JP2005079244A - Light emitting diode - Google Patents

Abstract

[Structure] The LED 10 includes an LED element 12, and the LED element 12 is covered with a lens 20 made of resin. An antireflection microstructure 22 is formed on the surface of the lens 20, and light emitted from the LED element 12 passes through the antireflection microstructure 22 and is emitted to the outside. On the other hand, external light applied to the LED 10 from the outside also passes through the antireflection microstructure 22 and enters the lens 20.
[Effect] Since the refractive index continuously changes from the lens 20 to the air layer by the antireflection microstructure 22, the light emitted from the LED element 12 and the light emitted to the LED 10 from the outside are applied. Reflection can be prevented, the light emission efficiency of the LED can be improved, and interference due to light emission and reflected light can be suppressed.
[Selection] Figure 1

Description

  The present invention relates to a light emitting diode (hereinafter referred to as “LED”), and more particularly, to an LED that is used in, for example, an illumination and a liquid crystal light source and includes a resin lens that seals an LED element.

An example of a conventional LED is disclosed in Patent Document 1. The semiconductor light emitting device of Patent Document 1 includes a semiconductor light emitting element, and the semiconductor light emitting element is sequentially covered with a core layer, an endothelial layer, and an outer skin layer. By reducing the refractive indexes of the light emitting element, the core layer, the endothelial layer, the outer skin layer, and the air layer (outside) in order, the light emitted from the outside to the semiconductor light emitting device is taken into the light emitting device, and at the same time, the light emitting element The light emitted from is emitted to the outside. Furthermore, the transmittance of light incident from the outside is set to the maximum by setting the thickness of the outer skin layer to 5 to 15 μm.
JP 2000-150965 A [H01L 33/00]

In the prior art of Patent Document 1, in order to cover a semiconductor light emitting element in turn with a core layer, an endothelial layer, and an outer skin layer, three types of materials corresponding to each layer must be prepared and each layer must be stacked. In addition, the production cost increases and there is a problem in productivity.
The refractive index of these light emitting elements, core layer, endothelial layer and outer skin layer is made smaller in order, but the core layer, inner skin layer and outer skin layer have different requirements as parts of semiconductor light emitting devices such as light transmittance in addition to the refractive index. And the optimum materials corresponding to the core layer, the endothelial layer and the outer skin layer are limited. In addition, when forming each layer, the layers may not be stacked due to the physical and chemical properties between the layers, and the selection of materials is further limited.

  Although the thickness of the outer skin layer is limited to 5 to 15 μm, when the thickness of the outer skin layer is controlled, production control of the outer skin layer becomes strict and the yield of the semiconductor light emitting device is deteriorated.

  By controlling the thickness and refractive index of the outer skin layer, reflected light generated at each interface is caused to interfere with each other to weaken the entire light reflection at the interface. For this reason, the wavelength range of light that can be prevented from being reflected by the layer having a specific thickness and refractive index is narrow, and it is not possible to cope with the wavelength of external light having a wide wavelength range and light emitted from various semiconductor elements.

  Therefore, a main object of the present invention is to provide an LED that can be easily manufactured and has high luminous efficiency while suppressing reflection on the lens surface of the LED.

  The invention of claim 1 is an LED in which an LED element is sealed and a lens made of resin is provided, and an antireflection microstructure is formed on the surface of the lens.

  In the invention of claim 1, for example, the LED includes an LED element, the LED element is mounted on one of the pair of terminals, and the upper surface thereof is connected to the other terminal by a gold wire. And an LED element, a gold wire, and a pair of terminal upper part are covered with resin, and a lens is formed.

  When manufacturing such an LED, the LED element is mounted on one terminal and then fixed with a conductive material such as silver paste. This LED element and the other terminal are connected by a gold wire.

  Thereafter, the LED element, the gold wire, and the upper end of the terminal are placed in the lens mold on which the antireflection microstructure has been formed, and, for example, epoxy resin is injected into the mold and thermally cured. As a result, an antireflection microstructure is formed on the lens surface, so that when the light emitted from the LED element passes through the lens surface, there is no sudden refractive index change at the interface between the lens and the air layer. Light reflection is suppressed at the interface. For this reason, LED can obtain high luminous efficiency.

  Similarly, when the LED is irradiated from the outside, since there is no sudden refractive index change at the interface between the lens and the air layer, external light is not reflected at this interface and the external light passes through the lens surface. . For this reason, the light emitted from the LED element and the reflected light generated on the lens surface by external light do not interfere with each other.

  If a mold having an antireflection microstructure is formed in advance on the lens mold, the antireflection microstructure and the lens can be integrally molded simply by injecting resin into the mold. In addition, this structure can be applied to many resin materials.

  According to a second aspect of the present invention, in the first aspect of the present invention, the antireflection microstructure has an angle of 1.33 to 2.8 times the directivity angle with respect to the normal line at the apex of the lens centering on the LED element. LED formed in a range.

  In the invention of claim 2, since the light emitted from the LED element has directivity, the light passes only through a narrow range centering on the apex of the lens that is directly in front of the LED element. Therefore, the LED element can be sufficiently emitted from the LED element only by forming the antireflection microstructure within an angle range of 1.33 to 2.8 times the directivity angle with respect to the normal line at the apex of the lens centering on the light emitting element. Light reflection can be prevented.

  A third aspect of the present invention is the LED according to the first or second aspect, wherein the antireflection microstructure is an aggregate of cones.

  In the invention of claim 3, by forming the antireflection microstructure into a cone, when the light emitted from the LED element is emitted from the lens to the outer air layer, the refractive index is continuous from the lens to the air layer. Therefore, reflection that occurs at the interface between the lens and the air layer with respect to incident light in a wide wavelength range can be prevented, and the luminous efficiency of the LED can be improved. Therefore, this antireflection effect does not select the wavelength of light emitted from the light emitting element, that is, the type of the light emitting element. Similarly, it is possible to prevent light reflection in a wide wavelength range with respect to external light applied to the lens from the outside.

  The invention of claim 4 is an LD unit comprising a cover glass covering a laser diode (hereinafter referred to as “LD”) element, wherein an antireflection microstructure is formed on the surface of the cover glass. is there.

  In the invention of claim 4, since the antireflection microstructure is formed on the surface of the cover glass, the laser light emitted from the LD element is abrupt between the cover glass and the air layer when passing through the cover glass. There is no change in refractive index, and laser light is not reflected at this interface. For this reason, the LD unit can obtain high luminous efficiency. Similarly, light reflection can be prevented with respect to external light irradiated on the cover glass from the outside.

  According to the present invention, since the antireflection microstructure is formed on the lens surface, the light emitted from the LED element and the light emitted to the LED from the outside do not reflect or reflect at the interface between the lens and the air layer. Therefore, the LED can obtain high luminous efficiency, and the light emitted from the LED does not interfere with the reflected light generated on the lens surface by external light.

  Since the antireflection microstructure and the lens can be integrally molded, the LED can be easily manufactured.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

  An LED 10 according to an embodiment of the present invention shown in FIG. 1 includes an LED element 12, and the LED element 12 is bonded onto a first terminal 14, and a lower electrode (not shown) of the LED element 12 is a first terminal 14. Connected to. An upper surface electrode (not shown) is formed on the upper surface of the LED element 12, and the upper surface electrode is wire-bonded with another second terminal 16 and a gold wire 18. A solid lens 20 is formed by covering the LED element 12, the gold wire 18 and the upper portions of the two terminals 14 and 16 with resin.

  The lens 20 is formed of a transparent resin such as an acrylic resin such as an epoxy resin, a polycarbonate resin, and polymethyl methacrylate, and has a dome shape. An antireflection microstructure 22 is formed on the surface of the lens 20.

  The formation range W of the antireflection microstructure 22 is an angle range in which the angle θ formed with respect to the normal line 24 at the apex 20a of the lens 20 around the LED element 12 that is the emission center is 1.33 to 2.8 times the directivity angle α. Preferably, the values shown in Table 1 are used. For example, the angle θ of the formation range of the antireflection fine structure 22 is 26.6 to 56 degrees with respect to the directivity angle α of 20 degrees, and the optimum is 40 to 45 degrees. The directivity angle α is an angle at which the relative light emission intensity becomes ½. As shown in FIG. 2, the antireflection microstructure 22 is an aggregate in which uniform quadrangular pyramidal projections 26 are continuously arranged in the horizontal and vertical directions. The pitch p of the projections 26 satisfies Equation 1 in relation to the wavelength λ of the incident light and the refractive index n of the projections 26, and the height h is set so that the aspect ratio is 1 or more.

  For example, when the LED element 12 covered with the resin 20 having a refractive index n of 1.5 emits light having a shortest wavelength λ of 400 nm, the pitch p of the protrusions 26 is 267 nm. p is 300 nm or less, and the height h is 300 nm or more.

  When manufacturing the LED 10, first, the LED element 12 is mounted on the bottom surface of the reflector 28 of the first terminal 14, and then fixed with silver paste or the like. The LED element 12 and the second terminal 16 are connected by a gold wire 18. Next, the LED element 12, the gold wire 18, the first terminal 14 and the second terminal 16 are put into the mold 30 shown in FIG. 3, and then an epoxy resin is injected and thermally cured to form the lens 20. To do. The inner surface of the mold 30 has a dome shape, and a mold 32 for forming the antireflection microstructure 22 on the surface of the lens 20 on the inner surface (this is a negative relative to the antireflection microstructure of FIG. 2). Having the following structure). The formation range W is such that the angle θ formed with respect to the normal line 24 at the dome-shaped apex 30a around the point 34 where the LED element 12 is disposed is 1.33 to 2.8 times the directivity angle α.

  When such an LED 10 is used, light is emitted from the upper surface of the LED element 12 when power is supplied to the LED element 12 through a pair of terminals 14 and 16. The light emitted from the LED element 12 reaches the lens 20 located in front, and the light is focused by the lens effect and emitted to the outside of the LED 10. Since the light emitted from the LED element 12 has directivity, the antireflection microstructure 22 is formed in a narrow range around the apex 20a of the lens 20 that is directly in front of the LED element 12, that is, on the lens 20 surface. It passes through the range W. As the light passes through the antireflection microstructure 22, the refractive index continuously changes as the volume of the resin, that is, the lens 20, with respect to the air gradually decreases. For this reason, reflection of light does not occur at the interface between the lens 20 and the air layer, and the light emitted from the LED element 12 is radiated to the outside (air layer).

  On the other hand, since the refractive index of the external light irradiated from the air layer to the lens 20 changes continuously as the volume of the lens 20 with respect to the air gradually increases, the external light is exposed at the interface between the lens 20 and the air layer. Light reflection does not occur, and external light irradiated from the air layer enters the lens 20.

By using a cone for the antireflection microstructure 22, the refractive index continues as the volume occupied by the antireflection microstructure 22 with respect to the air from the lens 20 to the air layer on the surface of the lens 20 gradually decreases. Therefore, reflection can be prevented with respect to light in a wide wavelength range. That is, when light emitted from the LED element 12 is emitted from the lens to the outer air layer, on the contrary, when entering the lens 20 of the LED 10 from the outside, light reflection on the surface of the lens 20 can be prevented. The light emission efficiency of the LED can be improved, and interference caused by light emission and reflected light can be suppressed.
As described above, since the antireflection microstructure 22 is formed in the range W in which the light emitted from the LED element 12 passes through the surface of the lens 20, the refractive index of the lens 20 continuously changes, and the LED element. The light emitted from 12 is not reflected at the interface between the lens 20 and the air layer. For this reason, the light loss in the surface of the lens 20 can be reduced and the luminous efficiency of LED10 can be improved.
For example, as shown in FIG. 4, in a glass (deposition AR) on which an antireflection film is deposited, the reflectance has a wavelength dependency and shows a low reflectance near a wavelength of 500 nm, but the wavelength range of 400 nm or less and 600 nm or more. Then, the reflectance increases rapidly. On the other hand, when the antireflection microstructure 22 (fine AR) is provided on the glass surface, the reflectance is low in the entire wavelength region. For this reason, the surface of the glass provided with the antireflection microstructure 22 is not affected by the wavelength, and a high antireflection effect can be obtained.

  Further, when the external light irradiated from the air layer to the LED 10 passes through the range W where the antireflection microstructure 22 on the surface of the lens 20 is formed, the external light is not reflected at the interface between the lens 20 and the air layer. In this range W, the light emitted from the LED and the reflected light generated on the lens surface by external light do not interfere with each other, so that the blinking of the LED can be distinguished.

  The antireflection microstructure 22 and the lens 20 can be integrally molded simply by injecting resin into the mold 30 of the lens 20 on which the mold of the antireflection microstructure 22 is formed. The LED 10 with improved luminous efficiency can be manufactured quickly and easily without the need for materials. Moreover, since this structure can be applied to many resin materials, it can be easily manufactured.

  Although the antireflection microstructure 22 is a quadrangular pyramid protrusion 26, a conical shape or the like may be used.

  An LD unit 100 according to another embodiment of the present invention shown in FIG. The LD element 102 is bonded to a heat sink 106 mounted on one surface of the stem 104, covered with a cap 108, and sealed in an inert gas atmosphere. A lead wire 110 is attached to the other surface of the stem 104. The cap 108 has a cylindrical shape, a circular bottom surface is vacant, and an end of the side surface on the bottom surface side is coupled to the stem 104. A hole 112 concentric with the upper surface is formed in the center of the upper surface of the cap 108, and a cover glass 114 is provided on the back side thereof.

  The cover glass 114 is a disc, and the antireflection microstructure 22 shown in FIG. The cover glass 114 is a resin having high translucency, and is formed of a resin such as polycarbonate, acrylic resin, PET (polyethylene terephthalate), or TAC (triacetyl cellulose). The antireflection microstructure 22 is the same as that of the LED 10 shown in FIG.

  As described above, when the antireflection microstructure 22 is provided on both surfaces of the cover glass 114, the light emitted from the LD element 102 is not reflected on the surface of the cover glass 114, so that the light emission efficiency of the LD unit 100 is good. That is, when light emitted from the LD element 102 to the outside passes through the cover glass 114, the volume occupied by the antireflection microstructure 22 with respect to the air gradually increases from the LD element 102 side toward the cover glass 114. Accordingly, since the refractive index also changes gradually, the light does not receive a sudden change in the refractive index and is not reflected on the surface of the cover glass 114 toward the LD element 102 side. Further, as the volume occupied by the antireflection microstructure 22 with respect to the air from the inside of the cover glass 114 toward the outside gradually decreases, the refractive index also changes gradually, so that light does not reflect into the cover glass 114. . For this reason, the light emitted from the LD element 102 can obtain high light emission efficiency without losing the amount of light on the surface of the cover glass 114.

  The antireflection microstructure 22 may be provided only on a part of the cover glass 114 or a part through which light emitted from the LD element 102 passes.

It is sectional drawing which shows LED of one Example of this invention. It is a perspective view which shows the microstructure for antireflection formed in the lens surface of LED of FIG. 1 Example. It is sectional drawing which shows the metal mold | die which forms the lens of LED of FIG. 1 Example. It is a graph which shows the light reflectivity with respect to the wavelength of light in the difference in the surface state of glass. It is sectional drawing which shows the LD unit of the other Example of this invention.

Explanation of symbols

10 ... LED
DESCRIPTION OF SYMBOLS 12 ... LED element 20 ... Lens 22 ... Fine structure for reflection prevention 100 ... LD unit 102 ... LD element 114 ... Cover glass

Claims (4)

In a light-emitting diode that seals a light-emitting diode element and includes a lens made of resin,
A light emitting diode, wherein an antireflection microstructure is formed on a surface of the lens.   2. The light emitting diode according to claim 1, wherein the fine structure is formed in an angle range of 1.33 to 2.8 times a directivity angle with respect to a normal line at a vertex of the lens with the light emitting diode element as a center.   The light emitting diode according to claim 1, wherein the fine structure is an aggregate of cones. In the laser diode unit comprising a cover glass covering the laser diode element,
A laser diode unit, wherein an antireflection microstructure is formed on the surface of the cover glass.

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