JP4282344B2 - Light emitting diode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting diode used in consumer equipment such as a personal computer, a printer, a PDA, a facsimile, a pager, and a mobile phone.
[0002]
[Prior art]
In recent years, a liquid crystal display device having a thin and easy-to-see backlight mechanism has been widely used as a display device of various electronic devices such as notebook personal computers equipped with optical communication functions, PDAs, and mobile phones. As a conventional electronic device equipped with such an LCD, a light emitting diode is widely used for LCD backlights of mobile phones and various key illuminations of mobile phones. (For example, unpublished patent document 1)
[0003]
[Unpublished Patent Document 1]
Patent application 2002-024811 (first page, FIG. 7)
[0004]
The above-mentioned unpublished patent document 1 was filed earlier by the present applicant, and FIG. 5 is disclosed as its prior art, and is a front view of a mobile phone that is generally used conventionally. is there. In FIG. 5, reference numeral 10 denotes a case main body, and a substantially rectangular LCD 11 is disposed on the upper side of the case main body. Reference numeral 12 denotes an LED package for an LCD backlight, which uses about 1 to 4 (3 in FIG. 5). In addition, a plurality of key switches 13 for operation are arranged on the lower side of the case body 10, and about 4 to 20 pieces (16 pieces in FIG. 5) are used for the backlight of these key switches 13. A number of LED packages 12 are used.
[0005]
An LED package (not shown) currently used is mounted with an LED chip on an insulating circuit substrate made of glass epoxy resin, for example, and is sealed with a translucent resin so as to cover the LED chip. .
[0006]
[Problems to be solved by the invention]
In the above-mentioned top-emitting LED package, side-emitting LED package, etc., consideration for light directivity is dilute, so a large number of LED packages must be used, and low-cost requirements must be satisfied. There was a problem that I could not.
[0007]
The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide an inexpensive light-emitting diode in which the number of LED packages used is reduced and the directivity can be controlled.
[0008]
[Means for Solving the Problems]
To achieve the above object, the light emitting diode of the present invention, an LED chip mounted on the circuit board, the light-emitting diode sealed the LED chips in the light-transmitting resin (first light-transmitting resin), the A reflective thin film is provided on the surface of the circuit board, and the first translucent resin is covered only with the second translucent resin having a different refractive index around the side surface of the first translucent resin . By setting the refractive index of the translucent resin 2 higher than the refractive index of the first translucent resin and arbitrarily selecting the difference in refractive index between the two, the side emission intensity of the light emitting diode is improved. It was made to be characterized.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the light-emitting diode according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a light emitting diode according to a first embodiment of the present invention.
[0012]
In FIG. 1, reference numeral 1 denotes a light emitting diode, and an electrode (not shown) necessary for mounting the LED chip 3 is formed on the surface of an insulating circuit board 2 made of glass epoxy resin or the like. The surface of the circuit board 2 is provided with a reflective thin film such as an Ag or Au plated portion at the time of electrode formation to improve the reflection efficiency. After mounting the LED chip 3 on the substantially central portion of the circuit board 2, the LED chip 3 is sealed with the first light-transmitting resin 4 so as to cover the LED chip 3, and then the periphery of the side surface is the first light-transmitting property. Cover with a second translucent resin 5 having a refractive index greater than that of the resin 4.
[0013]
The operation and effect of the light emitting diode configured as described above will be described. FIG. 3 is a ray tracing schematic diagram of the present invention, and FIG. 4 is a ray tracing schematic diagram of a conventional configuration as a comparative example. In FIG. 3, the first translucent resin 4 described above is an epoxy resin, and its refractive index is arbitrary. For example, n ₁ = 1.48, and the second translucent resin 5 is an epoxy resin. The refractive index is arbitrarily set, for example, about n ₂ = 1.55.
[0014]
Here, an optical fiber will be considered as an example. In the optical fiber, a confinement layer (clad) having a refractive index lower than that of the core is added to the center (core) portion and the periphery thereof. In this case, the light beam is confined by the cladding, and the light propagates with low loss. This is intended to deepen the critical angle by utilizing the refractive index difference.
[0015]
In FIG. 1 and FIG. 3, the light emitted from the LED chip 3 passes through the side surface of the first light-transmitting resin 4 (n ₁ = 1.48) and the second light-transmitting resin 5 (n ₂ = 1.55) to form a gradient structure. Unlike the above-described optical fiber, the reflection critical angle is made shallow to facilitate light emission. Thereby, the critical angle with respect to the light emitted in the side surface direction becomes shallow, and the side light emission intensity is improved as shown in the transmitted light (1). By arbitrarily selecting the refractive index, the directivity of the light emitting diode can be controlled.
[0016]
The ray tracing schematic diagram (FIG. 4) of the conventional configuration shown as a comparative example shows the first translucent resin 4 (n ₁ = 1.55) as the second translucent resin having a smaller refractive index. By covering with 5 (n ₂ = 1.00), the emitted light from the LED chip 3 has a deep critical angle with respect to the light emitted in the lateral direction due to the difference in refractive index, similar to the optical fiber described above. This light is confined and emitted as refracted light (2), and the side emission intensity is weakened.
[0017]
FIG. 2 is a cross-sectional view of a light emitting diode according to a second embodiment of the present invention. The difference from the first embodiment described above is that the entire periphery of the _first translucent resin 4 (n ₁ = 1.48) surrounds the second translucent resin 5 (n ₂ = 1.55). It is completely covered with.
[0018]
As in the first embodiment, the operation and effect of the light emitting diode having the above-described structure is that the emitted light from the LED chip 3 has a shallow critical angle with respect to the light emitted in the side surface direction, and the first transparent Refraction is repeated at the boundary between the light-transmitting resin 4 and the second light-transmitting resin 5 to double the transmitted light (1), and the side emission intensity is improved. By arbitrarily selecting the refractive index, the directivity angle of the light emitting diode can be controlled, and the directivity characteristics can be controlled.
[0019]
【The invention's effect】
As described above, according to the present invention, the slope ratio structure is formed by covering the side surface or the entire periphery of the sealing resin of the LED chip mounted on the circuit board with a resin having a higher refractive index than the sealing resin. To do. As a result, the critical angle of refraction changes and a wide directivity can be realized. By arbitrarily selecting the refractive index difference, the directivity can be controlled. By using the LED chip of the present invention for key illumination of a mobile phone, the number of components is reduced and light emission unevenness is alleviated. An inexpensive light-emitting diode can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a light emitting diode according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of a light emitting diode according to a second embodiment of the present invention.
FIG. 3 is a schematic diagram of ray tracing according to the present invention.
FIG. 4 is a ray tracing schematic diagram of a conventional configuration as a comparative example.
FIG. 5 is a front view of a mobile phone using a conventional top-emitting LED package.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Light emitting diode 2 Circuit board 3 LED chip 4 1st translucent resin 5 2nd translucent resin n ₁ Refractive index n of 1st translucent resin ₂ Refractive index of 2nd translucent resin

Claims (1)

In a light-emitting diode in which an LED chip is mounted on a circuit board, and the LED chip is sealed with a light-transmitting resin (first light-transmitting resin), a reflective thin film is provided on the surface of the circuit board, and the first The translucent resin is covered with the second translucent resin having a different refractive index only around the side surface of the first translucent resin, and the refractive index of the second translucent resin is changed to the first translucent resin . A light emitting diode characterized in that the side light emission intensity of the light emitting diode is improved by setting the refractive index larger than that of the light-sensitive resin and arbitrarily selecting a difference in refractive index between the two.

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