Multi-color LED lamp filament

Abstract

The invention relates to the technical field of LED illumination, and discloses a multi-color LED lamp filament which comprises the following components in parts by mass: 80-95 parts of a rare earth composite luminescent material; the quantum dot auxiliary spectrum adjusting layer accounts for 2 to 8 parts by mass; the optical microstructure coating accounts for 3 to 8 parts by mass; the thermal management coating accounts for 5 to 10 parts by mass; the wire base body adopts a gold wire or an alloy wire, the rare earth composite luminescent material comprises a matrix material and a rare earth activating agent, and the matrix material is selected from red fluorescent powder with the emission wave band of 580-700 nm, yellow fluorescent powder with the emission wave band of 540-580 nm, green fluorescent powder with the emission wave band of 480-540 nm, blue fluorescent powder / purple fluorescent powder with the emission wave band of 400-480 nm, silica gel and epoxy resin. Through the optimized design of the multi-layer composite structure, complete coverage of the spectrum and remarkable improvement of the lighting effect are achieved, and the light loss is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of LED lighting, and specifically to an LED filament with multiple colors. Background Art

[0002] In recent years, multi-color LED filaments have attracted much attention in the lighting field due to their energy-saving, high-efficiency, and diverse application scenarios. Different from traditional single-color LEDs, multi-color LED filaments achieve multi-color light output by combining light-emitting units with different wavelengths and have been widely used in home lighting, commercial decoration, and display fields. However, existing multi-color LED filament technologies still have obvious deficiencies in spectral coverage, light efficiency maintenance, thermal stability, and color temperature regulation. These technical bottlenecks severely limit their application value in high-end lighting and complex application scenarios. Therefore, in view of these performance limitations in the prior art, it is particularly necessary to develop more optimized technical solutions.

[0003] Existing multi-color LED filaments are composed of rare-earth luminescent materials, optical coatings, and thermal management coatings. In these technical solutions, rare-earth luminescent materials are used to provide RGB spectral output. However, due to limited emission band coverage, the intensities of blue and red lights are often insufficient, resulting in poor color rendering; the optical coating design is simple and fails to effectively reduce light loss, limiting the light flux output; the thermal management coating has low heat conduction efficiency, leading to serious heat accumulation problems and a significant decrease in luminous efficiency under high-temperature conditions. In addition, the color temperature regulation ability in the prior art is limited, and most filaments can only provide a fixed light color output, lacking flexible spectral adjustment ability. At the same time, there is a lack of systematic optimization between the functional layers, and the structural synergy is poor, further restricting the overall performance of the filament. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides an LED filament with multiple colors, which solves the problems of insufficient spectral coverage, low light efficiency output, poor thermal stability, and limited color temperature regulation ability of multi-color LED filaments in the prior art.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: An LED filament with multiple colors, comprising the following components:

[0006] Rare-earth composite luminescent material, accounting for 80 - 95 parts by mass percentage;

[0007] Quantum dot-assisted spectral adjustment layer, accounting for 2 - 8 parts by mass percentage;

[0008] Optical microstructure coating, accounting for 3 - 8 parts by mass percentage;

[0009] Thermal management coating, accounting for 5 - 10 parts by mass percentage;

[0010] The filament substrate is made of gold wire or alloy wire.

[0011] Preferably, the rare earth composite luminescent material includes a matrix material and rare earth activators, wherein:

[0012] The matrix material is selected from one or more of phosphor (red phosphor, green phosphor, yellow phosphor), silica gel, epoxy resin, modified resin, yttrium autoxidation (Y2O3), barium magnesium aluminate (BaMgAl10O17), strontium silicate (Sr2SiO4), color powder (titanium dioxide, iron oxide), and the mass fraction accounts for 80-95 parts;

[0013] The rare earth activator is Eu 3+ , Ce 3+ , Tb 3+ , Sm 3+ One or more of them, and the mass fraction accounts for 0.1-3 parts.

[0014] Preferably, the rare earth composite luminescent material further includes an energy transfer assistant, and the energy transfer assistant is Li + or F - , and the mass fraction accounts for 1-5 parts.

[0015] Preferably, the quantum dots of the quantum dot-assisted spectral adjustment layer are CdSe / ZnS or InP / ZnS quantum dots, the particle size range is 2-8 nm, and the mass fraction accounts for 2-8 parts.

[0016] Preferably, the quantum dot-assisted spectral adjustment layer contains a dispersant, and the dispersant is silicone oil or polymer dispersant, and the mass fraction accounts for 5-10 parts.

[0017] Preferably, the nanoparticles of the optical microstructure coating are selected from SiO2 or TiO2, the particle size range is 10-50 nm, and the mass fraction accounts for 3-8 parts.

[0018] Preferably, the optical microstructure coating further includes a surface treatment agent, and the surface treatment agent is a silane coupling agent or a fluoride, and the mass fraction accounts for 0.5-3 parts.

[0019] Preferably, the material of the thermal management coating is selected from AlN, Al2O3 or BN nanoparticles, the particle size range is 10-50 nm, and the mass fraction accounts for 5-10 parts.

[0020] Preferably, the material of the filament substrate is tungsten wire or nickel-chromium alloy wire, and its surface is coated with a rare earth composite luminescent material layer, a quantum dot-assisted spectral adjustment layer, an optical microstructure coating and a thermal management coating.

[0021] Preferably, the coating thickness of the rare earth composite luminescent material layer of the filament substrate is 50 - 200 μm, the coating thickness of the quantum dot-assisted spectrum adjustment layer is 20 - 100 μm, the thickness of the optical microstructure coating is 10 - 50 μm, and the thickness of the thermal management coating is 50 - 200 μm.

[0022] The present invention provides an LED filament with multiple colors, having the following beneficial effects:

[0023] 1. By adopting the technical solution of combining rare earth composite luminescent materials with a quantum dot-assisted spectrum adjustment layer, and through the optimized design of rare earth activators and matrix lattices, the present invention realizes the precise coverage and efficient luminescence of the RGB spectrum. Compared with the existing single rare earth luminescent material that is prone to insufficient spectrum coverage, the quantum dot compensation design of the present invention effectively fills the spectral gap and solves the deficiencies of low luminous efficiency and discontinuous spectrum of multi-color LED filaments.

[0024] 2. Through the introduction of a thermal management coating, the present invention uses high thermal conductivity materials to quickly disperse the heat generated by the light-emitting layer, significantly reducing the impact of heat accumulation on the luminous efficiency. Compared with the traditional filament technology that is prone to thermal quenching in a high-temperature environment, the design of the present invention ensures stable luminescence under high-temperature conditions and solves the problem of insufficient stability of the light-emitting layer in the prior art.

[0025] 3. The present invention adopts the optical microstructure coating technology. By constructing a nano-microstructure interface on the surface of the light-emitting layer, it effectively reduces the internal reflection and scattering losses of light. Different from the traditional LED filament that relies on a single-layer optical coating, the composite coating designed by the present invention improves the light output efficiency, overcomes the defect of serious light loss in the prior art, and significantly enhances the overall brightness.

[0026] 4. Through the optimized design of the rare earth ion energy transfer path and the precise control of the quantum dot particle size, the present invention realizes the dynamic color temperature adjustment in the range from 2700K to 6500K. In the prior art, the color temperature regulation of multi-color LED filaments is usually limited to a fixed range or a single mode, while the solution of the present invention can meet the application requirements in multiple scenarios and overcomes the deficiencies of traditional filaments in terms of color temperature regulation range and flexibility. Specific embodiments

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] The embodiments of the present invention provide an LED filament with multiple colors, including:

[0029] 1. Composition and Preparation of Rare Earth Composite Luminescent Materials

[0030] As the core light source of various color LED filaments, rare earth composite luminescent materials can provide stable and efficient RGB luminescence. Its composition includes matrix materials, rare earth activators, and energy transfer assistants, and the preparation is completed by the sol-gel method combined with high-temperature sintering process.

[0031] Composition and Ratio:

[0032] Matrix Materials:

[0033] Select inorganic matrix materials such as yttrium oxide (Y2O 3) , barium magnesium aluminate (BaMgAl 10 O 17) , strontium silicate (Sr2SiO 4) ), etc. The mass fraction accounts for 80 - 95 parts. These materials have good optical transparency, stability, and rare earth ion solubility, and can provide a suitable lattice environment for rare earth activators.

[0034] Rare Earth Activators:

[0035] Include Eu 3+ (red light, emission wavelength 610nm), Ce 3+ (blue light, emission wavelength 450nm), Tb 3+ (green light, emission wavelength 545nm), and Sm 3+ (orange light, emission wavelength 600nm), and the doping concentration range is 0.1% - 3%. Rare earth activators generate luminescence with specific wavelengths in the matrix materials through charge transfer excitation (CTB) or inner shell transition (f-f transition).

[0036] Energy Transfer Assistants:

[0037] Assistants such as Li+ or F-, and the doping concentration range is 1% - 5%. Their function is to optimize the lattice environment, reduce the mutual quenching effect between luminescence centers, and improve the excitation energy transfer efficiency.

[0038] Preparation Method:

[0039] Sol Preparation:

[0040] Dissolve the matrix material (such as YNO 33 ·6H2O) in deionized water to prepare a solution with a concentration of 0.5 - 2mol / L. Add rare earth activators (such as EuNO 33 ·6H2O) and energy transfer assistants (such as LiF), and stir at 40 - 60°C for 1 - 2 hours to form a homogeneous sol.

[0041] Gelation and Drying:

[0042] The sol is left standing for 12 - 24 hours at 50 - 80 °C to form a wet gel. The wet gel is dried at 100 - 120 °C for 6 - 12 hours to obtain a dry gel.

[0043] Sintering:

[0044] The dry gel is sintered in an air atmosphere at 1200 - 1400 °C for 2 - 4 hours with a heating rate of 5 - 10 °C / min. During the sintering process, the matrix lattice is stabilized, and at the same time, rare earth ions are embedded in the lattice to form stable luminescence centers.

[0045] The rare earth activator realizes luminescence in the matrix through electron transition. Ce 3+ produces blue light, Tb 3+ produces green light, Eu 3+ emits red light through charge transfer band emission. Auxiliaries such as Li + 、F - optimize the energy transfer path of the excited state by adjusting the lattice electric field, reduce the luminescence quenching effect, thereby improving the luminescence efficiency. The stable structure of the crystal also inhibits the thermal quenching effect and improves the stability of luminescence.

[0046] 2. Quantum dot-assisted spectral adjustment layer

[0047] The quantum dot-assisted spectral adjustment layer, as an auxiliary structure of the luminescent material, can achieve precise emission and supplementation of light with different wavelengths through particle size and concentration adjustment.

[0048] Composition and ratio:

[0049] Quantum dot material:

[0050] CdSe / ZnS or InP / ZnS quantum dots with a particle size range of 2 - 8 nm and a mass fraction of 2 - 8 parts. The particle size of the quantum dots directly determines the wavelength of the emitted light (2 - 4 nm for blue light, 5 - 6 nm for green light, 7 - 8 nm for red light).

[0051] Dispersant:

[0052] Silicone oil or polymer dispersant with a concentration range of 5% - 10%. The dispersant can stabilize the distribution of quantum dots and avoid agglomeration.

[0053] Preparation method:

[0054] Preparation of the dispersion:

[0055] The quantum dots and the dispersant are mixed in proportion and dispersed using ultrasonic waves (power 50 - 100 W, time 10 - 30 minutes) to form a uniform dispersion.

[0056] Coating:

[0057] The dispersion liquid is evenly coated on the substrate using a spin coating process (rotation speed 1000 - 3000 rpm, duration 30 - 60 seconds), and this is repeated 2 - 3 times.

[0058] Curing:

[0059] After coating, it is cured at 80 - 120 °C for 30 - 60 minutes.

[0060] The luminescence of quantum dots is based on the recombination of electron - hole pairs. By controlling the particle size, the emission wavelength can be precisely adjusted to ensure the proportional distribution of RGB light. The role of the dispersant is to prevent the aggregation of quantum dots and maintain the optical uniformity of the luminescent layer. The design of the quantum dot layer solves the problem of insufficient spectral coverage of rare - earth luminescent materials in certain wavelength bands and further optimizes the spectral distribution.

[0061] 3. Optical microstructure coating

[0062] The optical microstructure coating is used to enhance the light output efficiency, reduce light loss through optical design, and improve the overall brightness.

[0063] Composition and ratio:

[0064] Nanoparticles:

[0065] SiO2 or TiO2, with a particle size range of 10 - 50 nm and a mass fraction of 3 - 8 parts.

[0066] Surface treatment agent:

[0067] Silane coupling agent or fluoride, with a concentration range of 0.5% - 3%.

[0068] Preparation method:

[0069] Dispersion liquid preparation:

[0070] The nanoparticles and the surface treatment agent are stirred in deionized water for 30 - 60 minutes to form a stable dispersion liquid.

[0071] Coating:

[0072] It is evenly sprayed on the surface of the quantum dot layer using a spraying process (pressure 0.1 - 0.5 MPa).

[0073] Drying treatment:

[0074] After coating, it is dried at 100 - 150 °C for 1 - 2 hours.

[0075] The nanoparticles reduce internal reflection by constructing a microstructure interface, improving the light transmission efficiency. The surface treatment agent ensures the uniform distribution and adhesion of the coating by changing the wettability of the particle surface.

[0076] 4. Thermal management coating

[0077] The thermal management coating is used to optimize the heat dissipation performance of the filament and avoid performance degradation caused by heat accumulation during operation.

[0078] Composition and ratio:

[0079] Nanoparticles:

[0080] AlN, Al2O3 or BN, with a particle size range of 10 - 50 nm and a mass fraction of 5 - 10 parts.

[0081] Preparation method:

[0082] Preparation of dispersion:

[0083] Add the nanoparticles into epoxy resin and use ultrasonic dispersion (power 50 - 100 W, time 10 - 30 minutes) to form a homogeneous dispersion.

[0084] Coating:

[0085] Use the spin - coating process to coat on the outer layer of the optical microstructure coating, with a thickness range of 50 - 200 μm.

[0086] Curing treatment:

[0087] After coating, cure at 150 - 200 °C for 1 - 2 hours.

[0088] The thermal management coating, through the action of high - thermal - conductivity nanomaterials, significantly improves the thermal conductivity of the filament and quickly dissipates the heat generated by the light - emitting layer to the surrounding environment, thus maintaining the working stability of the filament.

[0089] Through the collaborative design of rare - earth luminescent materials, quantum dot auxiliary adjustment layers, optical microstructure coatings, and thermal management coatings, this technical solution solves problems such as non - uniform spectra, thermal quenching, and insufficient light extraction efficiency of multi - color LED filaments, and realizes high - efficiency, stable, and uniform light - emitting performance.

[0090] Example 1: Preparation of multi - color LED filament based on rare - earth composite luminescent materials

[0091] Ingredient preparation

[0092] Weigh 90 parts by mass of Y2O3 matrix, 2 parts by mass of Eu(NO3)3·6H2O activator, and 3 parts by mass of LiF assistant. Add the above materials into 500 mL of deionized water to prepare a 1 mol / L homogeneous solution.

[0093] Sol preparation

[0094] TEOS (tetraethyl orthosilicate) was dropped into the solution at a rate of 1 mL / min, with a stirring speed of 400 rpm and the temperature controlled at 50 °C. After stirring for 1.5 hours, a uniform sol was formed.

[0095] Gelation and drying

[0096] The sol was poured into a sealed container and placed in a constant temperature oven at 60 °C for 20 hours. After obtaining the wet gel, it was dried at 100 °C for 10 hours to form a dry gel.

[0097] Sintering

[0098] The dry gel was transferred to a high-temperature furnace, and the heating rate was controlled at 7 °C / min. The sintering temperature was set at 1300 °C, and after holding for 3 hours, it was naturally cooled to room temperature. Rare earth composite luminescent material powder was obtained.

[0099] Application to the filament

[0100] The above-mentioned luminescent material powder was coated on the tungsten wire substrate using the electrostatic spraying process, and the spraying thickness was 100 μm. It was heated and cured at 300 °C for 1 hour.

[0101] Example 2: Preparation of multicolor LED filaments with quantum dot-assisted spectral regulation

[0102] Preparation of quantum dot dispersion

[0103] 4 parts by mass of CdSe / ZnS quantum dots (particle size 5 nm) were taken and added to 50 mL of silicone oil. It was processed for 20 minutes using an ultrasonic dispersion device (power 70 W) to form a uniform dispersion.

[0104] Coating on the filament surface

[0105] Using a spin coating device, the quantum dot dispersion was uniformly coated on the surface of the filament already coated with rare earth luminescent material at a rotation speed of 1500 rpm. The coating time was set at 45 seconds, and the coating was repeated twice.

[0106] Curing treatment

[0107] The coated filament was placed in a drying oven at 100 °C and cured for 40 minutes. The final thickness of the quantum dot layer was controlled at 50 μm.

[0108] Function verification

[0109] The completed filament was subjected to spectral testing. The test results showed that the light intensity distribution in the blue light (450 nm), green light (545 nm), and red light (610 nm) bands was uniform, and the spectral coverage rate increased by 20% compared to the sample without adding quantum dots.

[0110] Example 3: Preparation of multicolor LED filaments with optical microstructural coatings to improve light extraction efficiency

[0111] Preparation of Nanoparticle Dispersion

[0112] Take 5 parts by mass of TiO2 nanoparticles (particle size 20 nm) and add them to 100 mL of deionized water. Add 1 part by mass of silane coupling agent and stir magnetically for 40 minutes to form a stable dispersion.

[0113] Coating Process

[0114] Using the spraying process, control the spraying pressure at 0.3 MPa and evenly spray the dispersion onto the surface of the quantum dot layer. Coating is carried out 2 times, with an interval of 10 minutes each time.

[0115] Drying Treatment

[0116] Dry at 120 °C for 1 hour to ensure complete adhesion of the coating. The final thickness of the optical microstructure coating is 30 μm.

[0117] Optical Testing

[0118] In the luminous flux test, the addition of this coating increases the overall brightness of the filament by 25% and significantly reduces the internal reflected light loss.

[0119] Example 4: Preparation of Multicolor LED Filament with Thermal Management Coating

[0120] Preparation of Thermal Management Dispersion

[0121] Take 8 parts by mass of AlN nanoparticles (particle size 30 nm) and add them to 50 mL of epoxy resin. Disperse using an ultrasonic device (power 80 W) for 15 minutes to form a uniform dispersion.

[0122] Spin Coating

[0123] Coat the thermal management dispersion onto the outer layer of the optical microstructure coating using the spin coating process at a rotation speed of 2000 rpm for 30 seconds.

[0124] Curing Treatment

[0125] Cure in an environment of 180 °C for 1 hour. The final coating thickness is 80 μm.

[0126] Thermal Stability Testing

[0127] After the filament with this thermal management coating works at a high temperature (85 °C) for 12 hours, the luminous efficiency decay is less than 5%, while the decay of the sample without the coating reaches 18%.

[0128] Example 5: Preparation of Multilayer Composite Structure LED Filament

[0129] Coating of Rare Earth Luminescent Material Layer

[0130] Preparation of rare earth luminescent material (Example 1). It was electrostatically sprayed on the tungsten wire substrate with a spraying thickness of 120 μm. Cured at 300 °C for 1 hour.

[0131] Coating of quantum dot auxiliary layer

[0132] Prepare the quantum dot dispersion according to the method of Example 2 and spin-coat it on the surface of the rare earth luminescent layer. The coating thickness is controlled at 50 μm and the curing temperature is 100 °C.

[0133] Coating of optical microstructure coating

[0134] Prepare the TiO2 microstructure coating (Example 3) and spray it on the surface of the quantum dot layer by spraying process. The spraying thickness is 20 μm.

[0135] Coating of thermal management coating

[0136] Prepare the AlN coating (Example 4), spin-coat it on the surface of the optical coating with a thickness of 100 μm. The curing temperature is 180 °C.

[0137] Overall performance test

[0138] This multi-layer structure filament is superior to the single-layer structure filament in terms of luminous efficiency, spectral uniformity and thermal stability. Among them, the luminous flux is increased by 30%, and the luminous efficiency retention rate at high temperature is increased by 50%.

[0139] Experiment 1: Luminous efficiency test of rare earth luminescent material

[0140] Experimental procedure

[0141] Sample preparation

[0142] Example 1: The rare earth luminescent material prepared according to the process of Example 1 was uniformly sprayed onto the tungsten wire substrate with a coating thickness controlled at 100 μm and cured at 300 °C for 1 hour.

[0143] Comparative Example 1: The rare earth luminescent material prepared according to the process of Comparative Example 1 was also sprayed onto the tungsten wire substrate with a coating thickness controlled at 100 μm and cured at 300 °C for 1 hour.

[0144] Luminous flux test

[0145] Fix the two groups of samples on the sample holder of the luminous flux test system respectively, ensure that the sample surface is perpendicular to the optical path of the test system, and the distance from the test light source is 10 cm.

[0146] Use a 365 nm ultraviolet light source with a power of 5 W and an irradiation time of 10 seconds, and record the luminous flux (lumen value) of the sample.

[0147] Spectral distribution test

[0148] Use a spectrophotometer to collect the light intensity distributions of two groups of samples at wavelengths of 450 nm (blue light), 545 nm (green light), and 610 nm (red light), and calculate the RGB spectral coverage rate.

[0149] Data recording and processing

[0150] Each group of samples was tested 3 times, and all data were recorded and averaged. All test procedures were strictly carried out under the same conditions to exclude environmental interference.

[0151] Experimental data

[0152] Table 1:

[0153]

[0154] The rare-earth luminescent material prepared in Example 1 has significantly better luminous flux and RGB spectral coverage rate than the sample in Comparative Example 1. This can be attributed to the reasonable doping concentration of the rare-earth activator, which forms an efficient luminescence center, and the relatively high sintering temperature ensures the integrity and stability of the crystal lattice. In contrast, the insufficient concentration of the rare-earth activator in Comparative Example 1 results in a low density of luminescence centers, unable to fully stimulate luminescence. In addition, the too low sintering temperature also fails to completely form the crystal structure, thus affecting the luminescence efficiency and spectral uniformity.

[0155] In Example 1, the luminescence mechanism of rare-earth ions originates from the 4f electron transition, and its transition process is more stable in the lattice environment. The high doping concentration ensures the effective transfer of excitation energy, and the Li+ additive further optimizes the lattice electric field, reducing the luminescence quenching effect. In Comparative Example 1, due to the too low doping amount of the activator, the luminescence centers in the lattice are sparse, and the energy transfer path is blocked, resulting in a significant decrease in luminous flux. This phenomenon is particularly reflected in the significant decrease in the intensities of green light and red light.

[0156] The significant improvement in the RGB spectral coverage rate reflects the comprehensive advantages of the material in Example 1 in terms of luminescence efficiency and color uniformity. The rare-earth activator provides multi-band strong light output through its luminescence at specific wavelengths, and the high-temperature sintering process ensures the stability and uniformity of the crystal, making the spectral coverage range wider. In contrast, the luminescence performance of the material in Comparative Example 1 is poor, especially weak in the blue and green light bands, indicating that the low-temperature sintering fails to completely eliminate lattice defects, thus inhibiting the efficiency of the luminescence centers.

[0157] Experiment 2: Test on the spectral adjustment ability of the quantum dot layer

[0158] Experimental procedure

[0159] Sample preparation

[0160] Example 2 Sample: Prepare the quantum dot dispersion according to the process of Example 2. The quantum dots have a particle size of 5 nm, an ultrasonic power of 70 W, and a dispersion time of 20 minutes. Coat it on a tungsten wire substrate at a spin coating speed of 1500 rpm for a coating time of 45 seconds, and repeat 2 times. The coating thickness is 50 μm, and cure at 100 °C for 40 minutes.

[0161] Comparative Example 2 Sample: Prepare the quantum dot dispersion according to the process of Comparative Example 2. The quantum dots have a particle size of 2 nm, an ultrasonic power of 30 W, and a dispersion time of 5 minutes. Coat it on the same tungsten wire substrate at a spin coating speed of 500 rpm for a coating time of 10 seconds, with a single coating. The coating thickness is 20 μm, and cure at 50 °C for 15 minutes.

[0162] Spectral Test

[0163] Use a spectrophotometer to test the spectral distribution of the sample. Measure the light intensity (unit: mW / cm 2 ) at three wavelengths of 450 nm (blue light), 545 nm (green light), and 610 nm (red light).

[0164] The excitation light source is a 5000K white LED with a power of 5 W, and the distance between the sample and the light source is fixed at 5 cm.

[0165] Spectral Coverage Calculation

[0166] According to the spectral distribution, calculate the RGB spectral intensity ratio to obtain the spectral coverage (percentage of the total light intensity).

[0167] Data Recording

[0168] Test each sample 3 times, record and take the average value. Ensure that the test conditions are consistent and avoid the interference of ambient light on the experiment.

[0169] Experimental Data

[0170] Table 2:

[0171]

[0172] The sample of Example 2 shows significant advantages in the RGB spectral intensity distribution and spectral coverage. This is mainly due to the reasonable design of the quantum dot particle size and the optimization of the dispersion process. The quantum dots with a particle size of 5 nm have concentrated luminescence and controllable wavelengths, ensuring a balanced distribution of intensities in each RGB band. The quantum dot layer treated by ultrasonic dispersion is evenly distributed, forming a more efficient spectral regulation ability. In contrast, in Comparative Example 2, the quantum dot particle size is too small, resulting in too high an intensity in the blue light band and unstable luminescence. At the same time, the insufficiently dispersed quantum dots are prone to agglomeration, forming non-uniform luminescent regions, which reduces the overall spectral coverage.

[0173] The uniformity of the RGB spectrum is particularly prominent in Example 2. The quantum dot layer emits light through the recombination of photoelectrons and holes. The more appropriate the particle size, the more efficient the energy level transition and the more stable the emitted light intensity. Combined with the full optimization of the dispersion process, the agglomeration phenomenon of quantum dots is effectively suppressed, the distribution of photons in the material is more uniform, and finally the balanced output of each spectral band is achieved. In Comparative Example 2, due to the short dispersion time and low power, the distribution of quantum dots is uneven, and some photons escape through paths that do not effectively recombine, resulting in a serious shortage of spectral intensity, especially in the red and green light bands.

[0174] In addition, the differences in coating thickness and process parameters also further affect the spectral adjustment ability. In Example 2, through multiple spin coatings, the thickness of the quantum dot layer is uniform and the adhesion is stronger. This not only enhances the photon capture efficiency but also reduces the scattering loss of internal light. In the sample of Comparative Example 2, the coating is too thin and the spin coating process is insufficient, resulting in a low photon absorption rate of the quantum dot layer and a significant decrease in the spectral output efficiency.

[0175] Experiment 3: Influence of the optical microstructure coating on the light extraction efficiency

[0176] Experimental procedure

[0177] Sample preparation

[0178] Sample of Example 3: Prepare an optical microstructure coating using the process of Example 3. The particle size of SiO2 is 20 nm, 1 part by mass of silane coupling agent is added, and the dispersion time is 40 minutes. The dispersion liquid is coated on the filament surface using the spraying process, the spraying pressure is 0.3 MPa, and it is sprayed 2 times repeatedly. The coating thickness is 30 μm, and it is dried at 120 °C for 1 hour.

[0179] Sample of Comparative Example 3: Prepare an optical coating using the process of Comparative Example 3. The particle size of SiO2 is 70 nm, no surface treatment agent is added, and the dispersion time is 10 minutes. Single spraying, the spraying pressure is 0.05 MPa, the coating thickness is 10 μm, and it is dried naturally at room temperature.

[0180] Light extraction efficiency test

[0181] Use an optical integrating sphere test system to record the luminous flux (unit: lumen) of the two groups of samples. The light source is a 405 nm blue LED with a power of 10 W, the test distance is 15 cm, and the irradiation time is 10 seconds.

[0182] Measure the reflection loss: Record the total light intensity of the reflected light through a spectral analyzer and calculate the reflection loss rate.

[0183] Test setup

[0184] Test each sample 3 times, record the data and calculate the average value. Keep the experimental ambient light constant to avoid interference from external light sources on the results.

[0185] Experimental data

[0186] Table 3:

[0187] Sample Luminous Flux (lumens) Reflection Loss Rate (%) Example 3 102.8 4.3 Example 3 (times) 105.2 4.1 Example 3 (times) 100.6 4.5 Comparative Example 3 73.4 18.7 Comparative Example 3 (times) 70.5 19.2 Comparative Example 3 (times) 75.1 17.9

[0188] The luminous flux of the sample in Example 3 is significantly higher than that in Comparative Example 3, and the reflection loss rate is significantly reduced. This benefits from the small particle size of SiO2 nanoparticles and the addition of surface treatment agents. The particle size of 20 nm provides a larger specific surface area, forming a denser and more uniform coating surface. The silane coupling agent improves the dispersibility and adhesion of the particles, making the coating bind more tightly to the filament surface and reducing the scattering and reflection of light at the interface. In Comparative Example 3, no surface treatment agent was added, resulting in easy agglomeration of particles and insufficient adhesion, leading to a rough coating surface and a significant increase in reflection loss.

[0189] The optical coating of Example 3 effectively reduces the internal reflection of light by forming a uniform microstructure on the filament surface. This microstructure is similar to the function of an antireflection film, optimizing the light propagation path and enabling more light to smoothly exit the filament surface. In contrast, the large particles and uneven distribution in Comparative Example 3 result in optical mismatch between interfaces, and some photons are reflected and even absorbed multiple times in the material, directly affecting the luminous flux output.

[0190] In addition, the optimization of the spraying process is also an important influencing factor in Example 3. Appropriate spraying pressure and multiple sprays ensure the uniformity of the coating thickness, further improving the light extraction efficiency. In Comparative Example 3, single spraying and lower pressure result in insufficient coating thickness, which not only weakens the antireflection ability of the coating but also increases the irregular scattering in light propagation, reducing the overall light extraction efficiency. These results indicate that optimizing the coating microstructure design and process are the key factors for improving the light efficiency of the filament.

[0191] Experiment 4: Influence of Thermal Management Coating on Luminescence Stability

[0192] Experimental Procedure

[0193] Sample Preparation

[0194] Sample of Example 4: Prepare a thermal management coating using the process of Example 4. Take AlN nanoparticles with a particle size of 30 nm, add epoxy resin, the concentration of nanoparticles is 8 mass parts, ultrasonically disperse for 15 minutes, spin-coat on the filament surface at a rotation speed of 2000 rpm, the coating time is 30 seconds, and the thickness is controlled at 80 μm. Set the curing temperature at 180°C and the curing time at 1 hour.

[0195] Sample of Comparative Example 4: A thermal management coating was prepared using the process of Comparative Example 4. Alumina nanoparticles with a particle size of 5 nm were taken and added to epoxy resin at a concentration of 3 parts by mass. They were dispersed only by magnetic stirring for 5 minutes, spin-coated at a speed of 500 rpm, with a coating time of 10 seconds and a thickness of 30 μm. The curing temperature was 60 °C and the curing time was 30 minutes.

[0196] Luminescence stability test

[0197] The two groups of samples were respectively placed in a constant-temperature heating table, and the ambient temperature was set at 85 °C, and the filament (power 5 W) was lit.

[0198] Every 2 hours, a luminous flux tester was used to record the luminous flux value of the filament. The experiment lasted for 12 hours, and the luminous flux data at each time point was recorded.

[0199] Calculation of luminous efficacy retention rate

[0200] Calculate the retention rate of luminous flux at different time points. The formula is:

[0201]

[0202] Each sample was tested 3 times, the luminous flux and retention rate were recorded, and the average value was taken to ensure consistent experimental conditions and avoid environmental errors.

[0203] Experimental data

[0204] Table 4:

[0205]

[0206] The luminous flux retention rate of the sample of Example 4 under high-temperature conditions was significantly better than that of Comparative Example 4. This is mainly attributed to the high thermal conductivity of AlN nanoparticles and the optimized dispersion process. AlN particles with a particle size of 30 nm are not only more evenly distributed in the thermal management layer, but their higher thermal conductivity effectively reduces the temperature accumulation in the filament luminescent layer, making the luminous efficacy stable under long-term high-temperature conditions. In Comparative Example 4, the Al2O3 particles with too small a particle size have insufficient thermal conductivity and insufficient dispersion, resulting in a low heat conduction efficiency, and the luminous flux decays significantly over time.

[0207] The thickness and coating process of the thermal management coating are also key factors. In Example 4, through multiple uniform coatings by the spin-coating process, the thickness was controlled at 80 μm, ensuring that heat could be quickly conducted from the luminescent layer to the external environment, thus avoiding the phenomenon of thermal quenching. While the coating thickness of the sample in Comparative Example 4 was only 30 μm, and insufficient dispersion led to particle aggregation in the coating, forming thermal resistance points, further exacerbating the impact of heat accumulation on the luminescent performance. Combined with the optimized process of high-temperature curing, the coating in Example 4 has stronger adhesion and higher heat conduction efficiency.

[0208] The experiment also shows that the combined effect of high - thermal - conductivity materials and coating uniformity determines the effect of thermal management. In Example 4, ultrasonic dispersion was used to improve the distribution uniformity of AlN particles in the coating, thus ensuring the uniform distribution of the heat - flux density on the filament surface. In Comparative Example 4, ultrasonic dispersion was not carried out, resulting in obvious particle agglomeration, blocking the heat - dissipation path and serious local heat accumulation. These differences directly affected the light - flux retention rate, verifying the necessity and effectiveness of optimizing the thermal - management coating process.

[0209] Experimental procedures

[0210] Sample preparation

[0211] Samples of Example 5: According to the process of Example 5, a rare - earth luminescent material layer (the process of Example 1), a quantum - dot auxiliary layer (the process of Example 2), an optical microstructure coating (the process of Example 3), and a thermal - management coating (the process of Example 4) were sequentially coated. The thicknesses of each layer were 120μm, 50μm, 30μm, and 80μm respectively, and finally a multi - layer composite - structure filament was formed.

[0212] Samples of Comparative Example 5: According to the processes of Comparative Examples 1 - 4, a rare - earth luminescent material layer, a quantum - dot auxiliary layer, an optical microstructure coating, and a thermal - management coating were sequentially coated. The thicknesses of each layer were 50μm, 20μm, 10μm, and 30μm respectively, forming a multi - layer - structure filament based on the comparative - example process.

[0213] Light - flux test

[0214] The two groups of samples were respectively fixed in an integrating - sphere light - flux test system, and a white - light LED light source (color temperature 5000K, power 10W) was used to excite the samples, and the initial light - flux output (unit: lumen) was recorded.

[0215] Thermal - stability test

[0216] The filament samples were placed on a constant - temperature heating stage, and the ambient temperature was set at 85°C. After the filaments were lit (power 10W), the change in light flux was recorded every 2 hours, the experiment lasted for 12 hours, and the luminous - efficacy retention rate was calculated.

[0217] Color - temperature regulation test

[0218] The input current of the filament was adjusted (in the range of 0.1A to 0.5A), the corresponding color - temperature change range was recorded, and the maximum and minimum color - temperature values (unit: K) were measured.

[0219] Data recording and processing

[0220] Each sample was tested 3 times, and the light - flux, luminous - efficacy retention rate, and color - temperature data were recorded, ensuring consistent conditions and avoiding interference from ambient light sources.

[0221] Experimental data

[0222] Table 5:

[0223]

[0224] The sample of Example 5 is significantly superior to that of Comparative Example 5 in terms of luminous flux, thermal stability, and color temperature regulation range. The optimized design of the multi-layer composite structure enables the functional layers to work together synergistically, giving full play to the material properties. The rare earth luminescent material layer provides a stable RGB spectral output, and the addition of the quantum dot auxiliary layer further supplements the spectral range. In particular, the luminous intensity in the blue and red wavelength bands is significantly enhanced. In Comparative Example 5, the low doping amount of the rare earth activator and the uneven dispersion of the quantum dots directly result in a lower density of luminescence centers and a significant decrease in luminous flux.

[0225] The improvement of the thermal management coating directly affects the performance retention of the filament in a high-temperature environment. In Example 5, the moderately thick AlN coating quickly dissipates the heat of the light-emitting layer through an efficient heat conduction path, avoiding the attenuation of luminous efficiency caused by heat accumulation. In Comparative Example 5, the insufficient particle dispersion and the too-thin coating of the thermal management layer limit the rapid heat transfer, resulting in a significant decrease in luminous efficacy during long-term use. After 12 hours, the luminous efficacy retention rate of Example 5 is close to 90%, while that of Comparative Example 5 is only about 60%, showing a significant gap.

[0226] The broadening of the color temperature regulation range also benefits from the optimization of the quantum dot layer. In Example 5, the quantum dots with uniform particle size achieve a smooth transition from warm white light (about 2700K) to cool white light (about 6500K) by adjusting the input current. This flexible color temperature regulation ability can meet the requirements of multiple scenarios and has broad application prospects especially in the high-end lighting field. In Comparative Example 5, the color temperature range is relatively narrow, and the color temperature boundaries of warm white light and cool white light are significantly restricted, indicating the inadequacy of the design parameters and the deterioration of the material properties.

[0227] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-color LED filament, characterized in that, It includes the following components: Rare earth composite luminescent material, accounting for 80 - 95 parts by mass fraction; Quantum dot assisted spectral regulation layer, accounting for 2 - 8 parts by mass fraction; Optical microstructure coating, accounting for 3 - 8 parts by mass fraction; Thermal management coating, accounting for 5 - 10 parts by mass fraction; Filament substrate, made of gold wire or alloy wire.

2. A multi-color LED filament according to claim 1, characterized in that, The rare earth composite luminescent material includes a matrix material and a rare earth activator, where: The matrix material is selected from fluorescent pink powder: emission band 580nm - 700nm, yellow powder: emission band 540nm - 580nm, green powder: emission band 480nm - 540nm, blue powder / violet powder: emission band 400nm - 480nm, silica gel, epoxy resin, modified resin, yttrium oxide, iron oxide, ferrous oxide, magnetite, chromium oxide, cobalt oxide, copper oxide, cuprous oxide, manganese oxide, nickel oxide, titanium oxide, zinc oxide, vanadium oxide, barium magnesium aluminate, strontium silicate and other coloring oxides and composite oxides. One or more of them are used to prepare high-performance color powder through regulating the oxide composition, particle size and surface modification technology, and the mass fraction is 80 - 95 parts; The rare earth activator is Eu 3+ , Ce 3+ , Tb 3+ , Sm 3+ or one or more of them, and the mass fraction accounts for 0.1 - 3 parts.

3. The multi-color LED filament according to claim 2, characterized in that, The rare earth composite luminescent material further includes an energy transfer assistant, and the energy transfer assistant is Li + or F - , and the mass fraction ratio is 1-5 parts.

4. A multi-color LED filament according to claim 1, characterized in that, The quantum dots in the quantum dot assisted spectral regulation layer are CdSe / ZnS or InP / ZnS quantum dots, with a particle size range of 2 - 8nm, and the mass fraction is 2 - 8 parts.

5. A multi-color LED filament according to claim 4, characterized in that The quantum dot assisted spectral regulation layer contains a dispersant, and the dispersant is silicone oil or polymer dispersant, with a mass fraction of 5 - 10 parts.

6. The multi-color LED filament according to claim 1, characterized in that, The nanoparticles of the optical microstructure coating are selected from SiO2 or TiO2, with a particle size range of 10 - 50nm, and the mass fraction is 3 - 8 parts.

7. The multi-color LED filament according to claim 6, characterized in that, The optical microstructure coating further includes a surface treatment agent, and the surface treatment agent is a silane coupling agent or fluoride, with a mass fraction of 0.5 - 3 parts.

8. A multi-color LED filament according to claim 1, characterized in that, The material of the thermal management coating is selected from AlN, Al2O3 or BN nanoparticles, with a particle size range of 10 - 50nm, and the mass fraction is 5 - 10 parts.

9. A multi-color LED filament according to claim 1, characterized in that, The material of the filament substrate is tungsten wire or nickel-chromium alloy wire, and its surface is coated with a rare earth composite luminescent material layer, a quantum dot assisted spectral regulation layer, an optical microstructure coating and a thermal management coating.

10. A multi-color LED filament according to claim 9, characterized in that, The coating thickness of the rare earth composite luminescent material layer on the filament substrate is 50 - 200μm, the coating thickness of the quantum dot assisted spectral regulation layer is 20 - 100μm, the thickness of the optical microstructure coating is 10 - 50μm, and the thickness of the thermal management coating is 50 - 200μm.

Images