JPH11243232A - Led display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen reduction in the luminous efficiency of a white light-emitting diode and a color shift of the color of emitted light at the high luminance of the above diode and even under the environment of the long-time use of the above diode, by a method wherein the white light-emitting diode is arranged to one picture element in addition to a light-emitting diode, which can emit red light, green light and blue light. SOLUTION: A white light-emitting diode is formed by combining a luminous layer with a gallium nitride compound semiconductor element having a high-energy band gap and a yttrium aluminium garnet fluorescent substance activated by cerium, which is a photoluminescence fluorescent substance. As a result, even in the case where high-energy light in the range of visible light emitted from a light-emitting element is radiated on the vicinity of the range at the high luminance of the diode for a long time, the white light-emitting diode can be formed into a light-emitting diode, which is very little in a color shift of the color of emitted light and reduction in a luminous luminance. Specially, blue light emission of an InGaN diode, which is used as a nitride compound semiconductor diode and the absorption spectrum of the yttrium aluminium garnet fluorescent substance activated by the cerium coincide well with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode used for an LED display, a backlight light source, a traffic light, an illuminated switch, various indicators, and the like, and in particular, converts light emitted from an LED chip as a light emitting element. The present invention relates to an LED display device using a light-emitting diode capable of emitting white light, which is a light-emitting device having high luminance and high efficiency regardless of the use environment and having a photoluminescent phosphor to emit light.

[0002]

2. Description of the Related Art Light-emitting diodes (hereinafter, also referred to as LEDs) are small, efficient, and emit bright colors. In addition, since it is a semiconductor element, there is no fear of breaking the ball. It has excellent driving characteristics and is resistant to vibration and repeated ON / OFF lighting. Therefore, it is used as various indicators and various light sources. Recently, light emitting diodes of RGB (red, green, blue) and the like have been developed as light emitting diodes of high brightness and high efficiency. Along with this, LED displays using the three primary colors of RGB are rapidly developing, taking advantage of features such as power saving, long life and light weight.

A light emitting diode can emit various emission wavelengths from ultraviolet to infrared depending on the semiconductor material of the light emitting layer used, the forming conditions, and the like. Also, it has an excellent monochromatic peak wavelength.

However, since a light emitting diode has an excellent monochromatic peak wavelength, in order to make it a white light emitting light source or the like, it is necessary to make LED chips capable of emitting RGB or the like emit light in close proximity to each other to diffuse and mix. is there. Such a light-emitting diode is effective as a light-emitting device that freely emits various colors, but also emits red-, green-, and blue-based light-emitting diodes or blue even when emitting only a color such as a white color. Green and yellow light emitting diodes must be used, respectively. LE
The D chip is a semiconductor, and there is still considerable variation in color tone and luminance. Further, when the LED chips as the semiconductor light emitting elements are formed using different materials,
The driving power of the ED chip is different, and it is necessary to secure a power supply individually. Therefore, white light must be emitted by adjusting the current and the like for each semiconductor. Similarly, since it is a semiconductor light emitting element, differences in individual temperature characteristics and changes with time are different, and the color tone is variously changed. Furthermore, LED
Uneven mixing of the light emitted from the chip may cause color unevenness.

Therefore, the present applicant has previously described light emitting diodes described in JP-A-5-152609 and JP-A-7-99345 as light-emitting diodes in which the emission color of an LED chip is color-converted by a phosphor. developed. With these light-emitting diodes, it is possible to emit another luminescent color such as white light using one type of LED chip.

[0006] Specifically, an LED chip having a large energy band gap of the light emitting layer is arranged on a cup provided at the tip of a lead frame. LED chip,
Each is electrically connected to a metal stem or a metal post provided with an LED chip. Then, a fluorescent material that absorbs light from the LED chip and converts the wavelength is included in a resin mold member that covers the LED chip.

[0007] As a light-emitting diode obtained by wavelength-converting the light emitted from the LED chip, a white light can be emitted by mixing the light emitted from a blue light-emitting diode with the light emitted from a phosphor that absorbs the emitted light and emits a yellow light. It can be a light emitting diode or the like. These light emitting diodes can emit light with sufficient luminance even when used as light emitting diodes that emit white light.

[0008]

The fluorescent substance excited by the light emitting diode includes various kinds of fluorescent dyes, fluorescent pigments, and organic and inorganic compounds. Some phosphors convert the light emission wavelength from a light emitting element from a short wavelength to a long wavelength, or convert the light emission wavelength from a light emitting element from a long wavelength to a short wavelength.

However, when converting from a long wavelength to a short wavelength, the conversion efficiency is extremely poor and not suitable for practical use. In addition, the phosphor disposed close to the periphery of the LED chip is exposed to a light beam having a strong irradiation intensity that is about 30 to 40 times that of sunlight. In particular, the light emitting element LE
In the case where the D chip is made of a semiconductor having a high energy band gap and the conversion efficiency of the phosphor is improved or the amount of the phosphor used is reduced, the light energy is reduced even if the light emitted from the LED chip is in the visible light range. Inevitably will be higher. In this case, if the emission intensity is further increased and used for a long period of time, the phosphor itself tends to deteriorate. When the phosphor is deteriorated, the color tone may be deviated, or the efficiency of taking out the darkened light from the phosphor may decrease. Similarly, the phosphor provided near the LED chip is also exposed to a high temperature such as an increase in the temperature of the LED chip or heating from an external environment. Further, although the light emitting diode is generally covered with a resin mold, it cannot completely prevent moisture from entering from an external environment or the like and cannot completely remove moisture attached during manufacturing. Depending on the fluorescent substance, such moisture may accelerate the deterioration of the fluorescent substance due to high-energy light or heat from the light emitting element. Further, in the case of an ionic organic dye, electrophoresis is caused by a DC electric field in the vicinity of the chip, and the color tone may be changed. Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide an LED display device using a light-emitting diode with a higher luminance, a reduced light emission rate and a very small color shift even under a long-time use environment. .

[0010]

According to the first aspect of the present invention, L
The ED display device includes an LED display in which one pixel composed of light-emitting diodes capable of emitting red, green, and blue light corresponding to the three primary colors of light is arranged in a matrix, and a light-emitting diode of the LED display. And a driving circuit for driving each of them. The LED display includes a white light emitting diode in addition to a light emitting diode capable of emitting red, green, and blue light in one picture element.

The white light emitting diode of the LED display device according to the second aspect of the present invention comprises an LED chip which is a gallium nitride compound semiconductor disposed in a cup of a mounting lead, and a cerium disposed on the LED chip. And an activated yttrium-aluminum-garnet-based phosphor.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of various experiments, the present inventor has found that an LED having a relatively high light energy in the visible light region is used.
In a light-emitting diode in which light emitted from a chip is color-converted by a photoluminescent phosphor, it has been found that by selecting a specific semiconductor and phosphor, it is possible to prevent a reduction in light efficiency and color shift during long-time use by selecting a specific semiconductor and phosphor. The present invention has been accomplished.

That is, L used for a light emitting diode
As an ED chip, The light emission characteristics of the LED chip are stable for long-term use. 2. It is required that a monochromatic peak wavelength of high luminance and high energy enough to excite the phosphor and perform secondary emission can be efficiently emitted. The photoluminescent phosphor used for the light emitting diode includes: Excellent light fastness is required. In particular, since it is strongly radiated from a minute area such as a semiconductor light emitting element, it is necessary to sufficiently withstand a strong irradiation intensity of about 30 to 40 times that of sunlight. 2. Efficiently emits blue light instead of ultraviolet light because it utilizes color mixture with light emitting elements. 3. Green to red light can be emitted in consideration of color mixing. 4. It has good temperature characteristics because it is arranged near the light emitting element. 5. The color tone can be continuously changed by a composition ratio or a mixture ratio of a plurality of phosphors. 6. It is required to have features such as weather resistance depending on the usage environment of the light emitting diode.

Assuming that these conditions are satisfied, a light emitting diode according to the present invention includes a gallium nitride-based compound semiconductor device having a high energy band gap in a light emitting layer, and a yttrium / aluminum activated with cerium, which is a photoluminescent phosphor.・ Combine with garnet phosphor. Thus, even when high-energy light in the visible light range emitted from the light-emitting element is irradiated with high luminance in the vicinity of the light for a long time, a light-emitting diode with extremely little color shift of the emission color and a decrease in emission luminance can be obtained. You can do it. In particular, as a nitride-based compound semiconductor,
The blue emission of nGaN and the absorption spectrum of the yttrium-aluminum-garnet-based phosphor activated with cerium match very well. In addition, the mixture of the fluorescence emitted by the yttrium-aluminum-garnet-based phosphor activated with cerium and the blue light of InGaN is an extremely unique performance unlike any other combination in that a good white color with good color rendering properties is obtained. Having.

FIG. 1 shows an example of a specific light emitting diode, and FIG. 2 shows a sectional view of a chip type LED. An LED chip 202 using a gallium nitride-based semiconductor is fixed in a chip type LED housing 204 using an epoxy resin or the like. A gold wire as the conductive wire 203 is electrically connected to each electrode of the LED chip 202 and each electrode 205 provided on the housing.
_{(RE 1-x Sm x)} 3 (Al y Ga 1-y) 5 O 12: Ce phosphor and LED chips which were mixed and dispersed in an epoxy resin, a mold to protect the conductive wires, such as from external stress The member 201 is uniformly cured and formed. By supplying power to such a light emitting diode, L
The ED chip 202 emits light. A light-emitting diode capable of emitting white light or the like can be obtained by mixing light emitted from the LED chip 202 with light emitted from the photoluminescent phosphor excited by the light emission. Less than,
The constituent members of the present invention will be described in detail.

(Phosphor) The photoluminescence phosphor used in the light emitting diode of the present invention is a photoluminescence phosphor that emits light when excited by visible light or ultraviolet light emitted from the semiconductor light emitting layer. The photoluminescent phosphor is an yttrium aluminum garnet phosphor activated with cerium.

In this specification, the yttrium-aluminum-garnet-based phosphor is to be interpreted in a particularly broad sense, and a part or the whole of yttrium is made of Lu, Sc,
Substituted with at least one element selected from the group consisting of La, Gd and Sm, or used in a broad sense including a phosphor in which part or all of aluminum is substituted with one or both of Ga and In.

More specifically, (RE _1-x Sm _x ) ₃ (Al _y
Ga _1-y ) ₅ O ₁₂ : Ce (provided that 0 ≦ x <1, 0 ≦ y ≦
1, RE is at least one selected from Y and Gd)
It is. When the light emitted from the LED chip using the gallium nitride-based compound semiconductor and the light emitted from the photoluminescent phosphor whose body color is yellow have a complementary color relationship, the light emission from the LED chip and the photoluminescent phosphor When light emission from the light emitting device is mixed and displayed, white light emission color display can be performed. Therefore, outside the light emitting diode, light emitted from the LED chip and light emitted from the photoluminescent phosphor must pass through the mold member. Therefore, the LE layer is formed on the phosphor layer formed by the photoluminescence phosphor by a sputtering method or the like.
Enclose the D chip and add L to the photoluminescent phosphor layer.
A light emitting diode having one or more openings through which light from the ED chip can be transmitted, or a thin film that can transmit light from the LED chip may be used. In the case of a phosphor formed by a sputtering method or the like, the binder in the coating portion can be omitted. The emission color can be adjusted by the film thickness. In addition, the powder of photoluminescent phosphor is contained in resin or glass to make LED
It may be formed thin enough to transmit light from the chip. Similarly, the powder of the photoluminescent phosphor may 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 photoluminescent phosphor 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 white.

Further, the content distribution of the photoluminescent phosphor also affects the color mixing property and durability. That is, when the distribution concentration of the photoluminescent phosphor is high from the surface side of the coating portion or the mold member containing the photoluminescent phosphor toward the LED chip, it is less susceptible to moisture and the like from the external environment. It is easy to suppress deterioration due to moisture. On the other hand, when the distribution density of the photoluminescent phosphor increases from the LED chip toward the mold member surface side, the distribution of the photoluminescent phosphor is easily affected by moisture from the external environment, but the influence of heat generation from the LED chip, irradiation intensity, etc. is more. The deterioration of the photoluminescent phosphor can be suppressed to a small extent. Such distribution of the photoluminescent phosphor can be variously formed by adjusting the member containing the photoluminescent phosphor, the forming temperature, the viscosity, the shape of the photoluminescent phosphor, the particle size distribution, and the like. . Therefore, the distribution concentration of the phosphor can be variously selected depending on the use conditions and the like.

The photoluminescent phosphor of the light emitting diode according to the present invention is particularly arranged in contact with or close to the LED chip and has an irradiation intensity of (Ee) = 3W.
· Cm even have sufficient light resistance in high efficiency ^-2 10 W · cm ^-2 or less, can be a light emitting diode having excellent emission characteristics.

Since the photoluminescent phosphor used in the present invention has a garnet structure, it is resistant to heat, light and moisture, and has a peak in the excitation spectrum of 45 as shown in FIG.
It can be set to around 0 nm. Further, as shown in FIG. 4, the emission peak is near 580 nm and has a broad emission spectrum with a tail extending to 700 nm.

Further, the photoluminescent phosphor of the present invention can increase the excitation light emission efficiency in a long wavelength region of 460 nm or more by containing Gd (gadolinium) in the crystal. By increasing the content of Gd,
The emission peak wavelength shifts to a longer wavelength, and the overall emission wavelength also shifts to a longer wavelength. That is, when a reddish luminescent color is required, it can be achieved by increasing the replacement amount of Gd. On the other hand, as Gd increases, the emission luminance of photoluminescence due to blue light tends to decrease.

Further, among the yttrium / aluminum / garnet-based phosphors having a garnet structure,
By substituting a part of Al with Ga, the emission wavelength shifts to the shorter wavelength side. Further, by substituting a part of Y in the composition with Gd, the emission wavelength shifts to the longer wavelength side.

When Al is substituted by Ga, it is preferable to set the ratio of Al: Ga = 6: 4 to 1: 1 in consideration of luminous efficiency and luminous wavelength. Similarly, replacing a part of Y with Gd is preferably set to a ratio of Y: Gd = 9: 1 to 1: 9, preferably from 4: 1 to 2: 3.
It is more preferable to set in the range. If the substitution with Gd is less than 20%, the green component is large and the red component is small. When the substitution with Gd is 60% or more, the luminance tends to sharply decrease although the red component increases. In particular, L
Depending on the emission wavelength of the ED chip, Y: Gd = 4: 1 in the composition of the yttrium-aluminum-garnet phosphor.
By setting the ratio to 2: 3, a light emitting diode capable of emitting white light approximately along the blackbody radiation locus can be obtained by using one kind of yttrium aluminum garnet phosphor. When Y: Gd is more than 2: 3 and 1: 4, the luminance can be reduced, but the light emitting diode can emit a light bulb color. Further, when Ce is contained (substituted) in a content of 0.003 to 0.2, the relative emission luminance becomes 70% or more. (The relative light emission luminance is 100% of the light emission luminance of the phosphor with q = 0.03.)
It is the light emission luminance in the case of. If the value is less than 0.003, the number of photoluminescence excitation centers by Ce decreases, and the luminance decreases. Conversely, if the value exceeds 0.2, concentration quenching occurs. (The term “concentration quenching” means that when the concentration of the activator is increased to increase the luminance of the phosphor, the emission intensity decreases at a concentration higher than a certain optimum value.)

By changing the composition of the photoluminescent phosphor according to the present invention, the emission color can be continuously adjusted. 254 nm or 36
Hg emission line such as 5 nm is hardly excited by 450 n
Excitation efficiency due to light from a blue LED chip near m is high. 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.

Table 1 shows an example of the composition and emission characteristics of the photoluminescent phosphor of the present invention. (Note that the measurement conditions were observed by excitation with blue light of 460 nm. The luminance and efficiency are represented by relative values.)

[0027]

[Table 1]

Further, an LE using a gallium nitride based semiconductor is used.
A light emitting diode having a D chip and a photoluminescent phosphor containing a rare earth element samarium (Sm) in a yttrium aluminum garnet phosphor (YAG) activated with cerium further increases the light efficiency. Can be improved.

Such a photoluminescent phosphor is:
As a raw material of Y, Gd, Ce, Sm, Al and Ga, an oxide or a compound which easily becomes an oxide at a high temperature is used, and these are sufficiently mixed in a stoichiometric ratio to obtain a raw material. Or
A mixture of 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, aluminum oxide, and gallium oxide is mixed. 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 put in a crucible in air at a temperature of 1350 to 1450 ° C. for 2 to 5 minutes.
It can be obtained by calcining for a time to obtain a calcined product, then ball-milling the calcined product in water, washing, separating, drying, and finally passing through a sieve.

Containing Sm (Y _{1 -pqr} Gd _p Ce _q S
The m _r ) ₃ Al ₅ O ₁₂ phosphor has a small decrease in temperature characteristics regardless of an increase in the Gd content. By including Sm in this way, the emission luminance of the photoluminescent phosphor 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 Gd was increased and redness was imparted to the emission color tone of the photoluminescent phosphor was more effective in improving the temperature characteristics by including Sm. (Note that the temperature characteristic here refers to room temperature (25 °
It is expressed as a relative value (%) of the emission luminance of the phosphor at a high temperature (200 ° C.) with respect to the excitation emission luminance of C). )

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.

[0032] Such photoluminescent phosphor in light emitting diodes in the present invention, two or more _{(RE 1-x Sm x)} 3 (Al y Ga 1-y) 5 O 12: Ce photoluminescent phosphor May be mixed. That is, A
l, Ga, the content of Y and Gd and Sm are two or more different _{(RE 1-x Sm x)} 3 (Al y Ga 1-y) 5 O 12: by mixing Ce photoluminescent phosphor RGB Can be increased. By using a color filter, it can be used for a full-color liquid crystal display device.

(LED chips 102, 202, 702)
The LED chip is, as shown in FIG.
4 buried. The LED chip used for the light emitting diode in the present invention is a nitride-based compound semiconductor that can efficiently excite a yttrium-aluminum-garnet-based phosphor activated with cerium. Here, as the nitride-based compound semiconductor (general formula In _i Ga _j Al _k N, where 0 ≦ i, 0 ≦ j, 0 ≦ k, i + j + k = 1), InGaN or GaN doped with various impurities is used. Initially, various things are included. An LED chip as a light emitting element 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. In particular, in the present invention, by forming the active layer of the LED chip with a single quantum well structure of InGaN, the LED can be used as a light emitting diode that emits light with higher luminance without deterioration of the photoluminescent phosphor.

When a gallium nitride-based 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 introducing a P-type dopant by heating with a furnace, irradiating a low-speed electron beam, irradiating a plasma, or the like after introducing 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 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, a very 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 the light emitting diode of the present invention emits white light, the light emission wavelength of the light emitting element is preferably 400 nm or more and 530 nm or less in consideration of the complementary color relationship with the photoluminescent phosphor and resin deterioration.
The thickness is more preferably from 490 nm to 490 nm. In order to further improve the efficiency of the LED chip and the efficiency of the photoluminescent phosphor, the thickness is more preferably 450 nm or more and 475 nm or less. FIG. 3 shows an emission spectrum of the white light emitting diode according to the present invention. Light emission having a peak around 450 nm is light emission from the LED chip,
The emission having a peak near nm is the photoluminescence emission excited by the LED chip. Note that, in addition to the LED chip of the present invention, an LED chip that does not excite the phosphor can be used together.

Specifically, in addition to the LED chip which is a nitride-based compound semiconductor capable of exciting the photoluminescent phosphor, a light emitting layer which does not substantially excite the photoluminescent phosphor is formed of gallium phosphide, gallium aluminum arsenide. And an LED chip made of gallium arsenide phosphorus or indium gallium aluminum phosphorus. Light from the LED chip that does not excite the photoluminescent phosphor is emitted outside without being absorbed by the phosphor itself. Therefore, a light emitting diode or the like that can efficiently emit red and white can be provided.

(Conductive Wires 103 and 203) As the conductive wires 103 and 203, the LED chip 10
Those having good ohmic properties, mechanical connectivity, electrical conductivity and thermal conductivity with the electrodes 2, 202 are required. The thermal conductivity is 0.01 cal / (s) (cm ² ) (° C./c
m) or more, more preferably 0.5 cal /
(S) (cm ² ) (° C./cm) or more. In addition, the diameter of the conductive wire is preferably Φ10 μm or more and Φ45 μm or less in consideration of workability and the like. In particular, the conductive wire is likely to be broken at the interface between the coating portion containing the phosphor and the mold member not containing the phosphor. Even if the same material is used, it is considered that disconnection is likely to occur because the amount of thermal expansion is substantially different due to the inclusion of the phosphor. Therefore, the diameter of the conductive wire is
The thickness is more preferably 25 μm or more, and even more preferably 35 μm or less from the viewpoint of the light emitting area and ease of handling. 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.

(Mount Lead 105) As the mount lead 105, the LED chip 102 is disposed, and it is sufficient that the mount lead 105 is large enough to be mounted on a die bonding device or the like. Further, when a plurality of LED chips are provided and the mount leads are used as a common electrode of the LED chips, sufficient electric conductivity and connectivity with a bonding wire or the like are required. In addition,
In the case where the LED chip is arranged in the cup on the lead and the phosphor is filled therein, it is possible to prevent false lighting by light from another light emitting diode arranged in the vicinity.

LED chip 102 and mount lead 1
Adhesion to the cup 05 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. Further, in order to adhere to the mount leads and electrically connect them with a face-down LED chip or the like, an Ag paste, a carbon paste, a metal bump, or the like can be used.
Further, in order to improve the light use efficiency of the light emitting diode, the surface of the mount lead on which the LED chip is arranged may be mirror-like, and the surface may have a reflection function. In this case, the surface roughness is preferably 0.1S or more and 0.8S or less. Further, the specific electric resistance of the mount lead is preferably 300 μΩ-cm or less, more preferably,
3 μΩ-cm 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, 0.01 cal / (s) (cm ² )
(° C./cm) or more, more preferably 0.5 ca
1 / (s) (cm ² ) (° C./cm) or more. Materials satisfying these conditions include iron, copper, copper with iron, copper with tin, and ceramics with metallized patterns.

(Inner Lead 106) The inner lead 106 is for connecting the conductive wire 103 connected to the LED chip 102 disposed on the mount lead 105. 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 should be 1.6 S or more 1 in consideration of adhesion.
0S or less is preferable. In order to form the tip of the inner lead into various shapes, the shape of the lead frame may be determined in advance with a mold and formed by punching, or after all the inner leads are formed, the upper part of the inner lead may be formed. May be formed by cutting a part of. Furthermore, after punching and forming the inner lead,
By applying pressure from the end face direction, a desired end face area and end face height can be simultaneously formed.

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 μΩ-cm or less, more preferably 3 μΩ
−cm or less. Materials satisfying these conditions include iron, copper, copper with iron, copper with tin, and aluminum, iron, and copper plated with copper, gold, and silver.

(Coating part 101) The coating part 101 used in the present invention is a mold member 104
Apart from this, it is provided on the cup of the mount lead and contains a photoluminescent phosphor for converting the light emission of the LED chip. As a specific material of the coating portion, a transparent resin having excellent weather resistance, such as an epoxy resin, a urea resin, or silicone, or glass is suitably used. Further, a diffusing agent may be contained together with the photoluminescent phosphor. As a specific diffusing agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide, or the like is suitably used.

(Mold member 104) Mold member 10
4 can be provided to protect the LED chip 102, the conductive wire 103, the coating portion 101 containing the photoluminescent phosphor, and the like from the outside according to the use application of the light emitting diode. The mold member is
Generally, it can be formed using a resin. Also,
Although the viewing angle can be increased by including the photoluminescent phosphor, the directivity from the LED chip 102 can be relaxed and the viewing angle can be further increased by including the diffusing agent in the resin mold. Furthermore, by forming the mold member 104 into a desired shape, it is possible to have a lens effect of converging or diffusing light emitted from the LED chip. Therefore, the mold member 104 may have a laminated structure. Specifically, the shape is a convex lens shape, a concave lens shape, an elliptical shape as viewed from the light emission observation surface, or a combination of a plurality of shapes. As a specific material of the mold member 104, a transparent resin excellent in weather resistance, such as an epoxy resin, a urea resin, or a silicone resin, or glass is preferably used.
As the diffusing agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide and the like are preferably used. Further, in addition to the diffusing agent, a photoluminescent phosphor can be contained in the mold member. Therefore, the photoluminescent phosphor may be contained in the mold member, or may be contained in other coating portions or the like. Alternatively, the coating portion may be formed using a resin containing a photoluminescent phosphor, and a mold member made of a different material such as glass. In this case, a light emitting diode with less influence of moisture or the like can be obtained with high productivity. Further, the mold member and the coating portion may be formed using the same member in consideration of the refractive index. In the present invention, when the mold member contains a diffusing agent or a coloring agent, the coloring of the phosphor viewed from the emission observation surface side can be hidden. Note that the coloring of the phosphor means that the photoluminescent phosphor of the present invention absorbs a blue component of light from strong external light and emits light. Therefore, it appears to be colored yellow. In particular, depending on the shape of the mold member such as a convex lens shape, the colored portion may appear enlarged. Such coloring may be undesirable in design or the like. The diffusing agent contained in the mold member can make the mold member milky white and the colorant in a desired color, thereby making the coloring invisible. Therefore, the color of the photoluminescent phosphor is not observed from such a light emission observation surface side. Also,
Main emission wavelength of light emitted from LED chip is 430n
Above m, it is more preferable to include an ultraviolet absorber as a light stabilizer in the mold member from the viewpoint of weather resistance.

(Display Device) When the light emitting diode of the present invention is used for an LED display, an LED using only a combination of light emitting diodes that respectively emit RGB light is used.
A white display can be displayed with higher definition than a display. This is because a device using a light emitting diode of the present invention can display white light with one light emitting diode, while a conventional device displays white light with three light emitting diodes. That is, in order to display a white color or the like by combining light emitting diodes, the conventional display device needs to
Each of the RGB light emitting diodes must emit light simultaneously. For this reason, the display area per pixel is larger than in the case of displaying a single color of red, green, and blue. Therefore, in the case of white display, it is not possible to display with higher definition compared to monochrome display of RGB single color. In addition, white display is displayed by adjusting the light emission output of each light emitting diode,
Various adjustments must be made in consideration of the temperature characteristics of each semiconductor. Furthermore, since the display is based on mixed colors, the RGB light-emitting diodes may be partially shielded and the display color may be changed depending on the direction and angle of viewing of the LED display.
A display device in which the light emitting diode of the present invention is used in place of the RGB light emitting diode has features that higher definition can be achieved, white light can be stably emitted, and color unevenness can be reduced. Further, the light emitting diode of the present invention can be used together with each of the RGB light emitting diodes. This display device can improve luminance.

FIG. 5 shows an LED display of the present invention. The LED display of this figure is used for a monochrome LED display device using only white light emitting diodes. The LED display for black and white is the light emitting diode 50 of the present invention.
Only 1 is arranged in a matrix or the like. The display device including the LED display of FIG. 1 does not include the RGB light emitting diodes. Therefore, a plurality of drive circuits for RGB light emitting diodes are not required. An LED display can be driven by a drive circuit for a white light emitting diode instead of a plurality of drive circuits.

The LED display is electrically connected to a driving circuit, such as a lighting circuit. A display or the like capable of displaying various images by an output pulse from the drive circuit can be provided. FIG. 6 shows the drive circuit. The drive circuit is a RAM (Random, Access, RAM) which is image data storage means for temporarily storing input display data.
Memory 603, a gradation control circuit 604 for calculating a gradation signal for lighting each light emitting diode of the LED display 601 to a predetermined brightness from data stored in the RAM 603, and a gradation control circuit 604. And a driver 602 which is turned on by the output signal of the light emitting diode to turn on the light emitting diode. Gradation control circuit 604
Calculates the light emitting diode lighting time of the LED display 601 from the data stored in the RAM 603 and outputs a pulse signal for blinking.

Therefore, the LED display for black and white is R
Unlike the GB full-color display, the circuit configuration can be simplified and the definition can be increased. Therefore, a display can be obtained at low cost without color unevenness due to the characteristics of the RGB light emitting diodes. Further, compared to the conventional LED display using only red and green, it is less irritating to human eyes and is suitable for long-time use.

The light emitting diode according to the present invention is used as a white light emitting diode (W) in addition to the light emitting diodes which respectively emit light of RGB as shown in FIG. In the figure, reference numeral 900 denotes a part of the LED display, and 900 constitutes one picture element. This LED display is electrically connected to a driving circuit, such as a lighting circuit. A display or the like capable of displaying various images by an output pulse from the drive circuit can be provided. The drive circuit is a RAM (Rando) which is image data storage means for temporarily storing input display data, like a monochrome display device.
m, Access, Memory), a gradation control circuit that calculates a gradation signal for lighting each light emitting diode to a predetermined brightness from data stored in the RAM, and a switching circuit that is switched by an output signal of the gradation control circuit. A driver for lighting each light emitting diode. However, this drive circuit requires a dedicated circuit for light emitting diodes that emit light in RGB and white light. The gradation control circuit is a RAM
, The lighting time of each light emitting diode is calculated from the data stored in the memory, and a pulse signal for blinking is output. Here, when a white display is performed, the pulse width of the pulse signal for lighting each of the RGB light emitting diodes is reduced, the peak value of the pulse signal is reduced, or no pulse signal is output. On the other hand, a pulse signal is output to the white light emitting diode so as to compensate for it. Thereby, the white color of the LED display is displayed.

Therefore, it is preferable to separately provide a CPU as a gradation control circuit for calculating a pulse signal for lighting the white light emitting diode with desired luminance. The pulse signal output from the gradation control circuit is input to the driver of the white light emitting diode to switch the driver. The white light emitting diode is turned on when the driver is turned on, and is turned off when the driver is turned off.

(Signal Signal) When the light emitting diode of the present invention is used as a signal signal which is a kind of display device,
There is a feature that light can be stably emitted for a long time and color unevenness does not occur even when a part of the light emitting diode is turned off. As a schematic configuration of a traffic light using a light emitting diode according to the present invention, a white light emitting diode is arranged on a substrate on which a conductive pattern is formed. A light emitting diode circuit in which such light emitting diodes are connected in series or in series / parallel is treated as a light emitting diode group. Two or more light emitting diode groups are used, and light emitting diodes are arranged in a spiral shape. When all the light emitting diodes are arranged, they are arranged in a circle on the entire surface. After connecting the power cords to be connected to the external power from the respective light emitting diodes and the board by soldering, the power cords are fixed in a railway signal housing. The LED display is disposed in an aluminum die-cast housing provided with a light-shielding member, and the surface thereof is sealed with a silicone rubber filler. The display surface of the housing is provided with a white lens. Further, the electrical wiring of the LED display is sealed through the rubber packing from the back surface of the housing to seal the inside of the housing. Thereby, a white traffic light can be formed.
The light-emitting diodes according to the present invention are divided into a plurality of groups, arranged in a spiral shape forming a ring from the center to the outside, and connected in parallel, whereby a more reliable signal can be obtained. The drawing of a ring from the center to the outside includes one that continuously draws a ring and one that is arranged intermittently. Therefore, it is possible to variously select the number of light emitting diodes and the number of light emitting diode groups arranged according to the display area of the LED display. With this traffic light, even if one light emitting diode group or some light emitting diodes are turned off due to some trouble, the other light emitting diode group or the remaining light emitting diode can make the traffic light emit uniformly in a circular shape. is there. Also, no color shift occurs. Since they are arranged in a spiral shape, the central portion can be arranged densely and can be driven without any uncomfortable feeling with a signal of light emission of a bulb.

(Surface Light Emitting Light Source) As shown in FIG. 7, the light emitting diode of the present invention may be a surface light emitting light source. The light emitting diode of the planar light source shown in the figure contains a photoluminescent phosphor in a coating portion or a scattering sheet 706 on a light guide plate. Alternatively, it may be applied to the scattering sheet 706 together with the binder resin to form a sheet 701, and the mold member may be omitted. Specifically, the LED chip 702 is fixed in a U-shaped metal substrate 703 on which an insulating layer and a conductive pattern are formed. After establishing electrical continuity between the LED chip and the conductive pattern, the photoluminescent phosphor is mixed and agitated with the epoxy resin, and the metal substrate 70 on which the LED chip 702 is mounted.
3. Fill on top. The LED chip fixed in this way is fixed to the end face of the acrylic light guide plate 704 with an epoxy resin or the like. On one main surface of the light guide plate 704, a film-like reflecting member 707 containing a white scattering agent is arranged to prevent a fluorescent phenomenon. Similarly, a reflection member 705 is provided on the entire rear surface of the light guide plate or on the end surface where the LED chips are not arranged to improve the light emission efficiency. Thus, a light emitting diode of a planar light source capable of obtaining sufficient brightness as a backlight of an LCD can be obtained.
When used as a liquid crystal display device, the light guide plate 704 is constituted by a polarizing plate disposed via a liquid crystal device injected between glass substrates having a light-transmitting conductive pattern (not shown) formed on a main surface of the light guide plate 704. Can be done. 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.

[0053]

(Example 1) A light-emitting element having an emission peak of 4
An InGaN semiconductor having a thickness of 50 nm and a half width of 30 nm was used for the light emitting layer. 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 nitride-based compound semiconductor is formed by MOCVD. Formed. At the time of film formation, a gallium nitride semiconductor having N-type conductivity or P-type conductivity is formed by switching between SiH ₄ and Cp ₂ Mg as a dopant gas. As a semiconductor light emitting device, a contact layer made of a gallium nitride semiconductor having N-type conductivity, a cladding 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 provided. Formed.
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. Further, a P-type semiconductor is annealed at 400 ° C. or more 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.

An LED chip was die-bonded with an epoxy resin to a mount lead having a cup at the tip of a silver-plated copper lead frame. Each electrode of the LED chip, the mount lead and the inner lead were wire-bonded with a gold wire having a diameter of 30 μm to establish electrical continuity.

On the other hand, the photoluminescent phosphor is Y,
A solution obtained by dissolving rare earth elements of 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 fired product in water,
It was washed, separated, dried and finally formed through a sieve. The photoluminescent phosphor is such that Y (yttrium) is Gd
(Y _0.8 Gd _0.2 ) ₃ Al ₅ O ₁₂ : Yttrium aluminum oxide substituted by about 20% with (gadolinium):
Ce was formed. The substitution of Ce was 0.03.

(Y _0.8 Gd _0.2 ) ₃ Al ₅ O _{12 formed} :
80 parts by weight of the Ce phosphor and 100 parts by weight of the epoxy resin were mixed well to form a slurry. This slurry was poured into a cup on the mount lead on which the LED chip was placed. After the injection, the resin containing the photoluminescent phosphor was cured at 130 ° C. for 1 hour. Thus LED
A coating portion containing a 120 μm thick photoluminescent phosphor was formed on the chip. In the coating portion, the photoluminescent phosphor is gradually increased toward the LED chip. The irradiation intensity is about 3.
It was 5 W / cm ² . Thereafter, a translucent epoxy resin was formed as a mold member for the purpose of further protecting the LED chip and the photoluminescent phosphor from external stress, moisture, dust and the like. The mold member was cured at 150 ° C. for 5 hours after inserting a lead frame on which a coating portion of the photoluminescent phosphor was formed into a shell-shaped mold frame, mixing a translucent epoxy resin. When the light emitting diode thus formed was viewed from the front side of the light emission observation, the center portion was colored yellowish by the body color of the photoluminescent phosphor.

The chromaticity point, color temperature and color rendering index of the thus obtained light emitting diode capable of emitting white light were measured.
The chromaticity points (x = 0.302, y = 0.28, respectively)
0), color temperature 8080K, Ra (color rendering index) = 87.
The performance was close to that of 5 and 3 wavelength fluorescent lamps. The luminous efficiency was 9.5 lm / w, which was equivalent to that of a white light bulb. Furthermore, as a life test, a temperature of 25 ° C. and a current of 60 mA, and a temperature of 25 ° C.
In each of the tests conducted at A and at 20 ° C. at a temperature of 60 ° C. and 90% RH, no change due to the phosphor was observed, and it was confirmed that there was no difference in the life characteristics from that of a normal blue light emitting diode.

(Comparative Example 1) A photoluminescent phosphor was converted from (Y _0.8 Gd _0.2 ) ₃ Al ₅ O ₁₂ : Ce to (ZnCd).
A light emitting diode formation and life test were performed in the same manner as in Example 1 except that S: Cu and Al were used. Immediately after energization, white light emission was confirmed in the formed light emitting diode as in Example 1, but the luminance was low. Further, in the life test, the output became zero in about 100 hours. As a result of analyzing the cause of deterioration, the phosphor was blackened.

This is photodegradation by light emitted from the light emitting element and moisture adhering to the phosphor or moisture entering from the external environment, and deposits colloidal zinc metal on the phosphor crystal surface and changes its appearance to black. it is conceivable that. Temperature 25 ℃ 2
FIG. 8 shows a life test result together with Example 1 when 0 mA current was applied and the current was 20 mA at a temperature of 60 ° C. and 90% RH. The luminance indicates a relative value based on the initial value. The solid line is Example 1 and the broken line is Comparative Example 1.

(Example 2) In the nitride compound semiconductor of the LED chip, the In content was increased from that of Example 1 so that the emission peak was 460 nm. Similarly, as a photoluminescent phosphor, the content of Gd was increased compared to Example 1 (Y
100 light emitting diodes were formed in the same manner as in Example 1 except that _0.6 Gd _0.4 ) ₃ Al ₅ O ₁₂ : Ce was used, and a life test was performed.

The chromaticity point, color temperature and color rendering index of the thus obtained light emitting diode capable of emitting white light were measured.
The chromaticity points (x = 0.375, y = 0.37, respectively)
0), color temperature 4400 K, Ra (color rendering index) = 86.
It was 0. Further, in the life test, an average of 100 formed light emitting diodes was performed. The luminous intensity before the life test was set to 100%, and the average luminous intensity after 1000 hours was examined. It was 98.8% after the life test, and it was confirmed that there was no difference in characteristics. FIGS. 10A, 10B, and 10C show the emission spectra of the photoluminescent phosphor of this example, the LED chip, and the light emitting diode, respectively.

Example 3 The photoluminescent phosphor was made to contain Sm in addition to the rare earth elements of Y, Gd and Ce (Y
_0.39 Gd _0.57 Ce _0.03 Sm _0.01 ) ₃ Al ₅ O ₁₂ Phosphor was used in the same manner as in Example 1 except that a light emitting diode was used.
0 were formed. Even when this light-emitting diode was turned on at a high temperature of 130 ° C., the average temperature characteristic was about 8% better than that of the light-emitting diode of Example 1.

Example 4 The light emitting diode of the present invention was used for a display which is one of the LED displays as shown in FIG. Light emitting diodes formed in the same manner as in Example 1 were arranged in a 16 × 16 matrix on a ceramic substrate on which a copper pattern was formed. The substrate and the light emitting diode were soldered using an automatic solder mounting device. Next, it was arranged and fixed inside the housing 504 formed of a phenol resin. Light blocking member 505
Is integrally formed with the housing. Silicon rubber 4 in which the housing, the light emitting diode, the substrate, and a part of the light shielding member are colored black by pigment except for the tip of the light emitting diode.
06. Thereafter, the silicone rubber was cured at room temperature for 72 hours to form an LED display. This LED display and a RAM (Random, Access, Memory) for temporarily storing input display data
ry) and a gradation control circuit for calculating a gradation signal for lighting the light emitting diode to a predetermined brightness from the data stored in the RAM, and a driver for lighting the light emitting diode by switching with the output signal of the gradation control circuit And the driving means of the CPU having
A display device was constructed. Drive LED display to make black and white LE
It was confirmed that the device could be driven as a D display device.

[0065] emitting diode (Example 5) Example 5 is represented by the general formula as photoluminescent phosphor (Y _{0. 2} G
100 light emitting diodes were formed in the same manner as in Example 1 except that the phosphor represented by d _0.8 ) ₃ Al ₅ O ₁₂ : Ce was used. The chromaticity point (average value) of the light-emitting diode thus obtained was (x = 0.450, y = 0.420), and it was possible to emit light of a bulb color. In addition, the light emitting diode of Example 5 was lower in luminance by about 40% than the light emitting diode of Example 1. However, in the life test, excellent weather resistance was shown as in Example 1. The respective emission spectra of the photoluminescent phosphor, LED chip and light emitting diode of this embodiment are shown in FIG.
(B) and (C) respectively.

(Embodiment 6) The light emitting diode of Embodiment 6 has a general formula Y ₃ Al ₅ O as a photoluminescent phosphor.
₁₂ : 100 light emitting diodes were formed in the same manner as in Example 1 except that the phosphor represented by Ce was used. The light emitting diode of Example 6 was slightly yellowish greenish white compared to the light emitting diode of Example 1. However, in the life test, excellent weather resistance was shown as in Example 1. The photoluminescent phosphor of this embodiment, L
Each emission spectrum of the ED chip and the light emitting diode,
This is shown in FIGS. 12 (A), (B) and (C).

(Embodiment 7) The light emitting diode of Embodiment 7 is a photoluminescent phosphor of the general formula Y ₃ (Al
100 light emitting diodes were formed in the same manner as in Example 1 except that a phosphor represented by _0.5 Ga _0.5 ) ₅ O ₁₂ : Ce was used. The light emitting diode of Example 7 was greenish and had low brightness. However, in the life test, excellent weather resistance was shown as in Example 1. The emission spectra of the photoluminescent phosphor, the LED chip, and the light emitting diode of this embodiment are sequentially shown in FIG.
(A), (B) and (C).

(Embodiment 8) The light emitting diode of the embodiment 8 has a general formula Gd ₃ (A
100 light-emitting diodes were formed in the same manner as in Example 1, except that a phosphor not containing Y represented by l _0.5 Ga _0.5 ) ₅ O ₁₂ : Ce was used. The light emitting diode of Example 8 had low luminance, but exhibited excellent weather resistance in the life test as in Example 1.

(Embodiment 9) The light emitting diode of the embodiment 9 has a general formula Y ₃ In ₃ as a photoluminescent phosphor.
100 light emitting diodes were formed in the same manner as in Example 1 except that a phosphor not containing Al represented by O ₁₂ : Ce was used. The light emitting diode of Example 9 had low luminance, but exhibited excellent weather resistance in the life test as in Example 1.

[0070]

The LED display device of the present invention realizes a light emitting diode having high luminous efficiency even when used for a long time at high luminance by combining a gallium nitride compound semiconductor light emitting element and a specific phosphor. Furthermore, the light-emitting diode according to the present invention can be used for lighting, in addition to display on a vehicle, in the aviation industry, and in general electric equipment, such as reliability, power saving, size reduction, and color temperature variability. In particular, the photoluminescent phosphor used in the present invention can be used as a light source having a short afterglow and a response speed of 120 ns. In addition, when the luminescent color is white and the human eye visually recognizes the light for a long time, a light-emitting diode that is less stimulating and easy on the eyes can be obtained. Further, even though the LED chip has a monochromatic peak wavelength, it has a high spectral rendering because it has a certain spectral width. This is an essential advantage when used widely as a light source. That is, a light source for a scanner having a wide spectrum width using a light emitting diode can be used.

In particular, the light-emitting diode of the present invention can be a light-emitting diode capable of emitting white light, which has a high degree of luminance and color shift even when used for a long time, and has a very small decrease in luminous efficiency. In addition, it is possible to suppress a decrease in luminance due to resin deterioration.

The light emitting diode of the present invention can emit light efficiently. That is, in general, it is more efficient to convert the phosphor from the short wavelength side to the long wavelength side. In a light-emitting diode, visible light is more preferable because ultraviolet light deteriorates resin (when resin is used for a mold member or a coating member). The present invention utilizes blue light on the short wavelength side of visible light, and can efficiently convert it to light on the longer wavelength side by the photoluminescent phosphor. Furthermore, the converted light has a longer wavelength side than the light emitted from the LED chip (that is, the light energy from the phosphor is smaller than the band gap of the LED chip). Therefore, even if the light is reflected and scattered by the photoluminescent phosphor on the non-light-emitting observation surface side such as the mount lead side, it is hard to be absorbed by the LED chip. Therefore, even if the light converted by the photoluminescent phosphor is directed to the LED chip side, the light is not absorbed by the LED chip but is reflected by a mount lead cup or the like, so that light can be emitted efficiently.

The light-emitting diode of the present invention can be various light-emitting diodes such as a light-emitting diode with high luminance and color shift even when used for a long time, and a light-emitting efficiency with a very small decrease. Even in the case where the light emitting diodes are arranged in the same manner, it is possible to prevent the phosphor from being excited by the light from the other light emitting diode and being simulated. Further, since the uneven light emission of the LED chip itself can be dispersed by the phosphor, a light emitting diode having more uniform light emission can be obtained. Normally, light emitted from an LED chip is emitted via an electrode that supplies power to the LED. The emitted light becomes a shadow of an electrode formed on the LED chip. A certain unnecessary light emission pattern is obtained by the electrodes. Therefore, light cannot be emitted uniformly in all directions. According to the present invention, the light emitted from the LED chip is scattered by the photoluminescent phosphor, so that the light emitting diode can emit light uniformly and does not take an unnecessary light emitting pattern.

[Brief description of the drawings]

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

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

FIG. 3 is a diagram showing an example of an emission spectrum of a light emitting diode according to the present invention.

FIG. 4A shows an example of an absorption spectrum of a photoluminescent phosphor used in the present invention, and FIG.
(B) is a diagram showing an example of an emission spectrum of the photoluminescent phosphor used in the present invention.

FIG. 5 is a schematic view of an LED display device using a light emitting diode according to the present invention.

FIG. 6 is a block diagram of the LED display device used in FIG. 5;

FIG. 7 is a schematic diagram of another LED display device using a light emitting diode according to the present invention.

FIG. 8 (A) shows a temperature of 25 ° C.2 with a light emitting diode of Comparative Example 1 shown for comparison with Example 1 of the present invention.
FIG. 8B shows a life test at a current of 20 mA at a temperature of 60 ° C. and 90% RH with a light emitting diode of Comparative Example 1 shown for comparison with Example 1 of the present invention. It is a graph shown.

FIG. 9 is a partial front view of a display device in which light-emitting diodes capable of emitting light of RGB are arranged as one picture element in addition to the light-emitting diodes of the present invention.

FIG. 10A shows (Y _0.6 Gd _0.4 ) ₃ Al ₅ O
₁₂ shows the emission spectrum of the photoluminescent phosphor of Example 2 represented by Ce. FIG. 10B shows an emission spectrum of the LED chip of Example 2 having a main peak wavelength of 460 nm. FIG. 10C shows an emission spectrum of the light emitting diode of Example 2.

FIG. 11A shows (Y _0.2 Gd _0.8 ) ₃ Al ₅ O
₁₂ shows the emission spectrum of the photoluminescent phosphor of Example 5 represented by Ce. FIG. 11B shows an emission spectrum of the LED chip of Example 5 having a main peak wavelength of 450 nm. FIG. 11C shows an emission spectrum of the light-emitting diode of Example 5.

FIG. 12 (A) shows an emission spectrum of the photoluminescent phosphor of Example 6 represented by Y ₃ Al ₅ O ₁₂ : Ce. FIG. 12B shows that the main peak wavelength is 450.
9 shows the emission spectrum of the LED chip of Example 6 having nm. FIG. 12C shows an emission spectrum of the light emitting diode in Example 6.

FIG. 13A shows Y ₃ (Al _0.5 Ga _0.5 ) ₅ O
₁₂ shows the emission spectrum of the photoluminescent phosphor of Example 7 represented by Ce. FIG. 13B shows an emission spectrum of the LED chip of Example 7 having a main peak wavelength of 450 nm. FIG. 13C shows an emission spectrum of the light-emitting diode of Example 7.

[Explanation of symbols]

101, 701: Coating portion containing photoluminescence 102, 202, 702: LED chip 103, 203: Conductive wire 104: Mold member 105: Mount lead 106・ Inner lead 201 ・ ・ ・ Mold member containing photoluminescence 204 ・ ・ ・ Case 205 ・ ・ ・ Electrode provided on the case 501 ・ ・ ・ Light emitting diode 504 ・ ・ ・ Case 505 ・ ・ ・Shielding member 506 Filler 601 LED display 602 Driver 603 RAM 604 Gradation control means 703 Metal substrate 704 Light guide plate 705, 707 ..Reflection member 706 ・ ・ ・ Scattering sheet

Claims (2)

[Claims] 1. A red system corresponding to three primary colors of light,
An LED display device comprising: an LED display in which one picture element composed of light-emitting diodes capable of emitting green and blue light is arranged in a matrix; and a driving circuit that drives each of the light-emitting diodes of the LED display. An LED display device, wherein a white light emitting diode is arranged in addition to a light emitting diode capable of emitting red, green and blue light in one picture element. 2. The LED chip, wherein the white light emitting diode is a gallium nitride-based compound semiconductor disposed in a cup of a mount lead, and a yttrium / aluminum / garnet system activated on cerium disposed on the LED chip. The LED display device according to claim 1, further comprising a phosphor.