Patent Application
20200003370
The present disclosure relates to a lighting module and a lighting apparatus including the same.
In recent years, in the fields of illumination, semiconductor light-emitting devices have begun to replace incandescent lamps and fluorescent lamps. A typical example of a semiconductor light-emitting device is an LED (Light Emitting Diode). A semiconductor light-emitting device makes it possible to realize a lighting apparatus that has a long lifetime and is low in power consumption, as compared to incandescent lamps and fluorescent lamps.
Depending on the semiconductor material used, a semiconductor light-emitting device is able to emit light of various emission wavelengths.
Therefore, semiconductor light-emitting devices of various emission colors may be combined to realize a lighting apparatus that permits color tuning.
Because a semiconductor light-emitting device is smaller than an incandescent lamp or a fluorescent lamp, it is also possible to realize a lighting apparatus that is thin or small in size, and/or of an attractive design.
For example, Japanese Laid-Open Patent Publication No. 2015-50122 discloses a lighting apparatus that includes a daylight color LED, a warm-white color LED, and a red LED, thus being capable of color tuning.
One embodiment of the present disclosure provides a lighting module and a lighting apparatus that takes advantage of the characteristic aspects of semiconductor light-emitting devices as mentioned above.
A lighting module according to one embodiment includes: a mounting board; a plurality of first light sources arranged on the mounting board; and at least one second light source arranged on the mounting board.
A wavelength range or correlated color temperature of the plurality of first light sources is different from a wavelength range or correlated color temperature of the at least one second light source. The quantity of the first light sources is greater than the quantity of the second light sources, and each of the at least one second light source has a greater light distribution angle than a light distribution angle of each of the plurality of the first light sources.
The second light sources, which are fewer in number, have a greater light distribution angle. As a result, between the first light sources and the second light sources, difference in evenness in luminance distribution within the light emitting surface can be reduced. Because the quantity of second light sources to be mounted can be reduced, it is possible to reduce the manufacturing cost.
In the case where a lighting apparatus includes light sources of warm-white color and light sources of daylight color, the quantity of warm-white light sources, which are mainly used during nighttime, may be smaller than the quantity of daylight color light sources. But in this case, a smaller quantity of warm-white light sources is provided per unit area of the lighting apparatus. Thus, when only the warm-white light sources are turned on, uneven luminance of the lighting apparatus tends to occur, which may degrade the appearance of the lighting apparatus when color adjusted to warm-white.
In order to maintain the appearance, a cover to diffuse light from the light sources may be provided spaced apart from the light sources, for example. However, this configuration increases the thickness of the entire lighting apparatus and will result in the entire lighting apparatus being thick, thus hindering one characteristic aspect of a semiconductor light-emitting device, which is being smaller than an incandescent lamp or a fluorescent lamp.
It might also be possible to provide the same quantity of warm-white light sources as the quantity of daylight color light sources, and control the warm-white light sources to be dimly lit by decreasing the power supplied thereto. In this case, however, the quantity of warm-white light sources cannot be reduced, and a control circuit for dimming needs to be provided, and so on, thus making it difficult to reduce the cost of the lighting apparatus.
In view of the foregoing, the inventors have conceived of a lighting module and a lighting apparatus having a novel structure. Hereinafter, an example lighting module and an example lighting apparatus according to an embodiment will be described in detail. The embodiments shown below are intended as illustrative to give a concrete form to technical ideas of the present invention, and the scope of the invention is not limited to those described below.
The housing 21 supports and accommodates the lighting module 22 and the control circuit 23. The housing 21 supports the cover 24 at a predetermined interspace from the lighting module 22. In the present embodiment, the housing 21 includes, for example, a bottom portion 21e and four lateral portions 21a, 21b, 21c and 21d, such that the lighting module 22 and the control circuit 23 are disposed on one surface of the bottom portion 21e. The lighting module 22 and the control circuit 23 are located within a space that is created by the bottom portion 21e and the four lateral portions 21a, 21b, 21c and 21d. As shown in
The lighting module 22 includes plural types of light sources 26, which differ in wavelength range or correlated color temperature. The structure of the lighting module 22 will be described later in detail.
The control circuit 23 includes, for example, a power circuit 23a and a receiver circuit 23b. The power circuit 23a converts externally-received power to a voltage and current that is suitable for the light sources 26 being provided in the lighting module 22, and outputs the result to the lighting module 22. In response to a manual input from an operator, the control circuit 23 performs ON/OFF control of the light sources 26, control of an electric current value, and so on, thereby effecting color tuning of the light which goes out from the entire lighting module 22. Adjustment of the light intensity, i.e., dimming, may also be performed.
Instructions from an operator may be given with, for example, a remote control 25. The remote control 25 receives an input from the operator, and transmits a control signal which is based on the input. The receiver circuit 23b receives the control signal which is transmitted from the remote control 25, this control signal being output to the power circuit 23a.
The cover 24 closes the space which is created by the housing 21, thus dust or other foreign material is less likely to enter into the housing 21. In the case where light emitted from the light sources 26 of the lighting module 22 is transmitted through the cover 24, diffusion is effected to reduce unevenness of light from the lighting module 22. In other words, the cover 24 functions as a light-diffusing plate.
In the present embodiment, the first light sources 31 and the second light sources 32 are placed in a two-dimensional array on the mounting board 30. As shown in
As shown in
Thus, in the lighting module 22, the quantity of second light sources 32 is smaller than the quantity of first light sources 31, and also the array pitch is relatively larger in the second light sources 32. Therefore, when lighted, unevenness in the luminance distribution is greater in the second light sources 32 than in the first light sources 31. In order to reduce the unevenness in luminance distribution within the plane of the second light sources 32, each second light source 32 has a broader light distribution angle than does each of the first light sources 31. A more detailed description on the light distributions of the light sources will be described below.
In the present embodiment, light that is emitted by the first light sources 31 differs in wavelength range or correlated color temperature from light which is emitted by the second light sources 32. The first light sources 31 and the second light sources 32 emit light of different wavelength ranges or correlated color temperatures, so that the color of light emitted from the lighting apparatus 11 can be adjusted by selectively lighting the first light sources 31 and the second light sources 32, or adjusting the electrical power supplied to the first light sources 31 and the second light sources 32.
The first light sources 31 and the second light sources 32 may emit white light of correlated color temperatures that are different from each other. In this case, the correlated color temperature of the second light sources 32 is preferably lower than the correlated color temperature of the first light sources 31. For example, it is preferable that the first light sources 31 emit daylight-like white light and that the second light sources 32 emit warm-white light. As described earlier, the illumination that would be required in the nighttime might be darker than that in the daytime. Therefore, the quantity of second light sources 32 to emit warm-white light, which is mainly used for nighttime illumination, may be decreased, thereby reducing the cost associated with the lighting apparatus. “Warm-white color” refers, for example, to a correlated color temperature in a range of 2000K to 4500K, and “daylight color” refers , for example, to a correlated color temperature in a range of 5000K to 6500K.
As shown in
Hereinafter, members that are common to the first light source 31 and the second light source 32 will be described first. The base 35 supports the first and second light-emitting element 41, 42. On a surface of the base 35, conductive wiring 36 is provided to supply power to the first and second light-emitting element 41, 42. In the case where the mounting board 30 is a flexible mounting board, material of the base 35 may be, for example, phenolic resins, epoxy resins, polyimide resins, BT resins, polyphthalamide (PPA), polyethylene terephthalate (PET), or other resins. These resins are preferably selected as the material of the base 35 from the standpoints of cost reduction and formability, among others. The thickness of the mounting board may be chosen as appropriate; the mounting board may be a flexible mounting board that is capable of being fabricated by roll-to-roll method, or a rigid mounting board. A rigid substrate of a small thickness that attains sufficient degree of flexibility may also be used. From the standpoints of cost reduction and formability, these resins are preferably selected as the base 35. Alternatively, from the standpoints of thermal resistance and light resistance, ceramics may be selected for the base 35. Examples of ceramics include alumina, mullite, forsterite, glass ceramics, nitride-type (e.g., AlN) ceramics, carbide-type (e.g., SiC) ceramics, and LTCC. Among those, ceramics which are composed of alumina or whose main component is alumina can be suitably used for the base 35.
In the case where a resin is used for the material composing the base 35, an inorganic filler such as glass fibers, SiO2, TiO2, or Al2O3 may be mixed in the resin for improving mechanical strength, reducing coefficient of thermal expansion, improving light reflectance, and so on. The base 35 is configured to electrically insulate the conductive wiring 36, and a so-called metal substrate; a metal member having an insulating layer formed thereon, may be used.
The conductive wiring 36 is electrically connected to electrodes of the first and second light-emitting element 41, 42 to supply external power to the first and second light-emitting element 41, 42. In other words, it serves as electrodes, or portions thereof, for enabling external powering. Usually, the conductive wiring is formed in at least two discrete pieces of positive and negative.
The conductive wiring 36 is formed on at least the upper surface of the base 35 supporting the first and second light-emitting element 41, 42. The material of the conductive wiring 36 may be appropriately chosen in accordance with the material which is used for the base 35, the manufacturing method, and the like. For example, in the case where a ceramic is used for the material of the base 35, the material of the conductive wiring 36 is preferably a material having a high melting point that withstands the firing temperature of a ceramic sheet; for example, a metal having a high melting point is preferably used, e.g., tungsten or molybdenum. On a material having a high melting point, another metal material such as nickel, gold, or silver may be provided by plating, sputtering, vapor deposition, or the like.
In the case where a glass epoxy resin is used for the material of the base 35, the material of the conductive wiring 36 is preferably a material that permits easy processing. Furthermore, a rigid substrate of a small thickness that attains sufficient degree of flexibility is preferably selected as the material of the base 35 in order to promote the effects of weight reduction in the lighting apparatus based on reduced mounting board weight as well as thinness of the lighting apparatus.
In the case of employing the base formed by an injection molding using an epoxy resin, the conductive wiring 36 is preferably formed of a material which readily accepts processing such as a punching process, an etching process, or a bending process, and which has a relatively good mechanical strength. Examples of the conductive wiring include metal layers, lead frames formed of metals such as copper, aluminum, gold, silver, tungsten, iron, or nickel, or a copper-nickel alloy, phosphor bronze, a copper-iron alloy, molybdenum, and the like. A surface of the conductive wiring may further be coated with a metal material. Material of the conductive wiring may be appropriately selected from, for example, silver alone, or an alloy between silver and copper, gold, aluminum, rhodium, or the like, or a multilayer film of silver and such an alloy. For the method of placing the metal material, a sputtering technique, a vapor deposition technique, or the like may be used instead of a plating technique.
The connecting members 38 fix the first and second light-emitting element 41, 42 to the base 35 or the conductive wiring 36. The connecting members 38 are electrically insulative or electrically conductive. As shown in
The electrically-conductive material composing the connecting members 38 may be in liquid form, paste form, solid form (a sheet, a block, powder, or a wire), as appropriately selected in accordance with the composition and the shape and the like of the base 35. Any such connecting member 38 may be formed of a single member, or several kinds thereof may be used in combination.
In the case where the connecting members 38 are electrically insulative, various resin adhesives or the like may be used. In this case, the connecting members 38 may connect the first and second light-emitting element 41, 42 to the base 35. The conductive wiring 36 is electrically connected to the first and second light-emitting element 41, 42.
Any portion of the conductive wiring 36 except for where it is electrically connected to the first and second light-emitting element 41, 42 or other elements is preferably covered with the insulating member 37. For example, the insulating member 37 may be an electrically insulating resin, e.g., solder resist, that covers the conductive wiring 36 and the exposed surface of the base 35, or a deposited electrically insulative layer of silicon oxide, silicon nitride, or the like. The electrically insulating resin can be a material which absorbs little light from the first and second light-emitting element 41, 42 and has an electrically insulative property. For example, epoxies, silicones, modified silicones, urethane resins, oxetane resins, acrylics, polycarbonates, polyimides, and the like may be used for the insulating member 37.
In the case where the insulating member 37 is provided, a whitish filler similar to the underfill material described below may be contained in the insulating member 37, thus not only providing insulation for the conductive wiring 36 but also reducing light leakage and absorption to enhance the light extraction efficiency of the lighting module 22.
In the case where the first or second light-emitting element 41, 42 is flip-chip mounted, it is preferable that an underfill 39 is formed between the first or second light-emitting element 41, 42 and the base 35. The underfill 39 contains a base material and a filler which is dispersed in the base material. The filler is added in order to allow light from the first or second light-emitting element 41, 42 to be efficiently reflected, and relax the stress which may be caused by a difference in thermal expansion coefficient between the first or second light-emitting element 41, 42 and the base 35.
The base material of the underfill 39 can be appropriately selected from materials which absorb little light from the light-emitting device. For example, epoxies, silicones, modified silicones, urethane resins, oxetane resins, acrylics, polycarbonates, polyimides, and the like may be used.
For the filler in the underfill 39, a white filler may be used to facilitate light reflection and enhance the light extraction efficiency. An inorganic compound can be preferably employed for the filler. As used herein, “white” encompasses, even if the filler itself may be transparent, any whitish appearance based on scattering due to a refractive index difference with the material around the filler.
The reflectance of the filler is preferably 50% or more, and more preferably 70% or more, with respect to light of the emission wavelength. In this manner, the light extraction efficiency of the lighting module 22 can be improved. An average particle size of the filler is preferably in a range of 1 nm to 10 μm. By ensuring that the filler has an average particle size in this range, the underfill attains good resin fluidity, such that it is sufficiently capable of covering even a narrow gap. The particle size of the filler is preferably in a range of 100 nm to 5 μm and more preferably in a range of 200 nm to 2 μm. The filler may be based on spherical shapes or scale shapes.
In order to secure the lateral surfaces of the light emitting element as light-extracting surfaces, it is preferable that the average particle size of the filler is appropriately adjusted and the material of the underfill is appropriately selected so that the lateral surfaces of the light emitting element are not covered by the underfill.
For the first and second light-emitting element 41, 42, a material known in the art may be used. In the present embodiment, light-emitting diodes are preferably used for the first and second light-emitting elements 41, 42. The emission wavelength ranges of the first and second light-emitting elements 41, 42 may be appropriately selected. For example, in order to emit blue or green light, a semiconductor layer which is composed of ZnSe, a nitride semiconductor (InxAlyGa1−x−yN, X+Y≤1), GaP, or the like may be included. In order to emit red light, a semiconductor layer which is composed of GaAlAs or AlInGaP may be included. Light-emitting devices which are made of any other semiconductor material may also be used. Semiconductor compositions, emission colors, sizes, and the numbers of light-emitting devices to be used can be selected as appropriate depending on the purpose. Various emission wavelengths can be selected based on the material and a composition ratio of the semiconductor layer.
Each of the first and second light-emitting elements 41, 42 includes a light-transmissive substrate and a semiconductor multilayer structure layered on the substrate. The semiconductor multilayer structure includes an active layer and an n type semiconductor layer and a p type semiconductor layer interposing the active layer. The first and second light-emitting element 41, 42 includes an n type electrode and a p type electrode which are electrically connected to the n type semiconductor layer and the p type semiconductor layer, respectively. In the first and second light-emitting element 41, 42, the n type electrode and the p type electrode may be on the same surface or on different surfaces. In the present embodiment, as shown in
The first cover member 51 is disposed on the mounting board 30 so as to cover at least the light emitting surface 41a of the first light-emitting element 41. Similarly, the second cover member 52 is disposed on the mounting board 30 so as to cover at least the light emitting surface 42a of the second light-emitting element 42. The first and second cover member 51, 52 protects the first and second light-emitting element 41, 42 from the external environment, and also optically controls the light emitted from the first and second light-emitting element 41, 42. In the present embodiment, the first and second cover member 51, 52 control the light emitted from the first and second light-emitting element 41, 42 so that the second light source 32 has a light distribution which is broader than that of the first light source 31.
For the material of the first and second cover member 51, 52, a light-transmissive material such as an epoxy resin, a silicone resin, or a resin mixture of these, glass can be used. Among those, a silicone resin is preferably selected in terms of light resistance and ease of forming.
The second cover member 52 preferably contains a light-diffusing material for diffusing the light emitted from the second light-emitting element 42. With a light-diffusing material, light which goes out from the second light-emitting element 42 in the optical axis L direction is diffused by the light-diffusing material in random directions, thus resulting in a broader light distribution. On the other hand, it is preferable for the first cover member 51 not to contain a light-diffusing material. The optical axes L are defined by normal of the light emitting surfaces 41a, 42a that passes through the center of the first and second light-emitting elements 41, 42.
The first and second cover member 51, 52 may contain: wavelength converting members that absorb light emitted from the first and second light-emitting element 41, 42 and emit light of at least one different wavelengths, e.g., a phosphor; a colorant corresponding to the emission color of the light-emitting element; and the like.
The wavelength converting member may be a component that absorbs light from the first or second light-emitting element 41, 42, and converts wavelength of the light into a different wavelength. Examples may include yttrium aluminum garnet (YAG)-based phosphors activated by cerium, lutetium aluminum garnet (LAG) activated by cerium, nitrogen-containing calcium aluminosilicate (CaO—Al2O3—SiO2)-type phosphors activated by europium and/or chromium, silicate ((Sr,Ba)2SiO4)-based phosphors activated by europium, β SiAlON phosphors, nitride-based phosphors such as CASN-based or SCASN-based phosphors, KSF-based phosphors (K2SiF6), sulfide-based phosphors, and the like. Phosphors other than the aforementioned phosphors which have similar performances, actions, and effects may also be used.
The wavelength converting member may be made of luminescent materials that are referred to as so-called nanocrystals or quantum dots, for example. Semiconductor materials may be used for such materials, e.g., II-VI group, III-V group, and IV-VI group semiconductors, specifically, nano-sized high-dispersion particles such as CdSe, core-shell type CdSxSe1−x/ZnS, and GaP.
In the case where the first and second cover member 51, 52 do not contain any wavelength converting member, the wavelength ranges and correlated color temperatures of the light emitted by the first light sources 31 and the second light sources 32 are determined by the semiconductor layer compositions of the first and second light-emitting elements 41, 42, respectively. On the other hand, in the case where the first and second cover member 51, 52 contain a wavelength converting member, the wavelength ranges and correlated color temperatures of the light emitted by the first light sources 31 and the second light sources 32 are determined by the fluorescence characteristics or emission characteristics of the wavelength converting member and the compositions of the semiconductor layers of the first and second light-emitting elements 41, 42.
For the light-diffusing material, specifically, oxides such as SiO2, Al2O3, Al(OH)3, MgCO3, TiO2, ZrO2, ZnO, Nb2O5, MgO, Mg(OH)2, SrO, In2O3, TaO2, HfO, SeO, Y2O3, CaO, Na2O, and B2O3, nitrides such as SiN, AlN, and AlON, and fluorides such as MgF2 can be used. Such materials may be used singly or in a mixture. Such light-diffusing materials may be provided as a plurality of layers layered in the first or second cover members 51, 52, respectively.
An organic filler may be used for the light-diffusing material. For example, various kinds of resins of particle shapes may be used. Examples of such resins include silicone resins, polycarbonate resins, polyether sulfone resins, polyarylate resins, polytetrafluoroethylene resins, epoxy resins, cyanate resins, phenolic resins, acrylic resins, polyimide resins, polystyrene resins, polypropylene resins, polyvinyl acetal resins, polymethyl methacrylate resins, urethane resins, and polyester resins.
The light-diffusing material is preferably a material that does not substantially convert the wavelengths of the light emitted from the first and second light-emitting elements 41, 42. In the case where the light-diffusing material has a wavelength converting function, when the first and second cover members 51, 52 have predetermined shapes as described below, color unevenness in light distribution may be caused due to differences in thickness of the first and second cover members 51, 52 from the respective light emitting surfaces 41a, 41b of the first and second light-emitting elements 41, 42 in the light-emitting directions. However, with the light-diffusing material that does not substantially convert the wavelengths of the light emitted from the first and second light-emitting elements 41, 42, a reduction in color unevenness in light distribution can be achieved.
The light-diffusing material may be contained in an amount sufficient to diffuse light, for example, in a range of about 0.01 wt % to about 30 wt %, and preferably in a range of about 2 wt % to about 20 wt %. The light-diffusing material may also have a size sufficient to similarly diffuse light, for example, in a range of about 0.01 μm to about 30 μm preferably in a range of about 0.5 μm to about 10 μm . The shape of the light-diffusing material may be spherical or scale-like, but a spherical shape is preferable to produce uniform diffusion of light. The amount of light-diffusing material can be adjusted based on the difference in refractive index and thickness with respect to those of the second cover member 52.
The shapes of the first and second cover members 51, 52 affect the light distribution characteristics of the first and second light sources 31 and 32, respectively. In the present embodiment, as shown in
Each of the first light sources 31 has a Lambertian or similar light distribution characteristic. On the other hand, each of the at least one second light source 32 preferably has a batwing light distribution characteristic. A Lambertian or similar light distribution characteristic is defined by an emission intensity distribution where the emission intensity is greatest at 0° and decreases with an increasing absolute value of the light distribution angle. In other words, in a Lambertian or similar light distribution characteristic, brightness is highest at a central portion and decreases toward the peripheral portion. On the other hand, in its broader definition, a batwing light distribution characteristic is defined as an emission intensity distribution where stronger emission intensities exist at angles with greater absolute values of light distribution angle than 0°. In its narrower sense, a batwing light distribution characteristic is defined as an emission intensity distribution where the emission intensity is strongest near absolute values of 50° to 60°. In other words, in a batwing light distribution characteristic, a center portion is darker than the peripheral portion.
In the present specification, in order to compare broadness of light distribution among light sources of various light distribution characteristics, the light distribution angle of a light source is defined as follows. In a light distribution characteristic in the plane containing the optical axis L as mentioned above, assuming that symmetric characteristics exist on the plus side and the minus side of an angle, an angle θ is determined which makes the relative emission intensity 0.8, whereby an angle 2θ is defined as the light distribution angle. For any light distribution characteristic whose relative emission intensity is largest at portions other than 0°, e.g., a batwing light distribution characteristic, the θ which makes the relative emission intensity 0.8 should be employed at portions of largest and smallest angles.
Given a light distribution characteristic as defined above, a batwing light distribution characteristic has a greater light distribution angle than the light distribution angle of a Lambertian or similar light distribution characteristic. In other words, in the case where each of the first light sources 31 has a Lambertian or similar light distribution characteristic and each of the at least one second light source 32 has a batwing light distribution characteristic, the second light sources 32 have a broader light distribution than do the first light sources 31. For example, in the light distribution characteristic shown in
When the second cover member 52 of each of the at least one second light source 32 contains a light-diffusing material, assuming that the light-diffusing material diffuses light in an ideal manner, the luminous intensity of light which goes out from the second light sources 32 is approximately proportional to the surface area of the second cover member 52 per light distribution angle. As shown in
On the other hand, when A>C, i.e., the ratio of the height A to the width C is greater than 1 (A/C>1), at an angle of greater than 0° but smaller than 90°, the relative light distribution intensity is higher than 0° and 90°. In other words, a batwing light distribution characteristic can be realized.
On the other hand, when the first cover member 51 of each of the first light sources 31 has a convex shape and does not contain a light-diffusing material, there is no particular limitation as to the height A and the width C of the first cover member 51. Generally, light which goes out from a light-emitting element has a Lambertian or similar light distribution characteristic; therefore, when the first cover member 51 has a convex shape, the first light source 31 will generally have a Lambertian or similar light distribution characteristic. Even when the first cover member 51 contains a light-diffusing material, so long as A<C is satisfied, the first light source 31 has a Lambertian or similar light distribution characteristic.
Generally, in the case of a long array pitch between the light sources, in order to reduce unevenness in the luminous intensity from the light source with a light-diffusing plate, a long distance is needed between the light source and the light-diffusing plate. With the lighting apparatus 11 of present embodiment, however, the second light sources 32, which are fewer in number and which have a greater array pitch, possess a broad light distribution characteristic; therefore, unevenness in the luminance of the cover 24 can be reduced without providing a larger distance from the cover 24. As shown in
For example, as shown in
0.7≤OD/P1≤12.0
0.2≤OD/P2≤0.8. (1)
Accordingly, as described above, when lighting the first and second light sources 31 and 32, unevenness in luminance at the cover 24 of the lighting apparatus 11 can be more reliably reduced.
For example, a typical value fof the optical distance OD that is estimated for a lighting apparatus is in a range of about 10 mm to about 40 mm. According to the inequalities (1), when the optical distance OD is 10 mm, P1 is in a range of about 7 mm to about 20 mm, and P2 is in a range of about 2 mm to about 8 mm. When the optical distance OD is 40 mm, P1 is in a range of about 28 mm to about 80 mm, and P2 is in a range of about 8 mm to about 64 mm.
The lighting module 22 can be manufactured by the method illustrated below, for example. First, a mounting board 30 having conductive wiring 36 in a pattern which is adapted to the arrangement of the first and second light sources 31 and 32 is provided. Then, the first and second light-emitting elements 41, 42 are bonded to the mounting board 30. For example, flip chip bonding may be used to mount the first and second light-emitting elements 41, 42 onto the mounting board 30.
Then, the first and second cover members 51, 52 are prepared according to the composition described above. The first and second cover member 51, 52 can be formed by compression molding or injection molding so as to cover the first and second light-emitting element 41, 42. Otherwise, the viscosity of a material of the first and second cover member 51, 52 may be optimized so that the material can be applied dropwise or in a manner of drawing onto the first and second light-emitting element 41, 42, thus allowing a shape as shown in
As described above, with the lighting module of the present embodiment, second light sources which are fewer in number have a broader light distribution, so that there is little difference in uniformity in luminance distribution within the light emitting surfaces between the first light sources and second light sources, across the entire lighting module. Therefore, in the case where either the first light sources or the second light sources are selectively turned on, there is little difference in the appearance between the two types of light sources. On the other hand, when the first light sources and the second light sources are simultaneously turned on, it is possible to uniformly mix the light from the two types of light sources. Since the quantity of second light sources to be mounted can be reduced, it is possible to reduce the manufacturing cost.
Moreover, with the lighting module of the present embodiment, each of the second light sources has a broader light distribution, so that unevenness in luminance on the cover when the second light sources are turned on can be reduced. The entire cover appears as if uniformly emitting light, whereby a lighting apparatus with good appearance can be realized. Further, a larger interspace is not needed between the cover and the mounting board on which the light sources are arranged, whereby a thin lighting apparatus can be realized.
Other embodiments and variants of the lighting apparatus and the lighting module are described below.
Firstly, in the above embodiment, the first light sources 31 each have a Lambertian or similar light distribution characteristic, whereas the second light sources 32 each have a batwing light distribution characteristic; however, other combinations of light distribution characteristics can be used. For example, as shown in
There are other variations in the shape of the cover member to realize a batwing light distribution characteristic in addition to that of the above embodiment. For example, a batwing light distribution characteristic can be realized also by using a light source 60 that is shown in
A light source 70 that is shown in
In top view, the cover member 72 has a circular shape. Moreover, the cover member 72 has a recess 72r on the optical axis L, and has a ridge 72p outside of the recess 72r as viewed in a plane containing the optical axis L. The ridge 72p of the cover member 72 has a circular shape in top view.
Preferably, the height A of the cover member 72 is smaller than the maximum width C′ of the cover member 72. It is preferable that the width C of a surface of the cover member that is in contact with the mounting board 30 is smaller than the maximum width C′. In other words, it is preferable that A>C′, C′>C. The cover member 72 with such a shape can create a batwing light distribution characteristic.
The embodiment describes that each light source of the lighting module is in the form of a bare chip; instead, packaged light sources may be mounted on the mounting board. For example, a light source 81 shown in
The light distribution characteristic of the light source 81 changes with a tilt angle a of the reflection surface 84a of the reflector 84, the material of the cover member 85, and the shape of the upper surface 85a. Therefore, by varying these elements, the light source 81 may have a broader or narrower light distribution, thus resulting in two kinds of light sources 81 with different light distribution characteristics which can be used for the first and second light sources described in the above embodiment. In this case, a cover member may or may not be formed on the light source 81.
Thus, the light distribution characteristic of each light source may be affected not only by the shape of the cover member, but also by other conditions, e.g., light outgoing characteristics of the light-emitting device, material characteristics of the cover member, presence or absence of a reflector, and so on.
Although the above embodiment illustrates that the light sources are disposed in a two-dimensional array in the lighting module, the lighting module may alternatively include light sources which are in a one-dimensional array. A lighting module 22′ shown in
The arrangement of light sources in the lighting module may be alternatives other than the arrangement being equally pitched along two directions. For example, in a lighting module 22″ shown in
The period with which the light sources are arrayed in the lighting module may not be constant across the entire lighting module; instead, the light sources may be arranged with periods which are locally different. In this case, at least in portions where the first and second light sources are arranged so as to satisfy the inequality relationship (1), a sufficient effect of reducing unevenness in luminance within the lighting apparatus can be obtained as described above. Some or all of the light sources on the mounting board may be randomly arranged. Also in this case, unevenness in luminance of the second light sources is reduced because of the greater light distribution angle of the second light sources, which are fewer in number. Especially, a sufficient effect of reducing unevenness in luminance within the lighting apparatus is obtained when the distance of every adjacent pair of light sources respectively satisfies the inequality relationship (1), even in a random arrangement.
The first light sources 31 and the second light sources 32 in the above embodiment emit white light of correlated color temperatures that are different from each other. However, this is not the only combination of light emitted by the first light sources 31 and light emitted by the second light sources 32. For example, either the first or second light sources 31 or 32 may emit white light, while the other light sources 32 or 31 may emit monochromatic light. More specifically, for example, the first light sources 31 may emit white light of daylight color, while the second light sources 32 may emit red light. In this case, the second light sources 32 are fewer in number but have a greater light distribution angle, so that unevenness in luminance with respect to red light is reduced across the entire lighting apparatus, whereby light of a reddish white color is distributed across the entire cover of the lighting apparatus. Thus, dimming with good color rendering properties can be realized. The first light sources 31 and the second light sources 32 may emit monochromatic light, while the first light sources 31 and the second light sources 32 have different wavelength ranges from each other. In this case, too, a lighting apparatus is realized in which light of two different wavelength ranges is uniformly mixed.
In order to confirm the effects of the lighting apparatus according to the embodiment, a simulation was conducted for evaluation. Specifically, non-uniform luminance across the cover in the case where the first and second light sources 31 and 32 were arranged as shown in
In
In
As indicated by the curve B50, when light sources each having a batwing light distribution characteristic are arranged at a pitch of 50 mm, the relative luminance ratio is not less than approximately 90% except at both ends of the array, indicative of very little unevenness in luminance. It can be seen from
Then, an appropriate range of OD/P2 was determined through a simulation. More specifically, second light sources 32 having batwing light distribution characteristics shown by the curves B1 and B2 in
As shown in
As shown in
With these results, it was found when OD/P2 is in a range of 0.2 to 0.8, the second light sources 32 will have their non-uniform luminance reduced by having a batwing light distribution characteristic. Through a similar simulation, it was found that OD/P1 is preferably in a range of 0.7 to 2.
A lighting module and a lighting apparatus according to embodiments of the present disclosure can be used for various applications, e.g., indoor lighting, various types of indicators, displays, backlights for liquid crystal displays, sensors, signal devices, automotive parts, and channel letter for signage.
While the present invention has been described with respect to exemplary embodiments thereof, it will be apparent to those skilled in the art that the disclosed invention may be modified in numerous ways and may assume many embodiments other than those specifically described above. Accordingly, it is intended by the appended claims to cover all modifications of the invention that fall within the true spirit and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-214661 | Oct 2015 | JP | national |
This application is a continuation of U.S. patent application Ser. No. 15/337,786, filed on Oct. 28, 2016, which claims priority to Japanese Patent Application No. 2015-214661, filed on Oct. 30, 2015, the disclosures of which are hereby incorporated by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15337786 | Oct 2016 | US |
| Child | 16567580 | US |
