JP4967754B2 - Surface lighting device - Google Patents

Description

  The present invention relates to a planar illumination device using a light source element such as a light emitting diode (hereinafter referred to as LED (Light-Emitting Diode)) as a light source.

  Conventionally, as a backlight for a liquid crystal display element, a light source is disposed opposite to one end face of a light guide plate, and light emitted from the light source is guided into the light guide plate and emitted from one main surface facing the liquid crystal display element. A sidelight type surface emitting backlight that emits in a planar shape from an area is used. As a light source in this case, a light source element such as a light emitting diode (hereinafter referred to as LED) is employed in order to reduce the size and thickness of a liquid crystal display module including a backlight. (For example, see Patent Document 1)

A surface-emitting backlight using the above-described light source element is required to increase the use efficiency of emitted light because the amount of absolute light emitted is smaller than that of a line-emitting light source such as a cold cathode tube. In order to effectively use the light emitted from the light source element as much as possible, it is necessary to first bring the light emission surface of the light source element into close contact with the end surface of the light guide plate as the light incident surface.
JP-A-8-313902

  However, in the surface emitting backlight using the light source element described above, the heat of the backlight components and the adhesive such as double-sided tape due to repeated heating and cooling by changing the environmental temperature or turning on / off the lighting device itself. Due to the difference in expansion rate or contraction rate, or due to the action of external force, the installation position or installation state of the light source element is displaced, and there is a gap between the light exit surface of the light source element and the light incident end surface of the light guide plate. It occurs, and light leaks from here, and the light utilization efficiency decreases.

  An object of the present invention is to provide a planar illumination device that efficiently uses light from a light source element and is advantageous for reduction in size and thickness.

In order to solve the above-described problem, an aspect of the planar lighting device according to the present invention is formed of a plurality of light source elements having a light emission surface and a transparent resin plate, and the light emission surface of the light source element is closely attached to an end surface. In this state, a plurality of pairs of engaging protrusions that elastically support the light source element are integrally provided, and light emitted from the light emitting surface is incident from the end surface, and one of the pair of main surfaces is incident. A light guide plate that is internally reflected by the main surface and emits in a planar shape from the other main surface; and a wiring board that supplies a driving current to the light source element, and the pair of engaging protrusions have their heads facing each other. A front slope is formed on the side where the light source element is inserted from a direction perpendicular to the end surface of the light guide plate with a ridge line interposed between the heads, and each of the pair of engaging protrusions The distance D1 between the ridge lines and the maximum distance D2 between the front slopes are the heads. Assuming that the width dimension of the light source element along the line connecting the two is A, D1 <A <D2 is set .

  According to the planar illumination device of the present invention, it is possible to efficiently use light, and it is possible to promote energy saving and reduction in size and thickness of applied equipment.

  FIG. 1 is a perspective view showing a liquid crystal display module to which a surface-emitting backlight according to an embodiment of the present invention is applied. FIGS. 2A and 2B are an exploded perspective view and a partially enlarged view showing the main part of the liquid crystal display module. It is a perspective view.

  The liquid crystal display module of the present embodiment includes a single-sided open type frame case 1 in which two storage spaces of different sizes are formed in two layers. The two storage spaces are a flat rectangular parallelepiped having a flat area reduced by the area of the partition shelf 11 than the front chamber 1a of a flat rectangular parallelepiped with the viewing side of the opened display as the front side. And a rear chamber 1b. The frame case 1 is molded from a resin material by, for example, an injection method.

  A liquid crystal display panel 2 is accommodated in the front chamber 1 a of the frame case 1. The liquid crystal display panel 2 includes a pair of rectangular glass substrates 21 and 22 each having an electrode (not shown) formed on one main surface thereof, and a frame-shaped sealing material (not shown) with the electrode forming surfaces facing each other. The liquid crystal (not shown) is sealed between the glass substrates 21 and 22 surrounded by a frame-shaped sealing material.

  Of the glass substrates 21 and 22, the rear glass substrate 22 is formed with a projecting edge portion 221 by projecting one short side edge outward from the corresponding end surface of the front glass substrate 21. A driver chip 3 as a liquid crystal driving circuit element is mounted on the surface of the protruding edge portion 221 (extension surface of the electrode forming surface) by a COG (Chip On Glass) method. In addition, connection terminals (not shown) of the lead wirings connected to the electrodes of the substrates 21 and 22 are arranged in parallel at the end of the protruding edge 221. A flexible wiring board (hereinafter referred to as FPC (Flexible Printed Circuit Board)) 4 for supplying a drive control signal is conductively joined to the connection terminal row of the protruding edge portion 221. The input side end of the FPC 4 is drawn out of the frame case 1 from a notch 121 formed in the case side wall 12.

A surface emitting backlight unit 5 is housed and installed in the back side opposite to the viewing side of the display of the liquid crystal display panel 2, that is, in the rear chamber 1b. As shown in FIG. 2A, the surface-emitting backlight unit 5 includes a light guide plate 51 made of a substantially transparent rectangular plate , and a light source element installed on one end surface (light incident end surface) of the light guide plate 51. LED as (light-emitting Diode) 52, FPC53 feed line circuits are formed for LED 52, the light emitting surface of the light guide plate 51 (the liquid crystal front is opposed to the display panel 2) 511 in the stacking arranged optical sheet laminate 54 , And a light reflecting sheet 55 disposed on the rear surface 512 of the light guide plate 31.

  The light guide plate 51 is molded into a substantially transparent rectangular plate using a resin material such as polycarbonate. As shown in FIG. 2A, a recess 5131 for accommodating the LED 52 is formed on the end surface 513 of the light guide plate 51 on the side where the LED 52 is disposed. In the present embodiment, the two LEDs 52, 52 are installed in a state of being accommodated in two recesses 5131, 5131 formed uniformly on the light source side end surface 513 of the light guide plate 51.

  As shown in FIG. 2B, a pair of engaging protrusions 514 and 514 for holding the LED 52 to be accommodated are provided upright in each of the recesses 5131, respectively. The pair of engaging protrusions 514 and 514 are erected with their heads facing each other on the entrance side edge of the side walls 5132 and 5132 of the recess 5131. A front slope 5142 and a rear slope 5143 are formed on the heads of the respective engagement protrusions 514 with the ridge line 5141 therebetween.

FIGS. 3A to 3B are explanatory views showing the operation when the LED 52 is press-fitted into the recess 5131, respectively. As shown in FIG. 3A, the distance D1 between the ridge lines 5141 and 5141 of the pair of engaging protrusions 514 and 514 facing the head and the maximum distance D2 between the front inclined surfaces 5142 and 5142 are maintained. When the width dimension of the LED 52 to be assumed is A,
D1 <A <D2 (1)
Is set to 3C, the distance D3 from the hook tip surface 5144 of each engagement protrusion 514 to the back wall surface 5133 of the recess 5131 and the distance D4 from the ridge line 5141 to the back wall surface 5133 are as follows. If the depth dimension is B,
D3 <B <D4 (2)
Is set to

  When the light guide plate 51 is resin-molded, the engaging protrusion 514 having the above-described dimension and shape is molded with the same material integrally with the light-guiding plate 51. As a result, it is possible to provide a robust engaging protrusion 514 having a necessary and sufficient elasticity.

  As shown in FIG. 1, two LEDs 52 are directly mounted on an FPC 53 by a COF (Chip On Film) method, and this FPC (hereinafter referred to as “light source FPC”) 53 is a light source side end portion of a light guide plate light emitting surface 511. Are attached adjacent to the optical sheet laminate 54. Although not shown, the light source FPC 53 is formed with a power supply wiring pattern and a dummy pattern as a light shielding film by photolithography. The dummy pattern is provided in order to promote uniformization of the luminance distribution of irradiation light, and blocks transmission of light emitted from the LED 52 and incident on the FPC 53. The light source FPC 53 is drawn out of the frame case 1 from a notch (not shown) formed in the side wall 12 of the frame case 1.

  The optical sheet laminate 54 includes a light diffusion sheet 541 and two prism sheets 542 and 543 that align the light emission direction, which are sequentially stacked on the light emission surface 511 of the light guide plate 51. In this case, in order to prevent the light source FPC 53 from being lifted, the light source side ends of the two prism sheets 542 and 543 are extended and superimposed on the light source FPC 53.

On the rear surface 512 of the light guide plate 51, a fine concave / convex pattern (not shown) is formed to reflect light incident on the light guide plate 51 on the inner surface over an area excluding the end where the concave portion 5131 is formed. . The concavo-convex pattern of this embodiment is a satin pattern in which a large number of fine protrusions are erected, and the erection density of the protrusions is set to increase as the distance from the light incident end surface 513 on the LED installation side increases. By forming the concavo-convex pattern in this way, planar light with a uniform light amount distribution is emitted from the light exit surface 511.

  And the light reflection sheet 55 is installed facing the rear surface 512 of the light guide plate 51. The light reflecting sheet 55 of this embodiment is a multilayer film that does not contain a metal component made of polyester, has a reflectance as high as 90% or more with respect to all wavelengths of light in the visible light range, and a thickness as thin as about 65 μm.

  In the surface-emitting backlight unit 5 configured as described above, the light emitted from the LED 52 enters the light guide plate 51 from the light incident end surface 513, and this incident light is a fine uneven pattern (not shown) on the rear surface 512. ) Most of the light is internally reflected toward the front surface 511 and emitted from the front surface 511 in a planar shape. The emitted light passes through the optical sheet laminate 54 and is irradiated onto the liquid crystal display panel 2 as planar irradiation light having a uniform luminance distribution and high front luminance. The light emitted outside the light guide plate 51 without being reflected on the inner surface is reflected by the light reflecting sheet 55 and re-enters the light guide plate 51 to be used as planar irradiation light.

  Here, the assembly procedure and operation of the surface-emitting backlight unit 5 of the present embodiment will be described with reference to FIGS.

As shown in FIG. 3A, the pair of LEDs 52 and 52 mounted on the light source FPC 52 with COF is positioned at the entrance of the corresponding recess 5131 . At this time, both side edges 522 and 522 of the light emission surface 521 of each LED 52 are positioned so as to abut against the corresponding front inclined surfaces 5142 and 5142 of the respective engagement protrusions 514.

When the LED 52 positioned as described above is pressed in the direction indicated by the white arrow, each edge 522 slides on the corresponding front slope 5142, and each engagement projection 514 is gradually bent by the slope effect, and the edge After the 522 exceeds the ridge line 5141, as shown in FIG. 3B, each side surface 523 of the LED 52 slides while being in contact with each ridge line 5141, and the LED 52 enters the recess 5131 .

Eventually, after the light emission surface 521 approaches the recess back wall surface 5133 and the rear side edges 524, 524 of the LED 52 exceed the corresponding ridge line 5141, each engagement protrusion 514 causes the rear inclined surface 5143 by its own elastic restoring force. The LED 52 is pressed against each edge 524 and pressed. The LED 52 elastically supported from both sides by the pair of engaging projections 514 and 514 has its light emitting surface 521 formed on the rear wall surface 5133 by a component force perpendicular to the light emitting surface 521 generated by the slope effect of each rear slope 5143. Is kept in close contact with the substrate. Since the elastic restoring forces of the pair of engaging projections 514 and 514 at this time are substantially equal, the component forces in the direction perpendicular to the side surface 523 sandwiching the LED 52 from both sides also act substantially equally and cancel each other. As a result, the LED 52 Is accurately held at the center in the width direction of the recess 513.

  The LED 52 sandwiched and supported by the pair of engaging protrusions 514 and 514 as described above is directly mounted on the light source FPC 53 by the COF method, and the light source FPC 53 is a light source on the light emitting surface 511 of the light guide plate 51. Since the end portions of the two prism sheets 542 and 543 are superposed on the side end portion, the light guide plate 51 is stably held at a predetermined position in the thickness direction.

  As described above, in the liquid crystal display module according to the present embodiment, the pair of members in which the LED 52 as the point light source element of the surface emitting backlight unit 5 is integrally formed on the light guide plate 51 without using an adhesive member such as a double-sided tape. Since the elastic restoring force of the mating protrusions 514 and 514 is used to sandwich and support the LED 52, the light emission surface 521 of the LED 52 is placed at a predetermined position on the light incident end surface 513 of the light guide plate 51 without being affected by changes in temperature conditions. It can be stably held for a long time in a close contact state. As a result, it is possible to stably emit desired irradiation light having a uniform light amount distribution to the liquid crystal display panel 2 by efficiently using the emission light without loss.

  Further, since the LED 52 can be mounted at a predetermined position by simply pressing the LED 52 without using an adhesive member or the like, the assembling work of the surface emitting backlight unit 5 is simplified, and the number of manufacturing steps of the liquid crystal display module is reduced.

  Next, another embodiment of the present invention will be described with reference to the schematic cross-sectional view of FIG. 4, a plan view showing the main constituent members of FIGS. 5A and 5B, and a partially enlarged view thereof. In addition, about the component which is the same as that of the said embodiment, or corresponding | corresponding, the code | symbol which is the same or corresponding respectively is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 4, in this embodiment, the light source FPC 63 in which the two LEDs 62 are COF-mounted is installed adjacent to the light reflecting sheet 65 that is installed facing the rear surface 612 of the light guide plate 61. . The input side end of the light source FPC 63 is conductively joined to the LED power supply wiring pattern formed on the glass substrate protruding edge 221 of the liquid crystal display panel 2. The protruding edge portion 221 is conductively joined to the FPC 7 in which a drive current supply wiring for the LED 62 is provided together with a drive control signal input wiring for the liquid crystal display panel 2. That is, the drive current of the LED 62 is supplied from the FPC 7 through the power supply wiring pattern of the glass substrate protrusion 221 and through the power supply wiring of the light source FPC 63.

  Then, as shown in FIG. 5A, two pairs of engaging protrusions for sandwiching and supporting the two LEDs 62 and 62 on the end surface 613 on which the light of the light guide plate 61 of the surface emitting backlight unit 6 is incident. 614 and 614 are erected directly by integral molding without providing a recess.

  As shown in FIG. 5B, each engaging projection 614 has a front slope 6142 and a rear slope 6143 formed on the head with a ridge line 6141 sandwiched between the engaging projections 514 of the above embodiment. The engaging protrusions 614 and 614 are formed so as to face the slopes 6142 and 6143, respectively. Then, the widths and depths A and B of the LED 62, the distance D1 between the ridge lines 6141 of the paired engaging projections 614 and 614, the maximum distance D2 between the front slopes 6142 and 6142, and between the rear slope 6143 and the light incident end face 613 The minimum distance D3 and the distance D4 between the ridge line 6141 and the light incident end face 613 are set to dimensions that satisfy the expressions (1) and (2).

  Also in this embodiment, when installing the LED 62 on the light guide plate 61, both side edges of the light emitting surface 621 are brought into contact with the corresponding front inclined surfaces 6142 of the corresponding pair of engaging projections 614 and 614, and the light incident end surface It is only necessary to push in at a right angle toward 613.

  Thus, as in the case of the above-described embodiment, the engagement protrusions 614 are elastically deformed by the slope effect of the front slope 6142 and the LED 62 smoothly enters, and after passing the ridge line 6141, the engagement protrusions 614 on both sides, The LED 62 is sandwiched and supported in a state in which the light emission surface 621 is in close contact with the light incident end surface 613 by the elastic restoring force acting via the rear slopes 6143 of 614. As shown in FIG. 4, the sandwiched and supported LED 62 is supported by being mounted COF on the light source FPC 63 mounted on the bottom surface of the frame case 1. Even if it does not shift, it is stably held at a predetermined position.

  As described above, in the liquid crystal display module of the present embodiment, the light incident end surface 613 of the light guide plate 61 is a flat surface that does not have a recess for accommodating the LED 62, and the flat light incident end surface 613 is integrally formed on the flat light incident end surface 613. Since the LED 62 is sandwiched and supported by utilizing the elastic restoring force of the pair of engaging protrusions 614 and 614 provided, even if the light incident end face 613 is flat, the pair of LEDs 62 is not precisely aligned. It can be installed accurately at a predetermined position by simply pushing between the engaging projections 614 and 614, and the desired mounting state in which the light emitting surface 621 is in close contact with the light incident end surface 613 is stable for a long time. Can be held. As a result, according to the liquid crystal display module of the present embodiment, the use efficiency of the light emitted from the LED 62 is improved and the liquid crystal display panel 2 is stably irradiated with the planar light having a uniform light amount distribution, thereby being small and thin. And energy saving are promoted, and good display quality can be stably obtained over a long period of time.

In addition, this invention is not limited to said embodiment.
For example, in the above embodiment, a rectangular parallelepiped LED is sandwiched and supported by a pair of engaging protrusions. However, the present invention is not limited to this, and as shown in FIG. 6, the LED 8 has a light emission surface 81 curved. Thus, the light incident end surface 91 of the light guide plate 9 is formed with a concave portion 911 whose wall surface forms the same curved surface as that of the light emitting surface 81, and is sandwiched and supported by the two pairs of engaging projections 92, 92 and 93, 93. It is good. Also in this case, the LED 8 is COF mounted on the light source FPC 10 disposed on the rear surface side of the light guide plate 9.

  Moreover, as a point light source element, not only LED but other various light source elements which radiate | emit light radially can be used.

It is typical sectional drawing which shows the liquid crystal display module as one Embodiment of this invention. (A) is the disassembled perspective view which shows the principal part structure of the said liquid crystal display module, (b) is the elements on larger scale which expanded and showed the principal part. (A)-(c) is explanatory drawing for every step which shows mounting | wearing operation | movement of LED in the said liquid crystal display module according to a step, respectively. It is typical sectional drawing which shows the liquid crystal display module as other embodiment of this invention. (A) is a top view which shows the principal part structure in the liquid crystal display module as said other embodiment, (b) is the elements on larger scale which show the principal part. It is a top view which shows the light source mounting part in the liquid crystal display module as further another embodiment of this invention, (b) is the front view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frame case 11 Partition shelf 2 Liquid crystal display panel 21, 22 Glass substrate 23, 24 Polarizing plate 3 Driver chip 4 FPC (For display drive signal supply)
5, 6 Surface emitting backlight units 51, 61, 9 Light guide plates 513, 613, 91 Light incident end surfaces 5131, 911 Recesses 514, 614, 92, 93 Engaging protrusions 52, 62, 8 LED
521, 621, 81 Light exit surface 53, 63, 10 FPC for light source
54, 64 Optical sheet laminate 55, 65 Light reflecting sheet

Claims (10)

A plurality of light source elements having a light exit surface ;
A plurality of engagement protrusions that are formed of a transparent resin plate material and elastically support the light source element in a state in which the light emission surface of the light source element is in close contact with an end surface, are integrally provided upright from the light emission surface. A light guide plate that causes the emitted light to be incident from the end face, to be internally reflected by one main surface of the pair of main surfaces, and to be emitted in a planar shape from the other main surface;
A wiring board for supplying a driving current to the light source element ;
Equipped with a,
The pair of engaging protrusions are erected with their heads facing each other, and a ridge line is sandwiched between the heads, and the light source element is inserted in front from a direction perpendicular to the end face of the light guide plate. A slope is formed,
The distance D1 between the ridge lines of the pair of engaging projections and the maximum distance D2 between the front slopes are set such that the width dimension of the light source element along the line connecting the heads is A,
D1 <A <D2
Set to
A planar illumination device characterized by that. When the light source element presses the pair of engaging protrusions from a direction perpendicular to the end face of the light guide plate, the front slopes of the pair of engaging protrusions are formed on the light emitting surface of the light source element. The planar illumination device according to claim 1, wherein the distance between the engagement protrusions is increased by the elastic deformation of the pair of engagement protrusions in contact with the edges . A rear slope opposite to the front slope across the ridge line of the pair of engagement protrusions is in contact with an edge of the back surface of the light source element and elastically supports both side portions of the light source element. The planar illumination device according to claim 1. The planar illumination device according to claim 1, wherein a concave portion for accommodating the light source element is formed on the end surface of the light guide plate on the side where the light source element is disposed. The pair of engaging protrusions for holding the light source element to be accommodated are erected in the recess, and the pair of engaging protrusions are respectively provided on the inlet side edges of the both side walls of the recess. The planar illumination device according to claim 4, wherein the planar illumination device is erected with its heads facing each other. The distance D3 from the front end surface of the hook, which is the front end portion of the engaging projection, to the back wall surface of the recess and the distance D4 from the ridge line to the back wall surface are the depth of the light source element along the direction perpendicular to the end surface. If the dimension is B,
D3 <B <D4
The planar illumination device according to claim 4, wherein the planar illumination device is set as follows. The planar illumination device according to claim 1, wherein the pair of engaging protrusions are resin-molded with the same material integrally with the light-guide plate when the light-guide plate is resin-molded. 2. The planar illumination device according to claim 1, wherein the light source element is a light emitting diode whose outer shape is a rectangular parallelepiped and whose light emission surface is a flat surface. 2. The planar illumination device according to claim 1, wherein the light guide plate has a rectangular shape and is made of polycarbonate. The wiring board is a flexible wiring board on which the light source element is directly mounted by a COF method, and the flexible wiring board is installed at a light incident side end of a main surface that emits light of the light guide plate. The planar illumination device according to claim 1, wherein

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