There is provided a light-emitting device including an anode electrode land, a cathode electrode land, and a first light-emitting unit and a second light-emitting unit electrically connected to the anode electrode land and the cathode electrode land and provided in parallel to each other, in which the first light-emitting unit and the second light-emitting unit each include blue light-emitting LED chips, the first light-emitting unit and the second light-emitting unit have different amounts of change in luminous flux with respect to an amount of change in current applied between the anode electrode land and the cathode electrode land, and a color temperature generated from an entire light-emitting unit including the first light-emitting unit and the second light-emitting unit can be adjusted.

TECHNICAL FIELD

The present invention relates to light-emitting devices.

BACKGROUND ART

Halogen lamps have an energy distribution closely analogous to that of perfect radiators, and thus exhibit excellent color rendering properties. Furthermore, depending on the magnitude of supplied power to a halogen lamp, the color temperature of light emitted from the halogen lamp can be changed, and the halogen lamp is thus used as a visible light source. However, the halogen lamps have problems, such as producing infrared emission and thus becoming at very high temperatures, requiring a reflector plate for inhibiting infrared radiation, having a life shorter than that of LEDs, having large power consumption. Thus, developments of white-light light-emitting device with small heat generation using longer-life light-emitting diodes (LEDs) have been performed.

In PTL 1 (Japanese Unexamined Patent Application Publication No. 2009-224656), a light-emitting device is disclosed which includes a base body having a recessed part where a plurality of tilted surfaces tilted in direction opposing to one another are formed on a bottom surface, light-emitting elements installed on the respective tilted surfaces, and wavelength converting members provided so as to cover the respective light-emitting elements to convert light emitted from the respective light-emitting elements into lights with wavelengths different from one another.

In PTL 2 (Japanese Unexamined Patent Application Publication No. 2011-159809), a white-light light-emitting device is disclosed which includes a first white-light generating system formed of ultraviolet or violet LED chips and phosphors to generate first white light and a second white-light generating system formed of blue LED chips and phosphors to generate second white light. The first and second white-light generating systems are spatially separated, the first white light has a color temperature lower than that of the second white light, and the white-light light-emitting device is configured to be able to emit mixed light including the first white light and the second white light.

In PTL 3 (Japanese Unexamined Patent Application Publication No. 2011-222723), a light-emitting device is disclosed which has a light source unit with a resistor connected in series to a first LED so that a ratio of a luminous flux of the first LED and a luminous flux of a second LED is not constant with a change in output voltage of a power source device.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the techniques of PTL 1 and PTL 2, power is supplied from different power sources to each light-emitting element. Thus, there are problems in which a plurality of wiring patterns are required and the structure of the light-emitting device becomes complex.

In the technique of PTL 3, the light source unit has a resistor. Thus, there is a problem in which a power loss at the resistor increases in accordance with an increase in charged power to decrease luminous efficiency of the light-emitting device.

The present invention was made to resolve the above-described problems, and has an object of providing a light-emitting device capable of adjusting color temperature by power supply from a single power source.

Solution to Problem

[1] A light-emitting device of the present invention is a light-emitting device including an anode electrode land, a cathode electrode land, and a first light-emitting unit and a second light-emitting unit electrically connected to the anode electrode land and the cathode electrode land and provided in parallel to each other, in which the first light-emitting unit and the second light-emitting unit each include blue light-emitting LED chips, the first light-emitting unit and the second light-emitting unit have different amounts of change in luminous flux with respect to an amount of change in current applied between the anode electrode land and the cathode electrode land, and a color temperature generated from an entire light-emitting unit including the first light-emitting unit and the second light-emitting unit can be adjusted.

[2] In the light-emitting device of the present invention, preferably, the first light-emitting unit and the second light-emitting unit each include a different number of the blue light-emitting LED chips.

[3] In the light-emitting device of the present invention, preferably, the blue light-emitting LED chips included in the first light-emitting unit and the blue light-emitting LED chips included in the second light-emitting unit have different amounts of change in forward-direction current with respect to an amount of change in applied voltage (forward current-forward voltage characteristics).

[4] In the light-emitting device of the present invention, preferably, the first light-emitting unit includes a plurality of first piece light-emitting units connected in series, and the second light-emitting unit includes a plurality of second piece light-emitting units connected in series.

[5] In the light-emitting device of the present implementation, preferably, the first light-emitting unit and the second light-emitting unit each include phosphors of at least two types, and a content rate of all phosphors included in the first light-emitting unit and a content rate of all phosphors included in the second light-emitting unit are different.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a light-emitting device capable of adjusting color temperature by power supply from a single power source.

DESCRIPTION OF EMBODIMENTS

In the following, a light-emitting device of the present invention is described by using the drawings. Note that the same reference characters represent the same portion or corresponding portion in the drawings of the present invention. Also, dimensional relations regarding length, width, thickness, depth, and so forth are changed as appropriate for the purpose of clarification and simplification of the drawings, and do not represent actual dimensional relations.

A light-emitting device according to a first embodiment is described by usingFIG. 1andFIG. 2.FIG. 1is a transparent plan view schematically depicting the light-emitting device according to the first embodiment of the present invention.FIG. 2is a schematic circuit view of the light-emitting device ofFIG. 1.

As depicted inFIG. 1andFIG. 2, a light-emitting device1includes, on a substrate7, an anode electrode land13, a cathode electrode land14, and first light-emitting units5at two locations and second light-emitting units6at three locations electrically connected to the anode electrode land13and the cathode electrode land14and provided in parallel. The first light-emitting units5and the second light-emitting units6are alternately and adjacently arranged.

The anode electrode land13and each of the first light-emitting units5at two locations are electrically connected via a lead wiring4connected to the anode electrode land13, a wiring pattern25aconnected to the lead wiring4, and a wire20connected to the wiring pattern25a. The cathode electrode land14and each of the first light-emitting units5at two locations are electrically connected via a lead wiring3connected to the cathode electrode land14, a wiring pattern25bconnected to the lead wiring3, and a wire20connected to the wiring pattern25b.

The anode electrode land13and each of the second light-emitting units6at three locations are electrically connected via the lead wiring4connected to the anode electrode land13, the wiring pattern25aconnected to the lead wiring4, and a wire20connected to the wiring pattern25a. The cathode electrode land14and each of the second light-emitting units6at three locations are electrically connected via a lead wiring2connected to the cathode electrode land14, a wiring pattern25cconnected to the lead wiring2, and a wire20connected to the wiring pattern25c.

Each of the first light-emitting units5at two locations includes first red phosphors60, second red phosphors61, green phosphors70, blue light-emitting LED chips8, and a light-transmitting resin17. In each of the first light-emitting units5, nine blue light-emitting LED chips8are connected in series via the wire20.

Each of the second light-emitting units6at three locations includes first red phosphors60, second red phosphors61, green phosphors70, blue light-emitting LED chips8, and a light-transmitting resin17. In each of the second light-emitting unit6, ten blue light-emitting LED chips8are connected in series via the wire20.

Outside the first light-emitting units5at two locations and the second light-emitting units6at three locations, a resin dam10is formed. The wiring patterns25a,25b, and25cand part of the wires20are covered with the resin dam10.

In the light-emitting device1, the first light-emitting units5and the second light-emitting units6emit light by power supply from a single power source. Lights emitted from the first light-emitting units5and lights emitted from the second light-emitting units6are mixed and emitted outside as light from the light-emitting device1.

In the light-emitting device1, the number of blue light-emitting LED chips8included in the first light-emitting unit5is nine, and the number of blue light-emitting LED chips8included in the second light-emitting unit6is ten. The numbers of blue light-emitting LED chips8included in the respective light-emitting units are different.

Using a graph ofFIG. 3, a description is made about changes in luminous flux of light emitted from each of the first light-emitting unit5and the second light-emitting unit6when the current value of current applied to the light-emitting device1is gradually increased from a state in which no current is let flow through the light-emitting device1.

When the current value of current applied to the light-emitting device1is gradually increased from a state in which no current is let flow through the light-emitting device1, firstly, current gradually flows through the first light-emitting unit5, causing the first light-emitting unit5to emit light. Here, current hardly flows through the second light-emitting unit6. That is, when the current value of the current applied to the light-emitting device1is small, a luminous flux ϕ1of light emitted from the first light-emitting unit is larger than a luminous flux ϕ2of light emitted from the second light-emitting unit. Subsequently, when the current value of the current applied to the light-emitting device1is gradually increased, current starts flowing through the first light-emitting unit5and also the second light-emitting unit6, causing the second light-emitting unit to also emit light. Subsequently, when the current value applied to the light-emitting device1is further increased, the luminous flux ϕ2of light emitted from the second light-emitting unit becomes larger than the luminous flux ϕ1of light emitted from the first light-emitting unit.

As depicted in the graph ofFIG. 3, the first light-emitting unit5and the second light-emitting unit6have different amounts of change in the luminous flux with respect to the amount of change in current applied between the anode electrode land13and the cathode electrode land14. When the magnitude of current applied to the light-emitting device1is changed, the color temperature of light emitted from the first light-emitting unit5and the color temperature of light emitted from the second light-emitting unit6are not changed, but a luminous flux ratio of light emitted from each light-emitting unit is changed. Therefore, the color temperature of light from the entire light-emitting unit, which is mixed light of lights from the first light-emitting unit5and the second light-emitting unit6, can be changed.

The anode electrode land13and the cathode electrode land14are electrodes for external connection (for example, for the purpose of power supply), and are made of a material such as Ag—Pt. The anode electrode land13and the cathode electrode land14are provided so as to be exposed outside the resin dam10.

The lead lines are made of 2, 3, 4, Ag—Pt, or the like, and are formed by a screen printing method or the like.

The wiring patterns25a,25b, and25care made of Ag—Pt or the like, and are formed by a screen printing method or the like.

The resin dam10is a resin for holding back the first light-emitting units5and the second light-emitting units6including the light-transmitting resin17, and is preferably configured of a colored material (which may be a colored material with less light absorption such as white, milk white, red, yellow, or green). The resin dam10is preferably formed so as to cover the wiring patterns25a,25b, and25cto decrease absorption of light radiated from the blue light-emitting LED chips or light converted by the phosphors.

The first light-emitting units5and the second light-emitting units6(hereinafter also referred to as a “light-emitting unit” including both units) include the blue light-emitting LED chips8, the light-transmitting resin17, and the first red phosphors60, the second red phosphors61, and the green phosphors70uniformly dispersed in the light-transmitting resin.

InFIG. 1, the first light-emitting units5and the second light-emitting units6are arranged inside the same circle. The circle is divided into five by four parallel lines that are axisymmetric. The second light-emitting units6are arranged in one center section and two sections on both sides, and the first light-emitting units5are arranged in the remaining two sections interposed by the second light-emitting units6. InFIG. 1, the first light-emitting units5and the second light-emitting units6are adjacent on boundary lines, and lights emitted from the light-emitting units of the respective first light-emitting units5and second light-emitting units6thus become easily mixed, allowing the entire light-emitting unit to emit light at a more uniform color temperature. Note that although the first light-emitting units5and the second light-emitting units6are preferably arranged adjacently, the first light-emitting units5and the second light-emitting units6do not have to make contact with each other as long as lights emitted from the light-emitting units of the respective first light-emitting units5and second light-emitting units6can be mixed together. In this case, the first light-emitting units5and the second light-emitting units6are preferably arranged in a distance as near as lights emitted from the respective light-emitting units can be sufficiently mixed together.

The shape of the entire light-emitting unit including the first light-emitting units5and the second light-emitting units6is not limited to the circle as inFIG. 1as long as lights emitted from the light-emitting units of the respective first light-emitting units5and second light-emitting units6can be mixed. For example, as the shape of the entire light-emitting unit, any shape can be adopted, such as a substantially rectangular shape, a substantially oval shape, or a polygon. The shape of each of the first light-emitting units5and the second light-emitting units6arranged inside the entire light-emitting unit is also not particularly limited. For example, it is preferable to form a shape so that the surface area of the first light-emitting unit5and the surface area of the second light-emitting unit6are equal to each other. This shape can be acquired by, for example, arranging the first light-emitting unit5in a first section acquired by equally dividing the entire light-emitting unit having a shape such as a circle, rectangle, oval, or regular polygon by a line passing through the center into two and arranging the second light-emitting unit6in a second section.

Also, if the color temperature of light emitted from the light-emitting unit of each of the first light-emitting units and the second light-emitting units can be adjusted, the surface area of the first light-emitting unit and the surface area of the second light-emitting unit may be different. For example, the first light-emitting unit can be formed in a circular shape, and the second light-emitting unit can be arranged in a donut shape so as to surround the outer periphery of the first light-emitting unit. According to this, lights emitted from the light-emitting units of the respective first light-emitting unit and second light-emitting unit become easily mixed, allowing the entire light-emitting unit to emit light at a more uniform color temperature.

In the light-emitting unit, part of primary light (for example, blue light) radiated from the blue light-emitting LED chips8is converted by the green phosphors and the red phosphors into green light and red light. Thus, the light-emitting device according to the present embodiment emits light with the primary light, the green light, and the red light mixed together, and suitably emits white-based light. Note that a mixture ratio of the green phosphors and red phosphors is not particularly restricted, and the mixture ratio is preferably set so that a desired characteristic is achieved. Also, the content rate of all phosphors included in the first light-emitting unit5and the content rate of all phosphors included in the second light-emitting unit6are preferably different.

By changing the magnitude of current flowing through each of the first light-emitting unit5and the second light-emitting unit6, the luminous flux of light emitted from the first light-emitting unit5and the luminous flux of light emitted from the second light-emitting unit6can be adjusted.

When the current flowing through the light-emitting unit is set to have a rated current value, the color temperature (hereinafter also referred to as Tcmax) of light emitted from the entire light-emitting device with a mixture of lights emitted from the first light-emitting units5and lights emitted from the second light-emitting units6is preferably 2700 K to 6500 K. If the magnitude of current is set smaller than the rated current value, the luminous fluxes of lights emitted from the first light-emitting units5and the second light-emitting units6become smaller, the luminous flux of light emitted from the entire light-emitting device (light-emitting unit) becomes smaller, and the color temperature is decreased. With the luminous flux of light emitted from the entire light-emitting device being taken as 100% when the current flowing through the light-emitting unit is set to have a rated current value and the luminous flux of light emitted from the entire light-emitting device being adjusted to be 20% by making the magnitude of current smaller, the color temperature of light emitted from the entire light-emitting device is preferably smaller than Tcmax by 300 K or more, in view of allowing acquirement of a wide range of color temperatures.

The blue light-emitting LED chips8radiate light including light with blue components having a peak luminous wavelength present in a blue region (a region with a wavelength equal to or longer than 430 nm and equal to or shorter than 480 nm). When LED chips with a peak luminous wavelength shorter than 430 nm are used, a contribution ratio of the blue-light components with respect to light from the light-emitting device is low, inviting degradation in color rendering properties. Thus, a decrease in practicality of the light-emitting device may be invited. When LED chips with a peak luminous wavelength exceeding 480 nm are used, a decrease in practicality of the light-emitting device may be invited. In particular, in InGaN-based LED chips, quantum efficiency is decreased, and thus a decrease in practicality of the light-emitting device is conspicuous.

The blue light-emitting LED chips8are preferably InGaN-based blue light-emitting LED chips. An example of the blue light-emitting LED chips8can be blue light-emitting LED chips with a peak luminous wavelength near 450 nm. Here, the “InGaN-based blue light-emitting LED chips” mean blue light-emitting LED chips in which a light-emitting layer is an InGaN layer.

The blue light-emitting LED chips8each have a structure in which light is radiated from its upper surface. Also, for connection of the blue light-emitting LED chips8adjacent to each other via the wire20and connection of the blue light-emitting LED chips8and the wiring patterns25a,25b, and25cvia the wire20, the blue light-emitting LED chip8has an electrode pad on its surface.

In the present embodiment, the number of blue light-emitting LED chips8connected in series and included in the first light-emitting unit5and the number of blue light-emitting LED chips8connected in series and included in the second light-emitting unit are made different, thereby making the amount of change in luminous flux of light emitted from the first light-emitting unit5with respect to the amount of change in current applied to the light-emitting device1and the amount of change in luminous flux of light emitted from the second light-emitting unit6with respect to the amount of change in current applied to the light-emitting device1different. In the present embodiment, it is possible to dispense with means which connects resistors to the lead wirings2,3, and4to change the magnitude of current flowing through the first light-emitting units5and the second light-emitting units6. Therefore, the light-emitting device1can decrease a power loss due to resistors and can have excellent luminous efficiency even if the value of the applied current increases.

The number of blue light-emitting LED chips8connected in series and included in the first light-emitting unit5and the number of blue light-emitting LED chips8connected in series and included in the second light-emitting unit are not particularly limited as long as they are different. Also, either of the number of blue light-emitting LED chips8included in the first light-emitting unit5or the number of blue light-emitting LED chips8included in the second light-emitting unit6can be larger.

The light-transmitting resin17included in the light-emitting unit is not limited as long as it is a resin with light transmittance. For example, an epoxy resin, silicone resin, urea resin, or the like is preferable.

The viscosity of the light-transmitting resin including the phosphors forming the first light-emitting unit5and the viscosity of the light-transmitting resin including the phosphors forming the second light-emitting unit6are preferably different. According to this, after a light-emitting unit made of a light-transmitting resin with high viscosity is formed, a light-emitting unit made of a light-transmitting resin with low viscosity is formed, allowing the light-emitting unit formed formerly to serve as a resin dam for the light-emitting unit formed later. Also, if the viscosity of the light-transmitting resin including the phosphors forming the first light-emitting unit5and the viscosity of the light-transmitting resin including the phosphors forming the second light-emitting unit6are different, mixture and intrusion of the phosphors included in each light-emitting unit can be reduced.

The first red phosphors60and the second red phosphors61(hereinafter also referred to as a “red phosphor” including both phosphors) are excited by primary light radiated from the blue light-emitting LED chips8, and radiate light with a peak luminous wavelength in a red region. The red phosphor neither emits light in a wavelength range equal to or longer than 700 nm nor absorbs light in a wavelength range equal to or longer than 550 nm and equal to or shorter than 600 nm. “The red phosphor does not emit light in a wavelength range equal to or longer than 700 nm” means that the light emission intensity of the red phosphor in the wavelength range equal to or longer than 700 nm at a temperature equal to or higher than 300 K is equal to or smaller than 1/100 times of the light emission intensity of the red phosphor in the peak luminous wavelength. “The red phosphor does not absorb light in a wavelength range equal to or longer than 550 nm and equal to or shorter than 600 nm” means that an integral value of an excitation spectrum of the red phosphor in the wavelength range equal to or longer than 550 nm and equal to or shorter than 600 nm at a temperature equal to or higher than 300 K is equal to or smaller than 1/100 times of an integral value of an excitation spectrum of the red phosphor in a wavelength range equal to or longer than 430 nm and equal to or shorter than 480 nm. Note that the measured wavelength of the excitation spectrum is assumed to be a peak wavelength of the red phosphor. The “red region” means a region with a wavelength equal to or longer than 580 nm and shorter than 700 nm in the specification.

Light emission of the red phosphor can be hardly confirmed in a long wavelength region equal to or longer than 700 nm. In the long wavelength region equal to or longer than 700 nm, human luminosity is relatively small. Thus, when the light-emitting device is used for the purpose of, for example, lighting, it is a great advantage to use red phosphor.

Also, the red phosphor does not absorb light in a wavelength range equal to or longer than 550 nm and equal to or shorter than 600 nm, and is thus difficult to absorb secondary light from the green phosphors. This can inhibit an occurrence of two-step light emission, in which the red phosphor absorbs secondary light from the green phosphor and emits light. Therefore, luminous efficiency is highly kept.

The red phosphor is not particularly limited as long as it is used in a wavelength conversion unit of the light-emitting device. For example, a (Sr, Ca)AlSiN3:Eu-based phosphor, CaAlSiN3:Eu-based phosphor, or the like can be used.

The green phosphors70are excited by primary light radiated from the blue light-emitting LED chips8, and radiate light with a peak luminous wavelength in a green region. The green phosphors are not particularly limited as long as they are used in a wavelength conversion unit of the light-emitting device. For example, a phosphor represented by a general formula (1): (M1)3-xCex(M2)5O12(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) or the like can be used. The “green region” means a region with a wavelength equal to or longer than 500 nm and equal to or shorter than 580 nm.

A half-width of a fluorescent spectrum of a green phosphor is preferably wider when a green phosphor of one type is used (for example, in the case of general lighting purpose), and is preferably, for example, equal to or longer than 95 nm. A phosphor with Ce as an activator, for example, a Lu3-xCexAl5O12-based green phosphor represented by the general formula (1), has a garnet crystal structure. This phosphor uses Ce as an activator, allowing a fluorescent spectrum with a wide half-width (a half-width equal to or longer than 95 nm) to be acquired. Thus, the phosphor with Ce as an activator is a suitable green phosphor for acquiring high color rendering properties.

The light-emitting unit may contain an additive such as, for example, SiO2, TiO2, ZrO2, Al2O3, or Y2O3, other than the light-transmitting resin, the green phosphors, and the red phosphors. If the light-emitting unit contains an additive as described above, it is possible to acquire an effect of inhibiting settling of phosphors such as the green phosphors and the red phosphors or an effect of efficiently diffusing light from the blue light-emitting LED chips, the green phosphors, and the red phosphors.

A light-emitting device according to a second embodiment is described by usingFIG. 5andFIG. 6.FIG. 5is a transparent plan view schematically depicting the light-emitting device according to the second embodiment.FIG. 6is a schematic perspective view of the light-emitting device ofFIG. 5.

As depicted inFIG. 5andFIG. 6, a light-emitting device21includes a reflector22formed of a housing with an opening at the top, an anode electrode terminal23and a cathode electrode terminal24provided on side walls of the reflector22, and a first light-emitting unit205at one location and second light-emitting units206at two locations electrically connected to the anode electrode terminal23and the cathode electrode terminal24and provided in parallel inside the reflector22. The first light-emitting unit205and the second light-emitting units206are alternately and adjacently arranged.

As depicted inFIG. 5, the first light-emitting unit205includes second red phosphors61, green phosphors70, a blue light-emitting LED chip8a, and a light-transmitting resin16. The anode electrode terminal23, one blue light-emitting LED chip8a, and the cathode electrode terminal24are electrically connected in the above-described sequence via wire20.

As depicted inFIG. 5, the second light-emitting unit206includes first red phosphors60, second red phosphors61, green phosphors70, a blue light-emitting LED chip8b, and the light-transmitting resin16. The anode electrode terminal23, one blue light-emitting LED chip8b, and the cathode electrode terminal24are electrically connected in the above-described sequence via the wire20.

In the light-emitting device21, the first light-emitting unit205and the second light-emitting units206emit light by power supply from a single power source. Light emitted from the first light-emitting unit205and lights emitted from the second light-emitting units206are mixed and emitted outside as light from the light-emitting device21.

In the light-emitting device21, the blue light-emitting LED chip8aincluded in the first light-emitting unit205and the blue light-emitting LED chips8bincluded in the second light-emitting unit206have different amounts of change in forward-direction current with respect to the amount of change in voltage applied to each blue light-emitting LED chip (forward current-forward voltage characteristics). Therefore, when the magnitude of current applied to the light-emitting device21is changed, the color temperature of light emitted from the first light-emitting unit205and the color temperature of lights emitted from the second light-emitting units206are not changed, but a luminous flux ratio of light emitted from each light-emitting unit is changed. Therefore, by changing the magnitude of current applied to the light-emitting device21, the color temperature of light from the entire light-emitting unit, that is, mixed light of lights emitted from the first light-emitting unit205and the second light-emitting unit206, can be changed.

In the light-emitting device21, the first light-emitting unit205and the second light-emitting units206are provided inside the reflector22. This causes light radiated from the blue light-emitting LED chips8aand8b, the red phosphors60and61, and the green phosphors70to the sides of the light-emitting device to be diffused and reflected on the surface of the reflector and distributed to an axial direction of the light-emitting device. Therefore, the light emission intensity on the axis of the light-emitting device becomes high, allowing a light-emitting device with excellent light directivity to be acquired.

The reflector is formed of a housing with an opening at the top. At least an inner surface of the housing is made of a material with excellent light reflection properties or covered with a material with excellent light reflection properties. As the material of the reflector, for example, a polyamide-based resin, liquid-crystal polymer, silicone, or the like can be used.

The shape of the reflector is not particularly limited as long as it is a housing with an opening at the top and can distribute lights emitted from the blue light-emitting LED chips to the axial direction of the light-emitting device. For example, a shape formed by hollowing out a rectangular parallelepiped into a cone shape, a shape formed by hollowing out a cylinder into a cone shape, a shape formed by hollowing out a rectangular parallelepiped into a barrel shape (semi-columnar shape), or the like can be used.

Any size of the reflector can be selected as appropriate in accordance with the purpose of a lighting device for use. The size of the opening can be formed in, for example, a rectangle with each side equal to or longer than 2 mm and equal to or shorter than 20 mm, preferably equal to or longer than 3 mm and equal to or shorter than 6 mm, or a circle with a diameter equal to or longer than 2 mm and equal to or shorter than 20 mm, preferably equal to or longer than 3 mm and equal to or shorter than 6 mm. The depth of the space inside the housing can be, for example, equal to or longer than 1 mm and equal to or shorter than 5 mm.

The anode electrode terminal23and the cathode electrode terminal24are electrodes for external connection (for example, for the purpose of power supply). Note that the anode electrode terminal23and the cathode electrode terminal24correspond to the anode electrode land13and the cathode electrode land14, respectively, of the first embodiment. That is, in the second embodiment, the electrode lands are referred to as electrode terminals. The anode electrode terminal23and the cathode electrode terminal24are made of a material such as Ag—Pt. The anode electrode terminal23and the cathode electrode terminal24are each provided so as to be at least partially exposed to the outside of the reflector22. Inside the reflector22, the anode electrode terminal23and the cathode electrode terminal24are connected to leads11, and the leads11are electrically connected to the blue light-emitting LED chips8aand8bvia the wires20.

The leads11are formed of a copper alloy or the like, with their surface formed of Ag plating or the like.

The first light-emitting unit205and the second light-emitting units206(hereinafter also referred to as a “light-emitting unit” including both units) include the blue light-emitting LED chips8aand8b, the light-transmitting resin16, and the green phosphors and the red phosphors uniformly dispersed in the light-transmitting resin. As the light-transmitting resin, the green phosphors, and the red phosphors, those similar to those in the first embodiment can be used.

In the light-emitting device21depicted inFIG. 5, the first light-emitting unit205and the second light-emitting units206are arranged inside the reflector22with a rectangular opening. Note that the shape of the opening is not limited to the rectangle, and any shape can be adopted, such as a quadrangle such as a square or rhombus, circle, oval, polygon, or the like.

Of sections acquired by dividing the opening of the reflector22into three by straight lines, the first light-emitting unit205is arranged in a section arranged at center, and the second light-emitting units206at two locations are arranged in second sections arranged on both sides of the first section. InFIG. 5, the first light-emitting unit205and the second light-emitting units206are adjacent on boundary lines, and lights emitted from the light-emitting units of the respective first light-emitting unit205and second light-emitting units206thus become easily mixed, allowing the entire light-emitting unit to emit light at a more uniform color temperature. Note that although the first light-emitting unit205and the second light-emitting units206are preferably arranged adjacently, the first light-emitting unit and the second light-emitting units do not have to make contact with each other as long as lights emitted from the light-emitting units of the respective first light-emitting unit and second light-emitting units can be mixed together. In this case, the first light-emitting unit and the second light-emitting units are preferably arranged in a distance as near as lights emitted from the respective light-emitting units can be sufficiently mixed together.

The shape of a top plane of the entire light-emitting unit including the first light-emitting unit and the second light-emitting units is not limited to the rectangle as inFIG. 5as long as lights emitted from the light-emitting units of the respective first light-emitting unit and second light-emitting units can be mixed together. For example, as the shape of the top plane of the entire light-emitting unit, any shape can be adopted, such as a circle, oval, or polygon. The shape of each of the first light-emitting unit and the second light-emitting units arranged inside the entire light-emitting unit is also not particularly limited. For example, it is preferable so that the surface area of the first light-emitting unit and the surface area of the second light-emitting unit are equal to each other. Also, if the color temperatures of lights emitted from the light-emitting units of the respective first light-emitting unit and second light-emitting units can be adjusted, the surface area of the first light-emitting unit and the surface area of the second light-emitting unit may be different.

Arrangement of the first light-emitting unit and the second light-emitting units is not particularly limited as long as lights emitted from the light-emitting units of the respective first light-emitting unit and second light-emitting units can be mixed together. For example, the rectangular opening of the reflector is divided by a straight line into two, and the first light-emitting unit can be arranged in one section, and the second light-emitting units can be arranged in other two sections. Also, the first light-emitting unit is formed in a circular shape, and the second light-emitting units can be arranged in a donut shape so as to surround the outer periphery of the first light-emitting unit. According to this, lights emitted from the light-emitting units of the respective first light-emitting unit and second light-emitting units become easily mixed, allowing the entire light-emitting unit to emit light at a more uniform color temperature.

As the blue light-emitting LED chips8aand8b, those similar to the blue light-emitting LED chips8of the first embodiment can be used. However, the blue light-emitting LED chips8aincluded in the first light-emitting unit and the blue light-emitting LED chips8bincluded in the second light-emitting unit have different amounts of change in forward-direction current with respect to the amount of change in voltage applied to each blue light-emitting LED chip (forward current-forward voltage characteristics). Therefore, with respect to the amount of change in magnitude of current applied to the light-emitting device21, the amount of change in luminous flux of light emitted from the first light-emitting unit205and the amount of change in luminous flux of light emitted from the second light-emitting unit206are different. Thus, by changing the magnitude of current applied to the light-emitting device21, the color temperature of light emitted from the first light-emitting unit205and the color temperature of light emitted from the second light-emitting unit206are not changed, but a luminous flux ratio of light emitted from each light-emitting unit is changed, and thus the color temperature of light emitted from the entire light-emitting device is changed.

In the light-emitting unit, part of primary light (for example, blue light) radiated from the blue light-emitting LED chips8aand8bis converted by the green phosphors and the red phosphors into green light and red light. Thus, the light-emitting device according to the present embodiment emits light with the primary light, the green light, and the red light mixed together, and suitably emits white-based light. Note that a mixture ratio of the green phosphors and red phosphors is not particularly restricted, and the mixture ratio is preferably set so that a desired characteristic is achieved.

In the present embodiment, it is possible to dispense with means which connects resistors to the leads11to change the magnitude of current flowing through the first light-emitting unit205and the second light-emitting units206. Therefore, the light-emitting device21can decrease a power loss due to resistors and can have excellent luminous efficiency even if the value of the applied current increases.

When the current flowing through the light-emitting unit is set to have a rated current value, the color temperature (hereinafter also referred to as Tcmax) of light emitted from the entire light-emitting device with a mixture of light emitted from the first light-emitting unit and the light emitted from the second light-emitting units is preferably 2700 K to 6500 K. If the magnitude of current is set smaller than the rated current value, the luminous fluxes of lights emitted from the first light-emitting unit and the second light-emitting units become smaller, the luminous flux of light emitted from the entire light-emitting device (light-emitting unit) becomes smaller, and the color temperature is decreased. With the luminous flux of light emitted from the entire light-emitting device being taken as 100% when the current flowing through the light-emitting unit is set to have a rated current value and the luminous flux of light emitted from the entire light-emitting device being adjusted to be 20% by making the magnitude of current smaller, the color temperature of light emitted from the entire light-emitting device is preferably smaller than Tcmax by 300 K or more, in view of allowing acquirement of a wide range of color temperatures.

A modification example of the light-emitting device according to the second embodiment is described by usingFIG. 7andFIG. 8.FIG. 7is a transparent plan view of the modification example of the light-emitting device ofFIG. 5.FIG. 8is a schematic perspective view of the light-emitting device ofFIG. 7.

A light-emitting device31depicted inFIG. 7andFIG. 8basically includes a structure similar to that of the light-emitting device21depicted inFIG. 5andFIG. 6. In the structure of the light-emitting device31, differences from the light-emitting device21are that a first light-emitting unit305at one location and a second light-emitting unit306at one location are included inside the reflector22, that five blue light-emitting LED chips8aconnected in series are included in the first light-emitting unit305, and that five blue light-emitting LED chips8bconnected in series are included in the second light-emitting unit306. In the light-emitting device31, the first light-emitting unit305and the second light-emitting unit306have the same number of blue light-emitting LED chips8aor8bwith different forward current-forward voltage characteristics. Thus, when the magnitude of current applied to the light-emitting device31is changed, the color temperature of light emitted from the first light-emitting unit305and the color temperature of light emitted from the second light-emitting unit306are not changed, but a luminous flux ratio of light emitted from each light-emitting unit is changed. Therefore, the color temperature of light from the entire light-emitting unit, that is, mixed light of lights emitted from the first light-emitting unit305and the second light-emitting unit306, can be changed.

In the present modification example, the numbers of blue light-emitting LED chips8aand8bin series inside the first light-emitting unit305and the second light-emitting unit306may be any number equal to or larger than two as long as they are the same. Also, the number of the first light-emitting units and the number of second light-emitting units arranged in parallel are not particularly limited, and may be the same or different.

FIG. 9is a plan view schematically depicting a light-emitting device according to a third embodiment of the present invention.

A light-emitting device600according to the present embodiment basically includes a structure similar to that of the light-emitting device1according to the first embodiment. Differences from the first embodiment are that five first piece light-emitting units601are connected in series on a wiring K1in a first light-emitting unit61, that five second piece light-emitting units602are connected in series on a wiring K2in a second light-emitting unit62, that the first piece light-emitting units601and the second piece light-emitting units602are not adjacent and are arranged in a distance as near as lights emitted from the respective piece light-emitting units can be sufficiently mixed together, that an anode electrode land621and a cathode electrode land620each have a shape of a right-angled triangle with two orthogonal sides installed in parallel with substrate end sides of a substrate610, and that the wirings K1and K2are directly connected to the anode electrode land621and the cathode electrode land620.

As depicted inFIG. 9, the light-emitting device600includes the anode electrode land621, the cathode electrode land620, and the wirings K1and K2connecting the anode electrode land621and the cathode electrode land620, arranged on the substrate610. The light-emitting unit61includes the five first piece light-emitting units601electrically connected in series on the wiring K1and the five second piece light-emitting units602electrically connected in series on the wiring K2. The first piece light-emitting units601and the second piece light-emitting units602are arranged in a distance as near as lights emitted from the respective piece light-emitting units can be sufficiently mixed together, and light emitted from the entire light-emitting device thus becomes light at a uniform color temperature. A distance between the first piece light-emitting units and the second piece light-emitting units is such that a minimum distance between outer peripheries of the respective piece light-emitting units is preferably equal to or shorter than 28 mm, further preferably equal to or shorter than 22 mm. If the distance between the first piece light-emitting units and the second piece light-emitting units is equal to or shorter than 28 mm, lights emitted from the respective first light-emitting unit and second light-emitting unit can be sufficiently mixed together.

The plurality of first piece light-emitting units601can each include blue light-emitting LED chips, red phosphors, green phosphors, and a light-transmitting resin. The plurality of second piece light-emitting units602can each include blue light-emitting LED chips, red phosphors, green phosphors, and a light-transmitting resin.

When the number of blue light-emitting LED chips included in each of the first piece light-emitting units601and the number of blue light-emitting LED chips included in each of the second piece light-emitting units602are the same and the blue light-emitting LED chips included in the first piece light-emitting unit601and the blue light-emitting LED chips603included in the second piece light-emitting unit602have different amounts of change in forward-direction current with respect to the amount of change in voltage applied to each blue light-emitting LED chip (forward current-forward voltage characteristics), if the magnitude of current applied to the light-emitting device600is changed, the color temperature of light emitted from the first piece light-emitting unit601and the color temperature of light emitted from the second piece light-emitting unit602are not changed, but a luminous flux ratio of light emitted from each piece light-emitting unit is changed. Therefore, the color temperature of light emitted from the entire light-emitting unit, that is, mixed light of lights emitted from the plurality of first piece light-emitting units601and the plurality of second piece light-emitting units602, can be changed.

In the present embodiment, it is possible to dispense with means which connects resistors to the wiring K1and the wiring K2to change the magnitude of current flowing through the first light-emitting unit61and the second light-emitting unit62. Therefore, the light-emitting device600can decrease a power loss due to resistors and can have excellent luminous efficiency even if the value of the applied current increases.

The anode electrode land621and the cathode electrode land620each have a shape of a right-angled triangle, and each electrode land thus allows external terminal connection from three directions.

FIG. 10is a plan view of a modification example of the light-emitting device according to the third embodiment of the present invention. In the present modification example, four first piece light-emitting units701are connected in series on a wiring K1in a first light-emitting unit71, and five first piece light-emitting units702are connected in series on a wiring K2in a second light-emitting unit72. That is, in the present modification example, the number of first piece light-emitting units connected in series and the number of second piece light-emitting units connected in series are different.

When the number of blue light-emitting LED chips included in each of the first piece light-emitting units701and the number of blue light-emitting LED chips included in each of the second piece light-emitting units702are the same and the blue light-emitting LED chips included in the first piece light-emitting unit701and the blue light-emitting LED chips included in the second piece light-emitting unit702have different amounts of change in forward-direction current with respect to the amount of change in voltage applied to each blue light-emitting LED chip (forward current-forward voltage characteristics), if the magnitude of current applied to the light-emitting device700is changed, the color temperature of light emitted from the first piece light-emitting unit701and the color temperature of light emitted from the second piece light-emitting unit702are not changed, but a luminous flux ratio of light emitted from each piece light-emitting unit is changed. Therefore, the color temperature of light emitted from the entire light-emitting unit, that is, mixed light of lights emitted from the plurality of first piece light-emitting units701and the plurality of second piece light-emitting units702, can be changed.

In the present modification example, the blue light-emitting LED chips included in the first piece light-emitting unit701and the blue light-emitting LED chips included in the second piece light-emitting unit702have the same amount of change in forward-direction current with respect to the amount of change in voltage applied to each blue light-emitting LED chip (forward current-forward voltage characteristics), but each number of piece light-emitting units is different. Thus, by changing current applied to the light-emitting device, the color temperature of light from the entire light-emitting unit can be changed.

The number of blue light-emitting LED chips included in each of the first piece light-emitting units701and the number of blue light-emitting LED chips included in each of the second piece light-emitting units702can be any as long as the number is equal to or larger than one.

As long as the number of first piece light-emitting units and the number of second piece light-emitting units are different, either of the numbers of light-emitting units may be larger. The first piece light-emitting units and the second piece light-emitting units may be each arranged inside the reflector, or may be of a surface-mounting type or in a dome shape.

FIG. 11is a transparent plan view schematically depicting a light-emitting device according to a fourth embodiment.

A light-emitting device41according to the present embodiment basically includes a structure similar to that of the light-emitting device1according to the first embodiment. Differences from the first embodiment are that a donut-shaped second light-emitting unit406is arranged so as to surround the periphery of a circular first light-emitting unit405, that six blue light-emitting LED chips8are connected in series in the first light-emitting unit405, that eight blue light-emitting LED chips8are connected in series in the second light-emitting unit406, that a wiring K1and a wiring K2each have its one end connected to a wiring pattern25aand the other end connected to a wiring pattern25b.

In the present embodiment, the first light-emitting unit405and the second light-emitting unit406are concentrically arranged, and light emitted from the entire light-emitting device thus becomes more uniform light in all directions.

FIG. 12is a transparent plan view of a modification example of the light-emitting device41according to the fourth embodiment. As depicted inFIG. 12, in a light-emitting device51, a resin dam210is provided between the first light-emitting unit405and the second light-emitting unit406. According to this, it is possible to inhibit a mixture of a light-transmitting resin including phosphors forming the first light-emitting unit405and a light-transmitting resin including phosphors forming the second light-emitting unit406and inhibit mixture and intrusion of the phosphors included in each light-emitting unit.

FIG. 13is a plan view schematically depicting a light-emitting device according to a fifth embodiment.

A light-emitting device81according to the present embodiment basically includes a structure similar to that of the light-emitting device700according to the modification example of the third embodiment. Differences from the light-emitting device700are that six circular first piece light-emitting units801are arranged on the circumference of the same circle and that eight circular second piece light-emitting units802are arranged outside the circumference formed of the first piece light-emitting units801.

In the present embodiment, six first piece light-emitting units801and eight second piece light-emitting units802are arranged on the circumferences of concentric circles, and light emitted from the entire light-emitting device thus becomes more uniform in all directions.

EXAMPLES

The present invention is further specifically described based on examples. However, the present invention is not limited by these examples.

First Example

In a first example, tests were performed by using a light-emitting device configured similarly to that ofFIG. 1andFIG. 2of the first embodiment.

As the substrate7, a ceramic substrate was used. In the first light-emitting units5and the second light-emitting units6, the first red phosphors60(CaAlSiN3:Eu), the second red phosphors61((Sr, Ca)AlSiN3:Eu), the green phosphors70(Lu3Al5O12:Ce), and the blue light-emitting LED chips8(with a luminous wavelength of 450 nm) are sealed with a silicone resin. The viscosity of the phosphor-containing silicone resin forming the first light-emitting unit5is larger than the viscosity of the phosphor-containing silicone resin forming the second light-emitting unit6. Therefore, the second light-emitting units6were formed after the first light-emitting units5were formed.

In each of the first light-emitting units5at two locations, nine blue light-emitting LED chips8are connected in series. In each of the second light-emitting units6at three locations, ten blue light-emitting LED chips8are connected in series. The blue light-emitting LED chips8are electrically connected via the wires20to any of the wiring patterns25a,25b, and25c. The wiring pattern25ais electrically connected to the anode electrode land13via the lead wiring4. The wiring pattern25bis electrically connected to the cathode electrode land14via the lead wiring3. The wiring pattern25cis electrically connected to the cathode electrode land14via the lead wiring2.

The light-emitting device of the first example is formed so that the color temperature of light emitted from the first light-emitting unit5is 2000 K and the color temperature of light emitted from the second light-emitting unit6is 3000 K. Next, a relation between the magnitude of a total of forward-direction currents flowing through the first light-emitting units5and the second light-emitting units6(hereinafter also referred to as a total forward-direction current) and the color temperature of light emitted from the light-emitting device was studied.

The color temperature of light emitted from the entire light-emitting device when a total forward-direction current of 350 mA flew was 2900 K, and the color temperature of light emitted from the entire light-emitting device when a total forward-direction current of 50 mA flew was 2000 K.

FIG. 4is a graph depicting a relation between relative luminous flux (%) of light and color temperature when the total forward-direction current is changed, with the luminous flux of light emitted from the entire light-emitting device at the time of a total forward-direction current of 350 mA being taken as 100%. FromFIG. 4, it can be found that the color temperature decreases when the relative luminous flux decreases.

It should be understood that the embodiments and the examples disclosed this time are exemplarily made illustrative in all aspects and are not restrictive. The scope of the present invention is indicated not by the above-described embodiments but by the scope of the claims for patent, and is intended to include all modifications within the sense and scope of the equivalents of the scope of the claims for patent.

REFERENCE SIGNS LIST