JP2016039362A - Ultraviolet light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet light source requiring a desired spectral distribution, such as an ultraviolet light source for use in spectrophotometer, or an ultraviolet light source used for curing a UV-curing resin.SOLUTION: In an ultraviolet light source mounting a plurality of LEDs having different emission peaks, the emission peak wavelength of each LED exists in a range of 220-350 nm, and the ratio of emission peak intensity of an LED having a minimum emission peak intensity to emission peak intensity of an LED having a maximum emission peak intensity, out of the plurality of LEDs, is 0.2 or more.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a novel ultraviolet light source. Specifically, a novel ultraviolet light source that requires a desired spectral distribution, such as a novel ultraviolet light source used in a spectrophotometer or a novel ultraviolet light source used to cure an ultraviolet curable resin (monomer and polymerization initiator) It is about.

  A spectrophotometer is a device that measures the absorbance of a sample by irradiating the sample with light of a target wavelength. The ultraviolet-visible spectrophotometer will be specifically described. The ultraviolet-visible spectrophotometer is a device that performs the following operations. First, the light emitted from the light source is monochromatized by a spectroscope, and the sample is irradiated with light having a target wavelength. Then, the absorbance is calculated from the light intensity before irradiation of the sample and the light intensity after irradiation. Next, the concentration of the sample can be quantified by comparing with a calibration curve created using the absorbance of the standard sample. Furthermore, even in a sample whose absorption wavelength is unknown, the absorption wavelength can be specified by irradiating light from the visible region to the ultraviolet region.

  As a light source for a spectrophotometer, a light source having a uniform irradiation intensity within a measurement wavelength range is required. By having a uniform irradiation intensity, a uniform S / N ratio can be obtained within the measurement wavelength range, so that the sample can be quantified relatively easily. The S / N ratio is the ratio of the signal amount (Singal) to the noise amount (Noise) in the measurement information measured with a spectrophotometer or the like. In order to quantify the sample, the S / N ratio is considered. There is a need to.

  Conventionally, a deuterium lamp having a continuous emission spectrum of 185 to 400 nm has been frequently used as an ultraviolet light source of a spectrophotometer. When the lamp is used, the irradiation intensity is highly wavelength-dependent. For example, when comparing the irradiation intensity at 220 nm and 350 nm, the irradiation intensity at 350 nm is a low value of about 1/10 of the irradiation intensity at 220 nm. That is, one of the problems of the deuterium lamp is that it does not have a uniform irradiation intensity within the irradiation wavelength range.

  Moreover, it is preferable that the S / N ratio is high, and therefore, a light source with high luminance (high irradiation intensity) is required. For example, when comparing the irradiation intensity at 350 nm of a halogen lamp often used as a visible light source of a spectrophotometer with the irradiation intensity at 350 nm of a deuterium lamp, the irradiation intensity of the deuterium lamp is the number of irradiation intensity of the halogen lamp. One of the problems of the deuterium lamp is that the irradiation intensity is as low as 1/10.

  Furthermore, when a single light source having a wide emission wavelength region is used, stray light increases and measurement accuracy may be reduced. Stray light means the ratio of the sum of the light intensities of wavelengths other than the set wavelength to the light intensity emitted from the wavelength selector (spectrometer). In particular, when the target wavelength range is narrow, it is considered preferable to use a light source that emits less light at wavelengths other than the measurement wavelength. For example, even if the measurement wavelength is 300 nm, if a deuterium lamp is used, a continuous spectrum of 185 to 400 nm is incident on the spectrometer, and stray light may increase depending on the spectrometer.

  As another technique, a high-pressure mercury lamp is usually used as an ultraviolet light source for curing an ultraviolet curable resin (monomer and polymerization initiator). Since the lamp has only a fixed emission wavelength, it is difficult to use an ultraviolet curable resin that cures at other wavelengths as a light source for irradiation, and there is a problem that uneven curing occurs.

  In order to solve these problems, it is conceivable to use a light emitting diode (hereinafter sometimes simply referred to as “LED”). Since the LED has wavelength selectivity, if the LED is used, the stray light amount can be reduced and the emission wavelength can be selected with respect to the above-described problems. For example, an ultraviolet irradiation device including a plurality of LEDs has been proposed (see, for example, Patent Document 1).

JP 2009-136996 A International Publication 2012/056928 Pamphlet International publication 2011/078252 pamphlet Japanese Patent No. 3499385 Applied Physics Express 5 (2012) 122101

  If it is the ultraviolet irradiation device of patent document 1, the reduction of stray light quantity and selection of the light emission wavelength are possible.

  However, the combination of conventional LEDs has a problem that the emission intensity decreases as the wavelength becomes shorter. Patent Document 1 proposes an ultraviolet irradiation device that diffuses in the range of 300 to 400 nm, but has a main LED having an emission peak at 360 to 370 nm and an emission peak other than 360 to 370 nm in the range of 300 to 400 nm. The sub LED is combined.

  According to the study by the present inventors, an LED having an emission peak in a short wavelength region of 350 nm or less, further a short wavelength of 300 nm or less, and particularly a short wavelength region of 280 nm or less has a problem of low emission intensity. That is, it is difficult to use a conventional ultraviolet irradiation device as a high-intensity light source having a uniform irradiation intensity like a deuterium lamp.

  Accordingly, an object of the present invention is to provide an ultraviolet light source having a uniformly high emission intensity in a desired light emission wavelength region.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. And when various examination was performed combining a plurality of LEDs having a short wavelength region, specifically, a peak emission wavelength in the range of 220 to 350 nm, the difference in the emission peak intensity of each LED should be adjusted. Thus, the inventors have found that the above-described problems can be solved, and have completed the present invention. Furthermore, it is found that the LED has a high emission peak intensity value, and such an LED preferably has an aluminum nitride single crystal substrate having good crystallinity and high transmittance. The invention has been completed.

That is, the present invention
An ultraviolet light source equipped with a plurality of LEDs,
The emission peaks of all LEDs are in the wavelength range of 220 to 350 nm,
Among the plurality of LEDs, the ratio (B / A) of the emission peak intensity (B) of the LED having the minimum emission peak intensity to the emission peak intensity (A) of the LED having the maximum emission peak intensity is 0.2 or more. It is an ultraviolet light source equipped with a plurality of LEDs having different emission peak wavelengths.

    In the present invention, the emission peak intensity of all LEDs is preferably 0.5 mW / nm or more. All the LEDs preferably have an aluminum nitride single crystal substrate. By using such an LED, the emission intensity distribution of the ultraviolet light source can be easily adjusted.

    The ultraviolet light source has a continuous emission spectrum in a certain range of 220 to 350 nm, from the emission peak wavelength of the LED having the shortest emission peak wavelength to the emission peak wavelength of the LED having the longest emission peak wavelength. In this range, the ratio (D / C) of the minimum emission intensity (D) to the maximum emission intensity (C) is preferably 0.5 or more.

  In this case, the difference (| λ1−λ2 |) between the adjacent emission peak wavelength (λ1) and the emission peak wavelength (λ2) is the same as that of the LED having the smallest half-value width of the emission peak among the plurality of LEDs. By setting it to a half-value width or less, an emission spectrum having an emission intensity distribution having a continuous region can be formed.

  Furthermore, by using a plurality of LEDs having the same emission peak wavelength, the longest emission peak wavelength is selected from the emission peak wavelength of the LED having the shortest emission peak wavelength among the plurality of LEDs mounted on the ultraviolet light source. The ratio (D / C) of the minimum light emission intensity (D) to the maximum light emission intensity (C) can be 0.5 or more in the range up to the light emission peak wavelength of the LED.

  By setting the emission intensity distribution to the above distribution, it is possible to irradiate with a uniform emission intensity in a continuous wavelength region, so that it becomes easy to obtain a uniform irradiation intensity in the wavelength region.

  Further, the emission spectrum of the ultraviolet light source may be an emission intensity distribution that exists independently without overlapping the emission spectra of the respective LEDs in the range of 220 to 350 nm.

  Furthermore, it is preferable that each LED has a light emission peak in a range of 220 to 280 nm, where the light emission intensity of the conventional LED is particularly low.

  According to the present invention, a plurality of LEDs are mounted, the emission peak wavelengths of all LEDs are in the range of 220 to 350 nm, and the emission peak intensity is the minimum with respect to the emission peak intensity of the LED having the maximum emission peak intensity. By setting the ratio of the emission peak intensity of the LED to be 0.2 or more, an emission spectrum having uniform emission intensity can be achieved.

  Furthermore, in all LEDs, when the emission peak intensity at a temperature of 25 ° C. and a drive current value of 150 mA is 0.5 mW / nm or more, an emission spectrum having a high emission intensity can be achieved.

  Measurement accuracy can be improved by using such an ultraviolet light source as a light source for a spectrophotometer.

  Moreover, according to this invention, the emission spectrum which exists independently without overlapping the emission spectrum of each LED in the range of 220-350 nm can also be taken. By using such an ultraviolet light source, for example, for curing a resin, it becomes possible to simultaneously cure a plurality of ultraviolet curable resins having different curing wavelengths and reduce curing unevenness. And since this wavelength can be selected in 220-350 nm, a wavelength can be selected according to the hardening wavelength of the target resin, and it can harden | cure efficiently.

6 is an emission spectrum diagram showing a light emission intensity distribution of a light emitting diode manufactured in Manufacturing Example 1. FIG. It is the emission spectrum figure which showed the emitted light intensity distribution of the ultraviolet-ray light source which is an example (Example 1) of this invention. It is the emission spectrum figure which showed the emitted light intensity distribution of the ultraviolet-ray light source which is an example (Example 2) of this invention. It is the emission spectrum figure which showed the emitted light intensity distribution of the ultraviolet-ray light source which is an example (Example 3) of this invention. It is the emission spectrum figure which showed the emitted light intensity distribution of the ultraviolet-ray light source which is an example of 1 aspect of this invention (Example 4). It is a cross-sectional schematic diagram of LED.

(UV light source)
The ultraviolet light source of the present invention has a plurality of LEDs mounted thereon. And the light emission peak wavelength of all LEDs exists in the range of 220-350 nm. That is, by mounting a plurality of LEDs having different emission peak wavelengths, it can be used as a light source for a spectrophotometer, a light source for curing an ultraviolet curable resin, or the like. Below, embodiment at the time of using for an ultraviolet visible spectrophotometer is described. In addition, the emission spectrum figure of LED produced by the manufacture example 1 mentioned later is shown in FIG. In the present invention, the emission peak intensity, the emission peak wavelength, and the half-value width of the emission peak are values of points or ranges shown in FIG.

  The ultraviolet light source of the present invention is equipped with a plurality of LEDs having different emission peak wavelengths in the range of 220 to 350 nm, and among the plurality of LEDs, the emission peak intensity (A) of the LED having the maximum emission peak intensity, The ratio (B / A) of the emission peak intensity (B) of the LED having the minimum emission peak intensity is 0.2 or more. When a conventional deuterium lamp is used, the ultraviolet light source of the present invention has a plurality of LEDs having different emission peak wavelengths, which has a low emission intensity and a high emission wavelength wavelength dependency. By mounting, an emission spectrum having uniformly high emission intensity can be obtained. The range of the emission peak wavelength of the LED used is preferably 220 nm or more and 300 nm or less, more preferably 220 nm or more and 280 nm or less. An LED having a high emission intensity in the range of 300 nm or less, particularly 280 nm or less, has not existed in the past because it was difficult to produce itself. By using an LED having an emission peak wavelength in such a short wavelength region, it is considered that analysis can be performed with the same measurement accuracy as that in the long wavelength region even in the short wavelength region.

  In the ultraviolet light source of the present invention, among the plurality of LEDs, the ratio of the emission peak intensity (B) of the LED having the minimum emission peak intensity to the emission peak intensity (A) of the LED having the maximum emission peak intensity (B / A) must be 0.2 or more. This ratio (B / A) is the ratio between the emission peak intensity (A) of one LED having the maximum emission peak intensity and the emission peak intensity (B) of one LED having the minimum emission peak intensity. is there.

  If the ratio (B / A) is less than 0.2, it is difficult to make the emission intensity of the emission spectrum uniform. In order to make the emission intensity of the emission spectrum uniform, it is possible to mount a plurality of LEDs having a low emission intensity. However, if the ratio (B / A) is less than 0.2, a large number of LEDs are required. Must be installed. In the ultraviolet light source of the present invention, since the ratio (B / A) is 0.2 or more, even when a plurality of LEDs having low emission intensity are mounted in order to obtain a uniform emission spectrum, the number is smaller. It ’s enough. Further, when the ratio (B / A) is less than 0.2, the irradiation intensity is made uniform by disposing the LED having a small emission intensity near the sample and disposing the LED having a large emission intensity far from the sample. Although it is possible, the apparatus becomes complicated and is not preferable. According to the present invention, since the ratio (B / A) is 0.2 or more, a uniform emission spectrum can be obtained without changing the distance between the sample and the light source, and the apparatus structure is simplified. To do. In order to reduce the number of LEDs mounted and further simplify the device structure, the ratio (B / A) is preferably 0.3 or more, and more preferably 0.5 or more. The upper limit of the ratio (B / A) is 1.0.

  In all the LEDs, it is preferable that the emission peak intensity at a temperature of 25 ° C. and a drive current value of 150 mA is 0.5 mW / nm or more. In order to reduce the size of the ultraviolet light source or increase the irradiation intensity of the sample, the emission peak intensity at a temperature of 25 ° C. and a driving current value of 150 mA is more than 0.8 mW / nm in all LEDs. Preferably, it is 1.0 mW / nm or more. The upper limit of the emission peak intensity is not particularly limited, but is 50 mW / nm in consideration of normal industrial production. By using such an LED, the problem that the light emission intensity of ultraviolet light is lower than that of visible light in a conventionally used light source can be solved with fewer LEDs.

(Emission distribution of ultraviolet light source)
Since the ultraviolet light source of the present invention has the above characteristics, the emission intensity distribution can be easily adjusted. Therefore, an ultraviolet light source having an emission spectrum having a continuous emission intensity region (see FIGS. 2 and 3) or an ultraviolet light having an emission spectrum having a plurality of independent emission peaks (emission spectra) (see FIG. 4). It can be a light source. These will be described.

(Ultraviolet light source with emission spectrum with continuous emission intensity region)
In one embodiment, the ultraviolet light source of the present invention is an ultraviolet light source having an emission spectrum having a continuous region in an arbitrary wavelength range of 220 to 350 nm, and an LED having the shortest emission peak wavelength in the region. The ratio (D / C) of the minimum light emission intensity (D) to the maximum light emission intensity (C) is 0.5 in the range from the light emission peak wavelength to the light emission peak wavelength of the LED having the longest light emission peak wavelength. It is easy to obtain the ultraviolet light source as described above. In the above-described deuterium lamp (existing ultraviolet light source), the ratio is about 0.1 at the minimum. By setting the ratio (D / C) to 0.5 or more, the difference in emission intensity is reduced. It is advantageous.

  Further, by adjusting the emission intensity and / or emission peak wavelength of the LED to be used, the ratio of the minimum emission intensity (D) to the maximum emission intensity (C) (D / C) is set to 0.8 or more. You can also. Although not particularly limited, the most preferable ratio (D / C) is 1.0, which is an upper limit value of the ratio (D / C).

  In the present invention, in order for the ultraviolet light source to have a continuous emission spectrum, the difference (| λ1−λ2 |) between the adjacent emission peak wavelength (λ1) and emission peak wavelength (λ2) of the plurality of LEDs included in the ultraviolet light source. Is preferably equal to or less than the half-value width of the LED having the smallest half-value width of the light emission peak among the plurality of LEDs. Here, the “half width” means the full width at half maximum. Usually, the LED has a single peak whose half-value width of the emission spectrum is 5 to 20 nm. Therefore, by making the absolute value of the difference between the light emission peak wavelength and the light emission peak wavelength of two adjacent LEDs of the light emission peak wavelength equal to or less than the half value width of the LED having the smallest half value width among the plurality of mounted LEDs. The emission intensity distribution having a continuous region can be easily obtained.

  Further, by using a plurality of LEDs having the same emission peak wavelength, from the emission peak wavelength of the LED having the shortest emission peak wavelength to the emission peak wavelength of the LED having the longest emission peak wavelength in the region. In the range, it becomes easy to obtain an ultraviolet light source in which the ratio (D / C) of the minimum emission intensity (D) to the maximum emission intensity (C) is 0.5 or more. Moreover, this ratio (D / C) can also be 0.8 or more by adjusting the light emission intensity and / or light emission peak wavelength of LED to be used. Although not particularly limited, the most preferable ratio (D / C) is 1.0, which is an upper limit value of the ratio (D / C). Moreover, it is preferable that the number of LEDs having the maximum emission peak intensity is one.

  An ultraviolet light source having such a continuous region can be used as an ultraviolet light source for a spectrophotometer.

(UV light source with independent emission spectrum)
In another embodiment, the ultraviolet light source of the present invention has an emission intensity distribution in which the emission spectrum of the ultraviolet light source exists independently without overlapping the emission spectrum of each LED in the range of 220 to 350 nm. it can. In this case, what is necessary is just to select and use the LED in which the area | region of a light emission spectrum does not overlap in the LED to be used, and what is necessary is just to select a light emission wavelength according to a use.

In the case of an ultraviolet light source having such an independent emission spectrum, by using a plurality of LEDs having the same emission peak wavelength, the maximum emission intensity (C at the emission peak wavelength of the independent emission spectrum of the ultraviolet light source) can be obtained. ) (D / C) of the minimum light emission intensity (D) with respect to ()) can be 0.5 or more. When the ratio (D / C) is 0.5 or more, the difference in emission intensity at a desired independent emission wavelength is reduced. For example, when used as a light source for curing an ultraviolet light curable resin, It becomes possible to simultaneously cure a plurality of ultraviolet light curable resins having different curing wavelengths, and to further reduce curing unevenness. Although not particularly limited, the most preferable ratio (D / C) is 1.0, which is the upper limit of the ratio (D / C). Note that the number of LEDs having the maximum emission peak intensity is preferably one.
Next, a method for producing the ultraviolet light source of the present invention exhibiting the above characteristics will be described.

(Method for manufacturing ultraviolet light source)
The ultraviolet light source of the present invention can be manufactured using an LED having a light emission peak wavelength in the range of 220 to 350 nm as a component. Among the plurality of LEDs, the ratio (B / A) of the emission peak intensity (B) of the LED having the minimum emission peak intensity to the emission peak intensity (A) of the LED having the maximum emission peak intensity is 0.2 or more. Thus, the ultraviolet light source of the present invention can be manufactured by using a combination of LEDs having different emission peak wavelengths.

  Therefore, commercially available LED can be used if the said conditions are satisfied. However, in the case where a light emission intensity difference at different wavelengths is small and a light emission intensity is high, it is preferable to use an LED manufactured by the following method.

(About LEDs mounted on UV light source)
The LED used in the present invention has an emission peak wavelength in the range of 220 to 350 nm, and the emission peak intensity with respect to the emission peak intensity (A) of the LED having the maximum emission peak intensity among the plurality of LEDs to be used. As long as the ratio (B / A) of the emission peak intensity (B) of the LED that is the minimum is 0.2 or more, the manufacturing method is not limited, and a commercially available LED can also be used. .

  In the present invention, in all the LEDs, the emission peak intensity at a temperature of 25 ° C. and a drive current value of 150 mA is preferably 0.5 mW / nm or more. And it is preferable that all the LEDs have an aluminum nitride single crystal substrate.

  The LED used in the present invention preferably has a light emission peak intensity of 0.5 mW / nm at 25 ° C. and a drive current value of 150 mA, and a drive voltage value of 10 V or less. When the driving voltage is 10 V or less, low power consumption and high durability can be realized, and it can be suitably used for the ultraviolet light source in the present invention.

  An LED having such characteristics can be manufactured by the following method.

Usually, an ultraviolet LED has a structure having an element layer (n-type layer, active layer, and p-type layer) and an electrode (n-type electrode and p-type electrode) on a base substrate. FIG. 6 shows a representative example. An ultraviolet LED (ultraviolet LED wafer) 1 has an n-type layer 3, an active layer 4, and a p-type layer 8 (this p-type layer is a p-type Al _X3 Ga _1-X3 N layer 5 on a substrate (underlying substrate) 2. , P-type Al _X4 Ga _{1 -X4} N layer 6 and p-type In _Y Ga ₁ -YN layer 7 are laminated on the active layer 4 in this order). An n-type electrode (layer) 9 is provided on the n-type layer 3, and a p-type electrode (layer) 10 is provided on the p-type layer 8. Although not shown, a buffer layer can be formed between the substrate 2 and the n-type layer 3, and unevenness is formed on the back surface side (side where the n-type layer 3 is not laminated) of the substrate. Can also be formed.

The substrate 2 of the LED 1 is not limited as long as it is a material that can reduce the dislocation density of the n-type layer 3 and the active layer 4 that are grown on the substrate 2, and sapphire, aluminum nitride single crystal (AlN A material such as a single crystal can be used. In order to further reduce the dislocation density, it is preferable to use an AlN single crystal. The n-type layer 3, the active layer 4, and the p-type layer 8 are preferably made of a group III nitride semiconductor containing Al (however, as will be described in detail below, the p-type electrode 10 of the p-type layer 8). It is preferable that the layer in contact with the substrate is made of a group III nitride semiconductor containing no Al). Among them, the LED of the present invention is an n-type composed of a group III nitride semiconductor represented by Al _X Ga _1-X N (where X is a rational number satisfying 0 ≦ X ≦ 1.0). A layered structure in which the layer 3, the active layer 4, and the p-type layer 8 are sequentially formed is preferable. The resistance value of the n-type electrode 9 is preferably in a range satisfying less than 1.0Ω.

The substrate 2 will be described below. An AlN single crystal is preferably used for the base substrate for forming the element layer of the LED. The dislocation density of the substrate is preferably 10 ⁶ cm ⁻² or less, more preferably 10 ⁵ cm ⁻² or less, and further preferably 10 ⁴ cm ⁻² or less. Furthermore, since it is necessary to suppress the absorption of ultraviolet light in the substrate in order to realize high emission intensity, the internal transmittance of the substrate 2 with respect to the ultraviolet light of the emission peak wavelength of the LED 1 is preferably 85% or more, Further, it is preferably 95% or more. The higher the internal transmittance is, the more preferable, ideally 100%. The thickness of the substrate 2 is preferably determined within a range where the internal transmittance is 85% or more and the operability is not deteriorated. Specifically, it is preferable that it is 50-500 micrometers. The AlN single crystal substrate may be obtained by thinning an AlN single crystal substrate having a dislocation density of 10 ⁶ cm ⁻² or less, or an HVPE method on an AlN single crystal substrate of 10 ⁴ cm ⁻² or less obtained by a sublimation method. The AlN single crystal layer may be grown by, and then the AlN single crystal layer may be separated to form an AlN single crystal substrate.

  The substrate 2 has an n-type layer 3, an active layer 4, and a p-type layer 8 stacked in this order on one surface, and a surface on which these layers are not formed becomes a light emitting main surface from which light is emitted. .

  Next, the n-type layer 3, the active layer 4, the p-type layer 8, the n-type electrode 9, and the p-type electrode 10 formed on the substrate 2 will be described.

  The n-type layer 3, the active layer 4, and the p-type layer 8 can be formed by a known crystal growth method such as a metal organic chemical vapor deposition (MOCVD) method or a molecular beam epitaxy (MBE) method. Of these, the MOCVD method, which has high productivity and is widely used industrially, is preferable. When the MOCVD method is adopted, it will be described in detail below. For example, it may be formed in the same manner as the method described in WO2012 / 056928 (Patent Document 2).

The n-type layer 3 preferably imparts n-type conductivity by doping the Al _X1 Ga _1-X1 N layer with a known n-type dopant material such as Si, O, or Ge. X1 of the Al composition ratio may be appropriately determined in a range of 0.1 ≦ X1 ≦ 0.95 according to a desired emission peak wavelength. The dislocation density of the n-type layer 3 is preferably 10 ⁸ cm ⁻² or less, and more preferably 10 ⁶ cm ⁻² or less. The thickness of the n-type layer 3 is not particularly limited, but is preferably 500 to 5000 nm.

  Of the known n-type dopant materials, the dopant material doped into the n-type layer 3 is preferably Si in consideration of controllability of the raw material concentration and ionization energy in the n-type layer 3. The n-type dopant concentration can be appropriately determined so as to obtain desired conductivity. The n-type layer 3 may be a single layer having a single Al composition and a single n-type dopant concentration, or a plurality of layers having different Al compositions and / or n-type dopant concentrations are laminated. You may have a structure.

  Further, in order to increase the n-type conductivity of the n-type layer 3, when the n-type layer 3 is grown, a defect of a group III element or a compound of a group III element and an impurity that acts as a compensation center for the n-type dopant is used. It is preferable to appropriately select growth conditions that can reduce the mixing of impurities other than the n-type dopant so that the formation of defects can be suppressed. Thereby, the contact resistance between the n-type layer 3 and the n-type electrode 9 can be reduced.

When the n-type layer 3 is formed by the MOCVD method, an n-type layer having a desired composition can be formed by adjusting the supply amounts of the group III source gas and the nitrogen source gas. At that time, the dopant gas flow rate can be adjusted so as to satisfy a desired dopant concentration. Further, in order to set the dislocation density of the n-type layer 3 to 10 ⁸ cm ⁻² or less, the substrate 2 has a low dislocation density AlN single crystal substrate, specifically, the dislocation density of 10 ⁶ cm ⁻² or less, more preferably It is preferable to employ an AlN single crystal substrate of 10 ⁴ cm ⁻² or less.

The active layer 4 is formed on the n-type layer, and preferably has a quantum well structure in which a quantum well layer and a barrier layer are combined in order to improve light emission efficiency in the active layer. The thickness of the well layer is preferably 2 to 10 nm, and the barrier layer is preferably 5 to 30 nm. In order to stably obtain high luminous efficiency, the active layer 4 preferably has three or more quantum well layers. The quantum well layer and the barrier layer are composed of a group III nitride single crystal, and among them, both are preferably Al _X Ga _1-X N layers. The Al composition (X) and thickness of each of the quantum well layer and the barrier layer can be appropriately determined so that a desired emission peak wavelength can be obtained. The quantum well layer and the barrier layer may be doped with impurities for the purpose of improving the light emission efficiency.

When the active layer 4 is formed by MOCVD, an active layer (quantum well layer and barrier layer) having a desired composition can be formed by adjusting the supply amounts of the group III source gas and nitrogen source gas. By forming an active layer on an n-type layer having a low dislocation density (specifically, for example, 10 ⁸ cm ⁻² or less), a high-performance ultraviolet light-emitting diode can be manufactured.

The p-type layer 8 is a conductive layer imparted with p-type conductivity by containing a known p-type dopant material. Of the known p-type dopant materials, Mg is preferably employed. Specifically, the p-type Al _X3 Ga _1-X3 N layer 5, the p-type Al _X4 Ga _1-X4 N layer 6, and the p-type In _y Ga _1-y N layer 7 are stacked in this order on the active layer. Good. About Al composition, what is necessary is just to determine suitably in the range of 0.5 <= X3 <= 1.0 and 0.2 <= X4 <= 0.9 according to a desired light emission wavelength. Among these, in order to enhance the effect of confining electrons in the active layer 4, it is preferable to satisfy X4 ≦ X3 within the above range. In order to obtain higher luminous efficiency, it is preferable to satisfy X1 ≦ X4 ≦ X3. However, X1 is Al composition ratio of the n-type _{Al X1 Ga 1-X1} N layer that constitutes the n-type layer shown in the above. The In composition in the p-type In _Y Ga _1-Y N layer 7 is preferably 0 ≦ Y ≦ 0.1. In order to reduce the contact resistance with the p-type electrode 10, Y = 0 More preferably.

When the p-type layer 8 is formed by the MOCVD method, a p-type layer having a desired composition can be formed by adjusting the supply amounts of the group III source gas and the nitrogen source gas. At that time, the dopant gas flow rate can be adjusted so as to satisfy a desired dopant concentration. A p-type layer having a desired composition can be formed by adjusting the supply amount of the group III source gas, nitrogen source gas, dopant source gas, and the like. Then, by adjusting the supply amount of these gases, a multilayer structure, for example, a p-type Al _X3 Ga _1-X3 N layer 5, a p-type Al _X4 Ga _1-X4 N layer 6, and a p-type In _Y Ga _{1-Y is used.} A p-type layer 8 having a multilayer structure composed of the N layer 7 can be formed.

  The n-type electrode 9 is formed on the n-type layer 3. The n-type electrode 9 can be formed using a known n-type ohmic electrode material and formation method. The n-type ohmic electrode material is not particularly limited as long as it can reduce the contact resistance value with the n-type layer 3. Each layer constituting the n-type electrode 9 can be formed by a vacuum deposition method, a sputtering method, or the like.

In order to reduce the contact resistance value between the n-type electrode 9 and the n-type layer 3, it is preferable to anneal in an inert gas atmosphere such as argon or nitrogen after the n-type electrode layer 9 is formed. The annealing temperature is not particularly limited, but is preferably 700 to 1100 ° C. Specifically, the n-type electrode 9 can be preferably formed by, for example, an n-type contact electrode forming method described in International Publication No. 2011/078252 (Patent Document 3). Patent Document 3 discloses an n-type ohmic electrode material containing Ti and Al and a method for forming the same. More specifically, Patent Document 3 discloses a method of forming an n-type contact electrode on an n-type semiconductor layer made of a group III nitride single crystal, and includes Ti, V, and Ta on the n-type semiconductor layer. Forming a first electrode metal layer composed of at least one metal layer selected from the group consisting of, and performing a heat treatment at a temperature of 800 ° C. or higher and 1200 ° C. or lower; and work on the first electrode metal layer function comprises a highly conductive metal layer a and the and the specific resistance is made of a metal which is ^{1.5 × 10 -6 Ω · cm~4.0 ×} 10 -6 Ω · cm 4.0eV~4.8eV A method of forming an n-type contact electrode is disclosed, including a step of performing a heat treatment at a temperature of 700 ° C. or higher and 1000 ° C. or lower after forming the second electrode metal layer. In the method, it is preferable to use Ti as the metal constituting the first metal electrode layer and Al as the metal constituting the highly conductive metal layer. In addition, the second electrode metal layer is Ti, A joining metal layer (preferably Ti) selected from the group consisting of V and Ta, preferably having a work function of 4.0 eV to 4.8 eV and a specific resistance of 1.5 × 10 ⁻⁶ Ω · cm 4.0 × 10 ⁻⁶ having a multi-layer structure including a highly conductive metal layer (preferably Al) made of a metal having a resistance of Ω · cm and a noble metal layer made of Au and / or Pt, and joining metal in the multi-layer structure It is preferable that the layer is disposed in the lowermost layer and the noble metal layer is disposed in an upper layer than the highly conductive metal layer.

  Further, the thickness of the n-type electrode (n-type electrode layer) 9 is not particularly limited, and the thickness of each layer constituting the n-type electrode layer 9 is within a range in which the contact resistance value after annealing can be reduced. What is necessary is just to determine suitably, but when the productivity of the n-type electrode layer 9 etc. are considered, it is preferable that total thickness shall be 50-500 nm.

The n-type electrode resistance value obtained by dividing the intrinsic contact resistance value (Ω · cm ² ) of the n-type electrode 9 by the electrode area (cm ² ) of the portion where the n-type electrode 9 is installed may be less than 1.0Ω. preferable. In consideration of current-voltage characteristics, the n-type electrode resistance is preferably as small as possible, more preferably 0.5Ω or less, and most preferably 0.4Ω or less. Further, the specific contact resistance value and the electrode area of the n-type electrode are not particularly limited as long as they satisfy the n-type electrode resistance value of less than 1.0Ω, but the following ranges are preferable. The specific contact resistance value is preferably 10 ⁻² Ω · cm ² or less, more preferably 10 ⁻³ Ω · cm ² or less. The lower limit of the specific contact resistance value is preferably as low as possible, but is 10 ⁻⁷ Ω · cm ² in view of industrial production. The electrode area may be adjusted as appropriate according to the n-type electrode resistance, and is usually in the range of 0.5 to 0.0001 cm ² depending on the size of the LED. By using such an n-type electrode, the driving voltage of the LED can be lowered.

  The specific contact resistance value can be measured by a known TLM method (Transmission Line Model). Specifically, in a plurality of electrodes formed for measuring the specific contact resistance value on the n-type layer 3, a given electrode area and electrode formation are obtained by calculating according to the TLM method based on the interelectrode distance and the resistance value. The specific contact resistance value in combination with the conditions can be obtained.

The p-type electrode 10 is not particularly limited, and a known electrode material and electrode structure can be adopted. Specifically, the material is not particularly limited as long as the material can reduce the contact resistance value with the p-type layer 8 (p-type In _Y Ga _1-Y N layer 7 in FIG. 1). An electrode material containing Ni and Au described in Japanese Patent No. 3499385 (Patent Document 4) can be preferably used.

The electrode area of the p-type electrode 10 refers to the area where the p-type electrode (p-type electrode layer) 10 and the p-type layer 8 are in contact. In the LED used in the present invention, the area of the p-type electrode corresponds to the area of the active layer that contributes to light emission. When the drive current value is as large as 150 mA, if the p-type electrode area is too small, the light emission output density is saturated, the drive voltage is increased, and the lifetime tends to be shortened. On the other hand, if the p-type electrode area is too large, the light emission output density decreases and the LED chip size increases, which is not preferable. Therefore, it is preferable that p-type electrode area is 0.0001～0.01Cm ^2, more preferably 0.0005~0.005cm ^2.

  The LED obtained by the above manufacturing method has an emission peak wavelength in the range of 220 to 350 nm, and the emission peak intensity at a driving current value of 150 mA at a temperature of 25 ° C. is 0.5 mW / nm or more. It can be an LED. In the present invention, the ratio (B / A) of the emission peak intensity (B) of the LED having the minimum emission peak intensity to the emission peak intensity (A) of the LED having the maximum emission peak intensity is 0.2 or more. Furthermore, since the emission peak intensity of all LEDs is 0.5 mW / nm or more, it is preferable to use LEDs having such characteristics.

  The ultraviolet light source of the present invention can be easily manufactured by variously combining a plurality of LEDs having the above characteristics. Then, an ultraviolet light source having an emission spectrum as shown in FIGS. 2, 3, and 4 can be manufactured by selecting an LED according to the purpose of use.

  Moreover, when using a cover for LED or the ultraviolet light source which mounts LED, it is preferable to use a thing with the high transmittance | permeability in a 220-350 nm wavelength range. This makes it possible to irradiate the sample without attenuating the light emission of the LED.

In the ultraviolet light emitting diode 1 of the present invention, the surface opposite to the surface on which the n-type layer 3 of the substrate 2 is laminated is the main light emitting surface from which light is emitted. And on this light emission main surface, you may laminate | stack the layer which consists of a material whose refractive index is 1.0-2.4. By forming a layer made of such a material, light can be extracted efficiently. The material having a refractive index of 1.0 to 2.4 is not particularly limited, and liquid materials such as H ₂ O in addition to inorganic materials such as Al ₂ O ₃ , SiO ₂ , CaF, and MgF are used. It can be illustrated.

  Moreover, in order to take out light efficiently, it is preferable to form a concavo-convex structure on the light emission main surface. The concavo-convex structure can be formed on the light-emitting main surface by a known method, for example, a method of etching a substrate. The concavo-convex structure may be appropriately adjusted according to the emission peak wavelength, but it is preferable to form a convex portion having a height and a width in the range of 100 to 1000 nm, respectively.

  Note that light can be extracted more efficiently by forming a layer made of a material having a refractive index of 1.0 to 2.4 on the light-emitting main surface having an uneven structure.

(About the LED circuit mounted on the UV light source)
The plurality of ultraviolet light emitting diodes mounted on the ultraviolet light source may be connected in series to one power source, or may be connected in parallel to one power source. Alternatively, a composite circuit combining a series circuit and a parallel circuit may be used, and a separate power source may be provided for each of a plurality of ultraviolet light emitting diodes using a plurality of power sources, and individual ultraviolet light emitting diodes may be controlled independently. Good. When a plurality of ultraviolet light emitting diodes are connected in series, the power supply voltage must be equal to or higher than the sum of the drive voltage values of all the ultraviolet light emitting diodes connected to the circuit. If the LED manufactured by the above manufacturing method is used for the ultraviolet light source of the present invention, the power supply voltage can be easily suppressed due to the low driving voltage value of the ultraviolet light emitting diode. When a plurality of ultraviolet light emitting diodes are connected in parallel, an overcurrent can be prevented from flowing through the ultraviolet light emitting diode having a small resistance by connecting a resistor in series with the ultraviolet light emitting diode. Alternatively, for example, among the plurality of ultraviolet light-emitting diodes, a large current is passed to an ultraviolet light-emitting diode having a light emission peak intensity smaller than that of other ultraviolet light-emitting diodes, so that the difference in light emission intensity is reduced. An ultraviolet light source having a small emission spectrum can be easily manufactured. In particular, since an ultraviolet light emitting diode manufactured by the above manufacturing method is used as a component, a relatively large current can be passed through the ultraviolet light emitting diode. Therefore, an ultraviolet light source having an emission spectrum with a small difference in light emission intensity is used. Manufacturing is easy. In addition, when each of the ultraviolet light emitting diodes is controlled independently using a plurality of power supplies, it is easy to control the current flowing through each of the ultraviolet light emitting diodes. As described above, a circuit can be assembled according to a desired form.

  EXAMPLES Next, although an Example demonstrates this invention in detail, this invention is not limited to a following example.

(Manufacture of LEDs)
Production Example 1
(Preparation of substrate)
An AlN single crystal substrate for producing the LED of the present invention was produced by the method described in Applied Physics Express 5 (2012) 122101 (Non-Patent Document 1). Specifically, first, an AlN thick film having a thickness of 250 μm is formed by a hydride vapor phase epitaxy (HVPE) method on an AlN seed substrate having a diameter of 25 mm produced by a physical vapor transport (PVT) method. Chemical mechanical (CMP) polishing of the film growth surface was performed. Such a laminate of HVPE AlN thick film / AlN seed substrate (growth substrate) was used as a growth substrate for an ultraviolet light emitting diode. As will be described in detail below, the AlN seed substrate is finally removed from the growth substrate. Four growth substrates were produced under exactly the same conditions.

  In order to use one growth substrate for analysis, the AlN seed substrate portion was removed. The half width of the X-ray rocking curve of the obtained AlN single crystal substrate (thickness 170 μm, HVPE AlN thick film part) was measured. Specifically, the (002) and (101) planes of the AlN single crystal substrate were subjected to a high-resolution X-ray diffractometer (Spectres' Panalical Division X'Pert) under the conditions of an acceleration voltage of 45 kV and an acceleration current of 40 mA. X-ray rocking curve measurement was performed. The full width at half maximum of the X-ray rocking curve was 30 arcsec or less. Further, on the other six growth substrates, the X-ray rocking curve measurement of the (002) and (101) planes of the polished AlN thick film portion was performed under the same conditions. As a result, the full width at half maximum of the X-ray rocking curve was 30 arcsec or less. From this, it was confirmed that the AlN single crystal substrate excluding the AlN seed substrate and the AlN thick film portion of the growth substrate were the same AlN single crystal having the same crystallinity.

As a result of measuring the internal transmittance of the AlN single crystal substrate for analysis with an ultraviolet-visible spectrophotometer (UV-2550, manufactured by Shimadzu Corporation), the internal transmittance at 265 nm is 95%, and within the range of 220 nm to 350 nm. The internal transmittance was 85% or more. The dislocation density measured by etch pit observation was 2 × 10 ⁵ cm ⁻² .

  Thereafter, three growth substrates were cut into a square shape of about 7 mm square (12 square growth substrates of about 7 mm square were prepared).

(Formation of n-type layer, active layer, p-type layer)
An n-type Al _0.70 Ga _0.30 N layer (1 μm: n-type layer), a triple quantum well layer (Al _{0. 50} Ga _0.50 N (4 nm) / Al _0.65 Ga _0.35 N layer (10 nm): active layer), p-type AlN layer (50 nm: p-type layer), p-type Al _0.80 Ga _0.20 N (50 nm: p-type layer) and p-type GaN layer (20 nm: p-type layer) were sequentially laminated to produce a laminate for ultraviolet light emission. Impurity doping is performed using tetraethylsilane and biscyclopentadidiide as dopants so that the Si concentration in the n-type layer is 2 × 10 ¹⁹ cm ⁻³ and the Mg concentration in the p-type layer is 3 × 10 ¹⁹ cm ^−3. The enilmagnesium flow rate was controlled.

(Formation of n-type electrode)
Next, a part of the laminate for ultraviolet light emission (part from the p-type layer side) was etched by an ICP etching apparatus until the n-type Al _0.8 Ga _0.2 N layer (n-type layer) was exposed. An n-type electrode made of Ti (20 nm) / Al (100 nm) / Ti (20 nm) / Au (50 nm) was formed on the exposed surface by vacuum deposition so that the n-type electrode area was 0.002 cm ² . . Thereafter, heat treatment was performed in a nitrogen atmosphere at 950 ° C. for 1 minute. The n-type electrode resistance value was 0.45Ω.

(Formation of p-type electrode)
Next, a p-type electrode made of Ni (20 nm) / Au (50 nm) was formed on the p-type GaN layer by vacuum deposition, and then heat treatment was performed in an oxygen atmosphere at 500 ° C. for 5 minutes. The p-type electrode area was 0.0008 cm ² .

(Removal of AlN seed substrate: manufacture of LED wafer)
Next, the AlN seed substrate portion was removed by mechanical polishing to complete the LED wafer. The remaining thickness of the HVPE AlN thick film layer after polishing was 170 μm.

(LED and its physical property evaluation)
Thereafter, the LED wafer was cut into a square shape of about 0.8 mm square to produce an LED chip and mounted on a polycrystalline AlN carrier to complete the LED. A schematic cross-sectional view of the LED manufactured in Manufacturing Example 1 is shown in FIG. The emission intensity and emission peak wavelength of the produced LED were measured using a 2-inch integrating sphere (Zenith coating manufactured by Sphere Optics) and a multichannel spectrometer (USB 4000 manufactured by Ocean Photonics). The emission peak wavelength of the LED was 265 nm. The emission spectrum of the LED manufactured in Manufacturing Example 1 is shown in FIG. The emission peak intensity (mW / nm) and the half width of the emission peak are summarized in Table 1. Moreover, the drive voltage value of LED manufactured by this manufacture example was 8.9V. These values are values measured at a drive current value of 150 mA and 25 ° C.

Production Example 2
The element layer formed on the AlN thick film of the growth substrate after cutting is an n-type Al _0.70 Ga _0.30 N layer (1 μm: n-type layer), a triplet well layer (Al _0.45 Ga _{0). .55} N (4 nm) / Al _0.60 Ga _0.40 N layer (10 nm): active layer), p-type AlN layer (50 nm: p-type layer), p-type Al _0.80 Ga _0.20 N (50 nm) : P-type layer) and p-type GaN layer (20 nm: p-type layer), except that the ultraviolet LED was completed and evaluated in the same manner as in Production Example 1. The emission peak wavelength was 273 nm. The obtained results are shown in Table 1. Further, the n-type electrode resistance value of the LED manufactured in this manufacturing example was 0.40Ω, and the drive voltage value was 9.0V.

Production Example 3
The element layer formed on the AlN thick film of the growth substrate after cutting is an n-type Al _0.65 Ga _0.35 N layer (1 μm: n-type layer), a triplet well layer (Al _0.40 Ga _{0). .60} N (4 nm) / Al _0.55 Ga _0.45 N layer (10 nm: active layer), p-type AlN layer (50 nm: p-type layer), p-type Al _0.75 Ga _0.25 N (50 nm) : P-type layer) and p-type GaN layer (20 nm: p-type layer), except that the ultraviolet LED was completed and evaluated in the same manner as in Production Example 1. The emission peak wavelength was 280 nm. The obtained results are shown in Table 1. Further, the n-type electrode resistance value of the LED manufactured in this manufacturing example was 0.40Ω, and the drive voltage value was 8.7V.

Production Example 4
The element layer formed on the AlN thick film of the growth substrate after cutting is an n-type Al _0.65 Ga _0.35 N layer (1 μm: n-type layer), a triplet well layer (Al _0.35 Ga _{0). .65} N (4 nm) / Al _0.50 Ga _0.50 N layer (10 nm): active layer), p-type AlN layer (50 nm: p-type layer), p-type Al _0.75 Ga _0.25 N (50 nm) : P-type layer) and p-type GaN layer (20 nm: p-type layer), except that the ultraviolet LED was completed and evaluated in the same manner as in Production Example 1. The emission peak wavelength was 288 nm. The obtained results are shown in Table 1. Further, the n-type electrode resistance value of the LED manufactured in this manufacturing example was 0.30Ω, and the drive voltage value was 8.7V.

Production Example 5
The element layer formed on the AlN thick film of the growth substrate after cutting is an n-type Al _0.65 Ga _0.35 N layer (1 μm: n-type layer), a triplet well layer (Al _0.30 Ga _{0). .70} N (4 nm) / Al _0.45 Ga _0.55 N layer (10 nm): active layer), p-type AlN layer (50 nm: p-type layer), p-type Al _0.75 Ga _0.25 N (50 nm) : P-type layer) and p-type GaN layer (20 nm: p-type layer), except that the ultraviolet LED was completed and evaluated in the same manner as in Production Example 1. The emission peak wavelength was 297 nm. The obtained results are shown in Table 1. Further, the n-type electrode resistance value of the LED manufactured in this manufacturing example was 0.20Ω, and the drive voltage value was 8.5V.

Production Example 6
The element layer formed on the AlN thick film of the growth substrate after cutting is an n-type Al _0.80 Ga _0.20 N layer (1 μm: n-type layer), a triplet well layer (Al _0.65 Ga _{0). .35} N (4 nm) / Al _0.75 Ga _0.25 N layer (10 nm): active layer), p-type AlN layer (50 nm: p-type layer), p-type Al _0.85 Ga _0.15 N (50 nm) : P-type layer) and p-type GaN layer (20 nm: p-type layer), except that the ultraviolet LED was completed and evaluated in the same manner as in Production Example 1. The emission peak wavelength was 245 nm. The obtained results are shown in Table 1. Further, the n-type electrode resistance value of the LED produced in this production example was 0.55Ω, and the drive voltage value was 9.3V.

Production Example 7
The element layer formed on the AlN thick film of the growth substrate after cutting is an n-type Al _0.80 Ga _0.20 N layer (1 μm: n-type layer), a triplet well layer (Al _0.60 Ga _{0). .40} N (4 nm) / Al _0.75 Ga _0.25 N layer (10 nm): active layer), p-type AlN layer (50 nm: p-type layer), p-type Al _0.85 Ga _0.15 N (50 nm) : P-type layer) and p-type GaN layer (20 nm: p-type layer), except that the ultraviolet LED was completed and evaluated in the same manner as in Production Example 1. The emission peak wavelength was 251 nm. The obtained results are shown in Table 1. Further, the n-type electrode resistance value of the LED manufactured in this manufacturing example was 0.50Ω, and the drive voltage value was 9.2V.

Production Example 8
The element layer formed on the AlN thick film of the growth substrate after cutting is an n-type Al _0.75 Ga _0.25 N layer (1 μm: n-type layer), a triplet well layer (Al _0.57 Ga _{0). .43} N (4 nm) / Al _0.70 Ga _0.30 N layer (10 nm): active layer), p-type AlN layer (50 nm: p-type layer), p-type Al _0.85 Ga _0.15 N (50 nm : P-type layer) and p-type GaN layer (20 nm: p-type layer), except that the ultraviolet LED was completed and evaluated in the same manner as in Production Example 1. The emission peak wavelength was 256 nm. The obtained results are shown in Table 1. Further, the n-type electrode resistance value of the LED manufactured in this manufacturing example was 0.45Ω, and the drive voltage value was 9.1V.

Production Example 9
The element layer formed on the AlN thick film of the growth substrate after cutting is an n-type Al _0.75 Ga _0.25 N layer (1 μm: n-type layer), a triplet well layer (Al _0.53 Ga _{0). .47} N (4 nm) / Al _0.68 Ga _0.32 N layer (10 nm): active layer), p-type AlN layer (50 nm: p-type layer), p-type Al _0.80 Ga _0.20 N (50 nm) : P-type layer) and p-type GaN layer (20 nm: p-type layer), except that the ultraviolet LED was completed and evaluated in the same manner as in Production Example 1. The emission peak wavelength was 261 nm. The obtained results are shown in Table 1. Further, the n-type electrode resistance value of the LED manufactured in this manufacturing example was 0.50Ω, and the driving voltage value was 9.0V.

Production Example 10
An ultraviolet light emitting diode wafer was produced in the same manner as in Production Example 6. After removing the AlN seed substrate portion by mechanical polishing, the mechanically polished surface is immersed in a potassium hydroxide aqueous solution, and an uneven structure by wet etching (an uneven structure having random protrusions each having a height and width of about 50 to 1000 nm) Except for producing the structure, an ultraviolet light emitting diode was completed in the same manner as in Example 6 and the same evaluation was performed. The emission peak wavelength was 279 nm. The obtained results are shown in Table 1. Further, the n-type electrode resistance value of the LED produced in this production example was 0.55Ω, and the drive voltage value was 9.2V.

Example 1
The LEDs manufactured in Manufacturing Examples 1 to 5 were made into separate circuits, and a DC power source with a maximum output voltage of 100 V was connected to each of them. The LED was controlled using a Peltier element so that the element temperature was constant at 25 ° C. An emission spectrum when driven at a constant current of 150 mA is shown in FIG. Among the LEDs used, the LED having the smallest emission peak intensity relative to the emission peak intensity ((A): 2.5 mW / nm) of the LED having the highest emission peak intensity (the LED produced in Production Example 5) The ratio (B / A) of the emission peak intensity ((B): 1.9 mW / nm) of the LED produced in Example 3 was 0.76. Then, in the emission spectrum of FIG. 2, the LED having the longest emission peak wavelength from the emission peak wavelength (265 nm) of the LED having the shortest emission peak wavelength (the LED produced in Production Example 1) (Production Example 5). In the wavelength range up to the emission peak wavelength (297 nm) of the LED manufactured in (1), the minimum emission intensity ((D) 2.5 mW / nm, with respect to the maximum emission intensity ((C): 3.1 mW / nm, 276 nm), 265 nm) ratio (D / C) was 0.81. Further, the difference (| λ1−λ2 |) between the adjacent emission peak wavelength and the emission peak wavelength is the half width (9 nm) of the LED (the LED manufactured in Production Example 5) in which the half width of the emission peak wavelength is minimized. It was the following.

Example 2
Three LEDs manufactured in Manufacturing Example 6, two LEDs manufactured in Manufacturing Example 7, one LED manufactured in Manufacturing Example 8, and one LED manufactured in Manufacturing Example 9 are set as separate circuits, and each has a maximum output voltage of 100V. DC power supply was connected. The element temperature was controlled at 25 ° C. in the same manner as in Example 1. FIG. 3 shows an emission spectrum when driven at a constant current of 150 mA DC. Among the LEDs used in Example 2, the light emission peak intensity is the minimum with respect to the light emission peak intensity ((A): 2.5 mW / nm) of the LED having the maximum light emission peak intensity (the LED produced in Production Example 9). The ratio (B / A) of the emission peak intensity ((B): 0.8 mW / nm) of the resulting LED (the LED manufactured in Manufacturing Example 6) was 0.32. In the emission spectrum of FIG. 3, the LED having the longest emission peak wavelength from the emission peak wavelength (245 nm) of the LED having the shortest emission peak wavelength (LED manufactured in Production Example 6) (Production Example 9). In the wavelength range up to the emission peak wavelength (261 nm) of the LED manufactured in (1), the minimum emission intensity ((D): 3.3 mW / nm) with respect to the maximum emission intensity ((C): 3.9 mW / nm, 250 nm). (245 nm) ratio (D / C) was 0.86. Further, the difference (| λ1−λ2 |) between the adjacent emission peak wavelength and the emission peak wavelength is the half width (8 nm) of the LED (the LED manufactured in Production Example 9) in which the half width of the emission peak wavelength is the smallest. It was the following.

Example 3
Three LEDs manufactured in Manufacturing Example 6 and one LED manufactured in Manufacturing Example 5 were made into separate circuits, and a DC power supply with a maximum output voltage of 100 V was connected to each of them. The driving temperature was controlled at 25 ° C. in the same manner as in Example 1. An emission spectrum when driven at a constant current of 150 mA is shown in FIG. Among the LEDs used in the examples, the emission peak intensity is the minimum with respect to the emission peak intensity ((A): 2.5 mW / nm) of the LED having the maximum emission peak intensity (the LED produced in Production Example 5). The ratio (B / A) of the emission peak intensity ((B): 0.8 mW / nm) of the resulting LED (the LED manufactured in Manufacturing Example 6) was 0.32. At the emission peak wavelengths of these independent emission spectra, the minimum emission intensity ((D): with respect to the maximum emission intensity ((C): 2.5 mW / nm: one LED manufactured in Example 5). The ratio (D / C) of 2.4 mW / nm: 3 LEDs manufactured in Example 6 was 0.96.

Example 4
Two LEDs manufactured in Manufacturing Example 10, two LEDs manufactured in Manufacturing Example 7, one LED manufactured in Manufacturing Example 8, and one LED manufactured in Manufacturing Example 9 are set as separate circuits, and each has a maximum output voltage of 100V. DC power supply was connected. The element temperature was controlled at 25 ° C. in the same manner as in Example 1. FIG. 3 shows an emission spectrum when driven at a constant current of 150 mA DC. Among the LEDs used in Example 2, the light emission peak intensity is the minimum with respect to the light emission peak intensity ((A): 2.5 mW / nm) of the LED having the maximum light emission peak intensity (the LED produced in Production Example 9). The ratio (B / A) of the emission peak intensity ((B): 1.1 mW / nm) of the resulting LED (the LED manufactured in Manufacturing Example 10) was 0.44. Then, in the emission spectrum of FIG. 5, the LED having the longest emission peak wavelength from the emission peak wavelength (245 nm) of the LED having the shortest emission peak wavelength (LED manufactured in Production Example 10) (Production Example 9). In the wavelength range up to the emission peak wavelength (261 nm) of the LED manufactured in (1), the minimum emission intensity ((D): 3.1 mW / nm) with respect to the maximum emission intensity ((C): 3.8 mW / nm, 252 nm). The ratio (D / C) of 245 nm was 0.82. Further, the difference (| λ1−λ2 |) between the adjacent emission peak wavelength and the emission peak wavelength is the half width (8 nm) of the LED (the LED manufactured in Production Example 9) in which the half width of the emission peak wavelength is the smallest. It was the following.

1 UV LED (UV LED wafer)
2 substrate 3 n-type layer 4 active layer 5 p-type Al _X3 Ga _1-X3 N layer 6 p-type Al _X4 Ga _1-X4 N layer 7 p-type In _Y Ga _1-Y N layer 8 p-type layer 9 n-type electrode (layer)
10 p-type electrode (layer)

Claims (10)

An ultraviolet light source equipped with a plurality of light emitting diodes,
The emission peak wavelength of all the light emitting diodes exists in the range of 220 to 350 nm,
The ratio (B / A) of the emission peak intensity (B) of the light emitting diode with the minimum emission peak intensity to the emission peak intensity (A) of the light emitting diode with the maximum emission peak intensity of the plurality of light emitting diodes is 0. An ultraviolet light source equipped with a plurality of light emitting diodes having different light emission peaks, characterized in that it is 2 or more.   2. The ultraviolet light source according to claim 1, wherein all of the light emitting diodes have an emission peak intensity of 0.5 mW / nm or more at a temperature of 25 ° C. and a driving current value of 150 mA.   3. The ultraviolet light source according to claim 1, wherein the substrate having the light emitting main surface is made of an aluminum nitride single crystal in all the light emitting diodes.   The light emission intensity distribution having a continuous region of the emission spectrum of the ultraviolet light source, and the longest wavelength from the emission peak wavelength of the light emitting diode having the shortest emission peak wavelength among the plurality of light emitting diodes mounted on the ultraviolet light source. The ratio (D / C) of the minimum light emission intensity (D) to the maximum light emission intensity (C) is 0.5 or more in the range up to the light emission peak wavelength of the light emitting diode having the light emission peak wavelength. The ultraviolet light source according to claim 1.   The difference (| λ1−λ2 |) between the adjacent emission peak wavelength (λ1) and emission peak wavelength (λ2) is the half value width of the light emitting diode having the smallest half value width of the emission peak among the plurality of light emitting diodes. The ultraviolet light source according to any one of claims 1 to 4, wherein the light emission intensity distribution has a region where the emission spectrum of the ultraviolet light source is continuous.   By using a plurality of light emitting diodes having the same emission peak wavelength, among the plurality of light emitting diodes mounted on the ultraviolet light source, the emission peak wavelength of the longest wavelength from the emission peak wavelength of the light emitting diode having the shortest emission peak wavelength. The ratio (D / C) of the minimum emission intensity (D) to the maximum emission intensity (C) in the range up to the emission peak wavelength of the light emitting diode having a wavelength is set to 0.5 or more. The ultraviolet light source in any one of 1-5.   The emission spectrum of the ultraviolet light source is a light emission intensity distribution that exists independently without overlapping the emission spectrum of each of the light emitting diodes in a range of 220 to 350 nm. The ultraviolet light source described.   By using a plurality of light emitting diodes having the same emission peak wavelength, the ratio (D / C) of the minimum emission intensity (D) to the maximum emission intensity (C) at the emission peak wavelength of the independent emission spectrum of the ultraviolet light source. The ultraviolet light source according to claim 7, wherein the ratio is 0.5 or more.   The ultraviolet light source according to claim 1, wherein the ultraviolet light source has only one light emitting diode having a maximum emission peak intensity.   The ultraviolet light source according to claim 1, wherein the emission peak wavelengths of all the light emitting diodes are in the range of 220 to 280 nm.

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