US3853675A

US3853675A - Materials adapted to exhibit varying visual appearances

Info

Publication number: US3853675A
Application number: US00213706A
Authority: US
Inventors: C Edwards
Original assignee: Rue T Int Ltd De
Current assignee: De la Rue International Ltd
Priority date: 1970-12-30
Filing date: 1971-12-29
Publication date: 1974-12-10
Anticipated expiration: 1991-12-10
Also published as: GB1375360A; FR2120128A1; FR2120128B1

Abstract

Sheet material comprising two superimposed differently coloured light-transmitting non-fibrous layers and between the layers and in substantially intimate contact therewith a partially lighttransmitting layer is herein defined, the colors of the lighttransmitting layers being so selected that when either face of the material is viewed by transmitted light from a source of a substantially white light, the color observed is different from that observed when either layer alone is viewed in like manner.

Description

States Pate 1191 Walworth 350/132 Unrt Edwards Dec; Ml", 19741 MATERIALS ADAPTED T0 EXHIBIT 2,961,365 11/1960 'sr66 ..L... 161/214 VARYING VISUAL APPEARANCES 1 fib 1xon [75] Inventor: Christopher John Edwards, Marlow, 3,065,120 11/1962 Avelar 154/461; England 3,163,554 12/1964 Gess ler 161/3 3,264,164 8/1966 Jerothe ct 211.... 161/6 [73] 'A P f dela Rue Imgmamnal 3,429,733 2/1969 WO1f6la1..... ..117 33.3 Llmlled LOndOIL England 3,442,755 5/1969 Walters et a1. 162/168 22 Filed. Dec 29 1971 3,451,877 6/1969 Herschman ..161/3 3,581,417 6/1971 Andrews 40/22 [21] I Appl, No.: 213,706 3,620,888 11/1971 Buzzell 161/1 30 1F Tell it A licfllio Prio it Data Prim? Amber 1 D :3 F r y 710/70 Assistant Examiner-:William R. Dixon, Jr.

tea n am Attorney, Agent, or Firm-Baldwin, Wight & Brown [52] US. Cl 161/3, 40/1.6, 40/5, 1

40/130 B, 40/130 F, 40/135, 40/219, 161/6, [57] ABSTRACT 161/228 0 0 i Sheet material comprising two superimposed differ- Km Cl M12 ently coloured light-transmitting non-fibrous. layers [58] Fieid 232 408 and between the layers and in substantially intimate 161/4O9 3 40/l 5 contact therewith a partially light-transmitting layer is 1 6 1 6 herein defined, the colors of the light-transmitting laye'rs being so selected that when either face of the ma- 56] References Cited terial is viewed by transmitted light from a source of a substantially white light, the color observed is differ- UNITED STATES PATENTS ent from that observed wheneither layer alone is 1,947,516 7 2/1934 Broadman .1 154/40 viewed in like manner. 2,333,641 11/1943 Corwin 2,892,383 6/1959 25 Claims, 41 Drawing Figures Ill/11111111177111 MATERIALS ADAPTED TO EXHIBIT VARYING VISUAL APPEARANCES This invention relates to improvements in sheet materials wherein at least one portion thereof exhibits a visual appearance which differs in color in accordance with the angle through which the materials are viewed and/or illuminated.

The said materials have utility in areas such as, for example, the construction of playthings, advertising and promotional media, printed articles generally, teaching, the conveyance of information, the identification of articles, and as artists or artistic materials per se.

It is desirable that certain printed and other articles, including those above mentioned should incorporate or constitute one or more features that attract the eye and attention of a viewer. By this means, information may be brought to the notice of an observer more emphatically than is the case with media not exhibiting such a feature.

According to this invention a sheet material comprises at least two superimposed differently colored light-transmitting non-fibrous organic polymer layers and between each adjacent pair of the layers and in substantially intimate contact therewith is a substantially planar partially light-transmitting layer as hereinafter defined, the colors of the light-transmitting layers being so selected that when either face of the material is viewed by transmitted light, from a source of substantially white light, the color observed is different from that observed when either layer alone is viewed in like manner.

By a partially light-transmitting layer it is meant a layer which serves partially to reflect and partially to,

transmit light falling upon it; the ratio of the intensity of the transmitted light to the reflected light being dependent upon the angle of incidence of the light and being a maximum when the angle of incidence is normal to the partially transmitting layer.

The partially light-transmitting layer maybe any suitable layer having the properties defined above and may comprise for example, a fibrillated plastics layer, a layer of tissue or similarly structured paper, an alpha cellulose or similar paper, a layer of particulate matter in spaced distribution, a' layer of transparent material having a surface finish adapted to confer a high degree of reflectance-upon the incidence thereupon of nonnormal light rays (for example, a transparent film printed on both sides with an ink containing discrete particles of a white highly refractive pigment such as titanium dioxide) or a web or mesh of textile fabric. The partially transmitting layer may be an adhesive suitable for bonding two light transmitting layers together and yet, when set, possessing the transmission characteristics required of such a layer. No particular limits are to be applied to the thickness of the partially light-transmitting layer other than that preferably it should be as thin as is commensurate with'the exhibition of the above defined characteristics.

The organic polymer light-transmitting layers a e preferably selected from the group comprising thermoplastic resins, regeneratedcellulose and cellulose esters and transparent compositions containing the same. However any colored non-fibrous transparent organic polymer material will suffice. The layers, which may be preformed or formed during the manufacture of articles according to this invention, are preferably each of a thickness within the range of 0.0001 inch to 0.1 inch and, preferably still, within the range 0.0005 inch to 0.05 inch. A light-transmitting layer may be continuous or non-continuous with respect to an adjacent partially light-transmitting layer; a non-continuous layer may be created by the application to a suitable partially lighttransmitting layer of organic polymer material by selective coating, printing or like techniques.

Optionally also one or more of the light-transmitting layers may comprise sheet materials converted to mesh-like configuration by a punching or like operation; depending upon the desired effect to be obtained from and the appearance desired of any given material, the partially light-transmitting layer or layers may or may not be perforated in accordance with the perforations of the associated light-transmitting layers. If more than one of the light-transmitting layers are perforated or comprise discrete shapes the colored portions of each layer must be so positioned that, in the sheet material, they are in at least partial register with at least some of the colored portions of at least one of the two other light-transmitting layers thus insuring that at least some of the light travelling normally or nearly normally through the colored portions of one of the layers also travels normally or nearly normally through at least some of the colored portions of at least one of the other light-transmitting layers.

The external surfaces of the light-transmitting layers may optionally be further patterned. or decorated by the application thereto of light-transmitting printed or similarly applied designs.

Materials according to this invention may be adapted to give variegated effects overall. For example, a material may comprise two adjacent portions, one in which the superimposed light-transmitting layers are, for example, yellow and blue and the other in which the supe rimposed layers are, for example, green and violet; thus when viewed under transmitted light one portion of the material will appear to be green and the adjacent portion will appear as grey. Such materials may be readily constructed by producing each element of such a composite separately and then arranging portions of each in desired adjacent relationship. When more than two light-transmitting layers are used they may each be of a different color or, according to the total number employed, two or more of them may be of the same color. However, in order to obtain the desired colored effect under transmitted light (when each is of a different color) three or more such layers must each be of such a configuration that the composite effect of two I layers is not marred by the presence of any other layer;

thus when using three or more such layers one or more of them is preferably colored in parts only or perforated to give an equivalent effect. By the use of a plurality of colored light-transmitting layers with uncolored portions or spaces between colored portions of each layer according to a predetermined overall pattern, viewing by transmitted light will produce a predetermined pattern, for example, according to the relative positioning of the colored portions of relevant layers, a recognizable pattern, word or legend in the composite color.

According to the nature and intended use of materials according to this invention, the partially lighttransmitting layer may be co-extensive with its adjacent light-transmitting layers or, provided it is always present between portions of such layers required to exhibit the desired effect under transmitted light, it may be discontinuous in relation to other portions of the lighttransrnitting layers; inv areas where the partially lighttransmitting layer is not present the combined effect of two adjacent light-transmitting layers, under transmitted light, will be different from that obtained if the partially light-transmitting layer were present. In any event, however, the partially light-transmitting layer, when present between two differently colored lighttransmitting layers may be modified to create special effects. For example, within an area of such a partially light-transmitting layer smaller areas corresponding to the shapes of, for example, letters may be created by stamping out or by selective transparentization of the layer; in such an instance the letters may appear, when viewed mainly by reflected light, as the color of either of the outermost layers of thelight-transmitting layers (on the background of the combinative color of the two layers) in dependence upon the side from which viewing takes place when viewed under mainly transmitted light, the letters would disappear, tend to disappear, or appear differently within the entire area encompassed by the partially transmitting layer. Conversely, by opacifying, e.g.,' by the application of opaque inks, portions of the said area of the light-transmitting layer in correspondence with, for example, the shapes of letters, the reverse effect will be obtained, that is to say the lettering will be weak under reflected light but will be seen more distinctly when the material is viewed under mainly transmitted light.

The colored light-transmitting layers and the partially transmitting layer may be firmly bonded together over substantially the whole of their co-extensive surfaces or may be bonded only at the peripheral regions thereof. It is preferred that the materials be bonded together over substantially the whole of their co-extensive surfaces in order to guarantee intimate contact and thus to maximize the effect peculiarthereto. It is, however, important when bonding the layers together to insure that-the properties necessary in the partially transmit ting layer are maintained'therein and not to employ bonding means or tecniques that deleteriously effect the defined properties of said partially transmitting layer. When bonding agents, e.g., adhesives, are used they must be'only'be compatible with and capable of bonding to the material of the light-transmitting layers but also of such a nature and present in such a quantity that they do not penetrate substantially into the body of the partially light-transmitting layer. To this end, when the partially light-transmitting layer paper, it is preferable'to use a calendered product.

It is preferred that the bonding of the layers is so performed that the bonded layers cannot be readily separated and more preferably it is so performed that at-- rial may be prepared by adhesively bonding the'preformed colored light-transmitting layers to the paper or fabric sheet; alternatively the colored layerslmay be prepared by extrusion techniques known per se for certain of vthe suitable materials and by positioning and bonding the partially transmitting layer during or im mediately after the extrusion in such a manner that the partially transmitting layer and the light-transmitting layers become bonded-togetheras a unitary structure during that period wherein one or both of the colored light-transmitting layers is in a flowable state.

The materials of the invention may be used alone or in combination with other materials. For example, dis play' cards may be fabricated entirely of the materials of our invention suitably printed and/or fashioned or a display card may be formed, from any suitable base material known for such purpose, having affixed into the base material, but selectively removable therefrom in a predetermined and controllable manner, a material according to our invention. Furthermore, printed arti cles can be fabricated in which the materials are incorporated in a non-removable manner. For example, if the base material for such articles is a thermoplastics 'material the materials of our invention can be nonremovably-incorp'orated therein by any suitable: means such as, for example welding, solvent bonding, extrusion or molding. If the base material is paper, ournovel materials may be incorporated into the paper. during the process of manufacturing the paper, preferably by laying materials according to this invention on a layer of paper pulp in the paper-making machine and then laying a further layer of paper pulp thereover. Obviously, the thickness of such paper pulp layers must not be such as to prevent the transmission of light through the incorporated sheet material. The use of a perforated version of our material facilitates the production ofa'coherent body as a result of the penetration of the paper fibres through the holes in the material so securwide range of thicknesses but irrespective of the thicktempts to separate'the bonded layers results in'the m echanical disruption of one or more of the layers. Suitably, this preferred. bonding isfp'erformed utilizing,

bonding agents and/or bonding'means such that the strength of the bonds .fonned between lighttransmitting layers and-the partially transmitting layer or layers exceeds the cohesive strength of the partially transmitting layeror/layers and/or'are' at least-as strong ness of the paper into which the novel materials are to be incorporated it is preferred'that the materials are so selected that in the'finished paper a layerof'paper fibres-at least 0.0005 inch thick overlays each'surface 'of the material provided that the thickness and/or opacity of thefiber layers does not prevent transmis sion of light through the sheet material. However, this restriction is not to be taken as limiting since, according to the use for the finished product, materials according .tothis invention, when incorporated in paper,

mayv have still thinner overlaying layers of paper fibre or may, in part, protrude through the surfacesof the paper. Composite articles comprising the novel materimaterials according to this invention and such materials may form a major or a minor part of such composites.

It will be appreciated that, in order for the materials of the invention to exhibit varying visual appearance, the manner in which they are utilized must be such that light will pass through and onto the materials and hence they must be so positioned that they may be viewed alternatively by essentially transmitted or essentially reflected light. The function of the partially transmitting layer is such that at low angles of incidence of viewing and/or illumination the ratio of transmitted light to reflected light is low and hence the color observed by a viewer is substantially that contained by the colored layer closer to his eye; as the angle of incidence increases towards normal the observed color changes until, at a normal angle of incidence, the color observed is a composite of thetwo differently colored lighttransmitting layers so long as the degree of illumination onto the surface farther away from the observer results in the majority of light falling onto the observers eye coming from that source of illumination.

In that embodiment of our invention wherein the novel material is incorporated within the body of a paper sheet the best effect is obtained when using a transparent or transparentized region of paper wherein the light entering or leaving the material through the paper layers is dispersed to a leaser extent than when using known papers. Conveniently, transparentization is efiected subsequent to the production of such paper composites by treating the surfaces thereof or the portions of such surfaces which enclose materials according to this invention with a suitable agent, for example a melamine formaldehyde resin, a derivative thereof or other cross-linkable compounds known per se as suitable for the transparentization of paper.

In order that it may be more fully understood certain non-limiting embodiments of the invention are exemplified below with reference to the accompanying drawings of which FIG. 1 is a diagrammatic exploded view of the componentsof the material described in Example I;

FIG. 2 is a plan view showing diagrammatically the disposition within a paper web of the separately produced components of Example-II;

FIG. 3 shows an exploded view of the components of the material described in Example III; and

FIG. 4 is an exploded view of the components described in Example IV.

EXAMPLE I This example describes a novel sheet material according to our invention suitable for incorporation into a paper web during its manufacture and also a method for preparing the materials.

As indicated hereinabove, for incorporation into a paper web during its manufacture our novel materials are preferably at least 0.001 inch thinner than the finished paper. The material described in this example is about 0.003 inch thick and thus is suitable for incorporation into papers having a finished thickness of at least 0.004 inch.

The novel material according to this example is in perforated web form (although for purposes of simplicity perforations are not shown in; the drawing) and comprises a central layer 1 of highly calendered alpha cellulose paper about 0.002 inch thick having adhered to one side thereof a blue dyed film 2 formed from polyethylene terephthalate and to the other side a ye]- low dyed film 3 formed from polyethylene terephthalate, each layer of polyethylene terephthalate being about 0.0005 inch thick.

The novel material was prepared as follows:

i. One surface of each of the films was coated with a two part adhesive 4 of the polyester-isocyanate type and the adhesive thoroughly dried by passage through an oven.

ii. The two films with their adhesive coated surfaces inwards were then arranged on either side of the paper web and the assembly passed through a hot nip laminator whereby the adhesive was activated and the assembly consolidated to a unitary structure in web form.

iii. The web was then passed between cooling rollers and then perforated before being wound upon a take-up spool.

The perforated web was incorporated into paper during a paper-making process by first laying down a layer of paper pulp, positioning the perforated web thereon, and thenapplying to the first down pulp layer and the tape further pulp to build up the paper to the desired thickness of about 0.004 inch. After drying and finishing the paper in the normal manner that area of the paper web corresponding to the perforated web material was treated in a known manner by a printing technique with a compositionknown for the transparentization of paper.

The material according to this example was suitable for use per se or in combination with materials other than paper-making pulp.

The novel material prepared as described exhibits, both alone and when incorporated into the paper web, a visual appearance varying in dependence upon the angle of the light path by which it was viewed. When viewed under transmitted light conditions the material appeared green while in reflected light the material appeared either blue or yellow dependingupon which side of the material was being viewed.

EXAMPLE in Example I was repeated up to and including step (iii) save for the use of a green dyed film of polyethylene terephthalate in place of the blue film and a violet dyed film of the same polymer in place of the yellow film;

A portion of the material so produced together with a portion of the material produced in accordance with Example I, was then incorporated in paper in accordance with the further description of Example I. The

' portior1 s of Example I and II materials were laid in This material was also suitable for use other than in the body of paper pulp.

EXAMPLE in This example relates to a triple'layer material forincorporation into paper web or sheet, and may be considered to be a symmetrical arrangement based on Example I.

The novel feature of this example is to provide a first color when paper incorporating the material is viewed from either side by reflected light, and a second color when viewed from either side by transmitted light.

Referring to FIG. 3 itwill be seen that the constituents of the material comprise a centrally disposed blue dyed film 8 formed from polyethylene terephthalate of thickness 0.0005 inch and two outwardly disposed yellow dyed films 9 and 10 (also of 0.0005 inch thickness) of a similar material. interposed between the dyed films are disposed alpha

cellulose paper sheets

11 and 12 having a thickness of about 0.002 inch.

The method of preparing the material comprised coating both surfaces of the film 8 and one surface each of film 9 and 10, with adhesive 13. Thereafter, the adhesive was dried, the components were than assembled in the manner shown in FIG. 3, and finally were consolidated by heat and pressure.

The material so formed may be perforated if desired and then incorporated into a paper web in the manner described in Example I.

When theh paper is viewed from either side by reflected light the material embedded therein will appear yellow, but when viewed by transmitted light it will appear green (i.e., the combined effect of all these films).

The optical effect may be enhanced by transparentization of the paper in the vicinity of the material.

The material described above was suitable for uses other than in the body of fibrous substances.

EXAMPLE IV This example relates to material comprising two continuous differently colored light-transmitting layers having therebetween a discontunuous partially transmitting layer which is co-extensive with only portions of the light-transmitting layers, in order to produce a special effect.

The materials are those referred to in Example I. Referring now to FIG. 4 layer 14 is yellow and layer 15 is blue. The adhesive layers are indicated at 16. The alpha cellulose layer 17 is shorter in length than either of the light-transmitting layers and is so disposed that, at each end of the composite material the yellow and blue layers, or rather the adhesive coatings thereof are in intimate contact with each other.

The alpha cellulose layer is perforated at 18, said perforations being representative of portions of letters, say D.L.R.

When material according to this example was viewed mainly by reflected light the portions not encompassing the alpha cellulose layer and those portions corresponding to the perforations in the alpha cellulose layer appeared green viewed'from either side, and the portions of the light-transmitting layers having the alpha cellulose layer therebetween appeared blue when viewed from the blue side and yellow when viewed from the yellow side. Thus the green lettering was EXAMPLE V Material according to this invention was produced from three superposed open-work webs of regenerated cellulose, one being colored violet, one being colored green and one being colored yellow and each having a thickness of 0.001 inch thick and two layers of tissue paper, one between each adjacent pair of regenerated cellulose webs and co-extensive therewith and each having a thickness of 0.01 inch. The webs were arranged in the above-mentioned order, that is with the green web centrally placed.

The layers of regenerated cellulose were bonded to the layers of the tissue paper by means of a nitrile rubber based adhesive applied to the webs prior to their use for the purpose of this invention.

Each web was initially a continuous sheet but each was converted to open-workform by the stamping-out of predetermined portions in a predetermined pattern. One portion of each element of the violet layer was arranged to overlie an element of the green layer and an- .other portion of the violet layer was arranged to overlie an element of the yellow layer.

When the resultant product was viewed by reflected light, one face appeared of clear violet and diffused green areas and the other face appeared of clear yellow and diffused green areas. When viewed from either side by light transmitted through the material, the appearance was a pattern of gray, green and brown areas.

Material according to this example was suitable for uses as a material in its own right although it was also suitable for incorporation within the body of a relatively thick paper fibre body.

In alternative embodiments of the invention which may be applied to any of the above examples or adaptations thereof, an equivalent optical effect may be obtained by coating the surfaces of the partially lighttransmitting layer sheets with light-transmitting color media, (for example by roller coating techniques). This method serves to provide an extremely compact material, and eliminates the need for adhesives.

Example V relates the use of a partially lighttransmitting layer with cut-out portions but in still further embodiments, which serve to provide additional unique and artistic effects, and which are also applicable to the above described examples, the partially lighttransmitting layers may be cut out to provide a pattern, discretely transparentized or printed 'upon with opaque inks or dyes in a predetermined manner before application of the layers or coatings.

By way of an example applicable to advertising,

' words may first be printed upon the partially lightclearly visible, on a yellow background when viewed transmitting layer in opaque ink and subsequent to the production of material according to this invention incorporating such a layer a second printing may be applied to the frontal surface of a paper sheet enclosing the said material. In use, a first source of illumination may be directed upon the front of the sheet to display the second printed matter. A further source of illumination may be positioned behind the composite sheet, and a suitable switching means may be arranged to render either or both sets of printing selectively visible.

What is claimed is:

1. Sheet material comprising at least two superimposed colored light-transmitting non-fibrous organic polymer film-forming layers, each layer of a pair of layers being differently colored, and between each adja- 9 cent pair of said layers and in substantially intimate contact therewith a single substantially planar layer which is partially light-reflecting and partially light-' transmitting with the ratio of the intensity of transmitted light to the intensity of reflected light being dependent upon the angle of incidence of the light and being a maximum when the angle of incidence is normal to said layer, the colors of the light-transmitting layers being 80 selected that when either face of the composite material is viewed by transmitted light from a source of substantially white light the color observed is different from that observed when any light-transmitting layer alone is viewed in like manner.

2. Sheet material as claimed in claim 1 in which each of the light-transmitting layers has a thickness within the range 0.0001 inch to 0.1 inch.

3. Sheet material as claimed in claim 2 in which the thickness of at least one light-transmitting layer is within the range 0.0005 inch to 0.05 inch.

4. Sheet material as claim in claim 1 in which the overall external surfaces thereof comprise continuous light-transmitting layers.

5. Sheet material as claimed in claim 1 in which at least one light-transmitting layer comprises a layer applied to said partially light-reflecting and partially lighttransmitting layer as a coating.

6. Sheet material as claimed in claim l in which at I discontinuous layer comprises discrete organic poly-' mer areas.

9. Sheet material as claimed in claim 1 in which all of the light-transmitting layers are discontinous, said layer being so disposed in relation to one another that at least some of the light travelling substantially normal to the colored portions of any one layer travels also substantially normal to at least some portions of at least one other layer.

10. Sheet material as claimed in claim 1 including three light-transmitting layers, the remotely disposed layers being of the same color and the other layer being of a different color and having partially light-reflecting and partially light-transmitting layers between each pair of light-transmitting layers.

11. Sheet material as claimed in claim l in which said partially light-reflecting and partially light-transmitting layer is formed of a fibrous material.

12. Sheet material as claimed in claim l in which said partially light-reflecting and partially light-transmitting layer is in the form of a calendlered material of the paper and fabric type.

13. Sheet material as claimed in claim lin which said partially light-reflecting and partially light-transmitting layer is in the form of a layer of spaced discrete particles of a light-reflecting material. I l

14. Sheet material as claimed in claim 1 in which said partially light-reflecting and partially light-transmitting layer is formed of a transparent material having a surface finish which is highly refiectant of light rays which are not normal thereto.

115. Sheet material as claimed in claim M in. which the partially light-reflecting and partially lighttransmitting layer is in the form of a transparent film printed on both sides with an ink containing discrete particles of a highly light-refractive pigment.

. 116. Sheet material as claimed in claim l in which there are adhesive means bonding-said partially lightreflecting and partially light-transmitting layer to said adjacent light-transmitting layers.

layer is coextensive with portions only of said adjacent light-transmitting layers.

1%. sheet material as claimed in claim l in which portions of said partially light-reflecting and partially lighttransmitting layer are transparent.

19. Sheet material as claimed in claim l in which portions of said partially light-reflecting and partially lighttransmitting layer are opaque.

20. A product comprising sheet material as claimed in claim 1 incorporated generally centrally within a paper base material with the sheet. material being viewable by light transmitted through said product.

21'. A product as claimed in claim 20 in which said paper base material includes a layer of paper fibres having a minimum layer thickness of 0.005 inch overlying each surface of the sheet material.

22. A product as claimed in claim 21 in which at least that portion of each layer of paper fibres overlying thesheet material are transparent.

23. Sheet material as claimed in claim l wherein said 25. Sheet material as claimed in claim ll wherein said film-forming materials are cellulose esters.

* i =l l= t

Claims

1. SHEET MATERIAL COMPRISING AT LEAST TWO SUPERIMPOSED COLORED LIGHT-TRANSMITTING NON-FIBROUS ORGANIC POLYMER FILMFORMING LAYERS, EACH LAYER OF A PAIR OF LAYERS BEING DIFFERENTLY COLORED, AND BETWEEN EACH ADJACENT PAIR OF SAID LAYERS AND IN SUBSTANTIALLY INTIMATE CONTACT THEREWITH A SINGLE SUBSTANTIALLY PLANAR LAYER WHICH IS PARTIALLY LIGHT-REFLECTING AND PARTIALLY LIGHT-TRANSMITTING WITH THE RATIO OF THE INTENSITY OF TRANSMITTED LIGHT TO THE INTENSITY OF REFLECTED LIGHT BEING DEPENDENT UPON THE ANGLE OF INCIDENCE OF THE LIGHT AND BEING A MAXIMUM WHEN THE ANGLE OF INCIDENCE IS NORMAL TO SAID LAYER, THE COLORS OF THE LIGHT-TRANSMITTING LAYERS BEING SO SELECTED THAT WHEN EITHER FACE OF THE COMPOSITE MATERIAL IS VIEWED BY TRANSMITTED LIGHT FROM A SOURCE OF SUBSTANTIALLY WHITE LIGHT THE COLOR OBSERVED IS DIFFERENT FROM THE OBSERVED WHEN ANY LIGHT-TRANSMITTING LAYER ALONE IS VIEWED IN LIKE MANNER.

5. Sheet material as claimed in claim 1 in which at least one light-transmitting layer comprises a layer applied to said partially light-reflecting and partially light-transmitting layer as a coating.

6. Sheet material as claimed in claim 1 in which at least one of light-transmitting layers is a discontinuous layers.

7. Sheet material as claimed in claim 6 in which the discontinuous layer is a perforated layer.

8. Sheet material as claimed in claim 6 in which the discontinuous layer comprises discrete organic polymer areas.

11. Sheet material as claimed in claim 1 in which said partially light-reflecting and partially light-transmitting layer is formed of a fibrous material.

12. Sheet material as claimed in claim 1 in which said partially light-reflecting and partially light-transmitting layer is in the form of a calendered material of the paper and fabric type.

13. Sheet material as claimed in claim 1 in which said partially light-reflecting and partially light-transmitting layer is in the form of a layer of spaced discrete particles of a light-reflecting material.

14. Sheet material as claimed in claim 1 in which said partially light-reflecting and partially light-transmitting layer is formed of a transparent material having a surface finish which is highly reflectant of light rays which are not normal thereto.

15. Sheet material as claimed in claim 14 in which the partially light-reflecting and partially light-transmitting layer is in the form Of a transparent film printed on both sides with an ink containing discrete particles of a highly light-refractive pigment.

16. Sheet material as claimed in claim 1 in which there are adhesive means bonding said partially light-reflecting and partially light-transmitting layer to said adjacent light-transmitting layers.

17. Sheet material as claimed in claim 1 in which said partially light-reflecting and partially light-transmitting layer is co-extensive with portions only of said adjacent light-transmitting layers.

18. sheet material as claimed in claim 1 in which portions of said partially light-reflecting and partially light-transmitting layer are transparent.

19. Sheet material as claimed in claim 1 in which portions of said partially light-reflecting and partially light-transmitting layer are opaque.

20. A product comprising sheet material as claimed in claim 1 incorporated generally centrally within a paper base material with the sheet material being viewable by light transmitted through said product.

21. A product as claimed in claim 20 in which said paper base material includes a layer of paper fibres having a minimum layer thickness of 0.005 inch overlying each surface of the sheet material.

22. A product as claimed in claim 21 in which at least that portion of each layer of paper fibres overlying the sheet material are transparent.

23. Sheet material as claimed in claim 1 wherein said film-forming materials are thermoplastic resins.

24. sheet material as claimed in claim 1 wherein said film-forming materials are regenerated cellulose.

25. Sheet material as claimed in claim 1 wherein said film-forming materials are cellulose esters.