncoated central areas of the films 146 or 164. As a further alternative either the film layer 148 (FIG. 13) or the central region of the films 146 or 164 can be coated or otherwise provided with a uniformly dark or black material for a uniform enhancement of the liquid crystalline color patterns, as mentioned previously. Alternatively again, the designs I50, 152 and 154 of FIGS. 12-14 can be replaced with random color patterns, or with messages of various kinds printed in contrasting colors or shades upon darker-hued or opaque films I46, 164, or on the overlying film layer 148, when used (FIG. 13), or on the transparent member 142.

As a further enhancement of the color pattern variation and interest therein, an air bubble 166 (FIG. 12) can be introduced into the liquid crystal area 156, along with the liquid crystalline material. The air bubble 166 operates to thin the juxtaposed portions of the contained liquid crystalline material, and such thinning provides an interesting variation in the resulting color patterns. Also. interesting differences in reflection occur at the air bubble, depending on viewing angle. In addition, as the flexible backing member 146 is depressed or deformational stresses are otherwise applied thereto, the bubble 166 tends to break up into a number of smaller bubbles exhibiting variable patterns, depending on the amount and area of pressure application, to further increase the viewers interest in the color patterns. The use of the bubble 166 is particularly fascinating in conjunction with the aforedescribed designs I50, 152, I54 and equivalents, as the presence of the air bubble enhances the delineation of those portions of the design which are juxtaposed thereto. The correspondingly thicker regions of the liquid crystal 144 removed outwardly from the bubble I66 tend to subdue the design delineations. The sharper delineations of the design 150 are denoted in FIG. 12 by shaded areas 1500 of the design 150. The air bubble 166, whenever broken up into a number of discrete smaller air bubbles, tends to reform as a single air bubble after removal of the deformational stresses. Similar air bubbles 168 (FIG. 14)

*and 170 (FIG. 15) can be employed in conjunction with the designs 152 and 154 of these figures respectively. The air bubbles 166-170 can be of differing relative sizes than as illustrated, as long as the area normally occupied by the bubble is substantially smaller than that of the liquid crystal.

In FIGS. 16 and 16A, another form of our novel color display device 172 is illustrated with optional commercial aspects. The display device 172 can be fabricated from relatively thin material, for example in the shape of a calling card or the like. In this case the liquid crystalline material 174 is encapsulated between a darker hued or opaque film 176 and a light-transmitting or fully transparent film 178, which are otherwise assembled after the manner illustrated in FIG. 13 or in accordance with the encapsulating technique described and claimed in a eopending, coassigned application of Frederick Davis filed Mar. 19, I969, Ser. No. 803,319 entitled Thermometric Articles and Methods for Preparing Same." The liquid crystalline material 174 can be selected to exhibit the requisite color play temperature at room temperature as in the case of the display devices described previously. In that case the display device 172 will normally exhibit the appearance of FIG. 16A. It will be understood, of course, that some other design motif can be substituted in place of the spherical portions 180a, 180b and the commercial message 1800, all of which are delineated by the encapsulated liquid crystalline material.

Alternatively, and to add a note of intrigue to the brilliant color pattern of the liquid crystalline material 174, the liquid crystalline material can be selected with a different color play temperature range, in the manner discussed previously, commencing above the normal room temperature range but, for example, below the temperature of the human body. Thus, the liquid crystalline pattern will assume the base color of the base film 176, which desirably is made a dark color or black for this purpose. In consequence, the display device 172 will assume a uniform dark or black color as evident from FIG. 16, against which the delineations of the liquid crystalline material (shown in dashed outline in FIG. 16 for illustrative purposes) are not visible at all, until the display device 172 is warmed to the requisite color play temperature range, for example by holding in the individual 5 hand.

A further modification of our novel display device 182 is shown in FIG. 17 and is arranged in this example as a largely transparent novelty such as a paper weight or the like. The display device 182 includes in this example a solid block 184 of transparent material, such as one of the polyacrylic resins. The transparent block 184 is provided in accordance with this aspect of our invention with a first embedment 186 of liquid crystalline material and a second embedment 188 of a design or lettering such as a slogan, motto, the owner's name or initials or the like. The second embedment 188 can be formed in the transparent block 184 for example by printing or lettering the design or message with opaque dark-hued ink on a transparent support or a support of darker transparent hues, as required.

The liquid crystalline embedment 186 can be provided after the manner described in connection with FIGS. 16, 16A with the exception that two transparent films are employed to permit viewing of the second embedment therethrough. The first embedment 186, as in the case of the second or conventional embedment 188, can then be suspended within the transparent block 184, when the latter is molded, by conventional techniques. When the liquid crystal embedment 186 is viewed through top face 190 of the transparent block 184 the design or message of the second embedment 188 is viewed through the color display afforded by the color patterns of the liquid crystalline material located in the first embedment 186. To

enhance the color display, the bottom face 192 of the transparent block 184 can have a relatively dark hue, or a black coating can be applied. Alternatively the design or message of 5 the second embedment 188 can be applied in lighter colors against a darker background, which can be opaque or more or less transparent as desired.

Means, (not shown) can be provided for the application of deformational stresses to the first or liquid crystal embedment 186, for example in accordance with the teachings of a copending and coassigned application of Edward N. Sharpless, filed concurrently herewith entitled Variable Color Display Device and Projection Means Therefor, Ser. No. 40,889. In the absence of such deformational means, the liquid crystal embedment 186 still yields an interesting variety of color patterns depending, for example, upon the character of light falling upon the transparent block 184, incident angle ofillumination, and individual viewing angles.

It is contemplated further that the liquid crystalline material 186 can be embedded by forming the insulating block 184 from bipartite transparent container sections, which are shallowly dished to encapsulate the liquid crystalline material 186 therebetween. The bipartite transparent member can be permanently joined after the liquid crystalline material 186 is injeeted therebetween, by heat or solvent welding, use of adhesive or cement, etc.

From FIG. 18, it is apparent that our novel display device 190 is similar to that of FIG. 15, in that a design, message, logo, artwork, or trademark 192 is incorporated in the package 190 and juxtaposed to the light-absorbing means 194 (FIG. 18A) thereof. Liquid crystalline material 196 is encapsulated after the manner of FIG. 13 between a relatively rigid transparent member 142 and an adhesive sheet 146. The light-absorbing member 194 which is, in this example, adhered to the adhesive sheet 146' to define the encapsulating area of the display device 190 is a transparent plastic sheet of polyvinyl material having a photoemulsion 198 thereon.

The emulsive layer 198 is exposed save for the areas defining the logo or other mark 192. The transparent areas 192 in the absorption means 194 provide a considerably enhanced delineation of the design, advertising message, logo, or the like 192 of the display device 190. This follows from use of a somewhat translucent adhesive sheet 146' such that a limited amount of transmitted light passes through the liquid crystalline material 196 at the transparent areas 192 in the absorption means 194. Other arrangements can, of course, be employed to enhance the design 192 by affording a limited light transmittance, for example, that disclosed in FIGS. 24, 24A and 24B described below.

A modification of the message means of FIG. 18 is illustrated by the display device 200 shown in FIGS. 19 and 19A. The display device 200 can be assembled in a similar manner, save that the light absorption means or sheet or film 202 is uniformly black or dark-hued. A message or design bearing member 204 is suspended within the body of the contained liquid crystal 206. As better shown in FIG. 19, the suspended member 204 can carry a design, logo, or message 207, which can be commercial or otherwise. The message 207 can, for example, be displayed against a background area 208 of the suspended member 204, which background can be the same, or a different color or texture from that of the light absorbing member 202. In the event that the suspended member 204 is provided with a dark or black background, the member 204 itself becomes an auxiliary light absorbing means.

In the package 200, depending upon the basic color of the liquid crystal 206 being utilized and on the color of the message or design'207, the liquid crystal material may partially or completely obscure the message 207 when the display device 200 is in its quiescent state. That is to say, the suspended member 204, fabricated in this example from a piece of polyvinyl plastic sheet, will gradually settle to the bottom of the display device 200, Le, against the light absorption means 202 thereof. Under these conditions, a substantial thickness of the liquid crystal 206 covers the message or design 207. With this construction, the message or design 207 only becomes evident when the flexible container portion 146' is depressed to move the suspended member 204 against the juxtaposed face of the relatively rigid container member 142'. This obscuration is enhanced by making the same color as the basic coloration of the liquid crystal. The design, then, becomes evident when the angle of incident illumination is changed, which changes the apparent basic coloration of the liquid crystal. Alternatively, the message or design 207 can be made more or less evident, as the case may be, by manipulating the container section 146' to position air bubble 210 over the design or message 207 or to displace the bubble 210 therefrom.

We contemplate, of course, that the package or display device construction of FIGS. 18, 19 and related figures need not be confined to flat or planar display devices. For example a display device of FIGS. 20, 20A demonstrates the principles of our novel container construction as applied to a hollow, cylindrical display device 212. In this arrangement, the display device 212 includes an outer cylindrical container section 214 of a clear or transparent material such as glass or polyacrylic resin. An inner container section 216 is formed from a rectangular sheet of a suitable plastic coated with pressure sensitive adhesive. The inner container section 216 can be rolled as better shown in FIG. 20A and lapped at 218. The major portion of the container section 216, in this example, is covered with a rectangular sheet 220 of light-absorbing material of a black or dark hue. The light-absorbing sheet can be likewise rolled and lapped, as denoted at 222.

A quantity of liquid crystal 224 is inserted between the light absorbing sheet 220 and the juxtaposed surfaces of the cylindrical outer container section 214. The sheet 216 desirably is provided with a coating of pressure-sensitive adhesive for adhering to the inner surfaces of the outer container section 214 adjacent the ends thereof as denoted by reference characters 226, 228 respectively (FIG. 20). Desirably, the internal diameter of the display device 212 is sufficient to afford access to an individuals finger or other means for applying deformational stresses to the flexible container section 216.

Alternatively, the flexible container section can be of clear material and applied to the exterior of the tubular member 214 after the manner of FIGS. 22, 22A. In such case, the liquid crystal 224 can be provided with a contained light-absorbing means as described below in connection with the latter figures.

Still other forms of hollow display devices can be made after the manner of the display device 230 illustrated in FIGS. 21-21A. In this arrangement, the display device 230 includes a container section 232 of exemplary, pyramidal configuration, although a differing geometric or nongeometric shape can be utilized. One face of the pyramid shape 232, for example the bottom face, is provided with a liquid crystal package 234, of which the adjacent surface of the pyramidal shape 232 forms a part, after the manner of FIGS. 6-9. Alternatively, two or more liquid crystalline packages can be provided after the manner of FIG. 5. The precise construction of the liquid crystal package 234 can be modified in accordance with one of several of the accompanying figures, for example after the manner of FIG. 22A or 228, substituting, of course, the pyramidal shape of FIG. 21 for the planar, rigid member of the latter figures.

The several reflections and refractions within the transparent pyramidal shape 232 are multiplied by the provision of a hollow core 236 within the solid transparent member 232. The core 236 can be sealed as shown in FIG. 21 or in the alternative conduit means 238 and 240 (FIG. 21A) can be coupled thereto.- In any event, the core 236 can be filled with a gas or liquid having a differing refractive index from that of the material comprising the transparent block 232. The differences in refractive indices and the several interfaces between the gas or liquid within the core 236, multiplies the number of reflections and refractions of the liquid crystalline pattern 238 and enhances the visual aspects of the display.

For further variety and enhancement of interest in the display device 230, we contemplate the partial filling of the core 236 as denoted by chain line 240 in FIG. 21A. In such case, the core 236 contains a liquid portion 242 with an air pocket 244 thereover. Alternatively, the air pocket 244 can be replaced by an immiscible liquid portion having a lower specific gravity than that of the liquid portion 242. For further variety in interest, the liquids 244 and 242 can be dyed with differing colors.

FIG. 21A also illustrates alternative means for filling or changing or circulating the fluid or fluids contained within the hollow core 236. Such means includes the aforementioned connecting conduits 238, 240, a pump 246 and suitable connecting conduits. Valved conduit sections 248, 250 can be coupled to a suitable source or sources (not shown) of appropriate fluids for filling the core 236. In the event that the core 236 is filled with two liquids 242, 244, the core can first be completely filled with the lighter liquid 244, from which subsequently a portion is displaced by circulation of a heavier liquid 242, to provide a liquid-liquid interface (chain line 240).

Another arrangement for packaging liquid crystalline materials for display purposes is illustrated by display device 252 in FIGS. 22, 22A. In this modification of our invention, the display device 252 exhibits a variable color pattern of liquid crystal 254 from both sides of the device 252. This is accomplished by utilizing a relatively rigid light transmitting or clear container section 256 and a resilient or flexible container section 258 of light-transmitting or clear plastic 258. A peripheral portion of the plastic sheet 258 is provided with pressure sensitive adhesive at 260 for peripheral sealing of the sheet to the container section 256 to encapsulate liquid crystal 254 therebetween. The liquid crystal 254 desirably is of the pressure-sensitive variety described previously.

To permit viewing of the color pattern of the liquid crystals from either side of the display device 252, under normal conditions and without the use of auxiliary viewing devices such as crossed nichols, we have unexpectedly found that light-absorbing means can be incorporated within the liquid crystalline material 254. Such light-absorbing means permit viewing of the liquid crystal patterns from either side of the device 252 by means of variably scattered light from the liquid crystalline material, while eliminating all or a substantial portion of the otherwise interfering transmitted light.

One form of such light-absorbing means includes the use of a black or dark-hued dye, for example a nigrazine dye. The nigrazine dye is miscible with the liquid crystalline material 254 and can be used in the range of about two percent to about 10 percent by volume. Alternatively, the light-absorbing means can comprise carbon black or other finely divided light absorbing material suspended within the liquid crystal, in an amount (in the case of carbon black) of from about I to about 30 percent by weight.

Another form of our display device 262 is illustrated in FIG. 228. The display device 262 presents a variable color pattern visible through flexible container section 258, which in this case is a transparent plastic sheet material such as Mylar. The other container section 256, which in this example is more or less rigid, is likewise transparent. The package 262 as described thus far is assembled after the manner of the display device 252 of FIG. 22A. To facilitate assembly a nonadhesive clear plastic sheet 264 can cover a central portion of the adhesive clear sheet 258' to demarcate the area occupied by the liquid crystal 266. In the case of the display device 262, however, the liquid crystalline material 266 does not have a selfcontained light-absorbing means such as the dye or carbon black mentioned above with reference to FIGS. 22, 22A. Instead, the light absorbing means is applied to the outer face of the more or less rigid container section 256'. The light-absorbing means can be applied as a black or dark-hued coating 268 on such outer face. Alternatively, an opaque black or darkhued plastic sheet provided with a coating of pressure sensitive adhesive can be substituted for the coating 268. The use of the dark-hued or black coating or sheet 268 eliminates or reduces substantially the reflection of transmitted light back through the liquid crystal 266, after the manner of the light absorption means 16 of FIGS. 1 and 2.

Claims (20)

1. A display device for exhibiting a varying color pattern, said device comprising container means having a light transmitting section, a quantity of cholesteric liquid crystalline material encapsulated within said container means, said material having characteristics of selective visual light scattering to exhibit color patterns within a range of temperatures at which said display device is normally utilized, and of transmitting a substantial quantity of impinging visual light, light absorbing means supported by at least one of said liquid crystalline material and said container means for absorbing at least a substantial proportion of said transmitted light, said container means being configured so as to permit substantial volumetric flow of said liquid crystalline material within said container means, said material having an additional characteristic of a selective light frequency scattering which is variable in accordance with applied deformational stresses, the color patterns exhibited by said material being substantially insensitive to a wide range of temperature variations, and means coupled to said container means for displacing said container means to apply said deformational stresses to said material in a direction to induce said volumetric flow, said displacing means comprising a relatively thin portion of said container means adjacent said light-transmitting section, said portion including deformable constriction and expansion areas for displacing and accommodating said flow respectively so that pronounced color changes are effected in said material as a result of said flow.

2. The combination according to claim 1 wherein said displacing means further includes an arm member engageable with an external surface of said container portion, means for retaining said external surface and said arm member in bearing engagement, and means for moving said arm member across said external surface while in bearing engagement therewith.

3. The combination according to claim 1 wherein said light-transmitting section is a substantially flat transparent member of about one-eighth inch in thickness.

4. The combination according to claim 1 wherein said liquid crystalline material includes at least one of the group consisting of alkyl carbonate and alkanoic cholesteric esters of cholesterol, B-sitosterol, stigmasterol, and ergosterol.

5. The combination according to claim 4 wherein said liquid crystalline material is a cholesteryl compound.

6. The combination according to claim 4 wherein a quantity of cholesteryl halide is admixed with said liquid crystalline material.

7. The combination according to claim 6 wherein said halide is selected from the group consisting of cholesteryl chloride, cholesteryl bromide, and cholesteryl iodide.

8. The combination according to claim 6 wherein said halide consists of cholesteryl chloride.

9. The combination according to claim 6 wherein said halide is present in the amount of about 15 to about 40 percent of the resulting composition.

10. The combination according to claim 4 wherein said cholesteric esters include at least one of the group consisting of the oleyl carbonates and the nonanoates, together with a quantity of cholesteryl halide.

11. The combination according to claim 10 wherein said oleyl carbonates include high cholesteryl oleyl carbonate and low cholesteryl oleyl carbonate.

12. The combination according to claim 11 wherein said cholesteryl halide is present in the amount of about 22 percent to about 27 percent, said high cholesteryl oleyl carbonate is present in the amount of about 50 percent to about 75 percent, said low cholesteryl oleyl carbonate is present in the amount of about 0 percent to about 23 percent, and said cholesteryl nonanoate is present in the amount of about 0 percent to about 15 percent.

13. The combination according to claim 1 wherein said light absorbing means are supported on said displacing means.

14. The combination according to claim 1 wherein said displacing means include a flexible membrane sealed to said container means so that a portion thereof can be displaced toward said container means while another portion thereof can be displaced away from said container means.

15. A display device for exhibiting a color pattern, said device comprising container means having a light-transmitting section and containing a thin sandwich of cholesteric liquid crystalline material within said container means, said material having characteristics of selective visual light scattering to exhibit substantially temperature insensitive color patterns within a range of temperatures at which said display device is normally utilized and of transmitting a substantial quantity of impinging visual light, light-absorbing means supported by at least one of said liquid crystalline material and said container means for absorbing at least a substantial proportion of said transmitted light, said container means being configured so as to permit substantial volumetric flow of said material within said container means, said material including a quantity of cholesteryl halide and having an additional characteristic of a selective light frequency scattering which is variable in accordance with applied deformational stresses, and means coupled to said container means for applying said stresses.

16. The combination according to claim 15 wherein said halide is selected from the group consisting of cholesteryl chloride, cholesteryl bromide and cholesteryl iodide.

17. The combination according to claim 15 wherein said halide consists of cholesteryl chloride.

18. The combination according to claim 15 wherein said halide is present in the amount of about 15 percent to about 40 percent of the resulting composition.

19. The combination according to claim 15 wherein said cholesteric material includes at least one of the group consisting of high and low oleyl carbonates and the nonanoates.

20. The combination according to claim 19 wherein said cholesteryl halide is present in the amount of about 22 percent to about 27 percent, high cholesteryl oleyl carbonate is present in the amount of about 50 percent to about 75 percent, low cholesteryl oleyl carbonate is present in the amount of 0 percent to about 23 percent, and cholesteryl nonanoate is present in the amount of 0 present to about 15 percent.

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