Electric lamp and discharge devices – With optical device or special ray transmissive envelope
Reexamination Certificate
2000-08-24
2002-09-03
Day, Michael H. (Department: 2879)
Electric lamp and discharge devices
With optical device or special ray transmissive envelope
C313S112000, C313S489000, C313S580000, C313S635000
Reexamination Certificate
active
06445112
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a colored luminaire, in particular a colored signal luminaire for motorcars, which includes a lamp and a cover, wherein the lamp comprises a bulb provided with a coating including a layer containing an iron-oxide pigment.
Colored luminaires are used at different locations in motorcars, where they are used, for example, for brake lights, turn signal lamps and fog lamps. In conventional, colored luminaires the bulb of the lamp is made of clear glass and the lamp is arranged under a colored, generally red or yellow, luminaire cover. More recently, there is a tendency to use, for the colored luminaires, colored lamps under a cover that is either colorless or of a uniform neutral color. This enables signal lamps of different colors to be mounted as a lamp ensemble under a uniform cover.
Luminaires comprising colored lamps under a cover that is either colorless or of a uniform neutral color have the advantage that they enable a flexible, optically attractive design for integrated front and rear luminaires. In addition, they are cheaper than luminaires having a multicolor housing or multicolor covers. In addition, these luminaires contribute to a higher traffic safety because the difference between the “on” and the “off”-state of the lighting at daylight can be more readily distinguished with lights comprising colored lamps situated under a cover which is either colorless or of a neutral color.
For the colored, pigment-containing bulb coating of colored lamps use can be made, in principle, of inorganic or organic color pigments. The well-known bulb coatings comprising red and yellow inorganic color pigments are stable for a long period of time, however, their color value leaves to be desired. JP 52063235 discloses, for example, an electrostatic coating for bulbs comprising a mixture of iron oxide powder having an average grain diameter in the range from 0.2 to 2.0 &mgr;m and 20 to 95% by weight silicon oxide powder. Bulb coatings comprising organic pigments, for example the coatings described in JP-A-60 116958 comprising red pigments of the group of the anthraquinone pigments, can be optimized as regards the color co-ordinates, however, they turn yellow in the course of time.
As in many other branches of industry, there is a trend to make lighting equipment in motorcars lamp smaller and smaller. Attempts are made to reduce the size of the entire lighting equipment used in a motorcar and, for example, integrate the signal luminaires into the headlights. In such lighting units, the lamps are exposed, however, to higher thermal loads.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a colored luminaire comprising a lamp and a cover, wherein the lamp includes a bulb having a coating containing an iron-oxide pigment, which luminaire has a long service life, also at increased ambient temperatures, as well as optimum color co-ordinates, and can suitably be used for a motorcar lighting unit.
In accordance with the invention, this object is achieved by a colored luminaire, comprising a lamp and a cover, wherein the lamp comprises a bulb having a coating of a first layer containing an iron-oxide pigment, a second layer containing an organic coloring material, and a transparent layer which is arranged between the first and the second layer and which contains a silicon-oxygen compound. By virtue of the combination of an iron-oxide pigment and an organic coloring material, the standard color value for signal luminaires, which is established for Europe by the E.C.E. and for the United States by the S.A.E., can be readily attained, whereas it is impossible to attain this standard color value when only a pigment is used. The layer comprising a silicon-oxygen compound provides for an improved bonding of the layer with respect to both the first and the second layer, as well as a smaller change in color value in the course of time and hence a longer service life of the bulb coating with respect to a bulb coating comprising only a pigment-containing layer. Also under extreme operating conditions, no chemical changes occur in the iron-oxide layer, which can be attributed to the fact that said layer is protected by the two layers overlying it when the iron-oxide layer is provided as an inner layer.
Within the scope of the invention, it is preferred that the organic coloring material is a pigment of the group formed by the azo pigments, anthraquinone pigments, pyrazolone pigments and triarylmethane pigments.
It is particularly preferred that the organic coloring material is a metal complex dye. These transparent metal complex dyes enable a desired standard color value to be attained already in a very thin layer. Layers containing a metal complex dye demonstrate a very good adhesion to layers containing a silicon-oxygen compound.
Within the scope of the invention, it is preferred that the iron-oxide pigment is a hematite pigment. Even when the layer, which contains an organic coloring material, is damaged, the luminaire still generates a colored signal light which matches the tone of the brownish-red hematite.
The invention is particularly advantageous with respect to the known state of the art when the iron-oxide pigment is a transparent iron oxide. Particularly the yellow to orange transparent iron-oxide pigments can change color when the temperature is increased. However, the transparent layer, which contains a silicon-oxygen compound, precludes this change in color. On the other hand, when the coating structure is such that the layer containing a transparent iron-oxide pigment is situated on the outside, and the layer containing an organic coloring material is situated on the inside, the iron-oxide layer protects the organic coloring material and, in particular, also the binder in the underlying layer from the influence of UV radiation, thereby increasing the service life of the lamp.
It may alternatively be preferred that the bulb comprises a transparent covering layer which contains a silicon-oxygen compound. When the coating is applied inside the bulb, the covering layer precludes that the coating is subject to chemical change. If the coatings are applied on the outside, then the covering layer forms a scratch-resistant surface which makes further processing of the bulb in the lamp production process easier. Preferably, use is made of a covering layer having a suitable refractive index so as to reduce scattering of the pigment-containing layers.
The invention also relates to a lamp comprising a bulb having a coating composed of a first layer containing an iron-oxide pigment, a second layer containing an organic coloring agent, and a transparent layer containing a silicon-oxygen compound, which transparent layer is situated between the first and the second pigment-containing layer.
DETAILED DESCRIPTION OF THE INVENTION
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.
A colored luminaire in accordance with the invention is provided with a lamp and a cover, which lamp comprises a bulb having a coating composed of a first layer containing an iron-oxide pigment, a second layer containing an organic coloring material, and a transparent layer which is arranged between the first and the second layer and which contains a silicon-oxygen compound.
The layer sequence of the coating may be such that the bulb, which serves as the substrate, is first provided with the iron-oxide pigment-containing layer and then with the two other layers. However, the layer sequence may also be reversed, so that the bulb, which serves as the substrate, is first provided with the layer containing an organic coloring agent. Dependent upon the structural shape of the lamp, the coating may be applied to one or more walls, i.e. both on the inside and the outside, of the lamp bulb. The bulb may also be provided, on the outside, on top of the other layers, with a transparent covering layer containing the silicon-oxygen compound.
The colored luminaire may also be provided with oth
Amrein Thomas
Denissen Kees
Gorisse Bertrand
Day Michael H.
Halajian Dicran
Koninklijke Philips Electronics , N.V.
Zimmerman Glenn
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