Fluorescent diaphragm and LED light-emitting device

Abstract

According to the fluorescent diaphragm and the LED light-emitting device provided by the utility model, the fluorescent diaphragm comprises the first diaphragm layer, the second diaphragm layer and the third diaphragm layer, and the first diaphragm layer, the second diaphragm layer and the third diaphragm layer are all prepared from the silica gel of which the hardness is greater than the preset hardness threshold value. The vapor permeation amount of silica gel for preparing the first film layer and the third film layer is smaller than a preset permeation threshold value; the second film layer is formed between the first film layer and the third film layer, the second film layer is prepared by doping silica gel with first fluorescent powder, and the first fluorescent powder is hygroscopic fluorescent powder. The first film layer and the third film layer with certain hardness and moisture resistance are respectively arranged on the two surfaces of the second film layer containing the hygroscopic fluorescent powder for protection, so that the hygroscopic fluorescent powder is effectively isolated from a working environment, the hygroscopic fluorescent powder is prevented from gradually losing efficacy due to absorption of moisture in air, the stability and reliability of the fluorescent diaphragm are improved, and the service life of the fluorescent diaphragm is prolonged. And the service life of the hygroscopic fluorescent powder is prolonged.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductors, in particular to a fluorescent film and an LED light-emitting device. Background Art

[0002] Currently, the following commercial LED phosphors are commonly found on the market: YAG yellow phosphor with a peak wavelength of 545-580nm (nanometers), GaYAG yellow-green phosphor with a peak wavelength of 522-545nm, LuAG green phosphor with a peak wavelength of 520-545nm, silicate green / yellow phosphor with a peak wavelength of 515-575nm, silicate orange phosphor with a peak wavelength of 580-600nm, nitride red phosphor with a peak wavelength of 612-675nm, oxynitride blue-green phosphor with a peak wavelength of 490-500nm, and fluoride red phosphor with a peak wavelength of 629-632nm. Additionally, there are α-SiAlON-based phosphors, β-SiAlON-based phosphors, and (LSN:Ce³⁺) nitride yellow phosphors.

[0003] Due to differences in preparation materials and processes, the reliability of these phosphors varies. Silicate-based phosphors and fluoride-based red phosphors exhibit relatively poor reliability. This is because, due to their structural characteristics, these phosphors absorb moisture from the air, affecting their luminescence performance if exposed to the environment for extended periods. Organic ligands are typically coated on their surfaces to provide stability and prevent aggregation. However, in humid environments, when phosphors come into contact with moisture in the air, the ligands on the quantum dot surface may undergo complex chemical reactions with water molecules, leading to ligand desorption, ligand exchange, and hydrolysis, thereby affecting the luminescence stability of the quantum dot material. In practical applications, high-power LEDs encapsulated with these phosphors experience significant lumen degradation after a short period of operation. Tests have shown that a 3W LED exhibits lumen degradation of over 25% after a week of continuous operation. Consequently, despite the advantages of these phosphors, such as high quantum efficiency, continuously tunable emission wavelength, and narrow half-width (FWHM), their application remains challenging. Utility Model Content

[0004] In order to overcome the above shortcomings, the utility model provides a fluorescent film and an LED light-emitting device. By setting protective layers on both sides of the fluorescent film, the hygroscopic fluorescent powder is effectively isolated from the working environment, preventing this type of fluorescent powder from absorbing moisture in the air and affecting its luminous performance.

[0005] The technical solution provided by this utility model is:

[0006] In one aspect, the present invention provides a fluorescent film, comprising:

[0007] The first film layer, the second film layer, and the third film layer are all made of silicone with a hardness greater than a preset hardness threshold, and the water vapor permeability of the silicone used to make the first and third film layers is less than the preset permeability threshold; the second film layer is formed between the first and third film layers, and the second film layer is made of silicone doped with a first phosphor, where the first phosphor is a hygroscopic phosphor.

[0008] In another aspect, the present invention provides an LED lighting device, comprising:

[0009] An LED chip, wherein the LED chip comprises a light-emitting top surface, a light-emitting side surface, and an electrode side surface;

[0010] The fluorescent film as described above, wherein one side of the first film layer or the third film layer of the fluorescent film is mounted close to the light-emitting surface of the LED chip; and

[0011] A covering structure is arranged around the light-emitting side of the LED chip and the side of the fluorescent film.

[0012] The fluorescent film and LED light-emitting device provided by the present invention respectively arrange a first film layer and a third film layer with certain moisture-proof properties on both sides of the second film layer containing hygroscopic fluorescent powder for moisture-proof protection, forming two barriers, which effectively isolate the hygroscopic fluorescent powder from the working environment, prevent water vapor from entering the second film layer and causing the hygroscopic fluorescent powder to gradually fail, thereby improving the stability and reliability of the fluorescent film, ensuring the luminous performance and extending the service life of the hygroscopic fluorescent powder; and the three fluorescent film layers are all made of silicone with a certain hardness, and will not shrink or deform during the continuous baking process, thereby ensuring the quality and stability of the fluorescent film. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic cross-sectional view of a fluorescent film in one embodiment of the present invention;

[0014] Figure 2 This is a schematic cross-sectional view of an LED packaging structure according to another embodiment of the present invention;

[0015] Figure 3 This is a schematic cross-sectional view of an LED packaging structure according to another embodiment of the present invention.

[0016] Reference numerals:

[0017] 10-fluorescent film, 11-first film layer, 12-second film layer, 13-third film layer, 20-LED chip, 21-light-emitting top surface, 22-light-emitting side surface, 23-electrode side surface, 30-encapsulation structure. DETAILED DESCRIPTION

[0018] In order to more clearly illustrate the implementation cases of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without inventive work.

[0019] An embodiment of the present utility model is a fluorescent film, comprising a first film layer, a second film layer and a third film layer, wherein the first film layer and the third film layer are made of silicone having a hardness greater than a preset hardness threshold; the second film layer is formed between the first film layer and the third film layer, and the second film layer is made of silicone doped with a first phosphor, and the first phosphor is a hygroscopic phosphor.

[0020] In this embodiment, the second film layer containing hygroscopic phosphor is securely encapsulated between the first and third film layers. This structural arrangement provides dual-layer protection for the second film layer, ensuring excellent sealing and moisture resistance. Furthermore, the first, second, and third film layers are all made of silicone with a hardness greater than a preset threshold, preventing shrinkage and deformation during continuous baking. Furthermore, the first and third film layers possess a certain degree of moisture resistance, effectively isolating the hygroscopic phosphor from the external environment and preventing moisture or other harmful substances from entering the second film layer. This allows the phosphor in the second film layer to remain dry even in humid working environments, ensuring its luminous properties are unaffected by the external environment and enabling the hygroscopic phosphor to function stably under various environmental conditions. The preset hardness threshold referred to here refers to the requirement that, during the preparation of the fluorescent film, the corresponding film layers are not susceptible to shrinkage after multiple baking cycles. Since the three film layers need to be baked sequentially, e.g., after the first film layer is baked, the second film layer is prepared and baked, and then the third film layer is prepared and baked. During the preparation of the three-layer film, especially when baking the third film layer (i.e., performing the third baking), if the hardness of the silicone is too low, the surface of the fluorescent film will gradually shrink, deform, and form wrinkles as it bakes, which is detrimental to the normal use of the film. Therefore, a specific hardness needs to be set based on the characteristics of the silicone and the fluorescent film preparation process to prevent the fluorescent film from shrinking and deforming due to heat. For example, in one example, the preset hardness threshold Shore D (Shore Hardness) of the silicone in the first and third film layers is 60. That is, as long as the hardness of the first and third film layers is greater than 60 HD, the film layers will not shrink or deform during the sequential baking and curing process, resulting in a fluorescent film that can be put into normal use. Theoretically, the harder the silicone used, the less likely it is to deform during baking. However, when the hardness is too high, the brittleness of the silicone increases and it is easy to break when subjected to external force. In actual application, the degree of thermal deformation and the brittleness of the silicone need to be comprehensively considered to determine the hardness of the film layer, so that it can avoid deformation due to heat during the baking process while ensuring the toughness and durability of the silicone.

[0021] At the same time, in the usage scenario of this fluorescent film, the silicone used to prepare the first film layer and the second film layer has a certain moisture resistance, which prevents water vapor from passing through the first film layer and the third film layer into the second film layer, and can prevent the phosphor in the second film layer from absorbing moisture and affecting the luminous performance; the moisture permeability of the material is generally characterized by the parameter of water vapor permeability. Water vapor permeability refers to the amount of water vapor passing through a unit area of material within 24 hours under specific temperature and humidity conditions. The smaller the water vapor permeability, the better the moisture resistance of the material. Therefore, in this embodiment, the water vapor permeability of the first film layer and the third film layer is required to be less than the preset permeability threshold. The preset permeability threshold can be determined through a red ink permeation test (also known as a red ink test). Specifically, a series of silicone materials with increasing water vapor permeability are prepared. The prepared silicone materials are placed in a container containing a drop of red ink, submerging the silicone in the liquid. The container, the red ink, and the prepared silicone are then placed in an 80°C oven and baked for 1 hour. If the red ink ultimately seeps into any of the prepared silicone materials, the moisture resistance does not meet the requirements, and the water vapor permeability of the silicone material needs to be reduced. If the red ink does not seep into any of the prepared silicone materials, the moisture resistance meets the requirements, and the water vapor permeability of that silicone material can be set to the preset permeability threshold. Therefore, the first and third film layers made of silicone materials with a water vapor permeability below the preset permeability threshold exhibit excellent sealing and moisture resistance, effectively isolating external moisture vapor from entering the second film layer through the first and third film layers. In one example, the preset water vapor permeability threshold (WVT) of the silicone materials in the first and third film layers is 100 g / m². 2 24h, that is, as long as the water vapor permeability of the silica gel used to prepare the first and third film layers is less than 100g / m 2 24h, which means that 1 m is passed within 24 hours. 2 If the water vapor content of a specific area of silica gel is less than 100g, then moisture from the external environment cannot penetrate the first and third layers and enter the second layer, thus meeting the sealing and moisture-proofing requirements of the fluorescent film. Theoretically, the moisture-proof properties of the fluorescent film can be achieved only if the water vapor permeability of the first and third layers is less than a predetermined permeability threshold. However, for manufacturing convenience, it is also possible to require that the water vapor permeability of all three layers be less than the predetermined permeability threshold.

[0022] The first phosphor doped into the silica gel of the second film layer is a hygroscopic phosphor, such as a silicate-based phosphor or a fluoride-based red phosphor. These phosphors can be doped into the second film layer individually, mixed with each other, or mixed with other phosphors. These phosphors typically have high light conversion efficiency. However, due to their structural characteristics, hygroscopic phosphors are sensitive to moisture in the air and have high hygroscopicity. These phosphors are easily affected by moisture in the air, especially in high humidity environments. This not only reduces luminescence performance but also degrades the material itself, affecting stability and lifespan, thus limiting their application. It should be understood that this embodiment does not require the moisture resistance of the silicone in the second film layer. Whether or not the silicone meets the same requirements as the first and third film layers, such as the preset permeability threshold, does not affect the sealing and moisture-proof protection of the second film layer by the first and third film layers. However, to facilitate process operation and enhance protection of the phosphor in the second fluorescent film layer, the second film layer is generally consistent with the first and third film layers. Alternatively, silicone with a water vapor permeability below the preset permeability threshold can be used to better protect the hygroscopic phosphor in the second film layer. Taking into account the impact on the color temperature and luminous efficiency of the LED chip, the thickness of the second film layer is typically 50µm-60µm. The thickness of the first and third film layers can be adjusted as long as they can effectively seal the second film layer. Considering the volume and cost of the LED chip, the total thickness of the first, second, and third film layers is generally controlled to not exceed 160µm.

[0023] In addition to silica gel having a hardness greater than a preset hardness threshold and a water vapor permeability less than a preset permeability threshold, the first film layer may also be doped with a second phosphor. This second phosphor is non-hygroscopic and highly reliable, and does not absorb moisture from the air. Even if it does absorb moisture, this does not adversely affect its luminescence performance or inherent properties. Examples include YAG yellow phosphor with a peak in the 545nm-580nm range, GaYAG yellow-green phosphor with a peak in the 522nm-545nm range, and LuAG green phosphor with a peak in the 520nm-545nm range. Because these phosphors are not adversely affected by moisture in the air, when added to the first film layer, their inherent properties are unaffected by the external environment, and the first film layer remains moisture-resistant. Even if the first film layer comes into contact with moisture in the air, this does not reduce the stability and reliability of the phosphor film. Similarly, in addition to the silica gel having a hardness greater than a preset hardness threshold and a water vapor permeability less than a preset permeability threshold, the third film layer may also be doped with a third phosphor. This third phosphor is non-hygroscopic and highly reliable, and does not absorb moisture from the air. Even if it does absorb moisture, this does not adversely affect the luminescence performance or inherent properties. Examples include YAG yellow powder with a peak in the 545nm-580nm range, GaYAG yellow-green powder with a peak in the 522nm-545nm range, and LuAG green powder with a peak in the 520nm-545nm range. Because these phosphors are not adversely affected by moisture in the air, when added to the third film layer, their inherent properties are unaffected by the external environment, and the third film layer remains moisture-resistant. Even if the third film layer comes into contact with moisture in the air, this does not reduce the stability and reliability of the phosphor film.

[0024] In the preparation process of the fluorescent film, first, the first film layer material is placed on the support film, the scraper height is set, and a certain thickness is scraped to form the first film layer, and then baked to an incompletely cured state (such as setting the baking conditions: temperature 130°C, baking time is 0.5h); at this time, the first film layer is in an incompletely cured state, has no fluidity but the surface is not completely cured and formed, and has a certain viscosity, which is conducive to the subsequent bonding with the second film layer, and to a certain extent avoids shrinkage and deformation caused by baking after curing, thereby affecting the properties of the first film layer in the final product; then, the first phosphor and silica gel are evenly mixed and coated on the surface of the first film layer, the scraper height is set, and a certain thickness is scraped to form the second film layer, and then baked. The first film layer and the second film layer are in an incompletely cured state (e.g., the baking conditions are set as follows: temperature 130°C, baking time 0.5h); at this time, the first film layer and the second film layer are in an incompletely cured state; thereafter, the third film layer material is coated on the surface of the second film layer to form a third film layer, and baked to a fully cured state (e.g., the baking conditions are set as follows: temperature 150°C, baking time 1h), at which time the first film layer, the second film layer and the third film layer are all fully cured. In addition, in order to make the phosphor of the phosphor film more evenly mixed during baking and curing and avoid precipitation due to gravity, other ingredients such as anti-precipitation agents and leveling powders may be added to the first film layer, the second film layer and the third film layer respectively before baking, but this embodiment does not limit this.

[0025] Another embodiment of the present invention provides an LED light-emitting device, comprising: an LED chip, the LED chip including a light-emitting top, a light-emitting side, and an electrode side; a fluorescent film as described above, wherein one side of the first film layer or the third film layer of the fluorescent film is mounted close to the light-emitting top of the LED chip; and a covering structure surrounding the light-emitting side of the LED chip and the side of the fluorescent film.

[0026] The LED chip can be vertical, upright, or flip-chip. As long as it can emit light, there are no restrictions on the shape and size of the chip. It can be round, square, polygonal, or even irregular. The shape and size of the phosphor film are basically the same as the shape and size of the LED chip's light-emitting surface. The area of the phosphor film layer is usually slightly larger than the light-emitting surface of the LED chip, and it can completely cover the light-emitting surface of the LED chip. The coating structure is made of resin and is formed not only around the LED chip but also on the sides of the phosphor film. It also forms an isolation barrier between the sides of the phosphor film and the external environment, preventing direct contact between the sides of the phosphor film and the external environment.

[0027] In addition, when a vertically structured LED chip is used, since the chip itself emits light on a single side, high-reflective particles do not need to be doped into the coating structure. In this case, the coating structure only serves as an isolation function. In this way, a protective structure that fully surrounds the second film layer in the fluorescent film is formed in the entire LED light-emitting device. The side of the fluorescent film is covered by the coating structure and is isolated from the external environment. The edge portion of the fluorescent film that protrudes from the surface of the first film layer or the third film layer above the light-emitting portion of the LED chip is also covered by the coating structure and is isolated from the external environment. Only the surface of the first film layer or the third film layer in the fluorescent film that is far from the light-emitting portion of the LED chip is in contact with the external environment. Since the first film layer and the third film layer are both made of silicone with a hardness greater than a preset hardness threshold and a water vapor permeability less than a preset permeability threshold, it can effectively prevent external water vapor from eroding into the internal second film layer, thereby avoiding adverse effects on the phosphor in the second film layer.

[0028] Those skilled in the art can determine whether to dope the coating structure with high-reflectivity particles based on the structural characteristics of the LED chip itself and the final product requirements. For example, when a flip-chip LED chip is used, the chip itself emits light from multiple sides, but the final LED product requires single-sided light. In this case, doping the coating structure with high-reflectivity particles not only serves as an isolation function, but also reflects the light emitted from the chip's light-emitting side and the side light emitted from the fluorescent film, preventing side light from emitting. The high-reflectivity particles in the coating structure are generally white inorganic pigments, such as oxides such as titanium oxide, zinc oxide, and zirconium oxide, carbonates such as white lead (lead carbonate) and calcium carbonate, and clay minerals such as kaolin (kaolinite), with titanium oxide being preferred. Since the purpose of forming the first adhesive layer on the light-emitting side of the LED chip is to prevent side light from emitting, the doping ratio of the high-reflectivity particles needs to be adjusted according to actual conditions in the application, so that the reflectivity reaches a high reflectivity above a preset value (such as 80%, 90%, 95%, etc.).

[0029] like Figure 2As shown, the LED chip 20 is a flip-chip chip with a light-emitting top surface 21 serving as the light-emitting surface, and a light-emitting side surface 22 adjoining the side edge of the light-emitting surface. Two chip electrodes (one positive and one negative) are also provided on the side of the LED chip opposite the light-emitting surface. The electrode side surface 23 serves as the side where the chip electrodes meet the chip contact surface. A fluorescent film 10 is adhered to the light-emitting surface of the LED chip. Typically, the area of the fluorescent film layer is slightly larger than the light-emitting surface of the LED chip. The portion of the fluorescent film 10 closest to the light-emitting surface of the LED chip can be either the first film layer 11 or the third film layer 13, without affecting the moisture-proof protection of the second film layer 12. This is not a limitation in this embodiment. The encapsulation structure 30, a mixture of resin and highly reflective particles, is formed around the LED chip 20 and the fluorescent film 10. The highly reflective particles reflect light emitted by the LED chip back, ensuring that the individual LED chips emit light only from the light-emitting top surface of the LED chip, resulting in a better light pattern. The encapsulation structure also isolates and protects the side edges of the fluorescent film and the protruding edges near the light-emitting top surface of the LED chip. In another embodiment, in order to make the light emitted from the chip electrode side also form reflection, as shown in FIG. Figure 3 As shown, in the LED packaging structure, the covering structure 30 is not only formed around the LED chip 20 and the fluorescent film 10, but also formed on the electrode side 23 of the LED chip, that is, the covering structure is flush with the chip electrode surface, which better reflects the light output from the non-light-emitting surface of the chip.

[0030] It should be noted that the above embodiments can be freely combined as needed. The above are only preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the present invention, and such improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fluorescent film, characterized in that: include: A first film layer, a second film layer and a third film layer, wherein the first film layer, the second film layer and the third film layer are all made of silicone having a hardness greater than a preset hardness threshold, and the water vapor permeability of the silicone used to prepare the first film layer and the third film layer is less than the preset permeability threshold; the second film layer is formed between the first film layer and the third film layer, and the second film layer is made of silicone doped with a first phosphor, and the first phosphor is a hygroscopic phosphor.

2. The fluorescent film according to claim 1, wherein: The first phosphor is one or more of silicate series phosphors and fluoride series red phosphors.

3. The fluorescent film according to claim 1 or 2, characterized in that: The first film layer is doped with a second phosphor, which is a non-hygroscopic phosphor.

4. The fluorescent film according to claim 1 or 2, characterized in that: The third film layer is doped with a third phosphor, and the third phosphor is a non-hygroscopic phosphor.

5. The fluorescent film according to claim 1 or 2, characterized in that: In the first film layer, the second film layer and the third film layer, the preset hardness threshold ShoreD of the silicone is 60.

6. The fluorescent film according to claim 1 or 2, characterized in that: In the first and third film layers, the preset permeability threshold WVT of the silica gel is 100 g / m 2 ·24h.

7. An LED light-emitting device, characterized in that: The LED lighting device comprises: An LED chip, wherein the LED chip comprises a light-emitting top surface, a light-emitting side surface, and an electrode side surface; The fluorescent film according to any one of claims 1 to 6, wherein one side of the first film layer or the third film layer of the fluorescent film is mounted close to the light-emitting surface of the LED chip; and A covering structure is arranged around the light-emitting side of the LED chip and the side of the fluorescent film.

8. The LED lighting device according to claim 7, wherein: The coating structure is doped with high reflectivity particles.

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