Multi-Stage Hierarchical Optical Cover System for LED Display

Abstract

The present invention relates to a multi-stage hierarchical optical cover system for an LED display. The LED display device comprises a PCB substrate having a plurality of LEDs arranged thereon and an optical cover structure covering the LED array on the PCB substrate. The optical cover structure comprises a plurality of first optical units configured to cover a first number of LEDs, a plurality of second optical units configured to cover a second number of LEDs greater than the first number and formed by combining a plurality of the first optical units, and a plurality of third optical units configured to cover a third number of LEDs greater than the second number and formed by combining a plurality of the second optical units. The first optical units, the second optical units, and the third optical units are sequentially stacked to form a multi-stage hierarchical optical structure, and the upper unit optical unit is formed by combining the lower unit optical unit. Through this multi-stage hierarchical structure, compared to a conventional single optical cover, the amount of thermal deformation is reduced to maintain alignment between the LEDs and optical elements. Additionally, maintenance time is shortened by allowing only the damaged parts to be selectively replaced, and manufacturing costs are reduced by producing molds for small optical cells, while optical quality is expected to be improved.

Description

Technology Field

[0001] The present invention relates to an LED display device, and more specifically, to a multi-stage layered optical cover structure disposed above a plurality of LED light sources to improve optical performance, suppress thermal deformation, and facilitate maintenance. Background Technology

[0002] An LED display device includes a plurality of LED light sources arranged on a PCB substrate and an optical cover structure positioned in front of these LEDs. The optical cover structure is an essential component for efficiently concentrating light from the LEDs and achieving a uniform illumination distribution.

[0003] As prior art, Korean Published Patent No. 10-2022-0126729 (hereinafter referred to as 'Prior Art 1') relates to a lens array, an LED lighting unit, an exposure device, and an exposure method, and discloses a structure in which a plurality of lenses are fixed to a lens plate, and a lens area where the lenses are fixed and a non-lens area where the lenses are not fixed are formed in a matrix. This prior art adopts a method of fixing the lens array to a base plate by placing a fastening means in the non-lens area.

[0004] However, conventional lens array structures including prior art 1 have the following problems.

[0005] First, since Prior Art 1 has a structure in which multiple lenses are integrally formed on a single lens array plate, the surface area of ​​the lens array plate is large, and consequently, thermal deformation (twisting, sagging) due to temperature changes and LED heat generation is likely to occur. Such thermal deformation causes misalignment between the relative positions of the LEDs and lenses, resulting in uneven light emission angles and light intensity, and consequently leading to a degradation of screen quality. In particular, this thermal deformation problem is even more severe in large LED displays.

[0006] Second, in the single lens array structure of Prior Art 1, precise alignment between the lens array and the LED array is very difficult. Even a slight misalignment of the lens array can cause hot spots, color deviations, and brightness deviations, and correcting this on-site consumes a lot of time and cost. In addition, if an alignment error occurs during initial assembly, there is a problem that the entire lens array must be reassembled.

[0007] Third, the lens array of Prior Art 1 is vulnerable to external impacts, scratches, and contamination, and since the entire lens array must be replaced even if only a part of it is damaged, there is a problem of extremely low maintenance efficiency and very high costs. In particular, large outdoor LED displays require frequent maintenance, but a single-structure lens array makes such maintenance work very inefficient.

[0008] Fourth, the single lens array structure of prior art 1 makes it difficult to configure optical patterns, diffusion structures, surface patterns, etc. differently for each region. Therefore, even in high-resolution LED displays, precise pattern implementation or optical optimization according to LED density is limited, and there is a problem in that it is difficult to impart different optical characteristics to different regions of the display.

[0009] Fifth, since Prior Art 1 is a two-dimensional structure in which lens regions and non-lens regions are simply arranged in a planar manner, it lacks a mechanism for dispersing and isolating thermal expansion in stages. Consequently, it is difficult to effectively suppress deformation of the entire lens array due to temperature changes.

[0010] Therefore, there is an urgent need to develop a technology that can simultaneously achieve suppression of thermal deformation, improved precision alignment, reduced maintenance time, enhanced ease of installation, improved pattern uniformity and visibility, and reduced manufacturing costs by providing a multi-stage hierarchical optical structure that is sequentially stacked from fine to large units based on the LED array on the PCB, rather than configuring the optical cover structure of an LED display as a single large mask or single lens array. The problem to be solved

[0011] The first problem that the present invention aims to solve is to maintain alignment between LEDs and optical elements and improve screen quality by subdividing the optical cover structure into multiple layers, configuring each layer to cover a different number of LEDs, and placing a thermal deformation absorption structure at the interface between each layer, thereby dispersing and isolating thermal expansion in stages.

[0012] The second problem that the present invention aims to solve is to significantly reduce maintenance time and improve the efficiency of installation work by adopting a multi-layered hierarchical structure of a fine pattern cell, a small pattern unit, and a medium pattern module, thereby allowing only the damaged parts to be selectively replaced and enabling independent assembly and alignment for each layer.

[0013] The third problem that the present invention aims to solve is to reduce production costs by manufacturing molds in the form of small optical cells and to enable different optical characteristics for each layer, thereby realizing fine patterns and optical effects and enabling optical optimization according to LED density and position, and to provide optical performance suitable for high-resolution LED displays. means of solving the problem

[0014] To achieve the above objectives, a multi-stage hierarchical optical cover system for an LED display according to one embodiment of the present invention is an optical cover system for covering an LED array on a PCB substrate having a plurality of LEDs arranged thereon, comprising: a plurality of first optical units configured to cover a first number of LEDs; a plurality of second optical units configured to cover a second number of LEDs greater than the first number and formed by combining a plurality of the first optical units; and a plurality of third optical units configured to cover a third number of LEDs greater than the second number and formed by combining a plurality of the second optical units, wherein the first optical units, the second optical units, and the third optical units are sequentially stacked to form a multi-stage hierarchical optical structure, and the upper unit optical unit is in contact with at least one lower unit optical unit simultaneously on the upper surface of the lower unit optical unit to combine the lower unit optical unit.

[0015] Preferably, the first optical unit is a fine pattern cell formed to include a predetermined number of LEDs as a single unit, the second optical unit is a small pattern unit formed by combining a plurality of the fine pattern cells into a frame structure, and the third optical unit is a medium pattern module formed by combining a plurality of the small pattern units.

[0016] It is preferable that the above micro-pattern cell be formed to include 2x2 or 3x3 LEDs as a single unit.

[0017] Preferably, the micro-pattern cell comprises an extension portion that accommodates the light output of the LED, a fixing portion that fixes the position of the LED, a guide portion that guides light from the LED forward, and a multilayer film structure comprising at least one of a light diffusion layer, a pattern layer, a UV protection layer, and a surface nano-coating layer.

[0018] It is preferable that the small pattern unit and the medium pattern module include a slit, a slot, or a floating compensation part at their respective interfaces to gradually disperse and isolate deformation caused by thermal expansion.

[0019] The medium-sized pattern module includes a coupling hole or coupling tab for combining a plurality of the small-sized pattern units, and it is preferable that the medium-sized pattern module be configured to be detachable at the site.

[0020] The above optical cover structure preferably further includes a final mask disposed on the upper part of the third optical unit to block external impact, scratches, contamination, and moisture.

[0021] It is desirable that the above-mentioned micro-pattern cell or the above-mentioned small pattern unit be configured to be individually replaceable in the event of damage or contamination, thereby enabling partial maintenance without disassembling the entire optical cover structure. Effects of the invention

[0022] According to the multi-stage layered optical cover system for LED displays of the present invention, the following remarkable effects can be obtained.

[0023] First, the present invention effectively suppresses thermal deformation by configuring the optical cover structure into a multi-layered structure consisting of a micro-pattern cell, a small-pattern unit, and a medium-pattern module. Since the size of each layer is small, the amount of thermal deformation occurring in each individual layer is minimized. Furthermore, thermal deformation absorption structures, such as slits, slots, and floating compensation parts placed at the interfaces between layers, disperse and isolate thermal expansion in stages, thereby maintaining the relative position between the LED and the optical element, which improves brightness and color uniformity and significantly enhances screen quality.

[0024] Second, the present invention dramatically improves maintenance efficiency. Since only the damaged parts can be selectively replaced at the level of a fine pattern cell or a small pattern unit, there is no need to disassemble the entire optical cover structure, and maintenance time is shortened compared to conventional technology. In addition, installation work can be performed at the level of a medium pattern module, significantly reducing on-site work time, and installation accuracy is further improved when used in conjunction with an AR / AI automatic alignment system. This improvement in maintenance efficiency contributes significantly to reducing operating costs, particularly in large outdoor LED displays.

[0025] Third, the present invention reduces manufacturing costs and improves optical performance. Since molds are manufactured at the small optical cell level without the need for large molds, initial investment costs are reduced and the defect rate is lowered. Furthermore, because optical patterns and films can be controlled at the micro-pattern cell level, delicate patterns and optical effects can be realized, and optical performance suitable for high-resolution LED displays can be provided. Brief explanation of the drawing

[0026] FIG. 1 is a schematic diagram of the overall system of a multi-stage layered optical cover system for an LED display according to one embodiment of the present invention. FIG. 2 is a detailed view of a micro-pattern unit according to an embodiment of the present invention. FIG. 3 is a detailed view of a small pattern unit according to an embodiment of the present invention. FIG. 4 is a detailed view of a medium-sized pattern unit according to one embodiment of the present invention. FIG. 5 is a partial cross-sectional view illustrating a coupling relationship for performing an inter-layer LED lens array function according to an embodiment of the present invention. FIG. 6 is a partial cross-sectional view illustrating an example of functional performance according to a thermal deformation absorption structure according to one embodiment of the present invention. FIG. 7 is a partial cross-sectional view illustrating a coupling form in the shape of a coupling tab according to one embodiment of the present invention. Specific details for implementing the invention

[0027] Hereinafter, various embodiments and / or aspects are disclosed with reference to the drawings. For illustrative purposes, numerous specific details are disclosed in the following description to aid in a general understanding of one or more aspects. However, it will also be recognized by those skilled in the art that these aspects may be practiced without such specific details. The following description and the accompanying drawings describe specific exemplary aspects of one or more aspects in detail. However, these aspects are exemplary, and some of the various methods in the principles of the various aspects may be used, and the description is intended to include all such aspects and their equivalents.

[0028] As used herein, terms such as "examples," "examples," "aspects," "examples," etc., may not be interpreted as implying that any aspect or design described is better or more advantageous than other aspects or designs.

[0029] Additionally, the terms “comprising” and / or “comprising” should be understood to mean that the relevant feature and / or component is present, but not to exclude the presence or addition of one or more other features, components and / or groups thereof.

[0030] Additionally, terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but said components are not limited by said terms. Such terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0031] Furthermore, in the embodiments of the present invention, all terms used herein, including technical or scientific terms, unless otherwise defined, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in the embodiments of the present invention.

[0032] FIG. 1 is a schematic diagram of the overall system of a multi-stage layered optical cover system for an LED display according to an embodiment of the present invention, FIG. 2 is a detailed view of a fine pattern unit according to an embodiment of the present invention, FIG. 3 is a detailed view of a small pattern unit according to an embodiment of the present invention, FIG. 4 is a detailed view of a medium pattern unit according to an embodiment of the present invention, FIG. 5 is a partial side cross-sectional view illustrating a coupling relationship for performing an inter-layer LED lens array function according to an implementation of an embodiment of the present invention, FIG. 6 is a partial side cross-sectional view illustrating an example of function performance according to a thermal deformation absorption structure according to an embodiment of the present invention, and FIG. 7 is a partial side cross-sectional view illustrating a coupling form in the shape of a coupling tab according to an embodiment of the present invention.

[0033] Meanwhile, in the following description, some components described in the drawings may be omitted or excessively enlarged or reduced in order to explain the function of each component of the present invention, but it will be understood that such illustrated components do not limit the technical features and scope of rights of the present invention.

[0034] In addition, in the following description, multiple drawings will be referred to simultaneously to explain a single technical feature or a component constituting the invention.

[0035] Referring to FIG. 1, a multi-stage hierarchical optical cover system for an LED display according to an embodiment of the present invention is an optical cover system for covering an LED array on a PCB substrate (1) having a plurality of LED elements (10) arranged thereon, comprising a plurality of first optical units (20) configured to cover a first number of LED elements (10), a plurality of second optical units (30) configured to cover a second number of LED elements (10) greater than the first number and formed by combining a plurality of the first optical units (20), and a plurality of third optical units (40) configured to cover a third number of LED elements (10) greater than the second number and formed by combining a plurality of the second optical units (30). The first optical units (20), the second optical units (30), and the third optical units (40) are sequentially stacked to form a multi-stage hierarchical optical structure, and an upper unit optical unit is formed by simultaneously contacting at least one lower unit optical unit on the upper surface of a lower unit optical unit to combine the lower unit optical units. It is characterized by.

[0036] Here, the PCB substrate (1) is a printed circuit board and serves as a structural support and electrical connection means for the LED display device. The PCB substrate (1) can be implemented in various forms, such as a glass fiber reinforced epoxy resin substrate made of FR-4 (Flame Retardant 4), a metal core PCB (MCPCB), a ceramic substrate, or a flexible PCB (FPCB). In particular, for high-power LED displays, using an MCPCB with an aluminum or copper core allows for efficient dissipation of heat generated from the LED element (10), which contributes to extending the lifespan of the LED element (10) and improving luminous efficiency. The thickness of the PCB substrate (1) is generally between 0.5 mm and 3 mm, and for large LED displays, a thickness of 1.6 mm to 2.4 mm is preferred to ensure structural rigidity. A circuit pattern electrically connected to an LED element (10) is formed on the surface of the PCB substrate (1), and this circuit pattern is formed with copper wiring and protected by coating a solder resist layer on top of it.

[0037] The LED element (10) is a light-emitting diode and is a semiconductor device that emits light when current flows. The LED element (10) can be implemented as a blue LED chip based on GaN (gallium nitride), a red LED chip based on AlGaInP (aluminum gallium indium phosphide), or an RGB LED chip that combines these. The LED element (10) can implement a full-color display by appropriately combining RGB elements. The size of the LED element (10) varies depending on the application; generally, for indoor LED displays, SMD (Surface Mount Device) type LEDs with sizes ranging from 1mm x 1mm to 3mm x 3mm are used, and for large outdoor displays, LEDs with sizes ranging from 5mm x 5mm to 10mm x 10mm can be used. LED elements (10) are arranged in a matrix form on a PCB substrate (1), and the pitch between adjacent LED elements (10) is determined according to the resolution of the display, with a fine pitch of 1 mm to 3 mm for a high-resolution display and a pitch of 5 mm to 20 mm for a standard resolution.

[0038] The core feature of the present invention is that the first optical unit (20), the second optical unit (30), and the third optical unit (40) are sequentially stacked to form a multi-stage hierarchical optical structure. This multi-stage hierarchical structure is based on a technical concept that is fundamentally different from a conventional single optical cover structure. Each layer covers a different number of LED elements (10), and the lower optical unit is joined by the upper optical unit contacting the lower optical unit on the upper surface of the lower optical unit and bonding it with an adhesive or a physical structure. This arrangement allows for the simultaneous achievement of various technical effects, such as the stepwise dispersion of thermal deformation, ease of precise alignment, efficiency of maintenance, and reduction of manufacturing costs.

[0039] Referring to FIG. 1 and FIG. 2 together, it is preferable that the first optical unit (20) is a fine pattern cell formed to include a predetermined number of LED elements (10) as a single unit, the second optical unit (30) is a small pattern unit formed by combining a plurality of the fine pattern cells into a frame structure, and the third optical unit (40) is a medium pattern module formed by combining a plurality of the small pattern units.

[0040] The micro-pattern cell, which is the first optical unit (20), is the lowest unit optical element in the multi-stage hierarchical optical structure of the present invention and corresponds directly to the LED element (10) to perform the function of primarily collecting light emitted from the LED element (10) and controlling its direction. Because the size of the micro-pattern cell is small, the amount of thermal deformation due to temperature changes is minimized, which critically contributes to maintaining precise alignment between the LED element (10) and the optical element. The micro-pattern cell can be formed from a transparent optical-grade plastic resin, such as PMMA (polymethyl methacrylate), PC (polycarbonate), COC (cyclic olefin copolymer), or optical-grade silicone resin, and these materials have optical properties such as excellent light transmittance (generally 90% or more), a low yellowness index, and an appropriate refractive index (range of 1.4 to 1.6). PMMA has excellent transparency and is inexpensive, making it suitable for mass production, but it has the disadvantage of being susceptible to scratches due to its relatively low surface hardness. PC has excellent durability with impact strength approximately 250 times higher than PMMA, but it has the disadvantage of being relatively expensive and prone to yellowing when exposed to ultraviolet rays for a long time. COC has low birefringence and excellent dimensional stability, making it suitable for precision optical components, but it has the disadvantage of being very expensive.

[0041] Referring to FIG. 2 (a) and (b), the micro-pattern cell is preferably formed to include 2x2 or 3x3 LED elements (10) as a single unit. Although a structure covering 2x2 LED elements (10) is illustrated in the drawings, this is merely one embodiment of the present invention, and it can be modified into various combinations such as 1x2, 2x3, 3x3, 2x4, 3x4, and 4x4 depending on the arrangement density of the LED elements (10), the size of the display, and the required optical performance. When 2x2 LED elements (10) are configured as a single micro-pattern cell, the size of the micro-pattern cell is small, so thermal deformation is minimized and manufacturing is easy. When 3x3 LED elements (10) are configured as a single micro-pattern cell, the number of micro-pattern cells is reduced, shortening assembly time and reducing the number of inter-layer interfaces, which has the advantage of reducing light loss. In practice, for a high-resolution display with a pitch of 2 mm or less of LED elements (10), a 2x2 configuration is preferred, and for a general-resolution display with a pitch of 5 mm or more of LED elements, a 3x3 or 4x4 configuration is preferred.

[0042] Referring to FIG. 2(b), the micro pattern cell (20) preferably includes an extension part (22) that receives the light output of the LED element (10), a fixing part (21) that fixes the position of the LED element (10), a guide part (23) that guides light from the LED element (10) forward, and a multilayer film structure (25) that includes at least one of a light diffusion layer, a pattern layer, a UV protection layer, and a surface nano-coating layer.

[0043] The fixing part (21) is formed at the bottom of the micro-pattern cell (20) and contacts the upper surface of the LED element (10) or the periphery of the LED element (10) to fix the relative position between the micro-pattern cell (20) and the LED element (10). The fixing part (21) may be formed in the shape of a concave receiving groove corresponding to the shape of the LED element (10) or in a shape that wraps around the LED element from the side. In this case, the LED element (10) is inserted into the receiving groove, etc., thereby achieving the effect of automatically aligning the position on the XY plane. The gap between the fixing part (21) and the LED element (10) is generally set in the range of 0.05 mm to 0.3 mm, and this gap is a suitable range for maintaining optical coupling while absorbing assembly tolerances. The thickness of the fixing part (21) is preferably in the range of 0.5 mm to 2 mm; if it is too thin, structural strength is insufficient, and if it is too thick, light loss increases. The fixing part (21) may be molded integrally with the main body of the micro-pattern cell (20), or it may be manufactured as a separate part and joined by adhesive or welding. When the fixing part (21) comes into direct contact with the LED element (10), reflection loss at the interface can be minimized through index matching by applying an optical-grade transparent adhesive between the fixing part (21) and the LED element (10). As such an optical adhesive, a UV-curing or thermo-curing silicone adhesive with a refractive index in the range of 1.4 to 1.6 may be used.

[0044] The extension portion (22) is a component formed on the upper part of the fixed portion (21) that provides a diffusion area for light emitted from the LED element (10). Since the LED element (10) has characteristics similar to a point light source, the light directly emitted from the LED element (10) has a narrow beam angle and high luminous intensity. The extension portion (22) diffuses the light of this point light source in a horizontal direction to enable uniform illumination of a wider area. The extension portion (22) may have a taper shape in which the diameter or width gradually increases from the part adjacent to the LED element (10) toward the top, and this taper shape performs the function of diffusing light laterally using total internal reflection of light. The taper angle of the extension portion (22) is generally in the range of 5 to 30 degrees; the smaller the taper angle, the gentler the diffusion of light occurs, and the larger the taper angle, the more rapid the diffusion of light occurs. A light diffusion pattern may be formed on the inner surface of the extension (22), and such light diffusion pattern may be implemented in the form of a micro-lens array, a prism pattern, a random uneven pattern, etc. In the case of a micro-lens array, the diameter of individual lenses may be in the range of 10㎛ to 500㎛ and the pitch between lenses may have a value similar to the lens diameter, and in the case of a prism pattern, the vertex angle of the prism may be in the range of 60 degrees to 120 degrees and the prism pitch may be in the range of 50㎛ to 1mm. The height of the extension (22) is preferably in the range of 1mm to 10mm and can be appropriately adjusted according to the size of the LED element (10) and the required diffusion angle.

[0045] The guide portion (23) is a component formed on the upper part of the extension portion (22) to guide light from the LED element (10) forward. The guide portion (23) generally has a cylindrical, prismatic, or tapered conical / pyramidal shape, and its internal space forms a light path. The main function of the guide portion (23) is to direct the light diffused from the extension portion (22) forward, block light leaking laterally, and prevent light from adjacent LED elements (10) from mixing. The inner surface of the guide portion (23) can be treated to have specular reflection characteristics or diffuse reflection characteristics; in the case of specular reflection, it can be achieved by depositing aluminum, silver, or a dielectric multilayer film, and in the case of diffuse reflection, it can be achieved by applying a reflective coating containing a white pigment (e.g., TiO2, BaSO4). The height of the guide section (23) is preferably in the range of 2 mm to 30 mm and is determined according to the pixel pitch and viewing angle requirements of the LED display. The size of the exit opening of the guide section (23) is set larger than the size of the LED element (10) so that light can be sufficiently diffused, and is generally set in the range of 1.5 to 5 times the size of the LED element (10). The wall thickness of the guide section (23) is preferably in the range of 0.3 mm to 3 mm and is determined considering structural strength and moldability. Referring to FIG. 5, it can be seen that the guide section (23) of the first optical unit (20), the corresponding structure of the second optical unit (30), the corresponding structure of the third optical unit (40), and the final mask (50) are connected in succession to form an extended structure of the guide section (23) to limit the wide angle of the LED element (10) as a single lens array. This extension structure allows for independent optical adjustment at each layer while maintaining light directivity by aligning the guide sections of each layer vertically to form a continuous optical path.

[0046] A transparent layer (24) may be formed on the upper surface of the micro-pattern cell (20), and this transparent layer (24) functions to concentrate or diffuse light by acting as a lens. The transparent layer (24) is a layer of transparent material that is identical to the extension part (22) or is placed in the guide part (23), that is, the area above the extension part (22), and is understood to refer to the configuration of an extension part of a kind of lens array.

[0047] The transparent layer (24) can be formed in various shapes, such as a flat surface, a convex lens surface, a concave lens surface, an aspherical surface, or a Fresnel lens surface. In the case of a convex lens surface, it has the effect of increasing brightness by focusing light, but has the disadvantage of a narrowed field of view. In the case of a concave lens surface, it has the effect of widening the field of view by diffusing light, but has the disadvantage of lowering brightness. In the case of an aspherical surface, optical performance can be optimized by minimizing spherical aberration, but has the disadvantage of being complex to manufacture and having high costs. The radius of curvature of the transparent layer (24) can be set in the range of 5mm to 100mm and is adjusted according to the required light concentration or diffusion.

[0048] The multilayer film structure (25) is formed on the uppermost part of the micro-pattern cell (20) or on the upper part of the transparent layer (24) and includes at least one of a light-diffusing layer, a pattern layer, a UV protection layer, and a surface nano-coating layer. The light-diffusing layer performs the function of diffusing direct light from the LED element (10) to eliminate hot spots and achieve a uniform brightness distribution. The light-diffusing layer is formed in a structure in which light-diffusing particles are dispersed within a transparent substrate. The transparent substrate may include PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), TAC (triacetylcellulose), etc., and the light-diffusing particles may include silica beads, PMMA beads, PS (polystyrene) beads, hollow particles, etc. The diameter of the light-diffusing particles is generally in the range of 1 μm to 30 μm. The smaller the particle size, the lower the haze and the higher the transparency; the larger the particle size, the higher the haze and the stronger the diffusion effect. The thickness of the light-diffusing layer is preferably in the range of 25㎛ to 500㎛, and the haze can be adjusted to a range of 30% to 95%. The pattern layer is a layer for displaying specific patterns or providing visual effects, and can be formed with printed patterns, holographic patterns, microprism patterns, etc. In the case of printed patterns, they are formed by methods such as screen printing, gravure printing, offset printing, or inkjet printing, and the line width of the pattern is in the range of 10㎛ to 1mm; in the case of holographic patterns, they are formed using laser interference and exhibit an effect where the color changes depending on the viewing angle. The UV protection layer performs the function of blocking ultraviolet rays to prevent internal optical elements from yellowing or deteriorating due to ultraviolet rays. The UV protection layer is formed as a transparent resin layer containing a UV absorber, and benzophenone-based, benzotriazole-based, triazine-based, and oxalanilide-based compounds are used as UV absorbers. The UV blocking rate of the UV protection layer is generally 95% or higher, and it effectively blocks UV-A and UV-B with wavelengths of 380nm or less.A surface nanocoating layer is formed on the outermost surface of a micro-pattern cell (20) to perform functions such as anti-contamination, waterproofing, scratch resistance, and anti-reflection. The surface nanocoating layer is formed by applying and curing a transparent coating agent containing nano-sized inorganic particles (e.g., SiO2, TiO2, Al2O3), and the thickness of the coating layer is in the range of 50 nm to 5 µm. The anti-contamination function is achieved by lowering the surface energy, and the water contact angle can be increased to 100 degrees or more by using a fluorine-based or silicone-based coating agent, and the anti-reflection function is achieved by forming a multilayer film structure with different refractive indices, and the reflectance in the visible light region can be reduced to 1% or less.

[0049] Referring to FIG. 3 (a) and (b), the small pattern unit, which is the second optical unit (30), is formed by combining a plurality of the micro pattern cells (20) into a frame structure. Although the drawing illustrates a structure in which 2x2 micro pattern cells (20) are combined, this is merely one embodiment of the present invention and can be modified and implemented in various combinations such as 2x3, 3x3, 3x4, 4x4, etc. The small pattern unit (30) performs the function of improving the efficiency of the assembly process, correcting alignment errors between micro pattern cells (20), and enabling maintenance on an area-by-area basis by integrating a plurality of micro pattern cells (20) into a single assembly unit.

[0050] The frame structure of the small pattern unit (30) can be manufactured by methods such as injection molding, 3D printing, and CNC machining, and the materials used may include ABS (acrylonitrile-butadiene-styrene), PC (polycarbonate), PA (polyamide), POM (polyoxymethylene), aluminum alloy, magnesium alloy, etc. ABS is inexpensive and has excellent moldability, but has relatively low heat resistance (80 to 90 degrees Celsius); PC is excellent in transparency and impact resistance, but is relatively expensive; PA is excellent in heat resistance and mechanical strength, but has hygroscopicity, so dimensional stability may be poor; POM is low in friction coefficient and has excellent dimensional stability, but is vulnerable to ultraviolet rays. Aluminum alloy has high thermal conductivity (about 200 W / mK), so it has excellent heat dissipation performance and is lightweight yet strong, but it is expensive and requires insulation treatment because it is electrically conductive; magnesium alloy is lighter than aluminum (about 35% lighter), but it is very expensive and vulnerable to corrosion.

[0051] Referring to FIG. 3(b), the small pattern unit (30) and the medium pattern module (40) are preferably configured to include a slit (31), a slot (31), or a floating compensation part (32) at their respective interfaces to gradually disperse and isolate deformation caused by thermal expansion.

[0052] The slit (31) is a narrow, long cut-line-shaped gap formed at the frame edge or boundary of the small pattern unit (30) and the medium pattern module (40), with a width ranging from 0.1 mm to 1 mm and a length ranging from 5 mm to 20 mm. The slit (31) can be formed in various shapes such as straight, curved, zigzag, or spiral. In the case of a straight shape, manufacturing is simple but stress concentration may occur; in the case of a curved shape, the stress distribution effect is excellent but manufacturing is complex; and in the case of a zigzag shape, deformation in the longitudinal direction can be effectively absorbed. The slit (31) can be placed between the fine pattern cells (20) and the fine pattern cells (20), between the small pattern unit (30) and the small pattern unit (30), or between the medium pattern module (40) and the medium pattern module (40). The main function of the slit (31) is to absorb deformation as the slit (31) narrows or widens during thermal expansion, to block stress transfer between adjacent optical units, and to allow each unit to move independently and finely. The spacing of the slit (31) is generally in the range of 10 mm to 50 mm, and the narrower the spacing, the greater the thermal deformation absorption effect but the lower the structural strength, and the wider the spacing, the structural strength is maintained but the thermal deformation absorption effect is reduced.

[0053] The slot (31) is a rectangular or elliptical opening wider than the slit, with a width ranging from 1 mm to 5 mm and a length ranging from 10 mm to 50 mm. The slot (31) is strategically placed near the corners or center of the frame structure and is formed in a location where it must allow for greater deformation than the slit (31). The main function of the slot (31) is to allow for a greater range of thermal expansion and contraction, to allow fastening means (bolts, screws, etc.) to move within the slot (31) within a certain range, and to allow for selective deformation in the X-axis or Y-axis direction. The shape of the slot (31) can be implemented in various ways, such as circular, elliptical, rectangular, or keyhole shapes. In the case of a keyhole shape, it has a narrow opening and a wide internal space, which allows for easy insertion of the fastening means while preventing it from coming loose.

[0054] Referring to FIG. 6, the slit or slot (31) may be formed by a pair of ribs (311), and the ribs (311) may be bent into the space formed by the slit or slot (31) by the thermal expansion force (P1) of the first optical unit (20) to effectively absorb thermal expansion. The ribs (311) have a protruding shape as part of the frame structure, and their thickness is in the range of 0.5 mm to 3 mm and their height is in the range of 2 mm to 10 mm. The ribs (311) must be formed of an elastically deformable material, and generally, thermoplastic resins such as PC, ABS, PA, or elastic materials such as silicone rubber or urethane rubber are used. The cross-sectional shape of the ribs (311) can be implemented in various ways, such as rectangular, triangular, or trapezoidal, and in the case of a triangular cross-section, it has the effect of preventing breakage by minimizing stress concentration. The spacing between a pair of ribs (311) corresponds to the width of the slit or slot (31). When the first optical unit (20) expands during thermal expansion, the ribs (311) bend into the space of the slit or slot (31) to absorb the expansion force, and when the ribs (311) contract during thermal contraction, they return to their original position to absorb the contraction force. Through this mechanism, stress caused by thermal expansion and contraction is locally relieved within each layer, and the stress transmitted to the upper layer is minimized, thereby maintaining the dimensional stability of the entire optical cover system.

[0055] The floating compensation member (32) is implemented as an elastic pad, spring structure, or flexible connecting member, and performs the function of absorbing pressure caused by thermal expansion through elastic deformation, allowing each optical unit to maintain a slightly "floating" state up, down, left, and right, and also absorbing vibrations and shocks. The floating compensation member (32) can be implemented in various forms, such as an elastic pad type, a spring type, or a flexible connecting type. The elastic pad type floating compensation member (32) has a structure in which an elastic material such as silicone, urethane, EPDM (ethylene-propylene-diene monomer), or NBR (nitrile butadiene rubber) is interposed between frames, and its thickness is preferably in the range of 0.5 mm to 3 mm and its hardness is preferably in the range of Shore A 30 to 70. In the case of silicone, it has excellent heat resistance (-50 to 200 degrees Celsius) and weather resistance and low compressive permanent strain, but relatively low mechanical strength; in the case of urethane, it has excellent wear resistance and mechanical strength but relatively low heat resistance (~80 degrees Celsius); in the case of EPDM, it has excellent ozone resistance and weather resistance and is inexpensive but has low oil resistance; and in the case of NBR, it has excellent oil resistance and solvent resistance but low ozone resistance. The spring-type floating compensation part (32) is a structure in which a plate spring or a coil spring is placed in the joint part, and in the case of the plate spring, a stainless steel or phosphor bronze plate with a thickness of 0.1 mm to 1 mm and a width of 5 mm to 20 mm is used, and in the case of the coil spring, a compression coil spring with a wire diameter of 0.3 mm to 2 mm, an outer diameter of 3 mm to 10 mm, and a free length of 5 mm to 30 mm is used. The flexible connection type floating compensation part (32) is implemented as a thin metal plate or plastic hinge structure, and for the metal plate, stainless steel, phosphor bronze, beryllium copper, etc. with a thickness of 0.05 mm to 0.5 mm is used, and for the plastic hinge, PP (polypropylene), PE (polyethylene), PET, etc. with a thickness of 0.3 mm to 2 mm is used.

[0056] Referring to FIGS. 3 and FIGS. 6 together, the slit or slot (31) and the floating compensation part (32) can be applied in combination to the second optical unit (30) and the third optical unit (40), as well as to the final mask (50), and their placement locations can be formed at various locations, such as the corners of each unit and intermediate connection areas. When placed at the corners, a thermal deformation absorption effect can be obtained while maintaining structural strength, and when placed at intermediate connection areas, sagging of the central part occurring in large-area units can be prevented. The combination method of the slit or slot (31) and the floating compensation part (32) can be selected according to various conditions, such as the overall size of the optical cover system, the amount of heat generated by the LED element (10), the temperature range of the usage environment, the required dimensional stability, and the manufacturing cost. For example, in the case of a small LED display (diagonal size of 1m or less), sufficient thermal deformation absorption is possible with only the slit (31), and for a medium LED display, it is desirable to set the width of the slit (31) or slot (31) large and set the elastic modulus of the floating compensation part (32) low. The most desirable embodiment in terms of lowering manufacturing costs is a configuration in which slits (31) are placed at four corners of the second optical unit (30) and slits (31) are not placed in the intermediate connection area, slots (31) are placed at four corners of the third optical unit (40) and floating compensation parts (32) are placed at two intermediate connection areas, and floating compensation parts (32) are placed only at four corners of the final mask (50).This configuration allows for the slit (31) to be applied primarily to the second optical unit (30) as it is the simplest and most cost-effective to process, the slot (31) to be applied to the corners of the third optical unit (40) of a larger size as it is more complex to process than the slit (31) but allows for greater deformation, and the floating compensation part (32) to be applied selectively only to the intermediate connection area of ​​the third optical unit (40) and the corners of the final mask (50) as it adds to the cost of parts but has excellent vibration absorption effect, thereby ensuring sufficient thermal deformation absorption performance while minimizing the overall manufacturing cost.

[0057] Referring to FIG. 4 (a) and (b), the third optical unit, which is the medium pattern module (40), is formed by combining a plurality of the small pattern units (30). Although the drawing illustrates a structure in which 2x2 small pattern units (30) are combined, this is merely one embodiment of the present invention and can be modified and implemented in various combinations such as 2x3, 3x3, 3x4, 4x4, etc. The medium pattern module (40) is manufactured in a size that is easy for a person to handle in the field, and generally, the length of one side is set to range from 300mm to 1000mm and the weight is set to range from 1kg to 10kg. If the size of the medium pattern module (40) is too small, the number of modules required to configure the entire LED display increases, the assembly time becomes longer, and the number of inter-layer interfaces increases, resulting in greater light loss. If the size of the medium pattern module (40) is too large, it becomes difficult to handle, the amount of thermal deformation increases, and the risk of damage increases.

[0058] Referring to FIG. 4, the medium pattern module (40) includes a coupling hole (42) or a coupling tab (41) for coupling a plurality of the small pattern units (30), and the medium pattern module (40) is preferably configured to be detachable at the site.

[0059] The coupling hole (42) is a circular or rectangular hole; in the case of a circular hole, it has a diameter of 3 mm to 10 mm and is positioned at a point requiring precise positioning, and is structured to allow for the insertion of bolts, rivets, pins, etc.; in the case of a rectangular hole, it has a width of 3 mm to 8 mm and a length of 10 mm to 30 mm, providing a margin for position adjustment during assembly and a clearance to allow for thermal expansion. The coupling hole (42) is symmetrically positioned near the four corners of the medium pattern module (40) to ensure even load distribution, and is positioned at two to four locations on each edge of the small pattern unit (30) frame. The main function of the coupling hole (42) is to allow a coupling bolt (43) or screw, which is a fastening means, to pass through and be fixed, and to serve as an alignment reference point between the upper and lower optical units. Referring to FIG. 4 (b), the coupling bolt (43) is coupled to the substrate (1) through the coupling hole (42) to fix the medium pattern module (40) onto the substrate (1). The connecting bolt (43) may have specifications such as M2, M2.5, M3, M4, etc., and may be made of stainless steel, brass, aluminum alloy, etc. The tightening torque of the connecting bolt (43) is generally set in the range of 0.5 Nm to 5 Nm, and since excessive tightening torque can cause deformation of the frame and insufficient tightening torque can cause a lack of fixing force, proper torque management is required.

[0060] The coupling tab (41) is a structure indicated by the coupling rib in FIG. 4 (a) and has a protruding latch or hook shape. The coupling tab (41) can be implemented in various forms, such as a protruding tab, a latch tab, or a slide tab. In the case of a protruding tab, it is a projection protruding 2 mm to 10 mm from the frame edge, with a thickness of 1 mm to 3 mm and a shape such as a rectangle, T-shape, or L-shape. In the case of a latch tab, it is a snap-fit ​​structure that is inserted and removed by elastic deformation and can be attached and detached without tools. In the case of a slide tab, it is coupled by sliding along a rail and can be inserted and removed in only one direction. The coupling tab (41) is placed on the upper, lower, left, and right edges of the frame and is positioned to interlock with the tab of an adjacent unit, and is generally placed in 4 to 8 locations. The main function of the coupling tab (41) is to enable assembly and disassembly by hand without tools, to enable quick on-site installation and maintenance, and to serve as a guide for accurate position alignment.

[0061] Referring to FIG. 7, a specific embodiment of a coupling tab is illustrated. FIG. 7 illustrates a coupling tab formed in a second optical unit (30), but it will be understood that this is an illustration and description of the specific structure of the coupling tab (41) of the third optical unit (40) illustrated in FIG. 4 (a).

[0062] A structure is illustrated in which a coupling jaw (26) is formed on the corner side of the first optical unit (20), and a coupling tab (locking part) is formed in an area corresponding to the coupling jaw (26) on a pair of ribs (311) forming a slot of the second optical unit (30). Accordingly, a structure can be formed in which the coupling tab is inserted into the coupling jaw (26) and locked to complete the coupling, thereby absorbing the expansion force. Specifically, the coupling jaw (26) of the first optical unit (20) is a stepped structure protruding in the horizontal direction formed on the outer surface of the micro-pattern cell (20), and its protrusion length is in the range of 0.5 mm to 3 mm and its thickness is in the range of 0.3 mm to 2 mm. The coupling tab formed on a pair of ribs (311) of the second optical unit (30) is a locking projection structure formed on the inner surface of the ribs (311), and its protrusion length is in the range of 0.3 mm to 2 mm and its thickness is in the range of 0.3 mm to 1.5 mm. When assembling, if the first optical unit (20) is inserted vertically into the slot (31) of the second optical unit (30), the rib (311) is elastically deformed and temporarily spreads apart. When the connecting jaw (26) reaches the position of the connecting tab, the rib (311) returns to its original position, and the connecting tab catches on the connecting jaw (26), completing the connection. This snap-fit ​​connection structure has the advantage of high work efficiency as it allows for manual assembly without tools, easy maintenance as it enables repeated attachment and detachment, and allows for intuitive confirmation of the completion of the connection through a "click" sound during connection. Additionally, even if an expansion force (P1) is applied when the first optical unit (20) undergoes thermal expansion, the connection structure of the connecting tab and the connecting jaw (26) has a clearance that allows for slight movement within the slot (31). Consequently, the expansion force is absorbed by the elastic deformation of the rib (311), thereby minimizing the stress transmitted to the second optical unit (30).

[0063] In practice, it is preferable to use a combination of the coupling hole (42) and the coupling tab (41). For primary alignment, the position is quickly aligned and pre-assembled using the coupling tab (41), and for secondary fixing, the final fastening is performed using a bolt through the coupling hole (42). For maintenance, it is efficient to configure it so that the tab structure can be easily separated by simply loosening the bolt.

[0064] Referring to FIG. 1, the optical cover structure preferably further includes a final mask (50) positioned on the upper part of the third optical unit (40) to block external impact, scratches, contamination, and moisture. The final mask (50) is a protective layer located at the top of the multi-stage layered optical structure of the present invention, and performs the function of protecting the lower first optical unit (20), second optical unit (30), and third optical unit (40) from the external environment, providing visual unity of the entire LED display, and providing additional optical effects.

[0065] The final mask (50) may be formed from tempered glass, an acrylic plate, a polycarbonate plate, a PET film, or a composite structure thereof. The thickness of the final mask (50) varies depending on the application, and is preferably in the range of 1 mm to 3 mm for small indoor displays, 3 mm to 6 mm for large indoor displays, and 5 mm to 10 mm for outdoor displays. Functional coatings such as an anti-reflective coating, an anti-fingerprint coating, an anti-fouling coating, and an anti-fogging coating may be applied to the surface of the final mask (50). The anti-reflective coating is formed as a multilayer thin film structure with different refractive indices to reduce the reflectance in the visible light region to 1% or less; the anti-fingerprint coating applies a fluorine-based or silicone-based water-repellent coating agent to minimize fingerprint adhesion; the anti-fouling coating applies a photocatalyst (e.g., TiO2) or a superhydrophobic coating to prevent the adhesion of dust and contaminants; and the anti-fogging coating applies a hydrophilic coating to form a thin water film without water droplets forming.

[0066] The final mask (50) may not be a simple transparent protective plate but may include an optical pattern structure or an artistic pattern structure to enhance the visual representation of the entire screen. Optical pattern structures may include a micro-lens array, a prism film, a brightness enhancement film (BEF), a viewing angle magnification film, etc., and artistic pattern structures may include a gradient pattern, a geometric pattern, an organic curve pattern, a holographic pattern, etc.

[0067] Referring to FIGS. 1 and 5, it is preferable that the micro pattern cell (20) or the small pattern unit (30) be configured to be individually replaceable in the event of damage or contamination, thereby enabling partial maintenance without disassembling the entire optical cover structure. This is one of the key advantages provided by the multi-stage layered structure of the present invention. In conventional single optical cover structures, there was inefficiency in having to replace the entire structure even if only a part was damaged, but in the present invention, only the damaged micro pattern cell (20) or small pattern unit (30) can be selectively replaced, thereby significantly reducing maintenance time and costs.

[0068] The specific maintenance procedure is as follows. First, the damaged part is identified by visual inspection or inspection equipment to determine the damaged micro-pattern cell (20) or small pattern unit (30). Next, the final mask (50) is removed; however, if the final mask (50) is a structure divided into multiple panels, only the panel containing the damaged part is removed. Afterward, the connecting bolt (43) of the medium pattern module (40) containing the damaged part is loosened to separate the medium pattern module (40). The damaged small pattern unit (30) is separated from the separated medium pattern module (40) using the connecting tab (41) or connecting bolt, and if necessary, the damaged micro-pattern cell (20) is separated from the small pattern unit (30). A new micro-pattern cell (20) or small pattern unit (30) is prepared and assembled in reverse order, with the connecting tab (41) being snap-fitted and the connecting bolt (43) being tightened with an appropriate torque. After reinstalling the medium pattern module (40) in its original position and securing it with a connecting bolt (43), the final mask (50) is reinstalled. Finally, the LED display is turned on to check if the brightness and color of the replaced part match the surroundings, and if necessary, the driving current of the LED element (10) is adjusted to correct it.

[0069] The embodiment illustrated in FIGS. 1, 2, 3, 4, 5, 6, and 7 illustrates a structure in which a first optical unit (20) covers 2x2 LED elements (10), a second optical unit (30) combines and covers 2x2 first optical units (20), a third optical unit (40) combines and covers 2x2 second optical units (30), and a final mask (50) covers all third optical units (40). However, this is merely one of the preferred embodiments of the present invention and does not limit the technical scope of the present invention. In actual implementation, the number and arrangement of LED elements (10) covered by each optical unit may be changed by considering various factors such as the size, resolution, use, installation environment, and manufacturing cost of the LED display.

[0070] For example, the first optical unit (20) can cover LED elements (10) in various combinations such as 1x2, 2x2, 2x3, 3x3, 2x4, 3x4, 4x4, etc., and the second optical unit (30) can combine the first optical unit (20) in various combinations such as 1x2, 2x2, 2x3, 3x3, 2x4, 3x4, 4x4, etc., and the third optical unit (40) can combine the second optical unit (30) in various combinations such as 1x2, 2x2, 2x3, 3x3, 2x4, 3x4, 4x4, etc. Additionally, the number and arrangement of sub-units covered by each optical unit may be the same or different for each optical unit. For example, a configuration is possible in which the first optical unit (20) covers all 2x2 LED elements (10), the second optical unit (30) combines all 3x3 first optical units (20), and the third optical unit (40) combines all 2x2 second optical units (30), or a mixed configuration is possible in which some of the first optical units (20) cover 2x2 LED elements (10) and others cover 3x3 LED elements (10).

[0071] Since the size and arrangement of each optical unit can be variably set, the multi-stage layered optical cover system of the present invention can be flexibly applied to LED displays of various specifications. For example, in the case of a high-resolution indoor LED display, the pitch of the LED elements (10) is very narrow from 1 mm to 3 mm, so a small configuration of the first optical unit (20) covering 2x2 or 1x2 LED elements (10) is preferred; in the case of a standard resolution indoor LED display, the pitch of the LED elements (10) is 3 mm to 6 mm, so a medium configuration of the first optical unit (20) covering 2x2 or 3x3 LED elements (10) is preferred; and in the case of a large outdoor LED display, the pitch of the LED elements (10) is wide from 5 mm to 20 mm, so a large configuration of the first optical unit (20) covering 3x3 or 4x4 LED elements (10) is preferred.

[0072] In addition, when high resolution is required only in a specific area of ​​the LED display (e.g., high resolution in the center and normal resolution in the periphery), the first optical unit (20) placed in the center covers 2x2 LED elements (10), and the first optical unit (20) placed in the periphery covers 3x3 or 4x4 LED elements (10), thereby allowing the overall manufacturing cost to be reduced while ensuring image quality in the core area.

[0073] The size and arrangement of the second optical unit (30) and the third optical unit (40) can also be variably set. Generally, it is desirable to combine a larger number of lower optical units with higher optical units in terms of assembly efficiency, but it is important to maintain an appropriate balance because if the size of the upper optical unit is too large, it is difficult to handle and the amount of thermal deformation increases. In practice, it is desirable to set the length of one side of the second optical unit (30) to a range of 50mm to 200mm and the length of one side of the third optical unit (40) to a range of 300mm to 1000mm.

[0074] As described above, the multi-stage hierarchical optical cover system for an LED display according to the present invention is formed by sequentially stacking a first optical unit (20), a second optical unit (30), and a third optical unit (40) to form a multi-stage hierarchical optical structure, and by having an upper unit optical unit simultaneously contact at least one lower unit optical unit on the upper surface of a lower unit optical unit to combine the lower unit optical units. This reduces the amount of thermal deformation compared to a conventional single optical cover structure, thereby maintaining alignment between the LED element (10) and the optical element, allows for selective replacement of only the damaged parts to shorten maintenance time, and enables significant effects such as reducing manufacturing costs through the production of molds for small optical cell units while improving optical quality.

[0075] Although the embodiments have been described above with reference to limited embodiments and drawings, those skilled in the art will understand that various modifications and variations are possible from the description above. Terms such as "include," "compose," or "have" as described above imply that components may be inherent unless specifically stated otherwise; therefore, they should be interpreted as allowing for the inclusion of additional components rather than excluding other components. Furthermore, the scope of protection of the present invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention.

Claims

Claim 1 An optical cover system for covering an LED array on a PCB substrate having a plurality of LEDs arranged thereon, comprising: a plurality of first optical units configured to cover a first number of LEDs; and a plurality of second optical units configured to cover a second number of LEDs greater than the first number, and formed by combining a plurality of the first optical units. A multi-stage hierarchical optical cover system for an LED display, comprising a plurality of third optical units formed by combining a plurality of second optical units, configured to cover a third number of LEDs greater than the second number, wherein the first optical unit is a fine pattern cell formed to include a predetermined number of LEDs as a single unit, the second optical unit is a small pattern unit formed by combining a plurality of the fine pattern cells into a frame structure, and the third optical unit is a medium pattern module formed by combining a plurality of the small pattern units, wherein the first optical unit, the second optical unit, and the third optical unit are sequentially stacked to form a multi-stage hierarchical optical structure, and wherein the upper unit optical unit is in contact with at least one lower unit optical unit simultaneously on the upper surface of the lower unit optical unit to combine the lower unit optical unit. Claim 2 delete Claim 3 A multi-stage layered optical cover system for an LED display according to claim 1, characterized in that the micro-pattern cell is formed to include 2x2 or 3x3 LEDs as a single unit. Claim 4 A multi-stage layered optical cover system for an LED display according to claim 1, wherein the micro-pattern cell comprises an extension portion for receiving the light output of the LED, a fixing portion for fixing the position of the LED, a guide portion for guiding light from the LED forward, and a multi-layer film structure including at least one of a light diffusion layer, a pattern layer, a UV protection layer, and a surface nano-coating layer. Claim 5 A multi-stage hierarchical optical cover system for an LED display according to claim 1, wherein the small pattern unit and the medium pattern module each include a slit, a slot, or a floating compensation part at their respective interfaces, configured to gradually disperse and isolate deformation caused by thermal expansion. Claim 6 A multi-stage layered optical cover system for an LED display according to claim 1, wherein the medium-sized pattern module includes a coupling hole or coupling tab for coupling a plurality of the small-sized pattern units, and the medium-sized pattern module is configured to be detachable at the site. Claim 7 A multi-stage layered optical cover system for an LED display according to claim 1, characterized in that the optical cover system further comprises a final mask disposed on the upper part of the third optical unit to block external impact, scratches, contamination, and moisture. Claim 8 A multi-stage layered optical cover system for an LED display according to claim 1, wherein the micro-pattern cell or the small pattern unit is configured to be individually replaceable in the event of damage or contamination, thereby enabling partial maintenance without disassembling the entire optical cover structure.

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