An LED light source with a high color rendering index

Abstract

The present invention relates to the technical field of LEDs. The present invention discloses an LED light source with a high color rendering index. By adding a compound capable of absorbing yellow-green visible light to the light-emitting formulation and matching the white light emitted by a blue light chip, the color rendering index of the LED lamp is improved. The compound for absorbing yellow-green visible light is preferably cobalt phosphate or lithium cobalt phosphate. By adding a relatively small mass ratio of cobalt phosphate or lithium cobalt phosphate, the effect of improving the color rendering index of the LED lamp can be achieved. The formulation is simple, and the materials are simple and easily available, solving the problems in the prior art that the formulation is complicated and the cost is relatively high due to the need to increase the types of phosphors or use long-wave nitrogen oxide red phosphors to improve the color rendering index.

Description

Technical Field

[0001] The invention relates to the technical field of LEDs, and in particular to an LED light source with a high color rendering index. Background Art

[0002] The color of an object is revealed after being exposed to light. The color of an object under the illumination of a light source will be different due to the different spectral distribution of the light source. For example, a red object observed under a daylight fluorescent lamp will become a maroon color when observed under a low-pressure sodium lamp. The color difference caused by the different spectral distribution of the light source reflects the difference in the color rendering performance of the light source. The color rendering index refers to the degree of various color content in the light emitted by the light source. The standard definition is a parameter that represents the degree to which the psychological sensory color produced by an object illuminated by a certain light source is consistent with the psychological color of the object under the illumination of a standard light source, which represents the color rendering ability of the light source for the object. In general, the higher the color rendering index of a light source, the more accurately it can express the original color of the substance, and the color seen by the human eye is closer to the natural primary color.

[0003] White light emitting diodes are known as the new generation of green lighting sources due to their small size, low power consumption, long life and environmental protection. 3+ The LEDs that use yellow phosphor to synthesize white light lack red light components in their emission spectrum, and their color rendering is poor, which seriously restricts their development in the lighting field. At present, the mainstream LED lighting products on the market are yellow-green phosphors and red phosphors combined with blue light chips to emit white light with a general color rendering index Ra of 80.

[0004] In order to meet the requirements of white light LEDs for high color rendering lighting, a Chinese patent with application publication number CN109423095A and application publication date March 5, 2019 provides a coating for improving the color rendering index of LED lamps, using red light phosphors, secondary excitation, to achieve red light emission from the coating. In addition, people have developed a method for near-ultraviolet excitation of red, green, and blue primary color phosphors, but this method is relatively complicated in the preparation process. At present, in order to obtain white light with a color rendering index Ra of 90, the method usually adopted is to use 530-537nm YAG green phosphors in the 530-537nm band and nitrogen oxide red phosphors in the 630-650nm band to match blue light chips to obtain white light, but the greater the proportion of long-wave red phosphors, the more types of phosphors increase, and the production cost will increase greatly.

[0005] As a new generation of green lighting source, light-emitting diodes require more methods or technologies to improve their color rendering index in order to meet people's daily needs to the greatest extent. Summary of the invention

[0006] In order to improve the color rendering index of white light-emitting diodes and further solve the technical problem of greatly increasing the types of phosphors required to obtain white light with a color rendering index Ra of 90 by matching a blue light chip with a YAG green phosphor in the 530-537 nm band and a red phosphor of a long-waveband 630-650 nm nitride oxide, the present invention provides a method for improving the color rendering index of an LED light source.

[0007] The specific technical solution of the present invention is as follows:

[0008] An LED light source with a high color rendering index, comprising a substrate, a blue light chip, and a fluorescent layer. The fluorescent layer and the blue light chip are disposed on the substrate. The material of the fluorescent layer includes a green phosphor, a red phosphor, and a compound capable of absorbing yellowish-green visible light. The fluorescent layer matches the blue light chip to emit white light with a color rendering index Ra of 90-96. The compound is preferably cobalt phosphate and / or lithium cobalt phosphate.

[0009] Since a high color rendering index Ra requires an average distribution of the white light spectrum in the visible light region, the light source of the present invention adds a compound capable of absorbing yellowish-green visible light to the green phosphor and the red phosphor in the original light-emitting formulation, so that the relative distribution of the emitted white light spectrum in the visible light region is more average, playing a role in improving the color rendering index.

[0010] In this way, by adding a compound that absorbs yellowish-green visible light to the original formulation to improve the color rendering index of the LED lamp, it avoids improving the color rendering index by using a long-waveband red phosphor in the prior art. At the same time, the present invention only adds a compound, and the light-emitting formulation materials are simple and easy to obtain, and it also solves the problem of increasing the types of phosphors required to improve the color rendering index in the prior art.

[0011] Specifically, the fluorescent layer includes a YAG green phosphor in the 530-537 nm band, a nitride oxide red fluorescence in the 620-630 nm band, silica gel, and a compound capable of absorbing yellowish-green visible light.

[0012] The fluorescent layer is a combination of a 530-537 nm YAG green phosphor, a 620-630 nm nitride oxide red phosphor, and silica gel, and then matches the blue light chip. At this time, white light with a color rendering index Ra of 78-86 can be emitted. After adding a compound capable of absorbing yellowish-green visible light to the light-emitting formulation, the color rendering index Ra of the emitted white light can reach 90-96.

[0013] Further preferably, the mass ratio of the green phosphor in the fluorescent layer is 15% - 35%, the mass ratio of the red phosphor in the fluorescent layer is 1% - 5%, and the mass ratio of the compound capable of absorbing yellowish-green visible light in the fluorescent layer is 0.1% - 0.6%. The relatively small mass ratio of the compound capable of absorbing yellowish-green visible light not only plays a role in improving the color rendering index of the LED light source but also has a simple material ratio.

[0014] Specifically, the method of adding the compound capable of absorbing yellowish-green visible light during the encapsulation of the LED lamp can be to mix it with the green phosphor, red phosphor, and silica gel first and then dispense the glue, or it can be to dispense it on the surface of the base layer after the green phosphor, red phosphor, and silica gel are mixed and dispensed to form the base layer of the fluorescent layer. Therefore, the fluorescent layer can have the following structures: one is a single-layer structure containing the green phosphor, red phosphor, the compound capable of absorbing yellowish-green visible light, and silica gel; the other is a double-layer structure including a base layer and a surface layer. The base layer contains the green phosphor, red phosphor, and silica gel, and the surface layer contains the compound capable of absorbing yellowish-green visible light and silica gel. The applicant has also verified through experiments that when the fluorescent layer is a double-layer structure, it has a better effect of improving the color rendering index.

[0015] Preferably, specifically, the blue light chip is fixedly soldered on the substrate, and the number of blue light chips is preferably multiple.

[0016] Further, the number of blue light chips is further preferably 20 - 30, and the blue light chips are connected in series.

[0017] Compared with the prior art, the present invention has the following technical effects:

[0018] (1) By adding a compound capable of absorbing yellowish-green visible light to the phosphor and matching it with the white light emitted by the blue light chip, the present invention can greatly improve the color rendering index of the emitted white light.

[0019] (2) The present invention adds a substance with a relatively small mass ratio, has a simple formula, and its materials are simple and easy to obtain, solving the problem in the prior art that it is necessary to increase the types of phosphors to improve the color rendering index.

[0020] (3) In the prior art, to obtain an LED lamp with a color rendering index Ra of more than 90, it is often necessary to use long-wavelength nitrogen oxide red phosphors, which increases the cost of the LED lamp. However, the present invention can obtain an LED lamp with a color rendering index Ra of more than 90 by adding a very small amount of cobalt phosphate or lithium cobalt phosphate, and does not require the use of long-wavelength nitrogen oxide red phosphors, with a relatively low manufacturing cost.

[0021] Description of the Drawings

[0022] Figure 1 is a schematic cross-sectional structure diagram of a light source of the present invention;

[0023] Figure 2 It is another schematic cross-sectional structure diagram of the light source of the present invention;

[0024] Figure 3 It is a relative spectral comparison diagram of the light sources of Example 1 and Comparative Example 1;

[0025] Figure 4 It is an absorption spectrum diagram of lithium cobalt phosphate.

[0026] The reference numerals in the drawings are: substrate 1, green phosphor 2, red phosphor 3, lithium cobalt phosphate 4, blue light chip 5, cobalt phosphate 6, fluorescent layer 7, base layer 8, surface layer 9. Detailed implementation manners

[0027] The present invention will be further described below in conjunction with embodiments.

[0028] General embodiment

[0029] An LED light source with a high color rendering index, comprising a substrate 1, a blue light chip 5 and a fluorescent layer 7. The fluorescent layer 7 and the blue light chip 5 are arranged on the substrate 1. The material of the fluorescent layer 7 includes a green phosphor 2, a red phosphor 3, a compound capable of absorbing yellowish-green visible light, and silica gel. The compound is cobalt phosphate and / or lithium cobalt phosphate. The fluorescent layer matches the blue light chip 5 to emit white light, and the color rendering index Ra of the white light is 90-96.

[0030] The green phosphor 2 is a YAG green phosphor in the 530-537 nm band, and the red phosphor 3 is a nitride red phosphor in the 620-630 nm band.

[0031] The mass ratio of the green phosphor 2 in the fluorescent layer is 15% - 35%, the mass ratio of the red phosphor 3 in the fluorescent layer is 1% - 5%, and the mass ratio of the compound in the fluorescent layer is 0.1% - 0.6%.

[0032] The fluorescent layer 7 can be a single-layer structure, and this single-layer structure contains a green phosphor 2, a red phosphor 3, a compound capable of absorbing yellowish-green visible light, and silica gel.

[0033] The fluorescent layer 7 can also be a double-layer structure, including a base layer 8 and a surface layer 9. The surface layer 9 is arranged on the outer surface of the base layer 8. The base layer contains a green phosphor 2, a red phosphor 3 and silica gel, and the surface layer contains a compound capable of absorbing yellowish-green visible light and silica gel.

[0034] The number of blue light chips is multiple, 20 - 30, and the blue light chips (5) are connected in series.

[0035] Example 1

[0036] An LED light source with a high color rendering index, such asFigure 1 As shown in the figure, it includes a substrate 1, a blue light chip 5 and a fluorescent layer 7. The fluorescent layer 7 and the blue light chip 5 are disposed on the substrate 1. The fluorescent layer 7 is a single-layer structure, and the single-layer structure contains 25% of YAG green fluorescent powder with a wavelength of 536 nm, 2% of oxynitride red fluorescent powder with a wavelength of 630 nm, 0.3% of lithium cobalt phosphate 4 powder, and 72.7% of silica gel. (The above percentages are the mass percentages of each substance in the fluorescent layer.)

[0037] The size of the substrate 1 is 50×15 mm, the size of the blue light chip 5 is 09×18 mil, the number of blue light chips 5 is 25, and the blue light chips 5 are fixedly soldered to the substrate 1 in series.

[0038] The fluorescent layer 7 matches the blue light chip 5 to emit white light.

[0039] Example 2

[0040] An LED light source with a high color rendering index includes a substrate 1, a blue light chip 5 and a fluorescent layer 7. The fluorescent layer 7 and the blue light chip 5 are disposed on the substrate 1. The fluorescent layer 7 is a single-layer structure, and the single-layer structure contains 15% of YAG green fluorescent powder with a wavelength of 530 nm, 1% of oxynitride red fluorescent powder with a wavelength of 620 nm, 0.05% of cobalt phosphate powder, 0.05% of lithium cobalt phosphate powder, and 83.9% of silica gel. (The above percentages are the mass percentages of each substance in the fluorescent layer.)

[0041] The size of the substrate 1 is 50×15 mm, the size of the blue light chip 5 is 09×18 mil, the number of blue light chips 5 is 20, and the blue light chips 5 are fixedly soldered to the substrate 1 in series.

[0042] The fluorescent layer 7 matches the blue light chip 5 to emit white light.

[0043] Example 3

[0044] An LED light source with a high color rendering index, as Figure 2 shown in the figure, includes a substrate 1, a blue light chip 5 and a fluorescent layer 7. The fluorescent layer 7 and the blue light chip 5 are disposed on the substrate 1. The fluorescent layer 7 is a double-layer structure, and the double-layer structure includes a base layer 8 and a surface layer 9. The base layer 8 contains 35% of YAG green fluorescent powder with a wavelength of 534 nm, 5% of oxynitride red fluorescent powder with a wavelength of 630 nm, and 53.4% of silica gel. The surface layer 9 contains 0.6% of cobalt phosphate 6 powder and 6% of silica gel. (The above percentages are the mass percentages of each substance in the fluorescent layer.)

[0045] The size of the substrate 1 is 50×15 mm, the size of the blue light chip 5 is 09×18 mil, the number of blue light chips 5 is 30, and the blue light chips 5 are fixedly soldered to the substrate 1 in series.

[0046] The fluorescent layer 7 matches the blue light chip 5 to emit white light.

[0047] Example 4

[0048] An LED light source with a high color rendering index, as Figure 2 shown, includes a substrate 1, a blue light chip 5 and a fluorescent layer 7. The fluorescent layer 7 and the blue light chip 5 are disposed on the substrate 1. The fluorescent layer 7 is a double-layer structure, and the double-layer structure includes a base layer 8 and a surface layer 9. The base layer 8 contains 35% of YAG green fluorescent powder with a wavelength of 536 nm, 5% of oxynitride red fluorescent powder with a wavelength of 630 nm, and 57.4% of silica gel. The surface layer 9 contains 0.6% of cobalt phosphate 6 powder and 2% of silica gel. (The above percentages are the mass percentages of each substance in the fluorescent layer.)

[0049] The substrate 1 has a size of 50×15 mm, the blue light chip 5 has a size of 09×18 mil, the number of blue light chips 5 is 30, and the blue light chips 5 are fixedly welded to the substrate 1 in series.

[0050] The fluorescent layer 7 matches the blue light chip 5 to emit white light.

[0051] Comparative Example 1 (The difference from Example 1 is that: the fluorescent layer composition does not contain lithium cobalt phosphate.)

[0052] An LED light source includes a substrate 1, a blue light chip 5 and a fluorescent layer 7. The fluorescent layer 7 and the blue light chip 5 are disposed on the substrate 1. The fluorescent layer 7 is a single-layer structure, and the single-layer structure contains 25% of YAG green fluorescent powder with a wavelength of 536 nm, 2% of oxynitride red fluorescent powder with a wavelength of 630 nm, and 73% of silica gel. (The above percentages are the mass percentages of each substance in the fluorescent layer.) The substrate 1 has a size of 50×15 mm, the blue light chip 5 has a size of 09×18 mil, the number of blue light chips 5 is 25, and the blue light chips 5 are fixedly welded to the substrate 1 in series.

[0053] The fluorescent layer 7 matches the blue light chip 5 to emit white light.

[0054] Comparative Example 2 (The difference from Example 1 is that: the content of lithium cobalt phosphate in the fluorescent layer composition is less than that in Example 1.) An LED light source includes a substrate 1, a blue light chip 5 and a fluorescent layer 7. The fluorescent layer 7 and the blue light chip 5 are disposed on the substrate 1. The fluorescent layer 7 is a single-layer structure, and the single-layer structure contains 25% of YAG green fluorescent powder with a wavelength of 536 nm, 2% of oxynitride red fluorescent powder with a wavelength of 630 nm, 0.09% of lithium cobalt phosphate powder, and 72.91% of silica gel. (The above percentages are the mass percentages of each substance in the fluorescent layer.)

[0055] The substrate 1 has a size of 50×15 mm, the blue light chip 5 has a size of 09×18 mil, the number of blue light chips 5 is 25, and the blue light chips 5 are fixedly welded to the substrate 1 in series.

[0056] The fluorescent layer 7 matches the blue light chip 5 to emit white light.

[0057] Comparative Example 3 (different from Example 1 in that: the content of lithium cobalt phosphate in the fluorescent layer composition is more than that in Example 1). An LED light source includes a substrate 1, a blue light chip 5, and a fluorescent layer 7. The fluorescent layer 7 and the blue light chip 5 are disposed on the substrate 1. The fluorescent layer 7 is a single-layer structure, and the single-layer structure contains 25% of YAG green fluorescent powder with a wavelength of 536 nm, 2% of nitride red fluorescent powder with a wavelength of 630 nm, 0.61% of lithium cobalt phosphate powder, and 72.39% of silica gel. (The above percentages are the mass percentages of each substance in the fluorescent layer.)

[0058] The size of the substrate 1 is 50×15 mm, the size of the blue light chip 5 is 09×18 mil, the number of blue light chips 5 is 25, and the blue light chips 5 are fixedly soldered to the substrate 1 in series.

[0059] The fluorescent layer 7 matches the blue light chip 5 to emit white light.

[0060] Comparative Example 4 (different from Example 4 in that: the fluorescent layer is a single-layer structure).

[0061] An LED light source includes a substrate 1, a blue light chip 5, and a fluorescent layer 7. The fluorescent layer 7 and the blue light chip 5 are disposed on the substrate 1. The fluorescent layer 7 is a single-layer structure, and the single-layer structure contains 35% of YAG green fluorescent powder with a wavelength of 536 nm, 5% of nitride red fluorescent powder with a wavelength of 630 nm, 0.6% of lithium cobalt phosphate powder, and 59.4% of silica gel. (The above percentages are the mass percentages of each substance in the fluorescent layer.)

[0062] The size of the substrate 1 is 50×15 mm, the size of the blue light chip 5 is 09×18 mil, the number of blue light chips 5 is 25, and the blue light chips 5 are fixedly soldered to the substrate 1 in series.

[0063] The fluorescent layer 7 matches the blue light chip 5 to emit white light.

[0064] Performance Test

[0065] The LED light sources obtained in Examples 1 to 3 and Comparative Example 1 were subjected to performance tests under the same conditions, and the obtained optoelectronic parameters are shown in Table 1.

[0066] Table 1

[0067] Φ(lm) Luminous efficacy (lm / W) x y Tc (K) Ra Example 1 249.8 158.5 0.455 0.412 2769 91.2 Example 2 248.0 158.8 0.456 0.412 2768 90.9 Example 3 245.1 157.5 0.455 0.411 2763 96.0 Example 4 245.9 159.4 0.455 0.412 2764 95.9 Comparative Example 1 269.7 176.5 0.458 0.411 2736 84.2 Comparative Example 2 258.9 164.3 0.456 0.411 2736 86.7 Comparative Example 3 238.2 151.0 0.456 0.402 2688 90.3 Comparative Example 4 245.2 159.1 0.456 0.412 2763 90.1

[0068] Data Analysis and Conclusion:

[0069] (1) Compared with Comparative Example 1, the color rendering index Ra of the LED light source in Example 1 has increased significantly. The difference in the production of the LED light sources in Example 1 and Comparative Example 1 lies in that only lithium cobalt phosphate powder with a mass ratio of 0.1% is added in Example 1, indicating that the addition of lithium cobalt phosphate powder helps to improve the color rendering index of the LED light source. To further verify the principle of improving the color rendering index of the LED light source, as Figure 3 shown in the relative spectral comparison diagram of the light sources in Example 1 and Comparative Example 1, it is found that the intensity of the yellow-green visible light wavelength band of the light source in Example 1 is stronger than that in Comparative Example 1. As Figure 4 shown, the absorption spectrum of lithium cobalt phosphate shows that it has an obvious absorption intensity at the yellow-green visible light wavelength band, indicating that after adding lithium cobalt phosphate, lithium cobalt phosphate absorbs the yellow-green visible light, making the relative distribution of the white light spectrum emitted by the LED lamp in the visible light region more uniform, thus playing a role in improving the color rendering index.

[0070] (2) Compared with Example 1, as shown in the optoelectronic parameters of Comparative Example 2, when the content of lithium cobalt phosphate in the phosphor layer is less than 0.1%, the color rendering index of the white light emitted by the LED lamp is only 86.7. Therefore, the added content of lithium cobalt phosphate should not be less than 0.1%; as shown in the optoelectronic parameters of Comparative Example 3, when the content of lithium cobalt phosphate in the phosphor layer is 0.61%, although the color rendering index of the white light emitted by the LED lamp is 90.3 and the color rendering index has increased, the luminous flux and luminous efficiency have decreased significantly. Therefore, the added content of lithium cobalt phosphate should be less than 0.61%.

[0071] (3) Compared with Example 4, the color rendering index of Comparative Example 4 is higher. The difference between the light sources in Comparative Example 4 and Example 4 lies in the structure of the phosphor layer. Therefore, it shows that when the phosphor layer is a double-layer structure, that is, when lithium cobalt phosphate powder is arranged on the surface of the phosphor powder, it has a better effect on improving the color rendering index.

[0072] The raw materials and equipment used in the present invention are all common raw materials and equipment in the field without special instructions; the methods used in the present invention are all conventional methods in the field without special instructions.

[0073] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. An LED light source with a high color rendering index, comprising a substrate (1), a blue light chip (5) and a fluorescent layer (7), wherein the fluorescent layer (7) and the blue light chip (5) are disposed on the substrate (1). Characterized in that: The material of the fluorescent layer (7) includes green phosphor (2), red phosphor (3), a compound capable of absorbing yellowish-green visible light, and silica gel; the compound is cobalt phosphate and / or lithium cobalt phosphate; the fluorescent layer matches the blue light chip (5) to emit white light. The color rendering index Ra of the white light is 90 - 96.

2. An LED light source with a high color rendering index according to claim 1, Characterized in that: The green phosphor is a YAG green phosphor in the 530 - 537 nm band, and the red phosphor is a nitride red phosphor in the 620 - 630 nm band.

3. An LED light source with a high color rendering index according to claim 1 or 2, Characterized in that: The mass proportion of the green phosphor (2) in the fluorescent layer is 15% - 35%, The mass proportion of the red phosphor (3) in the fluorescent layer is 1% - 5%, The mass proportion of the compound in the fluorescent layer is 0.1% - 0.6%.

4. An LED light source with a high color rendering index according to claim 1, Characterized in that: The fluorescent layer (7) is a single-layer structure, and the single-layer structure includes green phosphor (2), red phosphor (3), a compound capable of absorbing yellowish-green visible light, and silica gel.

5. An LED light source with a high color rendering index according to claim 1, Characterized in that: The fluorescent layer (7) is a double-layer structure, and the double-layer structure includes a base layer (8) and a surface layer (9). The surface layer (9) is disposed on the outer surface of the base layer (8). The base layer includes green phosphor (2), red phosphor (3) and silica gel, and the surface layer includes a compound capable of absorbing yellowish-green visible light and silica gel.

6. An LED light source with a high color rendering index according to claim 5, Characterized in that: The mass percentages of the materials of the base layer (8) in the fluorescent layer are respectively: 15% - 35% for green phosphor, 1% - 5% for red phosphor, and 53.4% - 59.4% for silica gel.

7. An LED light source with a high color rendering index according to claim 5, Characterized in that: The mass percentages of the materials of the surface layer (9) in the fluorescent layer are respectively: 0.1% - 0.6% for the compound capable of absorbing yellowish-green visible light, and 2 - 6% for silica gel.

8. An LED light source with a high color rendering index according to claim 1, Characterized in that: The number of the blue light chips is multiple.

9. An LED light source with a high color rendering index according to claim 8, Characterized in that: The number of the blue light chips (5) is 20 - 30.

10. An LED light source with a high color rendering index according to claim 1, Characterized in that: The blue light chips (5) are connected in series.

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