KR20210054436A - Method of transferring micro-light emitting diode for LED display - Google Patents

Abstract

Disclosed is a method of transferring a micro-light emitting diode (LED) for an LED display. According to an embodiment, the method of transferring a micro-LED transfers micro-LEDs onto a pixel array panel including a plurality of sub-pixel regions, on which the micro-LEDs are to be mounted. The micro-LEDs are sprayed in an inkjet manner to be transferred. The micro-LEDs comprise: a first portion for emitting light in a first direction; and a second portion for emitting the light in a second direction different from the first direction.

Description

Method of transferring micro-light emitting diode for LED display

The present disclosure relates to display manufacturing, and more particularly, to a method of transferring a micro LED used as a pixel light source in a light emitting diode (LED) display manufacturing process.

In the past, LCD (Liquid Crystal Display) has been widely used as a flat panel display, but as OLED (Organic Light Emitting Diode), which does not use liquid crystal, has been widely spread, the amount of LCD has been greatly reduced compared to the previous one. Recently, as a next-generation display, an LED display that uses micro LED directly as a light source for each pixel has been introduced. In an LED display, each pixel is a micro LED (R micro LED) that emits red light to a sub-pixel area that emits red light (R), a sub-pixel area that emits green light (G), and a sub-pixel area that emits blue light (B). ), a micro LED emitting green light (G micro LED) and a micro LED emitting blue light (B micro LED). When manufacturing an LED display, such a micro LED can be transferred to the pixel array panel through a transfer process.

It provides a micro LED transfer method for LED displays that can increase micro LED transfer efficiency.

It provides a micro LED transfer method for LED displays that can quickly and accurately transfer micro LEDs to large-area pixel array panels.

In the micro LED transfer method according to an embodiment, in a method of transferring a micro LED to a pixel array panel including a plurality of sub-pixel regions in which a micro LED is to be mounted, the micro LED is transferred by spraying in an inkjet method, and the micro LED is transferred by spraying the micro LED. The LED includes an active layer comprising a first portion emitting light in a first direction and a second portion emitting light in a second direction different from the first direction.

In one example, transferring the micro LEDs may include dividing the plurality of subpixel regions into a plurality of groups and transferring the plurality of micro LEDs to the plurality of groups. In one example, the process of transferring the plurality of micro LEDs includes the process of sequentially transferring the plurality of micro LEDs in sequence with respect to the plurality of groups, and a group selected from the plurality of groups in the process of sequentially transferring Micro LEDs can be simultaneously transferred to the sub-pixel areas of. The subpixel regions of the selected group may include subpixel regions to which the micro LED emitting red light, green light, or blue light is to be transferred.

The pixel array panel may be provided on a backplate of an LED display.

The subpixel regions of the selected group are a plurality of subpixel regions (hereinafter, R subpixel regions) emitting red light (R), a plurality of subpixel regions (hereinafter, G subpixel regions) emitting green light (G), and A plurality of pixels may be formed including a plurality of subpixel regions (hereinafter, B subpixel regions) emitting blue light B.

In one example, the process of simultaneously transferring the micro LEDs to the subpixel areas of the selected group includes transferring the first micro LEDs to the plurality of R subpixel areas using a first inkjet head, and a second ink jetting process. A process of transferring the second micro LED to the plurality of G subpixel areas using a head and transferring the third micro LED to the plurality of B subpixel areas using a third inkjet head may be included. A plurality of micro LEDs may be transferred to each of the plurality of sub-pixel regions. Including a process of removing the rest of the plurality of micro LEDs transferred to each sub-pixel area except for the micro LED that has been correctly transferred, and transferring the same micro LED as the micro LED that has been correctly transferred to the place where the micro LED has been removed. can do.

In one example, a bank may be provided between each subpixel area.

Each of the sub-pixel areas is divided into a plurality of areas, and one micro LED may be transferred to the plurality of areas. In one example, each of the plurality of regions may be defined by a mold guiding the transferred micro LED.

In one example, the micro LED includes a first semiconductor layer, the active layer, and a second semiconductor layer sequentially stacked to form a core-shell structure, and the micro LED may be a vertical electrode micro LED or a horizontal electrode micro LED. .

In another example, a micro LED emitting the same light may be transferred to all of the plurality of sub-pixel regions. The micro LED emitting the same light may be a micro LED emitting blue light. For example, the process of forming first and second photo-conversion material layers on the micro LEDs transferred to the R sub-pixel region and the G sub-pixel region of the plurality of sub-pixel regions, respectively, may be further included.

In the method of transferring a micro LED to a pixel array panel including a plurality of pixel areas, a micro LED transfer method according to another embodiment includes a process of transferring the micro LED to a first pixel area among the plurality of pixel areas and the plurality of The micro LED is transferred to a second pixel area of the pixel area of the above, and in the two processes, the micro LED is transferred by spraying an inkjet method, and the micro LED is a first portion emitting light in a first direction. And a second portion that emits the light in a second direction different from the first direction.

In an example, the first and second pixel regions are adjacent to or separated from each other, and the two processes may be performed simultaneously. In another example, the first and second pixel regions are adjacent to or separated from each other, and the two processes may be sequentially performed. In the above two processes, the same or different micro LEDs may be transferred. The micro LED may be transferred to the remaining pixel areas among the plurality of pixel areas using the inkjet head. Among the layers constituting the micro LED, the first semiconductor layer, the active layer, and the second semiconductor layer sequentially stacked form a core-shell structure, and the micro LED may be a vertical electrode micro LED or a horizontal electrode micro LED.

In an example, the process of transferring the micro LED to the first pixel area among the plurality of pixel areas may include spraying a solution mixed with the micro LED to the first pixel area using a first inkjet head. .

In another example, the process of transferring the micro LEDs to the first pixel area of the plurality of pixel areas includes transferring the plurality of first micro LEDs to the first sub-pixel area of the first pixel area using a first inkjet head. Process, a process of transferring a plurality of second micro LEDs to a second sub-pixel area of the first pixel area by using a second inkjet head, and a process of transferring a plurality of second micro LEDs to a second sub-pixel area of the first pixel area by using a third ink-jet head, and a third sub-pixel area of the first pixel area by using a third ink-jet head It may include a process of transferring the plurality of third micro LEDs to.

In one example, the process of transferring the plurality of first micro LEDs, the process of transferring the plurality of second micro LEDs, and the process of transferring the plurality of third micro LEDs may be performed sequentially. In another example, You can also do it at the same time.

In one example, the process of transferring the plurality of first micro LEDs, the process of transferring the plurality of second micro LEDs, and the process of transferring the plurality of third micro LEDs are sequentially performed, and the plurality of first micro LEDs After transferring the micro LED, the process of removing the rest of the transferred first micro LEDs other than the first micro LEDs correctly transferred and the same micro LEDs as the first micro LEDs correctly transferred to the place where the first micro LEDs were removed. Including the process of transferring the LED,

The removing process and the process of transferring the same micro LED may be performed even after the process of transferring the plurality of second micro LEDs and the process of transferring the plurality of third micro LEDs. The first to third subpixel regions may be surrounded by banks. Each of the first to third subpixel regions includes a plurality of regions, and one of the first to third micro LEDs may be transferred to regions belonging to different subpixel regions among the plurality of regions. The plurality of regions may be defined by a frame guiding the micro LED to be transferred.

In one example, the process of transferring the micro LEDs to the second pixel area of the plurality of pixel areas includes transferring the plurality of first micro LEDs to the first sub-pixel area of the second pixel area using a first inkjet head. Process, a process of transferring a plurality of second micro LEDs to a second subpixel area of the second pixel area using a second inkjet head, and a process of transferring a plurality of second micro LEDs to a second subpixel area of the second pixel area using a third inkjet head, and a third subpixel area of the second pixel area using a third inkjet head It may include a process of transferring the plurality of third micro LEDs to. In one example, the process of transferring the plurality of first micro LEDs, the process of transferring the plurality of second micro LEDs, and the process of transferring the plurality of third micro LEDs may be performed sequentially. In another example, It can be done at the same time. In one example, the process of transferring the plurality of first micro LEDs, the process of transferring the plurality of second micro LEDs, and the process of transferring the plurality of third micro LEDs are sequentially performed, and the plurality of first micro LEDs After transferring the micro LED, it may include a process of removing only the first micro LED that has been correctly transferred among the transferred plurality of first micro LEDs, and removing the remaining first micro LED, and the removing process is performed by the plurality of first micro LEDs. 2 The process of transferring the micro LED and the process of transferring the plurality of third micro LEDs may be carried out even after the process.

In one example, each of the first to third subpixel regions includes a plurality of regions, and one of the first to third micro LEDs is transferred to regions belonging to different subpixel regions among the plurality of regions. Can be. The plurality of regions may be defined by a frame guiding the micro LED to be transferred.

According to an exemplary embodiment, a method of transferring a micro LED to a pixel array panel of an LED display accurately transfers the micro LED to each pixel area using an inkjet head by applying an inkjet printing method. In this transfer process, one inkjet head or a plurality of inkjet heads may be used sequentially or simultaneously, so that micro LEDs may be transferred sequentially or simultaneously to a plurality of pixel areas or a plurality of subpixel areas. Therefore, when the disclosed micro LED transfer method is used, the micro LED can be quickly and accurately transferred to the pixel area or sub-pixel area to which the micro LED is to be transferred, thereby increasing the transfer efficiency, and in addition to The time to transfer the micro LED can also be shortened. In addition, the main layers of the micro LED to be transferred form a core-shell structure, and thus the reduction in light emission efficiency due to the reduction in the size of the LED may be alleviated.

1 is a plan view illustrating a process of transferring a micro LED to a pixel array panel using an inkjet head as a micro LED transfer method for an LED display according to an exemplary embodiment.
FIG. 2 is an enlarged plan view of a selected area A1 of FIG. 1, that is, a portion including two pixels adjacent to each other in a Y-axis direction.
3 is a cross-sectional view of FIG. 2 taken in the direction 3-3'.
4 is a cross-sectional view of FIG. 2 taken in a direction 4-4'
5 is a cross-sectional view showing another example of a cross-section of FIG. 1 cut in the direction 3-3'.
6 is a cross-sectional view showing another example of a cross-section of FIG. 2 cut in the 4-4' direction.
7 is a plan view showing another embodiment of the first area A1 of FIG. 1.
8 is a cross-sectional view of FIG. 7 taken in a direction 8-8'.
9 is a cross-sectional view of FIG. 7 taken in a direction 9-9'.
10 is a cross-sectional view showing another form of the frame of FIGS. 8 and 9.
11 to 13 are cross-sectional views illustrating an example of a method of transferring a micro LED to a pixel region described in FIGS. 2 to 4 using an inkjet head.
14 to 15 show a process of transferring a micro LED to a pixel area defined by the bank 520 described in FIGS. 2, 5 and 6 using an inkjet head.
16 is a plan view showing a micro LED transfer result according to the micro LED transfer method described in FIGS. 11 to 15.
FIG. 17 is a plan view showing a case where only micro LEDs mounted upside down in each subpixel of FIG. 16 are selectively removed so that only micro LEDs correctly mounted on each subpixel remain.
FIG. 18 is a plan view showing a case where only micro LEDs correctly mounted in each subpixel of FIG. 16 are selectively removed, and only micro LEDs mounted upside down in each subpixel remain.
19 is a cross-sectional view showing an example of a micro LED transferred by the micro LED transfer method of FIGS. 11 to 15.
FIG. 20 is a cross-sectional view of FIG. 16 taken in a direction of 20-20' when there is no bank around a subpixel on a substrate.
FIG. 21 is a cross-sectional view showing a case where all of the micro LEDs transferred in FIG. 20 are in contact with electrode wiring and are surrounded by a passivation layer.
22 is a cross-sectional view illustrating a case in which a bank is provided together with a second wiring layer on a substrate in the case of FIG.
23 is a cross-sectional view showing a case where all of the micro LEDs transferred in FIG. 22 are in contact with the electrode wiring and are surrounded by a passivation layer.
24 is a cross-sectional view illustrating an example of a micro LED transferred to the first to third subpixel regions of the pixels shown in FIGS. 7 to 9.
25 to 27 show micro LEDs in each pixel while moving the inkjet head in a direction parallel to the direction of the inkjet head (Y-axis direction) with respect to the pixel array panel of FIG. It is a cross-sectional view showing step by step the process of transferring.
28 is an enlarged cross-sectional view of a second subpixel area of the first pixel of FIG. 27.
29 is a cross-sectional view illustrating a case in which all micro LEDs transferred to the first to fourth regions of the second subpixel region of the first pixel are properly mounted.
30 to 32 are cross-sectional views illustrating a step-by-step process of transferring a horizontal electrode micro LED to different subpixel areas of each pixel in the micro LED transfer method according to an exemplary embodiment.
33 is a cross-sectional view showing a micro LED transfer method according to another embodiment.

Hereinafter, a micro LED transfer method for a micro LED display according to an embodiment will be described in detail with reference to the accompanying drawings. In this process, the thicknesses of layers or regions shown in the drawings may be exaggerated somewhat for clarity of the specification. And the embodiments described below are merely exemplary, and various modifications are possible from these embodiments. In addition, in the layered structure described below, the expressions “top” or “top” may include not only those that are directly above by contact but also those that are non-contactly above.

1 is a micro LED transfer method according to an embodiment for an LED display, and shows a process of transferring a micro LED to a pixel array panel 100 using an inkjet head 150. The pixel array panel 100 includes a plurality of pixel regions 120, and each pixel region 120 is a region to which a micro LED is to be transferred. The pixel array panel 100 may be provided on a backplate of an LED display. As the micro LEDs are transferred to each pixel area 120, each pixel area 120 becomes a pixel. The micro LED transferred to each pixel area 120 is used as a light source for each pixel. The plurality of pixel regions 120 may be divided into a plurality of groups. Each group may include some pixel areas of the plurality of pixel areas 120. When the total number of the plurality of pixel areas 120 is N _P and the number of groups is N _G , the number of pixel areas included in one group may be _{N P} /N _G. Therefore, the number of pixel areas 120 included in each group is smaller than the number of all pixel areas 120.

Meanwhile, among a plurality of sub-pixel regions included in the plurality of pixel regions, regions having the same light emission characteristics may be grouped into a group. For example, a plurality of subpixel regions (R subpixel regions) that emit red light included in the plurality of pixel regions may be grouped into a group and referred to as an R subpixel region group. In this way, the plurality of pixel regions 120 may be divided into various groups.

The inkjet head 150 includes an injection hole 154 through which a plurality of micro LEDs are injected. The pixel array panel 100 may be part or all of the pixel array panel corresponding to the entire LED display. The inkjet head 150 may be a member that transfers micro LEDs to each pixel area of the pixel array panel 100. For example, the inkjet head 150 may be designed to spray a solution in which micro LEDs are distributed instead of ink in an inkjet head structure applied to an inkjet printer. In the pixel array panel 100, a plurality of pixel regions 120 may be uniformly arranged horizontally and vertically or in the X and Y directions to form an array. The inkjet head 150 may transfer the micro LED to each pixel region 120 while crossing the pixel array panel 100 from one side of the pixel array panel 100 to the other. Transfer of the micro LED may be performed individually for each pixel area 120. The inkjet head 150 may be an inkjet head for transferring micro LEDs emitting red light (R). The inkjet head 150 may be an inkjet head for transferring a micro LED emitting green light (G). The inkjet head 150 may be an inkjet head for transferring micro LEDs emitting blue light (B). The inkjet head 150 may include a plurality of heads, for example, including a plurality of inkjet heads for simultaneously transferring the same type of micro LED, or a plurality of simultaneously or sequentially transferring different types of micro LEDs. It may also include an inkjet head.

In the process of transferring the micro LED, the inkjet head 150 may cross the pixel array panel 100 in a given direction, for example, from the bottom of the pixel array panel 100 to the top (in the Y-axis direction). In another exemplary embodiment, the inkjet head 150 may transfer the micro LED to the pixel array panel 100 while proceeding from left to right (in the X-axis direction) or in the opposite direction of the pixel array panel 100.

FIG. 2 is an enlarged plan view of a portion including the selected area A1 of FIG. 1, that is, two pixel areas 120 adjacent to each other in the Y-axis direction.

Referring to FIG. 2, each pixel region 120 includes first to third subpixel regions SP1, SP2, and SP3. The first subpixel area SP1 may be an area in which a micro LED emitting red light is mounted. The second subpixel area SP2 may be an area in which a micro LED emitting green light is mounted. The third subpixel area SP3 may be an area in which a micro LED emitting blue light is mounted. The first to third subpixel areas SP1 to SP3 are spaced apart from each other. The interval between the first to third subpixel areas SP1 to SP3 may be constant.

3 is a cross-sectional view of FIG. 2 taken in the direction 3-3'.

Referring to FIG. 3, a second wiring layer GL is formed on the second subpixel area SP2 of the substrate 110. The entire second subpixel area SP2 is covered with the second wiring layer GL. The second wiring layer GL may be a wiring that supplies power to the micro LED mounted in the second subpixel area SP2. The micro LED may be mounted on the wiring layer GL.

4 is a cross-sectional view of FIG. 2 taken in a direction 4-4'.

Referring to FIG. 4, a first wiring layer RL exists on a first subpixel area SP1 of a substrate 110. A second wiring layer GL is provided on the second subpixel area SP2. A third wiring layer BL is present on the third subpixel area SP3. The materials of the first to third wiring layers RL, GL, and BL are the same, but may be different from each other. A micro LED emitting red light may be mounted on the first wiring layer RL. A micro LED emitting green light may be mounted on the second wiring layer GL. A micro LED emitting blue light may be mounted on the third wiring layer BL. The first to third wiring layers RL, GL, and BL may have a constant spacing apart from each other, but may be different. The thicknesses of the first to third wiring layers RL, GL, and BL may be the same. One electrode of the micro LED may be connected to the power source through the first to third wiring layers RL, GL, and BL. The entire first subpixel area SP1 of the substrate 110 is covered with the first wiring layer RL. The entire second subpixel area SP2 of the substrate 110 may be covered with the second wiring layer GL. The entire third subpixel area SP3 of the substrate 110 may be covered with the third wiring layer BL.

5 shows another example of a cross section of FIG. 1 cut in the direction 3-3'.

Referring to FIG. 5, a bank 520 defining a second subpixel area SP2 is formed on a substrate 110. A second subpixel area SP2 exists between the banks 520. Horizontally, the bank 520 and the second subpixel area SP2 contact each other. The second wiring layer GL is on the second subpixel area SP2. The total thickness of the second wiring layer GL may be uniform. The second wiring layer GL and the bank 520 are in contact with each other. The bank 520 is higher than the second wiring layer GL. That is, the upper surface of the bank 520 is higher than the upper surface of the second wiring layer GL. The bank 520 may function as a fence for each of the sub-pixel areas SP1 to SP3. The bank 520 may be an insulating layer. The height 5H of the bank 520 may be greater than the sum of the thickness of each wiring layer RL, GL, and BL and the height of the micro LEDs to be transferred onto each wiring layer RL, GL, and BL. In other words, after the micro LEDs are transferred onto the respective wiring layers RL, GL, and BL, the maximum height of the transferred micro LEDs may be lower than the upper surface of the adjacent bank 520.

6 shows another example of a cross section of FIG. 2 cut in the direction 4-4'.

Referring to FIG. 6, banks 520 defining first to third subpixel regions SP1, SP2, and SP3 are formed on a substrate 110. The first to third subpixel areas SP1, SP2, and SP3 are located between the banks 520. A first wiring layer RL, a second wiring layer GL, and a third wiring layer BL are formed on the first to third subpixel regions SP1, SP2, and SP3 of the substrate 110, respectively. Each of the wiring layers RL, GL, and BL is in contact with an adjacent bank 520. The upper surface of the substrate 110 between the sub-pixel regions SP1, SP2, and SP3 may be completely covered with the bank 520. 5 and 6, it can be seen that the periphery of each subpixel area SP1, SP2, and SP3 of the substrate 110 is completely covered with the bank 520. Accordingly, the periphery of the pixel region 120 of the substrate 110 is also covered with the bank 520.

Micro LEDs having vertical electrodes may be mounted in each of the sub-pixel areas SP1, SP2, and SP3 shown in FIGS. 2 to 6. 7 shows another embodiment of the selected area A1 of FIG. 1.

7 illustrates only one pixel region 120 of two pixels included in the selected region A1 for convenience.

Referring to FIG. 7, the pixel region 120 includes first to third subpixel regions SP1 ′, SP2 ′, and SP3 ′. The first subpixel area SP1 ′ may be a subpixel area in which a micro LED emitting red light is mounted. The second subpixel area SP2' may be a subpixel area in which a micro LED emitting green light is mounted. The third subpixel area SP3 ′ may be a subpixel area in which a micro LED emitting blue light is mounted. The first subpixel area SP1' may include first to fourth areas R1, R2, R3, and R4. The first to fourth regions R1, R2, R3, and R4 are spaced apart from each other, and the spaced apart from each other may be constant. A mold 710 may exist between the first to fourth regions R1, R2, R3, and R4. That is, the first to fourth regions R1, R2, R3, and R4 may be regions defined by the frame 710. The second subpixel area SP2' may include first to fourth areas G1, G2, G3, and G4. The first to fourth regions G1, G2, G3, and G4 are spaced apart from each other, and are arranged in parallel with the first to fourth regions R1, R2, R3, and R4 of the first subpixel region SP1'. Has been. The first to fourth regions G1, G2, G3, and G4 of the second subpixel region SP2' are spaced apart from each other, and a frame 710 exists therebetween. The third subpixel area SP3' includes first to fourth areas B1, B2, B3, and B4. The first to fourth regions B1, B2, B3, and B4 are arranged in parallel with the first to fourth regions G1, G2, G3, and G4 of the second subpixel region SP2'. The first to fourth regions B1, B2, B3, and B4 of the third subpixel region SP3' are spaced apart from each other, and a frame 710 exists therebetween. The frame 710 surrounds the entire first to third subpixel areas SP1', SP2', and SP3'. Each subpixel area is also surrounded by the frame 710. Each of the regions R1-R4, G1-G4, and B1-B4 of the first to third subpixel regions SP1 ′, SP2 ′, and SP3 ′ may include the same electrode wiring layer. Taking the first subpixel region SP1 ′ as an example, the first region R1 of the first subpixel region SP1 ′ may include a first wiring layer 720 and a second wiring layer 730. The first wiring layer 720 and the second wiring layer 730 are spaced apart from each other. The first wiring layer 720 is formed in a direction parallel to the X axis. The second wiring layer 730 includes a component parallel to the X axis and a component parallel to the Y axis. The second wiring layer 730 is disposed to surround the first wiring layer 720. A portion of the second wiring layer 730 parallel to the X axis is disposed above and below the first wiring layer 720, and a portion of the second wiring layer 730 parallel to the Y axis is on the left side of the first wiring layer 720. It is located in The first wiring layer 720 may be bonded to any one of a P-type electrode and an N-type electrode of the micro LED to be mounted in the first region R1. The second wiring layer 730 may be bonded to the other of the two electrodes of the micro LED. For example, the first wiring layer 720 may be bonded to the P-type electrode of the micro LED mounted in the first region R1, and the second wiring layer 730 may be bonded to the N-type electrode of the micro LED. . The frame 710 defining each subpixel area SP1', SP2', SP3' in the pixel area 120 may be an insulating material layer, and each of the subpixel areas SP1', SP2', SP3' It can serve to guide the micro LED to the area. The first to third subpixel areas SP1 ′, SP2 ′, and SP3 ′ are each illustrated as including 4 areas, but are not limited to 4 areas, and may include 4 or less or 4 or more areas. have.

8 is a cross-sectional view of FIG. 7 taken in the direction 8-8'.

Referring to FIG. 8, a frame 710 is disposed on a substrate 110 at a given interval. The frame 710 defines the first to fourth regions G1-G4 of the second subpixel region SP2'. A first wiring layer 720 and a second wiring layer 730 are formed on each region of the substrate 110 corresponding to the first to fourth regions G1-G4. The height of the upper surface of the frame 710 is higher than that of the first and second wiring layers 720 and 730. Although described later, the cross-sectional shape of the frame 710 may have a different shape. For convenience, the cross section of the frame 710 is shown in a square shape. In each of the regions G1, G2, G3, and G3, the first wiring layer 720 is positioned between the second wiring layers 730.

9 is a cross-sectional view of FIG. 7 taken in the direction 9-9'.

Referring to FIG. 9, a frame 710 is disposed on a substrate 110. The frame 710 includes a second region R2 of the first subpixel region SP1 ′ and a second region G2 and a third subpixel region of the second subpixel region SP2 ′ on the substrate 110. The second area B2 of SP3') is defined. A first wiring layer 720 and a second wiring layer 730 are formed on the substrate 110 in each of the second regions R2, G2, and B2. The first wiring layer 720 is in contact with the frame 710 to the right. The second wiring layer 730 is in contact with the frame 710 to the left. A part of the right side of the first wiring layer 720 may be covered by the frame 710.

Meanwhile, the shape of the frame 710 in FIGS. 8 and 9 may be different. For example, as shown in FIG. 10, the frame 710 may have a shape having a lower end wider than an upper end. Soon, the frame 710 may have a narrower width from the bottom to the top. Accordingly, both side surfaces 7S1 and 7S2 of the frame 710 become inclined surfaces. This inclined surface may be a surface guiding the micro LEDs transferred to each subpixel area to each subpixel area. When the cross-section of the micro LED transferred to each sub-pixel area is transferred while maintaining the same shape as the cross-sectional shape of each sub-pixel area (e.g., an inverted rhombus that narrows downward), the transferred micro LED is the corresponding part. It can be properly mounted in the pixel area. On the contrary, when the micro LED transferred to each subpixel area is transferred in an upside down state, the cross section of the transferred micro LED becomes a rhombus, making it difficult to mount in the corresponding subpixel area.

As a result, the frame 710 having the inclined side surfaces 7S1 and 7S2 may be a self-alignment member or self-alignment means of the micro LEDs transferred to each sub-pixel area. Therefore, the transfer efficiency of the micro LED can be increased. Soon, by transferring the micro LEDs by the inkjet jet method, the number of micro LEDs accurately and correctly transferred to the sub-pixel area can be increased.

11 shows an example of a method of transferring a micro LED to a pixel area described in FIGS. 2 to 4 using an inkjet head.

11 shows a process of transferring a micro LED to the same sub-pixel area of a plurality of pixel areas. Here, the same subpixel area may be, for example, a region in which a micro LED emitting red light is mounted.

Referring to FIG. 11, the inkjet head 150 first drops (sprays) micro LED droplets 1150 on the first wiring layer RL1 of the first subpixel region of the first pixel region. The micro LED droplet 1150 may include a plurality of micro LEDs 1120 and a volatile solution 1130. The micro LED drop 1150 may include one or more micro LEDs 1120, for example, 1 to 6 micro LEDs 1120. The micro LED droplets 1150 are jetted through the jetting holes 154 of the inkjet head 150. The inkjet head 150 may accommodate a micro LED solution. The micro LED solution refers to a solution 1130 in which a plurality of micro LEDs 1120 are uniformly mixed (distributed). In one example, the solution 1130 may be water, a solvent, or a volatile organic material.

The inkjet head 150 may include a micro LED solution capable of transferring micro LEDs to a plurality of pixel areas.

As the first pixel region is sprayed (falling off) on the first wiring layer RL1 of the first subpixel region, a plurality of micro LED droplets 1150 are sprayed onto the first wiring layer RL1 as shown in FIG. The LEDs 1120 may be aligned (mounted). The solution 1130 covering the micro LEDs 1120 arranged in this way is soon volatilized, and only the plurality of micro LEDs 1120 remain on the first wiring layer RL1. In FIG. 12, for convenience, the micro LEDs 1120 are arranged on the first wiring layer RL1 at regular intervals, but as shown in FIG. 16, the distance between the transferred plurality of micro LEDs 1120 is It may not be constant. Also, some micro LEDs can be mounted upside down.

As shown in FIG. 12, after transferring the micro LED 1120 onto the first wiring layer RL1 of the first subpixel region of the first pixel, the inkjet head 150 is moved to the first subpixel region of the second pixel. After moving onto the first wiring layer RL2 of, a drop of micro LED droplet 1150 is sprayed (dropped) on the first wiring layer RL2.

Next, as shown in FIG. 13, a micro LED drop 1150 is sprayed onto the first wiring layer RL3 in the first subpixel area of the third pixel. This injection process is repeated up to the nth pixel. The n-th pixel may be the last pixel in the Y-axis direction in FIG. 1. After mounting the micro LED on the first wiring layer RLn by spraying the micro LED droplets 1150 on the first wiring layer RLn of the first subpixel area of the nth pixel, the second inkjet head is used. A second micro LED is mounted on the second wiring layer of each second subpixel area of the first to nth pixels. The second inkjet head may be structurally identical to the inkjet head 150 except that only the types of micro LEDs accommodated in the head are different. The wavelength of light emitted from the second micro LED may be different from the wavelength of light emitted from the micro LED 1120 (hereinafter, referred to as the first micro LED). For example, red light (R) may be emitted from the first micro LED 1120 and green light (G) may be emitted from the second micro LED. The transfer process of the micro LED using the second ink jet head may be the same as the transfer process of the micro LED using the ink jet head 150 (hereinafter, referred to as the first ink jet head).

After performing micro LED transfer using the second inkjet head, the third micro LED is mounted on the third wiring layer of each third subpixel region of the first to nth pixel regions using the third inkjet head. can do. The third inkjet head differs only in the type of micro LED to be transferred, and may be structurally the same as the first inkjet head 150 and the second inkjet head. The light emission characteristics of the third micro LED may be different from the light emission characteristics of the first micro LED 1120 and the second micro LED. For example, the third micro LED may be a micro LED that emits blue light (B).

In the process of transferring the first micro LED 1120 and the second and third micro LEDs, the first inkjet head 150 and the second and third inkjet heads may be moved sequentially or simultaneously. . For example, the first micro LED 1120 is transferred onto the wiring layers RL1, RL2, RL3, ??RLn of the first subpixel regions of the first to nth pixels using the first inkjet head 150 Then, the second micro LED is transferred onto the wiring layers of the second subpixel regions of the first to nth pixels using the second inkjet head, and the first to the third inkjet heads The third micro LED may be transferred onto the wiring layers of the third subpixel regions of the n-th pixel. Alternatively, wiring layers RL1, RL2, RL3, ??RLn of the first subpixel regions of the first to nth pixels by using the first inkjet head 150 and the second and third inkjet heads together, Subpixel regions of each pixel by simultaneously spraying the first micro LED 1120, the second micro LED, and the third micro LED on the wiring layers of the second sub-pixel regions and the wiring layers of the third sub-pixel regions, respectively. The micro LED emitting red light, the micro LED emitting green light, and the micro LED emitting blue light may be transferred to each other at the same time. The first inkjet head 150 may be moved from left to right of the pixel array panel 100 of FIG. 1, immediately in the X-axis direction. This movement can also be applied to the second and third inkjet heads.

14 and 15 show a process of transferring a micro LED to a pixel area defined by the bank 520 described in FIGS. 2, 5 and 6 using an inkjet head.

The micro LED transfer method shown in FIGS. 14 and 15 may be performed in the same manner as the micro LED transfer method described in FIGS. 11 to 13. 14 and 15, the inkjet head 150 is an inkjet head for transferring micro LEDs emitting red light, an inkjet head for transferring micro LEDs emitting green light, or an inkjet head for transferring micro LEDs emitting blue light Can be Accordingly, the micro LED 1120 ejected from the ink jet head 150 may be a micro LED that emits red light, a micro LED that emits green light, or a micro LED that emits blue light according to the use of the ink jet head 150.

16 shows micro LED transfer results according to the micro LED transfer method described in FIGS. 11 to 15.

Referring to FIG. 16, a plurality of micro LEDs 16RL, 16RD, 16GL, 16GD, 16BL, and 16BD exist in each of the first to third subpixels 16R, 16G, and 16B of the pixel 1600. The number of micro LEDs in each subpixel 16R, 16G, and 16B of each pixel 1600 may be the same or different. For example, there may be four micro LEDs 16RL and 16RD in the first sub-pixel 16R of the pixel 1600, and five micro LEDs 16RL and 16 R in the first sub-pixel 16R of the other pixel 1600n. 16RD) may exist. As such, the number of micro LEDs mounted on the corresponding subpixels between pixels may be the same or different. Even in the same pixel 1600, the total number of micro LEDs mounted on each of the sub-pixels 16R, 16G, and 16B may be the same or different. For example, as shown in FIG. 16, 5 micro LEDs may be mounted on the first subpixel 16R of the pixel 1600, and 4 micro LEDs may be mounted on the second and third subpixels 16G and 16B, respectively. LEDs can be mounted. In addition, even if the same number of micro LEDs are installed in each sub-pixel 16R, 16G, 16B of the same pixel 1600, the number of micro LEDs normally installed is the same for each sub-pixel 16R, 16G, 16B. Or it can be different. For example, among the micro LEDs 16RL and 16RD mounted on the first sub-pixel 16R, the number of normally mounted micro LEDs 16RL is two, and the micro LEDs 16GL and 16GD mounted on the second sub-pixel 16G. ), there are 3 micro LEDs (16GL) normally installed.

In each of the pixels 1600 and 1600n, the micro LEDs 16RL and 16RD disposed in the first subpixel 16R may be micro LEDs that emit red light. Accordingly, the first subpixel 16R becomes a subpixel that emits red light.

The spacing between the micro LEDs 16RL and 16RD existing in the first subpixel 16R of the pixel 1600 may be the same or different. In addition, the micro LEDs 16RL and 16RD in each of the subpixels 16R, 16G, and 16B may or may not be aligned in a line. Some (16RL, 16GL, 16BL) of the micro LEDs (16RL, 16RD, 16GL, 16GD, 16BL, 16BD) mounted on each sub-pixel (16R, 16G, 16B) are installed correctly, and the rest (16RD, 16GD, 16BD) was incorrectly mounted upside down. Herein, "correctly mounted" refers to micro LEDs (16RL, 16GL, 16BL) that normally emit light when a voltage for the operation of the micro LED is applied. In the case of the upside-mounted micro LEDs (16RD, 16GD, 16BD), light is not emitted even when the operating voltage is applied. Therefore, the micro LEDs (16RD, 16GD, 16BD) mounted upside down can be referred to as a dummy micro LED or a dummy pattern. These contents of the micro LEDs 16RL, 16RD, 16GL, 16GD, 16BL, and 16BD mounted on each subpixel 16R, 16G, 16B of the pixel 1600 may be applied to the code elements of other pixels.

As shown in FIG. 16, after micro LEDs 16RL, 16RD, 16GL, 16GD, 16BL, and 16BD are mounted on the pixels 1600 and 1600n, each subpixel 16R is applied through a pre-bonding process. , 16G, 16B) can selectively remove certain micro LEDs. For example, a pre-bonding process is performed in a direction that increases the adhesion of the micro LEDs (16RL, 16GL, 16BL) correctly mounted in each sub-pixel (16R, 16G, 16B) than the adhesion of the micro LEDs (16RD, 16GD, 16BD) mounted upside down. If implemented, only the micro LEDs (16RD, 16GD, 16BD) mounted upside down in each sub-pixel (16R, 16G, 16B) can be selectively removed. 17 shows these results.

Conversely, if you want to remove the micro LEDs (16RL, 16GL, 16BL) correctly mounted from each sub-pixel (16R, 16G, 16B) and use only the micro LEDs (16RD, 16GD, 16BD) mounted upside down, the pre-bonding The process can be carried out in a direction to relatively increase the adhesion of the micro LEDs (16RD, 16GD, 16BD) mounted upside down. As a result, as shown in Fig. 18, only the micro LEDs (16RL, 16GL, 16BL) properly mounted in each subpixel (16R, 16G, 16B) are selectively removed, and each subpixel (16R, 16G, 16B) Only micro LEDs (16RD, 16GD, 16BD) mounted upside down will remain. Through this pre-bonding, the direction of the transferred micro LED can be selected.

19 shows an example of a micro LED 1120 transferred by the micro LED transfer method of FIGS. 11 to 15.

Referring to FIG. 19, the micro LED 1120 may include a first semiconductor layer 1910, an active layer 1920, and a second semiconductor layer 1930. The first and second semiconductor layers 1910 and 1930 may be semiconductor layers of opposite types to each other. That is, one of the first and second semiconductor layers 1910 and 1930 may be a P-type semiconductor layer and the other may be an N-type semiconductor layer. For example, the first semiconductor layer 1910 may be a compound semiconductor layer doped with an N-type impurity, and the second semiconductor layer 1930 may be a compound semiconductor layer doped with a P-type impurity. The first and second semiconductor layers 1910 and 1930 may be a compound semiconductor layer or may include a compound semiconductor layer. For example, the compound semiconductor layer may be a GaN layer, and may include a group III-V compound semiconductor layer in addition to it. The active layer 1920 may be a light emitting layer or may include a light emitting layer. For example, the active layer 1920 may include a light emitting layer that emits red light, green light, or blue light. In one example, the active layer 1920 may be a material layer having a multiple quantum well (MQW). The first semiconductor layer 1910 may have a rhombic cross section. The active layer 1920 is formed on the upper surface 19T and both side surfaces 19S1 and 19S2 of the rhombic first semiconductor layer 1910. The active layer 1920 includes a first portion 19P1 covering the upper surface 19T of the first semiconductor layer 1910 and a second portion 19P2 covering both side surfaces 19S1 and 19S2 of the first semiconductor layer 1910. It may include. The first portion 19P1 may cover the entire upper surface 19T of the first semiconductor layer 1910. Light may be emitted from the first portion 19P1 in a first direction. The first direction may be a direction perpendicular to the length direction of the first portion 19P1. Here, the "vertical direction" may include not only a direction perpendicular to the length direction of the first portion 19P1, but also a direction inclined at an angle smaller than 45° to the left and right from the perpendicular direction. The second portion 19P2 may cover the entire side surfaces of the first semiconductor layer 1910. The second portion 19P2 may extend from both ends of the first portion 19P1 onto both side surfaces 19S1 and 19S2 of the first semiconductor layer 1910. The light may be emitted from the second portion 19P2 in a second direction. The second direction may be a different direction from the first direction. The thickness of the active layer 1920 may be uniform throughout. The first portion 19P1 of the active layer 1920 may be parallel to the upper surface 19T of the first semiconductor layer 1910. The second portion 19P2 of the active layer 1920 may be parallel to both side surfaces 19S1 and 19S2 of the first semiconductor layer 1910. The second semiconductor layer 1930 is formed on the top and side surfaces of the active layer 1920. The second semiconductor layer 1930 may cover the entire active layer 1920. A corner portion where the first portion 19P1 and the second portion 19P2 of the active layer 1920 meet is also covered with the second semiconductor layer 1930 to be protected. The upper surface of the second semiconductor layer 1930 may be parallel to the upper surface of the first portion 19P1 of the active layer 1920. Both side surfaces of the second semiconductor layer 1930 may be parallel to both side surfaces of the active layer 1920, that is, the second portion 19P2.

As a result, the entire first semiconductor layer 1910 is covered with the active layer 1920 except for the bottom surface, and most of the surface of the active layer 1920 is covered with the second semiconductor layer 1930. That is, the first semiconductor layer 1910, the active layer 1920, and the second semiconductor layer 1930 sequentially stacked have an upper layer surrounding the lower layer. This layered structure is referred to as a core-shell structure for convenience. In this core-shell structure, as described above, side surfaces and corner portions of the active layer 1920 are protected by the second semiconductor layer 1930. The micro LED having the above-described core-shell structure can be formed by growing on a _{crystallized membrane (eg, Al 2} O _{3 film).}

In order to mount a plurality of micro LEDs in a unit pixel, the size of the LED must be reduced. As the size of the LED is reduced to that of a micro LED, the light emission efficiency also decreases. However, by forming the micro LED to have a core-shell structure as shown in FIG. 19, the side and corner portions of the active layer 1920 are naturally protected by the second semiconductor layer 1930 and are not exposed. Accordingly, even if the size of the LED is reduced to a micro size, the decrease in light emission efficiency can be alleviated. Soon, since the micro LED 1120 has the core-shell structure, a rapid decrease in light emission efficiency due to the size reduction of the LED can be prevented. The size of the micro LED 1120 shown in FIG. 19 may be about 50 μm×50 μm, but is not limited to this value.

Subsequently, a stack consisting of the first semiconductor layer 1910, the active layer 1920, and the second semiconductor layer 1930 constituting a core-shell structure is surrounded by an insulating layer 1940. That is, the insulating layer 1940 is formed on the top and side surfaces of the second semiconductor layer 1930. The insulating layer 1940 extends over the bottom of the second semiconductor layer 1930, the bottom of the active layer 1920, and the bottom of the first semiconductor layer 1910. Except for a portion of the bottom surface of the first semiconductor layer 1910 and a portion of the top surface of the second semiconductor layer 1930, the entire surface of the stack is covered with an insulating layer 1940. The insulating layer 1940 may directly contact the corresponding surface of the material layer it covers. In other words, the insulating layer 1940 is in direct contact with the top, side and bottom surfaces of the second semiconductor layer 1930, and also directly contacts the bottom surface of the active layer 1920 and the bottom surface of the first semiconductor layer 1910. .

The insulating layer 1940 may be an oxide layer or a nitride layer, for example, a silicon oxide layer or a silicon nitride layer. The insulating layer 1940 may be used as a protective layer protecting the micro LED. The insulating layer 1940 includes a first contact hole 19h1 through which a portion of the bottom surface of the first semiconductor layer 1910 is exposed and a second contact hole 19h2 through which a portion of the upper surface of the second semiconductor layer 1930 is exposed. Includes. A first electrode layer 1960 filling the first contact hole 19h1 is provided on the bottom surface of the insulating layer 1940. A second electrode layer 1970 filling the second contact hole 19h2 is present on the upper surface of the insulating layer 1940. One of the first electrode layer 1960 and the second electrode layer 1970 may be a P-type electrode layer in contact with the P-type semiconductor layer, and the other may be an N-type electrode layer in direct contact with the N-type semiconductor layer. For example, the first electrode layer 1960 may be an N-type electrode layer, and the second electrode layer 1970 may be a P-type electrode layer. At least one of the first and second electrode layers 1960 and 1970 may be a material layer that is transparent to light and has conductivity. For example, an electrode layer formed in a direction in which light is emitted from the micro LEDs 16GL and 16GD may be a transparent material layer. For example, the first and second electrode layers 1960 and 1970 may be indium tin oxide (ITO) layers.

The micro LED 1120 of FIG. 19 has a structure in which first and second electrode layers 1960 and 1970 are vertically stacked or vertically distributed. In other words, the first and second electrode layers 1960 and 1970 face up and down with the active layer 1920 as the center. The first electrode layer 1960 is provided under the active layer 1920 and the second electrode layer 1970 is provided on the active layer 1920, respectively. Accordingly, the micro LED 1120 of FIG. 19 is referred to as a vertical electrode micro LED.

On the other hand, for convenience of illustration, the micro LED 1120 shown in FIG. 19 hereinafter is replaced by an equivalent (=) diagram at the bottom of FIG. 19.

FIG. 20 is a cross-sectional view of FIG. 16 taken in a direction 20-20' when there are no banks around subpixels on the substrate.

Referring to FIG. 20, a second wiring layer GL is provided on a substrate 110, and four micro LEDs 16GL and 16GD are disposed on the second wiring layer GL. The spacing between the four micro LEDs (16GL, 16GD) may or may not be constant. Of the four micro LEDs (16GL, 16GD), two (16GL) are correctly arranged, and the other two (16GD) are arranged upside down. In the case of the normally arranged micro LED 16GL, the second electrode layer (1970 in FIG. 19) is located below and the first electrode layer (1960 in FIG. 19) is located above, so that the second electrode layer 1970 is on the second wiring layer GL. Is in direct contact. When the operating voltage is applied to the normally mounted micro LED 16GL, normal light, that is, green light 20G, is emitted from the micro LED 16GL. However, in the case of the abnormally mounted micro LED (16GD), the first electrode layer 1960 is in contact with the second wiring layer GL, contrary to that of the normally mounted micro LED (16GL). ), even if the operating voltage is applied to the abnormally mounted micro LED (16GD) does not operate. Therefore, the light is not emitted from the abnormally mounted micro LED 16GD.

After the micro LEDs 16GL and 16GD are mounted on the second wiring layer GL, a passivation surrounding the micro LEDs 16GL and 16GD on the second wiring layer GL as shown in FIG. 21 A layer 2110 may be formed. The passivation layer 2110 may be an insulating material layer transparent to light. For example, the passivation layer 2110 may be a silicon oxide layer. The passivation layer 2110 may cover the entire second wiring layer GL around the micro LEDs 16GL and 16GD. The passivation layer 2110 may fill between the micro LEDs 16GL and 16GD. Accordingly, the micro LEDs 16GD and 16GL transferred onto the second wiring layer GL may be buried in the passivation layer 2110 except for the exposed upper surface. The height of the upper surface 21S1 of the passivation layer 2110 may be the same as the height of the upper surface of the micro LEDs 16GD and 16GL. In another example, the height of the upper surface 21S1 of the passivation layer 2110 may be lower than the height of the upper surface of the micro LEDs 16GD and 16GL. Accordingly, after the passivation layer 2110 is formed, the upper surfaces of all the transferred micro LEDs 16GD and 16GL are exposed. An electrode wiring 2130 is provided on the passivation layer 2110 and the micro LEDs 16GD and 16GL. The electrode wiring 2130 covers the entire upper surface of the micro LEDs 16GD and 16GL. The electrode wiring 2130 may cover the entire upper surface 21S1 of the passivation layer 2110 around the upper surface of the micro LEDs 16GD and 16GL. The electrode wiring 2130 may contact all of the micro LEDs 16GD and 16GL transferred onto the second wiring GL. The electrode wiring 2130 may contact the upper surfaces of all the transferred micro LEDs 16GD and 16GL. The electrode wiring 2130 is provided to come into contact with the upper surfaces of all micro LEDs 16GD and 16GL, but the upper surface of the micro LED 16GL transferred normally and the upper surface of the micro LED 16GD abnormally transferred are different from each other. . In other words, the polarities of the two upper surfaces are different. Therefore, even if the operating voltage is applied to the micro LEDs (16GD, 16GL) through the electrode wiring 2130, light (e.g., green light) is emitted only from the correctly transferred micro LEDs (16GL), and the micro LEDs (16GD) transferred in an inverted form. ), the light is not emitted.

As a result, desired light may be emitted only from the micro LEDs 16GL that are correctly transferred among the micro LEDs 16GD and 16GL transferred onto the second wiring GL.

The electrode wiring 2130 may be a material layer that is transparent to light and has conductivity. For example, the electrode wiring 2130 may be an ITO wiring.

Meanwhile, the properly mounted micro LED 16GL may not have the first electrode layer 1960 in the light emission direction. In this case, the first semiconductor layer (1910 of FIG. 19) of the micro LED 16GL may be the top surface. Accordingly, the electrode wiring 2130 may be directly connected to the first semiconductor layer 1910 of the micro LED 16GL.

FIG. 22 shows a case in which the bank 520 is provided together with the second wiring layer GL on the substrate 110 in the case of FIG. 20.

Referring to FIG. 22, banks 520 spaced apart from each other exist on a substrate 110. The bank 520 defines a region in which the second wiring layer GL is formed. In other words, the bank 520 serves to limit the subpixel area. Since the pixel includes R, G, and B subpixels, it can be seen that the bank 520 plays a role of limiting the pixel area. The second wiring layer GL is formed on the upper surface of the substrate 110 between the banks 520 and the micro LEDs 16GL and 16GD are provided on the second wiring layer GL are the same as in FIG. 20. The micro LEDs 16GL and 16GD are surrounded by a passivation layer 2110 as shown in FIG. 23. The passivation layer 2110 may cover the entire second wiring layer GL around the micro LEDs 16GL and 16GD between the banks 520. The passivation layer 2110 may fill between the micro LEDs 16GL and 16GD. The passivation layer 2110 may fill between the bank 520 and the micro LED 16GD. The configuration of FIG. 23 may be the same as the configuration described in FIG. 21 except that the bank 520 is provided. Accordingly, the arrangement and contact relationship between the passivation layer 2110, the micro LEDs 16GD and 16GL, and the electrode wiring 2130 between the banks 520 may be the same as described in FIG. 21.

Meanwhile, as described with reference to FIGS. 7 through 9, first and second wiring layers 720 and 730 are formed on the bottom of the first to third subpixel regions SP1 ′, SP2 ′, and SP3 ′ of the pixel region 120. When this is formed, at least the electrode arrangement of the micro LED having a core-shell structure that is transferred to the first to third sub-pixel regions SP1 ′, SP2 ′ and SP3 ′ of the pixel region 120 by the ink jet spraying method is shown. It may be different from the first and second electrode layers 1960 and 1970 of 19.

24 shows an example of the micro LED 2410 transferred to the first to third subpixel areas SP1 ′, SP2 ′, and SP3 ′ of the pixel region 120 illustrated in FIGS. 7 to 9.

Referring to FIG. 24, the micro LED 2410 includes first to third electrodes 24E1, 24E2, and 24E3. The stacked structure of the first semiconductor layer 1910, the second semiconductor layer 1930, and the active layer 1920 forming a core-shell structure in the micro LED 2410 may be the same as that of FIG. 19. All of the first to third electrodes 24E1, 24E2 and 24E3 may be disposed on one side of the micro LED 2410. For example, the first to third electrodes 24E1, 24E2, and 24E3 may be provided on opposite sides of the first semiconductor layer 1910 with the active layer 1920 as the center. That is, the first to third electrodes 24E1, 24E2, and 24E3 may be positioned on the upper surface of the second semiconductor layer 1930. The first and second electrodes 24E1 and 24E2 may be an N-type electrode layer in contact with the first semiconductor layer 1910. The third electrode 24E3 may be a P-type electrode layer in contact with the second semiconductor layer 1930.

First and second trenches 24h1 and 24h2 are formed in a stack of the first semiconductor layer 1910, the active layer 1920, and the second semiconductor layer 1930. The first trench 24h1 and the second trench 24h2 are spaced apart from each other. The bottoms of the first and second trenches 24h1 and 24h2 are positioned between both side surfaces 24S1 and 24S2 of the first semiconductor layer 1910. The first and second trenches 24h1 and 24h2 are formed from an upper surface of the second semiconductor layer 1930 toward the first semiconductor layer 1910. That is, the first and second trenches 24h1 and 24h2 sequentially pass through the second semiconductor layer 1930 and the active layer 1920. The first and second trenches 24h1 and 24h2 extend to the first semiconductor layer 1910 by a predetermined thickness. Accordingly, in portions of the first semiconductor layer 1910 corresponding to the first and second trenches 24h1 and 24h2, there are concave portions that become part of the first and second trenches 24h1 and 24h2. The concave portion becomes the lower end including the bottom of the first and second trenches 24h1 and 24h2. An insulating layer 1940 is formed on the top and side surfaces of the second semiconductor layer 1930. The insulating layer 1940 covers the entire upper surface of the second semiconductor layer 1930 around the first and second trenches 24h1 and 24h2. The insulating layer 1940 may also cover all sides of the second semiconductor layer 1930. The insulating layer 1940 fills a portion of the first and second trenches 24h1 and 24h2. In other words, the insulating layer 1940 covers inner side surfaces of the first and second trenches 24h1 and 24h2, and covers a part of the bottom. The insulating layer 1940 covers only a part of the bottom of each of the first and second trenches 24h1 and 24h2, and the bottom of the first and second trenches 24h1 and 24h2 through the first and second trenches 24h1 and 24h2. The rest of the, that is, a part of the first semiconductor layer 1910 is exposed. The rest of the first trench 24h1 is filled with the first electrode 24E1. That is, the first electrode 24E1 fills the rest of the first trench 24h1 and is formed on a part of the insulating layer 1940 around the first trench 24h1. The rest of the second trench 24h2 is filled with the second electrode 24E2. That is, the second electrode 24E2 fills the second trench 24h2 and is formed on a part of the insulating layer 1940 around the second trench 24h2. The first and second electrodes 24E1 and 24E2 are spaced apart from each other.

The insulating layer 1940 includes a via hole 24h3. The via hole 24h3 may be located between the first and second trenches 24h1 and 24h2. A part of the second semiconductor layer 1930 is exposed through the via hole 24h3. The via hole 24h3 is filled with the third electrode 24E3. The third electrode 24E3 is in contact with the exposed portion of the second semiconductor layer 1930 through the via hole 24h3. The third electrode 24E3 fills the via hole 24h3 and is formed on the insulating layer 1940 around the via hole 24h3. The third electrode 24E3 is disposed between the first and second electrodes 24E1 and 24E2. The third electrode 24E3 is spaced apart from the first and second electrodes 24E1 and 24E2. The heights of the top surfaces of the first to third electrodes 24E1, 24E2, and 24E3 may be the same. The first to third electrodes 24E1, 24E2, and 24E3 are all formed on the same side of the micro LED 2410, and the micro LED 2410 having such an electrode arrangement structure is referred to as a horizontal electrode micro LED.

Meanwhile, in the following description, the micro LED 2410 shown in FIG. 24 is replaced with a simple diagram indicated by an equivalent (=) at the bottom of FIG. 24 for convenience of illustration.

Next, a process of transferring the micro LED 2410 shown in FIG. 24 to each pixel area 120 of the pixel array panel 100 by the inkjet jetting method will be described with reference to FIGS. 25 to 27. In this case, the sub-pixel regions of each pixel region 120 are as described with reference to FIGS. 7 to 9.

25 to 27 show the inkjet head 150 in a direction parallel to the direction (Y-axis direction) of the inkjet head 150 with respect to the pixel array panel 100 of FIG. 1, that is, the direction 8-8' of FIG. 7. It shows step by step the process of transferring the micro LED 2410 to each pixel while moving.

Referring to FIG. 25, the inkjet head 150 is positioned on the second subpixel area 25G1 of the first pixel of the substrate 110. A drop of micro LED drop 1150 is sprayed from the inkjet head 150 to the second subpixel area 25G1 (dropped). The micro LED droplet 1150 may include a plurality of micro LEDs 2410, for example, 1 to 6 micro LEDs 2410. As the micro LED droplet 1150 is sprayed onto the second subpixel region 25G1, as shown in FIG. 26, the first to fourth regions G1, G2, G3, and G4 of the second subpixel region 25G1 are Can be placed one by one. Each of the first to fourth regions G1, G2, G3, and G4 may have a size in which one micro LED 2410 can be mounted. Therefore, the two micro LEDs 2410 cannot be mounted in each of the first to fourth regions G1-G4. When the number of micro LEDs 2410 included in the micro LED drop 1150 is greater than the number of areas G1-G4 included in the second subpixel area 25G1, the first to fourth areas G1-G4 The micro LED 2410 ′ remaining after being mounted on) may not be mounted on any one of the regions G1 to G4 and may be overlaid on the frame 710 between the regions G1 to G4. As described above, the micro LED 2410 ′, which cannot be mounted on each of the regions G1 to G4, and that extends outside the regions G1 to G4, may be removed in a subsequent process. The subsequent process may be a process of removing abnormally mounted micro LEDs after micro LED transfer for a given area or section of the pixel array panel 100 is completed. The solution 1130 covering the first subpixel region 25G1 is volatilized.

After transferring the micro LED 2410 to the first to fourth regions G1-G4 of the second subpixel region 25G1 of the first pixel, as shown in FIG. 26, the inkjet head 150 is It is moved onto the second subpixel area 25G2 of the second pixel next to the first pixel. Subsequently, the inkjet head 150 is aligned at a position suitable for spraying the micro LED drop 1150 on the second subpixel area 25G2. The movement and the alignment may be made continuously, but may not be. The movement and the alignment may be performed in one operation, but may not be.

The injection of the micro LED droplets 1150 using the inkjet head 150 may be performed in a manner similar or identical to that of ejecting ink from an inkjet head of an inkjet printer.

After the inkjet head 150 is aligned on the second subpixel area 25G2 of the second pixel, the micro LED drop 1150 is dropped on the second subpixel area 25G2. As the micro LED droplets 1150 are sprayed onto the second subpixel region 25G2, one each in the first to fourth regions G1-G4 of the second subpixel region 25G2 as shown in FIG. 27 The micro LED 2410 may be transferred. This transfer process is performed up to the second subpixel region 25Gn of the n (n=1, 2, 3, ??)-th pixel.

After the micro LED transfer process for the second subpixel areas 25G1-25Gn of each pixel is completed, the micro LED electronic process for the first subpixel area or the third subpixel area of each pixel may be performed. The first subpixel area may be a subpixel area emitting red light. The second subpixel regions 25G1-25Gn may be subpixel regions that emit green light. The third subpixel area may be a subpixel area emitting blue light.

In another example, the method of transferring the micro LED 2410 to each pixel may be performed by using a plurality of inkjet heads together. In this case, the micro LED transfer to the first to third subpixel regions of each pixel may be performed simultaneously or may be performed sequentially. For example, three inkjet heads may be used together to transfer micro LEDs, and in this case, the types of micro LEDs ejected from each inkjet head may be different. The micro LED ejected from the first inkjet head may be a micro LED emitting red light, the micro LED ejected from the second inkjet head may be a micro LED emitting green light, and the micro LED ejected from the third inkjet head It may be a micro LED that emits blue light.

Micro LED transfer using an inkjet head enables accurate transfer for each pixel and can be transferred quickly, thereby increasing the micro LED transfer efficiency for a pixel array panel having a relatively large area.

FIG. 28 is an enlarged view of the second subpixel area 25G1 of the first pixel of FIG. 27.

Referring to FIG. 28, the micro LED 2410B transferred to the first and fourth regions G1 and G4 is mounted such that an electrode is positioned on the top. Accordingly, the electrode of the micro LED 2410B does not contact the first and second wiring layers 720 and 730 formed on the substrate 110 of the first region G1. As a result, the micro LED 2410B becomes an inverted (mounted) or abnormally transferred (mounted) micro LED. Soon, the micro LED 2410B may be a dummy micro LED.

Conversely, in the case of the micro LED 2410A transferred to the second and third regions G2 and G3, the electrode was transferred so that the electrode is positioned at the bottom. In other words, the micro LED 2410A has been transferred normally. Accordingly, the micro LEDs 2410A mounted in the second and third regions G2 and G3 are in contact with the first and second wiring layers 720 and 730. Therefore, when an operating voltage is applied to the micro LED 2410A, light (eg, green light) may be emitted from the micro LED 2410A.

On the other hand, the frame 710 defining the first to fourth regions G1-G4 is so that the micro LED 2410 transferred to each region G1-G4 can be properly mounted in each region G1-G4. It can have a form that induces. For example, the frame 710 may be a rhombus shape whose width becomes narrower toward the top, as shown separately at the bottom.

29 shows a case in which all the micro LEDs 2410 transferred to the first to fourth regions G1-G4 are properly mounted.

30 to 32 are cross-sectional views illustrating a step-by-step process of transferring a horizontal electrode micro LED to different subpixel areas of each pixel. For convenience of illustration, the illustration of the micro LED included in the inkjet head and the micro LED drop in each drawing is omitted.

First, as shown in FIG. 30, after aligning the first inkjet head HD1 on the second area R2 of the first subpixel area of the selected pixel, the first micro LED drop is placed in the second area R2. Spray (3050). The first micro LED drop 3050 may be a solution containing the first micro LED. The first micro LED may be a micro LED emitting red light. Thereafter, the first inkjet head HD1 may be moved onto the second area of the first subpixel area of another selected pixel, and the micro LED may be transferred to the corresponding second area. This transfer process may be performed for the second area of the first sub-pixel area of other pixels.

Next, as shown in FIG. 31, after aligning the second inkjet head HD2 on the second area G2 of the second sub-pixel area of the selected pixel, a second micro LED drop is formed in the second area G2. Spray (3150). The second micro LED drop 3150 may include a second micro LED of a different type from the first micro LED. The second micro LED may be a micro LED emitting green light. The micro LED 3100 transferred to the second area R2 of the first subpixel area represents a micro LED transferred using the first inkjet head HD1 of FIG. 30.

The second inkjet head HD2 may be structurally the same as the first inkjet head HD1. The difference between the first inkjet head HD1 and the second inkjet head H2 is only the type of micro LED to be ejected. After the micro LED transfer to the second region G2 of the second subpixel region of the selected pixel is completed, the second inkjet head HD2 is moved over the second region of the second subpixel region of another pixel, The micro LED drop 3150 may be dropped on the second area below to transfer the micro LED to the second area. Subsequently, the second micro LED may be transferred to the second area of the second sub-pixel area of other pixels by the same transfer method.

Next, as shown in FIG. 32, after aligning the third inkjet head HD3 on the second area B2 of the third subpixel area of the selected pixel, a third micro LED drop is formed in the second area B2. Drop (3250). The third inkjet head HD3 may be structurally the same as the first and second inkjet heads HD1 and HD2. The difference between the third inkjet head HD3 and the first and second inkjet heads HD1 and HD2 is only the type of micro LEDs to be ejected. However, if there is no significant difference between the micro LED transfer process and the transfer efficiency, the structures of the first to third inkjet heads HD1-HD3 may be different from each other. The third micro LED drop 3250 may include a third micro LED of a different type from the first and second micro LEDs. The third micro LED may be a micro LED that emits blue light. After completing the micro LED transfer to the second area B2 of the third sub-pixel area of the selected pixel, the third inkjet head HD3 is moved to the second area of the third sub-pixel area of the other pixels to obtain a micro LED. You can perform transcription. In the same way, micro LED transfer may be performed on the second area of the third sub-pixel area of the remaining pixels. The micro LED 3200 mounted on the second area G2 of the second subpixel area represents the micro LED transferred by the transfer method using the second inkjet head HD2 of FIG. 31.

33 shows a micro LED transfer method using ink jet injection according to another embodiment.

Referring to FIG. 33, a first micro LED 3300 is transferred to all sub-pixel areas SP1 ′, SP2 ′, and SP3 ′ of the pixel 3000. Soon, the same micro LED is transferred to all sub-pixels SP1', SP2', and SP3' included in the pixel 3000. The first to third subpixel regions SP1 ′, SP2 ′, and SP3 ′ may be subpixel regions for horizontal electrode micro LED transfer. The first micro LED 3300 may be, for example, a horizontal electrode micro LED that emits blue light (B).

In another embodiment, the first to third subpixel regions SP1 ′, SP2 ′, and SP3 ′ may be replaced with subpixel regions for vertical electrode micro LED transfer. In addition, the first micro LED 3300 may be replaced with a vertical electrode micro LED.

The first micro LED 3300 may be transferred by the transfer method using the inkjet head described above. The first subpixel area SP1' is an area that emits red light R. The second subpixel area SP2' is an area that emits green light G. Accordingly, after the first micro LED 3300 is transferred, a subsequent process for emitting red light and green light from the first and second subpixel regions SP1 ′ and SP2 ′, respectively, may be performed. For example, the first micro LED 3300 mounted in the first subpixel area SP1' and the first micro LED 3300 mounted in the second subpixel area SP2' are transparent and insulating passivation layers Cover with (3340). The passivation layer 3340 may be formed to fill the first and second subpixel regions SP1 ′ and SP2 ′ between the first frame 3350, and at least the first and second wiring layers 720 and 730 The first micro LED 3300 may be formed to completely cover. The structure and material of the first frame 3350 may be the same as the frame 710 described above. The upper surface of the passivation layer 3340 may be flat. The height of the upper surface of the passivation layer 3340 may be the same as or different from the height of the upper surface of the first frame 3350, but may be lower, for example. As described above, the passivation layer 3340 is formed only in the first and second subpixel regions SP1 ′ and SP2 ′, and then the first light is formed on the passivation layer 3340 of the first subpixel region SP1 ′. A conversion material layer CT1 is formed, and a second light conversion material layer CT2 is formed on the passivation layer 3340 of the second subpixel area SP2'. The light conversion characteristics of the first and second light conversion material layers CT1 and CT2 are different from each other. The first and second light conversion material layers CT1 and CT2 are formed between the second mold 3360. In other words, the regions in which the first and second light conversion material layers CT1 and CT2 are formed may be defined (determined) by the second frame 3360. The second frame 3360 may be regarded as a partition wall that prevents optical interference between subpixel regions. The second frame 3360 may be positioned on the first frame 3350. Blue light emitted from the first micro LED 3300 mounted in the first subpixel area SP1' passes through the first light conversion material layer CT1 and is emitted. The blue light is converted into red light while passing through the first light conversion material layer CT1. To this end, the first light conversion material layer CT1 may include a member or material (eg, particles, quantum dots) that converts blue light into red light. The blue light emitted from the first micro LED 3300 transferred to the second subpixel area SP2' passes through the second light conversion material layer CT2 and is emitted. In this process, the blue light is converted into green light while passing through the second light conversion material layer CT2. To this end, the second light conversion material layer CT2 may include a member or material (eg, particles, quantum dots) that converts blue light into green light. Light traveling in the lateral direction during this light conversion process may be blocked by the second frame 3360. Accordingly, interference between light emitted from each of the sub-pixel regions SP1 ′, SP2 ′, and SP3 ′ can be prevented. In order to prevent such optical interference, a light absorbing layer 3370 may be provided between the second frame 3360 and the first and second light conversion material layers CT1 and CT2 as indicated by a dotted line.

Although many items are specifically described in the above description, they should be construed as examples of preferred embodiments rather than limiting the scope of the invention. Therefore, the scope of the present invention should not be determined by the described embodiments, but should be determined by the technical idea described in the claims.

5H: bank height 7S1, 7S2: both sides of the frame
16R, 16G, 16B: first to third subpixels
16RL, 16RD, 16GL, 16GD, 16BL, 16BD: Micro LED
19h1, 19h2: first and second contact holes 19S1, 19S2: both sides
19T: upper side 19P1: first part
19P2: Part 2 20G: Green light
24h3::Beer hole 24h1, 24h2: 1st and 2nd trench
24E1-24E3: first to third electrodes 25G1: second subpixel area
100: pixel array panel 110: substrate
150: inkjet head 154: injection port
520: bank 710: frame
720, 730: first and second wiring layers 1120: a plurality of micro LEDs
1130: Volatile solution 1150: Micro LED drop
1600: pixel 1910: first semiconductor layer
1920: active layer 1930: second semiconductor layer
1940: insulating layer 1960: first electrode layer
1970: second electrode layer 2110: passivation layer
2130: electrode wiring 21S1: upper surface of the passivation layer
2410: micro LED 2410': remaining micro LED
2410A: transferred micro LED 3000: pixels
3050: first micro LED drop 3100: transferred micro LED
3150: second micro LED bell 3200: mounted micro LED
3300: first micro LED 3340: passivation layer
3350: mold 3360: second frame
3370: light absorbing layer A1: selected area
BL: third wiring layer CT1, CT2: first and second light conversion material layers
G1-G4: first to fourth regions GL: second wiring layer
HD1-HD3: first to third inkjet heads
RL, RL1, RL2, RL3, RLn: first wiring layer SP1-SP3: first to third subpixel regions
B1-B4: first to fourth regions SP1'-SP3': first to third subpixel regions

Claims (34)

In the method of transferring a micro LED to a pixel array panel including a plurality of sub-pixel regions on which the micro LED is to be mounted,
The micro LED is transferred by spraying in an inkjet method,
The micro LED transfer method comprising an active layer comprising a first portion emitting light in a first direction and a second portion emitting light in a second direction different from the first direction. The method of claim 1,
The step of transferring the micro LED,
Dividing the plurality of subpixel areas into a plurality of groups; And
Transferring a plurality of micro LEDs to the plurality of groups; Micro LED transfer method comprising a. The method of claim 2,
The step of transferring the plurality of micro LEDs,
Including the step of sequentially transferring a plurality of micro LEDs sequentially with respect to the plurality of groups,
In the step of sequentially transferring, a micro LED transfer method of simultaneously transferring a micro LED to subpixel regions of a selected group among the plurality of groups. The method of claim 3,
The subpixel regions of the selected group include subpixel regions to which the micro LED emitting red light, green light, or blue light is to be transferred. The method of claim 1,
The pixel array panel is a micro LED transfer method provided on a backplate of an LED display. The method of claim 3,
The subpixel regions of the selected group include a plurality of R subpixel regions, a plurality of G subpixel regions, and a plurality of B subpixel regions to form a plurality of pixels. The method of claim 6,
The step of simultaneously transferring the micro LEDs to the subpixel regions of the selected group,
Transferring a first micro LED to the plurality of R subpixel areas using a first inkjet head;
Transferring a second micro LED to the plurality of G subpixel areas using a second inkjet head; And
Transferring a third micro LED to the plurality of B subpixel areas using a third inkjet head. The method of claim 2,
Micro LED transfer method for transferring the plurality of micro LEDs to each of the plurality of sub-pixel areas. The method of claim 8,
Removing the rest of the plurality of micro LEDs transferred to each of the sub-pixel areas except for the correctly transferred micro LEDs; And
Micro LED transfer method comprising; transferring the same micro LED as the correctly transferred micro LED to the place where the micro LED has been removed. The method of claim 8,
Micro LED transfer method in which a bank is provided between each of the sub-pixel areas. The method of claim 8,
Each of the sub-pixel areas is divided into a plurality of areas, and a micro LED transfer method for transferring one micro LED to the plurality of areas. The method of claim 11,
Each of the plurality of regions is a micro LED transfer method defined by a mold guiding the transferred micro LED. The method of claim 1,
The micro LED includes a first semiconductor layer, the active layer, and a second semiconductor layer sequentially stacked to form a core-shell structure,
The micro LED is a vertical electrode micro LED or a horizontal electrode micro LED micro LED transfer method. The method of claim 2,
A micro LED transfer method for transferring a micro LED emitting the same light to all of the plurality of sub-pixel areas. The method of claim 14,
The micro LED that emits the same light is a micro LED that emits blue light. The method of claim 14,
The micro LED transfer method further comprising forming first and second light conversion material layers on the micro LEDs transferred to the R sub-pixel region and the G sub-pixel region of the plurality of sub-pixel regions, respectively. In the method of transferring a micro LED to a pixel array panel including a plurality of pixel regions,
Transferring a micro LED to a first pixel area among the plurality of pixel areas; And
Transferring the micro LED to a second pixel region among the plurality of pixel regions; Including,
In the two steps, the micro LED is transferred by spraying in an inkjet method,
The micro LED transfer method comprising an active layer comprising a first portion emitting light in a first direction and a second portion emitting light in a second direction different from the first direction. The method of claim 17,
The first and second pixel regions are adjacent to or separated from each other, and the two steps are performed simultaneously. The method of claim 17,
The first and second pixel regions are adjacent to or separated from each other, and the two steps are sequentially performed. The method of claim 17,
Micro LED transfer method for transferring the same or different micro LEDs from each other in the two steps. The method of claim 17,
Micro LED transfer method of transferring the micro LED to the remaining pixel areas of the plurality of pixel areas by the inkjet method. The method of claim 17,
Among the layers constituting the micro LED, the first semiconductor layer, the active layer, and the second semiconductor layer sequentially stacked form a core-shell structure,
The micro LED is a vertical electrode micro LED or a horizontal electrode micro LED micro LED transfer method. The method of claim 17,
The step of transferring the micro LED to the first pixel region among the plurality of pixel regions,
Micro LED transfer method comprising; spraying a solution mixed with micro LEDs onto the first pixel area using a first inkjet head. The method of claim 17,
The step of transferring the micro LED to the first pixel region among the plurality of pixel regions,
Transferring a plurality of first micro LEDs to a first subpixel area of the first pixel area using a first inkjet head;
Transferring a plurality of second micro LEDs to a second subpixel area of the first pixel area using a second inkjet head; And
Transferring a plurality of third micro LEDs to a third sub-pixel area of the first pixel area by using a third inkjet head. The method of claim 24,
Transferring the plurality of first micro LEDs, transferring the plurality of second micro LEDs, and transferring the plurality of third micro LEDs are performed sequentially or simultaneously. The method of claim 25,
Transferring the plurality of first micro LEDs, transferring the plurality of second micro LEDs, and transferring the plurality of third micro LEDs are sequentially performed,
Transferring the plurality of first micro LEDs, and then removing the transferred plurality of first micro LEDs other than the correctly transferred first micro LEDs; And
Transferring the same micro LED as the first micro LED correctly transferred to the place where the first micro LED has been removed; includes,
The removing and transferring the same micro LEDs are performed even after transferring the plurality of second micro LEDs and transferring the plurality of third micro LEDs. The method of claim 24,
The first to third sub-pixel regions are enclosed in a bank. The method of claim 24,
Each of the first to third subpixel regions includes a plurality of regions,
Micro LED transfer method in which one of the first to third micro LEDs is transferred to regions belonging to different sub-pixel regions among the plurality of regions, respectively. The method of claim 28,
The micro LED transfer method in which the plurality of regions are defined by a frame guiding the micro LED to be transferred. The method of claim 17,
The step of transferring the micro LED to a second pixel region among the plurality of pixel regions,
Transferring a plurality of first micro LEDs to a first subpixel area of the second pixel area using a first inkjet head;
Transferring a plurality of second micro LEDs to a second subpixel area of the second pixel area using a second inkjet head; And
Transferring a plurality of third micro LEDs to a third sub-pixel area of the second pixel area by using a third inkjet head. The method of claim 30,
Transferring the plurality of first micro LEDs, transferring the plurality of second micro LEDs, and transferring the plurality of third micro LEDs are performed sequentially or simultaneously. The method of claim 31,
Transferring the plurality of first micro LEDs, transferring the plurality of second micro LEDs, and transferring the plurality of third micro LEDs are sequentially performed,
After transferring the plurality of first micro LEDs, leaving only the first micro LEDs correctly transferred among the transferred plurality of first micro LEDs, and removing the remaining first micro LEDs; Including,
The removing step is performed even after the step of transferring the plurality of second micro LEDs and the step of transferring the plurality of third micro LEDs. The method of claim 30,
Each of the first to third subpixel regions includes a plurality of regions,
Micro LED transfer method in which one of the first to third micro LEDs is transferred to regions belonging to different sub-pixel regions among the plurality of regions, respectively. The method of claim 33,
The micro LED transfer method in which the plurality of regions are defined by a frame guiding the micro LED to be transferred.

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