LAMP AND METHOD FOR PRODUCING A LAMP
DESCRIPTION
The present invention relates to a lamp and to a method for producing a lamp.
Lamps comprising LED chips as light sources are known in the state of the art. It is known to provide lamps comprising LED chips with bulbs which resemble traditional filament lamps.
It is an object of the present invention to provide a lamp. It is a further object of the present invention to provide a method for producing a lamp. These objectives are achieved by a lamp and by a method for producing a lamp with the features of the independent claims. Various embodiments are disclosed in the dependent claims.
A lamp comprises a carrier and a plurality of LED chips ar- ranged on the carrier. The carrier is arranged inside a glass tube. A coating comprising a wavelength conversion material is arranged on the glass tube.
The wavelength conversion material of the coating arranged on the glass tube of this lamp serves to convert at least parts of light emitted by the LED chips of this lamp into light with another wavelength. The wavelength conversion material can for example serve to convert light comprising a wave¬ length in the blue or ultraviolet spectral range into white light .
Since the wavelength conversion material of this lamp is comprised by the coating arranged on the glass tube, this lamp does not necessarily need to comprise a silicone to embed the wavelength conversion material. Advantageously, this prevents problems due to aging of silicone material which may in par¬ ticular occur under the influence of ultraviolet radiation. This allows to provide the lamp with LED chips emitting light in the ultraviolet range. Advantageously, ultraviolet light may allow for a highly efficient conversion into light of different wavelengths. The coating comprising the wavelength conversion material of this lamp is arranged on the glass tube and thus spaced apart from the LED chips of this lamp. This remote arrangement of the wavelength conversion material may increase the lifespan of this lamp and may allow for an increased system efficiency and a better colour stability.
In an embodiment of the lamp, the LED chips are designed for emitting light in the ultraviolet range. Advantageously, this allows for a highly efficient conversion of the light emitted by the LED chips into light of different wavelengths, for ex¬ ample into visible white light. Converting light from the ul¬ traviolet range into visible white light advantageously al¬ lows for a precise control of the colour point and for an im¬ proved colour rendering index (CRI) . A particular advantage of this lamp is that it does not need to contain silicone which might degrade under exposure of ultraviolet light. This may support a long lifespan of the lamp.
In an embodiment of the lamp, the coating is arranged on an outer surface of the glass tube. Advantageously, this allows for an easy and cost-effective production of the lamp by means of established standard processes like electrophoretic deposition . In an embodiment of the lamp, the coating covers at least 90% of the outer surface of the glass tube. Advantageously, this ensures that no or little unconverted light emitted by the LED chips of this lamp can exit this lamp. In an embodiment of the lamp, the glass tube comprises a cy¬ lindrical shape. Advantageously, this allows for an easy and cost-effective production of the tube and for an easy and cost-effective arrangement of the coating on the glass tube. A cylindrical glass tube is particularly suited for encapsu¬ lating the carrier.
In an embodiment of the lamp, the carrier is designed as a filament. To this end, the carrier may comprise a thin and elongated shape, for example the shape of a circular cylinder or of an elongated beam. Advantageously, the carrier carrying the plurality of LED chips of this lamp may resemble a fila¬ ment of a traditional filament lamp.
In an embodiment of the lamp, the carrier comprises a ceramic material, in particular AI2O3 or A1N. Advantageously, these materials are electrically insulating and comprise high ther¬ mal conductivity. This allows for an efficient removal of heat generated inside the LED chips during operation of the lamp. This allows to arrange the LED chips of the lamp close to each other.
In an embodiment of the lamp, the glass tube is arranged in- side a bulb. The bulb may for example comprise glass, plastic or a transparent ceramic material. The bulb may protect the glass tube arranged inside the bulb from external influences and may provide an appealing outer appearance of the lamp. In an embodiment of the lamp, the lamp comprises a plurality of glass tubes arranged inside the bulb. In each case a car¬ rier is arranged inside the glass tube. Advantageously, this allows to arrange a large number of LED chips inside the bulb of the lamp which allows the lamp to produce light with high brightness. The arrangement of several glass tubes in the bulb, each glass tube comprising a carrier comprising a plurality of LED chips, allows to spread the LED chips inside the bulb to produce light with increased homogeneity. Addi¬ tionally, spreading the LED chips inside the bulb allows for a reliable removal of heat generated inside the LED chips during operation of the lamp. A method for producing a lamp comprises steps of arranging a plurality of LED chips on a carrier, arranging a coating comprising a wavelength conversion material on a glass tube and arranging the carrier in the glass tube.
Advantageously, this method allows for producing a lamp which does not need to comprise a silicone and can thus have a pro¬ longed lifespan. A particular advantage of this method is that it allows to use LED chips which emit light in the ul- traviolet range. The method can be carried out in a simple and cost-effective manner using established standard process¬ es .
In an embodiment of the method, the coating is arranged on the glass tube by means of electrophoretic deposition. Advan¬ tageously, this allows a precise control of a thickness and a homogeneity of the coating arranged on the glass tube.
In an embodiment of the method, the method comprises an addi- tional step for arranging the glass tube in a bulb. The bulb may for example comprise glass, plastic or a transparent ce¬ ramic material. Advantageously, the bulb can protect the glass tube from external influences and may provide an ap¬ pealing outer appearance.
The above-described properties, features and advantages of this invention and the way in which they are achieved will become clearer and more clearly understood in association with the following description of the exemplary embodiments which are explained in greater detail in association with the drawings. Here in schematic illustration in each case:
Fig. 1 shows a sectional view of a glass tube encapsulating a carrier and a plurality of LED chips arranged on the carrier; and
Fig. 2 shows a sectional view of a lamp comprising a plurali¬ ty of glass tubes with encapsulated carriers and LED chips. Fig. 1 shows a schematic sectional view of a glass tube 200 which encapsulates a carrier 100 and a plurality of LED chips 110 arranged on the carrier.
The carrier 100 extends along a longitudinal direction and comprises a thin elongate shape, for example the shape of a long circular cylinder or of an elongate beam. That carrier 100 may also be referred to as a filament.
The carrier 100 comprises a surface 101 which is a barrel surface extending along the longitudinal direction of the carrier 100. The carrier 100 comprises an electrically insulating materi¬ al. It is practical for the material of the carrier 100 to comprise a high thermal conductivity. The carrier 100 may for example comprise a ceramic material. The carrier 100 may for example comprise AI2O3 or A1N.
The surface 101 of the carrier 100 may comprise a metalliza¬ tion which provides electrical contact areas and electrically conductive traces. The LED chips 110 are arranged on the surface 101 of the car¬ rier 100. Each LED chip 110 comprises an upper side 111 and a lower side 112 which is opposed to the upper side 111. The LED chips 110 are arranged on the surface 101 such that the lower sides 112 of the LED chips 110 face the surface 101 of the carrier 100.
The LED chips 110 are arranged on the surface 101 of the car¬ rier 100 in one or more strands 130. In the example depicted in Fig. 1, the LED chips 110 are arranged in two strands 130. It is however possible to arrange the LED chips 110 in only one strand 130 or in more than two strands 130. In the example depicted in Fig. 1, each strand 130 comprises five LED chips 110. The strands 130 can however comprise few¬ er or more than four LED chips 110 each. All strands 130 may comprise the same number of LED chips 110 as depicted in the example of Fig. 1. It is however possible to provide differ¬ ent strands 130 with different numbers of LED chips 110.
The LED chips 110 constituting one strand 130 are arranged one after another along the longitudinal direction of the carrier 100. The various strands 130 are arranged in parallel to each other and are distributed around the circumference of the carrier 100.
In the example depicted in Fig. 1, each LED chip 110 compris- es one electrical contact pad arranged on the upper side 111 and one electrical contact pad arranged on the lower side 112. The LED chips 110 are connected to the surface 110 of the carrier 100 by means of a conductive connection material such that the electrical contact pads arranged on the lower sides 112 of the LED chips 110 are electrically connected to electrical contact areas arranged on the surface 101 of the carrier 100. The conductive connection material may for exam¬ ple be a solder or a conductive adhesive. The electrical con¬ tact pads arranged on the upper sides 111 of the LED chips 110 are electrically connected to electrical contact areas on the surface 101 of the carrier 100 by means of bond wires 120.
In other embodiments, the LED chips 110 each comprise two electrical contact pads arranged on the respective upper side
111. In these embodiments, both electrical contact pads may be connected to electrical contact areas on the surface 101 of of the carrier 100 by means of bond wires 120. In other embodiments, each LED chip 110 comprises two elec¬ trical contact pads arranged on the respective lower side
112. In these embodiments, both electrical contact pads may be connected to electrical contact areas on the surface 101 of of the carrier 100 by means of a conductive connection ma¬ terial .
The LED chips 110 constituting one strand 130 may for example be electrically connected in series. The individual strand 130 may for example be electrically connected in parallel to each other.
The LED chips 110 are designed for emitting electromagnetic radiation (light) . The LED chips 110 may for example be de¬ signed for emitting light comprising a wavelength in the ultraviolet spectral range. Alternatively, the LED chips 110 may be designed for emitting light in the blue spectral range or in another spectral range.
The glass tube 200 comprises a cylindrical shape, for example the shape of a circular cylinder. The glass tube 200 compris¬ es an outer surface 201 and an inner surface 202. The glass tube 200 comprises a coating 210 arranged on the outer surface 201. It is practical that the coating 210 co¬ vers a large part of the outer surface 201 of the glass tube 200. The coating 210 may for example cover 50% or 90% or more of the outer surface 201 of the glass tube 200.
The coating 210 comprises a wavelength conversion material 220. The wavelength conversion material 220 may also be re¬ ferred to as a phosphor or as a luminescent material. The wavelength conversion material 220 is provided for converting at least a part of light emitted by the LED chips 110 into light comprising another wavelength. The wavelength conversion material 220 may for example be provided to convert light emitted by the LED chips 110 into visible white light. The coating 210 may comprise one or more different types of wavelength conversion material 220. Different types of wave¬ length conversion material 220 may serve to generate light of different wavelengths. The coating 210 may have been arranged on the glass tube 200 by means of electrophoretic deposition. It is possible to ar¬ range the coating 210 on the glass tube 200 by means of other processes, for example by means of established processes for coating conventional fluorescent tubes.
In an alternative embodiment, the coating 210 may be arranged on the inner surface 202 of the glass tube 200. It is also possible to arrange coatings 210 on both the outer surface 201 and the inner surface 202 of the glass tube 200.
The carrier 100 carrying the LED chips 110 is arranged inside the glass tube 200 such that all LED chips 110 are arranged inside the glass tube 200. A longitudinal end of the carrier 100 sticks out from the glass tube 200 at a longitudinal end of the glass tube 200. This longitudinal end of the carrier 100 may provide electrical contacts connected to the electri¬ cal contact areas arranged on the surface 101 of the carrier 100 and to the LED chips 110 to allow for providing the LED chips 110 with electric voltage and electric currents.
Since the LED chips 110 are encapsulated in the glass tube 200, light emitted by the LED chips 110 passes through the coating 210 arranged on the outer surface 201 of the glass tube 200 when leaving the glass tube 200 and is partially or entirely converted into light of different wavelengths.
The carrier 100 carrying the LED chips 110 may have been arranged inside the glass tube 200 after arranging the coating 210 on the outer surface 201 of the glass tube 200. It is al¬ so possible to first arrange the carrier 100 carrying the LED chips 110 inside the glass tube 200 and arrange the coating 210 on the glass tube 200 afterwards. Fig. 2 shows a schematic sectional view of a lamp 10. The lamp 10 may serve for illumination purposes. The lamp 10 may for example be used to replace a traditional filament light bulb . The lamp 10 comprises a bulb 300. The bulb 300 may for exam¬ ple comprise glass, plastic or a transparent ceramic materi¬ al. A support structure 310 is arranged inside the bulb 300. A plurality of glass tubes 200 is arranged on the support structure 310 inside the bulb 300. Each glass tube 200 com¬ prises a carrier 100 carrying a plurality of LED chips 110 as explained above with reference to Fig. 1. In the example depicted in Fig. 2, the lamp 10 comprises three glass tubes 200 arranged inside the bulb 300. It is possible, however, to provide the lamp 10 with fewer or more than three glass tubes 200. The lamp 10 may for example com¬ prise only one glass tube 200, two glass tubes 200 or more than three glass tubes 200.
The support structure 310 serves to carry the glass tubes 200 and to provide electrical connections for the LED chips 110 arranged in the glass tubes 200. The glass tubes 200 may for example be electrically connected in parallel to each other.
The invention has been illustrated and described in detail with the aid of the preferred exemplary embodiments. Never¬ theless, the invention is not restricted to the examples dis- closed. Rather, other variants by derived therefrom by a per¬ son skilled in the art without departing from the protective scope of the invention.
REFERENCE SYMBOLS
10 1amp 100 carrier
101 surface
110 LED chip
111 upper side
112 lower side
120 bond wire
130 strand
200 glass tube
201 outer surface
202 inner surface
210 coating
220 wavelength conversion material
300 bulb
310 support structure