Abstract:
An LED bulb, which includes a shell, a filler material within the shell of the bulb, at least one type of phosphor dispersed inside the filler material and at least one LED within the shell.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. Non-provisional application Ser. No. 12/678,287, filed Jun. 16, 2010, which is a 35 U.S.C. §371 National Stage filing of International Patent Application No. PCT/US08/10713, filed Sep. 12, 2008, which claims priority to U.S. Provisional Application No. 60/972,382, filed Sep. 14, 2007. The content of all of the above-referenced applications is incorporated herein by reference for all purposes. 
    
    
     BACKGROUND 
     1. Field 
     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. 
     2. Description of Related Art 
     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 120° 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. 
     BRIEF SUMMARY 
     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&#39; 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&#39;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&#39;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 &#39;259”), which is incorporated herein by reference in its entirety with regard to all aspects thereof. As set forth in the &#39;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 &#39;391 publication”), which is incorporated herein by reference in its entirety. As set forth in the &#39;391 publication, a liquid fluid is in contact with the light-emitting chip crystal. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a cross-sectional view of a present state-of-the-art LED showing its construction with phosphor in its shell. 
         FIG. 2  is a cross-sectional view of an LED bulb showing the LED mounted in a filler material containing phosphor. 
         FIG. 3  is a cross-sectional view of an LED bulb showing an LED without phosphor mounted in a filler material containing phosphor. 
         FIG. 4  is a cross-sectional view of an LED bulb showing the LED mounted in a filler material containing phosphor with an orientation preference. 
         FIG. 5  is a cross-sectional view of an LED bulb showing the LED mounted in a filler material containing multiple phosphors with an orientation and location preference. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     According to the design characteristics, a detailed description of the current practice and preferred embodiments is given below. 
       FIG. 1  is a cross-sectional view of a present state-of-the-art LED  10  showing its construction with phosphor in its shell. As shown in  FIG. 1 , the LED includes an LED die  30 , a base  20  to which the LED die  30  is mounted for electrical and thermal connection, and a shell  40 . The shell  40  is used to protect the LED die  30  from the air, forms optics for the LED die  30 , and contains phosphor  50  to convert the light spectrum emitted by the LED die  30  to a more desirable spectrum. 
       FIG. 2  is a cross-sectional view of an LED bulb  60  showing the LED  10  mounted in a filler material containing phosphor. As shown in  FIG. 2 , the LED includes an LED die  30 , a base  20  to which the LED die  30  is mounted, and a shell  40 . The shell  40  is used to protect the LED die  30  from the filler material, provides optics for the LED die  30 , and contains one or more phosphors  50 . The shell  70  of the LED bulb  60  contains both the LED  10  and a filler material  100 . The filler material contains dispersed in it phosphor  90 , to convert the light spectrum emitted by the LED  10  to a more desirable spectrum. Also shown is a screw base  80 , which makes contact with an electrical socket, and converts power from the electrical socket to power suitable for powering the LED. 
       FIG. 3  is a cross-sectional view of an LED bulb  60  showing an LED  10  mounted in a filler material containing phosphor. As shown in  FIG. 3 , the LED includes an LED die  30 , a base  20 , and a shell  40 . The shell  40  is used to protect the LED die  30  from the filler material, and may form optics, but contains no phosphor. The shell  70  of the LED bulb  60  contains both the LED  10  and a filler material  100 . Said filler material contains dispersed in it one or more phosphors  90 , to convert the light spectrum emitted by the LED  10  to a more desirable spectrum. Also shown is a screw base  80 , which makes contact with an electrical socket, and converts power from the electrical socket to power suitable for powering the LED. 
       FIG. 4  is a cross-sectional view of an LED bulb  60  showing the LED  10  mounted in a filler material containing phosphor with an orientation preference. As shown in  FIG. 4 , the LED includes an LED die  30 , a base  20 , and a shell  40 . The shell  40  is used to protect the LED die  30  from the filler material, but contains no phosphor. The shell  70  of the LED bulb  60  contains both the LED  10  and a filler material  100 . Said filler material contains dispersed in it a single phosphor  110  and  120 , to convert the light spectrum emitted by the LED  10  to a more desirable spectrum. Said phosphor is not uniformly distributed in the filler material  100 , but rather has a preferred orientation. Shown as an example, a portion of the phosphor  110  is concentrated towards the middle of the bulb  60 , whereas another portion of the phosphor  120  is distributed throughout the rest of said bulb. Also shown is a screw base  80 , which makes contact with an electrical socket, and converts power from the electrical socket to power suitable for powering the LED. 
       FIG. 5  is a cross-sectional view of an LED bulb  60  showing the LED  10  mounted in a filler material containing multiple phosphors with an orientation and location preference. As shown in  FIG. 5 , the LED includes an LED die  30 , a base  20 , and a shell  40 . The shell  40  is used to protect the LED die  30  from the filler material, but contains no phosphor. The shell  70  of the LED bulb  60  contains both the LED  10  and a filler material  100 . The filler material contains in this example dispersed in it two different phosphors  110 ,  130  (i.e., a first and a second phosphor  111 ,  130 ), to convert the light spectrum emitted by the LED  10  to more desirable spectra. In accordance with one embodiment, the phosphors  110 ,  130  are not uniformly distributed in the filler material  100 , but rather have a preferred orientation and location. As shown, a first phosphor  110  is preferentially distributed towards the middle of the bulb  60 , whereas a second phosphor  130  is preferentially distributed towards the outside of the bulb. Also shown is a screw base  80 , which makes contact with an electrical socket, and converts power from the electrical socket to power suitable for powering the LED. 
     It will be apparent to those skilled in the art that various modifications and variation can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.