CREE acquires LLF, a glimpse at the technology
On March 3, 2008 CREE announced the closing of its purchase of LED Lighting Fixtures Inc. (LLF). When the acquisition was announced it was stated that LLF’s LED lighting products implement patented color-mixing technology, producing high efficiency and superior color mixing. Certainly, in LLF’s press release of November 28, 2007 it was stated that a […]
On March 3, 2008 CREE announced the closing of its purchase of LED Lighting Fixtures Inc. (LLF). When the acquisition was announced it was stated that LLF’s LED lighting products implement patented color-mixing technology, producing high efficiency and superior color mixing. Certainly, in LLF’s press release of November 28, 2007 it was stated that a new lamp shattered the world record for lighting efficiency. This release further indicated that LLF had over 100 patent applications on a broad range of lighting technologies. Finally, an LLF press release on May 8, 2007 announced United States patent 7,213,940 (‘940 patent) as LLF’s first issued patent. With consideration to the above we took a brief look at the ‘940 patent and some published LLF applications to get a glimpse at the LLF technology.
A search of USPTO databases found that the ‘940 patent remains the one issued US patent and there are sixteen published applications. In both cases the search requested documents assigned to LLF. Thus the remaining eighty-four applications have either been filed in the last 18 months and are not yet visible, were filed in other jurisdictions or were not assigned to LLF at the time of filing. The reality is probably a combination of all of the above.
Let’s look at some of the disclosed technology.
The ‘940 patent, which was described as being central to LLF’s product development in their release of May 2007, discloses a lighting device and method. In general the use of two solid state light emitters and a group of lumiphors is disclosed, where the resultant light is a combination of the light originating from the above three sources.
The lighting device presented in Figure 4 shows a first packaged LED (16a) that emits red light and a second packaged LED (16b) that emits greenish-yellow light. As seen in the sectional view presented in Figure 5 there are in fact a plurality of LEDs in the hosing, with each red LED (16a) being surrounded by 5-6 greenish-yellow (16b) LEDs. Starting at col. 21, line 12 of the specification it is disclosed that the greenish-yellow LED (16b) comprises a blue light emitting diode chip (31), see Fig. 7, and a first group of lumiphors (35). It is currently understood that these are the only lumiphors in the lighting device.
Another lighting device is disclosed in United States published application 2007/0139923 (‘923 application). Fig. 5 presents a lighting device (50) appropriate for mounting with a hole in a ceiling (61). The lighting device (50) has a plurality of LEDs (52) located on an annular flange (57) inside the housing (51). At paragraph  it is noted that in one aspect of the invention at least a first and second solid-state emitter emitting first and second wavelengths, respectively, are comprised by the lighting device. Unlike the device disclosed in the ‘940 patent the luminescent material (53) of this lighting device is external to the LEDs. In fact the luminescent material (53) is presented as extending from the housing (51) to the flange (57), over the LEDs. This concept is disclosed in Figure 4 where regions of luminescent material capable of producing red (R), green (G) and yellow (Y) light are arranged in specified regions of the lighting device.
In reviewing the ‘940 patent and selected applications it appears that considerable effort has been invested into research around the nature of the resultant illumination. In particular, reference is often made to the 1931 CIE Chromaticity Diagram and the CRI. In fact, United States published application 2007/0139920 describes particular CRIs and the nature of the resultant lighting in great detail. At paragraph  it is indicated that exemplary suitable lighting devices are described in the ‘923 application. Finally, filed claim 1 recites a plurality of sources of visible light, that when illuminated emit a total of three different hues. Claim 1 further recites particulars of the illumination with reference to the 1931 CIE Chromaticity Diagram.
Moreover, the documents considered present at least two geometries of lighting device. While the device as presented in the ‘940 patent contains a plurality of LEDs of two groups, with one group having lumiphors located in the LED package, the device of the ‘923 application implements luminescent material that is located external to the LED. This may provide for a more flexible illumination as the luminescent material and/or arrangement might be tailored to the desired light characteristics. There are likely more device geometries in the LLF applications that are not yet visible.