Patent Publication Number: US-2020303603-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. 
     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, three light-emitting devices, a filling material, and a first encapsulation layer is provided. The three light-emitting devices are present on the substrate. Two of the three light-emitting devices have different emission wavelengths. The filling material is present on the substrate and the three light-emitting devices. The first encapsulation layer is present on the filling material and covers the three light-emitting devices. One of the first encapsulation layer and the filling material has three portions respectively covering the three light-emitting devices, and two of the three 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. 1A  is a cross-sectional view of a pixel encapsulating structure according to some embodiments of the present disclosure; 
         FIG. 1B  is a cross-sectional view of a pixel encapsulating structure according to some embodiments of the present disclosure; 
         FIG. 2A  is a cross-sectional view of a pixel encapsulating structure according to some embodiments of the present disclosure; 
         FIG. 2B  is a cross-sectional view of a pixel encapsulating structure according to some embodiments of the present disclosure; 
         FIG. 3  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  FIGS. 1A and 1B .  FIG. 1A  is a cross-sectional view of a pixel encapsulating structure  100 A according to some embodiments of the present disclosure.  FIG. 1B  is a cross-sectional view of a pixel encapsulating structure  100 B according to some embodiments of the present disclosure. In some embodiments, a pixel encapsulating structure  100 A including a substrate  110 , three light-emitting devices  122 ,  124 , and  126 , a filling material  130 A, and a first encapsulation layer  140 A is provided. The three light-emitting devices  122 ,  124 , and  126  are present on the substrate  110 . Two of the three light-emitting devices  122 ,  124 , and  126  have different emission wavelengths. In some embodiments, the three light-emitting devices  122 ,  124 , and  126  are a first light-emitting device  122 , a second light-emitting device  124 , and a third light-emitting device  126 , respectively. It should be noted that there may be more than said three light-emitting devices  122 ,  124 , and  126  present on the substrate  110 , and these cases will not be described herein in detail since they are only an extension of applications of embodiments in the present disclosure. The filling material  130 A is present on the substrate  110  and the three light-emitting devices  122 ,  124 , and  126 . In general, the filling material  130 A includes a dielectric material, a photoresist, or a combination thereof. The first encapsulation layer  140 A is present on the filling material  130 A. In general, the first encapsulation layer  140 A includes a dielectric material, a photoresist, or a combination thereof. The first encapsulation layer  140 A covers the three light-emitting devices  122 ,  124 , and  126  from a direction perpendicular to an extension of the substrate  110 . Specifically, the substrate  110  is extended in a direction Y as shown in all of the figures in the present disclosure, and the first encapsulation layer  140 A covers the three light-emitting devices  122 ,  124 , and  126  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. One of the first encapsulation layer  140 A (as referred to  FIG. 1A ) and the filling material  130 B (as referred to  FIG. 1B ) has three portions respectively covering the three light-emitting devices  122 ,  124 , and  126 . Two of the three portions have different refractive indices. 
     In some embodiments as illustrated in  FIG. 1A , the first encapsulation layer  140 A has three portions. The three portions are a first portion  142 , a second portion  144 , and a third portion  146 , respectively. In some embodiments, the first portion  142 , the second portion  144 , and the third portion  146  are respectively used to refract light emitted from the first light-emitting device  122 , light emitted from the second light-emitting device  124 , and light emitted from the third light-emitting device  126 . Specifically, the first portion  142 , the second portion  144 , and the third portion  146  are used to correct a color shift when viewed from an off angle with respect to a normal direction (i.e. off angle with respect to the direction Z) of the pixel encapsulating structure  100 A. 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  122  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  124  on the substrate  110 . In some embodiments, a vertical projection of the third portion  146  on the substrate  110  is at least partially overlapped with a vertical projection of the third light-emitting device  146  on the substrate  110 . In some embodiments, the refractive index of the first portion  142  is greater than the refractive index of the third portion  146 , and the emission wavelength of the first light-emitting device  122  is greater than the emission wavelength of the third light-emitting device  126 . For example, the first light-emitting device  122  can be a light-emitting diode which is configured to emit a red light, and the third light-emitting device  126  can be a light-emitting diode which is configured to emit a 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 configuration, 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 the high refractive index medium is used to refract the light. 
     In some embodiments, the first portion  142 , the second portion  144 , and the third portion  146  have different refractive indices. In some embodiments, the refractive index of the first portion  142  is greater than the refractive index of the second portion  144 , the refractive index of the second portion  144  is greater than the refractive index of the third portion  146 , the emission wavelength of the first light-emitting device  122  is greater than the emission wavelength of the second light-emitting device  124 , and the emission wavelength of the second light-emitting device  124  is greater than the emission wavelength of the third light-emitting device  126 . For example, the first light-emitting device  122  can be a light-emitting diode which is configured to emit the red light, the second light-emitting device  124  can be a light-emitting diode which is configured to emit a green light, and the third light-emitting device  126  can be a light-emitting diode which is configured to emit the blue light. 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. The colors mentioned above are just exemplifications and shall not be regarded as a limitation to the present disclosure. In some embodiments, the refractive indices of the first portion  142 , the second portion  144 , and the third portion  146  are defined under a wavelength selected from a range from about 400 nm to about 700 nm. In some embodiments, the refractive indices of the first portion  142 , the second portion  144 , and the third portion  146  are defined under a wavelength of about 550 nm. 
     In some embodiments as illustrated in  FIG. 1B , the filling material  130 B has three portions. The three portions are a first portion  132 , a second portion  134 , and a third portion  136 , respectively. In these embodiments, the first encapsulation layer  140 B may have a single refractive index. In some embodiments, the first portion  132 , the second portion  134 , and the third portion  136  are respectively used to refract the light emitted from the first light-emitting device  122 , the light emitted from the second light-emitting device  124 , and the light emitted from the third light-emitting device  126 . In some embodiments, the first portion  132  covers and surrounds the first light-emitting device  122 . In some embodiments, the second portion  134  covers and surrounds the second light-emitting device  124 . In some embodiments, the third portion  136  covers and surrounds the third light-emitting device  126 . In some embodiments, the refractive index of the first portion  132  is greater than the refractive index of the third portion  136 , and the emission wavelength of the first light-emitting device  122  is greater than the emission wavelength of the third light-emitting device  126 . For example, the first light-emitting device  122  can be a light-emitting diode which is configured to emit the red light, and the third light-emitting device  126  can be a light-emitting diode which is configured to emit the blue light. 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. The colors mentioned above are just exemplifications and shall not be regarded as a limitation to the present disclosure. 
     In some embodiments, the first portion  132 , the second portion  134 , and the third portion  136  have different refractive indices. In some embodiments, the refractive index of the first portion  132  is greater than the refractive index of the second portion  134 , the refractive index of the second portion  134  is greater than the refractive index of the third portion  136 , the emission wavelength of the first light-emitting device  122  is greater than the emission wavelength of the second light-emitting device  124 , and the emission wavelength of the second light-emitting device  124  is greater than the emission wavelength of the third light-emitting device  126 . For example, the first light-emitting device  122  can be a light-emitting diode which is configured to emit the red light, the second light-emitting device  124  can be a light-emitting diode which is configured to emit the green light, and the third light-emitting device  122  can be a light-emitting diode which is configured to emit the blue light. 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. The colors mentioned above are just exemplifications and shall not be regarded as a limitation to the present disclosure. In some embodiments, the refractive indices of the first portion  132 , the second portion  134 , and the third portion  136  are defined under the wavelength selected from a range from about 400 nm to about 700 nm. In some embodiments, the refractive indices of the first portion  132 , the second portion  134 , and the third portion  136  are defined under the wavelength of about 550 nm. 
     Reference is made to  FIGS. 2A and 2B .  FIG. 2A  is a cross-sectional view of a pixel encapsulating structure  200 A according to some embodiments of the present disclosure.  FIG. 2B  is a cross-sectional view of a pixel encapsulating structure  200 B according to some embodiments of the present disclosure. A difference between the embodiments illustrated in  FIG. 1A  and the embodiments illustrated in  FIG. 2A  is that the pixel encapsulating structure  200 A of  FIG. 2A  further includes a second encapsulation layer  150  present on the first encapsulation layer  140 A compared to the pixel encapsulating structure  100 A of  FIG. 1A . In general, the second encapsulation layer  150  includes a dielectric material, a photoresist, or a combination thereof. In some embodiments, the second encapsulation layer  150  has a single refractive index which is irrelevant to the refractive indices of the first encapsulation layer  140 A, and the filling material  130 A. In some embodiments as illustrated in  FIG. 2A , different parts of the second encapsulation layer  150  present on the first portion  142 , the second portion  144 , and the third portion  146  have the same refractive index. 
     A difference between the embodiments illustrated in  FIG. 1B  and the embodiments illustrated in  FIG. 2B  is that the pixel encapsulating structure  200 B of  FIG. 2B  further includes the second encapsulation layer  150  present on the first encapsulation layer  140 B compared to the pixel encapsulating structure  100 B of  FIG. 1B . In some embodiments as illustrated in  FIG. 2B , different parts of the second encapsulation layer  150  present above the first portion  132 , the second portion  134 , and the third portion  136  have the same refractive index. The “above” described herein means “above in the direction Z”. 
     Reference is made to  FIG. 3 .  FIG. 3  is a cross-sectional view of a pixel encapsulating structure  300  according to some embodiments of the present disclosure. A difference between the embodiments illustrated in  FIG. 1A  and the embodiments illustrated in  FIG. 3  is that the pixel encapsulating structure  300  of  FIG. 3  further includes the second encapsulation layer  150  present between the first encapsulation layer  140 A and the filling material  130 A compared to the pixel encapsulating structure  100 A of  FIG. 1A . Different parts of the second encapsulation layer  150  present below (in a negative z-direction) the first portion  142 , the second portion  144 , and the third portion  146  have the same refractive index. 
     Reference is made to  FIG. 4 .  FIG. 4  is a cross-sectional view of a pixel encapsulating structure  400  according to some embodiments of the present disclosure. A difference between the embodiments illustrated in  FIG. 4  and the embodiments illustrated in  FIG. 3  is that the first filling material  130 B of the pixel encapsulating structure  400  illustrated in  FIG. 4  has three portions. The three portions are a first portion  132 , a second portion  134 , and a third portion  136 , respectively. Details of the first filling material  130 B has been described in the embodiments illustrated in  FIG. 1B  and will not be repeated herein again. 
     In summary, embodiments of the present disclosure provide a pixel encapsulating structure in which at least one of a filling material and an encapsulation layer has a plurality of portions having different refractive indices to refract lights emitted from light-emitting devices with different 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.