Patent Application
20170102139
This application claims the benefit of priority of Japanese Patent Application Number 2015-201570 filed on Oct. 9, 2015, the entire content of which is hereby incorporated by reference.
1. Technical Field
The present disclosure relates to a lighting device and a lighting apparatus.
2. Description of the Related Art
A lighting device is known that emits white light by converting portion of blue light from a light source (laser diode (LD)) or a light emitting diode (LED) into yellow light using a phosphor (for example, see Japanese Patent No. 5,556,256).
However, from the viewpoint of supporting installation in various places, aesthetics, and manufacturing costs, there is a need to reduce the size of lighting devices.
The amount of heat produced by the phosphor upon converting the color (wavelength) of the light increases with the intensity of the light that excites the phosphor. Typically, the light converting performance of phosphor degrades in high temperature environments. Thus, there is a demand for a lighting device that avoids a degradation in light converting performance by efficiently dissipating heat generated by the phosphor out of the lighting device to inhibit the phosphor from increasing in temperature. The amount of heat dissipated out of the lighting device is typically increased by increasing the surface area of the heat dissipation mechanism in the lighting device, but increasing the surface area of the heat dissipation mechanism is problematic in that doing so increases the overall size of the lighting device, which is contradictory to the above-described need to reduce the size of lighting devices.
In light of this, the present disclosure has an object to provide a lighting device that both avoids an increase in overall size and efficiently dissipates heat.
In order to achieve the above object, a lighting device according to one aspect of the present disclosure includes: a substrate that is light transmissive and has one or more regions in which a phosphor layer is formed; a heat transfer plate having a first surface in surface-to-surface contact with a surface of the substrate and flaying one or more first apertures overlapping the one or more regions; and a heat dissipation plate having a surface in surface-to-surface contact with a second surface of the heat transfer plate opposite the first surface and having a second aperture overlapping the one or more first apertures.
With the lighting device according to the present disclosure, it is possible to avoid an increase in overall size and efficiently dissipate heat.
The figures depict one or more implementations in accordance with the present teaching, by way of examples only, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements.
The following describes a lighting device according to an embodiment of the present disclosure with reference to the drawings. Note that the embodiment described below shows a specific, preferred example of the present disclosure. The numerical values, shapes, materials, elements, the arrangement and connection of the elements, steps, order of the steps, etc.., indicated in the following embodiment are mere examples, and therefore do not intend to limit the inventive concept. Therefore, among the elements in the following embodiment, those not recited in any of the independent claims defining the most generic part of the inventive concept; are described as optional elements. Also note that the drawings are schematic in nature and not necessarily precise illustrations.
In this embodiment, a lighting device that both avoids an increase in overall size and efficiently dissipates heat will be described. Note that like reference signs indicate like elements. As such, overlapping descriptions may be omitted. Also note that the XYZ coordinate axes illustrated in the drawing's may be referenced in the following description
As illustrated in
Light source S is a light source that emits light, and is, for example, a laser diode (LD) or a light emitting diode (LED). More specifically, light source S is an LD or LED that emits blue light, but light source S may emit light of a different color.
Optical fiber F has a two-part structure configured of a core with a high refractive index and cladding with a low refractive index surrounding the core. Optical fiber F functions as a light transmission path for guiding light from light source S to lighting device 10. The core and the cladding are both made of quartz glass or plastic that is highly light transmissive.
Lighting device 10 illuminates its surrounding region by emitting out light transmitted from light source S via optical fiber F. Lighting device 10 has a phosphor layer that converts the color (wavelength) of all or a portion of the light received from optical fiber F. For example, phosphor layer is configured of a yellow phosphor, which converts blue light into yellow light, sealed with, for example, resin. In this case, lighting device 10 produces, and illuminates its surrounding area with, white light as a result of the yellow phosphor converting a portion of the blue light transmitted from light source S into yellow light.
Hereinafter, the configuration of lighting device 10 will be described in detail.
As illustrated in
Fiber coupling 12 is an optical component that is connected to optical fiber F and guides, into lighting device 10, light transmitted in the positive direction along the Z axis from light source S via optical fiber F.
Lens 14 is an optical component that changes the path of light incident thereon from fiber coupling 12.
Lens array 15 is an optical component that changes the path of light transmitted through lens 14. More specifically, lens array 15 changes (separates) the path of light by splitting light incident thereon into plurality of paths (for example, three) such that the paths of the split light are incident on phosphor component 20 in mutually different positions. The specific configuration of lens array 15 will he described later with a specific example. Note that lens array 15 may be disposed between fiber coupling 12 and phosphor component 20. In particular, lens array 15 may be disposed so as to be in contact with lens 14, and may be coupled with a portion of lens 14 (that is to say, may be integrally formed with lens 14).
Holder 16 is an enclosure that houses the elements of lighting device 10.
Phosphor component. 20 includes a phosphor that receives light transmitted through lens array 15, converts the color of the received, light, and emits the converted light. In addition to phosphor, phosphor component 20 also includes a heat transfer plate and a heat dissipation plate that function as a heat dissipation mechanism that dissipates heat generated by the phosphor out of lighting device 10. Configurations of these will be described in detail later.
Lens 30 is an optical component that adjusts the distribution properties of light from phosphor component 20 as it exits lighting device 10 (in the positive direction along the Z axis). Depending on its shape, lens 30 either reduces or increases the distribution angle of exiting light. A lens having light distribution properties appropriate for the usage of lighting device 10 may he used as lens 30.
Hereinafter, the configuration of phosphor component 20, etc., of lighting device 10 will be described in detail.
As illustrated in
Substrate 22 is light transmissive. Light from light source S is emitted onto substrate 22 via optical fiber F. Substrate 22 has a region which phosphor layer 24 is provided. Phosphor layer 24 changes the color of light received from light source S via optical fiber F. Phosphor layer 24 is exemplified as being coated onto substrate 22, but the method of forming phosphor layer 24 on substrate 22 is not limited, to this example. Note that the surface having the region in which phosphor layer 24 is coated is also referred to as the first surface, and the surface on the reverse side of substrate 22 is also referred to as the second surface. Moreover, light from optical fiber F is also exemplified as exiting substrate 22 through the second surface. Substrate 22 is, for example, a sapphire substrate.
Substrate 22 may be made of an arbitrary material such as glass or plastic. Here, the glass may be, for example, soda glass or alkali-free glass. Moreover, the plastic may be, for example, acrylic resin, polycarbonate, polyethylene terephthalate (PET), or polyethylene naphthalate (PEN). When substrate 22 is made of a material that is transparent and does not absorb light—that is to say, made of a material having an extinction coefficient of approximately zero—there is an advantage in that the amount of light that transmits through substrate 22 can be increased, resulting in an increase in light illuminating the region surrounding lighting device 10.
Phosphor layer 24 is a wavelength converting material that receives light from light source S via optical fiber and fiber coupling 12, and converts the color (wavelength) of the received light with phosphor particles. Phosphor layer 24 generates heat upon converting the color of the light.
More specifically, phosphor layer 24 includes yellow phosphor particles, such as yttrium aluminum garnet (YAG) phosphor particles, which receive blue light from light source S and emit yellow light, and a resin, such as silicon or epoxy, which seals the phosphor particles. Phosphor layer 24 produces white light as a result of the yellow light converted from a portion of the blue light from light source S by the phosphor particles and the unconverted, remaining blue light mixing together, and emits the produced white light in the positive direction along the Z axis. Typically, the color converting efficiency of phosphor layer 24 decreases (degrades) in high temperature environments. In light of this, lighting device 10 inhibits phosphor layer 24 from reaching high temperatures by sufficiently dissipating heat generated by phosphor layer 24, out of lighting device 10 via heat transfer plate 26 and heat dissipation plate 28 functioning as a heat dissipation mechanism. Note that a material having a high rate of heat conductivity, such as an inorganic oxide like ZnO, may he mixed into the resin included in phosphor layer 24 to increase heat dissipation.
Heat transfer plate 26 is a heat transfer body in the form of a plate, and transfers heat generated by phosphor layer 24 to heat dissipation plate 28. Heat transfer plate 26 has a surface in surface-to-surface contact with a surface of substrate 22, and inhibits phosphor layer 24 from reaching high temperatures by absorbing heat generated by phosphor layer 24 via substrate 22, and further transferring that heat to heat dissipation plate 28. Moreover, in sections in direct contact with phosphor layer 24, heat transfer plate 26 absorbs heat from phosphor layer 24 directly rather than through substrate 22. This inhibits phosphor layer 24 from reaching high temperatures. Heat transfer plate 26 is made of a metal having a relatively high rate of heat transfer (for example, aluminum or copper), or another material having a relatively high rate of heat transfer (for example, ceramic or resin). The surface of heat transfer plate 26 that is in contact with heat dissipation plate 28 is referred to as the first surface, and the surface that is in contact with substrate 22 on the reverse side of the first surface is referred to as the second surface. Heat transfer plate 26 is disposed such that its second surface is in surface-to-surface contact with the surface of substrate 22 that is coated with phosphor layer 24, and includes aperture 27 in a location that overlaps a region in which phosphor layer 24 is applied on the second surface.
Aperture 27 is for transmitting, in the positive direction along the Z axis, light passing through or produced by phosphor layer 24. More specifically, aperture 27 is located on an extension of a path of the blue light received by phosphor layer 24, and transmits white light produced from the blue light received by phosphor layer 24 and the yellow light produced by the conversion by phosphor layer 24. Note that aperture 27 corresponds to the first aperture.
Heat dissipation plate 28 is disposed so as to have a surface in surface-to-surface contact with the first surface of heat transfer plate 26, and has aperture 29 in a location that overlaps aperture 27 of heat transfer plate 26. Heat dissipation plate 28 absorbs heat from phosphor layer 24 via heat transfer plate 26 and dissipates the absorbed heat out of lighting device 10. Note that ribs are formed on the surface of heat dissipation plate 28 to increase the surface area and thus more efficiently dissipate heat out of lighting device 10.
Aperture 29 is for transmitting, in the positive direction along the Z axis, light passing through or produced by phosphor layer 24—that is to say, light transmitted through aperture 27—to emit light out of lighting device 10. More specifically, aperture 29 is located on an extension of a path of light, and transmits, out of lighting device 10, white light transmitted through aperture 27 of heat transfer plate 26. Note that aperture 29 corresponds to the second aperture.
Note that the Z axis thickness of phosphor layer 24 is designed to be less than or equal to the Z axis thickness of heat transfer plate 26. Moreover, the Z axis thickness of phosphor layer 24 is designed to be essentially equal to the Z axis thickness of heat transfer plate 26—that is to say, designed such that the interface between phosphor layer 24 and heat dissipation plate 28 and the interface between heat transfer plate 26 and heat dissipation plate 28 are flush with one another. With this, heat dissipation plate 28 absorbs heat generated by phosphor layer 24 directly rather than through substrate 22 and heat transfer plate 26, which increases the amount, of heat transferred.
As illustrated in
As illustrated in
Moreover, apertures 27A, etc. collectively form a substantially circular shape, and heat transfer plate 26 may include heat transfer bodies 74A, 74B, and 74C (hereinafter also referred to as “heat transfer bodies 74A, etc.”) which divide apertures 27A, etc. With this, heat transfer bodies 74A, etc., can appropriately dissipate heat generated by phosphor layer 24 out of lighting device 10 by transferring the heat to peripheral region 52 of heat transfer plate 26.
Moreover, heat transfer bodies 74A, etc., may extend from central region 70 of to peripheral region 72 of the circular shape formed by apertures 27A, etc. More specifically, heat transfer bodies 74A, etc., may extend from central region 70 to peripheral region 72 of the circular shape formed by apertures 27A, etc in a substantially straight line—that is to say, may be arranged radially. Since light from lens array 15 is incident on substrate 22 in a location relatively close to central region 50, and since thermal paths from central region 50 to peripheral region 52 are relatively long, heat generated by phosphor layer 24 easily pools in the vicinity of central region 50 of substrate 22. In light of this, heat transfer bodies 74A, etc., arranged as described above, can appropriately dissipate heat generated by phosphor layer 24 out of lighting device 10 by transferring heat generated by phosphor layer 24 from central region 50 to peripheral region 52.
Note that heat transfer bodies 74A, etc. may be equiangularly spaced about central region 70. With this, unevenness in the directionality of thermal paths from central region 50 to peripheral region 52 of substrate 22 can be reduced, and the temperature of phosphor layer 24 can be reduced.
Next, results of a simulation evaluating heat transfer properties inside the above-described lighting device 10 will be described.
The cross section in
Note that the simulation is performed by evaluating the temperature of the phosphor layer in a steady state in which the temperatures of each component in lighting device reach an essentially steady value (i.e., a state in which the temperatures of the components are saturated) when each of the above lighting devices are placed in a 30 degrees Celsius environment while they are emitting light.
The results of the simulations show that the highest temperature values for the phosphor layers in related technologies 1, 2, 3, and lighting device 10 were 159.6 degrees Celsius, 146.9 degrees Celsius, 152.7 degrees Celsius, and 144.7 degrees Celsius, respectively.
As the results show, among the four lighting devices subjected to the simulation, phosphor layer temperature is the highest when neither heat transfer plate 26 nor heat dissipation plate 28 are included, such as in related technology 1, and thus is the least efficient; in terms of heat dissipation. When either heat transfer plate 26 or heat dissipation plate 28 is included, (related technologies 2 and 3), heat dissipation efficiency improves over related technology 1 by a certain amount. Finally, as the results show, since lighting device 10 includes both heat transfer plate 26 and heat dissipation plate 28 and thus heat generated by phosphor layer 24 can be efficiently dissipated out of lighting device 10, the phosphor layer temperature in lighting device 10 was the lowest of all simulation results.
Hereinafter, the specific configuration of lens array 15 will be described.
Lens array 15 is disposed between fiber coupling 12 and phosphor component 20, and splits and separates light guided into lighting device 10 from light source S via optical fiber F and fiber coupling 12, and emits the split and separated light toward phosphor component 20. Lens array 15 is one example of, for example, a microlens array, and includes, for example, substrate 141 and diffractive lens array 142, as illustrated in
Substrate 141 is a microlens array substrate. Diffractive lens array 142 is formed on substrate 141. Note that substrate 141 may be made of an arbitrary material such as glass or plastic, similar to substrate 22.
Diffractive lens array 142 splits and separates light guided into lighting device 10, and emits the split and separated light toward phosphor component 20. Diffractive lens array 142 has a serrated cross-sectional shape in a plane perpendicular to the surface of incidence of phosphor component 20. Moreover, diffractive lens array 142 includes a plurality of regions. Within each region, the grating is aligned in the same direction. The alignment of the grating is different for each region.
In this embodiment, diffractive lens array 142 is exemplified as including three regions 142A, 142B, and 142C (hereinafter also referred to as “regions 142A, etc.”) exhibiting mutually different grating alignment directions, as illustrated in
Moreover, in the three regions 142A, etc., of diffractive lens array 142, the direction in which the grating is aligned is different, as illustrated in
Note that the material, used for diffractive lens array 142 is selected depending on the formation method, heat resistibility, and index of refraction of diffractive lens array 142. Methods of forming diffractive lens array 142 include, for example, nano printing, printing, photolithography, electron beam lithography, and particle orientation. Regarding the material used for diffractive lens array 142, when diffractive lens array 142 is formed by, for example, non printing or printing, an epoxy or acrylic resin may be selected as a UV curing resin, or polymethyl methacrylate (PMMA) may be selected as a thermoplastic resin. Moreover, taking into account heat resistance, glass or quartz may be selected as the material used for diffractive lens array 142, and diffractive lens array 142 may be formed by photolithography or electron beam lithography. Moreover, diffractive lens array 142 may be formed using a material having approximately the same refractive index as substrate 141 so that light can more easily enter substrate 141. Furthermore, similar to substrate 141, diffractive lens array 142 is preferably made of a material that is transparent and does not absorb light—that is to say, preferably made of a material having an extinction coefficient of approximately zero.
Next, paths of light inside lighting device 10 when the above-described diffractive lens array 142 is used will be described.
As illustrated in
Hereinafter, two variations of substrate 22 and heat transfer plate 26 will be described..
In this variation, a lighting device including a heat transfer plate having only one aperture will be described. Note that in the lighting device according to this variation, elements that are common with lighting device 10 according to the above embodiment have the same reference signs and description thereof is omitted.
Similar to lighting device 10, the lighting device according to this variation includes fiber coupling 12, lens 14, lens 30, lens array 15, holder 16, and phosphor component 20. Moreover, phosphor component 20 includes substrate 82, phosphor layer 24, heat transfer plate 86, and heat dissipation plate 28. All of the above elements except substrate 82 and heat transfer plate 86 are the same as the elements sharing the same name in the above embodiment, and as such, detailed description thereof will be omitted.
Substrate 82 is a light transmissive substrate having only one region in which phosphor layer 84 is disposed. Phosphor layer 84 receives, from the surface 82B side, beams of light 42A, 42B, and 42C (
Heat transfer plate 86 is disposed such that its second surface is in surface-to-surface contact with the surface of substrate 82 that is coated with phosphor layer 84, and includes one aperture 87 in the second surface in a location that overlaps a region in which the single phosphor layer 84 is applied. Aperture 87 is for transmitting, in the positive direction along the Z axis, light passing through or produced by phosphor layer 84.
The lighting device according to this variation can efficiently transfer heat generated by phosphor layer 84 to heat dissipation plate 28 via heat. transfer plate 86. In other words, the lighting device according to this variation can increase heat dissipation efficiency with heat, transfer plate 86.
In this variation, a lighting device including a heat transfer plate having two apertures will be described. Note that in the lighting device according to this variation, elements that are common with lighting device 10 according to the above embodiment have the same reference signs and description thereof is omitted.
Similar to lighting device 10, the lighting device according to this variation includes fiber coupling 12, lens 14, lens 30, lens array 15, holder 16, and phosphor component 20. Moreover, phosphor component 20 includes substrate 92, phosphor layer 24, heat transfer plate 96, and heat dissipation plate 28. All of the above elements except substrate 92 and heat transfer plate 96 are the same as the elements sharing the same name in the above embodiment, and as such, detailed description thereof will be omitted.
Substrate 92 is a light transmissive substrate having two regions in. which phosphor layer 94A and phosphor layer 94B are disposed, respectively. Phosphor layers 94A and 94B receive, from the surface 92B side, beams of light that have been introduced into lighting device 10 from optical fiber F and transmitted through lens array 15.
Heat transfer plate 96 is disposed such that its second surface is in surface-to-surface contact with a surface of substrate 92 coated with phosphor layers 94A and 9413, and includes apertures 97A and 97B in the second surface in a location that overlaps regions in which phosphor layers 94A and 94B are applied. Apertures 97A and 97B are for transmitting, in the positive direction along the Z axis, light passing through or produced by phosphor layers 94A and 94B.
The lighting device according to this variation can efficiently transfer heat generated by phosphor layers 94A and 94B to heat dissipation plate 28 via heat transfer plate 96. In other words, the lighting device according to this variation can increase heat dissipation efficiency with heat transfer plate 96.
As described above, lighting device 10 according to this embodiment includes: substrate 22 that is light transmissive and has one or more regions in which phosphor layer 24 is formed; heat transfer plate 26 having surface 26B in surface-to-surface contact with a surface of substrate 22 and having one or more apertures 27 overlapping the one or more regions; and heat dissipation plate 28 having a surface in surface-to-surface contact with surface 26A of heat transfer plate 26 opposite surface 2B and having aperture 29 overlapping the one or more apertures 27.
With this, heat generated upon phosphor layer 24 converting the wavelength of the light is absorbed by heat transfer plate 26 both directly and via substrate 22, and then transferred to heat dissipation plate 28. In this way, the inclusion of heat transfer plate 26 makes it possible to inhibit phosphor layer 24 from reaching high temperatures. Thus, with lighting device 10, it is possible to avoid an increase in overall size and efficiently dissipate heat.
For example, substrate 22 may have a plurality of the regions, and heat transfer plate 26 may have a plurality of apertures 27, each of which overlaps a different one of the plurality of regions.
With this, heat transfer plate 26 transfers heat generated by phosphor layer 24 to heat dissipation plate 28 even when phosphor layer 24 is disposed in a plurality of locations on substrate 22. Thus, with lighting device 10, it is possible to avoid an increase in overall size and efficiently dissipate heat.
For example, heat transfer plate 26 may have heat transfer bodies 74A, 74B, and 74C that extend from central, region 70 of heat transfer plate 26 to peripheral region 72 of heat transfer plate 26.
With this, heat transfer plate 26 transfers heat generated by phosphor layer 24 from central region 70 of heat transfer plate 26 to peripheral region 72 via heat transfer bodies as well as to heat dissipation plate 28. This makes it possible to inhibit central region 50 of phosphor layer 24, where heat generated by phosphor layer 24 easily pools, from reaching high temperatures.
For example, heat transfer bodies 74A, 74B, and 74C may be equiangularly spaced about central region 70.
With this, it is possible for heat transfer bodies 74A, 74B, and 74C to transfer heat evenly, without directional imbalance, from central region 70 of heat transfer plate 26 to peripheral region 72. This makes it possible to inhibit phosphor layer 24 from reaching high temperatures evenly, without directional imbalance from the perspective of central region 70 of heat transfer plate 26.
For example, an interface between phosphor layer 24 and heat dissipation plate 28 may be flush with an interface between heat transfer plate 26 and heat dissipation plate 28.
With this, heat dissipation plate 28 absorbs heat generated by phosphor layer 24 directly rather than through substrate 22 and heat transfer plate 26, which increases the amount of heat transferred. With this, phosphor layer 24 is can be further inhibited from reaching high temperatures.
For example, phosphor layer 24 may receive incident blue light and convert a portion of the received blue light into yellow light. The one or more apertures 27 of heat transfer plate 26 may be located on an extension of a path of the blue light received by phosphor layer 24, and transmit white light produced from the blue light received by phosphor layer 24 and the yellow light produced by the conversion by phosphor layer 24. Aperture 29 of heat dissipation plate 28 may be located on the extension of the path of the blue light, and transmit, in a direction leading out of lighting device 10, the white light transmitted through the one or more apertures 27 of heat transfer plate 26.
With this, lighting device 10 can use incident blue light to produce and emit out white light, and inhibit phosphor layer 24 from reaching high temperatures.
Lighting apparatus 1 according to the present embodiment includes: the above-described lighting device 10; light source S; and optical fiber F that guides light from light source S to lighting device 10. Phosphor layer 24 on substrate 22 in lighting device 10 receives the light guided by optical fiber F.
With this, lighting apparatus 1 achieves the same advantageous effects as lighting device 10.
Hereinbefore, a lighting device according to the present disclosure has been described based on the above embodiment, but the present disclosure is not limited to the above embodiment.
While the foregoing has described one or more embodiments and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may he implemented in various forms and examples, and that they may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all modifications and variations that fall within the true scope of the present teachings.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-201570 | Oct 2015 | JP | national |
