JP2008084790A - Surface light source device and image display module employing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light source device that can inhibit misregistration of a plurality of point light sources to a light guide plate and stably emit irradiation light with a uniform luminance distribution. <P>SOLUTION: An FPC 75 for a light source to which COF mounting is carried out with four LEDs 72 includes a strip-shaped trunk substrate 75a and a branch substrate 75b extended perpendicularly from one end thereof and has an L shape, wherein a light source arrangement portion 751, in which the four LEDs 72 are uniformly adjacently arranged at regular intervals so that each light emitting face 721 is located on a straight line L parallel to a longitudinal side of the trunk substrate 75a, is formed on the one end of the trunk substrate 75a, and a connection lead portion 752 is formed with an extension with a proper length, which is extended from one end of this light source arrangement portion 751 in a direction of adjacently arranging the LEDs, and the above branch substrate 75b. The extension in this connection lead portion 752 is folded in curve form and is electrically connected to a drive control circuit board 8 (see FIG. 3). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sidelight type surface light source device using a point light source and a flat panel image display module using the same.

  Conventionally, as a backlight for a flat panel display module such as a liquid crystal display module, a light source is disposed opposite to one end surface of a rectangular light guide plate, and light emitted from the light source is guided into the light guide plate and the back of the display panel A so-called side light type surface light source device that emits in a planar shape from a light emitting area of one main surface opposed to the light source is often used. As a light source in this case, a point light source such as a light emitting diode (hereinafter referred to as an LED (Light Emitting Diode)) is employed in order to promote a reduction in size and thickness of a display module including a backlight.

In recent years, liquid crystal display modules using the above-described side light type surface light source device using a point light source as a backlight have been used as a display for mobile devices such as mobile phones. Is done. As a surface light source device advantageous for further downsizing and thinning of a liquid crystal display module, a sidelight type surface as shown in Patent Document 1 in which LEDs are directly mounted on a flexible wiring board (hereinafter referred to as FPC (Flexible Printed Circuit Board)). A light source device is known.
JP-A-2005-17964

  In the surface light source device in which the above-described LEDs are directly mounted on the FPC, since the LEDs are supported by the flexible FPC, the plurality of LEDs are accurately and reliably positioned at predetermined positions with respect to the light incident end surface of the light guide plate. Difficult to position.

  In particular, as shown in FIGS. 4 and 9 of Patent Document 1, when the FPC is bent and electrically connected to an external drive control circuit board, the vicinity of the bent portion is caused by the elastic repulsive force of the bent portion of the FPC. The position of the LED tends to shift.

  If the position of each of the LEDs relative to the light guide plate is shifted and the light emission direction is shifted, it becomes impossible to emit planar illumination light with a uniform luminance distribution, resulting in display defects such as uneven brightness in the display of the liquid crystal display panel. Cause it to occur.

  An object of the present invention is to reduce a positional deviation of a plurality of point light sources mounted directly on an FPC with respect to a light guide plate, to stably emit emitted light having a uniform luminance distribution, and to a positional deviation of the point light source. An object of the present invention is to provide an image display module in which the occurrence of uneven brightness is suppressed.

  The surface light source device of the present invention has a plurality of point light sources and an end surface on which the plurality of point light sources are arranged so as to face each other. Light emitted from the point light source is incident from the end surface, and the incident light is reflected by internal reflection. A light guide plate that guides and emits in a planar shape from one main surface, a light source array portion in which the plurality of point light sources are installed in parallel, and at least a portion that continues to the light source array portion is in the direction in which the point light sources are arranged side by side And a flexible wiring board having a connection lead portion extending and electrically connected to the external control board.

  Further, the image display module of the present invention has a plurality of point light sources and an end face on which the plurality of point light sources are arranged to face each other, and emits light emitted from the point light source from the end face, and the incident light is incident on the inner surface. A light guide plate that is guided by reflection and emits in a planar shape from one main surface, an image display panel disposed on the light output surface side of the light guide plate, and a back surface side opposite to the light output surface of the light guide plate An installed drive control circuit board; a light source array portion in which the plurality of point light sources are installed in parallel; and at least a portion connected to the light source array portion; And a flexible wiring board having a connection lead portion bent to the side and electrically connected to the drive control circuit board.

  According to the surface light source device of the present invention, the connection lead portion for conducting connection to the external control board of the FPC in which a plurality of point light sources are arranged in parallel is perpendicular to the point light source arrangement direction, that is, the light emission direction of each point light source. Since it is formed extending in the direction, the elastic repulsion force when the connection lead portion is bent acts in a direction perpendicular to the light emission direction, and the emission direction is hardly deviated even if the light emission position is deviated. As a result, the light emission directions of the plurality of point light sources with respect to the light guide plate are not shifted, and a surface light source device that can stably emit irradiation light having a uniform luminance distribution is obtained.

  In addition, according to the image display module of the present invention, since the surface light source device is used, the display device is small and thin, and has high display quality in which occurrence of display defects such as luminance unevenness due to deviation of the light emission direction of the point light source is prevented. It can be maintained stably.

  1A and 1B are a plan view and a bottom view, respectively, showing a liquid crystal display module as an embodiment of the present invention with a housing omitted, and FIG. 2 is a sectional view taken along line II-II. FIG. 3 is a sectional view taken along line III-III.

  2 and 3, the housing of the present liquid crystal display module is configured such that a cover housing 2 having a shape in which a bottom plate is removed is mounted on a storage housing 1 having a shape in which a top plate of a box having a flat outer shape is removed. Become. Both the housings 1 and 2 are formed by processing a metal plate. A display window 22 for observing the display is formed in the top plate 21 of the cover housing 2.

  A frame case 3 is disposed in the casing. The frame case 3 of the present embodiment is formed by resin molding, for example, by an injection method using a resin material having elasticity such as a synthetic resin, and the front chamber of a space that forms a flat rectangular parallelepiped with the display viewing side as the front side 3a and the rear chamber 3b are formed in two steps. That is, as shown in FIG. 3, a step 33 is formed at a predetermined height position of the side plate 32 erected on the four peripheral edges of a rectangular bottom plate 31 (see FIG. 1B). As a boundary, the inside of the frame case 3 is divided into a front chamber 3a and a rear chamber 3b that overlap in two stages. Therefore, the area (area) of the front chamber 3a is wider than the rear chamber 3b by the area of the step 33.

  As shown in FIGS. 1A and 1B, notches 321 and 322 are formed in a pair of adjacent long side plates and short side plates, respectively, of the four side plates 32 of the frame case 3. ing.

  2 and 3, the liquid crystal display panel 4 is accommodated in the front chamber 3 a of the frame case 3. In the liquid crystal display panel 4, a pair of rectangular glass substrates 41 and 42 on which electrodes (not shown) are formed are joined to each other with the electrode forming surfaces facing each other with a frame-shaped sealing material 43 while maintaining a predetermined gap. The liquid crystal 44 is sealed between the opposing surfaces (hereinafter referred to as inner surfaces) of the glass substrates 41 and 42 surrounded by the frame-shaped sealing material 43. A pair of front and rear polarizing plates 45 and 46 are attached to the outer surfaces of the glass substrates 41 and 42, respectively. The liquid crystal display module of the present embodiment is a simple matrix type liquid crystal display module, and a plurality of scanning electrodes (not shown) parallel to each other are arranged on the opposed inner surfaces of the glass substrates 41, 42, and mutually orthogonal to each other. A plurality of parallel display electrodes (not shown) are provided.

  As shown in FIG. 1 (a), one of the glass substrates 41 and 42 has a pair of adjacent edges projecting outward from the corresponding end surface of the other glass substrate 41, A protruding edge 421 is formed. On the surface of the protruding edge 421 (extension surface of the electrode forming surface), connection terminals (not shown) of the lead wirings connected to the electrodes of the substrates 41 and 42 are arranged in parallel.

  A display driver 5a that outputs a display signal voltage to each display electrode is provided on the protruding edge 421a on the long side of the protruding edges 421 in which the electrode wiring and the connection terminal row are formed by a COG (Chip On Glass) method. It is installed directly. A flexible wiring board (hereinafter referred to as a display-side FPC (Flexible Printed Circuit Board)) 6a for supplying a display control signal is conductively joined to the connection terminal row of the long protruding edge 421a. The display-side FPC 6 a is pulled out of the frame case 3 from a notch 321 provided on the long side plate of the frame case 3, and is folded back to the back side of the bottom plate 31.

  In addition, a flexible wiring board (hereinafter referred to as a scanning side FPC (Flexible Printed Circuit Board)) 6b for supplying a scanning control signal is conductively joined to the connection terminal row of the short protruding edges 421b of the protruding edges 421. Yes. The scanning side FPC 6b is pulled out of the frame case 3 from a notch 322 provided on the short side plate of the frame case 3 and folded back to the back side of the bottom plate 31, and scanning signal voltages are applied to the folded portion. A scanning driver 5b (see FIG. 1B) for outputting to the scanning electrode is directly mounted by a COF (Chip On Film) method.

  As shown in FIG. 3, the liquid crystal display panel 4 configured as described above is fixed to a step 33 corresponding to both longitudinal edges of the large-area glass substrate 42 by a double-sided adhesive sheet 35.

  In the rear chamber 3b of the frame case 3, a side light type surface emitting backlight unit 7 is installed. The surface-emitting backlight unit 7 according to the present embodiment includes an LED (Light-Emitting Diode) as a point light source on one short end surface 711 of a transparent light guide plate 71 having a rectangular shape substantially corresponding to the liquid crystal display panel 4 to be irradiated. ) 72 are arranged, the optical sheet laminate 73 is installed on the front surface 712 of the light guide plate 71 facing the liquid crystal display panel 4, and the light reflecting sheet 74 is installed on the rear surface 713 on the opposite side. ing.

  FIG. 4 is a development view showing an FPC (hereinafter referred to as a light source FPC) 75 in which four LEDs 72 are installed. The light source FPC 75 has an L-shape including a trunk substrate 75a and a branch substrate 75b extending from the one end portion of the light source FPC 75 in a perpendicular direction over a predetermined length. A light source array portion 751 in which four LEDs 72 are arranged at equal intervals and directly mounted by a COF (Chip On Film) method is formed on one end side of a rectangular main substrate 75a. A connection lead portion 752 is formed by an extended portion in which the light source array portion of the trunk substrate 75a extends in the LED juxtaposition direction (array direction) and the branch substrate 75b.

  The four LEDs 72 are connected in series by a power supply wiring circuit 753, and a pair of lead wires 7531 and 7531 and connection terminals 7532 and 7532 constituting the power supply wiring circuit 753 are disposed on the branch substrate 75b.

  Here, the four LEDs 72 are arranged in parallel at equal intervals with their light emission surfaces 721 aligned on the same straight line L parallel to the longitudinal side of the trunk substrate 75a. As a result, the front direction in which light is emitted from each of the four LEDs 72 (hereinafter simply referred to as the light emission direction) is aligned in the same perpendicular direction with respect to the direction in which the four LEDs 72 are arranged (array direction). .

  As shown in FIG. 2, the light source FPC 75 configured as described above has one edge of the light source array portion 751 in a state where the light emitting surface 721 of each LED 72 is in close contact with the light incident surface 711 of the light guide plate 71. As shown in FIG. 3, the connection lead portion 752 is pulled out of the frame case 3 in the same manner as the display-side FPC 6a, and is attached to the bottom plate 31 at the extended portion. It is folded to the back side.

  Therefore, even when a force that lifts up due to the elastic repulsion force of the light source FPC 75 itself is applied when the extended portion of the light source array portion 751 in the connection lead portion 752 is folded back into a curved shape, the force of the connection lead portion 752 Since the light source array portion 751 acts along the longitudinal direction (direction parallel to the light guide plate light incident surface 711) and is away from the curved portion of the connection lead portion 752, the mounting portion of each LED 72 is provided. No direct force acts on the LED 72, the state where the light emitting surface 721 of each LED 72 is in close contact with the light guide plate light incident surface 711 is maintained, and one edge is further guided to the light guide plate light emitting surface 712. Therefore, the relative positions of the four LEDs 72 and the light incident side end portions of the light guide plate light exit surface 712 are not shifted, and therefore the uniform luminance distribution of the emitted light. It is maintained.

  Incidentally, when the connection lead portion 762 is branched from the LED mounting portion 761 in a right angle direction as in the light source FPC 76 as a comparative example shown in FIG. 4B, the connection lead portion 762 is folded back. Since the elastic repulsion force is biased mainly in the vicinity of the portion where the connection lead portion 762 branches off of the LED mounting portion 761 and acts in the short direction, the light emitting surfaces 721 of the four LEDs 72 are connected to the light guide plate light incident surface 711. It is difficult to maintain a state of being in close contact with each other, and as a result, the light emission direction of the LED 72 in the vicinity of the branching portion is mainly shifted to easily cause luminance unevenness.

  Returning to FIG. 2, an optical sheet laminate 73 as a light control member is installed on the light emitting surface (front surface) 712 of the light guide plate 71. The optical sheet laminate 73 is formed by sequentially laminating a lower diffusion sheet 731, a prism sheet 732, and an upper diffusion sheet 733 on the light emitting surface 712.

  On the rear surface 713 of the light guide plate 71, a concavo-convex pattern (not shown) is formed for uniformly reflecting the light emitted from each LED 72 and incident on the light guide plate 71 toward the front surface 712. A light reflecting sheet 74 made of a white PET (polyethylene terephthalate) sheet is installed on the rear surface 713.

  In the backlight unit 7 configured as described above, the light emitted from the four LEDs 72 each having the light exit surface 721 in close contact with the light guide plate light incident surface 711 is opposed to the light guide plate 71. When the incident light is incident substantially uniformly from the incident surface 711 and the incident light is incident on the concavo-convex pattern on the rear surface 713, the incident light is totally reflected toward the front surface 712 and emitted from the front surface 712 in a planar shape with a substantially uniform luminance distribution. The emitted light is transmitted through the optical sheet laminate 73 so that the luminance distribution is made more uniform, and the liquid crystal display panel 4 is irradiated with planar illumination light having high front luminance. There is also light that exits from the light guide plate 71 after entering the concavo-convex pattern. However, the emitted light is reflected by the light reflecting sheet 74 and re-entered into the light guide plate 71, thereby causing the light from the LED 72 to be reflected. The utilization efficiency of the emitted light is greatly increased.

  On the outer surface of the bottom plate 31 of the frame case 3, a drive control circuit board 8 for controlling the drive of the entire liquid crystal display module is mounted. Here, the drive control circuit board 8 is fitted and mounted in a recess 311 formed on the outer surface of the bottom plate 31 by reducing its thickness.

  As shown in FIG. 1B, three engaging hooks 34 and two support plates 35 are disposed around the recess 311. In this case, the three engagement hooks 34 are formed to extend in parallel with the short direction of the bottom plate 31, and the two support plates 35 are formed to extend in parallel with the longitudinal direction of the bottom plate 31 orthogonal thereto. Yes.

  The three engagement hooks 34 and the two support plates 35 are integrally formed by resin molding with the main body portion including the bottom plate 31 and the side plate 32 of the frame case 3. Thereby, the engagement hook 34 and the support plate 35 made of a liquid crystal polymer and having excellent elasticity are obtained.

  The drive control circuit board 8 is a rigid circuit board formed of an epoxy resin or the like, and as shown in FIG. 1B, the planar outer shape has a shape obtained by removing one corner portion of the rectangular board, and the module length An output terminal portion 81 of a wiring (not shown) for outputting a display control signal is formed along the longest edge parallel to the direction, and a scanning control signal is output to the longest edge among the edges parallel to the module short direction. An output terminal portion 82 of a wiring (not shown) is formed, and an input terminal portion 83 to which a display data signal and various drive control signals are input is provided on an edge adjacent to the longest edge of the edges facing the longest longest edge. Is formed.

  As described above, the display-side FPC 6a drawn out of the frame case 3 and folded back to the back side of the bottom plate 31 is connected to the output terminal 81 of the display control signal by a conductive adhesive member (non-conductive adhesive member). Conductive joining is performed via the figure. Further, a connector 9a is installed at the output terminal portion 82 of the scanning control signal, and the scanning side FPC 6b that is similarly turned back is connected to the connector 9a.

  Further, a connector 9b is installed in the input terminal portion 83, and an external signal input FPC (not shown) is conductively inserted into the connector 9b.

  Further, in the drive control circuit board 8, three rectangular engagement holes 84 are formed at predetermined positions corresponding to the three engagement hooks 34 provided on the bottom plate 31 side. Yes. A pair of solder pads 85, 85 are disposed in the vicinity of the scanning control signal output terminal portion 82, and a pair of solder pads 85, 85 on the branch substrate 75b of the folded light source FPC 75 are provided. Connection terminals 7532 and 7532 (see FIG. 4A) are connected by soldering.

  When the drive control circuit board 8 is fitted into the recess 311 of the frame case 3, the drive control circuit board 8 to which the display-side FPC 6 a is conductively joined is moved from the notch 321 of the long side plate to the bottom surface of the recess 311 and both short sides. Slide along the side wall of the hand. When the drive control circuit board 8 is slid and inserted until the front end surface of the drive control circuit board 8 comes into contact with the corresponding longitudinal side wall, each engagement hook 34 elastically deforms and enters into the corresponding engagement hole 84 of the drive control circuit board 8. Engage. The longitudinal edge portion (the display side FPC 6a joint edge portion) that is not locked by the engagement hook 34 of the inserted drive control circuit board 8 is supported on both sides by the pair of support plates 35, 35, and is prevented from dropping off. ing.

  After the sliding insertion of the drive control circuit board 8 is completed, the scanning side FPC 6b is folded back to the back side of the frame case 3, and the tip end portion where the connection terminals (not shown) are arranged in parallel is inserted into the connector 9a. Similarly, the connection lead portion 752 of the light source FPC 75 is folded back to the back side of the frame case 3 and the connection terminal 7532 is soldered to the corresponding solder pad 85.

  As a result, the drive control circuit board 8 is securely fitted in the recess 311 provided on the outer surface of the bottom plate 31 in the frame case 3 without rattling. As a result, the thickness of the image display module is reduced by the drive control circuit. Compared with the case where the substrate 8 is superimposed on the outer surface of the frame case bottom plate 31, the thickness is reduced by about the thickness of the drive control circuit substrate 8.

  As described above, the liquid crystal display module of the present embodiment uses the sidelight type surface emitting backlight unit 7 in which a plurality of LEDs 72 are arranged in parallel on the end surface 711 as the light incident surface of the light guide plate 71 as a light source device. In the FPC 75 for light source in which the plurality of LEDs 72 are mounted on the COF, connection lead portions 752 that are turned back to be electrically connected to the drive control circuit board 8 disposed on the back side of the light guide plate 71 are arranged in a parallel arrangement direction (array direction) of the plurality of LEDs 72. Since it is formed extending, the elastic repulsion force when the connection lead 752 is bent acts in the parallel direction of the LEDs 72, that is, in the direction parallel to the light guide plate light incident surface 711, and directly acts on the LEDs 72. Therefore, the state in which the light emitting surface 721 is in close contact with the light incident surface 711 is maintained. As a result, the relative displacement between each LED 72 and the light incident side end of the light guide plate light exit surface 712 is prevented, and the light emitted from each LED 72 is evenly incident on the light guide plate 71 at substantially the same incident angle. In addition, the liquid crystal display panel 4 has a uniform luminance distribution and is stably irradiated with a sufficient amount of planar emission light, and has high display quality with high front luminance and suppressed display defects such as luminance unevenness. Is obtained.

  Further, in the liquid crystal display module of the present embodiment, the drive control circuit board 8 is fitted into a recess provided in the bottom plate 31 of the frame case 3, and the liquid crystal display panel 4 and the sidelight type surface emitting backlight unit 7 are driven and controlled. Since the circuit board 8 and the circuit board 8 are electrically connected by folding the FPC, the module can be thinned.

In addition, this invention is not limited to said embodiment.
For example, an FPC for a light source on which a plurality of LEDs are mounted is a straight type without a branch substrate as shown in FIG. 5 by changing the conductive connection position (connection terminal pad arrangement position) in the drive control circuit board. Can be formed. Thus, by making the shape of the light source FPC 77 straight, compared to the L-shaped FPC 75 having the branch substrate 75b in the above embodiment, the loss cut portion when cutting from the parent substrate is reduced, and the use of the parent substrate material is used. The rate is improved.

  Further, as shown in FIG. 6A, the light source FPC 78 may be attached to the light incident side edge of the rear surface 713 of the light guide plate 71. In this case, the FPC 77 for straight light source shown in FIG. 5 is used, folded back to the back side of the frame case 3, and then folded again in a right angle direction as shown by a two-dot chain line in FIG. The solder control circuit board 8 may be soldered to the solder pads 85.

  Furthermore, the present invention is not limited to a surface light source device using a light emitting diode as a point light source, but is also effectively applied to a surface light source device using other various point light sources such as a micro light bulb.

  In addition, the present invention is not limited to the liquid crystal display module, and can naturally be applied to other various flat panel display modules including a surface light source device using a point light source.

(a) is a top view which shows the liquid crystal display module as one Embodiment of this invention which abbreviate | omits a housing | casing, (b) is the bottom view. It is the II-II sectional view taken on the line of the liquid crystal display module of FIG. FIG. 3 is a cross-sectional view of the liquid crystal display module of FIG. 1 taken along the line III-III. (a) is a development view showing a light source FPC used in the liquid crystal display module, and (b) is a development view showing a light source FPC as a comparative example. It is the expanded view which showed the modification of FPC for light sources used for the said liquid crystal display module. (a) is sectional drawing corresponding to FIG. 3 which showed the modification of the said liquid crystal display module, (b) is explanatory drawing which shows the mounting method of FPC for light sources used for it.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Storage housing 2 Cover housing 3 Frame case 31 Bottom plate 311 Recess 34 Engagement hook 35 Support plate 4 Liquid crystal display panel 5a Display driver 5b Scan driver 6a Display side FPC
6b Scanning side FPC
7 Backlight unit 71 Light guide plate 711 Light incident surface 712 Light exit surface (front surface)
713 Rear 72 LED (Light-Emitting Diode)
721 Light exit surface 75, 76, 77, 78 FPC for light source
75a Trunk board 75b Branch board 751 LED mounting part 752 Connection lead part 753 Power supply wiring circuit 7531 Lead wiring 7532 Connection terminal 8 Drive control circuit boards 9a, 9b FPC connector

Claims (3)

Multiple point sources,
A light guide plate having an end face on which the plurality of point light sources are opposed to each other, allowing light emitted from the point light source to be incident from the end face, and guiding the incident light by internal reflection to be emitted in a planar shape from one main surface. When,
A light source array portion in which the plurality of point light sources are arranged in parallel, and a connection lead portion for connecting at least a portion connected to the light source array portion in a direction in which the point light sources are arranged in parallel and electrically connected to an external control board; A surface light source device, comprising: a flexible wiring board.   The surface light source device according to claim 1, wherein the point light source is a light emitting diode whose outer shape forms a substantially rectangular parallelepiped. Multiple point sources,
A light guide plate having an end face on which the plurality of point light sources are opposed to each other, allowing light emitted from the point light source to be incident from the end face, and guiding the incident light by internal reflection to be emitted in a planar shape from one main surface. When,
An image display panel disposed on the light exit surface side of the light guide plate;
A drive control circuit board installed on the back side opposite to the light exit surface of the light guide plate;
The light source array section in which the plurality of point light sources are arranged in parallel, and at least a portion connected to the light source array section extends in the direction in which the point light sources are arranged side by side and is bent to the back side of the light guide plate to drive A flexible wiring board having a connection lead portion conductively connected to the control circuit board,
An image display module comprising: