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Luminescent sheet covering for leds

Luminescent sheet covering for leds description/claims

The present application relates to the art of the LED lighting systems that produce visible light. It finds application in general purpose lighting and will be described with particular reference thereto. Those skilled in the art will appreciate the applicability of the present application to a variety of applications such as ornamental, special effects lighting, and other.

Typically, the LED lighting systems, which produce white or visible light incorporate blue LEDs, are coated with phosphor that converts some of the blue light radiation to a complimentary color, e.g. yellow-green emission. Combined blue, yellow and green emissions produce a white light.

Some white LED lighting systems unitize a blue LED chip coated with phosphors which are designed to convert some of the blue radiation into complementary colors. An example of a commonly used phosphor for this purpose is the yellow emitting yttrium gadolinium aluminum garnet phosphor activated with Ce3+. Other types of white LED lighting systems use an ultra violet emitting (UV) chip coated with a combination of phosphors producing white light.

To produce a white light of a correct color, a uniform coating of the phosphor powder of precise thickness is required. For the blue-emitting chips, a uniform coating of the prespecified thickness is required to allow a fixed amount of blue radiation to be transmitted through the coating to produce the correct whiteness of the color. In addition, the uniform thickness of phosphor coating is required to avoid some regions of the coated chip emitting predominately blue radiation and other regions emitting predominantly yellow radiation, which produce a pattern of varying colors in the projected light.

Likewise, the uniform phosphor coating and precise thickness are required for the UV emitting chips of the white LED lighting systems. A thicker coating is needed to avoid a bleed-through of large amounts of the V, while an extra thick coating causes excessive scattering of the UV and visible light back onto the LED and surrounding structures. Some of the radiation, which is scattered or reflected back onto the LED, can be absorbed by the chip, reflector, submount, and/or lead structure resulting in a decrease of the light output.

One method to produce a phosphor coating is to use a phosphor slurry which includes phosphor in a liquid medium, an epoxy, or a silicone. In a slurry, phosphor particles are distributed randomly but settle quickly which results in different phosphor thicknesses over the geometry of the coating. Another method is to spray the chip with the slurry as in the screen printing. Yet another solution is to electrophoretically coat the chip or spray coat the lens.

However, because the LEDs and LED components are small and often irregular in shape, it is difficult to obtain a uniform distribution of coating. The coating naturally drains off corners and high points in the LED structure. Furthermore, it is difficult to produce a uniform thickness from one part of the LED to another.

The present application contemplates a new and improved apparatus that overcomes the above-reverenced problems and others.

In accordance with one aspect, a lighting apparatus is disclosed. At least one light emitting diode is disposed on an interconnect board to emit ultraviolet or blue radiation, which light emitting diode includes a first surface to emit radiation, and a second surface disposed opposite the first surface. A polymeric layer including a luminophor is disposed about the lighting apparatus to convert at least a portion of the radiation emitted from the LED into visible light, which polymeric layer is shrinkable to conform to a shape enclosing the light emitting diode.

In accordance with another aspect, a method of manufacturing a lighting apparatus is disclosed. A polymeric material is liquefied. Phosphor powder is stirred into the liquefied polymeric material until the phosphor powder is one of suspended, dispersed or substantially dissolved. A polymeric sheet is formed from the phosphor including polymeric liquid. At least one LED is positioned on a mounting surface. The phosphor including polymeric sheet is shrink-wrapped around objects to surround light emitted by the LED.

One advantage of the present application resides in improved uniformity of a phosphor coating.

Another advantage resides in a phosphor coating with controlled thickness of phosphor.

The application may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application.

FIG. 1 is a schematic view of an LED lighting assembly;

FIG. 2 is an illustration of forming a polymeric phosphor sheet;

FIG. 3 is an illustration of a polymeric phosphor roll;

FIG. 4 is a schematic view of another LED lighting assembly;

• Provisional Patent
• Utility Patent

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