DE102004053594A1 - Apparatus and method for emitting output light using a group IIB element selenide-based phosphor material - Google Patents

Abstract

An apparatus and method for emitting output light uses a Group IIB element selenide based phosphor material to convert at least a portion of the original light emitted by a light source of the device into a longer wavelength light to the optical spectrum to change the output light. Thus, the apparatus and method can be used to produce white color light. The Group IIB element selenide-based phosphor material is contained in a wavelength shift region optically coupled to the light source, which may be a cyan light emitting diode (LED) chip.

Description

at This application is a partial continuation of the application Ser. 10 / 761,762, filed January 21, 2004, claimed priority becomes. The whole older one Registration is incorporated herein by reference.

conventional Light sources, such. B. incandescent, halogen and fluorescent lamps, have not been essential in the past 20 years been improved. However, light emitting diodes ("LEDs") are in terms of operating efficiency has been improved to a point where LEDs are now the conventional ones Light sources in conventional monochromatic lighting applications, such. B. traffic signal lights and car taillights, replace. The reason for that lies partly in the fact that LEDs have many advantages over conventional ones Have light sources. These benefits include longer operating life, lower power consumption and smaller size.

LEDs are usually monochrome semiconductor light sources and are currently available in different colors from UV blue to green, yellow and red. On Because of the narrow band emission characteristics, single color LEDs can not directly for "white" light applications be used. Rather, the output light must be a monochrome LED mixed with another light of one or more different wavelengths become white To generate light. Two common Possible solutions to Generate white Light using single color LEDs include (1) packing together single red, greener and blue LEDs, so that the light emitted by these LEDs is combined to white Producing light; and (2) introducing fluorescent material in a UV, blue or green LED, so that part of the original light, which is emitted by the semiconductor chip of the LED, converted into light of longer wavelength will and with the original UV, blue or green light is combined to white To generate light.

From These two approaches to create white Light using single-color LEDs becomes the second approach the first solution generally preferred. Unlike the second approach requires the first solution a more complex driver circuitry, as the red, green and blue LEDs include semiconductor chips that have different operating voltage requirements exhibit. additionally to deteriorate to different operating voltage requirements the red, green and blue LEDs vary over their service life, what about a color control over a longer one Period of time using the first approach makes it difficult. Because only a single type of single-color LED for the second approach needed In addition, using the second approach, one can more compact device can be made, which is a simpler Structure and lower production costs. In addition, can the second approach give a broader light emission, giving a white output light, the higher color rendering characteristics would mean.

One Problem with the second approach to Generate white Light is that the fluorescent material that is currently is used to the original UV, blue or green light Converting leads to LEDs that do not have a straight line over time desirable Have luminance efficiency and / or light output stability.

in the In view of this problem, there is a need for an LED and a method of emitting white output light using a fluorescent phosphor material having a high luminance efficiency and a good light output stability.

It The object of the present invention is a device and a method of emitting output light with improved To create characteristics.

These The object is achieved by a device according to claim 1 or 8 and a Method according to claim 15 solved.

A Use apparatus and a method for emitting output light a Group IIB element selenide-based phosphor material, at least a part of the original one Light emitted from a light source of the device, longer in light wavelength to change the optical spectrum of the output light. Consequently can The device and the method used to light white color to create. The Group IIB element Selenide-based phosphor material is in a wavelength shift region included optically coupled with the light source, in the it is a chip of a blue-green light-emitting diode (LED) can act.

An output light emitting device according to an embodiment of the invention includes a light source that emits a first peak wavelength first light in the visible wavelength range and a wavelength shift region that is optically aligned with the light source is coupled to receive the first light. The wavelength shift region comprises a Group IIB element selenide based phosphor material having a property of converting at least a portion of the first light into a second light of a second peak wavelength. The second light is a component of the output light.

One A method for emitting an output light according to a embodiment of the invention comprises generating a first light of a first one Peak wavelength in the visible wavelength range, receiving the first light, which translates into at least one Part of the first light in a second light of a second peak wavelength below Use of a group IIB element selenide-based phosphor material and emitting the second light as a component of the output light.

Other Aspects and advantages of the present invention will become apparent from the following detailed description together with the accompanying drawings, illustrated by means of examples of the principles of the invention it can be seen. Show it:

1 a diagram of a white phosphor conversion LED according to an embodiment of the invention;

2A . 2 B and 2C Diagrams of white phosphor conversion LEDs with alternative lamp configurations according to one embodiment of the invention;

3A . 3B . 3C and 3D Diagrams of white phosphor conversion LEDs with a lead frame having a reflector shell according to an alternative embodiment of the invention;

4A and 4B the optical spectra of white phosphor conversion LEDs with blue and green LED chips according to an embodiment of the invention;

5 Figure 4 is a plot of luminance (IV) degradation versus time for a white phosphor conversion LED according to an embodiment of the invention; and

6 a flowchart of a method for emitting output light according to an embodiment of the invention.

With reference to 1 is a phosphor converted white light emitting diode (LED) 100 shown according to an embodiment of the invention. The LED 100 is designed to produce a "white" output light having a high luminance efficiency and a good light output stability.The white output light is generated by converting a part of the original light passing through the LED 100 is generated in longer wavelength light using Group IIB element selenide-based phosphor material. In an exemplary embodiment, the LED includes 100 only one type of phosphorus. Thus, the LED needed 100 In this embodiment, no complex mixture of different phosphors, as is the case with some conventional white phosphor conversion LEDs.

As it is in 1 4, the white phosphor conversion LED 100 is a lead frame mounted LED. The LED 100 includes an LED chip 102 , Lead frame 104 and 106 , a wire 108 and a lamp 110 , The LED chip 102 is a semiconductor chip that generates light of a certain peak wavelength. Thus, the LED chip 102 a light source for the LED 100 , In the exemplary embodiment, the LED chip is 102 designed to produce light having a peak wavelength in the visible wavelength range, such. In a range of 400-520 nm, which is in the blue-green region of the visible wavelength range. The LED chip 102 is located on the lead frame 104 and is over the wire 108 electrically with the other lead frame 106 connected. The lead frame 104 and 106 Deliver the electrical power that is needed to the LED chip 102 to drive. The LED chip 102 is in the lamp 110 encapsulated, which is a medium for the propagation of light from the LED chip 102 is. The lamp 110 includes a main section 112 and an output section 114 , In this embodiment, the output section 114 the lamp 110 dome-shaped to act as a lens. Thus, the light coming from the LED 100 is emitted as output light through the dome-shaped output section 114 the lamp 110 focused. In other embodiments, the output section 114 the lamp 100 however, be horizontally planar.

The lamp 110 white phosphor conversion LED 100 is made of a transparent substance, which may be any transparent material, such. B. clear epoxy, so that light from the LED chip 102 move through the lamp and out of the output section 114 the lamp can be emitted. In this embodiment, the lamp comprises 110 a wavelength shift region 116 , which is also a medium for spreading light which consists of a mixture of the transparent substance and a fluorescent phosphor material 118 based on Group IIB element selenide. The Group IIB element Selenide based phosphor material 118 It is used to remove part of the original light through the LED chip 102 is emitted to convert into a light of lower energy (longer wavelength). The Group IIB element Selenide based phosphor material 118 absorbs a portion of the original light from the LED chip 102 , which excites the atoms of the Group IIB element selenide-based phosphor material, and emits the longer wavelength light. The peak wavelength of the converted light is partly due to the peak wavelength of the original light and the Group IIB element selenide-based phosphor material 118 Are defined. The unabsorbed original light from the LED chip 102 and the converted light are combined to produce light of "white" color coming from the light emitting section 114 the lamp 110 as the output light of the LED 100 is emitted. In the exemplary embodiment, the Group IIB element comprises selenide-based phosphor material 118 a property on, part of the original light from the LED chip 102 into light of a longer peak wavelength in the red wavelength region of the visible spectrum, which is about 620 nm to 800 nm.

In one embodiment, the Group IIB element is selenide-based phosphor material 118 that in the wavelength shift region 116 the lamp 110 is included to phosphorus, which is made of zinc selenide (ZnSe), by one or more suitable dopants, such as. As copper (Cu), chlorine (Cl), fluorine (F), bromine (Br), silver (Ag) and rare earth elements is activated. In an exemplary embodiment, the Group IIB element selenide-based phosphor material 118 is phosphorus made from ZnSe activated by Cu, ie, ZnSe: Cu. Unlike conventional fluorescent phosphor materials that are used to produce white color light using LEDs, such as LED's. For example, those based on aluminum, oxide, sulfide, phosphate and halophosphate, ZnSe: Cu phosphor has a high efficiency in wavelength-to-wavelength conversion of light emitted from an LED chip. The reason for this is that most conventional fluorescent phosphor materials have a large band gap, which prevents the phosphor materials from transmitting light, e.g. B. blue-green light, efficiently absorb and convert to light longer wavelength. In contrast, the ZnSe: Cu phosphor has a smaller bandgap, which equates to higher wavelength-shift conversion efficiency via fluorescence.

The ZnSe-based phosphor is the preferred group IIB element selenide-based phosphor material 118 for the wavelength shift region 116 the lamp 110 , In the group IIB element selenide-based phosphor material 118 the wavelength shift region 116 however, it may be phosphorus made from cadmium selenide (CdSe), which may be replaced by one or more suitable dopants, e.g. As Cu, Cl, F, Br, Ag and rare earth elements is activated. Alternatively, the Group IIB element may be Selenide based phosphor material 118 the wavelength shift region 116 comprise a combination of ZnSe and CdSe activated by one or more suitable dopants.

Of the preferred ZnSe: Cu phosphor can be generated by various techniques become. One technique involves dry milling a predefined one Amount of undoped ZnSe material in fine powders or crystals, which can be less than 5 microns in size. A small amount of Cu dopant then becomes a solution from the alcohol family, such as. As methanol, added and with ball-milled the undoped ZnSe powders. The amount of Cu dopant, that to the solution added can, everywhere between a minimum amount up to about 6% of the total weight of ZnSe material and Cu dopant. The doped material It is then oven-dried at about one hundred degrees Celsius (100 ° C) resulting cake is dry-ground again to small particles to create. The ground material is loaded into a crucible, such as As a quartz crucible, and in an inert atmosphere at about one thousand degrees Celsius (1,000 ° C) sintered for one to two hours. The sintered materials can then, if necessary, sieved to ZnSe: Cu phosphor powder with a desired Particle size distribution, which may be in the micrometer range.

The ZnSe: Cu phosphor powders can be further processed to produce phosphor particles with a silica coating. The silica coating on the phosphor particles reduces grouping or agglomeration of the phosphor particles when the phosphor particles are mixed with a transparent substance to form a wavelength shift region in an LED, such as an LED. B. the wavelength shift region 116 the lamp 110 , to build. Grouping or agglomerating phosphor particles can yield an LED that produces output light that has a nonuniform color distribution.

To apply a silica coating to the ZnSe: Cu phosphor particles, the sieved materials are subjected to an annealing process to heal the phosphor particles and remove contaminants. Subsequently, the phosphor particles are mixed with silica powders, and then the mixture is heated in an oven at about 200 degrees Celsius. The applied heat forms a thin silica coating on the phosphor particles. The amount of silica on the phosphor particles is about 1% with respect to the phosphor particles. The resulting ZnSe: Cu phosphor particles having a silica coating may have a particle size of less than or equal to thirty (30) microns.

After completion of the synthesis process, the ZnSe: Cu phosphor powders can be coated with the same transparent substance of the lamp 110 , z. As epoxy, mixed and around the LED chip 102 be applied to the wavelength shift region 116 to form the lamp. The remaining part of the lamp 110 can be formed by applying the transparent substance without the ZnSe: Cu phosphor powder to the white phosphor conversion LED 100 to create. Although the wavelength shift region 116 the lamp 110 in 1 is shown to have a rectangular shape, the wavelength shift region in other shapes, such. B. a hemisphere, be configured. In addition, in other embodiments, it may be that the wavelength shift region 116 not physically with the LED chip 102 is coupled. Thus, the wavelength shift region can 116 in these embodiments elsewhere in the lamp 110 be positioned.

In the 2A . 2 B and 2C are white phosphor conversion LEDs 200A . 200B and 200C shown with alternative lamp configurations according to an embodiment of the invention. The white phosphor conversion LED 200A from 2A includes a lamp 210A in which the entire lamp is a wavelength shift region. Thus, in this configuration, the entire lamp 200A from the mixture of the transparent substance and the group IIB element-selenide-based phosphor material 118 produced. The white phosphor conversion LED 200B from 2 B includes a lamp 210B in which a wavelength shift region 216B is arranged on the outer surface of the lamp. Thus, in this configuration, the region of the lamp first becomes 210B without the group IIB element selenide-based phosphor material 118 over the LED chip 102 is formed, and then the mixture of the transparent substance and the group IIB element selenide-based phosphor material 118 applied over this region to the wavelength shift region 216B to form the lamp. The white phosphor conversion LED 200C from 2C includes a lamp 210C in which a wavelength shift region 216C a thin layer of the mixture of the transparent substance and the group IIB element selenide-based phosphor material 118 is that over the LED chip 102 is applied. Thus, in this configuration, the LED chip first becomes 102 with the mixture of the transparent substance and the group IIB element selenide-based phosphor material 118 coated or covered around the wavelength shift region 216C to form, and then can the remaining part of the lamp 210C by forming the transparent substance without the phosphor material over the wavelength shift region. For example, the thickness of the wavelength shift region 216C the LED 200C between ten (10) and sixty (60) microns, depending on the color of the light passing through the LED chip 102 is produced.

In an alternative embodiment, the lead frame of a white phosphor conversion LED on which the LED chip is positioned may comprise a reflector shell as shown in FIGS 3A . 3B . 3C and 3D is illustrated. The 3A - 3D show white phosphor conversion LEDs 300A . 300B . 300C and 300D with different lamp configurations, which has a lead frame 320 include a reflector cup 322 having. The reflector shell 322 provides a recessed region for the LED chip 102 is positioned so that a portion of the light generated by the LED chip from the lead frame 320 is reflected away to be emitted from the respective LED as Nutzausgangslicht.

The different lamp configurations described above are, can in other types of LEDs, such as. B. surface-mounted LEDs applied will come with other types of white phosphor conversion LEDs a Group IIB element selenide-based phosphor material according to the invention manufacture. additionally can these different lamp configurations in other types of light-emitting devices, such. B. semiconductor laser devices, be applied to other types of light-emitting devices according to the invention manufacture. It may be in these light-emitting devices at the light source to any other light source than act an LED chip, such as. B. a laser diode.

With current attention to 4A is the optical spectrum 424 a white phosphor conversion LED with a blue LED chip according to an embodiment of the invention. The wavelength shift region for this LED was formed with forty percent (40%) ZnSe: Cu phosphor relative to epoxide. The percentage or loading content of ZnSe: Cu phosphorus, which is included in the wavelength shift region of the LED can be varied according to the phosphorus efficiency. When the phosphorus efficiency is increased, e.g. B. by changing the amount of dopant, the loading content of the phosphor can be reduced. The optical spectrum 424 includes a first peak wavelength 426 at about 480 nm, which corresponds to the peak wavelength of the light emitted from the blue LED chip, and a second peak wavelength 428 at about 650 nm, which is the peak wavelength of the light that is converted by the ZnSe: Cu phosphor in the wavelength shift region of the LED. Similar is in 4B the optical spectrum 430 a white phosphor conversion LED with a green LED chip according to an embodiment of the invention. The wavelength shift region for this LED was formed with forty five percent (45%) ZnSe: Cu phosphor relative to epoxide. The optical spectrum 430 includes a first peak wavelength 432 at about 494 nm, which corresponds to the peak wavelength of the light emitted from the green LED chip, and a second peak wavelength 434 again at about 650 nm, which is the peak wavelength of the light converted by the ZnSe: Cu phosphor in the wavelength shift region of this LED. Thus, light of different peak wavelengths can be wavelength-shifted to about the same peak wavelength by adjusting the relative amount of ZnSe: Cu phosphor contained in the wavelength shift region of an LED.

5 Figure 12 is a plot of luminance (1v) degradation over time for a white phosphor conversion LED having a wavelength shift region of forty five percent (45%) ZnSe: Cu phosphor relative to epoxide according to one embodiment of the invention. As it is by the diagram of 5 is illustrated, the luminance characteristics of the white phosphor conversion LED experience little change over a long period of time while being exposed to a high-intensity light, ie, the light emitted from the semiconductor chip of the LED. Thus, the ZnSe: Cu phosphor used in the LED has good resistance to light. This light resistance is not limited to the light emitted from the semiconductor chip of an LED but also any external light such as light. As sunlight, including ultraviolet light. Thus, LEDs according to the invention are suitable for outdoor use and can provide stable luminance over time with minimal color shift. In addition, these LEDs can be used in applications requiring high response speeds because the duration of afterglow for the ZnSe: Cu phosphor is short.

A method of generating white output light according to an embodiment of the invention is described with reference to FIG 6 described. At block 602 For example, a first peak wavelength first light is generated in the visible wavelength range. The first light can by an LED chip, such. As a blue-green LED chip can be generated. Subsequently, at block 604 receive the first light, and a portion of the first light is converted to a second peak wavelength second light using the group IIB element selenide-based phosphor material. Subsequently, at block 606 the first light and the second light are emitted as components of the output light.

Even though specific embodiments of Invention have been described and illustrated, the invention not on the specific shapes or arrangements of so described and illustrated parts. In addition, the invention is not limited to devices and methods for generating white output light. The The invention also includes apparatus and methods for generating other types of output light. For example, the group IIB element may be selenide-based Phosphor material according to the invention be used in a light-emitting device in which practically all of the original Light that is generated by a light source, different in light wavelength In this case it can be that the color is converted the output light is not white. The scope of the invention should be determined by the claims appended hereto and their equivalents be defined.

Claims (20)

Apparatus for emitting output light, the apparatus comprising: a light source ( 102 ) emitting a first light of a first peak wavelength in the visible wavelength region; and a wavelength shift region ( 116 ; 210A . 216B ; 216C ) optically coupled to the light source to receive the first light, wherein the wavelength shift region is a Group IIB element selenide based phosphor material ( 118 ) having a property of converting at least a part of the first light into a second light of a second peak wavelength, the second light being a component of the output light. Apparatus according to claim 1, wherein the group IIB element is selenide-based phosphor material ( 118 ) of the wavelength shift region ( 116 ; 210A . 216B ; 216C ) is doped with at least one rare earth element. Apparatus according to claim 1 or 2, wherein the group IIB element is selenide-based phosphor material ( 118 ) of the wavelength shift region ( 116 ; 210A . 216B ; 216C ) Comprises phosphor particles. The device according to claim 3, wherein the phosphor particles of the group IIB element selenide-based phosphor material ( 118 ) have a silica coating. A device according to claim 3 or 4, wherein the phosphor particles of the Group IIB element selenide-based phosphor material ( 118 ) have a particle size of less than or equal to 30 microns. Device according to one of claims 1 to 5, wherein the group IIB element selenide-based phosphor material ( 118 ) of the wavelength shift region ( 116 ; 210A . 216B ; 216C ) Comprises zinc selenide. Device according to one of claims 1 to 5, wherein the group IIB element selenide-based phosphor material ( 118 ) of the wavelength shift region ( 116 ; 210A . 216B ; 216C ) Cadmium selenide. A device for emitting output light, the device comprising: a semiconductor chip ( 102 ) emitting a first light of a first peak wavelength in the visible wavelength region; and a phosphorus-containing medium positioned to receive the first light, wherein the phosphorus-containing medium is a Group IIB element selenide-based phosphor material ( 118 ) having a property of converting at least a part of the first light into a second light of a second peak wavelength, the second light being a component of the output light. Apparatus according to claim 8, wherein the group IIB element is selenide-based phosphor material ( 118 ) of the phosphorus-containing region is doped with at least one rare earth element. Apparatus according to claim 8 or 9, wherein the group IIB element is selenide-based phosphor material ( 118 ) of the phosphorus-containing region comprises phosphor particles. A device according to claim 10, wherein the phosphor particles of the group IIB element selenide-based phosphor material ( 118 ) have a silica coating. Apparatus according to claim 10 or 11, wherein the phosphor particles of the group IIB element selenide-based phosphor material ( 118 ) have a particle size of less than or equal to 30 microns. Apparatus according to any one of claims 8 to 12, wherein the group IIB element is selenide-based phosphor material ( 118 ) of the phosphorus-containing region comprises zinc selenide. Apparatus according to any one of claims 8 to 12, wherein the group IIB element is selenide-based phosphor material ( 118 ) of the phosphorus containing region cadmium selenide. A method of emitting output light, the method comprising the steps of: generating ( 602 ) a first light of a first peak wavelength in the visible wavelength region; Receive ( 604 ) of the first light, which comprises converting at least a portion of the first light into a second light of a second peak wavelength using a group IIB element selenide-based phosphor material ( 118 ); and issuing ( 606 ) of the second light as a component of the output light. A method according to claim 15, wherein the group IIB element is selenide-based phosphor material ( 118 ) is doped with at least one rare earth element. A method according to claim 15 or 16, wherein the group IIB element is selenide-based phosphor material ( 118 ) Comprises phosphor particles. A method according to claim 17, wherein the phosphor particles of the group IIB element selenide-based phosphor material ( 118 ) have a silica coating. A method according to claim 17 or 18, wherein the phosphor particles of the group IIB element selenide-based phosphor material ( 118 ) have a particle size of less than or equal to 30 microns. A method according to any one of claims 15 to 19, wherein the group IIB element is selenide-based phosphor material ( 118 ) comprises either zinc selenide or cadmium selenide.