JPH09298315A - Light-emitting diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting diode with no deterioration such as yellowing of a radiation surface of a reflection-type LED while having a good life characteristic and good optical characteristic such as a transmission factor characteristic. SOLUTION: This light-emitting diode is constituted by a method wherein the light-emitting element 1, leads 2a, 2b supplying the light-emitting element with power are sealed and a reflection surface 5 is formed by molding on the side opposing to a light-emitting surface of the light-emitting element 1 and a radiation surface is formed by molding on the rear side of the light-emitting element 1 and a distance from a lead 2a to be mounted with the light-emitting element 1 to above radiation surface is within 1.5mm or within 1/2 of the radius besides at least above radiation surface part is covered with a material being hard to be yellowed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a light emitting diode (hereinafter referred to as LED), and more particularly to improvement of life characteristics of a reflective LED.

[0002]

2. Description of the Related Art In a reflection type LED, a light emitting element is mounted on a lead frame via a conductive adhesive. The periphery of the light emitting element is sealed with a light transmissive material, and a reflecting surface is formed on the light emitting surface side of the light emitting element and a radiation surface is formed on the back surface side. The emitting surface is set so that the distance from the lead mounting the light emitting element to the emitting surface is within 1/2 of the radius. With such a structure, it is possible to obtain a thin reflective LED in which the light emitted from the light emitting element can be effectively emitted to the outside and the optical control can be sufficiently performed.

Further, unlike the lens type LED shown in FIG. 4, since the distance from the light emitting element to the resin interface is short, more heat generated from the light emitting element can be radiated to the outside from the resin interface. In FIG. 4, 11 is a light emitting element, and 12a and 12b.
Is a pair of lead frames, and 13 is a transparent resin that integrally seals them, and is molded into a lens shape. Further, since the heat generated by the light emitting element and transferred to the lead frame is short to the resin interface, the heat transferred to the lead frame can be radiated to the outside from the resin interface. For this reason, when the LED is used as a collective lamp or a dot matrix type display using this lamp, the lens type LED mainly transfers heat to the inside of the LED lamp by a frame and directly While the light is not radiated from the system to the outside, the reflection type LED can radiate from the system directly to the outside from the radiation surface, so that thermal damage to the light emitting element and the like can be reduced.

On the other hand, there are restrictions on the material for sealing the light emitting element of the LED. This is a material with a large refractive index for effectively extracting the light emitted in the light emitting element to the outside, a material that causes little stress damage to the light emitting element due to thermal contraction or curing contraction, and is emitted from the light emitting element. This is a constraint such as a material having a high transmittance so that light is not absorbed in the sealing resin. . Generally, an epoxy resin is used as a sealing material for a light emitting element of an LED.

[0005]

However, the transparent epoxy resin generally used as the sealing material for the light emitting element of the LED has a yellowing phenomenon due to heat. This is because the resin is activated by heat and reacts with the outside air, and as a result, the transmittance of light on the short wavelength side near the surface of the resin decreases. This phenomenon occurs when operating the LED in an atmosphere with a high ambient temperature. Further, in the reflective LED, there is a problem that the interface of the radiation surface rises more than the lens LED due to the heat generated by the light emitting element, and the yellowing phenomenon easily occurs. In particular, when a blue light emitting element is used, it is necessary to operate the LED in a high temperature atmosphere and consume a large amount of power. However, the yellowing phenomenon causes a remarkable decrease in light emission output, which is a major cause of deterioration in LED characteristics. Has become.

The present invention has been made in view of the above, and has no deterioration phenomenon such as yellowing of the emitting surface of the reflection type LED, has good life characteristics, and has good optical characteristics such as transmittance characteristics. It is intended to provide a diode.

[0007]

The present invention provides a light emitting device,
The leads for supplying electric power to the light emitting element and the reflection surface on the side facing the light emitting surface of the light emitting element and the emission surface on the back side of the light emitting element are formed by molding and sealing the leads, and the light emitting element is mounted. The distance from the lead to the radiation surface is 1.
It is characterized in that it is within 5 mm or within 1/2 of the radius, and at least the radiation surface portion is coated with a material that does not easily turn yellow. Further, the lead for mounting the light emitting element is characterized by being pulled out in the lateral direction while keeping the distance from the emitting surface within 1.5 mm or within 1/2 of the radius.

[0008]

With the above structure, a yellowing phenomenon does not occur on the radiation surface and the like, heat resistance is good, and a high-power light emitting diode can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 and 2 show an LED according to an embodiment of the present invention, in which a light emitting element 1 is mounted on one lead frame 2a via a conductive adhesive. Lead frames 2a, 2
b is pulled out in the lateral direction. The periphery of the light emitting element 1 is sealed with a light transmissive material 3, and a concave reflecting surface 4 is formed on the light emitting surface side of the light emitting element, and a flat emitting surface 5 is formed on the back surface side. . Further, an acrylic coating 6 is applied on the radiation surface side by a spray method.

With this structure, the light emitted from the light emitting element can be effectively radiated to the outside, and the optical control can be sufficiently performed. Further, unlike the lens-type LED, the distance from the light emitting element to the resin interface is short, so that more heat generated from the light emitting element can be radiated to the outside from the resin interface. Furthermore, since the heat generated by the light emitting element and transmitted by the lead frame is short to the resin interface, more heat transmitted to the lead frame can be radiated to the outside from the resin interface. For this reason, in the reflection type LED, radiation can be directly emitted from this system to the outside from the emission surface, so that thermal damage to the light emitting element and the like can be made small.

Since the acrylic coating is applied to the radiation surface side, it is used to seal the light emitting element, and has a refractive index for effectively extracting the light emitted in the light emitting element to the outside. The material is large, has little stress damage to the light emitting element due to heat shrinkage or curing shrinkage, and has a high transmittance so that light is not absorbed in the resin, and the resin is activated by heat and reacts with the outside air. The phenomenon that the transmittance of light on the short wavelength side near the surface of the is decreased is significantly reduced. For this reason, since the LED is operated in a high temperature atmosphere, it is necessary to consume a large amount of power, and even when using a blue light emitting element whose emission output is significantly reduced due to the yellowing phenomenon, in addition to the conventional characteristics. As a result, it is possible to reduce the characteristic deterioration of the LED caused by the restriction of the sealing material.

The coating material is not limited to an acrylic material, and may be any other material as long as it is a material that does not easily turn yellow at high temperatures. Further, those having ultraviolet absorption characteristics such as zirconium oxide and titanium oxide may be used. According to this, there is an advantage that it is possible to prevent yellowing due to ultraviolet rays and is most suitable for outdoor use. Further, the coating method is not limited to the spray method. The coating is not limited to coating, and may be a sheet-shaped thin glass plate or the like attached.

The shape of the optical surface of the light emitting diode is not limited to the axially symmetric shape, and heat is sufficiently dissipated from the emitting surface, and the distance from the lead mounting the light emitting element to the emitting surface is 1 mm. Anything within 0.5 mm is included in the present invention. This distance of 1.5 mm is about 1/2 of the radius of the commonly used LED size φ5 mm.

Next, a second embodiment is shown in FIG. The second embodiment differs from the first embodiment in that only the radiation surface side is coated in the first embodiment, but the entire outer surface of the transparent resin is coated by dipping or the like including the concave reflection surface. It is a point. The same members as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

[0015]

INDUSTRIAL APPLICABILITY As described above, the present invention has the advantages that the transparent resin has no deterioration phenomenon, has a long life, and has good optical characteristics such as radiation efficiency. Type light emitting diode can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a light emitting diode according to a first embodiment of the present invention.

FIG. 2 is likewise a front view of the first embodiment.

FIG. 3 is a sectional view of a main part of a light emitting diode according to a second embodiment of the present invention.

FIG. 4 is a side view of a conventional lens type light emitting diode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light emitting element 2a, 2b Lead frame 3 Transparent resin 4 Concave reflective surface 5 Reflective surface 6 Coating film

Claims (2)

[Claims] 1. A light emitting device, a lead for supplying electric power to the light emitting device, a mold for sealing the light emitting device and a reflecting surface on the side facing the light emitting surface of the light emitting device, and a radiation surface on the back side of the light emitting device. In the formed light emitting diode, the distance from the lead mounting the light emitting element to the emitting surface is 1.
A light emitting diode, which is within 5 mm or within 1/2 of a radius, and at least the radiation surface portion is covered with a material which is hard to yellow. 2. The lead for mounting the light emitting element has a distance to the emitting surface within 1.5 mm or 1 / radius.
The light emitting diode according to claim 1, wherein the light emitting diode is kept in a range of 2 or less and is drawn out in a lateral direction.