JPH10308536A - Led line light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED line light source whose irregularity in an optical output in its long direction can be eliminated as far as possible. SOLUTION: A linear hollow 6 is formed on an aluminum-based board 10 by a drawing and working method or the like. In the hollow 6, its bottom pat 62 is formed to be a flat face, and sidewall faces which are connected to the face are formed to be taper-shaped reflecting faces 63. LED's 21, 22 are arranged on the bottom part 62 to be linear in a row, and the reflecting faces 63 provide cone-shaped reflecting faces to the LED's 21, 22. Since the reflecting faces are formed along both sides of an LED arrangement line, beams of light which are radiated from side faces of the respective LED's can be taken out to the front, and it is possible to restrain an optical output from being dropped just above parts in which the LED's do not exist.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LED line light source suitable for a light source for a facsimile or a scanner.

[0002]

2. Description of the Related Art Generally, a large number of LEDs are mounted on a wiring board 1 such as a glass epoxy as shown in FIG.
Are known in the art. Here, in an LED line light source for a facsimile or a scanner, a structure is adopted in which the large number of LEDs are not of the same type, and two types of LEDs 21 and 22 having different normal emission colors are alternately arranged. The upper electrode of each LED and the glass epoxy wiring board are electrically connected to each other by a gold wire 3, and the gold wire 3 and L
The resin 4 for protecting the EDs 21 and 22 is applied. Further, in front of the glass epoxy wiring board 1,
A lens 5 for condensing light emitted from the LED to obtain predetermined light distribution characteristics is provided.

[0003]

However, in the above-mentioned LED line light source, when only one type of LED 21 is turned on and the light output of the line light source is measured, the light output is high in the region immediately above the mounting portion of the LED 21, but it is turned on. The light output tends to be low in a region where the LED 21 does not exist immediately below. That is, when the light output distribution is measured, it exhibits a wave-like characteristic as shown in FIG.
In order to smooth the wavy characteristic, it is sufficient to narrow the arrangement interval of the LEDs 21. However, the two types of LEDs 21 and 22 are used.
There is a limit in increasing the density due to the need to alternately arrange them.

If the difference in light output between the position where the LED exists and the position where the LED does not exist is significant as described above, when used as a light source for facsimile or scanner, color unevenness increases and the resolution deteriorates. There is a problem. An object of the present invention is to provide an LED line light source capable of eliminating such light output unevenness as much as possible.

[0005]

The LED line light source according to the present invention comprises:
A plurality of LEDs are arranged in a line on a wiring board, and each LED is arranged along both sides of the LED arrangement line.
And a reflection surface for reflecting the light emitted from the side surface toward the front of the wiring board.

As a mode of forming the above-mentioned reflection surface, a line-shaped depression is provided in a wiring board, and a plurality of LEDs are provided at the bottom thereof.
Are arranged in a line, and the side wall surface of the recess is
It is preferable that the light-emitting device be configured so as to have a reflecting surface that reflects light emitted from the side surface of D toward the front of the wiring board.

Further, it is a preferred embodiment of the present invention that the wiring substrate is an insulated metal substrate and the LED and the reflection surface are sealed with a resin.

[0008]

In the LED line light source according to the conventional structure described above, only the light emitted from the upper surface of the LED is exclusively used.
It is considered that this resulted in an extreme difference in light output between the existing portion and the non-existing portion of the LED. Then, L
By forming reflection surfaces along both sides of the ED arrangement line, light emitted from the side surface of each LED can be extracted to the front surface, and a drop in light output immediately above a portion where no LED is present can be suppressed. Can be.

If a line-shaped depression is provided in the wiring substrate itself, and a plurality of LEDs are arranged in a line at the bottom of the depression, and the side wall surface of the depression is used as the above-mentioned reflection surface, the reflection is made separately. There is no need to prepare surface components, and the number of parts can be reduced. In this case, it is preferable to use an insulated metal substrate as the substrate, since the above-mentioned depression can be formed relatively easily by drawing or the like.

Further, by sealing the LED and the reflection surface portion with resin, the emitted light is diffused inside the reflection mechanism portion, whereby the light taken out to the front surface of the substrate can be further smoothed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a perspective view showing an example of the LED line light source according to the present invention. In this embodiment, two kinds of LEDs 21 and 22 having different emission wavelengths are alternately arranged in a line on the surface of a wiring board 1 made of glass epoxy or the like, and reflected along both sides of the arrangement line of the LEDs 21 and 22. Containers 6a and 6b are additionally provided. This reflector 6a,
6b has a tapered reflecting surface 61, and these are arranged in a pair facing each other with the LED arrangement line interposed therebetween.
D21 and D22 are provided with a cone-shaped reflecting surface.

FIG. 4 shows another embodiment of the present invention. In this embodiment, an insulated metal substrate 10 such as an aluminum base substrate is used as a substrate, and a linear recess 6 is formed in the substrate by a method such as drawing. This is illustrated by way of example. The recess 6 has a flat bottom surface 62 and a side wall surface connected to the flat surface 63 is a tapered reflecting surface 63. The bottom 62 has an LED
21 and 22 are arranged in a line, and these LEDs
The opposing reflecting surface 63 provides a cone-shaped reflecting surface with respect to 21 and 22. Further, the cavity of the depression 60 is filled with a sealing resin P such as a silicone resin,
The LEDs 21 and 22 and the reflection surface 63 are sealed.

Next, the reflection mechanism will be described in detail with reference to FIG. First, the width W of the installation surface of a large number of LEDs, that is, the width in the cross-sectional direction of the bottom 62 of the recess 6 is 0.05 mm, assuming that the size W1 of the LED chip 2 to be used.
+ W1 ≦ W ≦ 1 mm + W1 is preferable, and more preferably, 0.1 mm + W1 ≦ W ≦ 0.5 mm + W1.
If the width of the installation surface is too narrow, the LED chip 2 will not be able to reflect the reflection surface 6 due to the variation in the die bonding position of the LED chip 2.
3 and may damage the LED chip 2. On the other hand, if the width is too wide, the utility of the reflection function is reduced, and the side emission light from the LED chip 2 tends to be unable to be used effectively.

The rising angle θ of the reflecting surface 63 is preferably 20 ° ≦ θ ≦ 90 °, and more preferably 30 ° ≦ θ ≦ 75 °. If the rising angle θ of the reflecting surface is smaller than 20 °, the tendency that the side emission light of the LED cannot be used effectively becomes conspicuous, while if the reflecting surface angle exceeds 90 °, light cannot be extracted to the front surface.

The depth T of the recess 6 is determined by using an LED.
Assuming that the height of the chip 2 is T1, −0.05 mm + T1
≦ T ≦ 5 mm + T1 is desirable, and more desirably,
0.1 mm + T1 ≦ T ≦ 1 mm + T1. If the depth T of the depression 6 is too low compared to the height T1 of the LED chip 2, the side emission light cannot be used effectively as described above. On the other hand, the depth T of the depression 6 is equal to the height T1 of the LED chip 2.
If the height is 5 mm or more, the reliability of wire bonding tends to deteriorate.

The sealing resin P filling the cavity of the depression 6
Is a transparent resin, and the refractive index n of the resin is desirably n = 1.2 or more, and more desirably, n = 1.4 or more. Examples of such a resin include an epoxy resin, a silicone resin, a polycarbonate resin, and an acrylic resin.

The surface of the reflection surface 63 is preferably subjected to good reflection processing, and is preferably subjected to a coating treatment or the like with a material having a reflectance of 0.2 or more, such as gold, silver, aluminum, and chromium. Depending on the use of the LED line light source of the present invention, reflection at the interface between the surface of the sealing resin P and air may be used, but in this case, the above-described coating treatment is not particularly required.

[0018]

EXAMPLE An LED line light source having the structure shown in FIG. 4 was prepared as an LED line light source according to the present invention. The aluminum-based insulating wiring board 10 is used as the wiring board, the rising angle of the reflection surface 63 is 45 °, and the width of the bottom 62 is 0.6.
A linear depression 6 having a depth of 0.4 mm and a depth of 0.4 mm was formed. On the bottom 62 of the substrate 10, a DH type AlG
aAs / AlGaAs red LED 21 (chip size 0.32 mm square, chip height 0.15 mm) and homojunction GaAs infrared LED 22 (chip size 0.32 mm)
Corners and a chip height of 0.23 mm) were alternately provided. LE
The number of D21 and D22 is 30 each, and the adjacent LED
Were set to 1.5 mm. Each LED2
In Examples 1 and 22, the light output values were checked in advance, and those whose light output values varied within ± 10% of each other were used.
Further, the surface of the reflection surface 63 was coated with a solder resist, and the cavity of the depression 6 was sealed with the silicone resin P to prepare an LED line light source.

[0019]

COMPARATIVE EXAMPLE For comparison with the LED line light source prepared above, as shown in FIG. 1, an LED line light source in which the same two types of LEDs 21 and 22 as in the above embodiment are alternately arranged on a glass epoxy wiring board 1. It was created. The number of LEDs was 30 and the pitch was 1.5 mm, and the LEDs used had a variation in light output value within ± 10% of each other. Note that a silicone resin was potted on each of the LEDs 21 and 22 and the bonding wires for protection.

Light output variations of the LED line light sources prepared in the above Examples and Comparative Examples were measured. The measurement is
The measurement was performed using a photosensor amplifier C6386 (manufactured by Hamamatsu Photonics) having a slit having a diameter of 1.5 mm attached to the tip of the optical fiber. The measurement position was 10 mm above the LED line light source, and the light output was measured sequentially at 1.5 mm pitch. The measurement procedure is as follows.
Only at a current value of 10 mA per LED, and the light output is measured from one end of the substrate to the other end.
The lamp was turned on at the current value of A, and the light output was measured in the same manner.

As a result of the above measurement, L
FIG. 6 shows the measurement results of the ED line light source, and L according to the comparative example.
FIG. 7 shows the measurement results of the ED line light source. As shown in the figure, in the comparative example product B, the light output immediately above the lit LED is large, but the light output is small in other portions, and the light output fluctuates greatly at a 1.5 mm pitch. Is admitted. On the other hand, in the example product, it is recognized that there is almost no change in the light output between immediately above the lit LED and the other portions, and according to the present invention, an LED line light source with less variation in the light output is provided. It was confirmed that it could be provided.

By the way, LEs according to the examples and comparative examples
For the D-line light source, the variation of the light output value within the effective illumination length of 84 mm was obtained by the formula: light output fluctuation = (maximum light output−minimum light output) / (maximum light output + minimum light output). The variation of the light output when the red LED 21 is turned on in the LED line light source according to the example is 7.7%, and the variation of the infrared LED 22 is 4.4.
%, The red LED 21 and the infrared LED 22 of the LED line light source according to the comparative example are 12.5% and 12.5%, respectively.
2.7%.

In the above embodiment, GaAs, AlGaAs
In the present invention, not only this but also InGaAlP-based, GaP-based, GaAs
It is needless to say that a P-based or InGaN-based LED can be used. Needless to say, the present invention can be applied to a case where two kinds of LEDs are not alternately arranged but one kind of LED is arranged in a line.

[0024]

As described above, according to the LED line light source of the present invention, it is possible to suppress the fluctuation of the light output between the portion where the LED is disposed and the portion where the LED is not disposed very low. Therefore, it is possible to obtain a linear light source having extremely stable light output in the longitudinal direction, and when used as a light source for facsimile or scanner, an excellent effect that color nonuniformity and deterioration of resolution are not caused.

[Brief description of the drawings]

FIG. 1 is a side view showing a conventional LED line light source.

FIG. 2 is a graph showing a light output distribution of a conventional LED line light source.

FIG. 3 is a perspective view showing an example of an LED line light source according to the present invention.

FIG. 4 is a perspective view showing another example of the LED line light source according to the present invention.

FIG. 5 is an explanatory diagram of a reflection mechanism in the LED line light source of the present invention.

FIG. 6 is a graph showing a light output distribution of an example product of the present invention.

FIG. 7 is a graph showing the light output distribution of a comparative example product.

[Explanation of symbols]

 1,10 Wiring board 21,22 LED 6a, 6b Reflector 6 Depression 61,63 Reflection surface 62 Bottom of depression P Sealing resin

Claims (4)

[Claims] 1. A plurality of LEDs are arranged in a line on a wiring board. A reflecting surface for reflecting light emitted from the side surface of each LED toward the front of the wiring board is provided along both sides of the arrangement line of the LEDs. An LED line light source formed. 2. A line-shaped depression is provided in a wiring substrate, and a plurality of LEDs are arranged in a line at the bottom of the depression, and a side wall surface of the depression transmits light emitted from a side surface of each LED to the front of the wiring substrate. An LED line light source having a reflection surface for reflecting light. 3. The LED line light source according to claim 1, wherein the wiring substrate is an insulated metal substrate. 4. The LED line light source according to claim 1, wherein the LED and the reflection surface are sealed with a resin.