JPH097409A - Led signal lamp - Google Patents

Abstract

(57) [Summary] [Objective] In an LED signal light in which the signal light of the blue-green light emitting portion is formed of a blue-green LED made of a gallium nitride-based compound semiconductor, the life deterioration of the blue-green LED and the change of the peak wavelength are prevented, and the life characteristics are improved. Excellent LED signal lamp is obtained. [Structure] A blue-green LED is sealed by a package having a hollow interior, and a lens for condensing the light emitted from the blue-green LED is provided on the emission observation surface side of the package.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal light using an LED (light emitting diode), and more particularly to a nitride semiconductor (In _X
Al _Y Ga _1-XY N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1).

[0002]

2. Description of the Related Art Nitride semiconductors have a band gap of 1.9.
It is from 5 eV to 6.0 eV, and has been attracting attention as a material for an ultraviolet to red light emitting device. Recently, blue LEDs and blue-green LEDs using this nitride semiconductor have been put to practical use and used in full-color displays, LED signal lights, and the like. In particular, in some prefectures, LED signal lights for traffic signals using blue-green LEDs have already been installed and tested. The LED signal lamp has a life of 10 times or more longer than that of the conventional light bulb signal lamp, and there is no problem of pseudo lighting even when the signal lamp is directly irradiated with sunlight, which is very useful in the traffic field.

A blue-green LED currently used for an LED signal lamp is composed of a laminated body of nitride semiconductors having a double hetero structure having InGaN as an active layer and has an emission wavelength of 480 to 480.
It is 490 nm. As shown in FIG. 3, this blue-green LED has a shape in which a nitride semiconductor LED chip 11 mounted on a lead frame 12 having a cup shape is molded into a lens shape with a weather resistant epoxy resin 13. ing. Those molded with resin in this way are shell-shaped L
Called ED, red and yellow LEDs of other traffic light colors
This is also a shell type.

[0004]

As described above, the normal L
The ED is a shell type LED in which an LED chip is molded in a lens shape with an epoxy resin. However, blue-green L
Since the ED has a shorter wavelength than the red LED and the yellow LED, there is a drawback that the epoxy resin deteriorates, which does not occur in the red and the yellow. When the epoxy resin deteriorates, the stress on the chip and the translucency change, so the LED
Problems such as deterioration of life of the device and change of peak wavelength occur.

Therefore, the present invention has been made to solve the above-mentioned drawbacks, and an object thereof is to prevent deterioration of the life of a blue-green LED, change of the peak wavelength, etc., and excellent life characteristics. To get an LED signal light.

[0006]

The LED signal lamp of the present invention is an LED signal lamp in which the signal lamp of the blue-green light emitting portion is formed of a blue-green LED made of a gallium nitride-based compound semiconductor, wherein the blue-green LED is hollow inside. It is characterized by being sealed with a package.

Such an LED is generally called a can type and has a structure as shown in FIG. The LED chip 1 mounted on the can type metal stem 2 is hermetically sealed with the can type metal cap 3 after the electrodes are wire-bonded. This metal cap 3
A glass 4 for taking out emitted light to the outside is embedded on the emission observation surface side of.

Next, the LED signal lamp of the present invention is characterized in that a lens 5 for collecting the light emitted from the blue-green LED is provided on the light emission observation surface side of the package. As shown in FIG. 2, a lens 5 is provided on the emission observation surface side of the can type metal cap 3 for collecting the emitted light of the LED and taking it out to the outside. By providing this lens 5, it is possible to efficiently take out the light emission of the LED to the outside. As the material of the lens 5, for example, quartz glass, potash glass, soda glass, lead glass, barium glass, sapphire glass or the like is used.

[0009]

Since the blue-green LED has a shorter wavelength than the red LED and the yellow LED, when the blue-green LED chip is molded with epoxy resin to form a bullet-shaped LED as in the conventional case, it does not occur in red or yellow. The deterioration of the epoxy resin, which was not present, occurs. This is because the short-wavelength light source has large energy and deteriorates the epoxy resin.
When the epoxy resin deteriorates, the stress on the chip and the translucency change, which causes problems such as the deterioration of the life of the LED and the change of the peak wavelength.

However, in the present invention, the can type package, not the epoxy resin, is used to seal the LED chip, so that the above problems associated with the deterioration of the epoxy resin are solved, and the LED has excellent life characteristics. A signal light is obtained.

Further, since the can type LED has a directional characteristic different from that of the LED molded with epoxy resin, for example, three colors of a can type blue LED and a shell type red and yellow LED are arranged in a dot shape to form a display. If you do, the image will be difficult to see. Therefore, the can type blue-green LED is not suitable for a display. However, since the signal light emits each of the three colors of red, turquoise, and yellow independently, it is not necessary to consider the difference in the directional characteristics with the LEDs of other colors like a display, and even if only the blue-green LED is of a can type. No problem.

[0012]

EXAMPLES The LED signal lamp of the present invention will be described based on examples.

[Example 1] I doped with Si and Zn
A blue-green LED chip 1 having a double hetero structure in which an nGaN active layer is sandwiched between n-type and p-type AlGaN cladding layers is prepared.

Subsequently, as shown in FIG. 1, the LED chip 1 is mounted on a can type metal stem 2, and then p-electrodes and n-electrodes are wire-bonded to their respective leads by Au wires. This is hermetically sealed with a can type metal cap 3. A glass 4 for extracting emitted light to the outside is embedded on the light emission observation surface side of the metal cap 3.

The can type blue-green LED thus obtained was assembled in a signal unit, installed outdoors and subjected to a forced life test at a forward current of 50 mA. After 1000 hours, the electrode There was no open or short circuit, and there was no change in wavelength or decrease in luminous intensity.

[Embodiment 2] The same blue-green LE as in Embodiment 1.
Prepare the D chip 1. After mounting the chip 1 on the can type metal stem 2 as in the first embodiment, the electrodes are wire-bonded and hermetically sealed with the can type metal cap 3. As shown in FIG. 2, a lens 5 for collecting the emitted light and taking it out to the outside is provided on the light emission observation surface side of the metal cap 3.

The can type blue-green LED thus obtained was incorporated in a signal unit and a life test was conducted under the same conditions as in Example 1. After 1000 hours, the electrodes were not opened or shorted. No change in wavelength or decrease in luminous intensity was observed.

[0018]

As described above, according to the present invention, L
Bullet-type LED molded with conventional epoxy resin by changing the blue-green LED used for the ED signal lamp to a can-type LED sealed in a package with a hollow inside.
It is possible to prevent deterioration of LED life, power down, change of peak wavelength, etc. due to resin deterioration of
An LED signal lamp with excellent life characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a blue-green LED used for one LED signal lamp of the present invention.

FIG. 2 is a schematic cross-sectional view showing the structure of a blue-green LED used for one LED signal lamp of the present invention.

FIG. 3 is a blue-green LE used in a conventional LED signal light
FIG. 3 is a schematic cross-sectional view showing the structure of D.

[Explanation of symbols]

 1, 11 ... LED chip 2 ... Can type stem 3 ... Can type cap 4 ... Glass 5 ... Condensing lens 12 ... Lead frame 13 ... ···Epoxy resin

Claims (2)

[Claims] 1. An LED in which a signal lamp of a blue-green light emitting portion is a blue-green LED made of a gallium nitride-based compound semiconductor.
In the signal light, the blue-green LED is sealed by a package having a hollow inside.
ED signal light. 2. The LED signal lamp according to claim 1, wherein a lens that collects the light emitted from the blue-green LED is provided on the light emission observation surface side of the package.