Patent Publication Number: US-2023163254-A1

Title: Color conversion unit, color conversion structure using the same, and light-emitting diode display using the same

Description:
This application claims the benefit of Taiwan application Serial No. 110143860. filed Nov. 24, 2021, the disclosure of which is incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     The disclosure relates in general to a color conversion unit, a color conversion structure using the same, and a light-emitting diode display using the same, and more particularly to a color conversion unit including micro light-emitting diodes, a color conversion structure using the same, and a light-emitting diode display using the same. 
     BACKGROUND 
     Recently, the demands for micro light-emitting diode displays in the market have been gradually increased. The micro light-emitting diode display can include a color conversion layer and an array of micro light-emitting diodes, wherein the color conversion layer can convert the light provided by the micro light-emitting diode into a desired wavelength. However, since the size of the micro light-emitting diode is much smaller than the size of the light-emitting diode, the size of the corresponding color conversion layer also needs to be reduced accordingly. For example, the thickness of the color conversion layer may be greatly reduced, making the existing micro light-emitting diodes displays still have the problem of insufficient color conversion efficiency. Therefore, there is still a great need to develop an improved micro light-emitting diode display to overcome the above-mentioned problems. 
     SUMMARY 
     According to an embodiment of the present disclosure, a color conversion unit is provided. The color conversion unit includes a substrate and a color conversion layer. The substrate includes a hole. The color conversion layer is embedded in the hole of the substrate, wherein a ratio of a width to a height of the color conversion layer is between 1:1 and 1:15, and a color conversion mixture used to form the color conversion layer is cured by excitation light wavelength between 385 nm and 1180 nm. A micro light-emitting diode disposed under the color conversion layer is used to provide light to the color conversion layer. 
     According to another embodiment of the present disclosure, a color conversion structure is proposed. The color conversion structure includes a plurality of color conversion units. The color conversion units include a substrate and a first color conversion layer, a second color conversion layer, and an optical cement adjacent to each other. The first color conversion layer, the second color conversion layer and the optical cement are respectively filled in a plurality of holes of the substrate. Emission wavelengths converted by the first color conversion layer, the second color conversion layer and the optical cement are different, and ratios of widths to heights of the first color conversion layer, the second color conversion layer and the optical cement are between 1:1 and 1:15, and color conversion mixtures used to form the first color conversion layer and the second color conversion layer are cured by excitation light wavelength between 385 nm and 1180 nm. A plurality of micro light-emitting diodes disposed under the first color conversion layer, the second color conversion layer and the optical cement are used to provide light to the first color conversion layer, the second color conversion layer and the optical cement. 
     According to a further embodiment of the present disclosure, a light-emitting diode display is provided. The light-emitting diode display includes a color conversion structure, an array of micro light-emitting diodes, and a backplane control structure. The color conversion structure includes a plurality of color conversion units, and the color conversion units include a substrate and a first color conversion layer, a second color conversion layer and an optical cement adjacent to each other. The substrate includes a plurality of holes. The first color conversion layer, the second color conversion layer and the optical cement are filled in the holes of the substrate. Emission wavelengths converted by the first color conversion layer, the second color conversion layer and the optical cement are different, and ratios of widths to heights of the first color conversion layer, the second color conversion layer and the optical cement is between 1:1 and 1:15, and color conversion mixtures used to form the first color conversion layer and the second color conversion layer are cured by excitation light wavelength between 385 nm and 1180 nm. The array of micro light-emitting diodes is disposed under the color conversion structure to provide light to the color conversion structure. The backplane control structure is disposed under the color conversion structure for controlling the array of micro light-emitting diodes. 
     In order to have a better understanding of the above and other aspects of the present disclosure, the following specific embodiments are given in conjunction with the accompanying drawings to describe in detail as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1 A to  1 D  show a flow chart for manufacturing a light-emitting diode display according to an embodiment of the present disclosure. 
         FIGS.  2 A to  2 G  show a flow chart for manufacturing a light-emitting diode display according to a further embodiment of the present disclosure. 
         FIGS.  3 A to  3 H  show a flow chart for manufacturing a light-emitting diode display according to a further embodiment of the present disclosure. 
         FIGS.  4 A to  4 C  show a flow chart for manufacturing a reflecting structure according to an embodiment of the present disclosure. 
     
    
    
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
     DETAILED DESCRIPTION 
     The present disclosure relates to a color conversion unit, a color conversion structure using the color conversion unit, and a light-emitting diode display using the color conversion unit. Compared with the existing micro light-emitting diode display, since the color conversion layers of the color conversion units, the color conversion structure and the light-emitting diode display used in the present disclosure have a higher aspect ratio, the color conversion layers can have a larger thickness, so the color conversion efficiency can be greatly improved. Moreover, compared with the comparative example that uses the black matrix to block light, since the color conversion layers of the present disclosure can be embedded in the holes of the substrate with a high aspect ratio, the substrate can effectively solve the problem of the cross-talk of light between the color conversion layers, and achieve a more excellent light blocking effect. 
     The following describes the implementations of the present disclosure in detail with reference to the accompanying drawings. It should be noted that the structure, manufacturing process, and content of the implementations proposed in the embodiments are for illustrative purposes only, and the scope to be protected by the present disclosure is not limited to the described implementations. It should be noted that the present disclosure does not show all possible embodiments, and those skilled in the art can change and modify the structure and manufacturing process of the embodiments without departing from the spirit and scope of the disclosure to meet actual requirements for applications. 
     Further, the same or similar reference numerals are used in the same or similar elements in the embodiments to facilitate clear description. In addition, the drawings have been simplified to clearly illustrate the content of the embodiments, and the sizes of elements in the drawings are not drawn in the same proportion related to the actual products, so they are not used to limit the protected scope of the present disclosure. 
     Furthermore, the ordinal numbers used in the specification and the scope of the present disclosure, such as the terms “first”, “second”, etc., are used to modify the elements in the scope of the present disclosure, and do not in themselves mean and represent any previous ordinal number of the claimed element, and does not represent the order of a certain claimed element and another claimed element, or the order of the manufacturing method. The use of these ordinal numbers is only used to enable a claimed element with a certain name to be clearly distinguished over another claimed element with the same name. 
       FIGS.  1 A to  1 D  show a flow chart for manufacturing a light-emitting diode display  10  according to an embodiment of the present disclosure.  FIGS.  1 A to  1 D  may correspond to cross-sectional views formed in a second direction (for example, Y direction) and a third direction (for example, Z direction). The second direction may be perpendicular to the third direction. 
     First, referring to  FIG.  1 A , a backplane control structure  101 , an array of micro light-emitting diodes  110 , and a substrate  112  are provided. The array of micro light-emitting diodes  110  is disposed above the backplane control structure  101 , and the substrate  112  is disposed above the array of micro light-emitting diodes  110 . The backplane control structure  101  and the array of micro light-emitting diodes  110  are electrically connected to each other through contact pads  103  and bumps  107 . The contact pads  103  are, for example, disposed in the insulating layer  105 . The backplane control structure  101  may include a Complementary Metal-Oxide-Semiconductor (CMOS) layer, a transistor layer, or other suitable electronic driving layers. The substrate  112  is, for example, a silicon substrate, an epitaxial wafer, or other suitable substrates. In some embodiments, the substrate  112  may include an oxide layer (not shown). The array of micro-light-emitting diodes  110  may include a plurality of micro-light-emitting diodes  110 A,  110 B,  110 C . . . which are arranged in a matrix, and each of the micro-light-emitting diodes  110 A,  110 B,  110 C . . . can correspond to a sub-pixel. 
     Thereafter, referring to  FIG.  1 B , a plurality of holes  112   u  are formed on the substrate  112  through an etching process, and each of holes  112   u  corresponds to and exposes a micro light-emitting diode  110 A,  110 E or  110 C . . . . That is, in the top view, holes  112   u  are arranged in a matrix (not shown) corresponding to the micro light emitting diodes. In the present embodiment, the micro light-emitting diodes  110 A,  110 B, and  110 C can correspond to three sub-pixels of different colors in one pixel, respectively, but the present disclosure is not limited thereto. According to an embodiment, the etching process is, for example, a dry etching process. A ratio (i.e., W 1 :H 1 ) of a width W 1  (for example, the maximum width) to a height H 1  (for example, the maximum height) of the hole  112   u  is, for example, between 1:1 and 1:15. In some embodiments, the ratio of the width W 1  to the height H 1  of the hole  112   u  is, for example, between 1:5 and 1:15, between 1:7 and 1:15, between 1:8 and 1:13, or in other suitable ranges. 
     After the holes  112   u  are formed, referring to  FIG.  1 C , fill the holes  112   u  with color conversion mixtures. The color conversion mixtures are used to form the color conversion layers  114 . For example, after the exposure step, the color conversion mixtures can be cured into the color conversion layers  114 . In the present embodiment, the ultraviolet light (e.g. 385 nm to 440 nm of the wavelength) is used for irradiation in the exposure step, but the present disclosure is not limited thereto. In other embodiments, near-infrared light (e.g. 780 nm to 820 nm of the wavelength), infrared light (e.g. 1030 nm to 1080 nm of the wavelength) or other suitable excitation light can be used for the irradiation in the exposure step. 
     The color conversion layers  114  may include a first color conversion layer  114 A, a second color conversion layer  114 B, and an optical cement  114 C. The optical cement  114 C may include scattering particles, and the present disclosure is not limited thereto. In the present embodiment, the micro light-emitting diodes  110 A,  110 B,  110 C . . . are blue light micro light-emitting diodes. In one pixel, the color conversion mixtures can correspond to a red sub-pixel, a green sub-pixel, and a blue sub-pixel, respectively. However, the present disclosure is not limited thereto. In other embodiments, the color conversion mixtures may correspond to sub-pixels of other colors, such as the yellow sub-pixel, the purple sub-pixel, or the other sub-pixel in suitable color. According to the present embodiment, the color conversion mixture corresponding to the red sub-pixel includes a quantum dot material that can release a red spectrum, a photoresist, a photoinitiator, and other suitable materials. The color conversion mixture corresponding to the green sub-pixel includes quantum dot materials that can release the green spectrum, photoresist, photoinitiator, and other suitable materials. The material corresponding to the blue sub-pixel may include a scattering material, a photoresist, a photoinitiator, air, and other suitable materials, and may not include a color conversion mixture. That is, in the present embodiment, the first color conversion layer  114 A includes a quantum dot material that can release a red spectrum, the second color conversion layer  114 B includes a quantum dot material that can release a green spectrum, and the optical cement  114 C does not include the color conversion mixture. In other embodiments, the micro light-emitting diode is a blue micro light-emitting diode, so the blue sub-pixel may not include the color conversion mixture. The solid content of the quantum dot materials is in between 10 wt % to 40 wt %, and the viscosity of the quantum dot materials is in between 5 cP to 90 cP. The scattering material is, for example, titanium dioxide (TiO 2 ), organic scattering particles or other suitable scattering materials. In the embodiment where ultraviolet light is used as the excitation light (that is, for curing the color conversion mixture), the color conversion mixture used to form the color conversion layer  114  may be cured between 385 nm and 440 nm, between 395 nm and 405 nm, between 400 nm and 420 nm, or in other suitable ranges of the excitation light wavelength. 
     In some embodiments that use ultraviolet light to cure the color conversion mixture (e.g. 385 nm to 440 nm of the excitation light wavelength that cures the color conversion mixture), the photoinitiator may be a compound without a nitrogen atom, such as 2-hydroxy-2-methylpropiophenone, diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide, 9,10-dibutoxyanthracene, 9,10-diethoxyanthracene, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, benzophenone, or the arbitrary combination of the above. 
     In some embodiments using near-infrared light to cure the color conversion mixture, the color conversion mixture is cured, for example, between 700 nm and 950 nm, between 700 nm and 850 nm, between 800 nm and 950 nm, or in other suitable ranges of the excitation light wavelength. 
     In some embodiments using near-infrared light to cure the color conversion mixture (e.g. 700 nm to 850 nm of the excitation light wavelength that cures the color conversion mixture), the photoinitiator may be bisdialkylamino-substituted diphenylpolyene, bisdiarylamino-substituted diphenylpolyene, bis(styryl)benzene, or the arbitrary combination of the above, for example, the chemical formula of the photoinitiator can be as shown in the following Formula 1 to Formula 8: 
     
       
         
         
             
             
         
       
     
     In Formula 1, “Me” represents a methyl group, “n-Bu” represents an n-butyl group, and “n” represents an integer of 3 to 5. The wavelength of light absorption of the photoinitiator shown in Formula 1 is, for example, 710 nm to 730 nm. 
     
       
         
         
             
             
         
       
     
     In Formula 2, the wavelength of light absorption of the photoinitiator shown in Formula 2 is, for example, 670 nm to 690 nm. 
     
       
         
         
             
             
         
       
     
     In Formula 3, “n-Bu” represents an n-butyl group. 
     
       
         
         
             
             
         
       
     
     In Formula 4, “n-Bu” represents an n-butyl group, and “Me” represents a methyl group. 
     
       
         
         
             
             
         
       
     
     In Formula 6, “R” represents C 12 H 25 . 
     
       
         
         
             
             
         
       
     
     In Formula 7, “n-Bu” represents an n-butyl group, and “Me” represents a methyl group. 
     
       
         
         
             
             
         
       
     
     In Formula 8, “R” represents C 12 H 25 . 
     In some embodiments of using near-infrared light to cure the color conversion mixture (e.g. 800 nm to 950 nm of the excitation light wavelength that cures the color conversion mixture), the photoinitiator may be donor-acceptor-donor distyrylbenzene, wherein the donor can be di-n-butyl, diphenylamino or other suitable donor groups, and the acceptor can be cyano or other suitable acceptor groups; for example, the chemical formula of the photoinitiator can be as shown in the following Formula 9 to Formula 13: 
     
       
         
         
             
             
         
       
     
     In Formula 9, “R” represents n-butyl or methyl. The wavelength of absorption light of the photoinitiator shown in Formula 9 is, for example, 830 nm. 
     
       
         
         
             
             
         
       
     
     In Formula 11, “R” represents n-butyl or methyl. The wavelength of absorption light of the photoinitiator shown in Formula 11 is, for example, 800 nm. 
     
       
         
         
             
             
         
       
     
     In Formula 13, “R” represents n-butyl or methyl. The wavelength of absorption light of the photoinitiator shown in Formula 13 is, for example, 730 nm. 
     In some embodiments using the infrared light to cure the color conversion mixture (e.g. 1030 nm to 1180 nm of the excitation light wavelength that cures the color conversion mixture), the photoinitiator can be squaraine, cyanine or other suitable ingredients; for example, the chemical formula of the photoinitiator can be as shown in the following Formula 14 to Formula 15: 
     
       
         
         
             
             
         
       
     
     In Formula 15, “R” represents CH 3  or C 3 H 7 . 
     According to some experimental data using ultraviolet light as the excitation light, it is known that the emission intensity of the color conversion mixture when absorbing the light from a light source of 365 nm is greater than the emission intensity of the color conversion mixture when absorbing the light from a light source of 385 nm. Therefore, the degree of absorption in the color conversion mixture for the light from the light source of 365 nm is greater than the degree of absorption in the color conversion mixture for the light from the light source of 385 nm, that is, the light from light source of 365 nm has a greater influence on the optical properties of the color conversion mixture. It should be noted that in the color conversion mixture of the present disclosure, the formula of the photoinitiator can be adjusted according to the light absorption spectrum or light emission spectrum of the quantum dot material. For example, the quantum dot material has a first main absorption band for ultraviolet light (for example, 365 nm), the photoinitiator has a second main absorption band for ultraviolet light (for example, greater than 365 nm), and most of the second main absorption band is different from the first main absorption band. That is, in the color conversion mixture, a photoinitiator that avoids the main light absorption band of the quantum dot material should be selected to prevent a large part of the exposed light from being absorbed by the quantum dot material during the exposure step, and the color conversion mixture can only be cured by a part of the light, resulting in that the color conversion mixture cannot be cured completely. Especially, when a color conversion layer  114  with a large thickness (that is, a high aspect ratio) is formed, the color conversion mixture at the bottom is less likely to absorb the exposed light and is difficult to be cured. If the amount of exposure is increased in order to make the color conversion mixture to be cured in a more complete way, it may cause the quantum dot material to be damaged by the excitation light. Compared with the comparative example in which the excitation light wavelength that cures the color conversion mixture greatly overlaps the main absorption band of the quantum dot material, since the excitation light wavelength that cures the color conversion mixture to form the color conversion layer  114  according to an embodiment of the present disclosure is between 385 nm and 1180 nm, most range of the excitation light wavelength that cures the color conversion mixture is different from the main absorption wavelength of the quantum dot material (for example, the excitation light wavelength that cures the color conversion mixture is greater than the main absorption wavelength of the quantum dot), which can prevent the absorption of the quantum dots from affecting the color conversion mixture to be cured into a film. This solves the problem of incomplete curing of the color conversion mixture. In addition, when the excitation light having a longer wavelength is used to cure the color conversion mixture, the excitation light having a longer wavelength can have stronger penetrating ability, which is beneficial to form the color conversion layer  114  with a larger thickness. The color conversion layer  114  with a larger thickness of film may have more excellent color conversion efficiency. 
     In the present embodiment, the micro light-emitting diodes  110 A,  110 B,  110 C . . . are blue light micro light-emitting diodes. After the emitted blue light is transmitted to the first color conversion layer  114 A, the second color conversion layer  114 B and the optical cement  114 C, the emitted blue light is converted into red light and green light through the first color conversion layer  114 A and the second color conversion layer  114 B, respectively; since the optical cement  114 C does not include the color conversion mixture, the blue light is directly transmitted through the optical cement  114 C and appears as blue light. That is, the first color conversion layer  114 A, the second color conversion layer  114 B, and the optical cement  114 C can respectively correspond to the red sub-pixel, the green sub-pixel, and the blue sub-pixel. However, the present disclosure is not limited thereto. In other embodiments, the first color conversion layer  114 A, the second color conversion layer  114 B, and the optical cement  114 C can respectively correspond to sub-pixels of other colors. 
     After the color conversion layer  114  is formed, the color conversion layer  114  and the substrate  112  may be covered by a sealing layer  116  to form the light-emitting diode display  10  as shown in  FIG.  1 D . The light-emitting diode display  10  includes a color conversion structure T 1 , an array of micro light-emitting diodes  110 , and a backplane control structure  101 . The array of micro light-emitting diodes  110  is disposed under the color conversion structure T 1 , and is used to provide light to the color conversion structure T 1 . The backplane control structure  101  is disposed under the color conversion structure T 1  for controlling the array of micro light-emitting diodes  110 . 
     In the present embodiment, the color conversion structure T 1  corresponds to a pixel including, for example, a red sub-pixel, a green sub-pixel, and a blue sub-pixel, but the present disclosure is not limited thereto. The array of micro light-emitting diodes  110  includes a plurality of micro light-emitting diodes  110 A,  110 B,  110 C . . . arranged in a matrix. The color conversion structure T 1  includes a plurality of color conversion units U 1 . The color conversion units U 1  include a substrate  112  and a first color conversion layer  114 A, a second color conversion layer  114 B, and an optical cement  114 C adjacent to each other. The substrate  112  includes a plurality of holes  112   u.  The holes  112   u  correspond to the micro light-emitting diodes  110 A,  110 B, and  110 C, respectively. The first color conversion layer  114 A, the second color conversion layer  114 E and the optical cement  114 C are filled in the holes  112   u  of the substrate  112 . The emission wavelengths converted by the first color conversion layer  114 A, the second color conversion layer  114 B, and the optical cement  114 C are different from each other. The micro light-emitting diodes  110 A,  110 B,  110 C . . . disposed under the first color conversion layer  114 A, the second color conversion layer  114 B and the optical cement  114 C are used to provide light to the first color conversion layer  114 A, the second color conversion layer  114 B and the optical cement  114 C. The sealing layer  116  and the array of micro light-emitting diodes  110  may be disposed on opposite sides of the color conversion layer  114 . 
     The ratios of widths to heights of the first color conversion layer  114 A, the second color conversion layer  114 B, and the optical cement  114 C are between 1:1 and 1:15, between 1:7 and 1:15, between 1:8 and 1:13 or in other suitable range. Moreover, when the ultraviolet light is used for curing, the color conversion mixture used to form the first color conversion layer  114 A and the second color conversion layer  114 B is cured by excitation light wavelength between 385 nm and 440 nm. In other embodiments, when the optical cement  114 C includes the color conversion mixture, the color conversion mixture is cured by excitation light wavelength between 385 nm and 440 nm. In some embodiments, the thickness of the first color conversion layer  114 A, the second color conversion layer  114 B, and the optical cement  114 C can be between 2 μm and 20 μm, between 5 μm and 15 μm, between 7 μm and 12 μm, or in other suitable range. In the present embodiment, the thickness of the first color conversion layer  114 A, the second color conversion layer  114 B, and the optical cement  114 C may be 5.5 μm, and the color conversion efficiency (CCE) of the first color conversion layer  114 A and the second color conversion layer  114 B can reach 50%. In a comparative example, the thickness of the first color conversion layer, the second color conversion layer, and the optical cement is 1.5 μm, and the color conversion efficiency of the first color conversion layer and the second color conversion layer is only 10%. It can be seen that the thickness of the color conversion layer  114  in the present disclosure is relatively large, which can greatly improve the color conversion efficiency. 
     Compared with the comparative example in which the excitation light wavelength that cures the color conversion mixture greatly overlaps the main absorption wavelength of the quantum dot material, since the excitation light wavelength that cures the color conversion mixture in the light-emitting diode display  10  of the present disclosure is between 385 nm and 1180 nm, which is greater than the main absorption wavelength of the quantum dot material, that is, the range of the excitation light wavelength that cures the color conversion mixture in the present disclosure is different from the main absorption wavelength of the quantum dot material, which can prevent the light absorption of the quantum dots from affecting the color conversion mixture to be cured into a film. Therefore, the formed color conversion layer  114  can have a good quality in curing. Moreover, it is beneficial in the present disclosure to form the color conversion layer  114  with a high aspect ratio (that is, a larger thickness) without a large amount of exposure. On the one hand, it can reduce the damage and degradation of the quantum dot material during exposure and improve the efficiency of the quantum dot; on the other hand, the color conversion layer  114  can have a sufficient thickness of the film to exhibit the color conversion efficiency to be more excellent. In addition, if the black matrix is disposed between the color conversion layers to block the light, the black matrix is limited by the process conditions, and the thickness of the black matrix is not large enough to effectively block the light; therefore, in comparison with the comparative example that the black matrix is disposed between the color conversion layers to block the light, since the color conversion layers  114  with sufficient thickness (for example, high aspect ratio) in the present disclosure can be embedded in the holes  112   u  of the substrate  112 , the substrate  112  can surround the color conversion layers  114  and is disposed between the color conversion layers  114 , the substrate  112  has an excellent effect for blocking the light, and can solve the problem of the cross-talk of light, accordingly. 
       FIGS.  2 A to  2 G  show a flow chart for manufacturing a light-emitting diode display  20  according to a further embodiment of the present disclosure.  FIGS.  2 A to  2 G  may correspond to cross-sectional views formed in the second direction (for example, Y direction) and the third direction (for example, Z direction). The elements in the light-emitting diode display  20  that are similar or identical to those of the light-emitting diode display  10  use the similar or identical reference numerals, and both have similar or identical physical and chemical properties, forming materials, forming methods, structures and functions. The repetition will not be described in detail. 
     First, referring to  FIG.  2 A , a substrate  212  is provided. The substrate  212  is, for example, a silicon substrate, an epitaxial wafer, or other suitable substrates. In some embodiments, the substrate  212  may include an oxide layer (not shown). 
     Thereafter, referring to  FIG.  2 B , a plurality of holes  212   u  are formed on the substrate  212  by an etching process, and each of the holes  212   u  corresponds to a predetermined position of a micro light-emitting diode (shown in  FIG.  2 G ). According to an embodiment, the etching process is, for example, a dry etching process. The ratio of the width to the height of the hole  212   u  is, for example, between 1:1 and 1:15. In some embodiments, the ratio of the width to the height of the hole  212   u  is, for example, between 1:5 and 1:15, between 1:7 and 1:15, between 1:8 and 1:13, or in other suitable ranges. 
     After the holes  212   u  are formed, as shown in  FIG.  2 C , the substrate  212  is bonded to a cover plate  222  having a mirror structure  220  by an adhesive  218 . The mirror structure  220  is, for example, a distributed Bragg reflector. The cover plate  222  is, for example, a glass cover plate or other suitable transparent cover plates. 
     Thereafter, referring to  FIG.  2 D , portions of the substrate  212  are removed by an etching process and the holes  212   u  are exposed. The holes  212   u  can expose portions of the mirror structure  220 . 
     As shown in  FIG.  2 E , the color conversion mixture is filled into the holes  212   u  to form the color conversion layer  214 . The color conversion layer  214  may include a first color conversion layer  214 A, a second color conversion layer  214 B, and an optical cement  214 C. The materials and functions of the first color conversion layer  214 A, the second color conversion layer  214 B and the optical cement  214 C may be the same as those of the first color conversion layer  114 A, the second color conversion layer  114 B, and the optical cement  114 C, respectively. 
     After filling the color conversion mixture, referring to  FIG.  2 F , a sealing layer  216  may be formed on the color conversion layers  214  and the substrate  212 . 
     Thereafter, referring to  FIG.  2 G , the sealing layer  216  is bonded to the array of micro light-emitting diodes  110  which is electrically connected to the backplane control structure  101  by flip bonding to form the light-emitting diode display  20 . The light-emitting diode display  20  includes a color conversion structure T 2 , an array of micro light-emitting diodes  110 , and a backplane control structure  101 . The array of micro light-emitting diodes  110  is disposed under the color conversion structure T 2 , and is used to provide the light to the color conversion structure T 2 . The backplane control structure  101  is disposed under the color conversion structure T 2  for controlling the array of micro light-emitting diodes  110 . 
     In the present embodiment, the color conversion structure T 2  corresponds to, for example, a pixel including a red sub-pixel, a green sub-pixel, and a blue sub-pixel, but the present disclosure is not limited thereto. The color conversion structure T 2  includes a plurality of color conversion units U 2 . The color conversion unit U 2  includes a substrate  212  and a first color conversion layer  214 A, a second color conversion layer  214 B, and an optical cement  214 C adjacent to each other. The sealing layer  216  and the mirror structure  220  may be disposed on opposite sides of the color conversion layer  214 . Moreover, the sealing layer  216  is closer to the array of micro light-emitting diodes  110  than the mirror structure  220 . The cover plate  222  is disposed on the mirror structure  220 , the substrate  212  and the color conversion layers  214 . 
       FIGS.  3 A to  3 H  show a flow chart for manufacturing a light-emitting diode display  30  according to a further embodiment of the present disclosure,  FIGS.  3 A,  3 B,  3 D, and  3 F to  3 H  are cross-sectional views of the manufacturing process of the light-emitting diode display  30 , which correspond to cross-sectional views formed by the second direction (for example, Y direction) and the third direction (for example, Z direction).  FIG.  3 C  shows a top view corresponding to  FIG.  3 B , that is,  FIG.  3 B  is a cross-sectional view taken along the line A-A′ of  FIG.  3 C ;  FIG.  3 E  shows a top view corresponding to  FIG.  3 D , that is,  FIG.  3 D  is a cross-sectional view taken along the line A-A′ of  FIG.  3 E . For example,  FIGS.  3 C and  3 E  correspond to the plane formed by the first direction (for example, X direction) and the second direction (for example, Y direction), and the first direction, the second direction and the third direction may be perpendicular to each other. The elements of the light-emitting diode display  30  that are similar or identical to those of the light-emitting diode display  10  use similar or identical reference numerals, and both have similar or identical physical and chemical properties, forming materials, structures, and functions, and the repetition will not be described in detail. 
     First, referring to  FIG.  3 A , a substrate  312  is provided. The substrate  312  may include an oxide layer  312   y.  The substrate  312  is, for example, a silicon substrate, an epitaxial wafer, or other suitable substrates. The material of the oxide layer  312   y  is, for example, silicon oxide. 
     Thereafter, referring to  FIGS.  3 B and  3 C  at the same time, a plurality of trenches  312   k  are formed on the substrate  312  by an etching process. The trenches  312   k  extend in a first direction (for example, X direction), and are separated from each other in a second direction (for example, Y direction). In other words, the trenches  312   k  can be separated by the substrate  312 . 
     After forming the trenches  312   k,  referring to  FIGS.  3 E and  3 D  at the same time, a plurality of holes  312   u  on the substrate  312  are formed by an etching process. Each of the holes  312   u  corresponds to a predetermined position of a micro light-emitting diode (as shown in  FIG.  3 G ). The hole  312   u  communicates with the corresponding one of the trenches  312   k.  According to an embodiment, the etching process is, for example, a dry etching process. The ratio of the width to the height of the hole  312   u  is, for example, between 1:1 and 1:15. In some embodiments, the ratio of the width to the height of the hole  312   u  is, for example, between 1:5 and 1:15, between 1:7 and 1:15, between 1:8 and 1:13 or in other suitable ranges. 
     After forming the holes  312   u,  as shown in  FIG.  3 F , the color conversion mixture is filled into the holes  312   u  by an inkjet printing process to form the color conversion layers  314 . The color conversion layers  314  may include a first color conversion layer  314 A, a second color conversion layer  314 B, and an optical cement  314 C. The materials and functions of the first color conversion layer  314 A, the second color conversion layer  314 B, and the optical cement  314 C may be similar to those of the first color conversion layer  114 A, the second color conversion layer  114 B, and the optical cement  114 C, respectively. 
     After that, referring to  FIG.  3 G , the sealing layer  316  can be covered on the color conversion layer  314  and the substrate  312 , and the sealing layer  316  can be bonded to the array of micro light-emitting diodes  110  which is electrically connected to the backplane control structure  101  by the flip bonding, 
     Referring to  FIG.  3 H , a portion of the substrate  312  is removed and the oxide layer  312   y  is exposed to form a light-emitting diode display  30 . The light-emitting diode display  30  includes a color conversion structure T 3 , an array of micro light-emitting diodes  110 , and a backplane control structure  101  The array of micro light-emitting diodes  110  is disposed under the color conversion structure T 3 , and is used to provide light to the color conversion structure T 3 . The backplane control structure  101  is disposed under the color conversion structure T 3  for controlling the array of micro light-emitting diodes  110 . 
     In the present embodiment, the color conversion structure T 3  corresponds to, for example, a pixel including a red sub-pixel, a green sub-pixel, and a blue sub-pixel, but the present disclosure is not limited thereto. The color conversion structure T 3  includes a plurality of color conversion units U 3 . The color conversion units U 3  include a substrate  312  and a color conversion layer  314  (i.e., a first color conversion layer  314 A, a second color conversion layer  314 B, and an optical cement  3140  adjacent to each other). The sealing layer  316  and the oxide layer  312   y  may be disposed on opposite sides of the color conversion layer  314 . The oxide layer  312   y  is disposed above the color conversion layer  314 . The sealing layer  316  is closer to the array of micro light-emitting diodes  110  than the oxide layer  312   y.    
       FIGS.  4 A to  4 C  show a flow chart for manufacturing a reflecting structure  424  according to an embodiment of the present disclosure. The reflecting structure  424  can be applied to the light-emitting diode displays  10  to  30  as described above or other suitable light-emitting diode displays. 
     Referring to  FIG.  4 A , a plurality of holes  412   u  are formed in the substrate  412 . The substrate  412  is, for example, disposed on a specific structure PL. When the present the embodiment is applied to the embodiment of the light-emitting diode display  10 , the specific structure PL is, for example, the array of micro light-emitting diode  110  as shown in  FIG.  1 B ; when the present the embodiment is applied to the embodiment of the light-emitting diode display  20 , the specific structure PL is, for example, a cover plate  222  having the mirror structure  220  as shown in  FIG.  2 D ; when the present the embodiment is applied to an embodiment of a light-emitting diode display  30 , the specific structure PL is, for example, the oxide layer  312   y  in the substrate  312  as shown in  FIG.  3 D . 
     After the holes  412   u  are formed, referring to  FIG.  4 B , a reflective layer  424 ′ conformal to the holes  412   u  and the substrate  412  is formed by a sputtering process. The material of the reflective layer  424 ′ is, for example, the metal material, a distributed Bragg reflector or other suitable materials. The metal material can be selected from gold, silver, aluminum, copper, titanium or the arbitrary combination thereof. The distributed Bragg reflector is a material known to those ordinary skilled in the art, and may be a stack of oxide/metal oxide, for example. 
     After that, referring to  FIG.  4 C , the reflective layer  424 ′ disposed at the bottom of the holes  412   u  and disposed on the substrate  412  are removed by an etch-back process, and the reflective layer  424 ′ disposed on the sidewalls of the holes  412   u  is remained to form reflecting structures  424 . That is, the reflecting structures  424  are disposed on the sidewalls of the holes  412   u  (for example, the holes  112   u,    212   u,  or  312   u  in the light-emitting diode display  10  to  30 ), and are disposed between the color conversion layer (for example, the color conversion layer  114 ,  214 , or  314 ) and the substrate  412  (for example, the substrate  112 ,  212 , or  312 ). In some embodiments, a thickness of the reflecting structures  424  may be 1000 angstroms to 2000 angstroms, and a pitch may be 1.5 μm. 
     In some embodiments, the embodiments of the light-emitting diode displays  10  to  30  can be combined arbitrarily, or the light-emitting diode displays  10  to  30  can be combined with other embodiments. According to some embodiments, a color filter (not shown) may be disposed on the color conversion layers  114 ,  214 , or  314 . For example, a color filter (not shown) may be disposed between the color conversion layers  214  and the mirror structure  220 . 
     In summary, according to an embodiment of the present disclosure, a color conversion unit is provided. The color conversion layer is filled in a hole of the substrate, wherein a ratio of a width to a height of the color conversion layer is between 1:1 and 1:15, and the color conversion mixture used to form the color conversion layer is cured by excitation light wavelength between 385 μm and 1180 μm. 
     Compared with the comparative example where the ratio of the width to the height of the color conversion layer is 1:0.4, since the ratio of the width to the height of the color conversion layer in an embodiment of the present disclosure is between 1:1 and 1:15, the color conversion layer has a relatively large thickness, so the color conversion efficiency can be improved. 
     Compared with the comparative example in which the excitation light wavelength that cures the color conversion mixture to form the color conversion layer is 365 nm, since the excitation light wavelength of the present disclosure is between 385 nm and 1180 nm, the excitation light wavelength that cures the color conversion mixture is different from the main absorption wavelength of the quantum dot material, which can prevent the light absorption of the quantum dots from affecting the curing of the color conversion mixture into a film, so the formed color conversion layer can have a good quality in curing. Moreover, the present disclosure is beneficial for forming a color conversion layer with a high aspect ratio (that is, a larger thickness) without a large amount of exposure. On the one hand, it can reduce the damage and degradation of the quantum dot material during exposure and improve the efficiency of the quantum dot; on the other hand, the color conversion layer can have a sufficient film thickness to exhibit the color conversion efficiency to be more excellent. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.