JP2006012507A - Backlight unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight unit of which size and thickness can be reduced while keeping an uniform brightness, further, high in freedom of designing outer shape. <P>SOLUTION: The edge light type backlight unit 1, having light sources 3 at side face side of a light guide plate 2, comprises a metallic reflection plate 12 with a locking part composed of a rectangular metallic reflection plate 12a arranged under the light guide plate 2, reflecting the light leaked from the light guide plate 2; and a resin-made locking part 12b formed into one body at the peripheral part of the metallic reflection plate 12a, at least locking the light guide plate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

    The present invention relates to a backlight unit suitable for reduction in thickness and size.

  Conventionally, electronic devices having a liquid crystal display unit have been developed and commercialized. Since the liquid crystal itself does not emit light, when the liquid crystal is transmissive or transflective, a backlight unit is mounted as a surface light source under the liquid crystal display (LCD).

The backlight unit is generally a method in which light from a light source 3 such as a cold cathode tube or an LED is incident from a side surface of a thin transparent resin plate called a light guide plate, and the light is uniformly emitted to a liquid crystal display surface. As shown in Patent Document 1, the backlight unit includes a light guide plate 2, a light source 3, a large number of sheets, and a resin case 8 that stores these sheets. A number of sheets are disposed below the light guide plate 2 and reflect the light leaking from the light guide plate 2 to return the light to the light guide plate 2 again. A diffusion sheet 4 that has a function of scattering and emitting light emitted from the light guide plate 2 evenly as a surface, and one sheet that condenses the light scattered on the diffusion sheet 4 within a certain angle range Or it is common to comprise with the two lens sheets 5 (refer FIG. 13).
JP 2002-170419 A

  As an item required for the development of the backlight, it is always required to reduce the thickness and the size as well as to improve the brightness and the brightness balance. For the purpose of reducing the thickness, it is necessary to reduce the thickness of the bottom surface. However, when the bottom surface portion 9 of the resin case 8 is made thin in order to reduce the thickness of the backlight unit 1, the bottom surface portion 9 is deformed due to a decrease in rigidity, strength, and heat resistance (see FIG. 14). It becomes impossible to maintain the shape of the light guide plate 2 accommodated in the plate 8. As a result, luminance unevenness occurs due to the deformed light guide plate.

  Further, in order to maintain the shape of the resin case 8, it is essential that the outer peripheral frame 10 is connected to all four sides, and the thickness is required to maintain the shape. Therefore, it is difficult to reduce the size, and design restrictions are large.

  Therefore, the object of the present invention is to solve the above-mentioned problems, achieve a reduction in thickness while maintaining a uniform luminance, can be reduced in size, and has a degree of freedom in designing the outer shape. It is to provide a high backlight unit.

  To achieve the above object, according to the present invention, in an edge light type backlight unit in which a light source is disposed on a side surface of a light guide plate, a rectangular shape that is disposed under the light guide plate and reflects light leaking from the light guide plate is provided. The metal reflector is provided with a locking part-attached metal reflector that is integrated with a peripheral part of the metal reflector and at least a resin locking part that locks the light guide plate.

  In addition, the metal reflector is configured to use a metal plate having a thickness of 0.1 to 0.5 mm selected from an aluminum plate, a steel plate, and a brass plate.

  Moreover, it comprised so that there might be a part in which the said resin-made latching | locking part is not arrange | positioned in some among the peripheral parts of the said metal reflecting plate.

  The metal reflector has a through hole, and the through hole is filled with the resin of the resin locking portion.

  Since the backlight unit of the present invention has the above-described configuration, the following effects are exhibited.

  That is, the backlight unit of the present invention includes a metal reflector with a latching portion that latches the light guide plate by a resin latching portion integrated with the peripheral edge of the rectangular metal reflector. Even if the metal reflector is thin, it is excellent in rigidity, strength, heat resistance, etc., so it does not deform, and the light guide plate locked by the resin locking part integrated with the metal reflector also maintains its shape. can do. Therefore, it is possible to obtain a uniform brightness by realizing a reduction in thickness and a non-deformable light guide plate.

  Further, since the metal reflector does not deform sufficiently, it is not always necessary to provide a thick outer peripheral frame that is continuous on all four sides like the bottom surface portion of a conventional resin case. Therefore, it is possible to reduce the size of the backlight module, and it is possible to increase the degree of freedom in designing the outer shape.

  In addition, since the metal reflector with a locking portion is provided with a function of reflecting light leaked from the light guide plate by integrating with the metal reflector at the molding stage of the resin locking portion, the assembly of the backlight unit is performed in advance. The operation of mounting the reflection sheet in the member for locking the light guide plate at the stage becomes unnecessary, and the assembly process can be streamlined.

  Hereinafter, embodiments of the backlight unit of the present invention will be described in more detail.

  FIG. 1 is an exploded view illustrating an example of a backlight unit according to the present invention. In the backlight unit 1 mounted as a surface light source under the LCD 11 in FIG. 1, a light source 3 is arranged on one side of a light guide plate 2, and the light source 3 is connected to an external terminal by an FPC (Flexible Printed Circuit) 6. Yes. On the upper side of the light guide plate 2 is a diffusion sheet 4 having a function of scattering light emitted from the light guide plate 2 and emitting light uniformly as a surface, and further, the light scattered on the diffusion sheet 4 within a range of a certain angle. Two lens sheets 5 to be condensed are arranged. And the metal reflector 12 with the latching | locking part which is the characteristics of this invention is only arrange | positioned under the light-guide plate 2, and a resin case and a reflective sheet do not exist.

  As the transparent resin plate used for the light guide plate 2, an acrylic resin, acrylonitrile-styrene copolymer resin, cellulose acetobutyrate resin, cellulose propionate resin, polymethylpentene resin having excellent transparency and light guide properties, Polycarbonate resins, polystyrene resins, polyester resins, cycloolefin resins, and norbornene resins are used.

  The light source 3 is a light emitting diode (LED). One or more LEDs are arranged on the light incident surface. In addition, in the backlight unit 1 which concerns on this invention, the arrangement | positioning location of the light source 3 is not limited to what is shown in FIG. Further, the number and shape of the light incident surfaces of the light guide plate 2 are appropriately set according to the arrangement location.

  The metal reflection plate 12 with the locking portion is disposed on the lower side of the light guide plate 2 and integrated with a rectangular metal reflection plate 12a that reflects light leaking from the light guide plate 2 and a peripheral portion of the metal reflection plate 12a. And at least a resin locking portion 12b for locking the light guide plate 2 (see FIG. 2).

  The metal reflector 12a is a metal plate having a thickness of 0.1 to 0.5 mm selected from an aluminum plate, a steel plate, and a brass plate. By using these metal plates, even if the metal reflector 12a is thin, it does not deform because it is excellent in rigidity, strength, heat resistance and the like. In order to reduce the thickness of the backlight unit 1, a thickness of 0.1 to 0.2 mm is more preferable.

  The reflection on the surface of the metal reflection plate 12a facing the light guide plate 2 may be performed only by reflection on the surface of the metal plate, or may be performed by a light reflection layer provided on the surface of the metal plate. As the light reflection layer, there is a metal thin film such as aluminum or silver formed by a method such as vacuum deposition, sputtering, or ion plating. In addition, there is a white ink layer formed by a coating method such as a roll coating method or a spray coating method, a printing method such as a gravure printing method or a screen printing method. Moreover, you may affix a sheet-like film with a reflective function on a metal plate as a light reflection layer.

  Moreover, you may arrange | position the adhesion prevention layer with the fine unevenness | corrugation which prevents adhesion | attachment with the light-guide plate 2 on the outermost surface of a light reflection surface, and you may provide a hard-coat layer on the outermost surface as damage prevention.

  The resin locking portion 12b is integrated with the peripheral portion of the metal reflecting plate 12a, positions the light guide plate 2 on the metal reflecting plate 12a, and is fixed so as to maintain the state. In FIG. 1 and FIG. 2, the L-shaped resin molded body is integrated into the four corners of the rectangular metal reflector 12a as the resin locking portion 12b, and is surrounded by these L-shaped resin molded bodies. The light guide plate 2 is positioned and accommodated therein.

  By the way, if only the light guide plate 2 is positioned and accommodated, a metal case obtained by bending a metal plate into a box shape is also possible. And if it is a metal case, there will be no problem of a deformation | transformation like the resin case 8 which concerns on a prior art. However, if the light guide plate 2 is simply accommodated without being fixed, it will fall off due to an impact such as a drop of the product, and uniform brightness cannot be obtained due to misalignment or the like. In the resin case 8 according to the prior art, in order to prevent the light guide plate 2 from dropping due to an impact such as dropping, a part of the resin plate protrudes from the side surface of the light guide plate 2 to form a protruding portion 2a (see FIG. 4). Although it was common to fit in the hollow part provided in the outer peripheral frame 10 of FIG. 8, in the case of the metal case which bent the metal plate in the box shape, formation of this hollow part is difficult.

  On the other hand, as for the metal reflecting plate 12 with a latching part of this invention, the resin-made latching | locking parts 12b are integrated with the peripheral part of the metal reflecting plate 12a. Since the resin locking portion 12b is excellent in moldability, the recessed portion 14 can be formed very easily in the molding stage of the resin locking portion 12b (see FIG. 2). In other words, the metal reflector 12 with the locking portion of the present invention has both the dimensional stability of the metal case (and hence the dimensional stability of the light guide plate) and the moldability of the resin case (and the fixability of the light guide plate). It has the advantages of In addition, although the case where the hollow part 14 is formed in the resin-made latching | locking part 12b is shown in drawing, the hollow part formed in the light-guide plate 2 side by forming the projection part in the resin-made latching | locking part 12b side, and You may make it fit (not shown). Further, the shape, number and arrangement of the recesses and protrusions are not limited to those shown in FIG.

  FIG. 3 shows an AA cross section of the metal reflector 12 with the locking portion in FIG. In FIG. 3, both ends of the end portion of the metal reflecting plate 12a are sandwiched by the resin locking portions 12b, and thereby the coupling between the metal reflecting plate 12a and the resin locking portion 12b is stronger. .

  Integration of the metal reflector 12a and the resin locking portion 12b is performed as follows. First, the metal reflector 12a is disposed in the injection mold 15 (see FIG. 9). At this time, after aligning the metal reflector 12a along the inner wall surface of the mold 15 and aligning it, the metal reflector 12a is fixed using the suction mechanism 16 or the like. Then, after the mold 15 is closed, the molten resin 17 is injected into the mold 15 from the injection port 18, and the resin is solidified in the cavity 19 (see FIG. 10), so that the resin locking portion 12b is reflected on the metal. It is made to unite with the peripheral part of board 12a.

  As described above, the metal reflecting plate 12 with the locking portion is previously provided with a function of reflecting light leaked from the light guide plate 2 by being integrated with the metal reflecting plate 12a in the molding stage of the resin locking portion 12b. In the assembly stage of the backlight unit 1, the work of mounting the reflection sheet 7 in the member for locking the light guide plate 2 as in the prior art becomes unnecessary, and the assembly process can be streamlined.

  Although the backlight unit 1 of the present invention has been described based on the embodiment shown in FIG. 1, the configuration of the backlight unit 1 of the present invention is not limited to the above-described embodiment. As shown in FIG. 5, the two resin locking parts 12b made of a U-shaped resin molded body are integrated with a rectangular metal reflector 12a so as to face each other. The light guide plate 2 may be positioned and accommodated in the enclosed region. Further, as shown in FIG. 6, a resin locking portion 12b made of a frame-shaped resin molded body is integrated with a rectangular metal reflector 12a, and is guided into an area surrounded by the frame-shaped resin molded body. The optical plate 2 may be positioned and accommodated. That is, according to the backlight unit 1 of the present invention, the metal reflector 12a alone does not sufficiently deform, so that it is always continuous and thick on all four sides like the bottom surface portion 9 of the resin case 8 of the prior art. The certain outer peripheral frame 10 may not be provided.

  Therefore, the backlight module 1 can be reduced in size and the degree of freedom in designing the outer shape can be increased. For example, as shown in FIG. 12, a portion where the resin locking portion 12 b is not disposed by configuring a part of the peripheral portion of the metal reflector 12 a so that the resin locking portion 12 b is not disposed. In this case, the area of the metal reflector 12a can be reduced, and the deleted space can be used for arrangement of devices other than the backlight module 1.

  In addition, a large number of metal reflectors 12 with locking portions in the integral molding can be obtained by forming a part of the peripheral portion of the metal reflector 12a where the resin locking portions 12b are not disposed. Easy to take. That is, if a plurality of metal reflectors 12a are connected to each other at a portion where the resin locking portion 12b is not arranged, the plurality of metal reflectors 12a can be inserted into the mold 15 at once. 11), the connecting portion 20 is easily removed because the resin locking portion 12b does not exist adjacent to the connecting portion 20.

  Further, in FIGS. 1 to 3 described above, the end portion of the metal reflector 12a is sandwiched from both surfaces by the resin locking portion 12b. However, as shown in FIG. . More preferable in terms of the binding force is the sandwiching embodiment. On the other hand, in the case of the embodiment shown in FIG. 7, the lowermost surface of the backlight unit 1 can be entirely smoothed, and the total thickness of the entire backlight unit 1 can be reduced.

  As a means for increasing the coupling force between the metal reflector 12a and the resin locking portion 12b, the metal reflector 12a has a through-hole 13 (see FIG. 8), and the resin-made engagement is provided in the through-hole 13. It can also be made to be filled with resin of stop part 12b. If this through-hole 13 is applied in the embodiment shown in FIGS. 1 to 3, it is perfect in terms of coupling force.

  Uses a metal reflector 12a, which is based on a rectangular aluminum plate with a thickness of 0.2 mm, vacuum-deposited high-purity aluminum on one side of the base, and a reflective oxide film is deposited on it to increase reflection. did.

  Next, the metal reflector 12a is placed in an injection mold 15 and injection molding is performed using a polycarbonate resin, and the L-shaped resin molded body serves as the resin locking portion 12b at the four corners of the metal reflector 12a. A metal reflector 12 with a locking part integrated with each other was obtained. The increased reflection processing surface of the metal reflecting plate 12 with the locking portion was disposed so as to face the back surface of the light guide plate 2. Further, the resin locking portions 12b are integrated so as to sandwich the end portion of the metal reflecting plate 12a from both sides, and two of them are provided with one recessed portion 14 facing each other.

  The light guide plate 2 was attached to the metal reflection plate 12 with a locking portion. The light guide plate 2 is a transparent resin plate made of a polyolefin resin, and a projection 2 a that fits into the recess 14 of the metal reflector 12 with a locking portion is provided on the side surface of the light guide plate 2. Three LEDs as light sources 3 were arranged uniformly on the incident surface of the light guide plate.

  A diffusion sheet was disposed on the light guide plate. As the diffusion sheet 4, a PET film coated with a light diffusing resin was used. Two lens sheets (3M BEF) 5 are arranged on the diffusion sheet 4.

  With this configuration, the light reflecting surface is formed at the same time when the case is molded, so that the thickness of the entire case and the backlight unit can be reduced, and the process can be shortened by integrating the reflecting sheet. did it.

  Using a metal reflector 12a based on a SUS plate having a thickness of 0.1 mm, vacuum-deposited silver on one side of the base, and depositing a transparent oxide film thereon to increase reflection, Example 2 was the same as Example 1 except that the two resin-made locking portions 12b made of a U-shaped resin molded body were integrated with the metal reflector 12a so as to face each other.

  The same procedure as in Example 1 was performed except that the resin locking portion 12b was attached and fixed only to the side of the increased reflection surface of the metal reflector 12a.

  Example 1 was the same as in Example 1 except that the metal reflector 12a had a through hole 13 and the resin was engaged in the resin engagement portion 12b.

  By adopting the configurations of the first to fourth embodiments, it is possible to reduce the thickness while maintaining a uniform luminance, and it is possible to reduce the size, and the outer shape has a high degree of design freedom, and the assembly process A streamlined backlight unit was obtained.

  The backlight unit of the present invention includes a cordless phone, a mobile phone, a calculator, a sub-notebook computer, a notebook computer, a liquid crystal monitor for a desktop personal computer, a liquid crystal TV, a PDA (personal digital assistant), a digital camera, a video camera, and a commercial communication. It is suitable for an electronic device equipped with a liquid crystal display such as a device.

It is the exploded view explaining an example of the backlight unit concerning the present invention. It is a perspective view which shows the example of arrangement | positioning of the resin-made latching | locking parts about the metal reflecting plate with a latching | locking part. It is sectional drawing (AA cross section of FIG.2, FIG.5 and FIG.6) which shows the example of integration of a metal reflecting plate and resin-made latching | locking parts about a metal reflector with a latching | locking part. It is a partial expansion perspective view which shows the example of formation of a projection part about a light-guide plate. It is a perspective view which shows the example of arrangement | positioning of the resin-made latching | locking parts about the metal reflecting plate with a latching | locking part. It is a perspective view which shows the example of arrangement | positioning of the resin-made latching | locking parts about the metal reflecting plate with a latching | locking part. It is sectional drawing which shows the example of integration of a metal reflecting plate and resin-made latching | locking parts about a metal reflector with a latching | locking part. It is a partial expansion perspective view which shows the example which provided the through-hole in the part integrated with the resin-made latching | locking parts about a metal reflecting plate. It is sectional drawing which shows the integration process of a metal reflecting plate and a resin-made latching | locking part about a metal reflector with a latching | locking part. It is sectional drawing which shows the integration process of a metal reflecting plate and a resin-made latching | locking part about a metal reflector with a latching | locking part. It is a perspective view which shows the example integrated with the resin-made latching | locking parts using the some metal reflecting plate connected mutually. It is a top view which shows the example of a change of an external shape about the metal reflecting plate with a latching | locking part. It is the exploded view explaining the backlight unit which concerns on a prior art. It is the perspective view explaining the deformation | transformation of the resin case.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Backlight unit 2 Light guide plate 2a Protrusion part 3 Light source 4 Diffusion sheet 5 Lens sheet 6 FPC
7 Reflective sheet 8 Resin case 9 Bottom portion 10 Outer frame 11 LCD
DESCRIPTION OF SYMBOLS 12 Metal reflecting plate 12a with a latching part Metal reflecting plate 12b Resin latching part 13 Through-hole 14 Depression 15 Mold 16 Suction mechanism 17 Molten resin 18 Injection port 19 Cavity 20 Connection part

Claims (4)

  In an edge light type backlight unit in which a light source is disposed on the side of a light guide plate, a rectangular metal reflector that is disposed under the light guide plate and reflects light leaked from the light guide plate, and a peripheral portion of the metal reflector A backlight unit comprising: a metal reflecting plate with a locking portion integrated with at least a resin locking portion for locking the light guide plate.   The backlight unit according to claim 1, wherein the metal reflector is a metal plate having a thickness of 0.1 to 0.5 mm selected from an aluminum plate, a steel plate, and a brass plate.   3. The backlight unit according to claim 1, wherein a part of the peripheral edge portion of the metal reflector is not provided with the resin locking portion. 4.   The backlight unit according to claim 1, wherein the metal reflector has a through-hole, and the resin of the resin-made locking portion is filled in the through-hole.

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