Light emitting diode device

A light emitting diode (LED) device includes a substrate, first and second LED chips arranged on the substrate, and a phosphor layer over the first and second LED chips. The phosphor layer includes a plurality of phosphor units, each including a phosphor particle and a silver halide layer encapsulating the phosphor particle. Light emitted from the second LED chip strikes the phosphor particles to generate a first light, which. combines with the light to generate a resultant light. The silver halide layer is reduced by the light from the first LED chip to produce silver particles around the phosphor particles. The silver particles can block the light emitted from the second LED chip from sticking the phosphor particles. By adjusting the current supplied to the first LED chip, the color temperature of the resultant light generated by the LED device can be changed.

BACKGROUND

1. Technical Field

The disclosure relates to illumination devices, and particularly to a light emitting diode (LED) device.

2. Discussion of Related Art

Light emitting diodes' (LEDs) many advantages, such as high luminosity, low operational voltage, low power consumption, compatibility with integrated circuits, easy driving, long term reliability, and environmental friendliness have promoted their wide use as a lighting source.

A typical LED device uses an LED chip as an initial light source to produce a first color light. The first color light emitted from the LED chip strikes a fluorescent substance dispersed within the LED device to generate a second color light. The second color light mixes with the first color light to form a resultant light having a desired color, such as a white light. However, the LED device emits light with only one color temperature, so when the color temperature is needed to change, the LED device also needs to be replaced, which is costly.

Therefore, what is needed is an LED device which can overcome the described limitations.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring toFIG. 1, a light emitting diode (LED) device100in accordance with an exemplary embodiment of the present disclosure is illustrated. The LED device100includes a substrate10, a first LED chip20and a second LED chip30arranged on the substrate10, and a phosphor layer50arranged above the first and second LED chips20,30.

The substrate10forms a cup110surrounding the first and second chips20,30and includes a top surface11and a bottom surface13opposite to the top surface11. The cup110of the substrate10defines a cavity15in a central portion thereof, which is recessed from the top surface11, for receiving the first and second LED chips20,30and the phosphor layer50therein. An inner side surface150of the cup110defining the cavity15is inclined, and a diameter of the cavity15gradually decreases along a direction from the top surface11toward the bottom surface13. In one embodiment, a reflective layer can be coated on the inner side surface150of the cup110defining the cavity15for reflecting light of the first and second LED chips20,30upwards.

A first electrical portion12, a second electrical portion14and a third electrical portion16are arranged at a bottom of the cavity15in sequence for left to right ofFIG. 1. The first and the third electrical portion12,16are spaced and insulated from each other, and extend horizontally along opposite directions from the bottom of the cavity15to a position beyond the substrate10, for connecting with peripheral power supply (not shown). The second electrical portion14is arranged between the first and third electrical portions12,16, and perpendicularly extends through the bottom surface13of the substrate10. The second electrical portion14is spaced and insulated from the first and third electrical portions12,16.

In the present embodiment, the first LED chip20is arranged on the first electrical portion12. Two electrodes of the first LED chip20are electrically connected to the first and third electrical portions12,16via two conductive wires60, respectively. The second LED chip30is arranged on the second electrical portion14. Two electrodes of the second LED chip30are electrically connected to the second and third electrical portions14,16, respectively, also via two conductive wires60. In the present embodiment, the first LED chip20is an ultraviolet (UV) LED chip, and the second LED chip20is a blue LED chip. The first LED chip20and the second LED chip30are controlled by independent power supply circuits. In an alternative embodiment, the second LED chip30can be arranged on the third electrical portion16; in a further alternative embodiment, the first and second LED chips20,30each can be formed as a flip chip. In a still further alternative embodiment, an encapsulant can be applied on the first and second LED chips20,30, for protecting the first and second LED chips20,30.

The phosphor layer50is arranged over the cavity15and seals a top of the cavity15, and a top surface of the phosphor layer50is substantially coplanar with the top surface11of the substrate10. Light emitted from the first and second LED chips20,30travels through the phosphor layer50to an outside of the LED device100for lighting. The phosphor layer50is made of transparent materials such as resin, and a plurality of phosphor units51are doped into the transparent materials. The phosphor units51are evenly distributed in the phosphor layer50. Referring toFIG. 2, each phosphor unit51includes a phosphor particle52and a silver halide layer54encapsulating the phosphor particle52. In the present embodiment, the silver halide layer54is doped with copper oxide. The phosphor particles52are yellow phosphor substances, and can be selected from Yttrium Aluminum Garnet (YAG), terbium doped YGA, silicates, or combination thereof. In other embodiment, the entire cavity15can be filled with the phosphor layer50.

During the use of the LED device100, when the first LED chip20is turned off and the second LED chip30is turned on, blue light is generated. A part of the blue light emitted from the second LED chip30strikes the phosphor layer50to generate a secondary yellow light. The combination of the secondary yellow light and residual blue light produces a white light with a first color temperature. When the first LED chip20and the second LED chip30are both turned on, the first LED chip20emits UV light, oxidation-reduction reaction is occurred to the silver halide layer54by an action of the UV light, and the silver halide layer54is reduced by the UV light to produce silver particles56around the phosphor particles52. The silver particles56are opaque and prevent light emitted from the first LED chip20from striking the phosphor particle52; therefore, the struck area of each phosphor particle52is decreased. In other words, the part of blue light emitted from the second LED chip30striking the phosphor particles52is decreased, and the residual blue light is increased. Thus, the combination of the yellow secondary color light and residual blue light produces a white light with a second color temperature different from the first color temperature. In the present embodiment, the second color temperature is larger than the first color temperature. When the first LED chip20is turned off again, the silver particles56are catalyzed by the copper oxide and combined with halogen particles to form silver halide layer54; therefore, the LED device100emits the white light with the first color temperature again.

In the present embodiment, the second color temperature of the LED device100can be changed by adjusting the current of the first LED chip20. When the first LED chip20and the second LED chip30are both turned on, oxidation-reduction reaction is occurred to the silver halide layer54by an action of the UV light generated by the first LED chip20, and the silver halide layer54is reduced by the UV light to produce silver particles56around the phosphor particles54. If the current of the first LED chip20is decreased, the degree of the oxidation-reduction reaction is decreased, and the silver particles56produced by the silver halide layer54are decreased; therefore, the struck area of each phosphor particle52by the light emitted from the second LED chip30is increased; thus, the second color temperature of light emitted from the LED device100is decreased. On the other hand, if the current of the first LED chip20is increased, the degree of the oxidation-reduction reaction is increased, and the silver particles56produced by the silver halide layer54are increased; therefore, the struck area of each phosphor particle52by the light from the second LED chip30is decreased; thus, the second color temperature of light emitted from the LED device100is increased.