Efficient white lamp for vehicle headlight

Abstract

An incandescent lamp for a vehicle headlight comprising a transparent vessel that encloses at least one filament and the vessel is at least partly covered with a coating. The coating comprises at least one pigment, which is arranged such that light emitted by the at least one filament and traversing the coating is transformed to transformed light. The transformed light is characterized by a chromaticity according to the CIE 1931 xy-chromaticity with y being in between the Planckian locus and y=0.5*x+0.205 and 0.36<x<0.42, and wherein the at least one pigment comprises a mixture of CoAl oxide and CoAlCr oxide, the mixture being characterized by a ratio of a concentration in mass percentage Cm(CoAl oxide) of CoAl oxide and a concentration in mass percentage Cm(CoAlCr oxide) of CoAlCr oxide in the coating of 90/10Cm(CoAl oxide)/Cm(CoAlCr oxide)30/70.

Claims

1. An incandescent lamp comprising: a transparent vessel, wherein the transparent vessel encloses at least one filament, wherein the transparent vessel is at least partly covered with a coating, wherein the coating comprises at least one pigment, wherein the at least one pigment is arranged such that light emitted by the at least one filament and traversing the coating is transformed to transformed light, wherein the transformed light is characterized by a chromaticity according to the CIE 1931 xy-chromaticity with y being in between the Planckian locus and y=0.5*x+0.205 and 0.36<x<0.42, and wherein the at least one pigment comprises a mixture of CoAl oxide and CoAlCr oxide, the mixture being characterized by a ratio of a concentration in mass percentage Cm(CoAl oxide) of CoAl oxide and a concentration in mass percentage Cm(CoAlCr oxide) of CoAlCr oxide in the coating of 90/10Cm(CoAl oxide)/Cm(CoAlCr oxide)30/70.

2. The incandescent lamp according to claim 1, wherein the ratio Cm(CoAl oxide)/Cm(CoAlCr oxide) is between 80/20 and 40/60.

3. The incandescent lamp according to claim 2, wherein the ratio Cm(CoAl oxide)/Cm(CoAlCr oxide) is between 75/25 and 45/55.

4. The incandescent lamp according to claim 1, wherein the coating is characterized by a layer thickness perpendicular to a surface of the vessel between 200 nm and 1000 nm, and wherein the coating comprises silicon oxide.

5. The incandescent lamp according to claim 1, wherein a maximum particle size of particles comprised by the at least one pigment is smaller than 200 nm.

6. The incandescent lamp according to claim 1 wherein y>0.6*x+0.15.

7. The incandescent lamp according to claim 1, wherein the incandescent lamp is at least one of H1, H4, H7, and H11 halogen lamp.

8. The incandescent lamp according to claim 7, wherein the incandescent lamp is at least one of H1 and H4 halogen lamp, and wherein the ratio Cm(CoAl oxide)/Cm(CoAlCr oxide) is between 75/25 and 65/35.

9. The incandescent lamp according to claim 7, wherein the incandescent lamp is at least one of H7 and H11 halogen lamp, and wherein the ratio Cm(CoAl oxide)/Cm(CoAlCr oxide) is between 55/45 and 45/55.

10. A vehicle headlight comprising: an incandescent lamp including a transparent vessel, wherein the transparent vessel encloses at least one filament, wherein the transparent vessel is at least partly covered with a coating, wherein the coating comprises at least one pigment, wherein the at least one pigment is arranged such that light emitted by the at least one filament and traversing the coating is transformed to transformed light, wherein the transformed light is characterized by a chromaticity according to the CIE 1931 xy-chromaticity with y being in between the Planckian locus and y=0.5*x+0.205 and 0.36<x<0.42, and wherein the at least one pigment comprises a mixture of CoAl oxide and CoAlCr oxide, the mixture being characterized by a ratio of a concentration in mass percentage Cm(CoAl oxide) of CoAl oxide and a concentration in mass percentage Cm(CoAlCr oxide) of CoAlCr oxide in the coating of 90/10Cm(CoAl oxide)/Cm(CoAlCr oxide)30/70.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

(2) The invention will now be described, by way of example, based on embodiments with reference to the accompanying drawings.

(3) In the drawings:

(4) FIG. 1 shows the color area obtainable with an inventive incandescent lamp.

(5) FIG. 2 shows a principal sketch of a first inventive incandescent lamp and a corresponding absorption diagram.

(6) FIG. 3 shows a principal sketch of a coating.

(7) FIG. 4 shows a principal sketch of a second inventive incandescent lamp and corresponding absorption diagram.

(8) FIG. 5 shows a principal sketch of an inventive vehicle headlight.

(9) In the Figures, like numbers refer to like objects throughout. Objects in the Figures are not necessarily drawn to scale.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(10) Various embodiments of the invention will now be described by means of the Figures.

(11) FIG. 1 shows the color area obtainable with the coating of an inventive incandescent lamp. The x-axis 12 corresponds to the x-value of the CIE 1931 xy-chromaticity and the y-axis corresponds to the y-value of the CIE 1931 xy-chromaticity. The dotted line shows the Planckian locus 30. Area 22 shows the area characterizing white light emitted by an incandescent lamp that would be in accordance with the regulation ECE R37 (Agreement concerning the adoption of uniform technical prescriptions for wheeled vehicles, equipment and parts which can be fitted and/or be used on wheeled vehicles and the conditions for reciprocal recognition of approvals granted on the basis of these prescriptions. Regulation No. 37: Uniform provisions concerning the approval of filament lamps for use in approved lamp units of power-driven vehicles and of their trailers). The smaller shaded area 24 above the Planckian locus 30 characterizes transformed light 55 being emitted by an inventive incandescent lamp. Chromium and cobalt-based pigments which are comprised by a coating provided on a vessel of the incandescent lamp are used to shift the characteristic of the light emitted by the filament of the incandescent lamp above the Planckian locus 30. The chromaticity of the transformed light 55 is characterized by y being in between the Planckian locus and y=0.5*x+0.205, more preferably y=0.5*x+0.202 and most preferably y=0.5*x+0.200 for 0.36<x<0.42, more preferably 0.37<x<0.41, most preferably 0.375<x<0.407. The shaded area 24 shows the most preferred characteristic of the transformed light 55.

(12) FIG. 2 shows a principal sketch of a first inventive incandescent lamp and a corresponding absorption diagram. The absorption 42 refers to the whole visual spectrum. The incandescent lamp comprises a lamp base 2 and a vessel 5, which is arranged on the lamp base 2. The vessel 5 encloses a lamp volume, which is filled with a protective gas. A filament 3 is arranged in the lamp volume and electrically connected by means of corresponding electrical conductors 4. The first inventive incandescent lamp comprises a top coating 1 and a stripe like coating 7 comprising a mixture of pigments as described above and below. The coating 7 is characterized by a maximum absorption 48 which is shown in section B in the lower part of FIG. 2. The ordinate shows the absorption 42 and the abscissa the longitudinal extension 44 of the vessel 5. The coating 7 is surrounded by sections A and C of the vessel 5 with lower absorption (minimum absorption 46). There is an intermediate gradient coating 6 which provides the transition from the low absorption sections A and C to the high absorption section B of the coating 7. The coating 7 is characterized by a thickness of 600 nm and comprises at least one pigment. The at least one pigment comprises first particles 8 (CoAl oxide particles) and second particles 9 (CoAlCr oxide particles). The first particles 8 and the second particles 9 are mixed in a ratio of a concentration in mass percentage Cm(CoAl oxide) of CoAl oxide and a concentration in mass percentage Cm(CoAlCr oxide) of CoAlCr oxide given by Cm(CoAl oxide)/Cm(CoAlCr oxide)=50/50.

(13) FIG. 3 shows a principal sketch of a coating 7 being coated on a glass vessel 5 and comprising the at least one pigment comprising, for example, first particles 8 and second particles 9 as discussed with respect to FIG. 2. The coating 7 is comprised by a H4 halogen lamp. The coating 7 is characterized by a thickness of 300 nm. The pigment comprises first CoAl oxide particles 8 with a maximum size of 130 nm and second CoAlCr oxide particles 9 with a maximum size of 200 nm. The first particles 8 and the second particles 9 are mixed in a ratio of a concentration in mass percentage Cm(CoAl oxide) of CoAl oxide and a concentration in mass percentage Cm(CoAlCr oxide) of CoAlCr oxide given by Cm(CoAl oxide)/Cm(CoAlCr oxide)=70/30.

(14) FIG. 4 shows a principal sketch of a second inventive incandescent lamp and a corresponding absorption diagram. The incandescent lamp comprises again a lamp base 2 and a vessel 5, which is arranged on the lamp base 2. The vessel 5 encloses a lamp volume, which is filled with a protective gas. A first filament 3a and a second filament 3b are arranged in the lamp volume and electrically connected by means of corresponding electrical conductors 4. The second incandescent lamp comprises a top coating 1 and a coating 7 that borders the top coating 1. The coating 7 is characterized by a maximum absorption 48 which is shown in the lower part of FIG. 4 in section A. The ordinate shows the absorption 42 and the abscissa the longitudinal extension 44 of the vessel 5. The coating 7, on its other side, borders an intermediate gradient coating 6, which provides the transition in section B from the low absorption section C to the high absorption section A. The coating 7 is characterized by a thickness of 400 nm and comprises at least one pigment comprising first particles 8 and second particles 9. The first particles 8 comprise CoAl oxide and the second particles 9 comprises CoAlCr oxide. The first particles 8 and the second particles 9 are mixed in a ratio of a concentration in mass percentage Cm(CoAl oxide) of CoAl oxide and a concentration in mass percentage Cm(CoAlCr oxide) of CoAlCr oxide given by Cm(CoAl oxide)/Cm(CoAlCr oxide)=60/40.

(15) FIG. 5 shows a principal sketch of an inventive automotive headlight 50. The automotive headlight 50 comprises a lamp socket 52, a reflector 54 and an inventive incandescent lamp. The incandescent lamp comprises one filament 3 and a vessel 5. The vessel 5 is coated with a coating (not shown) comprising a pigment comprising cobalt and chromium. The coating is characterized by a thickness of 500 nm and the particles of the pigments are smaller than 120 nm. An observer 60 and a corresponding viewing direction 61 indicate the perspective of the application measurements made to prove the improvement of the light quality described above.

(16) While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive.

(17) From reading the present disclosure, other modifications will be apparent to persons skilled in the art. Such modifications may involve other features which are already known in the art and which may be used instead of or in addition to features described herein.

(18) Variations to the disclosed embodiments can be understood and effected by those skilled in the art, from a study of the drawings, the disclosure and the appended claims. In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality of elements or steps. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

(19) Any reference signs in the claims should not be construed as limiting the scope thereof.

REFERENCE SIGNS

(20) 1 top coating 2 lamp base 3 filament 3a first filament 3b second filament 4 electrical conductors 5 vessel 6 gradient coating 7 coating 8 first particles 9 second particles 12 x axis CIE 1931 xy-chromaticity 14 y axis CIE 1931 xy-chromaticity 22 white area according to ECE R37 24 chromaticity area of transformed light 30 Planckian locus 42 absorption 44 longitudinal extension of lamp vessel 46 minimum absorption 48 maximum absorption 50 automotive headlight 52 lamp socket 54 reflector 55 transformed light 60 observer 61 viewing direction A, B, C absorption sections along longitudinal extension of lamp vessel