KR100712880B1 - White light emitting diode capable of reducing correlated color temperature variation - Google Patents

Abstract

A white light emitting diode that can reduce variations in color temperature is disclosed. The white light emitting diode according to the present invention includes an LED chip emitting blue light, a transparent resin layer formed to cover the LED chip, and a phosphor dispersed therein, and a lens bonded on the transparent resin layer. Blue light emitted from the LED chip and a diffuser for diffusely reflecting yellow light due to excitation of the phosphor are mixed. As a result, the light passing through the lens reduces the difference in the direction angles between the blue light and the yellow light, and as a result, the deviation of the color temperature can be reduced.

Color Temperature, Diffusion, Directional Angle, Blue Light, Yellow Light, Diffusion

Description

White light emitting diode capable of reducing correlated color temperature variation

1 is a cross-sectional view of a white LED device manufactured according to the prior art, Figure 1a is a lamp-shaped white LED device, Figure 1b is a white LED device manufactured by the transfer molding method, Figure 1c is an injection mold housing Figure showing a white LED device of a type manufactured using a package,

2 is a view showing an embodiment of a white light emitting diode according to the present invention;

3 is an enlarged view of an example of the LED chip of FIG.

4 is a view showing another embodiment of a white light emitting diode according to the present invention;

5 is a view showing another embodiment of a white light emitting diode according to the present invention;

6 is a view showing another embodiment of a white light emitting diode according to the present invention;

7 is a table comparing the transmittance according to the roughness (DF) of the lens, Figure 7a is a view comparing the central light, Figure 7b is a view comparing the amount of light, and

8 is a value comparing the results according to the present invention, FIG. 8A is a graph comparing the change in intensity, and FIG. 8B is a graph comparing the change in intensity.

Explanation of symbols on the main parts of the drawings

102: LED chip 104: phosphor

106, 142: transparent resin layer 108: lens

110: diffusion agent 144: diffusion resin layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white light emitting diode, and more particularly, to a white light emitting diode which can reduce the variation in color temperature by reducing the difference in the direction angles of the blue light and the yellow light passing through the lens.

In general, a light emitting diode (LED) is an electronic component that generates a small number of carriers (electrons or holes) injected using a pn junction structure of a semiconductor and emits light by recombination thereof. . In other words, a light emitting diode is a device made of a compound semiconductor that emits light of a specific wavelength while electrons move from a high energy level to a low energy state through electricity. Such a light emitting diode can emit light with high efficiency at low voltage, so it is a liquid crystal display (LCD) of mobiles, a back light for keypads, a large display board for outdoor colors, a traffic light, an automobile instrument panel, a home appliance, It is used in various places such as neon replacement signs, medical and surgical equipment.

In particular, the light emitting diode for lighting can dramatically improve energy consumption efficiency, such as about 10% to 15% lower power consumption, more than 100,000 hours of semi-permanent life, and environmentally friendly characteristics, compared to a luminaire represented by conventional fluorescent and incandescent lamps. As a result, it is attracting attention as a next-generation technology to replace a general lighting fixture.

For application in general lighting, first, white light using a light emitting diode should be obtained. There are three ways to implement a white light emitting diode. First, a method of implementing white by combining three light emitting diodes representing three primary colors of light, red, green, and blue. This method not only uses three light emitting diodes to create a single white light source, but also has the difficulty of controlling each light emitting diode. The second method is to implement white by exciting a yellow phosphor using a blue light emitting diode as a light source. This method has excellent luminous efficiency, low CRI (Color Rendering Index), and has a disadvantage in that it is difficult to obtain white light close to sunlight due to the characteristic that CRI changes according to current density. The third method is to create white by exciting three primary phosphors by using an ultraviolet light emitting diode as a light source. This method can be used under high current, and the color is excellent.

White LED devices are devices that emit white light as a whole by converting some of the light generated from the LED chip into light of longer wavelengths. An LED chip is a semiconductor device that forms a PN junction with a compound such as GaAsP, GaAlAs, GaP, InGaAlP, or GaN, and when a predetermined voltage is applied to the PN junction, electrons or holes move to combine with excess holes or electrons. Light energy is emitted.

The light energy emitted is light of a monochromatic wavelength, and a blue LED chip or an ultraviolet LED chip emits blue light (wavelength of about 440 nm to 475 nm) or ultraviolet light (wavelength of about 350 nm to 410 nm). In addition, the emitted ultraviolet light or blue light is converted into light having a different wavelength by the phosphor.

Phosphors are epoxy resins or silicone resins for protecting LED chips and are dispersed in a formed mold, and have a great influence on luminance and spectral distribution of emitted white light.

1 is a cross-sectional view of a white LED device manufactured according to the prior art, Figure 1a is a lamp-shaped white LED device, Figure 1b is a white LED device manufactured by the transfer molding method, Figure 1c is an injection mold housing It is a white LED device manufactured using a package.

1A to 1C, a white LED device includes a blue LED chip 14, an LED chip mounting member such as a printed circuit board or lead frame in which a circuit is configured, and a blue LED chip 14 for LED chip mounting. An adhesive 16 for adhering to the member, a bonding pad formed on the blue LED chip 14, and a bonding wire 18 and a mold electrically connected to the electrode 20 or the lead 22 of the LED chip mounting member. 12).

The mold 12 is evenly dispersed throughout the translucent epoxy resin or silicone resin 10 encapsulating the LED chip 14 and the bonding wire 18, and the light emitted from the blue LED chip 14 is converted into yellow light. Phosphor 12 to be converted. As the phosphor 12, a yttrium-aluminum-garnet (Y ₃ Al ₅ O ₁₂ : Ce, YAG) -based compound has been widely used as a yellow phosphor. However, white light emitting diodes using YAG: Ce phosphors tend to be converted to silicate or TAG series phosphors due to their low color temperature and color rendering index.

By the way, the blue light generated by the LED chip and the yellow light generated by being excited by the phosphor are diffused in the air when there is no lens, and are combined with each other to appear white.

However, when the lens is applied, the blue light and the yellow light pass through the lens before the respective paths are equalized by diffusion, so that the difference in the direction angles of the blue light and the yellow light is widened as shown in FIG. 2. There is a problem that a deviation occurs in the color temperature.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems. In a white light emitting diode to which a lens is applied, a white light emitting diode which can reduce the variation in color temperature as a result of narrowing the direction angle between blue light and yellow light passing through the lens. The purpose is to provide.

A first embodiment of a white light emitting diode according to the present invention for achieving the above object is a light emitting diode (LED) chip for emitting blue light; A transparent resin layer formed to cover the LED chip and having phosphors dispersed therein; And a lens bonded on the transparent resin layer, wherein the transparent resin layer is mixed with a blue light emitted from the LED chip and a diffuser for diffusely reflecting yellow light by excitation of the phosphor.

Here, the diffusion agent preferably contains at least one of barium titanate, titanium oxide, aluminum oxide, and silicon oxide.

A second embodiment of a white light emitting diode according to the present invention for achieving the above object is an LED chip for emitting blue light; A transparent resin layer formed to cover the LED chip and having phosphors dispersed therein; A second resin layer stacked on the transparent resin layer and diffusely reflecting light emitted from the LED chip and transmitted through the transparent resin layer; And a lens bonded to the second resin layer.

Here, the second resin layer is preferably a diffusion agent is mixed in the epoxy resin or silicone resin. In addition, the second resin layer is preferably laminated after the thermosetting of the transparent resin layer is completed.

A third embodiment of a white light emitting diode according to the present invention for achieving the above object is an LED chip for emitting blue light; A transparent resin layer formed to cover the LED chip; A second resin layer laminated on the transparent resin layer and having phosphors dispersed therein; And a lens bonded to the second resin layer.

Here, the phosphor is excited by blue light transmitted through the transparent resin layer and emits yellow light, and is preferably implemented to diffuse the blue light and yellow light.

A fourth embodiment of the white light emitting diode according to the present invention for achieving the above object is an LED chip for emitting blue light; A transparent resin layer formed to cover the LED chip and having phosphors dispersed therein; And a lens bonded on the transparent resin layer, wherein the lens is roughly bonded to the transparent resin layer in order to diffusely reflect blue light emitted from the LED chip and yellow light by excitation of the phosphor. It is characterized by.

Thus, the white light emitting diode according to the present invention can reduce the deviation of the color temperature by reducing the difference in the direct angle of the blue light and yellow light passing through the lens.

Hereinafter, a white light emitting diode according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a view showing an embodiment of a white light emitting diode according to the present invention. Referring to the drawings, the white light emitting diode 100 is formed to cover the LED chip 102 emitting the blue light, the LED chip 102, the transparent resin layer 106 in which the phosphor 104 is dispersed therein, and And a lens 108 bonded onto the transparent resin layer 106. At this time, the transparent resin layer 106 includes a diffuser 110 that diffusely reflects the blue light emitted from the LED chip 102 and the yellow light emitted by the excitation of the phosphor 104.

Here, the diffusing agent 110 includes at least one of barium titanate, titanium oxide, aluminum oxide, and silicon oxide, and diffuses the blue light and the yellow light to make the optical path between the two lights the same.

In addition, the transparent resin layer 106 may be implemented with a transparent heat-modifying resin such as a modified acrylic resin, an epoxy resin, or a silicone resin.

As a result, blue light emitted from the LED chip 102 and yellow light due to excitation of the phosphor 104 are diffusely reflected by the diffuser 110, and as a result, the optical path between the two lights becomes equal to each other, The orientation angle can be reduced.

3 is an enlarged view of an example of the LED chip of FIG. 2. Referring to the drawings, the LED chip 102 is a multi-layer structure by sequentially growing the n-type layer 132, the active layer 133, the p-type layer 134 on the substrate 131 is coated with a reflective film 121 at the bottom A semiconductor layer is formed.

The n-type electrode pad 135, the p-type electrode 136a, and the p-type electrode pad 136b are attached or formed according to the basic structure, or the n-type electrode 135, the p-type electrode 136a, and the p-type. It is formed by attaching the transparent electrode 136b. In this case, the p-type transparent electrode 136b serves to emit light uniformly.

The n-type electrode 135 and the p-type electrode 136a are wire bonded to a printed circuit board or a lead frame.

On the other hand, in order to use a white light emitting diode as an illumination, as well as the quality of the white light, light output of more than a thousand lumens (lm; luminous flux emitted per unit solid angle emitted from a candela light source) is required. In order to obtain such a high output light emitting device, the device should be manufactured in consideration of variables such as increasing luminous efficiency, increasing device size, and lowering thermal resistance. In order to satisfy these conditions, a flip chip method is currently widely used. Unlike conventional light emitting diodes emitting top light (top emitting), the flip-chip light emitting diodes emit light through the sapphire substrate. In terms of the extraction efficiency of the light, in the conventional light emitting device that emits light upward, the light is absorbed by a transparent electrode, a bonding pad, or an electrode bonding while the light is emitted upward from the light emitting layer. This results in the loss of light. In addition, the high resistance of the p-side transparent electrode portion prevents current spreading, and thus, the entire device does not contribute to light emission. However, in the flip chip method, the light emitted toward the sapphire can minimize the loss in the metal contact portion, the bonding pad, and the electrode connection portion. In addition, the current spreading phenomenon is improved by using a thick p-side metal to increase the size of the device, and by using a p-metal having good reflectivity, the light traveling toward the electrode is reflected toward the sapphire to increase the light extraction efficiency. do.

In the case of a high output light emitting diode, since a large amount of heat is generated when the injection current is large, it must be efficiently radiated. In the conventional upward light emitting diode, the thermal resistance is 300 ?? / W, whereas the flip chip structure uses thick p-type metal and the chip is connected to the silicon submount so that heat can be removed well. The thermal resistance is 15 ?? / W, which is 20 times smaller than the conventional one. Therefore, compared with a conventional white light emitting device that emits 25lm at an input power of 1W, the structure using a flip chip can apply 20 times more power, and thus can emit more than 0.5 klm. Therefore, the flip chip is currently applied to the white light emitting device for lighting because of the high light extraction efficiency, high power application, and low thermal resistance, and it is preferable to use the flip chip as the LED chip. Do. In the case of using a flip chip, wire bonding can be omitted.

4 is a view showing another embodiment of a white light emitting diode according to the present invention. In the drawings, the same reference numerals are assigned to the same components as those of FIG. 2.

Referring to the drawings, the white light emitting diode 140 is formed to cover the LED chip 102, the LED chip 102 emitting blue light, and the transparent resin layer 142 having the phosphor 104 dispersed therein, and the transparent water. A diffusion resin layer 144 stacked on the ground layer 142 and diffusely reflecting light transmitted through the transparent resin layer 142, and a lens 108 bonded on the diffusion resin layer 144.

The diffusion resin layer 144 refers to a mixture of the diffusion agent 110 in a transparent modified acrylic resin, an epoxy resin, or a silicone resin, and the diffusion agent, as described above, includes barium titanate, titanium oxide, aluminum oxide, and silicon oxide. At least one.

In addition, the diffusion resin layer 144 is preferably laminated after the thermosetting of the transparent resin layer 142 is completed. That is, the transparent resin layer 142 is a solid-state molding by mixing the phosphor 104 in a modified acrylic resin, epoxy resin, or silicone resin, and then mixing the curing agent epoxy component, such as thermosetting to prevent precipitation of the diffusion resin After the process is completed, it is preferable that the diffusion resin layer 144 is stacked. As the curing agent component, a liquid type such as MHHPA or MTHPA, or a solid type such as THPA or HHPA may be used. In this case, additives such as an antioxidant, a UV absorber, and a catalyst may be added to the main epoxy resin and the silicone resin. By the addition of the additive, the heat resistance and the moisture resistance of the transparent resin layer 142 are improved, and the moldability is also improved. The same applies to other embodiments of the white light emitting diodes.

As a result, the blue light emitted from the LED chip 102 and the yellow light due to the excitation of the phosphor 104 are diffusely reflected by the diffusing agent 110 of the diffusion resin layer 144 so that the optical path between the two lights is the same. As a result, the directivity angle between the two lights becomes smaller.

5 is a view showing another embodiment of a white light emitting diode according to the present invention. In the drawings, the same reference numerals are assigned to the same components as those of FIG. 2.

Referring to the drawings, the white light emitting diode 150 is laminated on the LED chip 102 emitting blue light, the transparent resin layer 152 and the transparent resin layer 152 formed to cover the LED chip 102, and phosphors therein. The second transparent resin layer 154 is dispersed in the 104, and the lens 108 bonded to the second transparent resin layer 154.

Here, the second transparent resin layer 154 is preferably laminated after the transparent resin layer 152 is completed by the curing agent as described above. In this case, the phosphor 104 of the second transparent resin layer 154 may be applied on the transparent resin layer 152 or may be uniformly dispersed in the second transparent resin layer 154.

The blue light transmitted through the transparent resin layer 152 excites the phosphor 104 of the second transparent resin layer 154 to emit yellow light, and blue light and yellow light are diffusely reflected by the phosphor 104 to emit light. The paths become equal, resulting in less direct angle between the two lights.

6 is a view showing another embodiment of a white light emitting diode according to the present invention. In the drawings, the same reference numerals are assigned to the same components as those of FIG. 5.

Referring to the drawings, the white light emitting diode 160 is formed to cover the LED chip 102 emitting the blue light, the LED chip 102 and the transparent resin layer 154 having the phosphor 104 dispersed therein, and transparent The lens 162 bonded to the resin layer 154 is included. In this case, the lens 162 is preferably roughly bonded to the transparent resin layer 154 in order to diffusely reflect the blue light emitted from the LED chip 102 and the yellow light due to excitation of the phosphor 104. At this time, since the bonding surface of the roughly processed LED chip 162 is more likely to cause diffuse reflection, irregularity is preferable. As a result, the blue light emitted from the LED chip 102 and the yellow light due to excitation of the phosphor 104 are diffused before passing through the lens 162 so that the paths of the two lights become equal to each other, and consequently the directing angle between the two lights. Can be reduced.

FIG. 7 is a table comparing transmittance according to roughness DF of the lens, and FIG. 7A is a diagram comparing the central luminance, and FIG. 7B is a comparison of the amount of light. In the drawing, No indicates a case without a lens, C indicates a case where a roughness is not applied, and DF-1, DF-2, and DF-3 indicate a case of different points in the roughened lens.

Referring to the drawing, when the roughness DF is applied to the lens, as shown in FIG. 8A, the center luminance decreases by about 77% compared to the case where there is no roughness, while the amount of light is generally as shown in FIG. 8B. It can be seen that the variation in color temperature can be reduced without significantly affecting the light extraction efficiency of the lens at about 96%.

Although the preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the present invention is not limited to the specific embodiments of the present invention without departing from the spirit of the present invention as claimed in the claims. Anyone skilled in the art can make various modifications, as well as such modifications are within the scope of the claims.

The white light emitting diode according to the present invention reduces the directivity angle between the two light passing through the lens by diffusing the blue light emitted from the LED chip and the yellow light caused by the excitation of the phosphor, thereby reducing the color temperature variation of the light passing through the lens. It becomes possible.

Claims (8)

delete delete delete delete delete delete An LED chip emitting blue light; A transparent resin layer formed to cover the LED chip; A second transparent resin layer laminated on the transparent resin layer and having phosphors dispersed therein; And It comprises a lens bonded on the second transparent resin layer, And the phosphor is excited by blue light transmitted through the transparent resin layer to emit yellow light, and the white light emitting diode is diffusely reflected from the blue light and yellow light. An LED chip emitting blue light; A transparent resin layer formed to cover the LED chip and having phosphors dispersed therein; And It includes a lens bonded on the transparent resin layer, The lens is a white light emitting diode, characterized in that the bonding surface with the transparent resin layer is roughened in order to diffuse the blue light emitted from the LED chip, and yellow light by excitation of the phosphor.

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