JP7675560B2 - Planar lighting device - Google Patents

Description

The present invention relates to a surface lighting device.

So-called direct type planar lighting devices are known in the past (see, for example, Patent Documents 1 and 2). In a direct type planar lighting device, a plurality of light sources such as LEDs (Light Emitting Diodes) are arranged two-dimensionally on a substrate, a reflector having a reflective surface surrounding each light source is provided on the substrate, and a lens array, diffuser (diffusion plate), etc. are arranged on the emission side of the reflector.

Such planar lighting devices are often used as backlights for liquid crystal display devices, and there is a high demand for narrower frame widths, mainly for design reasons. Also, from the perspective of appearance, there is a demand for improved luminance uniformity on the light-emitting surface (exit surface). With regard to luminance uniformity, particularly in the periphery (near the four sides of the rectangle), there is no adjacent light source on one side (two sides in the case of corners), which reduces the luminance uniformity, and this needs to be improved.

In order to simultaneously achieve a narrower frame and improved brightness uniformity, if the size of the housing and the number of light sources are the same, it is possible to slightly increase the pitch of the two-dimensional arrangement of the light sources, thereby bringing the edge light sources closer to the edge of the housing. By bringing the edge light sources closer to the edge of the housing, the brightness of the outer periphery increases, improving brightness uniformity.

JP 2020-4895 A JP 2019-46789 A

However, as the edge light source approaches the edge of the housing, the shape of the reflector's reflective surface becomes thin and narrow on the edge side, making it difficult to manufacture using resin injection molding or the like. As a result, it is not possible to move the edge light source close enough to the edge of the housing within the manufacturable range, making it impossible to simultaneously achieve a narrow frame and improved brightness uniformity. Note that although it is possible to improve brightness uniformity by covering the outer periphery with a light-shielding sheet or the like and narrowing the effective area, this goes against the goal of narrowing the frame.

The present invention has been made in consideration of the above, and aims to provide a surface lighting device that can simultaneously achieve a narrower frame and improved brightness uniformity.

In order to solve the above-mentioned problems and achieve the object, a planar lighting device according to one aspect of the present invention comprises a substrate, a reflector, and a bottom frame. A plurality of light sources are arranged two-dimensionally on the substrate. The reflector is provided on the substrate and has a reflective surface surrounding each of the light sources. The bottom frame houses the light sources, the substrate, and the reflector. At an end of the reflector facing a side wall of the bottom frame, a portion of the reflective surface facing the side wall of the bottom frame is removed. A reflective member is provided on the surface of the side wall of the bottom frame facing the light source.

The surface lighting device according to one aspect of the present invention can simultaneously achieve a narrower frame and improved brightness uniformity.

FIG. 1 is a perspective view of the appearance of a surface illumination device according to an embodiment. FIG. 2 is an exploded perspective view of the main part of the surface illumination device. FIG. 3 is a plan view of a corner of the surface illumination device with the lens array, diffuser, optical sheet, and top frame removed. FIG. 4 is a cross-sectional view taken along line YY in FIG. FIG. 5 is a plan view of a corner of the surface illumination device in the first comparative example with the lens array, diffuser, optical sheet, and top frame removed. FIG. 6 is a cross-sectional view of a surface illumination device of a first comparative example. FIG. 7 is a plan view of a corner of a surface illumination device in a second comparative example with the lens array, diffuser, optical sheet, and top frame removed. FIG. 8 is a cross-sectional view of a surface illumination device of a second comparative example.

The surface lighting device according to the embodiment will be described below with reference to the drawings. Note that the present invention is not limited to this embodiment. Furthermore, the dimensional relationships between elements in the drawings and the ratios between elements may differ from reality. The drawings may also include parts with different dimensional relationships and ratios. Furthermore, the contents described in one embodiment or modified example are, in principle, applicable to other embodiments or modified examples in the same way.

Figure 1 is an external perspective view of a surface lighting device 1 according to one embodiment. For convenience, in the figure, the longitudinal direction of the surface lighting device 1 is the X-axis direction, the lateral direction is the Y-axis direction, and the thickness direction is the Z-axis direction.

In FIG. 1, the surface lighting device 1 has a roughly rectangular (or roughly square) plate-like outer shape, and the housing is made up of a bottom frame (hidden behind in the figure) that is a box-like frame with a floor that houses a substrate and the like described below, and a top frame 11 that covers the open side of the bottom frame. The top frame 11 has an exit surface 1a formed by a roughly rectangular opening 11a, and light is emitted from the inside of the surface lighting device 1 to the outside. When the surface lighting device 1 is used as a backlight for an in-vehicle navigation device, indicator, etc., a liquid crystal display device or the like is attached to the side of the exit surface 1a.

Figure 2 is an exploded perspective view of the main parts of the surface lighting device 1, and is a view seen from the light output surface side, similar to Figure 1. In Figure 2, the surface lighting device 1 is configured such that a reflective member 3, a substrate 4 on which a light source 5 is arranged, a reflector 6, a lens array 7, a diffuser 8, and optical sheets 9 and 10 are attached to a bottom frame 2, and a top frame 11 fits into the bottom frame 2 to form a lid.

The bottom frame 2 has a bottom 2a and side walls 2b on the four sides of the periphery of the bottom 2a. The bottom 2a has a hole 2c through which an electrical connector (not shown) provided on the back surface of the substrate 4 passes. The bottom frame 2 is formed by die casting, sheet metal, etc.

A reflective member 3 made of reflective tape or the like is attached to the inside of the side wall 2b of the bottom frame 2. The reflective tape is a strip-shaped member with a reflective layer formed on one side and an adhesive layer formed on the other side.

The substrate 4 is fixed to the inside of the bottom 2a of the bottom frame 2 via a fixing member (not shown) such as double-sided tape. On the substrate 4, a plurality (a large number) of light sources 5 such as LEDs (Light Emitting Diodes) are arranged two-dimensionally (e.g., in a grid pattern).

Between the light sources 5 of the substrate 4, the back surface of the reflector 6 is fixed via a fixing member (not shown) such as a plurality of double-sided tape strips extending in the vertical direction (or horizontal direction) of the figure. The reflector 6 has a reflective surface surrounding each light source 5, and reflects the light emitted from the light source 5 at a wide angle toward the light output surface to increase brightness. The reflective surface of the reflector 6 has a substantially rectangular hole through which the light source 5 is placed, and four inclined reflective surfaces surrounding the hole that open toward the light output surface. At the end of the reflective surface of the reflector 6 that faces the side wall 2b of the bottom frame 2, the portion facing the side wall 2b has been removed. The reflector 6 is manufactured by injection molding of resin, etc.

The back surface of the lens array 7 is fixed to the lower end of the reflector 6 in the figure via a fixing member (not shown) made of a plurality of rectangular double-sided tape or the like. The lens array 7 is used to adjust the light distribution and brightness of the light emitted from the reflector 6. The lens array 7 is provided on its outer periphery with bosses (not shown) to maintain the distance from the diffuser 8.

The diffuser 8 is fixed to the lower end of the lens array 7 in the figure via a fixing member (not shown) such as a plurality of rectangular double-sided tape. The diffuser 8 is also called a diffusion sheet (diffusion film) or diffusion plate.

Optical sheets 9 and 10 are fixed to the lower end of diffuser 8 in the figure via multiple rectangular fixing members (not shown) such as double-sided tape. Optical sheets 9 and 10 adjust the light distribution and brightness of the light passing through them, and are prism sheets (prism films), brightness enhancement sheets (brightness enhancement films), louver sheets (louver films), etc.

A top frame 11 is disposed on the emission surface side of the optical sheet 10, and the top frame 11 is fixed to the bottom frame 2. The top frame 11 is formed by die casting, sheet metal, etc.

Figure 3 is a plan view of a corner of the surface lighting device 1 with the lens array 7, diffuser 8, optical sheets 9 and 10, and top frame 11 removed. Figure 4 is a Y-Y cross-sectional view in Figure 1 (a cross-sectional view of the area around the light source 5 at the right end of Figure 3 with the lens array 7, diffuser 8, optical sheets 9 and 10, and top frame 11 attached).

In Figures 3 and 4, the position of the light source 5 at the edge on the substrate 4 has been moved toward the edge compared to the case where no measures are taken to narrow the frame and improve brightness uniformity (first comparative example described later). In addition, the reflective surface of the reflector 6 surrounding the light source 5 has the portion facing the side wall 2b of the bottom frame 2 removed. That is, at the corners, portions of the reflective surface are removed in two directions, and at the other ends, portions are removed in one direction. This eliminates the problem of the reflective surface at the end becoming thin-walled, making it difficult to manufacture by injection molding of resin, and makes it easier to manufacture the reflector 6.

As a result, the edge light source 5 is closer to the edge of the housing (bottom frame 2, top frame 11), making it easier to narrow the frame and increasing the brightness of the outer periphery, improving brightness uniformity. Note that since one side of the housing (for example, the lower side in Figures 1 and 2) often does not require a narrow frame, part of the reflective surface of the reflector 6 can be left on that side without removing it.

In addition, the reflective surface at the end of the reflector 6 is removed, and instead of reflection by a portion of the reflective surface of the reflector 6, the light source 5 at the end is directly adjacent to the reflective member 3 attached to the side wall 2b of the bottom frame 2, and the light emitted at a wide angle from the light source 5 is reflected by the reflective member 3 toward the emission surface, compensating for the absence of a portion of the reflective surface of the reflector 6.

Figure 5 is a plan view of a corner of the surface lighting device 1' in the first comparative example with the lens array 7', diffuser 8', optical sheets 9', 10', and top frame 11' removed. Figure 6 is a cross-sectional view of the surface lighting device 1' in the first comparative example (a cross-sectional view of the periphery of the light source 5' at the right end of Figure 5 with the lens array 7', diffuser 8', optical sheets 9', 10', and top frame 11' attached).

5 and 6, the position of the edge light source 5' on the substrate 4' is farther away from the edge of the housing (bottom frame 2', top frame 11') than in the embodiment of FIG. 3. In addition, the reflecting surface of the reflector 6' surrounding the light source 5' has a uniform shape over the entire surface. Therefore, at the outer periphery of the housing (near the four sides of the rectangle), there is no adjacent light source 5' on one side (two sides at the corners), which reduces the brightness uniformity.

Figure 7 is a plan view of a corner of the surface lighting device 1" in the second comparative example with the lens array 7", diffuser 8", optical sheets 9", 10", and top frame 11" removed. Figure 8 is a cross-sectional view of the surface lighting device 1" in the second comparative example (a cross-sectional view of the area around the light source 5" at the right end of Figure 7 with the lens array 7", diffuser 8", optical sheets 9", 10", and top frame 11" attached).

In Figures 7 and 8, the position of the edge light source 5" on the substrate 4" has been moved toward the edge compared to the first comparative example in Figure 5. As a result, the shape of the reflective surface of the reflector 6" is thin with a short width on the edge side, making it difficult to manufacture by injection molding of resin or the like. As a result, the edge light source 5" cannot be moved sufficiently close to the edge of the housing as shown in the figure, and it is not possible to simultaneously achieve a narrow frame and improved brightness uniformity.

In contrast, in the embodiment of Figures 3 and 4, the reflector 6 has a manufacturable shape, so the light source 5 can be placed close enough to the edge of the housing, achieving both a narrow frame and improved brightness uniformity at the same time.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention.

As described above, the planar lighting device according to the embodiment includes a substrate on which a number of light sources are arranged in two dimensions, a reflector provided on the substrate and having a reflective surface surrounding each of the light sources, and a bottom frame housing the light sources, substrate, and reflector, and at the end of the reflector facing the side wall of the bottom frame, the portion of the reflective surface facing the side wall of the bottom frame has been removed. This makes it possible to simultaneously achieve a narrower frame and improved brightness uniformity.

In addition, a reflective member is provided on the side of the bottom frame's side wall that faces the light source. This compensates for the removal of the reflector's reflective surface, and there is no reduction in brightness.

The reflective member is made of a strip of reflective tape with a reflective layer formed on one side and an adhesive layer formed on the other side. This makes it easy to add the reflective member.

The reflector also has a lens array, diffuser and optical sheet on the output side, which allows the light distribution and brightness distribution to be adjusted.

It also has a top frame that fits into the side wall of the bottom frame. This allows the bottom frame and top frame to form a sturdy housing.

Furthermore, the present invention is not limited to the above-mentioned embodiment. The present invention also includes configurations in which the above-mentioned components are appropriately combined. Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above-mentioned embodiment, and various modifications are possible.

1 Planar lighting device, 2 Bottom frame, 3 Reflective member, 4 Substrate, 5 Light source, 6 Reflector, 7 Lens array, 8 Diffuser, 9, 10 Optical sheet, 11 Top frame

Claims (9)

A substrate on which a plurality of light sources are arranged in two dimensions;
a reflector provided on the substrate and having a reflective surface surrounding each of the light sources;
a bottom frame that houses the light source, the substrate, and the reflector;
Equipped with
the reflector has an end portion facing the side wall of the bottom frame, the end portion being removed from the reflective surface, the reflective surface being removed from the end portion facing the side wall of the bottom frame;
A reflective member is provided on a surface of the side wall of the bottom frame facing the light source.
Surface lighting device. A top frame is provided which fits onto a side wall of the bottom frame.
2. The spread illuminating device according to claim 1 . A substrate on which a plurality of light sources are arranged in two dimensions;
a reflector provided on the substrate and having a reflective surface surrounding each of the light sources;
a bottom frame that houses the light source, the substrate, and the reflector;
a top frame having at least a narrow frame portion and fitted to a side wall of the bottom frame;
Equipped with
The reflector has a portion of the reflective surface facing the side wall of the bottom frame removed at an end portion facing the side wall of the bottom frame corresponding to the narrowed frame portion.
Surface lighting device. A reflective member is provided on a surface of the side wall of the bottom frame facing the light source.
4. The spread illuminating device according to claim 3 . The reflective member is composed of a strip-shaped reflective tape having a reflective layer formed on one side and an adhesive layer formed on the other side.
5. A spread illuminating device according to claim 1 or 4 . A lens array, a diffuser and an optical sheet are provided on the output side of the reflector.
The spread illuminating device according to any one of claims 1 to 5 . The light source at the end where the reflective surface of the reflector is removed is disposed near the side wall of the bottom frame.
7. The spread illuminating device according to claim 1. The reflective surface of the reflector is removed along the entire length of at least one side constituting the outer periphery.
8. The spread illuminating device according to claim 1. The shape when viewed from above is substantially rectangular,
The reflecting surface of the reflector is removed along the entire length of at least three sides constituting the outer periphery.
8. The spread illuminating device according to claim 1.

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