News Column

Patent Issued for Phosphor-Containing LED Light Bulb

August 20, 2014

By a News Reporter-Staff News Editor at Electronics Newsweekly -- Switch Bulb Company, Inc. (San Jose, CA) has been issued patent number 8796922, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Lenk, Ronald J. (Woodstock, GA); Carsten, Bruce (Corvallis, OR).

This patent was filed on December 18, 2013 and was published online on August 5, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "The present invention relates to replacement of bulbs used for lighting by light emitting diode (LED) bulbs, and more particularly, to the dispersal of the phosphor used by the LEDs into the bulb in order to permit greater amounts of phosphor to be used, to permit cooler operating temperature of the phosphor, and to permit the LEDs to be run at higher power.

"An LED consists of a semiconductor junction, which emits light due to a current flowing through the junction. A white LED is typically made by using a blue or ultraviolet LED die, and adding a plastic coat to it, the coat containing a phosphor. The phosphor is used to convert the blue or ultraviolet light emitted by the LED die to a spectrum of light that more or less closely resembles white light or blackbody radiation.

"At first sight, it would seem that white LEDs should make an excellent replacement for the traditional tungsten filament incandescent bulb. At equal power, they give far more light output than do incandescent bulbs, or, what is the same thing, they use much less power for equal light; and their operational life is orders of magnitude larger, namely, 10-100 thousand hours vs. 1-2 thousand hours.

"However, LEDs have a number of drawbacks that have prevented them, so far, from being widely adopted as incandescent replacements. One of these is that, although LEDs require substantially less power for a given light output than do incandescent bulbs, it still takes many watts to generate adequate light for illumination. Whereas the tungsten filament in an incandescent bulb operates at a temperature of approximately 3000K, an LED cannot be allowed to get hotter than approximately C., and some are limited to even lower maximum temperatures. The LED thus has a substantial heat problem: If operated in vacuum like an incandescent, or even in air, the LED would rapidly get too hot and fail. This has limited available LED bulbs to very low power (less than approximately 3 W), producing insufficient illumination for incandescent replacements.

"One of the reasons that an LED is limited to such a low maximum temperature is due to the temperature characteristics of the phosphor rather than the LED die itself. Presently known phosphors, especially those in the red, tend to degrade quite rapidly at elevated temperatures. Once degradation has occurred, the white light output of the LED is reduced, thus ending the useful life of the LED and of the LED bulb."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "This invention has the object of developing a light emitting apparatus utilizing light emitting diodes (LEDs), such that the above-described primary problem is effectively solved. In accordance with one embodiment, a replacement bulb for incandescent lighting having a plurality of LEDs with a light output equal in intensity to that of an incandescent bulb, and wherein the LEDs' temperature may be permitted to rise much higher than the present state-of-the-art permits. The apparatus includes a bulb-shaped shell, preferentially formed of a plastic such as polycarbonate. The shell may be transparent, or may contain materials dispersed in it to disperse the light, making it appear not to have point sources of light.

"The shell is filled with a filler material, which can be a fluid, a gel, a plastic or other material, such as water or a hydrogel, which is preferentially thermally conductive. The filler material acts as a means to transfer the heat power generated by the LEDs to the shell, where it may be removed by radiation and convection, as in a normal incandescent bulb. In accordance with a preferred embodiment, the filler material contains phosphor dispersed throughout the material, which changes the bluish color of the LED dice's light to a more yellowish color, more closely resembling the light from normal incandescent bulbs. It can be appreciated that in accordance with another embodiment, the filler material and phosphor material therein may also be used for changing the color emitted by other LED dice. In accordance with a preferred embodiment, the filler is preferentially electrically insulating.

"In accordance with one embodiment, the phosphor may be uniformly distributed throughout the filler material. The phosphor density may be set to be higher or lower than that commonly used in LEDs today, a higher density producing more total conversion of the LED dice's light.

"In accordance with another embodiment, the phosphor may be distributed in the filler material with an orientation preference, wherein the orientation preference can be used to generate light that is more intense in converted light in one direction than another.

"In accordance with another embodiment, different phosphors may be distributed in the filler material with an orientation preference, wherein the orientation preference can be used to generate light that is different colors in one direction than another.

"According to the present invention, a phosphor is distributed in a filler inside an LED light bulb for the purpose of changing the color of the light emitted by the LED into a more desirable color for emission from the bulb. Such a color-changing application is described in detail and set forth in Stokes et al., U.S. Pat. No. 6,791,259 (hereinafter 'the '259'), which is incorporated herein by reference in its entirety with regard to all aspects thereof. As set forth in the '259 patent, a radiation-scattering material is located between the LEDs and the phosphor.

"Such a filler is described in detail and set forth in Diamantidis, U.S. Publication No. 20070090391 (hereinafter 'the '391 publication'), which is incorporated herein by reference in its entirety. As set forth in the '391 publication, a liquid fluid is in contact with the light-emitting chip crystal."

For the URL and additional information on this patent, see: Lenk, Ronald J.; Carsten, Bruce. Phosphor-Containing LED Light Bulb. U.S. Patent Number 8796922, filed December 18, 2013, and published online on August 5, 2014. Patent URL:

Keywords for this news article include: Light Bulb, Electronics, Switch Bulb Company Inc.

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Source: Electronics Newsweekly

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