JP2004080058A - Light emitting diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting diode with improved color tone unevenness due to a light emission observation direction.
The present invention relates to a light emitting device including an LED chip, a fluorescent material that absorbs at least a part of the light emitted from the LED chip and converts the wavelength to emit light, and a mold member that covers the fluorescent material and the LED chip. The light emitting diode is a diode, wherein the phosphor is disposed on a buffer layer provided on the LED chip. As a result, color tone unevenness on the emission observation surface and variation in emission color of each light emitting diode can be extremely reduced.
[Selection diagram] Fig. 1

Description

The present invention relates to a light emitting device used for an LED display, a backlight light source, a traffic light, an illuminated switch, various sensors, various indicators, and the like, and in particular, emits light by converting the wavelength of light emitted from an LED chip as a light emitting element. The present invention relates to a light emitting diode having a fluorescent material, which has improved light emitting direction, color tone unevenness, and mass productivity.

Light emitting diodes (hereinafter, also referred to as LEDs), which are light emitting devices, are small, efficient, and emit bright colors. In addition, since it is a semiconductor element, there is no risk of a broken ball. It has excellent drive characteristics and is resistant to vibration and ON / OFF lighting. Therefore, it is used as various indicators and various light sources. However, LEDs have an excellent monochromatic peak wavelength, and therefore cannot emit a light emission wavelength such as white light.

Therefore, the present applicant has proposed a light emitting diode capable of performing color conversion of light emitted from a blue light emitting diode by using a blue light emitting diode and a fluorescent substance to emit light of another color or the like, as disclosed in JP-A-5-152609 and JP-A-7-99345. A light-emitting diode described in Japanese Patent Application Publication No. 1993-175, etc. was developed. With these light-emitting diodes, one type of LED chip can emit another luminescent color such as white or green using a blue LED chip.

Specifically, an LED chip capable of emitting blue light is arranged on a cup provided at the end of the 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 resin mold member that covers the LED chip. By selecting a blue light emitting diode and a fluorescent substance that absorbs the emitted light and emits a yellow light, white light can be emitted using mixed colors.

JP-A-5-152609.

JP-A-7-99345.

However, such a light emitting diode is formed by incorporating a fluorescent substance into a resin and injecting it through a nozzle. Therefore, it takes an extremely long time for injection and it is difficult to apply a uniform amount. In particular, in the case of an LED display in which a plurality of LED chips are arranged, light emitted from the openings arranged in a dot matrix shape may appear to be different colors, which is a particular problem.

Further, there is a problem that color unevenness is slightly generated on the light emission observation surface of the light emitting diode. Specifically, when viewed from the light emission observation surface side, a central portion where the LED chips are arranged is blueish, and a yellow, green or redish portion may be seen in a ring shape around the central portion. 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.

Such color non-uniformity caused by directly viewing the light emission observation surface is not only unfavorable in quality but also causes color non-uniformity in the display surface when used in a display device and error in precision equipment such as an optical sensor. .

As another method, a method of forming a phosphor layer on an LED chip by precipitating a particulate phosphor can be considered. By such a method, a light emitting diode capable of emitting light uniformly can be obtained. However, on the light emitting diode formed by sedimentation of the phosphor, the phosphor is formed to an unnecessary portion, which is not preferable in mass production. An object of the present invention is to solve the above-mentioned problems and to provide a light-emitting diode with excellent mass productivity, in which color tone unevenness on a light-emission observation surface and variation among light-emitting diodes are extremely small.

The present invention is a light emitting diode having a fluorescent substance that absorbs at least a part of light emitted from an LED chip and converts the wavelength to emit light. In particular, the light-emitting diode of the present invention includes an LED chip, a fluorescent substance that absorbs at least a part of the light emitted from the LED chip and converts the wavelength to emit light, and a mold member that covers the fluorescent substance and the LED chip. Wherein the phosphor is disposed on a buffer layer provided on the LED chip.

色 The color unevenness on the light emitting surface and the variation among the light emitting diodes can be extremely reduced. Even if the amount of the fluorescent substance disposed on the LED is extremely small, the amount of the fluorescent substance can be controlled relatively uniformly. Therefore, it is possible to provide a light emitting diode with less color tone unevenness and variation on the light emission observation surface.

As a result of various experiments, the inventor of the present invention has found that, by arranging the fluorescent substance disposed on the LED chip via the buffer layer, the color tone unevenness on the light emission observation surface and the variation among light emitting devices are improved with good mass productivity. The inventors have found that a light emitting diode can be used, and have accomplished the present invention.

(1) An example of the light emitting diode of the present invention will be described with reference to FIG. In FIG. 1, a multi-layer laminated ceramic substrate is used as the substrate on which the LED chips are arranged. A large number of openings are provided in the ceramic substrate in a dot matrix shape. An LED chip is arranged in the opening, and is configured to be electrically connectable to a conductive pattern in a ceramic substrate. The ceramic substrate can be divided for each dot matrix.

ＬＥＤ Die-bond LED chips to each opening of the ceramic substrate using epoxy resin. As the LED chip, a nitride-based compound semiconductor element capable of emitting blue light was used.

The electrode of the LED chip and the conductive pattern formed on the ceramic substrate were bonded with an Ag paste. Then, a perylene-based organic fluorescent dye is selected and applied from an ink jet printer on the LED chips arranged in the respective openings. The organic fluorescent dye uses a perylene derivative capable of absorbing blue light from the LED chip and emitting yellow light. An LED display can be obtained by selectively disposing the LED chip and the fluorescent substance in the openings arranged in a dot matrix form. Further, if a cut is formed so that the dot matrix can be divided at the time of forming the ceramic substrate, the light emitting diode can be divided into a plurality of light emitting diodes by pressing. The divided ones can function as individual light emitting diodes capable of emitting white light. Hereinafter, the constituent members of the present invention will be described in detail.
(Inkjet printing method)
The ink jet printing method of the present invention is a method of driving the ink jet print head 200 based on the application data to apply the fluorescent material 101. In the ink jet printer head 200, the fluorescent substance 101 introduced into a minute pressure chamber is caused to fly from a nozzle 302 and adhere to the LED chip 103 or the like. Means for increasing the pressure in the pressure chamber include those that operate a piezoelectric element, those that instantaneously raise the temperature of a part of the pressure chamber to generate bubbles, and that cause the fluorescent substance to fly by the pressure of the bubble generation. Is mentioned. Therefore, in the case of a particulate phosphor, it is preferable to mix it with an alcohol, a silicone resin, an epoxy resin, or the like so that the particulate phosphor can be applied by an ink-jet printing method, so that it can be printed. In this case, if the phosphor particles are large with respect to the nozzle 302 of the inkjet printer head 200, clogging may occur. Further, if the particle diameter is irregular, clogging tends to occur even if the particle diameter of the phosphor is smaller than the nozzle diameter. Therefore, when the particulate phosphor is applied by the ink jet printing method, it is desirable to filter and make the particle diameter and the shape of about several μ uniform. Further, when a particulate phosphor is used, it is preferable to use a piezoelectric element because it can cope with a particulate phosphor having a larger particle diameter than a phosphor using bubbles. Inkjet printheads can have resolutions on the order of 600 dpi to 1200 dpi. Therefore, a fluorescent substance can be formed at an arbitrary position on the LED chip.

物質 As a substance emitted from the ink jet printer head, a light stabilizer or an infrared reflecting member can be mixed and emitted in addition to the phosphor. Examples of such a light stabilizer include a benzotriazole-based ultraviolet absorber, and titanium oxide as an infrared reflective member.

The following method is preferably mentioned as a specific method of driving the ink jet printer head and opening the package in a dot matrix form. The openings of the packages arranged in a matrix in advance are stored in the memory of the ink jet printer, and the ink jet printer head is driven vertically and horizontally along the memory. An alcohol or the like containing a phosphor is released from only the opening of the package arranged in a dot matrix form from the ink jet printer head, and the phosphor is coated on the buffer layer.

Next, in a state where each LED chip emits light, the light sensor is scanned to store the emission color and the location of the LED chip in the memory. When the amount of the fluorescent substance is smaller than the emission color of each LED chip read by the optical sensor and the reference emission color, the amount of the additional fluorescent substance is calculated. Based on the calculated application amount, a desired amount of the fluorescent substance is applied again from the ink jet printer head selectively only at the opening. (Alternatively, a desired amount of the fluorescent substance having a different composition is selectively applied again from the ink jet printer head only on the opening portion based on the calculated emission color.) Depending on the accuracy of the optical sensor and the ink jet printer head, In addition, it is possible to select which position in the package opening to apply the fluorescent substance.
(Fluorescent substance 101)
The fluorescent substance 101 used in the present invention is a substance that emits light when excited by at least light emitted from the semiconductor light emitting layer of the LED chip 103. When the light emitted by the LED chip 103 and the light emitted by the fluorescent substance 103 are in a complementary color relationship or the like, furthermore, the light from the LED chip 103 is ultraviolet light, and the light of two or more fluorescent substances excited by the ultraviolet light. Are complementary colors, white light can be emitted by mixing the respective lights. Specifically, the light from the LED chip 103 and the light of the fluorescent substance 101 excited and emitted by the LED chip 103 correspond to the three primary colors of light (red, green, and blue), or the LED chip emits light. Blue light and yellow light of a fluorescent substance which is excited and emits light by the blue light.

The emission color of the light emitting diode variously adjusts the amount of the fluorescent substance 101 disposed on the LED chip 103 (that is, the amount of the fluorescent substance applied by the inkjet printing method at one time, the number of times the inkjet printing method is repeated, and the like). In addition, by selecting the light emission wavelength of the LED chip 103, an arbitrary white color tone such as a bulb color can be provided.

Specific examples of the fluorescent substance 101 include a perylene-based fluorescent dye and a yttrium-aluminum-garnet-based fluorescent substance activated with cerium. In particular, at the time of high luminance and long-term use _{(Re 1-x Sm x)} 3 (Al 1-y Ga y) 5 O 12: Ce (0 ≦ x <1,0 ≦ y ≦ 1, where, Re Is at least one element selected from the group consisting of Y, Gd, and La). Fluorescent Particularly material _{101 (Re 1-x Sm x} ) 3 (Al 1-y Ga y) 5 O 12: in the case of using the Ce is placed in contact with the LED chip 103 or close to the irradiance (Ee ) = 3 W · cm ⁻² or more and 10 W · cm ⁻² or less, a light emitting diode having sufficient light resistance can be obtained with high efficiency.

_{(Re 1-x Sm x)} 3 (Al 1-y Ga y) 5 O 12: Ce phosphor 101, for garnet structure, heat, resistant to light and moisture, the peak of the excitation spectrum is like in the vicinity of 470nm be able to. Further, the emission peak is around 580 nm, and a broad emission spectrum with a tail extending to 720 nm can be provided. Moreover, the emission wavelength shifts to a short wavelength by replacing part of the Al in the composition with Ga, and shifts to the long wavelength by replacing 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 the white light emission such that the intensity on the long wavelength side can be continuously changed by the composition ratio of Gd.

Such a phosphor uses an oxide or a compound which easily becomes an oxide at a high temperature as a raw material of Y, Gd, Ce, Sm, Al, La and Ga, and sufficiently mixes them in a stoichiometric ratio. To obtain the raw material. Alternatively, a coprecipitated oxide obtained by calcining a solution obtained by dissolving a rare earth element of Y, Gd, Ce, and Sm in an acid at a stoichiometric ratio with oxalic acid, and aluminum oxide and gallium oxide Mix to obtain a mixed raw material. An appropriate amount of a fluoride such as ammonium fluoride is mixed into the crucible as a flux, and the mixture is baked in air at a temperature of 1350 to 1450 ° C. for 2 to 5 hours to obtain a baked product. Next, the fired product is ball-milled in water, washed, separated, dried, and finally passed through a sieve to obtain a desired particulate phosphor.

In the light emitting diode of the present invention, two or more kinds of fluorescent substances may be mixed. That, 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) 5 O 12: by mixing Ce phosphor RGB wavelength components can be increased. Further, at present, there is a variation in the emission wavelength of the LED chip which is a semiconductor light emitting element, so that desired white light or the like can be obtained by mixing and adjusting two or more kinds of fluorescent substances 101. Specifically, by adjusting and including the amount of the fluorescent substance 101 having different chromaticity points according to the emission wavelength of the light emitting element, an arbitrary point on the chromaticity diagram connected between the fluorescent substances and the light emitting element is emitted. be able to.
(Buffer layer 102)
The buffer layer 102 used in the present invention is arranged on the LED chip 103 to reduce unevenness caused by the LED chip 103 and external electrodes. Further, it is intended to reduce damage to the LED chip 103 and the like due to the fluorescent substance 101 flying by the ink jet printing method. Specific examples of the material of the buffer layer 102 include an epoxy resin, a silicone resin, and glass. Such a buffer layer 102 can be formed on the LED chip 103 at the opening of the package 105 by releasing and curing epoxy resin or the like from a nozzle.

Further, by providing the buffer layer 102, the light emitted from the LED chip 103 is not directly reflected or scattered by the fluorescent substance 101. Therefore, the high-energy light emitted from the LED chip 103 does not have a high density, and even if an organic fluorescent dye or the like is used, the fluorescent substance 101 and the buffer layer 102 are hardly deteriorated.
(LED chip 103)
The LED chip 103 used in the present invention can excite the fluorescent substance 101 to emit light. The LED chip 103 serving as a light-emitting element has a semiconductor such as GaAs, InP, GaAlAs, InGaAlP, InN, AlN, GaN, InGaN, AlGaN, or InGaAlN formed as a light-emitting layer on a substrate by MOCVD or the like. Examples of the semiconductor structure include a homostructure having a MIS junction, a PIN junction, and a PN junction, a heterostructure, and a double heterostructure. Various emission wavelengths can be selected depending on the material of the semiconductor layer and the degree of mixed crystal thereof. Further, 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. The LED chip 103 used in the present invention is preferably a nitride-based compound semiconductor (general formula: In _i Ga _j Al _k N, where 0 ≦≦), which can efficiently emit a relatively short wavelength capable of efficiently exciting the fluorescent substance 101. i, 0 ≦ j, 0 ≦ k, i + j + k = 1).

When a gallium nitride-based compound semiconductor is used, a material such as sapphire, spinel, SiC, Si, ZnO, or GaN is preferably used for the semiconductor substrate. In order to form gallium nitride having good crystallinity, it is more preferable to use a sapphire substrate. When a semiconductor film is grown on a sapphire substrate, it is preferable to form a buffer layer such as GaN or AlN and form a gallium nitride semiconductor having a PN junction thereon. Further, a GaN single crystal itself selectively grown on a sapphire substrate using SiO ₂ as a mask can be used as the substrate. In this case, the light emitting element and the sapphire substrate can be separated by etching and removing SiO ₂ after forming each semiconductor layer. Gallium nitride-based compound 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, it is preferable to appropriately introduce Si, Ge, Se, Te, C, or the like as an N-type dopant. On the other hand, when forming a P-type gallium nitride semiconductor, P-type dopants such as Zn, Mg, Be, Ca, Sr, and Ba are doped.

The gallium nitride-based compound semiconductor is difficult to be converted into a P-type simply by doping with a P-type dopant, so that it is preferable to convert the gallium nitride-based compound semiconductor into a P-type by introducing a P-type dopant and then annealing by heating with a furnace, low-speed electron beam irradiation, plasma irradiation, or the like. . As a specific layer configuration of the light emitting element, a gallium nitride, an aluminum-gallium nitride semiconductor, an n-type contact layer, a gallium nitride semiconductor, and a sapphire substrate having a buffer layer formed of gallium nitride, aluminum nitride, etc. An N-type cladding layer, an active layer of an indium gallium nitride semiconductor doped with Zn and Si, a P-type cladding layer of an aluminum-gallium nitride semiconductor, and a P-type contact layer of a gallium nitride semiconductor are laminated. Preferred examples are given. In order to form the LED chip 103, in the case of the LED chip 103 having a sapphire substrate, after forming an exposed surface of the P-type semiconductor and the N-type semiconductor by etching or the like, a sputtering method, a vacuum evaporation method, or the like is formed on the semiconductor layer. Each electrode of a desired shape is formed by using the same. In the case of a SiC substrate, a pair of electrodes can be formed using the conductivity of the substrate itself.

Next, the formed semiconductor wafer or the like is directly full-cut by a dicing saw in which a blade having a diamond cutting edge is rotated, or a groove having a width wider than the cutting edge width is cut (half cut). Crack the wafer. Alternatively, an extremely thin scribe line (meridian) is drawn on the semiconductor wafer, for example, in a grid pattern using 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, the LED chip 103 which is a nitride-based compound semiconductor can be formed.

When the light emitting diode of the present invention emits white light, the main emission wavelength of the LED chip 103 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 complementary color with the fluorescent substance 101. In order to further improve the efficiency of the LED chip 103 and the efficiency of the fluorescent substance 101, the thickness is more preferably 450 nm or more and 475 nm or less.
(External electrode 104)
The external electrode 104 is used for supplying power from outside the package 105 to the LED chip 103 disposed inside. Therefore, there are various types such as those using a conductive pattern provided on the package 105 and a lead frame. Further, the external electrode 104 can be formed in various sizes in consideration of heat dissipation, electric conductivity, characteristics of the LED chip 103, and the like. It is preferable that the external electrodes 104 have good thermal conductivity in order to dispose the LED chips 103 and radiate the heat emitted from the LED chips 103 to the outside. The specific electrical resistance of the external electrode 104 is preferably 300 μΩ · cm or less, more preferably 3 μΩ · cm or less. Further, specific heat conductivity, 0.01cal / (s) (cm 2) (℃ / cm) or more, more preferably ^{0.5cal / (s) (cm 2} ) (℃ / cm) or higher It is.

As the external electrode 104, a copper or phosphor bronze plate whose surface is plated with a metal such as silver, palladium or gold, or a solder plating is preferably used. When a lead frame is used as the external electrode 104, it can be variously used depending on electric conductivity and heat conductivity, but from the viewpoint of workability, the plate thickness is preferably 0.1 mm to 2 mm. As the external electrode 104 provided on a support such as glass epoxy resin or ceramic, a copper foil or a tungsten layer can be formed. When a metal foil is used on a printed circuit board, the thickness of the copper foil or the like is preferably 18 to 70 μm. Further, gold, solder plating, or the like may be applied on copper foil or the like.
(Package 105)
The package 105 functions as a support for fixing and protecting the LED chip 103. Further, an external electrode 104 which can be electrically connected to the outside is provided. A package 105 having a plurality of openings may be provided according to the number and size of the LED chips 103. The package 105 may be provided with a mold member 106 to further protect the LED chip 103 from the external environment. The package 105 preferably has good adhesion to the mold member 106 and high rigidity. It is desired that the LED chip 103 has an insulating property in order to electrically disconnect the LED chip 103 from the outside. Further, when the package 105 is affected by heat from the LED chip 103 and the like, it is preferable that the package 105 has a small coefficient of thermal expansion in consideration of adhesion to the mold member 106.

The package 105 may be formed integrally with the external electrode 104, or the package 105 may be divided into a plurality of parts and combined with each other by fitting or the like. The package 105 can be formed relatively easily by insert molding or the like. As a material of the package 105, a resin such as a polycarbonate resin, polyphenylene sulfide (PPS), a liquid crystal polymer (LCP), an ABS resin, an epoxy resin, a phenol resin, an acrylic resin, and a PBT resin, or a ceramic can be used. Further, it is preferable that the package is colored in a dark color such as black or gray in order to have a light shielding function, or that the light emission observation surface side of the package is colored in a dark color. Specifically, Cr ₂ O ₃ , MnO ₂ , Fe ₂ O ₃ , carbon black and the like are preferably exemplified.

(4) The bonding between the LED chip 103 and the package 105 can be performed with a thermosetting resin or the like. Specifically, an epoxy resin, an acrylic resin, an imide resin, or the like is used. In this case, it is preferable that the electrodes of the LED chip 103 and the external electrodes 104 provided on the package 105 are electrically connected by wire bonding with a conductive wire. In order to dispose and fix the LED chip 103 and electrically connect the LED chip 103 to the external electrode 104 of the package 105, an Ag paste, a carbon paste, an ITO paste, a metal bump, or the like is preferably used.

In particular, when a multilayer laminated ceramic substrate is used as the substrate, an LED display or a light emitting diode can be formed relatively easily using an inkjet printing method. Specifically, the package 105 can be formed by stacking and sintering green sheets having a large number of openings in a dot matrix shape. An LED chip 103, a buffer layer 102, a fluorescent substance 101, and the like can be arranged in each opening of the package. Therefore, a high-definition LED display can be configured by using this as it is. Also, a notch can be provided so that the dot can be divided for each dot when the ceramic substrate is formed. After the LED display is formed, it can be divided into light emitting diodes of a desired size by applying pressure along the cuts. The divided light emitting diodes can be light emitting diodes arranged in a line or a plurality of light emitting diodes depending on the shape of the division.
(Mold member 106)
The mold member 106 is suitably used for protecting the LED chip 103 and the fluorescent substance 101 from the outside, and is preferably one that can efficiently transmit light emitted from the LED chip 103 and the fluorescent substance 101. When the inorganic phosphor particles are applied by the inkjet printing method, it is preferable to provide the mold member 106 because the inorganic phosphor particles do not adhere when the solvent that melts the buffer layer 102 is not contained. The fluorescent material can be held in the package opening by the mold member 106. As such a specific material of the mold member 106, various materials such as a silicone resin, an epoxy resin, and glass are preferably exemplified. Hereinafter, although an example of the present invention is described, it goes without saying that the present invention is not limited to only specific examples.

(Example 1)
An In _0.2 Ga _0.8 N semiconductor having a main emission peak of 465 nm was used as an LED chip. For 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 are formed to form a PN junction. As a semiconductor light emitting device, a contact layer made of a gallium nitride semiconductor having N-type conductivity, a clad layer made of a gallium aluminum nitride semiconductor having P-type conductivity, and a contact layer made of a gallium nitride semiconductor having P-type conductivity are formed. I let it. A non-doped InGaN active layer having a thickness of about 3 nm and a single quantum well structure was formed between a contact layer having N-type conductivity and a cladding layer having P-type conductivity. (Note that a gallium nitride semiconductor is formed at a low temperature on a sapphire substrate to serve as a buffer layer. A semiconductor having P-type conductivity is annealed at 400 ° C. or more after film formation.)
After exposing the surface of each PN semiconductor on the sapphire substrate by etching, each electrode was formed by sputtering. After a scribe line was drawn on the semiconductor wafer thus completed, the wafer was divided by an external force to form a 350 μm square LED chip as a light emitting element.

On the other hand, a chip type LED package was formed by insert molding using a polycarbonate resin. The package of the chip type LED has an opening in which the LED chip is arranged. In the package, a silver-plated copper plate is arranged as an external electrode. The LED chip is fixed face down inside the package. For fixing, each electrode of the LED chip and the external electrode are made using an epoxy resin containing Ag, and the electrical connection is made at the same time. After curing the epoxy resin containing Ag, the epoxy resin was injected into the opening of the package to form a buffer layer. In this way, 8280 packages on which the LED chips were arranged were formed. A package in which 8280 LED chips are arranged is closely arranged in a dot matrix.

On the other hand, 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. The (Y _0.8 Gd _0.2 ) ₃ Al ₅ O ₁₂ : Ce _0.03 phosphor thus formed is dispersed and dispersed in alcohol.

(4) The openings of the packages arranged in a matrix in advance are stored in the memory of the ink jet printer, and the ink jet printer head is driven vertically and horizontally along the memory. Alcohol containing a fluorescent substance is released only from the opening of the package arranged in a dot matrix form from the ink jet printer head to apply the fluorescent substance on the buffer layer.

Next, in a state where each LED chip emits light, the light sensor is scanned to store the emission color and the location of the LED chip in the memory. When the amount of the fluorescent substance is smaller than the light emission color of each LED chip read by the optical sensor and the reference light emission color, the application amount of the fluorescent substance is calculated. Based on the calculated application amount, a desired amount of the fluorescent substance is applied again from the ink jet printer head selectively only at the opening.

(4) After the alcohol component in the package was removed by heating, a translucent epoxy resin was poured as a mold member into the package opening for the purpose of protecting the LED chip and the particulate phosphor from external stress, moisture, dust and the like. After injecting the translucent epoxy resin, the resin was cured at 150 ° C. for 5 hours. Thus, a light emitting diode as a light emitting device as shown in FIG. 1 was formed.

白色 White light can be emitted by supplying power to the obtained light emitting diode. The color temperature measured from the front of the light emitting diode was 8000K. Almost no color unevenness was observed on the light emission observation surface of each light emitting diode. Further, about 98% of the light emitting diodes were distributed in a range surrounded by x, y = (0.305, 0.320) ± 0.03 on the CIE chromaticity diagram.

FIG. 1 is a schematic sectional view of a chip type LED which is a light emitting diode of the present invention. FIG. 2 is a schematic front view of the LED display while a fluorescent substance is being applied by the inkjet printer head of the present invention. FIG. 3 is a schematic explanatory view for explaining the printing principle by the ink jet printer head for forming the light emitting diode of the present invention.

Explanation of reference numerals

101, 201, 301 ... fluorescent substance 102 ... buffer layers 103 and 203 ... LED chips 104 and 204 ... external electrodes 105 ... LED chips 106 ... molding members 200 and 300 ... Inkjet printer head 205: package having an opening in which LED chip and fluorescent substance can be arranged 302: nozzle capable of emitting fluorescent substance

Claims (1)

An LED chip, a fluorescent substance that absorbs at least a part of light emitted from the LED chip and emits light by wavelength conversion, and a light emitting diode having a mold member that covers the fluorescent substance and the LED chip,
The light emitting diode according to claim 1, wherein the fluorescent material is disposed on a buffer layer provided on the LED chip.

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