IN LED LIGHT BULBS

FIELD OF THE INVENTION [0001] The present invention relates to replacement of bulbs used for lighting by LED bulbs, and more particularly, it relates to the preferential scattering of certain wavelengths of light and dispersion of the light of the LEDs used in the replacement bulbs to match the color spectrum and spatial pattern of the light of the bulb being replaced.

BACKGROUND OF THE INVENTION

[0002] One method of building an LED light bulb (i.e., light-emitting diode light bulb) is to fill the bulb with a gel. The gel acts to convey the heat generated by the LEDs to the surface of the bulb, and to color shift and/or disperse the LED light. Color shifting is used if the light produced by the LEDs is not the desired color spectrum, while dispersion is used to change the beam nature of the light emitted from LEDs to a diffuse source. Both color shifting and light dispersion using a gel can be done with very low optical loss. [0003] It can be appreciated that there are at least two known methods for producing the color shifting and light dispersion in a gel. In one method, the gel has particles dispersed in it of such a size as to cause the relevant type of scattering, or, in the case of color shifting, fluorescence. In the other method, the gel itself does the color shifting or light dispersion. [0004] Accordingly, it would be desirable to develop a means to color shift (i.e., change the color spectrum) and/or disperse light from LEDs in a gel LED light bulb, using the gel itself rather than particles dispersed in the gel.

SUMMARY OF THE INVENTION

[0005] In one embodiment of the present invention, the gel inside the LED light bulb has density variations of such a size as to scatter the light from the LEDs. If the effective size of the higher density portions of the gel is smaller than the wavelength of the light, Rayleigh scattering occurs, shifting the color spectrum of the light. Alternatively, if the effective size of the higher density portions of the gel is larger by approximately 1-10 times than the wavelength of the light, Mie scattering occurs, dispersing the light independent of wavelength. In accordance with an exemplary embodiment, the density variations may be created by using pelletized polymer, and then gelling the pelletized polymer in such as way that the pellets retain some of their structure. [0006] In accordance with another embodiment of the present invention, the polymer to be gelled is cross-linked. The cross-linked sites form domains in the gel at which light scattering occurs. The size of the cross-linked area determines whether Rayleigh or Mie scattering or both occurs. The amount of such scattering can be controlled by the amount of cross-linking the polymer has prior to gelling. [0007] In accordance with a further embodiment of the present invention, a block co-polymer is used for the gel. For example, the chain may be -A-A-A-B-. When gelled, the A blocks remain linear, while the B blocks roll up into domains of such a size as appropriate for either Rayleigh or Mie scattering. The amount of the scattering can be controlled by the relative amount of B blocks with respect to the A blocks. In a further embodiment, the chain may be -A-A-A-B-C-. When gelled, the A blocks remain linear, while the B blocks roll up into domains of such a size as appropriate for Rayleigh scattering, while the C blocks roll up into domains of such a size as appropriate for Mie scattering. The relative and absolute amounts of each type of scattering can be controlled by the relative amounts of B blocks and C blocks with respect to the A blocks.

BRIEF DESCRIPTION OF THE DRAWINGS [0008] 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. In the drawings, [0009] FIG. 1 is a cross-sectional view of an LED bulb showing an LED embedded in a gel.

[0010] FIG. 2 is a cross-sectional view of density variations in a gel in an LED light bulb, showing Rayleigh and Mie scattering. [0011] FIG. 3 is a cross-sectional view of cross-linking in a gel in an LED light bulb, showing Rayleigh and Mie scattering.

[0012] FIG. 4 is a cross-sectional view of a gel using a block co-polymer gel in an LED light bulb, showing Rayleigh and Mie scattering.

DETAILED DESCRIPTION

[0013] 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 each preferred embodiment is given below.

[0014] FIG. 1 shows a cross-sectional view of an LED light bulb 10 showing the shell (or bulb) 20 enclosing at least one LED (light-emitting diode) 30 according to one embodiment. The light bulb 10 includes a screw-in base 40, which includes a series of screw threads 42 and a base pin 44. The screw-in base 40 is configured to fit within and make electrical contact with a standard electrical socket (not shown). The electrical socket is preferably dimensioned to receive an incandescent or other standard light bulb as known in the art. However, it can be appreciated that the screw-in base 40 can be modified to fit within any electrical socket, which is configured to receive an incandescent bulb, such as a bayonet style base. In use, the screw-in base 40 makes electrical contact with the AC power in a socket through its screw threads 42 and its base pin 44. As shown in FIG. 1, an inner portion 22 of the shell 20 of the bulb 10 contains a gel 60 having a density variation 50, which produces scattering of the light produced from the at least one LED 30 in accordance with both Rayleigh and Mie scattering, hi accordance with an exemplary embodiment, the inner portion 22 of the shell 20 can be filled or partially filled with a gel 60. For example, in accordance with an exemplary embodiment, the density variations 50 can be created by using pelletized polymer, and then gelling the pelletized polymer in such as way that the pellets retain some of their structure. However, it can be appreciated that the gel 60 can be a suitable material in a solid or solid state.

[0015] FIG. 2 is a cross-sectional view of density variations in a gel 60 in an LED light bulb 100, showing Rayleigh and Mie scattering, in accordance with a first embodiment. As shown in FIG. 2, typically the incoming light 110 will include a plurality of wavelength components, including a wavelength 150 based on the light- emitting material used within the LED (not shown). For example, in a typical LED emission spectrum, the wavelength 150 emitted from the LED corresponding to the color blue will be approximately 430 nm. As shown in FIG. 2, the incoming light 110 impinges on a density variation 140 in the gel 60 with an effective diameter 160. In FIG. 2, the density variation 140 of the gel 60 is shown with circular lines having a dashed out surface, which is representative of the variation in density of the gel 60 and is not intended to represent separate gel or gel structures within the gel 60. In one preferred embodiment, the effective diameter 160 is a fraction 162 of the dominant wavelength 150, which creates the condition for Rayleigh scattering of the incoming light 110. It can be appreciated that the density variation need not be spherical, or even approximately spherical, and may be diffuse rather than having a sharply defined outline. As shown in FIG. 2, the short wavelength components 130 are scattered by the density variation 140, while the transmitted light 170 having long wavelength components is substantially unaffected. The transmitted light 170 is thus enhanced in the color red relative to the incoming light 110, without significantly affecting light intensity. [0016] In another preferred embodiment, the effective diameter 160 of the density variations 140 is a small multiple 164 of the dominant wavelength 150, which creates the condition for Mie scattering of the incoming light 110, wherein each of the incoming wavelengths 150 are scattered into an outgoing wavelength 180. The transmitted light or outgoing wavelengths 180 are thus dispersed in directions relative to the incoming light 110, without significantly affecting the light intensity. [0017] In a further embodiment, the density variations 140 have multiple effective diameters 160, which creates the condition for both Rayleigh and Mie scattering of the incoming light 110. [0018] FIG. 3 is a cross-sectional view of cross-linking site 210 in a gel 60 in an LED light bulb 100, showing Rayleigh and Mie scattering. As shown in FIG. 3, the incoming light 110 impinges on a cross-link site 210 in the gel 60 with an effective diameter 160. In one preferred embodiment, the effective diameter 160 is a fraction 162 of the dominant wavelength 150, which creates the condition for Rayleigh scattering of the incoming light 110. As shown in FIG. 3, the short wavelength components 130 are scattered by the cross-link site 210, while the transmitted light 170 having long wavelength components is substantially unaffected. The transmitted light 170 is thus enhanced in the color red relative to the incoming light 110, without significantly affecting light intensity. In another preferred embodiment, the effective diameter 160 of the cross-link sites 210 is a small multiple 164 of the dominant wavelength 150, which creates the condition for Mie scattering of the incoming light 110, wherein each of the incoming wavelengths 150 are scattered into an outgoing wavelength 180. The transmitted light or outgoing wavelengths 180 are thus dispersed in directions relative to the incoming light 110, without significantly affecting the light intensity. In a further embodiment, the cross-link sites 210 have multiple effective diameters 160, which creates the condition for both Rayleigh and Mie scattering of the incoming light 110. [0019] FIG. 4 is a cross-sectional view of a gel 60 formed from a block co- polymer 212 in an LED light bulb, showing Rayleigh and Mie scattering. As shown in FIG. 4, the incoming light 110 impinges on a block 220 in the gel 60 with an effective diameter 160. In one preferred embodiment, the effective diameter 160 is a fraction 162 of the dominant wavelength 150, which creates the condition for Rayleigh scattering of the incoming light 110. As shown in FIG. 4, the short wavelength components 130 are scattered by the block 220, while the transmitted light 170 having long wavelength components is substantially unaffected. The transmitted light 170 is thus enhanced in the color red relative to the incoming light 110, without significantly affecting light intensity. In another preferred embodiment, the effective diameter 160 of the block 220 is a small multiple 164 of the dominant wavelength 150, which creates the condition for Mie scattering of the incoming light 110, wherein each of the incoming wavelengths 150 are scattered into an outgoing wavelength 180. The transmitted light or outgoing wavelengths 180 are thus dispersed in directions relative to the incoming light 110, without significantly affecting the light intensity. In a further embodiment, the blocks 220 have multiple effective diameters 160, which creates the condition for both Rayleigh and Mie scattering of the incoming light 110. It can be appreciated that block co- polymers are comprised of two or more homopolymer subunits linked by covalent bonds. The union of the homopolymer subunits may require an intermediate nonrepeating subunit, known as a junction block. Block co-polymers with two or three distinct blocks are called diblock co-polymers and triblock co-polymers, respectively. [0020] 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.