JP4744853B2 - Light emitting diode - Google Patents

Description

  The present invention relates to a light-emitting diode (LED) having a phosphor that emits light such as ultraviolet light emitted from an LED chip by converting the light into light such as visible light having a predetermined wavelength, and a method of manufacturing the same. The present invention relates to a high-intensity light emitting diode capable of improving the extraction efficiency of light wavelength-converted by a body and increasing the amount and surface area of a phosphor.

  FIG. 8 shows an example of a conventional LED having a phosphor. The light emitting diode 60 is directed upward from the bottom surface to the tip end portion 62a of the first lead frame 62 for mounting the light emitting diode chip. A concave portion having a substantially funnel shape with a gradually increasing hole diameter is provided, and a reflector 64 is formed by forming the inner surface of the concave portion as a reflecting surface. A light emitting diode chip (hereinafter referred to as an LED chip) 66 is formed on the bottom surface of the reflector 64 with Ag. The first lead frame 62 and one electrode (not shown) on the bottom surface of the LED chip 66 are electrically connected by die-bonding via a paste or the like. Further, the tip end portion 68 a of the second lead frame 68 and the other electrode (not shown) on the upper surface of the LED chip 66 are electrically connected via a bonding wire 70.

The upper surface and the side surface of the LED chip 66 are covered and sealed with a coating material 72 such as a translucent epoxy resin filled in the reflector 64, and the LED chip 66 includes A large number of phosphors 74 for wavelength conversion that convert emitted light such as ultraviolet rays into light such as visible light having a predetermined wavelength are mixed in a dispersed state.
Further, the LED chip 66 covered with the coating material 72, the upper ends of the tip portion 62a and the terminal portion 62b of the first lead frame 62, and the upper ends of the tip portion 68a and the terminal portion 68b of the second lead frame 68 are epoxy. It is made of resin or the like, and is covered and sealed by a translucent envelope 78 having a convex lens portion 76 at the tip.

  Thus, when a voltage is applied to the LED chip 66 through the first lead frame 62 and the second lead frame 68, the LED chip 66 emits light and emits light such as ultraviolet rays. By irradiating the phosphor 74 in the coating material 72, the wavelength is converted into light such as visible light having a predetermined wavelength, and the wavelength-converted light is condensed by the convex lens portion 76 of the envelope 78 and is transmitted to the outside. It is supposed to be emitted.

By the way, in the conventional LED 60, the light converted in wavelength by the phosphor 74 becomes transmitted light that passes through the phosphor 74 in the coating material 72. A part of the light was absorbed (self-absorbed) by the phosphor 74 before being emitted to the outside, and the light extraction efficiency was not good.
The brightness of the light emitted from the phosphor 74 is generally proportional to the amount and surface area of the phosphor 74. In the conventional LED 60, the coating material 72 filled in the reflector 64 is used. Since the amount of the phosphor 74 that can be mixed is limited, the amount of the phosphor 74 that can be mixed is limited. The effect was increased, resulting in a decrease in luminance.

  The present invention has been devised in view of the above-described conventional problems, and the object of the present invention is to improve the extraction efficiency of light wavelength-converted by the phosphor, and the amount of the phosphor and The object is to realize a high-intensity light-emitting diode capable of increasing the surface area.

In order to achieve the above object, a light-emitting diode according to the present invention includes:
An LED chip that emits light having a wavelength that excites a phosphor is covered with a nonwoven fabric formed by three-dimensionally intertwining a large number of fibers, and the phosphor is supported on the fibers constituting the nonwoven fabric. .

In the light emitting diode of the present invention, the LED chip is covered with a non-woven fabric formed by three-dimensionally intertwining many fibers, and the phosphor is supported on the fibers constituting the non-woven fabric. The converted light can be extracted as reflected light reflected by the phosphor. For this reason, the light extraction efficiency is improved and higher luminance can be achieved as compared with the conventional light emitting diode 60 in which the light whose wavelength is converted by the phosphor is extracted as transmitted light. Moreover, since the LED chip is covered with the nonwoven fabric, almost all the light emitted from the LED chip can be applied to the nonwoven fabric carrying the phosphor.

Further, since the light emitting diode of the present invention has the phosphor supported on the fiber constituting the nonwoven fabric having a very large surface area of the fiber per unit volume, the coating material filled in the reflector 64 like the conventional light emitting diode 60 compared with the case where the phosphor 74 mixed in 72, it is possible to dramatically increase the amount and surface area of the phosphor.
Since the light emitting diode of the present invention takes out the light whose wavelength is converted by the phosphor as reflected light, the light emitting diode of the conventional light emitting diode 60 that takes out the light as transmitted light even if the amount of the phosphor increases. As described above, the luminance does not decrease due to self-absorption of light by the phosphor.

Hereinafter, an embodiment of a light emitting diode according to the present invention will be described with reference to the drawings.
FIG. 1 shows a first light emitting diode 10 according to the present invention. The first light emitting diode 10 connects and fixes an LED chip 14 on a substrate 12 made of an insulating material such as resin or ceramic. It consists of The LED chip 14 is composed of a gallium nitride semiconductor crystal or the like, and emits light such as ultraviolet light or blue visible light having a wavelength that excites a phosphor to be described later.
A pair of external electrodes 16a and 16b extending from the front surface of the substrate 12 through the side surface to the back surface are formed in a state of being insulated from each other.

  One electrode (not shown) on the upper surface of the LED chip 14 is connected to one external electrode 16a via a bonding wire 18, and the other electrode (not shown) on the upper surface of the LED chip 14 is bonded. The wire 18 is connected to the other external electrode 16b.

The LED chip 14 and the bonding wire 18 are covered with a non-woven fabric 22 as an aggregate of dome-shaped fibers formed by carrying the phosphor 20 placed on the substrate 12. The dome-shaped non-woven fabric 22 is bonded and fixed on the substrate 12 by means such as adhesion.
As shown in FIGS. 2 and 3, the non-woven fabric 22 is formed by tangling a large number of fibers 24, and a large number of voids 26 (see FIG. 3) are formed between the fibers 24. In addition, since a large number of fibers 24 are intertwined in three dimensions, the surface area of the fibers 24 per unit volume is extremely large. The phosphor 20 is attached to and supported on the surface of the fiber 24 constituting the nonwoven fabric 22, and as shown in FIG. 4, a large number of particles of the phosphor 20 are attached to the surface of the fiber 24. Yes.
Note that the total surface area of the fibers 24 constituting the nonwoven fabric 22 can be arbitrarily increased or decreased by appropriately adjusting the fiber density of the fibers 24 constituting the nonwoven fabric 22, the thickness of the nonwoven fabric 22, the basis weight, and the like.

The fibers 24 are made of resin fibers such as nylon, polyester, acrylic, polypropylene, and polyvinyl chloride, cellulosic chemical fibers such as rayon, short fibers such as glass fibers and metal fibers, and the diameter thereof is 5 to 20 μm and long. The thickness is about 0.5 to 20 mm.
Of course, it is also possible to use fibers 24 made of long fibers having a length of about 50 to 100 mm.

When the phosphor 20 is irradiated with light such as ultraviolet rays, the phosphor 20 converts the wavelength of the light into light such as visible light having a predetermined wavelength. For example, a phosphor having the following composition can be used.
As a phosphor 20 for red light emission that converts light such as ultraviolet rays into red visible light, M ₂ O ₂ S: Eu (M is one of La, Gd, and Y), 0.5 MgF ₂ .3.5MgO. _{GeO 2: Mn, 2MgO · 2LiO} 2 · Sb 2 O 3: Mn, Y (P, V) O 4: Eu, YVO 4: Eu, (SrMg) 3 (PO 4): Sn, Y 2 O 3: Eu , CaSiO ₃ : Pb, Mn and the like.
Further, as a phosphor 20 for green light emission that converts light such as ultraviolet light into green visible light, BaMg ₂ Al ₁₆ O ₂₇ : Eu, Mn, Zn ₂ SiO ₄ : Mn, (Ce, Tb, Mn) MgAl ₁₁ O ₁₉ , LaPO ₄ : Ce, Tb, (Ce, Tb) MgAl ₁₁ O ₁₉ , Y ₂ SiO ₅ : Ce, Tb, ZnS: Cu, Al, ZnS: Cu, Au, Al, (Zn, Cd) S: Cu , Al, SrAl ₂ O ₄ : Eu, SrAl ₂ O ₄ : Eu, Dy, Sr ₄ Al ₁₄ O ₂₅ : Eu, Dy, Y ₃ Al ₅ O ₁₂ : Tb, Y ₃ (Al, Ga) ₅ O ₁₂ : There are Tb, Y ₃ Al ₅ O ₁₂ : Ce, Y ₃ (Al, Ga) ₅ O ₁₂ : Ce, and the like.
Furthermore, as a phosphor 20 for blue light emission that converts light such as ultraviolet rays into blue visible light, (SrCaBa) ₅ (PO ₄ ) ₃ Cl: Eu, BaMg ₂ Al ₁₆ O ₂₇ : Eu, (SrMg) ₂ P ₂ O ₇ : Eu, Sr ₂ P ₂ O ₇ : Eu, Sr ₂ P ₂ O ₇ : Sn, Sr ₅ (PO ₄ ) ₃ Cl: Eu, BaMg ₂ Al ₁₆ O ₂₇ : Eu, CaWO ₄ , CaWO ₄ : Pb There are blue phosphors, ZnS: Ag, Cl, ZnS: Ag, Al, (Sr, Ca, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu, and the like.
Various colors can be generated by appropriately selecting and mixing the phosphor 20 for red light emission, the phosphor 20 for green light emission, and the phosphor 20 for blue light emission.
Further, when obtaining white light using the LED chip 14 that emits blue visible light, as the phosphor 24 for yellow light emission that converts the light emitted from the LED chip 14 into yellow visible light as a complementary color, Y ₃ Al ₅ O ₁₂ : Ce, YBO ₃ : Ce, BaMgAl ₁₀ O ₁₇ : Eu, Mn, (Sr, Ca, Ba) (Al, Ga) ₂ S ₄ : Eu, Ba ₂ SiO ₄ : Eu, (Sr , Ba) ₂ SiO ₄ : Eu, SiAlON: Eu, and the like.
The phosphor 20 includes organic and inorganic fluorescent dyes and organic and inorganic fluorescent pigments.

  The LED chip 14 and the nonwoven fabric 22 are surrounded by a frame member 28 having a predetermined height disposed on the substrate 12, and a light-transmitting material such as an epoxy resin, a silicon resin, or an acrylic resin is provided in the frame member 28. It is sealed by a translucent lid member 30 formed by filling a conductive material.

  In the first light emitting diode 10 of the present invention, when a voltage is applied to the LED chip 14 via the pair of external electrodes 16a and 16b, the LED chip 14 emits light and excites the phosphor 20. Light such as ultraviolet light and visible light is emitted. This light is applied to the phosphor 20 carried on the dome-shaped non-woven fabric 22 covering the LED chip 14, is converted into light such as visible light having a predetermined wavelength, and then passes through the translucent lid member 30. Is radiated to the outside.

Thus, in the first light emitting diode 10 of the present invention, the LED chip 14 is covered with the dome-shaped non-woven fabric 22, and the phosphor 20 is supported on the surface of the fiber 24 constituting the non-woven fabric 22. The light whose wavelength is converted by the phosphor 20 can be extracted as reflected light reflected by the phosphor 20. For this reason, compared with the conventional light emitting diode 60 in which the light whose wavelength is converted by the phosphor 74 is extracted as transmitted light, the light extraction efficiency is improved and high luminance can be achieved. In addition, since the LED chip 14 is covered with the nonwoven fabric 22, almost all the light emitted from the LED chip 14 can be irradiated onto the nonwoven fabric 22 carrying the phosphor 20.
In addition, the first light emitting diode 10 of the present invention has the phosphor 20 supported on the surface of the fiber 24 constituting the nonwoven fabric 22 in which the surface area of the fiber 24 per unit volume is extremely large. As described above, compared to the case where the phosphor 74 is mixed in the coating material 72 filled in the reflector 64, the amount and surface area of the phosphor 20 can be dramatically increased. In this case, since the first light emitting diode 10 of the present invention takes out the light whose wavelength is converted by the phosphor 20 as reflected light as described above, it transmits light even if the amount of the phosphor 20 increases. Unlike the conventional light emitting diode 60 extracted as light, there is no reduction in luminance due to self-absorption of light by the phosphor.

  The nonwoven fabric 22 is not limited to a dome shape, and may be, for example, a hollow rectangular parallelepiped shape. In short, the LED chip 14 only needs to be covered with the nonwoven fabric 22.

Hereinafter, a method for supporting the phosphor 20 on the nonwoven fabric 22 in the first light emitting diode 10 of the present invention will be described.
First, a large number of composite fibers 34 (see FIG. 5) having a predetermined length obtained by coating fibers 24 made of a high melting point material such as polypropylene with fibers 32 made of a low melting point material such as polyethylene are prepared. Is used to form a sheet-like aggregate (web) composed of a large number of these composite fibers 34.

  Next, the sheet-like assembly is heated at a temperature higher than the melting point of the fiber 32 made of the low-melting-point material constituting the composite fiber 34 and lower than the melting point of the fiber 24 made of the high-melting-point material. Only the fibers 32 made of the melt are melted, and the particulate phosphor 20 is sprayed onto the aggregate.

As a result, the intersecting portion of the fibers 24 made of the high melting point material is bonded through the melted fibers 32 made of the low melting point material, whereby the sheet-like nonwoven fabric 22 is formed and the particulate phosphor 20 is formed. Then, it is bonded and supported on the surface of the fiber 24 constituting the nonwoven fabric 22 through the fiber 32 made of a molten low melting point material.
In the above method, by using the composite fiber 34 in which the fiber 24 made of the high melting point material is coated with the fiber 32 made of the low melting point material, only the fiber 32 made of the low melting point material is melted to function as an adhesive. Since the formation of the nonwoven fabric 22 and the loading of the phosphor 20 on the surface of the fibers 24 constituting the nonwoven fabric 22 can be performed almost simultaneously, it is extremely easy to manufacture.
The dome-shaped nonwoven fabric 22 is formed by punching the sheet-shaped nonwoven fabric 22 manufactured by the above method.

In addition to the above method, for example, the nonwoven fabric 22 is dipped in the dispersion resin solution of the phosphor 20 and then dried, or the dispersion resin solution of the phosphor 20 is dropped from above the nonwoven fabric 22, so that the nonwoven fabric 22 is dropped. Alternatively, the phosphor 20 may be attached to and supported on the surface of the fibers 24 constituting the.
Further, by heating the nonwoven fabric 22 and spraying the phosphor 20 in a state where the surface of the fiber 24 constituting the nonwoven fabric 22 is melted, the phosphor 20 is deposited on the surface of the fiber 24 constituting the nonwoven fabric 22. It can also be supported.
Further, the phosphor 20 heated at a high temperature is sprayed onto the nonwoven fabric 22, and the fibers 24 constituting the nonwoven fabric 22 are partially melted to adhere and carry the phosphor 20 on the surface of the fibers 24 constituting the nonwoven fabric 22. Also good.

FIG. 6 shows a second light emitting diode 40 according to the present invention, which is a material having a refractive index between the refractive index of air and the refractive index of the LED chip 14. The LED chip 14 is covered and sealed by the translucent member 42 configured as described above, and the other configuration is the same as that of the first light emitting diode 10.
The translucent member 42 is made of, for example, silicon resin. That is, the refractive index of silicon resin is about 1.5, and has a refractive index between air having a refractive index of 1 and an LED chip 14 having a refractive index of about 3.3 (for example, in the case of gallium nitride). is doing.
In the second light emitting diode 40, an uncured translucent member 42 is dropped on the LED chip 14 and then cured to seal the LED chip 14, and then the dome-shaped nonwoven fabric 22 is placed on the substrate 12. The LED chip 14 and the bonding wire 18 may be covered by mounting and bonding to each other. Alternatively, after covering the LED chip 14 and the bonding wire 18 with the dome-shaped non-woven fabric 22, the uncured translucent member 42 is hung from the non-woven fabric 22 toward the non-woven fabric 22, and dropped from the non-woven fabric 22. The LED chip 14 may be sealed with the translucent member 42.

In the second light emitting diode 40, the LED chip 14 was sealed with the light transmissive member 42 made of a material having a refractive index between the refractive index of air and the refractive index of the LED chip 14 as follows. Depending on the reason.
That is, since the difference between the refractive index of air and the refractive index of the LED chip 14 is large, a part of the light emitted from the LED chip 14 is reflected at the interface with the air and returned to the LED chip 14 so that the light is emitted. The extraction efficiency is poor. Therefore, if the LED chip 14 is sealed with a translucent member 42 having a refractive index between the refractive index of air and the refractive index of the LED chip 14 as in the second light emitting diode 40, the LED chip 14 and the transparent LED 42 are transparent. Since the difference in refractive index between the light-transmitting member 42 and the light-transmitting member 42 and the air is small, the interface between the LED chip 14 and the light-transmitting member 42, the interface between the light-transmitting member 42 and the air As a result, the amount of light reflected by the light source is small and the light extraction efficiency is improved.

FIG. 7 shows a modified example of the second light emitting diode 40. The modified example of the second light emitting diode 40 includes an LED chip 14 and a bonding wire 18 and a substantially cylindrical translucent frame. The LED chip 14 is covered and sealed by the light transmissive member 42 filled in the frame body 43, and the LED chip 14, the bonding wire 18, the light transmissive member 42, and the frame body 43, It is covered with a dome-shaped nonwoven fabric 22.
The frame body 43 and the translucent member 42 are preferably made of the same material so as not to cause a difference in refractive index in order to improve light extraction efficiency.

In this modification, after the LED chip 14 and the bonding wire 18 are surrounded by the frame body 43, the frame body 43 is filled with an uncured translucent member 42 and then cured to seal the LED chip 14. After stopping, the dome-shaped nonwoven fabric 22 may be placed on and bonded to the substrate 12 to cover the LED chip 14, the bonding wire 18, the translucent member 42, and the frame body 43.
Alternatively, after the LED chip 14 and the bonding wire 18 are surrounded by the frame body 43, the LED chip 14, the bonding wire 18, and the frame body 43 are covered with the dome-shaped nonwoven fabric 22, and then the uncured state from above the nonwoven fabric 22. The translucent member 42 may be hung toward the nonwoven fabric 22, and the LED chip 14 may be sealed by filling the frame 43 with the translucent member 42 that has dropped from the non-woven fabric 22.
In the modification of the second light emitting diode 40, the LED chip 14 and the bonding wire 18 are surrounded by the frame body 43, and the LED chip 14 is sealed by the translucent member 42 filled in the frame body 43. Even when the uncured translucent member 42 having a low viscosity is used, the translucent member 42 can be prevented from diffusing and flowing out onto the substrate 12.

  In the above, the case where the nonwoven fabric 22 is used has been described as an example of the fiber assembly, but the present invention is not limited to this, and a woven fabric formed by weaving a large number of fibers is used. A phosphor may be supported on the fibers constituting the woven fabric. Although this woven fabric does not reach the nonwoven fabric 22, the woven fabric has a large fiber surface area per unit volume.

Further, in the above description, the case where the phosphor 20 is supported on the “surface” of the fiber 24 constituting the nonwoven fabric 22 has been described as an example, but the present invention is not limited to this, for example, transparent The phosphors 20 may be supported on the fibers 24 constituting the nonwoven fabric 22 by kneading and mixing the particulate phosphors 20 with translucent fibers 24 made of resin or the like.
In this case, for example, after mixing a predetermined amount of a particulate phosphor in an uncured transparent resin, the transparent resin is stretched and cured, and then cut into a predetermined length to obtain the phosphor 20 A large number of fibers kneaded and mixed may be formed, and the nonwoven fabric 22 may be formed using a large number of fibers mixed with the phosphor 20.

It is a schematic sectional drawing which shows typically the 1st light emitting diode which concerns on this invention. It is the elements on larger scale which show typically the nonwoven fabric which carry | supported fluorescent substance. It is an enlarged view which shows typically the fiber which comprises a nonwoven fabric. It is sectional drawing which shows typically the fiber which comprises a nonwoven fabric. It is a schematic sectional drawing which shows a composite fiber. It is a schematic sectional drawing which shows typically the 2nd light emitting diode which concerns on this invention. It is a schematic sectional drawing which shows the modification of a 2nd light emitting diode typically. It is a schematic sectional drawing which shows the conventional light emitting diode typically.

10 First light emitting diode
12 Board
14 LED chip
16a external electrode
16b external electrode
18 Bonding wire
20 phosphor
22 Nonwoven fabric
24 fibers
28 Frame member
30 Lid member
34 Composite fiber
40 Second light emitting diode
42 Translucent material
43 Frame

Claims (1)

An LED chip that emits light having a wavelength that excites a phosphor is covered with a nonwoven fabric formed by three-dimensionally intertwining a large number of fibers, and the phosphor is supported on the fibers constituting the nonwoven fabric. Light emitting diode.

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