JPH11163414A - Light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve color mixture ratio of light by providing a plurality of LED chips in a region, with a slightly widened square of a prism, comprising a bottom surface of such shape which is divided with one or more straight lines containing vertical or diagonal straight line to a short side. SOLUTION: At an upper end part of a central lead terminal 15, a recessed part 15a having a tilted side wall 15c is formed, and to a bottom surface 15b of the recessed part 15a, LED chips 11 and 12 in which an anode and a cathode are formed on an upper surface and a lower surface, respectively are fixed with a conductive paste. The LED chips 11 and 12 are rectangular parallelopiped of the same size, with their bottom surfaces being square wherein a long side is 2 times or longer than a short side. In short, the bottom surfaces of the LED chips 11 and 12 are of such prisms as the square is bisected vertical to its short side. Thus, the color-mixture ratio of light emitted from the LEDs 11 and 12 is improved, while changes in ignition point position are suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device comprising a plurality of light emitting diode chips emitting light of different colors and emitting mixed color light.

[0002]

2. Description of the Related Art There is a light-emitting device that includes a plurality of light-emitting diodes (LEDs) that emit light of different colors, and emits mixed-color light in addition to light of the color emitted by each LED. FIG. 8 schematically illustrates an example of such a light emitting device. This light emitting device includes an LED chip 31 that emits red light and an LED chip 32 that emits green light.

By operating only the LED chip 31, red light is obtained, and by operating only the LED chip 32, green light is obtained. LED chips 31, 32
Are arranged close to each other, and by operating both at the same time, the red light and the green light emitted from each are mixed to obtain orange light. By utilizing the color mixture of light in this way, the number of light colors obtained is larger than the number of LED chips.

[0004] Such a light-emitting device has a simple structure and is used as a light-emitting device having a large amount of information for various uses including an indicator and a display device. When used as an indicator that indicates the operating status of the device,
It is possible to show a multi-stage state by itself, and when many are arranged and used as a dot matrix type display device, a part of the information can be emphasized by expressing it in a different color from the others.

[0005]

Generally, an LED chip has a directivity of emitting light about a direction perpendicular to the upper surface thereof. For this reason, as shown in FIG. 8, in the configuration in which the two LED chips 31 and 32 are arranged side by side, green light is emitted on both sides of the emission range O in which red light and green light are almost uniformly mixed to produce orange light. And a green light center emission range G containing only a small amount of red light. Therefore, even when the two LED chips are operated at the same time, red light or green light instead of orange light is observed from a direction oblique to the light emitting device.

However, in the conventional light emitting device, each L
Since the bottom surface of the ED chip has a square shape or a shape close thereto, the area where the LED chips are arranged is a rectangle long in the direction connecting the two chips. Although the LED chips are arranged close to each other, the center-to-center distance of each LED chip becomes longer, so that the emission range including only one light becomes larger, and a direction in which substantially uniform mixed color light can be observed. The range is narrow.

As a measure against this inconvenience, glass powder is added to a translucent resin mold covering the LED chip,
Light is diffused by disposing a ground glass or the like in the front of the light emission direction. This way,
Light is diffused and mixed over a larger area, and the emission range containing only one light is reduced. However, since much light is lost due to diffusion, the amount of light will be reduced.

In the conventional light emitting device, the distance between the centers of the LED chips is long, so that the position of the light emitting point is different between when one LED chip emits light and when the other LED chip emits light. to differ greatly. For this reason, even when observing the light emitting device from the front, the light emitting point may appear to move every time the color changes, giving an unnatural impression.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a light emitting device in which the rate of color mixture of light emitted from a plurality of LED chips is increased and the change in the position of a light emitting point is suppressed. Aim.

[0010]

In order to achieve the above object, the present invention comprises a plurality of LED chips which are arranged close to each other and emit light of different colors, and mixes the light emitted by the plurality of LED chips. In a light-emitting device that emits light, a plurality of LED chips are formed into a prism having a bottom surface in a shape obtained by dividing a rectangle by at least one straight line including a straight line perpendicular or oblique to a short side thereof, and Place it in the area of the expanded size.

This light emitting device is composed of two or more prismatic LED chips, and the shape of the bottom surface in a state where all the LED chips are in contact with the side surface is a rectangle. The rectangle here is
It is a shape that includes both rectangles and squares excluding squares. L
The ED chips are not in a state where the side surfaces are in contact with each other, but are arranged slightly apart from the contact state, and the area where all the LED chips are arranged has a substantially rectangular shape slightly larger than the bottom surface in the contact state. Become.

Lines dividing the bottom surface of the contacting rectangular shape include:
At least one line perpendicular or oblique to the short side, that is, a line not parallel to the short side is included. Therefore,
The surface on which at least one set of adjacent LED chips faces includes a surface that is non-parallel to the short side of the substantially rectangular area where all the LED chips are arranged.

The rate at which the light emitted by adjacent LED chips mixes increases as the distance between the centers of the two chips decreases. In a portion facing the non-parallel surface to the short side of the substantially rectangular area, the distance between the centers of the two LED chips is at most about 1/2 of the length of the short side of the area. For this reason, the ratio at which the light emitted from these two LED chips is mixed increases. In addition, even when the LED chip that emits light is switched, the position of the light emitting point moves slightly.

[0014] As the opposing surfaces of the two LED chips become closer to being perpendicular to the short side of the substantially rectangular area, the ratio of light color mixing increases, and the distribution of the color mixing ratio along the long side direction of the substantially rectangular area also increases. Become uniform. For example, if two LED chips are arranged side by side in the width direction as a narrow rectangular parallelepiped, almost all of the light emitted from both chips will be mixed, and the ratio of color mixture will be uniform over the entire long side direction regardless of the chip length. become.

The bottom surface of each LED chip may be a convex polygon or a concave polygon. In addition, all the LED chips may have the same shape, or may have different sizes or different shapes.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show a plan view and a front view of the light emitting device 1 of the first embodiment, respectively. The light emitting device 1 includes an LED chip 11 that emits red light, an LED chip 12 that emits green light, three lead terminals 13, 14, 15, two wires 16 and 17, and a resin mold 18.

At the upper end of the center lead terminal 15, a recess 15a having an inclined side wall 15c is formed.
The LED chip 11 and the LED chip 12 are respectively
An anode is formed on the upper surface, and a cathode is formed on the lower surface. The anode is fixed to the bottom surface 15b of the recess 15a of the lead terminal 15 with a conductive paste. The anodes of the LED chips 11 and 12 are connected to lead terminals 13 by gold wires 16 and 17, respectively.
And 14 are connected to the upper ends.

The lead terminals 13 and 14 are LE
The lead terminals 15 serve as individual anode terminals of the D chips 11 and 12, and the lead terminal 15 serves as a cathode terminal common to the LED chips 11 and 12. LED chip 11 and LED chip 12
The voltage application to the light-emitting device 1 is individually controlled, and the light-emitting device 1 has three kinds of light-emitting states, a state of emitting only red light, a state of emitting only green light, and a state of emitting both red light and green light. When both red light and green light are emitted, the two lights mix and become orange light.

The resin mold 18 is a transparent one formed by solidifying epoxy resin, and covers the entire LED chips 11 and 12, the wires 16 and 17, and the upper portions of the lead terminals 13, 14 and 15. The lower portion of the resin mold 18 has a cylindrical shape, and lead terminals 13, 14, and 15 protrude from the lower end surface. The upper part of the resin mold 18 has a hemispherical shape,
It functions as a lens that condenses the light emitted by the LED chips 11 and 12.

Side wall 15c of recess 15a of lead terminal 15
Of the light emitted by the LED chips 11 and 12 reflects upward a small amount of light traveling to the side. Due to this and the light-condensing action of the resin mold 18, the light-emitting device 1 emits most of the light within a conical area having a vertex angle of about 90 ° that spreads upward.

The two LED chips 11 and 12 are rectangular parallelepipeds having the same size, and their bottom surfaces are rectangles whose long sides exceed twice the short sides. That is, the LED chips 11, 1
The bottom surface of 2 has a shape obtained by bisecting a rectangle perpendicular to its short side. The LED chips 11 and 12 are arranged slightly parallel to each other with a slight distance from each other, and the entire area in which they are arranged (hereinafter, referred to as an arrangement area) is also rectangular.

The center of the LED chip 11 and the LED chip 1
2 is half (S + D) / 2 of the sum of the short side S of the arrangement area (FIG. 1) and the distance D between the two chips, and this distance is the difference between the position of the LED chips 11 and 12 Become.
This shift is smaller than the long side L of the arrangement area, that is, half of the length of both chips, and is small.

Therefore, the red light emitted from the LED chip 11 and the green light emitted from the LED chip 12 are almost all mixed. For this reason, the emission range R of the red light center and the emission range G of the green light center shown in FIG. 8 are very small. In addition, the direction in which light is emitted from the light emitting device 1 is limited to the above-described conical range, and the LED chips 11 and 12 emit light.
When light is emitted together, most of the light emitted from the light emitting device 1 is orange light.

Further, since the displacement of the LED chips 11 and 12 is small as described above, even when the light emitting state is switched between the above three types, the change of the position of the light emitting point is slight. That is, it is observed that all of the red light, green light, and orange light are emitted from substantially the same point.

FIGS. 3 and 4 are a plan view and a front view, respectively, of the light emitting device 2 of the second embodiment. The light emitting device 2 is one in which the LED chips 11 and 12 are mounted on a substrate 20 having three wiring patterns 23, 24 and 25 formed on a surface thereof, and molded with a resin 28.

The central wiring pattern 25 is provided from the center of the upper surface of the substrate 20 to the lower surface via the side surfaces.
The chips 11 and 12 are fixed to the wiring pattern 25 on the upper surface of the substrate 20 with a conductive paste. The wiring patterns 23 and 24 are respectively provided on the LE of the upper surface of the substrate 20.
It is provided from the vicinity of the D chips 11 and 12 to the lower surface via the side surface. The anodes of the LED chips 11 and 12 are connected to wiring patterns 23 and 24 by gold wires 26 and 27, respectively.

The wiring patterns 23 and 24 are respectively
It becomes the individual anode wiring of the LED chips 11 and 12,
The wiring pattern 25 is a common cathode wiring for the LED chips 11 and 12. The light emitting device 2 is of a surface mounting type, and is fixed to the surface of a circuit board by soldering or the like and is connected to the circuit wiring.

The resin mold 28 is a transparent one formed by solidifying epoxy resin, and covers the entire LED chips 11 and 12, the wires 26 and 27, and the ends of the wiring patterns 23, 24 and 25. The resin mold 28 has an upper surface formed to be flat, and the light emitting device 2 emits light emitted from the LED chips 11 and 12 to a wide range without particularly condensing the light.

The shapes and arrangement of the LED chips 11 and 12 are the same as those of the light emitting device 1 described above. Therefore, LED
The displacement between the chip 11 and the LED chip 12 is small,
Almost all of the red light and green light emitted by them are mixed to produce orange light. When the LED chips 11 and 12 emit light together, red light or green light is emitted from the substrate 2.
It is limited to an oblique direction that is nearly parallel to 0. In normal use, the light-emitting device 2 is not observed from such a direction, and the light-emitting device 2 emits uniform orange light in practical use.

The light-emitting devices 1 and 2 of the first and second embodiments can be used alone, for example, as indicators, or can be arranged in a two-dimensional array to form a dot-matrix display device. It can also be used to display graphics. In any of the usage modes, the amount of information provided is increased by properly using red light, green light, and orange light. In addition, since the orange light is not observed as red light or green light, there is no possibility that the observer may mistakenly recognize the information represented by the colors of the light emitting devices 1 and 2.

Also, when emitting any of red light, green light and orange light, there is no large shift in the position of the light emitting point, so that the light emitting point moves when the emitted color is switched. No impression is given to the observer.

In the above embodiment, an example is shown in which an LED chip that emits red light and an LED chip that emits green light are provided. However, an LED chip that emits light of any color may be used according to the application of the light emitting device. Good to combine.

The shape of the bottom surface of each LED chip is not limited to the rectangle shown in the above embodiment. The bottom surface of the LED chip may be a shape obtained by dividing a rectangle, and the dividing line may include at least one straight line perpendicular or oblique to the short side. Further, the number of LED chips is not limited to two, and may be three or more. Each LED
The chips are arranged so that the side surfaces thereof are in contact with each other and are separated from each other from a state in which all the bottom surfaces form a rectangle, so that the arrangement region becomes a substantially rectangular shape slightly larger than the original rectangle.

FIGS. 5 to 7 show other examples of the shape and arrangement of the bottom surface of the LED chip used in the light emitting device of the present invention. In these figures, the horizontal direction corresponds to the short side S of the arrangement area, and the vertical direction corresponds to the long side L.

FIG. 5 shows an example in which two LED chips are combined. The bottom of the LED chip is triangular in (a),
(B) is a trapezoid, (c) is a concave hexagon, and has the same shape. All are arranged point-symmetrically with respect to the center of the arrangement area. In (c), both LED chips face the other LED chip on three sides.

FIG. 6 shows an example in which three LED chips are combined. If all of the three LED chips emit light of different colors, a light emitting device that emits light of seven colors is obtained. In a set of LED chips that emit red light, green light and blue light, white light can be obtained by causing all to emit light simultaneously. 3 LEDs except (a)
One of the chips has a different bottom shape than the other two.

FIG. 7 shows an example in which four LED chips are combined. By using two LED chips that emit red light and two LED chips that emit green light and arranging them alternately as shown in this figure, the light emitting devices 1 and 2 of the first embodiment and the second embodiment can be used. The light emitting device emits light that is more uniformly mixed than the light emitting device.

In FIGS. 5 (c), 6 (b), 6 (c) and 5 (d), the shape of the arrangement area has irregularities in the outline and is not strictly rectangular. However, since the individual LED chips are not manufactured by cutting the same chip, it is easy to adjust one or a plurality of shapes to make the arrangement area rectangular. For example, FIG.
In the case of (c), if the length of each LED chip in the vertical direction is increased by the vertical spacing between the two LED chips, the arrangement area becomes rectangular.

The ratio of the length of the long side L to the length of the short side S is arbitrary. The long side L and the short side S may be equal to form a square. Even when the long side L is much longer than the short side S, light is uniformly mixed over the whole of the long side direction by making the straight line dividing the bottom surface perpendicular to the short side.

The shape of the LED chip may be selected in consideration of the difficulty in manufacturing and the strength. A rectangular bottom surface as shown in the first and second embodiments and FIGS. 6A and 7 is used for uniformity of light mixing, ease of manufacture, ease of handling, and strength. Is preferred. In terms of ease of wire bonding, it can be said that a wide one as shown in FIG. 5C or FIG. 6C is superior.

[0041]

According to the light emitting device of the present invention, since the displacement of the LED chips emitting light of different colors is small, the range in which the light is mixed is widened, and color separation of mixed light is prevented. You. For this reason, even when information is represented by the color of light, information can be transmitted correctly. Further, even when the color of the emitted light is switched, the light emitting point hardly moves, so that the observer does not receive an unnatural impression.

[Brief description of the drawings]

FIG. 1 is a plan view of a light emitting device according to a first embodiment.

FIG. 2 is a front view of the light emitting device according to the first embodiment.

FIG. 3 is a plan view of a light emitting device according to a second embodiment.

FIG. 4 is a front view of a light emitting device according to a second embodiment.

FIG. 5: LE of a light emitting device comprising two LED chips
The figure which shows typically the bottom shape and arrangement | positioning of a D chip.

FIG. 6: LE of a light emitting device comprising three LED chips
The figure which shows typically the bottom shape and arrangement | positioning of a D chip.

FIG. 7: LE of a light emitting device comprising four LED chips
The figure which shows typically the bottom shape and arrangement | positioning of a D chip.

FIG. 8 is a diagram showing a configuration of a conventional light emitting device and a state of color mixing of light.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 2 Light emitting device 11 LED chip (red) 12 LED chip (green) 13, 14 Anode lead terminal 15 Cathode lead terminal 15a Cathode lead terminal concave part 16, 17 Wire 18 Resin mold 20 Substrate 23, 24 Anode wiring pattern 25 Cathode wiring Pattern 26, 27 Wire 28 Resin mold

Claims (1)

[Claims] 1. A light emitting device comprising a plurality of light emitting diode chips arranged close to each other and emitting light of different colors, wherein the light emitted from the plurality of light emitting diode chips is mixed and emitted. The chip is a prism having a bottom surface in a shape obtained by dividing a rectangle by one or more straight lines including a straight line in a vertical direction or an oblique direction with respect to a short side thereof,
A light-emitting device, wherein the light-emitting device is arranged in an area having a size obtained by slightly expanding the rectangle.