JPH09181356A - Ultraviolet light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small and inexpensive ultraviolet light source which can be handled easily by employing a blue light emitting diode as a light source and applying a DC current higher than the rated current to the blue light emitting diode. SOLUTION: A light emitting diode 20 has composition of InGaN/AlGaN doped with Zn and emits light of 480nm wavelength, i.e., blue light, at a rated current of about 30mA. When a current higher than the rated current is fed to the blue light emitting diode 20, light of 380nm wavelength, i.e., ultraviolet light, can be emitted and a small, inexpensive and easy-to-handle ultraviolet light source can be realized using the light emitting diode 20. When a high DC current is applied simply to the blue light emitting diode 20, the service life is shortened but a long service life can be sustained when an extremely short current pulse is applied.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ultraviolet light source used as a light source for a spectroscopic analysis device, a light source for an optical communication device, a light source for plant forcing cultivation, and a light source for curing an ultraviolet curable adhesive.

[0002]

2. Description of the Related Art As an ultraviolet light source, SOR (sync
SOR light sources obtained from electron beams of hrotron orbital radiation) and arc lamp light sources such as xenon tubes and mercury lamps are known.

[0003]

However, although the above SOR light source can obtain a good light source with high coherence, it is unsuitable as a light source which is large in scale and easy to use. In addition, it is difficult to downsize the arc lamp light source due to the handling of the tube, its size, and measures against heat generation, and it is difficult to reduce the price.

Therefore, an object of the present invention is to provide an ultraviolet light source which is easy to handle and can be made compact and inexpensive.

[0005]

In order to achieve the above-mentioned object, the ultraviolet light source according to claim 1 of the present invention uses a blue light emitting diode as a light emitting source, and the blue light emitting diode has a rated current value higher than that of the blue light emitting diode. It is characterized in that a direct current having a large current value is applied.

Here, the blue light emitting diode has the composition In
A light emitting diode in which Zn is injected as a donor in GaN / AlGaN is used, and the wavelength is 480 nm at the rated current.
Light, that is, blue light can be obtained.

With the above structure, when a direct current having a current value larger than the rated current value is applied to the blue light emitting diode, the diode emits light having a wavelength of about 380 nm, that is, ultraviolet rays.

The ultraviolet light source according to claim 2 is characterized in that a blue light emitting diode is used as a light emitting source and an extremely short pulse current having a current value larger than the rated current value is applied to the blue light emitting diode. To do.

With the above structure, when a direct current having a current value larger than the rated current value is simply applied to the blue light emitting diode, the life of the diode is shortened. Therefore, by applying an extremely short pulse current, ultraviolet rays can be obtained. As a result, the life can be maintained, and the amount of ultraviolet light can be further improved.

Further, the ultraviolet light source according to claim 3 is the ultraviolet light source according to claim 2, wherein the pulse width is 1 to 5
It is characterized in that it is set to ns. With the above configuration, light with a wavelength of 480 nm (blue light)
Is suppressed, and only light (ultraviolet light) having a wavelength of 380 nm is obtained.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of an ultraviolet light source showing an embodiment of the present invention.

The ultraviolet light source of the present invention comprises a DC power supply 1, a pulse generator 2 which is fed from the DC power supply 1 to generate a pulse of a predetermined frequency, and a light emitting circuit (pulse current drive circuit) 3 which emits ultraviolet light. It is configured.

The light emitting circuit 3 has a voltage terminal 11 (applied voltage Va) connected to the output power terminal of the DC power source 1, and a resistor 12 (resistance value 50 kΩ) having one end connected to the voltage terminal 11.
And a signal input terminal 13 connected to the output terminal of the pulse generator 2, and a resistor 14 having one end connected to the signal input terminal 13.
(100 kΩ), the other end of the resistor 12 is connected to the collector, the other end of the resistor 14 is connected to the base, the emitter is grounded, and the bias resistor 16 connected between the base and the emitter of the transistor 15. (1 kΩ), a charging capacitor 17 (capacitance Cd) whose one end is connected to the collector of the transistor 15, and a coil 18 (inductance L) whose one end is connected to the other end of the capacitor 17 and whose other end is grounded.
A resistor 19 (1 kΩ) having one end connected to the other end of the capacitor 17 and the other end grounded; a light emitting diode 20 having a cathode connected to the other end of the capacitor 17;
The diode current limiting resistor 21 (resistor R) having one end connected to the anode and the other end grounded, and the current monitor terminal 22 connected to the anode of the light emitting diode 20.

The light emitting diode 20 has a composition of InGaN.
/ AlGaN uses a Zn-implanted diode as a donor and has a rated current (about 30 mA) and a wavelength of 480
It is possible to obtain nm light, that is, blue light. When a current having a current value larger than the rated current value was passed through the blue light emitting diode 20, light having a second peak at a wavelength of 380 nm, that is, ultraviolet rays was obtained as shown in FIG. The waveform shown in Fig. 2 shows a direct current of 20mA, 50mA, 1
It is the emission wavelength when 20 mA is applied. In the case of 20 mA below the rated current value, blue light with a peak of 430 nm is obtained. Has a peak. Further, FIG. 3 shows the spectral characteristics of the wavelength and the amount of light when the time (application time) of the direct current flowing through the diode 20 is 0 to 6 ns. When the application time is 1 to 5 ns, the wavelength is suppressed at 430 nm and 380 n
Only the wavelength of m appeared.

In the configuration of the above light source, the pulse generator 2
Frequency is 10 kHz, pulse width is 4 ns, applied voltage V
The time response characteristics of the current of the diode 20 detected at the current monitor terminal 22 and the light quantity of the diode 20 when a is 300 V, resistance R is 10 Ω, inductance L is 0.25 μH, and capacitance Cd is 100 pF. 4 shows.

The pulse width of light was about 4 nm at full width at half maximum, and the current was 2 A at peak. A large undershoot is seen at the trailing edge of the pulse, which is due to the influence of the inductance L. The applied voltage Va is 3
It was possible to obtain stable pulsed light emission at 50 V to 230 V without a time lag.

Under the same conditions, the capacitance Cd is set to 50 pF, 10 in FIG.
The time response characteristics of the light quantity of the diode 20 when 0 pF and 150 pF are shown. As the capacity Cd of the charging capacitor 17 increases, the amount of light increases and the pulse width also increases.

As described above, light having a wavelength of 380 nm, that is, ultraviolet rays can be obtained by applying a direct current having a current value larger than the rated current value to the blue light emitting diode 20, and by using the light emitting diode 20,
It is possible to obtain an ultraviolet light source that is inexpensive, easy to handle, and can be downsized.

When a direct current having a current value larger than the rated current value is simply applied to the blue light emitting diode 20, the life of the light emitting diode 20 is shortened, but the applied current of the light emitting diode 20 is an extremely short pulse of 1 to 5 nm. As a result, ultraviolet rays can be obtained and the life can be maintained. Further, by setting the extremely short pulse width to 1 to 5 ns, light having a wavelength of 480 nm (blue light) is suppressed, and only light having a wavelength of 380 nm (ultraviolet light) can be obtained.

In order to increase the brightness without widening the pulse width, an avalanche transistor is connected in cascade to the transistor 15 and the applied voltage Va is 350V.
It is preferable to use the above voltage. Moreover, the resistance R of the resistance 21 is set to 10Ω.
The pulse width can be shortened by the following, but an undershoot occurs after the pulse, and it is good to remove the coil 18 from the circuit to eliminate this undershoot, but the pulse width becomes wider ( Brightness increases slightly).

[0021]

As described above, according to the first aspect of the present invention, by applying a direct current having a current value larger than the rated current value to the blue light emitting diode, a wavelength of 380 nm is obtained.
By using a light emitting diode, it is possible to obtain an ultraviolet light source that is inexpensive, easy to handle, and can be miniaturized, while being able to obtain light in the vicinity, that is, ultraviolet light.

According to the second aspect of the invention, when a direct current having a current value larger than the rated current value is simply applied to the blue light emitting diode, the life of the diode is shortened, but the applied current is an extremely short pulse. Thus, ultraviolet rays can be obtained and the life can be maintained.

Further, according to the invention of claim 3, the light of wavelength 480 nm (blue light) is suppressed, and the wavelength of 380 n
Only light (ultraviolet rays) near m can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an ultraviolet light source showing an embodiment of the present invention.

FIG. 2 is a spectrum distribution diagram according to a direct current applied to a light emitting diode used for the same ultraviolet light source.

FIG. 3 is a spectrum change diagram of a light emitting diode used in the same ultraviolet light source immediately after a direct current is applied.

FIG. 4 is a time response diagram of a light amount and a current of a light emitting diode in the same ultraviolet light source.

FIG. 5 is a time response diagram of a light amount of a light emitting diode depending on a capacity of a charging capacitor in the same ultraviolet light source.

[Explanation of symbols]

 1 DC power supply 2 Pulse generator 3 Light emitting circuit 15 Transistor 17 Charging capacitor 18 Coil 20 Blue light emitting diode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukihiro Terada 5-3-8 Nishikujo 5-chome, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd.

Claims (3)

[Claims] 1. An ultraviolet light source configured to use a blue light emitting diode as a light emitting source and to apply a direct current having a current value larger than a rated current value to the blue light emitting diode. 2. An ultraviolet light source configured to use a blue light emitting diode as a light emitting source and to apply an ultrashort pulse current having a current value larger than the rated current value to the blue light emitting diode. 3. The ultraviolet light source according to claim 2, wherein the pulse width of the ultrashort pulse current is 1 to 5 ns.