Patent Description:
Semiconductor light emitting diodes and laser diodes (collectively referred to herein as "LEDs") are among the most efficient light sources currently available. The emission spectrum of an LED typically exhibits a single narrow peak at a wavelength determined by the structure of the device and by the composition of the semiconductor materials from which it is constructed. By suitable choice of device structure and material system, LEDs may be designed to operate at ultraviolet, visible, or infrared wavelengths.

LEDs may be combined with one or more wavelength converting materials (generally referred to herein as "phosphors") that absorb light emitted by the LED and in response emit light of a longer wavelength. For such phosphor-converted LEDs ("pcLEDs"), the fraction of the light emitted by the LED that is absorbed by the phosphors depends on the amount of phosphor material in the optical path of the light emitted by the LED, for example on the concentration of phosphor material in a phosphor layer disposed on or around the LED and the thickness of the layer. Phosphors may be embedded in a silicone matrix that is disposed in the path of light emitted by the LED.

Phosphor-converted LEDs may be designed so that all of the light emitted by the LED is absorbed by one or more phosphors, in which case the emission from the pcLED is entirely from the phosphors. In such cases the phosphor may be selected, for example, to emit light in a narrow spectral region that is not efficiently generated directly by an LED. Alternatively, pcLEDs may be designed so that only a portion of the light emitted by the LED is absorbed by the phosphors, in which case the emission from the pcLED is a mixture of light emitted by the LED and light emitted by the phosphors. By suitable choice of LED, phosphors, and phosphor composition, such a pcLED may be designed to emit, for example, white light having a desired color temperature and desired color-rendering properties.

<CIT> discloses a light-emitting device that includes: a first light-emitting element and a second light-emitting element; and a sealing member covering the first light-emitting element and the second light-emitting element, the sealing member containing a first fluorescent material. The first light-emitting element and the second light-emitting element are configured to be individually driven. The sealing member includes a protruding portion at an upper surface thereof. The first light-emitting element is disposed in a first region, which is located under the protruding portion. The second light-emitting element is disposed in a second region, which is located under the upper surface of the sealing member at a position different from the first region.

<CIT> discloses an LED light source, comprising an encapsulation substrate and a chip unit arranged on the encapsulation substrate, wherein the chip unit comprises at least one bare chip unit and at least one wrapped chip unit formed by covering the surface of the bare chip unit with a layer of first fluorescent layer (a); color temperatures of the bare chip unit and the wrapped chip unit are different; and a second fluorescent layer is further arranged to cover the bare chip unit and the wrapped chip unit.

<CIT> discloses an LED package module including a substrate having predetermined electrodes thereon; a plurality of LED chips mounted onto the substrate, separated from each other at predetermined intervals, and electrically connected to the electrodes; a first color resin portion molded around at least one of the plurality of LED chips; a second color resin portion molded around all of the LED chips except for the LED chip around which the first color resin portion is molded, and having a different color from the first color resin portion; and a third color resin portion encompassing both the first color resin portion and the second color resin portion and having a different color from the first color resin portion and the second color resin portion.

<CIT> discloses a light-emitting device adapted so that the whole of light emitted from a first LED and light emitted from a second LED is allowed to enter a common fluorescent member, and that synthetic light is emitted from the common fluorescent member, wherein the synthetic light contains and is synthesized from light which is emitted from the first LED in a wavelength-converted form, light which is emitted from the second LED in a wavelength-converted from, light which is produced by the wavelength conversion by the common fluorescent member, and light which pass through the common fluorescent member without undergoing the wavelength conversion by the common fluorescent member.

<CIT> discloses a lighting devices including a semiconductor light emitting device and first and second spaced-apart lumiphors. The first lumiphor has a first surface that is positioned to receive radiation emitted by the semiconductor light emitting device and a second surface opposite the first surface. The second lumiphor has a first surface that is positioned to receive radiation emitted by the semiconductor light emitting device and radiation emitted by the luminescent materials in the first lumiphor. The first lumiphor is a leaky lumiphor in that the luminescent materials therein wavelength convert less than <NUM>% of the radiation from the semiconductor light emitting device light that is incident on the first lumiphor.

<CIT> discloses a semiconductor light emitting device including a first semiconductor layer, a second semiconductor layer, a continuous insulating layer, a first fluorescer layer and a second fluorescer layer. The first semiconductor layer includes a first conductivity-type clad layer, an active layer, and a second conductivity-type clad layer stacked in the first semiconductor layer. The second semiconductor layer includes a first conductivity-type clad layer, an active layer, and a second conductivity-type clad layer stacked in the second semiconductor layer. The continuous insulating layer covers a side surface of the first semiconductor layer, a lower surface of the first semiconductor layer, a side surface of the second semiconductor layer, and a lower surface of the second semiconductor layer. The first fluorescer layer covers an upper surface of the first semiconductor layer. The second fluorescer layer covers an upper surface of the second semiconductor layer.

<CIT> describes a white light source with an arrangement of light-emitting diodes. The light-emitting diodes are divided into first light-emitting diodes and second light-emitting diodes. Furthermore, the white light source has a conversion element which is designed to absorb light emitted by the light-emitting diodes and to generate converted light with a longer wavelength than the emitted light. This conversion element has a first conversion phosphor in a first matrix material, the first matrix material with the first conversion phosphor being arranged flatly in a continuous layer above the first and second light-emitting diodes. In addition, the conversion element has a second conversion phosphor in a second matrix material, the second matrix material with the second conversion phosphor being arranged only above the second light-emitting diodes.

A color point is a point in a chromaticity diagram characterizing a particular spectrum of light as a color perceived by a human with normal color vision. A correlated color temperature ("CCT") is the temperature corresponding to the point on the blackbody curve in a chromaticity diagram to which a color point is most closely correlated.

In one aspect a lighting device is disclosed, the lighting device including a first LED configured to emit a first light, a second LED configured to emit a third light, a first phosphor disposed over the first LED and second LED, and arranged to absorb a portion of the first light and in response emit a second light of a longer wavelength than the first light, and a second phosphor disposed over the second LED, the second phosphor arranged to absorb a portion of the third light and in response emit a fourth light of a longer wavelength than the third light, and the fourth light exits the second phosphor into the first phosphor, and both the second light and fourth light exit the lighting device though the first phosphor.

The first phosphor includes a light emitting surface opposite the second LED, the first phosphor, and the first LED, and the second light, fourth light, an unconverted portion of the first light, and an unconverted portion of the third light passes through the light emitting surface.

The portion of third light absorbed by the second phosphor is greater than the portion of first light absorbed by the first phosphor.

The first light may have a first wavelength range, a first spectral power distribution of the second light and unconverted first light may have at least <NUM>% of total radiant power within the first wavelength range, and a second spectral power distribution of the fourth light and unconverted third light may have less than <NUM>% of total radiant power in the first wavelength range.

The lighting device may further include a third LED configured to emit a fifth light, and a third phosphor disposed over the third LED and arranged to absorb the fifth light and emit a sixth light, where the sixth light exits the third phosphor into the first phosphor and exits the lighting device through the first phosphor.

The first light, the second light, and the fifth light may each be blue light having a wavelength range of <NUM>-<NUM>, the second phosphor may be a red phosphor, and the third phosphor may be a green phosphor.

The first LED, second LED, and third LED may all be mounted within a single lead frame on a mounting surface, the first phosphor comprising a light emitting surface opposite the mounting surface.

Substantially all of the light emitted by the first LED and the second LED that exits the lighting device may pass through the first phosphor.

The first phosphor may include a light emitting surface opposite the second LED, the first phosphor, and the first LED.

The first phosphor may be in direct contact with the first LED and the second phosphor.

The first phosphor may include a light emitting surface, a first light emitted by the first LED enters the first phosphor from the first LED and exits the first phosphor from the light emitting surface, and a second light emitted by the second LED enters the second phosphor from the second LED, exits the second phosphor into the first phosphor, and exits the first phosphor through the light emitting surface.

The first phosphor may include a first phosphor material mixed into a first carrier material and the second phosphor may include a second phosphor material mixed into a second carrier material, and a concentration of second phosphor in second carrier material is higher than a concentration of first phosphor in first carrier material.

The first and second carrier materials may be silicone.

The first LED and second LED may both be mounted within a single lead frame on a mounting surface, the first phosphor having a light emitting surface opposite the mounting surface.

The mounting surface may include a barrier surrounding the second LED and the second phosphor is contained within the barrier.

The first LED, second LED, and third LED may be semiconductor diode structures configured to emit blue light having a wavelength in the range of <NUM>-<NUM>, the second phosphor may be configured to absorbs blue light and emit green light, and the third phosphor may be configured to absorb blue light and emit red light.

The first LED may include a first plurality of semiconductor diode structures and the second LED comprises a second plurality of semiconductor diode structures.

The following detailed description should be read with reference to the drawings, in which identical reference numbers refer to like elements throughout the different figures. The drawings, which are not necessarily to scale, depict selective embodiments and are not intended to limit the scope of the invention.

A particular color or white light CCT value of light from a single lighting device can be achieved by means of mixing two or more different colors of light that are emitted from two or more differently colored light sources. Using two or more differently colored light sources (which may be referred to as "primaries") in a lighting device is particularly useful for a tunable lighting device. In such tunable lighting devices, the color or white light CCT value of the emitted light can be adjusted by varying the amount of light output by the differently colored light sources, or primaries, to achieve varying colors or white light CCT values of the overall emitted light from the lighting device. For instance, color tuning with desaturated red, green, and blue pcLED primaries (as used, for example, in Lumileds Holdings B. 's LUXEON Fusion ® lighting devices) is an effective approach to achieving high efficacy and flux of white light over a wide CCT range while also providing high color fidelity.

The light sources, or primaries, used in such color tunable and white light CCT tunable lighting devices are typically implemented as discrete LED packages. Thus, two or more discrete LED packages, each emitting a different color of light, are combined to form the tunable lighting device. For example, a white light CCT tunable lighting device may include two discrete LED packages, which may be standard white LED packages, one having a CCT value of <NUM> and the other having a CCT value of <NUM>.

Combining discrete LED packages can, however, cause a large degree of color variation on the total light emitting surface ("LES") of the lighting device. This large degree of color variation can be a disadvantage in various optical designs. In directional lighting, color variation of the LES may be visible in the far field, and use of specifically designed secondary optics are required to provide color mixing and reduce color variation. The use of such secondary optics can cause optical efficiency losses and/or an increase in size and volume of the lighting device. In non-directional lighting, it is often desirable for the lighting device to have a uniform appearance, which is typically achieved by use of optical diffusers. As the color variation increases, however, a larger mixing distance and/or stronger optical diffusers, which increase light loss, are needed to achieve a uniform appearance.

<FIG> illustrates an example embodiment of a lighting device that combines two or more primaries and achieves a uniform appearance of light. The lighting device <NUM> of <FIG> includes a first LED <NUM> and a second LED <NUM>. First LED <NUM> and second LED <NUM> may be mounted on a mounting surface <NUM> of, for instance, a base <NUM>. A first phosphor <NUM> is disposed over both the first LED <NUM> and the second LED <NUM>. A second phosphor <NUM> is disposed over only the second LED <NUM>, such that the second phosphor is disposed between the first phosphor <NUM> and the second LED <NUM>, and is also disposed between the first LED <NUM> and the second LED <NUM>. As show in <FIG>, the second phosphor <NUM> may be in contact with the first phosphor <NUM>.

Lighting device <NUM> may include sidewalls <NUM>, which may surround the lighting device <NUM>. The base <NUM> and side walls <NUM> may be formed by a single lead frame. First LED <NUM> and second LED <NUM> are mounted within the single lead frame on the mounting surface <NUM> of base <NUM>. The first LED <NUM> and second LED <NUM> may be connected to a power source through the lead frame as is understood by a person having ordinary skill in the art. The first LED and second LED may have a common anode, common cathode or each have an individually addressable anode and cathode.

The first phosphor <NUM> forms a light emitting surface <NUM> on lighting device <NUM> that is opposite to the first LED <NUM> and second LED <NUM>, and opposite to the mounting surface <NUM>. The entire light emitting surface may be formed from an optically uniform material composed of the first phosphor <NUM>. The light emitting surface <NUM> may be continuous, unbroken, and regular across the entire surface. The light emitting surface <NUM> may be substantially flat. The light emitting surface <NUM> may entirely fill an area contained within sidewalls <NUM>, for instance, within a lead frame package. The light emitting surface <NUM> is the surface through which light output by the first LED <NUM> and second LED <NUM> exits the lighting device <NUM>, creating a uniform source appearance due to the scattering properties of the first phosphor <NUM>.

<FIG> illustrates the light path through lighting device <NUM>. First LED <NUM> is configured to emit a first light <NUM> which enters the first phosphor <NUM>. At least a portion of first light <NUM> is absorbed by first phosphor <NUM>, which down-converts the portion of first light <NUM> to a second light <NUM>. Second light <NUM> has longer wavelengths than first light <NUM>. Second light <NUM> exits lighting device <NUM> through the light emitting surface <NUM>.

First phosphor <NUM> may be formed such that a portion of first light <NUM> emitted from the first LED enters the first phosphor <NUM> and is not down-converted by phosphor <NUM>. The unconverted first light <NUM> passes through the first phosphor <NUM> and exits the light emitting surface <NUM> having the same range of wavelengths as the first light <NUM>.

Second LED <NUM> is configured to emit a third light <NUM>, which enters the second phosphor <NUM>. At least a portion of third light <NUM> is absorbed by the second phosphor <NUM>, which down-converts the portion of third light <NUM> to a fourth light <NUM>. Fourth light <NUM> has longer wavelengths than third light <NUM>. Fourth light <NUM> enters the first phosphor <NUM> from the second phosphor <NUM>.

The first phosphor <NUM> and second phosphor <NUM> may be chosen so that the fourth light <NUM> is not absorbed by the first phosphor <NUM>, in which case fourth light <NUM> passes through the first phosphor <NUM> and exits lighting device <NUM> through the light emitting surface <NUM>.

Second phosphor <NUM> may be formed such that a portion of third light <NUM> emitted from the second LED <NUM> enters the second phosphor <NUM> and is not down-converted by phosphor <NUM>. The unconverted third light <NUM> has the same range of wavelengths as third light <NUM>. The unconverted third light <NUM> enters the first phosphor <NUM> from the second phosphor <NUM>. Upon entering the first phosphor <NUM>, a portion of the unconverted third light <NUM> may remain unconverted. In such case any unconverted third light <NUM> not further converted by the first phosphor <NUM> exits the light emitting surface having the same range of wavelengths as the second light <NUM>. Depending on the wavelength range of third light <NUM> and the characteristics of the first phosphor, unconverted third light <NUM>, or a portion thereof, may be absorbed by first phosphor <NUM>, and down-converted to light <NUM> having longer wavelengths than unconverted third light <NUM>, and which may have a same range of wavelengths as second light <NUM>.

The second light <NUM>, unconverted first light <NUM>, fourth light <NUM>, and any unconverted third light <NUM> and light <NUM>, combine to form the desired color or white light CCT value of the lighting device <NUM>. The second light <NUM>, unconverted first light <NUM>, fourth light <NUM>, as well as any unconverted third light <NUM> and light <NUM>, pass through at least a portion of the first phosphor <NUM> and through the light emitting surface <NUM>, which gives lighting device <NUM> the appearance of a uniform color of light, due to the scattering properties of the first phosphor <NUM> and because the light is emitted through the single surface of uniform material, instead of through discrete LED packages. All of the light that leaves the lighting device <NUM> passes through some portion of the first phosphor <NUM> and through the uniform light emitting surface <NUM>.

First phosphor <NUM> and second phosphor <NUM> convert different amounts of first light <NUM> and third light <NUM>. Second phosphor <NUM> is arranged such that most or all of the third light <NUM> is down-converted by the second phosphor <NUM>, and none of, or only a small portion of third light <NUM> is not down-converted by second phosphor <NUM>. That is, little or no unconverted third light <NUM> enters the first phosphor <NUM>. According to the present invention, the second phosphor <NUM> converts more than <NUM>% of third light <NUM> to fourth light <NUM>, and <NUM>% or less of third light <NUM> may enter the first phosphor <NUM> as unconverted third light <NUM>. For example, second phosphor may convert more than <NUM>% of third light <NUM> to fourth light <NUM>, and <NUM>% or less of third light <NUM> may enter the first phosphor <NUM> as unconverted third light <NUM>. Increasing the amount of conversion of third light <NUM> reduces the effect of the first phosphor <NUM> on the color points, so that the first phosphor <NUM> mostly causes scattering of fourth light <NUM>.

This difference in conversion between the first phosphor <NUM> and second phosphor <NUM> can be observed in the light output by lighting device <NUM>. The "first primary" of lighting device <NUM> is defined as light emitted by first LED <NUM> that passes through first phosphor <NUM> and exits lighting device <NUM> through light emitting surface <NUM>, (that is, second light <NUM> and unconverted second light <NUM>). The "second primary" of lighting device <NUM> is defined as light from the second LED <NUM> that passes through the second phosphor <NUM> and then first phosphor <NUM>, and exits lighting device <NUM> through the light emitting surface <NUM>, (that is fourth light <NUM> and any unconverted third light <NUM> and light <NUM> that exits the lighting device <NUM>). If the first light <NUM> emitted by the first LED <NUM> has a first wavelength range, the spectral power distribution of the second primary may contain less than <NUM>% of the total radiant power within the wavelength ranges of the unconverted second light <NUM> (i.e., within the first wavelength range). The spectral power distribution of the first primary, may have at least <NUM>% of total radiant power within the wavelength ranges of the unconverted second light <NUM> (i.e., within the first wavelength range). The second phosphor <NUM> is arranged so that this difference in spectral power distribution between the first and second primaries remains even when the second LED <NUM> is configured to emit light in the first wavelength range, i.e., within the same wavelength range as the first LED <NUM>.

Any appropriate method may be used to form first phosphor <NUM> and second phosphor <NUM>. For example, first phosphor <NUM> may be formed by mixing a first phosphor material into a carrier material, such as silicone, to form a silicone slurry. Second phosphor <NUM> may be formed separately by mixing a second phosphor material into a carrier material, such as a silicone, to also form a silicone slurry. The second phosphor <NUM> mixture of the second phosphor material and carrier is deposited over the second LED <NUM> mounted on mounting frame <NUM> to form second phosphor <NUM>. The second phosphor <NUM> mixture of the second phosphor material and carrier is deposited in such a way that it is contained over and around the second LED <NUM> (methods for containment of the second phosphor are described in more detail below with respect to <FIG> and <FIG>). After the second phosphor <NUM> mixture is deposited, the first phosphor <NUM> mixture is deposited over the first LED <NUM> mounted on mounting surface <NUM>, the second phosphor <NUM> and the second LED <NUM>.

In another example method for forming first phosphor <NUM> and second phosphor <NUM>, the carrier is a ceramic, and the phosphor material is mixed into the ceramic and formed into a ceramic platelet. The ceramic platelet of the second phosphor <NUM> is sized to cover the second LED <NUM>, and is then positioned on the second LED <NUM>, but not the first LED <NUM>. The ceramic platelet of the first phosphor <NUM> is sized to cover both the first LED <NUM> and the second LED <NUM>, and is positioned over the first LED <NUM>, the second phosphor <NUM> ceramic plate, and the second LED <NUM>, such that the second phosphor <NUM> ceramic plate is positioned between the second LED <NUM> and the first phosphor <NUM> ceramic plate. If the first phosphor <NUM> and second phosphor <NUM> are formed as ceramic platelets, they may or may not be formed so as to also be positioned between first LED <NUM> and second LED <NUM>, but the two LEDs may instead be separated by an optical barrier, so the that ceramic platelets are positioned only on the top of the LEDs.

A person having ordinary skill in the art will understand how to achieve the difference in conversion between the first phosphor <NUM> and second phosphor <NUM> described above. For example, the first phosphor <NUM> may have a lower concentration of phosphor material than the second phosphor <NUM>, which concentration of phosphor material will depend on the particular phosphor material used. The size of the phosphor particle in the phosphor material used can also be used to adjust the extent of conversion.

The first phosphor <NUM> may also include a scattering agent, for example scattering particles such as TiO<NUM> or ZrO<NUM> to enhance the scattering performance of the first phosphor <NUM> and further increase the uniformity of light.

Any LED may be used as first LED <NUM> and second LED <NUM> depending on the desired color or white light CCT, and if applicable, the desired tuning range, of the lighting device <NUM>. For instance, first LED <NUM> and second LED <NUM> may be semiconductor diodes structures, or LED dies, such as III-nitride LEDs based on the InGaN materials system. First LED <NUM> and second LED <NUM> may be the same, emitting first light <NUM> and third light <NUM> having the same wavelength range, or first LED <NUM> and second LED <NUM> may be different, and first light <NUM> may have a different wavelength range than third light <NUM>.

The particular LEDs and particular phosphor materials chosen for use in lighting device <NUM> are selected to provide the desired color or white light CCT value of the lighting device, or range of colors and white light CCTs of lighting device <NUM> if lighting device <NUM> is tunable.

The lighting device <NUM> may configured to be tunable by varying the driving current provided to the first LED <NUM> and second LED <NUM>, such that the color or white light CCT value varies as more or less first light <NUM> and third light <NUM> are emitted. Because all light emitted from the lighting device <NUM> is emitted through the light emitting surface <NUM>, the light has a uniform appearance even as the different primaries are mixed to form different colors or white light CCT values.

Lighting devices as disclosed herein may be useful for producing a tunable white light lighting device having a uniform appearance. Such a lighting device may be made, for example, in a single LED package (a single lead frame) with three phosphor-converted colors that serve as the primaries for the color-tunable lighting device.

<FIG> illustrates a lighting device <NUM> useful for producing white light lighting devices in a single LED package, including white light lighting devices in a single LED package that are tunable between varying white light CCT values. The lead frame <NUM> contains first LED <NUM>, second LED <NUM> and third LED <NUM> disposed on mounting surface <NUM>. Second phosphor <NUM> is disposed over second LED <NUM>. Third phosphor <NUM> is disposed over third LED <NUM>. The first phosphor <NUM> is disposed over the first LED <NUM>, the second phosphor <NUM> and second LED <NUM>, and the third phosphor <NUM> and third LED <NUM>. The first phosphor <NUM> is disposed between the first LED <NUM> and the second LED <NUM>, as well as between the first LED <NUM> and the third LED <NUM>. The second phosphor <NUM> is disposed between the first phosphor <NUM> and the second LED <NUM>. The third phosphor <NUM> is disposed between the first phosphor <NUM> and the first LED <NUM>.

The first phosphor <NUM> covers the entire surface of the lead frame <NUM> LED package, to form the light emitting surface <NUM>, which creates a uniform appearance of the light due to the scattering properties of the first phosphor <NUM>, as described above with respect to <FIG> and <FIG>.

Similar to the second LED <NUM> and second phosphor in <FIG>, the third LED <NUM> is configured to emit light, a fifth light, which is absorbed, or mostly absorbed, by third phosphor <NUM> and down-converted to a sixth light having longer wavelengths than the fifth light. The sixth light exits the third phosphor <NUM> and enters and passes through the first phosphor <NUM>. The light emitted by the lighting device <NUM> through the light emitting surface <NUM> includes the sixth light, in addition to light emitted and down converted from the first LED <NUM> and first phosphor <NUM>, and second LED <NUM> and second phosphor <NUM>, and any unconverted light, as described above with respect to <FIG>.

The first LED <NUM>, second LED <NUM>, third LED <NUM>, first phosphor <NUM>, second phosphor <NUM>, and third phosphor <NUM> may be selected to produce white light with a tunable CCT. For example, reference is made to <CIT>, titled "LED and Phosphor Combinations for High Luminous Efficacy Lighting with Superior Color Control," for a detailed description of white light tuning with desaturated RGB primaries. The first LED <NUM>, second LED <NUM>, and third LED <NUM> may be LED dies configured to emit violet or blue light with a peak wavelength in the range of <NUM>-<NUM>. The phosphor mixtures may have different compositions of green and/or red phosphors. In particular, for example, second phosphor <NUM> may include a red phosphor material, and third phosphor <NUM> may include a green phosphor material. The first phosphor <NUM> may also include a green phosphor material, but at a low enough concentration that the combination of the unconverted first light emitted by LED <NUM>, and second light converted by the first phosphor <NUM> is substantially blue, that is, has a peak wavelength in the range of <NUM>-<NUM> (as shown, for example, in <FIG> described below). The light emitted by each LED die <NUM>, <NUM>, and <NUM> is at least partly down-converted by the respective phosphors <NUM>, <NUM>, <NUM> to longer wavelengths; thus, three primary spectra are formed. For example, the three primary spectra for such a white light lighting device <NUM> may have substantially blue, red, and green color points and other spectral characteristics described in more detail in <CIT>. <FIG> shows example primary spectra of blue <NUM>, red, <NUM>, and green <NUM>. The red and green primaries, those emitted from second LED <NUM> through the second phosphor <NUM>, and third LED <NUM> through third phosphor <NUM>, are almost fully converted. Therefore, having the light from those primaries pass through the first phosphor <NUM> of the blue primary has very little effect on the red and green primary color points and results mostly in scattering. This property is utilized in the embodiments of this disclosure by having the first phosphor <NUM> cover the entire light emitting surface <NUM> of the LED package <NUM>, to create a uniform source appearance.

As described above, the light from first LED <NUM> that passes through the first phosphor <NUM> that forms the light emitting surface <NUM> is less converted than that from the second and third LEDs <NUM>, <NUM> underneath the first phosphor <NUM> and, respectively, the second phosphor <NUM> and third phosphor <NUM>. Preferably, primary spectra of the light emitted by the second LED <NUM> and third LED <NUM> and having passed through the second phosphor <NUM> and third phosphor <NUM>, respectively, and the first phosphor <NUM> to exit the lighting device <NUM> through the light emitting surface <NUM> have a spectral power distribution that contains less than <NUM>% of total radiant power in the wavelength range of <NUM>-<NUM> of the LED dies used for the first, second and third LEDs <NUM>, <NUM>, and <NUM>, and the primary spectra of the light emitted by the first LED <NUM> and having passed through the first phosphor <NUM> to exit the lighting device <NUM> through the light emitting surface <NUM> has a spectral power distribution with more than <NUM>% of total radiant power in this wavelength range (<NUM>-<NUM>).

Lighting device <NUM> may be formed by forming three mixtures of phosphor materials dispensed in a silicone carrier to form a silicone slurry, one for each of the first, second, and third phosphor <NUM>, <NUM>, and <NUM>, respectively. The second phosphor <NUM> mixture and third phosphor <NUM> mixture, which are the red and green phosphor silicone slurries, respectively, are deposited on top of the respective LED dies, <NUM>, <NUM>, and are contained over and around the respective LED dies <NUM>, <NUM> due to surface tension and viscosity of the silicon slurry. After being deposited on the respective LED dies, <NUM>, <NUM>, the red phosphor and green phosphor silicone slurries may be partially or fully cured to preserve the shape of the deposited phosphor silicone slurry and to also help contain the phosphor silicone slurries over the respective LEDs. The mixture of the first phosphor material dispensed in a silicon slurry is then deposited over the first LED <NUM>, and the second and third phosphors <NUM> and <NUM>, and fills the cavity <NUM> of the lead frame <NUM> LED package.

<FIG> and <FIG> illustrate, respectively, a cross-sectional view and a plan view of a lighting device <NUM> which utilizes an alternative method for containing the separate phosphors. In lighting device <NUM>, the mounting surface <NUM> of lead package <NUM> is shaped to include inner walls (or dams) <NUM>, <NUM> inside the main cavity <NUM> of the lead frame <NUM> LED package. The first LED <NUM> is disposed on the mounting surface <NUM> of the lead package <NUM> between two the inner walls <NUM>, <NUM>. The second LED <NUM> is disposed on mounting surface <NUM> between inner wall <NUM> and the sidewall <NUM> of lead frame <NUM>. The third LED <NUM> is disposed on mounting surface <NUM> between inner wall <NUM> and sidewall <NUM> of lead frame <NUM>. A mixture of the second phosphor material and silicone slurry used to form second phosphor <NUM> is deposited over the second LED <NUM> and between the inner wall <NUM> and sidewall <NUM>, such that the mixture is contained by the inner wall <NUM> and sidewall <NUM>. Similarly, a mixture of the third phosphor material and carrier, such as a silicone slurry, used to form the third phosphor <NUM> is deposited over the third LED <NUM> and between inner wall <NUM> and sidewall <NUM>, such that the mixture is contained between inner wall <NUM> and sidewall <NUM>. A mixture of the first phosphor material and carrier, such as a silicon slurry, used to form the first phosphor <NUM> is then deposited over the first LED <NUM> to fill the cavity <NUM> between sidewalls <NUM>, covering the second phosphor <NUM> and third phosphor <NUM>, and forming light emitting surface <NUM>.

<FIG> illustrates a plan view of lighting device <NUM>. The lead frame <NUM> is rectangular. The inner walls <NUM>, <NUM> divide the cavity <NUM> into three rectangular wells <NUM>, <NUM>, and <NUM> which contain, respectively, the first LED <NUM>, second LED <NUM>, and third LED <NUM>. Second phosphor <NUM> is disposed within second well <NUM> and third phosphor <NUM> is contained within third well <NUM>. First phosphor <NUM> fills the first well <NUM> and the remainder of the cavity, forming the light emitting surface <NUM> within light emitting surface edge <NUM>.

Lighting devices according to the disclosure may have a variety of different geometries. <FIG> illustrates a lighting device <NUM> having a circular geometry. In lighting device <NUM> there are three inner walls <NUM>, <NUM>, and <NUM>. The three inner walls <NUM>, <NUM>, and <NUM> divide the circular cavity <NUM> in lead frame <NUM> into three wells, <NUM>, <NUM>, and <NUM> which contain, respectively, the first LED <NUM>, second LED <NUM>, and third LED <NUM>. The three wells <NUM>, <NUM>, and <NUM> are shown in <FIG> as having approximately equal volume, however, any suitable relationship of volumes may be used. Two inner walls <NUM> and <NUM>, along with the sidewall <NUM> of lead frame <NUM> contain the third phosphor <NUM>. Two inner walls <NUM> and <NUM>, along with the sidewall <NUM> of the lead frame <NUM> contain the second phosphor <NUM>.

In addition to providing a uniform light source, another advantage of the lighting device disclosed herein, is that it allows all of the primaries to be contained within a single LED package, which reduces the size of the device as compared to using multiple LED packages, and also simplifies the use of the device. For instance, a three primary conventional white light source would need three individual LED packages, one for red, green, and blue, which may be <NUM> x <NUM> each. In the lighting devices disclosed herein, for instance lighting devices <NUM> (<FIG> and <FIG>) and <NUM> (<FIG>), all three primaries are contained in a single LED package which may be <NUM> x <NUM>, which is significantly smaller. The size is further reduced because there is no need for additional optics that are required when the individual LED packages are used for each color to create uniform light.

Although described above in terms of red, green and blue primaries, in other embodiments primaries having different colors, and/or additional primaries may be employed. For example, a fourth LED may be included having a fourth phosphor also situated over the fourth LED and under the first phosphor material may be used. Any number of primaries (><NUM>) may be used.

Claim 1:
A lighting device (<NUM>, <NUM>, <NUM>, <NUM>) comprising:
a first LED (<NUM>) configured to emit a first light (<NUM>);
a second LED (<NUM>) configured to emit a third light (<NUM>);
a first phosphor (<NUM>, <NUM>, <NUM>) disposed over the first LED (<NUM>) and second LED (<NUM>) and in contact with the first LED (<NUM>), the first phosphor (<NUM>, <NUM>, <NUM>) arranged to absorb a portion of the first light (<NUM>) directly from the first LED (<NUM>) and in response emit a second light (<NUM>) of a longer wavelength than the first light (<NUM>); and
a second phosphor (<NUM>, <NUM>, <NUM>) disposed over and in contact with the second LED (<NUM>), the second phosphor (<NUM>, <NUM>, <NUM>) arranged to absorb a portion of the third light (<NUM>) directly from the second LED (<NUM>) and in response emit a fourth light (<NUM>) of a longer wavelength than the third light (<NUM>), ,
the fourth light (<NUM>) exits the second phosphor (<NUM>, <NUM>, <NUM>) directly into the first phosphor (<NUM>, <NUM>, <NUM>), the first phosphor (<NUM>, <NUM>, <NUM>) forming a light emitting surface (<NUM>, <NUM>, <NUM>) opposite the first LED (<NUM>) and the second LED (<NUM>) and covering the first LED (<NUM>), second LED (<NUM>) and second phosphor (<NUM>, <NUM>, <NUM>), and the second light (<NUM>), unabsorbed first light (<NUM>), and fourth light (<NUM>) exit the lighting device (<NUM>, <NUM>, <NUM>, <NUM>) through the light emitting surface
characterized in that
the portion of third light (<NUM>) converted by the second phosphor (<NUM>, <NUM>, <NUM>) being more than <NUM>% of the third light (<NUM>) emitted from the second LED (<NUM>), the portion of third light (<NUM>) absorbed by the second phosphor (<NUM>, <NUM>, <NUM>) is greater than the portion of first light (<NUM>) absorbed by the first phosphor (<NUM>, <NUM>, <NUM>).