Full-color LED display using ultra-thin LED elements and method of manufacturing the same

Abstract

The present invention relates to a full-color LED display, and more particularly, to a full-color LED display using an ultra-thin LED element and a manufacturing method thereof.

Description

TECHNICAL FIELD

[0001] The present application relates to a full-color LED display, and more particularly, to a full-color LED display using an ultra-thin LED element and a manufacturing method thereof. BACKGROUND

[0002] Mini-LEDs and nano-LEDs can achieve excellent color and high efficiency, and are environmentally friendly materials, and thus are being used as core materials for various light sources and displays. In line with this market situation, research is recently being conducted to develop a new nano-rod LED structure or a nano-wire LED coated with a shell through a new manufacturing process. Also, research is being conducted on a protective film material in order to achieve high efficiency and high stability of the protective film covering the outer surface of the nano-rod, or research and development of a ligand material that is advantageous for subsequent processes.

[0003] In line with research in this material field, a display TV using red, green, and blue mini-LEDs has recently been commercialized. A display using mini-LEDs and various light sources have advantages of high performance characteristics, theoretically long lifespan, very long and high efficiency, but need to arrange individual mini-LEDs on a miniaturized electrode in a limited area, and thus there are limitations in process technology when considering high cost, high process failure rate, and low productivity for a display in which mini-LEDs are arranged on an electrode using a pick-and-place technology, and it is a fact that it is difficult to manufacture a truly high-resolution commercial display or a light source having various sizes, shapes, and brightness from a smart phone to a television. Also, it is a fact that it is more difficult to arrange nano-LEDs, which are smaller than mini-LEDs, on an electrode using the same pick-and-place technology as the mini-LEDs.

[0004] In order to overcome this difficulty, the inventor of the present application has disclosed a display manufactured by a method of injecting a solution of mixed nano-rod type LEDs into a sub-pixel, then forming an electric field between two arranged electrodes, magnetically arranging nano-rod type LED elements on the electrodes, and further forming a sub-pixel in Patent No. 10-1436123. However, in the disclosed display, electrodes for applying current to the p-type semiconductor layer and the n-type semiconductor layer of the nano-rod type LED element exist in a horizontal direction with intervals, and thus there is a problem that horizontal and vertical electrodes for addressing are not easily arranged when manufacturing a sub-pixel. In addition, the nano-rod type LED used in the disclosed display has a small light extraction area and poor efficiency, and thus there is a problem that a larger number of LEDs need to be mounted in order to achieve a target efficiency, and there is a problem that the nano-rod type LED itself has a high possibility of defects inevitably occurring in the manufacturing process.

[0005] Specifically, the nanorod type LED itself has an inevitable defect. The nanorod type LED element is manufactured in a hybrid nano patterning process and dry etching / wet etching in a top-down method, or a method of directly growing in a bottom-up method on a substrate. In this nanorod type LED, the long axis of the LED is aligned with the stacking direction, that is, the stacking direction of each layer in the p-GaN / InGaN multi quantum well (MQW) / n-GaN stacked structure, and thus the light emitting area is small, and thus the influence of surface defects on the light emitting efficiency is large, but the area of the side surface formed by etching is relatively large than the upper or lower surface, and thus surface defects inevitably occur to cause a large reduction in light emitting efficiency. In addition, since it is difficult to optimize the recombination rate of electrons and holes, there is a problem in that the light emitting efficiency of the nanorod type LED is greatly reduced compared to the light emitting efficiency of the original wafer.

[0006] Therefore, in the urgent situation of developing a display based on a new LED material, the electrode configuration for addressing can be more easily implemented when making a sub-pixel, and the light emitting area is large, the reduction in efficiency due to surface defects is minimized or prevented, and the recombination rate of electrons and holes is optimized. SUMMARY

[0007] (PROBLEMS TO BE SOLVED)

[0008] The present application has been made to solve the above problems, and aims to provide a full color LED display manufacturing method using an LED material suitable for ink, which can easily implement a large area display, and a full color LED display implemented thereby.

[0009] In addition, another object of the present application is to provide a full color LED display manufacturing method that minimizes or prevents a reduction in efficiency due to surface defects and improves brightness using an LED material that optimizes the recombination rate of electrons and holes, and a full color LED display implemented thereby.

[0010] Further, another object of the present application is to provide a full color LED display and a manufacturing method thereof in which an electrode arrangement for addressing can be more easily designed and implemented when implementing a sub-pixel of a display.

[0011] (MEANS FOR SOLVING PROBLEMS)

[0012] To solve the above problems, a first embodiment of the present application provides a full-color LED display, which includes: a lower electrode line including a first electrode formed with a plurality of sub-pixel sites; a plurality of ultra-thin LED elements configured to have at least two in each sub-pixel site, including a first conductive semiconductor layer, a photoactive layer, a second conductive semiconductor layer, a ratio between a thickness in a stacking direction of the layers and a length of a major axis in a cross section perpendicular to the stacking direction is 1:0.5-1.5, and the elements actually emit light of the same color, and are vertically arranged on the first electrode in the thickness direction of the layers; an upper electrode line including a second electrode arranged on the plurality of ultra-thin LED elements; and a color-changing layer patterned on the second electrode corresponding to the sub-pixel sites, so that each of the sub-pixel sites becomes a sub-pixel site showing any one of blue, green and red colors.

[0013] In addition, a second embodiment of the present application provides a full-color LED display, which includes: a lower electrode line including a first electrode formed with a plurality of sub-pixel sites; a plurality of ultra-thin LED elements independently emitting light of blue, green or red color, respectively, and including a first conductive semiconductor layer, a photoactive layer, a second conductive semiconductor layer, a ratio between a thickness in a stacking direction of the layers and a length of a major axis in a cross section perpendicular to the stacking direction is 1:0.5-1.5, at least two elements actually emitting light of the same color are arranged in each sub-pixel site, so that the plurality of sub-pixel sites independently show any one of blue, green and red colors; and an upper electrode line including a second electrode arranged in upper contact with the plurality of ultra-thin LED elements.

[0014] According to an embodiment of the first and second embodiments of the present application, a lineup inducing layer is further included on either side or both sides of the thickness direction of the ultra-thin LED element and the first electrode in the sub-pixel site, and the lineup inducing layer is used to vertically arrange the ultra-thin LED element in the thickness direction; the lineup inducing layer can be a magnetic layer, a charge layer or a bonding layer.

[0015] In addition, the maximum surface area of the ultra-thin LED element can be 2.7 μm or less, more preferably the thickness can be 2.0 μm or less, and further more preferably can be 0.2-1.0 μm.

[0016] In addition, the thickness of the ultra-thin LED element can be 2 μm or less.

[0017] Further, in the ultra-thin LED element, the first conductive semiconductor layer is an n-type group III nitride semiconductor layer, and an electron delay layer can be further included on the opposite side of the first conductive semiconductor layer adjacent to the light active layer, so that the number of electrons and holes recombined in the light active layer is balanced.

[0018] Further, the electron delay layer can include one or more selected from the group consisting of CdS, GaS, ZnS, CdSe, CaSe, ZnSe, CdTe, GaTe, SiC, ZnO, ZnMgO, SnO2, TiO2, In2O3, Ga2O3, Si, poly(para-phenylenevinylene) and derivatives thereof, polyaniline, poly(3-alkylthiophene), and poly(paraphenylene).

[0019] Further, the first conductive semiconductor layer is a doped n-type group III nitride semiconductor layer, and the electron delay layer can be a group III nitride semiconductor having a doping concentration lower than that of the first conductive semiconductor layer.

[0020] Further, the full-color LED display can further include a protective film surrounding the exposed side of the ultra-thin LED element.

[0021] Further, the first conductive semiconductor layer of the ultra-thin LED element is an n-type group III nitride semiconductor layer, and the second conductive semiconductor layer is a p-type group III nitride semiconductor layer. The ultra-thin LED element can further include at least one of a hole push film surrounding the exposed side of the second conductive semiconductor layer or the exposed side of the second conductive semiconductor layer and at least a part of the exposed side of the light active layer to move the holes on the exposed side surface to the center side, and an electron push film surrounding the exposed side of the first conductive semiconductor layer to move the electrons on the exposed side surface to the center side.

[0022] Further, the ultra-thin LED element can include both the hole push film and the electron push film, and the electron push film can be provided as an outermost film surrounding the sides of the first conductive semiconductor layer, the light active layer, and the second conductive semiconductor layer.

[0023] Further, the hole push film can include one or more selected from the group consisting of AlN X , ZrO2, MoO, Sc2O3, La2O3, MgO, Y2O3, Al2O3, Ga2O3, TiO2, ZnS, Ta2O5, and n-MoS2.

[0024] In addition, the electronic pusher film can include one or more selected from the group consisting of Al2O3, HfO2, SiN x , SiO2, ZrO2, Sc2O3, AlN x , and Ga2O3.

[0025] In addition, in the first embodiment, the actual same light color can be blue, white, or UV.

[0026] In addition, the first embodiment of the present application provides a full-color LED display manufacturing method, the method comprising: step (1), preparing a lower electrode line including a first electrode formed with a plurality of sub-pixel regions; step (2), processing an ink composition on the first electrode to configure at least two ultra-thin LED elements in each sub-pixel region, wherein the ink composition includes a plurality of ultra-thin LED elements including a first conductive semiconductor layer, a photoactive layer, and a second conductive semiconductor layer stacked, and the ratio between the thickness in the stacking direction of the layers and the length of the major axis in the cross section perpendicular to the stacking direction is 1:0.5-1.5, and the actual emitted light color is the same; step (3), assembling the ultra-thin LED elements processed on the sub-pixel region on the first electrode with the thickness direction upright; step (4), forming an upper electrode line including a second electrode to be electrically connected to the opposite side opposite to the side of the ultra-thin LED element assembled on the first electrode; and step (5), patterning a color-changing layer on the second electrode corresponding to the sub-pixel region to make each of the plurality of sub-pixel regions a sub-pixel region exhibiting any one of blue, green, and red colors.

[0027] In addition, the second embodiment of the present application provides a full-color LED display manufacturing method, which includes: step (I), preparing a lower electrode line including a first electrode formed with a plurality of sub-pixel areas; step (II), processing a blue ultra-thin LED element ink composition, a green ultra-thin LED element ink composition and a red ultra-thin LED element ink composition on the first electrode, so that the plurality of sub-pixel areas independently present any one color of blue, green and red light, and each sub-pixel area is configured with at least two ultra-thin LED elements, wherein the blue ultra-thin LED element ink composition, the green ultra-thin LED element ink composition and the red ultra-thin LED element ink composition include a plurality of ultra-thin LED elements according to light color, the ultra-thin LED elements include a first conductive semiconductor layer, a photoactive layer and a second conductive semiconductor layer stacked, and the ratio between the thickness of the stacking direction as a layer and the length of the major axis in the cross section perpendicular to the stacking direction is 1:0.5-1.5; step (III), assembling the ultra-thin LED elements processed on the sub-pixel area on the first electrode in the thickness direction; and step (IV), forming an upper electrode line including a second electrode to be electrically connected to the opposite side of the side of the ultra-thin LED element assembled on the first electrode.

[0028] According to an embodiment of the first embodiment and the second embodiment of the present application, the step (3) and the step (III) can form a magnetic field in the vertical direction on the main surface of the first electrode, so that the ultra-thin LED element moves to the sub-pixel area and is arranged in the thickness direction.

[0029] In addition, the first charge layer with positive charge or negative charge is further provided on the side of the thickness direction of the ultra-thin LED element, and the second charge layer carrying the charge opposite to the first charge layer is further provided on the first electrode in the sub-pixel area; the step (3) and the step (III) form a magnetic field in the vertical direction on the main surface of the first electrode, so that the ultra-thin LED element moves to the sub-pixel area and is arranged in the thickness direction.

[0030] In addition, the step (3) and the step (III) assemble the ultra-thin LED element on the first electrode in the sub-pixel area through chemical bonding with the bonding layer as a medium between the side of the thickness direction of the ultra-thin LED element and the first electrode in the sub-pixel area, and the bonding layer can be arranged on either side or both sides of the first electrode in the sub-pixel area.

[0031] Hereinafter, the terms used in the present application are defined.

[0032] In describing the implementation examples of the present application, in the "on", "upper", "under", "lower" described in each layer, region, pattern or substrate, each layer, region, pattern, "on", "upper", "under", "lower" includes both "direct" and "indirect" meanings.

[0033] (EFFECTS OF THE INVENTION)

[0034] The full-color LED display of the present application inkjetizes the ultra-thin LED element and can be implemented by inkjet printing, so that a large-area display can be more easily implemented. In addition, compared to the conventional display using a nanorod-shaped LED element, the light emitting area of the element is increased, so that it is advantageous to implement high brightness and light efficiency. In addition, while the light emitting area of the element is increased, the light active layer area exposed to the surface is also greatly reduced, and further, the efficiency reduction caused by surface defects can be prevented or minimized, so that the brightness reduction of the display can be prevented or minimized. Further, for the used LED, the electron-hole recombination speed according to the imbalance of the electron and hole speed can be optimized, and a more improved light emitting efficiency can be implemented, so that a display having high brightness can be implemented. In addition, the electrode arrangement of the sub-pixel can be easily and simply designed, and it is also easy to implement, so that it can be widely used in various displays.

[0035] The present application was researched with the support of the following national R&D project, and detailed information of the national R&D project is as follows.

[0036] [Subject inherent number] 1711130702

[0037] [Subject number] 2021R1A2C2009521

[0038] [Ministry name] Ministry of Science and ICT

[0039] [Subject management (professional) agency name] Korea National Research Foundation

[0040] [Research project name] Support project for backbone researchers

[0041] [Research subject name] Development of Dot-LED materials and display originality / application technology

[0042] [Subject implementation agency name] National University-Industry Cooperation Team

[0043] [Research period] 2021.03.01 ~ 2022.02.28

[0044] [Subject inherent number] 1711105790

[0045] Project Number) 2016R1A5A1012966

[0046] Ministry of Science and ICT

[0047] Korean National Research Foundation

[0048] Research Project Name) Engineering Research Center(S / ERC)

[0049] Research Project Name) Circadian ICT Research Center using Hybrid Devices

[0050] Research Project Name) Circadian ICT Research Center using Hybrid Devices

[0051] Research Period) 2021. 01. 01 ~ 2021. 12. 31 BRIEF DESCRIPTION OF DRAWINGS

[0052] Figures 1 to 2 is a plan view of a full-color LED display of a first embodiment of the present invention and a cross-sectional view along the X-X' boundary line of Figure 1 .

[0053] Figures 3 to 4 is a plan view of a full-color LED display of a second embodiment of the present invention and a cross-sectional view along the Y-Y' boundary line of Figure 3 .

[0054] Figure 5 is a perspective view of an ultra-thin LED element for an embodiment of the present invention.

[0055] Figure 6 is a cross-sectional view along the Z-Z' boundary line of Figure 5 .

[0056] Figures 7a to 7c is a view of various embodiments of an arrangement inducing layer that an ultra-thin LED element for an embodiment of the present invention can have.

[0057] Figure 8 is a view for explaining the balance of electrons and holes in an LED element.

[0058] Figure 9 is a perspective view of an ultra-thin LED element used in an embodiment of the present invention.

[0059] Figure 10 is a cross-sectional view of an ultra-thin LED element used in an embodiment of the present invention.

[0060] Figure 11 and Figure 12is a mode diagram of a manufacturing method 1 of an ultra-thin LED element used in an embodiment of the present application.

[0061] Figure 13 is a mode diagram of a manufacturing method 2 of an ultra-thin LED element used in an embodiment of the present application.

[0062] Figure 14 is a mode diagram of a manufacturing method of an ultra-thin LED element used in an embodiment of the present application.

[0063] Figures 15 to 17 is a mode diagram showing various embodiments of a step of an ultra-thin LED display manufacturing method of an embodiment of the present application.

[0064] Figure 18 and Figure 19 is a SEM photograph in a specific step in a manufacturing method of an ultra-thin LED element used in an embodiment of the present application.

[0065] Figure 20 is a SEM photograph of an ultra-thin LED element used in an embodiment of the present application.

[0066] Figure 21 is a SEM photograph of an LED wafer left after manufacturing an ultra-thin LED element in a manufacturing process of an ultra-thin LED element used in an embodiment of the present application.

[0067] Figure 22 is a time period absorbance graph in which a spectral area of a visible light region of 380 nm to 780 nm is normalized by absorbance of each wavelength measured by time respectively using an ink composition in which an ultra-thin LED element and a rod-shaped LED element are respectively dispersed in acetone. DETAILED DESCRIPTION

[0068] Hereinafter, embodiments of the present application are described so that a person having ordinary knowledge in the technical field to which the present application pertains can easily practice the present application. The present application can be implemented in various different forms, and is not limited to the embodiments described herein.

[0069] First, as a display of a first implementation example of the present application, a full-color LED display implemented by LED elements actually emitting light of the same color is described.

[0070] Referring to Figure 1 and Figure 2To explain, the full-color LED display 1000 of the first embodiment of the present application includes: a lower electrode line 310 including first electrodes 311, 312, 313 formed with a plurality of sub-pixel areas S1, S2, S3, S4; an upper electrode line 320 including a plurality of ultra-thin LED elements 101 and second electrodes 321, 322, the plurality of ultra-thin LED elements 101 being configured so that each of the sub-pixel areas S1, S2, S3, S4 is configured with at least two and is vertically configured on the first electrodes 311, 312, 313 in a layer stacking direction, the second electrodes 321, 322 being configured to contact the upper portions of the plurality of ultra-thin LED elements 101; and a color changing layer 700 patterned on the upper electrode line 320 so that the sub-pixel areas S1, S2, S3, S4 become sub-pixel areas S1, S2, S3, S4 that exhibit any one of blue, green, and red colors.

[0071] First, before specifically describing each structure, the electrode line for the light-emitting ultra-thin LED element is explained.

[0072] The display 1000 of the first embodiment of the present application includes the upper electrode line 320 and the lower electrode line 310 that are configured to face each other with the ultra-thin LED element 101 interposed therebetween. The upper electrode line 320 and the lower electrode line 310 are not arranged in a horizontal direction, thus eliminating the complex electrode line of the display that has conventionally used electric field induction, i.e., two electrodes that are realized to have ultra-small thickness and width are arranged in a horizontal direction in a limited area of a plane with a spacing of micrometers or nanometers, the electrode can be very simply designed, and the electrode can be more easily realized. In addition, since the TFT arrangement is also easy, not only the source matrix drive but also the passive matrix drive, i.e., the x-y matrix drive, can be realized, thus having the advantage of making it easier to realize various types of displays.

[0073] In addition, the lower electrode line 310 and the upper electrode line 320 can each have a plurality of first electrodes 311, 312, 313 and second electrodes 321, 322, the number, the spacing, the configuration shape, etc. of which can be appropriately changed in consideration of the area, the brightness, etc. of the display to be realized, thus the present application not being particularly limited thereto.

[0074] In addition, as for the upper electrode line 320, in the case of being designed to contact the upper portion of the ultra-thin LED element 101 attached to the lower electrode line 310, the number, the configuration shape, etc. are not limited. However, as Figure 1If the lower electrode lines 310 are arranged in one direction, the upper electrode lines 320 are arranged perpendicularly to the one direction. This electrode configuration is widely used in conventional displays and the like, and has the advantage that the electrode configuration and control technology of the conventional display field can be directly used.

[0075] In addition, the lower electrode lines 310 and the upper electrode lines 320 can have the material, shape, width, and thickness of the electrodes used in a conventional display using LEDs, and can be manufactured using a known method, and thus the present application is not particularly limited thereto. For example, the first electrodes 311, 312, and 313 and the second electrodes 321 and 322 can each independently be aluminum, chromium, gold, silver, copper, graphene, ITO, or an alloy thereof, and the like, and can have a width of 2 μm to 50 μm and a thickness of 0.1 μm to 100 μm, but can be appropriately changed in consideration of the target size of the LED display and the like.

[0076] According to an embodiment of the present application, sub-pixel regions S1, S2, S3, and S4 in which the ultra-thin LED elements 101 are to be arranged can be formed on the first electrodes 311, 312, and 313. The sub-pixel regions S1, S2, S3, and S4 can be variously set according to the purpose, such as Figure 1 The sub-pixel regions S1, S2, S3, and S4 can be set at predetermined intervals, but are not limited thereto. On the other hand, the sub-pixel regions S1, S2, S3, and S4 refer to virtual regions that divide the main plane of the first electrodes 311, 312, and 313.

[0077] In addition, the unit area of the sub-pixel regions is less than 100 μm x 100 μm, for example, less than 30 μm x 30 μm, and for another example, less than 20 μm x 20 μm. The unit area of such a size is smaller than the unit sub-pixel area of a display using LEDs, and thus the area occupied by the LEDs can be minimized while a large area is pursued, and accordingly a high-resolution display can be advantageously implemented. On the other hand, the unit area of each sub-pixel region can be different from one another. In addition, a separate surface treatment can be performed on the surface of the sub-pixel regions or a groove can be formed.

[0078] On the other hand, in Figure 1 Although not shown, the electrode configuration of a data electrode, a gate electrode, and the like provided in a conventional display, but the electrode configuration not shown can employ the electrode configuration used in a conventional display.

[0079] Hereinafter, the ultra-thin LED elements 101 arranged between the lower electrode lines 310 and the upper electrode lines 320 described above will be described.

[0080] For the ultra-thin LED element 101, the plurality of sub-pixel regions S1, S2, S3, S4 on the first electrode 311, 312, 313 are configured to include at least two of the ultra-thin LED elements 101, whereby in the event of a defective element among the ultra-thin LED elements 101 configured in each sub-pixel, the predetermined light can also be emitted in all sub-pixels, thus preventing or minimizing the occurrence of defective pixels in the display.

[0081] In addition, the ultra-thin LED elements 101 configured in each sub-pixel region S1, S2, S3, S4 actually emit light of the same color. At this time, light of the same color does not mean that the wavelengths of the light are exactly the same, but generally refers to light belonging to a wavelength range that can be referred to as the same color. For example, in the case of light of the color blue, ultra-thin LED elements that emit light belonging to a wavelength range of 420 nm to 470 nm can all be considered to emit light of the same color. For example, the light emitted by the ultra-thin LED elements in the display according to the first embodiment of the present application can be blue, white, or UV.

[0082] Referring to Figure 5 and Figure 6 The ultra-thin LED element 101 configured in each sub-pixel region S1, S2, S3, S4 includes a first conductive semiconductor layer 10, a photoactive layer 20, and a second conductive semiconductor layer 30, and can further include a second electrode layer 60 formed under the first conductive semiconductor layer 10, a first electrode layer 40 formed on the second conductive semiconductor layer 30, and an alignment-inducing layer 70 formed on the outermost side of the second conductive semiconductor layer 30.

[0083] The above-mentioned layers are stacked in any one direction, and the ratio between the thickness in the stacking direction and the length of the long axis in the cross section perpendicular to the stacking direction satisfies 1:0.5-1.5, preferably 1:0.8-1.2, more preferably 1:0.9-1.1, whereby excellent dispersibility in a dispersion medium is achieved when the ultra-thin LED element is used as ink for inkjet, and it is possible to advantageously maintain the dispersed state for a long time without precipitation. In addition, since the geometry suitable for such ink does not require a separate additive for maintaining the dispersed state, it is possible to advantageously prevent the lower electrode line 310 or the circuit substrate from being contaminated by the separate additive. Further, when the ink containing the ultra-thin LED element is printed on the lower electrode line 310, the nanorod-type LED element having a large aspect ratio in the past is mostly laid almost flat on the electrode, whereas the ultra-thin LED element has the advantage of reducing the probability of being laid flat on the driving electrode. In addition, by forming the alignment-inducing layer 70 on either side in the thickness direction to be assembled on the first electrode in the thickness direction, it is possible to reduce the probability of the assembled direction of the plurality of elements being different from each other when assembled on the first electrode, in other words, the probability of being assembled on the first electrode in a direction in which the directions of the p-type conductive semiconductor layer and the n-type conductive semiconductor layer are different from each other, whereby it is possible to reduce the electric leakage due to reverse arrangement, and thus it is possible to advantageously improve the life. Here, the length of the long axis refers to the diameter in the case of a circular cross-sectional shape, the length of the long axis in the case of an elliptical shape, and the length of the longest side in the case of a polygonal shape. On the other hand, in the case where the cross sections of the ultra-thin LED elements are different from each other in the thickness direction, the cross section refers to the largest face in the cross section.

[0084] In addition, the ratio between the length of the short axis and the length of the long axis in the cross section is also 1:0.5-1.5, preferably 1:0.8-1.2, more preferably 1:0.9-1.1, whereby it is possible to more advantageously achieve the object of the present application described above. If, even if the ratio between the thickness and the length of the long axis satisfies 1:0.5-1.5, the ratio between the length of the short axis and the length of the long axis in the cross section exceeds 1:0.5-1.5, the LED element is difficult to maintain the dispersed state for a long time in the dispersion medium, and thus it can not be suitable for inkjet. In addition, in order to maintain the dispersed state for a long time in the dispersion medium for such an LED element having a geometry unsuitable for inkjet, it is necessary to contain an additive, and thus there is a risk of the driving electrode or the circuit substrate being contaminated due to the use of the additive. Here, the length of the short axis in the cross section refers to the longest length among the lengths of the axes perpendicular to the long axis.

[0085] On the other hand, for the LED element in which the cross section is a circular shape, the ratio between the thickness and the length of the long axis in the cross section satisfies 1:0.5-1.5, preferably 1:0.8-1.2, more preferably 1:0.9-1.1, whereby it is possible to advantageously achieve the object of the present application described above. Figure 5The illustrated ultra-thin LED element 101 has the same size as the cross section perpendicular to the stacking direction of the layers, but is not limited thereto, and the size of the cross section can vary depending on the thickness.

[0086] In addition, it should be noted that the shape of the ultra-thin LED element 101 can be an irregular shape in which the faces are not regular, such as a star shape, in addition to the illustrated cylindrical shape. Figure 5 The illustrated cylindrical shape is not limited thereto, and not only hexahedrons, octahedrons, decahedrons, and the like, but also irregular shapes having faces in the shape of a star.

[0087] According to an embodiment of the present application, in order to improve the dispersion retention performance in which the settling speed is slow and the dispersed state can be maintained for a long time when inked, the largest face of the ultra-thin LED element 101 can be 16 μm 2 Hereinafter, it is preferable that the largest face can be 9 μm 2 Hereinafter, it is more preferable that the largest face can be 4 μm 2 Hereinafter, it is further more preferable that the largest face can be 0.1 μm 2 to 2.5 μm 2 Here, the largest area refers to the maximum value among the areas of the perpendicular projections of the LED elements. If the largest area exceeds 16 μm 2 , the settling speed is accelerated, and there is a risk of reducing the dispersion retention performance, and thus it is not suitable for manufacturing ink, or there is a limitation in that an additional additive or a specific dispersion medium must be contained in order to be inked.

[0088] According to an embodiment of the present application, the thickness of the ultra-thin LED element 101 can be 2.7 μm or less, and it is more preferable that the thickness can be 2.0 μm or less, and it is further more preferable that the thickness can be 0.2 to 1.0 μm, and accordingly it is more suitable for maintaining the dispersed state for a long time when inked.

[0089] However, in the case of the LED element, in order to achieve a thin thickness, the position at which the combination between the electron and the hole is achieved is separated from the light active layer 20, and the light emission efficiency can be reduced. In particular, in the case of etching a large-area LED wafer to achieve an ultra-thin LED element, the thicknesses of the first conductive semiconductor layer, the light active layer, and the second conductive semiconductor layer are already determined in the LED wafer state, and unlike the thicknesses of the respective layers within the wafer that are already determined, only a portion is etched to achieve the ultra-thin LED element, and thus this problem inevitably occurs. This change in the position at which the combination between the electron and the hole is achieved is caused by the difference in the speed of the electron and the hole moving in the conductive semiconductor layer. For example, the mobility of the electron in the conductive semiconductor layer that is n-type GaN is 200 cm 2 Vs, and in contrast, the mobility of the hole in the conductive semiconductor layer that is p-type GaN is only 5 cm 2Vs, because of such an electron-hole velocity imbalance, depending on the thickness of the conductive semiconductor layer as p-type GaN and the thickness of the conductive semiconductor layer as n-type GaN, the position where electrons and holes are combined varies and can exceed the light active layer.

[0090] For this, referring to Figure 8 is explained, in the LED element 200 in which the conductive semiconductor layer 210 as n-type GaN, the light active layer 220, and the conductive semiconductor layer 230 as p-type GaN are laminated with a diameter of about 600 nm, in order to consider the electron mobility of the conductive semiconductor layer 210 as n-type GaN and the hole mobility of the conductive semiconductor layer 230 as p-type GaN, the number of electrons and holes combined at the point A2 within the light active layer 220 reaches a balance, and thus the thickness h of the conductive semiconductor layer 210 as n-type GaN must be thick at the time of design, and thus unless the thickness of the conductive semiconductor layer 230 as p-type GaN is made very thin, there is a high probability that the LED element is implemented as a rod-shaped LED element having a length in the thickness direction. In other words, in the case of the LED element in which the thickness of each layer is designed so that the position where the number of combined electrons and holes is balanced is located in the light active layer 220, even though the major axis length of an arbitrary end surface perpendicular to the thickness direction can be made small, it is difficult to reduce the thickness of the LED element to a predetermined level or less, and thus it is finally necessary to implement a rod-shaped LED element formed in the thickness direction of the LED element, and thus even though the number of holes and electrons combined in the light active layer reaches a balance, it is not suitable to be implemented as ink. In addition, when the n-type GaN conductive semiconductor layer 210 having a thin thickness is implemented in order to be suitable to be implemented as ink, the position where the number of combined electrons and holes reaches a balance varies from the point A2 within the light active layer 220 to the point A3 within the p-type GaN conductive semiconductor layer 230, and thus the light emission efficiency can be reduced.

[0091] Accordingly, the ultra-thin LED element of one embodiment of the present application can further include an electron delay layer adjacent to the n-type conductive semiconductor layer side to have a geometry suitable to be implemented as ink while the number of holes and electrons combined in the light active layer reaches a balance, and thus prevent the light emission efficiency from being reduced. For this, referring to Figure 9 is explained, in the case where the first conductive semiconductor layer is an n-type conductive semiconductor, the ultra-thin LED element 102 can have an electron delay layer 50 on the first conductive semiconductor layer 10, and thus even though the first conductive semiconductor layer 10 having a thin thickness is implemented, the light emission efficiency can be prevented from being reduced. In addition, the thinning of the thickness of the first conductive semiconductor layer 10 reduces the probability that electrons are trapped due to surface defects in the movement of the electrons in the thickness direction of the first conductive semiconductor layer 10, and thus has an advantage in that light emission loss can be minimized.

[0092] As an example, the electron delay layer 50 can contain one or more selected from the group consisting of CdS, GaS, ZnS, CdSe, CaSe, ZnSe, CdTe, GaTe, SiC, ZnO, ZnMgO, Sn02, Ti02, In203, Ga203, Si, poly(paraphenylenevinylene) and its derivatives, polyaniline, poly(3-alkylthiophene), and poly(paraphenylene). In addition, as another example, in the case where the first conductive semiconductor layer 10 is a doped n-type Group III nitride semiconductor layer, the electron delay layer 50 can be a Group III nitride semiconductor having a doping concentration lower than that of the first conductive semiconductor layer 10.

[0093] The thickness of the electron delay layer 50 can be 1 nm to 100 nm, but is not limited thereto, and can be appropriately changed in consideration of the material of the n-type conductive semiconductor layer, the material of the electron delay layer, and the like.

[0094] Hereinafter, each layer of the ultra-thin LED element 101 according to an embodiment of the present application will be described in detail.

[0095] In the case where either one of the first conductive semiconductor layer 10 and the second conductive semiconductor layer 30 is an n-type semiconductor layer and the other is a p-type semiconductor layer, which are well-known semiconductor layers used for light emitting diodes, there is no limitation. As an example, the n-type semiconductor layer and the p-type semiconductor layer can include a III-V semiconductor known as a Group III nitride material, and particularly, a binary, ternary, and quaternary alloy of gallium, aluminum, indium, and nitrogen.

[0096] As an example, the first conductive semiconductor layer 10 can be an n-type semiconductor layer, in which case the n-type semiconductor layer can be a semiconductor material having a composition formula of In x Al y Ga 1-x-y N (0≤x≤1, 0≤y≤1, 0≤x+y≤1), for example, one or more selected from the group consisting of InAlGaN, GaN, AlGaN, InGaN, AlN, InN, and the like, and can be doped with a first conductive dopant (e.g., Si, Ge, Sn, and the like). According to a preferred implementation of the present application, the thickness of the first conductive semiconductor layer 10 can be 100 nm to 1800 nm, but is not limited thereto.

[0097] In addition, the second conductive semiconductor layer 30 can be a p-type semiconductor layer, in which case the p-type semiconductor layer can be a semiconductor material having a composition formula of Inx Al y Ga 1-x-y The semiconductor material is composed of N (0≤x≤1, 0≤y≤1, 0≤x+y≤1), and may be selected from one or more of InAlGaN, GaN, AlGaN, InGaN, AlN, InN, etc., and may be doped with a second conductive dopant (e.g., Mg). According to a preferred embodiment of the present invention, the thickness of the second conductive semiconductor layer 30 may be 50nm to 150nm, but is not limited thereto.

[0098] Furthermore, the photoactive layer 20 located between the first conductive semiconductor layer 10 and the second conductive semiconductor layer 30 can be formed as a single or multiple quantum well structure. When the photoactive layer 20 is included in a typical LED element used for lighting, displays, etc., it can be used without limitation. A coating layer (not shown) doped with a conductive dopant can also be formed above and / or below the photoactive layer 20. This coating layer doped with the conductive dopant can be implemented using an AlGaN layer or an InAlGaN layer. In addition, materials such as AlGaN and AlInGaN can also be used for the photoactive layer 20. With this photoactive layer 20, when an electric field is applied to the element, electrons and holes moving from the conductive semiconductor layers located above and below the photoactive layer to the photoactive layer recombine in the photoactive layer, thus emitting light. In a preferred embodiment of the present invention, the thickness of the photoactive layer 20 can be 50 nm to 200 nm, but is not limited thereto.

[0099] On the other hand, a second electrode layer 60 may be provided below the first conductive semiconductor layer 10. Alternatively, an electron delay layer 50 may be provided between the first conductive semiconductor layer 10 and the second electrode layer 60. In addition, a first electrode layer 40 may be provided above the second conductive semiconductor layer 30.

[0100] The first electrode layer 40 and the second electrode layer 60 can be used without limitation as electrode layers typically included in LED components used for lighting, displays, etc. The first electrode layer 40 and the second electrode layer 60 can be separate layers formed independently of Cr, Ti, Al, Au, Ni, ITO, and oxides or alloys thereof, or composite layers formed by mixing two or more of these materials. For example, ... Figure 9 As shown, the ultra-thin LED element 102 may have a first electrode layer 40 with a stacked ITO layer and a first electrode composite layer 42 with a Ti / Au composite layer 41 on the second conductive semiconductor layer 30. In addition, the first electrode layer 40 and the second electrode layer 60 may be independent and have a thickness of 10nm to 500nm, but are not limited thereto.

[0101] In addition, the alignment inducing layer 70 can be formed on either one or both of the side of the thickness direction of the ultra-thin LED element 101 and the sub-pixel area S1, S2, S3, S4 of the first electrode 311, 312, 313 where the ultra-thin LED element 101 is to be arranged. The alignment inducing layer 70 is used to arrange the ultra-thin LED element 101 vertically in the thickness direction. The alignment inducing layer induces the ultra-thin LED element 101 to move to the target area, i.e. the sub-pixel area S1, S2, S3, S4, on the first electrode 311, 312, 313, and performs the function of arranging the ultra-thin LED element 101 vertically on the first electrode 311, 312, 313. The alignment inducing layer can be formed on the side of the ultra-thin LED element 101 and / or the target area, e.g. the sub-pixel area S1, S2, S3, S4, on the first electrode 311, 312, 313.

[0102] For the case where the alignment inducing layer is formed only on the first electrode 311, 312, 313, the alignment inducing layer can be the metal part of the ultra-thin LED element 101, or a bonding layer that is chemically bonded to the first electrode layer and / or the second electrode layer, for example. In this case, the bonding layer can be a layer formed to expose a thiol group to the outside, for example.

[0103] In addition, for the case where the alignment inducing layer is formed on the ultra-thin LED element 101, as shown in FIGS. 1A and 1B, the alignment inducing layer 70 can also be included on the first electrode layer 40. The alignment inducing layer 70 can vary in material depending on the specific inducing and binding method. For example, the alignment inducing layer 70 can be a charge layer with positive or negative charges, specifically, as shown in FIG. 1A, it can be a charge layer 71 with negative charges. The charge layer 71 induces the ultra-thin LED element to the first electrode by the electrophoresis method described later and can vertically assemble the ultra-thin LED element. Alternatively, as shown in FIG. 1B, the alignment inducing layer can be a bonding layer 72 that chemically binds the functional group exposed on the bonding layer 72 to other functional groups on the first electrode, or chemically binds to the metal material of the first electrode, for example, by adsorption. In addition, as shown in FIG. 1C, the alignment inducing layer 70 can be a magnetic layer 73 that can be assembled on the first electrode 311, 312, 313 under a magnetic field. Figure 5 Figures 7a to 7c For the case where the alignment inducing layer is formed only on the first electrode 311, 312, 313, the alignment inducing layer can be the metal part of the ultra-thin LED element 101, or a bonding layer that is chemically bonded to the first electrode layer and / or the second electrode layer, for example. In this case, the bonding layer can be a layer formed to expose a thiol group to the outside, for example. Figure 7a Figure 7b For the case where the alignment inducing layer is formed only on the first electrode 311, 312, 313, the alignment inducing layer can be the metal part of the ultra-thin LED element 101, or a bonding layer that is chemically bonded to the first electrode layer and / or the second electrode layer, for example. In this case, the bonding layer can be a layer formed to expose a thiol group to the outside, for example. Figure 7c

[0104] ​​​On the other hand, when the alignment induction layer 70 disposed on the ultra-thin LED element is a charge layer 71, a charge layer carrying a charge opposite to that of the charge layer 71 disposed on the ultra-thin LED element can be formed on the sub-pixel regions S1, S2, S3, and S4 within the first electrodes 311, 312, and 313. This provides the advantage of better inducing the ultra-thin LED element into the arrangement area while simultaneously improving the erection of the ultra-thin LED element. The charge layer can be used without limitation as long as it is formed with a material that carries either positive or negative charge and is suitable for forming layers or films.

[0105] Furthermore, when the alignment guiding layer 70 disposed on the ultra-thin LED element is a magnetic layer 73, a magnetic layer may also be included on the sub-pixel regions S1, S2, S3, and S4 within the first electrodes 311, 312, and 313. This provides the advantage of better guiding the ultra-thin LED element towards the placement area while simultaneously improving the upright placement of the ultra-thin LED element. In this case, the magnetic layer can be a strong magnet or a paramagnetic material.

[0106] On the other hand, Figure 5 and Figure 6 The alignment-inducing layer 70 is shown located on the first electrode layer 40, but it is not limited thereto; it can also be configured to be located on the second electrode layer 60. In other words, the alignment-inducing layer 70 can be configured on either side of the thickness direction of the ultrathin LED element, that is, it can be configured as the uppermost or lowermost layer on the ultrathin LED element.

[0107] Additionally, the ultra-thin LED element 101 may also include a protective film 80, which surrounds the side surface of the element when the surface parallel to the stacking direction is a side surface. The protective film 80 functions to protect the surfaces of the first conductive semiconductor layer 10, the photoactive layer 20, and the second conductive semiconductor layer 30. Furthermore, similar to a manufacturing method for the ultra-thin LED element described later, it can also protect the first conductive semiconductor layer 10 during the process of separating multiple LED pillars after etching the LED wafer in the thickness direction. As an example, the protective film 80 may contain any one or more of silicon nitride (Si3N4), silicon dioxide (SiO2), aluminum oxide (Al2O3), hafnium oxide (HfO2), zirconium oxide (ZrO2), yttrium oxide (Y2O3), titanium dioxide (TiO2), aluminum nitride (AlN), and gallium nitride (GaN). The thickness of the protective film 80 can be 5nm to 100nm, more preferably 30nm to 100nm, which can help protect the first conductive semiconductor layer 10 in the process of separating the LED pillar from the wafer in the LED pillar fabrication process described later.

[0108] On the other hand, such as Figure 10As shown, in order to achieve better luminous efficiency in addition to its protective function as a protective film, an ultra-thin LED element 103 of an embodiment of the present invention may have a protective film 80' composed of a hole-pushing film 81 and an electron-pushing film 82. The hole-pushing film 81 surrounds the exposed side of the second conductive semiconductor layer 30 or the exposed side of the second conductive semiconductor layer 30 and at least a portion of the exposed side of the photoactive layer 20 to move holes on the exposed side surface towards the center. The electron-pushing film 82 surrounds the exposed side of the first conductive semiconductor layer 10 to move electrons on the exposed side surface towards the center.

[0109] A portion of the charge moving from the first conductive semiconductor layer 10 to the photoactive layer 20 and a portion of the holes moving from the second conductive semiconductor layer 30 to the photoactive layer 20 can move along the side surface. In this case, due to defects present on the surface, electrons or holes may be hardened, thus posing a risk of reduced luminous efficiency. Even with a protective film, the problem of hardening caused by defects generated on the device surface before the protective film is formed cannot be avoided. However, when the protective film 80' is formed by the hole-pushing film 81 and the electron-pushing film 82, electrons and holes are concentrated towards the center of the device and guided towards the photoactive layer, thus having the advantage of preventing luminous efficiency loss due to surface defects even if defects exist on the device surface before the protective film is formed.

[0110] For example, the hole-pushing membrane 81 may comprise AlN X One or more of the following are selected from the group consisting of ZrO2, MoO, Sc2O3, La2O3, MgO, Y2O3, Al2O3, Ga2O3, TiO2, ZnS, Ta2O5, and n-MoS2; the electron-push film 82 may contain one or more of the following: Al2O3, HfO2, SiN x SiO2, ZrO2, Sc2O3, AlN x Choose one or more from the group consisting of Ga2O3.

[0111] In addition, such as Figure 10 As shown, when the ultra-thin LED element has both hole push film 81 and electron push film 82, the electron push film 82 can be configured as the outermost film surrounding the sides of the first conductive semiconductor layer 10, the photoactive layer 20 and the second conductive semiconductor layer 30.

[0112] In addition, the hole-pushing film 81 and the electron-pushing film 82 can be independent and have a thickness of 1nm to 50nm.

[0113] On the other hand, the first conductive semiconductor layer 10, the photoactive layer 20, and the second conductive semiconductor layer 30 of the above-described ultra-thin LED element can be included as the minimum constituent elements of the ultra-thin LED device, and it is noted that other phosphor layers, quantum dot layers, other active layers, semiconductor layers, hole blocking layers, and / or electrode layers can be further included above / below each layer.

[0114] In addition, according to an embodiment of the present application, as shown in Figure 2 The full-color LED display can further include a conductive metal layer 500 between one side of the ultra-thin LED element 101 and the first electrodes 311, 312, 313, which are in contact with the first electrodes 311, 312, 313, to reduce the contact resistance between the first electrodes 311, 312, 313 and the ultra-thin LED element 101. The conductive metal layer 500 can be a conductive metal layer of silver, aluminum, gold, etc., and can have a thickness of about 10 nm, for example.

[0115] In addition, an insulating layer 600 can be further included between the ultra-thin LED element 101 disposed on the lower electrode line 310 and the upper electrode line 320 in contact with the upper portion of the ultra-thin LED element 101. The insulating layer 600 prevents electrical contact between the two electrode lines 310, 320 facing each other in the vertical direction, and performs the function of more easily implementing the upper electrode line 320.

[0116] In addition, as shown in Figure 2 The color conversion layer 700 can be patterned with a blue color conversion layer 711, a green color conversion layer 712, and a red color conversion layer 713 to allow each of the plurality of sub-pixel regions to independently exhibit any one of blue, green, and red colors, respectively. The blue color conversion layer 711, the green color conversion layer 712, and the red color conversion layer 713 can be a publicly known color conversion layer that converts light passing through the color conversion layer by considering the wavelength of light emitted from the ultra-thin LED element 101 in the sub-pixel region to allow the light to have blue, green, and red colors, and thus the present application is not limited thereto. On the other hand, in the case where the ultra-thin LED element 101 is a blue light emitting element, the blue color conversion layer 711 is not required, and thus the color conversion layer 700 can include only the green color conversion layer and the red color conversion layer.

[0117] In addition, a protective layer 800 for protecting the above-described color conversion layer 700 can be further included, and the protective layer 800 can be appropriately used as a protective layer used in a general display having the color conversion layer 700, and thus the present application is not particularly limited thereto.

[0118] The full-color LED display 1000 of the first implementation example described above can be manufactured by the manufacturing method described later. Specifically, the method includes: step (1) preparing a lower electrode line, the lower electrode line including a first electrode having a plurality of sub-pixel sites; step (2) processing an ink composition including a plurality of ultra-thin LED elements on the first electrode, such that each sub-pixel site is configured with at least two ultra-thin LED elements, wherein the ultra-thin LED elements include a stacked first conductive semiconductor layer, a photoactive layer, and a second conductive semiconductor layer, and the ratio between the thickness in the stacking direction of the layers and the length of the long axis in the cross section perpendicular to the stacking direction is 1:0.5 to 1.5, and they emit light of the same color; step (3) assembling the ultra-thin LED elements on the sub-pixel sites in the thickness direction on the first electrode; step (4) forming an upper electrode line including a second electrode to electrically connect to the opposite side to the side of the ultra-thin LED elements assembled on the first electrode; and step (5) patterning a color-changing layer on the upper electrode line, such that each sub-pixel site of the plurality of sub-pixel sites becomes a sub-pixel site emitting any one of blue, green, and red. The following description of the manufacturing method omits the content described in the above description of the full-color LED display 1000.

[0119] First, as step (1) of the present invention, a lower electrode line 310 is prepared, the lower electrode line 310 including first electrodes 311, 312, 313 having a plurality of sub-pixel sites.

[0120] The first electrodes 311, 312, and 313 can be implemented into various known electrode patterns using known methods, and the present invention does not impose any particular limitation thereon. For example, ... Figure 1 As shown, a pattern can be implemented where multiple first electrodes 311, 312, and 313 are arranged side-by-side at predetermined intervals. The first electrodes 311, 312, and 313 can be formed on a substrate 400. For example, the substrate 400 can be any of a glass substrate, quartz substrate, sapphire substrate, plastic substrate, and flexible polymer film. Another example is that the substrate 400 can be transparent. However, it is not limited to the listed types; any type can be used when electrodes can generally be formed on the substrate. There is no limitation on the area of ​​the substrate 400; the area of ​​the substrate 400 can be varied by considering the area of ​​the first electrodes 311, 312, and 313 formed on the substrate 400. Furthermore, the thickness of the substrate 400 can be from 100 μm to 1 mm, but is not limited to this.

[0121] After that, as the step (2) of the present application, the ink composition including a plurality of the ultra-thin LED elements 101 is processed on the first electrode 311, 312, 313 to arrange at least two of the ultra-thin LED elements in each of the sub-pixel regions, wherein the ultra-thin LED element includes the first conductive semiconductor layer 10, the photoactive layer 20, and the second conductive semiconductor layer 30 stacked as layers, and the ratio between the thickness in the stacking direction of the layers and the length of the major axis in the cross section perpendicular to the stacking direction is 1:0.5-1.5, and actually emits light of the same color.

[0122] The ultra-thin LED element 101 is prepared so that the ink composition in which a plurality of the ultra-thin LED elements are inked, and the ultra-thin LED element aggregate 100 composed of a plurality of the ultra-thin LED elements 101 can be manufactured by Figure 11 and Figure 12 Manufacturing method 1 shown in Figure 13 or manufacturing method 2 shown in is useful if it is the case of the undoped n-type group III nitride semiconductor layer.

[0123] Manufacturing method 1 and manufacturing method 2 are the same in the process from manufacturing the LED wafer 100a to manufacturing the wafer (100h of Figure 11 , 100h of Figure 13 ) including a plurality of LED structures, and there is a difference in the method of separating the LED structure from the wafer. The process from manufacturing the LED wafer 100a to manufacturing the wafer (100h of Figure 11 , 100h of Figure 13 ) including a plurality of LED structures will be described by manufacturing method 1.

[0124] First, manufacturing method 1 will be described with reference to Figure 11 Manufacturing method 1 can include: step (A) of preparing the LED wafer 100a (a of Figure 11 ); step (B) of patterning the upper part of the LED wafer 100a to have a target shape and size in the plane perpendicular to the stacking direction of the layers in a single LED structure (b, c of Figure 11 , and then etching in the vertical direction to at least a part of the thickness of the first conductive semiconductor layer 10 to form a plurality of LED structures (d-h of Figure 11 ); step (C) of forming a protective film to surround the exposed surface of each of the plurality of LED structures and to expose the first part of the upper surface between the adjacent LED structures to the outside (f of Figure 11(k) of the above-described steps (a) to (j)); and step (E) of applying ultrasonic waves to the LED wafer to separate a plurality of LED structures from the first portion in which a plurality of air holes are formed Figure 11 (k) of the above-described steps (a) to (j)); and step (E) of applying ultrasonic waves to the LED wafer to separate a plurality of LED structures from the first portion in which a plurality of air holes are formed Figure 11 (k) of the above-described steps (a) to (j)); and step (E) of applying ultrasonic waves to the LED wafer to separate a plurality of LED structures from the first portion in which a plurality of air holes are formed

[0125] The LED wafer 100a prepared in step (A) is commercially available and can be used without any limitation as long as it is commercially available. For example, the LED wafer 100a can include at least a substrate 1, a first conductive semiconductor layer 10, a light active layer 20, and a second conductive semiconductor layer 30. At this time, the first conductive semiconductor layer 10 can be an n-type group III nitride semiconductor layer, and the second conductive semiconductor layer 30 can be a p-type group III nitride semiconductor layer. In addition, the n-type group III nitride semiconductor layer is etched until a target thickness is reached, and then the LED structure remaining after etching is separated on the LED wafer by steps (C) to (E), so there is no limitation on the thickness of the first conductive semiconductor layer 10 as the n-type group III nitride semiconductor layer within the LED wafer, and whether or not a separate sacrificial layer is present can be considered when selecting the wafer.

[0126] In addition, each layer within the LED wafer 100a can have a c-plane crystal structure. In addition, the LED wafer 100a can be subjected to a cleaning process, and the cleaning process can be appropriately performed using a general wafer cleaning solution and a cleaning process, so the present application is not particularly limited thereto. For example, the cleaning solution can be isopropyl alcohol, acetone, and hydrochloric acid, but is not limited thereto.

[0127] Then, a step of forming a first electrode layer 40 on the second conductive semiconductor layer 30 as a p-type group III nitride semiconductor layer can be performed before step (B) is performed. The first electrode layer 40 can be formed by a general method of forming an electrode on a semiconductor layer, for example, can be formed by deposition using sputtering. The material of the first electrode layer 40 is the same as described above, for example, can be ITO, and can be formed to a thickness of about 150 nm. The first electrode layer 40 can also be subjected to a rapid thermal annealing process after the deposition process, for example, can be processed at 600°C for 10 minutes, but can be appropriately adjusted in consideration of the thickness, material, etc. of the electrode layer, so the present application is not particularly limited thereto.

[0128] Subsequently, as step (B), the upper part of the LED chip can be patterned so that a plane perpendicular to the direction of the stacked layers in a single LED structure has a target shape and size. Figure 11 (b) to (c)). Specifically, a mask pattern layer may be formed on the upper surface of the first electrode layer 40. The mask pattern layer may be formed using known methods and materials used in etching LED wafers. The pattern of the pattern layer may be formed by applying conventional photolithography or nanoimprinting.

[0129] For example, such as Figure 11 As shown in (f), the mask pattern layer can be a stack of a first mask layer 2, a second mask layer 3, and a resin pattern layer 4' with a predetermined pattern formed on the first electrode layer 40. To briefly illustrate the method of forming the mask pattern layer, for example, it can be formed as follows: the first mask layer 2 and the second mask layer 3 are formed on the first electrode layer 40 by deposition, and a resin layer 4', which is the origin of the resin pattern layer 4', is formed on the second mask layer 3. Figure 11 (b) and (c) are then removed using conventional methods such as RIE (reactive ion etching) to remove the residual resin portion 4a of resin layer 4. Figure 11 (d)) The second mask layer 3 and the first mask layer 2 are sequentially etched along the pattern of the resin pattern layer 4'. Figure 11 (e) and (f)). In this case, for example, the first mask layer 2 can be formed of silicon dioxide, and the second mask layer 3 can be a metal layer such as aluminum or nickel. The etching of these can be performed by RIE and ICP (inductively coupled plasma), respectively. On the other hand, the resin pattern layer 4' can also be removed when etching the first mask layer 2 (see 100f).

[0130] Alternatively, the resin layer 4, which is the origin of the resin pattern layer 4', can be formed by nanoimprinting to create a mold corresponding to the predetermined pattern model of the target. Then, the resin is processed in the mold to form a resin layer. After that, the resin layer 4 is transferred onto the first electrode layer 40 so that the resin layer 4 is located on the wafer stack 100b on which the first mask layer 2 and the second mask layer 3 are formed. Then, the mold is removed, thereby realizing the wafer stack 100c on which the resin layer 4 is formed.

[0131] On the other hand, a method for forming patterns by nanoimprinting was explained, but it is not limited to this method. It can also be formed by photolithography using known photosensitive materials or known laser interference lithography, electron beam lithography, etc.

[0132] After that, as Figure 11As shown in (g), a portion of the thickness of the n-type Group III nitride semiconductor layer, i.e., the first conductive semiconductor layer 10, is etched in a direction perpendicular to the surface of the LED wafer 100f along the pattern of the mask pattern layer 2, 3 formed on the first electrode layer 40, and further, the LED wafer 100g formed with the LED structure can be manufactured, at this time, the etching can be performed by a general dry etching method such as ICP and KOH / TAMH wet etching. In this etching process, the aluminum constituting the mask pattern layer, i.e., the second mask layer 3, can be removed, and then the silicon dioxide constituting the mask pattern layer present on the first electrode layer 40 of each LED structure in the LED wafer 100g, i.e., the first mask layer 2, is removed, and thus the LED wafer 100h formed with a plurality of LED structures can be manufactured.

[0133] After that, as step (C), a step of forming a protective film 80a to surround the exposed surface of each of the plurality of LED structures in the LED wafer 100h formed with the plurality of LED structures in a predetermined thickness and to expose the upper surface S1 of the first portion a between the adjacent LED structures to the outside is performed (steps (i), (j) of FIG. 10). Figure 12 The protective film 80a is for preventing the LED structure from being damaged due to the performance of step (D) while also performing the function of protecting the side surface of the individual separated LED structure from external stimuli when the side surface of the LED structure separated from the LED wafer remains.

[0134] For steps (C) to (E), reference is made to Figure 12 For steps (C) to (E), reference is made to

[0135] The step C-1 is a step of depositing the protective film material on the LED wafer 100h formed with the plurality of LED structures (step C-1-1), and the step C-2 is a step of removing the protective film deposited on the upper surface S1 of the first portion a between the adjacent LED structures to expose the upper surface S1 of the first portion a to the outside (step C-2-1). Figure 12(a) In this case, the protective film material can be a known material that is not chemically corroded by the electrolyte in step (D) described later. For example, the material of the protective film 80 described above can be used without limitation, and may include one or more selected from the group consisting of silicon nitride (Si3N4), silicon dioxide (SiO2), aluminum oxide (Al2O3), hafnium oxide (HfO2), zirconium oxide (ZrO2), yttrium oxide (Y2O3), lanthanum oxide (La2O3), scandium oxide (Sc2O3), titanium dioxide (TiO2), aluminum nitride (AlN), and gallium nitride (GaN). In addition, the thickness of the protective film 80a formed by depositing the protective film material can be 5 nm to 100 nm, and more preferably 30 nm to 100 nm. If the thickness of the protective film 80a is less than 5 nm, it is difficult to prevent the LED structure from being corroded by the electrolyte in step (D) described later; when the thickness is greater than 100 nm, there may be problems with increased manufacturing costs and connections between LED structures.

[0136] Next, step C-2 is the step of removing the protective film deposited on the upper surface S1 of the first portion a between adjacent LED structures to expose the upper surface S1 of the first portion a between the LED structures to the outside. Figure 11 (b) Because of step C-1, a protective film material is also deposited on the upper surface S1 of the first portion a between adjacent LED structures, the electrolyte cannot contact the n-type III nitride semiconductor, i.e., the first conductive semiconductor layer 10, and thus the target pores cannot be formed in the first portion a. Accordingly, a step is performed to remove the protective film material covering the upper surface S1 of the first portion a to expose it to the outside. At this time, the removal of the protective film material can be performed by a known dry or wet etching method.

[0137] On the other hand, according to one embodiment of the present invention, the protective film 80a formed in step (3) is a temporary protective film for preventing damage to the LED structure caused by performing step (C), and a step of forming a surface protective film surrounding the sides of the LED structure after removing the temporary protective film may be included between steps (D) and (E). That is, as Figure 11 As shown, in step (C), the protective film 5' is only used as a temporary protective film to prevent damage to the LED structure in step (D). Figure 11 (i) to (k)), before performing step (E), the protective film 5' is removed, and then a surface protective film 80 can be formed to perform the function of preventing damage to the surface of the LED structure, so that the surface protective film 80 covers the side of the LED structure. Figure 11 (m)

[0138] On the other hand, such as Figure 11However, the planar shape, size, and interval between the LED structures of the manufactured LED structure can be considered to select the embodiment. In addition, when step (D) described later is performed, the protective film can be partially etched, and when the protective film in which etching occurs is left as a surface protective film of the single LED structure finally obtained, a case in which the surface protection function cannot be properly performed can occur, and thus it can be advantageous to re-form the protective film after removing the protective film on which step (D) is performed.

[0139] The manufacturing method 1 described above can be applied to the manufacturing method 2 described above. Figure 11 The manufacturing process shown in the drawing deposits a temporary protective film material 5 on an LED wafer 100h in which a plurality of LED structures are formed (i). Figure 11 The temporary protective film material 5 deposited on the upper surface S1 of the first portion a of the doped n-type III nitride semiconductor layer, i.e., the first conductive semiconductor layer 10, between the adjacent LED structures of the LED wafer 100i on which the protective film 5 is deposited can form a temporary protective film, i.e., a protective film 5', which protects the side surfaces and upper portions of the plurality of LED structures. Then, step (D) described later is performed (k). Figure 11 The protective film 5' is removed by etching (k). Figure 12 A surface protective film, i.e., a protective film material, which is used to protect the surface of the LED structure is deposited on the LED wafer 1001 (1), and then the protective film material formed on each of the upper portions of the LED structures is removed, and thus a protective film 80 that surrounds the side surfaces of the LED structures can be formed (m). Figure 11 At this time, not only the protective film material formed on the upper portions of the LED structures but also the protective film material deposited on the upper surface S1 of the first portion a of the doped n-type III nitride semiconductor layer, i.e., the first conductive semiconductor layer 10, between the adjacent LED structures of the LED wafer 100m can be removed together, and thus the bubbling solvent can come into contact with the upper surface S1 of the first portion a in step (E) described later, and the gas bubbles generated by ultrasonic waves can penetrate the pores P formed in the first portion a, and thus the LED structures can be separated by the gas bubbles.

[0140] On the other hand, the temporary protective film material and the surface protective film material are the same as the materials of the protective film described above, and the thickness of the thin film can also be realized within the range of the thickness of the protective film described above.

[0141] Then, as step (D) of the manufacturing method 1, the LED wafer is immersed in an electrolyte, and then any one terminal of a power source is electrically connected to the LED wafer, and the remaining terminal of the power source is electrically connected to an electrode immersed in the electrolyte, and then the power source is applied to form a plurality of pores in the first portion.

[0142] Specifically, referring to Figure 11To explain, after the LED wafer 100h2 on which the protective film 80a is formed is electrically connected to an arbitrary terminal of a power source, for example, an anode, and the remaining terminal of the power source, for example, a cathode, is electrically connected to an electrode immersed in an electrolyte, a power source is applied, and then the LED wafer 100h3 on which a plurality of pores P are formed in the first portion a of the doped n-type III- nitride semiconductor layer, that is, the first conductive semiconductor layer 10 can be manufactured. At this time, the pores P can be formed from the upper surface S1 of the first portion a of the doped n-type III-nitride semiconductor layer, that is, the first conductive semiconductor layer 10, which directly contacts the electrolyte, to the thickness direction and the side surface direction of the first portion a side corresponding to the lower portion of each of the plurality of LED structures.

[0143] The electrolyte used in the step (D) can include one or more oxygen-containing acids selected from the group consisting of oxalic acid, phosphoric acid, sulfurous acid, sulfuric acid, carbonic acid, acetic acid, chlorous acid, chloric acid, bromic acid, nitrous acid, and nitric acid; more preferably, oxalic acid can be used, whereby the advantage that damage to the first conductive semiconductor layer can be minimized. In addition, the electrode can use platinum (Pt), carbon (C), nickel (Ni), gold (Au), and the like, and a platinum electrode can be used as an example. In addition, the step (D) can be applying a voltage of 3 V or more as a power source for 1 minute to 24 hours, whereby the pores P can be smoothly formed to the first portion a side corresponding to the lower portion of each of the plurality of LED structures, and whereby the LED structures can be more easily separated from the wafer by the step (E). More preferably, the voltage can be 10 V or more, and further more preferably, 30 V or less can be applied. If a voltage of less than 3 V is applied, even if the time of applying the power source is increased, the pores cannot be smoothly formed to the first portion a side corresponding to the lower portion of each of the LED structures, and thus separation by the step (E) is difficult, or even if the shape of the separated one end surface of each of the plurality of LED structures is different, the plurality of LED structures can not exhibit uniform characteristics. In addition, in the case where a voltage exceeding 30 V is applied, the pores can be formed to the lower end portion of the LED structure, that is, the second portion b, which is contiguous to the first portion a of the doped n-type III-nitride semiconductor layer, and thus a decrease in light emission characteristics can occur. In addition, in the step (E) described later, the boundary point between the first portion a and the second portion b of the doped n-type III-nitride semiconductor layer is preferably separated in the LED structure, but separation can occur at a certain point on the second portion b side beyond the boundary point due to the pores formed on the second portion b side, and thus there is a risk that an LED structure having a n-type semiconductor layer with a thickness smaller than the originally designed n-type semiconductor layer thickness can be obtained. In addition, the power source application time also has an effect similar to that of the voltage strength, and in the case where the application time is long, there is a risk that the pores are formed to the second portion b, which is a portion other than the target portion, and conversely, in the case where the application time is short, the pores are not smoothly formed, and thus the LED structures can not be easily separated.

[0144] After step (D) and before the later-described step (E), the LED wafer 100h4 in which the protective film formed on the upper surface of each of the LED structures is removed from the protective film 80a can be manufactured to perform a step of electrically connecting to the first electrode layer 40 side after the LED structures are separated from the wafer. In addition, since only the protective film formed on the upper surface of the LED structure is removed, the protective film 80 formed on the side surface of the LED structure remains, and a function of protecting the side surface of the LED structure from the outside can be performed.

[0145] In addition, after step (D) and before the later-described step (E), a step of forming other layers on the first electrode layer 40 of the LED structure can be performed, and the other layers can be, for example, a Ti / Au composite layer or a selective bonding layer 70 (refer to Figure 11 (n)) of the first electrode layer material in addition to the ITO layer, the first electrode layer 40.

[0146] After that, as step (E) of the manufacturing method 1, a step of applying ultrasonic waves to the LED wafer 100h4 to separate the plurality of LED structures from the first portion a in which the plurality of pores P are formed is performed. At this time, the ultrasonic waves can be directly applied to the LED wafer 100h4 in which the pores are formed or the ultrasonic waves can be indirectly applied by immersing the LED wafer 100h4 in which the pores are formed in a solvent. However, in a manner of collapsing the pores P of the first portion a by physical external force generated by the ultrasonic waves themselves, the pores cannot be smoothly collapsed, and when the pores are excessively formed in order to be smoothly collapsed, there is a risk that the pores are formed up to the second portion b of the LED structure, and thus a side effect of lowering the quality of the LED structure can occur.

[0147] Accordingly, according to an embodiment of the present application, the step (E) can be performed using a sonochemistry method, specifically, by immersing the LED wafer 100h4 in a bubbling solution 76 (or, a solvent), and applying ultrasonic waves to the bubbling solution 76 (or, a solvent), and the energy collapse mechanism of the bubbles generated and grown by the sonochemistry mechanism when the bubbles burst at the air holes, and thus the plurality of LED structures can be separated. For this, in detail, the ultrasonic waves are alternately generated at a relatively high pressure portion and a relatively low pressure portion in the propagation direction of the sound waves, and the generated bubbles are repeatedly compressed and expanded by the high pressure portion and the low pressure portion, and then grown into bubbles having a higher temperature and pressure, and then collapsed at the time of the collapse, and become a local hot spot generating a high temperature of, for example, 4000K level and a high pressure of 1000 atm level, and thus the air holes generated at the LED wafer are collapsed by the energy, and thus the LED structures can be separated from the wafer. Finally, the ultrasonic waves not only perform the function of generating bubbles, growing bubbles, and moving and permeating the generated bubbles to the air holes P of the first portion a in the bubbling solution (or, a solvent), but also can easily separate the plurality of LED structures from the LED wafer by the air hole collapse mechanism of collapsing the air holes P by the external force generated at the time of the burst of the bubbles having an unstable state of high temperature and high pressure, which are permeated to the air holes P thereafter, and thus the LED assembly 100' including a plurality of ultra-thin LED elements 101' can be obtained.

[0148] The foaming solution 76 (or solvent) can be used without limitation if it generates bubbles when ultrasonic waves are applied and grows into bubbles having high pressure and high temperature, and preferably the foaming solution (or solvent) can have a vapor pressure of 100 mmHg (20°C) or less, and for another example, can have a vapor pressure of 80 mmHg (20°C) or less, 60 mmHg (20°C) or less, 50 mmHg (20°C) or less, 40 mmHg (20°C) or less, 30 mmHg (20°C) or less, 20 mmHg (20°C) or less, or 10 mmHg (20°C) or less. If a solvent having a vapor pressure exceeding 100 mmHg (20°C) is used, it is not possible to normally separate in a short time, and thus there is a risk of prolonging the manufacturing time and increasing the production cost. For the foaming solution 76 satisfying the physical properties as described above, one or more selected from the group consisting of γ-butyrolactone, propylene glycol methyl ether acetate, methylpyrrolidone, and 2-methoxyethanol can be used as an example. On the other hand, a solution (or solvent) having a vapor pressure of 100 mmHg at normal temperature, for example, 20°C, can also be used, but it is to be noted that step (E) is performed by adjusting the conditions other than this, and step (E) can also be performed from a condition in which the vapor pressure of the foaming solution (or solvent) is adjusted to be 100 mmHg or less (for example, a low-temperature condition or the like). The kind of solvent that can be used in this case can be more relaxed, and for example, a solvent such as water, acetone, chloroform, alcohol, or the like can also be used.

[0149] Further, for the wavelength of the ultrasonic waves applied in step (E), it is possible to be a frequency that can become a region in which an ultrasonic chemical reaction can be induced, and specifically, it is possible to be a frequency in which a bubble can grow and collapse to become a local hot spot in which high pressure and high temperature are generated at the time of bubble collapse, and for example, it can be 10 kHz to 2 MHz, and the ultrasonic wave application time can be 1 minute to 24 hours, and accordingly, the LED structure can be easily separated from the LED wafer. Even if the wavelength of the applied ultrasonic waves is within the range, in the case of low intensity or short application time, there is a risk that the LED structure is not separated from the LED wafer or the number of LED structures that are not separated increases. Further, if the intensity of the applied ultrasonic waves is large or the application time is long, there is a risk that the LED structure is damaged.

[0150] On the other hand, in order to form the second electrode layer 60 on the first conductive semiconductor layer 10, a step of attaching the support film 9 to the LED wafer 100n to form another layer, for example, the second electrode layer 60 or an electron delay layer (not shown) on the first conductive semiconductor layer 10 can also be performed before step (E) described above is performed. Figure 11 (E) is performed in a state in which the support film 9 is attached.Figure 13 (p)). Then, a second electrode layer 60 is formed by a known method, such as depositing a second electrode layer 60 on top of multiple LED structures in the state of an attached support film 9. Figure 13 (q)) After removing the support film, an assembly of multiple ultra-thin LED elements 101 can be obtained 100.

[0151] Then, refer to Figure 13 This describes a method for manufacturing ultra-thin LED components using manufacturing method 2.

[0152] As described above, the process from forming an LED wafer to an LED wafer 100h having multiple LED structures is the same as manufacturing method 1. Then, for the LED wafer 100h having multiple LED structures formed, the following steps can be performed: Step (i), forming an insulating film 8 to cover the exposed sides of the multiple LED structures (… Figure 13 (b)); Step (ii), in order to expose the upper surface S1 of the first conductive semiconductor layer 10 between adjacent LED structures, a portion of the insulating film formed on the upper part of the first conductive semiconductor layer 10 is removed. Figure 13 (c)); Step (iii) further etch the first conductive semiconductor layer 10 in the thickness direction through the exposed upper surface S1 of the first conductive semiconductor layer to form a first conductive semiconductor layer portion with a predetermined thickness exposed below the first conductive semiconductor layer of the LED pillar on which the insulating film 8' is formed. Figure 13 (c)); Step (iv) etch the first conductive semiconductor layer portion exposing the side surfaces from both sides toward the center side. Figure 13 (d)); Step (v), removing the insulating film 8 ( Figure 13 (e)); Step (vi), forming a protective film 80 on the sides of multiple LED structures. Figure 13 (f)); Step (vii), removing the protective film formed on the upper part of the multiple LED structures to expose the first electrode layer 40 ( Figure 10 (g)); Step (viii), forming an alignment-inducing layer 70 on the first electrode layer 40. Figure 14 (h) and step (x), separating multiple LED structures from the LED wafer to manufacture an ultra-thin LED assembly 100' comprising multiple ultra-thin LED elements 101'. On the other hand, the above-described manufacturing method 2 can be performed using known methods for manufacturing LED elements, the specific description of which is based on the inventor's patent application number 2020-0050884, which is incorporated herein by reference, and the specific description of each step of manufacturing method 2 is omitted here.

[0153] At this point, in step (ⅸ), the separation of multiple LED structures can be achieved by cutting with a cutting tool or by peeling off the adhesive film.

[0154] On the other hand, through Figures 11 to 13 The protective film 80', consisting of a hole-pushing film 81 and an electron-pushing film 82 to improve luminous efficiency, can be formed as a protective film. The manufacturing method for this will refer to... Figure 14 Please provide an explanation.

[0155] With the above Figure 14 The difference lies in executing the following process twice ( Figure 14 (b), (d), (e)): During vertical etching, instead of etching to a portion of the first conductive semiconductor layer 10 of the n-type semiconductor, the first etching is performed to a portion of the second conductive semiconductor layer 30 or the photoactive layer 20, or only to the photoactive layer 20. Figure 14 (a)), then a second etching is performed to a portion of the thickness of the first conductive semiconductor layer 10. Figure 14 (c) and deposit thin film material, removing the thin film material between multiple LED structures.

[0156] Specifically, the following process is performed: when etching the LED chip in a vertical direction, the etching does not reach the n-type semiconductor, i.e., a portion of the first conductive semiconductor layer 10, but instead, the etching first only reaches the second conductive semiconductor layer 30, or a portion of the second conductive semiconductor layer 30 and the photoactive layer 20, or only reaches the photoactive layer 20. Figure 14 (a)), followed by deposition of hole-push film material 81a ( Figure 11 (b) is then removed, followed by the removal of the hole-pushing film material formed between the LED structures. Afterwards, the following process can be performed: a second re-etching to a predetermined thickness of the first conductive semiconductor layer 10 ( Figure 14 (c) Then, an electron-push film material 82a is deposited on the LED structure having the hole-push film 81b. Figure 11 (d) After that, the electron-push film material formed on the upper surface S1 of the first conductive semiconductor layer 10 between the LED structures is removed again. Figure 12 (e)). Then, the above is executed. Figure 11 and Figure 12 The process of separating LED structures in the middle ( Figure 13 Below (k), Figure 13 (c) below) or in Figure 15 The process of separating LED structures in the middle ( Figure 16 (d) and below), thus the ultra-thin LED element 103 can be separated from the LED chip.

[0157] The ultrathin LED element 101, 102, 103 obtained by the above method can be realized as an inkjet ink composition. The ink composition can also include a dispersion medium, other additives, etc. as included in a known inkjet ink composition, and the present application does not particularly limit this. However, as described above, the ultrathin LED element 101 satisfies the above specific ratio with respect to the thickness and the length of the long axis of the cross section perpendicular to the stacking direction, and has the advantage of being able to maintain a dispersed state for a long time while delaying precipitation at the time of inkjetting. In addition, the concentration of the ultrathin LED element 101 dispersed in the ink composition, and the viscosity of the ink composition can be designed to be suitable for the inkjet printing device that prints the ink composition, and the present application does not particularly limit this. In addition, the inkjet printing device, as a device that prints the ink composition containing the ultrathin LED element on the first electrode, can be in a state using a known method such as a piezoelectric method or an electrostatic method, and therefore the present application does not particularly limit the inkjet printing device and the specific method of printing on the first electrode using the inkjet printing device.

[0158] Then, as step (3) of the present application, a step of assembling the ultrathin LED element 101, which is printed on the sub-pixel region S1, S2, S3, S4 of the first electrode 311, 312, 313, for example, by an inkjet printing device, is performed in a state in which the ultrathin LED element 101 is erected in the thickness direction on the first electrode.

[0159] Even if the plurality of ultrathin LED elements 101 dispersed in the ink composition are printed to have at least two in each of the sub-pixel regions S1, S2, S3, S4 of the first electrode 311, 312, 313, a part of the ultrathin LED elements 101 can be separated from the sub-pixel region S1, S2, S3, S4 after printing. In addition, even if the ultrathin LED elements 101, 102, 103 are located within the sub-pixel region S1, S2, S3, S4, it is not necessary that all of the ultrathin LED elements 101 are erected in the thickness direction on the first electrode 311, 312, 313.

[0160] Accordingly, as described above, in the full-color LED display 1000, either one side or both sides of the thickness direction side of the ultrathin LED element 101 and the sub-pixel region S1, S2, S3, S4 within the first electrode 311, 312, 313 can also include an arrangement inducing layer 70 that induces the ultrathin LED element 101 to move into the sub-pixel region S1, S2, S3, S4 and be arranged in an erected state in the thickness direction on the first electrode 311, 312, 313.

[0161] Reference Figure 17To be more specific, in the case where the arrangement-inducing layer 70 is a charge layer 71 having a positive or negative charge, an electric field is formed in a direction perpendicular to the main surface of the first electrode 311 by electrophoresis after or simultaneously with or before printing the ink composition containing the ultra-thin LED element, so as to move and vertically arrange the ultra-thin LED element 104 to the arrangement region. In addition, in order to facilitate the movement and vertical arrangement of the ultra-thin LED element to the arrangement region, when the charge layer provided in the ultra-thin LED element is a first charge layer having a positive or negative charge, a second charge layer having a charge opposite to that of the first charge layer can also be provided on the arrangement region of the first electrode. As an example, the thickness of the first and second charge layers can be 0.1 nm to 500 nm, but as long as it is a thickness sufficient to carry a charge, the present application is not particularly limited thereto.

[0162] In addition, the strength of the electric field used to move and vertically arrange the ultra-thin LED element in the arrangement region by electrophoresis can also be appropriately changed according to the number and size of the ultra-thin LED elements in the ink composition, and the present application is not particularly limited thereto.

[0163] Alternatively, referring to Figure 3In the case where the arrangement inducing layer 70 is a bonding layer 72, the ultra-thin LED element 105 can be vertically assembled on the arrangement region by chemical bonding with the bonding layer 72 as a medium. At this time, the bonding layer 72 can be arranged on one side in the thickness direction of the ultra-thin LED element 105 and / or on the arrangement region. In addition, as an example, the bonding layer can be formed by exposing a thiol group, an amine group, a carboxyl group, a DNA single strand, or the like to the outside, and specifically, can be formed by a compound such as aminoethanethiol, 1,2-ethanedithiol, 1,4-butanedithiol, 3-mercaptopropionic acid, a DNA single strand terminated with NH2, or the like. In addition, the chemical bonding can be a covalent bond or a non-covalent bond, and as an example, in the case of a bonding layer in which a thiol group is exposed to the outside, the first electrode can be non-covalently bonded to the first electrode as a metal. In addition, when an amine and a carboxyl group are combined to form an amide bond, the reaction speed is very slow, and thus 1-Ethyl-3-(3-Dimethylaminopropyl)Carbodiimide (EDC) is added to activate the carboxyl group to form an ester intermediate, and then a strong nucleophile, i.e., a primary amine, can rapidly form an amide bond. In addition, in order to stabilize the ester intermediate using EDC, sulfo N-Hydroxysuccinimide (NHS) can be used to stably perform amide bonding. In addition, the bonding layer can include a first bonding layer formed on the ultra-thin LED element side and a second bonding layer formed on the first electrode side, and the ultra-thin LED element can be vertically assembled on the first electrode by complementary binding between a first linker in the first bonding layer and a second linker in the second bonding layer.

[0164] Alternatively, referring to Figure 4 In the case where the arrangement inducing layer 70 is a magnetic layer 73, a magnetic field is formed in a direction perpendicular to the main surface of the first electrode 311 by magnetic force after or simultaneously with, or before, printing the ink composition containing the ultra-thin LED element, so that the ultra-thin LED element 106 moves to the arrangement region and is arranged in the thickness direction. In addition, in order to facilitate the movement and vertical arrangement of the ultra-thin LED element 106 on the arrangement region, a magnetic layer can also be arranged on the arrangement region in the first electrode. The magnetic layer can be a paramagnet or a ferromagnet. In addition, as an example, the thickness of the magnetic layer 73 can be 0.1 nm to 500 nm, but the present application is not particularly limited thereto.

[0165] Then, a step of fixing and Ohmic contacting the ultra-thin LED element 104, 105, 106 erected on the first electrode 311, 312, 313 to the first electrode 311, 312, 313 can be further performed. As an example, the fixing and Ohmic contacting can be performed by a rapid thermal annealing (RTA) process at the interface between the first electrode 311, 312, 313 and the ultra-thin LED element 101. Alternatively, a fixing layer having a low melting point can be further provided on the sub-pixel region in the first electrode 311, 312, 313, and then the ultra-thin LED element 101 is erected on the arrangement region, and then heating is performed to melt and solidify the fixing layer, and thus the ultra-thin LED element 101 can be firmly fixed on the first electrode 311, 312, 313. As an example, the fixing layer can be a solder serving as an electrical and electronic material.

[0166] On the other hand, in order to improve the electrical connectivity between the ultra-thin LED element 101 and the first electrode 311, 312, 313, a step of forming a conductive metal layer 500 can be further performed after step (3). The conductive metal layer 500 can be manufactured by patterning a line of the conductive metal layer to be deposited using a photolithography process using a photosensitive material and then depositing the conductive metal layer, or by patterning and etching the deposited metal layer. This process can be performed using a known method as appropriate, and Korean Patent Application No. 10-2016-0181410 of the inventor of the present application is incorporated by reference.

[0167] In addition, in order to be electrically insulated from the upper electrode line 320 to be formed in step (4) to be described later, a step of forming an insulating layer 600 on the lower electrode line 310 at a predetermined thickness can be further performed. The insulating layer 600 can be formed by depositing a known insulating material, as an example, by depositing an insulating material such as SiO2, SiN x , by a PECVD method, or by depositing an insulating material such as AlN, GaN by a MOCVD method, or by depositing an insulating material such as Al2O, HfO2, ZrO2, etc. by an ALD method. On the other hand, the insulating layer 600 is preferably formed not to cover the upper surface of the ultra-thin LED element 101 erected and assembled, and for this purpose, the insulating layer is formed to a thickness not to cover the upper surface of the ultra-thin LED element 101, or it can also be that the insulating layer is deposited to a thickness covering the upper surface of the ultra-thin LED element 101 and then dry etching is performed until the upper surface of the ultra-thin LED element 101 is exposed.

[0168] Then, as step (4) of the present application, a step of forming an upper electrode line 320 including the second electrodes 321, 322 to be electrically connected to the opposite side of the side of the ultra-thin LED elements 104, 105, 106 to which the first electrodes 311, 312, 313 are electrically connected is performed. The upper electrode line 320 can be realized by patterning the electrode line using a known photolithography method followed by deposition of the electrode material or by deposition of the electrode material followed by dry and / or wet etching, at this time, the electrode material can be a general electrode material used as an electrode of an electrical electronic material, for which the present application is not particularly limited.

[0169] Then, as step (5) of the present application, a step of patterning the color changing layer 700 on the upper electrode line 320 to make each of the plurality of sub-pixel regions S1, S2, S3, S4 a sub-pixel region S1, S2, S3, S4 that exhibits any one of blue, green, and red colors is performed.

[0170] The ultra-thin LED element 101 provided in the sub-pixel region can irradiate a blue, white, or UV light color, in this case, the step is a step of providing a color changing layer 700 in the upper portion of the sub-pixel region in order to change the irradiated light color to a different light color for displaying a color image. Preferably, in order to further improve color purity to improve color reproducibility, and to provide light that changes the color in the color changing layer from backside light emission to frontside, for example, green / red frontside light emission efficiency, a short wave filter (not shown) is formed on the upper portion of the sub-pixel region, and the color changing layer 700 can be formed in a region in the upper portion of the short wave filter.

[0171] The description is made assuming that the ultra-thin LED element 101 is a blue LED element, a short wave filter can be formed on the upper portion of the upper electrode line 320, and if the plane in which the upper electrode line 320 is formed is not flat, a planarization layer (not shown) for planarizing the plane in which the upper electrode line 320 is formed is further formed, and then a short wave transmission filter can be formed on the upper portion of the planarization layer. The short wave transmission filter can be a multilayer film in which thin films of a high refractive index / low refractive index material are repeatedly formed, and the structure of the multilayer film can be [(0.125) SiO2 / (0.25) TiO2 / (0.125) SiO2] m (m is the number of repetitions, m is 5 or more), to transmit blue and reflect light colors having a longer wavelength than blue. In addition, the thickness of the short wave transmission filter can be 0.5 μm to 10 μm, but is not limited thereto. The method of forming the short wave transmission filter can be any one of an e-beam, sputtering, and atomic deposition method, but is not limited thereto.

[0172] Then, a color changing layer 700 can be formed on the short wave filter, and specifically, for the color changing layer 700, a green color changing layer can be patterned on the short wave transmission filter corresponding to a selected portion of the sub-pixel area, and a red color changing layer can be patterned on the short wave transmission filter corresponding to a selected portion of the sub-pixel area. The patterning method can be performed by any one or more methods selected from the group consisting of a screen printing method, a photolithography method, and a dispensing method. On the other hand, the order of patterning of the green color changing layer and the red color changing layer is not limited, and the green color changing layer and the red color changing layer can be formed at the same time or in reverse order. In addition, the red color changing layer and the green color changing layer can use a color changing layer known in the field of illumination and display, and for example, can include a color changing material that is excited by a color filter or a blue LED element to change into a target light color, such as a fluorescent material, and a known color changing material can be used. For example, the green color changing layer is a fluorescent layer including a green fluorescent material, and specifically, can include any one or more fluorescent materials selected from the group consisting of SrGa2S4:Eu, (Sr,Ca)3SiO5:Eu, (Sr,Ba,Ca)SiO4:Eu, Li2SrSiO4:Eu, Sr3SiO4:Ce,Li, β-SiALON:Eu, CaSc2O4:Ce, Ca3Sc2Si3O 12 :Ce, Caα-SiALON:Yb, Caα-SiALON:Eu, Liα-SiALON:Eu, Ta3Al5O 12 :Ce, Sr2Si5N8:Ce, (Ca,Sr,Ba)Si2O2N2:Eu, Ba3Si6O 12 N2:Eu, γ-AlON:Mn, and γ-AlON:Mn,Mg, but is not limited thereto. In addition, the green color changing layer can include a fluorescent layer including a green quantum dot material, and specifically, can include any one or more quantum dots selected from the group consisting of CdSe / ZnS, InP / ZnS, InP / GaP / ZnS, InP / ZnSe / ZnS, and perovskite green nanocrystals, but is not limited thereto.

[0173] In addition, the red color conversion layer can be a fluorescent layer including a red fluorescent material, and specifically, can include any one or more selected from the group consisting of (Sr,Ca)AlSiN3:Eu, CaAlSiN3:Eu, (Sr,Ca)S:Eu, CaSiN2:Ce, SrSiN2:Eu, Ba2Si5N8:Eu, CaS:Eu, CaS:Eu,Ce, SrS:Eu, SrS:Eu,Ce, and Sr2Si5N8:Eu, but is not limited thereto. In addition, the red color conversion layer can be a fluorescent layer including a red quantum dot material, and specifically, can include any one or more selected from the group consisting of CdSe / ZnS, InP / ZnS, InP / GaP / ZnS, InP / ZnSe / ZnS, and perovskite red nanocrystal, but is not limited thereto.

[0174] A part of the sub-pixel region is a region in which only a short-wave filter is disposed on the uppermost layer, and a green color conversion layer and a red color conversion layer are not formed on the vertical upper portion, and in this region, blue light can be irradiated. In contrast, a part of the sub-pixel region in which a green color conversion layer is formed on the upper portion of the short-wave filter can irradiate green light through the green color conversion layer. In addition, the remaining sub-pixel region is a region in which a red color conversion layer is formed on the upper portion of the short-wave filter, and can irradiate red light, and accordingly, a blue source color LED display can be implemented as a first implementation example.

[0175] In addition, it is preferable that a long-wave transmission filter be further formed on the upper portion of the green and red color conversion layers, and the long-wave transmission filter functions as a filter for preventing a decrease in color purity due to mixing of blue light emitted from the element and color-converted green / red light. The long-wave transmission filter can be formed on the upper portion of a part or all of the green color conversion layer and the red color conversion layer, and is preferably formed only on the green / red color conversion layer. At this time, the long-wave transmission filter that can be used can be a multilayer film in which a thin film of a high-refractive / low-refractive material that can achieve the purpose of transmitting a long wave that reflects blue and reflecting a short wave is repeated, and the structure can be [(0.125)TiO2 / (0.25)SiO2 / (0.125)TiO2]. m (m = number of repeated layers, m is 5 or more). In addition, the thickness of the long-wave transmission filter can be 0.5 μm to 10 μm, but is not limited thereto. The method of forming the long-wave transmission filter can be any one of an e-beam, sputtering, and an atomic layer deposition method, but is not limited thereto. In addition, in order to form the long-wave transmission filter only on the upper portion of the green / red color conversion layer, a metal mask that exposes the green / red color conversion layer and can shield an area other than the green / red color conversion layer is used, and the long-wave transmission filter can be formed only in the target area.

[0176] Then, referring to Figure 12 and Figure 19The full-color display of the second embodiment of the present application includes: a lower electrode line 310' including first electrodes 314, 315, 316 formed with a plurality of sub-pixel regions S5, S6, S7; a plurality of ultra-thin LED elements 107, 108, 109 independently emitting blue, green or red light, respectively, and including a first conductive semiconductor layer, a photoactive layer, a second conductive semiconductor layer, a ratio between a thickness in a layer stacking direction and a length of a major axis in a cross section perpendicular to the layer stacking direction being 1:0.5-1.5, and each sub-pixel region S5, S6, S7 being provided with at least two elements actually emitting light of the same color so that the plurality of sub-pixel regions S5, S6, S7 respectively independently exhibit any one of blue, green and red colors; and an upper electrode line including a second electrode 323 provided in contact with the plurality of ultra-thin LED elements 107, 108, 109.

[0177] The full-color LED display 1000 of the first embodiment described above includes the ultra-thin LED element 101 actually emitting light of the same color, and in contrast, the full-color LED display 2000 of the second embodiment uses a plurality of ultra-thin LED elements 107, 108, 109 each of which emits blue, green or red light. Each sub-pixel region S5, S6, S7 is provided with at least two elements each of which emits light of any one of blue, green and red colors. In addition, the elements provided in the sub-pixel regions S5, S6, S7 themselves emit light of the target color of blue, green or red, and thus a separate color conversion layer is not required on the second electrode 323. On the other hand, the full-color LED display 2000 of the second embodiment can further include: a substrate 401 formed with the first electrodes 314, 315, 316; a conductive metal layer 501 for reducing the resistance of a contact portion between the first electrodes 314, 315, 316 and the ultra-thin LED elements 107, 108, 109; and an insulating layer 601 filling between the first electrodes 314, 315, 316 and the second electrode 323.

[0178] In addition, the full-color LED display 2000 of the second embodiment of the present application can be manufactured by a method including: step (I) of preparing a lower electrode line 310' including first electrodes 314, 315, 316 formed with a plurality of sub-pixel regions S5, S6, S7; step (II) of processing blue, green, and red ultra-thin LED element ink compositions on the first electrodes 314, 315, 316 so that the plurality of sub-pixel regions independently emit any one of blue, green, and red light, and so that each of the sub-pixel regions S5, S6, S7 is provided with at least two ultra-thin LED elements, wherein the blue, green, and red ultra-thin LED element ink compositions include a plurality of ultra-thin LED elements 107, 108, 109 by light color, the ultra-thin LED elements 107, 108, 109 including a first conductive semiconductor layer, a photoactive layer, and a second conductive semiconductor layer stacked, and a ratio between a thickness in a stacking direction of the layers and a length of a major axis in a cross section perpendicular to the stacking direction is 1:0.5-1.5; step (III) of vertically standing the ultra-thin LED elements 107, 108, 109 processed on the sub-pixel regions S5, S6, S7 in a thickness direction on the first electrodes 314, 315, 316; and step (IV) of forming an upper electrode line including a second electrode 323 to be electrically connected to an opposite side opposite to a side of the ultra-thin LED elements 107, 108, 109 assembled on the first electrodes 314, 315, 316.

[0179] The steps of the manufacturing method of the second embodiment are the same as those of the manufacturing method of the first embodiment except that three ink compositions containing ultra-thin LED elements exhibiting three colors different from each other are used as the ink compositions in step (II), and thus a detailed description is omitted. Note that the light colors included in the second embodiment can use ultra-thin LED elements emitting light of other colors in addition to the three colors described above, and accordingly the ink compositions can also include ink compositions of other light emission colors.

[0180] Hereinafter, the present application is more specifically described through the following examples, but the following examples do not limit the scope of the present application, but should be interpreted for understanding the present application.

[0181] (Preparation Example 1)

[0182] A conventional LED wafer (Epistar) was prepared in which an undoped n-type Group III nitride semiconductor layer, a Si-doped n-type Group III nitride semiconductor layer (4 μm thick), a photoactive layer (0.45 μm thick), and a p-type Group III nitride semiconductor layer (0.05 μm thick) were sequentially stacked on a substrate. On the prepared LED wafer, ITO (0.15 μm thick) was sequentially deposited as a first electrode layer, SiO2 (1.2 μm thick) as a first mask layer, and Al (0.2 μm thick) as a second mask layer, and then a transfer pattern SOG resin layer was transferred onto the second mask layer using a nanoimprint apparatus. Thereafter, the SOG resin layer was hardened using RIE, and a resin pattern layer was formed by etching the remaining resin portion of the resin layer using RIE. Thereafter, the second mask layer was etched along the pattern using ICP, and the first mask layer was etched using RIE. Thereafter, the first electrode layer, the p-type Group III nitride semiconductor layer, and the photoactive layer were etched using ICP, and then the doped n-type Group III nitride semiconductor layer was etched to a thickness of 0.78 μm, and then in order to make the side surface of the etched doped n-type Group III nitride semiconductor layer perpendicular to the layer side surface, a KOH wet etching was performed to manufacture an LED wafer in which a plurality of LED structures (850 nm in diameter and 850 nm in height) were formed. Thereafter, a protective film material, i.e., SiN x (Referring to Figure 20 the SEM photograph, the deposition thickness was 52.5 nm and 72.5 nm with respect to the side surface of the LED structure), and then the protective film material formed between the plurality of LED structures was removed by a reactive ion etching machine to expose the upper surface S1 of the first portion a of the doped n-type Group III nitride semiconductor layer.

[0183] Thereafter, the LED wafer on which the temporary protective film was formed was immersed in an electrolyte, i.e., 0.3 M aqueous oxalic acid solution, and then the anode terminal connected to a power source, and the cathode terminal connected to a platinum electrode immersed in the electrolyte, and then a voltage of 10 V was applied for 5 minutes, as shown in FIG. 6. Figure 21As shown in the SEM image, multiple pores are formed from the surface of the first portion a of the doped n-type III nitride semiconductor layer to a depth of 600 nm. Subsequently, a temporary protective film was removed by RIE, followed by the deposition of a 50 nm thick surface protective film, Al2O3, on the LED wafer, with the side of the LED structure as the reference. The surface protective films formed on the upper parts of the multiple LED structures and the surface protective film formed on the upper surface S1 of the first portion a of the doped n-type III nitride semiconductor layer were removed by ICP, exposing the upper surface S1 of the first portion a of the doped n-type III nitride semiconductor layer and the upper surface of the LED structure. The LED wafer was then immersed in a foaming solution, γ-butyrolactone, and then irradiated with ultrasound at a frequency of 40 kHz for 10 minutes to generate bubbles. These bubbles collapsed into the pores formed in the doped n-type III nitride semiconductor layer, thus... Figure 22 The SEM images show an ultra-thin LED assembly containing ultra-thin LED elements, formed by separating multiple LED structures from a wafer. Additionally, as... Figure 22 It can be confirmed that there are no unseparated LED structures on the chip.

[0184] (Compare Example 1)

[0185] A rod-shaped LED element assembly with a diameter of 650 nm and a height of 4.2 μm and having the same stacked structure as in Example 1 was fabricated from LED wafers using conventional methods.

[0186] (Experimental Example 1)

[0187] LED element assemblies prepared according to Preparation Example 1 and Comparative Preparation Example 1 were respectively immersed in acetone and then dispersed by ultrasonic irradiation at 100W. The absorbance was measured at 15-minute intervals to detect and confirm the dispersion state of the LED elements after 2 hours. The spectral area of ​​the visible light region from 380nm to 780nm was normalized using the detection results. ​ The absorbance curves for each time period are shown.

[0188] pass ​ It can be confirmed that the ultra-thin LED element of Preparation Example 1 has excellent long-term dispersion retention in acetone solvent compared to the rod-shaped LED element of Comparative Preparation Example 1.

[0189] The above describes one embodiment of the present invention. However, the concept of the present invention is not limited to the embodiment presented in this specification. Those skilled in the art who understand the concept of the present invention can easily propose other embodiments by adding, changing, deleting, or adding constituent elements within the same conceptual scope, and these are also included within the conceptual scope of the present invention.

Claims

1. A full-color LED display comprising: a lower electrode line including a first electrode formed with a plurality of sub-pixel regions; a plurality of super-thin LED elements configured to have at least two elements per sub-pixel region, each super-thin LED element including a first conductive semiconductor layer which is an n-type III-nitride semiconductor layer, a light active layer, a second conductive semiconductor layer which is a p-type III-nitride semiconductor layer, and at least one of a hole push film configured to surround an exposed side of the second conductive semiconductor layer or an exposed side of at least a portion of the light active layer to move holes on the exposed side surface side toward a center side, and an electron push film configured to surround an exposed side of the first conductive semiconductor layer to move electrons on the exposed side surface side toward the center side, each super-thin LED element being vertically disposed on the first electrode in a layer stacking direction of the layers with a ratio between a thickness in the layer stacking direction and a length of a major axis in a cross section perpendicular to the layer stacking direction being 1:0.5-1.5, and actually emitting light of the same color; and an upper electrode line including a second electrode disposed on the plurality of super-thin LED elements; and a color changing layer patterned on the second electrode corresponding to the sub-pixel regions to make each sub-pixel region a sub-pixel region exhibiting any one of blue, green, and red colors.

2. A full-color LED display comprising: a lower electrode line including a first electrode formed with a plurality of sub-pixel regions; a plurality of super-thin LED elements independently emitting blue, green, or red light, respectively, and including a first conductive semiconductor layer which is an n-type III-nitride semiconductor layer, a light active layer, a second conductive semiconductor layer which is a p-type III-nitride semiconductor layer, and at least one of a hole push film configured to surround an exposed side of the second conductive semiconductor layer or an exposed side of at least a portion of the light active layer to move holes on the exposed side surface side toward a center side, and an electron push film configured to surround an exposed side of the first conductive semiconductor layer to move electrons on the exposed side surface side toward the center side, each super-thin LED element being vertically disposed on the first electrode in a layer stacking direction of the layers with a ratio between a thickness in the layer stacking direction and a length of a major axis in a cross section perpendicular to the layer stacking direction being 1:0.5-1.5, wherein each sub-pixel region is configured to have at least two elements actually emitting light of the same color to make the plurality of sub-pixel regions independently exhibit any one of blue, green, and red colors, respectively; and an upper electrode line including a second electrode disposed in upper contact with the plurality of super-thin LED elements.

3. The full-color LED display according to claim 1 or 2, wherein The arrangement-inducing layer is a magnetic layer, a charge layer, or a bonding layer.

4. The full-color LED display according to claim 1 or 2, wherein 5. The full-color LED display according to claim 1 or 2, wherein The maximum surface area of the ultra-thin LED element is 16 μm 2 The following. The thickness of the ultrathin LED element is 2.7 μm or less.

6. The full-color LED display according to claim 1 or 2, wherein The ultrathin LED element further includes an electron-delay layer on the opposite side of the first conductive semiconductor layer to the light-active layer, so that the number of electrons and holes recombined in the light-active layer is balanced.

7. The full-color LED display according to claim 6, wherein The electron-delay layer includes one or more selected from the group consisting of CdS, GaS, ZnS, CdSe, CaSe, ZnSe, CdTe, GaTe, SiC, ZnO, ZnMgO, SnO2, TiO2, In2O3, Ga2O3, Si, poly-p-phenylenevinylene and derivatives thereof, polyaniline, poly(3-alkylthiophene), and poly-p-phenylene.

8. The full-color LED display according to claim 6, wherein The first conductive semiconductor layer is a doped n-type group-III nitride semiconductor layer, and the electron-delay layer is a group-III nitride semiconductor having a lower doping concentration than the first conductive semiconductor layer. The protective film surrounds the exposed side of the ultrathin LED element.

9. The full color LED display of claim 1 or 2, wherein, 10. The full-color LED display according to claim 1 or 2, wherein The ultrathin LED element includes both the hole-pushing film and the electron-pushing film, the electron-pushing film being disposed as the outermost layer, and the outermost layer surrounding the side of the first conductive semiconductor layer, the light-active layer, and the second conductive semiconductor layer.

11. The full-color LED display according to claim 1 or 2, wherein 12. The full-color LED display according to claim 1 or 2, wherein The hole pushing film comprises one or more selected from the group consisting of AlN X , Zr02, M0O, Sc203, La203, MgO, Y203, Al203, Ga203, Ti02, ZnS, Ta205, and n-MoS2.

13. The full-color LED display according to claim 1, wherein The electron-transporting film comprises one or more selected from the group consisting of Al2O3, HfO2, SiN x , SiO2, ZrO2, Sc2O3, AlN x , and Ga2O3. The light color is blue, white, or UV.

14. A method of manufacturing a full-color LED display, comprising: Step (1), preparing a lower electrode line including a first electrode formed with a plurality of sub-pixel regions; Step (2), processing an ink composition on the first electrode to dispose at least two ultrathin LED elements in each sub-pixel region, wherein the ink composition includes a plurality of ultrathin LED elements, and each of the plurality of ultrathin LED elements includes, in the order: a first conductive semiconductor layer that is an n-type group-III nitride semiconductor layer; a light-active layer; ​ a second conductive semiconductor layer which is a p-type Group III nitride semiconductor layer; and at least one of a hole pushing film and an electron pushing film, and a ratio between a thickness in a stacking direction of the layers and a length of a major axis in a cross section perpendicular to the stacking direction is 1:0.5-1.5, and actually emits light of the same color, wherein the hole pushing film is configured to surround an exposed side surface of the second conductive semiconductor layer or an exposed side surface of at least a part of the photoactive layer as well as the exposed side surface of the second conductive semiconductor layer to move holes on the exposed side surface side to a center side; and the electron pushing film is configured to surround an exposed side surface of the first conductive semiconductor layer to move electrons on the exposed side surface side to the center side; Step (3), assembling the ultra-thin LED element processed on the sub-pixel region on the first electrode in a thickness direction vertically; Step (4), forming an upper electrode line including a second electrode to be electrically connected to an opposite side opposite to a side of the ultra-thin LED element assembled on the first electrode; and Step (5), patterning a color changing layer on the second electrode corresponding to the sub-pixel region to make each of the plurality of sub-pixel regions a sub-pixel region presenting any one of blue, green and red colors.

15. A full-color LED display manufacturing method, comprising: Step (I), preparing a lower electrode line including a first electrode formed with a plurality of sub-pixel regions; Step (II), processing a blue ultra-thin LED element ink composition, a green ultra-thin LED element ink composition and a red ultra-thin LED element ink composition on the first electrode to make the plurality of sub-pixel regions respectively and independently present light of any one of blue, green and red colors, and make each sub-pixel region be configured with at least two ultra-thin LED elements, wherein the blue ultra-thin LED element ink composition, the green ultra-thin LED element ink composition and the red ultra-thin LED element ink composition include a plurality of ultra-thin LED elements according to light colors, each of the ultra-thin LED elements including layers of: a first conductive semiconductor layer which is an n-type Group III nitride semiconductor layer; a photoactive layer; a second conductive semiconductor layer which is a p-type Group III nitride semiconductor layer; and at least one of a hole pushing film and an electron pushing film, and a ratio between a thickness in a stacking direction of the layers and a length of a major axis in a cross section perpendicular to the stacking direction is 1:0.5-1.5, wherein the hole pushing film is configured to surround an exposed side surface of the second conductive semiconductor layer or an exposed side surface of at least a part of the photoactive layer as well as the exposed side surface of the second conductive semiconductor layer to move holes on the exposed side surface side to a center side; and the electron pushing film is configured to surround an exposed side surface of the first conductive semiconductor layer to move electrons on the exposed side surface side to the center side; Step (III), assembling the ultra-thin LED element processed on the sub-pixel region on the first electrode in a thickness direction vertically; and Step (5), patterning a color changing layer on the second electrode corresponding to the sub-pixel region to make each of the plurality of sub-pixel regions a sub-pixel region presenting any one of blue, green and red colors. Step (IV) forming an upper electrode line including a second electrode to be electrically connected to the opposite side of the ultra-thin LED element assembled on the first electrode on one side.

Images