Decorated article, method of fabricating the same and substrates used in connection therewith

The decorated article, for instance an instrument dial or watch dial, article of jewelry or ornamented article of use, possesses at least one surface or decorative layer which, in the presence of reflected light, appears to be colored, for instance yellow, red, blue or gray. This surface or decorative layer is formed by a silicon substrate or substratum, or lower layer as well as an upper or top layer fixedly connected thereto, for instance, connected by a reaction and/or deposition with the substratum. This top layer is permeable for optical light and comprises a silicon compound, preferably silicon dioxide, which under standard conditions is solid and practically inert, and has a thickness sufficient for interference-color formation, typically in the range of 50-1000 nm, preferably 90-500 nm. The surface or decorative layer can constitute the decorated article itself, for instance an instrument dial or watch dial or can be part of a decorated article, for instance a cigarette lighter.

BACKGROUND OF THE INVENTION 
The present invention relates to a new and improved decorated or ornamented 
article, to an improved method of fabricating such decorated articles, and 
to the use of silicon substrates coated with silicon compounds and serving 
as the decorated article or for use with the decorated article. 
As is well known very thin optical transparent layers in reflected light 
appear to the eye, owing to interference phenomena, as colored, although 
the layers consist of practically colorless material. Examples of such 
phenomena are the color effects of soap bubbles or mother-of-pearl and 
similar inorganic materials (opal) which are conventionally used for the 
fabrication of decorative or ornamental articles. There are furthermore 
known the so-called annealing or tempering colors which arise upon heating 
of iron alloys and which are predicated upon the formation of oxide 
layers. The thickness of such oxide layers is dependent upon the 
momentarily employed "annealing temperature", and which oxide layers 
appear to be colored ("annealing colors") when viewing the same in 
reflected light, without in reality being so inasmuch as the mass of the 
layer material is colorless. 
Typical in this regard is, for instance, the cyaneous color of watch 
springs, i.e., the interference color of a thin layer of iron oxide which 
forms at annealing temperatures of 295.degree. C. upon the metallic base 
or matrix material and having a thickness less than 100 nanometers (nm). 
Such annealing colors, generally, however, do not have any decorative 
functions, rather are the incidental consequence of temperature treatments 
for obtaining certain material properties. 
For the fabrication of decorative or ornamental articles there were hardly 
suitable the conventional annealing color layers of substrates formed of 
iron alloys in comparison to the conventional lacquer- or colored layers 
because of their comparatively high corrosion sensitivity, their 
relatively low mechanical strength (scratch sensitivity) and, in 
particular, due to the difficulties in producing reproduceable color 
effects. 
SUMMARY OF THE INVENTION 
Therefore, with the foregoing in mind it is a primary object of the present 
invention to provide a new and improved decorative article and a method of 
fabricating the same which is not associated with the aforementioned 
drawbacks and limitations heretofore discussed. 
Another important object of the present invention aims at providing silicon 
substrates coated with silicon compounds and serving as the decorated 
article or for use in the decorated article. 
Another important object of the present invention is to provide a surface 
or decorative layer which is suitable for use with decorated articles and 
appears colored in reflected light, this surface or decorative layer 
possessing high chemical resistance, allows for the color formation with 
good reproduceability and which is superior as concerns mechanical 
strength, temperature and aging resistance in comparison to the 
conventional organic and inorganic decorative layers heretofore known for 
decorative purposes. 
It has been surprisingly found according to the invention that different 
methods heretofore known from the semiconductor technology for the 
formation of layers which are well defined as concerns composition and 
thickness, these layers being formed of silicon compounds and deposited 
upon silicon substrates are beneficially suitable for use for fabricating 
colored-appearing layers employable for decorative purposes and which 
fulfill the aforementioned objectives. 
Under the term "decorative articles" or similar expressions as used herein, 
there is not simply to be understood typically articles of jewelry, but 
also other articles of use of the most various types which possess at 
least one surface having a colored appearance, which can be structured of 
a single or multi-colors and can possess image-, written-, or pattern-like 
contrasts. 
The inventive decorated or ornamental article possesses at least one 
surface, also referred to as a decorative layer, which appears to be 
colored in reflected light (daylight or polychromatic artificial light). 
This colored-appearing surface or decorative layer can be constructed to 
be flat, curved, domed or profiled and can possess a uniform or polyform 
and, if desired, image- and/or written- and/or pattern-type contrasted 
appearance. 
The inventive article is manifested by the features that the at least one 
surface or decorative layer, which in reflected light appears to be 
colored, for instance yellow, red, blue or gray, is formed by a silicon 
substrate or lower layer and an upper or top layer rigidly or fixedly 
connected with the substrate or lower layer and produced, for instance, 
reactively and/or depositively. This top or upper layer is permeable to 
optical light and consists of a silicon compound which under standard or 
normal conditions is solid, practically inert and preferably colorless. 
The silicon compound, in particular, may be silicon dioxide. This top or 
upper layer has a thickness adequate for interference-color formation, 
typically in the range of 50-1000 nm, preferably 90-500 nm. 
The decorated article, for instance the dial of a watch or an article of 
jewelry, can practically totally consist of the decorated layer, i.e., a 
self-supporting silicon substrate, the decoration of which at least 
partially consists of the top or upper layer displaying the interference 
colors. Such may be, for instance, in the form of a uniform or 
pattern-like or irregular colored surface upon which there can be produced 
ornamental patterns or the usual markings, for instance formed of opaque 
material, by imprinting or vapor deposition or in any other suitable 
manner, for instance by thickness differences of the top layer. 
The decorated article can, however, also consist of materials other than 
silicon. This decorated article can possess at least at one outer surface 
a decorative layer in the form of the silicon substrate which is applied 
by soldering, adhesive bonding or in some other suitable fashion. This 
decorative layer in conjunction with the top or upper layer formed of the 
silicon compound forms the desired uniform or polyform decoration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Describing now the drawings, in FIG. 1 there has been shown schematically 
in fragmentary and markedly enlarged sectional view a decorated or 
ornamental article 10, the surface 11 of which, also referred to as the 
decorative or decorated layer, appears colored in reflected light. This 
decorated article 10 is formed by a lower or base layer 14--also referred 
to as a substrate--composed of elementary silicon, for instance a 
self-supporting silicon plate or disc formed of technically obtained 
silicon. A particularly great purity of the silicon of the layer or 
substrate 14 is not required but also not disadvantageous. Generally, the 
silicon used as the base or matrix material for the production of 
semiconductors is suitable, and such silicon can be mono- or 
polycrystalline. The silicon substrate 14 has, for instance, a thickness 
of 0.05-5 mm or greater. 
When the silicon substrate 14, for instance as explained in conjunction 
with FIG. 2, is secured to a carrier formed of a different material, then 
the silicon substrate or layer 14 need not be self-supporting and then can 
be constructed to be correspondingly thinner. It is, if necessary, to be 
observed that during the reactive fabrication of the top or upper layer 
16, as will be explained more fully hereinafter, for instance by oxidation 
(SiO.sub.2) at elevated temperatures, part of the base layer is consumed, 
for instance 0.1 nm Si for each 0.2 nm SiO.sub.2, and that in this regard 
a certain minimum thickness of the substrate or layer 14 must be ensured 
for. 
At least the upper surface 140 of the substrate 14 is preferably smoothed 
in conventional manner, either mechanically or in some other appropriate 
fashion, in order to produce a dull or polished surface quality. This is 
done so that there can be obtained upper or top surfaces corresponding to 
those realized during the fabrication of semiconductor elements according 
to conventional methods for applying or forming layers having usually well 
defined composition and thickness upon silicon substrates. The surface 
quality (dull or polished) of the top layer 16 generally corresponds to 
that of the substrate or lower layer 14. 
For technological and economical reasons there are preferably employed for 
the invention usually upper or top layers 16 formed of silicon dioxide. 
However, there are basically suitable also upper or top layers 16 formed 
of other silicon compounds which are pervious for optical light, i.e., 
those which, as layers, have the thickness needed for the 
interference-color formation and are practically glass clear and possess 
at most a low inherent color; preferably the light permeability of the 
layer in the presence of throughpassing light amounts to more than 90%, 
i.e., the layer formed of the silicon compound, as the insulating layer, 
should absorb preferably less than 10% of the throughpassing light. 
However, at a top or upper layer 16 located upon the opaque lower layer or 
substrate 14 also appreciably more than 10% of the incident light can 
become lost due to reflection losses at the boundary layer or interface, 
without there thus being eliminated the formation of interference colors 
in the upper layer 16. 
This upper layer 16 consists of a silicon compound which is solid and 
generally practically inert in the sense that under standard or normal 
conditions of use and fabrication it is thermally and chemically stable. 
In other words, it does not significantly alter, for instance, either 
under the action of water or in the presence of temperatures up to 
100.degree. C. Examples of such type of silicon compounds are, apart from 
the oxides, the nitrides and carbides of silicon. Silicon dioxide is 
particularly preferred for reasons of its low costs. 
As is well known layers formed of silicon compounds can be reactively 
formed upon silicon substrates. In other words, due to the chemical 
reaction of the silicon base or matrix material in situ with the required 
reaction partner or partners which are present in an elementary or 
elemental form or as compounds and preferably present in each case in the 
form of a gas. Layers formed of silicon compounds can however be 
depositively formed, i.e. by deposition techniques, such as vapor 
deposition, while employing pre-formed compounds. 
The details of such suitable methods are well known in the art and in the 
relevant publications, for instance Meissel and Glang, Handbook of Thin 
Film Technology. Generally, there are preferred for the purposes of the 
present invention reactive methods which can be accomplished with 
acceptable technological expenditure for the formation of transparent 
layers formed of silicon compounds. A preferred examples is the conversion 
of the substrate-silicon with oxygen, wherein the activation energy can be 
delivered thermally, for instance by heating and/or electrically, for 
instance by glow discharge. It is possible to heat, for instance, the 
silicon substrate in the presence of oxygen or an oxygen-containing gas, 
such as air, under defined conditions of pressure, humidity and the like, 
to reaction temperatures exceeding 500.degree. C. 
Generally, there are technically obtainable silicon substrates having cover 
or protective layers formed of defined silicon compounds, such as 
SiO.sub.2, of suitable thickness as the base material for the 
semiconductor fabrication. The thickness of the top or upper layer 16, 
adequate for the interference-color formation, is, as above mentioned, 
usually in the range of 50-1000 nm. The suitable or optimum thickness of 
the layer 16, for a certain interference color, can be influenced by the 
specific optical properties, such as index of refraction, optical 
thickness, turbidity and the like, i.e., both from the nature of the 
silicon compound of the layer 16 and also from the method used for the 
layer formation. 
As exemplary embodiments there are hereinafter mentioned the following 
values for the color/thickness correlation of transparent SiO.sub.2 
-layers: 
______________________________________ 
Interference Color 
Layer Thickness in nm 
______________________________________ 
brown-white 68.5 
light brown 73.3 
dark brown 79.5 
reddish-brown 85.0 
purple 88.4 
dark violet 92.5 
dark blue 95.9 
light blue 112.0 
pale green 176.0 
light yellow 193.0 
golden yellow 206.0 
orange colors 241.0 
red 255.0 
dark purple colors 
265.0 
dark violet 274.5 
dark blue 277.9 
light blue 294.0 
pale green 358.0 
light yellow 375.0 
golden yellow 388.0 
orange colors 423.0 
red 437.0 
dark purple colors 
447.0 
______________________________________ 
The interference color/thickness relationship or ratio, as is well known, 
is dependent upon the wavelength .lambda. of the incident light, wherein 
the interference effects particularly arise at .lambda./4, .lambda./2, 
.lambda./1. Therefore, there can be realized a desired color with 
different thicknesses of the layer 16. Interference boundary regions for 
SiO.sub.2 lie at, for instance, 91, 273, 455, 637, 819 and 1002 nm. 
It should be understood that an exact measurement of the layer thickness is 
basically not critical or necessary, and in practice can be replaced or 
augmented by color comparison. Furthermore, the thickness of the top or 
upper layer 16 can be enlarged either by prolonged or intensified 
conditions of the reaction formation or deposition formation of the layer, 
or by controlled layer material removal methods, such as, for instance, 
etching, can be reduced over the entire area or in certain partial regions 
and the color effect in each case can be altered. 
The upper layer 16 can be provided with locally defined or limited overlays 
or coatings 18 formed or consisting of optically impervious (opaque) 
material, for instance from printing ink, metals, enamel and so forth, 
according to known techniques such as printing (for instance silk screen 
printing), vapor deposition (vacuum coating), adhesive bonding, 
painting-on and so forth, with or without the use of known masks, such as 
for instance photo lacquers. This is done, for instance, to form at an 
instrument dial of measuring devices, displays, watches and so forth, 
appropriate reference or luminous points, written markings, numbers and so 
forth. 
Alternatively, the substrate layer 14 can be provided with metallic 
coatings or overlays already prior to the formation of the top or upper 
layer 16, for instance by vapor deposition at certain regions (while 
utilizing appropriate masks or temporary protective layers) and thereafter 
can be treated for the formation of the top or upper layer 16 where the 
overlays or coatings then appear as inserts 19. In this case the top or 
upper layer 16 must be formed under conditions wherein the material or 
metal of the inserts 19 does not experience any disadvantageous 
alteration. 
Generally, in conjunction with FIGS. 1 and 2 it should be underscored that 
the momentary layer thickness or layer thickness relationships do not 
correspond in scale in any way to reality. 
In FIG. 2 there is depicted, similar to FIG. 1, a schematically 
illustrated, fragmentary sectional view of the top or upper surface of a 
decorated article 20. The substrate or lower layer 24 formed of silicon 
carries at a first region 21 the interference-color layer 26 formed of a 
silicon compound as above explained, preferably SiO.sub.2. The top or 
upper layer 26 is of thinner construction in a second region 222 and 223, 
respectively. Under circumstances this can be realized by appropriately 
covering the relevant regions during the formation of the layer 26, but 
preferably can be accomplished by subsequent material removal, for 
instance according to the usual chemical etching methods with appropriate 
covering or masking of the regions which are not to be etched. The 
localized material removal of the layer 26 can lead to a partial layer 
removal (region 222) or a complete layer removal (region 223) while 
exposing and, if desired, etching the silicon base or matrix material. 
The second partial region can, however, also be formed, as indicated by 
reference character 224, by a second or thicker applied interference-color 
layer 27. In each case, i.e., both when reducing the thickness of or 
removing parts of the layer 26 as well as also by accomplishing its 
localized intensification or material build-up or overlay, there can be 
obtained an optically discernable contrast between the first partial 
region 21 and the second partial region or the second partial regions 222, 
223, 224. Once again, a coating or overlay 28 formed or consisting of 
opaque material can lie directly, as shown in FIG. 1, or indirectly, by 
means of the thickened layer region 224, upon the layer 26, in order to 
render possible additional contrasts with decorative and/or informational 
characters or the like. 
With the decorated or ornamented articles 20, the surfaces of which 
normally are not composed of silicon, for instance decorated articles of 
use, such as cigarette lighters, it is possible, as already explained, to 
secure the silicon substrate 24 upon a surface 290 of the article which 
constitutes a carrier not composed of elementary silicon, for instance, by 
means of a solder or adhesive layer 291 or by other known fixation 
techniques, such as screws or rivets. 
The advantages of the inventively decorated articles reside in the good 
reproduceability of the interference colors of the layers 16, 26, the 
comparatively low costs of the materials and their processing, the 
outstanding mechanical and chemical resistance of layers formed of solid 
silicon compounds, such as silicon dioxide having a typical MOHS-hardness 
of 7, their resistance to light as well as the comparatively high thermal 
resistance of such layers. Such factors render possible both their use 
under comparatively extreme conditions and also simplifies the processing 
operations, for instance soldering to the carrier or support 29. 
For instance, the underside 240 of the silicon layer 24 can be provided 
with a layer 291 of a solder metal, for instance by bath-coating or vapor 
deposition, and can be heated to the soldering temperature for the purpose 
of connection with the carrier or support 29 without the need for any 
special protective measures. 
Conventional soft solder temperatures do not have any deleterious effect 
upon the color layer 26, since for the oxidation of silicon by heating in 
air higher temperatures would be necessary. If desired, for the thermal 
bond or connection with the carrier or support 29 there can be employed 
higher temperatures (hard soldering) in the presence of an inert gas, such 
as helium or argon. In the presence of oxygen or air silicon is normally 
first oxidized at temperatures exceeding 700.degree. C. Typical 
temperatures for the reactive formation of layers 16, 26 of silicon oxide 
by heating of elemental silicon in air lie in a range of 700.degree. C. up 
to the melting point of silicon (1414.degree. C.), preferably at most 
1380.degree. C. and, in particular, between 900.degree. C. and 
1100.degree. C. with a typical heating duration of 30 to 60 minutes. 
A noteworthy advantage of the invention is the lesser contamination of the 
environment during the production process in comparison to conventional 
methods, such as galvanizing. 
Examples of the inventively decorated articles of use or articles of 
jewelry are, for instance: pens, ball-point pens, lead pencils, toilet and 
hand mirrors, powder compacts, cartridges or sleeves for lipsticks and 
other cosmetic articles, watch cases and arm bands, articles of jewelry, 
such as broaches, pendants, cuff links, tie clips, jewelry boxes, arm 
bands, necklaces, earrings, toilet articles, such as makeup-pencil 
cartridges, perfume holders, pocket or hand mirrors, pocket or hand 
hairbrushes, shaving apparatuses and brushes, manicure devices and further 
articles of use, such as cigarette lighters, key rings and containers, 
writing devices, cigarette cases, religious artifacts, writing articles, 
vases, pots, saucers, table supports, lamps, candle holders, mosaics and 
mosaic parts, furniture, inlaid work (marquetry), game tables and boards 
and numerous other articles, which can require one or a number of 
pronounced decorations which are wear and aging resistant. 
While there are shown and described present preferred embodiments of the 
invention, it is to be distinctly understood that the invention is not 
limited thereto, but may be otherwise variously embodied and practiced 
within the scope of the following claims.