LED lamp bead, preparation method thereof and LED light source

Abstract

The invention provides an LED lamp bead and a preparation method thereof, and an LED light source, the LED lamp bead comprises a substrate, an LED chip and at least two light conversion layers, the LED chip is located on the substrate, the light conversion layers are sequentially stacked on the substrate and the LED chip, each light conversion layer is used for receiving excitation light and generating corresponding output light, and in the two adjacent light conversion layers, the closer to the substrate, the closer to the output light is, and the closer to the output light is, the closer to the output light is. The longer the wavelength of the output light generated by the light conversion layer is, the larger the thickness of the light conversion layer is, and the lower the concentration of the light conversion material in the light conversion layer is. The more difficult-to-excite light conversion layer is arranged closer to the substrate, so that the more difficult-to-excite light conversion layer can be excited first, and the excitation efficiency and the light emitting efficiency of the light conversion layer are integrally improved; meanwhile, the passing time of the exciting light in the light conversion layer which is more difficult to excite is longer, the probability that the light conversion material is excited is higher, and the excitation efficiency and the light emitting efficiency of the light conversion layer can be further improved.

Description

Technical Field

[0001] This application relates to the field of LED technology, and particularly to an LED lamp bead, a preparation method thereof, and an LED light source. Background Art

[0002] An LED (Light Emitting Diode) is a solid-state semiconductor device, which has the advantages of high brightness, low working voltage, low power consumption, easy matching with integrated circuits, simple driving, long lifespan, etc., and has been widely used as a light source in the lighting field.

[0003] Currently, the white light LED lamp beads mainly coat phosphors that can be excited by blue light on a blue light LED chip. The phosphors cover the periphery of the blue light LED chip, and the blue light emitted by the blue light LED chip is mixed with the light emitted by the phosphors to form white light. In this way, the excitation light emitted by the blue light LED chip cannot effectively excite the phosphors, and the color rendering index of the LED lamp beads cannot be further improved. In addition, in order to synchronously improve the color rendering index and luminous efficiency, such white light LED lamp beads are encapsulated by a layered dispensing method. Specifically, the phosphors are filled around the blue LED chip. First, a layer of red phosphors is filled, and then yellow-green phosphors are filled. This encapsulation method only improves the brightness in the case of improving the color rendering index at low color temperatures, and has no obvious improvement for high color temperatures. Moreover, the process of the layered dispensing method is difficult to control, and the yield is relatively low. Summary of the Invention

[0004] In view of this, the embodiments of this application are committed to providing an LED lamp bead, a preparation method thereof, and an LED light source to solve the problem that the blue LED chip in the prior art cannot fully excite the phosphors.

[0005] On the one hand, this application provides an LED lamp bead, including:

[0006] A substrate;

[0007] An LED chip, located on the substrate, for generating excitation light;

[0008] At least two light conversion layers, stacked on the substrate and the LED chip in sequence, and each light conversion layer is used to receive the excitation light and generate corresponding output light;

[0009] Wherein, in two adjacent light conversion layers, the closer to the substrate, the longer the wavelength of the output light generated by the light conversion layer, the greater the thickness of the light conversion layer, and the lower the concentration of the light conversion material in the light conversion layer.

[0010] In some embodiments, the light conversion layer includes:

[0011] A first light conversion layer, located on the substrate and the LED chip;

[0012] A second light conversion layer, located on the first light conversion layer;

[0013] The light conversion material in the first light conversion layer is a red light conversion material, the light conversion material in the second light conversion layer is a green light conversion material, or the light conversion material in the first light conversion layer is a red light conversion material, the light conversion material in the second light conversion layer is a yellow light conversion material, or the light conversion material in the first light conversion layer is a yellow light conversion material, and the light conversion material in the second light conversion layer is a green light conversion material.

[0014] In some embodiments, the light conversion layer includes:

[0015] A first light conversion layer, located on the substrate and the LED chip;

[0016] A second light conversion layer, located on the first light conversion layer;

[0017] A third light conversion layer, located on the second light conversion layer;

[0018] The light conversion material in the first light conversion layer is a red light conversion material, the light conversion material in the second light conversion layer is a yellow light conversion material, and the light conversion material in the third light conversion layer is a green light conversion material.

[0019] In some embodiments, the LED chip is a blue LED chip with a wavelength band of 450 nm to 470 nm, the excitation peak wavelength of the red light conversion material in the first light conversion layer is 640 nm to 660 nm, the excitation peak wavelength of the yellow light conversion material in the second light conversion layer is 550 nm to 570 nm, and the excitation peak wavelength of the green light conversion material in the third light conversion layer is 530 nm to 550 nm.

[0020] In some embodiments, there is also a transition layer between two adjacent light conversion layers, and the transition layer contains light conversion materials of all colors in the two adjacent light conversion layers.

[0021] In some embodiments, among two adjacent transition layers, the closer to the substrate, the greater the thickness of the transition layer and the lower the concentration of the light conversion material in the transition layer; and / or, the thickness of each transition layer is less than the thicknesses of the two adjacent light conversion layers.

[0022] Some embodiments of the present application also provide a method for manufacturing an LED lamp bead, including:

[0023] Providing a substrate;

[0024] Fix the LED chip on the substrate, and the LED chip is used to generate excitation light;

[0025] Form at least two light conversion layers, which are stacked on the substrate and the LED chip in sequence. Each light conversion layer is used to receive the excitation light and generate corresponding output light;

[0026] Wherein, among two adjacent light conversion layers, the closer to the substrate, the longer the wavelength of the output light generated by the light conversion layer, the greater the thickness of the light conversion layer, and the lower the concentration of the light conversion material in the light conversion layer.

[0027] In some embodiments, a transition layer is formed between two adjacent light conversion layers, and the transition layer contains light conversion materials of all colors in the two adjacent light conversion layers.

[0028] In some embodiments, among two adjacent transition layers, the closer to the substrate, the greater the thickness of the transition layer, and the lower the concentration of the light conversion material in the transition layer; and / or, the thickness of each transition layer is less than the thicknesses of the two adjacent light conversion layers.

[0029] Some embodiments of the present application further provide an LED light source, including the LED lamp bead.

[0030] The present application provides an LED lamp bead, its preparation method, and an LED light source, including a substrate; an LED chip located on the substrate for generating excitation light; at least two light conversion layers stacked on the substrate and the LED chip in sequence. Each light conversion layer is used to receive the excitation light and generate corresponding output light. Wherein, among two adjacent light conversion layers, the closer to the substrate, the longer the wavelength of the output light generated by the light conversion layer, the greater the thickness of the light conversion layer, and the lower the concentration of the light conversion material in the light conversion layer. Since the longer the wavelength of the output light generated by the light conversion layer, the more difficult it is to be excited, and the more difficult-to-excite light conversion layer is arranged closer to the substrate, so that the more difficult-to-excite light conversion layer can be excited earlier, which can overall improve the excitation efficiency of the light conversion layer and then improve the light output efficiency; at the same time, the more difficult-to-excite light conversion layer has a greater thickness and a lower concentration of the light conversion material. Without changing the amount of the light conversion material in each light conversion layer, the longer the time for the excitation light to pass through the more difficult-to-excite light conversion layer, the higher the probability of the light conversion material being excited, which can further improve the excitation efficiency and light output efficiency of the light conversion layer. Description of the Drawings

[0031] Figure 1 It is a flowchart of the preparation method of the LED lamp bead provided by an embodiment of the present application.

[0032] Figure 2 Schematic diagram of fixing an LED chip on a substrate provided by an embodiment of the present application.

[0033] Figure 3 Schematic diagram of the position of an LED chip on a substrate provided by an embodiment of the present application.

[0034] Figure 4 Schematic diagram of the structure of an LED lamp bead provided by an embodiment of the present application.

[0035] Figure 5 Schematic diagram of the structure of an LED lamp bead provided by another embodiment of the present application.

[0036] Figure 6 It is a contrast diagram of light flux with the thickness of the three-layer light conversion layer decreasing, the concentration increasing, and both the thickness and concentration being consistent.

[0037] Figure 7 It is a contrast diagram of light extraction efficiency with the thickness of the three-layer light conversion layer decreasing, the concentration increasing, and both the thickness and concentration being consistent.

[0038] Among them, the reference numerals are:

[0039] 100 - Substrate; 101 - Bowl cup; 200 - LED chip; 301 - First light conversion layer; 302 - Second light conversion layer; 303 - Third light conversion layer; 401 - First transition layer; 402 - Second transition layer. Detailed implementation manners

[0040] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0041] Figure 4 Schematic diagram of the structure of an LED lamp bead provided by this embodiment. As Figure 4As shown, the LED lamp bead includes a substrate 100, an LED chip 200, and at least two light conversion layers. Among them, the LED chip 200 is located on the substrate 100, and the light conversion layers are stacked on the substrate 100 and the LED chip 200 in sequence from bottom to top. The LED chip 200 is used to generate excitation light, and each light conversion layer is used to receive the excitation light and generate corresponding output light. In two adjacent light conversion layers, the closer to the substrate 100, the longer the wavelength of the output light generated by the light conversion layer, the greater the thickness of the light conversion layer, and the lower the concentration of the light conversion material in the light conversion layer. Since the longer the wavelength of the output light generated by the light conversion layer, the more difficult it is to be excited, the more difficult-to-excite light conversion layer is arranged closer to the substrate 100, so that the more difficult-to-excite light conversion layer can be excited earlier, which can overall improve the excitation efficiency of the light conversion layer and then improve the light extraction efficiency. At the same time, the more difficult-to-excite light conversion layer has a greater thickness and a lower concentration of the light conversion material. Without changing the amount of the light conversion material in each light conversion layer, the longer the time the excitation light passes through the more difficult-to-excite light conversion layer, the higher the probability that the light conversion material is excited, which can further improve the excitation efficiency and light extraction efficiency of the light conversion layer.

[0042] Specifically, the material of the substrate 100 can be selected from ceramic materials (including one or more of AlN, Al2O3, SiO, SiO2, Si3N4, and SiON) or metal materials (including aluminum or copper). There is a bowl cup 101 on the substrate 100. The bowl cup 101 is annular and is arranged on the substrate 100. The material of the bowl cup 101 can be selected from materials such as thermosetting epoxy resin, thermosetting silica gel, or thermoplastic plastic. Electrical connectors such as plugs and pads can be arranged in the substrate 100. The LED chip 200 and the light conversion layers can be arranged in the bowl cup 101, and the light conversion layers are stacked in sequence and jointly fill the space in the bowl cup 101.

[0043] Please continue to refer to Figure 1 , the inner side wall of the bowl cup 101 is inclined, and the opening width of the bowl cup 101 on the side close to the substrate 100 is smaller than the opening width on the side far from the substrate 100. Or it can also be understood in this way, the bowl cup 101 is frustum-shaped, its cross-sectional shape is trapezoidal, and its diameter gradually increases from bottom to top, so that the inner side wall of the bowl cup 101 is inclined. In this way, when the excitation light emitted by the LED chip 200 irradiates on the inner side wall of the bowl cup 101, the inner side wall of the bowl cup 101 can reflect the excitation light onto the light conversion layer, improving the light utilization rate, avoiding waste of light energy, and reducing power consumption.

[0044] In some embodiments, the bowl cup 101 may not be provided on the substrate 100. At this time, the light conversion layers can be hemispherical and stacked on the substrate 100 and the LED chip 200 in sequence.

[0045] In some embodiments, the LED chip 200 can be attached to the substrate 100 using die bonding glue, and then interconnected with the electrical connection components in the substrate 100 using leads. In some embodiments, the LED chip 200 can also be soldered to the substrate 100 in a flip-chip manner, so as to get rid of the constraints of leads and die bonding glue, making the LED chip 200 have a high thermal conductivity, a small thermal resistance, and can withstand high currents, with stronger reliability, a higher luminous flux maintenance rate, and a longer service life.

[0046] Furthermore, the excitation light generated by the LED chip 200 can be blue light, purple light, ultraviolet light, etc. Based on this, the LED chip 200 can be a blue LED chip, such as a GaN-based LED chip that emits blue light. The LED chip 200 can also be a purple or ultraviolet LED chip. The LED lamp bead can include only a single LED chip, but in some embodiments, at least two LED chips can also be provided.

[0047] Please continue to refer to Figure 4, in some embodiments, the light conversion layer has two layers, namely a first light conversion layer 301 and a second light conversion layer 302. The first light conversion layer 301 is located on the substrate 100 and the LED chip 200, and the second light conversion layer 302 is located on the first light conversion layer 301. The first light conversion layer 301 and the second light conversion layer 302 are two adjacent light conversion layers, and the first light conversion layer 301 is closer to the substrate 100 than the second light conversion layer 302. The wavelength of the output light generated by the first light conversion layer 301 is greater than the wavelength of the output light generated by the second light conversion layer 302. The first light conversion layer 301 is more difficult to be excited than the second light conversion layer 302. Therefore, the first light conversion layer 301 is closer to the substrate 100 and can preferentially receive the excitation light, so as to be preferentially excited, making the first light conversion layer 301 more fully excited; and the remaining excitation light then excites the second light conversion layer 302. Since the second light conversion layer 302 is more easily excited than the first light conversion layer 301, even if only the remaining excitation light after exciting the first light conversion layer 301 is used to excite the second light conversion layer 302, the second light conversion layer 302 can also be fully excited. Therefore, the excitation efficiency of the first light conversion layer 301 and the second light conversion layer 302 can be improved as a whole, and further the light extraction efficiency can be improved. Further, the thickness of the first light conversion layer 301 is greater than the thickness of the second light conversion layer 302, and the concentration of the light conversion material in the first light conversion layer 301 is less than the concentration of the light conversion material in the second light conversion layer 302. Although the concentration of the light conversion material in the first light conversion layer 301 is small, the thickness of the first light conversion layer 301 is large. Although the concentration of the light conversion material in the second light conversion layer 302 is large, the thickness of the second light conversion layer 302 is small. By this means, it can be ensured that there is a sufficient amount of light conversion material in both the first light conversion layer 301 and the second light conversion layer 302. And because the first light conversion layer 301 is thicker, the excitation light passes through the first light conversion layer 301 for a longer time, and the probability of the light conversion material in the first light conversion layer 301 being excited is higher, which can further improve the excitation efficiency and light extraction efficiency of the light conversion layer. It can be seen that in this application, the first light conversion layer 301 and the second light conversion layer 302 are arranged in layers, and the wavelength, thickness and concentration of the light conversion material of the generated output light are set in a gradient according to the corresponding order, ensuring that the emission spectrum of the second light conversion layer 302 and the absorption spectrum of the first light conversion layer 301 have the smallest overlap, and improving the excitation efficiency and light extraction efficiency of the first light conversion layer 301 and the second light conversion layer 302.

[0048] Both the first light conversion layer 301 and the second light conversion layer 302 may only have one kind of light conversion material. For example, the light conversion material in the first light conversion layer 301 may be a red light conversion material, and the light conversion material in the second light conversion layer 302 may be a green light conversion material. After the red light conversion material in the first light conversion layer 301 receives the excitation light, red light is generated. After the green light conversion material in the second light conversion layer 302 receives the excitation light, green light is generated. The wavelength of the red light is greater than that of the green light, meeting the requirement that the wavelength of the output light generated by the light conversion layer is longer the closer it is to the substrate 100, and both the red light conversion material and the green light conversion material can be more fully excited. Another example is that the light conversion material in the first light conversion layer 301 may be a red light conversion material, and the light conversion material in the second light conversion layer 302 is a yellow light conversion material. After the red light conversion material in the first light conversion layer 301 receives the excitation light, red light is generated. After the yellow light conversion material in the second light conversion layer 302 receives the excitation light, yellow light is generated. The wavelength of the red light is greater than that of the yellow light, meeting the requirement that the wavelength of the output light generated by the light conversion layer is longer the closer it is to the substrate 100, and both the red light conversion material and the yellow light conversion material can be more fully excited. Another example is that the light conversion material in the first light conversion layer 301 may be a yellow light conversion material, and the light conversion material in the second light conversion layer 302 is a green light conversion material. After the yellow light conversion material in the first light conversion layer 301 receives the excitation light, red light is generated. After the green light conversion material in the second light conversion layer 302 receives the excitation light, green light is generated. The wavelength of the yellow light is greater than that of the green light, meeting the requirement that the closer it is to the substrate 100, the longer the wavelength of the output light generated by the light conversion layer, and both the yellow light conversion material and the green light conversion material can be more fully excited.

[0049] Figure 5 Another structural schematic diagram of the LED lamp bead provided in this embodiment. As Figure 5As shown, the light conversion layer may also have three layers, namely a first light conversion layer 301, a second light conversion layer 302, and a third light conversion layer 303. The first light conversion layer 301 is located on the substrate 100 and the LED chip 200. The second light conversion layer 302 is located on the first light conversion layer 301. The third light conversion layer 303 is located on the second light conversion layer 302. The first light conversion layer 301 and the second light conversion layer 302 are two adjacent light conversion layers, and the first light conversion layer 301 is closer to the substrate 100 than the second light conversion layer 302. Therefore, the wavelength of the output light generated by the first light conversion layer 301 should be greater than the wavelength of the output light generated by the second light conversion layer 302. The thickness of the first light conversion layer 301 should be greater than the thickness of the second light conversion layer 302. The concentration of the light conversion material in the first light conversion layer 301 is less than the concentration of the light conversion material in the second light conversion layer 302. Similarly, the second light conversion layer 302 and the third light conversion layer 303 are two adjacent light conversion layers, and the second light conversion layer 302 is closer to the substrate 100 than the third light conversion layer 303. Therefore, the wavelength of the output light generated by the second light conversion layer 302 should be greater than the wavelength of the output light generated by the third light conversion layer 303. The thickness of the second light conversion layer 302 should be greater than the thickness of the third light conversion layer 303. The concentration of the light conversion material in the second light conversion layer 302 is less than the concentration of the light conversion material in the third light conversion layer 303.

[0050] Furthermore, the wavelengths of the output light generated by the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 decrease layer by layer. The first light conversion layer 301 is more difficult to be excited than the second light conversion layer 302 and the third light conversion layer 303. Therefore, the first light conversion layer 301 is closer to the substrate 100 and can preferentially receive the excitation light, thus being preferentially excited, enabling the first light conversion layer 301 to be more fully excited. The remaining excitation light then excites the second light conversion layer 302 and the third light conversion layer 303. Since the third light conversion layer 303 is more easily excited than the second light conversion layer 302, even if only the remaining excitation light after exciting the first light conversion layer 301 and the second light conversion layer 302 is used to excite the third light conversion layer 303, the third light conversion layer 303 can still be fully excited. Therefore, the excitation efficiency of the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 can be overall improved, and then the light extraction efficiency can be improved. Moreover, the thicknesses of the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 decrease layer by layer, and the concentrations of the light conversion materials in the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 increase layer by layer. This can ensure that there are sufficient amounts of light conversion materials in the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303. Since the first light conversion layer 301 is the thickest, the excitation light passes through the first light conversion layer 301 for the longest time, and the probability of the light conversion materials in the first light conversion layer 301 being excited is the highest, the probability of the light conversion materials in the second light conversion layer 302 being excited is the second highest, and the probability of the light conversion materials in the third light conversion layer 303 being excited is even lower. This further improves the excitation efficiency and light extraction efficiency of the light conversion layer. It can be seen that in this application, the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 are arranged in layers, and the wavelengths, thicknesses, and concentrations of the light conversion materials of the generated output light are set in gradients in the corresponding order, ensuring that the emission spectrum of the second light conversion layer 302 has the smallest overlap with the absorption spectrum of the first light conversion layer 301, and the emission spectrum of the third light conversion layer 303 also has the smallest overlap with the absorption spectrum of the second light conversion layer 302, improving the excitation efficiency and light extraction efficiency of the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303.

[0051] The first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 may each have only one type of light conversion material. For example, the light conversion material in the first light conversion layer 301 may be a red light conversion material, the light conversion material in the second light conversion layer 302 may be a yellow light conversion material, and the light conversion material in the third light conversion layer 303 may be a green light conversion material. After the red light conversion material in the first light conversion layer 301 receives the excitation light, it can quickly generate red light, supplement the long wavelength, ensure full conversion of the light conversion material, and avoid light efficiency loss at the same time; the yellow light conversion material in the second light conversion layer 302 generates yellow light after receiving the excitation light, which can adjust the main wavelength and balance the emission of the output light; the green light conversion material in the third light conversion layer 303 generates green light after receiving the excitation light, which can also avoid excessive scattering. The wavelength of red light is greater than that of yellow light, and the wavelength of yellow light is greater than that of green light, meeting the requirement that the closer to the substrate 100, the longer the wavelength of the output light generated by the light conversion layer. Moreover, the concentration of the red light conversion material in the first light conversion layer 301 is less than the concentration of the yellow light conversion material in the second light conversion layer 302, and the concentration of the yellow light conversion material in the second light conversion layer 302 is less than the concentration of the green light conversion material in the third light conversion layer 303, enabling the red light conversion material, the yellow light conversion material, and the green light conversion material to be more fully excited and improving the color rendering index of the LED lamp bead.

[0052] Furthermore, the LED chip 200 is a blue LED chip with a wavelength band of 450 nm to 470 nm. The excitation peak wavelength of the red light conversion material in the first light conversion layer 301 is 640 nm to 660 nm, the excitation peak wavelength of the yellow light conversion material in the second light conversion layer 302 is 550 nm to 570 nm, and the excitation peak wavelength of the green light conversion material in the third light conversion layer 303 is 530 nm to 550 nm. In this way, the overlap degree of the absorption spectra of adjacent two light conversion layers can be reduced, avoiding the mutual absorption of various colors of light, especially the absorption of the light emitted by the light conversion material with a shorter excitation wavelength (narrower absorption spectrum width) by the light conversion material with a longer excitation wavelength (wider absorption spectrum width), thereby greatly improving the utilization rate and luminous efficiency of the light conversion material.

[0053] It should be noted that the light conversion layer is not limited to having two or three layers, and may also have more than three layers. Each light conversion layer is not limited to having only one color of light conversion material, and may also have two or more colors of light conversion materials. However, it should be noted that no matter how many colors of light conversion materials there are in the light conversion, it is necessary to meet the requirements that the closer to the substrate 100 the light conversion layer is, the longer the wavelength of the output light generated, the greater the thickness, and the lower the concentration of the light conversion material therein.

[0054] Further, the light conversion layer in the present application can be formed by mixing a colloid and a light conversion material. The light conversion material can be quantum dots or phosphors, and the colloid can be a material such as silica gel. That is, the light conversion layer can be a quantum dot layer or a phosphor layer. Compared with the traditional white light solution that uses a layered dispensing method to simultaneously improve the color rendering index and luminous efficiency, the LED lamp beads in the present application can use quantum dots to replace phosphors, with easy process control, high yield, and being unaffected by high and low color temperatures, capable of simultaneously improving the light extraction efficiency, color rendering index, and reliability.

[0055] Please continue to refer to Figure 4 or Figure 5 , in some embodiments, there is also a transition layer between two adjacent light conversion layers. The transition layer contains the light conversion materials of all colors in the two adjacent light conversion layers, thereby reducing the light loss caused by interface reflection, further improving the light extraction efficiency of the LED lamp beads when the color rendering index is improved, and making the light output more uniform. For example, Figure 5 in [description], there is a first transition layer 401 between the first light conversion layer 301 and the second light conversion layer 302. The first transition layer 401 contains the light conversion materials of all colors in the first light conversion layer 301 and the second light conversion layer 302 (that is, red light conversion material and yellow light conversion material). There is a second transition layer 402 between the second light conversion layer 302 and the third light conversion layer 303. The second transition layer 402 contains the light conversion materials of all colors in the second light conversion layer 302 and the third light conversion layer 303 (that is, yellow light conversion material and green light conversion material).

[0056] Further, in two adjacent transition layers, the closer to the substrate 100, the greater the thickness of the transition layer and the lower the concentration of the light conversion material in the transition layer, thereby being able to improve the excitation efficiency of each transition layer and further improve the light extraction efficiency. For example, the first transition layer 401 and the second transition layer 402 are two adjacent transition layers, and the first transition layer 401 is closer to the substrate 100 than the second transition layer 402. The thickness of the first transition layer 401 should be greater than the thickness of the second transition layer 402, and the concentration of the light conversion material in the first transition layer 401 is greater than the concentration of the light conversion material in the second transition layer 402.

[0057] Further, the thickness of each transition layer is smaller than the thicknesses of the two adjacent light conversion layers, thereby being able to more effectively reduce interface reflection. For example, the thickness of the first transition layer 401 is smaller than the thicknesses of the first light conversion layer 301 and the second light conversion layer 302, and the thickness of the second transition layer 402 is smaller than the thicknesses of the second light conversion layer 302 and the third light conversion layer 303.

[0058] Since there can be at least two kinds of light conversion materials in both the light conversion layer and the transition layer, the concentration of the light conversion materials in the light conversion layer or the transition layer in this article refers to the total concentration of all the light conversion materials of all colors in the light conversion layer or the transition layer. Of course, for the case where there are at least two kinds of light conversion materials in the light conversion layer or the transition layer, the concentration of the light conversion material with a longer excitation wavelength in the same light conversion layer or the same transition layer can be greater.

[0059] Table 1 shows the comparison of the thickness and concentration (concentration of the light conversion material) of the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 provided in an embodiment of the present application, which are the same, and the thickness decreases while the concentration (concentration of the light conversion material) increases. It can be seen from Table 1 that when the thickness of the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 decreases and the concentration (concentration of the light conversion material) increases, the luminous flux is greater and the luminous efficiency is higher. Figure 6 Figure [not provided in the original] is a comparison diagram of the luminous flux of the three-layer light conversion layer when the thickness decreases and the concentration (concentration of the light conversion material) increases, and when the thickness and the concentration (concentration of the light conversion material) are the same. It can be seen from Figure 6 it that when the thickness and the concentration (concentration of the light conversion material) of the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 are the same, the luminous flux is 17.63 lm. When the thickness of the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 decreases and the concentration (concentration of the light conversion material) increases, the luminous flux is 18.68 lm, and the luminous flux increases by 5.95%. Figure 7 Figure [not provided in the original] is a comparison diagram of the light extraction efficiency of the three-layer light conversion layer when the thickness decreases and the concentration (concentration of the light conversion material) increases, and when the thickness and the concentration (concentration of the light conversion material) are the same. It can be seen from Figure 7 it that when the thickness and the concentration (concentration of the light conversion material) of the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 are the same, the light extraction efficiency is 95.75 lm / W. When the thickness of the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 decreases and the concentration (concentration of the light conversion material) increases, the light extraction efficiency is 101.09 lm, and the light extraction efficiency increases by 5.57%. It can be seen that by arranging the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 in layers, and setting the wavelength, thickness, and concentration of the generated output light in a gradient according to the corresponding order, the excitation efficiency of the first light conversion layer 301, the second light conversion layer 302, and the third light conversion layer 303 can be improved, and thus the light extraction efficiency can be improved.

[0060] Table 1: Comparison of the three-layer light conversion layer when the thickness decreases, the concentration increases, and the thickness and the concentration are the same

[0061]

[0062] Without doubt, the aforementioned LED lamp beads can be applied to various lighting fields. For example, they can be made into backlight modules for use in the display backlight field (which can be the backlight modules of terminals such as TVs, monitors, mobile phones, etc.). At this time, they can be applied to the backlight module. In addition to being applicable to the display backlight field, they can also be applied to the key backlight field, the shooting field, the household lighting field, the medical lighting field, the decoration field, the automotive field, the transportation field, etc. When applied to the key backlight field, they can be used as the key backlight light sources for devices with keys such as mobile phones, calculators, keyboards, etc.; when applied to the shooting field, they can be made into the flashlights of cameras; when applied to the household lighting field, they can be made into floor lamps, table lamps, lighting lamps, ceiling lamps, downlights, projection lamps, etc.; when applied to the medical lighting field, they can be made into surgical lamps, low-electromagnetic lighting lamps, etc.; when applied to the decoration field, they can be made into various decorative lamps, such as various colored lights, landscape lighting lamps, advertising lights; when applied to the automotive field, they can be made into automotive headlights, automotive indicator lights, etc.; when applied to the transportation field, they can be made into various traffic lights and can also be made into various street lamps. The above applications are only several applications exemplified in this embodiment. It should be understood that the applications of the LED lamp beads in this embodiment are not limited to the several fields exemplified above.

[0063] Based on this, some embodiments of the present application also provide an LED light source, and the LED light source includes at least one LED lamp bead. The LED lamp beads in the LED light source can be arranged in one row or multiple rows and can be used for direct-lit LED light sources, edge-lit LED light sources, etc.

[0064] Based on this, an embodiment of the present application provides a preparation method for an LED lamp bead. Figure 1 It is a schematic structural diagram corresponding to the corresponding steps of the preparation method for the LED lamp bead, as Figure 1 shown, the preparation method for the LED lamp bead includes:

[0065] Step S100: Provide a substrate 100;

[0066] Step S200: Fix the LED chip 200 on the substrate 100, and the LED chip 200 is used to generate excitation light;

[0067] Step S300: Form at least two light conversion layers, and the light conversion layers are stacked on the substrate 100 and the LED chip 200 in sequence. Each light conversion layer is used to receive the excitation light and generate corresponding output light;

[0068] Among them, in two adjacent light conversion layers, the closer to the substrate 100, the longer the wavelength of the output light generated by the light conversion layer, the greater the thickness of the light conversion layer, and the lower the concentration of the light conversion material in the light conversion layer.

[0069] Figures 2 to 5This is a schematic structural diagram corresponding to the respective steps of the method for manufacturing an LED lamp bead provided in an embodiment of the present application. Next, the method for manufacturing an LED lamp bead will be described in detail with reference to Figures 2 to 5 The method for manufacturing an LED lamp bead will be described in detail.

[0070] As Figure 2 and Figure 3 shown, perform step S100 to provide a substrate 100. The material of the substrate 100 can be selected from ceramic materials (including one or more of AlN, Al2O3, SiO, SiO2, Si3N4, and SiON) or metal materials (including aluminum or copper). A cup 101 is provided on the substrate 100. The cup 101 is annular and is disposed on the substrate 100. The material of the cup 101 can be selected from materials such as thermosetting epoxy resin, thermosetting silicone, or thermoplastic plastic. Electrical connectors such as plugs and pads can be provided in the substrate 100.

[0071] Please continue to refer to Figure 2 and Figure 3 shown, perform step S200 to fix the LED chip 200 on the substrate 100, and the LED chip 200 is located within the cup 101. The LED chip 200 can be attached to the substrate 100 using die bonding glue and then interconnected with the electrical connectors in the substrate 100 using leads. In some embodiments, the LED chip 200 can also be soldered to the substrate 100 in a flip-chip manner, so as to get rid of the constraints of leads and die bonding glue, enabling the LED chip 200 to have a high thermal conductivity, low thermal resistance, and can withstand high currents, with stronger reliability, higher luminous flux maintenance rate, and longer service life.

[0072] As Figure 4 or Figure 5 shown, perform step S300 to form at least two light conversion layers. The at least two light conversion layers are provided within the cup 101 and are stacked in sequence to jointly fill the space within the cup 101. The light conversion layers are formed layer by layer. For each formation of a light conversion layer, the corresponding light conversion layer's glue material can be extruded into the cup 101 and baked into shape.

[0073] In some embodiments, a transition layer is further formed between two adjacent light conversion layers, such that the transition layer is located between the two adjacent light conversion layers. Moreover, the transition layer contains light conversion materials of all colors in the two adjacent light conversion layers, thereby reducing the light loss caused by interface reflection, further improving the light extraction efficiency of the LED lamp bead when the color rendering index is improved, and making the light extraction more uniform. For example, after forming the first light conversion layer 301, a first transition layer 401 is formed on the first light conversion layer 301, and the first transition layer 401 contains light conversion materials of all colors in the first light conversion layer 301 and the second light conversion layer 302 (i.e., red light conversion materials and yellow light conversion materials); after forming the first transition layer 401, a second light conversion layer 302 is formed on the first transition layer 401; after forming the second light conversion layer 302, a second transition layer 402 is formed on the second light conversion layer 302, and the second transition layer 402 contains light conversion materials of all colors in the second light conversion layer 302 and the third light conversion layer 303 (i.e., yellow light conversion materials and green light conversion materials); after forming the second transition layer 402, a third light conversion layer 303 is formed on the second transition layer 402.

[0074] Furthermore, in two adjacent transition layers, the closer the transition layer is to the substrate 100, the greater the thickness of the transition layer and the lower the concentration of the light conversion materials in the transition layer, thereby improving the excitation efficiency of each transition layer and further improving the light extraction efficiency. For example, the first transition layer 401 and the second transition layer 402 are two adjacent transition layers, and the first transition layer 401 is closer to the substrate 100 than the second transition layer 402. The thickness of the first transition layer 401 should be greater than that of the second transition layer 402, and the concentration of the light conversion materials in the first transition layer 401 is greater than that in the second transition layer 402.

[0075] Furthermore, the thickness of each transition layer is less than the thicknesses of the two adjacent light conversion layers, thereby more effectively reducing interface reflection. For example, the thickness of the first transition layer 401 is less than the thicknesses of the first light conversion layer 301 and the second light conversion layer 302, and the thickness of the second transition layer 402 is less than the thicknesses of the second light conversion layer 302 and the third light conversion layer 303.

[0076] After all the light conversion layers and transition layers are formed, baking can be performed for a relatively long time to obtain the finished product of the LED lamp bead.

[0077] The quantum dots referred to in this application are zero-dimensional semiconductor nanocrystals. When their particle size is smaller than a certain size, they will emit light of a specific wavelength due to the size effect, thus generating unique differences. The properties of quantum dots are mainly determined by factors such as size, defects, impurities, crystallinity, and passivation methods. These factors will affect the quantum efficiency and emission wavelength of quantum dots. When quantum dots are excited by external energy, electrons jump from the ground state to the excited state, making the electrons and holes have higher energy. Then the electrons and holes can recombine and relax to a lower energy state, and finally return to the ground state. During the recombination and relaxation process, energy will be released in the form of radiation (photons) or non-radiation. The luminescence properties of quantum dots can be controlled by selecting appropriate materials and the size of the nanocrystals. When the excitation energy received by the quantum dots is higher than their energy gap and electrons jump to the energy band, the electrons in the conduction band and the holes in the valence band can recombine to emit light. This direct recombination is called band edge recombination, and here the unique property of the quantum confinement effect of quantum dots is also brought out. Therefore, quantum dots can adjust the energy gap by changing the particle size, and then change the wavelength of the emitted light. In optical applications, quantum dots of the same material with different particle sizes can be used to excite light of various wavelengths.

[0078] When there are defects in the crystal structure or on the surface of quantum dots, after the quantum dots receive excitation energy, the electrons and holes are captured by these defects and recombination occurs from these defects. At this time, the emission wavelength will shift. Therefore, the surface structure and existing defects of quantum dots have a crucial impact on the luminescence properties of quantum dots. An appropriate surface state is a necessary factor to promote high luminescence efficiency of quantum dots. The specific surface area of quantum dots is very large, and the electronic quantum state and surface state have a great impact on their optical properties. In the case of quantum dots with a high specific surface area, phenomena such as optical absorption, quantum efficiency, emission intensity, spectral position, and fluorescence excitation of quantum dots may be affected due to the high surface energy state density. To improve the surface energy state, surface passivation methods are generally used to improve the optical properties of quantum dots. A common way of surface passivation is to coat organic or inorganic compounds on the surface of quantum dots to completely passivate the unbonded structure on the surface of quantum dots, so that there is no surface energy state, thereby reducing the impact on the luminescence properties of quantum dots. Given that quantum dots can use a single material with different sizes to cooperate with energy excitation to emit light of various wavelengths, and have various excellent characteristics such as high quantum efficiency, controllable emission wavelength, narrow spectral half-width of the excitation light, and wide excitation light wavelength, using quantum dots to replace phosphors has great advantages, and this application can also effectively avoid the influence of the heat of the LED chip 200 on the service life of quantum dots.

[0079] In summary, this embodiment provides an LED lamp bead, a preparation method thereof, and an LED light source, including a substrate 100; an LED chip 200 located on the substrate 100 for generating excitation light; and at least two light conversion layers stacked on the substrate 100 and the LED chip 200 in sequence. Each light conversion layer is used to receive the excitation light and generate corresponding output light. Among them, in two adjacent light conversion layers, the closer to the substrate 100, the longer the wavelength of the output light generated by the light conversion layer, the greater the thickness of the light conversion layer, and the lower the concentration of the light conversion material in the light conversion layer. Since the longer the wavelength of the output light generated by the light conversion layer, the more difficult it is to be excited, the more difficult-to-excite light conversion layer is arranged closer to the substrate 100, so that the more difficult-to-excite light conversion layer can be excited first, which can improve the excitation efficiency of the light conversion layer as a whole, and then improve the light extraction efficiency; at the same time, the more difficult-to-excite light conversion layer has a greater thickness and a lower concentration of the light conversion material. Without changing the amount of the light conversion material in each light conversion layer, the longer the time for the excitation light to pass through the more difficult-to-excite light conversion layer, the higher the probability of the light conversion material being excited, which can further improve the excitation efficiency and light extraction efficiency of the light conversion layer.

[0080] It should be noted that the various embodiments in this specification are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0081] It should also be noted that although the present application has been disclosed above with preferred embodiments, the above embodiments are not intended to limit the present application. For any person skilled in the art, without departing from the scope of the technical solution of the present application, many possible changes and modifications can be made to the technical solution of the present application by using the technical content disclosed above, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application still belong to the scope of protection of the technical solution of the present application.

[0082] It should also be understood that unless otherwise specified or indicated, the terms "first", "second", "third", etc. in the specification are only used to distinguish the various components, elements, steps, etc. in the specification, rather than to represent the logical relationship or sequential relationship, etc. between the various components, elements, steps.

[0083] It should also be recognized that the terminology described herein is only used to describe particular embodiments and is not intended to limit the scope of the present application. It must be noted that the singular forms "a" and "an" used herein and in the appended claims include plural referents unless the context clearly dictates otherwise. For example, reference to "a step" or "a device" means reference to one or more steps or devices and may include sub-steps and sub-devices. All conjunctions used should be understood in their broadest sense. Also, the word "or" should be understood to have the definition of a logical "or" rather than a logical "exclusive or" definition unless the context clearly dictates otherwise. In addition, the implementation of the methods and / or devices in the embodiments of the present application may include performing selected tasks manually, automatically, or in combination.

Claims

1. An LED lamp bead, characterized in that, Comprising: a substrate (100); an LED chip (200) located on the substrate (100) for generating excitation light; at least two light conversion layers stacked in sequence on the substrate (100) and the LED chip (200), each light conversion layer being configured to receive the excitation light and generate corresponding output light; wherein, among two adjacent light conversion layers, the closer to the substrate (100), the longer the wavelength of the output light generated by the light conversion layer, the greater the thickness of the light conversion layer, and the lower the concentration of the light conversion material in the light conversion layer.

2. The LED lamp bead according to claim 1, wherein The light conversion layer includes: a first light conversion layer (301) located on the substrate (100) and the LED chip (200); a second light conversion layer (302) located on the first light conversion layer (301); the light conversion material in the first light conversion layer (301) is a red light conversion material, and the light conversion material in the second light conversion layer (302) is a green light conversion material, or the light conversion material in the first light conversion layer (301) is a red light conversion material, and the light conversion material in the second light conversion layer (302) is a yellow light conversion material, or the light conversion material in the first light conversion layer (301) is a yellow light conversion material, and the light conversion material in the second light conversion layer (302) is a green light conversion material.

3. The LED lamp bead according to claim 1, characterized in that, The light conversion layer includes: a first light conversion layer (301) located on the substrate (100) and the LED chip (200); a second light conversion layer (302) located on the first light conversion layer (301); a third light conversion layer (303) located on the second light conversion layer (302); the light conversion material in the first light conversion layer (301) is a red light conversion material, the light conversion material in the second light conversion layer (302) is a yellow light conversion material, and the light conversion material in the third light conversion layer (303) is a green light conversion material.

4. The LED lamp bead according to claim 3, characterized in that, The LED chip (200) is a blue LED chip with a wavelength band of 450 nm to 470 nm, the excitation peak wavelength of the red light conversion material in the first light conversion layer (301) is 640 nm to 660 nm, the excitation peak wavelength of the yellow light conversion material in the second light conversion layer (302) is 550 nm to 570 nm, and the excitation peak wavelength of the green light conversion material in the third light conversion layer (303) is 530 nm to 550 nm.

5. The LED lamp bead according to any one of claims 1 to 4, characterized in that, There is also a transition layer between two adjacent light conversion layers, and the transition layer contains light conversion materials of all colors in the two adjacent light conversion layers.

6. The LED lamp bead according to claim 5, wherein Among two adjacent transition layers, the closer to the substrate (100), the greater the thickness of the transition layer, and the lower the concentration of the light conversion material in the transition layer; and / or, the thickness of each transition layer is less than the thicknesses of the two adjacent light conversion layers.

7. A method for preparing an LED lamp bead, characterized in that, Comprising: providing a substrate (100); die-bonding an LED chip (200) on the substrate (100), the LED chip (200) being used for generating excitation light; Form at least two light conversion layers, which are stacked on the substrate (100) and the LED chip (200) in sequence, and each light conversion layer is configured to receive the excitation light and generate corresponding output light; Among them, in two adjacent light conversion layers, the closer to the substrate (100), the longer the wavelength of the output light generated by the light conversion layer, the greater the thickness of the light conversion layer, and the lower the concentration of the light conversion material in the light conversion layer.

8. The preparation method of the LED lamp bead according to claim 7, wherein, A transition layer is formed between two adjacent light conversion layers, and the transition layer contains light conversion materials of all colors in two adjacent light conversion layers.

9. The preparation method of the LED lamp bead according to claim 8, characterized in that, Among two adjacent transition layers, the closer to the substrate (100), the greater the thickness of the transition layer, and the lower the concentration of the light conversion material in the transition layer; and / or, the thickness of each transition layer is less than the thicknesses of its two adjacent light conversion layers.

10. An LED light source, characterized in that, Comprise at least one LED lamp bead according to any one of claims 1 to 6.

Images