US 3910033 A
A watch dial is covered with a transparent film of a thickness such as to give rise to interference between light reflected from the front and the rear surfaces thereof, thereby producing interference colors. The resultant appearance may be enhanced by the use of a dial having a pattern or color on the surface thereof.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Saito Oct. 7, 1975 WATCH DIAL WITH INTERFERENCE COLORS  Inventor: Yoshinori Saito, Suwa, Japan  Assignee: Kabushiki Kaisha Suwa Seikosha,
Tokyo, Japan  Filed: Jan. 16, 1975  Appl. No.: 541,677
Related U.S. Application Data  Continuation of Ser. No. 319,087, Dec. 29, 1972,
abandoned  Foreign Application Priority Data Dec. 29, 1971 Japan 46-725  U.S. Cl. 58/127 R; 58/127  Int. Cl. G04B 19/06  Field of Search..... 117/159; 106/148; 350/164, 350/165, 166, 163; 161/34; 58/127 R, 88 C  References Cited FOREIGN PATENTS OR APPLICATIONS 450,298 4/1968 Switzerland .1 58/127 Primary Examiner-Joseph W. Hartary Assistant ExaminerU. Weldon Attorney, Agent, or Firm--Blum, Moscovitz, Friedman & Kaplan  ABSTRACT 2 Claims, 3 Drawing Figures US. Patent Oct. 7,1975
WATCH DIAL WITH INTERFERENCE COLORS This is a continuation, of application Ser. No. 319,087, filed Dec. 29, 1972 now abandoned.
BACKGROUND OF THE INVENTION The watch industry, spanning as it does the range from movementless toys to chronometers, is always in search of new characteristics, functions and grades of precision but one of the most important'features is novelty of appearance since sales frequently depend on this last characteristic, particularly where the watch is classified as a novelty. Conventionally, watch dials have been composed of brass, aluminum or even gold and have been finished by gilding, painting, embossing and in other ways too numerous to mention.
Attention has been lavished upon the dial of a watch since this is the feature which most commonly is observed with close attention during reading of the indicated time. Consequently, a development which improves the appearance of the dial must of necessity be of substantial importance competitively. The present invention is concerned with a novel method of producing unusual colors and patterns on the face of a dial.
SUMMARY OF THE INVENTION A watch dial is coated with a transparent film of appropriate thickness so that interference colors are generated between the light reflected from the front surface of the film and the back surface of the film which is contiguous with the exterior surface of the dial. The dial itself may be colored and may have patterns impressed thereon as by embossing or printing. The combination of interference color from the transparent film and color on the dial itself gives hitherto unavailable color tones.
Accordingly, an object of the present invention is to provide a watch dial of improved appearance by reason of an interference color-producing film thereon.
Another object of the present invention is to provide a watch dial of improved appearance wherein interference colors produced by the transparent film in combination with the color of the watch dial gives hitherto unavailable color tones.
A further object of the present invention is to provide a watch dial of improved appearance utilizing a transparent film thereon which generates interference colors, enhancing the brightness and contrast of the watch dial.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises an article of manufacture possession the features, properties, and the relation of elements which will be exemplified in the article hereinafter described, and the scope of the invention will be indicated in the claims.
BRIEF DESCRIPTION OF THE DRAWING For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:
FIG. 1 is an edge view of a dial and a transparent coating thereon, the latter being in greatly enlarged scale, and showing the path of a light beam giving rise to an interference color;
FIG. 2 is an edge view of a watch dial having a transparent film thereon, the film being wedge-shaped in cross-section and shown in'greatly enlarged scale;
FIG. 3 represents a decorative pattern on a watch dial in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The way in which a transparent coating on a reflective surface gives rise to interference colors is shown in FIG. 1 where coating 13 on dial 14 is transparent and of suitable thickness. The beam 11 is reflected at the coating surface 13 and at the dial surface 12 to form the ray 12 which will have a color corresponding to the wave-length which is reinforced. The thickness required for interference depends on the index of refraction n of the particular material. The relation between refractive index n and thickness 'd for the production of specific colors is shown in the following table.
Since the index of refraction, n, is a pure number, the
' product nd where d is expressed in A is also in angstrom units.
The colors in the table above are observed when the film is viewed from near normal direction. I
Colors as listed in the table canbe obtained by employing films of silicon dioxide, silicon monoxidefsapphire, magnesium fluoride, and zince sulfide. Of these films, sapphire is preferred because of its superior adhesion to the substrate, namely the watch dial, and its hardness. Where the surface of the dial is itself colored, the color observed is the summation of the interference color and the color reflected by the dial itself. Satisfactory surface colors for the dial are silver, gold and black. As aforenoted, the sum of the colors from the dial surface and from interference produced by the coating results in color tones which have not been found in the past. Further, the surface of the dial can be decorated as by having a radial line finish or pattern (FIG. 3), a lattice-type line finish, a spiral line finish, or even an irregular surface.
As is well known, color of an interference film changes at each angle of view since a different wave length is reinforced for each particular angle. For instance, where a surface as described above is viewed at a right angle, the color of the surface is purple; however, when viewed from a different angle the color may range to blue or even to lighter colors.
The method of application of the surface coating onto the surface of the dial is preferably either by vacuum evaporation or by sputtering. Taking the deposition of sapphire on the surface as an example, this is carried out in a vacuum chamber where the chamber pressure is less than 3 X10 Torr. A suitable distance from the watch dial to be coated and the evaporation crucible is about 20 centimeters. The dial itself may have plated chromium upon it or plated gold or may have black chromium upon it. In general, the plane of the surface is perpendicular to a line joining the center of the surface and the crucible. Control of the thickness of the coating, is, of course, important as can be seen from the table given above. As a means of controlling the thickness, a quartz plate mounted to serve as a fre quency standard in an oscillating circuit may be positioned within the vacuum chamber so that it is coated simultaneously with the dial. The change in the frequency of oscillation of the quartz plate can then be used as an indication of the thickness of the deposit laid down on the dial. In this way, a pre-determined color may be obtained.
An especially pleasing effect may be obtained if the surface of the dial is placed at an angle other than 90 to the line joining the dial and the crucible. Under such an arrangement, the deposit is wedge-shaped in crosssection so that different parts of the dial will show different interference colors when illuminated. This can be seen clearly in FIG. 2 where 16 is the dial and is a wedge-shaped coating. A beam of light indicated by the double line numbered 17 strikes the top surface of coating 15. The left hand edge of the beam is reflected from the top surface of coating 15 to give line 18. The righthand edge of the beam is refracted at the top surface of coating 15, reflected from the top surface of dial l6 and refracted a second time as it emerges from coating 15 and leaves coating 15 along the ray 18. For reinforcement, the difference in path length must be equal to an integral number of wave lengths of the light to be reinforced. For the beam 19 reflected as ray 20, reinforcement takes place for a shorter wave length than for ray 17, it being assumed that first order reinforcement is being viewed.
Certain materials are difficult to evaporate due to their very low vapor pressure. In such a case, it fre quently happens that sputtering can be carried out under conditions such as to deposit a desired film. As
an example of such a film, cadmium can be sputtered in an oxygen atmosphere to deposit a film of cadmium oxide. Cadmium oxide results from the fact that as the cadmium deposits on the substrate, namely the watch dial, it is extremely reactive and combines with oxygen in the atmosphere.
It will be noted that the materials described are in general oxides, silicates or are sulfides and consequently are extremely resistant to corrosion. Further, the conditions of deposition are such that good adhe' sion is achieved. Finally, the products have been found to be very attractive in appearance.
It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above article without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.
What I claim is:
l. A watch dial of improved appearance, comprising a dial of brass, a layer of black chromium thereon and an adherent transparent coating of sapphire on said layer, said coating being of a thickness such as to produce color by interference between light reflected from the exterior surface of said layer and the exterior surface of said coating.
2. The watch dial as defined in claim 1 wherein the product of the index of refraction of said coating and the thickness of said coating lies between 1000 A and