JPH0370187A - Reflection-type light-emitting diode - Google Patents

Abstract

PURPOSE:To obtain a reflection-type LED with a large contrast when turning on and off light by using a material for enabling light of wavelength emitted by a light-emitting element to be transmitted selectively as a light-transmission material. CONSTITUTION:A light-emitting element 1, lead frames 2 and 3, and a wire 4 are sealed by a light-transmission material 5 for enabling light emitted by the light-emitting element 1 to be transmitted selectively. If for example the light-emitting element 1 is made of GaAlAs and has a peak at a light-emitting wavelength of 660nm, most of the wavelength emitted by the light-emitting element 1 is within + or -20-30nm for a peak value of 660nm. Thus, when the light- transmission material 5 for enabling light with a wavelength above 600nm to be transmitted selectively is used, light of 660nm + or -20-30nm wavelength emitted by the light-emitting element 1 is not absorbed by the light-transmission material 5 but is reflected by a reflection surface 6 and is radiated to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a reflective light emitting diode (hereinafter also referred to as a reflective LED) that emits light to the outside after reflecting the light emitted by a light emitting element by a -degree reflective surface. ).

[Conventional technology]

Conventionally, light emitting diodes with various structures have been devised in order to effectively radiate light emitted from a light emitting element of the light emitting diode in a direction. Figure 4 is a schematic cross-sectional view of a conventional reflective LED and an optical path diagram of light emitted by its light emitting element, and Figure 5 is a schematic cross-sectional diagram of a conventional reflective LED and an optical path diagram of external light incident on the reflective LED. , FIG. 6 is a schematic front view of the reflective LED. 4 to 6, 51 is a light emitting element, 52 and 53 are lead frames, 54 are wires, and 55
is a light-transmitting material, and 56 is a concave reflective surface formed on the lower surface of the light-transmitting material 55.

The light emitting element 51 is mounted on one lead frame 52 and electrically connected to the other lead frame 53 by a wire 54. Further, the light emitting element 51, the tips of the lead frames 52 and 53, and the wire 54 are sealed with a light-transmitting material 55, and a concave reflective surface 56 is formed on the lower surface of the light-transmitting material 55. Reflective surface 56
The lower surface of the light-transmitting material 55 is mirror-finished by metal vapor deposition, plating, or the like. On the other hand, the upper surface 55a of the light-transmitting material 55 is a planar radiation surface.

In FIG. 4, the light emitted by the light emitting element 51 is reflected by the reflecting surface 5G as indicated by the arrow, and is emitted to the outside from the emitting surface 55a. In this way, by reflecting the light emitted by the light emitting element 51 once on the concave reflecting surface 56 and then emitting it to the outside, the light emitted by the light emitting element 51 can be effectively emitted toward the front.

[Problem to be solved by the invention]

By the way, a conventional reflective LED uses a colorless and transparent resin as the light-transmitting material 55. For this reason, reflective LE
As shown in FIG. 5, the external light incident on D
is reflected and radiated to the outside again. Here, reflective type L
If the ED has strong directivity in the front direction, when the reflective LED is viewed from the front, the image of the light emitting element 1 (the hunting part in the same figure) will appear as shown in FIG. 6(a). ) is reflected on the entire reflective surface 56, and there is no effect of reflection of external light by the reflective surface 56. In other words, the light emitting element 1 absorbs most of the external light.

On the other hand, when the reflective LED has weak directivity toward the front, as the directivity becomes weaker, the
) and (C), the image of the light emitting element 1 reflected on the reflective surface 56 becomes smaller, and the influence of reflection of external light by the reflective surface 56 becomes larger. Furthermore, when the reflective LED is viewed from a direction other than the radiation direction of light emitted by the light emitting element 1, the reflective surface 56
The image of the light emitting element 1 is no longer reflected on the external light reflecting surface 56.
The influence of reflections caused by

In addition, in order to widen the viewing angle, as shown in Figure 7, if multiple reflective LEDs are arranged with different radiation directions, the area indicated by A in the figure will be greatly affected by external light for the reflective LED loa. Similarly, the range B for the reflective LHDlob and the range C for the reflective LEDIOC are greatly affected by external light. Therefore, when a plurality of reflective LEDs are arranged, even within the viewing angle range X, they will be strongly influenced by external light.

In this way, when conventional reflective LEDs are used for display purposes, especially outdoors during the daytime when outside light is strong, the outside light is reflected by the reflective surface 56, so even when the lights are turned off, they cannot be completely dark. However, there was a problem in that the contrast between the lights on and off was small, making it difficult to see.

The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to provide a reflective LED with a large contrast between when turned on and when turned off.

[Means to solve the problem]

To achieve the above object, the present invention includes a light emitting element, a lead portion for supplying power to the light emitting element, a reflecting surface provided opposite to a light emitting surface side of the light emitting element, and a light emitting element. In the reflective LED, the light transmitting material has a sealing light transmitting material, and the light emitted by the light emitting element is reflected by the reflecting surface and then emitted to the outside. It is characterized by being a material that selectively transmits.

Further, the light-transmitting material may seal the light-emitting element and a part of the lead part, and may also fill a space between the light-emitting element and the reflective surface.

[Effect]

According to the above-described structure, the light-transmitting material selectively transmits the light of the wavelength emitted by the light-emitting element, so that the light emitted by the light-emitting element can be radiated to the outside without reducing the radiation efficiency. Reflective LED
While all wavelengths of external light incident on the LED are reflected and radiated to the outside, in the present invention, the light-transmitting material absorbs light other than a specific wavelength and does not transmit it.
Of the external light incident on D, the amount of light reflected by the reflective surface and radiated to the outside is extremely small.

Therefore, the contrast between when the light is turned on and when the light is turned off can be increased.

Further, by sealing the light emitting element and a part of the lead part with a light-transmitting material and filling the space between the light emitting element and the reflective surface, it is possible to improve the light extraction efficiency.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3. Figure 1 shows a reflective LIE that is an embodiment of the present invention.
A schematic cross-sectional view of D and an optical path diagram of light emitted by the light emitting element,
FIG. 2 is a schematic front view of the reflective LED, and FIG. 3 is a schematic sectional view of the reflective LED according to an embodiment of the present invention and an optical path diagram of external light.

1 to 3, 1 is a light emitting element, 23 is a lead frame, 4 is a wire, 5 is a light-transmitting material, and 6 is a concave reflective surface formed on the lower surface of the light-transmitting material 5. .

The light emitting element 1 is mounted on one lead frame 2,
It is electrically connected to the other lead frame 3 by a wire 4. Also, light emitting element 1, lead frame 2.3
The wire 4 is sealed with a light-transmitting material 5 that selectively transmits light emitted from the light-emitting element 1. The reflective surface 6 is formed by forming the lower surface of the light-transmitting material 5 into a convex shape, and mirror-finishing the lower surface by metal vapor deposition, plating, or the like. Note that the reflective surface 6 is formed, for example, in the shape of a paraboloid of revolution or an ellipsoid of revolution, and the light emitting element 1 is disposed at its focal point. Also,
The upper surface of the light-transmitting material 5 is a radiation surface 5a that emits light to the outside.
It is.

In FIG. 1, the light emitted by the light emitting element 1 is reflected by the reflective surface 6 as shown by the arrow, and is radiated to the outside from the radiation surface 5a.

Now, for example, the light emitting element 1 is made of GaAlAs and has 660 n
When the light emitting element 1 has a peak emission wavelength at s, most of the wavelengths of the light emitted by the light emitting element 1 are within the range of ±20 to 30n with respect to the peak value of 660n. Therefore, in this case, if a material that selectively transmits light with a wavelength of 600 nm or more is used as the optical i3-transmissive material 5, the light with a wavelength of 660 nm±20 to 30 nm emitted by the light emitting element 1 will be The light is not absorbed by the transparent material 5, but is reflected by the reflective surface 6 and is all emitted to the outside. On the other hand, as shown by the dotted line in FIG. 3, when external light enters the reflective LED, light with a wavelength of 600 nw or less is absorbed by the light-transmitting material 5, and only the remaining light is reflected by the reflective surface 6. Therefore, less than 10% of the external light incident on the reflective LED is radiated to the outside.

According to the above configuration, the light-transmitting material 5 selectively transmits light of the wavelength emitted by the light-emitting element 1, so that the light-emitting element l
It is possible to suppress the amount of external light reflected without lowering the radiation efficiency of the light emitted to the outside, and as a result, the contrast between when the light is on and when the light is off can be increased.

In the above embodiment, a case where a single reflective LED is used has been described, but a plurality of reflective LEDs may be assembled in a case or the like.

At this time, reflective LEDs emitting light of different colors may be combined.

Furthermore, when using multiple reflective LEDs, the radiation direction of each reflective LED may be changed and arranged in order to widen the viewing angle. Even in this case, the influence of reflection of external light from the reflective surface can be minimized. It can be suppressed.

〔Effect of the invention〕

As explained above, according to the present invention, the light-transmitting material selectively transmits the light of the wavelength emitted by the light-emitting element, so that external light can be transmitted without reducing the radiation efficiency of the light emitted by the light-emitting element to the outside. Reflective type L4 that suppresses the amount of reflection and increases the contrast between when the light is on and when the light is off, making it easier for viewers to see.
D can be provided.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a reflective LED according to an embodiment of the present invention and an optical path diagram of light emitted by its light emitting element. FIG. 2 is a schematic front view of the reflective LED. Schematic sectional view of reflective LED of Example 1 and optical path diagram of external light, 4th
5 is a schematic sectional view of a conventional reflective LED and an optical path diagram of light emitted from its light emitting element. FIG. 5 is a schematic sectional diagram of a conventional reflective LED and an optical path diagram of external light incident on the reflective LED. The figure is a schematic front view of the reflective LED, and FIG. 7 is a schematic cross-sectional view when a plurality of conventional reflective LEDs are arranged. 1... Light emitting element, 2.3... Lead frame, 4...
... Wire, 5... Light-transmitting material, 5a... Emitting surface, 6... Reflecting surface.

Claims (2)

[Claims] (1) It has a light-emitting element, a lead portion that supplies power to the light-emitting element, a reflective surface provided opposite to the light-emitting surface of the light-emitting element, and a light-transmitting material that seals the light-emitting element. death,
In a reflective light emitting diode that emits light to the outside after reflecting the light emitted by the light emitting element on the reflective surface, the light transmitting material is a material that selectively transmits light having a wavelength emitted by the light emitting element. Features a reflective light emitting diode. (2) The reflective type according to claim 1, wherein the light-transmitting material seals the light-emitting element and a part of the lead part, and fills a space between the light-emitting element and the reflective surface. light emitting diode.