KR102408688B1 - Tunable ultra-broad band near-infrared light-emitting device - Google Patents

Abstract

The present invention is a high-power ultra-broadband light emission that exhibits a smooth emission spectrum distribution over the near-ultraviolet to near-infrared wavelength region (380 nm to 1000 nm) by a combination of two types of light emitting devices that emit light of near-infrared phosphor excited by a white LED having a high color temperature. It relates to a device and a light emitting device.

Description

Tunable ultra-broad band near-infrared light-emitting device

The present invention relates to a wavelength tunable ultra-wideband near-infrared light emitting device.

Recently, near-infrared rays in the 700 nm to 2500 nm region have been used in fields such as medical care, food management, and health maintenance. Existing white LEDs for general lighting do not include these wavelength ranges. In particular, near-infrared spectroscopy is important for food management. In particular, the Si photodiode, which is indispensable for sensing technology, corresponds to a wavelength range of 400 to 1100 nm, and its maximum sensitivity is around 900 nm.

For near-infrared light emission, single-unit semiconductor LEDs have been used so far. For this reason, the line width of an emission spectrum is narrow, and it is not suitable as a spectral-spectrum light source. In addition, manufacturing of halogen bulbs has been stopped today, and there is an urgent need to put a new broadband solid-state light source into practical use as a small replacement bulb in countries around the world.

Recently, a near-infrared phosphor having an emission band from 700 nm to 1150 nm has been developed. In 2016, Osram Opto Semiconductors commercialized the world's first broadband near-infrared LED (SFH4735) using blue LED and near-infrared phosphor.

However, this type of near-infrared LED is about a thousand times weaker in intensity of near-infrared emission compared to the blue wavelength, and furthermore, the emission spectrum distribution is discontinuous in the near-infrared region in the visible light. In addition, the present inventors have been mixing a plurality of near-infrared phosphors so far to develop a wide range of near-infrared LEDs for practical use. However, 810 nm phosphor emission was quenched and a flat light-emitting band was not obtained.

The present invention is a near-ultraviolet semiconductor LED chip having an emission peak at 400 to 410 nm for the purpose of elucidating the light emitting mechanism of 810 nm and practical use of a light emitting device having a flat light emission distribution without irregularities in a wavelength region of 700 to 1000 nm. A white LED having a high color temperature and a plurality of high-efficiency near-infrared phosphors are combined to provide an ultra-wideband light-emitting device and a light-emitting module capable of emitting continuous light over the near-ultraviolet, visible, and near-infrared regions.

The present invention uses white with a high color temperature as an excitation light source and emits separate near-infrared phosphors to emit a wide range of emission spectra without irregularities continuously by a phosphor conversion method in which each spectral wavelength distribution is controlled. Broadband near-infrared light-emitting device An object of the present invention is to provide a near-infrared light-emitting device including the above-mentioned device.

However, the technical problem to be achieved by the present invention is not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

The present invention is a white LED chip of a color temperature of 3000 ~ 4000K;

a first light emitting device including a phosphor layer in which three or more kinds of near-infrared phosphors that emit light by being excited by the emission wavelength of the white LED chip are dispersed; and

and a second light emitting device including a phosphor layer in which two or more kinds of near-infrared phosphors that emit light by being excited by the emission wavelength of the white LED chip are dispersed,

The near-infrared phosphor is excited in a wavelength range of 450 nm to 630 nm and has an emission peak at 710 nm, a second phosphor excited in a wavelength range of 470 nm to 630 nm and having an emission peak at 810 nm, and a wavelength of 630 nm Provided is a near-infrared light-emitting device, which is selected from a combination consisting of a third phosphor excited in the region and having an emission peak at 910 nm.

In an embodiment of the present invention, the first light emitting device includes a phosphor layer in which a first phosphor, a second phosphor, and a third phosphor are dispersed,

The second light emitting device may include a phosphor layer in which the first phosphor and the second phosphor are dispersed.

In another embodiment of the present invention, the first phosphor is Gd3Ga5O12:Cr having a central emission peak at 710 nm, the second phosphor is ScBO3:Cr having an emission peak at 810 nm, and the third phosphor has an emission peak at 910 nm It is characterized in that it is CaCuSi4O10 having

In another embodiment of the present invention, the phosphor layer of the first light emitting device,

The first phosphor, the second phosphor and the third phosphor are included in a weight ratio of 16-24: 5-24: 4-7.

In another embodiment of the present invention, the white LED chip is characterized in that it has an emission wavelength center peak of 600 nm to 700 nm.

In another embodiment of the present invention, the white LED chip,

As a cyan phosphor (Sr,Br)10(PO4)6Cl:Eu,

SiAlON:Eu as a green phosphor,

(Ba,Sr)Si2(O,Cl))2N2:Eu as a yellow phosphor, and

It is characterized in that it contains CaAlSi(ON)2:Eu as a red phosphor.

In another embodiment of the present invention, the cyan phosphor, the green phosphor, the yellow phosphor and the red phosphor are included in a weight ratio of 8-10: 1:0.1-0.9: 4-8.

In another embodiment of the present invention, the near-infrared light emitting device is characterized in that it has a broad emission spectrum distribution at 380 to 1200 nm.

Since the ultra-broadband light emitting device according to the present invention can cover a wavelength range of 380 to 1200 nm, it can replace small light sources such as incandescent bulbs, halogen bulbs, and xenon bulbs. In addition, it has a distribution similar to the solar spectrum distribution (AM1.5).

Since the light emitting device of the present invention has a broad emission spectrum, it is different from a single product near-infrared LED, and is not affected by forward current and temperature. In addition, since a method of emitting a phosphor with LED light is adopted, pulse driving is possible. Since the two types of light emission distributions are composed of different LED combinations, the light emission spectrum and its intensity can be adjusted arbitrarily. In addition, even when the forward current increases, the light emission intensity increases almost in proportion, so that it is easy to control the light emission intensity even as a light source for measurement.

1 is a diagram exemplarily showing the emission spectrum forward current dependence (curve 1: 65 mA, curve 2: 100 mA, curve 3: 150 mA) of a sample shown as a comparative example in which a second phosphor is not included (α: emission at 710 nm) intensity, β: emission intensity of 810 nm, γ: emission intensity of 910 nm).
2 is a diagram illustrating the emission spectrum forward current dependence (curve 1: 65 mA, curve 2: 100 mA, curve 3: 150 mA) of Example 1 Sample A containing 24% of the second phosphor.
3 is a diagram illustrating the luminescence spectrum forward current dependence (curve 1: 65 mA, curve 2: 100 mA, curve 3: 150 mA) of Example 2 Sample B not containing the third phosphor.
4 is a diagram schematically showing the structure of a light emitting module composed of a combination of two types of light emitting devices having different emission spectra.
5 is a diagram illustrating an emission spectrum when 150 mA is applied to Sample A of Example 1 and 65 mA is applied to Sample B of Example 2 at the same time.
6 is a diagram illustrating the forward dependence of the emission spectrum (curve 1: 65 mA, curve 2: 100 mA, curve 3: 150 mA) of a light emitting module sample C in which Example 1 Sample A and Example 2 Sample B are connected in parallel.

The present invention relates to a light-emitting element comprising three types of near-infrared phosphor excited by a white LED having an emission peak at 630 nm. In more detail, the present invention provides a near-infrared light emitting device including the above device, comprising: a white LED chip having a color temperature of 3000 to 4000K; a first light emitting device including a phosphor layer in which three or more kinds of near-infrared phosphors that emit light by being excited by the emission wavelength of the white LED chip are dispersed; and a second light emitting device including a phosphor layer in which two or more kinds of near-infrared phosphors that are excited by the emission wavelength of the white LED chip and emit light are dispersed, wherein the near-infrared phosphor is in a wavelength range of 450 nm to 630 nm. A first phosphor excited and having an emission peak at 710 nm, a second phosphor excited in a wavelength region of 470 nm to 630 nm and an emission peak at 810 nm, and a third phosphor excited in a wavelength region of 630 nm and having an emission peak at 910 nm It provides a near-infrared light emitting device, which is selected from the group consisting of phosphors.

The above-described white LED chip is a light emitting device having a color temperature of 3000 to 4000K, which is excited by a semiconductor LED chip having an emission peak at 380 nm or more and 410 nm or less, and includes a phosphor layer dispersed in a transparent resin layer. The phosphor layer described above includes the following four types of phosphors.

(Sr,Br)10(PO4)6Cl:Eu as a cyan phosphor

SiAlON:Eu as green phosphor

(Ba,Sr)Si2(O,Cl))2N2:Eu as yellow phosphor

CaAlSi(ON)2:Eu is included as a red phosphor.

The phosphor may be included in a weight ratio of 8-10: 1:0.1-0.9: 4-8, more preferably 9.23: 1:0.46: 5.77, in order to manufacture a white LED having a color temperature of 3000-4000K. Included. The luminous efficiency of the white LED chip is 53lm/W or more, and the average color rendering index (Ra) is 94 or more.

The semiconductor LED chip mounted on the above-described white LED may be made of an InGaN-based compound semiconductor having a central wavelength of 405 nm, a light emission half maximum width of 15 nm, and an external quantum efficiency of 50% or more. The aforementioned chip is flip-chip mounted on a substrate by inverting the chip using solder bumps, gold bumps, conductive paste, or the like. Further, this chip may be connected to a wiring conductor designed on the board by wire bonding.

In the ultra-wideband light-emitting device of the present invention, the transparent resin layer containing three kinds of near-infrared phosphors is excited by the light emission energy from the above-described white LED device. Accordingly, seven types of cyan, green, yellow, red, and near-infrared phosphors may be included. Alternatively, four types of phosphor layers and three types of phosphor layers may have a double structure.

Three types of near-infrared phosphors,

As the first phosphor, Gd3Ga5O12:Cr is preferable as the near-infrared phosphor that is excited in a wavelength region of 450 nm and 630 nm, and preferably has an emission peak at 710 nm.

As the second phosphor, ScBO3:Cr is preferable as a near-infrared phosphor that is excited in a wavelength region of 470 nm and 630 nm and preferably has an emission peak at 810 nm.

As the third phosphor, CaCuSi4O10 is preferable as the near-infrared phosphor that is excited in a wavelength region of 630 nm and preferably has an emission peak at 910 nm.

In addition, the weight ratio (wt%) of the phosphor used in the ultra-wideband light emitting device of the present invention is preferably the first phosphor: the second phosphor: the third phosphor = 16-24: 5-24: 4-7.

The light emitting part of the broadband light emitting device of the present invention includes the aforementioned phosphor and the transparent silicone resin as an encapsulant. Therefore, it is preferable that the seven types of phosphors are uniformly diffused in the silicone resin.

Only the above-described near-infrared phosphor may be separately diffused into the silicone resin and applied as a thin film.

The above-described broadband light emitting device preferably has an average color rendering index Ra of 80 or more and less than 100 when used as a light source for general lighting. It is preferable that a light distribution angle is 110 degrees or more and less than 120 degrees.

The present invention also provides a light emitting module including the above-described ultra-wideband light-emitting device, wherein the above-described light-emitting module is made of a combination of ultra-wideband light-emitting devices having different color temperatures.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention in more detail, and it will be apparent to those of ordinary skill in the art to which the present invention pertains that the scope of the present invention is not limited by these examples.

[Example]

Manufacturing of light emitting modules

The following materials were used as semiconductor LED chips, encapsulants, and phosphor materials to manufacture and evaluate white LEDs and ultra-wideband light emitting devices and light emitting modules.

(1) semiconductor LED chip

A semiconductor LED chip having an InGaN/GaN multi-quantum well structure having an emission peak wavelength of 405 nm and an emission half maximum width of 15 nm was used as the light emitting layer. The external quantum efficiency was more than 50%.

(2) encapsulant

In addition to the silicone resin, silica powder (SiO2) was used as a precipitation material.

(3) phosphor

As the phosphor, the following phosphor material was used.

1. Cyan phosphor: (Sr,Br)10(PO4)6Cl2:Eu

2. Green Phosphor: SiAlON:Eu

3. Yellow phosphor: (Ba,Sr)Si2(O,Cl)2N2:Eu

4. Red phosphor: CaAlSi(ON)2:Eu

5. Near-infrared first phosphor: Gd3Ga5O12:Cr

6. Near-infrared second phosphor: ScBO3:Cr

7. Near-infrared tertiary phosphor: CaCuSi4O10

(4) White LED production

The semiconductor LED chip having the above-described InGaN/GaN multi-quantum well structure is flip-chip mounted on a ceramic package (PKG) with electrode wiring, and the above-mentioned four types of phosphors 1. It was sealed using the dispersed phosphor-containing composition. The phosphor mixture was directly and seamlessly applied on the semiconductor LED chip using a dispenser.

(5) Ultra-wideband light emitting device and module manufacturing

Similarly, three types of near-infrared phosphors and a silicone resin mixture were applied using a dispenser. As for the light emitting module, as shown in FIG. 4 , a light emitting module was manufactured by assembling two types of light emitting devices having different emission spectra into one PKG.

Check the characteristics of the light emitting module

The emission spectrum measurement was carried out at room temperature under the application of a forward current of 65 to 150 mA and a forward current of 3.19 to 3.48 V. A single light emitting device was mounted on a ceramic PKG and mounted on a heat dissipation substrate to measure electrical and optical properties at room temperature. Two types of separate light emitting devices are manufactured in a single PKG structure (2 in 1 PKG), and in the same way, the emission spectrum measurement is performed at room temperature using an optoelectronic precision WHITELIGHT spectrometer (OPI-100 made in Korea) over a wavelength range of 350 nm to 1000 nm. proceeded.

Table 1 shows the reference samples (Comparative Example 1), Sample A (Example 1), and Sample B (Example 2) of 710 nm (first phosphor), 810 nm (second phosphor), 910 nm (third phosphor) near-infrared phosphors. content is indicated. The white LED using a 405 nm semiconductor LED chip (light emission half maximum width: 15 nm) as an excitation source has a color temperature of 3300 K, an average color rendering index Ra of 94 or more, and a luminous efficiency of 53 lm/W or more. There are four types of phosphor, yellow phosphor, and red phosphor. The weight ratio of each phosphor was 9.23 : 1 : 0.46 : 5.77 with respect to the weight of the green phosphor.

[Table 1]

<Excitation/Emission Characteristics of Phosphor>

Table 2 shows the peak positions of the maximum excitation peaks and emission wavelengths of the three types of near-infrared phosphors in Table 1 used in the present invention. In particular, CaCuSi4O10 phosphor is excited in the excitation band of 500-700 nm, and the maximum excitation wavelength is 630 nm. As can be seen from Table 2, the three types of near-infrared phosphors are characterized in that they emit light even at 630 nm excitation.

Since the first phosphor and the second phosphor contain Cr3+ as a luminescence center, the excitation process is caused by the d electron orbital of Cr ion being affected by the crystal field and splitting the excited state into two, 4A2 level -> 4T1 level and 4T2 level -> 4T2 level is due to the transition of On the other hand, since the third phosphor does not include a specific light emitting sensor, it is thought that an excitation process according to light absorption by a defect level or a conduction band and a valence band is contributing.

[Table 2]

<Comparative Example 1>

1 shows the emission spectrum forward current (If) dependence of the reference sample shown in Table 1 (Comparative Example 1). The correlated color temperature Tcc of the light emitting device is 3286K, and includes near-infrared phosphors of the first phosphor (710 nm) and the third phosphor (910 nm). Since the second phosphor (810 nm) is not included, light emission valleys occur in the 810 nm wavelength region.

However, as can be seen from FIG. 1 , light emission is observed at 810 nm, although fine. The cause is an apparent light emission band formed by overlapping the long wavelength side emission tail of 710 nm and the low wavelength side emission tail of 910 nm. At If=65ma, the luminous intensity height ratio (H=γ/β) of 810 nm and 910 nm is 0.2, and this ratio hardly changes even if the current is increased. At 65mA, Ra was 86 and the light output was 21.4mW.

<Example 1>

Fig. 2 shows the dependence of the light emitting element If when 24% of the phosphor of 810 nm is contained in Example 1 (Sample A) prepared at the weight ratio shown in Table 1. As can be seen from the figure, even when a phosphor of 810 nm was added, a new light emitting band having a peak at 810 nm did not appear. Even when the current was increased, there was no significant difference from the reference sample of Comparative Example 1, and H=0.4 was constant. Compared with the spectrum of FIG. 1, the vicinity of 810 nm increased slightly, but did not reach the appearance of a new light emitting band having a central wavelength at 810 nm. The cause of this will be explained in “Light Emission Mechanism” which will be described later. The optical output was 22.8mW at 65mA and 42.9mW at 150mA. The light distribution angle was 110 degrees.

<Example 2>

3 is the If dependence of the emission spectrum in the case of containing two types of phosphors of 710 nm and 810 nm and not including the 910 nm phosphor in Example (Sample B) prepared at the weight ratio shown in Table 1. In this figure, an emission band having a peak at 810 nm appears clearly. With the increase of the current, the emission peaks appear clearly separated. The optical output was 31.9mW at 65mA and 61.8mW at 150mA. The light distribution angle was 115 degrees.

As described above, in Comparative Example 1 and Examples 1 and 2 of the present invention, it became clear that 810 nm light emission did not appear in the light emitting device containing the 910 nm phosphor even though the 810 nm phosphor was included. And the sample of Example 2 was mounted on one PKG (2 in 1 PKG) to prepare a sample having a light emitting module structure as shown in FIG. 4 and measurement of the emission spectrum was carried out.

<Example 3>

FIG. 4 shows that sample A and sample B of Table 1 were mounted on one PKG (2 in 1 PKG), and emission spectrum measurements were performed. The PKG structure of this light emitting module (Sample C) is schematically shown.

<Example 4>

Fig. 5 is an emission spectrum when If = 65 mA and If = 150 mA are applied to sample A. The luminescence intensity at 810 nm increases significantly but does not peak. H increased to 0.7, but did not reach the emission peak. The light output was 63mW and Ra was 86.

<Example 5>

Fig. 6 is an emission spectrum when Sample A and Sample B are connected in parallel and energized at If = 65 mA, 100 mA, and 150 mA. As can be seen from FIG. 6 , the wavelength region of 700 nm to 950 nm is completely continuous, so that both peaks of 810 nm and 910 nm are shown. With increasing current, these peaks become distinct. It can be seen that the emission width reaches up to about 450 nm, and has a very wide distribution. The H value is almost close to 1. Ra was 87, and the light output was 63mW (0.5W). The light output is higher than that of the single light emitting devices (Examples 1 and 2). The light distribution angle was 115 degrees.

This structure is a module composed of each combination of light emitting elements, and the two types of emission spectra have different color temperatures. However, with simultaneous lighting, the emission spectrum was mixed. A light emitting module using this phenomenon is called a tunable light-emitting element.

As can be seen from FIG. 6 , the emission spectrum is very similar to the spectrum distribution of AM1.5, which is sunlight. Also, it was very similar to the reduced hemoglobin absorption curve in blood.

Table 3 shows the color temperature and optical properties of Sample A, Sample B, and Sample C of Example 5. The color temperature of sample C has an intermediate value of both samples. In addition, sample C had increased Ra/R9 and light output compared to samples A and B.

It has been found that the optical properties are clearly improved by synthesizing both emission spectra in the present invention.

[Table 3]

<About the light-emitting mechanism>

As shown in Table 2 and emission spectra (Comparative Example 1 and Examples 1 and 2), the excitation/emission process of the near-infrared phosphor is almost identical to that of the first phosphor and the second phosphor because Cr3+ ions are included as luminescence centers. Although the same characteristics are shown, the excitation process of the third phosphor is completely different. Therefore, in order to effectively excite the third phosphor, it is an important point of the present invention to make the emission distribution of the white LED as similar to the excitation characteristic (absorption curve) of the third phosphor as much as possible.

(1) First phosphor: This phosphor contains CR3+ as a light emitting sensor. It is slightly excited at 405 nm, but it is most strongly excited at visible light at 450 nm. It is also excited at 630 nm. As a result, light emission having a peak at 710 nm is produced. The emission width is about 110 nm.

(2) Second phosphor: Like the first phosphor, CR3+ ions are included in the luminescence center of this phosphor. At 405 nm, there is almost no excitation. It is most strongly excited in visible light at 470 nm. It is also excited at 630 nm. As a result, it has an emission peak at 810 nm. The emission width is about 120 nm.

(3) Third phosphor: This phosphor does not contain a special light emitting sensor. In light of 405 nm, it is not directly excited. It is excited by visible light from 450 to 700 nm, but the maximum wavelength of excitation is about 630 nm. As a result, light emission having a peak at 910 nm is produced. The emission width is about 150 nm.

As mentioned above, considering the excitation/emission process of the near-infrared phosphor of (1) to (3), the ultra-wideband light emitting device of the present invention includes a near-infrared phosphor including a Cr3+ light emitting sensor and a root including a light-emitting center derived from a defect. A phosphor mixed with an infrared phosphor is included. Accordingly, the three types of excitation efficiencies (absorption efficiencies) are superimposed, and in particular, the efficiencies of the second phosphor and the third phosphor differ by about two times at 630 nm, which is a common excitation wavelength. That is, since the absorption efficiency of the second phosphor is low, most of the excitation energy of 630 nm is consumed to excite the third phosphor when the third phosphor is mixed. It is difficult to efficiently generate light emission at 810 nm. Therefore, in order to efficiently generate 810 nm near-infrared light emission, the wavelength tunable light emitting module in which each light emitting element manufactured in the present invention is combined is effective.

Although preferred embodiments of the present invention have been described in detail above, the rights of the present invention are not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the right.

Claims (8)

White LED chip with a color temperature of 3000~4000K;
a first light emitting device including a phosphor layer in which three or more kinds of near-infrared phosphors that emit light by being excited by the emission wavelength of the white LED chip are dispersed; and
a second light emitting device including a phosphor layer in which two or more kinds of near-infrared phosphors that emit light by being excited by the emission wavelength of the white LED chip are dispersed;
The near-infrared phosphor is excited in a wavelength range of 450 nm to 630 nm and has an emission peak at 710 nm, a second phosphor excited in a wavelength range of 470 nm to 630 nm and having an emission peak at 810 nm, and a wavelength of 630 nm A near-infrared light emitting device, which is selected from the group consisting of a third phosphor excited in the region and having an emission peak at 910 nm.
According to claim 1,
The first light emitting device includes a phosphor layer in which a first phosphor, a second phosphor, and a third phosphor are dispersed,
The second light emitting device, the near-infrared light emitting device comprising a phosphor layer in which the first phosphor and the second phosphor are dispersed.
According to claim 1,
The first phosphor is Gd3Ga5O12:Cr having a central emission peak at 710 nm, the second phosphor is ScBO3:Cr having an emission peak at 810 nm, and the third phosphor is CaCuSi4O10 having an emission peak at 910 nm. Infrared light emitting device.
3. The method of claim 2,
The phosphor layer of the first light emitting device,
A near-infrared light emitting device comprising the first phosphor, the second phosphor, and the third phosphor in a weight ratio of 16 to 24: 5 to 24: 4 to 7.
According to claim 1,
The white LED chip will have an emission wavelength center peak of 600 nm to 700 nm, a near-infrared light emitting device.
6. The method of claim 5,
The white LED chip,
As a cyan phosphor (Sr,Br)10(PO4)6Cl:Eu,
SiAlON:Eu as a green phosphor,
(Ba,Sr)Si2(O,Cl))2N2:Eu as a yellow phosphor, and
A near-infrared light emitting device comprising CaAlSi(ON)2:Eu as a red phosphor.
7. The method of claim 6,
The cyan phosphor, the green phosphor, the yellow phosphor and the red phosphor are included in a weight ratio of 8-10: 1:0.1-0.9: 4-8, a near-infrared light emitting device.
According to claim 1,
The near-infrared light-emitting device will have a broad emission spectrum distribution in 380 ~ 1200nm, the near-infrared light-emitting device.

Images