Temperature change microcapsule preparation method, temperature change microcapsule and LED display module

Abstract

The invention relates to a temperature change microcapsule preparation method, a temperature change microcapsule and an LED display module, the temperature change microcapsule preparation method comprises the following steps: preparing a core material dispersion liquid based on a core material component, preparing a shell material premix liquid based on a shell material component, combining the core material dispersion liquid and the shell material premix liquid to carry out film passing emulsification treatment to obtain emulsion particles, and carrying out staged UV curing treatment on the emulsion particles to obtain the temperature change microcapsule. The core-loaded microcapsule is obtained. And finally, depositing and curing a functional layer on the surface of the core-loaded microcapsule to obtain the temperature change microcapsule sequentially comprising the core material, the shell material and the functional layer from inside to outside. According to the scheme, the preparation process accuracy and application compatibility of the temperature change microcapsule can be effectively improved, and the problem that the temperature change microcapsule is poor in performance suitability and process compatibility in the application of an LED display screen is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of LED display, in particular to a temperature-variable microcapsule preparation method, a temperature-variable microcapsule and an LED display module. BACKGROUND

[0002] LED (Light-Emitting Diode) display screens have been widely used in multi-scenarios such as conference centers, smart education, security monitoring, and commercial display, due to their seamless splicing, high brightness, wide viewing angle, and other advantages. With the iteration of Mini / Micro LED technology, the pixel pitch of display screens continues to shrink, and the requirements for picture contrast, optical clarity, and interactive experience are becoming increasingly stringent. Among them, the black state performance when the screen is off directly affects the contrast, and the light transmittance when the screen is on determines the display precision. Therefore, how to balance the black state performance when the screen is off and the light transmittance when the screen is on is particularly important.

[0003] Currently, the techniques for improving the black state performance of LED display screens mainly fall into two categories: one is to use light-blocking ink or black coating, which can enhance the blackness when the screen is off, but significantly reduces the light transmittance when the screen is on, sacrificing display brightness and clarity; the other is to use the phase change characteristics of temperature-sensitive materials to adjust the optical state through temperature changes, among which temperature-variable microcapsules have become a research hotspot due to their good core material packaging and strong color reversibility.

[0004] However, in related technologies, the temperature-variable microcapsules have poor performance adaptability and process compatibility in LED display screen applications. SUMMARY

[0005] Therefore, it is necessary to propose a temperature-variable microcapsule preparation method, a temperature-variable microcapsule and an LED display module to solve the problem of poor performance adaptability and process compatibility of temperature-variable microcapsules in LED display screen applications.

[0006] The present application provides a temperature-variable microcapsule preparation method, which includes: preparing a core material dispersion liquid based on core material components, and preparing a shell material pre-mixed liquid based on shell material components; performing membrane emulsification treatment based on the core material dispersion liquid and the shell material pre-mixed liquid to obtain emulsion particles; performing stage-by-stage UV curing treatment on the emulsion particles to obtain core-loaded microcapsules; depositing a functional layer on the surface of the core-loaded microcapsules to obtain temperature-variable microcapsules; wherein the deposition and curing temperature of the functional layer is greater than 40℃ and less than 70℃.

[0007] In one of the embodiments, the core material component-based preparation of the core material dispersion liquid comprises: stirring a first preset proportion of the compound temperature-sensitive color-changing dye, the compound color-developing agent, the compound phase change solvent, and the compound auxiliary dispersant at a first speed for a first preset time length to form a uniform transparent solution at a first preset temperature range; cooling the uniform transparent solution to a first preset temperature threshold and storing for a second preset time length to obtain the core material dispersion liquid; wherein the first preset temperature threshold is less than the minimum value of the first preset temperature range, and the second preset time length is less than the first preset time length.

[0008] In one of the embodiments, the method comprises at least one of the following items:

[0009] The first item: the compound temperature-sensitive color-changing dye comprises crystal violet lactone and 1,3,3-trimethylindolin-6'-nitrobenzospirpyran, and the mass ratio of the crystal violet lactone to the 1,3,3-trimethylindolin-6'-nitrobenzospirpyran is 1:0.8-1:1.2;

[0010] The second item: the compound color-developing agent comprises 4,4'-dihydroxydiphenyl sulfone and phenyl salicylate, and the mass ratio of the 4,4'-dihydroxydiphenyl sulfone to the phenyl salicylate is 1:1.5-1:2.5;

[0011] The third item: the compound phase change solvent comprises tetradecanol, hexadecanol, and hydrogenated castor oil, and the mass ratio of the tetradecanol, the hexadecanol, and the hydrogenated castor oil is (4-7):(2-5):1;

[0012] The fourth item: the compound auxiliary dispersant comprises polyoxyethylene sorbitan monooleate and sodium dodecyl benzene sulfonate, and the mass ratio of the polyoxyethylene sorbitan monooleate to the sodium dodecyl benzene sulfonate is 3:1-4:1.

[0013] In one of the embodiments, the shell material component-based preparation of the shell material pre-mixed solution comprises: stirring a second preset proportion of the shell material base, the photoinitiator, and the active crosslinking agent at a second speed in the dark for a third preset time length at a second preset temperature threshold to obtain the shell material pre-mixed solution.

[0014] In one of the embodiments, the method comprises at least one of the following items:

[0015] The first item: the shell material base comprises 2-hydroxyethyl acrylate and 1,6-hexanediol diacrylate, and the mass ratio of the 2-hydroxyethyl acrylate to the 1,6-hexanediol diacrylate is 1:2-1:3;

[0016] The second item: the photoinitiator comprises a derivative of 2-hydroxy-2-methyl-1-phenyl-1-propanone grafted polyethylene glycol;

[0017] The third item: The active crosslinking agent includes aliphatic polyurethane diacrylate and divinylbenzene, wherein the mass ratio of aliphatic polyurethane diacrylate to divinylbenzene is 4:1-6:1.

[0018] In one embodiment, the process of performing a membrane emulsification treatment based on the core material dispersion and the shell material premix to obtain emulsion particles includes: mixing the core material dispersion and the shell material premix at a preset mass ratio to obtain a dispersed phase; preparing a continuous phase based on an aqueous solution of polyvinyl alcohol; and applying a driving force to the dispersed phase to allow the dispersed phase to enter the continuous phase from a zirconia ceramic membrane component with a preset pore size to obtain emulsion particles.

[0019] In one embodiment, the step of performing staged UV curing treatment on the emulsion particles to obtain core-carrying microcapsules includes: irradiating the emulsion particles with ultraviolet light of a first wavelength for a fourth preset time to achieve pre-curing; after the pre-curing is completed, irradiating the emulsion particles with ultraviolet light of a second wavelength for a fifth preset time to achieve main curing, thereby obtaining core-carrying microcapsules; wherein the second wavelength is greater than the first wavelength, and the fifth preset time is greater than the fourth preset time.

[0020] In one embodiment, the deposition and curing of a functional layer on the surface of the carrier microcapsule to obtain thermochromic microcapsules includes: dispersing the carrier microcapsule in deionized water to obtain a suspension with a preset mass concentration; sequentially adding a modified nano-silica sol, a reactive silane coupling agent, and a hydroxyl-modified acrylic resin in a third preset ratio to the suspension, stirring at a third speed for a sixth preset time, and then adjusting the pH value to a preset value; stirring the suspension at the third speed for a seventh preset time at a third preset temperature threshold, and then curing it with ultraviolet light of a third wavelength for a seventh preset time to obtain preliminary thermochromic microcapsules; and washing and drying the preliminary thermochromic microcapsules to obtain thermochromic microcapsules.

[0021] This application provides a thermochromic microcapsule, which is prepared using the thermochromic microcapsule preparation method described above.

[0022] This application provides an LED display module, including a driving component, a substrate, LED beads, an encapsulation layer, and a temperature-sensitive color-changing coating prepared based on the above-mentioned temperature-sensitive microcapsules. The driving component is disposed on a first surface of the substrate, the LED beads are disposed on a second surface of the substrate, the encapsulation layer covers the surface of the LED beads, and the temperature-sensitive color-changing coating is disposed on the outer surface of the encapsulation layer.

[0023] The aforementioned method for preparing thermochromic microcapsules, the thermochromic microcapsules themselves, and the LED display module first involves preparing a core material dispersion based on the core material components and a shell material premix based on the shell material components. Then, the core material dispersion and shell material premix are combined and emulsified through a membrane to obtain emulsion particles. These emulsion particles are then subjected to staged UV curing to obtain core-carrying microcapsules. Finally, a cured functional layer is deposited on the surface of the core-carrying microcapsules, resulting in thermochromic microcapsules comprising a core material, a shell material, and a functional layer, arranged sequentially from the inside out. This approach, combining membrane emulsification, staged UV curing, and low-temperature deposition processes, prepares thermochromic microcapsules. The membrane emulsification process, compared to stirring emulsification, effectively improves the particle size uniformity of the thermochromic microcapsules. The staged UV curing ensures curing efficiency while avoiding the problems of over-curing the surface and incomplete curing of the interior caused by single-wavelength curing. The low-temperature deposition process avoids excessively high curing temperatures that could lead to microcapsule rupture. This can effectively improve the precision of the preparation process and the application compatibility of thermochromic microcapsules, and solve the problem of poor performance adaptability and process compatibility of thermochromic microcapsules in LED display applications. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the process for preparing thermochromic microcapsules in one embodiment of this application;

[0026] Figure 2 This is a schematic diagram of the emulsion particle preparation process in one embodiment of this application;

[0027] Figure 3 This is a schematic diagram of the process for preparing thermochromic microcapsules in another embodiment of this application;

[0028] Figure 4 This is a schematic diagram of the core-carrying microcapsule processing flow in one embodiment of this application;

[0029] Figure 5 This is a schematic diagram of the thermochromic microcapsule structure in one embodiment of this application;

[0030] Figure 6 This is a schematic diagram of the LED display module structure in one embodiment of this application. Detailed Implementation

[0031] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0032] Please see Figure 1 This application provides a method for preparing thermochromic microcapsules, including steps 102, 104, 106 and 108.

[0033] Step 102: Prepare a core material dispersion based on the core material components and a shell material premix based on the shell material components.

[0034] Specifically, the core material component is a collection of various chemical substances that constitute the core functional part of the thermochromic microcapsule (i.e., the core material), responsible for realizing the core thermosensitive color-changing function. The core material dispersion is a homogeneous and stable oil-phase liquid formed after pretreatment of the core material components through heating, stirring, and heat preservation, providing a qualified precursor for subsequent emulsification steps. The type of core material component is not unique. In one embodiment, it includes a thermochromic dye, a color developer, a phase change solvent, and a dispersant. The thermochromic dye is the source of color change, the color developer reacts with the dye to produce color, the phase change solvent is used to drive the occurrence and reversal of the color change reaction, and the dispersant is used to ensure that the above components can be uniformly mixed and stably dispersed.

[0035] The shell material component is a UV (ultraviolet) curable resin mixture used to encapsulate the core material and form the outer shell of the microcapsule. It serves as the protective shell for the microcapsule and directly affects its mechanical strength and sealing performance. The shell material premix refers to a resin mixture that can be directly used for emulsification, obtained by stirring and mixing the shell material components uniformly under certain temperature and light-protected conditions.

[0036] It should be noted that the proportions of various materials in the core material and the shell material are not unique; they can be selected according to actual needs, and no restrictions are imposed here.

[0037] Step 104: Perform a membrane emulsification treatment based on the core material dispersion and the shell material premix to obtain emulsion particles.

[0038] Specifically, membrane emulsification is a precision process that uses a porous membrane to prepare monodisperse emulsions. It allows a core material dispersion and a shell material premix to pass through a membrane with specific pore sizes under pressure, where they are sheared into uniform droplets (i.e., emulsion particles) in a continuous phase (such as an aqueous phase). Correspondingly, emulsion particles refer to tiny droplets formed after membrane emulsification, consisting of a core material as the inner core and a shell material as the outer coating, dispersed in an aqueous phase.

[0039] The emulsion particles can be regarded as the prototype of microcapsules. At this time, the core material has been encapsulated by the shell material premix liquid, but the shell material has not yet been cured and the structure is fragile. Its uniform particle size (e.g. 5μm-20μm) provides a consistent substrate for subsequent curing and functional layer deposition.

[0040] It is understood that the pore size of the porous membrane used in the membrane emulsification process is not unique; depending on the required temperature-sensitive microcapsule size, the pore size can be selected in different ways. For example, in one embodiment, the pore size of the porous membrane is 10 μm (micrometers) to 30 μm.

[0041] In a more detailed embodiment, a zirconia ceramic membrane module can be used as a porous membrane for emulsification and granulation. The zirconia ceramic membrane module has a pore size of 10μm-30μm, a porosity of 35%-45%, a channel length of 10cm-15cm, and a wall roughness Ra≤0.2μm. This method, due to the solvent resistance and smooth surface of zirconia, can reduce emulsion particle adhesion.

[0042] Step 106: Perform staged UV curing treatment on the emulsion particles to obtain core-carrying microcapsules.

[0043] Specifically, staged UV curing refers to the process of irradiating emulsion particles with ultraviolet light of different wavelengths in at least two stages, causing the outer shell (shell material) to polymerize from liquid resin into a solid cross-linked polymer network. Core-carrying microcapsules refer to solid particles obtained after staged UV curing treatment, with the core material as the core and the shell material as the cured shell material.

[0044] Core-carrying microcapsules can be considered as semi-finished microcapsules with basic functions. At this stage, the microcapsules have achieved core material encapsulation and have temperature-sensitive properties, but they have not yet undergone surface reinforcement treatment, and their mechanical strength and durability are insufficient to cope with the harsh operating environment of LED displays.

[0045] Step 108: Deposit and solidify a functional layer on the surface of the core-carrying microcapsule to obtain a thermochromic microcapsule.

[0046] Specifically, the deposition and curing temperature of the functional layer is greater than 40°C and less than 70°C. In this embodiment, an ultra-thin, dense, and high-hardness composite coating, i.e., the functional layer, is constructed on the surface of the core-carrying microcapsule through chemical reaction and UV curing. This is a finishing step to improve the durability and application performance of the microcapsule. A low-temperature deposition process can be used to form a dense coating with a thickness of 100nm to 300nm on the surface of the core-carrying microcapsule, significantly improving its scratch resistance, wear resistance, and interfacial adhesion with external resins.

[0047] It should be noted that the temperature used in the deposition process is not unique; as long as it is within the range of 40°C to 70°C, it is acceptable to ensure the reaction rate while avoiding irreversible damage to the core material, solvent evaporation, and microcapsule rupture. For example, in one embodiment, the surface deposition temperature can be configured to 40°C to 60°C. Furthermore, the surface deposition temperature can be configured to 45°C to 55°C.

[0048] It is understood that the method of providing temperature in the low-temperature deposition process is not unique. In one embodiment, it can be water bath heating, while in another embodiment, other methods can also be used. No specific limitation is made.

[0049] The solution described in this application provides a thermochromic microcapsule with a three-layer composite structure of "core material-shell material-functional layer". This microcapsule can reversibly switch between black and transparent states in response to temperature changes. For example, it can adapt to the temperature rise range of LED screens, achieving low light transmittance at room temperature (25℃) and high light transmittance at 38-42℃. More specifically, in one embodiment, the performance indicators of the thermochromic microcapsule are: light transmittance ≤10% at 25℃ (i.e., in a black state), light transmittance ≥90% at 40℃ (i.e., in a transparent state), and pencil hardness ≥3H.

[0050] The above-described method for preparing thermochromic microcapsules first involves preparing a core material dispersion based on the core material components and a shell material premix based on the shell material components. Then, the core material dispersion and shell material premix are combined and emulsified through a membrane to obtain emulsion particles. These particles are then subjected to staged UV curing to obtain core-carrying microcapsules. Finally, a cured functional layer is deposited on the surface of the core-carrying microcapsules, resulting in thermochromic microcapsules consisting of a core material, a shell material, and a functional layer, arranged sequentially from the inside out. This method, combining membrane emulsification, staged UV curing, and low-temperature deposition processes, prepares thermochromic microcapsules. The membrane emulsification process, compared to stirring emulsification, effectively improves the particle size uniformity of the thermochromic microcapsules. The staged UV curing ensures curing efficiency while avoiding the problems of over-curing the surface and incomplete curing of the interior caused by single-wavelength curing. The low-temperature deposition process avoids excessively high curing temperatures that could lead to microcapsule rupture. This can effectively improve the precision of the preparation process and the application compatibility of thermochromic microcapsules, and solve the problem of poor performance adaptability and process compatibility of thermochromic microcapsules in LED display applications.

[0051] In one embodiment, the preparation of a core material dispersion based on core material components includes: stirring a first-preset ratio of a compound thermosensitive color-changing dye, a compound color developer, a compound phase change solvent, and a compound dispersant at a first speed for a first-preset time within a first preset temperature range to form a homogeneous and transparent solution; cooling the homogeneous and transparent solution to a first preset temperature threshold and storing it at that temperature for a second preset time to obtain the core material dispersion. Wherein, the first preset temperature threshold is less than the minimum value of the first preset temperature range, and the second preset time is less than the first preset time.

[0052] Specifically, the core material preparation employs a two-step method: high-temperature dispersion followed by medium-temperature holding. The first step involves stirring at 70℃-75℃ and 600r / min-800r / min for 1.2h-1.8h, achieving a homogeneous and transparent solution through high-temperature dispersion. This ensures the complete dissolution of the thermosensitive dye and color developer in the phase change solvent. The second step involves cooling to 50℃ and holding for 30min, i.e., medium-temperature holding. This avoids the separation of components caused by excessively rapid cooling, resulting in a homogeneous and stable core material dispersion.

[0053] It should be noted that the first preset temperature, the first speed, the first preset temperature threshold, the second preset duration, and the magnitude of the first preset duration are not unique and are not limited to the values ​​shown in the above embodiments. They can be configured according to actual needs.

[0054] Similarly, the first preset ratio is not unique; it can be selected based on actual needs and is not limited here, as long as a uniform and stable core material dispersion can be obtained. For example, in one embodiment, the core material dispersion includes 2-15 parts of thermosensitive color-changing dye, 5-20 parts of color developer, and 10-50 parts of phase change solvent, while the dispersant is not limited.

[0055] In one embodiment, the method includes at least one of the following:

[0056] The first item: The compound thermosensitive color-changing dye includes crystal violet lactone and 1,3,3-trimethylindoline-6'-nitrobenzospiropyran, with a mass ratio of crystal violet lactone to 1,3,3-trimethylindoline-6'-nitrobenzospiropyran of 1:0.8-1:1.2.

[0057] The second item: The compound colorimetric agent includes 4,4'-dihydroxydiphenyl sulfone and phenyl salicylate, with a mass ratio of 1:1.5 to 1:2.5 between 4,4'-dihydroxydiphenyl sulfone and phenyl salicylate.

[0058] The third item is a compound phase change solvent consisting of tetradecyl alcohol, hexadecyl alcohol and hydrogenated castor oil, with a mass ratio of tetradecyl alcohol, hexadecyl alcohol and hydrogenated castor oil of (4~7):(2~5):1.

[0059] The fourth item is a compound dispersant that includes polyoxyethylene sorbitan monooleate and sodium dodecylbenzene sulfonate, with a mass ratio of polyoxyethylene sorbitan monooleate to sodium dodecylbenzene sulfonate of 3:1-4:1.

[0060] Specifically, a compound thermochromic dye includes at least two thermochromic dyes mixed in a certain proportion. A compound color developer includes at least two color developers mixed in a certain proportion. A compound phase change solvent includes at least two phase change solvents mixed in a certain proportion. A compound dispersant includes at least two dispersants mixed in a certain proportion.

[0061] Crystal violet lactone (CVL), also known as 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide, has the molecular formula C1. 26 H 29 N3O2 belongs to the phthaloyl group of compounds. 1,3,3-Trimethylindoline-6'-nitrobenzospiropyran (also known as: spiro[1,3,3-trimethylindoline-(6'-nitrobenzodihydropyran), SP1(DYE), NSC206176), with the molecular formula C 19 H 18 N2O3. The former reacts with the color developer at low temperatures to form a strong black color, while the latter can enhance the reversibility of the color change.

[0062] It is understandable that in the compound thermosensitive color-changing dye, 1 part by mass of crystal violet lactone can be compounded with 0.8-1.2 parts of 1,3,3-trimethylindoline-6'-nitrobenzospiropyran. The specific choice depends on actual needs and is not specifically limited here.

[0063] The molecular formula of 4,4'-dihydroxydiphenyl sulfone (bisphenol S) is C 12 H 10 O4S is a white crystalline powder with a melting point of 240-250℃. It is heat-resistant and oxidation-resistant, but has poor water solubility (1.1g / L, 20℃). It is soluble in organic solvents such as ethanol and chloroform. The compound color developer uses 4,4'-dihydroxydiphenyl sulfone and phenyl salicylate in a ratio of 1:1.5-1:2.5. By utilizing the difference in the strength of hydrogen bonding between the two phenolic substances, precise control of the color change temperature can be achieved, ensuring stable color development at room temperature (25℃) and rapid decolorization at 38℃-42℃.

[0064] Tetradecanoyl alcohol, also known as myristol, has the chemical formula C60. 14 H 30 O, a saturated straight-chain fatty alcohol, has a hydroxyl group at the end of the carbon chain and a long-chain alkyl structure. Cetyl alcohol, also known as cetyl alcohol, has the chemical formula C60. 16 H34 O, a saturated straight-chain fatty alcohol, has a longer carbon chain, a higher melting point, and stronger hydrophobicity. Hydrogenated castor oil is mainly composed of 12-hydroxystearic acid glyceride. It is formed after castor oil is hydrogenated and contains hydroxyl and ester groups, which significantly improves its chemical stability.

[0065] Polyoxyethylene sorbitan monooleate, also known as Tween 80 or polysorbate 80, is formed by the addition of sorbitan monooleate with 20 ethylene oxide units. It contains hydrophilic polyoxyethylene chains and lipophilic oleate groups, and is soluble in water, ethanol, ether, and most organic solvents, but insoluble in mineral oil. Sodium dodecylbenzenesulfonate, also known as LAS or linear alkylbenzenesulfonate, is an anionic surfactant. Its hydrophobic group is dodecylbenzene, and its hydrophilic group is sulfonate. It is readily soluble in water (1% solution, pH 7-9), slightly soluble in ethanol, and insoluble in organic solvents.

[0066] In practical applications, tetradecyl alcohol, hexadecyl alcohol, and hydrogenated castor oil can be blended in a ratio of (4-7):(2-5):1, i.e., 4-7 parts tetradecyl alcohol, 2-5 parts hexadecyl alcohol, and 1 part hydrogenated castor oil, to obtain a blended phase change solvent. Polyoxyethylene sorbitan monooleate and sodium dodecylbenzenesulfonate can be blended in a ratio of 3:1-4:1 to obtain a blended dispersant.

[0067] In one embodiment, the preparation of a shell material premix based on shell material components includes: stirring a shell material substrate, a photoinitiator, and an active crosslinking agent in a second preset ratio at a second speed in the dark for a third preset time at a second preset temperature threshold to obtain a shell material premix.

[0068] In more detail, the shell material component can be stirred at 25℃-30℃ and 300r / min-400r / min for 40min-50min, and stored in the dark to prevent premature decomposition of the photoinitiator and ensure subsequent curing efficiency. Thus, the preparation of the core material dispersion and shell material premix provides a homogeneous and highly stable precursor for subsequent emulsification and granulation, which is fundamental to ensuring the consistency of microcapsule performance.

[0069] It should be noted that the second preset temperature threshold can be any value between 25℃ and 30℃, the second speed can be any value between 300r / min and 400r / min, and the third preset duration can be any value between 40min and 50min. The appropriate value can be selected based on actual needs.

[0070] In one embodiment, the method includes at least one of the following:

[0071] The first item: The shell material base material includes 2-hydroxyethyl acrylate and 1,6-hexanediol diacrylate, and the mass ratio of 2-hydroxyethyl acrylate to 1,6-hexanediol diacrylate is 1:2-1:3.

[0072] The second item: Photoinitiators include derivatives of polyethylene glycol grafted with 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0073] The third item: the active crosslinking agent includes aliphatic polyurethane diacrylate and divinylbenzene, with a mass ratio of aliphatic polyurethane diacrylate to divinylbenzene of 4:1-6:1.

[0074] Specifically, the shell substrate can be formed by combining 2-hydroxyethyl acrylate and 1,6-hexanediol diacrylate in a ratio of 1:2 to 1:3. The former provides hydroxyl groups to enhance chemical bonding with the functional layers, while the latter introduces multifunctional groups to increase crosslinking density. The photoinitiator is a derivative of polyethylene glycol grafted with 2-hydroxy-2-methyl-1-phenyl-1-propanone. In this way, the introduction of polyethylene glycol segments improves the dispersibility of the photoinitiator in the resin, avoids uneven local curing, reduces its migration, and improves the long-term stability of the microcapsules.

[0075] The active crosslinking agent is a mixture of aliphatic polyurethane diacrylate and divinylbenzene at a mass ratio of 4:1 to 6:1. The long polyurethane chains act as flexible crosslinking bridges, significantly improving the toughness of the shell material while ensuring crosslinking density; the divinylbenzene acts as a rigid crosslinking point, synergistically constructing a three-dimensional network structure that combines rigidity and flexibility, effectively preventing core material leakage while avoiding shell material cracking due to excessive brittleness.

[0076] Please see Figure 2 In one embodiment, step 104 includes steps 202, 204 and 206.

[0077] Step 202: Mix the core material dispersion and the shell material premix according to a preset mass ratio to obtain the dispersed phase.

[0078] Step 204: Prepare a continuous phase based on an aqueous solution of polyvinyl alcohol.

[0079] Step 206: Apply a driving force to the dispersed phase so that the dispersed phase enters the continuous phase from the zirconia ceramic membrane component with a preset pore size to obtain emulsion particles.

[0080] More specifically, a zirconia ceramic membrane module is used for emulsification and granulation. The membrane pore size is 10μm-30μm, porosity is 35%-45%, channel length is 10cm-15cm, and wall roughness Ra≤0.2. The core material dispersion and shell material premix are prepared at a mass ratio of 1:2-1:5, containing 0.1wt%-0.5wt% polyvinyl alcohol (aqueous solution) as a continuous phase. The volume ratio of the continuous phase to the oil phase is 5:1-8:1, and a pushing pressure of 0.05MPa-0.15MPa is applied to ensure that the particle size variation coefficient of the emulsion is ≤8%. Compared with traditional stirred emulsification, membrane emulsification achieves precise particle size control through the uniformity of membrane pores, avoiding the temperature-dependent performance differences caused by wide particle size distribution, and providing a uniform substrate for subsequent curing and functional layer deposition.

[0081] Please see Figure 3 In one embodiment, step 106 includes steps 302 and 304.

[0082] Step 302: Irradiate the emulsion particles with ultraviolet light of the first wavelength for a fourth preset time to achieve pre-curing.

[0083] Step 304: After pre-curing is completed, the emulsion particles are irradiated with ultraviolet light of the second wavelength for a fifth preset time to achieve primary curing and obtain core-carrying microcapsules.

[0084] The second wavelength is longer than the first wavelength, and the fifth preset duration is longer than the fourth preset duration. The UV curing adopts a phased process of "pre-curing-main curing". First, it uses short-wavelength UV light of 200nm-280nm for 5s-8s to pre-cur the surface of the shell material to quickly cure it and form a preliminary shape, preventing the emulsion particles from deforming or fusing.

[0085] Then, a long-wavelength ultraviolet light (320nm-400nm) is used for primary curing for 15-25 seconds to deeply cure the shell material, with the total curing energy controlled at 100-130mJ / cm². This design ensures curing efficiency while avoiding the problems of over-curing the surface and incomplete curing of the interior caused by single-wavelength curing, resulting in a shell material gel rate of ≥95%. This effectively encapsulates the core material while maintaining appropriate elasticity to prevent cracking during subsequent processing.

[0086] It should be noted that the second wavelength is selected from 320nm-400nm, the first wavelength is selected from 200nm-280nm, the fifth preset duration is selected from 15s-25s, and the fourth preset duration is selected from 5s-8s. The specific values ​​are not limited and can be configured according to actual needs.

[0087] Please see Figure 4 In one embodiment, step 108 includes steps 402, 404, 406 and 408.

[0088] Step 402: Disperse the core-carrying microcapsules in deionized water to obtain a suspension with a preset mass concentration.

[0089] Step 404: Add the modified nano silica sol, reactive silane coupling agent and hydroxyl-modified acrylic resin in the suspension in the third preset ratio in sequence. After stirring at the third speed for the sixth preset time, adjust the pH value to the preset value.

[0090] Step 406: At the third preset temperature threshold, the suspension is stirred and reacted at the third speed for a seventh preset time, and then cured by ultraviolet light of the third wavelength for a seventh preset time to obtain preliminary temperature-sensitive microcapsules.

[0091] Step 408: Wash and dry the preliminary thermochromic microcapsules to obtain thermochromic microcapsules.

[0092] Specifically, the modified nano-silica sol uses an aqueous dispersion of surface-grafted methacryloyloxypropyltrimethoxysilane with a particle size of 15nm-30nm and a solid content of 20%-30%. The grafted organic functional group methacryloyloxy can undergo a polymerization reaction with the incompletely cured double bonds of the shell material, while simultaneously forming a chemical bond with the resin matrix, effectively preventing the agglomeration of nanoparticles; it forms a micro-nano reinforcing skeleton in the functional layer, directly improving the scratch resistance and wear resistance of the coating.

[0093] The reactive silane coupling agent selected is γ-methacryloyloxypropyltrimethoxysilane. The alkoxy group can undergo a condensation reaction with the hydroxyl group on the shell surface to form a chemical bond anchoring. The double bond can undergo a polymerization reaction with the graft groups of nano-silica and the resin matrix to build an inorganic-organic cross-linking bridge, strengthen the interfacial bonding between the functional layer and the shell, prevent delamination and peeling during use, and ensure long-term stability of hardness and wear resistance.

[0094] The hydroxyl value of the hydroxyl-modified acrylic resin is controlled between 80 mg KOH / g (hydroxyl value refers to the number of milligrams of potassium hydroxide required to neutralize the hydroxyl groups in 1 g of resin) and 120 mg KOH / g, with a glass transition temperature of 50℃-70℃. The hydroxyl groups can form multiple bonds with the shell material and coupling agent through hydrogen bonds, further improving interfacial compatibility. The high glass transition temperature ensures the resin maintains rigidity at LED operating temperatures, preventing coating softening and subsequent hardness reduction. Simultaneously, it provides a uniformly dispersed organic matrix for nano-silica, balancing the hardness-toughness relationship and preventing cracks in the coating due to excessive brittleness.

[0095] In more detail, the three components are compounded in a mass ratio of (15~22):(3~6):(8~13), that is, 15~22 parts of modified nano-silica sol (which can be 15, 22 or any value in between), 3~6 parts of reactive silane coupling agent (which can be 3, 6 or any value in between), and 8~13 parts of hydroxyl-modified acrylic resin (which can be 8, 13 or any value in between), forming a dense coating with a thickness of 100nm-300nm on the surface of the core-carrying microcapsule. The inorganic reinforcing phase and the organic matrix work together to achieve a dual improvement in hardness and wear resistance.

[0096] In a more detailed embodiment, the core-carrying microcapsules are first dispersed in deionized water to prepare a microcapsule suspension with a mass concentration of 10%-12%. Ultrasonic dispersion is used to ensure uniform dispersion of the microcapsules and avoid agglomeration that could affect the uniformity of the coating.

[0097] Then, modified nano-silica sol, γ-methacryloxypropyltrimethoxysilane (i.e., reactive silane coupling agent) and hydroxyl-modified acrylic resin were added to the suspension in proportion. After stirring and mixing for 5 minutes, the pH of the system was adjusted to 6.0-7.0 (the optimal range for coupling agent hydrolysis and nanoparticle dispersion) with dilute hydrochloric acid.

[0098] The system was placed in a water bath at 45℃-55℃ and stirred at 350r / min-450r / min for 1.5h-2.5h to allow the coupling agent hydrolysis products to react simultaneously with the shell material hydroxyl groups, nano-silica, and resin, achieving uniform adsorption and initial binding of the functional layer components on the microcapsule surface. 0.1%-0.3% (by weight of the suspension) of the photoinitiator 1-hydroxycyclohexylphenyl ketone was added to the system, stirred thoroughly, and then placed in a UV curing device.

[0099] Curing with 365nm UV light for 30-45 seconds induces the polymerization of double bonds, constructing a "nano-silica-resin" cross-linked network to enhance the density and structural strength of the functional layer. The coating is then centrifuged and washed multiple times (e.g., three times) with a mixture of ethanol and deionized water to remove unreacted coupling agents, resin monomers, and other impurities, preventing these impurities from affecting the coating's optical properties. Finally, the coating is dried at 70℃-75℃ for 2.5-3.5 hours. This drying temperature is below the boiling point of the core material solvent to prevent the microcapsules from rupturing due to increased internal pressure.

[0100] This solution addresses the shortcomings of weak interfacial bonding between the shell material and the functional layer, which easily leads to delamination and peeling. Furthermore, the functional layer design focuses on a single performance, which can result in an overly brittle coating when strengthening scratch and wear resistance, and makes it difficult to meet hardness requirements when considering flexibility. By modifying the chemical bonding design between the shell material and the functional layer components with hydroxyl groups, a cross-linked network of "inorganic reinforcing phase - organic binder phase" is constructed to prevent the functional layer from peeling off or breaking during use.

[0101] The technical solution of this application, through the chemical bonding design of hydroxyl-modified shell material and functional layer, significantly improves the interfacial bonding force between shell material and functional layer, effectively avoiding delamination and peeling problems. The synergistic effect of nano-reinforcing phase and organic binder phase in functional layer not only endows the coating with high hardness and excellent wear resistance, resisting friction damage in daily use, but also provides a physical protective barrier for microcapsules, reducing the erosion of the core material by the external environment and ensuring long-term stability of temperature-dependent properties.

[0102] Microcapsules prepared using membrane emulsification technology exhibit excellent particle size uniformity and dispersibility, laying the foundation for uniform and stable coating performance. A staged UV curing process ensures full curing of the shell material, improving the sealing performance of the core material and reducing the risk of leakage. The low-temperature curing process is not only compatible with commonly used film-forming resins such as waterborne polyurethane, avoiding microcapsule structure damage and core material failure caused by high temperatures, but also allows for control of coating thickness within a thin range, aligning with the trend towards lightweight LED displays.

[0103] Furthermore, through the design of a composite core material system, the microcapsules can precisely match the operating temperature changes of the LED display screen, presenting a stable and excellent black state effect at room temperature when the screen is off, significantly improving the contrast of the display screen. After the screen is turned on and heated, it quickly switches to a highly transparent state, ensuring the clarity and brightness of the displayed image, perfectly balancing the dual optical requirements of high black when the screen is off and high transparency when the screen is on. Moreover, it can maintain stable color-changing performance even after multiple thermal cycles, meeting long-term display quality requirements.

[0104] To facilitate understanding, this application will be explained and described below with reference to more detailed embodiments.

[0105] 1. Preparation of thermochromic core material

[0106] Weigh the following components: 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide: 9.0 g; 1,3,3-trimethylindoline-6'-nitrobenzospiropyran: 5.0 g; 4,4'-dihydroxydiphenyl sulfone: 6.0 g; phenyl salicylate: 10.0 g; tetradecyl alcohol: 18.0 g; hexadecyl alcohol: 11.0 g; hydrogenated castor oil: 4.0 g; polyoxyethylene sorbitan monooleate: 2.0 g; sodium dodecylbenzenesulfonate: 0.6 g. Place the above materials in a sealed container equipped with a stirrer and heater, and stir at 72°C and 700 rpm for 1.5 hours until all solid components are completely dissolved in the solvent, forming a homogeneous and transparent solution. Then cool the system to 50°C and maintain this temperature for 30 minutes to obtain a stable thermosensitive color-changing core material.

[0107] 2. Preparation of UV-curable shell material premix liquid

[0108] Weigh the following components: 2-hydroxyethyl acrylate: 15.0 g; 1,6-hexanediol diacrylate: 40.0 g; aliphatic polyurethane diacrylate: 8.0 g; divinylbenzene: 3.0 g; 2-hydroxy-2-methyl-1-phenyl-1-propanone grafted polyethylene glycol derivative: 1.65 g. Stir the above components at 25°C and 350 rpm in the dark for 45 minutes until completely mixed to obtain a UV-curable shell material premix. Store in the dark for later use.

[0109] 3. Membrane emulsification granulation and UV curing

[0110] The core material dispersion prepared above was mixed with the shell material premix at a mass ratio of 1:3.5 to form the dispersed phase. A 0.3 wt% polyvinyl alcohol aqueous solution was prepared as the continuous phase. Using a zirconia ceramic membrane emulsification device with a pore size of 20 μm, the dispersed phase was forced into the continuous phase under a pushing pressure of 0.1 MPa, and the volume ratio of the continuous phase to the dispersed phase was controlled at 6:1 to obtain emulsion particles.

[0111] The obtained emulsion was transferred to a UV curing device. Pre-curing was performed by irradiation with 250nm wavelength UV light for 6 seconds, followed immediately by irradiation with 365nm wavelength UV light for 20 seconds for primary curing. The total curing energy was controlled at 115mJ / cm². After curing, the pre-cured core-carrier microcapsules were obtained by filtration and washing with deionized water.

[0112] 4. Surface functional layer deposition

[0113] The microcapsules were dispersed in deionized water to prepare a suspension with a mass concentration of 11%. To 100g of the suspension, the following were added sequentially: 20g of modified nano-silica sol (particle size 20nm, solid content 25%); 4.5g of γ-methacryloyloxypropyltrimethoxysilane; and 10g of hydroxyl-modified acrylic resin (hydroxyl value 100mgKOH / g, Tg=60℃) (the mass ratio of the three components was approximately 20:4.5:10). The mixture was stirred at 400 r / min for 5 minutes, and the pH of the system was adjusted to 6.5 with dilute hydrochloric acid.

[0114] The system was placed in a 50°C water bath and stirred at 400 rpm for 2 hours. Then, 0.2 g of 1-hydroxycyclohexylphenyl ketone was added, and after thorough mixing, the mixture was again placed in a UV curing device and cured under 365 nm UV light for 35 seconds. After the reaction, the mixture was washed three times by centrifugation with a 1:1 volume ratio of ethanol / deionized water, and finally vacuum dried at 73°C for 3 hours to obtain the final thermochromic microcapsule product with a high-hardness surface functional layer.

[0115] This application provides a thermochromic microcapsule, which is prepared using the above-described thermochromic microcapsule preparation method.

[0116] Specifically, please refer to the following: Figure 5 The thermochromic microcapsule comprises, from the inside out, a core material, a shell material, and a functional layer. The core material is prepared by compounding thermosensitive color-changing dyes, compounding color developers, compounding phase change solvents, and compounding dispersants. The shell material is prepared by compounding shell material substrates, photoinitiators, and active crosslinking agents. The functional layer is prepared by compounding modified nano-silica sol, reactive silane coupling agents, and hydroxyl-modified acrylic resins, as shown in the above embodiments and accompanying drawings, and will not be repeated here.

[0117] The aforementioned thermochromic microcapsules are prepared by first preparing a core material dispersion based on the core material components and a shell material premix based on the shell material components. Then, the core material dispersion and shell material premix are combined and emulsified through a membrane to obtain emulsion particles. These emulsion particles are then subjected to staged UV curing to obtain core-carrying microcapsules. Finally, a cured functional layer is deposited on the surface of the core-carrying microcapsules, resulting in thermochromic microcapsules consisting of a core material, a shell material, and a functional layer, arranged sequentially from the inside out. This approach, combining membrane emulsification, staged UV curing, and low-temperature deposition processes, prepares thermochromic microcapsules. The membrane emulsification process, compared to stirring emulsification, effectively improves the particle size uniformity of the thermochromic microcapsules. The staged UV curing ensures curing efficiency while avoiding the problems of over-curing the surface and incomplete curing of the interior caused by single-wavelength curing. The low-temperature deposition process avoids excessively high curing temperatures that could lead to microcapsule rupture. This can effectively improve the precision of the preparation process and the application compatibility of thermochromic microcapsules, and solve the problem of poor performance adaptability and process compatibility of thermochromic microcapsules in LED display applications.

[0118] Please see Figure 6 This application provides an LED display module, including a driving component 51, a substrate 52, LED beads 53, an encapsulation layer 54, and a thermo-sensitive color-changing coating 55 prepared based on the above-mentioned thermo-sensitive microcapsules. The driving component 51 is disposed on the first surface of the substrate 52, the LED beads 53 are disposed on the second surface of the substrate 52, the encapsulation layer 54 covers the surface of the LED beads 53, and the thermo-sensitive color-changing coating 55 is disposed on the outer surface of the encapsulation layer 54.

[0119] Specifically, an LED display unit refers to a modular display component formed by arranging multiple LED display modules in a matrix. In practical scenarios, a display screen of a certain area can be constructed using one or more LED display units, without any specific limitation. The method for preparing the thermochromic coating specifically includes: mixing thermochromic microcapsules with waterborne polyurethane resin at a mass ratio of 1:4 to 1:6, followed by coating and baking at 60℃-80℃ for 20-60 minutes. During the mixing process, a solvent can be added to adjust the system viscosity to 150 MPa·s-250 MPa·s, and 0.3-0.5 wt% of defoamer can be added.

[0120] In a more detailed embodiment, the thermochromic microcapsules prepared above were mixed with an aqueous polyurethane resin with a solid content of 45% at a mass ratio of 1:5. An appropriate amount of propylene glycol methyl ether acetate was added to adjust the coating viscosity to approximately 200 MPa·s, and 0.4 wt% of defoamer was added. The coating was then uniformly applied to the surface of a molded P1.5 small-pitch LED display module using a spray coating process. The coated module was then placed in an oven at 70°C and baked for 30 minutes to form a dry film thickness of approximately 25 micrometers.

[0121] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing thermochromic microcapsules, characterized in that, include: Core material dispersions were prepared based on core material components, and shell material premixes were prepared based on shell material components. Emulsion particles are obtained by performing a membrane emulsification process on the core material dispersion and the shell material premix; The emulsion particles were subjected to staged UV curing treatment to obtain core-carrying microcapsules; A functional layer is deposited and cured on the surface of the core-carrying microcapsule to obtain a thermochromic microcapsule; wherein the deposition and curing temperature of the functional layer is greater than 40°C and less than 70°C.

2. The method for preparing thermochromic microcapsules according to claim 1, characterized in that, The preparation of the core material dispersion based on the core material components includes: Under a first preset temperature range, the compound thermosensitive color-changing dye, compound color developer, compound phase change solvent and compound dispersant in a first preset ratio are stirred at a first speed for a first preset time to form a homogeneous and transparent solution. The homogeneous and transparent solution is cooled to a first preset temperature threshold and kept at that temperature for a second preset time to obtain a core material dispersion; wherein, the first preset temperature threshold is less than the minimum value of the first preset temperature range, and the second preset time is less than the first preset time.

3. The method for preparing thermochromic microcapsules according to claim 2, characterized in that, Includes at least one of the following: The first item: The compound thermosensitive color-changing dye comprises crystal violet lactone and 1,3,3-trimethylindoline-6'-nitrobenzospiropyran, wherein the mass ratio of crystal violet lactone to 1,3,3-trimethylindoline-6'-nitrobenzospiropyran is 1:0.8-1:1.2; Second item: The compound colorimetric agent comprises 4,4'-dihydroxydiphenyl sulfone and phenyl salicylate, wherein the mass ratio of 4,4'-dihydroxydiphenyl sulfone to phenyl salicylate is 1:1.5-1:2.5; The third item is that the compound phase change solvent includes tetradecyl alcohol, hexadecyl alcohol and hydrogenated castor oil, and the mass ratio of tetradecyl alcohol, hexadecyl alcohol and hydrogenated castor oil is (4~7):(2~5):1; Fourthly, the compound dispersant comprises polyoxyethylene sorbitan monooleate and sodium dodecylbenzene sulfonate, wherein the mass ratio of polyoxyethylene sorbitan monooleate to sodium dodecylbenzene sulfonate is 3:1-4:

1.

4. The method for preparing thermochromic microcapsules according to claim 1, characterized in that, The preparation of the shell premix liquid based on shell components includes: At a second preset temperature threshold, the shell material substrate, photoinitiator and active crosslinking agent in a second preset ratio are stirred at a second speed in the dark for a third preset time to obtain a shell material premix.

5. The method for preparing thermochromic microcapsules according to claim 4, characterized in that, Includes at least one of the following: The first item: The shell material substrate comprises 2-hydroxyethyl acrylate and 1,6-hexanediol diacrylate, wherein the mass ratio of 2-hydroxyethyl acrylate to 1,6-hexanediol diacrylate is 1:2-1:3; Second item: The photoinitiator includes a derivative of 2-hydroxy-2-methyl-1-phenyl-1-propanone grafted with polyethylene glycol; The third item: The active crosslinking agent includes aliphatic polyurethane diacrylate and divinylbenzene, wherein the mass ratio of aliphatic polyurethane diacrylate to divinylbenzene is 4:1-6:

1.

6. The method for preparing thermochromic microcapsules according to claim 1, characterized in that, The emulsion particles obtained by the membrane emulsification treatment based on the core material dispersion and the shell material premix include: The core material dispersion and the shell material premix are mixed at a preset mass ratio to obtain a dispersed phase; Preparation of continuous phase based on aqueous solution of polyvinyl alcohol; A driving force is applied to the dispersed phase to allow it to enter the continuous phase from a zirconia ceramic membrane assembly with a preset pore size, resulting in emulsion particles.

7. The method for preparing thermochromic microcapsules according to any one of claims 1-6, characterized in that, The step-by-step UV curing treatment of the emulsion particles to obtain core-carrying microcapsules includes: The emulsion particles are irradiated with ultraviolet light of the first wavelength for a fourth preset time to achieve pre-curing; After pre-curing, the emulsion particles are irradiated with ultraviolet light of a second wavelength for a fifth preset time to achieve primary curing and obtain core-carrying microcapsules; wherein the second wavelength is greater than the first wavelength, and the fifth preset time is greater than the fourth preset time.

8. The method for preparing thermochromic microcapsules according to any one of claims 1-6, characterized in that, The deposition and curing of a functional layer on the surface of the carrier microcapsule to obtain a thermochromic microcapsule includes: The core-carrying microcapsules were dispersed in deionized water to obtain a suspension with a preset mass concentration. Modified nano silica sol, reactive silane coupling agent and hydroxyl-modified acrylic resin in a third preset ratio are added sequentially to the suspension. After stirring at a third speed for a sixth preset time, the pH value is adjusted to a preset value. At a third preset temperature threshold, the suspension is stirred and reacted at the third speed for a seventh preset time, and then cured by ultraviolet light of the third wavelength for a seventh preset time to obtain preliminary temperature-sensitive microcapsules. The preliminary thermochromic microcapsules were washed and dried to obtain thermochromic microcapsules.

9. A thermochromic microcapsule, characterized in that, The thermochromic microcapsules are prepared using the thermochromic microcapsule preparation method according to any one of claims 1-8.

10. An LED display module, characterized in that, The invention includes a driving component, a substrate, LED beads, an encapsulation layer, and a thermochromic coating prepared based on the thermochromic microcapsules of claim 9. The driving component is disposed on a first surface of the substrate, the LED beads are disposed on a second surface of the substrate, the encapsulation layer covers the surface of the LED beads, and the thermochromic coating is disposed on the outer surface of the encapsulation layer.

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