Ultra-thin LED electrode assembly, manufacturing method thereof and light source comprising ultra-thin LED electrode assembly

Abstract

The invention relates to an LED electrode assembly, in particular to an ultra-thin LED electrode assembly, a manufacturing method of the ultra-thin LED electrode assembly and a light source comprising the ultra-thin LED electrode assembly. Thus, even an LED element having a small aspect ratio in which it is difficult to obtain positive dielectric power can be self-aligned at a desired electrode, and the LED element can be self-aligned at the electrodes regardless of the distance between the two electrodes forming the electric field and the size of the LED element.

Description

Technical Field

[0001] The present invention relates to an LED electrode assembly, and more particularly, to an ultra-thin LED electrode assembly, a method of manufacturing the same, and a light source. Background Art

[0002] LEDs can achieve excellent color perception and high efficiency, and are environmentally friendly substances, so they can be used as core raw materials for various light sources and displays. In view of this market situation, recently, research and development of LED raw materials that can achieve high efficiency, low cost, and high stability have been actively carried out.

[0003] Regarding research in this raw material field, recently, in order to achieve high-resolution and high-brightness light sources, attempts have been made to reduce the size of LED elements used in light sources from mini-LEDs to micro-LEDs, and even nano-LEDs. However, in this attempt, there is a technical difficulty in how to install LED elements that have been reduced to a size indistinguishable to the naked eye on electrodes that have become smaller without defects.

[0004] Recently, attempts have been made to overcome this difficulty through self-alignment in which an LED element moves and is installed on an electrode by itself under the dielectric force that the LED element experiences under an electric field. As an example, Korean Registered Patent Publication No. 10-2414266 discloses a display that is embodied in such a way that an LED element is self-aligned across two electrodes by using a dielectric force through an electric field formed between the two electrodes.

[0005] However, regarding the self-alignment of LED elements using dielectric force, in terms of the movement and alignment mechanism of the elements, only when an LED element receives a positive dielectric force that moves between two electrodes forming an electric field can it be installed in contact with the two electrodes. If the length of the LED element is less than the interval between the two electrodes, it can only be aligned in contact with one side of the two electrodes. Therefore, in either case, it is impossible to align the LED element in electrical contact with two adjacent electrodes using the positive dielectric force. In addition, the positive dielectric force, which is the main force for self-aligning LED elements, is favorable for rod-shaped LED elements with a large aspect ratio in shape, and there is a need to limit the shape of the LED element, the length of the LED element, and the interval between the two electrodes so that self-alignment such as making the interval between the two electrodes less than or equal to the length of the LED element can be achieved. Summary of the Invention

[0006] Problems to be Solved

[0007] The present invention is proposed to solve the above problems. The object of the present invention is to provide an ultra-thin LED electrode assembly, a manufacturing method thereof, and a light source including the same, which can overcome the limitations of self-alignment based on positive dielectric force, enable LED elements with a small aspect ratio that cannot withstand positive dielectric force to perform self-alignment, and can achieve self-alignment of LED elements on electrodes regardless of the distance between two electrodes and the size of the LED elements.

[0008] Moreover, another object of the present invention is to provide an ultra-thin LED electrode assembly, a manufacturing method thereof, and a light source including the same, which can increase the ratio of ultra-thin LED elements that are installed in a drivable manner by means of an AC power supply in an ultra-thin LED element that achieves self-alignment on an electrode, so that the light-emitting surface of the LED element that is driven while minimizing side contact that may cause electrical short circuits can be installed facing the user or the required front surface.

[0009] Solution to the problem

[0010] To solve the above problems, the present invention provides a manufacturing method of an ultra-thin LED electrode assembly, which includes: a step of introducing a solution having a plurality of ultra-thin LED elements into a first electrode line in which at least two first electrodes having a top surface are spaced apart from each other; a step of applying a power supply having a frequency of 500 Hz or less to the first electrode to form an electric field; a step of moving the ultra-thin LED elements located in the electric field into the top surface of the first electrode; and a step of forming a second electrode line on the ultra-thin LED elements disposed in the top surface of the first electrode.

[0011] According to an embodiment of the present invention, the frequency of the power supply may be 1 Hz to 500 Hz, and the voltage may be 5 Vpp to 100 Vpp.

[0012] Moreover, the viscosity of the solvent in the solution may be 50 cP or less.

[0013] Moreover, the dielectric constant (ε) of the solvent in the solution may be 5 to 50.

[0014] Moreover, the ultra-thin LED element may be formed by laminating a plurality of layers including a first conductive semiconductor layer, a photoactive layer, and a second conductive semiconductor layer, and further has a rotation induction film for surrounding the side surface of the ultra-thin LED element in order to generate a rotational torque with respect to an axial direction perpendicular to the direction in which the plurality of layers are laminated.

[0015] Moreover, the dielectric constant (ε) of the rotation induction film may be 3 to 26.

[0016] Further, in the ultra-thin LED element, the ratio (b / a) of the major axis length (a) to the thickness (b) which is the length in the stacking direction of the plurality of layers in a cross-section perpendicular to the stacking direction of the layers may be greater than 0 to 2.0 or less.

[0017] Further, the ratio (b / a) of the ultra-thin LED element may be greater than 0 to 1.8 or less.

[0018] Moreover, the present invention provides an ultra-thin LED electrode assembly, which includes: a first electrode line including at least two first electrodes spaced apart from each other with their sides facing each other; a plurality of ultra-thin LED elements including a first ultra-thin LED element located within the top surface of the first electrode; and a second electrode line disposed on the first ultra-thin LED element, and the placement ratio within the top surface of the first electrode calculated according to the following Mathematical Formula 1 satisfies 40% or more.

[0019] [Mathematical Formula 1]

[0020]

[0021] Wherein, the number of ultra-thin LED elements means the total number of ultra-thin LED elements and the number of first ultra-thin LED elements disposed within a unit area (1 mm 2 ) of the first electrode line.

[0022] According to an embodiment of the present invention, the ultra-thin LED element is formed by stacking a plurality of layers including a first conductive semiconductor layer, a photoactive layer, and a second conductive semiconductor layer, and includes a first surface and a second surface facing each other in the thickness direction. The drivable installation ratio, which is the ratio of the total number of third ultra-thin LED elements installed in such a manner that the first surface contacts the top surface of the first electrode and the second surface contacts the second electrode line and the total number of fourth ultra-thin LED elements installed in such a manner that the second surface contacts the top surface of the first electrode and the first surface contacts the second electrode line among the number of first ultra-thin LED elements within a unit area (1 mm 2 ) of the first electrode line, is 40% or more. More preferably, it may be 45% or more, 50% or more, 55% or more, 60% or more, or 70% or more.

[0023] Further, the interval between adjacent first electrodes may be 2 μm to 10 μm.

[0024] Further, in the ultra-thin LED element, the thickness which is the length in the stacking direction of the plurality of layers may be 0.5 μm to 1.5 μm, and the major axis length in a cross-section perpendicular to the stacking direction of the plurality of layers may be 0.5 μm to 3.0 μm.

[0025] Moreover, the placement ratio within the top surface of the first electrode calculated according to Mathematical Formula 1 can be 80% or more, and the drivable mounting ratio can be 50% or more.

[0026] Furthermore, the present invention provides a light source, which includes the ultra-thin LED electrode assembly of the present invention.

[0027] According to an embodiment of the present invention, it may further include a color conversion substance excited by the light irradiated from the ultra-thin LED electrode assembly.

[0028] Moreover, the ultra-thin LED element included in the ultra-thin LED electrode assembly may be an element that emits one of the light colors of UV, blue, green, yellow, amber, and red.

[0029] Hereinafter, the terms used in the present invention will be defined.

[0030] In the description of the examples of the present invention, when it is described as being formed "above", "on the upper part", "above", "below", "on the lower part", "below" each layer (s) or region (s), "above", "on the upper part", "above", "below", "on the lower part", "below" include both the meanings of "directly" and "indirectly".

[0031] Moreover, as a term used in the present invention, the "drivable mounting ratio" means the number ratio of the entire LED elements mounted within the top surface of the first electrode that are mounted in a drivable form. At this time, the LED elements mounted in a drivable form mean the LED elements mounted in such a manner that the first surface facing the thickness direction in which the multiple layers forming the LED elements are stacked contacts the top surface of the first electrode and the LED elements mounted in such a manner that the second surface of the LED element contacts the top surface of the first electrode. As a result, the drivable mounting ratio is the ratio of the total number (L) of the first ultra-thin LED elements within the top surface of the first electrode per unit area (1 mm 2 ) of the first electrode line to the sum of the number (M) of the ultra-thin LED elements mounted in such a manner that the first surface contacts the top surface of the first electrode and the number (N) of the ultra-thin LED elements mounted in such a manner that the second surface contacts the top surface of the first electrode, and is calculated by the formula [(M + N) / L] × 100.

[0032] On the other hand, it should be clarified that the present invention was invented after receiving support from the following national R & D projects.

[0033] [National R & D Project 1 Supporting this Invention]

[0034] [Project ID]1711130702[Project ID]2021R1A2C2009521

[0035] [Partial name] Ministry of Science and ICT, Korea [Name of project management (specialty) agency] Korea Research Foundation

[0036] [Research Project Name] Project to Support Mid-Level Researchers

[0037] [Research Topic Name] Dot-LED Raw Materials and Display Source / Application Technology Development

[0038] [Contribution rate] 50 / 100 [Project execution organization name] Kookmin University Industry-Academic Cooperation Group

[0039] [Study period] March 1, 2021 to February 28, 2026

[0040] [National R&D Project 2 to support this invention]

[0041] [Project ID] 1711199993 [Project ID] 00281346 (RS-2023-00281346)

[0042] [Partial name] Ministry of Science and ICT, Korea [Name of project management (specialty) agency] Korea Research Foundation

[0043] [Research Project Name] Nano and Raw Material Technology Development Project (Strategic)

[0044] [Research topic name] Development of raw materials and process technology for 300ppi-class high-resolution inorganic light-emitting display that can achieve more than 30% intrinsic stretch [Contribution rate] 50 / 100

[0045] [Project implementing organization name] Hongik University Industry-Academic Cooperation Group, South Korea [Research period] August 1, 2023 - December 31, 2027

[0046] Effects of the Invention

[0047] The method for manufacturing the ultra-thin LED electrode assembly of the present invention can place the LED element at a high ratio within one electrode surface without being constrained by the distance between two electrodes forming an electric field or the size of the LED element, even when using an LED element having a small aspect ratio that is difficult to receive positive dielectric force or having no additional layer such as a magnetic layer for being attracted by the electrode. Furthermore, among the ultra-thin LED elements placed on the electrode surface, the ratio of the ultra-thin LED elements that are installed in a manner that can be driven by an AC power source is increased to minimize side contacts that can cause electrical short circuits, thereby being widely used as various light sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figures 1 to 2 It is a diagram of an ultra-thin LED electrode assembly based on an embodiment of the present invention. Figure 1 It is a top view of the ultra-thin LED electrode assembly. Figure 2 It is Figure 1 A schematic cross-sectional view of the X-X' boundary line of

[0049] Figure 3 It is a cross-sectional view of an ultra-thin LED element included in an embodiment of the present invention.

[0050] Figure 4 It is a schematic diagram for explaining the self-alignment of the ultra-thin LED element based on the dielectrophoretic force. Figure 4 Part (a) of Figure 4 is a diagram of treating a solution including an ultra-thin LED element with a first electrode separated from each other. Figure 4 Part (b) of

[0051] Figures 5 to 7 is a graph showing the distances moved by the ultra-thin LED element simulated under different conditions in a state where a solution of a cylindrical ultra-thin LED element including an n-type conductive semiconductor layer, a photoactive layer, and a p-type conductive semiconductor layer is treated on a first electrode with a width of 10 μm separated from each other by a distance of 2 μm, the thickness as the length in the stacking direction of multiple layers is 1.05 μm, and the surface diameter perpendicular to the stacking direction is 750 nm. Figure 5 is a graph showing the distances moved by the ultra-thin LED element simulated under the action of four forces at different frequencies in a state where the voltage of the power supply applied to the first electrode is fixed at 10 Vpp. Figure 6 is a graph showing the distances moved by the ultra-thin LED element simulated by changing the type of solvent. Figure 7 is a graph showing the distances moved by the ultra-thin LED element simulated by changing the voltage of the applied power supply.

[0052] Figure 8 It is a cross-sectional view of an ultra-thin LED element according to an embodiment of the present invention.

[0053] Figure 9 It is a schematic diagram showing that the ultra-thin LED element placed in a solvent above the first electrode with an electric field formed in the S3 step of an embodiment of the present invention moves into the top surface of the first electrode by electroosmotic pressure and then achieves self-alignment. Figure 9Part (a) is a diagram that patterns the rotational torque generated in the element with the x-axis perpendicular to the thickness direction d of the ultra-thin LED element. Figure 9 Part (b) is a diagram that patterns the method of mounting one end face in the thickness direction of the ultra-thin LED element in contact with the top surface of the first electrode by means of rotational torque.

[0054] Figure 10 This is a cross-sectional view of an ultra-thin LED element according to an embodiment of the present invention.

[0055] Figure 11 This is a schematic diagram of a light source based on an embodiment of the present invention.

[0056] Figure 12 and Figure 13 This is a schematic diagram of light sources according to multiple embodiments of the present invention.

[0057] Figures 14 to 18 This is an SEM photograph taken after step S3 in the manufacturing process of an ultra-thin LED electrode assembly according to multiple embodiments of the present invention.

[0058] Figure 19 This is a photograph taken of the state of an ultra-thin LED electrode assembly according to Example 1 emitting light after applying a 5V DC driving power supply. Detailed Description of the Embodiment

[0059] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those of ordinary skill in the art to which the present invention pertains can easily implement it. The present invention is not limited to the embodiments described herein and can be implemented in various different forms.

[0060] Refer to Figures 1 to 3 The following is an explanation. An ultra-thin LED electrode assembly 1000 according to an embodiment of the present invention includes: a first electrode wire 210, at least two first electrodes 211, 212 having top surfaces are spaced apart from each other in a manner facing the side surfaces; a plurality of ultra-thin LED elements 100; and a second electrode wire 220 disposed on the ultra-thin LED elements 100.

[0061] The manufacturing of the ultra-thin LED electrode assembly 1000 according to an embodiment of the present invention may include the following steps: a step of (step S1) introducing a first electrode line 210 having at least two first electrodes 211, 212 with opposite sides facing each other into a solution having a plurality of ultra-thin LED elements 100; a step of (step S2) applying a power supply with a frequency of 500 Hz or less to adjacent first electrodes 211, 212 to form an electric field; a step of (step S3) moving the ultra-thin LED elements 100 located within the electric field into the top surfaces of the first electrodes 211, 212; and a step of (step S4) forming a second electrode line 220 on the ultra-thin LED elements 100A, 100B, 100C disposed within the top surfaces of the first electrodes 211, 212.

[0062] First, as step S1, a step of introducing a solution including the ultra-thin LED elements 100 into a first electrode line 210 including at least two first electrodes 211, 212 will be described.

[0063] The first electrode line 210 includes at least two first electrodes 211, 212.

[0064] The first electrodes 211, 212 provide top surfaces, which are mounting surfaces for mounting the ultra-thin LED elements 100 introduced into the first electrode line 210. The top surfaces may be the exposed surfaces of the first electrodes 211, 212 that are substantially parallel to the surface of the base substrate 300 on which the first electrodes 211, 212 are formed.

[0065] Moreover, the first electrodes 211, 212 perform the function of forming an electric field that enables the movement and alignment of the ultra-thin LED elements 100 during the manufacturing process of the ultra-thin LED electrode assembly. For this purpose, at least two of the first electrodes 211, 212 are formed to be spaced apart from each other so as to form an electric field by means of the applied power supply. Also, the first electrodes 211, 212 may, together with the second electrodes 221, 222, perform the function of drive electrodes for causing the ultra-thin LED elements 100 to emit light in the realized ultra-thin LED electrode assembly 1000. In other words, when driving, the same type of power supply is applied to the first electrodes 211, 212. Therefore, even if the spacing between the first electrodes 211, 212 is designed to be narrow, there is no need to worry about electrical short circuits when driving the ultra-thin LED electrode assembly 1000. On the contrary, when manufacturing the ultra-thin LED electrode assembly 1000, a strong electric field can be formed. Thus, it is beneficial for the movement and alignment of the introduced ultra-thin LED elements 100, and the limitation on the design of the spacing between the first electrodes is reduced, thereby having the advantage of facilitating the design of the first electrode line 210.

[0066] On the other hand, the specific circuit design of the first electrode lines 210 in which the first electrodes 211 and 212 are designed to perform the functions described above can be appropriately adopted and modified by using the known circuit design techniques in the field of light sources. Therefore, the present invention does not impose special restrictions thereon. Moreover, the number, thickness, width, shape, and their arrangement patterns of the first electrodes 211 and 212 can adopt the known light source electrode lines or be appropriately modified according to requirements. Therefore, the present invention does not impose special restrictions thereon. As an example, the first electrodes 211 and 212 can be aluminum, chromium, gold, silver, copper, graphene, ITO, or their alloys, etc. The width can be 2 μm to 50 μm, and the thickness can be 0.1 μm to 100 μm.

[0067] Moreover, the first electrodes 211 and 212 can be formed on the base substrate 300. The base substrate 300 can perform the function of a support for supporting the ultra-thin LED electrode assembly. The base substrate 300 can be a known substrate used for light sources such as displays. The present invention does not impose special restrictions on the material, area, thickness, etc. of the base substrate 300. As an example, the base substrate 300 can be one selected from the group consisting of glass, plastic, ceramic, and metal, but is not limited thereto. Moreover, preferably, the base substrate 300 can use a transparent material to minimize the light loss emitted from the ultra-thin LED element 100. And, as an example, the base substrate 300 can be a curved raw material. And, the size and thickness of the base substrate 300 can be appropriately modified in consideration of the size and number of the ultra-thin LED elements and the specific design of the first electrode lines 210. The present invention does not impose special restrictions thereon.

[0068] On the other hand, different from Figure 2 as shown, the first electrode lines 210 can be formed on a passivation layer having a flat surface that is not the base substrate 300, and known circuit components such as thin film transistors can be disposed below the passivation layer.

[0069] Moreover, the solution having a plurality of ultra-thin LED elements 100 introduced into the above-mentioned first electrode lines 210 includes the ultra-thin LED elements 100 and a solvent.

[0070] The ultra-thin LED element 100 can be a known LED element for a light source. Along the direction of stacking of multiple layers, the ultra-thin LED element 100 can include a first conductivity semiconductor layer 110, a second conductivity semiconductor layer 130, and a photoactive layer 120 disposed between the first conductivity semiconductor layer 110 and the second conductivity semiconductor layer 130.

[0071] Further, one of the first conductivity semiconductor layer 110 and the second conductivity semiconductor layer 130 may include at least one n-type semiconductor layer, and the other conductivity semiconductor layer may include at least one p-type semiconductor layer. Hereinafter, the direction in which these multiple layers are stacked is defined as the thickness direction of the ultra-thin LED element 100, and the surfaces of the ultra-thin LED element 100 facing each other in the thickness direction are respectively described as the first surface and the second surface. As an example, in the case of an ultra-thin LED element formed of the first conductivity semiconductor layer 110, the photoactive layer 120, and the second conductivity semiconductor layer 130, the first surface is one surface of the first conductivity semiconductor layer 110 or the second conductivity semiconductor layer 130, and the second surface is one surface of the second conductivity semiconductor layer 130 or the first conductivity semiconductor layer 110.

[0072] In the case where the first conductivity semiconductor layer 110 includes an n-type semiconductor layer, the n-type semiconductor layer may be selected to have a semiconductor material with a structural 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 of InAlGaN, GaN, AlGaN, InGaN, AlN, InN, etc., and a first conductivity dopant (such as Si, Ge, Sn, etc.) may be doped. According to a preferred example of the present invention, the thickness of the first conductivity semiconductor layer 110 including the n-type semiconductor layer may be 0.2 μm to 3 μm, but is not limited thereto.

[0073] Further, in the case where the second conductivity semiconductor layer 130 includes a p-type semiconductor layer, the p-type semiconductor layer may be selected to have a semiconductor substance with a structural 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 of InAlGaN, GaN, AlGaN, InGaN, AlN, InN, etc., and a second conductivity dopant (such as Mg) may be doped. According to a preferred example of the present invention, the thickness of the second conductivity semiconductor layer 130 including the p-type semiconductor layer may be 0.01 μm to 0.35 μm, but is not limited thereto.

[0074] Then, the photoactive layer 120 may be formed between the first conductive semiconductor layer 110 and the second conductive semiconductor layer 130 and formed into a single quantum well structure or a multi - quantum well structure. As long as it is the photoactive layer included in a general LED element used for lighting, displays, etc., the photoactive layer 120 can be used without limitation. A cladding layer (not shown) doped with a conductive dopant may be formed on and / or under the photoactive layer 120, and the cladding layer doped with the conductive dopant may be implemented as an AlGaN layer or an InAlGaN layer. In addition, substances such as AlGaN and AlInGaN can also be used as the photoactive layer 120. For such a photoactive layer 120, 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, respectively, to the photoactive layer will undergo electron - hole pair recombination in the photoactive layer, thereby emitting light. According to a preferred embodiment of the present invention, the thickness of the photoactive layer 120 may be 30 nm to 300 nm, but is not limited thereto.

[0075] Moreover, it should be noted that the ultra - thin LED element 100 is shown to include the first conductive semiconductor layer 110, the photoactive layer 120, and the second conductive semiconductor layer 130 as the minimum structural elements. In addition, other active layers, conductive semiconductor layers, phosphor layers, hole - blocking layers, and / or electrode layers may be included above / below each layer. As an example, as Figure 10 shown, an electrode layer 140 may also be included. As long as it is a general electrode layer provided in an LED element, the electrode layer 140 can be used without limitation. As a non - restrictive example thereof, materials such as Cr, Ti, Al, Au, Ni, ZnO, AZO, ITO, and their oxides or alloys may be used alone or in combination, but are not limited thereto. Also, the thickness of the electrode layer 140 may be 10 nm to 500 nm, but is not limited thereto.

[0076] Moreover, it should be noted that the shape of the cross - section perpendicular to the direction in which the multiple layers are stacked of the ultra - thin LED element 100 is shown as circular, but is not limited thereto. The shape of the cross - section of the ultra - thin LED element can be used without limitation, such as ordinary polygons such as square, rectangle, rhombus, parallelogram, trapezoid, or even oval.

[0077] Moreover, the size of the ultra-thin LED element 100 can be on the nanometer or micrometer scale, which is difficult to install LED elements through mounting technology. As an example, the thickness, which is the length in the stacking direction of multiple layers of the ultra-thin LED element, can be 0.5 μm to 1.5 μm. Also, the size of the cross-section perpendicular to the stacking direction of multiple layers can be defined as different sizes according to the shape. As an example, when the shape of the cross-section is non-polygonal such as circular or elliptical, it can be the diameter of the line segment with the longest length across the edge of the cross-section, and the diameter can be 0.5 μm to 3.0 μm. Moreover, when the cross-section is polygonal, the length of one side can be 0.5 μm to 3.0 μm.

[0078] The above-mentioned ultra-thin LED element 100 is put into the first electrode line 210 in a solution state dispersed in a solvent. At this time, the solvent functions as a dispersion medium for dispersing the ultra-thin LED element 100. As long as the solvent does not cause physical or chemical damage to the ultra-thin LED element 100 and preferably can improve the dispersibility of the ultra-thin LED element 100, the solvent can be used without limitation. As an example, the solvent can be one or a mixture of two or more of solvents such as acetone, isopropyl alcohol, ethanol, polyethylene glycol, propylene glycol monomethyl ether acetate (PGMEA), hexane, dodecane, etc.

[0079] Moreover, the solution including the ultra-thin LED element 100 can be put into the first electrode line 210 by a known method. As an example, the solution can utilize a known device for discharging the solution, such as a printing device like an inkjet printer or a jetting device or a dispensing device. Also, the solution including the ultra-thin LED element 100 can be made into ink or paste to suit each discharging device, and the type of solvent can be appropriately selected considering physical properties such as the required viscosity. On the other hand, the input method of different discharging devices can follow the known methods of different discharging devices, and the present invention does not make special restrictions on this. Also, the solution usually can further include additives such as ink for the discharging device or a dispersant added to the paste. And the solution containing the ultra-thin LED element can include 0.01 wt% to 99.99 wt% of the ultra-thin LED element in the solution, and the present invention does not make special restrictions on this.

[0080] On the other hand, the above-mentioned first electrode line 210 may further include a partition (not shown). The partition (not shown) prevents the plurality of ultra-thin LED elements 100 put in from flowing to other parts of the area that is not the desired area, and includes side walls that surround the desired area at a specified height in order to centrally arrange the plurality of ultra-thin LED elements 100 in the desired area. A solution including the plurality of ultra-thin LED elements 100 can be put into the inside of the partition. The partition may be formed of an insulating material so that when the ultra-thin LED elements 100 are driven in the final ultra-thin LED electrode assembly 1000 realized by installing the ultra-thin LED elements 100, no electrical effect is generated. Preferably, the insulating material may use one or more of inorganic insulating materials such as silicon dioxide (SiO 2 ), silicon nitride (Si 3 N 4 ), aluminum oxide (Al 2 O 3 ), hafnium oxide (HfO 2 ), yttrium oxide (Y 2 O 3 ), and titanium dioxide (TiO 2 ) and various transparent polymer insulating materials. And the partition can be made through patterning and etching processes so that after the insulating material is formed on the first electrode line 210 at a specified height, it becomes the side wall surrounding the desired area.

[0081] At this time, in the case where the material is an inorganic insulating material, the partition can be formed by one method among chemical vapor deposition method, atomic layer deposition method, vacuum deposition method, electron beam deposition method, and spin coating method. And in the case where the material is a polymer insulating material, coating methods such as spin coating, spraying, and screen printing can be used to form it. And the patterning can be formed by photolithography using a photosensitive material or can be achieved by well-known nanoimprint technology, laser interference lithography, electron beam lithography, etc. At this time, the height of the formed partition is more than 1 / 2 of the thickness of the ultra-thin LED element 100. Generally, it is a thickness that will not affect the subsequent processes after self-alignment. Preferably, it can be 0.1 μm to 100 μm, and more preferably, it can be 0.3 μm to 10 μm. If the above range cannot be satisfied, it will affect the subsequent processes, making the manufacture of the ultra-thin LED electrode assembly difficult. In particular, when the height of the partition is too low compared to the thickness of the ultra-thin LED element 100, the solution including the ultra-thin LED element 100 overflows outside the partition, so it may be difficult to perform the function of the partition.

[0082] Also, when manufacturing the partition, considering the material of the insulator, the etching can be performed using an appropriate etching method. As an example, it can be carried out by a wet etching method or a dry etching method. Preferably, one or more dry etching methods such as plasma etching, sputter etching, reactive ion etching, and reactive ion beam etching can be used.

[0083] On the other hand, it should be noted that although the S1 step is described as putting the ultra-thin LED element 100 into the solution in a state of being mixed with the solvent, the ultra-thin LED element 100 can also be put into the first electrode wire 210 first and then the solvent, or conversely, the solvent can be put in first and then the ultra-thin LED element 100. As long as the final situation is the same as that of the input solution, it is also included in the S1 step.

[0084] Then, the manufacturing method of the ultra-thin LED electrode assembly 1000 according to an embodiment of the present invention includes a step (S2 step) of applying a power supply with a frequency of 500 Hz or less to adjacent first electrodes 211 and 212 to form an electric field. The S2 step can be performed before, simultaneously with, or after the above S1 step. That is, the power supply applied to the first electrodes 211 and 212 is applied before, simultaneously when, or after putting the solution including the ultra-thin LED element 100 into the first electrodes 211 and 212. Moreover, the present invention does not particularly limit the application timing of the power supply applied to the first electrodes 211 and 212.

[0085] The S2 step is a step of applying a power supply with a frequency of 500 Hz or less to the first electrodes 211 and 212. The electric field formed by applying the power supply emits a force that causes the ultra-thin LED element 100 to move and align to the top surface of the first electrodes 211 and 212. Hereinafter, the force will be described first.

[0086] The electric field formed by applying a power supply with a frequency of 500 Hz or less to the first electrodes 211 and 212 can move and align a plurality of ultra-thin LED elements 100 so that they are respectively independently located within the top surface of a certain first electrode 211 and 212. This movement and alignment mode is caused by the fact that electroosmotic pressure predominates among the multiple forces applied to the ultra-thin LED element 100, which is different from the mode in which the LED element achieves self-alignment when the dielectric force, which is another force competing with electroosmotic pressure, predominates.

[0087] Specifically, the mechanism of dielectrophoresis is described as follows. Dielectrophoresis means the phenomenon in which when a particle is placed in a non-uniform electric field, a directional force is applied to the particle through the dipole induced in the particle. At this time, the intensity of the force can vary according to the electrical properties of the particle and the medium, the induction characteristics, the frequency of the alternating electric field, etc. When dielectrophoresis is performed, the average force (F DEP ) is as shown in the following mathematical formula 1.

[0088] [Mathematical formula 1]

[0089]

[0090] In mathematical formula 1, r, ε m , and E respectively represent the radius of the particle, the relative permittivity of the medium, and the root mean square magnitude of the applied alternating electric field. And, Re[K(ω)], as a factor for determining the direction in which a nearly spherical particle moves, means the real part of the value of the following mathematical formula 2.

[0091] [Mathematical formula 2]

[0092]

[0093] Among them, ε p * and ε m * respectively serve as the complex relative permittivities of the particle and the medium, and ε * is given by the following mathematical formula 3.

[0094] [Mathematical formula 3]

[0095]

[0096] Among them, σ means the conductivity coefficient, ε means the relative permittivity, ω means each frequency (ω = 2πf), and j means the imaginary part

[0097] At this time, when dielectrophoresis is performed, the movement of the particle depends on the change magnitude of the factor in mathematical formula 2. Specifically, the movement of the particle located under the electric field is determined by the sign change of Re[K(ω)] of the frequency of the applied power supply. For example, when Re[K(ω)] has a positive value, the particle moves toward the high electric field region, that is, the two electrode sides where the electric field is formed, and this is called positive dielectrophoresis (positive DEP, p-DEP). And, when Re[K(ω)] has a negative value, the particle can move toward the region away from the high electric field region, that is, the direction away from the two electrodes where the electric field is formed, and this is called negative dielectrophoresis (negative DEP, n-DEP).

[0098] This mechanism of dielectrophoresis also applies to the ultra-thin LED element 100 that is located together with the solvent as the medium between two electrodes that form an electric field.

[0099] Refer to Figure 4 The following is an explanation. When the ultra-thin LED element 100, which is in a state of being mixed in the solvent 190 and located within an electric field formed by applying different power supplies to the mutually separated first electrodes 211, 212, 213, 214, is applied with Figure 4 In the state of part (a), depending on the magnitude of the electric field, frequency, dielectric constant of the solvent 190, shape of the ultra-thin LED element, and the negative dielectrophoretic force (n-DEP) or positive dielectrophoretic force (p-DEP) of the element material, if a negative dielectrophoretic force (n-DEP) is applied to the ultra-thin LED element 100, then as Figure 4 shown in part (b), the ultra-thin LED element 100 moves in a direction away from the region where the electric field is formed and aligns outside the outermost first electrodes 211, 214. Or, in Figure 4 the state of part (a), if a positive dielectrophoretic force (p-DEP) is applied to the ultra-thin LED element 100, then as Figure 4 shown in part (c), the ultra-thin LED element 100 moves and aligns between the two adjacent first electrodes 211, 212, 213 where the highest electric field is formed.

[0100] At this time, as Figure 4 shown in part (b), after the ultra-thin LED element 100 moves and aligns, it aligns at a place far from the first electrodes 211, 214. Therefore, the ultra-thin LED element cannot move and be installed on the top surface of the first electrode. And, as Figure 4 shown in part (c), in the case of the ultra-thin LED element 100 after moving and aligning, the ultra-thin LED element cannot move and be installed on the top surface of the first electrode. Furthermore, whether it is Figure 4 part (b) or Figure 4 part (c), the ultra-thin LED element is not driven. Only, it can be confirmed from Figure 4 part (c) that in the case of using the positive dielectrophoretic force, the LED elements can be aligned to move between two adjacent electrodes and simultaneously straddle the top surfaces of the two adjacent electrodes. Therefore, under the restrictive condition of lengthening the length of the LED element in order to apply a greater positive dielectrophoretic force and adjusting the interval between the first electrodes 211, 212, 213 to be less than the length of the LED element, the LED elements are aligned to straddle two adjacent first electrodes 211, 212, 213, thus having room for design change to a drivable state.

[0101] Therefore, whether in the case of using positive dielectrophoresis or negative dielectrophoresis, it is impossible to move and align the LED element within the top surface of one of the two adjacent first electrodes where an electric field is formed. In the case where the aspect ratio of the shape of the LED element is small, since the positive dielectrophoresis applied to the LED element is not large, even if the size of the LED element and the interval between the first electrodes are adjusted, self-alignment cannot be smoothly achieved.

[0102] In response to this, the inventor of the present invention learned during the process of continuing to study the movement and self-alignment mechanism of the LED element in the two electrodes where an electric field is formed that when the frequency intensity of the applied power supply is adjusted, electroosmotic pressure becomes the dominant force applied to the ultra-thin LED element, thereby achieving a self-alignment mode different from the previously known self-alignment mode of the LED element based on positive dielectrophoresis under an electric field, that is, the LED element can move and align within the top surface of one of the two adjacent electrodes where an electric field is formed, and thus the present invention is achieved.

[0103] Specifically, in the case of applying an electric field to the ultra-thin LED element, the forces applied to the ultra-thin LED element are gravity, Brownian motion force, dielectrophoresis force, and electroosmotic pressure. In this regard, the following description is made with reference to Figure 5 When the distance that the ultra-thin LED element moves is simulated with the frequency of the applied electric field as a variable by the respective forces applied to the ultra-thin LED element, the distance that the ultra-thin LED element moves based on gravity and Brownian motion force hardly changes with the frequency of the electric field. On the contrary, through electroosmotic pressure and dielectrophoresis force, the distance that the ultra-thin LED element moves becomes different with the frequency of the electric field. And according to the frequency, the ultra-thin LED element to which electroosmotic pressure becomes dominant moves to the top surface of one of the two adjacent first electrodes where an electric field is formed, and the ultra-thin LED element to which dielectrophoresis force becomes dominant moves between the two adjacent first electrodes, and these two forces can compete with each other.

[0104] Specifically, as Figure 5As shown, the thickness, which is the length in the stacking direction of multiple layers, is 1.05 μm, the surface diameter perpendicular to the stacking direction is 750 nm, and in a cylindrical ultra-thin LED element including an n-type conductive semiconductor layer, a photoactive layer, and a p-type conductive semiconductor layer, the distance between adjacent first electrodes is 2 μm, the strength of the applied power supply is 10 Vpp. When the solvent is acetone and the frequency of the power supply applied to the first electrode is below 1 kHz, the force applied to the ultra-thin LED element by electroosmotic pressure is the most dominant. When the frequency is above 1 kHz, the force applied to the ultra-thin LED element by dielectric force is the most dominant. As a result, when the frequency of the applied power supply is below 1 kHz, it is more beneficial for the ultra-thin LED element to move and align on the top surface of the first electrode.

[0105] And, as Figure 6 shown, it is also possible to make the frequency at which the dominant force applied to the ultra-thin LED element becomes electroosmotic pressure different according to the type of solvent that moves the ultra-thin LED element. However, it is known that even if the frequency at which electroosmotic pressure is maximized varies according to the specific type of solvent, it can be below 1 kHz, especially below 500 Hz. Therefore, below 1 kHz, especially below 500 Hz, electroosmotic pressure can become the dominant force.

[0106] However, as Figure 7 shown, it is known that when increasing the voltage of the power supply, although the moving distance of the ultra-thin LED element increases due to electroosmotic pressure, even if the voltage varies, the frequency at which electroosmotic pressure is maximized is still below 1 kHz, especially below 500 Hz. And even when the voltage increases, the force applied to the ultra-thin LED element does not transfer from the region dominated by electroosmotic pressure to the region dominated by dielectric force.

[0107] Accordingly, the manufacturing method of the ultra-thin LED electrode assembly 1000 according to an embodiment of the present invention includes a step (step S2) of applying a power supply with a frequency of 500 Hz or less to the first electrodes 211 and 212, such that the dominant force applied to the ultra-thin LED element 100 within the electric field formed by two adjacent first electrodes 211 and 212 becomes electroosmotic pressure. If the frequency of the applied power supply is greater than 500 Hz, the force applied to the ultra-thin LED element 100 will compete with the dielectric force, and as the frequency increases, the dielectric force becomes the dominant force. Therefore, compared to the number of ultra-thin LED elements input, the ratio of ultra-thin LED elements located on the top surface of the first electrode can be greatly reduced. Accordingly, preferably, the power supply applied to the first electrodes 211 and 212 can be 1 Hz to 500 Hz, and the voltage can be 5 Vpp to 100 Vpp. More preferably, the frequency can be 1 Hz to 50 Hz, and the voltage can be 5 Vpp to 80 Vpp. Further preferably, the frequency can be 1 Hz to 30 Hz, and the voltage can be 5 Vpp to 50 Vpp. More preferably, the frequency can be 5 Hz to 20 Hz, and the voltage can be 5 Vpp to 40 Vpp. Thus, not only can damage to the first electrode be prevented or minimized, but the ultra-thin LED elements can be efficiently moved and aligned into the top surface of the first electrode. If the voltage is greater than 100 Vpp, damage to the first electrode will occur, so that during the execution of step S3, the movement and alignment of the ultra-thin LED elements may be aborted due to a short circuit of the first electrode, or the ultra-thin LED elements may not emit light smoothly during driving due to excessive damage. Also, if the voltage is less than 1 Vpp, there is a concern that the ratio of ultra-thin LED elements placed within the top surface of the first electrode will be greatly reduced.

[0108] Moreover, in order to increase the dominance of the electroosmotic pressure of the ultra-thin LED element 100 according to an embodiment of the present invention and increase the ratio of multiple ultra-thin LED elements that move and align into the respective top surfaces of the first electrodes 211 and 212, in step S1, the viscosity of the solvent 190 in which the ultra-thin LED element 100 is dispersed can be 50 cP or less. More preferably, it is 5 cP to 15 cP. If the viscosity of the solvent is greater than 50 cP, there is a concern that the ratio of the number of ultra-thin LED elements that move and align into the top surface will be insufficient compared to the number of multiple ultra-thin LED elements input. Also, when the viscosity is less than 5 cP, since the evaporation rate is fast and there is a lack or absence of solvent during the movement and alignment of the ultra-thin LED elements, it may be difficult to ensure sufficient process time required for movement and alignment. Here, the viscosity is the viscosity measured using a Brookfield viscometer at 25°C, and the specific measurement method is achieved by a known method. The present invention omits the specific description thereof.

[0109] Then, as step S3, a step of moving the ultra-thin LED element 100 located within the electric field into the respective top surfaces of the first electrodes 211 and 212 is performed.

[0110] As described above, the electric field formed by applying a power supply after appropriately adjusting the frequency can move the ultra-thin LED element 100 into the top surfaces of the first electrodes 211 and 212.

[0111] Specifically, when steps S1 to S3 are performed under the appropriate conditions of the present invention, among the total number of ultra-thin LED elements 100 input in step S1, the placement ratio based on the following Mathematical Formula 1 corresponding to the quantity ratio of the first ultra-thin LED elements 100A, 100B, and 100C, which are the ultra-thin LED elements disposed within the top surfaces of the first electrodes 211 and 212, can be made 40% or more, preferably 50% or more, more preferably 60% or more, 65% or more, 75% or more, 80% or more, 85% or more, 89% or more, or 95% or more.

[0112] [Mathematical Formula 1]

[0113]

[0114] Among them, the quantity of the ultra-thin LED elements means the total number of ultra-thin LED elements and the number of the first ultra-thin LED elements disposed within the unit area (1 mm 2 ) of the first electrode lines. And, with respect to the first ultra-thin LED elements 100A, 100B, and 100C located within the top surfaces of the first electrodes 211 and 212, based on the total contact area of the contact surfaces of the ultra-thin LED elements that are in contact with the top surface of a certain first electrode 211 or 212, the present invention defines the ultra-thin LED elements with 50% or more of the area in contact with the top surfaces of the first electrodes 211 and 212. And, the case where one ultra-thin LED element is in contact with the top surfaces of two adjacent first electrodes 211 and 212 due to the narrow interval between the two adjacent first electrodes 211 and 212 is also regarded as belonging to the first ultra-thin LED elements.

[0115] On the other hand, after step S3, the ultra-thin LED element 100 input in step S1 is as Figure 1As shown, it includes first ultra-thin LED elements 100A, 100B, 100C disposed within the top surfaces of first electrodes 211, 212, and, optionally, may include a second ultra-thin LED element 100D. The second ultra-thin LED element 100D cannot be disposed within the top surfaces of the first electrodes 211, 212 and is located in the space between adjacent first electrodes 211, 212, or is in contact with only a certain first electrode 211, 212, but is placed such that the area of the contact surface is less than 50% of the single-sided area of the ultra-thin LED element with which it is in contact.

[0116] Moreover, the first ultra-thin LED elements 100A, 100B, 100C can be mounted on the electrode surfaces of the first electrodes 211, 212 in various forms. As an example, the first ultra-thin LED elements 100A, 100B, 100C may include: a third ultra-thin LED element 100C, which is mounted such that the first surface on the side of the first conductive semiconductor layer 110, among the first and second surfaces facing each other in the thickness direction of the multiple layers including the first conductive semiconductor layer 110, the photoactive layer 120, and the second conductive semiconductor layer 130 that form the first ultra-thin LED elements 100A, 100B, 100C, is in contact with the top surface of the first electrode 211; a fourth ultra-thin LED element 100A, which is mounted such that the second surface on the side of the second conductive semiconductor layer 130 is in contact with the top surface of the first electrode 211; and a fifth ultra-thin LED element 100B, which is mounted such that the side surface in the thickness direction is in contact with the top surface of the first electrode 211. At this time, in the mounting forms of the first ultra-thin LED elements 100A, 100B, 100C, even when second electrodes 221, 222 are formed on the first ultra-thin LED elements 100A, 100B, 100C in a later-described S4 step, the fifth ultra-thin LED element 100C cannot emit light. Thus, there is a concern that even if the ultra-thin LED elements 100 are moved and aligned into the top surfaces of the first electrodes 211, 212 by electroosmotic pressure, the drivable mounting ratio, which is the ratio of the ultra-thin LED elements that are mounted in a drivable manner, i.e., can emit light when a driving power source is applied, may not be large enough.

[0117] Therefore, according to an embodiment of the present invention, the materials or structures of the multiple ultra-thin LED elements 100 input in the above-described S1 step, the solvent 190 input therewith, and the frequency and voltage of the power source applied in the S2 step can be appropriately controlled such that, per unit area (1 mm 2) The drivable installation ratio is high for the total number of the first ultra-thin LED elements 100A, 100B, and 100C disposed inside and for the sum ratio of the number of the third ultra-thin LED element 100C and the fourth ultra-thin LED element 100A that are installed in a drivable manner on the top surfaces of the first electrodes 211 and 212.

[0118] First, in order to increase the ratio of movement and placement of the plurality of ultra-thin LED elements 100 on the top surfaces of the first electrodes 211 and 212 and to increase the drivable installation ratio, the dielectric constant of the solvent 190 can be 5 or more, more preferably 14 or more, further preferably 23 or more, and even more preferably 33 or more. If the dielectric constant of the solvent is less than 5, the ratio of the ultra-thin LED elements that move and are placed on the top surface of the first electrode itself will be small, or even if the ratio of the ultra-thin LED elements that move and are placed on the top surface of the first electrode is high, the ratio of the fifth ultra-thin LED element 100B that cannot emit light because the side surface of the ultra-thin LED element contacts the top surface among these ultra-thin LED elements will increase significantly, resulting in a lower brightness of the ultra-thin LED electrode assembly. And, as an example, the dielectric constant of the solvent 190 can be 50 or less. When the dielectric constant of the solvent is greater than 50, the ratio of the ultra-thin LED elements that move and are placed on the top surface of the first electrode or the drivable installation ratio may instead decrease, and there is a concern about electrode damage.

[0119] Then, in the ultra-thin LED element 100, in order to increase the ratio of the ultra-thin LED elements that move and are placed on the top surfaces of the first electrodes 211 and 212 and to increase the drivable installation ratio, the ultra-thin LED element can be deformed in terms of material / structure so that there are differences in the surface physical properties between the surfaces forming the ultra-thin LED element.

[0120] As an example, as Figure 8 shown, the ultra-thin LED element 101 can also have a rotation-inducing film 150 surrounding the side surface. Thus, physical property differences can be caused by the material between the side surface and the upper / lower surfaces of the ultra-thin LED element 101. As Figure 9As shown, the physical property difference caused by the material difference between the side and the upper / lower surface can generate a rotation torque T in the ultra-thin LED element 101 under an electric field, which is perpendicular to the x-axis direction d in which the multiple layers forming the ultra-thin LED element 101 are stacked. As a result, the ultra-thin LED element 101 having a rotation inducing film 150 on the side can be moved to the top surface of the first electrode 211 by means of electroosmotic pressure, and then rotated in the x-axis direction, thereby increasing the installation ratio of the upper surface or lower surface that is not the side surface in contact with the top surface. Preferably, the dielectric constant (ε) of the rotation inducing film 150 can be 30 or less, more preferably, 7 or less, and further preferably, 5.5 or less, as another example, 3.0 or more, thereby not only helping to increase the ratio (or number) of ultra-thin LED elements that are moved and placed on the top surface of the first electrode, but also helping to increase the drivable installation ratio. If the dielectric constant of the rotation inducing film is greater than 30, it is not possible to generate sufficient torque, so it may be difficult to increase the drivable installation ratio.

[0121] Furthermore, the rotation inducing film 150 can be used without restriction as long as the material has physical properties different from the upper surface / lower surface of the ultra-thin LED element 101. Preferably, the rotation inducing film 150 can be made of a material that satisfies the above-mentioned dielectric constant conditions. As an example, the rotation inducing film can be HfO 2 、ZrO 2 、Al 2 O 3 、SiO 2 and SiN x As another example, it can be Al 2 O 3 、SiO 2 and SiN x As another example, one or more materials may be SiO 2 and SiN x One or more materials in .

[0122] Moreover, in order to increase the drivable mounting ratio according to an embodiment of the present invention, the aspect ratio of the ultra-thin LED element can be controlled. Specifically, in the ultra-thin LED elements 100, 101, 102, the ratio (b / a) of the major axis length (a) to the thickness (b) as the length in the stacking direction of the plurality of layers in the cross-section perpendicular to the stacking direction of the plurality of layers may be greater than 0 to 2.0 or less. If the ratio (b / a) of the major axis length (a) to the thickness (b) is greater than 2.0, the mounting ratio on the side surface of the ultra-thin LED element is greatly increased, so there is a concern that the drivable mounting ratio may be reduced or the ratio of moving and placing within the electrode surface of the first electrode may be greatly reduced. More preferably, the ratio (b / a) of the major axis length (a) to the thickness (b) may be greater than 0 to 1.8 or less. Thus, the drivable mounting ratio can be greatly increased, which is beneficial to achieving the object of the present invention. On the other hand, when the ratio (b / a) of the major axis length (a) to the thickness (b) becomes smaller to greater than 0 to 1.0 or less, the probability that the ultra-small LED element placed on the first electrode is mounted with the first surface or the second surface contacting the first electrode more than the side surface can be increased due to the shape factor of the LED element.

[0123] Then, as the step S4, a step of forming the second electrode line 220 for the ultra-thin LED elements disposed on the top surfaces of the first electrodes 211, 212, specifically, the first ultra-thin LED elements 100A, 100B, 100C is performed.

[0124] As long as it is designed to be in electrical contact with the upper portions of the first ultra-thin LED elements 100A, 100B, 100C disposed on the first electrode line 210 described above, the number, arrangement, shape, etc. of the second electrode line 220 are not limited. However, as Figure 1 shown, if the first electrode line 210 is arranged side by side in a certain direction, the respective second electrodes 221, 222 constituting the second electrode line 220 may be arranged side by side in a direction perpendicular to the extending direction of the first electrodes 211, 212. And such an electrode arrangement, which has been widely used in displays and the like in the past, has the advantage that the electrode arrangement and drive control technology in the conventional display field can be directly used.

[0125] On the other hand, the second electrodes 221, 222 may have the materials, shapes, widths, and thicknesses of the electrodes used in the normal LED electrode assembly and can be manufactured by known methods. Therefore, the present invention does not make specific limitations thereto. As an example, the second electrodes 221, 222 may be aluminum, chromium, gold, silver, copper, graphene, ITO, or their alloys, etc. The width may be 2 μm to 50 μm, and the thickness may be 0.1 μm to 100 μm, and appropriate changes can be made in consideration of the size of the required LED electrode assembly, etc.

[0126] Further, the second electrode line 220 can be formed by depositing electrode materials after patterning the electrode line using well-known photolithography, or by performing dry and / or wet etching after depositing the electrode materials. Regarding the specific formation method, the description thereof will be omitted.

[0127] On the other hand, it is also possible to include a step of fixing and insulating each of the aligned first ultra-thin LED elements 100A, 100B, 100C in contact with the first electrode line 210 between the above steps S3 and S4, and forming a passivation layer on the first electrode line 210 where the ultra-thin LED element 100 is disposed in order to provide a surface for forming the second electrodes 221, 222 formed in step S4. In the case of a passivation material commonly used in electrical and electronic components, the passivation layer can be used without limitation. As an example, the passivation layer can be formed by depositing passivation materials such as SiO 2 and SiN x by PECVD, or depositing passivation materials such as AlN and GaN by MOCVD, or depositing passivation materials such as Al 2 O, HfO 2 and ZrO 2 by ALD. On the other hand, the passivation layer should be formed in such a way as not to cover the upper surface of the self-aligned ultra-thin LED element 100. To this end, the passivation layer can be formed by deposition corresponding to the thickness of the uncovered upper surface, or after deposition in a way that covers the upper surface, dry etching is performed to expose the upper surface of the ultra-thin LED element.

[0128] The ultra-thin LED electrode assembly 1000 realized by the above manufacturing method includes: a first electrode line 210 with at least two first electrodes 211, 212 having top surfaces spaced apart from each other; ultra-thin LED elements 100 including first ultra-thin LED elements 100A, 100B, 100C respectively disposed within the top surfaces of certain first electrodes 211, 212; and a second electrode line 220 disposed on the first ultra-thin LED elements 100A, 100B, 100C.

[0129] Preferably, the first ultra-thin LED elements 100A, 100B, 100C can be installed such that the sum ratio of the number of the third ultra-thin LED element 100C and the fourth ultra-thin LED element 100A installed in contact with the first electrodes 211, 212 and the second electrodes 221, 222 on the upper and lower surfaces as the first ultra-thin LED elements 100A, 100B, 100C is 40% or more, and as another example, 45% or more, 50% or more, 60% or more, or 70% or more. Thus, the ultra-thin LED electrode assembly 1000 can increase the driving rate and brightness of the installed ultra-thin LED elements 100.

[0130] Moreover, in the ultra-thin LED electrode assemblies 1000, 1000', as an example, the unit area that can be independently driven can be 1 μm 2 to 100 cm 2 and, more preferably, can be 10 μm 2 to 100 mm 2 However, it is not limited thereto. Also, in the ultra-thin LED electrode assemblies 1000, 1000', per unit area of 100×100 μm 2 can include 2 to 100,000 ultra-thin LED elements 101, but it is not limited thereto.

[0131] On the other hand, among the first ultra-thin LED elements 100A, 100B, 100C included in the ultra-thin LED electrode assembly 1000 shown in Figure 1 and Figure 2 , a part can include a fifth ultra-thin LED element 100C, and the fifth ultra-thin LED element 100C is installed in contact with the top surfaces of the first electrodes 211, 212 on its side surfaces. When the fifth ultra-thin LED element 100C is installed in contact with the top surface of the first electrode 211 on one side surface and is in contact with the second electrodes 221, 222 up to the other side surfaces of the LED element, when the implemented ultra-thin LED electrode assembly 1000 is activated, there is a concern that the fifth ultra-thin LED element 100C may cause an electrical short circuit, resulting in damage or short circuit of the first electrodes 211, 212 and the second electrodes 221, 222 and leakage of current. For this reason, according to an embodiment of the present invention, in the cross-section of the element in the direction perpendicular to the direction in which multiple layers of the element are stacked, the thickness of the ultra-thin LED element can be greater than the diameter or the length of a certain line segment forming the cross-section, thereby preventing the electrical short circuit or leakage caused by the simultaneous contact of the side surfaces of the ultra-thin LED element with the first electrode and the second electrode that may occur.

[0132] Moreover, the above-described ultra-thin LED electrode assemblies 1000 and 1000' according to an embodiment of the present invention can be applied to known light sources used in LED elements. As an example, with reference to Figures 11 to 13 The following is an explanation. The light sources 2000, 2000', and 3000 according to an embodiment of the present invention may include a support 1100, 1100', 1100" and the ultra-thin LED electrode assemblies 1000, 1001, 1002, 1003 provided in the support 1100, 1100', 1100".

[0133] The supports 1100, 1100', 1100" are used to support the ultra-thin LED electrode assemblies 1000, 1001, 1002, 1003. When they have a mechanical strength above a specified level for performing the support function, they can be used as supports without limitation regardless of the material. As a non-limiting example thereof, they can be one or more raw materials selected from the group consisting of organic resins, ceramics, metals, and inorganic resins. Moreover, the supports 1100, 1100', 1100" can be transparent or opaque.

[0134] Moreover, the shape of the supports 1100, 1100', 1100" can be, for example, Figure 12 the cup shape shown, or, for example, Figure 12 and Figure 13 the plate shape shown, but is not limited thereto, and can have various shapes according to the shape of the surface on which the light source is installed. Also, the area and / or volume of the supports 1100, 1100', 1100" are also appropriately adjusted in consideration of the brightness characteristics of the light source to be achieved, the number / configuration structure of the ultra-thin LED electrode assemblies 1000, 1001, 1002, 1003 provided thereby, and the use of the light source. Therefore, the present invention does not make any special limitation thereto. Also, the thickness of the supports 1100, 1100', 1100" can be appropriately selected in consideration of the strength of the material to support the ultra-thin LED electrode assemblies 1000, 1001, 1002, 1003.

[0135] Moreover, it should be noted that, in addition to the function of supporting the ultra-thin LED electrode assembly 1000, Figure 11 the support 1100 shown can also serve as the housing of the light source. Also, it should be noted that when the light source has the supports 1100, 1100', 1100", the ultra-thin LED electrode assemblies 1000, 1001, 1002, 1003 of the light source do not include the above-described base substrate formed with the first electrode line 210, and the first electrode line 210 can also be disposed on the supports 1100, 1100', 1100".

[0136] Moreover, one or more than two ultra-thin LED electrode assemblies 1000, 1001, 1002, 1003 may be provided in the light sources 2000, 2000', 3000. At this time, the ultra-thin LED elements included in a single ultra-thin electrode assembly 1000, 1001, 1002, 1003 may substantially be composed of elements emitting a certain color. As an example, the light color may be one of UV, blue, green, yellow, amber, and red. On the other hand, when two or more ultra-thin LED electrode assemblies 1001, 1002, 1003 are provided in the light sources 2000', 3000 and they are respectively configured to be independently driven, it is possible to realize a light source emitting a plurality of light colors, and such a light source may be used for a display such as an LCD or an OLED. Moreover, when two or more ultra-thin LED electrode assemblies 1000, 1001, 1002, 1003 are included, their arrangement may be linearly arranged in a certain direction as shown in Figure 12 or may be arranged in a planar manner as shown in Figure 13 to achieve a regular arrangement, or may be different therefrom to achieve a random arrangement.

[0137] Moreover, the light sources 2000, 2000', 3000 may further include a color conversion substance so that the light emitted from the ultra-thin LED electrode assemblies 1000, 1001, 1002, 1003 has a specific wavelength. The color conversion substance performs a function of being excited by the light released by the ultra-thin LED element to release light having a specific wavelength. As an example, as shown in Figure 11 , when the support 1100 has a receiving portion inside in a cup shape, the color conversion substance may be provided in the filling layer 1200 inside the receiving portion, and as shown in Figure 12 and Figure 13 , when the supports 1100', 1100'' are flat, the color conversion substance may be provided in the form of a coating layer 1200', 1300.

[0138] Furthermore, the color conversion substance can be determined in consideration of the light color emitted by the ultra-thin LED element. As an example, in the case of an element that emits UV, the color conversion substance can be one or more of blue, cyan, yellow, green, amber, and red. Thus, a single-color light source or a white light source of a certain color can be achieved. As an example of achieving a white light source, in the case of an element that emits UV, the color conversion substance can be a mixed substance of a certain type among blue / yellow, red / cyan, blue / green / red, and blue / green / amber / red. Thus, a white light source can be achieved. Also, in the case of an element that emits blue, the color conversion substance can be one or more of yellow, cyan, green, amber, and red. Thus, a single-color light source or a white light source can be achieved. As an example of achieving the white light source, two or more colors can be combined. Specifically, a white light source can be achieved by combining a mixed substance of a certain type among blue / yellow, red / cyan, blue / green / red, and blue / green / amber / red.

[0139] On the other hand, the color conversion substance can be a known phosphor or quantum dot for lighting, displays, etc. The present invention does not impose special restrictions on such specific types.

[0140] The above light sources 2000, 2000', 3000 themselves or in combination with other known structures are used to form electrical and electronic components or devices. As an example, the known structure can be an input unit that receives signals required to operate the ultra-thin LED electrode assemblies 1000, 1001, 1002, 1003, a heat dissipation unit such as a heat sink for transferring heat generated when the ultra-thin LED electrode assemblies 1000, 1001, 1002, 1003 are driven to the outside, and a housing for encapsulating the light source and other structures.

[0141] Also, the light sources 2000, 2000', 3000 can be used in various electrical and electronic devices required for light emitters. As an example, they can be various LED illuminations for home use / vehicle use, displays, medical devices, beauty devices, and various optical devices. On the other hand, as an example, the medical device can be a LED light source for optogenetics that emits light of a specified wavelength to the brain to activate the neural network, etc. at the corresponding part. The LED light source for optogenetics can include a plurality of ultra-thin LED electrode assemblies on a support. Also, as an example, the beauty device can be a LED mask for skin beauty, and can be implemented such that a plurality of ultra-thin LED electrode assemblies are provided on the inner side of the mask support that contacts the skin.

[0142] The present invention will be described more specifically by the following embodiments. However, the following embodiments do not limit the scope of the present invention, and this should be interpreted as being helpful for understanding the present invention.

[0143] Example 1

[0144] First, the following ultra-thin LED elements were prepared. Specifically, a normal LED wafer (Epistar) was prepared in which an undoped n-type III-nitride semiconductor layer, an n-type III-nitride semiconductor layer doped with Si (thickness: 4 μm), a photoactive layer (thickness: 0.15 μm), and a p-type III-nitride semiconductor layer (thickness: 0.05 μm) were sequentially stacked on a substrate. SiO 2 (thickness: 0.9 μm) was deposited as a first mask layer, and Al (thickness: 200 nm) was deposited as a second mask layer. Then, a SOG resin layer with a circular pattern of 0.55 nm in diameter transferred was transferred onto the second mask layer using a nanoimprint device. After that, the SOG resin layer was cured using RIE, and the remaining resin part of the resin layer was etched by RIE to form a resin pattern layer. Then, according to the pattern, the second mask layer was etched using ICP, and the first mask layer was etched using RIE. Then, the first electrode layer, the p-type III-nitride semiconductor layer, and the photoactive layer were etched using ICP. Next, the doped n-type III-nitride semiconductor layer was etched to a thickness of 0.8 μm, and an LED wafer with multiple LED structures having the mask pattern layer removed was fabricated by KOH wet etching. Then, a temporary protective film of SiO 2 (with a deposition thickness of 72 nm based on the side surface of the LED structure) was deposited on the LED wafer with multiple LED structures. After that, the temporary protective film material formed between the multiple LED structures was removed by RIE, exposing the upper surface of the doped n-type III-nitride semiconductor layer between the LED structures.

[0145] After that, the LED wafer with the temporary protective film formed was immersed in an electrolyte solution of 0.3 M oxalic acid aqueous solution, connected to the positive terminal of the power supply, and after connecting the negative terminal to a platinum electrode immersed in the electrolyte solution, a voltage of 15 V was applied for 5 minutes, thereby forming multiple pores in the thickness direction from the surface of the doped n-type III-nitride semiconductor layer between the LED structures. Then, the temporary protective film was removed by ICP, and the LED wafer was immersed in a 100% γ-butyrolactone bubble-forming solution. Then, ultrasonic waves were irradiated at an intensity of 160 W and 40 kHz for 10 minutes, and the pores formed in the doped n-type III-nitride semiconductor layer were destroyed using the generated bubbles, manufacturing multiple ultra-thin LED elements (diameter: 720 nm, thickness: 800 nm).

[0146] After that, a first electrode line was manufactured by alternating a plurality of first electrodes extending long in a first direction with a spacing of 2 μm in a second direction perpendicular to the first direction on a base substrate of quartz material with a thickness of 500 μm. At this time, the width of the first electrode was 10 μm, the thickness was 0.2 μm, the material of the first electrode was gold, and the area of ​​the region where the ultra-thin LED element was installed in the first electrode line was set to 1 mm 2 In addition, a SiO layer with a height of 0.5 μm is formed on the base substrate. 2 An insulating partition is provided to surround the area to be installed.

[0147] Afterwards, after making a solution in which 200 prepared ultra-thin LED elements are mixed in acetone with a dielectric constant of 20.7, the solution made in the installed area is dripped twice, 9 μl each time, and then a 1 Hz, 10 Vpp sinusoidal AC power supply is applied to the adjacent first electrode as a power source, so that the ultra-thin LED elements can be self-aligned.

[0148] Then, SiO2 with a height corresponding to the thickness of the ultra-thin LED elements is deposited on the region where the plurality of ultra-thin LED elements are mounted by using a PECVD construction method. 2 After the passivation material is applied, it extends in a second direction perpendicular to the first direction, and a plurality of second electrodes (with a width of 10 μm, a thickness of 0.2 μm, a spacing of 2 μm between electrodes, and a material of gold) separated from each other in the first direction are formed on the upper surface of the installed ultra-thin LED element, thereby realizing an ultra-thin LED electrode assembly.

[0149] Example 2 to Example 12

[0150] The method was implemented and manufactured in the same manner as in Example 1, and the frequency and / or voltage of the power applied to the first electrode was changed as shown in Table 1 below to realize an ultra-thin LED electrode assembly.

[0151] Comparative Examples 1 to 4

[0152] The method was implemented and manufactured in the same manner as in Example 1, and the frequency of the power applied to the first electrode was changed as shown in Table 1 below, thereby realizing an ultra-thin LED electrode assembly.

[0153] Experimental Example 1

[0154] For the ultra-thin LED electrode assemblies of Examples 1 to 12 and Comparative Examples 1 to 4, the ratio of the total number of ultra-thin LED elements put in and the ultra-thin LED elements placed on the top surface of the first electrode was evaluated as shown below, and the results are presented in the following Table 1.

[0155] Specifically, in the manufacturing process of the ultra-thin LED electrode assembly, after applying power, in a state where the ultra-thin LED elements are self-aligned, SEM photos are taken to count the number of ultra-thin LED elements in the top surface of the first electrode within the unit area (1 mm 2 ) of the first electrode wire, and it is presented in Table 1 below as a percentage of the number of ultra-thin LED elements input. And, in Figure 14 , SEM photos of a part of the area measured related to Examples 1 to 4 and Comparative Examples 2 to 3 are presented.

[0156] Moreover, for Example 1, Example 9, and Example 10, it was observed through an optical microscope whether the first electrode wire was damaged.

[0157] Observation results: In Example 1 and Example 9, no damage to the first electrode wire was observed, but in the case of Example 10, a color change occurred in a part of the first electrode wire, and it was confirmed that electrode damage might occur. Thus, it can be expected that when the applied voltage becomes stronger, problems such as electrode short-circuit may be caused.

[0158] Table 1

[0159]

[0160] From Table 1 and Figure 14 it can be confirmed that compared with Comparative Examples 1 to 4, the placement ratio of ultra-thin LED elements in the top surface of the first electrode in Examples 1 to 12 where the frequency of the applied power supply is 500 Hz or less is at least 2 times higher.

[0161] Examples 13 to 18

[0162] Implemented and manufactured in the same manner as Example 3, instead of acetone, the type of solvent used to disperse ultra-thin LED elements was changed as shown in the following Table 2, thereby manufacturing an ultra-thin LED electrode assembly.

[0163] Experimental Example 2

[0164] The ultra-thin LED electrode assemblies of Example 3 and Examples 13 to 18 were evaluated in the same manner as in Experimental Example 1, and the placement ratio of ultra-thin LEDs within the top surface of the first electrode was observed from SEM photographs. Also, for the ultra-thin LED elements in contact with the top surface of the first electrode, it was determined whether the surface in contact was the upper layer of the p-type conductive semiconductor layer, the lower layer of the n-type conductive semiconductor layer, or the side surface, and the numbers were counted. Specifically, among all the ultra-thin LED elements placed within the top surface, the number of LED elements belonging to the first group in contact with the lower layer of the n-type conductive semiconductor layer on the top surface and the number of LED elements belonging to the second group in contact with the upper layer of the p-type conductive semiconductor layer on the top surface were counted, and the drivable mounting ratio among all the ultra-thin LED elements placed within the top surface was calculated and presented in Table 2 below. Also, in Figure 15 SEM photographs of a part of the mounting area of the ultra-thin LED electrode assemblies of Example 3 and Examples 13 to 16 are presented.

[0165] Table 2

[0166]

[0167] From Table 2, it can be confirmed that in the cases of Example 17 where the dielectric constant of the solvent is less than 5 and Example 18 where the dielectric constant is greater than 50, the number of ultra-thin LED elements placed on the first electrode is significantly reduced.

[0168] Examples 19 to 31

[0169] They were implemented and manufactured in the same manner as in Example 3. By changing the manufacturing process of the ultra-thin LED elements, as shown in Table 3 below, a rotation-inducing film was formed on the side surface of the ultra-thin LED elements or an ultra-thin LED electrode assembly was manufactured using ultra-thin LED elements with adjusted thicknesses.

[0170] At this time, the rotation-inducing film formed a plurality of air holes in the LED wafer on which a plurality of LED structures were formed. After that, the temporary protective film was removed by ICP. Before immersing the LED wafer in a 100% γ-butyrolactone bubble-forming solution, a rotation-inducing film material was deposited to a thickness of 60 nm with reference to the side surface of the LED structures. After that, a process of removing the rotation-inducing film material formed between the LED structures by RIE to expose the upper surface of the doped n-type III-nitride semiconductor layer between the LED structures was also performed, thereby forming it on the side surface of the ultra-thin LED elements.

[0171] Also, the thickness variation of the ultra-thin LED elements was controlled by changing the depth of etching the LED wafer.

[0172] Experimental Example 3

[0173] The ultra-thin LED electrode assemblies of Examples 3 and 19 to 31 were evaluated in the same manner as in Experimental Example 1, and the placement ratio and drivable mounting ratio of the ultra-thin LEDs in the top surface of the first electrode were calculated and presented in Table 3 below.

[0174] Moreover, Figure 16 shows SEM photographs of a part of the mounting area of the ultra-thin LED electrode assemblies of Examples 3 and 19 to 21, Figure 17 shows SEM photographs of a part of the mounting area of the ultra-thin LED electrode assemblies of Examples 22 to 24, and Figure 18 shows SEM photographs of a part of the mounting area of the ultra-thin LED electrode assemblies of Examples 21 and 25 to 26.

[0175] Table 3

[0176]

[0177] It can be confirmed from Table 3 that in multiple examples, the placement ratio of the ultra-thin LED elements in the top surface of the first electrode is 76.5% or more, and the efficiency of moving and placing the multiple ultra-thin LED elements dispersed in the solvent onto the top surface of the first electrode is very excellent.

[0178] Moreover, it can be seen that in multiple examples having a rotation inducing film, the ratio of being mounted in a drivable manner is higher than that of Examples 3 and 19 without a rotation inducing film. However, in the case of Example 27 where the ratio of the thickness (b) / diameter (a) of the ultra-thin LED element is greater than 2.0 and Example 30 where the dielectric constant of the rotation inducing film is too large, it can be seen that the ratio of being mounted in a drivable manner is greatly reduced compared to other examples.

[0179] Although one embodiment of the present invention has been described above, the idea of the present invention is not limited to the embodiments presented in this specification. Those skilled in the art who understand the idea of the present invention can easily propose other embodiments by adding, changing, deleting, adding, etc. of structural elements within the scope of the same idea, and these also belong to the scope of the idea of the present invention.

Claims

1. A method for manufacturing an ultra-thin LED electrode assembly, characterized in that: include: The step of placing at least two first electrodes spaced apart from each other on the sides of the first electrodes into a solution having a plurality of ultra-thin LED elements; A step of applying a power source having a frequency of 500 Hz or less to the first electrode to form an electric field; The step of moving the ultra-thin LED element located in the electric field into the top surface of the first electrode; and The step of forming a second electrode line on the ultra-thin LED element disposed on the top surface of the first electrode.

2. The method for manufacturing an ultra-thin LED electrode assembly according to claim 1, characterized in that: The frequency of the power supply is 1 Hz to 500 Hz, and the voltage is 5 Vpp to 100 Vpp.

3. The method for manufacturing an ultra-thin LED electrode assembly according to claim 1, characterized in that: The viscosity of the solvent in the solution is 50 cP or less.

4. The method for manufacturing an ultra-thin LED electrode assembly according to claim 1, characterized in that: The dielectric constant (ε) of the solvent in the solution is 5-50.

5. The method for manufacturing an ultra-thin LED electrode assembly according to claim 1, characterized in that: The ultra-thin LED element is formed by stacking multiple layers including a first conductive semiconductor layer, a photoactive layer and a second conductive semiconductor layer. In order to generate a rotational torque in an axial direction perpendicular to the direction in which the multiple layers are stacked, it also has a rotation inducing film for surrounding the side of the ultra-thin LED element.

6. The method for manufacturing an ultra-thin LED electrode assembly according to claim 5, characterized in that: The dielectric constant (ε) of the spin inducing film is 3-26.

7. The method for manufacturing an ultra-thin LED electrode assembly according to claim 1, characterized in that: In the ultra-thin LED element, a ratio (b / a) of a major axis length (a) in a cross section perpendicular to a stacking direction of the plurality of layers to a thickness (b) as a length in the stacking direction is greater than 0 and less than 2.

0.

8. The method for manufacturing an ultra-thin LED electrode assembly according to claim 7, characterized in that: The ratio (b / a) of the ultra-thin LED element is greater than 0 and less than or equal to 1.

8.

9. An ultra-thin LED electrode assembly, characterized in that: include: A first electrode line includes at least two first electrodes spaced apart from each other in a side-to-side manner; a plurality of ultra-thin LED elements, including a first ultra-thin LED element located within a top surface of the first electrode; as well as A second electrode line is disposed on the first ultra-thin LED element, Furthermore, the placement ratio within the top surface of the first electrode calculated according to the following mathematical formula 1 satisfies 40% or more: [Mathematical formula 1] The number of ultra-thin LED elements means the number of LED elements arranged in a unit area (1mm 2 ) and the total number of ultra-thin LED components in the first ultra-thin LED component.

10. The ultra-thin LED electrode assembly according to claim 9, characterized in that: The ultra-thin LED element is formed by stacking a plurality of layers including a first conductive semiconductor layer, a photoactive layer and a second conductive semiconductor layer, and includes a first surface and a second surface facing each other in the thickness direction. As the unit area (1mm 2 ) in the first ultra-thin LED elements, the total ratio of the number of third ultra-thin LED elements installed in a manner that the first surface is in contact with the top surface of the first electrode and the second surface is in contact with the second electrode line, and the total ratio of the number of fourth ultra-thin LED elements installed in a manner that the second surface is in contact with the top surface of the first electrode and the first surface is in contact with the second electrode line is more than 40%.

11. The ultra-thin LED electrode assembly according to claim 9, characterized in that: The interval between adjacent first electrodes is 2 μm to 10 μm.

12. The ultra-thin LED electrode assembly according to claim 9, characterized in that: In the ultra-thin LED element, the thickness as the length in the direction in which the plurality of layers are stacked is 0.5 μm to 1.5 μm, and the major axis length in the cross section perpendicular to the stacking direction of the plurality of layers is 0.5 μm to 3.0 μm.

13. The ultra-thin LED electrode assembly according to claim 10, characterized in that: The placement ratio within the top surface of the first electrode calculated according to Mathematical Formula 1 is greater than 80%, and the drivable installation ratio is greater than 50%.

14. A light source, characterized in that: An ultra-thin LED electrode assembly comprising any one of claims 9 to 13.

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