Patent Document

This is a Divisional of U.S. application Ser. No. 11/233,039, filed Sep. 23, 2005 now U.S. Pat. No. 7,724,321, and allowed on Jan. 25, 2010, the subject matter of which is incorporated herein by reference. 
    
    
     RELATED APPLICATIONS 
     The present application claims the right of priority based on Taiwan Application Serial Number 093129157, filed Sep. 24, 2004; Taiwan Application Serial Number 094103538, filed Feb. 4, 2005; Taiwan Application Serial Number 094114630, filed May 6, 2005; Taiwan Application Serial Number 094121784, filed Jun. 29, 2005; and Taiwan Application Serial Number 094128643, filed Aug. 22, 2005, the disclosure of which is incorporated herein by reference in their entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a liquid crystal display (LCD) comprising a color filter layer and a backlight module, the backlight module comprising an ultraviolet unit, the color filter layer comprising a wavelength-converting material able to absorb the ultraviolet light emitted from the ultraviolet unit and emit green light. 
     BACKGROUND OF THE INVENTION 
     A liquid crystal display belongs to a non-self emitting display, and thus light emitting device is needed to act as a light source. Such a light emitting device is generally called a backlight module. Backlight modules are commonly divided into two types: a direct-light type and an edge-light type. The conventional backlight module uses a lamp tube such as a cold cathode florescent lamp (CCFL) as a light source. However, the CCFL fails to regenerate the real colors of objects due to the low color rendering index (CRI). 
     For better color rendering, a light-emitting diode (LED) is deemed a better solution for the light source of backlight module in the coming market. LEDs offer benefits such as small size, low power consumption, fast response time, long operating time, and durability, etc. A color filter is usually used in the LCD for separating the three primary colors, i.e. red, blue and green from the white light. Mixing the three primary colors in different percentages may create various desired colors. 
     There are several methods of forming white light by LEDs. (1) A blue LED used with a yellow phosphor, commonly yttrium-aluminum-garnet (YAG) phosphor, is one of the most popular measures forming white light. However, this type of white light is formed by mixing blue light with yellow light, and the spectrum thereof is mainly shown at two wavelengths of 460 nm and 550 nm, i.e. this type of while light lacks of red and green lights, and thus a LCD adopting this type of white light fails to show real color of object. (2) A blue LED is used to excite the red and green phosphors for generating red and green lights. The red light, the green light, and the blue are mixed to form white light. However, there is serious crosstalk among the red, blue and green colors generated by this method, i.e. the bandwidths of the red, blue and green colors are overlapped. (3) A ultraviolet. LED is used to excite three or more phosphors for generating three colors of red, blue and green. This method also causes serious crosstalk. (4) Three separate red, blue and green LEDs are used to generate white light. The white light made by this method can achieve NTSC 105% or more, which is 1.5 times higher than the conventional CCFL. However, due to the different illumination efficiencies of different colors LEDs, different numbers of the red, blue and green LEDs are required for practical application. Generally speaking, the efficiency of green LED is poorer, and thus more green LEDs are needed to balance with the light amount generated from other colored LEDs. However, the more LEDs the higher cost rises, and more space needs for accommodating the LEDs. 
     SUMMARY OF THE INVENTION 
     A liquid crystal display (LCD) of the present invention comprises a backlight module including an ultraviolet unit; a liquid crystal layer used for controlling light flux emitted from the backlight module; and a color filter layer comprising a plurality of pixels and a wavelength-converting material formed on one of the pixels, wherein the wavelength-converting material emits green light after being irradiated by the ultraviolet unit. 
     The backlight module further comprises a red-light unit and a blue-light unit, and preferably, at least one of the ultraviolet unit, the red-light unit and the blue-light unit is a light-emitting diode (LED). 
     The filter layer preferably has a reflection layer used for reflecting the specific light from the backlight module. Preferably, the color filter layer comprises a distributed bragg reflector (DBR) used for reflecting the light from the backlight module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and some attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a schematic diagram illustrating an embodiment of the present invention; 
         FIGS. 2   a  to  2   e  are schematic diagrams respectively illustrating a light-spreading device and an optically-conditioning surface in accordance with the embodiment of the present invention; and 
         FIGS. 3   a  and  3   b  are schematic diagrams illustrating the compositions of a semiconductor light-emitting element assembly in accordance with the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     First Embodiment 
       FIG. 1  is a schematic diagram illustrating the structure of a LCD  10  of the present invention. Some components of the LCD  10  are omitted for clarity in  FIG. 1 . 
     The LCD  10  comprises a backlight module  11  acting as a light source to the LCD  10 . Since the LCD  10  shows the image displayed in the visible wavelength range to a user, the backlight module  11  generally has to a light source in the visible wavelength range. The backlight module  11  generally has to provide white light, and the white light is preferably generated by the three primary colored light emitted from red, blue and green LEDs. 
     To increase the illumination efficiency of green light, the backlight module  11  of the present invention uses an ultraviolet emitter, such as an ultraviolet unit  1101 , preferably, an ultraviolet LED, and a wavelength-converting material  1402  (labeled as P) which can absorb ultraviolet light to generate green light. The wavelength of the ultraviolet light herein is between 10 nm-420 nm, and preferably between 200 nm-420 nm. White light can be formed by mixing red light emitted from a red-light unit  1102 , blue light emitted from a blue-light unit  1103 , and green light emitted from the wavelength-converting material  1402  radiated by the ultraviolet unit  1101 . The red-light unit  1102  and the blue-light unit  1103  includes by not limited to LEDs, florescent lamps, incandescent lamps and halogen lamps. 
     The wavelength-converting material  1402  is such as a phosphor able to being excited by the ultraviolet light emitted from the ultraviolet unit  1101  to generate green light. If the wavelength of the ultraviolet light from the ultraviolet unit  1101  ranges between 200 nm and 420 nm, preferably between 360 nm and 400 nm, the wavelength-converting material  1402  can use an alkaline earth metal silicate phosphor, and preferably an europium(Eu) activated alkaline earth metal silicate phosphor. The composition of the europium(Eu) activated alkaline earth metal silicate phosphor is (SrBaMg) 2 SiO 4 :Eu. The FWHM (Full Width Half Maximum) of the light generated by such a phosphor is smaller than 35 nm and that of green light emitted by InGaN LEDs. The europium(Eu) activated alkaline earth metal silicate phosphor is available from the commercial products fabricated by Intematix Corporation, California, USA, such as G400™/G380™/G360™ series. 
     Other phosphors that can be excited by UV light and emits green light is such as (Ba 1-x-y-z Ca x Sr y Eu z ) 2 (Mg 1-w Zn w )Si 2 O 7 , wherein x+y+z=1, 0.05&gt;z&gt;0 and w&lt;0.05; Ca 8 Mg(SiO 4 ) 4 Cl 2 :Eu,Mn; Ba 2 SiO 4 :Eu; Ba 2 MgSiO 7 Eu; BaAl 2 O 4 Eu; SrAl 2 O 4 :Eu; and BaMg 2 Al 16 O 27 :Eu, etc., wherein the excited wavelength thereof is 330 nm-420 nm. 
     The numbers of the ultraviolet unit  1101 , the red-light unit  1102  and the blue-light unit  1103  depends on the factors including but not limited to the size of the LCD  10 , the brightness required by the LCD  10 , the lighting intensity of each of the units  1101 ,  1102  and  1103 , and the optical design inside the backlight module  11 . The red, blue, and green (violet) LEDs can be arranged in a sequence including red-blue-green (violet), red-green (violet)-blue, blue-green (violet)-red, blue-red-green (violet), green (violet)-red-blue, green (violet)-blue-red, red-blue-green (violet)-red and red-green (violet)-blue-red. 
     In the present embodiment, since the ultraviolet light is invisible to human eyes, the mixture light  12  emitted from the backlight module  11  merely shows the light formed by mixing the red light with the blue light, i.e. the light in purple-red series. 
     A liquid crystal layer  13  comprises a liquid crystal material and a thin film transistor (TFT) layer. When a bias is applied to the TFT layer, the liquid crystal molecules will be tilted or rotated and accordingly the light flux of the mixture light  12  passing through the liquid crystal layer changed. 
     The mixture light  12  passes through the liquid crystal layer  13  and reaches a color filter layer  14 . The color filter layer  14  generally is formed on a glass substrate and comprises a plurality of pixels  1401  (labeled as R, P, B in  FIG. 1 ). A pixel set is usually formed by at least three single color pixels for separating red, blue, and green light from the mixture light  12 . 
     In the present embodiment, the wavelength-converting material  1402  is disposed inside one pixel (hereinafter is called a green pixel P) in one pixel set. The wavelength-converting material  1402  is excited by the ultraviolet light emitted from the ultraviolet unit  1101  and generates green light (G). The other two pixels in one pixel set are a red pixel (R) and a blue pixel (B). The red and blue pixels may be formed by organic material. The red pixel (R) permits only the red light of the mixture light  12  passing, while the blue pixel (B) permits only the blue light of the mixture light  12  passing. Consequently, the red pixel (R) displays red color, and the blue pixel (B) displays blue color. 
     Besides organic materials, the red pixel (R) and the blue pixel (B) also can be formed from the phosphors that can be excited by UV light to emit red light and blue light. The phosphors that can be excited by UV light to emit red light are such as Y 2 O 2 S:Eu,Bi; Y 2 O 3 S:Eu,Bi; and 3.5 MgO.0.5 MgF 2 .GeO 2 :Mn +4 , wherein the excited wavelength thereof is 330 nm-420 nm. The phosphors that can be excited by UV light to emit blue light are such as BaMg 2 Al 16 O 27 :Eu; (SaBaCa) 5  (PO 4 ) 3 Cl:Eu; and Sr 4 Al 14 O 25 :Eu, wherein the excited wavelength thereof is 220 nm-330 nm. 
     Each of the pixels permits only a portion of white light passing, in other hand, the amount of light passing exiting the pixels is less than that entering the pixels due to the other portion of light being absorbed by the pixels, and accordingly light-output efficiency decreases. In order to raise the light-output efficiency, a DBR  1404  is formed in front of the filtering layer  1401  for reflecting the light in a selected wavelength. For example, in front of the red pixel (R), a DBR layer that can reflect blue light or ultraviolet light is formed for preventing the blue light or the ultraviolet light from being absorbed by the red pixel (R) and reflecting the blue light or the ultraviolet light so as to enter the blue pixel (B) or the green pixel (P). As to the other pixels, the corresponding DBRs may be used. Besides, since ultraviolet light is reflected by the DBR  1404 , the ultraviolet light can be prevented from emitting the LCD  10 . 
     Further, the LCD  10  may also comprise other optical films, such as a prism sheet, a diffuser and a polarizer, etc., wherein the prism sheet and the diffuser is generally disposed in the backlight module  11  for unifying the light emitted from the light-emitting units  1101 - 1103  so as to generate the desired mixture light  12 . The polarizer is generally used with the liquid crystal layer  13 , so that the mixture light  12  is polarized before entering the liquid crystal  13 . 
     Although the method of using ultraviolet light to excite the wavelength-converting material  1402  for generating green light can increase the green light output efficiency, yet some components inside the LCD  10 , particularly the plastic components such as the prism sheet, the diffuser and the polarizer, etc., are easily deteriorated due to ultraviolet irradiation. Hence those optical films or plastic components are preferably made of ultraviolet resistant material. 
     Other technical references related to the present invention, such as US2005/0001537A1, US2004/0061810A1, U.S. Pat. No. 6,686,691, U.S. Pat. No. 6,791,636, U.S. Pat. No. 6,844,903, U.S. Pat. No. 6,809,781, U.S. Pat. No. 6,252,254, U.S. Pat. No. 6,255,670, U.S. Pat. No. 6,278,135, U.S. Pat. No. 6,294,800, EP1138747, WO0189000 and WO0189001, are listed herein for reference. 
     Second Embodiment 
     The backlight module disclosed in the present embodiment comprises a light-spreading device  15  and/or an optically-conditioning surface  16  having a wavelike array for guiding, mixing and/or spreading the light generated from each of the light-emitting units  1101 - 1103  towards the liquid crystal layer  13 , such as shown in  FIG. 2   a.    
     Such as shown in  FIG. 2   b , the light-spreading device  15  has a wing-shaped protrusion part  1501 , a recess  1502  and a light-entering surface  1503 . The light-spreading device  15  is formed in a longitudinal direction  1504 . The recess  1502  is located away from the light-entering surface  1503 , and preferably is located on the side opposite to the light-entering surface  1503 . A first wavelike array  1601  is formed on the light-conditioning surface  16  for diffusing and/or mixing the light emitted from the ultraviolet unit  1101 , the red-light unit  1102  and/or the blue unit  1103 , thereby preventing the backlight module  11  from generating light spots or showing unmixed colored light. A portion of the light passing through the light-entering surface  1503  of the light-spreading device  15  is total-internal-reflected on the recess  1502  to both sides thereof, i.e. to the wing-shaped protrusion part  1501 , and another portion of the light passing through the recess  1502  may be refracted in compliance with the Snell&#39;s law due to the difference of the refractive indexes between the light-spreading device  15  and the ambient optical medium. Since a portion of the light is total-internal-reflected in the recess  1502  and directed to the wing-shaped protrusion part  1501 , the light flux emitting from the recess  1502  is reduced. Preferably, the shape of the recess  1502  is similar to a V-shape or U-shape. The light inside wing-shaped protrusion part  1501  may be refracted, reflected or directly exit out of the light-spreading device  15 . For example, the light entering the light-spreading device  15  at a specific angle will be gradually mixed as uniform colored light after several times of total reflection inside the wing-shaped protrusion part  1501 . The light-entering surface  1503  is not limited to a planar surface, but also can be a concave shape or other shapes able to receive light. 
     A first wavelike array  1601  may be formed on the optically-conditioning surface  16 , and both of the optically-conditioning surface  16  and the first wavelike array  1601  may be formed on the light-entering surface  1503  of the light-entering surface  1503 . The first wavelike array  1601  is a wave-shaped surface. The wave-shaped surface has a wave propagation direction, i.e. the array direction or wavefront direction of the first wavelike array  1601 . The wave structures formed on the first wavelike array  1601  may be a plurality of micro-lenses. Light through the micro-lenses is blurred. The diameter of each micro-lens is about 50-60 μm. If the waves of the first wavelike array  1601  are constructed consecutively, a distance between two consecutive wave peaks or troughs is about between 100 μm and 120 μm. 
     The optically-conditioning surface  16  may optionally be formed inside the light-spreading device  15  by combining two light-pervious materials with different refractive indexes. The wavelike array is then formed on the interface of the two light-pervious materials, such as shown in  FIG. 2   c . The hatched portion has a material different from the other portion&#39;s. The first wavelike array  1601  is not limited to being disposed on the light-entering surface  1503 , but also can be disposed on the wing-shaped protrusion part  1501  or/and the recess  1502 , such as shown in  FIG. 2   e.    
     The material forming the light-spreading device  15  is such as acrylic resin, cyclo-olefin co-polymer (COC), polymethyl-methacrylate (PMMA), polycarbonate (PC), polyetherimide, fluorocarbon polymer, silicone, the combinations thereof, or other light-pervious material. 
     As shown in  FIG. 2   d , the optically-conditioning surface  16  may also be formed on an optical film  17  having a first surface  1701  and a second surface  1702  opposite to the first surface  1701 . The optically-conditioning surface  16  is formed on one of the first surface  1701  and the second surface  1702 . If the optically-conditioning surface  16  is formed on the first surface  1701 , the first wavelike array  1601  is then formed on the first surface  1701 . The optical film  17  can be installed above the light-spreading device  15  or the area between the light-spreading device  15  and the light-emitting units  1101 - 1103 . Further, a second optically-conditioning surface  18  can be formed on the second surface  1702 , and a second wavelike array  1801  is formed on the second optically-conditioning surface  18 . The array direction of the second wavelike array  1801  is different from that of the first wavelike array  1601 . In that case, a Moiré pattern can be formed by stacking the first wavelike array  1601  and the second wavelike array  1801  having different array directions. By properly adjusting the first wavelike array  1601  and the second wavelike array  1801 , the intensity of the light passing through the Moiré pattern can be re-distributed, thereby achieving the performance of scattering the light uniformly. The optical film  17  may be available from the product manufactured by S-Light Opt Electronics Inc., Taiwan. 
     The optically-conditioning surface  16  or  18  is not limited to being merely disposed on one of the light-spreading device  15  and the optical film  17 , but also can be formed on both of the light-spreading device  15  and the optical film  17 . The first wavelike array  1601  and the second wavelike array  1801  can have the same or different wave sizes, wave shapes and wave frequencies. 
     If the arrangement direction of the light-emitting units  1101 ,  1102  and/or  1103  is parallel to the array direction of the first wavelike array  1601 , i.e. to the wavefront direction thereof, a light pattern substantially parallel to the wavefront direction of the first wavelike array  1601  will be generated after the light passes through the first wavelike array  1601 . When the arrangement direction of the light sources  1101 ,  1102  and/or  1103  and the wavefront direction of the first wavelike array  1601  are formed in straight lines, the light will be distributed as straight lines; when the arrangement direction of the light sources  1101 ,  1102  and/or  1103  and the wavefront direction of the first wavelike array  1601  are formed in curved or radiating patterns, the light will be distributed as curved or radiating patterns. Theoretically, when the arrangement direction of the light sources  1101 ,  1102  and/or  103  is parallel or about parallel to the wavefront direction of the first wavelike array  1601 , the light emitted from the light sources  1101 ,  1102  and/or  1103  is distributed into the light pattern extending along the wavefront direction. 
     The detailed techniques of the light-spreading device and the wavelike array have been described in Taiwan Application Serial Number 093129157 and Taiwan Application Serial Number 094114630, which are listed herein for reference. 
     Third Embodiment 
     In the present embodiment, the light-emitting units are semiconductor light-emitting elements, such as LEDs, and preferably LED dies. With the power increasing, the heat generated from LEDs also increases accordingly. For providing heat dissipation for the LEDs, the present invention installs the ultraviolet unit  1101 , the red-light unit  1102  and/or the blue-light unit  1103  on a composite substrate  1901 , such as shown  FIG. 3   a .  19  indicates a semiconductor light-emitting element assembly, such as a LED package;  1901  indicates a composite substrate;  1902  indicates a connecting structure;  1903  indicates a circuit layout carrier;  1904  indicates an electrical contact; and  1905  indicates a conductive wire. 
     The circuit layout carrier  1903  is bonded to a composite substrate  1901  through a connecting structure  1902 . The ultraviolet unit  1101 , the red-light unit  1102  and/or the blue-light unit  1103  are fixed in a recess  1906 . Conductive wires  1905  or other electrically connecting means are used to connect the ultraviolet unit  1101 , the red-light unit  1102  and/or the blue-light unit  1103  to electrical contacts  1904  formed on the circuit layout carrier  1903 . The difference between the thermal expansion coefficient of the light-emitting units  1101 - 1103  and that of the composite substrate  1901  is approximately smaller than or equal to 10×10 −6 /° C., thus the thermal stress between the light-emitting units  1101 - 1103  and the composite substrate  1901  is reduced. 
     The thermal expansion coefficient of the LED die generally is between 1×10 −6 /° C. and 10×10 −6 /° C. For example, the thermal expansion coefficient of GaN is about 5.4×10 −6 /° C.; that of InP is about 4.6×10 −6 /° C.; that of GaP is about 5.3×10 −6 /° C. In order to decrease excessive thermal stress formed between the light-emitting units  1101 - 1103  and its contact material, a composite substrate  1901  is used as the supporting base of the semiconductor light-emitting element assembly  19 . Besides, the composite substrate  1901  is also used as a heat-dissipation media. The thermal expansion coefficient of the composite substrate  1901  is preferably smaller than or equal to 10×10 −6 /° C. 
     The composite material is usually formed from two or more materials, and these two or more materials do not form any other molecular or atomic structures. Generally speaking, the composite material can offer the benefits of the separate materials and has physical properties better than that of the original materials. The composite material usually has the benefits of lightweight, high strength, and good thermal properties etc. The composite material includes a metal matrix composite (MMC), a polymer matrix composite (PMC), and ceramic matrix composite (CMC). These composites are respectively formed by mixing carbon fibers or ceramic fibers with metals, polymers, and ceramics. The composite substrate  1901  preferably formed by the metal matrix composite with a thermal conductivity coefficient not smaller than 150 W/mK and a thermal expansion coefficient not greater than 10×10 −6 /° C., such as aluminum matrix composite (its thermal conductivity coefficient is about 100˜640 W/mK; and its thermal expansion coefficient of the composite substrate is about 5˜10×10 −6 /° C.). Nonetheless, a polymer matrix composite and ceramic matrix composite may also be used as the composite substrate  1901 . 
     The circuit layout carrier  1903  is, for example, a printed circuit board, a flexible printed circuit, a semiconductor substrate such as a Si substrate or a ceramic substrate, etc. The semiconductor substrate used as the circuit layer carrier  1903  can use various semiconductor processes such as etching, sputtering etc. to form the desired circuits thereon, and also can be integrated with the process for forming the semiconductor light-emitting diode. The semiconductor substrate such as the Si substrate has acceptable heat transfer properties (its thermal conductivity coefficient and thermal expansion coefficient are about 150 W/mK and 4×10 −6 /° C. respectively). Since the thermal conductivity coefficients and thermal expansion coefficients of a metal matrix composite substrate are close to those of s Si substrate, the thermal stress between the two kinds of materials can be effectively reduced and the conductive efficiency can be further improved. Nonetheless, the printed circuit board or the flexible printed circuit may also be used. 
     The circuit layout carrier  1903  is bonded to the composite substrate  1901  through the connecting structure  1902 . The connecting structure  1902  is made of adhesive material, preferably a flexible adhesive layer. The flexible adhesive layer preferably preserves adhesion at a room temperature or a medium low temperature. The material forming the flexible adhesive layer includes but not limited to benzocyclobutene (BCB), epoxy, polyimide, SOG (Spin On Glass), silicone, solder, equivalents thereof and combinations thereof. Those flexible adhesive materials can be cured at a relatively low temperature (commonly smaller than 300° C.), thereby reducing the thermal stress between the composite substrate  1901  and the light-emitting units  1101 - 1103  and/or between the composite substrate  1901  and the circuit layout carrier  1903  at high temperature, also lessening the damage to the light-emitting units  1101 - 1103  at high temperature. 
     As shown in  FIG. 3   b , the connecting structure  1902  is composed of a flexible adhesive layer  2001 , and a reaction layer  2002  and/or a reaction layer  2003 . The flexible adhesive layer  2001  can be formed by the material described above. The reaction layers  2002  and  2003  are formed respectively between the flexible adhesive layer  2001  and the circuit layout carrier  1903 ; and/or between the flexible adhesive layer  2001  and the composite substrate  1901 , for enhancing the adhesion between the flexible adhesive layer  2001  and the circuit layout carrier  1903  and/or the composite substrate  1901 . The material forming the reaction layers  2002  and  2003  includes but not limited to silicon nitride (SiN x ), epoxy, titanium (Ti), chromium (Cr), or combinations thereof. The reaction layer  2002  and/or the reaction layer  2003  can be formed on the circuit layout carrier  1903  and/or the composite substrate  1901  by the method of physical vapor deposition (PVD) or chemical vapor deposition (CVD). The flexible adhesive layer  2001  may be formed on one side of the circuit layout carrier  1903  and/or one side of the composite substrate  1901 . The circuit layout carrier  1903  is bonded to the composite substrate  1901  at certain pressure and temperature, such as 328 g/cm 2 -658 g/cm 2  and 150° C.-600° C., and preferably 505 g/cm 2  and 200° C.-300° C. 
     If the surface of the composite substrate  1901  is a rough surface, a planarizing layer  21  is formed on the surface of the composite substrate  1901  for flatting the rough surface of the composite substrate  1901  and improving the adhesion between the connecting structure  1902  and the composite substrate  1901 . The material forming the planarizing layer  21  is such as nickel (Ni) or any other materials adhesible to the connecting structure  1902 . 
     In the present embodiment, a wavelength-converting material  1402  covers the area above the light-emitting units  1101 ,  1102  and/or  1103 . Furthermore; a light-pervious member, such as a lens, is capped the wavelength-converting material  1402  for securing and/or protecting the wavelength-converting material  1402 . 
     The wavelength-converting material  1402  may be mixed with light-pervious material or other adhesive material and then is formed on the light-emitting units  1101 ,  1102  and/or  1103 . Alternatively, the wavelength-converting material  1402  may also be formed over the area above the light-emitting units  1101 ,  1102  and/or  1103  by sedimentation without the mixture of the light-pervious material or any adhesive material. 
     A reflection layer  22  may be optionally formed inside the recess  1906  for reflecting and guiding the light emitted by the light-emitting units  1101 - 1103 . The reflection layer  22  is formed by a light-reflection material, such as gold, silver, aluminum, and tin etc. The reaction layer  22  is formed on the partial or whole interior surface of the recess  1906  by using various known film deposition methods. Further, if the reflection layer  22  is electrical conductive, for keeping the insulation between the light-emitting units  1101 - 1103  and the reflection layer  22 , the reflection layer  22  is preferably not formed on the area above the light-emitting units  1101 - 1103  covering the composite substrate  1901 . In addition, for enabling the reflection layer  22  to achieve better reflection efficiency, the recess  1906  is formed in a tapered shape, i.e. the inner wall of the recess  1906  has a slope that forms a funnel-shaped volume inside the recess  1906 . 
     The detailed techniques of the light-spreading device and the wavelike array have been described in Taiwan Application Serial Number 094103538, which is listed herein for reference. 
     As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrated of the present invention rather than limiting of the present invention. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures.

Technology Category: 3