TWI595803B - White light illumination system - Google Patents

Description

White light illumination system

This invention relates to a white light illumination system, and more particularly to a white light illumination system that forms white light by mixing light.

White light-emitting diodes (LEDs) are emerging products that are favored in the LED industry. In the context of the global energy shortage, the white light-emitting diodes are in the foreground of the lighting market. Focused on the world.

The so-called white light is a mixture of multiple colors. At least two kinds of light must be mixed in the form of white light visible by human eyes, such as two wavelengths of light (blue light and yellow light) or three wavelengths of light (blue light, green light). Mixed with red light). At present, the main mixing method of the white light emitting diode element is to combine the blue light emitting diode chip with the yellow light fluorescent powder which can be effectively excited by the blue light. A part of the blue light is absorbed by the fluorescent powder, and the fluorescent powder is excited to emit yellow light. The emitted yellow light is mixed with the remaining blue light, and then their intensity ratios are adjusted to obtain white light of various color temperatures. However, such a hybrid method lacks a red band, so the Colour Rendering Index (CRI) is low. In order to improve the color rendering of the light-emitting diode, red phosphor powder is added to increase the coverage of the visible light spectrum. However, since the phosphor converts the light of the first wavelength into the light of the second wavelength, the energy of the light is lost, so that the luminous efficiency of the entire assembly is lowered. In particular, the lower the required color temperature, the more red phosphors are used, not only the loss of light efficiency, but also the cost-performance ratio.

As the production process of red light wafers is becoming more mature today, the brightness of red light wafers is getting higher and higher, so there is also a case where red light wafers are used to provide the required red light. Such a white light-emitting diode element can improve luminous efficiency by 10% or more as compared with a white light-emitting diode element combining a blue light wafer and red and yellow phosphor powder. In the related art, the use of a blue light wafer and a red light wafer with a yellow phosphor powder has been mentioned in the prior art, such as U.S. Patent Nos. 6,513,949, 7,126,274, 7,015, 074, and 7,005, 679, so that a better illumination system can be obtained. Color rendering. However, due to the poor stability of the red light wafer to temperature, there is a problem of hot/cold factor at high temperatures. As the operating temperature increases, the red light decay rate is greater than the blue and yellow light decay rate, the light emitted by the entire light-emitting diode component will have a serious color shift problem, and can not reach the Energy Star and The rank of the 7-step MacAdam Ellipse in the American National Standards Institute (ANSI).

The present invention provides a white light illumination system that has high luminous efficiency and low color deviation.

One embodiment of the present invention provides a white light illumination system. The white light illumination system includes a first light emitting chip, a second light emitting chip, and a wavelength conversion unit. The first illuminating wafer is adapted to emit a first light and the first light comprises a first red ray. The second luminescent wafer is adapted to emit a second light, wherein the second light has a different wavelength of light than the first light. The wavelength conversion unit is disposed on the first illuminating wafer and the second illuminating wafer, wherein when the second light is irradiated to the wavelength converting unit, the second light is converted into an excitation beam, and the excitation beam is excited Includes a second red light. Further, the excitation beam, the first light, and the second light are co-mixed into white light having a color temperature substantially similar to 3000K.

In an embodiment of the invention, the first illuminating wafer is a red ray wafer, and the second illuminating wafer is a plurality of blue ray wafers.

In an embodiment of the invention, the wavelength conversion unit further includes a first wavelength conversion material and a second wavelength conversion material. The first wavelength converting material converts the second light into a second red light. The second wavelength converting material converts the second light into a third light.

In an embodiment of the invention, the third light is a yellow light.

In an embodiment of the invention, the peak wavelength of the spectrum of the first red light is different from the peak wavelength of the spectrum of the second red light.

In an embodiment of the invention, the peak wavelength of the spectrum of the first red light is substantially equivalent to the peak wavelength of the spectrum of the second red light.

In one embodiment of the present invention, the white light illumination system maintains a white light color deviation emitted by the white light illumination system within a range of a MacAdam Ellipse at a temperature of 85 degrees Celsius.

In an embodiment of the invention, the material of the first wafer comprises a gallium phosphide compound or a gallium arsenide compound.

In an embodiment of the invention, the first wavelength converting material is a nitride or oxynitride phosphor.

One embodiment of the present invention provides a white light illumination system. The white light illumination system includes a plurality of light emitting wafers and a wavelength conversion unit. These luminescent wafers are adapted to emit more than two types of light, wherein the light comprises blue light and first red light. The wavelength conversion unit includes a first wavelength conversion material and a second wave The long conversion material, wherein the blue light is converted into a second red light by the first wavelength converting material, the second red light has a different wavelength than the first red light, and the blue light is converted into the yellow light by the second wavelength converting material. The light, yellow light and the second red light are mixed together into a white light, the white light has a color temperature close to 3000K, and the white light illumination system emits a white light color deviation at a temperature of 85 degrees Celsius in the 7th order MacAdam Ellipse (7-step MacAdam Ellipse) Within the scope of).

In an embodiment of the invention, the plurality of wafers includes a red light wafer and a plurality of blue light wafers.

Based on the above, the white light illumination system of the embodiment of the present invention increases the color rendering of the white light provided by the white light illumination system by using the first red light emitted by the first light emitting chip and the second red light converted by the wavelength conversion unit. Among them, the first light-emitting chip can maintain high luminous efficiency of red light, and the wavelength conversion unit reduces color deviation of red light at high operating temperature. Therefore, the white light illumination system of the embodiment of the present invention has both high light efficiency and low color deviation.

The above described features and advantages of the present invention will be more apparent from the following description.

1A is a schematic view of a white light illumination system according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line I-I' of FIG. 1A, wherein FIG. 1A omits a portion of the wavelength conversion unit. Referring to FIG. 1A and FIG. 1B, the white light illumination system 10 of the present embodiment includes a first light-emitting chip 12, a second light-emitting chip 13, and a wavelength conversion unit 14 (shown in FIG. 1B). The first luminescent wafer 12 is adapted to emit a first light L1, and the first light L1 Includes a first red light. The second illuminating wafer 13 is adapted to emit a second light L2, wherein the second light L2 has a different wavelength of light than the first light L1. The wavelength conversion unit 14 is disposed on the first luminescent wafer 12 and the second luminescent wafer 13, wherein when the second light L2 is irradiated to the wavelength conversion unit 14, the second light L2 is converted into an excitation light beam L3, and the excitation light beam L3 is included A second red light L3'. Further, the excitation light beam L3, the first light L1, and the second light L2 are collectively mixed to have white light having a color temperature substantially equivalent to 3000K.

Specifically, the white light illumination system 10 of the present embodiment may further include a pedestal 11 , and the first luminescent wafer 12 and the second luminescent wafer 13 may be disposed on the susceptor 11 by thermoelectric separation or thermoelectric integration. In this embodiment, eight luminescent wafers are mounted on the susceptor 11, including a red wafer and seven blue wafers. Further, the first illuminating wafer 12 may be one of the eight illuminating wafers, and the first illuminating wafer 12 may be selectively fixed on the insulating pedestal (not shown) to insulate electrical properties. The second luminescent wafer 13 may be the remaining seven of the eight luminescent wafers.

Please continue to refer to FIG. 1A to FIG. 1B. In the present embodiment, the wavelength conversion unit 14 is disposed above the eight light-emitting wafers. Specifically, the wavelength conversion unit 14 includes the first wavelength conversion material 14a and the second wavelength conversion material 14b. The first wavelength converting material 14a may be a red phosphor of nitride or oxynitride, and the second wavelength converting material 14b may be a garnet-type yellow phosphor, such as a compound of yttrium aluminum garnet phosphor, wherein nitrogen The compound is, for example, CaAlSiN ₃ , and the nitrogen oxide is, for example, SrSi ₂ O ₂ N ₂ .

In this embodiment, the second light-emitting chip 13 (for example, a blue light wafer) When the emitted second light L2 (e.g., blue light) is irradiated to the first wavelength converting material 14a (e.g., red phosphor), the first wavelength converting material 14a is excited to generate the second red light L3'. On the other hand, when the second light L2 (for example, blue light) emitted from the second light-emitting chip 13 (for example, a blue light wafer) is irradiated to the second wavelength converting material 14b (for example, yellow phosphor), the second wavelength converting material 14b is excited. The third light L3" is generated, which is, for example, yellow light. Thus, the first light L1 (first red light), the second light L2 (blue light), the second red light L3', and the third light L3" ( Huang Guang) can mix colors into white light, so that the entire white light illumination system 10 emits white light with a color temperature of about 3000K during operation. However, the invention is not limited thereto, and in other embodiments, a second luminescent wafer 13 of other colors, such as a green, yellow or amber luminescent wafer, may also be used. Thus, the first light-emitting chip 12 (red light wafer) and the red phosphor powder, or other color phosphor powder, can be used to generate light of other colors than white light or white light. In addition, in the white light illumination system of an embodiment, in addition to adding yellow and red phosphor powder, green phosphor powder may be functionally added to achieve different illumination effects.

In this embodiment, the peak wavelength of the spectrum of the second red light L3' generated by the excitation of the first wavelength converting material 14a is different from the peak wavelength of the spectrum of the first red light emitted by the first light emitting chip 12, thus compensating The red spectrum of the white light illumination system 10, however, in other embodiments, the two can be substantially identical.

Referring to FIG. 1A , for example, the first illuminating wafer of the embodiment may be a gallium phosphide type or a gallium arsenide type red light emitting diode, and the emitted light has a wavelength ranging from 600 nm to 700 nm. Second luminescence of an embodiment The wafer may be an indium gallium nitride or gallium nitride type blue light emitting diode wafer having a wavelength of light ranging from 405 nm to 470 nm. In addition, the wavelength conversion unit 14 of the present embodiment is a phosphor, however, in other embodiments, the wavelength conversion unit 14 may be in other forms, such as a ceramic plate with phosphor powder.

In one embodiment, the phosphor directly covers the second luminescent wafer 13 (blue wafer) and the first luminescent wafer 12 (red wafer) to form a conformal structure over the wafer, while in other implementations In the example, the phosphor powder can also be kept at a distance from the second luminescent blue wafer and the red ray wafer. In addition, the fluorescent powder can be applied by spraying, dispensing, electrophoresis or molding.

Several experimental results are listed below to verify the effects of the present invention.

Two comparative examples of the white light illumination system 10 of the embodiment of Fig. 1A are provided herein, Comparative Example 1 and Comparative Example 2. The structure of the first control is the same as that of the white light illumination system 10, but there are four red light wafers among the eight light-emitting chips, and the other four are blue light-emitting chips, and an appropriate amount of yellow phosphor powder is disposed above the eight light-emitting crystals to make the entire illumination. The system emits white light with a color temperature of about 3000K during operation. The structure of the second embodiment is also the same as that of the white light illumination system 10, but the eight light-emitting chips are blue light wafers, and the appropriate amount of yellow and red phosphor powder is disposed above the blue light wafer, so that the entire light-emitting device emits a color temperature of about 3000K during operation. White light.

Next, please refer to FIG. 2. FIG. 2 is a comparison diagram of the color shift of the white light illumination system of the embodiment of FIG. 1 and the control example 1 at a higher operating temperature in a CIE chromaticity coordinate system. As shown in FIG. 2, the fold lines 21 and 22 respectively indicate white light illumination. The amount of color shift of the white light emitted by the system 10 and the control example 1 from the temperature rise of 25 ° C to 85 ° C under the CIE (Commission International de l'Eclairage) chromaticity diagram. According to the US Energy Star standard, the white light color shift of the white light illumination system 10 needs to be maintained within the larger elliptical ring of Figure 2, ie, Energy Star and the American National Standards Institute ( The American National Standards Institute (ANSI) ranks the 7th-order MacAdam Ellipse. A better condition is that the white light color shift of the white light illumination system 10 is maintained within a small elliptical ring, that is, to reach the fourth stage of the Energy Star and the American National Standards Institute (ANSI). The rating of the MacAdam Ellipse. In fact, the human eye cannot perceive the amount of color shift in the 4th-order MacAdam Ellipse, and the human eye does not easily distinguish the amount of color shift in the larger 7th-order MacAdam Ellipse.

As shown in FIG. 2, the color shift of the white light at 85 degrees Celsius (85 ° C) in the comparative example 1 far exceeds the larger elliptical ring, and the white light illumination system 10 of the embodiment of FIG. 1 is white at 85 ° C. The color shift amount can be maintained in a large elliptical ring, and the human eye generally does not feel the color shift feeling.

For Comparative Example 1 with four red-light wafers, since the red light wafer is less stable to temperature, the thermal attenuation occurring at high temperature operation is more severe than that of the blue light wafer, so the light emission of the red and blue light crystals at high temperatures The amount of change in intensity is inconsistent, causing a color shift in the entire white light illumination system. The first light emitting chip (red light wafer) 12 is disposed in the white light illumination system 10 of the embodiment of FIG. 1A, and the number of red light wafers is not limited to FIG. 1A. The number shown. In one embodiment, a red light wafer is used and the remaining red light is provided by red phosphor. Since the thermal decay of the red phosphor is less pronounced, the color shift of the entire white illumination system 10 is much smaller than that of the first example in which only red light is used to provide red light.

Figure 3 is a graph showing the luminous efficiency of the white light illumination system of the embodiment of Figure 1 and Comparative Example 2 operating at different currents. Referring to FIG. 3, curves 31 and 32 are luminous efficiency curves of the white light illumination system 10 and the second control in the forward current of 200 mA to 400 mA, respectively. It can be observed that the current is in the range of 200 mA to 400 mA, and the luminous efficiency of the white light illumination system 10 of the embodiment of FIG. 1A is higher than that of the second comparative example. In the second comparative example in which red light is used to provide red light, since the red fluorescent powder has low luminous efficiency, the luminous efficiency of the entire light-emitting device is not high. The white light illumination system 10 of the embodiment of FIG. 1A is provided with a first light-emitting wafer 12 (red light wafer), and the number of red light wafers is not limited to the number illustrated. In one embodiment, a red wafer 12 is used, thus replacing the function of a portion of the red phosphor and providing a portion of the red light required by the white illumination system 10. Since the luminous efficiency of the red light wafer is high, the overall luminous efficiency of the white light illumination system 10 is higher than that of the second comparative example.

4 is an excitation spectrum of the white light illumination system of the embodiment of FIG. 1 and Comparative Example 2. Referring to FIG. 4, the excitation spectrum 42 of the white light illumination system 10 is provided with a second light L2 (blue light) and a first light emitting chip 12 (red light wafer) and a first light emitting chip 12 (red light), respectively. Red light is used to excite the second wavelength converting material (yellow phosphor) and the first wavelength converting material (red phosphor). The excitation spectrum 41 of Comparative Example 2 is composed of eight The blue light wafer is formed by exciting yellow phosphor powder and red phosphor powder. Figure 4 shows that the excitation spectrum 42 is spectrally similar to the excitation spectrum 41.

The following will cite the data of the experiment of the white light illumination system of the above embodiment of Fig. 1. It should be noted that the data listed in Table 1 below is not intended to limit the present invention, and any one of ordinary skill in the art can make appropriate changes to its parameters or settings after referring to the present invention. However, it should still fall within the scope of the invention.

As shown in Table 1, the white light illumination system 10 can obtain better luminous efficiency than the second embodiment.

FIG. 5 is a schematic diagram of a white light illumination system according to another embodiment of the present invention. For a schematic diagram of the wavelength conversion unit, reference may be made to the situation shown in FIG. 1B. Referring to FIG. 5, the white light illumination system 50 of the present embodiment uses a plurality of second light-emitting chips 53 that are smaller in volume, and the second light-emitting chip is, for example, a blue light wafer. The number of light-emitting wafers is not limited to the present embodiment, and in one embodiment, a white light illumination system 50 having fifteen light-emitting wafers is used. In the present embodiment, a first light-emitting chip 52 (for example, a red light wafer) and fourteen second light-emitting chips 53 (blue light wafers) are mounted on the susceptor 51 of the white light illumination system 50. An illuminating wafer is provided with an appropriate amount of a second wavelength converting material (not shown) and a first wavelength converting material (not shown), wherein the second wavelength converting material is yellow phosphor, the first wavelength conversion The material is red fluorescent powder. In this way, the white light illumination system 50 emits white light during operation and is white light having a color temperature of about 3000 K. Therefore, the white light illumination system 50 has better color uniformity and heat dissipation effect. Since the difference between the white light illumination system 50 and the white light illumination system 10 of the embodiment of FIG. 1A is mainly the number of the light-emitting chips, a detailed description of the white light illumination system 50 can be referred to the embodiment of FIG. 1A, and therefore no further details are provided herein.

6(A), 6(B) and 7 are circuit diagrams of a white light illumination system according to three embodiments of the present invention. Referring first to FIG. 6(A), the white light illumination system 61 of the present embodiment has eight light-emitting wafers including seven second light-emitting wafers 63 (blue light wafers) and one first light-emitting wafer 62 (red light wafer). The eight light-emitting wafers are electrically connected to each other in series such that the white light illumination system 61 can still emit white light having a color temperature of about 3000 K while in operation.

Next, referring to FIG. 6(B), the white light illumination system 65 of the present embodiment may include a plurality of second light-emitting chips 64 (blue light wafers) having a smaller volume, or a plurality of second light-emitting chips 64 having the same volume. (Blue light wafer), then with a first light emitting chip 62 (red light wafer). Specifically, the white light illumination system 65 of the embodiment includes two sets of second transmissions in parallel. The optical wafer (blue light wafer) string 65a, the second light emitting wafer (blue light wafer) string comprises seven blue light wafers connected in series, and the two sets of second light emitting wafer (blue light wafer) strings 65a are connected in parallel to the first light emitting wafer 62 ( The red light wafers are connected in series so that the white light illumination system 65 can still emit white light having a color temperature of about 3000 K while in operation.

Referring then to Figure 7, the white light illumination system 71 of the present embodiment has eight light emitting wafers including seven second light emitting wafers 73 (blue light wafers) and one first light emitting wafer 72 (red light wafer). The eight illuminating wafers are electrically connected to each other in series. The arrangement of the red and blue ray wafers and the number of wafers are not limited to the illustrated embodiment, but the preferred embodiment is the second illuminating wafer 73 ( The blue light wafer) surrounds the first light emitting wafer 72 (red light wafer) to obtain better color uniformity. The white light illumination system 71 of the present embodiment may include a heat dissipation module (not shown), so as to avoid a phenomenon in which the brightness of the blue light wafer and the red light wafer are inconsistent due to high temperature, thereby causing color shift.

In this embodiment, the white light illumination system 71 may further include a driving circuit or a driver (not shown), such as a variable resistor, a capacitor, or a pulse width modulation system (PWM system). In order to regulate the color shift of the blue light wafer and the red light wafer at a high temperature, or to adjust the light emission ratio of the blue light wafer and the red light crystal in the white light illumination system 71, the white light color temperature can be maintained at about 3000K. In addition, the white light illumination system 71 can be used in different types of lighting devices, such as lighting devices such as bulb balls, lamps, or headlights.

In summary, the white light illumination system of the embodiment of the present invention utilizes the first A light emitting wafer (such as a red light wafer) and a second light emitting wafer (such as a blue light wafer) are used in conjunction with a wavelength conversion unit to generate white light. Wherein, the first illuminating wafer and the second illuminating wafer maintain high luminous efficiency of the white illuminating system, and the wavelength converting unit reduces the color deviation of the white illuminating system at a high operating temperature. Further, a portion of the red light required for the white light illumination system of one embodiment of the present invention is provided by a red light wafer, thereby ensuring high luminous efficiency. Another portion of the red light is provided by the red phosphor, such that the color deviation as a function of operating temperature is reduced. By virtue of both the red light crystal and the red fluorescent powder, the white light illumination system of one embodiment of the present invention achieves higher luminous efficiency and lower color deviation.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

10, 50, 61, 65, 71‧‧‧ white light illumination system

11‧‧‧Base

12, 52, 62, 72‧‧‧ first illuminating wafer

13, 53, 63, 64, 73‧‧‧ second illuminating wafer

14‧‧‧wavelength conversion unit

14a‧‧‧First wavelength conversion material

14b‧‧‧second wavelength conversion material

65a‧‧‧Second light-emitting chip string

L1‧‧‧First light

L2‧‧‧second light

L3‧‧‧Excitation beam

L3’‧‧‧second red light

L3”‧‧‧ Third Light (Yellow Light)

FIG. 1A is a schematic diagram of a white light illumination system according to an embodiment of the invention.

Fig. 1B is a schematic cross-sectional view taken along line I-I' of Fig. 1A.

2 is a comparison diagram of the color shift of the white light illumination system of the embodiment of FIG. 1 and the control example 1 at a higher operating temperature in a CIE chromaticity coordinate system.

Figure 3 is a graph showing the luminous efficiency of the white light illumination system of the embodiment of Figure 1 and Comparative Example 2 operating at different currents.

4 is an excitation spectrum of the white light illumination system of the embodiment of FIG. 1 and Comparative Example 2.

FIG. 5 is a schematic diagram of a white light illumination system according to another embodiment of the present invention.

6(A), 6(B) and 7 are circuit diagrams of a white light illumination system according to three embodiments of the present invention.

10‧‧‧White lighting system

11‧‧‧Base

12‧‧‧First illuminating chip

13‧‧‧Second light-emitting chip

Claims (12)

A white light illumination system comprising: a first light emitting chip adapted to emit a first light, the first light comprising a first red light; and a second light emitting chip adapted to emit a second light, wherein the second light The wavelength of the light is different from the wavelength of the light of the first light; and a wavelength conversion unit is disposed on the first light emitting chip and the second light emitting chip, wherein the second light is converted when the second light is irradiated to the wavelength converting unit For an excitation beam, the excitation beam includes a second red light and the excitation beam, the first light, and the second light are co-mixed into a white light. The white light illumination system of claim 1, wherein the first light emitting wafer is a red light wafer, and the second light emitting wafer is a plurality of blue light wafers. The white light illumination system of claim 1, wherein the wavelength conversion unit further comprises: a first wavelength converting material to convert the second light into the second red light; and a second wavelength converting material to Converting the second light into a third light. The white light illumination system of claim 3, wherein the third light is a yellow light. The white light illumination system of claim 1, wherein a peak wavelength of the first red light spectrum is different from a peak wavelength of the second red light spectrum. The white light illumination system of claim 1, wherein the peak wavelength of the spectrum of the first red light is substantially equivalent to the peak wavelength of the spectrum of the second red light. For example, in the white light illumination system described in claim 1, the color deviation of the white light emitted by the white light illumination system is maintained in the range of the 7th-order MacAdam Ellipse at an operating temperature of 85 degrees Celsius. within. The white light illumination system of claim 1, wherein the material of the first wafer comprises a gallium phosphide compound or a gallium arsenide compound, and the first wavelength conversion material is nitride or oxynitride fluorescent powder. The white light illumination system of claim 1, wherein the white light has a color temperature substantially similar to 3000K. A white light illumination system comprising: a plurality of light emitting chips adapted to emit blue light and a first red light; and a wavelength conversion unit comprising a first wavelength converting material and a second wavelength converting material, wherein the blue light is the first Converting the wavelength converting material into a second red light having a wavelength different from the wavelength of the first red light, and the blue light is converted into yellow light by the second wavelength converting material, the light, the yellow The light and the second red light are co-mixed into a white light, and the white light illumination system emits the white light with a color deviation within a range of 7th order MacAdam Ellipse. The white light illumination system of claim 10, wherein the wafers comprise a red light wafer and a plurality of blue light wafers. A white light illumination system as described in claim 10, The white light has a color temperature substantially similar to 3000K.