Patent Application
20170268734
The present invention relates to a light emitting device and a lighting device that enable a color temperature to be adjusted.
A halogen lamp exhibits an excellent color rendering property because the energy distribution thereof approximates closely to that of a perfect radiator. The color temperature of light emitted from the halogen lamp can be changed in accordance with the magnitude of power supplied to the halogen lamp, and accordingly, the halogen lamp is used as a visible light source. The halogen lamp, however, has problems in that the temperature of the halogen lamp becomes very high because the halogen lamp emits infrared light, and the halogen lamp needs a reflector for preventing infrared light radiation, has a lifetime shorter than that of a LED, and has a large power consumption. In view of this, white light emitting devices with light-emitting diodes (LED) that generate less heat and have a longer lifetime have been developed.
PTL 1 (Japanese Unexamined Patent Application Publication No. 2009-224656) discloses a light emitting device including a base having a recessed portion having inclined surfaces that are formed as bottom surfaces and that are inclined in directions in which the inclined surfaces face each other, light-emitting elements disposed on the respective inclined surfaces, and wavelength-converting members that cover the respective light-emitting elements and that convert light emitted from the respective light-emitting elements into light with different wavelengths.
PTL 2 (Japanese Unexamined Patent Application Publication No. 2011-159809) discloses a white light emitting device having a first white-light-generating system that is formed of an ultraviolet or violet LED chip and a phosphor and that generates first white light and a second white-light-generating system that is formed of a blue LED chip and a phosphor and that generates second white light, in which the first and second white-light-generating systems are spatially separated from each other, the color temperature of the first white light is lower than the color temperature of the second white light, and mixed light including the first white light and the second white light can be emitted.
PTL 3 (Japanese Unexamined Patent Application Publication No. 2011-222723) discloses a light emitting device including a light source that includes first and second light-emitting diodes having different luminescent colors and connected to each other in parallel and that emits, as emitted light, mixed color light from the first and second light-emitting diodes when a drive voltage is applied across both ends, in which the light source is connected to the first light-emitting diode in series such that variation characteristics of the color temperature of the emitted light with respect to a variation in the luminous flux of the emitted light are desired characteristics in a state where the drive voltage is applied and the light-emitting diodes illuminate, and a resistor that differentiates the variation characteristics of forward current with respect to a variation in the drive voltage between the first light-emitting diode and the second light-emitting diode is provided.
PTL 4 (Japanese Unexamined Patent Application Publication No. 2012-64925) discloses a LED light emitting device that emits combined light created by combining visible light emitted from a first LED and visible light emitted from a second LED, in which a drive-controlling unit controls a first drive current supplied to the first LED and a second drive current supplied to the second LED so that the luminescent color can be clearly varied over the entire variation range of the luminescent color, and a clearly distinguishable luminescent color can be achieved in an intermediate area within the variation range of the luminescent color.
PTL 1: Japanese Unexamined Patent Application Publication No. 2009-224656
PTL 2: Japanese Unexamined Patent Application Publication No. 2011-159809
PTL 3: Japanese Unexamined Patent Application Publication No. 2011-222723
PTL 4: Japanese Unexamined Patent Application Publication No. 2012-064925
In the related art in PTL 1 and PTL 2, power is supplied from different power sources to the light-emitting elements, and accordingly, there are problems in that wiring patterns are needed, and the structure of the light emitting devices is complex.
In the related art in PTL 3, the light-emitting diodes of red and orange luminescent colors are used, the temperature characteristics and lifetime of the light-emitting diodes differ from those of a light-emitting diode of a blue luminescent color, and accordingly, there is a problem in that the mixed light color varies. In addition, a substrate circuit is required to arrange two kinds of the light-emitting diodes thereon, and there are problems in that a light-emitting portion is large and it is difficult for a uniformly mixed color to be achieved near the light-emitting portion.
In the related art in PTL 4, circuits are required to drive respective elements, and there is a problem in that the structure of the light emitting device is complex, as in PTL 1 and PTL 2.
The present invention has been accomplished to solve the above problems, and it is an object of the present invention to provide a light emitting device that can adjust the color temperature by using power supply from a single power source, and a lighting device including the light emitting device.
(1) The present invention provides a light emitting device including a reflector formed of a housing having an opening at an upper portion, an anode electrode terminal and a cathode electrode terminal that are disposed on a side wall or a bottom surface of the housing, and a first light-emitting portion and a second light-emitting portion that are arranged in parallel inside the reflector so as to be electrically connected to the anode electrode terminal and the cathode electrode terminal and that are adjacent to each other. The first light-emitting portion includes a first resistance member. A color temperature of light emitted from an entire light-emitting portion including the first light-emitting portion and the second light-emitting portion can be adjusted.
(2) It is preferable that, in the light emitting device according to the present invention, the first light-emitting portion and the second light-emitting portion be each arranged on a lead frame or a ceramic and the first light-emitting portion and the second light-emitting portion each include a LED element that emits blue light, a translucent resin, and at least two kinds of phosphors.
(3) The light emitting device according to the present invention preferably includes an electrostatic capacity member arranged in parallel with the first light-emitting portion and the second light-emitting portion, and a second resistance member arranged in series with the first light-emitting portion and the second light-emitting portion.
(4) In the light emitting device according to the present invention, the second resistance member is preferably a resistor or an inductor.
(5) The present invention provides a lighting device including the light emitting device in any one of the above (1) to (4), and a PWM signal type dimmer electrically connected to the light emitting device.
The present invention can provide a light emitting device that can adjust the color temperature by using power supply from a single power source and a lighting device including the light emitting device.
A light emitting device and a lighting device according to an embodiment of the present invention will hereinafter be described with reference to the drawings. In the drawings, like symbols designate like or corresponding components. The dimensional relationships of, for example, a length, a width, a thickness, and a depth are appropriately changed for clarification and simplification of the drawings, and the actual dimensional relationships are not illustrated.
A light emitting device according to a first embodiment will be described with reference to
As illustrated in
As illustrated in
As illustrated in
In the light emitting device 1, the first light-emitting portion 5 and the second light-emitting portion 6 illuminate by using power supply from a single power source. Light emitted from the first light-emitting portion 5 and light emitted from the second light-emitting portion 6 are mixed and emitted as light from the light emitting device 1 to the outside.
In the case where a ratio between the electric current flowing to the first light-emitting portion 5 and the electric current flowing to the second light-emitting portion 6 is changed, a luminous flux ratio between the light-emitting portions changes, although the color temperature of light emitted from the first light-emitting portion 5 and from the second light-emitting portion 6 does not change. Accordingly, the color temperature of light from the entire light-emitting portion, which is mixed light of light emitted from the first light-emitting portion 5 and the second light-emitting portion 6, can be changed.
In the light emitting device 1, the first light-emitting portion 5 and the second light-emitting portion 6 are disposed inside the reflector 2. Thus, light emitted from the LED elements 8, the red phosphors 60 and 61, and the green phosphors 70 to the side of the light emitting device is diffusely reflected from a surface of the reflector and distributed in the axial direction of the light emitting device. Accordingly, the emission intensity of the light emitting device along the axis increases, and a light emitting device having excellent directivity can be obtained.
The reflector is formed of the housing having the opening at the upper portion. At least the inner side surface of the housing is made of a material having excellent light reflectivity or coated with a material having excellent light reflectivity. The material of the reflector may be, for example, a polyamide resin, a liquid-crystal polymer, or silicone.
The shape of the reflector is not particularly limited, provided that the reflector is formed of the housing having the opening at the upper portion and enables light emitted from the LED elements to be distributed in the axial direction of the light emitting device. For example, the reflector may be hollowed from a rectangular cuboid into a cone, hollowed from a column into a cone, or hollowed from a rectangular cuboid into a convex shape (semi-cylinder).
The size of the reflector can be appropriately selected in accordance with the use of a lighting apparatus to be used. Regarding the size of the opening, the opening may be formed, for example, in a rectangular shape whose sides are each no less than 2 mm and no more than 20 mm, preferably, no less than 3 mm and no more than 6 mm, or a circular shape whose diameter is no less than 2 mm and no more than 20 mm, preferably, no less than 3 mm and no more than 6 mm. The depth of a space in the housing may be, for example, no less than 1 mm and no more than 5 mm.
The anode electrode terminal 3 and the cathode electrode terminal 4 are electrodes for external connection (for example, for power supply) and made of a material such as Ag—Pt. At least a part of the anode electrode terminal 3 and a part of the cathode electrode terminal 4 are exposed to the outside of the reflector 2. Inside the reflector 2, the anode electrode terminal 3 and the cathode electrode terminal 4 are connected to corresponding leads 11. The leads 11 are electrically connected to the light-emitting elements with wires K1 and K2 interposed therebetween.
The leads 11 are formed of, for example, a copper alloy, and the surface is formed of, for example, Ag plating.
The first light-emitting portion 5 and the second light-emitting portion 6 (a portion including both is also referred to below as a “light-emitting portion”) include the translucent resin 16, and the green phosphors and the red phosphors that are uniformly dispersed in the translucent resin.
In the light emitting device illustrated in
The first light-emitting portion 5 is located in a first section of two sections into which the rectangular opening of the reflector 2 is divided by a straight line, and the second light-emitting portion 6 is located in a second section. In
The shape of the upper surface of the entire light-emitting portion including the first light-emitting portion and the second light-emitting portion is not limited to a rectangle as illustrated in
The arrangement of the first light-emitting portion and the second light-emitting portion is not particularly limited, provided that light emitted from the first light-emitting portion and light emitted from the second light-emitting portion can be mixed. For example, as illustrated in
At the light-emitting portion, part of primary light (for example, blue light) emitted from the LED elements 8 is converted into green light and red light by using the green phosphors and the red phosphors. Thus, the light emitting device according to the present embodiment emits mixed light of the primary light, the green light, and the red light and preferably emits white light. A mixing ratio of the green phosphors and the red phosphors is not particularly limited and is preferably determined such that desired characteristics are achieved.
The luminous flux of light emitted from the first light-emitting portion and the luminous flux of light emitted from the second light-emitting portion can be adjusted in a manner in which the value of the electric current flowing through the first light-emitting portion and the second light-emitting portion is changed.
In the case where the value of the electric current flowing through the light-emitting portion is regarded as a rated current value, the color temperature (also referred to below as Tcmax) of mixed light of light emitted from the first light-emitting portion and light emitted from the second light-emitting portion, which is emitted from the entire light emitting device, is preferably 2700 K to 6500 K. In the case where the value of the electric current is less than the rated current value, the luminous flux of light emitted from the first light-emitting portion and the second light-emitting portion decreases, the luminous flux of light emitted from the entire light emitting device (light-emitting portion) decreases, and the color temperature decreases. From the viewpoint of achieving a wide range of color temperatures, it is preferable that the luminous flux of light emitted from the entire light emitting device be 100% in the case where the value of the electric current flowing through the light-emitting portion is equal to the rated current value, and the color temperature of the light emitted from the entire light emitting device be lower than the Tcmax by 300 K or more in the case where the value of the electric current is decreased to adjust the luminous flux of the light emitted from the entire light emitting device to be 20%.
The first light-emitting portion 5 includes the first resistance member 7. Specifically, the resistance member 7 is connected, in series with the LED elements 8, to a wiring including the wires K1 that electrically connect the anode electrode terminal 3 and the cathode electrode terminal 4 to each other. The value of the electric current flowing through the first light-emitting portion and the second light-emitting portion can be adjusted in a manner in which the resistance value is changed. The change in the value of the electric current flowing through the first light-emitting portion and the second light-emitting portion changes the luminous flux of light emitted from the LED elements connected to the first light-emitting portion or the second light-emitting portion, changing the luminous flux of light emitted from the first light-emitting portion and the second light-emitting portion. Since the change in the luminous flux of light emitted from the light-emitting portion changes the color temperature of the light, the color temperature of light emitted from the entire light emitting device can be adjusted in a manner in which the resistance value is changed.
A chip resistor or a print resistor may be used as a resistor.
According to the first embodiment, a resistor is connected to only the first light-emitting portion. However, a resistor may be connected also to the second light-emitting portion. In this case, the resistors connected to the respective light-emitting portions are selected such that the resistance value of the first light-emitting portion is larger than the resistance value of the second light-emitting portion.
The LED elements are preferably LED elements that emit light including light of a blue component that has a peak emission wavelength in a blue range (range in which the wavelength is no less than 430 nm and no more than 480 nm). In the case where a light-emitting element whose peak emission wavelength is less than 430 nm is used, a contribution ratio of a blue light component with respect to light from the light emitting device decreases. Accordingly, in some cases, the color rendering property becomes worse, and the utility of the light emitting device reduces. In some cases where a LED element whose peak emission wavelength exceeds 480 nm is used, the utility of the light emitting device reduces. In particular, an InGaN LED element has a reduced quantum efficiency, and accordingly, the utility of the light emitting device greatly reduces.
Each LED element is preferably an InGaN LED element. An example of the LED element may include an LED element whose peak emission wavelength is close to 450 nm. The “InGaN LED element” means an LED element in which a light-emitting layer is an InGaN layer.
Each LED element has a structure that emits light from the upper surface thereof. The LED element includes an electrode pad for connecting the adjoining LED elements to each other with wires on the surface interposed therebetween and an electrode pad for connecting the LED element to a wiring pattern or an electrode terminal.
The translucent resin contained in the light-emitting portion is not limited, provided that the translucent resin is a resin having translucency. For example, the translucent resin is preferably an epoxy resin, a silicone resin, or a urea-formaldehyde resin.
The red phosphors are excited by primary light emitted from the LED elements and emit light whose peak emission wavelength is in a red range. The red phosphors do not illuminate within a wavelength range of 700 nm or more and do not absorb light within a wavelength range of no less than 550 nm and no more than 600 nm. The phrase “the red phosphors do not illuminate within a wavelength range of 700 nm or more” means that the emission intensity of the red phosphors within a wavelength range of 700 nm or more at a temperature of 300 K or more is 1/100 or less of the emission intensity of the red phosphors at the peak emission wavelength. The phrase “the red phosphors do not absorb light within a wavelength range of no less than 550 nm and no more than 600 nm” means that the integrated value of the excitation spectrum of the red phosphors within a wavelength range of no less than 550 nm and no more than 600 nm at a temperature of 300 K or more is 1/100 or less of the integrated value of the excitation spectrum of the red phosphors within a wavelength range of no less than 430 nm and no more than 480 nm. The wavelength of the excitation spectrum to be measured is a peak wavelength of the red phosphors. In the description, the “red range” means a range in which the wavelength is no less than 580 nm and less than 700 nm.
The illumination of the red phosphors can hardly be confirmed in a long wavelength range of 700 nm or more. In a long wavelength range of 700 nm or more, the luminosity factor of humans is relatively low. Accordingly, in the case where the light emitting device is used for, for example, illumination, the use of the red phosphors is very advantageous.
The red phosphors do not absorb light within a wavelength range of no less than 550 nm and no more than 600 nm and are unlikely to absorb secondary light from the green phosphors. Thus, two-step illumination, in which the red phosphors absorb secondary light from the green phosphors and illuminate, can be prevented from occurring. Accordingly, a high luminous efficacy can be maintained.
The red phosphors are not particularly limited, provided that the red phosphors can be used for a wavelength-converting portion of the light emitting device. For example, (Sr, Ca)AlSiN3:Eu phosphors or CaAlSiN3:Eu phosphors can be used.
The green phosphors are excited by primary light emitted from the LED elements and emit light whose peak emission wavelength is in a green range. The green phosphors are not particularly limited, provided that the green phosphors can be used for the wavelength-converting portion of the light emitting device. For example, a phosphor that is expressed by a general formula (1): (M1)3-xCex(M2)5O12 can be used (in the formula, (M1) represents at least one of Y, Lu, Gd, and La, (M2) represents at least one of Al and Ga, and x representing a composition ratio (concentration) of Ce satisfies 0.005≦x≦0.20). The “green range” means a range in which the wavelength is no less than 500 nm and no more than 580 nm.
The half width of the fluorescence spectrum of the green phosphors is preferably wide, for example, 95 nm or more in the case where a kind of green phosphor is used (for example, in the case of typical illumination use). A phosphor that uses Ce as an activator, for example, a Lu3-xCexAl5O12 green phosphor that is expressed by the general formula (1) has a garnet crystal structure. Since this phosphor uses Ce as an activator, a fluorescence spectrum having a wide half width (half width is 95 nm or more) is achieved. Accordingly, the phosphor that uses Ce as an activator is a preferred green phosphor to achieve a high color rendering property.
The light-emitting portion may include an additive such as SiO2, TiO2, ZrO2, Al2O3, or Y2O3 in addition to the translucent resin, the green phosphors, and the red phosphors. In the case where the light-emitting portion includes such an additive, settling of the phosphors such as the green phosphors and the red phosphors can be prevented, and light from the LED elements, the green phosphors, and the red phosphors can be efficiently diffused.
A light emitting device 31 according to the present embodiment has the same basic structure as the light emitting device 1 according to the first embodiment. A difference from the first embodiment is to include an electrostatic capacity member 9 arranged in parallel with the first light-emitting portion 5 and the second light-emitting portion 6 and a second resistance member 17 arranged in series with the first light-emitting portion 5 and the second light-emitting portion 6. The electrostatic capacity member 9 is electrically connected to one of the leads 11 and the second resistance member 17 with a conductive wiring K3 interposed therebetween.
In the light emitting device 31, a circuit including the electrostatic capacity member 9 and the second resistance member 17 forms a low-pass filter. Accordingly, as illustrated in
Digital-analog conversion (also referred to below as D/A conversion) in the case where an electric signal of the PWM signal type dimmer passes through the low-pass filter will be described with reference to
According to the present embodiment, a pulse signal from the PWM signal type dimmer 15 can be D/A converted into a signal of a direct voltage as illustrated in
The electrostatic capacity member 9 may be, for example, a chip capacitor, an electrolytic capacitor, or a film capacitor.
The second resistance member 17 may be a chip resistor or an inductor.
The electrostatic capacity member 9 and the second resistance member 17 may be formed inside the reflector. This enables the size of the light emitting device 31 to be decreased. In addition, absorption of light emitted from the LED elements 8 by the electrostatic capacity member 9 and the second resistance member 17 can be suppressed, and a noise component can be reduced.
A light emitting device according to a third embodiment of the present invention will be described with reference to
In the case where the substrate 10 is a metallic substrate, insulation layers are formed below the anode electrode land 13, the cathode electrode land 14, and the wiring patterns 12. The insulation layers are preferably colored (for example, white or milk white) to reflect light emitted from the LED elements. The shape of the substrate 10 may be any one of a polygon, a circle, and, a rectangle in plan view.
In the light emitting device 71 illustrated in
The present invention is not limited to the above embodiments. Various modifications can be made within the scope shown in claims. Embodiments obtained by appropriately combining technical measures disclosed in the different embodiments are included in the technical scope of the present invention.
The present invention will be described in more detail with reference to examples. The present invention, however, is not limited to the examples.
In an example 1, a light emitting device having the same structure as the light emitting device according to the first embodiment illustrated in
At the first light-emitting portion 5, the second red phosphors 61 ((Sr, Ca)AlSiN3:Eu), the green phosphors 70 (Lu3Al5O12:Ce), and blue-light-emitting LED elements 8 (emission wavelength of 450 nm) are sealed with a silicone resin. At the second light-emitting portion 6, the first red phosphors 60 (CaAlSiN3:Eu), the second red phosphors 61 ((Sr, Ca)AlSiN3:Eu), the green phosphors 70 (Lu3Al5O12:Ce), and blue-light-emitting LED elements 8 (emission wavelength of 450 nm) are sealed with a silicone resin. The blue-light-emitting LED elements 8 and the wiring patterns 12 are electrically connected to each other by using wires. The wiring patterns 12 are electrically connected to the anode electrode terminal 3 or the cathode electrode terminal 4. The silicone resin used for the first light-emitting portion 5 is more thixotropic than the silicone resin used for the second light-emitting portion 6. Accordingly, when the light-emitting portion was disposed inside the reflector, the silicone resin for the first light-emitting portion was applied, and the silicone resin for the second light-emitting portion was subsequently applied.
The light emitting device in the example 1 is formed such that the color temperature of light emitted from the first light-emitting portion is 2000 K and the color temperature of light emitted from the second light-emitting portion is 3000 K. Subsequently, the relationship between the total value of the forward current (also referred to below as the total forward current) flowing through the wires K1 and K2 and the color temperature of light emitted from the light emitting device was investigated.
The color temperature of light emitted from the entire light emitting device when a total forward current of 350 mA flowed was 2900 K, and the color temperature of the light emitted from the entire light emitting device when a total forward current of 50 mA flowed was 2000 K.
In an example 2, the light emitting device according to the second embodiment illustrated in
The reflector 2 is formed of a metallic lead frame and a resin. The first resistance member 7 is a chip resistor having a resistance value of 60Ω. The second resistance member 17 is a chip resistor having a resistance value of 10Ω. The electrostatic capacity member 9 is a chip capacitor having an electrostatic capacity of about 100 μF when a PWM frequency is 1 kHz.
At the first light-emitting portion 5, the second red phosphors 61 ((Sr, Ca)AlSiN3:Eu), the green phosphors 70 (Lu3Al5O12:Ce), and the blue-light-emitting LED elements 8 (emission wavelength of 450 nm) are sealed with a silicone resin. At the second light-emitting portion 6, the first red phosphors 60 (CaAlSiN3:Eu), the second red phosphors 61 ((Sr, Ca)AlSiN3:Eu), the green phosphors 70 (Lu3Al5O12:Ce), and the blue-light-emitting LED elements 8 (emission wavelength of 450 nm) are sealed with a silicone resin. The blue-light-emitting LED elements 8 and the wiring patterns 12 are electrically connected to each other by using the wires K1. The wiring patterns 12 are electrically connected to the anode electrode terminal 3 or the cathode electrode terminal 4. The silicone resin used for the first light-emitting portion 5 is more thixotropic than the silicone resin used for the second light-emitting portion 6. Accordingly, when the light-emitting portion was disposed inside the reflector, the silicone resin for the first light-emitting portion was applied, and the silicone resin for the second light-emitting portion was subsequently applied.
The light emitting device 31 in the example 2 is formed such that the color temperature of light emitted from the first light-emitting portion is 2000 K and the color temperature of light emitted from the second light-emitting portion is 3000 K. Subsequently, the relationship between the total value of the forward current (also referred to below as the total forward current) flowing through the wires K1 and K2 and the color temperature of light emitted from the light emitting device was investigated.
The color temperature of light emitted from the entire light emitting device when a total forward current of 350 mA flowed was 2900 K, and the color temperature of light emitted from the entire light emitting device when a total forward current of 50 mA flowed was 2000 K.
It should be understood that the embodiments and examples are disclosed by way of example in all aspects and are not restrictive. It is intended that the scope of the present invention is not shown by the above embodiments but is shown by claims and contains all modifications having the same content and scope as the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-241653 | Nov 2014 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/073809 | 8/25/2015 | WO | 00 |
