Ultraviolet-excited solar spectrum-like white light LED and preparation method thereof

Abstract

The invention provides an ultraviolet-excited solar spectrum-like white light LED. The ultraviolet-excited solar spectrum-like white light LED comprises a conductive and heat-conducting substrate, a soldering tin layer, an ultraviolet LED chip and a wide-spectrum fluorescent powder glue layer which are arranged in sequence, the electric conduction and heat conduction substrate is fixedly connected with the ultraviolet LED chip through the soldering tin layer, and the ultraviolet LED chip is directly coated with the wide-spectrum fluorescent powder glue layer. The wavelength range of the ultraviolet LED chip is between 300 nm and 390 nm; the wide-spectrum fluorescent powder glue layer comprises wide-spectrum blue-light fluorescent powder and wide-spectrum orange-red-light fluorescent powder with optimized luminous intensity, and the mass ratio of the wide-spectrum blue-light fluorescent powder to the wide-spectrum orange-red-light fluorescent powder ranges from 1.2 to 2. According to the invention, through ultraviolet LED excitation, two wide-spectrum fluorescent materials of blue and orange red are used to prepare the solar spectrum-like white light LED.

Description

Technical Field

[0001] The invention belongs to the technical field of white light LED preparation, and in particular relates to an ultraviolet excited solar spectrum-like white light LED and a preparation method thereof. Background Art

[0002] The widely used white light LED is realized by the combination of blue LED + yellow phosphor. Compared with traditional incandescent lamps and other light sources, it has higher luminous efficiency and can provide sufficient brightness at lower power to achieve energy saving effect. In addition, the large-scale mass production of blue LED chips and the increasingly mature production technology of yellow phosphors have made the white light solution based on blue LED chips + yellow phosphors have great cost advantages and can be promoted on a large scale. However, this solution also has some disadvantages: there is a strong harmful blue light in the 400-445nm band on the high-energy side of the blue light emission peak of the blue LED. Long-term exposure to high-energy short-wave blue light will increase the probability of cell damage in the macular area and cause macular degeneration. At the same time, it will also inhibit the secretion of melatonin and affect the circadian rhythm of the human body. In addition, the white light obtained by this solution is composed of blue light and yellow light, lacking light components of other wavelengths, resulting in the inability to restore the true color of specific colors such as red objects when irradiated, that is, the spectral energy distribution deviates seriously from the standard solar spectrum, resulting in poor color restoration ability.

[0003] The energy distribution of solar spectrum LEDs is targeted at sunlight, which can effectively avoid strong high-energy short-wave blue light and enhance color reproduction capabilities. Currently, there are two methods for manufacturing phosphor-converted solar spectrum white light LEDs:

[0004] 1. Blue light LED + three or more phosphors such as green, cyan and red; However, when using blue light LED as the excitation source, there is also the problem of blue light spillover.

[0005] 2. Ultraviolet LED + three or more phosphors such as blue, green and red. Although ultraviolet-excited white light LEDs avoid blue light excitation and have better phosphor selectivity, and can show better spectral continuity and color rendering, the choice of ultraviolet LED excitation usually requires three or more phosphors: on the one hand, the spectrum of the phosphors used is relatively narrow (small half-width), and on the other hand, it increases manufacturing costs and the probability of color drift. In addition, thickness control is also a process issue that requires special attention, especially for ultraviolet-excited white light LEDs. Thin thickness will cause ultraviolet light to overflow and harm human health, and thicker thickness will reduce the light output efficiency of white light LEDs, so it needs to be improved. Summary of the invention

[0006] The object of the present invention is to provide an ultraviolet-excited solar-spectrum white light LED and a preparation method thereof, wherein the solar-spectrum white light LED is prepared by using two broad-spectrum fluorescent materials, blue and orange-red, through ultraviolet LED excitation.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A UV-excited solar spectrum-like white light LED comprises a conductive and thermally conductive substrate, a solder layer, a UV LED chip and a wide-spectrum phosphor adhesive layer which are arranged in sequence; the conductive and thermally conductive substrate is fixedly connected to the UV LED chip through the solder layer, and the wide-spectrum phosphor adhesive layer is directly coated on the UV LED chip;

[0009] The wavelength range of the ultraviolet LED chip is between 300-390nm;

[0010] The wide-spectrum phosphor glue layer includes wide-spectrum blue light phosphor and wide-spectrum orange-red light phosphor with optimized luminous intensity, and the mass ratio of the wide-spectrum blue light phosphor to the wide-spectrum orange-red light phosphor is in the range of 1.2-2.

[0011] In the above description, the conductive and thermally conductive substrate is a copper substrate, which can provide electrical connection for the ultraviolet LED chip so that it can be powered on and lit, and can also provide an efficient heat dissipation channel for the heat generated during the power-on and lighting process of the ultraviolet LED chip. The function of the solder layer is to conveniently and quickly achieve mechanical fixation, electrical connection, and heat transfer between the conductive and thermally conductive copper substrate and the ultraviolet LED chip by soldering. Preferably, the wavelength of the ultraviolet LED chip is 330nm, which can achieve maximum excitation of the wide-spectrum phosphor glue layer.

[0012] In the above description, the wide-spectrum blue phosphor is used to provide a blue emission component in white light, and the wide-spectrum orange-red phosphor is used to provide an orange-red emission component.

[0013] Furthermore, the wide-spectrum phosphor glue layer also includes ultraviolet curing glue, and the wide-spectrum blue phosphor and the wide-spectrum orange-red phosphor are both dispersed in the ultraviolet curing glue to form a wide-spectrum phosphor glue;

[0014] The luminescent center wavelength of the wide-spectrum blue phosphor is 470nm;

[0015] The luminescent center wavelength of the wide-spectrum orange-red phosphor is 625 nm.

[0016] Furthermore, the mass concentration range of the broad spectrum phosphor in the UV curing adhesive is 0.1-10 g / mL;

[0017] The wide-spectrum phosphor consists of wide-spectrum blue light phosphor and wide-spectrum orange-red light phosphor.

[0018] Furthermore, the mass concentration of the broad spectrum phosphor in the UV curing adhesive is 1.3 g / mL;

[0019] The mass ratio of the wide-spectrum blue phosphor to the wide-spectrum orange-red phosphor is 1.67: 1. Under this ratio, a good simulation of the standard solar spectrum can be achieved.

[0020] Furthermore, the half-widths of the wide-spectrum blue phosphor and the wide-spectrum orange-red phosphor are both at least greater than 90 nm.

[0021] Furthermore, the chemical formula of the wide-spectrum blue light phosphor is: [N(CH3CH2)4]2[Cu2Br4], and its half-width is 95nm; it has a fluorescence quantum yield of up to 98.9%.

[0022] The chemical formula of the wide-spectrum orange-red phosphor is [N(C3H7)4]2[Cu4Br6], its half-width is 161nm, and its fluorescence quantum yield is also close to perfect at 99.2%.

[0023] Furthermore, the thickness of the wide-spectrum phosphor glue layer is preferably such that there is no residual ultraviolet emission peak in the emission spectrum of the white light LED to avoid ultraviolet light spillover.

[0024] Furthermore, the general color rendering index R of the white light LED is a =91, red color rendering index R9 =86, extended color rendering index R e =90.

[0025] The present invention uses an ultraviolet LED chip to excite a wide-spectrum phosphor glue layer, wherein the wide-spectrum blue light phosphor emits blue light under ultraviolet excitation, and the wide-spectrum orange-red light phosphor emits orange-red light. The two colors of light can obtain white light under specific conditions (when the light intensity ratio is appropriate). In addition, since the two phosphors have a large half-height width, the spectrum of the obtained white light is close to the standard solar spectrum (i.e., a quasi-solar spectrum). Figure 2 As shown, its general color rendering index R a =91, red color rendering index R9 =86, extended color rendering index R e =90, effectively improving the color rendering index of white light LED and increasing its ability to restore the color of objects.

[0026] A method for preparing a UV-excited solar spectrum-like white light LED comprises the following steps:

[0027] S1. Fixing the UV LED chip on the conductive and thermally conductive substrate by soldering;

[0028] S2, applying the broad spectrum phosphor glue on the light emitting surface of the UV LED chip, and curing it by ultraviolet irradiation for at least 15 seconds to obtain a broad spectrum phosphor glue layer, and then obtaining a white light LED;

[0029] S3, conducting a power-on test on the white light LED in step S2 to detect whether there is any residual ultraviolet emission peak in the emission spectrum of the white light LED. If there is any residual ultraviolet emission peak, a wide-spectrum phosphor glue layer is re-coated and thickened until there is no residual ultraviolet emission peak in the emission spectrum of the white light LED.

[0030] In the present invention, the wide-spectrum phosphor glue is coated on the light-emitting surface of the ultraviolet LED chip, and the coating method includes but is not limited to spot coating, surface coating, spin coating, pressure coating, roller coating, etc.

[0031] In the above description, as a preference, the ultraviolet irradiation condition of step S2 is 365 nm ultraviolet irradiation for 20 seconds for curing.

[0032] Furthermore, the brightness of the white light LED is at least 25000 cd / m 2 , and there is no residual ultraviolet emission peak in the emission spectrum.

[0033] Furthermore, in order to ensure that there is no residual ultraviolet emission peak in the emission spectrum of the white light LED, the following conditions need to be met: UV,out ≤∈;

[0034] Among them, the ultraviolet light intensity I UV,out :This is the intensity of ultraviolet light after passing through the wide-spectrum phosphor glue layer, which can be measured by a spectrometer;

[0035] ∈ is a very small threshold, indicating the amount of residual UV light allowed. Usually, ∈ can be set to a very small proportion of the initial UV light intensity according to actual application requirements, for example, ∈ = 10 -3 I UV,in .

[0036] Initial luminous intensity I UV,in : This is the initial luminous intensity of the UV LED chip, which can be measured by a spectrometer.

[0037] It can be seen that the present invention can achieve high-efficiency light emission of white light LED (brightness of at least 25000cd / m 2 ) and ensure that there is no residual UV emission peak in the emission spectrum.

[0038] The beneficial effects of the present invention are mainly reflected in:

[0039] (1) The present invention uses an ultraviolet LED chip to excite a wide-spectrum phosphor glue layer to obtain white light with a spectral shape close to the standard solar spectrum. This setting has the following three advantages: 1. Using ultraviolet LED excitation instead of blue light LED excitation avoids the impact of high-energy short-wave blue light spillover on human health; 2. The application of wide-spectrum phosphors achieves an approximate simulation of the solar spectrum and improves the color rendering index of white light LEDs; 3. The number of types of phosphors used is reduced, effectively reducing manufacturing costs and reducing the probability of color drift that is positively correlated with the number of types of phosphors.

[0040] (2) The present invention relates to a phosphor composition for producing white light LEDs. As is well known, in order to produce white light, the emission spectrum of the phosphor must cover the entire range of light visible to the human eye, i.e., 380nm to 780nm. This usually requires the use of a variety of phosphors to ensure the continuity and balance of the spectrum. However, the wide-spectrum blue phosphor and the wide-spectrum orange-red phosphor of the present invention cannot produce a solar-spectrum-like white light LED by mixing them in any proportion or by selecting any combination of phosphors. Figure 1 As shown, there is an obvious green spectrum gap between the wide spectrum blue light phosphor and the wide spectrum orange-red light phosphor of the present invention. Since the human eye is very sensitive to green light (500-570nm), the unoptimized mixed light will tend to be blue or orange, rather than white light.

[0041] The present invention optimizes the spectral distribution of the mixed light by selecting specific wide-spectrum blue phosphor and wide-spectrum orange-red phosphor and optimizing the ratio of the two, making it closer to the spectral distribution of sunlight. Specifically, the following key factors jointly determine the spectral distribution of the mixed light to obtain a white light LED with a spectral distribution close to that of sunlight:

[0042] 1. The chemical formula of the wide-spectrum blue phosphor of the present invention is [N(CH3CH2)4]2[Cu2Br4], and its half-width is 95nm; the chemical formula of the wide-spectrum orange-red phosphor is [N(C3H7)4]2[Cu4Br6], and its half-width is 161nm. Figure 1 As shown, the spectra of the two phosphors overlap to a certain extent between 500-600nm. The green spectrum is usually between 500-600nm, and the overlapping area of ​​the two phosphors just covers part of the green spectrum, which makes it possible to generate green light.

[0043] 2. If Figure 1 As shown, the emission center wavelength of the wide-spectrum blue phosphor is 470 nm, and the emission center wavelength of the wide-spectrum orange-red phosphor is 625 nm, and the PLQY of both are close to 100%, showing approximately the same excellent luminescence ability.

[0044] 3. If Figure 2 As shown, the present invention optimizes the ratio of the two phosphors (the mass ratio of the wide-spectrum blue phosphor to the wide-spectrum orange-red phosphor is between 1.2-2), thereby optimizing the spectral intensity of the overlapping area, thereby obtaining a white light LED with a spectral distribution close to that of sunlight. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The fluorescence spectra of two wide-spectrum phosphors used in the wide-spectrum phosphor glue layer adopted in Example 1 of the present invention are shown;

[0046] Figure 2 The spectrum diagram of the ultraviolet-excited solar spectrum white light LED prepared in Example 1 of the present invention is based on the standard solar spectrum diagram as a reference standard;

[0047] Figure 3 This is a schematic diagram of the structure of a solar spectrum white light LED using ultraviolet excitation provided in Example 1 of the present invention.

[0048] Description of the drawings: 1. Electrically conductive and thermally conductive substrate; 2. Solder layer; 3. UV LED chip; 4. Broad-spectrum phosphor adhesive layer. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0050] Embodiment 1:

[0051] like Figure 3 As shown, the present invention provides a UV-excited solar-spectrum-like white light LED, comprising a conductive and thermally conductive substrate 1, a solder layer 2, a UV LED chip 3, and a wide-spectrum phosphor adhesive layer 4 arranged in sequence, wherein the conductive and thermally conductive copper substrate is connected and fixed to the UV LED chip via the solder layer, and the wide-spectrum phosphor adhesive layer is directly coated on the UV LED chip.

[0052] A method for preparing a UV-excited solar spectrum-like white light LED, the specific steps are as follows:

[0053] S1. Fixing the UV LED chip on the conductive and thermally conductive substrate by soldering;

[0054] S2. In an inert atmosphere, apply the broad-spectrum phosphor glue on the light-emitting surface of the UV LED chip, and irradiate the broad-spectrum phosphor glue with 365nm ultraviolet light for about 20 seconds to complete curing to obtain a broad-spectrum phosphor glue layer, thereby obtaining a white light LED;

[0055] S3, conducting a power-on test on the white light LED in step S2 to detect whether there is any residual ultraviolet emission peak in the emission spectrum of the white light LED. If there is any residual ultraviolet emission peak, a wide-spectrum phosphor glue layer is re-coated and thickened until there is no residual ultraviolet emission peak in the emission spectrum of the white light LED.

[0056] Among them, the following methods can be used to configure the wide spectrum phosphor glue:

[0057] The broad-spectrum blue phosphor and the broad-spectrum orange-red phosphor were uniformly mixed at a mass ratio of 1.67:1. After measuring an appropriate volume of UV-curing glue and placing it on a smooth flat material, a certain amount of the uniformly mixed phosphor was added to the UV-curing glue on the smooth flat material. After fully and uniformly mixing, a broad-spectrum phosphor glue with a mass concentration of 1.3 g / mL was obtained.

[0058] The smooth plane material in this embodiment is specifically a smooth glass sheet, which serves to provide a rigid and smooth platform that is supportive and convenient for liquid flow for the preparation of the wide-spectrum phosphor glue.

[0059] In the above description, the chemical formula of the wide-spectrum blue phosphor is:

[0060] [N(CH3CH2)4]2[Cu2Br4], its half-width is 95nm; it has a fluorescence quantum yield as high as 98.9%.

[0061] The chemical formula of the wide-spectrum orange-red phosphor is [N(C3H7)4]2[Cu4Br6], its half-width is 161nm, and its fluorescence quantum yield is also close to perfect at 99.2%.

[0062] Furthermore, the thickness of the wide-spectrum phosphor glue layer can be regulated by powering on the prepared white light LED to test its emission spectrum. Whether the thickness of the wide-spectrum phosphor glue layer is appropriate can be determined based on whether there is any residual ultraviolet emission peak in the spectrum. If there is any residue, it can be reapplied in time to effectively avoid ultraviolet light overflow and damage to the human eye. For example, excessive ultraviolet radiation may cause inflammation of the cornea and conjunctiva, leading to symptoms such as eye pain, redness, swelling, tearing, and blurred vision.

[0063] The brightness of the white light LED prepared in Example 1 is about 26480 cd / m 2 .

[0064] Comparative Example 1:

[0065] The difference from Example 1 is that the wide spectrum blue light phosphor and the wide spectrum orange-red light phosphor are configured and used at a mass ratio of 2.5:1, and the other steps are the same. The prepared LED cannot achieve solar spectrum-like white light.

[0066] Comparative Example 2:

[0067] The difference from Example 1 is that the wide spectrum blue light phosphor and the wide spectrum orange-red light phosphor are configured and used at a mass ratio of 0.5:1, and the other steps are the same. The prepared LED cannot achieve solar spectrum white light.

[0068] The present invention illustrates the detailed preparation method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed preparation method, that is, it does not mean that the present invention must rely on the above-mentioned products and detailed preparation methods to be implemented. It should be clear to those skilled in the art that any improvement of the present invention, the combination or equivalent replacement of the raw materials of the product of the present invention, all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A UV-excited solar spectrum white light LED, characterized in that: It comprises a conductive and thermally conductive substrate, a solder layer, an ultraviolet LED chip and a wide-spectrum phosphor adhesive layer which are arranged in sequence; the conductive and thermally conductive substrate is fixedly connected to the ultraviolet LED chip through the solder layer, and the wide-spectrum phosphor adhesive layer is directly coated on the ultraviolet LED chip; The wavelength range of the ultraviolet LED chip is between 300-390nm; The wide-spectrum phosphor glue layer includes wide-spectrum blue light phosphor and wide-spectrum orange-red light phosphor with optimized luminous intensity, and the mass ratio of the wide-spectrum blue light phosphor to the wide-spectrum orange-red light phosphor is in the range of 1.2-2.

2. The ultraviolet-excited solar spectrum white light LED according to claim 1, characterized in that: The wide-spectrum phosphor glue layer also includes an ultraviolet curing glue, and the wide-spectrum blue phosphor and the wide-spectrum orange-red phosphor are both dispersed in the ultraviolet curing glue to form a wide-spectrum phosphor glue; The luminescent center wavelength of the wide-spectrum blue phosphor is 470nm; The luminescent center wavelength of the wide-spectrum orange-red phosphor is 625 nm.

3. The ultraviolet-excited solar spectrum white light LED according to claim 2, characterized in that: The mass concentration range of the broad spectrum phosphor in the UV curing adhesive is 0.1-10 g / mL; The wide-spectrum phosphor consists of wide-spectrum blue light phosphor and wide-spectrum orange-red light phosphor.

4. The ultraviolet-excited solar spectrum white light LED according to claim 3, characterized in that: The mass concentration of the broad spectrum phosphor in the UV curing adhesive is 1.3 g / mL; The mass ratio of the wide-spectrum blue light phosphor to the wide-spectrum orange-red light phosphor is 1.67:

1.

5. The ultraviolet-excited solar spectrum white light LED according to claim 4, characterized in that: The half-widths of the wide-spectrum blue phosphor and the wide-spectrum orange-red phosphor are both at least greater than 90 nm.

6. The ultraviolet-excited solar spectrum white light LED according to claim 1, characterized in that: The chemical formula of the wide spectrum blue phosphor is [N(CH3CH2)4]2[Cu2Br4], its half-width is 95nm; the chemical formula of the wide-spectrum orange-red phosphor is [N(C3H7)4]2[Cu4Br6], its half-width is 161nm.

7. The ultraviolet-excited solar spectrum white light LED according to claim 5 or 6, characterized in that: The thickness of the wide-spectrum phosphor glue layer is preferably such that there is no residual ultraviolet emission peak in the emission spectrum of the white light LED to avoid ultraviolet light overflow.

8. The ultraviolet-excited solar spectrum white light LED according to claim 7, characterized in that: The general color rendering index R of the white light LED a =91, red color rendering index R9 =86, extended color rendering index R e =90.

9. A method for preparing a UV-excited solar spectrum-like white light LED according to any one of claims 2 to 6, characterized in that: The steps include: S1. Fixing the UV LED chip on the conductive and thermally conductive substrate by soldering; S2, applying the broad spectrum phosphor glue on the light-emitting surface of the UV LED chip, and curing it by ultraviolet irradiation for at least 15 seconds to obtain a broad spectrum phosphor glue layer, and then obtaining a white light LED; S3, conducting a power-on test on the white light LED in step S2 to detect whether there is any residual ultraviolet emission peak in the emission spectrum of the white light LED. If there is any residual ultraviolet emission peak, a wide-spectrum phosphor glue layer is re-coated and thickened until there is no residual ultraviolet emission peak in the emission spectrum of the white light LED.

10. The method for preparing a UV-excited solar spectrum-like white light LED according to claim 9, characterized in that: The brightness of the white light LED is at least 25000 cd / m 2 , and there is no residual ultraviolet emission peak in the emission spectrum.

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