US20180198039A1 - Light-emitting apparatus - Google Patents

Abstract

The present application discloses a light-emitting apparatus having a light-emitting device and a wavelength conversion layer. The light-emitting device has a first top surface and a first side surface, and the wavelength conversion layer has a second top surface and a second side surface and covers the first top surface. A ratio of a distance between the first top surface to the second top surface and a distance between the first side surface and the second side surface is between 1.1˜1.3.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• This application is a Continuation of co-pending application Ser. No. 14/810,180 filed Jul. 27, 2015 for which priority is claimed under 35 U.S.C. § 120; and this application claims priority of U.S. Provisional Application No. 62/029,977 filed on Jul. 28, 2014 under 35 U.S.C. § 119(e), the entire contents of all of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTIONField of the Invention
• The present disclosure relates to a light-emitting apparatus and in particular to a light-emitting apparatus having a semiconductor light-emitting element and an optical element.
Brief Description of the Related Art
• A light-emitting device having light-emitting diode (LED) is gradually taking the place of traditional incandescent light for energy saving, environmental protection, long operation life, compact, and so on.
• Various kinds of optical elements, such as lens, reflector, and wavelength convertor, can be used to change the optical properties of the light-emitting device. The lens can be used to collect or redistribute light from LEDs. The reflector can redirect light from LEDs to a desired direction. Moreover, the wavelength convertor, such as phosphor, dye, or quantum dot, can convert color light from LEDs to another one.
SUMMARY OF THE DISCLOSURE
• The present application discloses a light-emitting apparatus having a light-emitting device and a wavelength conversion layer. The light-emitting device has a first top surface and a first side surface, and the wavelength conversion layer has a second top surface and a second side surface and covers the first top surface. A ratio of a distance between the first top surface to the second top surface and a distance between the first side surface and the second side surface is between 1.1˜1.3.
• A light-emitting apparatus has a light-emitting device, a wavelength conversion layer covering the light-emitting device, a first lens on the light-emitting device, a second lens on the first lens, and a wavelength conversion layer connected to the second lens. The first lens ha a top surface bent in a first direction, and the second lens has an inner surface bent in a second direction which is different from the first direction.
• A light-emitting apparatus has a first light-emitting device, a second light-emitting devices spaced from first light-emitting device by a first distance, a diffusion layer covering the first and second light-emitting devices, a prism layer on the diffusion layer, and an LCD module on the prism layer. The first light-emitting device or the second light-emitting device is configured to provide a light field on the LCD module and having a radius two or more times larger than the first distance.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIGS. 1A-1H show light-emitting devices in accordance with embodiments of the present disclosure.
• FIGS. 2A-2D show properties of light-emitting devices in accordance with embodiments of the present disclosure.
• FIG. 3A shows a light-emitting apparatus in accordance with an embodiment of the present disclosure.
• FIGS. 3B-3C show structures in accordance with an embodiment of the present disclosure.
• FIGS. 3D-3E show light properties of light-emitting apparatuses in accordance with embodiments of the present disclosure.
• FIGS. 4A-4C show structures in accordance with an embodiment of the present disclosure.
• FIGS. 4D-4F show light properties of light-emitting apparatuses in accordance with embodiments of the present disclosure.
• FIGS. 5A-5C show light-emitting devices in accordance with embodiments of the present disclosure.
• FIGS. 6A-6F show light-emitting devices in accordance with embodiments of the present disclosure.
• FIGS. 7A-7J show light-emitting apparatuses and light properties in accordance with embodiments of the present disclosure.
• FIGS. 8A-8D show a light-emitting apparatus in accordance with embodiments of the present disclosure.
• FIGS. 9A-9D show a light-emitting apparatus in accordance with embodiments of the present disclosure.
• FIGS. 10A-10D show a light-emitting apparatus in accordance with embodiments of the present disclosure.
• FIGS. 11A-11H show a light-emitting apparatus and related optical properties in accordance with an embodiment of the present disclosure.
• FIGS. 12A-12E show measuring instruments related to a light-emitting device and related results in accordance with an embodiment of the present disclosure.
• FIG. 13 shows a light-emitting apparatus in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• The drawings illustrate the embodiments of the disclosure and, together with the description, serve to illustrate the principles of the application. The same name or the same reference numeral given or appeared in different paragraphs or figures along the specification can has the same or equivalent meaning(s) while it is once defined anywhere of the disclosure. The thickness or the shape of an element in the specification can be expanded or narrowed.
• FIG. 1A shows a light-emitting device1000A in accordance with an embodiment of the present disclosure. The light-emitting device1000A includes a light-emittingdiode2 and awavelength conversion layer4 which is directly formed on the light-emittingdiode2 and surrounds the light-emittingdiode2. The light-emitting device1000B has atransparent layer6 formed between thewavelength conversion layer4 and the light-emittingdiode2. Thetransparent layer6 covers the top surface, side surface of the light-emitting diode2 and laterally extends to edges of the light-emitting device1000B. Therefore, the light-emittingdiode2 is separated from thewavelength conversion layer4 by thetransparent layer6.
• The light-emitting device1000C has atransparent cover8 formed on thewavelength conversion layer4. The light-emitting device1000D has atransparent cover8, awavelength conversion layer4, atransparent layer6 and a light-emittingdiode2 stacked in sequence from top to bottom. Thewavelength conversion layer4 of the light-emitting device1000D has a bottom surface with a contour identical or similar to that of a top surface of thetransparent layer6, and a top surface with a contour identical or similar to that of a bottom surface of thetransparent cover8. Moreover, the top and bottom surfaces of thewavelength conversion layer4 of the light-emitting device1000D can have identical or different contours. Thewavelength conversion layer4 of the light-emittingdevice1000D has two surfaces (top and bottom surfaces) parallel to each other. Thewavelength conversion layer4 of the light-emittingdevice1000E is formed on thetransparent layer6 and has a bottom surface close to thetransparent layer6 and with a contour identical or similar to the top surface of thetransparent layer6, and a top surface formed in a flat contour or parallel to a top surface of the light-emittingdevice1000E or thetransparent cover8. Thewavelength conversion layer4 of the light-emittingdevice1000E has a bottom surface stretching along the contour of the light-emittingdiode2 and a flat top surface.
• The light-emittingdevice1000F has atransparent layer6 which covers the top surface and side surfaces of the light-emittingdiode2. In one embodiment, the outer surfaces of thetransparent layer6 are respectively parallel to the inner surfaces of thetransparent layer6. In other words, thetransparent layer6 has a uniform thickness.
• The light-emittingdevice1000G has atransparent layer6 which covers the top surface and side surfaces of the light-emittingdiode2. Awavelength conversion layer4 covers the top surface and side surfaces oftransparent layer6. Atransparent cover8 having a rectangular cross-section is formed on the top surface of thewavelength conversion layer4. Thewavelength conversion layer4 has a top thickness at the top of the light-emittingdiode2 and a lateral thickness at the lateral of the light-emittingdiode2. The lateral thickness is greater than the top thickness.
• The light-emittingdiode2 has an active layer to emit an incoherent light. The light emitted from the light-emittingdiode2 has a first light intensity, a first light field, and a first color. Thewavelength conversion layer4 has a wavelength conversion material having a particle size ranged between 8˜50 μm, such as 8, 17, 20, 32 or 46 μm. The particle size can be a diameter or a characteristic length. Thetransparent layer6 and thetransparent cover8 have transparent material. At least 60% of the light emitted from the light-emittingdiode2 can pass through thetransparent layer6 or thetransparent cover8 without being absorbed, i.e. thetransparent layer6 or thetransparent cover8 has a 60% transparency to the light from the light-emittingdiode2. The light-emittingdevices1000A˜1000H can emit a light having a second light intensity, a second light field, and a second color. The second light intensity is smaller than the first light intensity, due to part of the light form the light-emittingdiode2 is absorbed by or trapped in thewavelength conversion layer4, thetransparent layer6 or thetransparent cover8. The second light field can be identical with or different from the first light field. Diffusion particles can be added to thetransparent layer6 or thetransparent cover8 to scatter light and change light field. The light path in the aforementioned embodiments can be visualized by adopting an appropriate simulation model, such as Monte Carlo ray tracing method. The light propagation within thewavelength conversion layer4 can be visualized by using a simulation model based on Mie Scattering theory.
• Referring toFIGS. 1B and 1D, thetransparent layer6 has a curved contour. The curved contour is convexly bent on the top surface of the light-emittingdiode2. Thewavelength conversion layer4 is formed on the curved top surface of thetransparent layer6 and therefore has a concavely-bent bottom surface. Thetransparent layer6 further has a lower surface which has a contour similar to the shape of the light-emittingdiode2. Referring toFIGS. 1F, 1G and 1H, thetransparent layer6 and thewavelength conversion layer4 substantially have reversed-U shapes. Referring toFIG. 1H, thetransparent cover8 also has a reversed-U shape, while the reversed-U shape has a top portion and a lateral portion with is thinner than the top portion.
• FIGS. 2A-2D show characteristics of light-emitting devices in accordance with an embodiment of the present disclosure.FIG. 2A shows the light extraction efficiency of the light-emittingdevices1000A˜1000H. The light extraction efficiencies are ranged between 100˜140 lm/w. The light-emittingdevice1000F has the best light extraction efficiency.FIG. 2B shows the color temperature variance over angle within a range between −90°˜+90° of the light field of the light-emittingdevices1000A˜1000H. The variance are ranged between 100˜450 K.FIGS. 2C˜2D show the difference of color over angle in two different units, wherein the differences of Δu′v′ are between 0.001˜0.009 and the differences of Δy are between 0.01˜0.1.
• FIG. 3A show a structure having a light-emitting apparatus1003A in accordance with an embodiment of the present disclosure. The light-emitting apparatus1003A has a light-emittingdevice1000C formed on atop surface100 of thecarrier10 throughconductive portions120 and122. Theside walls140 and142 of the light-emitting apparatus1003A can be Lambertian scattering surfaces which can scatter light, as shown inFIG. 3B. Thetop surface100 can be a surface with a reflectivity of 90% and an absorptivity of 10%, or a Lambertian surface which can scatter light, as shown inFIG. 3C.FIG. 3D shows the color variance over angle within a range between −90°˜+90° of 8 light-emitting apparatuses (light-emittingdevices1000A˜1000H) with different types oftop surfaces100 andside walls140 and142. Referring toFIG. 3D, the structure having a Lambertian scattering side wall has a worse color space uniformity compared with the structure having a flat side wall.
• FIG. 3E shows the light extraction efficiency (LEE) of 8 light-emitting apparatuses with different types oftop surfaces100 andside walls140 and142. Each of the light-emitting apparatus is measured under four different conditions. Thetop surface100 is a Lambertian scattering surface and theside walls140 and142 are flat in the first type condition. Thetop surface100 and theside walls140 and142 are Lambertian scattering surfaces in the second type condition. Thetop surface100 is a reflective surface and has a 90% reflectivity related to the light from the light-emitting diode, and theside walls140 and142 are flat in the third type condition. Thetop surface100 is a reflective surface, and theside walls140 and142 are Lambertian scattering surfaces in the fourth type condition. According toFIGS. 3D-3E, the light-emitting apparatuses which comprises light-emittingdevice1000F and1000 B have light-emitting efficiencies larger than 130 lm/W and color temperature variance less than 0.004 under some conditions.
• FIGS. 4A and 4B show structures in accordance with an embodiment of the present disclosure. When the thickness of thewavelength conversion layer4 inFIGS. 4A and 4B are increased, the light extraction efficiencies of the structures are increased, the uniformities of color within a space of the light-emitting structures are improved, and the color temperature uniformity of the light-emitting structures are improved. Moreover, the thickness increase of thewavelength conversion layer4 has more notable effect upon the structure inFIG. 4B. To be more specific, the light extraction efficiency of structure inFIG. 4B increases 4.89%, the ΔCCT decreases from 486K to 128K, and the Δu′v′ decreases from 0.0088 to 0.002 with an increase of thickness from 100 μm to 300 μm; while the light extraction efficiency of structure inFIG. 4A increases 10.97%, the ΔCCT decreases from 529K to 289K, and the Δu′v′ decreases from 0.0089 to 0.0055 with an increase of thickness from 100 μm to 400 μm. However, the optical properties of structure inFIG. 4B are improved substantially equal to those inFIG. 4A with less increase of thickness of thewavelength conversion layer4.
• FIGS. 4C-4F show structures and their optical properties. InFIGS. 4D˜4F, ordinates represent optical properties, such as light extraction efficiency, ΔCCT and color space uniformity Δu′v′. Abscissas represent the width W between the light-emittingdiode2 and thewavelength conversion layer4, as shown inFIG. 4C. With the increase of height(H) from 50 μm to 350 μm and the increase of width(W) from 50 μm to 350 μm, the light extraction efficiency improves by about 7.53% from 135 lm/W, as shown inFIG. 4D. The color space uniformity Δu′v′ improves by about 34.8% from 0.02 to less than 0.01, as shown inFIG. 4F. The color temperature variance ΔCCT decreases from 1100K around to less than 500K, as shown inFIG. 4E. The light extraction efficiency is remarkably improved when the height H is larger than 250 μm. The color space uniformity Δu′v′ is about 0.01 when the height H is 50 μm and width W is 150 μm.
• FIGS. 5A-5C show structures in accordance with an embodiment of the present disclosure. Referring to structure of light-emitting device inFIG. 5A, with the height H of about 750 μm and the size of the light-emitting device in a square of 2×2 mm², the light extraction efficiency is larger than 135 lm/W, the color space uniformity Δu′v′ is about of 0.004, and the color temperature variance ΔCCT is about 200K. The light-emitting device inFIG. 5A has better optical properties, such as light extraction efficiency, color space uniformity Δu′v′ and color temperature variance ΔCCT, when the height H is 350 μm and size is of 1×1 mm²′ or when the height H is 450 μm and size is of 1.2×1.2 mm².
• Referring toFIG. 5B, the color space uniformity Δu′v′ is about of 0.002, and the color temperature variance ΔCCT is about 100K, when the distance H is about 750 μm and the size of the light-emitting device is in a square of 1.8×1.8 mm². The light extraction efficiency is larger than 135 lm/Watt when the distance H is about 750 μm and the size of the light-emitting device is a square of 2×2 mm². The light-emitting device inFIG. 5B has better optical properties, such as light extraction efficiency, color space uniformity Δu′v′ and color temperature variance ΔCCT, when the distance H is 350 μm and size is of 1.2×1.2 mm²or when the distance H is 450 μm and size is of 1.2×1.2 mm².
• Compared with structure of light-emitting device inFIG. 5B, the light-emitting device inFIG. 5C has better optical properties, such as light extraction efficiency, color space uniformity Δu′v′ and color temperature variance ΔCCT, when the distance H is 350 μm and size of 1.2×1.2 mm², when the distance H is 450 μm and size of 1.2×1.2 mm², or when the distance H is 750 μm and size of 1.4×1.4 mm². The light provided by light-emitting devices inFIGS. 5A-5C has better performance at a specific sizes of distance H and distance W. For example, the color space uniformity Δu′v′ is better with a ratio, HWR (HWR=H/W), between 1.1˜1.3, and the light has a color space uniformity Δu′v′ within four MacAdam ellipse when the HWR is larger than 0.7.
• Provided the light-emitting devices shown in either ofFIGS. 5A˜5C can be arranged on thecarrier10 shown inFIG. 3A, and the light provided by the light-emitting devices inFIG. 5A˜5C are affected by thetop surface100. For example, when the direct reflectance of thetop surface100 decreases from 100% around to 90%, the light extraction efficiency can decrease by 18.42%, 18.13% and 20.28%. In another embodiment, when thetop surface100 changes from a surface having a reflectance of about 100% to a Lambertian surface of about 90% reflectance, the light extraction efficiency of the light-emitting apparatus decrease by 11.56%, 12.14% and 11.93%. In another embodiment, when the color temperature of the light emitted from the light-emitting device changes from 6500K to 30000K, the light extraction efficiency of the light-emitting devices inFIGS. 5A˜5C can decrease by 7.63%, 7.58% and 6.22%. The properties of light emitted from the structures inFIGS. 1,3A-3B, 4A-4C or 5A-5C are affected by the size ofwavelength conversion layer4, the size of total structure, the reflective rate of thetop surface100, or the color temperature of the light emitted from the light-emitting device.
• FIGS. 6A-6F show light-emitting devices in accordance with embodiments of the present disclosure. Theparticles3 are added in thewavelength conversion layer4 of the light-emittingdevices2000A,2000B and2000E, added in thetransparent layer6 of the light-emittingdevices2000C and2000F, and added in thetransparent cover8 of the light-emittingdevice2000D. Theparticles3 are used to improve light scattering or reflection. Theparticles3 are not transparent, and can absorb at least a portion of the light emitted from the light-emitting diode. With the addition ofparticle3, the color spaces uniformities of the light-emittingdevices2000A˜2000F can be improved, although the light extraction efficiencies of the light-emittingdevices2000A˜2000F are lowered by about 35%, 5%, 31%, 54%, 4% and 43% respectively.
• As shown inFIGS. 3A-3E, the light extraction efficiency is not greatly affected by the reflectance of the surface of the sidewalls, no matter the surface is a Lambertian surface or a surface having about 100% reflectivity. As shown inFIGS. 1A˜1H,4A˜4C,5A˜5C and6A˜6F, the light extraction efficiency is more likely affected by the reflectance of the surface of thecarrier10 or the sizes of the light-emitting device. For example, the higher reflectance of the surface of thecarrier10 can improve light extraction efficiency by about 18%˜20%. Or, a reflective layer can be formed between thecarrier10 and the light-emitting device to improve light extraction efficiency by about 11%˜12%. Moreover, the light-emitting devices having similar color space uniformity can have improved light extraction efficiencies by increasing the size of the light-emitting devices. For example, when the size of the light-emitting device is increased to 25 times, or more, larger than the size of the light-emitting diode, the light extraction efficiency of the light-emitting device is increased from 127 lm/W to 138 lm/W, which is substantially equal to an 8% increase.
• Besides, the ratio, HWR, or theparticles3 within the structures can affect the uniformity of light form the light-emitting device. For example, the color space uniformity Δu′v′ over the angle is less than 0.04 when the HWR is between 1.1˜1.3. The color space uniformity Δu′v′ over the angle between −80°˜+80° is less than 0.01 when the concentration of theparticles3 in the structure is about 5%.
• FIGS. 7A-7F show light-emitting apparatuses and some light properties in accordance with embodiments of the present disclosure. The bended lines with arrows in theFIGS. 7A, 7C and 7E represent the light paths within the light-emitting apparatuses.FIGS. 7B, 7D, 7F show the light pattern images of the light-emitting apparatuses.
• The light-emitting apparatus inFIG. 7A has a light-emittingdevice3000 formed on acarrier10, afirst lens160 covering the light-emittingdevice3000, asecond lens162 arranged on thefirst lens160, and awavelength conversion layer4 arranged on thesecond lens162. Light from the light-emittingdevice3000 is firstly redirected by thefirst lens160 and moves into thesecond lens162. The light from thefirst lens160 is then redirected by thesecond lens162 and moves in a direction substantially perpendicular to thecarrier10. As shown inFIG. 7B, the light pattern has a brighter inner portion. The inner portion is substantially corresponding to the size and shape of thefirst lens160. The area ratio of the inner portion to the entire light pattern is substantially corresponding to the area ratio of the frontal projected areas between thefirst lens160 and thesecond lens162.
• In detail, as shown inFIG. 7A, thelens162 has a top surface connected to thewavelength conversion layer4, a bottom surface, side walls, and a cavity for accommodating thelens160 and the light-emittingdevice3000. The cavity has a convex surface which is bulged toward the light-emittingdevice3000 and has a width substantially equal to or slightly greater than that of thelens160. The side walls can inwardly approach with each other from the top surface to the bottom surface. In other words, the top surface is wider/bigger than the bottom surface in a cross section/top view. The side wall can be constructed by a flat surface, a curved surface, or both. In some embodiments, the top surface or the bottom surface can be made in a circle, oval, rectangle, triangle, or other geometric shape. Moreover, the top surface and the bottom surface can have identical or different shapes. Light from the light-emittingdevice3000 can be reflected and/or refracted at the side wall or the convex surface when the incident angle is varied. The convex surface can converge or collimate more light to the central area of the top surface of thelens162 than to the peripheral area thereof, as shown inFIG. 7B.
• As shown inFIG. 7C, most of light from the light-emittingdevice3000 is redirected to the edge or rim of thethird lens164 after refracting by thefirst lens160 and refracting and reflecting by thethird lens164. Consequently, as shown inFIG. 7D, the edge or rim of light pattern is brighter than the inner portion.
• In detail, as shown inFIG. 7C, thelens164 has a top surface connected to thewavelength conversion layer4, a bottom surface, side walls, and a cavity for accommodating thethird lens164 and the light-emittingdevice3000. The cavity has a triangular cross section with slanted edges and a bottom width. The bottom width is greater than the greatest width of thelens160. In some embodiments, the slanted edges or surfaces can diverge more light to the peripheral area of the top surface of thelens166 than the central area thereof, as shown inFIG. 7D.
• As shown inFIG. 7E, thefourth lens166 has a structure similar to that of thesecond lens162. In detail, as shown inFIG. 7E, thelens166 has a flat top surface connected to thewavelength conversion layer4, a bottom surface, side walls, and a cavity for accommodating thelens160 and the light-emittingdevice3000. The cavity has a convex surface with a curvature radius smaller than that of thelens162. The light from the light-emittingdevice3000 is firstly bent by thelens160 and divergently moves into thelens166. Compared with the structure shown inFIG. 7A, the light is diverged by thelens166, especially by the convex surface, rather than collimated in a direction substantially perpendicular to thecarrier10, as shown inFIG. 7A. Besides, the light from the light-emittingdevice3000 is also reflected by the sidewalls of thelens166. The light pattern shown inFIG. 7F is more uniform than that shown inFIG. 7B in light intensity distribution.
• FIG. 7G shows the forward emission light (L1) and the backward emission light (L2) radiated from thewavelength conversion layer4 in the light-emitting apparatus. The forward emission light (L1) and the backward emission light (L2) can have different optical properties for different light apparatuses. A table showing the optical property differences between the light apparatuses shown inFIGS. 7A, 7C, and 7E is listed below. For example, the difference of color temperature between the light (L1) and the light (L2) of the apparatus inFIG. 7A is less than 1000K, and the difference of the light extraction efficiency between the light (L1) and the light (L2) is larger than 101 m/W.

• light emitting apparatus	FIG. 7A	FIG. 7C	FIG. 7E
  Phosphor concentration_	30%_	30%/10%_	50%_
  thickness	0.5 mm	0.45 mm	0.25 mm
  CCT of L1	8455.27	6396.92	6568.98
  CCT of L2	9813.29	11430.87	8962.41
  Standard deviation of CCT	2720.383	3487.41	1741.87
  between L1/L2 (K)
  Light extraction efficiency_L1	75.3189	47.40	75.62
  (lm/W)
  Light extraction efficiency _L2	62.9374	87.85	65.59
  (lm/W)
  Total Light extraction	138.256	135.25	141.21
  efficiency (lm/W)

• Thewavelength conversion layer4 inFIG. 7A has a 30% concentration of wavelength conversion material and a thickness of 0.5 mm, while that in theFIG. 7E has a 50% concentration of wavelength conversion material of 50% and a thickness of 0.25 mm. Thewavelength conversion layer4 inFIG. 7C has a 30% concentration of wavelength conversion material at outer portion, 10% concentration at inner portion (as shown inFIG. 7 H) and a thickness of 0.45 mm. In an embodiment, the angle between the light beam from the light-emitting device and the wavelength conversion layer is not likely to affect the optical property of the light provided by the light-emitting apparatus. Referring toFIGS. 7I˜7J, the angles between the wavelength conversion layer and three light beams are 45°, 60° and 90° respectively, as shown inFIG. 7I. The corresponding intensities of the three light beams, which are measured at the side of the wavelength conversion layer opposite to the light beams, are almost the same, as shown inFIG. 7J.
• FIG. 8A shows a light-emittingapparatus1008A with a stack including a firstwavelength conversion layer40, a secondwavelength conversion layer42, and atransparent layer60 formed between the first and second wavelength conversion layers40,42. The optical properties of light emitted from the light-emittingapparatus1008A are affected by some factors of the stack. For example, the thickness of the first or second wavelength conversion layer and the weight percentage concentration (wt %) of the first or second wavelength conversion layer are all factors possibly affecting the light extraction efficiency of the light-emittingapparatus1008A. The light is more likely to be absorbed by the wavelength conversion layer with higher weight percentage concentration of the wavelength conversion material. The light extraction efficiency is therefore reduced when higher percentage of light is absorbed by the wavelength conversion layer. The light can pass through longer distance when the wavelength conversion layer has a larger thickness. The light is more likely to be absorbed, and the light extraction efficiency is therefore reduced. In another embodiment, referring toFIG. 8B, the stack is designed to reflect light back and forth between the first wavelength conversion layers40 and the secondwavelength conversion layer42 before the light passing through thewavelength conversion layer42. In an embodiment, referring to the table below, the firstwavelength conversion layer40 has a 70% concentration. The secondwavelength conversion layer42 has a 5% concentration. The thicknesses of the firstwavelength conversion layer40 and the secondwavelength conversion layer42 are both 0.3 mm. The standard deviation of CCT between the forward emission light (L1) and the backward emission light (L2) is 2720.383 for theapparatus1007A inFIG. 7A and 1258.146 for theapparatus1008A inFIG. 8A. The light-emitting apparatuses inFIGS. 7A and 8A have similar total light extraction efficiencies (≈138.256 lm/W and ≈137.087, respectively). Theapparatus1008A can retain the light extraction efficiency and provide a better standard deviation of CCT between the front side and back side by adopting a structure with two phosphor layers. In an embodiment, the concentration of the firstwavelength conversion layer40 has higher influence on the CCT of the forward emission light (L1); while the concentration of the secondwavelength conversion layer42 has higher influence on the CCT of the backward emission light (L2).

• 	light emitting apparatus	FIG. 7A	FIG. 8A
  	Phosphor concentration _	30%_0.5 mm	70%/5%_
  	thickness		0.3 mm/0.3 mm
  	CCT of L1	8455.27	7248.63
  	CCT of L2	9813.29	8114.13
  	Standard deviation of CCT	2720.383	1258.146
  	between L1/L2 (K)
  	Light extraction efficiency_L1	75.3189	66.6028
  	(lm/W)
  	Light extraction efficiency _L2	62.9374	70.4841
  	(lm/W)
  	Total light extraction efficiency	138.256	137.087
  	(lm/W)

• FIGS. 8C-8D show two light-emitting apparatus in accordance with embodiments of the present disclosure. Theapparatus1008C inFIG. 8C includes two light-emittingdevices3000 which is arranged on twocarriers10 to emit light in a left direction and a right direction, respectively. The left side and the right side of thewavelength conversion layer44, formed between thelens170aand170b, can absorb and convert light respectively coming from the two light-emittingdevices3000. The two light-emittingdevices3000 can emit the same color light, such as infrared, red light, green light, blue light, and UV light. In an embodiment, the CCT of the light-emittingapparatus1008C can be decreased down to about 6500K when the concentration of the wavelength conversion material in thewavelength conversion layer44 is increased. However, the CCT is then kept unchanged at 6500K around when the concentration of the wavelength conversion material in thewavelength conversion layer44 is even increased to 30% or more. The light extraction efficiency can be increased up to 290 (lm/W) around with the increase of the concentration of the wavelength conversion material in thewavelength conversion layer44. However, the light-emitting efficiency is kept unchanged around 290 (lm/W) when the concentration of the wavelength conversion material in thewavelength conversion layer44 is even increased to 30% or more.
• The light-emittingapparatus1008D inFIG. 8D includes a light-emittingdevice3000 positioned on thecarrier10, two wavelength conversion layers46 and48, and alens172 covering the light-emittingdevice3000 and the wavelength conversion layers46 and48. Referring toFIG. 8D, the lights L1 and L3 are redirected to incident the front side of the wavelength conversion layers46 and48. The lights L2 and L4 are redirected to incident the back side of the wavelength conversion layers46 and48. In an embodiment, the wavelength conversion layers46 and48 have the same thickness of 0.55 mm.
• The light properties of the light-emitting apparatus are listed below. Thelens172 is symmetric with a central axis or a central plan (not shown), and therefore, can generate a symmetrical light paths. In other words, lights L1 and L3 are mirror images of each other; lights L2 and L4 are also mirror images of each other. The standard deviation of CCT between L1 and L2, or L3 and L4 is less than 600K, which is less than that of the light-emitting apparatus shown inFIG. 7A. The light-emitting efficiency is larger than 150 lm/W, which is larger than the light-emitting efficiency of the light-emitting apparatus shown inFIG. 7A.

• 	light emitting apparatus	FIG. 7A	FIG. 8D
  	Phosphor concentration _	30%_0.5 mm	30%_0.5 mm
  	thickness
  	CCT of L1	8455.27	6691.231
  	CCT of L2	9813.29	7251.631
  	Standard deviation of CCT	2720.383	548.4152
  	between L1/L2 (K)
  	Light extraction efficiency_L1	75.3189	62.67172
  	(lm/W)
  	Light extraction efficiency _L2	62.9374	96.07058
  	(lm/W)
  	Total light extraction efficiency	138.256	158.7423
  	(lm/W)

• FIGS. 9A-9D show light-emitting apparatuses in accordance with embodiments of the present disclosure. Referring toFIG. 9A, thelens174 is optically coupled with awavelength conversion layer50. The light can enter into the lens from one side and escape it at another side. The light can be reflected back and forth in thelens174 if the incident angle of the light is properly controlled to create a total reflection at the top and bottom inner surfaces of thelens174. The light can be absorbed by thewavelength conversion layer50 with strikes at different positions. With absorption of more light, more converted light can be generated by thewavelength conversion layer50.
• As shown inFIG. 9B, the light-emittingapparatus1009B has a light-emittingdevice4000 formed on acarrier10, alens174 having acavity1740, and awavelength conversion layer50 arranged on thelens174. The light-emittingdevice4000 is arranged in thecavity1740 and fully covered by thelens174.FIG. 9C shows a light pattern viewed on a front side of thelens174.FIG. 9D shows a light pattern viewed on a bottom side of thelens174. The optical properties of theapparatus1009B are listed below, wherein the standard deviation of CCT between light L1 and L2 is lower than 200K, the total light extraction efficiency is around 140 lm/W.

• 	light emitting apparatus	FIG. 7A	FIG. 9B
  	Phosphor concentration _	30%_0.5mm	24%_0.45 mm
  	thickness
  	CCT of L1	8455.27	6593.7
  	CCT of L2	9813.29	6292.65
  	Standard deviation of CCT	2720.383	160.89
  	between L1/L2 (K)
  	Light extraction efficiency _L1	75.3189	61.76
  	(lm/W)
  	Light extraction efficiency _L2	62.9374	73.42
  	(lm/W)
  	Total light extraction efficiency	138.256	135.18
  	(lm/W)

• FIGS. 10A-10D show a light-emitting apparatus in accordance with embodiments of the present disclosure. Referring toFIG. 10A-10B, the light is reflected back and forth in thelens176. Thelens176 has afirst wing1760 and asecond wing1762 which are inclined against thecarrier10 by angles θ1 and θ2, respectively. In one embodiment, the angle θ1 is 30°, which is equal to that of θ2. As shown inFIG. 10A, the light L1 is reflected two or more times within thesecond wing1762 before passing through thewavelength conversion layer52. The light L2 is reflected two or more times within thesecond wing1762 and can leave thesecond wing1762 towards a direction far away from thewavelength conversion layer52 without passing through thewavelength conversion layer52. Thewavelength conversion layer52 is not only formed on the surfaces S1 and S2 between thefirst wing1760 andsecond wing1762 but also on the edges E1 and E2 of thefirst wing1760 andsecond wing1762. As shown inFIG. 10B, thefirst wing1760 andsecond wing1762 are bifurcated above the light-emittingdevice5000 in a V/U-like shape. The lights L1 and L3 are moving in similar paths as shown in the drawing. With adopting lens shown inFIGS. 10A-10B, the lights L1˜L3 are more likely converted by thewavelength conversion layer52. The light-emitting apparatus inFIG. 10B has a light-emittingdevice5000 formed on acarrier10, alens176 having afirst wing1760 andsecond wing1762, and awavelength conversion layer52.FIG. 10C shows a front image of thelens176.FIG. 10D shows bottom image of thelens176. The optical properties of the apparatus are listed below, wherein the standard deviation of CCT is lower than 700K and the total light extraction efficiency is larger than 1501 m/W.

• 	light emitting apparatus	FIG. 7A	FIG. 10B
  	Phosphor concentration _	30%_0.5mm	4%_0.5 mm
  	thickness
  	CCT of L1	8455.27	6342.11
  	CCT of L2	9813.29	7416.94
  	Standard deviation of CCT	2720.383	657.92
  	between L1/L2 (K)
  	Light extraction efficiency_L1	75.3189	77.5
  	(lm/W)
  	Light extraction efficiency _L2	62.9374	80.87
  	(lm/W)
  	Total light extraction efficiency	138.256	158.37
  	(lm/W)

• Referring toFIG. 11A, the apparatus has several light-emitting devices6000 (fivedevices6000 are shown in the drawing, but the number can be less or more), adiffusion layer18 distant from the light-emittingdevices6000, aprism layer20 on thediffusion layer18, and an liquid crystal display (LCD)module22 on theprism layer20. The light-emittingdevices6000, thediffusion layer18, andprism layer20 can be integrated into a backlight module of LCD display. TheLCD module22 has a lens. Thediffusion layer18 can redistribute light from the light-emittingdevices6000, and increase the light uniformity of the light-emittingdevices6000. Theprism layer20 has numerous lenses to concentrate light. The light uniformity of theLCD module22 is therefore increased. In an embodiment, the distance between the lens in theLCD module22 and the light-emittingdevice6000 is larger than that between the adjacent light-emitting devices.
• FIG. 11B shows a schematic view of the apparatus. The symbol H represents the distance between the light-emittingdevice6000 and theLCD module22, and the symbol R represents the radius of the light field showing on theLCD module22. The symbol d represents the lateral distance between adjacent light-emitting devices. The shorter H implies a smaller light field with a shorter radius R at theLCD module22. In an embodiment, the light-emittingdevice6000 provides a light field on the LCD module22 (or on the lens) having a radius R two or more times larger than the distance d. TheFIGS. 11C-11D show a schematic top view of the arrangement of the light-emittingdevices6000. The light-emittingdevices6000 are arranged in a connected rectangular shape, as shown inFIG. 11C. The light-emittingdevices6000 are arranged in a connected triangular shape, as shown inFIG. 11D. Different arrangements of the light-emitting devices can provide different illumination distribution.FIG. 11E shows an illumination distribution image of a unit area of the array shown inFIG. 11C.FIG. 11F shows an illumination distribution image of a unit area of the array shown inFIG. 11D. In the embodiment, the radius R of the light field of a single light-emittingdevice6000 can be set equal to the shortest distance between two adjacent light-emittingdevices6000. As shown inFIGS. 11E and 11F, different colors represent different illuminance level. The detail of the color mapping can be referred to the legend of respective diagram.
• FIG. 11G is a diagram showing that the uniformity of illumination varies with a displacement of a light-emittingdevice6000 in x direction.FIG. 11H is another diagram showing that the uniformity of the illumination varies with a displacement of a light-emittingdevice6000 in y direction. The abscissa of theFIG. 11G orFIG. 11H represents the displacement of one light-emittingdevice6000 with respect to an original position in the light-emitting apparatus. The ordinate of theFIG. 11G orFIG. 11H represents the normalized uniformity of illuminance of a light-emitting apparatus. As shown inFIGS. 11G and 11H, the positive (x>0 or y>0) and negative (x<0 or y<0) displacements result in similar decreasing levels of illumination uniformities in the rectangular arrangement. However, the positive (x>0 or y>0) and negative (x<0 or y<0) displacements result in different decreasing levels of illumination uniformities in the triangle arrangement. Specifically, in the triangle arrangement, the negative displacement results in a more rapid drop in the illumination uniformity than the positive displacement does. In either rectangular or triangle arrangement, the illuminance uniformity is substantially lower than 0.9 when the absolute value of the displacement is about 0.1 mm.
• FIGS. 12A-12B show measuring instruments in accordance with embodiments of the present disclosure. The instrument inFIG. 12A can measure the light properties of a light-emittingdevice7000 in far-field. The light from the light-emittingdevice7000 can pass through afirst iris178aand asecond iris178band be received by aspectrometer24. Thefirst iris178aand thesecond iris178bcan remove part of the light and retain light in a specific angle to be detected by thespectrometer24. The instrument inFIG. 12B can measure the light properties of a light-emittingdevice7000 in mid-field. The light from the light-emittingdevice7000 can pass through aconvex lens180 and be received by thespectrometer24.
• FIGS. 12C-12E show some results measured by the instrument shown inFIG. 12A. 0 degree inFIGS. 12C-12E substantially corresponds to the center of the light-emittingdevice7000. The angle represents the angle between the measuring point and the center of the light-emittingdevice7000.FIG. 12C shows the normalized intensities of blue light, yellow light, and total light. The total light can include the blue light, the yellow light, or other color light. As shown in the drawing, different lights have different intensities at the same angle.FIG. 12D shows the light intensity ratio of the yellow light to the blue light (YBR). The ratio increases with the increase of absolute value of the angle. Specifically, yellow light can be more easily observed at larger angle, which results in a light pattern having a yellowish peripheral region. Referring toFIG. 12E, the correlated color temperature (CCT) decreases from over 6500K at 0 degree (around the center of the light-emitting device) to about 4500K at 90 degree (around the peripheral region of the light-emitting device).
• As shown inFIG. 13, alens184 can be arranged on the light-emittingdevice8000 to render a more uniform illuminance and/or color distribution. Thelens184 can direct the blue light to a direction with a larger angle and the yellow light to a direction with a smaller angle. Thelens184 has a main body and acavity1840 which is built from a bottom surface of the main body and defines a space for accommodating the light-emittingdevice8000. Thecavity1840 has a top inner surface with a bell/dome-like shape/contour and a bottom inner surface with a tail extending to the bottom surface of thelens1840 in a cross-sectional view. The top inner surface and the bottom inner surface can have identical or different curvatures. Moreover, the top inner surface itself or the bottom inner surface itself can have one or more curvatures. Thelens184 has an outer contour with several sections connected with each other (the section can be seen as a line in a cross sectional view, as shown inFIG. 13). The transition portion of two adjacent sections preferably has a perceived angular change to redirect specific color light to a predetermined direction. For example, the color light with shorter wavelength, such as a blue light, can be bended downward after striking a higher section of thelens184; the color light with longer wavelength, such as a yellow light, can be bended upward after striking the a lower section portion of thelens184.
• It will be apparent to those having ordinary skill in the art that various modifications and variations can be made to the devices in accordance with the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure covers modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.

Claims (13)

1. A backlight module, comprising:

a light-emitting device having a bottom surface and a color space uniformity Δu′v′ less than 0.005, comprising:

a light-emitting diode comprising a first top surface opposite to the bottom surface, and a first side surface; and

a transparent layer covering the first top surface and the first side surface, and having a second top surface and a second side surface.

2. The light-emitting apparatus according toclaim 1, further comprising a wavelength conversion layer covering the transparent layer.

3. The light-emitting apparatus according toclaim 1, further comprising a carrier having a third top surface connected to the bottom surface.

4. The light-emitting apparatus according toclaim 3, wherein the third top surface is a Lambertian scattering surface.

5. The light-emitting apparatus according toclaim 1, wherein a ratio of a distance between the first side surface and the second side surface to a distance between the first top surface and the second top surface is not larger than 5.

6. A backlight module, comprising:

a light-emitting device having a bottom surface and a color space uniformity Δu′v′ within four MacAdam ellipse, comprising:

a light-emitting diode comprising a first top surface opposite to the bottom surface, and a first side surface;

a wavelength conversion layer covering the first top surface; and

an outmost transparent cover covering the wavelength conversion layer and having a second top surface and a second side surface.

7. The light-emitting apparatus according toclaim 6, further comprising a transparent layer formed between the light-emitting diode and the wavelength conversion layer.

8. The light-emitting apparatus according toclaim 7, wherein the wavelength conversion layer has an upper surface with a contour identical or similar to that of a lower surface of the outmost transparent cover.

9. The light-emitting apparatus according toclaim 7, wherein the wavelength conversion layer has an upper surface not parallel to that of the second top surface.

10. The light-emitting apparatus according toclaim 7, wherein the wavelength conversion layer covers the first side surface.

11. The light-emitting apparatus according toclaim 6, further comprising a carrier having a third top surface connected to the bottom surface.

12. The light-emitting apparatus according toclaim 11, wherein the third top surface is a Lambertian scattering surface.

13. The light-emitting apparatus according toclaim 6, wherein a ratio of a distance between the first side surface and the second side surface to a distance between the first top surface and the second top surface is larger than 0.7.

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