JP7174688B2 - surface light emitting device - Google Patents

Description

The present invention relates to a surface light-emitting device in which LEDs are arranged in a plane.

2. Description of the Related Art Conventionally, there has been known a surface light emitting device having a light emitting surface formed by arranging a plurality of LEDs in a matrix on the surface of a substrate (for example, Patent Document 1). In such a surface emitting device, as shown by the dashed line in FIG. 7A, uniform luminance is obtained in the central portion of the light emitting surface where the LEDs are arranged at equal pitches, but luminance is lowered, and the uniformity of the brightness of the entire light emitting surface is lowered.

In order to solve such a problem, for example, by making the pitch of the LEDs in the periphery of the light-emitting surface narrower than the pitch in the center, the mounting density of the LEDs in the periphery is made higher than in the center. It is considered to improve the brightness of the part.

However, in this case, although the uniformity of the brightness of the light emitting surface can be improved, problems arise such as the layout of the LEDs being complicated and the design being time-consuming.

JP 2015-106524 A

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above problems at once. The main object is to improve the uniformity of luminance.

That is, the surface emitting device according to the present invention comprises a substrate, LEDs mounted on a mounting surface of the substrate in a vertical and horizontal matrix at equal pitches in the vertical direction and equal pitches in the horizontal direction, and LEDs mounted on the mounting surface. and a resistive element for limiting the current flowing through the LED, wherein the ratio of the occupied area of the resistive element to the occupied area of the LED within a predetermined range in plan view is defined as a resistive element mounting ratio of 1 from the outermost LED. The ratio of the resistance element mounting ratio in the range outside the outer tangent line to the resistance element mounting ratio in the range inside the outer tangent line circumscribing each of the LEDs mounted on the inner side is 0.2 or less. characterized by being

With such a structure, the mounting ratio of the resistance elements in the central portion of the substrate is made higher than the mounting ratio of the resistance elements in the peripheral portion, thereby reducing the reflectance in the central portion of the surface of the substrate and increasing the Reflectance in the peripheral portion can be improved. As a result, the intensity of the reflected light from the central portion of the substrate is reduced to reduce the luminance at the central portion of the light emitting surface, and the intensity of the reflected light from the peripheral portion of the substrate is increased to increase the luminance at the peripheral portion of the light emitting surface. can be improved. As a result, as shown by the solid line in FIG. 7A, it is possible to widen the range in which the luminance is uniform in the central portion of the light-emitting surface and to narrow the range in which the luminance decreases in the peripheral portion. As a result, it is possible to improve the luminance uniformity of the entire light emitting surface.
In addition, since the uniformity of brightness on the light emitting surface can be improved by adjusting the mounting position of the resistance element, the arrangement of the LEDs does not become complicated, such as by partially changing the pitch of the LEDs.
Furthermore, in order to reduce the reflectance of the substrate, the resistor elements necessary for the circuit configuration are used, and many of these are placed in the center of the substrate instead of the peripheral portion of the substrate, so the number of parts is increased and the size of the device is increased. It is possible to improve the uniformity of the brightness of the light emitting surface without increasing the cost.

Preferably, in the surface emitting device, the resistive element is mounted only inside the outer tangent line.
In this way, the reflectance of the central portion of the substrate can be further reduced, and the reflectance of the peripheral portion of the substrate can be further improved. The uniformity of brightness as a whole can be further improved.

In order to make the distribution of reflectance uniform in the central region of the substrate and to widen the uniform range of luminance in the central portion of the light emitting surface, the surface emitting device has the distribution of the resistive elements inside the outer tangent line. is preferably uniform.

As a specific aspect of the surface light-emitting device in which the distribution of the resistive elements is uniform, when the region inside the outer tangent line is divided into 3×3 matrix-like partitions having a uniform area, the above-described The ratio of the minimum value to the maximum value of the occupied area of the resistance element can be 0.5 or more.

As an aspect of the surface light-emitting device that remarkably exhibits the effect of the present invention, the surface light-emitting device has a reflecting surface formed on the mounting surface for reflecting the light emitted from the LED.

In order to improve heat dissipation, it is preferable that the surface emitting device is not mounted with the resistance element on the back surface of the substrate.
In this way, a member having excellent heat dissipation such as aluminum can be attached directly to the back surface of the substrate, or can be attached in close contact with the back surface of the substrate via a heat dissipation member having insulation as necessary. can be done.

Further, the surface emitting device of the present invention comprises a substrate, LEDs mounted on a mounting surface of the substrate in a vertical and horizontal matrix, and resistor elements mounted on the mounting surface for limiting a current flowing through the LEDs, In a circuit in which the LEDs and the resistance elements are connected in series, the ratio of the number of the resistance elements to the number of the LEDs is 0.35 or more, and in a plan view, the area occupied by the LEDs within a predetermined range. The ratio of the occupied area of the resistor element is defined as the resistor element mounting ratio, and the outer tangent line to the resistor element mounting ratio in the range inside the outer tangent line that circumscribes each of the LEDs mounted one inside from the outermost LED. The ratio of the resistance element mounting ratio in the range outside is 0.2 or less.
Even with such a surface emitting device, the effects of the present invention described above can be obtained.

Further, the surface emitting device of the present invention comprises a substrate, LEDs mounted on a mounting surface of the substrate in a vertical and horizontal matrix at equal pitches in the vertical direction and at equal pitches in the horizontal direction, and LEDs mounted on the mounting surface, a resistor element for limiting the current flowing through the LED; a frame provided so that the inner peripheral surface surrounds the LED in a plan view; a light diffusion plate for diffusing light, wherein the ratio of the area occupied by the resistor element to the area occupied by the LED within a predetermined range in plan view is defined as a resistor element mounting ratio, and the inner peripheral surface of the frame is used as the mounting ratio. A ratio of the resistance element mounting ratio in the range outside the offset surface to the resistance element mounting ratio in the range inside the offset surface offset inward by a distance of 75% of the distance between the surface and the light diffusion plate. is 0.2 or less.
Even with such a surface emitting device, the effects of the present invention described above can be obtained.

According to the present invention configured as described above, in a surface light-emitting device in which LEDs are mounted in a matrix on a substrate, it is possible to improve the uniformity of luminance on the light-emitting surface without complicating the arrangement of the LEDs. .

The figure which shows typically the whole structure of the coaxial illuminating device of this embodiment. The perspective view which shows typically the whole structure of the surface-emitting device of the same embodiment. The exploded perspective view which shows typically the structure of the surface-emitting device of the same embodiment. FIG. 2 is a cross-sectional view of the surface light-emitting device of the same embodiment taken along the line X-X'; The top view which shows typically the structure of the surface-emitting device of the same embodiment. The typical circuit diagram which shows the circuit structure of the surface-emitting device of the same embodiment. FIG. 4 is a diagram schematically explaining the luminance distribution of a surface emitting device;

An embodiment of a surface emitting device according to the present invention will be described below with reference to the drawings.

A surface light emitting device 100 according to the present embodiment is applied to a coaxial illumination device 200 that emits light coaxially with respect to an observation axis A of a camera C, as shown in FIG. The coaxial illumination device 200 is used for surface inspection or the like in which a work W, which is an object such as a product, is irradiated with light, and flaws, characters, etc. on the surface of the work W are observed by a camera C or the like and automatically inspected. It is a thing. Specifically, this coaxial illumination device 200 includes a surface light emitting device 100 that emits diffused light from a light emitting surface S, and a half mirror M that reflects the light emitted from the surface light emitting device 100 toward the work W. The surface emitting device 100 will be described in detail below.

As shown in FIGS. 2 and 3, the surface emitting device 100 includes a substrate 1, a plurality of LEDs 3 and a plurality of resistance elements 4 mounted on one surface 11 (hereinafter also referred to as a mounting surface) of the substrate 1, A frame-shaped reflector member 5 arranged on the peripheral edge of the substrate 1 and having a reflecting surface (here, a mirror surface) formed on the inner peripheral surface 52 , and a light diffusion plate 6 provided in the opening of the reflector member 5 . It is what I did.

The substrate 1 is a printed wiring board having a square flat plate shape. On the mounting surface 11 of the substrate 1, as shown in FIG. 4, a reflective film 2 (insulating film ) is provided to form a reflective surface. The reflective film 2 is made of, for example, a white solder resist.

The LED 3 emits light of any color tone such as white light. Here, it is a surface mount type in which an LED element is arranged in the center of a package that is square in plan view. Each LED 3 is of the same standard, and is mounted in a vertical and horizontal matrix as shown in FIG. Here, the respective LEDs 3 are arranged in a matrix of 13 vertical×14 horizontal, with an equal pitch P _V in the vertical direction and an equal pitch _{P H} in the horizontal direction. It is set to be larger than _PH . The vertical pitch _PV is the distance along the vertical direction between the light emitting centers of the LEDs 3 (ie, the centers of the LED elements). The same is true for the horizontal pitch _PH . The uniform pitch means that the ratio of the minimum pitch to the maximum pitch in one direction is 0.85 or more. In addition, the number of LEDs 3 and the pitch length between the LEDs 3 may be appropriately changed according to the purpose and application of the surface emitting device 100 .

A resistor element 4 is for limiting the current flowing through the LED 3 . In this embodiment, each resistive element 4 has the same standard and has a rectangular plate shape in a plan view. Here, the resistance element 4 is mounted only on the mounting surface 11 of the substrate 1 and is not mounted on the rear surface 12 side of the substrate 1 .

The reflector member 5 is for reflecting the light emitted from each LED 3 and guiding it mainly to the periphery of the light emitting surface S. As shown in FIG. Specifically, as shown in FIGS. 3 and 5, four horizontally elongated flat plates 51 having the same shape are erected at right angles from the mounting surface 11 of the substrate 1 so as to have the same height, and the inside of the substrate 1 when viewed from above. It is configured by arranging so that the peripheral surface forms a rectangular shape. Each horizontally long flat plate 51 is arranged on the outer edge of the mounting surface 11 of the substrate 1 so that its long sides are parallel to the sides of the substrate 1 . Thereby, the inner peripheral surface 52 of the reflector member 5 surrounds each LED3.

The light diffusion plate 6 transmits and diffuses the light emitted from the LEDs 3, and has a square shape in plan view. The light diffusion plate 6 is arranged so as to block the opening of the reflector member 5, as shown in FIGS.

As shown in FIG. 6, the circuit configuration of the surface emitting device 100 is such that a plurality of LEDs 3 are connected in series to form an LED series circuit 7, and a plurality of the LED series circuits 7 are connected in parallel. In each LED series circuit 7, a plurality of resistance elements 4 are connected in series with the LEDs 3. FIG. A constant voltage is applied from a constant voltage type power supply V to the plurality of LED series circuits 7 connected in parallel. Here, in each LED series circuit 7, the ratio of the number of resistance elements 4 to the number of LEDs 3 is set to 0.35 or more.

Thus, the surface emitting device 100 of the present embodiment improves the uniformity of the brightness of the light emitting surface S, in plan view, each outer circumference (specifically Practically speaking, with the outer tangent line L circumscribing the package) as a boundary, the mounting ratio of the resistance element 4 in the region _RC (also referred to as the central region) inside the outer tangent line L (hereinafter also referred to as the resistance element mounting ratio) , the resistance elements 4 are arranged so that the ratio of the mounting ratio of the resistance elements 4 in the region R _S (also referred to as the peripheral region) outside the external tangent line L is 0.2 or less. In this embodiment, as shown in FIG. 5, the resistive element 4 is not mounted in the peripheral region R _S but is mounted only in the central region R _C (that is, the peripheral region R _S with respect to the central region R _C ). The ratio of the resistance element mounting ratio is 0).

Here, the resistive element mounting ratio is the ratio of the occupied area (A _R ) of the resistive element 4 to the occupied area (A _L ) of the LED 3 within a predetermined range in plan view (that is, the resistive element mounting ratio=A _R /A _L ). That is, the "resistive element mounting ratio in the central region" is the ratio of the total area of the resistive elements 4 to the total area of the LEDs 3 in the central region _RC in plan view. Also, the "resistive element mounting ratio in the peripheral area" is the ratio of the total area of the resistor elements 4 to the total area of the LEDs 3 in the peripheral area _RS in plan view. When the resistive element 4 is positioned on the external tangent line L, the area of the portion of the resistive element 4 located inside the external tangent line L in plan view is counted as the area of the resistive element 4 in the central region _RC , The area of the portion outside the external tangent line _L is counted as the area of the resistive element 4 in the peripheral region RS.

In the central region _RC , the resistance elements 4 are mounted so that their distribution is substantially uniform. Specifically, as shown in FIG. 5, when the square inner region surrounded by the external tangent line L is divided into 9 matrixes of 3 columns×3 columns each having a uniform area, the resistance element 4 in each partition is The ratio of the minimum value to the maximum value of the total occupied area is set to 0.5 or more. The closer the ratio is to 1, the better. In addition, when the resistance element 4 is arranged across the boundary dividing the partition, the area of the part inside the boundary (that is, inside the partition) of the area of the resistance element 4 is the area occupied by the resistance element 4 in the partition. Count as area.

Furthermore, in this embodiment, the resistance elements 4 are arranged so that the area occupied by the resistance elements 4 in each section is vertically symmetrical and laterally symmetrical with respect to the central section. Further, in the present embodiment, the arrangement of the resistance elements 4 is symmetrical in the vertical direction and symmetrical in the horizontal direction with respect to the center of the central region _RC .

In this embodiment, as shown in FIG. 5, the distance D1 from the outermost LED ₃ to the reflecting surface 52 along the vertical direction is 35% or more and 65% or less of the pitch _PV in the vertical direction. The reflector members 5 are arranged such that the distance D2 from the outermost LED ₃ to the reflecting surface 52 along the _.DELTA . Here, “the distance from the outermost LED to the reflecting surface” is the shortest distance from the light emission center (the center of the LED element) of one LED 3 on the outermost periphery to the reflecting surface 52 .

According to the surface emitting device 100 of this embodiment configured in this way, by increasing the mounting ratio of the resistance elements 4 in the central region R _C of the substrate 1 than the mounting ratio of the resistance elements 4 in the peripheral region R _S , The reflectance in the central region _RC of the substrate 1 can be reduced and the reflectance in the peripheral region _RS can be increased. As a result, the intensity of the reflected light from the central portion of the substrate 1 is reduced to reduce the luminance at the central portion of the light emitting surface S, and the intensity of the reflected light from the peripheral portion of the substrate 1 is increased to increase the intensity of the light emitting surface S. Brightness in the periphery can be improved. As a result, the range in which the brightness is uniform in the central portion of the light emitting surface S can be widened, and the range in which the brightness decreases in the peripheral portion can be narrowed. As a result, the uniformity of the brightness of the entire light emitting surface S can be improved. Further, since the uniformity of brightness of the light emitting surface S is improved by adjusting the mounting position of the resistance element 4, the arrangement of the LEDs 3 is not complicated, such as by partially changing the pitch of the LEDs 3.

Furthermore, in order to partially adjust the reflectance of the substrate 1, the resistive elements 4 necessary for the circuit configuration are utilized, and many of these are arranged in the central portion of the substrate 1 rather than in the peripheral portion of the substrate 1, thus reducing the number of components. The uniformity of the brightness of the light-emitting surface S can be improved without increasing the number of light-emitting devices 100, increasing the size of the surface light-emitting device 100, and increasing the cost.

In addition, since the inner peripheral surface 52 forming the reflecting surface is provided with the reflector member 5 configured to surround the LEDs 3, the light emitted from each LED 3 is reflected by the inner peripheral surface 52 to A decrease in brightness can be reduced, and a light emitting surface S with more uniform brightness can be obtained.

It should be noted that the present invention is not limited to the above embodiments.

Although the resistive element 4 is mounted only in the central region _RC in the above embodiment, the present invention is not limited to this. In other embodiments, the resistive element 4 may also be mounted in the peripheral region _RS .

In the above-described embodiment, the vertical pitch PV of the LEDs 3 is larger than the horizontal pitch _PH . However, the vertical pitch _PV is _smaller than the horizontal pitch _PH . Alternatively, the pitch PV in the vertical direction may be _equal to the pitch _PH in the horizontal direction.

In the above embodiment, the resistive elements 4 are mounted so as to be distributed substantially uniformly, but the present invention is not limited to this. The distribution of the resistive elements 4 may not be substantially uniform. Also, the resistance elements 4 may not be arranged so as to be symmetrical in the vertical direction and symmetrical in the horizontal direction with respect to the center of the central region _RC .

In the above embodiment, the distance D1 from the outermost LED ₃ along the vertical direction to the reflecting surface 52 is 35% or more and 65% or less of the pitch _PV in the vertical direction, and from the outermost LED 3 along the horizontal direction Although the reflector members 5 are arranged such that the distance D2 to the reflecting surface 52 is 35% or _more and 65% or less of the horizontal pitch _PH , the present invention is not limited to this. The reflector member 5 may be arranged so that the distance from the outermost LED 3 to the reflecting surface 52 is out of the range.

Moreover, although the surface emitting device 100 of the above-described embodiment includes the reflector member 5 and the light diffusion plate 6, one or both of these may be omitted. Further, instead of the reflector member 5, a frame having no reflecting surface formed on the inner peripheral surface may be provided, and the light diffusion plate 6 may be provided so as to close the opening of the frame.

In the above embodiment, in the constant voltage circuit, the ratio of the number of resistance elements 4 to the number of LEDs 3 is set to 0.35 or more, but the ratio is not limited to this and may be less than 0.35.

In the above embodiment, the outer tangent line L that circumscribes the outer periphery of each of the LEDs 3 laid one inside the outermost LED 3 is used as a boundary to define the resistance element mounting ratio in the central region _RC and the peripheral region _RS . but it is not limited to this. In another embodiment, in a plan view, the inner peripheral surface 52 of the reflector member ₅ is offset inward by a distance of 75% of the distance D3 between the mounting surface 11 and the light diffusion plate 6. The resistance elements 4 may be arranged so that the ratio of the resistance element mounting ratio in the region outside the offset plane to the resistance element mounting ratio in the region inside the offset plane is 0.2 or less.

Although the resistive element 4 of the above embodiment has the same rectangular plate shape in plan view, it is not limited to this. In other embodiments, each resistive element 4 may be of a different standard and may have a different shape from each other.

Although the surface light emitting device 100 of the above embodiment is applied to the coaxial lighting device 200, the surface light emitting device 100 may be used alone. It may also be applied to other types of lighting devices.

In addition, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications are possible without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100... Surface-emitting device 1... Substrate 11... Mounting surface 3... LED
4 Resistive element S Light-emitting surface _L External tangential line PV Vertical pitch _PH Horizontal pitch

Claims (8)

a substrate;
LEDs mounted on the mounting surface of the substrate in a vertical and horizontal matrix at equal pitches in the vertical direction and equal pitches in the horizontal direction;
a resistive element mounted on the mounting surface for limiting current flowing through the LED;
In a plan view, a ratio of the area occupied by the resistor element to the area occupied by the LED within a predetermined range is defined as a resistor element mounting ratio, and an outer tangent line circumscribing each of the LEDs mounted one inside from the outermost LED. A surface emitting device, wherein the ratio of the resistance element mounting ratio in the range outside the outer tangent line to the resistance element mounting ratio in the range inside is 0.2 or less. 2. A surface emitting device according to claim 1, wherein said resistive element is mounted only inside said outer tangent line. 3. The surface emitting device according to claim 1, wherein the distribution of the resistive elements is uniform inside the outer tangent line. When the region inside the outer tangent line is divided into 3×3 matrix-shaped partitions having a uniform area, the ratio of the minimum value to the maximum value of the occupied area of the resistive element in each partition is 0.5 or more. 4. The surface emitting device according to claim 3. 5. The surface emitting device according to claim 1, wherein the mounting surface is provided with a reflecting surface for reflecting the light emitted from the LED. 6. The surface emitting device according to claim 1, wherein the resistive element is not mounted on the rear surface of the substrate. a substrate;
LEDs mounted in a vertical and horizontal matrix on the mounting surface of the substrate;
a resistive element mounted on the mounting surface for limiting current flowing through the LED;
In a circuit in which the LEDs and the resistance elements are connected in series, the ratio of the number of the resistance elements to the number of the LEDs is 0.35 or more,
In plan view, the ratio of the area occupied by the resistor element to the area occupied by the LED within a predetermined range is defined as a resistor element mounting ratio, and the outer tangent line circumscribing each of the LEDs mounted one inside from the outermost LED A surface light-emitting device, wherein the ratio of the resistance element mounting ratio in the range outside the outer tangent line to the resistance element mounting ratio in the inner range is 0.2 or less. a substrate;
LEDs mounted on the mounting surface of the substrate in a vertical and horizontal matrix at equal pitches in the vertical direction and equal pitches in the horizontal direction;
a resistive element mounted on the mounting surface for limiting a current flowing through the LED;
a frame provided so that an inner peripheral surface surrounds the LED in plan view;
A light diffusion plate provided to block the opening of the frame and diffusing the light emitted by the LED,
In a plan view, the ratio of the area occupied by the resistor element to the area occupied by the LED within a predetermined range is defined as a resistor element mounting ratio, and the inner peripheral surface of the frame is 75 of the distance between the mounting surface and the light diffusion plate. A surface emitting device, wherein the ratio of the resistance element mounting ratio in the range outside the offset surface to the resistance element mounting ratio in the range inside the offset surface offset inward by a distance of % is 0.2 or less. .

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