NL1001894C2 - Light-emitting device. - Google Patents

Description

Titleï Light-emitting device

The invention relates to a light-emitting device. More particularly, the invention relates to a very bright lamp with a very high efficiency.

Various types of lamps are already known in the art, the best known examples being the incandescent lamp and the fluorescent lamp. With an incandescent lamp, a filament is heated by an electric current to such a high temperature that the spiral emits light. With 10 fluorescent lamps, UV radiation is generated within a transparent envelope, which radiation is converted into visible light by a luminescent material applied on the inside of that envelope.

These known lamp types have some shortcomings. A major drawback of an incandescent lamp is the low energy efficiency: a large part of the electrical energy supplied to the lamp is converted into heat. Furthermore, although the spectrum of the light emitted by an incandescent lamp is in good approximation a continuum, but because the lamp is a thermal radiator, the incandescent lamp emits relatively much radiation at yellow and orange wavelengths and relatively little at green and blue wavelengths.

Compared to an incandescent lamp, a fluorescent lamp has an improved efficiency. An important drawback of fluorescent lamps is that it is particularly difficult to give the luminescent material such a composition that the spectrum of the emitted light extends over the entire visible area. Developments in this field require one or more rare earth ions to produce the luminescent materials, which makes these materials relatively expensive.

1001894 2

An important object of the present invention is to provide a light-emitting device with a considerably increased efficiency, compared to existing techniques, expressed in lumen / Watt.

A further important object of the present invention is to provide a light-emitting device capable of emitting white light in a very good approximation, ie light in which the different wavelengths are represented substantially equally strong over the entire visible range. to be.

A light-emitting device according to the present invention is based on a different operating principle than the two mentioned lamp types. The operating principle of the present invention is based on the phenomenon that dimer molecules can return from an excited electron state achieved by absorption of UV light to the ground state with visible light emission. This principle of operation is known per se for use in a laser, as described, for example, in international patent application PCT / EP95 / 02250. The dimer molecules are arranged between two mirrors, one of which is at least partially transmissive and functions as an output for the generated laser light. Laser light is characterized, inter alia, by a substantially one-dimensional propagation direction, and is therefore, although particularly useful for certain applications, not suitable for lighting purposes such as an incandescent lamp.

In a laser device as described, for example, in the said international patent application PCT / EP95 / 02250, a separate light source is present for generating a beam of UV laser light, which beam is guided by optical means to a holder containing the dimer molecules . Thus, such a laser device is relatively complicated. An object of the invention is to provide a compact device having a UV light source integrated therein as well as the dimer medium for converting the UV light into visible light.

1001894 3

According to the invention, a light-emitting device is designed as described in claim 1. Thus, the device comprises at least two workspaces separated from each other by a UV-permeable partition. One workspace is designed to produce UV radiation; the other working space is adapted to receive said UV radiation via said partition, and preferably contains a dimer medium which at least partially absorbs said UV radiation, and as a result emits visible radiation.

If desired, the device can be provided with a luminescent material for absorbing UV radiation not absorbed by the dimer medium, for further increasing the efficiency. If desired, a color correction can be applied to the emitted light by choosing a suitable composition of said luminescent material.

The device can be manufactured in various shapes. In a particularly useful embodiment, the device has the appearance of a conventional incandescent lamp, and is therefore interchangeable.

These and other aspects, features and advantages of the present invention will be elucidated by the following description of a preferred embodiment of a light-emitting device according to the invention, with reference to the drawing, in which: Figure 1 schematically shows a preferred embodiment of the light-emitting device according to the invention shows; and Figure 2 shows the energy scheme of a dimer molecule.

Figure 1 schematically shows a preferred embodiment of a light-emitting device 1 according to the present invention, which will also be referred to hereinafter as a dimer lamp. The dimer lamp 1 comprises a support 2, with a glass balloon 20 attached to it and a UV-generating member 10 disposed within said balloon 20. The space between 1001894 4 said balloon 20 and the UV-generating member 10 is filled first. chamber 21. The shapes of the UV generating member 10 and of the balloon 20 are not critical; in the illustrated embodiment, the shape of the UV-generating member 10 is substantially cigar-shaped, and the shape of the balloon 20 extending around it is substantially pear-shaped, but said parts may also be cylindrical or spherical.

In principle, the UV generating member 10 can be of any suitable type. In the preferred embodiment shown, the UV generating member 10 is configured as a mercury discharge lamp. To this end, the UV-generating member 10 comprises an envelope 11 surrounding a second chamber 12 and two electrodes 13 and 14 arranged opposite each other and extending into said second chamber 12. The second chamber 12 may be filled with a conventional gas mixture for a mercury discharge lamp, as will be apparent to one skilled in the art.

Said electrodes 13 and 14 are attached by means of conductors 15 and 16 to terminals 3 and 4 for receiving electrical energy, for example from a mains network 5, which terminals 3 and 4 are arranged on a base part 6 of the carrier 2. The conductors 15 and 16 extend at least partly through the carrier 2. In the preferred embodiment shown, the foot portion 6 with the terminals 3 and 4 is designed as a conventional threaded fitting for an incandescent lamp. Thus, the dimer lamp 1 according to the invention can be connected to a standard incandescent lamp luminaire. The foot portion 6 with terminals 3 and 4 may also be of the bayonet type.

In conventional mercury discharge lamps, the envelope is normally arranged to block UV light. However, in the dimer lamp 1 of the present invention, the envelope 11, which also functions as the entrance wall portion of the first chamber 21, is substantially transmissive to UV light, so that the generated UV light can reach the first chamber 21. In the described arrangement, the 1001894 5 generated UV light reaches the first chamber 21 substantially without loss.

In the first chamber 21, there is provided a medium for converting UV light to visible light, which leaves the first chamber 21 substantially without loss through passage of the balloon 20, which functions as the exit wall portion of the first chamber 21 and for that purpose at least permeable to visible light. Preferably, the medium is a dimer medium. The operating principle of the conversion of UV light to visible light by the dimer medium will be explained later. Suffice it to note now that the conversion of the UV light to visible light takes place with very high efficiency, and that the spectrum of the visible light generated comprises substantially all wavelength components of the visible region. A suitable dimer medium is, for example, sulfur (S2). The described embodiment of the dimer lamp 1 is suitable for emitting visible light in a wide spatial angle.

The extent to which the UV light generated by the member 10 is converted to visible light by the dimer medium in the first chamber 21 depends on the dimensions of the first chamber 21 and on the amount of dimer medium therein. In principle, it may happen that part of that UV light 25 is not converted, so that UV light could pass through balloon 20 and reach the environment. To prevent this, the dimer lamp 1 can be provided with means for removing UV light from the generated light. For this purpose, balloon 20 can be arranged to absorb UV light. Preferably, however, the dimer lamp 1, as illustrated in Figure 1, is provided with screen wall 30 which extends substantially completely around the balloon 20 and is also attached to the carrier 2, said means for removing UV light from the light leaving the first chamber 21 35 to include a layer of a luminescent fabric 31 applied to the inside of said screen wall 30. Said fabric may also be applied to the outside of 1001894 6 the balloon 20. In a simplified embodiment, such layers of a luminescent material 31 may be provided on the inside of the balloon 20, whereby the screen wall 30 can then be omitted, but the illustrated embodiment has the advantage that there is no danger that said luminescent material 31 is attacked by the dimer. medium in the first chamber 21. The space 32 between the balloon 20 and the screen wall 30 may be, for example, vacuum, or may be filled, for example with an inert gas.

Said luminescent material 31 has been chosen for absorbing UV light and emitting visible light. Thus, the UV light not utilized by the dimer medium is also rendered harmless on the one hand and is usefully converted into visible light on the other, which contributes to the high efficiency of the dimer lamp 1.

In addition, the luminescent material 31 may be selected to correct the spectrum of the visible light emitted by the dimer lamp 1. For example, if the selected dimer medium emits relatively little red light, said luminescent material 31 may be chosen to emit relatively much red light, as will be apparent to one skilled in the art.

Referring now to Figure 2, the principle of operation of the dimer lamp will be briefly explained.

Figure 2 outlines part of the energy levels of a diatomic molecule, in particular a dimer.

Here, the mutual distance R between the two atoms is plotted in arbitrary units along the horizontal axis, and the potential energy U of the molecule is plotted in arbitrary units along the vertical axis. The ground state is indicated as X.

By absorbing an energy quant the size of the hppump, the molecule reaches an energy level of an excited state A which is characterized by the vibration and rotation quantum numbers v 'and J'. From this excited state, the molecule can return to the ground state 1001894 7 emitting a light quantum with energy hvim. In addition, the molecule can return to a large number of multiple vibration / rotation levels (v ", J") of the ground state X. Consequently, the light emitted by an ensemble of dimer molecules 5 will consist of contributions with different discrete values for νι , ^, which values depend on the exact heights of the levels (v ", J") in the ground state X and on the exact height of the level (ν ', J') of the excited state A. It will be clear that this last mentioned height is partly determined by the energy hvpvunp of the absorbed quant.

Suitable values for vpump are in the UV portion of the spectrum. It will be clear from the energy diagram of Figure 2 that HV rubble may have different values for achieving different levels (ν ', J') of the excited state A. If, therefore, UV radiation is supplied to the dimer medium from which the spectrum has a relatively large width, the light generated by the dimer medium contains contributions from transitions 20 from a large number of different vibration / rotation levels (ν ', J') from the excited state A to a large number vibration / rotation levels (v ", J") of the ground state X, in a wide variety of combinations. As a result, the total emitted light contains a very large number of spectral-25 lines distributed over the entire visible area, at a relatively short distance from each other, so that the spectrum of the total emitted light can be considered as a continuous spectrum.

In a suitable embodiment, sulfur (S2) 30 is used as a dimer medium, but other substances such as selenium (Se2), tellurium (Τβ2), iodine (I2), and bromine (Br2) can be used, the main requirement being, that the fabric can absorb UV radiation and then emit visible light. In addition to the dimer medium, the first chamber 21 may be empty or filled with an inert gas. Under normal conditions (room temperature), sulfur is a solid. When the lamp 1 is turned on, it will initially produce little 1001894 8 light, because only little S2 is present in vapor form. The heat inevitably produced by the UV source 10 is usefully used to vaporize and keep the sulfur vapor so that the lamp produces little or no IR radiation. The temperature in the first chamber 21, and therefore the sulfur pressure and the power of the lamp, can be controlled by an appropriate selection of the dimensions and shapes of the walls 20 and 30, and by an appropriate choice of the type and pressure of the gas in the space 32 (heat conductivity).

Due to the particularly high efficiency, the dimer lamp 1 can be made with small spatial dimensions, so that it can be considered almost as a point source, while still achieving a very high brightness. These properties make the dimer lamp 1 according to the present invention eminently suitable for use in a projector, such as for film screening in a cinema, it is also of great advantage that the light produced by the lamp 20 has a full color content and no spherical or color aberration, so that less optical correction means are needed, while it is furthermore advantageous that the lamp does not require cooling: conventional cinema projector lamps produce so much heat that they have to be cooled with water.

Due to the good color content of the light produced by the dimer lamp 1, which corresponds well with the color content of sunlight (daylight), the dimer lamp 1 according to the present invention is ideally suited for use in TV studios, and for use in the clothing industry, in short generally where good color reproduction of objects to be illuminated is important.

For household use it is recommended to give the screen wall 30 a suitable size for handling, for example a diameter of the order of 5 cm, as with conventional incandescent lamps. However, the diameter of the screen wall 30 can also be chosen to be larger, for example on the order of 25 cm or more, while it is further possible that the screen wall 30 has a non-round shape, for example the shape of a polygon or a fantasy shape, so that the dimer lamp 1 can be used directly as an ornament with a certain aesthetic value.

The dimer lamp 1 according to the invention can also be designed in an embodiment which provides such a lot of light that it is ideally suited for illuminating large spaces or surfaces, such as factory spaces, airports, public roads and the like.

It will be clear to a person skilled in the art that it is possible to change or modify the illustrated embodiment of the device 15 according to the invention without leaving the inventive idea or the scope of protection.

For example, it is possible that the first chamber is arranged next to the UV source instead of surrounding it.

It is also possible that the lamp comprises a combination of two or more dimer substances.

1001894

Claims (10)

Apparatus (1) for generating visible light, comprising: a first chamber (21) with an entrance wall section (11) and an exit wall section (20), wherein the entrance wall section 5 (11) is at least transparent to UV light and wherein the exit wall section (20) is at least transparent to visible light; means (10) fixed at the entrance wall portion (11) relative to the first chamber (21) for generating υνί 0 light; means (13, 14) for supplying energy to the UV generating means (10); and a substance contained in the first chamber (21) capable of converting UV light to visible light. 15 The device of claim 1, wherein said substance comprises a dimer medium, preferably S2. The device of claim 1 or 2, wherein the first 20 chamber (21) is defined by a balloon-shaped exit wall (20) that extends substantially completely around the UV generating means (10). The device of claim 3, wherein the UV generating means (10) comprises a second chamber (12) surrounded by a balloon-shaped envelope (11) that functions as said entrance wall portion of the first chamber (21). The device of claim 4, wherein the UV generating means (10) comprises a mercury discharge lamp. 1001894 The device of any preceding claim, further comprising means (31) for removing UV light from the light exiting the first chamber (21). The device of claim 6, wherein said means (31) for removing UV light from the light exiting the first chamber (21) is adapted to convert residual UV light to visible light, in particular red light, in order to increase the light output and / or correct the spectrum of the visible light emitted by the dimer. The device of claim 6 or 7, further comprising a screen wall (30) extending substantially completely around the first chamber (21), said means (31) for removing UV light from the light entering the first chamber (21) include a layer of a luminescent material applied to the inside of said screen wall (30) and / or on the outside of said exit wall portion (20) 20 of the first chamber (21). Device according to any one of the preceding claims, further comprising a carrier (2) to which said walls (11; 20; 30) are attached, and terminals 25 (3, 4) attached to said carrier (2) for receiving electrical energy, which terminals (3, 4) are connected to said UV generating means (10) by means of conductors (15, 16) extending along or through the carrier (2). Device according to claim 9, wherein said terminals (3, 4) are arranged on a foot portion (6) of the carrier (2), said foot portion (6) with said terminals (3, 4) being designed as screw thread fitting or bayonet fitting for fitting in conventional lamp luminaires. 1001894