Abstract:
Disclosed is an illuminative module for enhancing the white balance while reducing thermal drift and color blocks. The illuminative module includes a substrate and light-emitting elements provided on the substrate to emitting light of the primary colors and a fourth color, respectively, so that the light of the primary colors is mixed with the light of the fourth color to provide white light.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates to a white light (“WL”) lighting module based on light-emitting diodes (“LEDs”) and, more particularly, to a method for making an LED-based WL lighting module that prevents glare and provides adjustable color temperature. 
       BACKGROUND OF INVENTION 
       [0002]    III-V semiconductors are used to make photoelectric elements such as LEDs to emit light based on the electro-luminescence conversion effect. An LED is high in electroluminescence conversion efficiency but low in energy consumption. Hence, a lot of efforts have been made to develop LEDs for general lighting applications. There is a trend to use LEDs instead of current illuminative devices. 
         [0003]    As disclosed in U.S. Pat. No. 6,765,237, a conventional LED includes a chip, a fluorescent layer provided on the chip and epoxy for packaging the chip and the yellow fluorescent layer. Based on the conversion effect, the chip emits blue light. The blue light turns the electrons of the fluorescent layer into an excited state from a ground state. In the excited state, the fluorescent layer emits yellow light. The blue light is mixed with the yellow light, thus providing WL. This is sometimes called “LED color-mixing technology.” 
         [0004]    This conventional LED is the mainstream product since its making and using are simple. However, the fluorescent layer is vulnerable to heat generated from the chip so that the wavelength of the light emitted from the LED changes, and the intensity of the illumination or luminance of the LED decays. This is sometimes called “fluorescent decay.” 
         [0005]    Currently, most LEDs emit WL based on the chemical color mixture. However, they suffer the above-discussed problems that have not been overcome. Therefore, such LEDs are not suitable for long-term applications. 
         [0006]    Referring to  FIG. 1 , another conventional multi-chip LED lighting module includes a chip  1  for emitting red light (“RL”), another chip  2  for emitting green light (“GL”) and another chip  3  for emitting blue light (“BL”). The wavelengths and intensities of the light of the primary colors must be carefully selected to provide WL. Even with careful selection, WL only exists in an area where the light beams of the primary colors overlap. Light turns to the primary colors away from the area. There are various color blocks. 
         [0007]    The illuminative angles of the chips can be enlarged to mitigate the effect of color blocks. However, human eyes are more sensitive to GL with a wavelength of 555 nm than any other light. This is called spectrum sensitivity as shown in  FIG. 2 . Moreover, the conventional LED shown in  FIG. 1  causes glare to human eyes. 
         [0008]    Referring to  FIG. 3 , another conventional lighting module includes chips  4 ,  5  and  6  for respectively emitting BL, GL and RL, a package  7  for wrapping the chips  4 ,  5  and  6 , a substrate  8  for supporting the chips  4 ,  5  and  6  and the package  7  and scattering particles  9  provided in the package  7 . The scattering particles  9  scatters and mixes the RL, GL and BL respectively emitted from the chips  4 ,  5  and  6  into WL. 
         [0009]    The conventional lighting module shown in  FIG. 3  provides good mixture of the RL, GL and BL. It has not been made available on the market because it exhibits unacceptable color blocks. Moreover, the chips  4 ,  5  and  6  are provided in the single package  7  so that this conventional lighting module suffers overheating and does not last long. 
         [0010]    Another conventional lighting module includes a WL LED, an RL LED, a GL LED and a BL LED. The WL LED is used as a major lighting module, and the RL LED, GL LED and BL LED color temperature-compensating units. If necessary, at least some of the color temperature-compensating units are activated to emit light to compensate the changes in the color temperature of white light emitted from the WL LED due to the thermal drift of the wavelength. The brightness, color temperature and color blocks of this conventional lighting module change tremendously after the WL LED decays. Moreover, it is difficult and uneconomic to precisely control currents provided to the LEDs. 
         [0011]    Moreover, the wavelength of light emitted from an LED is determined by the structure of the epitaxy, materials used therein and the matching of lattices. The wavelength of the light emitted from the LED suffers thermal drift. That is, at the moment when the multi-chip LED lighting is actuated, the intensity of the red light is high so that the white light tends to be a warm color. As the multi-chip LED lighting goes on, the intensity of the blue light gets higher so that the white light tends to be a cold color. The thermal drift of the white light might be too big to achieve a good white balance. The intensity of illumination would be compromised accordingly. 
         [0012]    Therefore, the present invention is intended to obviate or at least alleviate the problems encountered in prior art. 
       SUMMARY OF INVENTION 
       [0013]    It is the primary objective of the present invention to provide a method for making a lighting module for preventing glare and providing adjustable color temperature. 
         [0014]    To achieve the foregoing objective, the method includes the steps of providing a carrier, connecting red LED packages to the carrier, connecting green LED packages to the carrier and connecting blue LED packages to the carrier. Each of the red LED packages includes a red LED chip, a cover for covering the red LED chip and scattering particles scattered in the cover. Each of the green LED packages includes a green LED chip, a cover for covering the blue LED chip and scattering particles scattered in the cover. Each of the blue LED packages includes a blue LED chip, a cover for covering the blue LED chip and scattering particles scattered in the cover. The numbers and positions of the LED packages on the carrier are changeable to adjust the color temperature of light emitted from the lighting module and therefore prevent glare. 
         [0015]    Other objectives, advantages and features of the present invention will become apparent from the following description referring to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]    The present invention will be described via detailed illustration of embodiments versus the prior art referring to the drawings. 
           [0017]      FIG. 1  is a cross-sectional view of a conventional lighting module. 
           [0018]      FIG. 2  is a table of a human eye&#39;s sensitivities to various wavelengths of light. 
           [0019]      FIG. 3  is a cross-sectional view of another conventional lighting module. 
           [0020]      FIG. 4  is a top view of a lighting module according to a first embodiment of the present invention. 
           [0021]      FIG. 5  is an enlarged cross-sectional view of an LED package used in the lighting module shown in  FIG. 4 . 
           [0022]      FIG. 6  is a cross-sectional view of the lighting module of  FIG. 4 . 
           [0023]      FIG. 7  is a top view of a lighting module according to a second embodiment of the present invention. 
           [0024]      FIG. 8  is a top view of a lighting module according to a third embodiment of the present invention. 
           [0025]      FIG. 9  is a top view of a lighting module according to a fourth embodiment of the present invention. 
           [0026]      FIG. 10  is a top view of a lighting module according to a fifth embodiment of the present invention. 
           [0027]      FIG. 11  is a cross-sectional view of a lighting module according to a sixth embodiment of the present invention. 
           [0028]      FIG. 12  is a C. I. E. chromaticity diagram. 
           [0029]      FIG. 13  is a cross-sectional view of a lighting module according to a seventh embodiment of the present invention. 
           [0030]      FIG. 14  is a cross-sectional view of a lighting module according to an eighth embodiment of the present invention. 
           [0031]      FIG. 15  is a cross-sectional view of a lighting module according to a ninth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0032]    Referring to  FIG. 4 , shown is a lighting module  100  for preventing glare and providing adjustable color temperature according to a first embodiment of the present invention. The lighting module  100  includes a carrier  10 , three RL LED packages  20 , three GL LED packages  30  and three BL LED packages  40 . The carrier  10  is preferably a printed circuit board (“PCB”) provided with a layout of a circuit. 
         [0033]    Referring to  FIG. 5 , each of the RL LED packages  20  includes an RL LED chip  21 , a cover  22  and scattering particles  23 . The RL LED chip  21  is connected to the circuit of the carrier  10  so that the circuit of the carrier  10  can energize the RL LED chip  21  to emit RL. The cover  22  is made of a transparent material such as epoxy, silicone and glass. The cover  22  is provided over the RL LED chip  21 . The scattering particles  23  are scattered in the cover  22 . The RL LED packages  20  are located in predetermined positions on the carrier  10 . 
         [0034]    Each of the GL LED packages  30  includes a GL LED chip  31 , a cover  32  and scattering particles  33 . The GL LED chip  31  is connected to the circuit of the carrier  10  so that the circuit of the carrier  10  can energize the GL LED chip  31  to emit GL. The cover  32  is made of a transparent material such as epoxy, silicone and glass. The cover  32  is provided over the GL LED chip  31 . The scattering particles  33  are scattered in the cover  32 . The scattering particles  33  are made of a highly reflective or scattering material such as silver, resin and silicon. The GL LED packages  30  are located in predetermined positions on the carrier  10 . 
         [0035]    Each of the BL LED packages  40  includes a BL LED chip  41 , a cover  42  and scattering particles  43 . The BL LED chip  41  is connected to the circuit of the carrier  10  so that the circuit of the carrier  10  can energize the BL LED chip  41  to emit BL. The cover  42  is made of a transparent material such as epoxy, silicone and glass. The cover  42  is provided over the BL LED chip  41 . The scattering particles  43  are scattered in the cover  42 . The scattering particles  43  are made of a highly reflective or scattering material such as silver, resin and silicon. The BL LED packages  40  are located in predetermined positions on the carrier  10 . 
         [0036]    The scattering particles  23 ,  33  and  43  are made of at least one highly reflective or scattering material. For example, they can be made of silver, calcium carbonate (CaCO 3 ) and/or silicon dioxide (SiO 2 ) alone or in combination with resin. 
         [0037]    Referring to  FIG. 6 , the RL LED packages  20  emit RL beams. The GL LED packages  30  emit GL beams. The BL LED packages  40  emit BL beams. The scattering particles  23 ,  33  and  43  cause the light beams to cast similar light spots that almost completely overlap one another, leaving small color blocks. Therefore, the RL, GL and RL are well mixed into WL. It should be noted that the numbers of the scattering particles  23 ,  33  and  43  within the LED packages  20 ,  30  and  40  are different from one another. The density of the scattering particles  23 ,  33  or  43  may change within the cover  22 ,  32  or  42 . 
         [0038]    Moreover, the LED chips  21 ,  31  and  41  are packaged independent of one another. Hence, the heat radiation of the lighting module  100  is better than that of a conventional lighting module with LED chips packaged in a common cover. 
         [0039]    Furthermore, for including three RL LED packages  20 , three GL LED packages  30  and three BL LED packages  40 , their positions on the carrier  10  can be replaced with one another or changed to enable adjustment of the color temperature from cold to warm. For example, color temperature for indoor use may be different from color temperature for outdoor use. The color temperature of the light emitted from the lighting module  100  is adjustable without having to use a complicated mechanism to change a circuit or voltage provided thereto. 
         [0040]    Referring to  FIG. 7 , there is shown a lighting module  200  according to a second embodiment of the present invention. The lighting module  200  is like the lighting module  100  except including a carrier  50  instead of the carrier  10 . The carrier  50  includes three PCBs  51  connected to one another. One of the PCBs  51  carries the RL LED packages  20 . Another one of the PCBs  51  carries the GL LED packages  30 . The other one of the PCBs  51  carries the BL LED packages  40 . The cost of the lighting module  200  is lower than that of the lighting module  100 . 
         [0041]    Referring to  FIG. 8 , there is shown a lighting module  300  according to a third embodiment of the present invention. The lighting module  300  is like the lighting module  100  except including a carrier  60  instead of the carrier  10 . The carrier  60  includes nine PCBs  61  connected to one another. Each of the PCBs  61  carries a related one of the LED packages  20 ,  30  and  40 . The cost of the lighting module  300  is lower than that of the lighting module  100 . 
         [0042]    Referring to  FIG. 9 , there is shown a lighting module  400  according to a fourth embodiment of the present invention. The lighting module  400  is like the lighting module  100  except including 4 RL LED packages  20  and 5 GL LED packages  30 . There are totally 12 LED packages arranged in a 4×3 array. The color temperature of light emitted from the lighting module  400  is different from light emitted from the lighting module  100 . 
         [0043]    Referring to  FIG. 10 , there is shown a lighting module  500  according to a fifth embodiment of the present invention. The lighting module  500  is like the lighting module  100  except including 5 RL LED packages  20 , 7 GL LED packages  30  and 4 BL LED packages  40 . There are totally 16 LED packages arranged in a 4×4 array. The color temperature of light emitted from the lighting module  500  is different from light emitted from the lighting module  100 . 
         [0044]    Referring to  FIG. 11 , there is shown a lighting module  600  according to a six embodiment of the present invention. The lighting module  600  is like the lighting module  100  except including at least one LED package  70  including an LED chip  71 , a cover  72  and scattering particles  73 . The LED chip  71  is connected to the circuit of the carrier  10  so that the circuit of the carrier  10  can energize the LED chip  71  to emit light of a fourth color. The cover  72  is made of a transparent material such as epoxy, silicone and glass. The cover  72  is provided over the LED chip  71 . The scattering particles  73  are scattered in the cover  72 . The scattering particles  73  are made of a highly reflective or scattering material such as silver, resin and silicon. 
         [0045]    Referring to  FIG. 12 , the wavelength of the fourth color is 560 to 610 nm or 470 to 500 nm. The fourth color is yellow if the wavelength is 560 to 610 nm or cyan if the wavelength is 470 to 500 nm. Preferably, the light of the fourth color is yellow light, which is a mixture of red light with green light. Yellow light can be mixed with blue light to provide white light. Yellow light can be mixed with greenish, reddish or bluish white light to provide white light with the color temperature falling in the central portion of the C. I. E. chromaticity diagram. Thermal shift of the wavelength in the spectrum is reduced, thus enhancing the white balance. The resultant white light is close to real white light. 
         [0046]    Referring to  FIG. 13 , a lighting module  700  according to a seventh embodiment of the present invention is shown. The lighting module  700  is like the lighting module  100  except including a scattering panel  80  extending parallel to the carrier  10  so that the scattering panel  80  is at a same distance from the LED packages  20 ,  30  and  40 . The scattering panel  80  includes a transparent panel  81  and scattering particles  82  evenly scattered in the transparent panel  81 . The transparent panel  81  is made of epoxy, silicone, glass or any other proper material. The scattering particles  82  are made of a highly reflective or scattering material such as silver, resin and silicon. The scattering panel  80  causes the RL, GL and BL to be mixed with one another again. With this enhanced color mixture, there is no color block at all. 
         [0047]    Referring to  FIG. 14 , a lighting module  800  according to an eighth embodiment of the present invention is shown. The lighting module  800  is like the lighting module  700  except including an enhancing panel  91  extending parallel to the scattering panel  80 . The enhancing panel  91  concentrates the WL so that the WL beam travels further than without the enhancing panel  91 . 
         [0048]    Referring to  FIG. 15 , a lighting module  900  according to a ninth embodiment of the present invention is shown. The lighting module  900  is like the lighting module  100  except including a cover  92  for covering and protecting the LED packages  20 ,  30  and  40  from external objects. The cover  92  is made of a transparent material such as epoxy, silicone and glass. 
         [0049]    In the above-mentioned embodiments, each of the LED chips  21 ,  31 ,  41  and  71  is packaged within a related one of the covers  22 ,  32 ,  42  and  72 . The covers  22 ,  32 ,  42  and  72  can however be omitted and the LED chips  21 ,  31 ,  41  and  71  can be covered with a cover in which scattering particles are evenly scattered. 
         [0050]    The present invention has been described through the detailed illustration of the embodiments. Those skilled in the art can derive variations from the embodiments without departing from the scope of the present invention. Therefore, the embodiments shall not limit the scope of the present invention defined in the claims.