JP2005267881A - Planar lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planer lighting device capable of easily and surely holding a plurality of point light sources (LED) in proper position, respectively, when mounting the light sources on an FPC. <P>SOLUTION: The FPC 10 is composed of a first FPC part 10a and a second FPC part 10b extending from the first FPC. The plurality of point light sources 2 are mounted on the first FPC part 10a and arranged in the proximity of an incident face 4 of a lightguide plate 1, and the first FPC part 10a is fixed to the lightguide guide plate 1 by using a double-sided adhesive tape 17. The top end part of the second FPC part 10b is arranged at lower side of a housing frame 11 and connected to a base board P through a connector. The second FPC part 10b is arranged on the outer wall face side of one sidewall 19 of a housing frame 11, in a state of being bent in an arc shape. The second FPC part 10b is inserted and locked in a notched part 20a formed on the sidewall 19, and a force applied added to the first FPC part 10a, caused by the bending force of the second FPC part 10b, is suppressed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sidelight type planar illumination device, and more particularly to a planar illumination device using a flexible printed circuit board on which a point light source is mounted.

  Liquid crystal display devices that are characterized by being thin, occupying a small volume, and being light are used in many electric products such as mobile phones and personal computers. By the way, since the liquid crystal itself of the liquid crystal display device does not emit light itself, the liquid crystal is irradiated separately from the liquid crystal display device when used in a dark place where the brightness of sunlight or room illumination cannot be taken in sufficiently. A lighting means is required. At present, further downsizing of the liquid crystal display device is desired. On the other hand, the liquid crystal display unit of the liquid crystal display device is desired to be increased in size. However, it has become necessary to reduce the size and further reduce the power consumption.

  Therefore, in order to realize downsizing and low power consumption of the illumination means, an LED that is a point light source is used as the light source of the illumination means, or the light emitting element is emitted from the light emitting element while being fixed at a predetermined position. The one that efficiently uses the light is being developed. For example, an LED or a light emitting element as the light source is mounted on a flexible wiring board (FPC) (see Patent Document 1). In Patent Document 1, as shown in FIG. 6 (FIG. 11 of Patent Document 1), the FPC is wound below the bottom portion 32a of the frame body, and the protruding portion 36a of the FPC is formed on the side wall 32b of the frame body. A configuration is disclosed in which the light emitting element 50 inserted into and supported by the guide slit 32g and mounted on the FPC overhanging portion 36a is accurately positioned to the side of the light guide plate. Further, as shown in FIG. 7 (FIG. 23 of Patent Document 1), the FPC overhanging portion 36a is adhered to the side surface of the light guide plate disposed on the bottom of the frame 32 by an adhesive member 60 such as a double-sided adhesive tape. In addition, a configuration is described in which the protruding portion 36a and the light emitting element 50 are positioned by a guide portion 46d and a concave portion provided on a part of the side surface of the light guide plate 46.

JP 2003-90993 A

  However, the invention of Patent Document 1 describes the configuration when one light emitting element is mounted on the FPC, but does not describe the configuration when multiple light emitting elements are mounted on the same FPC. Absent. If a plurality of light emitting elements are mounted on the same FPC, the configuration of the invention of Patent Document 1 has a disadvantage that the configuration is complicated and disadvantageous in terms of manufacturing cost. Moreover, only the vertical position of the FPC is held with respect to the protruding portion of the FPC bonded by the adhesive, and the displacement due to the extension force of the bent FPC (deviation due to peeling of the adhesive portion) is maintained. There was a bug that was not addressed.

  Therefore, the present invention has been made in view of such circumstances, and even when a plurality of point light sources are mounted on the FPC as light sources, each point light source is easily and reliably held at an appropriate position. An object of the present invention is to provide a planar lighting device that can be used.

  In order to solve the above problems, the invention of a planar illumination device according to claim 1 includes a light guide plate made of a translucent material, and a plurality of point light sources arranged to face one side surface of the light guide plate. The light guide plate and a housing frame for storing the point light source, the plurality of point light sources are mounted, and a part of the light guide plate is disposed on the surface side of the light guide plate stored in the housing frame. One flexible printed circuit board part and one side extending from one side of the first flexible printed circuit board, and a part of the flexible printed circuit board is arranged outside the housing frame so as to form an arc on one side of the housing frame. A planar lighting device comprising a flexible printed circuit board comprising a second flexible printed circuit board part, wherein the first flexible printed circuit board part is a surface of the light guide plate. In order to adhere to the first flexible printed circuit board part, the first flexible printed circuit board part is attached to the first flexible printed circuit board by an extension force of the second flexible printed circuit board part curved in a state of drawing the arc. In order to suppress the force applied to the housing frame, a cutout portion for locking the second flexible printed circuit board portion is provided on the side wall of the housing frame.

  Adhesive means, for example, a flexible printed circuit board on which a plurality of point light sources are mounted with a double-sided tape can be attached to the surface of the light guide plate, thereby ensuring a large margin for bonding the flexible printed circuit board. The position of the point light source mounted on the printed board can be accurately fixed. Also, the force applied to the flexible printed circuit board affixed to the surface of the light guide plate due to the stretching force of the flexible printed circuit board is secured by locking the flexible printed circuit board arranged in an arc with a notch formed in the housing frame. And the peeling of the flexible printed circuit board attached to the light guide plate is surely prevented.

  In order to solve the above-mentioned problem, the invention of the planar lighting device according to claim 2 is characterized in that, in the invention of claim 1, the adhesive means is made of double-sided tape.

  According to the planar illumination device of the present invention, a flexible printed circuit board on which a plurality of point light sources is mounted is adhered to the surface of the light guide plate by an adhesive means, and is also arranged in an arcuate state and has a stretching force. By locking the printed circuit board with the notch formed in the light guide plate, the flexible printed circuit board can be securely fixed and the point light source can be easily and reliably held at an appropriate position.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of a planar lighting device according to the invention will be described with reference to the accompanying drawings.
FIG. 1 is an exploded perspective view showing a planar illumination device M, an object N to be illuminated above the planar illumination device M, and a circuit board P disposed below the planar illumination device M. FIG. The planar illumination device M includes a light guide plate 1, a reflection plate 6, a light diffusion sheet 7, brightness enhancement films 8 and 9, a point light source 2, and a flexible printed circuit board 10 on which the point light source 2 is mounted. A housing frame 11 in which these members are accommodated is schematically configured.
FIG. 2 is an enlarged perspective view showing the planar illumination device M in a state where each member is accommodated in the housing frame 11. FIG. 3 is a plan view showing the planar illumination device M in a state where each member is accommodated in the housing frame 11.

  1 to 3, the point light source 2 housed in the housing frame 11 is disposed on the one end face 4 side of the light guide plate 1. For example, an LED is used as the point light source 2. The LED 2 has a configuration in which an LED chip is covered with a resin case, and an emission window is formed in the case so that emitted light is efficiently emitted in one direction from the emission window. . Hereinafter, one direction of the LED from which the emitted light is efficiently emitted is referred to as a light emission direction side and is referred to as the front surface of the LED. A plurality of LEDs 2 are provided, and the front surfaces thereof are arranged close to each other so as to face the one side end face 4. Therefore, most of the light emitted from the LED 2 enters the light guide plate 1 from the one end face 4. Hereinafter, the one end face 4 of the light guide plate 1 is also referred to as an incident face 4. However, although LED2 has the structure covered with the resin case, some light radiate | emitted from LED chip is light leaking from surfaces other than the front of LED2, for example, the upper surface of LED, a lower surface, and right and left side surfaces. Is emitted.

  The LED 2 is mounted on a flexible printed circuit board (hereinafter referred to as FPC) 10 by soldering. The FPC 10 is composed of two parts: a first FPC 10a on which the LED 2 is mounted and a second FPC 10b that connects the first FPC 10a and a substrate P described later. The LED 2 is mounted near one side 12 of the first FPC 10a. In the FPC 10, a pattern for supplying power to the LED 2 is formed. This pattern is formed on the upper side of the LED 2, that is, closer to one side 13 of the first FPC 10a in FIG. The first FPC 10 a on which the LED 2 is mounted has a part of the surface 3 (the emission surface region 14 in FIG. 1), a part of which is the emission surface of the light guide plate 1, and one side wall 19 of the housing frame 11. The portion (stepped portion 19 ′ in FIG. 3) is arranged so as to overlap.

  This will be described with reference to FIG. 4. FIG. 4 shows the LED 2 mounted on the first FPC 10a and the wiring pattern 15 formed on the first FPC 10a and the second FPC 10b. Since the front surface of the LED 2 is disposed in close proximity to the one end face 4 of the light guide plate 1, the first FPC 10 a has a region 16 in which the wiring pattern 15 is formed and an output surface region 14 of the light guide plate 1. It is arranged overlapping. Further, the region 16 ′ disposed on the back side of the LED 2 is disposed so as to overlap the stepped portion 19 ′ of the housing frame 11. In addition, the first FPC 10a is formed so that the longitudinal width thereof is substantially the same as the width of the light guide plate 1 (the longitudinal width of the incident surface 4), from one end of the light guide plate 1 to the other. It is arranged to cover up to the end.

  Further, as shown in FIG. 1, an adhesive means 17 is provided in the region 16 ′ of the first FPC 10 a that overlaps the emission region 14 of the light guide plate 1 and the region 16 ′ that overlaps the step portion 19 ′ of the housing frame 11. Yes. The bonding means is made of, for example, a double-sided tape, and covers the entire area 16 and the area 16 ′, that is, from one end to the other end of the exit surface area 14 of the light guide plate 1 and the step portion 19 ′ of the housing frame 11. It is provided to cover. The first FPC 10 a is bonded and fixed to the light guide plate 1 and the housing frame 11 by the double-sided tape 17.

  With such a configuration, it is possible to provide a large double-sided tape as an adhesive means, and the first FPC 10a can be easily and reliably fixed to the light guide plate 1 and the housing frame 11, and is mounted on the first FPC 10a. All the existing LEDs can be fixed at appropriate positions. Further, by arranging the portion of the first FPC 10a on which the wiring pattern 15 is formed so as to overlap the light guide plate 1, the area of the first FPC 10a arranged on the back side of the LED 2, that is, outside the light guide plate 1, is reduced. Thus, the size of the housing frame 11 that accommodates these members can be reduced, and as a result, the planar lighting device M can be reduced in size.

  The light guide plate 1 is made of a material having good transparency, such as polycarbonate, polyester, polymethylmethacrylate, glass, and the like. The light emitted from the LED 2 enters from the incident surface 4 of the light guide plate 1 and is emitted from the output surface 3 by repeating refraction and reflection. A light reflection pattern (not shown) is provided on the back surface 5 of the light guide plate 1, that is, the surface facing the light exit surface 3, so that light incident from the LED 2 into the light guide plate 1 can be uniformly emitted on the entire light exit surface 3. Is formed.

  Further, a reflective plate 6 is provided on the back surface 5 side of the light guide plate 1 so as to cover the back surface 5. The reflection plate 6 is made of a reflective material such as a white resin or a silver plating plate, and reflects light emitted to the outside from the back surface 5 of the light guide plate 1 so as to be re-input into the light guide plate 1. Therefore, the member that reflects this light is not limited to the reflector 6, and for example, a reflective material is applied to the bottom of the housing frame 11 that houses and holds each member in an integrated manner so that the function of the reflector is achieved. You may comprise so that it may serve as well.

  A light diffusion sheet 7 is provided on the front side of the light guide plate 1, that is, on the emission surface 3 side. The light diffusion sheet 7 is for diffusing light so that the user does not visually recognize the shape of the pattern formed on the light guide plate 1, for example, the shape of the light reflection pattern (not shown). There are agents kneading type, random unevenness processing type, etc. The light diffusion sheet 7 has a thickness of usually 10 μm or more, preferably 20 to 300 μm. The light diffusion sheet 7 is made of a transparent resin, and examples of the resin include polycarbonate, polyester, polymethyl methacrylate, and the like.

  Further, on the upper side of the light diffusion sheet 7, brightness enhancement films 8 and 9 are laminated. The brightness enhancement films 8 and 9 are made of an optical film in which a prism pattern is precisely formed on the surface of polyester, acrylic resin or the like having excellent transparency. By arranging the film in which the fine prism structures are arranged in this manner so as to overlap with the upper side of the emission surface 3 of the light guide plate 1, the luminance of the light emitted to the illuminated object N side can be improved. By superimposing the two brightness enhancement films 8 and 9 in the direction in which the prism structure has a tolerance of 90 degrees, the performance is improved, the blurring of the screen is eliminated, and the striped pattern (reflective moire) of the shining part and the diffusing part of the light is improved. ).

  As described above, for example, a liquid crystal display device is disposed as an object to be illuminated N on the light guide plate 1 on which the light diffusion sheet 7 and the brightness enhancement films 8 and 9 are provided (on the emission surface 3 side). The liquid crystal display device N is provided with a display region 21 in which a liquid crystal display element is disposed and a non-display region 22 that is a peripheral portion in which no liquid crystal display element is disposed. The liquid crystal display device N is a so-called backlight type display device that is irradiated from the back side of the liquid crystal display device N by light emitted from the light exit surface 3 of the light guide plate 1. Thereby, the brightness | luminance of the liquid crystal display device N improves and visibility improves.

  Next, the substrate P is a circuit substrate on which drive circuits for the LEDs 2 and the object to be illuminated N are formed, and is disposed below the housing frame 11. On the substrate P, chip components such as a resistor, a capacitor, an IC, and a connector 31b, which are connecting means to the second FPC 10b, are mounted.

  The second FPC 10b constituting the FPC 10 is a substrate connecting the first FPC 10a and the substrate P, and extends from one side 12 of the first FPC 10a (the first FPC 10a and the second FPC 10b). Is continuous). And the connector 31a as a connection means is attached to the front-end | tip part, ie, the one end part which is not continuous with the 1st FPC10a, as FIG. 4 shows. A wiring pattern 15 is formed on the second FPC 10b, and the connector 31a is connected to a connector 31b as a connecting means attached to the substrate P, whereby the first FPC 10a It is electrically connected to the substrate P through the FPC 10b.

  The second FPC 10 b is arranged in a state where the outer wall surface side of the one side wall 19 of the housing frame 11 is curved in an arc, the tip portion reaches the lower side of the housing frame 11, and is connected to the board P by a connector. The second FPC 10b disposed in such a curved state is subjected to an extension force by FPC. Therefore, a force acts on the first FPC 10a in the direction in which the first FPC 10a bonded to the light guide plate 1 is to be peeled off by the extension force of the second FPC 10b.

  The housing frame 11 is a member that houses and holds the other members constituting the planar illumination device M and the liquid crystal display device N, and is made of a material such as a liquid crystal polymer. The housing frame 11 is provided with a recess 18 for accommodating the member. Each member is held in a predetermined position by a step formed in the recess 18 and a side wall constituting the housing frame 11. ing. A cutout 20 for locking the second FPC 10b is formed in one side wall 19 of the housing frame 11. The notch 20 includes a notch 20 a formed in a part of the one side wall 19 and a notch 20 b formed from the upper surface to the lower surface of the one side wall 19. The cutout portion 20a is formed in a direction parallel to the first FPC 10a disposed by being bonded to the light guide plate 1, and the cutout portion 20b is formed from the upper surface of the one side wall 19 to the middle of the one side wall 19 in the vertical direction. ing.

  The notch portion 20a is a notch portion that actually locks the second FPC 10b in a state where each member is assembled. The notch portion 20b allows the second FPC 10b to be fitted into the notch portion 20a when assembling each member. It is a notch for passage used for the purpose. Therefore, the notch 20a is located at the same height as the position of the first FPC 10a disposed on the light guide plate 1 and has a thickness substantially equal to the thickness of the second FPC 10b or the thickness of the second FPC 10b. It is desirable to form a little thicker. As a result, the second FPC 10b fitted in the notch 20a can be locked at an appropriate position, and the first FPC 10a is bent by an extension force of the second FPC 10b arranged in an arcuate state. The applied force can be suppressed, and peeling of the first FPC 10a bonded to the light guide plate 1 can be prevented. And each position of LED2 with respect to the entrance plane 4 of the light-guide plate 1 can be hold | maintained in an appropriate position, the emitted light from LED2 is efficiently entered into the entrance plane 4 of the light-guide plate 1, and the whole exit surface 3 is made. Brightness can be improved.

  In the above embodiment, the cutout portion 20 is formed on the left side of the one side wall 19. However, the present invention is not limited to this form, and may be formed on the right side of the one side wall 19 or near the center. Moreover, it is not limited to the case where it forms in the one side wall 19, You may make it form in the other one side wall 25 or 26. In these cases, the second FPC 10b that connects the first FPC 10a and the substrate P is located on the right side, near the center of the first FPC 10a (one side 12), depending on the position where the notch 20 is formed. Alternatively, it is formed on one side wall 25 side and 26 side.

FIG. 5 shows another form of the planar lighting device. FIG. 5A is a perspective view of the planar illumination device M ′ showing a state in which each member is housed in the housing frame 11, and FIG. FPC 10a and second FPC 10b.
The planar illumination device M ′ includes a light guide plate 1, a reflection plate 6, a light diffusion sheet 7, brightness enhancement films 8 and 9, a point light source 2, and a point light source 2 in the same manner as shown in FIG. Is composed of a flexible printed circuit board 10 on which is mounted, and a housing frame 11 in which these members are stored. The members omitted in FIG. 5 are the same as the members having the same numbers in FIG.

  The FPC includes a first FPC 10a on which the LED 2 is mounted, and a second FPC 10b that connects the first FPC 10a and the substrate P. The first FPC 10a is disposed so as to overlap with the emission surface region 14 of the light guide plate 1, and is adhered and fixed to the light guide plate 1 by an adhesive means (for example, double-sided tape) 17 provided in the overlapping region. The substrate P is disposed on the lower side of the housing frame 11, and the drive circuit for the LED 2 and the drive circuit for the illuminated object N are mounted thereon.

  On one side wall 19 of the housing frame 11, a notch (through hole) 30 for locking the second FPC 10 b is formed. The through hole 30 is formed in a part of the one side wall 19 in a direction parallel to the first FPC 10 a disposed by being bonded to the light guide plate 1. The through hole 30 is a hole into which the second FPC 10 b is inserted in a state where the respective members are assembled, and is formed through the one side wall 19. Further, the through hole 30 is located at the same height as the position of the first FPC 10 a disposed on the light guide plate 1, with a thickness substantially equal to the thickness of the second FPC 10 b or the thickness of the second FPC 10 b. Is also formed slightly thicker.

  One end of the second FPC 10b is continuous with the first FPC 10a. And the connector 31a which is a connection means with the board | substrate P is attached to the one end part by the side which is not continuous of 2nd FPC10b. Further, a connector 31b, which is a connection means with the second FPC 10b, is attached to the substrate P. The second FPC 10 b fitted into the through hole 30 of the one side wall 19 of the housing frame 11 is disposed in a state where the outer wall surface side of the one side wall 19 is curved in an arc and is disposed below the housing frame 11. Connected to the connector 31b of the board P.

  The second FPC 10b arranged in the curved state is subjected to an extension force due to the FPC, and the first FPC 10a bonded to the light guide plate 1 by the extension force of the second FPC 10b. The force acts in the direction in which the FPC 10a is to be peeled off. However, since the second FPC 10b is fitted into the through hole 30 formed in the one side wall 19, the second FPC 10b is locked at an appropriate position. The force applied to the FPC 10a is suppressed, and the first FPC 10a bonded to the light guide plate 1 can be prevented from peeling off. And each position of LED2 with respect to the entrance plane 4 of the light-guide plate 1 can be hold | maintained in an appropriate position, the emitted light from LED2 is efficiently entered into the entrance plane 4 of the light-guide plate 1, and the whole exit surface 3 is made. Brightness can be improved.

  Note that the position of the second FPC 10 b that is continuous with the first FPC 10 a is changed as appropriate according to the position of the through hole 30 formed in the one side wall 19. That is, as shown in FIG. 5A, if the planar illumination device M ′ is configured such that the through hole 30 is formed on the left side of the one side wall 19, the second FPC 10 b also corresponds to the position of the through hole 30. As shown in FIG. 5B, if the first FPC 10a is provided on the left side and the through hole 30 is formed near the center of the one side wall 19 or on the right side, the second FPC 10b also has the through hole 30. The first FPC 10a is provided near the center or on the right side of the first FPC 10a. In addition, if the through hole 30 is configured to be formed in the one side wall 25 or 26, the second FPC 10b also corresponds to the position of the through hole 30, and the position on the one side wall 25 or 26 side of the first FPC 10a. Provided.

It is a disassembled perspective view which shows one form of the planar illuminating device which concerns on this invention. It is a partial expansion perspective view when the planar illuminating device shown in FIG. 1 is assembled. It is a top view of the planar illuminating device which concerns on this invention. It is a figure which shows FPC by which the point light source of the planar illuminating device shown in FIG. 1 was mounted. (A) is a perspective view which shows another one form of the planar illuminating device which concerns on this invention. (B) is a perspective view which shows FPC used for (a). It is a figure which shows one form of the conventional backlight structure for liquid crystal display devices. It is a figure which shows one form of the conventional backlight structure for liquid crystal display devices.

Explanation of symbols

M Surface illumination device N Object to be illuminated (liquid crystal display device)
P substrate 1 Light guide plate 2 Point light source (LED)
DESCRIPTION OF SYMBOLS 3 Outgoing surface 4 Incident surface 5 Back surface 6 Reflecting plate 7 Light diffusion sheet 8, 9 Brightness enhancement film 10a First FPC
10b Second FPC
11 Housing frame 20a, 20b Notch 30 Through hole

Claims (2)

A light guide plate made of a translucent material;
A plurality of point light sources disposed to face one side of the light guide plate;
A housing frame for housing the light guide plate and the point light source;
A first flexible printed circuit board portion on which the plurality of point light sources are mounted and disposed so as to overlap a part of the surface of the light guide plate housed in the housing frame; and one side of the first flexible printed circuit board A planar shape including a flexible printed circuit board extending from the second flexible printed circuit board portion, a portion of which is curved and arranged on one side of the housing frame in an arcuate state outside the housing frame In the lighting device,
In order to adhere the first flexible printed circuit board part to the surface of the light guide plate, an adhesive means attached to the first flexible printed circuit board;
In order to suppress the force applied to the first flexible printed circuit board part by the extension force of the second flexible printed circuit board part curved in the state of drawing the arc, the second flexible printed circuit board part is provided on the side wall of the housing frame. A planar illumination device provided with a notch portion for locking the lens. The planar lighting device according to claim 1, wherein the bonding unit is made of a double-sided tape.

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