Thermochromic coating composition, thermochromic coating, application of thermochromic coating and display screen input power adjusting method

Abstract

The invention relates to the field of LED display screen industry, in particular to a thermochromic coating composition, a thermochromic coating, application of the thermochromic coating and a display screen input power adjusting method. The thermochromic coating composition provided by the invention comprises the following components in percentage by weight: 0.5-5.0% of nano carbon black; 20 wt% to 87 wt% of polyethylene oxide; 0.5 wt% to 15 wt% of lithium perchlorate; and 10 wt% to 70 wt% of polydimethylsiloxane. The coating formed by the thermochromic coating provided by the invention solves the problem that the light transmittance of a static adhesive film is non-adjustable, so that the light transmittance of the coating is improved (more than 90% in actual measurement) along with the rise of the temperature of a display screen during light emission, the temperature of the display screen is reduced when the screen is turned off, shading is gradually recovered (the light transmittance is less than 40%), and the light transmittance of the coating is not adjustable. The input power of the display screen is reduced on the premise that the brightness is not reduced while the light transmittance is increased, and the effects of cooling the display surface and saving energy are achieved.

Description

Technical Field

[0001] This invention relates to the LED display industry, specifically to thermochromic coating compositions, thermochromic coatings and their applications, and methods for adjusting the input power of displays. Background Technology

[0002] To improve the contrast and uniformity of existing LED displays, a black coating or film with a light transmittance of ≤40% is often added to the surface of the adhesive film, so that its contrast ratio should reach 10000:1 or higher. Figure 1 As shown, Figure 1 This is a schematic diagram of the cross-sectional structure of an LED module. However, this static coating or film will permanently reduce the light transmittance (the original light transmittance of the film drops from 90% to 36%), resulting in a significant loss of brightness. To achieve the set brightness, the power consumption of the display screen needs to be increased, further increasing the temperature rise of the display screen and reducing its reliability and lifespan. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a thermochromic coating composition, a thermochromic coating and its application, and a method for adjusting the input power of a display screen. The coating made of the thermochromic coating provided by the present invention can achieve a light transmittance that switches between ≤40% and ≥85% as the temperature rises and falls when emitting light. When applied to a display screen, it can reduce the input power of the display screen by up to 50% while maintaining the brightness, thus achieving the effects of both cooling the display screen and saving energy.

[0004] This invention provides a thermochromic coating composition, comprising:

[0005] 0.5 wt%~5.0 wt% nano carbon black;

[0006] 20 wt%~87 wt% polyethylene oxide;

[0007] 0.5 wt%~15 wt% lithium perchlorate;

[0008] 10 wt%~70 wt% of polydimethylsiloxane.

[0009] Preferably, the thermochromic coating composition provided by the present invention comprises:

[0010] 0.5 wt%~5.0 wt% nano carbon black;

[0011] 20 wt%~70 wt% polyethylene oxide;

[0012] 0.5 wt%~15 wt% lithium perchlorate;

[0013] 10 wt%~70 wt% of polydimethylsiloxane.

[0014] More preferably, the thermochromic coating composition provided by the present invention comprises:

[0015] 0.5 wt%~5.0 wt% nano carbon black;

[0016] 40 wt%~70 wt% polyethylene oxide;

[0017] 0.5 wt%~5.0 wt% lithium perchlorate;

[0018] 20 wt%~50 wt% of polydimethylsiloxane.

[0019] Most preferably, the thermochromic coating composition provided by the present invention comprises:

[0020] 1.0 wt%~3.0 wt% nano carbon black;

[0021] 60 wt%~70 wt% polyethylene oxide;

[0022] 1.0 wt%~3.0 wt% lithium perchlorate;

[0023] 20 wt%~30 wt% of polydimethylsiloxane.

[0024] The thermochromic coating composition provided by this invention is a coating containing a thermochromic material of a polydimethylsiloxane (PDMS), polyethylene oxide (PEO), and lithium perchlorate polymer blend system. Its initial state is black. To maintain the black color of the coating in its initial state and a light transmittance of approximately 40%, nano-carbon black needs to be added. Nano-sized carbon black can optimize scattering and avoid excessive light blocking. The thermochromic coating composition provided by this invention includes 0.5 wt% to 5.0 wt% of nano-carbon black, wherein the particle size of the nano-carbon black is 50 nm to 100 nm.

[0025] Preferably, the nano-carbon black of the present invention is a modified nano-carbon black composed of alumina and nano-carbon black, exhibiting superior hydrophilicity; the alumina is γ-Al2O3 or amorphous Al2O3. Specifically, the nano-carbon black is a nano-carbon black with an alumina and nano-carbon black composite structure formed by coating a mixed solution of Al2(SO4)3 and NaOH with high-temperature calcination. More specifically, nano-carbon black with an alumina and nano-carbon black composite structure is obtained by hydrolyzing nano-carbon black, Al2(SO4)3 solution, and NaOH solution, followed by calcination.

[0026] The thermochromic coating composition provided by the present invention further includes polyethylene oxide, the chemical structure of which is shown in Formula 1, and its molecular weight is 40,000 to 100,000, preferably 50,000 to 100,000.

[0027] Formula 1;

[0028] The polyethylene oxide (PEO) described in this invention, as a crystallization phase regulating component, enhances thermal responsiveness through a hydrogen bonding network. Its crystallization-melting phase transition temperature (35℃~40℃) matches the target temperature range. Specifically, it undergoes a crystallization-melting phase transition at 35℃~40℃, driving the coating transmittance from 40% at 25℃ to 90% at 38℃. The PEO described in this invention also functions as an ion-conducting aid. When combined with lithium perchlorate, it forms an ion-conducting network, regulating the local order of the polymer chains through lithium ion migration and accelerating the kinetics of temperature-triggered phase transitions. This synergistic effect enhances the material's temperature-responsive sensitivity. Furthermore, the PEO described in this invention optimizes optical properties. Its polar etheroxy groups (-O-) interact with the carbon black surface through van der Waals forces, helping to stabilize carbon black dispersion at room temperature. When the temperature exceeds 38℃, the PEO segments rearrange and form an enriched phase, encapsulating carbon black particles in localized regions (PEO domains), blocking light scattering and achieving high transmittance. The polyethylene oxide described in this invention is pre-dried to remove moisture, thus avoiding interference with Li. + migrate.

[0029] The thermochromic coating composition provided by this invention further includes lithium perchlorate, which, as an ion conductor, can promote ion migration during the phase transition process and simultaneously adjust the phase transition temperature to the target range. Specifically, the addition of LiClO4 can lower the crystallization temperature of PEO, making the phase transition window (25℃~35℃) closer to the room temperature requirement. Simultaneously, LiClO4 readily decomposes to produce chlorine gas, and its combination with PDMS can improve thermal stability. The lithium perchlorate of this invention has a particle size <1 μm, preferably 100 nm or larger and less than 1.0 μm; submicron-sized lithium perchlorate ensures uniform mixing with PEO.

[0030] The thermochromic coating composition provided by this invention further includes polydimethylsiloxane, the chemical structure of which is shown in Formula 2, wherein n>2:

[0031] Formula 2;

[0032] The polydimethylsiloxane described in this invention, as a flexible matrix, can regulate the mechanical properties and phase separation temperature of the material, providing high hydrophobicity and flexibility, and enhancing the weather resistance and mechanical stability of the coating. Simultaneously, its siloxane backbone structure can inhibit oxidative degradation, significantly improving the long-term stability of the coating. It also possesses phase separation regulation capabilities; when blended with PEO, PDMS can regulate the thermally induced phase separation behavior of the polymer, achieving a balance between high transparency (~85%) at room temperature (25°C) and temperature responsiveness (50%~60% transmittance at 35°C). The viscosity of the polydimethylsiloxane described in this invention is 50 cSt~1000 cSt, preferably 100 cSt~1000 cSt, and more preferably 100 cSt~500 cSt. Lower viscosity polydimethylsiloxanes exhibit better compatibility with PEO.

[0033] This invention provides a thermochromic coating, which is obtained from any of the thermochromic coating compositions described above and a solvent. The solvent used in this invention is an organic solvent, preferably a mixture of chloroform and tetrahydrofuran (THF). In some embodiments of this invention, the solvent is a mixture of chloroform and THF in a volume ratio of 1:1.

[0034] This invention provides a method for preparing the above-mentioned thermochromic coating, comprising the following steps:

[0035] S1) Dissolve PEO and PDMS in a solvent to obtain a PDMS-PEO polymer solution;

[0036] S2) The PDMS-PEO polymer solution obtained in step S1), LiClO4 and nano carbon black are mixed to obtain a thermochromic coating.

[0037] This invention first dissolves PEO and PDMS in a solvent, specifically by dissolving PEO and PDMS in a solvent, and then ultrasonically disperses them at 35℃~45℃ for 25 min~35 min to obtain a PDMS-PEO polymer solution. After obtaining the PDMS-PEO polymer solution, this invention mixes the obtained PDMS-PEO polymer solution, LiClO4, and nano carbon black. Specifically, the obtained PDMS-PEO polymer solution and LiClO4 are mixed until completely dissolved, and then nano carbon black is added. The mixture is ultrasonically treated at 200 W~400 W for 25 min~35 min, and centrifuged at 4000 rpm~6000 rpm for 8 min~12 min to remove agglomerates and ensure uniform distribution, thus obtaining a thermochromic coating.

[0038] This invention also provides an LED display module adhesive film, comprising a base film and a thermochromic coating disposed on the surface of the base film; the thermochromic coating is formed from the aforementioned thermochromic coating material. This invention does not specifically limit the base film; any base film known to those skilled in the art suitable for use in LED display module adhesive films is acceptable. The LED display module adhesive film of this invention includes, but is not limited to, COB display modules, COS display modules, GOB display modules, and MIP display modules. The thermochromic coating material of this invention is the same as described above and will not be repeated. The thickness of the thermochromic coating material of this invention is 20 μm to 40 μm, preferably 28 μm to 32 μm, and more preferably 30 μm.

[0039] The present invention also provides a method for preparing the above-mentioned LED display module adhesive film, comprising the following steps: coating the above-mentioned thermochromic coating on a base film, annealing it at a temperature of 70°C to 90°C for 0.5 h to 1.5 h after curing, and cooling it to room temperature at a rate of 3°C / min to 8°C / min to obtain the LED display module adhesive film.

[0040] The curing temperature described in this invention is 55℃~65℃, and the curing time is 1.5 h~2.5 h. The annealing described in this invention promotes PEO crystallization and optimizes the phase transformation response rate. The preferred annealing temperature is 75℃~85℃, and the preferred annealing time is 0.8 h~1.2 h. After annealing, the temperature is preferably reduced to room temperature at a rate of 3℃ / min~6℃ / min to avoid PEO crystallization defects. Room temperature as described in this invention refers to 20℃~25℃.

[0041] The LED display module adhesive film provided by this invention, based on a coating formed by the thermochromic coating described in this invention, is applied to the display screen to enable module lighting (video mode). When the module temperature rises to 35°C, the thermochromic material begins a phase change, the black coating becomes transparent, and the light transmittance of the LED adhesive film layer increases. When the temperature reaches 38°C, the light transmittance reaches approximately 90%. To precisely control the light transmittance through temperature changes, the mechanism and preparation method of the thermochromic coating described in this invention are explained in detail below:

[0042] A. At room temperature (25℃): Black and opaque (40% light transmittance);

[0043] PEO segment state: At room temperature, PEO segments are in an ordered coiled state due to intermolecular hydrogen bonds and van der Waals forces, which has high compatibility with PDMS matrix and forms a uniform and continuous polymer network.

[0044] Carbon black dispersion behavior: Carbon black particles are uniformly dispersed in the polymer matrix through the interaction between the polar ether oxygen groups (-O-) of PEO and the carbon black surface. At this time, the carbon black particles are small in size and densely distributed, resulting in strong scattering and absorption of visible light, which leads to the coating being black with a light transmittance of only 40%.

[0045] Ionic interaction: Li⁺ in lithium perchlorate coordinates with the ether oxygen groups of PEO segments, further stabilizing the ordered structure of PEO and maintaining the uniform dispersion of carbon black.

[0046] B. Phase transition begins (35℃): Semi-transparent state (60% light transmittance);

[0047] PEO phase transition triggering: When the temperature rises to 35℃ (close to the lowest critical solution temperature of PEO, LCST), the thermal motion of PEO chain segments intensifies, the intermolecular forces weaken, and the chain segments gradually change from ordered coiling to disordered extension. At this time, the compatibility between PEO and PDMS decreases, and microphase separation begins to occur.

[0048] Carbon black dispersion changes: PEO chain segment extension weakens its binding force on carbon black, and some carbon black particles begin to aggregate to form small-sized agglomerates (micrometer scale). With fewer and smaller agglomerates, the scattering ability of light decreases, and the light transmittance increases from 40% to 60%, resulting in a semi-transparent coating.

[0049] Ion conduction aid: Li + The migration ability in PEO segments increases with increasing temperature, promoting the untangling and phase separation process of PEO segments and accelerating the initial aggregation of carbon black particles.

[0050] C. High temperature (above 38℃): Transparent state (90% light transmittance);

[0051] PEO phase separation is complete: When the temperature exceeds 38℃, the PEO segments fully extend, and the phase separation from PDMS intensifies, forming independent PEO-enriched domain regions. At this time, the PEO domain regions act as "encapsulated phases," physically encapsulating most of the carbon black particles.

[0052] Carbon black agglomeration and encapsulation: Carbon black particles aggregate in large quantities within the PEO domain region, forming large agglomerates (tens of micrometers) that are isolated by the PEO domain region. Because the agglomerates are encapsulated within the PEO domain region and are no longer dispersed throughout the coating, the scattering and absorption of visible light are significantly reduced. Simultaneously, the PDMS continuous phase, lacking carbon black particles, restores light transmittance, resulting in an overall coating transmittance of 90% and a transparent appearance.

[0053] Structural stability: The PDMS matrix provides good mechanical support, preventing PEO phase separation from causing coating structure collapse and ensuring the stability of the transparent state at high temperatures.

[0054] D. Cooling (below 35℃): Restores the black, opaque state;

[0055] PEO segment contraction: When the temperature decreases, the thermal motion of PEO segments weakens, the intermolecular forces recover, the segments curl up again, the compatibility with PDMS increases, the phase separation structure disappears, and the PEO domain region disintegrates.

[0056] Carbon black redispersibility: PEO segments re-bind carbon black particles, causing them to deaggregate from the aggregated state and disperse uniformly back into the entire polymer matrix. The ability to scatter and absorb light is restored, the coating turns black again, and the light transmittance drops to 40%.

[0057] Reversibility mechanism: The phase transition of PEO and the dispersion-aggregation behavior of carbon black are both physical changes throughout the process, without chemical structural damage, thus exhibiting good thermochromic reversibility.

[0058] This invention also provides an LED display module, comprising: a PCB board, a light-emitting element connected to the PCB board, and the aforementioned LED display module adhesive film covering the light-emitting element. The LED display module adhesive film of this invention, like the one described above, has a thermochromic coating on its surface, allowing its light transmittance to switch between ≤40% and ≥85% depending on the display screen's illumination state.

[0059] The present invention also provides a method for adjusting the input power of a display screen including the above-mentioned LED display module, comprising:

[0060] Obtain the average temperature of the display screen;

[0061] Based on the average temperature of the display screen, the input power of the display screen is adjusted while maintaining the brightness of the display screen.

[0062] The present invention first obtains the average temperature of the display screen. Specifically, based on the temperature distribution on the display module, the locations of the high temperature point and the low temperature point on each display module are identified, and the temperature of the back of the corresponding display module is obtained, thereby obtaining the average temperature of the display screen.

[0063] When the LED display module enters the working state, the luminous flux of the display screen begins to increase until it reaches the preset luminous flux. As the temperature of the display screen rises, the light transmittance of the LED display module film changes. In order to maintain a constant brightness of the display screen, it is both possible and necessary to adjust the input power of the display screen. Based on this, by adjusting the input power of the display screen according to its temperature while maintaining a constant brightness, the display effect can be maintained. This allows for dynamic adjustment of the input power based on the display screen's temperature during the display process, reducing power consumption by as much as 50%, thus achieving energy conservation and emission reduction. It should be noted that constant brightness is not an absolute physical constant, but rather a constant that is imperceptible to the human eye.

[0064] This invention provides a thermochromic coating composition, a thermochromic coating, its application, and a method for adjusting the input power of a display screen. The thermochromic coating composition provided by this invention comprises: 0.5 wt%~5.0 wt% nano-carbon black; 20 wt%~87 wt% polyethylene oxide; 0.5 wt%~15 wt% lithium perchlorate; and 10 wt%~70 wt% polydimethylsiloxane. The coating formed by the thermochromic coating provided by this invention solves the problem of the unadjustable transmittance of static films. When the screen is illuminated, its transmittance increases as the display screen temperature rises (measured >90%), and when the screen is off, the display screen temperature decreases, gradually restoring its opaque state (transmittance <40%). While increasing transmittance, the input power of the display screen is reduced without decreasing brightness, achieving both cooling and energy-saving effects on the display surface. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of the cross-sectional structure of an LED module;

[0066] Figure 2 This is a schematic diagram of the phase transition mechanism;

[0067] Figure 3 A test image of a handprint on a thermochromic coating;

[0068] Figure 4 This is a flowchart illustrating the dynamic adjustment design of the LED display screen according to the present invention.

[0069] Figure 5 This is the dynamic energy-saving adjustment curve for the LED display screen of the present invention. Detailed Implementation

[0070] This invention discloses a thermochromic coating composition, a thermochromic coating, its application, and a method for adjusting the input power of a display screen. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art will clearly be able to modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0071] The present invention will be further described below with reference to the embodiments:

[0072] Example 1

[0073] For the coating of the present invention, an optimization experiment was first conducted on the addition ratio of carbon black, as follows:

[0074] (1) Material selection and pretreatment:

[0075] ① Modified nano carbon black: Nano carbon black is treated with a coating method (Al2(SO4)3 / NaOH solution) to improve its hydrophilicity, and then formed into a carbon black / alumina composite structure by high-temperature calcination, with a particle size of 50 nm~100 nm.

[0076] The specific processing method is as follows:

[0077] Accurately weigh 1.0 g of nano-carbon black powder into a beaker, add 200 mL of deionized water and a small amount of polyethylene glycol (PEG) dispersant (to improve the initial dispersibility of the carbon black). Place the beaker on a magnetic stirrer and stir at high speed for 2 hours. The goal is to break up the agglomerates of nano-carbon black and form a uniform and stable carbon black suspension. This step is crucial for subsequent uniform coating and ultimately yields the nano-carbon black suspension.

[0078] Based on the required Al2O3 coating amount (the target composite contains 20% Al2O3 by mass), calculate and weigh the corresponding mass of Al2(SO4)3·18H2O, and prepare a 0.5 mol / L Al2(SO4)3 solution with deionized water. Prepare a NaOH solution (1.0 mol / L) with a higher concentration than Al2(SO4)3 as a precipitant.

[0079] The prepared nano-carbon black suspension was transferred to a three-necked flask equipped with a magnetic stirrer. The flask was placed in a constant-temperature water bath, and the reaction temperature was controlled at 60°C while maintaining medium-speed stirring. Using two dropping funnels, Al2(SO4)3 solution and NaOH solution were added simultaneously and slowly at approximately the same rate to the nano-carbon black suspension, respectively. The pH value of the reaction system was closely monitored during the addition of NaOH solution. When the pH value reached the range of 7-9, Al2(SO4)3 solution was added. 3+ It will completely hydrolyze to form a white, gelatinous Al(OH)3 precipitate. This newly formed Al(OH)3 will deposit and grow on the surface of the nano-carbon black particles, using them as nucleation centers, forming a coating layer. After the addition is complete, continue stirring at a constant temperature for 2 hours to age the mixture, obtaining the reacted mixture.

[0080] The mixture after the reaction was filtered, and the filter cake was repeatedly washed with a large amount of deionized water until SO4 was no longer detectable in the filtrate with BaCl2 solution. 2- Continue until no white precipitate forms, to remove excess Na⁺ and SO₄²⁻. 2- Impurity ions were removed. The filter cake was transferred to a desiccant and placed in a drying oven, where it was dried at 100°C for 16 hours to obtain a black "nano carbon black / Al(OH)3" precursor powder.

[0081] The dried precursor powder was placed in a crucible and then placed in a muffle furnace. The temperature was increased at a slow rate (3°C / min) in air to ensure uniform heat and mass transfer. The temperature was raised to 500°C and held for 3 hours. At this high temperature, the Al(OH)3 coated on the carbon black surface underwent a dehydration reaction, transforming into γ-Al₂O₃ or amorphous Al₂O₃, yielding modified nano-carbon black.

[0082] ② Polyethylene oxide (PEO): PEO with a molecular weight of 50,000 was selected, whose crystallization-melting phase transition temperature (35℃~40℃) matches the target temperature range. Vacuum drying at 80-120°C for 12 hours was performed to remove moisture and avoid affecting Li⁺ migration.

[0083] ③ Lithium perchlorate (LiClO4): Grind to submicron level (particle size <1 μm) to ensure uniform mixing with PEO.

[0084] ④ Polydimethylsiloxane (PDMS): Choose a low viscosity type (100 cSt) for better compatibility with PEO. Its hydrophobicity and thermal stability can improve coating durability.

[0085] ⑤ Solvent: Chloroform / THF mixed solvent (volume ratio 1:1) is used.

[0086] (2) Component ratio:

[0087] The optimization of the carbon black particle ratio mainly occurred before the phase transition temperature (35℃), so the mass ratio of PDMS and PEO did not need to be too precise. A mass ratio of 1:4 as shown in Table 1 was adopted, and the contents of other components are also shown in Table 1.

[0088] Table 1

[0089]

[0090] (3) Mixing method:

[0091] PEO and PDMS were dissolved in the above solvent and ultrasonically dispersed at 40°C for 30 minutes to obtain a PDMS-PEO polymer solution. LiClO4 was added to the obtained PDMS-PEO polymer solution, and the mixture was mechanically stirred for 2 hours until completely dissolved. Then, modified nano-carbon black was slowly added dropwise, and the mixture was ultrasonically treated at 300 W for 30 minutes to prevent agglomeration and uneven room temperature transmittance. The mixture was centrifuged at 5000 rpm for 10 minutes to remove agglomerates and ensure uniform distribution, resulting in a black coating containing a PDMS-PEO-lithium perchlorate polymer blend system of thermochromic material.

[0092] (4) Equipment settings:

[0093] Use a spin coater (such as WS-650MZ-23NPP) with a spin speed gradient of 500 rpm (5 seconds) → 3000 rpm (30 seconds) to ensure a coating thickness of 30±2 μm. Ambient humidity <30% RH, temperature 25±2℃.

[0094] (5) Post-processing:

[0095] After spin coating, vacuum dry on a 60°C hot plate for 2 hours to remove residual solvent. Then anneal at 80°C for 1 hour to ensure complete crosslinking.

[0096] (6) Test:

[0097] The transmittance, chromaticity L* value, and surface morphology of the obtained coating are tested and listed in Table 2.

[0098] Table 2 (Transmittance test temperature is at room temperature (25℃))

[0099]

[0100] Note: When the carbon black content is 2%, the light transmittance is close to the target value (40%), and the L value reaches the deep black standard (L<20).

[0101] The obtained coating was subjected to long-term stability tests: ① After 100 cycles of -20℃ to 50℃, the light transmittance decreased by <3%, and the phase change temperature drift was <1°C. ② After damp heat aging (60%RH / 60°C / 30 days), the coating resistivity change rate was <10%.

[0102] Example 2

[0103] For the coating of the present invention, optimization experiments were conducted on the formulation ratio of PDMS and PEO, which are the main components, as follows:

[0104] (1) Material selection and pretreatment: Same as in Example 1.

[0105] (2) Composition ratio: as shown in Table 3:

[0106] Table 3

[0107]

[0108] (3) Mixing method: Same as in Example 1.

[0109] (4) Testing: Test the effect of different PDMS and PEO ratios on light transmittance;

[0110] ①Key parameters:

[0111] 25℃ transmittance (target 40%): PEO content needs to be ≥70% to maintain blackness.

[0112] Transmittance change at 35℃~38℃ (target 50%~90%): Increasing the proportion of PDMS can lower the phase transition temperature, but excessive phase separation should be avoided.

[0113] ②Testing process:

[0114] a. Coating and curing processes

[0115] The blend was coated onto a plasma-treated glass substrate using a spin coating method, followed by heat treatment for curing.

[0116] Spin coating: Spin coat at 3000 rpm for 30 seconds, controlling the thickness to 30±5 μm.

[0117] Curing conditions: Vacuum drying at 60℃ for 2 hours.

[0118] Heat treatment: Anneal at 80℃ for 1 hour to promote PEO crystallization and optimize the phase transformation response rate; cool down to room temperature at a rate of 5℃ / min to avoid PEO crystallization defects.

[0119] b. Performance Testing

[0120] Transmittance test: The transmittance at 25℃, 35℃ and 38℃ was measured by a UV-Vis spectrophotometer (400 nm~800 nm), with target values ​​of 40%, 50%~60% and 90% respectively.

[0121] DSC analysis: Differential scanning calorimetry was used to verify the consistency between the PEO crystallization peak (34.5±0.5℃) and the target temperature range.

[0122] The experimental results and analysis are shown in Table 4:

[0123] Table 4

[0124]

[0125] As shown in Table 4:

[0126] PDMS ratio and phase transition temperature: The higher the PDMS content, the lower the phase transition temperature (7:3 ratio is 5.7℃ lower than 1:9), which is attributed to the destructive effect of PDMS segments on PEO crystallization.

[0127] Transmittance response: The 1:4 ratio achieves 88% transmittance at 38℃, close to the target value (90%), and the response steepness is better than other ratios.

[0128] Cyclic stability: The 3:7 ratio showed the lowest decay rate (8%), indicating that a moderate PDMS content can balance crystallinity and durability.

[0129] c. Optimal Ratio Recommendation

[0130] Optimal ratio: 3:7 (PDMS:PEO) + 2% LiClO4, phase transition temperature 35.1℃, transmittance change 50% (40%→90%), excellent cycle stability.

[0131] By adjusting the PDMS / PEO ratio, a thermochromic coating meeting the required specifications was successfully prepared. The 3:7 blend system achieved a high-contrast optical response within the temperature range of 35℃ to 38℃, providing a reliable solution for energy conservation.

[0132] Example 3

[0133] In order to accurately control the phase transition rate (change in coating transmittance) based on temperature changes, an optimization experiment was conducted on the proportion of lithium perchlorate (LiClO4), which plays an important role in the regulation of phase transition temperature. The experiment was based on the premise that the addition of LiClO4 should be optimized to balance ionic conductivity and thermal stability while ensuring the coating transmittance (40% at 25℃, 90% at 38℃) and phase transition temperature (35℃~38℃).

[0134] (1) Material selection and pretreatment: Same as in Example 1.

[0135] (2) Composition ratio: as shown in Table 5:

[0136] Table 5

[0137]

[0138] (3) Mixing method: Same as in Example 1.

[0139] (4) Test

[0140] a. Coating and curing process: Same as in Example 2.

[0141] b. Performance testing:

[0142] Transmittance test: The transmittance at 25℃ (black state), 35℃ (phase transition initiation), and 38℃ (transparent state) was measured using a UV-Vis spectrophotometer (400 nm~800 nm).

[0143] Thermal analysis: DSC test (heating rate 10℃ / min) verified the PEO crystallization peak (target 34.5±0.5℃).

[0144] c. Data Report:

[0145] The transmittance test results are shown in Table 6:

[0146] Table 6

[0147]

[0148] DSC analysis results:

[0149] The 1% LiClO4 sample showed a PEO crystallization peak temperature of 34.5℃, consistent with the target value.

[0150] d. Conclusion

[0151] The optimal ratio is 1%~2%. LiClO4 has the best overall performance, with a transmittance of 40±2% at 25℃ and 90±3% at 38℃.

[0152] Thermal stability: No LiClO4 decomposition peak was detected by DSC (<200℃).

[0153] e. Handprint test of thermochromic coating

[0154] like Figure 3 As shown, Figure 3This is a test image of a handprint imprint on a thermochromic coating. When a hand is pressed against the coating for approximately 10 seconds (the hand temperature is around 35-36°C), a phase transition occurs in the coating. The phase transition does not recover within 2 seconds after the hand is removed, resulting in a transparent handprint shape.

[0155] Example 4

[0156] Based on the experimental results of Examples 1-3, the optimal coating formulation was selected for coating preparation, post-spraying performance verification, and dynamic adjustment energy-saving effect testing. The optimal coating formulation is: PDMS:PEO (mass ratio) of 3:7, that is, PDMS content of 28.8%, PEO content of 67.2%, LiClO4 content of 2%, and carbon black content of 2%.

[0157] (1) Coating preparation: Same as in Example 2.

[0158] (2) Substrate pretreatment:

[0159] For the epoxy adhesive layer on the surface of the LED light module, surface treatment is performed: grease is removed by wiping with isopropyl alcohol, and plasma treatment (50W power, 2 minutes) is used to improve surface energy and ensure coating adhesion.

[0160] Temperature control: The ambient temperature during construction should be kept stable at 25±2℃ and the humidity should be <60% to avoid solvent residue.

[0161] The spraying parameters are as follows:

[0162] Spray gun pressure: 0.5 MPa;

[0163] Spraying distance: 20 cm;

[0164] Film thickness control: 30 μm (adjustable by spin coating speed)

[0165] Curing conditions: Heat curing at 80℃ for 12 hours, with a vacuum degree ≤0.1 MPa to eliminate air bubbles.

[0166] (4) Performance verification:

[0167] Optical testing: The transmittance at 25℃ / 38℃ meets the switching requirement of 40%→90%, and ΔT≥50%.

[0168] Durability: After 100 cycles of testing at -20℃ to 50℃, the light transmittance change rate is <15%.

[0169] (5) Dynamic adjustment design:

[0170] This invention requires that when the LED module is lit and operating (video mode), the thermochromic material begins a phase change when the module temperature rises to 35°C. The black coating then becomes transparent, and the light transmittance of the COB film layer increases. When the temperature reaches 38°C, the light transmittance reaches approximately 90%. This effect can be achieved by using the coating of this invention combined with a dynamic adjustment design. Figure 4 As shown, Figure 4 This is a flowchart illustrating the dynamic adjustment design of the LED display screen according to the present invention. Details are as follows:

[0171] First, the temperature distribution on the module is tested under working conditions using simulation analysis or temperature measuring equipment such as infrared imagers and thermocouples. The locations of high and low temperature points on each module are identified. Then, thermistors are installed on the back of the corresponding modules to record the temperature under working conditions in real time. At the same time, the temperature data is transmitted to the receiving card, which calculates the average value of all temperature data at the same time in real time.

[0172] When the average temperature reaches 38℃, the light transmittance of the thermochromic material layer is around 80%, a 100% increase from the initial 40%, and the light output of the LED also doubles. According to the relationship between COB luminous efficacy and input power: luminous efficacy (η) = luminous flux / input power, with the same luminous flux, the input power can be reduced by 50%.

[0173] If the temperature rise of the display screen is approximately 13℃ at room temperature (25℃), and referring to the display screen's thermal resistance R = temperature rise ΔT / heat dissipation q, under constant thermal resistance, temperature rise is directly proportional to heat dissipation. Heat dissipation is also directly proportional to input power. Therefore, if the input power is reduced by 50%, the temperature rise will also be reduced by 50%, i.e., 13 * 50% = 6.5℃. The absolute temperature of the display screen is 38 - 6.5 = 31.5℃. At this temperature, the operating temperature of the thermochromic material (35℃) has not yet been reached, resulting in the brightness not being as high as preset. Therefore, the input power cannot be reduced by 50%.

[0174] Therefore, based on the absolute temperature of 35℃ at which the thermochromic material starts working, the temperature rise decreases by 3℃, or about 23%. So we can define the input power as reduced by 20%, which means we can adjust the current gain of the COB LED or adjust the duty cycle using PWM to reduce it by 20%, and the brightness will not decrease at this time.

[0175] Similarly, the decrease in input power is linearly proportional to the temperature of the display screen; when the display screen temperature exceeds 43℃, the input power decreases by 50%. When the temperature is below 43℃, to avoid the continuous adjustment of input power when the temperature hovers around 43℃, which would cause short-term repeated changes in display brightness, the input power decreases in increments of 2℃. That is, the input power begins to increase when the temperature is below 41℃, and the decrease in temperature and the increase in input power change linearly until the temperature is below 33℃, at which point the input power returns to normal.

[0176] Overall adjustment curve as follows Figure 5 As shown, Figure 5 This invention presents a dynamic energy-saving adjustment curve for the LED display screen. Without affecting the display effect, the input power is dynamically adjusted according to the screen temperature during the display process, reducing power by as little as 50%, thus achieving energy saving and emission reduction. Based on a conventional COB display screen (brightness 600 nits~800 nits), the display surface temperature is around 40℃ in video mode at a normal temperature of 25℃, and its power density is approximately 200 W / m². 2 Using the design scheme of this invention, the display surface temperature is maintained at 37~38℃, at which point the power consumption is reduced by approximately 25%, or 50 W / m. 2 The display brightness will not decrease and will remain basically stable.

[0177] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A thermochromic coating composition, characterized in that, include: 0.5 wt%~5.0 wt% nano carbon black; 20 wt%~87 wt% polyethylene oxide; 0.5 wt%~15 wt% lithium perchlorate; 10 wt%~70 wt% of polydimethylsiloxane.

2. The thermochromic coating composition according to claim 1, characterized in that, include: 0.5 wt%~5.0 wt% nano carbon black; 40 wt%~70 wt% polyethylene oxide; 0.5 wt%~5.0 wt% lithium perchlorate; 20 wt%~50 wt% of polydimethylsiloxane.

3. The thermochromic coating composition according to claim 1, characterized in that, include: 1.0 wt%~3.0 wt% nano carbon black; 60 wt%~70 wt% polyethylene oxide; 1.0 wt%~3.0 wt% lithium perchlorate; 20 wt%~30 wt% of polydimethylsiloxane.

4. The thermochromic coating composition according to claim 1, characterized in that, The particle size of the nano carbon black is 50 nm to 100 nm; The molecular weight of the polyethylene oxide is 40,000 to 100,000; The lithium perchlorate has a particle size of <1 μm; The viscosity of the polydimethylsiloxane is 50 cSt to 1000 cSt.

5. The thermochromic coating composition according to claim 1, characterized in that, The nano carbon black is a modified nano carbon black composed of alumina and nano carbon black.

6. A thermochromic coating, characterized in that, It is obtained from the thermochromic coating composition and solvent described in any one of claims 1 to 5.

7. An LED display module adhesive film, characterized in that, It includes a base film and a thermochromic coating disposed on the surface of the base film; The thermochromic coating is formed from the thermochromic paint of claim 6.

8. The LED display module adhesive film according to claim 7, wherein the thickness of the thermochromic coating is 20 μm to 40 μm.

9. An LED display module, characterized in that, include: The PCB board, the light-emitting element connected to the PCB board, and the LED display module adhesive film according to claim 7 or 8 covering the light-emitting element.

10. A method for adjusting the input power of a display screen including the LED display module of claim 9, characterized in that, include: Obtain the average temperature of the display screen; Based on the average temperature of the display screen, the input power of the display screen is adjusted while maintaining the brightness of the display screen.

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