CN103672450B - light emitting device - Google Patents

Abstract

An embodiment of the invention discloses a light-emitting device, which comprises a first light source, a second light source and a control unit, wherein the first light source is set to emit first light at a first low temperature and a first high temperature and has a first heat and cold coefficient; a second light source, which is set to emit a second light at the first low temperature and the first high temperature and has a second heat-cooling coefficient larger than the first heat-cooling coefficient; and an optical element configured to be excited by the first light to generate a third light and to reach a second high temperature higher than the first high temperature under irradiation of the first light.

Description

light emitting device

technical field

The present invention relates to a lighting device, in particular to a lighting device whose color temperature variation is less perceived by users, such as a lighting device using LEDs of various colors.

Background technique

There are several ways to form white light using Light-Emitting Diode (LED). One is to use more than three monochromatic color (Monochromatic Color) light sources to generate white light, for example, red, blue, and green LEDs. Another way is to mix two color lights that are complementary colors to each other, for example, blue light and yellow light. Usually, blue light is produced by nitride LEDs, and yellow light is produced by phosphors excited by blue light. Compared with the white light produced by using three monochromatic light sources, the white light produced by using two complementary color light sources generally has higher luminous efficiency (Luminous Efficiency) but the color rendering index (Color Rendering Index; CRI) is poor. .

Color rendering (Color Rendering) is an indicator to measure the true color of a light source compared to sunlight. A light source with a high color rendering index can better present the true color of the object. Halogen lamps and incandescent bulbs are the ones with the best color rendering among the current artificial light sources, and their color rendering index can reach 100. The color rendering index of fluorescent light is usually between 60 and 85. The color rendering index of white light produced by blue light-emitting diodes and yellow phosphors is only about 70. Combining blue light-emitting diodes with more than two kinds of phosphors, for example, yellow and red phosphors, can improve the color rendering index to about 80, but it will reduce the luminous efficiency by about 30%.

Contents of the invention

An embodiment of the present invention discloses a light emitting device, which includes a first light source, which is set to emit a first light at a first low temperature and a first high temperature, and has a first thermal coefficient; The second light source is set to emit a second light at the first low temperature and the first high temperature, and has a second heat-cooling coefficient greater than the first heat-cooling coefficient; and an optical element is set Can be excited by the first light to generate a third light, and can reach a second high temperature higher than the first high temperature when irradiated by the first light.

In another embodiment of the present invention, the first light, the second light, and the third light can be mixed into a mixed light, and the chromaticity coordinates of the mixed light between the first low temperature and the first high temperature The difference is (△x,△y), and △y/△x is greater than -0.2.

In another embodiment of the present invention, the first light, the second light, and the third light can be mixed into a mixed light, and the mixed light has a first chromaticity coordinate at the first low temperature, where There is a second chromaticity coordinate at the first high temperature, and the first chromaticity coordinate and the second chromaticity coordinate are respectively located on two sides of the black body radiation curve.

In another embodiment of the present invention, the first light, the second light, and the third light can be mixed into a mixed light, and the mixed light has a first chromaticity coordinate at the first low temperature, where There is a second chromaticity coordinate at the first high temperature, and the first chromaticity coordinate and the second chromaticity coordinate are located on the same side of the black body radiation curve.

In another embodiment of the present invention, the first light, the second light, and the third light can be mixed into a mixed light, and the mixed light has a first chromaticity coordinate at the first low temperature, where There is a second chromaticity coordinate at the first high temperature, and the connecting line between the first chromaticity coordinate and the second chromaticity coordinate is substantially parallel to the black body radiation curve.

In yet another embodiment of the present invention, the first light, the second light, and the third light can be mixed into a mixed light, and the mixed light has a first correlated color temperature at the first low temperature, and at the first A high temperature has a second correlated color temperature, and the second correlated color temperature is greater than the first correlated color temperature.

In yet another embodiment of the present invention, the difference between the first high temperature and the second high temperature is between 30°C and 40°C.

In yet another embodiment of the present invention, the first light includes blue light, and the second light includes red light.

In yet another embodiment of the present invention, the optical element includes a wavelength conversion material that can be disposed on the optical element away from the second light source.

In yet another embodiment of the present invention, the optical element comprises a frustum.

Description of drawings

FIG. 1 is a configuration diagram illustrating a light emitting device according to an embodiment of the present invention;

FIG. 2 illustrates a light emitting device according to yet another embodiment of the present invention;

3 is a comparative example illustrating a light emitting device according to an embodiment of the present invention; and

FIG. 4 illustrates a light emitting device according to yet another embodiment of the present invention.

[Description of main component labels]

10 first light source 30c phosphor layer

20 second light source 100 light emitting device

30 optics 200 light emitting device

30a Notch 300 Lighting device

30b phosphor layer 400 light emitting device

30b’ phosphor layer

detailed description

Embodiments of the present invention are described below with drawings.

As shown in FIG. 1 , an embodiment of the present invention discloses a light emitting device 100 , which at least includes a first light source 10 , a second light source 20 , and an optical element 30 . The shortest distance between the first light source 10 and the optical element 30 is D1, the shortest distance between the second light source 20 and the optical element 30 is D2, and D1 and D2 may be equal or different. The optical element 30 can be a single structure or comprise several independent structures. A light source 10 can generate a first light L1, and the second light source 20 can generate a second light L2 different (all or part of the wavelength is different) from the first light L1. The first light L1, the second light L2, or both can illuminate the optical element 30 (for example, the optical element 30 can cover the first light source 10, the second light source 20, or both), and make the optical element 30 generates at least one third light L3 different from the first light L1 or the second light L2. If the first light L1 is only mixed with the third light L3, the fourth light L4 can be generated (or not mixed, that is, there is no fourth light L4 in the drawing). The first ray L1 , the second ray L2 , and the third ray L3 (or the third ray L3 and the fourth ray L4 ) can be mixed into a fifth ray L5 at a spatial position. This spatial position can be outside the optical element 30 and inside the light emitting device 100 , or outside the light emitting device 100 . The quantity, size, and position of the light emitting device 100 , the first light source 10 , the second light source 20 , and the optical element 30 in FIG. 1 are examples, but not necessarily limiting the present invention.

For example, the light-emitting device 100 is a light source, such as a light bulb or a lamp tube; the first light source 10 is a light-emitting diode, and the first light L1 is blue light (not limited to monochromatic light sources, but also includes light sources with blue light bands in the spectrum, the same below. ); the second light source 20 is another light-emitting diode, and the second light L2 is red light (not limited to monochromatic light sources, but also includes light sources containing red light bands in the spectrum, the same below); the third light L3 is yellow light (not limited to It is limited to monochromatic light sources, and also includes light sources that include yellow light bands in the spectrum, the same below); the fourth light L4 is white light with a relatively high color temperature (for example, the correlated color temperature (Correlated Color Temperature; CCT) is above 4000K); the fifth light L5 is Lower color temperature white light (eg, correlated color temperature below 4000K). The optical element 30 may contain phosphors that can be excited by blue light and produce yellow light, such as Yttrium Aluminum Garnet (YAG) phosphors, Silicate-based phosphors, Terbium Aluminum Garnet Stone type (Terbium Aluminum Garnet; TAG) phosphor, nitrogen oxide (Oxynitride) phosphor. Each of the phosphors listed in this specification has its own operating characteristics. For example, yttrium aluminum garnet-type phosphors have better luminous efficiency at high temperatures (for example, above 100°C), nitrogen oxide phosphors have better luminous efficiency at medium and low temperatures (for example, Below 100°C) has better luminous efficiency. Therefore, when the light-emitting device 100 is used in a high-temperature operating environment, yttrium-aluminum-garnet-type phosphors can be selected; when used in a medium-low temperature operating environment, oxynitride phosphors can be selected. However, the above selection suggestions are not absolute, and can still be adjusted according to design requirements.

For example, the light emitting device 100 is a light source, such as a bulb or a lamp tube; the first light source 10 is a light emitting diode, and the first light L1 is blue light; the second light source 20 is another light emitting diode, and the second light L2 is red light; Light L3 is green light (not limited to monochromatic light sources, but also includes light sources that include green light bands in the spectrum, the same below); the fourth light L4 is cyan light (cyan; not limited to monochromatic light sources, also includes cyan light in the spectrum) The light source in the light band, the same below); the fifth light L5 is white light. The optical element 30 may contain phosphors that can be excited by blue light and generate green light, such as silicate phosphors, yttrium aluminum garnet phosphors, LuAG (Lutetium Aluminum Garnet), and beta-SiAlON. The specific chemical composition is exemplified as follows: (Sr,Ba) ₂ SiO ₄ :Eu ²⁺ , SrGa ₂ S ₄ :Eu ²⁺ , Y ₂ SiO ₅ :Tb, CeMgA _l1 1O ₁₉ :Tb, Zn ₂ SiO ₄ :Mn, LaPo ₄ : Ce, Tb, Y ₃ Al ₅ O ₁₂ : Tb, Y ₂ O ₂ S: Tb, Dy, BaMgA _l1 1O ₁₇ : Eu, Mn, GdMgZnB ₅ O ₁₀ : Ce, Tb, Gd ₂ O ₂ S: Tb, Dy.

The first light source 10 may have a first heat/cold factor, and the second light source 20 may have a second heat/cold factor different from the first heat/cold factor. The so-called Hot/Cold Factor, or Temperature Coefficient (TC), means the ratio of the luminous flux of the light source at high temperature divided by the luminous flux at low temperature. If the luminous flux at high temperature is smaller than that at low temperature, the heat-cold coefficient is less than 1, otherwise it is greater than 1. The larger the heat and cold coefficient, the smaller the luminous flux or luminous efficiency due to temperature attenuation. For example, the heat and cold coefficient of a light-emitting diode is X. If the luminous flux at 25°C is used as a reference value, the luminous flux at 100°C will only be (100*X)% of the reference value. In other words, the decrease in luminous flux is (100 -X)%. If the input power remains the same, the greater the decrease in luminous flux, the worse the luminous efficiency of the light source.

In another embodiment, the light emitting device 100 can emit light at a _first temperature T1 and a _second temperature T2, and the _second temperature T2 is higher _than the _first temperature T1 ₍ between T1 and T2 can be light or not), and the first light source 10 has a first thermal-cold coefficient HC ₁ , the second light source 20 has a second thermal-cold coefficient HC ₂ , and HC ₁ >HC ₂ . The luminous flux ratio of the first ray L1 and the second ray L2 at T ₁ is FR ₁ , and at T ₂ the luminous flux ratio is FR ₂ . Since the second ray L2 is more attenuated by heat than the first ray L1, FR ₁ < FR ₂ . At T1, the correlated color temperature _of the fifth ray L5 (which can be pure L1 and L2 mixed light, or L1, L2 and L3 mixed light.) is CT ₁ , and at T2, the correlated color temperature of the fifth ray L5 is CT ₂ Since the mixing ratio of the first light L1 and the second light L2 is different between T ₁ and T ₂ (FR ₁ ≠FR ₂ ), CT ₁ and CT ₂ are also different accordingly. Therefore, the heat and cold coefficient may also affect the color temperature of the mixed light.

The working temperature of the light emitting device 100 tends to rise with the use time increasing. If the light emitted by the light emitting device 100 includes colored lights produced by several light sources with different thermal and cooling coefficients, the color temperature of the light emitted by the light emitting device 100 will change due to the change of the operating temperature. In order to alleviate the color temperature change of the mixed light at high and low temperatures or to meet the expected color temperature design requirements, the application further proposes the following embodiments.

In one embodiment of the present invention, the shortest distance between the first light source 10 and the optical element 30 is D1, the shortest distance between the second light source 20 and the optical element 30 is D2, D1 and D2 can be equal or different, and D1 and None of D2 is equal to zero. The optical element 30 includes a wavelength converting material 40 capable of converting the first light L1 into the third light L3. The wavelength conversion material 40 is, for example, phosphor powder (the specific material is as described above), dye, semiconductor, and the like. The wavelength conversion material 40 has a specific conversion efficiency, and converts the excitation light (such as the first light L1) into the emission light (such as the third light L3) in a certain proportion, and the excitation light that is not converted into the emission light may leave the wavelength conversion The material 40 is either converted into heat which raises the temperature of the optical element 30 . If the temperature of the wavelength conversion material 40 or the optical element 30 is higher than the temperature of the light source, keeping them away from the light source or separating them with a transparent heat insulating material can also reduce the heat transferred to the light source. Once the temperature of the light source drops, the influence on the color temperature due to the heat and cold coefficient can be slowed down. Conversely, if the temperature of the optical element 30 is lower than the temperature of the light source, making the optical element 30 close to the light source to absorb the heat of the light source can lower the temperature of the light source and slow down the influence of the heat-cooling coefficient on the color temperature.

As shown in the light emitting device 200 shown in FIG. 2 , the first light source 10 is a blue light emitting diode, the second light source 20 is a red light emitting diode, and the thermal coefficient of the first light source 10 is greater than that of the second light source 20 . The optical element 30 is a reversed cone frustum, and has a notch 30a thereon, and a phosphor layer 30b is disposed in the notch 30a. The first light source 10 and the second light source 20 can be selectively disposed on a carrier 50 . The carrier 50 is, for example, a printed circuit board (Printed Circuit Board; PCB), a ceramic substrate, a metal substrate, a plastic substrate, glass, a silicon substrate, and the like. Besides the light emitting diode, the space between the optical element 30 and the carrier 50 can be filled with other materials, such as colloid, heat conducting material, light scattering material and so on. In one embodiment, the first light source 10 and the second light source 20 start to operate at room temperature until the temperature of the light source and the optical element 30 reaches a steady state or a quasi-steady state.

For example, the optical element 30 is a frustum as shown in FIG. , the distance between the phosphor layer 30a and the first light source 10 and the second light source 20 is about 5 mm). Initially, the first light source 10 and the second light source 20 start to operate at about 25°C and emit blue light and red light respectively. The blue light can excite the optical element 30 to generate yellow light, and the blue light, red light and yellow light can be mixed into a low color temperature white light , its correlated color temperature is about 2500K, and the CIE (x1, y1) _initial chromaticity coordinates are about (0.4733, 0.4047). After several minutes, the temperature no longer rises significantly. At this time, the temperature of the first light source 10 and the second light source 20 is about 70°C to 90°C, and the temperature of the optical element 30 is about 100°C to 130°C, so the temperatures of the first light source 10 and the second light source 20 are higher than the optical temperature. Element 30 is about 30°C to 40°C cooler. At this steady state temperature, blue light, red light and yellow light can be mixed to form a high color temperature white light, the correlated color temperature is about 3000K, and the CIE (x1, y1) _stable chromaticity coordinates are about (0.4395, 0.4104). That is, from low temperature to high temperature, the correlated color temperature difference of white light is about 500K, the change of chromaticity coordinates (△x1,△y1) is about (-0.0339,0.0057), and △y1/△x1 is about -0.17. Since △x1 is much larger than △y1 (0≧△y1/△x1≧-0.2), the slope of the chromaticity coordinate change between low temperature and high temperature is slow, CIE(x1,y1) _initial and CIE(x1,y1) _stable The connecting line of the chromaticity coordinates will be parallel or approximately parallel to the blackbody radiation curve. That is, the line connecting the chromaticity coordinates of low temperature and high temperature will be on one side of the black body radiation curve, or cross the black body radiation curve with a smaller slope. In this example, CIE(x1,y1) _initial is located below the blackbody radiation line, and CIE(x1,y1) _stable is located above the blackbody radiation line.

In comparison, if the optical element 30 is not used, the phosphor powder is directly covered on the first light source 10 and the second light source 20 (that is, the phosphor powder is not far away from the light source), but other conditions remain unchanged, the CIE of low color temperature white light (x2 ,y2) The _initial chromaticity coordinates are about (0.4806,0.43), and the CIE(x2,y2) _stable chromaticity coordinates of high color temperature white light are about (0.4531,0.4504). Although the correlated color temperature gap of white light is still about 500K, the chromaticity The change of the coordinates (△x2, △y2) is about (-0.0275, 0.0204), and △y2/△x2 is about -0.74. The slope of the chromaticity coordinate change between low temperature and high temperature is steeper, and the moving line segment of the chromaticity coordinate or its extension line will cross the black body radiation curve. And because △y2 is much larger than △y1 (△y2/△y1=3.58), (x2, y2) moves toward the green light region (520nm～560nm) in the chromaticity coordinates more than (x1, y1). Since the human eye is more sensitive to green light, the greater the amount of change in green light, the more the human eye can perceive the change in light color or color temperature.

In addition, since the optical element 30 is kept away from the light source, the light source is also kept away from the heat source, thereby lowering the temperature and improving its luminous efficiency. For example, as shown in FIG. 2 , from low temperature to high temperature, the luminous efficiency of the light emitting device 200 decreases by about 24%. However, if the phosphor layer 30b' directly covers the first light source 10 and the second light source 20, and then covers the optical element 30, the luminous efficiency of the light emitting device 300 will decrease by 27%, as shown in FIG. 3 .

Therefore, by adopting the configuration or method of the above-mentioned embodiments of the present invention, the sensitivity of human eyes to color temperature changes can be reduced, and the luminous efficiency of the light source can be improved.

In another embodiment of the present invention, as shown in FIG. 4 , the light emitting device 400, the first light source 10 is a blue light emitting diode, and the second light source 20 is a red light emitting diode. The optical element 30 is an inverted conical frustum with a notch 30a on it, and a fluorescent powder layer 30c is provided in the notch 30a and on the side surface of the frustum. The first light source 10 and the second light source 20 can be selectively disposed on a carrier 50 . The carrier 50 is, for example, a printed circuit board, a ceramic substrate, a metal substrate, a plastic substrate, glass, a silicon substrate, or the like. Besides the light emitting diode, the space between the optical element 30 and the carrier 50 can be filled with other materials, such as colloid, heat conducting material, light scattering material and so on. Since the top and side surfaces of the optical element 30 are covered with the phosphor layer 30c, the colors on the top and bottom of the light emitting device 100 can be made more uniform. For example, the chromaticity coordinates (Δu', Δv') ₄₀₀ of the light emitting device 400 are about (0.010, 0.014), while the (Du', Dv') ₂₀₀ of the light emitting device 200 are about (0.014, 0.023). In addition, if a scattering material, such as TiO ₂ , is added to the optical element 30 , the phosphor layer 30 c, or both, it is also helpful to form a light field with a more uniform color.

Although the above drawings and descriptions only correspond to specific embodiments, however, the components, implementation methods, design principles, and technical principles described or disclosed in each embodiment are unless they conflict with each other, contradict, or are difficult to implement together. In addition, we can refer to, exchange, match, coordinate, or merge arbitrarily according to our needs.

Although the present invention has been described above, it is not intended to limit the scope, implementation sequence, or used materials and process methods of the present invention. Various modifications and changes made to the present invention do not depart from the spirit and scope of the present invention.

Claims (10)

1. a kind of light-emitting device, comprising：

One first light source, being set can send one first light under one first low temperature and one first high temperature, and with one first The cold coefficient of heat；

One secondary light source, being set can send one second light under first low temperature and first high temperature, and be more than with one Second hot cold coefficient of the first hot cold coefficient；And

One optical element, being set can be excited to produce one the 3rd light and irradiated by first light by first light Second high temperature for being higher than first high temperature can be reached down.

2. light-emitting device according to claim 1, wherein first light, second light and the 3rd light can mix Into a mixed light, between first low temperature and first high temperature, the difference of its chromaticity coordinate is (△ x, △ y), △ to the mixed light Y/ △ x are greater than -0.2.

3. light-emitting device according to claim 1, wherein first light, second light and the 3rd light can mix Into a mixed light, the mixed light under first low temperature have one first chromaticity coordinate, under first high temperature have one second Chromaticity coordinate, first chromaticity coordinate and second chromaticity coordinate are respectively positioned at the both sides of blackbody radiance curve.

4. light-emitting device according to claim 1, wherein first light, second light and the 3rd light can mix Into a mixed light, the mixed light under first low temperature have one first chromaticity coordinate, under first high temperature have one second Chromaticity coordinate, first chromaticity coordinate and second chromaticity coordinate are the homonymies for being located at blackbody radiance curve.

5. light-emitting device according to claim 1, wherein first light, second light and the 3rd light can mix Into a mixed light, the mixed light under first low temperature have one first chromaticity coordinate, under first high temperature have one second The line of chromaticity coordinate, first chromaticity coordinate and second chromaticity coordinate is to be in substantially parallel relationship to blackbody radiance curve.

6. light-emitting device according to claim 1, wherein first light, second light and the 3rd light can mix Into a mixed light, the mixed light under first low temperature have one first correlated colour temperature, under first high temperature have one second Correlated colour temperature, second correlated colour temperature is more than first correlated colour temperature.

7. light-emitting device according to claim 1, the difference of wherein first high temperature and second high temperature be between 30 DEG C~ 40℃。

8. light-emitting device according to claim 1, wherein first light include blue light, and second light includes feux rouges.

9. light-emitting device according to claim 1, the wherein optical element include a material for transformation of wave length, and it can be set On the optical element and away from the secondary light source.

10. light-emitting device according to claim 1, the wherein optical element include a frustum.