JP3087828B2 - LED display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display capable of displaying various data, a light source and a display of a line sensor, and more particularly to an LED display having a light emitting portion capable of emitting white light with high definition.

[0002]

2. Description of the Related Art Today, LED chips capable of emitting ultra-high luminance of up to 1000 mcd in RGB (red, green, and blue) have been developed. Along with this,
2. Description of the Related Art LED displays that perform full-color display by performing mixed-color light emission using respective LED chips that can emit red (R), green (G), and blue (B) light are being installed. Examples of the purpose of use of such an LED display include a large-sized video device using a full-color type, as well as a character display board used indoors and outdoors. Specifically, as shown in FIG. 3, the LED chips capable of emitting RGB light are respectively arranged in the cup of the mount lead, and each LED chip and the inner lead are electrically connected to each other using a conductive wire or the like. It is. Further, an LED lamp is formed by covering at least a part of each LED chip, conductive wire and lead frame with a mold resin. When configuring an LED display using such an LED lamp,
When mounted on a printed wiring board in a dot matrix, etc.
It is formed by connecting to the ED drive circuit board using connection pins or connectors. Such an LED display can emit white light by causing each LED chip in the LED lamp to emit light.

[0003]

SUMMARY OF THE INVENTION However, LEDs
Since the chip has an excellent monochromatic peak wavelength, each LED chip has to be driven even in a black-and-white display that displays only white display. Also, each L
In order to dispose the ED chip and establish electrical connection, the LED lamp on the substrate needs a certain size. Furthermore, in order to improve the color mixing of RGB, it may not be enough to just bring the LED chips closer. In order to improve the color mixing, it was necessary to use a mold member or the like having a lens effect. Therefore, there is a limit to miniaturization of an LED display using an LED lamp.

Therefore, for high-density display applications, it is difficult to reduce the dot pitch because the diameter is limited to a single LED lamp diameter (3 to 5φ) in which RGB LED lamps and the like are arranged. For example, in a matrix display having 16 × 16 dots, even if a 5φ LED lamp is used, the production of a display substrate of about 96 mm square having a dot pitch of about 6 mm is currently limited.

In addition, in the LED lamp structure having a lead frame, a through hole is required in a printed circuit board at the time of mounting, so that the complexity of wiring design and the arrangement of connection pins or connectors due to the reduction in the wiring area of the board are reduced. The problem that it becomes difficult arises. Furthermore, the lamp height is 10
Since it is about 15 mm, it is difficult to reduce the thickness of the display unit. In addition, the directional characteristics of the light source are limited by the lens shape of the LED lamp (for example, the half-value angle ±
(30 degrees, etc.) There is a case where it is unsuitable for a display device having a high viewing angle.

Surface mount type LEDs (hereinafter referred to as chip type L)
Also called ED. In the case of (2), the outer size can be made slightly smaller than that of a shell-type lamp LED or the like. However, in order to arrange a large number in the same plane, an interval between adjacent LED chips is required in consideration of a surface mounting device and a repair process. Therefore, even for a surface-mount type LED, the RG
When the LED chips of B are mounted, it is difficult to mount them at high density.

Further, in a high-density mounting LED display using LED chips capable of emitting three colors of RGB,
Heat radiation from the lead frame of the ED lamp or the like is not sufficient. Therefore, heat dissipation from the substrate is required, which is considered to be difficult with a printed wiring board. Therefore, the present invention solves the above-described problems, and has a high minuteness and a high viewing angle,
It is an object of the present invention to provide a highly reliable and thin LED display.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided a substrate provided with a conductor wiring and having two or more concave openings, and a gallium nitride-based compound semiconductor electrically connected to the conductor wiring in the concave opening. An LED chip included in the light emitting layer, and (RE _1-x Sm _x ) ₃ (Al _1-y G _ay )
An LED display sealed with a coating member having ₅ O ₁₂ : Ce fluorescent material, wherein the substrate is a ceramic,
An LED display, which is one selected from a metal substrate and a heat-resistant organic resin containing a thermally conductive filler. (However, 0 ≦ x <1, 0 ≦ y ≦ 1, RE is Y, G
At least one element selected from the group consisting of d and La. )

[0009]

According to the present invention, an LED chip having a gallium nitride-based compound semiconductor capable of emitting blue light and a (RE _1-x S
(m _X ) ₃ (Al _{1 -y} G _ay ) ₅ O ₁₂ : Ce fluorescent substance is arranged on a substrate having a conductor wiring layer having excellent heat dissipation and two or more concave openings provided in close proximity. In this case, an LED display capable of emitting white light with higher definition and a higher viewing angle can be obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of various experiments, the present inventor has selected a specific semiconductor light emitting element, a fluorescent substance and a matrix substrate to obtain an LED display capable of high-density white light emission with good color mixing. The inventors have found that the present invention can be performed, and have accomplished the present invention.

That is, when an LED chip and a fluorescent substance excited by light from the LED chip are arranged on a substrate having two or more adjacent openings, the LED chip is made of a gallium nitride based semiconductor and a fluorescent substance. RE _1-x Sm _X )
_{3 (Al 1-y Ga y} ) 5 O 12: Ce, 2 or more ceramic substrates having a concave opening, a metal substrate, color mixing by 1 that Tsutosa cells selected from the thermally conductive filler-containing heat-resistant organic resin This is an LED display capable of emitting white light with high precision and fineness.

The LED chip can emit blue light with high luminance. Fluorescent materials are efficient due to light emission from LED chips and have good light resistance even under high irradiation.
Light emission having a complementary color relationship with the light emission color from the chip is possible. In addition, the substrate is required to have such a feature that the LED chip and the fluorescent substance can be arranged with high precision and that the heat from the LED chip can be efficiently released to the outside.
By adopting the configuration of the present invention that satisfies these conditions, even under ultra-high density such as a dot pitch of 2 mm and an opening diameter of about 1.5 mm, an LED display with very little color shift and a decrease in emission luminance is obtained. It can be a vessel.

As a specific example, an LED display device is shown in FIG. An LED chip using a gallium nitride-based semiconductor is fixed to a light-emitting portion in an opening arranged in a dot matrix of a ceramic substrate using an epoxy resin or the like. LED gold wire as conductive wire
Each electrode of the chip is electrically connected to a gold plating pattern formed on a ceramic substrate. A mixture of (RE _1-x Sm _x ) ₃ (Al _1-y G _ay ) ₅ O ₁₂ : Ce fluorescent material dispersed in silicon rubber is injected and uniformly cured. Light can be emitted by supplying power to such an LED display.
Such light emission can emit white light or the like by mixing colors of light emission from the LED chip and light emission from a fluorescent substance excited by the light emission. Hereinafter, the constituent members of the present invention will be described in detail.

(Substrate 101) The substrate 101 used in the present invention includes an electric connection member such as an LED chip 102 and a conductive wire 104 and a conductor wiring layer 105 provided with a plurality of concave openings containing a fluorescent substance. It has. 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. Can not be sufficiently radiate the heat from the LED chip, also _{(RE 1-x Sm X)} 3 (Al 1-y Ga y) 5 O 12: Ce fluorescent material coating portion if is uniformly dispersed in the resin In some cases, degradation such as partial cracking or coloring may occur.

Therefore, as the substrate having the conductor wiring layer 105 provided with the concave opening used in the present invention,
Coating part 10 containing fluorescent material with excellent heat dissipation
It is desired that the adhesiveness with No. 3 is good. Examples of the wiring substrate material having such a concave opening include a ceramic substrate, a metal substrate based on a metal and having a conductive wiring layer via an insulating layer, and a heat-resistant organic resin substrate containing a thermally conductive filler. In these substrates, it is possible to form a concave opening and a wiring portion layer with the same material, and to laminate a perforated substrate for a ceramic substrate, press processing for a metal substrate, and resin molding for an organic resin substrate. An LED display with an integrated wiring portion can be easily formed.

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% by weight, and 1500 to 17
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. Wiring 105
Can be formed by screen printing or the like into a desired shape on a green sheet or the like as a wiring pattern using a resin binder containing a high melting point metal such as tungsten or molybdenum. Also, by laminating the opened green sheets in multiple layers, the openings for containing the LED chips and the fluorescent substance can 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.

[0018] In addition, Cr ₂
Substrate surface 1 formed by incorporating O ₃ , MnO ₂ , TiO ₂ , Fe ₂ O _3, etc. into the green sheet itself
Only 06 can be made dark. 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. Further, the depth of the concave opening is determined by an angle within a range that does not block the direct light from the LED chip while preventing the slurry in which the fluorescent substance is dispersed from flowing out. Therefore, the depth of the concave opening is preferably 0.3 mm or more, and 0.5 mm or more and 2.0 mm or more.
mm is more preferable.

The concave opening of the substrate is for disposing the LED chip and the fluorescent substance therein. Therefore, L
It is sufficient that the ED chip has a size large enough to be directly mounted on a die bonding device or the like and to make electrical connection with the LED chip by wire bonding or the like. A plurality of concave openings can be provided as desired, and 16x
Various selections such as a 16 or 24 × 24 dot matrix and a linear shape can be made. When the dot pitch of the concave opening is 4 mm or less, the dot pitch can be greatly reduced as compared with the case where a bullet-type LED lamp is mounted. In addition, the configuration of the present invention provides a particularly excellent high-density LED display device that can solve various problems related to the heat radiation from the LED chip even in such a high minuteness. 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. Also, face-down LED
Ag paste, ITO, etc. are used to bond and electrically connect the wiring provided on the substrate with a chip or the like.
Paste, carbon paste, metal bumps and the like can be used. In addition, silver, gold, copper, platinum and their alloys are deposited or plated on the wiring formed on the substrate in order to improve the conductivity, the reflectance at the bottom of the substrate where the LED chips and the fluorescent substance are disposed, and the like. It can also be formed by performing processing or the like.

(Fluorescent substance) The fluorescent substance used in the present invention is a fluorescent substance which emits light when excited by visible light and ultraviolet light emitted from the semiconductor light emitting layer. Specific examples of the fluorescent substance include (RE _1-x Sm _x ) ₃ (Al _1-y G _ay ) ₅
O ₁₂ : Ce fluorescent material (provided that 0 ≦ x <1, 0 ≦ y ≦ 1,
RE is at least one element selected from the group consisting of Y, Gd, and La). When light emitted from an LED chip using a gallium nitride-based compound semiconductor and light emitted from a fluorescent substance are in a complementary color relationship or the like, white light is displayed when mixed light emission from the LED chip and light emission from the fluorescent substance is performed. System can be displayed. In order to fill the concave opening with a fluorescent substance, the fluorescent substance powder or the like can be contained in a resin or glass so as to be thin enough to transmit light from the LED chip. By variously adjusting the ratio, application and filling amount of the fluorescent substance and the resin, and selecting the emission wavelength of the light emitting element, it is possible to provide an arbitrary color tone such as a light bulb color including a white color having a high color temperature.

Further, the content distribution of the fluorescent substance also affects the color mixing property and durability. That is, when the distribution concentration of the fluorescent substance is higher from the surface side of the concave opening portion containing the fluorescent substance toward the LED chip, the fluorescent substance is less susceptible to moisture and the like from the external environment, so that deterioration due to moisture is easily suppressed.
On the other hand, when the distribution concentration of the fluorescent substance increases from the LED chip toward the surface of the concave opening, the distribution concentration is easily affected by moisture from the external environment, but heat generation from the LED chip,
The influence of the irradiation intensity and the like is smaller and the deterioration of the fluorescent substance can be suppressed. Such a distribution of the fluorescent substance can be variously formed by adjusting the member containing the fluorescent substance, the forming temperature, the viscosity, the shape of the fluorescent substance, the particle size distribution, and the like. Therefore, the distribution concentration of the fluorescent substance can be variously selected depending on the use conditions and the like.

The fluorescent substance of the present invention is particularly arranged in contact with or close to the LED chip and has an irradiance of (E
e) Even at 3 W · cm ^{−2 to} 10 W · cm ⁻² , sufficient light resistance can be obtained with high efficiency.

Since the fluorescent substance used in the present invention has a garnet structure, it is resistant to heat, light and moisture, and can have an excitation spectrum peak near 450 nm. Also, the main emission peak is around 530 nm and 700
It has a broad emission spectrum extending down to nm. 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 an ideal condition for converting the blue light emission of the nitride semiconductor into the white light emission such that the intensity on the long wavelength side can be continuously changed by the composition ratio of Gd.

In addition, LE using a gallium nitride based semiconductor
The light efficiency can be further improved by having a D chip and a fluorescent material containing a rare earth element samarium (Sm) in a yttrium aluminum garnet fluorescent material (YAG) activated with cerium.

Such fluorescent materials include Y, Gd, Ce,
An oxide or a compound which easily becomes an oxide at a high temperature is used as a raw material of Sm, Al, La and Ga, and these are sufficiently mixed in a stoichiometric ratio to obtain a raw material. Or Y, Gd,
A co-precipitated oxide obtained by calcining a solution obtained by dissolving a rare earth element of Ce, Sm, and La in an stoichiometric ratio with an acid in oxalic acid, and aluminum oxide and gallium oxide are mixed and mixed. Get the raw materials. 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.

[0027] _{(Y 1-pqr Gd p Ce} q Sm r) 3 Al 5 O 12
By containing Gd in the crystal of the fluorescent substance, it is possible to increase the excitation light emission efficiency particularly in a long wavelength region of 460 nm or more. Due to the increase in the content of gadolinium, the emission peak wavelength shifts to a longer wavelength from 530 nm to 570 nm, and the entire emission wavelength shifts to the longer wavelength side. When a reddish luminescent color is required, it can be achieved by increasing the substitution amount of Gd. On the other hand, as Gd increases, the emission luminance of photoluminescence due to blue light gradually decreases. Therefore, p is preferably 0.8 or less, and more preferably 0.7 or less. More preferably, it is 0.6 or less.

Containing Sm (Y _{1 -pqr} Gd _p Ce _q S
m _{r) 3} Al ₅ O ₁₂ phosphor, lowering of the temperature characteristics is small regardless of the increase in the content of Gd. By including Sm in this manner, the emission luminance of the fluorescent substance at a high temperature is greatly improved. The degree of the improvement increases as the content of Gd increases. That is, it was found that a composition in which the Gd was increased and the emission color tone of the fluorescent substance was imparted with reddish color was more effective in improving the temperature characteristics by the Sm content. (Note that the temperature characteristic here is expressed as a relative value (%) of the emission luminance of the same fluorescent substance at a high temperature (200 ° C.) with respect to the excitation emission luminance at room temperature (25 ° C.) of 450 nm blue light. Yes.)

The content of Sm is 0.0003 ≦ r ≦ 0.0
In the range of 8, the temperature characteristic is preferably 60% or more. When r is smaller than this range, the effect of improving the temperature characteristics is reduced. When r is larger than this range, the temperature characteristic is deteriorated. In the range of 0.0007 ≦ r ≦ 0.02, the temperature characteristic is most preferably 80% or more.

Ce has a relative light emission luminance of 70% or more in the range of 0.003 ≦ q ≦ 0.2. When q is 0.003 or less, the luminance decreases due to a decrease in the number of excitation and emission centers of photoluminescence by Ce. Conversely, when q exceeds 0.2, concentration quenching occurs.

In the present invention, two or more kinds of such fluorescent substances may be mixed. That is, Al, Ga, Y,
La and two or more (R) having different contents of Gd and Sm
E _1-x Sm _x ) ₃ (Al _1-y G _ay ) ₅ O ₁₂ : Ce phosphor can be mixed to increase the RGB wavelength components. Thereby, an LED display having higher color purity can be obtained.

(LED Chip 102) The LED chip 102 used in the present invention is (RE _1-x Sm _x ) ₃ (A
l _1-y Ga _y ) ₅ O ₁₂ : A nitride-based compound semiconductor that can efficiently excite a Ce fluorescent material. LED that is a light emitting element
The chip has a semiconductor such as InGaN 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. 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
And the like, 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, Si, G
It is preferable to appropriately introduce e, Se, Te, C, and the like.
On the other hand, when forming a P-type gallium nitride semiconductor, P
Type dopants Zn, Mg, Be, Ca, Sr, B
a and the like are doped. Gallium nitride based compound semiconductors
Since it is difficult to form a P-type by simply doping with a P-type dopant, it is preferable to form the P-type by annealing with heating in a furnace, low-speed electron beam irradiation, plasma irradiation, or the like after the introduction of the P-type dopant. After the exposed surfaces of the P-type semiconductor and the N-type semiconductor are formed by etching or the like, each electrode having a desired shape is formed on the semiconductor layer by 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 cutting edge rotates, or after a groove having a width wider than the cutting edge 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 of emitting white light in the present invention, the 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 complementary color relationship with the fluorescent substance and resin deterioration.
In order to further improve the efficiency of the LED chip and the efficiency of the fluorescent material, the thickness is more preferably 450 nm or more and 475 nm or less. FIG. 2 shows an example of the emission spectrum of the present invention.
Emission having a peak around 450 nm is emission from the LED chip, and emission having a peak around 570 nm is L
This is the emission of a fluorescent substance excited by the ED chip.

(Coating Member 103) The coating member 103 contains a fluorescent substance that converts the light emitted from the LED chip 102. As a specific material of the binder constituting the coating member, a transparent resin having excellent weather resistance, such as an epoxy resin, a urea resin, or silicone, or glass is suitably used. When the LED chips are arranged at a high density, it is more preferable to use an epoxy resin, a silicone resin, or a combination thereof in consideration of the disconnection of the conductive wire due to thermal shock. Although the fluorescent substance itself has a scattering property, a diffusing agent may be contained in order to further increase the viewing angle.
As a specific diffusing agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide, or the like is suitably used.

(Conductive Wire 104) The conductive wire 104 is a kind of electrical connection member for connecting the electrode of the LED chip 102 and the wiring of the substrate, and has ohmic properties, mechanical connectivity, and electrical conductivity. And those having good thermal conductivity are required. The thermal conductivity is 0.01 cal /
cm ² / cm / ° C. or higher, more preferably 0.1 cm ² / cm / ° C.
5 cal / cm ² / cm / ° C. or more. Also, the diameter of the conductive wire in consideration of workability and the like, preferably,
Φ10 μm or more and Φ45 μm 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 is used for each LE.
The electrode of the D chip and the conductive pattern provided on the substrate can be easily connected by a wire bonding device.

(Display Apparatus) By connecting the LED display of the present invention to driving means, it is possible to make a black-and-white LED display apparatus. The black-and-white LED display is configured by arranging concave openings having an LED chip and a fluorescent substance therein in a matrix or the like. LED chip, L
It is electrically connected to a driving circuit, such as a lighting circuit, through an external terminal of the ED display. A display or the like capable of displaying various images by an output pulse from the drive circuit can be provided. The driving circuit includes a RAM (Random, Acc) for temporarily storing input display data.
ess, Memory), a gradation control circuit for calculating a gradation signal for lighting the light-emitting portion to a predetermined brightness from data stored in the RAM, and switching by an output signal of the gradation control circuit to emit light. And a driver for lighting the unit. The gradation control circuit calculates a lighting time of the light emitting section from data stored in the RAM and outputs a pulse signal.

Accordingly, the LED display device for black and white is
Unlike a full-color display using each LED chip of RGB, the circuit configuration can be simplified and the definition can be increased. Therefore, it is possible to provide a display without color unevenness or the like due to different semiconductor characteristics of each of the RGB LED chips. Also, since the light from the LED chip is scattered by the fluorescent substance and becomes a white light source,
Compared to an LED display using only red and green, it has less irritation to human eyes and is suitable for long-time use. Moreover, the viewing angle is widened because the fluorescent substance emits light isotropically and the light emitted from the LED chip is scattered by the fluorescent substance. Hereinafter, specific examples of the present invention will be described in detail.

[0040]

【Example】

(Example 1) A ceramic substrate was used as a wiring substrate having a concave opening in a dot matrix shape. The concave opening was formed by laminating a perforated green sheet having no wiring layer during the production of the ceramic substrate. The wiring layer was formed by screen-printing a tungsten-containing binder into a desired shape. Each green sheet is
It is formed by overlapping. Note that the green sheet corresponding to the surface layer 106 contains chromium oxide for improving the contrast of the substrate. This was sintered to form a ceramic substrate. The dot pitch of the concave opening is 2.0 mm and the opening depth is 1.0 m
A ceramic substrate with a total length of 32 mm square and 16 × 16 dots is used. Wiring layers are provided with common and signal lines corresponding to the dot matrix. The surface is plated with Ni / Ag. To take out the signal line from the ceramic substrate, a connection pin made of a metal cover was formed by silver brazing.

A GaInN semiconductor having a main light emission peak of 450 nm was used as an LED chip as a semiconductor light emitting element. 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 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 is annealed at 400 ° C. or higher after film formation.)

After exposing the surface of each PN semiconductor 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 external force to form LED chips as light emitting elements. 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. After that, a 25 μm gold wire was connected to each electrode of the LED chip,
Electrical connection was made by wire-bonding to wiring on the substrate.

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. 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 : 80 parts by weight of Ce fluorescent substance and 90 parts by weight of silicone rubber were mixed well to form a chiller. The LED chip is arranged on this thriller, 16x1
No. 6 was injected into the concave openings of the ceramic substrate. After the injection, the resin containing the fluorescent substance
Cured in time to form an LED display. L at this time
The thickness of the ED display is 2.0 mm for the thickness of the ceramic substrate
However, it was possible to significantly reduce the thickness as compared with a display device using a bullet-type LED lamp.

This 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.

The thus-obtained LE capable of emitting white light
Average chromaticity point, color temperature,
Each color rendering index was measured. The chromaticity points (x
= 0.302, y = 0.291, color temperature 8085K, R
a (color rendering index) = 87.3, indicating a performance close to that of a three-wavelength fluorescent lamp. In addition, no change was observed when a current of 60 mA was applied to one LED chip for 100 hours at a temperature of 25 ° C. as a life test. At this time, it was confirmed that there was almost no temperature difference between the vicinity of the light emitting portion and the back side of the ceramics substrate, and heat was efficiently radiated.
Since the thermal conductivity of the ceramic substrate was good, it was also confirmed that measures for radiating heat from the LED element could be easily performed by mounting radiating fins or forced air cooling. In addition, the present invention relates to an LED
The yield was higher than that in which an LED display was constituted by a lamp. This is because, in the case of an LED lamp, mounting reliability due to poor soldering is low. However, in the present invention, it is considered that the mounting reliability was high due to the connection by wire bonding.

(Example 2) An LED display was made in the same manner as in Example 1 except that a metal substrate having a conductor wiring layer via an insulating layer was used instead of a ceramic substrate having a concave opening. The vessel was configured. It was confirmed that the metal substrate can be freely formed into a linear taper or a side wall shape having a curved surface without reducing the reflectance from the LED chip by press molding.

[0047]

As is apparent from the above description, the present invention is applicable to a case where an LED chip and a fluorescent substance excited by light from the LED chip are arranged on a substrate having two or more adjacent openings. The LED chip is a gallium nitride based semiconductor, and the fluorescent material is (RE _1-x Sm _x ) ₃ (Al _1-y G _ay ) ₅
O ₁₂ : Ce, a substrate having two or more concave openings is selected from ceramics, a metal substrate, and a heat-resistant organic resin containing a thermally conductive filler, thereby achieving a thinner, higher viewing angle than ever before. A white LED display capable of forming a high-density dot matrix structure of 4 mm dots or less (for example, 2 mm pitch) can be provided. Also, L
The directivity characteristics of the ED chip can be used as is, and ± 60
It is possible to manufacture a high viewing angle LED display device having a half-degree angle.

[Brief description of the drawings]

FIG. 1A is a schematic front view showing an LED display of the present invention, and FIG. 1B is a partial cross-sectional view thereof.

FIG. 2 is a spectrum diagram of light emitted from the LED display device of the present invention measured by an integrating sphere.

[FIG. 3] FIG. 3 is a diagram showing RGB for comparison with the present invention.
It is a typical sectional view of the LED lamp which has each LED chip.

[Description of sign]

101 ceramic substrate 102 LED chip 103 coating member 104 conductive wire 105 wiring pattern 106 surface layer 301 mold resin 302 LED chip 303・ ・ ・ Inner lead 304 ・ ・ ・ Mount lead on which RGB LED chips are arranged

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-288341 (JP, A) JP-A-7-99345 (JP, A) JP-A-49-122292 (JP, A) JP-A 8- 120265 (JP, A) JP-A-7-83927 (JP, A) JP-A-5-287269 (JP, A) JP-A-10-107325 (JP, A) JP-A-4-111767 (JP, U) Hikaru 4-77270 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 33/00

Claims (1)

(57) [Claims] An LED chip having a gallium nitride-based compound semiconductor in a light-emitting layer, wherein the substrate has two or more concave openings, and a gallium nitride-based compound semiconductor electrically connected to the conductive wirings in the concave openings. (RE _1-x Sm _x )
_{3 (Al 1-y Ga y} ) 5 O 12: an LED indicator encapsulated with a coating member having a Ce fluorescent material selected from, the substrate is a ceramic, a metal substrate, the thermally conductive filler-containing heat-resistant organic resin An LED display characterized in that it is one that is performed. Where 0 ≦ x <1, 0 ≦ y ≦
1, RE is at least one element selected from the group consisting of Y, Gd, and La.