US 3353895 A
Description (OCR text may contain errors)
OILHIWH KW! X Wmc 1967 E. s. EMERSON LIGHT POLARIZER COMPRISING FILAMENTOUS PARTICLES ON SURFACE OF TRANSPARENT SHEET AND METHOD OF MAKING SAME Filed April 16, v 1962 FIG. I
DEPOSITION FIGZ DIRECTION OF os osmou ATTORNEYS" FIG?) United States Patent 3,353,895 LIGHT POLARIZER COMPRISING FILAMENTOUS PARTICLES 0N SURFACE OF TRANSPARENT SHEET AND METHOD OF MAKING SAME Eugene S. Emerson, Allston, Mass., assignor to Polaroid Corporation, Cambridge, Mass., a corporation of Delaware Filed Apr. 16, 1962, Ser. No. 187,679 19 Claims. (Cl. 350-155) This invention relates to a novel and economical method of forming optically anisotropic materials, more pa-rticularly light polarizing materials of high efficiency and other desirable characteristics, and to light polarizing products of various and useful types produced by the method.
The present invention is, in general, concerned with an improved rapid and highly flexible method of producing light polarizing materials of several categories such as plane or circular polarizers and light polarizing images or patterns, in sheet and other utilitarian forms, of large or small area according to functional requirements. The method basically involves the controlled directional deposition-in-vacuum of selected evaporable materials adapted to the purpose onto and along, in the direction of deposition, a proper carrying surface or substrate, the direction of the vapor stream from the evaporation source downwardly toward the surface being at a selected angle or angles. The vacuum deposition is performed, preferably employing a very high vacuum, in such a manner as to produce a multiplicity of microscopic laterally-spaced filamentous areas or particles which may be compared to minute threads or fibers evaporated onto and distributed throughout the surface of a receiving or carrying layer in a predetermined substantially oriented arrangement according to the intended polarizing structure and function. The long dimension of the filaments thus evaporated, as above stated, is predominantly in the direction of deposition or propagation or at least along that direction in which they are caused to flow immediately prior to incidence upon the carrier surface as provided by said direction of deposition in conjunction with barrier, shadowing, an externally applied field-of-force, or other functionally related means integral with or adjacent to the receiving surface. In a uniformly polarizing sheet, the sideby-side relation of adjacent filaments is generally parallel but this condition may be varied gradually or abruptly between laterally placed masses of filaments in producing a non-uniformly polarizing area by varying the direction of deposition relative to the receiving surface. After the deposition step a stabilizing after-treatment is preferably performed to at least firmly anchor particles of the deposited material together and to the carrying surface and pretreatment of the surface may also be performed.
Assuming, for example, the light polarizer of the present invention to be in the form of a light-transmitting area as, for instance, a sheet material, a transparent base or support such as a sheet of glass or plastic is employed for receiving the deposited filaments. Evaporable materials contemplated by the present invention for deposition on the carrier element include both metals and dyes as well as other materials mentioned hereinafter which are capable of producing extremely eflicient polarizers, e.g., polarizers having a density (dichroic) ratio in excess of 15, and which are adapted to polarize and transmit up to fifty percent of the incident light, thus approaching the transmission characteristics of an ideal polarizer. Polarization may be plane, extending in one uniform direction throughout the sheet, or it may extend in a plurality of directions. Again, polarization may be of a circular type or the product may constitute a plane polarizer operating in a radial manner, that is, in the latter instance, the polarizing directions may, for example, extend outwardly as a plurality of spolres from a centrally located point. Wherein the base is glass and the deposited substances are unaffected by high temperatures as, for example, where they are suitable metallic substances, it is possible to provide a coating of molten glass on the deposition thereby to produce a glass encased polarizer having practically infinite permanence. In the case of a plastic carrier, a layer of a suitable plastic may be cast on or otherwise applied to the surface carrying the deposited filaments. Light polarizers of the present invention may, optionally, be of types which transmit light preferentially of a given wavelength or wavelengths in the visible or invisible portions of the spectrum including the near and far infrared, or they may be of a type predominantly transmitting substantially white light.
In accordance with the foregoing considerations a principal object of the present invention is to provide a method of forming a highly efficient light polarizer by a relatively simple, rapid and economical vacuum deposition operation wherein a plurality of appropriate minute filamentous elements is laid down on a suitable receiving surfacewith their long dimensions substantially parallel to the direction in which they are deposited.
Other objects are to provide a method of the character described wherein a combination of vapor-emitting and direction-controlling means, when taken with the structure of the carrier or substrate upon which the substance is deposited, provides the lengthwise orientation of the filaments; to provide a method as stated in which either a metal, a dye or another suitable substance is used for evaporation and deposition purposes and wherein various readily procurable materials may be employed for receiving the deposition; to provide a method of the type mentioned wherein auxiliary electrical, magnetic, electromagnetic or other supplementary forces are employed to maintain, redirect or otherwise modify the inherently linear paths of evaporated substances from a heater to a receiving surface; to provide a method of the character described in which an aditional substance or substances are deposited on or embodied in the receiving material to modify the light polarizing characteristics produced by the basic filamentous deposition; to provide a method of stabilizing and protectively coating or shielding the deposited filaments as, for example, by an after-treatment, a pre-treatment, or both; to provide an interference type of light polarize-r by the deposition in vacuum of a metallic substance of a given thickness and refractive index, at a given acute angle, on a surface of a light-transmitting carrier layer of a different refractive index so as to produce a plurality of filaments distributed in substantially parallel relation throughout said surface and, thereafter, as may be necessary, to apply a transparent layer to the exposed surfaces of the carrier layer and filaments, the thickness of the filaments in the direction of the light to be transmitted being less than one-half the wavelength of said light; to provide a deposition-in-vacuum method of forming light polarizing images and geometric patterns; and to provide light polarizing products either in the form of polarizing sheet materials which uniformly polarize or which differentially polarize incident light throughout their areas, said materials being characterized by high efliciency, stability, high density (dichroic) ratios and other desirable qualities.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the several steps and the relation and order of one or more of such steps with respect to each of the others, and the product possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure,
and the scope of the application of which will be indicated in the claims.
For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanyin g drawing wherein:
FIGURE 1 is a diagrammatic side view, with certain parts broken away and others greatly exaggerated, which illustrates one method of producing a light polarizing sheet material of the invention;
FIG. 2 is a small section, greatly magnified, of a light polarizing sheet material such as may be produced by the method of FIG. 1; and
FIG. 3 is a diagrammatic representation of a masking means suitable for use in the method of the invention.
The ability of a proper arrangement of spaced metallic wire elements to polarize incident spectra has been known for a considerable period. An early forbear of a so-called grid type of polarizer was fabricated in 1888 by the eminent German scientist, Heinrich Hertz. This device was made of wires of 0.040" diameter arranged on a large frame for the purpose of polarizing radio waves. Other examples include the optical polarizers of du Bois and Rubens (Annalen der Physik, 1911, vol. 35, page 243),
who wound platinum, copper, gold and silver wires of as little as 0.0010" diameter between spaced frame members thus forming wire structures capable of polarizing radiation in the far infrared to 24 microns. Further ways of forming an assembly of wires for light polarization purposes were disclosed by C. H. Brown in 1940-1942 (U.S. Patents Nos. 2,224,214 and 2,287,598).
The methods suggested by the foregoing individuals in forming polarizing bodies generally require the building up of a structure by a cumulative procedure, usually by manipulating a continuous length of extremely thin and fragile wire in a preconceived manner, as, by winding it back and forth between or around spaced frame members or around a drum, together with various supplementary operations. These procedures are of a type which indicate that, at the very least, extreme care must be taken to insure proper spacing between the wires and to prevent their breaking and the suggested methods would appear to be useful only for the fabrication of relatively small areas in which comparatively large wire elements are employed. Furthermore, these earlier suggestions, which necessitate repeating the entire delicate and time-consuming operation for each polarizer produced, are adapted rather to an experimental than to a quantity type of production.
It has further been shown in the copending US. patent applications, Serial Nos. 786,414, now issued as US. Patent 3,046,839 and 165,138, assigned to Polaroid Corporation, Cambridge, Massachusetts, U.S.A. that a light polarizer, apparently related in principle to the Hertzian structure, can be produced by the deposition-in-vacuum of an evaporable metal on a preformed grid-like configuration of the nature of a diffraction grating in which a plurality of microscopic ridges extending transversely of the direction of deposition are coated with the metal to provide a form of metalized grid. One possible criticism of this method is the extremely minute nature of the manually-formed grid structure necessary and the attendant difficulty of manufacture and expense involved in producing a grating composed of microscopic elements of the character needed, e.g., one comprising 10,000 to 100,000 or more ridges to the inch which is the number required to achieve an efficient polarizing function. Another difficulty of the aforesaid method appears to be the critical angle of deposition required to place the metal on a given minute portion of each ridge. A third somewhat arduous requirement is that the metalized elements must be substantially uniform. Among further limitations is the desirability of maintaining such a grating essentially flat to preserve its optical properties.
The deposition-in-vacuum method of the present invention avoids the aforesaid handicaps through such instrumentalities as the ability to employ a considerable range of workable deposition angles; the use of receiving materials or substrates for the evaporated substance which are readily procurable and inexpensive and which may be used more or less in their natural states and procured in large areas or in continuous lengths; and the non-essentiality of uniformity between the filamentous particles. Also, as a distinguishing feature, the present invention involves the evaporation and deposition of dyes and other substances in addition to metals, as well as depositions performed in various directions and on non-planar as well as plane surfaces. Wherein the present invention appears to involve surface irregularities of the substrate, a definite pattern or direction of arrangement of elements forming the same, such as that of the aforesaid ridges, is not essential.
Referring to FIG. 1, one method of forming a light polarizing material of the invention is shown. A transparent carrier sheet material 10 as, for example, a flexible length of polymethyl methacrylate, poly CF CFCI, or other suitable plastic is moved in a direction indicated by arrow 12 by suitable drive means such as pairs of powered drive rolls (not shown). An elongated strip of vaporizable material 14, e.g., a metal such as aluminum or silver or a dye powder, of a length approximating the width of sheet 10, is mounted within an electric heater 16, the latter extending transversely of sheet 10 and being mounted for both vertical and pivotal movement by slots 18 and threaded positioning nuts 2-0 to fixed frame 22 to permit angular variation of the heater orifice 16:: with respect to the upper surface of sheet 10. It will be noted that the mouth or orifice 16a is disposed downwardly at a small angle relative to the plane of sheet 10, e.g., at an angle of 5, so that vaporized particles 14a of the strip 14 are being deposited augularly on the surface of sheet 10. An enclosing tank or chamber 24, in which a high vacuum is established, as through evacuation of air by an exhaust pump, not shown, surrounds the above-described elements and portions of the sheet 10, as illustrated. A pair of slots 26 having sealing means 28 for maintaining the vacuum is provided to enable passing the sheet 10 into tank 24 and withdrawing it therefrom, either as a continuous or an intermittent operation.
With regard to the present invention, it is believed that a very large number of irregularities, which are more or less naturally present or preliminarily superimposed on the surfaces of substrates employed, contributes importantly to the light polarizing effects obtainable, although other factors related to the vaporization and bombardment or to the substrate may also be involved and are mentioned hereinafter. In accordance with the abovedescribed surface structure, a plurality of small moundlike irregularities such as eminences or protuberances 30 is shown, in highly exaggerated size, on the surface of sheet 10, no attempt having been made to depict exact physical shapes or quantities thereof; These surface nonconformities are microscopic in size and so very small and inconspicuous that the surface may even appear highly polished to the naked eye. They are believed to occur to a large and functional extent in commercial grades of sheet glass and plastic so that, where thus present, no special pre-treatment of the sheet is necessary, it being required merely to select a suitable material and adjust the deposition angle according to height considerations relating to the heights of the irregularities. Assuming, at least for purposes of the method now described, that the aforesaid protuberances are present, although the exact stage of their formation is subject to further explanation below, the following steps are performed. As the sheet 10 is .moved past the orifice 16a, the heated strip 14 emits minute particles, e.g., of molecular size, which emanate in straight lines and a broad but thin vaporized composite layer or stream of the evaporable substance 14a is directed substantially linearly thereupon. However, due to the protuberances 30 and the chosen angle of deposition,
part of the evaporated material is obstructed by the mound-like structure of the protuberances and is prevented from reaching the surface of the sheet in the areas thus shadowed" by the protuberances. Between the protuberances 30, in a direction transverse of the sheet and in a lengthwise direction where no shadow exists, the evaporated material is principally laid down on the sheet surface in the form of substantially parallel filaments 32, as shown more clearly in the highly exaggerated section of FIG. 2.
After the deposition of the filaments 32 on the surface of sheet 10, a binding and protective coating 34 of a clear plastic or lacquer, suitably of a similar material and preferably having a refractive index similar to that of base 10, is applied as, for example, from a dispensing tank 36 having an orifice 36a, to the surface of sheet 10. Electric heater 38 and air-circulating means 40 serve to rapidly dry and solidify the coating 34. The sheet material thus formed is a plane light polarizer and is ready for cutting into sections or other treatment for whatever use may be contemplated. Any portion of the evaporable substance deposited on the surfaces of the protuberances which face the heater apparently does not impair the etficiency of the polarizer and may, in some manner, not as yet understood, contribute thereto.
It may generally be assumed that the transmitted component of incident light vibrates in a direction transversely of the long dimension of the filaments while the nontransmitted component vibrates in a direction parallel therewith. For general purposes in the visible range, it may be stated that a proper quantity of the vaporizable substance has been deposited if substantial opacity results in viewing the polarizer in superimposed relation with an analyzer which transmits a beam of light having an electric vector parallel to the long dimension of the filaments 32. A very slight thickness of the filaments in the direction of light transmittance, in general, produces a highly efficient polarizer and contributes to the desirable high transmission objective. Increasing amounts of the deposition reduce the transmission and eventually result in a light polarizer transmitting in the invisible region of the spectrum, e.g., in the infrared. It will be understood that such factors as heater temperature and duration of the deposition period affect the thickness and opacity of the filaments in the sense just described.
Assuming, for instance, the filamentous particles 32 to be composed of a deposited metal, a certain amount of light incident on the completed polarizer will be reflected. The reflected light is at least partially polarized in a di rection other than that of the transmitted light. Thus, although the present invention is principally directed toward a transmission type of polarizer, it also applies to a refleeting polarizer. The amount of polarization of the reflected component depends principally upon the angle at which the polarizer is mounted with respect to an optical path or axis. As previously intimated, at least certain commercial grades of glass or plastic sheeting are believed to possess, more or less inherently, a multitude of individual minute moundor node-like surface differences or protuberances which appear to contribute in the manner described, that is, in conjunction with a proper angular deposition of materials, to the production of the filaments. Where the surface is deficient in such an irregular formation, pre-treatment, as described below, may be applied thereto to facilitate such a formation. Assuming their significant function, the microscopic protuberances distributed in a generally random manner provide, by reason of their blocking function, the aforesaid shadow areas which, in turn, cause a minute spacing to exist between the filaments, as they are being formed. This spacing is, in general, far less than one wavelength of the radiation to be polarized, an essential condition of an efficient polarizer. The density (dichroic) ratio tends to increase as the ratio of the transmitted wavelength to the transverse spacing between the filaments increases.
The method of FIG. 1 is also adapted to the manufacture of an interference type of monochromatic or colortransmitting polarizer, that is, one transmitting light of a given wavelength band or hands. This is achieved by depositing, in a high vacuum, a multiplicity of filaments of a substance having a high refractive index, a metal being eminently suitable, in the manner hereinbefore described, the deposited filaments distinguishing in refractive index from the base or carrier and having a thickness, in the direction of transmitted light, which is a proper fraction of the wavelength of said light to be transmitted e.g., one-half of the wavelength. A material, not classified as a metal but having a high index of refraction such as silver bromide or carbon, would also be operative in producing an interference type of polarizer.
As previously intimated, a considerable range of vaporizable substances may be employed in forming light polarizers of the type contemplated herein by a deposition-in-vacuum method. Among possible metals are, for example, aluminum, silver, platinum, palladium, gold, chromium, tungsten, carbon, iron, cobalt, nickel, and alloys thereof. Certain organic dyes supplied in powder form may also be employed, such as the dye Isoviolanthrone (C.I. 6000), Copper Phthalocyanine (C.I. 74160) and Direct Blue 87 (CI. 74200). These would be deposited as filaments in the manner shown in FIG. 1.
Other special purpose evaporable materials used in making light polarizers of the present invention comprise high-index, transparent and colorless materials adapted to be rendered birefringent, such as zinc sulphide or silver chloride. A quarter-wave retardation layer of either of the aforesaid birefringent materials deposited, as minute filaments of the character described, upon the layer 10 in a direction at 45 to the long direction of filaments 32 provides a circular polarizer. Another method of making a circular polarizer involves a deposition of the filaments of the invention on a suitably oriented doubly-refracting layer of a proper retardation value, e.g., one-quarter or three-quarters of a wavelength, etc. Thus, for example, a deposition of the filaments on a section of mica having a retardation value of three-quarters of a wavelength, the direction of deposition being at 45 to a principal axis of said section, was accomplished and provided such a polarizer.
Other materials adapted to form light polarizers within the scope of the invention include phosphors such, for exal iple, as zinc sulphide, cadmium sulphide and calcium tungstate. By placing the mask or screen 42 of FIG. 3, having a plurality of minute apertures 44, between the heater, containing an evaporable phosphor, and the carrier surface, a plurality of both light polarizing and electronexcitable configurations, each configuration composed of a plurality of filaments arranged in the manner previously described, would be produced as, for example, on the screen of a television receiver tube. While on the subject of employing an intermediate screen or mask, it will be understood that such a screen, e.g., a silk screen, mask, stencil or the like, may be employed between the heater and carrying sheet, employing either an evaporable metal or dye, to form a light polarizing image and that two such images, formed on the carrier in slightly displaced steroscopic relation by filaments 32, deposited in directions preferably substantially at 90 to one another, would provide a composite stereoscopic image which could be seen in three dimensions through properly oriented light polarizing viewers.
It is within the scope of the invention to deposit, in a vacuum Without using a mask, photosensitive substances of microscopic size and filament-like shape for subsequent conversion to visible light polarizing images. Among such contemplated substances are silver halides and diazo compounds. Images, thus produced and rendered, for example,
in silver, are believed to have various uses, particularly where a plurality of light polarizing images in slightly 7 offset or substantially superimposed relation is of advantage for stereoscopic or other visual effects.
Wherein a dye rather than a metal is employed to form the deposited filaments 32, a polarization phenomenon somewhat different from that previously described appears to be involved. Although the exact nature of the phenomenon is not entirely clear, its complete understanding is not essential to a working comprehension of the present invention. Thus, although it is desired not to be held strictly to the following explanation, it is believed that the use of a dye rather than a metal in the deposition process involves so-called textural dichroism, namely, a dichroism produced by refractive index and absorption differences between the filaments and their surround taken with a periodic geometric array of the filaments. An intrinsic dichroism of the dye may as well be involved.
Example In producing a section of the light polarizer of the invention by a non-continuous method, the following steps were performed. A glass plate 1" x 3", namely a fiat section of so-callcd soda glass, was mounted in a highvacuum enclosing tank. The plate was adjusted so that an angle of 5 was established between a line extending from a piece of aluminum mounted in a heater within the tank and the plane of the plate at a location extending transversely as a line across the plate at its center. A vacuum between torr and 10* torr was produced in the tank. The aluminum was heated to its sublimation temperature, namely to approximately 660 C. It was permitted to evaporate and form a deposition on the glass surface for approximately seconds. No special emission bafile or guide means was employed so that vaporization was directed, in terms of its vertical dimension, in a somewhat fiared or conically shaped manner. This produced a light polarizer which in the area contiguous with the aforesaid center line had a proper density and an essentially neutral transmittance characteristic. The polarizer was removed and found to have a density (dichroic) ratio of 15.
In addition to, or in place of, the means shown for controlling the direction of deposition or the size or shape of the vaporized stream as, for example, by the guide elements forming orifice 16a, an entirely different type of control may be exercised. Among contemplated means for the purpose are fields-of-force applied from various external locations as produced, for instance, by electric, magnetic, or electro-magnetic devices, not shown. These devices would be so positioned as to influence the course of the evaporated substances during passage through said fields-of-force while enroute from the heater to the areas of deposition. Wherein the vaporized substance is, for instance, a metal, it may be provided as an ionized metal having a given charge. The material upon which the metal is to be deposited would, either of itself, have an opposite charge to facilitate or control the direction of deposition, or such a charge would be placed, for example, on an element closely adjacent thereto, such as on an underlying plate.
As mentioned hereinbefore, a range of deposition angles may be employed. Theoretically, any angle other than 90 will produce a deposition resulting in some polarization of incident light. However, an angle within a range of from 0 to has been found most practicable and a more specific angle within this range, such as that previously mentioned of 5, is best in a given instance. Assuming that different materials have different receptivity characteristics, e.g., different heights of surface irregularities, the relation of certain chosen deposition angles thereto becomes apparent and various specific angles would be employed, accordingly, it being indicated that extremely acute angles are, in general, those best adapted to the purpose. Other factors relating to vaporization characteristics or the substrate, suggested hereinafter, may also well be involved.
As will be evident from the methods and structures presented herein, a wide range of light polarizing materials and devices may thereby be produced. It will also be noted that the methods generally involve a relatively simple and rapid production technique and what is believed to be an unprecedented flexibility with respect to possible complex orientations merely by changing the deposition direction or substrate position.
Further considering the subject of surface irregularities, which have been mentioned hereinbefore either as inerent in the substrates themselves or as preliminarily added thereto or formed therein, namely, irregularities of the filament-carrying surfaces which apparently have an important influence on the process of the invention, one explanation is that they may be formed through environmental conditions or influences to which the surfaces are exposed or subjected. Thus, for example, the irregularities may be caused by gases adsorbed on the substrate surface, either prior to or during the early stages of the deposition process, through bombardment of the surface by adsorbable molecules from a surrounding gas. Another explanation holds that, at its beginning, the bombardment of the surface by each portion of the vapor stream quic-k- 1y builds up a multiplicity of spaced mounds on the surface which then function, relative to further depositions, in the manner previously described relative to the formation of the filaments, that is, by casting shadow areas and the production of the filaments in non-shadowed areas. A still further explanation suggeststhat the bombard ment causes deformities of the type described to be initially produced in the material of the substrate itself. Still nother theory minimizes the presence of or need for the surface protuberances at all and suggests that the filamentous deposition occurs by reason of some other operation as, for example, through the instrumentality of a plurality of laterally spaced individual vapor streams which form the individual filaments as for example h vapor bursts or the like.
Since certain changes may be made in the above process and product without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense. What is claimed is:
1. A transmission-type light polarizing material of high efiiciency and relatively simple construction, comprising a transparent substrate composed of a sheet material selected from the group consisting of transparent glasses and plastics, the surfaces of which are perceptibly smooth consistent with casting and extrusion methods of production, a multiplicity of abbreviated microscopic mound-like protuberances distributed randomly throughout a surface of said substrate of a minuteness contributing to the smoothness of said surface, and a multiplicity of short, laterally and longitudinally spaced filamentous particles oriented predominantly in one given direction and distributed throughout and adhering to said substrate surface so as to be contiguous with given portions of said protuberances exclusive of their elevated portions but to be spaced from other portions thereof said particles when oriented in said given direction forming a plurality of side-by-side essentially-parallel filaments of a thickness and spacing less than one wavelength of the incident light to be transmitted to polarize said light.
2. A light polarizing material, as defined in claim 1, wherein said filamentous particles are predominantly composed of a metal.
3. A light polarizing material, as defined in claim 1, wherein said filamentous particles are predominantly composed of an organic dye.
4. A light polarizing material, as defined in claim 1, wherein said filamentous particles are composed of a substance in the form of a polarizing image.
5. A light polarizing material, as defined in claim 1, wherein said filamentous particles are composed of a 9 substance selected from the group consisting of silver said filamentous particles are composed.
6. A light polarizing material, as defined in claim 1, wherein said mound-like protuberances are composed of a material selected from the group consisting of the material of said substrate, per se, and the substance of which said filamentous particles are composed.
7. An improved vacuum deposition process for producing a linearly light polarizing element having a principal polarizing axis normal to the direction of said deposition, comprising the steps of mounting a transparent perceptibly-smooth-surfaced element serving as a supporting base within a high-vacuum chamber so as to be positioned for transmitting incident light therethrough and for receiving a deposition of an evaporable substance in said chamber, said smooth surface of said element having a multiplicity of abbreviated mound-like protuberances distributed randomly throughout said surface of a minuteness contributing to the smoothness of said surface, mounting a quantity of a given evaporable substance of a given shape in a heater element withinsai-d chamber at a predetermined location and spacing relative to said base ele ment, said substance being of a type adapted to polarize light when converted to a filamentous form and arranged predeterminedly in quantity on a transparent substrate, evacuating the air from said chamber to produce a given high vacuum therewithin, heating said evaporable substance to a prearranged temperature to effect its vaporization at a rate substantially determined by the nature of said substance and the degree of said given vacuum and of said prearranged temperature, guiding a given quantity of said substance in the form of a predetermincdly contoured vapor stream linearly within given acute angular limits toward a predetermined area of said base element to provide, deposited on said area of said element, a plurality of minute, laterally-spaced filamentous particles of said substance which are oriented longitudinally in the general direction of flow of said vapor stream said particles being contiguous with given portions of said protuberances exclusive of their elevated portions but to be spaced from other portions thereof, concurrently viewing said area of said base element and said light passing therethrough through a light polarizing analyzer having a principal polarizing axis oriented in a direction essentially parallel to said direction of fiow of said vapor stream, and terminating the heating of said evaporable substance to effect cessation of its vaporization immedi ately upon said area of said base element assuming a substantially opaque appearance when thus viewed.
8. A process, as defined in claim 7, wherein said evaporable substance is a metal, wherein a very-high vacuum is produced within said chamber, wherein said metal is heated to a sublimation temperature to provide an emission of minute particles thereof substantially of molecular size, wherein said base element and said evaporable substance are relatively movable, and wherein one of said base element and substance is moved relative to the other as a step of said process to vary the area of said base element upon which said vapor stream is incident and to determine the period to which any portion of said area is subjected to said deposition of said metal.
9. A process, as defined in claim 8, wherein said highvacuum is between 10- torr and 111-" torr, wherein movecut of one of said base element and substance is effected continuously and evenly at a given speed, and wherein said speed is controlled to provide a deposition of said metal throughout each portion of said area of approximately 15 seconds duration.
10. A process, as defined in claim 7, wherein said evaporable substance is in the form of an elongated strip and is so placed in said high-vacuum chamber as to be positioned laternally athwart of and substantially equidistant throughout its length from said base element.
11. A process, as defined in claim 7, wherein said vapor stream is acutely angularly incident upon said base element within a range of 0 to 25.
12. 'A process, as defined in claim 7, wherein said substance is deposited on said base element to an amount providing a thickness of said filamentous particles which, taken in the direction of incident radiation to be polarized, is less than one-half of the wavelength of said radiation.
13. A process, as defined in claim 7, wherein said substance is deposited on said base element to an amount providing a lateral spacing between said filamentous particles which is less than one wavelength of the radiation to be polarized.
14. A process, as defined in claim 11, wherein the angle at which said vapor stream is incident upon said base element is provided by introducing a restrictive balfie into given portions of the path of said vapor stream.
15. A process, as defined in claim 11, wherein the angle at which said vapor stream is incident upon said base element is provided by an application of electromagnetic force to said vapor stream.
16. A process, as defined in claim 14, wherein said vapor stream is so guided as to be incident on said base element in a plurality of directions.
17. A process, as defined in claim 7, wherein a high vacuum and velocity of said vapor stream is provided such as to preliminarly effect the formation of a multiplicity of said microscopic mound-like protuberances on the receiving surface of said base element.
18. A process, as defined in claim 7, wherein said vapor stream is passed through a perforated mask, introduced between said heater element and said base element, to form an image on said base element.
19. A process, as defined in claim 7, wherein is added the final step of applying a protective transparent film material to said area carrying said filamentous particles.
References Cited UNITED STATES PATENTS 2,204,604 6/1940 Land 88-65- 2,458,168 1/1949 Husek 350-153 X 2,860,221 11/1958 Kohl 117-107 X 3,046,839 7/1962 Bird et al. 88-65 3,086,889 11/1963 Strong 117-107 X 3,218,926 11/1965 Boone 350-158 X DAVID H. RUBIN, Primary Examiner.
JEWELL H. PEDERSEN, Examiner.
P. R. MILLER, I. S. GOLDHAMMER,
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,353,895 November 21, 1967 Eugene S. Emerson It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
Column 9, line 2, strike out "said filamentous particles are composed" and insert instead halides and diazo compounds column 10, line 9, for "laternally" read laterally line 37, for "preliminarly" read preliminarily line 55 for "11/63" read 4/63 Signed and sealed this 8th day of April 1969.
Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissioner of Patents