JP2979961B2 - Full color 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 an LED display in which a plurality of LED lamps (hereinafter, referred to as LEDs) whose light emitting chips are molded with resin, glass or the like are connected on the same circuit board. The present invention relates to a full-color LED display in which constituent red, green and blue LEDs are connected on the same circuit board.

[0002]

2. Description of the Related Art As an LED display, there is known an LED display in which a light emitting chip mounted on a lead frame is sealed with a resin, glass, or the like, for example, in a lens shape, and is regularly arranged on a substrate. I have. At present, a multi-color LED display using a red LED and a green LED has already been put to practical use, but a full-color display has not yet been put into practical use at the stage of trial production.

[0003] Currently, a full-color LED display being prototyped uses a red LED as a material for a light emitting chip.
aAlAs, GaAsP, GaP for green LED, blue L
SiC is used for the ED. However, the luminous intensity of the green LED and the blue LED is lower than the luminous intensity of the red LED. In particular, since the blue LED has only 1/100 or less, there is a disadvantage that a display with high luminance cannot be obtained.

For the purpose of compensating for this drawback, the display increases the number of green LEDs and blue LEDs relative to the number of red LEDs in one pixel. There is a drawback that the overall resolution is poor and the power consumption is large. Furthermore, when displaying white, the luminous intensity ratio of the LED of each emission color, so-called white balance, is determined by an LE composed of three types of light-emitting chips.
The use of D has a drawback that the directional characteristics of each LED are different, and thus are not constant.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and an object of the present invention is to use a high-luminance LED to provide a display with high brightness and low power consumption. Full-color LED that achieves stable white balance by combining LEDs that can easily adjust the directional characteristics while realizing
The realization of a display.

[0006]

In order to improve the brightness of a full color LED display, it is necessary to use green LEDs and blue LEDs having high luminous intensity. Furthermore, in order to obtain a stable white balance, it is necessary to arrange a small number of LEDs having the same directivity as one pixel. We can satisfy the demand at the same time full color L
Red LED that constitutes one pixel as ED display
Full-color LED in which a lamp, a green LED lamp, and a blue LED lamp are connected on the same circuit board
In the display, the green LED lamp is covered with a mold lens and has a thickness of 150 μm or less, a green light-emitting chip made of a gallium nitride-based compound semiconductor formed on a sapphire substrate, and the blue LED lamp is covered with a mold lens. A blue light emitting chip made of a gallium nitride-based compound semiconductor and having a thickness of 150 μm or less and formed on a sapphire substrate;
D lamp is covered with a molded lens and the maximum thickness of the blue light emitting chip and the green light emitting chip is 150
each of the LED lamps has a half-value angle in the range of ± 20 ° to ± 70 ° with respect to the center of the LED lens, and the half-value angle of the directional characteristic of the lamp is The above problem has been solved by adjusting the distance between the surface of each light emitting chip and the top of the mold member so as to be substantially the same.

As the red LED used in the LED display of the present invention, an LED comprising a conventional light emitting chip material such as GaAlAs or GaAsP can be used, and these LEDs have a luminous intensity of 1 cd or more and a luminous output of 1 mW or more. ing.

Next, a green LED and a blue LED, which are features of the present invention, are a gallium nitride-based compound semiconductor (InXAlYGa1-X-YN, 0≤X, 0
≦ Y, X + Y ≦ 1). The light emitting chip preferably has a double hetero structure in which InGaN is used as an active layer and GaN or GaAlN is used as a cladding layer. This is because the light emitting chip using InGaN as an active layer has a composition ratio of In to Ga (In / G
By setting a) to 0.4 or less, a wavelength of 380 nm to
The light emission color can be changed from a blue-violet region of 580 nm to a green region. In addition, since the gallium nitride-based compound semiconductor is a direct transition semiconductor, an LED with high luminous intensity can be realized when used as a light-emitting chip. In particular,
The luminous intensity of the green LED and the blue LED used in the LED display of the present invention both has a luminance of 1 cd or more, and preferably has a light output of 0.5 mW or more.

The half-value angle of the red, green and blue LEDs is L
It is preferable to adjust the range of ± 20 ° to ± 70 ° with respect to the center of the ED lens. When the angle is smaller than 20 °, the directivity of the display becomes strong and the white balance is hardly stabilized, and when the angle is larger than 70 °, the luminance decreases.

There are various methods for adjusting the half-value angle of each LED. When the green LED and the blue LED are light emitting chips made of a gallium nitride-based compound semiconductor, the height of the surface of the red LED chip is reduced. The half-value angle is adjusted to be the same as the height of the gallium-based compound semiconductor light emitting chip. This is because the thickness of the gallium nitride-based compound semiconductor light emitting chip is only 150 μm or less, while the thickness of the red LED light emitting chip such as GaAlAs is 300 μm.
m or more. LEDs used in displays often have the same lead frame shape and lens shape. If they are the same, adjust the surface height of the red LED chip to match that of the green and blue LEDs. By doing so, the directional characteristics of the three types of LEDs can be matched. This uses a gallium nitride-based compound semiconductor light-emitting chip with a thickness of 150 μm or less for green and blue LEDs, and a red light-emitting chip made of a material different from the gallium nitride-based compound semiconductor on a thickness of more than 150 μm. This is a special effect when doing.

[0011]

The LED display of the present invention has a green LED,
By using the same material for the light emitting chips constituting the blue LED, the size of the light emitting chip, the shape of the lead frame on which the light emitting chip is mounted, and the shape of the lens such as the resin for sealing the light emitting chip and the lead frame can be made the same. . Since the green and blue LEDs are the same, the half-value angle of the mold lens is also the same, and white balance can be easily stabilized when a display is constructed.

The gallium nitride-based compound semiconductor is also a direct transition type semiconductor, and both LEDs using the same have a luminous intensity of 1 cd or more and a light output of 0.5 mW or more. Therefore, by using these LEDs as a green component and a blue component, it is possible to achieve a much higher luminance by reducing the number of LEDs as compared with a display made of a conventional material.

Further, since the green LED and the blue LED are the same, the half value angle of the molded lens can be adjusted by adjusting only the red LED. For this purpose, the half-value angle can be adjusted by making the distance between the surface of the light emitting chip of the red LED and the vertex of the mold lens the same as that of the green LED and the blue LED. Thereby, all the half-value angles of the three colors are aligned, and a stable white balance can be obtained.

[0014]

FIG. 1 is a plan view showing an embodiment of a full-color LED display according to the present invention. This shows the display screen, red LED (R), green LED
(G) and one each of the blue LEDs (B) are arranged in a shape of Δ to form one pixel. FIG. 2 is a schematic cross-sectional view showing the structure of one pixel of the display of FIG. 1, and a red LED (R) and
The green LED (G) and the lead frame 2 of the blue LED (B) are electrically connected to each other. In addition, blue L
The lead frame of the ED is not particularly shown.

The red LED (R) has a red light emitting chip 3R of 100 μm in thickness and 350 μm square in which GaAlAs is laminated on a GaAs substrate.
The lead frame 2R on which R is mounted is molded into a lens shape with a transparent epoxy resin to form a molded lens 4. The thickness of the red light emitting chip 3R is adjusted by polishing the GaAs substrate so that the thickness of the red light emitting chip 3R becomes the same as the thickness of the green light emitting chip and the blue light emitting chip. Also, the mold lens 4 has a directional characteristic with a half value angle of B,
G and R are all molded using a mold that is ± 30 ° from the center of the lens. The luminous intensity of this red LED (R) is 2 mA at 10 mA and 2 V, and the emission wavelength is 640 nm.
have.

Next, the green LED (G) has a thickness of 10 g in which a gallium nitride compound semiconductor is laminated on a sapphire substrate.
It has a green light emitting chip 3G of 0 μm and 350 μm square. The green light emitting chip has InGaN as an active layer and GaAs.
It has a double heterostructure with 1N as a cladding layer. This green light emitting chip 3G is also mounted on a lead frame 2G having the same shape as the lead frame 2R, and is molded with the same lens shape as the red LED (R) with the transparent epoxy resin 4 similarly. The light intensity of this green LED (G) is 4 cd at 20 mA and 3.6 V, and the emission wavelength is 420.
nm.

Next, the blue LED (B) has the same thickness and the same size except that the composition of InGaN of the active layer is different from that of the green light emitting chip 3G, and the luminous intensity of the blue LED is 20 m.
A: It has 1 cd at 3.6 V and an emission wavelength of 360 nm.

Further, in order to adjust the directional characteristics, the substrate of the red light emitting chip 3R of the red LED (R) is polished so that the distance (lr) from the surface of the chip to the top of the mold lens 4R is reduced. , The green LED (G)
From the surface of the green light emitting chip 3G
Is approximately equal to the distance (lg) to the vertex of. In addition,
It goes without saying that the green LED (G) and the blue LED (B) are the same.

Further, FIG. 3 is a plan view showing the shape of the red light emitting chip 3R viewed from the mold lens 4R side and a plan view showing the shape of the green light emitting chip 3G also viewed from the mold lens 4G side. . The hatched portion in FIG. 3 indicates a light emitting portion of the light emitting chip. Needless to say, the shapes of the green light emitting chip 3G and the blue light emitting chip 3B are the same. As described above, since the green light emitting chip 3G uses sapphire as a substrate, as shown in this figure, both positive and negative electrodes are formed from the same surface side. Further, the positions of the balls at the time of wire-bonding the two electrodes are arranged diagonally so that the central portion of the chip emits light. On the other hand, the ball of the red light-emitting chip is usually provided at the center of the rectangular chip, but in the present invention, the ball is arranged at the corner so that the light-emitting portion of the red light-emitting chip 3R is at the center. As described above, by aligning the position of the light emitting portion of the red light emitting chip 3R with the green light emitting chip 3G and the blue light emitting chip 3B, it is possible to further enhance the directivity of the LED display.

As described above, the full-color LED display of the present invention is obtained by arranging the pixels in which the R, G, and B LEDs are arranged in a Δ array each one by 480 vertically and 640 horizontally. It was tens of times brighter than conventional ones using a green LED and a blue LED, and could be used outdoors. Further, this display had a very good white balance, and had the same color white within an angle of ± 30 ° from the front of the display.

[0021]

As described above, according to the present invention, a full-color display can be realized by each of the red LED, the green LED, and the blue LED, so that one pixel can be made smaller than the conventional display, and the resolution can be reduced. Dramatically improved. Also, in the directional characteristics, since the green LED and the blue LED are made of the same material, 3
Only the red LED needs to be adjusted when the colors are arranged, and maintenance is very easy.

Further, as a secondary effect, the chip size of the light emitting chip of the conventional red LED is usually 200 mm.
In contrast to the extremely small size of less than μm square, in the present invention, the size of the red light emitting chip is 350 μm square, which is the same size as the green light emitting chip and the blue light emitting chip. The life of the red LED itself is improved, and the reliability of the display is improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a full-color LED display of the present invention.

FIG. 2 is a schematic sectional view showing the structure of one pixel of the display of FIG.

FIG. 3 shows a red light emitting chip 3 viewed from the mold lens side.
The top view which shows the shape of R and the shape of the green light emitting chip 3G in comparison.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Lead frame 3 ... Light emitting chip 4 ... Mold lens

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 33/00 G09F 9/33

Claims (1)

(57) [Claims] A red LED lamp constituting one pixel;
In a full-color LED display in which a green LED lamp and a blue LED lamp are connected on the same circuit board, the green LED lamp is formed on a sapphire substrate with a thickness of 150 μm or less covered by a mold lens. A green light-emitting chip made of a gallium nitride-based compound semiconductor, a blue light-emitting chip made of a gallium nitride-based compound semiconductor formed on a sapphire substrate, wherein the blue LED lamp is covered with a mold lens and has a thickness of 150 μm or less, A red LED lamp is covered with a molded lens, the red LED chip having a thickness greater than 150 μm, which is the maximum thickness of the blue light emitting chip and the green light emitting chip, and each LED lamp has a half-value angle of the LED lens. ± 20 ° to center
Full color, wherein the distance between the surface of each light emitting chip and the vertex of the mold member is adjusted so that the half-value angle of the directivity characteristic of the lamp is substantially the same in the range of ± 70 °. LED display.