LED encapsulation adhesive and preparation method thereof, LED device

Abstract

The application provides an LED encapsulating glue and a preparation method thereof, and belongs to the technical field of photoelectric device encapsulating materials; the technical problem to be solved is that the prior art cannot reflect continuous temperature values, gradient distribution and accurate positions of hot spots, and does not have the heat regulation and control ability of sensing and responding; the technical scheme for solving the technical problem is that an organic silicon resin matrix is arranged on a chip, the organic silicon resin matrix comprises a gradient temperature sensing unit and a dynamic optical regulation unit, the gradient temperature sensing unit is used for presenting at least two distinguishable color states according to temperature changes, and the dynamic optical regulation unit is used for changing light scattering ability according to temperature changes; the application is applied to the fields of Mini / Micro LED display backlight, vehicle-mounted display, high-power special lighting and the like.

Description

Technical Field

[0001] This application relates to the field of optoelectronic device packaging materials technology, and in particular to an LED encapsulating adhesive, its preparation method, and an LED device. Background Technology

[0002] With the evolution of new display technologies such as Mini / Micro-LED, chip sizes are continuously shrinking and integration density is constantly increasing, leading to a sharp increase in heat flux density per unit area. The resulting localized heat accumulation and non-uniform temperature fields have become core challenges restricting the optoelectronic performance, color consistency, and long-term reliability of devices. Therefore, developing packaging materials capable of sensing and intelligently responding to temperature changes in situ is of great significance for the thermal management of high-end LED devices.

[0003] Currently, research has explored incorporating thermochromic materials into encapsulants to achieve temperature visualization. A typical approach involves dispersing thermochromic microcapsules with a single color-changing temperature within a resin. When a local temperature exceeds a set threshold, the material changes color to issue a warning. However, this approach has significant limitations: First, it only provides a binary overheat alarm ("yes or no"), failing to reflect the specific numerical value of the chip surface temperature, its gradient distribution, and the precise location of hotspots. For Mini / Micro-LED arrays containing thousands of independent light-emitting points, this lack of information makes accurate diagnosis and intervention difficult. Second, its function remains at the passive warning level; the color change itself does not trigger any changes in material properties that help alleviate overheating, lacking a closed-loop "sensing-response" capability.

[0004] In addition, existing thermochromic systems often face challenges in terms of material compatibility, long-term aging resistance, and environmental friendliness when applied to demanding LED packaging.

[0005] Different technological concepts exist in other fields. For example, some technologies use external circuitry to actively heat and trigger the color change and deformation of multilayer thin films, mainly for anti-counterfeiting purposes. Their technological path and goals are completely different from the purpose of this invention, which is to passively sense the self-heating of the chip and serve thermal management. Other technologies focus on rapid detection and alarm of a single fault temperature point in specific equipment (such as power insulators). Their functional goals are singular, do not involve the visual representation of continuous temperature field distribution, and do not integrate any form of optical or thermal regulation mechanism. Summary of the Invention

[0006] To address the aforementioned technical problems, this application proposes an LED encapsulating adhesive, its preparation method, and an LED device.

[0007] The technical solution adopted in this application is: an LED encapsulating adhesive, comprising an organosilicon resin matrix, wherein the organosilicon resin matrix is ​​disposed on a chip, and the organosilicon resin matrix includes a gradient temperature sensing unit and a dynamic optical control unit. The gradient temperature sensing unit is used to present at least two distinguishable color states according to temperature changes, and the dynamic optical control unit is used to change the light scattering capability according to temperature changes.

[0008] Furthermore, the gradient temperature sensing unit comprises at least two types of thermochromic microcapsules, each of which has a different color-changing temperature.

[0009] Furthermore, the gradient temperature sensing unit includes a thermochromic material, the color of which changes sequentially within a continuous temperature range.

[0010] Furthermore, the dynamic optical control unit includes temperature-sensitive refractive index adjustment particles, the refractive index of which undergoes a reversible change as the temperature increases.

[0011] Furthermore, the temperature-sensitive refractive index adjusting particle includes a shell and a core, wherein the shell is a transparent rigid material and the core is a temperature-sensitive polymer.

[0012] Furthermore, the silicone resin matrix also includes a thermally conductive filler, the surface of which is provided with active groups, which are used to chemically bond with the silicone resin matrix.

[0013] Furthermore, it also includes an anti-glare layer disposed on the side of the silicone resin matrix away from the chip.

[0014] Furthermore, the preparation method of the above-mentioned LED encapsulating adhesive includes the following steps: Step 1: Perform surface modification treatment on the gradient temperature sensing unit, the dynamic optical control unit, and the thermally conductive filler; Step 2: Mix the surface-modified gradient temperature sensing unit, the dynamic optical control unit, and the thermally conductive filler with the silicone resin prepolymer and additives to form a homogeneous composite. Step 3: Apply the homogeneous composite to the chip surface and cure it.

[0015] Furthermore, an LED device is encapsulated using the aforementioned LED encapsulating adhesive.

[0016] The advantages of this application over the prior art are as follows: 1. Achieving Visualization and Refinement of Thermal Management: This application is the first to achieve visualized imaging of the two-dimensional temperature distribution on the LED encapsulation layer, breaking through the limitations of traditional single-threshold alarms. This enables device designers, manufacturers, and even users to intuitively and quickly identify hotspot locations, evaluate the quality of heat dissipation designs, and diagnose abnormal operating conditions, providing an unprecedented intuitive tool for thermal management; 2. Endowing the encapsulation material with inherent intelligent response characteristics: By deeply coupling temperature sensing with optical control functions, this invention makes the encapsulation adhesive no longer just a static protective material, but an intelligent response material that can actively adjust its own optical state according to environmental changes in order to seek a better thermal balance, thereby improving the overall adaptability and robustness of the device. 3. Expected Improvement in Overall Device Performance and Reliability: Intelligent light scattering modulation is expected to improve light emission uniformity without excessively sacrificing brightness, and may enhance energy efficiency by improving light extraction. Simultaneously, strengthened interfacial chemical bonding helps ensure the functional and structural integrity of materials under harsh environments such as long-term high temperature and humidity, and thermal cycling. 4. Possesses good process compatibility and application potential: The composite and molding process of this material can be integrated with existing mature LED packaging processes, making it easy to introduce into industrial production. Attached Figure Description

[0017] The following description, in conjunction with the accompanying drawings, further illustrates this application: Figure 1 This is a schematic diagram of the LED encapsulating adhesive used in this application; Figure 2 This is a schematic diagram of the structure of the silicone resin matrix in this application; Figure 3 This is a schematic diagram illustrating the microscopic synergistic effect between the gradient temperature sensing unit and the dynamic optical control unit in this application; Figure 4 This is a schematic diagram illustrating the application effect of the LED encapsulating adhesive in this application; In the diagram: 1 is the silicone resin matrix, 2 is the chip, 3 is the anti-glare layer, 4 is the gradient temperature sensing unit, 5 is the dynamic optical control unit, 6 is the thermally conductive filler, 7 is the activated gradient temperature sensing unit, 8 is the activated dynamic optical control unit, 9 is the thermochromic microcapsule, 10 is the temperature-sensitive refractive index adjustment particle, 11 is the LED encapsulation adhesive, A is the low-temperature zone, B is the high-temperature zone, C is the temperature change curve, and D is the overheated pixel. Detailed Implementation

[0018] like Figures 1 to 4 As shown, this application provides an LED encapsulating adhesive, its preparation method, and an LED device.

[0019] An LED encapsulant includes an organosilicon resin matrix 1 disposed on a chip 2. The organosilicon resin matrix 1 includes a gradient temperature sensing unit 4 and a dynamic optical control unit 5. The gradient temperature sensing unit 4 is used to display at least two distinguishable color states according to temperature changes, and the dynamic optical control unit 5 is used to change light scattering ability according to temperature changes. The gradient temperature sensing unit 4 contains at least two types of thermochromic microcapsules 9, each of which has a different color-changing temperature. The gradient temperature sensing unit 4 also contains a thermochromic material, the display color of which changes sequentially within a continuous temperature range. The dynamic optical control unit 5 includes temperature-sensitive refractive index adjusting particles 10, the refractive index of which changes reversibly with increasing temperature; the temperature-sensitive refractive index adjusting particles 10 include a shell and a core, the shell being a transparent rigid material and the core being a temperature-sensitive polymer; the silicone resin matrix 1 also includes a thermally conductive filler 6, the surface of which is provided with active groups, which are used to chemically bond with the silicone resin matrix 1; the LED encapsulating adhesive 11 also includes an anti-glare layer 3, which is disposed on the side of the silicone resin matrix 1 away from the chip 2.

[0020] like Figure 2 As shown, the core function of the gradient temperature sensing unit 4 is to transform the spatial temperature distribution into a visually discernible color distribution. The key technology lies in achieving non-binary, temperature-dependent color output. This can be achieved through two main technical paths: First, a physical compounding strategy is used to uniformly disperse multiple thermochromic microcapsules 9 with precise and different color-changing characteristic temperatures within the substrate. When different regions are at different temperatures, the dominant microcapsule types differ, thus exhibiting differentiated colors. Second, a materials science strategy is employed, utilizing a thermochromic material whose intrinsic color continuously changes with temperature over a wide temperature range (such as a temperature-sensitive liquid crystal with a specific formulation), which is protected and dispersed through microencapsulation. In the embodiments of this application, the thermochromic microcapsules 9 and the thermochromic material are not specifically limited, as long as they meet the requirement of making the encapsulating adhesive appear as a "color contour map" reflecting the temperature field of the underlying chip 2.

[0021] The core function of the dynamic optical regulation unit 5 is to intelligently adjust the optical properties of the encapsulating adhesive under temperature triggering, based on the temperature-sensitive refractive index characteristics. This unit consists of temperature-sensitive refractive index adjusting particles 10, which have a highly matched refractive index with the silicone resin matrix 1 at room temperature, and the material has excellent light transmittance. When the temperature rises to its response range, the temperature-sensitive refractive index adjusting particles 10 cause a significant change in refractive index due to internal phase change, conformational change or volume change, resulting in an obvious refractive index mismatch with the silicone resin matrix 1; according to the optical principle, this will trigger a strong light scattering effect microscopically. To ensure the long-term stable operation of each functional unit under complex thermo-mechanical stress, the present invention implements surface interface engineering on the thermochromic microcapsules 9, temperature-sensitive refractive index adjusting particles 10 and thermal conductive fillers 6, and endows them with active functional groups that can react with the curing system of the silicone resin matrix 1 through chemical grafting, so that they are firmly anchored in the three-dimensional cross-linked network by covalent bonds during the curing process.

[0022] As Figure 3 shown, the thermochromic microcapsules 9 in the figure are divided into three types, namely solid circles, single-slash-filled circles and cross-filled circles, which have different color-changing temperatures T1, T2, T3 respectively, where T1 < T2 < T3. In the low-temperature state (such as T < T1), all microcapsules show the same baseline color (light blue); as the temperature rises, the internal structure of the microcapsules reaching T1 changes, and the filling pattern or color changes (for example, from a solid circle to a single-slash-filled circle); when the temperature reaches T2 and T3, the corresponding microcapsules also change their internal filling patterns in turn (such as becoming single-slash-filled circles, cross-filled circles). Under the microscope, the microcapsules in different regions show different "pattern mixing ratios" due to the different temperatures they are in, and a color gradient is formed macroscopically.

[0023] The central small circle of the dynamic optical regulation core-shell particle is a temperature-sensitive polymer, and the outer ring is a transparent rigid material, such as silica. In the low-temperature state ( Figure 3 the left part in): the refractive index of the particle core is very close to that of the particle shell and the outer silicone resin matrix 1, and at this time the small circle is transparent, and the light arrow can directly pass through; in the high-temperature state ( Figure 3 the right part in): due to thermal expansion or phase change of the particle core, the refractive index changes significantly, and at this time the small circle presents a single-slash state, and the light arrow is deflected and scattered when hitting the particle.

[0024] During operation, when the chip 2 array experiences temperature differences due to uneven driving current and heat dissipation conditions, the gradient temperature sensing unit 4 is activated first. This causes different areas of the encapsulating adhesive to stably display a preset specific color or color depth according to their specific temperature, thus mapping the invisible microscopic temperature field into a macroscopic color image that can be seen with the naked eye, achieving the localization, qualitative, and semi-quantitative analysis of heat distribution. In areas where the temperature has reached or entered a higher range, the dynamic optical control unit 5 is activated. The enhanced light scattering caused by refractive index mismatch will first broaden the spatial distribution of the light beam, and the local light intensity peak may be moderately alleviated. This can be regarded as a passive "optical negative feedback," which helps to regulate the balance between heat generation and heat dissipation in this area. Secondly, the enhanced light scattering may change the photon escape path, which helps to reduce the multiple reflections and absorption losses of photons inside the chip 2, thereby potentially improving the light extraction efficiency and indirectly reducing the heat load.

[0025] Example 1: Gradient temperature sensing function achieved by compounding multiple thermochromic microcapsules with single color-changing points. Select or synthesize at least two thermochromic microcapsules 9 with different characteristic color-changing temperatures (e.g., a difference of approximately 10-20°C). The wall material of these thermochromic microcapsules 9 should possess good light transmittance and mechanical strength, and the core material should preferably be an environmentally friendly reversible color-changing system. To improve compatibility, the surface of the microcapsules can be functionalized, for example, by grafting active groups such as vinyl groups and epoxy groups. Then, a core-shell structured particle with a defined thermal response threshold (e.g., thermosensitive refractive index regulating particle 10) is prepared as the dynamic optical control unit 5, such as using a thermosensitive polymer (poly(N-isopropylacrylamide) and its copolymers) as the core and a transparent inorganic oxide (silica) as the shell. By adjusting the polymer composition, its volumetric phase transition temperature (corresponding to the refractive index abrupt change point) can be designed. The particle surface also requires activity modification. The surface-modified thermochromic microcapsules 9, temperature-sensitive refractive index adjusting particles 10, and similarly modified thermally conductive fillers 6 (such as aluminum nitride and boron nitride) are uniformly mixed with a high-refractive-index silicone resin prepolymer, a crosslinking agent, and a catalyst. A homogeneous composite is obtained through vacuum degassing. Subsequently, this homogeneous composite is applied to chip 2 using precision dispensing or molding processes and cured by heating. During the curing process, the active groups on the surface of each functional unit participate in the crosslinking reaction of the resin, forming chemical bonds.

[0026] Example 2: Gradient temperature sensing function achieved through a single wide-temperature-range thermochromic material.

[0027] A thermochromic material (such as a cholesteric liquid crystal mixture with a specific ratio) whose color can continuously and gradually change within a target temperature range (e.g., 60°C to 120°C) is selected or synthesized. This material is encapsulated using a suitable microencapsulation technique to protect its function and improve its dispersibility. The obtained wide-temperature-range thermochromic microcapsules are then surface-modified. The dynamic optical control unit 5 and subsequent composite and encapsulation processes remain consistent with those in Example 1. In the embodiments of this application, the response temperature of the dynamic optical control unit 5 is adjusted accordingly to match or connect with the main operating range of the wide-temperature-range thermochromic material.

[0028] An LED device is encapsulated using the aforementioned LED encapsulating adhesive. The LED device is a Mini LED or MicroLED device. The LED encapsulating adhesive 11 covers the chip 2 and can use different colors to indicate the relative temperature differences between different parts of the chip 2. Figure 1 As shown, during operation, the beam angle of the LED encapsulant 11 on chip 2 differs in the higher temperature region from that in the lower temperature region.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An LED encapsulating adhesive, comprising an organosilicon resin matrix (1), wherein the organosilicon resin matrix (1) is disposed on a chip (2), characterized in that: The silicone resin matrix (1) includes a gradient temperature sensing unit (4) and a dynamic optical control unit (5). The gradient temperature sensing unit (4) is used to present at least two distinguishable color states according to temperature changes, and the dynamic optical control unit (5) is used to change the light scattering ability according to temperature changes.

2. The LED encapsulating adhesive according to claim 1, characterized in that: The gradient temperature sensing unit (4) contains at least two types of thermochromic microcapsules (9), each of which has a different color-changing temperature.

3. The LED encapsulating adhesive according to claim 1, characterized in that: The gradient temperature sensing unit (4) contains a thermochromic material, the color of which changes sequentially within a continuous temperature range.

4. The LED encapsulating adhesive according to claim 2 or 3, characterized in that: The dynamic optical control unit (5) includes a temperature-sensitive refractive index adjustment particle (10), the refractive index of which changes reversibly with increasing temperature.

5. The LED encapsulating adhesive according to claim 4, characterized in that: The temperature-sensitive refractive index regulating particle (10) includes a shell and a core, wherein the shell is a transparent rigid material and the core is a temperature-sensitive polymer.

6. The LED encapsulating adhesive according to claim 5, characterized in that: The silicone resin matrix (1) further includes a thermally conductive filler (6), the surface of which is provided with active groups, which are used to chemically bond with the silicone resin matrix (1).

7. The LED encapsulating adhesive according to claim 6, characterized in that: It also includes an anti-glare layer (3), which is disposed on the side of the silicone resin matrix (1) away from the chip (2).

8. A method for preparing the LED encapsulating adhesive as described in claim 7, characterized in that, Includes the following steps: Step 1: Surface modification treatment is performed on the gradient temperature sensing unit (4), the dynamic optical control unit (5), and the thermally conductive filler (6); Step 2: The surface-modified gradient temperature sensing unit (4), the dynamic optical control unit (5) and the thermally conductive filler (6) are mixed with the silicone resin prepolymer and additives to form a homogeneous composite. Step 3: Apply the homogeneous composite to the surface of the chip (2) and cure it.

9. An LED device, characterized in that, Encapsulation is performed using the LED encapsulating adhesive as described in any one of claims 1-3 and 5-7.

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