Patent Publication Number: US-11396990-B2

Title: Phosphor module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/KR2019/004536, filed on Apr. 16, 2019, which claims the benefit of U.S. Provisional Application No. 62/658,601, filed on Apr. 17, 2018. The disclosures of the prior applications are incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a phosphor module for a laser light source. 
     BACKGROUND 
     A vehicle may include a lamp. For example, as shown  FIG. 1 , a vehicle  1  may include a lamp device  100  for providing driver&#39;s visibility or notifying other vehicles of the driving state of the vehicle  1  when ambient light is low during driving. 
     In some examples, a vehicle lamp device may include a head lamp provided at a front side of the vehicle and a rear lamp provided at a rear side of the vehicle. The head lamp may illuminate the front side during night driving. The rear lamp may include a brake lamp that is turned on when the driver operates a brake and a turn signal lamp that informs the advancing direction of the vehicle. 
     In some cases, a vehicle may use a laser light source. For example, as shown in  FIG. 3 , the lamp device  100  may include a laser light source  10 , which may have an improved energy efficiency. In some cases, light emitted from a laser diode may be excellent in straightness, and an irradiation distance of the lamp may increase without interfering visibility of oncoming vehicles. 
     In some examples, a white lamp may be implemented using a laser diode. 
     For example, white light may be generated by mixing light emitted from three types of laser diodes. Here, the three types of laser diodes may emit three primary colors of light, respectively. 
     In some cases, white light may be generated by converting light emitted from a blue laser diode into yellow light, and then mixing the yellow light with light emitted from the blue laser diode. In this way, white light may be implemented using a single type of laser. 
     In some examples, a phosphor may be used for light conversion of blue light emitted from a laser diode. The laser diode emits light with high output power, and the temperature of the phosphor may rise above 150° C. when light emitted from the laser diode is photo-converted. 
     In some cases of a resin phosphor, a phosphor-in-glass (PIG; hereinafter, referred to as a “glass phosphor”) may be used in an LED light source. In some cases, thermal quenching may occur during the light conversion process of laser light. 
     In some cases, yellow light converted from the phosphor may be scattered to spread widely, and part of the yellow light converted from the phosphor may be emitted to the outside. For example, yellow light emitted to the periphery of a light emitting area of the laser light source may generate a “yellow ring.” 
     SUMMARY 
     The present disclosure describes a structure for minimizing a yellow ring generated from a phosphor module. 
     The present disclosure also describes a structure for minimizing blue noise generated from the phosphor module. 
     The present disclosure further describes a structure for increasing the light uniformity of a light source. 
     According to one aspect of the subject matter described in this application, a phosphor module for a laser light source includes a radiating body, a phosphor layer disposed at the radiating body, the phosphor layer being configured to absorb light having a first wavelength and emit light having a second wavelength different from the first wavelength, a reflective layer that surrounds a side surface of the phosphor layer and is configured to reflect light, and a black matrix layer disposed at the reflective layer and configured to absorb light. The black matrix layer is disposed at an edge of the phosphor layer. 
     Implementations according to this aspect may include one or more of the following features. For example, the black matrix layer may extend to the phosphor layer to thereby overlap with a portion of the phosphor layer. In some examples, the reflective layer may include a first reflective layer in contact with the side surface of the phosphor layer, and a second reflective layer that surrounds the first reflective layer. The black matrix layer may be disposed at both of the first reflective layer and the second reflective layer. 
     In some implementations, the radiating body may define a recess portion that is recessed from a top surface of the radiating body and accommodates the phosphor layer and the reflective layer. In some examples, the black matrix layer may extend from the reflective layer to an upper portion of the radiating body. In some implementations, the black matrix layer may be made of a mixture including carbon black and a glass frit or a polymer material, and the black matrix layer may be coated on the reflective layer and has a thickness of 5 to 30 μm. 
     In some examples, the black matrix layer may be a diamond-like carbon (DLC) coating layer having a thickness of 1.5 to 3 μm. In some examples, the black matrix layer may be made of metal nitride or metal oxide including two or more metal elements, and the black matrix layer may be coated on the reflective layer and has a thickness of 1.5 to 10 μm. 
     In some implementations, the phosphor module may further include a diffuser layer disposed on the phosphor layer and configured to scatter light. In some examples, the reflective layer may extend to a side surface of the diffuser layer. In some examples, the diffuser layer may cover at least a part of an upper surface of the reflective layer. In some examples, the diffuser layer may be made of porous silica and a glass frit, and has a thickness of 20 to 100 μm. 
     In some implementations, the top surface of the radiating body may be flush with a top surface of the reflective layer and a top surface of the phosphor layer. In some examples, the black matrix layer may be disposed outside of the phosphor layer. In some implementations, the radiating body may be made of metal or a metal alloy and configured to dissipate heat generated from the phosphor layer, and the reflective layer may be made of metal oxide. 
     In some implementations, the phosphor module may further include an adhesive layer disposed between an upper surface of the radiating body and bottom surfaces of the reflective layer and the phosphor layer. In some examples, the reflective layer and the phosphor layer may be attached to an upper surface of the adhesive layer. In some examples, the black matrix layer may extend from the side surface of the phosphor layer to an outer edge of the reflective layer, and the outer edge of the reflective layer may be disposed at an outer surface of the adhesion layer. 
     In some implementations, the phosphor module may further include a diffuser layer disposed on an upper surface of the phosphor layer and configured to scatter light, where the diffuser layer is in contact with the black matrix layer. In some examples, the diffuser layer may extend to an upper surface of the reflective layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a conceptual view showing a vehicle. 
         FIG. 2  is a cross-sectional view showing a lamp device included in a vehicle. 
         FIG. 3  is a conceptual view showing a reflective laser light source. 
         FIG. 4  is a conceptual view showing a traveling path of light within the reflective laser light source illustrated in  FIG. 3 . 
         FIGS. 5 through 7  are cross-sectional views showing examples of a phosphor module. 
         FIGS. 8 and 9  are cross-sectional views showing examples of a phosphor module including a radiating body defining a recess portion. 
         FIGS. 10 through 12  are cross-sectional views showing examples of a phosphor module including a diffuser layer. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, the implementations disclosed herein will be described in detail with reference to the accompanying drawings, and the same or similar elements are designated with the same numeral references regardless of the numerals in the drawings and their redundant description will be omitted. 
     Prior to describing a phosphor module, a laser light source used for the phosphor module according to the present disclosure will be described. 
       FIG. 3  is a conceptual view showing an example of a reflective laser light source, and  FIG. 4  is a conceptual view showing an example of a traveling path of light within the reflective laser light source illustrated in  FIG. 3 . 
     In some examples, a laser light source  10  may include the structure of  FIG. 3 . Referring to  FIG. 1 , the laser light source  10  may include a blue laser diode  20 , a condensing lens  30 , a reflector  40 , a phosphor module  50 , and an auxiliary condenser lens  60 . 
     More specifically, referring to  FIG. 4 , blue light  21  emitted from the blue laser diode  20  may pass through the condensing lens  30  to be reflected by the reflector  40 . The blue light  22  reflected by the reflector  40  passes through the condensing lens  30  to enter the phosphor module  50 . 
     Part of blue light incident on the phosphor module  50  may be converted into yellow light. In some examples, the phosphor module  50  may include a reflective layer, and part of the blue light incident on the phosphor module  50  may be reflected. Accordingly, yellow light and blue light reflected from the phosphor module  50  may be combined to become white light. The white light may be condensed by the auxiliary condenser lens  60 , and then emitted 24 to the outside. 
     In this specification, a laser light source having a structure described in  FIGS. 3 and 4  may be referred to as a “reflective laser light source.” As described above, the reflective laser light source may include the phosphor module  50 . 
     In some implementations, the phosphor module  50  may include a phosphor layer for converting blue light into yellow light. In some cases, due to the characteristics of a laser diode with high output power, when a resin phosphor or a glass phosphor used in an LED light source or the like for light conversion of the laser diode, thermal quenching may occur in the phosphor. 
     In some cases, in order to avoid the problem that occurs when laser light is photo-converted using a resin phosphor or a glass phosphor, a ceramic phosphor may be used. However, in the case of the ceramic phosphor, since its sintering temperature is high above 1500° C., it may be difficult to control the particle size and pores of the ceramic phosphor. 
     When the particle size and pores of the phosphor layer are not controlled, a degree of scattering in the phosphor layer may be increased. When scattering factor increases since the ceramic phosphor is included in the phosphor layer, there is a problem that yellow light is emitted to the periphery of a light emitting area of the laser light source (hereinafter, referred to as a “yellow ring”). 
     The present disclosure provides a structure of a phosphor module capable of minimizing a yellow ring even when using a ceramic phosphor that is difficult to control the degree of scattering. 
     Specifically, the present disclosure describe a structure that may minimize an area of the phosphor layer included in the phosphor module. When the area of the phosphor layer decreases, the area of the yellow ring may also decrease, but several problems may occur. 
     First, when the area of the phosphor layer decreases, the light conversion efficiency of the phosphor layer may decrease. Accordingly, when laser light is irradiated to the phosphor module, the brightness of light emitted from the phosphor module may be reduced. For this reason, in a phosphor module in some cases, the area of the phosphor layer may not be reduced to a predetermined level or less. 
     Second, when the area of the phosphor layer decreases, a contact area between the phosphor layer and the radiating body may be reduced to decrease heat dissipation efficiency, which may cause a thermal quenching phenomenon in the phosphor layer. 
     The present disclosure describes a structure that may reduce the area of the phosphor layer to a predetermined level or less. Through this, the present disclosure may minimize the area of a yellow ring. Hereinafter, example structures of a phosphor module will be described in detail. 
     In some implementations, the phosphor module may not emit light by itself, but emit light through light conversion when irradiated with laser light. In the present specification, the expression “brightness of the phosphor module” denotes the brightness of light output from the phosphor module when laser light is irradiated to the phosphor module. In some examples, the brightness of the phosphor module may vary depending on the amount of laser light irradiated to the phosphor module, but the expression “increasing/decreasing the brightness of the phosphor module” in the present specification shows a result of comparing the amounts of light being output when the same amount of laser light is irradiated to the phosphor module. 
     In some implementations, an upper direction of the phosphor module  200  may be defined as a direction in which a reflective surface reflecting light traveling to the phosphor module faces. Hereinafter, according to these criteria, an upper or lower surface of the components constituting the phosphor module is defined. For example, light directed to a lower side of the phosphor module may not be output to the outside, and light directed to an upper side of the phosphor module may be output to the outside. The amount of light of the phosphor module may be determined according to the amount of light directed toward an upper side of the phosphor module. 
       FIGS. 5 through 7  are cross-sectional views showing examples of a phosphor module. 
     For example, the phosphor module  200  according to the present disclosure may include a radiating body  210 , a phosphor layer  220 , a reflective layer  230 , and an adhesive layer  240 . Hereinafter, the above-described components will be described in detail. 
     The radiating body  210  may be disposed under the phosphor layer  220  to improve the heat dissipation performance of the phosphor module  50 . The radiating body  210  may rapidly discharge heat generated during photo-conversion from the phosphor layer  220  to the outside, thereby helping to prevent the phosphor layer  220  from being thermally quenched. As a contact area between the phosphor layer  220  and the radiating body  210  increases, the heat dissipation efficiency of the radiating body  210  may increase. In some examples, the radiating body  210  may be a heat sink. 
     In some examples, the radiating body  210  may reflect blue light that has passed through the phosphor layer  220  and yellow light emitted from the phosphor layer  220 . In some cases, a reflection function of the radiating body  210  may be an additional function. For instance, when a reflective material is disposed between the radiating body  210  and the phosphor layer  220 , the radiating body  210  may not need to perform a reflective function. 
     The radiating body  210  may be made of a metal or alloy having a high thermal conductivity. For example, the radiating body  210  may be made of Al alloys (ADC12, AC4C). 
     The phosphor layer  220  is disposed above the radiating body  210 . The phosphor layer  220  absorbs the irradiated laser light to emit light having a wavelength different from that of the absorbed laser light. 
     Specifically, the phosphor layer  220  absorbs blue light emitted from a laser diode to emit yellow light. To this end, the phosphor layer  220  may include a yellow phosphor. For example, the phosphor layer  220  may include at least one of YAG: Ce, LuAG: Ce, Sr2SiO4: Eu, and nitride-based yellow phosphors. 
     In some implementations, the phosphor layer  220  may be made of a mixture of a phosphor and a base material. For example, the phosphor may be sintered and used in a certain form, and the base material may be a material used to secure sinterability for sintering the phosphor. Depending on the type of base material, the type of the phosphor layer may be different. For example, when the base material is a glass frit, the phosphor layer is a glass phosphor, and when the base material is ceramic, the phosphor layer becomes a ceramic phosphor. 
     Depending on the type of base material, the physical and optical properties of the phosphor layer  220  may vary. Here, the physical properties that may vary depending on the type of base material is a heat dissipation performance of the phosphor layer  220 . Compared to the ceramic phosphor, the heat dissipation performance of the glass phosphor is low. When the glass phosphor is used for photo-conversion of laser light having high output power, phosphor contained in the glass phosphor is deteriorated since the glass phosphor does not rapidly release heat energy generated in the photo-conversion process. Specifically, when light is converted into laser light, the temperature of the phosphor layer  220  may increase above 150° C., at which temperature the phosphor may be deteriorated. 
     In some examples, the physical properties that may vary depending on the type of base material is a degree of scattering in the phosphor layer. The boundaries, pores, and bonds between particles made of base materials may be scattering factors that scatter light photo-converted from the phosphor. When the scattering factors increase in the phosphor layer, the photo-converted yellow light spreads widely around the phosphor module, and thus is emitted to the outside without being combined with blue light. Accordingly, a yellow ring is formed around the laser light source. 
     An area of the yellow ring decreases as an area of the phosphor layer  220  decreases. The present disclosure uses a ceramic phosphor, but reduces the area of the phosphor layer  220  to minimize the yellow ring. 
     When the area of the phosphor layer  220  decreases, the foregoing two problems may occur. In order to solve this, the present disclosure includes a reflective layer  230  disposed on a side surface of the phosphor layer  220 . 
     In some examples, as shown in  FIG. 5 , the reflective layer  230  may surround the side surface of the phosphor layer  220 . The role of the reflective layer  230  may be largely divided into two types. 
     First, the reflective layer  230  serves to reflect light directed toward the side surface of the phosphor layer  220 . The reflective layer  230  reflects light traveling toward the side surface of the phosphor layer  220  to travel to an upper side of the phosphor layer  220 . Through this, the reflective layer  230  increases a ratio of the amount of light toward the upper side of the phosphor layer  220  to the total amount of yellow light output from the phosphor layer  220 . Accordingly, the brightness of the phosphor module may be increased. 
     In addition, yellow light traveling toward the side surface of the phosphor layer  220  spreads widely around the phosphor module, and the reflective layer  230  reduces the amount of yellow light spreading widely toward the center of the phosphor module to reduce the area of the yellow ring. 
     As described above, the reflective layer  230  reflects yellow light traveling to the side surface of the phosphor layer  220 , thereby increasing the brightness of the phosphor module and reducing the area of the yellow ring. 
     Second, the reflective layer  230  performs a heat dissipation function for the phosphor layer  220 . When the area of the phosphor layer  220  is reduced, the contact area between the phosphor layer  220  and the radiating body  210  may be reduced, thereby decreasing heat dissipation efficiency. In order to compensate for this, the reflective layer  230  emits heat generated from the phosphor layer  220  to the side surface of the phosphor layer  220 . 
     In order for the reflective layer  230  to perform the foregoing two functions, the reflective layer  230  may be made of a material having a high reflectivity and a high thermal conductivity. For example, the reflective layer may be made of at least one of TiO2, Ti2O3, or Al2O3. 
     In some implementations, the reflective layer  230  may be formed by etching a portion of the previously prepared phosphor layer, and then filling a material constituting the reflective layer  230  in the etched position, and then performing calcination. For this reason, an additional adhesive material need not be disposed between the phosphor layer  220  and the reflective layer  230 . However, since the phosphor layer  220  and the radiating body  210  are separately fabricated and assembled, an additional adhesive material may be disposed between the phosphor layer  220  and the radiating body  210 . 
     Specifically, the adhesive layer  240  bonds the phosphor layer  220  and the reflective layer  230  to the radiating body  210 . To this end, the adhesive layer  240  is disposed between each of the phosphor layer  220  and the reflective layer  230  and the radiating body  210 . 
     Since the adhesive layer  240  transfers the heat of the phosphor layer  220  and the reflective layer  230  to the radiating body  210 , it may be made of a material having a high thermal conductivity. Specifically, a thermal conductivity of the adhesive layer  240  may be higher than those of the phosphor layer  220  and the reflective layer  230 . Through this structure, the adhesive layer  240  may quickly transfer the heat of the phosphor layer  220  and the reflective layer  230  to the radiating body  210 . 
     In some examples, when a reflectance of the radiating body  210  is below a predetermined level, the adhesive layer  240  may be made of a material having a high reflectance. For example, the adhesive layer  55  is made of a white bonding material including at least one of Al2O3, SiO2, ZrO2, and ZnO having a reflectance of 90% or more in the visible light region, or made of a metal bonding material containing 90 wt. % of silver or more. The adhesive layer  240  may serve as a reflective layer. 
     In some examples, when the reflectance of the radiating body  210  is higher than a predetermined level, the adhesive layer  240  may be made of a material having a high light transmittance. For example, the adhesive layer  240  may be made of at least one of poly-methyl methacrylate (PMMA), poly-urethane (PU), poly-carbonate (PC) and a siloxane-based bonding material. 
     As described above, an area of the phosphor layer used in the phosphor module may be be reduced to a predetermined level or less. Through this, the present disclosure minimizes the area of the yellow ring. 
     In some examples, when the foregoing reflective layer is applied, the reflective layer reflects part of light incident on the phosphor module to emit blue light to the outside. The present disclosure provides a structure capable of further reducing an area of the yellow ring while avoiding blue noise generated by the reflective layer. 
     Referring to  FIG. 5 , a black matrix layer  250  that absorbs light may be layered on the reflective layer. The black matrix layer  250  is disposed at an edge of the phosphor layer  220 . 
     The black matrix layer  250  absorbs the noise peak of blue laser incident on the phosphor module, and absorbs yellow light emitted from the phosphor layer  220  toward the side surface of the phosphor module. 
     The area of the black matrix layer  250  may be the same as that of the reflective layer  230 . The effect that the reflective layer  230  reduces the yellow ring is generated only on the side surface of the reflective layer  230  in contact with the phosphor layer  220 . Therefore, an entire upper surface of the reflective layer  230  that may generate unnecessary noise may be preferably covered by the black matrix layer  250 . In some implementations, the present disclosure is not limited thereto, the black matrix layer  250  may have a larger area than the reflective layer  230 . 
     For example, referring to  FIG. 6 , the black matrix layer  250  may extend in the direction toward the phosphor layer  220 , and may overlap with a portion of the phosphor layer  220 . In this case, the black matrix layer  250  further includes an extension portion  251  overlapping with the phosphor layer  220 . In some examples, the black matrix layer  250  may cover an upper surface of the reflective layer  230  and an upper surface of the phosphor layer  220 . 
     Since the yellow ring is likely to be generated by light emitted from an edge of the phosphor layer  220 , the extension portion  251  may absorb yellow light emitted from the edge of the phosphor layer  220 , thereby minimizing the area of the yellow ring. 
     In some implementations, the black matrix layer  250  may be made of various materials. 
     In some examples, the black matrix layer  250  may be made of a glass frit or a mixture of polymer and carbon black, and may be formed by the reflective layer  230  printing method. In some examples, a thickness of the black matrix layer  250  may be adjusted to 5 to 30 μm such that an absorption rate of the black matrix layer  250  may be set to 90 to 96% (reflectance of 4 to 10%). 
     In some implementations, the black matrix layer  250  may be a diamond-like carbon (DLC) coating layer, and may be coated with Plasma-enhanced chemical vapor deposition (PECVD) equipment at room temperature. In some examples, a thickness of the black matrix layer  250  may be adjusted to 1.5 to 3 μm such that an absorption rate of the black matrix layer  250  may be set to 90 to 96% (reflectance of 4 to 10%). 
     In some implementations, the black matrix layer  250  may be made of a metal nitride or oxide containing two or more types of metal elements, and may be coated by the physical vapor deposition (PVD) or chemical vapor deposition (CVD) method. In some examples, a thickness of the black matrix layer  250  may be adjusted to 1.5 to 10 μm such that an absorption rate of the black matrix layer  250  may be set to 90 to 96% (reflectance of 4 to 10%). 
     The present disclosure provides various examples to solve the problems that may occur when reducing the area of the phosphor layer. Hereinafter, examples of the present disclosure will be described with reference to the accompanying drawings. 
     The present disclosure provides a structure for simultaneously increasing the thermal conductivity and reflectance of the foregoing reflective layer. 
       FIG. 7  is a cross-sectional view showing an example of a phosphor module including a plurality of reflective layers. 
     The reflective layer  230  may be configured to rapidly dissipate heat generated from the phosphor layer  220  and reflect light directed toward a side surface of the phosphor layer  220  to an upper side of the phosphor layer  220 . 
     In some examples, the reflective layer  230  may include a plurality of layers. For example, referring to  FIG. 7 , the reflective layer  230  may include a first reflective layer  230   a  in contact with a side surface of the phosphor layer  220  and a second reflective layer  230   b  surrounding the first reflective layer  230   a.    
     Here, the reflectivity of the material constituting the first reflective layer  230   a  may be higher than that of the material constituting the second reflective layer  230   b . In some implementations, the thermal conductivity of the material constituting the second reflective layer  230   b  may be higher than that of the material constituting the first reflective layer  230   a.    
     Through the foregoing first and second reflective layers, the present disclosure may increase the reflectance of the reflective layer while at the same time increasing the thermal conductivity of the entire reflective layer. In some implementations, the first and second reflective layers may have different thicknesses. For example, a width of the first reflective layer  230   a  may be smaller than that of the second reflective layer  230   a . The first reflective layer  230   a  may be formed only at a thickness sufficient to allow the reflective layer  230  to perform a reflective function, and the second reflective layer  230   b  performing a heat dissipation function may be formed at a large width, thereby maximizing the reflectance and heat dissipation efficiency of the reflective layer  230 . 
     In some examples, the reflective layer  230  may not include a plurality of layers. Specifically, the reflective layer  230  may be made of a mixture of a material having a high reflectivity and a material having a high thermal conductivity. For example, the reflective layer  230  may be made of a mixture of at least one of alumina (Al2O3), spinel (MgAl2O4), and AlON, and Ti oxide. When a reflective layer is formed by mixing an aluminum oxide material having a high thermal conductivity and a Ti oxide having a high reflectivity, the reflectance and the thermal conductivity of the reflective layer may be increased together. 
     In some cases, the black matrix layer  250  may be layered on the first and second reflective layers  230   a  and  230   b , respectively. This structure may help to prevent blue noise from being generated by the first and second reflective layers  230   a  and  230   b , respectively. 
     In some examples, the present disclosure may increase the thermal conductivity of the reflective layer using the above-described heat sink. 
       FIGS. 8 and 9  are cross-sectional views showing examples of a phosphor module including a radiating body having a recess portion. 
     A recess portion may be formed in the radiating body included in the phosphor module. Referring to  FIG. 8 , the radiating body may be formed with a recess portion having a plurality of side surfaces  211  and a bottom surface  212 . 
     In some examples, the phosphor layer  220  and the reflective layer  230  may be disposed on the bottom surface  212 . Here, a thickness of the phosphor layer  220  and the reflective layer  230  may be equal to or smaller than a depth of the recess portion. In this case, the phosphor layer  220  and the reflective layer  230  are disposed within the recess portion. 
     In some implementations, in order to fix the phosphor layer  220  and the reflective layer  230  to the recess portion, an adhesive layer  240  may be formed on the bottom surface  212  of the recess portion. The adhesive layer  240  transfers heat of each of the phosphor layer  220  and the reflective layer  230  to the radiating body  210 . According to the structure described with reference to  FIG. 8 , since heat of the reflective layer  230  may be discharged to a side surface of the recess portion, the heat dissipation performance of the phosphor module may be improved. 
     In some examples, the structure described with reference to  FIG. 8  may be fabricated by forming a recess portion in the radiating body  210 , and then coating an adhesive to a bottom surface of the recess portion, and then placing the phosphor layer  220  and the reflective layer  230  on the coated adhesive. Even in this case, the black matrix layer  250  may be formed on the reflective layer  230 . In some examples, the top surface of the radiating body  210  may be flush with a top surface of the reflective layer  230  and a top surface of the phosphor layer  220 . 
     In some implementations, as illustrated in  FIG. 9 , the black matrix layer  250  may extend from the reflective layer  230  to cover a portion of the radiating body  210 . In this case, the black matrix layer  250  may include a second extension portion  252  overlapping with at least part of the radiating body  210 . 
     The second extension portion  252  may help to prevent part of light incident on the phosphor module from being reflected from a surface of the radiating body  210  to generate noise. 
     In some examples, where the phosphor layer  220  and the reflective layer  230  are disposed within the recess portion defined in the radiating body  210 , the durability and heat dissipation performance of the phosphor module may be improved. In addition, the black matrix layer  250  may help to prevent noise from being generated by reflecting blue light from the radiating body and the reflective layer, and reduce the area of the yellow ring. 
     In some implementations, the phosphor module may further include an additional structure for reducing the area of the yellow ring. 
       FIGS. 10 through 12  are cross-sectional views showing examples of a phosphor module including a diffuser layer. 
     Referring to  FIG. 10 , the present disclosure may further include a diffuser layer  260  layered on the phosphor layer  220  to scatter light. The diffuser layer  260  scatters light emitted from the phosphor layer  220  and light reflected from the phosphor layer  220  to improve color uniformity of white light. 
     The diffuser layer  260  may be arranged in various forms. For example, as shown in  FIG. 10 , the diffuser layer  260  may be disposed on the phosphor layer  220 , and the black matrix layer  250  may be disposed at an edge of the diffuser layer  260 . 
     In some implementations, referring to  FIG. 11 , the reflective layer  230  may extend to a side surface of the diffuser layer  260 . In some examples, the reflective layer  230  reflects even light emitted to the side surface of the diffuser layer  260 . The structure of  FIG. 11  is a structure capable of concentrating white light into the center of the phosphor module. 
     In some cases, the black matrix layer  250  may be disposed to overlap with a portion of the diffuser layer  260 . The black matrix layer  250  may absorb light scattered at the edge of the diffuser layer  260  to reduce the area of the yellow ring. 
     In some implementations, referring to  FIG. 12 , the diffuser layer  260  may be formed to cover a portion of the upper surface of the reflective layer  230 . In this case, the diffuser layer  260  extends from the phosphor layer  220  toward the reflective layer  230 . The structure of  FIG. 12  is a structure in which white light may be widely spread around the phosphor module. 
     In some implementations, the diffuser layer  260  may be formed of a mixture of porous silica (particle size of 1 to 5 μm) and a glass frit. The diffuser layer  260  may be fabricated by calcinating the mixture at 500 to 800° C. The diffuser layer may have a thickness of 20 to 100 μm so that the diffuser layer has a transmittance of 85 to 95%. 
     According to the present disclosure, yellow light traveling toward a side surface of a phosphor layer may be reflected and directed toward a front surface of the phosphor layer, thereby minimizing an area of a yellow ring. 
     In some examples, the phosphor module may include a black matrix that may absorb yellow light emitted from an edge of the phosphor layer, thereby minimizing the area of the yellow ring. In addition, the black matrix may absorb blue light incident on a reflective layer, thereby disallowing the blue light to be reflected on an upper surface of the reflective layer. Through this, the present disclosure may remove blue noise generated from a phosphor module. 
     In some examples, the phosphor module may include a diffuser layer that overlaps with the phosphor layer and is configured to uniformly scatter white light, thereby improving the light uniformity of the phosphor module. 
     It is obvious to those skilled in the art that the present disclosure can be implemented in other specific forms without departing from the concept and essential characteristics thereof. 
     The detailed description thereof should not be construed as restrictive in all aspects but considered as illustrative. The scope of the disclosure should be determined by reasonable interpretation of the appended claims and all changes that come within the equivalent scope of the disclosure are included in the scope of the disclosure.