Patent Publication Number: US-2020303602-A1

Title: Pixel encapsulating structure

Description:
BACKGROUND 
     Field of Invention 
     The present disclosure relates to a pixel encapsulating structure for encapsulating a light-emitting device therein. 
     Description of Related Art 
     The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art. 
     In recent years, micro devices have become popular in various applications. One of the important subfields is micro light-emitting devices. Among all technical aspects of micro light-emitting devices, color shift viewed by a user in different angles with respect to a normal direction of a display is an important and long-standing issue. 
     SUMMARY 
     According to some embodiments of the present disclosure, a pixel encapsulating structure including a substrate, a first light-emitting device, a second light-emitting device, and a filling material is provided. The first light-emitting device is on the substrate. The second light-emitting device is on the substrate. The first light-emitting device and the second light-emitting device have different emission wavelengths. The filling material is on the substrate, the first light-emitting device, and the second light-emitting device. The filling material has two portions respectively covering the first light-emitting device and the second light-emitting device, and said two portions have different refractive indices. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the disclosure as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG. 1  is a cross-sectional view of a pixel encapsulating structure according to some embodiments of the present disclosure; 
         FIG. 2  is a cross-sectional view of a pixel encapsulating structure according to some embodiments of the present disclosure; 
         FIG. 3A  is a cross-sectional view of a pixel encapsulating structure according to some embodiments of the present disclosure; 
         FIG. 3B  is a cross-sectional view of a pixel encapsulating structure according to some embodiments of the present disclosure; 
         FIG. 3C  is a cross-sectional view of a pixel encapsulating structure according to some embodiments of the present disclosure; 
         FIG. 3D  is a cross-sectional view of a pixel encapsulating structure according to some embodiments of the present disclosure; and 
         FIG. 4  is a cross-sectional view of a pixel encapsulating structure according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     In various embodiments, description is made with reference to figures. However, certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions, and processes, etc., in order to provide a thorough understanding of the present disclosure. In other instances, well-known semiconductor processes and manufacturing techniques have not been described in particular detail in order to not unnecessarily obscure the present disclosure. Reference throughout this specification to “one embodiment,” “an embodiment”, “some embodiments” or the like means that a particular feature, structure, configuration, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrase “in one embodiment,” “in an embodiment”, “in some embodiments” or the like in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments. 
     The terms “over,” “to,” “between” and “on” as used herein may refer to a relative position of one layer with respect to other layers. One layer “over” or “on” another layer or bonded “to” another layer may be directly in contact with the other layer or may have one or more intervening layers. One layer “between” layers may be directly in contact with the layers or may have one or more intervening layers. Although most of terms described in the following disclosure use singular nouns, said terms may also be plural in accordance with figures or practical applications. 
     References are made to  FIG. 1 .  FIG. 1  is a cross-sectional view of a pixel encapsulating structure  100  according to some embodiments of the present disclosure. In some embodiments, a pixel encapsulating structure  100  including a substrate  110 , a first light-emitting device  120 , a second light-emitting device  130 , and a filling material  140  is provided. The first light-emitting device  120  and the second light-emitting device  130  are on the substrate  110 . The first light-emitting device  120  and the second light-emitting device  130  have different emission wavelengths. In some embodiments, the first light-emitting device  120  and the second light-emitting device  130  are different light-emitting devices and are structurally separated. The “structurally separated” means not physically and directly connected, whereas remote electrical connections through an electrode or a wire in which a connection point is outside of  FIG. 1  (e.g., the connection point in a power supply used to provide voltages for the pixel encapsulating structure  100 ) is allowed. The filling material  140  is on the substrate  110 . In some embodiments, the filling material  140  is also on the first light-emitting device  120  and the second light-emitting device  130 . In general, the filling material  140  includes a dielectric material, a photoresist, or a combination thereof. The filling material  140  has two portions respectively covering the first light-emitting device  120  and the second light-emitting device  130 . The two portions have different refractive indices. In some embodiments, one of the two portions is a first portion  142 , and the other of the two portions is a second portion  144 . Specifically, the substrate  110  is extended in a direction Y as shown in all of the figures in the present disclosure, and the filling material  140  covers the first light-emitting device  120  and the second light-emitting device  130  at least from a direction Z as shown in all of the figures in the present disclosure. Generally, the direction Y is perpendicular to the direction Z. In some embodiments, the filling material  140  not only covers but also surrounds the first light-emitting device  120  and the second light-emitting device  130 . 
     In some embodiments, the first portion  142  and the second portion  144  are respectively used to refract light emitted from the first light-emitting device  120  and light emitted from the second light-emitting device  130 . Specifically, the first portion  142  and the second portion  144  are used to correct a color shift when viewed from different angles with respect to a normal direction (i.e. off angles with respect to the direction Z) of the pixel encapsulating structure  100 . In some embodiments, a vertical projection of the first portion  142  on the substrate  110  is at least partially overlapped with a vertical projection of the first light-emitting device  120  on the substrate  110 . In some embodiments, a vertical projection of the second portion  144  on the substrate  110  is at least partially overlapped with a vertical projection of the second light-emitting device  130  on the substrate  110 . In some embodiments, the refractive index of the first portion  142  is greater than the refractive index of the second portion  144 , and the emission wavelength of the first light-emitting device  120  is greater than the emission wavelength of the second light-emitting device  130 . For example, the first light-emitting device  120  can be a light-emitting diode which is configured to emit red light, and the second light-emitting device  130  can be a light-emitting diode which is configured to emit blue light. The colors mentioned above are just exemplifications and shall not be regarded as a limitation to the present disclosure. Due to the snell&#39;s law, the dispersion relation, and the above configurations, the correction of the color shift can be realized, so that a wavelength distribution of light received when viewed from the off angle with respect to the direction Z can be more close to a wavelength distribution of light received when viewed from a direction parallel to the direction Z. To put it briefly, the shorter the wavelength of the light, the lower the refractive index for a portion of the filling material  140  is used to refract the light. In some embodiments, the refractive indices of the first portion  142  and the second portion  144  are defined under a wavelength of about 550 nm. 
     Reference is made to  FIG. 2 .  FIG. 2  is a cross-sectional view of a pixel encapsulating structure  100 ′ according to some embodiments of the present disclosure. A difference between embodiments illustrated by  FIG. 2  and the embodiments illustrated by  FIG. 1  is that a first portion  142 ′ and a second portion  144 ′ of a filling material  140 ′ are separated from one another in the embodiments illustrated by  FIG. 2 , whereas the first portion  142  and the second portion  144  of the filling material  140  are in contact with one another in the embodiments illustrated by  FIG. 1 . A benefit of the above configuration is similar to the benefit of the correction of the color shift which has been described before and will not be repeated again herein. 
     Reference is made to  FIGS. 3A to 3D .  FIGS. 3A to 3D  are cross-sectional views of pixel encapsulating structures  100 A,  100 B,  100 C, and  100 D according to some embodiments of the present disclosure. In some embodiments, each of the pixel encapsulation structures  100 A,  100 B,  100 C, and  100 D further include a sidewall  150  as compared to the pixel encapsulation structure  100  as shown in  FIG. 1 . The sidewall  150  is on the substrate  110  and surrounds the first light-emitting device  120  and the second light-emitting device  130  as shown in  FIGS. 3A to 3D . In some embodiments, a part of the sidewall  150  is between the first light-emitting device  120  and the second light-emitting device  130 . The sidewall  150  may include a light reflective portion  152  (as referred to  FIG. 3B ), a light absorbing portion  154  (as referred to  FIG. 3C ), or a combination thereof (as referred to  FIG. 3D ). Said combination may be a multi-layer structure including the light reflective portion  152  and the light absorbing portion  154 . In some embodiments, the light reflective portion  152  is on the substrate  110 . The light absorbing portion  154  is on the light reflective portion  152  and is spaced apart from the substrate  110  by the light reflective portion  152 . A reflectance of the light reflective portion  152  is greater than a reflectance of the light absorbing portion  154 . In some embodiments, the sidewall  150  includes resin or photoresist, but should not be limited thereto. In some embodiments, the light reflective portion  152  includes tin dioxide (TiO 2 ) particles or/and zirconium dioxide (ZrO 2 ) particles, so as to increase the reflectance of the light reflective portion  152 . In some embodiments, a height H 1  of the sidewall  150  relative to the substrate  110  is greater than a height H 2  of the first light-emitting device  120  relative to the substrate  110 . In some embodiments, the height H 1  of the sidewall  150  relative to the substrate  110  is greater than a height H 3  of the second light-emitting device  130  relative to the substrate  110 . As a result, light emitted from the first light-emitting device  120  and the second light-emitting device  130  can be better reflected or absorbed. Individual and combinations of the above conditions for the sidewall  150  reduce interference or cross talk of light from different light-emitting devices (or equivalently, from different pixels) and enhance the light extraction (e.g., using said combination of the light reflective portion and the light absorbing portion) of the first light-emitting device  120  and the second light emitting device  130 . 
     Reference is made to  FIG. 4 .  FIG. 4  is a cross-sectional view of a pixel encapsulating structure  200  according to some embodiments of the present disclosure. In some embodiments, a pixel encapsulating structure  200  further includes a third light emitting device  160  on the substrate  110  as compared to the embodiments illustrated by  FIG. 1 . The third light-emitting device  160  has an emission wavelength different from the emission wavelengths of the first light-emitting device  120  and the emission wavelength of the second light-emitting device  130 . In some embodiments, a filling material  140 ″ further includes a third portion  146  as compared to the embodiments illustrated by  FIG. 1 . The third portion  146  covers the third light-emitting device  160 . The third portion  146  has a refractive index different from the refractive indices of the first portion  142  and the second portion  144 . In some embodiments, the refractive index of the third portion  146  is greater than the refractive index of the second portion  144  and smaller than the refractive index of the first portion  142 , and the emission wavelength of the third light-emitting device  160  is greater than the emission wavelength of the second light-emitting device  130  and smaller than emission wavelength of the first light-emitting device  120 . In some embodiments, the refractive index of the third portion  146  is greater than both of the refractive index of the first portion  142  and the refractive index of the second portion  144 , and the emission wavelength of the third light-emitting device  160  is greater than both of the emission wavelength of the first light-emitting device  120  and the emission wavelength of the second light-emitting device  130 . In some embodiments, the first light-emitting device  120 , the second light-emitting device  130 , and the third light-emitting device  160  can be a combination of light-emitting diodes configured to emit red light, blue light, and green light, but should not be limited thereto. 
     In summary, embodiments of the present disclosure provide a pixel encapsulating structure in which a filling material has a plurality of portions having different refractive indices to refract lights emitted from light-emitting devices with different emission wavelengths within one pixel, so as to correct a color shift phenomenon. 
     Although the present disclosure has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of 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 cover modifications and variations of this disclosure provided they fall within the scope of the following claims.