JPH11161197A - Image display device - Google Patents

Abstract

(57) Abstract: Provided is an image display device that improves luminance without increasing the amount of light emission by adopting a structure that reduces attenuation of light emitted from a light emitting element and improves a light collection rate. thing. In addition, an electrode around the light emitting element is eliminated, thereby realizing a small light emitting module. SOLUTION: By forming an electrode 2 of a light emitting element 1 only on a surface in contact with a circuit board 7, emitted light is not blocked by the electrode. In addition, by adopting a structure sandwiched between the circuit board 7 and the glass substrate 13, no electrode is provided around the light emitting element 1, and a reflector can be formed near the element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device used for a circuit of an electronic device.

[0002]

2. Description of the Related Art In recent years, image display devices such as a liquid crystal panel and a plasma display have been receiving attention. Light-emitting diodes (LEDs) are used in large image display devices installed in stadiums and stations, and recent trends demand higher brightness, higher definition, and lower cost. Have been.

A conventional image display apparatus using LEDs will be described with reference to FIGS. FIG. 7 shows a conventional image display device. In order to display a color image, the image display device has a red LED 26 and a green LED 27 which are three primary colors of light.
And a blue LED 28, a surface electrode 24, which is a lead of each LED, is inserted into a hole formed in the circuit board 23, and the surface electrode 6 formed on the circuit board 23 is electrically connected to the surface electrode 6 by a solder 10 by a DIP soldering method. Physically and physically.

FIG. 8 shows a detailed sectional view of the red LED 26. The red LED 26 has a red light emitting element 15 as a light source, and the red light emitting element 15 is joined to the surface concave portion of the lead 24 by the conductive adhesive 17. Since the periphery of the red light emitting element 15 is surrounded by the lead 24, the reflected light of the red light emitting element 15 is reflected by the lead 24 and becomes upward reflected light 31. The red light emitting element 15 is a substrate side electrode 18
And electrodes on two surfaces of the front electrode 2 and emit light by applying a voltage between the two electrodes. The substrate-side electrode 18 is made of a material that provides good electrical bonding with the conductive adhesive 17. Generally, an aluminum film having a good reflection effect of light emitted inside the red light-emitting element 15 is used. The surface of the red light emitting element 15 on the surface electrode 2 side is covered with a transparent protective film 3 having a role of physically protecting the element surface other than the surface electrode 2.
The surface electrode 2 blocks the light 32 emitted inside the red light-emitting element 15, so that it is necessary to reduce the area as much as possible. The surface electrode 2 is connected by a gold wire 21 by a wire bonding method in order to obtain electrical conduction with the lead 24. As the gold wire 21, a thin wire is used as much as possible to block light emitted from the red light emitting element 15. After fixing the red light-emitting element 15 on the lead 24 and obtaining electrical connection, it is sealed with a transparent or red-colored transparent resin to complete a red LED 26.

FIG. 9 shows a green LED 27 and a blue LED 28.
FIG. Green LED 27 and Blue LED 28
Has the same other structure except for the light emitting element. The red light-emitting element 15 has two electrodes as shown in FIG. 8, while the blue light-emitting element 1 and the green light-emitting element 25 are supplied with power from the outside. Therefore, as shown in FIG. In addition, the blue light emitting element 1 and the green light emitting element 25 are bonded on the lead 24 with the adhesive 22. This adhesive 22
May be conductive or insulative, and it is important to make the reflected light 30 emitted from each of the light emitting elements 1 and 25 as strong as possible. The respective light emitting elements 1 and 25 fixed to the leads 24 are connected between the surface electrode 2 and the leads 24 by gold wires 21 by a wire bonding method in order to obtain electrical conduction. Since the surface electrode 2 blocks light emitted inside each of the light emitting elements 1 and 25, it is necessary to reduce the area as much as possible. Further, the protective film 3 needs to be made of a material having a good light transmittance. In order to protect the blue LED element, the green LED element, and the gold wire, they are sealed with a transparent resin or a transparent resin colored in each color to complete a blue LED 28 or a green LED 27.

[0006]

However, in the above-mentioned conventional structure, an electrode for shielding light and a gold wire are formed on the upper surface of the light emitting element, which causes a reduction in the brightness of the LED. Further, light is attenuated by the transparent protective film of the light emitting element, which is a factor of reducing the brightness of the LED.

[0007] Further, since the adhesive having a light reflection effect for fixing the lead and the light emitting element is composed of a metal component that reflects light and a resin component that obtains an adhesion effect, the light reflection adhesive is compared with a metal film. The rate is low, and this is a factor in lowering the luminance. In addition, when the gold wire establishes electrical continuity with the external electrode, an electrode for bonding the gold wire is formed in the vicinity of the side surface of the light emitting element, and the reflection plate is formed outside the electrode, so that the amount of reflected light is reduced, When the reflector is provided inside the electrode, a gold wire is formed above the reflector, which causes a problem of blocking light.

SUMMARY OF THE INVENTION In view of the above problems, the present invention maximizes the amount of light emitted from a light-emitting element to improve the brightness as viewed from above, and can reduce the size of an LED and provide a high-definition image display device. The purpose is to provide.

[0009]

The image display device of the present invention has a structure in which all the electrodes of the light emitting element are provided on the surface in contact with the substrate, so that light is blocked on the light emitting element when viewed from above. Without, it is possible to improve the brightness viewed from above, and also possible to increase the size of the electrode of the light emitting element, increase the amount of light reflected and at the same time improve the reliability of the junction, A light-emitting element can be mounted on a semiconductor element.

[0010] Further, by adopting a structure in which a transparent electrode is provided on a glass substrate provided for protecting the element, gold wires can be eliminated, and a reflector can be formed near the light emitting element. In addition, an element having electrodes on only one surface and an element having electrodes on two surfaces can be mounted on the same circuit board.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a first aspect of the present invention, all electrodes of a light emitting device are provided on one surface in contact with a circuit board, and are electrically connected to electrodes on the circuit board. The light emitting element is mounted on the light emitting element. Since there is nothing obstructing the light above the light emitting element, the brightness can be improved, and the electrode of the light emitting element can be enlarged. Therefore, it has the effect of increasing the amount of light reflection and improving the reliability of bonding. Furthermore, since there is no electrode around the light emitting element,
It has the function of realizing a small LED as compared with a conventional LED.

According to a second aspect of the present invention, the electrode on the circuit board is provided on a semiconductor element fixed on the circuit board. In addition, the provision of the semiconductor element has an effect of protecting the light emitting element from abnormal voltage due to static electricity or the like. The invention according to claim 3 is characterized in that the electrodes of the light emitting element are formed in 70% to 100% of the area of the light emitting element, and the reflected light is reflected at the interface between the light emitting element and the electrode. Yes, in addition to the function of the invention of claim 1,
Since the reflected light is reflected at the interface with the electrode occupying 70 to 100% of the area of the light emitting element, it has the effect of improving the reflectance.

According to a fourth aspect of the present invention, the electrode on the surface of the circuit board in contact with the light emitting element is conductive with the back electrode provided on the back surface of the circuit board. Can be made extremely short, and has an effect of providing a small-sized light-emitting module that is resistant to static electricity. According to a fifth aspect of the present invention, the light emitting device has electrodes on two surfaces, the electrode on one surface of the light emitting device is conductive with the electrode on the circuit board on which the reflector is formed, and the electrode on the other surface is The light emitting element is mounted on the circuit board by conducting with the transparent electrode on the glass substrate, and there is no gold wire above the light emitting element. Since the light is not blocked by the gold wire, and the side light does not have an electrode for the gold wire, the light is reflected upward by the reflector provided near the side surface of the light emitting element, and has an effect of improving brightness. Furthermore, as in the first aspect of the invention, a small LED
Has the effect of realizing

According to a sixth aspect of the present invention, the electrode on the circuit board is provided on a semiconductor element fixed on the circuit board. In addition, the provision of the semiconductor element has an effect of protecting the light emitting element from abnormal voltage due to static electricity or the like. The invention according to claim 7 is characterized in that a reflection plate for reflecting light emitted from the light emitting element is provided near the side surface of the light emitting element on the circuit board, and above the reflection plate. There is no gold wire, which is a factor in lowering the brightness, so the reflected light is not blocked, and the reflector can be provided near the side of the light emitting device, maximizing the light emission of the light emitting device and improving the brightness Has the effect of causing.

The invention according to claim 8 is characterized in that the circuit board has a plurality of recesses, and conduction between the electrode of the light emitting element and the electrode of the circuit board is obtained at the bottom of the recess. Yes, a high-brightness module can be mounted at a high density, and further, there is an effect that red, green, and blue light-emitting elements can be mounted on the same circuit board. According to a ninth aspect of the present invention, the concave portion on the circuit board is covered with a glass substrate on which a transparent electrode is formed, and has the same function as the eighth aspect of the present invention.

Hereinafter, an image display device according to the present invention will be described with reference to the drawings. In the following description, the same components as those of the conventional device shown in FIGS.
The description is omitted. (Embodiment 1) FIG. 1 shows an image display apparatus according to Embodiment 1 of the present invention. In FIG. 1, 1 and 25 are blue and green light emitting elements, 2 is an electrode, 3 is a protective film, 4 is a protrusion, 5 is a conductive adhesive, 6 is a surface electrode, 7 is a circuit board,
Reference numeral 8 denotes wiring in the substrate, 9 denotes a back electrode, 10 denotes solder, 11 denotes a light reflecting plate, 12 denotes a waterproof conductive adhesive, 13 denotes a glass substrate, and 14 denotes a sealing resin.

A method for manufacturing an LED having the above configuration will be described. First, the circuit board 7 having conductivity between the front surface electrode 6 and the back surface electrode 9 through the electric wiring 8 and having the concave portion on which the light emitting elements 1 and 25 are mounted is manufactured by a normal printed circuit board manufacturing process. I do. Next, the solder 10 is formed on the back electrode 9 by plating or cream solder printing. Next, the light reflecting plate 11 is attached to the inner wall of the concave portion of the circuit board 7 near the side surfaces of the light emitting elements 1 and 25.

Next, the area of the electrodes 2 of the light emitting elements 1 and 25 is set to 70 to 100% of the area of the light emitting elements, and the projections 4 having a height of about 40 μm are formed on the electrodes 2 of the light emitting elements 1 and 25. Form. The projections 4 are formed by bonding a gold wire to an electrode by a wire bonding method and then cutting the gold wire in the vicinity of the bonding. Further, the projections 4 can be formed on the electrodes by using a plating method which has been conventionally used.

The light emitting elements 1 and 25 having the projections 4 having a height of about 40 microns are immersed on a conductive adhesive thinly extended to a thickness of about 25 microns, and the conductive adhesive 5 is placed on the projections 4. Transcribe. After aligning the light emitting elements 1 and 25 with the conductive adhesive 5 transferred onto the protrusions 4 with the circuit board 7, they are mounted at predetermined positions. Next, the conductive adhesive 5 is cured, and conduction between the circuit board 7 and the light emitting element 1 is obtained. Thereafter, in order to improve the bonding reliability and protect the light emitting elements 1 and 25, the sealing resin 14 is poured between the circuit board 7 and the light emitting element 1, and the sealing resin 14 is cured by heating, and the mounting process is performed. finish. Next, a waterproof conductive adhesive 12 is applied on the circuit board 7 to protect the light emitting elements 1 and 25, and the glass substrate 13 on which the transparent electrode 16 is formed is fixed to complete the light emitting module.

According to the light emitting module having the above-described structure, the direct light 29 emitted from the light emitting elements 1 and 25 does not pass through the protective film of the conventional module. Does not occur, and the reflected light 30 is reflected at the interface between the light emitting elements 1 and 25 and the electrode 2 by the electrode 2 formed on the light emitting elements 1 and 25 with an area of 70% to 100%. In the conventional module, the light emitting element is bonded to the electrode with an adhesive, so that the reflected light is reflected by the adhesive and causes a decrease in luminance. However, according to this module, the reflected light is generated inside the element. , The reflectance can be improved. Further, since there is no electrode for the gold wire, the side surface light 31 is reflected upward by the reflector 11 provided near the side surface of the light emitting elements 1 and 25. Also, in the module having the above configuration, the light emitting elements 1 and 25 have the same light emission amount because they do not have the protective film and the adhesive layer which have caused the luminance reduction, which the conventional module has. However, since the light attenuation is reduced and the light collection rate is also improved, the brightness of the LED is greatly improved to about 150% as compared with the conventional one.

The size of the light emitting module is about 6 times smaller than that of the conventional module because gold wire electrodes are not required.
It became 0%. (Embodiment 2) FIG. 2 shows an image display apparatus according to Embodiment 2 of the present invention. In FIG. 2, 15 is a red light emitting element, 3
Is a transparent protective film, 4 is a protrusion formed on the electrode 2, 5 is a conductive adhesive, 6 is a surface electrode, 13 is a glass substrate, 16
Is a transparent electrode, 17 is a light reflection type conductive adhesive, and 18 is an electrode.

A method of manufacturing an LED having the above configuration will be described. First, the protrusions 4 are formed on the circuit board 7 and the electrodes 2 of the red light emitting element 15 as in the first embodiment, and the conductive adhesive 5 is transferred. Next, a light-reflective conductive adhesive 17 is applied on the surface electrodes 6 of the circuit board 7. Next, the red light emitting element 15 is mounted on the circuit board 7 after being positioned. Next, the adhesive 17 is heated to about 50 degrees and temporarily cured, and the surface electrode 6 on the circuit board 7 and the electrode 18 on the red light emitting element 15 are electrically connected and fixed by the light reflective conductive adhesive 17. Is done. Next, a waterproof conductive adhesive 12 is applied on the circuit board 7, and the projections 4 coated with the conductive adhesive 5 at predetermined positions on the circuit board 7 and the glass on which the transparent electrodes 16 are formed It is mounted after being aligned with the substrate 13. At this time, conduction between the projection 4 and the transparent electrode 12 is obtained by the conductive adhesive. The transparent electrode 16 on the glass substrate 13 is electrically connected to the back electrode 9 by the waterproof conductive adhesive 12 and the wiring 8 in the substrate. Further, the front surface electrode 6 and the back surface electrode 9 are also conductive by the wiring in the substrate.

According to the light emitting module having the above-described configuration, the direct light 29 emitted from the red light emitting element 15 is not transmitted to the gold wire because the gold wire of the conventional module is not provided. Unobstructed and side light 31
Since there is no gold wire electrode, the light is reflected upward by the reflector 11 installed near the side surface of the light emitting element 15. As described above, according to the present embodiment, since the gold wire and the electrode for joining the gold wire are not provided, the light emitting element 15
Even though the amount of light emitted is the same, the light is not blocked much,
Since the light collection rate was also improved, the brightness of the LED was significantly improved to about 130% as compared with the conventional one. (Embodiment 3) FIG. 3 shows an image display apparatus according to Embodiment 3 of the present invention. 3, reference numerals 1 and 25 denote blue and green light-emitting elements, 19 denotes a semiconductor element, 20 denotes an upper electrode of the semiconductor element, 21 denotes a gold wire, 22 denotes an adhesive, and otherwise has the same configuration as in the first embodiment. Yes, the first embodiment is applied.

The difference from the first embodiment is that the semiconductor element 19 is fixed on the circuit board 7 as described above, and there is conductivity between the semiconductor element 19 and the surface electrode by a gold wire by a wire bonding method. The light emitting elements 1 and 25 are vulnerable to abnormal voltages such as static electricity.
To protect 25, a diode is needed. In this embodiment, the semiconductor element 19 which is a diode is provided. However, in order to protect the light emitting element from being damaged by static electricity, the electric wiring between the diode and the light emitting elements 1 and 25 may be as short as possible. is necessary.

According to the structure shown in FIG. 3, the wiring between the semiconductor element 19, which is a diode, and the light emitting elements 1, 25 is about 4 mm.
With a structure as short as 0 microns, a light emitting module that is strong against static electricity can be provided. (Embodiment 4) FIG. 4 shows an image display apparatus according to Embodiment 4 of the present invention. In FIG. 4, 15 is a red light emitting element,
19 is a semiconductor element, 20 is an upper electrode of the semiconductor element, 21 is a gold wire, and otherwise has the same configuration as that of the second embodiment.
This is an application of the second embodiment.

The difference from the second embodiment is that the semiconductor device 1
9 is fixed on the circuit board 7, and there is conductivity between the semiconductor element 19 and the surface electrode by the gold wire by the wire bonding method. The red light emitting element 15 is vulnerable to an abnormal voltage such as static electricity, and a diode is required to protect the light emitting element 15 from the abnormal voltage. In the present embodiment, a semiconductor element 19, which is the same diode as in the third embodiment, is provided, and the electric wiring between the diode and the light emitting element 15 is made as short as possible.

According to the structure shown in FIG. 4, the wiring between the semiconductor element 19 as a diode and the light emitting element 15 is
8 is about 20 microns, and between the electrodes 2 is the gold wire 2
1 and a length of about 2 mm that conducts through the wiring 8 in the substrate and the transparent electrode 16, a short structure as a whole is possible, and a light emitting module resistant to static electricity can be provided. (Embodiment 5) FIG. 5 shows an image display apparatus according to Embodiment 5 of the present invention. In FIG. 5, reference numeral 1 denotes a blue light emitting element;
5 is a red light emitting element, 25 is a green light emitting element, 7 is a circuit board, 13 is a glass substrate, 10 is solder, 23 is a circuit board of an image display device, and 24 is an electrode.

The image display device has three primary colors of light, red,
It is composed of light emitting elements of three colors, green and blue. FIG. 5A shows the light emitting module for each color described in the first to fourth embodiments mounted on a circuit board 23 of an image display device. With such a structure, a module with high luminance can be mounted at a high density. Also,
According to the embodiment shown in FIG. 5B, red, green, and blue light emitting elements can be mounted on the same circuit board 7,
One pixel of the image display device can be formed. (Embodiment 6) FIG. 6 shows an image display apparatus according to Embodiment 6 of the present invention. In FIG. 6, reference numeral 7 denotes a circuit board on which a large number of concave portions are formed. FIG. 6A is an application example of the first embodiment, FIG. 6B is an application example of the first and second embodiments, FIG.
(C) is an application example of the first embodiment.

By forming a large number of recesses on the circuit board 7 and mounting light emitting elements of each color in the recesses, the circuit board 7 itself becomes an image display device having a plurality of pixels.

[0030]

According to the image display apparatus of the present invention, even if the light emission amount of the light-emitting element is the same, the attenuation of light is reduced and the amount of condensed light is increased, so that the luminance is improved and the image display apparatus with high luminance is realized. Can be realized. Further, since there is no electrode portion around the light emitting element, a small LED can be realized as compared with a conventional LED. Further, the image display device can be mounted on the substrate of the image display device at high density, and a high-definition image display device can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view according to a second embodiment of the present invention.

FIG. 3 is a sectional view according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view according to a fourth embodiment of the present invention.

FIGS. 5A and 5B are cross-sectional views according to a fifth embodiment of the present invention.

FIGS. 6 (a), (b) and (c) are cross-sectional views according to a sixth embodiment of the present invention.

FIG. 7 is a schematic view of a conventional embodiment.

FIG. 8 is a sectional view of a conventional embodiment.

FIG. 9 is a sectional view of a conventional embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Blue light-emitting element 2 Electrode 3 Protective film 4 Projection 5 Conductive adhesive 6 Surface electrode 7 Circuit board 8 In-board wiring 9 Back electrode 10 Solder 11 Light reflector 12 Waterproof conductive adhesive 13 Glass substrate 14 Sealing Resin 15 Red light emitting element 16 Transparent electrode 17 Light reflective conductive adhesive 18 Electrode 19 Semiconductor element 20 Semiconductor element upper electrode 21 Gold wire 22 Adhesive 23 Circuit board of image display device 24 Surface electrode 25 Green light emitting element 26 Red LED 27 Green LED 28 Blue LED 29 Direct light 30 Reflected light 31 Side light 32 Blocked light

Claims (9)

[Claims] 1. An image display wherein all electrodes of a light emitting element are provided on one surface in contact with a circuit board, electrically connected to electrodes on the circuit board, and the light emitting element is mounted on the circuit board. apparatus. 2. The image display device according to claim 1, wherein the electrodes on the circuit board are provided on a semiconductor element fixed on the circuit board. 3. The image according to claim 1, wherein the electrodes of the light emitting element are formed in an area of 70% to 100% of the area of the light emitting element, and reflected light is reflected at an interface between the light emitting element and the electrode. Display device. 4. The image display device according to claim 1, wherein an electrode on a surface of the circuit board in contact with the light emitting element has conductivity with a back electrode provided on a back surface of the circuit board. 5. The light emitting device has electrodes on two surfaces, one electrode of the light emitting device is electrically connected to an electrode on a circuit board on which a reflection plate is formed, and the other electrode is on a glass substrate. An image display device, which is electrically connected to a transparent electrode and has a light emitting element mounted on a circuit board. 6. The image display device according to claim 5, wherein the electrodes on the circuit board are provided on a semiconductor element fixed on the circuit board. 7. The image display device according to claim 1, wherein a reflection plate for reflecting light emitted from the light emitting element is provided near a side surface of the light emitting element on the circuit board. 8. The circuit board according to claim 1, wherein the circuit board has a plurality of recesses, and conduction between an electrode of the light emitting element and an electrode of the circuit board is obtained at a bottom surface of the recess. Image display device. 9. The image display device according to claim 8, wherein the concave portion on the circuit board is covered with a glass substrate on which a transparent electrode is formed.