LED light-emitting structure, manufacturing method thereof and light-emitting device

Abstract

The invention discloses an LED light-emitting structure, a manufacturing method thereof and a light-emitting device, the LED light-emitting structure is of a multi-layer structure, and the LED light-emitting structure sequentially comprises an LED light source, a grating layer, a gradient refraction layer and a micro-lens array layer from bottom to top; the grating layer is used for diffracting light rays emitted by the LED light source to the gradient refraction layer at different angles; the gradient refraction layer comprises a bottom refraction layer, a middle refraction layer and a top refraction layer, the refractive indexes of the bottom refraction layer, the middle refraction layer and the top refraction layer are sequentially reduced, the bottom refraction layer is connected with the grating layer, the top refraction layer is connected with the micro-lens array layer, and the gradient refraction layer is used for increasing the emergent angle of light; the micro-lens array layer is used for uniformly distributing the light rays emitted by the gradient refraction layer at a larger angle; in combination with three optical structures of the grating layer, the gradient refraction layer and the micro-lens array layer, step-by-step modulation control of light is realized, functional complementation and synergistic interaction of all the layers are realized, the light emitting angle can be obviously increased, the light emitting uniformity can be enhanced, and in the gradient refraction layer, the refractive index gradient can be smoothed so as to improve the light distribution uniformity.

Description

Technical Field

[0001] The present invention relates to the technical field of LED devices, and in particular, to an LED light-emitting structure, a manufacturing method thereof, and a light-emitting device. Background Art

[0002] The existing LED light-emitting angle regulation technology mainly relies on a single optical structure for regulation. Exemplarily, the optical structure is a microlens array layer or a scattering layer, and it is difficult to simultaneously achieve a large light-emitting angle and uniform light-emitting characteristics. The traditional LED device exhibits a typical Lambertian radiation characteristic: I(θ) = I0·cos(θ), so the maximum light-emitting angle of the LED is limited. Summary of the Invention

[0003] The present invention provides an LED light-emitting structure, a manufacturing method thereof, and a light-emitting device to solve the problem that the maximum light-emitting angle of traditional LED devices is limited.

[0004] In a first aspect, the present invention provides an LED light-emitting structure, which is a multi-layer structure and sequentially includes an LED light source, a grating layer, a gradient refractive index layer, and a microlens array layer from bottom to top;

[0005] The grating layer is used to diffract the light emitted by the LED light source to the gradient refractive index layer at different angles;

[0006] The gradient refractive index layer includes a bottom refractive index layer, an intermediate refractive index layer, and a top refractive index layer with sequentially decreasing refractive indices. The bottom refractive index layer is connected to the grating layer, and the top refractive index layer is connected to the microlens array layer. The gradient refractive index layer is used to increase the exit angle of the light;

[0007] The microlens array layer is used to uniformly distribute the light emitted from the gradient refractive index layer at a larger angle.

[0008] The LED light-emitting structure is a multi-layer structure and sequentially includes an LED light source, a grating layer, a gradient refractive index layer, and a microlens array layer from bottom to top;

[0009] The grating layer is used to diffract the light emitted by the LED light source to the gradient refractive index layer at different angles;

[0010] The gradient refractive index layer includes a bottom refractive index layer, an intermediate refractive index layer, and a top refractive index layer with sequentially decreasing refractive indices. The bottom refractive index layer is connected to the grating layer, and the top refractive index layer is connected to the microlens array layer. The gradient refractive index layer is used to increase the exit angle of the light;

[0011] The microlens array layer is used to uniformly distribute the light emitted from the gradient refractive index layer at a larger angle.

[0012] Optionally, the period of the grating layer ranges from 400 nm to 2 μm.

[0013] Optionally, the grating shape of the grating layer is rectangular.

[0014] Optionally, the number of the intermediate refractive index layers is greater than or equal to 1 layer.

[0015] Optionally, when the number of the intermediate refractive index layers is greater than 1 layer, the refractive index of the intermediate refractive index layers decreases successively from bottom to top.

[0016] Optionally, the refractive index of the bottom refractive index layer is equal to the refractive index of the grating layer.

[0017] Optionally, the refractive index of the top refractive index layer is equal to the refractive index of the microlens array layer.

[0018] Optionally, the microlens array layer is arranged in a hexagonal pattern.

[0019] In a second aspect, the present invention provides a method for manufacturing an LED light-emitting structure, including:

[0020] Providing an LED light source;

[0021] Configuring a grating layer above the LED light source;

[0022] Depositing a transition connection layer on the surface of the grating layer and pressing the grating layer and the gradient refractive index layer together;

[0023] Spin-coating an optical adhesive on the upper surface of the gradient refractive index layer, and bonding the microlens array layer to the upper surface of the gradient refractive index layer through the optical adhesive to form a microlens array layer on the upper surface of the gradient refractive index layer;

[0024] Curing the optical adhesive by UV light irradiation;

[0025] Performing heat treatment on the overall structure to obtain the LED light-emitting structure.

[0026] In a third aspect, the present invention provides a light-emitting device, including at least one LED light-emitting structure according to any one of the first aspect.

[0027] The beneficial effects of the present invention are as follows:

[0028] By combining three optical structures of a grating layer, a gradient refractive index layer, and a microlens array layer to achieve step-by-step modulation control of light, the functions of each layer are complementary and synergistic, which can significantly increase the emission angle (up to ±80°) and enhance the emission uniformity (greater than 85%). In the gradient refractive index layer, the light direction is adjusted through a transitional refractive index, which can smooth the refractive index gradient and reduce mutations, thereby improving the light distribution uniformity.

[0029] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. Brief Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0031] Figure 1 is a schematic diagram of an LED light-emitting structure provided by an embodiment of the present invention;

[0032] Figure 2 is a schematic diagram of a rectangular grating structure provided by an embodiment of the present invention;

[0033] Figure 3 is a schematic diagram of the diffraction effect of a grating layer provided by an embodiment of the present invention;

[0034] Figure 4 is a schematic diagram of a hexagonal arrangement of microlens structures provided by an embodiment of the present invention;

[0035] Figure 5 is a flowchart of a method for manufacturing an LED light-emitting structure provided by an embodiment of the present invention. Detailed Description of the Embodiments

[0036] In order to enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0037] Figure 1 is a schematic diagram of an LED light-emitting structure provided by an embodiment of the present invention, as Figure 1As shown, the LED light-emitting structure is a multi-layer structure, which sequentially includes an LED light source 10, a grating layer 20, a gradient refractive layer 30, and a microlens array layer 40 from bottom to top; the grating layer 20 is used to diffract the light emitted by the LED light source 10 at different angles to the gradient refractive layer 20; the gradient refractive layer 30 includes a bottom refractive layer, a middle refractive layer, and a top refractive layer with sequentially decreasing refractive indices. The bottom refractive layer is connected to the grating layer 20, and the top refractive layer is connected to the microlens array layer. The gradient refractive layer 30 is used to increase the exit angle of the light; the microlens array layer 40 is used to uniformly distribute the light exiting from the gradient refractive layer 30 at a larger angle.

[0038] In the LED light-emitting structure, the grating layer is a periodic structure grating. For the grating layer, its main function is to diffract the emitted light. The distance between the grating layer and the LED light source is 0.5 mm to 2 mm. When the light passes through the periodic grating structure, a diffraction effect will occur, causing the light to scatter at different angles.

[0039] The key parameters of the grating include:

[0040] Grating period: It needs to be optimized according to the LED emission wavelength and is usually on the sub-wavelength scale;

[0041] Grating depth: Affects the diffraction efficiency;

[0042] Grating shape: Different cross-sections such as rectangular, triangular, or sinusoidal can be selected.

[0043] The grating period refers to the distance between two adjacent identical structural units in the grating structure. The periodic structure of the grating causes light to diffract when passing through the grating, thereby affecting the propagation direction and intensity distribution of the light. By adjusting the period, duty cycle, and depth of the grating, the propagation characteristics of the light can be controlled.

[0044] For the gradient refractive layer, it includes a bottom refractive layer, a middle refractive layer, and a top refractive layer with sequentially decreasing refractive indices. The bottom refractive layer receives the light diffracted by the grating layer, preliminarily adjusts the light direction, and provides a basis for subsequent angle expansion; the middle refractive layer is an intermediate transition region, providing a transitional refractive index change, further adjusting the light direction, and smoothing the refractive index gradient, that is, reducing the refractive index change amplitude from the bottom refractive layer to the top refractive layer, thereby improving the light distribution uniformity; the top refractive layer adjusts the final light exit angle and optimizes the angle distribution of the light entering the microlens.

[0045] For the microlens array layer, its function is to further spread the light of the gradient refractive layer to enhance the light uniformity and emission angle.

[0046] It can be seen that the LED light-emitting structure of the embodiment of the present invention combines three optical structures, namely, a grating layer, a gradient refractive index layer, and a microlens array layer, to achieve step-by-step modulation control of light. The functions of each layer are complementary and synergistic, which can significantly increase the light-emitting angle (up to ±80°) and enhance the light-emitting uniformity (greater than 85%). In the gradient refractive index layer, the light direction is adjusted through the transitional refractive index, which can smooth the refractive index gradient and reduce mutations, thereby improving the light distribution uniformity.

[0047] Optionally, the period of the grating layer can be set within the range of 400 nm to 2 μm. Generally, the smaller the period, the larger the light-emitting angle, but the greater the processing difficulty. Therefore, a suitable grating period can be selected according to actual needs. The core objective is to regulate the diffraction behavior of light waves by optimizing structural parameters (such as period, duty cycle, depth, etc.), thereby enhancing the light extraction efficiency, regulating the light output direction, or improving the light-emitting uniformity.

[0048] Optionally, the grating can be selected with different cross-sections such as rectangular, triangular, or sinusoidal. Considering that the rectangular grating has mature technology and low large-scale production cost, the grating shape of the grating layer is set as a rectangular grating. The preparation of the grating layer mainly adopts the method of combining thin-film deposition and photolithography technology.

[0049] In a specific example, the structure of the grating layer is rectangular. Figure 2 It is a schematic diagram of a rectangular grating structure, as Figure 2 shown. The parameters of the grating layer are set as follows: period 2 μm, depth 400 nm, and duty cycle 0.5.

[0050] The period is controlled within 2 μm (error range ±0.5 μm). If the period is too small, the color difference of the LED light will be too large after passing through the composite film (the structure from the grating layer to the microlens array layer), while if the period is too large, the diffraction angle will become smaller, and at this time, the increase amplitude of the LED light-emitting angle is smaller. The depth is set to 400 nm ± 50 nm, which can take into account the diffraction efficiency of RGB. The duty cycle is the ratio of the width of the effective signal (ridge width) to the length of the signal period. A duty cycle of 0.5 can not only provide the best optical performance but also has good process feasibility. In practical applications, we usually allow an error range of ±0.1, that is, the duty cycle is set to 0.5 ± 0.1, which not only ensures a high diffraction efficiency but also leaves a reasonable tolerance for process manufacturing.

[0051] Figure 3 It is a schematic diagram of the diffraction effect of a grating layer, which shows the characteristics of multi-level diffraction. The intensity of the 0th-order diffracted light is the largest. The ±1st-order diffractions are usually used in practical applications. The ±2nd-order diffractions can be used to further increase the divergence angle. The diffraction angle can be controlled by adjusting the period. In addition, there can also be ±3rd-order diffractions, but the energy of this order of diffraction is weak. If there is a need to further expand the angle, the ±3rd-order diffraction effect can be optimized.

[0052] Optionally, the number of the intermediate refractive index layers is greater than or equal to 1 layer. Wherein, when the number of the intermediate refractive index layers is greater than 1 layer, the refractive index of the intermediate refractive index layers decreases successively from bottom to top. Such a setting can make the change range of the refractive index smaller, and further improve the uniformity of light distribution. The specific number of the intermediate refractive index layers can be set in combination with actual requirements and process difficulty.

[0053] Optionally, the refractive index of the bottom refractive index layer is equal to that of the grating layer. According to the optical refraction theory, if light passes through the interface of two media with similar refractive indices, the reflectivity will be smaller. Therefore, setting the refractive index of the bottom refractive index layer to be equal to that of the grating layer can minimize the loss of light flux caused by light reflection when light enters the bottom refractive index layer from the grating layer.

[0054] Optionally, the refractive index of the top refractive index layer is equal to that of the microlens array layer. Similarly, such a setting can reduce the loss of light flux caused by light reflection when light enters the microlens array layer from the top refractive index layer.

[0055] In a specific example, the theoretical refractive index of the grating layer is 2.1, the theoretical refractive index of the microlens array layer is 1.45, and the design scheme of the gradient refractive index layer is as follows:

[0056] Bottom refractive index layer: thickness 14μm ± 2μm, refractive index 2.1, matching the refractive index of the grating layer, reducing interface reflection loss and matching the refractive index of the grating layer to reduce interface reflection;

[0057] Intermediate refractive index layer: the number is 1 layer, thickness 14μm ± 2μm, refractive index 1.7, providing a transitional refractive index change;

[0058] Top refractive index layer: thickness 8μm ± 2μm, refractive index 1.45 ± 0.05, matching the refractive index of the microlens material, adjusting the final exit angle.

[0059] The working benefits of this design are as follows: realizing the progressive modulation of the light angle, reducing the interface reflection loss, improving the uniformity of the light intensity distribution, providing good mechanical stability, and the light angle can be expanded to 28° after the light passes through the gradient layer. Among them, the gradient refractive index layer is formed by depositing three materials with different refractive indices, and appropriate heat treatment is carried out after each deposition to optimize the optical performance and reduce the internal stress.

[0060] Optionally, the microlens array layer is arranged in a hexagonal pattern, that is, the lenses are spread out in a hexagonal pattern according to the area of the actual composite film. The microlens array layer arranged in a hexagonal pattern has the same divergence angle in all directions, the light rays in six directions overlap and enhance, the edge diffraction effect is the strongest, the energy utilization rate is high, and the edge transition is smooth.

[0061] In an optional example, the complete design parameters of the hexagonal-arrangement microlens array are as follows:

[0062] Parameters of a single microlens: lens diameter (D): 100 ± 0.5 μm, lens height (h): 25 ± 0.5 μm, radius of curvature (R): 40 ± 0.5 μm; if the lens diameter (D) is too large, total internal reflection of marginal rays will occur, if it is too small, the processing difficulty will be great and the light acceptance range will be limited. When the lens diameter (D) is 100 μm, the distribution is uniform and the chromatic aberration is small.

[0063] Figure 4 It is a schematic diagram of a hexagonal-arrangement microlens structure, as Figure 4 shown. Except for the lens at the center position, the number of lenses in the first outer ring is 6, and the number of lenses in the second outer ring is 12, and so on.

[0064] The microlens array layer is prepared by hot embossing technology.

[0065] In an optional example, the change process of the angle in different layers is as follows:

[0066] 1. Grating layer

[0067] The normally incident light (0°) is perpendicular to the surface of the grating layer, and the grating period is 2 μm;

[0068] Diffraction angle of the grating (first-order diffraction):

[0069] Blue light (450 nm): sin-1(450 nm / 2000 nm) = ±13.0°;

[0070] Yellow light (560 nm): sin-1(560 nm / 2000 nm) = ±16.3°;

[0071] Red light (700 nm): sin-1(700 nm / 2000 nm) = ±20.5°;

[0072] The output angle range of the grating layer is ±20.5°.

[0073] 2. Gradient refractive index layer

[0074] The refractive indices of the three-layer structure from bottom to top are 2.1, 1.7, and 1.45 respectively. The incident angle range of the light is: ±20.5°. The angle change of the light when passing through different layers from bottom to top is:

[0075] The first layer (refractive index n = 2.1 → 1.7): the angle expands by about 20%;

[0076] The second layer (refractive index n = 1.7 → 1.45): the angle expands by about 15%

[0077] The third layer (refractive index n = 1.45 → 1.45): The angle remains unchanged;

[0078] The total expansion effect of the gradient layer is about 38%, and the output angle range of the gradient layer is ±28.3°.

[0079] 3. Microlens layer

[0080] Incident angle range: ±28.3°, microlens curvature radius: 40 μm;

[0081] Utilize the diffusion effect of the microlens: Diffuse the light of ±28.3° to ±65°, then the output angle range of the microlens layer is ±65°.

[0082] 4. Total system effect

[0083] For the normally incident light (0°) passing through the complete system: It is diffused to ±65°. Considering the contribution of the original light emission of the LED (±60°), the final light emission angle of the system is ±80°. Such a multi-layer design realizes the effect of diffusing the normally incident light to ±65°. Combining with the original light emission characteristics of the LED, the total light emission angle (half-intensity value) of the LED can be finally expanded from 120° to 140° - 160°.

[0084] It should be noted that considering the production precision limitations of the machine, the above parameters can all be set with different error ranges according to the actual situation. The following are some examples of the limitation of parameter error ranges:

[0085] I. Grating layer

[0086] 1. Total thickness: 0.85 ± 0.15 μm;

[0087] 2. Grating period: 2 ± 0.5 μm;

[0088] 3. Grating depth: 0.4 ± 0.1 μm;

[0089] 4. Duty cycle: 0.5 ± 0.1;

[0090] 5. Refractive index of the substrate material: 2.1 ± 0.1;

[0091] II. Gradient refractive layer

[0092] 1. The first layer (high refractive index layer):

[0093] Thickness: 14 ± 2 μm;

[0094] Refractive index: 2.1 ± 0.1;

[0095] Layer thickness uniformity: ≥95%;

[0096] 2. The second layer (medium refractive index layer):

[0097] Thickness: 14 ± 2 μm;

[0098] Refractive index: 1.7 ± 0.1;

[0099] Layer thickness uniformity: ≥ 95%;

[0100] 3. The third layer (low refractive index layer):

[0101] Thickness: 8 ± 2 μm;

[0102] Refractive index: 1.45 ± 0.05;

[0103] Layer thickness uniformity: ≥ 95%;

[0104] 4. Total thickness: 36 ± 5 μm;

[0105] III. Tolerance of the parameters of the microlens array layer

[0106] 1. Microlens geometric parameters:

[0107] Diameter: 100 ± 10 μm;

[0108] Radius of curvature: 40 ± 5 μm;

[0109] Central height: 25 ± 3 μm;

[0110] Aspect ratio: 0.25 ± 0.03 μm;

[0111] 2. Arrangement parameters:

[0112] Center-to-center spacing: 102 ± 2 μm;

[0113] Row pitch: 88.4 ± 2 μm;

[0114] Lens gap: 2 ± 0.5 μm;

[0115] Fill factor: ≥ 88%

[0116] 3. Substrate layer:

[0117] Thickness: 5 ± 1 μm;

[0118] Refractive index: 1.45 ± 0.05 μm;

[0119] 4. Total thickness: 30 ± 3 μm.

[0120] The LED light-emitting structure of the embodiment of the present invention has the following advantages:

[0121] 1) By combining three optical structures, namely a grating layer, a gradient layer, and microlenses, the step-by-step modulation of light is achieved, with the functions of each layer being complementary and synergistic, featuring a unique optical design concept.

[0122] 2) The emission angle is significantly expanded: the emission angle can reach ±80°.

[0123] High strong uniformity: the uniformity > 85%;

[0124] 3) The grating layer adopts a fixed-period design, simplifying the process;

[0125] The gradient refractive layer adopts a three-layer structure to optimize the refractive index matching;

[0126] The microlens array layer adopts a hexagonal close packing to improve the filling rate;

[0127] 4) A single LED can cover a larger space;

[0128] 5) Taking the ambient light as an example, the number of LEDs required in the same area is reduced.

[0129] In an optional embodiment, the present invention also provides a method for manufacturing an LED light-emitting structure. Figure 5 It is a flowchart of a method for manufacturing an LED light-emitting structure. As Figure 5 shown, the method for manufacturing an LED light-emitting structure includes:

[0130] S1. Provide an LED light source;

[0131] S2. Configure a grating layer above the LED light source;

[0132] S3. Deposit a transition connection layer on the surface of the grating layer and press the grating layer and the gradient refractive layer together;

[0133] S4. Spin-coat an optical adhesive on the upper surface of the gradient refractive layer and bond the microlenses to the upper surface of the gradient refractive layer through the optical adhesive to form a microlens array layer on the upper surface of the gradient refractive layer;

[0134] S5. Cure the optical adhesive by UV light irradiation;

[0135] S6. Perform heat treatment on the overall structure to obtain the LED light-emitting structure.

[0136] Among them, a low-temperature pressing process (70 - 90 °C) is used to combine the grating layer and the gradient refractive layer, and the heat treatment temperature is between 100 °C and 130 °C. The heat treatment has the effects of improving strength, increasing toughness, and improving hardness, etc.; after the heat treatment, the edge repair and surface cleaning of the LED light-emitting structure are usually also carried out. In the method for manufacturing an LED light-emitting structure, the LED light source, the grating layer, the gradient refractive layer, and the microlens array layer all correspond to the components in the LED light-emitting structure provided by the embodiments of the present invention.

[0137] In an alternative embodiment, the present invention further provides a light-emitting device, including at least one LED light-emitting structure as described in any of the above embodiments.

[0138] It should be understood that various forms of the processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved, and no limitations are imposed herein.

[0139] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An LED light emitting structure, characterized in that: The LED light emitting structure is a multi-layer structure, which includes an LED light source, a grating layer, a gradient refraction layer and a microlens array layer from bottom to top; The grating layer is used to diffract the light emitted by the LED light source to the gradient refraction layer at different angles; The gradient refraction layer comprises a bottom refraction layer, a middle refraction layer and a top refraction layer with refractive indices decreasing in sequence, the bottom refraction layer is connected to the grating layer, the top refraction layer is connected to the microlens array layer, and the gradient refraction layer is used to increase the exit angle of light; The microlens array layer is used to evenly distribute the light emitted from the gradient refraction layer at a larger angle.

2. The LED light emitting structure according to claim 1, characterized in that: The period of the grating layer is in the range of 400 nm to 2 μm.

3. The LED light emitting structure according to claim 1, characterized in that: The grating shape of the grating layer is rectangular.

4. The LED light emitting structure according to claim 1, characterized in that: The number of the intermediate refractive layers is greater than or equal to one.

5. The LED light emitting structure according to claim 4, characterized in that: When the number of the intermediate refractive layers is greater than one, the refractive indices of the intermediate refractive layers decrease from bottom to top.

6. The LED light emitting structure according to any one of claims 1 to 5, characterized in that: The refractive index of the bottom refractive layer is equal to the refractive index of the grating layer.

7. The LED light emitting structure according to any one of claims 1 to 5, characterized in that: The refractive index of the top refractive layer is equal to the refractive index of the microlens array layer.

8. The LED light emitting structure according to any one of claims 1 to 5, characterized in that: The microlens array layer is arranged in a hexagonal shape.

9. A method for manufacturing an LED light emitting structure, characterized in that: include: Provide LED light source; A grating layer is arranged above the LED light source; Depositing a transition connection layer on the surface of the grating layer and pressing the grating layer and the gradient refraction layer together; Spin-coating an optical adhesive on the upper surface of the gradient refractive layer, and bonding the microlens array layer to the upper surface of the gradient refractive layer through the optical adhesive to form a microlens array layer on the upper surface of the gradient refractive layer; Curing the optical adhesive using UV light; The whole structure is subjected to heat treatment to obtain the LED light-emitting structure.

10. A light-emitting device, comprising at least one LED light-emitting structure according to any one of claims 1 to 8.

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