LLB bulb having light extracting rough surface pattern (LERSP) and method of fabrication

This application is a continuation-in-part of application Ser. No. 13/303,398 filed Nov. 23, 2011, which is a continuation-in-part of application Ser. No. 12/558,476 filed Sep. 11, 2009, which claims priority from Taiwan application no. 98115567 filed May 11, 2009.

This disclosure relates generally to light emitting diode (LED) lighting systems and more particularly to light emitting diode light bulbs (LLB).

LLB bulbs have been developed that are interchangeable with conventional light bulbs having incandescent and fluorescent light sources. A LLB bulb typically includes a base, a power supply, a LED light source on the base having one or more LED light sources, and a lens/cover. Advantageously, LLB bulbs have higher conversion efficiencies, longer lifetimes and lower operating voltages than conventional light bulbs.

One aspect of LLB bulbs is that light reflection can occur from the inner or outer surface of the lens/cover. In particular, if the angle of incidence of light from the LED light source to the lens/cover is less than a critical angle, then light can be transmitted through the lens/cover. If the angle of incidence is greater than the critical angle, the light reflects from the lens back to the LED light source. In addition, a LLB bulb having a very bright LED light source, such as a packaged light emitting diode (PLED), can produce glare. Glare is unpleasant and makes it difficult for a person's eyes to see correctly. Briefly, glare is caused by a significant ratio of luminance between the task (that which is being looked at) and the glare source. Factors such as the angles between the task, the glare source and the eyes also have a significant impact on glare.

Glare can generally be divided into two types, discomfort glare and disability glare. Discomfort glare causes an instinctive desire to look away from a bright light source making the task more difficult to see. Disability glare renders the task impossible to view, such as when driving westward at sunset. Disability glare is often caused by the inter-reflection of light within the eyeball, reducing the contrast between the task and the glare source to the point where the task cannot be distinguished. When glare is so intense that vision is completely impaired, it is sometimes called dazzle. Because of bright glare from a LLB having a PLED light source, some LLB bulbs include lens/covers made of semi-transparent (ST) plastic or glass. However, these semi-transparent materials also reduce the light output of a LLB bulb. LLB bulbs can also have a lens/cover with a built in particle diffuser. Although particle diffusers reduce reflection, they also reduce the light output of the LLB bulb. The present disclosure is directed to LLB bulbs having a lens/cover with a light extraction surface that reduces glare and reflection with minimal light loss, producing improved light output from the LLB bulbs with reduced glare.

A LLB bulb includes a base, a LED light source on the base configured to emit electromagnetic radiation, and a lens/cover having a light extracting rough surface pattern (LERSP) configured to reduce glare and reflection in the LLB bulb without reducing the output of electromagnetic radiation from the LLB bulb. The LLB bulb can also include a wavelength conversion layer (or lens) for changing the electromagnetic radiation output of the LLB bulb. For example, the LED light source can be configured to emit electromagnetic radiation from a blue spectral range, and the wavelength conversion layer (or lens) can be configured to convert some of the electromagnetic radiation into a yellow spectral range. The combination of radiation from the blue spectral range and the yellow spectral range produces an electromagnetic radiation output for the LLB bulb corresponding to a perceived white light having a particular color temperature.

A method for fabricating the LLB bulb includes the steps of providing the lens/cover, and forming the light extracting rough surface pattern (LERSP) on the lens/cover. Suitable processes for forming the light extracting rough surface pattern (LERSP) include bead blasting, sand blasting, etching (chemical or plasma) and molding.

Exemplary embodiments are illustrated in the referenced figures of the drawings. It is intended that the embodiments and the figures disclosed herein are to be considered illustrative rather than limiting.

FIG. 1A is a schematic cross sectional view of a LLB bulb having a lens/cover with a LERSP on an outside surface thereof;

FIG. 1B is an enlarged schematic cross sectional view taken along line 1 B of FIG. 1A illustrating a lens/cover with a LERSP on an outside surface thereof;

FIG. 1C is an enlarged schematic cross sectional view equivalent to FIG. 1A illustrating the lens/cover with a LERSP on both the outside and inside surfaces thereof;

FIG. 2 is a schematic cross sectional view of a second LLB bulb having a lens/cover with a LERSP on an outside surface thereof and a wave length conversion layer on an inside surface thereof configured to produce a perceived white light having a selected color temperature; and

FIG. 3 is a schematic cross sectional view of a third LLB bulb having a lens/cover with a LERSP on an outside surface thereof and a separate wavelength conversion lens configured to produce a perceived white light having a selected color temperature.

As used herein, the term “LERSP” means light extracting rough surface pattern. As used herein, the term “rough” means a surface having multi-faceted symmetrical or non-symmetrical features containing points, ridges and multifaceted edges and angles. As used herein, the term “millimeter roughness” means the dimensions of the features, such as the height, the width and the spacing, are measured in millimeters. As used herein, the term “micron roughness” means the dimensions of the features are measured in microns. As used herein, the term “submicron roughness” means the dimensions of the features are less than about one micron (1000 nm). As used herein, the term “high aspect ratio” means that the average ratio of height to width of a feature is greater than about 2. It is to be understood that when an element is stated as being “on” another element, it can be directly on the other element or intervening elements can also be present. However, the term “directly” means there are no intervening elements. In addition, although the terms “first”, “second” and “third” are used to describe various elements, these elements should not be limited by the term. Also, unless otherwise defined, all terms are intended to have the same meaning as commonly understood by one of ordinary skill in the art.

Referring to FIGS. 1A-1B , a LLB bulb 10 A includes a base 12 A having a power supply 14 A, and an LED light source 16 A mounted to the base 12 A in electrical communication with the power supply 14 A configured to emit electromagnetic radiation having a selected wavelength. The LLB bulb 10 A also includes a lens/cover 18 A attached to the base 12 A having a light extracting rough surface pattern LERSP 20 ( FIG. 1B ). As shown in FIG. 1B , the LERSP 20 can be formed on the outside surface of the lens/cover 18 A. Alternately, as shown in FIG. 1C , an inner LERSP 20 can be formed on just the inside surface of the lens/cover 18 A, or on both the inside surface and the outside surface of the lens/cover 18 A. In addition, although the LLB bulb 10 A is disclosed with a particular configuration, it can have any light bulb configuration including but not limited to spotlight, form factor, vivid, miniature, subminiature, Dulux, u-shape, circline, octron, slimline, automotive and special purpose.

The LLB bulb 10 A also includes a threaded ring 22 A attached to the lens/cover 18 A configured to attach the lens/cover 18 A to the base. In addition, the lens/cover 18 A attaches to the threaded ring 22 A using a suitable attachment mechanism such as an adhesive or threads (not shown). The threaded ring 22 A can include female threads that mate with the male threads on the base 12 A. Alternately, rather than having threads, the threaded ring 22 A can include other attachment features such as screws, snap fits, press fits, compression rings, snap taps, adhesives or various fasteners known in the art.

As shown in FIG. 1A , the base 12 A has a metal screw cap configuration with an electrical contact 28 A at the tip and continuous threaded contacts 30 A that also provide mechanical support in a mating socket. Alternately, the base 12 A can have other contact arrangements such as bayonet, candelabra, mogul, or screw terminals for connection to wires. The base 12 A also includes the power supply 14 A for the LED light source 16 A, which can include an AC-DC converter, a driver circuit and any other electrical components necessary for operating the LED light source 16 A. The base 12 A also includes a heat sink 24 A in thermal communication with the LED light source 16 A and wires 26 A that electrically connect the LED light source 16 A to the contacts 28 A, 30 A. The base 12 A also includes a threaded connector 34 A having male threads that mate with female threads on the threaded ring 22 A. The elements of the base 12 A can be combined into a unitary structure using fabrication techniques that are known in the art such as machining, casting and attaching the individual elements.

The LED light source 16 A can include one or more LED devices 32 A, such as LED dice or PLED, configured to emit electromagnetic radiation having a selected wavelength range. For example, each LED device 32 A can be configured to emit electromagnetic radiation from the visible spectral region (e.g., 400-770 nm), the violet-indigo spectral region (e.g., 400-450 nm), the blue spectral region (e.g., 450-490 nm), the green spectral region (e.g., 490-560 nm), the yellow spectral region (e.g., 560-590 nm), the orange spectral region (e.g., 590-635 nm) or the red spectral region (e.g., 635-700 nm). The LED devices 32 A can also include a wavelength conversion layer, such as a layer of phosphor, configured to convert at least some of the electromagnetic radiation from the device to produce a perceived white light having a selected color temperature (e.g., warm, neutral, cool). In addition, each LED device 32 A can include a light extracting rough structure on it's individual lens, as described in parent application Ser. No. 13/303,398, which is incorporated herein by reference.

The lens/cover 18 A can be configured to protect the LED light source 16 A, and can also be configured to collimate or focus the electromagnetic radiation emitted by the LED light source 16 A. The lens/cover 18 A can comprise a transparent, or a semi-transparent material, such as a plastic (e.g., polycarbonate), or a glass, formed in a desired shape. For example, the lens/cover 18 A can have a semi-circular or concave shape as shown, or any other suitable shape (e.g., flat, tubular, rectangular, dome, convex).

As shown in FIG. 1B , the lens/cover 18 A includes the LERSP 20 formed on the outside surface thereof. Alternately, as shown in FIG. 1C , a LERSP 20 can be formed on just the inside surface or on both the inside and outside surfaces of the lens/cover 18 A. In addition, the LERSP 20 can be formed over the entire outside area of the lens/cover 18 A, or multiple separate LERSPs 20 can be formed on selected portions of the lens/cover 18 A. The LERSP 20 can have a textured morphology comprised of a plurality of symmetrical or non-symmetrical features 36 . For example, the features 36 can have a jagged, multifaceted, pyramidal, conical or semi-rounded morphology configured to optimally scatter the electromagnetic radiation emitted by the LED light source 16 A. As another example, the features 36 can be rough and non-symmetrical thereby increasing the number and type of edges or angles presented on the surface of the lens/cover 18 A for enhancing electromagnetic extraction and reducing glare and reflection without reducing the output of the LLB bulb 10 A. By way of example and not limitation, the features can have an aspect ratio of about 2 to about 10 A, an average diameter and spacing of about 10 nm to about 200 nm and a depth or a height of from about 0.1 μm to about 50 μm.

The LERSP 20 can be formed using a suitable process such as bead blasting, sand blasting, etching (chemical or plasma), or molding. In addition, each of the processes can be controlled such that the features 36 have a high aspect ratio and a sum-millimeter, micron or submicron roughness configured to improve light extraction and to direct the electromagnetic radiation outward from the light bulb. U.S. Pat. Nos. 7,186,580 B2; 7,473,936 B2; 7,524,686 B2; 7,563,625 B2 and 7,629,195 B2, all of which are incorporated herein by reference, disclose a photo-electrochemical (PEC) oxidation and etching process for fabricating light emitting diodes (LEDs) with a rough surface. This process can also be used to form the LERSP 20 on the lens/cover 18 A. In the case of molding, parent application Ser. No. 13/303,398 describes a molding process wherein the mold includes a rough inner surface configured to mold the lenses for LED device with a rough surface. In this case, the rough inner surface of the mold can be made using a suitable process such as machining or etching. This molding process can be used to mold the lens/cover 18 A with LERSP 20 .

Referring to FIG. 2 , a second LLB bulb 10 B has an “A-type” form factor light bulb. The LLB bulb 10 B includes a base 12 B having a power supply 14 B, a LED light source 16 B mounted to the base 12 B in electrical communication with the power supply 14 B configured to emit electromagnetic radiation having a selected wavelength range, a heat sink 24 B on the base 12 B, and a lens/cover 18 B containing a light extracting rough surface pattern (LERSP) 20 on an outer surface thereof, and a wavelength conversion layer 38 B on an inner surface thereof.

The base 12 B has a metal screw cap configuration with an electrical contact 28 B at the tip and threaded contacts 30 B, which also provide mechanical support in a mating socket. Alternately, the base 12 B can have other contact arrangements such as bayonet, candelabra, mogul, or screw terminals for connection to wires. The base 12 B also includes the power supply 14 B for the LED light source 16 B, which can include an AC-DC converter, a driver circuit and any other electrical components necessary for operating the LED light source 16 B.

The lens/cover 18 B can comprise a transparent, or a semi-transparent material, such as a plastic (e.g., polycarbonate), or a glass, formed in a desired shape. For example, the lens/cover 18 B can have a bulbous shape as shown, or can have any other suitable shape (e.g., tubular, rectangular, dome, convex, concave).

The wavelength conversion layer 38 B can comprise a layer of material configured to convert at least some of the electromagnetic radiation produced by the LED light source 16 B into electromagnetic radiation having a different wavelength. For example, the wavelength conversion layer 38 B can comprise a layer of phosphor which covers the inside surface of the lens/cover 18 B. The electromagnetic radiation emitted by the LED light source 16 B combined with the electromagnetic radiation converted by wavelength conversion layer 38 B produces the electromagnetic radiation produced by the LLB bulb 10 B. The wavelength conversion layer 38 B can be deposited on the cover lens/cover 18 B using a suitable process such as spraying, dipping, spin coating, rolling, electro deposition or vapor deposition to a desired thickness. Rather than being a deposited layer, the wavelength conversion layer 38 B can also be incorporated into the material of the lens/cover 18 B using a suitable process, such as mixing with a molded plastic material or a rolled glass material. As with the previous LLB bulb 10 A (FIG. 1 A), the LLB bulb 10 C is configured to reduce glare and reflection with minimal light loss.

Referring to FIG. 3 , a third LLB bulb 10 C is substantially similar to the LLB bulb 10 ( FIG. 1A ), but includes a removable lens/cover 18 C having a light extracting rough surface pattern LERSP 20 on an outer surface thereof and a wavelength conversion lens 40 C in contact with an inner surface thereof. The LLB bulb 10 C also includes a base 12 C having a power supply 14 C, a LED light source 16 C mounted to the base 12 C having a plurality of LED devices 32 C configured to emit electromagnetic radiation having a selected wavelength range, and a heat sink 24 C on the base 12 C. The LLB bulb 10 C also includes a threaded ring 22 C having female threads that mate with the male threads on a threaded connector 34 C attached to the base 12 C. The threaded ring 22 C is configured to retain the lens/cover 18 C and the wavelength conversion lens 20 C but is removable so that the wavelength conversion lens 20 C can be removed and replaced with a different wavelength conversion lens. This feature is further described in application Ser. No. 13/165,853 filed Jun. 22, 2011, which is incorporated herein by reference.

The wavelength conversion lens 40 C can comprise a transparent, or a semi-transparent material, such as a plastic or a glass, formed in a desired shape, such as the flat circular shape shown. The wavelength conversion lens 40 C includes a material configured to convert at least some of the electromagnetic radiation emitted by the LED light source 16 C into electromagnetic radiation having a different wavelength range. For example, the wavelength conversion lens 40 C can include a layer of material, covering one or more major surfaces thereof, configured to convert the electromagnetic radiation emitted by the LED light source 16 C into electromagnetic radiation having a higher wavelength. For example, if the LED light source 16 C emits electromagnetic radiation in a blue spectral range, the wavelength conversion lens 40 C can include a phosphor layer for converting some of this radiation to a yellow spectral range. A layer of phosphor can be deposited using a suitable process such as spraying, dipping, spin coating, rolling, electro deposition or vapor deposition to a desired thickness. Rather than being a deposited layer, wavelength conversion material, such as phosphor, can also be incorporated into the material of the wavelength conversion lens 40 C using a suitable process, such as mixing with a molded plastic material or a rolled glass material.

The electromagnetic radiation emitted by the LED light source 16 C combined with the electromagnetic radiation converted by the wavelength conversion lens 40 C produces an electromagnetic radiation output for the LLB bulb 10 C. In addition, this electromagnetic radiation output can be selected to achieve a perceived light color. For example, the LED light source 16 C and the wavelength conversion lens 40 C can be configured such that the LLB bulb 10 C emits a perceived white light having a selected color temperature. In addition, by interchanging the wavelength conversion lens 40 C a user can vary the color of the light emitted by the LLB bulb 10 C. For example, white light can have many degrees of white that are described by a Kelvin temperature. Color temperatures over 5,000 K are called cool colors (blueish white), while lower color temperatures (2,700-3,000 K) are called warm colors (yellowish white through red). The user and install a particular lens to produce a desired white light output.

Thus the disclosure describes an improved LLB bulb having a lens/cover with a light extracting rough surface pattern. While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and subcombinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.