WO2011127622A1

WO2011127622A1 - Method for improving emitted light color based on light wavelength conversion

Info

Publication number: WO2011127622A1
Application number: PCT/CN2010/000476
Authority: WO
Inventors: 杨毅; 李文超; 李屹
Original assignee: 绎立锐光科技开发(深圳)有限公司
Priority date: 2010-04-12
Filing date: 2010-04-12
Publication date: 2011-10-20

Abstract

A method for improving emitted light color based on light wavelength conversion is disclosed. The method includes following steps: guiding an exciting light to emit to a wavelength conversion layer (1) to excite the excited light with a first dominant wavelength λ₁; determining the wavelength of the excited lightλ_E which needs to be enhanced in the light converting output spectrum of the light wavelength conversion material; choosing an angle selection filter (2) which has a transmission property corresponding to λ_E, and setting it on one side of the wavelength conversion layer (1) to generate an emitted light with a second dominant wavelength λ₂; enhancing the light withλE to "PULL" λ₁ reachλ₂ byλ₁<λ₂<λ_E or λ₁>λ₂>λ_E; reflecting the excited light emitting to the emitting surface by setting a reflection surface (5) on the other side of the wavelength conversion layer (1). The method improves the brightness of the emitted light greatly.

Description

Method for improving the color of emitted light based on wavelength conversion of light

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the color of a light source, and more particularly to a gating control method for the intensity, color or direction of light of a device or device.

BACKGROUND OF THE INVENTION Conventional semiconductor light-emitting diodes (LEDs) are mainly used for signal indicators, television remote controls, and low-speed short-distance optical fiber communication because of low output power and low brightness. Since the early 1990s, a new generation of semiconductor optoelectronic materials based on InGaAlP and InGaN has developed rapidly. Various high-power and high-brightness LED light sources such as red, yellow, blue, green, ultraviolet and white have emerged. It has emerged in an endless stream and is used more and more widely in various display and lighting fields. However, in the field of display and illumination, in order to greatly reduce the cost, the existing light source uses a lower cost light source (such as, but not limited to, a blue LED), and uses a wavelength conversion scheme to obtain a predetermined color of the emitted light. Avoid using LEDs that are the same color as the exiting light and have a higher cost. The wavelength conversion of light typically utilizes shorter wavelength light from a source of illumination to excite light of the wavelength conversion material to emit light of a different wavelength. The light wavelength conversion material includes a phosphor, a dye or a nano luminescent material, or a mixture of two or more of these materials, and a phosphor is more commonly used at present. For example, Nichia's white LED patent discloses a technical solution for exciting white YAG phosphors with white light by using 470 'nano blue LED chips. The scheme is simple in structure, low in manufacturing cost, and highly practical in products. Sex. The above light source based on optical wavelength conversion also has the advantages of rich color and easy design. U.S. Patent No. 7,234,820 teaches the use of LEDs to excite phosphors and to mix the excited light with other color lights. Generally, the light emitted from the wavelength conversion material is not bright. In order to make the light source based on optical wavelength conversion more suitable for the application requirements in the display field, U.S. Patent No. 7,070,300 discloses a phosphor brightening structure for improving the brightness of the light emitted by the light source. The solution uses an angle selection filter to illuminate the small-angle incident excitation light from the phosphor, thereby improving the utilization of the large-angle excited light in the light emitted from the light source, so that the light output brightness of the light source can exceed the same color LED. Light output brightness. The light source wavelength conversion based light source is disadvantageous in that, in the case of a phosphor, the light wavelength conversion material generally has a wide light conversion output spectrum, so that the color purity of the light emitted from the light source is not good, and the color of the emitted light is not good. It is not bright enough and bright, even if the brightness of the emitted light is strong enough, it is difficult to be used in specific occasions (such as display field).

SUMMARY OF THE INVENTION The technical problem to be solved by the present invention is to address the above-mentioned deficiencies of the prior art, and to propose a method for improving the color of the outgoing light of the light source based on the wavelength conversion of light, and at the same time, it is also advantageous to enhance the brightness of the emitted light. In order to solve the above technical problem, the basic idea of the present invention is that a light wavelength conversion material has a wider light conversion output spectrum, and if the intensity of light of a specific wavelength in the spectrum is designed to be enhanced, the human eye of the output light can be changed. Visual effects, thereby achieving the purpose of improving the color of the emitted light; therefore, the present invention utilizes the phosphor brightening structure of the prior art and designs the band pass or low pass filter to a predetermined wavelength range incident only at a small angle The excited light inside enhances the brightness of the emitted light and improves the color of the emitted light. As a technical solution for realizing the concept of the present invention, a method for improving the color of emitted light based on optical wavelength conversion is provided, which is used for a light source, including steps:

Directing excitation light to a wavelength conversion layer comprising a light wavelength conversion material to excite an excitation light having a first dominant wavelength 4;

An angle selection filter is disposed on the other side of the wavelength conversion layer to guide the excitation light smaller than the predetermined exit angle to transmit the filter through the angle in a transmissive manner, and to simultaneously reflect the excited light larger than the predetermined exit angle. ;

In particular, it also includes the steps:

Determining the wavelength of the excited light to be enhanced in the light conversion output spectrum of the light wavelength conversion material, selecting the angle selection filter to have a transmission characteristic corresponding to the wavelength of the excitation light to be enhanced, to generate the second main wavelength of the emitted light ₁₂ having; 4 wherein said first main wavelength, ^ needs to be a relationship between the wavelength of light ₁₂ and a second main excitation wavelength is enhanced by: <λ ₂ <or ^>! > . In the above solution, the angle selection filter has a transmission characteristic of: at a predetermined incident angle, the transmittance curve of the excitation light of different wavelengths has a low-pass or band-pass characteristic; and the transmittance on the falling edge of the transmittance curve The wavelength corresponding to approximately 50% is the wavelength of the excited light to be enhanced. In the above solution, the predetermined incident angle α is set as the light collecting system collecting angle of the light source. In the above solution, a dielectric film having a low refractive index is disposed between the wavelength conversion layer and the angle selection filter, and a refractive index of the dielectric film is lower than a refractive index nl of the wavelength conversion layer. To totally reflect the large angle incident light from the wavelength conversion layer. In the above aspect, a reflective surface opposite to the angle selection filter is disposed on the other side of the wavelength conversion layer to reflect the excitation light incident on the reflective surface. In the above solution, the method further includes the steps of: selecting a glass or a film having selective absorption characteristics for a predetermined wavelength, and superimposing the glass or the film with the angle selection filter to adjust and improve the second main wavelength. By adopting the above various technical solutions, the brightness can be greatly improved while the illuminating color can be greatly improved, so that it conforms to the display standard. At the same time, each technical solution has the advantages of simple structure, simple and feasible.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic structural view of a light wavelength conversion light source based on the present invention;

2 is an embodiment of a filter transmission spectrum for a light source with a red phosphor; FIG. 3 is a diagram showing an example of a filter transmission spectrum used in place of the embodiment of FIG. 2; FIG. 4 is FIG. 2 or FIG. An example of an exiting light spectrum of a light source embodiment;

Figure 5 is a diagram showing an example of a green phosphor light conversion output spectrum for a light source;

6 is a transmission spectrum embodiment of a filter used in the embodiment of the light source of FIG. 5. FIG. 7 is an example of a light spectrum of the light source of the embodiment of the light source of FIG.

8 is a light emission spectrum of still another embodiment of a light source with red phosphor; FIG. 9 is a schematic diagram of a light transmittance curve of red glass in the embodiment of FIG. 8; wherein the reference numerals in FIG. 1 are: Wavelength conversion layer, 2 - filter, 3 - a dielectric film; 40 - an excitation light, 41 ~ 43 - an excited light; 5 - a reflective surface, 6 - one LED / LED chip layer.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be further described with reference to the preferred embodiments shown in the drawings. The light source shown in FIG. 1 : The wavelength conversion layer 1 comprises a light wavelength conversion material, which may be composed of a colloid containing the wavelength conversion material; the light source may be an LED, a laser source or a conventional light source (for example, an arc lamp). Take, but not limited to, the LED/LED chip layer 6 as an example. The way the light source works includes the steps:

Directing excitation light 40 from the illumination source to the wavelength conversion layer 1 to excite the optical wavelength conversion material to generate excited light having a first dominant wavelength; An angle selecting filter 2 is disposed on one side of the wavelength conversion layer 1 to guide the excited light 41 or 42 smaller than the predetermined exit angle to transmit the filter through the angle in a transmissive manner while being excited by the predetermined exit angle. The light is reflected back to the wavelength conversion layer 1 , and the diffused reflection of the excited light by the light wavelength conversion material is used to change the exit angle of the excited light for secondary or multiple use, thereby improving the brightness of the light emitted by the light source. . In addition, if a reflective surface 5 opposite to the angle selection filter 2 is disposed on the other side of the wavelength conversion layer 1 by referring to the prior art to reflect the excitation light incident on the reflective surface, By limiting and reducing the divergence angle of the excited light and contributing to the secondary use of the excitation light to change the exit angle, it is more advantageous to increase the brightness of the light emitted by the light source. Since the existing angle selection filter does not change the color of the emitted light within a predetermined exit angle range, the color change of the emitted light is not greatly changed or even deteriorated. To this end, the method of the invention further comprises the steps of:

Determining, in the light converted output spectrum of the light wavelength conversion material, a wavelength of the excited light that needs to be enhanced; selecting the angle selection filter 2 to have a transmission characteristic corresponding to the wavelength of the excited light that needs to be enhanced, To produce an exiting light having a second dominant wavelength. The method of the present invention allows 4 < Α ₂ < or 4 > ^ > to be utilized if the first dominant wavelength, the wavelength of the excited light to be enhanced, and the second dominant wavelength are respectively denoted by Λ, and Get enhanced to "pull" 4 to reach.

Since the response curve of human vision to the spectrum is most sensitive at 555 nm (yellow-green light), it is attenuated to both sides; when the second dominant wavelength is closer to the distance of 555 nm, the wavelength of the excited light needs to be enhanced by 4 to the dominant wavelength. The "pull" effect is obvious, that is, |4- 4| > |^2 - A|. Conversely, when the second dominant wavelength is farther away from 555 nm, the "pull" is weaker, that is, l^-^^A - Al.

Specifically, a light source including a red phosphor having a light-converted output spectrum shown by a solid black solid line in FIG. 4 is taken as an example. The dominant wavelength 4 of the excited light of the phosphor is 613 nm, and the color adjustment scheme of the light source emitted by the light source is ^ < λ ₂ < λ _Ε . When the color is desired to be more vivid, for example, the red light outputting l ₂ = 616« At the time, since the red wavelength is different from the 555 nm yellow-green light wave, it is better to first select ^ according to the experience of _2-3 about 3-5 times. The spectral characteristics of the filter are then determined based on the light collection angle of the light collection system in the light source. Depending on the application, the light source can be designed as a light collecting system with different structures to further process and utilize the emitted light after passing through the filter; the present invention will refer to the characteristic parameter of the light collecting angle inherent in the light collecting system, and not Prior art light collection systems that are not the focus of the present invention are set forth.

The angle selection filter 2 selected by the present invention should have a transmission characteristic of: at a predetermined incident angle, the transmission curve of the excitation light of different wavelengths has a low-pass or band-pass characteristic. The preferred embodiment of the present invention is a design For the sake of simplicity, The wavelength at which the transmittance is about 50% at the lower edge of the transmittance curve is the wavelength of the excited light that needs to be enhanced. The predetermined angle of incidence a may be set to a collection angle of the light collection system of the light source (generally less than or equal to 45 degrees), or an angle smaller than the collection angle to increase the light utilization of the system.

Take a light collection system with a 35 degree light collection angle as an example. It is assumed that the first embodiment selects an angle selection filter having the characteristics as shown in Fig. 2: The five curves from right to left correspond to the transmittance characteristics at incident angles of 0, 10, 20, 30 and 40 degrees, respectively. It can be seen that 50% of the falling edge of the 35 degree transmittance curve of the filter corresponds to about 630 nm of the excited light to be enhanced. The second embodiment selects an angle selection filter having the characteristics shown in FIG. 3: the five curves from right to left correspond to transmittance characteristics at incident angles of 0, 10, 20, 30, and 40 degrees, respectively. The 50% of the falling edge of the degree transmittance curve corresponds approximately to the wavelength of the excited light that needs to be enhanced by 640 nm. Fig. 4 is a view showing the above-described outgoing light spectrum in several cases using the conventional angle selecting filter, the angle selecting filter using the characteristics shown in Fig. 2, and the angle selecting filter using the characteristics shown in Fig. 3. The data of the light emitted by the light source is determined as follows:

It can be seen that the color of the emitted light will deteriorate to an orange offset using the existing filter, and the red color of the emitted light in both embodiments using the method of the present invention becomes more vivid. In particular, in the first embodiment (using the filter having the characteristics of Fig. 2), the color of the emitted light is significantly improved while maintaining high output brightness. For green light, color change is much easier because the difference between the dominant wavelength and 555nm is small. Taking a light source including a green phosphor having the light conversion output spectrum shown in FIG. 5 as an example, the achievable light source color adjustment scheme is 4 > ₂ > ^. 4 by the first dominant wavelength of 547nra, according to the selected ratio only A _£ 2 ~ 5 nm experiences A _£. Taking a light collecting system with a 20-degree light collecting angle as an example, FIG. 6 is a filter characteristic for selecting a filter corresponding to a selected angle: a corresponding transmittance angle corresponding to a 20-degree incident angle is selected to correspond to a transmittance of approximately 50% at a falling edge. The wavelength is approximately 535 wavelengths of the excited light to be enhanced; then the spectrum of the light exiting the light source of Fig. 7 (the spectrum of the light exiting the light source without the angle selection filter is shown by a solid black line, using the characteristic filter of Fig. 6 The spectrum of the light emitted by the light source is as shown by the gray solid line. The spectrum of the light emitted by the light source using the normal angle selection filter is as shown by the gray solid line. It will correspond to the test data in the following table: Color coordinate main wavelength (nm) Color Purity brightness (lumen) Phosphors of the original spectrum (0. 2839, 0. 6845) 547 0. 929 311 using the existing filter (0. 3059, 0. 6727) 550. 4 0. 953 624 using the filter of the present invention (0. 2202 , 0. 7426) 538 0. 945 609

It can be seen that with the existing filter, although the emitted light is slightly better in brightness, its dominant wavelength is 550 nm, and the color shift to yellow is deteriorated. By using the method of the invention, the brightness of the emitted light is greatly enhanced, and the color of the emitted light is effectively improved, and the color coordinate is greatly close to the green color coordinate standard (0.21, 0.71) in the NTSC display standard, and the displayed green visually is better than the NTSC standard. It must be brighter; and the color purity of the emitted light is also improved to some extent. The test also shows that the difference between the wavelengths corresponding to the transmittance at the falling edge of 75% to 25 % is not more than 30 nm, and the smaller the better. The present invention further improves the structure of the light source of the present invention in order to improve the color of the emitted light while improving the color of the emitted light, as shown in FIG. Between the wavelength conversion layer 1 and the angle selection filter 2, or between the wavelength conversion layer 1 and the reflective surface 5, a dielectric film 3 having a low refractive index is disposed, and the medium is made The refractive index n2 of the film 3 is lower than the refractive index n1 of the wavelength conversion layer 1 to totally reflect the large-angle incident light from the wavelength conversion layer 1, and the small-angle outgoing rays 41, 42 are refracted through the medium. Membrane 3. The large angle incident light includes excitation light or excited light having an incident angle greater than arcs in (n2/nl). When it is excitation light, it can provide the opportunity to be absorbed and utilized by the phosphor, thereby improving the fluorescence conversion extraction efficiency; when it is the excited light, the light may be changed in the direction of the light due to the diffuse reflection of the phosphor. An angle of the exiting light (e.g., light 43) is refracted through the dielectric film 3. In the above embodiment, the dielectric film 3 having a low refractive index may be an air gap. The refractive index of the air gap is 1, and if the refractive index of the dielectric film 3 is set to be smaller than the refractive index n1 of the wavelength conversion layer 1, the brightness enhancement effect is undoubtedly better: for example, the dielectric film is made of low-pressure air. Or the wavelength conversion layer 1 is made of a material having a high refractive index (for example, greater than 1.5) such as glass or ceramic. Taking half of the refractive index n1 as an example, when the excitation light is emitted from the wavelength conversion layer 1 to the dielectric film 3, only about (n2/nl) ² = 25 % cannot be reflected back, and another 75 % can no doubt be used again. The dielectric film 3 may also be a dielectric film composed of two or more layers of different optical refractive index materials. It is even possible to combine these dielectric films with an intermediate overhead structure, for example, to make the dielectric film 3 a hollow optical sheet. The dielectric film 3 may also be an optical film containing a regularly arranged photonic crystal, or the optical film may be different from the above. A composite film of an optical refractive index material medium. The smaller the thickness of the dielectric film 3 having a low refractive index, the better, preferably less than 1/15 of the radius of the inscribed circle of the wavelength conversion layer itself. Because of the wide variety of existing phosphors, the characteristics are different. When selecting a phosphor, it is necessary to consider various factors such as efficiency, excitation spectrum, and emission spectrum. In order to make the invention applicable to a plurality of phosphors, the method of the invention further comprises the steps of: selecting a glass or film having selective absorption characteristics for a predetermined wavelength, the glass or film and the angle selection filter (2) The second dominant wavelength A _{2 is} superimposed to improve the color of the outgoing light. An example in which another red phosphor is used as shown in Fig. 8 is taken as an example. If the method of the present invention is not used, the color coordinates of the emitted light of the phosphor are (0. 574, 0.425), and the dominant wavelength is 590 nm. In the test, the method of the present invention is used, but the step of setting the above glass or film is not carried out, and the spectrum of the emitted light of the light source will be as shown by a thin solid line, and the measured color coordinates are (0.6253, 0. 3711), and the dominant wavelength is 599. . 4nm. This color obviously does not meet the display requirements. To this end, further selecting a glass having a transmittance curve as shown in FIG. 9 and arranging the glass to closely follow the angle selection filter (2), the light spectrum of the light source will be as shown in FIG. 5纳米。 The measured color coordinates are (0. 6713, 0. 3299), the dominant wavelength is 611.5 nm. Therefore, in the case where the brightness of the emitted light does not change much, the color of the emitted light is greatly improved. For a light source with a red phosphor, the present invention provides a high-pass characteristic of the transmittance curve of the glass or film. If the wavelength corresponding to the rising edge of the transmittance curve is 50%, the corresponding wavelength at the 20% peak intensity of the rising edge of the outgoing light spectrum under the angle selection filter (2) is D20. when the L50> D20 ', a second main wavelength adjusted ₁₂ will be greater than the second main wavelength before adjustment, and the main wavelength is also greater than the adjusted L50. Experiments with a variety of red phosphors confirmed the establishment of the above settings. Conversely, for other color phosphors, adjusting the transmittance curve characteristics of the glass or film to selectively absorb light of a predetermined wavelength to adjust the second dominant wavelength 1 ₂ also embodies the method of the present invention. Spirit, which will fall within the scope of the present invention. In a practical application, when the glass is selected and used, the angle selection filter (2) can be replaced with an angle selective filter film directly plated on the glass.

Claims

Claim

1. A method for improving the color of emitted light based on optical wavelength conversion, for a light source, comprising the steps of:

Directing excitation light to the wavelength conversion layer (1) including the optical wavelength conversion material to excite the generated excitation light having the first dominant wavelength Λ;

An angle selection filter U) is disposed on one side of the wavelength conversion layer (1) to guide the excitation light smaller than the predetermined exit angle to pass through the angle selection filter (2) while being larger than the predetermined emission. The angled excitation light is reflected back;

It is characterized in that it further comprises the steps of:

Determining the wavelength of the excited light to be enhanced in the light-converted output spectrum of the light-wavelength converting material to select the angle-selecting filter (2) so as to have a transmission characteristic corresponding to the wavelength of the excited light to be enhanced, generating a second outgoing light having a dominant wavelength of _12; wherein said first main wavelength 4, f should be increased by the relationship between the excitation light wavelength and a second main wavelength ^ is: <λ ₂ <^ lj or > λ ₂ > Α _Ε .

2. The method for improving the color of emitted light based on optical wavelength conversion according to the requirements of claim 1, wherein

The angle selection filter (2) has a transmission characteristic of: at a predetermined incident angle, the transmittance curve of the excitation light of different wavelengths has a low-pass or band-pass characteristic; and the transmittance is substantially on the falling edge of the transmittance curve. The wavelength corresponding to 50% is the wavelength of the excited light that needs to be enhanced.

3. The method for improving the color of emitted light based on optical wavelength conversion according to the requirements of claim 2, characterized in that:

The predetermined angle of incidence is set to a collection angle of the light collection system of the light source.

4. The method according to claim 3, wherein the color of the emitted light is improved based on the wavelength conversion of the light, characterized in that:

The predetermined incident angle α is less than or equal to 45 degrees.

5. A method for improving the color of emitted light based on optical wavelength conversion according to claim 2, characterized in that:

The difference between the wavelengths corresponding to the transmittance at the falling edge of 75% to 25 % is less than ³⁰ nm.

6. A method for improving the color of emitted light based on optical wavelength conversion according to the requirements of claim 1, characterized in that:

When the excited light is red light, Λ < When the excited light is green, ^>^> ^.

7. The method for improving the color of emitted light based on optical wavelength conversion according to the requirements of claim 1, characterized in that:

Providing a dielectric film (3) having a low refractive index between the wavelength conversion layer (1) and the angle selection filter (2), and having a refractive index lower than that of the dielectric film (3) The refractive index n1 of the wavelength conversion layer (1) is used to totally reflect the large-angle incident light from the wavelength conversion layer (1).

8. A method for improving the color of emitted light based on optical wavelength conversion according to claim 1 or 7, characterized in that:

A reflecting surface (5) opposite to the angle selecting filter (2) is disposed on the other side of the wavelength conversion layer (1) to reflect the excited light incident on the reflecting surface.

9. The method according to claim 8, wherein the color of the emitted light is improved based on optical wavelength conversion, wherein:

Providing a dielectric film (3) having a low refractive index between the wavelength conversion layer (1) and the reflective surface (5), and having a refractive index lower than the wavelength conversion layer of the dielectric film (3) The refractive index n1 of (1) is used to totally reflect the large-angle incident light from the wavelength conversion layer (1).

10. A method for improving the color of emitted light based on optical wavelength conversion according to claim 7 or 9, characterized in that:

The dielectric film (3) having a low refractive index is an air gap.

11. The method according to claim 10, wherein the color of the emitted light is improved based on the wavelength conversion of the light, characterized in that:

The thickness of the air gap is less than 1/15 of the radius of the inscribed circle of the wavelength conversion layer itself.

12. The method according to claim 1, wherein the color of the emitted light is improved based on optical wavelength conversion, wherein

' Also includes the steps of: selecting a glass or film having selective absorption characteristics for a predetermined wavelength, superimposing the glass or film with the angle selection filter (2) to adjust and improve the second dominant wavelength ₂ .

13. The method according to claim 12, wherein the color of the emitted light is improved based on the wavelength conversion of the light, characterized in that:

The angle selection filter (2) is replaced by an angle selective filter film directly plated on the glass.