Light emitting diode

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a light emitting diode (hereinafter referred to as an LED) in which a light emitting element is surrounded by a resin mold, and more particularly to a wavelength conversion light emitting diode capable of emitting a large number of types with one type of light emitting element and having a higher brightness.

【0002】

[Conventional technology]

Generally, an LED has a structure as shown in FIG. 1 is a light emitting element made of, for example, GaAlAs, GaP, etc. cut into 1 mm square or less, 2 is a metal stem, 3 is a metal post, and 4 is a resin mold surrounding the light emitting element. The back electrode of the light emitting element 1 is electrically connected to the metal stem 2 with silver paste or the like, and the front electrode of the light emitting element 1 is a wire on the front surface by a gold wire extended from a metal post 3 which is another terminal. It is bonded, and the light emitting element 1 is further molded with a transparent resin mold 4.

【0003】

Normally, for the resin mold 4, a resin having a high refractive index and high transparency is selected for the purpose of efficiently emitting the light emitted from the light emitting element into the air, but in addition, the light emitting color of the light emitting element is converted. An inorganic pigment or an organic pigment may be mixed as a colorant in the resin mold 4 for the purpose of correcting the color or for the purpose of correcting the color.

【0004】

[Problems to be Solved by the Invention]

However, conventionally, the technique of adding a colorant to a resin mold to convert the wavelength has hardly been put into practical use, and the technique of color correction by a colorant is only slightly used. This is because if a colorant, which is a non-luminescent substance capable of converting wavelengths, is added to the resin mold, the brightness of the LED itself is greatly reduced.

【0005】

By the way, at present, LEDs that emit infrared, red, yellow, and green are practically used, and blue or ultraviolet LEDs have not yet been put into practical use. Research on blue and ultraviolet light emitting devices using semiconductor materials such as II-VI group ZnSe, IV-IV group SiC, and III-V group GaN has been advanced recently, and the general formula is Ga among them._xAl_1-xIt has been announced that gallium nitride-based compound semiconductors represented by N (where X is 0 X 1) exhibit relatively excellent light emission at room temperature, and are attracting attention. In addition, LEDs that have realized pn junctions for the first time using gallium nitride compound semiconductors have been announced (Applied Physics, Vol. 60, No. 2, p163 to p166, 1991). According to it, the emission wavelength of an LED having a pn-junction gallium nitride compound semiconductor is mainly around 430 nm, and also has an emission peak in the ultraviolet region around 370 nm. The wavelength is the shortest wavelength among the above semiconductor materials. However, the LED has a drawback that the visibility is poor because it has an emission color close to purple as indicated by the emission wavelength.

【0006】

The present invention has been made in view of such circumstances, and an object of the present invention is to improve the visual sensitivity of an LED having a light emitting element and to improve its brightness.

【0007】

[Means for solving problems]

The light-emitting diode of the present invention includes a light-emitting element which is a gallium nitride-based compound semiconductor which is arranged on a metal and laminated in n-type and p-type, and a resin having a convex cross section surrounding the light-emitting element. It has a fluorescent dye or a fluorescent pigment in the convex lens-shaped resin surrounding the light emitting element, which is excited by visible light from the light emitting element and emits visible light having a wavelength longer than the excitation wavelength.

【0008】

As the light emitting diode of the present invention, a fluorescent dye or a fluorescent pigment excited by a wavelength in the vicinity of 420 to 440 nm can be used.

【0009】

The light emitting element of the light emitting diode according to claim 3 of the present invention has a pair of electrodes wire bonded to the same surface located on the opposite side of the surface facing the metal. Further, one electrode is an ohmic electrode connected to a portion where a gallium nitride based compound semiconductor is etched to expose the surface of the n-type layer.

【0010】

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 2 is an example showing the structure of the LED of the present invention. 11 is a blue light emitting element in which GaAlN is laminated in n-type and p-type on a sapphire substrate, 2 and 3 are metal stems and metal posts as in FIG. 1, and 4 is a resin mold surrounding the light emitting element. Since the back surface of the light emitting element 11 is an insulating substrate of sapphire and the electrode cannot be taken out from the back surface, the n electrode of the GaAlN layer is electrically connected to the metal stem 2, so that the surface of the n-type layer is exposed by etching the GaAlN layer. A method is adopted in which an ohmic electrode is attached and electrically connected by a gold wire. The other electrodes are wire-bonded on the surface of the p-type layer by a gold wire extending from the metal post 3 as in FIG. Further, a fluorescent dye 5 that is excited by a wavelength in the vicinity of 420 to 440 nm and emits a wavelength having an emission peak at 480 nm is added to the resin mold 4.

【0011】

[Effect of the invention]

The fluorescent dye or fluorescent pigment of the light emitting diode of the present invention is excited by short wavelength light excited from the light emitting element and emits light having a wavelength longer than the excitation wavelength. Conversely, some fluorescent pigments are excited by long-wavelength light to emit short-wavelength light, but they are very energy inefficient and emit only weakly. As described above, the gallium nitride based compound semiconductor has its emission peak on the shortest wavelength side among the semiconductor materials used for LEDs. Therefore, when it is used as a material for a light emitting element, the fluorescent substances can be most preferably excited by adding a fluorescent dye or a fluorescent pigment to the resin mold surrounding the light emitting element. Therefore, not to mention the color correction of the blue LED, it is possible to convert light of various wavelengths depending on the type of fluorescent dyeing and fluorescent pigment. Further, since the light emitting diode of the present invention changes light having a short wavelength to a long wavelength, it is energy efficient, requires a small amount of fluorescent dye or fluorescent pigment to be added, and is very convenient in terms of a decrease in brightness.

[Simple explanation of drawings]

[Figure 1]

Schematic cross-sectional view showing the structure of a conventional LED.

[Figure 2]

The schematic cross-sectional view which shows the structure of one Example of the LED of this invention.

[Explanation of symbols]

11 Light emitting element 2 Metal stem 3 Metal post 4 Resin mold 5 Fluorescent dye