JP2000216434A - Light emitting diode and its forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light emitting diode using fluorescent material capable of uniform light emission of high luminance, and a forming method of the diode. SOLUTION: This light emitting diode has an LED chip 103 wherein gallium nitride based compound semiconductor is applied to a light emitting layer and blue based light emission is enabled, a pair of external electrodes connected with the respective electrodes of the LED chip 103, and coating parts 101, 102 formed on the LED chip 103. The coating parts consists of a first transparent coating part 101, and a second transparent coating part 102 which is arranged on the first coating part 101 and contains fluorescent material which is excited by a visible light outputted from the LED chip 103 and outputs a visible light subjected to wavelength conversion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight light source, a read / write light source such as an optical sensor and an optical printer, and a light emitting diode used for a display device capable of displaying various data, and particularly to a fluorescent material. The present invention relates to a light emitting diode having high brightness and uniform light emission, and a method for forming the same.

[0002]

2. Description of the Related Art At present, light-emitting elements (hereinafter, also referred to as LED chips) capable of emitting light with an ultra-high luminance of 1000 mcd or more in RGB (red, green, and blue) have been developed. Along with this, a full-color LED display is being installed by causing each of the LED chips capable of emitting red (R), green (G), and blue (B) to emit mixed color light. Examples of such an LED display include a character display board using a single color display, in addition to a full-color large-sized image device. As a single color display, a white system is different from a color that draws attention, such as a red system, and is therefore less tiring even when viewed for a long time. For this reason, a single color LED display such as a white color display is particularly desired.

On the other hand, LED chips have an excellent monochromatic peak wavelength. Therefore, when displaying a white color or the like, two colors such as RGB, B (blue) and Y (yellow) are mixed.
It is necessary to mix colors of light emitted from more than one type of LED chip. However, in an LED display or the like used for a destination display board or the like, it is not always necessary to use two or more types of LED chips to display white or the like.

Accordingly, the applicant of the present application has proposed a light emitting diode capable of emitting light of another color by converting the color of light emitted from a blue light emitting diode by using an LED chip and a fluorescent substance as disclosed in Japanese Patent Application Laid-Open Nos. 5-152609 and 7-99345. The light-emitting diode described in Japanese Patent Publication No. 1993-216, etc. was developed. With these light-emitting diodes, various kinds of luminescent colors such as white light can be emitted using one type of LED chip.

Specifically, an LED chip having a large energy band gap of a light emitting layer is disposed on a cup provided at the tip of a lead frame. The LED chip is electrically connected to a metal stem or a metal post provided with the LED chip. Then, a fluorescent material that absorbs light from the LED chip and converts the wavelength is contained in a mold member that covers the LED chip.

In this case, by selecting a blue light emitting diode and a fluorescent substance that absorbs the emitted light and emits a yellow light, a white light can be emitted by using a mixed color of these lights. Such a light emitting diode can be used as a light emitting diode that emits sufficient luminance even when used as a light emitting diode that emits white light.

[0007]

However, if an LED chip and a fluorescent substance are simply mounted in a reflection cup on a mount lead used for a light emitting diode, color unevenness may occur on a light emission observation surface. More specifically, when viewed from the light emission observation surface side, the center where the LED chip is arranged is blueish, and the periphery thereof is yellow in a ring shape,
Green or reddish parts may be seen. Human tone perception is particularly sensitive in white. Therefore, even a slight difference in color tone is perceived as reddish white, greenish white, yellowish white, or the like.

[0008] Such color unevenness caused by looking directly at the light emission observation surface is not only unfavorable in terms of quality, but also uneven color tone of the display surface when applied to an LED display, and errors in precision equipment such as an optical sensor. Will also occur. Further, such a light emitting device has a problem that the light emission luminance tends to decrease with time. It is an object of the present invention to provide a light emitting diode capable of solving the above-mentioned problems and having a very small color tone unevenness on a light emission observation surface and capable of emitting white light or the like with high luminance and a method of forming the same.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a light emitting device that emits blue light using a gallium nitride compound semiconductor as a light emitting layer.
It is a light emitting diode having an ED chip, a pair of external electrodes respectively connected to each electrode of the LED chip, and a coating portion provided on the LED chip. In particular,
The coating unit includes a light-transmitting first coating unit,
A light-emitting diode disposed on the first coating portion and having a light-transmitting second coating portion containing a fluorescent substance that emits visible light whose wavelength has been converted by being excited by visible light emitted from the LED chip; It is.

A light emitting diode according to a second aspect of the present invention displays white light by a mixed color display of visible light emitted from an LED chip and visible light whose wavelength has been converted from a fluorescent substance.

[0011] A light emitting diode according to a third aspect of the present invention is a light emitting diode in which a mold member is provided on the second coating portion.

According to a fourth aspect of the present invention, there is provided a light emitting diode, wherein the light emitting diode passes through a coating portion containing a fluorescent substance.
The first coating portion and the LED chip are arranged via the second coating portion so as to reduce the color unevenness by substantially reducing the optical path length difference of the light from the ED chip.

According to a fifth aspect of the present invention, there is provided a light emitting diode wherein an LED chip is formed on a sapphire substrate.
It has a light emitting layer of GaN.

[0014] The light emitting diode according to claim 6 of the present invention, a fluorescent substance _{(Re 1-x Sm x)} 3 (Al 1-y Ga y) 5 O
₁₂ : Ce. Here, 0 ≦ x <1, 0 ≦ y ≦ 1, and Re is at least one element selected from the group consisting of Y, Gd, La, Lu, and Sc.

In a light emitting diode according to a seventh aspect of the present invention, the first and second coating members are made of a translucent resin or glass.

The light emitting diode according to claim 8 of the present invention is an LED chip capable of emitting blue light using a gallium nitride compound semiconductor as a light emitting layer, a coating portion provided on the LED chip, It has a pair of external electrodes respectively connected to each electrode. In particular, the coating part is a light emitting diode formed by adhering a thin film containing a fluorescent substance that emits visible light whose wavelength is converted by being excited by visible light from the LED chip at least partially on the LED chip. .

According to a ninth aspect of the present invention, there is provided an LED chip capable of emitting blue light, wherein a light emitting layer disposed in a reflection cup of a mount lead is a gallium nitride-based compound semiconductor; Inner leads electrically connected using conductive wires, and LEDs
It has a chip, a conductive wire, a mounting lead, and a mold member that covers a part of the inner lead.
In particular, in the reflection cup, a light-transmitting first coating portion provided on the LED chip, and a wavelength conversion device which is disposed on the first coating portion and is excited by visible light emitted from the LED chip to perform wavelength conversion. And a light-transmitting second coating portion containing a fluorescent material that emits visible light.

In a light emitting diode according to a tenth aspect of the present invention, the mold member has a lens shape.

According to a method of forming a light-emitting diode according to the present invention, an LED capable of emitting blue light having a light-emitting layer made of a nitride-based compound semiconductor disposed in a cup is provided.
A step of injecting a translucent resin onto the D chip to form a first coating portion, and forming an LED on the first coating portion
Forming a second coating portion by injecting a translucent resin containing a fluorescent substance that emits visible light whose wavelength has been converted by being excited by visible light emitted from the chip.

[0020]

According to the present invention, an optical path length difference of light emitted from an LED chip is reduced by forming a first coating portion near an LED chip and a second coating portion having a fluorescent substance on the first coating portion. Substantially reducing the color tone unevenness of the light emitting device and alleviating light confinement due to the provision of the fluorescent substance can be achieved. Therefore, a light-emitting diode or the like that can emit uniform light with a small decrease in emission luminance even when used for a long time can be provided.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of various experiments, the present inventors have found that by setting a light emitting element and a fluorescent substance in a specific arrangement relationship, it is possible to improve color tone unevenness and luminance reduction on a light emission observation surface. Invented the invention.

Although it is not clear that the structure of the present invention can improve the uneven color tone and the reduction in luminance, it is considered as follows. In other words, the light emitted from the light emitting element is
As shown in (A), (a), (b), (c), (d),
(E) and (f) are emitted at various angles. Such light has different optical path lengths passing through the coating portion containing the fluorescent substance. In particular, light having a smaller angle of light emitted from the LED chip tends to have a longer optical path length. For this reason, the amount of light converted into the fluorescent substance varies depending on the optical path length difference, and color tone unevenness occurs. In particular, in the regions (d) and (e), since the light path length is long, the light from the LED chip whose wavelength is converted by the fluorescent substance increases, and it is considered that color tone unevenness is likely to occur when viewed from the light emission observation surface side. Further, the light emitted from the LED chip is light (f) which propagates and is emitted like a waveguide in the semiconductor.
It is considered that such light also causes uneven color tone around the LED chip.

Further, when the coating portion having the fluorescent material is directly disposed on the LED chip, the ratio of the fluorescent material reflecting and scattering light from the LED chip increases. In particular, in the vicinity of the LED chip, the number of times that the visible light from the LED chip is reflected and scattered by the fluorescent substance is extremely increased, and the light density is increased. As a result, it is considered that the organic resin or the like, which is the base material of the coating portion, is liable to deteriorate, and the luminance tends to eventually decrease.

According to the present invention, as shown in FIG. 5B, by forming a first coating portion and a second coating portion on the LED chip, a difference in optical path length can be reduced, and light near the LED chip can be reduced. It is possible to reduce scattering and suppress a decrease in luminance.

FIG. 2 shows a chip type LED as an example of a specific light emitting device. As the chip type LED, a package having external electrodes and a concave portion was used. LE with gallium nitride-based compound semiconductor as light emitting layer in recess
The D chip is die-bonded with an epoxy resin. Each electrode of the LED chip and the external electrode are wire-bonded using a gold wire. An epoxy resin was applied as a first coating portion on the recessed LED chip and dried. Next, as a second coating part, (Re _1-x Sm _x ) ₃
A material containing (Al _1-y G _ay ) ₅ O ₁₂ : Ce phosphor was formed on the first coating portion.

The first coating and the second coating have a laminated structure. Also, as shown in FIG. 2, the cross-sectional end of the first coating portion is raised. Therefore, the surface of the first coating portion has a concave spherical shape as viewed from the light emission observation surface side. When the first coating portion has a concave spherical shape, the fluorescent substance in the second coating portion can be collected closer to the center. Such a shape can be created by controlling the viscosity and the curing temperature and time of the epoxy resin as the first coating portion.
As a result, a substantial difference in optical path length can be reduced, and a light emitting device with less color tone unevenness and lower luminance can be obtained. Hereinafter, the constituent members of the present invention will be described in detail.

(Coating sections 101, 102, 20
1, 202, 401, 402) The coating part of the present invention protects the LED chip from the external environment and the like. The coating portion is provided on the LED chip, and is at least partially made of a resin or glass containing a fluorescent substance that emits visible light when excited by visible light from the LED chip. In any case, the coating portion can sufficiently mix the visible light from the LED chip and the fluorescent substance by reducing the difference in the path length of the visible light from the LED chip. In particular, the coating portion of the present invention is provided so that the difference in the optical path length of the light emitted from the LED chip is smaller than that of a simple layer shape containing a fluorescent substance. In addition, it has a multilayer structure so that it is efficiently emitted to the outside. Therefore, the shape of the coating portion includes a convex lens shape, various multilayer shapes, and the like. Alternatively, it may be formed by bonding a coating portion formed on a thin film.

The base material of the first coating part 101 and the base material of the second coating part 102 may be made of the same material or different materials. When a different material is used, it is preferable to use a weather-resistant material on the side closer to the outside. Further, it is preferable to use a material having a smaller expansion as the material is located further inside. As a specific base material constituting such a coating portion, epoxy resin,
Translucent resins such as urea resin, acrylic resin, and silicone resin, glass, and the like are preferably used. Further, the thickness of the first coating portion and the thickness of the second coating portion may be the same or different. Examples of the fluorescent substance include various substances such as organic and inorganic dyes and pigments in consideration of light from the LED chip.

The first and / or second coating portions may contain a diffusing agent, a coloring agent and a light stabilizer. By including a coloring agent, a filter effect of cutting light from the LED chip and / or the fluorescent substance as desired can be provided. By including a diffusing agent, the directional characteristics can be adjusted as desired. By incorporating an ultraviolet absorber as a light stabilizer, it is possible to suppress deterioration of the resin or the like constituting the coating portion. As a specific diffusing agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide, or the like is suitably used. Examples of the light stabilizer include benzotriazole, benzophenone, salicylate, cyanoacrylate, and hindered amine.

The main material of the coating portion may be the same material as the mold member or may be a different member. When the coating portion is formed of a different member, external stress and thermal stress applied to the LED chip, the conductive wire, and the like can be further reduced.

(Fluorescent substance) The fluorescent substance used in the present invention means a fluorescent substance which emits visible light when excited by at least visible light emitted from the semiconductor light emitting layer. L
When the visible light emitted from the ED chip and the visible light emitted from the fluorescent substance are in a complementary color relationship or the like, the visible light from the LED chip and the visible light of the fluorescent substance excited and emitted by the light are respectively three primary colors (red). System, green system, blue system)
When light emission from the LED chip and light emission from the fluorescent substance are mixed and displayed, white light emission color display can be performed. Therefore, L
It is necessary that the light emitted from the ED chip and the light emitted from the fluorescent substance pass through the coating part and the like. For such adjustment, the ratio between the fluorescent substance and the resin and the like, the application and the filling amount are variously adjusted. Alternatively, an arbitrary color tone such as a light bulb color including white can be provided by variously selecting the emission wavelength of the light emitting element.

Further, the content distribution of the fluorescent substance in the second coating portion affects the color mixing property and the durability.
That is, LE from the outer surface side of the second coating portion.
When the distribution concentration of the fluorescent substance is high toward the D chip,
It is less susceptible to moisture and the like from the external environment, and it is easy to suppress deterioration due to moisture and the like.

On the other hand, if the concentration distribution of the fluorescent substance increases from the LED chip toward the surface of the mold member, the distribution of the fluorescent substance is likely to be affected by moisture from the external environment, but the influence of heat generation and irradiation intensity from the LED chip is more. The deterioration of the fluorescent substance can be suppressed to a small extent. Therefore, various selections can be made according to the use environment. Such a distribution of the fluorescent substance, the base material containing the fluorescent substance, the formation temperature,
Various shapes can be formed by adjusting the viscosity, the shape of the fluorescent substance, the particle size distribution, and the like.

The fluorescent substance excited by the semiconductor light emitting layer includes various substances such as an inorganic fluorescent substance, an organic fluorescent substance, a fluorescent dye and a fluorescent pigment. Specific fluorescent substances include:
Perylene derivatives and yttrium with cerium
Aluminum garnet phosphor (Re _1-x S
_{m x) 3 (Al 1-} y Ga y) 5 O 12: Ce (0 ≦ x <1,0
≦ y ≦ 1, where Re is Y, Gd, La, Lu, Sc
At least one element selected from the group consisting of ). In particular, as a fluorescent substance (Re
_{1-x Sm x) 3 (} Al 1-y Ga y) 5 O 12: in the case of using the Ce is greater nitride compound semiconductor energy band gap LED chip and contact or proximity using the light-emitting layer (Ee) = 3W · cm as irradiance
It can be a light emitting device having sufficient light resistance in high efficiency ^-2 10 W · cm ^-2 or less.

(Re _1-x Sm _x ) ₃ (Al _1-y G _ay )
_{Since the 5} O ₁₂ : Ce phosphor has a garnet structure, it is resistant to heat, light and moisture, and has a peak of an excitation spectrum of 470 nm.
It can be made nearby. The emission peak is 5
A broad emission spectrum that is near 30 nm and extends down to 720 nm can be provided. In addition, the emission wavelength shifts to a short wavelength by substituting a part of the Al in the composition with Ga, and the emission wavelength shifts to a long wavelength by substituting a part of the Y in the composition with Gd. By changing the composition in this way, the emission color can be continuously adjusted. Therefore, there is provided an ideal condition for converting the blue light emission of the nitride semiconductor to white light emission such that the intensity on the long wavelength side can be continuously changed by the composition ratio of Gd.

Such phosphors include Y, Gd, Ce, S
An oxide or a compound which easily becomes an oxide at a high temperature is used as a raw material of m, Al, La and Ga, and these are sufficiently mixed in a stoichiometric ratio to obtain a raw material. Or Y, Gd, C
e, a co-precipitated oxide obtained by calcining a solution obtained by dissolving a rare earth element of Sm in an acid at a stoichiometric ratio with oxalic acid, and aluminum oxide, gallium oxide, etc., and mixing raw materials Get. An appropriate amount of a fluoride such as ammonium fluoride is mixed as a flux into the crucible, and calcined in air at a temperature in the range of 1350 to 1450 ° C. for 2 to 5 hours to obtain a calcined product. It can be obtained by ball milling, washing, separating, drying and finally passing through a sieve.

In the light emitting device of the present invention, the fluorescent substance may be a mixture of two or more fluorescent substances. That is,
Al, Ga, Y, the content of La and Gd and Sm are two or more kinds of _{(Re 1-x Sm x)} 3 (Al 1-y Ga y)
By mixing ₅ O ₁₂ : Ce phosphor, the wavelength components of RGB can be increased.

(LED chips 103, 203, 403)
The LED chip used in the present invention is preferably a nitride-based compound semiconductor capable of efficiently exciting a fluorescent substance and emitting light at a relatively short wavelength efficiently. Such an LED chip is formed on a substrate by MOCVD or the like.
A semiconductor such as GaN can be formed as the light emitting layer. Examples of the semiconductor structure include a homo structure, a hetero structure, and a double hetero structure having an MIS junction, a PIN junction, a pn junction, and the like. Various emission wavelengths can be selected depending on the material of the semiconductor layer and the degree of mixed crystal thereof. Also, a single quantum well structure or a multiple quantum well structure in which the semiconductor active layer is formed as a thin film in which a quantum effect occurs can be used.

When a gallium nitride compound semiconductor is used, sapphire, spinel, SiC, S
Materials such as i and ZnO are used. In order to form gallium nitride having good crystallinity, a sapphire substrate is preferably used. GaN, AlN on this sapphire substrate
Is formed at a low temperature, and a gallium nitride semiconductor having a pn junction is formed thereon. Gallium nitride-based semiconductors exhibit n-type conductivity without being doped with impurities. When a desired n-type gallium nitride semiconductor is formed, for example, to improve luminous efficiency, S is used as an n-type dopant.
It is preferable to appropriately introduce i, Ge, Se, Te, C, and the like. On the other hand, when a p-type gallium nitride semiconductor is formed, p-type dopants such as Zn, Mg, Be, Ca, and S
Doping with r, Ba, etc.

A gallium nitride-based compound semiconductor is hardly converted into a p-type by simply doping it with a p-type dopant. After the introduction of the p-type dopant, the gallium nitride-based compound semiconductor is annealed by heating in a furnace, low-speed electron beam irradiation, plasma irradiation, or the like. Is preferred. P-type semiconductor and n
After the exposed surface of the mold semiconductor is formed, each electrode having a desired shape is formed on the semiconductor layer by using a sputtering method, a vacuum evaporation method, or the like.

Next, the formed semiconductor wafer or the like is directly full-cut by a dicing saw in which a blade having a diamond blade is rotated, or after a groove having a width larger than the blade width is cut (half cut). The semiconductor wafer is broken by external force. Alternatively, an extremely thin scribe line (meridian) is drawn on the semiconductor wafer, for example, in a checkerboard pattern by a scriber in which a diamond needle at the tip reciprocates linearly, and then the wafer is cut by an external force and cut into chips from the semiconductor wafer. Thus, an LED chip that is a gallium nitride-based compound semiconductor can be formed.

In the case where white light is emitted in the light emitting device of the present invention, the main emission wavelength of the light emitting element is preferably 400 nm or more and 530 nm or less, more preferably 420 nm or more and 490 nm or less in consideration of the color complementary to the fluorescent substance. L
In order to further improve the efficiency of the ED chip and the efficiency of the fluorescent substance, respectively, the thickness is more preferably 450 nm or more and 475 nm or less. Note that, in addition to the LED chip mainly used in the present invention, an LED chip that does not excite a fluorescent substance or emits only light that does not substantially emit visible light or the like from the fluorescent substance even when excited may be disposed together. it can. In this case, a light emitting device capable of emitting white light, red light, yellow light, and the like can be provided.

(Mount Lead 104) The mount lead 104 preferably has a cup on which the LED chip 103 is arranged and a fluorescent substance is accommodated. Such a cup can also function as an opening in the present invention. When a plurality of LED chips are provided and the mount leads are used as a common electrode of the LED chips, it is preferable that the LED chips have sufficient electrical conductivity and connectivity with a bonding wire or the like.

The specific electric resistance of the mount lead is preferably 300 μΩcm or less, more preferably,
It is 3 μΩcm or less. Also, when a plurality of LED chips are mounted on the mount leads, good heat conductivity is required because the amount of heat generated from the LED chips increases. Specifically, it is preferably at least 0.01 cal / cm ² / cm / ° C., more preferably 0.5 cal / cm ² / c
m / ° C. or more. Materials satisfying these conditions include iron, copper, copper with iron, copper with tin, and ceramics with metallized patterns.

(Inner Lead 105) The inner lead 105 is for connecting a conductive wire connected to the LED chip 103 disposed on the mount lead 104. In the case where a plurality of LED chips are provided on the mount lead, it is necessary to arrange the conductive wires so that the conductive wires do not contact each other. Specifically, as the distance from the mount lead increases, the area of the end face of the inner lead to which wire bonding is performed can be increased to prevent contact of the conductive wire connected to the inner lead further away from the mount lead. it can. The roughness of the connection end face with the conductive wire is preferably 1.6S or more and 10S or less in consideration of adhesion.

In order to form the tips of the inner leads into various shapes, the shape of the lead frame may be determined in advance with a mold and punched out, or after all the inner leads have been formed, It may be formed by cutting a part of the upper part of the inner lead. Further, after the inner lead is punched and formed, a desired end face area and end face height can be simultaneously formed by pressing from the end face direction.

The inner leads are required to have good connectivity with a conductive wire such as a bonding wire and good electrical conductivity. The specific electric resistance is 3
00 μΩcm or less, more preferably 3 μΩc
m or less. Materials meeting these conditions include:
Examples include iron, copper, copper with iron, copper with tin, and aluminum, iron, and copper plated with copper, gold, and silver.

(Electrical Connection Member 106) As the conductive wire 106 or the like as the electrical connection member, one having good ohmic properties, mechanical connectivity, electrical conductivity, and thermal conductivity with the electrodes of the LED chip 103 is preferable. Desired. The thermal conductivity is preferably 0.01 cal / cm ² / cm / ° C. or more, more preferably 0.5 cal / cm ² / cm / ° C.
That is all. Further, in the case of a conductive wire in consideration of workability and the like, preferably, the diameter is Φ10 μm or more, and Φ45 μm.
m or less. Specific examples of such conductive wires include conductive wires using metals such as gold, copper, platinum, and aluminum and alloys thereof. Such a conductive wire can easily connect an electrode of each LED chip to an inner lead, a mount lead, and the like by a wire bonding device.

(Mold member 107) Mold member 10
7 is an LED chip 10 according to the usage of the light emitting device.
3. The conductive wire 106, the coating portion 102 containing the fluorescent material, and the like can be suitably provided to protect the coating from the outside. The mold member 107 can be formed using various resins, glass, or the like. By forming the mold member into a desired shape, it is possible to have a lens effect of converging or diffusing light emitted from the LED chip. Therefore, a structure in which a plurality of mold members are stacked may be employed. Specifically, a convex lens shape, a concave lens shape, and a combination of a plurality of shapes such as an elliptical shape and a circular shape when viewed from the light emission observation surface are exemplified.
In the case where the light from the LED chip is condensed to form a lens, the light emitting surface is enlarged when viewed from the light emission observing surface side, so that the color tone unevenness of the light source is particularly remarkable. Therefore, the effect of suppressing color unevenness of the present invention is particularly large.

As a specific material of the mold member, a translucent resin having excellent weather resistance, such as an epoxy resin, a urea resin, or silicone, or glass is preferably used.
Further, by including a diffusing agent in the mold member, the directivity from the LED chip can be reduced and the viewing angle can be increased. As a specific material of the diffusing agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide, or the like is suitably used. Further, the mold member and the coating portion may be formed by different members. Further, the mold member and the coating portion can be formed using the same member in consideration of the refractive index.

(Substrate 404) As a substrate 403 for a high-definition, high-viewing-angle, small-sized and thin LED display on which a large number of LED chips 403 are arranged, a plurality of LED chips 403 and an electrical connection member and a plurality of fluorescent materials are contained. One having a conductor wiring layer provided with a concave opening is preferably mentioned. In such a substrate, when a plurality of LED chips are directly mounted on the same substrate at a high density, the amount of heat radiation from the LED chips increases. The heat from the LED chip cannot be sufficiently dissipated, and if the fluorescent substance is not uniformly dispersed in the resin, the coating may be partially degraded such as cracking or coloring.

Therefore, it is desired that a substrate having a conductor wiring layer provided with a concave opening has good heat dissipation and good adhesion to a coating portion containing a fluorescent substance. Suitable examples of the wiring substrate material having such a concave opening include a ceramic substrate, a metal substrate having a conductive wiring layer based on a metal via an insulating layer, and a heat-resistant organic resin substrate containing a heat conductive filler. In these substrates, the concave opening and the wiring layer can be formed integrally. It is possible to easily form an LED display in which a concave opening and a wiring portion are integrated by laminating a perforated substrate on a ceramic substrate, press working on a metal substrate, and resin molding on an organic resin substrate.

In particular, a ceramic substrate mainly composed of alumina is more preferable in terms of heat dissipation and weather resistance. Specifically, 90 to 96% by weight of the raw material powder is alumina,
Viscosity, talc, magnesia, calcia, silica, etc. are added as sintering aids in an amount of 4 to 10 wt%,
A ceramic substrate sintered at a temperature of 00 ° C., and 40 to 60% by weight of the raw material powder are alumina, and 60 to 40% by weight of borosilicate glass, cordierite, forsterite, mullite, etc. are added as a sintering aid. 800-120
A ceramic substrate or the like sintered in a temperature range of 0 ° C.

Such a substrate can take various shapes at the green sheet stage before firing. The wiring can be formed by screen printing or the like into a desired shape on a green sheet or the like using a wiring pattern made of a resin binder containing a high melting point metal such as tungsten or molybdenum. In addition, LED is achieved by bonding open green sheets in multiple layers.
An opening for containing a chip and a fluorescent substance can also be freely formed. Therefore, it is also possible to form a stepped side wall of an opening by stacking green sheets having different cylindrical or hole diameters. By sintering such a green sheet, a ceramic substrate is obtained. Further, after sintering, they may be bonded and used.

The green sheet on the outermost surface includes Cr
_{By including 2} O ₃ , MnO ₂ , TiO ₂ , Fe ₂ O _3, etc. in the green sheet itself, only the substrate surface formed can be made to have a dark color. The substrate having such an outermost surface improves the contrast and makes the light emission of the LED chip and the fluorescent substance more conspicuous.

The side wall extending toward the opening can further improve the reflectance. The side wall shape of the concave opening is a taper angle or a curved surface on a straight line that is optically suitable for reflection in order to avoid loss of light emission from the LED chip.
Or a step shape is mentioned. In addition, the depth of the concave opening is within a range that does not prevent the chiller serving as the first coating portion or the slurry in which the fluorescent material serving as the second coating portion is dispersed from flowing out, and does not block the direct light from the LED chip. Is determined by the angle of Therefore, the depth of the concave opening is preferably 0.3 mm or more, and 0.5 mm or more.
It is more preferably not less than 2.0 mm.

The concave opening of the substrate is for disposing the LED chip, the electrical connection member, the first and second coating portions, and the like inside. Therefore, it is only necessary that the LED chip be large enough to be directly mounted on the die bonding device or the like, and be electrically connected to the LED chip by wire bonding or the like. A plurality of concave openings can be provided as desired, and 16x16 or 24x
Various selections such as 24 dot matrices and linear shapes can be made. When the dot pitch of the concave opening is 4 mm or less, the dot pitch can be significantly reduced as compared with the case where a shell type light emitting diode lamp is mounted. In addition, an LED display using such a substrate can be a high-density LED display device that can solve various problems related to heat dissipation from an LED chip. The bonding between the LED chip and the bottom of the substrate can be performed with a thermosetting resin or the like. Specifically, an epoxy resin, an acrylic resin, an imide resin, and the like can be given. In addition, an Ag paste, an ITO paste, a carbon paste, a metal bump, or the like can be used for bonding and electrically connecting a wiring provided on a substrate with a face-down LED chip or the like.

The wiring formed on the substrate may be formed of silver, gold, copper, platinum, palladium, or the like in order to improve the conductivity, the reflectance of the bottom of the substrate on which the LED chips and the fluorescent substance are arranged, and the like. The alloy can also be formed by performing vapor deposition, plating, or the like.

(LED Display Device) An example of an LED display using the light emitting diode of the present invention will be described. In the present invention, an LED display device for black and white can be formed by using only the white light emitting device. The black-and-white LED display is configured such that the light-emitting diodes, which are the light-emitting devices of the present invention, are arranged in a matrix or the like, or have an LED chip and a coating portion on a substrate having a plurality of concave portions arranged as desired. be able to. A drive circuit for driving each LED chip and the LED display are electrically connected. A display or the like capable of displaying various images by an output pulse from the drive circuit can be provided. A RAM (Random, Access, Memory) for temporarily storing input display data as a drive circuit
A gradation control circuit for calculating a gradation signal for lighting the LED display to a predetermined brightness from data stored in the RAM; and a light emitting device which is switched by an output signal of the gradation control circuit to light the light emitting device And a driver to make it. The gradation control circuit calculates a lighting time of the light emitting device from data stored in the RAM and outputs a pulse signal.

Such an LED display for black and white is RG
Unlike the B full-color display, the circuit configuration can be simplified and the definition can be increased. Therefore, a display without color unevenness due to the characteristics of the RGB light emitting device can be provided. In addition, since the power consumption can be reduced to about one third, the use time can be extended in the case of connection with a battery power supply. Furthermore, compared to the conventional LED display using only red and green, it is less irritating to humans and is suitable for long-time use. Hereinafter, embodiments of the present invention will be described, but it goes without saying that the present invention is not limited to only specific embodiments.

[0061]

(Example 1) I having a main emission peak of 460 nm
An LED chip having a light emitting layer of an n _0.4 Ga _0.6 N semiconductor was used. In the LED chip, a TMG (trimethyl gallium) gas, a TMI (trimethyl indium) gas, a nitrogen gas, and a dopant gas are flowed together with a carrier gas on a cleaned sapphire substrate, and a gallium nitride-based compound semiconductor is formed by MOCVD. Formed. By switching between SiH ₄ and Cp ₂ Mg as the dopant gas, a gallium nitride-based semiconductor having n-type conductivity and a gallium nitride-based semiconductor having P-type conductivity were obtained.
On a sapphire substrate, Ga having n-type conductivity as a first contact layer is interposed via GaN as a buffer layer.
N, InGaN as a light emitting layer, AlGaN with p-type conductivity as a first cladding layer, and GaN with p-type conductivity as a second contact layer are formed. (Note that the p-type semiconductor is annealed at 400 ° C. or higher after film formation. The thickness of the light emitting layer is 3 nm, which is such that a quantum effect occurs.) After exposing each pn semiconductor surface by etching Each electrode was formed by a sputtering method. After a scribe line is drawn on the semiconductor wafer thus completed, the wafer is divided by an external force to obtain a light emitting element of 350 mm.
A μm square LED chip was formed.

On the other hand, a silver-plated copper lead frame was formed by punching. The formed lead frame has a cup at the tip of the mounting lead. The LED chip was die-bonded to the cup with an epoxy resin containing Ag. Each electrode of the LED chip, the mount lead and the inner lead were each wire-bonded with a gold wire to establish electrical continuity. Silicone rubber was injected onto the LED chip onto the cup on which the LED chip was placed. After the injection, the coating was cured at 125 ° C. for about 1 hour to form a first coating portion.

As a fluorescent substance, a solution obtained by dissolving rare earth elements of Y, Gd, and Ce in an stoichiometric ratio in an acid was coprecipitated with oxalic acid. This is mixed with a coprecipitated oxide obtained by calcination and aluminum oxide to obtain a mixed raw material. This was mixed with ammonium fluoride as a flux, packed in a crucible, and fired in air at a temperature of 1400 ° C. for 3 hours to obtain a fired product. The calcined product was ball milled in water, washed, separated, dried, and finally formed through a sieve.

(Y _0.4 Gd _0.6 ) ₃ Al ₅ O ₁₂ :
40 parts by weight of the Ce phosphor and 100 parts by weight of the epoxy resin were mixed well to form a slurry. The slurry was poured over the first coating in the cup of the mount lead. After the injection, the resin containing the fluorescent
Curing was performed at about 1 hour. Thus, as shown in FIG.
A second coating portion containing a fluorescent material having a thickness of about 0.4 mm was formed on the first coating portion. Further, a translucent epoxy resin was formed as a mold member for the purpose of protecting the LED chip and the fluorescent substance from external stress, moisture, dust and the like. The mold member was inserted into a shell frame having a fluorescent material coated portion and mixed with a translucent epoxy resin.
Cured in 5 hours. Thus, a light emitting diode as a light emitting device as shown in FIG. 1 was formed.

The color temperature and the color rendering were measured from the front of the thus obtained light emitting diode capable of emitting white light. Color temperature 8080K, Ra (color rendering index) = 87.4
showed that. Furthermore, the measurement point is set to 45 degrees from 0 degrees to 180 degrees.
The light-emitting device was moved each time over the center of the light-emitting device, and the chromaticity points at each point were measured. Also, If = 60 mA, Ta
= 25 ° C.

Comparative Example 1 A gallium nitride-based compound semiconductor LED was formed in the same manner as in Example 1 except that the first coating portion was not formed and the coating portion was formed using only the second coating portion. only the cup chips are arranged as a fluorescent substance _{(Y 0.4 Gd 0 .6) 3} Al 5 O
₁₂ : Ce phosphor-containing resin was injected and cured. The chromaticity point and the life test result of the light emitting diode thus formed were measured in the same manner as in Example 1. The measurement results are shown in FIGS. In FIG. 7, the values are shown based on the first embodiment.

(Example 2) A ceramic substrate was used as a wiring substrate having concave openings in a dot matrix. The concave opening was formed by laminating a perforated green sheet having no wiring layer during the production of the ceramic substrate.
The dot pitch of the concave opening of the 16 × 16 dot matrix was 3.0 mm, the diameter of the opening was 2.0 mmφ, and the depth of the opening was 0.8 mm. The total length was a 48 mm square substrate.
The wiring layer was formed by screen-printing a tungsten-containing binder into a desired shape. Each green sheet is formed by overlapping. In addition, the green sheet corresponding to the surface layer contains chromium oxide for improving the contrast of the substrate. This was sintered to form a ceramic substrate. Wiring layers are provided with common and signal lines corresponding to the dot matrix, and the surface is plated with Ni / Ag. For taking out signal lines from the ceramic substrate, connection pins made of metal cover were formed by silver brazing. The diameter of the stepped opening is 1.7 mmφ in the lower layer, and the opening diameter in the upper layer is 2.
3 mmφ.

On the other hand, as an LED chip as a semiconductor light emitting element, In _0.05 Ga _0.95 having a main emission peak of 450 nm was used.
An N semiconductor was used. The LED chip is made of TMG (trimethylgallium) gas, TM
An I (trimethyl indium) gas, a nitrogen gas and a dopant gas were flowed together with a carrier gas, and a gallium nitride-based compound semiconductor was formed by MOCVD. SiH ₄ and Cp ₂ Mg as dopant gas
By switching between the above, a gallium nitride semiconductor having n-type conductivity and a gallium nitride semiconductor having p-type conductivity were formed, and a pn junction was formed. (Note that the p-type semiconductor was annealed at 400 ° C. or higher after the film formation.) After exposing the surface of each pn semiconductor by etching, each electrode was formed by sputtering. After a scribe line is drawn on the semiconductor wafer thus completed, the wafer is divided by an external force and the LED is used as a light emitting element.
Chips were formed. The LED chip capable of emitting blue light was die-bonded to a predetermined location in the substrate opening with epoxy resin, and then fixed by thermosetting. Then 25
Electrical connection was established by wire bonding a gold wire of μm to each electrode of the LED chip and the wiring on the substrate. Silicone resin was injected as a first coating part in the lower part in the concave part and cured at 130 ° C. for one hour. The thickness of the first coating was about 0.4 mm.

As a fluorescent substance, a solution in which rare earth elements of Y, Gd, and Ce were dissolved in an acid at a stoichiometric ratio was coprecipitated with oxalic acid. A co-precipitated oxide obtained by calcining this and aluminum oxide are mixed to obtain a mixed raw material. This was mixed with ammonium fluoride as a flux, packed in a crucible, and fired in air at a temperature of 1400 ° C. for 3 hours to obtain a fired product. Ball-mill the baked product in water, wash, separate,
Dried and finally formed through a sieve. Formed (Y
_0.5 Gd _0.5 ) ₃ Al ₅ O ₁₂ : Ce fluorescent substance 10 parts by weight and silicone resin 90 parts by weight were mixed well to form a slurry. The slurry was injected into each of the upper concave portions on the first coating portion. After the injection, the resin containing the fluorescent substance is cured at 130 ° C for 1 hour, and the LED is
An indicator was formed. The thickness of the second coating was 0.4 mm. In addition, the thickness of the LED display at this time was only 2.0 mm of the thickness of the ceramic substrate, and it was possible to significantly reduce the thickness as compared with a display device using a shell-type LED lamp.

The LED display and a RAM (Random, Acc) for temporarily storing input display data
ess, memory) and data stored in the RAM, a gradation control circuit for calculating a gradation signal for lighting the light emitting diode to a predetermined brightness, and a light emitting diode which is switched by an output signal of the gradation control circuit to light the light emitting diode An LED display device was constructed by electrically connecting a CPU driving means having a driver for driving the CPU. Even in the vicinity of the LED display, color tone unevenness in each opening was not confirmed.

[0071]

According to the constitution of the present invention, it is possible to obtain a light emitting diode having high luminance and high reliability with less color tone unevenness due to color mixture even at a high viewing angle.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a light emitting diode of the present invention.

FIG. 2 is a schematic sectional view showing another light emitting diode of the present invention.

FIG. 3 shows an LE to which the light emitting device of the present invention is applied.
It is a schematic diagram of a D display.

FIG. 4 is a partial schematic cross-sectional view taken along the line AA of FIG. 3;

FIG. 5 is a schematic cross-sectional view for explaining the operation of the present invention, and FIG. 5A is a cross-sectional view of a light-emitting device shown for comparison, and FIG. FIG. 1 is a schematic sectional view of the present invention.

FIG. 6 is a drawing showing color tone unevenness of Example 1 and Comparative Example 1, wherein a solid line indicates Example 1 and a broken line indicates Comparative Example 1.

FIG. 7 is a graph showing life test results of Example 1 and Comparative Example 1, where a solid line indicates Example 1 and a broken line indicates Comparative Example 1.

[Description of sign]

 101, 201, 401: first coating portion 102, 202, 402: second coating portion 103, 203, 403: LED chip 104: mount lead 105: inner lead 106, 206: Electrical connection member 107: Mold member 204: External electrode 207: Package 404: Substrate 405: Conductor wiring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hayato Takeuchi 491 Kagaminakacho, Anan-shi, Tokushima Prefecture 100 Nichia Chemical Industry Co., Ltd.

Claims (11)

[Claims] 1. An LED chip capable of emitting blue light using a gallium nitride-based compound semiconductor as a light emitting layer, a pair of external electrodes respectively connected to respective electrodes of the LED chip, and provided on the LED chip. A light emitting diode having a coating portion, wherein the coating portion is disposed on the first coating portion and is excited by visible light emitted from the LED chip while being disposed on the first coating portion. A light-emitting diode comprising a light-transmitting second coating portion containing a fluorescent substance that emits visible light whose wavelength has been converted. 2. The light emitting diode according to claim 1, wherein a white color is displayed by a mixed color display of the visible light emitted from the LED chip and the wavelength-converted visible light from the fluorescent substance. 3. The light emitting diode according to claim 1, wherein a mold member is provided on the second coating portion. 4. The method according to claim 1, wherein a difference in optical path length of light from the LED chip passing through the coating portion containing the fluorescent material is substantially reduced, so that color unevenness is reduced through the second coating portion. The light emitting diode according to claim 1, wherein the first coating portion and the LED chip are arranged. 5. The light emitting diode according to claim 1, wherein in the LED chip, the light emitting layer formed on a sapphire substrate is made of InGaN. 6. The fluorescent substance is (Re _1-x Sm _x )
_{3 (Al 1-y Ga y} ) 5 O 12: light emitting diode according to claim 1 is Ce. Here, 0 ≦ x <1, 0 ≦ y ≦ 1, and Re is at least one element selected from the group consisting of Y, Gd, La, Lu, and Sc. 7. The light emitting diode according to claim 1, wherein the first and second coating members are made of a transparent resin or glass. 8. An LED chip capable of emitting blue light using a gallium nitride-based compound semiconductor as a light emitting layer, a coating portion provided on the LED chip, and a pair of electrodes respectively connected to the electrodes of the LED chip. A light emitting diode having an external electrode, wherein the coating portion includes a thin film containing a fluorescent substance that emits visible light whose wavelength has been converted by being excited by visible light from the LED chip at least in part on the LED chip. A light-emitting diode formed by bonding. 9. An LED chip capable of emitting blue light, wherein the light emitting layer disposed in the reflection cup of the mount lead is a gallium nitride compound semiconductor, and electrically connected to the LED chip using a conductive wire. A light-emitting diode having an inner lead and an LED chip, a conductive wire, and a mold lead that covers a part of the mount lead and the inner lead, wherein the reflection cup is provided on the LED chip. A first coating portion having a light-transmitting property, and a fluorescent material disposed on the first coating portion and emitting visible light whose wavelength has been converted by being excited by visible light emitted from the LED chip. A light-emitting diode comprising: a light-transmitting second coating portion. 10. The light emitting diode according to claim 9, wherein the mold member has a lens shape. 11. An LE capable of emitting blue light having a light-emitting layer made of a nitride-based compound semiconductor disposed in a cup.
A step of injecting a translucent resin onto the D chip to form a first coating part; and a step of converting visible light excited by visible light emitted from the LED chip onto the first coating part and wavelength-converted. Injection of a translucent resin containing a fluorescent substance that emits
Forming a coating part of the light emitting diode.